Inkjet printer

Abstract

To provide an inkjet printer which can be suppressed in clogging of ink due to stray light.SOLUTION: The inkjet printer comprise: an inkjet head which ejects ultraviolet-curable ink to a recording medium; an ultraviolet irradiator which irradiates ink with ultraviolet and is provided adjacently to the inkjet head in a main scanning direction in which the inkjet head moves relatively with respect to the recording medium; and a control portion controlling the ultraviolet irradiator. The ultraviolet irradiator includes an inner illumination region provided at the inkjet head side in the main scanning direction, and an outer illumination region provided at the opposite side of the inkjet head with the inner illumination region interposed between the outer illumination region and the inkjet head in the main scanning direction. The control portion has an inner reducing irradiation mode in which illuminance in the inner illumination region is made lower than illuminance in the outer illumination region and then the region is lighted up, and an inner / outer same irradiation mode in which the inner illumination region and the outer illumination region are lighted up with same luminance.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to an inkjet printer that ejects ultraviolet-curable ink. [Background technology]

[0002] Conventionally, as an inkjet printer, an inkjet recording device equipped with an inkjet head that ejects ultraviolet-curable ink and an ultraviolet ray irradiation means that irradiates the ink with ultraviolet rays is known (for example, see Patent Document 1). In this inkjet recording device, the ultraviolet ray irradiation means is disposed adjacent to the inkjet head at a predetermined distance in order to prevent clogging of the ink in the inkjet head. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2004-284141 A Summary of the Invention [Problem to be solved by the invention]

[0004] In an inkjet printer, the head gap, which is the gap formed between the inkjet head and the recording medium, is adjusted. The head gap is adjusted, for example, according to the surface roughness of the recording medium, and the rougher the surface of the recording medium, the larger the head gap is set. In this case, the larger the head gap is, the farther the inkjet head is from the recording medium. In this case, so-called stray light is generated, in which part of the ultraviolet light irradiated by the ultraviolet irradiating means is irradiated to the inkjet head due to reflection on the recording medium, etc. In this way, the larger the head gap is, the more stray light increases, making it easier for ink to clog in the inkjet head.

[0005] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an inkjet printer capable of suppressing ink clogging caused by stray light. [Means for solving the problem]

[0006] The inkjet printer of the present invention comprises an inkjet head which ejects ultraviolet-curable ink onto a recording medium, an ultraviolet irradiator which is disposed adjacent to the inkjet head in a main scanning direction in which the inkjet head moves relative to the recording medium and irradiates the ink with ultraviolet light, and a control unit which controls the ultraviolet irradiator, wherein the ultraviolet irradiator includes an inner illumination area disposed on the inkjet head side in the main scanning direction, and an outer illumination area disposed on the opposite side of the inkjet head in the main scanning direction, sandwiching the inner illumination area therebetween, and the control unit has a first illumination mode in which the inner illumination area is turned off and the outer illumination area is turned on, and a second illumination mode in which the inner illumination area is turned on and the outer illumination area is turned on.

[0007] According to this configuration, when stray light occurs, the first irradiation mode can be used to turn off the inner illumination area of ​​the ultraviolet irradiator. In other words, the illumination area closer to the inkjet head can be turned off, so irradiation of the inkjet head with ultraviolet light can be suppressed. This reduces stray light to the inkjet head, and prevents ink clogging due to stray light. When ink clogging due to stray light does not occur, the second irradiation mode can be used to quickly cure the ink.

[0008] The inkjet printer of the present invention comprises an inkjet head which ejects ultraviolet-curable ink onto a recording medium, an ultraviolet irradiator which is disposed adjacent to the inkjet head in a main scanning direction in which the inkjet head moves relative to the recording medium and irradiates the ink with ultraviolet light, and a control unit which controls the ultraviolet irradiator, wherein the ultraviolet irradiator includes an inner illumination area disposed on the inkjet head side in the main scanning direction, and an outer illumination area disposed on the opposite side of the inkjet head in the main scanning direction, sandwiching the inner illumination area therebetween, and the control unit has a third irradiation mode in which the inner illumination area is turned on with an illuminance lower than that of the outer illumination area, and a fourth irradiation mode in which the inner illumination area and the outer illumination area are turned on with the same illuminance.

