Printing system

Abstract

Provided is a printing system that suppresses skew misregistration of an image formed by a plurality of image forming devices. In the disclosed printing system for printing an image on a base material, a travel direction correcting device for correcting the travel direction of the base material in a second image forming device on the basis of a measurement result from a travel direction measuring device includes a transport correction mechanism which is disposed between a first image forming device and the second image forming device on a transport pathway of a transporting device for transporting the base material in the order of the first image forming device and the second image forming device, and which mechanically corrects the direction of transport of the base material by the transporting device.

Description

Printing System

[0001] The present invention relates to a printing system, and more particularly to a technique for suppressing misregistration of images formed by a plurality of image forming apparatuses.

[0002] Printing devices that print on long substrates are known, and techniques for correcting meandering of the substrate in such printing devices are known.

[0003] For example, Patent Document 1 describes a double-sided printing device that adjusts the inclination of a print medium relative to the front-to-rear direction based on the meandering state of the print medium.

[0004] Japanese Patent Application Laid-Open No. 2020-049745

[0005] However, the double-sided printing device described in Patent Document 1 adjusts the meandering before front-side printing and back-side printing, which causes a problem in that misregistration between the front and back sides occurs if the printing medium meanders between the front and back side printing.

[0006] The present invention has been made in view of the above circumstances, and has an object to provide a printing system that suppresses misregistration of the skew of images formed by a plurality of image forming apparatuses.

[0007] In order to achieve the above object, a printing system according to a first aspect of the present disclosure is a printing system for printing an image on a substrate, the printing system comprising: a first image forming device that forms a first image on the substrate based on first image data; a second image forming device that forms a second image on the substrate based on second image data; a conveying device that conveys the substrate along a conveying path in the order of the first image forming device and the second image forming device; a proceeding direction measuring device that measures the difference between the assumed proceeding direction and the actual proceeding direction of the substrate in the second image forming device; and a proceeding direction correcting device that corrects the actual proceeding direction of the substrate in the second image forming device based on the measurement result of the proceeding direction measuring device, wherein the proceeding direction correcting device is disposed between the first image forming device and the second image forming device on the conveying path, and includes a conveying correction mechanism that mechanically corrects the conveying direction of the substrate by the conveying device.

[0008] A printing system according to a second aspect of the present disclosure is preferably the printing system according to the first aspect, wherein the conveying device includes a pass roller that conveys the substrate by rotating in contact with the substrate, and the conveying correction mechanism mechanically corrects the conveying direction of the substrate by adjusting the mounting angle of the pass roller.

[0009] A printing system according to a third aspect of the present disclosure is the printing system according to the second aspect, wherein the direction in which the mounting angle of the pass rollers is adjusted is preferably a direction parallel to the printing surface of the substrate. The conveying device may convey the substrate so that the printing surface of the substrate is horizontal. In this case, the direction in which the mounting angle of the pass rollers is adjusted is the horizontal direction.

[0010] In a printing system according to a fourth aspect of the present disclosure, in the printing system according to any one of the first to third aspects, it is preferable that the travel direction correction device includes an image formation correction mechanism that mechanically corrects the installation position of the second image forming device.

[0011] In a printing system according to a fifth aspect of the present disclosure, in the printing system according to the fourth aspect, it is preferable that the image formation correction mechanism rotates one side of the second image forming device across the transport path of the second image forming device as a fulcrum, and the other side of the second image forming device is rotated parallel to the printing surface of the substrate.

[0012] A printing system according to a sixth aspect of the present disclosure is the printing system according to any one of the first to fifth aspects, wherein the travel direction correction device preferably includes an image data correction device that corrects the second image data.

[0013] A printing system according to a seventh aspect of the present disclosure is preferably a printing system according to any one of the first to sixth aspects, wherein the first image forming device forms a mark on the substrate, and the travel direction measuring device includes a sensor that detects the mark.

[0014] A printing system according to an eighth aspect of the present disclosure is the printing system according to the seventh aspect, wherein the first image forming device forms two marks, and the travel direction measuring device preferably includes two optical sensors that detect the two marks, and the two marks are preferably spaced apart at a constant interval in a direction perpendicular to the assumed travel direction.

[0015] In a printing system according to a ninth aspect of the present disclosure, in the printing system according to the eighth aspect, it is preferable that the travel direction measurement device calculates the amount of tilt between the assumed travel direction and the actual travel direction of the substrate from the difference in detection timing between the two optical sensors.

[0016] A printing system according to a tenth aspect of the present disclosure is the printing system according to the ninth aspect, wherein the travel direction measurement device obtains the tilt angle from the amount of tilt using distance information between two optical sensors. The distance information between the two optical sensors may be distance information in a direction perpendicular to the assumed travel direction.

[0017] In a printing system according to an eleventh aspect of the present disclosure, in the printing system according to any one of the first to tenth aspects, it is preferable that the direction of travel measurement device includes two edge sensors spaced at a fixed interval apart to detect the position of one edge of the substrate.

[0018] In a printing system according to a twelfth aspect of the present disclosure, in the printing system according to the eleventh aspect, it is preferable that the travel direction measuring device obtains the amount of tilt between the assumed travel direction and the actual travel direction of the substrate from the detection results of the two edge sensors.

[0019] A printing system according to a thirteenth aspect of the present disclosure is the printing system according to the twelfth aspect, wherein the travel direction measurement device preferably calculates the tilt angle from the amount of tilt using distance information between the two edge sensors.

[0020] A printing system according to a fourteenth aspect of the present disclosure is preferably the printing system according to the tenth or thirteenth aspect, wherein the transport correction mechanism mechanically corrects the transport direction of the substrate using the calculated tilt angle.

[0021] A printing system according to a fifteenth aspect of the present disclosure is the printing system according to any one of the first to fourteenth aspects, wherein the first image forming apparatus includes a first ejection device that ejects a first liquid, the second image forming apparatus includes a second ejection device that ejects a second liquid, and further includes a first drying device that dries the first liquid ejected onto the substrate, a second drying device that dries the second liquid ejected onto the substrate, a first measuring device that measures the state of the substrate, a second measuring device that measures the state of the substrate, a third measuring device that measures the state of the substrate, and a and an expansion / contraction correction device that corrects the first image data and the second image data, wherein the conveying device conveys the substrate in the order of the first discharge device, the first measuring device, the first drying device, the second discharge device, the second measuring device, the second drying device, and the third measuring device, and the expansion / contraction correction device preferably calculates a first correction value for correcting the first image data based on the measurement results of the first measuring device and the measurement results of the third measuring device, and calculates a second correction value for correcting the second image data based on the measurement results of the second measuring device and the measurement results of the third measuring device.

[0022] A printing system according to a sixteenth aspect of the present disclosure is preferably the printing system according to the fifteenth aspect, wherein the position of the first image and the position of the second image on the substrate are aligned.

