Printing device, method for controlling printing device, and method for setting printing medium

Abstract

Provided is a printing device for printing onto an outer peripheral surface of a printing medium having a columnar shape, a frustoconical shape or a conical shape, the printing device making it possible to shorten the printing time required to print onto the printing medium while ensuring the print quality of the printing medium.　The printing device comprises: a rotation mechanism 21 which rotates a printing medium 2, with the axis of the printing medium 2 serving as the center of rotation; and an inkjet head which is disposed above the printing medium 2 and which ejects ink toward the outer peripheral surface of the printing medium 2. The rotation mechanism 21 includes a motor 25 as a drive source, and rotates the printing medium 2 during printing of the printing medium 2. Print data for printing onto the printing medium 2 are input into to a control unit that controls the printing device, and the control unit controls the rotational speed of the motor 25 on the basis of the print data during printing of the printing medium 2.

Description

Printing device, control method for printing device, and method for setting a printing medium

[0001] The present invention relates to a printing apparatus for printing on the outer peripheral surface of a printing medium having a cylindrical, truncated conical or conical outer shape, a method for controlling the printing apparatus, and a method for setting the printing medium in the printing apparatus.

[0002] Conventionally, there has been known a printing apparatus for printing using ultraviolet-curable ink on the outer peripheral surface of a printing medium having a cylindrical, truncated conical, or conical outer shape (see, for example, Patent Document 1). The printing apparatus described in Patent Document 1 includes an inkjet head that ejects ink toward the outer peripheral surface of the printing medium, an ultraviolet irradiation device that cures the ink ejected onto the outer peripheral surface of the printing medium, a stage having a table on which the ultraviolet irradiation device is placed, a carriage on which the inkjet head is mounted, a carriage drive mechanism that moves the carriage in the main scanning direction, a stage drive mechanism that moves the stage in the sub-scanning direction, and a table lifting mechanism that raises and lowers the table.

[0003] In the printing device described in Patent Document 1, the ultraviolet irradiation device includes a rotation mechanism that holds the printing medium and rotates the printing medium around its axis. The rotation mechanism includes a first rotating unit that holds one end of the printing medium, a second rotating unit that holds the other end of the printing medium, a motor for rotating the printing medium, and a power transmission mechanism that connects the first rotating unit to the motor. The power transmission mechanism is composed of, for example, a pulley and a belt. In the printing device described in Patent Document 1, while the printing medium is rotated by the rotation mechanism, ink is ejected from an inkjet head that is stopped in a fixed position to print on the outer peripheral surface of the printing medium.

[0004] In the printing device described in Patent Document 1, an inkjet head is formed with a large number of nozzles that eject ink. The lower surface of the inkjet head is an ink ejection surface on which a large number of nozzles are formed. On the ink ejection surface, a nozzle row is formed with a plurality of nozzles arranged in the sub-scanning direction. The ultraviolet irradiation device includes a rotation mechanism that holds the print medium and rotates the print medium around its axis, an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the print medium to which ink is attached, and a cover that covers the ultraviolet irradiator from above. The ultraviolet irradiator includes an LED board on which a large number of LED chips that emit ultraviolet rays are mounted. The cover is formed with an opening through which the upper end of the print medium is positioned.

[0005] In the printing device described in Patent Document 1, the ultraviolet irradiation device is mounted on a table so that the axis of the print medium, when viewed from above, coincides with the sub-scanning direction. The length of the print medium in the sub-scanning direction set on the rotation mechanism is longer than the width of the inkjet head in the sub-scanning direction. In this printing device, the stage is stopped at a fixed position, and while the print medium is rotated by the rotation mechanism, ink is ejected from the inkjet head, which is stopped at a fixed position, to print a portion of an image on the outer peripheral surface of the print medium. The stage is then moved a predetermined distance in the sub-scanning direction and stopped. After that, while the print medium is again rotated by the rotation mechanism, ink is ejected from the inkjet head, which is stopped at a fixed position, to print a portion of an image on the outer peripheral surface of the print medium.

[0006] The printing device described in Patent Document 1 repeats the above operations to print on the outer peripheral surface of the substrate. When printing on the substrate, the ultraviolet irradiator irradiates the outer peripheral surface of the substrate with ultraviolet light. In the printing device described in Patent Document 1, the length of the LED substrate in the sub-scanning direction is longer than the length of the portion of the substrate where printing is performed in the sub-scanning direction, so that the ink applied to the outer peripheral surface of the substrate can be cured.

[0007] JP 2023-88834 A

[0008] In the printing device described in Patent Document 1, it is difficult to ensure print quality on the substrate unless the motor of the rotation mechanism is rotated at an appropriate rotation speed. For example, if the resolution of the image to be printed on the outer surface of the substrate is high, it is difficult to print accurately on the outer surface of the substrate unless the rotation speed of the motor is slowed down to slow down the rotation speed of the substrate. On the other hand, if the resolution of the image to be printed on the outer surface of the substrate is low, slowing down the rotation speed of the motor to slow down the rotation speed of the substrate will result in an unnecessarily long printing time on the substrate.

[0009] Furthermore, for example, if the viscosity of the ink used to print on the substrate is high, the speed of the ink ejected from the inkjet head will slow down and it will take a long time for the ink to reach the substrate, so in this case, it will be difficult to print accurately on the outer circumferential surface of the substrate unless the rotation speed of the motor is slowed down to slow down the rotation speed of the substrate. On the other hand, if the viscosity of the ink used to print on the substrate is low, the speed of the ink ejected from the inkjet head will increase and the time for the ink to reach the substrate will be short, but even in this case, slowing down the rotation speed of the motor to slow down the rotation speed of the substrate will make the printing time longer than necessary.

[0010] Therefore, an object of the present invention is to provide a printing device for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which is capable of shortening the printing time required to print on the printing substrate while ensuring the print quality of the printing substrate.Another object of the present invention is to provide a printing device control method for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which is capable of shortening the printing time required to print on the printing substrate while ensuring the print quality of the printing substrate.

[0011] The present inventors have also considered printing multiple ink layers on the outer peripheral surface of a substrate using the printing device described in Patent Document 1. According to the inventors' studies, it has become clear that printing multiple ink layers on the outer peripheral surface of a substrate while rotating the substrate using the printing device described in Patent Document 1 may result in a decrease in printing accuracy on the substrate.

[0012] Therefore, an object of the present invention is to provide a printing device for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which can ensure the print quality of the printing substrate even when printing multiple ink layers on the outer peripheral surface of the printing substrate while rotating the printing substrate.Another object of the present invention is to provide a printing device control method for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which can ensure the print quality of the printing substrate even when printing multiple ink layers on the outer peripheral surface of the printing substrate while rotating the printing substrate.

[0013] Furthermore, the inventors' investigations revealed that in the printing device described in Patent Document 1, if the entire LED board is turned on during printing on a substrate, excessive ultraviolet light may be irradiated onto the outer periphery of the substrate, causing the temperature of the substrate to rise excessively. If the temperature of the substrate rises excessively, problems such as deformation of the substrate may occur. Furthermore, the inventors' investigations revealed that, depending on the type of ink, irradiation of excessive ultraviolet light onto the outer periphery of the substrate may cause the ink to over-cure, resulting in cracks in the dried ink (i.e., cracks in the image printed on the substrate).

[0014] Therefore, an object of the present invention is to provide a printing device for printing using ultraviolet-curable ink on the outer peripheral surface of a printing medium having a cylindrical, truncated conical or conical outer shape, which is capable of preventing excessive ultraviolet light from being irradiated onto the outer peripheral surface of the printing medium, even if the length in the sub-scanning direction of the ultraviolet irradiator that irradiates ultraviolet light toward the outer peripheral surface of the printing medium is longer than the length in the sub-scanning direction of the printing portion that is the portion of the printing medium where printing is performed, and the width in the sub-scanning direction of the inkjet head is narrower than the length in the sub-scanning direction of the printing portion.

[0015] Another object of the present invention is to provide a control method for a printing device that uses ultraviolet-curable ink to print on the outer peripheral surface of a printing medium having a cylindrical, truncated cone, or conical outer shape, and that can prevent excessive ultraviolet light from being irradiated onto the outer peripheral surface of the printing medium even when the length of the ultraviolet light irradiating section in the sub-scanning direction is longer than the length of the printing medium in the sub-scanning direction and the width of the inkjet head in the sub-scanning direction is narrower than the length of the printing medium in the sub-scanning direction.

[0016] In the printing device described in Patent Document 1, images of various resolutions are printed on the outer peripheral surface of a substrate. When printing a high-resolution image on the outer peripheral surface of a substrate, it is necessary to slow down the rotation speed of the substrate that rotates during printing in order to ensure the quality of the printed image. On the other hand, when printing a low-resolution image on the outer peripheral surface of a substrate, it is possible to ensure the quality of the printed image even if the rotation speed of the substrate that rotates during printing is increased. Therefore, when printing a low-resolution image on the outer peripheral surface of a substrate, it is preferable to increase the rotation speed of the substrate that rotates during printing to shorten the time required to print the substrate.

[0017] However, in the printing device described in Patent Document 1, if the rotation speed of the rotating print medium during printing is increased, the irradiation time of ultraviolet light irradiated from the ultraviolet irradiator toward the outer peripheral surface of the rotating print medium during printing on the print medium becomes shorter, and the accumulated amount of ultraviolet light irradiated from the ultraviolet irradiator toward the outer peripheral surface of the print medium becomes less than the accumulated amount of ultraviolet light required to cure the ink adhered to the outer peripheral surface of the print medium, which may result in poor curing of the ink adhered to the outer peripheral surface of the print medium. Even if the rotation speed of the print medium rotating during printing is increased, if the intensity (illuminance) of ultraviolet light irradiated from the ultraviolet irradiator is increased, it is possible to prevent poor curing of the ink adhered to the outer peripheral surface of the print medium.

[0018] However, the inventors' investigations revealed that, in the printing device described in Patent Document 1, if the intensity of the ultraviolet light emitted from the ultraviolet irradiator is increased, an excessive amount of ultraviolet light may be irradiated onto the outer peripheral surface of the substrate when the rotation speed of the substrate slows during printing, causing the temperature of the substrate to rise excessively. If the temperature of the substrate rises excessively, problems such as deformation of the substrate may occur. Furthermore, the inventors' investigations revealed that, depending on the type of ink, irradiating the outer peripheral surface of the substrate with an excessive amount of ultraviolet light may cause the ink to over-cure, resulting in cracks in the dried ink (i.e., cracks in the image printed on the substrate).

[0019] Therefore, an object of the present invention is to provide a printing device for printing with ultraviolet-curable ink on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical, or conical outer shape, which is capable of irradiating an appropriate amount of ultraviolet light onto the ink adhering to the outer peripheral surface of the printing substrate even when the rotation speed of the printing substrate changes depending on the resolution of the image to be printed on the outer peripheral surface of the printing substrate.Another object of the present invention is to provide a printing substrate setting method for setting the printing substrate in such a printing device.

[0020] Furthermore, an object of the present invention is to provide a control method for a printing device that uses ultraviolet-curable ink to print on the outer surface of a substrate having a cylindrical, truncated cone, or conical outer shape, and that is capable of irradiating an appropriate amount of ultraviolet light onto the ink adhering to the outer surface of the substrate, even when the rotation speed of the substrate changes depending on the resolution of the image to be printed on the outer surface of the substrate.

[0021] In order to solve the above problems, the printing device of the present invention is a printing device for printing on the outer surface of a printing substrate having a cylindrical, truncated cone or conical outer shape, and is equipped with a rotation mechanism that holds the printing substrate and rotates the printing substrate around its axis as the center of rotation, an inkjet head that is arranged above the printing substrate and ejects ink toward the outer surface of the printing substrate, and a control unit for controlling the printing device, wherein the rotation mechanism has a motor as a drive source and a power transmission mechanism for transmitting the power of the motor to the printing substrate, and rotates the printing substrate when printing on the printing substrate, and the control unit receives print data for printing on the printing substrate, and the control unit controls the rotation speed of the motor based on the print data when printing on the printing substrate.

[0022] In the present invention, the control unit calculates the optimum rotation speed of the motor based on the print data, and rotates the motor at the calculated rotation speed when printing on the printing medium.

[0023] In the printing device of the present invention, print data for printing on a substrate is input to the control unit. Therefore, in the present invention, if the print data includes data on the resolution of the image to be printed on the outer surface of the substrate and data on the viscosity of the ink used to print on the substrate, the control unit can determine the resolution of the image to be printed on the outer surface of the substrate and the viscosity of the ink used to print on the substrate based on the input print data. Also, in the present invention, the control unit controls the rotation speed of the motor based on the print data when printing on the substrate.

[0024] Therefore, in the present invention, for example, when the resolution of the image, etc. printed on the outer peripheral surface of the print medium is high or the viscosity of the ink used is high, it is possible to slow down the rotation speed of the motor to slow down the rotation speed of the print medium, and when the resolution of the image, etc. printed on the outer peripheral surface of the print medium is low or the viscosity of the ink used is low, it is possible to increase the rotation speed of the motor to increase the rotation speed of the print medium. Therefore, in the present invention, it is possible to shorten the printing time required to print on the print medium while ensuring the print quality of the print medium.

[0025] In the present invention, for example, a printing device includes multiple inkjet heads, a carriage on which the multiple inkjet heads are mounted, and a carriage drive mechanism that moves the carriage in a direction perpendicular to the axis of the print medium when viewed from above, where print data is set for each inkjet head, and where a control unit controls the rotation speed of a motor when printing on the print medium based on the print data set for the inkjet head located directly above the print medium. In this case, even when multiple inkjet heads are used to print on the print medium, the control unit controls the rotation speed of the motor based on the print data set for the inkjet head that actually ejects ink. Therefore, even when multiple inkjet heads are used to print on the print medium, it is possible to reduce the printing time required to print on the print medium while ensuring the print quality of the print medium.

[0026] In the present invention, the printing device includes a carriage on which one or more inkjet heads are mounted and a carriage drive mechanism that moves the carriage in a direction perpendicular to the axis of the print medium when viewed from above. The inkjet heads each have a plurality of nozzles formed on their undersides, each nozzle array being aligned in the direction of the axis of the print medium when viewed from above. The total number of nozzle arrays formed on all inkjet heads mounted on the carriage is two or more. Print data is set for each nozzle array. The control unit may control the rotation speed of the motor based on the print data set for the nozzle array positioned directly above the print medium when printing on the print medium. In this case, even when printing on the print medium using multiple nozzle arrays, the control unit controls the rotation speed of the motor based on the print data set for the nozzle array that actually ejects ink. Therefore, even when printing on the print medium using multiple nozzle arrays, it is possible to reduce the printing time required to print on the print medium while ensuring print quality on the print medium.

[0027] In the present invention, the rotation mechanism preferably rotates the substrate in a predetermined first direction when printing on the substrate, and also rotates the substrate in the first direction when setting the printing origin, which is an operation to align the origin position of the substrate with respect to the inkjet head in the rotation direction of the substrate before printing on the substrate. In this case, for example, the printing device includes a pointer that emits light onto the outer surface of the substrate, and the power transmission mechanism includes a gear train or at least two toothed pulleys and a toothed belt stretched over the toothed pulleys. With this configuration, the rotation direction of the substrate during printing is the same as the rotation direction of the substrate when the printing origin was set. This suppresses the effects of backlash in the gear train of the power transmission mechanism, etc., and enables the substrate to accurately start rotating from the origin position when printing on the substrate. This improves the print quality of the substrate.

[0028] In the present invention, the rotation mechanism preferably includes an encoder for detecting the rotational position and rotational speed of the target object, an inkjet head formed with multiple nozzles for ejecting ink, and multiple ejection energy generating elements for ejecting ink from each of the multiple nozzles. When printing on the target object, the control unit generates an ejection trigger signal to start ejecting ink from the nozzles based on the output signal of the encoder, transmits a drive signal to the ejection energy generating elements to eject ink from the nozzles starting from the ejection trigger signal, and sets an ejection flag starting from the ejection trigger signal and clears the flag when transmission of the drive signal ends. If the motor rotation speed is normal, the next ejection trigger is generated after the ejection flag is cleared. If the next ejection trigger is generated while the ejection flag is cleared, the control unit preferably executes a predetermined error process. This configuration makes it possible to stop printing on the target object if the motor rotation speed increases for some reason, causing the ink to land incorrectly. This reduces the occurrence of printing defects on the target object.

[0029] In addition, in order to solve the above-mentioned problems, the control method for a printing device of the present invention is a printing device for printing on the outer surface of a printing substrate having a cylindrical, truncated cone-shaped or conical outer shape, and is equipped with a rotation mechanism that holds the printing substrate and rotates the printing substrate around the axis of the printing substrate as the center of rotation, and an inkjet head that is arranged above the printing substrate and ejects ink toward the outer surface of the printing substrate, the rotation mechanism is equipped with a motor as a drive source and a power transmission mechanism for transmitting the power of the motor to the printing substrate, and is a control method for a printing device that rotates the printing substrate when printing on the printing substrate, and is characterized in that the rotation speed of the motor is controlled based on print data for printing on the printing substrate when printing on the printing substrate.

[0030] In the control method for a printing device of the present invention, when printing on a substrate, the rotation speed of the motor is controlled based on print data for printing on the substrate. Therefore, in the present invention, if the print data includes data on the resolution of the image, etc. to be printed on the outer peripheral surface of the substrate and data on the viscosity of the ink used to print on the substrate, for example, if it is determined based on the print data that the resolution of the image, etc. to be printed on the outer peripheral surface of the substrate is high or if it is determined that the viscosity of the ink used to print on the substrate is high, it is possible to slow down the rotation speed of the motor and thereby slow down the rotation speed of the substrate.

[0031] Furthermore, with the present invention, for example, if it is determined based on the print data that the resolution of the image to be printed on the outer peripheral surface of the print medium is low, or if it is determined that the viscosity of the ink used is low, it is possible to increase the rotation speed of the motor and thereby increase the rotation speed of the print medium. Therefore, by controlling the printing device with the control method of the present invention, it is possible to shorten the printing time required to print on the print medium while ensuring the print quality of the print medium.

[0032] Furthermore, in order to solve the above-mentioned problems, the inventors of the present application conducted various studies and found that, when printing a plurality of ink layers on the outer peripheral surface of a print substrate while the print substrate is being rotated, the outer diameter of the print substrate including the ink layers varies depending on the number of ink layers already printed on the outer peripheral surface of the print substrate, and the circumferential speed (speed in the circumferential direction of the print substrate) of the portion where ink ejected from the inkjet head lands varies, and therefore, when printing a plurality of ink layers on the outer peripheral surface of the print substrate while the print substrate is being rotated, the landing position of the ink may be shifted in the circumferential direction of the print substrate depending on the number of ink layers already printed on the outer peripheral surface of the print substrate.

[0033] Furthermore, as a result of various studies, the inventors of the present application have come to the knowledge that, since the outer diameter of the print substrate, including the ink layers, varies depending on the number of printed ink layers printed on the outer peripheral surface of the print substrate, and this varies the distance between the area where the ink ejected from the inkjet head lands and the ink ejection surface of the inkjet head, when printing multiple ink layers on top of each other on the outer peripheral surface of the print substrate while rotating the print substrate, the ink landing position in the circumferential direction of the print substrate may be shifted depending on the number of printed ink layers printed on the outer peripheral surface of the print substrate.The inventors have also come to the knowledge that this shift in the ink landing position may result in a decrease in printing accuracy on the print substrate.

[0034] The printing device of the present invention is based on this new finding, and is a printing device for printing by overlapping a plurality of ink layers on the outer peripheral surface of a printing medium having a cylindrical, truncated conical or conical outer shape, and is provided with a rotation mechanism that holds the printing medium and rotates the printing medium around its axis as the center of rotation, an inkjet head that is disposed above the printing medium and ejects ink toward the outer peripheral surface of the printing medium, and a control unit that controls the printing device, wherein the inkjet head is formed with a plurality of nozzles that eject ink, and the inkjet head is provided with a plurality of ejection energy generating elements for ejecting ink from each of the plurality of nozzles, and the rotation mechanism is provided with a drive source and and a power transmission mechanism for transmitting the power of the motor to the substrate to be printed, and the substrate to be printed is rotated when the substrate is printed, and the control unit calculates the number of ink layers printed on the outer peripheral surface of the substrate to be printed when the substrate is printed, and performs at least one of the following controls: motor rotation speed control for controlling the rotation speed of the motor based on the calculated number of ink layers; ink ejection speed control for controlling the ejection speed of ink from the nozzles by the ejection energy generating elements based on the calculated number of ink layers; and ink ejection timing control for controlling the timing of ink ejection from the nozzles by the ejection energy generating elements based on the calculated number of ink layers.

[0035] Furthermore, based on this new finding, a method for controlling a printing device of the present invention is a printing device for printing by overlapping a plurality of ink layers on the outer peripheral surface of a printing medium having a cylindrical, truncated conical or conical outer shape, the printing device comprising: a rotation mechanism for holding the printing medium and rotating the printing medium around the axis of the printing medium as the center of rotation; and an inkjet head disposed above the printing medium and ejecting ink toward the outer peripheral surface of the printing medium, the inkjet head having a plurality of nozzles for ejecting ink, the inkjet head having a plurality of ejection energy generating elements for ejecting ink from each of the plurality of nozzles; the rotation mechanism comprising a motor as a drive source; and a power transmission mechanism for transmitting the power of the ink jet head to the print medium, and a control method for rotating the print medium when printing on the print medium, the control method comprising the steps of: calculating the number of ink layers printed on the outer peripheral surface of the print medium when printing on the print medium; and executing at least one of the following controls: motor rotation speed control for controlling the rotation speed of the motor based on the calculated number of ink layers; ink ejection speed control for controlling the ink ejection speed from the nozzles by the ejection energy generating element based on the calculated number of ink layers; and ink ejection timing control for controlling the timing of ink ejection from the nozzles by the ejection energy generating element based on the calculated number of ink layers.

[0036] In this invention, when printing on a substrate, at least one of the following control operations is performed: motor rotation speed control, which calculates the number of ink layers printed on the outer peripheral surface of the substrate and controls the rotation speed of the motor based on the calculated number of ink layers; ink ejection speed control, which controls the ink ejection speed from the nozzles by the ejection energy generating elements based on the calculated number of ink layers; and ink ejection timing control, which controls the ink ejection timing from the nozzles by the ejection energy generating elements based on the calculated number of ink layers. Therefore, this invention makes it possible to suppress deviations in the ink landing position in the circumferential direction of the substrate, regardless of the number of ink layers already printed on the outer peripheral surface of the substrate. Therefore, this invention makes it possible to ensure the print quality of the substrate even when multiple ink layers are printed on top of each other on the outer peripheral surface of the substrate while the substrate is rotating.

[0037] In the present invention, it is preferable that the control unit executes all of the motor rotation speed control, ink ejection speed control, and ink ejection timing control, or executes two controls arbitrarily selected from the motor rotation speed control, ink ejection speed control, and ink ejection timing control. This configuration effectively suppresses deviations in the ink landing position in the circumferential direction of the printing substrate, regardless of the number of ink layers already printed on the outer peripheral surface of the printing substrate. Therefore, it is possible to improve the print quality of the printing substrate, even when printing multiple ink layers on the outer peripheral surface of the printing substrate while rotating the printing substrate.

