Image forming apparatus and image forming method

Abstract

To enable a surface temperature of a recording medium to rise up to a proper temperature in a case where the recording medium such as a tack paper having a multilayer structure is used so as to achieve a proper diameter of ink.SOLUTION: An image forming device 1 conveys a recording medium 9 along a predetermined conveyance passage and performs image formation by ejecting ink from an inkjet head 51 to a surface of the recording medium 9 when the recording medium 9 passes a predetermined drawing position. The image forming device 1 comprises a first heating part 31, provided at an upstream side of the drawing position on the conveyance passage, and heating the recording medium 9, and a controller 7 that controls the first heating part 31. The first heating part 31 has a front surface heating part 32 that heats a front face side of the recording medium 9 and a back face heating part 33 that heats a back face side of the recording medium 9. The controller 7 controls temperatures of the front face heating part 32 and the back face heating part 33 individually in a case where the recording medium 9 has a multilayer structure.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus and an image forming method for forming an image on a recording medium by an inkjet system. [Background technology]

[0002] An inkjet type image forming apparatus that ejects solvent-based ink to form an image on a recording medium transports a recording medium such as printing paper along a predetermined transport path, and ejects ink that is molten at a high temperature when the recording medium passes a predetermined drawing position to form an image on the surface of the recording medium. The ink that lands on the surface of the recording medium spreads over a certain area on the surface of the recording medium, resulting in a predetermined ink diameter and forming an image with a predetermined resolution.

[0003] The way ink that lands on the surface of the recording medium spreads varies depending on the temperature. For example, if the temperature of the recording medium is low, the ink that lands on the surface of the recording medium hardens immediately, resulting in a state in which the ink diameter does not fill a certain area, which causes deterioration of image quality. If the temperature of the recording medium is too high, the ink that lands on the surface of the recording medium spreads beyond a certain area, which causes the ink diameter to increase and causes bleeding in the image, which also causes deterioration of image quality.

[0004] Meanwhile, there are known techniques for heating a recording medium before the recording medium transported along a transport path reaches a drawing position (e.g., Patent Documents 1 and 2). These conventional techniques all heat the recording medium before it reaches the drawing position, thereby controlling the surface temperature of the recording medium to a predetermined temperature. This makes it possible to prevent, to a certain extent, the ink diameter of the ink that lands on the surface of the recording medium at the drawing position from becoming too small or too large. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-54437 A [Patent Document 2] JP 2014-139011 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, when forming an image using a recording medium having a multi-layer structure, such as tack paper used in label printing, it is difficult to make the surface temperature of the recording medium pass the drawing position at a predetermined temperature with the temperature control of the above-mentioned conventional technology. Generally, tack paper has a three-layer structure, with fine paper or film provided on the front side where ink adheres, an adhesive layer as an intermediate layer, and release paper or the like provided on the back side. The thickness of each layer varies depending on the type of recording medium, but generally, the thickness of the fine paper or film on the front side is the thickest, and the adhesive layer and release paper are thinner than that. In such a recording medium having a multi-layer structure, the materials and thicknesses of each layer are different, so that the heat transfer coefficients of each layer are different. In particular, the adhesive layer contains impurities and minute cavities, which cause unevenness in the heat transfer coefficient of the recording medium. Therefore, it is difficult to raise the surface of the recording medium to a predetermined temperature just by heating both the front and back sides of the recording medium evenly. Therefore, in the conventional technology, when a recording medium having a multi-layer structure such as tack paper is used as the recording medium, it is difficult to achieve an appropriate ink diameter, which causes a problem of image quality deterioration.

[0007] Therefore, the present invention has been made to solve the above problems, and aims to provide an image forming apparatus and an image forming method that are capable of raising the surface temperature of the recording medium to an appropriate temperature and achieving an appropriate ink diameter when a recording medium having a multi-layer structure such as tack paper is used. [Means for solving the problem]

[0008] In order to achieve the above object, the invention according to claim 1 is an image forming apparatus which transports a recording medium along a predetermined transport path and forms an image by ejecting ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, the image forming apparatus comprising: a first heating means which is provided on the transport path upstream of the drawing position and which heats the recording medium; and a control means which controls the first heating means, the first heating means having a surface heating means which heats a surface side of the recording medium and a back heating means which heats a back side of the recording medium, and the control means controls the first heating means when the recording medium is a medium having a multi-layer structure. a temperature to which the surface heating means is heated is set according to the characteristics of the recording medium; The temperatures of the front surface heating means and the back surface heating means are controlled separately. The characteristics of the recording medium include the material and thickness of each layer forming the multi-layer structure. The configuration is characterized by the above. The invention of claim 2 is an image forming device that transports a recording medium along a predetermined transport path and forms an image by ejecting ink onto the surface of the recording medium when the recording medium passes a predetermined drawing position, the image forming device comprising: a first heating means that is provided upstream of the drawing position on the transport path and heats the recording medium; and a control means that controls the first heating means, the first heating means having a surface heating means that heats the surface side of the recording medium and a back side heating means that heats the back side of the recording medium, the control means being configured to individually control the temperatures of the surface heating means and the back side heating means when the recording medium is a medium having a multi-layer structure, and to set the transport speed of the recording medium in accordance with the characteristics of the recording medium, the characteristics of the recording medium including the material and thickness of each layer that forms the multi-layer structure. The invention of claim 3 is an image forming device that transports a recording medium along a predetermined transport path and forms an image by ejecting ink onto the surface of the recording medium when the recording medium passes a predetermined drawing position, and is equipped with a first heating means that is provided upstream of the drawing position on the transport path and heats the recording medium, a control means that controls the first heating means, and a temperature measuring means that measures the surface temperature and back temperature of the recording medium transported along the transport path, wherein the first heating means has a surface heating means that heats the surface side of the recording medium and a back side heating means that heats the back side of the recording medium, and the control means is configured to individually control the temperature of the surface heating means and the back side heating means when the recording medium is a medium having a multi-layer structure, and is characterized in that the temperature of the surface heating means is adjusted based on the surface temperature and back side temperature of the recording medium measured by the temperature measuring means. The invention of claim 4 is an image forming device that transports a recording medium along a predetermined transport path and forms an image by ejecting ink onto the surface of the recording medium when the recording medium passes a predetermined drawing position, and is equipped with a first heating means that is provided upstream of the drawing position on the transport path and heats the recording medium, a control means that controls the first heating means, and a temperature measuring means that measures the surface temperature and back temperature of the recording medium transported along the transport path, wherein the first heating means has a surface heating means that heats the surface side of the recording medium and a back side heating means that heats the back side of the recording medium, and the control means controls the temperatures of the surface heating means and the back side heating means individually when the recording medium is a medium having a multi-layer structure, and adjusts the transport speed of the recording medium based on the surface temperature and back side temperature of the recording medium measured by the temperature measuring means.

[0009] Claim 5 The invention according to claim 1 or 4 In the image forming apparatus, the control means raises the temperature of the back surface heating means to a predetermined target temperature, and raises the temperature of the front surface heating means to a temperature higher than the target temperature.

[0010] Claim 6 The invention according to claim 1 or 5 In the image forming apparatus, the control means is configured to control the surface temperature and the back surface temperature of the recording medium to match a predetermined target temperature when the recording medium reaches the drawing position.

[0011] Claim 7 The invention relates to claims 1 to 6 In any one of the image forming apparatuses, a second heating means is provided between the first heating means and the drawing position, for heating the back side of the recording medium, and the control means is further configured to control the second heating means.

[0012] Claim 8 The invention according to claim7 In the image forming apparatus, the control means is configured to raise the temperature of the second heating means to a predetermined target temperature.

[0013] Claim 9 The invention according to claim 7 or 8 In the image forming apparatus, the control means controls the second heating means to cause the recording medium to reach the drawing position while maintaining the surface temperature of the recording medium at a predetermined target temperature.

[0014] Claim 10 The invention relates to claims 1 to 9 In any one of the image forming apparatuses described above, the image forming apparatus further comprises a fixing means provided downstream of the drawing position on the transport path for fixing ink ejected onto the front surface of the recording medium, and a third heating means provided between the drawing position and the fixing means for heating the rear surface of the recording medium, and the control means is further configured to control the third heating means.

[0015] Claim 11 The invention according to claim 10 In the image forming apparatus, the control means is configured to raise the temperature of the third heating means to a predetermined target temperature.

[0016] Claim 12 The invention according to claim 10 In the image forming apparatus, the control means calculates a drawing rate for the recording medium based on image data to be printed, and sets the temperature of the third heating means based on the drawing rate.

