JP2016145098A - Printer and printing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a medium taken up to a take-up shaft in an overlapping manner from deviating in an axial direction of the take-up shaft in a printing technique for taking up the medium to the take-up shaft while applying tension thereto.SOLUTION: A printer comprises: a printing part which prints an image on a first medium; a take-up shaft which takes up the first medium by rotating the first medium on which the image is printed; and a control part which controls tension applied to the first medium. The control part performs control so that the tension applied to the first medium is larger than 0[N] and less than 8[N] at the time of taking up the first medium to the take-up shaft.SELECTED DRAWING: Figure 7

Description

  The present invention relates to a technique for winding a medium on which an image is printed on a winding shaft.

  Patent Document 1 discloses a technique for controlling a winding tension when winding an inkjet recording sheet. Specifically, the winding tension is controlled to 5 to 40 [kg], that is, 50 [N] to 400 [N] with respect to the width of 1 meter.

JP 2002-265103 A

  By the way, in a printing apparatus that winds a medium around a take-up shaft while applying tension, a force corresponding to the tension acts between the media wound around the take-up shaft. At this time, if a large tension as in Patent Document 1 is applied to the medium, a large force directed in the axial direction of the take-up shaft is generated between the wound media, and these may be shifted in the axial direction. It was.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following forms.

  In order to achieve the above object, a printing apparatus according to a first aspect of the present invention includes a printing unit that prints an image on a first medium, and a winding shaft that winds the first medium on which the image is printed by rotating the printing medium. And a control unit that controls the tension applied to the first medium. The control unit has a tension applied to the first medium that is greater than 0 [N] when the first medium is wound around the winding shaft. Control to be as follows.

  The printing method according to the first aspect of the present invention includes a step of printing an image on a medium, and a step of winding the medium on which the image is printed on a rotating rotary shaft, and winding the medium on a winding shaft. In addition, the tension applied to the medium is controlled to be greater than 0 [N] and less than or equal to 8 [N].

  Thus, in the first embodiment of the present invention (printing apparatus, printing method), when the first medium (medium) is wound around the take-up shaft, the tension applied to the first medium is greater than 0 [N (Newton)]. [N] Control is performed so as to be the following. Therefore, it is possible to suppress the first medium wound on the take-up shaft from shifting in the axial direction of the take-up shaft.

  By the way, a force corresponding to the tension acts between the first medium wound on the take-up shaft, so that the image printed on the first medium is pressed against the adjacent medium with a large force. There may be a mark on one medium. When such a mark becomes a problem, the control unit controls the printing apparatus so as to control the tension applied to the medium to be 5 [N] or less when the first medium is wound on the winding shaft. It may be configured. As a result, it is possible to suppress the formation of a mark on the first medium.

  In addition, the control unit may configure the printing apparatus so as to control the tension applied to the first medium to be 5 [N] or more when the first medium is wound on the winding shaft. This makes it possible to reliably wind the first medium around the winding shaft while applying an appropriate tension to the first medium.

  In addition, when the control unit winds up the second medium of a different material from the first medium around the winding shaft, the tension applied to the second medium when the second medium is wound around the winding shaft. In addition, the printing apparatus may be configured so that the tension is greater than the tension applied to the first medium when the first medium is wound. Accordingly, the medium can be wound around the winding shaft with an appropriate tension according to the type of the medium (first medium, second medium).

  In addition, when the control unit winds up the second medium having a width wider than the first medium width in the axial direction of the take-up shaft, the second medium is taken up when the second medium is taken up by the take-up shaft. The printing apparatus may be configured to control the tension applied to the tension higher than the tension applied to the first medium when the first medium is wound on the winding shaft. Thus, the medium can be wound around the winding shaft with an appropriate tension according to the width of the medium (first medium, second medium).

  In addition, the printing unit includes a head that ejects a liquid that cures when irradiated with light to the first medium, and a light irradiator that emits light that cures the liquid, and the liquid ejected by the head onto the first medium. It is particularly preferable to apply the present invention to a printing apparatus that prints an image on a first medium by curing the film by irradiating light from a light irradiator. That is, an image printed by curing the liquid by light irradiation has a large thickness. When the first medium on which the image having such a thickness is printed is wound around the take-up shaft, the above-described problem of the displacement of the first medium is likely to occur. Therefore, it is preferable to apply the present invention to suppress the displacement of the first medium.

  In order to achieve the above object, a printing apparatus according to a second aspect of the present invention includes a printing unit that prints an image on a medium, a winding shaft that winds the medium on which the image is printed, and a medium that rotates. And a control unit that controls the tension. When the width of the medium is 120 mm or less, the control unit has a tension applied to the medium that is greater than 0 [N] when the medium is wound on the take-up shaft. When the width of the medium is larger than 120 mm and not larger than 195 mm, the tension applied to the medium when winding the medium on the winding shaft is larger than 0 [N] and not larger than 20 [N]. When the width of the medium is wider than 340 mm, the tension applied to the medium when winding the medium on the take-up shaft is controlled to be greater than 0 [N] and less than or equal to 30 [N]. .