[0038] In the present invention, for example, the ejection energy generating element is a piezoelectric element, and the control unit controls the voltage applied to the piezoelectric element in ink ejection speed control. Also, in the present invention, for example, the rotation mechanism includes an encoder for detecting the rotation position and rotation speed of the motor or the print medium, and the control unit generates an ejection trigger signal for starting ink ejection from the nozzles based on the output signal of the encoder when printing on the print medium, and controls the ink ejection start time from the point in time when the ejection trigger signal is generated in ink ejection timing control.

[0039] In the present invention, it is preferable that the printing device is equipped with an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the substrate to which ink is adhered, the ink layer is made of ultraviolet-curable ink, and multiple ink layers with different ultraviolet transmittances are superimposed on the outer peripheral surface of the substrate, the control unit has the ultraviolet transmittance of each of the multiple ink layers stored in advance and is input with printing data for printing on the substrate, and the control unit ejects ink from the inkjet head based on the ultraviolet transmittances of the ink layers stored in the control unit and the printing data so that the ultraviolet transmittance of the ink layer located on the outer peripheral side of the multiple ink layers is higher than the ultraviolet transmittance of the ink layer located on the inner peripheral side.

[0040] With this configuration, after printing the ink layer located on the outer periphery of the substrate, when the ultraviolet irradiator irradiates ultraviolet light toward the surface of this ink layer, it is possible for the ultraviolet light to reach the ink layer located on the inner periphery of the substrate. Therefore, even if the time for irradiating ultraviolet light toward the surface of this ink layer after printing the ink layer located on the inner periphery of the substrate is shortened, it is possible to ensure the cumulative amount of ultraviolet light irradiated onto this ink layer and cure this ink layer. As a result, it is possible to shorten the printing time of the substrate.

[0041] Furthermore, in order to solve the above-mentioned problems, the printing device of the present invention is a printing device for printing with ultraviolet-curable ink on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical or conical outer shape, and includes a rotation mechanism that holds the printing substrate and rotates the printing substrate around the axis of the printing substrate as the center of rotation, an inkjet head that is arranged above the printing substrate and ejects ink toward the outer peripheral surface of the printing substrate, an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the printing substrate to which the ink has adhered, a movement mechanism that moves the inkjet head relative to the rotation mechanism and the ultraviolet irradiator in a sub-scanning direction that is orthogonal to the up-down direction and parallel to the axis of the printing substrate when viewed from the up-down direction, and a position detection mechanism that detects the relative position of the inkjet head in the sub-scanning direction with respect to the rotation mechanism and the ultraviolet irradiator. and a control unit for controlling the ink jet head, wherein the ink jet head is formed with a plurality of nozzles that eject ink, the underside of the ink jet head is an ink ejection surface on which the plurality of nozzles are formed, and a nozzle row is formed on the ink ejection surface by a plurality of nozzles arranged in the sub-scanning direction, the length in the sub-scanning direction of the ultraviolet irradiation unit that is the part of the ultraviolet irradiator that irradiates ultraviolet light is longer than the length in the sub-scanning direction of the printing part that is the part on the printed material where printing is performed, the width in the sub-scanning direction of the ink jet head is narrower than the length in the sub-scanning direction of the printing part, the ultraviolet irradiation unit is made up of a plurality of divided irradiation units that are divided in the sub-scanning direction, and the plurality of divided irradiation units can be turned on individually, and the control unit controls the lighting range of the ultraviolet irradiation units in the sub-scanning direction based on the detection result of the position detection mechanism when printing on the printed material.

[0042] Furthermore, in order to solve the above-mentioned problems, a method for controlling a printing device of the present invention is a printing device for printing on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical or conical outer shape using ultraviolet-curable ink, the printing device comprising: a rotation mechanism for holding the printing substrate and rotating the printing substrate around the axis of the printing substrate as the center of rotation; an inkjet head disposed above the printing substrate and ejecting ink toward the outer peripheral surface of the printing substrate; an ultraviolet irradiator for irradiating ultraviolet rays toward the outer peripheral surface of the printing substrate to which the ink has adhered; a movement mechanism for moving the inkjet head relative to the rotation mechanism and the ultraviolet irradiator in a sub-scanning direction that is orthogonal to the up-down direction and parallel to the axis of the printing substrate when viewed from the up-down direction; and a position detection mechanism for detecting the relative position of the inkjet head in the sub-scanning direction with respect to the rotation mechanism and the ultraviolet irradiator. a plurality of nozzles for ejecting ink are formed in the inkjet head, the bottom surface of the inkjet head is an ink ejection surface on which the plurality of nozzles are formed, and a nozzle row is formed on the ink ejection surface by a plurality of nozzles arranged in the sub-scanning direction; the length in the sub-scanning direction of the ultraviolet irradiation section of the ultraviolet irradiator which is the section that irradiates ultraviolet light is longer than the length in the sub-scanning direction of the printable section which is the section on which printing is performed on the printable material; the width in the sub-scanning direction of the inkjet head is narrower than the length in the sub-scanning direction of the printable section; the ultraviolet irradiation section is made up of a plurality of divided irradiation sections which are divided in the sub-scanning direction, and the plurality of divided irradiation sections can be turned on individually.

[0043] In the present invention, the ultraviolet irradiation unit is composed of multiple divided irradiation units divided in the sub-scanning direction, and each divided irradiation unit can be turned on individually. Furthermore, in the present invention, when printing on a substrate, the lighting range of the ultraviolet irradiation unit in the sub-scanning direction is controlled based on the detection results of a position detection mechanism that detects the relative position of the inkjet head in the sub-scanning direction with respect to the rotation mechanism and the ultraviolet irradiator. Therefore, in the present invention, when printing on a substrate, it is possible to light only the portion of the ultraviolet irradiation unit necessary for curing the ink, without lighting the entire ultraviolet irradiation unit. Therefore, in the present invention, even if the length of the ultraviolet irradiation unit in the sub-scanning direction is longer than the length of the substrate in the sub-scanning direction and the width of the inkjet head in the sub-scanning direction is narrower than the length of the substrate in the sub-scanning direction, it is possible to prevent excessive ultraviolet light from being irradiated onto the outer peripheral surface of the substrate.

[0044] In the present invention, it is preferable that one end of the inkjet head in the sub-scanning direction is defined as a first head end, the other end of the inkjet head in the sub-scanning direction is defined as a second head end, and the range between the first head end and the second head end in the sub-scanning direction is defined as a head arrangement range, and the control unit turns on the divided irradiation units of the ultraviolet irradiation unit that have at least a portion included in the head arrangement range. With this configuration, all of the divided irradiation units of the ultraviolet irradiation unit that have at least a portion included in the head arrangement range are turned on, making it possible to irradiate ultraviolet rays onto the entire portion of the printed area immediately after ink ejected from the inkjet head lands. Therefore, it is possible to properly cure the entire ink adhering to that portion of the printed area.

[0045] In the present invention, when the first head end is located at the same position as the boundary between two divided irradiation units in the sub-scanning direction, the control unit preferably also turns on the divided irradiation unit that is adjacent to the boundary and located outside the first head end in the sub-scanning direction, and when the second head end is located at the same position as the boundary between two divided irradiation units in the sub-scanning direction, the control unit also turns on the divided irradiation unit that is adjacent to the boundary and located outside the second head end in the sub-scanning direction. This configuration makes it possible to reliably irradiate ultraviolet rays to the edges of a portion of the printed area in the sub-scanning direction immediately after ink ejected from the inkjet head lands. Therefore, it is possible to properly cure ink that has adhered to the edges of a portion of the printed area in the sub-scanning direction.

[0046] In the present invention, it is preferable that the intensities of the ultraviolet rays irradiated from the multiple divided irradiation units are individually adjustable. With this configuration, it is possible to adjust the finish of the image printed on the outer peripheral surface of the printing medium by adjusting the intensities of the ultraviolet rays irradiated from the divided irradiation units.

[0047] In the present invention, the intensities of the ultraviolet rays irradiated from the plurality of divided irradiation units can be individually adjusted, and the control unit prints a first printing unit by ejecting ink from the inkjet head toward the outer circumferential surface of the print medium while stopping the inkjet head relative to the rotation mechanism and the ultraviolet irradiator in the sub-scanning direction, and then moves the inkjet head a predetermined amount relative to the rotation mechanism and the ultraviolet irradiator in the sub-scanning direction and stops it, and then ejects ink from the inkjet head toward the outer circumferential surface of the print medium to print a second printing unit, and determines the location of the print medium where the first printing unit is to be printed as a second printing unit. If the first divided printing section is designated as the first divided printing section and the portion of the printing section where the second printing section is to be printed is designated as the second divided printing section, it is preferable that when printing the first printing section, the ultraviolet irradiation section is irradiated with ultraviolet light of a first intensity that semi-cures the ink adhering to the printing section, and when printing the second printing section, the ultraviolet irradiation section is irradiated with ultraviolet light of the first intensity toward the second divided printing section, and ultraviolet light of a second intensity higher than the first intensity is irradiated toward the first divided printing section, and after printing the second printing section, the ultraviolet irradiation section is irradiated with ultraviolet light of the second intensity toward the second divided printing section. With this configuration, by repeating the printing operation as described above, it is possible to perform gloss printing (gloss printing) on ​​the outer peripheral surface of the printing material.

[0048] In addition, in order to solve the above problems, the printing device of the present invention is a printing device for printing using ultraviolet-curable ink on the outer peripheral surface of a substrate having a cylindrical, truncated cone-shaped, or conical outer shape, and is equipped with a rotation mechanism that holds the substrate and rotates the substrate around its axis as the center of rotation, an inkjet head that is positioned above the substrate and ejects ink toward the outer peripheral surface of the substrate, an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the substrate to which the ink is attached, and a control unit for controlling the printing device, wherein the rotation mechanism rotates the substrate when printing on it, and the control unit controls the intensity of the ultraviolet rays irradiated onto the substrate from the ultraviolet irradiator based on the rotation speed of the substrate when printing on it.

[0049] In the present invention, for example, printing data for printing on a substrate is input to the control unit, the printing data includes resolution data which is data on the resolution of the image to be printed on the substrate, and the rotation speed of the substrate is set based on the resolution data.

[0050] In addition, in order to solve the above-mentioned problems, the control method for a printing device of the present invention is a printing device for printing using ultraviolet-curable ink on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical or conical outer shape, and is equipped with a rotation mechanism that holds the printing substrate and rotates the printing substrate around the axis of the printing substrate as the center of rotation, an inkjet head that is positioned above the printing substrate and ejects ink toward the outer peripheral surface of the printing substrate, and an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the printing substrate to which the ink is adhered, and the rotation mechanism rotates the printing substrate when printing on the printing substrate, and is characterized in that the control method for a printing device controls the intensity of ultraviolet rays irradiated onto the printing substrate from the ultraviolet irradiator based on the rotation speed of the printing substrate when printing on the printing substrate.

[0051] In the present invention, the intensity of ultraviolet light irradiated from the ultraviolet irradiator onto the substrate is controlled based on the rotation speed of the substrate when printing is performed on the substrate. Therefore, in the present invention, when the rotation speed of the substrate slows down and the irradiation time of ultraviolet light irradiated onto the outer peripheral surface of the substrate becomes longer, the intensity of ultraviolet light irradiated from the ultraviolet irradiator can be reduced, and when the rotation speed of the substrate increases and the irradiation time of ultraviolet light irradiated onto the outer peripheral surface of the substrate becomes shorter, the intensity of ultraviolet light irradiated from the ultraviolet irradiator can be increased.

[0052] That is, with the present invention, as the rotation speed of the substrate increases during printing, the intensity of the ultraviolet light irradiated onto the substrate from the ultraviolet irradiator can be increased. Therefore, with the present invention, even if the rotation speed of the substrate changes depending on the resolution of the image printed on the outer peripheral surface of the substrate, it is possible to irradiate the ink adhering to the outer peripheral surface of the substrate with an appropriate amount of ultraviolet light.

[0053] In the present invention, for example, the ultraviolet irradiator includes an LED board on which a plurality of light-emitting elements that emit ultraviolet light are mounted, and the control unit controls the current value of the LED board based on the rotation speed of the substrate when printing on the substrate.

[0054] In the present invention, the inkjet head is formed with a plurality of nozzles for ejecting ink, and the lower surface of the inkjet head serves as an ink ejection surface on which the plurality of nozzles are formed. Preferably, the control unit controls the intensity of ultraviolet light irradiated from the ultraviolet irradiator onto the substrate during printing based on the ultraviolet transmittance of the substrate. This configuration makes it possible to reduce the intensity of ultraviolet light irradiated onto the substrate from the ultraviolet irradiator as the ultraviolet transmittance of the substrate increases. This makes it possible to reduce the amount of ultraviolet light that passes through the substrate and reaches the ink ejection surface of the inkjet head. As a result, it is possible to suppress hardening of the ink in the nozzles and prevent nozzle clogging.

[0055] In the present invention, if the cumulative amount of ultraviolet light irradiated from the ultraviolet irradiator toward the outer peripheral surface of the substrate during printing on the substrate is less than the cumulative amount of ultraviolet light required to cure the ink adhering to the outer peripheral surface of the substrate, it is preferable that the control unit causes the ultraviolet irradiator to irradiate additional ultraviolet light toward the outer peripheral surface of the substrate after printing on the substrate. With this configuration, since the substrate has high ultraviolet transmittance, even if the intensity of ultraviolet light irradiated from the ultraviolet irradiator to the substrate is reduced, it is possible to irradiate the outer peripheral surface of the substrate with the amount of ultraviolet light required to cure the ink adhering to the outer peripheral surface of the substrate.

[0056] In the present invention, for example, print substrate shape data, which is data on the shape of the print substrate, and ink type data, which is data on the type of ink ejected by the inkjet head, are input to the control unit, and the control unit calculates the cumulative amount of ultraviolet light required to cure the ink attached to the outer surface of the print substrate based on the input print substrate shape data and ink type data. In this case, the control unit can control the intensity of ultraviolet light irradiated from the ultraviolet irradiator to the print substrate, taking into account the calculated cumulative amount of light.

[0057] In the present invention, the rotation mechanism comprises a first holding member that contacts the substrate to hold one end of the substrate and rotates together with the substrate, and a second holding member that contacts the substrate to hold the other end of the substrate and rotates together with the substrate, and it is preferable that at least one of the first holding member and the second holding member is formed from a material that is light-blocking and thermally conductive.

[0058] With this configuration, at least one of the first and second holding members is made of a light-blocking material, which prevents ultraviolet light reflected by the first and second holding members from reaching the ink ejection surface of the inkjet head. This prevents ink from hardening in the nozzles, thereby reducing nozzle clogging. Furthermore, with this configuration, at least one of the first and second holding members is made of a thermally conductive material, which allows heat from the substrate to escape via the first and second holding members. This prevents the temperature of the substrate from rising excessively due to ultraviolet light irradiating the outer peripheral surface of the substrate.

[0059] In the present invention, the substrate is preferably cylindrical, the rotation mechanism includes an insert member inserted into the substrate's inner periphery, and the insert member is preferably made of a material with light-blocking and thermal conductivity. With this configuration, the insert member inserted into the substrate's inner periphery is made of a material with light-blocking properties, so even if the substrate has high UV transmittance, the insert member can prevent UV rays from passing through the substrate. Therefore, even if the substrate has high UV transmittance, UV rays can be prevented from reaching the ink ejection surface of the inkjet head, thereby suppressing ink hardening in the nozzles and preventing nozzle clogging. Furthermore, with this configuration, the insert member is made of a thermally conductive material, so heat from the substrate can be dissipated through the insert member. Therefore, it is possible to prevent the temperature of the substrate from becoming excessively high due to UV rays irradiated onto the outer periphery of the substrate.

[0060] In the present invention, for example, the printing device includes a cover that covers the ultraviolet irradiator from above, and the cover has an opening formed therein in which the upper end of the printing medium is placed.

[0061] A method for setting a substrate to be printed on a rotating mechanism in a printing device of the present invention includes, for example, a substrate setting step for setting the substrate to the rotating mechanism, and an ultraviolet measurement step for irradiating ultraviolet light from an ultraviolet irradiator onto the outer peripheral surface of the substrate while rotating the substrate using the rotating mechanism after the substrate setting step and measuring the amount of ultraviolet light above the opening. In this substrate setting method, the substrate is repeatedly reset to the rotating mechanism until the amount of ultraviolet light measured in the ultraviolet measurement step falls below a predetermined reference value. Setting the substrate to the rotating mechanism using this substrate setting method reduces the amount of ultraviolet light that passes through the opening formed in the cover and reaches the ink ejection surface of the inkjet head during printing on the substrate. This reduces ink hardening in the nozzles and reduces nozzle clogging.

[0062] As described above, the present invention makes it possible to shorten the printing time required to print on a substrate having a cylindrical, truncated cone, or conical shape while ensuring the printing quality of the substrate in a printing device for printing on the outer surface of the substrate.

[0063] Furthermore, as described above, in the present invention, in a printing device for printing on the outer surface of a substrate having a cylindrical, truncated cone, or conical outer shape, it is possible to ensure the printing quality of the substrate, even when printing multiple ink layers on top of each other on the outer surface of the substrate while rotating the substrate.

[0064] Furthermore, as described above, in the present invention, in a printing device for printing using ultraviolet-curable ink on the outer peripheral surface of a substrate having a cylindrical, truncated cone-shaped or conical outer shape, even if the length in the sub-scanning direction of the ultraviolet irradiation section, which is the part of the ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the substrate, that irradiates ultraviolet rays, is longer than the length in the sub-scanning direction of the printing section, which is the part of the substrate where printing is performed, and even if the width in the sub-scanning direction of the inkjet head is narrower than the length in the sub-scanning direction of the printing section, it is possible to prevent excessive ultraviolet rays from being irradiated onto the outer peripheral surface of the substrate.

[0065] Furthermore, as described above, in the present invention, in a printing device for printing using ultraviolet-curable ink on the outer surface of a substrate having a cylindrical, truncated cone-shaped or conical outer shape, it is possible to irradiate an appropriate amount of ultraviolet light onto the ink adhering to the outer surface of the substrate, even if the rotation speed of the substrate changes depending on the resolution of the image to be printed on the outer surface of the substrate.

[0066] 1 is a front view illustrating the configuration of a printing device according to a first embodiment of the present invention. FIG. 1 is a block diagram illustrating the configuration of the printing device shown in FIG. 1. (A) is a bottom view of the inkjet head and carriage shown in FIG. 1, and (B) is a bottom view illustrating the configuration of the inkjet head shown in (A). FIG. 1 is a front view illustrating the configuration of the ultraviolet irradiation device shown in FIG. 1. FIG. 4 is a side view illustrating the configuration of the rotation mechanism shown in FIG. 4. FIG. 4 is a side view illustrating the configuration of the rotation mechanism shown in FIG. 4. FIG. 1 is a diagram illustrating a method for setting a printing origin for aligning the origin position of a printing medium in the rotation direction of the printing medium in the printing device shown in FIG. 1. FIG. 1 is a flowchart illustrating an example of a control method for printing a printing medium using the printing device shown in FIG. 1. FIG. 1 is a timing chart illustrating ink ejection timing and the like when printing a printing medium using the printing device shown in FIG. 1. FIG. 1 is a diagram illustrating the configuration of a power transmission mechanism according to another modified example of the present invention. FIG. 11 is a front view illustrating the configuration of a printing device according to a second embodiment of the present invention. FIG. 12 is a block diagram illustrating the configuration of the printing device shown in FIG. 11. (A) is a bottom view of the inkjet head and carriage shown in FIG. 11, and (B) is a bottom view illustrating the configuration of the inkjet head shown in (A). 14 is a front view illustrating the configuration of the ultraviolet irradiation device shown in FIG. 11. FIG. 15 is a side view illustrating the configuration of the rotation mechanism shown in FIG. 14. FIG. 16 is a side view illustrating the configuration of the rotation mechanism shown in FIG. 14. FIG. 17 is a schematic view illustrating a cross section of a printing medium after printing by the printing apparatus shown in FIG. 11. FIG. 18 is a schematic view illustrating the vertical distance between a portion where ink ejected from the inkjet head shown in FIG. 11 lands and the ink ejection surface of the inkjet head. FIG. 19 is a timing chart illustrating the ink ejection timing when printing on a printing medium by the printing apparatus shown in FIG. 11. FIG. 20 is a front view illustrating the configuration of a printing apparatus according to a third embodiment of the present invention. FIG. 21 is a block diagram illustrating the configuration of the printing apparatus shown in FIG. 20. FIG. 21(A) is a bottom view of the inkjet head and carriage shown in FIG. 20, and FIG. 21(B) is a bottom view illustrating the configuration of the inkjet head shown in FIG. 20.28. FIG. 31 is a front view for explaining the configuration of the ultraviolet irradiation device shown in FIG. 20. FIG. 32 is a side view for explaining the configuration of the rotation mechanism shown in FIG. 23. FIG. 33 is a side view for explaining the configuration of the rotation mechanism shown in FIG. 23. FIG. 34 is a view for explaining the configuration of the ultraviolet irradiation unit shown in FIG. 23. FIG. 35 is a view for explaining a method of controlling the lighting of the ultraviolet irradiation unit according to a modified example of the present invention. FIG. 36 is a front view for explaining the configuration of a printing device according to a fourth embodiment of the present invention. FIG. 37 is a block diagram for explaining the configuration of the printing device shown in FIG. 1. (A) is a bottom view of the inkjet head and carriage shown in FIG. 28, and (B) is a bottom view for explaining the configuration of the inkjet head shown in (A). FIG. 38 is a front view for explaining the configuration of the ultraviolet irradiation device shown in FIG. 28. FIG. 39 is a side view for explaining the configuration of the rotation mechanism shown in FIG. 31. FIG. 39 is a side view for explaining the configuration of the rotation mechanism shown in FIG. 31. FIG. 39 is a process diagram for explaining a setting method when setting a print medium in the rotation mechanism shown in FIG. 32. FIG. 39 is a view for explaining a control method of an ultraviolet irradiator according to a modified example of the present invention. FIG. 39 is a schematic view for explaining the configuration of the rotation mechanism according to a modified example of the present invention.

[0067] First Embodiment A first embodiment of the present invention will be described below with reference to the drawings.

[0068] (Overall configuration of printing device) Fig. 1 is a front view illustrating the configuration of a printing device 1 according to a first embodiment of the present invention. Fig. 2 is a block diagram illustrating the configuration of the printing device 1 shown in Fig. 1. Fig. 3(A) is a bottom view of the inkjet head 3 and carriage 7 shown in Fig. 1, and Fig. 3(B) is a bottom view illustrating the configuration of the inkjet head 3 shown in Fig. 3(A).

[0069] The printing device 1 of this embodiment is a device for printing on the outer peripheral surface of a printing substrate 2 having a cylindrical, truncated conical, or conical outer shape, and is, for example, a commercial inkjet printer. The printing device 1 prints on the outer peripheral surface of the printing substrate 2 using ultraviolet-curable ink. The printing substrate 2 is formed, for example, in a cylindrical shape. That is, the printing substrate 2 is formed in a cylindrical, truncated conical, or conical cylindrical shape. The printing substrate 2 is also formed, for example, from resin. The printing device 1 is capable of printing on multiple types of printing substrates 2 with different outer diameters and lengths.

