Image forming apparatus

Abstract

To reduce possibility of occurrence of an image defect when an image is formed on a sheet to which a foil is transferred in advance.SOLUTION: When forming an image on a sheet on which a foil has been transferred in advance, an image forming apparatus acquires foil region data indicating a foil region which is a region on the sheet on which the foil has been transferred. When the image forming apparatus determines, based on input image data and foil region data, that a print region on the sheet, which is a region to which toner is transferred by image formation based on the input image data, overlaps with the foil region, the image forming apparatus displays warning information on an operation unit.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] Foil printing technology is used in the fields of bookbinding, commercial printing, card business, and plastic molding such as cosmetic containers. Letters or images made of foil can achieve a metallic feel and luster that is difficult to achieve with print. Foil printing is also used for holograms on credit cards. Patent documents 1 and 2 propose a foil printing device that forms a toner image on a sheet in advance and transfers the foil onto the sheet using the toner image as an adhesive. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-156723 [Patent Document 2] Patent Publication No. 2021-116185 Summary of the Invention [Problem to be solved by the invention]

[0004] As described above, an image may be formed by an image forming device on a sheet onto which foil has been transferred (printed). In such a case, if a toner image is formed in the area on the sheet onto which the foil has been transferred, there is a risk that image defects may occur in the image formed on the sheet.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to reduce the possibility of image defects occurring when an image is formed on a sheet onto which foil has already been transferred. [Means for solving the problem]

[0006] According to one aspect of the present invention, an image forming device is provided which, when forming an image on a sheet onto which foil has already been transferred, comprises: an acquisition means for acquiring foil area data indicating the foil area, which is the area on the sheet onto which foil has been transferred; and a control means for displaying warning information on a display means when it is determined, based on input image data and the foil area data, that the printing area on the sheet, which is the area onto which toner is transferred by image formation based on the input image data, overlaps with the foil area. [Effects of the Invention]

[0007] According to the present invention, when an image is formed on a sheet onto which foil has been transferred in advance, it is possible to reduce the possibility of image defects occurring. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a schematic configuration example of an image forming apparatus. [Figure 2] Block diagram showing an example of the configuration of the main control unit [Figure 3] FIG. 10 is an explanatory diagram of a process for detecting a foil region using a CIS. [Figure 4] FIG. 1 is a cross-sectional view showing a schematic configuration example of a CIS. [Figure 5] 10 is a flowchart showing an example of a procedure for a printing process. [Figure 6] FIG. 2 is a diagram showing an example of a UI screen (main screen). [Figure 7] FIG. 10 is a diagram showing an example of a UI screen. [Figure 8] FIG. 10 is a diagram showing an example of a UI screen. [Figure 9] FIG. 10 is a diagram showing an example of a UI screen. [Figure 10] FIG. 10 is a diagram showing an example of a UI screen. [Figure 11] FIG. 10 is a diagram showing an example of a UI screen. [Figure 12] FIG. 10 is a diagram showing an example of a binarized image showing a foil area and a print area. [Figure 13] FIG. 10 is a diagram showing an example of a UI screen. [Figure 14] FIG. 10 is a cross-sectional view showing a schematic configuration example of an image forming apparatus (second embodiment). [Figure 15] FIG. 10 is an explanatory diagram of a detection process of a foil region using a CIS (second embodiment). [Figure 16] FIG. 10 is a cross-sectional view showing a schematic configuration example of a CIS (second embodiment). [Figure 17] FIG. 10 is an explanatory diagram of a process for detecting a foil region using a CIS. [Figure 18] 10 is a flowchart showing an example of a procedure for print processing (second embodiment). [Figure 19] FIG. 10 is a cross-sectional view showing a schematic configuration example of an image forming apparatus (third embodiment). [Figure 20] FIG. 10 is an explanatory diagram of a detection process of a foil region using a CIS (third embodiment). [Figure 21] FIG. 11 is a diagram showing an example of a UI screen (third embodiment). DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the invention according to the claims. Although multiple features are described in the embodiments, not all of these multiple features are necessarily essential to the invention, and multiple features may be combined arbitrarily. Furthermore, in the accompanying drawings, the same reference numerals are used to designate the same or similar components, and redundant explanations will be omitted.

[0010] [First embodiment] In the first embodiment, an image forming apparatus capable of forming an image on a sheet onto which a foil has been transferred (printed) in advance will be described.

[0011] <Configuration of image forming device> FIG. 1 shows a schematic configuration example of an image forming apparatus 100 according to this embodiment. In the example of FIG. 1, the image forming apparatus 100 is configured as a multifunction peripheral having multiple functions, such as an image forming (printing) function, an image reading (scanning) function, and a copy function. The image forming apparatus 100 is capable of forming full-color images using an electrophotographic method, and forms a toner image on a sheet S (also referred to as a recording material). A sheet onto which foil has been transferred (printed) in advance can be used as the sheet S. Note that the image forming apparatus 100 may be configured to have a printing function capable of forming monochrome images instead of the printing function capable of forming full-color images.

[0012] The image forming apparatus 100 includes a cassette 5, a manual feed tray 6, a conveying unit 10, an image forming unit 20, a fixing unit 30, an operation unit 40, and a main control unit 101. The image forming apparatus 100 further includes a document reading unit (image reading unit) 50. The document reading unit 50 may include an ADF (automatic document feeder).

[0013] The image forming unit 20 includes process units 21Y, 21M, 21C, and 21K, an intermediate transfer belt 22, and a belt cleaner 29, and is an example of an image forming means. The process units 21Y, 21M, 21C, and 21K are arranged in parallel along the direction of movement of the intermediate transfer belt 22 and form yellow, magenta, cyan, and black toner images, respectively. Note that the letters YMCK added to the end of the reference numerals in FIG. 1 may be omitted when describing matters common to all four colors. The intermediate transfer belt 22 is stretched and rotated around multiple rollers. As described below, toner images of four color components are transferred onto the intermediate transfer belt 22 in a superimposed manner (primary transfer), thereby forming a full-color toner image. The intermediate transfer belt 22 carries and transports this full-color toner image to a secondary transfer position T2.

[0014] The cassette 5 stores a stack of sheets. While FIG. 1 shows an example in which the image forming apparatus 100 includes only one cassette 5, the image forming apparatus 100 may include multiple cassettes 5 that can store sheets S of different types (for example, sizes, thicknesses, or whether or not they have a surface coating). In this case, the type of sheets S specified in each job is fed from the corresponding cassette 5. Note that the sheets S may also be fed from the manual feed tray 6 instead of the cassette 5. Furthermore, a separate paper feeder (not shown) may be connected to the image forming apparatus 100.