[0017] Claim 13 The invention according to claim 10 ~ 12In any one of the image forming apparatuses, the control means controls the third heating means to cause the recording medium to reach the fixing means while maintaining the surface temperature of the recording medium at a predetermined target temperature.

[0023] Claim 14 The invention according to claim 1 or 2 In the image forming apparatus, for each type of the recording medium, characteristic information of the recording medium and an ideal temperature for the recording medium are stored. change and a storage means for storing medium information associated with control information for realizing the above, wherein when a medium in which the medium information is already stored in the storage means is specified as the recording medium, the control means reads out the medium information from the storage means and controls the temperatures of the front surface heating means and the back surface heating means individually based on the control information.

[0024] Claim 15 The invention according to claim 14 In the image forming apparatus, a temperature measuring unit is further provided for measuring a front surface temperature and a rear surface temperature of the recording medium conveyed along the conveying path at a plurality of points, and the control unit is configured to determine a temperature of the recording medium based on the front surface temperature and the rear surface temperature of the recording medium measured at the plurality of points on the conveying path by the temperature measuring unit. Shows actual temperature change The configuration is characterized in that a temperature profile is created and stored in the storage means.

[0025] Claim 16 The invention according to claim 15 In the image forming apparatus, when a new medium for which the medium information is not stored in the storage means is specified as the recording medium, the control means determines an ideal temperature corresponding to the new medium based on the medium information already stored in the storage means and the temperature profile. change Determine the temperature change The temperature to be increased by the surface heating means is set based on the above.

[0027] Claim17 The present invention relates to an image forming method for forming an image by conveying a recording medium along a predetermined conveying path and discharging ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, the method including a first heating step of heating the recording medium upstream of the drawing position, the first heating step being, when the recording medium is a medium having a multi-layer structure, setting a temperature of the front side of the recording medium in accordance with the characteristics of the recording medium; The front side and the back side of the recording medium are heated to different temperatures. The characteristics of the recording medium include the material and thickness of each layer forming the multi-layer structure. The configuration is characterized by the above. The invention of claim 18 is an image forming method for forming an image by transporting a recording medium along a predetermined transport path and ejecting ink onto a surface of the recording medium as the recording medium passes a predetermined drawing position, the method comprising: a first heating step of heating the recording medium upstream of the drawing position; and a step of setting a transport speed of the recording medium according to characteristics of the recording medium, wherein, when the recording medium is a medium having a multi-layer structure, the first heating step heats the front side and the back side of the recording medium to different temperatures, and the characteristics of the recording medium include the material and thickness of each layer forming the multi-layer structure. The invention of claim 19 is an image forming method for forming an image by transporting a recording medium along a predetermined transport path and ejecting ink onto a surface of the recording medium as the recording medium passes a predetermined drawing position, the method comprising: a first heating step for heating the recording medium upstream of the drawing position; and a temperature measurement step for measuring the surface temperature and back temperature of the recording medium transported along the transport path, wherein the first heating step is characterized in that, when the recording medium is a medium having a multi-layer structure, the front and back sides of the recording medium are heated to different temperatures, and the temperature to which the front side of the recording medium is heated is adjusted based on the surface temperature and back temperature of the recording medium measured by the temperature measurement step. The invention of claim 20 is an image forming method for forming an image by transporting a recording medium along a predetermined transport path and ejecting ink onto a surface of the recording medium as the recording medium passes a predetermined drawing position, the method comprising: a first heating step of heating the recording medium upstream of the drawing position; a temperature measurement step of measuring the surface temperature and back surface temperature of the recording medium transported along the transport path; and a step of adjusting the transport speed of the recording medium based on the surface temperature and back surface temperature of the recording medium measured by the temperature measurement step, wherein the first heating step is characterized in that when the recording medium is a medium having a multi-layer structure, the front side and back side of the recording medium are heated to different temperatures.

[0028] The invention according to claim 21 is Any of 17 to 20 In the image forming method, the first heating step is characterized in that the back side of the recording medium is heated to a predetermined target temperature, and the front side of the recording medium is heated to a temperature higher than the target temperature.

[0029] The invention according to claim 22 is Any of 17 to 21 This image forming method is characterized in that it further comprises a second heating step of heating the back side of the recording medium in the section until the recording medium reaches the drawing position after the first heating step.

[0030] The invention according to claim 23 is the image forming method according to claim 22, characterized in that the second heating step maintains the back side of the recording medium at a predetermined target temperature.

[0031] The invention according to claim 24 is 17 24. In any one of the image forming methods to 23, the method further comprises a third heating step of heating the back side of the recording medium in the section until the recording medium passes through the drawing position and reaches a fixing means downstream.

[0032] The invention according to claim 25 is the image forming method according to claim 24, characterized in that the third heating step maintains the back side of the recording medium at a predetermined target temperature.

[0033] The invention of claim 26 is an image forming method of any of claims 20 to 25, characterized in that the first heating process sets the temperature of the surface side of the recording medium in accordance with the characteristics of the recording medium.

[0034] The invention of claim 27 is characterized in that, in the image forming method of any of claims 20 to 26, it further comprises a step of setting a conveying speed of the recording medium in accordance with the characteristics of the recording medium.

[0035] The invention according to claim 28 is the image forming method according to claim 26 or 27, characterized in that the characteristics of the recording medium include the material and thickness of each layer forming the multi-layer structure.

[0036] The invention of claim 29 is an image forming method according to any of claims 20 to 28, further comprising a temperature measurement process for measuring the surface temperature and back surface temperature of the recording medium transported along the transport path, and the first heating process is characterized in that it adjusts the temperature to which the surface side of the recording medium is heated based on the surface temperature and back surface temperature of the recording medium measured by the temperature measurement process.

[0037] The invention of claim 30 is an image forming method according to any one of claims 20 to 28, further comprising a temperature measurement step of measuring the surface temperature and the back surface temperature of the recording medium transported along the transport path, and a step of adjusting the transport speed of the recording medium based on the surface temperature and the back surface temperature of the recording medium measured by the temperature measurement step. Effect of the Invention

[0038] According to the present invention, when a recording medium having a multilayer structure such as tack paper is used, it is possible to raise the surface temperature of the recording medium to an appropriate temperature, making it possible to form an image with an appropriate ink diameter. [Brief description of the drawings]

[0039] [Figure 1] FIG. 1 illustrates an example of a configuration of an image forming apparatus. [Diagram 2] 1A and 1B are diagrams illustrating an example of a cross-sectional structure of a single-layer recording medium and an ideal temperature profile thereof. [Diagram 3] 1A and 1B are diagrams showing an example of a cross-sectional structure of a recording medium having a multi-layer structure and an ideal temperature profile thereof; [Figure 4] FIG. 2 is a block diagram showing a configuration example of a controller. [Diagram 5] 10 is a flowchart illustrating an example of a processing procedure by a controller. [Figure 6] 13A to 13C are diagrams showing screen transitions when a user specifies a recording medium. [Figure 7] 10 is a flowchart showing a processing procedure performed by the controller when a new recording medium is designated by a user. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0040] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following embodiments, elements common to each other are designated by the same reference numerals, and redundant description thereof will be omitted.

[0041] 1 is a diagram showing an example of the configuration of an image forming apparatus 1 according to one embodiment of the present invention. This image forming apparatus 1 is an apparatus that transports a recording medium 9 along a predetermined transport path and forms an image on the recording medium 9 by ejecting a solvent-based ink onto the surface of the recording medium 9 at a predetermined drawing position within the transport path. As an example, this embodiment will be described taking as an example an apparatus in which the image forming apparatus 1 transports a long web-like recording medium 9 by a roll-to-roll method and ejects ink onto the surface of the long web-like recording medium 9 to form an image.

[0042] The image forming apparatus 1 includes a paper feed section 2, a preheat section 3, a leveling section 4, an image forming section 5, a collection section 6, and a controller 7. The image forming apparatus 1 transports a recording medium 9 in the direction indicated by an arrow F from the paper feed section 2 to the collection section 6. In the transport path formed between the paper feed section 2 and the collection section 6, the preheat section 3, the leveling section 4, and the image forming section 5 are arranged in this order from the upstream side in the transport direction of the recording medium 9.