[0023] According to the present invention, it is possible to suppress misregistration of the inclination of images formed by a plurality of image forming apparatuses.

[0024] FIG. 1 is a diagram illustrating an example of an inkjet printing system. FIG. 2 is a block diagram illustrating the electrical configuration of the inkjet printing system. FIG. 3 is a diagram illustrating registration of a color image and a white image. FIG. 4 is a schematic diagram illustrating the operation of a twist roller. FIG. 5 is a diagram illustrating an example of the configuration of a second measurement device. FIG. 6 is a diagram illustrating tilt alignment using a mark sensor. FIG. 7 is a flowchart illustrating an automatic tilt adjustment process for automatically performing tilt alignment. FIG. 8 is a diagram illustrating another example of the configuration of the second measurement device. FIG. 9 is a diagram illustrating tilt alignment using an edge sensor. FIG. 10 is a diagram illustrating tilt alignment by tilting an inkjet head. FIG. 11 is a flowchart illustrating a size adjustment process for registration alignment in the inkjet printing system.

[0025] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0026] [Overall Configuration of Printing System] The printing system is a system that produces printed matter by printing an image on a substrate. The substrate may be sheet-fed or a continuous, long substrate. Printing may be inkjet printing, screen printing, letterpress printing, intaglio printing, offset printing, gravure printing, flexographic printing, or the like. Here, an inkjet printing system that prints on a long substrate using an inkjet method will be described. FIG. 1 is a diagram showing an example of an inkjet printing system. The inkjet printing system 10 shown in FIG. 1 transports a long, non-permeable substrate 1 and outputs a printed image including a color image and a white image on the printing surface of the substrate 1.

[0027] The substrate 1 is an impermeable medium, such as a transparent film substrate used for flexible packaging. Examples of the film substrate include PET (Polyethylene Terephthalate), OPP (Oriented Polypropylene), and NY (Nylon). The inkjet printing system 10 produces reverse-printed printed matter in which the printing target is visible from the non-printed side, which is the side opposite the printed side of the substrate 1.

[0028] "Non-permeable" refers to being non-permeable to aqueous inks, which will be described later. "Flexible packaging" refers to packaging made of a material that deforms depending on the shape of the packaged item. "Transparent" refers to a visible light transmittance of 30% to 100%, preferably 70% to 100%.

[0029] The inkjet printing system 10 includes a transport device 20 , a first printing device 30 , a second printing device 40 , and a substrate information acquisition unit 50 .

[0030] The conveying device 20 conveys the substrate 1 along a conveying path from an unwinding roll (not shown) to a take-up roll (not shown) using a roll-to-roll system. The conveying device 20 includes a plurality of pass rollers 22 and a twist roller 24. The pass rollers 22 and the twist roller 24 rotate in contact with the substrate 1 to convey the substrate 1 in the conveying direction. The substrate 1 may be conveyed in a state in which tension is applied. The movement speed (conveying speed) of the substrate 1 in the conveying direction is, for example, 50 meters / minute.

[0031] In the example shown in FIG. 1, the conveying device 20 conveys the substrate 1 in a conveying direction along the Y direction, but the conveying direction of the substrate 1 may be changed to a direction other than the Y direction as appropriate using a turning roller (not shown).

[0032] The first printing device 30 and the second printing device 40 are arranged in this order from the upstream side on the transport path of the substrate 1 .

[0033] The first printing device 30 includes a first discharging device 30A and a first drying device 30B. The substrate 1 transported to the first printing device 30 is guided by a pass roller 22 and transported to the first discharging device 30A.

[0034] The first ejection device 30A (an example of a "first image forming device") includes inkjet heads 32K, 32C, 32M, and 32Y. The inkjet heads 32K, 32C, 32M, and 32Y eject black (K), cyan (C), magenta (M), and yellow (Y) color inks (an example of a "first liquid"), respectively. Each color ink is an aqueous ink in which a coloring material such as a dye or pigment is dissolved or dispersed in water and a water-soluble solvent. The inkjet heads 32K, 32C, 32M, and 32Y are each supplied with the corresponding color ink from an ink tank (not shown) via a piping path (not shown).

[0035] Inkjet heads 32K, 32C, 32M, and 32Y are arranged at regular intervals along the transport path of substrate 1. Inkjet heads 32K, 32C, 32M, and 32Y are each a line-type recording head capable of forming an image by a single scan on substrate 1 transported by transport device 20. Inkjet heads 32K, 32C, 32M, and 32Y may each be configured by connecting a plurality of head modules in the width direction perpendicular to the transport direction of substrate 1.

[0036] Inkjet heads 32K, 32C, 32M, and 32Y are arranged such that their nozzle surfaces (not shown) face the transport path of substrate 1. A plurality of nozzles, which are ejection ports for color inks, are two-dimensionally arranged on the nozzle surfaces of inkjet heads 32K, 32C, 32M, and 32Y.

[0037] Droplets of color ink are ejected from at least one of inkjet heads 32K, 32C, 32M, and 32Y based on color version image data (an example of "first image data") toward the printing surface of substrate 1 being transported by transport device 20, and the ejected droplets adhere to the printing surface of substrate 1, thereby forming a color image (an example of "first image") on the printing surface of substrate 1.

[0038] Although a configuration using four color inks is shown here, the ink colors and the number of colors are not limited to those in this embodiment. For example, inkjet heads that eject light color inks such as light magenta and light cyan, special color inks such as green, orange, and violet, clear ink, metallic ink, etc. may be added. Furthermore, the arrangement order of the inkjet heads for each color is not limited.

[0039] The substrate 1 on which the color image has been formed by the first ejection device 30A is guided by a pass roller 22 and transported to the first drying device 30B.

[0040] The first drying device 30B is a device that dries the color ink on the printing surface of the substrate 1 that is transported by the transport device 20. The first drying device 30B includes a plurality of hot air heaters (not shown).

[0041] The hot air heaters are each arranged with an air outlet (not shown) facing the printed surface of the substrate 1. Each hot air heater functions as a heating device that blows hot air from the air outlet toward the printed surface of the substrate 1 to heat the substrate 1 and dry the color ink adhering to the printed surface.

[0042] The base material 1 transported to the outside of the first drying device 30B has dried color ink on its printed surface. Drying refers to a state in which the ink on the printed surface of the base material 1 does not bleed through to the non-printed surface when the base material 1 is wound up, for example.

[0043] The substrate 1 on which the color ink has been dried by the first drying device 30B is discharged from the first printing device 30 and transported to the second printing device 40 via the twist rollers 24. The twist rollers 24 will be described in detail later.

[0044] The second printing device 40 includes a second discharging device 40A and a second drying device 40B. The substrate 1 transported to the second printing device 40 is guided by a pass roller 22 and transported to the second discharging device 40A.