[0070] The printing device 1 is equipped with inkjet heads 3 (hereinafter referred to as "heads 3") that eject ultraviolet-curable ink toward the outer peripheral surface of the print medium 2. The printing device 1 of this embodiment is equipped with multiple heads 3. Specifically, the printing device 1 is equipped with four heads 3. The printing device 1 also includes an ultraviolet irradiation device 4 for curing the ink ejected onto the outer peripheral surface of the print medium 2, a stage 6 having a table 5 on which the ultraviolet irradiation device 4 is placed, a carriage 7 on which the multiple heads 3 are mounted, a Y-bar 8 that holds the carriage 7 so as to allow movement in the main scanning direction, and a main frame 9 that holds the stage 6 so as to allow movement in the up-down direction (vertical direction) and in a sub-scanning direction perpendicular to the main scanning direction.

[0071] The printing device 1 also includes a carriage drive mechanism 11 that moves the carriage 7 relative to the Y bar 8 in the main scanning direction, a stage drive mechanism 12 that moves the stage 6 relative to the main frame 9 in the sub-scanning direction, a table lifting mechanism 13 that raises and lowers the table 5, and a control unit 14 for controlling the printing device 1. The carriage drive mechanism 11 includes, for example, a motor 15 as a drive source and a power transmission mechanism such as a belt and pulleys that transmits the power of the motor 15 to the carriage 7. The stage drive mechanism 12 includes, for example, a motor as a drive source and a power transmission mechanism such as a belt and pulleys that transmits the power of the motor to the stage 6. The table lifting mechanism 13 includes, for example, a motor as a drive source and a power transmission mechanism such as a ball screw that transmits the power of the motor to the table 5.

[0072] In the following description, the sub-scanning direction (X direction in Fig. 1, etc.) is the front-to-rear direction, and the main scanning direction (Y direction in Fig. 1, etc.) is the left-to-right direction. In the following description, the X1 direction side in Fig. 5, etc., which is one side of the front-to-rear direction, is referred to as the "front" side, the X2 direction side in Fig. 5, etc., which is the opposite side, is referred to as the "rear" side, the Y1 direction side in Fig. 4, etc., which is one side of the left-to-right direction, is referred to as the "right" side, and the Y2 direction side in Fig. 4, etc., which is the opposite side, is referred to as the "left" side.

[0073] The upper surface of the table 5 is a plane perpendicular to the up-down direction. The ultraviolet irradiation device 4 placed on the table 5 is arranged below the head 3. The print medium 2 is held by the ultraviolet irradiation device 4 and arranged below the head 3. In other words, the head 3 is arranged above the print medium 2. The head 3 ejects ink downward. The ink ejected by the head 3 lands on the outer peripheral surface of the print medium 2 at the upper end of the print medium 2.

[0074] The head 3 has a plurality of nozzles 3a formed therein that eject ink. Specifically, the large number of nozzles 3a are formed on the underside of the head 3. On the underside of the head 3, a nozzle row 3b is formed by the large number of nozzles 3a that are arranged in the sub-scanning direction (front-rear direction). On the underside of the head 3, a plurality of nozzle rows 3b that are arranged in the main scanning direction (left-right direction) are formed. The head 3 has a plurality of piezoelectric elements (piezo elements) 16 that eject ink from each of the plurality of nozzles 3a. The piezoelectric elements 16 in this embodiment are ejection energy generating elements.

[0075] As shown in FIG. 3A , for example, three of the four heads 3 mounted on the carriage 7 are positioned at the same position in the front-to-rear direction and are arranged in the left-to-right direction. The remaining head 3 is positioned offset from the three heads 3 in the front-to-rear direction. Three of the four heads 3 eject color inks, and the remaining head 3 ejects white ink. The viscosity of the white ink is higher than the viscosity of the color inks. A pointer 17 is mounted on the carriage 7, which irradiates the outer peripheral surface of the print medium 2 with light. That is, the printing device 1 is equipped with a pointer 17 that irradiates the outer peripheral surface of the print medium 2 with light. The pointer 17 is, for example, an LED pointer. The pointer 17 is positioned above the print medium 2.

[0076] A motor 15 and a plurality of piezoelectric elements 16 are electrically connected to the control unit 14. A PC (personal computer) 18 is also electrically connected to the control unit 14. The PC 18 generates print data for printing on the print substrate 2. When printing on the print substrate 2, the print data generated by the PC 18 is sent from the PC 18 to the control unit 14. In other words, when printing on the print substrate 2, the print data sent from the PC 18 is input to the control unit 14. The print data in this embodiment is set for each head 3.

[0077] (Configuration of Ultraviolet Irradiation Device) Fig. 4 is a front view illustrating the configuration of the ultraviolet irradiation device 4 shown in Fig. 1. Figs. 5 and 6 are side views illustrating the configuration of the rotation mechanism 21 shown in Fig. 4.

[0078] The ultraviolet irradiation device 4 includes a rotation mechanism 21 that holds the substrate 2 and rotates the substrate 2 around its axis, an ultraviolet irradiator 22 that irradiates ultraviolet rays toward the outer peripheral surface of the substrate 2 to which ink is attached, and a cover 23 that covers the rotation mechanism 21 and the ultraviolet irradiator 22 from above. The cover 23 has an opening 23a in which the upper end of the substrate 2 is positioned.

[0079] The ultraviolet irradiation device 4 is placed on the table 5 so that the direction of the axis of the substrate 2 to be printed when viewed from above coincides with the front-to-back direction. In other words, the direction of the axis of the substrate 2 to be printed when viewed from above coincides with the front-to-back direction. The carriage drive mechanism 11 moves the carriage 7 in a direction perpendicular to the axis of the substrate 2 to be printed when viewed from above. The nozzle row 3b is arranged in the direction of the axis of the substrate 2 to be printed when viewed from above. The nozzle row 3b, which ejects ink toward the substrate 2 to be printed when printing on the substrate 2, is positioned directly above the substrate 2 to be printed.

[0080] The rotation mechanism 21 rotates the printing substrate 2 when printing on the printing substrate 2. In this embodiment, printing is performed on the printing substrate 2 while the rotation mechanism 21 rotates the printing substrate 2 with the carriage 7 stopped at a fixed position. When printing on the printing substrate 2, the rotation mechanism 21 rotates the printing substrate 2 in a counterclockwise direction when viewed from the front (hereinafter, this direction will be referred to as the "counterclockwise direction"). In other words, the rotation mechanism 21 rotates the printing substrate 2 only in the counterclockwise direction when printing on the printing substrate 2. The counterclockwise direction in this embodiment is a predetermined first direction.

[0081] In this embodiment, the length of the print medium 2 (length in the axial direction) is longer than the front-to-rear width of the head 3. Therefore, when printing on the print medium 2, the table 5 is moved in stages in the front-to-rear direction (sub-scanning direction). Note that the length of the print medium 2 may be equal to the front-to-rear width of the head 3, or may be shorter than the front-to-rear width of the head 3.

[0082] The rotation mechanism 21 includes a motor 25 as a drive source and a power transmission mechanism 26 for transmitting the power of the motor 25 to the printing medium 2. The rotation mechanism 21 also includes a first rotating unit 27 that holds one end of the printing medium 2, a first holding unit 28 that rotatably holds the first rotating unit 27, a second rotating unit 29 that holds the other end of the printing medium 2, a second holding unit 30 that rotatably holds the second rotating unit 29, a rotating frame 31 to which the first holding unit 28 and the second holding unit 30 are attached, and an encoder 32 for detecting the rotational position and rotational speed of the printing medium 2. The motor 25 and the encoder 32 are electrically connected to the control unit 14. Note that the power transmission mechanism 26 and other components are not shown in FIG. 4.

[0083] The first rotating unit 27 and the second rotating unit 29 rotate together with the substrate 2. The first rotating unit 27 holds the rear end of the substrate 2, and the second rotating unit 29 holds the front end of the substrate 2. The power transmission mechanism 26 connects the first rotating unit 27 to the motor 25. The power transmission mechanism 26 includes a gear train 33. The gear train 33 includes a drive gear fixed to the output shaft of the motor 25 and a driven gear fixed to the first rotating unit 27. The encoder 32 is connected to the rear end of the first rotating unit 27. The second holding unit 30 is movable in the direction of the axis of the substrate 2. In this embodiment, the positions of the second rotating unit 29 and the second holding unit 30 in the direction of the axis of the substrate 2 are adjusted according to the length of the substrate 2.

[0084] The rotating frame 31 is rotatable relative to a lower frame 34 that constitutes the bottom surface of the ultraviolet irradiation device 4, with the left-right direction as the rotation axis. The rotating frame 31 is also rotatable relative to the lower frame 34, with the rear end of the rotating frame 31 as the rotation center. In this embodiment, by rotating the rotating frame 31 relative to the lower frame 34, it is possible to adjust the inclination of the rotation mechanism 21 with respect to the horizontal direction when viewed from the left-right direction. In other words, by rotating the rotating frame 31 relative to the lower frame 34, it is possible to adjust the inclination of the axis of the printing medium 2 with respect to the horizontal direction.

[0085] In this embodiment, when printing on a substrate 2 having a cylindrical outer shape, the axis of the substrate 2 coincides with the front-to-rear direction (see FIG. 5). On the other hand, when printing on a substrate 2 having a truncated cone or conical outer shape, the axis of the substrate 2 is tilted relative to the front-to-rear direction (see FIG. 6). In other words, the tilt of the rotation mechanism 21 is adjusted when printing on the outer peripheral surface of a substrate 2 having a truncated cone or conical outer shape. Specifically, the tilt of the rotation mechanism 21 is adjusted so that the top end of the substrate 2 is parallel to the front-to-rear direction.

[0086] The ultraviolet irradiator 22 includes an LED substrate on which a number of LED chips that emit ultraviolet light are mounted. The ultraviolet irradiator 22 is disposed to the left of the substrate 2 and irradiates the substrate 2 with ultraviolet light from the left side. In this embodiment, the vertical position of the ultraviolet irradiator 22 is adjustable. The horizontal position of the ultraviolet irradiator 22 and the inclination of the ultraviolet irradiator 22 relative to the axis of the substrate 2 when viewed from the vertical direction are also adjustable. In this embodiment, when printing on a substrate 2 having a cylindrical outer shape, the ultraviolet irradiator 22 is installed so that the ultraviolet light emission surface of the ultraviolet irradiator 22 is parallel to the front-to-back direction. When printing on a substrate 2 having a truncated cone or conical outer shape, the inclination of the ultraviolet irradiator 22 is adjusted so that the ultraviolet light emission surface of the ultraviolet irradiator 22 is parallel to the left edge of the substrate 2.

[0087] (Method of Setting the Origin Position of the Printing Material) FIG. 7 is a diagram for explaining a method of setting the printing origin for aligning the origin position of the printing material 2 in the rotation direction of the printing material 2 in the printing device 1 shown in FIG.

[0088] Before printing on the substrate 2 with the printer 1, a printing origin is set, which is an operation to align the origin position of the substrate 2 with the head 3 in the rotation direction of the substrate 2. An origin mark 2a, which is the target origin position, is marked on the outer circumferential surface of the substrate 2 (see FIG. 7). When setting the printing origin, the operator manually operates a jog key provided on the operation panel of the printer 1 to gradually rotate the substrate 2 at a low speed (see FIG. 7(B)).

[0089] Furthermore, when setting the printing origin, the operator rotates and stops the printing medium 2 while visually checking the position where the light emitted from the pointer 17 illuminates the origin mark 2a while irradiating the outer peripheral surface of the printing medium 2 with light emitted from the pointer 17 (see FIG. 7(C)). Once the printing medium 2 has been rotated and stopped to the position where the light emitted from the pointer 17 illuminates the origin mark 2a, the operator performs a predetermined operation to reset the encoder 32. Once the encoder 32 has been reset, setting of the printing origin is complete.

[0090] As described above, the rotation mechanism 21 rotates the printing medium 2 only in the counterclockwise direction (counterclockwise when viewed from the front) when printing on the printing medium 2 (see the arrow in FIG. 7A). Also, when setting the printing origin, if the operator operates the jog key, the rotation mechanism 21 rotates the printing medium 2 in the counterclockwise direction (see the arrow in FIG. 7B). In other words, when setting the printing origin, the rotation mechanism 21 rotates the printing medium 2 in the same direction as the rotation direction of the printing medium 2 during printing.

[0091] (Method of controlling the printing device) Fig. 8 is a flowchart for explaining an example of a method of controlling the printing device 1 when printing on the printing medium 2 using the printing device 1 shown in Fig. 1. Fig. 9 is a timing chart for explaining the ink ejection timing etc. when printing on the printing medium 2 using the printing device 1 shown in Fig. 1.

[0092] As described above, when printing is performed on the substrate 2 by the printing device 1, print data transmitted from the PC 18 is input to the control unit 14. Also, as described above, print data is set for each head 3, and when printing is performed on the substrate 2, the print data set for each head 3 is input to the control unit 14. The print data in this embodiment includes, for example, data on one of the four heads 3 that will perform printing, data on the resolution of the image, etc., printed on the outer peripheral surface of the substrate 2 by this head 3, and data on the viscosity of the ink ejected from this head 3. Below, an example of a method for controlling the printing device 1 when printing on the substrate 2 using multiple heads 3 with the stage 6 stopped (i.e., with the substrate 2 positioned at a predetermined position in the front-to-rear direction) will be described.

[0093] When printing on the substrate 2 using multiple heads 3 while the stage 6 is stopped, as shown in FIG. 8 , the control unit 14 first receives print data (step S1). The control unit 14 then selects the head 3 that will immediately perform printing based on the received print data, moves the carriage 7 to a position where the selected head 3 is positioned directly above the substrate 2, and stops the carriage 7 (step S2). The control unit 14 also calculates, based on the print data, the optimal rotation speed of the motor 25 when printing with the selected head 3, and stores the calculated rotation speed (step S3). That is, in step S3, the control unit 14 calculates and stores the optimal rotation speed of the substrate 2 when printing with the selected head 3 based on the print data.

[0094] In step S3, the control unit 14 calculates the optimal rotation speed of the motor 25, for example, depending on the resolution of the image, etc. to be printed on the outer peripheral surface of the print medium 2 by the head 3 selected in step S2, the viscosity of the ink ejected from this head 3, etc. For example, as the resolution of the image, etc. to be printed on the outer peripheral surface of the print medium 2 by the selected head 3 increases, the optimal rotation speed of the motor 25 calculated in step S3 decreases. Also, for example, as the viscosity of the ink ejected from the selected head 3 increases, the optimal rotation speed of the motor 25 calculated in step S3 decreases.

[0095] The control unit 14 then rotates the motor 25 at the rotation speed calculated in step S3, while ejecting ink from the head 3 selected in step S2 to print on the substrate 2 (step S4). The control unit 14 then receives print data for printing with a head 3 different from the head 3 selected in step S2 (step S5). The control unit 14 then selects the head 3 that will immediately perform printing based on the print data received in step S5, and moves the carriage 7 to a position where the selected head 3 is positioned directly above the substrate 2, and stops the carriage 7 there (step S6).

[0096] Based on the print data received in step S5, the control unit 14 also calculates the optimal rotation speed of the motor 25 when printing with the selected head 3 (step S7). In step S7, the control unit 14 calculates the optimal rotation speed of the motor 25, similar to step S3. Thereafter, the control unit 14 compares the rotation speed of the motor 25 calculated in step S7 with the rotation speed of the motor 25 stored in step S3 (step S8), and determines whether the two compared rotation speeds are the same (step S9).

[0097] If the two rotational speeds compared in step S9 are different, the control unit 14 changes the rotational speed of the motor 25 stored in the control unit 14 to the rotational speed calculated in step S7 and stores the changed rotational speed (step S10). On the other hand, if the two rotational speeds compared in step S9 are the same, the control unit 14 maintains the rotational speed of the motor 25 stored in the control unit 14 as is (step S11). Thereafter, the control unit 14 ejects ink from the head 3 selected in step S6 to print on the printing medium 2 while rotating the motor 25 at the rotational speed stored in step S10 or the rotational speed maintained in step S11 (i.e., the rotational speed calculated in step S7) (step S12).

[0098] Thereafter, the control unit 14 determines whether printing by all heads 3 used in printing the current print medium 2 (i.e., printing the print medium 2 while the stage 6 is stopped) has been completed (step S13). If printing by all heads 3 has been completed in step S13, printing of the print medium 2 using multiple heads 3 while the stage 6 is stopped is completed. On the other hand, if printing by all heads 3 has not been completed in step S13, the process returns to step S5.

[0099] After printing on the printing medium 2 using the multiple heads 3 has started with the stage 6 stopped, at least in the first step S13, it is determined that printing by all of the heads 3 has not been completed, and the process returns to step S5. In step S8 after step S13, the rotation speed of the motor 25 stored in step S10 or the rotation speed maintained in step S11 is compared with the rotation speed of the motor 25 calculated in the immediately preceding step S7.

[0100] In this embodiment, as described above, the length of the print medium 2 (length in the axial direction) is longer than the front-to-rear width of the head 3. Therefore, if printing on the entire print medium 2 has not been completed, when printing on the print medium 2 according to the control flow shown in Fig. 8 is completed, the control unit 14 moves the stage 6 in the front-to-rear direction (i.e., moves the print medium 2 in the front-to-rear direction), and then prints on the print medium 2 according to the control flow shown in Fig. 8.

[0101] As described above, in this embodiment, the control unit 14 calculates the optimal rotation speed of the motor 25 based on the print data, and rotates the motor 25 at the calculated rotation speed when printing on the print substrate 2. Specifically, the control unit 14 calculates the optimal rotation speed of the motor 25 based on the print data set for the head 3 located directly above the print substrate 2, and rotates the motor 25 at the calculated rotation speed when printing on the print substrate 2. In other words, the control unit 14 controls the rotation speed of the motor 25 based on the input print data when printing on the print substrate 2. Specifically, the control unit 14 controls the rotation speed of the motor 25 based on the print data set for the head 3 located directly above the print substrate 2 when printing on the print substrate 2.

[0102] In steps S4 and S12, when printing on the print medium 2, the control unit 14 generates an ejection trigger signal for causing the nozzle 3 a of the selected head 3 to start ejecting ink based on the output signal of the encoder 32 (see FIG. 9 ). Specifically, the control unit 14 generates the ejection trigger signal when the count number of encoder pulses reaches a predetermined value. The control unit 14 also sends a drive signal to the piezoelectric element 16 for ejecting ink from the nozzle 3 a, starting from the ejection trigger signal. Specifically, the control unit 14 sends a drive signal to the piezoelectric element 16 for ejecting one dot of ink from the nozzle 3 a, starting from the ejection trigger signal, and ejects ink from the nozzle 3 a.

[0103] 9, the control unit 14 sets a discharge flag starting from the discharge trigger signal, and clears the flag when transmission of the drive signal to the piezoelectric element 16 is completed. If the rotation speed of the motor 25 and the rotation speed of the printing medium 2 are normal, the discharge flag is cleared and the next discharge trigger is generated. On the other hand, if the rotation speed of the motor 25 increases for some reason (see part E in FIG. 9), the next discharge trigger is generated while the discharge flag is set. If the next discharge trigger is generated while the discharge flag is set, the control unit 14 sets an error flag and executes a predetermined error process.

[0104] (Major Effects of the Present Embodiment) As described above, in the present embodiment, print data for printing on the print substrate 2 is input to the control unit 14, and the print data includes data on the resolution of the image, etc. to be printed by the head 3, data on the viscosity of the ink ejected from the head 3, and the like. Therefore, in the present embodiment, the control unit 14 can specify, based on the input print data, the resolution of the image, etc. to be printed on the outer peripheral surface of the print substrate 2 and the viscosity of the ink used to print on the print substrate 2. Also, in the present embodiment, the control unit 14 calculates, based on the input print data, the optimal rotation speed of the motor 25 (the rotation speed of the print substrate 2) when printing with the head 3, and rotates the motor 25 and the print substrate 2 at the calculated rotation speed when printing on the print substrate 2. That is, in the present embodiment, the control unit 14 controls the rotation speed of the motor 25 and the print substrate 2 based on the print data when printing on the print substrate 2.

[0105] Therefore, in this embodiment, when the resolution of the image, etc. printed on the outer peripheral surface of the print substrate 2 is high or when the viscosity of the ink used is high, it is possible to slow down the rotation speed of the motor 25 and slow down the rotation speed of the print substrate 2. Also, in this embodiment, when the resolution of the image, etc. printed on the outer peripheral surface of the print substrate 2 is low or when the viscosity of the ink used is low, it is possible to increase the rotation speed of the motor 25 and speed up the rotation speed of the print substrate 2. Therefore, in this embodiment, it is possible to shorten the printing time required to print on the print substrate 2 while ensuring the print quality of the print substrate 2.

[0106] In this embodiment, when printing on the print substrate 2, the control unit 14 controls the rotation speed of the motor 25 based on print data set for the head 3 positioned directly above the print substrate 2. That is, in this embodiment, the control unit 14 controls the rotation speed of the motor 25 based on print data set for the head 3 that actually ejects ink. Therefore, in this embodiment, even when printing on the print substrate 2 using multiple heads 3, it is possible to shorten the printing time required to print on the print substrate 2 while ensuring the print quality of the print substrate 2.

[0107] In this embodiment, when the printing origin is set, the rotation mechanism 21 rotates the printing medium 2 in the same direction as the rotation direction of the printing medium 2 during printing. Therefore, in this embodiment, when printing on the printing medium 2, the influence of backlash in the gear train 33 is suppressed, and it is possible to start rotation of the printing medium 2 from the origin position with high accuracy. Therefore, in this embodiment, it is possible to improve the printing quality of the printing medium 2.

[0108] In this embodiment, the control unit 14 executes error processing when the next ejection trigger is generated while the ejection in progress flag is set, as shown in Fig. 9. Therefore, in this embodiment, if the rotation speed of the motor 25 increases for some reason and the ink landing position is shifted, it is possible to stop printing on the print medium 2. Therefore, in this embodiment, it is possible to prevent printing defects from occurring on the print medium 2.

[0109] (Modification 1 of Printing Device Control Method)

[0110] In the above-described embodiment, printing on the print substrate 2 may be performed using only one head 3 with the stage 6 stopped. In this case, when step S4 in the flowchart shown in FIG. 8 is completed, printing on the print substrate 2 with the stage 6 stopped is completed. Also, in this case, the control unit 14 does not need to store the calculated rotation speed of the motor 25 in step S3. Even in this case, because the control unit 14 controls the rotation speed of the motor 25 based on the print data when printing on the print substrate 2, it is possible to shorten the printing time required to print on the print substrate 2 while ensuring the print quality of the print substrate 2.

