Image forming device and foil printing system

Abstract

To reduce the possibility that the quality of a foil image is deteriorated.SOLUTION: There is provided an image forming device comprising: image forming means for forming a toner image on a sheet on the basis of image data; setting means for setting a first mode in which the toner image is formed to bond a foil onto the sheet via the toner image; and control means for controlling display means for displaying a warning according to an index related to a toner area per unit area of the toner image formed by the image forming means when the first mode is set by the setting means. There is also provided a foil printing system including the image forming device and a foil printing device which prints a foil image on the sheet by bonding the foil onto the sheet via the toner image.SELECTED DRAWING: Figure 14

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus and a foil printing system. [Background technology]

[0002] Conventionally, in order to impart a metallic feel or gloss to printed matter, which is difficult to achieve with a general printer, characters or pictures made of metal foil have been transferred onto a sheet. Methods for transferring foil onto a sheet include, for example, foil stamping using a mold, masking, and selective foil adhesion by irradiating an ultraviolet (UV)-curing adhesive with UV light.

[0003] Patent Documents 1 and 2 disclose methods for using toner from a toner image formed on a sheet as glue for adhering foil to the sheet. This method allows for the formation of a toner image using the configuration of a typical electrophotographic printer, making it relatively easy to create printed foil images with a high degree of freedom. The foil printing device of Patent Document 1 has a fan that blows air toward the adhesive position between the sheet and foil film to improve the peelability of the foil image from the foil film. The foil printing device of Patent Document 2 is integrated with an image forming device that forms a regular full-color toner image, and allows for the use of only a specific color toner as glue for adhering the foil. [Prior art documents] [Patent documents]

[0004] [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]

[0005] However, when attempting to adhere foil onto a sheet via a toner image, there is a risk that the quality of the foil image may be degraded depending on the toner image formed on the sheet.

[0006] In view of the above, the present invention aims to provide a mechanism for reducing the possibility of the quality of a foil image being degraded. [Means for solving the problem]

[0007] According to one aspect, there is provided an image forming apparatus including: an image forming means that forms a toner image on a sheet based on image data; a setting means that sets a first mode in which the toner image is formed to adhere foil onto the sheet via the toner image; and a control means that, when the first mode is set by the setting means, controls a display means to display a warning in accordance with an index related to a toner area per unit area of ​​the toner image formed by the image forming means. According to another aspect, there is provided a foil printing system that includes the image forming apparatus and a foil printing device that prints a foil image on the sheet by adhering the foil onto the sheet via the toner image. [Effects of the Invention]

[0008] According to the present invention, it is possible to reduce the possibility that the quality of the foil image will be reduced. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram showing an example of the configuration of a foil printing system according to an embodiment; [Figure 2] FIG. 2 is an explanatory diagram showing an example of the configuration of a foil. [Figure 3] FIG. 10 is an explanatory diagram showing how foil is printed on a sheet. [Figure 4] FIG. 10 is a first explanatory diagram for explaining the relationship between gradation and glue area ratio. [Figure 5] FIG. 2 is a second explanatory diagram for explaining the relationship between gradation and glue area ratio. [Figure 6]FIG. 2 is a block diagram showing an example of the functional configuration of an image forming apparatus according to an embodiment. [Figure 7] FIG. 1 is a block diagram showing an example of the functional configuration of a foil printing apparatus according to an embodiment. [Figure 8] FIG. 4 is a block diagram showing an example of a detailed configuration of a process that can be executed to issue a warning according to the glue area ratio in the first embodiment. [Figure 9] FIG. 11 is a first explanatory diagram showing an example of the configuration of a print setting screen according to the first embodiment. [Figure 10] FIG. 2 is a second explanatory diagram showing an example of the configuration of the print setting screen according to the first embodiment. [Figure 11] FIG. 4 is an explanatory diagram showing an example of the configuration of a warning setting screen according to the first embodiment. [Figure 12] FIG. 4 is an explanatory diagram showing an example of the configuration of a warning screen according to the first embodiment. [Figure 13] FIG. 10 is an explanatory diagram showing an example of the configuration of a menu screen according to a modified example. [Figure 14] 10 is a flowchart showing an example of the flow of a print control process according to the first embodiment. [Figure 15] FIG. 11 is an explanatory diagram showing an example of the configuration of a warning screen according to the second embodiment. [Figure 16] 10 is a flowchart showing an example of the flow of a print control process according to a second embodiment. [Figure 17] FIG. 10 is an explanatory diagram showing an example of the configuration of a warning setting screen according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. Note that the following embodiments do not limit the scope of the invention claimed. 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.

[0011] <1. System Overview> As shown in Figure 1, foil printing system 1 includes image forming apparatus 100 and foil printing apparatus 200. Image forming apparatus 100 forms a toner image on a sheet (also called a recording material). Foil printing apparatus 200 prints foil on the sheet using the toner of the toner image as adhesive. In other words, foil printing apparatus 200 adheres foil onto the sheet via the toner image.

[0012] In this embodiment, the foil printing system 1 is a so-called offline system in which the foil printing apparatus 200 is not mechanically connected to the image forming apparatus 100. In this case, the sheet S on which the toner image is formed is ejected from the image forming apparatus 100 and then manually fed into the foil printing apparatus 200 by a user (see the arrow in the figure). In another embodiment, an inline system in which the foil printing apparatus 200 is connected to the image forming apparatus 100 may be provided. In this case, the sheet S is automatically transferred from the image forming apparatus 100 to the foil printing apparatus 200. In yet another embodiment, an integrated printing apparatus in which the foil printing function of the foil printing apparatus 200 is incorporated inside the image forming apparatus 100 may be provided.

[0013] <1-1. Example of configuration of image forming device> Image forming apparatus 100 may be a color printer or a monochrome printer. In the example of Fig. 1, image forming apparatus 100 is a tandem full-color printer capable of forming full-color images using an electrophotographic method. 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.

[0014] The image forming unit 20 is an image forming means including process units 21Y, 21M, 21C, and 21K, an intermediate transfer belt 22, and a belt cleaner 29. 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. 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 (primary transfer) onto the intermediate transfer belt 22 in a superimposed manner, 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.