  Thus, in the second embodiment of the present invention (printing apparatus), the medium is wound up with a tension according to the width of the medium. Therefore, it is possible to suppress the medium wound on the winding shaft from shifting in the axial direction of the winding shaft.

  In addition, when the width of the medium is 120 mm or less, the control unit controls the tension applied to the medium when winding the medium on the winding shaft to be greater than 0 [N] and less than or equal to 5 [N], When the width of the medium is larger than 120 mm and not more than 195 mm, the tension applied to the medium when winding the medium on the take-up shaft is controlled to be larger than 0 [N] and not larger than 10 [N]. When the width is wider than 340 mm, the tension applied to the medium when winding the medium on the winding shaft may be controlled to be greater than 0 [N] and less than or equal to 20 [N]. Accordingly, it is possible to more reliably suppress the medium wound on the winding shaft from being displaced in the axial direction of the winding shaft.

  A plurality of constituent elements of each aspect of the present invention described above are not indispensable, and some or all of the effects described in the present specification are to be solved to solve part or all of the above-described problems. In order to achieve the above, it is possible to appropriately change, delete, replace with another new component, and partially delete the limited contents of some of the plurality of components. In order to solve part or all of the above-described problems or to achieve part or all of the effects described in this specification, technical features included in one embodiment of the present invention described above. A part or all of the technical features included in the other aspects of the present invention described above may be combined to form an independent form of the present invention.

1 is a front view schematically illustrating the configuration of a printer to which the invention is applied. FIG. 2 is a block diagram schematically illustrating an electrical configuration for controlling the printer illustrated in FIG. 1. The block diagram which shows the feedback control performed with respect to winding tension. The fragmentary sectional view which shows typically the state of the web wound around the winding shaft. The figure which shows typically an example of the shift | offset | difference to the axial direction which arose in the wound web. The figure which shows typically the image for the test formed in experiment. The figure which shows the result of having evaluated the shift | offset | difference of the web whose width Ws is 340 [mm]. The figure which shows the result of having evaluated the printing trace of the web whose width Ws is 340 [mm]. The figure which shows the result of having evaluated the shift | offset | difference of the web whose width Ws is 195 [mm]. The figure which shows the result of having evaluated the printing trace of the web whose width Ws is 195 [mm]. The figure which shows the result of having evaluated the shift | offset | difference of the web whose width Ws is 120 [mm]. The figure which shows the result of having evaluated the printing trace of the web whose width Ws is 120 [mm].

  FIG. 1 is a front view schematically illustrating the configuration of a printer to which the present invention is applied. As shown in FIG. 1, in the printer 1, a single web S having both ends wound around a feed shaft 20 and a take-up shaft 40 in a roll shape is stretched along a conveyance path. While being transported in the transport direction Ds from the feed shaft 20 toward the take-up shaft 40, image recording is received. The web S is roughly divided into a paper system and a film system. Specific examples include high-quality paper, cast paper, art paper, coated paper, and the like, and film types include synthetic paper, PET (Polyethylene terephthalate) film, and PP (polypropylene) film. Schematically, the printer 1 includes a feeding unit 2 (feeding region) for feeding the web S from the feeding shaft 20, a process unit 3 (process region) for recording an image on the web S fed from the feeding unit 2, and a process. A winding unit 4 (winding region) for winding the web S on which the image is recorded in the unit 3 around the winding shaft 40 is provided. In the following description, of both surfaces of the web S, the surface on which an image is recorded is referred to as the front surface, and the opposite surface is referred to as the back surface.

  The feeding unit 2 includes a feeding shaft 20 around which the end of the web S is wound, and a driven roller 21 around which the web S drawn from the feeding shaft 20 is wound. The feeding shaft 20 supports the end of the web S by winding it with the surface of the web S facing outward. Then, the web S wound around the feed shaft 20 is fed to the process unit 3 via the driven roller 21 as the feed shaft 20 rotates clockwise in FIG. Incidentally, the web S is wound around the feeding shaft 20 via a core tube 22 that can be attached to and detached from the feeding shaft 20. Therefore, when the web S of the feeding shaft 20 is used up, it is possible to replace the web S of the feeding shaft 20 by attaching a new core tube 22 around which the roll-shaped web S is wound to the feeding shaft 20. It has become. Here, as the core tube 22, a flexible core tube 22 such as a paper core tube 22 (paper tube) can be used.