[0043] The paper feed unit 2 is for supplying the recording medium 9 toward the transport path. The paper feed unit 2 includes a paper feed roller 21 around which the web-like recording medium 9 is wound, a roller 22, and a motor 23 that drives the paper feed roller 21. For example, the motor 23 drives and rotates the shaft core of the paper feed roller 21, thereby sending out the web-like recording medium 9 toward the transport path via the roller 22. The paper feed unit 2 feeds the recording medium 9 with the surface (the surface on which an image is formed with ink) facing upward.

[0044] The preheating section 3 is for heating the recording medium 9 supplied from the paper feed section 2. The preheating section 3 has a first heating section 31. The first heating section 31 is capable of simultaneously heating both the front and back sides of the recording medium 9. Specifically, the first heating section 31 includes a front heating section 32 and a back heating section 33 that are arranged to face each other across the transport path of the recording medium 9. The front heating section 32 heats the front side of the recording medium 9. The back heating section 33 heats the back side of the recording medium 9. For example, the front heating section 32 and the back heating section 33 are configured as planar heaters, and multiple rod-shaped heaters 34 are built into the inside of a metal plate member with high thermal conductivity. The multiple rod-shaped heaters 34 are driven to uniformly heat the surface of the metal plate member facing the transport path. A gap is formed between the front heating section 32 and the back heating section 33 at a predetermined interval through which the recording medium 9 can pass, and the transport path is formed by the gap. This preheating section 3 is provided in a section of a predetermined length along the transport direction of the recording medium 9. Therefore, the preheating section 3 can continuously heat the front and back surfaces of the recording medium 9 while the recording medium 9 is transported in the section of the predetermined length.

[0045] The leveling unit 4 is provided to uniformly level the temperature of the recording medium 9 heated by the preheating unit 3, and is provided downstream of the preheating unit 3 in the transport direction of the recording medium 9. The leveling unit 4 includes temperature sensors 41 and 42 that measure the temperature of the recording medium 9 sent out from the preheating unit 3, a second heating unit 43 that heats the back side of the recording medium 9, and temperature sensors 44 and 45 that measure the temperature of the recording medium 9 immediately before it enters the image forming unit 5. The leveling unit 4 is provided in a section of a predetermined length along the transport direction of the recording medium 9.

[0046] The temperature sensor 41 measures the surface temperature of the recording medium 9 immediately after it has passed through the preheating unit 3. Moreover, the temperature sensor 42 measures the back surface temperature of the recording medium 9 immediately after it has passed through the preheating unit 3. These temperature sensors 41, 42 are installed, for example, at multiple locations in the width direction (direction perpendicular to the transport direction) of the recording medium 9. The temperature sensors 41, 42 may be contact sensors that measure the temperature by contacting the front or back surface of the recording medium 9, or may be non-contact sensors such as infrared sensors.

[0047] The second heating section 43 is disposed below the conveying path of the recording medium 9 and heats the back side of the recording medium 9. The second heating section 43 includes a plurality of heaters 43a, 43b, and 43c that heat the back side of the recording medium 9. These heaters 43a, 43b, and 43c are configured as planar heaters, for example, similar to the back heating section 33 of the first heating section 31, and a plurality of rod-shaped heaters are built inside a metal plate member having high thermal conductivity, so that the upper surface of the metal plate member can be heated evenly. When the recording medium 9 is conveyed along the conveying path, it is conveyed to a position close to the upper surface of the second heating section 43 constituted by the heaters 43a, 43b, and 43c when it is conveyed through the leveling section 4. In this embodiment, the second heating section 43 is configured by a plurality of heaters 43a, 43b, and 43c arranged along the conveying path, but this is not limited thereto, and it may be configured by one heater. In this case, one heater is disposed in a range capable of covering the entire area from the start point to the end point of the leveling unit 4 in the conveying direction of the recording medium 9.

[0048] Temperature sensor 44 measures the surface temperature of recording medium 9 just before it passes through leveling section 4 and enters image forming section 5. Temperature sensor 45 measures the back surface temperature of recording medium 9 just before it passes through leveling section 4 and enters image forming section 5. Similar to the above-mentioned temperature sensors 41 and 42, these temperature sensors 44 and 45 are also installed at multiple locations in the width direction (direction perpendicular to the transport direction) of recording medium 9. Furthermore, temperature sensors 44 and 45 may be contact sensors or non-contact sensors.

[0049] The image forming unit 5 is a processing unit that forms an image with ink on the surface of the recording medium 9 downstream of the leveling unit 4. The image forming unit 5 includes an inkjet head 51 that is arranged upstream in the transport direction of the recording medium 9, a third heating unit 52 that heats the back side of the recording medium 9, and a fixing unit 53 that is arranged downstream in the transport direction of the recording medium 9. The image forming unit 5 is provided in a section of a predetermined length along the transport direction of the recording medium 9.

[0050] The inkjet head 51 is provided above a drawing position defined in the transport path of the recording medium 9. The inkjet head 51 forms an image corresponding to image data to be printed by ejecting ink onto the surface of the recording medium 9 passing through the drawing position. For example, in this embodiment, the drawing position is provided at a position immediately after the end of the smoothing section by the smoothing unit 4. In addition, in this embodiment, since a solvent-based ink is used, the inkjet head 51 holds the ink in a molten state at a high temperature and ejects the molten ink droplets. The inkjet head 51 is filled with four colors of ink, yellow (Y), magenta (M), cyan (C), and black (K), and has a large number of nozzles that can eject the ink of each color individually. The large number of nozzles are arranged at predetermined intervals along the width direction (main scanning direction) of the recording medium 9. Therefore, the inkjet head 51 can form a color image on the recording medium 9.

[0051] The third heating section 52 includes a plurality of heaters 52a, 52b, and 52c for heating the back side of the recording medium 9. The heaters 52a, 52b, and 52c are configured as planar heaters, for example, similar to the second heating section 43, and a plurality of rod-shaped heaters are built inside a metal plate member with high thermal conductivity. When the recording medium 9 is transported along the transport path and transported through the image forming section 5, the recording medium 9 is transported to a position close to the upper surface of the third heating section 52, which is configured by the heaters 52a, 52b, and 52c. In this embodiment, the third heating section 52 is also configured by a plurality of heaters 52a, 52b, and 52c, similar to the second heating section 43, but this is not limited to this, and the third heating section 52 may be configured by one heater. In this case, one heater is disposed in a range that can cover the start point to the end point of the image forming section 5 in the transport direction of the recording medium 9.

[0052] The fixing unit 53 is disposed downstream of the inkjet head 51 and at the end position of the image forming unit 5. The fixing unit 53 fixes the ink ejected onto the surface of the recording medium 9 to the surface of the recording medium 9. For example, the ink used in this embodiment is a UV ink that has the property of being cured by irradiation with ultraviolet rays. Therefore, the fixing unit 53 is provided at a position above the transport path, and cures the ink by irradiating ultraviolet rays onto the surface of the recording medium 9 onto which the ink has been ejected, thereby fixing the ink to the surface of the recording medium 9.

[0053] The recovery unit 6 is for recovering the recording medium 9 on whose surface an image has been formed with ink, and includes a roller 61, a winding roller 62, and a motor 63. The recording medium 9 sent out from the image forming unit 5 advances via the roller 61 in the direction in which the winding roller 62 is located, and is wound around the winding roller 62 in sequence. For example, the motor 63 can rotate the shaft core of the winding roller 62 to wind the recording medium 9 around the winding roller 62.

[0054] The rollers 22 of the paper feed unit 2 and the rollers 61 of the recovery unit 6 apply a certain tension to the recording medium 9 which is transported along the transport path through the preheat unit 3, the leveling unit 4, and the image forming unit 5 in sequence. Therefore, the recording medium 9 is designed to maintain a certain positional relationship with respect to each of the first heating unit 31, the second heating unit 43, and the third heating unit 52 when passing through each of the preheat unit 3, the leveling unit 4, and the image forming unit 5.

[0055] The controller 7 is a control means for controlling the operation of each of the above-mentioned parts. For example, the controller 7 controls the motors 23 and 63 to control the transport speed of the recording medium 9. The controller 7 also controls the first heating section 31, the second heating section 43, and the third heating section 52 to control the temperature of the recording medium 9 transported along the transport path. The controller 7 can determine whether the actual temperature profile of the recording medium 9 is an ideal temperature profile based on the temperature of the recording medium 9 measured by the temperature sensors 41, 42, 44, and 45, and can control the first heating section 31, the second heating section 43, and the third heating section 52 so that the actual temperature profile of the recording medium 9 becomes the ideal temperature profile, and can also adjust the transport speed of the recording medium 9. When controlling the first heating section 31, the controller 7 can apply the same temperature control to the front heating section 32 and the back heating section 33, and can also apply individual temperature control to the front heating section 32 and the back heating section 33.