[0015] The cassette 5 is a storage means for storing 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 of different types (for example, sizes, thicknesses, or whether or not they have a surface coating). In this case, sheets of the type specified for each job are fed from the corresponding cassette 5. Note that sheets may also be fed from the manual feed tray 6 instead of the cassette 5. Furthermore, the foil printing system 1 may include a paper feeder (not shown) separate from the image forming apparatus 100.

[0016] The conveying unit 10 is a conveying means including a conveying path and a plurality of rollers. A feeding roller 11 feeds a sheet one by one from the stack of sheets 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 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.

[0017] 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 (photosensitive member) that rotates counterclockwise in the drawing. The charger 24 may be, for example, a corona charger that irradiates charged particles by corona discharge, charging 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. The developing unit 26 contains a developer made of toner and carrier, for example, inside, 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.

[0018] As an example, the developer may be a two-component developer containing a non-magnetic toner and a magnetic carrier. The toner may contain a binder resin, a colorant, and a release agent (wax).

[0019] 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 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.

[0020] Yellow, magenta, cyan, and black toner images formed by process units 21Y, 21M, 21C, and 21K, respectively, are transferred onto intermediate transfer belt 22 in a superimposed manner, thereby forming a full-color toner image containing the four color components.

[0021] 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 outer secondary transfer roller 16 transfers the full-color toner image carried by the intermediate transfer belt 22 onto the sheet 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.

[0022] The fixing unit 30 is a fixing means 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 by heating and pressurizing the sheet onto which the toner image has been transferred. The sheet 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)).

[0023] When double-sided printing is performed, the sheet with the toner image formed on its first side is conveyed to conveyance path 17. The sheet reverses its traveling direction, passes through double-sided conveyance path 18, and returns to conveyance path 12 upside down. Then, at secondary transfer position T2, the toner image is transferred to the second side of the sheet. Fixing unit 30 fixes the toner image to the second side of the sheet by again heating and pressurizing the sheet. The sheet is then ejected outside of image forming apparatus 100.

[0024] The operation unit 40 is an operation means that provides a user interface to a user of the foil printing system 1. The operation unit 40 includes, for example, a touch panel (display means) 41. The touch panel 41 displays images and information under the control of the main control unit 101, which will be described later, and accepts touch inputs by 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).

[0025] The main control unit 101 is a control unit that 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 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. Although not shown in FIG. 1 , the image forming apparatus 100 may further include a scanner unit (document reading means). In other words, the image forming apparatus 100 may be a multifunction peripheral. In this example, 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 based on read image data generated by the scanner unit reading a document.

[0026] <1-2. Example of foil printing equipment configuration> The foil printing device 200 includes a transport roller 211 , a discharge roller 212 , a heating roller 221 , a pressure roller 222 , a supply reel 231 , a collection reel 232 , and a discharge tray 240 .

[0027] The conveying roller 211 receives the sheet S on which the toner image has been formed and sends the sheet S to the bonding position T3. At the bonding position T3, a heating roller 221 and a pressure roller 222 are disposed so as to face each other. A foil 250 is wound around a supply reel 231. The leading end of the foil 250 is fixed to a recovery reel 232. The supply reel 231 and the recovery reel 232 suspend the foil 250 via the underside of the heating roller 221 while maintaining a predetermined tension to prevent wrinkles from forming in the foil 250. Although not shown in FIG. 1 , the foil printing apparatus 200 may be provided with an additional suspension roller to stably maintain the tension of the foil 250.

[0028] The supply reel 231 rotates clockwise in the figure and supplies the foil 250 to the bonding position T3. The heating roller 221 heats the sheet S that has reached the bonding position T3. This melts at least one type of toner used as adhesive among the toners that make up the toner image. The pressure roller 222, together with the heating roller 221, presses the foil 250 against the sheet S, adhering the foil to the sheet S in the areas where the toner has melted. The recovery reel 232 rotates counterclockwise in the figure and takes up the foil 250. At this time, the portion of the foil 250 that has adhered to the sheet S is peeled off from the remaining portion, forming a foil image on the sheet S. The discharge roller 212 discharges the sheet S that has passed the bonding position T3 to the discharge tray 240.

[0029] <1-3. Foil composition examples> FIG. 2 shows an example of the configuration of the foil 250. The foil 250 includes a foil layer 251 and a backup layer 252. The foil layer 251 is a sheet-like layer made of a metal material. The metal material of the foil layer 251 may be, for example, aluminum, tin, silver, copper, chromium, nickel, gold, or iron, or an alloy of two or more of these (for example, nickel-chromium steel, bronze, or aluminum bronze). The backup layer 252 is a sheet-like layer made of resin that supports the foil layer 251. The resin material of the backup layer 252 may be, for example, polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polypropylene (PP), polyethersulfone (PES), or polyimide (PI).

[0030] <1-4. Formation of foil image> Figure 3 shows an enlarged view of the vicinity of adhesion position T3 while foil printing apparatus 200 is operating. In the example of Figure 3, a heating roller 221 located above adhesion position T3 and a pressure roller 222 located below it sandwich sheet S on which toner image TN has been formed and foil 250. Heating roller 221 and pressure roller 222 rotate following the rotation of collection reel 232 driven by a motor (not shown), and transport sheet S and foil 250 in transport direction D1.

[0031] The surface temperature of the heating roller 221 is controlled so that the temperature of the toner in the toner image TN reaches its melting point. When the temperature of the toner reaches its melting point at the adhesion position T3, the toner melts and its viscosity increases, acting as glue. The toner image TN is further pressed by the pressure roller 222 and adheres to the foil layer 251 of the foil 250. Therefore, when the sheet S and the foil 250 pass the adhesion position T3, the portion of the foil layer 251 that contacts the toner image TN (adhered portion) F1 is peeled off from the backup layer 252 of the foil 250 while remaining adhered to the sheet S. On the other hand, the portion of the foil layer 251 that does not contact the toner image TN (non-adhered portion) F2 is not adhered to the sheet S and remains on the backup layer 252 while being collected by the collection reel 232. As a result, the foil layer 251 is selectively transferred to the sheet S according to the pattern of the toner image TN on the sheet S, forming a foil image on the sheet S.

