JP7607421B2 - Printing device, printing system, and printing method - Google Patents

Description

This invention relates to a technology for printing images by ejecting ink from a printing unit while transporting a print medium with a drive roller.

In the printing device described in Patent Document 1, drive rollers are arranged on both sides of the inkjet head that ejects ink onto the printing medium from above, and the drive rollers transport the printing medium by rotating while wrapping the printing medium around them. In this way, the inkjet head ejects ink onto the printing medium transported between the two drive rollers, printing an image on the printing medium. This printing device also has built-in heaters, such as an under-heater and an after-heater, which dry the printing medium.

WO2017/138436

However, if a large amount of ink is ejected onto the print medium, it becomes difficult for the heater built into the printing device to adequately dry the print medium. As a solution, a system can be considered in which a drying device is provided separately from the printing device, and the printing medium discharged from the printing device is dried by the drying device. However, in such a system, of the two driving rollers located on either side of the printing unit, such as the inkjet head, the angle at which the latter driving roller wraps around the print medium cannot be secured.

In other words, the print medium sent out from the downstream drive roller is transported from the printing device to the drying device. Therefore, it is preferable to be able to send out the print medium horizontally from the downstream drive roller. This is because when arranging the heater along the print medium in the drying device, the heater can be arranged horizontally without tilting, allowing the drying device to be configured compactly in the vertical direction. This situation can also occur in systems that perform processes other than drying (e.g., cutting). For this reason, the wrap angle of the print medium around the downstream drive roller cannot be increased, making it difficult to stably transport the print medium by the drive roller.

This invention was developed in consideration of the above problems, and aims to enable stable transport of the print medium by a drive roller in a configuration in which the print medium onto which ink has been ejected from the printing unit is sent out horizontally by the drive roller.

The printing device according to the present invention includes a first drive roller and a second drive roller that rotate around the non-recording side of a long strip-shaped print medium having a recording side and a non-recording side opposite the recording side, a transport section that transports the print medium from the second drive roller to the first drive roller, and a first printing section that faces the recording side of the print medium between the second drive roller and the first drive roller and ejects ink onto the recording side, the first drive roller horizontally sends out the print medium transported from the second drive roller with the recording side facing upward, the angle at which the first drive roller wraps the print medium is smaller than the angle at which the second drive roller wraps the print medium, the first drive roller is a suction roller that sucks in the print medium, and the diameter of the first drive roller is larger than the diameter of the second drive roller.

The printing method according to the present invention includes a step of transporting the print medium from the second drive roller to the first drive roller by the first drive roller and the second drive roller that rotate around the non-recording side of a long strip-shaped print medium having a recording side and a non-recording side opposite the recording side, and a step of ejecting ink onto the recording side from a first printing unit that faces the recording side of the print medium between the second drive roller and the first drive roller, the first drive roller horizontally sends out the print medium transported from the second drive roller with the recording side facing upward, the angle at which the first drive roller wraps the print medium is smaller than the angle at which the second drive roller wraps the print medium, the first drive roller is a suction roller that sucks in the print medium, and the diameter of the first drive roller is larger than the diameter of the second drive roller.

In the present invention (printing device and printing method) configured in this manner, an image is printed on the print medium by ejecting ink from the printing unit onto the print medium transported from the second drive roller to the first drive roller. The print medium on which the image has been printed in this manner is sent out horizontally by the first drive roller. This allows a device (e.g., a drying device) that processes the print medium discharged from the printing device to be configured compactly in the vertical direction. In addition, the angle at which the first drive roller wraps the print medium is smaller than the angle at which the second drive roller wraps the print medium, and the wrap angle of the print medium around the first drive roller is kept small. In this way, the inclination of the print medium reaching the first drive roller is kept small.

Moreover, in the present invention, the first drive roller is a suction roller. Therefore, the rotation of the first drive roller can be securely transmitted to the print medium. Furthermore, the diameter of the first drive roller is larger than the diameter of the second drive roller. In this way, by increasing the diameter of the first drive roller, the contact area between the first drive roller and the print medium can be secured, even though the winding angle of the print medium around the first drive roller is small, and the rotation of the first drive roller can be more reliably transmitted to the print medium. As a result, the print medium can be stably fed by the first drive roller. In this way, in the configuration in which the print medium on which ink has been ejected from the printing unit is fed horizontally by the drive roller, the present invention makes it possible to stably transport the print medium by the drive roller.

The printing device may further include a second printing unit that ejects ink onto the recording surface of the printing medium transported to one side by the transport unit, and the transport unit further includes a third driving roller that is arranged on the other side opposite to the one side of the second driving roller and rotates while wrapping the printing medium, transporting the printing medium from the third driving roller to the second driving roller with the recording surface facing upward, and the second printing unit may be configured to face the recording surface of the printing medium between the third driving roller and the second driving roller. In this configuration, the printing medium on which an image has been printed by the second printing unit is transported by the second driving roller toward the first printing unit. At this time, since the wrapping angle of the printing medium around the second driving roller is large, the printing medium is stably transported by the second driving roller while moving toward the first printing unit. Therefore, the first printing unit can print an image by ejecting ink onto the printing medium transported stably in this manner. This makes it possible to stably print an image by the first printing unit on the printing medium on which an image has been printed by the second printing unit.

