JP2010102239A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which can vary gloss level in multiple stages, using a color toner and a clear toner, which can correct a difference of glossiness due to the change over time, such as change of environmental conditions and change of property of an apparatus due to endurance and which can always realize printing with the same level of glossiness. <P>SOLUTION: The image forming apparatus detects glossiness of a gradation patch of the clear toner on a gradation test pattern and corrects the image-forming conditions, for example, γ table. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a printer or a copying machine, and more particularly to an image forming apparatus using transparent toner.

  Conventionally, an electrophotographic method is known for a color image forming apparatus. In the image forming process, first, a photosensitive drum is uniformly charged by a charging device, and an electrostatic latent image is formed by a laser. Develop with toner. In the tandem system, this is performed for each magenta, cyan, yellow, and black color photosensitive drum, and each formed color toner image is superimposed on an intermediate transfer belt and transferred to a recording material such as paper. A color image is formed by a method in which the toner image superimposed on the recording material is fixed to the recording material by heat.

  In recent years, there has been an increasing demand for higher image quality, and a technique has been proposed in which transparent toner is used together with magenta, cyan, yellow, and black color toners in order to obtain an image with excellent surface gloss in an electrophotographic system.

  For example, in Patent Document 1, a transparent toner is transferred to a portion having a small amount of toner corresponding to the thickness of a toner layer formed with a color toner image, and the thickness of the toner layer is made substantially the same in the image area. It is described to obtain gloss. However, in this method, when the thickness of the color toner layer is small, the thickness of the transparent toner layer is inevitably reduced. Therefore, gloss unevenness may occur due to the influence of the surface property of the paper. In general, components such as waxes and fatty acids are added to the transparent toner in order to give gloss, and the glossiness is high in the high density image portion formed with the color toner and the image portion using the transparent toner. May be unnatural. In order to solve this problem, for example, in Patent Document 2, a transparent toner image is superimposed on a color toner image corresponding to the color toner image, and the glossiness is controlled in multiple stages by changing the amount of the transparent toner to be superimposed. The technology to do is described.

On the other hand, in a conventional color image forming apparatus that does not use transparent toner, a technique for stabilizing image quality is used regardless of fluctuations in apparatus characteristics due to environmental fluctuations and durability. In this method, after starting an image forming apparatus and forming a specific gradation test pattern on a recording material, the density of the gradation test pattern of the formed recording material is read by an image reading unit, and the image is read. Based on the information, for example, a method of feeding back to an image forming condition determining unit such as a γ correction unit is used as a known technique. In a color image forming apparatus using a transparent toner, a similar technique is necessary to maintain a stable glossiness regardless of environmental changes and changes with time of the apparatus.
JP 2000-147863 A JP 2002-82508 A

  However, the above prior art has the following problems.

  The density test pattern density of the color toner formed on the recording material is read by the CCD sensor of the scanner which is the image reading means, but the CCD sensor is composed of RGB 3-line color sensors, and the image density Is input to the A / D converter as R (Red), G (Green), and B (Blue) image data, so it is difficult to capture the loading amount of the transparent toner as density data, and it is formed on the paper. There is a problem that the gradation pattern of the transparent toner cannot be read.

  The present invention has been made to solve the above-described problems of the prior art, and an object of the present invention is to provide an image forming apparatus in which the gloss level can be varied in multiple stages using color toner and transparent toner. It is an object of the present invention to provide an image forming apparatus capable of always printing printed matter having the same glossiness by correcting a difference in glossiness due to a change with time such as a change in environmental conditions and a characteristic change due to durability of the apparatus.

In order to solve the above problems, an image forming apparatus according to the present invention provides:
In claim 1,
In an image forming apparatus that forms an image using color toner and transparent toner,
Means for forming a plurality of gradation patch toner images on the recording material; means for fixing the patch toner image formed on the recording material; and a first means for reading the color toner gradation patches on the recording material after fixing. It has a reading means and a second reading means for reading a gradation patch using the transparent toner on the recording material after fixing, and the image forming condition is corrected using the read result.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the patch using the color toner patch and the transparent toner is read in a special operation mode different from the normal image forming operation.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, at least one of an image processing parameter, a laser power, a charging bias, a developing bias, and a transfer bias is corrected as an image forming condition to be further corrected.

