Droplet discharge device and method for manufacturing printed material

Abstract

The invention provides a liquid droplet discharge device and a method for manufacturing a printed matter, wherein the liquid droplet discharge device can maintain a good discharge state regardless of ink used. The liquid droplet ejecting apparatus includes: a liquid droplet ejecting head that ejects a liquid; a relative movement mechanism that moves the substrate and the droplet ejection head relative to each other; and a control device that prints an image on the base material by moving the base material and the droplet ejection head relative to each other and ejecting the liquid from the droplet ejection head, the space between the droplet ejection head and the base material being vacuum, the droplet ejection head including a circulation flow path that circulates the liquid, and the control device circulating the liquid at least during printing.

Description

Technical Field

[0001] The present invention relates to a liquid droplet ejection device and a method for manufacturing a printed matter, and in particular to a technology for stabilizing an ejection state. Background Art

[0002] In order to expand the application range of inkjet technology, there is a problem of making droplets land on the substrate without being strongly affected by air resistance even when the distance between the inkjet head and the substrate is wide.

[0003] In response to this problem, Patent Document 1 discloses a printing system that performs printing by inkjet method, which is a printing system having the following components: an inkjet head having a nozzle that discharges droplets of curable ink that is cured according to energy received from the outside toward a medium; an ultraviolet irradiation unit, which is a curing energy generating unit that generates energy to cure the ink landed on the medium; a decompression chamber that accommodates at least the inkjet head and the medium; a pump, which is a decompression mechanism that reduces the air pressure in the decompression chamber to a pressure lower than the atmospheric pressure; and a water cooling device, which is a cooling mechanism that cools the ultraviolet irradiation unit by using a refrigerant having a higher specific heat than the air in the decompressed decompression chamber.

[0004] Previous technical literature

[0005] Patent Literature

[0006] Patent Document 1: Patent No. 5738513

[0007] Patent Document 2: Japanese Patent Application Publication No. 2017-65159 Summary of the invention

[0008] Technical issues to be solved by the invention

[0009] However, the printing system described in Patent Document 1 has a problem that the usable ink is limited. For example, there is a problem that the solvent component in the ink evaporates depending on the type of ink, and the ejection state deteriorates.

[0010] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid droplet discharge device and a method for manufacturing a printed matter that can maintain a good discharge state even in a reduced pressure environment.

[0011] Means for solving technical problems

[0012] In order to achieve the above-mentioned object, the first embodiment of the present invention is a liquid droplet ejection device comprising: a liquid droplet ejection head for ejecting liquid; a relative movement mechanism for relatively moving the substrate and the liquid droplet ejection head; and a control device for relatively moving the substrate and the liquid droplet ejection head so that the liquid droplet ejection head ejects liquid, thereby printing an image on the substrate, wherein there is a vacuum between the liquid droplet ejection head and the substrate, the liquid droplet ejection head has a circulation flow path inside the liquid droplet ejection head, and the control device is a liquid droplet ejection device for circulating the liquid in the circulation flow path at least during printing. According to this embodiment, a good ejection state can be maintained.

[0013] The droplet ejection device involved in the second embodiment of the present invention is, in the droplet ejection device involved in the first embodiment, preferably, the droplet ejection head has an ejection element including a nozzle, a pressure chamber and an ejection energy generating element, and the circulation flow path includes a supply flow path for supplying liquid to the ejection element and a recovery flow path for recovering liquid from the ejection element.

[0014] The droplet ejection device involved in the third embodiment of the present invention, in the droplet ejection device involved in the first embodiment or the second embodiment, preferably has a first liquid tank and a second liquid tank for storing liquid, and the control device supplies liquid from the first liquid tank to the droplet ejection head through the water level difference, and recovers liquid from the droplet ejection head to the second liquid tank through the water level difference.

[0015] The droplet ejection device involved in the fourth embodiment of the present invention, in the droplet ejection device involved in the third embodiment, preferably comprises: a chamber that accommodates the droplet ejection head, the relative movement mechanism, the first liquid tank, and the second liquid tank; and an exhaust mechanism that makes the interior of the chamber a vacuum, and the reference of the water level difference is the pressure inside the chamber.

[0016] The liquid droplet discharge device according to a fifth aspect of the present invention is the liquid droplet discharge device according to the fourth aspect, and preferably includes a liquid delivery mechanism that supplies liquid from the second liquid tank to the first liquid tank, wherein the liquid delivery mechanism is disposed outside the chamber.

[0017] The liquid droplet ejection device according to a sixth aspect of the present invention is the liquid droplet ejection device according to any one of the first to fifth aspects, wherein the control device preferably causes the circulation amount of the liquid during printing to be greater than the circulation amount of the liquid during non-printing.

[0018] A liquid droplet ejection device according to a seventh aspect of the present invention is the liquid droplet ejection device according to any one of the first to sixth aspects, wherein the control device preferably stops the circulation of the liquid during non-printing.

[0019] A droplet ejection device according to an eighth aspect of the present invention is the droplet ejection device according to any one of the first to seventh aspects, wherein the control device preferably provides vibration to the non-ejection nozzles during printing to such an extent that droplets are not ejected.

[0020] The droplet ejection device involved in the 9th mode of the present invention is a droplet ejection device involved in any one of the 1st to 8th modes, wherein the liquid preferably contains a solvent, and is provided with a concentration measuring device for measuring the concentration of the circulating liquid, and a control device adds a solvent to the liquid to replenish the amount of evaporated solvent.

[0021] The liquid droplet discharge device according to a tenth aspect of the present invention is the liquid droplet discharge device according to the fourth aspect, wherein the liquid preferably includes a solvent, and the solvent is disposed in an open state inside the chamber.