The printing device may also be configured such that the transport unit transports the print medium transported from the second drive roller in a downward direction, then changes its direction of travel to the other side and transports it, thereby inverting the recording and non-recording sides of the print medium upside down and transporting the print medium from one side to the other side, then transports the print medium in an upward direction and then changes its direction of travel to one side, thereby again inverting the recording and non-recording sides of the print medium upside down and transporting the print medium from the other side to one side to the first drive roller, and the transport unit transports the print medium from the second drive roller to the first drive roller only by rollers that contact the non-recording side of the print medium, and the first printing unit faces the recording side that has been inverted upside down again by the transport unit and faces upward.

In this configuration, the transport unit inverts the print medium twice from the second drive roller to the first drive roller, and the first print unit prints an image by ejecting ink onto the recording surface that faces upward after the two inversions. Therefore, a distance sufficient to perform two inversions is ensured between the printing by the second print unit and the printing by the first print unit, and the image printed by the second print unit can be printed by the first print unit in a state in which the image printed by the second print unit is somewhat dry. Therefore, it is possible to prevent the ink ejected from the second print unit from mixing with the ink ejected from the first print unit. Moreover, since there is no member that comes into contact with the recording surface of the print medium from the second drive roller to the first drive roller, the image printed by the second print unit is not disturbed. This allows the image printed by the first print unit to be printed while maintaining the image printed by the second print unit in good condition.

The printing device may also be configured so that the first printing unit ejects white ink and the second printing unit ejects ink of a color other than white. In this configuration, the first printing unit can print a white background on the image printed by the second printing unit.

The printing device may also be configured so that the second drive roller is a suction roller that sucks in the print medium. In this configuration, the second drive roller can transport the print medium more stably toward the first printing unit.

The printing device may also be configured to further include a suction blower, a first connection portion connecting the suction blower to the first drive roller, and a second connection portion connecting the suction blower to the second drive roller, and the first drive roller and the second drive roller suck the non-recording side of the print medium with the suction force generated by the suction blower. In this configuration, the suction blower can be shared between the first drive roller and the second drive roller, simplifying the device configuration.

The printing system according to the present invention comprises the above-mentioned printing device and a drying section that dries the print medium transported from the printing device. The drying section comprises an air-blowing chamber having a plurality of nozzles that are arranged horizontally and face the print medium, and dries the print medium by spraying gas onto the print medium from the nozzles of the air-blowing chamber. Therefore, in a configuration in which the print medium onto which ink has been ejected from the printing section is sent out horizontally by a drive roller, the print medium can be transported stably by the drive roller.

As described above, according to the present invention, in a configuration in which the print medium onto which ink has been ejected from the printing unit is sent out horizontally by a drive roller, the print medium can be transported stably by the drive roller.

FIG. 1 is a front view showing a schematic diagram of an example of a printing system according to the present invention. FIG. 2 is a front view showing a schematic diagram of a printing device included in the printing system shown in FIG. 1 . FIG. 4 is a diagram illustrating a suction mechanism provided for each driving roller, which is a suction roller. FIG. 4 is a side view showing a schematic relationship between the printing medium and two drive rollers that support the printing medium on either side of a white printed portion.

Figure 1 is a front view showing a schematic example of a printing system according to the present invention. In Figure 1 and the following figures, the horizontal direction X and the vertical direction Z are appropriately indicated. As shown in Figure 1, the printing system 1 includes a printing device 3 and a drying device 6 arranged in the horizontal direction X. This printing system 1 transports a long strip-shaped printing medium M from a pay-out roll 11 to a take-up roll 12 in a roll-to-roll manner. The material of the printing medium M is a film such as OPP (oriented polypropylene) or PET (polyethylene terephthalate). However, the material of the printing medium M is not limited to film, and may be paper or the like. Such a printing medium M is flexible. In the following, the surface on which an image is printed of both sides of the printing medium M is appropriately referred to as the front surface M1, and the surface opposite the front surface M1 is appropriately referred to as the back surface M2.

The printing device 3 prints an image on the surface M1 of the printing medium M by ejecting water-based ink by inkjet printing onto the surface M1 of the printing medium M transported from the pay-out roll 11 to the take-up roll 12. The configuration of the printing device 3 will be described in detail later with reference to FIG. 2 etc. The printing medium M on which the image has been printed in this manner is transported in the horizontal direction X from the printing device 3 towards the drying device 6.

The drying device 6 includes a drying oven 60, which dries the printing medium M discharged from the printing device 3 as it is transported from the pay-out roll 11 to the take-up roll 12. The drying oven 60 includes two upper blowing units 61u arranged in the horizontal direction X, two middle blowing units 61m arranged in the horizontal direction X below the upper blowing units 61u, and two lower blowing units 61l arranged in the horizontal direction X below the middle blowing units 61m.

The printing medium M discharged from the discharge port 312 of the printing device 3 passes through two upper blowing units 61u in the horizontal direction X, and is then folded back by a pair of rollers 62 toward two middle blowing units 61m. Next, the printing medium M passes through two middle blowing units 61m in the horizontal direction X, and is then folded back by a pair of air turn bars 63 toward two lower blowing units 61l. Furthermore, the printing medium M passes through two lower blowing units 61l in the horizontal direction X, and is then discharged outside the drying device 6.

