JP2009069243A - Image forming apparatus and image forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus and an image forming method capable of easily forming an original image which can be distinguished from a copied one. <P>SOLUTION: The image forming apparatus 10 has an information processing device 12 and a printer 14. The printer 14 has a fixing device for fixing toner on paper with at least either heat or pressure, and forms an image on the paper by using the fixing device. In the image forming apparatus 10, a first image is formed on the paper, and a second image is formed on the first image after the first image is formed, so that glossiness is made different between the first image excepting an area where the second image is formed and the second image. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and an image forming method.

  As an image forming apparatus, there is known an image forming apparatus in which a toner image transferred to a sheet is fixed on the sheet by heat and pressure. Patent Document 1 discloses that a toner image held on a sheet is fixed a plurality of times in order to obtain a toner image having high glossiness. Patent Document 2 discloses that fixing is performed twice for a photographic image that requires high glossiness, and fixing is performed once for a character image that requires low glossiness. To do.

JP 2002-258712 A JP 2004-294575 A

  An object of the present invention is to provide an image forming apparatus and an image forming method capable of easily forming an original image that can be distinguished from a copy.

  According to a first aspect of the present invention, there is provided a fixing device that fixes toner on a sheet by at least one of heat and pressure, and an image forming unit that forms an image on the sheet using the fixing device; A first control unit that controls the image forming unit so that an image is formed; and a second image formed on the first image after the first image is formed on the sheet by the first control unit. And an image forming apparatus having a second control unit for controlling the image forming unit so that the image forming unit is formed.

  The present invention according to claim 2 is the image forming apparatus according to claim 1, wherein the first image and the second image have substantially the same color.

  The present invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the first image has a larger amount of black toner per unit area than the second image.

  According to the fourth aspect of the present invention, the image forming unit uses yellow, magenta, cyan and black toners, and the first image is yellow, magenta and cyan or yellow, magenta, cyan and black toners. The image forming apparatus according to claim 1, wherein the second image is formed from black toner.

  According to a fifth aspect of the present invention, the image forming unit includes a paper conveyance path for double-sided printing, and the second control unit causes the second paper to pass through the paper conveyance path twice by passing the paper twice. 5. The image forming apparatus according to claim 1, wherein the image forming apparatus is controlled so as to form an image.

  According to a sixth aspect of the present invention, when the second control means passes the paper through the paper transport path for the first time, at least during the time when the paper passes through the fixing device, the heat or pressure of the fixing device. The image forming apparatus according to claim 5, wherein at least one of the first image and the second image is controlled to be smaller than when the first image and the second image are fixed.

  According to the seventh aspect of the present invention, the toner is fixed to the paper by at least one of heat and pressure to form the first image on the paper, and after the first image is formed, the second image is formed on the first image. In this image forming method, the second image is formed on the paper by fixing the toner to the paper with at least one of heat and pressure so that the image of FIG.

  According to the first aspect of the present invention, it is possible to provide an image forming apparatus capable of easily forming an original image that can be distinguished from a copy.

  According to the second aspect of the present invention, in addition to the effect of the first aspect, in the case of the original, the first image and the second image can be distinguished by the difference in gloss. In the case of an object, it is difficult or impossible to distinguish between the first image and the second image, and it is possible to easily distinguish the original from the copy.

  According to the third aspect of the present invention, in addition to the effect of the first or second aspect, the second image is formed on the first image, so that the toner layer of the second image portion is formed. However, by increasing the amount of black toner in the first image, the difference between the first image and the second image can be reduced except for the glossiness. There is an effect that discrimination from a copy can be performed more easily.

  According to the fourth aspect of the present invention, in addition to the effect of the first aspect of the invention, in the case of the original, the first image and the second image can be distinguished by the difference in gloss. In the case of an object, it is difficult or impossible to distinguish between the first image and the second image, and it is possible to easily distinguish the original from the copy.

  According to the present invention of claim 5, in addition to the effects of the present invention of any one of claims 1 to 4, an effect that can be realized with a simpler configuration by using a paper transport path for double-sided printing. Play.

