Inkjet device for conductive inks

Abstract

To provide an ink jet device suitable for printing by conductive ink.SOLUTION: An ink jet device 1 includes: an ink jet head 10; a main tank 20; a circulation line 30 which circulates conductive ink A so as to pass the ink jet head 10; and a supply line 40 which supplies the conductive ink A from the main tank 20 to the circulation line 30. In the ink jet device 1, liquid feeding pipes 31 to 34 constituting the circulation line 30 are inclined toward a vertical direction Z. Therefore, deposition of conductive particles can be suppressed in the liquid feeding pipes 31 to 34 of the circulation line 30. As a result, printing by the conductive ink in which quality variation due to the deposition of the conductive particles in the pipes is easily generated can be suitably executed.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Inkjet printing may be used to form conductive patterns of electronic components. This inkjet ink (conductive ink) for printing conductive patterns is prepared by mixing a liquid medium and 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] Also, a general inkjet device includes an inkjet head that discharges ink, a tank that stores ink, and a supply line that supplies ink from the tank to the inkjet head. In this type of inkjet device, a circulation line for circulating ink may be formed so as to pass through the inkjet head. Thereby, clogging of the inkjet head can be suppressed. An example of an inkjet device provided with this type of circulation line is disclosed in Patent Document 2.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In recent years, the formation of conductive patterns using inkjet printing has become increasingly popular, and there is a growing demand for inkjet devices optimized for printing conductive inks. The technology disclosed herein was developed to meet this demand and aims to provide an inkjet device suitable for printing conductive inks. [Means for solving the problem]

[0006] To achieve the above objectives, an inkjet apparatus for conductive inks (hereinafter also simply referred to as the "inkjet apparatus") disclosed herein is provided.

[0007] The conductive inkjet apparatus disclosed herein prints conductive ink onto a predetermined printing surface. The inkjet apparatus comprises an inkjet head for ejecting conductive ink, a main tank for storing conductive ink, a circulation line for circulating the conductive ink through the inkjet head, and a supply line for supplying conductive ink from the main tank to the circulation line. The liquid supply pipe constituting the circulation line is inclined in the vertical direction.

[0008] The inventors of this invention investigated means to suppress the precipitation and accumulation of conductive particles when realizing an inkjet device optimized for printing conductive inks. Specifically, conductive particles in conductive inks have a higher specific gravity than pigments (such as Zr-containing particles) in general coating inks. Therefore, conductive particles may settle in the liquid delivery pipes of the inkjet device's circulation line. If this inkjet device is used for a long period of time, conductive particles will accumulate (adhere) in the liquid delivery pipes of the circulation line. When a large amount of conductive particles accumulated in these liquid delivery pipes are mixed back into the ink, the concentration of conductive particles in the conductive ink at the time of ejection increases rapidly. This accumulation of conductive particles in the liquid delivery pipes can cause variations in the quality of manufactured electronic components. In contrast, the inkjet device disclosed herein has a circulation line composed of liquid delivery pipes that are inclined vertically. In other words, the circulation line of the inkjet device disclosed herein is configured so that there are no liquid delivery pipes extending horizontally. This suppresses the accumulation of conductive particles in the liquid delivery pipes of the circulation line. In other words, the inkjet apparatus disclosed herein can print conductive ink with stable quality.

[0009] In a preferred embodiment of the inkjet apparatus disclosed herein, the circulation line comprises a first sub-tank located downstream of the inkjet head, a second sub-tank located upstream of the inkjet head, a circulation pump that draws conductive ink from the first sub-tank and discharges the conductive ink toward the second sub-tank, a first liquid supply pipe connecting the inkjet head and the first sub-tank, a second liquid supply pipe connecting the first sub-tank and the circulation pump, a third liquid supply pipe connecting the circulation pump and the second sub-tank, and a fourth liquid supply pipe connecting the second sub-tank and the inkjet head. Each of the first, second, third, and fourth liquid supply pipes is inclined in the vertical direction. This allows for more effective suppression of the accumulation of conductive particles within the liquid supply pipes of the circulation line.

[0010] Furthermore, in a preferred embodiment of the inkjet apparatus disclosed herein, the first and second liquid delivery tubes are inclined at an angle of inclination of 55° or less with respect to the vertical. The first and second liquid delivery tubes are suction tubes through which conductive ink is drawn by a circulation pump. In such suction tubes, the accumulation of conductive particles can be significantly reduced by setting the inclination angle to 55° or less.

[0011] Furthermore, in a preferred embodiment of the inkjet apparatus disclosed herein, the third and fourth liquid delivery pipes are inclined at an angle of inclination of 70° or less with respect to the vertical. The third and fourth liquid delivery pipes are discharge pipes through which conductive ink is discharged from a circulation pump. In such discharge pipes, the accumulation of conductive particles can be significantly reduced by setting the inclination angle to 70° or less.