The upper blowing unit 61u has two blowing chambers 64 arranged to sandwich the printing medium M passing in the horizontal direction X from the vertical direction Z. Each blowing chamber 64 has multiple nozzles 65 arranged in the horizontal direction X, and each nozzle 65 sprays hot air (gas at 60 degrees or higher) onto the printing medium M. In this way, the printing medium M is dried by the hot air sprayed from the nozzles 65 of these blowing chambers 64 as it passes between the two blowing chambers 64 arranged above and below. Similarly to the upper blowing unit 61u, each of the middle blowing unit 61m and the lower blowing unit 61l also has two blowing chambers 64 that sandwich the printing medium M from the vertical direction Z.

The specific configuration of the upper blower unit 61u is not limited to this example. For example, instead of the lower blower chamber 64 of the upper and lower blower chambers 64 of the upper blower unit 61u, multiple rollers arranged in the horizontal direction X may be provided. In this configuration, the back surface M2 of the printing medium M can be supported from below by the multiple rollers, while hot air can be sprayed from the upper blower chamber 64 onto the front surface M1 of the printing medium M.

Figure 2 is a front view showing a schematic of a printing device provided in the printing system of Figure 1. In Figure 2, one side X1 and the other side X2 of the horizontal direction X are appropriately shown. Here, one side X1 is the side facing the drying device 6 from the printing device 3, and the other side X2 is the opposite side to one side X1. The printing device 3 includes a housing 31, a color printing unit 32 arranged in the housing 31, a white printing unit 33 arranged above the color printing unit 32 within the housing 31, and a transport unit 4 that transports the printing medium M by a plurality of rollers arranged within the housing 31.

The color printing unit 32 has multiple (six) ejection heads 321 arranged in the direction of travel of the printing medium M (direction from the other side X2 to the one side X1) above the printing medium M transported by the transport unit 4. Each of the multiple ejection heads 321 has a nozzle that faces the surface M1 of the printing medium M that passes below it from above, and ejects color inks of different colors from the nozzles using an inkjet method. Here, color ink means ink other than white, and includes inks such as cyan, magenta, yellow, and black. In this way, each of the multiple ejection heads 321 of the color printing unit 32 prints a color image on the surface M1 of the printing medium M by ejecting color inks from above onto the surface M1 of the printing medium M that passes below it.

The white printing unit 33 also has a single ejection head 331 arranged above the printing medium M transported by the transport unit 4. The ejection head 331 has a nozzle that faces from above the surface M1 of the printing medium M that passes below it, and ejects white ink from the nozzle using an inkjet method. In this way, the ejection head 331 of the white printing unit 33 prints a white image on the surface M1 of the printing medium M by ejecting white ink from above onto the surface M1 of the printing medium M that passes below it.

An inlet 311 opens in the side wall of the other side X2 of the housing 31, and the print medium M is carried into the housing 31 through the inlet 311. In contrast, the transport unit 4 has an inlet section 41. The inlet section 41 has a number of rollers 411 arranged below the color printing unit 32 from the other side X2 to the one side X1 in the horizontal direction X, and transports the print medium M carried in through the inlet 311 from the other side X2 to the one side X1 while supporting it with the rollers 411.

The transport section 4 also has an upward transport section 42 provided on one side X1 of the carry-in section 41. The upward transport section 42 has a number of rollers 421 arranged in the vertical direction Z outside (one side X1) of the color printing section 32. The upward transport section 42 bends the print medium M transported from the carry-in section 41 upwards using the roller 421 located at the bottom of the multiple rollers 421, thereby changing the travel direction of the print medium M from the one side X1 to the upwards, and then transports the print medium M upwards while being supported by the multiple rollers 421.

The transport unit 4 further includes an upper transport unit 43 disposed above the color printing unit 32. The upper transport unit 43 includes a plurality of rollers 431 arranged above the color printing unit 32 from one side X1 to the other side X2 in the horizontal direction X. The upper transport unit 43 bends the print medium M transported from the upward transport unit 42 to the other side X2 using a roller 431 located at the end of the one side X1 among the plurality of rollers 431, thereby changing the traveling direction of the print medium M from the upper side to the other side X2, and then transports the print medium M to the other side X2 while being supported by the plurality of rollers 431.

The conveying unit 4 also has a downward conveying unit 44 provided on the other side X2 of the upper conveying unit 43. The downward conveying unit 44 has a plurality of rollers 441 arranged in the vertical direction Z on the outside (other side X2) of the color printing unit 32. The downward conveying unit 44 bends the print medium M conveyed from the upper conveying unit 43 downward by the roller 441 located at the upper end of the plurality of rollers 441, thereby changing the direction of travel of the print medium M from the other side X2 to the lower side, and then conveys the print medium M downward while supporting it with the roller 441. Of the plurality of rollers 441 that the downward conveying unit 44 has, the upper end roller 441 is located above each ejection head 321 of the color printing unit 32, and the lower end roller 441 is located below each ejection head 321 of the color printing unit 32. In other words, the downward conveying unit 44 conveys the print medium M from above the color printing unit 32 to below.

The transport unit 4 further includes a color transport unit 45 provided below the upper transport unit 43 and on one side X1 of the downward transport unit 44. The color transport unit 45 includes a plurality of rollers 451 arranged from the other side X2 to the one side X1 in the horizontal direction X and contacting the back surface M2 of the print medium M, and the print medium M transported from the downward transport unit 44 is supported below the color printing unit 32 by the plurality of rollers 451. In this way, the plurality of rollers 451 of the color transport unit 45 transport the print medium M from the other side X2 to the one side X1 while supporting the print medium M from below by contacting the back surface M2 of the print medium M transported from the downward transport unit 44 from below. The color printing unit 32 then ejects color ink from above onto the front surface M1 of the print medium M transported along its front surface M1 by the color transport unit 45.