[0015] The conveying unit 10 includes a conveying path and a plurality of rollers and is an example of a conveying means. A feeding roller 11 feeds a sheet one by one from the stack of sheets S in the cassette 5 to a conveying path 12. A conveying roller 13 conveys the sheet along the conveying path 12. A registration roller 14 sends the sheet S to the secondary transfer position T2 in synchronization with the timing at which the toner image on the intermediate transfer belt 22 reaches the secondary transfer position T2.

[0016] The process units 21Y, 21M, 21C, and 21K may have similar configurations, and are therefore referred to as process units 21. The process unit 21 includes a photosensitive drum 23, a charger 24, an exposure device 25, a developing device 26, a primary transfer roller 27, and a drum cleaner 28. The photosensitive drum 23 is a cylindrical image carrier that rotates counterclockwise in the drawing. The charger 24 may be, for example, a corona charger that irradiates charged particles by corona discharge, and charges the surface of the photosensitive drum 23 to a uniform potential (e.g., a negative dark potential). The charger 24 may also include a discharge roller or wire. The exposure device 25 includes, for example, a semiconductor laser as a light source, and forms an electrostatic latent image on the surface of the photosensitive drum 23 by scanning the surface of the photosensitive drum 23 with laser light according to input image data.

[0017] The developing unit 26 contains a developer made of toner and carrier, for example, and supplies the developer to the photosensitive drum 23 to develop the electrostatic latent image on the surface of the photosensitive drum 23 and form a toner image. As an example, the developer may be a two-component developer containing non-magnetic toner and magnetic carrier. The toner may contain a binder resin, a colorant, and a release agent (wax).

[0018] The primary transfer roller 27 is disposed at a primary transfer position T1 so as to face the photosensitive drum 23. A high-voltage primary transfer bias is applied to the primary transfer roller 27, which transfers the toner image (yellow in this case) on the surface of the photosensitive drum 23 to the intermediate transfer belt 22. The drum cleaner 28 removes toner remaining on the surface of the photosensitive drum 23 after the primary transfer.

[0019] Similar to the process unit 21Y, magenta, cyan, and black toner images are formed in the process units 21M, 21C, and 21K, respectively. These toner images are then transferred onto the yellow toner image on the intermediate transfer belt 22 in order, superimposed thereon.

[0020] The outer secondary transfer roller 16 is disposed at the secondary transfer position T2 so as to face the inner secondary transfer roller 15, which is one of the rollers around which the intermediate transfer belt 22 is stretched. A high voltage secondary transfer bias is applied to the outer secondary transfer roller 16, and the full-color toner image carried by the intermediate transfer belt 22 is transferred to the sheet S that has reached the secondary transfer position T2 (secondary transfer). A belt cleaner 29 removes toner remaining on the intermediate transfer belt 22 after the secondary transfer.

[0021] The fixing unit 30 is disposed downstream of the secondary transfer position T2. ​​The fixing unit 30 has a fixing roller (or a cylindrical heating film) and a pressure roller, and fixes the toner image to the sheet S by heating and pressurizing the sheet S onto which the toner image has been transferred. The sheet S that has passed through the fixing unit 30 is discharged to the outside of the image forming apparatus 100 (for example, to an output tray (not shown)).

[0022] When double-sided printing is performed, the sheet S, on which a toner image is formed on its first side, is conveyed to the conveying path 17. There, the sheet S reverses its traveling direction and enters the double-sided conveying path 18. The sheet S returns to the conveying path 12 upside down. The toner image is transferred to the second side of the sheet S at the secondary transfer position T2. ​​The fixing unit 30 fixes the toner image to the second side of the sheet S by again heating and pressurizing the sheet S. The sheet S is then discharged to the outside of the image forming apparatus 100. In this way, when forming images on both sides of a sheet, the double-sided conveying path 18 is used to convey the sheet, on which an image is formed on its first side, from the downstream side of the transfer position (secondary transfer position T2) where the toner image is transferred to the sheet conveyed along the conveying path 12 to the upstream side of the transfer position.

[0023] The operation unit 40 provides a user interface (UI) to a user of the image forming apparatus 100. The operation unit 40 includes, for example, a touch panel 41. The touch panel 41 displays images and information under the control of the main control unit 101 (described later) and accepts touch inputs from the user. Instead of (or in addition to) the touch panel 41, the operation unit 40 may include an output device (e.g., a liquid crystal display, a speaker) and an input device (e.g., a button, a switch, a keypad, a microphone).

[0024] The main control unit 101 controls the overall operation of the image forming apparatus 100. For example, when an instruction to execute a print job is received, the main control unit 101 controls the image forming unit 20 to form an image on a sheet S based on input image data received from an external device. The external device here may be, for example, a personal computer (PC) or an external controller. When an instruction to execute a copy job is received, the main control unit 101 controls the image forming unit 20 to form an image on a sheet S based on read image data generated by the document reading unit 50 reading a document.

[0025] <Control configuration of image forming apparatus> FIG. 2 is a block diagram showing an example configuration of the main control unit 101. The CPU 102 controls the image forming apparatus 100 by executing a control program stored in the ROM 103. The ROM 103 stores various programs such as the control program, and various data such as control data required for controlling the image forming apparatus 100. The ROM 103 is an example of a non-volatile memory device. A non-volatile memory device that allows data to be electrically erased can also be used instead of the ROM 103. The RAM 104 is used to store temporary data when the CPU 102 controls the image forming apparatus 100. The RAM 104 is an example of a volatile memory device.

[0026] <Foil processing> The image forming apparatus 100 of this embodiment is capable of forming an image on a sheet (also referred to as a foil sheet) onto which foil has been previously transferred (printed). By performing foil printing (foil stamping), which prints foil on a sheet, it is possible to express the unique luster and texture of metal, unlike sheets that have been normally printed. In foil printing, for example, a ductile metal that has been hammered into a thin film or a metal vapor-deposited metal is used, and various metals such as gold, silver, copper, iron, aluminum, or titanium are used as the metal.

[0027] Foil printing is generally performed by printing foil onto a sheet using a die with heat and pressure. This type of foil printing results in the formation of hot stamp foil. Hot stamp foil consists of, in order from the surface of the sheet, an adhesive layer, a metal layer or a metal-deposited layer, and (optionally) a colored layer. With hot stamp foil, the foil is printed only in the areas of the sheet where heat and pressure have been applied, eliminating the need for masking and enabling cost reduction compared to painting.

