Image forming device and foil printing system

Abstract

To reduce the possibility that the quality of a foil image is degraded.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 stick a foil onto the sheet via the toner image; and control means for controlling display means so as to display a warning according to the shape 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 sticking 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 so as 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 the shape 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 4A] FIG. 10 is a first explanatory diagram showing how the bonded portion of the foil separates from the non-bonded portion. [Figure 4B] FIG. 2 is a second explanatory diagram showing how the bonded portion of the foil separates from the non-bonded portion. [Figure 5A]10A and 10B are diagrams illustrating degradation of the quality of a foil image due to insufficient glue width. [Figure 5B] 10A and 10B are diagrams illustrating degradation of foil image quality due to insufficient gap width. [Figure 6] FIG. 10 is a further illustration of the quality degradation associated with fine lines in a toner image. [Figure 7] FIG. 2 is a block diagram showing an example of the functional configuration of an image forming apparatus according to an embodiment. [Figure 8] FIG. 1 is a block diagram showing an example of the functional configuration of a foil printing apparatus according to an embodiment. [Figure 9] FIG. 4 is a block diagram showing an example of a detailed configuration of a process that can be executed for a warning related to a thin line in the first embodiment. [Figure 10] FIG. 11 is a first explanatory diagram showing an example of the configuration of a print setting screen according to the first embodiment. [Figure 11] FIG. 2 is a second explanatory diagram showing an example of the configuration of the print setting screen according to the first embodiment. [Figure 12] FIG. 4 is an explanatory diagram showing an example of the configuration of a warning setting screen according to the first embodiment. [Figure 13] FIG. 4 is an explanatory diagram showing an example of the configuration of a warning screen according to the first embodiment. [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. 10 is an explanatory diagram showing an example of how pixels on both sides of a thin line region are thinned out. [Figure 16] FIG. 11 is an explanatory diagram showing an example of the configuration of a print setting screen according to a second embodiment. [Figure 17] FIG. 11 is an explanatory diagram showing an example of the configuration of a correction setting screen according to the second embodiment. [Figure 18] FIG. 11 is an explanatory diagram showing an example of the configuration of a warning screen according to the second embodiment. [Figure 19] 10 is a flowchart showing an example of the flow of a print control process according to a second embodiment. 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 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. 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. Configuration example of foil printing equipment> 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] 4A and 4B further show how the adhered portion F1 of the foil layer 251 separates from the non-adhered portion F2.

[0033] In the example of FIG. 4A, a letter or thin line that forms part of the toner image TN is formed in the center of the sheet S. The left side of the figure shows the state of the sheet S before it reaches the bonding position T3. When the sheet S reaches the bonding position T3 (center of the figure), the toner in the toner image TN melts and is pressed by the pressure roller 222 to adhere to the foil layer 251. This potentially forms a pattern of adhesive portions F1 in contact with the toner image TN on the foil layer 251, but at this point, the adhesive portions F1 are not separated from the non-adhesive portions F2. The width W1 of the adhesive portions F1 is equal to the width of the portion where glue is present (glue width). When the sheet S and the foil 250 pass the bonding position T3 (right side of the figure), the adhesive portions F1 are pulled toward the sheet S by the adhesive force of the glue, while the non-adhesive portions F2 tend to remain on the backup layer 252 due to the tension of the foil 250. As a result, the adhesive portion F1 and the non-adhesive portion F2 split at their boundary, and the adhesive portion F1 separates from the non-adhesive portion F2 and is transferred to the sheet S. If the adhesive width W1 is large enough to ensure the adhesive force required for the adhesive portion F1 to separate from the non-adhesive portion F2, a pattern similar to the toner image TN is reproduced by the foil image transferred to the sheet S.

[0034] In the example of FIG. 4B , a gap in the toner image TN exists in the center of the sheet S. This gap may be, for example, the white portion of a white character. When the sheet S reaches the bonding position T3, the toner in the toner image TN melts and is pressed by the pressure roller 222 to adhere to the foil layer 251. This potentially forms a pattern of adhered portions F1 on the foil layer 251 where the toner image TN contacts. The width W2 of the non-adhesive portion F2 in the figure is equal to the width of the gap (gap width) where no glue is present. When the sheet S and the foil 250 pass the bonding position T3, the adhered portion F1 is separated from the non-adhesive portion F2 and transferred to the sheet S, as in the example of FIG. 4A . If the gap width W2 is large enough to ensure tension for the non-adhesive portion F2 to remain on the backup layer 252, the foil image on the sheet S will reproduce the same white pattern as that represented by the toner image TN.

