Printing device

Abstract

To provide a technique which enables a control unit of a printing device to automatically generate a dummy print image for suppressing winding misalignment during winding of a printing medium and also enables reduction of an ink amount used for printing the dummy print image.SOLUTION: A control unit 50 of this printing device includes a dummy print image generation unit 56 and a printing control unit 57. The dummy print image generation unit 56 generates a dummy print image D2 to be printed in a region of the lateral side of a real printing region in a width direction on the basis of a real print image D1 to be printed in the real printing region of a printing medium. The printing control unit 57 controls a conveyance mechanism 10 and an ink jet head 311, 321 so as to print the real print image D1 and the dummy print image D2. The dummy print image generation unit 56 generates the dummy print image D2 having a printing rate corresponding to that of the real print image D1. Thus, an ink amount used for printing the dummy print image D2 can be prevented from becoming excessive.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an inkjet printing apparatus. [Background technology]

[0002] 2. Description of the Related Art A printing device that prints an image on a film sheet for flexible packaging by an inkjet method is known. A conventional printing device for flexible packaging is described in, for example, Patent Document 1. [Prior art documents] [Non-patent literature]

[0003] [Patent Document 1] JP 2022-052068 A Summary of the Invention [Problem to be solved by the invention]

[0004] In this type of printing device, water-based pigment ink may be used to reduce the environmental load. However, since the film sheet for flexible packaging does not absorb ink, the thickness of the part of the film sheet where the ink is discharged becomes large after printing. That is, in the film sheet after printing, the part with a high printing rate becomes thicker, and the part with a low printing rate becomes thinner. Therefore, if there is a bias in the printing rate, when the film sheet after printing is wound up, the difference in thickness may cause a winding deviation. The printing rate represents the amount of ink applied per unit area to the film sheet, and is a value expressed as a percentage, for example, assuming that the state in which the ink is applied to the entire surface of the film sheet is 100.

[0005] In order to prevent such misalignment, for example, it is possible to print a dummy print image, different from the actual print image used for packaging, on both ends of the width direction of the film sheet. By printing a dummy print image, it is possible to control the part of the film sheet that becomes thicker after printing. This makes it possible to suppress misalignment of the film sheet.

[0006] However, it is difficult for a user of a printing device to create an appropriate dummy print image that corresponds to an actual print image. Also, while it is more effective to increase the printing rate and thickness of the dummy print image, increasing the printing rate too much results in excessive ink consumption.

[0007] The present invention has been developed in consideration of the above circumstances, and aims to provide a technology that enables the control unit of a printing device to automatically create a dummy print image to suppress winding misalignment when winding up the printing medium, and that can reduce the amount of ink used to print the dummy print image. [Means for solving the problem]

[0008] In order to solve the above problems, the first invention of the present application comprises a transport mechanism that transports a long strip of printing medium in a transport direction along the longitudinal direction, an inkjet head that ejects ink droplets from nozzles arranged in the width direction of the printing medium toward the printing medium transported by the transport mechanism to print an image on the printing medium, and a control unit that controls the transport mechanism and the inkjet head, wherein the transport mechanism has a take-up roller that winds up the printing medium downstream of the inkjet head in the transport direction, and the control unit has a dummy print image creation unit that creates a dummy print image to be printed in a region to the side of the actual printing area in the width direction based on an actual print image to be printed in the actual printing area of ​​the printing medium, and a print control unit that controls the transport mechanism and the inkjet head to print the actual print image and the dummy print image, and the dummy print image creation unit creates a dummy print image with a print rate corresponding to the print rate of the actual print image.

[0009] The second invention of the present application is a printing device of the first invention, wherein the dummy print image creation unit varies the printing rate of the dummy print image so that, in each calculation range in the transport direction, the printing rate of the dummy print image is equal to or greater than the maximum value of the printing rate of the actual print image.

[0010] The third invention of the present application is a printing device of the first or second invention, wherein the dummy print image creation unit creates the dummy print image so that the integrated value of the printing rate of the dummy print image in the transport direction is greater than the integrated value of the printing rate of the actual print image in the transport direction.

