JP2010117736A - Image forming machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To accurately recognize identification information when visible information and the identification information are formed over the same medium. <P>SOLUTION: This image forming device includes a first image forming unit having a developing device which develops an image carrier and an electrostatic latent image using an invisible developer; a second image forming unit having a developing device which develops an image carrier and an electrostatic latent image using a visible developer; an exposure device which forms the electrostatic latent images; a transfer unit for transferring a developer image onto a medium; a fusion device for fusing the developer image onto the medium; a receiving unit for receiving identification information and image data from a higher-level device; a data identifying unit for identifying the identification information and the image data; a first print control unit which performs printing based on the identification information; and a second print control unit which performs printing based on the image data. When visible information and identification information are formed over the same medium, it is possible to accurately recognize the identification information. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus such as a printer, a copying machine, a facsimile, or the like, for example, a printer, forms an image based on image forming conditions optimized for forming a desired image. The image forming conditions are set by correcting a reference value set in advance by an experiment with correction values according to the number of printed sheets, the environment in which the printer is used, the type of paper as a medium, and the like.

  In particular, the image density, that is, the image density affects the image quality and needs to be stabilized. Therefore, a predetermined pattern is transferred to the intermediate transfer member, the image density of the transferred pattern is measured by the density sensor, and the change (time-dependent change) of the image formed by the printer is detected based on the measured image density. By doing so, the image density is corrected and stabilized (for example, see Patent Document 1).

Japanese Patent Laid-Open No. 11-230031

  However, in the conventional printer, the density measurement result is obtained by averaging the image density for the area that can be measured by the density sensor in the pattern, so that the entire image can be obtained. The average image of the image can be improved, but when viewed in units of dots (elements) that form the image, the image density cannot be accurately measured, and the measured image density varies. End up.

  In addition, when printing an barcode, a security background pattern, or the like by forming an image composed of ultrafine lines, extremely small-diameter halftone dots, etc. in the printer, it is necessary to reproduce the image in units of several tens of microns.

  Therefore, it is conceivable to measure the image density in units of dots and adjust the thickness of the fine line after printing, the diameter of the minimum halftone dot, etc. In that case, the image formed by the printer is separately increased. Read with a resolution scanner, measure the thickness of the fine line after printing, the diameter of the halftone dot with a dedicated measuring instrument, and then adjust each image forming parameter based on the measurement result. Yes. Therefore, the work for correcting the image density becomes troublesome.

  In addition, when the visible information is formed on the same sheet by the image and the identification information is formed by embedding predetermined information in the image, the color contained in the stealth toner as a developer for forming the identification information The identification information may not be accurately recognized due to the influence of the material.

  The present invention solves the problems of the conventional printer, can correct the image density with high accuracy, can simplify the work for correcting the image density, and can also display the visible information and the identification information. An object of the present invention is to provide an image forming apparatus capable of accurately recognizing identification information when formed on the same medium.

  Therefore, in the image forming apparatus of the present invention, the image carrier and the electrostatic latent image formed on the image carrier are developed with an invisible developer that absorbs light in a predetermined wavelength region. Development that develops a first image forming unit including a developing device for forming an image, an image carrier, and an electrostatic latent image formed on the image carrier with a visible developer to form a developer image A second image forming unit provided with a device, an exposure device for exposing the surface of each image carrier to form the electrostatic latent image, a transfer unit for transferring the developer image to a medium, and a transfer unit. A fixing device that fixes the developer image on the medium, a receiving unit that receives identification information and image data from a host device, a data determination unit that determines the identification information and image data, and a data determination unit On the basis of the identified identification information, the first image forming unit Has a first printing control unit that performs printing based on the image data discriminated by the data discriminating unit, and a second printing control unit for printing by said second image forming unit.

  According to the present invention, in an image forming apparatus, an image carrier and an electrostatic latent image formed on the image carrier are developed with an invisible developer that absorbs light in a predetermined wavelength region. Development that develops a first image forming unit including a developing device for forming an image, an image carrier, and an electrostatic latent image formed on the image carrier with a visible developer to form a developer image A second image forming unit provided with a device, an exposure device for exposing the surface of each image carrier to form the electrostatic latent image, a transfer unit for transferring the developer image to a medium, and a transfer unit. A fixing device that fixes the developer image on the medium, a receiving unit that receives identification information and image data from a host device, a data determination unit that determines the identification information and image data, and a data determination unit On the basis of the identification information thus printed, the first image forming unit A first printing control unit that performs, based on the image data discriminated by the data discriminating unit, and a second printing control unit for printing by said second image forming unit.

  In this case, printing is performed by the first image forming unit based on the identification information determined by the data determining unit, and printing is performed by the second image forming unit based on the image data determined by the data determining unit. As a result, the identification information can be accurately recognized when the visible information and the identification information are formed on the same medium.

1 is a block diagram illustrating a printer control device according to a first embodiment of the present invention. FIG. 1 is a diagram illustrating an image forming system according to a first embodiment of the present invention. 1 is a schematic diagram of a printer according to a first embodiment of the present invention. FIG. 2 is a diagram illustrating an image forming unit and its periphery in the first embodiment of the present invention. It is a figure which shows the printing control selection screen in the 1st Embodiment of this invention. FIG. 5 is a relationship diagram between a dot diameter of dots and an image density in the first embodiment of the present invention. It is a flowchart which shows operation | movement of the density correction process means in the 1st Embodiment of this invention. It is a 1st figure which shows the image pattern in the 1st Embodiment of this invention. It is a 2nd figure which shows the image pattern in the 1st Embodiment of this invention. It is a 3rd figure which shows the image pattern in the 1st Embodiment of this invention. It is a 4th figure which shows the image pattern in the 1st Embodiment of this invention. It is a 5th figure which shows the image pattern in the 1st Embodiment of this invention. It is a 6th figure which shows the image pattern in the 1st Embodiment of this invention. It is a figure which shows the correlation of a dot diameter when changing the duty in the 1st Embodiment of this invention, and an image density. It is the schematic of the printer in the 2nd Embodiment of this invention. It is a figure which shows the structure of the glossiness sensor in the 2nd Embodiment of this invention. It is a block diagram which shows the principal part of the control apparatus of the printer in the 2nd Embodiment of this invention. It is a schematic diagram of the dot formed in the surface of the various paper in the 2nd Embodiment of this invention. It is a figure which shows the correlation of a dot diameter and image density when printing with respect to the various paper in the 2nd Embodiment of this invention. It is the schematic of the printer in the 3rd Embodiment of this invention. It is a figure which shows the characteristic of the stealth toner in the 3rd Embodiment of this invention. It is a figure which shows the printing control selection screen in the 3rd Embodiment of this invention. It is a figure which shows the basic pattern in the 4th Embodiment of this invention. It is a figure which shows the Anoto pattern in the 4th Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In this case, a printer as an image forming apparatus will be described.

  FIG. 2 is a diagram showing an image forming system according to the first embodiment of the present invention, and FIG. 3 is a schematic diagram of the printer according to the first embodiment of the present invention.

  As shown in the figure, 101 is a printer, 59 is a host computer as a host device, 202 is a network connecting the printer 101 and the host computer 59, and the host computer 59 is a CPU 301 as an arithmetic unit, a display unit A display 302 and a keyboard 303 as an operation unit and as an input unit.