[0012] Furthermore, in a preferred embodiment of the inkjet apparatus disclosed herein, the liquid delivery pipe constituting the supply line is inclined in the vertical direction. This suppresses the deposition of conductive particles in the supply line, thereby more effectively preventing variations in the quality of electronic components after manufacturing.

[0013] Furthermore, in a preferred embodiment of the inkjet apparatus disclosed herein, the supply line comprises a supply pump that draws conductive ink from a main tank and discharges the conductive ink toward a circulation line, a fifth liquid delivery pipe connecting the main tank and the supply pump, and a sixth liquid delivery pipe connecting the supply pump and the circulation line. The fifth and sixth liquid delivery pipes are inclined vertically. This allows for more effective suppression of the accumulation of conductive particles within the liquid delivery pipes of the supply line.

[0014] Furthermore, in a preferred embodiment of the inkjet apparatus disclosed herein, the conductive ink contains at least one conductive particle selected from the group consisting of W particles, Ag particles, Ni particles, Au particles, Pt particles, Pd particles, and Rh particles. These conductive particles are widely used for forming conductive patterns in electronic components, while also having the characteristic of being prone to precipitation in conductive inks. For this reason, the inkjet apparatus disclosed herein is particularly suitable for printing conductive inks containing the above-mentioned conductive particles.

[0015] Furthermore, in a preferred embodiment of the inkjet apparatus disclosed herein, the apparatus comprises a carriage housing an inkjet head and a drive mechanism for moving the carriage relative to the printing object, the carriage further housing a main tank, a circulation line, and a supply line. With this configuration, the inclination angle of the liquid supply pipe can be maintained even when the inkjet head is moved, thereby allowing the deposition suppression effect of the disclosed technology to be exhibited more appropriately. [Brief explanation of the drawing]

[0016] [Figure 1] This is a conceptual diagram schematically showing an inkjet apparatus according to one embodiment. [Figure 2] This is a schematic cross-sectional view showing the inkjet head in Figure 1. [Figure 3] This is a schematic plan view showing an inkjet apparatus according to one embodiment. [Figure 4] This is a conceptual diagram schematically showing the test equipment used in the example test. [Figure 5] This graph shows the relationship between the tilt angle and the amount of remaining ink in the test example. [Modes for carrying out the invention]

[0017] Hereinafter, embodiments of the technology disclosed herein will be described with reference to the drawings. However, the following description is not intended to limit the technology disclosed herein to the embodiments described later. Matters other than those specifically mentioned in this specification and necessary for the implementation of the technology disclosed herein (such as the manufacturing method of each member) can be grasped as the design matters of those skilled in the art based on the prior art in the relevant field. The technology disclosed herein can be implemented based on the content disclosed in this specification and the common technical knowledge in the relevant field. Also, in the following description and drawings, members and parts having the same function are denoted by the same reference numerals, and duplicate descriptions may be omitted or simplified. In addition, the dimensional relationships (length, width, thickness, etc.) in each figure do not necessarily accurately reflect the actual dimensional relationships.

[0018] [Inkjet device] FIG. 1 is a conceptual diagram schematically showing the inkjet device according to this embodiment. FIG. 2 is a cross-sectional view schematically showing the inkjet head in FIG. 1. FIG. 3 is a plan view schematically showing the inkjet device according to this embodiment. In the figures, reference symbol X indicates the "width direction", reference symbol Y indicates the "depth direction", and reference symbol Z indicates the "height direction (vertical direction)". Also, the arrow F in FIG. 1 indicates the liquid feeding direction of the conductive ink.

[0019] The inkjet device 1 according to this embodiment prints the conductive ink A on a predetermined printing target. As shown in FIG. 1, this inkjet device 1 includes an inkjet head 10, a main tank 20, a circulation line 30, and a supply line 40. Hereinafter, each component will be described.

[0020] 1. Inkjet head The inkjet head 10 is a member that discharges the conductive ink A. As an example of an inkjet head, a piezo-type inkjet head 10 as shown in FIG. 2 can be cited. Inside the case 12 of this inkjet head 10, a retention part 13 for retaining the conductive ink A is provided. And this retention part 13 communicates with the discharge part 16 via the liquid supply path 15. Further, the discharge part 16 is provided with a discharge port 17 opened to the outside of the case 12 and a piezo element 18 facing the discharge port 17. In the inkjet head 10 having such a configuration, when the piezo element 18 vibrates, the conductive ink A in the discharge part 16 is discharged to the outside from the discharge port 17. Although not shown in FIG. 2, the circulation line 30 (the first liquid supply pipe 31 and the fourth liquid supply pipe 34) shown in FIG. 1 is connected to the retention part 13 of this inkjet head 10. Also, as shown in FIG. 1, the inkjet head 10 is arranged below the other members (the first sub-tank 35, the second sub-tank 36, the circulation pump 37, etc.) in the vertical direction Z.

[0021] 2. Main Tank The main tank 20 is a member that stores the conductive ink A. The structure of the main tank 20 is not particularly limited, and a conventionally known 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 about 100 ml to 2000 ml (preferably 500 ml to 1000 ml). Also, it is preferable that the main tank 20 is provided with a stirrer for stirring the internal conductive ink. Thereby, precipitation of the conductive particles in the main tank can be suppressed.