[0011] The fourth invention of the present application is a printing device of any one of the first to third inventions, wherein the dummy print image creation unit creates the dummy print image so that the printing rate of the dummy print image gradually decreases toward the rear end side in the transport direction.

[0012] A fifth invention of the present application is a printing device of any one of the first to fourth inventions, wherein the dummy print image creation unit creates the dummy print image on both sides of the actual printing area in the width direction.

[0013] The sixth invention of the present application is a printing device of any one of the first to fifth inventions, wherein, when the actual print image is biased to one side in the width direction within the actual printing area, the dummy print image creation unit creates the dummy print image on the other side in the width direction of the actual printing area.

[0014] The seventh invention of the present application is a printing device of any one of the first to sixth inventions, further comprising a nip roller arranged parallel to the winding roller, the nip roller pressing the printing medium being wound onto the winding roller toward the winding roller. Effect of the Invention

[0015] According to the first to seventh aspects of the present application, a dummy print image for suppressing misalignment when winding up a print medium can be created in a control unit of a printing device. In addition, the control unit creates a dummy print image with a print rate corresponding to the print rate of an actual print image. This makes it possible to prevent an excessive amount of ink from being used to print the dummy print image.

[0016] In particular, according to the third aspect of the present invention, the diameter of the portion of the roll of print medium on which the dummy print image is printed can be made larger than the diameter of the portion on which the actual print image is printed after winding.

[0017] In particular, according to the fourth aspect of the present invention, the printing rate of the dummy print image is particularly high in the area where the roll diameter is small at the beginning of winding, thereby making it possible to reduce the amount of ink used to print the dummy print image while ensuring a sufficient diameter for the part of the roll of printing medium where the dummy print image is printed after winding.

[0018] In particular, according to the sixth aspect of the present invention, a dummy print image is printed on the other side of the actual print area, farther from the actual print image, out of the two sides in the width direction of the actual print area, thereby making it possible to suppress misalignment due to the actual print image being biased. [Brief description of the drawings]

[0019] [Figure 1] FIG. 1 illustrates a configuration of a printing device. [Diagram 2] 1A and 1B are diagrams illustrating an actual print image and a dummy print image according to an embodiment; [Diagram 3] 4 is a block diagram conceptually showing the functions of a control unit related to the creation and printing of a dummy print image. FIG. [Figure 4] 11 is a graph showing an example of the printing rate of an actual print image and a dummy print image in a certain calculation range. [Diagram 5] FIG. 4 is a diagram showing the external shape of a roll of print medium after being wound up. [Figure 6] 13A and 13B are diagrams showing an actual print image and a dummy print image according to a first modified example. [Figure 7] 13A and 13B are diagrams showing an actual print image and a dummy print image according to a second modified example. [Figure 8] 13A and 13B are diagrams showing an actual print image and a dummy print image according to a third modified example. [Figure 9] 13A and 13B are diagrams showing an actual print image and a dummy print image according to a fourth modified example. [Figure 10] 13A and 13B are diagrams showing an actual print image and a dummy print image according to a fifth modified example. [Figure 11] 13A and 13B are diagrams showing an actual print image and a dummy print image according to a sixth modified example. [Figure 12] 13A and 13B are diagrams showing an actual print image and a dummy print image according to a seventh modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] <1. Printer configuration> Fig. 1 is a diagram showing the configuration of a printing device 1 according to one embodiment of the present invention. This printing device 1 is a device that prints images on a long strip-shaped printing medium M by an inkjet method. The printing medium M is a film sheet for soft packaging. For the printing medium M, a resin such as OPP (oriented polypropylene) or PET (polyethylene terephthalate) is used.

[0022] As shown in FIG. 1, the printing apparatus 1 includes a transport mechanism 10, a coating processing section 20, a printing processing section 30, a drying processing section 40, and a control section 50.

[0023] The transport mechanism 10 is a mechanism that transports the printing medium M along a predetermined transport path. The transport mechanism 10 has a pay-out roller 11, multiple transport rollers 12, and a winding roller 13. The pay-out roller 11 is located at the most upstream side of the transport path. The printing medium M before transport is wound around the pay-out roller 11. The winding roller 13 is located at the most downstream side of the transport path. The printing medium M after transport is wound around the winding roller 13. The printing medium M is stretched across the multiple transport rollers 12 between the pay-out roller 11 and the winding roller 13.

