Ink ejection head and inkjet printing device

Abstract

To provide a technique capable of reducing adhesion of ink mist to a device by generating a uniform air flow on a base material at a desired speed regardless of the shape of an ink discharge head and the arrangement of piping and wiring around the ink discharge head.SOLUTION: An ink discharge head 21 comprises: an ink discharge port group 210 which is constituted by a plurality of ink discharge ports 211 discharging ink toward a base material 9; an air exhaust port 214 which is located on the downstream side in the conveyance direction with respect to the ink discharge port group 210 and exhausts the air toward the base material 9; and air piping 215 which supplies the air toward the air exhaust port 214. The air exhaust port 214 is provided in the vicinity of the ink discharge port 211 located on the most downstream side in the conveyance direction out of the ink discharge ports 211 constituting the ink discharge port group 210, and is not provided in the vicinity of the ink discharge port 211 located on the most upstream side in the conveyance direction out of the ink discharge ports 211 constituting the ink discharge port group 210.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an ink ejection head and an inkjet printing apparatus. [Background technology]

[0002] It is known that ink mist is generated when inkjet printing devices eject tiny ink droplets toward a substrate. If the ink mist adheres and accumulates inside the device, such as around the ink ejection ports, it can turn into large ink droplets that fall onto the substrate, resulting in a decrease in print quality.

[0003] Patent Document 1 describes a device in which a slit-shaped through-hole (airflow hole) is provided adjacent to the downstream side of the ink ejection head in the transport direction in which the substrate is transported, and the airflow hole has an air ejection port that opens near the bottom end of the ink ejection head. A fan is provided near the airflow hole, and air blown into the airflow hole by the fan is ejected from the air ejection port, causing ink mist floating above the substrate to adhere to the substrate. This prevents ink mist from adhering to the inside of the device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-74998 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the case of conventional technology, the ink ejection head is surrounded by piping and wiring, such as ink supply pipes, making it difficult to generate a uniform air flow across the entire width of the substrate. Also, depending on the shape of the ink ejection head, it can be difficult to provide air flow holes in appropriate positions.

[0006] The object of the present invention is to provide a technology that can reduce ink mist adhesion to the device by generating a uniform airflow at a desired speed on a substrate, regardless of the shape of the ink ejection head or the arrangement of piping and wiring around the ink ejection head. [Means for solving the problem]

[0007] In order to solve the above problems, the first invention of the present application is: The fixing member is fitted into a mounting hole of a base plate arranged along the conveying path, An ink ejection head that ejects ink onto a substrate that is transported in a transport direction along a transport path, a lower surface facing the substrate and a side surface on the downstream side in the conveying direction; an ink ejection port group consisting of a plurality of ink ejection ports that eject ink toward the substrate; an air ejection port that is located downstream of the ink ejection port group in the transport direction and ejects air toward the substrate; an ink pipe that supplies ink toward the ink ejection port; and an air pipe that supplies air toward the air ejection port, the ink ejection orifice group and the air ejection orifice are provided on the lower surface, The air ejection port is provided in the vicinity of the ink ejection port located most downstream in the transport direction among the ink ejection ports constituting the ink ejection port group, and is provided in the vicinity of the ink ejection port located most upstream in the transport direction among the ink ejection ports constituting the ink ejection port group. The air pipe is an air flow path formed in the ink ejection head at a location upstream of the downstream side surface of the ink ejection head in the transport direction. .

[0008] A second invention of the present application is an ink ejection head according to the first invention, wherein the distance in the transport direction between the ink ejection port located most downstream in the transport direction among the ink ejection ports constituting the ink ejection port group and the air ejection port is 7.8 mm or less, and no air ejection port is provided in an area within 7.8 mm upstream of the ink ejection port located most upstream in the transport direction among the ink ejection ports constituting the ink ejection port group.

[0009] The third invention of the present application is an ink ejection head according to the second invention, wherein the distance in the transport direction between the ink ejection port located furthest downstream in the transport direction among the ink ejection ports constituting the ink ejection port group and the air ejection port is 1.4 mm or less, or 5 mm or more and 7.8 mm or less.

[0010] A fourth aspect of the present invention is the ink ejection head of any one of the first to third aspects, wherein air is ejected from the air ejection port at a speed of 0.1 m / s or more and 0.55 m / s or less.

[0011] A fifth aspect of the present invention is the ink ejection head according to any one of the first to fourth aspects, further comprising an air-permeable filter member inside the air pipe.

[0012] A sixth aspect of the present invention is an ink ejection head according to any one of the first to fifth aspects, which includes a straightening plate inside the air pipe that straightens the flow of air passing through the inside of the air pipe. The seventh invention of the present application is: In the ink ejection head of the first invention, the air pipe is an air flow path formed so as to extend from the upper end to the lower end of the ink ejection head.

