Recording apparatus and recording method

Abstract

To react a radical generated by irradiating the surface of a recorded medium with corona from a corona irradiation part with ink bonded to a discharge part, and suppress occurrence of discharge failure of ink.SOLUTION: A recording device 1 drives a surface potential adjustment part so that a surface potential becomes a plus potential in a predetermined range when performing recording on a predetermined kind of a recorded medium stored in a storage part 123. The recording device 1 can suppress bonding of ink I to a discharge part 110, and can suppress occurrence of discharge failure of the ink I.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a recording apparatus and a recording method.

Background Art

[0002] Conventionally, various recording apparatuses that eject ink from a discharge unit onto a recording medium for recording have been used. For example, Patent Document 1 discloses a printing apparatus that includes a corona processor that modifies the surface of a recording medium by irradiating the surface of the recording medium with corona, and that forms an image by ejecting ultraviolet curable ink from a discharge head onto a roll-shaped recording medium.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There are various types of recording media, such as recording media made of resin. Among such resin-made recording media, when recording is performed on a recording media wound in a roll shape, when the roll-shaped recording media is peeled off from the roll, the inner back surface may be charged with a negative potential due to peeling electrification, and accordingly, the outer surface may be charged with a positive potential. For example, the main dots of the ink ejected from the ejection part of an inkjet head connected to the ground (GND) are charged with a negative potential, and the satellite dots generated accompanying the main dots are charged with a positive potential. Here, if the surface of the recording media is charged with a positive potential, since the satellite dots are charged with a positive potential, a repulsive force acts on the surface of the recording media, and the satellite dots may adhere to the ejection part. When the satellite dots adhere to the ejection part, the satellite dots may be fixed and cause ejection failure. This is considered to be because radicals are present on the surface of the recording media with the irradiation of corona, and the radicals on the surface of the recording media react with the satellite dots adhering to the ejection part to generate fixed substances of satellite dots that do not redissolve. Note that the satellite dots are particularly likely to cause ejection failure when adhering near the nozzles of the ejection part.

[0005] Here, the printing apparatus of Patent Document 1 includes an ionizer and can potentially neutralize the surface of the recording media by supplying negative ions to the surface of the recording media. Therefore, the adhesion of the satellite dots to the ejection part can be reduced. However, when ejecting ink from the ejection head, in addition to the main dots and the satellite dots, ink mist, which are minute dots, may be generated.

[0006] As a result of intensive studies by the present inventors, when satellite dots adhere to the ejection unit, although the satellite dots may adhere near the nozzles of the ejection unit, they are likely to adhere to portions other than near the nozzles, such as between the nozzle rows. Although this may cause ink to drip onto the surface of the recording medium when it accumulates, it has been found that satellite dots are not particularly likely to adhere near the nozzles of the ejection unit. On the other hand, as a result of intensive studies by the present inventors, when ink mist adheres to the ejection unit, it has been found that the ink mist is likely to adhere near the nozzles of the ejection unit. Here, the ink mist of the ink ejected from the ejection unit of the inkjet head connected to the ground (GND) is also charged to a negative potential. Naturally, even if the ink mist adheres to the ejection unit, it can cause ejection failure, similar to the case where satellite dots adhere to the ejection unit. That is, the present inventors have found that ink mist is more likely to adhere near the nozzles of the ejection unit than satellite dots, and the ink mist adhering near the nozzles of the ejection unit can be the main cause of ejection failure. Since ink mist is not particularly attracted to a recording medium whose surface potential has been neutralized, in the printing apparatus of Patent Document 1, it adheres not only to the surface of the recording medium but also to the ejection head, and ejection failure can also occur in the printing apparatus of Patent Document 1.

Means for Solving the Problems

[0007] The recording apparatus of the present invention for solving the above problems includes a conveyance unit that conveys a recording medium, a corona irradiation unit that is disposed in the conveyance path of the recording medium and modifies the surface of the recording medium by irradiating the surface with a corona, a discharge unit that is disposed downstream of the corona irradiation unit in the conveyance path and discharges an ultraviolet curable ink onto the surface, a surface potential adjustment unit that is disposed between the corona irradiation unit and the discharge unit in the conveyance path and adjusts the surface potential which is the potential of the surface, a control unit that controls the driving of the conveyance unit, the corona irradiation unit, the discharge unit, and the surface potential adjustment unit, and a storage unit that stores a predetermined type of recording medium which is a predetermined type among the recording media, and when performing recording on the predetermined type of recording medium stored in the storage unit, the control unit controls the driving of the surface potential adjustment unit so that the surface potential becomes a positive potential within a predetermined range.

[0008] Also, the recording method of the present invention for solving the above problems is a recording method executable using a recording apparatus including a conveyance unit that conveys a recording medium, a corona irradiation unit that is disposed in the conveyance path of the recording medium and modifies the surface of the recording medium by irradiating the surface with a corona, a discharge unit that is disposed downstream of the corona irradiation unit in the conveyance path and discharges an ultraviolet curable ink onto the surface, a surface potential adjustment unit that is disposed between the corona irradiation unit and the discharge unit in the conveyance path and adjusts the surface potential which is the potential of the surface, and a storage unit that stores a predetermined type of recording medium which is a predetermined type among the recording media, and when performing recording on the predetermined type of recording medium stored in the storage unit, the surface potential adjustment unit is driven so that the surface potential becomes a positive potential within a predetermined range.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

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Figure 7

Figure 8

Figure 9

Mode for Carrying Out the Invention

[0010] First, the present invention will be schematically described. A recording apparatus according to a first aspect of the present invention for solving the above problems includes a conveyance unit that conveys a recording medium, a corona irradiation unit that is disposed in a conveyance path of the recording medium and modifies the surface by irradiating the surface of the recording medium with corona, a discharge unit that is disposed downstream of the corona irradiation unit in the conveyance path and discharges ultraviolet-curable ink onto the surface, a surface potential adjustment unit that is disposed between the corona irradiation unit and the discharge unit in the conveyance path and adjusts a surface potential that is the potential of the surface, a control unit that controls the driving of the conveyance unit, the corona irradiation unit, the discharge unit, and the surface potential adjustment unit, and a storage unit that stores a predetermined type of recording medium that is a predetermined type among the recording media, and the control unit controls the driving of the surface potential adjustment unit so that the surface potential becomes a positive potential within a predetermined range when recording on the predetermined type of recording medium stored in the storage unit.

