WO2016152606A1

WO2016152606A1 - Printing apparatus and printing method

Info

Publication number: WO2016152606A1
Application number: PCT/JP2016/057919
Authority: WO
Inventors: 大西　勝
Original assignee: 株式会社ミマキエンジニアリング
Priority date: 2015-03-24
Filing date: 2016-03-14
Publication date: 2016-09-29
Also published as: JP6426038B2; JP2016179591A

Abstract

The present invention prints more appropriately on a medium for which the surface to be printed is curved. A printing apparatus 10 for printing on a medium 50 is provided with inkjet heads for jetting ink droplets from multiple nozzles, a main scan-driving unit 18, and a carriage 14, which is a head-holding unit for holding the inkjet heads so as to face the medium 50. The inkjet heads have nozzle rows in which multiple nozzles line up in a predetermined nozzle row direction. In a cross-section of the medium 50 by a plane that is orthogonal to the main scanning direction, at least the edge on the side facing the inkjet heads is curved. The carriage 14 holds the inkjet heads so that the nozzle row direction is inclined with respect to a secondary scanning direction, which is a direction orthogonal to the main scanning direction.

Description

Printing apparatus and printing method

The present invention relates to a printing apparatus and a printing method.

Conventionally, an ink jet printer that performs printing by an ink jet method has been widely used (see, for example, Patent Document 1). In recent years, media having various shapes other than planar media such as paper and sheets may be used as media (media) used in ink jet printers. More specifically, for example, a medium having a curved surface to be printed may be used, such as a cylindrical medium.

Japanese Patent Laid-Open No. 09-52368

2. Description of the Related Art Conventionally, a configuration having a nozzle row in which a plurality of nozzles are arranged in a predetermined nozzle row direction is widely used as an inkjet head for performing printing in an inkjet printer. In this case, the nozzle row direction is usually set in a direction parallel to the sub-scanning direction orthogonal to the main scanning direction. As an ink jet printer, a serial ink jet printer that causes an ink jet head to perform a main scanning operation (scanning operation) is widely used. *

On the other hand, in the ink jet printer having such a configuration, for example, when a medium having a curved surface to be printed is used, a difference (gap) between the nozzles and the medium is generated depending on the nozzles in the nozzle row. Become. More specifically, for example, when a cylindrical medium is used, even if the gap is adjusted with reference to some nozzles in the nozzle row (for example, the nozzle in the center of the nozzle row), other nozzles (for example, the nozzle row) In some cases, an appropriate gap cannot be set in the nozzle at the end of the nozzle. As a result, it may be difficult to perform printing appropriately for some of the nozzles. *

Therefore, conventionally, there has been a demand for a configuration capable of more appropriately printing on a medium having a curved surface to be printed such as a cylindrical medium. Accordingly, an object of the present invention is to provide a printing apparatus and a printing method that can solve the above-described problems.

The inventor of the present application has conducted intensive research on the above problems. And it discovered that it could print more appropriately by hold | maintaining an inkjet head in the state which inclined the nozzle row direction with respect to the medium whose printing surface is a predetermined curved surface. In order to solve the above problems, the present invention has the following configuration. *

(Configuration 1) A printing apparatus that performs printing on a medium, and includes an inkjet head that ejects ink droplets from a plurality of nozzles, and a main scanning operation that ejects ink droplets while moving in a preset main scanning direction. A main scanning drive unit to be performed by the inkjet head; and a head holding unit that holds the inkjet head so as to face the medium. The inkjet head has a nozzle row in which a plurality of nozzles are arranged in a preset nozzle row direction. In the cross section of the medium by a plane perpendicular to the main scanning direction, at least the outer edge on the side facing the inkjet head is curved, and the head holding portion is in the sub-scanning direction, which is the direction perpendicular to the main scanning direction. The inkjet is held with the nozzle row direction tilted. *

When such a medium is used, the gap, which is the distance between each nozzle and the medium, changes depending on the position in the sub-scanning direction according to the curved surface shape of the medium. In this case, if the length of the nozzle row in the sub-scanning direction is long, the gap difference that is the difference between the maximum value and the minimum value of the gap in the nozzle row tends to increase. As a result, it may be difficult to adjust to an appropriate gap for all nozzles in the nozzle row. *

On the other hand, when configured in this way, the length of the nozzle row in the sub-scanning direction is reduced by holding the inkjet head in a state where the nozzle row direction is inclined with respect to the sub-scanning direction. It can be made smaller than the length. Thereby, the gap difference in a nozzle row can be suppressed appropriately. *

Furthermore, in this case, the length of the nozzle row in the sub-scanning direction can be variously changed by adjusting the angle at which the nozzle row direction is inclined. This also makes it possible to adjust all the nozzles in the nozzle row to an appropriate gap in accordance with the shape of the medium. Therefore, with this configuration, it is possible to perform printing more appropriately on a medium having a curved surface to be printed. *

In this configuration, all the nozzles in the nozzle row may be, for example, nozzles excluding dummy nozzles among a plurality of nozzles constituting the nozzle row. The dummy nozzle is a nozzle (non-ejection nozzle) set in advance so as not to eject ink droplets. The dummy nozzle is set, for example, at a part of the end of the nozzle row in accordance with the structure of the inkjet head. *

Further, with respect to the head holding portion, holding the inkjet head in a state in which the nozzle row direction is inclined with respect to the sub-scanning direction means that the relationship between the sub-scanning direction and the nozzle row direction is in a non-parallel and non-right angle state, Holding the inkjet head. In this case, the angle formed by the nozzle row direction with respect to the sub-scanning direction is preferably 5 to 85 °, for example. The angle is more preferably about 25 to 65 °, for example. *

(Configuration 2) The medium is a cylindrical body whose axial direction is the main scanning direction, and the inkjet head ejects ink droplets onto the side surface of the cylindrical medium. If comprised in this way, it can print more appropriately with respect to the medium of a cylindrical body. The cylindrical medium is an example of a medium in which at least the outer edge on the side facing the ink jet head is curved in the cross section of the medium by a plane orthogonal to the main scanning direction. *

(Configuration 3) The medium is a cylindrical medium. If comprised in this way, it can print more appropriately with respect to a cylindrical medium. The cylindrical medium is an example of a cylindrical medium. *

Further, in other configurations, it is possible to use a medium having a shape other than the cylindrical shape as the medium of the cylindrical body, for example, a cylindrical medium having various shapes such as an ellipse, a kamaboko type, and a peanut type. It is possible to use it. An elliptical, kamaboko-type, or peanut-shaped cylindrical medium is a medium in which the cross section of the medium by a plane orthogonal to the axial direction is an ellipse, kamaboko-type, or peanut-type. Further, in the cylindrical medium, the cross-sectional shape of the medium by a plane orthogonal to the axial direction may be other than the above. In this case, the cross-sectional shape is preferably a shape in which the outer edge is a smooth closed curve. *

(Configuration 4) The image forming apparatus further includes a rotation driving unit that rotates the medium around the rotation axis of the medium parallel to the axial direction of the cylindrical body, and the rotation driving unit rotates the medium between main scanning operations. The area facing the inkjet head in is changed. *

In such a configuration, by rotating the medium by the rotation driving unit, it is possible to sequentially change the area to be printed in each main scanning operation on the side surface of the medium. Accordingly, it is possible to appropriately perform printing on each position on the side surface of the medium. *

(Configuration 5) The head holding unit has a gap that is a distance between each nozzle and the medium in the nozzle row, and a maximum gap and a minimum gap among the gaps at the positions of the nozzles in the nozzle row The inkjet head is held so that the gap difference, which is the difference between the two, is less than 3 mm. The gap difference is preferably less than 2 mm. The gap difference is more preferably less than 1 mm. *

If comprised in this way, the gap difference in a nozzle row can be suppressed appropriately. Thereby, it can print more appropriately with respect to the medium whose printing surface is a curved surface. *

The positional relationship between the nozzle row and the medium is preferably set so that the gap is minimized at the position of the nozzle in the center of the nozzle row. The nozzle at the center of the nozzle row is a nozzle at or near the center of the nozzle row. In this case, the gap is maximized at the position of the nozzle at the end of the nozzle row. The nozzle at the end of the nozzle may be a nozzle at the end of the nozzle row except for the dummy nozzle. *

(Configuration 6) An angle adjustment unit that adjusts a head inclination angle that is an angle at which the nozzle row direction is inclined with respect to the sub-scanning direction is further provided, and the angle adjustment unit adjusts the head inclination angle to an angle at which the gap difference is less than 3 mm. To do. The angle adjustment unit preferably adjusts the head tilt angle so that the gap difference is less than 2 mm. Further, it is more preferable to adjust the head tilt angle so that the gap difference is less than 1 mm. *