  According to the sixth aspect of the present invention, in addition to the effect of the present invention according to the fifth aspect, it is possible to reduce the influence on the glossiness of the first image when passing the fixing device for the first time.

  According to the seventh aspect of the present invention, it is possible to provide an image forming method capable of easily forming an original image that can be distinguished from a copy.

  Embodiments of the present invention will be described below. In addition, the following description is only an example in implementing this invention, and this invention is not necessarily limited to the matter demonstrated below, It can change suitably as needed.

FIG. 1 is a configuration diagram illustrating an image forming apparatus 10 according to an embodiment of the present invention.
In the image forming apparatus 10, an information processing apparatus 12 and a printing apparatus 14 are connected via a cable 16. The information processing apparatus 12 is a personal computer, for example. The printing device 14 is, for example, an electrophotographic color printing device. The cable 16 is, for example, a USB cable.

  The information processing apparatus 12 includes an input unit 18, a control unit 20, an output unit 22, a storage unit 24, and an external input interface unit 26. The input unit 18 includes a keyboard, a mouse, and the like, and inputs data. The control unit 20 includes a CPU and controls the entire information processing apparatus 12. The output unit 22 is a display device such as a display, for example, and displays and outputs processing results and input / output data. The storage unit 24 includes a ROM, a RAM, a hard disk, and the like, and an operating system 28, a printer driver 30, and application software 32 are installed on the hard disk.

  The printing apparatus 14 includes a storage unit 34, an external interface unit 36, a control unit 38, and an image forming unit 40. The storage unit 34 includes a ROM, a RAM, a hard disk, and the like, and stores data and programs. The external interface unit 36 exchanges control signals and data with the information processing apparatus 12. The control unit 38 includes a CPU and controls the entire printing apparatus 14.

FIG. 2 is a cross-sectional view showing the image forming unit 40 of the printing apparatus 14.
The image forming unit 40 includes a housing 42, in which a photosensitive member 44, a charging device 46, an optical writing device 48, a developing device 50, an intermediate transfer device 52, a cleaning device 54, and a fixing device 56 are accommodated. Yes. The photoreceptor 44 is used as a latent image carrier on which a latent image is formed. The charging device 46 includes a charging roll that uniformly charges the photosensitive member 44. The optical writing device 48 writes a latent image on the photosensitive member 44 charged by the charging device 46 with a laser beam.

  The developing device 50 includes a rotating body 59 that rotates counterclockwise (counterclockwise in FIG. 1) about the rotation shaft 58, and yellow, yellow, magenta, and cyan (attached to the rotating body 59). Cyan) and black (Black) toner images of four colors are formed.

  The rotator 59 holds the developing devices 60a to 60d at 90 ° intervals, and rotates them by 90 ° to move the developing devices 60a to 60d to a position where the latent image formed on the photosensitive member 44 is developed. The developing devices 60a to 60d have developing rolls 62a to 62d, respectively, and these developing rolls 62a to 62d move so as to face the photoreceptor 44, respectively.

  The intermediate transfer device 52 transfers an intermediate transfer belt 64 that is an endless intermediate transfer member used as an image carrier that holds a toner image on the surface, and a toner image on the photosensitive member 44 to the intermediate transfer belt (primary transfer). A primary transfer roll 66, a wrap-in roll 68 and a wrap-out roll 70 that are located in the vicinity of the photosensitive member 44 and hold the intermediate transfer belt 64 from the inside, and a toner image formed on the intermediate transfer belt 64 is transferred to a sheet. A secondary transfer roll 72 used as a transfer section, a backup roll 74 for backing up the secondary transfer roll 72, an intermediate transfer cleaner 76 for cleaning the intermediate transfer belt 64, and an intermediate transfer cleaner 76 across the intermediate transfer belt 64. And a brush backup roll 80 provided at a position facing the.

