Inkjet device for conductive ink

Abstract

To reuse a diluted ink to be disposed of to reduce a disposal amount of an ink in an inkjet device for a conductive ink.SOLUTION: An inkjet device 1 includes an inkjet head 10, a main tank 20, a circulation line 30 for circulating a liquid, a first supply line 40 for supplying a conductive ink from the main tank 20 to the circulation line 30; buffer solution supply means 50 configured to supply a buffer solution to the circulation line 30; a liquid feed line 60 for feeding the liquid in the circulation line 30 to the outside of the circulation line 30; a relay tank 70 for storing the liquid fed from the circulation line 30 through the liquid feed line 60; a second supply line 80 for supplying the conductive ink from the main tank 20 to the relay tank 70; and a third supply line 90 for supplying the liquid in the relay tank 70 to the circulation line 30. The structure allows reuse of a diluted ink in which the conductive ink and the buffer solution are mixed and thus a disposal amount of the ink can be reduced.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed herein relates to an inkjet device used to print conductive ink. [Background technology]

[0002] Inkjet printing is sometimes used to form conductive patterns on electronic components. Inkjet ink (conductive ink) for printing such conductive patterns is prepared by mixing a liquid medium with conductive particles. Examples of such conductive particles include metal particles such as Ag particles, Au particles, Pt particles, Pd particles, and Rh particles (see Patent Document 1, etc.).

[0003] A typical inkjet device includes an inkjet head that ejects ink, a tank that stores the ink, and a supply line that supplies ink from the tank to the inkjet head. Some inkjet devices also include a circulation line that circulates the ink through the inkjet head. This prevents ink from curing during standby periods when printing is stopped, thereby preventing clogging of the inkjet head. Patent Document 2 discloses an example of an inkjet device that includes a circulation line. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-345322 [Patent Document 2] Patent Publication No. 2021-104642 Summary of the Invention [Problem to be solved by the invention]

[0005] In recent years, the formation of conductive patterns using inkjet printing has become increasingly common. For this reason, inkjet devices optimized for printing conductive inks are being developed. For example, typical conductive inks use high-density metal particles as conductive particles. Therefore, if the standby period is prolonged, the conductive particles may settle and cause blockage of the circulation line. For this reason, inkjet devices for conductive inks are sometimes configured to implement a standby mode in which a liquid (buffer solution) that does not contain conductive particles is circulated through the circulation line. This prevents blockage of the circulation line due to the settlement of conductive particles.

[0006] In an inkjet device with the above configuration, the buffer solution in the circulation line is discharged from the inkjet head before exiting standby mode and starting normal printing. However, if the discharge of the buffer solution is insufficient, diluted ink (hereinafter referred to as "diluted ink"), a mixture of the buffer solution and the conductive ink, is produced in the circulation line. If this diluted ink is used for printing, the performance (e.g., conductivity) of manufactured electronic components may be significantly reduced. For this reason, in the past, after supplying conductive ink to the circulation line when normal printing resumed, the liquid in the circulation line was discarded until a certain time had elapsed. This prevents the production of defective products even if the buffer solution is not properly discharged.

[0007] However, in recent years, there has been a demand for reducing the amount of ink wasted in the manufacture of electronic components, due to growing awareness of environmental issues and the need to reduce manufacturing costs. The technology disclosed herein has been made to meet these demands. [Means for solving the problem]

[0008] To solve the above-mentioned problems, the present inventors have considered reusing diluted ink generated when switching from standby mode to normal printing mode. Specifically, because the amount of diluted ink generated in the circulation line is relatively small, it can be reused as recycled ink of a standard concentration by mixing it with a large amount of conductive ink. One example of a method for preparing this recycled ink is to supply the diluted ink in the circulation line to a main tank for storing conductive ink. However, with this preparation method, if the diluted ink contains impurities, all of the conductive ink in the main tank will be contaminated. In this case, there is a risk that the amount of ink wasted will increase. Therefore, the present inventors have considered providing a separate tank (relay tank) to store the diluted ink generated in the circulation line. By mixing the diluted ink and conductive ink in this relay tank, recycled ink can be prepared in a tank other than the main tank. This minimizes the amount of ink wasted, even if the diluted ink is contaminated. The inkjet device for conductive ink disclosed herein is based on the above findings.

[0009] The inkjet device disclosed herein is a conductive ink inkjet device that prints conductive ink on a predetermined printing target. The inkjet device includes an inkjet head that ejects the conductive ink, a main tank that stores the conductive ink, a circulation line that circulates the conductive ink so that it passes through the inkjet head, a first supply line that supplies the conductive ink from the main tank to the circulation line, a buffer solution supply means that supplies a buffer solution to the circulation line, a liquid delivery line that delivers liquid from the circulation line to the outside of the circulation line, a relay tank that stores the liquid delivered from the circulation line through the liquid delivery line, a second supply line that delivers the conductive ink from the main tank to the relay tank, and a third supply line that delivers the liquid from the relay tank to the circulation line.