[0032] <1-5. Ensuring sufficient adhesive surface area> When forming a foil image using the toner of a toner image as glue, as in the foil printing device 200, if a sufficient amount of toner is transferred to the sheet, the adhesive strength of the glue will be insufficient, resulting in a deterioration in the quality of the foil image. For example, if the amount of glue is insufficient, the foil layer 251 may not peel off from the backup layer 252 in the correct position, resulting in a shaky outline of the foil image or a color that differs from the desired color. To avoid such a deterioration in foil image quality, it is important that the ratio of the area of ​​toner adhesion per unit area (toner area) does not fall below a certain lower limit, regardless of the local area where the foil image is to be transferred. In this specification, the ratio of the toner area per unit area of ​​the toner image, i.e., the glue area ratio, is used as an indicator of the adhesive strength of the glue. As long as it is guaranteed that the glue area ratio does not fall below a predetermined lower limit in all areas where the foil image is to be transferred, the aforementioned deterioration in foil image quality due to insufficient toner amount will not occur.

[0033] The local glue area ratio depends on the gradation of the corresponding portion of the image region. Figures 4 and 5 are explanatory diagrams for explaining the relationship between gradation and glue area ratio. Generally, input image data for an image formation job is converted through rasterization and color conversion into a format in which the gradation of each pixel of each color component is represented by a multi-level (e.g., 8-bit) signal value. The image data is then converted into binary bitmap data representing the area gradation by halftoning. There are several halftoning techniques, such as dithering and error diffusion. Figure 4 shows an example in which dithering is used, in which the gradation corresponds to the area of ​​the exposure dots assigned to each block. At the maximum gradation (255 in the case of 8 bits), the percentage of the area occupied by the exposure dots in each converted block, i.e., the area ratio, is 100%. The smaller the gradation, the smaller the area ratio. Figure 5 shows an example in which error diffusion is used, in which the gradation corresponds to the number of dots assigned to each block. Here too, when the gradation is maximum, the proportion of the area occupied by the exposure dots in each block after conversion, i.e., the area ratio, is 100%, and the smaller the gradation, the smaller the area ratio. Note that the technology disclosed herein is not limited to a specific method for halftoning.

[0034] As can be understood from the above explanation, the local adhesive area ratio of a toner image can be predicted by checking the gradation of the image data of an image forming job. Therefore, in the embodiment described below, the foil printing system 1 determines whether there are any parts in the image where the adhesive area ratio is insufficient when the toner of the toner image formed by the image forming apparatus 100 is used as adhesive, and issues a warning to the user based on the determination result.

[0035] <2. Function details> <2-1. Example of functional configuration of image forming device> 6 shows an example of the functional configuration of an image forming apparatus 100 according to an embodiment. Referring to Fig. 6, a main control unit 101 of the image forming apparatus 100 includes a CPU 102, a memory 103, a storage 104, a communication interface (I / F) 105, an operation I / F 106, a printer I / F 107, and an image processing circuit 108.

[0036] A central processing unit (CPU) 102 controls various functions of the image forming apparatus 100. For example, when an instruction to execute an image forming job (print job or copy job) is received, the CPU 102 controls the conveying unit 10, the image forming unit 20, and the fixing unit 30 so as to form a toner image on a sheet based on image data processed by the image processing circuit 108. In this embodiment, the CPU 102 also controls a warning to the user according to the adhesive area ratio when toner is used as adhesive. The warning according to the adhesive area ratio will be described in detail later.

[0037] The memory 103 is a storage means that may include, for example, a random access memory (RAM) and a read-only memory (ROM). The storage 104 is a large-capacity storage means such as a hard disk drive (HDD) or a solid-state drive (SSD). Computer programs executed by the CPU 102, as well as various data such as setting data and image data (described later), can be stored in the memory 103 and the storage 104.

[0038] The communication I / F 105 is an interface that allows the image forming apparatus 100 to communicate with other devices. In the example of FIG. 6, the communication I / F 105 is connected to an external device 3 (e.g., a PC) via a network 2. The network 2 may be a wired network or a wireless network. Note that the image forming apparatus 100 may be connected to the external device via some kind of communication cable instead of the network 2.

[0039] The operation I / F 106 is an interface for connecting the operation unit 40 to the main control unit 101. The CPU 102 can acquire user input received by the operation unit 40 via the operation I / F 106. The CPU 102 can also display an image on the touch panel 41 of the operation unit 40 by outputting an image signal to the operation unit 40 via the operation I / F 106.

[0040] The printer I / F 107 is an interface that mediates communication between the CPU 102 and the conveying unit 10, the image forming unit 20, and the fixing unit 30. For example, the CPU 102 controls the sheet conveying speed and conveying timing in the conveying unit 10, the image forming conditions in the image forming unit 20, and the fixing temperature in the fixing unit 30.

[0041] In this embodiment, the CPU 102 sets an operating mode related to the formation of a toner image in the image forming apparatus 100. Typically, the CPU 102 prompts the user to select one of multiple operating modes and sets the selected operating mode. The CPU 102 then controls the execution of an image formation job in the set operating mode. The first of the multiple operating modes is a foil printing mode. The foil printing mode is an operating mode in which a toner image is formed to adhere foil to a sheet via the toner image. A sheet bearing a toner image formed in the foil printing mode is fed into the foil printing apparatus 200 after being ejected from the image forming apparatus 100. The second of the multiple operating modes is a normal mode. In the normal mode, the toner of the toner image is not intended to be used as adhesive. That is, a sheet bearing a toner image formed in the normal mode is not fed into the foil printing apparatus 200 after being ejected from the image forming apparatus 100. The CPU 102 may control the conveying unit 10, the image forming unit 20, and the fixing unit 30 in the foil printing mode to form a toner image under image formation conditions different from those in the normal mode. For example, the CPU 102 may set the target value of the fixing temperature of the fixing unit 30 in the foil printing mode to a value different from that in the normal mode. In an embodiment in which the foil printing system 1 is an inline system, the first mode may be set automatically (without user selection) based on the foil printing apparatus 200 being connected to the image forming apparatus 100.

[0042] The image processing circuit 108 converts the format of the input image data of a job into a format suitable for driving the image forming unit 20. Typically, the input image data received from an external device is PDL data written in a page description language (PDL) such as PostScript (PS) or Printer Command Language (PCL). For example, the color space of the PDL data is RGB space (or grayscale), and the bit depth is 8 bits. The image processing circuit 108 converts such PDL data into binary image data of each color component of YMCK. An example of a more detailed configuration of the image processing circuit 108 will be further described later.