[0045] The second ejection device 40A (an example of a "second image forming device") includes inkjet heads 42WA and 42WB. Both inkjet heads 42WA and 42WB eject white ink (an example of a "second liquid"), which is a white (W) water-based ink. The white ink is supplied to the inkjet heads 42WA and 42WB from an ink tank (not shown) via a piping path (not shown).

[0046] The inkjet heads 42WA, 42WB are arranged at regular intervals along the transport path of the substrate 1. The inkjet heads 42WA, 42WB are line-type recording heads that can form an image on the substrate 1 transported by the transport device 20 with one scan each. The inkjet heads 42WA, 42WB may each be configured by connecting a plurality of head modules in the width direction of the substrate 1.

[0047] The inkjet heads 42WA and 42WB are disposed such that their nozzle surfaces (not shown) face the transport path of the substrate 1. A plurality of nozzles, which are ejection ports for ejecting white ink, are two-dimensionally arranged on each nozzle surface of the inkjet heads 42WA and 42WB.

[0048] Droplets of white ink are ejected from at least one of inkjet heads 42WA, 42WB based on white image data (an example of "second image data") toward the printing surface of substrate 1 being transported by transport device 20, and the ejected droplets adhere to the printing surface of substrate 1, thereby forming a white image (an example of "second image") on the printing surface of substrate 1.

[0049] In this example, the image data for the color plates and the image data for the white plate are separated from the same print image data. Therefore, the inkjet heads 42WA and 42WB eject white ink onto the color images formed by the inkjet heads 32K, 32C, 32M, and 32Y. As a result, a white image is formed on the printing surface of the substrate 1, superimposed on the color image.

[0050] The substrate 1 on which the white image has been formed by the second ejection device 40A is guided by a pass roller 22 and transported to the second drying device 40B.

[0051] The second drying device 40B is a device that dries the white ink on the printing surface of the substrate 1 transported by the transport device 20. The configuration of the second drying device 40B is similar to that of the first drying device 30B, and therefore detailed description thereof will be omitted.

[0052] The substrate 1 on which the white ink has been dried by the second drying device 40B is discharged from the second printing device 40.

[0053] In this way, the inkjet printing system 10 produces a final printed matter by printing a color image on the substrate 1 in the first printing device 30 and printing a white image on the substrate 1 in the second printing device 40.

[0054] The substrate information acquisition section 50 measures the state of the substrate 1. The substrate information acquisition section 50 includes a first measuring device 52A, a second measuring device 52B, and a third measuring device 52C.

[0055] The first measuring device 52A is disposed at a first position between the first discharging device 30A and the first drying device 30B on the transport path of the substrate 1. The second measuring device 52B is disposed at a second position between the second discharging device 40A and the second drying device 40B on the transport path of the substrate 1. The third measuring device 52C is disposed at a third position downstream of the second drying device 40B on the transport path of the substrate 1.

[0056] That is, the conveying device 20 conveys the substrate 1 in the following order: the first discharge device 30A, the first measuring device 52A, the first drying device 30B, the second discharge device 40A, the second measuring device 52B, the second drying device 40B, and the third measuring device 52C.

[0057] The first measuring device 52A, the second measuring device 52B, and the third measuring device 52C may have the same configuration. The configurations of the first measuring device 52A, the second measuring device 52B, and the third measuring device 52C will be described in detail later.

[0058] [Electrical Configuration of Inkjet Printing System] Fig. 2 is a block diagram showing the electrical configuration of the inkjet printing system 10. As shown in Fig. 2, the inkjet printing system 10 includes an integrated control unit 100, a transport control unit 102, a discharge control unit 104, a drying control unit 106, a measurement control unit 108, an input device 110, and an output device 112.

[0059] The central control unit 100 centrally controls each unit of the inkjet printing system 10. The central control unit 100 includes a processor 100A and a memory 100B.

[0060] The processor 100A executes instructions stored in the memory 100B. The hardware structure of the processor 100A is various processors as shown below. The various processors include a CPU (Central Processing Unit), which is a general-purpose processor that executes software (programs) and functions as various functional units, a GPU (Graphics Processing Unit), which is a processor specialized for image processing, a PLD (Programmable Logic Device), which is a processor whose circuit configuration can be changed after manufacture such as an FPGA (Field Programmable Gate Array), and a dedicated electrical circuit, which is a processor having a circuit configuration designed specifically for executing specific processing such as an ASIC (Application Specific Integrated Circuit).

[0061] A single processing unit may be configured with one of these various processors, or may be configured with two or more processors of the same or different types (e.g., multiple FPGAs, a combination of a CPU and an FPGA, or a combination of a CPU and a GPU). Multiple functional units may also be configured with a single processor. Examples of multiple functional units configured with a single processor include: a first configuration, as typified by a client or server computer, in which a single processor is configured with a combination of one or more CPUs and software, and this processor operates as multiple functional units; and a second configuration, as typified by a SoC (System On Chip), in which a processor is used to realize the functions of an entire system including multiple functional units on a single IC (Integrated Circuit) chip. In this way, the various functional units are configured with one or more of the above-mentioned various processors as a hardware structure.

[0062] Furthermore, the hardware structure of these various processors is, more specifically, an electric circuit made up of a combination of circuit elements such as semiconductor elements.

[0063] The memory 100B stores instructions to be executed by the processor 100A. The memory 100B includes a RAM (Random Access Memory) and a ROM (Read Only Memory), both not shown. The processor 100A uses the RAM as a working area, executes software using various programs and parameters stored in the ROM, and also executes various processes of the inkjet printing system 10 by using parameters stored in the ROM, etc.

[0064] The transport control unit 102 controls the transport device 20 to transport the substrate 1 along the transport path. The transport control unit 102 controls a motor (not shown) to adjust the mounting angle of a twist roller 24 (described later).

[0065] The ejection control unit 104 controls the first ejection device 30A to eject color inks from the inkjet heads 32K, 32C, 32M, and 32Y, respectively, and print a color image on the substrate 1. The ejection control unit 104 also controls the second ejection device 40A to eject white ink from the inkjet heads 42WA and 42WB, respectively, and print a white image on the substrate 1.

[0066] The drying control unit 106 controls the first drying device 30B and the second drying device 40B to heat and dry the color inks and the white ink.

[0067] The measurement control unit 108 controls the substrate information acquisition unit 50 to measure the state of the substrate 1 and acquires the measurement results.

[0068] The input device 110 includes, for example, a mouse (not shown) and a keyboard (not shown), and receives input to the inkjet printing system 10 from the mouse and keyboard.

[0069] The output device 112 includes, for example, a display (not shown), and presents information about the inkjet printing system 10 to the user.

[0070] The input device 110 and the output device 112 may include a communication interface (not shown) for transmitting and receiving information between the inkjet printing system 10 and other devices.