[0022] The liquid droplet discharge device according to the eleventh aspect of the present invention is the liquid droplet discharge device according to the fourth aspect or the tenth aspect, and preferably includes a circuit element for driving the liquid droplet discharge head, and the circuit element is arranged outside the cavity.

[0023] The liquid droplet discharge device according to a twelfth aspect of the present invention is the liquid droplet discharge device according to any one of the first to eleventh aspects, wherein the vacuum is preferably 0.5 to 0.01 atmospheric pressure.

[0024] The liquid droplet ejection device according to a thirteenth aspect of the present invention is the liquid droplet ejection device according to any one of the first to twelfth aspects, wherein the liquid is preferably an aqueous ink containing water as a solvent.

[0025] In order to achieve the above-mentioned object, the method for manufacturing a printed matter according to the 14th aspect of the present invention is a method for manufacturing a printed matter comprising the following steps: creating a vacuum between a liquid droplet ejection head and a substrate, moving the substrate and the liquid droplet ejection head relative to each other and ejecting liquid from the liquid droplet ejection head, thereby printing an image on the substrate; and circulating the liquid in a circulation flow path of the liquid droplet ejection head at least during printing. According to this aspect, a good ejection state can be maintained.

[0026] Effects of the Invention

[0027] According to the present invention, a good discharge state can be maintained even in a reduced pressure environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a side view schematically showing the printing device.

[0029] Figure 2 It is a plan view schematically showing a printing device.

[0030] Figure 3 This is a three-dimensional diagram of the droplet ejection head.

[0031] Figure 4 It is a plan perspective view showing a structural example of a silicon mold.

[0032] Figure 5 yes Figure 4 Sectional view 5-5.

[0033] Figure 6 The modification example involves Figure 4 Sectional view 5-5.

[0034] Figure 7 This is a schematic diagram showing an example of the configuration of the vacuum environment and ink circulation of a printing device.

[0035] Figure 8 It is a schematic diagram showing a configuration example of a printing device according to the second embodiment.

[0036] Fig. 9 It is a schematic diagram showing a configuration example of a printing device according to a third embodiment.

[0037] Fig.10 It is a schematic diagram showing a configuration example of a printing device according to a fourth embodiment.

[0038] Fig.11 It is a schematic diagram showing a configuration example of a printing device according to a fifth embodiment.

[0039] Fig.12 It is a schematic diagram showing a configuration example of a printing device according to a sixth embodiment.

[0040] Fig.13 This is a block diagram showing the electrical configuration of the printing device. DETAILED DESCRIPTION

[0041] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the description of each embodiment, the same drawings and descriptions as those of other embodiments are appropriately omitted.

[0042] <Outline of Printing Device: First Embodiment>

[0043] Figure 1 is a schematic side view showing the printing device 10, Figure 2 1 is a plan view schematically showing the printing device 10. The printing device 10 is a liquid droplet ejecting device that prints an image on a substrate 1.

[0044] The printing device 10 includes a conveying device 12 and a droplet ejection head 14. The conveying device 12 is a relative movement mechanism that conveys the substrate 1 in the horizontal direction, i.e., the Y direction, so as to relatively move the substrate 1 and the droplet ejection head 14. The droplet ejection head 14 is an inkjet head that ejects droplets 1 of aqueous ink (an example of "liquid") containing water as a solvent in an inkjet manner.

[0045] The printing device 10 forms an image by ejecting ink droplets I from a droplet ejection head 14 on a recording surface of a substrate 1 transported in the Y direction by a transport device 12. The substrate 1 is, for example, a printed substrate, and the ink is, for example, conductive ink containing a conductive substance. The printing device 10 may also include a head carriage that moves the droplet ejection head 14 in the X direction.

[0046] In the printing device 10, at least the space S between the droplet ejection head 14 and the substrate 1 becomes a low vacuum with a pressure (negative pressure) relatively lower than the atmospheric pressure. Atmospheric pressure refers to the pressure of the atmosphere of the printing device 10, which can be 1 atmosphere. In addition, the so-called negative pressure means 0.5 atmosphere to 0.01 atmosphere at room temperature, but is not limited to this. The negative pressure is a value measured by a vacuum gauge (e.g., EA106B manufactured by ESCO).

[0047] By making the space S a low vacuum, the air resistance to the droplets I can be reduced. Thus, the printing device 10 can maintain a good discharge state and accurately land the droplets I on the substrate 1 even when the distance between the droplet discharge head 14 and the substrate 1 is relatively wide, such as 5 mm to 30 mm. In general printing devices, the distance between the droplet discharge head and the substrate for accurate landing is about 0.5 mm to 2 mm.

[0048] [Structure of the droplet ejection head]

[0049] If the space S is made into a low vacuum, there is a concern that the ejection may be deteriorated due to the evaporation of the ink solvent. In this embodiment, even if the evaporation of the ink solvent occurs, the droplet ejection head is used to circulate the ink around the nozzle to stabilize the ejection state.

[0050] Figure 3 It is a perspective view of the liquid drop ejection head 14. The liquid drop ejection head 14 includes an L-shaped bracket 16, a silicon mold 24, an ink supply path 18, an ink recovery path 20, and a filter case 22.

[0051] The L-shaped bracket 16 is a member for fixing the droplet ejection head 14 to a head support member (not shown).

[0052] The ink supply path 18 and the upper ink tank 32 (refer to Figure 7 ) is connected. The ink supply path 18 supplies ink from the upper ink tank 32 to the droplet ejection head 14. The ink recovery path 20 is connected to the lower ink tank 34 (refer to Figure 7 The ink recovery path 20 recovers the ink supplied to the droplet ejection head 14 into the lower ink tank 34 .

[0053] The filter case 22 accommodates a filter for removing foreign matter and the like contained in the ink inside the liquid drop ejection head 14 .