[0043] The image data converted by the image processing circuit 108 is temporarily stored in a frame memory and output to the image forming unit 20 when execution of a job starts. The image forming unit 20 forms a toner image on a sheet based on this image data. For example, the exposure device 25 of each process unit 21 exposes the surface of the photosensitive drum 23 by turning on and off a laser beam in accordance with a signal value indicated by the image data of the corresponding color component.

[0044] <2-2. Example of functional configuration of foil printing device> Fig. 7 shows an example of the functional configuration of a foil printing apparatus 200 according to an embodiment. Referring to Fig. 7, the foil printing apparatus 200 includes a control unit 201, a temperature adjustment unit 210, a conveyance unit 220, and a foil supply unit 230. The control unit 201 includes a CPU 202, a memory 203, a communication I / F 205, and a device I / F 207.

[0045] The CPU 202 performs control to properly operate the foil printing function of the foil printing apparatus 200. For example, when the CPU 202 detects that a sheet has been inserted into the foil printing apparatus 200, it activates a heater (not shown) of the temperature adjustment unit 210 and controls the temperature of the heating roller 221 to maintain a target temperature based on the temperature measured by a thermistor (not shown). The CPU 202 also drives a motor (not shown) of the conveyance unit 220 to rotate the conveyance roller 211 and the discharge roller 212 and convey the sheet. The CPU 202 also drives a motor (not shown) of the foil supply unit 230 to rotate the collection reel 232 and supply the foil 250 from the supply reel 231 to the bonding position T3.

[0046] The memory 203 is a storage means for storing computer programs executed by the CPU 202 and data. The memory 203 may be, for example, any combination of RAM and ROM. The communication I / F 205 is an interface that allows the foil printing apparatus 200 to communicate with other devices. In the example of FIG. 8, the communication I / F 205 is connected to the network 2. The device I / F 207 is an interface that mediates communication between the CPU 202 and the temperature adjustment unit 210, the transport unit 220, and the foil supply unit 230.

[0047] Although not shown in Fig. 7, the foil printing apparatus 200 may have an operation means similar to the above-mentioned operation unit 40. In this case, the CPU 202 can acquire user input received by the operation means. The CPU 202 may also have a display means capable of displaying images.

[0048] <2-3. Warnings according to adhesive area ratio> In this embodiment, the image forming apparatus 100 issues a warning to alert the user that a lack of toner area may result in a deterioration in foil printing quality. For example, warning conditions corresponding to the adhesive area ratio are stored in advance in the memory 103 or the storage 104. When the main control unit 101 determines that the toner image formed by the image forming unit 20 satisfies the warning conditions, it controls the operation unit 40 or the display of the external device 3 to display a warning.

[0049] Typically, the main control unit 101 determines whether the toner image satisfies the warning conditions by analyzing input image data before the image forming unit 20 forms a toner image on a sheet. If it is determined that the toner image satisfies the warning conditions, a warning is issued to the user before the job is executed, so that the user can interrupt the job execution and correct the toner image as necessary.

[0050] For example, when a warning condition is satisfied for a specific portion of a toner image, the main control unit 101 may cause a preview of the toner image to be displayed on the display in a manner that makes the specific portion discernible.

[0051] In this embodiment, the warning condition includes a condition in which the glue area ratio value (hereinafter also referred to as the index value) determined based on the gradation of the image area of ​​the toner image is lower than a first threshold value TH1 corresponding to the allowable lower limit. For each partial area, the main control unit 101 determines a predicted index value based on the gradation of the partial area. The main control unit 101 then compares the determined index value with the first threshold value TH1 to determine whether the warning condition is met. The index value here may correspond to a statistical value (e.g., average, maximum, or minimum) of the gradations of multiple pixels belonging to each partial area. The partial area may be, for example, a small square area, with the length of one side being 10 millimeters (mm), 5 mm, or 1 mm. However, if the partial area is located on the boundary between the image area and the non-image area, the partial area does not have to be square because pixels belonging to the non-image area are excluded. As an example, assuming that the area of ​​the exposure dots expands by about 25% during the fixing process, if the area ratio of the exposure dots in the toner image formed in the image forming unit 20 is 80%, the final adhesive area ratio will theoretically reach 100%. Therefore, in one embodiment, it is considered to adopt the average value of the gradation of each partial area as the index value and set the first threshold value TH1 to 80%. However, this embodiment is not limited to these specific values.

[0052] In reality, even if the gradation of a pixel represented by image data is the same, the amount of toner transferred to the sheet at that pixel may vary depending on the toner deposition characteristics of the image forming unit 20. Therefore, the main control unit 101 may determine the index value by correcting the statistical value of the gradation of each partial region with a correction coefficient related to the toner deposition characteristics of the image forming unit 20. For example, if the index value is determined by multiplying the gradation value by the correction coefficient, the correction coefficient will be larger for an apparatus that has the characteristic of transferring more toner to the sheet. The memory 103 or the storage 104 may further store such correction coefficients. Note that the correction coefficients may be dynamically updated depending on environmental factors such as temperature and humidity.

[0053] In this embodiment, the main control unit 101 may exclude portions having a gradation equal to or lower than the second threshold TH2, which corresponds to the gradation of non-image regions, from image regions subject to warning condition determination. This means that warning condition determination is not performed for non-image regions to which a foil image is not to be transferred. As an example, when the background region is given as a completely white region, such as in a computer graphics (CG) image, the second threshold TH2 may be set to 0%. As another example, for images in which the background region is not necessarily completely white, such as scanned images or photographic images, or for images that may contain noise, the second threshold TH2 may be set to a larger value. The index value may be determined for each partial region set within such an image region having a gradation higher than the second threshold TH2.

[0054] Two examples of the control accompanied by a warning according to the glue area ratio described above will be described in more detail below.

[0055] <3. First Example> <3-1. Processing configuration> 8 shows an example of a detailed configuration of processes that can be executed by the CPU 102 and the image processing circuit 108 to issue a warning according to the glue area ratio in the first embodiment. Referring to Fig. 8, the processes executed by the image processing circuit 108 include rasterization 111, color matching 112, color conversion 113, gamma correction 114, and halftoning 115. The processes executed by the CPU 102 include image region extraction 131, warning condition determination 132, and warning output 133. The memory 103 stores setting data 123 that includes the first threshold value TH1 and second threshold value TH2 described above.

