A set of cleaning solution and rinsing solution, a cleaning method, and a liquid dispensing device.

Abstract

To provide a set of cleaning liquid and rinsing liquid which can easily remove adhering matter of inks having various types of composition such as a metallic film forming ink while preventing abrasives from remaining.SOLUTION: A set of cleaning liquid and rinsing liquid includes the cleaning liquid and the rinsing liquid. The cleaning liquid includes particles and liquid not dissolving the particles. The rinsing liquid includes liquid capable of dissolving the particles. Preferably, the set of cleaning liquid and rinsing liquid is for cleaning a flow path and a discharge port of a liquid discharge device, in a mode of a maximum particle diameter of the particles being 1 / 3 or less of an inner diameter of the discharge port or in a mode of the maximum particle diameter of the particles being 100 μm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a set of a cleaning liquid and a rinsing liquid, a cleaning method, and a liquid ejection device. [Background Art]

[0002] Development of technology for printing functional films on electronic devices and the like utilizing inkjet printing technology has been progressing. A typical example of the functional film is a metal film for electromagnetic wave shielding on the surface of an integrated circuit (IC) package.

[0003] In liquid conveyance using fine flow paths such as those in inkjet, deposits of ink materials lead to abnormal liquid conveyance and ejection failure, so cleaning is performed periodically or as needed when an abnormality occurs.

[0004] Conventionally, cleaning liquids that perform chemical cleaning have been reported as cleaning liquids after printing for inkjet heads using inks containing poorly water-soluble resins (see, for example, Patent Document 1). On the other hand, in inks for forming metal films, the binder is not an organic substance such as a resin, but is formed by bonding of the metal itself. Removing metal deposits may require an action different from that of methods for removing organic substances such as resins.

[0005] Although it is not for use after inkjet printing, as a method for manufacturing an inkjet recording head, when cutting ejection elements of the head to form ejection ports, a method has been reported in which a liquid mixed with an abrasive is pressurized from the ink flow path toward the ejection port via a liquid chamber, and the liquid mixed with the abrasive is sprayed from the ejection port when the ejection port is opened (see, for example, Patent Document 2). However, when such a technology is applied to a cleaning method, there are problems of clogging of flow paths by the abrasive and residual abrasive. [Summary of the Invention] [Problem to be Solved by the Invention]

[0006] The present invention aims to provide a set of cleaning solution and rinsing solution that can easily remove solidified inks of various compositions, such as metal film-forming inks, while preventing the residue of abrasive materials. [Means for solving the problem]

[0007] As a means for solving the aforementioned problems, the present invention provides a set of cleaning solution and rinsing solution comprising a cleaning solution and a rinsing solution, wherein the cleaning solution comprises particles and a liquid that does not dissolve the particles, and the rinsing solution comprises a liquid that can dissolve the particles. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a set of cleaning solution and rinsing solution that can easily remove solidified inks of various compositions, such as metal film-forming inks, and prevent the residue of abrasive materials. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is an external perspective view illustrating an example of a liquid dispensing head in the liquid dispensing device of this embodiment. [Figure 2] Figure 2 is a cross-sectional diagram illustrating the liquid discharge head shown in Figure 1, in a direction perpendicular to the nozzle arrangement direction. [Figure 3] Figure 3 is a schematic diagram showing an example of the liquid dispensing device of this embodiment. [Figure 4] Figure 4 is a schematic diagram showing an example of the liquid dispensing device of this embodiment. [Figure 5] Figure 5 is a schematic diagram showing an example of the liquid dispensing device of this embodiment. [Figure 6] Figure 6 is a schematic diagram showing an example of the liquid dispensing device of this embodiment. [Figure 7] Figure 7 is a schematic diagram showing the flow path and discharge port of the liquid discharge head shown in Figure 2, with solidified material adhering to them. [Figure 8A]Figure 8A is a schematic diagram (part 1) showing how the liquid discharge head shown in Figure 7 has its flow path and discharge port cleaned using the cleaning method of this embodiment. [Figure 8B] Figure 8B is a schematic diagram (part 2) showing how solidified material in the flow path and discharge port of the liquid discharge head shown in Figure 7 is cleaned using the cleaning method of this embodiment. [Figure 8C] Figure 8C is a schematic diagram (part 3) showing how the liquid discharge head shown in Figure 7 has its flow path and discharge port cleaned using the cleaning method of this embodiment. [Modes for carrying out the invention]