[0022] The conductive ink A in the main tank 20 is prepared by dispersing conductive particles in a liquid medium. Here, "conductive particles" as used herein refer to conductive metal particles. Such conductive particles become the main components of the conductive pattern (conductive film) after printing. The type of conductive particles is not particularly limited, and a wide variety of metal particles can be used. Examples of such 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 need to be particles consisting of only one metal element (single element 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. On the other hand, these conductive particles have a high specific gravity of 8.5 or more (typically 10 or more), and therefore tend to precipitate particularly easily in conductive inks. However, the inkjet apparatus 1 according to this embodiment can suppress the accumulation of conductive particles in the liquid delivery pipe of the circulation line 30, even when conductive particles that tend to precipitate are used. In other words, the inkjet apparatus 1 according to this embodiment can be used particularly suitably for printing conductive inks containing the above-mentioned conductive particles.

[0023] Furthermore, the content of conductive particles relative to the total weight of conductive ink A 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 electronic component after manufacturing, conductive ink A containing such a high concentration of conductive particles may be used. Such a high-concentration ink is particularly prone to precipitate of conductive particles, thus allowing the deposition suppression effect of the inkjet apparatus 1 according to this embodiment to be exhibited more favorably. The upper limit of the conductive particle content is not particularly limited and may be 95 wt% or less, or 90 wt% or less.

[0024] Furthermore, the viscosity of the conductive ink A 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 ink A has excellent ejection properties from the inkjet head 10, but it also has the characteristic that conductive particles tend to settle. However, according to the inkjet apparatus 1 of this embodiment, even when using low-viscosity conductive ink A, the accumulation of conductive particles in the liquid delivery pipe of the circulation line 30 can be suppressed. 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.

[0025] 3. Circulation line The circulation line 30 is a liquid delivery path that circulates conductive ink A so that it passes through the inkjet head 10. In this embodiment, the inkjet apparatus 1 is configured so that conductive ink A circulates within the circulation line 30 when conductive ink A is not being ejected (printed). This suppresses clogging due to solidification of conductive ink A. Furthermore, circulating conductive ink A also suppresses the precipitation of conductive particles.

[0026] In this embodiment of the inkjet apparatus 1, the liquid delivery pipes 31-34 constituting the circulation line 30 are inclined in the vertical direction Z. In other words, the circulation line 30 in this embodiment is configured so that there are no liquid delivery pipes extending along the horizontal direction (width direction X or depth direction Y). As a result, even if the precipitation of conductive particles occurs, the conductive particles slide down along the inclined liquid delivery pipes 31-34, thus suppressing the accumulation of conductive particles within the liquid delivery pipes 31-34.

[0027] The circulation line 30 shown in Figure 1 comprises a first sub-tank 35, a second sub-tank 36, a circulation pump 37, a first liquid delivery pipe 31, a second liquid delivery pipe 32, a third liquid delivery pipe 33, and a fourth liquid delivery pipe 34. The structure of the circulation line 30 will be described below, followed by a detailed explanation of the deposition suppression effect of the inkjet apparatus 1 according to this embodiment.

[0028] (1) Sub-tank No. 1 The first sub-tank 35 is a tank located downstream of the inkjet head 10 in the liquid delivery direction F. That is, conductive ink A that is not ejected by the inkjet head 10 is recovered in the first sub-tank 35. The first sub-tank 35 is also located above the inkjet head 10. Similar to the main tank 20, the structure of the first sub-tank 35 is not particularly limited, and conventionally known ink tanks can be used without any particular restrictions. The capacity of the first sub-tank 35 is, for example, about 10 ml to 100 ml (preferably 20 ml to 50 ml).

[0029] A first liquid supply pipe 31 is connected to the bottom 35a of the first sub-tank 35. A second liquid supply pipe 32 is inserted into the interior of the first sub-tank 35. The lower end of this second liquid supply pipe 32 extends to the vicinity of the bottom 35a of the first sub-tank 35. The bottom 35a of the first sub-tank 35 has a sloped surface that descends towards the connection point with the first liquid supply pipe 31. This suppresses the accumulation of conductive particles on the bottom 35a of the first sub-tank 35. Furthermore, a first depressurization mechanism 35c is attached to the upper part 35b of the first sub-tank 35 in this embodiment. This first depressurization mechanism 35c sucks air from inside the first sub-tank 35, creating a negative pressure state inside the first sub-tank 35. Although not shown in the figures, a first sensor for detecting the amount of ink in the tank is attached to the first sub-tank 35.

[0030] (2) Second sub-tank The second sub-tank 36 is a tank positioned upstream of the inkjet head 10 in the liquid delivery direction F. Furthermore, the second sub-tank 36 is positioned above the inkjet head 10. Similar to the main tank 20 and the first sub-tank 35, the second sub-tank 36 can use any conventionally known ink tank without particular restriction. The capacity of the second sub-tank 36 is, for example, approximately 10 ml to 100 ml (preferably 20 ml to 50 ml).

