Image forming apparatus and printing system

Abstract

Achieves excellent visual effects. [Solution] The device comprises a non-glossy image forming unit capable of forming a non-glossy image on a first surface of a light-transmitting medium, a glossy image forming unit capable of forming a glossy image on a second surface opposite to the first surface, and a control unit that controls the non-glossy image forming unit and the glossy image forming unit. When the non-glossy image and the glossy image are facing each other on the light-transmitting medium, the control unit controls the glossy image forming unit so that a first region is formed on the second surface of the light-transmitting medium where the transmittance of white light passing through the glossy image and the non-glossy image is a first transmittance, and a second region where the transmittance is a second transmittance higher than the first transmittance, and adjusts the amount of the glossy image formed on the second surface of the light-transmitting medium.

Description

Technical Field

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

Background Art

[0002] Conventionally, as an image forming apparatus, when performing color printing, toners such as black, magenta, cyan, and yellow (hereinafter collectively referred to as colored) (hereinafter these are referred to as colored toners (developers)) are combined to form a colored image (i.e., print) on a medium such as paper. Also, among image forming apparatuses, there are those that can form a shiny image on paper by using a toner having a shiny property such as silver or gold (hereinafter these are also referred to as shiny colors) (hereinafter this is referred to as a shiny toner (developer)).

[0003] Also, as an image forming apparatus, there has been proposed one that forms an image (i.e., prints) having a visual effect in which the image appears and disappears by overlapping a colored image with a colored toner on a shiny image with a shiny toner (for example, see Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in images printed by the image forming apparatus described above, there are areas where glossy toner is placed and areas where it is not. Therefore, in media where a colored image is overlaid on this glossy image, steps are formed in each region of the colored toner layer that makes up the colored image. As a result, differences in glossiness occur in each region of this media, and the image may be visible against the user's will, resulting in an insufficient visual effect.

[0006] This invention has been made in consideration of the above points, and aims to propose an image forming apparatus and an image forming method that can achieve good visual effects. [Means for solving the problem]

[0007] To solve the above problems, the image forming apparatus of the present invention comprises a non-glossy image forming unit capable of forming a non-glossy image on a first surface of a light-transmitting medium, a glossy image forming unit capable of forming a glossy image on a second surface opposite to the first surface, and a control unit that controls the non-glossy image forming unit and the glossy image forming unit. When the non-glossy image and the glossy image are facing each other on the light-transmitting medium, the control unit controls the glossy image forming unit so that a first region is formed on the second surface of the light-transmitting medium where the transmittance of white light passing through the glossy image and the non-glossy image is a first transmittance, and a second region where the transmittance is a second transmittance higher than the first transmittance, thereby adjusting the amount of the glossy image formed on the second surface of the light-transmitting medium.

[0008] Furthermore, the printing system of the present invention is a printing system having a host device and an image forming apparatus connectable to the host device, the host device includes a printer driver for controlling the image forming apparatus, the image forming apparatus includes a non-glossy image forming unit capable of forming a non-glossy image on a first surface of a light-transmitting medium, a glossy image forming unit capable of forming a glossy image on a second surface opposite to the first surface, and a control unit for controlling the non-glossy image forming unit and the glossy image forming unit, the printer driver, when the non-glossy image and the glossy image are facing each other on the light-transmitting medium, includes image data for forming the non-glossy image on the first surface of the light-transmitting medium and the light-transmitting Print data is generated, which includes image data that adjusts the amount of the luminous image formed on the second surface of the light-transmitting medium, for forming a first region on the second surface of the light-transmitting medium where the transmittance of white light passing through the luminous image and the non-luminous image is a first transmittance, and a second region where the transmittance is a second transmittance higher than the first transmittance, and this data is sent to the image forming apparatus. The control unit controls the non-luminous image forming unit and the luminous image forming unit based on the print data sent from the host device, so that the non-luminous image is formed on the first surface of the light-transmitting medium and the luminous image is formed on the second surface of the light-transmitting medium.

[0009] The present invention forms a non-glossy image on the first surface of a light-transmitting medium and forms a first region and a second region with a difference in transmittance on the second surface. This creates a visual effect where, when the light-transmitting medium is viewed from the first surface side, the second region appears and disappears relative to the first region on the second surface depending on the viewing angle of the light-transmitting medium and the positional relationship between the light-transmitting medium and the light source. [Effects of the Invention]

[0010] According to the present invention, an image forming apparatus and a printing system capable of achieving excellent visual effects can be realized. [Brief explanation of the drawing]

[0011] [Figure 1]This is a longitudinal cross-sectional view showing the configuration of an image forming apparatus according to the first embodiment. [Figure 2] This is a longitudinal cross-sectional view showing the configuration of an image forming unit according to the first embodiment. [Figure 3] This is a block diagram showing the circuit configuration of an image forming apparatus according to the first embodiment. [Figure 4] This figure shows the configuration of the printing pattern printed on the surface of the medium during decorative printing according to the first embodiment. [Figure 5] This figure shows the configuration of the printing pattern to be printed on the back surface of the medium during decorative printing according to the first embodiment. [Figure 6] This figure shows the state in which the light source and the observer's viewpoint are located on the surface side of the printed material according to the first embodiment. [Figure 7] This figure shows the state in which the observer's viewpoint is located on the front side of the printed material according to the first embodiment, and the light source is located on the back side. [Figure 8] This table shows the results of an evaluation test (yellow, magenta) to determine the decorative effect according to the first embodiment. [Figure 9] This table shows the results of evaluation tests (cyan, black) to determine the decorative effect according to the first embodiment. [Figure 10] This figure shows the configuration of the printing pattern to be printed on the back surface of the medium during decorative printing according to the second embodiment. [Figure 11] This figure shows the state in which the light source and the observer's viewpoint are located on the surface side of the printed material according to the second embodiment. [Figure 12] This table shows the results of the evaluation test (yellow, magenta, cyan, black) to determine the decorative effect according to the second embodiment. [Modes for carrying out the invention]

[0012] The embodiments for carrying out the invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

[0013] [1. First Embodiment] [1-1. Configuration of the Image Forming Apparatus] FIG. 1 is a longitudinal sectional view of an image forming apparatus 1 according to the first embodiment. As shown in FIG. 1, the image forming apparatus 1 is an electrophotographic color printer and can form (i.e., print) a color image on a medium M such as paper.

[0014] Various components are arranged inside a housing 2 formed in a substantially box shape. Incidentally, hereinafter, the right end portion in FIG. 1 will be taken as the front of the image forming apparatus 1, and the vertical direction, the horizontal direction, and the front-back direction when viewed facing this front will be defined, respectively, before the explanation.

[0015] The entire image forming apparatus 1 is comprehensively controlled by a control unit 3. This control unit 3 is connected to a host device 100 (FIG. 3) such as a computer device by wireless or wired means. When image data representing an image to be printed is given from the host device 100 and printing of the image data is instructed, a printing process for forming a printed image on the surface of the medium M is executed. The display unit 4 is a display device such as a liquid crystal panel and is arranged on the front side of the upper surface of the housing 2. This display unit 4 displays various information based on the control of the control unit 3.

[0016] On the upper side inside the housing 2, five image forming units 10K, 10C, 10M, 10Y, and 10S are arranged in order from the front side to the rear side. The image forming units 10K, 10C, 10M, 10Y, and 10S respectively correspond to the colors black (K), cyan (C), magenta (M), yellow (Y), and special color (S). Although only the colors are different, they are all similarly configured.

[0017] Black (K), cyan (C), magenta (M), and yellow (Y) are all colors commonly used in color printers (hereinafter referred to as "colored"). Spot colors (S), on the other hand, are special colors such as white, clear (transparent or colorless), or silver. For the sake of explanation, the image forming units 10K, 10C, 10M, 10Y, and 10S will be collectively referred to as the image forming unit 10 below.

[0018] As shown in Figure 2, the image forming unit 10 is broadly composed of an image forming body 11, a toner container 12, a toner supply unit 13, and an LED (Light Emitting Diode) head 14. Incidentally, the image forming unit 10 and each of its constituent parts have sufficient length in the left-right direction, corresponding to the left-right length of the medium M. For this reason, many parts have a relatively longer left-right length compared to their front-to-back and up-to-down lengths, and are formed in an elongated shape along the left-right direction.

[0019] The toner container 12, also called a toner cartridge, contains toner as a developer and is configured to be detachable from the image forming unit 10. When the toner container 12 is attached to the image forming unit 10, it is attached to the image forming body 11 via the toner supply unit 13. Incidentally, in the special color (S) image forming unit 10S, the toner container 12 containing toner of a color (such as transparent or silver) selected in advance by the user is attached to the image forming body 11 via the toner supply unit 13.

[0020] The image forming main unit 11 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 photoreceptor 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 photoreceptor drum 26, and the charging roller 27 are each cylindrical in shape with their central axis aligned in the left-right direction, and are each rotatably supported by the image forming housing 20.

[0021] The toner storage space 21 stores the toner supplied from the toner container 12 via the toner supply unit 13. The first supply roller 22 and the second supply roller 23 each have an elastic layer made of conductive urethane rubber foam or the like formed on their circumferential surfaces. The developing roller 24 has an elastic layer and a conductive surface layer formed on its circumferential surface. The developing blade 25 is made of, for example, a stainless steel plate of a predetermined thickness, and in a slightly elastically deformed state, a portion of it is in contact with the circumferential surface of the developing roller 24.

[0022] The photoreceptor drum 26, which serves as the image carrier, has thin-film charge generation layers and charge transport layers sequentially formed on its circumferential surface, allowing it to be charged. The charging roller 27 has a conductive elastic material coated on its circumferential surface, and this surface is in contact with the circumferential surface of the photoreceptor drum 26. The cleaning blade 28 is made of, for example, a thin plate-shaped resin, and in a slightly elastically deformed state, a portion of it is in contact with the circumferential surface of the photoreceptor drum 26.

[0023] The LED head 14, which serves as the exposure unit, is located above the photosensitive drum 26 in the image forming main unit 11. This LED head 14 has multiple light-emitting chips arranged linearly along the left-right direction, and each light-emitting chip is made to emit light according to a light emission pattern based on the image data signal supplied from the control unit 3 (Figure 1).

[0024] The image forming unit 11 is driven by 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 also rotates the photoreceptor drum 26 in the direction of arrow R2 (counterclockwise in the figure). Furthermore, based on the control of the control unit 3, the image forming unit 11 charges the first supply roller 22, the second supply roller 23, the developing roller 24, the developing blade 25, and the charging roller 27 by applying a predetermined bias voltage to each.

[0025] The first supply roller 22 and the second supply roller 23, by charging, cause toner in the toner storage space 21 to adhere to their circumferential surfaces, and by rotation, this toner adheres to the circumferential surface of the developing roller 24. The developing blade 25 removes excess toner from the circumferential surface of the developing roller 24, and the toner, now adhering in a thin film, is brought into contact with the circumferential surface of the photoreceptor drum 26.

[0026] Meanwhile, the charging roller 27, while charged, comes into contact with the photoreceptor drum 26, thereby uniformly charging the peripheral surface of the photoreceptor drum 26. The LED head 14 sequentially exposes the photoreceptor drum 26 by performing an exposure process that emits light at predetermined time intervals based on an image data signal supplied from the control unit 3 (Figure 1). As a result, electrostatic latent images are sequentially formed on the peripheral surface of the photoreceptor drum 26 near its upper end.

[0027] Next, the photoreceptor 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 adheres to the peripheral surface of the photoreceptor drum 26 based on the electrostatic latent image, and a toner image based on the image data is developed. The photoreceptor drum 26 rotates further in the direction of arrow R2, bringing the toner image to the vicinity of the lower end of the photoreceptor drum 26.

[0028] An intermediate transfer section 30 is positioned below each image forming unit 10 within the housing 2 (Figure 1). The intermediate transfer section 30 is equipped with 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, driven roller 32, backup roller 33, each of the primary transfer rollers 35, secondary transfer rollers 36, and reverse bending roller 37 are all formed in a cylindrical shape with their central axis aligned in the left-right direction, and are rotatably supported by the housing 2.