[0010] (Set includes cleaning solution and rinsing solution) The cleaning solution and rinsing solution set of the present invention comprises a cleaning solution and a rinsing solution, wherein the cleaning solution comprises particles and a liquid that does not dissolve the particles, and the rinsing solution comprises a liquid that can dissolve the particles, and may further include other liquids or other components as needed. The set of cleaning solution and rinsing solution is a set of cleaning solution and rinsing solution for cleaning the flow path and outlet of a liquid discharge device, and it is preferable that the maximum particle size is 1 / 3 or less of the inner diameter of the outlet. Furthermore, it is preferable that the set of the washing solution and rinsing solution has a maximum particle size of 100 μm or less. The cleaning solution and rinsing solution set of the present invention can be suitably used as a cleaning solution and rinsing solution set for cleaning the flow path and outlet of a liquid dispensing device.

[0011] <Cleaning solution> The cleaning solution comprises particles and a liquid that does not dissolve the particles, and may further contain other components as needed. It is preferable that the maximum particle size of the aforementioned particles satisfies at least one of the following conditions: 1 / 3 or less of the inner diameter of the discharge port, and 100 μm or less.

[0012] <<Particle>> The particles are not particularly limited as long as they are insoluble in the liquid and soluble in the rinsing liquid, and can be appropriately selected according to the purpose. Examples include NaCl, KCl, MgSO4, CaCO3, apatite (Ca 10 (PO4)6(OH)2) and other ionic crystals; molecular crystals such as sucrose; and the like. The particles function as an abrasive, and can peel and remove deposits adhered to flow paths and discharge ports of a liquid discharge apparatus through physical action caused by contact of the particles.

[0013] The maximum particle diameter of the particles is preferably 1 / 3 or less of the inner diameter of the discharge port, and more preferably 1 / 6 or more and 1 / 3 or less of the inner diameter of the discharge port. Further, when the inner diameter of the discharge port is small (for example, 30 µm inner diameter), the maximum particle diameter is preferably 10 µm or less. Specifically, when cleaning a liquid discharge apparatus having an inkjet head GEN5 series (manufactured by Ricoh Co., Ltd.) having discharge ports with a nozzle diameter of 26 µm, the maximum particle diameter is preferably 8.7 µm or less, more preferably 4.7 µm or more and 8.7 µm or less. Further, when cleaning a liquid discharge apparatus having discharge ports with an inner diameter of 200 µm, the maximum particle diameter is preferably 66.7 µm or less, more preferably 33.3 µm or more and 66.7 µm or less. Further, the maximum particle diameter of the particles can be appropriately selected according to the flow paths and discharge ports of the liquid discharge apparatus to be cleaned, and is preferably 100 µm or less, more preferably 80 µm or less, still more preferably 60 µm or less. When the inner diameter of the discharge port is small (for example, 30 µm or less inner diameter), the maximum particle diameter is preferably 10 µm or less. From the viewpoint of the efficiency of particle collision and contact, the lower limit of the maximum particle diameter of the particles is preferably 3 µm or more, more preferably 5 µm or more. By limiting the maximum particle diameter of the particles, clogging of flow paths or discharge ports of the liquid discharge apparatus can be prevented, and cleaning of the flow paths and discharge ports can be achieved by the physical action caused by particle collision and contact.

[0014] The maximum particle size of the particles can be controlled, for example, by performing filtration using a membrane filter having a predetermined pore diameter and using a cleaning solution from which particles having a particle diameter equal to or larger than the pore diameter have been removed. In this case, the cleaning solution before filtration may contain particles having a particle diameter larger than the maximum particle diameter.

[0015] There are no particular limitations on the average particle diameter of the particles, and it can be appropriately selected according to the flow path and the discharge port of the liquid discharge device to be cleaned, but it is preferably not less than 1 / 6 and not more than 1 / 3 of the inner diameter of the discharge port.

