Image-forming device, image-forming medium, and image-forming method

Abstract

To form a medium allowing a different image to be visually recognized according to an angle without requiring any complex configuration.SOLUTION: An image-forming device 1 prints a switchable image PC in which multiple first images P1 and multiple second images P2 are alternately disposed along an X direction on a first surface F1 of a transparent medium MD, and prints a shielding image PS in which multiple third images P3 are disposed for each gap G along the X direction on a second surface F2 of the medium MD. Accordingly, the image-forming device 1 uses the medium MD in which both of the first surface F1 and the second surface F2 are flat, does not require toner with a particular color like metallic toner and clear toner, and can switch an observed image to the first image P1 or the second image P2 according to an observation angle θ when a created switching image print medium MDC is observed by an observer.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus, an image forming medium, and an image forming method, and is suitable for application to, for example, printing on a medium that allows different images to be viewed depending on the angle. [Background technology]

[0002] A method has been known for creating a medium that allows different images to be seen depending on the viewing angle by combining a printed material in which multiple images are divided into strips and arranged alternately with a lenticular lens.

[0003] In addition, an image forming device has been proposed that prints images on a flat medium using metallic toner and clear toner, which are so-called special colors, in addition to color toners that express general colors, thereby creating a medium on which different images can be viewed depending on the angle without using a lenticular lens (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-82516 A (Fig. 3, etc.) Summary of the Invention [Problem to be solved by the invention]

[0005] However, with an image forming device of this configuration, in addition to images using toner of general colors, it is necessary to form images using metallic toner and images using clear toner, and since it is necessary to provide many image forming units in order to form images using many types of toner, there is a problem in that the configuration becomes complicated.

[0006] The present invention has been made in consideration of the above points, and aims to propose an image forming apparatus and image forming method that can form a medium on which different images can be viewed depending on the angle, without requiring a complex configuration such as when using special color toner, as well as an image forming medium on which different images can be viewed depending on the angle, with a simple configuration. [Means for solving the problem]

[0007] In order to solve this problem, the image forming apparatus of the present invention is provided with an image forming unit that forms an image on a first surface or the opposite second surface of a medium that transmits at least a portion of visible light, and a control unit that controls the formation of images by the image forming unit, and the control unit controls the image forming unit to form a first image and a second image on the first surface of the medium in a state where they are arranged side by side along a first direction, and to form a third image on the second surface of the medium at a location opposite the first image and second image.

[0008] In addition, the image forming medium of the present invention has a first image provided on a first surface of the medium that transmits at least a portion of visible light, a second image provided on the first surface of the medium and arranged alongside the first image along a first direction, and a third image provided on a second surface of the medium that is the opposite surface to the first surface, and the third image is arranged so that when the first surface is viewed through the medium from the second surface side along a first observation direction that forms a first angle between the normal direction of the second surface and the second direction, the third image blocks the first image more preferentially than the second image, and when the first surface is viewed through the medium from the second surface side along a second viewing direction that forms a second angle symmetrical to the first angle with respect to the normal direction of the second surface, the third image allows the second image to be observed more preferentially than the first image.

[0009] Furthermore, the image forming medium of the present invention has a first image provided on a first surface of the medium that transmits at least a portion of visible light, a second image provided on the first surface of the medium and arranged alongside the first image along a first direction, and a third image provided on a second surface of the medium that is the opposite side of the first surface, and the third image is arranged in a position opposite the first image and the second image across the medium.

[0010] Furthermore, the image forming method of the present invention includes a first image forming step in which an image forming unit forms a first image and a second image on a first surface of a medium that transmits at least a portion of visible light, with the first image and the second image arranged side by side along a first direction, and a second image forming step in which, before or after the first image forming step, the image forming unit forms a third image on a second surface of the medium that is the opposite side to the first surface, and the third image is arranged at a location on the second surface of the medium that faces at least a portion of the first image and at least a portion of the second image.

[0011] The present invention provides a method for observing the first surface from the second surface side of the medium through a portion where the third image is not formed, by switching between observing the first image or the second image formed on the first surface depending on the observation angle, i.e., achieving a visual effect similar to that achieved when using a lenticular lens. [Effects of the Invention]

[0012] According to the present invention, it is possible to realize an image forming apparatus and an image forming method that can form a medium on which different images can be viewed depending on the angle, without requiring a complex configuration such as when using special color toner, and an image forming medium on which different images can be viewed depending on the angle, with a simple configuration. [Brief explanation of the drawings]

[0013] [Figure 1] FIG. 1 is a schematic diagram illustrating an overall configuration of an image forming apparatus. [Figure 2] FIG. 2 is a schematic diagram illustrating a configuration of an image forming unit. [Figure 3] FIG. 2 is a block diagram showing a circuit configuration of the image forming apparatus. [Figure 4] FIG. 2 is a schematic perspective view showing the configuration of a switching image printing medium. [Figure 5] FIG. 2 is a schematic diagram illustrating a configuration of a switching image. [Figure 6] FIG. 2 is a schematic diagram illustrating the configuration of a masking image. [Figure 7]10 is a schematic diagram showing a viewing direction of a switching image printing medium. FIG. [Figure 8] 3A to 3C are schematic diagrams illustrating images observed in accordance with the observation direction. [Figure 9] 4 is a schematic diagram showing an observation angle and an observation range in a first observation state. FIG. [Figure 10] 10 is a schematic diagram showing the observation angle and observation range in a second observation state. FIG. [Figure 11] 10 is a schematic diagram showing the observation angle and observation range in a third observation state. [Figure 12] 10 is a schematic diagram showing the observation angle and observation range in a fourth observation state. [Figure 13] 10 is a table showing the relationship between the length of each portion and the observation angle for each thickness of the medium. [Figure 14] 10A and 10B are schematic diagrams showing observation angles that are symmetric with respect to the normal direction. [Figure 15] 10 is a flowchart showing a procedure for a switching image print medium creation process. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, modes for carrying out the invention (hereinafter referred to as embodiments) will be described with reference to the drawings.

[0015] [1. Configuration of image forming device] 1, the image forming apparatus 1 according to this embodiment is an electrophotographic color printer that can form (i.e., print) a color image on a medium MD such as paper. Incidentally, the image forming apparatus 1 does not have an image scanner function for reading a document or a communication function using a telephone line, and is a single-function SFP (Single Function Printer) that has only a printer function.

[0016] Various components are arranged inside a roughly box-shaped housing 2 of the image forming apparatus 1. In the following description, the right end portion in Fig. 1 is defined as the front of the image forming apparatus 1, and the up-down direction, left-right direction, and front-rear direction are defined when viewed from the front.

[0017] The image forming apparatus 1 is controlled overall by a control unit 3. As will be described later, this control unit 3 executes various processes by reading and executing predetermined programs. The control unit 3 is also connected wirelessly or by wire to a host device 100 (FIG. 3) such as a computer device, and when image data representing an image to be printed is provided from the host device and an instruction to print the image data is given to the control unit 3, the control unit 3 executes a printing process to form a print image on the surface of the medium MD.

[0018] The display operation unit 4 is a touch panel that combines a display device such as a liquid crystal panel with an operation device such as a touch sensor, and is disposed on the front side of the top surface of the housing 2. Based on the control of the control unit 3, the display operation unit 4 displays various information and notifies the control unit 3 of the contents of operation inputs by the user.

[0019] Five image forming units 10K, 10C, 10M, 10Y, and 10S are arranged in this order from the front to the rear on the upper side inside the housing 2. The image forming units 10K, 10C, 10M, 10Y, and 10S correspond to the colors black (K), cyan (C), magenta (M), yellow (Y), and spot color (S), respectively, but the only difference is the color; all of them are configured similarly.

[0020] Black (K), cyan (C), magenta (M), and yellow (Y) are all colors used in general color printers (hereinafter referred to as normal colors or non-bright colors). On the other hand, special colors (S), such as gold and silver, are special colors that exhibit a metallic luster, i.e., have a bright appearance (hereinafter also referred to as bright colors). These special colors may be used alone or may be used over a normal color. In this embodiment, an example will be described in which silver is used as a special color.

[0021] 2, the image forming unit 10 is broadly composed of an image forming main body 11, a toner container 12, a toner supply unit 13, and an LED (Light Emitting Diode) head 14. The toner container 12, which serves as a developer container or a developer container, contains toner T (also called a developer or a developer) therein and is configured to be detachable from the image forming unit 10. When the toner container 12 is mounted on the image forming unit 10, it is attached to the image forming main body 11 via the toner supply unit 13. Incidentally, the toner container 12 is sometimes called a toner cartridge.

[0022] The image forming main body 11 (FIG. 2) incorporates an image forming housing 20, a toner storage space 21, a first supply roller 22, a second supply roller 23, a developing roller 24, a developing blade 25, a photosensitive drum 26, a charging roller 27, and a cleaning blade 28. Of these, the first supply roller 22, the second supply roller 23, the developing roller 24, the photosensitive drum 26, and the charging roller 27 are each configured in a cylindrical shape with their central axes aligned in the left-right direction, and are each rotatably supported by the image forming housing 20.

[0023] The toner storage space 21 stores the toner T supplied from the toner storage container 12 via the toner supply unit 13. The first supply roller 22 and the second supply roller 23 each have an elastic layer formed on their circumferential side, the elastic layer being made of a conductive urethane rubber foam or the like. The developing roller 24 has an elastic layer and a conductive surface layer formed on its circumferential side. The developing blade 25 is made of, for example, a stainless steel plate of a predetermined thickness, and a portion of it abuts against the circumferential side of the developing roller 24 in a state where it is slightly elastically deformed.