[0013] The first part of this application 8 The invention , an inkjet printing apparatus, First to second inventions 7 An ink ejection head according to any one of the inventions and the base plate and, a substrate transport mechanism that faces the lower surface of the ink ejection head and transports the substrate in a transport direction along a transport path; and a compressor that is provided separately from the substrate transport mechanism and the ink ejection head and supplies high-pressure air. The aforementioned Ink ejection head an ink supply pipe for supplying ink to the ink pipe; One end is connected to the compressor, and the other end is connected to the air pipe of the ink ejection head, and air supplied from the compressor is supplied to the ink ejection head. For the air piping hand and an air supply pipe for supplying the air. A ninth invention of the present application is an inkjet printing device according to the eighth invention, wherein the base plate has a plurality of mounting holes into which a plurality of the ink ejection heads are fitted, and the air ejection port of the ink ejection head located downstream in the transport direction among the air ejection ports of the plurality of ink ejection heads ejects an amount of air that is smaller than the amount of air ejected by the air ejection port of the ink ejection head located upstream in the transport direction. [Effects of the Invention]

[0014] The first to third inventions of this application 9According to the invention, air can be sent directly from the air piping to the air nozzle, which allows a uniform air flow to be generated on the substrate at a desired speed regardless of the shape of the ink ejection head or the arrangement of piping and wiring around the ink ejection head, thereby reducing ink mist adhesion to the device.

[0015] In particular, according to the fourth aspect of the present invention, the air flow ejected from the air outlet presses the ink mist further toward the substrate, thereby more effectively reducing adhesion of the ink mist to the device.

[0016] In particular, according to the fifth aspect of the present invention, the pressure loss in the air piping is increased by providing a breathable filter member in the air piping, thereby making it possible to make the air flow inside the air piping uniform.

[0017] In particular, according to the sixth aspect of the present invention, a straightening plate that straightens the air flow is provided in the air pipe, thereby increasing the pressure loss in the air pipe, thereby making the air flow inside the air pipe uniform. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of an inkjet printing apparatus. [Figure 2] FIG. 2 is a vertical cross-sectional view of an image recording unit and a support unit. [Figure 3] FIG. 2 is a plan view showing an image recording unit. [Figure 4] FIG. 2 is a perspective view showing a base plate and an ink ejection head. [Figure 5] 3A and 3B are diagrams illustrating the bottom surface of the ink ejection head and the bottom surface of the base plate. [Figure 6] FIG. 3 is an enlarged vertical cross-sectional view showing the periphery of an air pipe and an air discharge port. [Figure 7] FIG. 10 is a diagram showing the results of simulating the behavior of ink mist. [Figure 8]10 is a graph showing the results of simulating the behavior of ink mist. [Figure 9] FIG. 10 is a diagram showing the results of simulating the behavior of ink mist. [Figure 10] 10 is a graph showing the results of simulating the behavior of ink mist. [Figure 11] FIG. 10 is a partial cross-sectional view of an ink ejection head in which a filter member is provided inside an air pipe. [Figure 12] FIG. 10 is a partial cross-sectional view of an ink ejection head when a rectifying plate is provided inside an air pipe. [Figure 13] FIG. 10 is a bottom view of an ink ejection head according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. Note that the components described in the embodiment are merely examples and are not intended to limit the scope of the present invention. In the drawings, the dimensions and numbers of each part may be exaggerated or simplified as necessary to facilitate understanding.

[0020] <1. Embodiment> FIG. 1 is a diagram showing a schematic configuration of an inkjet printing apparatus 1 according to an embodiment. The inkjet printing apparatus 1 is an apparatus that forms an image on a recording surface 9a of a band-shaped substrate 9 (e.g., printing paper) by ejecting ink droplets (ink drops) from a plurality of ink ejection heads 21 while transporting the substrate 9. The inkjet printing apparatus 1 uses ultraviolet-curable ink that cures when irradiated with ultraviolet rays, which are electromagnetic waves. The ultraviolet-curable ink may contain a curing initiator as a component to promote curing. Note that the inkjet printing apparatus 1 may also use inks other than ultraviolet-curable ink (e.g., water-based ink or oil-based ink).

[0021] The inkjet printing apparatus 1 includes a substrate transport mechanism 10, an image recording unit 20, a support unit 30, a processing chamber 40, an inert gas supply unit 50, an irradiation unit 70, and a control unit 80. All units other than the control unit 80 (including the image recording unit 20 and the processing chamber 40) are housed in a box-shaped apparatus housing 90.

[0022] The substrate conveying mechanism 10 is a mechanism that conveys the substrate 9 in a direction along its longitudinal direction. The substrate conveying mechanism 10 has an unwinding section 11, multiple conveying rollers 12, a chill roller 13, and a winding section 14. The multiple conveying rollers 12 include a switching roller 121 and a nip roller 122, which will be described later. The substrate 9 is unwound from the unwinding section 11 and conveyed along a conveying path formed by the multiple conveying rollers 12. Each conveying roller 12 rotates about a horizontal axis to guide the substrate 9 downstream in the movement direction. After conveyance, the substrate 9 is collected in the winding section 14. In this way, the substrate 9 is conveyed along the predetermined conveying path TR by being supported by the conveying rollers 12, chill roller 13, and the like, which are arranged in predetermined positions.

[0023] In the following description, the direction in which the substrate 9 moves along the transport path TR will be simply referred to as the "transport direction." The downstream side of this transport direction will be simply referred to as the "downstream side," and the upstream side of the transport direction will be simply referred to as the "upstream side." Furthermore, the direction perpendicular to the transport direction and parallel to the surface of the substrate 9 will be referred to as the "width direction."

