JP2017024374A - Image formation apparatus, image formation method and production method of printed matter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image formation apparatus which improves the adhesion state of a developer to an image part.SOLUTION: An image formation apparatus includes an exposure device exposing the surface of an image carrier on the basis of an image pattern having an image part and a non-image part. The exposure device executes: a first exposure method of exposing a plurality of pixels constituting the image part with a first light output value; and a second exposure method for exposing at least the pixels in the boundary with the non-image part out of the pixels constituting the image part as the high output exposure pixels to be exposed with a second light output value 110P1 higher than the first light output value 110P2, and exposing partial pixels other than the high output exposure pixels out of the pixels constituting the image part as the low output exposure pixels to be exposed at the lower duty ratio with respect to the first exposure method.SELECTED DRAWING: Figure 31

Description

  The present invention relates to an image forming apparatus, an image forming method, and a printed matter production method.

  There is a phenomenon in which toner does not adhere to a part of an image portion of an image pattern transferred to paper, which is called hollowing out or insect eating. In order to prevent such a phenomenon, an image forming apparatus that obtains a necessary amount of an anti-missing agent from a toner consumption amount and supplies the anti-missing agent into the developing device is known (for example, see Patent Document 1). ).

  However, with the technology disclosed in Patent Document 1, it is difficult to control the amount of toner, and thus it is difficult to prevent worms. Further, in the technique disclosed in Patent Document 1, since the anti-missing agent is supplied based on the consumption amount of toner, it is difficult to prevent worm-eating based on characteristics such as the shape of the image pattern.

  SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus capable of improving the state of adhesion of a developer to an image portion.

  The present invention is an image forming apparatus having an exposure device that exposes the surface of an image carrier based on an image pattern including an image portion and a non-image portion, and the exposure device includes a plurality of pixels constituting the image portion. A first exposure method in which exposure is performed with a first light output value; and a second light output value that is higher than the first light output value for a pixel at least at a boundary with a non-image portion among a plurality of pixels constituting the image portion And exposure as a low-power exposure pixel that exposes some pixels other than the high-power exposure pixel at a low duty ratio with respect to the first exposure method. And performing a second exposure method.

  According to the present invention, the adhesion state of the developer to the image portion can be improved.

1 is a central sectional view showing an embodiment of an image forming apparatus according to the present invention. It is a schematic diagram which shows the corotron type charging device of the said image forming apparatus. FIG. 2 is a schematic diagram illustrating a scorotron charging device of the image forming apparatus. It is a schematic diagram which shows the example of the optical scanning device which comprises the said image forming apparatus. It is a schematic diagram which shows the example of the light source of the said optical scanning device. It is a schematic diagram which shows another example of the light source of the said optical scanning device. FIG. 2 is a block diagram illustrating an example of a printer control device and a scan control device that constitute the image forming apparatus of FIG. 1. 2 is a block diagram illustrating an image processing unit of the image forming apparatus. FIG. It is a block diagram which shows the image processing unit of the said image processing part. It is a center sectional view showing an example of an electrostatic latent image measuring device. It is a center sectional view showing an example of a vacuum chamber of the above-mentioned electrostatic latent image measuring device. It is a schematic diagram which shows the relationship between an acceleration voltage and electrification. It is a graph which shows the relationship between an acceleration voltage and a charging potential. It is a schematic diagram which shows the electric potential distribution by the secondary electron on a sample surface. It is a schematic diagram which shows the charge distribution by the secondary electron on a sample surface. FIG. 5 is a schematic diagram illustrating an example of a latent image pattern by the optical scanning device in FIG. 4. FIG. 5 is a schematic diagram illustrating another example of a latent image pattern by the optical scanning device in FIG. 4. It is a schematic diagram which shows another example of the latent image image pattern by the optical scanning device of FIG. It is a schematic diagram which shows another example of the latent image image pattern by the optical scanning device of FIG. It is a center sectional view showing an example of measurement by grid mesh arrangement. It is a schematic diagram showing the behavior of incident electrons when | Vacc | ≧ | Vp |. It is a schematic diagram showing the behavior of incident electrons when | Vacc | <| Vp |. It is a schematic diagram which shows the example of the measurement result of a latent image depth. It is a schematic diagram which shows the example of the electrostatic latent image formation method in a reference example. It is a schematic diagram which shows the example of the electrostatic latent image formation method which concerns on this Embodiment. It is a schematic diagram which shows another example of the said electrostatic latent image formation method. It is a schematic diagram which shows another example of the said electrostatic latent image formation method. It is a schematic diagram which shows the example of the image pattern in this Embodiment. It is a schematic diagram which shows the image pattern of a reference example. It is a schematic diagram showing an example of (a) exposure pattern, (b) photoreceptor potential, and (c) toner adhesion amount in a reference example. It is a schematic diagram showing an example of (a) exposure pattern, (b) photoreceptor potential, and (c) toner adhesion amount in the present embodiment. FIG. 2 is a schematic diagram illustrating a photosensitive drum and a toner detection sensor of the image forming apparatus. It is a schematic diagram which shows the example of a writing pattern. It is a schematic diagram which shows the example of the surface of the photosensitive drum after the transfer of the said writing pattern. It is a schematic diagram showing an example in which worm-eating occurs on the surface of the photosensitive drum after transfer of the writing pattern. It is a schematic diagram which shows the example of the toner detection sensor for black toner. It is a schematic diagram showing an example of a toner detection sensor for color toner. 4 is a graph showing a relationship between a developing toner amount and a primary transfer rate. 6 is a graph showing a relationship among a developing toner amount, a transfer residual toner amount, and an insect bite level. 3 is a flowchart of an image forming method according to the present embodiment. It is a schematic diagram which shows another example of the image pattern in this Embodiment. It is a schematic diagram which shows the exposure pattern of the image pattern of FIG. It is a schematic diagram which shows the duty ratio of an exposure pattern. 6 is a flowchart of an image forming method according to another embodiment of the present invention.

  Embodiments of an image forming apparatus, an image forming method, and a printed material production method according to the present invention will be described below with reference to the drawings.

● Image forming device ●
An image forming apparatus 2000 that is an embodiment of an image forming apparatus according to the present invention will be described. As shown in FIG. 1, the image forming apparatus 2000 is a multifunction machine having functions of a copying machine, a printer, and a facsimile machine, and includes a main body device 1001, a reading device 1002, an automatic document feeder 1003, and the like.

  The main body device 1001 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow) and executes a printed matter production method. In the main body device 1001, devices for performing an electrophotographic process such as charging, exposure, development, transfer, and cleaning are arranged around the photosensitive drum 2030 in the above order along the rotation direction of the photosensitive drum 2030. ing. Further, the main body apparatus 1001 includes a communication control apparatus 2080 and a printer control apparatus 1060 as apparatuses that control apparatuses for executing the above-described electrophotographic process.

  The main body device 1001 includes a charging device 2032 that executes a charging process, an optical scanning device 2010 that executes an exposure process, a transfer belt 2040 as a transfer body that executes a transfer process, and a transfer roller 2042. Further, the main body apparatus 1001 includes a photosensitive drum 2030 that executes a developing process, a developing roller 2033, a toner cartridge 2034, and a cleaning unit 2031 that executes a cleaning process. The main body device 1001 includes a fixing roller 2050, a paper feed roller 2054, a registration roller pair 2056, a paper discharge roller 2058, a paper feed tray 2060, and a paper discharge tray 2070.

  The communication control device 2080 controls bidirectional communication with a host device such as a personal computer via a communication network. The printer control device 1060 controls each unit provided in the image forming apparatus 2000 in an integrated manner.

  The printer control device 1060 includes a CPU (Central Processing Unit) and a ROM (Read Only Memory). The printer control device 1060 includes a RAM (Random Access Memory) and an A / D (Analog / Digital) converter. The printer control device 1060 comprehensively controls each unit in response to a request from the host device, and sends image information from the host device to the optical scanning device 2010.

  The ROM stores a program written in a code readable by the CPU and various data used when executing this program. The RAM is a temporarily writable memory for work of the CPU. The A / D converter converts an analog signal into a digital signal.

  A photoconductive photosensitive drum 2030 formed in a cylindrical shape as an image carrier that is exposed by the optical scanning device 2010 and forms an electrostatic latent image is provided below the paper surface of the transfer belt 2040. The photosensitive drum 2030 is arranged in the order of yellow 2032d, magenta 2030c, cyan 2030b, and black 2030a from the moving direction of the transfer belt 2040, that is, upstream in the counterclockwise direction in FIG.