  A sheet feeding cassette 11 serving as a medium accommodating portion that accommodates a sheet P serving as a medium is disposed in the main body of the printer 101, that is, the lower portion of the apparatus main body 31. Reference numeral 12 denotes a paper feed roller as a paper feed member that is adjacent to the front end of the paper feed cassette 11 and separates the paper P one by one and feeds it in the direction of arrow B. The sheet P thus passed passes through the conveyance path 13 and is sent to a conveyance roller 14 as a conveyance member. Thereafter, as the conveyance belt 17 as a first transfer member travels, the conveyance belt 17 It is conveyed and passes between image forming units 16Bk, 16Y, 16M, and 16C as a plurality of image forming units and transfer rollers 51Bk, 51Y, 51M, and 51C as second transfer members.

  The conveying belt 17 is stretched between a driving roller R1 as a first roller and an idle (driven) roller R2 as a second roller. Further, the transfer belt 17, the driving roller R 1, the idle roller R 2, the transfer rollers 51 Bk, 51 Y, 51 M, and 51 C constitute a transfer device.

  In this embodiment, the image forming units 16Bk, 16Y, 16M, and 16C are arranged in this order from the upstream side to the downstream side in the conveyance direction of the paper P. However, the image forming units 16Y and 16M are arranged in this order. , 16C, and 16Bk.

  Next, each of the image forming units 16Bk, 16Y, 16M, and 16C is based on toner (not shown) as a developer of each color of black, yellow, magenta, and cyan, and photosensitive drums 52Bk, 52Y, and 52M as image carriers. , 52C, toner images as developer images of the respective colors are formed, and the transfer rollers 51Bk, 51Y, 51M, 51C sequentially superimpose and transfer the respective toner images onto the conveyed paper P, thereby forming a color toner image. Form.

  Subsequently, the paper P on which the color toner image is formed is sent to a fixing device 18 as a fixing device. The fixing unit 18 includes a fixing roller 24 having a heating body 25 and a pressure roller 26, and fixes a color toner image on the paper P to form a color image. The paper P discharged from the fixing device 18 is transported in the direction of arrow B by transport rollers 19 and 20 as transport members, and is then discharged out of the apparatus main body 31 by a discharge roller 22 as a discharge member.

  In order to expose the surfaces of the photosensitive drums 52Bk, 52Y, 52M, and 52C to form an electrostatic latent image, the LED heads 21Bk, 21Y, 21M, and 21C as exposure devices are respectively connected to the image forming units 16Bk, 16Y, Adjacent to 16M and 16C and facing the photosensitive drums 52Bk, 52Y, 52M and 52C. Each of the LED heads 21Bk, 21Y, 21M, and 21C converges light generated by causing each LED to emit light, an LED array as a light emitting element array formed by arranging LEDs (not shown) as a plurality of light emitting elements. A rod lens array. When each of the LED heads 21Bk, 21Y, 21M, and 21C is driven based on the image data, each LED is selectively emitted, and the emitted LED light is converged by the rod lens array. Irradiate the surfaces of 52Bk, 52Y, 52M, and 52C.

  Each of the image forming units 16Bk, 16Y, 16M, and 16C is detachably disposed with respect to the apparatus main body 31. For this purpose, the upper cover 23 is disposed on the upper part of the apparatus main body 31 so as to be freely opened and closed. The LED heads 21Bk, 21Y, 21M, and 21C are held by the upper cover 23.

  Reference numeral 27 denotes a density sensor as a density detection unit that detects the density of the toner image formed on the conveying belt 17 as an image density. The density sensor 27 is located near the driving roller R1 below the transfer unit. Further, it is disposed so as to face the conveyor belt 17. Reference numeral 32 denotes a cleaning blade as a cleaning member that scrapes off the toner image on the conveyor belt 17, and the cleaning blade 32 is disposed in contact with the conveyor belt 17 near the idle roller R2 below the transfer unit. Established. The toner of the toner image scraped off by the cleaning blade 32 is collected as waste toner.

  Reference numeral 103 denotes an image formation control unit as a first control unit, and reference numeral 104 denotes a printer control unit as a second control unit.

  Next, the image forming units 16Bk, 16Y, 16M, and 16C will be described. Since the image forming units 16Bk, 16Y, 16M, and 16C have the same structure, only the image forming unit 16Bk will be described, and the description of the image forming units 16Y, 16M, and 16C will be omitted.

  FIG. 4 is a diagram showing the image forming unit and its periphery in the first embodiment of the present invention.

  The image forming unit 16Bk includes a photosensitive drum 52Bk, a charging roller 30 as a charging member that uniformly charges the surface of the photosensitive drum 52Bk, a developing roller 28 as a developer carrier that holds toner 33, and the development. A toner supply roller 29 as a developer supply member for supplying the toner 33 to the roller 28, a toner cartridge 35 as a developer accommodating portion for accommodating the toner 33, and the like are provided. A developing device is constituted by the developing roller 28, the toner supply roller 29, and the like.

  The photoconductive drum 52Bk is formed of a conductive base layer made of aluminum or the like and a surface layer made of an organic photoconductor, and the charging roller 30 has a conductive metal shaft made of semiconductive roll-shaped rubber such as epichlorohydrin rubber. The developing roller 28 is formed by covering a conductive metal shaft with a semiconductive rubber such as silicone, and the toner supply roller 29 is configured to convey the toner 33 onto the conductive metal shaft. In order to improve the properties, a rubber formed by adding a foaming agent is coated during kneading.

  The charging roller 30 and the developing roller 28 are disposed in contact with the photosensitive drum 52Bk, and the toner supply roller 29 is disposed in contact with the developing roller 28. A power supply for development and a power supply for toner supply (not shown) are connected to the development roller 28 and the toner supply roller 29, respectively, and apply a bias voltage to the development roller 28 and the toner supply roller 29.

  Further, an LED head 21Bk is disposed outside the image forming unit 16Bk, and light emitted by the LED head 21Bk is charged in the rotation direction of the photosensitive drum 52Bk (rotation direction when forming an image). The surface of the photosensitive drum 52Bk is irradiated further downstream and upstream of the developing roller 28.

  In the image forming unit 16Bk having the above-described configuration, at the time of printing, the developing roller 28 and the toner supply roller 29 are rotated counterclockwise in the drawing by driving a drive motor (not shown) as a drive unit for supplying the developer. The toner 33 is supplied to the developing roller 28 by the toner supply roller 29. The toner 33 supplied to the developing roller 28 is sent to a contact portion between the developing roller 28 and a developing blade (not shown) as the developing roller 28 rotates, and the excess toner 33 is scraped off by the developing blade, so that the thin toner Then, the toner is fed to the photosensitive drum 52Bk as the developing roller 28 rotates.

  On the other hand, the photosensitive drum 52Bk is rotated clockwise (in the direction of arrow A) in the drawing by driving a drum motor (not shown) as an image forming drive unit, and the surface of the photosensitive drum 52Bk is charged. The toner 30 is uniformly charged by the roller 30 and exposed by the LED head 21Bk to form an electrostatic latent image, and the toner 33 on the developing roller 28 is electrostatically attached to the electrostatic latent image to form a toner image. Is formed. Note that 51Bk is a transfer roller, 55 is a voltage supply unit, 61 is an LED head control unit, and P is paper.

  Next, the control device of the printer 101 will be described.

  FIG. 1 is a block diagram illustrating a printer control apparatus according to the first embodiment of the present invention, and FIG. 5 is a diagram illustrating a print control selection screen according to the first embodiment of the present invention.

  In FIG. 1, a printer 101 includes an interface (I / F) 102 as a receiving unit connected to a host computer 59, an image formation control unit 103, and a printer control unit 104.