[0056] Rasterization 111 is a process that interprets an image represented at a high level by PDL data 121 according to the resolution specified by the job and converts the PDL data 121 into bitmap data of the three RGB color components. Color matching 112 is a process that adjusts RGB signal values ​​to maintain consistent color tones in the printed result regardless of differences in color reproducibility between devices. Color conversion 113 is a process that converts image data represented in RGB space into image data in YMCK space corresponding to the four color developers (toners). Gamma correction 114 is a process that corrects the signal values ​​of each color component using a gamma curve selected according to the density output characteristics of the process units 21Y, 21M, 21C, and 21K. Halftoning 115 is a process that converts gradations represented by multilevel signal values ​​for each pixel into spatial area gradations using, for example, a dithering method or an error diffusion method. As a result of halftoning 115, image data 122 is generated that represents the toner image of each YMCK color component using binary signal values ​​for each pixel.

[0057] Image region extraction 131 is a process for extracting an image region that is to be subject to warning condition determination from the image data of each color component after gamma correction. Here, the explanation focuses on image data of one color component, but if toners of multiple color components are used as adhesive, the explanation applies to image data of those color components. CPU 102 compares the gradation of each pixel in the bitmap image data after gamma correction with a second threshold value TH2 stored in memory 103, and determines that pixels exhibiting a gradation higher than the second threshold value TH2 belong to the image region. On the other hand, CPU 102 determines that pixels exhibiting a gradation equal to or lower than the second threshold value TH2 belong to the non-image region. By repeating this determination for all pixels, an image region consisting only of pixels exhibiting a gradation higher than the second threshold value TH2 (excluding the background) is extracted.

[0058] The warning condition determination 132 is a process for determining whether the image area extracted as a result of the image area extraction 131 satisfies the warning condition. For example, the CPU 102 sets partial areas in a grid pattern within the image area, determines an index value representing the glue area ratio for each of the partial areas, and compares the determined index value with a first threshold TH1 stored in the memory 103. As described above, the index value here may be the average value of the gradations of multiple pixels belonging to each partial area or another statistical value. The CPU 102 may also correct the index value using a correction coefficient related to toner application characteristics. The CPU 102 determines that a partial area whose index value is equal to or greater than the first threshold TH1 does not satisfy the warning condition, and determines that a partial area whose index value is lower than the first threshold TH1 satisfies the warning condition. After this determination for all partial areas is completed and no partial area is determined to satisfy the warning condition, the CPU 102 skips the warning output 133 and starts the image formation job. On the other hand, if a partial area determined to satisfy the warning condition exists, the CPU 102 outputs the warning 133.

[0059] Warning output 133 is a process for outputting a warning to make the user aware that a lack of toner area may result in a deterioration in foil printing quality. In this embodiment, CPU 102 displays a warning message on the display of operation unit 40 or external device 3. Note that in other embodiments, the warning may be output by other methods, such as audio output, sending a text message, or outputting log data. Some examples of user interfaces for such warnings are described in the next section.

[0060] <3-2. Example of User Interface (UI)> 9 and 10 show an example of the configuration of a print setting screen 150 according to the first embodiment. The print setting screen 150 includes a normal mode tab 151 and a foil printing mode tab 152. If the user wishes to form an image in normal mode, the user selects the normal mode tab 151. If the user plans to print foil on a sheet using the toner of the toner image as glue, the user selects the foil printing mode tab 152.

[0061] FIG. 9 shows an example of the screen configuration of the normal mode tab 151. The normal mode tab 151 includes a preview window 153, several setting items, an OK button 154, and a cancel button 155. In normal mode, the user can set items such as the cassette to be used as the paper source, sheet size, magnification, layout, single-sided / double-sided printing, margins, and post-processing. The preview window 153 is a window that displays a preview of the toner image to be printed in normal mode. When the user operates the OK button 154, the CPU 102 starts executing the job in normal mode. When the user operates the cancel button 155, the CPU 102 cancels the execution of the job and closes the print setting screen 150.

[0062] 10 shows an example of the screen configuration of the foil printing mode tab 152. The foil printing mode tab 152 includes a warning setting button 156 in addition to screen elements similar to those of the normal mode tab 151. When the user operates the warning setting button 156, the CPU 102 displays a warning setting screen 160 shown in FIG.

[0063] 11 shows an example of the configuration of a warning setting screen 160 according to Example 1. The warning setting screen 160 includes a check box 161, pull-down menus 162 and 163, an OK button 168, and a back button 169.

[0064] Check box 161 is an object for receiving a user setting (first user setting) indicating whether a warning should be output about a lack of toner area. If the user wishes to receive a warning, he or she turns check box 161 on. The above-mentioned warning output 133 can be performed when check box 161 is set to on, i.e., when the first user setting indicates that a warning should be output. If check box 161 is set to off, warning output 133 does not have to be performed.

[0065] The pull-down menu 162 is an object for accepting the setting of a first threshold value TH1 (warning threshold value) corresponding to the lower limit of the allowable glue area ratio. In the example of FIG. 11, the threshold value is set in the form of a percentage (%) of the maximum gradation value. As another example, the first threshold value TH1 may be set in the form of an integer value within the gradation range (0 to 255 in the case of 8 bits). By allowing the user to set the first threshold value TH1 via such a UI, the user can flexibly adjust the sensitivity of the warning output in accordance with the characteristics of the foil printing device, the characteristics of the toner or foil, or the level of quality degradation that the user is willing to tolerate. For example, a user who places more importance on saving toner than on forming a high-quality foil image can set the first threshold value TH1 to a relatively low value. If the user does not select a value for the first threshold value TH1, a default value is used for the first threshold value TH1.

[0066] The pull-down menu 163 is an object for accepting the setting of a second threshold TH2 (exclusion threshold) for excluding non-image regions (extracting image regions). For example, the user may set the second threshold TH2 to a different value depending on the type of input image data (e.g., CG image, scanned image, or photographic image). By allowing the user to set the second threshold TH2 via such a UI, it is possible to reduce the possibility of unnecessary warnings being output due to inaccurate determination of image regions. If the user does not select a value for the second threshold TH2, a default value is used for the second threshold TH2.

[0067] When the user operates OK button 168, CPU 102 acquires the setting contents changed on warning setting screen 160 and stores them in memory 103 or storage 104. When the user operates back button 169, CPU 102 discards the setting changes on warning setting screen 160, closes warning setting screen 160, and displays print setting screen 150 again.