[0056] The controller 7 also controls the inkjet head 51 to maintain the ink filled in the head at a predetermined temperature and to eject the ink based on image data to be printed. Furthermore, the controller 7 controls the fixing unit 53 to irradiate the recording medium 9 with ultraviolet light and fix the image formed by the ink on the recording medium 9.

[0057] The image forming apparatus 1 configured as above can use a medium having a single layer structure such as plain paper as the recording medium 9, and can also use a medium having a multi-layer structure such as tack paper. The ink discharged from the inkjet head 51 is in a high temperature state, for example, about 80°C. The higher the temperature of the molten ink, the higher the fluidity, and the lower the temperature, the lower the fluidity. Therefore, the controller 7 controls the ink diameter of the ink that has landed on the surface of the recording medium 9 by appropriately managing the surface temperature of the recording medium 9. For example, if the surface temperature of the recording medium 9 needs to be kept within a range of 40 to 45°C to achieve an appropriate ink diameter, the target temperature of the recording medium 9 is 42 to 43°C. In this case, the controller 7 controls the surface temperature of the recording medium 9 to reach the target temperature by the time the recording medium 9 fed from the paper feed unit 2 reaches the drawing position by the inkjet head 51.

[0058] 2(a) shows the cross-sectional structure of a single-layered recording medium 9. As shown in FIG. 2(a), the inside of the single-layered recording medium 9 is made of one material, so the heat transfer coefficient of the recording medium 9 is uniform. Therefore, the controller 7 evenly controls the front-side heating section 32 and the back-side heating section 33 of the first heating section 31. That is, when the recording medium 9 passes through the preheat section 3, the controller 7 evenly heats the front and back sides of the recording medium 9, thereby controlling the temperature of the entire recording medium 9, including the front, inside, and back side, to be uniformly set to a predetermined target temperature (e.g., 43°C).

[0059] FIG. 2(b) shows an example of an ideal temperature profile for a single-layered recording medium 9. The temperature profile shown in FIG. 2(b) is a profile in which the surface temperature T10 of the recording medium 9 is raised to a predetermined target temperature in the preheating section 3, and the surface temperature is maintained in the acclimatization section 4. In order to realize this temperature profile, when the recording medium 9 is heated by the first heating section 31 of the preheating section 3, the controller 7 controls the heating of the front heating section 32 and the back heating section 33 to an equal temperature. At this time, the controller 7 raises the surface temperature of the recording medium 9 from room temperature (e.g., 25° C.) to a predetermined target temperature (e.g., 43° C.) while the recording medium 9 is passing through the preheating section by the preheating section 3, by raising the temperature of both the front heating section 32 and the back heating section 33 to a temperature higher than the target temperature of the recording medium 9. The controller 7 then sets the temperature of the second heating section 43 provided in the acclimatization section 4 to the target temperature of the recording medium 9 (e.g., 43° C.), and continues heating the recording medium 9 in the acclimatization section 4. As a result, the surface temperature T10 of the recording medium 9 is maintained at the target temperature in the leveling unit 4. Therefore, when the recording medium 9 reaches the position for drawing by the inkjet head 51, it is possible to maintain the surface temperature of the recording medium 9 at a predetermined target temperature, and the area in which the ink that has landed on the surface of the recording medium 9 spreads can be made to be a constant area, thereby realizing an appropriate ink diameter.

[0060] Next, FIG. 3(a) shows a cross-sectional structure of a recording medium 9 having a multi-layer structure such as tack paper. FIG. 3(a) shows a recording medium 9 having a three-layer structure. As shown in FIG. 3(a), the recording medium 9 having a three-layer structure has a first layer 9a made of fine paper or film arranged on the front side, a second layer 9b made of adhesive arranged as an intermediate layer, and a third layer 9c made of release paper arranged on the back side. In this recording medium 9, the materials and thicknesses of the layers are different. In particular, the first layer 9a is the thickest, and the second layer 9b and the third layer 9c are formed thinner than the first layer 9a. In such a recording medium 9, the heat transfer coefficients of the layers are different. Therefore, even if the front side and the back side of the recording medium 9 are heated evenly, the front temperature and the back temperature of the recording medium 9 cannot be raised evenly. When ink is discharged onto the surface of the recording medium 9 having a multi-layer structure such as tack paper, it is preferable to manage not only the surface of the recording medium 9 but also the back side and the inside of the recording medium so that they reach a predetermined target temperature. Even if only the surface side reaches the target temperature, if the back side temperature and the inside temperature do not reach the target temperature, the surface temperature will drop immediately and the ink will not be able to spread over a certain area. Therefore, the controller 7 of this embodiment is configured to individually control the front side heating section 32 and the back side heating section 33 of the first heating section 31 when the recording medium 9 having a multi-layer structure is used. Specifically, since the heat capacity of the first layer 9a is larger than that of the second layer 9b and the third layer 9c, the controller 7 controls the recording medium 9 to give a strong amount of heat to the front side and a weaker amount of heat to the back side when the recording medium 9 passes through the preheat section 3. Then, the controller 7 controls the front side, the inside, and the back side of the recording medium 9 to reach a predetermined target temperature in the smoothing section 4.

[0061] Fig. 3(b) shows an example of an ideal temperature profile of the recording medium 9 having a multi-layer structure. The temperature profile shown in Fig. 3(b) shows a surface temperature T20 of the first layer 9a, a temperature T21 of the boundary between the first layer 9a and the second layer 9b, a temperature T223 of the boundary between the second layer 9b and the third layer 9c, and a back surface temperature T23 of the third layer 9c. In this temperature profile, the surface temperature T20 of the recording medium 9 is raised to a temperature higher than a predetermined target temperature (e.g., 43°C) in the preheating section by the preheating unit 3, and the back surface temperature T23 is raised to a temperature lower than the predetermined target temperature, and then, in the acclimatization section by the acclimatization unit 4, the surface temperature T20 and the back surface temperature T23 of the recording medium 9 are made to coincide with the predetermined target temperature.

[0062] In order to realize this temperature profile, when the recording medium 9 is heated by the first heating section 31 of the preheating section 3, the controller 7 sets the set temperature of the front heating section 32 and the set temperature of the back heating section 33 to different temperatures, and controls the front heating section 32 and the back heating section 33 individually. Specifically, the controller 7 controls the back heating section 33 to rise to a predetermined target temperature (e.g., 43°C), and the front heating section 32 to a temperature higher than the target temperature (e.g., about 70°C). That is, the controller 7 sets the temperature of the front heating section 32 to a temperature higher than the predetermined target temperature, and sets the temperature of the back heating section 33 to the predetermined target temperature, and simultaneously heats both the front and back sides of the recording medium 9. As a result, in the preheating section, the front side of the recording medium 9 is heated by the front heating section 32, and the surface temperature T20 is heated to a temperature higher than the predetermined target temperature. On the other hand, the back side of the recording medium 9 is heated by the back heating section 33, and therefore the temperature rise rate is lower than that of the front side. In addition, since the recording medium 9 passes through the preheat section in about 0.5 seconds, the back surface heating unit 33 cannot raise the back surface temperature T23 of the recording medium 9 to the predetermined target temperature, and heats the recording medium 9 to a temperature lower than the predetermined target temperature. Therefore, as shown in FIG. 3(b), the recording medium 9 immediately after passing through the preheat section is in a state in which the surface temperature T20 has risen to a temperature higher than the target temperature, and the back surface temperature T23 has risen to a temperature lower than the target temperature. At this time, the boundary temperatures T21 and T22 inside the recording medium 9 are between the surface temperature T20 and the back surface temperature T23. In addition, the boundary temperature T21 between the first layer 9a and the second layer 9b is higher than the boundary temperature T22 between the second layer 9b and the third layer 9c.

[0063] The controller 7 performs the heating as described above in the preheat section, and then heats only the back side of the recording medium 9 in the leveling section so that the front temperature T20 and the back temperature T23 of the recording medium 9 match each other at a target temperature (e.g., 43°C). At this time, the controller 7 sets the temperatures of the multiple heaters 43a, 43b, and 43c of the second heating section 43 to a predetermined target temperature (e.g., 43°C) and heats only the back side of the recording medium 9.

