JP2017173800A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable tracking of forged bills and obtain a satisfactory image in an image forming mode of increasing the density of an image.SOLUTION: In a first image forming mode, an image forming apparatus forms an image at a first development contrast C1, and forms a specific dot pattern at a second development contrast C2 smaller than the first development contrast C1; in a second image forming mode, the image forming apparatus forms an image at a third development contrast C3, and forms a specific dot pattern at a fourth development contrast C4 smaller than the third development contrast C3; when the ratio of the second development contrast C2 to the first development contrast C1 is ΔC1(=C2/C1) and the ratio of the fourth development contrast C4 to the third development contrast C3 is ΔC2(=C4/C3), ΔC2 is smaller than ΔC1.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an image forming apparatus that forms an image on a recording medium using electrophotographic technology.

  Conventionally, in an image forming apparatus such as a laser beam printer, an in-line color system in which a plurality of image forming stations are provided in the moving direction of an intermediate transfer belt is known. In an in-line color image forming apparatus, first, an electrostatic latent image is formed on the surface of a photosensitive drum at a plurality of image forming stations. The electrostatic latent image formed on the photosensitive drum is developed as a toner image by a developing device. In addition, the toner images of the respective colors formed at the plurality of image forming stations are primarily transferred to be superimposed on the intermediate transfer belt. Then, the toner images of the respective colors primarily transferred to the intermediate transfer belt are secondarily transferred to a sheet such as paper. Thereafter, the sheet on which the toner image is secondarily transferred is heated and pressed by the fixing device, whereby the toner image is fixed on the sheet. In this way, an image is formed on the sheet. Here, it is desirable that the density of the image formed on the sheet is the density desired by the user. Also, it is desirable that the color of the image formed on the sheet has the color desired by the user.

  Therefore, in the technique disclosed in Patent Literature 1, the color gamut of the image is expanded and the upper limit value of the image density is increased by changing the peripheral speed difference between the photosensitive drum and the developing roller. Further, the technique disclosed in Patent Document 1 suppresses scattering of toner, blurring of an image, and the like due to an increase in the peripheral speed difference between the photosensitive drum and the developing roller. Specifically, the peripheral speed difference between the photosensitive drum and the developing roller is not increased by increasing the peripheral speed of the developing roller, but the peripheral speed difference between the photosensitive drum and the developing roller is decreased by decreasing the peripheral speed of the photosensitive drum. It is spreading. As a result, toner scattering and image fading are suppressed.

  In recent years, new problems have arisen due to widespread use of image forming apparatuses capable of stably printing high-quality images. That is, it is possible to easily print items similar to banknotes and securities using a full-color image forming apparatus. In order to solve this problem, in the technology disclosed in Patent Document 2, when printing an image, a regular dot pattern indicating the machine number of the image forming apparatus is driven on the paper. Thereby, when a printed matter similar to a banknote is discovered, the machine body number is determined from the dot pattern struck on the banknote, and it can be specified by which image forming apparatus the printed matter is printed.

  In the technique disclosed in Patent Document 3, the density of a portion near a portion to which a dot pattern indicating information related to the image forming apparatus is added is detected on the sheet, and the dot pattern is changed according to the concentration near the portion. Yes. Specifically, when the density in the vicinity of the portion to which the dot pattern is added is high, the dot pattern can be recognized by narrowing the interval between the dots constituting the dot pattern. On the other hand, when the density in the vicinity of the portion to which the dot pattern is added is low, the pattern is prevented from being visualized by widening the interval between the dots constituting the dot pattern.

JP 2013-210489 A Japanese Patent Application Laid-Open No. 10-077635 JP 2001-103282 A

However, when the technique disclosed in Patent Literature 2 and Patent Literature 3 is adopted, the dot pattern hit on the paper is visualized by increasing the image density. There is a fear. Specifically, in an image forming apparatus that forms on a sheet a dot pattern that cannot be visually confirmed to identify a manufacturer or the like, when the image density is increased by the peripheral speed ratio between the photosensitive drum and the developing roller, the dot pattern Concentration will also increase. In this case, there is a possibility that a good image cannot be obtained because the dot pattern hit on the paper has a density visible to the user.
Accordingly, an object of the present invention is to provide a technique capable of obtaining a good image even when the peripheral speed ratio between an image carrier and a developer carrier during image formation is changed.

In order to achieve the above object, an image forming apparatus of the present invention includes:
A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier is set to a first peripheral speed ratio ΔV1 to form an image based on the image information. Image formation mode,
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image formation mode, an image is formed with a first development contrast C1, the specific dot pattern is formed with a second development contrast C2 smaller than the first development contrast C1,
In the second image forming mode, an image is formed with a third development contrast C3, the specific dot pattern is formed with a fourth development contrast C4 smaller than the third development contrast C3,
The ratio between the second development contrast C2 and the first development contrast C1 is ΔC1 (= C2 / C1), and the ratio between the fourth development contrast C4 and the third development contrast C3 is ΔC2 (= C4 / C3). When
ΔC2 <ΔC1
It is characterized by being.
In order to achieve the above object, the image forming apparatus of the present invention includes:
A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier is set to a first peripheral speed ratio ΔV1 to form an image based on the image information. Image formation mode,
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image formation mode, an image is formed with a first development contrast C1, the specific dot pattern is formed with a second development contrast C2 smaller than the first development contrast C1,
In the second image forming mode, an image is formed with a third development contrast C3, the specific dot pattern is formed with a fourth development contrast C4 smaller than the third development contrast C3,
The absolute value of the difference between the second development contrast C2 and the first development contrast C1 is ΔC1 (= | C2-C1 |), and the absolute value of the difference between the fourth development contrast C4 and the third development contrast C3 is ΔC2. (= | C4-C3 |)
ΔC2 <ΔC1
It is characterized by being.
In order to achieve the above object, the image forming apparatus of the present invention includes:
A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A first image for forming an image based on the image information by setting a peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier to a first peripheral speed ratio ΔV1. Formation mode;
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
The interval between two adjacent dots among the plurality of dots forming the specific dot pattern in the second image forming mode is wider than the interval between the two dots in the first image forming mode. To do.
In order to achieve the above object, the image forming apparatus of the present invention includes:
A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A first image for forming an image based on the image information by setting a peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier to a first peripheral speed ratio ΔV1. Formation mode;
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image forming mode, an image is formed by supplying a developer to the image carrier so that the first developer loading amount M1 is in a region corresponding to the image, and the image corresponds to the specific dot pattern. Supplying the developer to the image carrier so that the second developer loading amount M2 is smaller than the first developer loading amount in the region, and forming the specific dot pattern;
In the second image forming mode, an image is formed by supplying a developer to the image carrier so that the third developer amount M3 is provided in an area corresponding to the image, and corresponding to the specific dot pattern. A developer is supplied to the image carrier so as to have a fourth developer loading amount M4 smaller than the third developer loading amount in a region to be formed to form the specific dot pattern;
The ratio between the second developer loading amount M2 and the first developer loading amount M1 is ΔM1 (= M2 / M1), and the ratio between the fourth developer loading amount M4 and the third developer loading amount M3 is ΔM2. (= M4 / M3)
ΔM2 <ΔM1
It is characterized by being.
In order to achieve the above object, the image forming apparatus of the present invention includes:
A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A first image for forming an image based on the image information by setting a peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier to a first peripheral speed ratio ΔV1. Formation mode;
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image forming mode, an image is formed by supplying a developer to the image carrier so that the first developer loading amount M1 is in a region corresponding to the image, and the image corresponds to the specific dot pattern. Supplying the developer to the image carrier so that the second developer loading amount M2 is smaller than the first developer loading amount in the region, and forming the specific dot pattern;
In the second image forming mode, an image is formed by supplying a developer to the image carrier so that the third developer amount M3 is provided in an area corresponding to the image, and corresponding to the specific dot pattern. A developer is supplied to the image carrier so as to have a fourth developer loading amount M4 smaller than the third developer loading amount in a region to be formed to form the specific dot pattern;
The absolute value of the difference between the second developer applied amount M2 and the first developer applied amount M1 is ΔM1 (= | M2−M1 |), and the fourth developer applied amount M4 and the third developer applied amount. When the absolute value of the difference of M3 is ΔM2 (= | M4-M3 |),
ΔM2 <ΔM1
It is characterized by being.