[0035] <1-5. Quality degradation related to thin lines> FIG. 5A is an explanatory diagram of the degradation of foil image quality due to insufficient glue width W1. The left side of the figure shows four straight lines that may be included in the toner image, with line widths of 0.2 points (p), 0.5p, 1.0p, and 3.0p, from top to bottom. Note that 1p is equivalent to approximately 0.35 mm. When foil is transferred to this toner image, parts of the lines may be missing, as shown on the right side of the figure. The missing lines occur in lines whose line width is smaller than a certain limit value. In the example shown, the 0.2p line is interrupted in many places.

[0036] FIG. 5B is an explanatory diagram illustrating the degradation of foil image quality due to insufficient gap width W2. The left side of the figure depicts four white lines that can be included in a toner image, with line widths of 0.2p, 0.5p, 1.0p, and 3.0p, from top to bottom. When foil is transferred to this toner image, some of the lines may become distorted, as shown on the right side of the figure. Distortion occurs in lines whose white line width is smaller than a certain limit. In the illustrated example, the 0.2p and 0.5p lines are distorted in several locations. Comparing FIGS. 5A and 5B, it can be seen that the limit for line width in a white image is larger than the limit for line width in a normal image. In other words, white images are more likely to suffer quality degradation even with larger line widths.

[0037] Figure 6 further illustrates the quality degradation associated with thin lines in a toner image. The upper part of Figure 6 shows the sheet S and foil 250 after passing through the adhesion position T3, viewed from the extension direction Dn of the straight line included in the toner image TN. The adhesive width W1 of the toner image TN is equal to the line width of this straight line, but is smaller than the limit value at which quality degradation of the foil image begins to appear (for example, W1 = 0.2p). An adhesive portion F1 is adhered to the toner image TN, and the adhesive portion F1 appears to be peeled off from the foil 250.

[0038] The lower part of Figure 6 shows the sheet S as viewed from the direction normal to the sheet surface. In the example shown, the outline of the foil image transferred to the toner image TN does not match the outline of the straight lines in the toner image TN. In section Q1, the foil has not been partially transferred to the sheet S on both sides of the straight lines, resulting in a jagged outline of the foil image. In section Q2, the foil is missing, resulting in a broken line in the foil image. In section Q3, the outline of the foil image is also jagged, but part of it extends beyond the straight lines.

[0039] The cause of such rattles, discontinuities, or extrusions is thought to be an imbalance or variation in the tensile forces acting on the adhesive portion F1 and the non-adhesive portion F2 when the adhesive portion F1 attempts to peel off from the foil 250. For example, if the adhesive width W1 is small, the adhesive area of ​​the adhesive portion F1 relative to the toner image TN becomes smaller, and the tensile force P1 pulling the adhesive portion F1 toward the sheet also becomes smaller. This causes the variation in tensile force to become relatively dominant, and the balance with the opposite tensile force P2 that attempts to leave the non-adhesive portion F2 on the backup layer 252 becomes disturbed in the foil's in-plane direction. This can cause rattles or extrusions. Alternatively, if the tensile force P1 pulling the adhesive portion F1 toward the sheet cannot overcome the opposite tensile force P2, the adhesive portion F1 loses adhesion to the toner image TN, and the adhesive portion F1 remains on the backup layer 252. This can cause the discontinuities.

[0040] In a hollow image, if the gap width W2 is small, the tensile force that tries to leave the non-adhesive portion F2 in the gap between the adhesives on the backup layer 252 is small. As a result, the balance position with the tensile force in the opposite direction that pulls the adhesive portion F1 toward the sheet is disturbed in the plane direction of the foil. If the former tensile force cannot overcome the latter tensile force, the non-adhesive portion F2, along with the adhesive portions F1 on both sides, will peel off from the backup layer 252 and be transferred to the sheet S. This can cause crushing.