At this time, the surface M1 of the printing medium M transported by the color transport unit 45 faces upward, and the back surface M2 of the printing medium M faces downward. In detail, the printing medium M is transported from the entrance 311 with its surface M1 facing upward, and is transported by the transport unit 41 from the other side X2 to the one side X1. The printing medium M that has passed through the transport unit 41 is transported by the upper transport unit 43 from the one side X1 to the other side X2 in a state in which it is turned upside down by the upward transport unit 42 and the upper transport unit 43. Therefore, the surface M1 of the printing medium M transported by the upper transport unit 43 faces downward. The printing medium M that has passed through the upper transport unit 43 is transported by the color transport unit 45 from the other side X2 to the one side X1 in a state in which it is turned upside down by the downward transport unit 44 and the color transport unit 45. Therefore, the surface M1 of the printing medium M transported by the color transport unit 45 faces upward.

The transport unit 4 also has rollers 461, 462, and 463 arranged upstream of the color transport unit 45 in the traveling direction of the print medium M. The roller 461 is a drive roller that drives the print medium M by rotating by the driving force of the motor while wrapping the front surface M1 of the print medium M around it. The roller 462 is a nip roller that presses the print medium M against the roller 461 by sandwiching the print medium M between the roller 461 and the roller 462. The roller 463 is a driven roller that has a tension sensor that detects the tension applied to the print medium M, and wraps the back surface M2 of the print medium M transported from the drive roller 461 around it. The drive roller 461 and the driven roller 463 function to adjust the tension of the print medium M, as described below.

Furthermore, the transport unit 4 has a reversing transport unit 47 that turns upside down the print medium M transported from the color transport unit 45 to the one side X1 twice. This reversing transport unit 47 has a plurality of rollers 471, 472 that are arranged in the vertical direction Z on the one side X1 of the color transport unit 45 and contact the back surface M2 of the print medium M. Of the rollers 471, 472, the upper end roller 471 is a drive roller that drives the print medium M by rotating by the driving force of the motor while wrapping the back surface M2 of the print medium M around it. This drive roller 471 changes the traveling direction of the print medium M from the one side X1 to the downward side by folding the print medium M transported from the color transport unit 45 downward. Also, of the rollers 471, 472, the lower end roller 472 is a driven roller having a tension sensor that detects the tension applied to the print medium M, and wraps the back surface M2 of the print medium M around it. This driven roller 472 bends the print medium M transported from the drive roller 471 to the other side X2, thereby changing the direction of travel of the print medium M from the bottom to the other side X2. In this way, the print medium M is turned upside down by the rollers 471 and 472 that contact the back surface M2 of the print medium M, so that the back surface M2 of the print medium M faces upward and the front surface M1 of the print medium M faces downward. The drive roller 471 and roller 472 function to adjust the tension of the print medium M, as described below.

The reverse transport section 47 also has a number of rollers 473 arranged below the color transport section 45 and on the other side X2 of the roller 472. The rollers 473 are arranged from one side X1 to the other side X2 in the horizontal direction X, and contact the back surface M2 of the print medium M. In this way, the print medium M with the back surface M2 facing upward is transported from the one side X1 to the other side X2 by the rollers 473 contacting the back surface M2 of the print medium M.

Furthermore, the reverse transport section 47 has a plurality of rollers 473 and a plurality of rollers 474, 475, 476 provided on the other side X2 of the downward transport section 44. These rollers 474 to 476 are arranged from the bottom to the top in the vertical direction Z and contact the back surface M2 of the print medium M. Of the plurality of rollers 474 to 476, the bottom roller 474 bends the print medium M transported from the plurality of rollers 473 to the top, thereby changing the traveling direction of the print medium M from the other side X2 to the top, and the top roller 476 bends the print medium M transported from roller 474 via roller 475 to one side X1, thereby changing the traveling direction of the print medium M from the top to one side X1. In this way, the rollers 474-476 contacting the back surface M2 of the print medium M turn the print medium M upside down, so that the front surface M1 of the print medium M faces upward and the back surface M2 of the print medium M faces downward.

The reverse transport section 47 also has a roller 477 that is disposed above the upper transport section 43 and on one side X1 of the roller 476, and that contacts the back surface M2 of the print medium M. The roller 477 transports the print medium M transported from the roller 476 from the other side X2 to the one side X1. In this way, the roller 477 that contacts the back surface M2 of the print medium M transports the print medium M with its front surface M1 facing upward from the other side X2 to the one side X1.

In this way, the reverse transport unit 47 transports the print medium M transported from the color transport unit 45 downward by the rollers 471 and 472, and then changes the direction of travel of the print medium M to the other side X2 by the roller 472, thereby inverting the front surface M1 and back surface M2 of the print medium M upside down. Next, the reverse transport unit 47 transports the print medium M from one side X1 to the other side X2 by the multiple rollers 473, and then transports the print medium M upward by the rollers 474 to 476. Furthermore, the reverse transport unit 47 changes the direction of travel of the print medium M to one side X1 by the roller 476, thereby again inverting the front surface M1 and back surface M2 of the print medium M upside down, and transports the print medium M from the other side X2 to one side X1 by the roller 477.

