Printing device

Abstract

A control unit (50) of this printing device has a dummy printing image creation unit (56) and a printing control unit (57). The dummy printing image creation unit (56) creates a dummy printing image (D2) to be printed in a side area in the width direction of an actual printing area on the basis of an actual printing image (D1) to be printed in the actual printing area of a printing medium. The printing control unit (57) controls a conveyance mechanism (10) and inkjet heads (311, 321) so as to print the actual printing image (D1) and the dummy printing image (D2). The dummy printing image creation unit (56) creates the dummy printing image (D2) having a printing ratio corresponding to a printing ratio of the actual printing image (D1). Thus, the control unit of the printing device can automatically create the dummy printing image (D2) for suppressing winding misalignment during winding of the printing medium, and the amount of ink used for printing the dummy printing image (D2) can be suppressed.

Description

printing device

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

[0002] 2. Description of the Related Art Conventionally, there has been known a printing device that prints an image on a film sheet for flexible packaging using an inkjet method. A conventional printing device for flexible packaging is described in, for example, Patent Document 1.

[0003] Japanese Patent Application Laid-Open No. 2022-052068

[0004] In this type of printing device, aqueous pigment inks are sometimes used to reduce environmental impact. However, because flexible packaging film sheets do not absorb ink, the thickness of the printed film sheet increases in the areas where ink is ejected. That is, the printed film sheet has a thicker area where the printing rate is high and a thinner area where the printing rate is low. Therefore, if the printing rate is uneven, the difference in thickness can cause misalignment when the printed film sheet is wound up. The printing rate represents the amount of ink applied per unit area to the film sheet, and is expressed as a percentage, with 100 representing a state in which ink is applied to the entire surface of the film sheet.

[0005] To prevent such misalignment, it is possible to print a dummy print image, separate from the actual print image used for packaging, on both widthwise ends of the film sheet. By printing a dummy print image, it is possible to control the portion of the film sheet that will become thicker after printing. This makes it possible to prevent misalignment of the film sheet.

[0006] However, it is difficult for a printing device user to create an appropriate dummy print image that corresponds to the actual print image. Also, while it is 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 these circumstances, and aims to provide a technology that enables the control unit of a printing device to automatically create a dummy print image to prevent misalignment when winding up the printing medium, and that can reduce the amount of ink used to print the dummy print image.

[0008] In order to solve the above problem, 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 an area to the side of the actual print area in the width direction based on an actual print image to be printed in the actual print 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 that corresponds 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 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.

[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 conveying direction is greater than the integrated value of the printing rate of the actual print image in the conveying 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 as it moves toward the rear end in the transport direction.

[0012] A fifth invention of the present application is a printing device according to any one of the first to fourth inventions, wherein the dummy print image creation unit creates the dummy print images 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 fourth inventions, wherein the dummy print image creation unit creates the dummy print image on the other side of the width of the actual printing area when the actual printing image is biased to one side of the width 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, and the nip roller presses the printing medium being wound onto the winding roller toward the winding roller.

[0015] According to the first to seventh aspects of the present invention, the control unit of the printing device can create a dummy print image to prevent misalignment when the print medium is wound up. The control unit also creates a dummy print image with a print rate that corresponds to the print rate of the actual print image. This prevents the amount of ink used to print the dummy print image from becoming excessive.

[0016] In particular, according to the third aspect of the present invention, the diameter of the portion of the roll of printing 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 reducing the amount of ink used to print the dummy print image and ensuring a sufficient diameter for the portion 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, of the two sides in the width direction of the actual print area, thereby suppressing misalignment due to bias in the actual print image.

[0019] 1 is a diagram showing the configuration of a printing device; FIG. 2 is a diagram showing actual print images and dummy print images according to an embodiment; FIG. 3 is a block diagram conceptually showing the functions of a control unit involved in creating and printing dummy print images; FIG. 4 is a graph showing an example of the print coverage rate of actual print images and dummy print images in a certain calculation range; FIG. 5 is a diagram showing the external shape of a roll of printing medium after being wound up; FIG. 6 is a diagram showing actual print images and dummy print images according to a first modified example; FIG. 7 is a diagram showing actual print images and dummy print images according to a second modified example; FIG. 8 is a diagram showing actual print images and dummy print images according to a third modified example; FIG. 9 is a diagram showing actual print images and dummy print images according to a fourth modified example; FIG. 10 is a diagram showing actual print images and dummy print images according to a fifth modified example; FIG. 11 is a diagram showing actual print images and dummy print images according to a sixth modified example; FIG. 12 is a diagram showing actual print images and dummy print images according to a seventh modified example.