[0041] The tensile force acting on the bonded portion F1 and the non-bonded portion F2 also depends on the direction of the boundary between the two portions. For example, the direction and magnitude of the tensile force may differ depending on whether the boundary is parallel to the conveyance direction of the sheet S, perpendicular to it, or in other cases. In addition, variations in the contours of the lines contained in the toner image TN, uneven toner loading (film thickness), and thinning of dots during image formation may also cause variations in the tensile force, which may result in the jaggedness, discontinuity, protrusion, or crushing of thin lines in the foil image.

[0042] The above-mentioned degradation in the quality of the foil image can be prevented by ensuring a sufficient line width in the toner image when the toner of the toner image is intended to be used as glue. If the line width (e.g., glue width or gap width) is large enough, the effect of variations in the tensile force is relatively small compared to the magnitude of the tensile force. This reduces the disturbance of the balanced position of the tensile force, reducing the wobbling and protrusion of the lines in the foil image and preventing breaks and crushing.

[0043] Therefore, when the toner of the toner image formed by the image forming device 100 is used as glue, the foil printing system 1 determines whether thin lines in the toner image may cause a decrease in quality, and warns the user based on the determination result.

[0044] <2. Function details> <2-1. Example of functional configuration of image forming device> 7 shows an example of the functional configuration of an image forming apparatus 100 according to an embodiment. Referring to Fig. 7, 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.

[0045] 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 warnings to the user regarding thin lines when toner is used as glue. Warnings regarding thin lines will be described in detail later.

[0046] 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.

[0047] 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. 7, 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] <2-2. Example of functional configuration of foil printing device> Fig. 8 shows an example of the functional configuration of a foil printing apparatus 200 according to an embodiment. Referring to Fig. 8, 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.

[0054] 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.

[0055] 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.

[0056] Although not shown in Fig. 8, the foil printing apparatus 200 may have an operation means similar to the above-mentioned operation unit 40. In that 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.

[0057] <2-3. Warnings regarding thin lines> In this embodiment, the image forming apparatus 100 issues a warning to the user to alert them to the possibility of a reduction in foil printing quality depending on the shape of the toner image. For example, warning conditions related to thin lines when toner in a toner image is used as glue 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.

[0058] 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.

[0059] 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.

[0060] In this embodiment, the warning condition includes that a feature of image data that affects the width of a thin line (hereinafter referred to as a thin line feature) is smaller than a threshold. The thin line feature here may include at least one of the following: Feature A1 - Width of the line in the image Feature A2 - Size of characters in the image Feature A3 - The number of pixels arranged in the width direction of the thin line region in the image (hereinafter referred to as the thin line region width)

[0061] The feature quantities A1 and A2 are typically obtained by extracting attributes of image components from image data written in PDL format. The first threshold value compared with the line width (feature quantity A1) may be, for example, 1.0 point. In this case, the main control unit 101 determines that the warning condition is met when the image contains a thin line with a width smaller than 1.0 point. The second threshold value compared with the character size (feature quantity A2) may be, for example, 14 points. In this case, the main control unit 101 determines that the warning condition is met when the image contains a character written in a character size smaller than 14 points.

[0062] The feature A3 is obtained by detecting a thin line region in an image represented in bitmap format and determining the number of pixels aligned in the width direction of the detected thin line region. The detection of the thin line region may be performed using any known method, such as those described in Japanese Patent Application Laid-Open Nos. 2016-167777 and 2019-139083. For example, Japanese Patent Application Laid-Open No. 2016-167777 discloses a method for determining whether each pixel of interest constitutes a thin line by comparing a pixel value matrix within a window consisting of a pixel of interest and its neighboring pixels with a predetermined matrix pattern representing a local thin line. The window size and matrix pattern are determined in advance based on the width of the thin line region to be detected. By repeatedly performing this determination while moving the position of the pixel of interest within the image represented in bitmap format, pixels belonging to the thin line region and other pixels are distinguished. The width of the thin line region detected in this manner can be determined by counting the number of pixels aligned in the width direction of the thin line region.

[0063] The third threshold value to be compared with the thin line region width (feature amount A3) may be, for example, 10 pixels (equivalent to approximately 0.42 mm at 600 dpi). In this case, the main control unit 101 determines that the warning condition is met when a thin line region whose width is less than 10 pixels exists in the image.