[0029] The drive roller 31 is located on the rear lower side of the image forming unit 10S and rotates in the direction of arrow R1 when driven by a belt motor (not shown). The driven roller 32 is located on the front lower side of the image forming unit 10K. The upper ends of the drive roller 31 and the driven roller 32 are located at or slightly below the lower end of the photoreceptor drum 26 (Figure 2) in each image forming unit 10. The backup roller 33 is located on the front lower side of the drive roller 31 and on the rear lower side of the driven roller 32.

[0030] The intermediate transfer belt 34 is constructed as an endless belt using a high-resistance plastic film and is stretched 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 positioned below the portion of the intermediate transfer belt 34 stretched between the drive roller 31 and the driven roller 32, that is, directly below each of the five image forming units 10, and facing each photoreceptor drum 26 across the intermediate transfer belt 34. A predetermined bias voltage is applied to these primary transfer rollers 35 based on the control of the control unit 3.

[0031] The secondary transfer roller 36 is located directly below the backup roller 33 and is biased toward the backup roller 33. In other words, the intermediate transfer section 30 sandwiches the intermediate transfer belt 34 between the secondary transfer roller 36 and the backup roller 33. A predetermined bias voltage is also 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 section 39.

[0032] The reverse-bending roller 37 is positioned slightly below the front of the drive roller 31 and slightly behind the upper side of the backup roller 33, biasing the intermediate transfer belt 34 in the forward and upward direction. As a result, the intermediate transfer belt 34 maintains tension between each roller without any slack. In addition, a reverse-bending backup roller 38 is provided at a position above the front of the reverse-bending roller 37, sandwiching the intermediate transfer belt 34.

[0033] The intermediate transfer unit 30 rotates the drive roller 31 in the direction of arrow R1 using driving force supplied from a belt motor (not shown), thereby causing the intermediate transfer belt 34 to travel in the direction of arrow E1. Each primary transfer roller 35 also rotates in the direction of arrow R1 while a predetermined bias voltage is applied. As a result, each image forming unit 10 transfers the toner image that had reached near the lower end of the peripheral surface of the photoreceptor drum 26 (Figure 2) to the intermediate transfer belt 34, and sequentially superimposes the toner images of each color. At this time, the toner images of each color are superimposed on the surface of the intermediate transfer belt 34 in order from the upstream special color (S). By moving this intermediate transfer belt 34, the intermediate transfer unit 30 brings the toner images transferred from each image forming unit 10 to the vicinity of the backup roller 33.

[0034] Furthermore, a transport path W for transporting the medium M is formed inside the housing 2 (Figure 1). This transport path W starts from the lower front end of the housing 2, moves forward and upward, makes about a half-turn, and then proceeds backward along the underside of the intermediate transfer section 30. Subsequently, the transport path W moves upward, proceeds upward along the rearside of the intermediate transfer section 30 and the image forming unit 10S, and then moves forward. In other words, the transport path W is formed to resemble the capital letter "S" in Figure 1. Various components are arranged inside the housing 2 along this transport path W.

[0035] A first paper feeding section 40 is located near the lower end inside the housing 2 (Figure 1). The first paper feeding section 40 is equipped with 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. Incidentally, the pickup roller 42, feed roller 43, retard roller 44, and transport roller pairs 46, 47, and 48 are all formed in a cylindrical shape with their central axis aligned in the left-right direction.

[0036] The paper cassette 41 is constructed as a hollow rectangular parallelepiped and is detachable from the housing 2. The paper cassette 41 stores the paper sheets of the media M stacked vertically inside it, i.e., in an accumulated state.

[0037] The pickup roller 42 is in contact with the vicinity of the front edge of the uppermost surface of the media M 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 located below the feed roller 43, forming a gap between it and the feed roller 43 that corresponds to the thickness of one sheet of media M.

[0038] When the first paper feeding unit 40 receives driving force from a paper feeding motor (not shown), it 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 top sheets of media M stored in the paper cassette 41. The feed roller 43 and retard roller 44 feed the top sheet of media M further forward while blocking the second and subsequent sheets. In this way, the first paper feeding unit 40 feeds the media M forward, separating them one sheet at a time.

[0039] The transport guide 45 is positioned in the front lower part of the transport path W, and moves the medium M forward and upward along this transport path W, and then further backward and upward. The transport roller pairs 46 and 47 are positioned near the center and near the upper end of the transport guide 45, respectively, and are driven by a paper feed motor (not shown) to rotate in a predetermined direction. As a result, the transport roller pairs 46 and 47 move the medium M along the transport path W.

[0040] Furthermore, a second paper feeding section 50 is provided in front of the transport roller pair 47 in the housing 2. The second paper feeding section 50 is equipped with a paper tray 51, a pickup roller 52, a feed roller 53, and a retard roller 54, etc. The paper tray 51 is formed in a thin plate shape in the vertical direction, and the media M2 is placed on top of it. Incidentally, the paper tray 51 is used to place media M2 that differs in size and paper quality from the media M stored in the paper cassette 41, for example.

[0041] 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 feeding unit 40. When the second paper feeding unit 50 is supplied with driving force from a paper feeding motor (not shown), it rotates or stops the pickup roller 52, feed roller 53, and retard roller 54 as appropriate, thereby feeding out the top sheet of media M2 on the paper tray 51 to the rear while blocking the second sheet and subsequent sheets. Thus, the second paper feeding unit 50 feeds out the media M2 one sheet at a time to the rear. The fed-out media M2 is then transported along the transport path W by the transport roller pair 57 in the same way as media M. For the sake of explanation, media M2 will not be distinguished from media M below and will simply be referred to as media M.

[0042] Incidentally, the rotation of the transport roller pair 47 is appropriately suppressed, and by applying frictional force to the medium M, the so-called slanting, where the sides of the medium M are inclined relative to the direction of travel, is corrected, and the leading and trailing edges are aligned in the left-right direction before being sent to the rear. The transport roller pair 48 is located at a predetermined distance behind the transport roller pair 47, and rotates in the same way as the transport roller pair 46, etc., supplying driving force to the medium M being transported along the transport path W, and causing the medium M to move further to the rear along the transport path W.

[0043] Behind the transport roller pair 48, the secondary transfer section 39 of the aforementioned intermediate transfer section 30, namely the backup roller 33 and the secondary transfer roller 36, are positioned. In this secondary transfer section 39, the toner image formed in the image forming unit 10 and transferred to the intermediate transfer belt 34 comes into close proximity as the intermediate transfer belt 34 moves, and a predetermined bias voltage is applied to the secondary transfer roller 36. Therefore, the secondary transfer section 39 transfers the toner image from the intermediate transfer belt 34 to the medium M that has been transported along the transport path W, and then moves it further backward.

[0044] Furthermore, a temperature sensor DS is provided inside the housing 2, on the rear lower side of the driven roller 32. The temperature sensor DS detects the temperature of the toner in the toner image transferred to the surface of the intermediate transfer belt 34 and notifies the control unit 3 of the obtained detection result. In response, the control unit 3 performs density correction to correct the density of the toner in the toner image of each color formed in each image forming unit 10, and provides feedback control of the bias voltage and other components so that the toner density reaches the desired value.

[0045] A fixing unit 60 is located behind the secondary transfer unit 39. The fixing unit 60 consists of a heating unit 61 and a pressurizing unit 62, which are arranged opposite each other across the transport path W. The heating unit 61 has a heating belt made of a hollow endless belt, inside which a heat-generating heater and multiple rollers are arranged. The pressurizing unit 62 is formed as a cylindrical pressurizing roller with its central axis aligned in the left-right direction, and its upper surface is pressed against the lower surface of the heating unit 61 to form a nip.

[0046] 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 and rotates the rollers appropriately to move the heating belt in the direction of arrow R1, and also rotates the pressurizing unit 62 in the direction of arrow R2. Then, when the fixing unit 60 receives the medium M on which the toner image has been transferred by the secondary transfer unit 39, it grips (i.e., nips) it with the heating unit 61 and the pressurizing unit 62, applies heat and pressure to fix the toner image to the medium M, and then feeds it backward.

[0047] A pair of transport rollers 64 is positioned behind the fixing unit 60, and a switching unit 65 is positioned behind that. The switching unit 65 switches the direction of travel of the medium M to either the upper or lower side according to the control of the control unit 3. A paper discharge unit 70 is provided above the switching unit 65. The paper discharge unit 70 consists of a transport guide 71 that guides the medium M upward along the transport path W, and pairs of transport rollers 72, 73, 74, and 75 that face each other across the transport path W.

[0048] Furthermore, a re-transport section 66 is positioned below the switching section 65, the fixing section 60, and the secondary transfer section 39. The re-transport section 66 has transport guides and transport roller pairs (not shown) that constitute the re-transport path Z. The re-transport path Z starts from below the switching section 65, moves downwards, then proceeds forward, and merges with the transport path W downstream of the transport roller pair 47.

[0049] When the control unit 3 discharges the medium M, the switching unit 65 switches the direction of travel of the medium M towards the upper paper discharge unit 70. The paper discharge unit 70 transports the medium M received from the switching unit 65 upward and discharges it from the discharge port 76 to the paper discharge tray 2T. When the control unit 3 returns the medium M with its front and back sides reversed, the switching unit 65 switches the direction of travel of the medium M towards the lower re-transport unit 66. The re-transport unit 66 transports the medium M received from the switching unit 65 to the re-transport path Z, and eventually reaches the downstream side of the transport roller pair 57, so that the medium M is transported again along the transport path W. In this way, the image forming apparatus 1 returns the medium M to the transport path W with its paper surface reversed, so-called double-sided printing can be performed.

[0050] In this way, the image forming apparatus 1 forms a toner image using toner in the image forming unit 10 and transfers it to the intermediate transfer belt 34, the secondary transfer unit 39 transfers the toner image from the intermediate transfer belt 34 to the medium M, and the fixing unit 60 fixes it, thereby forming an image on the medium M, that is, printing an image.

[0051] For example, the image forming apparatus 1 can transfer and fix a colored or spot-colored toner image onto the surface of the medium M. As a result, the medium M becomes a printed material with a colored or spot-colored image printed on its surface.

[0052] Furthermore, the image forming apparatus 1 can, for example, transfer and fix a colored toner image to the surface of the medium M, then invert the medium M using the re-transport unit 66 and return it to the downstream side of the transport roller pair 47, thereby transferring and fixing a special color toner image to the back surface of the medium M. As a result, the medium M becomes a printed material with a colored image printed on the front surface and a special color image printed on the back surface.

[0053] Furthermore, as will be described in more detail later, the image forming apparatus 1 can use a light-transmitting medium M (a so-called transparent medium M) to print a solid image of one of the four colored colors on the surface of the medium M, and also print a silver image, one of the special colors, on the back surface of the medium M, and further divide the silver image on the back surface into two areas with different transmittances. As a result, the medium M becomes a printed material that has a visual effect (called a decorative effect) in which a part of the silver image printed on the back surface of the medium M is visible or hidden depending on the viewing angle. This type of printing is called decorative printing. In other words, the image forming apparatus 1 is capable of performing decorative printing in addition to normal printing. The image forming apparatus 1 is also configured to perform decorative printing based on the print data received from the host device 100 if the print data includes an instruction to perform decorative printing.

[0054] Next, the circuit configuration of the image forming apparatus 1 will be explained with reference to the block diagram in Figure 3. The image forming apparatus 1 has a CPU 81, a memory 82, and a sensor 83. The CPU 81 executes a program read from the memory 82 and functions as a control unit 3, an interface unit 84, a display control unit 85, a process control unit 86, a development voltage control unit 87, a supply voltage control unit 88, an exposure control unit 89, a transfer voltage control unit 90, a motor control unit 91, and a data presence / absence determination unit 92.