  The image forming control unit 103 includes a heating body (F) 25, a charging roller (CH) 30, a toner supply roller (SB) 29, a developing roller (DB) 28, a transfer roller (TR) 51Bk, 51Y, 51M, 51C, LED head controller 61 for controlling the LED heads 21Bk (FIG. 3), 21Y, 21M, and 21C, the heating body 25, the charging roller 30, the toner supply roller 29, the developing roller 28, and the transfer rollers 51Bk, 51Y, 51M, and 51C. A voltage supply unit 55 that controls the fixing unit 18, a fixing unit control unit 63 that controls the fixing unit 18, a transfer unit control unit 64 that controls the transfer unit, and an image that controls the image forming units 16Bk, 16Y, 16M, and 16C. A forming unit controller 65 is provided.

  The printer control unit 104 includes a CPU 71 as an arithmetic device that functions as a computer, a ROM 72 as a first storage device used as a work area, and a RAM 73 as a second storage device.

  The ROM 72 includes areas of an operation control program storage unit 75, an image formation parameter storage unit 76, a density-dot diameter conversion unit 77 as a density conversion storage unit, a density correction pattern storage unit 78, and a density determination unit 79. The RAM 73 is a region of the LED head lighting time storage unit 84 as an image data storage unit 81, an image formation parameter temporary storage unit 82, a reference density storage unit 83, and a correction variable storage unit and as an exposure output storage unit. Is provided.

  When the operator activates the printer 101 and performs printing (image formation), the print control program of the host computer 59 is activated, and a display processing unit (display processing unit) (not shown) of the CPU 301 (FIG. 2) of the host computer 59 is activated. ) Performs a display process, and forms a print control selection screen 201 as a setting screen as shown in FIG.

  The print control selection screen 201 includes a print quality selection unit q1 for selecting print quality representing the resolution of the image, a color adjustment unit q2 for performing color adjustment by selecting the brightness of the image, and the number of prints. Number of prints designating part q3 for designating, paper type designating part q4 for designating the type of paper P, paper size designating part q5 for designating the size of paper P, dot diameter representing the size of dots (dots) A dot size designation part q6 for designating (size). The dot diameter represents raw point information regarding dots.

  In this case, the operator operates the keyboard 303 to select the print quality and brightness of the image to be printed based on the image data, specify the number of prints, The print information is input by designating the type, size, thickness, etc. of the paper P to be formed. At this time, when it is desired to accurately specify the dot diameter of the dots constituting the image to be printed, the operator inputs a desired dot diameter as print information in the dot size designation portion q6 of the print control selection screen 201. Can do.

  As print information, the print setting information is configured by the print quality, the brightness of the image, the number of printed sheets, the medium information is configured by the type, size, thickness, and the like of the paper P, and the dot information is configured by the dot diameter.

  Next, based on the input print information, a print control processing unit (print processing unit) (not shown) of the CPU 301 performs print control processing, generates image data of a print image according to the print control program, and stores the image data. The print setting information, medium information, and dot information are transmitted to the printer 101. In the printer 101, an image formation processing unit (not shown) of the CPU 71 performs image formation processing, and receives the image data, print setting information, medium information, and dot information as printer control information, and stores predetermined data from the ROM 72 and RAM 73. Information is read and an image is formed based on the printer control information.

  For this purpose, the image forming condition setting processing unit (image forming condition setting processing unit) of the image forming processing unit performs image forming condition setting processing and stores the image data in the image data storage unit 81 in the RAM 73. Each image formation parameter (print parameter) is read from the image formation parameter storage unit 76 in the ROM 72 based on the print setting information and the medium information, and stored in the image formation parameter temporary storage unit 82 in the RAM 73.

  The image forming parameter storage unit 76 is applied to the developing roller 28, a fixing temperature in the fixing device 18 used when the printer 101 performs a printing operation, a drum charging voltage representing a voltage applied to the charging roller 30, and the developing roller 28. Image forming conditions such as a developing bias voltage representing a voltage to be applied, a supply bias voltage representing a voltage applied to the toner supply roller 29, and a transfer voltage representing a voltage applied to the transfer rollers 51Bk, 51Y, 51M and 51C. The parameters are stored, and the image forming condition setting processing unit uniquely selects and reads out the image forming parameters in correspondence with the contents of the print setting information and the medium information.

  Further, the ROM 72 is provided with a density-dot diameter conversion unit 77, which is obtained by a method described later, and is used as a dot diameter, an image density, and a correction variable. Then, a relational expression representing the relation of the lighting time as the exposure output is stored. The lighting time is the exposure (driving) time of the LED heads 21Bk, 21Y, 21M, and 21C, and represents the time for forming one dot by causing each LED to emit light.

  When the image data is stored in the image data storage unit 81 and the image formation parameters are stored in the image formation parameter temporary storage unit 82, the operation control processing unit (control processing unit) of the image formation processing unit performs the operation control. Processing is performed, and a printing operation is started in accordance with the operation control program in the operation control program storage unit 75.

  That is, the operation control processing means sends a print operation command to the image forming unit control unit 65, the transfer device control unit 64, the fixing device control unit 63, a paper feed / conveyance control unit (not shown), a roller drive control unit, and the like. The image forming unit control unit 65, the transfer device control unit 64, and the fixing device control unit 63 read out the parameter values stored in the image forming parameter temporary storage unit 82, and send a control signal to the voltage supply unit 55, so that the photoconductor The drum charging voltage is applied to the drums 52Bk, 52Y, 52M, and 52C, the developing bias voltage and the supply bias voltage are applied to the developing roller 28 and the toner supply roller 29, respectively, the charging voltage is applied to the charging roller 30, and the transfer roller Printing on the paper P is performed by applying a transfer voltage to 51Bk, 51Y, 51M, and 51C.

  Incidentally, the photosensitive drums 52Bk, 52Y, 52M, 52C and the toner 33 (FIG. 4) and the toner 33 (FIG. 4) may have the same image forming conditions even under the same image forming conditions. The surface potential of the toner 33 may change, and the amount of toner 33 forming the toner layer, that is, the toner amount may change. For example, if the same image density is to be maintained when the toner amount changes and decreases, the lighting times of the LED heads 21Bk, 21Y, 21M, and 21C need to be changed and lengthened.

  FIG. 6 is a diagram showing the relationship between the dot diameter of the dots and the image density in the first embodiment of the present invention. In the figure, the horizontal axis represents the dot diameter and the lighting times of the LED heads 21Bk (FIG. 3), 21Y, 21M, and 21C, and the vertical axis represents the image density.

  In the figure, L1 is a line representing the relationship between the dot diameter of the dots obtained in advance with high accuracy and the image density, and L2 is the photosensitive drums 52Bk, 52Y, 52M, 52C and the toner 33, as will be described later. L3 is a line representing the relationship between the lighting time and the image density when there is no change over time, change in environment, etc., and L3 is turned on due to change over time in the photoconductor drums 52Bk, 52Y, 52M, 52C and toner 33, change in the environment, etc. It is a line that virtually represents a state in which the relationship between time and image density has transitioned.

  By the way, for example, when the operator designates and inputs the dot diameter da in the dot size designation part q6 (FIG. 5), the CPU 71 refers to the density-dot diameter conversion part 77 and is necessary for forming an image. The image density ODa to be calculated is calculated (read out). In addition, the CPU 71 refers to the density-dot diameter conversion unit 77, and based on the relationship between the lighting time represented by the line L2 and the image density, the LED heads 21Bk, 21Y, 21M, and 21C corresponding to the image density ODa. The lighting time STBa is acquired, and the lighting time STBa is set as a lighting time when printing is performed. Note that when there is no aging of the photosensitive drums 52Bk, 52Y, 52M, 52C and the toner 33, no change in environment, etc., the line L2 itself does not change, and the image density measured by the density sensor 27 is a value in the vicinity of Oda. Indicates.