  The process unit 3 performs processing by the functional units 51, 52, 61, 62, and 63 arranged along the outer peripheral surface of the rotating drum 30 while supporting the web S fed from the feeding unit 2 by the rotating drum 30. An image is recorded on the web S as appropriate. In the process unit 3, a front drive roller 31 and a rear drive roller 32 are provided on both sides of the rotary drum 30, and the web S conveyed from the front drive roller 31 to the rear drive roller 32 is supported by the rotary drum 30. And receive an image record.

  The front driving roller 31 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and winds the web S fed from the feeding unit 2 from the back side. The front drive roller 31 rotates in the clockwise direction in FIG. 1 to convey the web S fed from the feeding unit 2 to the downstream side of the conveyance path. A nip roller 31 n is provided for the front drive roller 31. The nip roller 31n is in contact with the surface of the web S while being urged toward the front drive roller 31 and sandwiches the web S between the front drive roller 31 and the nip roller 31n. Thereby, the frictional force between the front drive roller 31 and the web S is ensured, and the web S can be reliably conveyed by the front drive roller 31.

  The rotary drum 30 is a cylindrical drum having a diameter of, for example, 400 [mm] supported by a support mechanism (not shown) so as to be rotatable in both the transport direction Ds and the opposite direction. The web S conveyed to the driving roller 32 is wound from the back side. The rotating drum 30 supports the web S from the back side while receiving the frictional force with the web S and rotating in the conveyance direction Ds of the web S. Incidentally, the process unit 3 is provided with driven rollers 33 and 34 for folding the web S on both sides of the winding part around the rotary drum 30. Among these, the driven roller 33 wraps the surface of the web S between the front drive roller 31 and the rotary drum 30 and folds the web S. On the other hand, the driven roller 34 wraps the surface of the web S between the rotating drum 30 and the rear drive roller 32 and folds the web S. As described above, by folding the web S on the upstream and downstream sides in the transport direction Ds with respect to the rotating drum 30, it is possible to secure a long winding portion of the web S around the rotating drum 30.

  The rear driving roller 32 has a plurality of minute protrusions formed by thermal spraying on the outer peripheral surface, and winds the web S conveyed from the rotating drum 30 via the driven roller 34 from the back surface side. Then, the rear driving roller 32 rotates clockwise in FIG. 1 to convey the web S to the winding unit 4. A nip roller 32n is provided for the rear drive roller 32. The nip roller 32 n is in contact with the surface of the web S while being biased toward the rear drive roller 32, and sandwiches the web S with the rear drive roller 32. Thereby, the frictional force between the rear drive roller 32 and the web S is ensured, and the web S can be reliably conveyed by the rear drive roller 32.

  Thus, the web S conveyed from the front drive roller 31 to the rear drive roller 32 is supported on the outer peripheral surface of the rotary drum 30. In the process unit 3, in order to record a color image on the surface of the web S supported by the rotary drum 30, a plurality of recording heads 51 corresponding to different colors are provided. Specifically, four recording heads 51 corresponding to yellow, cyan, magenta, and black are arranged in the transport direction Ds in this color order. Each recording head 51 is opposed to the surface of the web S wound around the rotary drum 30 with a slight clearance, and ejects the corresponding color ink (colored ink) from the nozzles by an ink jet method. Then, each recording head 51 ejects ink onto the web S conveyed in the conveyance direction Ds, whereby a color image is formed on the surface of the web S.

  Incidentally, as the ink, UV (ultraviolet) ink (photo-curable ink) that is cured by irradiating ultraviolet rays (light) is used. Therefore, in the process unit 3, UV irradiators 61 and 62 (irradiation devices) are provided to cure the ink and fix it on the web S. The ink curing is performed in two stages, temporary curing and main curing. A temporary curing UV irradiator 61 is disposed between each of the plurality of recording heads 51. That is, the UV irradiator 61 cures (temporarily cures) the ink to such an extent that the method of wetting and spreading the ink is sufficiently slow compared with the case of not irradiating the ultraviolet ray by irradiating the ultraviolet ray having a weak irradiation intensity. It does not cure the ink. On the other hand, a UV irradiator 62 for main curing is provided downstream of the recording heads 51 in the transport direction Ds. That is, the UV irradiator 62 is cured (mainly cured) by irradiating ultraviolet rays having a stronger irradiation intensity than the UV irradiator 61 so that the wetting and spreading of the ink stops.