[0054] The silicon mold 24 includes a nozzle surface 200 (see Figure 5 ). Figure 4 is a plan perspective view showing a structural example of the silicon mold 24, Figure 5 yes Figure 4 Sectional view 5-5.

[0055] The silicon mold 24 includes a nozzle plate 230 having a nozzle 202 as an outlet for ejecting ink droplets, and a flow path plate 232 having a flow path for ink. The nozzle plate 230 and the flow path plate 232 are stacked and bonded. The flow path plate 232 is a structure in which one or more substrates are stacked. The nozzle plate 230 and the flow path plate 232 can be made of silicon and processed into a desired shape through a semiconductor manufacturing step.

[0056] The silicon mold 24 has a plurality of nozzles 202 on the bottom surface, i.e., the nozzle surface 200. In addition, a plurality of ink chamber assemblies 206, which are composed of pressure chambers 204 and the like provided corresponding to the nozzles 202, are arranged two-dimensionally in a certain arrangement pattern. Thus, a high density of the substantial nozzle intervals projected in an arrangement in the X direction is achieved.

[0057] The pressure chamber 204 is connected to the supply branch 210 through the supply throttling section 208, and each supply branch 210 is connected to the common flow path 212. In addition, the diffuser 214 connected to each pressure chamber 204 is connected to the circulation common flow path 220 through the ink circulation path 216 and the recovery branch 218. The silicon mold 24 is provided with an ink supply port 18A and an ink discharge port 20A. The ink supply path 18 (see Figure 3 The ink discharge port 20A is connected to an ink recovery path 20 (refer to Figure 3 ).

[0058] In this way, the ink supply port 18A and the ink discharge port 20A of the silicon mold 24 are connected through the common flow path 212, the supply branch 210, the supply throttling section 208, the pressure chamber 204, the diffuser 214, the ink circulation path 216, the recovery branch 218 and the circulation common flow path 220.

[0059] Thus, the ink supplied from the ink supply path 18 to the ink supply port 18A flows through the common flow path 212, the supply branch 210, the supply throttling portion 208, the pressure chamber 204 and the diffuser 214, and a portion of the ink is ejected from each nozzle 202, and the remaining ink is discharged from the ink discharge port 20A to the ink recovery path 20 via the ink circulation path 216, the recovery branch 218 and the circulation common flow path 220.

[0060] Furthermore, a piezoelectric actuator 228 having individual electrodes (not shown) is connected to a vibration plate 226 that serves as a common electrode and constitutes the top surface of the pressure chamber 204. When a predetermined voltage is applied to the individual electrodes, the piezoelectric actuator 228 is deformed in a direction that contracts the pressure chamber 204. Thus, ink is ejected from the nozzle 202. Then, the piezoelectric actuator 228 is deformed in a direction that expands the pressure chamber 204. Thus, new ink is supplied from the common flow path 212 to the pressure chamber 204 through the supply branch 210 and the supply throttle 208.

[0061] Here, the piezoelectric actuator 228 is used as the ejection energy generating element for ejecting ink from the nozzle 202 , but a thermal method may be applied in which a heater is provided in the pressure chamber 204 and ink is ejected using pressure due to film boiling caused by heating of the heater.

[0062] Thus, the droplet ejection head 14 includes an ejection element 222 including a nozzle 202, a pressure chamber 204, and a piezoelectric actuator 228. The droplet ejection head 14 includes a supply branch 210 (an example of a "supply flow path") for supplying ink to the ejection element 222 and a recovery branch 218 (an example of a "recovery flow path") for recovering ink from the ejection element 222. The supply branch 210 and the recovery branch 218 constitute a "circulation flow path".

[0063] It is preferable that the ink circulation path 216 is provided around the nozzle 202. Here, the ink circulation path 216 is a region connected to the diffuser 214, and is provided in a region connected to the nozzle plate 230 of the flow path plate 232. Thus, the ink circulates near the nozzle 202, thereby preventing the ink inside the nozzle 202 from becoming thicker and enabling stable discharge.

[0064] Figure 6 The modification example involves Figure 4 Sectional view 5-5. Figure 6 In the modified example shown, the ink circulation path 216 is an area connected to the diffuser 214 and is provided in an area connected to the vibration plate 226. Even in the case of such a configuration, the effect is lower than Figure 5 The ink chamber assembly 206 is shown, but the ink circulates near the nozzle 202 and can be discharged stably.

[0065] [Control of the droplet ejection head]

[0066] By using the droplet ejection head 14 with ink circulation, although the solvent of the ink from the nozzle 202 evaporates, new ink is continuously supplied to the ink chamber assembly 206. Therefore, even in a vacuum environment, the ejection state can be maintained. In particular, water has a high vapor pressure and is easy to evaporate, so it is difficult to use water-based ink in a printing device using a vacuum, but water-based ink can be used by ink circulation. In addition, as described later, for insufficient heat dissipation of the droplet ejection head 14 due to reduced thermal conductivity in a vacuum, the heat generated by the droplet ejection head 14 can be discharged to the outside through the ink by ink circulation.

[0067] It is desirable to change the ink circulation amount both when the printing device 10 is printing and when it is not printing. The so-called printing time includes at least the state where the droplet ejection head 14 is opposite to the substrate 1. The printing device 10 prints by applying ink through the droplet ejection head 14 while conveying the substrate 1 through the conveying device 12. In this embodiment, the printing time is from the time when the substrate 1 reaches the position opposite to the droplet ejection head 14 to the time when it completely passes the position opposite to the droplet ejection head 14, and the rest is the non-printing time.