[0071] [Registration Alignment] In the inkjet printing system 10, the transport path of the substrate 1 in the first drying device 30B for drying the ink ejected by the first ejection device 30A is long, and the distance between the first ejection device 30A and the second ejection device 40A is 10 meters or more. This can cause misregistration between the color image and the white image. To address this, three tasks are performed for "registration alignment," which is part of the manufacturing method for printed matter: "tilt alignment," "size alignment," and "position alignment."

[0072] FIG. 3 is a diagram illustrating the registration of the color image IC and the white image IW. F3A in FIG. 3 shows a state in which the color image IC and the white image IW have different inclinations, sizes, and positions. The image data of the color plates and the image data of the white plates are separated from the same print image data, and it is preferable that the color image IC and the white image IW are printed with the same inclination, size, and position. The inclination of the color image IC and the white image IW is, for example, the angle of rotation of the white image around the axis normal to the printing surface of the substrate 1, when the color image is used as a reference.

[0073] 3 shows the state after tilt alignment from the state of F3A. Here, the white image IW is rotated around the printing surface by a predetermined rotation angle, with the normal to the printing surface of the substrate 1 as the axis, to align the tilts of the color image IC and the white image IW. As shown in F3B, the tilt between the color image IC and the white image IW is eliminated.

[0074] 3C shows the state after size adjustment from the state of F3B, where the vertical size of the color image IC is relatively small and the horizontal size is relatively large, eliminating the difference in size between the color image IC and the white image IW.

[0075] 3D shows the state after alignment has been performed from the state of F3C. In this state, the position of the white image IW has been moved vertically upward and horizontally to the left, eliminating the positional discrepancy between the color image IC and the white image IW. In this way, the registration between the color image IC and the white image IW is performed.

[0076] [Tilt Alignment] When the substrate 1 is a relatively soft substrate used in flexible packaging, the image is likely to be misaligned at an angle. In the inkjet printing system 10, the conveyance direction of the substrate 1 may change slightly in the first drying device 30B depending on the color image layout, substrate type, and lot differences, which may cause the substrate 1 to be tilted.

[0077] For example, if the tilt of substrate 1 is adjusted to match PET12 (12-micrometer-thick polyethylene terephthalate) and the same image is printed on OPP20 (20-micrometer-thick biaxially oriented polypropylene), the resulting printout will have a tilt offset of approximately 0.04° between the color image and the white image (≈0.5 mm for an image width of 730 mm). Note that this tilt value varies depending on the substrate lot and image pattern (layout and amount of ink used for printing), and is therefore not a uniquely determined value.

[0078] Hereinafter, the relative movement direction of the substrate 1 with respect to the second discharge device 40A will be referred to as the “travel direction.” The inkjet printing system 10 includes a travel direction correction device that corrects the actual travel direction of the substrate 1 in the second discharge device 40A based on the measurement results of the difference between the assumed travel direction and the actual travel direction of the substrate 1 in the second discharge device 40A.

[0079] The inkjet printing system 10 includes a transport correction mechanism as a travel direction correction device that mechanically corrects the transport direction of the substrate 1 by the transport device 20. The inkjet printing system 10 includes a twist roller 24 with an adjustable mounting angle as an example of the transport correction mechanism. The twist roller 24 (an example of a "path roller") is disposed on the transport path of the substrate 1 immediately before the second discharge device 40A.

[0080] Fig. 4 is a schematic diagram of the operation of the twist roller 24. In Fig. 4, the assumed traveling direction of the substrate 1 in the second discharge device 40A is the Y direction. F4A in Fig. 4 shows a state in which the actual traveling direction of the substrate 1 is deviated from the Y direction. In F4A, the rotation axis of the twist roller 24 is parallel to the X direction, similar to the rotation axis of the pass roller 22, for example.

[0081] The twist roller 24 is provided with an adjustable mounting angle. The mounting angle is the angle between the traveling direction of the substrate 1 and the rotation axis of the twist roller 24. The direction in which the mounting angle of the twist roller 24 is adjusted is a direction parallel to the printed surface of the substrate 1. The most desirable mechanism for adjusting the mounting angle of the twist roller 24 is one that rotates around the center of the substrate 1 in the width direction, but this increases the number of components and increases costs. Therefore, in consideration of cost-effectiveness, in the example shown in FIG. 4 , the twist roller 24 adjusts the mounting angle by rotating the OPS (Operation Panel Side) side of the rotation axis (e.g., the back side in FIG. 4 ) as a fulcrum, with the NOPS side as a fulcrum, parallel to the printed surface of the substrate 1. The twist roller 24 can also be configured so that the NOPS side as a fulcrum rotates parallel to the printed surface of the substrate 1, but this also results in a complex component configuration. The mounting angle of the twist roller 24 may be adjusted manually or by a motor (not shown).

[0082] 4 shows a state in which the mounting angle of the twist roller 24 has been adjusted so that the actual traveling direction of the substrate 1 coincides with the Y direction. In this way, the twist roller 24 performs tilt alignment by mechanically fine-tuning the transport direction of the substrate 1 of the second discharge device 40A.

[0083] The worker visually checks the output printout, measures the amount of angular misalignment between the color image and the white image using a steel ruler or the like, adjusts the conveying direction of the substrate 1 with the twist roller 24, and outputs the printout again, following this procedure to align the tilt.

[0084] However, this method requires that the transport of the substrate 1 be stopped in order to measure the printed matter, which reduces productivity and increases waste paper due to acceleration and deceleration when the machine is stopped.

[0085] In contrast, the inkjet printing system 10 measures and calculates the amount of tilt inline and adjusts the twist roller 24 in conjunction with the amount of tilt, thereby adjusting the tilt without stopping the transport of the substrate 1.

[0086] [Measurement of Tilt Amount] The second measuring device 52B functions as a travel direction measuring device that measures the difference between the assumed travel direction and the actual travel direction of the substrate 1 in the second discharging device 40A. The difference between the assumed travel direction and the actual travel direction of the substrate 1 is represented by the amount of tilt of the color image. The difference between the assumed travel direction and the actual travel direction of the substrate 1 may be represented by the tilt angle of the color image.

[0087] 5 is a diagram illustrating an example of the configuration of the second measuring device 52B. The second measuring device 52B includes two mark sensors 54A and 54B. The substrate 1 includes a plurality of cue marks MC.

[0088] The mark sensor 54A is disposed on the GS (Gear Side) side of the conveyance path of the substrate 1. The mark sensor 54B is disposed on the OS (Operator Side) side across the conveyance path from the GS side of the conveyance path of the substrate 1, at the same position as the mark sensor 54A in the assumed traveling direction of the substrate 1 (Y direction in FIG. 5 ), and at a distance W from the mark sensor 54A.

[0089] The mark sensors 54A and 54B are optical sensors for detecting the cue marks MC. Each of the mark sensors 54A and 54B is integrally formed with a light-emitting unit (not shown) that emits light onto the substrate 1 and a light-receiving unit (not shown) that receives reflected light of the emitted light. Each of the mark sensors 54A and 54B detects the cue marks MC based on the light-receiving results of the light-receiving unit.