[0064] In the break-in section, the surface side of the recording medium 9 is not heated and heat is released, so that the temperature of the surface side, which has been heated to a temperature higher than the target temperature by the preheat unit 3, gradually drops. Therefore, when the recording medium 9 enters the break-in section, the surface temperature T20 of the recording medium 9 gradually drops, as shown in Fig. 3(b). Then, when the break-in section ends, the surface temperature T20 of the recording medium 9 coincides with the target temperature.

[0065] On the other hand, the back side of the recording medium 9 is continuously heated by the second heating unit 43. Therefore, even after the recording medium 9 enters the break-in period, the back side temperature T23 of the recording medium 9 continues to rise. Then, when the break-in period ends, the back side temperature T23 of the recording medium 9 reaches the target temperature.

[0066] Therefore, when the smoothing section is completed, both the surface temperature T20 and the backside temperature T23 of the recording medium 9 coincide with the target temperature. At this time, the boundary temperatures T21 and T22 inside the recording medium 9 also coincide with the target temperature, and the temperature inside the recording medium 9 is equalized to a state in which there is no temperature unevenness. In other words, when an image is formed using the recording medium 9 having a multi-layer structure, the controller 7 controls each of the first heating section 31 and the second heating section 43 so as to obtain a temperature profile as shown in FIG. 3(b), and when the recording medium 9 reaches the drawing position, both the surface temperature T20 and the backside temperature T23 of the recording medium 9 coincide with a predetermined target temperature (for example, 43° C.). As a result, even when a recording medium 9 having a multi-layer structure is used, it is possible to raise the surface temperature T20 of the recording medium 9 to a predetermined target temperature when the recording medium 9 reaches the drawing position, and an appropriate ink diameter can be achieved.

[0067] During the transport of the recording medium 9 having a multi-layer structure, the controller 7 acquires the surface temperature T20 and the back surface temperature T23 of the recording medium 9 measured by the temperature sensors 41, 42, 44, and 45. Based on the actually measured surface temperature T20 and back surface temperature T23, the controller 7 creates an actual temperature profile from when the recording medium 9 enters the preheat section to when it reaches the drawing position, and judges whether the actual temperature profile matches the ideal temperature profile. If the actual temperature profile does not match the ideal temperature profile, the controller 7 adjusts either or both of the set temperature of the surface heating unit 32 and the transport speed of the recording medium 9 so that the actual temperature profile becomes the ideal temperature profile.

[0068] Furthermore, the controller 7 controls the third heating section 52 so that the surface temperature T20 of the recording medium 9 does not change suddenly after the image is formed with ink at the drawing position until the recording medium 9 passes through the fixing section 53. For example, the controller 7 sets the temperatures of the heaters 52a, 52b, and 52c of the third heating section 52 to a predetermined target temperature (e.g., 43°C) and heats only the back side of the recording medium 9. This maintains the warm state of the recording medium 9, making it possible to prevent the surface temperature T20 of the recording medium 9 from dropping suddenly before the recording medium 9 reaches the fixing section 53, and to maintain the surface temperature T20 of the recording medium 9 at a constant state until the recording medium 9 has passed through the fixing section 53.

[0069] Incidentally, the ink discharged onto the surface of the recording medium 9 at the drawing position is in a high temperature state of about 80°C. Therefore, when a large amount of ink is discharged onto the surface of the recording medium 9, the surface temperature T20 of the recording medium 9 temporarily rises, and a phenomenon that the ink diameter becomes large may occur. To prevent this, the controller 7 may calculate the drawing ratio (the ratio of the drawing area to the entire paper surface) for the recording medium 9 based on the image data to be printed, and adjust the set temperature of the third heating unit 52 based on the drawing ratio. For example, when the drawing ratio is greater than a predetermined value, the controller 7 sets the set temperatures of the heaters 52a, 52b, and 52c in the third heating unit 52 to a temperature lower than a predetermined target temperature (for example, 43°C) to promote heat dissipation from the surface of the recording medium 9, thereby preventing the surface temperature T20 from temporarily becoming higher than the target temperature. At this time, the controller 7 may uniformly lower the set temperatures of the heaters 52a, 52b, and 52c, or may set only the set temperature of the heater 52a located directly below the inkjet head 51 to a lower temperature. Furthermore, the controller 7 may not only lower the set temperatures of the heaters 52a, 52b, and 52c, but also turn off the power to the heaters 52a, 52b, and 52c to stop the heating process.

[0070] Next, the controller 7 that performs the above control will be described in detail. FIG. 4 is a block diagram showing an example of the configuration of the controller 7. The controller 7 includes a processor 10, a storage unit 11, and an operation panel 12. The processor 10 is a hardware processor that performs various arithmetic processing for the above control by executing a predetermined computer-readable program. The storage unit 11 is a non-volatile storage device that is configured, for example, by a hard disk drive (HDD) or a solid state drive (SSD). The operation panel 12 is a user interface when a user operates the image forming apparatus 1.

[0071] The storage unit 11 stores medium information 13 related to the recording medium 9 that is registered in advance in the image forming apparatus 1. The medium information 13 includes characteristic information 14 indicating the characteristics of the recording medium 9, profile information 15 indicating an ideal temperature profile of the recording medium 9, and control information 16 for realizing the ideal temperature profile. The characteristic information 14 records information such as the material and thickness of each layer forming the multi-layer structure. The profile information 15 records a temperature profile such as that shown in FIG. 3(b). The control information 16 records information such as the set temperatures of the front heating unit 32 and the back heating unit 33 of the first heating unit 31, the set temperatures of the second heating unit 43, the set temperatures of the third heating unit 52, and the conveying speed of the recording medium 9.

[0072] The storage unit 11 also stores an actual temperature profile 17 that is created based on the temperatures measured by the temperature sensors 41, 42, 44, and 45 while the recording medium 9 is being transported.

[0073] The operation panel 12 includes a display unit 12a that displays a screen that can be operated by the user, and an operation unit 12b that accepts operations by the user. The user can use the operation panel 12 to select or specify the recording medium 9.

[0074] The processor 10 functions as an operation reception unit 71, a characteristics analysis unit 72, a print control unit 74, a temperature detection unit 77, and an adjustment unit 79 by executing a predetermined program.

[0075] The operation reception unit 71 receives a user's operation to select or specify a recording medium 9. For example, the operation reception unit 71 reads out the medium information 13 from the storage unit 11, and displays a list screen of recording media 9 registered in advance in the image forming apparatus 1 on the display unit 12a of the operation panel 12. The user can select a recording medium 9 to be used for image formation from the list screen.

[0076] The characteristic analysis unit 72 analyzes the characteristics of the recording medium 9 specified by the user, and sets the conveying speed and target temperature of the recording medium 9 based on the characteristics, and determines an ideal temperature profile corresponding to the recording medium 9. The characteristic analysis unit 72 then sets the temperatures to which the first heating unit 31, the second heating unit 43, and the third heating unit 52 are to be heated. For example, when a recording medium 9 registered in advance in the image forming apparatus 1 is selected by the user, the characteristic analysis unit 72 reads out the medium information 13 of the recording medium 9 selected by the user, and determines the conveying speed and target temperature of the recording medium 9 based on the control information 16 included in the medium information 13, and determines the set temperatures for each of the first heating unit 31, the second heating unit 43, and the third heating unit 52.

[0077] The characteristic analysis unit 72 includes an inference unit 73. When a new recording medium 9 is designated by a user, the inference unit 73 is a processing unit that infers an ideal temperature profile corresponding to the new recording medium 9. The details of the processing by the inference unit 73 will be described later.

[0078] The print control unit 74 controls printing on the recording medium 9 based on a job execution start instruction from a user. The print control unit 74 forms an image based on image data to be printed on the surface of the recording medium 9 by controlling the operations of the paper feed unit 2, the preheat unit 3, the leveling unit 4, the image forming unit 5, and the recovery unit 6. The print control unit 74 includes a heating control unit 75 and a speed control unit 76. The heating control unit 75 drives each of the first heating unit 31, the second heating unit 43, and the third heating unit 52 to raise the temperature to the temperature determined by the characteristic analysis unit 72, thereby controlling the heating process on the recording medium 9. The speed control unit 76 controls the transport speed of the recording medium 9.

[0079] The temperature detection unit 77 acquires the temperatures measured by the temperature sensors 41, 42, 44, and 45 while the recording medium 9 is being conveyed, and detects the front and back temperatures of the recording medium 9. The temperature detection unit 77 includes a profile creation unit 78. The profile creation unit 78 creates an actual temperature profile based on the front and back temperatures of the recording medium 9 measured by the temperature sensors 41, 42, 44, and 45. After creating the actual temperature profile, the profile creation unit 78 stores the temperature profile in the storage unit 11. Furthermore, after creating the actual temperature profile, the profile creation unit 78 compares the actual temperature profile with an ideal temperature profile. As a result, if the actual temperature profile does not match the ideal temperature profile, the profile creation unit 78 activates the adjustment unit 79.