[0024] The photosensitive drum 26, which serves as an image carrier, has a thin-film charge generating layer and a charge transport layer formed in that order on its circumferential surface, enabling it to be charged. The charging roller 27 has a conductive elastic body coated on its circumferential surface, which is in contact with the circumferential surface of the photosensitive drum 26. The cleaning blade 28 is made of, for example, a thin resin plate, and a portion of it is in contact with the circumferential surface of the photosensitive drum 26 while being slightly elastically deformed.

[0025] The LED head 14 serving as an exposure unit is located above the photosensitive drum 26 in the image forming main body 11. This LED head 14 has multiple light-emitting element chips arranged linearly in the left-right direction, and causes each light-emitting element to emit light in a light emission pattern based on image data signals supplied from the control unit 3 (FIG. 1).

[0026] The image forming main body 11 receives a driving force from a motor (not shown) to rotate the first supply roller 22, the second supply roller 23, the developing roller 24, and the charging roller 27 in the direction of arrow R1 (clockwise in the figure), and rotates the photosensitive drum 26 in the direction of arrow R2 (counterclockwise in the figure). Furthermore, under the control of the control unit 3, the image forming main body 11 applies a predetermined bias voltage to the first supply roller 22, the second supply roller 23, the developing roller 24, the developing blade 25, and the charging roller 27, thereby charging them.

[0027] The first supply roller 22 and the second supply roller 23 are charged to cause the toner T in the toner storage space 21 to adhere to their circumferential surfaces, and then rotate to cause the toner T to adhere to the circumferential surface of the developing roller 24. The developing roller 24 has excess toner T removed from the circumferential surface by the developing blade 25, and with the toner T adhering in the form of a thin film, the circumferential surface is brought into contact with the circumferential surface of the photosensitive drum 26.

[0028] Meanwhile, the charging roller 27, in a charged state, contacts the photosensitive drum 26, thereby uniformly charging the circumferential surface of the photosensitive drum 26. The LED head 14 sequentially exposes the photosensitive drum 26 by performing an exposure process in which it emits light at predetermined time intervals in an emission pattern based on an image data signal supplied from the control unit 3 (FIG. 1). As a result, electrostatic latent images are sequentially formed on the circumferential surface of the photosensitive drum 26 near its upper end.

[0029] Next, the photosensitive drum 26 rotates in the direction of arrow R2, bringing the area where the electrostatic latent image is formed into contact with the developing roller 24. As a result, toner T adheres to the circumferential surface of the photosensitive drum 26 based on the electrostatic latent image, and a toner image based on the image data is developed. The photosensitive drum 26 further rotates in the direction of arrow R2, causing the toner image to reach the vicinity of the bottom end of the photosensitive drum 26.

[0030] An intermediate transfer section 30 is disposed below each image forming unit 10 within the housing 2 (FIG. 1). The intermediate transfer section 30 includes a drive roller 31, a driven roller 32, a backup roller 33, an intermediate transfer belt 34, five primary transfer rollers 35, a secondary transfer roller 36, and a reverse bending roller 37. Of these, the drive roller 31, the driven roller 32, the backup roller 33, the primary transfer rollers 35, the secondary transfer rollers 36, and the reverse bending roller 37 are all formed in a cylindrical shape with their central axes aligned in the left-right direction, and are rotatably supported by the housing 2.

[0031] The drive roller 31 is disposed below and rearward of the image forming unit 10S, and rotates in the direction of arrow R1 when a driving force is supplied from a belt motor (not shown). The driven roller 32 is disposed below and frontward of the image forming unit 10K. The upper ends of the drive roller 31 and the driven roller 32 are positioned at the same level as or slightly below the lower ends of the photosensitive drums 26 (FIG. 2) in the respective image forming units 10. The backup roller 33 is disposed below and frontward of the drive roller 31 and below and rearward of the driven roller 32.

[0032] The intermediate transfer belt 34 is configured as an endless belt made of a high-resistance plastic film, and is stretched so as to go around the drive roller 31, the driven roller 32, and the backup roller 33. Furthermore, in the intermediate transfer section 30, five primary transfer rollers 35 are disposed below the portion of the intermediate transfer belt 34 that is stretched between the drive roller 31 and the driven roller 32, i.e., directly below each of the five image forming units 10, at positions facing each of the photosensitive drums 26 across the intermediate transfer belt 34. A predetermined bias voltage is applied to these primary transfer rollers 35 under the control of the control section 3.

[0033] The secondary transfer roller 36 is located directly below the backup roller 33 and is biased toward the backup roller 33. That is, the intermediate transfer unit 30 sandwiches the intermediate transfer belt 34 between the secondary transfer roller 36 and the backup roller 33. A predetermined bias voltage is applied to the secondary transfer roller 36. Hereinafter, the secondary transfer roller 36 and the backup roller 33 will be collectively referred to as the secondary transfer unit 39.

[0034] The reverse bending roller 37 is located at a position lower and front of the drive roller 31 and rear and above the backup roller 33, and urges the intermediate transfer belt 34 in an upward and front direction. This prevents the intermediate transfer belt 34 from becoming loose, and tension acts between each roller. In addition, a reverse bending backup roller 38 is provided at a position above and in front of the reverse bending roller 37, sandwiching the intermediate transfer belt 34 therebetween.

[0035] The intermediate transfer unit 30 rotates the drive roller 31 in the direction of arrow R1 using a driving force supplied from a belt motor (not shown), thereby moving the intermediate transfer belt 34 in the direction of arrow E1. Each primary transfer roller 35 rotates in the direction of arrow R1 with a predetermined bias voltage applied. This allows each image forming unit 10 to transfer the toner image that has reached the lower end of the circumferential surface of the photosensitive drum 26 (FIG. 2) onto the intermediate transfer belt 34, and toner images of each color are sequentially superimposed on the surface of the intermediate transfer belt 34. At this time, toner images of each color are sequentially superimposed on the surface of the intermediate transfer belt 34, starting with silver (S) on the upstream side. By moving the intermediate transfer belt 34, the intermediate transfer unit 30 causes the toner images transferred from each image forming unit 10 to reach the vicinity of the backup roller 33.

[0036] Incidentally, a transport path W, which is a path for transporting the medium MD, is formed inside the housing 2 (FIG. 1). This transport path W heads upward from the front of the bottom end of the housing 2, makes approximately a half turn, and then proceeds rearward below the intermediate transfer unit 30. The transport path W then heads upward, traveling upward along the rear side of the intermediate transfer unit 30 and the image forming unit 10S, before heading forward. That is, the transport path W is shaped as if it were a capital letter "S" in FIG. 1. Various components are arranged inside the housing 2 along this transport path W.

[0037] A first paper supply unit 40 is disposed near the bottom end inside the housing 2 (FIG. 1). The first paper supply unit 40 includes a paper cassette 41, a pickup roller 42, a feed roller 43, a retard roller 44, a transport guide 45, and transport roller pairs 46, 47, and 48. The pickup roller 42, the feed roller 43, the retard roller 44, and the transport roller pairs 46, 47, and 48 are all formed in a cylindrical shape with their central axes aligned in the left-right direction.

[0038] Paper cassette 41 is configured in the shape of a hollow rectangular parallelepiped, and is detachable from housing 2. Paper cassette 41 stores media MD in a stacked state, i.e., in a piled state, with the paper surfaces facing up and down.

[0039] In this embodiment, the medium MD is a so-called OHP (Overhead Projector) film, specifically, for example, CG3700 (manufactured by 3M Japan Ltd.). This medium MD has a sufficiently high transmittance for visible light and is formed as a so-called transparent film. That is, each surface of the medium MD is formed flat, allowing for good transfer and fixation of toner images, i.e., good printing of images.

[0040] The pickup roller 42 is in contact with the vicinity of the front end of the top surface of the medium MD stored in the paper cassette 41. The feed roller 43 is positioned slightly in front of the pickup roller 42. The retard roller 44 is positioned below the feed roller 43, and forms a gap between it and the feed roller 43 that corresponds to the thickness of one sheet of medium MD.

[0041] When a driving force is supplied from a paper feed motor (not shown), the first paper feed unit 40 rotates or stops the pickup roller 42, feed roller 43, and retard roller 44 as appropriate. As a result, the pickup roller 42 feeds forward one or more of the topmost sheets of media MD stored in the paper cassette 41. The feed roller 43 and retard roller 44 feed the topmost sheet of media MD further forward while blocking the second and subsequent sheets. In this way, the first paper feed unit 40 feeds the media MD forward while separating them one by one.

[0042] Conveyance guide 45 is disposed in the front lower portion of conveyance path W, and advances medium MD in a front-upper direction and then in a rear-upper direction along conveyance path W. Conveyance roller pairs 46 and 47 are disposed near the center and near the upper end of conveyance guide 45, respectively, and are supplied with driving force from a paper feed motor (not shown) to rotate in a predetermined direction. In this way, conveyance roller pairs 46 and 47 advance medium MD along conveyance path W.

[0043] A second paper feed unit 50 is provided in front of the pair of transport rollers 47 in the housing 2. The second paper feed unit 50 is provided with a paper tray 51, a pickup roller 52, a feed roller 53, a retard roller 54, etc. The paper tray 51 is formed in the shape of a thin plate extending vertically, and is designed to accommodate a medium MD2 on its upper side. Incidentally, the medium MD2 placed on the paper tray 51 has a size and paper quality different from that of the medium MD stored in the paper cassette 41, for example.