[0010] The inkjet device having the above configuration includes a relay tank that stores liquid (such as diluted ink) delivered from the circulation line. The inkjet device is also configured to supply conductive ink from the main tank to the relay tank via a second supply line. This allows recycled ink of a concentration within the standard to be prepared in the relay tank. The liquid (such as recycled ink) in the relay tank can then be supplied to the inkjet head via a third supply line and the circulation line. This configuration allows diluted ink that would otherwise be discarded to be reused, thereby contributing to a reduction in the amount of ink wasted. Furthermore, because the inkjet device disclosed herein prepares recycled ink in the relay tank, it is possible to prevent ink from being discarded due to contamination of the main tank. As described above, the inkjet device disclosed herein can reduce the amount of ink wasted in the manufacture of electronic components. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram schematically illustrating an inkjet device according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically showing the inkjet head in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0012] Embodiments of the technology disclosed herein will be described below with reference to the drawings. However, the following description is not intended to limit the technology disclosed herein to the respective embodiments described below. It should be noted that matters other than those specifically mentioned in this specification and necessary for implementing the technology disclosed herein (such as detailed ink components) can be understood as design matters for those skilled in the art based on prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and common technical knowledge in the relevant field. Furthermore, in the following description and drawings, components and parts that perform the same function are designated by the same reference numerals, and redundant descriptions may be omitted or simplified. Furthermore, the dimensional relationships (length, width, thickness, etc.) in each figure do not necessarily accurately reflect the actual dimensional relationships.

[0013] [Inkjet device] FIG. 1 is a conceptual diagram illustrating an inkjet device according to this embodiment. FIG. 2 is a cross-sectional view illustrating an inkjet head in FIG. 1. The inkjet device 1 according to this embodiment is a device that prints conductive ink on a predetermined printing target. As shown in FIG. 1, the inkjet device 1 includes an inkjet head 10, a main tank 20, a circulation line 30, a first supply line 40, a buffer solution supply means 50, a liquid feed line 60, a relay tank 70, a second supply line 80, and a third supply line 90.

[0014] The inkjet device 1 according to this embodiment is configured to be able to perform three operations: a normal printing mode, a standby mode, and an ink regeneration mode. In the normal printing mode, the inkjet device 1 ejects conductive ink from the inkjet head 10. In the standby mode, the inkjet device 1 circulates a buffer solution through the circulation line 30. In the ink regeneration mode, the inkjet device 1 prepares regenerated ink in the relay tank 70. Below, the configuration of the inkjet device 1 will be described, followed by a detailed description of its operation.

[0015] A. Inkjet device configuration 1. Inkjet head An inkjet head 10 is a component that ejects conductive ink. One example of this inkjet head 10 is a piezoelectric inkjet head 10 shown in FIG. 2. A reservoir 13 for retaining the conductive ink is provided within a case 12 of this inkjet head 10. The reservoir 13 is connected to an ejection section 16 via a liquid transfer path 15. The ejection section 16 is provided with an ejection port 17 that opens to the outside of the case 12 and a piezoelectric element 18 that faces the ejection port 17. In the inkjet head 10 configured as described above, the piezoelectric element 18 vibrates, causing the conductive ink in the ejection section 16 to be ejected from the ejection port 17 to the outside. Although not shown in FIG. 2, a circulation line 30 (circulation piping 31) shown in FIG. 1 is connected to the reservoir 13 of this inkjet head 10. In addition, the inkjet head 10 is preferably disposed below the other members in the circulation line 30 (the first sub-tank 35, the second sub-tank 36, the circulation pump 37, etc.).

[0016] 2. Main Tank The main tank 20 is a tank that stores conductive ink. The structure of the main tank 20 is not particularly limited, and any conventional ink tank that can be used in an inkjet device can be used without particular limitation. Although not intended to limit the technology disclosed herein, the capacity of the main tank 20 is approximately 100 ml to 2000 ml (preferably 500 ml to 1000 ml). Furthermore, the main tank 20 is preferably equipped with a stirrer that stirs the conductive ink inside. This can prevent the conductive particles from settling inside the main tank 20.

[0017] The conductive ink in the main tank 20 is prepared by dispersing conductive particles in a liquid medium. In this specification, "conductive particles" refers to metal particles having electrical conductivity. These conductive particles are the main component of the printed conductive pattern (conductive film). The type of conductive particles is not particularly limited, and a wide variety of metal particles can be used. Examples of conductive particles include particles containing tungsten (W), silver (Ag), nickel (Ni), gold (Au), platinum (Pt), palladium (Pd), rhodium (Rh), molybdenum (Mo), cobalt (Co), iron (Fe), chromium (Cr), copper (Cu), ruthenium (Ru), osmium (Os), iridium (Ir), etc. The conductive particles do not necessarily have to be particles consisting of only one metal element (single particles) but may also be alloy particles containing two or more metal elements. Among the conductive particles mentioned above, W particles (specific gravity: 19.3), Ag particles (specific gravity: 10.5), Ni particles (specific gravity: 8.9), Au particles (specific gravity: 19.3), Pt particles (specific gravity: 21.4), and Pd particles (specific gravity: 12) have particularly excellent conductivity and are therefore widely used in the manufacture of electronic components. However, these conductive particles have a high specific gravity of 8.5 or more (typically 10 or more), making them particularly susceptible to settling in conductive ink. However, the inkjet device 1 according to this embodiment is equipped with a buffer solution supply unit 50, which will be described later. This prevents clogging of the circulation line 30 due to the settling of conductive particles, even during extended standby periods when printing is stopped. In other words, the inkjet device 1 according to this embodiment is particularly suitable for use in printing conductive inks containing conductive particles with high specific gravity.