  As described above, the image forming apparatus of the present invention is an image forming apparatus in which the gloss level can be varied in multiple stages using color toner and transparent toner. It is possible to always print a printed matter having the same glossiness by correcting the difference in glossiness due to changes over time.

  Next, details of the present invention will be described in accordance with the description of the embodiments.

Example 1
FIG. 2 is a longitudinal sectional view showing a schematic configuration of a full-color copying machine as an example of the image forming apparatus according to the present invention.

  In the figure, reference numeral 200 denotes a digital color image reader unit (hereinafter referred to as a reader unit), and a digital color image printer unit (hereinafter referred to as a printer unit) 201 is provided below the digital color image reader unit. is doing.

  In the reader unit 200, an original is placed on the original table glass 211, and the original scanning unit 215 including the exposure lamps 213 and 214 is exposed and scanned at a predetermined constant speed by the optical system reading drive motor 212. Then, the reflected light image from the original is condensed on a full color sensor (CCD) 217 by a lens 216 to obtain a color color separation image signal. As the full-color sensor 217, a three-line CCD with R (red), G (green), and B (blue) filters disposed adjacent to each other is used. The color-separated image signal is subjected to image processing by the image processing unit 218 and then sent to the printer unit 201.

  An operation unit is provided around the platen glass 211, and switches for setting various modes related to the copy sequence and a display for display and a display are arranged.

  Next, the printer unit 201 will be described.

  In the printer unit 201, the control unit 59 is a controller unit, which is configured by a controller board including a CPU, a RAM, a ROM, and the like. Based on a control program stored in the ROM, a paper feeding unit, an intermediate transfer unit, a transport unit, The operation of the fixing unit and the operation unit is comprehensively controlled.

  The image forming unit is configured as described below. Photosensitive drums 11a, 11b, 11c, 11d, and 11e as image carriers are pivotally supported at the centers thereof and are rotationally driven by a drive motor (not shown) in the direction of the arrow. Roller chargers 12a, 12b, 12c, 12d, 12e, scanners 13a, 13b, 13c, 13d, 13e, developing units 14a, 14b, 14c, 14d, in the rotational direction facing the outer peripheral surfaces of the photosensitive drums 11a to 11e, 14e, photosensitive drum cleaning devices 15a, 15b, 15c, 15d, and 15e are disposed. The roller chargers 12a to 12e apply a uniform charge amount to the surfaces of the photosensitive drums 11a to 11e.

  Next, the photosensitive drums 11a to 11e are exposed to light beams, such as laser beams, modulated by the scanners 13a to 13e according to the recording image signal, thereby forming electrostatic latent images thereon. Further, the electrostatic latent image is visualized by developing devices 14a to 14d that respectively store four color developers (color toners) such as yellow, magenta, cyan, and black and a developing device 14e that stores transparent toner. The visualized visible image is transferred to the intermediate transfer belt 30. Thereafter, the residual toner remaining on the photosensitive drums 11a to 11e is collected by the photosensitive drum cleaning devices 15a to 15e. By the process described above, image formation with color toner and image formation with transparent toner are sequentially performed.

  Next, the paper feeding unit includes a portion for storing the recording material P, a roller for conveying the recording material P, a sensor for detecting the passage of the recording material P, and a sensor for detecting the presence or absence of the recording material P. And a guide (not shown) for transporting the recording material P along the transport path.

  21a, 21b, 21c, and 21d are cassettes, 27 is a manual feed tray, and 28 is a deck. 22a, 22b, 22c and 22d are pickup rollers for feeding the recording material P from the cassettes 21a to 21d one by one from the top.

  In the pickup rollers 22a to 22d, a plurality of recording materials P may be sent out, but only one sheet is reliably separated by the BC rollers 23a, 23b, 23c, and 23d. The recording material P separated by only one sheet by the BC rollers 23 a to 23 d is further transported by the drawing rollers 24 a to 24 d and the pre-registration roller 26 and is transported to the registration roller 25.

  The recording material P stored in the manual feed tray 27 is separated by a BC roller 29 and conveyed to a registration roller 25 by a pre-registration roller 26. A plurality of recording materials P stored in the deck 28 are conveyed to the paper feed roller 61 by the pickup roller 60, and only one sheet is reliably separated by the paper feed roller 61 and conveyed to the drawing roller 62. Further, the recording material P is conveyed to the registration roller 25 by the pre-registration roller 26.