  In this way, the UV irradiator 61 disposed between each of the plurality of recording heads 51 temporarily cures the colored ink ejected to the web S from the recording head 51 on the upstream side in the transport direction Ds. Accordingly, the ink ejected from the one recording head 51 onto the web S is temporarily cured before reaching the recording head 51 adjacent to the one recording head 51 on the downstream side in the transport direction Ds. As a result, the occurrence of color mixing such as mixing of colored inks of different colors is suppressed. In a state in which the color mixture is suppressed in this way, the plurality of recording heads 51 eject colored inks of different colors to form a color image on the web S. Further, a UV irradiator 62 for main curing is provided downstream of the plurality of recording heads 51 in the transport direction Ds. Therefore, the color image formed by the plurality of recording heads 51 is permanently cured by the UV irradiator 62 and fixed on the web S.

  Furthermore, a recording head 52 is provided downstream of the UV irradiator 62 in the transport direction Ds. The recording head 52 is opposed to the surface of the web S wound around the rotary drum 30 with a slight clearance, and discharges transparent UV ink from the nozzles onto the surface of the web S by an inkjet method. That is, the transparent ink is further ejected with respect to the color image formed by the recording heads 51 for four colors. The transparent ink is ejected over the entire surface of the color image, and gives the color image a texture such as a glossy feeling or a matte feeling. A UV irradiator 63 (irradiation device) is provided downstream of the recording head 52 in the transport direction Ds. The UV irradiator 63 irradiates ultraviolet rays stronger than the UV irradiator 61 to fully cure the transparent ink ejected by the recording head 52. Thereby, the transparent ink can be fixed on the surface of the web S.

  As described above, in the process unit 3, ink ejection and curing are appropriately performed on the web S wound around the outer peripheral portion of the rotary drum 30, and a color image coated with the transparent ink is formed. Then, the web S on which the color image is formed is conveyed to the winding unit 4 by the rear drive roller 32.

  The winding unit 4 includes a driven roller 41 that winds the web S from the back side between the winding shaft 40 and the rear drive roller 32 in addition to the winding shaft 40 around which the end of the web S is wound. The winding shaft 40 winds and supports the end of the web S with the surface of the web S facing outward. That is, when the winding shaft 40 rotates clockwise in FIG. 1, the web S conveyed from the rear drive roller 32 is wound around the winding shaft 40 via the driven roller 41. Incidentally, the web S is wound around the winding shaft 40 via a core tube 42 that can be attached to and detached from the winding shaft 40. Therefore, when the web S wound around the winding shaft 40 becomes full, the web S can be removed together with the core tube 42. Here, as the core tube 42, a flexible core tube 42 such as a paper core tube 42 (paper tube) can be used.

  The above is the outline of the device configuration of the printer 1. Subsequently, an electrical configuration for controlling the printer 1 will be described. FIG. 2 is a block diagram schematically illustrating an electrical configuration for controlling the printer illustrated in FIG. 1. In the printer 1, a printer control unit 100 that controls each unit of the printer 1 is provided. The respective units of the recording head, the UV irradiator, and the web conveyance system are controlled by the printer control unit 100. Details of the control of the printer control unit 100 for each part of the apparatus are as follows.

  The printer control unit 100 controls the ink discharge timing of each recording head 51 that forms a color image according to the conveyance of the web S. Specifically, the control of the ink ejection timing is executed based on the output (detection value) of a drum encoder E30 that is attached to the rotating shaft of the rotating drum 30 and detects the rotational position of the rotating drum 30. That is, since the rotating drum 30 is driven and rotated as the web S is conveyed, the conveying position of the web S can be grasped by referring to the output of the drum encoder E30 that detects the rotational position of the rotating drum 30. Therefore, the printer control unit 100 generates a pts (print timing signal) signal from the output of the drum encoder E30, and controls the ink ejection timing of each recording head 51 based on this pts signal, so that each recording head 51 has the same function. The discharged ink is landed on the target position of the web S to be transported to form a color image.

  Similarly, the timing at which the recording head 52 discharges the transparent ink is also controlled by the printer controller 100 based on the output of the drum encoder E30. Thereby, it is possible to accurately eject the transparent ink to the color image formed by the plurality of recording heads 51. Further, the printer controller 100 also controls the timing of turning on / off the UV irradiators 61, 62, and 63 and the amount of irradiation light.

  The printer control unit 100 controls a function of controlling the conveyance of the web S described in detail with reference to FIG. That is, motors are connected to each of the feeding shaft 20, the front driving roller 31, the rear driving roller 32, and the winding shaft 40 among members constituting the web conveyance system. The printer control unit 100 controls the conveyance of the web S by controlling the speed and torque of each motor while rotating these motors. The details of the conveyance control of the web S are as follows.