[0068] Since it is desired that fresh ink always flows into the ink chamber assembly 206 during printing, the ink circulation amount is increased as much as possible. The ink circulation amount during printing is preferably 2 times or more, more preferably 3 times or more, and even more preferably 5 times or more, compared to the general ink circulation of 1000 pL / sec to 10000 pL / sec per nozzle for the same ink.

[0069] On the other hand, since it is desirable to suppress ink evaporation as much as possible when not printing, it is desirable to reduce the ink circulation amount when the nozzle 202 is printing at a non-solidified level by ink evaporation. For example, as long as the air pressure is 0.1, the nozzle 202 will not be clogged for several minutes even if it is water-based ink. Therefore, in this case, stopping the ink circulation for only a short time can also be selected as a method for suppressing solvent evaporation. That is, when not printing, the circulation stop → several minutes later → circulation → several minutes later → circulation stop... can also be repeated. In this way, stopping the ink circulation at an unnecessary time or reducing the ink circulation amount can reduce unnecessary ink evaporation.

[0070] Furthermore, in order to suppress the adverse effects of ejection caused by evaporation of the ink solvent, it is preferred that the non-ejection nozzles that do not eject ink during printing are subjected to vibrations (so-called meniscus vibrations) to such an extent that no ink is ejected. By combining this with ink circulation, fresh ink can be supplied to the nozzles 202, thereby further suppressing the increase in ink viscosity of the nozzles 202 and achieving more stable ejection.

[0071] [Composition of vacuum environment and ink circulation]

[0072] Figure 7 Schematic diagram showing a configuration example of a vacuum environment and ink circulation of the printing device 10. The printing device 10 includes a chamber 30, an exhaust mechanism 31, an upper ink tank 32, a lower ink tank 34, a return flow path 36, and an ink pump 38.

[0073] The chamber 30 accommodates the conveying device 12 ( Figure 7 The chamber 30 includes a liquid drop ejection head 14, an upper ink tank 32, a lower ink tank 34, a return flow path 36, and an ink pump 38. The chamber 30 is provided with an exhaust port (not shown). The chamber 30 is depressurized inside by an exhaust mechanism 31 such as a vacuum pump through the exhaust port. Here, the inside of the chamber 30 is maintained in a low vacuum atmosphere of 0.1 atmosphere. That is, the space S between the liquid drop ejection head 14 and the substrate 1 is a low vacuum of 0.1 atmosphere.

[0074] The upper ink tank 32 (an example of a "first liquid tank") is a container for storing ink supplied to the droplet ejection head 14. The upper ink tank 32 is connected to the droplet ejection head 14 through the ink supply path 18. The interior of the upper ink tank 32 is open to the atmosphere inside the chamber 30. The upper ink tank 32 is moved in the vertical direction (Z direction) by a first up-and-down mechanism 72 (see FIG. Fig.13 ) supports and are arranged at the height of the desired water level difference.

[0075] The lower ink tank 34 (an example of a "second liquid tank") is a container for storing ink recovered from the droplet ejection head 14. The lower ink tank 34 is connected to the droplet ejection head 14 through the ink recovery path 20. The interior of the lower ink tank 34 is open to the atmosphere inside the chamber 30. The lower ink tank 34 is moved in the vertical direction by a second vertical movement mechanism 74 (see Fig.13 ) supports and are arranged at the height of the desired water level difference.

[0076] The return flow path 36 connects the upper ink tank 32 and the lower ink tank 34 . An ink pump 38 of a liquid feeding mechanism is provided in the return flow path 36 , and feeds ink from the lower ink tank 34 to the upper ink tank 32 .

[0077] In this way, the printing device 10 is provided with the droplet ejection head 14 between the upper ink tank 32 and the lower ink tank 34. The upper ink tank 32 and the lower ink tank 34 are mechanisms for causing ink to flow by using the water head difference using gravity with respect to the pressure inside the chamber 30 as a reference. In this way, a simple ink circulation structure is formed, and there is no need to prepare a mechanism for following pressure changes in the low vacuum region, making control easy.

[0078] Of course, as described in Patent Document 2, the ink may also be circulated by controlling the pressure of the pump based on the atmospheric pressure. Figure 7 The method shown is simple and easy to control.

[0079] The ink circulation amount can be controlled by the first vertical movement mechanism 72 and the second vertical movement mechanism 74. To minimize the influence on ejection, it is desirable to perform the vertical movement of the upper ink tank 32 and the lower ink tank 34 when ink is not ejected from the droplet ejection head 14.

[0080] <Ink Pump Arrangement: Second Embodiment>

[0081] It is preferable that the ink pump 38 is not disposed in the low vacuum region. There are pumps that can cope with the low vacuum region, but the cost becomes high and there is also a concern that the grease in the ink pump 38 may evaporate. Therefore, the ink pump 38 is disposed outside the low vacuum region.

[0082] Figure 8 1 is a schematic diagram showing a configuration example of a printing device 10A according to the second embodiment. Figure 8 In the example shown, the ink pump 38 is arranged outside the chamber 30 .

[0083] Thus, by installing the ink pump 38 in the atmospheric pressure region, the ink pump 38 can be operated in an environment where the operation is easy. Fig.13 ) detection result, confirming that the ink stored in the upper ink tank 32 is reduced, if the second liquid level sensor 78 (reference Fig.13 ) detection result shows that the ink stored in the lower ink tank 34 is sufficient, the ink pump 38 can be operated to suck ink from the lower ink tank 34 to the upper ink tank 32.

[0084] Furthermore, the hose of the return flow path 36 disposed in the atmospheric pressure region needs to be a hard hose or pipe so as not to be crushed by the external pressure when the ink in the negative pressure state flows.