[0028] Also, unlike hot stamping foil, foil consisting of only a metal layer without an adhesive layer (e.g., commercially available 0.01 mm thick copper foil) may be printed. In this case, spot varnish or remelted toner after printing is used as the adhesive. Compared to the hot stamping method described above, this method can reduce costs by not using a mold, and the foil is easy to handle and a wide variety of foils can be selected.

[0029] In this way, because metal is used for the foil printed on the sheet, the sheet is endowed with properties such as the luster and thermal conductivity that are unique to metal. In other words, when foil is printed on a sheet, the properties of the portion of the sheet where the foil is printed will be different from those of the other portions.

[0030] When an image (toner image) is formed by the image forming apparatus 100 on a foil sheet onto which foil has been previously transferred (printed), if toner is transferred to the foil area on the foil sheet where the foil has been transferred, image defects may occur in the image formed on the foil sheet. This is because toner offset may occur during the fixing process by the fixing unit 30 due to the affinity between the metal part of the foil and the components of the toner.

[0031] Therefore, in order to prevent the occurrence of the above-mentioned image defects, the image forming apparatus 100 of this embodiment is configured to notify the user of warning information when there is a possibility that toner will be transferred to the foil area on the foil sheet due to image formation based on input image data. This notifies the user in advance of the possibility of image defects occurring, allowing the user to decide whether to continue or cancel the printing process.

[0032] <Detection process of foil area on foil sheet> In order to determine the possibility that a toner image will be transferred to the foil area on the foil sheet, the image forming apparatus 100 of this embodiment performs a detection process for the foil area on the foil sheet used for image formation using the document reading unit 50. The document reading unit 50 includes a contact image sensor (CIS) 300. The document reading unit 50 is used as a detection unit for detecting the foil area on the sheet.

[0033] FIG. 3 is an explanatory diagram of the foil region detection process using the CIS 300. FIG. 4 is a cross-sectional view showing a schematic configuration example of the CIS 300, viewed in a direction (main scanning direction or width direction) perpendicular to both the conveyance direction (sub-scanning direction) of the sheet S and the normal direction of the sheet S. The CIS 300 includes a light source 301, a lens 302, and a light receiving element 303. The light source 301 is configured to irradiate the sheet S with light across the entire main scanning direction (width direction) of the sheet S. The light source 301 is, for example, a white LED that outputs white light. The lens 302 is configured to focus the scattered reflected light from the sheet S, which is irradiated by the light source 301 onto the light receiving element 32, and is, for example, a cylindrical rod lens. The light receiving element 303 is provided across the entire main scanning direction of the sheet S and is, for example, a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0034] For each area on the sheet S illuminated with light from the light source 301, the CIS 300 outputs a signal indicating the amount of scattered reflected light received by the light receiving element 303 from that illuminated area. As shown in FIG. 3, this signal is output as one-dimensional luminance information indicating the luminance of each area (position) in the main scanning direction. FIG. 3 shows an example of one-dimensional luminance information at sub-scanning positions P1 and P2. The main control unit 101 generates two-dimensional luminance information indicating the luminance of each area (position) on the sheet S based on the one-dimensional luminance information at each sub-scanning position output from the CIS 300.

[0035] As shown in Figure 4(A), light source 301 irradiates areas of sheet S where no foil has been transferred (non-foil areas), and the light is scattered and reflected from (the surface of) sheet S, which is then focused by lens 302 onto light receiving element 303. Also, as shown in Figure 4(B), the light irradiated onto the foil areas of sheet S is totally reflected by being absorbed and re-emitted by the movement of free electrons in the metal contained in the foil. Therefore, the amount of scattered light reflected from the foil areas of sheet S is smaller than the amount of scattered light reflected from the non-foil areas of sheet S.

[0036] 3, the brightness indicated by the brightness information output from the CIS 300 is smaller when the light source 301 irradiates the foil area on the sheet S than when the light source 301 irradiates the non-foil area on the sheet S. Therefore, the main control unit 101 sets the threshold D as the amount of light received by the light receiving element 303 in the light irradiated area on the sheet S. Th An area where the amount of received light corresponding to a brightness lower than the first threshold value is obtained is detected as a foil area (a candidate foil area). Th For example, the brightness obtained when light is irradiated from light source 301 onto a solid black image formed in a non-foil area (i.e., the image that appears darkest among the non-foil images) is acquired in advance, and the brightness is set in advance so that brightness below this brightness can be detected.

[0037] When document reading unit 50 is used both for detecting foil areas on sheet S and for reading normal documents, CIS 300 may output luminance information indicating low luminance for both the non-foil area where a black solid image is formed and the foil area. In this case, a foil area detection mode may be provided in which the amount of light irradiated onto sheet S by light source 301 is greater than in the document reading mode, so that the foil area can be distinguished from the non-foil area where a black solid image is formed. Furthermore, document reading unit 50 may be configured to use a reduction optical (CCD) one-dimensional sensor, a two-dimensional area camera, or the like, in addition to the CIS type.

[0038] <Foil sheet mode printing process> 5 is a flowchart showing an example of a procedure for a printing process for forming an image on a foil sheet by the image forming apparatus 100 of this embodiment. In this example, it is assumed that a foil sheet prepared in advance by a user is used for printing.

[0039] In this example, the main control unit 101 displays a main screen 600 shown in FIG. 6 on the operation unit 40 as an operation screen (UI screen) for selecting functions of the image forming apparatus 100 in accordance with a user operation received by the operation unit 40. The main screen 600 includes a button 601 for selecting a foil paper print (foil sheet print) function for forming an image on a foil sheet. When the user presses the button 601, the main control unit 101 sets the operation mode of the image forming apparatus 100 to foil sheet mode and starts executing the process shown in FIG. 5. The foil sheet mode is an operation mode (print mode) for forming an image on a foil sheet based on input image data. The main control unit 101 can use input image data received from an external device, such as a personal computer (PC) or an external controller, or input image data previously stored in the ROM 103.

[0040] In S101, the main control unit 101 displays a UI screen on the operation unit 40 to prompt the user to select a paper tray (paper feed unit) to be used, and receives the selection of a paper tray from the user through the UI screen. The user uses the UI screen displayed on the operation unit 40 to select a paper tray into which to set the foil sheet for feeding.

