Inkjet printing equipment

Abstract

This technology provides an effective way to detect high-temperature abnormalities in the printed area. [Solution] The inkjet printing apparatus comprises a transport unit that transports a substrate 9 in the transport direction d1, an inkjet unit that ejects multiple colored inks onto the substrate 9 being transported by the transport unit, a print control unit that controls the inkjet unit based on image data and prints a target image 61 represented by the image data onto the substrate 9, a drying unit 4 located downstream of the inkjet unit in the transport direction d1 and irradiating the substrate 9 with infrared light to dry the ink ejected onto the substrate 9, a temperature sensor 5 that measures the temperature of a measurement target area A51 on the substrate 9 irradiated with infrared light, and a monitoring unit that monitors the temperature of the measurement target area A51 measured by the temperature sensor 5. The measurement target area A51 of the temperature sensor 5 is an area in which the infrared absorptivity is greater than the average value of the infrared absorptivity shown by the image data.

Description

Technical Field

[0001] The subject matter disclosed herein relates to an inkjet printing apparatus.

Background Art

[0002] Conventionally, there has been known an inkjet printing apparatus that performs printing by ejecting ink onto the surface of a long strip-shaped base material while conveying the base material by a plurality of conveyance rollers or the like. Such an inkjet printing apparatus is provided with a drying device that dries ink while conveying a continuous base material (for example, Patent Document 1).

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0004] As a drying device, drying can be efficiently performed by using a heat source with relatively high infrared (or far-infrared) output such as a carbon heater. However, if the infrared output becomes excessive, the temperature of the base material will exceed its heat-resistant temperature, and there is a risk that the base material may be damaged. In addition, when release paper or the like is bonded via an adhesive, if the temperature of the adhesive exceeds the heat-resistant temperature, the release paper may lift and cause creases.

[0005] During printing, ink is applied onto the base material. Depending on the color and type of ink, the applied portion absorbs more infrared rays than the non-applied portion, and tends to reach a higher temperature. As a result, high-temperature abnormalities are more likely to occur in printed areas. For this reason, there is a demand for a technology that can appropriately detect high-temperature abnormalities in printed areas.

[0006] An object of the present invention is to provide a technology capable of appropriately detecting a high-temperature abnormality in a printed portion. [Means for solving the problem]

[0007] To solve the above problems, the first embodiment is an inkjet printing apparatus comprising: a transport unit that transports a substrate in a transport direction; an inkjet unit that ejects multiple colored inks onto the substrate being transported by the transport unit; a print control unit that controls the inkjet unit based on image data and prints a target image represented by the image data onto the substrate; a drying unit located downstream of the inkjet unit in the transport direction and irradiating the substrate with infrared rays to dry the ink ejected onto the substrate; a temperature sensor that measures the temperature of a target area on the substrate irradiated with infrared rays; and a monitoring unit that monitors the temperature of the target area measured by the temperature sensor, wherein the target area of ​​the temperature sensor is an area having an infrared absorptivity greater than the average value of the infrared absorptivity shown by the image data.

[0008] The second embodiment is an inkjet printing apparatus according to the first embodiment, wherein the print control unit controls the inkjet unit to print a patch image with an infrared absorptive value greater than the average value of the infrared absorptive values ​​shown by the image data onto the measurement target area, and the temperature sensor measures the temperature of the measurement target area on the substrate where the patch image has been printed.

[0009] A third embodiment is an inkjet printing apparatus according to the second embodiment, wherein the print control unit controls the inkjet unit to print the patch image in a color with the maximum infrared absorptivity value indicated by the image data or a higher infrared absorptivity value.

[0010] A fourth embodiment is an inkjet printing apparatus according to the second or third embodiment, further comprising: a storage unit that stores correspondence information showing the correspondence between the ink densities of the multiple colors and the infrared absorptivity; and an absorptivity analysis unit that analyzes the infrared absorptivity shown by the image data using the correspondence information.

[0011] The fifth embodiment is an inkjet printing apparatus according to any of the second to fourth embodiments, wherein the print control unit prints the black patch image on the measurement target area.

[0012] The sixth embodiment is an inkjet printing apparatus according to the second to fifth embodiments, wherein the print control unit controls the inkjet unit to print the patch image upstream of the target image in the transport direction.