[0044] The pickup roller 52, feed roller 53, and retard roller 54 are configured similarly to the pickup roller 42, feed roller 43, and retard roller 44 of the first paper supply unit 40. When a driving force is supplied from a paper supply motor (not shown), the second paper supply unit 50 appropriately rotates or stops the pickup roller 52, feed roller 53, and retard roller 54 to feed the bottommost sheet of media MD2 on the paper tray 51 rearward while blocking the second and subsequent sheets. In this way, the second paper supply unit 50 separates the media MD2 one by one while feeding them rearward. The fed media MD2 are transported along the transport path W by the transport roller pair 57 in the same manner as the media MD. For convenience of explanation, hereinafter, the media MD2 will be referred to simply as the media MD without being distinguished from the media MD.

[0045] The rotation of the conveying roller pair 47 is appropriately suppressed, and by applying a frictional force to the medium MD, it corrects the inclination of the sides of the medium MD relative to the direction of travel, i.e., so-called skew, and sends the medium MD rearward after aligning the leading and trailing edges. The conveying roller pair 48 is located a predetermined distance rearward from the conveying roller pair 47, and rotates in the same manner as the conveying roller pair 46, etc., to supply a driving force to the medium MD being conveyed along the conveying path W, causing the medium MD to move further rearward along the conveying path W.

[0046] The secondary transfer section 39 of the intermediate transfer section 30 described above, i.e., the backup roller 33 and the secondary transfer roller 36, is disposed behind the pair of conveying rollers 48. In this secondary transfer section 39, the toner image formed in the image forming unit 10 and transferred to the intermediate transfer belt 34 approaches the intermediate transfer belt 34 as the intermediate transfer belt 34 travels, and a predetermined bias voltage is applied to the secondary transfer roller 36. Therefore, the secondary transfer section 39 transfers the toner image onto the medium MD conveyed from the intermediate transfer belt 34 along the conveying path W, and then causes the medium MD to proceed further rearward.

[0047] A fixing unit 60 is disposed behind the secondary transfer unit 39. The fixing unit 60 is composed of a heating unit 61 and a pressure unit 62, which are disposed opposite each other with the transport path W in between. The heating unit 61 has a heater that generates heat, multiple rollers, and the like disposed inside a heating belt that is a hollow endless belt. The pressure unit 62 is formed as a cylindrical pressure roller with its central axis aligned in the left-right direction, and presses its upper surface against the lower surface of the heating unit 61 to form a nip.

[0048] Based on the control of the control unit 3, the fixing unit 60 heats the heater of the heating unit 61 to a predetermined temperature, rotates the roller appropriately to cause the heating belt to run so as to rotate in the direction of arrow R1, and rotates the pressure unit 62 in the direction of arrow R2. Then, when the fixing unit 60 receives the medium MD onto which the toner image has been transferred by the secondary transfer unit 39, it sandwiches (i.e. nips) it between the heating unit 61 and the pressure unit 62 and applies heat and pressure to fix the toner image to the medium MD, and then sends it out rearward.

[0049] A pair of conveying rollers 64 is disposed behind the fixing unit 60, and a switching unit 65 is disposed behind the pair of conveying rollers 64. The switching unit 65 switches the traveling direction of the medium MD to either upward or downward in accordance with the control of the control unit 3. A paper discharge unit 70 is provided above the switching unit 65. The paper discharge unit 70 is composed of a conveying guide 71 that guides the medium MD upward along the conveying path W, pairs of conveying rollers 72, 73, 74, and 75 that face each other across the conveying path W, and a discharge port 76.

[0050] Further, a re-conveying unit 66 is disposed below the switching unit 65, the fixing unit 60, the secondary transfer unit 39, etc. The re-conveying unit 66 has a conveying guide, a pair of conveying rollers (not shown), etc. that constitute a re-conveying path Z. The re-conveying path Z heads downward from below the switching unit 65, then advances forward, and merges with the conveying path W downstream of the pair of conveying rollers 57.

[0051] When discharging the medium MD, the control unit 3 uses the switching unit 65 to switch the traveling direction of the medium MD toward the upper discharge unit 70. The discharge unit 70 transports the medium MD received from the switching unit 65 upward and discharges it from the discharge port 76 to the discharge tray 2T. When returning the medium MD upside down, the control unit 3 uses the switching unit 65 to switch the traveling direction of the medium MD toward the lower re-conveyance unit 66. The re-conveyance unit 66 transports the medium MD received from the switching unit 65 to the re-conveyance path Z, and eventually reaches the downstream side of the transport roller pair 57, causing the medium MD to be transported again along the transport path W. In this way, the image forming apparatus 1 can return the medium MD to the transport path W with the paper surface of the medium MD turned upside down, thereby performing so-called double-sided printing.

[0052] In this way, in the image forming device 1, a toner image is formed using toner T in the image forming unit 10 and transferred to the intermediate transfer belt 34, and the toner image is transferred from the intermediate transfer belt 34 to the medium MD in the secondary transfer section 39, and then fixed in the fixing section 60, thereby printing an image on the medium MD, i.e., forming an image.

[0053] Next, the circuit configuration of the image forming apparatus 1 will be described with reference to the block diagram in Fig. 3. The control unit 3 of the image forming apparatus 1 is centered around a print control unit 80 that provides overall control. Connected to this print control unit 80 are a CPU (Central Processing Unit) 81, a storage unit 82, an interface unit 83, a display control unit 84, a sensor 85, a print data processing unit 86, a process control unit 91, a development voltage control unit 92, a supply voltage control unit 93, an exposure control unit 94, a transfer voltage control unit 95, and a motor control unit 96.

[0054] The CPU 81 performs various arithmetic processing by reading and executing various programs from the storage unit 82. The storage unit 82 is a volatile or non-volatile storage medium such as a ROM (Read Only Memory) or a RAM (Random Access Memory), and stores various information.

[0055] The interface unit 83 functions as an interface for a wired LAN (Local Area Network) conforming to standards such as IEEE (Institute of Electrical and Electronics Engineers) 802.3u / ab / an / ae, or a wireless LAN conforming to standards such as IEEE 802.11a / b / g / n / ac / ax, etc. The interface unit 83 can transmit and receive various information to and from the higher-level device 100, a predetermined server device (not shown), etc.

[0056] Based on instructions from the print control unit 80, the display control unit 84 creates display screen data representing various display screens on which characters, figures, etc. are appropriately arranged, and sends the display screen data to the display operation unit 4, thereby causing the display screen to be displayed on the display operation unit 4.

[0057] The sensor 85 is, for example, a temperature sensor or a humidity sensor, and is provided at a predetermined location inside the housing 2. This sensor 85 measures the ambient temperature and humidity, the temperature at a predetermined location (for example, near the fixing unit 60), etc., and notifies the print control unit 80 of the obtained measurement data.

[0058] A data conversion table 86T is provided in the print data processing unit 86. This data conversion table 86T stores data for converting the color representing each pixel of the image data from various formats such as RGB (red, green, and blue) format to CMYK (cyan, magenta, yellow, and black) format or a format that adds a spot color (silver) to CMYK format, i.e., the colors corresponding to each color of the image forming unit 10.

[0059] The print data processing unit 86 extracts image data to be printed by performing predetermined conversion processing on the print data acquired from the higher-level device 100 via the interface unit 83. The print data processing unit 86 also converts the color format of this image data by referring to a data conversion table 86T, and generates color-specific image data corresponding to each color of the image forming unit 10.

[0060] The process control unit 91 controls the voltages and the like of each unit in the image forming unit 10 for each color based on instructions from the print control unit 80. The development voltage control unit 92 controls the development voltage applied to the development roller 24 and the development blade 25 (FIG. 2) based on instructions from the print control unit 80. The supply voltage control unit 93 controls the supply voltage applied to the first supply roller 22 and the second supply roller 23 (FIG. 2) based on instructions from the print control unit 80.

[0061] The exposure control unit 94 controls the turning on and off of each light-emitting element chip provided in the LED head 14 based on instructions from the print control unit 80. The transfer voltage control unit 95 controls the transfer voltage applied to the primary transfer roller 35, secondary transfer roller 36 (FIG. 2), etc. based on instructions from the print control unit 80. The motor control unit 96 controls the rotation of the photosensitive drum 26 (FIG. 2) and each roller, etc. based on instructions from the print control unit 80.

[0062] The host device 100 is an information processing device such as a personal computer, and executes various application programs such as document creation, spreadsheets, and image editing based on user operations. A printer driver for printing documents, images, and the like on the image forming device 1 is pre-installed on the host device 100. When the host device 100 receives a print instruction from a user in an application program for document data, image data, and the like, it executes the printer driver to generate print data based on the document data, image data, and the like and transmits the print data to the image forming device 1.

[0063] [2. Configuration of switching image print media] Next, the configuration of a switching image printing medium MDC, which has predetermined images printed on both sides of the medium MD, and the images to be observed will be described.

[0064] As shown in a schematic perspective view in Figure 4, the switching image printing medium MDC has a switching image PC formed on one surface of the medium MD (hereinafter also referred to as the first surface F1) and a shielding image PS formed on the opposite surface (hereinafter also referred to as the second surface F2).