[0024] As shown in FIG. 1, when the substrate 9 is unwound from the unwinding section 11, it first passes through the cleaner 15. The cleaner 15 includes multiple suction rolls 151 arranged closely above and below. The multiple suction rolls 151 rotate while contacting the recording surface 9a and the back surface 9b of the substrate 9. Foreign matter adhering to the recording surface 9a and the back surface 9b is adsorbed and removed by the suction rolls 151. This reduces the number of foreign matter adhering to the substrate 9 before printing. This reduces printing defects, such as ink being repelled or seeping out due to foreign matter. The cleaner 15 may use a system other than the suction rolls 151, such as a suction mechanism.

[0025] After passing through the cleaner 15, the substrate 9 moves substantially horizontally below the image recording unit 20 along the arrangement direction of the ink ejection heads 21. At this time, the recording surface 9a of the substrate 9 faces upward (toward the ink ejection heads 21). The switching roller 121, chill roller 13, and nip roller 122 are disposed downstream of the image recording unit 20.

[0026] Although not shown in the figure, a static elimination mechanism (ionizer) is disposed downstream of the cleaner 15 and upstream of the image recording unit 20. The static elimination mechanism removes static electricity from the substrate 9. In this way, since the cleaner 15 and the static elimination mechanism are disposed upstream of the image recording unit 20, the substrate 9 can be supplied to the image recording unit 20 in a state where foreign matter and static electricity have been removed.

[0027] The nip roller 122 actively rotates at a constant speed while contacting the recording surface 9a and the back surface 9b of the substrate 9 and gripping the substrate 9. The substrate conveying mechanism 10 adjusts the rotation speed of the unwinding section 11 relative to the rotation speed of the nip roller 122. This applies tension to the substrate 9. As a result, sagging and wrinkling of the substrate 9 during conveyance are suppressed.

[0028] The image recording unit 20 is a mechanism that ejects ultraviolet-curable ink onto the substrate 9 transported by the substrate transport mechanism 10. The image recording unit 20 has four types of ink ejection heads 21 that eject ink of different colors. The multiple ink ejection heads 21 are arranged along the direction of movement of the substrate 9. During printing, droplets of ink of each color—cyan (C), magenta (M), yellow (Y), and black (K), which are the color components of a color image—are ejected from the four types of ink ejection heads 21 toward the recording surface 9a of the substrate 9. In this way, a color image is formed on the recording surface 9a of the substrate 9. Note that the inkjet printing device 1 may also be equipped with ink ejection heads that eject ink of other colors (such as white).

[0029] The support unit 30 includes a plurality of base plates 31 arranged along the transport path TR of the substrate 9, and a pair of support frames 32 (see FIG. 3) that support both widthwise ends of each base plate 31. The pair of support frames 32 extend substantially parallel to the transport path TR and are arranged parallel to each other with a gap in the widthwise direction. The plurality of base plates 31 are arranged with a gap in the transport direction.

[0030] Each ink ejection head 21 is attached to one of the base plates 31. This supports each ink ejection head 21 and fixes the relative positions of the ink ejection heads 21. Each base plate 31 has a through-hole (an attachment hole 311, described later) into which the lower end of each ink ejection head 21 is fitted. Therefore, the lower surface 212 of the ink ejection head 21 attached to the base plate 31 faces the recording surface 9a of the substrate 9 without being obstructed by the base plate 31. The structures of the image recording unit 20 and the support unit 30 will be described in more detail later.

[0031] As shown in FIG. 1, a switching roller 121 is disposed downstream as viewed from the image recording unit 20. The switching roller 121 rotates about a horizontal axis extending in the width direction while contacting the back surface 9b of the substrate 9. This causes the substrate 9 to bend in the opposite direction to the recording surface 9a. As a result, the movement direction of the substrate 9 is switched from a first direction (a substantially horizontal direction in this embodiment) to a second direction (a vertically downward direction in this embodiment).

[0032] The switching roller 121 comes into contact with the back surface 9b of the substrate 9. Therefore, the surface of the switching roller 121 does not come into contact with uncured ink. This prevents the image quality on the substrate 9 from being reduced due to contact with the switching roller 121. Furthermore, no member for switching the moving direction of the substrate 9 is arranged on the recording surface 9a side of the substrate 9.

[0033] The chill roller 13 rotates around a horizontal axis extending in the width direction while contacting the rear surface 9b of the substrate 9. The chill roller 13 is disposed substantially vertically above the processing chamber 40 and the irradiation unit 70. The diameter of the outer circumferential surface of the chill roller 13 is larger than the diameters of the outer circumferential surfaces of the front and rear transport rollers 12. Cooling water is stored inside the chill roller 13. The cooling water is circulated appropriately by a circulator (not shown). This cools the surface of the chill roller 13, maintaining its temperature.

[0034] The processing chamber 40 is disposed downstream of the image recording unit 20. The processing chamber 40 has an inlet and an outlet for passing the substrate 9. The upper side of the processing chamber 40 is covered by the outer peripheral surface of the chill roller 13.

[0035] The inert gas supply unit 50 supplies an inert gas (such as nitrogen gas) to the inside of the processing chamber 40, thereby filling the inside of the processing chamber 40 with a high concentration of inert gas. More specifically, the inert gas supply unit 50 supplies nitrogen gas, which is an inert gas, toward the recording surface 9a of the substrate 9 inside the processing chamber 40.