  The printer control unit 100 rotates the feeding motor M <b> 20 that drives the feeding shaft 20, and supplies the web S from the feeding shaft 20 to the front drive roller 31. At this time, the printer control unit 100 controls the torque of the feeding motor M20 to adjust the tension of the web S from the feeding shaft 20 to the front drive roller 31 (feeding tension Ta). That is, a tension sensor S21 for detecting the magnitude of the feeding tension Ta is attached to the driven roller 21 disposed between the feeding shaft 20 and the front drive roller 31. The tension sensor S21 can be constituted by, for example, a load cell that detects the magnitude of the force received from the web S. Then, the printer control unit 100 adjusts the feeding tension Ta of the web S by feedback controlling the torque of the feeding motor M20 based on the detection result (detected value) of the tension sensor S21.

  Further, the printer control unit 100 rotates the front drive motor M31 that drives the front drive roller 31 and the rear drive motor M32 that drives the rear drive roller 32. As a result, the web S fed from the feeding unit 2 passes through the process unit 3. At this time, speed control is executed for the front drive motor M31, while torque control is executed for the rear drive motor M32. That is, the printer control unit 100 adjusts the rotation speed of the front drive motor M31 to be constant based on the encoder output of the front drive motor M31. As a result, the web S is conveyed at a constant speed by the front drive roller 31.

  On the other hand, the printer control unit 100 controls the torque of the rear drive motor M32 to adjust the tension (process tension Tb) of the web S from the front drive roller 31 to the rear drive roller 32. That is, a tension sensor S34 that detects the size of the process tension Tb is attached to the driven roller 34 disposed between the rotary drum 30 and the rear drive roller 32. The tension sensor S34 can be constituted by a load cell that detects the magnitude of the force received from the web S, for example. The printer controller 100 adjusts the process tension Tb of the web S by feedback controlling the torque of the rear drive motor M32 based on the detection result (detection value) of the tension sensor S34.

  Further, the printer control unit 100 rotates the winding motor M <b> 40 that drives the winding shaft 40, and winds the web S conveyed by the rear driving roller 32 around the winding shaft 40. At this time, the printer control unit 100 controls the torque of the winding motor M40 to adjust the tension of the web S from the rear drive roller 32 to the winding shaft 40 (winding tension Tc). That is, the tension sensor S41 for detecting the winding tension Tc is attached to the driven roller 41 disposed between the rear drive roller 32 and the winding shaft 40. The tension sensor S41 can be configured by a load cell that detects a force received from the web S, for example. The printer control unit 100 adjusts the winding tension Tc of the web S by feedback controlling the torque of the winding motor M40 based on the detection result of the tension sensor S41.

  FIG. 3 is a block diagram showing feedback control executed for the winding tension of the winding unit. As shown in the figure, the control amount obtained by performing PID (Proportional-Integral-Derivative) control on the deviation between the target value Tct of the winding tension Tc and the detected value Tcd of the tension sensor S41 is input to the winding motor M40. Then, feedback control is executed. Thus, the winding tension Tc is controlled so that the detected value Tcd of the winding tension Tc becomes the target value Tct of the winding tension Tc (that is, the deviation becomes zero). In particular, in the present embodiment, the winding tension Tc is adjusted so that the web S wound around the winding shaft 40 can be prevented from shifting in the axial direction of the winding shaft 40. Subsequently, after describing the displacement of the web S, a specific value of the winding tension Tc that contributes to suppression of the displacement will be described.

  FIG. 4 is a partial cross-sectional view schematically showing the state of the web wound around the winding shaft. As shown in the figure, the webs S wound around the winding shaft 40 overlap each other in the thickness direction. Therefore, a force having a magnitude corresponding to the winding tension Tc acts between the adjacent webs S. At this time, if the take-up tension Tc is excessive, a large force directed in the axial direction Da of the take-up shaft 40 is generated between the wound webs S, and the webs S are shifted in the axial direction Da. There was a case. In particular, an image P obtained by curing UV ink is printed on the surface of the web S, and the image P has a thickness (for example, about 1 to 10 [μm]). For this reason, the web S is likely to be displaced.

  FIG. 5 is a diagram schematically illustrating an example of an axial shift generated in the web wound around the winding shaft. As shown in the figure, at one end in the axial direction Da of the roll R on which the web S is wound, one end of the web S protrudes outward in the axial direction Da as it goes inward in the radial direction of the roll R. As a result, at one end in the axial direction Da of the roll R, between the end of the web S closest to one end side in the axial direction Da and the end of the web S closest to the other end side in the axial direction Da, There is a maximum deviation ΔS. In the experiment described later, this maximum deviation amount ΔS is employed as an amount for evaluating the degree of deviation of the web S. Note that FIG. 5 shows an example in which the end of the web S monotonously shifts to one side in the axial direction Da as it goes inward in the radial direction, but the end of the web S as it goes inward in the radial direction. The web S may be displaced in such a manner that the wave is undulated. Even in this case, the maximum shift amount ΔS can be defined in the same manner.