[0065] The switching image PC on the first screen F1 is configured such that a plurality of first images P1 generated based on the first overall image PA1 and a plurality of second images P2 generated based on the second overall image PA2 are alternately arranged along a predetermined X direction (hereinafter also referred to as the first direction), as shown in the schematic diagram of Fig. 5. Here, it is assumed that both the first images P1 and the second images P2 are images centered around relatively bright colors.

[0066] The first overall image PA1 and the second overall image PA2 are both surrounded by a side along the X direction and a side along the Y direction (hereinafter also referred to as the second direction) perpendicular to the X direction. Each of the first and second images P1 and P2 is formed by dividing the first and second overall images PA1 and PA2 into a plurality of elongated rectangular (i.e., strip-like) portions by a plurality of division lines DE (FIG. 5(A)) along the Y direction. That is, the length of each of the first and second images P1 and P2 along the Y direction is sufficiently longer than the length along the X direction.

[0067] Furthermore, the first images P1 and second images P2 constituting the switching image PC are arranged while maintaining the order in the X direction of the first images P1 and second images P2 in the first overall image PA1 and second overall image PA2 before division, as shown in Fig. 5. Hereinafter, the lengths of the first image P1 and the second image P2 in the X direction will be referred to as lengths LP1 and LP2, respectively.

[0068] 5, the masked image PS on the second surface F2 is configured such that a plurality of third images P3 generated based on the third overall image PA3 are arranged along the X direction with a gap G between each of them. That is, each third image P3 is arranged at a position facing at least a portion of the first image P1 and at least a portion of the second image P2, respectively, via the medium MD.

[0069] Similar to the first overall image PA1, the third overall image PA3 is surrounded by sides along the X direction and sides along the Y direction. Each third image P3 is formed by dividing the third overall image PA3 into a plurality of elongated rectangular (i.e., strip-like) portions by a plurality of division lines DE (FIG. 5(A)) along the Y direction. That is, the length of each third image P3 along the Y direction is sufficiently longer than the length along the X direction.

[0070] The third images P3 constituting the switching image PC are arranged while maintaining the order in the X direction of the third images P3 in the third overall image PA3 before division. Hereinafter, the length of the third image P3 in the X direction will be referred to as length LP3, and the length of the gap G will be referred to as length LG. The third image P3 is, for example, a solid black image, and is mainly composed of colors with high light-blocking properties, so that it hardly transmits visible light.

[0071] Furthermore, in this embodiment, the length LP1 of the first image P1, the length LP2 of the second image P2, the length LP3 of the third image P3, and the length LN of the gap G are all equal in the X direction. Therefore, in the switching image printing medium MDC, the switching period CC at which the first image P1 and the second image P2 appear in the X direction on the first surface F1, and the shielding period CS at which the third image P3 and the gap G appear in the X direction on the second surface F2 are equal to each other.

[0072] 7, when a viewer views this switching-image printing medium MDC from the second surface F2 side, the viewer can see the third image P3 of the shielding image PS, and can also see a portion of the switching image PC on the first surface F1 through the medium MD from the gap G. Incidentally, FIG. 7 shows the switching-image printing medium MDC cut along a virtual cutting plane that is perpendicular to the first surface F1 and along the X direction.

[0073] Here, the third image P3 is, for example, a plain black image, and is darker in color than the first image P1 and the second image P2. For this reason, the viewer is likely to focus their attention on the first image P1 and the second image P2, which are relatively bright in color.

[0074] Next, let us define the direction perpendicular to the X and Y directions as the Z direction, and consider a case where the direction from which the viewer views the switching image printing medium MDC is changed within the XZ plane. In this case, the switching image printing medium MDC changes the portion of the switching image PC that can be viewed through the gap G depending on the viewing direction of the viewer.

[0075] For example, when an observer observes the switching image printing medium MDC, if the direction of the line of sight is along the observation direction line DP1 (Figure 7), the second image P2 is blocked by the third image P3, and the first image P1 is visible through the gap G via the medium MD, as shown in the schematic diagram of Figure 8 (A).

[0076] Furthermore, when an observer observes the switching image printing medium MDC, if the direction of the line of sight is along the observation direction line DP2 (Figure 7), the first image P1 is blocked by the third image P3, and the second image P2 is visible through the gap G via the medium MD, as shown in the schematic diagram of Figure 8 (B).

[0077] Therefore, the switching image printing medium MDC allows the viewer to switch the viewed image between the first image P1 and the second image P2 by changing the viewing direction or angle within the XZ plane.

[0078] In the following, with respect to the direction and angle in the XZ plane when an observer observes the switching image printing medium MDC, the angle between the normal NF1 (i.e., the Z direction) of the first surface F1 and each observation direction line is referred to as the observation angle θ. Also, in the following, the observation direction lines DP1 and DP2 are also referred to as observation straight lines.

[0079] [3. Relationship between image switching and viewing angle in switched image printing media] Next, we will explain the relationship between the image observed by the observer when the switching image printing medium MDC is observed from the second surface F2 side and the observation angle θ. Also, as a premise, the first surface F1 and the second surface F2 of the medium MD are parallel, and the normal directions of both surfaces are both parallel to the Z direction.

[0080] In the following, it is assumed that the position of the -X side end of the third image P3 is aligned with the position of the -X side end of the first image P1 in the X direction, as shown in Figure 7, which corresponds to Figure 9. Also, as in the case described above, it is assumed that the shading period CS of the shading image PS of the second surface F2 is equal to the switching period CC of the switching image PC of the first surface F1. These relationships can be expressed mathematically as the following equations (1A), (1B), and (1C).

[0081]

number

[0082] However, in the X direction, the length LP3 of the third image P3 is equal to or greater than the length LN of the gap G, and accordingly, the length LP3 is equal to or greater than the length LP1 of the first image P1 and the length LP2 of the second image P2.

[0083] Furthermore, the end point of the first image P1 on the first surface F1 on the X direction side, i.e., the connection point between the first image P1 and the second image P2, is defined as an image connection point QJ1, and the point obtained by projecting the image connection point QJ1 onto the third image P3 on the second surface F2 along the Z direction (i.e., the direction parallel to the normal NF1 of the first surface F1) is defined as a connection projection point QC. In other words, the connection projection point QC is a point opposite the image connection point QJ1 in the Z direction.

[0084] Furthermore, the length from the end point QE1 on the -X direction side in the third image P3 to the connection projection point QC is defined as length LC1, and the length from the end point QE2 on the X direction side in the third image P3 to the connection projection point QC is defined as length LC2. The central point in the X direction in the third image P3 is defined as the third image midpoint QP3, and the distance from the third image midpoint QP3 to the connection projection point QC is defined as length LD. Of these, length LC1 is equivalent to lengths LP1 and LP2 (FIGS. 5 and 6). For convenience of notation, the length along the X direction in the third image P3 (length LP3) is defined as length LB.

[0085] In addition, the distance from the first surface F1 to the second surface F2 in the Z direction, that is, the thickness of the medium MD, is defined as a length LA.

[0086] Here, we summarize the relationship between the lengths of each part of the switching image printing medium MDC. The length from the end point QE1 on the -X direction side of the third image P3 to the third image midpoint QP3 is 1 / 2 the length LB along the X direction of the third image P3. The length LD from the third image midpoint QP3 to the connection projection point QC can be expressed as the following equation (2) using the lengths LB and LC1.

[0087]

number

[0088] Furthermore, the relationship of the following formula (3) holds between the length LB, the length LC1, and the length LC2.

[0089]

number

[0090] Applying this equation (3) to equation (2) and rearranging the length LD, the following equation (4) can be obtained.

[0091]

number

[0092] On the other hand, if the imaginary midpoint of gap G in the X direction is defined as gap midpoint QG, the length from the end point QE0 on the -X direction side of gap G to gap midpoint QG, and the length from gap midpoint QG to end point QE1 on the X direction side of gap G are both 1 / 2 of the length LG of gap G in the X direction.

[0093] Here, the following relationship as shown in equation (5) holds among the lengths LG, LB, LC1 and LD.

[0094]

number

[0095] That is, the length from the end point QE0 to the gap midpoint QG in the gap G and the length LG / 2 from the gap midpoint QG to the end point QE1 are both equal to the length LD.

[0096] In the following, the range of the switching image PC on the first surface F1 that the viewer can view through the gap G and the medium MD is referred to as the observation range RB. This observation range RB is the portion of the switching image PC sandwiched between two observation direction lines D0 and D1 that pass through the end point QE0 of the gap G on the -X direction side and the end point QE1 on the X direction side, respectively.

[0097] [3-1. First observation state] Figure 9 shows the state in which the proportions of the first image P1 and the second image P2 included in the observation range RB are initially equal when the observation direction lines D0 and D1 are gradually tilted counterclockwise from a direction parallel to the normal line NF1. Hereinafter, this state will be referred to as the first observation state. Furthermore, the angle of the observation direction line D1 relative to the normal line NF1 in this first observation state will be referred to as the observation angle θ1 or first angle. Furthermore, the observation direction line D1 at this time will also be referred to as the first straight line.

[0098] In this first observation state, the observation direction line D1 passes through the end point QE1 on the -X direction side in the third image P3 and reaches a point QD1 located a length LD in the X direction from the image connection point QJ0 on the -X direction side in the first image P1.

[0099] Here, the distance from point QJ0 to point QE1 is length LA, which is the thickness of the medium MD, and the distance from point QJ0 to point QD1 is length LD. Then, the following equation (6) holds for the observation angle θ1.