If comprised in this way, a gap difference can be adjusted more appropriately. Thereby, it can print more appropriately with respect to the medium whose printing surface is a curved surface. *

The angle adjustment unit adjusts the length of the nozzle row in the sub-scanning direction by adjusting the head tilt angle. In addition, the head tilt angle is adjusted so that the gap difference is within a desired range. As the angle adjusting unit, for example, it is conceivable to use means for automatically adjusting the head tilt angle. Further, it is conceivable to use a means for adjusting the head tilt angle by a manual operation by the user as the angle adjusting unit. *

(Arrangement 7) The head holding unit is configured to perform the operation of the ink formed by the adjacent nozzles in the nozzle row with respect to the ink dots formed on the medium by the ink droplets ejected from each nozzle in one main scanning operation. The inkjet head is held in an inclined state so that the positions of at least some of the dots in the sub-scanning direction overlap, and the printing apparatus performs one main scanning operation for each position of the medium in one pass. The printing operation is performed on the medium. *

In such a configuration, the influence of the ejection characteristics of the individual nozzles can be reduced by setting at least some of the ink dots to overlap in the sub-scanning direction. This also makes it possible to appropriately suppress the influence of the ejection characteristics of the nozzles on the image quality of the printed image even when, for example, the ejection characteristics of some of the nozzles are abnormal. As a result, for example, the influence of variation in the ejection characteristics of the nozzles can be appropriately suppressed without performing multi-pass printing. *

Furthermore, in this case, the nozzle interval in the sub-scanning direction is made smaller than the nozzle pitch in the nozzle row by inclining the nozzle row direction with respect to the sub-scanning direction. In this case, the nozzle pitch in the nozzle row is, for example, a nozzle interval in the nozzle row direction. Therefore, when configured in this way, it is not necessary to perform multi-pass printing for the purpose of increasing the printing resolution in the sub-scanning direction. *

Therefore, if configured in this way, printing can be performed more appropriately on a medium having a curved surface to be printed by a printing operation in one pass. In addition, this makes it possible to appropriately increase the printing speed as compared with the case where printing is performed by the multipass method. *

In addition, regarding the ink dots formed on the medium by the ink droplets ejected from each nozzle in one main scanning operation, at least a part of the ink dots formed by the adjacent nozzles in the nozzle row The overlapping of the positions in the scanning direction means, for example, that the dot interval in the sub-scanning direction is smaller than the dot diameter. In this case, the dot interval in the sub-scanning direction is a distance between centers in the sub-scanning direction between adjacent dots in the sub-scanning direction. *

(Configuration 8) Nozzle row of an inkjet head held in an inclined state with respect to the dot interval corresponding to the highest resolution determined according to the diameter of the ink dots formed on the medium by the ink droplets ejected from the nozzles When the interval between the nozzles in the sub-scanning direction is smaller, the inkjet head ejects ink droplets from only some of the nozzles in the nozzle row in each main scanning operation. *

When the nozzle row direction is tilted with respect to the sub-scanning direction, if other conditions are the same, the amount of ink ejected per unit area is larger than when the nozzle row direction is not tilted. As a result, the amount of ink may be excessive depending on the angle at which the nozzle row direction is inclined.

More specifically, for example, when the nozzle interval in the sub-scanning direction is smaller than the dot interval corresponding to the highest resolution determined according to the diameter of the ink dots, the angle that simply tilts the nozzle row direction If only is changed, the amount of ink may become excessive. *

On the other hand, with this configuration, the nozzles to be used can be thinned out appropriately by ejecting ink droplets from only some of the nozzles in each main scanning operation. Thereby, it can prevent appropriately that the amount of ink becomes excessive. *

(Configuration 9) Nozzle row of an inkjet head held in an inclined state with respect to a dot interval corresponding to the highest resolution determined according to the diameter of the ink dots formed on the medium by the ink droplets ejected from the nozzles When the interval between the nozzles in the sub-scanning direction is larger, the main scanning drive unit sets the moving speed for moving the inkjet head during the main scanning operation to the first preset speed, and the highest resolution. When the nozzle spacing in the sub-scanning direction of the inkjet head held in an inclined state is smaller than the dot spacing corresponding to, the main scanning driving unit determines the first moving speed during the main scanning operation. A second speed higher than the speed is set. *

As described above, for example, when the nozzle interval in the sub-scanning direction is smaller than the dot interval corresponding to the highest resolution determined according to the ink dot diameter, the angle at which the nozzle row direction is simply tilted is changed. If only the change is made, the amount of ink may become excessive. On the other hand, when configured in this manner, the moving speed of the inkjet head during the main scanning operation can be appropriately changed according to the change in the nozzle interval in the sub-scanning direction depending on the angle at which the nozzle row direction is inclined. it can. In addition, this makes it possible to appropriately adjust the amount of ink ejected with respect to the unit area by changing the feed amount in the main scanning direction, which is the distance that the inkjet head moves in the main scanning direction per unit time. . Therefore, with this configuration, it is possible to appropriately prevent the amount of ink from becoming excessive. *

(Configuration 10) The image forming apparatus further includes a control unit that controls the operation of the printing apparatus, and the head holding unit can select at least a plurality of types of angles as the angle at which the nozzle row direction is inclined with respect to the sub-scanning direction. The operation of at least the inkjet head and the main scanning drive unit is controlled according to the angle at which the nozzle row direction is inclined with respect to the sub-scanning direction. *

If comprised in this way, the angle which inclines a nozzle row direction can be adjusted appropriately to various angles. Further, by controlling each part according to the angle at which the nozzle row direction is inclined, printing can be appropriately performed even when the angle at which the nozzle row direction is inclined is changed. *

In addition, it is preferable that a control part controls operation | movement according to the angle which inclines a nozzle row direction also about the other structure in a printing apparatus. For example, when the printing apparatus further includes a rotation drive unit, the operation of the rotation drive unit is preferably controlled according to the angle at which the nozzle row direction is inclined. *

(Configuration 11) The head holding unit can hold the inkjet head even in a state where the sub-scanning direction and the nozzle row direction are parallel to each other. The state in which the sub-scanning direction and the nozzle row direction are parallel to each other is a state in which the head holding unit holds the inkjet head without tilting the nozzle row direction with respect to the sub-scanning direction. In this case, it is preferable that the printing apparatus performs printing by a multi-pass method. *

When configured in this way, printing with the same configuration as a conventional inkjet printer can be performed as necessary. Therefore, with this configuration, printing can be performed under more various conditions. *

(Configuration 12) A printing method for performing printing on a medium, wherein an ink jet head that discharges ink droplets from a plurality of nozzles is held opposite to the medium, and the main scanning direction set in advance on the ink jet head The ink jet head has a nozzle row in which a plurality of nozzles are arranged in a preset nozzle row direction, and the section of the medium is cut by a plane orthogonal to the main scanning direction. In this case, at least the outer edge on the side facing the inkjet head is curved, and holds the inkjet head in a state in which the nozzle row direction is inclined with respect to the sub-scanning direction that is a direction orthogonal to the main scanning direction. If comprised in this way, the effect similar to the structure 1 can be acquired.

According to the present invention, it is possible to more appropriately perform printing on a medium having a curved printing surface.

1 is a diagram illustrating an example of a configuration of a printing apparatus 10 according to an embodiment of the present invention. FIG. 3 is a diagram for explaining a method of holding an inkjet head by a carriage and a more specific configuration of a head unit. FIG. 2A shows an example of how the inkjet head 102 is held by the carriage 14. FIG. 2B is an enlarged view showing an example of the configuration of the inkjet head 102 in the head unit 12. It is a figure explaining in more detail about a head inclination angle. It is a figure which shows the example at the time of tilting the inkjet head 102 so that head inclination-angle (theta) may be 84.26 degrees. 6 is a diagram illustrating an example when the inkjet head 102 is tilted so that the head tilt angle θ is 78.46304 °. FIG. It is a figure which shows the example at the time of tilting the inkjet head 102 so that head inclination-angle (theta) may be 75.5225 degrees. It is a figure which shows the example at the time of tilting the inkjet head 102 so that head inclination-angle (theta) may be 60 degrees. It is a figure explaining the modification of a structure of the head part. FIG. 8A shows an example of the configuration of a conventional head unit. FIG. 8B shows a configuration of a modified example of the head unit 12. FIG. 8C shows a configuration of a further modification of the head unit 12. It is a figure explaining the further modification of the structure of the head part. FIG. 9A shows a configuration of a further modified example of the head unit 12. FIG. 9B shows a configuration of a further modification of the head unit 12. It is a figure explaining the further modification of the structure of the head part.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. FIG. 1 shows an example of the configuration of a printing apparatus 10 according to an embodiment of the present invention. In this example, the printing apparatus 10 is an ink jet printer that performs printing on a cylindrical medium 50, and includes a head unit 12, a carriage 14, a guide rail 16, a main scanning drive unit 18, a rotation drive unit 20, An angle adjustment unit 22 and a control unit 24 are provided. In FIG. 1, the main scanning direction is the Y direction shown in the figure. Except as described below, the printing apparatus 10 of this example may have the same or similar configuration as the known printing apparatus 10. *