[0064] Feature A3 can be used, for example, in addition to feature A1 and A2 to complement and determine whether a warning condition exists. This is because, during the bitmapping and binarization process of image data for image formation, pixels constituting a thin line region are thinned out, resulting in an insufficient line width. Figure 15 shows an example of how pixels on both sides of thin line region R1 are thinned out during image processing. This thinning results in a partial reduction in the line width of thin line region R1. Because this insufficient line width cannot be detected from the attributes described in the PDL data, it is beneficial to use feature A3 complementarily to prevent overlooking the insufficient line width. Note that the warning condition may be determined using only feature A3, without using feature A1 and A2.

[0065] The specific values ​​of the first, second, and third thresholds described above are merely examples for the purpose of explanation. Of course, other values ​​may be used as thresholds for determining whether a warning condition exists. The memory 103 of the main control unit 101 stores these thresholds.

[0066] Two examples for the control with the thin line related warnings mentioned above are described in more detail below.

[0067] <3. First Example> <3-1. Processing configuration> In the first embodiment, analysis of input image data and extraction of thin line feature amounts are performed by the image processing circuit 108. The image processing circuit 108 stores feature amount data 123 indicating the extracted thin line feature amounts in the memory 103. The CPU 102 determines whether the toner image satisfies the warning conditions based on this feature amount data 123, and issues a warning to the user according to the determination result.

[0068] 9 shows an example of a detailed configuration of processing that can be executed by the CPU 102 and image processing circuit 108 for issuing a warning related to thin lines in the first embodiment. Referring to Fig. 9, the processing executed by the image processing circuit 108 includes rasterization 111, color matching 113, color conversion 114, thin line determination 115, gamma correction 116, and halftoning 117. The rasterization 111 includes feature extraction 112. The processing executed by the CPU 102 includes warning condition determination 131 and warning output 132.

[0069] 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 three color components (RGB). For example, the PDL data 121 specifies the position and type of each object (component) that makes up the image. Candidate types of objects include, for example, lines, characters, graphics, and photos. A line object has line width as an attribute. This line width corresponds to the feature A1 described above. A character object has character size as an attribute. This character size corresponds to the feature A2 described above. The image processing circuit 108 extracts these features from the PDL data 121 and generates feature data 123. In the feature data 123, each feature is stored in association with the position of the corresponding object.

[0070] Color matching 113 is a process for adjusting RGB signal values ​​in order to maintain a consistent color tone in the printed result without being affected by differences in color reproducibility between devices.

[0071] Color conversion 114 is a process for converting image data expressed in RGB space into image data in YMCK space corresponding to four colors of developer (toner).

[0072] Thin line determination 115 is a process that detects thin line areas from bitmap data for each YMCK color component and determines the thin line area width, expressed in number of pixels. This thin line area width corresponds to the feature A3 described above. When one or more thin line areas are detected in an image, image processing circuit 108 adds the determined thin line area width for each thin line area to feature data 123, associating it with the detected position of the thin line area. Note that when only some toners among multiple color components are used as adhesive, image processing circuit 108 may perform thin line determination 115 only on bitmap data for the color component of the toner used as adhesive.

[0073] The gamma correction 116 is a process for correcting the signal values ​​of the respective color components using a gamma curve selected in accordance with the density output characteristics of the process units 21Y, 21M, 21C, and 21K.

[0074] Halftoning 117 is a process that converts the gradation expressed by multi-level signal values ​​for each pixel into spatial area gradation using, for example, dithering or error diffusion. As a result of halftoning 117, image data 122 is generated that expresses the toner image of each color component of YMCK using binary signal values ​​for each pixel.

[0075] The warning condition determination 131 is a process for determining whether the toner image satisfies the warning conditions using the thin line feature values ​​extracted or determined in the image processing described above. In this embodiment, when the foil printing mode is set among the foil printing mode and the normal mode, the CPU 102 executes the warning condition determination 131 based on the feature value data 123. For example, the CPU 102 may determine that the toner image satisfies the warning conditions if at least one of the feature values ​​A1, A2, and A3 contains a value smaller than the corresponding threshold value. If the CPU 102 determines that the toner image does not satisfy any of the warning conditions, it skips the warning output 132 and starts the image formation job. On the other hand, if the CPU 102 determines that the toner image satisfies at least one of the warning conditions, it executes the warning output 132.

[0076] Warning output 132 is a process that outputs a warning to alert the user that thin lines in the toner image may cause a deterioration in the quality of foil printing. 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.

[0077] <3-2. Example of User Interface (UI)> 10 and 11 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.