[0036] The irradiation unit 70 is disposed downstream of the inert gas supply unit 50 and approximately vertically below the chill roller 13. The irradiation unit 70 is also disposed directly below the processing chamber 40. The irradiation unit 70 performs an irradiation process by irradiating the substrate 9 supported by the chill roller 13 with irradiation light. The irradiation light from the irradiation unit 70 includes ultraviolet light in a wavelength band effective for curing the ink and has a sufficient amount of light. When the ink on the substrate 9 is irradiated, the ink is cured and fixed to the substrate 9. As a result, an image is recorded on the recording surface 9a of the substrate 9.

[0037] The control unit 80 is configured by a computer having an arithmetic processing unit such as a CPU, a memory such as RAM, and a storage unit such as a hard disk drive. The control unit 80 is electrically connected to, for example, the unwinding unit 11, the winding unit 14, the multiple ink ejection heads 21, the irradiation unit 70, the nip roller 122, a compressor 171 (described later), and a regulator 172 (described later). The control unit 80 temporarily reads a computer program stored in the storage unit into memory, and controls the operation of each of the above units by having the arithmetic processing unit perform arithmetic processing based on the computer program. This control allows the printing process in the inkjet printing device 1 to proceed.

[0038] Fig. 2 is a vertical cross-sectional view of the image recording unit 20 and the support unit 30. Fig. 3 is a plan view showing the image recording unit 20. Fig. 4 is a perspective view showing the base plate 31 and the ink ejection head 21. Fig. 5 is a view showing the lower surface 212 of the ink ejection head 21 and the lower surface 31b of the base plate 31.

[0039] As shown in FIGS. 2 and 5, a plurality of ink ejection heads 21 are disposed above the transport path TR. Each ink ejection head 21 has a lower surface 212. The lower surface 212 of each ink ejection head 21 faces the transport path TR. A plurality of ink pipes 213 are provided inside the ink ejection head 21. Each ink pipe 213 opens toward the transport path TR at the lower surface 212 and forms a plurality of ink ejection orifices 211 that eject ink droplets. The plurality of ink ejection orifices 211 are regularly arranged in the width direction and the transport direction, forming an ink ejection orifice group 210. An air pipe 215 is provided on the downstream side of each ink ejection head 21. The air pipe 215 opens in the lower surface 212 of the ink ejection head 21 in the shape of a slit extending in the width direction, forming an air ejection orifice 214. As shown in FIG. 2, the ink ejection head 21 is fixed to the base plate 31 with its lower end fitted into a mounting hole 311 provided in the base plate 31. The ink ejection head 21 has a lower surface 212 which is a flat surface provided with an ink ejection orifice group 210 and air ejection orifices 214. The lower surface 212 is disposed so as to be substantially parallel to the recording surface 9a of the substrate 9.

[0040] 1 and 2, directly below the image recording unit 20, the plurality of transport rollers 12 are arranged in an arch shape that is convex upward. Therefore, the substrate 9 is transported while curving convexly upward (toward the recording surface 9a) directly below the image recording unit 20. In other words, directly below the image recording unit 20, the transport path TR is curved convexly upward. The plurality of base plates 31 are arranged along the curved shape of the transport path TR, and therefore the plurality of ink ejection heads 21 are also arranged in an arch shape along the transport path TR.

[0041] As shown in FIG. 4, the base plate 31 is a plate-like member that is rectangular in plan view. The base plate 31 has three mounting holes 311 that penetrate the base plate 31 in the thickness direction. The mounting holes 311 open in a rectangular shape extending in the width direction on the upper surface 31a and the lower surface 31b of the base plate 31. Of the three mounting holes 311, two are located on the upstream side, and the other is located on the downstream side. The two upstream mounting holes 311 are located spaced apart in the width direction, and the downstream mounting hole 311 is disposed in the center of the two upstream mounting holes 311 in the width direction. Both widthwise ends of the downstream mounting hole 311 are disposed so as to overlap the two upstream mounting holes 311 in the conveying direction. In the following description, the inner wall on the upstream side of the mounting hole 311 is referred to as inner wall 311a, and the inner wall on the downstream side is referred to as inner wall 311b.

[0042] The lower end of the ink ejection head 21, which is rectangular in plan view, is inserted into each of the three mounting holes 311 and fixed via fasteners such as screws. The ink ejection head 21 is fixed to the mounting holes 311 so that the air ejection ports 214 are positioned downstream of the ink ejection port group 210. The gap between the lower end of the ink ejection head 21 and the base plate 31 is sealed with a sealing member (not shown). Specifically, the ink ejection head 21 is fitted into the mounting hole 311 with the upstream side surface 21a of the ink ejection head 21 facing the upstream inner wall 311a of the mounting hole 311 and the downstream side surface 21b of the ink ejection head 21 facing the downstream inner wall 311b of the mounting hole 311.

[0043] 2, an ink supply pipe 161 and an air supply pipe 162 are connected to the upper end of each ink ejection head 21. The ink supply pipe 161 is connected to an ink pipe 213 of the ink ejection head 21 and supplies ink to the ink ejection head 21. The air supply pipe 162 is connected to an air pipe 215 of the ink ejection head 21 and supplies air to the ink ejection head 21. An ink discharge pipe for circulating ink may be connected to the upper end of each ink ejection head 21. The ink supply pipe 161, ink discharge pipe, and air supply pipe 162 may be connected to the ink ejection head 21 from a portion other than the upper end of the ink ejection head 21.