[0090] The cue marks MC are marks that indicate the printing start position of the desired print image IP (color image and white image). The cue marks MC are printed on both ends of the substrate 1 in the width direction (X direction in the example shown in FIG. 5) by, for example, the inkjet head 32K of the first ejection device 30A. In other words, the cue marks MC are a type of color image that is not included in the desired print image IP. The tilt amount and tilt angle of the cue marks MC correspond to the difference between the expected traveling direction and the actual traveling direction of the substrate 1.

[0091] The cue mark MC is a filled rectangle with sides parallel to the transport direction (the Y direction in the example shown in FIG. 5 ) and width direction of the substrate 1, and is 6 mm long in the transport direction and 12 mm long in the width direction. The cue mark MC is located 18 mm away in the X direction from the edge on the OS side of the substrate 1, and 18 mm away in the −X direction from the edge on the GS side, i.e., the cue mark MC is located at the same position in the transport direction of the substrate 1. In other words, the cue mark MC on the OS side and the cue mark MC on the GS side are formed by ink being ejected at the same time from the inkjet head 32K.

[0092] The cue marks MC are placed at the printing start position of the print image IP. Therefore, the cue marks MC are placed in the transport direction at intervals equal to the size of the print image IP in the transport direction. The size of the print image IP that can be printed in the inkjet printing system 10 in the transport direction is 100 to 1400 mm. In other words, the cue marks MC are placed at intervals of 100 to 1400 mm in the transport direction of the substrate 1. The size of the cue marks MC and their placement positions within the substrate 1 are not limited to this example, and various embodiments are possible.

[0093] The second measuring device 52B detects the time at which the cue mark MC passes on the substrate 1 during transport using the mark sensor 54A. As a result, the integrated control unit 100 (see FIG. 2) acquires a numerical value of the deformation of the substrate 1 in the transport direction in the second discharge device 40A.

[0094] The second measuring device 52B also detects the GS-side cue mark MC and the OS-side cue mark MC (an example of "two marks"), which are arranged at the same position in the conveyance direction of the substrate 1. That is, the second measuring device 52B uses the mark sensor 54A to detect the passage of the GS-side cue mark MC of the substrate 1 during conveyance, and uses the mark sensor 54B to detect the passage of the OS-side cue mark MC of the substrate 1. The integrated control unit 100 then compares the passage timing of the GS-side cue mark MC with that of the OS-side cue mark MC to measure the tilt of the color image as it passes through the second discharge device 40A.

[0095] FIG. 6 is a diagram illustrating tilt alignment using mark sensors 54A and 54B. First, an operator produces a printed matter using an initial installation substrate (e.g., PET 12) as substrate 1. Next, the operator aligns the tilts of the color image IC and the white image IW while checking the output printed matter. F6A in FIG. 6 shows the state in which the tilt alignment has been performed, eliminating the tilt between the color image IC and the white image IW.

[0096] In this state, the mark sensors 54A and 54B are positioned so that the timing at which the mark sensor 54A detects the cue mark MC and the timing at which the mark sensor 54B detects the cue mark MC coincide with each other.

[0097] Next, the worker produces a printed material using a substrate (for example, OPP 20) different from the initial installation substrate as substrate 1. The second measuring device 52B measures the detection timing T2 (unit: milliseconds) of the mark sensor 54B relative to the detection timing T1 (unit: milliseconds) of the cue mark MC by the mark sensor 54A when the substrate 1 is transported at transport speed v.

[0098] Furthermore, the integrated control unit 100 (see FIG. 2) calculates the difference ΔT12 (= T1 - T2) [unit: milliseconds] between T1 and T2, and calculates the amount of tilt L of the color image IC from ΔT12. F6B in FIG. 6 indicates the amount of tilt L of the color image IC. As shown in F6B, L = v × ΔT12, which is obtained by multiplying ΔT12 by the conveying speed v of the substrate 1 near the positions of the mark sensors 54A and 54B, is the amount of tilt L of the color image IC.

[0099] Furthermore, the integrated control unit 100 calculates the tilt angle θ of the color image IC from the tilt amount L of the color image IC. Since the distance between the mark sensors 54A and 54B (an example of "distance information between two optical sensors") is W, the tilt angle θ can be calculated by tan θ = L ÷ W. In this way, the inkjet printing system 10 can perform tilt adjustment using only the color image without checking the white image.

[0100] 7 is a flowchart showing the automatic tilt adjustment process for automatically adjusting the tilt. The automatic tilt adjustment process is realized by the processor 100A (see FIG. 2) reading and executing an automatic tilt adjustment program from the memory 100B (see FIG. 2).

[0101] In step S1, the conveyance control unit 102 causes the conveyance device 20 to convey the substrate 1 at a conveyance speed v. The discharge control unit 104 causes the first discharge device 30A to form a cue mark MC. The drying control unit 106 causes the first drying device 30B to dry the cue mark MC.

[0102] Furthermore, the measurement control unit 108 measures the detection timing T1 of the cue mark MC by the mark sensor 54A and the detection timing T2 by the mark sensor 54B. Then, the overall control unit 100 obtains the difference ΔT12 between T1 and T2.

[0103] In step S2, the integrated control unit 100 calculates the tilt angle θ from ΔT12 acquired in step S1 and the distance W between the mark sensors 54A and 54B by tan θ=L÷W.

[0104] In step S3, the central control unit 100 determines whether the tilt angle θ calculated in step S2 is within a predetermined range. The predetermined range is, for example, an angle at which the tilt between the color image and the white image is not visible.

[0105] If the tilt angle θ is within the predetermined range, the process of this flowchart ends. On the other hand, if the tilt angle θ is not within the predetermined range, the process proceeds to step S4.

[0106] In step S4, the conveyance control unit 102 controls a motor (not shown) in accordance with the tilt angle θ calculated in step S2, and adjusts the mounting angle of the twist roller 24.

[0107] Thereafter, the process returns to step S1, and the same process is repeated. As a result, the adjustment of the mounting angle of the twist roller 24 is repeated until the tilt angle θ falls within the predetermined range, and finally, the tilt angle θ can be brought into the predetermined range.

[0108] According to the automatic tilt adjustment process, the tilt angle of the substrate in the direction of travel is measured and calculated inline, and the tilt angle of the substrate in the direction of travel is fed back to the mounting angle of the twist roller 24, thereby enabling tilt adjustment to be performed without stopping the printing operation.

[0109] Here, the automatic tilt adjustment process for automatically adjusting the tilt has been described, but the adjustment of the mounting angle of the twist roller 24 in step S4 does not necessarily have to be performed automatically and may be performed manually by the user. When the user manually adjusts the mounting angle of the twist roller 24, the automatic tilt adjustment program may be a program that causes the processor 100A to execute the processes of steps S1 to S3.