[0078] FIG. 10 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 that will be the paper source, the sheet size, the magnification, the 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 that will 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.

[0079] 11 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.

[0080] 12 shows an example of the configuration of a warning setting screen 160 according to the first embodiment. The warning setting screen 160 includes check boxes 161, 162, and 163, pull-down menus 164, 165, and 166, a help button 167, an OK button 168, and a back button 169. The check boxes 161, 162, and 163 are objects that allow the user to set whether or not to determine warning conditions for the line width, character size, and thin line area width, respectively.

[0081] If the user wishes to be warned about insufficient line width, the user turns on check box 161 and selects a desired value for the first threshold in pull-down menu 164. If the user does not select a threshold, a default value is used for the first threshold. If the user wishes to be warned about insufficient character size, the user turns on check box 162 and selects a desired value for the second threshold in pull-down menu 165. If the user does not select a threshold, a default value is used for the second threshold. If the user wishes to be warned about insufficient thin line region width, the user turns on check box 163 and selects a desired value for the third threshold in pull-down menu 166. If the user does not select a threshold, a default value is used for the third threshold.

[0082] As in this example, by allowing the user to set the threshold value that is compared with the thin line feature, the user can flexibly adjust the warning conditions to suit the characteristics of the foil printing device, the characteristics of the toner or foil, or the degree of quality degradation that the user is willing to tolerate.

[0083] When the user operates help button 167, a further screen is displayed that describes each warning condition. When the user operates OK button 168, CPU 102 acquires the settings 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 changes made to the settings on warning setting screen 160, closes warning setting screen 160, and displays print setting screen 150 again.

[0084] 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 determination of at least one warning condition is enabled. If determination of at least one warning condition is enabled, the CPU 102 determines whether the toner image satisfies the warning condition based on the feature data 123 output from the image processing circuit 108. If it is determined that the toner image satisfies at least one warning condition, the CPU 102 displays a warning screen 170 shown in FIG. 13 on the display.

[0085] FIG. 13 shows an example of the configuration of a warning screen 170 according to the first embodiment. The warning screen 170 includes a judgment result field 171, a preview window 172, a continue button 175, and a cancel button 176. The judgment result field 171 is a field in which the results of judgment on the warning conditions based on the input image data of the job are written. In the example of FIG. 13, text is displayed indicating that, although there are no portions where the line width is smaller than the threshold, one portion where the character size is smaller than the threshold and one portion where the thin line region width is smaller than the threshold have been detected. The preview window 172 is a window that displays a preview of the toner image printed in foil printing mode. In the example of FIG. 13, indicators 173 and 174 are superimposed on the preview window 172. The indicator 173 indicates the position of the character that satisfies the warning condition. The indicator 174 indicates the position of the thin line region that satisfies the warning condition. By viewing such a preview, the user can easily determine which portions of the input image need to be corrected to avoid a deterioration in quality in the subsequent foil printing. When the user operates the continue button 175, the CPU 102 starts executing the job in the foil printing mode. When the user operates the cancel button 176, the CPU 102 stops executing the job.

[0086] <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'.

[0087] 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.

[0088] 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.

[0089] 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 acquires thin line feature amounts (e.g., line width, character size, and thin line area width) of the toner image to be formed based on the input image data.

[0090] Next, in S113 to S117, the main control unit 101 compares the thin line feature amount with a default threshold or a threshold set by the user. For example, if the determination of a warning condition for line width is enabled, the main control unit 101 compares the line width extracted from the PDL data with a first threshold in S113. If the determination of a warning condition for character size is enabled, the main control unit 101 compares the character size extracted from the PDL data with a second threshold in S115. If the determination of a warning condition for thin line region width is enabled, the main control unit 101 compares the thin line region width, which represents the width of a thin line detected in the bitmap data, with a third threshold in S117.

[0091] Next, in S119, the main control unit 101 determines whether the toner image satisfies at least one warning condition based on the results of threshold comparison in S113 to S117. If at least one warning condition is satisfied, the process proceeds to S121. If no warning condition is satisfied, the process proceeds to S125.

[0092] In S121, the main control unit 101 displays the above-mentioned warning screen 170 on the display. Next, in S123, the main control unit 101 accepts a 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 S125. On the other hand, if an instruction to cancel the job is given, the print control process in FIG. 14 ends without forming a toner image on the sheet.