[0024] The pay-out roller 11, the take-up roller 13, and some of the transport rollers 12 are drive rollers that rotate when driven by a motor. The other transport rollers 12 are driven rollers that rotate in accordance with the movement of the print medium M in the transport direction. When the printing device 1 is in operation, the print medium M is paid out from the pay-out roller 11 by the rotation of the drive roller, and is transported in the longitudinal direction along a transport path defined by the multiple transport rollers 12. Then, after transport, the print medium M is taken up by the take-up roller 13.

[0025] In FIG. 1, an arrow indicating the transport direction is added to the front side of the print medium M on which an image is printed.

[0026] 1, the transport mechanism 10 may have a nip roller 14 near the winding roller 13. The nip roller 14 is disposed parallel to the winding roller 13. The nip roller 14 presses the printing medium M being taken up by the winding roller 13 toward the winding roller 13. This can prevent the printing medium M being taken up by the winding roller 13 from becoming wrinkled. In addition, since air can be prevented from being mixed in between the printing medium M, misalignment of the printing medium M caused by air being mixed in can be prevented.

[0027] The coating processing unit 20 is a processing unit for coating a primer serving as a base material on the surface of the printing medium M. The coating processing unit 20 is located downstream of the payout roller 11 and upstream of the print processing unit 30 on the transport path of the printing medium M.

[0028] As shown in FIG. 1, the coating processing section 20 has a pan 21 and a gravure roller 22. A liquid primer is stored in the pan 21. The lower end of the gravure roller 22 is immersed in the primer stored in the pan 21. The gravure roller 22 is rotatable about an axis arranged parallel to the width direction of the printing medium M. The printing medium M passes through the coating processing section 20 with its front surface facing downward. At that time, the gravure roller 22 rotates while contacting the surface of the printing medium M. As a result, the primer in the pan 21 is applied to the surface of the printing medium M via the outer circumferential surface of the gravure roller 22.

[0029] The print processing unit 30 is a processing unit that prints an image by ejecting aqueous pigment-type ink onto the surface of the print medium M to which the primer has been applied. The print processing unit 30 is located downstream of the coating processing unit 20 and upstream of the drying processing unit 40 on the transport path of the print medium M.

[0030] 1, the print processing unit 30 has a color printing unit 31 and a white printing unit 32. The color printing unit 31 and the white printing unit 32 are arranged in a common printing chamber 33. The printing medium M passes through the color printing unit 31 and the white printing unit 32 in sequence with the surface facing upward.

[0031] The color printing unit 31 has four inkjet heads 311. Each of the four inkjet heads 311 has a plurality of nozzles arranged along the width direction of the printing medium M. Each inkjet head 311 ejects ink droplets from the plurality of nozzles toward the surface of the printing medium M transported by the transport mechanism 10. The four inkjet heads 311 eject ink droplets of different colors. For example, the four inkjet heads 311 eject cyan, magenta, yellow, and black ink droplets, respectively.

[0032] The white printing unit 32 has one inkjet head 321. The inkjet head 321 has a plurality of nozzles arranged along the width direction of the printing medium M. The inkjet head 321 ejects white ink droplets from the plurality of nozzles toward the surface of the printing medium M.

[0033] The print processing unit 30 may have a first pre-drying unit between the color printing unit 31 and the white printing unit 32 on the transport path of the print medium M. This may allow the ink ejected from the color printing unit 31 to start drying early. The print processing unit 30 may have a second pre-drying unit between the white printing unit 32 and the drying processing unit 40 on the transport path of the print medium M. This may allow the ink ejected from the white printing unit 32 to start drying early.

[0034] The drying processing unit 40 is a processing unit that dries the ink ejected onto the surface of the printing medium M in the print processing unit 30. The drying processing unit 40 has a drying furnace 41. The drying furnace 41 is disposed adjacent to the printing chamber 33. The printing medium M is heated by hot air blown from a hot air unit (not shown) while being transported in a substantially S-shaped manner within the drying furnace 41. This causes moisture to evaporate from the ink adhering to the surface of the printing medium M. As a result, the ink is fixed on the surface of the printing medium M.