  However, when there is a secular change of the photosensitive drums 52Bk, 52Y, 52M, 52C and the toner 33, an environmental change, or the like, the image density actually measured by the density sensor 27 even if the input dot diameter is da. May decrease to ODb (<ODa), for example, rather than ODA which is a value that should originally be obtained. This appears as if the relationship between the image density and the LED lighting time has transitioned from the line L2 to the line L3 due to aging of the photosensitive drums 52Bk, 52Y, 52M, 52C and the toner 33, environmental changes, and the like.

  In this case, the relationship between the image density and the LED lighting time should be represented by the line L3, but the device itself cannot know that the line has transitioned to the line L3, and the LED lighting time is output by STBa based on the line L2. Resulting in. Therefore, printing based on ODb instead of the required image density ODA may be performed. In this case, it is as if the point b on the line L1, that is, the dot diameter db is input. Correspondingly, the image quality is significantly lowered.

  Therefore, in the present embodiment, as described above, when the dot diameter is designated in the dot size designation unit q6, the density correction processing means (density correction processing unit) (not shown) of the CPU 71 performs density correction processing. The image density is corrected based on the designated dot diameter.

  For this purpose, a predetermined photosensitive drum among the photosensitive drums 52Bk, 52Y, 52M, and 52C, in this embodiment, the black photosensitive drum 52Bk is selected, and the density-dot diameter converter 77 performs correction. A relational expression representing the relationship between the dot diameter of the reference dot and the image density is stored in advance. The density-dot diameter conversion unit 77 can store the relationship between the dot diameter and the image density in a table instead of the relational expression.

  FIG. 7 is a flowchart showing the operation of the density correction processing means in the first embodiment of the present invention.

  First, the reference density calculation processing means (density reading processing section) of the density correction processing means performs reference density calculation processing, and when the dot diameter d1 is designated and inputted, the dot diameter d1 is read and density-dot diameter conversion is performed. The reference image density corresponding to the dot diameter d1 is read as the reference density OD1 with reference to the unit 77 (FIG. 1) and stored in the reference density storage unit 83 of the RAM 73. Note that image density information is constituted by the reference density OD1.

  Subsequently, the exposure output calculation processing means as the correction variable calculation processing means of the density correction processing means performs the exposure output calculation processing as the correction variable calculation processing, reads the dot diameter d1, and sets the density-dot diameter conversion section 77. The LED head lighting time storage unit 84 of the RAM 73 reads out (calculates) the lighting time STB of the LED head 21Bk (FIG. 3) corresponding to the dot diameter d1. The lighting time STB corresponding to the dot diameter d1 constitutes a reference lighting time as a reference correction variable.

  Next, the density correction image formation processing means of the density correction processing means performs density correction image formation processing to form an image of the density correction pattern, that is, a density correction image on the transport belt 17. In this case, the density correction image is formed by using black toner in the image forming unit 16Bk.

  For this purpose, the density correction image forming processing unit first instructs the image forming unit controller 65 and the LED head controller 61 to form a toner image of a density correction pattern on the photosensitive drum 52Bk. . The image forming unit controller 65 charges the surface of the photosensitive drum 52Bk by the charging roller 30 (FIG. 4) according to the instruction, and the LED head controller 61 reads the density correction pattern from the density correction pattern storage unit 78. The pattern image data is read, the LED head 21Bk is driven in accordance with the image data, a predetermined LED emits light during the lighting time STB, the photosensitive drum 52Bk is exposed, and the density correction pattern is statically exposed on the surface of the photosensitive drum 52Bk. An electrostatic latent image is formed.

  Subsequently, the image forming unit controller 65 attaches the toner 33 to the electrostatic latent image to form a toner image having a density correction pattern. For this purpose, a negative supply bias voltage is applied to the toner supply roller 29 disposed in contact with the bottom of the toner cartridge 35, while supplying the toner 33 in the toner cartridge 35 to the developing roller 28. The toner 33 is charged.

  Then, the toner 33 is supplied to the developing roller 28 and further charged by the developing roller 28 to form a toner layer having a uniform thickness, and is attached to the surface of the photosensitive drum 52Bk to form a black toner image. Form.

  Subsequently, the density correction image forming processing unit instructs the transfer device controller 64 to transfer the toner image formed on the surface of the photosensitive drum 52Bk to the transport belt 17. The transfer device controller 64 applies a transfer voltage having a positive polarity to the transfer roller 51Bk, and transfers the toner image to a portion of the transport belt 17 sandwiched between the photosensitive drum 52Bk and the transfer roller 51Bk.

  In this way, a toner image having a density correction pattern is formed on the surface of the transport belt 17, and the toner image becomes a density correction image.

  Subsequently, when the density correction image reaches a position facing the density sensor 27 as the transport belt 17 travels, the density sensor 27 detects the image density of the density correction image and sends the sensor output to the CPU 71.

  The density comparison processing unit (density comparison processing unit) of the density correction processing unit performs density comparison processing, and the image density detected by the density sensor 27 with respect to the density determination unit 79 and the reference density storage unit 83. Is instructed to be compared with the reference concentration OD1 stored in. The density determination unit 79 converts the sensor output sent from the density sensor 27 into an image density (detected density) OD2 according to the instruction, reads the reference density OD1 from the reference density storage unit 83, and sets the image density OD2 and the reference density OD1. Compare

  Next, exposure output adjustment processing means as correction variable adjustment processing means (correction variable adjustment processing section) of the density correction processing means performs exposure output adjustment processing as correction variable adjustment processing, and the comparison result by the density comparison processing means Based on the above, the lighting time STB is adjusted.

  That is, when the image density OD2 is lower than the reference density OD1, it can be seen that an image for density correction is formed with an image density OD2 lower than the reference density OD1 corresponding to the input dot diameter d1, so the exposure output adjustment processing means Then, the lighting time STB is changed to increase the minute adjustment amount Δt. This is performed based on the well-known tendency that the longer the lighting time, the higher the image density. In this case, the dot diameter d1 increases as the lighting time STB is increased. The adjustment amount Δt is sufficiently smaller than the difference δT between the lighting times STBa and STBb shown in FIG.

  On the other hand, when the image density OD2 is higher than the reference density OD1, it can be seen that the image for density correction is formed with an image density OD2 higher than the reference density OD1 corresponding to the input dot diameter d1, so the exposure output adjustment processing means The lighting time STB is changed to shorten the minute adjustment amount Δt. In this case, the dot diameter d1 of the dot is reduced by the amount that the lighting time STB is shortened.

  Subsequently, the image forming processing unit for density correction notifies the changed lighting time STB to the image forming unit control unit 65, and again notifies the image forming unit control unit 65 and the LED head control unit 61 of the photoconductor. An instruction is given to form a toner image having a density correction pattern on the drum 52Bk. The image forming unit controller 65 charges the surface of the photosensitive drum 52Bk by the charging roller 30 according to the instruction, and the LED head controller 61 drives the LED head 21Bk according to the image data of the density correction pattern. Then, a predetermined LED is caused to emit light at the changed lighting time STB, the photosensitive drum 52Bk is exposed, and an electrostatic latent image of a density correction pattern is formed on the surface of the photosensitive drum 52Bk.

  Similarly, the electrostatic latent image of the density correction pattern is developed into a toner image, and the toner image is transferred to the conveyance belt 17 to become a density correction image. Subsequently, when the density correction image reaches a position facing the density sensor 27 as the transport belt 17 travels, the density sensor 27 detects the image density OD2 of the density correction image, and the detected image density OD2 is detected. The reference concentration OD1 is compared.

  In this way, the image density OD2 and the reference density OD1 are compared, and when the image density OD2 and the reference density OD1 are different, the lighting time STB is changed, and the density on the transport belt 17 is changed based on the changed lighting time STB. A correction image is formed, and this operation is repeated until the image density OD2 is equal to the reference density OD1.