[0009] According to this configuration, when stray light occurs, the third irradiation mode can be used to reduce the illuminance of the inner illumination area of ​​the ultraviolet irradiator. In other words, the illuminance of the illumination area closer to the inkjet head can be reduced, thereby suppressing irradiation of ultraviolet light to the inkjet head. This reduces stray light to the inkjet head, and suppresses ink clogging due to stray light. Note that when ink clogging due to stray light does not occur, the fourth irradiation mode can be used to quickly cure the ink.

[0010] It is also preferable that the control unit has a gap control unit that adjusts a head gap, which is the gap between the recording medium and the inkjet head, and executes the first irradiation mode or the third irradiation mode when the head gap is equal to or larger than a threshold value, and executes the second irradiation mode or the fourth irradiation mode when the head gap is smaller than the threshold value.

[0011] According to this configuration, since the stray light increases as the head gap becomes larger, the stray light to the inkjet head can be reduced by using the first irradiation mode or the third irradiation mode. On the other hand, since stray light is less likely to occur when the head gap is small, the ink can be quickly cured by using the second irradiation mode or the fourth irradiation mode. The threshold value is a value that determines whether or not ink clogging due to stray light occurs.

[0012] It is also preferable that a plurality of types of recording media having different reflectances are prepared, and that the control unit executes the first irradiation mode or the third irradiation mode when the reflectance of the recording medium is equal to or greater than a threshold value, and executes the second irradiation mode or the fourth irradiation mode when the reflectance of the recording medium is less than the threshold value.

[0013] According to this configuration, since stray light increases in proportion to the reflectance of the recording medium, the first irradiation mode or the third irradiation mode can be used to reduce stray light to the inkjet head. On the other hand, when the reflectance of the recording medium is low, stray light is less likely to occur, so the ink can be quickly cured by using the second irradiation mode or the fourth irradiation mode. In this case, the threshold value is also set to a value that determines whether or not ink clogging due to stray light will occur.

[0014] It is also preferable that the control unit has a speed control unit that adjusts the scanning speed of the inkjet head, and executes the first irradiation mode or the third irradiation mode when the scanning speed of the inkjet head is equal to or lower than a threshold value, and executes the second irradiation mode or the fourth irradiation mode when the scanning speed of the inkjet head is faster than the threshold value.

[0015] According to this configuration, when the scanning speed of the inkjet head is slow, the stray light increases in proportion to the increase in the integrated light amount, so by using the first irradiation mode or the third irradiation mode, it is possible to reduce the stray light to the inkjet head. On the other hand, when the scanning speed of the inkjet head is fast, stray light is less likely to occur, so by using the second irradiation mode or the fourth irradiation mode, it is possible to quickly cure the ink. Note that in this case as well, the threshold value is a value that determines whether or not ink clogging due to stray light will occur.

[0016] It is also preferable that the ultraviolet irradiators are provided on both sides of the inkjet head in the main scanning direction, the two ultraviolet irradiators have the same structure, and are arranged in point symmetry with a phase difference of 180 degrees around a symmetric point within a plane including the main scanning direction and a sub-scanning direction perpendicular to the main scanning direction.

[0017] According to this configuration, by arranging the two ultraviolet irradiators point symmetrically, the two ultraviolet irradiators can be made to have the same structure, so that an increase in the cost of the device can be suppressed. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a perspective view of an inkjet printer according to a first embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing the configuration around the inkjet head. [Diagram 3] FIG. 3 is a plan view showing the nozzle surface side of the inkjet head. [Figure 4] FIG. 4 is a plan view showing the nozzle surface side of the inkjet head according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to this embodiment. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially the same. Furthermore, the components described below can be appropriately combined, and when there are multiple embodiments, each embodiment can be combined.