[0013] The seventh embodiment is an inkjet printing apparatus according to any of the first to sixth embodiments, further comprising a sensor moving unit that moves the temperature sensor in the width direction so that the temperature sensor measures the temperature of a portion of the target image represented by the image data that has an infrared absorptive value greater than the average value of the infrared absorptive values. [Effects of the Invention]

[0014] According to the inkjet printing apparatus of the first to seventh embodiments, high-temperature abnormalities in the printed portion of the target image can be appropriately detected by measuring the temperature of areas that tend to become hot.

[0015] According to the inkjet printing apparatus of the second embodiment, high-temperature abnormalities in the printed portion of the target image can be detected based on the temperature measurement results of the patch image.

[0016] According to the inkjet printing apparatus of the third embodiment, the infrared absorptivity of the patch image becomes greater than or equal to the maximum infrared absorptivity of the target image. Therefore, by measuring the temperature of the patch image, high-temperature abnormalities in the printed portion of the target image can be appropriately detected.

[0017] According to the inkjet printing apparatus of the fourth embodiment, the color of the patch image can be appropriately set by analyzing the infrared absorption degree shown by the image data using corresponding information.

[0018] According to the inkjet printing apparatus of the fifth aspect, by measuring the temperature of the black patch image having the maximum infrared absorption, high-temperature abnormality in the printed portion of the target image can be appropriately detected.

[0019] According to the inkjet printing apparatus of the sixth aspect, high-temperature abnormality in the printed portion of the target image can be detected in advance. Therefore, countermeasures against high-temperature abnormality can be implemented.

[0020] According to the inkjet printing apparatus of the seventh aspect, since the temperature of the printed portion of the target image that tends to become high temperature is directly detected, high-temperature abnormality of the target image can be appropriately detected. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an inkjet printing apparatus according to an embodiment. [Figure 2] FIG. 2 is a diagram illustrating a lower surface of a head unit. [Figure 3] FIG. 3 is a top view schematically illustrating a part of an inkjet printing apparatus. [Figure 4] FIG. 4 is a block diagram illustrating an electrical connection between a control unit and a controlled object. [Figure 5] FIG. 5 is a top view schematically illustrating a substrate on which an image is printed. [Figure 6] FIG. 6 is a front view schematically illustrating a cross-section of the substrate at the A-A position shown in FIG. 5. [Figure 7] FIG. 7 is a diagram conceptually illustrating an example of correspondence information showing a correspondence relationship between ink colors and absorbance. [Figure 8] FIG. 8 is a diagram for explaining an example of setting a distance between a target image and a patch image. [Figure 9] FIG. 9 is a top view showing a modified example of a printing position of a patch image. [Figure 10] FIG. 10 is a front view schematically illustrating a temperature sensor 5 of an inkjet printing apparatus 1 according to a second embodiment. [Figure 11] FIG. 11 is a front view schematically illustrating a temperature sensor 5 of an inkjet printing apparatus 1 according to a third embodiment. [Modes for carrying out the invention]

[0022] Embodiments of the present invention will be described below with reference to the attached drawings. Note that in the drawings, the dimensions and number of parts may be exaggerated or simplified for ease of understanding.

[0023] <1. First Embodiment> Figure 1 shows the configuration of an inkjet printing apparatus 1 according to an embodiment. The inkjet printing apparatus 1 is an inkjet-type printing machine that, while transporting a long, strip-shaped substrate 9, discharges ink droplets from a plurality of head units 31 of the inkjet unit 3 toward the substrate 9, thereby recording images such as characters and drawings on the surface of the substrate 9. The ink discharged by the head units 31 is water-based ink. However, the ink discharged by the head units 31 is not limited to water-based ink; for example, it may be oil-based ink. The substrate 9 is, for example, continuous paper. However, the substrate 9 may be a film or a composite substrate consisting of multiple layers. As a composite substrate, for example, a material in which release paper and a surface substrate are joined with an adhesive can be used.

[0024] As shown in Figure 1, the inkjet printing apparatus 1 comprises a transport unit 2, an inkjet unit 3, a drying unit 4, a temperature sensor 5, and a control unit 8.