[0041] The UI screen displayed in S101 is configured to clearly indicate the paper tray for which foil area data (foil area information) has been set, for example, as in the UI screen 700 shown in FIG. 7. When foil area data is set for a paper tray, the foil area data is stored in ROM 103 in association with the paper tray. For example, foil area data used in a previous printing process using a foil sheet is stored in ROM 103 in association with the paper tray used in the printing process (unless it has been deleted since then). If previously set foil area data exists in ROM 103, the main control unit 101 displays the UI screen 700 so that the user can recognize the paper tray with which the foil area data is associated (the manual feed tray in the example of FIG. 7). Furthermore, the main control unit 101 performs normal display for other paper trays (paper trays 1 to 4 in the example of FIG. 7).

[0042] When the user selects a paper tray, the main control unit 101 determines in S102 whether or not foil area data associated with the selected paper tray (selected tray) exists. If foil area data associated with the selected tray exists in ROM 103, the main control unit 101 acquires the foil area data from ROM 103 and proceeds to S105. If foil area data associated with the selected tray does not exist in ROM 103, the main control unit 101 proceeds to S103.

[0043] In S103, the main control unit 101 performs a scan process for the foil sheet to be used. To this end, the main control unit 101 displays a UI screen on the operation unit 40 that shows a guide for reading (scanning) the foil sheet by the document reading unit 50, and accepts a scan instruction from the user. For example, the UI screen 800 shown in FIG. 8 is displayed on the operation unit 40. The user places the first page of the foil sheet on the document table of the document reading unit 50 according to the guide shown on the UI screen 800, and presses the scan start button 801. This causes the main control unit 101 to accept a scan instruction via the operation unit 40. The main control unit 101 controls the document reading unit 50 to scan the foil sheet in accordance with the accepted scan instruction. This allows the main control unit 101 to acquire the read image data generated by the document reading unit 50.

[0044] Each time the scanning process of one page of the foil sheet is completed, the main control unit 101 updates the UI screen 800 to display a guide for placing the foil sheet of the next page (e.g., page 2) on the platen. The UI screen 800 of this example also includes a button 802 for receiving an input indicating that the page to be scanned does not have a foil area. When the button 802 is pressed, the main control unit 101 may omit the scanning process of that page and update the UI screen 800 to display a guide for placing the foil sheet of the next page on the platen.

[0045] When the scanning process of the foil sheet is completed, in S104, the main control unit 101 detects the foil area on the foil sheet based on the scanned image data, thereby acquiring foil area data. In this example, the main control unit 101 detects potential foil areas on the foil sheet based on the luminance information acquired as the scanned image data (described above with reference to FIG. 3), and displays an image indicating the potential foil areas as a preview image on the operation unit 40. The UI screen 900 in FIG. 9(A) is a UI screen including such an image. The UI screen 900 is displayed on the operation unit 40 to prompt the user to confirm and specify the detected potential foil areas. The user specifies, via the operation unit 40, the potential foil area in the displayed image that corresponds to the area where the foil is actually transferred (printed) on the foil sheet. The main control unit 101 acquires data indicating the foil area specified by the user as foil area data. After acquiring the foil area data, the main control unit 101 proceeds from S104 to S105.

[0046] In the above example, the foil area is detected by detecting foil area candidates based on the luminance information obtained by scanning the foil sheet using CIS 301 and allowing the user to select a foil area from the displayed foil area candidates. However, other methods may be used. For example, the scanned image obtained by scanning the foil sheet using CIS 301 may be displayed on operation unit 40 as shown in UI screen 910 in FIG. 9B, and the user may specify a foil area to detect the foil area. Furthermore, main control unit 101 may acquire foil area data by automatically detecting the foil area based on scanned image data (luminance information) without prompting the user for confirmation via a UI screen. In addition to being acquired using document scanning unit 50, foil area data may also be acquired from an external device, such as a PC, that can communicate via a network. In this case, for example, an image file may be received from the external device, and the foil area data may be acquired based on the received image file.

[0047] In S105, the main control unit 101 determines whether or not to use the foil area data acquired from the ROM 103 in S102 or acquired in S104 for printing in the foil sheet mode. Specifically, the main control unit 101 displays a UI screen including a preview image showing the foil area on the foil sheet on the operation unit 40 based on the acquired foil area data, and accepts a selection from the user via the UI screen as to whether or not to use the foil area data.

[0048] 10 is an example of a UI screen displayed in S105, and includes a preview image showing the foil area on the foil sheet, generated based on the foil area data. The UI screen 1000 includes a button 1001 for a user who has checked the preview image to instruct the use of the foil area data that has already been acquired (current foil area data), and buttons 1002 and 1003 for instructing the change (modification) of the foil area data. For example, the user can specify a specific page (e.g., page 1) and instruct the re-acquisition of foil area data for the foil sheet of that page.

[0049] If the main control unit 101 does not use the acquired foil area data in accordance with the user's selection (i.e., if the foil area data is to be changed), the process returns from S105 to S103. On the other hand, if the main control unit 101 uses the acquired foil area data, the process proceeds from S105 to S106. In S106, the main control unit 101 associates the acquired foil area data with the selected tray and stores it in the ROM 103. Note that the foil area data already associated with the selected tray acquired from the ROM 103 does not need to be stored in the ROM 103 again.

[0050] Thereafter, in S107, the main control unit 101 displays a UI screen on the operation unit 40 to guide the user in setting the foil sheet in the selected tray (selected paper feed unit), and proceeds to S108. A UI screen 1100 in FIG. 11 is an example of the UI screen displayed in S107. The UI screen 1100 includes a guide to prevent the user from mistaking the orientation and front and back of the sheet S when placing the foil sheet in the selected tray. The UI screen 1100 further includes a button 1101 for instructing the user to execute a printing process using the foil area data, and a button 1102 for instructing the user not to execute a printing process.

[0051] In S108, the main control unit 101 determines whether or not to execute printing processing using the acquired foil area data based on instructions input by the user. If the user instructs not to execute printing processing (for example, if button 1102 on the UI screen 1100 is pressed), the main control unit 101 ends the processing according to the procedure in FIG. 5. In this case, the main control unit 101 returns the printing mode from foil sheet mode to normal mode. In the next printing processing in foil sheet mode, by using the foil area data stored in ROM 103 in association with the selected tray, it is possible to omit the foil sheet scanning process (S103) to acquire the foil area data.