[0111] (Modification 2 of Printing Apparatus Control Method) As described above, the underside of the head 3 has a plurality of nozzle rows 3b arranged in the left-right direction. In the above-described embodiment, when printing on the substrate 2, the print data transmitted from the PC 18 to the control unit 14 and input may be set for each nozzle row 3b. That is, when printing on the substrate 2, print data set for each nozzle row 3b may be input to the control unit 14. In this case, the print data includes, for example, data on one of the plurality of nozzle rows 3b that will perform printing, data on the resolution of an image, etc., printed on the outer peripheral surface of the substrate 2 by this nozzle row 3b, and data on the viscosity of ink ejected from this nozzle row 3b. Hereinafter, with reference to the flowchart shown in FIG. 8 , a control method of the printing apparatus 1 according to Modification 2 when printing on the substrate 2 using the plurality of nozzle rows 3b while the stage 6 is stopped will be described.

[0112] 8 , the control unit 14 receives print data in step S1. In step S2, the control unit 14 selects the nozzle row 3b that will immediately execute printing based on the received print data, and moves and stops the carriage 7 to a position where the selected nozzle row 3b is positioned directly above the substrate 2. In step S3, the control unit 14 calculates the optimal rotation speed of the motor 25 when printing with the selected nozzle row 3b based on the print data, and stores the calculated rotation speed. In step S3, the control unit 14 calculates the optimal rotation speed of the motor 25 based on, for example, the resolution of an image to be printed on the outer peripheral surface of the substrate 2 by the nozzle row 3b selected in step S2, the viscosity of the ink ejected from the nozzle row 3b, and the like.

[0113] Then, in step S4, the control unit 14 ejects ink from the nozzle row 3b selected in step S2 while rotating the motor 25 at the rotation speed calculated in step S3, to print on the print substrate 2. Then, in step S5, the control unit 14 receives print data for printing with a nozzle row 3b different from the nozzle row 3b selected in step S2. Then, in step S6, the control unit 14 selects the nozzle row 3b that will immediately perform printing based on the print data received in step S5, and moves and stops the carriage 7 to a position where the selected nozzle row 3b is positioned directly above the print substrate 2.

[0114] Furthermore, in step S7, the control unit 14 calculates, based on the print data received in step S5, the optimum rotation speed of the motor 25 when printing is performed with the selected nozzle row 3b. Thereafter, the control unit 14 executes steps S8 to S11, as in the embodiment described above, and then in step S12, ejects ink from the nozzle row 3b selected in step S6 to print on the print medium 2 while rotating the motor 25 at the rotation speed stored in step S10 or the rotation speed maintained in step S11 (i.e., at the rotation speed calculated in step S7).

[0115] Thereafter, in step S13, the control unit 14 determines whether printing by all nozzle rows 3b used in the current printing of the print medium 2 (i.e., printing of the print medium 2 performed with the stage 6 stopped) has been completed. If printing by all nozzle rows 3b has been completed in step S13, printing of the print medium 2 using the plurality of nozzle rows 3b with the stage 6 stopped is completed. On the other hand, if printing by all nozzle rows 3b has not been completed in step S13, the process returns to step S5.

[0116] Thus, in this modified example, the control unit 14 calculates the optimal rotation speed of the motor 25 based on the print data set for the nozzle row 3b arranged directly above the print substrate 2, and rotates the motor 25 at the calculated rotation speed when printing on the print substrate 2. In other words, the control unit 14 controls the rotation speed of the motor 25 based on the print data set for the nozzle row 3b arranged directly above the print substrate 2 when printing on the print substrate 2.

[0117] In this modified example, even if printing on the substrate 2 is performed using multiple nozzle rows 3b, the control unit 14 controls the rotation speed of the motor 25 based on the print data set for the nozzle rows 3b that actually eject ink, so even if printing on the substrate 2 is performed using multiple nozzle rows 3b, it is possible to shorten the printing time required to print the substrate 2 while ensuring the print quality of the substrate 2.

[0118] In this modified example, the heads 3 mounted on the carriage 7 may include a head 3 having only one nozzle row 3b formed therein. Also, in this modified example, the number of heads 3 mounted on the carriage 7 may be one. In this case, multiple nozzle rows 3b are formed in the head 3. In other words, in this modified example, it is sufficient that the total number of nozzle rows 3b formed in all heads 3 mounted on the carriage 7 (i.e., one or multiple heads 3) is two or more.

[0119] (Other Modifications) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this and various modifications can be made within the scope that does not change the gist of the present invention.

[0120] 10 , instead of the gear train 33, the power transmission mechanism 26 may include a toothed pulley 43 fixed to the output shaft of the motor 25, a toothed pulley 44 fixed to the first rotating part 27, and a toothed belt 45 stretched around the toothed pulleys 43 and 44. In the above-described embodiment, when the printing origin is set, the rotation mechanism 21 rotates the printing medium 2 in the same direction as the rotation direction of the printing medium 2 during printing. Therefore, even in this case, when printing on the printing medium 2, it is possible to suppress the effects of backlash of the toothed pulleys 43 and 44 and the toothed belt 45 and to start rotation of the printing medium 2 accurately from the origin position.

[0121] In the embodiment described above, the rotation mechanism 21 may rotate the substrate 2 only in a clockwise direction when viewed from the front (hereinafter, this direction will be referred to as the "clockwise direction") when printing on the substrate 2. In this case, it is preferable that the rotation mechanism 21 rotates the substrate 2 in the clockwise direction, the same as the rotation direction of the substrate 2 during printing, when setting the printing origin. Also, as in the embodiment described above, if the rotation mechanism 21 rotates the substrate 2 only in the counterclockwise direction when printing on the substrate 2, the rotation mechanism 21 may also rotate the substrate 2 in the clockwise direction when setting the printing origin. Furthermore, in the embodiment described above, the rotation mechanism 21 may rotate the substrate 2 in both the counterclockwise and clockwise directions when printing on the substrate 2.

[0122] In the above-described embodiment, the printing data input to the control unit 14 does not need to include data on the resolution of the image, etc., printed on the outer peripheral surface of the substrate 2 by the head 3, or data on the viscosity of the ink ejected from the head 3. Also, in the above-described embodiment, if the printing device 1 only prints on substrates 2 having a fixed outer diameter, the vertical position of the ultraviolet irradiator 22 does not need to be adjustable. Furthermore, in the above-described embodiment, if the printing device 1 only prints on substrates 2 having a cylindrical outer shape, the tilt of the rotation mechanism 21 with respect to the horizontal when viewed from the left and right does not need to be adjustable, and the tilt of the ultraviolet irradiator 22 with respect to the axis of the substrate 2 when viewed from the top and bottom does not need to be adjustable.

[0123] In the above-described embodiment, the ultraviolet irradiation device 4 may be placed on the table 5 so that the direction of the axis of the print medium 2 when viewed from the top-bottom direction coincides with the left-right direction. Also, in the above-described embodiment, the ultraviolet irradiator 22 may be disposed below the print medium 2. Furthermore, in the above-described embodiment, the printing apparatus 1 may be provided with a Y-bar drive mechanism that moves the Y-bar 8 in the sub-scanning direction instead of the stage drive mechanism 12. Also, in the above-described embodiment, the ejection energy generating element for ejecting ink from the nozzle 3 a may be a heater (heat generating element). Also, in the above-described embodiment, the printing apparatus 1 may have only one head 3.

[0124] Second Embodiment A second embodiment of the present invention will be described below with reference to the drawings.

[0125] (Overall configuration of printing device) Fig. 11 is a front view illustrating the configuration of a printing device 101 according to a second embodiment of the present invention. Fig. 12 is a block diagram illustrating the configuration of the printing device 101 shown in Fig. 11. Fig. 13(A) is a bottom view of the inkjet head 103 and carriage 107 shown in Fig. 11, and Fig. 13(B) is a bottom view illustrating the configuration of the inkjet head 103 shown in Fig. 13(A).

[0126] The printing device 101 of this embodiment is a device for printing on the outer peripheral surface of a printing substrate 102 having a cylindrical, truncated conical, or conical outer shape, and is, for example, a commercial inkjet printer. The printing device 101 prints on the outer peripheral surface of the printing substrate 102 using ultraviolet-curable ink. The printing substrate 102 is formed, for example, in a cylindrical shape. That is, the printing substrate 102 is formed in a cylindrical, truncated conical, or conical cylindrical shape. The printing substrate 102 is also formed, for example, from resin. The printing device 101 is capable of printing on multiple types of printing substrates 102 with different outer diameters and lengths.

[0127] The printing device 101 includes inkjet heads 103 (hereinafter referred to as "heads 103") that eject ultraviolet-curable ink toward the outer peripheral surface of the print medium 102. The printing device 101 of this embodiment includes multiple heads 103. Specifically, the printing device 101 includes four heads 103. The printing device 101 also includes an ultraviolet irradiation device 104 for curing the ink ejected onto the outer peripheral surface of the print medium 102, a stage 106 having a table 105 on which the ultraviolet irradiation device 104 is placed, a carriage 107 on which the multiple heads 103 are mounted, a Y-bar 108 that holds the carriage 107 so as to allow movement in the main scanning direction, and a main frame 109 that holds the stage 106 so as to allow movement in the up-down direction (vertical direction) and in a sub-scanning direction perpendicular to the main scanning direction.

[0128] The printing apparatus 101 also includes a carriage drive mechanism 111 that moves the carriage 107 in the main scanning direction relative to the Y bar 108, a stage drive mechanism 112 that moves the stage 106 in the sub-scanning direction relative to the main body frame 109, a table lifting mechanism 113 that raises and lowers the table 105, and a control unit 114 for controlling the printing apparatus 101. The carriage drive mechanism 111 includes, for example, a motor 115 as a drive source and a power transmission mechanism such as a belt and pulley that transmits the power of the motor 115 to the carriage 107. The stage drive mechanism 112 includes, for example, a motor as a drive source and a power transmission mechanism such as a belt and pulley that transmits the power of the motor to the stage 106. The table lifting mechanism 113 includes, for example, a motor as a drive source and a power transmission mechanism such as a ball screw that transmits the power of the motor to the table 105.

[0129] In the following description, the sub-scanning direction (X direction in FIG. 11, etc.) is the front-to-rear direction, and the main scanning direction (Y direction in FIG. 11, etc.) is the left-to-right direction. In the following description, the X1 direction side in FIG. 15, etc., which is one side of the front-to-rear direction, is referred to as the "front" side, the X2 direction side in FIG. 15, etc., which is the opposite side, is referred to as the "rear" side, the Y1 direction side in FIG. 14, etc., which is one side of the left-to-right direction, is referred to as the "right" side, and the Y2 direction side in FIG. 14, etc., which is the opposite side, is referred to as the "left" side.

[0130] The upper surface of the table 105 is a plane perpendicular to the up-down direction. The ultraviolet irradiation device 104 placed on the table 105 is arranged below the head 103. The printing medium 102 is held by the ultraviolet irradiation device 104 and arranged below the head 103. In other words, the head 103 is arranged above the printing medium 102. The head 103 ejects ink downward. The ink ejected by the head 103 lands on the outer peripheral surface of the printing medium 102 at the upper end of the printing medium 102.

[0131] The head 103 is formed with a plurality of nozzles 103a that eject ink. Specifically, the plurality of nozzles 103a are formed on the bottom surface of the head 103. The bottom surface of the head 103 serves as an ink ejection surface 103c on which the plurality of nozzles 103a are formed. On the ink ejection surface 103c, a nozzle row 103b is formed by the plurality of nozzles 103a that are arranged in the sub-scanning direction (front-back direction). On the ink ejection surface 103c, a plurality of nozzle rows 103b that are arranged in the main scanning direction (left-right direction) are formed. The head 103 is equipped with a plurality of piezoelectric elements (piezo elements) 116 that cause ink to be ejected from each of the plurality of nozzles 103a. In this embodiment, the piezoelectric elements 116 are ejection energy generating elements.

[0132] 13A, for example, three of the four heads 103 mounted on the carriage 107 are disposed at the same position in the front-to-rear direction and are arranged in the left-to-right direction. The remaining head 103 is disposed at a position offset from the three heads 103 in the front-to-rear direction. Three of the four heads 103 eject color inks, and the remaining head 103 ejects white ink. The viscosity of the white ink is higher than the viscosity of the color inks.

[0133] The control unit 114 is electrically connected to a motor 115 and a plurality of piezoelectric elements 116. The control unit 114 is also electrically connected to a PC (personal computer) 118. The PC 118 generates print data for printing on the print substrate 102. When printing on the print substrate 102, the print data generated by the PC 118 is transmitted from the PC 118 to the control unit 114. In other words, when printing on the print substrate 102, the print data transmitted from the PC 118 is input to the control unit 114.

[0134] (Configuration of Ultraviolet Irradiation Device) Fig. 14 is a front view for explaining the configuration of the ultraviolet irradiation device 104 shown in Fig. 11. Figs. 15 and 16 are side views for explaining the configuration of the rotation mechanism 121 shown in Fig. 14.

[0135] The ultraviolet irradiation device 104 includes a rotation mechanism 121 that holds the substrate 102 and rotates it around its axis, an ultraviolet irradiator 122 that irradiates ultraviolet rays toward the outer peripheral surface of the substrate 102 to which ink is attached, and a cover 123 that covers the rotation mechanism 121 and the ultraviolet irradiator 122 from above. The cover 123 has an opening 123a through which the upper end of the substrate 102 is positioned. The ultraviolet irradiation device 104 is placed on the table 105 so that the axis of the substrate 102, when viewed from above, coincides with the front-to-back direction. In other words, the axis of the substrate 102, when viewed from above, coincides with the front-to-back direction. The nozzle array 103b that ejects ink toward the substrate 102 during printing is positioned directly above the substrate 102.

[0136] The rotation mechanism 121 rotates the printing substrate 102 when printing on the printing substrate 102. In this embodiment, printing is performed on the printing substrate 102 while the rotation mechanism 121 rotates the printing substrate 102 with the carriage 107 stopped at a fixed position. When printing on the printing substrate 102, the rotation mechanism 121 rotates the printing substrate 102, for example, counterclockwise when viewed from the front. Also, in this embodiment, the length (length in the direction of the axis) of the printing substrate 102 is longer than the width of the head 103 in the front-to-rear direction. Therefore, when printing on the printing substrate 102, the table 105 is moved in stages in the front-to-rear direction (sub-scanning direction). Note that the length of the printing substrate 102 may be equal to the width of the head 103 in the front-to-rear direction, or may be shorter than the width of the head 103 in the front-to-rear direction.

[0137] The rotation mechanism 121 includes a motor 125 as a drive source and a power transmission mechanism 126 for transmitting the power of the motor 125 to the printing substrate 102. The rotation mechanism 121 also includes a first rotating unit 127 that holds one end of the printing substrate 102, a first holding unit 128 that rotatably holds the first rotating unit 127, a second rotating unit 129 that holds the other end of the printing substrate 102, a second holding unit 130 that rotatably holds the second rotating unit 129, a rotating frame 131 to which the first holding unit 128 and the second holding unit 130 are attached, and an encoder 132 for detecting the rotational position and rotational speed of the printing substrate 102. The motor 125 and the encoder 132 are electrically connected to the control unit 114. Note that the power transmission mechanism 126 and other components are not shown in FIG. 14 .

[0138] The first rotating unit 127 and the second rotating unit 129 rotate together with the printing substrate 102. The first rotating unit 127 holds the rear end of the printing substrate 102, and the second rotating unit 129 holds the front end of the printing substrate 102. The power transmission mechanism 126 connects the first rotating unit 127 to the motor 125. The power transmission mechanism 126 includes a gear train 133. The gear train 133 includes a drive gear fixed to the output shaft of the motor 125 and a driven gear fixed to the first rotating unit 127. The encoder 132 is connected to the rear end of the first rotating unit 127. The second holding unit 130 is movable in the direction of the axis of the printing substrate 102. In this embodiment, the positions of the second rotating unit 129 and the second holding unit 130 in the direction of the axis of the printing substrate 102 are adjusted depending on the length of the printing substrate 102.

[0139] The rotating frame 131 is rotatable relative to a lower frame 134 that constitutes the bottom surface of the ultraviolet irradiation device 104, with the left-right direction as the rotation axis. The rotating frame 131 is also rotatable relative to the lower frame 134, with the rear end of the rotating frame 131 as the rotation center. In this embodiment, by rotating the rotating frame 131 relative to the lower frame 134, it is possible to adjust the inclination of the rotation mechanism 121 relative to the horizontal direction when viewed from the left-right direction. In other words, by rotating the rotating frame 131 relative to the lower frame 134, it is possible to adjust the inclination of the axis of the printing medium 102 relative to the horizontal direction.

[0140] In this embodiment, when printing on a printing substrate 102 having a cylindrical outer shape, the axis of the printing substrate 102 is aligned with the front-to-rear direction (see FIG. 15 ). On the other hand, when printing on a printing substrate 102 having a truncated cone or conical outer shape, the axis of the printing substrate 102 is tilted relative to the front-to-rear direction (see FIG. 16 ). In other words, the tilt of the rotation mechanism 121 is adjusted when printing on the outer peripheral surface of a printing substrate 102 having a truncated cone or conical outer shape. Specifically, the tilt of the rotation mechanism 121 is adjusted so that the top end of the printing substrate 102 is parallel to the front-to-rear direction.

[0141] The ultraviolet irradiator 122 is equipped with an LED substrate on which a large number of LED chips that emit ultraviolet light are mounted. The ultraviolet irradiator 122 is disposed on the left side of the substrate 102. The ultraviolet irradiator 122 irradiates the substrate 102 with ultraviolet light from the left side immediately after ink has been ejected onto it. In this embodiment, the vertical position of the ultraviolet irradiator 122 is adjustable. In addition, the horizontal position of the ultraviolet irradiator 122 and the inclination of the ultraviolet irradiator 122 with respect to the axis of the substrate 102 when viewed from the vertical direction are adjustable. In this embodiment, when printing on a substrate 102 that has a cylindrical outer shape, the ultraviolet irradiator 122 is installed so that the ultraviolet light emission surface of the ultraviolet irradiator 122 is parallel to the front-to-rear direction. In addition, when printing on a substrate 102 having a truncated cone or conical outer shape, the inclination of the ultraviolet irradiator 122 is adjusted so that the ultraviolet light emission surface of the ultraviolet irradiator 122 is parallel to the left edge of the substrate 102.

[0142] (Method of controlling printing device) Fig. 17 is a schematic diagram for explaining a cross section of the printing medium 102 after printing by the printing device 101 shown in Fig. 11. Fig. 18 is a schematic diagram for explaining the vertical distance between the portion where ink ejected from the head 103 shown in Fig. 11 lands and the ink ejection surface 103c of the head 103. Fig. 19 is a timing chart for explaining the ink ejection timing when printing is performed on the printing medium 102 by the printing device 101 shown in Fig. 11.

[0143] As described above, when printing is performed on the print substrate 102 by the printing device 101, print data sent from the PC 118 is input to the control unit 114. The control unit 114 performs printing on the print substrate 102 based on the input print data. The printing device 101 of this embodiment prints a plurality of ink layers L1, L2 on the outer peripheral surface of the print substrate 102 by overlapping them. The ink layers L1, L2 are made of ultraviolet-curable ink.

[0144] For simplicity of explanation, the following describes an example of a control method for the printing device 101 when two ink layers L1 and L2 are printed on the outer peripheral surface of the print substrate 102 in this order from the inner periphery to the outer periphery of the print substrate 102. Three or more ink layers may be printed on the outer peripheral surface of the print substrate 102. Note that when the printing area of ​​an image or the like to be printed on the outer peripheral surface of the print substrate 102 is large, multiple ink layers L1 and L2 are printed on the outer peripheral surface of the print substrate 102 in overlapping fashion. In this case, for example, the ink layer L1 is a so-called solid white lower layer made of white ink.

[0145] When printing on the print medium 102, the control unit 114 generates an ejection trigger signal for starting the ejection of ink from the nozzle 103a of the head 103 based on the output signal of the encoder 132 (see FIG. 19 ). Specifically, the control unit 114 generates the ejection trigger signal when the count number of encoder pulses reaches a predetermined value. The control unit 114 also transmits a drive signal to the piezoelectric element 116 for ejecting ink from the nozzle 103a based on the ejection trigger signal. Specifically, the control unit 114 transmits a drive signal to the piezoelectric element 116 for ejecting one dot of ink from the nozzle 103a based on the ejection trigger signal, thereby ejecting ink from the nozzle 103a.

[0146] As described above, in this embodiment, the carriage 107 is stopped at a fixed position, and the print substrate 102 is rotated while printing multiple ink layers L1, L2 on the outer peripheral surface of the print substrate 102. When printing two ink layers L1, L2 on the outer peripheral surface of the print substrate 102, the outer diameter of the print substrate 102, including the ink layers L1, L2, varies depending on the ink layers L1, L2 printed on the outer peripheral surface of the print substrate 102. Furthermore, if the outer diameter of the print substrate 102, including the ink layers L1, L2, varies, when the print substrate 102 is rotated at a constant rotational speed, the circumferential speed (the speed in the circumferential direction of the print substrate 102) of the portion where the ink ejected from the head 103 lands will vary.

[0147] For example, as shown in Figure 18, if the portion of the outer surface of the substrate 102 where the ink ejected from the head 103 lands when no ink layer is printed on the outer surface of the substrate 102 is designated as landing portion P1, and if the portion of the surface of the ink layer L1 where the ink ejected from the head 103 lands when only the ink layer L1 is printed on the outer surface of the substrate 102 is designated as landing portion P2, the circumferential speed of landing portion P2 when the substrate 102 is rotated at a constant rotational speed will be faster than the circumferential speed of landing portion P1.

[0148] Furthermore, when two ink layers L1, L2 are printed on top of each other on the outer peripheral surface of the print substrate 102, the outer diameter of the print substrate 102 including the ink layers L1, L2 varies depending on the ink layers L1, L2 printed on the outer peripheral surface of the print substrate 102, and this causes a change in the distance between the landing portions P1, P2 and the ink ejection surface 103c of the head 103. In other words, the distance D1 between the landing portion P1 and the ink ejection surface 103c is longer than the distance D2 between the landing portion P2 and the ink ejection surface 103c.

[0149] Therefore, when printing two ink layers L1 and L2 on top of each other on the outer peripheral surface of the substrate 102 while rotating the substrate 102, if the substrate 102 is rotated at a constant rotational speed, ink is ejected from the nozzle 103a at a constant speed, and the time from the generation of the ejection trigger signal to the ejection of ink from the nozzle 103a (i.e., the timing of ink ejection from the nozzle 103a) is made the same, the ink landing position when printing ink layer L1 and the ink landing position when printing ink layer L2 will be shifted in the circumferential direction of the substrate 102.

[0150] In this embodiment, in order to suppress deviation in the ink landing position, when printing on the print substrate 102, the control unit 114 first calculates the number of ink layers L1, L2 printed on the outer peripheral surface of the print substrate 102. For example, the control unit 114 calculates the number of printed ink layers L1, L2 printed on the outer peripheral surface of the print substrate 102 based on at least one of the following data: the amount of rotation of the print substrate 102 calculated based on the detection result of the encoder 132, the print data input to the control unit 114, and the number of drive signals sent to the piezoelectric element 116 (i.e., the number of times the piezoelectric element 116 is driven (the number of times ink is ejected from the nozzle 103 a)).