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

[0021] 1. Configuration of the Printing Device 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 using an inkjet method. The printing medium M is a film sheet for flexible packaging. For the printing medium M, a resin such as OPP (oriented polypropylene) or PET (polyethylene terephthalate) is used, for example.

[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 feed roller 11, multiple transport rollers 12, and a take-up roller 13. The feed roller 11 is located at the most upstream side of the transport path. The printing medium M before transport is wound around the feed roller 11. The take-up roller 13 is located at the most downstream side of the transport path. The printing medium M after transport is wound around the take-up roller 13. The printing medium M is stretched across the multiple transport rollers 12 between the feed roller 11 and the take-up roller 13.

[0024] The supply 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 rotation of the drive roller causes the print medium M to be unwound from the supply roller 11 and transported in the longitudinal direction along a transport path defined by the multiple transport rollers 12. The transported print medium M is then taken up by the take-up roller 13.

[0025] In FIG. 1, an arrow indicating the transport direction is attached 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 take-up roller 13. The nip roller 14 is arranged parallel to the take-up roller 13. The nip roller 14 presses the printing medium M being taken up by the take-up roller 13 toward the take-up roller 13. This makes it possible to prevent wrinkles from forming in the printing medium M being taken up by the take-up roller 13. Furthermore, since it is possible to prevent air from being mixed in between the printing medium M, it is possible to prevent misalignment of the printing medium M due to the mixed air.

[0027] The coating processing unit 20 is a processing unit for coating a primer, which serves as a base material, on the surface of the printing medium M. The coating processing unit 20 is located downstream of the feed 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 unit 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 that is arranged parallel to the width direction of the print medium M. The print medium M passes through the coating processing unit 20 with its front surface facing downward. During this process, the gravure roller 22 rotates while making contact with the surface of the print medium M. As a result, the primer in the pan 21 is applied to the surface of the print 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 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 section 30 has a color printing section 31 and a white printing section 32. The color printing section 31 and the white printing section 32 are arranged in a common printing chamber 33. The print medium M passes through the color printing section 31 and the white printing section 32 in sequence with its 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 print medium M. Each inkjet head 311 ejects ink droplets from the plurality of nozzles toward the surface of the print 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 earlier. The print processing unit 30 may also 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 earlier.

[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 oven 41. The drying oven 41 is arranged adjacent to the printing chamber 33. The printing medium M is transported in a roughly S-shaped manner within the drying oven 41 and heated by hot air blown from a hot air unit (not shown). This causes moisture to evaporate from the ink adhering to the surface of the printing medium M. As a result, the ink is fixed to 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 apparatus 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, coating processing unit 20, and print processing unit 30, respectively.

[0036] The storage unit 53 stores a computer program P for executing a process for creating a dummy print image D2 (described below) 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 in accordance with 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 in accordance with 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 print medium M.

[0037] 2. Creation and Printing of Dummy Print Image Next, 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 one 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 at 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 and misalignment when the print medium M is wound onto 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] 3 is a block diagram conceptually illustrating 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 printing 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 printing 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 within 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 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 actual print image D1.

[0043] The printing rate calculation unit 55 calculates the printing rate for each preset calculation range H in the transport direction. 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 also be a range in the transport direction corresponding to one actual print image D1, or a range in the transport direction spanning multiple actual print images D1. The calculation range H may also be a range in the transport direction equivalent to one turn of the paper when taken up by the take-up 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 of 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 of the width direction of each of the multiple actual print images D1 arranged at intervals in the transport direction. Also, in the example of FIG. 2, no dummy print image D2 is placed in positions in the transport direction where no actual print image D1 is placed.

