Liquid discharge device, liquid discharge method, and article manufacturing method

Abstract

To reduce occurrence of density unevenness of a component of a liquid inside a liquid tank.SOLUTION: A liquid discharge device includes a liquid tank, a discharge head for discharging a liquid, and a liquid circulation device for circulating the liquid. The liquid circulation device has a first circulation flow passage from the liquid tank through the discharge head to the liquid tank, and a second circulation flow passage from the liquid tank without through the discharge head to the liquid tank. The second circulation flow passage includes a first port as an outlet of the liquid from the liquid tank, and a second port as a return port of the liquid to the liquid tank. The second port is provided above the first port.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a technique for a liquid ejection device and the like. [Background technology]

[0002] As an example of a liquid ejection device, an inkjet printer that ejects ink onto a medium such as paper to print an image on the medium is known. In recent years, inkjet printers have been used in the commercial field to print images on paper media that do not have a white background, and on media other than paper, such as film.

[0003] In addition, in the industrial field, liquid ejection devices are used to eject ink onto a wide variety of media, such as glass substrates, semiconductor substrates, and building materials. Furthermore, inks include solvent-based inks with high drying speeds and inks containing additives that impart performance to the coating film. In recent years, inks that are in particularly high demand contain fine particles with a relatively high specific gravity, such as titanium oxide, as additives. Insoluble solids such as these fine particles tend to settle inside liquid tanks and inside pipes.

[0004] In this type of liquid ejection device, liquid such as ink is circulated between a liquid tank and an ejection head. However, it is difficult to reduce the settling of components contained in the liquid, such as insoluble solids, inside the liquid tank or inside the piping, using only the liquid circulation flow path between the liquid tank and the ejection head. When insoluble solids settle inside the liquid tank, uneven concentration of the components contained in the liquid occurs inside the liquid tank. Patent Document 1 discloses the provision of a circulation flow path that does not pass through the ejection head, separate from the circulation flow path that circulates ink between the ejection head and the ink tank. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2019-98737 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, even if a separate circulation flow path is connected to the liquid tank, there is a risk that unevenness in the concentration of the components contained in the liquid inside the liquid tank will occur, and further improvements were required.

[0007] The present disclosure aims to reduce the occurrence of unevenness in the concentration of components of the liquid inside a liquid tank. [Means for solving the problem]

[0008] One aspect of the present disclosure is a liquid ejection device comprising a liquid tank, an ejection head that ejects liquid, and a liquid circulation device that circulates the liquid, wherein the liquid circulation device has a first circulation flow path that returns to the liquid tank from the liquid tank via the ejection head, and a second circulation flow path that returns to the liquid tank from the liquid tank without passing through the ejection head, wherein the second circulation flow path includes a first port that serves as an outlet for liquid from the liquid tank, and a second port that serves as a return port for liquid to the liquid tank, and the second port is located above the first port. Effect of the Invention

[0009] According to the present disclosure, convection of the liquid is more likely to occur inside the liquid tank, making it possible to reduce unevenness in the concentration of the liquid components. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of a liquid ejection device according to a first embodiment. [Diagram 2] 1(a) to 1(c) are schematic diagrams of an ink tank according to the first embodiment. [Diagram 3] 4 is a flowchart of the operation of the liquid ejection device according to the first embodiment. [Figure 4] 5A to 5C are explanatory diagrams of the operation of the liquid ejection device according to the first embodiment. [Diagram 5] 5A to 5C are explanatory diagrams of the operation of the liquid ejection device according to the first embodiment. [Figure 6] 5A to 5C are explanatory diagrams of the operation of the liquid ejection device according to the first embodiment. [Figure 7] 1A is a schematic diagram of a portion of a liquid ejection device according to a second embodiment, FIG. 1B is a schematic diagram of a portion of a liquid ejection device according to a third embodiment, and FIG. 1C is a schematic diagram of a portion of a liquid ejection device according to a fourth embodiment. [Figure 8] 13A is a schematic diagram of a liquid ejection device according to a fifth embodiment, and FIG. 13B is a schematic diagram of an ink tank according to the fifth embodiment. [Figure 9] 13(a) and 13(b) are schematic diagrams of a portion of a liquid ejection device according to a sixth embodiment. [Figure 10] 1A is an explanatory diagram of a modified example of the first embodiment, and FIG. 1B is an explanatory diagram of a modified example of the third embodiment. [Figure 11] FIG. 4 is a schematic diagram of a portion of a liquid ejection device of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the drawings. The following embodiments are illustrative of preferred configurations of the present disclosure, and for example, those skilled in the art can appropriately modify the detailed configurations without departing from the spirit of the present disclosure. In addition, in the drawings referred to in the following description of the embodiments, elements indicated by the same reference numbers have the same functions unless otherwise noted. In addition, these drawings are represented diagrammatically for convenience of illustration and explanation, and therefore may not strictly match the shape, size, arrangement, etc. of the actual objects.

[0012] In this specification, the liquid handled in the liquid ejection device may be described as "ink", but the ink according to the embodiment is not limited to a liquid containing a recording material for forming characters or images. For example, the ink may be a liquid containing a functional material for forming a functional element such as a functional thin film such as an electrode or an optical filter, or an organic EL element, or may be a liquid containing an insoluble solid content. In addition, the ejection of a liquid to apply it to an object may be described as "recording", but the recording referred to here is not necessarily limited to recording information such as characters or images. For example, it also includes applying a liquid containing a raw material for manufacturing an article such as a functional thin film, a functional element, or a three-dimensional object to an object. In addition, the object to which the liquid is applied may be described as a "recording medium", but it is not limited to a medium for recording information such as characters or images, and includes a component (e.g., a substrate) that serves as a base material for manufacturing an article such as a functional thin film, a functional element, or a three-dimensional object.

[0013] [First embodiment] 1 is a schematic diagram of a liquid ejection device 100 according to a first embodiment. The liquid ejection device 100 includes an ink tank 2, which is an example of a liquid tank. The ink tank 2 is a container capable of storing ink, which is an example of a liquid. The liquid ejection device 100 also includes an inkjet head (hereinafter simply referred to as "head") 1, which is an example of an ejection head that ejects liquid, and a liquid circulation device 30.

[0014] The ink contains a solvent and insoluble solids. The settling rate of the insoluble solids depends on the particle size of the insoluble solids, the density of the insoluble solids, the density of the solvent, and the viscosity of the ink. In order to reduce settling of the insoluble solids, a certain flow rate must be provided to the circulating ink.

[0015] An example of the insoluble solid content of the ink is TiO2. When the insoluble solid content is TiO2, the median particle size of the insoluble solid content is 200 nm, and the particle size distribution of the insoluble solid content is 100 nm to 700 nm. The main component of the ink is acrylic monomer. The concentration of the insoluble solid content is 7% by weight. At room temperature, the viscosity of the ink is 10 mPa s (shear rate is 1 1 / s).

[0016] The components of the insoluble solids, the particle size of the insoluble solids, the viscosity of the ink, the main component of the ink, etc. are not limited to the above examples. For example, the particle size may be 50 nm or more and 2 μm or less. The viscosity of the ink may be 1 mPa·s or more and 40 mPa·s or less. The main component of the ink is determined by the physical properties of the coating film, and is not limited to acrylic monomers, and may be, for example, methacrylic resin, epoxy resin, phenolic resin, or urethane resin.

[0017] The head 1 has multiple nozzles (not shown) that eject ink droplets as liquid droplets, a common flow path (not shown) that distributes ink from an ink tank 2 to each nozzle, and individual flow paths (not shown) that connect the common flow path and the nozzles.

[0018] The liquid circulation device 30 has a circulation flow path 31 which is an example of a first circulation flow path, and a circulation flow path 32 which is an example of a second circulation flow path. Each of the circulation flow paths 31, 32 is configured with piping and the like. The circulation flow path 31 is a main circulation flow path for ink that returns to the ink tank 2 via the head 1 from the ink tank 2. The circulation flow path 32 is a sub-circulation flow path for ink that returns to the ink tank 2 from the ink tank 2 without passing through the head 1. The circulation flow path 32 is provided independently of the circulation flow path 31. In other words, the circulation flow path 32 is not a flow path that branches off from the middle of the circulation flow path 31.

[0019] The circulation flow path 31 is a flow path that circulates ink between the ink tank 2 and the head 1 in order to reduce drying of the solvent contained in the ink from the nozzles and to reduce settling of insoluble solids in the piping due to ink stagnation.

[0020] The circulation flow path 31 has an outlet 201 for ink from the ink tank 2, and an ink return port 202 for ink to the ink tank 2. Ink stored in the ink tank 2 is output from the outlet 201 to the circulation flow path 31, and is supplied to the head 1 through the circulation flow path 31. The remaining ink that has not been ejected from the head 1 is returned to the ink tank 2 from the return port 202 through the circulation flow path 31. In this way, the ink circulates between the ink tank 2 and the circulation flow path 31. The outlet 201 is an example of a fourth port.

[0021] The liquid circulation device 30 has a pump 4, which is an example of a first pump, a damper 5, and a filter 6, which are arranged in the circulation flow path 31. The pump 4 is a pump for pumping out ink, which is a liquid. The pump 4 is, for example, a diaphragm pump, a tubing pump, or a piston pump. The damper 5 is for reducing pulsation of the ink pumped out to the pump 4. The filter 6 is for removing foreign matter contained in the ink. The circulation flow path 31 may be provided with a degassing module (not shown) for removing dissolved gas from the ink.

[0022] The circulation flow path 32 has one or more outlets for ink from the ink tank 2, and one or more return ports for ink to the ink tank 2. It is preferable that the circulation flow path 32 has two or more return ports. In the first embodiment, the circulation flow path 32 has an outlet 203 for ink from the ink tank 2, and return ports 204, 205 for ink to the ink tank 2. The outlet 203 is an example of a first port, the return port 204 is an example of a second port, and the return port 205 is an example of a third port. The return port 205 is a port arranged at a position different from the return port 204.

[0023] The circulation flow path 32 includes a main flow path 33 and branch flow paths 34, 35 that are arranged downstream of the main flow path 33 and branch off from the main flow path 33. The outlet 203 is included in the main flow path 33. The return port 204 is included in the branch flow path 34. The return port 205 is included in the branch flow path 35. Ink stored in the ink tank 2 is output from the outlet 203 to the main flow path 33 of the circulation flow path 32, passes through the branch flow paths 34 and 35, and is returned to the ink tank 2 from the return ports 204 and 205. In this way, the ink circulates between the ink tank 2 and the circulation flow path 32.