[0020] [Embodiment 1] The inkjet printer 1 according to the first embodiment (hereinafter, simply referred to as the printer 1) is a device that prints an image on a medium 2 as a recording medium by an inkjet method. As the medium 2, for example, a non-permeable medium using metal, resin, etc. that is non-permeable to ink, or a permeable medium using cloth, paper, etc. that is permeable to ink, can be applied, and any material can be applied as long as the medium 2 is capable of image formation. Such media 2 has a different reflectance of a printing surface (surface) onto which ink is ejected depending on the type. In addition, the medium 2 is transported by a roll-to-roll method, and printing is performed on the medium 2 unwound from a feed roll, and the printed medium 2 is wound up by a take-up roll. In addition, for example, an ultraviolet-curable ink (UV ink) that is cured by ultraviolet light is applied as the ink. The UV ink is an ink that has a high viscosity in a temperature range of room temperature (for example, 15°C to 25°C).

[0021] Next, a printer 1 will be described with reference to Fig. 1 to Fig. 3. Fig. 1 is a perspective view of an inkjet printer according to this embodiment. Fig. 2 is a schematic diagram showing the configuration around an inkjet head. Fig. 3 is a plan view showing the nozzle surface side of the inkjet head.

[0022] As shown in Fig. 1 and Fig. 2, the printer 1 includes an inkjet head 3 (hereinafter simply referred to as the head 3), a carriage 4, a platen 5, an ultraviolet irradiator 7, a carriage drive unit 8, a guide rail 9, an ink tank 10, and a control unit 15. Here, in Fig. 1 and Fig. 2, the X direction is the direction in which the medium 2 is transported, which is the sub-scanning direction. Also, in Fig. 3, the medium 2 is transported from the top to the bottom of Fig. 3. The Y direction is the direction in which the inkjet head 3 is moved, which is the main scanning direction. The Z direction is a direction perpendicular to the main scanning direction and the sub-scanning direction, and is the vertical direction when, for example, a plane including the main scanning direction and the sub-scanning direction is a horizontal plane.

[0023] The head 3 is provided on the carriage 4 and ejects the UV ink toward the medium 2. As shown in FIG. 3, two heads 3 are provided on the carriage 4. One of the two heads 3 is a color head 3a that ejects ink of four colors, CMYK, and the other is a clear head 3b that ejects clear ink. The printer 1 has two heads 3, the color head 3a and the clear head 3b, and is therefore capable of printing with clear ink overlaid on color ink. For example, gloss printing is one such type of printing, and in gloss printing, printing is performed so that the clear ink is smooth. The color head 3a is disposed upstream of the clear head 3b in the transport direction of the medium 2. The color head 3a and the clear head 3b each have a nozzle row 21 consisting of a plurality of nozzles aligned in the X direction (sub-scanning direction). In addition, in the color head 3a, a plurality of nozzle rows 21 are provided according to the type of color used, and for example, nozzle rows 21 for the four colors, CMYK, are aligned in the Y direction. In the clear head 3b, the nozzle rows 21 are provided in the same number as in the color head 3a, and are aligned in the Y direction.

[0024] The platen 5 is disposed opposite the head 3 in the Z direction. The medium 2 is placed on the platen 5. The platen 5 heats the placed medium 2, and heats the ink ejected onto the medium 2 through the medium 2, thereby promoting drying of the ink.

[0025] The carriage 4 is equipped with an ultraviolet irradiator 7 in addition to the head 3. The carriage drive unit 8 moves the carriage 4 along a guide rail 9. The guide rail 9 is provided to extend in the Y direction. Therefore, the carriage drive unit 8 moves the carriage 4 along the Y direction. The carriage drive unit 8 also moves the carriage 4 along the Z direction to adjust the head gap, which is the gap between the head 3 and the medium 2. At this time, the carriage 4 moved by the carriage drive unit 8 moves the head 3 and the ultraviolet irradiator 7 together. The head 3 and the ultraviolet irradiator 7 are integrally configured as a head unit 11, and ink is supplied to the head unit 11 from an ink tank 10 via an ink supply line 12.

[0026] The ultraviolet irradiators 7 are provided on both sides of the two heads 3 in the Y direction. The two ultraviolet irradiators 7 are provided on the carriage 4, and irradiate ultraviolet rays toward the medium 2 to harden the ink attached to the medium 2. As shown in Fig. 3, the ultraviolet irradiators 7 are provided extending in the X direction, and have a head-side irradiation unit 7a provided on one side in the X direction (upper side in Fig. 3) and a head-external irradiation unit 7b provided on the other side in the X direction (lower side in Fig. 3).