[0052] On the other hand, if the user instructs to execute the printing process (for example, if button 1101 is pressed on UI screen 1100), the main control unit 101 proceeds from S108 to S109. In S109, the main control unit 101 compares the foil area on the foil sheet indicated by the foil area data (foil area information) with the print area specified based on the input image data. The print area here is the area on the foil sheet to which toner is transferred by the printing process (image formation) by the image forming unit 20 based on the input image data. For example, the main control unit 101 generates a binary image indicating the foil area based on the foil area data, as in the binary image shown in FIG. 12, and also generates a binary image indicating the print area based on the input image data. The main control unit 101 compares the foil area with the print area based on the generated binary image.

[0053] In S110, the main control unit 101 determines whether the print area is likely to overlap with the foil area based on the comparison result of S109. For example, the main control unit 101 determines that the print area is likely to overlap with the foil area if at least a portion of the print area overlaps with the foil area. The main control unit 101 may also use an area obtained by enlarging the print area identified based on the input image data, taking into account sheet transport misalignment and misalignment of the formed image, for its determination. In this case, the main control unit 101 determines that the print area is likely to overlap with the foil area if at least a portion of such an area overlaps with the foil area.

[0054] If the main control unit 101 determines that there is no possibility that the printing area overlaps the foil area, the process proceeds from S110 to S113. In S113, the main control unit 101 controls the conveying unit 10 and the image forming unit 20 to start a printing process that forms (prints) an image on the foil sheet based on the input image data. When the printing process is completed, the main control unit 101 ends the process according to the procedure in FIG. 5 and returns the printing mode from the foil sheet mode to the normal mode.

[0055] On the other hand, if the main control unit 101 determines that there is a possibility that the print area overlaps the foil area, the process proceeds from S112 to S111. In S111, the main control unit 101 displays warning information on the operation unit 40 indicating that there is a possibility that the print area overlaps the foil area (there is a possibility that an image defect will occur on the foil sheet). As a result, the main control unit 101 notifies the user of the warning information and prompts the user to select whether or not to continue the printing process. The warning screen 1300 in FIG. 13 is an example of the warning screen displayed in S111. The warning screen 1300 includes a button (display object) for accepting the selection of whether or not to continue the printing process. The warning screen 1300 may also include a preview image of the output image that will be obtained if the printing process is continued.

[0056] After displaying the warning information, in S112 the main control unit 101 determines whether or not to continue the printing process. For example, if an instruction to continue the printing process is given via the warning screen 1300, the main control unit 101 proceeds to S113. In this case, in S113 the main control unit 101 controls the conveying unit 10 and the image forming unit 20 to start the printing process of forming (printing) an image on a foil sheet based on the input image data. When the printing process is completed, the main control unit 101 ends the process according to the procedure in FIG. 5 and returns the printing mode from the foil sheet mode to the normal mode.

[0057] 5 without executing the printing process, and returns the printing mode from the foil sheet mode to the normal mode. In this way, after notifying the user of the warning information, the main control unit 101 stops image formation based on the input image data when it receives an instruction from the user to stop image formation.

[0058] As described above, in the image forming apparatus 100 of this embodiment, when forming an image on a sheet to which foil has been previously transferred, the main control unit 101 acquires foil area data indicating the foil area on the sheet to which the foil has been previously transferred. If the main control unit 101 determines, based on the input image data and the foil area data, that the print area on the sheet to which toner will be transferred by image formation based on the input image data overlaps with the foil area, the main control unit 101 displays warning information on the operation unit 40 (display unit). According to this embodiment, when forming an image on a sheet to which foil has been previously transferred, the image forming apparatus 100 can warn the user that toner may be transferred to the foil area on the sheet. This allows the user to decide whether to stop image formation. Therefore, it is possible to reduce the possibility of image defects occurring when forming an image on a sheet to which foil has been previously transferred.

[0059] [Second embodiment] In the second embodiment, an example will be described in which a detection unit (CIS) for detecting a foil area on a sheet is arranged on the conveying path 12 in the image forming apparatus 100. The following will mainly describe the differences from the first embodiment.

[0060] <Configuration of image forming device> FIG. 14 shows a schematic configuration example of an image forming apparatus 100 of this embodiment. Compared to the image forming apparatus 100 of the first embodiment (FIG. 1), the image forming apparatus 100 of this embodiment further includes an inline CIS 310 on the conveying path 12 between the paper feed unit (cassette 5 or manual feed tray 6) and the secondary transfer position T2 as a detection unit for detecting the foil area on the sheet. Note that the image forming apparatus 100 does not necessarily have to include the document reading unit 50. In that case, the image forming apparatus 100 is configured as a tandem full-color printer capable of forming full-color images by electrophotography, rather than as a multifunction peripheral.

[0061] <Detection process of foil area on foil sheet> To determine the possibility of a toner image being transferred to the foil area on the foil sheet, the image forming apparatus 100 of this embodiment uses the inline CIS 310 described above to detect the foil area on the foil sheet used for image formation. The main control unit 101 acquires foil area data based on the detection results from the CIS 310 (detection unit). The CIS 310 is disposed at a predetermined distance (e.g., 0.8 mm) from the surface of the sheet S being conveyed along the conveying path 12. The configuration and operation of the CIS 310 are similar to those of the CIS 300 described with reference to FIG. 4 in the first embodiment.

[0062] 15, the main control unit 101 generates two-dimensional luminance information indicating the luminance of each region (position) on the sheet S based on the one-dimensional luminance information of each sub-scanning position output from the CIS 310. Note that each sub-scanning position corresponding to the one-dimensional luminance information can be identified based on the conveyance speed of the sheet S and the time when the one-dimensional luminance information is output. As in the first embodiment, the main control unit 101 determines the amount of light received by the light receiving element 303 in the light irradiation region on the sheet S as a threshold D ThAn area where the amount of received light corresponding to a luminance smaller than the (first threshold value) is obtained is detected as a foil area (a candidate foil area).

[0063] When CIS 310 is used for both detecting a foil area on sheet S and as another media sensor, a foil area detection mode may be provided in which the amount of light that light source 301 irradiates onto sheet S is an amount of light that is suitable for detecting the foil area. Also, instead of CIS 310, a one-dimensional sensor using a reduction optical system (CCD system), a two-dimensional area camera, or the like may be used.

[0064] Furthermore, the CIS 310 is not limited to the configuration shown in FIG. 4 and may have, for example, the configuration shown in FIG. 16. In this example, the CIS 310 has a light source 311 and a light receiving element 312. The light source 311 is configured to irradiate the sheet S with near-infrared light having a wavelength ranging from 1.3 to 4.6 nm over the entire main scanning direction (width direction) of the sheet S. Near-infrared light has a wavelength that is easily transmitted through the sheet S and easily absorbed by the sheet S. The light receiving element 312 is provided over the entire main scanning direction (width direction) of the sheet S and is, for example, a CMOS sensor. The light receiving element 312 is arranged to receive specular reflection light from the sheet S of the near-infrared light irradiated by the light source 311.