[0031] Furthermore, a fourth liquid supply pipe 34 is connected to the bottom 36a of the second sub-tank 36. A third liquid supply pipe 33 is connected to the upper part 36b of the second sub-tank 36. The bottom 36a of the second sub-tank 36 has a sloping surface that descends towards the connection point with the fourth liquid supply pipe 34. This suppresses the accumulation of conductive particles on the bottom 36a of the second sub-tank 36. In addition, a second depressurization mechanism 36c is attached to the upper part 36b of the second sub-tank 36 in this embodiment. This second depressurization mechanism 35c sucks air from inside the second sub-tank 36, creating a negative pressure state inside the second sub-tank 36. Although not shown in the figures, a second sensor for detecting the amount of ink in the tank is attached to the second sub-tank 36.

[0032] (3) Circulation pump The circulation pump 37 is positioned between the first sub-tank 35 and the second sub-tank 36 in the liquid delivery direction F. The circulation pump 37 draws conductive ink from the first sub-tank 35 and discharges the conductive ink toward the second sub-tank 36. In this embodiment, the circulation pump 37 is positioned above the first sub-tank 35 and the second sub-tank 36. That is, the circulation pump 37 draws conductive ink upward in the vertical direction Z and then discharges the conductive ink downward. The structure of the circulation pump 37 is not particularly limited, and any ink discharge pump that can be used in conventionally known inkjet devices can be used without any particular restriction. An example of this circulation pump 37 is a diaphragm pump. The liquid delivery rate by the circulation pump 37 is preferably about 5 ml / min to 100 ml / min (preferably 30 ml / min to 50 ml / min). This can more effectively suppress the precipitation of conductive particles in the circulation line 30.

[0033] (4) Liquid delivery pipe As shown in Figure 1, the circulation line 30 in this embodiment is equipped with four liquid supply pipes: the first liquid supply pipe 31 to the fourth liquid supply pipe 34. Specifically, the first liquid supply pipe 31 is a pipe that connects the inkjet head 10 to the first sub-tank 35. The second liquid supply pipe 32 is a pipe that connects the first sub-tank 35 to the circulation pump 37. As described above, this second liquid supply pipe 32 is inserted into the first sub-tank 35 and extends to the vicinity of the bottom 35a of the first sub-tank 35. The third liquid supply pipe 33 is a pipe that connects the circulation pump 37 to the second sub-tank 35. The fourth liquid supply pipe 34 is a pipe that connects the second sub-tank 35 to the inkjet head 10. In other words, the first liquid supply pipe 31 to the fourth liquid supply pipe 34 construct the circulation line 30 by connecting the inkjet head 10 to the first sub-tank 35, the circulation pump 37, and the second sub-tank 35, respectively. The diameter (inner diameter) of each liquid delivery pipe is preferably around 2 mm to 10 mm (preferably 4 mm to 6 mm). This ensures a sufficient volume of conductive ink is delivered.

[0034] (5) Ink circulation Next, the circulation of conductive ink A in the inkjet device 1 according to this embodiment will be described. First, in this inkjet device 1, the first depressurization mechanism 35c and the second depressurization mechanism 35c are operated to reduce the internal pressure of the first sub-tank 35 and the second sub-tank 36, respectively. At this time, in the inkjet device 1 according to this embodiment, the internal pressure of each tank is adjusted so that the first sub-tank 35 is at a lower pressure (negative pressure) than the second sub-tank 36. As a result, conductive ink A is supplied in the order of the second sub-tank 36, the fourth supply pipe 34, the inkjet head 10, the first supply pipe 31, and the first sub-tank 35, as shown in the liquid supply direction F in Figure 1. As a result, conductive ink A can be ejected from the inkjet head 10, and unused conductive ink A can be stored in the first sub-tank 35. On the other hand, if the supply of liquid from the second sub-tank 36 to the first sub-tank 35 continues, the amount of ink in the second sub-tank 36 will decrease. In contrast, in the inkjet device 1 according to this embodiment, the circulation pump 37 is activated when the amount of ink in the second sub-tank 36 falls below a predetermined amount. As a result, conductive ink A is supplied in the order of first sub-tank 35, second liquid supply pipe 32, circulation pump 37, third liquid supply pipe 33, and second sub-tank 36. As a result, the amount of ink in the second sub-tank 36 increases, so that conductive ink A can be stably supplied to the inkjet head 10. As described above, in the inkjet device 1 according to this embodiment, conductive ink A is circulated in a circulation line 30 having two sub-tanks. This makes it possible to suppress pulsation of the ink supplied to the inkjet head 10 with a relatively simple structure.