[0011] According to this aspect, when recording on a predetermined type of recording medium, the surface potential adjustment unit is driven so that the surface potential becomes a positive potential within a predetermined range. That is, even if minute ink mist is generated as the ink is ejected, the ink mist is attracted to the surface of the recording medium and is made easier to move, that is, it becomes difficult for the ink mist to adhere to the ejection unit, and the surface potential of the recording medium is adjusted. For this reason, it is possible to suppress the occurrence of defective ink ejection caused by the reaction between the radicals generated by irradiating the surface of the recording medium with corona from the corona irradiation unit and the ink adhering to the ejection unit.

[0012] The recording apparatus according to the second aspect of the present invention is characterized in that, in the first aspect, it includes a surface potential measurement unit that measures the surface potential, and the control unit controls the driving of the surface potential adjustment unit based on the measurement result of the surface potential measurement unit.

[0013] According to this aspect, the surface potential adjustment unit is driven based on the measurement result of the surface potential measurement unit. For this reason, based on the measurement result of the surface potential measurement unit, it is possible to accurately make the surface potential a positive potential within a predetermined range.

[0014] The recording apparatus according to the third aspect of the present invention is characterized in that, in the second aspect, it includes a rotating body that rotates while supporting the recording medium including a position facing the ejection unit, and the surface potential measurement unit is disposed at a position facing the rotating body and upstream of the ejection unit in the conveyance direction of the recording medium.

[0015] According to this aspect, the surface potential measurement unit is disposed at a position facing the rotating body and upstream of the ejection unit in the conveyance direction of the recording medium. For this reason, it is possible to measure the surface potential immediately before ejecting the ink from the ejection unit, and it is possible to particularly accurately make the surface potential a positive potential within a predetermined range.

[0016] In the recording apparatus according to the fourth aspect of the present invention, in the first aspect, the storage unit stores data associated with the predetermined type of recording medium so that the surface potential becomes a positive potential within the predetermined range, and the control unit controls the driving of the surface potential adjustment unit based on the data.

[0017] According to this aspect, the storage unit stores data associated with the predetermined type of recording medium so that the surface potential becomes a positive potential within the predetermined range, and the control unit controls the driving of the surface potential adjustment unit based on the data. Therefore, based on the data, it is possible to easily make the surface potential become a positive potential within the predetermined range.

[0018] In the recording apparatus according to the fifth aspect of the present invention, in any one of the first to fourth aspects, the positive potential within the predetermined range is characterized in that it is 150V or more and 400V or less.

[0019] According to this aspect, the positive potential within the predetermined range is 150V or more and 400V or less. By setting such a range, it is possible to effectively suppress the occurrence of poor ink ejection.

[0020] In the recording apparatus according to the sixth aspect of the present invention, in any one of the first to fifth aspects, a maintenance unit for maintaining the ejection unit is provided, and the control unit controls the maintenance unit to make the maintenance interval by the maintenance unit when recording on the predetermined type of recording medium stored in the storage unit shorter than the maintenance interval by the maintenance unit when recording on a medium other than the predetermined type of recording medium.

[0021] According to this aspect, when controlling the maintenance unit to perform recording on a predetermined type of recording medium stored in the storage unit, the maintenance interval by the maintenance unit when recording on a predetermined type of recording medium is made shorter than the maintenance interval by the maintenance unit when recording on a medium other than the predetermined type of recording medium. By driving the surface potential adjustment unit so that the surface potential becomes a positive potential within a predetermined range, there is a case where positively charged satellite dots adhere to the ejection unit and accumulate, and the ink caused by the satellite dots drips onto the recording medium. However, by shortening the maintenance interval, the risk of the ink caused by such satellite dots dripping onto the recording medium can be reduced.

[0022] The recording apparatus according to the seventh aspect of the present invention is characterized in that, in any one of the first to sixth aspects, the predetermined type of recording medium is a resin-made recording medium containing resin as a material.

[0023] According to this aspect, the predetermined type of recording medium is a resin-made recording medium containing resin as a material. The resin-made recording medium is prone to peeling electrification and the surface is prone to charging. However, by using the resin-made recording medium as the predetermined type of recording medium, it is possible to effectively suppress the occurrence of ink ejection failure even when the resin-made recording medium is used.

[0024] The recording apparatus according to the eighth aspect of the present invention is characterized in that, in the seventh aspect, the predetermined type of recording medium contains at least one of polyethylene terephthalate, polyethylene, and polypropylene as a material.

[0025] According to this aspect, the predetermined type of recording medium contains at least one of polyethylene terephthalate, polyethylene, and polypropylene as a material. A recording medium containing at least one of polyethylene terephthalate, polyethylene, and polypropylene as a material is particularly likely to generate peeling charge and is particularly likely to have its surface charged. However, by using a resin recording medium as a recording medium containing at least one of polyethylene terephthalate, polyethylene, and polypropylene as a material, even when using this recording medium, it is possible to effectively suppress the occurrence of ink ejection failure.

[0026] The recording method according to the ninth aspect of the present invention is a recording method executable using a recording apparatus including a conveyance unit that conveys a recording medium, a corona irradiation unit that is disposed in a conveyance path of the recording medium and modifies the surface by irradiating the surface of the recording medium with corona, a discharge unit that is disposed on the downstream side of the corona irradiation unit in the conveyance path and discharges ultraviolet-curable ink onto the surface, a surface potential adjustment unit that is disposed between the corona irradiation unit and the discharge unit in the conveyance path and adjusts the surface potential, which is the potential of the surface, and a storage unit that stores a predetermined type of recording medium, which is a predetermined type among the recording media. When performing recording on the predetermined type of recording medium stored in the storage unit, the surface potential adjustment unit is driven so that the surface potential becomes a positive potential within a predetermined range.