[0044] 2, the air supply pipe 162 is connected to a compressor 171 that supplies high-pressure air. A regulator 172 that controls the pressure of the air supplied from the compressor 171 is provided between the air supply pipe 162 and the compressor 171. The pressure of the air supplied from the compressor 171 is adjusted by the regulator 172 and supplied to the air supply pipe 162. Note that a different compressor 171 and regulator 172 may be provided for each of the multiple air discharge ports 214. This allows air to be discharged at a different flow rate from each air discharge port 214.

[0045] The air pipe 215 forms a flow path for air from the air supply pipe 162 to the air outlet 214. The air pipe 215 also opens in the lower surface 212 to form the air outlet 214. The air outlet 214 is arranged adjacent to the downstream side of the ink outlets 211 that make up the ink outlet group 210 and that are arranged on the most downstream side. The air outlet 214 ejects air toward the substrate 9 that is transported along the transport path. This allows a uniform air flow to be generated on the substrate 9.

[0046] 6 is an enlarged vertical cross-sectional view showing the periphery of the air piping 215 and the air ejection port 214. As shown in Fig. 6, an air piping 215 that is short in the transport direction and long in the width direction is formed in a location close to the downstream side surface 21b of the ink ejection head 21. The lower end of the air piping 215 opens toward the substrate 9 as an air ejection port 214. Therefore, the air ejection port 214 has a slit shape that is short in the transport direction and long in the width direction when viewed horizontally.

[0047] As shown in FIG. 6 , ink mist M generated from ink droplets ejected from the ink ejection orifices 211 floats between the substrate 9 and the lower surface 212 of the ink ejection head 21, and moves downstream as the substrate 9 moves. In this state, air is ejected from the air ejection orifices 214, causing the ink mist M floating above the substrate 9 to adhere to the substrate 9. This reduces adhesion of the ink mist M to the lower surface 212 of the ink ejection head 21 or the lower surface 31b of the base plate 31. Note that the amount of ink mist M is extremely small compared to the ink droplets ejected from the ink ejection orifices 211 for image formation. Therefore, even if the ink mist M adheres to the substrate 9, the degradation of print quality is small. Furthermore, because adhesion of the ink mist M to the lower surface 212 of the ink ejection head 21 and the lower surface 31b of the base plate 31 can be reduced, the frequency of cleaning by the user can be reduced.

[0048] 2 and 3, a sealing member 33 is provided between all of the base plates 31 adjacent to each other in the conveyance direction. The sealing member 33 extends in the width direction and closes the gap between the adjacent base plates 31. The sealing member 33 can prevent airflow from being generated in the gap between the base plates 31. This can prevent the air flow over the substrate 9 from being disturbed between the base plates 31.

[0049] It is desirable that the lower surface of the sealing member 33 be flush (at the same height) with the lower surface 31b of the base plate 31 located on the upstream and downstream sides thereof. This makes it possible to suppress the occurrence of turbulence between the base plates 31, 31, thereby reducing adhesion of the ink mist M to the base plate 31.

[0050] 3, the image recording unit 20 includes a light irradiation unit 26 and a suction unit 28. The light irradiation unit 26 has a light source such as an LED, and irradiates light from the light source onto the recording surface 9a of the substrate 9. The light irradiation unit 26 is located downstream of the ink ejection head 21, which is located on the most downstream side, and semi-cures the ink ejected onto the substrate 9.

[0051] Although not shown, the suction unit 28 has a slit-shaped suction port facing the recording surface 9a of the substrate 9, and sucks air through the suction port. By the suction unit 28 sucking air downstream of the four base plates 31, it is possible to easily form an airflow flowing downstream between each base plate 31 and the substrate 9. This allows the ink mist M generated at each ink ejection port 211 to move downstream.

[0052] It is not essential that suction unit 28 be provided near light irradiation unit 26, and suction unit 28 may be provided, for example, near switching roller 121. It is also not essential that suction unit 28 be provided downstream of light irradiation unit 26, and suction unit 28 may be provided upstream of light irradiation unit 26.

[0053] 5, the air ejection port 214 extends in the width direction. The widthwise length of the air ejection port 214 is approximately the same as the widthwise length of the lower surface 212 of the ink ejection head 21. The air ejection port 214 extends outward in the width direction further than the adjacent ink ejection port group 210 on the upstream side. Therefore, no matter which ink ejection port 211 generates ink mist M, the ink mist M can be attached to the substrate 9 by the downflow from the air ejection port 214. This reduces adhesion of ink mist M to the lower surface 31b of the base plate 31 on which the ink ejection head 21 is provided, or to the lower surface 31b of the base plate 31 located further downstream.

[0054] Next, the position of the air outlet 214 and the ejection speed of the air ejected from the air outlet 214 will be described, in order to effectively adhere the ink mist M to the substrate 9 and further reduce adhesion of the ink mist M to the lower surface 31b of the base plate 31, etc. In the following description, of the arrangement of the multiple ink outlets 211 that form the ink outlet group 210, the row on the most upstream side will be referred to as the "front row," and the row on the most downstream side will be referred to as the "rear row."