[0068] When the user operates the OK button 154 on the foil printing mode tab 152, the CPU 102 refers to the latest warning settings and checks whether warning output is enabled. If warning output is enabled, the CPU 102 executes the image area extraction 131 and warning condition determination 132 described above for the image data processed by the image processing circuit 108. If it is determined that the warning conditions are met, the CPU 102 displays a warning screen 170 shown in FIG. 12 on the display.

[0069] FIG. 12 shows an example of the configuration of a warning screen 170 according to the first embodiment. The warning screen 170 includes a warning message 171, a preview window 172, a continue button 175, and a cancel button 176. The warning message 171 is a text message that warns the user of the possibility of a deterioration in foil printing quality. The preview window 172 displays a preview of the toner image printed in foil printing mode. In the example shown in FIG. 12, indicators 173a and 173b are superimposed on the preview window 172. These indicators 173a and 173b indicate the location of a partial area determined to satisfy the warning condition. By viewing this preview, the user can easily determine which portion of the input image data needs to be corrected to avoid a deterioration in the quality of subsequent foil printing. When the user operates the continue button 175, the CPU 102 begins executing the job in foil printing mode. When the user operates the cancel button 176, the CPU 102 cancels the job.

[0070] The UIs shown in FIGS. 9 to 11 are merely illustrative examples. Each screen may have a configuration different from that shown. FIG. 13 shows an example of the configuration of a menu screen 180 according to a modified example. The menu screen 180 may be a screen displayed on the display of the operation unit 40 when the image forming apparatus 100 is a multifunction peripheral, for example. The menu screen 180 includes a normal mode button 181 and a foil printing mode button 182. When a user operates the normal mode button 181, the CPU 102 displays a print setting screen for the normal mode, similar to the normal mode tab 151 described with reference to FIG. 9, on the display. On the other hand, when a user operates the foil printing mode button 182, the CPU 102 displays a print setting screen for the foil printing mode, similar to the foil printing mode tab 152 described with reference to FIG. 10, on the display. As such, various modifications can be envisioned for the transition between screens. Generally, the technology according to the present disclosure is not limited to any example of a UI configuration.

[0071] <3-3. Processing flow> Fig. 14 is a flowchart showing an example of the flow of print control processing that can be executed by the main control unit 101 of the image forming apparatus 100 in this embodiment. The print control processing in Fig. 14 is started, for example, in response to the user invoking the above-mentioned print setting screen 150 via the operation unit 40 or the external device 3. In the following explanation, processing steps are abbreviated as 'S'.

[0072] First, in S101, the main control unit 101 accepts the user's selection of an operating mode and sets the selected operating mode to the device. In this case, normal mode or foil printing mode is set. Next, in S103, the main control unit 101 acquires job settings. For example, the main control unit 101 acquires settings for several setting items that can be specified on the print setting screen 150. Furthermore, when the foil printing mode is selected, the main control unit 101 acquires settings for warning conditions that can be specified on the warning setting screen 160.

[0073] The subsequent processing branches depending on the operation mode set in S105. If the user selects the normal mode and instructs to start job execution (S105-NO), the processing proceeds to S107. In S107, the main control unit 101 controls the conveying unit 10, the image forming unit 20, and the fixing unit 30 to form a toner image on a sheet in the normal mode.

[0074] If the user selects the foil printing mode and instructs the start of job execution (S105-YES), the process proceeds to S109. In S109, the main control unit 101 converts the format of the input image data from PDL format to binary bitmap format. In addition, in S111, the main control unit 101 extracts an image area by excluding from the entire image portions having gradations equal to or less than the second threshold value TH2, based on the image data of the color components of the toner used as glue.

[0075] Next, in S113, the main control unit 101 determines an index value representing the glue area ratio for each partial area set within the image area and compares the determined index value with a first threshold value TH1 (warning threshold value). After completing the comparison for all partial areas, in S115 the main control unit 101 determines whether there is a partial area showing an index value lower than the first threshold value TH1. If there is a partial area showing an index value lower than the first threshold value TH1, the process proceeds to S117. On the other hand, if there is no partial area showing an index value lower than the first threshold value TH1, the process proceeds to S123.

[0076] In S117, the main control unit 101 refers to the user settings for the foil printing mode and determines whether warning output is enabled (for example, according to the first user settings). If warning output is enabled, in S119, the main control unit 101 displays the above-mentioned warning screen 170 on the display to warn the user of the possibility of a decrease in foil printing quality. Next, in S121, the main control unit 101 accepts user input on the warning screen 170 instructing whether or not to continue the job. If an instruction to continue the job is given, the process proceeds to S123. On the other hand, if an instruction to cancel the job is given, the print control process of FIG. 14 ends without forming a toner image on the sheet.

[0077] If it is determined in S117 that the warning output is disabled, the warning output in S119 is skipped. At this time, the main control unit 101 may record in a log file that it has been determined that the toner image satisfies the warning conditions. In one modified example, it may be determined whether the warning output is enabled before extracting the image area and determining the warning conditions, and if the warning output is disabled, extraction of the image area and determination of the warning conditions may be skipped.

[0078] In S123, the main control unit 101 controls the conveying unit 10, the image forming unit 20, and the fixing unit 30 to form a toner image on the sheet in foil printing mode. The sheet on which the toner image has been formed passes through the fixing unit 30 and is then discharged from the image forming apparatus 100. When the user inserts this sheet into the foil printing device 200, the foil printing device 200 prints foil on the sheet using the toner of the toner image as glue.

[0079] In this section, an example has been described in which a warning condition is determined and a warning is issued to the user before execution of a job begins, i.e., before the image forming unit 20 forms a toner image, but the timing of determining whether a warning condition exists and issuing a warning is not limited to this example. For example, the main control unit 101 may determine whether a toner image satisfies a warning condition in parallel with the image formation operation. If the main control unit 101 determines that a toner image satisfies a warning condition, it may warn the user on a screen showing the job execution result, or may record the determination result in a log file.

[0080] <4. Second Example> In the second embodiment, the user can instruct the formation of a toner image by improving the glue area ratio during image formation. Specifically, the main control unit 101 accepts a user setting (second user setting) indicating whether or not to improve the glue area ratio during image formation when it is determined that the warning condition is satisfied, and controls image formation by the image forming unit 20 in accordance with the second user setting.