[0080] When the actual temperature profile does not match the ideal temperature profile, the adjustment unit 79 adjusts the actual temperature profile to match the ideal temperature profile by rewriting the control information 16. For example, the adjustment unit 79 controls the actual temperature profile to match the ideal temperature profile by adjusting either or both of the set temperature of the surface heating unit 32 and the conveying speed of the recording medium 9, both of which are included in the control information 16.

[0081] FIG. 5 is a flowchart showing an example of a processing procedure by the controller 7. First, the controller 7 accepts a user's operation to specify the recording medium 9 (step S10). When the user specifies the recording medium 9, the controller 7 judges whether or not a recording medium 9 having a multi-layer structure has been specified (step S11). When the recording medium 9 having a multi-layer structure has been specified (YES in step S11), the controller 7 reads the medium information 13 from the storage unit 11 and analyzes the characteristics of the recording medium 9 based on the characteristic information 14 included in the medium information 13 (step S12). Then, the controller 7 sets the transport speed of the recording medium 9 based on the control information 16 included in the medium information 13 (step S13) and sets the target temperature of the recording medium 9 (step S14). Next, the controller 7 determines an ideal temperature profile based on the profile information 15 included in the medium information 13 (step S15). As a result, the temperature profile shown in FIG. 3(b) is determined as the ideal temperature profile.

[0082] Next, the controller 7 sets the temperature to which the back surface heating unit 33 of the first heating unit 31 is heated to the target temperature of the recording medium 9 based on the control information 16 (step S16). That is, the controller 7 makes the target temperature of the back surface heating unit 33 coincide with the target temperature of the recording medium 9. Also, the controller 7 sets the temperature to which the front surface heating unit 32 of the first heating unit 31 is heated to a temperature higher than the target temperature of the recording medium 9 based on the control information 16 (step S17). How much higher the front surface heating unit 32 is heated to than the target temperature of the recording medium 9 depends on the characteristics of the recording medium 9. However, since the temperature of the front surface heating unit 32 to be set to realize an ideal temperature profile is recorded in advance in the control information 16, the controller 7 sets the temperature recorded in the control information 16.

[0083] Next, the controller 7 sets the temperature to which each of the heaters 43a, 43b, and 43c constituting the second heating section 43 is heated to the target temperature of the recording medium 9 (step S18). Furthermore, the controller 7 sets the temperature to which each of the heaters 52a, 52b, and 52c constituting the third heating section 52 is heated to the target temperature of the recording medium 9 (step S19). However, as described above, the controller 7 may set the temperature to which each of the heaters 52a, 52b, and 52c is heated to a temperature lower than the target temperature of the recording medium 9 based on the drawing rate based on the image data.

[0084] When the temperature settings for the first heating unit 31, the second heating unit 43, and the third heating unit 52 are completed as described above, the controller 7 drives each of the first heating unit 31, the second heating unit 43, and the third heating unit 52 to perform warm-up before starting a printing operation. When the warm-up is completed, the controller 7 conveys the recording medium 9 and starts printing on the recording medium 9.

[0085] When the printing operation is started, the controller 7 measures the front and back temperatures of the recording medium 9 based on the outputs from the temperature sensors 41, 42, 44, and 45 (step S22), and creates an actual temperature profile (step S23). The controller 7 then compares the actual temperature profile with an ideal temperature profile, and determines whether adjustment is necessary (step S24). If adjustment is necessary (YES in step S24), the controller 7 adjusts either or both of the set temperature of the front surface heating unit 32 and the conveying speed of the recording medium 9, so that the actual temperature profile becomes the ideal temperature profile (step S25). If adjustment is not necessary (NO in step S24), step S25 is skipped.

[0086] After that, the controller 7 judges whether or not the printing is completed (step S26). If the printing is not completed, the controller 7 repeats the above-mentioned steps S22 to S25. Then, when the printing is completed, the processing by the controller 7 ends.

[0087] On the other hand, if the recording medium 9 specified by the user does not have a multi-layer structure (NO in step S11), the controller 7 determines that the recording medium 9 has a single-layer structure. In this case, the controller 7 reads the medium information 13 from the storage unit 11 and analyzes the characteristics of the recording medium 9 based on the characteristic information 14 included in the medium information 13 (step S31). Then, the controller 7 sets the transport speed of the recording medium 9 based on the control information 16 included in the medium information 13 (step S32) and sets the target temperature of the recording medium 9 (step S33). Next, the controller 7 determines an ideal temperature profile based on the profile information 15 included in the medium information 13 (step S34). As a result, the temperature profile shown in FIG. 2(b) is determined as the ideal temperature profile.

[0088] Then, the controller 7 sets the front surface heating unit 32 and the back surface heating unit 33 of the first heating unit 31 to a uniform temperature based on the control information 16 (step S35). At this time, the temperatures set for the front surface heating unit 32 and the back surface heating unit 33 are higher than the target temperature of the recording medium 9. How much higher the temperatures of the front surface heating unit 32 and the back surface heating unit 33 should be than the target temperature of the recording medium 9 depends on the characteristics of the recording medium 9. However, since the temperatures of the front surface heating unit 32 and the back surface heating unit 33 that should be set to realize an ideal temperature profile are recorded in advance in the control information 16, the controller 7 sets them to the temperatures recorded in the control information 16.

[0089] Next, the controller 7 sets the temperature to which each of the heaters 43a, 43b, and 43c constituting the second heating section 43 is heated to the target temperature of the recording medium 9 (step S18). Furthermore, the controller 7 sets the temperature to which each of the heaters 52a, 52b, and 52c constituting the third heating section 52 is heated to the target temperature of the recording medium 9 (step S19). However, as described above, the controller 7 may set the temperature to which each of the heaters 52a, 52b, and 52c is heated to a temperature lower than the target temperature of the recording medium 9 based on the drawing rate based on the image data.

[0090] Thereafter, the controller 7 performs the processes of steps S21 to S26 in the same manner as described above, and forms an image on the single-layered recording medium 9. However, if it is determined in step S24 that adjustment is necessary while printing is being performed on the single-layered recording medium 9, the controller 7 adjusts the set temperatures of both the front surface heating unit 32 and the back surface heating unit 33, rather than just the front surface heating unit 32.

[0091] By executing the above-mentioned process in the controller 7, it is possible to control the ink diameter of the ink ejected onto the recording medium 9 to a constant state, and it is possible to suppress deterioration of image quality. In particular, even if a recording medium 9 having a multi-layer structure is specified as the recording medium 9, an ideal temperature profile according to the characteristics of the recording medium 9 having a multi-layer structure is realized, so that it is possible to form a high-quality image on the surface of tack paper or the like.

[0092] Furthermore, in order to create an ideal temperature profile for the recording medium 9 having a multi-layer structure, the controller 7 employs a relatively simple control method in which the front surface heating section 32 and the back surface heating section 33 of the first heating section 31 are individually controlled, and the front surface heating section 32 is heated to a higher temperature than the back surface heating section 33. This has the advantage that there is no need for complex control, and the ink diameter can be maintained at a constant level without increasing the load on the processor 10.

[0093] Next, a process when a new recording medium 9 is specified by the user will be described. FIG. 6 is a diagram showing screen transitions when the user specifies the recording medium 9. When the user specifies the recording medium 9, a recording medium specification screen G1 is displayed on the display unit 12a of the operation panel 12 at first. On the recording medium specification screen G1, a button 81 for specifying a single-layer structure and a button 82 for specifying a multi-layer structure are displayed as the structure of the recording medium 9. For example, when the user operates the button 82 for specifying a multi-layer structure, the screen displayed on the display unit 12a transitions to a recording medium selection screen G2. On the recording medium selection screen G2, a list display section 83 and a button 84 for new registration are displayed. On the list display section 83, a list of recording media 9 with a multi-layer structure that have already been registered in the image forming apparatus 1 is displayed. Therefore, the user can select a recording medium 9 to be used for image formation from among the multiple recording media 9 displayed on the list display section 83. On the other hand, when the recording medium 9 to be used for image formation is not included in the list display section 83, the user operates the new registration button 84.