[0100]

number

[0101] By rearranging this equation (6) for the observation angle θ1 and applying equation (4), we obtain the following equation (7).

[0102]

number

[0103] [3-2. Second observation state] Figure 10 shows a state in which the observation direction line D1 in the state shown in Figure 9 is further tilted counterclockwise to become observation direction line D2, and the second image P2 is no longer included in the observation range RB. Hereinafter, this state will be referred to as the second observation state. In addition, the angle of the observation direction line D1 relative to the normal line NF1 in this second observation state will be referred to as the observation angle θ2 or second angle. Furthermore, the observation direction line D2 at this time will also be referred to as the second straight line.

[0104] In this second observation state, the observation direction line D2 passes through point QE1 and reaches point QD2, which is located a length 2LD in the X direction from image connection point QJ0 on the −X direction side in the first image P1.

[0105] Here, the distance from point QJ0 to point QE1 is length LA, which is the thickness of the medium MD, and the distance from point QJ0 to point QD2 is length 2LD. Then, the following equation (8) holds for the observation angle θ2.

[0106]

number

[0107] By rearranging this equation (8) for the observation angle θ2 and applying equation (4), we obtain the following equation (9).

[0108]

number

[0109] [3-3. Third observation state] Figure 11 shows the state in which the observation direction line D2 from the state in Figure 10 is further tilted counterclockwise to become observation direction line D3, and this observation direction line D3 reaches image connection point QJ1. Hereinafter, this state will be referred to as the third observation state. Furthermore, in this third observation state, the angle of observation direction line D3 relative to normal line NF1 will be referred to as observation angle θ3 or third angle. Furthermore, observation direction line D3 at this time will also be referred to as the third straight line.

[0110] In this third observation state, the observation direction line D3 passes through the point QE1 and then reaches the image connection point QJ1 as described above.

[0111] Here, the distance from point QJ0 to point QE1 is length LA, which is the thickness of the medium MD, and the distance from image connection point QJ0 to image connection point QJ1 is length LC1. Then, the following equation (10) holds for observation angle θ3.

[0112]

number

[0113] When this equation (10) is rearranged with respect to the observation angle θ3, the following equation (11) is obtained.

[0114]

number

[0115] [3-4. Fourth observation state] Figure 12 shows a state in which the observation direction line D3 from the state shown in Figure 11 is further tilted counterclockwise to become observation direction line D4, and the proportions of the first image P1 and the second image P2 included in the observation range RB are again equal. Hereinafter, this state will be referred to as the fourth observation state. Furthermore, in this fourth observation state, the angle of the observation direction line D4 relative to the normal line NF1 will be referred to as the observation angle θ4 or fourth angle. Furthermore, the observation direction line D4 at this time will also be referred to as the fourth straight line.

[0116] In this fourth observation state, the observation direction line D4 passes through the end point QE1 on the -X direction side in the third image P3 and reaches a point QD4 located a length LD in the X direction from the image connection point QJ1 in the second image P2.

[0117] Here, the length from point QJ0 to point QE1 is length LA, which is the thickness of the medium MD, and the length from point QJ0 to point QD4 is the sum of length LC1 and length LD. Then, the following equation (12) holds for the observation angle θ4.

[0118]

number

[0119] By rearranging this equation (12) for the observation angle θ4 and applying equation (4), the following equation (13) is obtained.

[0120]

number

[0121] [3-5. Observation angles at which images can be observed] Thus, in the switching-image-printed medium MDC, when the observation angle θ is increased from 0 degrees, the second image P2 is observed more predominantly if the observation angle θ is less than the observation angle θ1 (FIG. 9). However, in the switching-image-printed medium MDC, when the observation angle θ exceeds the observation angle θ1, the first image P1 is observed more predominantly, and when the observation angle θ further exceeds the observation angle θ2 (FIG. 10), only the first image P1 is observed.

[0122] Thereafter, on the switching image printing medium MDC, only the first image P1 is observed until the observation angle θ becomes the observation angle θ3 (Figure 11), but when the observation angle θ exceeds the observation angle θ3, the proportion of the second image P2 increases, and eventually when the observation angle θ exceeds the observation angle θ4 (Figure 12), the second image P2 becomes predominantly observed.

[0123] Thus, with the switching image printing medium MDC, the first image P1 can be viewed more preferentially than the second image P2 as long as the observation angle θ is greater than the observation angle θ1 and less than the observation angle θ4. Hereinafter, this range will be referred to as the dominant observation range. That is, the lower limit of the dominant observation range is the observation angle θ1, and the upper limit of the dominant observation range is the observation angle θ4.

[0124] Furthermore, with the switching image printing medium MDC, as long as the observation angle θ is within the range of observation angle θ2 or more and observation angle θ3 or less, only the first image P1 can be observed, without the second image P2 being observed at all. Hereinafter, this range will be referred to as the exclusive observation range. That is, the observation angle θ that is the lower limit of the exclusive observation range is observation angle θ2, and the observation angle θ that is the upper limit of the exclusive observation range is observation angle θ3.

[0125] Next, we will introduce specific numerical examples of the length of each part of the switching image printing medium MDC and the observation angle θ. Here, the length LB along the X direction of the third image P3 is set to 200 μm, and the length LC1 is set to five different values: 190, 180, 150, 120, and 100 μm. The observation angle θ was calculated for each case. Note that the calculated angle values ​​have been rounded to the nearest whole number.

[0126] Figures 13, 14 and 15 show in table form the values ​​of observation angles θ1 to θ4 calculated when the thickness of the medium MD (i.e., the length LA in the Z direction) is set to 100, 200 or 300 μm and the length LC1 is changed in each of the five ways described above.

[0127] In this way, in the switching image printing medium MDC, when the length LA, which is the thickness of the medium MD, and the length LC1, which corresponds to the length along the X direction in the first image P1, are made to differ in various ways, the observation angle θ, which is the upper and lower limits of the dominant observation range, and the observation angle θ, which is the upper and lower limits of the exclusive observation range, will each be different values.

[0128] Furthermore, experimental results showed that when the observation angle θ exceeded 66 degrees, the visibility of the contents of the first image P1 or the second image P2, i.e., the characters and images, deteriorated. From this, it can be said that with regard to the switching image printing medium MDC, it is desirable that at least the upper limit of the exclusive observation range be 66 degrees or less, and it is even more desirable that the upper limit of the dominant observation range be 66 degrees or less.

[0129] [3-6. Determining the length according to the observation angle] Incidentally, when creating a new switching image printing medium MDC, one possible procedure is to first determine the upper and lower limits of the exclusive observation range, respectively, of the observation angle θ, and then determine the lengths LA and LC1 according to the determined observation angle θ. Furthermore, with regard to the length LA, which represents the thickness of the medium MD, it is likely that in many cases an appropriate one will be selected from multiple thicknesses prepared by the manufacturer of the medium MD.

[0130] Here, the relationships among the observation angle θ, length LA, length LC1, etc. are expressed by the above-mentioned formulas (6) to (13), etc. Therefore, once the values ​​of multiple observation angles θ and length LA are determined, the values ​​of other lengths such as lengths LC1, LC2, and LB can be calculated by appropriately using formulas (6) to (13), etc.

[0131] For example, let us assume that the values ​​of the observation angles θ1 and θ4, which are the lower and upper limits of the dominant observation range, and the length LA are also determined. First, by transforming equation (7), we obtain the following equation (14).

[0132]

number

[0133] Next, by transforming equation (13), the following equation (15) is obtained.

[0134]

number

[0135] By eliminating the length LC2 from equations (14) and (15) and rearranging the equations with respect to the length LC1, the following equation (16) can be obtained.

[0136]

number

[0137] Furthermore, by substituting equation (16) into equation (14) and rearranging it for the length LC2, the following equation (17) can be obtained.

[0138]

number

[0139] Furthermore, by substituting the length LC1 of equation (16) and the length LC2 of equation (17) into equation (3), the following equation (18) is obtained.

[0140]

number

[0141] Now, let us assume that the values ​​of the observation angles θ2 and θ3, which are the lower and upper limits of the exclusive observation range, have been determined, and the length LA has also been determined. First, by rearranging equation (10) with respect to length LC1, we obtain the following equation (14).

[0142]

number

[0143] Next, by rearranging equation (9) with respect to length LC2 and substituting length LC1 into equation (19), the following equation (20) is obtained.

[0144]

number

[0145] Furthermore, by substituting the length LC1 of equation (19) and the length LC2 of equation (20) into equation (3), the following equation (21) is obtained.

[0146]

number

[0147] In any of the examples, as can be seen from equations (1) to (3), the switching period CC and the shielding period CS are twice the length LC1.

[0148] In this way, when the values ​​of the observation angles θ1 and θ4, which are the lower and upper limits of the dominant observation range, are determined, and when the values ​​of the observation angles θ2 and θ3, which are the lower and upper limits of the exclusive observation range, are determined, once the value of the length LA is determined, the length of each part related to the first image P1, etc., i.e., length LC1, etc., can be calculated.

[0149] Incidentally, in some switching image printing media MDC, as shown in Figure 14, which corresponds to Figures 9 to 12, a third image midpoint QP3, which is the midpoint of the third image P3, may be placed on the Z-direction side of the image connection point QJ1 where the first image P1 and the second image P2 are connected.