  The present invention can obtain a good image even when an image is formed with a larger peripheral speed ratio.

1 is a schematic sectional view of an image forming apparatus according to a first embodiment. 1 is a schematic sectional view of a process cartridge according to a first embodiment. 1 is a schematic cross-sectional view of a fixing device according to Embodiment 1. FIG. 10 is a diagram illustrating a flow of processing executed by the image forming apparatus according to the first embodiment. FIG. 6 is a diagram illustrating a relationship between the amount of toner placed on paper and the density of an image in the first embodiment. The figure which shows the relationship between the electric potential of a photosensitive drum, and the toner amount mounted on a recording material. The figure which shows the tracking pattern in normal image formation mode The figure which shows the tracking pattern in wide color gamut image formation mode The figure which shows the tracking pattern in normal image formation mode The figure which shows the tracking pattern in wide color gamut image formation mode The figure which shows the tracking pattern in normal image formation mode The figure which shows the tracking pattern in wide color gamut image formation mode

  Embodiments of the present invention are illustrated below with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described in the embodiments should be appropriately changed depending on the configuration of the apparatus to which the invention is applied and various conditions. This is not intended to limit the scope to the following embodiments.

Example 1
<Overall Configuration of Image Forming Apparatus 200>
In this embodiment, the normal image forming mode in which an image is formed at a normal density, and the peripheral speed ratio Vd / Vdr between the peripheral speed Vdr of the photosensitive drum 201 and the peripheral speed Vd of the developing roller 302 are changed to change the color of the image. A wide color gamut image forming mode for enlarging the gamut can be executed. In each image forming mode, the peripheral speed ratio between the photosensitive drum 201 as the image carrier and the developing roller 302 as the developer carrier is different. Here, the peripheral speed ratio between the photosensitive drum 201 and the developing roller 302 is expressed by the peripheral speed ratio = the peripheral speed of the developing roller 302 / the peripheral speed of the photosensitive drum 201 × 100 (%). When the photosensitive drum and the developing roller are in contact with each other and rotating in the same direction as shown in the figure, the peripheral speed ratio is as follows. When the photosensitive drum is rotating at 200 mm / sec and the developing roller is rotating at 200 mm / sec, the peripheral speed ratio is 100%. On the other hand, when rotating in a different direction at the contacting portion, the peripheral speed ratio becomes −100%.

  In the normal image forming mode, the toner as the developer attached to the developing roller 302 is caused by the development contrast between the potential of the electrostatic latent image as the electrostatic image formed on the photosensitive drum 201 and the potential of the developing roller 302. It is conveyed to the photosensitive drum 201. Thereby, the electrostatic latent image as the electrostatic image formed on the photosensitive drum 201 as the image carrier is developed as a toner image. On the other hand, in the wide color gamut image forming mode, the toner supply amount per unit area from the developing roller 302 to the photosensitive drum 201 is increased by increasing the peripheral speed ratio between the photosensitive drum 201 and the developing roller 302. As a result, the maximum amount of toner that can adhere to the developing roller 302 by the action of the developing contrast between the potential of the electrostatic latent image formed on the photosensitive drum 201 as the image carrier and the potential of the developing roller is the photosensitive drum. It is conveyed to 201.

  Hereinafter, the process cartridge 208 and the image forming apparatus 200 according to the present embodiment will be described. FIG. 1 is a schematic cross-sectional view of an image forming apparatus 200 according to the first embodiment. The image forming apparatus 200 according to the present embodiment is an inline-type full-color laser printer that employs an intermediate transfer method. The image forming apparatus 200 can form a full-color image on a recording material P (for example, recording paper) as a recording medium according to the image information. Image information is received in the image forming apparatus 200 from an image reading apparatus (not shown) connected to the image forming apparatus 200 or a host device (not shown) such as a personal computer connected to the image forming apparatus 200 so as to be communicable. It is input to the provided CPU 20.

  Further, the image forming apparatus 200 forms first to fourth image formations for forming images of each color of yellow (Y), magenta (M), cyan (C), and black (K) as a plurality of image forming units. Part S (SY, SM, SC, SK). Here, the image forming unit S includes a process cartridge 208 and a primary transfer roller 212 (212Y to 212K) disposed to face the photosensitive drum 201 with the intermediate transfer belt 205 interposed therebetween. In the present embodiment, the first to fourth image forming units SY to SK are arranged in a line in a direction intersecting the vertical direction and the horizontal direction. In the present embodiment, the configurations and operations of the first to fourth image forming units SY to SK are substantially the same except that the colors of the formed images are different. Accordingly, the subscripts Y, M, C, and K are omitted and collectively described unless otherwise distinguished. However, the present invention is not limited to this, and the black (K) shape may be large and the image forming unit may be larger than the other image forming units. Further, it is effective in a configuration having a fifth image forming unit using white toner or transparent toner.

  The image forming apparatus 200 includes, as a plurality of image carriers, a photosensitive drum 201 that is four drum-type electrophotographic photosensitive members arranged side by side in a direction crossing the vertical direction. The photosensitive drum 201 as an image carrier is rotationally driven by a driving force of a motor (see FIG. 2) in the direction of arrow A (clockwise) in FIG. In addition, an electrostatic latent image is formed on the photosensitive drum 201 by irradiating a laser on the periphery of the photosensitive drum 201 as a charging unit 202 that uniformly charges the surface of the photosensitive drum 201 and a laser based on image information. A scanner unit 203 to be formed is arranged.

  Further, around a photosensitive drum 201 as an image carrier, a developing unit 204 that develops an electrostatic latent image as a toner image, and toner as a developer remaining on the surface of the photosensitive drum 201 after the toner image is transferred. A cleaning blade 206 is provided for removing water. Further, a pre-exposure LED 216 for discharging the potential on the photosensitive drum 201 is disposed around the photosensitive drum 201. Further, an intermediate transfer belt 205 for transferring a toner image on the photosensitive drum 201 to a recording material P as a recording medium is disposed so as to face the four photosensitive drums 201.