[0094] When the user operates the new registration button 84, the screen displayed on the display unit 12a transitions to a new registration screen G3. In this new registration screen G3, a display field 85a displaying the characteristics of the first layer, a display field 85b displaying the characteristics of the second layer, and a display field 85c displaying the characteristics of the third layer are displayed, and a plurality of setting buttons 86a, 86b, and 86c are displayed adjacent to the display fields 85a, 85b, and 58c. For example, the user can set the characteristic information 14 of the new recording medium 9 by inputting the material and thickness of each layer constituting the new recording medium 9 in each of the display fields 85a, 85b, and 85c, and operating the setting buttons 86a, 86b, and 86c. When the characteristic information 14 is input by the user, the controller 7 generates medium information 13 corresponding to the new recording medium 9 and stores it in the storage unit 11.

[0095] Furthermore, when the user inputs the characteristic information, the screen displayed on the display unit 12a transitions to a conveying speed setting screen G4. A conveying speed display field 87, a setting button 88, and an automatic setting button 89 are displayed on this conveying speed setting screen G4. When the user manually sets the conveying speed of the recording medium 9, the user inputs a desired speed in the display field 87 and operates the setting button 88. When the user performs automatic setting, the user operates the automatic setting button 89. For example, when the automatic setting button 89 is operated by the user, the controller 7 automatically sets a conveying speed that can achieve the maximum throughput in the image forming apparatus 1.

[0096] FIG. 7 is a flowchart showing a processing procedure when a new recording medium 9 is specified by the user. The processing procedure shown in FIG. 7 is a process replacing steps S10 to S15 shown in FIG. 5. First, the controller 7 accepts a user's operation to specify the recording medium 9 (step S40). When the user specifies the recording medium 9, the controller 7 judges whether or not a recording medium 9 having a multi-layer structure is specified (step S41). When the user specifies a single-layer structure rather than a multi-layer structure (NO in step S41), the processing by the controller 7 proceeds to step S31 in FIG. 5. When the user specifies a recording medium 9 having a multi-layer structure (YES in step S41), the controller 7 judges whether or not a new registration is to be performed (step S42). When the user specifies a new registration is not to be performed (NO in step S42), the processing by the controller 7 proceeds to step S12 in FIG. 5. On the other hand, when the user specifies a new registration is to be performed (YES in step S42), the controller 7 displays a new registration screen G3 on the display unit 12a and accepts an input of the characteristic information 14 by the user (step S43). Next, the controller 7 displays the conveying speed setting screen G4 on the display unit 12a, and receives a conveying speed input by the user (step S44).

[0097] Next, the controller 7 starts a process for determining an ideal temperature profile corresponding to a new recording medium 9 designated by the user. First, the controller 7 reads the existing medium information 13 and the temperature profile 17 stored in the storage unit 11 (step S45). When the medium information 13 and the temperature profile 17 of a plurality of recording media 9 are stored, the controller 7 reads all the medium information 13 and the temperature profile 17 corresponding to each of the plurality of recording media 9. Then, the controller 7 executes an inference process for inferring a temperature profile to be applied to the new recording medium 9 based on the medium information 13 and the temperature profile 17 read from the storage unit 11 (step S46). At this time, the controller 7 performs machine learning using the medium information 13 and the temperature profile 17 read from the storage unit 11 as teacher data, thereby deriving a temperature profile that is most suitable to be applied to the new recording medium 9. Then, the controller 7 determines the temperature profile derived by the inference process as the ideal temperature profile corresponding to the new recording medium 9 (step S47). When the ideal temperature profile is determined, the controller 7 determines the temperatures of the front heating section 32 and the back heating section 33 of the first heating section 31, the temperature of the second heating section 43, and the temperature of the third heating section 52 that can realize the ideal temperature profile while referring to the control information 16 included in the existing medium information 13, and generates the control information 16 corresponding to the new recording medium 9 (48). The controller 7 then creates the medium information 13 including the characteristic information 14, the profile information 15, and the control information 16, and stores it in the storage section 11 (step S49). Therefore, when the same recording medium 9 is used thereafter, the medium information 13 stored in the storage section 11 can be used.

[0098] Thereafter, the process by the controller 7 proceeds to step S16 in Fig. 5. That is, the controller 7 sets the temperature based on the medium information 13 created in step S49, performs warm-up, and then starts printing. If the actual temperature profile created based on the front and back temperatures of the recording medium 9 measured using the temperature sensors 41, 42, 44, and 45 does not match the ideal temperature profile determined in step S47, it is preferable that the controller 7 performs an adjustment process (step S25) and corrects the control information 16 included in the medium information 13 based on the adjustment result.

[0099] By executing the above-mentioned process in the controller 7, even when a new recording medium 9 is used, it is possible to automatically create an ideal temperature profile for the new recording medium 9 by utilizing the medium information 13 already registered in the image forming device 1 and the temperature profile 17 based on actual measurements. Therefore, when using a new recording medium 9, there is an advantage that the user does not need to create an ideal temperature profile himself / herself and can start printing efficiently.

[0100] Furthermore, when using a new recording medium 9, the user may perform a test print at the start of printing to verify whether the desired image quality is achieved. If the result of verifying the printout by the test print indicates that the desired image quality is not achieved, the user may manually change the setting of the temperature of the surface heating section 32 of the first heating section 31 or change the setting of the conveying speed of the recording medium 9. The user may also manually modify the ideal temperature profile. When the user changes the setting or modifies the ideal temperature profile, the controller 7 changes the control information 16 and the profile information 15 of the medium information 13 to values ​​designated by the user. As a result, the medium information 13 corresponding to the new recording medium 9 is updated to information that reflects the results of the test print. As a result, when the actual printout is performed after the test printout, it becomes possible to form an image of high image quality that the user desires.

[0101] A preferred embodiment of the present invention has been described above. However, the present invention is not limited to the above embodiment, and various modifications are possible.

[0102] For example, in the above embodiment, the image forming apparatus 1 is an apparatus that transports the web-like recording medium 9 by a roll-to-roll method. However, the image forming apparatus in the present invention is not necessarily limited to an apparatus that transports the recording medium 9 by a roll-to-roll method. In other words, the heating control (temperature control) described in the above embodiment is also applicable to an image forming apparatus of a type that takes out sheets stacked in the paper feed unit 2 one by one and transports them sequentially to a transport path.

[0103] In the above embodiment, the front surface heating section 32 and the back surface heating section 33 constituting the first heating section 31 are each configured by a planar heater. However, each of the front surface heating section 32 and the back surface heating section 33 is not necessarily limited to a planar heater. For example, the front surface heating section 32 and the back surface heating section 33 may be configured by roller-shaped heaters arranged to face each other across the transport path of the recording medium 9. In this case, a roller-shaped heater arranged on the upper side across the transport path is provided as the front surface heating section 32, and a roller-shaped heater arranged on the lower side is provided as the back surface heating section 33. These roller-shaped heaters form a nip portion, and rotate with the recording medium 9 sandwiched in the nip portion to transport the recording medium 9 downstream in the transport direction. The first heating section 31 may be a plurality of such roller-shaped heaters provided along the transport direction of the recording medium 9. The same configuration can be applied to the second heating section 43 or the third heating section 52.

[0104] However, the roller-shaped heater can only heat the recording medium 9 when the recording medium 9 is sandwiched in the nip portion. For example, even if multiple roller-shaped heaters are provided, the surface temperature of the recording medium 9 can only be raised stepwise, and the heating efficiency is reduced. Therefore, if the above-mentioned temperature control is applied, the preheating section becomes long, and the device becomes large. Therefore, in order to prevent the device from becoming large, it is preferable to configure each of the front surface heating section 32 and the back surface heating section 33 constituting the first heating section 31 by a planar heater, as described in the above embodiment. [Explanation of symbols]

[0105] 1. Image forming device 3 Preheat section 4. Leveling section 5. Image forming section 7 Controller (control means) 9 Recording media 11 Storage unit (storage means) 13 Media information 31 First heating section (first heating means) 32 Surface heating section (surface heating means) 33 Back surface heating unit (back surface heating means) 41, 42 Temperature sensor (temperature measuring means) 43 Second heating section (second heating means) 44, 45 Temperature sensor (temperature measuring means) 51 Inkjet head 52 Third heating section (third heating means) 53 Fixing section (fixing means)

Claims

1. An image forming apparatus that conveys a recording medium along a predetermined conveying path and forms an image by ejecting ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, a first heating unit that is provided on the transport path upstream of the image drawing position and that heats the recording medium; A control means for controlling the first heating means; Equipped with the first heating means includes a front surface heating means for heating a front surface side of the recording medium and a back surface heating means for heating a back surface side of the recording medium, the control means is configured to set a temperature to which the front surface heating means is heated in accordance with characteristics of the recording medium when the recording medium has a multi-layer structure, and to control the temperatures of the front surface heating means and the back surface heating means separately; The image forming apparatus according to the present invention, wherein the characteristics of the recording medium include the material and thickness of each layer forming a multi-layer structure.