  The toner image on the photoconductor 44 is primarily transferred to the intermediate transfer belt 64 in the order of, for example, yellow, magenta, cyan, and black by the primary transfer roll 66, and the intermediate transfer belt 64 transfers the primary transferred toner image to the intermediate transfer belt 64. The sheet is conveyed between the next transfer roll 72 and the backup roll 74.

  The wrap-in roll 68 and the wrap-out roll 70 hold the intermediate transfer belt 64 so that the intermediate transfer belt 64 wraps around the photoconductor 44 in a wide area, and the intermediate transfer belt 64 and the photoconductor 44 are in contact with each other. A primary transfer nip which is an area and a primary transfer position is formed.

  A secondary transfer roll 72 is in contact with the secondary transfer backup roll 74 with the intermediate transfer belt 64 interposed therebetween. The sheet is conveyed between the secondary transfer backup roll 74 and the secondary transfer roll 72, and the toner image primarily transferred to the intermediate transfer belt 64 is transferred to the sheet.

  The cleaning device 54 includes a cleaning blade 82 that scrapes off toner remaining on the photosensitive drum 44 after temporary transfer, and a toner collection bottle 84 that collects toner scraped off by the cleaning blade 82.

  The fixing device 56 includes a heating roll 86 and a pressure roll 88. The fixing device 56 applies heat and pressure to the paper passing between the heating roll 86 and the pressure roll 88, and the second-transferred toner image is supplied to the paper. To settle.

Next, the paper transport system will be described.
The paper transport system in this embodiment includes, for example, two stages of paper supply devices 90 and 90. Each of the paper supply devices 90 includes a paper supply cassette 92 that stores paper, a pickup roll 94 that sends out the paper from the paper supply cassette 92, a feed roll 96 that conveys the paper sent out by the pickup roll 94, and a sheet. It has the retard roll 98 which rolls one by one.

  The paper discharge unit 100 is provided on the upper surface of the housing 42. A discharge port 102 is formed in the housing 42 toward the discharge unit 100. The main transport path 104 is a transport path from the feed roll 96 to the discharge port 102. The main transport path 104 includes a first transport roll 106, a second transport roll 108, a resist roll 110, a secondary roll from the bottom. A transfer roll 72, a secondary transfer backup roll 74, a fixing device 56, and a discharge roll 112 are disposed.

  The registration roll 110 temporarily stops the conveyed sheet and conveys the sheet in accordance with the timing at which the toner image formed on the intermediate transfer belt 64 is conveyed. The discharge roll 112 rotates forward and backward, and rotates forward to discharge the sheet conveyed along the main conveyance path 104 to the discharge unit 100. When images are formed on both sides of the paper, the discharge roll 112 rotates reversely with the trailing edge of the paper left, and the paper is sent to the paper conveyance path 114 for double-sided printing.

  The sheet conveyance path 114 is a conveyance path from the discharge roll 112 to the second conveyance roll 108, and conveys the sheet to the second conveyance roll 108 while inverting the sheet on which the image is formed on the surface. A third transport roll 116 and a fourth transport roll 118 are provided along the paper transport path 114.

  The manual feed unit 120 includes a manual feed tray 122 protruding from the housing 42, a manual pickup roll 124 that feeds the uppermost paper stacked on the manual feed tray 122, and a second paper that is fed by the manual pickup roll 124. And a manual conveyance path 126 that conveys to the conveyance roll 108.

  In the printing apparatus 40 described above, the photosensitive member 44 is uniformly charged by the charging device 46, and a latent image is formed on the charged photosensitive member 44 by the laser light emitted from the optical writing device 48. . The latent image of the photoconductor 44 formed by the optical writing device 48 is developed into yellow, magenta, cyan, and black toner images by the developing device 50 and is primarily transferred onto the intermediate transfer belt 64. Waste toner remaining on the photoreceptor 44 after the primary transfer is scraped off and collected by the cleaning device 54.