  When the image density OD2 becomes equal to the reference density OD1, the density correction processing means stores the lighting time STB at that time in the LED head lighting time storage unit 84, and ends the process.

  When the density correction process is completed in this way, the image forming processing unit starts normal printing on the paper P based on the lighting time STB stored in the LED head lighting time storage unit 84.

  In the present embodiment, the density correction image is formed by using the black toner 33 in the image forming unit 16Bk, but other colors are used in the other image forming units 16Y, 16M, and 16C. The toner 33 can be used. In this case, the density-dot diameter conversion unit 77 stores the dot diameter and the reference density in association with each other for the toner 33 of other colors.

  In the present embodiment, among the image forming processes in the printer 101, in the exposure process for forming an electrostatic latent image, the image density is corrected by changing the lighting time STB as a correction variable. However, in other image forming processes, for example, a drum charging process, a toner charging process, a development process, a transfer process, etc., predetermined correction variables, for example, a drum charging voltage applied to the charging roller 30, a toner supply roller The image density can be corrected or a plurality of image forming processes can be combined by changing the supply bias voltage applied to the developing roller 29, the developing bias voltage applied to the developing roller 28, the transfer voltage applied to the transfer roller 51Bk, and the like. To correct the image density by changing the predetermined correction variable It can be.

  For example, when correcting the image density in the development process, if the image density OD2 is lower than the reference density OD1, a density correction image is formed at an image density OD2 lower than the reference density OD1 corresponding to the input dot diameter d1. Thus, the voltage adjustment processing unit as the correction variable adjustment processing unit performs the voltage adjustment processing as the correction variable adjustment processing, and changes the development bias voltage applied to the developing roller 28 to change the minute adjustment amount Δv. Only increase in absolute value.

  On the other hand, when the image density OD2 is higher than the reference density OD1, it can be seen that the image for density correction is formed with an image density OD2 higher than the reference density OD1 corresponding to the input dot diameter d1, so the voltage adjustment processing means Then, the developing bias voltage applied to the developing roller 28 is changed to lower the absolute value by a minute adjustment amount Δv. In this way, the image density OD2 and the reference density OD1 can be made equal.

  For example, when the exposure process and the toner charging process are combined, the image density OD2 and the reference density OD1 can be made equal by changing the lighting time STB and the supply bias voltage as correction variables.

  As described above, in the present embodiment, the image density can be accurately corrected based on the density correction pattern stored in advance. Further, since it is not necessary to provide a high-resolution reading device for measuring the dot diameter of the dots inside and outside the apparatus main body 31, the work for correcting the image density can be simplified.

  In addition, since density correction processing is performed immediately before actual printing is performed, an image is always formed with a stable image density regardless of changes in the state of the printer 101, such as the use environment of the printer 101, the number of printed sheets, and the like. And dot reproducibility can be increased.

Next, a flowchart will be described.
Step S1 Wait for the dot diameter d1 to be input. When the dot diameter d1 is input, the process proceeds to step S2.
Step S2: Read the input reference density OD1 of the dot diameter d1.
Step S3 Read the lighting time STB of the LED head 21Bk corresponding to the dot diameter d1.
Step S4: A density correction image is formed.
Step S5: The image density OD2 of the density correction image is detected.
Step S6: It is determined whether the image density OD2 is equal to the reference density OD1. If the image density OD2 is equal to the reference density OD1, the process proceeds to step S7. If the image density OD2 is not equal to the reference density OD1, the process proceeds to step S8.
Step S7: The lighting time STB is stored, and the process is terminated.
Step S8: It is determined whether the image density OD2 is lower than the reference density OD1. If the image density OD2 is lower than the reference density OD1, the process proceeds to step S10. If the image density OD2 is higher than the reference density OD1, the process proceeds to step S9.
Step S9: A value obtained by subtracting the adjustment amount Δt from the lighting time STB is set to the lighting time STB, and the process returns to Step S4.
Step S10: A value obtained by adding the adjustment amount Δt to the lighting time STB is set to the lighting time STB, and the process returns to step S4.

  Next, a method for calculating the relational expression stored in the density-dot diameter conversion unit 77 will be described.

  FIG. 8 is a first diagram showing an image pattern in the first embodiment of the present invention, FIG. 9 is a second diagram showing an image pattern in the first embodiment of the present invention, and FIG. 10 is a diagram of the present invention. FIG. 11 is a fourth diagram showing an image pattern in the first embodiment of the present invention, and FIG. 12 is a first embodiment of the present invention. FIG. 13 shows the image pattern in the first embodiment of the present invention, FIG. 13 shows the image pattern in the first embodiment of the present invention, and FIG. 14 shows the case where the duty in the first embodiment of the present invention is changed. It is a figure which shows the correlation with the dot diameter of this and image density.

  In this case, in order to calculate the reference density OD1, as shown in FIGS. 8 to 13, the duty is changed to 20%, 40%, 60%, 70%, An image pattern for each duty was created by setting six levels of 80 [%] and 90 [%]. The duty is the print density of the image and represents the ratio of the number of print dots to the total number of dots in the print area. The image pattern is created by arranging 960 dots in the main scanning direction in a matrix for 720 lines in the sub-scanning direction.

  In the present embodiment, the duty is set to six stages and six image patterns are created. However, the duty can be further increased and the image pattern can be increased.

  Then, the dot diameter is input on the print control selection screen 201 (FIG. 5), and the image patterns of the respective duties are printed side by side on one sheet P (FIG. 3) as an image carrier. Subsequently, the image density of each image pattern is printed for each duty pattern printed by a density measuring device (“x-rite 528” manufactured by X-Rite) and a dot diameter measuring device (“Techkon DMS 910 IR” manufactured by Techkon). And the dot diameter is measured. In this case, the concentration measuring device has higher accuracy (repetition accuracy (OD value): ± 0.005) than the concentration sensor 27, and the dot diameter measuring device has an accuracy of ± 1 [μm] or less. The density sensor 27 has an accuracy of ± 0.1 (OD value). As a result, as shown in FIG. 14, with respect to the dot diameter of one dot, six image densities of the image pattern for each duty can be obtained and plotted vertically.

  Then, the above operation is repeated while changing the dot diameter, and the graph shown in FIG. 14 is obtained by measuring six image densities for five dot diameters.

  Next, a correlation coefficient of each image density is calculated for each duty, and a regression curve (least square approximation curve) is calculated by the least square method based on each image density of the duty having the highest correlation coefficient. In FIG. 14, each image density with a duty of 80 [%] has the highest correlation coefficient, and a regression curve (straight line in FIG. 14) k calculated based on each image density is represented by the dot diameter and the image density. A relational expression representing the relation is used, and the relational expression is stored in the density-dot diameter conversion unit 77 (FIG. 1).

  When the relationship between the dot diameter and the image density is seen by changing the duty, in the image pattern having a low duty and a medium duty (duty of 20% or more and 70% or less), the dot diameter is changed. The change in image density when changed is small. This is because, when measuring the image density, the influence of the density of the background paper P on the density of the toner image forming the image of the image pattern is large, and the image density cannot be measured accurately.

  On the other hand, in an image pattern with a high duty (that is, 90 [%] duty), if the dot diameter is increased, adjacent dots are too close to each other and the image density cannot be measured accurately.

  From this, in the image pattern with a duty of 80 [%], the change in the image density when the dot diameter is changed represents the most accurate correlation.

  Therefore, a duty of 80 [%] is set as a specified duty, and an image pattern of the specified duty is set as a density correction pattern. In this case, when the image dot diameter is d and the image density is OD, the relational expression is expressed by the equation (1).