[0035] The control unit 50 is a unit for controlling the operation of each part of the printing device 1. As shown in Fig. 1, the control unit 50 is configured by a computer having a processor 51 such as a CPU, a memory 52 such as a RAM, and a storage unit 53 such as a hard disk drive. The control unit 50 is also electrically connected to the above-mentioned transport mechanism 10, the coating processing unit 20, and the print processing unit 30.

[0036] The storage unit 53 stores a computer program P for executing a process for creating a dummy print image D2, which will be described later, and a process for printing the dummy print image D2 and the actual print image D1. When the actual print image D1 to be printed is input, the control unit 50 creates a dummy print image D2 corresponding to the actual print image D1 according to the computer program P. The control unit 50 then operates the transport mechanism 10, the coating processing unit 20, and the print processing unit 30 according to the computer program P. As a result, the actual print image D1 and the dummy print image D2 are printed on the surface of the printing medium M.

[0037] <2. Creating and printing dummy print images> Next, the creation and printing of the dummy print image D2 will be described. Fig. 2 is a diagram showing an actual print image D1 and a dummy print image D2 according to an embodiment.

[0038] The actual print image D1 is an image to be printed in an actual print area A, which is used as packaging, of the print medium M. In the example of Fig. 2, the actual print area A is set in the center in the width direction of the print medium M. Then, a plurality of actual print images D1 are arranged in the actual print area A with intervals in the transport direction.

[0039] The dummy print image D2 is an image printed on the print medium M in an area outside the actual print area A (i.e., an area not used as packaging) in order to prevent wrinkles or misalignment when the print medium M is wound around the winding roller 13. In the example of Fig. 2, the dummy print image D2 is arranged in areas on both sides of the actual print area A in the width direction.

[0040] Fig. 3 is a block diagram conceptually showing the functions of the control unit 50 related to the creation and printing of the dummy print image D2. As shown in Fig. 3, the control unit 50 has an actual print image input unit 54, a printing rate calculation unit 55, a dummy print image creation unit 56, and a print control unit 57. The functions of the actual print image input unit 54, the printing rate calculation unit 55, the dummy print image creation unit 56, and the print control unit 57 are realized by the processor 51 of the control unit 50 operating in accordance with the computer program P described above.

[0041] The actual print image input unit 54 accepts input of the actual print image D1 from outside. The actual print image D1 is input to the actual print image input unit 54, for example, from a server installed outside the printing device 1. The actual print image input unit 54 acquires the actual print image D1 from outside, and stores the acquired actual print image D1 in the memory unit 53 in the control unit 50.

[0042] The printing rate calculation unit 55 calculates the printing rate of the actual print image D1. The printing rate represents the amount of ink ejected from the inkjet heads 311, 321 when printing the actual print image D1. The printing rate calculation unit 55 reads out the actual print image D1 from the storage unit 53, and calculates the total value of the printing rates of all color components of the read out actual print image D1.

[0043] The printing rate calculation unit 55 calculates the printing rate for each calculation range H in the transport direction that is set in advance. The calculation range H may be a range equivalent to one pixel in the transport direction, or a range of multiple pixels. The calculation range H may be a range in the transport direction that corresponds to one actual print image D1, or a range in the transport direction that spans multiple actual print images D1. The calculation range H may be a range in the transport direction that corresponds to one turn when wound up by the winding roller 13.

[0044] The dummy print image creation unit 56 creates a dummy print image D2 based on the actual print image D1. Specifically, the dummy print image creation unit 56 acquires the print rate for each calculation range H of the actual print image D1 from the print rate calculation unit 55. Then, the dummy print image creation unit 56 creates a dummy print image D2 according to the print rate.

[0045] The dummy print image creation unit 56 creates dummy print images D2 in the areas on both sides in the width direction of the actual print area A, as shown in Fig. 2, for example. Each dummy print image D2 is a strip-shaped image extending in the transport direction. In the example of Fig. 2, a dummy print image D2 is created for each actual print image D1. That is, a dummy print image D2 is created on both sides in the width direction of each of the multiple actual print images D1 that are arranged at intervals in the transport direction. Also, in the example of Fig. 2, no dummy print image D2 is placed in any position in the transport direction where no actual print image D1 is placed.

