Inkjet recording apparatus and fixing control method

Abstract

To provide an inkjet recording device and a fixing control method that are able to fix ink to a medium easily and reliably.SOLUTION: An inkjet recorder includes: a recording operation unit that ejects, onto a medium, ink that is fixed to the medium by a predetermined active energy ray; an emitting unit that emits the active energy ray to the ink ejected by the recording operation unit and landed on the medium; and a control unit that causes the emitting unit to emit the active energy ray in an amount of emission corresponding to the state of the ink on the medium.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to an inkjet recording apparatus. and fixing control method Regarding. [Background technology]

[0002] Inkjet recording devices eject ink onto a medium to form and record images, thin films, or structures. Some inks are cured by ultraviolet (UV) or other energy rays and then hardened and fixed on the medium. The ink spreads over the surface between impact and fixation. The degree of this spreading over a certain period of time depends on the viscosity of the ink.

[0003] The viscosity of ink is highly dependent on temperature. Furthermore, minute ink droplets rapidly change temperature depending on the temperature of the medium, which changes the way the ink spreads on the medium. Conventionally, this difference in spread has led to a deterioration in image quality, as it differs from what was expected. Patent Document 1 discloses a technology for suppressing defects in images on the medium by controlling the temperature of the medium. Patent Document 2 also discloses a technology for increasing or decreasing the amplitude of a discharge control signal depending on the temperature when the ink is discharged.

[0004] On the other hand, in recent years, in response to demands for higher image precision, the arrangement density of nozzles that eject ink has increased, and the intervals between impacted ink droplets have become narrower, so that the degree of spreading does not affect, or the degree to which it affects, degradation of image quality has become smaller.Since temperature changes have poor response and it takes time to change to an appropriate temperature depending on the recording medium and ambient conditions, it is possible to reduce the effort required for temperature adjustment and increase the speed. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-4831 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-136257 Summary of the Invention [Problem to be solved by the invention]

[0006] However, if the ink spreads differently, a uniform fixing operation may not fix the ink reliably, which is a problem.

[0007] An object of the present invention is to provide an ink jet recording apparatus capable of fixing ink to a medium easily and reliably. and fixing control method The purpose is to provide [Means for solving the problem]

[0008] To achieve the above objectives, Book The invention In the sol state a recording operation unit that ejects ink onto a medium; The recording operation unit ejects the liquid onto the medium. Gel with an irradiation unit that irradiates the ink with active energy rays to fix the ink; a control unit that changes the amount of irradiation of the active energy rays in accordance with the distance from the surface of the ink droplet to the innermost portion at the time of irradiation with the active energy rays, thereby curing the ink at the innermost portion; The inkjet recording apparatus is characterized by comprising: [Effects of the Invention]

[0009] According to the present invention, there is an effect that ink can be fixed to a medium easily and reliably. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram illustrating the overall configuration of an inkjet recording apparatus according to a first embodiment. [Figure 2] FIG. 2 is a block diagram illustrating a functional configuration of the inkjet printing apparatus. [Figure 3]FIG. 10 is a diagram illustrating a fixed state of ink. [Figure 4] 10 is a flowchart showing a control procedure of a fixing setting control process. [Figure 5] FIG. 10 is a schematic overall view showing an inkjet recording apparatus according to a second embodiment. [Figure 6] 10 is a flowchart showing a control procedure of a fixing setting control process according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [First embodiment] FIG. 1 is a schematic diagram showing the overall configuration of an inkjet recording apparatus 1 according to the first embodiment. Here, the inkjet recording apparatus 1 is shown as seen from the front.

[0012] The inkjet recording device 1 of this embodiment includes a medium supply unit 10, a recording main body unit 20, a medium discharge unit 30, and a control unit 40. In this inkjet recording device 1, based on the control of the control unit 40, a recording medium M (medium) stored in the medium supply unit 10 is sent and transported to the recording main body unit 20, an image is recorded on it, and then it is discharged to the medium discharge unit 30.

[0013] The medium supply unit 10 sends the recording media M stored therein to the recording main unit 20 one by one. As the recording medium M, various materials that can be curved and carried on the outer peripheral surface of the image recording drum 21 are used here, such as printing paper of various thicknesses, resin substrates such as cells, films, and boards, and fabrics.

[0014] The medium supply unit 10 has a supply tray 11 that stores recording media M, and a feeder board 12 that transports the recording media M from the supply tray 11 to the recording main body unit 20. The supply tray 11 is a plate-like member that is capable of loading one or more recording media M. The supply tray 11 is configured to move up and down depending on the amount of recording media M loaded on the supply tray 11, and in the direction of the up and down movement, the topmost recording media M is held at a position where it can be transported by the feeder board 12. The feeder board 12 has a conveying mechanism that drives a circular belt 123 carried by a plurality of (for example, two) rollers 121 and 122 on the inside to convey the recording medium M on the belt 123, and a supply unit that transfers the top recording medium M placed on the supply tray 11 onto the belt 123. The feeder board 12 transports the recording medium M transferred onto the belt 123 by the supply unit so that it follows the belt 123.

[0015] The recording main body 20 includes an image recording drum 21 (mounting member), a delivery unit 22, a head unit 24 (recording operation unit), an irradiation unit 25, a delivery unit 26, an inversion unit 27, and the like.