[0027] According to this aspect, when performing recording on a predetermined type of recording medium, the surface potential adjustment unit is driven so that the surface potential becomes a positive potential within a predetermined range. For this reason, it is possible to suppress the occurrence of ink ejection failure caused by the reaction between radicals generated by irradiating the surface of the recording medium with corona from the corona irradiation unit and the ink attached to the discharge unit.

[0028] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. First, an overview of the recording apparatus 1 according to an embodiment of the present invention will be described with reference to FIGS. 1 and 2. The recording apparatus 1 of this embodiment is a recording apparatus that forms an image on a recording medium M such as paper, cloth, or a resin film, and is communicably connected to a PC 2 as shown in FIG. 2. Note that the recording apparatus 1 of this embodiment is configured to be able to record on a recording medium M wound in a roll shape as shown in FIG. 1. However, the configuration is not limited to one that can use such a recording medium, and for example, a configuration that can use a recording medium in a shape where a long recording medium is alternately folded may be used.

[0029] As shown in FIG. 1, the recording apparatus 1 of this embodiment includes a feeding unit 101 that can feed out the recording medium M by setting and rotating the roll-shaped recording medium M. By the feeding unit 101, the recording medium M is fed out to the first driving roller 106 via the driven roller 102 and the first tension roller 103. Then, the recording medium M is conveyed in the conveying direction A by the first driving roller 106. Here, "driven" means moving along with the movement of the contacting recording medium M.

[0030] Near the driven roller 102, a corona irradiation unit 201 that irradiates the conveyed recording medium M with corona is provided. By irradiating the surface of the recording medium M with corona, the surface of the recording medium M is modified and the recording quality is improved.

[0031] The tension of the recording medium M fed out from the feeding unit 101 is detected by the first tension roller 103, and the torque of the feeding motor 127 shown in FIG. 2 is controlled by the control unit 120. Between the first tension roller 103 and the first driving roller 106, an end sensor 104 that detects the end of the recording medium M and a joint sensor 105 that detects the joint of the recording medium M are provided. When the recording medium M is conveyed in a meandering manner, the control unit 120 controls based on the detection result of the end sensor 104, and the meandering conveyance is corrected by interlocking the feeding unit 101 and the first tension roller 103.

[0032] Also, an ionizer 202 for irradiating ions is provided between the first tension roller 103 and the first drive roller 106. The surface of the recording medium M may be charged when the recording medium M is pulled out and peeled off from the rolled portion. However, the surface of the recording medium M can be discharged by irradiating ions with a charge opposite to that of the ions charged on the surface of the recording medium M from the ionizer 202.

[0033] A driven roller 108 is provided on the downstream side of the first drive roller 106 in the conveyance direction A, and a driven drum 109 serving as a support portion for the recording medium M is provided further downstream in the conveyance direction A. An eye mark sensor 107 for detecting an eye mark recorded on the recording medium M is provided between the first drive roller 106 and the driven roller 108. Here, the eye mark is a mark used for controlling the timing of recording when recording is temporarily stopped and then resumed, or when further recording is performed following the previous recording. Note that the eye mark may be recorded on the recording medium M together with an image by a head 110 serving as a discharge unit, or may be recorded on the recording medium M in advance.

[0034] At a position facing the driven drum 109, a plurality of heads 110 as ejection units for ejecting ink and a plurality of ultraviolet irradiation units 111 are provided. Since the recording apparatus 1 of the present embodiment uses ultraviolet curable ink that cures when irradiated with ultraviolet light for any ink, it is provided with an ultraviolet irradiation unit 111 to cure the ink. Further, in the recording apparatus 1 of the present embodiment, as the head 110, heads 110a and 110b for ejecting white ink for forming a background image, heads 110c, 110d, 110e, and 110f for ejecting colored ink for forming a colored image, and a head 110g for ejecting post-treatment ink, are provided with seven heads 110, and as the ultraviolet irradiation unit 111, it is provided with three ultraviolet irradiation units 111, namely, ultraviolet irradiation unit 111a, ultraviolet irradiation unit 111b, and ultraviolet irradiation unit 111c. However, the number and arrangement of the heads 110 and the ultraviolet irradiation units 111 are not particularly limited.

[0035] At a position facing the head 110 and the ultraviolet irradiation unit 111, the recording medium M is conveyed in a state of being wound around the driven drum 109. The driven drum 109 is provided with an encoder 130 as shown in FIG. 2, and the encoder 130 detects the rotational speed of the driven drum 109 corresponding to the conveyance speed of the recording medium M, and the control unit 120 controls the ejection timing of the ink from the head 110 so that a desired image is formed at a desired position of the recording medium M. Note that the conveyance distance of the recording medium M is also managed by the control unit 120 based on the detection result of the encoder 130.

[0036] At a position facing the driven drum 109 and upstream of the head 110a in the conveyance direction A, a surface potential measurement unit 203 for measuring the surface potential of the recording medium M is provided. The control unit 120 inputs the measurement result of the surface potential measurement unit 203 and can drive an ionizer 202 as a surface potential adjustment unit that adjusts the surface potential, which is the surface potential of the recording medium M, to a desired range according to the measurement result.

[0037] On the downstream side of the driven drum 109 in the conveying direction A, a second driving roller 113 is provided via a second tension roller 112. The tension in the conveying direction A applied to the recording medium M wound around the driven drum 109 is detected by the second tension roller 112, and based on the detection result at the second tension roller 112, the torque of the second conveying motor 131 represented in FIG. 2, which is the driving motor of the second driving roller 113, is controlled by the control unit 120 to obtain a desired tension.

[0038] On the downstream side of the second driving roller 113 in the conveying direction A, a third tension roller 114, a driven roller 115, and a driven roller 116 are arranged in sequence. And on the downstream side of the driven roller 116 in the conveying direction A, a winding unit 118 is provided. The winding unit 118 can wind the recording medium M in a roll shape by rotating. The tension applied to the winding unit 118 can be detected by the third tension roller 114, and based on the detection result of the third tension roller 114, the torque of the winding motor 133 represented in FIG. 2, which is the driving motor of the winding unit 118, is controlled by the control unit 120 to obtain a desired tension. Note that the tension can also be changed according to the winding diameter of the recording medium M wound around the winding unit 118.