[0024] The liquid circulation device 30 has a pump 14, which is an example of a second pump, disposed in a main flow path 33 of a circulation flow path 32, a damper 15, and a filter 16. The pump 14 is a pump for pumping out ink, which is a liquid. The pump 14 is, for example, a diaphragm pump, a tubing pump, or a piston pump. The damper 15 is for reducing pulsation of the ink pumped out to the pump 14. The filter 16 is for removing foreign matter contained in the ink. The circulation flow path 32 may be provided with a degassing module (not shown) for removing dissolved gas from the ink.

[0025] The liquid circulation device 30 also has a flow rate adjustment valve 17 disposed at a branching portion where the main flow path 33 branches into the branch flow paths 34, 35. The flow rate adjustment valve 17 is, for example, a three-way valve, and has one input port and two output ports. The flow rate adjustment valve 17 adjusts the flow rate of ink output to each of the branch flow paths 34, 35 based on the flow rate of the input ink.

[0026] The liquid ejection device 100 also includes a liquid level sensor 40 and a control device 50 that controls the entire liquid ejection device 100 .

[0027] The liquid level sensor 40 is a sensor that detects the height (level) of the liquid surface inside the ink tank 2. The control device 50 includes a CPU (not shown), a memory device (not shown), an input / output interface (not shown), and the like, and is capable of acquiring a signal indicating the detection result from the liquid level sensor 40 and controlling the head 1, the pump 4, the pump 14, and the flow rate adjustment valve 17.

[0028] Here, a liquid ejection device of a comparative example will be described. FIG. 11 is a schematic diagram of a part of the liquid ejection device of the comparative example. In FIG. 11, the outlet 203X and the return port 204X of the sub-circulation flow path are both arranged at the bottom of the ink tank 2X. In the case of this comparative example, since the return port 204X is located at the lower side inside the ink tank 2X, as shown in the left diagram of FIG. 11, the ink is circulated only near the inner bottom surface of the ink tank 2X. Therefore, the concentration of the insoluble solids of the ink at the lower side inside the ink tank 2X is higher than the concentration of the insoluble solids of the ink at the upper side inside the ink tank 2X. In this way, uneven concentration of the insoluble solids occurs inside the ink tank 2X.

[0029] In the first embodiment, the ink output from the outlet 203 to the outside of the ink tank 2 flows through the circulation flow path 32 and is returned to the inside of the ink tank 2 from a return port 204 provided above the outlet 203. By circulating the ink in this manner, the ink inside the ink tank 2 is agitated, and settling of the insoluble solid content of the ink inside the ink tank 2 is reduced. This reduces unevenness in the concentration of the insoluble solid content contained in the ink inside the ink tank 2, and ink with a uniform concentration of the insoluble solid content is supplied to the head 1 via the circulation flow path 31.

[0030] Furthermore, in the circulation flow path 32, the ink does not pass through the head 1 on the way. Therefore, in the circulation flow path 32, it is possible to circulate the ink at a higher speed than in the circulation flow path 31. The flow speed of the ink in the circulation flow path 32 is preferably three times or more faster than the flow speed of the ink in the circulation flow path 31. This makes it possible to effectively reduce settling of the insoluble solid content of the ink inside the ink tank 2. This makes it possible to effectively reduce uneven concentration of the insoluble solid content contained in the ink inside the ink tank 2.

[0031] 2(a) to 2(c) are schematic diagrams of the ink tank 2 according to the first embodiment, viewed in a horizontal direction. The arrows indicating the rotation direction inside the ink tank 2 in Figs. 2(a) and 2(b) indicate the direction of ink convection. Here, a three-dimensional Cartesian coordinate system with X-axis, Y-axis, and Z-axis based on the ink tank 2 is defined. The X-axis, Y-axis, and Z-axis are mutually orthogonal. The directions of the arrows indicating the X-axis, Y-axis, and Z-axis are defined as positive directions. The X-axis and Y-axis directions are horizontal, and the Z-axis direction is opposite to the direction of gravity.

[0032] The positive direction of the X axis is the +X direction, and the negative direction of the X axis is the -X direction. The positive direction of the Y axis is the +Y direction, and the negative direction of the Y axis is the -Y direction. The positive direction of the Z axis is the +Z direction, and the negative direction of the Z axis is the -Z direction. In other words, the -Z direction is the direction of gravity, and the +Z direction is the direction opposite to the direction of gravity. The -Z direction is also the downward direction, and the +Z direction is also the upward direction or height direction. Figures 2(a) to 2(c) are schematic diagrams of the ink tank 2 when viewed in the Y axis direction (+Y direction).

[0033] The return port 204 is provided above the outlet 203, i.e., on the +Z direction side of the outlet 203. In other words, the outlet 203 is provided below the return port 204, i.e., on the −Z direction side of the return port 204.

[0034] As shown in Figure 2(a), the area inside the ink tank 2 is divided into two by a virtual plane PZ, defining areas R1 and R2. Area R1 is on the +Z side of the virtual plane PZ, i.e., the upper half of the area in the Z-axis direction (+Z direction). Area R2 is on the -Z side of the virtual plane PZ, i.e., the lower half of the area in the Z-axis direction (+Z direction).

[0035] The imaginary plane PZ is an imaginary plane parallel to the XY plane that passes through the midpoint between the apex in the Z-axis direction and the bottom point in the Z-axis direction inside the ink tank 2. The apex is the point (uppermost point) that is the maximum value in the Z-axis direction, and the bottom point is the point (lowest point) that is the minimum value in the Z-axis direction. In the spatial region inside the ink tank 2, the region above the imaginary plane PZ is region R1, and the region below the imaginary plane PZ is region R2.

[0036] The return port 204 of the circulation flow path 32 is disposed in region R1, and the outlet 203 of the circulation flow path 32 is disposed in region R2. This makes it easier for convection to occur in the ink stored inside the ink tank 2, effectively agitating the ink inside the ink tank 2, and effectively reducing settling of insoluble solids contained in the ink.

[0037] 2(b), the area inside the ink tank 2 is divided into two by a virtual plane PX, defining areas R3 and R4. Area R3 is the area on the +X side of the virtual plane PX. Area R4 is the area on the -X side of the virtual plane PX.

[0038] The imaginary plane PX is an imaginary plane parallel to the YZ plane that passes through the midpoint between the point inside the ink tank 2 that is the maximum value in the X-axis direction and the point that is the minimum value in the X-axis direction.

[0039] The return port 204 of the circulation flow path 32 is disposed in region R3, and the outlet 203 of the circulation flow path 32 is disposed in region R4. This makes it easier for convection to occur in the ink stored inside the ink tank 2, effectively agitating the ink inside the ink tank 2, and effectively reducing settling of insoluble solids contained in the ink.

[0040] Moreover, it is more preferable that the outlet 203 is disposed in a common area where the regions R2 and R4 overlap, and it is more preferable that the return port 204 is disposed in a common area where the regions R1 and R3 overlap.

[0041] The return port 205 is preferably disposed below the return port 204, i.e., on the -Z direction side of the return port 204. In other words, the return port 204 is preferably disposed above the return port 205, i.e., on the +Z direction side of the return port 205. This makes it easier for convection to occur in the ink stored inside the ink tank 2, effectively agitating the ink inside the ink tank 2, and effectively reducing settling of insoluble solids contained in the ink.

[0042] In addition, it is preferable that the return port 205 is disposed in the region R2, which makes it easier for convection to occur in the ink stored inside the ink tank 2, effectively stirring the ink inside the ink tank 2 and effectively reducing settling of insoluble solids contained in the ink.

[0043] In addition, it is preferable that the return port 205 is disposed in the region R3, which makes it easier for convection to occur in the ink stored inside the ink tank 2, effectively stirring the ink inside the ink tank 2 and effectively reducing settling of insoluble solids contained in the ink.

[0044] Moreover, it is more preferable that the return port 205 is disposed in a common area where the area R2 and the area R3 overlap.

[0045] The interior of the ink tank 2 may have various shapes, such as a rectangular parallelepiped, cylindrical, or polygonal prism. The ink tank 2 has an inner top surface 21, an inner bottom surface 22, and an inner side surface 23, which define the interior area of ​​the ink tank 2. The inner side surface 23 is a surface that extends along the Z-axis direction (+Z direction). If the interior of the ink tank 2 is rectangular parallelepiped or polygonal prism-shaped, it is a surface that extends along, for example, the YZ plane. If the interior of the ink tank 2 is cylindrical, it is, for example, the side surface of the cylinder. The inner bottom surface 22 is a surface that extends along, for example, the XY plane.

[0046] The outlet 203 is defined on the inner bottom surface 22 of the ink tank 2. The return port 204 is defined on the inner side surface 23 of the ink tank 2. As a result, the insoluble solids accumulated in the lower part of the ink tank 2 are returned to the upper part of the ink tank 2, the ink in the ink tank 2 is effectively stirred, and the settling of the insoluble solids contained in the ink is effectively reduced. In addition, the ink in the ink tank 2 is output from the outlet 203 in the -Z direction and returned from the return port 204 in the -X direction. As a result, a convection current that rotates across the regions R1 and R2 as shown by the arrows in FIG. 2(a) is generated in the ink in the ink tank 2, and a convection current that rotates across the regions R3 and R4 as shown by the arrows in FIG. 2(b) is generated. The ink in the ink tank 2 is effectively stirred by such ink convection, and the settling of the insoluble solids contained in the ink is effectively reduced.

[0047] The return port 205 is defined on the inner bottom surface 22 of the ink tank 2. This makes it possible to effectively generate rotating convection currents in the ink inside the ink tank 2 as shown by the arrows in Figures 2(a) and 2(b) by the ink returned to the inside of the ink tank 2 from the return port 204 and the ink returned to the inside of the ink tank 2 from the return port 205. In other words, it is possible to effectively generate vertical and horizontal convection currents in the ink inside the ink tank 2. This effectively agitates the ink inside the ink tank 2, effectively reducing the settling of insoluble solids contained in the ink.

[0048] The flow rate of ink returned from each of the return ports 204, 205 of the circulation flow path 32 to the inside of the ink tank 2 is greater than the flow rate of ink returned from the return port 202 of the circulation flow path 31 to the inside of the ink tank 2. In other words, the flow rate of ink returned from the return port 202 of the circulation flow path 31 to the inside of the ink tank 2 is smaller than the flow rate of ink returned from each of the return ports 204, 205 of the circulation flow path 32. The outlet 201 and the return port 202 of the circulation flow path 31 are preferably disposed at positions that generate ink convection in a direction that does not cancel out the ink convection formed by the circulation flow path 32, i.e., in a direction that assists it.