[0093] At S125, 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.

[0094] This section has mainly described an example in which a warning condition is determined and a warning is issued to the user before job execution begins, i.e., before the image forming unit 20 forms a toner image, but the timing of determining a warning condition 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 output data indicating the warning to a log file.

[0095] <4. Second Example> In the second embodiment as well, the analysis of input image data and the extraction of thin line feature amounts are performed by the image processing circuit 108. The image processing circuit 108 stores feature amount data 123 indicating the extracted thin line feature amounts in the memory 103. The CPU 102 determines whether the toner image satisfies the warning conditions based on this feature amount data 123, and issues a warning to the user according to the determination result.

[0096] In the second embodiment, the user is further enabled to instruct correction of image data to compensate for the lack of thin line feature amounts. That is, when it is determined that the thin line feature amounts acquired from the image data satisfy at least one warning condition (are smaller than the corresponding threshold value), the CPU 102 corrects the image data in accordance with the user settings to compensate for the lack of thin line feature amounts. Then, the CPU 102 controls the image forming unit 20 to form a toner image based on the corrected image data.

[0097] The correction of image data in this embodiment may include one or both of thickening thin lines in the image and increasing the density of thin lines in the image. The thickening and density increase here may be performed using any known method, such as those described in Japanese Patent Application Laid-Open Nos. 2016-167777 and 2019-139083.

[0098] Line thickening may be performed, for example, by changing the line width of a line object or the character size of a character object described in the PDL data before rasterization 111. Alternatively, line thickening may be performed by rewriting the pixel values ​​of adjacent pixels adjacent to thin line regions after rasterization 111. Density boosting may typically be performed before gamma correction 116.

[0099] Japanese Patent Application Laid-Open No. 2017-156723 discloses a method for halftoning pixels in a thin line region using a dither matrix that is less likely to cause breaks in the thin lines. Japanese Patent Application Laid-Open No. 2019-139083 discloses a method for expanding or reducing the line width in a toner image by variably controlling the emission width of a laser beam.

[0100] 16 shows an example of the configuration of a print setting screen 350 according to the second embodiment. The print setting screen 350 includes a normal mode tab 151 and a foil printing mode tab 352. If the user plans to print foil on a sheet using the toner of a toner image as glue, the user selects the foil printing mode tab 352.

[0101] 16, the foil printing mode tab 352 includes screen elements similar to those of the foil printing mode tab 152 according to the first embodiment, as well as a correction setting button 357. When the user operates the correction setting button 357, the CPU 102 displays a correction setting screen 360 shown in FIG.

[0102] FIG. 17 shows an example of the configuration of a correction setting screen 360 according to the second embodiment. The correction setting screen 360 includes check boxes 361 and 362, a pull-down menu 363, an OK button 368, and a back button 369. The check box 361 is an object that allows the user to set whether to thicken characters and lines. The check box 362 is an object that allows the user to set whether to increase the density of characters and lines. If the user wants to thicken characters and lines, the user turns on the check box 361. If the user wants to increase the density of characters and lines, the user turns on the check box 362. If both the check boxes 361 and 362 are off, the image data is not corrected. The pull-down menu 363 is an object that allows the user to select the magnification for increasing the density.

[0103] When the user operates the OK button 368, the CPU 102 acquires the setting contents changed on the correction setting screen 360 and stores them in the memory 103 or the storage 104. When the user operates the back button 369, the CPU 102 discards the setting changes on the correction setting screen 360, closes the correction setting screen 360, and displays the print setting screen 350 again.

[0104] FIG. 18 shows an example of the configuration of a warning screen 370 according to the second embodiment. The warning screen 370 includes a judgment result field 171, a preview window 172, a check box 373, a correction setting button 374, a continue button 375, and a cancel button 176. The check box 373 is an object that allows the user to select whether to continue the job after correcting the image data according to the settings described above. The correction setting button 374 is a button for calling the correction setting screen 360 described with reference to FIG. 17. That is, the user can change settings related to image data correction when receiving a warning about insufficient line width. For example, when the user switches the check box 373 on and then operates the continue button 375, the CPU 102 corrects the input image data according to the settings accepted on the correction setting screen 360 and then starts execution of the job in foil printing mode.