  The photosensitive drum 201, the charging roller 202, the developing unit 204, and the cleaning blade 206 as an image carrier are integrally configured as a process cartridge 208. The process cartridge 208 is detachable from the apparatus main body of the image forming apparatus 200. In the present embodiment, the process cartridges 208 for each color have the same shape, and yellow (Y), magenta (M), cyan (C), and blank (K) are contained in the process cartridges 208 for each color. Each toner is stored as a developer of each color. In this embodiment, a toner having a negative charging characteristic is used as the toner as the developer. In this embodiment, the process cartridge in which the photosensitive drum and the developing unit are integrally configured is described. However, the present invention is not limited to this. The photosensitive unit having the photosensitive drum and the developing unit having the developer carrying member may be configured to be detachable from the apparatus main body of the image forming apparatus. The toner is also a one-component developer, but may be two-component or magnetic depending on the configuration.

  The intermediate transfer belt 205 formed of an endless belt abuts on all the photosensitive drums 201 and moves in the direction of arrow B (counterclockwise) in FIG. The intermediate transfer belt 205 is stretched by a driving roller 209, a secondary transfer counter roller 210, and a driven roller 211. Four primary transfer rollers 212 are juxtaposed on the inner peripheral surface side of the intermediate transfer belt 205 so as to face each photosensitive drum 201. A bias (positive polarity in this embodiment) having a polarity opposite to the normal charging polarity of the toner is applied to the primary transfer roller 212 from a primary transfer bias power source (not shown). As a result, the toner image on the photosensitive drum 201 is transferred onto the intermediate transfer belt 205.

  Further, on the outer peripheral surface side of the intermediate transfer belt 205, a secondary transfer roller 213 is disposed at a position facing the secondary transfer counter roller 210. A bias having a polarity opposite to the normal charging polarity of the toner is applied to the secondary transfer roller 213 from a secondary transfer bias power source (not shown). As a result, the toner image on the intermediate transfer belt 205 is transferred to a recording material P as a recording medium.

<Configuration of Process Cartridge 208>
Next, the overall configuration of the process cartridge 208 that is attached to and detached from the image forming apparatus 200 according to the present embodiment will be described with reference to FIG. FIG. 2 is a schematic cross-sectional view of the process cartridge 208 according to the first embodiment. Specifically, FIG. 2 is a schematic cross-sectional view of the process cartridge 208 viewed from the direction of the rotation center axis of the photosensitive drum 201. In the present embodiment, the configuration and operation of the process cartridge 208 for each color are the same except for the type (color) of the toner to be stored. Of course, depending on the configuration, the configuration and operation of each process cartridge can be changed as appropriate.

The process cartridge 208 includes a photosensitive unit 301 including a photosensitive drum 201 as an image carrier, and a developing unit 204 including a developing roller 302 as a developer carrier. The photoreceptor unit 301 includes a cleaning frame 303 that supports various elements in the photoreceptor unit 301. A photosensitive drum 201 is rotatably attached to the cleaning frame 303 via a bearing (not shown). In addition, the photosensitive drum 201 as an image bearing member transmits a driving force of a motor (see FIG. 2) to the photosensitive unit 301, so that an arrow A direction (clockwise direction) in FIG. 2 corresponds to an image forming operation. ).

  For the photosensitive drum 201 which is the center of the image forming process, an organic photoreceptor is used in which an undercoat layer, a carrier generation layer, and a carrier transport layer, which are functional films, are sequentially coated on the outer peripheral surface of an aluminum cylinder. In addition, a cleaning blade 206 and a charging roller 202 are disposed in the photoreceptor unit 301 so as to come into contact with the peripheral surface of the photosensitive drum 201. Further, the transfer residual toner removed from the surface of the photosensitive drum 201 by the cleaning blade 206 is accommodated in the cleaning frame 303.

  A charging roller 202 serving as a charging unit rotates following the photosensitive drum 201 when a roller portion of conductive rubber is pressed against the photosensitive drum 201. Here, a predetermined DC voltage is applied to the core of the charging roller 202, thereby forming a uniform dark portion potential (Vd) on the surface of the photosensitive drum 201. Further, as described above, the scanner unit 203 as an exposure apparatus exposes the photosensitive drum 201 with the laser light emitted corresponding to the image data.

  Then, the electric charge on the surface of the photosensitive drum 201 is lost by the carrier from the carrier generation layer, so that the potential of the exposed surface of the photosensitive drum 201 is lowered. As a result, on the surface of the photosensitive drum 201, a portion exposed by the laser has a predetermined bright portion potential (Vl), and an unexposed portion not exposed by the laser has a predetermined dark portion potential (Vd). As a result, an electrostatic latent image as an electrostatic image is formed on the photosensitive drum 201.

  The developing unit 204 has a developing roller 302 (rotated in the direction of arrow D), a developing blade 308, and a toner supply roller 304 (rotated in the direction of arrow E) as a developer carrier. The developing unit 204 has a toner storage chamber 306 that stores toner as a developer. The toner as the developer is stirred in the toner storage chamber 306 by the movement of the stirring member 307 (rotated in the arrow G). In this embodiment, a predetermined DC bias is applied to the developing roller 302 as the developer carrying member. In the developing portion where the photosensitive drum 201 and the developing roller 302 abut, toner adheres to the bright portion potential portion of the photosensitive drum 201 due to a potential difference between the photosensitive drum 201 and the developing roller 302. Thereby, an electrostatic latent image as an electrostatic image on the photosensitive drum 201 is visualized.

<Configuration of fixing device>
FIG. 3 is a schematic cross-sectional view of the fixing device 400 according to the first embodiment. The fixing device 400 according to this embodiment is a pressure roller driving type fixing device, and includes a heating body 410, a cylindrical film 430 that is in sliding contact with the heating body 410, and the heating body 410 and the fixing nip via the film 430. And a pressure roller 440 that forms part N. The recording material P as a recording medium is nipped and conveyed in the fixing nip portion N and is heated by heat from the heating body 410. As a result, the unfixed image formed on the recording material P as the recording medium is heated and fixed to the recording material P.

  The heating body 410 is in pressure contact with a pressure roller 440 that is a pressure member through a cylindrical film 430 as a flexible member while being held by the heating body support 420. . Further, the pressure roller 440 is driven to rotate in the direction of arrow H in FIG. When the pressure roller 440 rotates, the film 430 rotates in the direction of arrow I in FIG. 3 by sliding with the outer peripheral surface of the film 430. Specifically, the film 430 rotates in the direction of arrow I around the heating body support 420 that holds the heating body 410.

  In addition, the heating body 410 is energized and heated by supplying electric power from the commercial power supply to the heating body 410 by the heating body driving circuit 470. The heating body 410 is controlled to a predetermined print temperature control. In this state, the recording material P carrying the unfixed toner image T is nipped and conveyed in the direction of the arrow F at the fixing nip N. Then, the heat of the heating body 410 is applied to the recording material P through the film 430, whereby the unfixed toner image T is fixed to the recording material P. Thereafter, the recording material P that has passed through the fixing nip N is discharged after being separated from the surface of the film 430 by curvature. In the fixing device 400 according to the present exemplary embodiment, the sheet passing reference of the recording material P is the central portion in the longitudinal direction of each member (the direction perpendicular to the arrow F direction of the recording material P).

  For the cylindrical film 430, for example, a thin film cylinder based on polyimide or SUS having a thickness of about 30 μm to 100 μm is used. Then, by applying a coating such as PFA or PTFE on the base layer via a primer layer, the releasability from the toner is maintained. In addition, a sliding grease (not shown) is applied between the inner peripheral surface of the film 430 and the heating body support 420, thereby maintaining the slidability between the film 430 and the heating body support 420. Yes.