The cylindrical medium 50 is, for example, a medium (printed cylinder) in which the cross section of the medium is a circular shape by a plane orthogonal to the axial direction that is the direction in which the cylinder extends. In this case, that the cross section of the medium 50 is circular means that, for example, the outer edge of the cross section is a circle. Further, the cylindrical medium 50 used in this example is an example of a cylindrical medium. In another example of the configuration of the printing apparatus 10, it is also possible to use a cylindrical medium having various shapes such as an ellipse, a kamaboko type, and a peanut type as the cylindrical medium. In this case, the medium having an elliptical, kamaboko-type, or peanut-type cylindrical body is, for example, a medium in which the cross section of the medium by a plane orthogonal to the axial direction is an ellipse, kamaboko-type, or peanut-type. Further, in the cylindrical medium, the cross-sectional shape of the medium by a plane orthogonal to the axial direction may be other than the above. In this case, the cross-sectional shape is preferably a shape in which the outer edge is a smooth closed curve. *

The cylindrical medium is an example of a medium having a curved printed surface. In this case, the medium having a curved surface to be printed is, for example, a cross section of a plane perpendicular to the main scanning direction (scanning direction) and having a curved outer edge at least on the side facing the head portion 12. It is. In this example, the main scanning direction is a direction set in advance as the moving direction of the head unit 12 during the main scanning operation. In this case, the main scanning operation is, for example, an operation in which the ink jet head in the head unit 12 moves in the main scanning direction while ejecting ink droplets. *

The head portion 12 is a portion having an inkjet head that ejects ink droplets from a plurality of nozzles. In this example, the head unit 12 has a plurality of inkjet heads. Each inkjet head has a nozzle row in which a plurality of nozzles are arranged in a preset nozzle row direction. In each nozzle row, the plurality of nozzles are arranged so that the nozzle pitch P, which is the interval in the nozzle row direction, is constant. *

As the ink jet head in the head unit 12, for example, a known ink jet head can be suitably used. In this example, the ink jet head in the head unit 12 discharges ink droplets onto the medium 50 by performing a main scanning operation. A more specific configuration of the head unit 12 will be described in more detail later. *

The carriage 14 is an example of a head holding unit, and holds the inkjet head in the head unit 12 facing the medium 50. In this example, the carriage 14 holds the inkjet head in a state where the nozzle row direction is inclined with respect to the sub-scanning direction. In this case, the sub-scanning direction is a direction orthogonal to the main scanning direction. In the configuration shown in FIG. 1, the sub-scanning direction is a direction parallel to the X direction shown in the drawing. The X direction is a direction orthogonal to the Y direction in the horizontal plane. The method of holding the ink jet head by the carriage 14 will also be described in more detail later. *

The guide rail 16 is a rail member (Y bar) extending in the main scanning direction, and holds the carriage 14 so as to be movable in the main scanning direction. Accordingly, the guide rail 16 guides the movement of the carriage 14 in the main scanning direction. *

The main scanning drive unit 18 is a drive unit that causes the inkjet head to perform a main scanning operation. In this example, the main scanning drive unit 18 moves the carriage 14 along the guide rail 16 to move the inkjet head in the head unit 12 in the main scanning direction. Further, based on the image to be printed, ink droplets are ejected to the moving inkjet head. Thereby, the main scanning drive unit 18 causes the inkjet head in the head unit 12 to perform a main scanning operation based on the image to be printed. *

The rotation drive unit 20 is a drive unit that rotates the medium 50 around the rotation axis of the medium 50 that extends parallel to the axial direction of the cylindrical medium 50. In this example, the rotation drive unit 20 holds the medium 50 in a direction in which the axial direction of the medium 50 is parallel to the main scanning direction. The rotation driving unit 20 causes the inkjet head and the side surface of the medium 50 to face each other so that the inkjet head in the head unit 12 ejects ink droplets onto the side surface of the cylindrical medium 50. *

In this example, the rotation driving unit 20 changes the area of the medium 50 facing the head unit 12 by rotating the medium 50 between main scanning operations. In this case, due to the rotation of the medium 50, the area of the medium 50 facing the head unit 12 moves in the sub-scanning direction (X direction in FIG. 1) orthogonal to the main scanning direction. Accordingly, the rotation driving unit 20 also functions as a sub-scanning driving unit that sends the medium 50 in the sub-scanning direction between main scanning operations. *

In this case, the movement of the region in the sub-scanning direction may mean that the region moves in the sub-scanning direction with an accuracy according to the print quality. Further, the movement direction of the region may be a tangential direction of movement caused by rotation. *

In this example, the rotation driving unit 20 includes a housing unit 32, a driven roller 34, and a driving roller 36. The housing part 32 is a housing part of the rotation driving unit 20 and holds the driven roller 34 and the driving roller 36 rotatably with the axial direction of the driven roller 34 and the driving roller 36 parallel to the main scanning direction. In this example, the casing 32 is driven by the driven roller 34 at a position opposite to the head 12 side in the circumferential direction of the medium 50 with each axial direction parallel to the main scanning direction. And the driving roller 36 is held. Thereby, the driven roller 34 and the driving roller 36 support the medium 50 from the side opposite to the head portion 12 side.

The driven roller 34 is a roller that rotates in accordance with the rotation of the medium 50, and is in contact with the side surface of the medium 50 on one side in the sub-scanning direction from the axis of the medium 50. The drive roller 36 is a roller that is rotationally driven by a motor or the like (not shown), and is in contact with the side surface of the medium 50 on the other side in the sub-scanning direction from the axis of the medium 50. Thereby, the drive roller 36 rotates the medium 50 according to its rotation. In this case, the medium 50 rotates around its own axis. *

By rotating the medium 50 by the rotation driving unit 20, it is possible to sequentially change the area to be printed in each main scanning operation on the side surface of the medium 50. Accordingly, it is possible to appropriately perform printing on each position on the side surface of the medium 50. *

As described above, in this example, the rotation drive unit 20 is configured such that the drive roller 36 and the driven roller 34 are paired. However, the configuration of the rotation drive unit 20 is not necessarily limited to this configuration, and can be variously modified. For example, when a heavy cylindrical medium 50 is used, a configuration in which two drive rollers are paired may be used. If comprised in this way, even when the weight of the medium 50 is large, for example, the medium 50 can be rotated more appropriately. *

The angle adjustment unit 22 is a configuration for adjusting a head tilt angle (tilt angle) that is an angle at which the inkjet head of the head unit 12 is tilted. In this case, the head tilt angle is more specifically an angle at which the nozzle row direction in the inkjet head is tilted with respect to the sub-scanning direction. As the angle adjusting unit 22, for example, it is conceivable to use means for automatically adjusting the head tilt angle. In this case, for example, it is conceivable to automatically adjust the head tilt angle in accordance with conditions such as the diameter of the cylindrical medium 50. Further, it is conceivable to use means for adjusting the head tilt angle by a manual operation by the user as the angle adjusting unit 22. The specific operation of the angle adjustment unit 22 will be described in more detail later. *

The control unit 24 is, for example, a CPU of the printing apparatus 10 and controls each unit of the printing apparatus 10. According to this example, it is possible to appropriately perform printing on a cylindrical medium 50 or the like. *

Next, a method for holding the inkjet head by the carriage 14 and a more specific configuration of the head unit 12 will be described in more detail. In this example, the carriage 14 can select at least a plurality of types of angles as the head tilt angle. Further, the inkjet head can be held even when the sub-scanning direction and the nozzle row direction are parallel to each other. In this case, the state in which the sub-scanning direction and the nozzle row direction are parallel to each other is a state (normal arrangement) where the carriage 14 holds the inkjet head without tilting the nozzle row direction with respect to the sub-scanning direction. In FIG. 1, a range indicated by a broken line around the head portion 12 indicates the position of the head portion 12 in the normal arrangement. Further, the carriage 14 holds the head unit 12 so as to be rotatable in the nozzle surface, for example, and the head unit 12 in the sub-scanning direction is held by holding the head unit 12 in an inclined state (diagonal arrangement) in the nozzle row direction. The width of 12 is variously changed within the range indicated by the broken line in the figure. *

In this case, tilting and holding the head unit 12 means holding the nozzle row direction of the inkjet head included in the head unit 12 in a state tilted with respect to the sub-scanning direction. Moreover, being rotatable in the nozzle surface means being rotatable in a plane parallel to the surface on which the nozzle is formed in the inkjet head. *