  The charging device 2032 uniformly charges the surface of the photosensitive drum 2030. For the charging device 2032, for example, a contact-type charging roller that generates less ozone, or a corona charger that uses corona discharge can be used.

  The charging device 2032 may be a corotron charging device shown in FIG. 2, a scorotron charging device shown in FIG. 3, or a roller charging device.

  As shown in FIG. 1, the photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a are used as a set, and constitute an image forming station that forms a black (K) image.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, the toner cartridge 2034b, and the cleaning unit 2031b are used as a set and constitute an image forming station that forms a cyan (C) image.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, the toner cartridge 2034c, and the cleaning unit 2031c are used as a set and constitute an image forming station that forms a magenta (M) image.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, the toner cartridge 2034d, and the cleaning unit 2031d are used as a set and constitute an image forming station that forms a yellow (Y) image.

  The optical scanning device 2010 is an optical writing device that performs optical writing on the photosensitive drum 2030, and executes an exposure process of an electrophotographic process. The optical scanning device 2010 is charged with a light beam modulated to each color based on image information of multiple colors such as black, cyan, magenta, and yellow from a host device connected to the communication control device 2080. The surface of the photosensitive drum 2030 is irradiated. On the surface of the photoconductor drum 2030, the charge disappears only in the portion irradiated with the light beam, and an electrostatic latent image corresponding to the image information is formed. The formed electrostatic latent image is a so-called negative latent image, and moves in the direction of the corresponding developing roller 2033 as the photosensitive drum 2030 rotates. Details of the optical scanning device 2010 will be described later.

  The toner cartridge 2034a stores black toner, the toner cartridge 2034b stores cyan toner, the toner cartridge 2034c stores magenta toner, and the toner cartridge 2034d stores yellow toner. The toner of each color as the developer stored in the toner cartridge 2034 is supplied to the corresponding developing roller 2033.

  The toner from the corresponding toner cartridge 2034 is thinly and uniformly applied to the surface of the developing roller 2033 as the developing roller 2033 rotates. When the toner applied to the surface of the developing roller 2033 comes into contact with the surface of the photosensitive drum 2030 corresponding to each color, the toner adheres to the electrostatic latent image formed on the surface of the photosensitive drum 2030 and becomes electrostatic latent image. Is visualized to form a toner image (hereinafter also referred to as “toner image”). The formed toner image moves in the direction of the transfer belt 2040 as the photosensitive drum 2030 rotates.

  The yellow, magenta, cyan, and black toner images are sequentially transferred and superimposed on the transfer belt 2040 at a predetermined timing to form a color image.

  The paper feed tray 2060 stores transfer paper that is a recording medium. A paper feed roller 2054 is disposed in the vicinity of the paper feed tray 2060. The uppermost sheet of transfer paper stored in the paper supply tray 2060 is pulled out by the paper supply roller 2054, and the leading end of the transferred transfer paper is captured by the registration roller pair 2056. The registration roller pair 2056 sends the transfer paper toward the gap between the transfer belt 2040 and the transfer roller 2042 in accordance with the timing at which the toner image on the photosensitive drum 2030 moves to the transfer position. The color image on the transfer belt 2040 is transferred to the transferred transfer paper. The transfer paper on which the color image is transferred is sent to the fixing roller 2050.

  Heat and pressure are applied to the transfer paper sent to the fixing roller 2050, and the toner is fixed on the transfer paper. The transfer paper on which the toner is fixed is sent to the paper discharge tray 2070 via the paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070.

  The cleaning unit 2031 removes toner (residual toner) remaining on the surface of the photosensitive drum 2030 after the toner image is transferred. The surface of the photosensitive drum 2030 from which the residual toner has been removed returns to the position facing the corresponding charging device 2032 again.

  In the image forming apparatus according to the present invention, an electrostatic latent image is formed by the charging device, the optical scanning device, the photosensitive member, and the image processing unit for converting the image pattern into the light output. That is, the charging device, the optical scanning device, the photoconductor, and the image processing unit constitute the exposure device according to the present embodiment.

  The process for obtaining an output image in an electrophotographic system such as a copying machine or a laser printer is as follows. In the electrophotographic system, a photosensitive member, which is one of latent image carriers, is uniformly charged in a charging step, and light is partially emitted by irradiating the photosensitive member with light in an exposure step. By doing so, in the electrophotographic system, an electrostatic latent image can be formed on the photoreceptor.

Configuration of Optical Scanning Device Next, the configuration of the optical scanning device 2010 that constitutes the image forming apparatus will be described.

  As shown in FIG. 4, the optical scanning device 2010 includes a light source 11, a collimating lens 12, a cylindrical lens 13, a mirror 14, a polygon mirror 15, and a first scanning lens 21. The optical scanning device 2010 includes a second scanning lens 22, a mirror 24, a synchronization detection sensor 26, and a scanning control device. The optical scanning device 2010 is assembled at a predetermined position of the optical housing.

  In the following description, the direction along the longitudinal direction (rotation axis direction) of the photosensitive drum 2030 is defined as the Y-axis direction of the XYZ three-dimensional orthogonal coordinate system, and the direction along the rotation axis of the polygon mirror 15 is defined as the Z-axis direction. The direction perpendicular to both the Y axis and the Z axis is taken as the X axis direction.

  In the following description, a direction corresponding to the main scanning direction of each optical member is a main scanning corresponding direction, and a direction corresponding to the sub scanning direction is a sub scanning corresponding direction.

  The light source 11 has, for example, a plurality of light emitting units arranged two-dimensionally. The light emitting units are arranged so that the intervals between the light emitting units are equal when all the light emitting units are orthogonally projected onto a virtual line extending in the sub-scanning corresponding direction. As the light source 11, a semiconductor laser (LD: Laser Diode), a light emitting diode (LED: Light Emitting Diode), or the like can be used.

  In FIG. 5, the light source 11A of the optical scanning device 2010 is a semiconductor laser array configured by arranging four semiconductor lasers as a multi-beam light source. Further, the light source 11 </ b> A is disposed perpendicular to the optical axis direction of the collimating lens 12.

  In FIG. 6, a light source 11B, which is another example of the light source of the optical scanning device 2010, is a vertical cavity surface emitting device having a light emitting point disposed on a plane including the Y-axis direction and the Z-axis direction, for example, having a wavelength of 780 nm. Laser (Vertical Cavity Surface Emitting LASER).

  The light source 11B has a total of 12 light emitting points, for example, three in the main scanning direction, that is, the Y-axis direction, and four in the sub-scanning direction, that is, the Z-axis direction. When applied to the optical scanning device 2010, the light source 11B can simultaneously scan four scanning lines in the vertical direction by scanning three scanning points arranged in the horizontal direction on one scanning line. In the following description, the “light emitting section interval” refers to the distance between the centers of two light emitting sections.

  Returning to FIG. 4, the collimating lens 12 is disposed on the optical path of the light emitted from the light source 11 and refracts the light into parallel light or substantially parallel light.

  The cylindrical lens 13 focuses the light that has passed through the collimating lens 12 only in the sub-scanning direction in the vicinity of the deflection reflection surface of the polygon mirror 15. The cylindrical lens 13 forms light emitted from the light source 11 in the vicinity of the reflection surface of the polygon mirror 15 as a line image that is long in the main scanning direction (Y-axis direction).

  The mirror 14 reflects the light imaged through the cylindrical lens 13 toward the polygon mirror 15.

  The optical system arranged on the optical path between the light source 11 and the polygon mirror 15 is also called a pre-deflector optical system.

  The polygon mirror 15 is a polygon mirror that rotates around a rotation axis in a direction orthogonal to the longitudinal direction of the photosensitive drum 2030. Each mirror surface of the polygon mirror 15 is a deflection reflection surface. The polygon mirror 15 rotates at a desired speed at a constant speed by a driving IC (Integrated Circuit) giving an appropriate clock to the motor unit. When the polygon mirror 15 is rotated at a constant speed in the direction of the arrow by the motor unit, a plurality of light beams reflected by the deflecting reflection surface are respectively deflected and deflected at a constant angular velocity.

  The first scanning lens 21, the second scanning lens 22, the mirror 24, and the synchronization detection sensor 26 constitute a scanning optical system. The scanning optical system is disposed on the optical path of the light deflected by the polygon mirror 15.