[0025] The conveying unit 2 includes an unwinding roller 21, a plurality of conveying rollers 22, a winding roller 23, and a rotational drive unit 24. The unwinding roller 21, conveying rollers 22, and winding roller 23 are rotatable about an axis extending horizontally. A motor 211 is connected to the rotation axis of the winding roller 23. The rotational drive unit 24 controls the motor 211 to rotate the winding roller 23 around its axis. The rotational drive unit 24 may also rotate rollers other than the winding roller 23 (for example, several conveying rollers 22) around their axes.

[0026] The base material 9 is wound in a roll on the unwinding roller 21. As the unwinding roller 21 rotates, the base material 9 is continuously unwound. Each transport roller 22 is positioned along the transport path TR of the base material 9. Multiple transport rollers 22 support the base material 9 fed out from the unwinding roller 21 on the predetermined transport path TR. The winding roller 23 winds the base material 9 that has passed through the transport path TR into a roll. In the inkjet printing apparatus 1, the rotation drive unit 24 rotates the winding roller 23, so that the base material 9 is continuously transported roll to roll from the unwinding roller 21 to the winding roller 23.

[0027] In the following explanation, the direction in which the substrate 9 is conveyed by the conveying unit 2 will be referred to as the "conveying direction d1". Also, with respect to the substrate 9 being conveyed by the conveying unit 2, the winding roller 23 side will be referred to as the downstream side of the conveying direction d1, and the unwinding roller 21 side will be referred to as the upstream side of the conveying direction d1. Furthermore, the horizontal direction perpendicular to the conveying direction d1 will be referred to as the "width direction d2".

[0028] The inkjet unit 3 has a plurality of (four in this example) head units 31. The plurality of head units 31 are arranged at intervals in the transport direction d1. Each head unit 31 ejects ink of a different color (cyan (C), magenta (M), yellow (Y), and black (K) in this example) to record a monochrome image on the surface of the substrate 9. A multicolor image is formed on the upper surface of the substrate 9 by superimposing the monochrome images of different colors.

[0029] Figure 2 shows the underside of the head unit 31. The head unit 31 has multiple (four in this example) inkjet heads 35. The multiple inkjet heads 35 are arranged in the width direction d2. In the example shown in Figure 2, the multiple inkjet heads 35 are arranged in a staggered pattern with their positions offset from each other in the transport direction d1. The inkjet heads 35 may also be arranged in a straight line in the width direction d2.

[0030] As shown in Figure 2, the inkjet head 35 has an ejection surface 35S facing the substrate 9. The ejection surface 35S has a plurality of nozzles 351 arranged at equal intervals in the width direction. The plurality of nozzles 351 eject ink. The method of ejecting ink from the nozzles 351 may be a piezoelectric method using a piezoelectric element (piezo element) or a so-called thermal method in which the ink is heated by a heater.

[0031] Figure 3 is a schematic top view showing a part of the inkjet printing apparatus 1. As shown in Figures 1 and 3, the drying unit 4 is located downstream of the inkjet unit 3 in the transport direction d1. The drying unit 4 heats the substrate 9 printed by the inkjet unit 3 and transported by the transport unit 2 to dry the ink applied to the surface of the substrate 9. The drying unit 4 is equipped with a plurality of (three in this example) carbon heaters 41, and irradiates the substrate 9 with infrared rays from the carbon heaters 41 to dry the ink on the substrate 9. The plurality of carbon heaters 41 extend parallel to the transport direction d1 and are arranged at equal intervals in the width direction d2. The plurality of carbon heaters 41 may also extend in a direction intersecting the transport direction d1 (for example, in the width direction d2). In addition to irradiating with infrared rays, the drying unit 4 may also be configured to blow heated drying air onto the substrate 9.

[0032] As shown in Figures 1 and 3, the temperature sensor 5 is positioned downstream of the drying unit 4 in the transport direction d1 and measures the temperature of the substrate 9 irradiated with infrared radiation. The temperature sensor 5 is a non-contact type radiation thermometer that detects the intensity of infrared radiation emitted from an object. In this embodiment, the measurement target area A51 on the substrate 9 that the temperature sensor 5 can measure is set at one end of the substrate 9 in the width direction d2. The width of the measurement target area A51 (dimension in the width direction d2) corresponds, for example, to the field of view of the detector of the temperature sensor 5. The temperature sensor 5 inputs a signal indicating the measured temperature to the control unit 8. The temperature sensor 5 is preferably a non-contact type, but may also be a contact type.