OD = 6.60E-3 × d + 0.430 (1)
In this embodiment, when printing is performed by specifying a dot diameter, density correction processing is always performed before actual printing is performed, but printing is performed without specifying a dot diameter. In either case where printing is performed by designating the dot diameter, the amount of adhesion of the toner 33 (FIG. 4) to the photosensitive drum 52Bk does not change, depending on the use frequency of the printer 101, or The density correction processing can be performed periodically according to the supply amount (number of ejections) of the toner 33 from the toner cartridge 35, the accumulated number of rotations of the photosensitive drum 52Bk, and the like.

  By the way, the smoothness of the surface of the paper P differs depending on the type of the paper P. If the smoothness is different, the image density is different even if dots having the same dot diameter are formed. Therefore, a second embodiment of the present invention in which the image density can be corrected according to the smoothness of the surface of the paper P will be described. In addition, about the thing which has the same structure as 1st Embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  FIG. 15 is a schematic view of a printer according to the second embodiment of the present invention, FIG. 16 is a diagram showing the structure of a glossiness sensor according to the second embodiment of the present invention, and FIG. 17 is a second embodiment of the present invention. FIG. 18 is a schematic diagram of dots formed on the surface of various types of paper in the second embodiment of the present invention, and FIG. 19 is a second diagram of the present invention. It is a figure which shows the correlation of a dot diameter and image density when printing with respect to the various paper in embodiment of this.

  In the figure, 91 is a glossiness sensor as a glossiness detection unit for detecting the glossiness of the paper P as a medium, and the glossiness sensor 91 is upstream of the transport roller 14 as a transport member in the transport direction of the paper P. It is arranged. Reference numeral 92 denotes a medium determination unit as medium determination processing means for determining the type of the paper P based on the glossiness detected by the glossiness sensor 91.

  The RAM 73 includes an area of a medium type storage unit 111, and the medium type storage unit 111 stores glossiness of various types of paper P. Therefore, the medium determination unit 92 performs a medium determination process, reads the sensor output of the glossiness sensor 91, refers to the medium type storage unit 111, and determines the type of paper P corresponding to the sensor output.

  By the way, as shown in FIG. 16, the glossiness sensor 91 includes a housing 401, and a bottom portion of the housing 401 is associated with a measured portion Q1 for detecting the glossiness of the paper P. An opening 402 is formed. The gloss sensor 91 includes a light source 94 disposed toward the measurement target Q1 in the housing 401, and a lens 304 as a converging member disposed between the light source 94 and the opening 402. A light receiver 97 disposed toward the opening 402 on the opposite side of the light source 94 across the opening 402, a lens 305 as a converging member disposed between the light receiver 97 and the opening 402, and the like. Have.

  In the glossiness sensor 91 having the above-described configuration, the light emitted from the light source 94, passed through the light source opening 95, and irradiated on the surface of the paper P at an angle θ with respect to the normal extending upward from the surface of the paper P is Reflected by the measured part Q1. In this case, the light is irregularly reflected at a certain rate depending on the state of the surface of the paper P, and a part of the light is specularly reflected at the same angle θ. Only the light that has passed through the light receiving window 96 is received by the light receiver 97.

  Note that the surface of the paper P is smoother, and the higher the smoothness, the smaller the amount of light that is diffusely reflected, and the greater the intensity of the light received by the light receiver 97, the higher the glossiness. Become. On the other hand, as the surface of the paper P is uneven and the smoothness is lower, the amount of light that is diffusely reflected increases, the intensity of the light received by the light receiver 97 decreases, and the glossiness decreases accordingly. . That is, the smoothness and the glossiness have a predetermined correspondence relationship.

  Therefore, in the present embodiment, as described above, the medium determination unit 92 reads the sensor output of the glossiness sensor 91, refers to the medium type storage unit 111, and the type of paper P corresponding to the sensor output. Is determined.

  By the way, when the type of the paper P is different, the shape of the dots formed on the surface of the paper P is different. For example, in FIG. 18, P1 is a rough paper which is a sheet having a low surface smoothness, P2 is a high quality paper which is a general sheet having a smooth surface, P3 is a glossy paper which is a sheet having a high surface smoothness, 37 is a dot formed on the surface of the rough paper P1, 38 is a dot formed on the surface of the high quality paper P2, and 39 is a dot formed on the surface of the glossy paper P3.

The dot diameter of the dots 37 formed on the rough paper P1 is dr, the dot diameter of the dots 38 formed on the surface of the fine paper P2 is dm, and the dot diameter of the dots 39 formed on the surface of the glossy paper P3 is Assuming dg, each dot diameter dr, dm, dg is
dr <dm <dg
become.

  Therefore, as in the first embodiment, when the operator inputs a desired dot diameter as print information in the dot size designation section q6 of the print control selection screen 201 (FIG. 5), depending on the type of the paper P, If the dot diameters of actually formed dots are different, the image density cannot be corrected with high accuracy.

  Therefore, the ROM 72 includes areas of density-dot diameter conversion units A113 to C115 as density conversion storage units for each type of paper P. The density-dot diameter conversion units A113 to C115 respectively include rough paper P1 and high quality. Regarding the paper P2 and the glossy paper P3, the relationship between the dot diameter, the image density, the correction variable, and the lighting time as the exposure output when there is no change over time of the photosensitive drum 52Bk and the toner 33, environmental change, etc. Is stored.

  For example, when the operator designates and inputs a dot diameter in the dot size designation unit q6, first, the reference density calculation processing unit of the density correction processing unit reads the dot diameter and is discriminated by the medium discrimination unit 92. The type of the paper P is read, the density-dot diameter conversion unit corresponding to the type of the paper P among the density-dot diameter conversion units A113 to C115 is selected and referred to, and the standard corresponding to the type of the paper P and the dot diameter Is read as the reference density OD1 and stored in the reference density storage unit 83 of the RAM 73.

  Since the operator can designate the type of the paper P in the paper type designation unit q4, the medium determination unit 92 reads the type of the paper P designated in the paper type designation unit q4, and The type is determined, and the reference density calculation processing unit selects and refers to the density-dot diameter conversion unit corresponding to the type of the paper P among the density-dot diameter conversion units A113 to C115, and determines the type of the paper P and The reference image density corresponding to the dot diameter can be read out as the reference density OD1.

  Next, the density-dot diameter conversion units A113 to C115 will be described.

  In this case, as in the first embodiment, the image patterns of each duty are printed side by side on each of the rough paper P1, the high quality paper P2, and the glossy paper P3 as the image carrier, and for each duty. A correlation coefficient of each image density is calculated, and a regression curve is calculated by the least square method based on each image density of the duty having the highest correlation coefficient. As shown in FIG. 19, each image density with a duty of 80 [%] has the highest correlation coefficient, and regression curves (straight lines in FIG. 19) kA to kC calculated based on each image density are rough papers. The relational expressions represent the relationship between the dot diameter and the image density in P1, high-quality paper P2, and glossy paper P3, and the respective relational expressions are stored in the density-dot diameter conversion units A113 to C115, respectively. Then, an image pattern having a duty of 80 [%] is set as a density correction pattern.

  Further, as shown in FIG. 19, compared to the general fine paper P2, the rough paper P1 has a smaller dot diameter even if the image density of the density correction pattern is increased, while the glossy paper P3. In, the dot diameter increases even if the image density of the density correction pattern is lowered.

  As shown in FIG. 18, this varies depending on how much the toner of the formed dots 37 to 39 is absorbed by the irregularities on the surfaces of the rough paper P1, the high quality paper P2, and the glossy paper P3. That is, the dot 37 formed on the rough paper P1 has a small dot diameter because a large amount of toner enters the surface unevenness, and the dot 39 formed on the glossy paper P3 has a small surface unevenness so that the toner is on the surface. The dot diameter increases.