[0027] The head-side irradiation unit 7a is provided at a position overlapping the head 3 in the X direction when viewed from the Y direction. On the other hand, the head-external irradiation unit 7b is provided at a position not overlapping the head 3 in the X direction when viewed from the Y direction.

[0028] The head-side illumination unit 7a is divided into two, and includes an inner illumination area 7a2 and an outer illumination area 7a1. The inner illumination area 7a2 is an illumination area provided on the head side in the Y direction. The outer illumination area 7a1 is an illumination area provided on the opposite side of the head 3, sandwiching the inner illumination area 7a2 in the Y direction. The inner illumination area 7a2 and the outer illumination area 7a1 are illumination areas that can be controlled by the control unit 15 in a predetermined illumination mode. The inner illumination area 7a2 is configured to include a plurality of irradiation blocks Bx divided in the X direction. Similarly, the outer illumination area 7a1 is configured to include a plurality of irradiation blocks Bx divided in the X direction. The irradiation block Bx is an irradiation block having a predetermined number of elements of the light-emitting element, and is the minimum control unit that can be individually controlled by the control unit 15. The irradiation block Bx of the inner illumination area 7a2 is, for example, 11 blocks of irradiation blocks Bx having the same number of elements (for example, 4) arranged in the X direction. That is, the irradiation blocks Bx of the inner illumination area 7a2 are arranged in the X direction, each having the same number of elements. On the other hand, the irradiation blocks Bx of the outer illumination area 7a1 are arranged in the X direction, each having a different number of elements. Specifically, the outer illumination area 7a1 is provided with an irradiation block Bx(12) having 12 elements, an irradiation block Bx(4) having 4 elements, an irradiation block Bx(4) having 4 elements, an irradiation block Bx(4) having 8 elements, and an irradiation block Bx(4) having 12 elements, which are arranged in the X direction, in order from the color head 3a side to the clear head 3b side.

[0029] The head external irradiation unit 7b is configured to include a plurality of irradiation blocks By. The irradiation block By is an irradiation block having a predetermined number of light-emitting elements, and is the minimum control unit that can be individually controlled by the control unit 15. The irradiation block By of the head external irradiation unit 7b is an irradiation block extending in the Y direction. Specifically, the irradiation block By extends in the Y direction over a range overlapping with the outer illumination area 7a1 and the inner illumination area 7a2 when viewed from the X direction. In addition, the irradiation block By is, for example, three irradiation blocks By having the same number of elements (for example, 8) arranged in the X direction. In other words, the irradiation block By of the head external irradiation unit 7b is a plurality of irradiation blocks By having the same number of elements arranged in the X direction.

[0030] Here, the positional relationship between the two heads 3 and the two ultraviolet irradiators 7 will be described. The nozzle rows 21 of the two heads 3 are provided on both sides of the irradiation block Bx(4) on the downstream side of the outer illumination area 7a1 in the transport direction (X direction) of the medium 2. Specifically, the nozzle row 21 of the color head 3a is provided over a range from the irradiation block Bx(12) on the upstream side of the outer illumination area 7a1 to the irradiation block Bx(4) on the downstream side in the X direction. In addition, the nozzle row 21 of the color head 3a is provided over a range of four irradiation blocks Bx of the inner illumination area 7a2 in the X direction. The nozzle row 21 of the clear head 3b is provided over a range from the irradiation block Bx(4) on the downstream side of the outer illumination area 7a1 to the irradiation block Bx(12) on the downstream side in the X direction. In addition, the nozzle row 21 of the clear head 3b is provided over a range of four irradiation blocks Bx of the inner illumination area 7a2 in the X direction.

[0031] The control unit 15 is connected to the head 3, the ultraviolet irradiator 7, and the carriage drive unit 8. The control unit 15 includes an integrated circuit such as a CPU (Central Processing Unit). As an example, the control unit 15 controls the head 3 to control the ejection of ink. The control unit 15 also controls the ultraviolet irradiator 7 to control the irradiation of ultraviolet light. The control unit 15 also controls the carriage drive unit 8 to control the speed of the head 3 in the main scanning direction. The control unit 15 also controls the carriage drive unit 8 to adjust the head gap of the head 3.