  On the other hand, the paper supplied from the paper supply devices 90 and 90 or the manual feed unit 120 is guided to the main conveyance path 104 and is temporarily stopped by the registration roll 110, and the secondary transfer roll 72 and the secondary transfer backup are timed. Guided between the roll 74. When the sheet is guided between the secondary transfer roll 72 and the secondary transfer backup roll 74, the toner image primarily transferred to the intermediate transfer belt 64 is secondarily transferred to the sheet. After the secondary transfer, waste toner remaining on the intermediate transfer belt 64 is scraped off and collected by the intermediate transfer body cleaner 76.

  The sheet on which the toner image has been transferred is guided to the fixing device 56, and the toner image is fixed on the sheet by heat and pressure generated by the heating roll 86 and the pressure roll 88. When an image is formed only on the front surface (single-sided printing mode), the fixed paper is discharged from the discharge port 102 to the discharge unit 100 by the normal rotation of the discharge roll 112. On the other hand, when image formation is performed on both sides (double-sided printing mode), when the trailing edge of the paper reaches the discharge roll 112, the discharge roll 112 rotates in the reverse direction and is switched to the paper conveyance path 114 side. Guided to path 114.

  The paper guided to the paper transport path 114 is transported downward by the third transport roll 116 and the fourth transport roll 118, and the back surface is reversed in a direction facing the intermediate transfer belt 64. Then, it is guided to the resist roll 110 through the second transport roll 108. Then, the toner image is secondarily transferred to the back surface of the sheet guided to the registration roll 110 by the secondary transfer roll 72, the toner image is fixed by the fixing device 56, and discharged to the discharge unit 106 by the discharge roll 112. The

Next, a case where an original is created using the image forming unit 40 (original creation mode) will be described.
Here, the original is an original document to be copied. In this embodiment, it is possible to determine whether the original is using the difference in gloss.

  FIG. 3 shows an original 128 and a copy 130 obtained by copying the original 128. As shown in FIG. 3A, in the original 128, in addition to the text 132 created by the application software 32 of the information processing apparatus 12 described above, an authentication code portion 134 indicating the original is printed at a predetermined position. Has been.

  The authentication code part 134 includes a first image 136 that is a background part, and a second image 138 that is a code of, for example, “original” formed on the first image 136. When the first image 136 other than the region where the second image 138 is formed is compared with the second image 138, the colors are substantially the same, but the gloss is different. For example, the second image 138 is formed. The first image 136 other than the above-mentioned area has a higher glossiness than the second image 138. High glossiness is a state in which the reflection of light from the light source does not diffuse so much as in a mirror surface and faces a certain direction. That is, when viewed from an angle at which the incident angle and the reflection angle of light from the white light source are the same, the image appears to shine white. Accordingly, an image having a difference in gloss may or may not differ depending on the direction of the light source and the direction in which the image is viewed.

  However, when copying with a normal copying machine, as shown in FIG. 3B, the area 140 corresponding to the text of the copy 130 is restored as it is, but from the area 142 corresponding to the first image 136. The code “original” will disappear. This is because in ordinary copying machines, the light source is devised so that the color of the original material can be reproduced without being affected by reflected light even in high-gloss areas, and the difference in gloss is not strong. Because it is. That is, the read signals of the first image 136 and the second image 138 are substantially the same, and the copied material 130 has the same color and the same gloss.

Next, a specific flow of the original creation mode will be described.
FIG. 4 is a flowchart showing the control operation of the image forming apparatus 10 in the original creation mode.
First, in the information processing apparatus 12, after print data is created or processed by the application software 32, when print setting is instructed (step S10), a print condition setting instruction command is sent to the printer driver 30, and the printer driver 30 displays a screen for setting an authentication code and setting various functions (printing conditions) included in the printing apparatus 14, and when the operator sets these, setting information is acquired (steps S12 and S14). ).