[0085] Similarly, the hose of the return flow path 36 disposed in the low vacuum region also generates pressure changes, and therefore, a hard hose is preferably used. On the other hand, in order to handle the hose accompanying the operation of the droplet ejection head 14, a cable bracket (registered trademark) not shown is used for the hose of the return flow path 36. Therefore, the hose of the return flow path 36 is preferably hard enough to withstand the movement of the cable bracket (registered trademark). For example, NOVATEC (registered trademark) LD-LA320 manufactured by Japan Polyethylene Corporation is preferably used.

[0086] <Replenishment of ink: third embodiment>

[0087] Furthermore, it is preferable to perform ink replenishment from outside the low vacuum area. Fig. 9 It is a schematic diagram showing a configuration example of a printing device 10B according to the third embodiment.

[0088] The printing apparatus 10B includes a first ink pump 38A, a first valve 40 , a replenishing ink tank 42 , a replenishing flow path 44 , a second ink pump 46 , and a second valve 48 .

[0089] The first ink pump 38A is disposed outside the chamber 30. The first valve 40 is provided in the return flow path 36 outside the chamber 30. The first valve 40 is controlled by the control device 70 (see Fig.13 ) is controlled to switch the passage and cutoff of ink in the return flow path 36.

[0090] The replenishing ink tank 42 is provided outside the chamber 30. The replenishing ink tank 42 is a container for storing ink for replenishing the lower ink tank 34. The replenishing ink tank 42 communicates with the return flow path 36 via the replenishing flow path 44. The inside of the replenishing ink tank 42 is open to the atmosphere of atmospheric pressure outside the chamber 30.

[0091] The second ink pump 46 and the second valve 48 are provided in the replenishment flow path 44. The second ink pump 46 delivers ink from the replenishment ink tank 42 to the upper ink tank 32. The second valve 48 is controlled by the control device 70 (refer to Fig.13 ) is controlled to switch the passage and cutoff of ink in the replenishment flow path 44.

[0092] In the printing device 10B configured as above, when the ink in the upper ink tank 32 and the lower ink tank 34 is insufficient, printing is performed until the division point is reached, and then the interior of the chamber 30 is opened to the atmosphere. Then, the second valve 48 is opened, and the first ink pump 38A and the second ink pump 46 are driven, thereby enabling the ink stored in the replenishing ink tank 42 to be sent to the upper ink tank 32. When sending ink to the lower ink tank 34, the first valve 40 and the second valve 48 are opened, and the second ink pump 46 is driven, thereby enabling the ink stored in the replenishing ink tank 42 to be sent to the lower ink tank 34.

[0093] Although not preferred, when the ink stored in the replenishing ink tank 42 is to be replenished in the upper ink tank 32 during printing, the first ink pump 38A and the second ink pump 46 may be slowly driven after the second valve 48 is opened.

[0094] Furthermore, the solvent evaporates faster in the low vacuum region, so the solvent in the ink gradually decreases even though the ink is circulating. Therefore, the ink is extracted from the ink extraction position (not shown) located in the atmospheric pressure region and the concentration sensor 80 (reference Fig.13 , an example of a "concentration measuring device") to evaluate the composition of the ink, thereby being able to determine whether the ink is in an appropriate state. Fig.13 ) The insufficient solvent can be added to the ink to adjust the ink to an appropriate concentration.

[0095] Furthermore, when it is confirmed that the solvent in the ink has been significantly reduced, the thickened ink may be drawn out from an ink hose (not shown) for treatment, and new ink may be supplied from the replenishing ink tank 42 .

[0096] <Preventing Solvent Evaporation: Fourth Embodiment>

[0097] In order to prevent the ink solvent from evaporating from the liquid surface of the upper ink tank 32 and the lower ink tank 34, a thin film or beads may be floated on the liquid surface to reduce the exposed surface area.

[0098] Furthermore, the upper ink tank 32 and the lower ink tank 34 may be blocked by a membrane that is soft and can follow the change of external pressure like a damping membrane, rather than being open to the atmosphere inside the chamber 30. The upper ink tank 32 and the lower ink tank 34 may also be made of an entirely deformable ink like a bag.

[0099] Furthermore, in order to prevent the evaporation of the solvent from the nozzle 202 of the droplet ejection head 14 , only the solvent may be added in advance inside the chamber 30 . Fig.10 1 is a schematic diagram showing a configuration example of a printing device 10C according to the fourth embodiment. The printing device 10C includes a container 50 inside the chamber 30. The container 50 is arranged at a position below the droplet ejection head 14 in the vertical direction. The container 50 contains an ink solvent (water in this case) inside, and the solvent is in an open state relative to the space inside the chamber 30. Thus, the solvent inside the container 50 evaporates naturally. As a result, the vacuum degree inside the chamber 30 decreases to some extent, but the partial pressure of the solvent can be increased, thereby preventing the ink from the nozzle 202 from evaporating.

[0100] <Heat generation of droplet ejection head: Fifth embodiment>

[0101] If the droplet ejection head is processed in a low vacuum area, there is a concern that the droplet ejection head itself may heat up. In the case of an inkjet head using a piezoelectric actuator, the ASIC (Application Specific Integrated Circuit) that outputs the voltage used to control the piezoelectric actuator itself and the driving voltage of the piezoelectric actuator will heat up. Of course, the substrate that sends power supply and signals to the inkjet head will also heat up.

[0102] It is naturally preferred that the substrate be disposed outside the low vacuum region. Also, the ASIC is preferably not mounted on the inkjet head itself but disposed at a position away from the inkjet head, outside the low vacuum region.

[0103] Fig.11 Schematic diagram showing a configuration example of a printing device 10D according to the fifth embodiment. The printing device 10D includes a control substrate 52 , an ASIC 54 , and a flexible cable 56 .