[0032] The control unit 15 has a gap control unit 25 and a speed control unit 26. The gap control unit 25 adjusts the head gap according to the type of the medium 2 placed on the platen 5. For example, the gap control unit 25 increases the head gap in the case of the medium 2 whose printing surface has a rough surface roughness, while decreasing the head gap in the case of the medium 2 whose printing surface has a smooth surface roughness. The gap control unit 25 adjusts the size of the head gap in stages, for example. Specifically, the gap control unit 25 adjusts the head gap to three stages, "small head gap," "medium head gap," and "large head gap," according to the type of the medium 2. The gap control unit 25 may continuously adjust the size of the head gap. The speed control unit 26 controls the scanning speed of the head 3 in the main scanning direction.

[0033] The control unit 15 has a first irradiation mode and a second irradiation mode, and selectively switches between the first irradiation mode and the second irradiation mode based on a threshold value. The first irradiation mode is a mode in which each irradiation block Bx is controlled to turn off the inner illumination area 7a2 and turn on the outer illumination area 7a1. The second irradiation mode is a mode in which the inner illumination area 7a2 and the outer illumination area 7a1 are turned on. The threshold value is a value that determines whether or not ink clogging of the head 3 due to stray light occurs. If the control unit 15 determines based on the threshold value that ink clogging of the head 3 will occur, the control unit 15 executes the first irradiation mode. On the other hand, if the control unit 15 determines based on the threshold value that ink clogging of the head 3 will not occur, the control unit 15 executes the second irradiation mode.

[0034] Specifically, the control unit 15 selectively executes the first irradiation mode and the second irradiation mode depending on at least one state of the head gap, the reflectance on the printing surface of the medium 2, and the scanning speed of the head 3. Regarding the head gap, the control unit 15 executes the first irradiation mode when the head gap adjusted by the gap control unit 25 is equal to or greater than a threshold value. On the other hand, the control unit 15 executes the second irradiation mode when the head gap is smaller than the threshold value. Furthermore, regarding the reflectance on the printing surface of the medium 2, the control unit 15 executes the first irradiation mode when the reflectance of the selected medium 2 is equal to or greater than a threshold value. On the other hand, the control unit 15 executes the second irradiation mode when the reflectance is smaller than the threshold value. Furthermore, regarding the scanning speed of the head 3, the control unit 15 executes the first irradiation mode when the scanning speed of the head 3 controlled by the speed control unit 26 is equal to or less than a threshold value. On the other hand, the control unit 15 executes the second irradiation mode when the scanning speed of the head 3 is faster than the threshold value.

[0035] The control unit 15 also controls each irradiation block Bx in the outer illumination area 7a1 according to the printing conditions. For example, when performing glossy printing, the control unit 15 turns off two irradiation blocks Bx(4) on the clear head 3b side among the irradiation blocks Bx in the outer illumination area 7a1 located at the same position as the nozzle row 21 of the color head 3a in the X direction. When performing glossy printing, the control unit 15 turns off the irradiation blocks Bx(8) and Bx(12) in the outer illumination area 7a1 located at the same position as the nozzle row 21 of the clear head 3b in the X direction. Note that the control unit 15 also turns off the inner illumination area 7a2 when performing glossy printing. By turning off the irradiation blocks Bx, the control unit 15 suppresses ultraviolet irradiation from the irradiation blocks Bx on the color head 3a side to the clear ink discharged from the clear head 3b and landing on the medium 2. In this way, the control unit 15 suppresses hardening of the clear ink and promotes smoothing by the wetting and spreading of the clear ink.

[0036] As described above, according to the first embodiment, when stray light occurs in the head 3, the inner illumination area 7a2 of the ultraviolet irradiator 7 can be turned off by switching to the first irradiation mode. In other words, since the illumination area closer to the head 3 can be turned off, irradiation of ultraviolet light to the head 3 can be suppressed. This makes it possible to reduce stray light to the head 3, and suppress clogging of the ink due to stray light. On the other hand, when clogging of the ink due to stray light does not occur, the ink can be quickly cured by switching to the second irradiation mode.