  The first scanning lens 21 is disposed on the optical path of the light deflected by the polygon mirror 15.

  The second scanning lens 22 is disposed on the optical path of the light that passes through the first scanning lens 21.

  The mirror 24 is a long plane mirror and bends the optical path of the light passing through the second scanning lens 22 in a direction toward the photosensitive drum 2030.

  The light deflected by the polygon mirror 15 is applied to the photosensitive drum 2030 through the first scanning lens 21 and the second scanning lens 22 to form a light spot on the surface of the photosensitive drum 2030.

  The light spot on the surface of the photosensitive drum 2030 moves along the longitudinal direction of the photosensitive drum 2030 as the polygon mirror 15 rotates. The moving direction of the light spot on the surface of the photosensitive drum 2030 is the main scanning direction, and the rotation direction of the photosensitive drum 2030 is the sub-scanning direction.

  The synchronization detection sensor 26 receives light from the polygon mirror 15 and outputs a signal photoelectric conversion signal corresponding to the amount of received light to the scanning control device. The output signal of the synchronization detection sensor 26 is also referred to as a synchronization detection signal.

  As shown in FIG. 4, the optical scanning device 2010 simultaneously scans a plurality of lines on the surface to be scanned of the photosensitive drum 2030 by scanning with one deflection reflection surface of the polygon mirror 15. Print data for one line corresponding to each light emission point is stored in the buffer memory in the image processing unit that controls the light emission signal at each light emission point.

  The print data is read for each deflecting reflection surface of the polygon mirror 15, and the light beam blinks corresponding to the print data on the scanning line on the photosensitive drum 2030 as the latent image carrier, and according to the scanning line. An electrostatic latent image is formed.

Printer Control Device / Scanning Control Device Next, a printer control device and a scanning control device of the image forming apparatus according to the present invention will be described.

  As shown in the block diagram of the printer control device 1060 and the scan control device 16 in FIG. 7, the printer control device 1060 has a control unit that comprehensively controls each component of the image forming apparatus 2000, an image processing unit 1060a, an exposure unit. An amount setting unit 1060b and the like are included.

  The image processing unit 1060a outputs image data on which image processing to be described later is performed, tag data for identifying object information, and the like to the exposure setting unit 1060b.

  The exposure amount setting unit 1060b sets the exposure amount of each exposure pixel of the image data after the image processing from the image processing unit 1060a, and outputs the image data, the tag data, etc. after the exposure amount setting to the scanning control device 16. .

  In the image data sent from the image processing unit 1060a to the exposure amount setting unit 1060b, a white part (non-exposure part) and a black part (exposure part) are designated for each pixel.

The exposure amount setting unit 1060b will be described in detail later.

  The scanning control device 16 scans the surface of the photosensitive drum 2030 based on the image data after the exposure amount setting from the exposure amount setting unit 1060b, tag data, and the like, and an electrostatic latent image is formed on the surface of the photosensitive drum 2030. Form.

  The scanning control device 16 generates light source drive information based on image data, tag data, and the like from the exposure amount setting unit 1060b as necessary, and drives each light emitting unit of the light source using the drive information.

  The scanning control device 16 includes a reference clock generation circuit 422, a pixel clock generation circuit 425, a light source modulation data generation circuit 407, a light source selection circuit 414, a write timing signal generation circuit 415, and a light source drive circuit 420.

  The arrows in FIG. 7 indicate the flow of typical signals and information, and do not represent the entire connection relationship of each block.

  The reference clock generation circuit 422 generates a high frequency clock signal that serves as a reference for the light source driving circuit 420.

  The pixel clock generation circuit 425 mainly includes a PLL (Phase Locked Loop) circuit. The pixel clock generation circuit 425 generates a pixel clock signal based on the synchronization signal s1 and the high frequency clock signal from the reference clock generation circuit 422.

  The pixel clock signal has the same frequency as the high-frequency clock signal and the phase matches the synchronization signal s1.

  Therefore, the pixel clock generation circuit 425 can control the writing position for each scan by synchronizing the image data with the pixel clock signal.

  The generated pixel clock signal is supplied to the light source drive circuit 420 as one piece of drive information, and is also supplied to the light source modulation data generation circuit 407. The pixel clock signal supplied to the light source modulation data generation circuit 407 is used as a clock signal for the write data s16.

  The light source modulation data generation circuit 407 corresponds to a light source driving unit of the image forming apparatus according to the present invention. The light source modulation data generation circuit 407 creates write data s16 for each light emitting unit based on image information from an image processing unit (IPU). The write data s16 is supplied to the light source drive circuit 420 as one piece of drive information at the timing of the pixel clock signal.

  The light source modulation data generation circuit 407 exposes image data using PM + PWM signals based on image pattern information and tag information from the image processing unit in order to form a latent image by the electrostatic latent image forming method according to the present embodiment. Convert to pattern.

  The light source selection circuit 414 is a circuit used when the light source includes a plurality of light emitting units. When the image surface of the scanning light reaches the scanning end, a plurality of light emitting units used to detect the start of the next scanning, For example, 32 light emitting units are selected and a signal designating the selected light emitting unit is output. The output signal s14 from the light source selection circuit 414 is supplied to the light source drive circuit 420 as one piece of drive information. Note that the light source selection circuit 414 is not necessarily provided when a single light emitting unit is used as the light source.

  The write timing signal generation circuit 415 obtains the write start timing based on the synchronization signal s1, and outputs the output signal s15, which is the timing signal, to the light source drive circuit 420 as one of the drive information.

  The light source driving circuit 420 generates a driving current of each light emitting unit of the light source, for example, a pulse current based on the driving information, and supplies the driving current to the light emitting unit.

  In the image forming apparatus 2000, exposure is performed while changing the light output value corresponding to the position of the image portion in the main scanning direction, that is, corresponding to the time from the start of exposure of the image portion. With the configuration shown in FIG. 7, the light source driving circuit 420 can generate a light source driving current by simultaneously performing pulse width modulation (PWM modulation) and light amount modulation (PW modulation).

  Since the light source driving circuit 420 can convert the light source modulation signal obtained from the light source modulation data into a current, the image forming apparatus 2000 can generate a PM + PWM modulation signal capable of controlling the light output and the lighting time simultaneously. it can.

  As shown in the block diagram of FIG. 8, the image processing unit includes an image processing unit 101, a controller unit 102, a memory unit 103, an optical writing output unit 104, and a scanner unit 105.

  As shown in the block diagram of FIG. 9, the image processing unit 101 includes a density conversion unit 101a, a filter unit 101b, a color correction unit 101c, a selector unit 101d, a gradation correction unit 101e, and a gradation processing unit 101f. And.

  The density conversion unit 101a converts RGB image data from the scanner unit 105 into density data using a look-up table, and outputs the density data to the filter unit 101b.

  The filter unit 101b performs image correction processing such as smoothing processing and edge enhancement processing on the density data input from the density conversion unit 101a, and outputs the result to the color correction unit 101c.

  The color correction unit 101c performs color correction, that is, masking processing.

  Under the control of the image processing unit 101, the selector unit 101d performs any of C (Cyan), M (Magenta), Y (Yellow), and K (Key Plate) on the image data input from the color correction unit 101c. Select. The selector unit 101d outputs the selected C, Y, M, and K data to the gradation correction unit 101e.

  The gradation correction unit 101e stores C, M, Y, and K data input from the selector unit 101d in advance. The tone correction unit 101e is set with a γ curve that provides linear characteristics with respect to input data.

  The gradation processing unit 101 f performs gradation processing such as dither processing on the image data input from the gradation correction unit 101 e and outputs a signal to the optical writing output unit 104.

  Returning to FIG. 8, the controller unit 102 performs processing such as rotation, repeat, aggregation, and compression / decompression on the image data, and then outputs the processed image data to the IPU again.

  The memory unit 103 has a lookup table for storing various data.

  The optical writing output unit 104 performs light modulation of the light source 11 according to the lighting data by the control driver, and forms an electrostatic latent image on the photosensitive drum 2030. The optical writing output unit 104 forms an electrostatic latent image based on an input signal from a gradation processing unit described later. The formed electrostatic latent image forms an image on a recording sheet by the developing device 1032 and the transfer device 1033 described above.