FIG. 2 is a diagram for explaining a method of holding the ink jet head by the carriage 14 and a more specific configuration of the head unit 12. FIG. 2A shows an example of how the inkjet head 102 is held by the carriage 14. FIG. 2B is an enlarged view showing an example of the configuration of the inkjet head 102 in the head unit 12. *

In the present example, the head unit 12 includes a plurality of inkjet heads 102. The plurality of inkjet heads 102 ejects ink droplets of different colors, for example. Each inkjet head 102 has a nozzle row 202 in which a plurality of nozzles 204 are arranged in the nozzle row direction, which is the longitudinal direction of the inkjet head 102. *

In FIG. 2A, regarding the configuration of the head unit 12, a state in which the sub-scanning direction and the nozzle row direction are parallel to each other is indicated by a solid line, and a state in which the nozzle row direction is inclined with respect to the sub-scanning direction is indicated by a dotted line. Is shown. FIG. 2B shows an example of a state in which the nozzle array direction is inclined with respect to the sub-scanning direction as viewed from the medium 50 side. *

When printing is performed using the inkjet head 102 having the nozzle array 202, the inkjet head 102 forms a plurality of ink dots arranged at a predetermined density by ejecting ink droplets from the nozzles 204 in the nozzle array 202. To do. In this case, the width of the band region (width in the sub-scanning direction), which is a region where ink droplets are ejected by the inkjet head 102 in one main scanning operation, is equal to the length of the nozzle row 202 in the sub-scanning direction. *

More specifically, in this example, the plurality of inkjet heads 102 are arranged side by side in the main scanning direction with the same head inclination angle. In this case, the range in the sub-scanning direction of the region where the nozzles 204 are arranged in each inkjet head 102, that is, the length of the nozzle row 202 in the sub-scanning direction is in the range of the width Lx determined according to the head tilt angle. . The width Lx is maximized when the nozzle row direction is not tilted, and gradually decreases as the head tilt angle increases within an angle range of 90 ° or less. *

Therefore, in this example, when the inkjet head 102 is held with the nozzle row direction tilted, the length of the nozzle row 202 in the sub-scanning direction is smaller than the length of the nozzle row 202 in the nozzle row direction. As a result, the width of the band area (print width) is also maximized when the nozzle row direction is not tilted, and gradually becomes narrower as the head tilt angle increases within an angle range of 90 ° or less. . *

Here, when printing is performed by the inkjet method, the inkjet head 102 ejects ink droplets to the medium 50 in a non-contact state with a gap between the inkjet head 102 and the medium 50. In addition, when a medium 50 having a curved surface to be printed is used, such as the cylindrical medium 50, the gap that is the distance between each nozzle 204 and the medium 50 in the inkjet head 102 is the curved shape of the medium 50. Accordingly, it changes depending on the position in the sub-scanning direction. In this case, if the length of the nozzle row 202 in the sub-scanning direction is long, the difference (gap difference) between the maximum value and the minimum value of the gap in the nozzle row 202 tends to increase. As a result, it may be difficult to adjust to an appropriate gap for all nozzles in the nozzle row 202. *

On the other hand, in this example, the length of the nozzle row 202 in the sub-scanning direction can be changed variously by adjusting the head tilt angle, for example. Accordingly, it is possible to appropriately suppress a gap difference in the nozzle row 202 and adjust all the nozzles 204 in the nozzle row 202 to an appropriate gap. Therefore, according to this example, it is possible to perform printing more appropriately on the cylindrical medium 50 or the like. *

In this case, all the nozzles in the nozzle row 202 may be the nozzles 204 excluding the dummy nozzles among the plurality of nozzles 204 constituting the nozzle row 202. The dummy nozzle is a nozzle (non-ejection nozzle) set in advance so as not to eject ink droplets. The dummy nozzle is set at a part of the end of the nozzle row 202 according to the structure of the inkjet head 102, for example. *

As described above, in this example, at least a plurality of types of angles can be selected as the head tilt angle. In this case, the control unit 24 (see FIG. 1) preferably controls the operation of each unit of the printing apparatus 10 according to the head tilt angle. For example, it is conceivable that the control unit 24 controls the operations of the plurality of inkjet heads 102 and the main scanning drive unit 18 (see FIG. 1) according to the head tilt angle. In this case, more specifically, for example, changing the moving speed of the head unit 12 during the main scanning operation according to the head tilt angle may be considered. *

It is also conceivable that the control unit 24 controls the operation of the rotation drive unit 20 (see FIG. 1), for example, according to the head tilt angle. In this case, more specifically, for example, the rotation amount by which the medium 50 is rotated by the rotation drive unit 20 between main scanning operations may be set according to the width of the band region determined according to the head tilt angle. Conceivable. With this configuration, for example, the feeding amount of the medium 50 in the sub-scanning direction can be appropriately adjusted as the band area is narrowed by the oblique arrangement of the head unit 12. *

With such a configuration, the head tilt angle can be appropriately adjusted to various angles. Further, by controlling each unit according to the head tilt angle, it is possible to perform printing appropriately even when the head tilt angle is changed. *

Further, when the nozzle row direction is inclined with respect to the sub-scanning direction as in this example, the interval between the nozzles 204 in the sub-scanning direction also changes. As a result, the density of ink dots formed on the medium 50 in the sub-scanning direction also changes according to the interval between the nozzles 204 in the sub-scanning direction. *

More specifically, for example, when the nozzle row direction and the sub-scanning direction are parallel, the interval between the nozzles 204 in the sub-scanning direction is equal to the nozzle pitch P that is the interval between the nozzles in the nozzle row. As a result, the density of ink dots in the sub-scanning direction becomes a density corresponding to the nozzle pitch P. *

On the other hand, when the nozzle row direction is tilted with respect to the sub-scanning direction, the interval between the nozzles 204 in the sub-scanning direction is reduced according to the head tilt angle. As a result, the nozzle interval in the sub-scanning direction is smaller than the nozzle pitch P. Therefore, when configured in this way, the density of ink dots in the sub-scanning direction is higher than the density corresponding to the nozzle pitch P. *

Therefore, according to this example, it is possible to increase the density of ink dots in the sub-scanning direction by inclining the nozzle row direction with respect to the sub-scanning direction. Thereby, the printing resolution in the sub-scanning direction can be increased. Further, by adjusting the head tilt angle, it is possible to adjust the ink dot density, the printing resolution, and the like in the sub-scanning direction. *

In this case, the inkjet head 102 is inclined by the carriage 14 so that, for example, at least a part of the ink dots formed by the adjacent nozzles 204 in the nozzle row 202 overlap in the sub-scanning direction. It is conceivable to hold it with. In this case, at least a portion of the ink dots in the sub-scanning direction is overlapped means that the ink dots formed on the medium by the ink droplets discharged from the respective nozzles 204 in one main scanning operation. In other words, at least some positions in the sub-scanning direction overlap. *

In such a configuration, for example, the influence of the ejection characteristics of the individual nozzles 204 can be reduced by overlapping the positions of at least some of the ink dots in the sub-scanning direction. Accordingly, for example, even when the ejection characteristics of some of the nozzles 204 are abnormal, it is possible to appropriately suppress the ejection characteristics of the nozzles 204 from affecting the image quality of the printed image. As a result, for example, the influence of variations in the ejection characteristics of the nozzles 204 can be appropriately suppressed without performing multi-pass printing. In this case, the multi-pass method is a method in which, for example, a main scanning operation is performed a plurality of times for each position of a printing area where printing is performed on the medium 50.