  The pressure roller 440 is a rotating body in which an elastic layer such as silicone rubber is formed on a cored bar. In this embodiment, a release layer such as FEP or PFA having a thickness of about 10 to 100 μm is provided on the base layer via a primer layer. Thereby, the releasability with the toner is maintained. In addition, the heating body support 420 is made of a high heat-resistant resin such as PPS, PAI, PI, PEEK, or liquid crystal polymer having heat insulation, high heat resistance, and rigidity, or a composite of these resins with ceramics, metal, glass, or the like. It is made of materials. PPS is polyphenylene sulfide, PAI is polyamideimide, PI is polyimide, and PEEK is polyetheretherketone. The rotation driving unit 480 includes a motor 481 that rotates the pressure roller 440 and a control unit 482 (CPU) that controls the rotation of the motor 481. As the motor 481, for example, a DC motor or a stepping motor can be used.

<Explanation of tracking pattern>
In this embodiment, a dot pattern that cannot be seen with the naked eye is formed on the recording material P on which an image is formed. As a result, the machine number of the image forming apparatus that is the manufacturer can be determined from the hit dot pattern. Therefore, it can be specified by which image forming apparatus which is the manufacturer that the banknote is printed. This method is generally called a tracking pattern method. The tracking pattern is usually formed using yellow toner with low visibility. The tracking pattern indicates various information such as the manufacturer name of the output device, the model name, the machine number, and the output status when the image is output to the recording material P. In this embodiment, the tracking pattern is a dot pattern formed from a plurality of dots. The position where the dot pattern is added on the image is obtained by using means such as converting information to be superimposed based on a certain rule. Various rules for converting to position information can be considered. For example, it is conceivable that the machine number and model name of the printer main body are expressed in binary series, and “1” and “0” are each expressed by the presence or absence of a dot pattern. However, the method is not particularly limited in this embodiment. In this embodiment, the image formed on the recording material P by the image forming apparatus 200 is a digital image formed from a plurality of dots. The tracking pattern is read using a dedicated reading device. Contrary to the process of converting the information to be superimposed into the dot pattern, an appropriate process for converting the dot pattern into the information is performed. As a result, the machine number and model name of the printer main body that outputs the printed matter can be specified. In this embodiment, the toner application amount of the tracking pattern is 60% or less of the toner application amount of the portion other than the tracking pattern (corresponding to “other than dot pattern”). That is, it is 60% or less of the applied toner amount in a portion where a normal image is formed. In this embodiment, the size of the dots constituting the tracking pattern varies depending on the laser output. Specifically, the scanner unit 203 irradiates the photosensitive drum 201 with a laser according to the image information converted by the printer driver. The size of the dots constituting the tracking pattern is determined by the laser output.

  FIG. 4 is a flowchart illustrating a process executed by the image forming apparatus 200 according to the first embodiment. As shown in FIG. 4, the tracking pattern is generated by an additional information generation process that is independent of a normal image information processing process. In order to prevent the tracking pattern from being intentionally changed by the user, the tracking pattern is independent of the normal image information processing process. Then, the information about the tracking pattern is added to the normal image information by the additional information superimposing process performed after the normal image information processing process is completed. In this way, the tracking pattern is output for each image forming apparatus 200 without being affected by a normal image processing process.

  As shown in FIG. 4, the image information input from the image input terminal is first converted from information about RGB (red, green, blue) to information about CMYK (cyan, magenta, yellow, black) by a color conversion process. Is converted to Next, information about CMYK is corrected by various correction processes. For example, the color expressed in RGB and the color expressed in CMYK do not necessarily match, and thus the color expressed in CMYK is corrected so as to be as close as possible to the color expressed in RGB.

  In the pseudo gradation processing process, dithering is performed so that the density of an image formed on the recording material P as a recording medium becomes smooth. Further, the additional information generated by the additional information generation process is added to the image information by the additional information superimposing process. In the present embodiment, in the additional information generation process, information about a tracking pattern for specifying an image forming apparatus that has printed a special banknote or the like is generated. Thereafter, the image information to which the additional information is added is output from the image output terminal.

<Normal image formation mode and wide color gamut image formation mode>
In this embodiment, the image forming apparatus 200 can execute a wide color gamut image forming mode for expanding the color gamut of the image so that a higher quality image can be formed. In the wide color gamut image forming mode as the second image forming mode, the peripheral speed ratio (peripheral speed ratio) between the photosensitive drum 201 and the developing roller 302 is changed to be conveyed from the developing roller 302 to the photosensitive drum 201. The toner supply amount can be increased. The peripheral speed ratio (peripheral speed ratio) between the photosensitive drum 201 and the developing roller 302 can be changed by increasing the peripheral speed of the developing roller 302 or decreasing the peripheral speed of the photosensitive drum 201.

  In this embodiment, in the photosensitive drum 201 as the image carrier, the dark portion potential that is the potential of the portion not exposed by the laser is set to −500 [V], and the bright portion potential that is the potential of the portion exposed by the laser is set. −100 [V]. In this embodiment, the bright portion potential is measured by measuring the surface of the photosensitive drum 201 with an electrometer when an image pattern (for example, a solid black image) that forms an image on the entire recording material P is formed. I got it. Then, by setting the developing potential of the developing roller to −350 [V], the difference between the bright portion potential on the photosensitive drum 201 and the potential of the developing roller 302 and the dark portion potential on the photosensitive drum 201 and the potential of the developing roller 302 are calculated. Each difference was Δ250 [V]. Here, the difference between the bright portion potential on the photosensitive drum 201 and the potential on the developing roller 302 and the difference between the dark portion potential on the photosensitive drum 201 and the potential on the developing roller 302 are referred to as development contrast.

In the present embodiment, the toner amount per unit area (hereinafter referred to as M / S) is 3.0 × 10 ⁻³ [kg / m ^2] for the toner adhering to the developing roller 302 as the developer carrying member. ]
It is said. Further, the charged charge amount of the toner per unit area (hereinafter referred to as Q / S) is set to −0.15 × 10 ⁻³ [C / m ² ]. In this embodiment, the peripheral speed of the photosensitive drum 201 is set to 0.2 [m / s] (constant), and the peripheral speed of the developing roller 302 is changed with respect to the photosensitive drum 201 to confirm the toner supply amount. . The circumferential speed of the photosensitive drum 201 and the developing roller 302 is the same as 100%, and the circumferential speed of the developing roller 302 is 1.4 times the circumferential speed of the photosensitive drum 201. The ratio is 140%. In addition, since there is a deep relationship between the color of the image and the density of the image, the present embodiment will be described by focusing on the density of the image. In this embodiment, the ratio of the peripheral speed of the photosensitive drum 201 to the peripheral speed of the developing roller 302 is increased by making the peripheral speed of the developing roller 302 relatively higher than the peripheral speed of the photosensitive drum 201. Yes.

The toner image formed on the photosensitive drum 201 as the image carrier is finally fixed on the recording material P. Here, FIG. 5 is a diagram illustrating the relationship between the amount of toner forming an image and the density of the image in the first embodiment. Since there is no difference in the experimental results with YMC toner, the experimental results will be described using cyan toner. Here, when the peripheral speed ratio is 120%, a density of 1.45 (Macbeth RD-918) generally required for office documents can be obtained, and the amount of applied toner on the recording material P is 3 It was 6 × 10 ⁻³ kg / m ² . When the peripheral speed ratio is further increased to 200%, a density of 1.72 can be obtained, and the amount of applied toner on the recording material P is 6.0 × 10 ⁻³ kg / m ^2. It was.