[0039] Next, the electrical configuration of the recording apparatus 1 in this embodiment will be described with reference to FIG. 2. The recording apparatus 1 of this embodiment is connected to the PC 2 and includes a control unit 120 inside the recording apparatus 1, but is not limited to such a configuration. For example, a configuration in which the PC 2 connected to the recording apparatus 1 also serves as at least a part of the role of the control unit of the recording apparatus 1 may be adopted.

[0040] The control unit 120 is provided with a CPU 121 that controls the entire recording apparatus 1. The CPU 121 is connected via a system bus 122 to a storage unit 123 having a ROM that stores various control programs and the like executed by the CPU 121, a RAM that can temporarily store data, and an EEPROM. The storage unit 123 stores a predetermined type of recording medium, which is a specific recording medium among the recording media M that can be used by the recording apparatus 1 of this embodiment, and stores data on under what conditions ions are to be irradiated from the ionizer 202 corresponding to the corona illuminance by the corona irradiation unit 201 and the predetermined type of recording medium.

[0041] Further, the CPU 121 is connected via the system bus 122 to a head drive unit 124 for driving each head 110 to eject ink. Also, the CPU 121 is connected via the system bus 122 to an ultraviolet irradiation unit drive unit 125 for driving each ultraviolet irradiation unit 111 to irradiate ultraviolet light.

[0042] Further, the CPU 121 is connected via the system bus 122 to a corona irradiation unit drive unit 211 for driving the corona irradiation unit 201 to irradiate corona. Also, the CPU 121 is connected via the system bus 122 to an ionizer drive unit 212 for driving the ionizer 202 to irradiate ions.

[0043] Further, the CPU 121 is connected to a motor drive unit 126 which is connected via a system bus 122 to a feed motor 127, a first conveyance motor 129, a second conveyance motor 131, a discharge motor 132, a take-up motor 133, a head movement motor 221, and a maintenance unit drive motor 222. Here, the feed motor 127 is a drive motor of the feed unit 101. The first conveyance motor 129 is a drive motor of the first drive roller 106. The second conveyance motor 131 is a drive motor of the second drive roller 113. The discharge motor 132 is a drive motor of the discharge roller 117. The take-up motor 133 is a drive motor of the take-up unit 118. The head movement motor 221 is a drive motor that constitutes a gap adjustment unit for changing the distance between the head 110 and the driven drum 109, that is, the distance PG (paper gap) between the head 110 and the recording medium M, by moving the head 110. The maintenance unit drive motor 222 is a drive motor for a wiper, a suction cap, etc. (not shown) capable of maintaining the head 110, and constitutes a maintenance unit together with the wiper, the suction cap, etc. By performing maintenance on the head 110, deposits adhering to the nozzles of the head 110 are removed, and the amount of radicals present in the head 110 decreases.

[0044] Also, the CPU 121 is connected via the system bus 122 to an end sensor 104, a joint sensor 105, an eye mark sensor 107, and a surface potential measurement unit 203. The CPU 121 is also connected via the system bus 122 to a first tension roller 103, a second tension roller 112, and a third tension roller 114. The CPU 121 is further connected via the system bus 122 to a PC 2 for transmitting and receiving data and signals such as image data, via an input / output unit 134.

[0045] Next, an example of a control method for an ionizer as a surface potential adjustment unit of a conventional recording apparatus that records on a roll-shaped recording medium M and the recording apparatus 1 of the present embodiment will be described with reference to FIG. 3. In a conventional recording apparatus and the recording apparatus 1 of the present embodiment that record on a roll-shaped recording medium M, as shown in the leftmost state diagram of FIG. 3, when the recording medium M is peeled off from the roll, the back surface Mb, which is the inner surface, is charged to a negative potential, and the front surface Ma on the side opposite to the back surface Mb is charged to a positive potential.

[0046] In a conventional recording apparatus that records on a roll-shaped recording medium M, as shown in the second upper state diagram from the left in FIG. 3, in order to neutralize the positive potential of the front surface Ma, an appropriate amount of negative ions is irradiated from the ionizer to the front surface Ma to neutralize the positive potential of the front surface Ma. Then, as shown in the upper rightmost state diagram of FIG. 3, the front surface Ma becomes a substantially plus-minus zero charged state, and ink is ejected from the head 110 to perform recording on the recording medium M in such a charged state. Thus, in a conventional recording apparatus, the drive of the ionizer is controlled so that the front surface Ma becomes a substantially plus-minus zero charged state by irradiating ions from the ionizer before recording.

[0047] On the other hand, in the recording apparatus 1 of the present embodiment, as shown in the second lower state diagram from the left in FIG. 3, for example, positive ions are irradiated from the ionizer to the front surface Ma in order to charge the front surface Ma to a positive potential within a predetermined range. Then, as shown in the lower rightmost state diagram of FIG. 3, the front surface Ma becomes a charged state with a positive potential within a predetermined range, and ink is ejected from the head 110 to perform recording on the recording medium M in such a charged state. Thus, in the recording apparatus 1 of the present embodiment, the drive of the ionizer 202 is controlled so that the front surface Ma becomes a charged state with a positive potential within a predetermined range by spraying ions from the ionizer 202 before recording. When the front surface Ma has a positive potential equal to or higher than a predetermined range in the leftmost state diagram of FIG. 3, there are cases where ions are not sprayed from the ionizer 202, and there are also cases where negative ions are sprayed from the ionizer 202.

[0048] The recording apparatus 1 of this embodiment can use various types of recording media M. In a conventional recording apparatus, when using a resin recording medium M, especially a polyethylene terephthalate recording medium M, there were many ink ejection failures. This is considered to be due to the large amount of radicals generated by corona treatment when using a polyethylene terephthalate recording medium M. Therefore, next, the radical generation mechanism by corona treatment when using a polyethylene terephthalate recording medium M will be described with reference to FIG. 4.