[0110] [Another Example of Tilt Amount Measurement] The measurement of tilt amount is not limited to the example using two mark sensors 54A and 54B. Fig. 8 is a diagram for explaining another example of the configuration of the second measurement device 52B. The second measurement device 52B includes edge sensors 56A, 56B, and 56C.

[0111] Edge sensor 56A is disposed on the GS side of substrate 1. Edge sensor 56B is disposed on the OS side of substrate 1 at the same position as edge sensor 56A in the conveyance direction (Y direction in FIG. 8 ) of substrate 1. Edge sensor 56C is disposed on the GS side of substrate 1 at a distance D (unit: millimeters) upstream of edge sensor 56A in the conveyance path of substrate 1.

[0112] The edge sensors 56A, 56B, and 56C are each optical sensors for detecting the edge ED of the substrate 1. Each of the edge sensors 56A, 56B, and 56C includes a light-projecting unit (not shown) that projects a strip of light perpendicular to the printing surface of the substrate 1 onto the edge of the substrate 1, and a light-receiving unit (not shown) that is disposed opposite the light-projecting unit across the substrate 1 and receives the projected light. Each of the edge sensors 56A, 56B, and 56C detects the position of the edge ED of the substrate 1 in the X direction based on the light-receiving result of the light-receiving unit.

[0113] The second measuring device 52B uses edge sensors 56A and 56B to detect the X-direction positions of the edges ED at both ends of the substrate 1. As a result, the integrated control unit 100 (see FIG. 2) acquires a numerical value of the deformation of the substrate 1 in the width direction in the second discharge device 40A.

[0114] The second measuring device 52B also uses edge sensors 56A and 56C to detect the X-direction position of the edge ED on the GS side of the substrate 1. The integrated control unit 100 then compares the edge position detected by the edge sensor 56C with the edge position detected by the edge sensor 56A (an example of a "detection result") to measure the tilt of the substrate 1 in the traveling direction as it passes through the second discharge device 40A, i.e., the tilt of the color image.

[0115] FIG. 9 is a diagram illustrating tilt adjustment using edge sensors 56A and 56C. First, an operator produces a printed material using an initial installation substrate (e.g., PET 12) as substrate 1. Next, the operator adjusts the tilt between the color image and the white image while checking the output printed material. F9A in FIG. 9 shows a state in which the tilt between the color image and the white image has been eliminated by performing tilt adjustment. In the state shown in F9A, the operator performs zero adjustment of edge sensor 56A and zero adjustment of edge sensor 56C.

[0116] Next, the worker produces a printed material using a substrate (for example, OPP 20) different from the initial installation substrate as substrate 1. Second measuring device 52B measures the position X1 [unit: millimeters] of edge ED of substrate 1 in the X direction on edge sensor 56A, and the position X3 [unit: millimeters] of edge ED of substrate 1 in the X direction on edge sensor 56C.

[0117] Furthermore, the integrated control unit 100 (see FIG. 2) calculates the amount of tilt ΔX13 (=X1−X3) [unit: millimeters], which is the difference between X1 and X3. F9B in FIG. 9 indicates the amount of tilt ΔX13 of the substrate 1.

[0118] Furthermore, the integrated control unit 100 calculates the tilt angle θ of the substrate 1, i.e., the tilt angle θ of the color image IC, from the tilt amount ΔX13 of the substrate 1. Since the distance between the edge sensors 56A and 56C (an example of "distance information between two edge sensors") is D, the tilt angle θ can be calculated by tan θ = ΔX13 ÷ D.

[0119] The processes in steps S1 and S2 of the flowchart shown in FIG. 7 may be performed using edge sensors 56A and 56C instead of the mark sensors 54A and 54B.

[0120] [Another Example of Tilt Alignment] So far, an example has been described in which the transport direction of the substrate 1 is mechanically corrected by a transport correction mechanism as a correction of the traveling direction of the substrate 1, but the correction of the traveling direction of the substrate 1 is not limited to this example.

[0121] The inkjet printing system 10 may include an image data correction device that corrects white plate image data as the travel direction correction device. For example, the integrated control unit 100 may tilt the print image data according to the tilt angle θ and perform RIP (Raster Image Processor) processing to generate white plate image data. By ejecting white ink droplets from at least one of the inkjet heads 42WA and 42WB based on the white plate image data generated in this manner, a white image tilted similarly to the color image is formed on the printing surface of the substrate 1. The image data correction device may be a device separate from the inkjet printing system 10. The inkjet printing system 10 may acquire the tilt-corrected white plate image data via a communication interface (not shown) or a medium reading device (not shown).

[0122] The inkjet printing system 10 may include, as a travel direction correction device, an image formation correction mechanism that mechanically corrects the installation position of the second ejection device 40A. For example, the image formation correction mechanism mechanically tilts the installation positions of the inkjet heads 42WA and 42WB relative to the travel direction of the substrate 1 according to a tilt angle θ. The direction in which the installation positions of the inkjet heads 42WA and 42WB are corrected is a direction parallel to the printing surface of the substrate 1.

[0123] Fig. 10 is a diagram for explaining tilt adjustment for tilting the inkjet heads 42WA and 42WB. Fig. 10 shows a state in which the traveling direction of the substrate 1 is tilted with respect to the Y direction, with F10A in Fig. 10 showing the state before tilt adjustment is performed and F10B in Fig. 10 showing the state after tilt adjustment is performed.

[0124] The second ejection device 40A has inkjet heads 42WA and 42WB fixed parallel to each other in advance. As shown in FIG. 10 , the second ejection device 40A has a fulcrum 42P on the GS side (an example of "one side") of the substrate 1 as an image formation correction mechanism. The second ejection device 40A is configured to be rotatable about the fulcrum 42P on the OS side (an example of "the other side") of the substrate 1 of the second ejection device 40A parallel to the printing surface of the substrate 1 (in a direction perpendicular to the Z direction in FIG. 10 ). The rotational movement of the second ejection device 40A may be performed manually or by a motor (not shown). As shown in FIG. 10 , the tilt angle of the traveling direction is fed back to the installation positions of the inkjet heads 42WA and 42WB, and the orientation of the second ejection device 40A relative to the traveling direction of the substrate 1 is tilted by the tilt angle of the substrate 1. This allows for tilt alignment.

[0125] Here, both inkjet heads 42WA and 42WB are rotated around one fulcrum, but inkjet heads 42WA and 42WB may be rotated around different fulcrums.

[0126] 7 may be performed by combining adjustment by the conveyance correction mechanism, adjustment by the image data correction device, and adjustment by the image formation correction mechanism. If the amount of correction by the twist roller 24 in the traveling direction of the substrate 1 becomes relatively large, wrinkles or the like may occur in the substrate 1. Therefore, when the amount of correction is relatively large, it is preferable to perform image data correction and / or correction by tilting the inkjet heads 42WA and 42WB in addition to correction by the twist roller 24.