[0018] Furthermore, the content of conductive particles relative to the total weight of the conductive ink is preferably 45 wt% or more, more preferably 50 wt% or more, even more preferably 55 wt% or more, and particularly preferably 60 wt% or more. Depending on the performance required of the manufactured electronic component, a conductive ink containing a high concentration of conductive particles as described above may be used. Such high-concentration ink is particularly prone to conductive particle precipitation, so the inkjet device 1 according to this embodiment can more effectively exhibit its deposition suppression effect. The upper limit of the conductive particle content is not particularly limited and may be 95 wt% or less, or may be 90 wt% or less.

[0019] Furthermore, the liquid medium for dispersing the conductive particles can be a wide variety of conventionally known liquids that can be used to prepare conductive inks. High-boiling-point nonaqueous solvents are particularly suitable for use as such liquid media. This prevents rapid drying during the drying process and allows for stable formation of a dried film. Furthermore, low-viscosity nonaqueous solvents are preferred as the liquid medium. This improves ink ejection performance from the inkjet head 10. Examples of such nonaqueous solvents include glycol acetate, glycol ether, and aliphatic monoalcohols.

[0020] Examples of glycol acetates include ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, diethylene glycol monobutyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, propylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether acetate, butyl glycol acetate, and butyl diglycol acetate. Examples of glycol ethers include diethylene glycol dibutyl ether and diethylene glycol butyl methyl ether. Examples of aliphatic monoalcohols include linear or branched aliphatic alcohols such as methanol, ethanol, propanol, isopropanol, butanol, n-amyl alcohol, hexanol, heptanol, n-octanol, 2-ethylhexanol, isooctanol, nonanol, decanol, isoundecanol, lauryl alcohol, cetyl alcohol, and stearyl alcohol.

[0021] The conductive ink may also contain any additive component. Materials that can be used in inkjet inks can be used as such additive components without any particular restrictions, as long as they do not significantly impair the effects of the technology disclosed herein. An example of such an additive component is a binder. A binder is an organic component used to adjust the ink viscosity and fixability. An example of such a binder is polyvinyl acetal resin. Another example of an additive component is a dispersant. A dispersant can suppress aggregation and precipitation of conductive particles. An example of a dispersant is a cationic dispersant.

[0022] The viscosity of the conductive ink is preferably 100 cP or less, more preferably 90 cP or less, even more preferably 80 cP or less, and particularly preferably 70 cP or less. Low-viscosity conductive inks are excellent in ejection properties from the inkjet head 10, but have the property that the conductive particles tend to settle. However, because the inkjet device 1 according to this embodiment is equipped with the buffer solution supply means 50 described below, clogging of the circulation line 30 due to the precipitation of conductive particles can be suppressed even when low-viscosity conductive ink is used. The lower limit of the ink viscosity is not particularly limited, and may be 2 cP or more, 4 cP or more, or 6 cP or more.

[0023] 3.Circulation Line The circulation line 30 is a liquid delivery path that circulates liquid so that it passes through the inkjet head 10. Specifically, in the normal printing mode described below, conductive ink circulates within the circulation line 30. This makes it possible to prevent clogging due to hardening of the conductive ink. In addition, in the standby mode, a buffer solution circulates within the circulation line 30. This makes it possible to prevent clogging of the circulation line 30 due to precipitation of conductive particles. In addition, in the ink regeneration mode, recycled ink circulates within the circulation line 30. This recycled ink is ejected from the inkjet head 10 via the circulation line 30.

[0024] The circulation line 30 shown in FIG. 1 includes a circulation pipe 31, a first sub-tank 35, a second sub-tank 36, and a circulation pump 37.

[0025] The circulation pipe 31 is a circular pipe that constitutes the circulation line 30. This circulation pipe 31 connects, in clockwise order, the first sub-tank 35, the inkjet head 10, the second sub-tank 36, and the circulation pump 37. The pipe diameter (inner diameter) of each circulation pipe 31 is preferably about 2 mm to 10 mm (more preferably 4 mm to 6 mm). This ensures a sufficient amount of liquid to be sent through the circulation line 30.

[0026] The first sub-tank 35 is a tank located upstream of the inkjet head 10 in the circulation direction. Like the main tank 20, the first sub-tank 35 can also be a conventionally known ink tank without any particular restrictions. The capacity of the first sub-tank 35 is, for example, approximately 10 ml to 100 ml (preferably 20 ml to 50 ml). Although not shown, the first sub-tank 35 is equipped with a pressure reduction mechanism. This pressure reduction mechanism sucks air from the first sub-tank 35, creating a negative pressure state in the first sub-tank 35. The first sub-tank 35 also has a sensor (not shown) that detects the amount of liquid in the tank.

[0027] The second sub-tank 36 is a tank located downstream of the inkjet head 10 in the circulation direction. Conductive ink not ejected by the inkjet head 10 is collected in the second sub-tank 36. As with the main tank 20 and the first sub-tank 35, the structure of the second sub-tank 36 is not particularly limited, and any conventionally known ink tank can be used without any particular restrictions. The capacity of the second sub-tank 36 is, for example, approximately 10 ml to 100 ml (preferably 20 ml to 50 ml). As with the first sub-tank 35, the second sub-tank 36 also has a pressure reduction mechanism and a sensor.

[0028] The circulation pump 37 is disposed between the second sub-tank 36 and the first sub-tank 35. This circulation pump 37 sucks the liquid from the second sub-tank 36 and transfers it to the first sub-tank 35. The structure of the circulation pump 37 is not particularly limited, and any ink ejection pump that can be used in conventional inkjet devices can be used without particular limitation. An example of this circulation pump 37 is a diaphragm pump. The amount of liquid delivered by the circulation pump 37 is preferably approximately 5 ml / min to 100 ml / min (preferably 30 ml / min to 50 ml / min). This more effectively prevents the precipitation of conductive particles in the circulation line 30.