[0049] As represented by the structural formula on the left side of FIG. 4, polyethylene terephthalate has a structure having carbonyl groups on both sides of the benzene ring, and has a structure in which a plurality of them are connected. Here, when polyethylene terephthalate is irradiated with corona from the corona irradiation unit 201 by corona treatment, as represented by the structural formula on the right side of FIG. 4, the benzene ring and the carbonyl group are cleaved, and radicals represented by compound S1, compound S2, and compound S3 are formed. Here, the symbol R in the figure is an alkyl group having various structures.

[0050] Some of the radicals generated in this way form oxalic acid or oxalic acid-like compounds with each other, but those remaining as radicals may react with the ink. Since radicals can act as polymerization initiators for ultraviolet curable inks, the radicals generated in this way react with the ink near the nozzles of the head 110 and can cause ejection failures.

[0051] Next, the mechanism by which ink adheres to the vicinity of the nozzles of the head 110 will be described with reference to FIGS. 5 and 6. The head 110 of the recording apparatus 1 of this embodiment has a nozzle N and a piezo element (not shown) that extrudes the ink from the nozzle N. Here, FIG. 5 is a graph showing an example of the waveform of the voltage applied to the piezo element, and FIG. 6 is a schematic diagram showing the state near the nozzle N corresponding to the waveform example of FIG. 5.

[0052] As shown in FIG. 5, when discharging ink I from nozzle N, a negative voltage is first applied to the piezo element from a state where voltage application is stopped. Then, subsequently, a positive voltage is applied to the piezo element. Then, voltage application is stopped again. The waveform in FIG. 5 is a waveform corresponding to the discharge of ink I for one dot.

[0053] The leftmost state diagram in FIG. 6 represents the state corresponding to the position P1 of the waveform in FIG. 5 where voltage application to the piezo element is stopped. In the leftmost state diagram in FIG. 6, the interface Ia of ink I at nozzle N forms a meniscus that is concave inward.

[0054] The second state diagram from the left in FIG. 6 represents the state corresponding to the position P2 of the waveform in FIG. 5 where a negative voltage is applied to the piezo element. By applying a negative voltage to the piezo element, the piezo element is displaced to apply a negative pressure to ink I at nozzle N. As shown in the second state diagram from the left in FIG. 6, when the piezo element is displaced to apply a negative pressure to ink I at nozzle N, the interface Ia of ink I at nozzle N is greatly concave inward.

[0055] The third state diagram from the left in FIG. 6 represents the state corresponding to the position P3 of the waveform in FIG. 5 during the process where a positive voltage is applied to the piezo element to change from a negative voltage to a positive voltage. In such a voltage application state, the piezo element is displaced to apply a positive pressure to ink I at nozzle N. As shown in the third state diagram from the left in FIG. 6, when the piezo element is displaced to apply a positive pressure to ink I at nozzle N, the interface Ia of ink I at nozzle N greatly protrudes outward at the central portion of nozzle N.

[0056] The fourth state diagram from the left in FIG. 6 represents the state corresponding to the position P4 of the waveform in FIG. 5 where a positive voltage is applied to the piezoelectric element. As shown in the fourth state diagram from the left in FIG. 6, with respect to the third state diagram from the left in FIG. 6, the piezoelectric element is displaced so as to further apply a positive pressure to the ink I at the nozzle N, and thus the interface Ia of the ink I at the nozzle N protrudes further outward in the central portion of the nozzle N.

[0057] The rightmost state diagram in FIG. 6 represents the state corresponding to the position P5 of the waveform in FIG. 5 where the voltage applied to the piezoelectric element changes from the state where a positive voltage is applied to the piezoelectric element to a state where the voltage approaches zero. As shown in the rightmost state diagram in FIG. 6, the ink I that protruded greatly outward in the fourth state diagram from the left in FIG. 6 separates into the main dot I1, the satellite dot I2, and the minute ink mist I3. Here, when the head 110 is connected to the ground (GND), it is considered that the main dot I1 is charged negatively, the satellite dot I2 is charged positively, and the minute ink mist I3 is charged negatively. Since the main dot I1 and the satellite dot I2 are heavy and the ejection energy associated with being ejected from the nozzle N is large, substantially all of the main dot I1 and most of the satellite dot I2 land on the surface Ma of the recording medium M. On the other hand, since the minute ink mist I3 is light and has a small ejection energy, it may become a floating mist or adhere near the nozzle N. That is, it can be considered that the adhesion of the ink I near the nozzle N of the head 110 is caused by the ink mist I3 generated when the ink I is ejected from the nozzle N.

[0058] Next, an example of a recording method executable in the recording apparatus 1 will be described with reference to FIG. 7. For example, when recording data is input from a PC 2 or the like and the recording method of this embodiment is started, as shown in FIG. 7, first, in step S110, the control unit 120 checks the recording conditions from the recording data. The check of the recording conditions is, for example, a check such as the type of the recording medium M and whether to record a background image. Here, the check of the type of the recording medium M includes a check of whether to record on a predetermined type of recording medium stored in the storage unit 123 and a check of the irradiation conditions of ions from the specific ionizer 202 when recording on a predetermined type of recording medium.

[0059] When the recording conditions are checked in step S110, in step S120, the conveyance of the recording medium M is started. Then, in step S130, the control unit 120 determines whether to irradiate the corona from the corona irradiation unit 201 at a desired position of the recording medium M. The determination of whether to irradiate the corona is made based on the content of the recording data checked in step S110. If it is determined in step S130 that the corona is to be irradiated, the process proceeds to step S140, where the corona is irradiated from the corona irradiation unit 201 at a desired position of the recording medium M, and then the process proceeds to step S150. On the other hand, if it is determined in step S130 that the corona is not to be irradiated, the process proceeds to step S150 without proceeding to step S140.