[0127] [Size Adjustment] Figure 11 is a flowchart showing the "size adjustment" process of registration adjustment in the inkjet printing system 10. It is assumed that "tilt adjustment" is performed using the twist roller 24. Size adjustment is performed by obtaining expansion / contraction information of the substrate, correcting image data in accordance with the expansion / contraction information, and printing based on the corrected image data. The size adjustment process is realized by the processor 100A (see Figure 2) reading and executing a size adjustment program from the memory 100B (see Figure 2).

[0128] In step S11, the discharge control unit 104, in accordance with a command from the integrated control unit 100, causes the first discharge device 30A to print multiple cue marks on the substrate 1. The multiple cue marks are arranged at equal intervals along the traveling direction only on the GS side, as shown in FIG.

[0129] In step S12, the measurement control unit 108 measures the state of the substrate 1 at the first position using the first measuring device 52A in accordance with instructions from the integrated control unit 100. Here, the first measuring device 52A acquires the time interval T11 (unit: seconds) between the passage of two cue marks MC using the mark sensor 54A. The first measuring device 52A also acquires the width W11 (unit: millimeters) of the substrate 1 using the edge sensors 56A and 56B.

[0130] In step S13, the measurement control unit 108, in accordance with a command from the integrated control unit 100, measures the state of the substrate 1 at the second position using the second measuring device 52B. Here, the second measuring device 52B acquires the time interval T12 (unit: seconds) between the passage of two cue marks MC using the mark sensor 54A. The second measuring device 52B also acquires the width W12 (unit: millimeters) of the substrate 1 using the edge sensors 56A and 56B.

[0131] The measurement timing in the second measuring device 52B is preferably later than the measurement timing in the first measuring device 52A. The cue mark MC detected by the mark sensor 54A of the second measuring device 52B in step S13 is preferably at the same position as the cue mark MC detected by the mark sensor 54 of the first measuring device 52A in step S12. Furthermore, the width position of the substrate 1 detected by the edge sensors 56A, 56B of the second measuring device 52B in step S13 is preferably the same position as the width position of the substrate 1 detected by the edge sensors 56A, 56B of the first measuring device 52A in step S12.

[0132] In step S14, the measurement control unit 108, in accordance with a command from the integrated control unit 100, measures the state of the substrate 1 at the third position using the third measuring device 52C. Here, the third measuring device 52C acquires the time interval T13 (unit: seconds) between the passage of two cue marks MC using the mark sensor 54A. The third measuring device 52C also acquires the width W13 (unit: millimeters) of the substrate 1 using the edge sensors 56A and 56B.

[0133] The measurement timing of the third measuring device 52C is preferably later than the measurement timing of the second measuring device 52B. The cue mark MC detected by the mark sensor 54A of the third measuring device 52C in step S14 is preferably at the same position as the cue mark MC detected by the mark sensor 54 of the first measuring device 52A in step S12. Furthermore, the width position of the substrate 1 detected by the edge sensors 56A, 56B of the third measuring device 52C in step S14 is preferably the same position as the width position of the substrate 1 detected by the edge sensors 56A, 56B of the first measuring device 52A in step S12.

[0134] In step S15, the integrated control unit 100 calculates a first correction value for correcting the size of the image data in the traveling direction based on the state of the substrate 1 at each position acquired in steps S12 to S14.

[0135] First, the integrated control unit 100 acquires the conveying speeds v11, v12, and v13 (unit: meters / minute) in the traveling direction of the substrate 1 at the first position, the second position, and the third position. The conveying speeds v11, v12, and v13 may be measured by a speedometer (not shown), but here, the set values ​​set in the inkjet printing system 10 are used.

[0136] In addition, the integrated control unit 100 calculates the spacing L11, L12, L13 [unit: millimeters] between the cue marks at the first position, the second position, and the third position based on the time intervals T11, T12, T13 [unit: seconds] and the conveying speeds v11, v12, v13 [unit: meters / minute] using the following equations 1 to 3.

[0137] L11=T11×v11 / 60×10 3 ...(Formula 1) L12=T12×v12 / 60×10 3 ...(Formula 2) L13=T13×v13 / 60×10 3 ...(Formula 3)

[0138] Here, the expansion / contraction rate SLC [unit: %] of the color image in the traveling direction and the expansion / contraction rate SLW [unit: %] of the white image in the traveling direction can be calculated by the following formulas 4 and 5, respectively.

[0139] SLC=L13 / L11×100…(Formula 4) SLW=L13 / L12×100…(Formula 5)

[0140] The reciprocal of the expansion / contraction rate SLC becomes the correction value in the progression direction of the image data of the color plane, and the reciprocal of the expansion / contraction rate SLW becomes the correction value in the progression direction of the image data of the white plane.

[0141] In step S16, the integrated control unit 100 calculates a second correction value for correcting the size in the width direction of the image data based on the state of the substrate 1 at each position acquired in steps S12 to S14.

[0142] For example, the expansion / contraction ratio SWC (unit: %) of the color image in the width direction and the expansion / contraction ratio SWW (unit: %) of the white image in the width direction can be calculated by the following formulas 6 and 7, respectively.

[0143] SWC=W13 / W11×100…(Formula 6) SWW=W13 / W12×100…(Formula 7)

[0144] The reciprocal of the expansion / contraction ratio SWC is the correction value for the width direction of the image data of the color plate, and the reciprocal of the expansion / contraction ratio SWW is the correction value for the width direction of the image data of the white plate.

[0145] In step S17, the integrated control unit 100 (an example of a "scaling correction device") corrects the size of the image data based on the correction values ​​calculated in steps S15 and S16. If the true size (target size) of the image data in the progression direction is PL and the true size in the width direction is PW, the corrected size of the color plate image data in the progression direction PLC and the width direction PWC can be calculated using the following equations 8 and 9, respectively.

[0146] PLC=PL×SLC / 100…(Formula 8) PWC=PW×SWC / 100…(Formula 9)

[0147] Furthermore, the size PLW in the progress direction and the size PWW in the width direction of the corrected white separation image data can be calculated using the following equations 10 and 11.

[0148] PLW=PL×SLW / 100…(Formula 10) PWW=PW×SWW / 100…(Formula 11)

[0149] In step S18, the ejection control unit 104, in accordance with a command from the integrated control unit 100, causes printing to be performed based on the image data corrected in step S17. That is, the ejection control unit 104 causes the inkjet heads 32K, 32C, 32M, and 32Y to eject color inks based on the corrected image data for the color plates, thereby printing a color image on the substrate 1. The ejection control unit 104 also causes the inkjet heads 42WA and 42WB to eject white ink based on the corrected image data for the white plate, thereby printing a white image on the substrate 1.