  Then, the inventors conducted an experiment for obtaining a range of the winding tension Tc that can suppress the deviation of the web S wound around the winding shaft 40. In this experiment, the web S1 on which the test image P (FIG. 6) is formed is wound around the winding shaft 40 to check whether or not the web S1 is displaced for a plurality of different winding tensions Tc. is there. Specifically, a web S1 having a configuration in which two different film materials are adhered in a layer form with glue (specifically, a configuration in which PET is provided on the front surface side and PP is provided on the back surface side) is applied to the transport direction Ds. The web S1 was wound around the winding shaft 40 while forming a test image P (FIG. 6) over 1000 m.

  FIG. 6 is a diagram schematically showing a test image formed in an experiment. As shown in the figure, a plurality of images P arranged in a matrix were formed on a web S1 having a width Ws. Each image P is composed of a rectangular frame, has a width Pw in the axial direction Da, and a length Pl in the transport direction Ds. The frame line has a line width of about 5 [mm] and a thickness of about 6 [μm]. In the axial direction Da, an interval Wa is provided between the adjacent images P, and a margin Wb is provided between the end of the web S1 and the image P. In addition, an interval Lb is provided between adjacent images P in the transport direction Ds.

In the experiment shown here, four rows of images P were formed. Each condition value is
Ws = 340 [mm],
Pw = 80 [mm],
Pl = 50 [mm],
Wa = 3 [mm],
Wb = 6 [mm],
Lb = 30 [mm]
It is.

  FIG. 7 is a table showing the results of evaluating the web displacement for the web S1 having a width Ws of 340 [mm]. In each case where the target value Tct of the winding tension Tc is 5 [N (Newton)], 8 [N], 15 [N], 20 [N], 22 [N], 26 [N], 30 [N] FIG. 7 shows the result of evaluating the maximum deviation amount ΔS [mm] generated when the web S1 of 1000 [m] on which the image P is formed is wound on the winding shaft 40. In actual use, the maximum deviation amount ΔS is acceptable if it is less than 10 [mm]. Therefore, in the range of 5 [N] to 30 [N] shown in FIG. More specifically, it can be seen that the maximum deviation amount ΔS can be effectively suppressed to a small value of 0.5 [mm] in the range of 5 [N] to 26 [N].

  By the way, the force corresponding to the winding tension Tc works between the webs S1 wound around the winding shaft 40, and the image P printed on the web S1 is pressed against the adjacent web S1 with a large force. As a result, the web S1 may have a mark (print mark). In particular, an image P obtained by curing UV ink is printed on the surface of the web S1, and the image P has a thickness (for example, about 1 to 10 [μm]). Therefore, print marks are likely to occur on the web S1. Therefore, the occurrence of print marks was also confirmed.

  FIG. 8 is a diagram showing, as a table, the results of evaluating web print marks for the web S1 having a width Ws of 340 [mm] used in the above experiment. In this print mark evaluation, the web S1 wound on the winding shaft 40 is left for 3 days and then the web S1 is unwound (that is, the web S1 is pulled out from the roll R to cancel the roll state), and This is a visual evaluation of whether print marks remain on the web S1 when left for 3 days. In the figure, a circle mark indicates that the print mark cannot be visually recognized, and a triangle mark indicates that the print mark can be visually recognized. As shown in FIG. 8, it can be seen that the occurrence of printing marks can be effectively suppressed in the range of 20 [N] or less.

  Incidentally, in the range of less than 5 [N], the web S1 wound around the winding shaft 40 is loosened due to its own rigidity, and it is difficult to reliably wind the winding shaft 40 around the web S1. It was.

  Further, when the web S1 is wound around the winding shaft 40, a taper tension that reduces the winding tension Tc as the diameter of the roll R increases is executed. In the experiment, a taper tension that reduces the winding tension Tc by 50% from the start of winding to winding of 1000 [m] was performed. However, the displacement of the web S1 and the print marks are the most in the winding start region where the winding tension Tc is maximum (the region where the winding amount of the web S1 around the winding shaft 40 is equal to or less than the circumferential length of the winding shaft 40). It becomes noticeable and becomes less noticeable as the winding tension Tc decreases. That is, what has a great influence on the displacement of the web S1 and the print marks is the winding tension Tc applied to the web S1 in the region of the winding start on the winding shaft 40, and the degree and presence of the taper tension have a great influence. Absent.

  As described above, when the web S1 is wound around the winding shaft 40, the winding tension Tc is controlled so that the winding tension Tc applied to the web S1 is greater than 0 [N] and not greater than 30 [N]. By doing so, the maximum deviation amount ΔS of the wound web S1 can be generally suppressed to less than 10 [mm].