[0055] 7 shows the results of a simulation of the behavior of ink mist M when the position of the air outlet 214, which ejects air at a speed of 0.25 m / s, is changed to 0.3 mm, 1.8 mm, 3.8 mm, and 5.8 mm from the last row of the ink outlet group 210, and when no air outlet 214 is provided. The white arrows in FIG. 7 indicate the position of air ejected from the air outlet 214. As shown in FIG. 7, when air is ejected from the air outlet 214, the ink mist M is pressed against the substrate 9. This makes it possible to reduce the amount of ink mist M that adheres to the lower surface 212 of the ink ejection head 21 or the lower surface 31b of the base plate 31 downstream of the air outlet 214.

[0056] On the other hand, as shown in FIG. 7, the degree to which ink mist M accumulates between the last row of the ink ejection orifice group 210 and the air ejection orifice 214 changes depending on the position of the air ejection orifice 214. FIG. 8 is a graph showing the changes in the number of adhering mist particles and the density of adhering mist when the position of the air ejection orifice 214 is changed. The solid line in the graph shows analytical values ​​based on simulation results, and the dotted line shows predicted values. Here, the number of adhering mist particles indicates the total number of ink mist particles M adhering to the underside 212 of the ink ejection head 21 between the last row of the ink ejection orifice group 210 and the air ejection orifice 214. The mist adhering density is the number of adhering ink mist particles M in the area with the most adhering ink mist M among the areas divided into 1-mm intervals in the transport direction on the underside 212 of the ink ejection head 21 between the last row of the ink ejection orifice group 210 and the air ejection orifice 214. The ink mist M present at a distance of 0.25 mm or less from the lower surface 212 of the ink ejection head 21 in the direction toward the substrate 9 was counted as the ink mist M adhering to the lower surface 212 of the ink ejection head 21. The values ​​of the first and second axes are relative values, with the value when no air ejection port 214 is provided being set to 1.

[0057] Here, the mist adhesion density is an index that indicates whether ink mist M is accumulating between the last row of the ink ejection port group 210 and the air ejection port 214, causing localized mist adhesion to a portion of the underside 212 of the ink ejection head 21. If ink mist M is concentrated and adheres to a portion, it will accumulate and turn into ink droplets, which are likely to fall onto the substrate 9, so a low mist adhesion density is preferable.

[0058] In Figure 8, the number of mist particles adhering to the underside 212 of the ink ejection head 21 and the mist adhesion density are compared for three cases: when the air ejection port 214 is located at a distance of 1.4 mm or less from the last row of the ink ejection port group 210 (area A), when it is located at a distance of 1.4 mm or more and 5 mm or less (area B), and when it is located at a distance of 5 mm or more and 7.8 mm or less (area C).

[0059] In region A, the number of mist deposits is reduced to approximately 0.1 times or less compared to when the air ejection port 214 is not provided, and in regions B and C, it is reduced to approximately 0.1 to 0.3 times when the air ejection port 214 is not provided. In region A and region C, the mist deposition density is reduced to approximately 0.5 times or less compared to when the air ejection port 214 is not provided, and in region B, it is reduced to approximately 0.5 to 0.7 times when the air ejection port 214 is not provided. As mentioned above, the lower the ink deposition density, the less likely it is that ink mist M will locally adhere to part of the underside 212 of the ink ejection head 21. Therefore, when region B is compared to region C, region C is a more preferable location for providing the air ejection port 214.

[0060] Therefore, it is preferable that the air outlet 214 be located downstream from the last row of the ink outlet group 210 at a distance of 7.8 mm or less, more preferably at a distance of 1.4 mm or less, or 5 mm to 7.8 mm, and even more preferably at a distance of 1.4 mm or less.

[0061] Figure 9 shows the results of a simulation of the behavior of the ink mist M when the air ejection speed is changed. Here, the air ejection port 214 was located 0.3 mm away from the last row of the ink ejection port group 210 in the transport direction (the position indicated by the white arrow in Figure 8). As shown in Figure 9, as the ejection speed increases, the ink mist M is pressed more toward the substrate 9 downstream of the air ejection port 214. On the other hand, on the upstream side of the air ejection port 214, the greater the ejection speed, the more ink mist M adheres to the underside 212 of the ink ejection head 21.

[0062] 10 is a graph showing the behavior of ink mist M when the air ejection speed is changed. The value on the first axis is the number of ink mist M adhering to the lower surface 212 of the ink ejection head 21. Note that ink mist M present at a distance of 0.25 mm or less from the lower surface 212 of the ink ejection head 21 toward the substrate 9 is counted as ink mist M adhering to the lower surface 212 of the ink ejection head 21, and this value is a relative value when the value when no air ejection orifices 214 are provided is set to 1. The value on the second axis is the vertical distance between the lower surface 31b and the ink mist M nearest to the lower surface 31b in the vertical direction, among the ink mist M located 0.8 mm or more downstream from the last row of the ink ejection orifice group 210, and indicates the pressing distance D by which air ejected from the air ejection orifices 214 presses the ink mist M downward.

[0063] The number of ink mist M adhering to the lower surface 212 of the ink ejection head 21 is smaller when the ejection speed is in the range of 0.1 m / s or more and 0.55 m / s or less than that when the air ejection port 214 is not provided, and is smallest at an air speed of 0.3 m / s. Furthermore, as shown in Fig. 10, the pressing distance D is maintained at 0.25 mm or more when the air ejection speed is 0.1 m / s or more, so there is little possibility that the ink mist M will adhere to the lower surface 212 of the ink ejection head 21 downstream of the air ejection port 214. Therefore, the ejection speed of the air ejected from the air ejection port 214 is preferably 0.1 m / s or more and 0.55 m / s or less, and more preferably 0.3 m / s.