[0035] In this embodiment of the inkjet apparatus 1, the first liquid supply pipe 31, the second liquid supply pipe 32, the third liquid supply pipe 33, and the fourth liquid supply pipe 34 are each inclined toward the vertical direction Z. This suppresses the accumulation of conductive particles in the liquid supply pipes of the circulation line 30 while the conductive ink A described above is being circulated. For example, if a precipitate of conductive particles occurs inside the first liquid supply pipe 31, the precipitated conductive particles slide down into the inkjet head 10 along the first liquid supply pipe 31, which is inclined at a predetermined inclination angle θ1. Since the inkjet head 10 periodically ejects conductive ink A to perform printing, accumulation of conductive particles is unlikely to occur. Similarly, in the fourth liquid supply pipe 34, the precipitated conductive particles slide down into the inkjet head 10, thus suppressing the accumulation of conductive particles in the liquid supply pipe. On the other hand, if a precipitate of conductive particles occurs in the second liquid supply pipe 32 or the third liquid supply pipe 33, the conductive particles slide down into the sub-tanks (first sub-tank 35, second sub-tank 36). In this sub-tank, stirring occurs due to the circulation of the conductive ink A as described above, making it difficult for conductive particles to settle or accumulate. As described above, the inkjet apparatus 1 according to this embodiment can suppress the accumulation (adhesion) of conductive particles in the circulation line 30.

[0036] Furthermore, it is preferable to set the inclination angles θ1 to θ4 of each liquid delivery pipe 31 to 34 taking into consideration the liquid delivery direction F of the conductive ink A. Specifically, it is preferable to set the inclination angle θ1 of the first liquid delivery pipe 31 and the inclination angle θ2 of the second liquid delivery pipe 32 to 55° or less (more preferably 50° or less, and particularly preferably 45° or less) with respect to the vertical direction Z. These first liquid delivery pipe 31 and second liquid delivery pipe 32 are liquid delivery pipes (suction pipes) through which the conductive ink A is drawn in by the circulation pump 37. Experiments have confirmed that the accumulation of conductive particles can be significantly reduced in these suction pipes by setting the inclination angle to 55° or less. Although it is not intended to limit the technology disclosed herein, it is presumed that the reason for this effect is that in the suction pipe, a flow occurs in which the ink is drawn up in the vertical direction Z, and therefore an inclination close to the vertical direction Z (0°) is necessary to allow the conductive particles to slide off. Furthermore, the lower limits of the inclination angle θ1 of the first liquid delivery pipe 31 and the inclination angle θ2 of the second liquid delivery pipe 32 are not particularly limited and may be 0° or greater, 1° or greater, 5° or greater, or 10° or greater.

[0037] On the other hand, the inclination angle θ3 of the third liquid delivery pipe 33 and the inclination angle θ4 of the fourth liquid delivery pipe 34 are preferably 70° or less (more preferably 65° or less) with respect to the vertical direction Z. The third liquid delivery pipe 33 and the fourth liquid delivery pipe 34 are delivery pipes (discharge pipes) through which conductive ink A is discharged from the circulation pump 37. Experiments have confirmed that the accumulation of conductive particles can be significantly reduced in these discharge pipes by setting the inclination angle to 70° or less. Although not intended to limit the technology disclosed herein, it is presumed that this effect occurs because, in the discharge pipes, the ink is pumped downwards in the vertical direction Z, so conductive particles slide down sufficiently even with an inclination close to the horizontal direction (90°). The lower limits of the inclination angle θ3 of the third liquid delivery pipe 33 and the inclination angle θ4 of the fourth liquid delivery pipe 34 are not particularly limited and may be 0° or more, 1° or more, 5° or more, or 10° or more.

[0038] 4. Supply Line The supply line 40 is a liquid supply line that supplies conductive ink A from the main tank 20 to the circulation line 30. In the inkjet apparatus 1 according to this embodiment, when the amount of conductive ink A in the circulation line 30 decreases due to continuous printing, conductive ink A is supplied from the main tank 20 to the circulation line 30 via the supply line 40.

[0039] Furthermore, in the inkjet apparatus 1 according to this embodiment, the liquid delivery pipes 45-46 constituting the supply line 40 are also inclined toward the vertical direction Z. In other words, the supply line 40 in this embodiment is configured so that there are no liquid delivery pipes 45-46 extending along the horizontal direction (width direction X or depth direction Y). This suppresses the accumulation of settled conductive particles within the supply line 40, thereby more effectively preventing variations in the quality of electronic components after manufacturing.

[0040] The supply line 40 shown in Figure 1 includes a supply pump 42, a fifth liquid delivery pipe 45, and a sixth liquid delivery pipe 46. The detailed structure of the supply line 40 will be described below.

[0041] (1) Supply pump The supply pump 42 is a pump installed between the main tank 20 and the circulation line 30. This supply pump 42 draws conductive ink A from the main tank 20 and discharges the conductive ink A toward the circulation line 30. The supply pump 42 is positioned vertically Z above the connection point (first sub-tank 35) to the main tank 20 and the circulation line 30. The supply pump 42 can be any conventionally known ink discharge pump (e.g., a diaphragm pump) without any particular limitations. The specific liquid flow rate from the supply pump 42 is preferably around 5 ml / min to 100 ml / min (preferably 30 ml / min to 50 ml / min).