  FIG. 5 shows an example of the authentication code setting screen 144 displayed on the information processing apparatus 12 when setting the authentication code. The authentication code setting screen 144 includes an authentication code color setting unit 146, an authentication code setting unit 148, a font setting unit 150, a size setting unit 152, a file setting unit 154, a position setting unit 156, a confirmation screen area 158, an instruction operation unit 160, and the like. It is composed of

  The authentication code color setting unit 146 is a part for setting the color of the authentication code. The toner used for the first image and the second image with respect to the color of the authentication code is stored as the table 162 in the storage unit 24 described above. FIG. 6 shows an example of this table. For example, when the color of the authentication code is set to yellow or cyan, the second image that is the authentication code uses only Y (yellow) or C (cyan) toner, whereas the first image that is the background portion. These images are set so that their color contains a little black (K) toner. That is, the first image is set so that the amount of black toner per unit area is larger than that of the second image. In this embodiment, as shown in FIG. 7, the first image 136 that is the background portion is first formed, and then the second image 138 that is the authentication code is formed on the first image 136. The first image 136 is affected by the background color of the paper, and the brightness is higher than the set color, whereas the second image 138 is less affected by the background color of the paper because the toner layer is thick. For this reason, when the first image 136 and the second image 138 are formed with the same color toner, the second image 138 is darkened, and the brightness of the first image 136 is lowered. On the other hand, as in this embodiment, by slightly adding black to the first image 136 that is the background portion, the authentication code and the color of the other background portion can be made the same. It should be noted that the rate at which black toner is added to the first image 136 is obtained in advance by experiment, and the value is stored in a table.

  In addition, when the color of the authentication code is set to black, both may be the same black (K) toner, but in the present embodiment, the first image 136 as the background portion is yellow (Y), Whereas magenta (M) and cyan (C) toners are mixed to produce black (process black), the second image 138, which is an authentication code, is a single color black produced only with black (K) toner. is there. The gloss is also affected by the components forming the toner, but in the present embodiment, each toner made up in such a configuration that the process black has a higher gloss is used. If the process black is composed of only three types of toners of yellow (Y), magenta (M), and cyan (C), and the color difference is conspicuous, the four types of toner mixed with the black (K) toner are mixed. Process black can also be used. When the first image 136 made of process black is formed and then the second image 138 made of monochrome black is formed on the first image 136 as in this embodiment, the difference in gloss is increased. Can do.

  In FIG. 5, an authentication code setting unit 148 is a part for setting an authentication code, and here, the characters “original” are set. The font setting unit 150 is a part for setting the font of the authentication code. The size setting unit 152 is a part for setting the size of the authentication code. The file setting unit 154 is a part for setting a file for storing the authentication code. The position setting unit 154 is a part for setting a position for printing the authentication code. The confirmation screen area 154 displays the authentication code unit 134 on the screen based on information set by the authentication code color setting unit 146, the authentication code setting unit 148, the font setting unit 150, the size setting unit 152, and the position setting unit 156. It is an area to do. The difference in gloss between the image 136 and the image 138 is displayed by replacing it with the difference in brightness. The instruction operation unit 160 includes an OK button, a cancel button, a help button, and the like.

  Returning to FIG. 4, when the printer driver 30 acquires the authentication code setting information and the various printing condition setting information in step S14, the printer driver 30 notifies the application software 32 of the end of the printing conditions. The application software 32 that has been notified of the end of the printing conditions transitions the display screen to the print instruction screen.

  When printing is instructed on the print instruction screen (step S16), the printer driver 30 acquires the print data instructed to print, and print data including various print condition information is converted into print information that can be interpreted by the output destination printer 14. A converted print job is created (step S18). In the next step S20, a printing instruction is given, and the print job created in step S18 is transmitted to the printing apparatus 14 together with the printing instruction information.

  The printing apparatus 14 that has received the print job analyzes the print information included in the print job, and outputs the print data on the paper based on the print condition information (step S22). In the next step S24, it is determined whether or not all printing has been completed. If the printing has not been completed, the process returns to step S20. If the printing has been completed, the printing apparatus 14 terminates the print job. Is notified to the printer driver 30 and the processing is terminated.