[0033] Returning to Figure 1, the control unit 8 is an information processing device for controlling each part of the inkjet printing apparatus 1. The control unit 8 includes a processor 81 and a storage unit 83. The processor 81 includes, for example, a CPU (Central Processing Unit). The storage unit 83 includes an auxiliary storage device such as RAM (Random Access Memory), ROM (Read-Only Memory), or a hard disk drive. Some or all of the functions of the control unit 8 may be implemented by hardware circuits such as application-specific integrated circuits (ASICs).

[0034] The storage unit 83 stores a computer program P for executing printing processes, such as printing while transporting the substrate 9. The control unit 8 is a computer program product including the computer program P. The computer program P is provided to the control unit 8 via a non-transient recording medium M. The computer program P is recorded on the recording medium M in a readable format by the control unit 8, which is a computer. The recording medium M is a semiconductor memory, optical disk, or magnetic disk, etc. The computer program P may also be provided to the control unit 8 via a network.

[0035] The storage unit 83 stores print data 831 and corresponding information 833. The print data 831 is data representing the image to be printed on the substrate 9. In the print data 831, images are managed on a sheet basis. One sheet corresponds to, for example, one page in a PDF (Portable Document Format) file that can be used as submission data.

[0036] Here, the data corresponding to one sheet (or page) represented by the print data 831 is referred to as image data D61, and the image represented by said image data D61 is referred to as the target image 61. Note that image data D61 does not necessarily have to be data corresponding to one sheet; it may be data corresponding to multiple sheets.

[0037] Correspondence information 833 is information that shows the correspondence between the color of the image formed by the inkjet unit 3 and the infrared absorbance (hereinafter also simply referred to as "absorbance"). Details of correspondence information 833 will be described later.

[0038] Figure 4 is a block diagram showing the electrical connections between the control unit 8 and the controlled object. The control unit 8 functions as a printing control unit 811, an absorption analysis unit 813, and a monitoring unit 815. These functions are realized by the processor 81 executing procedures defined in the computer program P.

[0039] The print control unit 811 controls the transport unit 2 and the multiple head units 31 to execute the printing process. Specifically, the print control unit 811 controls the transport unit 2 (more specifically, the motor 211) to transport the substrate 9 to the transport unit 2. The print control unit 811 also controls each head unit 31 based on the print data 831 and prints an image by ejecting ink from each head unit 31 onto the substrate 9. The print control unit 811 controls the ejection of ink from each head unit 31 based on a signal indicating the amount of substrate 9 transported from the transport unit 2 (for example, the output signal of the rotary encoder).

[0040] Figure 5 is a schematic top view showing the substrate 9 on which the image is printed. Figure 6 is a schematic front view showing a cross-section of the substrate 9 at position AA shown in Figure 5. In Figure 6, the carbon heater 41 and temperature sensor 5 of the drying section 4 are also shown.

[0041] As shown in Figure 5, the print control unit 811 prints a patch image 63 onto the substrate 9 separately from the target image 61 represented by the image data D61. The print control unit 811 prints the patch image 63 on the measurement target area A51 where the temperature sensor 5 measures the temperature. As shown in Figure 6, the patch image 63, like the target image 61, receives infrared radiation emitted from the carbon heater 41 of the drying unit 4. Therefore, the temperature sensor 5 measures the temperature of the patch image 63 that has absorbed the infrared radiation.

[0042] Patch image 63 is, for example, an image printed uniformly with a specific ink density. Ink density refers to the density of each CMYK ink. Furthermore, ink density can be expressed, for example, as the dot area ratio, which is the percentage of the area occupied by the halftone dots.