[0016] The image recording drum 21 has a cylindrical outer shape, carries up to three recording media M on the outer peripheral surface of the cylindrical portion, and transports the recording media M in response to rotation about the central axis of the cylinder. Inside the image recording drum 21, a drum heater 23 (see FIG. 2) that heats the outer peripheral surface and a temperature measurement unit 55 that measures the temperature of the outer peripheral surface are provided. The outer peripheral surface of the image recording drum 21 is heated to a predetermined temperature by the drum heater 23, thereby further heating the recording media M carried thereon. For example, in the case where ink that is in a gel state at room temperature and becomes a sol state at a high temperature (temperature-dependent ink) is used, this predetermined temperature is set to a temperature at which the ink ejected in a sol state and landed on the recording medium M returns to a gel state appropriately while being transported on the image recording drum 21, i.e., a temperature lower than the ink temperature at the time of ejection at which the ink gels. An image is recorded on the recording medium M carried on the image recording drum 21 by ink being ejected from each nozzle of the head unit 24 at a position opposite the head unit 24 (image recording position) and landing at an appropriate position on the surface of the recording medium M opposite the contact surface with the image recording drum 21 (one recording target surface).

[0017] The transfer unit 22 transfers the recording medium M transferred from the medium supply unit 10 to the image recording drum 21. The transfer unit 22 has a swing arm unit 221 that supports one end of the recording medium M transported by the feeder board 12, and a cylindrical transfer drum 222 that transfers the recording medium M supported by the swing arm unit 221 to the image recording drum 21. The swing arm unit 221 picks up the recording medium M on the feeder board 12 and transfers it to the transfer drum 222, thereby guiding the recording medium M in a direction along the outer circumferential surface of the image recording drum 21 and transferring it to the image recording drum 21.

[0018] The head unit 24 records an image by ejecting ink droplets at appropriate timing onto a recording surface of the recording medium M, which moves in accordance with the rotation of the image-recording drum 21, from multiple nozzle openings provided on the surface (nozzle surface) of the head unit 24 that faces the recording surface of the recording medium M. The head unit 24 includes one or more recording heads each provided with multiple nozzles. In the inkjet recording apparatus 1 of this embodiment, multiple head units 24 are arranged at predetermined intervals in the transport direction of the recording medium M. Here, four head units 24 are arranged, one for each of the four colors of ink. The four head units 24 output C (cyan), M (magenta), Y (yellow), and K (black) ink, respectively. The arrangement order of these head units 24 may be determined as appropriate. These inks are cured and fixed to the recording medium M by irradiation with electromagnetic waves of a predetermined wavelength, in this case, ultraviolet rays, as active energy rays. The ink is heated and maintained at an appropriate temperature inside and / or outside the head unit 24 by an ink heater 61 (see FIG. 3). The temperature of the ink or the components of the ink tank that stores the ink may be measured by the temperature measuring unit 55 separately from the temperature of the image recording drum 21 .

[0019] Each of the head units 24 here has a plurality of nozzle openings arranged across the image recording width of the recording medium M in a width direction perpendicular to the transport direction of the recording medium M transported on the image recording drum 21, and is equipped with a line head that can record an image by a single pass method by ejecting ink from the nozzle openings onto the recording medium M while moving the recording medium M in the transport direction. The head unit 24 is attached to a support unit (carriage) not shown.

[0020] The irradiation unit 25 irradiates the ink ejected from the head unit 24 onto the recording medium M with active energy rays (ultraviolet rays in this case) to cause a reaction that hardens and fixes the ink. The irradiation unit 25 has, for example, a light-emitting diode (LED) that emits ultraviolet rays, and applies a voltage to the LED to cause a current to flow, causing the LED to emit light and irradiate ultraviolet rays. The irradiation unit 25 is configured to irradiate ultraviolet rays onto the recording medium M (i.e., onto the landed ink) after the ink is ejected from the head unit 24 onto the recording medium M transported by the rotation of the image recording drum 21 and before the recording medium M reaches the delivery unit 26. The irradiation unit 25 may also be provided with a light-shielding wall or the like to prevent ultraviolet rays from leaking outside the desired irradiation range, as necessary.

[0021] The configuration for emitting ultraviolet light in the irradiation unit 25 is not limited to an LED. The irradiation unit 25 may have, for example, a mercury lamp. Furthermore, if the ink has the property of being cured and fixed by receiving active energy rays other than ultraviolet light (which are not particularly limited, but are mainly shorter in wavelength than visible light and are easily attenuated as they pass through the ink), the irradiation unit 25 may have a well-known emission source (light source) that emits active energy rays that cure the ink, instead of the above-mentioned configuration for emitting ultraviolet light.

[0022] The delivery unit 26 transports the recording medium M, on which an image has been recorded and the recorded image (ink) has been fixed, to the medium discharge unit 30. The delivery unit 26 has a cylindrical discharge selection roller 261, a delivery roller 262, a plurality of (for example, two) rollers 263 and 264, and a ring-shaped belt 265 supported on the inner surface by the rollers 263 and 264.

[0023] The discharge selection roller 261 switches between discharging the recording medium M to the medium discharge unit 30 or returning it to the supply side of the recording medium M. The delivery roller 262 receives the recording medium M to be discharged to the medium discharge unit 30 from the discharge selection roller 261 and guides it onto the belt 265. The delivery unit 26 transports the recording medium M delivered from the delivery roller 262 onto the belt 265 by moving it together with the belt 265, which moves in rotation as the rollers 263 and 264 rotate, and sends it out to the medium discharge unit 30.