Further, in this case, the interval between the nozzles 204 in the sub-scanning direction is smaller than the nozzle pitch P by tilting the nozzle row direction with respect to the sub-scanning direction. Therefore, for example, it is not necessary to perform multi-pass printing for the purpose of increasing the printing resolution in the sub-scanning direction. *

Therefore, in this example, for example, printing can be appropriately performed on the cylindrical medium 50 by a printing operation in one pass. In this case, the printing operation in one pass is an operation for performing printing by performing one main scanning operation for each position of the medium 50. In addition, this makes it possible to appropriately increase the printing speed, for example, compared to the case where printing is performed using a multi-pass method. That is, according to this example, for example, high-speed decoration can be more appropriately performed on a medium 50 such as a cylinder using an inkjet head having a sufficiently long length (nozzle width) in the nozzle row direction. it can. *

Further, in this example, by increasing the density of ink dots in the sub-scanning direction by the oblique arrangement, it is possible to increase the amount of ink ejected per unit area in one main scanning operation. In this case, for example, with respect to the amount of ink ejected per unit area, the amount of ink ejected per unit area is several times to several tens of times compared to the normal arrangement in which the nozzle row direction is not inclined with respect to the sub-scanning direction. It is possible to increase *

In this case, it is preferable to adjust the amount of ink ejected per unit area so that the amount of ink does not become excessive. As such adjustment, for example, a method of thinning out some of the nozzles 204 in the nozzle row 202, a method of changing the moving speed (feed amount in the main scanning direction) of the head unit 12 during the main scanning operation, or the like. Can be considered. *

Such adjustment is performed by adjusting the interval of the nozzles 204 in the sub-scanning direction in the nozzle row 202 held in an inclined state rather than the dot interval corresponding to the highest resolution determined according to the diameter of the ink dots. This can be done when is small. In this case, the highest resolution determined according to the diameter of the ink dot is the highest resolution for the ink dot formed in one main scanning operation. The highest resolution determined according to the diameter of the ink dot is a resolution at which the dot interval corresponding to the resolution is equal to the diameter of the ink dot. In this case, the dot interval corresponding to the highest resolution is a dot interval equal to the dot diameter. *

The diameter of the ink dot is the diameter of the ink dot formed on the medium 50 by the ink droplet ejected from the nozzle 204. The ink dot diameter may be, for example, a standard dot diameter. Further, the diameter of the ink dot may be an average diameter of the actually formed ink dot. In practice, the dot diameter may be, for example, a designed diameter. *

Further, when adjusting the amount of ink to be ejected per unit area, for example, it is conceivable that the ink jet head 102 causes ink droplets to be ejected from only some of the nozzles 204 in the nozzle row 202 in each main scanning operation. . If comprised in this way, the nozzle 204 used in each main scanning operation | movement can be thinned out appropriately, for example. In addition, this makes it possible to appropriately prevent the amount of ink from becoming excessive. *

Further, as described above, the adjustment of the amount of ink ejected per unit area may be performed by a method of changing the moving speed of the head unit 12 during the main scanning operation. For example, the movement of moving the inkjet head during the main scanning operation according to the magnitude relationship between the dot spacing corresponding to the highest resolution and the spacing of the nozzles 204 in the sub-scanning direction of the inkjet head 102 held in an inclined state It is possible to vary the speed. More specifically, when the interval between the nozzles 204 in the sub-scanning direction of the inkjet head 102 held in an inclined state is larger than the dot interval corresponding to the highest resolution, the main scanning drive unit 18 (FIG. 1). Is set to a preset first speed with respect to the moving speed for moving the inkjet head 102 during the main scanning operation. When the nozzle interval in the sub-scanning direction of the inkjet head 102 held in an inclined state is smaller than the dot interval corresponding to the highest resolution, the main scanning driving unit 18 performs the inkjet operation during the main scanning operation. The moving speed of the head 102 is set to a second speed that is faster than the first speed. *

When configured in this manner, the moving speed of the inkjet head 102 during the main scanning operation can be appropriately changed according to the change in the interval between the nozzles 204 in the sub-scanning direction depending on the head tilt angle. In addition, this makes it possible to appropriately adjust the amount of ink ejected per unit area by changing the feed amount in the main scanning direction, which is the distance that the inkjet head 102 moves in the main scanning direction per unit time. it can. Therefore, even when configured in this way, it is possible to appropriately prevent the amount of ink from becoming excessive. *

Here, with respect to the printing apparatus 10 of this example, supplementary explanation will be given regarding more specific various features. The ink used in the inkjet head 102 of this example is not limited to a specific ink, and various known inks can be used. For example, it is conceivable to use an energy ray curable ink such as an ultraviolet curable ink (UV ink), a solvent UV ink (SUV ink), a latex ink, or a solvent ink. The specific configuration of the printing apparatus 10 is preferably changed as appropriate according to the ink to be used. *

Further, the color of the ink is not limited to a specific color, and various colors of ink can be used. For example, Y (yellow), M (magenta), C (cyan), K (black), or light color inks such as LM (light magenta), LC (light cyan), LK (light black) are used. Can be considered. Also, clear color, white color, metallic color, and other various special color inks may be used. *

Further, as the ink jet head 102, for example, a piezo ink jet head can be used. In this case, the inkjet head 102 has a piezoelectric element at the position of each nozzle 204. *

In addition, as described above, in this example, the inkjet head 102 can be held even in a state where the sub-scanning direction and the nozzle row direction are parallel to each other. In this case, the printing apparatus 10 may perform printing by a multi-pass method, for example, in the same or similar manner to a known inkjet printer. *

In addition, as described above, the printing apparatus 10 is not limited to the cylindrical medium 50 having a perfect cross section, and may have various shapes such as an ellipse, a kamaboko type, and a peanut type. The use of body media is also conceivable. In this case, it is preferable that the side surface to be printed is a curved surface that can rotate. In the case where various cylindrical media are used, the diameter of the media may vary along the axial direction. In this case, the printing apparatus 10 preferably has a mechanism for changing the position of the head unit 12 in the height direction. In this case, the height direction is a direction orthogonal to the main scanning direction and the sub-scanning direction. Further, the height direction may be a direction connecting the inkjet head 102 and the medium 50. If comprised in this way, the position of the inkjet head 102 can be adjusted appropriately according to the change of the diameter of a medium. *

Next, regarding the specific operation of the angle adjusting unit 22 shown in FIG. 1, the angle at which the inkjet head 102 is held by the carriage 14 will be described in more detail. As described above, in this example, the carriage 14 holds the plurality of inkjet heads 102 in a state where the nozzle row direction is inclined with respect to the sub-scanning direction. In this case, holding the inkjet head in a state in which the nozzle row direction is inclined with respect to the sub-scanning direction means that the relationship between the sub-scanning direction and the nozzle row direction is non-parallel and non-perpendicular, Is to hold. In this case, the angle formed by the nozzle row direction with respect to the sub-scanning direction is preferably 5 to 85 °, for example. The angle is more preferably about 25 to 65 °, for example. *

FIG. 3 is a diagram for explaining the head tilt angle in more detail. In the case where a plurality of inkjet heads of the head unit 12 are held with the nozzle row direction tilted, the positional relationship between the head unit 12 and the medium 50 is shown. An example is shown. *

As described above, when the cylindrical medium 50 or the like is used, the gap that is the distance between each nozzle 204 and the medium 50 in the inkjet head 102 is sub-scanned according to the curved surface shape of the medium 50. Varies with position in direction. In this case, if the length of the nozzle row 202 in the sub-scanning direction is long, the gap difference that is the difference between the maximum value and the minimum value of the gap in the nozzle row 202 tends to increase. *

On the other hand, in this example, adjustment is performed so that the length of the nozzle row 202 in the sub-scanning direction becomes shorter by adjusting the head inclination angle by the angle adjustment unit 22 (see FIG. 1). This prevents the gap difference from becoming too large. More specifically, the angle adjusting unit 22 adjusts the head tilt angle to an angle at which the gap difference is less than 3 mm. Further, it is preferable that the angle adjusting unit 22 adjusts the head tilt angle so that the gap difference is more preferably less than 2 mm, and even more preferably less than 1 mm. If comprised in this way, the gap difference in a nozzle row can be suppressed appropriately. Moreover, it is possible to perform printing more appropriately on a cylindrical medium 50 or the like. *

Here, the gap and gap difference generated in the configuration of this example will be described more specifically. For example, when a medium 50 having a curved surface to be printed is used, such as a cylindrical medium 50, the positional relationship between the nozzle array 202 and the medium 50 in the inkjet head 102 is, for example, a nozzle at the center of the nozzle array 202. It is preferable to set the gap at the position 204 to be minimum. In this case, the nozzle 204 at the center of the nozzle row 202 is a nozzle 204 at or near the center of the nozzle row 202. In this case, the gap is maximized at the position of the nozzle 204 at the end of the nozzle row 202. The nozzle 204 at the end of the nozzle row 202 may be, for example, the nozzle 204 at the end of the nozzle row 202 excluding the dummy nozzle. *

More specifically, FIG. 3 is a cross-sectional view of the head unit 12 and the medium 50 taken along a plane orthogonal to the main scanning direction. The nozzle row direction is inclined with respect to the sub-scanning direction, and the length of the nozzle row in the sub-scanning direction. The gap difference ΔLg is specifically shown for the case where the length becomes Dh. In this case, Dh is the maximum print width by the obliquely arranged head unit 12. In FIG. 3, the range indicated by a broken line around the head portion 12 indicates the position of the head portion 12 in the normal arrangement as in FIG. 1. *

In FIG. 3, point A indicates the position of the nozzle 204 at the center of the nozzle row 202. The nozzle 204 is a nozzle at a position where the gap is minimized. Point B indicates the position of the nozzle 204 at the end of the nozzle row 202. The nozzle 204 is a nozzle 204 at a position where the gap is maximized. A point C indicates an intersection of a straight line connecting the point A and the center of the medium 50 and a side surface of the medium 50. A point D indicates an intersection of a straight line connecting the point B and the center of the medium 50 and a side surface of the medium 50. In this case, the center of the medium 50 is a position corresponding to the rotation axis of the medium 50 in the cross section shown in the figure.