[0049] The return port 202 is preferably located above the outlet 201. The return port 202 is preferably located in region R1, and the outlet 201 is preferably located in region R2. The return port 202 is preferably defined on the inner side surface 23, and the outlet 201 is preferably defined on the inner bottom surface 22. In addition, the outlet 201 is preferably located between the outlet 203 and the return port 205, for example, at the center of the interior of the ink tank 2 in the X-axis and Y-axis directions.

[0050] As shown in Figures 2(a) and 2(b), it is preferable that the return port 202 is located below the return port 204, but this is not limited to this, and the return port 202 may be located at the same height as the return port 204 or may be located above the return port 204.

[0051] In addition, it is preferable that the outlet 203, the return port 204, and the return port 205 of the circulation flow path 32 are disposed at the same position in the Y-axis direction, that is, at positions that intersect with an imaginary plane parallel to the XZ plane. This makes it possible to effectively generate ink convection inside the ink tank 2, and effectively reduce settling of insoluble solids.

[0052] In addition, it is preferable that the outlet 201 and the return port 202 of the circulation channel 31 are also disposed at the same positions in the Y-axis direction as the outlet 203, the return port 204, and the return port 205. This makes it possible to effectively assist the convection of ink by the circulation channel 31.

[0053] The flow rate of ink in the circulation channels 31 and 32 will be described. The flow rate of ink in the circulation channels 31 and 32 is determined by the capacity of the pumps 4 and 14 and the inner diameter of the piping. When the flow rate of ink generated by the operation of the pumps 4 and 14 is constant, the smaller the inner diameter of the piping, the higher the flow rate of ink. It is preferable that the flow rate of ink in the return ports 204 and 205 of the circulation channel 32 is higher than the flow rate of ink in the return port 202 of the circulation channel 31. Therefore, it is effective to make the return ports 204 and 205 have a smaller inner diameter than the return port 202. On the other hand, when the flow rate is constant, the smaller the inner diameter of the piping, the lower the flow rate of ink that can flow in the piping. Therefore, in order to obtain a predetermined flow rate in the return ports 202, 204, and 205, an appropriate inner diameter of the piping is determined in balance with the capacity of the pumps 4 and 14. If the flow rate of ink can be adjusted in the pumps 4, 14, the pumps 4, 14 can be made the same size, making it possible to reduce the size of the liquid ejection device 100. Therefore, it is preferable that the inner diameter of the return ports 204, 205 of the circulation channel 32 is smaller than the inner diameter of the return port 202 of the circulation channel 31. In the circulation channel 32, the inner diameter of the main channel 33 is larger than the inner diameters of the branch channels 34, 35.

[0054] The piping lengths of the circulation flow paths 31 and 32 will now be described. In the circulation flow path 31, since the flow velocity of the ink is low, it is advantageous to make the piping length as short as possible in order to reduce settling of insoluble solids. On the other hand, since the flow velocity of the ink in the circulation flow path 32 is higher than that in the circulation flow path 31, the piping length of the circulation flow path 32 may be longer than that of the circulation flow path 31. In other words, the piping length of the circulation flow path 31 may be shorter than that of the circulation flow path 32.

[0055] The pressure in the nozzles (not shown) of the head 1 is controlled to a negative pressure. The control device 50 adjusts the pressure in the nozzles by controlling the pressure in the ink tank 2 to a negative pressure. The control device 50 can control the pressure in the ink tank 2 to a negative pressure by using a gas pressure reducing pump (not shown). Note that the method of controlling the pressure in the nozzles is not limited to this.

[0056] The liquid level sensor 40 is an example of a sensor that detects the remaining amount of ink (liquid) inside the ink tank 2. The control device 50 can adjust the amount of ink output from each of the return ports 204, 205 by controlling the flow rate adjustment valve 17 arranged at the branching portion of the circulation flow path 32 so that ink convection is generated in the ink tank 2, depending on the level of ink in the ink tank 2 detected by the liquid level sensor 40 provided inside the ink tank 2, i.e., the remaining amount of ink in the ink tank 2.

[0057] In the first embodiment, as shown in Fig. 2(c), threshold values ​​TH1, TH2, and TH3 corresponding to the height of the liquid surface inside the ink tank 2 are set in the control device 50. Threshold value TH1 is larger than threshold values ​​TH2 and TH3. Threshold value TH2 is smaller than threshold value TH1 and larger than threshold value TH3. Threshold value TH3 is smaller than threshold values ​​TH1 and TH2.

[0058] The threshold value TH1 is a height value corresponding to the amount of remaining ink inside the ink tank 2 being amount B1, for example 400 ml. The amount B1 is an example of a first amount. The threshold value TH2 is a height value corresponding to the amount of remaining ink inside the ink tank 2 being amount B2, for example 200 ml. The amount B2 is an example of a second amount. The threshold value TH3 is a height value corresponding to the amount of remaining ink inside the ink tank 2 being amount B3, for example 50 ml. The amount B3 is an example of a third amount. The amount B1 is greater than the amounts B2 and B3. The amount B2 is smaller than the amount B1 and greater than the amount B3. The amount B3 is smaller than the amounts B1 and B2. The amounts B1, B2, and B3 are volumes. The amounts B1, B2, and B3 may be weights, in which case the sensor that detects the remaining amounts of ink is, for example, a weight sensor.

[0059] A method for manufacturing an article using a liquid ejection method by the liquid ejection device 100 will be described. Fig. 3 is a flowchart of the operation of the liquid ejection device 100 according to the first embodiment. Figs. 4 to 6 are explanatory diagrams of the operation of the liquid ejection device 100 according to the first embodiment. First, it is assumed that the ink inside the ink tank 2 is empty.

[0060] In step S1, the control device 50 of the liquid ejection device 100 starts the operation of the pump 14 of the circulation flow path 32. As shown in Fig. 4, the control device 50 operates the pump 14 so that the flow rate of the ink becomes flow rate A5 (for example, 150 ml / min, the inner diameter of the piping of the main flow path 33 is 4 mm, and the flow rate is 199 mm / sec). Flow rate A5 is an example of a fifth flow rate.

[0061] In step S2, the control device 50 controls a valve (not shown) provided on a pipe connecting the ink tank 2 and the main tank so that a predetermined amount (e.g., 500 ml) of ink is filled into the ink tank 2 from the main tank (not shown). As a result, the amount of ink remaining inside the ink tank 2 becomes greater than the amounts B1 to B3 shown in FIG. 2(c). Note that the amount of ink supplied to the ink tank 2 is an amount that does not cause the ink to overflow from the ink tank 2. When the ink tank 2 is filled with ink, the operation of the pump 14 causes the ink to circulate between the ink tank 2 and the circulation flow path 32.

[0062] The control device 50 also controls the flow rate adjustment valve 17 to adjust the flow rate of ink returned to the ink tank 2 from the return port 204 to a flow rate A1, and adjust the flow rate of liquid returned to the ink tank 2 from the return port 205 to a flow rate A2. The flow rate A1 is an example of a first flow rate, and the flow rate A2 is an example of a second flow rate. The flow rate A1 is greater than the flow rate A2. Furthermore, each of the flow rates A1, A2, and A5 is greater than a flow rate A10, which will be described later. Furthermore, the flow rate A5 is the total flow rate of the flow rates A1 and A2.

[0063] Step S3 is performed for a certain time T1, for example, 30 minutes. The process of step S3 is called filtering. In step S3, the pump 4 provided in the circulation flow path 31 is stopped, that is, the flow rate of the pump 4 is zero. In other words, filtering in step S3 is performed with the pump 4 stopped. By operating the pump 14 arranged in the circulation flow path 32 for the time T1, the ink filled in the ink tank 2 flows through the circulation flow path 32 and passes through the filter 16, and the remnants contained in the ink are removed by the filter 16. The time T1 may be determined by the particle size of the insoluble solid content of the ink, the filtering particle size of the filter 16, the amount of ink input, and the flow rate of the pump 14.

[0064] The filtering in step S3 is performed to prevent foreign matter from being supplied to the circulation flow path 31, i.e., the head 1. Since a filter 6 is also installed in the circulation flow path 31 upstream of the head 1, the filtering in step S3 serves as pre-filtering. In addition, by circulating ink between the ink tank 2 and the circulation flow path 32 for a certain period of time T1, the concentration of ink inside the ink tank 2 is made uniform.

[0065] In step S4, the control device 50 starts the operation of the pump 4 of the circulation flow path 31.

[0066] In step S5, the control device 50 operates the pump 4 so that the flow rate of the ink becomes a flow rate A10 (for example, 50 ml / min, the inner diameter of the piping of the circulation flow path 31 is 4 mm, and the flow rate is 66 mm / sec). The flow rate A10 is a flow rate smaller than the flow rate A5. This step S5 is performed for a certain time T2, for example, 30 minutes. The processing of step S5 is also called filtering. Note that the states of the pump 14 and the flow rate adjustment valve 17 are maintained from step S3. That is, the flow rate of the pump 14 is the flow rate A5, the flow rate of the ink returned from the return port 204 to the inside of the ink tank 2 is the flow rate A1, and the flow rate of the ink returned from the return port 205 to the inside of the ink tank 2 is the flow rate A2. At this time, the ink flow rate A5 is, for example, 150 ml / min, and the flow rates A1 and A2 are 75 ml / min. When the inner diameter of the piping of main flow path 33 is 4 mm and the inner diameter of the piping of branch flow paths 34, 35 is 3 mm, the flow velocities of main flow path 33 and branch flow paths 34, 35 are 199 mm / sec, 177 mm / sec, and 177 mm / sec, respectively.

[0067] In step S6, the control device 50 starts discharging ink from the head 1. The pumps 4 and 14 continue to operate, and ink is discharged from the head 1 with the ink flow rate in the pump 4 set to flow rate A10 (steady state).

[0068] The control device 50 controls the flow rate adjustment valve 17 to adjust the flow rate of ink returned from the return port 204 to the ink tank 2 and the flow rate of ink returned from the return port 205 to the ink tank 2 according to the remaining amount of liquid inside the ink tank 2. A specific description will be given below.

[0069] In step S7, the control device 50 determines whether the height of the liquid level is equal to or lower than a threshold value TH1 based on the detection result obtained from the liquid level sensor 40. The threshold value TH1 is set to a height value lower than the return port 204, for example, a height value corresponding to the remaining amount of ink inside the ink tank 2 being the amount B1 (400 ml).