[0042] (2) Liquid delivery pipe As shown in Figure 1, the supply line 40 in this embodiment is equipped with two liquid supply pipes: a fifth liquid supply pipe 45 and a sixth liquid supply pipe 46. Specifically, the fifth liquid supply pipe 45 is a pipe that connects the main tank 20 and the supply pump 42. The fifth liquid supply pipe 45 is inserted inside the main tank 20, and its lower end extends to near the bottom of the main tank 20. The sixth liquid supply pipe 46 is a pipe that connects the supply pump 42 and the circulation line 30. The sixth liquid supply pipe 46 shown in Figure 1 is connected to the upper part 35b of the first sub-tank 35. The pipe diameter (inner diameter) of each liquid supply pipe 45 to 46 is preferably about 2 mm to 10 mm (preferably 4 mm to 6 mm). This allows a sufficient amount of conductive ink to be easily supplied to the circulation line 30.

[0043] (3) Ink supply Next, the supply of ink to the circulation line 30 in the inkjet device 1 according to this embodiment will be described. First, as described above, in this inkjet device 1, a portion of the conductive ink A circulating in the circulation line 30 is ejected from the inkjet head 10. If this ink ejection continues, the total amount of ink in the circulation line 30 will decrease. In response to this, in the inkjet device 1 according to this embodiment, the supply pump 42 is activated when the amount of ink in the first sub-tank 35 falls below a predetermined amount. As a result, conductive ink A is supplied in the following order: main tank 20, fifth liquid supply pipe 45, supply pump 42, sixth liquid supply pipe 46, and first sub-tank 35. As a result, the total amount of ink in the circulation line 30 can be maintained at an appropriate level.

[0044] Here, it is preferable to set the inclination angles θ5 to θ6 of the liquid delivery pipes 45 to 46 of the supply line 40 taking into consideration the direction of liquid delivery of the conductive ink. For example, the fifth liquid delivery pipe 45 is a suction pipe through which conductive ink A is drawn up toward the supply pump 42 located above in the vertical direction Z. For this reason, it is preferable to set the inclination angle θ5 of the fifth liquid delivery pipe 45 to 55° or less (more preferably 50° or less, and particularly preferably 45° or less) with respect to the vertical direction Z. On the other hand, the sixth liquid delivery pipe 46 is a discharge pipe through which conductive ink A is discharged downward from the supply pump 42. For this reason, it is preferable to set the inclination angle θ6 of the sixth liquid delivery pipe 46 to 70° or less (more preferably 65° or less) with respect to the vertical direction Z. Furthermore, the lower limits of the inclination angles θ5 of the fifth liquid delivery pipe 45 and θ6 of the sixth liquid delivery pipe 46 are not particularly limited and may be 0° or more, 1° or more, 5° or more, or 10° or more.

[0045] 5. Carriage Furthermore, the inkjet device 1 according to this embodiment includes a carriage 50 that houses the inkjet head 10. As shown in Figure 3, this carriage 50 is connected to a drive mechanism 60 that moves the carriage 50 relative to the printing target W. This drive mechanism 60 includes a guide shaft 62 that extends along the width direction X and an X-axis moving means (not shown) that reciprocates the carriage 50 along the guide shaft 62. In addition, the inkjet device 1 according to this embodiment also includes a Y-axis moving means (not shown) that moves the printing target W in the depth direction Y relative to the guide shaft 62. As a result, the inkjet head 10 can be positioned at any position on the printing target W, so that a conductive pattern of a desired shape can be printed on the surface of the printing target W.

[0046] Furthermore, as shown in Figure 1, in the inkjet apparatus 1 according to this embodiment, in addition to the inkjet head 10, the main tank 20, circulation line 30, and supply line 30 are each housed in the carriage 50. With this configuration, the inclination angle of the liquid supply pipe can be maintained even when the inkjet head 10 is moved for printing conductive patterns, so the deposition suppression effect of the technology disclosed herein can be exhibited more appropriately. In addition, since the supply path from the main tank 20 to the inkjet head 10 is shortened, the deposition of conductive particles may be less likely to occur.

[0047] [Other embodiments] The above describes an inkjet apparatus according to one embodiment of the technology disclosed herein. It should be noted that the above-described embodiment is not intended to limit the technology disclosed herein. That is, in the technology disclosed herein, various configurations can be modified from the inkjet apparatus 1 according to the above-described embodiment.

[0048] For example, in the above-described embodiment, the inkjet head 10, main tank 20, circulation line 30, and supply line 30 are each housed in the carriage 50. However, the technology disclosed herein is not limited to the above configuration and can also be applied to an inkjet device in which only the inkjet head is housed in the carriage. In this case, the drive mechanism is attached to the base for fixing the object to be printed, and the carriage housing the inkjet head is fixed to it. This makes it possible to move the inkjet head and the object to be printed relatively without moving the carriage, thereby printing the desired conductive pattern. Furthermore, when such a configuration is adopted, even if the circulation line and the like are placed outside the carriage, it is possible to prevent the inclination angle of the liquid supply pipe from changing during printing.