[0055] Memory 82 consists of ROM and RAM and stores various information (e.g., software programs) such as information indicating the printing procedure and calculation formulas for various corrections. Sensor 83 detects the position of the transported medium M, as well as temperature and humidity. This sensor 83 includes the temperature sensor DS mentioned above.

[0056] The control unit 3 controls the operation of the entire image forming apparatus 1. The interface unit 84 receives print data transmitted from a higher-level device 100, such as a computer, and provides the print data to the control unit 3.

[0057] The host device 100 executes various application programs, such as document creation, spreadsheets, or image editing, based on user operations. The host device 100 also has a printer driver 101 pre-installed for printing with the image forming apparatus 1. When the host device 100 receives a print command for application data from the user in an application program, the printer driver 101 generates print data based on that application data and sends it to the image forming apparatus 1.

[0058] The display control unit 85 controls the display state of the display unit 4 based on instruction signals from the control unit 3. The process control unit 86 controls the voltages of each part in the image forming unit 10 for each color. The development voltage control unit 87 controls the bias voltage of the development roller 24 (i.e., the voltage applied to the development roller 24). The supply voltage control unit 88 controls the bias voltages of the first supply roller 22, the second supply roller 23, and the development blade 25.

[0059] The exposure control unit 89 controls the lighting and extinguishing of each light-emitting chip provided on the LED head 14. The transfer voltage control unit 90 controls the bias voltage of the primary transfer roller 35. The motor control unit 91 controls the rotation of the photoreceptor drum 26 and each roller.

[0060] The data presence / absence determination unit 92 analyzes the print data received from the host device 100 by the interface unit 84 and determines whether or not there is image data to be printed by the image forming unit 10.

[0061] This data presence / absence determination unit 92 has a data conversion table 93 and a special silver data conversion table 94. These data conversion tables 93 and special silver data conversion table 94 are stored in memory 82. The data conversion table 93 stores conversion formulas for converting the image data to be printed contained in the received print data into print patterns for the image forming units 10K, 10C, 10M, 10Y, and 10S.

[0062] When the data presence / absence determination unit 92 receives print data in which a color such as red 100% is specified in RGB output by an application program on the host device 100, it determines, according to the conversion formula stored in the data conversion table 93, that the image data contained in the print data should be printed in magenta (M) 100% and yellow (Y) 100% and notifies the control unit 3 of this determination result. Based on this determination result, the control unit 3 converts the image data contained in the received print data into a magenta (M) 100% print pattern and a yellow (Y) 100% print pattern and performs printing. Alternatively, the data presence / absence determination unit 92 may convert the image data contained in the received print data into a magenta (M) 100% print pattern and a yellow (Y) 100% print pattern and send the converted print pattern to the control unit 3.

[0063] Here, magenta (M) 100[%] means that the print duty cycle of magenta (M) is 100[%]. The same applies to black (K), cyan (C), yellow (Y), and spot color (S). Print duty cycle represents the amount of toner formed per unit area on the medium M. Specifically, print duty cycle is the ratio of the area where toner is used in the printed image based on the print data, when the area where a solid image is printed in the image-forming area of ​​the medium M is set to 100[%], and is also the ratio of the area on the medium M where a toner image is formed. Incidentally, a solid image is a toner image on the medium M formed by exposure of the entire area within the printable range of the photoreceptor drum 26, and is an image in which toner is used in all dots.

[0064] In other words, the print duty is the ratio of the number of dots used in the actual toner image based on the print data to the total number of dots that make up the area on the medium M in which an image can be formed, and is sometimes called the print coverage ratio.

[0065] On the other hand, the special silver data conversion table 94 stores the print duty cycle values ​​for each of the two areas that make up the silver image printed on the back of the medium M when decorative printing is performed. As will be explained in more detail later, the silver image printed on the back of the medium M during decorative printing consists of two areas: a decorative effect designated area and a non-decorative effect designated area. Of these, the decorative effect designated area is the part that is visible or hidden from the non-decorative effect designated area. The special silver data conversion table 94 stores the print duty cycle values ​​specified for each of the decorative effect designated area and the non-decorative effect designated area, such that the transparency of the decorative effect designated area is higher than that of the non-decorative effect designated area.

[0066] The data presence / absence determination unit 92, if the print data received from the host device 100 includes an instruction to perform decorative printing, obtains the print duty cycle values ​​for two areas (decorative effect specification area and non-decorative effect specification area) included in the silver image from the special silver data conversion table 94 and notifies the control unit 3 of these values. The instruction to perform decorative printing includes information that a non-glossy image, which is image data for the front surface, and a glossy image, which is image data for the back surface, should be placed facing each other on a transparent medium M, which is a light-transmitting medium. Upon receiving this information, the control unit 3 converts the image data for the front surface included in the received print data into a solid color print pattern and prints it on the front surface. Based on the two print duty cycle values ​​obtained from the data presence / absence determination unit 92, it converts the image data for the back surface included in the received print data into a silver print pattern and prints it on the back surface, thereby performing decorative printing. Furthermore, the data presence / absence determination unit 92 may convert the image data for the front side included in the received print data into a solid color print pattern, and convert the image data for the back side included in the received print data into a silver print pattern, and send these to the control unit 3.

[0067] [1-2. Toner Configuration] Next, the toners stored in the toner container 12 of the image forming unit 10 (Figure 2) will be described. For the colored toners, black (K), cyan (C), magenta (M), and yellow (Y), commercially available toners for each color (black (K), cyan (C), magenta (M), and yellow (Y)) manufactured by OKI Electric Industry Co., Ltd. for the C941dn were used.

[0068] In this embodiment, a silver toner containing a luminous pigment was used for the special color (S). Since silver toner is a developer with luminosity, the silver image formed with silver toner is a luminous image with luminosity. On the other hand, colored toner is a developer that does not have luminosity, and the colored image formed with colored toner is a non-luminous image without luminosity. The silver toner was manufactured, for example, by the method shown below. Note that the method shown below is just one example, and the silver toner may be manufactured by other methods.

[0069] First, in order to obtain an aqueous medium in which an inorganic dispersant is dispersed, 600 parts by weight of industrial trisodium phosphate dodecahydrate is added to 18,400 parts by weight of pure water and dissolved at a liquid temperature of 60°C, and then dilute nitric acid for pH adjustment is added. To this aqueous solution, an aqueous calcium chloride solution is added in which 300 parts by weight of industrial anhydrous calcium chloride is dissolved in 2,600 parts by weight of pure water, and while maintaining the liquid temperature at 60°C, the mixture is rapidly stirred at a rotation speed of 3,566 revolutions per minute using a line mill (Primix Corporation) for 50 minutes to prepare the aqueous phase, which is an aqueous medium in which a suspension stabilizer (inorganic dispersant) is dispersed.

[0070] Furthermore, assuming an oily material dispersion medium, a pigment dispersion is prepared by mixing 7000 parts by weight of ethyl acetate with 470 parts by weight of a luminous pigment (volume median diameter 5.4 [μm]) and 23 parts by weight of a charge control agent (BONTRON E-84: manufactured by Orient Chemical Industry Co., Ltd.).

[0071] In this embodiment, a lustrous pigment with a volume-average particle size (also called the volume median diameter) of 5.4 [μm] was used, but it is not limited to this. Specifically, the volume-average particle size of the lustrous pigment is preferably 5 [μm] or more and 20 [μm] or less, and more preferably in the range of 5.3 to 5.7 [μm].

[0072] Subsequently, while maintaining the temperature of the pigment dispersion at 60°C, 175 parts by weight of ester wax (WE-4: manufactured by NOF Corporation) and 1670 parts by weight of polyester resin are added, and the mixture is stirred until no solid matter remains. In this way, the oil phase, which is the pigment dispersion oily medium, is prepared.

[0073] Next, the oil phase is added to the aqueous phase, whose temperature has been lowered to 55°C, and the mixture is suspended by stirring at a rotation speed of 1000 revolutions per minute for 5 minutes, forming particles in the suspension. Then, the ethyl acetate is removed from the suspension by vacuum distillation to form a slurry containing toner. Nitric acid is added to this slurry to lower the pH to 1.6 or less, and the mixture is stirred to dissolve the tricalcium phosphate, which is a suspension stabilizer, and then dehydrated to form the toner. After that, the toner is redispersed in pure water and stirred, washed with water, and then subjected to a dehydration process, a drying process and a classification process to produce toner matrix particles.

[0074] Next, silver toner is obtained by adding 1.5% by weight of small silica (RY200: manufactured by Nippon Aerosil Co., Ltd.), 2.29% by weight of colloidal silica (X24-9163A: manufactured by Shin-Etsu Chemical Co., Ltd.), and 0.37% by weight of melamine particles (EPOSTAR S: manufactured by Nippon Shokubai Co., Ltd.) to the generated toner matrix particles as an external additive step and mixing them. The median volume diameter of the silver toner prepared in this way was measured to be 15.01 μm. Note that the median volume diameter of the silver toner is not limited to 15.01 μm; for example, it could be 10 to 20 μm.

[0075] [1-3. Decorative effects of decorative printing] Next, the decorative effect of decorative printing will be explained. As described above, when decorative printing is performed, the image forming apparatus 1 uses a light-transmitting medium M to print a solid image of one of the four colored colors on the surface of the medium M, and prints a silver image, which is one of the special colors, on the back surface of the medium M, and on the back surface the silver image is printed in two areas with different transmittances (decorated area and non-decorated area).

[0076] Here, Figure 4 shows an example of a printing pattern Pt1 printed on the surface of the medium M during decorative printing. The printing pattern Pt1 printed on the surface of the medium M is a printing pattern that prints a solid image in one of the four colored colors (black (K), cyan (C), magenta (M), yellow (Y)).

[0077] The medium M shown in Figure 4 is a light-transmitting A4-sized (210 mm high, 297 mm wide) medium with margins of 10 mm on both the front and back sides. Any light-transmitting medium M can be used if its white light transmittance, measured under ISO 5 / 2 (ISO Visual) conditions, is 90% or higher; commonly known as an OHP sheet or transparent sheet can be used.

[0078] Next, Figure 5 shows an example of a printing pattern Pt2 that is printed on the back side of the medium M during decorative printing. The printing pattern Pt2 printed on the back side of the medium M is a printing pattern that prints a silver image consisting of two areas: a decorative effect designation area Ar1 and a non-decorative effect designation area Ar2.

[0079] The decorative effect designation area Ar1 is the area where halftone (i.e., printing duty cycle less than 100%) silver printing is performed, while the non-decorative effect designation area Ar2, which is the other area, is the area where silver printing with a printing duty cycle of 100% is performed.

[0080] The print pattern Pt2 shown in Figure 5 is an example in which the vertical and horizontal dimensions of the non-decorative effect designation area Ar2 are the same as the solid color image of the print pattern Pt1 printed on the surface, and multiple decorative effect designation areas Ar1, which are smaller in vertical and horizontal dimensions than the non-decorative effect designation area Ar2, are arranged inside the non-decorative effect designation area Ar2. Specifically, in the print pattern Pt2, the vertical and horizontal dimensions of the decorative effect designation area Ar1 are 25 [mm] each, and multiple decorative effect designation areas Ar1 are arranged with a spacing of 60 [mm] vertically and horizontally.

[0081] As mentioned above, the print duty cycle values ​​for the decorative effect specification section Ar1 and the non-decorative effect specification section Ar2 are specified by the special silver data conversion table 94 so that the transmittance of the decorative effect specification section Ar1 is higher than that of the non-decorative effect specification section Ar2. Specifically, the print duty cycle of the non-decorative effect specification section Ar2 is set to 100%, and the print duty cycle of the decorative effect specification section Ar1 is set to a value less than 100%.

[0082] In other words, a medium M on which the printing pattern Pt1 shown in Figure 4 is printed on the front surface and the printing pattern Pt2 shown in Figure 5 is printed on the back surface becomes a printed material (referred to as a decorated printed material) in which the transparency differs between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2.