[0024] The reversing unit 27 reverses the recording medium M, one side of which has an image recorded, to change the recording surface and guides the recording medium M back onto the outer circumferential surface of the image recording drum 21. The reversing unit 27 has an reversing drum 271, a reversing swing device 272, and the like. When images are to be recorded on both sides of the recording medium M, the recording medium M, one side of which has an image recorded, is not sent to the delivery roller 262 by the discharge selection roller 261, and the reversing drum 271 receives the recording medium M from the image recording drum 21.

[0025] The reversing swing device 272 is provided at a position equidistant from the outer circumferential surface of the reversing drum 271 and the outer circumferential surface of the image recording drum 21. When the trailing end in the transport direction of the recording medium M on the reversing drum 271 reaches a position opposite the reversing swing device 272, the reversing swing device 272 grips the trailing end and guides it along the outer circumferential surface of the image recording drum 21. The recording medium M is reversed so that the side on which the image was previously recorded by the head unit 24 comes into contact with the outer circumferential surface, i.e., the surface to be recorded is changed, and the recording medium M is again transported by the image recording drum 21 from the upstream side in the transport direction of the head unit 24. At this time, the trailing end in the transport direction of the recording medium M in the first image recording operation becomes the leading end in the transport direction in the second image recording operation.

[0026] When the same surface of the recording medium M is used as the recording surface multiple times in succession without inverting the recording surface, neither the discharge selection roller 261 nor the inversion drum 271 acquires the recording medium M, and the recording medium M on the image recording drum 21 is rotated toward the supply side while remaining placed on the outer peripheral surface.

[0027] The medium ejection unit 30 stores the recording medium M sent from the recording main body unit 20 by the delivery unit 26 until the recording medium M is removed by the user. The medium ejection unit 30 has a plate-shaped ejection tray 31 and the like, on which the recording medium M after the recording operation is placed.

[0028] The control unit 40 controls the operation of the medium supply unit 10, the recording main unit 20, and the medium discharge unit 30, and records an image on the recording medium M according to the data of the image to be recorded by the image recording command (job) and settings related to the image recording operation.

[0029] FIG. 2 is a block diagram showing the functional configuration of the inkjet recording apparatus 1. As shown in FIG. In addition to the head unit 24, irradiation unit 25, control unit 40, and temperature measurement unit 55, the inkjet recording device 1 also includes a transport motor 211 and transport control unit 41, an irradiation control unit 45, a heating operation unit 60, an operation reception unit 51, a display unit 52, a communication unit 54, etc.

[0030] The transport motor 211 has motors that drive the respective parts that operate to move the recording medium M in the medium supply unit 10 and the recording main body unit 20. The transport control unit 41 operates the transport motors 211 at appropriate timings, synchronously as necessary.

[0031] The head unit 24 includes a head control unit 44, a head drive unit 241, an electromechanical conversion element 242, and the like. The head unit 24 of this embodiment is not particularly limited, but has piezo elements (electromechanical conversion elements 242) provided along ink flow paths (particularly ink chambers) that communicate with each nozzle that ejects ink. By deforming the piezo elements in response to fluctuations in the voltage applied to the piezo elements, pressure fluctuations are generated in the ink, causing the ink to be ejected from the nozzles. The head drive unit 241 outputs a voltage signal (drive voltage signal) of a waveform to be applied to the piezo elements (electromechanical conversion elements 242) based on a control signal from the head control unit 44.

[0032] The irradiation control unit 45 controls the timing, duration, and intensity of irradiation of ultraviolet rays (active energy rays) by the irradiation unit 25. The irradiation unit 25 causes the LED to emit light based on a control signal from the irradiation control unit 45, thereby emitting ultraviolet rays.

[0033] The heating unit 60 includes the drum heater 23 (heat source), the ink heater 61, and the heater control unit 48. The drum heater 23 heats the outer peripheral surface of the image recording drum 21 (the surface opposite the ink landing surface) to heat the placed recording medium M to an appropriate temperature. The ink heater 61 heats the ink in the ink flow path member to an appropriate temperature. The drum heater 23 and the ink heater 61 each have, for example, an electric heating wire, and generate Joule heat by passing an electric current through them. The heater control unit 48 intermittently controls the drum heater 23 and the ink heater 61 to turn them on and off so that the outer peripheral surface of the image recording drum 21 and the ink flow path member are maintained within an appropriate temperature range. Note that if the heat generation amounts of the drum heater 23 and the ink heater 61 can be controlled, the heater control unit 48 may control not only the on and off control but also the heat generation amount (current value, etc.). The control operation of the heater control unit 48 may be performed based on temperature data measured by the temperature measurement unit 55. The drum heater 23 and the image recording drum 21 constitute a heating section of this embodiment.

[0034] The operation reception unit 51 receives input operations from an external user or the like and outputs the operations as input signals to the control unit 40. The operation reception unit 51 includes, for example, a touch panel and push button switches. The touch panel may be positioned so as to overlap the display screen of the display unit 52. The operation reception unit 51 may also include various other operation switches.

[0035] The display unit 52 displays various statuses, menus, and the like on a display screen under the control of the control unit 40. The display unit 52 has, for example, a display screen and LED lamps. The display screen is not particularly limited, but is, for example, an LCD (Liquid Crystal Display). The LED lamps are lit by the control unit 40 in positions and colors corresponding to the power supply status, abnormality occurrence status, and the like.