[0151] The control unit 114 also performs at least one of the following controls: motor rotation speed control, which controls the rotation speed of the motor 125 based on the calculated number of ink layers L1, L2 (i.e., in accordance with the number of ink layers L1, L2 that overlap on the outer circumferential surface of the print medium 102); ink ejection speed control, which controls the ink ejection speed from the nozzle 103 a by the piezoelectric element 116 based on the calculated number of ink layers L1, L2; and ink ejection timing control, which controls the timing of ink ejection from the nozzle 103 a by the piezoelectric element 116 based on the calculated number of ink layers L1, L2. In this embodiment, the control unit 114 performs all of the motor rotation speed control, ink ejection speed control, and ink ejection timing control.

[0152] In the motor rotation speed control, the control unit 114 changes the rotation speed of the motor 125 when printing ink layer L1 and when printing ink layer L2. That is, in the motor rotation speed control, the control unit 114 changes the rotation speed of the motor 125 depending on which ink layer L1 or L2 is being printed. Specifically, the control unit 114 makes the rotation speed of the motor 125 when printing ink layer L2 slower than the rotation speed of the motor 125 when printing ink layer L1. That is, the control unit 114 makes the rotation speed of the printing medium 102 when printing ink layer L2 slower than the rotation speed of the printing medium 102 when printing ink layer L1.

[0153] In ink ejection speed control, the control unit 114 controls the voltage applied to the piezoelectric element 116, thereby controlling the ink ejection speed from the nozzle 103a by the piezoelectric element 116. Furthermore, in ink ejection speed control, the control unit 114 changes the ink ejection speed when printing ink layer L1 and the ink ejection speed when printing ink layer L2. That is, in ink ejection speed control, the control unit 114 changes the ink ejection speed depending on which ink layer is being printed. Specifically, the control unit 114 makes the ink ejection speed when printing ink layer L2 slower than the ink ejection speed when printing ink layer L1.

[0154] In the ink ejection timing control, the control unit 114 controls the ink ejection timing from the nozzle 103a by controlling the ink ejection start time from the point in time when the ejection trigger signal is generated. Also, in the ink ejection timing control, the control unit 114 changes the ink ejection timing when printing the ink layer L1 and the ink ejection timing when printing the ink layer L2. That is, in the ink ejection timing control, the control unit 114 changes the ink ejection timing depending on which ink layer is being printed. Specifically, the control unit 114 delays the ink ejection timing when printing the ink layer L2 compared to the ink ejection timing when printing the ink layer L1.

[0155] As described above, for example, two ink layers L1 and L2 are printed on the outer peripheral surface of the print substrate 102. In this embodiment, the ultraviolet-curable ink constituting ink layer L1 has a different ultraviolet transmittance from the ultraviolet-curable ink constituting ink layer L2. That is, ink layers L1 and L2 with different ultraviolet transmittances are stacked on top of each other on the outer peripheral surface of the print substrate 102. Specifically, the ultraviolet transmittance of the upper ink layer L2 (on the outer peripheral side) is higher than the ultraviolet transmittance of the lower ink layer L1 (on the inner peripheral side).

[0156] The control unit 114 stores in advance the ultraviolet transmittance of each of the ink layers L1 and L2. That is, the control unit 114 stores in advance the ultraviolet transmittance of the ink constituting the ink layer L1 and the ultraviolet transmittance of the ink constituting the ink layer L2. When printing on the print substrate 102, the control unit 114 ejects ink from the head 103 based on the ultraviolet transmittances of the ink layers L1 and L2 stored in the control unit 114 and the print data input to the control unit 114, so that the ultraviolet transmittance of the ink layer L2 arranged on the outer periphery of the print substrate 102 is higher than the ultraviolet transmittance of the ink layer L1 arranged on the inner periphery of the print substrate 102.

[0157] When printing the ink layer L1, the control unit 114 moves the carriage 107 and the head 103 so that the nozzles 103a that eject the ink that constitutes the ink layer L1 are positioned directly above the print substrate 102. When printing the ink layer L2, the control unit 114 moves the carriage 107 and the head 103 so that the nozzles 103a that eject the ink that constitutes the ink layer L2 are positioned directly above the print substrate 102.

[0158] (Major Effects of the Present Embodiment) As described above, in the present embodiment, the control unit 114 calculates the number of ink layers printed on the outer peripheral surface of the print substrate 102 during printing on the print substrate 102, and executes motor rotation speed control, ink ejection speed control, and ink ejection timing control based on the calculation result of the number of ink layers. Therefore, in the present embodiment, it is possible to suppress deviation of the ink landing position in the circumferential direction of the print substrate 102, regardless of the number of ink layers printed on the outer peripheral surface of the print substrate 102. Therefore, in the present embodiment, it is possible to ensure the print quality of the print substrate 102, even when printing multiple ink layers L1, L2 on top of each other on the outer peripheral surface of the print substrate 102 while rotating the print substrate 102.

[0159] In particular, in this embodiment, the control unit 114 executes all of the motor rotation speed control, ink ejection speed control, and ink ejection timing control during printing on the print substrate 102, making it possible to effectively suppress deviations in the ink landing position in the circumferential direction of the print substrate 102, regardless of the number of ink layers already printed on the outer peripheral surface of the print substrate 102. Therefore, in this embodiment, it is possible to improve the print quality of the print substrate 102, even when printing multiple ink layers L1, L2 on top of each other on the outer peripheral surface of the print substrate 102 while rotating the print substrate 102.

[0160] In this embodiment, the control unit 114 ejects ink from the head 103 to print on the print substrate 102 based on the ultraviolet transmittances of the ink layers L1 and L2 stored in the control unit 114 and the print data input to the control unit 114, such that the ultraviolet transmittance of the ink layer L2 arranged on the outer periphery of the print substrate 102 is higher than the ultraviolet transmittance of the ink layer L1 arranged on the inner periphery of the print substrate 102. Therefore, in this embodiment, after printing the ink layer L2, when the ultraviolet irradiator 122 irradiates ultraviolet light toward the surface of the ink layer L2, it is possible for the ultraviolet light to reach the ink layer L1 arranged on the inner periphery of the print substrate 102. Therefore, in this embodiment, even if the time for which the ultraviolet irradiator 122 irradiates ultraviolet light toward the surface of the ink layer L1 after printing the ink layer L1 arranged on the inner periphery of the print substrate 102 is shortened, it is possible to ensure the integrated light amount of ultraviolet light irradiated onto the ink layer L1 and cure the ink layer L1. As a result, in this embodiment, it is possible to reduce the printing time for the printing medium 102.

[0161] (Other Modifications) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this and various modifications can be made within the scope that does not change the gist of the present invention.

[0162] In the above-described embodiment, the control unit 114 may execute two controls arbitrarily selected from motor rotation speed control, ink ejection speed control, and ink ejection timing control when printing on the print substrate 102. Also, in the above-described embodiment, the control unit 114 may execute only one of motor rotation speed control, ink ejection speed control, and ink ejection timing control when printing on the print substrate 102. Even in these cases, it is possible to suppress deviations in the ink landing positions in the circumferential direction of the print substrate 102, regardless of the number of ink layers that have already been printed on the outer peripheral surface of the print substrate 102.

[0163] In the embodiment described above, the rotation mechanism 121 may be provided with an encoder for detecting the rotational position and rotational speed of the motor 125, instead of the encoder 132. In this case, the control unit 114 calculates the number of printed ink layers printed on the outer peripheral surface of the printing medium 102, for example, based on the amount of rotation of the motor 125 calculated based on the detection result of the encoder during printing on the printing medium 102.

[0164] In the above-described embodiment, the control unit 114 may perform printing on the print medium 102 by ejecting ink from the head 103 so that the ultraviolet transmittance of the ink layer L2 arranged on the outer periphery of the print medium 102 is lower than the ultraviolet transmittance of the ink layer L1 arranged on the inner periphery of the print medium 102. Also, in the above-described embodiment, the ultraviolet transmittance of the ink layer L2 may be made equal to the ultraviolet transmittance of the ink layer L1.

[0165] In the above-described embodiment, if only printing on a substrate 102 having a fixed outer diameter is performed by the printing device 101, the vertical position of the ultraviolet irradiator 122 does not have to be adjustable. Also, in the above-described embodiment, if only printing on a substrate 102 having a cylindrical outer shape is performed by the printing device 101, the inclination of the rotation mechanism 121 with respect to the horizontal direction when viewed from the left and right does not have to be adjustable, and the inclination of the ultraviolet irradiator 122 with respect to the axis of the substrate 102 when viewed from the top and bottom does not have to be adjustable.

[0166] In the above-described embodiment, the ultraviolet irradiation device 104 may be placed on the table 105 so that the direction of the axis of the print medium 102 when viewed from the top-bottom direction coincides with the left-right direction. Also, in the above-described embodiment, the ultraviolet irradiator 122 may be disposed below the print medium 102. Furthermore, in the above-described embodiment, the printing apparatus 101 may be provided with a Y-bar drive mechanism that moves the Y-bar 108 in the sub-scanning direction instead of the stage drive mechanism 112. Also, in the above-described embodiment, the ejection energy generating element for ejecting ink from the nozzle 103 a may be a heater (heat generating element). Also, in the above-described embodiment, the printing apparatus 101 may have only one head 103.

[0167] Third Embodiment A third embodiment of the present invention will now be described with reference to the drawings.

[0168] (Overall configuration of printing device) Fig. 20 is a front view illustrating the configuration of a printing device 201 according to a third embodiment of the present invention. Fig. 21 is a block diagram illustrating the configuration of the printing device 201 shown in Fig. 20. Fig. 22(A) is a bottom view of the inkjet head 203 and carriage 207 shown in Fig. 20, and Fig. 22(B) is a bottom view illustrating the configuration of the inkjet head 203 shown in Fig. 22(A).

[0169] The printing device 201 of this embodiment is a device for printing on the outer peripheral surface of a printing substrate 202 having a cylindrical, truncated conical, or conical outer shape, and is, for example, a commercial inkjet printer. The printing device 201 prints on the outer peripheral surface of the printing substrate 202 using ultraviolet-curable ink. The printing substrate 202 is formed, for example, in a cylindrical shape. That is, the printing substrate 202 is formed in a cylindrical, truncated conical, or conical cylindrical shape. The printing substrate 202 is also formed, for example, from resin. The printing device 201 is capable of printing on multiple types of printing substrates 202 with different outer diameters and lengths.

[0170] The printing device 201 includes inkjet heads 203 (hereinafter referred to as "heads 203") that eject ultraviolet-curable ink toward the outer peripheral surface of the print medium 202. The printing device 201 of this embodiment includes multiple heads 203. Specifically, the printing device 201 includes four heads 203. The printing device 201 also includes an ultraviolet irradiation device 204 for curing the ink ejected onto the outer peripheral surface of the print medium 202, a stage 206 having a table 205 on which the ultraviolet irradiation device 204 is placed, a carriage 207 on which the multiple heads 203 are mounted, a Y-bar 208 that holds the carriage 207 so as to enable movement in a main scanning direction perpendicular to the up-down direction (vertical direction), and a main body frame 209 that holds the stage 206 so as to enable movement in a sub-scanning direction perpendicular to the up-down direction and the main scanning direction.

[0171] The printing device 201 also includes a carriage drive mechanism 211 that moves the carriage 207 in the main scanning direction relative to the Y bar 208, a stage drive mechanism 212 that moves the stage 206 in the sub-scanning direction relative to the main frame 209, a table lifting mechanism 213 that raises and lowers the table 205, a control unit 214 that controls the printing device 201, and a position detection mechanism 215 that detects the position of the stage 206 in the sub-scanning direction.

[0172] The carriage drive mechanism 211 includes, for example, a motor as a drive source and a power transmission mechanism such as a belt and pulleys that transmits the power of the motor to the carriage 207. The stage drive mechanism 212 includes, for example, a motor 216 as a drive source and a power transmission mechanism such as a belt and pulleys that transmits the power of the motor 216 to the stage 206. The stage drive mechanism 212 moves the table 205 in the sub-scanning direction together with the stage 206. The table lifting mechanism 213 includes, for example, a motor as a drive source and a power transmission mechanism such as a ball screw that transmits the power of the motor to the table 205.

[0173] In the following description, the sub-scanning direction (X direction in Fig. 20, etc.) is the front-to-rear direction, and the main scanning direction (Y direction in Fig. 20, etc.) is the left-to-right direction. In the following description, the X1 direction side in Fig. 24, etc., which is one side of the front-to-rear direction, is referred to as the "front" side, the X2 direction side in Fig. 24, etc., which is the opposite side, is referred to as the "rear" side, the Y1 direction side in Fig. 23, etc., which is one side of the left-to-right direction, is referred to as the "right" side, and the Y2 direction side in Fig. 23, etc., which is the opposite side, is referred to as the "left" side.

[0174] The upper surface of the table 205 is a plane perpendicular to the up-down direction. The ultraviolet irradiation device 204 placed on the table 205 is arranged below the head 203. The printing medium 202 is held by the ultraviolet irradiation device 204 and arranged below the head 203. In other words, the head 203 is arranged above the printing medium 202. The head 203 ejects ink downward. The ink ejected by the head 203 lands on the outer peripheral surface of the printing medium 202 at the upper end of the printing medium 202.

[0175] The head 203 is formed with a plurality of nozzles 203a that eject ink. Specifically, the large number of nozzles 203a are formed on the bottom surface of the head 203. The bottom surface of the head 203 is an ink ejection surface 203c on which the plurality of nozzles 203a (specifically, the large number of nozzles 203a) are formed. On the ink ejection surface 203c, a nozzle row 203b is formed by the large number of nozzles 203a that are arranged in the sub-scanning direction (front-back direction). On the ink ejection surface 203c, a plurality of nozzle rows 203b that are arranged in the main scanning direction (left-right direction) are formed. The head 203 is equipped with a plurality of piezoelectric elements (piezo elements) that eject ink from each of the plurality of nozzles 203a.

[0176] 22A , for example, three of the four heads 203 mounted on a carriage 207 are disposed at the same position in the front-to-rear direction and are arranged in the left-to-right direction. The remaining head 203 is disposed at a position offset from the three heads 203 in the front-to-rear direction. Three of the four heads 203 eject color inks, and the remaining head 203 ejects white ink. The viscosity of the white ink is higher than the viscosity of the color inks.

[0177] The position detection mechanism 215 is, for example, an encoder (rotary encoder) for detecting the rotational position and rotational speed of the motor 216. The position detection mechanism 215 detects the position of the stage 206 in the sub-scanning direction (front-to-back direction) based on the amount of rotation of the motor 216. The position detection mechanism 215 and the motor 216 are electrically connected to the control unit 214. A PC (personal computer) 218 ​​is also electrically connected to the control unit 214. The PC 218 generates print data for printing on the print substrate 202. When printing on the print substrate 202, the print data generated by the PC 218 is transmitted from the PC 218 to the control unit 214. That is, when printing on the print substrate 202, the print data transmitted from the PC 218 is input to the control unit 214.

[0178] (Configuration of ultraviolet irradiation device) Fig. 23 is a front view for explaining the configuration of the ultraviolet irradiation device 204 shown in Fig. 20. Figs. 24 and 25 are side views for explaining the configuration of the rotation mechanism 221 shown in Fig. 23. Fig. 26 is a diagram for explaining the configuration of the LED substrate 236 shown in Fig. 23, etc.

[0179] The ultraviolet irradiation device 204 includes a rotation mechanism 221 that holds the print substrate 202 and rotates the print substrate 202 around the axis of the print substrate 202, an ultraviolet irradiator 222 that irradiates ultraviolet rays toward the outer peripheral surface of the print substrate 202 to which ink is attached, and a cover 223 that covers the rotation mechanism 221 and the ultraviolet irradiator 222 from above. The cover 223 has an opening 223a through which the upper end of the print substrate 202 is positioned. The ultraviolet irradiation device 204 is placed on the table 205 so that the direction of the axis of the print substrate 202 when viewed from the top and bottom coincides with the front-to-back direction. In other words, the direction of the axis of the print substrate 202 when viewed from the top and bottom coincides with the front-to-back direction, and the sub-scanning direction is parallel to the axis of the print substrate 202 when viewed from the top and bottom. The nozzle row 203 b that ejects ink toward the print medium 202 when printing on the print medium 202 is disposed directly above the print medium 202 .

[0180] The rotation mechanism 221 rotates the printing substrate 202 when printing on the printing substrate 202. In this embodiment, printing is performed on the printing substrate 202 while the rotation mechanism 221 rotates the printing substrate 202 with the stage 206 and carriage 207 stopped at a fixed position. When printing on the printing substrate 202, the rotation mechanism 221 rotates the printing substrate 202 in a counterclockwise direction when viewed from the front, for example. The rotation mechanism 221 includes a motor 225 as a drive source and a power transmission mechanism 226 for transmitting the power of the motor 225 to the printing substrate 202.

[0181] The rotation mechanism 221 also includes a first rotating part 227 that holds one end of the printing medium 202, a first holding part 228 that rotatably holds the first rotating part 227, a second rotating part 229 that holds the other end of the printing medium 202, a second holding part 230 that rotatably holds the second rotating part 229, a rotating frame 231 to which the first holding part 228 and the second holding part 230 are attached, and an encoder (rotary encoder) 232 for detecting the rotational position and rotational speed of the printing medium 202. Note that the power transmission mechanism 226 and the like are not shown in Figure 23.

[0182] The first rotating unit 227 and the second rotating unit 229 rotate together with the printing substrate 202. The first rotating unit 227 holds the rear end of the printing substrate 202, and the second rotating unit 229 holds the front end of the printing substrate 202. The power transmission mechanism 226 connects the first rotating unit 227 to the motor 225. The power transmission mechanism 226 includes a gear train 233. The gear train 233 includes a drive gear fixed to the output shaft of the motor 225 and a driven gear fixed to the first rotating unit 227. The encoder 232 is connected to the rear end of the first rotating unit 227. The second holding unit 230 is movable in the direction of the axis of the printing substrate 202. In this embodiment, the positions of the second rotating unit 229 and the second holding unit 230 in the direction of the axis of the printing substrate 202 are adjusted according to the length of the printing substrate 202. The power transmission mechanism 226 may be configured by a pulley, a belt, or the like.

[0183] The rotating frame 231 is rotatable with the left-right direction as the axis of rotation relative to a lower frame 234 that constitutes the bottom surface of the ultraviolet irradiation device 204. The rotating frame 231 is also rotatable with the rear end of the rotating frame 231 as the rotation center relative to the lower frame 234. In this embodiment, by rotating the rotating frame 231 relative to the lower frame 234, it is possible to adjust the inclination of the rotation mechanism 221 with respect to the horizontal direction when viewed from the left-right direction. In other words, by rotating the rotating frame 231 relative to the lower frame 234, it is possible to adjust the inclination of the axis of the printing medium 202 with respect to the horizontal direction.

[0184] In this embodiment, when printing on a printing substrate 202 having a cylindrical outer shape, the axis of the printing substrate 202 is aligned with the front-to-rear direction (see FIG. 24). On the other hand, when printing on a printing substrate 202 having a truncated cone or conical outer shape, the axis of the printing substrate 202 is tilted relative to the front-to-rear direction (see FIG. 25). In other words, the tilt of the rotation mechanism 221 is adjusted when printing on the outer peripheral surface of a printing substrate 202 having a truncated cone or conical outer shape. Specifically, the tilt of the rotation mechanism 221 is adjusted so that the top end of the printing substrate 202 is parallel to the front-to-rear direction.

[0185] The ultraviolet irradiator 222 includes an LED substrate 236 on which a number of light-emitting elements that emit ultraviolet light (ultraviolet light) are mounted. The light-emitting elements are LED chips (UVLED chips). The ultraviolet irradiator 222 is disposed on the left side of the substrate 202. The ultraviolet irradiator 222 irradiates the substrate 202 with ultraviolet light from the left side immediately after ink has landed thereon. In this embodiment, the vertical position of the ultraviolet irradiator 222 is adjustable. Furthermore, the horizontal position of the ultraviolet irradiator 222 and the inclination of the ultraviolet irradiator 222 relative to the axis of the substrate 202 when viewed from the vertical direction are adjustable. In this embodiment, when printing on a substrate 202 having a cylindrical outer shape, the ultraviolet irradiator 222 is installed so that the ultraviolet light emission surface of the ultraviolet irradiator 222 (i.e., the ultraviolet light emission surface of the LED substrate 236) is parallel to the front-to-rear direction. In addition, when printing on a substrate 202 having a truncated cone or conical outer shape, the inclination of the ultraviolet irradiator 222 is adjusted so that the ultraviolet light emission surface of the ultraviolet irradiator 222 is parallel to the left edge of the substrate 202.

[0186] As described above, the stage driving mechanism 212 moves the table 205, on which the ultraviolet irradiation device 204 is placed, together with the stage 206 in the front-to-rear direction. In this embodiment, the relative positions of the rotation mechanism 221 and the ultraviolet irradiator 222 in the front-to-rear direction do not change. That is, in this embodiment, the relative positions of the printing medium 202 held by the rotation mechanism 221 and the ultraviolet irradiator 222 in the front-to-rear direction do not change. The stage driving mechanism 212 in this embodiment is a moving mechanism that moves the head 203 in the sub-scanning direction relative to the rotation mechanism 221 and the ultraviolet irradiator 222. Also, as described above, the position detection mechanism 215 detects the position of the stage 206 in the front-to-rear direction based on the amount of rotation of the motor 216. That is, the position detection mechanism 215 in this embodiment is provided to detect the relative position of the head 203 in the sub-scanning direction relative to the rotation mechanism 221 and the ultraviolet irradiator 222.

[0187] The LED board 236 is formed in the shape of a long, narrow rectangular plate. The LED board 236 is arranged so that the thickness direction of the LED board 236 coincides with the left-right direction. When viewed from the left-right direction, the LED board 236 is arranged so that the direction of the short side of the rectangular LED board 236 coincides with the up-down direction and the direction of the long side of the LED board 236 coincides with the front-to-back direction. The ultraviolet light emission surface of the LED board 236 faces to the right. The LED board 236 in this embodiment serves as an ultraviolet light irradiation unit that irradiates ultraviolet light from the ultraviolet irradiator 222.

[0188] The front-to-rear length of the LED board 236 is longer than the front-to-rear length of the printing medium 202 when it is attached to the rotation mechanism 221. If the portion (range) of the printing medium 202 where printing is performed is defined as the printing portion 202a (see FIG. 26 ), the length of the printing portion 202a is equal to or shorter than the length of the printing medium 202. In other words, the front-to-rear length of the LED board 236 is longer than the front-to-rear length of the printing portion 202a when the printing medium 202 is attached to the rotation mechanism 221. Furthermore, the front-to-rear length of the LED board 236 is longer than the front-to-rear length of the longest printing medium 202 among the printing mediums 202 on which printing is performed by the printing device 201.

[0189] The width of the head 203 in the front-to-rear direction is narrower than the length of the printing portion 202a in the front-to-rear direction when the printing medium 202 is attached to the rotation mechanism 221. In other words, the length of the printing portion 202a in the front-to-rear direction is longer than the width of the head 203 in the front-to-rear direction. Therefore, when printing on the printing medium 202, the printing medium 202 is moved in stages in the front-to-rear direction (sub-scanning direction) together with the table 205, the rotation mechanism 221, etc., and printing is performed sequentially on the outer peripheral surface of the printing medium 202.