  Therefore, in the normal image forming mode as the first image forming mode for office use or the like, the peripheral speed ratio is set to 120% as the first peripheral speed ratio ΔV1 so that the image density is 1.45. In this embodiment, in the wide color gamut image forming mode as the second image forming mode, the peripheral speed ratio is set to 200% as the second peripheral speed ratio ΔV2 so that the image density becomes 1.7 or more. . As a result, when the peripheral speed ratio was changed from 120% to 200%, it was possible to secure 10 or more ΔE target enlargement amount for red. Note that “the ΔE target enlargement amount is 10 or more” indicates that the value in the coordinates of the L * · a * · b * color system has increased by 10 or more. The red color is generated by mixing Y and M toners at a ratio of 1: 1.

  In addition, the measuring instrument used when measuring a color is i1pro by X-rite. The measurement was performed under the conditions of backing black, D50 light source, and 2 degree visual field. The paper used for sampling is Canon GFC081. In the fixing device 400, after 10 seconds have passed since the temperature at the outlet of the nip between the film 430 and the pressure roller 440 reaches 180 ° C., the recording material is placed in the nip between the film 430 and the pressure roller 440. P was transported.

<Formation of tracking pattern>
Conventionally, when the state of the tracking pattern is confirmed, the tracking pattern is invisible in the normal image forming mode, but in the wide color gamut image forming mode, the tracking pattern is visualized by increasing the density of the tracking pattern. There is a fear. Here, the reference of “invisible” and “visible” of the tracking pattern is whether or not the original image (an image other than the tracking pattern) is affected by the naked eye. For example, even if the tracking pattern can be confirmed when the tracking pattern is viewed with a magnifying glass, it becomes “invisible” if the tracking pattern cannot be confirmed with the naked eye. In the wide color gamut image forming mode as the second image forming mode, a large amount of toner is supplied to the dots forming the tracking pattern, thereby increasing the density of the tracking pattern. In the wide color gamut image forming mode as the second image forming mode, a large amount of toner is supplied to the dots forming the tracking pattern, so that the dots forming the tracking pattern become larger than the normal image forming mode. It was. Thereby, in the wide color gamut image forming mode as the second image forming mode, the tracking pattern may be visualized.

Therefore, in this embodiment, in the wide color gamut image forming mode, when an image is formed on the recording material P, the light portion potential of the portion corresponding to the dots forming the tracking pattern on the surface of the photosensitive drum 201 is −400. The amount of laser light is adjusted to be [V]. That is, the exposure amount on the portion corresponding to the tracking pattern on the photosensitive drum 201 is an exposure amount that is 260 V lower than the potential other than the portion corresponding to the tracking pattern. Here, the bright portion potential is a potential of a portion of the photosensitive drum 201 exposed by the scanner unit 203 as an exposure device. In this embodiment, the toner adheres to the bright portion, whereby the electrostatic latent image as the electrostatic image formed on the photosensitive drum 201 is developed as a toner image.

  For example, the image forming apparatus 200 may include a storage unit 500 that stores information about the image forming apparatus 200. The storage unit 500 is a storage medium such as a hard disk drive or a memory. The storage unit 500 may previously store an exposure amount to the tracking pattern in the normal image formation mode as the first image formation mode and an exposure amount to the tracking pattern in the wide color gamut image formation mode. . In this case, the control unit 600 provided in the image forming apparatus 200 executes the program stored in the storage unit 500, so that the exposure amount to the tracking pattern is set in the normal image forming mode and the wide color gamut image forming mode. The exposure amount is set in advance. The control unit 600 adds, to the image information, additional information (corresponding to the first information) about the exposure amount to the tracking pattern in the normal image formation mode, or about the exposure amount to the tracking pattern in the wide color gamut image formation mode. Additional information (corresponding to the second information) is added. Then, the control unit 600 controls the exposure amount of the scanner unit 203 as an exposure device based on the image information to which the additional information is added, and forms an image on the recording material P.

ここで、通常画像形成モードにおける画像部のコントラストをＣ１（第１現像コントラストＣ１）、追跡パターン部のコントラストをＣ２（第２現像コントラストＣ２）とする。同様に広色域画像形成モードにおける画像部のコントラストをＣ３（第３現像コントラストＣ３）、追跡パターン部のコントラストをＣ４（第４現像コントラストＣ４）とする。通常画像形成モードでは画像部に比べて追跡パターン部のコントラストを小さくすることで、追跡パターン部のトナーの載り量を画像部よりも少なくし、追跡パターンを肉眼で見にくくしている。同様に広色域画像形成モードにおいて、追跡パターン部のコントラス
トは画像部に比べて小さく、追跡パターン部のトナーの載り量は少なくなっている。このため、広色域画像形成モードにおいても追跡パターンは肉眼で確認できない状態である。
さらにそれぞれのモードでの画像部と追跡パターン部のコントラスト比をΔＣ１＝Ｃ２／Ｃ１、ΔＣ２＝Ｃ４／Ｃ３とすると
ΔＣ１＝Ｃ２／Ｃ１＝１００Ｖ／２５０Ｖ＝２／５
ΔＣ２＝Ｃ４／Ｃ３＝１４０Ｖ／４００Ｖ＝７／２０
となり、
ΔＣ２＜ΔＣ１
の関係が成り立つ。これは広色域画像形成モードではトナーの載り量が多くなるため、コントラスト比が通常画像形成モードと同程度では追跡パターン部の載り量が増えてしまい、追跡パターンが肉眼で確認できる状態になってしまうことを防止するためである。広色域画像形成モードでは通常画像形成モードよりもコントラスト比を小さくすることで、追跡パターン部のトナーの載り量を抑え、追跡パターンが肉眼で見えない状態を保っている。
なお、ΔＣ１およびΔＣ２については、「比率」ではなく、「差分の絶対値」として用いることもできる。例えば、ΔＣ１＝｜Ｃ２−Ｃ１｜とし、ΔＣ２＝｜Ｃ４−Ｃ３｜としてもよい。この場合、ΔＣ２＜ΔＣ１の関係も成立する。
この効果により、本実施例では広色域画像形成モードにおける画像部ではトナーの載り量は０．６０ｍｇ／ｍ^２と通常画像形成モードからの増加量が０．２４ｍｇ／ｍ^２であるのに対し、追跡パターン部のトナーの載り量は０．２２ｍｇ／ｍ^２と通常画像形成モードからの増加量が０．０７ｍｇ／ｍ^２に抑えられている。 Here, FIG. 6A is a diagram showing the potential on the photosensitive drum 201 of the image portion and the tracking pattern portion in both the normal image formation mode and the wide color gamut image formation mode in the first embodiment. The contrast (development contrast) in the figure is the difference between the development potential and the bright portion potential, and the amount of toner adhering to the photosensitive drum is determined in proportion to the magnitude of the contrast. Since the toner on the photosensitive drum is directly transferred to the recording material, the amount of toner on the recording material is also determined in proportion to the contrast. FIG. 6B is a diagram showing the amount of toner placed on the recording material under each condition shown in FIG. By comparing FIG. 6B and FIG. 6A, it can be seen that the amount of toner applied on the recording material is determined by the magnitude of contrast. The following table summarizes the potential of each part and the amount of toner applied on the recording material under each condition.