[0065] As shown in Fig. 16, near-infrared light irradiated onto the foil region on sheet S is totally reflected by being absorbed and re-emitted by the movement of free electrons in the metal contained in the foil. On the other hand, near-infrared light irradiated onto the non-foil region on sheet S is transmitted through or absorbed by sheet S. Therefore, as shown in Fig. 17, the luminance indicated by the luminance information output from CIS 310 is greater when near-infrared light is irradiated from light source 311 onto the foil region on sheet S than when near-infrared light is irradiated from light source 311 onto the non-foil region on sheet S.

[0066] Therefore, in this example, the main control unit 101 determines the amount of light received by the light receiving element 312 in the near-infrared light irradiation area on the sheet S as a threshold D ThThe area where the amount of received light corresponding to the brightness greater than the threshold D is detected as a foil area (a candidate foil area). Th is preset so as to be able to detect a luminance exceeding the maximum value of the luminance corresponding to the light reflected from the non-foil area, for example.

[0067] <Foil sheet mode printing process> FIG. 18 is a flowchart showing an example of the procedure for a printing process in which the image forming apparatus 100 of this embodiment forms an image on a foil sheet. In this example, a foil sheet prepared in advance by a user is used for printing. As in the first embodiment (FIG. 5), the main control unit 101 displays the main screen 600 on the operation unit 40, and sets the operating mode (printing mode) of the image forming apparatus 100 to foil sheet mode in response to pressing of a button 601. The main control unit 101 then starts executing the process according to the procedure in FIG. 18. The main control unit 101 performs the printing process using input image data received from an external device or input image data previously stored in the ROM 103.

[0068] In S201, the main control unit 101 displays a UI screen on the operation unit 40 that prompts the user to select a paper tray (paper feed unit) to be used, and accepts the selection of a paper tray from the user through the UI screen. The user uses the UI screen displayed on the operation unit 40 to select a paper tray into which to set the foil sheet for feeding. Note that the paper tray selection may be performed in a print job received from an external device. Thereafter, in S202, the main control unit 101 accepts an instruction to execute the print process from the user through the UI screen displayed on the operation unit 40, and proceeds to S203.

[0069] In S203, the main control unit 101 controls the conveying unit 10 to start conveying the foil sheets one by one from the selected paper tray (selected tray). The foil sheet conveyed by the conveying unit 10 along the conveying path 12 passes a position (detection position) opposite the CIS 310. In S204, the main control unit 101 acquires foil area data by performing a detection process using the CIS 310 to detect the foil area on the foil sheet being conveyed along the conveying path 12. The main control unit 101 also controls the conveying unit 10 to temporarily stop the foil sheet that has passed the detection position of the CIS 310 at a position between the detection position and the secondary transfer position T2 (for example, the position of sheet S' in FIG. 14).

[0070] After acquiring the foil area data, the main control unit 101 compares the foil area on the foil sheet indicated by the foil area data (foil area information) with the print area specified based on the input image data in S203, similar to S109. Then, in S204, the main control unit 101 determines whether or not there is a possibility that the print area overlaps with the foil area based on the comparison result in S203, similar to S110.

[0071] If the main control unit 101 determines that there is no possibility that the printing area overlaps the foil area, the process proceeds from S204 to S208. In S208, the main control unit 101 controls the conveying unit 10 and the image forming unit 20 to perform a printing process to form (print) an image on the foil sheet based on the input image data. In the printing process, the main control unit 101 causes the conveying unit 10 to resume conveying the foil sheet that has stopped upstream of the secondary transfer position T2 on the conveying path 12, and causes the toner image to be transferred onto the foil sheet at the secondary transfer position T2.

[0072] When image formation on the foil sheet is complete, in S209, the main control unit 101 determines whether to end the printing process. For example, when performing image formation on multiple foil sheets, the main control unit 101 returns to S203 when image formation on the next foil sheet is to be performed, and repeats the steps from S203 onwards for the next foil sheet. Also, when performing double-sided printing, after image formation on the first side of a foil sheet is completed, when image formation on the second side is to be performed, the main control unit 101 returns to S203 and repeats the steps from S203 onwards for the second side of the foil sheet. When performing double-sided printing, the main control unit 101 transports the foil sheet with an image formed on its first side via the double-sided transport path 18 to a position upstream of the CIS 310 on the transport path 12. As a result, the main control unit 101 performs foil area detection (S203) for the second side of the foil sheet using the CIS 310. In S209, when the printing process for all pages to be printed is completed, the main control unit 101 ends the process according to the procedure in FIG. 18 and returns the printing mode from the foil sheet mode to the normal mode.

[0073] Furthermore, if the main control unit 101 determines that the printing area may overlap the foil area, the process proceeds from S204 to S205. In S205, the main control unit 101, as in S111, displays warning information on the operation unit 40 indicating that the printing area may overlap the foil area (there is a possibility of image defects on the foil sheet). After displaying the warning information, in S206, the main control unit 101 determines whether to continue the printing process, as in S112. If the user instructs the main control unit 101 to continue the printing process, the process proceeds to S208. In this case, as described above, the main control unit 101 controls the conveying unit 10 and the image forming unit 20 to perform the printing process to form (print) an image on the foil sheet based on the input image data. On the other hand, if the user instructs the main control unit 101 not to continue (stop) the printing process, the main control unit 101 stops the printing process and proceeds to S207.

[0074] In S207, the main control unit 101 controls the removal of the foil sheet stopped (waiting) in the transport path 12 so that the user can remove the foil sheet from the image forming apparatus 100. For example, the main control unit 101 controls the transport unit 10 to transport the foil sheet to a position where it can be removed, and controls the transport rollers to de-energize or de-pressurize in order to prevent damage to the foil sheet during removal. The main control unit 101 may also display the foil sheet removal procedure on the operation unit 40. Alternatively, the main control unit 101 may control the transport unit 10 to automatically transport the foil sheet to a position where it can be discharged, such as the paper output tray or evacuation tray of the image forming apparatus 100. When the main control unit 101 completes the foil sheet removal control, it ends the processing according to the procedure in FIG. 18 and returns the printing mode from the foil sheet mode to the normal mode.