[0190] The LED substrate 236 is divided into a plurality of blocks in the front-to-rear direction and is composed of a plurality of divided irradiation sections 237 to 248 divided in the front-to-rear direction. In this embodiment, the LED substrate 236 is composed of 12 divided irradiation sections 237 to 248. The divided irradiation sections 237 to 248 are arranged in this order, for example, from the front to the rear. The divided irradiation sections 237 to 248 have the same width in the front-to-rear direction. Note that the LED substrate 236 may be composed of 13 or more divided irradiation sections, or may be composed of a plurality of divided irradiation sections less than 11.

[0191] Each of the divided irradiation units 237 to 248 is electrically connected to the control unit 214. That is, the divided irradiation units 237 to 248 are individually connected to the control unit 214. The divided irradiation units 237 to 248 are current-controlled by the control unit 214. In this embodiment, the control unit 214 is capable of individually current-controlling the divided irradiation units 237 to 248. That is, the 12 divided irradiation units 237 to 248 can be individually turned on, and the control unit 214 turns each of the divided irradiation units 237 to 248 on or off individually. Furthermore, the intensity (illuminance) of the ultraviolet light emitted from the 12 divided irradiation units 237 to 248 can be individually adjusted.

[0192] (Control Method of LED Board) As described above, when printing on the print substrate 202, print data transmitted from the PC 218 is input to the control unit 214. The control unit 214 prints on the print substrate 202 based on the input print data. Also, as described above, when printing on the print substrate 202, the print substrate 202 is moved in stages in the front-to-rear direction together with the table 205, the rotation mechanism 221, etc., to sequentially print on the outer circumferential surface of the print substrate 202. For example, the print substrate 202 is moved in stages from the rear side to the front side, and printing is sequentially performed on the outer circumferential surface of the print substrate 202 from the front side to the rear side of the print substrate 202. That is, with the print substrate 202 stopped at a fixed position in the front-to-rear direction, the print substrate 202 is rotated by the rotation mechanism 221, and ink is ejected from the head 203 stopped at a fixed position to first print on the front portion of the print substrate 202a, as shown in FIG. 26(A) .

[0193] Thereafter, the printing substrate 202 is moved forward a predetermined distance together with the stage 206, table 205, etc. and stopped (i.e., the head 203 is moved backward relatively to the printing substrate 202 and stopped (see FIG. 26(B))), and while the printing substrate 202 is again rotated by the rotation mechanism 221, ink is ejected from the head 203, which has been stopped at a fixed position, to perform printing on the middle portion of the printing section 202a. Thereafter, in the same manner, the printing substrate 202 is moved forward a predetermined distance and stopped (i.e., the head 203 is moved backward relatively to the printing substrate 202 and stopped (see FIG. 26(C))), and while the printing substrate 202 is again rotated by the rotation mechanism 221, ink is ejected from the head 203, which has been stopped at a fixed position, to perform printing on the rear portion of the printing section 202a.

[0194] When printing on the substrate 202, the ultraviolet irradiator 222 irradiates the substrate 202 with ultraviolet light. Specifically, when printing on the substrate 202, the LED board 236 irradiates the substrate 202 with ultraviolet light. A method for controlling the LED board 236 when printing on the substrate 202 will be described below. In the following description, as an example, a method for controlling the LED board 236 will be described when the total front-to-rear width of the three divided irradiation units 237 to 248 is equal to the front-to-rear width of the head 203. In addition, the following description will describe a method for controlling the LED board 236 when the substrate 202 and the LED board 236 are moved forward in stages by a distance equal to the front-to-rear width of the head 203 (i.e., when the head 203 is moved backward in stages relative to the substrate 202 and the LED board 236), as shown in FIG. 26 .

[0195] When printing on the print medium 202, the control unit 214 controls the lighting range of the LED board 236 in the front-to-rear direction based on the detection result of the position detection mechanism 215. Specifically, when printing on the print medium 202, the control unit 214 selects a divided irradiation unit to be lit from among the divided irradiation units 237 to 248 based on the relative position in the front-to-rear direction of the head 203 with respect to the rotation mechanism 221 and the ultraviolet irradiator 222 (i.e., the relative position in the front-to-rear direction of the head 203 with respect to the print medium 202 and the LED board 236) that is specified based on the detection result of the position detection mechanism 215, and turns on the selected divided irradiation units 237 to 248.

[0196] In this embodiment, the front end of head 203, which is one end of head 203 in the sub-scanning direction, is designated as first head end 203e, the rear end of head 203, which is the other end of head 203 in the sub-scanning direction, is designated as second head end 203f, and the range between first head end 203e and second head end 203f in the sub-scanning direction is designated as head placement range S. Control unit 214 lights up divided irradiation units 237 to 248 of LED board 236, at least a portion of which is included within head placement range S.

[0197] For example, as shown in FIG. 26A, when printing is performed on the front portion of the printing target portion 202a, the control unit 214 turns on divided irradiation units 238 and 239, which are entirely included within the head arrangement range S, and divided irradiation units 237 and 240, which are partially included within the head arrangement range S. That is, the control unit 214 turns on all divided irradiation units 237 to 240, at least partially included within the head arrangement range S (divided irradiation units 237 to 240 shown hatched in FIG. 26A). At this time, the control unit 214 does not turn on the remaining divided irradiation units 241 to 248. That is, at this time, only divided irradiation units 237 to 240 are turned on, and the remaining divided irradiation units 241 to 248 are turned off.

[0198] Furthermore, when printing is performed on the middle portion of the printing area 202a, as shown in FIG. 26(B), the control unit 214 lights up the divided irradiation units 241 and 242 whose entirety is included within the head placement range S, and the divided irradiation units 240 and 243 whose part is included within the head placement range S (i.e., lights up all of the divided irradiation units 240 to 243 hatched in FIG. 26(B)), and does not light up the remaining divided irradiation units 237 to 239, 244 to 248. Furthermore, when printing on the rear portion of the printing target portion 202a, as shown in Figure 26 (C), the control unit 214 lights up the divided irradiation units 244 and 245, which are entirely within the head placement range S, and the divided irradiation units 243 and 246, which are partially within the head placement range S (i.e., all of the divided irradiation units 243 to 246 hatched in Figure 26 (C) are turned on), and does not light up the remaining divided irradiation units 237 to 242, 247, 248.

[0199] 26(D), for example, when first head end 203e is disposed at the same position as the boundary between divided irradiation units 237 and 238 in the front-to-rear direction, control unit 214 also lights up divided irradiation units 237 that are not included in head arrangement range S. In other words, when first head end 203e is disposed at the same position as the boundary between two divided irradiation units 237, 238 in the sub-scanning direction, control unit 214 also lights up divided irradiation units 237 that are in contact with the boundary between divided irradiation units 237, 238 and are disposed outside (i.e., in front of) first head end 203e in the sub-scanning direction.

[0200] 26(D), for example, when second head end 203f is arranged at the same position as the boundary between divided irradiation units 240 and 241 in the front-to-rear direction, control unit 214 also turns on divided irradiation units 241 that are not included in head arrangement range S. In other words, when second head end 203f is arranged at the same position as the boundary between two divided irradiation units 240, 241 in the sub-scanning direction, control unit 214 also turns on divided irradiation units 241 that are in contact with the boundary between divided irradiation units 240, 241 and that are arranged outside (i.e., behind) second head end 203f in the sub-scanning direction.

[0201] (Major Effects of the Present Embodiment) As described above, in the present embodiment, the LED substrate 236 is composed of a plurality of divided irradiation units 237-248 that are divided in the front-rear direction, and the plurality of divided irradiation units 237-248 can be individually turned on. Also, in the present embodiment, the control unit 214 controls the lighting range of the LED substrate 236 in the front-rear direction based on the detection results of the position detection mechanism 215 during printing on the print medium 202. Specifically, as shown in Figures 26(A) to 26(C), the control unit 214 lights up the divided irradiation units 237-248 of the LED substrate 236 that are at least partially included within the head arrangement range S, and does not light up the remaining divided irradiation units 237-248.

[0202] Furthermore, as shown in FIG. 26 (D), when the first head end 203e is positioned at the same position as the boundary between the two divided irradiation units 237 to 248 in the front-to-back direction, or when the second head end 203f is positioned at the same position as the boundary between the two divided irradiation units 237 to 248 in the front-to-back direction, the control unit 214 lights up not only the divided irradiation units 237 to 248 that are at least partially included within the head placement range S, but also the divided irradiation units 237 to 248 that are in contact with the boundary between the two divided irradiation units 237 to 248 and are positioned outside the first head end 203e and the second head end 203f in the front-to-back direction.

[0203] Therefore, in this embodiment, it is possible to light up only the portion of the LED board 236 that is necessary for curing the ink. Therefore, in this embodiment, even if the length of the LED board 236 in the front-rear direction is longer than the length of the printing portion 202a in the front-rear direction and the width of the head 203 in the front-rear direction is narrower than the length of the printing portion 202a in the sub-scanning direction, it is possible to prevent excessive ultraviolet light from being irradiated onto the outer circumferential surface of the printing medium 202.

[0204] 26A to 26C, the control unit 214 turns on the divided irradiation units 237 to 248 of the LED board 236, at least a part of which is included within the head arrangement range S, so that it is possible to irradiate ultraviolet rays onto the entire part of the printing target 202a immediately after the ink ejected from the head 203 lands. Therefore, in this embodiment, it is possible to properly cure the entire ink that has adhered to that part of the printing target 202a.

[0205] Furthermore, in this embodiment, when the first head end 203e is positioned at the same position as the boundary between the two divided irradiation units 237-248 in the front-to-back direction, or when the second head end 203f is positioned at the same position as the boundary between the two divided irradiation units 237-248 in the front-to-back direction, the control unit 214 not only lights up the divided irradiation units 237-248 that are at least partially included in the head arrangement range S, but also the divided irradiation units 237-248 that are in contact with the boundary between the two divided irradiation units 237-248 and are positioned outside the first head end 203e and the second head end 203f in the front-to-back direction, so that it is possible to reliably irradiate ultraviolet light to the front-to-back edges of a portion of the printed portion 202a immediately after the ink ejected from the head 203 lands. Therefore, in this embodiment, it is possible to properly cure ink that has adhered to the front-to-back edges of a portion of the printed portion 202a.

[0206] In this embodiment, it is possible to individually adjust the intensity of the ultraviolet light emitted from the multiple divided irradiation units 237 to 248. Therefore, in this embodiment, by adjusting the intensity of the ultraviolet light emitted from the divided irradiation units 237 to 248, it is possible to adjust the finish of the image printed on the outer peripheral surface of the printing medium 202.

[0207] (Modification of LED Board Control Method) FIG. 27 is a diagram for explaining a method of controlling the lighting of an LED board 236 according to a modification of the present invention.

[0208] In the embodiment described above, when gloss printing (gloss printing) is performed on the outer peripheral surface of the print substrate 202 using clear ink (transparent ink) ejected from the head 203, the control unit 214 controls the lighting range of the LED board 236 in the front-to-rear direction based on the detection result of the position detection mechanism 215 during printing on the print substrate 202, for example, as follows: In the following explanation, a method of controlling the LED board 236 when the total front-to-rear width of the two divided irradiation units 237 to 248 is equal to the front-to-rear width of the head 203 is described.

[0209] In the following description, the control unit 214 prints the print section P1 by ejecting ink from the head 203 toward the outer periphery of the print substrate 202 while rotating the print substrate 202 with the rotation mechanism 221, with the print substrate 202 stopped at a fixed position in the front-to-back direction (i.e., with the head 203 stopped relative to the print substrate 202 in the sub-scanning direction) (see FIG. 27A ). The control unit 214 then moves the print substrate 202 forward by the width of the head 203 in the front-to-back direction and stops it (i.e., moves the head 203 a predetermined distance relative to the print substrate 202 in the sub-scanning direction and stops it). Then, while rotating the print substrate 202 with the rotation mechanism 221, the control unit 214 ejects ink from the head 203 toward the outer periphery of the print substrate 202, printing the print section P2 (see FIG. 27B ). The control unit 214 then prints the print sections P3 and P4 in the same manner (see FIGS. 27C and 27D ). The width of the printing units P1 to P4 in the front-rear direction is equal to the width of the head 203 in the front-rear direction, for example.

[0210] In the following explanation, the portion of the printed portion 202a where the printed portion P1 is printed will be referred to as divided printed portion 202b, the portion of the printed portion 202a where the printed portion P2 is printed will be referred to as divided printed portion 202c, the portion of the printed portion 202a where the printed portion P3 is printed will be referred to as divided printed portion 202d, and the portion of the printed portion 202a where the printed portion P4 is printed will be referred to as divided printed portion 202e.

[0211] In this embodiment, in the relationship between printing unit P1 and printing unit P2, printing unit P1 is the first printing unit, and printing unit P2 is the second printing unit. Furthermore, in the relationship between printing unit P2 and printing unit P3, printing unit P2 is the first printing unit, and printing unit P3 is the second printing unit. Furthermore, in the relationship between printing unit P3 and printing unit P4, printing unit P3 is the first printing unit, and printing unit P4 is the second printing unit. Furthermore, in this embodiment, in the relationship between divided printed unit 202b and divided printed unit 202c, divided printed unit 202b is the first divided printed unit, and divided printed unit 202c is the second divided printed unit. Furthermore, in the relationship between divided printed unit 202c and divided printed unit 202d, divided printed unit 202c is the first divided printed unit, and divided printed unit 202d is the second divided printed unit. Furthermore, in the relationship between the divided printing portion 202d and the divided printing portion 202e, the divided printing portion 202d is a first divided printing portion, and the divided printing portion 202e is a second divided printing portion.

[0212] When gloss printing is performed on the outer peripheral surface of the printing substrate 202, the control unit 214, during printing of the printing portion P1, causes the LED substrate 236 to irradiate the divided printing portion 202b with ultraviolet light of a first intensity (i.e., a first intensity sufficient to partially cure the ink adhered to the printing portion 202a) toward the divided printing portion 202b. Specifically, as shown in FIG. 27A, the divided irradiation unit 239 (the divided irradiation unit 239 hatched in FIG. 27A) located at the same position in the front-to-back direction as the rear portion of the divided printing portion 202b is turned on to irradiate the divided printing portion 202b with ultraviolet light of the first intensity. At this time, the control unit 214 does not turn on the remaining divided irradiation units 237, 238, 240 to 248. In other words, the remaining divided irradiation units 237, 238, 240 to 248 are turned off.

[0213] Furthermore, during printing of the printing portion P2, the control unit 214 causes the LED substrate 236 to irradiate the divided printing portion 202c with ultraviolet light of a first intensity, and causes the LED substrate 236 to irradiate the divided printing portion 202b with ultraviolet light of a second intensity higher than the first intensity. Specifically, as shown in FIG. 27B , a divided irradiation unit 241 (divided irradiation unit 241 hatched in FIG. 27B ) arranged at the same position as the rear portion of the divided printing portion 202c in the front-to-back direction irradiates the divided printing portion 202c with ultraviolet light of the first intensity, and two divided irradiation units 238, 239 (divided irradiation units 238, 239 hatched in the opposite direction to the hatching applied to the divided irradiation unit 241 in FIG. 27B ) arranged at the same position as the divided printing portion 202b in the front-to-back direction irradiate the divided printing portion 202b with ultraviolet light of the second intensity. At this time, the control unit 214 does not turn on the remaining divided irradiation units 237, 240, 242 to 248. The ultraviolet light of the second intensity is ultraviolet light that is strong enough to completely cure the ink in the printing unit P1.

[0214] Similarly, when printing the printing section P3, the control section 214 causes the LED board 236 to irradiate the divided printing section 202d with ultraviolet light of a first intensity, and causes the LED board 236 to irradiate the divided printing section 202c with ultraviolet light of a second intensity. That is, after printing the printing section P2, the control section 214 causes the LED board 236 to irradiate the divided printing section 202c with ultraviolet light of the second intensity. Specifically, as shown in FIG. 27(C) , the divided irradiation section 243, which is arranged at the same position as the rear portion of the divided printing section 202d in the front-to-back direction, irradiates the divided printing section 202d with ultraviolet light of the first intensity, and the two divided irradiation sections 240, 241, which are arranged at the same position as the divided printing section 202c in the front-to-back direction, irradiate the divided printing section 202c with ultraviolet light of the second intensity.

[0215] Furthermore, when printing the printing section P4, the control section 214 causes the LED board 236 to irradiate the divided printing section 202e with ultraviolet light of a first intensity, and causes the LED board 236 to irradiate the divided printing section 202d with ultraviolet light of a second intensity. That is, after printing the printing section P3, the control section 214 causes the LED board 236 to irradiate the divided printing section 202d with ultraviolet light of the second intensity. Specifically, as shown in FIG. 27(D) , the divided irradiation section 245, which is arranged at the same position as the rear portion of the divided printing section 202e in the front-to-back direction, irradiates the divided printing section 202e with ultraviolet light of the first intensity, and the two divided irradiation sections 243 and 244, which are arranged at the same position as the divided printing section 202d in the front-to-back direction, irradiate the divided printing section 202d with ultraviolet light of the second intensity. After printing the printing portion P4, the control unit 214 causes the LED board 236 to irradiate the divided printing portion 202e with ultraviolet light of the second intensity.

[0216] In this modified example, it is also possible to light up only the portion of the LED board 236 that is necessary for curing the ink. Therefore, in this modified example, as in the above-described embodiment, even if the length of the LED board 236 in the front-rear direction is longer than the length of the printing portion 202a in the front-rear direction and the width of the head 203 in the front-rear direction is narrower than the length of the printing portion 202a in the sub-scanning direction, it is possible to prevent excessive ultraviolet light from being irradiated onto the outer peripheral surface of the printing medium 202.

[0217] (Other Modifications) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this and various modifications can be made within the scope that does not change the gist of the present invention.

[0218] In the above-described embodiment, when printing on the print medium 202, if the first head end 203e is positioned at the same position as the boundary between the two divided irradiation units 237-248 in the front-to-back direction, or if the second head end 203f is positioned at the same position as the boundary between the two divided irradiation units 237-248 in the front-to-back direction, the control unit 214 may turn on only the divided irradiation units 237-248 that are at least partially included within the head arrangement range S, and may not turn on the divided irradiation units 237-248 that are in contact with the boundary between the two divided irradiation units 237-248 and are positioned outside the first head end 203e or the second head end 203f in the front-to-back direction. Also, in the above-described embodiment, when printing on the print medium 202, the control unit 214 may turn on only the divided irradiation units 237-248 that are entirely included within the head arrangement range S, and may not turn on the divided irradiation units 237-248 that are only partially included within the head arrangement range S.

[0219] In the above-described embodiment, the position detection mechanism 215 for detecting the relative position of the head 203 in the sub-scanning direction with respect to the rotation mechanism 221 and the ultraviolet irradiator 222 does not have to be a rotary encoder for detecting the rotational position and rotational speed of the motor 216. For example, the position detection mechanism 215 may be a linear encoder for directly detecting the position of the stage 206, or may be an image sensor such as a camera installed above the table 205. Also, in the above-described embodiment, the intensities of the ultraviolet rays irradiated from the divided irradiation units 237 to 248 do not have to be individually adjustable.

[0220] In the above-described embodiment, the printing apparatus 201 may be provided with a Y-bar drive mechanism that moves the Y-bar 208 in the sub-scanning direction together with the head 203 and carriage 207, instead of the stage drive mechanism 212. In this case, the Y-bar drive mechanism serves as a movement mechanism that moves the head 203 in the sub-scanning direction relative to the rotation mechanism 221 and the ultraviolet irradiator 222. Also, in the above-described embodiment, the divided irradiation units 237 to 248 may include divided irradiation units whose front-to-rear widths differ from those of the other divided irradiation units 237 to 248. Furthermore, in the above-described embodiment, the ultraviolet irradiation unit that irradiates ultraviolet light of the ultraviolet irradiator 222 may be something other than the LED board 236.

[0221] In the above-described embodiment, if the printing device 201 only prints on the substrate 202 having a fixed outer diameter, the vertical position of the ultraviolet irradiator 222 does not have to be adjustable. Furthermore, in the above-described embodiment, if the printing device 201 only prints on the substrate 202 having a cylindrical outer shape, the tilt of the rotation mechanism 221 relative to the horizontal when viewed from the left and right does not have to be adjustable, and the tilt of the ultraviolet irradiator 222 relative to the axis of the substrate 202 when viewed from the top and bottom does not have to be adjustable. Furthermore, in the above-described embodiment, the ultraviolet irradiator 222 may be disposed below the substrate 202 or to the right of the substrate 202. Furthermore, in the above-described embodiment, the printing device 201 may have only one head 203.

[0222] A fourth embodiment of the present invention will be described below with reference to the drawings.

[0223] (Overall configuration of printing device) Fig. 1 is a front view illustrating the configuration of a printing device 301 according to a fourth embodiment of the present invention. Fig. 29 is a block diagram illustrating the configuration of the printing device 301 shown in Fig. 28. Fig. 30(A) is a bottom view of the inkjet head 303 and carriage 307 shown in Fig. 28, and Fig. 30(B) is a bottom view illustrating the configuration of the inkjet head 303 shown in Fig. 30(A).

[0224] The printing device 301 of this embodiment is a device for printing on the outer peripheral surface of a printing substrate 302 having a cylindrical, truncated conical, or conical outer shape, and is, for example, a commercial inkjet printer. The printing device 301 prints on the outer peripheral surface of the printing substrate 302 using ultraviolet-curable ink. The printing substrate 302 is formed, for example, in a cylindrical shape. That is, the printing substrate 302 is formed in a cylindrical, truncated conical, or conical cylindrical shape. The printing substrate 302 is also formed, for example, from resin. The printing device 301 is capable of printing on multiple types of printing substrates 302 with different outer diameters and lengths.

[0225] The printing device 301 is equipped with inkjet heads 303 (hereinafter referred to as "heads 303") that eject ultraviolet-curable ink toward the outer peripheral surface of the print medium 302. The printing device 301 of this embodiment is equipped with multiple heads 303. Specifically, the printing device 301 is equipped with four heads 303. The printing device 301 also includes an ultraviolet irradiation device 304 for curing the ink ejected onto the outer peripheral surface of the print medium 302, a stage 306 having a table 305 on which the ultraviolet irradiation device 304 is placed, a carriage 307 on which the multiple heads 303 are mounted, a Y-bar 308 that holds the carriage 307 so as to enable movement in a main scanning direction perpendicular to the up-down direction (vertical direction), and a main body frame 309 that holds the stage 306 so as to enable movement in a sub-scanning direction perpendicular to the up-down direction and the main scanning direction.

[0226] The printing device 301 also includes a carriage drive mechanism 311 that moves the carriage 307 in the main scanning direction relative to the Y bar 308, a stage drive mechanism 312 that moves the stage 306 in the sub-scanning direction relative to the main frame 309, a table lifting mechanism 313 that raises and lowers the table 305, and a control unit 314 that controls the printing device 301. The carriage drive mechanism 311 includes, for example, a motor as a drive source and a power transmission mechanism such as a belt and pulley that transmits the motor's power to the carriage 307. The stage drive mechanism 312 includes, for example, a motor as a drive source and a power transmission mechanism such as a belt and pulley that transmits the motor's power to the stage 306. The stage drive mechanism 312 moves the table 305 in the sub-scanning direction together with the stage 306. The table lifting mechanism 313 includes, for example, a motor as a drive source and a power transmission mechanism such as a ball screw that transmits the motor's power to the table 305.