Here, the contrast of the image portion in the normal image forming mode is C1 (first development contrast C1), and the contrast of the tracking pattern portion is C2 (second development contrast C2). Similarly, the contrast of the image portion in the wide color gamut image forming mode is C3 (third development contrast C3), and the contrast of the tracking pattern portion is C4 (fourth development contrast C4). In the normal image forming mode, the amount of toner applied to the tracking pattern portion is smaller than that of the image portion by making the contrast of the tracking pattern portion smaller than that of the image portion, thereby making it difficult to see the tracking pattern with the naked eye. Similarly, in the wide color gamut image forming mode, the contrast of the tracking pattern portion is smaller than that of the image portion, and the amount of applied toner in the tracking pattern portion is small. Therefore, the tracking pattern cannot be confirmed with the naked eye even in the wide color gamut image forming mode.
Further, if the contrast ratio between the image portion and the tracking pattern portion in each mode is ΔC1 = C2 / C1 and ΔC2 = C4 / C3, then ΔC1 = C2 / C1 = 100V / 250V = 2/5
ΔC2 = C4 / C3 = 140V / 400V = 7/20
And
ΔC2 <ΔC1
The relationship holds. This is because the amount of toner applied increases in the wide color gamut image formation mode, and therefore the amount of application of the tracking pattern portion increases when the contrast ratio is the same as that of the normal image formation mode, so that the tracking pattern can be confirmed with the naked eye. This is to prevent this from happening. In the wide color gamut image formation mode, the contrast ratio is made smaller than that in the normal image formation mode, so that the amount of toner on the tracking pattern portion is suppressed, and the tracking pattern is kept invisible to the naked eye.
Note that ΔC1 and ΔC2 can be used not as “ratio” but as “absolute value of difference”. For example, ΔC1 = | C2-C1 | and ΔC2 = | C4-C3 |. In this case, the relationship ΔC2 <ΔC1 is also established.
This effect, the amount of applied toner in the image portion in Hiroiroiki image forming mode in the present embodiment is to increase the amount from 0.60 mg / m ² and normal image forming mode that is 0.24 mg / m ² The amount of toner on the tracking pattern portion is 0.22 mg / m ^2, and the increase from the normal image forming mode is suppressed to 0.07 mg / m ² .

Here, in the normal image forming mode, the applied toner amount in the image portion (region corresponding to the image) is M1 (first developer applied amount M1), and the applied toner amount in the tracking pattern portion (region corresponding to the dot pattern) is M2. (Second developer loading M2). Similarly, in the wide color gamut image forming mode, the applied toner amount in the image portion is M3 (third developer applied amount M3), and the applied toner amount in the tracking pattern portion is M4 (fourth developer applied amount M4). Assuming that the toner amount ratio between the image portion and the tracking pattern portion in each mode is ΔM1 = M2 / M1 and ΔM2 = M4 / M3, ΔM1 = M2 / M1 = 0.15 mg / m ² /0.36 mg / m ² = 5/12
ΔM2 = M4 / M3 = 0.22 mg / m ² /0.60 mg / m ² = 11/30
And
ΔM2 <ΔM1
The relationship holds.
It should be noted that ΔM2 and ΔM1 can also be used as “absolute value of difference” instead of “ratio”. For example, ΔM1 = | M2-M1 | and ΔM2 = | M4-M3 |. In this case, the relationship ΔM2 <ΔM1 is also established.

Since it is difficult to actually measure the amount of applied toner in the tracking pattern portion, a solid image is formed on the recording material under the same contrast conditions as the tracking pattern portion for the toner applied amount shown here. Substituted by measuring the amount.
Normally, when measuring the amount of toner on the recording material, the toner is placed on the recording material under the measurement conditions (type of recording material, each potential condition, etc.), and the toner is collected without fixing. Measure its mass. At the same time, the area of the range where the toner is placed is measured, and the “toner applied amount” in the above table is calculated from the measured toner mass and area.
For example, when measuring the amount of toner applied to the image area in the normal image forming mode, first, on an appropriate recording material (for example, Canon image coat gloss 158 paper), the same conditions as the image area (D roller peripheral speed ratio: 120%) The toner is placed at a dark portion potential of −500 V, a developing potential of −350 V, a light portion potential of −100 V, and a contrast of 250 V. The area on which the toner is placed is set in advance, for example, a rectangle of 20 mm × 50 mm = 1000 mm ² . By collecting the toner placed in this range and measuring its weight, the applied toner amount (here, “0.36 mg / m ² ”) in the above table is calculated. The method for measuring the amount of applied toner in the wide color gamut image formation mode is the same except that the D roller peripheral speed ratio and each potential condition are changed to be equivalent to the wide color gamut image formation mode.
By the way, the tracking pattern portion is normally surrounded by the image portion, and the tracking pattern portion is finely divided on the recording material. Therefore, it is normal printing operation to measure the toner applied amount only in the tracking pattern portion. Then it is impossible. Therefore, when measuring the toner application amount of the tracking pattern (herein, the normal image forming mode will be described as an example) on the appropriate recording material (for example, Canon Image Coat Gloss 158 paper), the same conditions as the tracking pattern portion ( D roller peripheral speed ratio: 120%, dark portion potential: -500V, development potential: -350V, light portion potential: -250V, contrast: 100V), and the weight of the toner is measured. It is used as a loading amount. In the wide color gamut image forming mode, the amount of toner applied to the tracking pattern portion is also measured by changing the D roller peripheral speed ratio and each potential condition corresponding to the wide color gamut image forming mode.
As described above, in this embodiment, even in the wide color gamut image forming mode, by adjusting the contrast on the photosensitive drum, the toner amount on the recording material is suppressed and the tracking pattern is prevented from being visualized. can do.

  In the present embodiment, the case where two modes of the normal image forming mode as the first image forming mode and the wide color gamut image forming mode as the second image forming mode are executed has been described. However, it is not necessarily limited to this. For example, the image forming apparatus 200 includes a first wide color gamut image forming mode (density 1.7 or higher, peripheral speed ratio 200%) and a second wide color gamut image forming mode (density 1.9 or higher, peripheral speed ratio 300%). ) Two wide color gamut image forming modes. In this case, the amount of laser light applied to the portion corresponding to the tracking pattern on the photosensitive drum 201 may be set in each of the first wide color gamut image forming mode and the second wide color gamut image forming mode. Thereby, in both the first wide color gamut image forming mode and the second wide color gamut image forming mode, the exposure amount of the portion corresponding to the tracking pattern is adjusted (the density of the tracking pattern is set to a predetermined density or less). Thus, visualization of the tracking pattern can be suppressed.

  As described above, in the present embodiment, in the wide color gamut image forming mode as the second image forming mode, the density of the tracking pattern is increased and the density of the entire image including the tracking pattern is increased in the wide color gamut image forming mode. It is lower than the density of the tracking pattern in the case. This suppresses the tracking pattern from being visible to the user in the wide color gamut image forming mode.

(Example 2)
In the present embodiment, portions having the same functions as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted. In the present embodiment, unlike the first embodiment, in the wide color gamut image forming mode, the tracking pattern is suppressed from being visualized by widening the interval between two adjacent dots in a plurality of dots forming the tracking pattern. . Here, the tracking pattern is usually formed by a plurality of dots. In this embodiment, the tracking pattern is set separately for each of the normal image formation mode and the wide color gamut image formation mode. In this embodiment, in the wide color gamut image forming mode in which the density of the image formed on the recording material P is high (the amount of applied toner is large), the interval between dots forming the tracking pattern is set larger than in the normal image forming mode. Wide. That is, in this embodiment, the pattern shape of the tracking pattern is changed between the wide color gamut image forming mode and the normal image forming mode.