[0060] In step S150, in the control unit 120, it is also determined whether to irradiate ions from the ionizer 202 to a desired position on the recording medium M, and if ions are to be irradiated, it is also determined whether the recording medium M is a predetermined type of recording medium and under what conditions the ions are to be irradiated. The determination of whether to irradiate ions is made based on the content of the recording data confirmed in step S110. Further, the determination of under what conditions the ions are to be irradiated is made by first determining whether the recording medium M is a predetermined type of recording medium, and if it is a predetermined type of recording medium, it can be determined based on the data stored in the storage unit 123 or the measurement result of the surface potential measurement unit 203. Here, the data stored in the storage unit 123 is data corresponding to the relationship between the predetermined type of recording medium and the corona illuminance from the corona irradiation unit 201. In any case, if it is a predetermined type of recording medium, the control unit 120 controls the driving of the ionizer 202 so that the surface potential, which is the potential of the surface Ma of the recording medium M, becomes a positive potential within a predetermined range.

[0061] FIG. 8 is a graph showing the relationship between the corona illuminance from the corona irradiation unit 201 and the surface potential of the target recording medium M adjusted by the ionizer 202 when polyethylene terephthalate (PET) and polypropylene (PP) are used as the recording medium M, which is a predetermined type of recording medium, corresponding to the data stored in the storage unit 123. In this embodiment, for example, ions are irradiated so that the surface potential becomes 150 V or more and 400 V or less. When polyethylene terephthalate (PET) and polypropylene (PP) are used as the recording medium M, the value changes under the influence of the conveyance speed of the recording medium M, but the surface potential of the recording medium M before irradiating ions from the ionizer 202 is about 0 to 50 V in each case. For this reason, for example, when polyethylene terephthalate is used as the recording medium M, the surface potential of the recording medium M before irradiating ions from the ionizer 202 is 50 V, and the corona illuminance is 500 W, positive charge ions are irradiated from the ionizer 202 so that the surface potential of the recording medium M increases by approximately 150 V. Further, for example, when polypropylene is used as the recording medium M, the surface potential of the recording medium M before irradiating ions from the ionizer 202 is 50 V, and the corona illuminance is 500 W, positive charge ions are irradiated from the ionizer 202 so that the surface potential of the recording medium M increases by approximately 100 V.

[0062] Similarly, for example, when polyethylene terephthalate is used as the recording medium M, the surface potential of the recording medium M before irradiating ions from the ionizer 202 is 50 V, and the corona illuminance is 2000 W, positive charge ions are irradiated from the ionizer 202 so that the surface potential of the recording medium M increases by approximately 350 V. Further, for example, when polypropylene is used as the recording medium M, the surface potential of the recording medium M before irradiating ions from the ionizer 202 is 50 V, and the corona illuminance is 2000 W, positive charge ions are irradiated from the ionizer 202 so that the surface potential of the recording medium M increases by approximately 250 V.

[0063] If it is determined in step S150 that ions are to be irradiated, the process proceeds to step S160, where ions are irradiated from the ionizer 202 to a desired position on the recording medium M, and then the process proceeds to step S170. On the other hand, if it is determined in step S150 that ions are not to be irradiated, the process proceeds to step S170 without proceeding to step S160.

[0064] In step S170, the control unit 120 determines whether to record a background image at a desired position on the recording medium M. The determination of whether to record a background image is made based on the content of the recording data confirmed in step S110. If it is determined in step S170 that a background image is to be recorded, the process proceeds to step S180, where white ink is ejected from the heads 110a and 110b to form a background image at a desired position on the recording medium M, and then the process proceeds to step S190. On the other hand, if it is determined in step S170 that a background image is not to be recorded, the process proceeds to step S190 without proceeding to step S180.

[0065] In step S190, a colored image is recorded at a desired position on the recording medium M. Here, if a background image is recorded in step S180, the colored image is recorded at the formation position of the background image. The recording of the colored image is performed by ejecting black ink, cyan ink, magenta ink, and yellow ink as colored inks from the heads 110c, 110d, 110e, and 110f, and ejecting post-treatment ink from the head 110g as necessary. Also, in steps S180 and S190, ultraviolet irradiation from each ultraviolet irradiation unit 111 is performed in accordance with the ejection of each ink from each head.

[0066] After the end of step S190, the process proceeds to step S200, where the control unit 120 determines whether all of the input recording data has been recorded. If it is determined that all of the input recording data has been recorded, the recording method of this embodiment is terminated. On the other hand, if it is determined that not all of the input recording data has been recorded, the process returns to step S130, and steps S130 to S190 are repeated until it is determined that all of the input recording data has been recorded.

[0067] Here, once the recording apparatus 1 of this embodiment is summarized, the recording apparatus 1 of this embodiment includes a first drive roller 106 and a second drive roller 113 as a conveyance unit for conveying the recording medium M, a corona irradiation unit 201 disposed on the conveyance path of the recording medium M for modifying the surface Ma by irradiating the surface Ma of the recording medium M with corona, a head 110 as a discharge unit disposed on the downstream side of the corona irradiation unit 201 in the conveyance path of the recording medium M for discharging an ultraviolet curable ink I onto the surface Ma, an ionizer 202 as a surface potential adjustment unit disposed between the corona irradiation unit 201 and the head 110 in the conveyance path of the recording medium M for adjusting the surface potential which is the potential of the surface Ma, a control unit 120 for controlling the driving of the first drive roller 106, the second drive roller 113, the corona irradiation unit 201, the head 110, and the ionizer 202, and a storage unit 123 for storing a predetermined type of recording medium which is a predetermined type among the recording media M. And when performing recording on the predetermined type of recording medium stored in the storage unit 123, the control unit 120 controls the driving of the ionizer 202 so that the surface potential becomes a positive potential within a predetermined range.

[0068] In other words, when performing recording on the predetermined type of recording medium stored in the storage unit 123 using the recording apparatus 1 of this embodiment, a recording method can be executed to drive the ionizer 202 so that the surface potential becomes a positive potential within a predetermined range. Thus, when performing recording on a predetermined type of recording medium, by driving the surface potential adjustment unit so that the surface potential becomes a positive potential within a predetermined range, even if minute ink mist I3 is generated when discharging the ink I, the ink mist I3 can be attracted to the surface Ma of the recording medium M and made to be easily directed, that is, it can be made difficult for the ink mist I3 to adhere to the head 110. For this reason, the recording apparatus 1 of this embodiment can suppress the occurrence of poor discharge of the ink I due to the reaction between the radicals generated by irradiating the surface Ma of the recording medium M with corona from the corona irradiation unit 201 and the ink I adhering to the head 110.