  The scanner unit 105 reads an image and generates image data such as RGB (Red Green Blue) data based on the image.

  The image processing unit 101 outputs image data before image processing or image data after image processing, that is, density data to the controller unit 102 as necessary.

Next, the configuration of the electrostatic latent image measuring apparatus that can confirm the state of the electrostatic latent image formed by the electrostatic latent image forming method according to the present embodiment. explain.

  In FIG. 10, an electrostatic latent image measuring device 300 includes a charged particle irradiation system 400, an optical scanning device 1010, a sample stage 401, a detector 402, an LED 403, a control system, a discharge system, a driving power source, and the like. I have.

  The charged particle irradiation system 400 is disposed in the vacuum chamber 340. The charged particle irradiation system 400 includes an electron gun 311, an extraction electrode 312, an acceleration electrode 313, a condenser lens 314, a beam blanker 315, and a partition plate 316. The charged particle irradiation system 400 includes a movable diaphragm 317, a stigmator 318, a scanning lens 319, and an objective lens 320.

  In the following description, the traveling direction of the light beam of the electron gun 311 will be referred to as a c-axis direction, and two directions orthogonal to each other in a plane orthogonal to the c-axis direction will be described as an a-axis direction and a b-axis direction.

  The electron gun 311 generates an electron beam as a charged particle beam. In the following description, the traveling direction of the electron beam of the electron gun 311 is defined as the + c axis direction.

  The extraction electrode 312 is disposed on the + c axis side of the electron gun 311 and controls the electron beam generated by the electron gun 311.

  The acceleration electrode 313 is disposed on the + c axis side of the extraction electrode 312 and controls the energy of the electron beam.

  The condenser lens 314 is disposed on the + c axis side of the acceleration electrode 313 and focuses the electron beam.

  The beam blanker 315 is disposed on the + c axis side of the condenser lens 314, and turns on or off the electron beam irradiation.

  The partition plate 316 is disposed on the + c axis side of the beam blanker 315 and has an opening at the center.

  The movable diaphragm 317 is disposed on the + c-axis side of the partition plate 316 and adjusts the beam diameter of the electron beam that has passed through the opening of the partition plate 316.

  The stigmeter 318 is disposed on the + c axis side of the movable diaphragm 317 and corrects astigmatism.

  The scanning lens 319 is disposed on the + c axis side of the stigmator 318, and deflects the electron beam via the stigmator 318 in the ab plane.

  The objective lens 320 is disposed on the + c axis side of the scanning lens 319 and converges the electron beam that has passed through the scanning lens 319. The electron beam passing through the objective lens 320 passes through the beam emission opening 321 and is irradiated on the surface of the sample 323. A driving power source is connected to each lens and the like.

  Charged particles are particles that are affected by an electric field or magnetic field. For example, an ion beam may be used as the beam for irradiating the charged particles instead of the electron beam. In this case, a liquid metal ion gun or the like is used instead of the electron gun.

  The sample 323 is a photoconductor, and has a conductive support, a charge generation layer (CGL), and a charge transport layer (CTL).

  The charge generation layer includes a charge generation material (CGM) and is formed on the surface on the −c axis side of the conductive support. The charge transport layer is formed on the −c-axis side surface of the charge generation layer.

  When the sample 323 is exposed with the surface charged, that is, the surface on the −c side, the light is absorbed by the charge generation material of the charge generation layer, and positive and negative charge carriers are generated. One of these carriers is injected into the charge transport layer and the other into the conductive support by an electric field.

  The carriers injected into the charge transport layer move to the surface of the charge transport layer by an electric field, and are combined with the charge on the surface and disappear. As a result, a charge distribution, that is, an electrostatic latent image is formed on the surface of the sample 323 (the surface on the −c side).

  The optical scanning device 1010 includes a light source, a coupling lens, an aperture plate, a cylindrical lens, a polygon mirror, a scanning optical system, and the like. The optical scanning device 1010 also has a scanning mechanism for scanning light in a direction parallel to the rotation axis of the polygon mirror.

  The light emitted from the optical scanning device 1010 irradiates the surface of the sample 323 through the reflection mirror 372 and the window glass 368.

  The irradiation position of the light emitted from the optical scanning device 1010 on the surface of the sample 323 is along two directions orthogonal to each other on a plane orthogonal to the c-axis direction due to deflection by the polygon mirror and deflection by the scanning mechanism. Change. At this time, the change direction of the irradiation position due to deflection by the polygon mirror is the main scanning direction, and the change direction of the irradiation position due to deflection by the scanning mechanism is the sub-scanning direction. Here, the a-axis direction is set to the main scanning direction, and the b-axis direction is set to the sub-scanning direction.

  As described above, the electrostatic latent image measuring device 300 can two-dimensionally scan the surface of the sample 323 with the light emitted from the optical scanning device 1010. The electrostatic latent image measuring apparatus 300 can form a two-dimensional electrostatic latent image on the surface of the sample 323.

  The optical scanning device 1010 is provided outside the vacuum chamber 340 so that vibrations and electromagnetic waves generated by the polygon mirror drive motor do not affect the trajectory of the electron beam. Thereby, the influence of the disturbance which acts on a measurement result can be suppressed.

  The detector 402 is disposed in the vicinity of the sample 323 and detects secondary electrons from the sample 323.

  The LED 403 is disposed in the vicinity of the sample 323 and emits light that illuminates the sample 323. The LED 403 is used to erase charges remaining on the surface of the sample 323 after measurement.

  The optical housing that holds the scanning optical system may be configured to cover the entire scanning optical system with a cover and shield external light incident on the inside of the vacuum chamber.

  In the scanning optical system, the scanning lens has an fθ characteristic, and the light beam moves at a substantially constant speed with respect to the image plane when the optical polarizer rotates at a constant speed. . Further, the scanning optical system is configured such that the beam spot diameter can be scanned substantially constant.

  In the electrostatic latent image measuring apparatus 300, since the scanning optical system is arranged away from the vacuum chamber, vibration generated when driving an optical deflector such as a polygon scanner is directly transmitted to the vacuum chamber 340. There is little influence by.

  By providing an anti-vibration means such as a damper on the structure holding the scanning optical system, a higher anti-vibration effect can be obtained.

  By providing the scanning optical system, the electrostatic latent image measuring device 300 can form an arbitrary latent image pattern including a line pattern in the bus line direction of the photoreceptor.

  In order to form a latent image pattern at a predetermined position, a synchronization detection sensor 26 that detects a scanning beam from the light deflection unit may be provided. The shape of the sample may be a flat surface or a curved surface.

  As shown in FIG. 11, the vacuum chamber 1 is provided with a glass window for allowing light from the light source to enter the vacuum chamber 1 from the outside at a position of 45 ° with respect to the vertical axis. An optical scanning device 171 having the same configuration as that of the optical scanning device 1010 is disposed outside the vacuum chamber 1.

  The optical scanning device 171 includes a light source, a polygon mirror as an optical deflector, a scanning lens, a synchronization detection unit, and the like. The optical housing that holds the optical scanning device 171 may cover the entire optical scanning device 171 with a cover and shield external light (harmful light) that enters the vacuum chamber.

● Method of electrostatic latent image measurement Next, a method of electrostatic latent image measurement will be described.

  In the electrostatic latent image measuring apparatus 300, the electron beam is irradiated to the sample 323 of the photosensitive member in the electrostatic latent image measurement.

  As shown in FIG. 12, in the electrostatic latent image measuring device 300, the acceleration voltage | Vacc |, which is a voltage applied to the acceleration electrode 313, is higher than the voltage at which the secondary electron emission ratio at the sample 323 becomes 1. The voltage is set. By setting the acceleration voltage in this way, in the sample 323, the amount of incident electrons exceeds the amount of emitted electrons, so that electrons are accumulated in the sample 323 and charge up occurs. As a result, in the electrostatic latent image measuring apparatus 300, the surface of the sample 323 can be uniformly charged with a negative charge.

  As shown in FIG. 13, there is a certain relationship between the acceleration voltage and the charging potential. For this reason, in the electrostatic latent image measuring device 300, by appropriately setting the acceleration voltage and the irradiation time, a charging potential similar to that of the photosensitive drum 2030 in the image forming device 2000 can be formed on the surface of the sample 323. it can.

  In addition, since the one where an irradiation current is large can reach the target charging potential in a short time, the irradiation current is set to several nA here.