  Further, by controlling the winding tension Tc so that the winding tension Tc tension applied to the web S1 when winding the web S1 around the winding shaft 40 is larger than 0 [N] and 26 [N] or less, The maximum deviation amount ΔS of the wound web S1 can be effectively suppressed to a small value such as 0.5 [mm].

  Further, when the web S1 is wound around the winding shaft 40, a printing mark is generated on the web S1 by controlling the winding tension Tc so that the winding tension Tc applied to the web S1 is 20 [N] or less. Can be suppressed.

  Further, when winding the web S1 around the winding shaft 40, the winding tension Tc is controlled so that the winding tension Tc applied to the web S1 becomes 5 [N] or more. The web S1 can be reliably wound around the winding shaft 40 while being applied to the web S1.

  Further, the image P formed by curing the UV ink discharged onto the web S1 by light irradiation has a large thickness. When the web S1 on which the image P having such a thickness is printed is wound around the winding shaft 40, the web S1 is liable to be displaced or printed. Therefore, it is preferable to suppress the displacement of the web S1 and the print marks by configuring as described above.

  As described above, in the present embodiment, the printer 1 corresponds to an example of the “printing apparatus” of the present invention, and the recording heads 51 and 52 and the UV irradiators 62, 62, and 63 cooperate to form the “printing unit” of the present invention. , The winding shaft 40 corresponds to an example of the “winding shaft” of the present invention, the printer control unit 100 corresponds to an example of the “control unit” of the present invention, and the UV irradiators 62 and 62. 63 correspond to an example of the “light irradiator” of the present invention, and the web S1 corresponds to an example of the “medium” of the present invention.

  The present invention is not limited to the above-described embodiment, and various modifications can be made to the above-described one without departing from the spirit of the present invention. Therefore, for example, the winding tension Tc may be decreased in accordance with the decrease in the width Ws of the web S in the axial direction Da. That is, for the web S having a width Ws of 340 [mm] or more, the winding tension Tc may be controlled within the above range. On the other hand, as shown in the following experimental results, when the width of the web S is narrowed, the displacement of the web S and the print marks may become noticeable.

FIG. 9 is a table showing the results of evaluating the web displacement for the web S2 having the same material as the web S1 and the width Ws of 195 [mm]. FIG. 10 is a diagram showing, as a table, the results of evaluating web print marks for the web S2 having a width Ws of 195 [mm]. In the experiments in both figures, two rows of images P were formed. Each condition value is
Ws = 195 [mm],
Pw = 92 [mm],
Pl = 50 [mm],
Wa = 4 [mm],
Wb = 3.5 [mm],
Lb = 30 [mm]
It is.

  According to FIG. 9, in the range of 5 [N] or more and 20 [N] or less, the maximum deviation amount ΔS of the web S2 is generally well suppressed to less than 10 [μm]. Therefore, the width Ws is 195 [mm] or more and less than 350 [mm] than the winding tension Tc (fourth tension) when the web S having a width Ws of 350 [mm] or more is wound around the winding shaft 40. The winding tension Tc may be controlled so that the winding tension Tc (third tension) when the web S is wound around the winding shaft 40 becomes small. Thus, the web S can be wound around the winding shaft 40 with an appropriate winding tension Tc corresponding to the width of the web S. At this time, if the winding tension Tc when the web S having a width Ws of 195 [mm] or more and less than 350 [mm] is wound around the winding shaft 40 is controlled within a range of 20 [N] or less, The deviation of the web S can be suppressed almost satisfactorily. Furthermore, according to FIG. 10, it can be seen that the occurrence of printing marks can be effectively suppressed by controlling in a range of 10 [N] or less.

FIG. 11 is a table showing the results of evaluating the web displacement for the web S3 having the same material as the web S1 and having a width Ws of 120 [mm]. FIG. 12 is a table showing the results of evaluating web print marks for the web S3 having a width Ws of 120 [mm]. In the experiments in both figures, one line of image P was formed. Each condition value is
Ws = 120 [mm],
Pw = 110 [mm],
Pl = 70 [mm],
Wb = 5 [mm],
Lb = 30 [mm]
It is.

  According to FIG. 11, in the range of 5 [N] or more and 8 [N] or less, the maximum deviation amount ΔS of the web S3 is generally well suppressed to less than 10 [μm]. Therefore, the width Ws is 120 [mm] or more and less than 195 [mm] than the winding tension Tc (fourth tension) when the web S having a width Ws of 350 [mm] or more is wound around the winding shaft 40. The winding tension Tc may be controlled so that the winding tension Tc (third tension) when the web S is wound around the winding shaft 40 becomes small. Thus, the web S can be wound around the winding shaft 40 with an appropriate winding tension Tc corresponding to the width of the web S. At this time, if the winding tension Tc when the web S having a width Ws of 120 [mm] or more and less than 195 [mm] is wound around the winding shaft 40 is controlled within a range of 8 [N] or less, The deviation of the web S can be suppressed almost satisfactorily. Furthermore, according to FIG. 12, it can be understood that the occurrence of printing marks can be effectively suppressed by controlling the range to 5 [N] or less.