The distance r is a radius of a circle that becomes a cross section of the medium 50. Θ is an angle formed by a straight line from the center of the medium 50 toward the point A and a straight line from the center of the medium 50 toward the point B. Lgc is a gap at the position of the point A. In the illustrated case, Lgc is the minimum gap. Lge is a gap at the position of the point D. In the illustrated case, Lge is the maximum gap. In this case, the gap difference ΔLg is a distance calculated by ΔLg = Lge−Lgc. *

In FIG. 3, the distance HΘ represents the distance in the height direction from the center of the medium 50 to the point D. In the illustrated case, HΘ = r · cosΘ. In this case, as is apparent from the figure, the gap difference ΔLg can be expressed as ΔLg = r−HΘ = r (1−cosΘ). *

At the time of printing, for example, based on the relationship between these parameters, the head tilt angle is adjusted automatically or manually by the angle adjusting unit 22 according to the cylindrical diameter of the medium 50 or the like. In this case, the gap difference ΔLg (absolute value) is preferably set to less than 3 mm as described above. Further, the gap difference Lg is more preferably less than 2 mm, and still more preferably less than 1 mm. *

If comprised in this way, gap difference (DELTA) Lg can be suppressed appropriately. In addition, for example, printing can be performed more appropriately on a medium 50 such as a cylindrical shape. *

Further, as can be seen from the figure, in the illustrated case, the distance between the point A and the point B is Dh / 2. Further, the circumferential length between the points C and D is 2πr (Θ / 360). In this case, in adjusting the head tilt angle, it is preferable to further adjust the ratio Ra = (Dh / 2) / {2πr (Θ / 360)} to be less than 3/1000. With such a configuration, it is possible to appropriately prevent the image printed on the side surface of the medium 50 from being distorted. The ratio Ra is more preferably less than 1/1000. If comprised in this way, distortion of an image can be prevented more appropriately. *

Further, as described above, when the head tilt angle is changed, the printing resolution in the sub-scanning direction also changes due to the change in the nozzle interval in the sub-scanning direction. Therefore, the adjustment of the head tilt angle is preferably performed in consideration of the change in resolution. *

Next, the state where the head tilt angle is set to various angles will be described in more detail. 4 to 7 show examples of the relationship between the head tilt angle and the length of the nozzle row 202 in the sub-scanning direction for various head tilt angles. 4 to 7 show a state in which the head inclination angle θ is variously different for one ink-jet head 102 in contrast to the case where the ink-jet head 102 is not inclined. *

FIG. 4 shows an example in which the inkjet head 102 is tilted so that the head tilt angle θ is 84.26 °. In the drawing, the inkjet head 102 indicated by reference numeral A indicates the inkjet head 102 in a state where it is not tilted. In this case, the state of not tilting is a state in which the nozzle row direction and the sub-scanning direction are parallel to each other. In this case, the plurality of nozzles 204 in the nozzle row 202 are arranged in a range of a width L0 equal to the length of the nozzle row in the sub-scanning direction. *

In addition, an inkjet head 102 denoted by reference numeral B indicates the inkjet head 102 in a state where it is inclined by an angle θ. In this case, the state inclined by the angle θ is a state in which the angle formed between the nozzle row direction and the sub-scanning direction is θ by rotating the inkjet head 102. In this case, the plurality of nozzles 204 in the nozzle row 202 are arranged in the range of the width Lx narrower than the width L0 in the sub-scanning direction. More specifically, when θ is 84.26 °, the width Lx is 1/10 of the width L0. *

That is, by setting the head tilt angle θ in this way, the length of the nozzle row 202 in the sub-scanning direction can be reduced to 1/10 that when the inkjet head 102 is not tilted. Thereby, even when a cylindrical medium or the like is used, the gap difference can be appropriately suppressed. *

In this case, the nozzle resolution in the sub-scanning direction in the state where the inkjet head 102 is tilted is 10 times that in the case where the inkjet head 102 is not tilted. The nozzle resolution in the sub-scanning direction is a resolution corresponding to the interval between the nozzles 204 in the sub-scanning direction. Therefore, in this case, 10 times more ink can be ejected to the medium 50 per unit length in the sub-scanning direction than when the inkjet head 102 is not tilted. Thereby, the amount of ink discharged per unit area can be increased appropriately. *

In this case, it is conceivable to adjust the moving speed of the ink jet head 102 during the main scanning operation according to the head tilt angle, and set the speed to 1/10 when the ink jet head 102 is not tilted. With this configuration, the amount of ink discharged per unit area can be increased by a factor of 100 compared to when the inkjet head 102 is not tilted. *

Here, as described above, in this example, the ink ejection amount per unit area is increased, and the ink dots formed by the adjacent nozzles 204 in the nozzle row 202 are formed at the positions. At least a part of which overlaps in the sub-scanning direction. With this configuration, for example, the influence of variation in the ejection characteristics of the nozzles 204 can be appropriately suppressed without performing multi-pass printing. Further, it is possible to appropriately perform printing on a cylindrical medium or the like by a printing operation in one pass. Also, such an effect can be obtained in the same way when described below with reference to FIGS. *

However, for example, when the amount of ink per unit area becomes excessive, as described above, the method of thinning out some nozzles in the nozzle row and the moving speed of the head unit during the main scanning operation are set. It is preferable to adjust the amount of ink by changing it. If comprised in this way, it can prevent appropriately that the amount of ink becomes excessive. Further, such adjustment is preferably performed in the same manner as necessary even when described below with reference to FIGS. *

FIG. 5 shows an example in which the inkjet head 102 is tilted so that the head tilt angle θ is 78.46304 °. Except as described below, in FIG. 5, the configuration denoted by the same reference numeral as in FIG. 4 has the same or similar features as the configuration in FIG. 4. *

Also in this case, the plurality of nozzles 204 in the nozzle row 202 are arranged in the range of the width Lx narrower than the width L0 in the sub-scanning direction. More specifically, when θ is this angle, the width Lx is 1/5 of the width L0. That is, by setting the head tilt angle θ in this way, the length of the nozzle row 202 in the sub-scanning direction can be reduced to 1/5 that when the inkjet head 102 is not tilted. Thereby, even when a cylindrical medium or the like is used, the gap difference can be appropriately suppressed. *

In this case, the nozzle resolution in the sub-scanning direction in the state where the inkjet head 102 is tilted is five times that in the case where the inkjet head 102 is not tilted. In addition, this makes it possible to eject five times more ink per unit length in the sub-scanning direction onto the medium 50 than when the inkjet head 102 is not tilted. Therefore, also in this case, the ink discharge amount per unit area can be appropriately increased. *

In this case, it is conceivable to adjust the moving speed of the inkjet head 102 during the main scanning operation according to the head tilt angle, and set the speed to 1/5 when the inkjet head 102 is not tilted. With this configuration, the amount of ink discharged per unit area can be increased by 25 times compared to the case where the inkjet head 102 is not tilted. *

FIG. 6 shows an example in which the inkjet head 102 is tilted so that the head tilt angle θ is 75.5225 °. Except as described below, the configuration in FIG. 6 assigned the same reference numerals as those in FIG. 4 or 5 has the same or similar features as the configuration in FIG. 4 or FIG. *

Also in this case, the plurality of nozzles 204 in the nozzle row 202 are arranged in the range of the width Lx narrower than the width L0 in the sub-scanning direction. More specifically, when θ is this angle, the width Lx is ¼ of the width L0. That is, by setting the head tilt angle θ in this way, the length of the nozzle row 202 in the sub-scanning direction can be reduced to ¼ that when the inkjet head 102 is not tilted. Thereby, even when a cylindrical medium or the like is used, the gap difference can be appropriately suppressed. *

In this case, the nozzle resolution in the sub-scanning direction in the state where the inkjet head 102 is tilted is four times that in the case where the inkjet head 102 is not tilted. In addition, this makes it possible to eject four times as much ink per unit length in the sub-scanning direction as compared with the case where the inkjet head 102 is not tilted. Therefore, also in this case, the ink discharge amount per unit area can be appropriately increased. *

In this case, it is conceivable to adjust the moving speed of the inkjet head 102 during the main scanning operation according to the head tilt angle, and to set the speed to ¼ when the inkjet head 102 is not tilted. With this configuration, the amount of ink discharged per unit area can be increased 16 times compared to the case where the inkjet head 102 is not tilted. *