[0046] 4 is a graph showing an example of the printing rate of the actual print image D1 and the 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, as shown in FIG. 4 , in each calculation range H in the transport direction, 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 manner, the ink height of the dummy print image D2 on the printed printing medium M is higher than the ink height of the actual print image D1. In other words, on the printed printing medium M, the ink dimension of the dummy print image D2 in the thickness direction of the printing medium M is larger than the ink dimension of the actual print image D1 in the thickness direction of the printing medium M. As a result, 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 the occurrence of tight winding in the actual printing area A when the printing medium M is wound onto the winding roller 13. Therefore, it is possible to prevent wrinkles caused by tight winding from occurring in the actual printing area A of the printing medium M. Furthermore, by increasing the ink height at both ends of the printing medium M in the width direction, it is possible to prevent the occurrence of winding misalignment in the printing medium M when the printing medium M is wound onto the winding roller 13.

[0049] However, if the printing rate of the dummy print image D2 is made higher than necessary, excessive ink usage will result. Therefore, the dummy print image creation unit 56 varies the printing rate of the dummy print image D2 in accordance with fluctuations in the printing rate of the actual print image D1, while maintaining 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. Furthermore, 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 ink usage while ensuring the printing rate necessary 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 , dummy print images D2 with relatively low printing rates are arranged on both sides of the actual print image D1 with a low printing rate. Furthermore, as in the third actual print image D1 from the downstream side in the transport direction in FIG. 2 , dummy print images D2 with relatively high printing rates are arranged on both sides of the actual print image D1 with a high printing rate.

[0051] 5 is a diagram showing the external shape of a roll of printing medium M printed with the actual print image D1 and dummy print image D2 of FIG. 2 when it is wound onto 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 printing medium M wound onto the winding roller 13, the diameter of the portion printed with the dummy print image D2 is larger than the diameter of the portion printed with the actual print image D1. In this way, the diameter of the roll of printing medium M near both ends in the width direction after winding is larger than the diameter near the center in the width direction. Therefore, it is possible to prevent the printing medium M from shifting in the width direction when wound onto 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 greater 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 , the diameter of the portion of the roll of printing medium M on which the dummy print image D2 is printed can be made larger than the diameter of the portion on which the actual print image D1 is printed after winding.

[0053] 3, the dummy print image creating unit 56 creates the dummy print image D2 as described above. The dummy print image creating unit 56 then stores the created dummy print image D2 in the storage unit 53.

[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 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 actual print image D1 and dummy print image D2. In other words, the print control unit 57 controls the transport mechanism 10 and the multiple inkjet heads 311, 321 so that specified amounts of ink droplets are 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 this printing device 1, the control unit 50 automatically creates a dummy print image D2 based on the input actual print image D1. The created dummy print image D2 is then printed on the printing medium M together with the actual print image D1. This prevents wrinkles and misalignment from occurring when the printing medium M is wound onto the winding roller 13. The dummy print image creation unit 56 also creates a dummy print image D2 with a printing rate that corresponds to the printing rate of the actual print image D1. This allows the dummy print image D2 with an appropriate printing rate that corresponds to the actual print image D1 to be printed on the printing medium M. As a result, it is possible to prevent an excessive amount of ink from being used to print the dummy print image D2.

[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 modifications will be described below, focusing on the differences from the above embodiment.

[0057] 3-1. First Modification FIG. 6 shows an actual print image D1 and a dummy print image D2 according to a first modification. In the above embodiment, the dummy print image D2 was created intermittently 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. Also, in the example of FIG. 6, the printing rate of the dummy print image D2 is constant regardless of its 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 Modification Example> Fig. 7 shows an actual print image D1 and a dummy print image D2 according to a second modification example. The example of Fig. 7 differs from the example of Fig. 2 in that the dummy print images D2 are arranged in order of printing rate. Specifically, in the example of Fig. 7, the printing rate of the dummy print image D2 on the most downstream side (leading 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 (trailing 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 is 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) 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 when 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 gradually decreases toward the upstream side (rear end) in the transport direction. This reduces 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 Modification Example> Figure 8 shows an actual print image D1 and a dummy print image D2 according to a third modification example. The configuration of Figure 8 is a combination of the configuration of Figure 6 and the configuration of Figure 7. That is, in the example of Figure 8, the dummy print image D2 extends continuously in the transport direction along the multiple actual print images D1. Also, in the example of Figure 8, the printing rate of the dummy print image D2 gradually decreases toward the upstream side (rear end) in the transport direction. This reduces 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 Modification Figure 9 shows an actual print image D1 and a dummy print image D2 according to a fourth modification. In the above embodiment, the actual print image D1 was arranged across substantially the entire width of the actual printing area A. In contrast, in the example of Figure 9, the actual print image D1 is arranged at a position offset to one side in the width direction within the actual printing area A. Therefore, in the example of Figure 9, if the dummy print image D2 were not present, 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 this positional deviation of the actual print image D1 and create a dummy print image D2 in a corresponding position. For example, as shown in FIG. 9 , the dummy print image D2 may be created only on one side of the width direction of the actual print area A, the side farthest from the actual print image D1. This allows the diameter of the other side of the width direction of the roll of printing medium M to be increased after winding. 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> Figure 10 is a diagram showing an actual print image D1 and a dummy print image D2 according to a fifth modification. In the example of Figure 10, two actual print areas A are set on the printing medium M, spaced apart in the width direction. An actual print image D1 is then placed in each of the two actual print areas A. In this case, a dummy print image D2 may also be placed between the two actual print areas A.