[0104] The control substrate 52 sends a control signal for controlling the droplet ejection head 14 to the ASIC 54. The ASIC 54 (an example of a "circuit element") distributes the signal received from the control substrate 52 to the plurality of piezoelectric actuators 228, and outputs a driving voltage. The flexible cable 56 is a wiring for transmitting signals and driving voltages between the control substrate 52, the ASIC 54, and the droplet ejection head 14.

[0105] The control substrate 52 is disposed at the end of the flexible cable 56, and the ASIC 54 is disposed at a position between the two ends of the flexible cable 56. The control substrate 52 and the ASIC 54 are disposed outside the chamber 30. In this way, by disposing a heat source outside the chamber 30, heat can be released outside the chamber 30, and the temperature rise of the low vacuum region inside the chamber 30 can be prevented.

[0106] In addition, of course, the ink circulation also has an effect of dissipating heat from the liquid droplet ejection head 14. The ink circulation has an effect on both the situation that the liquid droplet easily evaporates and the situation that the thermal conductivity deteriorates in the low vacuum region.

[0107] In order to suppress the evaporation of the ink as much as possible, it is preferable to cool the ink before use. By providing an ink cooling mechanism 84 (see Fig.13 ), which can cool the ink. The ink cooling mechanism 84 can use a cooler through which cooling water flows, a Peltier element, etc. The ink cooling mechanism 84 cools the ink to 20° C., for example. In the case where the viscosity of the ink increases after cooling, the voltage waveform applied to the piezoelectric actuator 228 of the droplet ejection head 14 can be increased.

[0108] <Loading and unloading of substrate: Sixth embodiment>

[0109] Fig.12 The chamber 30 of the printing apparatus 10E according to the sixth embodiment is schematically shown. The chamber 30 of the printing apparatus 10E includes an inlet slit 60A, an outlet slit 60B, and first, second, third, and fourth gates 64A, 64B, 64C, and 64D that can be opened and closed.

[0110] The carrying-in slit 60A is a slit-shaped opening for carrying the substrate 1 from the outside into the chamber 30 . The carrying-out slit 60B is an opening for carrying the substrate 1 from the inside of the chamber 30 to the outside.

[0111] The first gate 64A, the second gate 64B, the third gate 64C, and the fourth gate 64D are respectively arranged on the transport path of the substrate 1 by the transport device 12. The first gate 64A is arranged at the carrying-in slit 60A to open and close the carrying-in slit 60A. The fourth gate 64D is arranged at the carrying-out slit 60B to open and close the carrying-out slit 60B.

[0112] The chamber 30 has a first pressure regulating chamber 66A between the first gate 64A and the second gate 64B, which is a relatively narrow space relative to the low vacuum region in which the droplet ejection head 14 and the like are arranged inside the chamber 30. Furthermore, the chamber 30 has a second pressure regulating chamber 66B between the third gate 64C and the fourth gate 64D, which is a relatively narrow space relative to the low vacuum region inside the chamber 30. The first pressure regulating chamber 66A and the second pressure regulating chamber 66B are each provided with a vacuum pump (not shown).

[0113] The second gate 64B switches between opening and closing the first pressure regulating chamber 66A and the low vacuum region. The third gate 64C switches between opening and closing the low vacuum region and the second pressure regulating chamber 66B.

[0114] When the substrate 1 outside the chamber 30 is transported into the chamber 30, first, the first gate 64A is opened, the substrate 1 is moved into the first pressure adjustment chamber 66A by the transport device 12, and the first gate 64A is closed. Then, the first pressure adjustment chamber 66A is made into a low vacuum state (for example, 0.1 atmosphere) by a vacuum pump, the second gate 64B is opened, the substrate 1 is moved into the low vacuum area of ​​the chamber 30 by the transport device 12, and the second gate 64B is closed.

[0115] Furthermore, when the substrate 1 in the chamber 30 is transported to the outside of the chamber 30, first, the first pressure adjustment chamber 66A is made into a low vacuum state by the vacuum pump. Then, the third gate 64C is opened, the substrate 1 is transported into the second pressure adjustment chamber 66B by the transport device 12, and the third gate 64C is closed. Then, the fourth gate 64D is opened, the substrate 1 is transported out of the chamber 30 by the transport device 12, and the fourth gate 64D is closed. Then, the second pressure adjustment chamber 66B is made into a low vacuum state.

[0116] By conveying the substrate 1 as described above, the substrate 1 can be carried into the low vacuum region having the liquid droplet ejection head 14 without introducing a large amount of air into the low vacuum region.

[0117] <Electrical structure>

[0118] Fig.13 This is a block diagram showing the electrical configuration of the printing apparatuses 10, 10A, 10B, 10C, 10D, and 10E. The printing apparatuses 10, 10A, 10B, 10C, 10D, and 10E include a control device 70. The control device 70 includes a processor 70A and a memory 70B.

[0119] The processor 70A executes the commands stored in the memory 70B. The hardware structure of the processor 70A is various processors (processors) as shown below. The various processors include: a general-purpose processor that executes software (programs) and functions as various functional units, namely a CPU (Central Processing Unit), a processor specialized in image processing, namely a GPU (Graphics Processing Unit), a processor whose circuit structure can be changed after manufacturing, such as an FPGA (Field Programmable Gate Array), namely a PLD (Programmable Logic Device), and a processor having a circuit structure specially designed for executing specific processing, such as an ASIC (Application Specific Integrated Circuit), namely a dedicated circuit, etc.