[0069] Also, as described above, the storage unit 123 stores data associated with a predetermined type of recording medium so that the surface potential becomes a positive potential within a predetermined range. And the control unit 120 can control the driving of the ionizer 202 based on this data. Therefore, the recording apparatus 1 of the present embodiment can easily make the surface potential become a positive potential within a predetermined range based on this data.

[0070] On the other hand, as described above, the recording apparatus 1 of the present embodiment includes a surface potential measurement unit 203 that measures the surface potential, and the control unit 120 can also control the driving of the ionizer 202 based on the measurement result of the surface potential measurement unit 203. Therefore, the recording apparatus 1 of the present embodiment can accurately make the surface potential become a positive potential within a predetermined range based on the measurement result of the surface potential measurement unit 203.

[0071] Also, as described above, the recording apparatus 1 of the present embodiment includes a driven drum 109 that is a rotating body that supports and rotates the recording medium M including a position facing the head 110, and the surface potential measurement unit 203 is disposed at a position facing the driven drum 109 and upstream of the head 110 in the conveyance direction A of the recording medium M. Therefore, the recording apparatus 1 of the present embodiment can measure the surface potential immediately before discharging the ink from the head 110, and can particularly accurately make the surface potential become a positive potential within a predetermined range.

[0072] Also, as described above, in the recording apparatus 1 of this embodiment, the positive potential within a predetermined range is 150 V or more and 400 V or less. By setting the surface potential of the recording medium M to a positive potential within such a range, it is possible to effectively suppress the occurrence of ink ejection failures. FIG. 9 is a graph showing an example of the relationship between the surface potential of surface Ma and the number of ejection failure nozzles when the corona illuminance is 500 W and a polyethylene terephthalate film is used as the recording medium M. Compared with the case where the surface potential is plus or minus 0 V, when the surface potential is +200 V and when the surface potential is +400 V, even if the recording distance to the recording medium M becomes longer when continuous recording is performed, the number of ejection failure nozzles can be significantly suppressed. Although not shown in FIG. 9, it is known that in the range where the surface potential is from +150 V to +400 V, such as when the surface potential is +150 V, the number of ejection failure nozzles can be significantly suppressed even if the recording distance to the recording medium M becomes longer.

[0073] Also, as described above, the recording apparatus 1 of this embodiment includes a maintenance unit drive motor 222, a wiper, a suction cap (not shown), etc., and is provided with a maintenance unit capable of maintaining the head 110. Then, the control unit 120 controls the maintenance unit to make the maintenance interval by the maintenance unit when recording on a predetermined type of recording medium stored in the storage unit 123 shorter than the maintenance interval by the maintenance unit when recording on a recording medium other than the predetermined type of recording medium.

[0074] By driving the ionizer 202 so that the surface potential becomes a positive potential within a predetermined range, positively charged satellite dots I2 may adhere to and accumulate on the head 110, and the ink I due to the satellite dots I2 may drip onto the recording medium M. However, the recording apparatus 1 according to the present embodiment reduces the maintenance interval under the condition that the positively charged satellite dots I2 are likely to adhere to the head 110 due to the repulsive force by charging the surface Ma of the recording medium M positively, thereby reducing the risk that the ink I due to such satellite dots I2 accumulates on the head 110 and drips onto the recording medium M. Note that since the satellite dots I2 have a larger dot diameter than the minute ink mist I3, when the satellite dots I2 adhere to the head 110, the possibility that the ink I adhering to the head 110 drips onto the recording medium M is higher than when the ink mist I3 adheres to the head 110.

[0075] Here, in the present embodiment, the predetermined type of recording medium is a resin-made recording medium containing resin as a material. The resin-made recording medium is likely to generate peeling charge and the surface Ma is likely to be charged. However, by using the resin-made recording medium as the predetermined type of recording medium, it is possible to effectively suppress the occurrence of poor ink ejection even when the resin-made recording medium is used.

[0076] Here, as the predetermined type of recording medium, it is preferable to store in the storage unit 123 a medium containing at least any one of polyethylene terephthalate, polyethylene, and polypropylene as a material. The recording medium M containing at least any one of polyethylene terephthalate, polyethylene, and polypropylene as a material is particularly likely to generate peeling charge and the surface Ma is particularly likely to be charged. However, by using the resin-made recording medium as the recording medium M containing at least any one of polyethylene terephthalate, polyethylene, and polypropylene as a material, it is possible to effectively suppress the occurrence of poor ink ejection even when the recording medium M is used.

[0077] The present invention is not limited to the above-described embodiments, and can be realized in various configurations without departing from the gist thereof. For example, the technical features in the embodiments corresponding to the technical features in each form described in the summary of the invention can be appropriately replaced or combined in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects. Further, if the technical feature is not described as essential in this specification, it can be appropriately deleted.

Explanation of Signs

[0078] 1... Recording device, 2... PC, 101... Feeding unit, 102... Driven roller, 103... First tension roller, 104... End sensor, 105... Joint sensor, 106... First driving roller (transport unit), 107... Eye mark sensor, 108... Driven roller, 109... Driven drum (rotating body), 110... Head (discharge unit), 110a... Head, 110b... Head, 110c... Head, 110d... Head, 110e... Head, 110f... Head, 110g... Head, 111... Ultraviolet irradiation unit, 111a... Ultraviolet irradiation unit, 111b... Ultraviolet irradiation unit, 111c... Ultraviolet irradiation unit, 112... Second tension roller, 113... Second driving roller (transport unit), 114... Third tension roller, 115... Driven roller, 116... Driven roller, 117... Discharge roller, 118... Take-up unit, 120... Control unit, 121... CPU, 122... System bus, 123... Storage unit, 124... Head driving unit, 125... Ultraviolet irradiation unit driving unit, 126... Motor driving unit, 127... Feeding motor, 129... First transport motor, 130... Encoder, 131... Second transport motor, 132... Discharge motor, 133... Take-up motor, 134... Input / output unit, 201... Corona irradiation unit, 202... Ionizer (surface potential adjustment unit), 203... Surface potential measurement unit, 211... Corona irradiation unit driving unit, 212... Ionizer driving unit, 221... Head movement motor (spacing adjustment unit), 222... Maintenance unit driving motor (maintenance unit), M... Recording medium