[0070] If step S7 is NO, that is, if the remaining amount of ink inside the ink tank 2 is greater than the amount B1, the flow rate of the pump 14 is maintained at flow rate A5, the flow rate of the ink from the return port 204 is maintained at flow rate A1, and the flow rate of the ink from the return port 205 is maintained at flow rate A2. That is, the control device 50 controls the flow rate adjustment valve 17 to maintain the flow rate of the ink from the return port 204 at flow rate A1 and to maintain the flow rate of the ink from the return port 205 at flow rate A2, while maintaining the flow rate of the pump 14 at flow rate A5.

[0071] If step S7 is YES, that is, if the remaining amount of ink inside the ink tank 2 is equal to or less than the amount B1, the process proceeds to the next step S8. In step S8, as shown in FIG. 5, the control device 50 controls the flow rate adjustment valve 17 to adjust the flow rate of ink returned from the return port 204 to the ink tank 2 to a flow rate A3 smaller than the flow rate A1, and adjust the flow rate of ink returned from the return port 205 to a flow rate A4 larger than the flow rate A2. The flow rate A3 is an example of a third flow rate, and the flow rate A4 is an example of a fourth flow rate. The flow rate A4 is larger than the flow rate A3. Moreover, each of the flow rates A3, A4, and A5 is larger than the flow rate A10. Moreover, the flow rate A5 is the total flow rate of the flow rates A3 and A4. At this time, the flow rate A5 of the ink is, for example, 150 ml / min, the flow rate A3 is 60 ml / min, and the flow rate A4 is 90 ml / min. When the inner diameter of the piping of main flow path 33 is 4 mm and the inner diameter of the piping of branch flow paths 34, 35 is 3 mm, the flow velocities of main flow path 33 and branch flow paths 34, 35 are 199 mm / sec, 141 mm / sec, and 212 mm / sec, respectively.

[0072] When the ink level inside the ink tank 2 is higher than the return port 204, the ink returned from the return port 204 to the inside of the ink tank 2 has a large effect of stirring the ink inside the ink tank 2. On the other hand, when the ink level inside the ink tank 2 is lower than the return port 204, the stirring effect becomes small, so the amount of ink returned from the lower return port 205 is increased to induce stirring inside the ink tank 2.

[0073] In step S9, the control device 50 determines whether the height of the liquid level is equal to or lower than a threshold value TH2 based on the detection result obtained from the liquid level sensor 40. The threshold value TH2 is set to a height value corresponding to the remaining amount of ink inside the ink tank 2 being the amount B2 (200 ml), for example.

[0074] If step S9 is NO, that is, if the remaining amount of ink inside the ink tank 2 is equal to or less than the amount B1 and greater than the amount B2, the flow rate of the pump 14 is maintained at the flow rate A5, the flow rate of the ink from the return port 204 is maintained at the flow rate A3, and the flow rate of the ink from the return port 205 is maintained at the flow rate A4. That is, the control device 50 controls the flow rate adjustment valve 17 to maintain the flow rate of the ink from the return port 204 at the flow rate A3 and to maintain the flow rate of the ink from the return port 205 at the flow rate A4, while maintaining the flow rate of the pump 14 at the flow rate A5.

[0075] If step S9 is YES, that is, if the remaining amount of ink inside the ink tank 2 is equal to or less than the amount B2, the process proceeds to the next step S10. In step S10, as shown in FIG. 6, the control device 50 controls the pump 14 to adjust the flow rate of the pump 14 to a flow rate A6 that is smaller than the flow rate A5. The flow rate A5 is, for example, 150 ml / min, and the flow rate A6 is, for example, 100 ml / min. The flow rate A6 is an example of a sixth flow rate. Also, the flow rate A6 is larger than the flow rate A10.

[0076] Since the flow rate of the pump 14 is adjusted to a flow rate A6 smaller than the flow rate A5, the flow rate of the ink returned from the return port 204 to the ink tank 2 decreases from a flow rate A3 to a flow rate A7, and the flow rate of the ink returned from the return port 205 to the ink tank 2 decreases from a flow rate A4 to a flow rate A8. The flow rate A7 is smaller than the flow rate A3, and the flow rate A8 is smaller than the flow rate A4. The flow rate A6 is the total flow rate of the flow rates A7 and A8. At this time, the ink flow rate A6 is, for example, 110 ml / min, and the flow rates A7 and A8 are 55 ml / min. When the inner diameter of the pipe of the main flow path 33 is 4 mm and the inner diameter of the pipe of the branch flow paths 34 and 35 is 3 mm, the flow velocities of the main flow path 33 and the branch flow paths 34 and 35 are 199 mm / sec, 130 mm / sec, and 130 mm / sec, respectively.

[0077] When the remaining amount of ink inside the ink tank 2 falls to an amount B2, for example 200 ml, the flow rate of the pump 14 is reduced from flow rate A5 to flow rate A6, so that pulsation of the ink surface inside the ink tank 2 is reduced.

[0078] In step S11, the control device 50 determines whether the height of the liquid level is equal to or lower than a threshold value TH3 based on the detection result obtained from the liquid level sensor 40. The threshold value TH3 is set to a height value corresponding to the remaining amount of ink inside the ink tank 2 being an amount B3 (50 ml), for example.

[0079] If step S11 is NO, that is, if the remaining amount of ink inside the ink tank 2 is equal to or less than the amount B2 and is greater than the amount B3, the flow rate of the pump 14 is maintained at the flow rate A6, the flow rate of the ink from the return port 204 is maintained at the flow rate A7, and the flow rate of the ink from the return port 205 is maintained at the flow rate A8. That is, the control device 50 controls the flow rate adjustment valve 17 to maintain the flow rate of the ink from the return port 204 at the flow rate A7 and to maintain the flow rate of the ink from the return port 205 at the flow rate A8, while maintaining the flow rate of the pump 14 at the flow rate A6.

[0080] If step S11 is YES, that is, if the remaining amount of ink inside the ink tank 2 is equal to or less than the amount B3, the process proceeds to the next step S12. In step S12, the control device 50 stops the head 1 from ejecting ink, and stops the operation of the pump 4. The control device 50 also operates the pump 14 so that the ink flow rate becomes flow rate A5 (for example, 150 ml / min, the inner diameter of the piping of the circulation flow path 31 is 4 mm, and the flow rate is 199 mm / sec), and the process returns to step S2.

[0081] In step S2, the control device 50 controls a valve (not shown) provided on a pipe connecting the ink tank 2 and the main tank so as to replenish the ink tank 2 with an amount (e.g., 450 ml) that is less than a predetermined amount (e.g., 500 ml) by an amount B3 from the main tank (not shown). In other words, ink is replenished inside the ink tank 2 so that the remaining amount of ink inside the ink tank 2 becomes a predetermined amount.

[0082] According to the first embodiment, by making the ink flow rate in the circulation flow path 32 faster than a predetermined flow rate, the ink inside the ink tank 2 can be effectively stirred, while by making the ink flow rate in the circulation flow path 31 slower than the predetermined flow rate, the occurrence of twisting can be reduced, and ink can be ejected stably from the head 1.

[0083] Furthermore, the ink can be convected over a wide range between the top and bottom inside the ink tank 2, reducing the occurrence of uneven concentration of the insoluble solids contained in the ink inside the ink tank 2. This allows ink with reduced uneven concentration to be stably ejected from the head 1. As a result, the physical properties of the ink ejected from the head 1 are stabilized, reducing the variation in the ejection state (e.g., ejection speed and ejection amount) of the ink ejected from the head 1, and making it possible to manufacture, with good yield, articles including, for example, functional thin films or functional elements.

[0084] Example 1 Example 1 is an experimental example conducted using a liquid ejection device 100 corresponding to the first embodiment. In Example 1, ink was used in which 7% by weight of TiO2 was added as an insoluble solid content to an acrylic monomer, which was the main component. The particle size of the TiO2 added to the ink had a median particle size of 200 nm and a particle size distribution of 100 nm to 700 nm. The internal shape of the ink tank 2 was a rectangular parallelepiped. The inner diameter of the piping of the circulation flow path 31 was 4 mm, and the inner diameter of the piping of the circulation flow path 32 was 4 mm in the main flow path 33 and 3 mm in the branch flow paths 34 and 35.

[0085] A diaphragm pump manufactured by KNF was used as the pump 4, and the flow rate was 50 ml / min. A pulsation reduction damper FPD manufactured by KNF was used as the damper 5. A filter with a filtration size of 5 μm was selected as the filter 6.

[0086] A diaphragm pump manufactured by KNF was used as the pump 14, and the flow rate was 150 ml / min. The damper 15 was the same as the damper 5. The filter 16 was the same as the filter 6.

[0087] The liquid ejection device 100 was operated for 10 consecutive days under the conditions exemplified in the first embodiment, following the flow chart shown in Fig. 3. The droplet speed and landing accuracy from the head 1 were evaluated, and a comparison was made between the initial evaluation and the evaluation after 10 days. As a result, it was confirmed that there was no change in the evaluation between the initial and 10 days.

[0088] The droplet speed was determined by observing the ink ejected from head 1 with a high-speed camera. The landing accuracy was determined by combining two methods: measuring the amount of deviation from the target position by measuring the position of the ink that landed on the substrate, and calculating the amount of deviation from the target position using continuous images from the high-speed camera.

[0089] After operating the liquid ejection device 100 for 10 consecutive days, the concentration of the insoluble solids in the ink remaining in the ink tank 2 was measured using a thermogravimetric analyzer. As a result, it was confirmed that the concentration of the insoluble solids was within the measurement accuracy range of the measuring device and had not changed since the beginning.

[0090] In addition, the ink applied to the substrate was dried to form a coating film, and performance evaluations (transmittance and reflectance measurements) were carried out. As a result, it was confirmed that the performance of the film formed on the 10th day was no different from that of the film formed at the initial stage.

[0091] As described above, the experimental results of embodiment 1 confirmed that it is possible to reduce the settling of insoluble solids contained in the ink inside the ink tank 2, and that ink droplets can be ejected stably from the head 1.

[0092] [Second embodiment] A second embodiment of the present disclosure will be described. In the following, elements with the same reference symbols as those in the first embodiment will have substantially the same configurations and functions as those described in the first embodiment unless otherwise specified, and differences from the first embodiment will be mainly described.

[0093] 7(a) is a schematic diagram of a portion of a liquid ejection device according to the second embodiment. In the second embodiment, a return port 206 provided in an ink tank 2 is added to the circulation flow path 32 of the first embodiment. The rest of the configuration is the same as that of the liquid ejection device 100 of the first embodiment, and a description thereof will be omitted.

[0094] In the second embodiment, the circulation flow path 32 has one outlet 203 and three return ports 204, 205, and 206 branched from the main flow path 33. Specifically, the return port 204 is formed in one of the two branch flow paths 34 branched from the main flow path 33. Downstream of the other branch flow path 35, the flow path is further branched into two branch flow paths 36 and 37. The return port 205 is formed in the branch flow path 36, and the return port 206 is formed in the branch flow path 37. In other words, the circulation flow path 32 has two or more return ports 205 and 206 as third ports.