2. An image forming apparatus that conveys a recording medium along a predetermined conveying path and forms an image by ejecting ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, a first heating unit that is provided on the transport path upstream of the image drawing position and that heats the recording medium; A control means for controlling the first heating means; Equipped with the first heating means includes a front surface heating means for heating a front surface side of the recording medium and a back surface heating means for heating a back surface side of the recording medium, the control means is configured to individually control the temperatures of the front surface heating means and the back surface heating means when the recording medium is a medium having a multi-layer structure, and to set a conveying speed of the recording medium in accordance with characteristics of the recording medium; The image forming apparatus according to the present invention, wherein the characteristics of the recording medium include the material and thickness of each layer forming a multi-layer structure.

3. An image forming apparatus that conveys a recording medium along a predetermined conveying path and forms an image by ejecting ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, a first heating unit that is provided on the transport path upstream of the image drawing position and that heats the recording medium; A control means for controlling the first heating means; a temperature measuring means for measuring a front surface temperature and a rear surface temperature of the recording medium transported along the transport path; Equipped with the first heating means includes a front surface heating means for heating a front surface side of the recording medium and a back surface heating means for heating a back surface side of the recording medium, The control means is configured to individually control the temperature of the surface heating means and the back heating means when the recording medium is a medium having a multi-layer structure, and is characterized in that the image forming apparatus adjusts the temperature of the surface heating means based on the surface temperature and back temperature of the recording medium measured by the temperature measuring means.

4. An image forming apparatus that conveys a recording medium along a predetermined conveying path and forms an image by ejecting ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, a first heating unit that is provided on the transport path upstream of the image drawing position and that heats the recording medium; A control means for controlling the first heating means; a temperature measuring means for measuring a front surface temperature and a rear surface temperature of the recording medium transported along the transport path; Equipped with the first heating means includes a front surface heating means for heating a front surface side of the recording medium and a back surface heating means for heating a back surface side of the recording medium, The image forming apparatus is characterized in that the control means controls the temperatures of the front surface heating means and the back surface heating means individually when the recording medium is a medium having a multi-layer structure, and adjusts the conveying speed of the recording medium based on the front surface temperature and back surface temperature of the recording medium measured by the temperature measuring means.

5. 5. The image forming apparatus according to claim 1, wherein the control unit controls the back surface heating unit to heat up to a predetermined target temperature, and the front surface heating unit to heat up to a temperature higher than the target temperature.

6. 6. An image forming apparatus according to claim 1, wherein the control means controls the surface temperature and the back surface temperature of the recording medium to match a predetermined target temperature when the recording medium reaches the drawing position.

7. a second heating means provided between the first heating means and the image drawing position, the second heating means heating a back side of the recording medium; 7. The image forming apparatus according to claim 1, wherein the control unit further controls the second heating unit.

8. 8. The image forming apparatus according to claim 7, wherein the control unit controls the second heating unit to increase its temperature to a predetermined target temperature.

9. 9. The image forming apparatus according to claim 7, wherein the control means controls the second heating means to cause the recording medium to reach the drawing position while maintaining the surface temperature of the recording medium at a predetermined target temperature.

10. a fixing unit provided on the transport path downstream of the image drawing position, the fixing unit fixing the ink ejected onto the surface of the recording medium; a third heating means provided between the image forming position and the fixing means, the third heating means configured to heat a back surface side of the recording medium; Further comprising:

10. The image forming apparatus according to claim 1, wherein the control unit further controls the third heating unit.

11. 11. The image forming apparatus according to claim 10, wherein the control unit controls the third heating unit to have a temperature increased to a predetermined target temperature.

12. 11. The image forming apparatus according to claim 10, wherein the control unit calculates a coverage rate for the recording medium based on image data to be printed, and sets the temperature of the third heating unit based on the coverage rate.

13. 13. The image forming apparatus according to claim 10, wherein the control means controls the third heating means to cause the recording medium to reach the fixing means while maintaining the surface temperature of the recording medium at a predetermined target temperature.

14. a storage means for storing medium information for each type of the recording medium, the medium information being associated with characteristic information of the recording medium and control information for realizing an ideal temperature change for the recording medium; Further comprising: The image forming apparatus according to claim 1 or 2, characterized in that when a medium for which the medium information is already stored in the memory means is specified as the recording medium, the control means reads the medium information from the memory means and individually controls the temperatures of the front surface heating means and the back surface heating means based on the control information.

15. a temperature measuring means for measuring a front surface temperature and a rear surface temperature of the recording medium transported along the transport path at a plurality of points; Further comprising: The image forming apparatus according to claim 14, wherein the control means creates a temperature profile indicating the actual temperature change of the recording medium based on the surface temperature and back surface temperature of the recording medium measured at multiple points on the transport path by the temperature measuring means, and stores the temperature profile in the memory means.

16. The image forming apparatus according to claim 15, characterized in that when a new medium for which no medium information is stored in the storage means is specified as the recording medium, the control means determines an ideal temperature change corresponding to the new medium based on the medium information already stored in the storage means and the temperature profile, and sets the temperature to which the surface heating means is heated based on the temperature change.

17. 1. An image forming method for forming an image by conveying a recording medium along a predetermined conveying path and discharging ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, comprising: a first heating step of heating the recording medium upstream of the drawing position; having In the first heating step, when the recording medium is a medium having a multi-layer structure, a temperature of the front side of the recording medium is set according to characteristics of the recording medium, and the front side and the back side of the recording medium are heated to different temperatures, respectively; The image forming method according to the present invention, wherein the characteristics of the recording medium include the material and thickness of each layer forming a multi-layer structure.

18. 1. An image forming method for forming an image by conveying a recording medium along a predetermined conveying path and discharging ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, comprising: a first heating step of heating the recording medium upstream of the drawing position; setting a conveying speed of the recording medium in accordance with characteristics of the recording medium; having In the first heating step, when the recording medium has a multi-layer structure, a front side and a back side of the recording medium are heated to different temperatures, respectively; The image forming method according to the present invention, wherein the characteristics of the recording medium include the material and thickness of each layer forming a multi-layer structure.

19. 1. An image forming method for forming an image by conveying a recording medium along a predetermined conveying path and discharging ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, comprising: a first heating step of heating the recording medium upstream of the drawing position; a temperature measuring step of measuring a front surface temperature and a rear surface temperature of the recording medium transported along the transport path; having The image forming method is characterized in that, when the recording medium is a medium having a multi-layer structure, the first heating process heats the front side and back side of the recording medium to different temperatures, and adjusts the temperature to which the front side of the recording medium is heated based on the front side temperature and back side temperature of the recording medium measured by the temperature measurement process.

20. 1. An image forming method for forming an image by conveying a recording medium along a predetermined conveying path and discharging ink onto a surface of the recording medium when the recording medium passes a predetermined drawing position, comprising: a first heating step of heating the recording medium upstream of the drawing position; a temperature measuring step of measuring a front surface temperature and a rear surface temperature of the recording medium transported along the transport path; a step of adjusting a conveying speed of the recording medium based on the front surface temperature and the back surface temperature of the recording medium measured in the temperature measuring step; having The image forming method is characterized in that, in the first heating step, when the recording medium has a multi-layer structure, the front side and the back side of the recording medium are heated to different temperatures.

21. 21. The image forming method according to claim 17, wherein the first heating step heats the back side of the recording medium to a predetermined target temperature and heats the front side of the recording medium to a temperature higher than the target temperature.

22. a second heating step of heating the back side of the recording medium in a section until the recording medium reaches the drawing position after the first heating step; 22. The image forming method according to claim 17, further comprising:

23. 23. The image forming method according to claim 22, wherein the second heating step maintains the back side of the recording medium at a predetermined target temperature.

24. a third heating step of heating the back side of the recording medium in a section until the recording medium passes the image forming position and reaches a fixing means on the downstream side; 24. The image forming method according to claim 17, further comprising:

25. 25. The image forming method according to claim 24, wherein the third heating step maintains the back side of the recording medium at a predetermined target temperature.

Images