  Next, the intermediate transfer unit will be described in detail.

  30 is an intermediate transfer belt. As a material thereof, a conductive elastic layer made of urethane rubber, silicon rubber, CR rubber or the like is formed on a base layer made of PI, PVdF, or the like, and its surface is made of fluororesin, FKM, or the like. Forming a surface layer. A drive roller 32 transmits driving force to the intermediate transfer belt 30, and includes a tension roller 33 that applies an appropriate tension to the intermediate transfer belt 30 by urging of a spring (not shown), and a secondary transfer region across the intermediate transfer belt. Is supported by a driven roller 34.

  The drive roller 32 is rotationally driven by a stepping motor (not shown). A primary transfer roller 35a for applying a high pressure for transferring a toner image to the intermediate transfer belt 30 on the back of the intermediate transfer belt 30 at a position facing each of the photosensitive drums 11a to 11e across the intermediate transfer belt 30. To 35e are arranged. A secondary transfer roller 36 is disposed so as to face the driven roller 34, and a secondary transfer region is formed by a nip with the intermediate transfer belt 30. The secondary transfer roller 36 is pressed against the intermediate transfer belt with an appropriate pressure.

  A cleaning device 50 for cleaning the image forming surface of the intermediate transfer belt 30 is disposed on the intermediate transfer belt 30 and downstream of the secondary transfer region. The cleaning device 50 includes a conductive fur brush 51 and a fur brush. A bias roller (not shown) for applying a bias to the toner and a waste toner box 52 for storing waste toner.

  The fixing unit 40 includes a fixing roller 41a having a heat source such as a halogen heater therein and 41b pressed by the roller (this roller may also have a heat source), and the recording material discharged from the roller pair. It consists of an internal paper discharge roller 44 for conveying P.

  On the other hand, the recording material P conveyed to the registration roller 25 stops and temporarily stops the rotation of the upstream roller from the registration roller 25, and the upstream roller including the registration roller 25 is synchronized with the image formation timing of the image forming unit. The rotational drive is resumed. The recording material P is sent out to a secondary transfer area described later.

  The recording material P to which the image has been transferred in the secondary transfer area and the image has been fixed in the fixing unit 40 passes through the inner paper discharge roller 44 and is then switched by the switching flapper 73. When the switching flapper 73 is on the face-up discharge side, the recording material P is discharged to the face-up discharge tray 2 by the outer discharge roller 45.

  On the other hand, when the switching flapper 73 is on the face-down paper discharge side, the recording material P is conveyed in the direction of the reverse rollers 72 a, 72 b, 72 c and discharged to the face-down paper discharge tray 3.

  A plurality of sensors are arranged in the conveyance path of the recording material P to detect the passage of the recording material P, and the paper feeding retry sensors 64a, 64b, 64c, 64d, the deck paper feeding sensor 65, the deck pulling out. There are a sensor 66, a registration sensor 67, an internal paper discharge sensor 68, a face-down paper discharge sensor 69, a double-sided pre-registration sensor 70, a double-sided paper re-feed sensor 71, and the like.

  The cassettes 21a to 21d that store the recording material P are provided with cassette paper presence / absence sensors 63a, 63b, 63c, and 63d that detect the presence or absence of the recording material P, and the manual feed tray 27 records on the manual feed tray 27. A manual tray paper presence / absence sensor 74 for detecting the presence or absence of the material P is disposed, and a deck paper presence / absence sensor 75 for detecting the presence or absence of the recording material P in the deck 28 is disposed on the deck 28.

  Next, a description will be added in accordance with the operation of the apparatus. As an example, a case where the recording material P is transported from the cassette 21a will be described.

  After a predetermined time has elapsed from the start of the job, first, the transfer material P is sent out one by one from the cassette 21a by the pickup roller 22a. Then, the transfer material P is conveyed by the paper feed roller 23 to the registration roller 25 via the drawing roller 24 a and the pre-registration roller 26. At that time, the registration roller 25 is stopped, and the leading edge of the paper hits the nip portion.