FIG. 7 shows an example in which the inkjet head 102 is tilted so that the head tilt angle θ is 60 °. Except as described below, the configuration in FIG. 7 denoted by the same reference numerals as in FIGS. 4 to 6 has the same or similar characteristics as the configuration in FIGS. *

Also in this case, the plurality of nozzles 204 in the nozzle row 202 are arranged in the range of the width Lx narrower than the width L0 in the sub-scanning direction. More specifically, when θ is this angle, the width Lx is ½ of the width L0. That is, by setting the head tilt angle θ in this way, the length of the nozzle row 202 in the sub-scanning direction can be reduced to ½ that when the inkjet head 102 is not tilted. Thereby, even when a cylindrical medium or the like is used, the gap difference can be appropriately suppressed. *

In this case, the nozzle resolution in the sub-scanning direction in the state in which the inkjet head 102 is tilted is twice that in the case where the inkjet head 102 is not tilted. In addition, this makes it possible to discharge twice as much ink to the medium 50 per unit length in the sub-scanning direction as compared with the case where the inkjet head 102 is not tilted. Therefore, also in this case, the ink discharge amount per unit area can be appropriately increased. *

In this case, it is conceivable to adjust the moving speed of the inkjet head 102 during the main scanning operation according to the head tilt angle, and to set the speed to ½ when the inkjet head 102 is not tilted. With this configuration, the amount of ink discharged per unit area can be increased four times as compared with the case where the inkjet head 102 is not tilted. *

As described above, according to this example, the length of the nozzle row 202 in the sub-scanning direction can be changed variously by changing the head tilt angle in various ways. In addition, this makes it possible to adjust the head tilt angle according to the diameter of the cylindrical medium and appropriately suppress the gap difference.

Here, in order to simplify the description, the configuration in which the length of the nozzle row in the sub-scanning direction is changed only by adjusting the head tilt angle while the length of the nozzle row in the nozzle row direction is constant will be described. Did. However, in a modified example of the configuration of the printing apparatus 10 (see FIG. 1), for example, in addition to the adjustment of the head tilt angle, the number of dummy nozzles set at the end of the nozzle row may be adjusted. . For example, when the diameter of the medium is small, the gap difference cannot be sufficiently suppressed only by adjusting the head tilt angle, or if the head tilt angle is simply increased, the amount of ink per unit area becomes too large. If it is difficult to make adjustments, it may be possible to set a larger number of dummy nozzles. More specifically, for example, when the radius of curvature of the area facing the head portion in the medium is smaller than a preset lower limit value, the number of dummy nozzles may be set to be larger. If comprised in this way, it can print more appropriately with respect to the medium of various shapes. *

Subsequently, a modified example of the configuration of the head unit 12 will be described. In an ink jet printer, when performing color printing, a method of expressing various colors by color mixing using a process color ink which is a predetermined basic color is widely used. Also, as process color inks, inks of each color of Y (yellow), M (magenta), C (cyan), and K (black) are generally used. Therefore, in FIG. 2 and the like, the configuration in the case where the head unit 12 has four inkjet heads corresponding to each of these colors is illustrated. However, as a modified example of the configuration of the head unit 12, for example, it may be possible to use an inkjet head for ink of a special color other than the process color. *

FIG. 8 is a diagram for explaining a modified example of the configuration of the head unit 12. Except as described below, in FIG. 8, the configuration denoted by the same reference numerals as those in FIGS. 1 to 7 has the same or similar features as the configurations in FIGS. *

FIG. 8A shows an example of the configuration of a conventional head unit. In the conventional head unit, for example, a plurality of inkjet heads 102 arranged in the main scanning direction with their positions in the sub-scanning direction aligned are used. In addition, as the plurality of inkjet heads 102, for example, inkjet heads 102 for each color of YMCK, which is each color of the printing process color, are used. In these inkjet heads 102, the nozzle row direction is fixed in a direction parallel to the sub-scanning direction. On the other hand, in the head unit 12 according to the modified example described below, the inkjet head 102 can be held in an inclined state as in the case described with reference to FIGS. *

FIG. 8B shows a configuration of a modified example of the head unit 12. In this modification, the head unit 12 further includes, as a plurality of inkjet heads 102, an inkjet head 102 for a special color (special color 1) in addition to the inkjet heads 102 for each color of YMCK. The plurality of inkjet heads 102 are arranged side by side in the main scanning direction with their positions in the sub-scanning direction aligned. Further, in the present modification, the plurality of inkjet heads 102 of the head unit 12 are held in an inclined state at various angles. With this configuration, by using the spot color inkjet head 102, it is possible to perform more various printing on the medium. More specifically, as the spot color ink, for example, it is conceivable to use a clear, white, or metallic ink that is a transparent color. It is also conceivable to use various other special color inks. *

FIG. 8C shows a configuration of a further modification of the head unit 12. In the present modification, the head unit 12 includes a plurality of inkjet heads 102 for special colors as the plurality of inkjet heads 102. The plurality of inkjet heads 102 are arranged side by side in the main scanning direction with their positions in the sub-scanning direction aligned. Also in this modification, the plurality of inkjet heads 102 of the head unit 12 are held in a state where they are inclined at various angles. *

In the illustrated case, the head unit 12 includes three inkjet heads 102 that eject ink droplets of different colors (special colors 1 to 3). In this case, each special color ink is pre-adjusted according to the color used for printing. Accordingly, in the case of this modification, the printing apparatus 10 performs printing on the medium 50 using directly the special color inks that have been toned in advance, instead of the method of mixing different color inks. Even in such a configuration, various printing can be performed on the medium by using inks of special colors of various colors. *

In the above description, a case has been described in which the plurality of inkjet heads 102 in the head unit 12 are mainly arranged in the main scanning direction with their positions in the sub-scanning direction aligned. However, in a further modified example of the configuration of the head unit 12, it is conceivable that at least some of the inkjet heads 102 are arranged so that their positions in the sub-scanning direction are shifted from other inkjet heads 102. *

When the inkjet head 102 is held at an angle, the ink discharge amount per unit area increases as described above. In this case, if a large number of inkjet heads 102 are arranged in the main scanning direction with their positions in the sub-scanning direction aligned, the amount of ink per unit area becomes excessive when the head tilt angle is increased. In some cases. Therefore, in such a case, at least a part of the ink-jet heads 102 is arranged with a position in the sub-scanning direction shifted from that of the other ink-jet heads 102 to reduce the amount of ink ejected to the same region in each main scanning operation. It is conceivable. *

FIG. 9 is a diagram for explaining a further modification of the configuration of the head unit 12. Except as described below, in FIG. 9, the configuration denoted by the same reference numerals as those in FIGS. 1 to 8 has the same or similar features as the configurations in FIGS. *

FIG. 9A shows a configuration of a further modified example of the head unit 12. In the present modification, the head unit 12 includes an inkjet head 102 for each color of YMCK and an inkjet head 102 for a special color (special color 1) as a plurality of inkjet heads 102. Each of these inkjet heads 102 may be the same as or similar to each inkjet head 102 used in the configuration of FIG. Further, as shown in the drawing, the plurality of ink jet heads 102 are disposed with their positions in the sub-scanning direction shifted from each other. *

With this configuration, it is possible to appropriately reduce the amount of ink ejected to the same region in each main scanning operation. This also makes it possible to appropriately prevent the amount of ink per unit area from becoming excessive even when, for example, the head tilt angle is increased. *

In addition, when a plurality of inkjet heads 102 are arranged with the positions in the sub-scanning direction being shifted, ink that is pre-adjusted according to the color used for printing may be used. FIG. 9B shows a configuration of a further modification of the head unit 12. In the present modification, the head unit 12 includes a plurality of inkjet heads 102 for special colors (special colors 1 to 3) as the plurality of inkjet heads 102. Each of these inkjet heads 102 may be the same as or similar to each inkjet head 102 used in the configuration of FIG. Further, as shown in the drawing, the plurality of ink jet heads 102 are disposed with their positions in the sub-scanning direction shifted from each other. *

In the configuration shown in FIGS. 9A and 9B, for example, when a cylindrical medium is used, the distance between each inkjet head 102 and the medium depends on the position difference in the sub-scanning direction. Will be different. As a result, the minimum value and the maximum value of the gap in the nozzle row 202 in each inkjet head 102 also differ depending on the inkjet head 102. *

However, in this case as well, the gap difference for the nozzles 204 in the nozzle row 202 of the inkjet head 102 only needs to be appropriately suppressed for each inkjet head 102. More specifically, in the nozzle row 202 of each inkjet head 102, the gap difference may be less than 3 mm (preferably less than 2 mm, more preferably less than 1 mm). If comprised in this way, the printing to a medium can be appropriately performed by each inkjet head 102. FIG. *