[0049] Furthermore, the specific structure of the circulation line is not limited to the embodiments described above. For example, one or both of the pair of sub-tanks may be omitted. Even in this case, if the liquid delivery pipe is inclined vertically, the conductive ink can be circulated while suppressing the accumulation of conductive particles. In addition, the circulation line can be fitted with conventionally known components that can be attached to the ink circulation line without particular limitations, as long as they do not significantly hinder the accumulation suppression effect of the technology disclosed herein. Examples of components that can be attached to the circulation line include check valves, bypass piping, filters, and degassing modules. When liquid delivery pipes such as bypass piping are added, it is preferable to also inclin the liquid delivery pipes vertically. This allows for more effective suppression of conductive particle accumulation.

[0050] Furthermore, it is preferable that the inkjet head is configured to periodically eject conductive ink when not printing on a surface. This more effectively prevents the accumulation of conductive particles inside the inkjet head. When using an inkjet head that periodically ejects ink, it is preferable that the inkjet device includes a waste liquid recovery unit for recovering ink ejected for purposes other than printing. This waste liquid recovery unit may include, for example, a tray for receiving ink ejected from the inkjet head and a waste liquid tank for storing the ink received in the tray. This helps to keep the area around the inkjet device clean.

[0051] [Example Test] The following describes examples of tests relating to the technology disclosed herein. These examples are preliminary tests conducted as a preliminary step before creating the technology disclosed herein, and are not intended to limit the scope of the technology disclosed herein.

[0052] 1. Preparing the ink In this test, a conductive ink was prepared by mixing conductive particles, an organic solvent, a binder resin, and a dispersant. Specifically, a conductive ink containing 60 wt% conductive particles (tungsten particles with an average particle size of 200-300 nm) was prepared. Methyl benzoate was used as the organic solvent. Polyvinyl acetal resin (manufactured by Sekisui Chemical Co., Ltd., model: BL-S) was used as the binder resin. A cationic dispersant (manufactured by Croda Japan Co., Ltd., model: Hypermer KD-1) was used as the dispersant. The viscosity of the prepared conductive ink at 25°C was 10 cP.

[0053] 2. Configuration of the test apparatus In this test, a preliminary test apparatus 100, as shown in Figure 4, was constructed. This preliminary test apparatus 100 comprises a first tank 110, a suction pipe 120, a pump 130, a discharge pipe 140, and a second tank 150. As shown in the liquid delivery direction F in Figure 4, this preliminary test apparatus 100 is configured to draw conductive ink A from the first tank 110 towards the pump 130 and discharge the conductive ink towards the second tank 150. In this test, the inclination angle θα of the suction pipe 120 and the inclination angle θβ of the discharge pipe 140 were each changed within the range of 0° to 90°, and 100 ml of conductive ink A was delivered from the first tank 110 to the second tank 150 each time the inclination angle was changed. After each delivery, the preliminary test apparatus 100 was disassembled, and the amount of ink remaining in the liquid delivery pipe was measured. The measurement results are shown in Figure 5.

[0054] As shown in Figure 5, in both the suction pipe 120 (θα) and the discharge pipe 140 (θβ), a tendency was observed for the amount of ink remaining to decrease as the liquid delivery pipe was tilted from the horizontal to the vertical (decreasing from 90°). From this, it can be expected that even when constructing an actual inkjet device, tilting the liquid delivery pipe vertically will suppress the retention (accumulation) of conductive particles in the liquid delivery pipe. Furthermore, as shown in Figure 5, in the suction pipe 120, the amount of ink remaining decreased significantly when the tilt angle θα was 55° or less. Also, in the discharge pipe 140, the amount of ink remaining decreased significantly when the tilt angle θβ was 70° or less.

[0055] The technologies disclosed herein have been described in detail above, but these are merely illustrative examples and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. In other words, the technologies disclosed herein encompass the forms described in items 1 to 7 below.

[0056] <Item 1> A conductive inkjet device for printing conductive ink onto 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 the conductive ink so that it passes through the inkjet head, A supply line that supplies the conductive ink from the main tank to the circulation line. Equipped with, The liquid supply pipe constituting the circulation line is inclined vertically in an inkjet device for conductive ink.

[0057] <Item 2> The aforementioned circulation line is, A first sub-tank is located downstream of the inkjet head, A second sub-tank is located upstream of the aforementioned inkjet head, A circulation pump that draws the conductive ink from the first sub-tank and discharges the conductive ink toward the second sub-tank, A first liquid supply pipe connecting the inkjet head and the first sub-tank, A second liquid supply pipe connecting the first sub-tank and the circulation pump, A third liquid supply pipe connecting the circulation pump and the second sub-tank, A fourth liquid supply pipe connecting the second sub-tank and the inkjet head, It is equipped with, The conductive inkjet apparatus according to item 1, wherein each of the first liquid delivery tube, the second liquid delivery tube, the third liquid delivery tube, and the fourth liquid delivery tube is inclined in the vertical direction.