[0043] In this example, as shown in Figure 5, the patch image 63 is printed between two adjacent target images 61 in the transport direction d1. The length of the patch image 63 (dimension in the transport direction d1) is sufficiently small compared to the length of the target images 61. In the example shown in Figure 5, the length of the patch image 63 is smaller than the distance between the two adjacent target images 61 in the transport direction d1. The patch image 63 may also be printed at a position adjacent to the target images 61 in the width direction (between the upstream and downstream ends of the target images 61).

[0044] In order for the temperature sensor 5 to accurately measure the temperature of the patch image 63, it is desirable that the residence time of the patch image 63 within the field of view of the temperature sensor 5's detector is longer than the response time of the temperature sensor 5. This residence time is proportional to the length of the patch image 63 and inversely proportional to the transport speed of the substrate 9 by the transport unit 2. For this reason, the length of the patch image 63 is set in proportion to the transport speed. That is, the patch image 63 should be made longer as the transport speed increases, and shorter as the transport speed decreases.

[0045] Furthermore, the width of the patch image 63 (dimension in the width direction d2) is not particularly limited, but it is the same as or larger than the width of the measurement area A51 of the temperature sensor 5. The patch image 63 is printed so as to extend beyond the measurement area A51 on both sides in the width direction d2.

[0046] Returning to Figure 4, the absorptive analysis unit 813 uses the correspondence information 833 to perform a process of analyzing the infrared absorptive value indicated by the image data D61. Specifically, the absorptive analysis unit 813 performs a process to identify the maximum value (maximum absorptive value) of the infrared absorptive value indicated by the image data D61. The absorptive analysis unit 813 also passes color information that has the same or greater absorptive value as the identified maximum absorptive value to the print control unit 811. Based on this, the print control unit 811 prints the patch image 63.

[0047] Figure 7 is a conceptual diagram illustrating an example of correspondence information 833 showing the relationship between ink color and absorption. In this correspondence information 833, the information indicating the ink color is the respective concentrations of CMYK inks. Furthermore, the infrared absorption is defined as the temperature of the printed area (hereinafter referred to as the "absorption temperature") when the printed area with the corresponding ink concentration absorbs infrared radiation.

[0048] The absorption temperature may be an actually measured value. For example, in an inkjet printing apparatus 1, the density of each CMYK ink may be changed in stages, printing may be performed in the inkjet section 3, the resulting printed area may be dried in the drying section 4, and then measured with the temperature sensor 5. Alternatively, the absorption temperature may be obtained using a printing apparatus other than the inkjet printing apparatus 1.

[0049] The correspondence information 833 in Figure 7 contains the absorption temperatures of multiple types of substrates 9 (in this case, substrates A, B, and C). In this example, with substrate A as the reference, the absorption temperatures of substrates B and C are obtained by adding +x1 and +x2, respectively, to the absorption temperature of substrate A (n1, n2...). x1 and x2 are temperatures corresponding to the characteristics (infrared absorption characteristics) of substrate B or substrate C relative to substrate A. The absorption analysis unit 813 refers to the absorption temperature of the type of substrate corresponding to the substrate 9 actually used. Note that infrared absorptivity is not limited to the absorption temperature shown in Figure 7. Infrared absorptivity can be any information indicating the degree of infrared absorption, such as infrared absorptivity.

[0050] The absorption analysis unit 813 divides the target image 61 represented by the image data D61 into multiple unit regions in the transport direction d1 and the width direction d2, and obtains the absorption value corresponding to the representative value of the ink density of each obtained unit region from the corresponding information 833. The representative value is the average or median, etc. Furthermore, the absorption analysis unit 813 identifies the maximum absorption value from the absorption values ​​of each unit region and passes the ink density of that maximum absorption value, or an absorption value greater than that, to the print control unit 811. As a result, the print control unit 811 prints a patch image 63 at the position corresponding to the target image 61 with the passed ink density.

[0051] The determination of the maximum absorbance by the absorbance analysis unit 813 is performed, for example, before the inkjet unit 3 prints the target image 61 represented by the target image data D61. This allows the patch image 63 to be printed upstream of the target image 61. Alternatively, the determination of the maximum absorbance may be performed before printing targeting the print data begins. In this case, print data including patch image data representing the patch image 63 may be generated.