Next, the process of step S22 described above will be described in detail.
FIG. 8 is a flowchart showing the control operation of the printing apparatus 14 in the original creation mode.
First, in step S26, the text 132 and the first image 136 shown in FIG. 3 are developed into a bitmap. The first image 136 is, for example, a rectangular area surrounding the authentication code, and has a color selected from the table shown in FIG.

  In the next step S28, the text 132 and the first image 136 developed in step S26 are printed. That is, referring to FIG. 1, the image data of the text 132 and the first image 136 expanded into a bitmap is sent to the optical writing device 48, and modulated by the optical writing device 48 according to the image data. A laser beam is applied to the photosensitive member 44 that is converted into laser light and uniformly charged by the charging device 46, and a latent image is formed on the photosensitive member 44. The latent image on the photoconductor 44 is developed into yellow, magenta, cyan, and black toner images by the developing device 50 and is primarily transferred onto the intermediate transfer belt 64. On the other hand, the paper supplied from the paper supply devices 90 and 90 or the manual feed unit 120 is guided to the main conveyance path 104 and is temporarily stopped by the registration roll 110, and the secondary transfer roll 72 and the secondary transfer backup are timed. Guided between the roll 74. When the sheet is guided between the secondary transfer roll 72 and the secondary transfer backup roll 74, the toner image primarily transferred to the intermediate transfer belt 64 is secondarily transferred to the sheet. The sheet on which the toner image has been transferred is guided to the fixing device 56, and the toner image is fixed on the sheet by heat and pressure generated by the heating roll 86 and the pressure roll 88.

  In the next step S30, the paper on which the text 132 and the first image 136 are formed is reversed twice. That is, referring to FIG. 1, when the trailing edge of the paper on which the text 132 and the first image 136 are formed reaches the discharge roll 112, the discharge roll 112 rotates backward and is switched to the paper conveyance path 114 side. Then, the sheet is guided to the sheet conveyance path 114. Further, the sheet is returned to the main conveyance path 104 via the sheet conveyance path 114. The sheet returned to the main conveyance path 104 is in a state where the back side faces the secondary transfer roll 72, and no image is formed on the sheet, and the secondary transfer roll 72 and the secondary transfer backup roll 74 and the fixing device 56.

  In this case, since the surface smoothness of the heating roll 86 and the pressure roll 88 is usually different, when the sheet passes through the fixing device 56 on the back surface, if the fixing device 56 is heated, the gloss of the first image 136 is increased. Therefore, the temperature of the indirect roll 86 is controlled to be lower than the normal fixing temperature. In this case, the pressure between the heating roll 86 and the pressure roll 88 may be lowered, or both heat and pressure may be lowered.

  When the paper that has passed through the fixing device 56 reaches the discharge roll 112 at the rear end of the paper, the discharge roll 112 rotates reversely and is switched to the paper conveyance path 114, and the paper is guided to the paper conveyance path 114. . Further, the sheet is returned to the main conveyance path 104 via the sheet conveyance path 114.

  In the next step S32, the second image 138 is developed into a bitmap, and in the next step S34, the second image 138 developed in this bitmap is transferred to the main conveyance path 104 by the same method as in step S28. It forms on the returned paper, and the process ends.

  As shown in FIG. 7, the second image 138 is formed so as to overlap the first image 136. Of the first image 136, the portion of the second image 138 where the toner is not placed is subjected to heat and pressure twice by the fixing device 56, and the gloss becomes high. The reason for this is that it is once melted in the first fixing step and melted again in a state where the thermal efficiency is improved, and the time for receiving heat and pressure in the fixing device 56 is increased in total. Since the second image 138 passes through the fixing device 56 for the first time when the image is formed for the second time and is melted for the first time, the gloss is lower than the other portions. In addition, when the toner in the second image portion is melted, the toner in the first image underneath also seems to be remelted, which is considered to reduce the total amount of heat given to the toner in the second image, which is also Works in the direction of decreasing gloss.