[0083] Here, for example, as shown in Figure 6, we assume that the light source LS and the observer's viewpoint VP are located on the front side of a decorated printed material Md, where the colored image Cp of print pattern Pt1 is printed on the front surface of the medium M, and the silver image Sp of print pattern Pt2 is printed on the back surface. In this case, the decorated printed material Md reflects light from the light source LS well with the colored image Cp printed on its front surface, and can deliver light of sufficient intensity from the colored image Cp to the observer's eye. The decorated printed material Md also allows some of the light from the light source LS to pass through the colored image Cp on the front surface and the medium M to reach the silver image Sp on the back surface. Some of the light that reaches the silver image Sp is reflected and passes through the medium M and the colored image Cp on the front surface to reach the observer's viewpoint VP.

[0084] If we focus on the intensity of light reaching the observer's viewpoint VP, the intensity of light reflected by the colored image Cp on the front surface is significantly greater than the intensity of light reflected by the silver image Sp on the back surface. Therefore, when the observer looks at the front side of the decorated printed material Md, the colored image Cp on the front surface is clearly visible, while the silver image Sp on the back surface is almost invisible, and the observer cannot distinguish between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 of the silver image Sp. In other words, in the state shown in Figure 6, the decorated printed material Md can hide the image printed on the decorative effect designated area Ar1 of the silver image Sp from the observer.

[0085] Next, as shown in Figure 7, consider the case where the observer's viewpoint VP is located on the front side of the decorated printed material Md, while the light source LS is located on the back side of the decorated printed material Md. In this case, because the light source LS is located on the back side of the decorated printed material Md, the light from the light source LS shines on the back side. As a result, relatively weak light from the colored image Cp reaches the observer's eye. On the other hand, some of the light from the light source LS passes through the silver image Sp printed on the back side, the medium M, and the colored image Cp printed on the front side, and reaches the observer's viewpoint VP.

[0086] Focusing on the intensity of light reaching the observer's viewpoint VP, the intensity of light reflected by the colored image Cp on the surface is not significantly greater than the intensity of light that has passed through the silver image Sp on the back, the medium M, and the colored image Cp on the surface. Therefore, when the observer looks at the surface side of the decorated printed material Md, they can see the colored image Cp on the surface to some extent, while also being able to see the silver image Sp on the back. At this time, since there is a difference in transmittance between the decorated effect designated area Ar1 and the non-decorated effect designated area Ar2 of the silver image Sp, a difference in density occurs in the images printed in the decorated effect designated area Ar1 and the non-decorated effect designated area Ar2. By recognizing this difference in density, the observer can distinguish between the decorated effect designated area Ar1 and the non-decorated effect designated area Ar2 of the silver image Sp. In other words, in the state shown in Figure 7, the decorated printed material Md can show the observer the image printed on the decorated effect designated area Ar1 of the silver image Sp.

[0087] The decorative printed material Md has a silver image Sp printed on its reverse side, with a decorative effect designation area Ar1 and a non-decorative effect designation area Ar2 having different transmittances. This allows for a decorative effect where the image printed on the decorative effect designation area Ar1 becomes visible or invisible depending on the viewing angle and the positional relationship with the light source LS, such as by tilting the decorative printed material Md.

[0088] Incidentally, the image forming apparatus 1 can also output a printed material in which the silver image Sp printed on the back side of the medium M is a solid color, and the colored image Cp printed on the front side has two areas with different transmittances. However, in this case, when the printed material is viewed from the front side, the images of the two areas will always be visible, so no decorative effect can be obtained. In other words, in order to obtain a decorative effect, it is necessary to have two areas with different transmittances in the silver image Sp printed on the back side.

[0089] [1-4. Evaluation Tests] Next, regarding the decorated printed material Md that was printed using the image forming apparatus 1, in order to find the conditions for obtaining a good visual effect, several types of evaluation printed materials were created with different combinations of the color used in the colored image Cp and the printing duty cycle of the decorative effect specification part Ar1 in the silver image Sp, and evaluation tests were conducted for each.

[0090] In this evaluation test, A4-sized CG3500 (manufactured by 3M) was used as the medium M. This medium M has a light transmittance of 90% or higher.

[0091] In this evaluation test, print data including instructions for decorative printing was transmitted from the host device 100 to the image forming apparatus 1, with a colored print pattern Pt1 shown in Figure 4 as the first page and a silver print pattern Pt2 shown in Figure 5 as the second page. The double-sided printing function of the image forming apparatus 1 created an evaluation printout in which the colored image Cp of print pattern Pt1 was printed on the front of the medium M and the silver image Sp of print pattern Pt2 was printed on the back.

[0092] Furthermore, in this evaluation test, as a pre-adjustment process, for the colored (black (K), cyan (C), magenta (M), yellow (Y)) printed by the image forming apparatus 1, various bias voltages (voltages applied to the developing roller 24, etc.) in the image forming units 10K, 10M, 10C, and 10Y were adjusted so that the optical density OD value measured using a spectrophotometer (X-Rite eXact: X-Rite Corporation) was 1.4 regardless of which color was printed.

[0093] Furthermore, in this evaluation test, for each case where black (K), cyan (C), magenta (M), and yellow (Y) were used for the colored image Cp printed on the front surface, the printing duty cycle of the decorative effect specification area Ar1 in the silver image Sp printed on the back surface was varied in 12 steps from 97% to 60% in intervals of several percent, thereby creating 12 evaluation prints for each color.

[0094] On the other hand, the printing duty cycle for the non-decorative effect designation section Ar2 in the silver image Sp is fixed at 100%, and as a pre-adjustment process, various bias voltages in the image forming unit 10S (such as the voltage applied to the developing roller 24) were adjusted so that the value of the luminous reflectance difference ΔY in this non-decorative effect designation section Ar2 becomes 26.

[0095] The difference in luminous reflectance ΔY in the non-decorative effect designated area Ar2 is measured by using white paper as the medium M and printing a solid silver image with a printing duty cycle of 100% on the white paper. The white paper used is A4 size with a weighing capacity of 127 g / m². 2 OS coated paper (manufactured by Fujifilm Business Innovation Co., Ltd.) was used.

[0096] The luminous reflectance difference ΔY is calculated by subtracting the luminous reflectance Y2 of unprinted OS coated paper from the luminous reflectance Y1 of a solid silver image with a 100% print duty cycle printed on OS coated paper. A spectrophotometer CM-2600d (manufactured by Konica Minolta Japan, Inc.) was used to measure the luminous reflectance difference ΔY. The measurement conditions for the luminous reflectance difference ΔY were a colorimetric auxiliary illuminant C (6774[K]) as the light source, an angle of 2°, and the specular reflection processing method SCE (Specular Reflectance Emission Control).

[0097] Furthermore, in this evaluation test, for each of the 12 color patterns of evaluation prints created, it was determined whether the observer could visually perceive the image of the decorative effect designation part Ar1 under the same observation conditions as in Figure 6, i.e., observation conditions in which the light source LS and the observer's viewpoint VP are located on the front side of the evaluation print (referred to as Condition 1), and under the same observation conditions as in Figure 7, i.e., observation conditions in which the observer's viewpoint VP is located on the front side of the evaluation print and the light source LS is located on the back side of the evaluation print (referred to as Condition 2).

[0098] As shown in Figure 6, under Condition 1, the light source LS was positioned so that the angle of incidence to the surface of the evaluation printout was 40-50°. Furthermore, under Condition 1, the line of sight from the observer's viewpoint VP was also positioned at 40-50° to the surface of the evaluation printout.

[0099] Furthermore, as shown in Figure 7, under condition 2, there was no specification regarding the incident angle of the light source LS, and the line of sight from the observer's viewpoint VP was set to be 40-50° relative to the surface of the evaluation printout.

[0100] In both Condition 1 and Condition 2, a fluorescent lamp was used as the light source (LS). Furthermore, in both Condition 1 and Condition 2, the evaluation printouts were observed in a darkroom to eliminate the influence of other lighting.

[0101] In this evaluation test, transmittance is used as an indicator of the density of the images printed on the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2, respectively. Here, the transmittance of the decorative effect designated area Ar1 indicates the proportion of light irradiated onto the front or back side of the evaluation print that passes through the decorative effect designated area Ar1 of the colored image Cp printed on the front, the medium M, and the silver image Sp printed on the back. The transmittance of the non-decorative effect designated area Ar2 indicates the proportion of light irradiated onto the front or back side of the evaluation print that passes through the non-decorative effect designated area Ar2 of the colored image Cp printed on the front, the medium M, and the silver image Sp printed on the back.

[0102] The transmittance of the decorative effect designation area Ar1 can be obtained by measuring the transmittance D of the image printed on the decorative effect designation area Ar1 using a visual transmittance densitometer (X-Rite 361 T, manufactured by X-Rite Corporation), and converting the measured transmittance D to transmittance T using the following equation (1).

[0103] T=10 (-D) ...(1)

[0104] Similarly, the transmittance of the non-decorative effect designated area Ar2 can be obtained by measuring the transmittance D of the image printed on the non-decorative effect designated area Ar2 using a visual transmittance densitometer (X-Rite 361 T, manufactured by X-Rite Corporation), and converting the measured transmittance D to transmittance T using the above-described formula (1).

[0105] Before measuring the transmittance density D, calibration was performed using a transmission reference plate. Then, a 2850K color temperature illumination light source was shone from the silver image Sp side on the back, and the transmitted light was received from the colored image Cp side on the front, and the transmittance density D was measured once on each side.

[0106] In this evaluation test, the transmittance of the decorative effect designated area Ar1 obtained in this manner is defined as T1, the transmittance of the non-decorative effect designated area Ar2 is defined as T2, and the difference between T1 and T2 is defined as the transmittance difference ΔT. Furthermore, since T1 > T2 is a condition for obtaining the decorative effect, all evaluation print materials created in this evaluation test satisfy T1 > T2.

[0107] Figures 8 and 9 show the results of this evaluation test. In this evaluation test, a colored image Cp on the front surface was printed in yellow (Y), and a silver image Sp was printed on the back surface. Evaluation tests were then conducted on 12 patterns of evaluation print materials Ye-A to Ye-L, each with 12 different printing duty cycles for the decorative effect designation area Ar1 of the silver image Sp. Similarly, evaluation tests were conducted on 12 evaluation prints, Ma-A to Ma-L, in which the colored image Cp on the front surface was printed in magenta (M) and the printing duty cycle of the decorative effect designation area Ar1 on the silver image Sp on the back surface was varied in 12 steps; 12 evaluation prints, Cy-A to Cy-L, in which the colored image Cp on the front surface was printed in cyan (C) and the printing duty cycle of the decorative effect designation area Ar1 on the silver image Sp on the back surface was varied in 12 steps; and 12 evaluation prints, Bk-A to Bk-L, in which the colored image Cp on the front surface was printed in black (K) and the printing duty cycle of the decorative effect designation area Ar1 on the silver image Sp on the back surface was varied in 12 steps.

[0108] In this evaluation test, for each of the evaluation print materials Ye-A~Ye-L, Ma-A~Ma-L, Cy-A~Cy-L, and Bk-A~Bk-L, the transmittance T1 of the decorative effect designated area Ar1, the transmittance T2 of the non-decorative effect designated area Ar2, and the transmittance difference ΔT were calculated.

[0109] Furthermore, as shown in Figures 8 and 9, in this evaluation test, for each of the evaluation print materials Ye-A~Ye-L, Ma-A~Ma-L, Cy-A~Cy-L, and Bk-A~Bk-L, the image judgment result in Condition 1 was marked as ○ if the observer could visually see the image of the decorative effect designated area Ar1 under Condition 1 shown in Figure 6, and as × if the observer could not visually see it. Similarly, in this evaluation test, for each of the evaluation print materials Ye-A~Ye-L, Ma-A~Ma-L, Cy-A~Cy-L, and Bk-A~Bk-L, the image judgment result in Condition 2 was marked as ○ if the observer could visually see the image of the decorative effect designated area Ar1 under Condition 2 shown in Figure 7, and as × if the observer could not visually see it.