[0064] It is also desirable not to arrange the air outlets 214 near the upstream side of the ink outlet group 210. In particular, it is desirable not to arrange the air outlets 214 within a distance of 7.8 mm upstream from the front row of the ink outlet group 210. If the air outlets 214 are arranged near the upstream side of the ink outlet group 210 and air is ejected, the ink mist M floating near the lower surface 212 of the ink outlet head 21 will likely rise up and adhere to the lower surface 212 of the ink outlet head 21.

[0065] 6, the distance d1 between the lower surface 31b of the base plate 31 and the substrate 9 is larger than the distance d2 between the lower surface 212 of the ink ejection head 21 and the substrate 9. As a result, the pressure loss in the gap between the lower surface 31b of the base plate 31 and the substrate 9 downstream of the air ejection port 214 is smaller than the pressure loss in the gap between the lower surface 212 of the ink ejection head 21 and the substrate 9 upstream of the air ejection port 214. In this way, by making the distance d1 downstream of the air ejection port 214 larger than the distance d2 upstream of the air ejection port 214, it is possible to easily create an airflow that flows downstream of the air ejection port 214. If the air from the air ejection port 214 were not guided downstream, the downstream airflow generated over the substrate 9 due to the transport of the substrate 9 would mix with the downflow from the air ejection port 214, causing turbulence. When such turbulence occurs, the floating ink mist M may be stirred up and adhere to the base plate 31 or the lower surface 212 of the ink ejection head 21. For this reason, as shown in Figure 7, by forming an air flow that flows downstream at the air ejection port 214, it is possible to reduce adhesion of the ink mist M to the base plate 31, etc.

[0066] Furthermore, the gap d3 in the transport direction of the air pipe 215 is smaller than the gap d1 between the substrate 9 and the lower surface 212 of the ink ejection head 21 on the downstream side of the air ejection port 214. As a result, the pressure loss in the internal space of the air pipe 215 is greater than the pressure loss in the gap space between the substrate 9 and the lower surface 212 of the ink ejection head 21 on the downstream side of the air ejection port 214. As a result, the air supplied to the air pipe 215 is shaped into a downflow with a uniform flow rate in the width direction inside the air pipe 215, and is ejected from the air ejection port 214 towards the substrate 9.

[0067] In order to form an air flow toward the downstream side, the amount of air (flow rate) discharged from the air discharge ports 214 located downstream among the multiple air discharge ports 214 may be made smaller than the amount of air discharged from the air discharge ports 214 located upstream. For example, the amount of air discharged from the air discharge ports 214 may be made smaller in stages as it goes downstream.

[0068] FIG. 11 is a partial cross-sectional view of the ink ejection head 21 when a breathable filter member 218 is provided inside the air pipe 215. FIG. 12 is a partial cross-sectional view of the ink ejection head 21 when a rectifying plate 219 that regulates the flow of air is provided inside the air pipe 215. As shown in FIGS. 11 and 12, by providing the filter member 218 or the rectifying plate 219 inside the air pipe 215, the resistance when air passes through the air pipe 215 increases. As a result, the pressure loss of the air in the air pipe 215 becomes greater than the pressure loss of the air in the air supply pipe 162. As a result, the flow rate of air supplied to the air pipe 215 can be regulated uniformly in the width direction inside the air pipe 215, and can be ejected from the air ejection port 214 toward the substrate 9.

[0069] A filter member 218 or a rectifying plate 219 may be provided to increase the resistance inside the air pipe 215 and reduce the flow rate of air discharged from the air discharge port 214. Also, a filter member 218 may be provided to purify the air discharged from the air discharge port 214.

[0070] <2. Variations> Although the embodiments have been described above, the present invention is not limited to the above and various modifications are possible.

[0071] In the above embodiment, the air outlet 214 is a slit-shaped opening extending in the width direction. However, the air outlet 214 may be, for example, a plurality of outlets arranged at predetermined intervals in the width direction.

[0072] Fig. 13 is a bottom view of an ink ejection head 21 according to a modified example. In the above embodiment, one ink ejection head 21 has one ink ejection orifice group 210 arranged on the bottom surface 212, and one air ejection orifice 214 provided adjacent to the downstream side of the last row of the ink ejection orifice group 210. However, as shown in Fig. 13, two or more ink ejection orifice groups 210 may be provided for one ink ejection head so as to overlap in the transport direction or width direction. Furthermore, each ink ejection orifice group 210 may have multiple air ejection orifices 214 provided adjacent to the downstream side of the last row.

[0073] As described above, it is desirable not to dispose the air outlet 214 near the upstream side of the ink outlet group 210. However, as shown in Fig. 13, there are cases where the first ink outlet group 210A and the second ink outlet group 210B are arranged so that they overlap in the transport direction. In this case, where the distance L is the last row of the first ink outlet group 210A and the front row of the second ink outlet group 210B, the air outlet 214A may be provided in an area within L / 2 downstream from the last row of the first ink outlet group 210A, which is located near the downstream side of the first ink outlet group 210A.