  If the same relational expression as that of the dots 38 formed on the high-quality paper P2 having a general smoothness is used, a large error occurs in the image density. Accordingly, it is necessary to derive different relational expressions as follows. In this case, assuming that the dot diameter of the image is d and each image density when using the rough paper P1, the high quality paper P2 and the glossy paper P3 is ODA to ODC, the respective relational expressions are expressed by the equations (2) to (4). Can be represented.

ODA = 9.4E-3 × d + 0.172 (2)
ODB = 6.6E-3 × d + 0.430 (3)
ODC = 5.4E-3 × d + 0.437 (4)
The relational expressions for each type of paper P calculated in this way are stored in the density-dot diameter conversion units A113 to C115, respectively.

  Therefore, the reference density calculation processing means of the density correction processing means reads the dot diameter when the dot diameter is designated and inputted, and refers to the density-dot diameter conversion units A113 to C115 according to the type of the paper P. Then, the reference image density corresponding to the dot diameter is read as the reference density OD1 and stored in the reference density storage unit 83 of the RAM 73.

  As described above, in the present embodiment, a plurality of density-dot diameter conversion units A113 to C115 that determine the reference density from the dot diameter are provided according to the types of paper P having different surface smoothness. Regardless of the type of paper P, the image density can be accurately corrected.

  In the present embodiment, the relational expression between the dot diameter and the image density is stored in the density-dot diameter conversion units A113 to C115 in accordance with the smoothness of the surface of different types of paper P. A relational expression is calculated based on a difference in affinity between the toner 33 and the surface of the paper P due to other medium characteristic values of the paper P, such as an electrical resistance value, a thickness of the paper P, and the like. A relational expression can be calculated by combining characteristic values.

  Next, a third embodiment of the present invention will be described. In addition, about the thing which has the same structure as the said 1st, 2nd embodiment, the same code | symbol is provided and the effect of the embodiment is used about the effect of the invention by having the same structure.

  20 is a schematic diagram of a printer according to the third embodiment of the present invention, FIG. 21 is a diagram illustrating characteristics of stealth toner according to the third embodiment of the present invention, and FIG. 22 is a diagram illustrating the third embodiment of the present invention. It is a figure which shows the printing control selection screen in a form. In FIG. 21, the horizontal axis represents wavelength and the vertical axis represents absorption rate.

  In FIG. 20, 16S, 16Y, 16M, and 16C are a plurality of image forming units as four image forming units in the present embodiment, and the image forming unit 16S among them is a special developer. In addition, stealth toner as an invisible developer is used and disposed upstream of the other image forming units 16Y, 16M, and 16C in the transport direction of the paper P as a medium. In this case, since the stealth toner is first transferred to the transfer belt, transfer omission does not occur. If necessary, the image forming unit 16S can be disposed on the downstream side of the other image forming units 16Y, 16M, and 16C in the transport direction of the paper P. In this case, since the infrared rays from the density sensor 27 are directly irradiated to the stealth toner, the detection accuracy can be increased.

  Next, the stealth toner will be described.

  In FIG. 21, L11 is the emission wavelength of the density sensor 27 as a density detector, and L12 is the infrared light absorption wavelength of the stealth toner. The stealth toner is a toner containing a material that absorbs infrared light (light in the infrared wavelength band) (hereinafter referred to as “infrared light absorbing material”) in a transparent resin material, and an image in which predetermined information is embedded. That is, it is used to form an information image as identification information. In this case, identification information for identifying the embedded information is constituted by the information image, and the identification information is sent from the host computer 59 as the host device.

  In the present embodiment, as shown in FIG. 21, the infrared light absorbing material does not absorb light in the wavelength region of less than 800 [nm], that is, in the visible light region, and becomes transparent or white. A material that absorbs light in the wavelength range of [nm] to 1000 [nm], that is, a non-visible light region, for example, glass powder doped with CuO, a resin in which copper ions are introduced into a polymer, or the like can be used. . The infrared light absorbing material constitutes a light absorbing material. Further, since the infrared light absorbing material does not absorb light in the visible light region but absorbs light in the invisible light region, an invisible image is formed by the information image.

  Further, as the transparent resin material, a resin that is transparent in the visible light region, such as polycarbonate resin, polyester resin, methacrylic resin, styrene resin, polyvinyl chloride resin, polyolefin resin, polyamide resin, etc. Can be used.

  Then, a print control selection screen 201 as a setting screen as shown in FIG. 22 is formed on the display 302 (FIG. 2), and toner 33 as a developer for forming an information image is formed on the print control selection screen 201. An information image forming portion q7 for selecting the type of (FIG. 4) is formed. In the information image forming unit q7, the operator can designate the type of toner in order to instruct the formation (printing) of the information image based on the identification information. The information image forming part q7 constitutes a toner type designation part as a developer designation part.

  As described above, in the first and second embodiments, the normal toner 33 is used to adjust the dot diameter and the image density when forming an image on the paper P. In this embodiment, the stealth toner image is superimposed on the normal toner 33 toner image.

  In the printer 101 configured as described above, when the interface 102 serving as a receiving unit receives the identification information and image data sent from the host computer 59, a data determination unit (not shown) of the CPU 71 determines the identification information and the image data. The first print control unit (not shown) of the CPU 71 uses the stealth toner as the invisible developer by the image forming unit 16S as the first image forming unit to form an information image based on the identification information. A second print control unit (not shown) uses toner as visible developer of yellow, magenta, and cyan by image forming units 16Y, 16M, and 16C as second image forming units, and displays an image based on visible information. Form.

  As described above, in the present embodiment, by using the stealth toner, in addition to the visible information by the yellow, magenta, and cyan toner images, other information can be embedded on the paper P. In addition, the image quality does not deteriorate accordingly.

  Therefore, the identification information can be accurately recognized when the visible information and the identification information are formed on the same sheet.

  In the present embodiment, as in the first embodiment, the operator operates the keyboard 303 to select the print quality of the image to be printed, the brightness of the image, etc. The print information is input by specifying, specifying the type, size, thickness, etc. of the paper P to be printed, or specifying the dot diameter. In the information image forming unit q7, it is possible to select toner used for the information image as print information.

  The print setting information depends on the print quality, the brightness of the image, the number of printed sheets, the medium information depends on the type, size, thickness, etc. of the paper P, the dot information depends on the dot diameter, and the toner used in the information image. Developer information is configured.

  Next, based on the input print information, the print control processing unit of the CPU 301 generates image data of a print image according to a print control program, and the image data is converted into the print setting information, medium information, dot information, and It is transmitted to the printer 101 together with the developer information. In the printer 101, when the image forming processing unit of the CPU 71 receives the image data, print setting information, medium information, dot information, and developer information as printer control information, it reads predetermined information from the ROM 72 and RAM 73. Then, an image is formed based on the printer control information.

  The density correction processing unit of the CPU 71 corrects the image density based on the designated dot diameter before printing is started.

  By the way, a density sensor 27 is provided to detect the image density of the density correction image, and the density sensor 27 is formed by normal toner 33 formed on the conveyance belt 17 as the first transfer member. The image density of the toner image and the image density of the toner image formed by the stealth toner are detected.

  The density sensor 27 is provided with a photo reflector using a near-infrared LED as a light source, and detects the image density by generating near-infrared light by the photo reflector. However, as shown in FIG. 21, the emission wavelength L11 of the near-infrared LED of the density sensor 27 has a peak at about 1000 [nm], but the infrared light absorption wavelength L12 of the stealth toner is about 900 [ nm] has a peak.