  Thereafter, the registration roller 25 starts rotating in accordance with the timing at which the image forming unit starts image formation. The rotation timing is set so that the transfer material P and the toner image primarily transferred from the image forming unit onto the intermediate transfer belt exactly coincide with each other in the secondary transfer region.

  On the other hand, in the image forming unit, when an image forming operation start signal is issued, a high voltage is applied to the toner image formed on the photosensitive drum 11a that is the most upstream in the rotation direction of the intermediate transfer belt 30 by the process described above. By the transferred transfer roller 35a, primary transfer is performed to the intermediate transfer belt 30 in the primary transfer region. The primarily transferred toner image is conveyed to the next primary transfer area.

  Here, image formation is performed with a delay of the time during which the toner image is conveyed between the image forming units, and the next toner image is transferred with the leading edge of the image aligned on the previous image. The same process is repeated thereafter, and a four-color toner image and a transparent toner image are primarily transferred onto the intermediate transfer belt 30.

  Thereafter, when the recording material P enters the secondary transfer area and contacts the intermediate transfer belt 30, a high voltage is applied to the secondary transfer roller 36 in accordance with the passing timing of the recording material P. Then, the toner image formed on the intermediate transfer belt by the process described above is transferred onto the surface of the recording material P. Thereafter, the recording material P is guided to the fixing roller nip portion. The toner image is fixed on the paper surface by the heat of the roller pair 41a and 41b and the pressure of the nip. Thereafter, the sheet is discharged to the face-up discharge tray 2 or the face-down tray 3 according to the switching direction of the switching flapper 73.

  In the case of face-down paper discharge, the gloss of the image formed on the recording material P can be detected by the gloss sensor 80.

  FIG. 8 is a control block diagram of the control unit 59.

  The CPU 801 performs basic control of the full color copying machine. A ROM 802 in which a control program is written and a work RAM 803 for processing are connected to the CPU 801 via an address bus and a data bus. It is assumed that the ROM stores a control procedure, a gradation test pattern, and the like shown in FIG. The reader control unit 806 and the printer control unit 807 are electric circuits including an input / output port for controlling each component of the reader unit and the printer unit, respectively. The control CPU 801 controls the reader control unit 806 and the printer control unit 807 according to the contents of the control program, and executes an image forming operation.

  The image processing unit 805 performs various types of image processing on the digital data of the document image converted by the reader control unit 806.

  An operation unit 900 is connected to the CPU 801. FIG. 9A shows a schematic diagram of the operation unit 900, which includes a key input unit 9000 and a touch panel unit 9001. FIG. 9 (b) and FIG. 9 (c) show details of each, and details of each will be described below.

  First, FIG. 9 (b) shows a key input portion that can perform routine operation settings.

  The operation unit power switch 901 switches between a standby mode (normal operation state) and a sleep mode (state in which power consumption is suppressed), and is controlled with the main power switch that supplies power to the entire image forming apparatus being ON. be able to.

  The power saving key 902 is a key that can reduce the power consumption by lowering the control temperature of the fixing device in the standby mode and taking time until it can be printed. The control temperature can be lowered by setting the power saving rate.

  A start key 903 is a key for instructing the start of copying or the like, and a stop key 904 is a key for interrupting it.

  A numeric keypad 905 is a key for performing various setting numbers, and a clear key 906 is a key for canceling the number. The ID key 907 is a key for inputting a preset password for authenticating the operator of the apparatus.

  A reset key 908 is a key for invalidating various settings and returning to a default state. A help key 909 is a key for displaying guidance and help, and a user mode key 910 is a key for shifting to a user mode screen for performing system settings and various adjustments.

  A counter confirmation key 911 is a key for displaying the number of output sheets stored in a soft counter that counts the number of printed sheets. Depending on the operation mode such as copy / print / scan, color mode such as color / monochrome, paper size such as large / small, the number of output sheets can be displayed.

  The image contrast dial 912 is a dial for adjusting the visibility of the screen by adjusting the backlight of the liquid crystal display of the touch panel unit.

  The execution / memory lamp 913 is a lamp that flashes to notify during job execution or access to the memory, and the error lamp 914 indicates an error such as a case where the job cannot be executed or a serviceman call, or a jam or exhaustion. It is a lamp that flashes and notifies when an operator call is made to notify that the product is out of stock.