Claims

1. A transport unit that transports a recording medium, A corona irradiation unit that is disposed in the transport path of the recording medium and irradiates the surface of the recording medium with corona to modify the surface, A discharge unit that is disposed downstream of the corona irradiation unit in the transport path and discharges ultraviolet-curable ink onto the surface, A surface potential adjustment unit that is disposed between the corona irradiation unit and the discharge unit in the transport path and adjusts the surface potential, which is the electric potential of the surface, A control unit that controls the driving of the transport unit, the corona irradiation unit, the discharge unit, and the surface potential adjustment unit, A storage unit that stores a predetermined type of recording medium, which is a predetermined type among the recording media, The control unit controls the driving of the surface potential adjustment unit so that the surface potential becomes a positive potential within a predetermined range when recording on the predetermined type of recording medium stored in the storage unit. A recording apparatus characterized by that.

2. The recording apparatus according to claim 1, further comprising a surface potential measurement unit that measures the surface potential, The control unit controls the driving of the surface potential adjustment unit based on the measurement result of the surface potential measurement unit. A recording apparatus characterized by that.

3. In the recording apparatus according to claim 2, When the surface potential in the measurement result of the surface potential measurement unit is a negative potential outside a predetermined range, the control unit sprays positive ions onto the surface of the predetermined type of recording medium so that the surface potential becomes a positive potential within the predetermined range, and controls the driving of the surface potential adjustment unit, When the surface potential in the measurement result of the surface potential measurement unit is a positive potential outside a predetermined range, the control unit sprays negative ions onto the surface of the predetermined type of recording medium or does not spray ions so that the surface potential becomes a positive potential within the predetermined range, and controls the driving of the surface potential adjustment unit. A recording apparatus characterized by that.

4. In the recording apparatus according to claim 3, When recording on the predetermined type of recording medium stored in the storage unit, the control unit controls the driving of the surface potential adjustment unit so that the higher the corona illuminance of the corona irradiation unit, the higher the surface potential becomes at the positive potential within the predetermined range. A recording apparatus characterized by that.

5. The recording apparatus according to claims 2 to 4, further comprising a rotating body that rotates while supporting the recording medium including a position facing the discharge unit. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ 、 The surface potential measurement unit is disposed at a position facing the rotating body and on the upstream side in the conveyance direction of the recording medium with respect to the ejection unit. A recording apparatus characterized by this. **Claim 6** In the recording apparatus according to claim 1, the storage unit stores data associated with the predetermined type of recording medium such that the surface potential becomes a positive potential within the predetermined range, and the control unit controls the driving of the surface potential adjustment unit based on the data. A recording apparatus characterized by this. **Claim 7** In the recording apparatus according to any one of claims 1 to 6, the positive potential within the predetermined range is 150 V or more and 400 V or less. A recording apparatus characterized by this. **Claim 8** In the recording apparatus according to any one of claims 1 to 7, a maintenance unit for maintaining the ejection unit is provided, and the control unit controls the maintenance unit to make the maintenance interval by the maintenance unit when recording on the predetermined type of recording medium stored in the storage unit shorter than the maintenance interval by the maintenance unit when recording on a recording medium other than the predetermined type of recording medium. A recording apparatus characterized by this. **Claim 9** In the recording apparatus according to any one of claims 1 to 8, the predetermined type of recording medium is a resin-made recording medium containing resin as a material. A recording apparatus characterized by this. **Claim 10** In the recording apparatus according to claim 9, the predetermined type of recording medium contains at least any one of polyethylene terephthalate, polyethylene, and polypropylene as a material. **Claim 11** In the recording apparatus according to claim 1, when recording on the predetermined type of recording medium stored in the storage unit, the control unit controls the driving of the surface potential adjustment unit such that the higher the corona illuminance of the corona irradiation unit, the higher the surface potential becomes at the positive potential within the predetermined range. A recording apparatus characterized by this. **Claim 12** A conveyance unit for conveying the recording medium, a corona irradiation unit disposed in the conveyance path of the recording medium and irradiating the surface of the recording medium with corona to modify the surface, an ejection unit disposed on the downstream side of the corona irradiation unit in the conveyance path and ejecting ultraviolet curable ink onto the surface, and a surface potential adjustment unit disposed between the corona irradiation unit and the ejection unit in the conveyance path and adjusting the surface potential which is the potential of the surface. ​ ​ ​ A storage unit that stores a predetermined type of recording medium, which is a predetermined type among the recording media; Comprising: A recording method executable using a recording apparatus, When recording on the predetermined type of recording medium stored in the storage unit, the surface potential is made to be a positive potential within a predetermined range by driving the surface potential adjustment unit. A recording method characterized by this.

13. In the recording method according to claim 12, When the surface potential in the measurement result of the surface potential measurement unit is a negative potential outside the predetermined range, positive ions are sprayed onto the surface of the predetermined type of recording medium so that the surface potential becomes a positive potential within the predetermined range, and the surface potential adjustment unit is driven. When the surface potential in the measurement result of the surface potential measurement unit is a positive potential outside the predetermined range, negative ions are sprayed onto the surface of the predetermined type of recording medium or no ions are sprayed, and the surface potential becomes a positive potential within the predetermined range. The surface potential adjustment unit described above is driven. A recording method characterized by this.

14. In the recording apparatus according to claim 13, When recording on the predetermined type of recording medium stored in the storage unit, the higher the corona illuminance of the corona irradiation unit, the higher the surface potential becomes at the positive potential within the predetermined range. A recording method characterized by driving the surface potential adjustment unit. ​

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