[0227] In the following description, the sub-scanning direction (X direction in Fig. 28, etc.) is the front-to-rear direction, and the main scanning direction (Y direction in Fig. 28, etc.) is the left-to-right direction. In the following description, the X1 direction side in Fig. 32, etc., which is one side of the front-to-rear direction, is referred to as the "front" side, the X2 direction side in Fig. 32, etc., which is the opposite side, is referred to as the "rear" side, the Y1 direction side in Fig. 31, etc., which is one side of the left-to-right direction, is referred to as the "right" side, and the Y2 direction side in Fig. 31, etc., which is the opposite side, is referred to as the "left" side.

[0228] The upper surface of the table 305 is a plane perpendicular to the up-down direction. The ultraviolet irradiation device 304 placed on the table 305 is arranged below the head 303. The printing medium 302 is held by the ultraviolet irradiation device 304 and arranged below the head 303. In other words, the head 303 is arranged above the printing medium 302. The head 303 ejects ink downward. The ink ejected by the head 303 lands on the outer peripheral surface of the printing medium 302 at the upper end of the printing medium 302.

[0229] The head 303 is formed with a plurality of nozzles 303a that eject ink. Specifically, the large number of nozzles 303a are formed on the bottom surface of the head 303. The bottom surface of the head 303 is an ink ejection surface 303c on which the plurality of nozzles 303a (specifically, the large number of nozzles 303a) are formed. On the ink ejection surface 303c, a nozzle row 303b is formed by the large number of nozzles 303a that are arranged in the sub-scanning direction (front-back direction). On the ink ejection surface 303c, a plurality of nozzle rows 303b that are arranged in the main scanning direction (left-right direction) are formed. The head 303 is equipped with a plurality of piezoelectric elements (piezo elements) for ejecting ink from each of the plurality of nozzles 303a.

[0230] As shown in Figure 30A, for example, three of the four heads 303 mounted on a carriage 307 are arranged at the same position in the front-to-rear direction and are aligned in the left-to-right direction. The remaining head 303 is arranged at a position offset from the other three heads 303 in the front-to-rear direction. Three of the four heads 303 eject color inks, and the remaining head 303 ejects white ink. The viscosity of the white ink is higher than the viscosity of the color inks.

[0231] A PC (personal computer) 318 is electrically connected to the control unit 314. The PC 318 generates print data for printing on the print substrate 302. When printing on the print substrate 302, the print data generated by the PC 318 is sent from the PC 318 to the control unit 314. In other words, when printing on the print substrate 302, the print data sent from the PC 318 is input to the control unit 314.

[0232] (Configuration of Ultraviolet Irradiation Device) Fig. 31 is a front view for explaining the configuration of the ultraviolet irradiation device 304 shown in Fig. 28. Figs. 32 and 33 are side views for explaining the configuration of the rotation mechanism 321 shown in Fig. 31.

[0233] The ultraviolet irradiation device 304 includes a rotation mechanism 321 that holds the printing substrate 302 and rotates the printing substrate 302 around its axis, an ultraviolet irradiator 322 that irradiates ultraviolet rays toward the outer peripheral surface of the printing substrate 302 to which ink is attached, and a cover 323 that covers the rotation mechanism 321 and the ultraviolet irradiator 322 from above. The cover 323 has an opening 323a through which the upper end of the printing substrate 302 is positioned. The ultraviolet irradiation device 304 is placed on the table 305 so that the axis of the printing substrate 302, when viewed from above, coincides with the front-to-back direction. In other words, the axis of the printing substrate 302, when viewed from above, coincides with the front-to-back direction. A nozzle array 303b that ejects ink toward the printing substrate 302 during printing on the printing substrate 302, is positioned directly above the printing substrate 302.

[0234] The rotation mechanism 321 rotates the printing substrate 302 when printing on the printing substrate 302. In this embodiment, printing is performed on the printing substrate 302 while the rotation mechanism 321 rotates the printing substrate 302 with the stage 306 and carriage 307 stopped at a fixed position. When printing on the printing substrate 302, the rotation mechanism 321 rotates the printing substrate 302, for example, counterclockwise when viewed from the front. In this embodiment, the length (length in the axial direction) of the printing substrate 302 is longer than the width of the head 303 in the front-to-rear direction. Therefore, when printing on the printing substrate 302, the printing substrate 302 is moved in stages in the front-to-rear direction (sub-scanning direction) together with the table 305, the rotation mechanism 321, etc. Note that the length of the printing substrate 302 may be equal to or shorter than the width of the head 303 in the front-to-rear direction.

[0235] The rotation mechanism 321 includes a motor 325 as a drive source and a power transmission mechanism 326 for transmitting the power of the motor 325 to the printing substrate 302. The rotation mechanism 321 also includes a first rotating unit 327 that holds one end of the printing substrate 302, a first holding unit 328 that rotatably holds the first rotating unit 327, a second rotating unit 329 that holds the other end of the printing substrate 302, a second holding unit 330 that rotatably holds the second rotating unit 329, a rotating frame 331 to which the first holding unit 328 and the second holding unit 330 are attached, and an encoder 332 for detecting the rotational position and rotational speed of the printing substrate 302. The motor 325 and the encoder 332 are electrically connected to the control unit 314. Note that the power transmission mechanism 326 and other components are not shown in FIG. 31 .

[0236] The first rotating unit 327 and the second rotating unit 329 rotate together with the printing medium 302. The first rotating unit 327 holds the rear end of the printing medium 302, and the second rotating unit 329 holds the front end of the printing medium 302. The motor 325 is disposed to the right of the printing medium 302. The power transmission mechanism 326 connects the first rotating unit 327 and the motor 325. The power transmission mechanism 326 includes a gear train 333. The gear train 333 includes a drive gear fixed to the output shaft of the motor 325 and a driven gear fixed to the first rotating unit 327, etc. The encoder 332 is connected to the rear end of the first rotating unit 327. The second holding unit 330 is movable in the direction of the axis of the printing medium 302. In this embodiment, the positions of the second rotating part 329 and the second holding part 330 in the direction of the axis of the printing medium 302 are adjusted according to the length of the printing medium 302. The power transmission mechanism 326 may be configured by a pulley, a belt, etc.

[0237] The rotating frame 331 is rotatable relative to a lower frame 334 that forms the bottom surface of the ultraviolet irradiation device 304, with the left-right direction as the rotation axis. The rotating frame 331 is also rotatable relative to the lower frame 334, with the rear end of the rotating frame 331 as the rotation center. In this embodiment, by rotating the rotating frame 331 relative to the lower frame 334, it is possible to adjust the inclination of the rotation mechanism 321 relative to the horizontal direction when viewed from the left-right direction. In other words, by rotating the rotating frame 331 relative to the lower frame 334, it is possible to adjust the inclination of the axis of the printing medium 302 relative to the horizontal direction.

[0238] In this embodiment, when printing on a printing substrate 302 having a cylindrical outer shape, the axis of the printing substrate 302 is aligned with the front-to-rear direction (see FIG. 32). On the other hand, when printing on a printing substrate 302 having a truncated cone or conical outer shape, the axis of the printing substrate 302 is tilted relative to the front-to-rear direction (see FIG. 33). In other words, the tilt of the rotation mechanism 321 is adjusted when printing on the outer peripheral surface of a printing substrate 302 having a truncated cone or conical outer shape. Specifically, the tilt of the rotation mechanism 321 is adjusted so that the top end of the printing substrate 302 is parallel to the front-to-rear direction.

[0239] The ultraviolet irradiator 322 includes an LED substrate 336 on which multiple light-emitting elements (specifically, numerous light-emitting elements) that emit ultraviolet rays (ultraviolet light) are mounted. The light-emitting elements are LED chips (UVLED chips). The LED substrate 336 is formed in the shape of a long, narrow rectangular plate. The LED substrate 336 is disposed so that the thickness direction of the LED substrate 336 coincides with the left-right direction. Furthermore, the LED substrate 336 is disposed so that the direction of the short side of the rectangular LED substrate 336 coincides with the up-down direction when viewed from the left-right direction, and the direction of the long side of the LED substrate 336 coincides with the front-to-back direction. The ultraviolet light emission surface of the LED substrate 336 faces right.

[0240] The ultraviolet irradiator 322 is disposed to the left of the printing substrate 302. The ultraviolet irradiator 322 irradiates the printing substrate 302 with ultraviolet light from the left side immediately after ink has landed thereon. In this embodiment, the vertical position of the ultraviolet irradiator 322 is adjustable. The horizontal position of the ultraviolet irradiator 322 and the inclination of the ultraviolet irradiator 322 relative to the axis of the printing substrate 302 when viewed from the vertical direction are also adjustable. In this embodiment, when printing on a printing substrate 302 having a cylindrical outer shape, the ultraviolet irradiator 322 is installed so that the ultraviolet light emission surface of the ultraviolet irradiator 322 (i.e., the ultraviolet light emission surface of the LED substrate 336) is parallel to the front-to-rear direction. When printing on a printing substrate 302 having a truncated cone or conical outer shape, the inclination of the ultraviolet irradiator 322 is adjusted so that the ultraviolet light emission surface of the ultraviolet irradiator 322 is parallel to the left edge of the printing substrate 302.

[0241] The LED substrate 336 is divided into a plurality of blocks in the front-rear direction and is composed of a plurality of divided irradiation units divided in the front-rear direction. For example, the LED substrate 336 is composed of 12 divided irradiation units. The LED substrate 336 is electrically connected to the control unit 314. Specifically, each of the divided irradiation units is electrically connected to the control unit 314. Each of the divided irradiation units is current-controlled by the control unit 314. That is, the LED substrate 336 is current-controlled by the control unit 314.

[0242] In this embodiment, the intensity (illuminance) of ultraviolet light emitted from the LED substrate 336 can be controlled by controlling the current flowing through the LED substrate 336. That is, the control unit 314 can control the intensity of ultraviolet light emitted from the ultraviolet irradiator 322. Specifically, the control unit 314 can individually control the current of each of the multiple divided irradiation units, and can individually turn on and off each of the multiple divided irradiation units and individually adjust the intensity of ultraviolet light emitted from each of the multiple divided irradiation units, thereby controlling the intensity of ultraviolet light emitted from the ultraviolet irradiator 322.

[0243] (Method of Controlling the Ultraviolet Irradiator) As described above, when printing on the printing substrate 302, print data transmitted from the PC 318 is input to the control unit 314. The control unit 314 prints on the printing substrate 302 based on the input print data. The print data includes resolution data, which is data on the resolution of the image to be printed on the printing substrate 302. The control unit 314 sets the rotation speed of the printing substrate 302 during printing on the printing substrate 302 based on the resolution data. That is, the rotation speed of the printing substrate 302 is set based on the resolution data. Specifically, as the resolution of the image to be printed on the printing substrate 302 increases, the rotation speed of the printing substrate 302 during printing decreases, and as the resolution of the image to be printed on the printing substrate 302 decreases, the rotation speed of the printing substrate 302 during printing increases. That is, as the resolution of the image to be printed on the printing substrate 302 decreases, the rotation speed of the printing substrate 302 during printing increases.

[0244] When printing on the printing substrate 302, the ultraviolet irradiator 322 irradiates ultraviolet light onto the printing substrate 302. Specifically, when printing on the printing substrate 302, the LED board 336 irradiates ultraviolet light onto the printing substrate 302. When printing on the printing substrate 302, the control unit 314 controls the intensity of the ultraviolet light irradiated onto the printing substrate 302 from the ultraviolet irradiator 322 based on the rotation speed of the printing substrate 302. In other words, when printing on the printing substrate 302, the control unit 314 controls the current value of the LED board 336 based on the rotation speed of the printing substrate 302 (in accordance with the rotation speed of the printing substrate 302).

[0245] Specifically, if the rotation speed of the printing medium 302, which is set based on the resolution data, during printing is slower and the irradiation time of ultraviolet light irradiated onto the outer peripheral surface of the printing medium 302 is longer, the control unit 314 reduces the intensity of ultraviolet light irradiated from the ultraviolet irradiator 322. On the other hand, if the rotation speed of the printing medium 302 during printing is faster and the irradiation time of ultraviolet light irradiated onto the outer peripheral surface of the printing medium 302 is shorter, the control unit 314 increases the intensity of ultraviolet light irradiated from the ultraviolet irradiator 322. In other words, during printing on the printing medium 302, the control unit 314 increases the intensity of ultraviolet light irradiated onto the printing medium 302 from the ultraviolet irradiator 322 as the rotation speed of the printing medium 302 increases.

[0246] (Method of Setting the Printing Material) FIG. 34 is a process diagram for explaining a method of setting the printing material 302 on the rotation mechanism 321 shown in FIG.

[0247] When setting the printing substrate 302 on the rotation mechanism 321, first, the type and shape of the printing substrate 302 are selected (steps ST1 and ST2). In steps ST1 and ST2, for example, an operator selects the type and shape of the printing substrate 302 on an operation panel of the printing device 301. Also, for example, in step ST1, the operator selects whether the printing substrate 302 is transparent or opaque, and in step ST2, the operator selects whether the shape of the printing substrate 302 is cylindrical, truncated conical, or conical.

[0248] Thereafter, the printing substrate 302 is set on the rotation mechanism 321 (printing substrate setting step, step ST3). In step ST3, the printing substrate 302 is held by the first rotating unit 327 and the second rotating unit 329, thereby attaching the printing substrate 302 to the rotation mechanism 321. Also, in step ST3, adjustments are made, as necessary, to the positions of the second rotating unit 329 and the second holding unit 330 in the direction of the axis of the printing substrate 302, and the inclination of the rotation mechanism 321 relative to the horizontal direction. Also, in step ST3, the cover 323 is set while adjusting its position so that the upper end of the printing substrate 302 is positioned in the opening 323a of the cover 323.

[0249] Thereafter, while the printing medium 302 is rotated by the rotation mechanism 321, ultraviolet light is irradiated onto the outer peripheral surface of the printing medium 302 from the ultraviolet irradiator 322, and the amount of ultraviolet light above the opening 323a is measured (ultraviolet light measurement step, step ST4). That is, in step ST4, the amount of stray ultraviolet light leaking from the opening 323a is measured. In step ST4, the amount of ultraviolet light above the opening 323a is measured using an illuminance meter. At this time, the carriage 307 is not positioned above the ultraviolet irradiation device 304. Also, in step ST4, the amount of ultraviolet light above the opening 323a is measured while changing the irradiation range of the LED board 336 (i.e., changing the number of divided irradiation units that are turned on) and changing the illuminance of the LED board 336.

[0250] If the amount of ultraviolet light measured in step ST4 (i.e., the amount of stray light) is equal to or less than a predetermined reference value, the operator determines that resetting of the printing substrate 302 is not necessary and completes the setting of the printing substrate 302 on the rotation mechanism 321. On the other hand, if the amount of ultraviolet light measured in step ST4 exceeds the reference value, the operator determines that resetting of the printing substrate 302 is necessary. In this case, for example, the amount of ultraviolet light measured in step ST4 (i.e., the amount of stray light) is stored in the control unit 314 (step ST5). Then, the process returns to step ST3, and the printing substrate 302 is set again on the rotation mechanism 321. That is, the resetting of the printing substrate 302 on the rotation mechanism 321 is repeatedly performed until the amount of ultraviolet light measured in step ST4 becomes equal to or less than the reference value.

[0251] (Major Effects of the Present Embodiment) As described above, in the present embodiment, the control unit 314 controls the intensity of ultraviolet light irradiated from the ultraviolet irradiator 322 onto the print substrate 302 based on the rotation speed of the print substrate 302 during printing on the print substrate 302. Specifically, when the rotation speed of the print substrate 302 during printing is slow and the irradiation time of ultraviolet light irradiated onto the outer peripheral surface of the print substrate 302 is long, the control unit 314 reduces the intensity of ultraviolet light irradiated from the ultraviolet irradiator 322, and when the rotation speed of the print substrate 302 during printing is fast and the irradiation time of ultraviolet light irradiated onto the outer peripheral surface of the print substrate 302 is short, the control unit 314 increases the intensity of ultraviolet light irradiated from the ultraviolet irradiator 322. Therefore, in the present embodiment, even if the rotation speed of the print substrate 302 changes depending on the resolution of the image printed on the outer peripheral surface of the print substrate 302, it is possible to irradiate an appropriate amount of ultraviolet light onto the ink adhering to the outer peripheral surface of the print substrate 302.

[0252] In this embodiment, when the printing substrate 302 is set on the rotation mechanism 321, ultraviolet light is irradiated from the ultraviolet irradiator 322 onto the outer peripheral surface of the printing substrate 302 while the printing substrate 302 is rotated by the rotation mechanism 321, and the amount of ultraviolet light above the opening 323a is measured in step ST4. The printing substrate 302 is repeatedly reset on the rotation mechanism 321 until the amount of ultraviolet light measured falls below a reference value. Therefore, in this embodiment, it is possible to reduce the amount of ultraviolet light that passes through the opening 323a and reaches the ink ejection surface 303c of the head 303 during printing on the printing substrate 302. Therefore, in this embodiment, it is possible to suppress hardening of the ink in the nozzles 303a and prevent the nozzles 303a from clogging.

[0253] (Modification of Method for Controlling Ultraviolet Irradiator) FIG. 35 is a diagram for explaining a method for controlling an ultraviolet irradiator 322 according to a modification of the present invention.

[0254] In the above-described embodiments, the printing substrate 302 may be formed of a material that easily transmits ultraviolet light (for example, a transparent material), or may be formed of a material that does not easily transmit ultraviolet light (for example, an opaque material). For example, if the printing substrate 302 is formed of a material that transmits ultraviolet light, as shown in Figure 35 (A), ultraviolet light irradiated from the ultraviolet irradiator 322 is more likely to pass through the printing substrate 302 and reach the ink ejection surface 303c of the head 303. In other words, in this case, after being irradiated toward the printing substrate 302 from the ultraviolet irradiator 322, an increased amount of ultraviolet light passes through the printing substrate 302 and reaches the ink ejection surface 303c.

[0255] 35B, if the printing substrate 302 is made of a material that does not transmit ultraviolet light, the ultraviolet light irradiated from the ultraviolet irradiator 322 does not penetrate the printing substrate 302, and therefore does not reach the ink ejection surface 303c. If the amount of ultraviolet light that is irradiated from the ultraviolet irradiator 322 toward the printing substrate 302 and then penetrates the printing substrate 302 to reach the ink ejection surface 303c increases, there is a risk that the ink will harden inside the nozzles 303a during printing on the printing substrate 302, causing the nozzles 303a to become clogged.

[0256] In this modified example, in order to prevent clogging of the nozzles 303a due to ultraviolet light that passes through the print substrate 302 and reaches the ink ejection surface 303c, the control unit 314 controls the intensity of ultraviolet light irradiated from the ultraviolet irradiator 322 onto the print substrate 302 based on the ultraviolet light transmittance of the print substrate 302 during printing on the print substrate 302. Specifically, the control unit 314 reduces the intensity of ultraviolet light irradiated from the ultraviolet irradiator 322 onto the print substrate 302 as the ultraviolet light transmittance of the print substrate 302 increases. Therefore, in this modified example, it is possible to reduce the amount of ultraviolet light that passes through the print substrate 302 and reaches the ink ejection surface 303c, which in turn prevents the ink from hardening in the nozzles 303a and prevents clogging of the nozzles 303a.

[0257] The ultraviolet transmittance of the printing substrate 302 is input by an operator, for example, via an operation panel of the printing device 301. The ultraviolet transmittance of the printing substrate 302 input via the operation panel of the printing device 301 is input to the control unit 314 as ultraviolet transmittance data. The control unit 314 controls the intensity of ultraviolet light irradiated onto the printing substrate 302 from the ultraviolet irradiator 322 based on the input ultraviolet transmittance data when printing on the printing substrate 302. Note that instead of the ultraviolet transmittance of the printing substrate 302, the operator may input whether the printing substrate 302 is transparent or opaque via the operation panel of the printing device 301.

[0258] In this modified example, as a result of reducing the intensity of the ultraviolet light irradiated from the ultraviolet irradiator 322 onto the printing substrate 302, there may arise a case where the cumulative amount of ultraviolet light irradiated from the ultraviolet irradiator 322 toward the outer peripheral surface of the printing substrate 302 during printing on the printing substrate 302 is less than the cumulative amount of ultraviolet light required to cure the ink adhered to the outer peripheral surface of the printing substrate 302. In this case, the control unit 314 causes the ultraviolet irradiator 322 to irradiate additional ultraviolet light toward the outer peripheral surface of the printing substrate 302 after printing on the printing substrate 302.

[0259] Specifically, the cumulative amount of ultraviolet light required to cure the ink attached to the outer peripheral surface of the print substrate 302 is stored in advance in the control unit 314, and the control unit 314 calculates the cumulative amount of ultraviolet light to be irradiated from the ultraviolet irradiator 322 toward the outer peripheral surface of the print substrate 302 when printing on the print substrate 302. The control unit 314 compares the calculated cumulative amount of light with the cumulative amount of ultraviolet light required to cure the ink attached to the outer peripheral surface of the print substrate 302, and if the cumulative amount of ultraviolet light irradiated onto the outer peripheral surface of the print substrate 302 is insufficient, the control unit 314 causes the ultraviolet irradiator 322 to irradiate additional ultraviolet light toward the outer peripheral surface of the print substrate 302 after printing on the print substrate 302 to make up the shortage. As a result, in this modified example, since the ultraviolet transmittance of the substrate 302 is high, even if the intensity of the ultraviolet light irradiated from the ultraviolet irradiator 322 to the substrate 302 is reduced, it is possible to irradiate the outer surface of the substrate 302 with the amount of ultraviolet light necessary to harden the ink adhering to the outer surface of the substrate 302.

[0260] (Modification of Rotation Mechanism) FIG. 36 is a schematic diagram for explaining the configuration of a rotation mechanism 321 according to a modification of the present invention.

[0261] In the embodiment described above, the first rotating unit 327 includes a holding member 341 as a first holding member that contacts the printed material 302 and holds one end of the printed material 302, and the second rotating unit 329 includes a holding member 342 as a second holding member that contacts the printed material 302 and holds the other end of the printed material 302. That is, the rotating mechanism 321 includes the holding member 341 that contacts the printed material 302 and holds one end of the printed material 302 and rotates together with the printed material 302, and the holding member 342 that contacts the printed material 302 and holds the other end of the printed material 302 and rotates together with the printed material 302.

[0262] The holding member 341 is in contact with, for example, the inner circumferential surface of the printing medium 302. The holding member 342 is in contact with, for example, the inner circumferential surface and the front end of the printing medium 302. The holding members 341, 342 are formed of a highly elastic material that adheres closely to the printing medium 302. In this modified example, the holding members 341, 342 are formed of a material that is light-blocking and thermally conductive. For example, the holding members 341, 342 are formed of black rubber containing a thermally conductive carbon filler.