  Next, FIG. 9C is a schematic diagram showing a touch panel display composed of an LCD (Liquid Crystal Display) and a transparent electrode pasted thereon, and corresponds to a key displayed on the LCD. When the transparent electrode is touched with a finger, it is detected in advance, and another operation screen is displayed. This figure is an initial screen in the standby mode, and various operation screens can be displayed according to the setting operation.

  A color selection setting key 950 is a key for selecting in advance whether color copying, black-and-white copying, or automatic selection, and a magnification setting key 951 is a key for changing to a screen for setting magnification such as equal magnification, enlargement, reduction, etc. , Post-processing setting key 952 is a key for transitioning to a screen for setting the presence / absence, number, position, etc. of stapling and punching. Double-side setting key 953 is a key for transitioning to a screen for selecting single-sided printing or double-sided printing A setting key 954 is a key for transitioning to a screen for selecting a paper feed stage, paper size, and media type. An image mode setting key 955 is a key for selecting an image mode suitable for a document image such as a character mode or a photo mode. A density setting key 956 is a key for adjusting the output image to be darker or lighter.

  Next, the status display unit 960 is a display unit that displays simple status such as standby state, warming up, jam, error, etc., and the magnification display unit 961 displays the magnification set with the magnification setting key. The paper size display section 962 displays the paper size and mode set with the paper size setting key, and the number display section 963 displays the number of sheets specified with the numeric keypad, and the number of sheets being printed during operation Or display.

  Furthermore, the interrupt key 957 is used to interrupt another job during the copying operation, and the application mode key 958 is used for various image processing and layout such as page continuous shooting, cover / interleaf setting, reduced layout, and image movement. It is a key for transitioning to a screen for setting such as.

  FIG. 3 is a block diagram showing an internal configuration of the image processing unit 805 in FIG.

  The original image formed on the CCD sensor 217 is converted into an analog electric signal by the CCD sensor 217. The converted image information is input to the analog signal processing unit 300 for sample & hold, dark level correction, and the like, and then the analog / digital conversion (A / D conversion) is performed by the A / D / SH processing unit 301. Further, shading correction is performed on the digitized signal. In the shading correction, correction for variation of each pixel of the CCD sensor 217 and correction of variation in light quantity depending on the position based on the light distribution characteristic of the document illumination lamp are performed.

  Thereafter, RGB line correction is performed in the RGB line correction unit 302. Since the light input to the RGB light receiving portions of the CCD sensor 217 at a certain time is shifted on the document according to the positional relationship of the RGB light receiving portions, the RGB signals are synchronized here.

  Thereafter, the conversion unit 303 converts RGB into a YMC signal by direct mapping. Next, in background removal 304, a K signal is generated from the Y, M, and C signals. In this case, the minimum value among the densities of the Y, M, and C signals is subtracted as a gray component to obtain respective density signals Dy, Dm, and Dc. Then, the gray component is subjected to gain adjustment to obtain a K density signal Dk.

Next, the gloss component generation unit 305 generates a transparent toner signal T from the Y, M, C, and K signals. This obtains the density signal Dt of the transparent toner, which is a gloss component, from the density signals Dy, Dm, Dc, and Dk of the Y, M, C, and K signals. In this embodiment, Dt is obtained by subtracting the sum of Dy, Dm, Dc, and Dk from a predetermined maximum density value Dmax. Ie
Dt = Dmax-(Dy + Dm + Dc + Dk)
As required.

  The halftone correction unit 306 uses YLUT-4C, which will be described later, for Y, M, C, and K so that the image density at the initial setting of the printer engine unit matches the output density image processed according to the γ characteristics. The image density signals Dy, Dm, Dc and Dk are converted into For transparent toner T, γLUT-T, which will be described later, is used to convert the image density at the initial setting of the printer engine unit and the image density into a gloss signal, and the output image gloss processed by the γ characteristic has a predetermined linear relationship. The image density signal Dt is converted so that

  The image density signal thus converted is input to the laser driver 308 as a signal subjected to pulse width modulation by the pulse width modulation unit 307.

  A pulse generator 310 generates a gradation test pattern to be described later. In this embodiment, gradation reproduction means using pulse width modulation processing in which pixels are arranged in the sub-scanning direction is used for all colors, and static characteristics having gradation characteristics due to dot area changes on the photosensitive drums 11a to 11e by scanning with laser light. An electrostatic latent image is formed.