  Thereafter, in the electrostatic latent image measuring apparatus 300, the amount of incident electrons in the sample 323 is set to 1/100 to 1/1000 times so that the electrostatic latent image can be observed.

  In the electrostatic latent image measuring device 300, the optical scanning device 1010 is controlled to optically scan the surface of the sample 323 two-dimensionally, thereby forming an electrostatic latent image on the sample 323. The optical scanning device 1010 is adjusted so that a light spot having a desired beam diameter and beam profile is formed on the surface of the sample 323.

  The exposure energy required for forming the electrostatic latent image is determined by the sensitivity characteristic of the sample, but is usually about 2 to 10 mJ / m2. For samples with low sensitivity, the required exposure energy may be 10 mJ / m 2 or more. That is, the charging potential and necessary exposure energy are set in accordance with the photosensitive characteristics and process conditions of the sample. The exposure conditions of the electrostatic latent image measuring device 300 are set in the same manner as the exposure conditions matched to the image forming device 2000.

  Therefore, in such a case, the electrostatic latent image profile and the electron trajectory are calculated in advance, and the detection result is corrected based on the calculation result to obtain the electrostatic latent image profile with high accuracy. it can.

  In FIG. 14, the potential distribution in the space between the detector 402 that captures charged particles and the sample 323 is illustrated by contour lines. The surface of the sample 323 is uniformly charged to a negative polarity except for a portion where the potential is attenuated due to light attenuation, and a positive potential is applied to the detector 402. Therefore, in the potential contour line group indicated by the solid line, the potential increases as it approaches the detector 402 from the surface of the sample 323.

  Therefore, the secondary electrons e11 and e12 generated at the Q1 and Q2 points that are uniformly charged in the negative polarity are attracted to the positive potential of the detector 402 and displaced as indicated by the arrows G1 and G2. And captured by the detector 402.

  On the other hand, the point Q3 is a portion where the negative potential is attenuated by light irradiation, and in the vicinity of the point Q3, the arrangement of the potential contour lines spreads in a semicircular ripple shape centering on the point Q3 as shown by a broken line. In the ripple-like potential distribution, the closer to Q3 point, the higher the potential.

  In other words, the electric force restrained on the sample 323 side acts on the secondary electrons e13 generated in the vicinity of the point Q3, as indicated by the arrow G3. For this reason, the secondary electrons e <b> 13 are captured in the potential holes indicated by the broken-line potential contour lines and cannot move toward the detector 402.

  In FIG. 15, potential holes are schematically shown. A portion where the intensity of secondary electrons (number of secondary electrons) detected by the detector 402 is large is a portion of the electrostatic latent image, that is, a portion that is uniformly negatively charged, or points Q1 and Q2 in FIG. Corresponds to the representative part. The intensity of the secondary electrons detected by the detector 402, that is, the portion where the number of secondary electrons is small corresponds to the image portion of the electrostatic latent image, that is, the portion irradiated with light or the portion represented by the point Q3 in FIG. To do.

  Therefore, if the electrical signal obtained from the output of the detector 402 is sampled at an appropriate sampling time, the surface potential distribution (potential contrast image) V (a, b) is a minute value corresponding to the sampling using the sampling time T as a parameter. Can be specified for each area.

  Then, if the surface potential distribution V (a, b) is configured as two-dimensional image data and displayed on a display device or printed by a printer, an electrostatic latent image can be obtained as a visible image. Can do.

  For example, if the intensity of secondary electrons to be captured is expressed in terms of brightness, the image portion of the electrostatic latent image is dark, the ground portion is bright and contrasted, and the surface charge distribution Can be expressed, that is, output as a bright and dark image according to the above. Further, if the surface potential distribution can be known for the electrostatic latent image, the surface charge distribution can also be known.

  Note that the electrostatic latent image can be measured with higher accuracy by obtaining a profile of the surface charge distribution and surface potential distribution for the electrostatic latent image.

  As shown in FIG. 16, as the latent image pattern by the optical scanning device, what is called a so-called one-dot isolated pattern or one-dot lattice pattern can be cited.

  As shown in FIG. 17, as the latent image pattern by the optical scanning device, a so-called two-dot isolated pattern can be cited.

  As shown in FIG. 18, as the latent image pattern by the optical scanning device, there is a so-called 2by2 pattern.

  As shown in FIG. 19, as the latent image pattern by the optical scanning device, a so-called two-dot line pattern can be cited.

  Note that the latent image pattern by the optical scanning device is not limited to the above-described one, and various patterns can be formed.

  The detection target of the detector 402 is not limited to the secondary electrons from the sample 323. For example, the detector 402 may detect electrons repelled in the vicinity of the surface of the sample 323 (hereinafter also referred to as “primary repulsive electrons”) before the incident electron beam reaches the surface of the sample 323.

  As shown in FIG. 20, in the measurement example using the grid mesh arrangement, an insulating member 404 and a conductive member 405 are provided between the sample stage 401 and the sample 323, and a voltage of ± Vsub is applied to the conductive member 405. ing.

  A voltage application unit capable of applying a voltage ± Vsub is connected to the lower conductive member 405 of the sample 323. Further, a grid mesh 325 is disposed on the upper side of the sample 323 in order to suppress the incident electron beam from being affected by the sample charge. With the above configuration, the detector 402 detects primary repulsive electrons.

  The detector 402 may be provided with a conductive plate 324 and a side grid so as to face the detector 402.

  In general, the acceleration voltage is generally expressed as positive, but since Vacc is negative, the acceleration voltage is expressed as negative (Vacc <0). Further, the potential of the sample 323 is set to Vp (<0).

  Since the potential is the electrical potential energy of the unit charge, the incident electrons move at a speed corresponding to the acceleration voltage Vacc at the potential 0 (V). That is, assuming that the charge amount of electrons is e and the mass of electrons is m, the initial velocity of electrons v0 is represented by mv02 / 2 = e × | Vacc |. Here, in a vacuum, due to the law of energy conservation, electrons move at a constant speed in a region where the acceleration voltage does not work.

  As the sample 323 approaches, the potential increases, and the speed of the electrons decreases due to the influence of Coulomb repulsion due to the charge of the sample 323. Therefore, the following phenomenon generally occurs.

  As shown in FIG. 21, when | Vacc | ≧ | Vp |, the speed of the incident electrons is reduced, but reaches the sample 323.

  As shown in FIG. 22, when | Vacc | <| Vp |, the velocity of the incident electrons is gradually decelerated under the influence of the potential potential of the sample 323, and the velocity becomes zero before reaching the sample 323. And go in the opposite direction.

  In a vacuum without air resistance, the law of conservation of energy is almost valid. Therefore, the potential on the surface of the sample 323 can be measured by measuring the condition where the energy on the surface of the sample 323 when the energy of the incident electrons is changed, that is, the landing energy is almost zero.

  Since the amount of secondary electrons generated when the incident electrons reach the sample 323 and the primary repulsive electrons differ greatly from each other, they can be distinguished from the border of contrast between light and dark.

  A scanning electron microscope or the like has a backscattered electron detector. In this case, the backscattered electrons are generally reflected (scattered) from the back surface due to the interaction with the sample material, and the sample surface. It refers to the electrons that jump out of the.

  The energy of the reflected electrons is comparable to the energy of the incident electrons. The velocity vector of reflected electrons is assumed to be larger as the atomic number of the sample is larger. In addition, the reflected electrons are used to detect the difference in the composition of the sample and the unevenness of the surface.

  On the other hand, primary repulsive electrons are electrons that are affected by the potential distribution on the sample surface and reverse before reaching the sample surface, and are completely different from reflected electrons.

  FIG. 23 shows an example of the result of measuring the electrostatic latent image. Vth is a difference between Vacc and Vsub (= Vacc−Vsub).

  Further, the potential distribution V (a, b) can be obtained from Vth (a, b) when the landing energy is almost zero at each scanning position (a, b). Vth (a, b) has a unique correspondence with the potential distribution V (a, b). If the charge distribution is gentle, Vth (a, b) is approximately the potential distribution V (a, b). ) Is equivalent.

  A curve indicating the relationship between Vth and the distance from the center of the electrostatic latent image in FIG. 23A is an example of the surface potential distribution generated by the charge distribution on the sample surface.

  Here, Vacc is set to −1800V. At the center of the electrostatic latent image, the potential is about −600 V, and the potential increases toward the minus side as the distance from the center of the electrostatic latent image increases. The potential in the peripheral region exceeding 75 μm from the center of the electrostatic latent image is about −850V.