[0052] Returning to Figure 4, the monitoring unit 815 monitors the measured temperature, which is the measurement result of the temperature sensor 5. That is, the monitoring unit 815 monitors the measured temperature of the patch image 63 measured by the temperature sensor 5. For example, the monitoring unit 815 determines whether the measured temperature exceeds a predetermined threshold temperature that is considered a high-temperature abnormality. The determination result may then be recorded in log information 835. The threshold temperature may be, for example, a heat resistance temperature set in advance for each type (A, B, C) of the substrate 9, or it may be lower than that heat resistance temperature.

[0053] Furthermore, if the measured temperature of a specific patch image 63 exceeds the threshold temperature, a high-temperature anomaly may occur in the target image 61 corresponding to that specific patch image 63. Therefore, by having the monitoring unit 815 create log information 835, the user can easily identify the target image 61 (sheet) in which a high-temperature anomaly may have occurred from the log information 835.

[0054] Furthermore, if the monitoring unit 815 detects a high-temperature anomaly, it may notify the outside via a predetermined output device of information (for example, sheet identification information) to identify the target image 61 corresponding to the patch image 63 in which the high-temperature anomaly was detected. A display or printer can be used as the output device. Also, if the monitoring unit 815 detects a high-temperature anomaly, it may mark the target image 61 or the surrounding area on the substrate 9 where the high-temperature anomaly was detected. For example, an inspection device (not shown) that inspects the printing results of the substrate 9 may be configured to apply the mark.

[0055] If patch image 63 is printed upstream of the corresponding target image 61, a high-temperature anomaly can be detected in patch image 63 before it occurs in target image 61. Therefore, countermeasures can be taken to prevent the high-temperature anomaly from occurring.

[0056] To avoid high-temperature abnormalities, the monitoring unit 815 may control the amount of infrared radiation emitted by the carbon heater 41 in the drying unit 4 according to the measured temperature. For example, if the measured temperature of the patch image 63 exceeds a predetermined upper limit, the monitoring unit 815 may reduce the output of the carbon heater 41. Also, if the measured temperature of the patch image 63 falls below a predetermined lower limit, the monitoring unit 815 may increase the output of the carbon heater 41. Furthermore, if the monitoring unit 815 detects a high-temperature abnormality in the patch image 63, it may stop the printing process by stopping the operation of the transport unit 2 and the inkjet unit 3.

[0057] Figure 8 is a diagram illustrating an example of setting the distance between the target image 61 and the patch image 63. In order for the monitoring unit 815 to properly take action against a high-temperature anomaly (such as reducing the output of the carbon heater 41 or stopping the printing process), the separation distance D in the transport direction d1 between the target image 61 and the patch image 63 should be made sufficiently larger than the distance the substrate 9 is transported before the action is taken.

[0058] For example, the separation distance D may be made larger than the distance Dt1 (see Figure 3) in the transport direction d1 from the inlet (upstream end) of the drying unit 4 to the measurement position of the temperature sensor 5. In this case, the high temperature anomaly of the patch image 63 can be detected before the target image 61 is dried, thus effectively avoiding the high temperature anomaly in the printed portion of the target image 61. Alternatively, the separation distance D may be made larger than the distance Dt2 (see Figure 3) from the inlet (downstream end) of the inkjet unit 3 to the detection position of the temperature sensor 5. In this case, the high temperature anomaly of the patch image 63 can be detected before the target image 61 is printed, thus more effectively avoiding the high temperature anomaly in the printed portion of the target image 61.

[0059] Furthermore, it is not essential that multiple separation distances D be the same size. For example, if the print data 831 contains multiple types of image data D61, as shown in Figure 9, multiple types of target images 61, 61a are printed, along with multiple types of patch images 63, 63a corresponding to each. In this case, the separation distance D between the target image 61 and the patch image 63, and the distance D between the target image 61a and the patch image 63a do not necessarily have to be the same, and may be different.

[0060] As described above, the inkjet printer 1 prints a patch image 63 with an ink density equal to or greater than the maximum absorptivity of the target image 61, and measures the temperature of the patch image 63. In this case, in principle, the maximum temperature of the target image 61 that can be reached by infrared irradiation will be the same as or less than the measured temperature of the patch image 63. Therefore, by monitoring the measured temperature of the patch image 63, it is possible to appropriately predict high-temperature anomalies in the printed portion of the target image 61.