[0029] 4. First supply line The first supply line 40 is a liquid transfer path that supplies conductive ink from the main tank 20 to the circulation line 30. In the inkjet device 1 according to this embodiment, conductive ink is supplied from the main tank 20 to the inkjet head 10 via the first supply line 40 and the circulation line 30. The first supply line 40 shown in FIG. 1 includes a first supply pipe 41 and a supply pump 42.

[0030] The first supply pipe 41 is a pipe that forms a flow path from the main tank 20 to the circulation line 30. Specifically, one end 41a of the first supply pipe 41 is connected to the main tank 20. The other end 41b of the first supply pipe 41 is connected to the circulation line 30 (specifically, the second sub-tank 36). The pipe diameter (inner diameter) of the first supply pipe 41 is preferably about 2 mm to 10 mm (more preferably 4 mm to 6 mm). This ensures a sufficient amount of liquid to be sent through the first supply line 40.

[0031] The supply pump 42 is a pump provided between the main tank 20 and the circulation line 30. As will be described in detail later, by operating the supply pump 42, various liquids (conductive ink, buffer solution, recycled ink) can be supplied to the circulation line 30 through the first supply pipe 41. Note that the supply pump 42 can also be any conventionally known ink discharge pump (for example, a diaphragm pump) without any particular restrictions. The specific liquid delivery rate by the supply pump 42 is preferably approximately 5 ml / min to 100 ml / min (preferably 30 ml / min to 50 ml / min).

[0032] Furthermore, in the inkjet device 1 according to this embodiment, a first three-way valve 43 is provided between the main tank 20 and the supply pump 42. A third supply pipe 92 of a third supply line 90 (described later) is connected to this first three-way valve 43. By switching this first three-way valve 43, the connection destination of the first supply line 40 can be switched between the main tank 20 and the relay tank 70.

[0033] In this embodiment, a relief valve 49 is provided in the first supply line 40. This relief valve 49 has the function of releasing pressure in the piping of the first supply line 40. This prevents unintended liquid from being supplied to the circulation line 30. As will be described in detail later, the second sub-tank 36 in the circulation line 30 is maintained in a reduced pressure state. Therefore, even when the supply pump 42 is stopped, there is a risk that liquid will be supplied to the second sub-tank 36 due to a pressure difference. In response to this, the relief valve 49 can eliminate the pressure difference with the second sub-tank 36, thereby preventing unintended liquid supply. Note that, as shown in FIG. 1, the relief valve 49 is preferably disposed between the first three-way valve 43 and the supply pump 42. This prevents unintended liquid from being supplied from each of the multiple tanks (the main tank 20, the buffer tank 52, and the relay tank 70).

[0034] 5.Buffer supply means The buffer solution supplying means 50 is a liquid transfer path that supplies a buffer solution to the circulation line 30. As described above, conductive ink contains metallic conductive particles. Therefore, if the standby period during which printing is stopped is prolonged, there is a risk that the circulation line 30 will be clogged due to precipitation of the conductive particles. In response to this, the inkjet device 1 according to this embodiment operates in a standby mode in which the buffer solution is supplied from the buffer solution supplying means 50 to the circulation line 30 and the buffer solution is circulated through the circulation line 30. This makes it possible to suppress precipitation of the conductive particles in the circulation line 30.

[0035] The buffer solution supplying means 50 according to this embodiment is configured to supply a buffer solution to the circulation line 30 via the first supply line 40. Specifically, the buffer solution supplying means 50 shown in FIG. 1 includes a buffer solution tank 52 and a buffer solution supply pipe 54. The buffer solution tank 52 is a tank for storing a buffer solution. Like the other tanks, a conventionally known ink tank can be used for the buffer solution tank 52 without any particular restrictions. The buffer solution supply pipe 54 is a pipe connecting the buffer solution tank 52 and the first supply line 40. Specifically, one end 54a of the buffer solution supply pipe 54 is connected to the buffer solution tank 52. The other end 54b of the buffer solution supply pipe 54 is connected to the first supply line 40 (for example, between the main tank 20 and the first three-way valve 43). A second three-way valve 55 is installed between the buffer solution tank 52 and the first supply line 40. By operating the second three-way valve 55, supply of the buffer solution to the first supply line 40 can be started or stopped.

[0036] The buffer solution can be any liquid that can be used as a liquid medium for conductive ink. For example, the buffer solution is preferably a liquid with the same components as the conductive ink in the main tank 20, except that it does not contain conductive particles. This allows for relatively easy reuse of diluted ink, which is a mixture of the buffer solution and the conductive ink. However, the composition of the buffer solution is not particularly limited, as long as it does not significantly impair the effects of the technology disclosed herein. For example, the liquid medium for the conductive ink and the buffer solution may be different, as long as the recycled ink, described below, can be used to manufacture electronic components.