  Next, FIG. 4 shows a 4-limit chart showing the characteristics for reproducing the density of an original image for Y, M, C, and K. FIG. In FIG. 4, quadrant I indicates the characteristics of the reading unit that converts the document density into a density signal, and quadrant II indicates the characteristics of γLUT-4C for converting the density signal into a laser output signal. The third quadrant shows the characteristics of the printer that converts the laser output signal to the printer output density, and the fourth quadrant shows the relationship between the document density and the printer output density. In this embodiment, in order to make the gradation characteristics linear as shown in the fourth quadrant, the recording characteristic distortion of the printer unit shown in the third quadrant is corrected by the γLUT-4C shown in the second quadrant. . In this embodiment, since the image signal is processed as an 8-bit digital signal, the number of gradations is 256.

  Next, FIG. 5 shows a 4-limit chart showing characteristics for gloss reproduction of the transparent toner T. In FIG. 5, the quadrant I is the relationship between the transparent toner density and the gloss signal and indicates the characteristics of the gloss sensor. The second quadrant shows the characteristics of γLUT-T for converting the gloss signal into a laser output signal. The third quadrant shows the characteristics of the printer that converts the laser output signal to the printer output gloss, and the fourth quadrant shows the relationship between the density signal and the printer output gloss. In this embodiment, in order to make the glossy gradation characteristic linear as shown in the fourth quadrant, the distortion of the recording characteristics of the printer unit shown in the third quadrant is corrected by γLUT-T shown in the second quadrant. Yes. In this embodiment, since the image signal is processed as an 8-bit digital signal, the number of gradations is 256.

  Next, a method for detecting a gloss signal will be described. FIG. 6A shows the configuration of the gloss sensor 80, and FIG. 6B shows the operating principle. In FIG. 6A, reference numeral 601 denotes a light source, for example, a visible red LED. Reference numeral 602 denotes a detection unit that uses, for example, a line sensor, and detects a regular reflection component in which light from a light source is reflected by an object. Reference numeral 603 denotes an amplifier that amplifies the signal from the detection unit 602 and outputs an amplified signal 604. In FIG. 6B, when the object is irradiated with light, the reflection state changes according to the glossiness of the reflection surface, and the detection portion spot 610 changes. When the glossiness is high, the light projection spot is specularly reflected as it is, and when the glossiness is low, the light spot is irregularly reflected, so the light receiving state of the line sensor 611 changes. Correspondingly, the output 612 changes, and the glossiness is determined based on this difference.

  Next, in the present invention, a method for correcting gradation of glossiness will be described in detail.

  A user mode screen 700 shown in FIG. 7A is displayed by the user mode key 910 in FIG. 9B. Various setting and adjustment item keys are displayed on the user mode screen, and when an “adjustment / cleaning” key 701 is selected, an adjustment / cleaning screen 710 shown in FIG. 7B is displayed. On the adjustment / cleaning screen 710, there is an automatic gradation correction key 711 for executing automatic gradation correction.

  FIG. 7C shows an automatic gradation correction screen 720 displayed when the automatic gradation correction key 711 is selected. 721 is an execution key for outputting a test print, and 722 is a cancel key for returning to the adjustment / cleaning screen 710.

  FIG. 7D shows a scan screen 730 displayed after the test print key 721 is selected. Reference numeral 731 denotes a key for executing a scan of the output test print, and reference numeral 732 denotes a cancel key for returning to the adjustment / cleaning screen 710.

  Next, the procedure of the gradation correction operation will be described using the flowchart of FIG.