[0075] As described above, according to this embodiment, similar to the first embodiment, when forming an image on a sheet onto which foil has been previously transferred in the image forming apparatus 100, it is possible to warn the user of the possibility that toner may be transferred to the foil area on the sheet. This allows the user to decide whether or not to stop image formation. Therefore, it is possible to reduce the possibility of image defects occurring when forming an image on a sheet onto which foil has been previously transferred.

[0076] [Third embodiment] In the third embodiment, an example will be described in which, when there is a possibility that toner may be transferred to the foil area on the sheet, warning information is displayed, etc., while the sheet is made to wait in the double-sided conveying path in the image forming apparatus 100. The following will mainly describe the differences from the second embodiment.

[0077] <Configuration of image forming device> FIG. 19 shows a schematic configuration example of an image forming apparatus 100 of this embodiment. Like the image forming apparatus 100 of the second embodiment (FIG. 14), the image forming apparatus 100 of this embodiment includes an inline CIS 310 on the transport path 12 between the paper feed unit (cassette 5 or manual feed tray 6) and the secondary transfer position T2. ​​Note that the image forming apparatus 100 does not necessarily have to include the document reading unit 50. In that case, the image forming apparatus 100 is configured as a tandem full-color printer capable of forming full-color images by electrophotography, rather than as a multifunction peripheral.

[0078] In the image forming apparatus 100 of this embodiment, the CIS 310 is disposed on the second surface (rear surface) side of the sheet S, which is opposite to the first surface (front surface) onto which the toner image is transferred at the secondary transfer position T2. ​​That is, as shown in FIG. 20 , the CIS 310 is disposed so as to detect the foil area on the rear surface of the sheet S (foil sheet) conveyed along the conveyance path 12. The position at which the CIS 310 is disposed is not limited to the above-described position on the conveyance path along which the sheet S is conveyed. For example, the CIS 310 may be disposed at a position on the duplex conveyance path 18 that ensures a distance from the CIS 310 to the secondary transfer position T2 that allows the sheet S to wait (stop). When the CIS 310 is disposed at a position subsequent to the reversal unit where the traveling direction of the sheet S is reversed, the CIS 310 is disposed so as to detect the foil area on the front surface of the sheet S.

[0079] <Foil sheet mode printing process> In the image forming apparatus 100 of this embodiment, the printing process in the foil sheet mode is executed according to the procedure shown in FIG. 18 , as in the second embodiment. However, the orientation of the foil sheet when it is set in the selected tray is reversed from that in the second embodiment to match the arrangement of the CIS 310. Specifically, in the second embodiment, the foil sheet is set in the selected tray with the printing surface (front surface) of the foil sheet facing up, whereas in this embodiment, the foil sheet must be set with the printing surface (front surface) of the foil sheet facing down. For this reason, after the paper tray (paper feed tray) to be used is selected in S201, the main control unit 101 may display the UI screen 2100 shown in FIG. 21 on the operation unit 40 to guide the user as to the orientation in which to set the foil sheet.

[0080] When conveyance of a foil sheet set on the selected tray with its print surface (front side) facing downward begins in S203, a foil area detection process is performed on the print surface of the foil sheet using the CIS 310 positioned as shown in Fig. 19. In this embodiment, the main control unit 101 controls the conveyance unit 10 to pass the foil sheet that has passed the detection position of the CIS 310 through the secondary transfer position T2 and the fixing unit 30 without the image forming unit 20 forming a toner image. The main control unit 101 further controls the conveyance unit 10 to convey the foil sheet to the duplex conveyance path 18 and temporarily stop it at a position on the duplex conveyance path 18 (for example, the position of sheet S' in Fig. 19).

[0081] The main control unit 101 performs the processes of S203 to S206 while the foil sheet is stopped (waiting) on ​​the double-sided conveying path 18. In this way, by configuring the image forming apparatus 100 so that the foil sheet can be made to wait on the double-sided conveying path 18 while warning information is displayed, etc., it is possible to realize a relatively small device configuration while achieving the same processes as in the second embodiment and obtaining the same effects. In S207, the main control unit 101 controls the removal of the foil sheet stopped (waiting) on ​​the double-sided conveying path 18 so that the user can remove the foil sheet from the image forming apparatus 100.

[0082] The present invention can also be realized by supplying a program that implements one or more of the functions of the above-described embodiments to a system or device via a network or a storage medium, and having one or more processors in the computer of the system or device read and execute the program.The present invention can also be realized by a circuit (e.g., ASIC) that implements one or more of the functions.