[0046] Fig. 4 is a graph showing an example of the printing rate of an actual print image D1 and a dummy print image D2 in a certain calculation range H. The horizontal axis of Fig. 4 represents the position in the width direction, and the vertical axis of Fig. 4 represents the printing rate.

[0047] The dummy print image creation unit 56 determines the printing rate of the dummy print image D2 based on the printing rate of the actual print image D1. In this embodiment, in each calculation range H in the transport direction, as shown in FIG. 4, the printing rate of the dummy print image D2 is determined so that the printing rate of the dummy print image D2 is equal to or greater than the maximum printing rate of the actual print image D1. In this way, on the printing medium M after printing, the ink height of the dummy print image D2 (the ink dimension in the thickness direction of the printing medium M) is higher than the ink height of the actual print image D1. In other words, the ink height near both ends of the printing medium M in the width direction is always higher than the ink height near the center of the printing medium M.

[0048] In this way, it is possible to prevent tight winding in the actual printing area A when the printing medium M is wound around the winding roller 13. Therefore, it is possible to prevent wrinkles caused by tight winding in the actual printing area A of the printing medium M. Furthermore, by increasing the height of the ink at both ends in the width direction of the printing medium M, it is possible to prevent misalignment of the printing medium M when the printing medium M is wound around the winding roller 13.

[0049] However, if the printing rate of the dummy print image D2 is made higher than necessary, the amount of ink used will be excessive. Therefore, the dummy print image creation unit 56 varies the printing rate of the dummy print image D2 in accordance with the variation in the printing rate of the actual print image D1 while keeping the printing rate of the dummy print image D2 higher than the printing rate of the actual print image D1. Specifically, in the calculation range H where the printing rate of the actual print image D1 is high, the printing rate of the dummy print image D2 is also increased, and in the calculation range H where the printing rate of the actual print image D1 is low, the printing rate of the dummy print image D2 is also decreased. This makes it possible to reduce the amount of ink used while ensuring the printing rate required for the dummy print image D2.

[0050] In the example of FIG. 2, the range of one actual print image D1 in the transport direction is one calculation range H. Therefore, the printing rate of the dummy print image D2 is constant for each calculation range H. The printing rate of the dummy print image D2 is determined according to the printing rate of each actual print image D1. Therefore, as in the second actual print image D1 from the downstream side in the transport direction in FIG. 2, a dummy print image D2 with a relatively low printing rate is arranged on both sides of the actual print image D1 with a low printing rate. Also, as in the third actual print image D1 from the downstream side in the transport direction in FIG. 2, a dummy print image D2 with a relatively high printing rate is arranged on both sides of the actual print image D1 with a high printing rate.

[0051] FIG. 5 is a diagram showing the external shape of the roll of the printing medium M on which the actual print image D1 and the dummy print image D2 of FIG. 2 are printed when the printing medium M is wound around the winding roller 13. As described above, in this embodiment, in each calculation range H in the transport direction, the ink height of the dummy print image D2 is equal to or greater than the ink height of the actual print image D1. Therefore, in the roll of the printing medium M wound around the winding roller 13, the diameter of the portion on which the dummy print image D2 is printed is larger than the diameter of the portion on which the actual print image D1 is printed. In this way, in the roll of the printing medium M after winding, the diameter near both ends in the width direction is larger than the diameter near the center in the width direction. Therefore, it is possible to suppress the printing medium M from shifting in the width direction when wound around the winding roller 13.

[0052] Note that the printing rate of the dummy print image D2 does not necessarily have to be equal to or higher than the printing rate of the actual print image D1 in all calculation ranges H. In some calculation ranges H, the printing rate of the dummy print image D2 may be lower than the printing rate of the actual print image D1. Even in this case, it is sufficient that the integrated value of the printing rate of the dummy print image D2 in the transport direction is greater than the integrated value of the printing rate of the actual print image D1 in the transport direction. In this way, as shown in FIG. 5, in the roll of printing medium M after winding, the diameter of the portion where the dummy print image D2 is printed can be made larger than the diameter of the portion where the actual print image D1 is printed.