  In the above embodiment, the case where the web S composed of two film materials (PET, PP) is used has been described. However, the type of the web S is not limited to this. The web S is provided with a film on the front surface side, the paper is provided on the back surface side and adhered in a layered manner, or the paper S is provided on the front surface side, and the film is provided on the back surface side to be layered. A bonded web S can be used. Incidentally, in the web S having paper as a material, the above-described deviation of the web S and printing traces are difficult to occur. Therefore, the winding tension Tc may be changed according to the type of the web S.

  That is, the type (second type) of web S that includes paper is used rather than the winding tension Tc (first tension) when the type of web S that does not include paper (first type) is wound on the winding shaft 40. The winding tension Tc may be controlled so as to increase the winding tension Tc (second tension) when winding on the winding shaft 40. Thereby, winding of the web S around the winding shaft 40 can be executed with an appropriate winding tension Tc according to the type of the web S.

  Various changes can be made to the specific configuration of the printer 1. For example, the member that supports the web S to be conveyed is not limited to the cylindrical shape such as the rotating drum 30. Therefore, it is also possible to use a flat platen that supports the web S on a flat surface.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 51, 52 ... Recording head, 62, 62, 63 ... UV irradiator, 40 ... Winding shaft, 100 ... Printer control part, S ... Web

Claims (9)

A printing unit for printing an image on a first medium;
A winding shaft that winds the first medium on which the image is printed by rotating the first medium;
A control unit for controlling the tension applied to the first medium,
The control unit is a printing apparatus that controls the tension applied to the first medium to be greater than 0 [N] and less than or equal to 8 [N] when the first medium is wound on the winding shaft.   The printing apparatus according to claim 1, wherein the control unit controls the tension applied to the first medium to be 5 [N] or less when the first medium is wound on the winding shaft.   The printing apparatus according to claim 1, wherein the control unit controls the tension applied to the first medium to be 5 [N] or more when the first medium is wound around the winding shaft.   In the case where the control unit winds the second medium of a material different from that of the first medium around the take-up shaft, the tension applied to the second medium when the second medium is taken up on the take-up shaft. 2. The printing apparatus according to claim 1, wherein when the first medium is wound on the winding shaft, the tension is controlled to be greater than the tension applied to the first medium.   When the control unit winds the second medium having a width wider than the first medium in the axial direction of the winding shaft around the winding shaft, when the second medium is wound around the winding shaft, 5. The control according to claim 1, wherein the tension applied to the second medium is controlled to be greater than the tension applied to the first medium when the first medium is wound on the winding shaft. The printing apparatus as described.   The printing unit includes a head that discharges a liquid that cures when irradiated with light onto the first medium, and a light irradiator that emits light that cures the liquid, and the head is applied to the first medium. The printing apparatus according to claim 1, wherein the image is printed on the first medium by curing the discharged liquid by irradiation with light from the light irradiator. A printing section for printing an image on a medium;
A take-up shaft that winds up by rotating the medium on which the image is printed;
A control unit for controlling the tension applied to the medium,
The controller is
When the width of the medium is 120 mm or less, the tension applied to the medium when winding the medium on the winding shaft is controlled to be greater than 0 [N] and less than or equal to 8 [N],
When the width of the medium is greater than 120 mm and equal to or less than 195 mm, the tension applied to the medium when the medium is wound around the winding shaft is controlled to be greater than 0 [N] and less than 20 [N]. And
When the width of the medium is wider than 340 mm, the tension applied to the medium when the medium is wound around the winding shaft is controlled to be greater than 0 [N] and less than or equal to 30 [N].
Printing device. The controller is
When the width of the medium is 120 mm or less, the tension applied to the medium when winding the medium on the winding shaft is controlled to be greater than 0 [N] and less than or equal to 5 [N],
When the width of the medium is greater than 120 mm and equal to or less than 195 mm, the tension applied to the medium when the medium is wound around the winding shaft is controlled to be greater than 0 [N] and less than or equal to 10 [N]. And
When the width of the medium is wider than 340 mm, the tension applied to the medium when the medium is wound around the winding shaft is controlled to be greater than 0 [N] and less than or equal to 20 [N].
The printing apparatus according to claim 5. Printing an image on a medium;
Winding the medium on which the image is printed on a rotating rotating shaft,
A printing method for controlling the tension applied to the medium to be greater than 0 [N] and equal to or less than 8 [N] when the medium is wound on the winding shaft.

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