[0105] 19 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. 19 is started in response to, for example, the user invoking the above-described print setting screen 350 via the operation unit 40 or the external device 3.

[0106] 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 350. 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.

[0107] 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 a description thereof will be omitted here.

[0108] In S219, the main control unit 101 determines whether the toner image satisfies at least one warning condition based on the results of threshold comparison in S213 to S217. If at least one warning condition is satisfied, the process proceeds to S221. If no warning condition is satisfied, the process proceeds to S225.

[0109] In S221, the main control unit 101 displays the above-mentioned warning screen 370 on the display. Next, in S222, the main control unit 101 accepts a user input on the warning screen 370 instructing whether or not to continue the job. If an instruction to continue the job is given, the process proceeds to S223. On the other hand, if an instruction to cancel the job is given, the print control process in FIG. 19 ends without forming a toner image on the sheet.

[0110] In S223, the main control unit 101 determines whether it is set to correct the image data when continuing the job. If it is set to correct the image data, the process proceeds to S224. In S224, the main control unit 101 corrects the image data to be output to the image forming unit 20 in accordance with the settings accepted on the correction setting screen 360. If it is not set to correct the image data, S224 is skipped.

[0111] Next, 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. 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.

[0112] <5. Summary> 1 to 19 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 when it is determined that a warning condition related to the shape of the toner image is satisfied. This configuration prevents a user from feeding a sheet that may produce a low-quality foil image due to an insufficient line width into the foil printing apparatus, thereby preventing the formation of a low-quality foil image and avoiding foil waste.

[0113] 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.

[0114] 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.

[0115] In the above-described embodiment, the warning condition is a condition related to thin lines when toner is used as adhesive. In particular, the condition related to thin lines may be a condition based on a comparison between a threshold value and a feature of image data that affects the width of the thin line. For example, by determining whether a feature that has a positive correlation with the width of the thin line is smaller than a threshold value, defects such as jaggedness, discontinuities, overflow, or crushing of the thin line can be appropriately predicted and a warning can be output. Furthermore, by extracting object attributes from image data written in a page description language format, the above feature values ​​can be easily acquired. Additionally, by detecting thin line regions in a bitmap image and determining the width of the thin line regions, insufficient line width can be accurately detected.

[0116] In one embodiment, if the feature amount is smaller than a threshold, a toner image may be formed on a sheet based on image data that has been corrected to compensate for the insufficient line width. This configuration allows a toner image with the insufficient line width corrected to be immediately formed without the user having to temporarily stop the job and correct the image data. This reduces the workload on the user and improves productivity in producing deliverables.

[0117] <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.

[0118] 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]

[0119] 1: foil printing system, 2: network, 3: external device, 10: transport unit, 20: image forming unit (image forming means), 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: feature data, 150, 350: print setting screen, 160: warning setting screen, 360: correction setting screen, 170, 370: warning 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 the sheet via the toner image; a control means for controlling a display means to display a warning in accordance with the shape 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 unit controls the display unit to display the warning when it is determined that the toner image satisfies a warning condition related to thin lines when the first mode is set.

4. 4. The image forming apparatus according to claim 3, wherein the control unit determines whether the toner image 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 makes the specific portion distinguishable when the warning condition is met for the specific portion of the toner image.

6. The image forming apparatus according to claim 3 , wherein the warning condition includes a condition that a feature amount of the image data that affects the width of a thin line is smaller than a threshold value.

7. 7. The image forming apparatus according to claim 6, wherein said control means acquires said feature amounts by extracting attributes of image components from said image data described in a page description language format.

8. The image forming apparatus according to claim 7 , wherein the feature amount includes a size of a character in the image.

9. The image forming apparatus according to claim 7 , wherein the feature amount includes a width of a line in the image.

10. 7. The image forming apparatus according to claim 6, wherein said control means acquires said feature amount by determining the number of pixels aligned in the width direction of a thin line region in an image expressed in a bitmap format.

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

12. The control means If the feature amount is smaller than the threshold value, correcting the image data so as to compensate for the lack of the feature amount; causing the image forming means to form a toner image based on the corrected image data; The image forming apparatus according to claim 6 .

13. 13. The image forming apparatus according to claim 12, wherein the control unit corrects the image data by thickening thin lines in the image or increasing the density of the thin lines in the image.

14. The image forming apparatus according to any one of claims 1 to 13, 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