[0053] Returning to Fig. 3, the dummy print image creating unit 56 creates the dummy print image D2 as described above. Then, the dummy print image creating unit 56 causes the storage unit 53 to store the created dummy print image D2.

[0054] The print control unit 57 performs control for printing the actual print image D1 and the dummy print image D2 on the print medium M. Specifically, the print control unit 57 reads out the actual print image D1 and the dummy print image D2 from the storage unit 53. The print control unit 57 then controls the transport mechanism 10 and the multiple inkjet heads 311, 321 based on the read out actual print image D1 and dummy print image D2. That is, the print control unit 57 controls the transport mechanism 10 and the multiple inkjet heads 311, 321 so that a specified amount of ink droplets is ejected at positions specified by the actual print image D1 and the dummy print image D2. As a result, the actual print image D1 and the dummy print image D2 are printed on the surface of the print medium M.

[0055] As described above, in the printing device 1, the control unit 50 automatically creates a dummy print image D2 based on the input actual print image D1. Then, the created dummy print image D2 is printed on the printing medium M together with the actual print image D1. This makes it possible to prevent wrinkles and misalignment from occurring when the printing medium M is wound around the winding roller 13. In addition, the dummy print image creation unit 56 creates a dummy print image D2 with a printing rate corresponding to the printing rate of the actual print image D1. Therefore, the dummy print image D2 with an appropriate printing rate corresponding to the actual print image D1 can be printed on the printing medium M. As a result, it is possible to prevent the amount of ink used to print the dummy print image D2 from becoming excessive.

[0056] <3. Modifications> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment. Various modified examples will be described below, focusing on the differences from the above embodiment.

[0057] <3-1. First modified example> FIG. 6 is a diagram showing an actual print image D1 and a dummy print image D2 according to a first modified example. In the above embodiment, the dummy print image D2 is intermittently created for each actual print image D1. In contrast, in the example of FIG. 6, the dummy print image D2 extends continuously in the transport direction along the multiple actual print images D1. In addition, in the example of FIG. 6, the printing rate of the dummy print image D2 is constant regardless of the position in the transport direction. In the example of FIG. 6, the range in the transport direction spanning the multiple actual print images D1 is the calculation range H. In this case, the dummy print image creation unit 56 may set the printing rate of the dummy print image D2 to, for example, a value equal to or greater than the average printing rate of the multiple actual print images D1.

[0058] <3-2. Second modified example> Fig. 7 is a diagram showing an actual print image D1 and a dummy print image D2 according to a second modified example. The example in Fig. 7 is different from the example in Fig. 2 in that the dummy print images D2 are arranged in order of the printing rate. Specifically, in the example in Fig. 7, the printing rate of the dummy print image D2 on the most downstream side (front end side) in the transport direction is the highest, and the printing rate of the dummy print image D2 gradually decreases toward the upstream side (rear end side).

[0059] In the initial stage of winding the printing medium M onto the winding roller 13, the roll diameter is small, so the number of turns per unit length in the transport direction of the printing medium M is large. Therefore, in the initial stage of winding, the ink height is likely to overlap, so the ink height is likely to contribute to the roll diameter. On the other hand, in the final stage of winding, the roll diameter becomes large, so the number of turns per unit length in the transport direction of the printing medium M is small. Therefore, in the final stage of winding, the ink height is less likely to overlap, so the ink height is less likely to contribute to the final roll diameter.

[0060] 7, the printing rate of the dummy print image D2 is particularly high on the downstream side (front end side) in the transport direction where the roll is wound in the initial stage. This ensures the diameter of the portion where the dummy print image D2 is printed at both ends of the roll width direction. In this way, by increasing the printing rate of the dummy print image D2 in the initial stage where the number of windings can be increased, the diameter of both ends of the roll width direction can be efficiently ensured.