[0036] The communication unit 54 controls transmission and reception of data (signals) with external devices, etc., in accordance with a predetermined communication standard. The communication unit 54 controls communication in accordance with, for example, a LAN (Local Area Network) standard. The communication unit 54 may also be connectable to peripheral devices, etc., in accordance with the USB (Universal Serial Bus) standard.

[0037] The control unit 40 includes a CPU 401 (Central Processing Unit), a RAM 402 (Random Access Memory), a storage unit 403, and the like. The CPU 401 performs various arithmetic operations to perform control operations. The RAM 402 provides the CPU 401 with a working memory space and stores temporary data. The storage unit 403 includes a non-volatile memory and stores various setting data, programs, and the like. The setting data includes irradiation amount information 403a. The irradiation amount information 403a is data for changing and adjusting the amount of ultraviolet light irradiated by the irradiation unit 25 depending on the situation, as described below. The programs include a control program related to the fixing setting control process described below, which changes and controls the irradiation amount of the irradiation unit 25 so that the ink deposited on the recording medium M is reliably fixed depending on its state (deposit state). The storage unit 403 may also include a large-capacity volatile memory and be capable of storing job data, associated work data (processing data), and the like.

[0038] The transport control unit 41, head control unit 44, irradiation control unit 45, and heater control unit 48 may each be operated by a processor (such as a CPU) separate from the control unit 40, or in practice, the CPU 401 may commonly perform each process.

[0039] Next, the ink fixing operation will be described. 3 is a diagram illustrating the fixed state of ink. Note that, for the sake of explanation, the size of the ink is shown exaggerated compared to the size of the irradiation unit 25. As shown in Figure 3(a), ink droplets I1 that land on the recording surface of recording medium M are cured and fixed by ultraviolet light irradiated from irradiation unit 25 on recording medium M. When the viscosity of the ink is high (or becomes high) or when the wettability of the ink to recording medium M is low, the ink droplets I2 do not spread thinly, and instead, as shown in Figure 3(b), they do not spread as much on the surface of recording medium M as ink droplets I1 in Figure 3(a), and instead rise into a hemispherical shape or the like.

[0040] Ink curing progresses according to the amount of UV light irradiated onto the photopolymerization initiator contained in the ink. Therefore, to cure the deepest part of the ink droplet, farthest from the surface, a larger amount of radiation is required to compensate for the amount of radiation absorbed and reflected on the way from the surface to the deepest part. On the other hand, if the amount of radiation is greater than necessary, it can lead to unnecessary energy consumption and deterioration of various parts. Because the distances from the surface to the deepest part differ between ink droplets I1 and I2, the appropriate amount of UV radiation also differs. In other words, to cure and fix the ink, ink droplet I2 requires a greater amount of radiation than ink droplet I1.

[0041] The viscosity of ink depends largely on the ink temperature as well as the ink characteristics themselves. The temperature of the ink droplets when ejected is kept roughly constant by the operation of the ink heater 61, and changes depending on the heat exchange between the ink droplets and the recording medium M after they land. The temperature of the recording medium M is lower than that of the ink, so the temperature of the ink droplets drops.

[0042] In the inkjet recording device 1 of this embodiment, the heating temperature of the drum heater 23, i.e., the temperature of the outer peripheral surface of the image recording drum 21, is kept substantially constant (within a certain range) by control of the heater control unit 48. When a recording medium M at approximately room temperature supplied from the medium supply unit 10 is placed on this outer peripheral surface, heat is transferred from the image recording drum 21 to the recording medium M, and the temperature of the recording medium M approaches that of the image recording drum 21.

[0043] However, since the time from when the recording medium M is placed on the outer peripheral surface until ink is ejected onto the recording medium M is usually shorter than the time it takes to reach thermal equilibrium between the recording medium M and the image recording drum 21, the degree of heat transfer varies depending on the characteristics of the recording medium M. For example, the lower the thermal conductivity of the recording medium M and the thicker the recording medium M, the less the temperature of the recording surface of the recording medium M (i.e., the surface opposite the surface in contact with the outer peripheral surface) will rise (be low) when ink droplets land on it. As a result, the temperature of the tiny ink droplets that land on such recording medium M quickly drops and their viscosity increases before they spread over the surface. In other words, the state of the ink changes significantly from when it was ejected, and the ink does not spread sufficiently but instead gathers in a narrow area and is raised, and is irradiated with ultraviolet rays by the irradiation unit 25.

[0044] In addition to these factors, when multiple colors of ink are deposited on top of each other in a color image, the cumulative effect is that ultraviolet light does not reach all of the ink droplets sufficiently, so the amount of ultraviolet light irradiation may be increased. Furthermore, when a large amount of ink is deposited per recording medium M, the ink droplets tend to combine with other ink droplets, making it difficult for ultraviolet light to reach all of the ink. In this case, the amount of irradiation may be determined based on the ink amount that is most difficult to harden, i.e., the ink that is least easily reached by ultraviolet light. On the other hand, when a monochromatic image is recorded using a color with a high ultraviolet light absorption rate, such as black ink, sufficient hardening can be achieved with less ultraviolet light than in a normal color image.

[0045] The increase or decrease in the amount of irradiation is mainly controlled by the irradiation intensity, that is, the magnitude of the intensity of ultraviolet light emitted by the irradiation unit 25. However, this is not limitative, and the amount of irradiation can also be changed by increasing or decreasing the time during which ultraviolet light is emitted by the irradiation unit 25 (i.e., the irradiation time).