  FIG. 23B is an image of the output of the detector 402 when Vsub = −1150 V is set. At this time, Vth = −650V.

  FIG. 23C is an image of the output of the detector 402 when Vsub = −1100 V is set. At this time, Vth = −700V.

  In the method for obtaining the profile of the electrostatic latent image by detecting the primary repulsive electrons, the surface of the sample is measured by scanning the sample surface with an electron beam while changing Vacc or Vsub and measuring Vth (a, b). Potential information can be obtained. By using a method for obtaining the profile of the electrostatic latent image by detecting the primary repulsive electrons, the profile of the electrostatic latent image, which has been difficult in the past, can be visualized on the order of microns.

  In the method of obtaining the profile of the electrostatic latent image by detecting the primary repulsive electrons, the energy of the incident electrons changes drastically, so that the trajectory of the incident electrons shifts, the scanning magnification changes, or distortion occurs. There is.

  In such a case, the electrostatic latent image profile can be obtained with high accuracy by calculating the electrostatic field environment and the electron trajectory in advance and correcting the detection result based on the calculation result.

  As described above, by using the electrostatic latent image measuring device 300, the electric charge distribution, surface potential distribution, electric field strength distribution, and electric field strength in the direction perpendicular to the sample surface in the electrostatic latent image can be accurately measured. Can be sought.

● Image formation method ●
Next, an embodiment of the image forming method according to the present invention will be described.

  In the image forming method according to the present embodiment, the light output waveform used for latent image formation is a predetermined light output value necessary for obtaining a target image density for an image portion including a line image or a solid image. This is a waveform for exposing the photoconductor for time.

  The image portion is a portion that includes a plurality of pixels and forms an image by attaching toner in the image pattern. Further, the non-image portion is a portion in which no toner is attached and an image is not formed in the image pattern.

  In the following description, the target image density is referred to as “target image density”. In the following description, a predetermined light output value necessary for obtaining a target image density is referred to as “target exposure output value” or “reference light output value”. In the following description, a predetermined time for exposing the entire pixels of the image portion with the target exposure output value to obtain the target image density is referred to as “target exposure time”.

  In the following description, an exposure method in which exposure is performed for a target exposure time with a target exposure output value is referred to as “standard exposure”. Furthermore, in the following description, a solid image refers to an image portion having a larger area than a line image.

  Furthermore, in the following description, exposing a photoconductor for an exposure time shorter than the target exposure time with a light output value stronger than the target exposure output value is referred to as “time-concentrated exposure”. In time-concentrated exposure, for example, when one pixel is exposed, a total of four pixels of light output values obtained by adding a target exposure output value for three pixels to a target exposure output value for one pixel are used as an exposure time for one pixel. To expose.

  In the following description, time-intensive exposure is also referred to as TC (Time Concentration) exposure.

  As shown in FIG. 24, a method of forming an electrostatic latent image by standard exposure in the image forming method of the reference example (hereinafter referred to as “exposure method 1”) is applied to a 1-dot image portion including a line image and a solid image. On the other hand, as described above, the photosensitive member is exposed for the target exposure time with the target exposure output value. Here, the target exposure output value is set to a light output value of 100%, and the target exposure time is set to a duty ratio of 100%.

  As shown in FIG. 25, an example of a method of forming an electrostatic latent image by time-concentrated exposure (hereinafter referred to as “exposure method 2”) of the image forming method according to the present embodiment is 200% of the target exposure output value. The photosensitive member is exposed at a duty ratio of 50% with respect to the target exposure time at the light output value of. Here, if the width of the image portion is 1, the width of the section to be exposed is 4/8 pixels.

  As shown in FIG. 26, another example (hereinafter referred to as “exposure method 3”) of forming an electrostatic latent image by time-concentrated exposure in the present embodiment is a light output of 400% of the target exposure output value. The photosensitive member is exposed at a duty ratio of 25% with respect to the target exposure time. If the width of the image portion is 1, the width of the section to be exposed is 2/8 pixel.

  As shown in FIG. 27, an example of a method of forming an electrostatic latent image by time-concentrated exposure in the present embodiment (hereinafter referred to as “exposure method 4”) is a light output value that is 800% of a target exposure output value. The photosensitive member is exposed at a duty ratio of 12.5% with respect to the target exposure time. If the width of the image portion is 1, the width of the section to be exposed is 1/8 pixel.

  In the exposure methods 2 to 4 described above, the pulse width is narrower than that of the exposure method 1. In other words, in exposure methods 2 to 4, the latent image formed becomes smaller when exposed with the same light amount as exposure method 1, so the light amount is controlled according to the pulse width so that the integrated light amount at the time of latent image formation is equal. doing. Further, in the exposure methods 2 to 4 by time-intensive exposure, exposure is performed with a short pulse width and a strong light amount as compared with the exposure method 1 by standard exposure.

  In the above description, in each of the exposure methods 2 to 4, the light output value is set so that the integrated light amount is constant, but the light output value in the image forming method according to the present embodiment is limited to this. Is not to be done.

● Application example of exposure processing (1)
Next, an application example of exposure processing in the image forming method according to the present embodiment will be described.

  FIG. 28 shows a part of the image pattern 100 of the character image “a”, which includes an image portion 110 composed of a plurality of pixels and to which toner is fixed on recording paper, and a non-image portion 120 to which toner is not fixed. It is an enlarged view. The image unit 110 has a contour 111 of the image unit 110 at the boundary with the non-image unit 120. In FIG. 28, only a part of the image portion 110 and the contour portion 111 shown by hatching is drawn.

  As shown in FIG. 29, in the image pattern 200 of an electrophotographic image, in particular, a character image, a worm-eaten portion 211 in which toner does not adhere to a part of the image portion 210 of the image pattern 200 transferred to the recording paper (hereinafter, “ "Insect-eating phenomenon") occurs. The worm-eating phenomenon degrades the image quality of the image pattern 200, for example, by reducing the sharpness and readability of characters in the case of character images.

  FIG. 30 shows an example of (a) the light output value 210P of the exposure pattern, (b) the change in the photoreceptor potential 210E, and (c) the amount of toner 210T attached in the image pattern 200 of the reference example. In the reference example, the entire photosensitive drum corresponding to the image unit 210 is exposed with a light output value 201P that is 100% of the target exposure output value and a standard exposure with a target exposure time of 100%. Therefore, the photoreceptor potential 210E when forming the image pattern 200 is a substantially uniform value in the image portion 210. As a result, the height of the toner 210T of the image portion 210 on the photosensitive drum increases in an arch shape near the center of the image portion 210 and decreases in other portions. The worm-eating phenomenon of the character image is likely to occur around the center portion where the adhesion amount of the toner 210T is the largest, away from the boundary B of the image portion 210.

  The worm-eating phenomenon occurs, for example, during the primary transfer from the photosensitive drum to the transfer belt. During the primary transfer, the toner may be slightly deformed by being strongly compressed from the photosensitive drum to the transfer belt. The worm-eaten phenomenon is that when the toner is minutely deformed, the van der Waals force between the photosensitive drum and the toner increases, so that the adhesion force to the photosensitive drum increases and a part of the toner remains on the photosensitive member. It occurs by ending.

  In the image forming method according to the present embodiment, the surface of the photosensitive drum is exposed based on the image pattern 100 to form an electrostatic latent image on the surface of the photosensitive drum in order to prevent or suppress the worm-eating phenomenon. In addition, the exposure processing described below is applied.

  In the image forming method according to the present embodiment, a plurality of pixels in the image area of the photosensitive drum are exposed with a first light output value necessary for exposure of the photosensitive drum, that is, a target light output value (standard exposure). ) And a second exposure method different from the first exposure method. Specifically, in the second exposure method, among the plurality of pixels constituting the image portion, the portion corresponding to the pixel at the boundary with the non-image portion on the photosensitive drum is the first light of the first exposure method. A high output exposure pixel is exposed with a second light output value higher than the output value. Further, in the second exposure method, a low output in which some pixels other than the high output exposure pixels are exposed with a lower duty ratio or a third light output value lower than the first light output value with respect to the first exposure method. Let it be an exposure pixel.

  FIG. 31 shows an example of (a) exposure pattern 110P and (b) change in photoreceptor potential 110E and (c) toner 110T adhesion amount in an image pattern 200 formed by the image forming method according to the present embodiment.