[0016] There are no particular limitations on the content of the particles, and it can be appropriately selected according to the purpose. From the viewpoint of the efficiency of peeling and removing adhered substances due to contact of the particles, the content is preferably 5% by volume or more and 30% by volume or less, and more preferably 10% by volume or more and 20% by volume or less.

[0017] There are no particular limitations on the upper limit of the Mohs hardness of the particles, and it can be appropriately selected according to the purpose, but it is preferably equal to or lower than the Mohs hardness of the main material in the flow path. Regarding the main material for the flow path, inkjet heads in which flow paths, liquid chambers, and discharge ports are formed by laminating stainless steel (SUS) or the like, and inkjet heads in which flow paths, liquid chambers, and discharge ports are formed by etching or the like using a silicon process are known. All stainless steels (SUS) such as SUS304, SUS316, and SUS430 have a Mohs hardness of 4, and silicon has a Mohs hardness of 7. Therefore, when the main material in the flow path is stainless steel, the Mohs hardness of the particles is preferably 4 or less, and when the main material in the flow path is silicon, the Mohs hardness of the particles is preferably 7 or less. This makes it possible to efficiently peel off and remove adhered substances fixed to the flow paths and discharge ports without polishing and damaging the main material in the flow paths.

[0018] Further, as the lower limit of the Mohs hardness of the particles, it is preferably equal to or higher than the Mohs hardness of the adhered substance fixed to the flow path. In the embodiments described later, when a metal film was formed on the deposits adhering to the aforementioned channel using a metal film-forming ink, the silver film formed with silver complex ink or silver nanoparticle dispersion ink both had a Mohs hardness of 2, while the copper film formed with copper complex ink or copper nanoparticle dispersion ink both had a Mohs hardness of 3. Metal films exhibiting conductivity close to that of bulk metal have a high purity of 99.9% or more, and it is thought that metal films with few impurities exhibit a Mohs hardness equivalent to that of bulk metal. Therefore, when the deposits adhering to the flow path are silver films, the Mohs hardness of the particles is preferably 2 or higher, and when the deposits adhering to the flow path are copper films, the Mohs hardness of the particles is preferably 3 or higher. This allows for efficient peeling and removal of deposits adhering to the flow path and discharge port.

[0019] Here, "Mohs hardness" is a measure of hardness that uses scratch resistance as an indicator, and can be used in the selection of the aforementioned particles. Mohs hardness can be measured using standard minerals corresponding to Mohs hardness levels 1 through 10, as shown in Table 1, following the procedure below. Specifically, when material A is rubbed against apatite (hardness 5), a standard mineral, if both are scratched, then material A has a Mohs hardness of 5. Similarly, if neither material A nor the apatite is scratched, the Mohs hardness of material A is also 5. Furthermore, if material B is rubbed against apatite and only material B is scratched, it indicates that material B is softer than apatite. Next, if material B is rubbed against fluorite (hardness 4), and only fluorite is scratched, it indicates that material B is harder than fluorite. In this case, material B has a hardness between fluorite (hardness 4) and apatite (hardness 5), resulting in a Mohs hardness of 4.5.

[0020] [Table 1]

[0021] <<Liquid that does not dissolve particles>> The liquid that does not dissolve the particles can be appropriately selected depending on the combination with the particles, and examples include water, methanol, ethanol, 1-butanol, 2-propanol, acetone, ethyl acetate, hexane, methyl ethyl ketone, and N-methyl-2-pyrrolidone. These may be used individually or in combination of two or more types.

[0022] Here, "does not dissolve particles" can be defined by the "degree of dissolution" based on the JIS K8001 General Rules for Reagent Testing Methods (item 3.2, see Table 1). Specifically, when a certain amount of solute is added to a solvent after being powdered if the sample is solid, and shaken vigorously for 30 seconds every 5 minutes at 20°C ± 5°C, the volume of solvent (mL) required to dissolve it within 30 minutes is defined. This means that the amount of solvent required to dissolve 1 g or 1 mL of solute is 1,000 mL or more but less than 10,000 mL (very poorly soluble), or 10,000 mL or more (almost insoluble). When converted to the solubility of particles (solute) per 100 mL of liquid (solvent) [g / 100 mL], the solubility is preferably 0.1 g / 100 mL or less (very poorly soluble or almost insoluble), more preferably 0.05 g / 100 mL or less, and even more preferably 0.01 g / 100 mL or less (almost insoluble).