[0083] The disclosure of the present specification includes the following image forming apparatus. (Item 1) An image forming apparatus, an acquisition means for acquiring foil area data indicating a foil area on a sheet onto which foil has been transferred in advance, when forming an image on the sheet; a control means for displaying warning information on a display means when it is determined based on the input image data and the foil area data that a print area on the sheet, which is an area to which toner is transferred by image formation based on the input image data, overlaps with the foil area; An image forming apparatus comprising: (Item 2) further comprising an image forming means for forming an image on the sheet; The control means When it is determined that the printing area does not overlap the foil area, the image forming means is controlled to form an image on the sheet based on the input image data; When it is determined that the printing area overlaps the foil area, the warning information is displayed on the display means. Item 2. The image forming apparatus according to item 1. (Item 3) and when the control unit receives an instruction to form an image from a user after displaying the warning information, the control unit controls the image forming unit to form an image on the sheet based on the input image data. Item 3. The image forming apparatus according to item 2. (Item 4) When the control unit receives an instruction to stop image formation from a user after displaying the warning information, the control unit stops image formation based on the input image data. Item 4. The image forming apparatus according to item 2 or 3. (Item 5) The control means causes the display means to display the warning information when at least a part of the print area specified based on the input image data overlaps with the foil area. 5. The image forming apparatus according to any one of items 1 to 4. (Item 6) the control means causes the display means to display the warning information when at least a part of an area obtained by enlarging the print area specified based on the input image data overlaps with the foil area. 5. The image forming apparatus according to any one of items 1 to 4. (Item 7) further comprising an image reading unit that reads an image on the sheet; the acquiring means acquires the foil area data based on a reading result by the image reading unit of the sheet onto which foil has been previously transferred. 7. The image forming apparatus according to any one of items 1 to 6. (Item 8) the acquiring means acquires the foil area data from an external device capable of communicating via a network. 7. The image forming apparatus according to any one of items 1 to 6. (Item 9) a detection unit that is disposed between a sheet feeding unit that feeds a sheet to a conveying path and a transfer position where a toner image is transferred onto the sheet conveyed on the conveying path, and that detects the foil area on the sheet; The acquisition means acquires the foil area data based on the detection result by the detection means. 7. The image forming apparatus according to any one of items 1 to 6. (Item 10) the control unit causes the display unit to display the warning information, and causes the sheet to wait in the conveyance path between the detection position of the detection unit and the transfer position until an instruction from a user is received. Item 10. The image forming apparatus according to item 9. (Item 11) a double-sided conveying path for conveying the sheet having the image formed on a first side thereof from a downstream side of the transfer position to an upstream side of the transfer position in the conveying path when forming images on both sides of the sheet; the control unit causes the display unit to display the warning information, and causes the sheet to wait in the duplex conveying path until an instruction from a user is received. Item 10. The image forming apparatus according to item 9. (Item 12) a double-sided conveying path for conveying the sheet, on which an image has been formed on a first side, from a downstream side of a transfer position where a toner image is transferred onto the sheet conveyed through the conveying path to an upstream side of the transfer position, when forming images on both sides of the sheet; a detection means disposed on the double-sided conveying path for detecting the foil area on the sheet; The acquisition means acquires the foil area data based on the detection result by the detection means. 7. The image forming apparatus according to any one of items 1 to 6. (Item 13) the control unit causes the display unit to display the warning information, and causes the sheet conveying device to wait downstream of the detection unit on the double-sided conveying path until an instruction from a user is received. Item 13. The image forming apparatus according to item 12. (Item 14) The detection means a light source that irradiates light onto the sheet; and a light receiving element that is arranged to receive scattered reflected light of the light irradiated onto the sheet by the light source, Among the light-irradiated areas on the sheet, an area where the light-receiving element receives an amount of light corresponding to a luminance smaller than a first threshold is detected as the foil area. 14. The image forming apparatus according to any one of items 9 to 13. (Item 15) The detection means a light source that irradiates the sheet with near-infrared light; and a light-receiving element that is arranged to receive specularly reflected light of the near-infrared light irradiated onto the sheet by the light source, Among the areas on the sheet irradiated with near-infrared light, an area where the amount of light received by the light receiving element corresponds to a luminance greater than a second threshold is detected as the foil area. 14. The image forming apparatus according to any one of items 9 to 13.

[0084] The invention is not limited to the above-described embodiments, and various changes and modifications can be made without departing from the spirit and scope of the invention. Accordingly, the following claims are appended to apprise the public of the scope of the invention. [Explanation of symbols]

[0085] 100: Image forming apparatus, 101: Main control section, 40: Operation section, 10: Conveyance section, 20: Image forming section

Claims

1. An image forming apparatus, an acquisition means for acquiring foil area data indicating a foil area on a sheet onto which foil has been transferred in advance, when forming an image on the sheet; a control means for displaying warning information on a display means when it is determined based on the input image data and the foil area data that a print area on the sheet, which is an area to which toner is transferred by image formation based on the input image data, overlaps with the foil area; An image forming apparatus comprising:

2. further comprising an image forming means for forming an image on the sheet; The control means When it is determined that the printing area does not overlap the foil area, the image forming means is controlled to form an image on the sheet based on the input image data; When it is determined that the printing area overlaps the foil area, the warning information is displayed on the display means. The image forming apparatus according to claim 1 .

3. and when the control unit receives an instruction to form an image from a user after displaying the warning information, the control unit controls the image forming unit to form an image on the sheet based on the input image data. The image forming apparatus according to claim 2 .

4. When the control unit receives an instruction to stop image formation from a user after displaying the warning information, the control unit stops image formation based on the input image data. The image forming apparatus according to claim 2 .

5. the control means causes the display means to display the warning information when at least a part of the printing area specified based on the input image data overlaps with the foil area. The image forming apparatus according to claim 1 .

6. the control means causes the display means to display the warning information when at least a part of an area obtained by enlarging the print area specified based on the input image data overlaps with the foil area. The image forming apparatus according to claim 1 .

7. further comprising an image reading unit that reads an image on the sheet; the acquiring means acquires the foil area data based on a reading result by the image reading unit of the sheet onto which foil has been previously transferred. The image forming apparatus according to claim 1 .

8. the acquiring means acquires the foil area data from an external device capable of communicating via a network. The image forming apparatus according to claim 1 .

9. a detection unit that is disposed between a sheet feeding unit that feeds a sheet to a conveying path and a transfer position where a toner image is transferred onto the sheet conveyed on the conveying path, and that detects the foil area on the sheet; The acquisition means acquires the foil area data based on the detection result by the detection means. The image forming apparatus according to claim 1 .

10. the control unit causes the display unit to display the warning information, and causes the sheet to wait in the conveyance path between the detection position of the detection unit and the transfer position until an instruction from a user is received. The image forming apparatus according to claim 9 .

11. a double-sided conveying path for conveying the sheet having the image formed on a first side thereof from a downstream side of the transfer position to an upstream side of the transfer position in the conveying path when forming images on both sides of the sheet; the control unit causes the display unit to display the warning information, and causes the sheet to wait in the duplex conveying path until an instruction from a user is received. The image forming apparatus according to claim 9 .

12. a double-sided conveying path for conveying the sheet, on which an image has been formed on a first side, from a downstream side of a transfer position where a toner image is transferred onto the sheet conveyed through the conveying path to an upstream side of the transfer position, when forming images on both sides of the sheet; a detection means disposed on the double-sided conveying path for detecting the foil area on the sheet; The acquisition means acquires the foil area data based on the detection result by the detection means. The image forming apparatus according to claim 1 .

13. the control unit causes the display unit to display the warning information, and causes the sheet conveying device to wait downstream of the detection unit on the double-sided conveying path until an instruction from a user is received. The image forming apparatus according to claim 12.

14. The detection means a light source that irradiates light onto the sheet; and a light receiving element that is arranged to receive scattered reflected light of the light irradiated onto the sheet by the light source, Among the light-irradiated areas on the sheet, an area where the light-receiving element receives an amount of light corresponding to a luminance smaller than a first threshold is detected as the foil area. The image forming apparatus according to claim 9 .

15. The detection means a light source that irradiates the sheet with near-infrared light; and a light-receiving element that is arranged to receive specularly reflected light of the near-infrared light irradiated onto the sheet by the light source, Among the areas on the sheet irradiated with near-infrared light, an area where the light receiving element receives an amount of light corresponding to a luminance greater than a second threshold is detected as the foil area. The image forming apparatus according to claim 9 .

Images