In this way, the inverting and conveying unit 47 inverts the front surface M1 and back surface M2 of the print medium M twice, using only the rollers 471-477 that come into contact with the back surface M2 of the print medium M and rotate while wrapping the back surface M2 around it. In other words, the inverting and conveying unit 47 can invert the front surface M1 and back surface M2 of the print medium M twice, without providing any support members such as rollers or air turn bars on the front surface M1 side of the print medium M.

The transport unit 4 also has a white transport unit 48 that is provided above the upper transport unit 43 and on one side X1 of the roller 477 of the reverse transport unit 47. This white transport unit 48 has a roller 481, and the print medium M transported from the roller 477 of the reverse transport unit 47 is supported below the white printing unit 33 by the roller 481. In this way, the roller 481 of the white transport unit 48 transports the print medium M from the other side X2 to the one side X1 while supporting the print medium M from below by contacting the back surface M2 of the print medium M transported from the roller 477 of the reverse transport unit 47 from below. Then, the white printing unit 33 ejects white ink from above onto the front surface M1 of the print medium M transported along its front surface M1 by the white transport unit 48.

Furthermore, the transport section 4 has an exit section 49 that is provided above the upper transport section 43 and on one side X1 of the white transport section 48. The exit section 49 has a number of rollers 491, 492, 493 arranged from the other side X2 to one side X1 of the horizontal direction X. The upper ends of these rollers 491 to 493 are aligned parallel to the horizontal direction X and contact the back surface M2 of the print medium M. These rollers 491 to 493 transport the print medium M horizontally from the other side X2 to one side X1 of the horizontal direction X. In particular, the drive roller 491 is a drive roller that drives the print medium M by rotating by the driving force of the motor while wrapping the back surface M2 of the print medium M transported from the roller 481 around it. Meanwhile, an exit port 312 opens in the side wall of the one side X1 of the housing 31. Therefore, the print medium M is transported parallel to the horizontal direction X by the discharge section 49 and discharged from the discharge opening 312.

In this way, the transport unit 4 does not have a support member on the front surface M1 side of the print medium M, which supports the print medium M that enters the color transport unit 45, is turned upside down twice, and reaches the discharge port 312, but only on the back surface M2 side of the print medium M.

The printing device 3 also includes a pre-drying section 34 arranged in the housing 31. The pre-drying section 34 is arranged between the carry-in section 41 and the reverse transport section 47 in the vertical direction Z. The pre-drying section 34 has a plurality of nozzles 341 arranged in the traveling direction of the printing medium M transported from one side X1 to the other side X2 by the plurality of rollers 473 of the reverse transport section 47. Each nozzle 341 faces the surface M1 of the printing medium M transported by the plurality of rollers 473 from below, and sprays room temperature air from below onto the surface M1 of the printing medium M. In other words, the surface M1 of the printing medium M onto which the color ink is ejected from the color printing section 32 is dried by the pre-drying section 34. Note that the pre-drying section 34 is not necessarily limited to being between the carry-in section 41 and the reverse transport section 47, and the position at which the pre-drying section 34 is arranged is not limited as long as it can adopt a positional relationship in which air can be sprayed onto the surface M1 of the printing medium M transported by the reverse transport section 47. That is, the pre-drying unit 34 can be positioned so that air can be sprayed onto the surface M1 of the printing medium M after the color printing unit 32 has ejected color ink onto the surface of the printing medium M and before the white printing unit 33 ejects white ink onto the surface M1 of the printing medium M. However, if the pre-drying unit 34 is positioned between the entrance unit 41 and the reversing and conveying unit 47, the space below the reversing and conveying unit 47 can be used as the space for the pre-drying unit, which has the advantage of making the printing device smaller in the horizontal direction.

The printing device 3 further includes an upper drying section 35 disposed within the housing 31. The upper drying section 35 is disposed above the discharge section 49. The upper drying section 35 has a plurality of nozzles 351 arranged in the traveling direction of the print medium M transported by the discharge section 49 from the other side X2 to the one side X1. Each nozzle 351 faces the surface M1 of the print medium M transported by the discharge section 49 from above, and sprays room temperature air from above onto the surface M1 of the print medium M. In other words, the surface M1 of the print medium M onto which white ink has been ejected from the white printing section 33 is dried by the upper drying section 35.

As described above, the transport unit 4 has three drive rollers 461, 471, and 491, and the printing medium M is transported in this order. In addition, each ejection head 321 of the color printing unit 32 faces the printing medium M between the drive roller 461 and the drive roller 471 from above, and each ejection head 321 ejects ink onto the surface M1 of the printing medium M transported from the drive roller 461 on the other side X2 to the drive roller 471 on one side X1. Furthermore, the surface M1 and the back surface M2 of the printing medium M are inverted up and down twice between the drive roller 471 and the drive roller 491, and the surface M1 of the printing medium M before reaching the drive roller 491 faces upward. In this way, the ejection head 331 of the white printing unit 33 faces the surface M1 of the printing medium M facing upward between the drive roller 471 and the drive roller 491 from above. Then, the ejection head 331 ejects ink onto the surface M1 of the print medium M that is transported from the drive roller 471 to the drive roller 491.

At this time, each of the drive rollers 461, 471, 491 rotates at a speed corresponding to the tension of the print medium M detected by the tension sensors of the driven rollers 463, 472, respectively, thereby adjusting the tension of the print medium M transported by the transport unit 4 to a predetermined target tension throughout. This allows the color ink and white ink to be ejected onto the print medium M while applying an appropriate tension to the print medium M.