[0095] The return ports 205, 206 are defined on the inner bottom surface 22 of the ink tank 2. The outlet 201 and the outlet 203 are defined on the inner bottom surface 22 between the return port 205 and the return port 206. That is, the return ports 205, 206 are defined on the inner bottom surface 22 outside the outlets 201, 203. Specifically, on the inner bottom surface 22, the outlet 201 is defined between the outlet 203 and the return port 206, and the outlet 203 is defined between the outlet 201 and the return port 205.

[0096] Since two return ports 205, 206 are defined on the inner bottom surface 22 as two or more third ports, ink convection can be effectively generated inside the ink tank 2, and settling of insoluble solids can be effectively reduced.

[0097] In addition, since insoluble solids tend to settle at the ends of the inner bottom surface 22, by arranging the return ports 205, 206 outside the outlets 201, 203 at the inner bottom surface 22, the settling of insoluble solids on the inner bottom surface 22 can be effectively reduced.

[0098] Example 2 Example 2 is an experimental example conducted using a liquid ejection device corresponding to the second embodiment. In Example 2, ink was used in which 7% by weight of TiO2 was added as an insoluble solid content to acrylic monomer, which is the main component. The particle size of the TiO2 added to the ink was a median particle size of 200 nm, with a particle size distribution of 100 nm to 700 nm. The internal shape of the ink tank 2 was a rectangular parallelepiped.

[0099] A diaphragm pump manufactured by KNF was used as the pump 4, and the flow rate was 50 ml / min. A pulsation reduction damper FPD manufactured by KNF was used as the damper 5. A filter with a filtration size of 5 μm was selected as the filter 6.

[0100] A diaphragm pump manufactured by KNF was used as the pump 14, and the flow rate was 150 ml / min. The damper 15 was the same as the damper 5. The filter 16 was the same as the filter 6.

[0101] In Example 2, under the conditions exemplified in the first embodiment, i.e., the conditions of Example 1, the liquid ejection device was operated for 10 consecutive days according to the flow chart shown in Fig. 3. The droplet speed and landing accuracy from the head 1 were evaluated, and a comparison was made between the initial evaluation and the evaluation after 10 days. As a result, it was confirmed that there was no change in the evaluation between the initial period and the 10 days.

[0102] The droplet speed was determined by observing the ink ejected from head 1 with a high-speed camera. The landing accuracy was determined by combining two methods: measuring the amount of deviation from the target position by measuring the position of the ink that landed on the substrate, and calculating the amount of deviation from the target position using continuous images from the high-speed camera.

[0103] After operating the liquid ejection device for 10 consecutive days, the concentration of the insoluble solids in the ink remaining in the ink tank 2 was measured using a thermogravimetric analyzer. As a result, it was confirmed that the concentration of the insoluble solids was within the measurement accuracy range of the measuring device and had not changed from the initial value.

[0104] In addition, the ink applied to the substrate was dried to form a coating film, and performance evaluations (transmittance and reflectance measurements) were carried out. As a result, it was confirmed that the performance of the film formed on the 10th day was no different from that of the film formed at the initial stage.

[0105] As described above, the experimental results of Example 2 confirmed that it is possible to reduce the settling of insoluble solids contained in the ink inside the ink tank 2, and that ink droplets can be ejected stably from the head 1.

[0106] [Third embodiment] A third embodiment of the present disclosure will be described. In the following, elements with the same reference symbols as those in the first or second embodiment will have substantially the same configurations and functions as those described in the first or second embodiment unless otherwise specified, and differences from the first or second embodiment will be mainly described.

[0107] 7(b) is a schematic diagram of a portion of a liquid ejection device according to a third embodiment. In the third embodiment, an ink tank 2B is disposed instead of the ink tank 2. In the third embodiment, similarly to the second embodiment, the circulation flow path 32 has an outlet 203 and return ports 204-206. Other configurations are similar to those of the liquid ejection device 100 according to the first embodiment, and therefore description thereof will be omitted.

[0108] The ink tank 2B has an inner top surface 21, an inner bottom surface 22, an inner side surface 23, and an inclined surface 24, which define the interior area of ​​the ink tank 2B. The inner side surface 23 is a surface that extends along the Z-axis direction (+Z direction). The inner bottom surface 22 is a surface that extends along, for example, the XY plane.

[0109] The inclined surface 24 is disposed between the inner side surface 23 and the inner bottom surface 22. The inclined surface 24 is connected to the inner bottom surface 22 and inclines upward from the inner bottom surface 22.

[0110] The return port 204 and the return port 202 are defined in the inner side surface 23. The return port 205 and the return port 206 are defined in the inclined surface 24 of the ink tank 2. The outlet 201 and the outlet 203 are defined in the inner bottom surface 22.

[0111] The outlet 201 and the outlet 203 are defined between the return port 205 and the return port 206. That is, the return ports 205 and 206 are defined on the inner bottom surface 22 outside the outlets 201 and 203.

[0112] Since two return ports 205, 206 are defined on the inclined surface 24 as two or more third ports, ink convection can be effectively generated inside the ink tank 2, and settling of insoluble solids can be effectively reduced.

[0113] Furthermore, settling of insoluble solids is less likely to occur on the inclined surface 24 than on a horizontal surface. Since the inclined surface 24 is inclined toward the inner bottom surface 22, the insoluble solids that have settled on the inclined surface 24 are guided to the inner bottom surface 22. The insoluble solids guided to the inner bottom surface 22 are then sucked into the outlet 203 disposed on the inner bottom surface 22, and returned to the inside of the ink tank 2 through the return port 204. This makes it possible to reduce unevenness in the concentration of the insoluble solids in the ink inside the ink tank 2.

[0114] Although insoluble solids are less likely to settle on the inclined surface 24 than on a horizontal surface, by providing the return ports 205, 206 on the inclined surface 24, it is possible to effectively reduce the settling of insoluble solids on the inclined surface 24. In addition, since the outlet 203 is provided on the inner bottom surface 22, it is possible to effectively reduce the settling of insoluble solids on the inner bottom surface 22.

[0115] Example 3 Example 3 is an experimental example conducted using a liquid ejection device corresponding to the third embodiment. In Example 3, ink was used in which 7% by weight of TiO2 was added as an insoluble solid content to acrylic monomer, which was the main component. The particle size of TiO2 added to the ink had a median particle size of 200 nm and a particle size distribution of 100 nm to 700 nm.

[0116] A diaphragm pump manufactured by KNF was used as the pump 4, and the flow rate was 50 ml / min. A pulsation reduction damper FPD manufactured by KNF was used as the damper 5. A filter with a filtration size of 5 μm was selected as the filter 6.

[0117] A diaphragm pump manufactured by KNF was used as the pump 14, and the flow rate was 170 ml / min. The damper 15 was the same as the damper 5. The filter 16 was the same as the filter 6.

[0118] In Example 3, the liquid discharger was operated for 10 consecutive days according to the flow chart shown in FIG. 3 under conditions different from those exemplified in the first embodiment, i.e., conditions different from those in Example 1. In step S1, the flow rate of the pump 14 was set to 170 ml / min as the flow rate A5. In step S3, the time T1 was set to 10 minutes. In step S4, the flow rate of the pump 4 was set to 55 ml / min as the flow rate A10. In step S5, the time T2 was set to 60 minutes. The threshold value TH1 was set to a height value corresponding to 400 ml as the amount B1. The threshold value TH2 was set to a height value corresponding to 200 ml as the amount B2. The threshold value TH3 was set to a height value corresponding to 50 ml as the amount B3. In step S10, the flow rate of the pump 14 was set to 100 ml / min as the flow rate A6.

[0119] The droplet velocity and landing accuracy from head 1 were evaluated, and a comparison was made between the initial evaluation and the evaluation after 10 days. As a result, it was confirmed that there was no change in the evaluation between the initial evaluation and the evaluation after 10 days.

[0120] The droplet speed was determined by observing the ink ejected from head 1 with a high-speed camera. The landing accuracy was determined by combining two methods: measuring the amount of deviation from the target position by measuring the position of the ink that landed on the substrate, and calculating the amount of deviation from the target position using continuous images from the high-speed camera.

[0121] After operating the liquid ejection device 100 for 10 consecutive days, the concentration of the insoluble solids in the ink remaining in the ink tank 2 was measured using a thermogravimetric analyzer. As a result, it was confirmed that the concentration of the insoluble solids was within the measurement accuracy range of the measuring device and had not changed since the beginning.

[0122] In addition, the ink applied to the substrate was dried to form a coating film, and performance evaluations (transmittance and reflectance measurements) were carried out. As a result, it was confirmed that the performance of the film formed on the 10th day was no different from that of the film formed at the initial stage.

[0123] As described above, the experimental results of Example 3 confirmed that it is possible to reduce the settling of insoluble solids contained in the ink inside the ink tank 2, and that ink droplets can be ejected stably from the head 1.

[0124] [Fourth embodiment] A fourth embodiment of the present disclosure will be described. In the following, elements with the same reference symbols as those in the first to third embodiments have substantially the same configurations and functions as those described in the first to third embodiments unless otherwise specified, and differences from the first to third embodiments will be mainly described.

[0125] 7(c) is a schematic diagram of a portion of a liquid ejection device according to a fourth embodiment. In the fourth embodiment, similar to the second embodiment, the circulation flow path 32 has an outlet 203 and return ports 204-206. However, unlike the second embodiment, in the fourth embodiment, the return ports 204-206 are not defined in the ink tank 2, but are defined in piping extending inside the ink tank 2.

[0126] More specifically, the branch flow path 34 has a pipe 301 that extends into the ink tank 2 and has a return port 204 formed therein. The pipe 301 is an example of a first pipe. The branch flow path 36 has a pipe 302 that extends into the ink tank 2 and has a return port 205 formed therein. The branch flow path 37 has a pipe 303 that extends into the ink tank 2 and has a return port 206 formed therein. The pipes 302 and 303 are each an example of a second pipe. That is, in the fourth embodiment, the circulation flow path 32 has two or more second pipes.

[0127] The relative positional relationship in the height direction of the return ports 204 to 206 is as described in the second embodiment. That is, the return port 204 is disposed above the return ports 205 and 206. The outlet 201, the outlet 203, and the return port 202 are disposed in the same positions as in the second embodiment. The pipes 301 to 303 are disposed, for example, penetrating an upper member of the ink tank 2.