[0037] 6. Liquid transfer line The liquid supply line 60 is a liquid supply path that sends the liquid (conductive ink, diluted ink, recycled ink, etc.) in the circulation line 30 to the outside of the circulation line 30. By providing this liquid supply line 60, it is possible to prevent different liquids from mixing within the circulation line 30. As a result, it is possible to prevent a large change in the composition of the ink during printing. The liquid supply line 60 shown in FIG. 1 includes a liquid supply tube 61 and a liquid supply pump 62. One end 61a of the liquid supply tube 61 of the liquid supply line 60 is connected to the circulation line 30. The other end 61b of the liquid supply tube 61 is connected to a relay tank 70. The liquid supply pump 62 is installed between the circulation line 30 and the relay tank 70. By operating this liquid supply pump 62, the liquid in the circulation line 30 can be sent toward the relay tank 70. The liquid supply line 60 shown in FIG. 1 is connected to the first sub-tank 35 of the circulation line 30. However, as long as the connection space can be secured, the liquid supply line 60 may be connected to any of the components constituting the circulation line 30 (the first sub-tank 35, the second sub-tank 36, and the circulation pipe 31).

[0038] 7. Relay Tank The relay tank 70 is a tank that stores the liquid sent from the circulation line 30 via the liquid sending line 60. This allows the liquid in the circulation line 30 (conductive ink, buffer solution, diluted ink, recycled ink, etc.) to be preserved without being discarded. As will be described in detail later, the liquid stored in the relay tank 70 can be reused as recycled ink by adjusting the conductive particle concentration. Note that the relay tank 70 is preferably equipped with a stirrer such as a magnetic stirrer. This allows the liquid in the relay tank 70 to be mixed efficiently, making it easier to prepare recycled ink. In addition, the relay tank 70 in this embodiment is equipped with a concentration measuring means 72 that measures the conductive particle concentration of the liquid in the relay tank 70. This allows for more accurate preparation of recycled ink. Note that, like the other tanks, the relay tank 70 can be any conventional ink tank without any particular restrictions. The capacity of the relay tank 70 is, for example, approximately 100 ml to 2000 ml (preferably 500 ml to 1000 ml).

[0039] 8. Second supply line The second supply line 80 is a liquid transfer path that supplies conductive ink from the main tank 20 to the relay tank 70. This allows the conductive ink and diluted ink to be mixed in the relay tank 70 to prepare recycled ink. The second supply line 80 shown in FIG. 1 includes a second supply pipe 82 and a concentration adjustment pump 84. One end 82a of the second supply pipe 82 is connected to the main tank 20. The other end 82b of the second supply pipe 82 is connected to the relay tank 70. The concentration adjustment pump 84 is installed between the main tank 20 and the relay tank 70. By operating this concentration adjustment pump 84, the conductive ink in the main tank 20 can be supplied to the relay tank 70. This increases the conductive particle concentration of the liquid in the relay tank 70.

[0040] 9. Third supply line The third supply line 90 is a liquid transfer path that supplies the liquid in the relay tank 70 to the circulation line 30. This allows the recycled ink prepared in the relay tank 70 to be used for printing. The third supply line 90 shown in FIG. 1 is configured to supply the liquid in the relay tank 70 to the circulation line 30 via the first supply line 40. Specifically, the third supply line 90 includes a third supply pipe 92. One end 92a of the third supply pipe 92 is connected to the relay tank 70. Meanwhile, the other end 92b of the third supply pipe 92 is connected to the first three-way valve 43 of the first supply line 40.

[0041] 10. Control equipment The inkjet device 1 according to this embodiment also includes a control unit (not shown) that controls the operation of each of the components described above. Note that the configuration of the control unit itself does not characterize the technology disclosed herein, and therefore a detailed description thereof will be omitted.

[0042] B. Inkjet Device Operation As described above, the inkjet device 1 according to this embodiment is configured to be able to perform three operations: a normal printing mode, a standby mode, and an ink regeneration mode. Specifically, the control unit includes a calculation unit (CPU), a storage unit (memory), an input unit, an output unit, etc. The storage unit stores various programs for executing each of the above-mentioned modes. The calculation unit then operates each of the above-mentioned components (pumps, valves, etc.) based on the programs in the storage unit. This allows for the realization of a liquid flow corresponding to each mode. Each mode will be described below.

[0043] (1) Normal printing mode The normal printing mode is an operating mode in which the conductive ink in the main tank 20 is ejected from the inkjet head 10. In this normal printing mode, first, conductive ink is supplied from the main tank 20 to the circulation line 30. Specifically, at the start of the normal printing mode, the control unit switches the first three-way valve 43 and the second three-way valve 55 so that the main tank 20 and the second sub-tank 36 are connected via the first supply line 40. Specifically, the second three-way valve 55 is switched so that the main tank 20 and the first supply line 40 are connected and the buffer tank 52 and the first supply line 40 are disconnected. In addition, the first three-way valve 43 is switched so that the main tank 20 and the second sub-tank 36 are connected and the relay tank 70 and the second sub-tank 36 are disconnected. In this state, when the supply pump 42 is operated, conductive ink is supplied from the main tank 20 to the second sub-tank 36 (see F1 and F2 in FIG. 1). Then, when a certain amount of conductive ink or more is stored in the second sub-tank 36, the control unit stops the supply pump 42.