The drive roller 471 and the drive roller 491 are suction rollers that suck the print medium M. This allows the drive rollers 471 and 491 to accurately transmit rotation to the print medium M by suction force, thereby driving the print medium M. In response to this, the transport unit 4 has a suction mechanism for sucking the inside of each drive roller 471 and 491 (Figure 3).

Figure 3 is a schematic diagram showing the suction mechanism provided for each drive roller, which is a suction roller. The suction mechanism 5 has a suction blower 51, a common pipe 52 attached to the suction blower 51, a branch pipe 53 connecting the common pipe 52 to the drive roller 471, and a branch pipe 54 connecting the common pipe 52 to the drive roller 491.

When the suction blower 51 sucks the common pipe 52, the inside of the drive roller 471 (suction roller) is sucked through the branch pipe 53. As a result, negative pressure is applied to the multiple suction holes that open on the circumferential surface of the drive roller 471, and the print medium M is sucked into the drive roller 471 by the suction force generated on the circumferential surface of the drive roller 471 by this negative pressure.

Similarly, when the suction blower 51 sucks the common pipe 52, the inside of the drive roller 491 (suction roller) is sucked through the branch pipe 54. As a result, negative pressure is applied to the multiple suction holes opening on the circumferential surface of the drive roller 491, and the print medium M is sucked into the drive roller 491 by the suction force generated on the circumferential surface of the drive roller 491 by this negative pressure.

Figure 4 is a side view showing a schematic diagram of the relationship between the print medium M and two drive rollers that support the print medium M on either side of the white printed portion. As shown in the "Front drive roller 471" column in Figure 4, the drive roller 471 wraps the print medium M at a wrap angle θ471 while in contact with the back surface M2 of the print medium M. Here, the wrap angle θ471 is the angle that the contact area between the circumferential surface of the drive roller 471 and the print medium M forms around the rotation axis of the drive roller 471 when viewed from the direction in which the rotation axis of the drive roller 471 extends (a direction perpendicular to the vertical direction Z and the horizontal direction X). This drive roller 471 has a radius R471.

As shown in the "Subsequent drive roller 491" column in Figure 4, the drive roller 491 wraps the print medium M at a wrap angle θ491 while in contact with the back surface M2 of the print medium M. Here, the wrap angle θ491 is the angle that the contact area between the circumferential surface of the drive roller 491 and the print medium M forms around the rotation axis of the drive roller 491 when viewed from the direction in which the rotation axis of the drive roller 491 extends (a direction perpendicular to the vertical direction Z and the horizontal direction X). This drive roller 491 has a radius R491.

As shown in FIG. 4, the wrap angle θ491 of the drive roller 491 with respect to the print medium M is smaller than the wrap angle θ471 of the drive roller 471 with respect to the print medium M. For example, the wrap angle θ471 is approximately 39 degrees, while the wrap angle θ491 is 12 degrees to 14 degrees, and the wrap angle θ491 can be set to 1/2 or less than 1/3 times the wrap angle θ471.

As described above, the ejection head 331 is the last of the multiple ejection heads 321, 331 provided in the printing device 3 to eject ink onto the printing medium M. The printing medium M from which ink has been ejected from the ejection head 331 is then discharged from the discharge port 312 by the drive roller 491. In other words, of the multiple ejection heads 321, 331, the ejection head 331 is the ejection head that ejects ink onto the printing medium M just before the drive roller 491. In contrast, by reducing the wrap angle θ491, the inclination of the printing medium M before and after the drive roller 491 is suppressed. As a result, it is possible to suppress the inclination of the ejection head 331 just before the drive roller 491 while sending out the printing medium M horizontally from the drive roller 491.

In other words, the drive roller 491 sends out the print medium M parallel to the horizontal direction X toward the discharge port 312. In this way, the print medium M reaching the discharge port 312 from the drive roller 491 is kept parallel to the horizontal direction X. On the other hand, because the wrap angle θ491 of the drive roller 491 with respect to the print medium M is small, the inclination of the print medium M with respect to the horizontal direction X immediately before it reaches the drive roller 491 is small. Therefore, the inclination of the ejection head 331 facing this print medium M can also be kept small. As a result, the inclination of the ink ejection direction from the ejection head 331 to the print medium M with respect to the vertical direction Z can be reduced.

On the other hand, the diameter R491 of the drive roller 491 is larger than the diameter R471 of the drive roller 471. For example, the diameter R491 is 300 mm, while the diameter R471 is 150 mm, so that the diameter R491 can be more than twice the diameter R471. In this way, by using a drive roller 491 with a large diameter R491, it is possible to ensure a sufficient contact area between the drive roller 491 and the printing medium M, even though the winding angle θ491 of the drive roller 491 is small.

In the printing device 3 described above, an image is printed on the printing medium M by ejecting ink from the white printing section 33 (first printing section) onto the printing medium M transported from the drive roller 471 (second drive roller) to the drive roller 491 (first drive roller). The printing medium M on which the image has been printed is sent horizontally toward the discharge port 312 by the drive roller 491. Therefore, a device (e.g., the drying device 6) that processes the printing medium M discharged from the printing device 3 can be configured compactly in the vertical direction Z. In addition, the angle θ491 at which the driving roller 491 wraps the printing medium M is smaller than the angle θ471 at which the driving roller 471 wraps the printing medium M, and the wrapping angle θ491 of the printing medium M around the driving roller 491 is small. This keeps the inclination of the printing medium M to the drive roller 491 small. As a result, the ink ejection surface of the white printed area 33 that faces the print medium M can be kept nearly horizontal, preventing problems such as ink flowing down the ink ejection surface of the white printed area 33 and solidifying on the ink ejection surface.