In this case, it is preferable to sufficiently suppress the gap difference not only in the range of the individual inkjet heads 102 but also in the range including all the inkjet heads 102 used for printing in the head unit 12. For example, it is preferable that the gap difference is less than 3 mm with respect to the gaps at the positions of all the nozzles of all the ink jet heads 102. If comprised in this way, it can print more appropriately with respect to a medium, such as a cylindrical shape, with the some inkjet head 102 arrange | positioned by shifting the position in a subscanning direction. The gap difference is preferably less than 2 mm, more preferably less than 1 mm. *

In the above description, the arrangement of the plurality of inkjet heads in the head unit 12 has been described as the arrangement of the positions of the ends of the nozzle rows 202 in the inkjet heads 102 in a straight line. However, in a further modification of the head unit 12, it is conceivable that the positions of the ends of the nozzle row 202 are not aligned in a straight line, for example, shifted in a jagged manner. *

FIG. 10 is a diagram for explaining a further modification of the configuration of the head unit 12 and shows an example of a region in which ink droplets are ejected in one main scanning operation by a plurality of inkjet heads in the head unit 12. *

In the head unit 12 of this modification, the plurality of inkjet heads 102 are arranged side by side in the main scanning direction so that positions in at least a part overlap in the sub scanning direction. In addition, for the inkjet heads adjacent in the main scanning direction, the positions of the ends of the nozzle row 202 in the sub scanning direction are shifted from each other. Accordingly, the plurality of inkjet heads 102 are arranged side by side so that the positions of the ends of the nozzle row 202 are sequentially shifted. *

More specifically, in the illustrated case, the head unit 12 includes an inkjet head 102 for each color of YMCK. The YMCK ink jet head 102 ejects ink droplets to each of the

regions

302y, 302m, 302c, and 302k (hereinafter referred to as regions 302y to k) in the medium 50 in each main scanning operation. To do. In this case, as shown in the figure, the regions 302y to 302k are arranged on the medium 50 so that the positions in the sub-scanning direction are shifted from each other in a jagged manner according to the arrangement of the corresponding inkjet heads 102. . *

Further, in this case, the length Dh of the nozzle row 202 in the sub-scanning direction in the entire head unit 12 is as shown in the drawing in the entire sub-scanning direction of the regions 302y to k formed in each main scanning operation. Think of it as length. A band region in which the length (band width) in the sub-scanning direction is Dh includes a region 402 in which ink droplets are ejected by all the inkjet heads 102 and a region 404 that is closer to one end in the sub-scanning direction than the region 402. And the region 406 located on the other end side in the sub-scanning direction with respect to the region 402.

In this case, the area 402 is an area where printing on the medium 50 is completed by one main scanning operation. On the other hand, when only one main scanning operation is performed, the edges of

areas

404 and 406 are printed in a jagged shape. Therefore, the region 404 and the region 406 are regions where printing is completed by two main scanning operations in combination with the previous or subsequent main scanning operations. *

When comprised in this way, it can prevent appropriately that the influence of the edge of a nozzle row overlaps and is visually recognized. Thereby, it is possible to appropriately prevent the occurrence of band stripes due to the influence of the end of the nozzle row. *

In this case, as is apparent from the figure, the inkjet head for each color ejects ink droplets in one of the two main scanning operations for the region 404 and the region 406. Will do. Therefore, in this case as well, the number of printing passes can be considered as one time. Further, it is conceivable that the shift amount of the position in the sub-scanning direction between the inkjet heads adjacent in the main scanning direction is larger than the distance corresponding to the spatial frequency at which the human visual sensitivity is maximized, for example. Further, more simply, the shift amount may be set to 200 μm or more, for example. If comprised in this way, the influence of the edge of a nozzle row can be suppressed more appropriately. *

Further, in FIG. 10, for convenience of illustration, the result of performing the main scanning operation without tilting the nozzle row direction with respect to the sub-scanning direction is illustrated. However, in this modification as well, it is conceivable to adjust the head tilt angle as appropriate in accordance with the diameter of the medium, etc., in the same or similar manner as described with reference to FIGS. . If comprised in this way, it can print more appropriately, for example with respect to cylindrical media. *

As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the above embodiment. It is apparent from the description of the scope of claims that embodiments with such changes or improvements can be included in the technical scope of the present invention.

The present invention can be suitably used for a printing apparatus, for example.

Claims

A printing apparatus that performs printing on a medium, an inkjet head that ejects ink droplets from a plurality of nozzles, and a main scanning operation that ejects ink droplets while moving in a preset main scanning direction. A main scanning drive unit to be performed; and a head holding unit that holds the inkjet head so as to face the medium. The inkjet head has a nozzle row in which the plurality of nozzles are arranged in a preset nozzle row direction. In the cross section of the medium by a plane orthogonal to the main scanning direction, at least the outer edge on the side facing the inkjet head is curved, and the head holding portion is a direction orthogonal to the main scanning direction. Holding the inkjet head in a state where the nozzle row direction is inclined with respect to the sub-scanning direction; Printing apparatus according to symptoms.
2. The medium according to claim 1, wherein the medium is a cylindrical body having the main scanning direction as an axial direction, and the inkjet head ejects ink droplets onto a side surface of the medium of the cylindrical body. Printing device.
The printing apparatus according to claim 2, wherein the medium is a cylindrical medium.
A rotation drive unit that rotates the medium around a rotation axis of the medium parallel to the axial direction of the cylindrical body; and the rotation drive unit rotates the medium between the main scanning operations. The printing apparatus according to claim 2, wherein a region of the medium facing the inkjet head is changed.
The head holding unit is a gap that is a distance between each nozzle and the medium in the nozzle row, and the largest gap among the gaps at the positions of the nozzles in the nozzle row; The printing apparatus according to claim 1, wherein the inkjet head is held such that a gap difference that is a difference from the minimum gap is less than 3 mm.
An angle adjustment unit that adjusts a head inclination angle that is an angle at which the nozzle row direction is inclined with respect to the sub-scanning direction is further provided. The printing apparatus according to claim 5, wherein adjustment is performed.
The head holding unit is formed by the adjacent nozzles in the nozzle row for ink dots formed on the medium by ink droplets ejected from the nozzles in one main scanning operation. The inkjet head is held in an inclined state so that at least some of the ink dots overlap in the sub-scanning direction, and the printing apparatus performs one main scanning operation for each position of the medium. The printing apparatus according to claim 1, wherein printing on the medium is performed by a printing operation in one pass.
The nozzles of the inkjet head held in an inclined state with respect to the dot interval corresponding to the highest resolution determined according to the diameter of the ink dots formed on the medium by the ink droplets ejected from the nozzles When the interval between the nozzles in the sub-scanning direction in the row is smaller, in each main scanning operation, the inkjet head ejects ink droplets from only some of the nozzles in the nozzle row. The printing apparatus according to claim 1, wherein:
The nozzles of the inkjet head held in an inclined state with respect to the dot interval corresponding to the highest resolution determined according to the diameter of the ink dots formed on the medium by the ink droplets ejected from the nozzles When the interval between the nozzles in the sub-scanning direction in the row is larger, the main scanning driving unit sets the moving speed for moving the ink-jet head during the main scanning operation to a preset first speed. If the nozzle spacing in the sub-scanning direction of the inkjet head held in the tilted state is smaller than the dot spacing corresponding to the highest resolution, the main scanning drive unit The moving speed during the main scanning operation is set to a second speed that is faster than the first speed. The printing apparatus according to Motomeko 1.
And a control unit that controls the operation of the printing apparatus, wherein the head holding unit is capable of selecting at least a plurality of types of angles as the angle at which the nozzle row direction is inclined with respect to the sub-scanning direction. The printing apparatus according to claim 1, wherein at least operations of the inkjet head and the main scanning drive unit are controlled in accordance with an angle at which the nozzle row direction is inclined with respect to the sub-scanning direction.
The printing apparatus according to claim 1, wherein the head holding unit is capable of holding the inkjet head even when the sub-scanning direction and the nozzle row direction are parallel to each other.
A printing method for performing printing on a medium, wherein an ink jet head that discharges ink droplets from a plurality of nozzles is held by a head holding unit so as to face the medium, and a predetermined main value is set on the ink jet head. A main scanning operation is performed to eject ink droplets while moving in the scanning direction, and the inkjet head has a nozzle row in which the plurality of nozzles are arranged in a preset nozzle row direction, and is orthogonal to the main scanning direction. In a cross section of the medium by a plane, at least an outer edge on the side facing the ink jet head is curved, and the head holding portion is arranged in the nozzle row with respect to a sub-scanning direction that is a direction orthogonal to the main scanning direction. A printing method, wherein the inkjet head is held in a state where the direction is inclined.