[0044] Next, in the normal printing mode, printing is performed while circulating conductive ink through the circulation line 30. Specifically, the control unit operates the circulation pump 37 to transfer conductive ink from the second subtank 36 to the first subtank 35 (see F3 in FIG. 1). Then, when a certain amount of conductive ink is stored in the first subtank 35, the control unit stops the circulation pump 37. Next, the control unit operates the pressure reduction mechanisms of the first subtank 35 and the second subtank 36. At this time, the internal pressure of each tank is adjusted so that the second subtank 36 has a lower pressure (negative pressure) than the first subtank 35. As a result, the conductive ink is transferred in the order of the first subtank 35, the inkjet head 10, and the second subtank 36 (see F4 and F5 in FIG. 1). At this time, by vibrating the piezo element 18 of the inkjet head 10 (see FIG. 2), the ink can be ejected from the inkjet head 10. Furthermore, when no ink is being ejected from the inkjet head 10, unused conductive ink is stored in the second subtank 36. If this liquid transfer to the second subtank 36 continues, the amount of ink in the first subtank 35 decreases. As a result, if the amount of ink in the first subtank 35 falls below a predetermined amount, the control unit operates the circulation pump 37 again. This allows conductive ink to be transferred from the second subtank 36 to the first subtank 35. Furthermore, if the total amount of ink stored in the first subtank 35 and the second subtank 36 falls below a certain level, the control unit operates the supply pump 42 of the first supply line 40 again. This allows conductive ink to be replenished into the circulation line 30.

[0045] As described above, in the normal printing mode of the inkjet device 1 according to this embodiment, the conductive ink in the main tank 20 is supplied to the circulation line 30, and printing is performed while the conductive ink is circulated through the circulation line 30. This prevents the conductive ink from hardening during short standby periods, such as when replacing the printing target. Furthermore, in this embodiment, the conductive ink is circulated through two sub-tanks. This prevents sudden changes in the ink flow rate in the circulation line 30, thereby stabilizing the ejection of ink.

[0046] (2) Standby mode The standby mode is an operating mode in which a buffer solution is circulated through the circulation line 30. The standby mode is implemented, for example, when printing is stopped for an extended period of time, such as for maintenance or ink replacement. In this standby mode, first, the conductive ink in the circulation line 30 is sent via the liquid sending line 60. Specifically, at the start of the standby mode, the control unit stops depressurizing the first subtank 35 and the second subtank 36 and operates the circulation pump 37. This causes the conductive ink in the circulation line 30 to be stored in the first subtank 35. Next, the control unit operates the liquid sending pump 62 of the liquid sending line 60. This causes the conductive ink in the first subtank 35 to be sent from the circulation line 30 (see F6 in FIG. 1 ). The conductive ink sent from the circulation line 30 is then supplied to the relay tank 70 via the liquid sending pipe 61. This conductive ink sent to the relay tank 70 is used to prepare recycled ink, which will be described later.

[0047] Next, in standby mode, the buffer solution is supplied to the circulation line 30. Specifically, the control unit switches the first three-way valve 43 and the second three-way valve 55 so that the first supply line 40 and the third supply line 90 are connected. Specifically, the second three-way valve 55 is switched so that the buffer solution tank 52 is connected to the first supply line 40 and the main tank 20 is disconnected from the first supply line 40. Furthermore, the first three-way valve 43 is switched so that the buffer solution tank 52 is connected to the second sub-tank 36 and the relay tank 70 is disconnected from the second sub-tank 36. In this state, the control unit operates the supply pump 42. As a result, the buffer solution is supplied from the buffer solution tank 52 to the second sub-tank 36 (see F7 and F2 in FIG. 1). At this time, the first supply line 40 and the third supply line 90 are connected by switching the first three-way valve 43, preventing the buffer solution from being mixed into the main tank 20.

[0048] Next, the buffer solution supplied to the circulation line 30 circulates through the circulation line 30. This circulation of the buffer solution can be performed using the same procedure as the circulation of the conductive ink described above. Specifically, the control unit sets the pressure in the second sub-tank 36 to a lower pressure than that of the first sub-tank 35 and operates the circulation pump 37. As a result, the buffer solution circulates through the circulation line 30 along the arrows F3 to F5 in FIG. 1. As described above, in the standby mode, the conductive ink in the circulation line 30 is pumped to the outside, and the buffer solution is circulated through the circulation line 30. This prevents clogging of the circulation line 30 due to the precipitation of conductive particles, even if the standby time is extended. Note that in the standby mode, the conductive ink remaining in the circulation line 30 may mix with the buffer solution. In this case, depending on the amount of conductive ink mixed in, clogging of the circulation line 30 due to the precipitation of conductive particles may occur. For this reason, in the standby mode, it is preferable to perform a substitution process, as needed, in which the buffer solution is supplied from the buffer tank 52 to the circulation line 30 while the buffer solution is discharged from the inkjet head 10.

[0049] (3) Ink regeneration mode The ink regeneration mode is an operating mode in which regenerated ink is prepared in the relay tank 70. This ink regeneration mode is executed after the standby mode ends and before the normal printing mode starts. In the ink regeneration mode, first, the liquid (buffer solution) in the circulation line 30 is discharged from the inkjet head 10. Specifically, at the start of the ink regeneration mode, the control unit opens the first sub-tank 35 and the second sub-tank 36 to the atmosphere while operating the circulation pump 37, thereby eliminating the negative pressure in the circulation line 30. This allows the buffer solution in the circulation line 30 to be discharged from the inkjet head 10. Next, when the buffer solution in the circulation line 30 has been mostly discharged, the control unit again reduces the pressure in the first sub-tank 35 and the second sub-tank 36. This prevents the liquid in the circulation line 30 from being discharged from the inkjet head 10 due to its own weight. In this state, the control unit supplies conductive ink from the main tank 20 to the circulation line 30. The procedure for supplying conductive ink to the circulation line 30 is the same as in the normal printing mode, so a repeated description will be omitted. At this time, if the buffer solution remains in the circulation line 30, conductive ink diluted by the buffer solution (diluted ink) will be produced in the circulation line 30. In response to this, the control unit sends the liquid (diluted ink) in the circulation line 30 to the relay tank 70. Specifically, the control unit operates the liquid feed pump 62 on the liquid feed line 60. As a result, the diluted ink in the circulation line 30 is transferred to the relay tank 70 via the first sub-tank 35 and the liquid feed line 60 (see F6).