[0046] Before starting an image recording operation, the irradiation control unit 45 acquires information about the recording medium M (medium characteristics), information about the ink (ink type and color), and information about the ink ejection amount (amount of ejected ink) based on the image to be recorded, and acquires or calculates an appropriate irradiation amount corresponding to the state (spreading level) of the ink that will land on the recording medium M, which is estimated based on the information. The irradiation amount may be set in association with, for example, a preset combination of the type of recording medium M (medium characteristics) and the type of ink (which may include information such as wettability under conditions (predetermined states) when the ink lands), and stored as irradiation amount information 403a. Alternatively, an increase / decrease rate relative to a reference irradiation amount may be set for each type of recording medium M and each type of ink. The type of recording medium M is indicated, for example, by a combination of differences in material and surface treatment, such as plain paper, coated paper, or resin substrate, and its thickness.

[0047] Alternatively, the reference irradiation amount may be determined based on a known, very thin recording medium with high thermal conductivity, and the irradiation amount may be increased when a different recording medium is used. In this case, the drum heater 23 may be operated so that the recording surface of the reference recording medium M reaches approximately the set temperature by the time the first ink droplet lands on the recording medium M. Various setting information related to the recording medium and ink may be added periodically or manually. Furthermore, if type information is not stored in advance, an appropriate irradiation amount may be calculated based on the thickness and thermal conductivity parameters of the recording medium M received by the operation reception unit 51, and / or the ink's viscosity and temperature change rate at the reference temperature. Even if the irradiation amount information 403a provides an irradiation amount corresponding to the medium characteristics and ink type, the obtained irradiation amount may be further adjusted based on the amount of ink ejected per recording medium M, the image color (the ink actually used), and the like.

[0048] FIG. 4 is a flowchart showing a control procedure by the control unit 40 of the fixing setting control process executed in the inkjet recording apparatus 1.

[0049] This fixing setting control process is started, for example, after a job is acquired and various settings related to the recording operation are made, but before the actual recording operation is started. When the fixing setting control process is started, the control unit 40 (CPU 401) acquires type information of the recording medium M on which recording is to be performed (step S101). The control unit 40 acquires ink settings (information) for each color to be ejected (step S102). The control unit 40 acquires information on the amount of ink ejected for each color per sheet of recording medium M (step S103).

[0050] The control unit 40 sets the amount of ultraviolet light emitted from the irradiation unit 25 according to the medium type and ink settings (step S104). The control unit 40 increases or decreases the set amount of irradiation according to the ink ejection amount (step S105). Then, the control unit 40 ends the fixing setting control process.

[0051] [Second embodiment] FIG. 5 is a schematic overall view showing an inkjet recording apparatus 1a according to the second embodiment. In this inkjet recording device 1a, in addition to the head unit 24, a head unit 24W that ejects white ink is added, and is lined up with the other head units 24 with its ink ejection surface facing the image recording drum 21. The other configurations are the same, so the same reference numerals are used and detailed explanations will be omitted.

[0052] The white ink ejected from the head unit 24W may be used in the same way as the other CMYK color inks, and may also be ejected and applied before image recording with CMYK, for example, to generate a background layer on the surface of the recording medium M. In such cases, for example, during the first pass (first rotation), the background layer is recorded and fixed once using only the white ink, and then the recording medium M is returned to the supply side without being ejected, and an image is recorded using the CMYK color inks during the second pass (second rotation).

[0053] Because white ink has a higher reflectivity to ultraviolet light than inks of other colors, it is necessary to irradiate white ink with a larger amount of ultraviolet light than inks of other colors. Furthermore, when recording is performed multiple times on the same side as described above, or when recording images on both sides of recording medium M that has been inverted by inversion unit 27, the recording medium M, which is gradually heated as described above, rotates around image recording drum 21 (via inversion unit 27 in the case of double-sided recording) and returns to the supply side, during which time heat is transferred inside recording medium M, causing the temperature to rise. Therefore, when fixing the second or subsequent recorded image, the amount of irradiation can be less than when fixing the first recorded image, taking into account the increase in ink viscosity due to insufficient temperature rise. Furthermore, if the ink that is fixed during the fixing operation of the first recorded image generates heat, the temperature of the ink that lands during the second recording operation may rise further, so the irradiation amount may be determined taking such temperature rise into consideration.

[0054] FIG. 6 is a flowchart showing a control procedure by the control unit 40 of the fixing setting control process executed in the inkjet recording apparatus 1a of the second embodiment. This fixing setting control process is the same as the fixing setting control process executed in the inkjet recording apparatus 1 of the first embodiment shown in Fig. 4, except that steps S106 and S107 are added after the final step S105. The same processing contents are assigned the same reference numerals, and detailed explanations will be omitted.

[0055] After the process of step S105, the control unit 40 determines whether or not to perform ink ejection onto the same medium multiple times (step S106). If it is determined that ink will be ejected multiple times ("YES" in step S106), the control unit 40 sets the amount of irradiation by the irradiation unit 25 for the second and subsequent ejections to be reduced from the first amount (step S107). The irradiation amounts for the second and subsequent ejections may all be the same, or may be set to gradually approach a predetermined reference value. Then, the control unit 40 ends the fixing setting control process. If it is determined that ink will not be ejected onto the same medium multiple times ("NO" in step S106), the control unit 40 ends the fixing setting control process.