[0058] <Item 3> The inkjet apparatus for conductive ink according to item 2, wherein the first liquid delivery pipe and the second liquid delivery pipe are inclined at an angle of inclination of 55° or less with respect to the vertical direction.

[0059] <Item 4> The inkjet apparatus for conductive ink according to item 2 or 3, wherein the third liquid delivery pipe and the fourth liquid delivery pipe are inclined at an angle of inclination of 70° or less with respect to the vertical direction.

[0060] <Item 5> The inkjet apparatus for conductive ink according to any one of items 1 to 4, wherein the liquid supply pipe constituting the supply line is inclined in the vertical direction.

[0061] <Item 6> The aforementioned supply line is A supply pump that draws the conductive ink from the main tank and discharges the conductive ink toward the circulation line, A fifth liquid supply pipe connecting the main tank and the supply pump, A sixth liquid supply pipe connecting the supply pump and the circulation line. It is equipped with, An inkjet apparatus for conductive ink according to any one of items 1 to 5, wherein the fifth liquid delivery tube and the sixth liquid delivery tube are each inclined in the vertical direction.

[0062] <Item 7> The conductive ink comprising at least one conductive particle selected from the group consisting of W particles, Ag particles, Ni particles, Au particles, Pt particles, Pd particles, and Rh particles, is an inkjet apparatus for conductive ink according to any one of items 1 to 6.

[0063] <Item 8> A carriage for housing the aforementioned inkjet head, A drive mechanism for moving the carriage relative to the printing target, Equipped with, The inkjet apparatus for conductive ink according to any one of items 1 to 7, wherein the carriage further houses the main tank, the circulation line, and the supply line, respectively. [Explanation of Symbols]

[0064] 1. Inkjet device 10 inkjet heads 12 cases 13 Retention part 15. Liquid supply channel 16 Discharge part 17 Discharge port 18 Piezo elements 20 Main Tanks 30 Circulation Line 31. First liquid delivery pipe 32 Second liquid delivery pipe 33 Third liquid delivery pipe 34. Fourth liquid delivery pipe 35. First Sub-tank 36. Second Sub-tank 37 Circulation pump 40 supply lines 42 Supply pump 45 Fifth liquid delivery pipe 46. ​​No. 6 liquid delivery pipe 50 Carriage 60 Drive mechanism 62 Guide axis

Claims

1. A conductive inkjet device for printing conductive ink onto 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 the conductive ink so that it passes through the inkjet head, A supply line that supplies the conductive ink from the main tank to the circulation line. Equipped with, An inkjet device for conductive ink, wherein all liquid supply pipes constituting the circulation line are inclined in the vertical direction.

2. The aforementioned circulation line is, A first sub-tank is located downstream of the inkjet head, A second sub-tank is located upstream of the inkjet head, A circulation pump that draws the conductive ink from the first sub-tank and discharges the conductive ink toward the second sub-tank, A first liquid supply pipe connecting the inkjet head and the first sub-tank, A second liquid supply pipe connecting the first sub-tank and the circulation pump, A third liquid supply pipe connecting the circulation pump and the second sub-tank, A fourth liquid supply pipe connecting the second sub-tank and the inkjet head, It is equipped with, The inkjet apparatus for conductive ink according to claim 1, wherein each of the first liquid delivery pipe, the second liquid delivery pipe, the third liquid delivery pipe, and the fourth liquid delivery pipe is inclined in the vertical direction.

3. The inkjet apparatus for conductive ink according to claim 2, wherein the first liquid supply pipe and the second liquid supply pipe are inclined at an angle of inclination of 55° or less with respect to the vertical direction.

4. The inkjet apparatus for conductive ink according to claim 2, wherein the third liquid supply pipe and the fourth liquid supply pipe are inclined at an angle of inclination of 70° or less with respect to the vertical direction.

5. The inkjet apparatus for conductive ink according to claim 1 or 2, wherein the liquid supply pipe constituting the supply line is inclined in the vertical direction.

6. The aforementioned supply line is A supply pump that draws the conductive ink from the main tank and discharges the conductive ink toward the circulation line, A fifth liquid supply pipe connecting the main tank and the supply pump, A sixth liquid supply pipe connecting the supply pump and the circulation line. It is equipped with, The inkjet apparatus for conductive ink according to claim 5, wherein each of the fifth liquid delivery pipe and the sixth liquid delivery pipe is inclined in the vertical direction.

7. The conductive ink comprising at least one conductive particle selected from the group consisting of W particles, Ag particles, Ni particles, Au particles, Pt particles, Pd particles, and Rh particles, according to claim 1 or 2, an inkjet apparatus for conductive ink.

8. A carriage for housing the aforementioned inkjet head, A drive mechanism for moving the carriage relative to the printing target, Equipped with, The inkjet apparatus for conductive ink according to claim 1 or 2, wherein the carriage further accommodates the main tank, the circulation line, and the supply line, respectively.

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