[0150] Here, an observation direction line D11 (hereinafter also referred to as the first viewing direction) that passes through the end point QE1 on the -X direction side of the third image P3 and the image connection point QJ1 is defined, and an observation angle θ11 is defined as the angle that the observation direction line D11 makes with the normal line NF1 of the first surface F1. Also, an observation direction line D12 (hereinafter also referred to as the second viewing direction) that passes through the end point QE2 on the X direction side of the third image P3 and the image connection point QJ1 is defined, and an observation angle θ12 is defined as the angle that the observation direction line D12 makes with the normal line NF1 of the first surface F1.

[0151] Therefore, on this switching image printing medium MDC, the viewing direction lines D11 and D12 are symmetrical with respect to the normal line NF1 passing through the image connection point QJ1, and the viewing angles θ11 and θ12 are also symmetrical with respect to each other. In other words, the viewing angles θ11 and θ12 have the same absolute value and opposite signs.

[0152] [4. Creating a switching image print medium] Next, we will explain a series of processes when printing a switching image PC (Figure 5) on the first surface F1 of a medium MD in the image forming device 1 and printing a shielding image PS (Figure 6) on the second surface F2, i.e., when creating a switching image printing medium MDC.

[0153] When the control unit 3 of the image forming device 1 receives an instruction to create a switching image printing medium MDC and three pieces of image data from the upper device 100, it reads and executes a switching image printing medium creation program from the memory unit 82, thereby starting the switching image printing medium creation processing procedure RT1 shown in Figure 15 and proceeding to the first step SP1.

[0154] In step SP1, the control unit 3 stores the image data for three sheets received from the higher-level device 100 together with an instruction to create a switching image printing medium MDC in the storage unit 82, and then proceeds to the next step SP2. At this time, the control unit 3 stores the received first image as the first overall image PA1 (FIG. 5), the second image as the second overall image PA2, and the third image as the third overall image PA3 (FIG. 6).

[0155] In step SP2, the control unit 3 displays a predetermined input screen on the display / operation unit 4 and prompts the user to input the observation angle θ, then proceeds to the next step SP3. Specifically, the control unit 3 provides a selection field on the input screen for selecting either the dominant observation range or the exclusive observation range, and prompts the user to select one of them. The control unit 3 also displays input fields on the input screen for the lower and upper limit observation angles θ of the selected dominant observation range or exclusive observation range, and prompts the user to input the respective values.

[0156] For example, if a dominant observation range is selected, the input lower and upper limits correspond to the observation angles θ1 and θ4, respectively. Also, if an exclusive observation range is selected, the input lower and upper limits correspond to the observation angles θ2 and θ3, respectively.

[0157] In step SP3, the control unit 3 continues to have the value of the thickness (that is, length LA) of the medium MD to be used input on the input screen displayed on the display operation unit 4, and then proceeds to the next step SP4.

[0158] In step SP4, the control unit 3 calculates lengths LC1, LC2, and LB in the X direction based on the input values ​​of each observation angle θ and length LA, and further calculates length LP1 of the first image P1, length LP2 of the second image P2, length LP3 of the third image P3, and length LG of the gap G, and then proceeds to the next step SP5.

[0159] Specifically, when a dominant observation range is selected, the control unit 3 applies the input observation angles θ1 and θ4 and the value of the length LA to equations (16) to (18) to calculate lengths LC1, LC2, LB, etc., and further calculates lengths LP1, LP2, LP3, etc. When an exclusive observation range is selected, the control unit 3 applies the input observation angles θ2 and θ3 and the value of the length LA to equations (19) to (21) to calculate lengths LC1, LC2, LB, etc., and further calculates lengths LP1, LP2, LP3, etc.

[0160] In step SP5, the control unit 3 generates a switching image PC based on the first overall image PA1 and the second overall image PA2, and generates a shielding image PS based on the third overall image PA3 using the print control unit 80 (Figure 3), and then proceeds to the next step SP6.

[0161] Specifically, the print control unit 80 divides the image data of the first overall image PA1 (FIG. 5) stored in the storage unit 82 into a plurality of first images P1 along a plurality of division lines DE along the Y direction, with the X-direction spaced apart by a length LP1. The print control unit 80 also divides the image data of the second overall image PA2 (FIG. 5) stored in the storage unit 82 into a plurality of second images P2 along a plurality of division lines DE along the Y direction, with the X-direction spaced apart by a length LP2. The print control unit 80 then alternately arranges the image data of the first images P1 and the second images P2 along the X direction while maintaining the order of the first images P1 in the first overall image PA1 and the order of the second images P2 in the second overall image PA2, thereby generating image data of the switching image PC and storing this in the storage unit 82.

[0162] Next, the control unit 3 divides the image data of the third overall image PA3 (FIG. 6) stored in the memory unit 82 into multiple third images P3 using multiple division lines DE along the Y direction, with the X-direction spacing being a length LP3. Furthermore, the control unit 3 uses the print control unit 80 to arrange the image data of each third image P3 along the X direction so that a gap G of length LG is sandwiched between each of the image data of the third images P3, thereby generating image data of the masked image PS, and stores this in the memory unit 82.

[0163] In step SP6, the control unit 3 appropriately controls the image forming units 10 (Figure 1) of each color to form a toner image of the switching image PC on the intermediate transfer belt 34, transfers the toner image to the first surface F1 of the medium MD by the secondary transfer unit 39, and then fixes the toner image to the medium MD by the fixing unit 60, before proceeding to the next step SP7.

[0164] In step SP7, the control unit 3 returns the medium MD to the transport path W by the re-transport unit 66 (FIG. 1) and turns it over, and then proceeds to the next step SP8.

[0165] In step SP8, the control unit 3 appropriately controls the image forming units 10 (FIG. 1) of each color to form a toner image of the shielding image PS on the intermediate transfer belt 34, transfers the toner image to the second surface F2 of the medium MD by the secondary transfer unit 39, and then fixes the toner image to the medium MD by the fixing unit 60. Then, the process proceeds to the next step SP9. As a result, the medium MD becomes a switching image printing medium MDC.

[0166] In step SP9, the control unit 3 causes the paper discharge unit 70 (FIG. 1) to discharge the medium MD (ie, the switching image printing medium MDC) onto the paper discharge tray 2T, and then proceeds to the next step SP10 to end the switching image printing medium creation processing procedure RT1.

[0167] [5. Effects, etc.] In the above configuration, the image forming apparatus 1 according to this embodiment prints a switching image PC on a first surface F1 of a transparent medium MD, in which a plurality of first images P1 and a plurality of second images P2 are arranged alternately along the X direction, and also prints a shielding image PS on a second surface F2 of the medium MD, in which a plurality of third images P3 are arranged at gaps G along the X direction.

[0168] Therefore, when the created switching image printing medium MDC is observed by an observer, the image forming device 1 can switch the observed image between the first image P1 or the second image P2 by appropriately changing the observation angle θ.

[0169] From another perspective, the switching image printing medium MDC created by the image forming apparatus 1 does not use a medium with a special shape such as a lenticular lens, but like a lenticular lens, it can switch the image to be viewed according to the observation angle θ. Furthermore, since the image forming apparatus 1 does not require special color toner such as metallic toner or clear toner, it can reduce the number of image forming units 10 required compared to the method described in Patent Document 1, and therefore does not complicate the device configuration.

[0170] Furthermore, the medium MD used to create the switching-image-printed medium MDC is commercially available, for example, as OHP film, and is extremely easy to obtain. That is, the image forming apparatus 1 can create the switching-image-printed medium MDC by using the medium MD, which is commercially available and highly available, and by performing a printing process using toners of the normal colors (cyan, magenta, yellow, and black) that are commonly used in color printing.

[0171] Furthermore, in the process of creating the switching image print medium MDC, the image forming device 1 prompts the user to select an exclusive observation range or a dominant observation range and input the observation angle θ, which is the upper and lower limit of the range, and the length LA, which is the thickness of the medium MD. Based on these values, the image forming device 1 then calculates the length LP1 of the first image P1, the length LP2 of the second image P2, the length LP3 of the third image P3, and the length LG of the gap G in the X direction, and generates the switching image PC and the shielding image PS based on the first overall image PA1, the second overall image PA2, and the third overall image PA3.

[0172] That is, the image forming apparatus 1 can adjust the range of the observation angle θ at which the first image P1 can be preferentially or exclusively observed when the observer observes the created switching-image print medium MDC to the upper and lower limits input by the user. In other words, the image forming apparatus 1 can easily create a switching-image print medium MDC that has the exclusive observation range or dominant observation range desired by the user simply by having the user input these values, without requiring the user to calculate the length LP1, etc.

[0173] Furthermore, in the process of creating the switching image print medium MDC, the image forming device 1 allows the user to select either the exclusive observation range or the dominant observation range, and then input the upper and lower limits of the observation angle θ. Therefore, the image forming device 1 allows the user to select, according to the user's will, whether to specify a range of observation angle θ that allows at least the first image P1 to be dominantly observed, or to specify a range of observation angle that allows only the first image P1 to be exclusively observed.

[0174] According to the above configuration, the image forming apparatus 1 according to the present embodiment prints a switching image PC on the first surface F1 of a transparent medium MD, in which a plurality of first images P1 and a plurality of second images P2 are arranged alternately along the X direction, and also prints a shielding image PS on the second surface F2 of the medium MD, in which a plurality of third images P3 are arranged at intervals G along the X direction. As a result, the image forming apparatus 1 uses a medium MD whose first surface F1 and second surface F2 are both flat, and does not require special color toner such as metallic toner or clear toner. When a viewer views the created switching image printed medium MDC, the image being viewed can be switched between the first image P1 and the second image P2 according to the viewing angle θ.