[0150] By printing based on the corrected image data in this manner, a printed material of the desired size can be produced. Furthermore, in this embodiment, the correction accuracy can be improved by measuring the cue mark printed on the substrate 1 immediately before by the first ejection device 30A using the first measurement device 52A, the second measurement device 52B, and the third measurement device 52C. For example, when measuring and correcting a mark printed by another device, it is necessary to consider the difference between that mark and the actual ejection by the first ejection device 30A. This has the disadvantage of complicating the process and reducing the correction accuracy.

[0151] The inkjet printing system 10 may perform a "registration" process after the "size adjustment" process shown in Fig. 11. This enables registration between the color image and the white image.

[0152] [Other] A twist roller 24 may be disposed immediately before the first discharge device 30A on the transport path of the substrate 1, and the traveling direction of the substrate 1 in the first discharge device 30A may be mechanically fine-tuned. In this case, the inkjet printing system 10 measures and calculates the tilt angle of the traveling direction of the substrate using the two mark sensors 54A, 54B of the first measurement device 52A or the two edge sensors 56A, 56C of the first measurement device 52A, and feeds back the tilt angle of the traveling direction to the mounting angle of the twist roller 24 disposed immediately before the first discharge device 30A. This allows tilt adjustment to be performed without stopping the printing operation.

[0153] While the inkjet printing system 10 for producing reverse-printed printed materials has been described above, the present disclosure can also be applied to an inkjet printing system for producing front-printed printed materials. In this case, the first ejection device 30A may eject droplets of white ink to form a white image, and the second ejection device 40A may eject droplets of color ink to form a color image. Alternatively, the first ejection device 30A may eject droplets of CMYK (cyan, magenta, yellow, and black) ink to form a CMYK image, and the second ejection device 40A may eject droplets of OGV (orange, green, and violet) ink to form an OGV image. The second ejection device 40A may also eject droplets of ink such as clear ink or metallic ink.

[0154] In the case of surface printing, the substrate 1 is not limited to a transparent substrate, and a non-transparent substrate such as paper can also be used.

[0155] The technical scope of the present invention is not limited to the scope described in the above embodiments. The configurations and the like in each embodiment can be appropriately combined with each other within the scope that does not deviate from the spirit of the present invention.

[0156] REFERENCE SIGNS LIST 1...Substrate 10...Inkjet printing system 20...Conveying device 22...Pass roller 24...Roller 30...First printing device 30A...First ejection device 30B...First drying device 32C...Inkjet head 32K...Inkjet head 32M...Inkjet head 32Y...Inkjet head 40...Second printing device 40A...Second ejection device 40B...Second drying device 42P...Support point 42WA...Inkjet head 42WB...Inkjet head 50...Substrate information acquisition unit 52A...First measuring device 52B...Second measuring device 52C...Third measuring device 54A...Mark sensor 54B...Mark sensor 56A...Edge sensor 56B...Edge sensor 56C...Edge sensor 100...General control unit 100A...Processor 100B...Memory 102...Conveying control unit 104...Ejection control unit 106: Drying control unit 108: Measurement control unit 110: Input device 112: Output device IC: Color image IP: Printed image IW: White image MC: Cue mark S1 to S4: Automatic tilt adjustment process steps S11 to S18: Size adjustment process steps

Claims

1. A printing system for printing an image on a substrate, comprising: a first image forming device that forms a first image on the substrate based on first image data; a second image forming device that forms a second image on the substrate based on second image data; a transport device that transports the substrate along a transport path in the order of the first image forming device and the second image forming device; a travel direction measuring device that measures the difference between the assumed travel direction of the substrate in the second image forming device and the actual travel direction of the substrate; and a travel direction correcting device that corrects the actual travel direction of the substrate in the second image forming device based on the measurement result of the travel direction measuring device, wherein the travel direction correcting device is disposed between the first image forming device and the second image forming device on the transport path, and includes a transport correction mechanism that mechanically corrects the transport direction of the substrate by the transport device.

2. The printing system according to claim 1, wherein the transport device includes a pass roller that rotates in contact with the substrate to transport the substrate, and the transport correction mechanism adjusts the mounting angle of the pass roller to mechanically correct the transport direction of the substrate.

3. The printing system according to claim 2, wherein the direction in which the mounting angle of the pass roller is adjusted is a direction parallel to the printing surface of the substrate.

4. The printing system according to claim 1, wherein the travel direction correction device includes an image formation correction mechanism that mechanically corrects the installation position of the second image forming device.

5. The printing system according to claim 4, wherein the image formation correction mechanism rotates one side of the second image forming device across the transport path of the second image forming device as a fulcrum, and the other side of the second image forming device is rotated parallel to the printing surface of the substrate.

6. The printing system according to claim 1, wherein the travel direction correction device includes an image data correction device that corrects the second image data.

7. The printing system according to claim 1, wherein the first image forming device forms a mark on the substrate, and the travel direction measuring device includes a sensor that detects the mark.

8. The printing system according to claim 7, wherein the first image forming device forms two of the marks, and the progress direction measuring device includes two optical sensors that detect the two marks, respectively.

9. The printing system according to claim 8, wherein the travel direction measuring device calculates the amount of tilt between the assumed travel direction and the actual travel direction of the substrate from the difference in detection timing between the two optical sensors.

10. The printing system according to claim 9, wherein the travel direction measuring device obtains the tilt angle from the amount of tilt using distance information between the two optical sensors.

11. The printing system according to claim 1, wherein the travel direction measuring device includes two edge sensors that detect the position of one edge of the substrate at a fixed interval.

12. The printing system according to claim 11, wherein the travel direction measuring device obtains the amount of tilt between the assumed travel direction and the actual travel direction of the substrate from the detection results of the two edge sensors.

13. The printing system according to claim 12, wherein the travel direction measuring device calculates the tilt angle from the amount of tilt using distance information between the two edge sensors.

14. The printing system according to claim 10 or 13, wherein the transport correction mechanism mechanically corrects the transport direction of the substrate using the calculated tilt angle.

15. The first image forming apparatus comprises a first ejection device that ejects a first liquid, and the second image forming apparatus comprises a second ejection device that ejects a second liquid, and further comprises: a first drying device that dries the first liquid ejected onto the substrate; a second drying device that dries the second liquid ejected onto the substrate; a first measuring device that measures the state of the substrate; a second measuring device that measures the state of the substrate; a third measuring device that measures the state of the substrate; and an enlargement / reduction correction device that corrects the first image data and the second image data, wherein the transport device transports the substrate in the order of the first ejection device, the first measuring device, the first drying device, the second ejection device, the second measuring device, the second drying device, and the third measuring device, and the enlargement / reduction correction device calculates a first correction value that corrects the first image data based on the measurement result of the first measuring device and the measurement result of the third measuring device, The printing system according to claim 1 , further comprising: calculating a second correction value for correcting the second image data based on the measurement results of the second measurement device and the measurement results of the third measurement device.

16. The printing system of claim 15, wherein the position of the first image and the position of the second image on the substrate are aligned.

Images