[0050] Next, in the ink regeneration mode, conductive ink is supplied to the relay tank 70, which stores diluted ink. This allows recycled ink with a concentration within the standard to be prepared. Specifically, after the supply of diluted ink from the circulation line 30 to the relay tank 70 is completed, the control unit operates the concentration adjustment pump 84 of the second supply line 80. This causes conductive ink to be supplied from the main tank 20 to the relay tank 70 via the second supply line 80 (see F8). As a result, the conductive particle concentration of the diluted ink in the relay tank 70 increases. The control unit then continues to supply conductive ink to the relay tank 70 until the concentration of the ink in the relay tank 70 reaches the standard for the printing target. This allows recycled ink that can be used to manufacture electronic components to be prepared.

[0051] As described above, the inkjet device 1 according to this embodiment is equipped with a concentration measuring means 72 that measures the concentration of conductive particles in the liquid in the relay tank 70. In this case, it is preferable that the control unit adjusts the amount of conductive ink supplied from the main tank 20 to the relay tank 70 based on the measurement results of the concentration measuring means 72. This allows conductive ink to be supplied into the relay tank 70 while reflecting the conductive particle concentration of the liquid in the relay tank 70. As a result, the recycled ink can be prepared more accurately.

[0052] Next, the control unit supplies the recycled ink in the relay tank 70 to the circulation line 30. Specifically, the control unit switches the first three-way valve 43 so that the first supply line 40 and the third supply line 90 are connected, and operates the supply pump 42 of the first supply line 40. As a result, the recycled ink in the relay tank 70 passes through the third supply line 90 and the first supply line 40 and is supplied to the circulation line 30 (the second sub-tank 36) (see F9 and F2 in FIG. 1). The recycled ink then circulates within the circulation line 30 and is ejected appropriately from the inkjet head 10. Note that the recycled ink supplied to the circulation line 30 at the beginning of the ink regeneration mode is preferably sent again to the relay tank 70 via the liquid sending line 60. This prevents the concentration of the recycled ink ejected from the inkjet head 10 from being reduced by the diluted ink remaining in the circulation line 30.

[0053] When the ink concentrations of the recycled ink and the conductive ink become approximately the same, the control unit preferably stops the ink regeneration mode and starts the normal printing mode. Specifically, the control unit in this embodiment stores the concentration X of the conductive ink in the main tank 20. While the ink regeneration mode is being executed, the control unit continues to compare the measurement result of the concentration measurement means 72 (the concentration Y of the recycled ink in the relay tank 70) with the concentration X of the conductive ink. When the ratio (XY / X) of the difference between the concentration X of the conductive ink and the concentration Y of the recycled ink, where the concentration X of the conductive ink is 100%, becomes equal to or less than a certain value (preferably 5% or less, more preferably 2.5% or less, and particularly preferably 1% or less), the control unit determines that the concentration Y of the recycled ink and the concentration X of the conductive ink have become approximately the same. At this time, the control unit stops the concentration adjustment pump 84 and continues supplying recycled ink from the relay tank 70 to the circulation line 30. Then, when the relay tank 70 becomes empty, the control unit switches the first three-way valve 43 so that the main tank 20 and the second sub-tank 36 are connected, thereby stopping the ink regeneration mode and starting the normal printing mode.

[0054] As described above, the inkjet device 1 according to this embodiment can prepare recycled ink from diluted ink generated during standby mode. This allows diluted ink that would otherwise be discarded to be reused, contributing to a reduction in the amount of ink wasted. Furthermore, because the inkjet device 1 according to this embodiment prepares recycled ink within the relay tank 70, it is possible to prevent ink from being discarded due to contamination of the main tank 20. Therefore, the inkjet device 1 according to this embodiment can reduce the amount of ink wasted in the manufacture of electronic components.

[0055] [Other embodiments] The inkjet device according to one embodiment of the technology disclosed herein has been described above. Note that the above embodiment is not intended to limit the technology disclosed herein. In other words, the technology disclosed herein allows various configuration changes to be made to the inkjet device 1 described above.

[0056] For example, the buffer solution supplying means 50 in the above-described embodiment is connected to the first supply line 40. However, the buffer solution supplying means is not limited to the above-described configuration as long as it is able to supply the buffer solution to the circulation line. For example, the buffer solution supplying means may be directly connected to the circulation line (e.g., the first sub-tank, the second sub-tank, etc.). However, the inkjet device 1 according to the above-described embodiment can supply the buffer solution to the circulation line 30 using the supply pump 42 of the first supply line 40. This can contribute to reducing equipment costs.

[0057] In the inkjet device 1 according to the above embodiment, the third supply line 90 is also connected to the circulation line 30 via the first supply line 40. However, the third supply line is not limited to the above configuration as long as it can supply ink from the relay tank to the circulation line. For example, the third supply line may also be directly connected to the circulation line. However, according to the above embodiment, recycled ink can be supplied to the circulation line 30 using the supply pump 42 of the first supply line 40, which contributes to reducing equipment costs.