[0175] 6. Other Embodiments In the above-described embodiment, the first image P1 and the second image P2 are arranged in the switching image PC (FIG. 5) without any gaps or overlaps in the X direction. However, the present invention is not limited to this. For example, the first image P1 and the second image P2 may be arranged with a gap between them in the X direction, or a part of the first image P1 and a part of the second image P2 may be arranged to overlap each other.

[0176] In the above-described embodiment, the shielding image PS (FIG. 6) is a monochrome black image. However, the present invention is not limited to this. The shielding image PS may be a bright color such as silver, a monochrome white image made with white toner, or an image of various colors that is a mixture of multiple colors. In these cases, it is sufficient that the shielding image PS has the property of sufficiently blocking visible light, so that a portion of the switching image PC is blocked from the viewer viewing the switching image printing medium MDC, allowing only the remaining portion of the switching image PC to be viewed through the gap G.

[0177] Furthermore, in the above-described embodiment, the first image P1 and the second image P2 are both images primarily made up of relatively bright colors. However, the present invention is not limited to this. For example, the first image P1 and the second image P2 may each be made up of any single color, or may each be made up of an appropriate combination of multiple colors. Alternatively, the first image P1 and the second image P2 may each be made up of the same color, or may each be made up of different colors.

[0178] Furthermore, in the above-described embodiment, the switching image PC (FIG. 5) is configured by alternately arranging two types of images (first image P1 and second image P2) in the X direction. However, the present invention is not limited to this. For example, the switching image PC may be configured by cyclically arranging three or more types of images in the X direction. In this case, it is sufficient that the switching period CC in the switching image PC and the blocking period CS in the blocking image PS match.

[0179] Furthermore, in the above-described embodiment, in step SP2 of the switching image print medium creation processing procedure RT1 (FIG. 15), the user is prompted to select either the dominant observation range or the exclusive observation range and then input the lower and upper limit observation angles θ. However, the present invention is not limited to this. For example, the exclusive observation range may be determined in advance, and the user may be prompted to input the lower and upper limit observation angles θ.

[0180] Furthermore, in the above-described embodiment, step SP2 of the switching image print medium creation processing procedure RT1 (FIG. 15) involves inputting a lower limit observation angle θ and an upper limit observation angle θ. However, the present invention is not limited to this. For example, in FIG. 7, the third image midpoint QP3 of the third image P3 may be positioned on the Z-axis side (along the normal line NF1) of the image connection point QJ1, and the upper and lower limit values ​​of the observation angle θ may be set symmetrically with respect to the normal line NF1, and then the user may be prompted to input one observation angle θ. In this case, the sign of the observation angle θ can be inverted and treated as the other observation angle θ.

[0181] Furthermore, in the above-described embodiment, the user is prompted to input the values ​​of the observation angle θ that are the upper and lower limits of the dominant observation range or exclusive observation range selected by the user. However, the present invention is not limited to this. For example, the user may be prompted to input values ​​for the lengths LC1, LC2, and LB, as well as the switching period CC, and a switching image PC may be generated based on these values.

[0182] Furthermore, in the above-described embodiment, the user is prompted to input the value of the length LA, which is the thickness of the medium MD. However, the present invention is not limited to this. For example, a table showing the relationship between the thickness and the manufacturer name, model number, etc. of the medium MD may be stored in advance in the storage unit 82 (FIG. 3), and a list of the manufacturer name, model number, etc. may be displayed on the display operation unit 4 for the user to select. Alternatively, for example, the user may be prompted to input the observation angle θ, which is the upper and lower limits of the selected dominant observation range or exclusive observation range, and the length LC1 (i.e., length LP1) of the first image P1. The length LA is calculated using the relationships in equations (6) to (13), and the calculated value is displayed on the display operation unit 4. In this case, when creating the switching image print medium MDC, the image forming apparatus 1 simply prompts the user to prepare a medium MD whose thickness is the displayed length LA.

[0183] 9 to 12, the embodiment has been described in which the position of point QE1, which is the end on the -X side of the third image P3, and the position of image connection point QJ0, which is the end on the -X side of the first image P1, are aligned in the X direction. However, the present invention is not limited to this, and the positions of point QE1 and image connection point QJ0 may be shifted in the X direction.

[0184] 9 to 12, the embodiment has been described in which the length LP3 of the third image P3 is longer than the length LN of the gap G, the length LP1 of the first image P1, and the length LP2 of the second image P2. However, the present invention is not limited to this, and for example, the length LP3, the length LN, the length LP1, and the length LP2 may be equal to one another.

[0185] Furthermore, in the above-described embodiment, in step SP7 of the switching image print medium creation procedure RT1 (FIG. 15), the medium MD, on which the switching image PC has been transferred and fixed to its first side F1, is returned to the conveyance path W in an inverted state by the re-conveyance unit 66, and the masking image PS is transferred and fixed to its opposite side, the second side F2. However, the present invention is not limited to this. For example, the medium MD, on which the switching image PC has been transferred and fixed to its first side F1, may be discharged by the paper discharge unit 70, and the user may be prompted to turn the medium over and set it in the paper cassette 41, after which the masking image PS is transferred and fixed to its second side F2. In this case, the re-conveyance unit 66 and the like may be omitted from the image forming apparatus 1.

[0186] Furthermore, in the above-described embodiment, an OHP film with a sufficiently high visible light transmittance is used as the medium MD. However, the present invention is not limited to this. For example, the switching image printing medium MDC may be created using a medium MD made of a material with a lower visible light transmittance than general OHP film. In this case, it is sufficient for the medium MD to have a certain level of visible light transmittance so that the viewer can view the switching image PC on the first surface F1 to some extent through the gap G on the second surface F2 and the medium MD.

[0187] Furthermore, in the above-described embodiment, the host device 100 transmits image data of the third overall image PA3 to the image forming apparatus 1 in addition to the first overall image PA1 and the second overall image PA2. However, the present invention is not limited to this. For example, if the third overall image PA3 is a monochrome image of black, the host device 100 may transmit information indicating that the third overall image PA3 is a monochrome image of black to the image forming apparatus 1 instead of image data. In this case, the image forming apparatus 1 may generate black image data corresponding to the third image P3 based on this information. Furthermore, the image forming apparatus 1 may automatically generate image data corresponding to the masking image PS having a size corresponding to the switching image PC without transmitting information about the third overall image PA3 from the host device 100 to the image forming apparatus 1.

[0188] Furthermore, in the above-described embodiment, in steps SP2 and SP3 of the switching image print medium creation processing procedure RT1 (FIG. 15), the user is prompted to select either the dominant observation range or the exclusive observation range via the display operation unit 4 of the image forming apparatus 1 and to input the lower and upper limit observation angles θ. However, the present invention is not limited to this. For example, the host device 100 may execute a predetermined application or printer driver to prompt the user to select either the dominant observation range or the exclusive observation range and input the lower and upper limit observation angles θ, and then transmit the selection and input results to the image forming apparatus 1.

[0189] Furthermore, in the above-described embodiment, when creating the switching image print medium MDC, the image forming apparatus 1 generates image data for the switching image PC, etc., based on image data for the first overall image PA1, etc., supplied from the host device 100 to the image forming apparatus 1, and prints the switching image PC, etc., based on this data on the medium MD. However, the present invention is not limited to this. For example, the host device 100 may generate image data for the switching image PC, etc., based on image data for the first overall image PA1, etc., and send the image data to the image forming apparatus 1 for printing. In this case, for example, the host device 100 may execute a predetermined printer driver or a predetermined application, allowing the user to select a dominant observation range or an exclusive observation range, input the values ​​of the observation angle θ, which are the upper and lower limits of the range, and further input the value of the length LA, which is the thickness of the medium MD.

[0190] Furthermore, in the above-described embodiment, the image forming apparatus 1 receives data including all of the first, second, and third images from the host device 100, and forms images on the medium MD using the image forming apparatus 1. However, the present invention is not limited to this. For example, the image forming apparatus 1 may receive data including the first and second images and data including the third image from the host device 100, respectively, and form the respective images on each side of the medium MD in the image forming apparatus 1. Alternatively, for example, the image forming apparatus 1 may receive data including the first image, data including the second image, and data including the third image from the host device 100, respectively, and create a switching image print medium MDC in the image forming apparatus 1. In these cases, the respective data may be received from different host devices.

[0191] Furthermore, in the above-described embodiment, the image forming apparatus 1 is provided with image forming units 10 for five colors (FIG. 1). However, the present invention is not limited to this, and the image forming apparatus 1 may be provided with image forming units 10 for four or less colors or six or more colors.

[0192] Furthermore, in the above-described embodiment, a switching image printing medium MDC is created by an intermediate transfer type image forming apparatus 1, in which a toner image formed by the image forming unit 10 is transferred to the intermediate transfer belt 34, and the toner image is then transferred from the intermediate transfer belt 34 to the medium MD. However, the present invention is not limited to this, and the switching image printing medium MDC may be created by, for example, a direct transfer type image forming apparatus, in which a toner image formed by the image forming unit 10 is directly transferred to the medium MD.