[0056] As described above, the inkjet recording device 1 of this embodiment includes a head unit 24 that ejects ink onto the recording medium M, which is fixed to the recording medium M by ultraviolet rays, an irradiation unit 25 that irradiates ultraviolet rays onto the ink ejected by the head unit 24 and landing on the recording medium M, and a control unit 40 that causes the irradiation unit 25 to irradiate ultraviolet rays in an amount that corresponds to the condition of the ink on the recording medium M. In this way, by variably adjusting the amount of ultraviolet light emitted by the irradiation unit 25 according to the degree of spread of the ink, ink of any degree of spread can be easily and reliably cured and fixed to the recording medium M without irradiating ultraviolet light more than necessary, thereby avoiding increased power consumption and unnecessary deterioration. In particular, if there is no problem even if the degree of spreading of the ink onto the recording medium M when it is fixed varies slightly, for example, if the ink landing density is sufficiently high compared to the ink landing area and there is no need to worry about gaps being created even if the ink spreads slightly less, then there is no need to strictly control the temperature of the ink (the landing surface of the recording medium M). This allows the ink to be reliably cured and fixed while shortening the time required for temperature adjustment, which generally has a slow response speed.

[0057] The inkjet recording device 1 also includes a drum heater 23 that heats the surface of the recording medium M opposite the ink landing surface, and an image recording drum 21, and the control unit 40 determines the amount of irradiation depending on the state of the ink corresponding to the characteristics of the recording medium M. In other words, when the heating operation is controlled to a constant value, the temperature of the ink landing surface can change depending on characteristics such as the thickness and thermal conductivity of the recording medium M, and the temperature of the ink decreases and the degree of spread changes depending on these characteristics. Therefore, in the inkjet recording device 1, by changing the amount of ultraviolet light irradiated by the irradiation unit 25 depending on the characteristics of the recording medium M, the ink can be cured and fixed with an appropriate amount of ultraviolet light irradiated depending on the degree of spread of the ink.

[0058] The heating section also has a drum heater 23 and an image recording drum 21 on which the recording medium M is placed from before the ink lands until the active energy rays are irradiated, and the control section 40 operates the drum heater 23 so as to maintain the outer peripheral surface of the image recording drum 21 within a certain temperature range. In this way, there is no need to change the temperature setting depending on the type of recording medium, and therefore there is no need to wait until the temperature, which has a slow response, changes to an appropriate temperature and stabilizes.

[0059] Furthermore, the characteristics of the recording medium M include thermal conductivity, and the control unit 40 increases the irradiation amount as the thermal conductivity decreases. If the thermal conductivity is low, it becomes difficult for the temperature of the landing surface to rise to the desired temperature when the ink lands, and the temperature of the landed ink drops, increasing its viscosity and making it difficult for the ink to spread to the landing surface. Therefore, by increasing the amount of UV irradiation to the ink, the UV rays can be reliably delivered to the deepest part of the gathered ink without spreading, initiating photopolymerization and allowing the ink to harden and fix.

[0060] The characteristics of the recording medium M also include the thickness of the recording medium M. The control unit 40 increases the amount of ultraviolet light irradiated as the thickness increases. If the recording medium M is thick, it takes time for heat to be transferred from the heating surface to the ink landing surface, making it difficult for the temperature of the ink landing surface to rise to the desired temperature. This causes the temperature of the ink to drop and the viscosity to increase, making it difficult for the ink to spread across the landing surface. Therefore, by increasing the amount of ultraviolet light irradiated onto the ink, the ultraviolet light can be reliably delivered to the deepest part of the ink that has gathered without spreading, thereby hardening and fixing the ink.

[0061] The inkjet recording apparatus 1 also includes a storage unit 403 that stores the ultraviolet irradiation amount information 403a in association with the characteristics of the recording medium M. The control unit 40 acquires the ultraviolet irradiation amount corresponding to the recording medium M to be recorded from the storage unit 403. By storing the association between the recording medium M and the irradiation amount in advance in this way, an appropriate ultraviolet irradiation amount can be easily and quickly set and the ink can be cured and fixed without waste, without the need for testing or adjusting the fixation degree when starting to record an image.

[0062] Furthermore, the control unit 40 adjusts the amount of ultraviolet light irradiation in accordance with the amount of ink ejected onto the recording medium M by the head unit 24. If a large amount of ink is ejected, the ink film thickness tends to increase regardless of how the ink spreads, so the inkjet recording device 1 adjusts the amount of ultraviolet light irradiation accordingly, thereby ensuring that the ink is cured and fixed.

[0063] The control unit 40 adjusts the amount of ultraviolet light irradiation depending on the wettability of the ink in a predetermined state relative to the recording medium M. Depending on the combination of ink and recording medium M, the wettability may be low and the ink may not spread easily, so in the inkjet recording device 1, by adjusting the amount of ultraviolet light irradiation depending on the wettability, the ink can be more reliably cured and fixed.

[0064] Furthermore, the control unit 40 adjusts the amount of ultraviolet light irradiation depending on the color of the ink to be ejected. Since the reflectance of ultraviolet light varies depending on the color of ink, the inkjet recording device 1 adjusts the amount of irradiation for each color, thereby more reliably curing and fixing the ink of each color.