[0110] In this evaluation test, if the image judgment result under condition 1 was × and the image judgment result under condition 2 was ○, it was determined that there was a decorative effect where the decorative effect designated part Ar1 was partially or completely obscured by changing the observation conditions (i.e., changing the positional relationship with the light source LS, etc.). In all other cases, it was determined that there was no decorative effect.

[0111] Figure 8 shows the results of this evaluation test for evaluation print materials Ye-A to Ye-L and evaluation print materials Ma-A to Ma-L. As is clear from Figure 8, in evaluation print materials Ye-A to Ye-L and evaluation print materials Ma-A to Ma-L, the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 increases as the printing duty cycle of the decorative effect designated area Ar1 decreases.

[0112] Furthermore, among the evaluation prints Ye-A to Ye-L, the decorative effect was determined to be present in evaluation print Ye-C, which had a transmittance difference ΔT of 2.0%, evaluation print Ye-D, which had a transmittance difference ΔT of 3.3%, evaluation print Ye-E, which had a transmittance difference ΔT of 4.4%, and evaluation print Ye-F, which had a transmittance difference ΔT of 4.7%.

[0113] From this, it can be seen that when printing a colored image Cp on the surface with yellow (Y) during decorative printing, a good decorative effect can be obtained if the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 is within the range of 2.0[%] to 4.7[%].

[0114] Similarly, in the evaluation print materials Ma-A to Ma-L, the decorative effect was determined to be present in evaluation print material Ma-C, where the transmittance difference ΔT was 1.5[%], evaluation print material Ma-D, where the transmittance difference ΔT was 1.7[%], evaluation print material Ma-E, where the transmittance difference ΔT was 1.7[%], and evaluation print material Ma-F, where the transmittance difference ΔT was 2.5[%].

[0115] From this, it can be seen that when printing a colored image Cp on the surface with magenta (M) during decorative printing, a good decorative effect can be obtained if the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 is within the range of 1.5[%] to 2.5[%].

[0116] Figure 9 shows the results of this evaluation test for evaluation print materials Cy-A to Cy-L and evaluation print materials Bk-A to Bk-L. As is clear from Figure 9, for both evaluation print materials Cy-A to Cy-L and evaluation print materials Bk-A to Bk-L, the smaller the printing duty cycle of the decorative effect designated area Ar1, the larger the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 becomes.

[0117] Furthermore, among the evaluation print materials Cy-A to Cy-L, evaluation print material Cy-D, with a transmittance difference ΔT of 2.0[%], evaluation print material Cy-E, with a transmittance difference ΔT of 2.5[%], evaluation print material Cy-F, with a transmittance difference ΔT of 2.8[%], and evaluation print material Cy-G, with a transmittance difference ΔT of 3.0[%] were judged to have a decorative effect.

[0118] From this, it can be seen that when printing a colored image Cp on the surface with cyan (C) during decorative printing, a good decorative effect can be obtained if the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 is within the range of 2.0[%] to 3.0[%].

[0119] Similarly, in the evaluation print materials Bk-A to Bk-L, the decorative effect was determined to be present in evaluation print material Bk-J, which had a transmittance difference ΔT of 2.0 [%], and in evaluation print material Bk-K, which had a transmittance difference ΔT of 3.6 [%].

[0120] From this, it can be seen that when printing a colored image Cp on the surface in black (K) during decorative printing, a good decorative effect can be obtained if the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 is within the range of 2.0[%] to 3.6[%].

[0121] Furthermore, the above results show that if the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 is within the range of 2.0[%] to 2.5[%], a good decorative effect can be obtained during decorative printing, regardless of whether the colored image Cp on the surface is printed with black (K), cyan (C), magenta (M), or yellow (Y).

[0122] Therefore, the optimal value for the transmittance difference ΔT that yields a good decorative effect for all colored materials is set to 2.25%, which is the median of the effective range of transmittance difference ΔT, which is 2.0% to 2.5%. The special silver data conversion table 94 specifies that the print duty cycle of the non-decorative effect specification section Ar2 is set to 100%, and also specifies the print duty cycle of the decorative effect specification section Ar1 so that the transmittance difference ΔT is 2.25%. Note that the print duty cycle of the decorative effect specification section Ar1 so that the transmittance difference ΔT is 2.25% varies depending on the color of the colored image Cp printed on the surface, so the special silver data conversion table 94 specifies the print duty cycle of the decorative effect specification section Ar1 for each color of the colored image Cp.

[0123] In this way, during decorative printing, the image forming apparatus 1 controls the image forming unit 10S via the control unit 3, printing the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 with the printing duty cycle specified in the special silver data conversion table 94. This allows the apparatus to output a decorative printed material Md that provides a good decorative effect regardless of the color used to print the colored image Cp.

[0124] [1-5. Summary and Effects] As described above, the image forming apparatus 1 of the first embodiment includes image forming units 10K, 10M, 10C, and 10Y, which are examples of non-glossy image forming units capable of forming a colored image Cp, which is an example of a non-glossy image, on the first surface of a medium M, which is an example of a light-transmitting medium; an image forming unit 10S, which is an example of a glossy image forming unit capable of forming a silver image Sp, which is an example of a glossy image, on the back surface, which is the second surface opposite the first surface of the medium M; and a control unit 3 that controls the image forming units 10K, 10M, 10C, 10Y, and 10S.

[0125] Furthermore, when the image forming apparatus 1 performs decorative printing with a colored image Cp and a silver image Sp facing each other on a medium M, the control unit 3 controls the image forming unit 10S so that a non-decorative effect designation area Ar2, which is an example of a first region where the transmittance of white light passing through the colored image Cp and silver image Sp via the medium M is a first transmittance (transmittance T2), and a decorative effect designation area Ar1, which is a second region with a transmittance higher than the first transmittance (transmittance T2) is a second transmittance (transmittance T1), are formed as a silver image Sp on the back surface of the medium M. The control unit 3 adjusts the printing duty cycle, which indicates the respective amount of the decorative effect designation area Ar1 and the non-decorative effect designation area Ar2 formed on the medium M in the silver image Sp.

[0126] In the first embodiment, the image forming apparatus 1 is equipped with a special silver data conversion table 94, which is an example of a recording unit. The special silver data conversion table 94 records the respective printing duty cycles of the decorative effect designation unit Ar1 and the non-decorative effect designation unit Ar2, as information regarding the transmittance T1 of the decorative effect designation unit Ar1 and the transmittance T2 of the non-decorative effect designation unit Ar2, so that the transmittance T1 of the decorative effect designation unit Ar1 is higher than the transmittance T2 of the non-decorative effect designation unit Ar2.

[0127] The control unit 3 then controls the image forming unit 10S based on the printing duty cycle values ​​of the decorative effect specification unit Ar1 and the non-decorative effect specification unit Ar2, respectively, recorded in the special silver data conversion table 94, and adjusts the printing duty cycles of the decorative effect specification unit Ar1 and the non-decorative effect specification unit Ar2.

[0128] In this way, the image forming apparatus 1 forms a colored image Cp on the surface of the medium M and forms a decorative effect designated area Ar1 and a non-decorative effect designated area Ar2 on the back surface with a silver image Sp that has a difference in transmittance. As a result, when the medium M is viewed from the surface side, a visual effect (decorative effect) can be obtained in which the decorative effect designated area Ar1 appears and disappears from view of the non-decorative effect designated area Ar2 on the back surface, depending on the viewing angle of the medium M and the positional relationship between the medium M and the light source.

[0129] Thus, the image forming apparatus 1 can achieve good visual effects (decorative effects). In other words, the image forming apparatus 1 can output printed materials that have good visual effects (decorative effects).

[0130] Furthermore, in the first embodiment, the data conversion table 94 dedicated to special silver ink is configured to record the print duty cycle values ​​of the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2, respectively, in order to set the transmittance difference ΔT, which is the difference between the transmittance T1 of the decorative effect designation section Ar1 and the transmittance T2 of the non-decorative effect designation section Ar2, to 2.0 or more and 2.5 or less. In this embodiment, verification has shown that in order to obtain a good visual effect (decorative effect) regardless of the color of the colored image Cp formed on the surface of the medium M, it is sufficient to set the transmittance difference ΔT of the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 to 2.0 [%] or more and 2.5 [%] or less.

[0131] The control unit 3 then controls the image forming unit 10S based on the printing duty cycle values ​​of the decorative effect specification unit Ar1 and the non-decorative effect specification unit Ar2, which are recorded in the special silver data conversion table 94. The control unit 3 adjusts the printing duty cycles of the decorative effect specification unit Ar1 and the non-decorative effect specification unit Ar2 so that the transmittance difference ΔT between them is 2.0% or more and 2.5% or less. In this way, the image forming apparatus 1 can achieve a good decorative effect regardless of the color used to print the colored image Cp.

[0132] Furthermore, in the first embodiment, verification results showed that when the colored image Cp formed on the surface of the medium M is yellow (Y), in order to obtain a good decorative effect, the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 should be 2.0% or more and 4.7% or less.

[0133] Similarly, it has been found that when a colored image Cp formed on the surface of a medium M is formed with magenta (M), a good decorative effect can be obtained by setting the transmittance difference ΔT to 1.5% or more and 2.5% or less; when a colored image Cp formed on the surface of a medium M is formed with cyan (C), a good decorative effect can be obtained by setting the transmittance difference ΔT to 2.0% or more and 3.0% or less; and when a colored image Cp formed on the surface of a medium M is formed with black (K), a good decorative effect can be obtained by setting the transmittance difference ΔT to 2.0% or more and 3.6% or less.

[0134] In the first embodiment, the control unit 3 adjusts the printing duty cycles of the decorative effect designation unit Ar1 and the non-decorative effect designation unit Ar2 using the special silver data conversion table 94, so that the transmittance difference ΔT between the decorative effect designation unit Ar1 and the non-decorative effect designation unit Ar2 is within a common range of 2.0% or more and 2.5% or less, which is necessary to obtain a good decorative effect for each color.

[0135] In addition to the above, when the control unit 3 forms a colored image Cp on the surface of the medium M in yellow (Y), it may adjust the printing duty cycles of the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 using the special silver data conversion table 94 so that the transmittance difference ΔT between the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 is within the range of 2.0% to 4.7% for obtaining a good decorative effect in yellow (Y).

[0136] Similarly, when the control unit 3 forms a colored image Cp on the surface of the medium M using magenta (M), it may adjust the print duty cycles of the decorative effect designation unit Ar1 and the non-decorative effect designation unit Ar2 using the special silver data conversion table 94 so that the transmittance difference ΔT between the decorative effect designation unit Ar1 and the non-decorative effect designation unit Ar2 is within the range of 1.5% to 2.5% for obtaining a good decorative effect with magenta (M).

[0137] Furthermore, when the control unit 3 forms a colored image Cp on the surface of the medium M using cyan (C), it may adjust the printing duty cycles of the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 using the special silver data conversion table 94 so that the transmittance difference ΔT between the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 is within the range of 2.0% to 3.0% for obtaining a good decorative effect with cyan (C).

[0138] Furthermore, when the control unit 3 forms a colored image Cp on the surface of the medium M in black (K), it may adjust the printing duty cycles of the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 using the special silver data conversion table 94 so that the transmittance difference ΔT between the decorative effect designation section Ar1 and the non-decorative effect designation section Ar2 is within the range of 2.0% to 3.6% for obtaining a good decorative effect with black (K).

[0139] Furthermore, when specifying the range of the transmittance difference ΔT between the decorative effect specification section Ar1 and the non-decorative effect specification section Ar2 for each color, the special silver data conversion table 94 should record the respective printing duty cycle values ​​of the decorative effect specification section Ar1 and the non-decorative effect specification section Ar2 for each color, so that the transmittance difference ΔT between the decorative effect specification section Ar1 and the non-decorative effect specification section Ar2 becomes the optimal value (for example, the median value of the range of transmittance difference ΔT for each color).