[0193] Furthermore, in the above-described embodiment, the image forming apparatus 1 is configured as a single-function printer. However, the present invention is not limited to this, and the image forming apparatus 1 may be configured as, for example, an MFP (Multi Function Peripheral) having the functions of a copier or facsimile machine.

[0194] Furthermore, in the above-described embodiment, the switching image print medium MDC is created by the image forming apparatus 1 that prints an image on a medium by an electrophotographic method using toner as a developer. However, the present invention is not limited to this, and the switching image print medium MDC may be created by various image forming apparatuses that form images on a medium by various well-known methods, such as an inkjet method or a thermal transfer method that uses ink as a developer. Furthermore, the configuration is not limited to using toner or ink as the developer, and various color materials may be used as the developer as long as they exhibit the colors described in the above-described embodiment.

[0195] Furthermore, the present invention is not limited to the above-described embodiments and other embodiments, and the scope of application of the present invention extends to embodiments in which the above-described embodiments and other embodiments are combined in part or in whole, or in which only a part of the above-described embodiments is extracted.

[0196] Furthermore, in the above-described embodiment, the image forming apparatus 1 is configured as an image forming apparatus by the image forming unit 10 as an image forming section and the control section 3 as a control section. However, the present invention is not limited to this, and the image forming apparatus may be configured by an image forming section and a control section having various other configurations. [Industrial Applicability]

[0197] The present invention can be used in an image forming apparatus that forms an image on a medium by electrophotography, for example. [Explanation of symbols]

[0198] 1...image forming apparatus, 3...control section, 4...display operation section, 10...image forming unit, 80...print control section, 81...CPU, 82...storage section, 83...interface section, 84...display control section, 86...print data processing section, 100...host device, CC...switching cycle, CS...shielding cycle, DP1, DP2, D0, D1, D2, D3, D4, D11, D12...observation direction line, DE...division line, F1...first surface, F2...second surface, G...gap, M D...medium, MDC...switching image printing medium, NF1...normal, P1...first image, P2...second image, P3...third image, PA1...first overall image, PA2...second overall image, PA3...third overall image, PC...switching image, PS...occluded image, QC...connection projection point, QE0, QE1, QE2...end points, QJ0, QJ1...image connection point, QP3...third image midpoint, RB...observation range, θ, θ1, θ2, θ3, θ4, θ11, θ12...observation angle.

Claims

1. an image forming unit that forms an image on a first surface or a second surface opposite to the first surface of a medium that transmits at least a part of visible light; a control unit that controls the formation of an image by the image forming unit; Equipped with The control unit forming a first image and a second image side by side on the first surface of the medium along a first direction; and controlling the image forming unit to form a third image at a location on the second surface of the medium opposite to the first image and the second image; An image forming apparatus characterized by:

2. In a virtual cut plane of the medium that is perpendicular to the first surface and along the first direction, The distance from the first surface to the second surface is defined as a length LA, a length LB of the third image along the first direction; When the third image is divided at a connection projection point QC obtained by projecting an image connection point QJ1 at which the first image and the second image are connected onto the second surface along the normal direction of the first surface, the lengths of the first image side and the second image side are defined as length LC1 and length LC2, respectively; an angle θ1 between a virtual first straight line passing through an end portion in the third image in the first direction and a normal line to the first surface satisfies the following formula (1), an angle θ4 formed by a virtual fourth line that passes through an end in the third image in the first direction and is different from the first line and a normal to the first surface satisfies the following formula (2): When the medium is observed from the second surface side in a direction along a virtual observation line, the first image is observed more preferentially than the second image in a range in which an observation angle θ, which is an angle between a virtual observation line passing through an end portion of the third image in the first direction and a normal line to the first surface, is larger than the angle θ1 and smaller than the angle θ4.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium. [Equation 1] [Equation 2]

3. an angle θ2 between a virtual second straight line passing through an end portion in the third image in the first direction and a normal line to the first surface satisfies the following formula (3), an angle θ3 formed by a virtual third straight line that passes through an end in the third image in the first direction and is different from the second straight line and a normal to the first surface satisfies the following formula (4): When the medium is observed from the second surface side in a direction along the observation straight line, the first image is observed without the second image being observed, in a range in which an observation angle θ, which is an angle between a virtual observation straight line passing through an end of the third image in the first direction and a normal to the first surface, is larger than the angle θ2 and smaller than the angle θ3.

3. The image forming apparatus according to claim 2, wherein the image forming apparatus is a recording medium. [Equation 3] [Equation 4]

4. The control unit controls the image forming unit so that lengths of the first image, the second image, and the third image are equal to each other in the first direction.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

5. The control unit controls the image forming unit so that the interval between the third images in the first direction is equal to the length of the third images in the first direction.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

6. The control unit controls the image forming unit so that lengths of the first image, the second image, and the third image in a second direction orthogonal to the first direction in the first plane are shorter than lengths of the first image, the second image, and the third image in the first direction, respectively.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

7. The control unit controls the image forming unit so as to prevent a gap from being formed between the first image and the second image that are closest to each other in the first direction.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

8. The control unit controls the image forming unit to overlap a portion of the first image and a portion of the second image that are closest to each other in the first direction.

8. The image forming apparatus according to claim 7,

9. The control unit controls the image forming unit to form a predetermined gap between the first image and the second image that are closest to each other in the first direction.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

10. the first image is a portion obtained by dividing a first entire image into a plurality of portions by a plurality of division lines along a second direction intersecting the first direction, the second image is a portion obtained by dividing a second entire image into a plurality of portions by a plurality of division lines along the second direction, The control unit controls the image forming unit to form the plurality of first images and the plurality of second images on the first surface of the medium in a state where the first images and the second images are arranged alternately in the first direction while maintaining the order in the first direction of the first entire image and the second entire image.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

11. the third image is a portion obtained by dividing a third entire image into a plurality of parts by a plurality of division lines along a second direction intersecting the first direction, The control unit controls the image forming unit to form the plurality of third images on the second surface of the medium at positions facing the first image and the second image, respectively, while maintaining the order in the third entire image in the first direction, with the third images arranged at intervals from each other in the first direction.

2. The image forming apparatus according to claim 1, wherein the image forming apparatus is a recording medium.

12. a first image provided on a first surface of a medium that transmits at least a portion of visible light; a second image provided on the first surface of the medium and arranged alongside the first image along a first direction; a third image provided on a second surface of the medium, the second surface being the opposite surface of the first surface; and The third image is when the first surface is viewed from the second surface side through the medium along a first line of sight direction that forms a first angle between a normal direction of the second surface and the first direction, the first image is occluded by the third image with higher priority than the second image, The third image is arranged so that, when the first surface is viewed from the second surface side through the medium along a second line of sight that forms a second angle symmetrical to the first angle with respect to a normal direction of the second surface, the second image is observed more preferentially than the first image. An image-forming medium characterized by:

13. The lengths of the first image, the second image, and the third image in the first direction are shorter than the lengths of the first image, the second image, and the third image in a second direction orthogonal to the first direction within the first plane.

13. The imaging medium of claim 12.

14. a first image provided on a first surface of a medium that transmits at least a portion of visible light; a second image provided on the first surface of the medium and arranged alongside the first image along a first direction; a third image provided on a second surface of the medium, the second surface being the opposite surface of the first surface; and The third image is disposed at a position opposite to the first image and the second image across the medium. An image-forming medium characterized by:

15. In a virtual cut plane of the medium that is perpendicular to the first surface and along the first direction, The distance from the first surface to the second surface is defined as a length LA, a length LB of the third image along the first direction; When the third image is divided at a connection projection point QC obtained by projecting an image connection point QJ1 at which the first image and the second image are connected onto the second surface along the normal direction of the first surface, the lengths of the first image side and the second image side are defined as length LC1 and length LC2, respectively; an angle θ1 between a virtual first straight line passing through an end portion in the third image in the first direction and a normal line to the first surface satisfies the following formula (5), an angle θ4 formed by a virtual fourth line that passes through an end in the first direction in the third image and is different from the first line and a normal to the first surface satisfies the following formula (6): When the medium is observed from the second surface side in a direction along a virtual observation line, the first image is observed more preferentially than the second image in a range in which an observation angle θ, which is an angle between a virtual observation line passing through an end portion of the third image in the first direction and a normal line to the first surface, is larger than the angle θ1 and smaller than the angle θ4.

15. The imaging medium of claim 14. [Equation 5] [0060]

16. an angle θ2 between a virtual second straight line passing through an end portion in the third image in the first direction and a normal line to the first surface satisfies the following formula (7), an angle θ3 formed by a virtual third line that passes through an end in the third image in the first direction and is different from the second line and a normal to the first surface satisfies the following formula (8): When the medium is observed from the second surface side in a direction along the observation straight line, the first image is observed without the second image being observed, in a range in which an observation angle θ, which is an angle between a virtual observation straight line passing through an end of the third image in the first direction and a normal to the first surface, is larger than the angle θ2 and smaller than the angle θ3.

15. The imaging medium of claim 14. [Equation 7] [Equation 8]

17. a first image forming step of forming, by an image forming unit, a first image and a second image on a first surface of a medium that transmits at least a part of visible light, in a state where the first image and the second image are arranged side by side along a first direction; a second image forming step of forming a third image on a second surface of the medium, the second surface being an opposite surface to the first surface, by the image forming unit, before or after the first image forming step; and The third image is provided on the second surface of the medium at a location facing at least a portion of the first image and at least a portion of the second image. An image forming method comprising:

Images