[0061] In particular, by printing the patch image 63 in the color of the target image 61 with the highest absorption, the measured temperature of the patch image 63 can be brought as close as possible to the maximum temperature that the printed portion of the target image 61 can actually reach. This reduces the false detection of high-temperature anomalies in the printed portion of the target image 61.

[0062] It is not mandatory to print a patch image 63 with an absorbance value greater than or equal to the maximum absorbance shown in the image data D61. However, in order to accurately estimate the maximum temperature that the target image 61 can reach when exposed to infrared radiation, it is desirable for the print control unit 811 to print the patch image 63 with an ink density that makes the absorbance of the patch image 63 greater than the average absorbance value (average absorbance) shown in the image data. In this case, the absorbance analysis unit 813 may calculate the average absorbance value shown in the image data D61. By measuring the temperature of the patch image with a color greater than the average absorbance value, the temperature of areas in the target image 61 that are prone to high temperatures can be measured using the patch image 63. Therefore, high temperature anomalies in the printed portion of the target image 61 can be appropriately detected.

[0063] Figure 9 is a top view showing a modified example of the printing position of the patch image 63. In the examples shown in Figures 5 and 6, the patch image 63 is printed outside the printing area A61 of the target image 61 (one end of the substrate 9) in the width direction d2. However, as shown in Figure 9, the patch image 63 may be printed inside the printing area A61 in the width direction d2. In this case, the measurement target area A51 of the temperature sensor 5 is also set inside the printing area A61 to match the printing position of the patch image 63.

[0064] As shown in Figure 6, when multiple carbon heaters 41 extending in the transport direction d1 are installed in the width direction d2, the amount of infrared light received near the edges of the substrate 9 in the drying section 4 may be less than that received near the center of the substrate 9. In this case, as shown in Figure 9, by setting the printing position of the patch image 63 inside the printing area A61, the amount of infrared light received by the patch image 63 can be brought closer to the amount of infrared light received by the target image 61. Therefore, by monitoring the measured temperature of the patch image 63, high-temperature abnormalities in the target image 61 can be detected more appropriately.

[0065] <2. Second Embodiment> Next, a second embodiment will be described. In the following description, elements having the same function as those already described will be given the same reference numeral or a reference numeral with an additional alphabetic character, and detailed descriptions may be omitted.

[0066] In the first embodiment, the absorption analysis unit 813 analyzes the infrared absorption of the image data D61 to calculate the maximum absorption (or average absorption) shown by the image data D61, and determines the color (ink density) of the patch image 63 accordingly. However, it is not essential to determine the color of the patch image 63 based on the absorption of the image data D61.

[0067] Figure 10 is a schematic diagram showing the temperature sensor 5 of the inkjet printing apparatus 1 according to the second embodiment. In this embodiment, the print control unit 811 controls the inkjet unit 3 to print a black (K100%) patch image 63. Since black generally has the highest infrared absorption, monitoring the measured temperature of the black patch image 63 makes it possible to reliably predict high-temperature abnormalities in the printed portion of the target image 61.

[0068] If the color of the patch image 63 is set to black only, the absorption analysis unit 813 and the corresponding information 833 can be omitted. This reduces the processing load on the control unit 8.

[0069] <3. Third Embodiment> In the first and second embodiments, a patch image 63 is printed on the measurement target area A51 of a temperature sensor 5 fixed in a fixed position, and a high-temperature anomaly in the printed portion of the target image 61 is detected from the measured temperature of the patch image 63. However, the temperature of the target image 61 may be measured instead of the patch image 63.

[0070] Figure 11 is a schematic front view showing the temperature sensor 5 of the inkjet printing apparatus 1 according to the third embodiment. As shown in Figure 11, the inkjet printing apparatus 1 of this embodiment further comprises a sensor moving unit 51 and a moving control unit 817. The sensor moving unit 51 is a mechanism that moves the temperature sensor 5 in the width direction d2. The sensor moving unit 51 has a linear drive mechanism such as a ball screw mechanism or a linear motor mechanism. The moving control unit 817 is a function realized by the processor 81 of the control unit 80.