[0061] 7, the printing rate of the dummy print image D2 is gradually decreased toward the upstream side (rear end side) in the transport direction. This makes it possible to reduce the amount of ink used to print the dummy print image D2. The printing rate of the dummy print image D2 near the rear end in the transport direction may be equal to or greater than the printing rate of the actual print image D1, or may be lower than the printing rate of the actual print image D1. It is sufficient that the integrated value of the printing rates of the multiple dummy print images D2 in the transport direction is greater than the integrated value of the printing rate of the actual print image D1 in the transport direction.

[0062] <3-3.Third modified example> FIG. 8 is a diagram showing an actual print image D1 and a dummy print image D2 according to a third modified example. The embodiment in FIG. 8 is a combination of the embodiment in FIG. 6 and the embodiment in FIG. 7. That is, in the example in FIG. 8, the dummy print image D2 extends continuously in the transport direction along the multiple actual print images D1. Also, in the example in FIG. 8, the printing rate of the dummy print image D2 gradually decreases toward the upstream side (rear end side) in the transport direction. This makes it possible to reduce the amount of ink used to print the dummy print image D2, while ensuring a sufficient diameter for the portion of the roll of printing medium M where the dummy print image D2 is printed after winding.

[0063] <3-4. Fourth modified example> Fig. 9 is a diagram showing an actual print image D1 and a dummy print image D2 according to a fourth modified example. In the above embodiment, the actual print image D1 was arranged over substantially the entire width of the actual print area A. In contrast, in the example of Fig. 9, the actual print image D1 is arranged at a position offset to one side in the width direction within the actual print area A. For this reason, in the example of Fig. 9, if there was no dummy print image D2, the diameter of the roll of printing medium M after winding would be larger on one side in the width direction and smaller on the other side in the width direction. This would make it easier for the printing medium M to become misaligned.

[0064] The dummy print image creation unit 56 may detect such a positional deviation of the actual print image D1 and create a dummy print image D2 at a position corresponding to the deviation. For example, as shown in FIG. 9, the dummy print image D2 may be created only on the other side of the actual print area A that is far from the actual print image D1, out of the two sides in the width direction of the actual print area A. In this way, the diameter of the other side in the width direction of the roll of the printing medium M after winding can be increased. As a result, misalignment of the printing medium M caused by the deviation of the actual print image D1 can be suppressed.

[0065] <3-5. Fifth Modification> Fig. 10 is a diagram showing an actual print image D1 and a dummy print image D2 according to a fifth modified example. In the example of Fig. 10, two actual print areas A are set on the printing medium M with a gap therebetween in the width direction. An actual print image D1 is arranged in each of the two actual print areas A. In this case, a dummy print image D2 may also be arranged between the two actual print areas A.

[0066] Furthermore, after printing, the printing medium M may be cut along the line between the two actual printing areas A before being wound around the winding roller 13, and the two cut pieces of printing medium M may be wound around separate winding rollers 13. In such a case, two dummy print images D2 may be printed between the two actual printing areas A so that the dummy print image D2 remains on each of the two cut pieces of printing medium M.

[0067] <3-6. Sixth Variation> Fig. 11 is a diagram showing an actual print image D1 and a dummy print image D2 according to a sixth modified example. In the example of Fig. 11, two dummy print images D2 are arranged widthwise at a distance from each other on one side of the width of the actual print area A. In this way, the width of each of the dummy print images D2 can be narrowed while ensuring the overall width of the dummy print image D2. This makes it possible to reduce the amount of ink used to print the dummy print image D2.

[0068] <3-7. Seventh Variation> FIG. 12 is a diagram showing an actual print image D1 and a dummy print image D2 according to the seventh modified example. In the example of FIG. 12, the dummy print image D2 is composed of a plurality of figures arranged at intervals from each other. Specifically, the dummy print image D2 is an arrangement of linear figures extending obliquely with respect to the transport direction, spaced apart in the transport direction. In this way, an air flow path is formed between adjacent figures. Therefore, when the print medium M is wound around the winding roller 13, it is possible to prevent air from accumulating inside the dummy print image D2 in the width direction. Therefore, it is possible to prevent the print medium M from being misaligned due to air accumulation.

[0069] <3-8. Other variations> The dummy print image D2 does not necessarily have to be a linear image. For example, the dummy print image D2 may be an image that extends in the transport direction while meandering in the width direction.