  In the above embodiment, the image forming apparatus is configured by connecting the information processing apparatus and the printing apparatus with a cable. However, the present invention is not limited to this, and the information processing apparatus and the printing apparatus are configured. May be connected via a network, or the information processing apparatus and the printing apparatus may be integrated to form an image forming apparatus.

  In the above embodiment, the first image and the second image have substantially the same color. However, the present invention is not limited to this, and the first image and the second image may have different colors. It only needs to have a different gloss. In this case, the second image cannot be erased from a copy obtained by copying the original, but the gloss is different between the first image and the second image in the original, whereas the first image is copied from the copy. Since there is no difference in gloss between the first image and the second image, the original and the copy can be distinguished.

  In the above-described embodiment, a so-called heat roll type fixing device that fixes an image on paper with heat and pressure is used. However, the present invention is not limited to this, and flash exposure is performed with heat. A pressure fixing method for fixing by a method or pressure may be used.

  In the above embodiment, the second image is automatically formed on the first image by using the paper conveyance path for double-sided printing. However, the present invention is not limited to this. Instead, the paper on which the first image is formed may be temporarily ejected, and the ejected paper may be set on, for example, a manual feed tray, and the second image may be formed on the paper set on the manual feed tray. .

1 is a block diagram illustrating an image forming apparatus according to an embodiment of the present invention. It is sectional drawing which shows the printing apparatus used for embodiment of this invention. (A) is a top view which shows the original formed with the image forming method which concerns on embodiment of this invention, (b) is a top view which shows the copy which copied the original of (a). 3 is a flowchart illustrating a control operation of the image forming apparatus according to the embodiment of the present invention. It is a screen figure which shows the authentication code setting screen displayed on the information processing apparatus used for embodiment of this invention. 6 is a table showing a relationship between a toner color of a first image and a toner color of a second image. 3 is a flowchart illustrating an image forming method according to an embodiment of the present invention. 6 is a flowchart illustrating a control operation of the printing apparatus according to the embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image forming apparatus 12 Information processing apparatus 14 Printing apparatus 40 Image forming part 44 Photoconductor 46 Charging apparatus 48 Optical writing apparatus 50 Developing apparatus 56 Fixing apparatus 64 Intermediate transfer belt 66 Primary transfer roll 72 Secondary transfer roll 90 Paper supply apparatus 104 Main Conveying path 112 Discharging roll 114 Paper conveying path 128 Original 130 Copy 134 Authentication code part 136 First image 138 Second image

Claims (7)

An image forming unit that includes a fixing device that fixes the toner to the paper by at least one of heat and pressure, and forms an image on the paper using the fixing device;
First control means for controlling the image forming unit so that a first image is formed on a sheet;
And a second control unit that controls the image forming unit so that a second image is formed on the first image after the first image is formed on the sheet by the first control unit. Image forming apparatus. The image forming apparatus according to claim 1, wherein the first image and the second image have substantially the same color.
  The image forming apparatus according to claim 1, wherein the first image has a larger amount of black toner per unit area than the second image.   The image forming unit uses yellow, magenta, cyan and black toners, the first image is formed from yellow, magenta and cyan toners, or yellow, magenta, cyan and black toners, and the second image is The image forming apparatus according to claim 1, wherein the image forming apparatus is formed from black toner.   The image forming unit includes a paper conveyance path for double-sided printing, and the second control unit controls the second image to be formed by passing the paper through the paper conveyance path twice. The image forming apparatus according to claim 1.   When the sheet is passed through the sheet conveyance path for the first time, the second control unit is configured to use at least one of the heat and pressure of the fixing device and the first image and at least while the sheet passes through the fixing device. The image forming apparatus according to claim 5, wherein the image forming apparatus is controlled so as to be less than a case where the second image is fixed. A toner is fixed to the paper by at least one of heat and pressure to form a first image on the paper;
An image that forms the second image on the paper by fixing the toner to the paper with at least one of heat and pressure so that the second image is formed on the first image after the first image is formed. Forming method.

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