[0071] The movement control unit 817 controls the sensor movement unit 51 to move the temperature sensor 5 in the width direction d2 so that the temperature sensor 5 measures the temperature of the portion of the target image 61 represented by the image data D61 that has the maximum absorptivity (or an absorptivity greater than the average absorptivity of the target image 61). The maximum absorptivity of the target image 61 is determined by the absorptivity analysis unit 813.

[0072] According to this embodiment, since the temperature of the target image 61 is measured directly, rather than the patch image 63, high-temperature anomalies in the area where the target image 61 is printed can be directly detected.

[0073] <4. Variation> Although embodiments have been described above, the present invention is not limited to those described above, and various modifications are possible.

[0074] For example, it is not mandatory to print the corresponding patch images 63 for multiple target images 61 contained in a single print data 831; only the patch images 63 corresponding to some of the target images 61 may be printed.

[0075] Furthermore, multiple patch images 63 may be formed for a single target image 61. For example, the target image 61 may be divided into multiple regions in the transport direction d1, and a corresponding patch image 63 may be formed for each region.

[0076] In the above embodiment, the correspondence information 833 is defined as a table of information specifying a particular ink concentration and its absorption rate. However, the correspondence information 833 may also be a function that calculates the absorption rate using the ink concentration as input.

[0077] Although this invention has been described in detail, the above description is illustrative in all respects, and the invention is not limited thereto. It is understood that countless variations not illustrated can be conceived without falling outside the scope of this invention. The components described in each of the above embodiments and variations can be combined or omitted as appropriate, as long as they do not contradict each other. [Explanation of Symbols]

[0078] 1: Inkjet printing device 2: Conveyor Unit 3: Inkjet section 4:Drying section 5: Temperature sensor 8: Control Unit 9: Base material 51: Sensor movement unit 61: Target image 63: Patch image 80: Control Unit 83: Storage section 811: Printing Control Unit 813: Absorption Analysis Department 815: Monitoring Department 833: Support Information A51: Measurement target area D61: Image data

Claims

1. An inkjet printing device, A conveying unit that conveys the base material in the conveying direction, The inkjet unit ejects multiple colors of ink onto the substrate being transported by the transport unit, A print control unit that controls the inkjet unit based on image data and prints the target image represented by the image data onto the substrate, A drying unit located downstream of the inkjet unit in the transport direction, which irradiates the substrate with infrared light to dry the ink ejected onto the substrate, A temperature sensor that measures the temperature of a measurement target area on the substrate irradiated with infrared light, A monitoring unit that monitors the temperature of the area to be measured, as measured by the temperature sensor, Equipped with, An inkjet printing apparatus in which the measurement target area of ​​the temperature sensor is an area having an infrared absorptivity greater than the average value of the infrared absorptivity shown in the image data.

2. An inkjet printing apparatus according to claim 1, The print control unit controls the inkjet unit to print a patch image with an infrared absorption value greater than the average value of the infrared absorption values ​​shown in the image data onto the measurement target area. The temperature sensor is an inkjet printing apparatus that measures the temperature of the area to be measured on the substrate where the patch image is printed.

3. An inkjet printing apparatus according to claim 2, An inkjet printing apparatus comprising: a print control unit that controls the inkjet unit to print the patch image in a color with the maximum infrared absorption value indicated by the image data or a greater infrared absorption value.

4. An inkjet printing apparatus according to claim 2, A storage unit that stores correspondence information showing the correspondence between the ink density of the multiple colors and the infrared absorption rate, An absorption analysis unit analyzes the infrared absorption shown in the image data using the aforementioned correspondence information, An inkjet printing device that also features [additional features].

5. An inkjet printing apparatus according to claim 2, The print control unit is an inkjet printing device that prints the black patch image onto the measurement target area.

6. An inkjet printing apparatus according to claims 2 to 5, The print control unit controls the inkjet unit to print the patch image upstream of the target image in the transport direction, in an inkjet printing apparatus.

7. An inkjet printing apparatus according to claim 1, A sensor movement unit moves the temperature sensor in the width direction so that the temperature sensor measures the temperature of the portion of the target image represented by the image data that has an infrared absorption value greater than the average value of infrared absorption values. An inkjet printing device that also features [additional features].

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