[0070] Furthermore, the dummy print image creation unit 56 may change the dummy print image D2 according to the type or thickness of the printing medium M. In this case, the type or thickness of the printing medium M may be stored in advance in the storage unit 53. Then, the dummy print image creation unit 56 changes the dummy print image D2 based on the type or thickness of the printing medium M read out from the storage unit 53. In this way, a more optimal dummy print image D2 can be created according to the type or thickness of the printing medium M.

[0071] The dummy print image D2 may be a single-color image or an image using multiple colors. The dummy print image creation unit 56 may create the dummy print image D2 by using, among the multiple colors of ink ejected from the multiple inkjet heads 311, 321, a color that is low cost, a color that is in high stock, or a color that is close to its expiration date. In this case, information on the low cost color, the color that is in high stock, or the color that is close to its expiration date may be stored in the storage unit 53 in advance. Then, the dummy print image creation unit 56 may create the dummy print image D2 based on the information read from the storage unit 53.

[0072] In the above embodiment, the actual print image D1 and the dummy print image D2 are printed by the same inkjet heads 311, 321. However, the actual print image D1 and the dummy print image D2 may be printed by separate inkjet heads.

[0073] In the above embodiment, a water-based pigment ink is used as the ink. However, instead of the water-based pigment ink, an oil-based ink or a dye ink may be used. Also, in the above embodiment, a film sheet is used as the printing medium. However, instead of the film sheet, a paper-based printing medium may be used, and the material is not important.

[0074] Furthermore, the elements appearing in the above-described embodiments and modifications may be combined as appropriate to the extent that no contradiction arises. [Explanation of symbols]

[0075] 1:Printing device 10: Transport mechanism 11: Feed roller 12: Transport roller 13: Winding roller 14: Nip roller 20: Coating processing section 30: Print processing unit 31: Color printing department 32: White printing section 33: Printing room 40: Drying processing section 41:Drying oven 50: Control section 54: Actual print image input unit 55:Print rate calculation section 56: Dummy print image creation section 57: Print control unit 311: Inkjet head 321: Inkjet head A: Actual printing area D1: Actual printed image D2: Dummy print image H: Calculation range M:Print media

Claims

1. A transport mechanism that transports a long strip of print medium in a transport direction along the longitudinal direction; an inkjet head that ejects ink droplets from nozzles arranged in a width direction of the print medium toward the print medium transported by the transport mechanism, thereby printing an image on the print medium; a control unit for controlling the transport mechanism and the inkjet head; Equipped with The transport mechanism includes: A take-up roller that takes up the print medium downstream of the inkjet head in the transport direction. having The control unit is a dummy print image creation unit that creates a dummy print image to be printed in a lateral area in a width direction of the actual print area based on an actual print image to be printed in the actual print area of ​​the print medium; a print control unit that controls the transport mechanism and the inkjet head so as to print the actual print image and the dummy print image; having The dummy print image creating unit creates a dummy print image having a printing rate corresponding to a printing rate of the actual print image.

2. 2. The printing device according to claim 1, The dummy print image creation unit varies the printing rate of the dummy print image so that the printing rate of the dummy print image is equal to or greater than the maximum value of the printing rate of the actual print image in each calculation range in the transport direction.

3. 2. The printing device according to claim 1, The dummy print image creating unit creates the dummy print image so that an integrated value of a printing rate of the dummy print image in a transport direction is greater than an integrated value of a printing rate of the actual print image in the transport direction.

4. 2. The printing device according to claim 1, The dummy print image creating unit creates the dummy print image such that a printing rate of the dummy print image gradually decreases toward a rear end side in the transport direction.

5. 2. The printing device according to claim 1, The dummy print image creating unit creates the dummy print image on both sides of the actual print area in a width direction.

6. 2. The printing device according to claim 1, The dummy print image creation unit creates the dummy print image on the other side of the actual print area in the width direction when the actual print image is biased to one side of the actual print area in the width direction.

7. A printing device according to any one of claims 1 to 6, A nip roller disposed parallel to the winding roller Further equipped with The nip roller presses the print medium being wound around the winding roller toward the winding roller.

Images