[0120] One processing unit may be composed of one of these various processors, or may be composed of two or more processors of the same or different types (for example, multiple FPGAs, or a combination of a CPU and an FPGA, or a combination of a CPU and a GPU). Furthermore, multiple functional units may be composed of one processor. As an example of multiple functional units composed of one processor, first, there is a method in which a processor is composed of a combination of one or more CPUs and software, represented by a computer such as a client or a server, and the processor acts as multiple functional units. Second, there is a method in which a processor is used, represented by a SoC (System On Chip), etc., in which a processor that implements the overall functions of a system including multiple functional units is used by one IC (Integrated Circuit) chip. In this way, various functional units are composed of one or more of the above-mentioned various processors as a hardware structure.

[0121] Furthermore, the hardware structure of these various processors is, more specifically, a circuit that combines circuit elements such as semiconductor elements.

[0122] The memory 70B stores commands for the processor 70A to execute. The memory 70B includes a RAM (Random Access Memory) and a ROM (Read Only Memory). The processor 70A uses the RAM as a work area, executes software using various programs and parameters stored in the ROM, and executes various processes for controlling the printing devices 10, 10A, 10B, 10C, 10D, and 10E by using parameters stored in the ROM.

[0123] The control device 70 controls the exhaust mechanism 31. That is, the control device 70 depressurizes the inside of the chamber 30 through the exhaust mechanism 31, so that the inside of the chamber 30 is maintained at a low vacuum atmosphere of, for example, 0.1 atmosphere. In addition, when the substrate 1 is carried in and carried out, the control device 70 depressurizes the inside of the first pressure adjustment chamber 66A and the second pressure adjustment chamber 66B through a vacuum pump (not shown) to achieve a low vacuum state.

[0124] The control device 70 controls the droplet ejection head 14. That is, the control device 70 causes the droplets 1 of the ink to be ejected from the nozzles 202 of the droplet ejection head 14 to form an image on the substrate 1. Furthermore, the control device 70 applies vibrations to the piezoelectric actuators 228 of the nozzles 202 that do not eject ink during printing, thereby vibrating the meniscus of the nozzles 202 that do not eject ink.

[0125] The control device 70 controls the conveying device 12, the first gate 64A, the second gate 64B, the third gate 64C, and the fourth gate 64D. That is, the control device 70 conveys the substrate 1 in the Y direction through the conveying device 12. Furthermore, when the control device 70 carries the substrate 1 into the chamber 30, the first gate 64A and the second gate 64B are opened and closed in sequence to prevent a large amount of air from entering the low vacuum area inside the chamber 30. Furthermore, when the control device 70 carries the substrate 1 out of the chamber 30, the third gate 64C and the fourth gate 64D are opened and closed in sequence to prevent a large amount of air from entering the low vacuum area inside the chamber 30.

[0126] The control device 70 controls the ink pump 38. That is, the control device 70 causes the ink pump 38 to suck ink from the lower ink tank 34 to the upper ink tank 32.

[0127] The control device 70 controls the first ink pump 38A, the second ink pump 46, the first valve 40, and the second valve 48. That is, the control device 70 opens the first valve 40, drives the first ink pump 38A, and sends ink from the lower ink tank 34 to the upper ink tank 32. In addition, the control device 70 opens the second valve 48, drives the first ink pump 38A and the second ink pump 46, and sends ink from the replenishing ink tank 42 to the upper ink tank 32. Furthermore, the control device 70 opens the first valve 40 and the second valve 48, drives the second ink pump 46, and sends ink from the replenishing ink tank 42 to the lower ink tank 34.

[0128] The control device 70 controls the first up-and-down moving mechanism 72 and the second up-and-down moving mechanism 74. That is, the control device 70 adjusts the vertical position of the upper ink tank 32 through the first up-and-down moving mechanism 72 to adjust the water level difference between the upper ink tank 32 and the droplet ejection head 14, and adjusts the vertical position of the lower ink tank 34 through the second up-and-down moving mechanism 74 to adjust the water level difference between the droplet ejection head 14 and the lower ink tank 34, thereby controlling the circulation of the ink in the droplet ejection head 14.

[0129] The control device 70 increases the circulation amount of ink during printing by the liquid drop ejection head 14 compared to the circulation amount of ink during non-printing. The control device 70 stops the circulation of ink during non-printing.

[0130] The control device 70 obtains detection results from the first liquid level sensor 76 and the second liquid level sensor 78. That is, the control device 70 confirms the amount of ink stored in the upper ink tank 32 from the detection result of the first liquid level sensor 76. In addition, the control device 70 confirms the amount of ink stored in the lower ink tank 34 from the detection result of the second liquid level sensor 78.

[0131] The control device 70 acquires the detection result from the density sensor 80. That is, the control device 70 confirms the amount of the solvent in the ink from the detection result of the density sensor 80.

[0132] The control device 70 controls the solvent adding device 82. That is, the control device 70 adds a solvent in an amount according to the detection result of the concentration sensor 80 to the ink to adjust the concentration of the ink solvent.

[0133] The control device 70 controls the ink cooling mechanism 84. That is, the control device 70 cools the ink to a desired temperature through the ink cooling mechanism 84.

[0134] According to the printing devices 10, 10A, 10B, 10C, 10D, and 10E constructed as above, a method for manufacturing printed matter can be implemented, which includes the following steps: making the space S between the droplet ejection head 14 and the substrate 1 a low vacuum; circulating the ink in the droplet ejection head 14; and relatively moving the substrate 1 and the droplet ejection head 14 through the conveying device 12 to eject ink from the droplet ejection head 14, thereby printing on the substrate 1.

[0135] According to the printing apparatuses 10, 10A, 10B, 10C, 10D, and 10E, the space S between the droplet ejection head 14 and the substrate 1 is a low vacuum, so that the air resistance with respect to the droplets 1 can be reduced. Furthermore, by circulating the ink in the droplet ejection head 14, even when the solvent from the ink evaporates, the ejection state can be stabilized.