Moreover, the drive roller 491 is a suction roller. Therefore, the rotation of the drive roller 491 can be securely transmitted to the printing medium M. Furthermore, the diameter R491 of the drive roller 491 is larger than the diameter R471 of the drive roller 471. In this way, by increasing the diameter R491 of the drive roller 491, even though the winding angle θ491 of the printing medium M by the drive roller 491 is small, the contact area between the drive roller 491 and the printing medium M can be secured, and the rotation of the drive roller 491 can be more reliably transmitted to the printing medium M. As a result, the printing medium M can be stably sent out by the drive roller 491. In this way, in the configuration in which the printing medium M on which ink has been ejected from the white printing section 33 is sent out horizontally by the drive roller 491 in this embodiment, the printing medium M can be stably transported by the drive roller 491.

Also, a color printing unit 32 (second printing unit) is provided that ejects ink onto the surface M1 (recording surface) of the printing medium M transported to one side X1 by the transport unit 4, facing the surface M1. The transport unit 4 has a drive roller 461 (third drive roller) arranged on the other side X2 of the drive roller 471, and the drive roller 461 rotates while wrapping the printing medium M. Then, the printing medium M is transported from the drive roller 461 to the drive roller 471 with the surface M1 facing upward, and the color printing unit 32 faces the surface M1 of the printing medium M between the drive roller 461 and the drive roller 471. In this configuration, the printing medium M on which an image is printed by the color printing unit 32 is transported toward the white printing unit 33 by the drive roller 471. At this time, since the winding angle θ471 of the printing medium M to the drive roller 471 is large, the printing medium M is stably transported by the drive roller 471 toward the white printing unit 33. Therefore, the white printing unit 33 can print an image by ejecting ink onto the print medium M that is transported stably in this manner. This allows the white printing unit 33 to stably print an image onto the print medium M on which an image has been printed by the color printing unit 32.

In addition, from the drive roller 471 to the drive roller 491, the carry-in unit 41 turns the print medium M upside down twice, and the white printing unit 33 ejects ink onto the surface M1 that faces upward after the two upside-down inversions to print an image. Therefore, a distance sufficient to perform two upside-down inversions is secured between the printing by the color printing unit 32 and the printing by the white printing unit 33, and the image printed by the color printing unit 32 can be printed by the white printing unit 33 in a state in which the image printed by the color printing unit 32 is somewhat dry. Therefore, it is possible to prevent the ink ejected from the color printing unit 32 from mixing with the ink ejected from the white printing unit 33. Moreover, since there is no member that comes into contact with the surface M1 of the print medium M from the drive roller 471 to the drive roller 491, the image printed by the color printing unit 32 is not disturbed. As a result, the image printed by the color printing unit 32 can be printed by the white printing unit 33 while maintaining the image printed by the color printing unit 32 in good condition.

The white printing unit 33 ejects white ink, and the color printing unit 32 ejects ink of a color different from white. In this configuration, the white printing unit 33 can print a white background on the image printed by the color printing unit 32.

The drive roller 471 is also a suction roller that sucks the print medium M. In this configuration, the drive roller 471 can transport the print medium M more stably toward the white print section 33.

The printing device 3 also includes a suction mechanism 5 that sucks the drive roller 471 and the drive roller 491. The suction mechanism 5 includes a suction blower 51, a common pipe 52 and a branch pipe 54 (first connection) that connect the suction blower 51 and the drive roller 491, and a branch pipe 53 and a common pipe 52 (second connection) that connect the suction blower 51 and the drive roller 471. The drive roller 491 and the drive roller 471 suck the back surface M2 of the printing medium M by the suction force generated by the suction blower 51. In this way, the suction blower 51 can be shared between the drive roller 491 and the drive roller 471, simplifying the configuration of the printing device 3.

In the embodiment described above, the printing system 1 corresponds to an example of the "printing system" of the present invention, the printing device 3 corresponds to an example of the "printing device" of the present invention, the color printing unit 32 corresponds to an example of the "second printing unit" of the present invention, the white printing unit 33 corresponds to an example of the "first printing unit" of the present invention, the conveying unit 4 corresponds to an example of the "conveying unit" of the present invention, the drive roller 461 corresponds to an example of the "third drive roller" of the present invention, the drive roller 471 corresponds to an example of the "second drive roller" of the present invention, the drive roller 491 corresponds to an example of the "first drive roller" of the present invention, and the suction blower 51 corresponds to an example of the "suction blower" of the present invention. , common pipe 52 and branch pipe 54 correspond to an example of a "first connection part" of the present invention, common pipe 52 and branch pipe 53 correspond to an example of a "second connection part" of the present invention, drying device 6 corresponds to an example of a "drying part" of the present invention, air blowing chamber 64 corresponds to an example of an "air blowing chamber" of the present invention, print medium M corresponds to an example of a "print medium" of the present invention, front surface M1 corresponds to an example of a "recording surface" of the present invention, back surface M2 corresponds to an example of a "non-recording surface" of the present invention, one side X1 corresponds to an example of a "one side" of the present invention, and the other side X2 corresponds to an example of a "other side" of the present invention.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, the ink ejected from the ejection head 331 immediately before the drive roller 491 that ejects the print medium M from the printing device 3 is not limited to white ink.