[0037] Furthermore, according to the first embodiment, when the head gap is equal to or greater than the threshold value, the stray light increases in proportion to the size of the head gap, so by using the first irradiation mode, it is possible to reduce the stray light to the head 3. On the other hand, when the head gap is smaller than the threshold value, stray light is less likely to occur, so by using the second irradiation mode, it is possible to quickly cure the ink.

[0038] Furthermore, according to the first embodiment, when the reflectance of the medium 2 is equal to or greater than the threshold value, the amount of stray light increases in proportion to the amount of reflectance, and therefore, by using the first irradiation mode, it is possible to reduce stray light reaching the inkjet head. On the other hand, when the reflectance of the medium 2 is smaller than the threshold value, stray light is less likely to occur, and therefore, by using the second irradiation mode, it is possible to quickly cure the ink.

[0039] Furthermore, according to the first embodiment, when the scanning speed of the head 3 is equal to or lower than the threshold (slow), stray light increases in proportion to the increase in the integrated light amount on the ink, so by using the first irradiation mode, it is possible to reduce stray light on the head 3. On the other hand, when the scanning speed of the head 3 is fast, stray light is less likely to occur, so by using the second irradiation mode, it is possible to quickly cure the ink.

[0040] In the first embodiment, the application to UV ink has been described, but the present invention is not limited to UV ink.

[0041] In the present embodiment, the head-side irradiation unit 7a is divided into two in the Y direction, but may be divided into three. In other words, the number of divisions of the head-side irradiation unit 7a is not particularly limited as long as the head-side irradiation unit 7a includes the inner illumination region 7a2 and the outer illumination region 7a1.

[0042] [Embodiment 2] Next, an inkjet printer 1 according to an embodiment 2 will be described. Note that in the embodiment 2, only the parts that are different from the embodiment 1 will be described, and the same parts will be denoted by the same reference numerals.

[0043] In the printer 1 of the second embodiment, the control unit 15 executes a third irradiation mode and a fourth irradiation mode instead of the first irradiation mode and the second irradiation mode of the first embodiment. Specifically, the control unit 15 has a third irradiation mode and a fourth irradiation mode, and executes the third irradiation mode and the fourth irradiation mode by selectively switching between them based on a threshold value. The third irradiation mode is a mode in which the illuminance of the inner illumination area 7a2 is lowered to be lower than the illuminance of the outer illumination area 7a1 and turned on. In addition, the control unit 15 sets the illuminance of the inner illumination area 7a2 to 50 μW or less in the third irradiation mode. The fourth irradiation mode is a mode in which the inner illumination area 7a2 and the outer illumination area 7a1 are turned on with the same illuminance. The threshold value is a value that determines whether or not the ink clogging of the head 3 due to stray light occurs, as in the first embodiment. When the control unit 15 determines that the ink clogging of the head 3 occurs based on the threshold value, the control unit 15 executes the third irradiation mode. On the other hand, when the control unit 15 determines based on the threshold value that ink clogging of the head 3 will not occur, it executes the fourth irradiation mode.

[0044] Specifically, the control unit 15 selectively executes the third irradiation mode and the fourth irradiation mode according to at least one state of the head gap, the reflectance on the printing surface of the medium 2, and the scanning speed of the head 3, as in the first embodiment. Regarding the head gap, the control unit 15 executes the third irradiation mode when the head gap adjusted by the gap control unit 25 is equal to or greater than a threshold value. On the other hand, the control unit 15 executes the fourth irradiation mode when the head gap is smaller than the threshold value. Furthermore, regarding the reflectance on the printing surface of the medium 2, the control unit 15 executes the third irradiation mode when the reflectance of the selected medium 2 is equal to or greater than a threshold value. On the other hand, the control unit 15 executes the fourth irradiation mode when the reflectance is smaller than the threshold value. Furthermore, regarding the scanning speed of the head 3, the control unit 15 executes the third irradiation mode when the scanning speed of the head 3 controlled by the speed control unit 26 is equal to or less than a threshold value. On the other hand, the control unit 15 executes the fourth irradiation mode when the scanning speed of the head 3 is faster than the threshold value.