[0074] In the above embodiment, the air pipe 215 is provided close to and along the downstream side surface 21b of the ink ejection head 21. However, as long as the air ejection port 214 is arranged adjacent to the downstream side of the last row of the ink ejection port group 210, the air pipe 215 may be provided somewhere other than the downstream side surface 21b of the ink ejection head 21. For example, the air pipe 215 may be provided so as to pass through the center inside the ink ejection head 21.

[0075] In the above embodiment, the ink ejection head 21 of the image recording unit 20 ejects ultraviolet curable ink onto the substrate 9. However, the ink ejection head 21 may also eject non-ultraviolet curable ink, for example, aqueous ink, onto the substrate 9.

[0076] Although the present invention has been described in detail, the above description is merely illustrative in all respects and does not limit the present invention. It is understood that countless variations not illustrated are conceivable without departing from the scope of the present invention. The configurations described in the above embodiments and variations can be combined or omitted as appropriate as long as they are not mutually inconsistent. [Explanation of symbols]

[0077] 1: Inkjet printing device 9: Base material 9a: Recording surface 9b: Back 10: Substrate transport mechanism 11: Unwinding section 12: Transport roller 13: Chill Roller 14: Winding section 15: Cleaner 20: Image recording unit 21: Ink ejection head 21a:Upstream side 21b: Downstream side 26: Light irradiation unit 28: Suction part 30: Support unit 31: Base plate 31a:Top surface 31b: Bottom surface 32: Support frame 33: Sealing material 40: Processing room 50: Inert gas supply unit 70: Irradiation unit 80: Control unit 90: Equipment housing 121: Switching roller 122: Nip roller 151: Adsorption roll 161: Ink supply pipe 162: Air supply pipe 171: Compressor 172: Regulator 210: Ink ejection orifice group 210A: First ink ejection orifice group 210B: Second ink ejection orifice group 211: Ink outlet 212: Bottom surface 213: Ink piping 214: Air outlet 214A: Air outlet 215: Air piping 218: Filter member 219: Rectifier plate 311: Mounting hole 311a: Upstream inner wall 311b: Downstream inner wall M: Ink Mist TR: Transport route

Claims

1. An ink ejection head that is fitted into a mounting hole of a base plate arranged along a transport path and ejects ink onto a substrate that is transported in a transport direction along the transport path, a lower surface facing the substrate; a downstream side surface in the conveying direction; an ink ejection port group including a plurality of ink ejection ports that eject ink toward the substrate; an air ejection port located downstream of the ink ejection port group in the transport direction and configured to eject air toward the substrate; an ink pipe for supplying ink toward the ink ejection port; an air pipe for supplying air toward the air outlet; Equipped with the ink ejection orifice group and the air ejection orifice are provided on the lower surface, The air outlet is the ink ejection port is provided in the vicinity of the ink ejection port located most downstream in the transport direction among the ink ejection ports constituting the ink ejection port group, the ink ejection opening is not provided in the vicinity of the ink ejection opening located most upstream in the transport direction among the ink ejection openings constituting the ink ejection opening group, the air pipe is an air flow path formed in the ink ejection head at a location upstream of the downstream side surface of the ink ejection head in the transport direction; Ink ejection head.

2. 2. The ink ejection head according to claim 1, a distance in the transport direction between the ink ejection port located furthest downstream in the transport direction among the ink ejection ports constituting the ink ejection port group and the air ejection port is 7.8 mm or less; the air ejection port is not provided in an area within 7.8 mm upstream in the transport direction from the ink ejection port located most upstream in the transport direction among the ink ejection ports constituting the ink ejection port group; Ink ejection head.

3. 3. The ink ejection head according to claim 2, a distance in the transport direction between the ink ejection port located most downstream in the transport direction among the ink ejection ports constituting the ink ejection port group and the air ejection port is 1.4 mm or less, or 5 mm or more and 7.8 mm or less; Ink ejection head.

4. 4. The ink ejection head according to claim 1, The ink ejection head ejects air from the air ejection port at a speed of 0.1 m / s or more and 0.55 m / s or less.

5. 5. The ink ejection head according to claim 1, A breathable filter member is provided inside the air piping. Ink ejection head.

6. 6. The ink ejection head according to claim 1, A straightening plate is provided inside the air piping to straighten the flow of air passing through the inside of the air piping. Ink ejection head.

7. An ink ejection head according to claim 1, the air pipe is an air flow path formed to extend from the upper end to the lower end of the ink ejection head; Ink ejection head.

8. An ink ejection head and the base plate according to any one of claims 1 to 7, a substrate transport mechanism that faces the lower surface of the ink ejection head and transports the substrate in a transport direction along a transport path; a compressor that is provided separately from the substrate transport mechanism and the ink ejection head and that supplies high-pressure air; an ink supply pipe that supplies ink toward the ink pipe of the ink ejection head; an air supply pipe, one end of which is connected to the compressor and the other end of which is connected to the air pipe of the ink ejection head, for supplying air supplied from the compressor to the air pipe of the ink ejection head; An inkjet printing apparatus comprising:

9. The inkjet printing apparatus of claim 8, the base plate has a plurality of mounting holes; A plurality of the ink ejection heads are fitted into the plurality of mounting holes, an air ejection port of an ink ejection head located downstream in the transport direction among the air ejection ports of the plurality of ink ejection heads ejects an amount of air that is smaller than an amount of air ejected by an air ejection port of an ink ejection head located upstream in the transport direction; Inkjet printing device.

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