[0128] The ink returned to the inside of the ink tank 2 from the return ports 205 and 206 flows horizontally when it hits the inner bottom surface 22 of the ink tank 2, and then forms an upward convection current along the inner side surface 23. The ink returned to the inside of the ink tank 2 from the return port 204 causes the ink on the upper side to convect downward.

[0129] As described above, according to the fourth embodiment, as in the second embodiment, it is possible to generate ink convection inside the ink tank 2, to effectively agitate the ink inside the ink tank 2, and to effectively reduce settling of the insoluble solid content contained in the ink inside the ink tank 2. This makes it possible to reduce unevenness in the concentration of the insoluble solid content contained in the ink inside the ink tank 2.

[0130] In addition, since the ink is returned toward the inner bottom surface 22, accumulation of insoluble solids contained in the ink on the inner bottom surface 22 can be effectively reduced.

[0131] Example 4 Example 4 is an experimental example conducted using a liquid ejection device corresponding to the fourth embodiment. In Example 4, ink was used in which 7% by weight of TiO2 was added as an insoluble solid content to acrylic monomer, which is the main component. The particle size of the TiO2 added to the ink was a median particle size of 200 nm, with a particle size distribution of 100 nm to 700 nm. The internal shape of the ink tank 2 was a rectangular parallelepiped.

[0132] A diaphragm pump manufactured by KNF was used as the pump 4, and the flow rate was 50 ml / min. A pulsation reduction damper FPD manufactured by KNF was used as the damper 5. A filter with a filtration size of 5 μm was selected as the filter 6.

[0133] A diaphragm pump manufactured by KNF was used as the pump 14, and the flow rate was 150 ml / min. The damper 15 was the same as the damper 5. The filter 16 was the same as the filter 6.

[0134] In Example 4, the liquid ejection device was operated for 10 consecutive days under the conditions exemplified in the first embodiment, i.e., the conditions of Example 1, according to the flow chart shown in Fig. 3. The droplet speed and landing accuracy from the head 1 were evaluated, and a comparison was made between the initial evaluation and the evaluation after 10 days. As a result, it was confirmed that there was no change in the evaluation between the initial period and the 10 days.

[0135] The droplet speed was determined by observing the ink ejected from head 1 with a high-speed camera. The landing accuracy was determined by combining two methods: measuring the amount of deviation from the target position by measuring the position of the ink that landed on the substrate, and calculating the amount of deviation from the target position using continuous images from the high-speed camera.

[0136] After operating the liquid ejection device for 10 consecutive days, the concentration of the insoluble solids in the ink remaining in the ink tank 2 was measured using a thermogravimetric analyzer. As a result, it was confirmed that the concentration of the insoluble solids was within the measurement accuracy range of the measuring device and had not changed from the initial value.

[0137] In addition, the ink applied to the substrate was dried to form a coating film, and performance evaluations (transmittance and reflectance measurements) were carried out. As a result, it was confirmed that the performance of the film formed on the 10th day was no different from that of the film formed at the initial stage.

[0138] As described above, the experimental results of Example 4 confirmed that it is possible to reduce the settling of insoluble solids contained in the ink inside the ink tank 2, and that ink droplets can be ejected stably from the head 1.

[0139] [Fifth embodiment] A fifth embodiment of the present disclosure will be described. In the following, elements having the same reference symbols as those in the first to fourth embodiments will have substantially the same configurations and functions as those described in the first to fourth embodiments unless otherwise specified, and differences from the first to fourth embodiments will be mainly described.

[0140] Fig. 8(a) is a schematic diagram of a liquid ejection device 100D according to a fifth embodiment. The liquid ejection device 100D includes a head 1, an ink tank 2, a liquid circulation device 30D, and a control device 50. Fig. 8(b) is a schematic diagram of the ink tank 2 according to the fifth embodiment, viewed in the horizontal direction.

[0141] The liquid circulation device 30D has a circulation flow path 31, which is an example of a first circulation flow path, and a circulation flow path 32D, which is an example of a second circulation flow path. The circulation flow path 31 has the same configuration as described in the first embodiment. In the circulation flow path 31, a pump 4, a damper 5, a filter 6, and a head 1 are arranged.

[0142] The circulation flow path 32D has outlets 203, 207 provided in the ink tank 2 as two or more first ports that serve as outlets for ink from the ink tank 2. In addition, the circulation flow path 32D has a return port 204 provided in the ink tank 2 as a second port that serves as a return port for the liquid to the liquid tank.

[0143] The circulation flow path 32D has a main flow path 33 and two sub flow paths 38, 39 provided on the upstream side of the main flow path 33. The outlet 203 is formed at the upstream end of the sub flow path 38, and the outlet 207 is formed at the upstream end of the sub flow path 39. The return port 204 is formed at the downstream end of the main flow path 33. A filter 16, a pump 14, and a damper 15 are arranged in the main flow path 33.

[0144] The outlets 203 and 207 are defined in the inner bottom surface 22 of the ink tank 2, and are disposed at positions spaced from the inner side surface 23 of the ink tank 2 by approximately ¼ of the length of the inner bottom surface 22 in the X-axis direction.

[0145] In the above configuration, as in the first embodiment, the ink output from the outlets 203, 207 to the outside of the ink tank 2 flows through the circulation flow path 32 and is returned to the inside of the ink tank 2 from the return port 204 provided above the outlets 203, 207. By circulating the ink in this manner, the ink inside the ink tank 2 is agitated, and it is possible to reduce settling of the insoluble solid content of the ink inside the piping of the circulation flow path 31 and inside the ink tank 2. This reduces unevenness in the concentration of the insoluble solid content contained in the ink inside the ink tank 2.

[0146] Moreover, the outlet 201 is disposed at the center of the inner bottom surface 22 of the ink tank 2. The outlet 201 of the circulation flow path 31 is disposed between the outlet 203 and the outlet 207 of the circulation flow path 32. With this arrangement, the ink convecting inside the ink tank 2 and having reduced unevenness in the concentration of the insoluble solids can be stably supplied to the head 1.

[0147] Example 5 Example 5 is an experimental example conducted using a liquid ejection device 100D corresponding to the fifth embodiment. In Example 5, ink was used in which 7% by weight of TiO2 was added as an insoluble solid content to acrylic monomer, which is the main component. The particle size of the TiO2 added to the ink had a median particle size of 200 nm and a particle size distribution of 100 nm to 700 nm. The internal shape of the ink tank 2 was a rectangular parallelepiped.

[0148] A diaphragm pump manufactured by KNF was used as the pump 4, and the flow rate was 50 ml / min. A pulsation reduction damper FPD manufactured by KNF was used as the damper 5. A filter with a filtration size of 5 μm was selected as the filter 6.

[0149] A diaphragm pump manufactured by KNF was used as the pump 14, and the flow rate was 130 ml / min. The damper 15 was the same as the damper 5. The filter 16 was the same as the filter 6.

[0150] In Example 5, under the conditions exemplified in the first embodiment, i.e., the conditions of Example 1, the liquid ejection device was operated for 10 consecutive days according to the flow chart shown in Fig. 3. The droplet speed and landing accuracy from the head 1 were evaluated, and a comparison was made between the initial evaluation and the evaluation after 10 days. As a result, it was confirmed that there was no change in the evaluation between the initial period and the 10 days.

[0151] The droplet speed was determined by observing the ink ejected from head 1 with a high-speed camera. The landing accuracy was determined by combining two methods: measuring the amount of deviation from the target position by measuring the position of the ink that landed on the substrate, and calculating the amount of deviation from the target position using continuous images from the high-speed camera.

[0152] After operating the liquid ejection device for 10 consecutive days, the concentration of the insoluble solids in the ink remaining in the ink tank 2 was measured using a thermogravimetric analyzer. As a result, it was confirmed that the concentration of the insoluble solids was within the measurement accuracy range of the measuring device and had not changed from the initial value.

[0153] In addition, the ink applied to the substrate was dried to form a coating film, and performance evaluations (transmittance and reflectance measurements) were carried out. As a result, it was confirmed that the performance of the film formed on the 10th day was no different from that of the film formed at the initial stage.

[0154] According to the experimental results of Example 5, it was confirmed that the settling of insoluble solids contained in the ink inside the ink tank 2 can be reduced, and ink droplets can be ejected stably from the head 1.

[0155] [Sixth embodiment] A sixth embodiment of the present disclosure will be described. In the following, elements with the same reference symbols as those in the first to fifth embodiments have substantially the same configurations and functions as those described in the first to fifth embodiments unless otherwise specified, and differences from the first to fifth embodiments will be mainly described.

[0156] Figures 9(a) and 9(b) are schematic diagrams of a portion of a liquid ejection device according to a sixth embodiment. Note that Figure 9(a) is a schematic diagram of the ink tank 2 viewed in the -Z direction, and Figure 9(b) is a schematic diagram of the ink tank 2 viewed in the +Y direction.

[0157] In the sixth embodiment, similarly to the first embodiment, the circulation flow path 32 has an outlet 203 and return ports 204 and 205. However, in the sixth embodiment, the positions of the return ports 204 and 205 are different from those in the first embodiment. The return port 204 is an example of a second port, and the return port 205 is an example of a third port. The outlets 201 and 203 are disposed on the inner bottom surface 22 of the ink tank 2.

[0158] The return port 204 and the return port 205 are disposed in positions and oriented symmetrically with respect to the center point C0 of the ink tank 2. The center point C0 is an example of a predetermined point.

[0159] For example, as shown in Figures 9(a) and 9(b), the return port 204 is inclined at an acute angle with respect to the -X direction, at an acute angle with respect to the +Y direction, and at an acute angle with respect to the +Z direction. In contrast, the return port 205 is inclined at an obtuse angle with respect to the -X direction (acute angle with respect to the +X direction), at an obtuse angle with respect to the +Y direction (acute angle with respect to the -Y direction), and at an obtuse angle with respect to the +Z direction (acute angle with respect to the -Z direction). In this way, the return port 205 is inclined in the opposite direction to the return port 204.

[0160] Therefore, the ink is returned from the return ports 204, 205 into the ink tank 2 in directions inclined relative to the imaginary vertical and horizontal planes, so that the ink convects in a spiral shape when viewed from a direction horizontal to the liquid surface and a direction perpendicular to the liquid surface. This agitates the ink inside the ink tank 2, reducing settling of the insoluble solid content of the ink inside the piping of the circulation flow path 31 and inside the ink tank 2. This reduces uneven concentration of the insoluble solid content contained in the ink inside the ink tank 2.