  In the image forming method according to the present embodiment, the portion corresponding to the pixel located in the contour portion 111 of the image portion 110 indicated by the boundary B in the portion of the photosensitive drum corresponding to the image portion 110 is set as the high output exposure pixel. The exposure is performed with the light output value 110P1 exceeding the target exposure output value.

  In the image forming method according to the present embodiment, a portion closer to the center than the end of the image portion 110 corresponding to a pixel other than the high output exposure pixel is used as a low output exposure pixel, which is necessary for exposing the photosensitive drum. Exposure is performed with a light output value 110P3 lower than the target exposure output value. The portion corresponding to the low output exposure pixel is adjacent to the portion exposed at the target light output value 110P2 or the high output exposure pixel. Whether or not to execute the second exposure method is determined based on, for example, the amount of toner adhered to the surface of the photosensitive drum.

  As described above, in the image forming method according to the present embodiment, pixels other than the low output exposure pixels in the portion corresponding to the pixels other than the high output exposure pixels are exposed with the target light output value 110P2 by the first exposure method. To do.

  In the image forming method according to the present embodiment, the integrated value of the light output value 110P1, the target light output value 110P2, and the light output value 110P3 is the integrated value of the light output value 210P when a portion corresponding to the image pattern 200 is exposed. It is the same. That is, in the image forming method according to the present embodiment, the portion of the light output value 110P1 of the high output exposure pixel that exceeds the target light output value 110P2 is thinned from the target light output value 110P2 of the low output exposure pixel. Is added. For the light amount control of the target light output value 110P2 and the light output value 110P3 of the low output exposure pixel, for example, the light source driving circuit 420 may perform pulse width modulation (PWM modulation), light amount modulation (PW modulation), or PWM modulation with a constant duty ratio. And PW modulation.

  In order to expose the photosensitive drum with the light output value as described above, in the image forming method according to the present embodiment, the photosensitive member potential 110E is lower than the photosensitive member potential 210E shown in FIG. Obviously higher than the department.

  By exposing the photosensitive drum with the light output value as described above, in the image forming method according to the present embodiment, the toner 110T adhesion amount on the image portion 110 on the photosensitive drum is reduced particularly in the central portion. In the image forming method according to the present embodiment, the shape of the toner 110T in the height direction approaches a trapezoidal shape from the arch shape of the toner 210T shown in FIG. In the image forming method according to the present embodiment, the shape of the toner 110T in the height direction reduces the pressure applied by the photosensitive drum to the toner 110T at the time of transfer, and the adhesion between the toner 110T and the photosensitive drum is reduced. An increase in wearing force is suppressed.

  As described above, according to the image forming method according to the present embodiment, the worm-eaten phenomenon can be suppressed by reducing the adhesion amount of the toner 110T around the central portion in the image portion 110 of the image pattern 100.

Next, a residual toner detection mechanism for the photosensitive drum in the image forming apparatus 2000 that executes the image forming method according to the present embodiment will be described.

  In the image forming apparatus 2000, the amount of toner attached to the photosensitive drum 2030 changes as the toner characteristics change over time during use.

  As shown in FIG. 32, the image forming apparatus 2000 detects toner remaining on the surface of the photosensitive drum 2030 at a position where the photosensitive drum 2030 rotates after the toner is transferred to the transfer belt 2040. A detection sensor 2035 is provided. The toner detection sensor 2035 is arranged at the above position so as to detect the state of the surface of the photosensitive drum 2030.

  As shown in FIG. 33, the image forming apparatus 2000 outputs, for example, a writing pattern P1 for forming a solid black image as a test pattern for specifying the state of the worm-eaten phenomenon.

  As shown in FIG. 34, after the writing pattern P1 is transferred to the transfer belt 2040, no toner remains on the surface of the photosensitive drum 2030 in a normal state.

  On the other hand, as shown in FIG. 35, after the writing pattern P1 is transferred to the transfer belt 2040, toner T1 remaining on the photosensitive drum 2030 is generated on the surface of the photosensitive drum 2030 on which the worm-eaten phenomenon has occurred.

  As shown in FIGS. 36 and 37, the toner detection sensor 2035 includes a regular reflection light source 20351 for irradiating the black toner T11 with the detection light L1, and a diffused light source 20352 for irradiating the color toner T12 with the detection light L2. Is provided. In addition, the toner detection sensor 2035 includes a light receiving sensor 20353 that receives the reflected light RL1 of the detection light L1 and the reflected light RL2 of the detection light L2.

  The detection method of the toner detection sensor 2035 differs depending on the color of toner to be detected. In other words, when detecting the black toner T11, the regular reflected light source 20351 irradiates the black toner T11 with the regular reflected light detection light L1 as shown in FIG. When the color toner T12 is detected, the diffused light source 20352 irradiates the color toner T12 with diffused light detection light L2 as shown in FIG.

  The image forming apparatus 2000 uses the toner detection sensor 2035 to transfer the transfer image onto the transfer belt 2040, based on the toner adhesion amount remaining on the photosensitive drum 2030, and the toner adhesion amount to the photosensitive drum 2030. The presence or absence of worm-eaten phenomenon can be identified.

  In the image forming apparatus 2000, the printer controller 1060 stores the toner adhesion amount M1 used in the writing pattern P1. Further, the printer control device 1060 calculates the residual toner amount M2 on the photosensitive drum 2030 based on the table that specifies the relationship between the reflected light amount and the worm-eaten area shown in Table 1 from the reflected light amount detected by the toner detection sensor 2035. Identify.

The printer control device 1060 calculates the primary transfer rate Tr by the following equation based on the toner adhesion amount M1 and the residual toner amount M2. When the worm-eaten phenomenon does not occur, the primary transcription rate Tr is approximately 98% or more.

  Tr = (M1-M2) / M1

  As shown in FIG. 38, when the adhesion amount M1 increases due to a change in the conditions of the photoconductor drum 2030 and the like over time, the transfer pressure from the photoconductor drum 2030 to the toner increases, and an insect erosion phenomenon occurs. Due to the occurrence of the worm-eaten phenomenon, the residual toner amount M2 increases, and the primary transfer rate Tr decreases.

  As shown in FIG. 39, when the residual toner amount M2 decreases, the worm-eaten level LV tends to decrease. For this reason, the printer control apparatus 1060 can perform the exposure process as described above when the primary transfer rate Tr reaches a specified value, for example, 80%. By doing so, in the image forming method according to the present embodiment, in order to reduce the adhesion amount of the toner T1 inside the character image, the light output is performed using the central portion of the image portion 110 of the image pattern 100 as the low output exposure pixel. Lowering the value can suppress the worm-eaten phenomenon.

Flowchart of electrostatic latent image forming process The image forming method according to the present embodiment described above will be described using the flowchart of FIG.

  In the image forming apparatus 2000, in the test mode of the writing pattern P1, the toner detection sensor 2035 detects the residual toner amount M2 on the photosensitive drum 2030 after transferring the writing pattern P1 to the transfer belt 2040 (S101).

  In the image forming apparatus 2000, the printer control device 1060 determines that the residual toner amount M2 is equal to or greater than a specified value based on the detected residual toner amount M2 and the toner adhesion amount M1, that is, the primary transfer rate Tr is equal to or less than the specified value. Is determined (S102).

  If the residual toner amount M2 is equal to or greater than the predetermined value (S102: YES), the printer control device 1060 determines that the worm-eating phenomenon has occurred, and corresponds to the high output exposure pixel and the low output exposure pixel of the write data. The light output value of the portion to be changed is changed (S103). By changing the light output value, the exposure amount of the write data is reduced (S104).

  If the residual toner amount M2 is equal to or less than the specified value (S102: NO), the printer control device 1060 determines that no worm-eaten phenomenon has occurred, and performs normal writing (S105).

Effects of Embodiment As described above, in the image forming method according to the present embodiment, when outputting an image pattern such as a character image, a low output is applied to a portion where the toner adhesion amount in the image portion 110 increases. Exposure pixels are provided to intermittently expose the photosensitive drum 2030. By doing so, according to the image forming method according to the present embodiment, the adhesion amount between the surface of the photosensitive drum 2030 and the toner is not increased by reducing the amount of toner adhered to the photosensitive drum 2030. In this way, the worm-eaten phenomenon can be suppressed.