[0140] [2. Second Embodiment] Next, a second embodiment will be described. In this second embodiment, the decorative effect designation section Ar1 is classified into a narrow decorative effect designation section and a wide decorative effect designation section, so that the decorative effect is changed in stages in response to changes in the observation conditions for the decorated printed material (the viewing angle of the medium M and the positional relationship between the medium M and the light source).

[0141] In this context, a "narrow decorative effect area" refers to a decorative effect area where the range of observation conditions under which the image of the decorative effect area can be seen is narrow, while a "wide decorative effect area" refers to a decorative effect area where the range of observation conditions under which the image of the decorative effect area can be seen is wide. Therefore, for example, if the observation conditions are changed by tilting the decorated printed material, at a certain point the image of the wide decorative effect area will become visible, and if the observation conditions are changed further thereafter, the image of the wide decorative effect area will remain visible, and at a certain point the image of the narrow decorative effect area will also become visible.

[0142] This section will primarily describe only the parts that differ from the first embodiment, and will omit explanations of parts that are the same as the first embodiment as appropriate. For example, the configuration of the image forming apparatus 1 is the same in the first embodiment and the second embodiment, so its explanation will be omitted.

[0143] [2-1. Print Patterns] First, Figure 10 shows an example of a printing pattern Pt3 printed on the back surface of the medium M during decorative printing. Note that the printing pattern printed on the front surface is the same as in the first embodiment, so its explanation is omitted. The printing pattern Pt3 printed on the back surface of the medium M is a printing pattern that prints a silver image composed of three areas: two decorative effect designation areas Ar10 and Ar11 and a non-decorative effect designation area Ar12.

[0144] The decorative effect designation areas Ar10 and Ar11 are areas where halftone (i.e., printing duty cycle less than 100%) silver printing is performed, while the non-decorative effect designation area Ar12 is an area where silver printing with a printing duty cycle of 100% is performed.

[0145] This print pattern Pt3 is an example in which multiple decorative effect designation areas Ar10 and Ar11, which are smaller in both length and width than the non-decorative effect designation area Ar12, are arranged inside the non-decorative effect designation area Ar12. Specifically, in print pattern Pt3, the length and width of the decorative effect designation areas Ar10 and Ar11 are each 25 mm, and the decorative effect designation areas Ar10 and Ar11 are arranged adjacent to each other in the horizontal direction. Furthermore, the multiple decorative effect designation areas Ar10 are arranged with a gap of 60 mm in both length and width, and similarly, the multiple decorative effect designation areas Ar11 are also arranged with a gap of 60 mm in both length and width.

[0146] Furthermore, the printing duty cycles for both the decorative effect designation section Ar10 and the decorative effect designation section Ar11 are specified by the special silver data conversion table 94 so that their transmittance is higher than that of the non-decorative effect designation section Ar12 (referred to as T12).

[0147] Furthermore, in this embodiment, the print duty cycles for each are specified by the special silver data conversion table 94 such that the transmittance of the decorative effect specification section Ar11 (let's call it T11) is higher than the transmittance of the decorative effect specification section Ar10 (let's call it T10).

[0148] In other words, a medium M on which the printing pattern Pt1 shown in Figure 4 is printed on the front surface and the printing pattern Pt3 shown in Figure 10 is printed on the back surface becomes a decorated printed material Mdx with different transmittances in the decorative effect designated areas Ar10, Ar11 and the non-decorative effect designated area Ar12.

[0149] This decorative print Mdx can, for example, conceal the images printed on the decorative effect designation areas Ar10 and Ar11 of the silver image Sp from the observer under the observation conditions shown in Figure 6.

[0150] Furthermore, under the observation conditions shown in Figure 7, for example, this decorative print Mdx can show the observer the images printed on the decorative effect designation areas Ar10 and Ar11 of the silver image Sp.

[0151] Furthermore, under the observation conditions shown in Figure 11, for example, this decorative print Mdx can show the observer the image printed on the decorative effect designation section Ar11 of the silver image Sp, while concealing the image printed on the decorative effect designation section Ar10.

[0152] Furthermore, in the observation conditions shown in Figure 11, the light source LS and the observer's viewpoint VP are positioned on the surface side of the decorated printed material Mdx, similar to the observation conditions shown in Figure 7. However, compared to the observation conditions shown in Figure 7, the angle of incidence of the light source LS to the surface of the decorated printed material Mdx is smaller, and the intensity of the light reflected by the colored image Cp printed on the surface and reaching the observer's eye is weaker than in the observation conditions shown in Figure 7. In other words, the intensity of the light reflected by the colored image Cp printed on the surface and reaching the observer's eye decreases in the order of Figure 6, Figure 11, and Figure 7.

[0153] In other words, when the decorative printed material Mdx is tilted and the observation conditions are changed sequentially as shown in Figures 6, 11, and 7, when the observation conditions shown in Figure 11 are met, the image printed on the decorative effect designation area Ar11, which has a higher transmittance than the decorative effect designation area Ar10, becomes visible. Subsequently, when the observation conditions shown in Figure 7 are met, the image printed on decorative effect designation area Ar10 becomes visible in addition to the image printed on decorative effect designation area Ar11, thus achieving a gradual decorative effect. In other words, the decorative effect designation area Ar11 with higher transmittance is a wider decorative effect designation area, and the decorative effect designation area Ar10 with lower transmittance is a narrower decorative effect designation area.

[0154] [2-2. Evaluation Test] Next, regarding the decorated printed material Mdx, which was printed using the image forming apparatus 1, in order to explore the conditions for obtaining a good visual effect, several types of evaluation printed materials were created with different combinations of the color used in the colored image Cp and the printing duty cycle of the decorative effect designation parts Ar10 and Ar11 in the silver image Sp, and evaluation tests were conducted for each.

[0155] In this evaluation test, for each case where black (K), cyan (C), magenta (M), or yellow (Y) was used for the colored image Cp printed on the front side, the printing duty cycle of the decorative effect specification section Ar10 and the decorative effect specification section Ar11 on the silver image Sp printed on the back side was gradually changed to create at least one evaluation print for each color.

[0156] As shown in Figure 11, in condition 3, the light source LS was positioned so that the angle of incidence to the surface of the evaluation printout was 5 to 15°. Furthermore, in condition 3, the line of sight from the observer's viewpoint VP was set to 85 to 95° to the surface of the evaluation printout.

[0157] Furthermore, in this evaluation test, based on the results of the evaluation test of the first embodiment, the transmittance difference ΔT (hereinafter referred to as ΔT1) between the decorative effect designated area Ar10 and the non-decorative effect designated area Ar12, and the transmittance difference ΔT (hereinafter referred to as ΔT2) between the decorative effect designated area Ar11 and the non-decorative effect designated area Ar12 were selected so that under condition 1, the images of both the decorative effect designated areas Ar10 and Ar11 were not visible, and under condition 2, the images of both the decorative effect designated areas Ar10 and Ar11 were visible.

[0158] In other words, the evaluation test results of the first embodiment showed that when printing the colored image Cp on the surface with yellow (Y), the range of transmittance difference ΔT in which a good decorative effect can be obtained between condition 1 and condition 2 is 2.0[%] to 4.7[%].

[0159] Therefore, in this evaluation test, for evaluation prints in which the colored image Cp on the surface is printed in yellow (Y), the transmittance difference ΔT1 between the decorative effect designated area Ar10 and the non-decorative effect designated area Ar12, and the transmittance difference ΔT2 between the decorative effect designated area Ar11 and the non-decorative effect designated area Ar12 were both set to fall within the range of 2.0[%] to 4.7[%].

[0160] Similarly, for evaluation printouts printed with magenta (M) on a colored image Cp on the surface, the transmittance difference ΔT1 and transmittance difference ΔT2 were both kept within the range of 1.5% to 2.5%.

[0161] Furthermore, for evaluation prints where cyan (C) was printed onto the colored image Cp on the surface, the transmittance difference ΔT1 and transmittance difference ΔT2 were both kept within the range of 2.0% to 3.0%.

[0162] Furthermore, for evaluation prints where black (K) was printed on the colored image Cp on the surface, the transmittance difference ΔT1 and transmittance difference ΔT2 were both kept within the range of 2.0% to 3.6%.

[0163] Furthermore, in this evaluation test, for each color of the evaluation printouts created, the observer determined whether the decorative effect designations Ar10 and Ar11 could be visually identified under the same observation conditions as in Figure 11 (referred to as Condition 3).

[0164] As mentioned above, the print materials used for evaluation of each color were selected with transmittance differences ΔT1 and ΔT2 such that under Condition 1, neither image of the decorative effect designation areas Ar10 and Ar11 was visible, and under Condition 2, both images of the decorative effect designation areas Ar10 and Ar11 were visible. Therefore, in this evaluation test, the determination was made based on whether or not the decorative effect designation areas Ar10 and Ar11 were visible under Condition 3.

[0165] Figure 12 shows the results of this evaluation test. In this evaluation test, a colored image Cp on the front surface was printed in yellow (Y), and a silver image Sp was printed on the back surface. The printing duty cycle of the decorative effect designation areas Ar10 (listed as decorative effect designation area 1 in the table in Figure 12) and Ar11 (listed as decorative effect designation area 2 in the table in Figure 12) of the silver image Sp was varied in three stages within the range where the transmittance difference ΔT1 and transmittance difference ΔT2 were 2.0[%] to 4.7[%]. Evaluation tests were then conducted for each of the three evaluation printouts Ye-M to Ye-O.

[0166] Similarly, evaluation tests were conducted on three evaluation printouts, Ma-M to Ma-O, in which the colored image Cp on the surface was printed in magenta (M), and the printing duty cycle of the decorative effect designation areas Ar10 and Ar11 of the silver image Sp on the back surface was varied in three steps within a range where the transmittance difference ΔT1 and transmittance difference ΔT2 were between 1.5% and 2.5%.

[0167] Furthermore, evaluation tests were conducted on two evaluation printouts, Cy-M and Cy-N, in which the colored image Cp on the surface was printed with cyan (C), and the printing duty cycle of the decorative effect designation areas Ar10 and Ar11 of the silver image Sp on the back surface was varied in two stages within a range where the transmittance difference ΔT1 and transmittance difference ΔT2 were between 2.0% and 3.0%.

[0168] Furthermore, evaluation tests were conducted on evaluation print Bk-M, in which the colored image Cp on the surface was printed in black (K), and the printing duty cycles of the decorative effect designation areas Ar10 and Ar11 of the silver image Sp on the reverse side were selected so that the transmittance difference ΔT1 was 2.0 [%] and the transmittance difference ΔT2 was 3.6 [%].

[0169] In this evaluation test, for each of the evaluation print materials Ye-M~Ye-O, Ma-M~Ma-O, Cy-M~Cy-N, and Bk-M, the transmittance difference ΔT3, which is the difference between the transmittance difference ΔT1 and the transmittance difference ΔT2 (i.e., the difference between the transmittance of the decorative effect designated area Ar10 and the transmittance of the decorative effect designated area Ar11), was calculated.

[0170] Furthermore, as shown in Figure 12, in this evaluation test, for each of the evaluation print materials Ye-M~Ye-O, Ma-M~Ma-O, Cy-M~Cy-N, and Bk-M, under Condition 3 shown in Figure 11, if the observer could see only the image of the decorative effect designated part Ar11 out of the decorative effect designated parts Ar10 and Ar11, the image judgment result under Condition 3 was marked as ○, and otherwise the image judgment result was marked as ×.

[0171] In this evaluation test, if the image judgment result under condition 3 was ○, the observation conditions were changed to condition 1, condition 3, and condition 2 (i.e., the positional relationship with the light source LS was changed), and it was determined that there was a gradual decorative effect in which the images printed on the decorative effect designation parts Ar10 and Ar11 became visible in order. In all other cases, it was determined that there was no decorative effect.

[0172] As is clear from Figure 12, in the evaluation prints Ye-M to Ye-O, a gradual decorative effect was determined to be present in evaluation print Ye-M, where the transmittance difference ΔT3 was 2.7[%], and in evaluation print Ye-N, where the transmittance difference ΔT3 was 2.4[%]. In evaluation print Ye-O, where the transmittance difference ΔT3 was 1.4[%], no decorative effect was determined.