Furthermore, the specific configuration for transporting the print medium M from the drive roller 471 to the drive roller 491 is not limited to the above example. Therefore, it is not necessary to perform two upside-down inversions on the print medium M between the drive roller 471 and the drive roller 491.

Also, the drive roller 471 does not have to be a suction roller.

In addition, the type of ink ejected by the printing device 3 is not limited to water-based ink.

In addition, the processing performed on the print medium M discharged from the printing device 3 is not limited to drying by the drying device 6.

The present invention is applicable to all printing devices that eject ink onto a printing medium M using an inkjet method.

1: Printing system 3: Printing device 32: Color printing unit (second printing unit)
33...White printing section (first printing section)
4...Transportation section 461...Drive roller (third drive roller)
471...driving roller (second driving roller)
491...driving roller (first driving roller)
51: Suction blower 52: Common piping (first connection part, second connection part)
53...Branch pipe (second connection part)
54...Branch pipe (first connection part)
6...Drying device (drying section)
64: Air blowing chamber M: Printing medium M1: Surface (recording surface)
M2: Back side (non-recording side)
X1: One side X2: Other side

Claims (6)

a conveying section including a first driving roller and a second driving roller that rotate around a non-recording surface of a long strip-shaped print medium having a recording surface and a non-recording surface opposite to the recording surface, and that conveys the print medium from the second driving roller to the first driving roller;
a first printing unit that faces the recording surface of the print medium between the second driving roller and the first driving roller and ejects ink onto the recording surface;
a second printing unit that faces the recording surface of the print medium transported to one side by the transport unit and ejects ink onto the recording surface,
the first drive roller horizontally feeds out the print medium conveyed from the second drive roller with the recording surface facing upward;
an angle at which the first drive roller wraps the print medium is smaller than an angle at which the second drive roller wraps the print medium;
the first drive roller is a suction roller that attracts the print medium,
The diameter of the first drive roller is larger than the diameter of the second drive roller,
the transport section further includes a third drive roller that is disposed on the other side of the second drive roller opposite to the one side and rotates around the print medium, and transports the print medium from the third drive roller to the second drive roller with the recording surface facing upward;
the second printing unit faces the recording surface of the print medium between the third drive roller and the second drive roller,
the transport unit transports the print medium transported from the second drive roller in a downward direction, then changes its traveling direction to the other side and transports the print medium, thereby inverting the recording surface and the non-recording surface of the print medium upside down and transporting the print medium from the one side to the other side, then transports the print medium in an upward direction, then changes its traveling direction to the one side, thereby performing an operation of inverting the recording surface and the non-recording surface of the print medium upside down again and transporting the print medium from the other side to the one side to the first drive roller,
the transport unit transports the print medium from the second drive roller to the first drive roller only by rollers that contact the non-recording surface of the print medium;
The first printing unit faces the recording surface that faces upward as a result of the operation of being turned upside down again by the transport unit. The printing device according to claim 1, wherein the first printing unit ejects white ink, and the second printing unit ejects ink of a color different from white. The printing device according to any one of claims 1 to 2, wherein the second drive roller is a suction roller that sucks the print medium. A suction blower;
a first connection portion that connects the suction blower and the first drive roller;
a second connection portion that connects the suction blower and the second drive roller,
The printing apparatus according to claim 3 , wherein the first drive roller and the second drive roller suck the non-recording surface of the print medium by a suction force generated by the suction blower. A printing device according to any one of claims 1 to 4,
a drying unit that dries the print medium transported from the printing device;
The drying section is a printing system that includes an air blowing chamber having a plurality of nozzles arranged horizontally and facing the printing medium, and dries the printing medium by spraying gas from the nozzles of the air blowing chamber onto the printing medium. A step of transporting a long strip-shaped print medium having a recording surface and a non-recording surface opposite to the recording surface from the second drive roller to the first drive roller by a transport unit including a first drive roller and a second drive roller that rotate around the non-recording surface of the print medium;
ejecting ink onto the recording surface from a first printing unit facing the recording surface of the print medium between the second drive roller and the first drive roller;
a step of transporting the print medium from the third drive roller to the second drive roller with the print medium facing upward by the transport unit further including a third drive roller arranged on the other side opposite to the one side of the second drive roller and rotating around the print medium;
a step in which a second printing unit facing the recording surface of the print medium between the third drive roller and the second drive roller faces the recording surface of the print medium transported to the one side by the transport unit and ejects ink onto the recording surface;
Equipped with
the first drive roller horizontally feeds out the print medium conveyed from the second drive roller with the recording surface facing upward;
an angle at which the first drive roller wraps the print medium is smaller than an angle at which the second drive roller wraps the print medium;
the first drive roller is a suction roller that attracts the print medium,
The diameter of the first drive roller is larger than the diameter of the second drive roller,
the transport unit transports the print medium transported from the second drive roller in a downward direction, then changes its traveling direction to the other side and transports the print medium, thereby inverting the recording surface and the non-recording surface of the print medium upside down and transporting the print medium from the one side to the other side, then transports the print medium in an upward direction, then changes its traveling direction to the one side, thereby performing an operation of inverting the recording surface and the non-recording surface of the print medium upside down again and transporting the print medium from the other side to the one side to the first drive roller,
the transport unit transports the print medium from the second drive roller to the first drive roller only by rollers that contact the non-recording surface of the print medium;
The printing method, wherein the first printing unit faces the recording surface that faces upward as a result of the operation of being turned upside down again by the transport unit.

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