  That is, the photo reflector generates light having an emission wavelength suitable for measuring the image density of the toner image formed by the normal toner 33, but the infrared light absorption characteristics of the stealth toner have been described above. Thus, it is selected in accordance with the absorption characteristic of infrared light in a dedicated measuring instrument.

  Accordingly, when the image density of the toner image formed by the stealth toner is detected by the density sensor 27, the value is about 85% of the image density of the toner image formed by the normal toner 33. In this case, an error occurs when the dot diameter is converted into the image density with the same relational expression as that of the normal toner 33. Therefore, when the dot diameter of the image formed by the stealth toner is d and the image density is OD ′, the relational expression can be expressed by Expression (5).

OD ′ = (6.6E−3 × d + 0.430) /1.18 (5)
The relational expression for the stealth toner thus derived is stored in the density-dot diameter conversion unit 77 of the ROM 72 (FIG. 1).

  The image formed by the image forming unit 16S and the images formed by the image forming units 16Y, 16M, and 16C are detected by a detection unit (not shown), and the image formation is performed based on the detection result of the image by the detection unit. First and second correction amounts for changing the printing conditions of the unit 16S and the image forming units 16Y, 16M, and 16C can be calculated. Based on the first and second correction amounts, the printing condition change processing unit of the CPU 71 changes the printing conditions of the image forming unit 16S and the image forming units 16Y, 16M, and 16C.

  In the present embodiment, a transparent resin material including an infrared light absorbing material is used as the stealth toner. However, depending on the density sensor 27, light in a different wavelength band (for example, It is also possible to use a material that absorbs (ultraviolet light), that is, an ultraviolet light absorbing material as the light absorbing material.

  In this embodiment, stealth toner is used instead of black toner. However, in a single color printer, stealth toner can be used instead of black toner.

  By the way, each of the above embodiments can be applied to a printing technique (“Valcode” (manufactured by Oki Electric Industry Co., Ltd.)) for preventing falsification, forgery, etc. of a document. In the printing technique, for example, when printing characters, numbers, and the like, a plurality of dots are printed in a predetermined pattern on the background of the paper P, that is, Anoto pattern (Anoto Corporation).

  Next, a fourth embodiment of the present invention will be described. In addition, about the thing which has the same structure as 1st-3rd embodiment, the same code | symbol is provided and the effect of the same embodiment is used about the effect of the invention by having the same structure.

  In this case, a predetermined storage unit is formed in the ROM 72 (FIG. 1), and the density correction image, identification information, and information (dot size) regarding the prime point of the identification information are stored in the storage unit. The image forming units 16S, 16Y, 16M, and 16C read the identification information or the density correction image from the storage unit, and form an image. Then, the dot conversion point information and the image density information are stored in the density conversion storage unit in association with each other.

  FIG. 23 is a diagram showing a basic pattern in the fourth embodiment of the present invention, and FIG. 24 is a diagram showing an Anoto pattern in the fourth embodiment of the present invention.

  In this case, the Anoto pattern is an image pattern that forms a characteristic pattern, and is formed by printing a plurality of marks m having a circular (dot-shaped) shape, and a plurality of rasters formed orthogonal to each other. Identification information is formed by the positional relationship between the intersection f between the lines u and the mark m formed on the predetermined raster line u.

  23A to 23D show basic patterns in which the position of the mark m with respect to the intersection point f is made different. In each basic pattern, the distance between the intersection point f and the mark m is made different, and the position and the distance The identification information is represented by a combination of.

  The mark m has a dot diameter of about 0.04 [mm] and is arranged at intervals of about 0.3 [mm] to form a 6 × 6 matrix, and one identification information is formed by the matrix. Is done.

  In this case, it is possible to accurately recognize the identification information based on each mark m by correcting the image density of each mark m by the method described above.

  In each of the above-described embodiments, as an example, the printing is performed according to the printing control program on the host computer 59 (that is, printing is performed by specifying the dot diameter on the printing control selection screen 201). It is also possible to perform print settings by operating an operation panel as an operation unit of the printer 101.

  In addition, an input unit for inputting selection information as to whether or not to print a special pattern image (for example, an Anoto pattern) using a predetermined stealth toner can be provided in the print control program or the operation panel of the printer 101. . In this case, it is necessary to register a preset default setting value (fixed value) in the density correction pattern storage unit 78 with a predetermined dot size and printing conditions. When selection information for printing a special pattern image with stealth toner is input by the input unit, the default setting value is appropriately read from the density correction pattern storage unit 78 to print the stealth toner image. Done. Further, in the print control selection screen 201 in the third embodiment, the dot size is specified for the stealth toner, but in addition to this configuration, the dot size is set for each of yellow, magenta, and cyan toners. Can be specified. In this case, the dot diameter and the image density corresponding to each toner can be stored in the density-dot diameter conversion unit 77. Since each toner has a different wavelength characteristic (light absorption rate), a density sensor including an LED having a peak value of the emission wavelength corresponding to each toner is provided as a detection unit, or a white LED is provided. Further, the light can be dispersed according to the toner by the diffraction grating.

  In each of the above-described embodiments, a direct transfer method in which a color toner image is directly transferred to the paper P is described. However, instead of the direct transfer method, a color toner image is temporarily transferred to an intermediate transfer member. Then, an intermediate transfer method in which the image is transferred onto the paper P can also be used.

  In each of the above-described embodiments, an example in which the present invention is applied to a printer as an image forming apparatus has been described. However, the present invention can be applied to a copying machine, a facsimile machine, a multifunction machine, and the like.

  The present invention is not limited to the embodiments described above, and various modifications can be made based on the spirit of the present invention, and these are not excluded from the scope of the present invention.

16Bk, 16Y, 16M, 16C, 16S Image forming unit 17 Conveying belt 18 Fixing device 21Bk, 21Y, 21M, 21C LED head 28 Developing roller 29 Toner supply roller 33 Toner 52Bk, 52Y, 52M, 52C Photosensitive drum 59 Host computer 71 CPU
101 Printer 102 Interface P Paper

Claims (5)

(A) An image carrier and a developing device that develops an electrostatic latent image formed on the image carrier with an invisible developer that absorbs light in a predetermined wavelength region to form a developer image. A first image forming unit;
(B) a second image forming unit including an image carrier and a developing device that develops the electrostatic latent image formed on the image carrier with a visible developer to form a developer image;
(C) an exposure device that exposes the surface of each image carrier to form the electrostatic latent image;
(D) a transfer portion that transfers the developer image to a medium;
(E) a fixing device for fixing the transferred developer image to the medium;
(F) a receiving unit that receives identification information and image data from a host device;
(G) a data discriminating unit for discriminating between the identification information and the image data;
(H) a first print control unit that performs printing by the first image forming unit based on the identification information determined by the data determination unit;
(I) An image forming apparatus comprising: a second print control unit that performs printing by the second image forming unit based on image data determined by the data determining unit. (A) the visible developer contains a colorant;
The image forming apparatus according to claim 1, wherein the invisible developer contains a material that absorbs light in an infrared wavelength band. (A) a detection unit that detects an image formed by the first and second image forming units;
(B) First and second correction amounts for calculating first and second correction amounts for changing the printing conditions of the first and second image forming units based on the detection result of the image by the detection unit. A correction unit;
(C) a printing condition changing unit that changes the printing conditions of the first and second image forming units based on the first and second correction amounts calculated by the first and second correcting units. The image forming apparatus according to claim 1, which has the image forming apparatus. (A) a plurality of the second image forming units are disposed;
(B) The image forming apparatus according to claim 1, wherein the first image forming unit is disposed upstream of the second image forming unit. (A) a plurality of the second image forming units are disposed;
(B) The image forming apparatus according to claim 1, wherein the first image forming unit is disposed downstream of the second image forming unit.

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