  The image forming apparatus determines whether or not the test print key 721 in FIG. 7C, which is an automatic gradation correction execution key, is pressed in step S1 in FIG. 1, and if the test print key 721 is pressed, in step S2. A gradation patch is formed. In step S2, latent images of gradation test patterns for all colors are formed on the color drums according to the gradation test patterns registered in the ROM 802 of FIG. 8 by the pattern generator 310 of FIG. Thereafter, it is transferred and fixed on the recording material. When outputting the gradation pattern of all the colors, as shown in FIG. 3, the γLUT-4C and γLUT-T of the halftone correction unit are output without acting. An example of the gradation pattern of all colors is shown in FIG. 10. A pattern in which the density level of transparent toner is changed is 1001, a pattern in which the density level of yellow toner is changed is 1002, and a pattern in which the density level of magenta toner is changed is 1003. A pattern in which the density level of cyan toner is changed is 1004, and a pattern in which the density level of black toner is changed is 1005. In step S3, the glossiness of the gradation patch of the transparent toner is detected. In step S3, the glossiness of the transparent toner gradation patch on the recording material conveyed by being reversed and discharged is read by the gloss sensor 80 of FIG. 2, and the glossiness of each gradation level is stored in the RAM 803 of FIG. In step S4, γLUT-T is created. In step S4, the relationship between the laser output level and the read glossiness when the gradation test pattern is created is obtained and stored in the RAM 803. Based on this relationship, the printer characteristics shown in the third quadrant of FIG. 5 are obtained. Then, by changing the input / output relationship of this characteristic, the printer gamma correction characteristic shown in the second quadrant is determined for each density, and γLUT-T is set. In creating γLUT-T, there is only data of the number of gradation patterns of the gradation test pattern, so that the laser output level can correspond to all levels from 0 to 255 of the density signal. Set by performing interpolation.

  Next, in step S5, the recording material on which the gradation test pattern discharged from the apparatus is formed is placed on the original platen glass 211 shown in FIG. 2 as an original, and the scan key 731 shown in FIG. , Cyan and black gradation patches are read and stored in the RAM 803 of FIG. 8 as density data. In step S6, γLUT-4C is created. In step S6, the relationship between the laser output level and the reading density when the gradation test pattern is created is obtained and stored in the RAM 803. Based on this relationship, the printer characteristics shown in the third quadrant of FIG. 4 are obtained. Then, by switching the input / output relationship of this characteristic, the printer γ correction characteristic shown in the second quadrant is determined for each density, and γLUT-4C is set. In creating γLUT-4C, there is only data of the number of gradation patterns of the gradation test pattern, so that the laser output level can correspond to all levels from 0 to 255 of the density signal. Set by performing interpolation.

  Thus, the process ends and the printer enters a standby state.

(Other examples)
In this embodiment, the glossiness of the transparent toner of the gradation test pattern is detected and the γLUT is set.However, the laser power, the charging bias, the developing bias, or the transfer bias is determined based on the glossiness detection result. It is also possible to control the gradation of glossiness by correcting.

  As described above, according to the image forming apparatus of the present invention, the automatic gradation correction mode is executed in the image forming apparatus in which the gloss level can be changed in multiple stages using the color toner and the transparent toner. It is possible to always print a printed matter having the same glossiness by correcting a difference in glossiness due to a change over time such as a change in conditions and a characteristic change due to durability of the apparatus.

5 is a flowchart illustrating a tone correction processing procedure according to an embodiment of the present invention. 1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention. The block diagram of the image processing part in the Example of this invention. FIG. 4 is a diagram illustrating tone reproduction characteristics of color toners according to an embodiment of the present invention. FIG. 6 is a diagram illustrating tone reproduction characteristics of a transparent toner according to an embodiment of the present invention. Explanatory drawing of the gloss sensor in the Example of this invention. The figure which shows the user mode screen in the Example of this invention. 1 is a control block diagram of an image forming apparatus in an embodiment of the present invention. FIG. 3 is an explanatory diagram of an operation unit of the image forming apparatus according to the embodiment of the present invention. FIG. 6 is a diagram illustrating an output example of a gradation test pattern in the embodiment of the present invention.

Claims (3)

In an image forming apparatus that forms an image using color toner and transparent toner,
Means for forming a plurality of gradation patch toner images on the recording material; means for fixing the patch toner image formed on the recording material; and a first means for reading the color toner gradation patches on the recording material after fixing. An image forming method comprising: a reading unit; and a second reading unit that reads a gradation patch using a transparent toner on a recording material after fixing, and correcting an image forming condition using the read result apparatus.   The image forming apparatus according to claim 1, wherein a patch using a color toner patch and a transparent toner is read in a special operation mode different from a normal image forming operation.   The image forming apparatus according to claim 1, wherein at least one of an image processing parameter, a laser power, a charging bias, a developing bias, and a transfer bias is corrected as an image forming condition to be corrected.

Images