On the other hand, in the normal image forming mode in which the density of the image formed on the recording material P is not high, the interval between dots forming the tracking pattern is not widened. In this embodiment, the tracking pattern formed on the recording material P can be read using a dedicated reading device. In order to make it easy to read the tracking pattern by the reading device, in the normal image forming mode, the interval between dots forming the tracking pattern is set to an appropriate interval. In this embodiment, in the normal image forming mode, the interval between dots forming the tracking pattern is narrower than in the wide color gamut image forming mode.

  Specifically, for example, the storage unit 500 stores in advance a tracking pattern in the normal image formation mode and a tracking pattern in the wide color gamut image formation mode. Here, as described above, in the wide color gamut image forming mode, the interval between dots forming the tracking pattern is wider than that in the normal image forming mode. In this case, the control unit 600 provided in the image forming apparatus 200 executes a program stored in the storage unit 500, so that a tracking pattern set in advance in the normal image forming mode and the wide color gamut image forming mode is obtained. It is formed on the recording material P. The control unit 600 adds additional information about the tracking pattern in the normal image forming mode as the first image forming mode or additional information about the tracking pattern in the wide color gamut image forming mode to the image information. Then, the control unit 600 controls the operation of the image forming apparatus 200 so that a tracking pattern is formed and an image is formed on the recording material P based on the image information to which the additional information is added. The control unit 600 is an arithmetic device such as a CPU, for example, and can control the operation of devices in the image forming apparatus 200 by executing a program stored in the storage unit 500.

  FIG. 7 is a diagram showing the tracking pattern A formed in the normal image forming mode as the first image forming mode. FIG. 8 is a diagram showing the tracking pattern B formed in the wide color gamut image forming mode. Here, for example, it is assumed that the tracking pattern formed on the recording material P in the normal image forming mode is the tracking pattern A (see FIG. 7). In the normal image forming mode as the first image forming mode, the tracking pattern A is formed on the recording material P on which the image is formed. At this time, the tracking pattern A formed on the recording material P is invisible.

  However, when the tracking pattern A is formed in the wide color gamut image forming mode as the second image forming mode, the amount of toner per unit area in the tracking pattern A is increased, so that a part of the tracking pattern A is visualized. There is a risk of being. In the wide color gamut image forming mode, more toner is loaded on the tracking pattern A than in the normal image forming mode. Therefore, there is a possibility that the toner may spread to the margin between the dots forming the tracking pattern A. In this case, since the blank space between the dots forming the tracking pattern A is filled, a plurality of separate dots become one large dot as shown in FIG. Thereby, the tracking pattern A may be visualized.

FIG. 9 is a diagram illustrating the tracking pattern B in the normal image forming mode as the first image forming mode. FIG. 10 is a diagram showing the tracking pattern B in the wide color gamut image forming mode. In this embodiment, in the first wide color gamut image forming mode (density 1.7 or more, peripheral speed ratio 200%), the tracking pattern B has an interval between dots forming the tracking pattern as shown in FIG. It is getting wider. In this embodiment, by increasing the interval between dots forming the tracking pattern B, it is possible to prevent a plurality of dots forming the tracking pattern B from becoming one large dot. As a result, in the first wide color gamut image forming mode, even when a larger amount of toner than usual is placed on the dots forming the tracking pattern B, the dots are sufficiently separated from each other. Visualization can be reduced. Here, in order for the dots to play the role of the tracking pattern, it is necessary to ensure the independence of the dots constituting the tracking pattern. If the dots constituting the tracking pattern can be recognized, the dots have “independence”. On the other hand, when the adjacent dots are connected and the dots cannot be recognized, the dots do not have “independence”. For this reason, in this embodiment, at least the dot on which the toner is placed is not formed next to the dot constituting the tracking pattern. Here, generally, the tracking pattern is formed in a size of about 3 × 3 dots (a square with 3 dots on one side) to 5 × 5 dots (a square with 5 dots on a side). When a large tracking pattern is used, the authenticity deteriorates, so the size of the tracking pattern is set to a certain size. Therefore, in this embodiment, when the dot interval is enlarged in the color gamut enlargement image forming mode, it is appropriate that the tracking pattern has a size of about 10 × 10 dots (a square with 10 dots on one side).

  FIG. 11 is a diagram showing a tracking pattern C in the normal image forming mode. FIG. 12 is a diagram showing a tracking pattern C in the wide color gamut image forming mode. In this embodiment, the tracking pattern C is formed on the recording material P in the second wide color gamut image forming mode (density 1.9 or more, peripheral speed ratio 300%). The interval between the dots forming the tracking pattern C is wider than the interval between the dots forming the tracking pattern B. Therefore, the toner amount per unit area in the second wide color gamut image formation mode is larger than the toner amount per unit area in the first wide color gamut image formation mode, but also in the second wide color gamut image formation mode. Visualization of the tracking pattern C can be suppressed.

  As described above, in this embodiment, in the wide color gamut image forming mode, the interval between the plurality of dots forming the tracking pattern is increased by the wide color gamut image forming mode. The interval is larger than the case. This suppresses the tracking pattern from being visible to the user in the wide color gamut image forming mode.

In each embodiment, it is not always necessary to change the color gamut and density of the image depending on the peripheral speed ratio between the photosensitive drum 201 and the developing roller 302. For example, the color gamut and density of the image may be changed by changing the exposure amount of the scanner unit 203 with respect to the photosensitive drum 201.
In the first embodiment, the exposure amount of the scanner unit 203 for the photosensitive drum 201 is not necessarily stored in the storage medium in advance. For example, the density of the tracking pattern may be adjusted by correcting the exposure amount of the scanner unit 203 with respect to the photosensitive drum 201 as an image carrier.

In the second embodiment, the interval between dots forming the tracking pattern does not necessarily need to be stored in the storage medium in advance. For example, the interval between the dots forming the tracking pattern may be increased by correcting the interval between the dots forming the tracking pattern.
In the second embodiment, the tracking pattern A, the tracking pattern B, and the tracking pattern C are used as the tracking patterns, but the present invention is not necessarily limited to this. It is not limited to the tracking patterns A to C, and is not particularly limited as long as the tracking pattern can obtain the same effect.