[0263] In this modified example, the holding members 341 and 342 are formed from a light-blocking material, which prevents ultraviolet light reflected by the holding members 341 and 342 from reaching the ink ejection surface 303c of the head 303. This prevents the ink from hardening in the nozzles 303a, thereby preventing clogging of the nozzles 303a. Furthermore, in this modified example, the holding members 341 and 342 are formed from a thermally conductive material, which allows heat from the print substrate 302 to escape via the holding members 341 and 342. This prevents the temperature of the print substrate 302 from becoming excessively high due to ultraviolet light irradiated onto the outer peripheral surface of the print substrate 302. Note that either the holding members 341 or 342 does not have to be formed from a material that is light-blocking and thermally conductive.

[0264] In the above-described embodiment, the rotation mechanism 321 may include an insert member 343 that is inserted into the inner periphery of the printing medium 302. In this case, the insert member 343 is made of a material that is light-blocking and thermally conductive. For example, the insert member 343 is made of black rubber containing a thermally conductive carbon filler.

[0265] In this case, because the insert member 343 is formed of a light-blocking material, it is possible to prevent ultraviolet light from passing through the substrate 302, even if the substrate 302 has a high ultraviolet light transmittance. Therefore, even if the substrate 302 has a high ultraviolet light transmittance, it is possible to prevent ultraviolet light from reaching the ink ejection surface 303c. As a result, it is possible to suppress ink hardening in the nozzles 303a and prevent clogging of the nozzles 303a. Furthermore, in this case, because the insert member 343 is formed of a thermally conductive material, it is possible to dissipate heat from the substrate 302 through the insert member 343. Therefore, it is possible to prevent the temperature of the substrate 302 from becoming excessively high due to ultraviolet light irradiated onto the outer peripheral surface of the substrate 302.

[0266] (Other Modifications) The above-described embodiment is one example of a preferred embodiment of the present invention, but the present invention is not limited to this and various modifications can be made within the scope that does not change the gist of the present invention.

[0267] In the above-described embodiment, when printing is performed on the print substrate 302, print substrate shape data, which is data on the shape of the print substrate 302, and ink type data, which is data on the type of ink to be ejected by the head 303, may be input to the control unit 314. In this case, for example, the shape of the print substrate 302 input by an operator on the operation panel of the printing device 301 is input to the control unit 314 as print substrate shape data. Also, for example, the ink type data is included in the print data, and the ink type data is input to the control unit 314 from the PC 318.

[0268] In this case, the control unit 314 calculates the cumulative amount of ultraviolet light required to cure the ink attached to the outer peripheral surface of the print substrate 302 based on the input print substrate shape data and ink type data. In this case, the control unit 314 is able to control the intensity of the ultraviolet light irradiated from the ultraviolet irradiator 322 to the print substrate 302, taking into account the calculated cumulative amount of light. The shape of the print substrate 302 may also be input to the PC 318. In this case, for example, print substrate shape data is included in the print data, and the print substrate shape data is input from the PC 318 to the control unit 314. The type of ink may also be input via the operation panel of the printing device 301. In this case, the type of ink input via the operation panel of the printing device 301 is input to the control unit 314 as ink type data.

[0269] In the above-described embodiment, if only printing on a printing medium 302 having a fixed outer diameter is performed by the printing device 301, the vertical position of the ultraviolet irradiator 322 does not have to be adjustable. Also, in the above-described embodiment, if only printing on a printing medium 302 having a cylindrical outer shape is performed by the printing device 301, the inclination of the rotation mechanism 321 with respect to the horizontal direction when viewed from the left and right does not have to be adjustable, and the inclination of the ultraviolet irradiator 322 with respect to the axis of the printing medium 302 when viewed from the top and bottom does not have to be adjustable.

[0270] In the above-described embodiment, the ultraviolet irradiation device 304 may be placed on the table 305 so that the direction of the axis of the printing medium 302 when viewed from the top-bottom direction coincides with the left-right direction. Also, in the above-described embodiment, the ultraviolet irradiator 322 may be disposed below the printing medium 302 or to the right of the printing medium 302. Furthermore, in the above-described embodiment, the printing device 301 may be provided with a Y-bar drive mechanism that moves the Y-bar 308 in the sub-scanning direction together with the head 303 and carriage 307, instead of the stage drive mechanism 312. Also, in the above-described embodiment, the printing device 301 may have only one head 303.

[0271] 1, 101, 201, 301 Printing device 2, 102, 202, 302 Printing medium 3, 103, 203, 303 Head (inkjet head) 3a, 103a, 203a, 303a Nozzle 3b, 203b Nozzle row 203c, 303c Ink ejection surface 203e First head end 203f Second head end 7 Carriage 11 Carriage drive mechanism 14, 114, 214, 314 Control unit 16, 116 Piezoelectric element (ejection energy generating element) 17 Pointer 21, 121, 221, 321 Rotation mechanism 25, 125 Motor 26, 126 Power transmission mechanism 32, 132 Encoder 33 Gear train 43, 44 Toothed pulley 45 Toothed belt 122, 222, 322 Ultraviolet irradiator L1, L2 Ink layer 202a Printed part 202b Divided printed part (first divided printed part) 202c, 2d Divided printed part (first divided printed part, second divided printed part) 202e Divided printed part (second divided printed part) 212 Stage drive mechanism (moving mechanism) 215 Position detection mechanism 236, 336 LED board (ultraviolet irradiation part) 237-248 Divided irradiation part P1 Printing part (first printing part) P2, P3 Printing part (first printing part, second printing part) P4 Printing part (second printing part) S Head arrangement range X Sub-scanning direction 323 Cover 323a Opening 341 Holding member (first holding member) 342 Holding member (second holding member) 343 Insertion member ST3 Printing material setting process ST4 Ultraviolet light measurement process

Claims

1. A printing device for printing on the outer surface of a printing substrate having a cylindrical, truncated cone, or conical outer shape, comprising: a rotation mechanism that holds the printing substrate and rotates it around its axis as the center of rotation; an inkjet head that is positioned above the printing substrate and ejects ink toward the outer surface of the printing substrate; and a control unit that controls the printing device; wherein the rotation mechanism comprises a motor as a drive source and a power transmission mechanism that transmits the power of the motor to the printing substrate, and rotates the printing substrate when printing on the printing substrate; and wherein printing data for printing on the printing substrate is input to the control unit, and the control unit controls the rotation speed of the motor based on the printing data when printing on the printing substrate.

2. A printing device as described in claim 1, characterized in that the control unit calculates the optimal rotation speed of the motor based on the print data and rotates the motor at the calculated rotation speed when printing on the printing medium.

3. A printing device as described in claim 1 or 2, characterized in that it comprises a plurality of inkjet heads, a carriage on which the plurality of inkjet heads are mounted, and a carriage drive mechanism that moves the carriage in a direction perpendicular to the axis of the substrate when viewed from above, wherein the printing data is set for each inkjet head, and the control unit controls the rotation speed of the motor based on the printing data set for the inkjet head positioned directly above the substrate when printing on the substrate.

4. A printing device as described in claim 1 or 2, characterized in that it comprises a carriage on which one or more inkjet heads are mounted, and a carriage drive mechanism that moves the carriage in a direction perpendicular to the axis of the substrate when viewed from above, wherein a plurality of nozzles that eject ink are formed on the underside of the inkjet head, a nozzle row is formed on the underside of the inkjet head by the plurality of nozzles that are arranged in the direction of the axis of the substrate when viewed from above, the total number of nozzle rows formed on all of the inkjet heads mounted on the carriage is two or more, the print data is set for each nozzle row, and the control unit controls the rotation speed of the motor based on the print data set for the nozzle row positioned directly above the substrate when printing on the substrate.

5. A printing device as described in claim 1 or 2, characterized in that the rotation mechanism rotates the substrate in a predetermined first direction when printing on the substrate, and rotates the substrate in the first direction when setting the printing origin, which is an operation to align the origin position of the substrate with the inkjet head in the rotation direction of the substrate before printing on the substrate.

6. A printing device according to claim 5, characterized in that it is provided with a pointer that irradiates light onto the outer peripheral surface of the printing medium, and the power transmission mechanism comprises a gear train or at least two toothed pulleys and a toothed belt stretched over the toothed pulleys.

7. The printing device described in claim 1 or 2, characterized in that the rotation mechanism is equipped with an encoder for detecting the rotational position and rotational speed of the printing medium, the inkjet head is formed with a plurality of nozzles for ejecting ink, the inkjet head is equipped with a plurality of ejection energy generating elements for ejecting ink from each of the plurality of nozzles, the control unit, when printing on the printing medium, generates an ejection trigger signal for starting the ejection of ink from the nozzle based on the output signal of the encoder, sends a drive signal for ejecting ink from the nozzle to the ejection energy generating element starting from the ejection trigger signal, and sets an ejection in progress flag starting from the ejection trigger signal, and clears the ejection in progress flag when transmission of the drive signal is completed, if the rotation speed of the motor is normal, the next ejection trigger is generated after the ejection in progress flag is cleared, and the control unit executes a predetermined error processing when the next ejection trigger is generated while the ejection in progress flag is set.

8. A printing device for printing on the outer surface of a printing substrate having a cylindrical, truncated cone or conical outer shape, comprising: a rotation mechanism that holds the printing substrate and rotates it around its axis as the center of rotation; and an inkjet head that is positioned above the printing substrate and ejects ink toward the outer surface of the printing substrate, the rotation mechanism comprising a motor as a drive source and a power transmission mechanism for transmitting the power of the motor to the printing substrate, and a control method for a printing device that rotates the printing substrate when printing on the printing substrate, characterized in that the rotation speed of the motor is controlled based on print data for printing on the printing substrate when printing on the printing substrate.

9. A printing device for printing by overlapping multiple ink layers on the outer peripheral surface of a printing substrate having a cylindrical, truncated cone or conical outer shape, comprising: a rotation mechanism for holding the printing substrate and rotating the printing substrate around the axis of the printing substrate as the center of rotation; an inkjet head disposed above the printing substrate and ejecting ink toward the outer peripheral surface of the printing substrate; and a control unit for controlling the printing device; wherein the inkjet head is formed with multiple nozzles for ejecting ink; and the inkjet head is equipped with multiple ejection energy generating elements for ejecting ink from each of the multiple nozzles; and the rotation mechanism comprises a motor as a drive source and a power transmission mechanism for transmitting the power of the motor to the printing substrate, and rotates the printing substrate when printing on the printing substrate; The control unit calculates the number of ink layers printed on the outer peripheral surface of the substrate when printing on the substrate, and performs at least one of the following controls: motor rotation speed control, which controls the rotation speed of the motor based on the calculated number of ink layers; ink ejection speed control, which controls the ink ejection speed from the nozzle by the ejection energy generating element based on the calculated number of ink layers; and ink ejection timing control, which controls the timing of ink ejection from the nozzle by the ejection energy generating element based on the calculated number of ink layers.

10. A printing device as described in claim 9, characterized in that the control unit executes all of the motor rotation speed control, the ink ejection speed control, and the ink ejection timing control, or executes two controls arbitrarily selected from the motor rotation speed control, the ink ejection speed control, and the ink ejection timing control.

11. A printing device according to claim 9 or 10, characterized in that the ejection energy generating element is a piezoelectric element, and the control unit controls the voltage applied to the piezoelectric element in controlling the ink ejection speed.

12. A printing device as described in claim 9 or 10, characterized in that the rotation mechanism is equipped with an encoder for detecting the rotational position and rotational speed of the motor or the printing medium, and the control unit generates an ejection trigger signal for starting ink ejection from the nozzle based on the output signal of the encoder when printing on the printing medium, and controls the ink ejection start time from the point in time when the ejection trigger signal is generated in the ink ejection timing control.

13. A printing device as described in claim 9 or 10, characterized in that it comprises an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the substrate to which ink is adhered, the ink layer is made of ultraviolet-curing ink, a plurality of ink layers with different ultraviolet transmittances are superimposed on the outer peripheral surface of the substrate, the control unit stores the ultraviolet transmittance of each of the plurality of ink layers in advance and receives print data for printing on the substrate, and the control unit ejects ink from the inkjet head based on the ultraviolet transmittance of the ink layers stored in the control unit and the print data so that the ultraviolet transmittance of the ink layer located on the outer peripheral side of the plurality of ink layers is higher than the ultraviolet transmittance of the ink layer located on the inner peripheral side.

14. A printing device for printing by overlapping multiple ink layers on the outer peripheral surface of a printing substrate having a cylindrical, truncated cone, or conical outer shape, comprising: a rotation mechanism for holding the printing substrate and rotating the printing substrate around the axis of the printing substrate as the center of rotation; and an inkjet head disposed above the printing substrate and ejecting ink toward the outer peripheral surface of the printing substrate, wherein the inkjet head is formed with multiple nozzles for ejecting ink and the inkjet head is equipped with multiple ejection energy generating elements for ejecting ink from each of the multiple nozzles, and the rotation mechanism comprises a motor as a drive source and a power transmission mechanism for transmitting the power of the motor to the printing substrate, and a control method for a printing device that rotates the printing substrate when printing on the printing substrate, A control method for a printing device, characterized by performing at least one of the following controls: motor rotation speed control, which calculates the number of ink layers printed on the outer peripheral surface of the print medium during printing, and controls the rotation speed of the motor based on the calculated number of ink layers; ink ejection speed control, which controls the ink ejection speed from the nozzle by the ejection energy generating element based on the calculated number of ink layers; and ink ejection timing control, which controls the timing of ink ejection from the nozzle by the ejection energy generating element based on the calculated number of ink layers.

15. A printing device for printing with ultraviolet curable ink on the outer peripheral surface of a printing substrate having a cylindrical, truncated conical or conical outer shape, comprising: a rotation mechanism for holding the printing substrate and rotating the printing substrate around the axis of the printing substrate as the center of rotation; an inkjet head disposed above the printing substrate and ejecting ink toward the outer peripheral surface of the printing substrate; an ultraviolet irradiator for irradiating ultraviolet rays toward the outer peripheral surface of the printing substrate to which the ink has adhered; a movement mechanism for moving the inkjet head relative to the rotation mechanism and the ultraviolet irradiator in a sub-scanning direction that is perpendicular to the vertical direction and parallel to the axis of the printing substrate when viewed from the vertical direction; a position detection mechanism for detecting the relative position of the inkjet head in the sub-scanning direction with respect to the rotation mechanism and the ultraviolet irradiator; and a control unit for controlling the printing device; wherein the inkjet head is formed with a plurality of nozzles for ejecting ink; the lower surface of the inkjet head is an ink ejection surface on which the plurality of nozzles are formed; and a nozzle row is formed on the ink ejection surface by the plurality of nozzles arranged in the sub-scanning direction; a printing device characterized in that the length in the sub-scanning direction of the ultraviolet irradiation section of the ultraviolet irradiator, which is the section that irradiates ultraviolet light, is longer than the length in the sub-scanning direction of the printing section, which is the section where printing is performed on the printing medium; the width in the sub-scanning direction of the inkjet head is narrower than the length in the sub-scanning direction of the printing section; the ultraviolet irradiation section is composed of a plurality of divided irradiation sections that are divided in the sub-scanning direction; the plurality of divided irradiation sections can be turned on individually; and the control section controls the lighting range of the ultraviolet irradiation section in the sub-scanning direction based on the detection result of the position detection mechanism when printing on the printing medium.

16. A printing device as described in claim 15, characterized in that one end of the inkjet head in the sub-scanning direction is defined as a first head end, the other end of the inkjet head in the sub-scanning direction is defined as a second head end, and the range between the first head end and the second head end in the sub-scanning direction is defined as a head placement range, wherein the control unit turns on the divided irradiation units of the ultraviolet irradiation unit that have at least a portion included within the head placement range.

17. A printing device as described in claim 16, characterized in that when the first head end is positioned at the same position as the boundary between two of the divided irradiation units in the sub-scanning direction, the control unit also lights up the divided irradiation unit that is in contact with the boundary and is positioned outside the first head end in the sub-scanning direction, and when the second head end is positioned at the same position as the boundary between two of the divided irradiation units in the sub-scanning direction, the control unit also lights up the divided irradiation unit that is in contact with the boundary and is positioned outside the second head end in the sub-scanning direction.

18. A printing device according to any one of claims 15 to 17, characterized in that the intensities of the ultraviolet rays emitted from the plurality of divided irradiation units can be adjusted individually.

19. The intensity of the ultraviolet light emitted from the plurality of divided irradiation units can be adjusted individually, and the control unit, while stopping the inkjet head relative to the rotation mechanism and the ultraviolet irradiator in the sub-scanning direction, ejects ink from the inkjet head toward the outer circumferential surface of the substrate to print a first printing unit, then moves the inkjet head a predetermined distance in the sub-scanning direction relative to the rotation mechanism and the ultraviolet irradiator and stops it, and then ejects ink from the inkjet head toward the outer circumferential surface of the substrate to print a second printing unit, and when the portion of the substrate where the first printing unit is printed is designated as a first divided printing unit and the portion of the substrate where the second printing unit is printed is designated as a second divided printing unit, A printing device as described in claim 15, characterized in that when printing the first printing section, the ultraviolet irradiation section is caused to irradiate the first divided printing section with ultraviolet light of a first intensity that semi-cures ink adhering to the printing section, and when printing the second printing section, the ultraviolet irradiation section is caused to irradiate the second divided printing section with ultraviolet light of the first intensity, and the ultraviolet irradiation section is caused to irradiate the first divided printing section with ultraviolet light of a second intensity higher than the first intensity, and after printing the second printing section, the ultraviolet irradiation section is caused to irradiate the second divided printing section with ultraviolet light of the second intensity.

20. A printing device for printing with ultraviolet curable ink on the outer periphery of a printing substrate having a cylindrical, truncated cone or conical outer shape, comprising: a rotation mechanism for holding the printing substrate and rotating the printing substrate around the axis of the printing substrate; an inkjet head disposed above the printing substrate and ejecting ink toward the outer periphery of the printing substrate; an ultraviolet irradiator for irradiating ultraviolet rays toward the outer periphery of the printing substrate to which the ink is attached; a movement mechanism for moving the inkjet head relative to the rotation mechanism and the ultraviolet irradiator in a sub-scanning direction that is perpendicular to the vertical direction and parallel to the axis of the printing substrate when viewed from the vertical direction; and a movement mechanism for moving the inkjet head relative to the rotation mechanism and the ultraviolet irradiator in the sub-scanning direction. a position detection mechanism for detecting a relative position of the inkjet head, wherein the inkjet head is formed with a plurality of nozzles that eject ink, the underside of the inkjet head is an ink ejection surface on which the plurality of nozzles are formed, and a nozzle row is formed on the ink ejection surface by the plurality of nozzles that are arranged in a sub-scanning direction, the length in the sub-scanning direction of the ultraviolet irradiation section of the ultraviolet irradiator that is the section that irradiates ultraviolet light is longer than the length in the sub-scanning direction of the printing section that is the section on the printing medium where printing is performed, the width in the sub-scanning direction of the inkjet head is narrower than the length in the sub-scanning direction of the printing section, the ultraviolet irradiation section is made up of a plurality of divided irradiation sections that are divided in the sub-scanning direction, and the plurality of divided irradiation sections can be turned on individually, 21. A printing device for printing with ultraviolet-curable ink on the outer peripheral surface of a substrate having a cylindrical, truncated cone, or conical outer shape, comprising: a rotation mechanism that holds the substrate and rotates it around its axis; an inkjet head that is positioned above the substrate and ejects ink toward the outer peripheral surface of the substrate; an ultraviolet irradiator that irradiates ultraviolet rays toward the outer peripheral surface of the substrate to which the ink is attached; and a control unit that controls the printing device; wherein the rotation mechanism rotates the substrate when printing on it, and the control unit controls the intensity of the ultraviolet rays irradiated onto the substrate from the ultraviolet irradiator based on the rotation speed of the substrate when printing on it.

22. A printing device as described in claim 21, characterized in that printing data for printing on the printing medium is input to the control unit, the printing data includes resolution data which is data on the resolution of the image to be printed on the printing medium, and the rotation speed of the printing medium is set based on the resolution data.

23. A printing device as described in claim 21 or 22, characterized in that the ultraviolet irradiator is provided with an LED board on which a plurality of light-emitting elements that emit ultraviolet light are mounted, and the control unit controls the current value of the LED board based on the rotation speed of the printing medium when printing on the printing medium.

24. A printing device as described in claim 21 or 22, characterized in that the inkjet head is formed with a plurality of nozzles for ejecting ink, the underside of the inkjet head is an ink ejection surface on which the plurality of nozzles are formed, and the control unit controls the intensity of ultraviolet light irradiated from the ultraviolet irradiator to the substrate to be printed based on the ultraviolet transmittance of the substrate to be printed when printing on the substrate.

25. A printing device as described in claim 24, characterized in that if the cumulative amount of ultraviolet light irradiated from the ultraviolet irradiator toward the outer surface of the substrate during printing on the substrate is less than the cumulative amount of ultraviolet light required to harden the ink adhering to the outer surface of the substrate, the control unit causes the ultraviolet irradiator to irradiate additional ultraviolet light toward the outer surface of the substrate after printing on the substrate.

26. A printing device as described in claim 21 or 22, characterized in that the control unit receives print substrate shape data, which is data on the shape of the print substrate, and ink type data, which is data on the type of ink ejected by the inkjet head, and the control unit calculates the cumulative amount of ultraviolet light required to harden the ink adhered to the outer surface of the print substrate based on the print substrate shape data and ink type data that have been input.

27. A printing device as described in claim 21 or 22, characterized in that the rotation mechanism comprises a first holding member that contacts the substrate to hold one end of the substrate and rotates together with the substrate, and a second holding member that contacts the substrate to hold the other end of the substrate and rotates together with the substrate, and at least one of the first holding member and the second holding member is formed from a material that is light-blocking and thermally conductive.

28. A printing device as described in claim 21 or 22, characterized in that the printing medium is formed in a cylindrical shape, the rotation mechanism includes an insertion member that is inserted into the inner periphery of the printing medium, and the insertion member is formed from a material that is light-blocking and thermally conductive.

29. A printing device according to claim 21 or 22, characterized in that it comprises a cover that covers the ultraviolet irradiator from above, and the cover has an opening in which the upper end of the printing medium is placed.

30. A method for setting a substrate to be printed on the rotating mechanism in a printing device as described in claim 29, comprising: a substrate to be printed setting step for setting the substrate to the rotating mechanism; and an ultraviolet measurement step for, after the substrate to be printed setting step, rotating the substrate to be printed by the rotating mechanism while irradiating ultraviolet light from the ultraviolet irradiator onto the outer surface of the substrate to be printed and measuring the amount of ultraviolet light above the opening, characterized in that the substrate to be printed is repeatedly reset to the rotating mechanism until the amount of ultraviolet light measured in the ultraviolet measurement step becomes equal to or less than a predetermined reference value.

31. A printing device for printing with ultraviolet-curing ink on the outer surface of a substrate having a cylindrical, truncated cone, or conical outer shape, comprising: a rotation mechanism that holds the substrate and rotates it around its axis; an inkjet head that is positioned above the substrate and ejects ink toward the outer surface of the substrate; and an ultraviolet irradiator that irradiates ultraviolet rays toward the outer surface of the substrate to which the ink is attached, wherein the rotation mechanism rotates the substrate when printing on it. A control method for a printing device, characterized in that the intensity of ultraviolet rays irradiated onto the substrate from the ultraviolet irradiator is controlled based on the rotation speed of the substrate when printing on it.

Images