[0045] As described above, according to the second embodiment, when stray light occurs in the head 3, the illuminance of the inner illumination area 7a2 of the ultraviolet irradiator 7 can be reduced by switching to the third irradiation mode. In other words, the illuminance of the illumination area closer to the head 3 can be reduced, so irradiation of ultraviolet light to the head 3 can be suppressed. This makes it possible to reduce stray light to the head 3, and suppress clogging of the ink due to stray light. On the other hand, when clogging of the ink due to stray light does not occur, the ink can be quickly cured by switching to the fourth irradiation mode.

[0046] Furthermore, according to the second embodiment, when the head gap is equal to or greater than the threshold value, the stray light increases in proportion to the increase in the head gap, so by using the third irradiation mode, it is possible to reduce the stray light to the head 3. On the other hand, when the head gap is smaller than the threshold value, stray light is less likely to occur, so by using the fourth irradiation mode, it is possible to quickly cure the ink.

[0047] Furthermore, according to the second embodiment, when the reflectance of the medium 2 is equal to or greater than the threshold value, the stray light increases in proportion to the increase in the reflectance, and therefore, by using the third irradiation mode, it is possible to reduce the stray light reaching the inkjet head. On the other hand, when the reflectance of the medium 2 is smaller than the threshold value, stray light is less likely to occur, and therefore, by using the fourth irradiation mode, it is possible to quickly cure the ink.

[0048] Furthermore, according to the second embodiment, when the scanning speed of the head 3 is equal to or lower than the threshold (slow), stray light increases in proportion to the increase in the integrated light amount on the ink, so by using the third irradiation mode, it is possible to reduce stray light on the head 3. On the other hand, when the scanning speed of the head 3 is fast, stray light is less likely to occur, so by using the fourth irradiation mode, it is possible to quickly cure the ink.

[0049] In addition, the first embodiment and the second embodiment may be combined. That is, the control unit 15 may execute the first irradiation mode, the second irradiation mode, the third irradiation mode, and the fourth irradiation mode. In this case, the second irradiation mode and the fourth irradiation mode are almost the same irradiation mode, so they may be unified.

[0050] [Embodiment 3] Next, an inkjet printer 1 according to a third embodiment will be described with reference to Fig. 4. Fig. 4 is a plan view showing the nozzle surface side of an inkjet head according to the third embodiment. Note that in the third embodiment, only the parts different from the first and second embodiments will be described, and the same parts will be denoted by the same reference numerals.

[0051] In the printer 1 of the third embodiment, the two ultraviolet irradiators 7 provided on the carriage 4 have the same structure. As shown in FIG. 4, the ultraviolet irradiators 7 have the same structure and are arranged in point symmetry with a phase difference of 180 degrees around the symmetric point P in a plane including the X and Y directions. That is, one ultraviolet irradiator 7 is rotated by 180 degrees around the symmetric point P with respect to the other ultraviolet irradiator 7 in the XY plane including the X and Y directions. Therefore, the inner illumination area 7a2 and the outer illumination area 7a1 of the two ultraviolet irradiators 7 are also arranged in point symmetry with a phase difference of 180 degrees around the symmetric point P.

[0052] Here, the outer illumination area 7a1 is a concave-shaped area in which the illumination areas on both ends in the X direction extend in the Y direction toward the head 3 in the XY plane. The inner illumination area 7a2 is disposed inside the concave-shaped outer illumination area 7a1, and both ends of the inner illumination area 7a2 in the X direction are in contact with the outer illumination area 7a1.

[0053] As described above, according to the third embodiment, the two ultraviolet irradiators 7 are arranged point symmetrically, so that the two ultraviolet irradiators 7 can have the same structure, thereby making it possible to suppress an increase in the cost of the device.

[0054] The outer illumination area 7a1 and the inner illumination area 7a2 may be areas extending in the X direction as in the first embodiment, and may have any shape as long as they have a left-right symmetrical structure when the two ultraviolet irradiators 7 are arranged point-symmetrically.