[0065] Furthermore, the control unit 40 changes the amount of ultraviolet light irradiated by changing the irradiation intensity of the irradiation unit 25. By making the irradiation intensity variable, it is no longer necessary to significantly or completely change the irradiation time, and the time required for fixing does not need to be changed. In particular, even if it is necessary to increase the irradiation amount, there is no need to significantly increase the irradiation time. This makes it possible to irradiate the desired area with ultraviolet light evenly and reliably in a short time. In particular, this completely eliminates the need to change the transport speed of the recording medium M during fixing, making control easier.

[0066] On the other hand, the control unit 40 changes the amount of ultraviolet light irradiation by changing the irradiation time of the irradiation unit 25. If it is possible to change the ultraviolet light irradiation intensity by a large amount or not at all, it is not necessary to improve the performance of the irradiation unit 25, and therefore it is not necessary to improve the performance of the irradiation unit 25.

[0067] Furthermore, when ink is ejected onto the recording medium M by the head unit 24 in multiple separate ejections, the control unit 40 reduces the irradiation amount for the second and subsequent ink ejections compared to the irradiation amount for the first ink ejection. When ink is ejected onto the same recording medium M multiple times, the recording medium M is further heated between the first and second ejections and rises to a desired temperature. This reduces the viscosity of the ink, making it more likely to spread across the landing surface of the recording medium M than in the first ejection. As a result, the ink is reliably fixed even with a reduced amount of UV radiation. Therefore, reducing the amount of UV radiation in accordance with the heating level can prevent unnecessary power consumption and deterioration of the recording medium M. Furthermore, it can prevent various adverse effects caused by excessive heat generation due to excessive ink fixing reaction and excessive temperature rise of the recording medium M.

[0068] The ink fixation control method in the inkjet recording apparatus 1 of this embodiment also includes an irradiation amount setting step of causing the irradiation unit 25 to irradiate the recording medium M with ultraviolet light at an irradiation amount that corresponds to the state of the ink on the recording medium M. In this way, by variably adjusting the amount of ultraviolet light emitted by the irradiation unit 25 according to the degree of spread of the ink, ink of any degree of spread can be easily and reliably cured and fixed to the recording medium M without irradiating ultraviolet light more than necessary, thereby avoiding increased power consumption and unnecessary deterioration.

[0069] The present invention is not limited to the above-described embodiment, and various modifications are possible. For example, in the above embodiment, the parameters for changing the irradiation amount have been described as recording medium characteristics (thermal conductivity, thickness), wettability, ink ejection amount, and color, but these can be combined in any way as long as they do not contradict each other. Parameters other than these may also be included. For example, if the conveyance speed of the recording medium can be changed, the conveyance speed may be taken into consideration.

[0070] Furthermore, in the above embodiment, multiple inks of multiple colors are caused to land and fix on the recording medium M on a single image recording drum 21, but they may also be on different image recording drums 21. Furthermore, the recording medium M does not have to be transported by a cylindrical image recording drum 21, but may be transported and moved on the plane of a transport belt. Similarly, when ink is caused to land on the same surface multiple times, the ink may be configured to land on the recording medium M on different image recording drums 21 the first time (for example, white ink) and the second time (CMYK inks).

[0071] In the above embodiment, the temperature of the image recording drum 21 controlled by the drum heater 23 is constant regardless of the recording medium, but this does not mean that the controlled temperature range can be changed slightly. For example, the amount of heat may be increased slightly for a thick medium with extremely low thermal conductivity, or the controlled temperature range may be narrower than usual for a heat-sensitive medium.

[0072] In addition, in the above embodiment, we have described a case where the amount of irradiation is changed depending on the difference in temperature of the recording medium M at the time of the first and second ink landing, but the amount of irradiation can also be changed in cases where the gloss is intentionally changed between the first and second landings.

[0073] Furthermore, in the above embodiment, an example was given in which ink is landed on the same surface multiple times, but images may be recorded on both sides of the recording medium M.

[0074] Furthermore, the ink that is deposited on the recording medium M is not limited to colored ink, but may be transparent ink, etc. Furthermore, the ink does not have to be ink that changes phase between sol-gel depending on the temperature.

[0075] Furthermore, the characteristics of the recording medium M, such as the thickness, are not limited to being input and acquired, but may be partially or entirely measured directly. Furthermore, the recording medium M is not limited to a medium divided into predetermined sizes, such as sheets of paper, but may be continuous paper or the like.

[0076] Furthermore, when ink is to be landed or fixed on the same surface multiple times, instead of rotating the recording medium M multiple times along the image recording drum 21, the recording medium M may be moved once along the transport direction, reversed, returned to the supply side, and then moved again in the normal transport direction while the ink is landed or fixed.

[0077] Furthermore, in the above embodiment, the side of the recording medium M opposite to the ink landing surface is heated, but the ink landing surface may be temporarily heated before the ink lands. In this case, the temperature of the ink landing surface after heating can change depending on the heat capacity and thermal conductivity of the recording medium M, and the amount of ultraviolet light (active energy rays) applied may be changed depending on the characteristics of this change.