[0136] <Other>

[0137] Here, a printing device for imparting conductive ink to a printed substrate as a droplet ejection device is described, but the substrate and the ink are not limited thereto. The droplet ejection device can be applied to substrates having uneven surfaces such as paper, cloth, leather, metal, resin, glass, and wood. The substrate is not limited to being accommodated in the chamber as a whole, and can also be a long-length substrate that spans inside and outside the chamber.

[0138] The droplet ejection device can be used for inks such as color inks containing color materials, ultraviolet curing inks that are cured by ultraviolet irradiation, and insulating inks having insulating properties. The droplet ejection device can use droplet ejection heads in the number according to the type of ink, and multiple droplet ejection heads can be arranged in one cavity, or cavities can be set for each droplet ejection head.

[0139] The technical scope of the present invention is not limited to the scope described in the above-mentioned embodiment. The configuration of each embodiment and the like can be appropriately combined between the embodiments without departing from the spirit of the present invention.

[0140] Explanation of symbols

[0141] 1-substrate, 10-printing device, 10A-printing device, 10B-printing device, 10C-printing device, 10D-printing device, 10E-printing device, 12-transport device, 14-droplet ejection head, 16-L-shaped bracket, 18-ink supply path, 18A-ink supply port, 20-ink recovery path, 20A-ink discharge port, 22-filter housing, 24-silicon mold, 30-chamber, 31-exhaust mechanism, 32-upper ink tank, 34-lower ink tank, 36-return flow path, 38-ink pump, 38A-first ink pump, 40-first valve, 42-replenishment ink tank, 44-replenishment flow path, 46-second ink pump, 48-second valve, 50-container, 52-control substrate, 54-ASIC, 56-flexible cable, 60A-carry-in slit, 60B-carry-out slit, 64A-first gate, 64B-Second gate, 64C-Third gate, 64D-Fourth gate, 66A-First pressure regulating chamber, 66B-Second pressure regulating chamber, 70-Control device, 70A-Processor, 70B-Memory, 72-First up-and-down moving mechanism, 74-Second up-and-down moving mechanism, 76-First liquid level sensor, 78-Second liquid level sensor, 80-Concentration sensor, 82-Solvent adding device, 84-Ink cooling Mechanism, 200-nozzle face, 202-nozzle, 204-pressure chamber, 206-ink chamber combination, 210-supply branch, 212-common flow path, 214-diffuser, 216-ink circulation path, 218-recovery branch, 220-circulating common flow path, 222-ejection element, 226-vibration plate, 228-piezoelectric actuator, 230-nozzle plate, 232-flow path plate, I-droplet, S-space.

Claims

1. A liquid droplet discharge device, comprising: The droplet spits out its head and spits out liquid; A relative movement mechanism causes the substrate and the droplet ejection head to move relative to each other; and A control device is provided to move the substrate and the liquid droplet ejection head relative to each other so that the liquid droplet ejection head ejects liquid, thereby printing an image on the substrate. There is a vacuum between the droplet ejection head and the substrate. The droplet ejection head includes a circulation flow path inside the droplet ejection head. The control device circulates the liquid in the circulation flow path at least during printing.

2. The liquid droplet discharge device according to claim 1, wherein: The droplet ejection head has an ejection element including a nozzle, a pressure chamber, and an ejection energy generating element. The circulation flow path includes a supply flow path for supplying liquid to the discharge element and a recovery flow path for recovering liquid from the discharge element.

3. The liquid droplet discharge device according to claim 1, comprising a first liquid tank and a second liquid tank for storing liquid, The control device supplies liquid from the first liquid tank to the liquid droplet ejection head by a water head difference, and recovers liquid from the liquid droplet ejection head to the second liquid tank by a water head difference.

4. The liquid droplet discharge device according to claim 3, comprising: a chamber that accommodates the droplet ejection head, the relative movement mechanism, the first liquid tank, and the second liquid tank; and The exhaust mechanism makes the interior of the chamber a vacuum. The reference of the water head difference is the pressure inside the chamber.

5. The liquid droplet discharge device according to claim 4, comprising: a liquid feeding mechanism for supplying liquid from the second liquid tank to the first liquid tank, The liquid delivery mechanism is arranged outside the chamber.

6. The liquid droplet discharge device according to claim 1, wherein: The control device makes the circulation amount of the liquid during printing greater than the circulation amount of the liquid during non-printing.

7. The liquid droplet discharge device according to claim 1, wherein: The control device stops the circulation of the liquid when printing is not in progress.

8. The liquid droplet discharge device according to claim 1, wherein: The control device provides vibration to the non-discharging nozzles during printing to such an extent that droplets are not discharged.

9. The liquid droplet discharge device according to claim 1, wherein: The liquid comprises a solvent, A concentration measuring device for measuring the concentration of the circulating liquid is provided, The control device adds solvent to the liquid in an amount that replenishes the evaporated solvent.

10. The liquid droplet discharge device according to claim 4, wherein: The liquid comprises a solvent, The solvent is disposed in an open state inside the chamber.

11. The liquid droplet ejection device according to claim 4, comprising a circuit element for driving the liquid droplet ejection head. The circuit element is disposed outside the chamber.

12. The liquid droplet discharge device according to claim 1, wherein: The vacuum is 0.5 atmospheres to 0.01 atmospheres.

13. The liquid droplet discharge device according to any one of claims 1 to 12, wherein: The liquid is an aqueous ink containing water as a solvent.

14. A method for producing a printed matter, comprising the following steps: Creating a vacuum between a liquid droplet ejection head and a substrate, causing the substrate and the liquid droplet ejection head to move relative to each other and ejecting liquid from the liquid droplet ejection head, thereby printing an image on the substrate; and At least during printing, liquid is circulated in the circulation flow path of the liquid droplet ejection head.

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