[0161] Example 6 Example 6 is an experimental example conducted using a liquid ejection device corresponding to the sixth embodiment. In Example 6, ink was used in which 7% by weight of TiO2 was added as an insoluble solid content to acrylic monomer, which is the main component. The particle size of the TiO2 added to the ink was a median particle size of 200 nm, with a particle size distribution of 100 nm to 700 nm. The internal shape of the ink tank 2 was a rectangular parallelepiped.

[0162] A diaphragm pump manufactured by KNF was used as the pump 4, and the flow rate was 50 ml / min. A pulsation reduction damper FPD manufactured by KNF was used as the damper 5. A filter with a filtration size of 5 μm was selected as the filter 6.

[0163] A diaphragm pump manufactured by KNF was used as the pump 14, and the flow rate was 150 ml / min. The damper 15 was the same as the damper 5. The filter 16 was the same as the filter 6.

[0164] In Example 6, the liquid ejection device was operated for 10 consecutive days under the conditions exemplified in the first embodiment, i.e., the conditions of Example 1, according to the flow chart shown in Fig. 3. The droplet speed and landing accuracy from the head 1 were evaluated, and a comparison was made between the initial evaluation and the evaluation after 10 days. As a result, it was confirmed that there was no change in the evaluation between the initial period and the 10 days.

[0165] The droplet speed was determined by observing the ink ejected from head 1 with a high-speed camera. The landing accuracy was determined by combining two methods: measuring the amount of deviation from the target position by measuring the position of the ink that landed on the substrate, and calculating the amount of deviation from the target position using continuous images from the high-speed camera.

[0166] After operating the liquid ejection device for 10 consecutive days, the concentration of the insoluble solids in the ink remaining in the ink tank 2 was measured using a thermogravimetric analyzer. As a result, it was confirmed that the concentration of the insoluble solids was within the measurement accuracy range of the measuring device and had not changed from the initial value.

[0167] In addition, the ink applied to the substrate was dried to form a coating film, and performance evaluations (transmittance and reflectance measurements) were carried out. As a result, it was confirmed that the performance of the film formed on the 10th day was no different from that of the film formed at the initial stage.

[0168] As described above, the experimental results of Example 6 confirmed that it is possible to reduce the settling of insoluble solids contained in the ink inside the ink tank 2, and that ink droplets can be ejected stably from the head 1.

[0169] Example 7 Example 7 is an experimental example conducted using a liquid ejection device corresponding to the first embodiment. However, the head 1 of Example 7 has a lower resolution than the head 1 of Example 1, i.e., the number of nozzles is smaller than that of the head 1 of Example 1.

[0170] The ink flow rate of the piping of the circulation flow path 31 for stably ejecting ink to the head 1 is calculated as the sum of the flow rates required for one nozzle. In other words, the fewer the number of nozzles in the head 1, the smaller the flow rate of the circulation flow path 31 for stably ejecting ink to the head 1. For this reason, the inner diameter of the piping of the circulation flow path 31 was set to 4 mm in Example 1, but was set to 2.5 mm in Example 7. Since the flow rate of the circulation flow path 31 passing through the head was reduced, the flow rate of the circulation flow path 32 was also reduced, and the inner diameter of the piping of the circulation flow path 32 was set to 3 mm in the main flow path 33 and 2 mm in the branch flow paths 34 and 35.

[0171] In Example 7, ink was used in which 7% by weight of TiO2 was added as an insoluble solid content to the acrylic monomer, which was the main component. The particle size of the TiO2 added to the ink was a median particle size of 200 nm, with a particle size distribution of 100 nm to 700 nm. The internal shape of the ink tank 2 was a rectangular parallelepiped.

[0172] A diaphragm pump manufactured by KNF was used for the pump 4, and the flow rate was 12 ml / min. A pulsation reduction damper FPD manufactured by KNF was used for the damper 5. A filter with a filtration size of 5 μm was selected for the filter 6.

[0173] A diaphragm pump manufactured by KNF was used as the pump 14, and the flow rate was 85 ml / min. The damper 15 was the same as the damper 5. The filter 16 was the same as the filter 6.

[0174] In Example 7, the liquid discharge device was operated for 10 consecutive days according to the flow chart shown in Fig. 3 under conditions different from those exemplified in the first embodiment, i.e., conditions different from those in Example 1. That is, in step S1, the flow rate of the pump 14 was set to 85 ml / min as flow rate A5. The branch flow paths 34 and 35 each had the same flow rate (42.5 ml / min). When the inner diameter of the piping of the main flow path 33 was 3 mm and the inner diameter of the piping of the branch flow paths 34 and 35 was 2 mm, the flow velocities of the main flow path 33 and the branch flow paths 34 and 35 were 200 mm / sec, 225 mm / sec, and 225 mm / sec, respectively.

[0175] In step S4, the flow rate of the pump 4 was set to 12 ml / min as a flow rate A10. When the inner diameter of the piping of the circulation flow path 31 was 2.5 mm, the flow velocity of the circulation flow path 31 was 41 mm / sec.

[0176] In step S8, the flow rate A5 remains the same at 85 ml / min, but the flow rates A3 and A4 are the same, but the ratio of the flow rate A4 is increased. The ratio is 1.5 times the flow rate A3, as in Example 1, so that the flow rate A3 is 34 ml / min and the flow rate A4 is 51 ml / min. The flow velocity corresponding to the flow rate A3 at this time is 180 mm / sec, and the flow velocity corresponding to the flow rate A4 is 270 mm / sec.

[0177] In a low-resolution head 1, when the remaining amount of ink inside the ink tank 2 becomes small, the head 1 becomes easily affected by the pulsation of the ink inside the ink tank 2. Therefore, in step S10, the flow rate of the pump 14 is set to 60 ml / min as flow rate A6, and 30 ml / min as flow rates A7 and A8. At this time, the flow velocities of the main flow path 33 and the branch flow paths 34 and 35 are 141 mm / sec, 159 mm / sec, and 159 mm / sec, respectively. In the seventh embodiment, the setting conditions other than the above flow rates are the same as those in the first embodiment.

[0178] The droplet velocity and landing accuracy from head 1 were evaluated, and a comparison was made between the initial evaluation and the evaluation after 10 days. As a result, it was confirmed that there was no change in the evaluation between the initial evaluation and the evaluation after 10 days.

[0179] The droplet speed was determined by observing the ink ejected from head 1 with a high-speed camera. The landing accuracy was determined by combining two methods: measuring the amount of deviation from the target position by measuring the position of the ink that landed on the substrate, and calculating the amount of deviation from the target position using continuous images from the high-speed camera.

[0180] After operating the liquid ejection device for 10 consecutive days, the concentration of the insoluble solids in the ink remaining in the ink tank 2 was measured using a thermogravimetric analyzer. As a result, it was confirmed that the concentration of the insoluble solids was within the measurement accuracy range of the measuring device and had not changed from the initial value.

[0181] In addition, the ink applied to the substrate was dried to form a coating film, and performance evaluations (transmittance and reflectance measurements) were carried out. As a result, it was confirmed that the performance of the film formed on the 10th day was no different from that of the film formed at the initial stage.

[0182] As described above, the experimental results of Example 7 confirmed that it is possible to reduce the settling of insoluble solids contained in the ink inside the ink tank 2, and that ink droplets can be ejected stably from the head 1.

[0183] [Variations] The present disclosure is not limited to the above-described embodiments, and many modifications of the above-described embodiments are possible within the technical concept of the present disclosure. Fig. 10(a) is an explanatory diagram of a modification of the first embodiment, and Fig. 10(b) is an explanatory diagram of a modification of the third embodiment.

[0184] In addition, Figures 10(a) and 10(b) show the outlet 203 and return port 204 of the circulation flow path 32, and in Figures 10(a) and 10(b), the outlet and return port of the circulation flow path 31 are omitted.

[0185] As shown in FIG. 10(a), the outlet 203 is disposed at the bottom of the ink tank 2, and the return port 204 is disposed at the top of the ink tank 2. In the modified example of the first embodiment, the circulation flow path 32 does not have the return port 205. Even in this case, it is possible to reduce the settling of the insoluble solid content contained in the ink inside the ink tank 2 and reduce the uneven concentration of the insoluble solid content. However, the flow of the ink proceeds in an approximately straight line from the return port 204 to the outlet 203. Therefore, it is more preferable to provide the return port 205 as in the first embodiment.

[0186] Also, as shown in FIG. 10(b), the outlet 203 is disposed at the bottom of the ink tank 2B, and the return port 204 is disposed at the top of the ink tank 2B. In the modified example of the second embodiment, the circulation flow path 32 does not have the return port 205. Even in this case, it is possible to reduce the settling of the insoluble solids contained in the ink inside the ink tank 2B and reduce the uneven concentration of the insoluble solids. However, inside the ink tank 2B, the concentration of the insoluble solids on the inclined surface 24 may be slightly higher than the concentration in other parts. Therefore, it is preferable that the return port 205 is disposed on the inclined surface 24 as in the third embodiment.

[0187] The effects described in this embodiment are merely a list of the most preferable effects resulting from the embodiment of the present disclosure, and the effects of the embodiment of the present disclosure are not limited to those described in this embodiment. In addition, at least two of the above-mentioned embodiments and modified examples may be combined.

[0188] The disclosure of the above embodiments includes the following sections.