[0066] Furthermore, after printing, the print medium M may be cut along the gap between the two actual printing areas A before being taken up by the take-up roller 13, and the two cut pieces of print medium M may be taken up onto separate take-up 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 print medium M.

[0067] 3-6. Sixth Modification Example> Figure 11 shows an actual print image D1 and a dummy print image D2 according to a sixth modification example. In the example of Figure 11, two dummy print images D2 are spaced apart in the width direction on one side of the actual print area A. This allows the width of each dummy print image D2 to be narrowed while maintaining the overall width of the dummy print image D2. This reduces the amount of ink used to print the dummy print image D2.

[0068] 3-7. Seventh Modification Example> FIG. 12 shows an actual print image D1 and a dummy print image D2 according to a seventh modification example. In the example shown in FIG. 12, the dummy print image D2 is composed of multiple figures spaced apart from one another. Specifically, the dummy print image D2 is composed of linear figures extending obliquely relative to the transport direction, arranged at intervals in the transport direction. This creates an air flow path between adjacent figures. Therefore, when the printing medium M is wound onto the winding roller 13, air accumulation can be prevented from occurring inside the dummy print image D2 in the width direction. This can prevent misalignment of the printing medium M due to air accumulation.

[0069] <3-8. Other Modifications> 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] The dummy print image creation unit 56 may also change the dummy print image D2 depending on 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. The dummy print image creation unit 56 then changes the dummy print image D2 based on the type or thickness of the printing medium M read from the storage unit 53. In this way, a more optimal dummy print image D2 can be created depending on 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 preferentially using, among the multiple colors of ink ejected from the multiple inkjet heads 311, 321, colors that are low-cost, have a high inventory, or are close to their expiration date. In this case, information about low-cost colors, colors that are high-inventory, or colors that are close to their expiration date may be stored in the storage unit 53 in advance. The dummy print image creation unit 56 then creates 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 using the same inkjet heads 311 and 321. However, the actual print image D1 and the dummy print image D2 may be printed using separate inkjet heads.

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

[0074] Furthermore, the elements appearing in the above-described embodiments and modifications may be combined as appropriate within the scope of not causing any contradiction.

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

Claims

1. A printing device comprising: a transport mechanism which transports a long strip of printing medium in a transport direction along the longitudinal direction; an inkjet head which 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 which controls the transport mechanism and the inkjet head, wherein the transport mechanism has a take-up roller which 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 which creates a dummy print image to be printed in a region to the side of the actual print area in the width direction based on an actual print image to be printed in the actual print area of ​​the printing medium, and a print control unit which 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.

2. A printing device as described in claim 1, wherein 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 printing rate of the actual print image in each calculation range in the transport direction.

3. A printing device as described in claim 1, wherein the dummy print image creation unit creates the dummy print image so that an integrated value of the printing rate of the dummy print image in the transport direction is greater than an integrated value of the printing rate of the actual print image in the transport direction.

4. A printing device as described in claim 1 or claim 3, 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.

5. A printing device according to any one of claims 1 to 4, wherein the dummy print image creation unit creates the dummy print image on both sides of the actual printing area in the width direction.

6. A printing device as described in any one of claims 1 to 4, wherein the dummy print image creation unit creates the dummy print image on the other side of the width of the actual printing area when the actual printing image is biased to one side of the width of the actual printing area.

7. A printing device according to any one of claims 1 to 6, further comprising a nip roller arranged parallel to the winding roller, the nip roller pressing the printing medium being wound around the winding roller against the winding roller.

Images