[0058] The specific structure of the circulation line is not limited to that of the above-described embodiment. For example, the circulation line 30 in the above-described embodiment is provided with a first sub-tank 35 and a second sub-tank 36. However, it is possible to circulate liquid (such as conductive ink) through the circulation line without providing sub-tanks. However, from the perspective of stabilizing the amount of ink ejected from the inkjet head 10, it is preferable to provide the first sub-tank 35 and the second sub-tank 36 in the circulation line 30.

[0059] Furthermore, the inkjet device 1 according to the above-described embodiment is configured so that each device operates automatically based on instructions from a control unit. However, the inkjet device disclosed herein is not limited to a device that operates automatically by a control unit. For example, the inkjet device disclosed herein may be configured so that each device can be operated by an operator as needed. Even when such a configuration is adopted, the amount of ink wasted in the manufacture of electronic components can be reduced by preparing recycled ink in the relay tank.

[0060] The technology disclosed herein has been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples exemplified above. Furthermore, the technology disclosed herein encompasses the aspects described in items 1 to 7 below.

[0061] <Item 1> An inkjet device for conductive ink that prints conductive ink on a predetermined printing target, an inkjet head that ejects the conductive ink; a main tank for storing the conductive ink; a circulation line for circulating a liquid through the inkjet head; a first supply line for supplying the conductive ink from the main tank to the circulation line; a buffer solution supply means for supplying a buffer solution to the circulation line; a liquid transfer line that transfers the liquid in the circulation line to the outside of the circulation line; a relay tank that stores the liquid sent from the circulation line through the liquid sending line; a second supply line for supplying the conductive ink from the main tank to the relay tank; a third supply line that supplies the liquid in the relay tank to the circulation line; An inkjet device for conductive ink, comprising:

[0062] <Item 2> Item 2. The ink jet device for conductive ink according to item 1, wherein the buffer solution supplying means is configured to supply a buffer solution to the circulation line via the first supply line.

[0063] <Item 3> 3. The inkjet device for conductive ink according to item 1 or 2, wherein the third supply line is configured to supply the liquid in the relay tank to the circulation line via the first supply line.

[0064] <Item 4> The circulation line is a first sub-tank disposed upstream of the inkjet head; a second sub-tank disposed downstream of the inkjet head; 4. The ink-jet device for conductive ink according to any one of items 1 to 3, comprising:

[0065] <Item 5> 5. The inkjet device for conductive ink according to item 4, wherein the liquid supply line is connected to the first sub-tank and is configured to supply the liquid stored in the first sub-tank toward the relay tank.

[0066] <Item 6> 6. The ink-jet device for conductive ink according to any one of items 1 to 5, wherein the conductive ink contains at least one type of conductive particles selected from the group consisting of W particles, Ag particles, Ni particles, Au particles, Pt particles, Pd particles, and Rh particles.

[0067] <Item 7> a concentration measuring means for measuring the concentration of the conductive particles in the liquid in the relay tank; a control unit that adjusts the amount of conductive ink supplied from the main tank to the relay tank based on the measurement result of the concentration measurement means; Item 7. An ink jet device for conductive ink according to item 6, comprising: [Explanation of symbols]

[0068] 1: Inkjet device 10: Inkjet head 20: Main tank 30: Circulation line 40: First supply line 50: Buffer supply means 60: Liquid transfer line 70: Relay tank 80: Second supply line 90: Third supply line

Claims

1. An inkjet device for conductive ink that prints conductive ink on a predetermined printing target, an inkjet head that ejects the conductive ink; a main tank for storing the conductive ink; a circulation line for circulating a liquid through the inkjet head; a first supply line for supplying the conductive ink from the main tank to the circulation line; a buffer solution supply means for supplying a buffer solution to the circulation line; a liquid transfer line that transfers the liquid in the circulation line to the outside of the circulation line; a relay tank that stores the liquid sent from the circulation line through the liquid sending line; a second supply line for supplying the conductive ink from the main tank to the relay tank; a third supply line that supplies the liquid in the relay tank to the circulation line; An inkjet device for conductive ink, comprising:

2. 2. The ink jet device for conductive ink according to claim 1, wherein the buffer solution supplying means is configured to supply the buffer solution to the circulation line via the first supply line.

3. The ink jet device for conductive ink according to claim 1 , wherein the third supply line is configured to supply the liquid in the relay tank to the circulation line via the first supply line.

4. The circulation line is a first sub-tank disposed upstream of the inkjet head; a second sub-tank disposed downstream of the inkjet head; 10. The conductive ink jet device of claim 1, comprising:

5. 5. The inkjet device for conductive ink according to claim 4, wherein the liquid supply line is connected to the first sub-tank and is configured to supply the liquid stored in the first sub-tank toward the relay tank.

6. 6. The inkjet device for conductive ink according to claim 1, wherein the conductive ink contains at least one type of conductive particles selected from the group consisting of W particles, Ag particles, Ni particles, Au particles, Pt particles, Pd particles, and Rh particles.

7. a concentration measuring means for measuring the concentration of the conductive particles in the liquid in the relay tank; a control unit that adjusts the amount of conductive ink supplied from the main tank to the relay tank based on the measurement result of the concentration measurement means; 7. The conductive ink jet device according to claim 6, comprising:

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