[0081] In this embodiment, the second user setting is accepted after determining that the warning condition is met. That is, in response to determining that the toner image meets the warning condition, the main control unit 101 queries the user as to whether to improve the glue area ratio during image formation, and accepts the second user setting in response to the query. The user's query is typically made on a screen that warns the user about the possibility of a deterioration in foil printing quality. In this case, the user can select a response tailored to the individual situation for each job, such as instructing the user to improve the glue area ratio, canceling the job and manually correcting the image data, or continuing the job without improving the glue area ratio. When the warning screen indicates a portion of the image that meets the warning condition, the user can select a desired response, taking into account the importance of the quality of that portion of the foil image.

[0082] The improvement of the glue area ratio can be realized, for example, by performing at least one of the following controls on pixels that exhibit a gradation lower than the first threshold value TH1 among the pixels belonging to the image region (or on partial regions that exhibit an index value lower than the first threshold value TH1): - Correct the gradation indicated by the image data to a value equal to or greater than the first threshold value TH1 The exposure amount when the exposure device 25 of the image forming unit 20 exposes the photosensitive drum 23 is adjusted (for example, by extending the exposure time or increasing the laser output). Adjusting the dark potential when the charger 24 of the image forming unit 20 charges the photosensitive drum 23 In either case, the elimination of localized toner area shortages results in the elimination or reduction of the potential for quality degradation when the foil image is formed.

[0083] FIG. 15 shows an example of the configuration of a warning screen 370 according to the second embodiment. The warning screen 370 includes a warning message 171, a preview window 172, a check box 374, a continue button 375, and a cancel button 176. The check box 374 is an object for accepting a second user setting indicating whether or not to automatically improve the insufficient gradation. If the user desires automatic improvement, the user turns on the check box 374. When the user operates the continue button 375 with automatic improvement enabled, the CPU 102 starts execution of the job in foil printing mode and causes the image forming unit 20 to form a toner image with an improved adhesive area ratio.

[0084] 16 is a flowchart showing an example of the flow of print control processing that can be executed by the main control unit 101 of the image forming apparatus 100 in this embodiment. The print control processing in FIG. 16 is started in response to, for example, the user invoking the above-mentioned print setting screen 150 via the operation unit 40 or the external device 3.

[0085] First, in S201, the main control unit 101 accepts the user's selection of an operation mode and sets the selected operation mode in the device. Next, in S203, the main control unit 101 acquires job settings. For example, the main control unit 101 acquires settings for several setting items that can be specified on the print setting screen 150. Furthermore, when the foil printing mode is selected, the main control unit 101 acquires settings for warning conditions that can be specified on the warning setting screen 160.

[0086] The subsequent processing of S205 to S217 may be the same as the processing of S105 to S117 described with reference to FIG. 14, and therefore the description thereof will be omitted here.

[0087] If it is determined in S215 that there is a partial area within the image area that has an index value lower than the warning threshold, and if it is determined in S217 that warning output is enabled, then in S220 the main control unit 101 displays the above-mentioned warning screen 370 on the display. On this screen, the main control unit 101 asks the user whether or not to automatically improve the glue area ratio during image formation.

[0088] Subsequent processing branches in S221 and S222 depending on user input. For example, if the user instructs the job to be stopped (S221-NO), the print control processing in FIG. 16 ends without a toner image being formed on the sheet. If the user instructs the job to continue with automatic improvement of the glue area ratio enabled (S221-YES, S222-YES), the main control unit 101 performs processing to improve the glue area ratio in S224. Then, in S225, the main control unit 101 controls the conveying unit 10, the image forming unit 20, and the fixing unit 30 to form a toner image on the sheet in foil printing mode. If the user instructs the job to continue without enabling automatic improvement of the glue area ratio (S221-YES, S222-NO), S224 is skipped, and a toner image is formed on the sheet in foil printing mode in S225 without improving the glue area ratio.

[0089] In this embodiment as well, the sheet on which the toner image is formed is discharged from the image forming apparatus 100 after passing through the fixing unit 30. When the user inserts this sheet into the foil printing apparatus 200, the foil printing apparatus 200 prints foil on the sheet using the toner of the toner image as glue.

[0090] In a modification of this embodiment, the second user settings may be accepted as common settings prior to the execution of each job. That is, the main control unit 101 accepts the second user settings before the image data for the job is input. Then, when the second user settings indicate that the glue area ratio should be improved, the main control unit 101 may control the image forming unit 20 to form a toner image with an improved glue area ratio when it is determined that the warning condition is satisfied.

[0091] Fig. 17 shows an example of the configuration of a warning setting screen 360 according to this modification. The warning setting screen 360 can be displayed on the display when, for example, the warning setting button 156 of the foil printing mode tab 152 described with reference to Fig. 10 is operated. The warning setting screen 360 includes a check box 161, a pull-down menu 162, a check box 364, an OK button 368, and a back button 169. Although not shown in Fig. 17, the warning setting screen 360 may further include a pull-down menu 163 for accepting the setting of the second threshold value TH2 shown in Fig. 11.

[0092] Check box 364 is an object for receiving a user setting indicating whether to automatically improve gradation when a portion that satisfies the warning conditions exists within the image area. If the user desires automatic improvement for jobs that will be executed in the future, the user turns on check box 364. When the user operates OK button 368, CPU 102 acquires the setting contents changed on warning setting screen 360 and stores them in memory 103 or storage 104. If this user setting indicates that gradation should be automatically improved, the user may be notified that the glue area ratio has been automatically improved on a screen showing the job execution results, instead of outputting a warning about a lack of toner area.

[0093] In this modified example, the user does not need to take the time to input a response to an inquiry each time a job is executed, which can reduce the workload on the user.

[0094] <5. Summary> 1 to 17 have been used to describe embodiments of the technology disclosed herein, as well as various related examples and modifications. In the above-described embodiments, in an image forming apparatus that forms a toner image on a sheet based on image data, a warning is displayed by a display unit in accordance with an index related to the toner area per unit area of ​​the toner image. This configuration prevents a user from feeding a sheet into the foil printing apparatus that may result in a low-quality foil image due to a lack of toner area, thereby preventing the formation of a low-quality foil image and avoiding foil waste.