[0055] In addition, in embodiments 1 to 3, the head-side irradiation section 7a of the ultraviolet irradiator 7 includes the inner illumination area 7a2 and the outer illumination area 7a1, but the inner illumination area 7a2 may be omitted as long as the ink can be sufficiently cured by irradiation of ultraviolet light from the outer illumination area 7a1. [Explanation of symbols]

[0056] 1. Inkjet printer 2. Media 3 Inkjet head 4 Carriage 5 Platen 7 Ultraviolet irradiator 7a Head side irradiation part 7b Head external irradiation part 7a1 Outside lighting area 7a2 Inner lighting area 8 Carriage drive unit 9 Guide Rail 10 Ink tank 11 Head Unit 12 Ink supply line 15 Control section 21 nozzle rows Bx Irradiation Block By Irradiation Block

Claims

1. An inkjet head that ejects ultraviolet-curable ink onto a recording medium; an ultraviolet irradiator that is provided adjacent to the inkjet head in a main scanning direction in which the inkjet head moves relative to the recording medium, and that irradiates the ink with ultraviolet light; A control unit that controls the ultraviolet irradiator, The ultraviolet irradiator includes: an inner illumination area provided on the inkjet head side in the main scanning direction; an outer illumination area provided on an opposite side of the inkjet head with respect to the inner illumination area in the main scanning direction; The control unit is a gap control unit that adjusts a head gap, which is a gap between the recording medium and the inkjet head, and executes an inner reduced illumination mode in which the inner illumination area is illuminated with an illuminance lower than that of the outer illumination area, and an inner and outer identical illumination mode in which the inner illumination area and the outer illumination area are illuminated with the same illuminance, Executing the inside dip illumination mode when the head gap is equal to or greater than a threshold value; When the head gap is smaller than a threshold value, the inside and outside same irradiation mode is executed. Inkjet printer.

2. An inkjet head that ejects ultraviolet-curable ink onto a recording medium; an ultraviolet irradiator that is provided adjacent to the inkjet head in a main scanning direction in which the inkjet head moves relative to the recording medium, and that irradiates the ink with ultraviolet light; A control unit that controls the ultraviolet irradiator, The ultraviolet irradiator includes: an inner illumination area provided on the inkjet head side in the main scanning direction; an outer illumination area provided on an opposite side of the inkjet head with respect to the inner illumination area in the main scanning direction; A plurality of types of recording media having different reflectances are prepared, The control unit is an inner lower illumination mode in which the illuminance of the inner illumination area is lowered below that of the outer illumination area, and an inner and outer same illumination mode in which the inner illumination area and the outer illumination area are illuminated at the same illuminance; executing the inner reduced illumination mode when the reflectance of the recording medium is equal to or greater than a threshold value; When the reflectance of the recording medium is smaller than a threshold value, the inside and outside identical irradiation mode is executed. Inkjet printer.

3. An inkjet head that ejects ultraviolet-curable ink onto a recording medium; an ultraviolet irradiator that is provided adjacent to the inkjet head in a main scanning direction in which the inkjet head moves relative to the recording medium, and that irradiates the ink with ultraviolet light; A control unit that controls the ultraviolet irradiator, The ultraviolet irradiator includes: an inner illumination area provided on the inkjet head side in the main scanning direction; an outer illumination area provided on an opposite side of the inkjet head with respect to the inner illumination area in the main scanning direction; The control unit is a speed control unit that adjusts a scanning speed of the inkjet head, and executes an inner reduced illumination mode in which the inner illumination area is illuminated with an illuminance lower than that of the outer illumination area, and an inner and outer identical illumination mode in which the inner illumination area and the outer illumination area are illuminated with the same illuminance; Executing the inner reduced illumination mode when a scanning speed of the inkjet head is equal to or less than a threshold value; When the scanning speed of the inkjet head is faster than a threshold value, the inside and outside identical irradiation mode is executed. Inkjet printer.

4. the ultraviolet irradiators are provided on both sides of the inkjet head in the main scanning direction, The two ultraviolet irradiators have the same structure and are arranged in point symmetry with a phase difference of 180 degrees around a symmetrical point in a plane including the main scanning direction and the sub-scanning direction perpendicular to the main scanning direction.

4. The inkjet printer according to claim 1.

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