[0189] (Section 1) A liquid tank; A discharge head that discharges liquid; A liquid circulation device that circulates the liquid, The liquid circulation device includes: a first circulation flow path that flows from the liquid tank to the liquid tank via the ejection head; a second circulation flow path that returns to the liquid tank from the liquid tank without passing through the ejection head, the second circulation flow path includes a first port serving as an outlet for liquid from the liquid tank and a second port serving as a return port for liquid to the liquid tank, The second port is provided above the first port. A liquid ejection device comprising:

[0190] (Section 2) the first port is provided in a lower half region in a height direction of the interior of the liquid tank, The second port is provided in an upper half region in the height direction inside the liquid tank. 2. The liquid ejection device according to item 1,

[0191] (Section 3) the second circulation flow path includes a third port different from the second port, the third port being a return port for the liquid to the liquid tank; 3. The liquid ejection device according to item 1 or 2,

[0192] (Section 4) The third port is provided below the second port. 4. The liquid ejection device according to item 3,

[0193] (Section 5) The third port is provided in a lower half region in a height direction inside the liquid tank. 5. The liquid ejection device according to item 3 or 4,

[0194] (Section 6) The liquid tank has an inner bottom surface, The first port is defined in the inner bottom surface of the liquid tank. 6. The liquid ejection device according to any one of items 1 to 5,

[0195] (Section 7) The liquid tank has an inner bottom surface, The first port and the third port are defined in the inner bottom surface of the liquid tank. 6. The liquid ejection device according to any one of items 3 to 5,

[0196] (Section 8) the first circulation flow path includes a fourth port that serves as an outlet for liquid from the liquid tank, The fourth port is disposed between the first port and the third port. 8. The liquid ejection device according to item 7,

[0197] (Section 9) the liquid tank has an inner bottom surface and an inclined surface that is connected to the inner bottom surface and inclined upward from the inner bottom surface, the first port is defined in the inner bottom surface of the liquid tank; The third port is defined in the inclined surface of the liquid tank. 6. The liquid ejection device according to any one of items 3 to 5,

[0198] (Section 10) the first circulation flow path includes a fourth port that serves as an outlet for liquid from the liquid tank, The fourth port is defined in the inner bottom surface. 10. The liquid ejection device according to item 9, characterized in that

[0199] (Section 11) The second circulation flow path has two or more of the third ports. 11. The liquid ejection device according to any one of items 7 to 10,

[0200] (Section 12) The liquid tank has an inner surface extending in a height direction, The second port is defined in the inner surface of the liquid tank. There are 12. The liquid ejection device according to any one of items 1 to 11,

[0201] (Section 13) The second circulation flow path is a first pipe extending into the liquid tank and having the second port formed therein; 6. The liquid ejection device according to any one of items 1 to 5,

[0202] (Section 14) the second circulation flow path has a second pipe extending into the liquid tank and having the third port formed therein; 6. The liquid ejection device according to any one of items 3 to 5,

[0203] (Section 15) The second circulation flow path has two or more of the second pipes. 15. A liquid ejection device according to item 14, characterized in that

[0204] (Section 16) The second circulation flow path includes two or more of the first ports. 16. The liquid ejection device according to any one of items 1 to 15,

[0205] (Section 17) the second circulation flow path includes a third port different from the second port, the third port being a return port for liquid to the liquid tank; The second port and the third port are arranged in positions and orientations that are point-symmetrical with respect to a predetermined point. 3. The liquid ejection device according to item 1 or 2,

[0206] (Section 18) The liquid circulation device includes: A first pump disposed in the first circulation flow path; A second pump disposed in the second circulation flow path, When the first pump and the second pump are operating, a flow rate of the liquid returned from the second circulation flow path to the liquid tank is faster than a flow rate of the liquid returned from the first circulation flow path to the liquid tank. Item 18. The liquid ejection device according to any one of items 1 to 17.

[0207] (Section 19) A control device is further provided, the liquid circulation device is disposed at a branching portion of the second circulation flow path where the main flow path branches into the second port and the third port, and has a flow rate adjustment valve controllable by the control device; the control device controls the flow rate regulating valve to regulate a flow rate of the liquid returned to the liquid tank from the second port and a flow rate of the liquid returned to the liquid tank from the third port in accordance with a remaining amount of liquid in the liquid tank. Item 18. The liquid ejection device according to any one of items 3 to 5, 7 to 11, 14, 15, and 17,

[0208] (Section 20) The control device includes: when the remaining amount of liquid inside the liquid tank is greater than a first amount, a flow rate of the liquid returned from the second port to the liquid tank is set to a first flow rate, and a flow rate of the liquid returned from the third port to the liquid tank is set to a second flow rate; when the remaining amount of liquid inside the liquid tank is equal to or less than the first amount, a flow rate of liquid returned from the second port to the liquid tank is set to a third flow rate which is smaller than the first flow rate, and a flow rate of liquid returned from the third port to the liquid tank is set to a fourth flow rate which is larger than the second flow rate. 20. A liquid ejection device according to item 19, characterized in that

[0209] (Section 21) the liquid circulation device has a second pump that is disposed in the second circulation flow path and is controllable by the control device; The control device includes: When the remaining amount of liquid in the liquid tank is greater than a second amount that is smaller than the first amount, the flow rate of the second pump is set to a fifth flow rate; When the remaining amount of liquid in the liquid tank is equal to or less than the second amount, the flow rate of the second pump is set to a sixth flow rate which is lower than the fifth flow rate. 21. A liquid ejection device according to item 20, characterized in that

[0210] (Section 22) The control device includes: refilling the liquid tank with liquid when the remaining amount of liquid inside the liquid tank is equal to or less than a third amount which is smaller than the second amount; 22. A liquid ejection device according to item 21, characterized in that

[0211] (Section 23) The liquid is an ink containing insoluble solids. 23. The liquid ejection device according to any one of items 1 to 22,

[0212] (Section 24) Using the liquid ejection device according to any one of items 1 to 23, the liquid is ejected from the liquid tank. A liquid ejection method comprising:

[0213] (Section 25) The liquid is a liquid containing a functional material for forming a functional thin film or a functional element. 25. A liquid ejection method according to item 24,

[0214] (Section 26) Item 26. A method for manufacturing an article, comprising discharging a liquid containing a raw material for a functional thin film or a functional element onto a substrate by the liquid discharge method according to item 25. [Explanation of symbols]

[0215] 1... inkjet head (ejection head), 2... ink tank (liquid tank), 30... liquid circulation device, 31... circulation flow path (first circulation flow path), 32... circulation flow path (second circulation flow path), 203... outlet (first port), 204... return port (second port), 205... return port (third port)

Claims

1. A liquid tank; A discharge head that discharges liquid; A liquid circulation device that circulates the liquid, The liquid circulation device includes: a first circulation flow path that flows from the liquid tank to the liquid tank via the ejection head; a second circulation flow path that returns to the liquid tank from the liquid tank without passing through the ejection head, the second circulation flow path includes a first port serving as an outlet for liquid from the liquid tank and a second port serving as a return port for liquid to the liquid tank, The second port is provided above the first port. A liquid ejection device comprising:

2. the first port is provided in a lower half region in a height direction of the interior of the liquid tank, The second port is provided in an upper half region in the height direction inside the liquid tank. The liquid ejection device according to claim 1 .

3. the second circulation flow path includes a third port different from the second port, the third port being a return port for the liquid to the liquid tank; The liquid ejection device according to claim 1 .

4. The third port is provided below the second port.

4. The liquid ejection device according to claim 3.

5. The third port is provided in a lower half region in a height direction inside the liquid tank.

4. The liquid ejection device according to claim 3.

6. The liquid tank has an inner bottom surface, The first port is defined in the inner bottom surface of the liquid tank. The liquid ejection device according to claim 1 .

7. The liquid tank has an inner bottom surface, The first port and the third port are defined in the inner bottom surface of the liquid tank.

4. The liquid ejection device according to claim 3.

8. the first circulation flow path includes a fourth port that serves as an outlet for liquid from the liquid tank, The fourth port is disposed between the first port and the third port.

8. The liquid ejection device according to claim 7.

9. the liquid tank has an inner bottom surface and an inclined surface that is connected to the inner bottom surface and inclined upward from the inner bottom surface, the first port is defined in the inner bottom surface of the liquid tank; The third port is defined in the inclined surface of the liquid tank.

4. The liquid ejection device according to claim 3.

10. the first circulation flow path includes a fourth port that serves as an outlet for liquid from the liquid tank, The fourth port is defined in the inner bottom surface. The liquid ejection device according to claim 9 .

11. The second circulation flow path has two or more of the third ports.

8. The liquid ejection device according to claim 7.

12. The liquid tank has an inner surface extending in a height direction, The second port is defined in the inner surface of the liquid tank. There are The liquid ejection device according to claim 1 .

13. The second circulation flow path is a first pipe extending into the liquid tank and having the second port formed therein; The liquid ejection device according to claim 1 .

14. The second circulation flow path has a second pipe extending into the liquid tank and having the third port formed therein.

4. The liquid ejection device according to claim 3.

15. The second circulation flow path has two or more of the second pipes. The liquid ejection device according to claim 14 .

16. The second circulation flow path includes two or more of the first ports. The liquid ejection device according to claim 1 .

17. the second circulation flow path includes a third port different from the second port, the third port being a return port for liquid to the liquid tank; The second port and the third port are arranged in positions and orientations that are point-symmetrical with respect to a predetermined point. The liquid ejection device according to claim 1 .

18. The liquid circulation device includes: A first pump disposed in the first circulation flow path; a second pump disposed in the second circulation flow path, When the first pump and the second pump are operating, a flow rate of the liquid returned from the second circulation flow path to the liquid tank is faster than a flow rate of the liquid returned from the first circulation flow path to the liquid tank. The liquid ejection device according to claim 1 .

19. A control device is further provided, the liquid circulation device is disposed at a branching portion of the second circulation flow path where the main flow path branches into the second port and the third port, and has a flow rate adjustment valve controllable by the control device; the control device controls the flow rate regulating valve to regulate a flow rate of the liquid returned to the liquid tank from the second port and a flow rate of the liquid returned to the liquid tank from the third port in accordance with a remaining amount of liquid in the liquid tank.

4. The liquid ejection device according to claim 3.

20. The control device includes: when the remaining amount of liquid inside the liquid tank is greater than a first amount, a flow rate of the liquid returned from the second port to the liquid tank is set to a first flow rate, and a flow rate of the liquid returned from the third port to the liquid tank is set to a second flow rate; when the remaining amount of liquid inside the liquid tank is equal to or less than the first amount, a flow rate of the liquid returned from the second port to the liquid tank is set to a third flow rate which is smaller than the first flow rate, and a flow rate of the liquid returned from the third port to the liquid tank is set to a fourth flow rate which is larger than the second flow rate.

20. The liquid ejection device according to claim 19.

21. the liquid circulation device has a second pump that is disposed in the second circulation flow path and is controllable by the control device; The control device includes: When the remaining amount of liquid in the liquid tank is greater than a second amount that is smaller than the first amount, the flow rate of the second pump is set to a fifth flow rate; When the remaining amount of liquid in the liquid tank is equal to or less than the second amount, the flow rate of the second pump is set to a sixth flow rate which is smaller than the fifth flow rate.

21. The liquid ejection device according to claim 20.

22. The control device includes: refilling the liquid tank with liquid when the remaining amount of liquid inside the liquid tank is equal to or less than a third amount which is smaller than the second amount; 22. The liquid ejection device according to claim 21.

23. The liquid is an ink containing insoluble solids. The liquid ejection device according to claim 1 .

24. The liquid is discharged from the liquid tank by using the liquid discharge device according to any one of claims 1 to 23. A liquid ejection method comprising:

25. The liquid is a liquid containing a functional material for forming a functional thin film or a functional element.

25. The liquid ejection method according to claim 24.

26. A method for manufacturing an article, comprising discharging a liquid containing a raw material for a functional thin film or a functional element onto a substrate by the liquid discharge method according to claim 25.

Images