[0173] From this, it can be seen that when printing a colored image Cp on the surface in yellow (Y) during decorative printing, a gradual decorative effect can be obtained if the transmittance difference ΔT3 between the decorative effect designation area Ar10 and the decorative effect designation area Ar11 is within the range of 2.4[%] to 2.7[%].

[0174] Similarly, in the evaluation print materials Ma-M to Ma-O, evaluation print material Ma-M, where the transmittance difference ΔT was 1.0[%], and evaluation print material Ma-O, where the transmittance difference ΔT was 0.8[%], were judged to have a gradual decorative effect, while evaluation print material Ma-N, where the transmittance difference ΔT3 was 0.2[%], was judged to have no decorative effect.

[0175] From this, it can be seen that when printing a colored image Cp on the surface with magenta (M) during decorative printing, a gradual decorative effect can be obtained if the transmittance difference ΔT3 between the decorative effect designation area Ar10 and the decorative effect designation area Ar11 is within the range of 0.8[%] to 1.0[%].

[0176] Furthermore, in the evaluation print materials Cy-M to Cy-N, evaluation print material Cy-M, which had a transmittance difference ΔT of 0.8[%], was judged to have a gradual decorative effect, while evaluation print material Cy-N, which had a transmittance difference ΔT3 of 0.5[%], was judged to have no decorative effect.

[0177] From this, it can be seen that when printing a colored image Cp on the surface with cyan (C) during decorative printing, a stepped decorative effect can be obtained if the transmittance difference ΔT3 between the decorative effect designation area Ar10 and the decorative effect designation area Ar11 is set to 0.8 [%].

[0178] Furthermore, the evaluation printout Bk-M had a transmittance difference ΔT of 1.6 [%], and was determined to have a gradual decorative effect.

[0179] From this, it can be seen that when printing a colored image Cp on the surface in black (K) during decorative printing, a stepped decorative effect can be obtained if the transmittance difference ΔT3 between the decorative effect designation area Ar10 and the decorative effect designation area Ar11 is set to 1.6 [%].

[0180] Based on the above results, for yellow (Y), the optimal value for the transmittance difference ΔT3 that obtains a gradual decorative effect is set to 2.55%, for example, the median of the effective range of transmittance difference ΔT3, which is 2.4% to 2.7%. Similarly, for magenta (M), the optimal value for the transmittance difference ΔT3 that obtains a gradual decorative effect is set to 0.9%, for example, the median of the effective range of transmittance difference ΔT3, which is 0.8% to 1.0%. Furthermore, for cyan (C), the optimal value for the transmittance difference ΔT3 that obtains a gradual decorative effect is set to 0.8%. Finally, for black (K), the optimal value for the transmittance difference ΔT3 that obtains a gradual decorative effect is set to 1.6%.

[0181] Furthermore, in the special silver data conversion table 94, the printing duty cycle of the non-decorative effect specification section Ar12 is specified as 100[%], and for each color, the printing duty cycle values ​​of the decorative effect specification section Ar10 and the decorative effect specification section Ar11 are specified so that the transmittance difference ΔT3 between the decorative effect specification section Ar10 and the decorative effect specification section Ar11 is the optimal value.

[0182] In this way, the image forming apparatus 1 of the second embodiment can output a decorated printed material Mdx that provides a gradual decorative effect by printing the decorative effect designation sections Ar10, Ar11 and the non-decorative effect designation section Ar12 with the printing duty cycle specified in the special silver data conversion table 94 during decorative printing.

[0183] [2-3. Summary and Effects] As explained above, in the image forming apparatus 1 of the second embodiment, when decorative printing is performed with a colored image Cp and a silver image Sp facing each other on a medium M, the control unit 3 controls the image forming unit 10S so that a non-decorative effect designation area Ar12, which is an example of a first region where the transmittance of white light transmitted through the colored image Cp and silver image Sp via the medium M is a first transmittance (transmittance T12), a decorative effect designation area Ar10, which is an example of a second region where the transmittance of white light is higher than the first transmittance (transmittance T12), and a decorative effect designation area Ar11, which is an example of a third region where the transmittance of white light is higher than the second transmittance (transmittance T11), are formed as a silver image Sp on the back surface of the medium M, and the control unit 3 adjusts the printing duty cycle which indicates the amount of each of the decorative effect designation areas Ar10, Ar11 and the non-decorative effect designation area Ar12 formed on the medium M in the silver image Sp.

[0184] In the second embodiment, the special silver data conversion table 94 records information regarding the transmittance T10 of the decorative effect designation section Ar10, the transmittance T11 of the decorative effect designation section Ar11, and the transmittance T12 of the non-decorative effect designation section Ar12. This information is set to make the transmittances T10 and T11 of the decorative effect designation sections Ar10 and Ar11 higher than the transmittance T12 of the non-decorative effect designation section Ar12, and to make the transmittance T11 of the decorative effect designation section Ar11 higher than the transmittance T10 of the decorative effect designation section Ar10.

[0185] The control unit 3 then controls the image forming unit 10S based on the print duty cycle values ​​of the decorative effect specification units Ar10 and Ar11 and the non-decorative effect specification unit Ar12, which are recorded in the special silver data conversion table 94, and adjusts the print duty cycles of the decorative effect specification units Ar10 and Ar11 and the non-decorative effect specification unit Ar12.

[0186] In this way, the image forming apparatus 1 forms a colored image Cp on the surface of the medium M and forms decorative effect designation areas Ar10, Ar11 and non-decorative effect designation area Ar12 on the back surface with a silver image Sp having different transmittances. As a result, when the medium M is viewed from the surface side, a gradual visual effect (decorative effect) can be obtained in which the decorative effect designation areas Ar10 and Ar11 become visible in stages relative to the non-decorative effect designation area Ar12 on the back surface, depending on the viewing angle of the medium M and the positional relationship between the medium M and the light source.

[0187] Thus, the image forming apparatus 1 can achieve a gradual visual effect (decorative effect). In other words, the image forming apparatus 1 can output printed materials that produce a gradual visual effect (decorative effect).

[0188] [3. Other Embodiments] [3-1. Other Embodiments 1] In the first embodiment described above, if the control unit 3 of the image forming apparatus 1 receives print data from the host device 100 and includes an instruction to perform decorative printing, it converts the surface image data included in the received print data into a colored print pattern Pt1 based on the conversion formula stored in the data conversion table 93.

[0189] At this time, the control unit 3 converts the image data for the reverse side included in the received print data into a silver print pattern Pt2 based on the respective print duty cycle values ​​of the decorative effect specification unit Ar1 and the non-decorative effect specification unit Ar2, which are specified in the special silver data conversion table 94.

[0190] This is not limited to this example. For instance, the higher-level device 100 may be provided with a data conversion table 93 and a data conversion table 94 specifically for special silver ink. When the printer driver 101 generates print data based on application data, if it is instructed to perform decorative printing, the printer driver 101 may convert the surface image data included in the application data into colored image data (for example, image data of print pattern Pt1) based on the conversion formula stored in the data conversion table 93. In other words, the printer driver 101 may convert the surface image data included in the application data into colored image data with adjusted print duty cycles based on the conversion formula stored in the data conversion table 93.

[0191] In addition, the printer driver 101 may convert the image data for the back side included in the application data into silver image data (for example, image data of print pattern Pt2) based on the respective print duty cycle values ​​of the decorative effect specification section Ar1 and the non-decorative effect specification section Ar2 specified in the special silver data conversion table 94.

[0192] In this case, the printer driver 101 transmits print data, which includes colored image data for the front side and silver image data for the back side, to the image forming apparatus 1. In the image forming apparatus 1, the control unit 3 uses the colored image data for the front side included in the received print data to print the front side, and uses the silver image data for the back side to print the back side.

[0193] Thus, instead of the image forming apparatus 1, the higher-level device 100 may use the printer driver 101 to convert the image data for the front surface included in the application data for decorative printing into colored (black (K), magenta (M), cyan (C), yellow (Y)) image data, and the image data for the back surface into a special silver image data, and then transmit the print data containing the converted image data to the image forming apparatus 1. This printing system reduces the load on the image forming apparatus 1. The same applies to the second embodiment.

[0194] [3-2. Other Embodiments 2] Furthermore, in the first embodiment described above, when performing decorative printing, the printing pattern Pt2 printed on the back surface of the medium M is formed with a glossy silver toner. However, the invention is not limited to this, and the printing pattern Pt2 printed on the back surface of the medium M may be formed with a glossy toner other than silver toner. Note that when printing the printing pattern Pt2 with a glossy toner other than silver toner, the range of the transmittance difference ΔT required to obtain the decorative effect may differ from 2.0% or more and 2.5% or less. Similarly, in the second embodiment, the printing pattern Pt3 printed on the back surface of the medium M may be formed with a glossy toner other than silver toner.

[0195] Furthermore, in the first embodiment described above, when performing decorative printing, the print pattern Pt1 printed on the surface of the medium M is formed using one of four non-glossy colored toners: black (K), cyan (C), magenta (M), and yellow (Y). However, the print pattern Pt1 printed on the surface of the medium M may also be formed using a non-glossy toner other than the four toners black (K), cyan (C), magenta (M), and yellow (Y). The same applies to the second embodiment.

[0196] [3-3. Other Embodiments 3] Furthermore, in the first embodiment described above, when performing decorative printing, a solid color print with a printing duty cycle of 100% was performed on the surface of the medium M using a colored material. However, the method is not limited to this, and printing with a predetermined printing duty cycle of less than 100% using a colored material may also be performed on the surface of the medium M. The same applies to the second embodiment.

[0197] Furthermore, in the first embodiment described above, when performing decorative printing, the non-decorative effect designation area Ar2 included in the silver image Sp printed on the back side of the medium M is printed as a solid color with a printing duty cycle of 100% using silver. However, the embodiment is not limited to this, and the non-decorative effect designation area Ar2 may be printed with silver using a predetermined printing duty cycle of less than 100%. The same applies to the second embodiment.

[0198] [3-4. Other Embodiments 4] Furthermore, in the first embodiment described above, the optimal value of the transmittance difference ΔT for obtaining a good decorative effect common to all colored materials was set to, for example, the median value of 2.25% within the effective range of 2.0% to 2.5% for the transmittance difference ΔT. However, the optimal value of the transmittance difference ΔT can be any value that falls within the range of 2.0% to 2.5%. The same applies to the second embodiment.

[0199] [3-5. Other Embodiments 5] Furthermore, in the first embodiment described above, in order to obtain a good decorative effect common to all colored materials, the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 was set to be 2.0% or more and 2.5% or less. In this case, a good decorative effect means a decorative effect that is easily visible to the human eye. On the other hand, a decorative effect can be obtained by at least creating a difference in transmittance between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2. In this case, the decorative effect may be small and difficult to see with the human eye, but it can be a sufficiently good decorative effect for devices such as those that photograph images of printed materials and perform image analysis.

[0200] In other words, the present invention makes it possible to obtain a decorative effect by creating a difference in transmittance between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2. Furthermore, by setting the transmittance difference ΔT between the decorative effect designated area Ar1 and the non-decorative effect designated area Ar2 to 2.0% or more and 2.5% or less, a decorative effect that can be easily seen with the human eye can be obtained.

[0201] [3-6. Other Embodiments 6] Furthermore, in the second embodiment described above, two decorative effect designation areas Ar10 and Ar11 with different transmittances are printed on the back surface of the medium M. However, the invention is not limited to this, and three or more decorative effect designation areas with different transmittances may be printed on the back surface of the medium M.

[0202] [3-7. Other Embodiments 7] Furthermore, the first and second embodiments described above describe the case in which five image forming units 10 are provided in the image forming apparatus 1 (Figure 1). However, the image forming apparatus 1 may be provided with four or fewer image forming units 10, or six or more image forming units 10. For example, when four image forming units 10 are provided, three colors may be used for the colored parts and silver for the glossy parts.