[0095] In the above-described embodiment, before the image forming apparatus forms a toner image, it can determine whether the toner image satisfies a warning condition through analysis of image data. Therefore, a user can stop the job and correct the image data before a toner image that may result in a low-quality foil image is formed on a sheet. This also prevents the waste of sheets and toner.

[0096] In the above-described embodiment, when a foil printing mode is set in which a toner image is formed to adhere foil to a sheet via the toner image, a determination is made as to whether the toner image satisfies a warning condition, and a warning may be displayed according to the determination result. Therefore, when a normal job in which foil printing is not scheduled is executed, the determination of whether the warning condition exists and the warning display are not performed, so the user will not be bothered by unnecessary warnings.

[0097] In the above-described embodiment, the index has a value determined based on the gradation of the image area of ​​the toner image, and when the value is lower than a first threshold corresponding to the allowable lower limit, it can be determined that the warning condition is met. Since the gradation of the image area correlates with the ratio of the area occupied by toner transferred to the sheet per unit area, by performing such threshold determination based on the gradation, it is possible to predict a shortage of toner area without requiring a complex algorithm.

[0098] In the above-described embodiment, the index value is determined for each partial area set in the image area, and the determined index value can be compared with the first threshold value. This makes it possible to locally identify which part of the input image data may cause a quality degradation of the foil image. If the index value is determined based on a coefficient related to the toner placement characteristics of the image forming unit in addition to the gradation of the toner image, the accuracy of determining the warning condition can be further improved by taking into account individual differences between devices.

[0099] In the above-described embodiment, when determining whether the warning condition is satisfied, a portion having a gradation equal to or less than a second threshold corresponding to the gradation of the non-image area can be excluded from the image area, thereby preventing unnecessary determination of the warning condition for the non-image area to which the foil image does not need to be transferred.

[0100] In one embodiment, the user can set whether to improve the indicator during image formation when it is determined that the warning condition is met. This configuration allows the user to immediately form a toner image in which the toner area deficiency is resolved without having to temporarily stop the job and correct the image data. This reduces the user's workload and improves productivity in producing finished products.

[0101] <6. Other embodiments> The above-described embodiment can also be realized in the form of a process in which a program for realizing one or more functions is supplied to a system or device via a network or a storage medium, and one or more processors in a computer of the system or device read and execute the program, or by a circuit (e.g., ASIC) that realizes one or more functions.

[0102] 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]

[0103] 1: foil printing system, 2: network, 3: external device, 10: transport unit, 20: image forming unit (image forming means), 23: photosensitive member, 25: exposure unit, 30: fixing unit, 40: operation unit (operation means), 41: touch panel (display means), 100: image forming device, 101: main control unit (setting means / control means), 103: memory, 104: storage, 108: image processing circuit, 123: setting data, 150: print setting screen, 160, 360: warning setting screen, 170, 370: warning screen, 180: menu screen, 200: foil printing device, 221: heating roller, 222: pressure roller, 231: supply reel, 232: recovery reel, 250: foil, F1: adhesive area, F2: non-adhesive area, S: sheet, TN: toner image

Claims

1. an image forming means for forming a toner image on a sheet based on image data; a setting means for setting a first mode for forming the toner image so as to adhere a foil onto a sheet via the toner image; a control means for controlling a display means to display a warning in accordance with an index related to a toner area per unit area of ​​the toner image formed by the image forming means when the first mode is set by the setting means; An image forming apparatus comprising:

2. 2. The image forming apparatus according to claim 1, wherein said setting unit sets said first mode when said first mode is selected by a user from among a plurality of operation modes related to the formation of said toner image.

3. 2. The image forming apparatus according to claim 1, wherein the control means controls the display means to display the warning when the indicator related to the toner area per unit area of ​​the toner image is determined to satisfy a warning condition when the first mode is set.

4. 4. The image forming apparatus according to claim 3, wherein the control unit determines whether the indicator satisfies the warning condition by analyzing the image data before the image forming unit forms the toner image.

5. 5. The image forming apparatus according to claim 4, wherein the control unit controls the display unit to display a preview of the toner image in a manner that allows the specific portion to be identified when the warning condition is met for the specific portion of the toner image.

6. the index has a value determined based on the gradation of an image area of ​​the toner image, The control means determines that the warning condition is satisfied when the value of the index is lower than a first threshold value corresponding to an allowable lower limit. The image forming apparatus according to claim 3 .

7. The control means determining a value of the index for each partial area set in the image area based on the gradation of the partial area; comparing the determined value of the index with the first threshold to determine whether the warning condition is met; The image forming apparatus according to claim 6 .

8. 8. The image forming apparatus according to claim 7, wherein the control unit determines the value of the index for the partial region based on the gradation of the partial region and a coefficient related to a toner deposition characteristic of the image forming unit.

9. 7. The image forming apparatus according to claim 6, wherein the control unit excludes from the image area a portion having a gradation equal to or less than a second threshold value corresponding to a gradation of a non-image area in determining whether the warning condition is satisfied.

10. The image forming apparatus according to claim 6 , wherein the first threshold value can be set by a user.

11. The image forming apparatus according to claim 9 , wherein the second threshold value can be set by a user.

12. The control means Accepting a first user setting indicating whether to output a warning about a lack of toner area; controlling the display means to display a warning if the first user setting indicates that a warning should be output; The image forming apparatus according to claim 1 .

13. The control means accepting a second user setting indicating whether or not to improve the indicator during image formation when it is determined that the warning condition is satisfied; controlling the image formation by the image forming means in accordance with the second user setting; The image forming apparatus according to claim 3 .

14. In response to a determination that the warning condition is satisfied, the control means: Inquiring a user about whether or not to improve the indicator during the image formation; accepting the second user setting in response to the inquiry; The image forming apparatus according to claim 13.

15. The control means accepting the second user setting before the image data is input; and when it is determined that the warning condition is satisfied, controlling the image forming means so as to form a toner image with an improved indicator when the second user setting indicates that the indicator should be improved during the image formation. The image forming apparatus according to claim 13.

16. Improving the index modifying the gradation represented by the image data; adjusting the amount of exposure when the exposure device of the image forming means exposes the photosensitive member; adjusting the dark potential when the charger of the image forming means charges the photosensitive member; The image forming apparatus of claim 13 , comprising at least one of:

17. The image forming apparatus according to any one of claims 1 to 16, a foil printing device that prints a foil image on the sheet by adhering the foil onto the sheet via the toner image; Foil printing system including:

Images