  DESCRIPTION OF SYMBOLS 200 ... Image forming apparatus, 201 ... Photosensitive drum, 302 ... Developing roller, P ... Recording medium

Claims (21)

A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier is set to a first peripheral speed ratio ΔV1 to form an image based on the image information. Image formation mode,
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image formation mode, an image is formed with a first development contrast C1, the specific dot pattern is formed with a second development contrast C2 smaller than the first development contrast C1,
In the second image forming mode, an image is formed with a third development contrast C3, the specific dot pattern is formed with a fourth development contrast C4 smaller than the third development contrast C3,
The ratio between the second development contrast C2 and the first development contrast C1 is ΔC1 (= C2 / C1), and the ratio between the fourth development contrast C4 and the third development contrast C3 is ΔC2 (= C4 / C3). When
ΔC2 <ΔC1
An image forming apparatus. A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier is set to a first peripheral speed ratio ΔV1 to form an image based on the image information. Image formation mode,
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image formation mode, an image is formed with a first development contrast C1, the specific dot pattern is formed with a second development contrast C2 smaller than the first development contrast C1,
In the second image forming mode, an image is formed with a third development contrast C3, the specific dot pattern is formed with a fourth development contrast C4 smaller than the third development contrast C3,
The absolute value of the difference between the second development contrast C2 and the first development contrast C1 is ΔC1 (= | C2-C1 |), and the absolute value of the difference between the fourth development contrast C4 and the third development contrast C3 is ΔC2. (= | C4-C3 |)
ΔC2 <ΔC1
An image forming apparatus.   3. The image forming apparatus according to claim 1, wherein the specific dot pattern becomes invisible by setting the density of the specific dot pattern to a predetermined density or less. 4.   In the second image forming mode, the density of the specific dot pattern is higher than the density of the specific dot pattern when the density of the entire image including the specific dot pattern is increased in the second image forming mode. 3. The image forming apparatus according to claim 1, wherein the specific dot pattern is less visible by lowering the height. An exposure apparatus that forms the electrostatic image on the image carrier by exposing the image carrier;
The density of the specific dot pattern to be developed is lowered by adjusting an exposure amount of the electrostatic image corresponding to the specific dot pattern from the exposure device in the image carrier. Item 5. The image forming apparatus according to Item 4. A storage unit for storing predetermined information;
The exposure amount to the specific dot pattern in the first image formation mode and the exposure amount to the specific dot pattern in the second image formation mode are stored in the storage unit in advance. The image forming apparatus according to claim 5.   In forming the image on the recording medium in the second image forming mode, the potential of the portion corresponding to the specific dot pattern in the image carrier is set to the density of the entire image including the specific dot pattern. The exposure amount to the specific dot pattern is lowered so as to be lower than the potential of the portion corresponding to the specific dot pattern when it is increased in the second image forming mode. The image forming apparatus described.   In the image carrier, the difference between the potential of the portion corresponding to the specific dot pattern and the potential of the developer carrier is increased by increasing the density of the entire image including the specific dot pattern by the second image forming mode. 8. The density of the specific dot pattern is lowered by making it smaller than the difference between the potential of the portion corresponding to the specific dot pattern and the potential of the developer carrying member. The image forming apparatus described in 1.   In the first image forming mode, the first information that does not change the amount of exposure to the portion corresponding to the specific dot pattern is added to the image information formed on the recording medium. The image forming apparatus according to claim 5, wherein the exposure amount of a portion corresponding to the specific dot pattern is not changed.   In the second image forming mode, by adding second information for changing the exposure amount to a portion corresponding to the specific dot pattern to the image information formed on the recording medium, The image forming apparatus according to claim 5, wherein the exposure amount of a portion corresponding to the specific dot pattern is changed.   The density of the specific dot pattern formed in the second image formation mode is 60% or less of the density of an image other than the specific dot pattern formed in the second image formation mode. The image forming apparatus according to claim 3. A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A first image for forming an image based on the image information by setting a peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier to a first peripheral speed ratio ΔV1. Formation mode;
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
The interval between two adjacent dots among the plurality of dots forming the specific dot pattern in the second image forming mode is wider than the interval between the two dots in the first image forming mode. Image forming apparatus.   In the second image forming mode, the interval between a plurality of dots forming the specific dot pattern is set when the density of the entire image including the specific dot pattern is increased by the second image forming mode. The image forming apparatus according to claim 12, wherein the specific dot pattern is made difficult to be seen by making the size larger than.   In the first image formation mode, the interval between a plurality of dots forming the specific dot pattern is changed by adding first information that does not change the interval to the image information formed on the recording medium. The image forming apparatus according to claim 13, wherein the image forming apparatus is not.   In the second image forming mode, the second information for changing the interval is added to the image information formed on the recording medium, thereby changing the interval between a plurality of dots forming the specific dot pattern. The image forming apparatus according to claim 14. A storage unit for storing predetermined information;
16. The image forming apparatus according to claim 15, wherein the storage unit stores the first information and the second information in advance.   In the second image forming mode, the peripheral speed Vd of the developer carrier is relatively higher than the peripheral speed Vdr of the image carrier, and the second peripheral speed ratio ΔV2 is increased, thereby recording. The image forming apparatus according to claim 1, wherein a color gamut of an image formed on the medium is expanded as compared with the first image forming mode.   In the second image forming mode, the peripheral speed Vdr of the image carrier is fixed, and only the peripheral speed Vd of the developer carrier is increased, thereby increasing the second peripheral speed ratio ΔV2. The image forming apparatus according to claim 17. A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A first image for forming an image based on the image information by setting a peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier to a first peripheral speed ratio ΔV1. Formation mode;
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image forming mode, an image is formed by supplying a developer to the image carrier so that the first developer loading amount M1 is in a region corresponding to the image, and the image corresponds to the specific dot pattern. Supplying the developer to the image carrier so that the second developer loading amount M2 is smaller than the first developer loading amount in the region, and forming the specific dot pattern;
In the second image forming mode, an image is formed by supplying a developer to the image carrier so that the third developer amount M3 is provided in an area corresponding to the image, and corresponding to the specific dot pattern. A developer is supplied to the image carrier so as to have a fourth developer loading amount M4 smaller than the third developer loading amount in a region to be formed to form the specific dot pattern;
The ratio between the second developer loading amount M2 and the first developer loading amount M1 is ΔM1 (= M2 / M1), and the ratio between the fourth developer loading amount M4 and the third developer loading amount M3 is ΔM2. (= M4 / M3)
ΔM2 <ΔM1
An image forming apparatus. A rotatable image carrier on which an electrostatic image is formed;
A rotatable developer carrier for developing the electrostatic image by supplying a developer to the image carrier;
Processing means for processing the image information so as to add a specific dot pattern to the formed image;
Have
A first image for forming an image based on the image information by setting a peripheral speed ratio Vd / Vdr between the peripheral speed Vd of the developer carrier and the peripheral speed Vdr of the image carrier to a first peripheral speed ratio ΔV1. Formation mode;
A second image forming mode in which an image is formed based on the image information by setting a second peripheral speed ratio ΔV2 larger than the first peripheral speed ratio ΔV1;
An image forming apparatus capable of executing
In the first image forming mode, an image is formed by supplying a developer to the image carrier so that the first developer loading amount M1 is in a region corresponding to the image, and the image corresponds to the specific dot pattern. Supplying the developer to the image carrier so that the second developer loading amount M2 is smaller than the first developer loading amount in the region, and forming the specific dot pattern;
In the second image forming mode, an image is formed by supplying a developer to the image carrier so that the third developer amount M3 is provided in an area corresponding to the image, and corresponding to the specific dot pattern. A developer is supplied to the image carrier so as to have a fourth developer loading amount M4 smaller than the third developer loading amount in a region to be formed to form the specific dot pattern;
The absolute value of the difference between the second developer applied amount M2 and the first developer applied amount M1 is ΔM1 (= | M2−M1 |), and the fourth developer applied amount M4 and the third developer applied amount. When the absolute value of the difference of M3 is ΔM2 (= | M4-M3 |),
ΔM2 <ΔM1
An image forming apparatus.   21. The image forming apparatus according to claim 1, further comprising a control unit capable of executing the first image forming mode and the second image forming mode.

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