  Further, according to the image forming method according to the present embodiment, since the residual toner amount M2 is detected by the toner detection sensor 2035, the conditions for suppressing the worm-feeding phenomenon are reflected based on characteristics such as the shape of the image pattern. be able to.

  Further, according to the image forming method according to the present embodiment, since the primary transfer rate Tr is calculated from the residual toner amount M2 and the toner adhesion amount is controlled, it can be optimized to the toner amount for forming an image, Character readability can be maintained.

● Application example of exposure processing (2)
Next, another application example of the exposure process in the image forming method according to the present embodiment will be described. In the present embodiment, only the exposure pattern forming process is different from the example described above.

  FIG. 42 shows an exposure pattern in a part X of the image portion 110 of the image pattern 100 shown in FIG.

  As shown in FIG. 42, in the image forming method according to the present embodiment, in order to reduce the toner adhesion amount in the image pattern 100, the exposure unit 112 and the non-exposure unit 113 are arranged in the sub-scanning direction in the image unit 110. Are alternately arranged and exposed in stripes.

  As shown in FIG. 43, the control of the light output values of the exposure unit 112 and the non-exposure unit 113 controls the duty ratio of the exposure time of the exposure unit 112 and the non-exposure unit 113 of the light source 11 of the optical scanning device 2010. By doing. That is, in the image forming method according to the present embodiment, the toner adhesion amount in the image unit 110 is controlled by controlling the duty ratio of the exposure time.

  According to the image forming method according to the present embodiment, the light output value is changed as in the application example described above by changing the duty ratio of the exposure time between the exposure unit 112 and the non-exposure unit 113. As in the case, the toner adhesion amount can be adjusted.

Flowchart of electrostatic latent image forming process The image forming method according to the present embodiment described above will be described using the flowchart of FIG.

  In the image forming apparatus 2000, in the test mode of the writing pattern P1, the toner detection sensor 2035 detects the residual toner amount M2 on the photosensitive drum 2030 after the writing pattern P1 is transferred to the transfer belt 2040 (S201).

  In the image forming apparatus 2000, the printer control device 1060 determines that the residual toner amount M2 is equal to or greater than a specified value based on the detected residual toner amount M2 and the toner adhesion amount M1, that is, the primary transfer rate Tr is equal to or less than the specified value. It is determined whether or not (S202).

  If the residual toner amount M2 is equal to or greater than the specified value (S202: YES), the printer control device 1060 determines that a worm-eaten phenomenon has occurred, and the exposure unit 112 and the non-exposure unit 113 for the image unit 110 of the write data. And change the data (S203). The printer controller 1060 refers to the look-up table (LUT) and reduces the write duty ratio between the exposure unit 112 and the non-exposure unit 113 (S204).

  If the residual toner amount M2 is equal to or less than the specified value (S202: NO), the printer control device 1060 determines that no worm-feeding phenomenon has occurred, and performs normal writing (S205).

As described above, in the image forming method according to the present embodiment, the duty ratio of the exposure unit 112 is decreased to reduce the toner adhesion amount, thereby reducing the amount of toner attached from the photosensitive drum 2030 during primary transfer. The pressure applied to the transfer belt 2040 is dispersed. As a result, in the image forming method according to the present embodiment, the adhesion force between the surface of the photoconductor drum 2030 and the toner does not increase, and thus the residual toner amount M2 on the photoconductor drum 2030 is reduced to suppress the worm-eaten phenomenon. Can do.

  Further, according to the image forming method according to the present embodiment, the exposed portion 112 and the non-exposed portion 113 are formed in stripes in the sub-scanning direction, so that the image to be formed is hardly affected by jitter. As a result, unevenness is less likely to occur and a good image can be provided.

11: Light source 12: Collimating lens 13: Cylindrical lens 14: Mirror 15: Polygon mirror 16: Scanning control device 21: First scanning lens 22: Second scanning lens 24: Mirror 26: Sync detection sensor 100: Image pattern 101: Image Processing unit 102: Controller unit 103: Memory unit 104: Optical writing output unit 105: Scanner unit 110: Image unit 111: Contour unit 112: Exposure unit 113: Non-exposure unit 120: Non-image unit 171: Optical scanning device 172: Glass window 200: Image pattern 210: Image part 211: Non-image part 300: Electrostatic latent image measuring device 407: Light source modulation data generation circuit 414: Light source selection circuit 415: Write timing signal generation circuit 420: Light source drive circuit 422: Reference Clock generation circuit 425: Pixel clock generation circuit 001: Main body device 1002: Reading device 1003: Automatic document feeder 1010: Optical scanning device 1032: Developing device 1033: Transfer device 1060: Printer control device 2000: Image forming device 2010: Optical scanning device 2030: Photosensitive drum 2031: Cleaning unit 2032: Charging device 2033: Developing roller 2034: Toner cartridge 2035: Toner detection sensor 2040: Transfer belt 2042: Transfer roller 2050: Fixing roller 2054: Feed roller 2056: Registration roller pair 2058: Paper discharge roller 2060: Paper feed Tray 2070: Paper discharge tray 2080: Communication control device 20351: Light source for regular reflection light 20352: Light source for diffused light 20353: Light receiving sensor

JP 2006-308659 A

Claims (8)

An image forming apparatus having an exposure device that exposes the surface of an image carrier based on an image pattern including an image portion and a non-image portion,
The exposure apparatus includes:
A first exposure method in which a plurality of pixels constituting the image portion are exposed with a first light output value; and at least a pixel at a boundary with the non-image portion among the plurality of pixels constituting the image portion is the first A high-power exposure pixel that is exposed with a second light output value that is higher than the light output value, and a portion of the plurality of pixels that constitute the image portion other than the high-power exposure pixel is the first exposure. And a second exposure method for performing exposure as a low-power exposure pixel that is exposed at a low duty ratio. An image forming apparatus having an exposure device that exposes a surface of an image carrier based on an image pattern including an image portion and a non-image portion,
The exposure apparatus includes:
A first exposure method in which a plurality of pixels constituting the image portion are exposed with a first light output value; and at least a pixel at a boundary with the non-image portion among the plurality of pixels constituting the image portion is the first A high output exposure pixel that is exposed with a second light output value that is higher than the light output value, and a part of the plurality of pixels constituting the image portion other than the high output exposure pixel is the first pixel. An image forming apparatus that executes a second exposure method in which exposure is performed as a low-power exposure pixel that is exposed with a third light output value lower than the light output value. The low output exposure pixel is adjacent to another pixel constituting the image portion,
The image forming apparatus according to claim 1. The exposure apparatus determines whether or not to perform the second exposure method based on the amount of developer attached to the electrostatic latent image of the image pattern formed on the surface of the image carrier.
The image forming apparatus according to claim 1. The amount of the developer attached to the image carrier is specified based on the amount of the developer remaining on the image carrier after the transfer image of the electrostatic latent image is transferred to the transfer body. The
The image forming apparatus according to claim 4. The exposure apparatus sets M1 as the amount of the developer that adheres to the image carrier when the transfer image is transferred to the transfer body, and M2 as the amount of the developer that remains on the image carrier. Then,
(M1-M2) / M1 <0.80
The image forming apparatus according to claim 5, wherein exposure is performed by the second exposure method when satisfying the condition. An image forming method for exposing the surface of an image carrier based on an image pattern including an image portion and a non-image portion to form an image corresponding to the image pattern,
The surface of the image carrier has a first exposure method for exposing a plurality of pixels constituting the image portion with a first light output value, and at least the non-image portion of the plurality of pixels constituting the image portion. The pixel at the boundary is a high output exposure pixel that is exposed with a second light output value that is higher than the first light output value. And a second exposure method in which exposure is performed as a low-power exposure pixel in which exposure is performed with a lower duty ratio than in the case of exposing the pixels in the first exposure method. A method for producing a printed matter comprising a step of exposing a surface of an image carrier based on an image pattern including an image portion and a non-image portion,
In the step of exposing the surface of the image carrier,
A first exposure method in which a surface of the image carrier exposes a plurality of pixels constituting the image portion with a first light output value; and at least the non-image portion of the plurality of pixels constituting the image portion; The pixel at the boundary is a high output exposure pixel that is exposed with a second light output value that is higher than the first light output value. And a second exposure method in which exposure is performed as a low output exposure pixel that is exposed with a lower duty ratio than in the case of exposing the pixels in the first exposure method.