[0078] Furthermore, in the above embodiment, the inkjet recording device 1 has been described as having a line head and performing an image recording operation using a single pass method, but this is not limited to this. For example, a configuration may be adopted in which a scan head is provided, and ink is ejected and landed on the recording medium M while the head unit 24 is scanned, and the landed ink is cured and fixed. In this case, the irradiation unit 25 may also be scanned, and the heating surface of the recording medium M is not limited to a transport surface such as the outer circumferential surface of the image recording drum 21. It may also be a mounting surface of a fixed recording medium M, or the recording medium M may be transported and moved by separate rollers or the like. Furthermore, the specific details of the configuration, structure, content and procedures of the setting operations shown in the above embodiments can be modified as appropriate without departing from the spirit of the present invention. The scope of the present invention includes the scope of the invention described in the claims and its equivalents. [Explanation of symbols]

[0079] 1, 1a Inkjet recording device 10 Media supply section 11 Supply tray 12 Feeder Board 121, 122 Roller 123 Belt 20 Recording main body 21 Image recording drum 211 Transport motor 22 Delivery Unit 221 Swing arm section 222 Delivery drum 23 Drum heater 24, 24W head unit 241 Head drive unit 242 Electromechanical transducer 25 Irradiation unit 26 Delivery Department 261 Ejection selection roller 262 Delivery Roller 263, 264 Roller 265 Belt 27 Reversal section 271 Reversing Drum 272 Inverted Swing Device 30 Media discharge section 31 Discharge tray 40 Control Unit 401 CPU 402 RAM 403 Storage section 403a Radiation dose information 41 Transport control section 44 Head control unit 45 Irradiation control unit 48 Heater control unit 51 Operation reception section 52 Display section 54 Communications Department 55 Temperature measurement section 60 Heating operation part 61 Ink heater I1, I2 ink droplets M Recording medium

Claims

1. A recording operation unit that ejects ink in a sol state onto a medium; an irradiation unit that irradiates the ink ejected by the recording unit and gelled on the medium with active energy rays to fix the ink; a control unit that changes the amount of irradiation of the active energy rays in accordance with the distance from the surface of the ink droplet to the innermost portion at the time of irradiation with the active energy rays, thereby curing the ink at the innermost portion; An inkjet recording apparatus comprising:

2. An inkjet recording device as described in Claim 1, characterized in that the control unit changes the amount of irradiation of the active energy rays depending on the distance from the surface of the ink droplet to the innermost part of the recording medium at the time of irradiation of the active energy rays.

3. The inkjet recording device of claim 1, characterized in that the control unit increases the amount of irradiation of the active energy rays to ink droplets whose distance from the surface to the innermost part at the time of irradiation with the active energy rays is a first distance, compared to the amount of irradiation of the active energy rays to ink droplets whose distance from the surface to the innermost part at the time of irradiation is a second distance smaller than the first distance.

4. An inkjet recording device as described in claim 1, characterized in that it is provided with a heating unit that heats the side of the medium opposite to the surface on which the ink lands.

5. The heating unit has a heat source and a mounting member on which the medium is placed from before the ink lands until the active energy rays are irradiated, The control unit operates the heating unit to maintain the temperature of the mounting member within a certain range.

5. The ink jet recording apparatus according to claim 4.

6. An inkjet recording device as described in any one of claims 1 to 5, wherein the ink includes ink of each color of cyan, magenta, yellow, black, and white.

7. An inkjet recording device as described in any one of claims 1 to 6, characterized in that the control unit changes the irradiation amount depending on the characteristics of the medium.

8. An inkjet recording device as described in claim 7, characterized in that the characteristics of the medium include a thickness of the medium.

9. An inkjet recording device as described in claim 7 or 8, characterized in that it is provided with a memory unit that stores the characteristics of the medium and the irradiation amount in correspondence with each other.

10. An inkjet recording device as described in Claim 9, characterized in that the control unit obtains the irradiation amount corresponding to the medium to be recorded from the memory unit.

11. An inkjet recording device as described in any one of claims 1 to 6, characterized in that the control unit changes the irradiation amount depending on the type of the medium.

12. The inkjet recording apparatus according to claim 11, wherein the medium is plain paper, coated paper, or a resin substrate.

13. An inkjet recording device as described in any one of claims 1 to 12, characterized in that the control unit changes the irradiation amount by changing the irradiation intensity by the irradiation unit.

14. An inkjet recording device as described in any one of claims 1 to 13, characterized in that the control unit changes the irradiation amount by changing the irradiation time by the irradiation unit.

15. An inkjet recording device as described in any one of claims 1 to 14, characterized in that the control unit controls the timing of irradiation of the active energy rays by the irradiation unit.

16. An inkjet recording device as described in any one of claims 1 to 15, characterized in that the control unit changes the irradiation amount according to the transport speed of the medium.

17. The control unit: ejecting the ink onto the medium while causing the recording operation unit to scan the medium; While the irradiation unit is scanned across the medium, the ink that has been ejected by the recording operation unit and landed on the medium is irradiated with the active energy rays.

17. The inkjet recording apparatus according to claim 1, wherein the inkjet recording apparatus is a recording medium.

18. An inkjet recording apparatus according to claim 1, wherein the medium is continuous paper.

19. An inkjet recording apparatus according to claim 1, wherein the active energy rays are ultraviolet rays.

20. A method for controlling fixation of ink in an inkjet recording device comprising: a recording operation unit that ejects ink in a sol state onto a medium; and an irradiation unit that irradiates the ink ejected by the recording operation unit and gelling on the medium with active energy rays to fix the ink, the method comprising: an irradiation amount setting step of changing the irradiation amount of the active energy rays in accordance with the distance from the surface of the ink droplet to the innermost portion when the active energy rays are irradiated, thereby curing the ink in the innermost portion; A fixing control method comprising:

Images