[0203] Furthermore, in the first and second embodiments described above, the image forming apparatus (Figure 1) is configured in a so-called intermediate transfer method, in which the toner image formed in each image forming unit 10 is first transferred to an intermediate transfer belt 34, and the toner image is secondarily transferred from the intermediate transfer belt 34 to the medium M. However, the invention is not limited to this configuration, and for example, the image forming apparatus 1 may be configured in a so-called direct transfer method, in which the toner image formed in each image forming unit 10 is directly transferred to the medium M.

[0204] Furthermore, the first embodiment described above described the case in which the present invention is applied to an image forming apparatus 1 which is a single-function printer. However, the present invention is not limited to this, and may also be applied to image forming apparatuses with various other functions, such as an MFP (Multi-Function Peripheral) that has the functions of a copier or a facsimile machine.

[0205] [3-8. Other Embodiments 8] Furthermore, the first and second embodiments described above describe the application of the present invention to an electrophotographic image forming apparatus 1 that forms an image using toner as a developer. However, the present invention is not limited to this and can also be applied to an inkjet image forming apparatus that forms an image using ink. In the case of using ink, as with the case of using toner, an image using non-glossy ink can be formed on the surface of a light-transmitting medium, and an image using glossy ink can be formed on the back surface. However, even in a medium where a printing process is performed by an inkjet image forming apparatus in which a colored image formed with colored ink is superimposed on a glossy image formed with glossy ink, steps are formed in each region due to the colored pigment contained in the colored ink that constitutes the colored image. As a result, differences in glossiness occur in each region of this medium, and the image can be seen against the will, resulting in an insufficient visual effect. However, by applying the present invention, a good visual effect can be achieved even in an inkjet image forming apparatus.

[0206] Furthermore, toner and ink are collectively referred to as image agents. In other words, the present invention can be applied to various image forming apparatuses that can form an image on the surface of a light-transmitting medium with a non-glossy image agent and an image on the back surface with a glossy image agent.

[0207] [3-9. Other Embodiments 9] Furthermore, the present invention is not limited to the embodiments described above and other embodiments. That is, the scope of application of the present invention extends to embodiments that arbitrarily combine some or all of the embodiments described above and other embodiments, as well as embodiments that extract some of them.

[0208] [4. Addendum] The various aspects of the present invention are summarized below as appendices.

[0209] [4-1. Addendum 1] A non-glossy image forming unit capable of forming a non-glossy image on the first surface of a light-transmitting medium, A luminous image forming unit capable of forming a luminous image on the second surface, which is the opposite surface to the first surface, The non-luminous image forming unit and the control unit that controls the luminous image forming unit. Equipped with, The control unit, When the non-glossy image and the glossy image are placed facing each other on the light-transmitting medium, the glossy image forming unit is controlled and the amount of the glossy image formed on the second surface of the light-transmitting medium is adjusted so that a first region is formed on the second surface of the light-transmitting medium where the transmittance of white light passing through the glossy image and the non-glossy image is a first transmittance, and a second region is formed where the transmittance is a second transmittance which is higher than the first transmittance. An image forming apparatus characterized by the following:

[0210] [4-2. Appendix 2] The light-transmitting medium further comprises a recording unit that records information regarding the transmittance of the first region and the transmittance of the second region formed on the second surface of the light-transmitting medium. The control unit, Based on the above information, the luminous image forming unit is controlled to adjust the amount of the luminous image formed on the second surface of the light-transmitting medium. The image forming apparatus according to Appendix 1, characterized in that it is a picture forming apparatus.

[0211] [4-3. Appendix 3] The non-glossy image forming unit is capable of forming the non-glossy image using at least one of the imaging agents: black, yellow, magenta, or cyan. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is 2.0 or more and 2.5 or less. The image forming apparatus according to Appendix 1 or 2, characterized by the features described herein.

[0212] [4-4. Appendix 4] The non-glossy image forming unit is capable of forming the non-glossy image using a cyan imaging agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is 2.0 or more and 3.0 or less. The image forming apparatus according to Appendix 1 or 2, characterized by the features described herein.

[0213] [4-5. Appendix 5] The non-glossy image forming unit is capable of forming the non-glossy image using a black imaging agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is between 2.0 and 3.6. The image forming apparatus according to Appendix 1 or 2, characterized by the features described herein.

[0214] [4-6. Appendix 6] The non-glossy image forming unit is capable of forming the non-glossy image using a yellow imaging agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is between 2.0 and 4.7. The image forming apparatus according to Appendix 1 or 2, characterized by the features described herein.

[0215] [4-7. Appendix 7] The non-glossy image forming unit is capable of forming the non-glossy image using a magenta image agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is between 1.5 and 2.5. The image forming apparatus according to Appendix 1 or 2, characterized by the features described herein.

[0216] [4-8. Appendix 8] The control unit, The luminous image forming unit is controlled and the amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that a first region is formed on the second surface of the light-transmitting medium, the first region is formed on the second surface of the light-transmitting medium on which white light passing through the luminous image and the non-luminous image has a first transmittance, the second region is formed on the second surface of the light-transmitting medium on which white light passing through has a second transmittance higher than the first transmittance, and the third region is formed on the second surface of the light-transmitting medium on which white light passing through has a third transmittance higher than the second transmittance. The image forming apparatus according to Appendix 1, characterized in that it is a picture forming apparatus.

[0217] [4-9. Appendix 9] A printing system comprising a higher-level device and an image forming apparatus connectable to the said higher-level device, The aforementioned higher-level device is The image forming apparatus is equipped with a printer driver that controls the image forming apparatus, The image forming apparatus is A non-glossy image forming unit capable of forming a non-glossy image on the first surface of a light-transmitting medium, A luminous image forming unit capable of forming a luminous image on the second surface, which is the opposite surface to the first surface, The non-luminous image forming unit and the control unit that controls the luminous image forming unit. Equipped with, The aforementioned printer driver When the non-glossy image and the glossy image are placed facing each other on the light-transmitting medium, print data is generated that includes image data for forming the non-glossy image on the first surface of the light-transmitting medium, and image data that adjusts the amount of the glossy image formed on the second surface of the light-transmitting medium for forming a first region on the second surface of the light-transmitting medium where the transmittance of white light passing through the glossy image and the non-glossy image is a first transmittance, and a second region where the transmittance is a second transmittance which is higher than the first transmittance, and this data is sent to the image forming apparatus. The control unit, Based on the print data sent from the above-level device, the non-glossy image forming unit and the glossy image forming unit are controlled to form the non-glossy image on the first surface of the light-transmitting medium and the glossy image on the second surface of the light-transmitting medium. A printing system characterized by the following features.

[0218] [4-10. Appendix 10] Light-transmitting media and A non-glossy image formed on the first surface of the light-transmitting medium, On the second surface, which is the opposite surface of the first surface, a luminous image is formed so as to face the luminous image via the light-transmitting medium. It has, The luminous image includes a first region where the transmittance of white light transmitted through the light-transmitting medium to the luminous image and the non-luminous image is a first transmittance, and a second region where the transmittance is a second transmittance that is higher than the first transmittance. A printed material characterized by the following features.

[0219] [4-11. Appendix 11] The transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is 2.0 or greater and 2.5 or less. The printed material described in Appendix 10, characterized by the features described herein. [Industrial applicability]

[0220] The present invention can be widely used in, for example, an image forming apparatus capable of forming a non-glossy image and a glossy image on the front and back surfaces of a medium. [Explanation of Symbols]

[0221] 1...Image forming apparatus, 3...Control unit, 10, 10C, 10K, 10M, 10S, 10Y...Image forming unit, 92...Data presence / absence determination unit, 93...Data conversion table, 94...Special silver dedicated data conversion table, 100...Host device, 101...Printer driver, Ar1, Ar10, Ar11...Decoration effect specification unit, Ar2, Ar12...Non-decoration effect specification unit, Cp...Colored image, M, M2...Medium, Md, Mdx...Decorated printed material, Pt1, Pt2, Pt3...Print pattern, Sp...Silver image, T, T1, T2, T10, T11, T12...Transmittance, ΔT, ΔT1, ΔT2, ΔT3...Transmittance difference.

Claims

1. A non-glossy image forming unit capable of forming a non-glossy image on the first surface of a light-transmitting medium, A luminous image forming unit capable of forming a luminous image on the second surface, which is the opposite surface to the first surface, The non-luminous image forming unit and the control unit that controls the luminous image forming unit. Equipped with, The control unit, When the non-glossy image and the glossy image are placed facing each other on the light-transmitting medium, the glossy image forming unit is controlled and the amount of the glossy image formed on the second surface of the light-transmitting medium is adjusted so that a first region is formed on the second surface of the light-transmitting medium where the transmittance of white light passing through the glossy image and the non-glossy image is a first transmittance, and a second region is formed where the transmittance is a second transmittance which is higher than the first transmittance. An image forming apparatus characterized by the following:

2. The light-transmitting medium further comprises a recording unit that records information regarding the transmittance of the first region and the transmittance of the second region formed on the second surface of the light-transmitting medium. The control unit, Based on the above information, the luminous image forming unit is controlled to adjust the amount of the luminous image formed on the second surface of the light-transmitting medium. The image forming apparatus according to feature 1.

3. The non-glossy image forming unit is capable of forming the non-glossy image using at least one of the imaging agents: black, yellow, magenta, or cyan. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is 2.0 or more and 2.5 or less. The image forming apparatus according to claim 1 or 2.

4. The non-glossy image forming unit is capable of forming the non-glossy image using a cyan imaging agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is 2.0 or more and 3.0 or less. The image forming apparatus according to claim 1 or 2.

5. The non-glossy image forming unit is capable of forming the non-glossy image using a black imaging agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is between 2.0 and 3.

6. The image forming apparatus according to claim 1 or 2.

6. The non-glossy image forming unit is capable of forming the non-glossy image using a yellow imaging agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is between 2.0 and 4.

7. The image forming apparatus according to claim 1 or 2.

7. The non-glossy image forming unit is capable of forming the non-glossy image using a magenta image agent. The control unit, The amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that the transmittance difference, which is the difference between the first transmittance of the first region and the second transmittance of the second region, is between 1.5 and 2.

5. The image forming apparatus according to claim 1 or 2.

8. The control unit, The luminous image forming unit is controlled and the amount of the luminous image formed on the second surface of the light-transmitting medium is adjusted so that a first region is formed on the second surface of the light-transmitting medium where the transmittance of white light passing through the luminous image and the non-luminous image is a first transmittance, a second region is formed where the transmittance of white light is a second transmittance higher than the first transmittance, and a third region is a third transmittance higher than the second transmittance. The image forming apparatus according to feature 1.

9. A printing system comprising a higher-level device and an image forming apparatus connectable to the said higher-level device, The aforementioned higher-level device is The image forming apparatus is equipped with a printer driver that controls the image forming apparatus, The image forming apparatus is A non-glossy image forming unit capable of forming a non-glossy image on the first surface of a light-transmitting medium, A luminous image forming unit capable of forming a luminous image on the second surface, which is the opposite surface to the first surface, The non-luminous image forming unit and the control unit that controls the luminous image forming unit. Equipped with, The aforementioned printer driver When the non-glossy image and the glossy image are placed facing each other on the light-transmitting medium, print data is generated that includes image data for forming the non-glossy image on the first surface of the light-transmitting medium, and image data that adjusts the amount of the glossy image formed on the second surface of the light-transmitting medium for forming a first region on the second surface of the light-transmitting medium where the transmittance of white light passing through the glossy image and the non-glossy image is a first transmittance, and a second region where the transmittance is a second transmittance higher than the first transmittance, and this data is sent to the image forming apparatus. The control unit, Based on the print data sent from the above-level device, the non-glossy image forming unit and the glossy image forming unit are controlled to form the non-glossy image on the first surface of the light-transmitting medium and the glossy image on the second surface of the light-transmitting medium. A printing system characterized by the following features.

Images