[0023] <<Other ingredients>> Other components that can be applied include, for example, surfactants that do not dissolve particles but help remove adhered substances.

[0024] <rinse solution> The rinsing solution contains a liquid capable of dissolving the particles. This liquid can be appropriately selected depending on the combination with the particles, and examples include water, carbonated water, methanol, ethanol, 1-butanol, 2-propanol, and acetone. Among these, a liquid mainly composed of water is preferred, and water is preferred. These may be used individually or in combination of two or more types.

[0025] Here, "dissolvable of particles" can be defined by the "degree of solubility" based on the JIS K8001 General Rules for Reagent Testing Methods (item 3.2, see Table 1) mentioned above, and means that the amount of solvent required to dissolve 1 g or 1 mL of solute is 1 mL or more but less than 10 mL (easily soluble), or less than 1 mL (very easily soluble). When converted to the solubility of particles (solute) per 100 mL of liquid (solvent) [g / 100 mL], the solubility is preferably greater than 10 g / 100 mL (easily soluble or very soluble), more preferably 15 g / 100 mL or more, and even more preferably 20 g / 100 mL or more.

[0026] [Suitable combinations of particles, cleaning solution, and rinsing solution] There are no particular limitations on suitable combinations of particles, washing solution, and rinsing solution, and they can be appropriately selected based on the Mohs hardness relationships described above, the degree of particle dissolution, and other requirements. For example, when using sodium chloride (NaCl, Mohs hardness 2) as particles, a combination of ethanol (particle solubility 0.051 g / 100 mL) and 1-butanol (particle solubility 0.004 g / 100 mL) as the washing solution and water (particle solubility 35.9 g / 100 mL) as the rinsing solution is preferable. When using magnesium sulfide (MgSO4, Mohs hardness 2) as particles, a combination of ethanol (particle solubility 0.018 g / 100 mL) as the washing solution and water (particle solubility 26.9 g / 100 mL) as the rinsing solution is preferable.

[0027] When calcium carbonate (CaCO3, Mohs hardness 3) is used as the particle, it is special because it is insoluble in water. Therefore, water (particle solubility 0.015 g / 100 mL) is preferred as the washing solution. When carbonated water (particle solubility 16.6 g / 100 mL) is used as the rinsing solution, it changes as shown in Equation 1 and becomes water-soluble. (Formula 1) CaCO3 + H2O + CO2 → Ca(HCO3)2 In addition, the combinations shown in the examples in Tables 2-1 and 2-2 can be suitably used.

[0028] (Liquid discharge device) The liquid dispensing device of the present invention comprises the above-described set of cleaning liquid and rinsing liquid, a storage section for containing the liquid, a flow path through which the liquid can flow, and a liquid dispensing head having a discharge port for dispensing droplets made of the liquid, and further comprises other components as necessary. The liquid dispensing device is capable of distributing the cleaning solution and the rinsing solution as liquids. Preferably, the flow path is a flow path through which the liquid can circulate, and that the cleaning solution and the rinsing solution can each be circulated as the liquid. Furthermore, it is preferable that the liquid dispensing device further comprises a cleaning liquid container containing the cleaning liquid and a rinsing liquid container containing the rinsing liquid, and that each of the cleaning liquid container and the rinsing liquid container is detachable from the liquid dispensing device.

[0029] Liquid ejection devices such as inkjet printers are equipped with a recording head consisting of an ejection head that ejects ink droplets. While transporting the object to be coated, the ink droplets adhere to it, forming a film and creating an image. By ejecting droplets from numerous tiny pores called nozzles (also referred to as ejection ports) of such an ejection head, it is possible to form patterns on the object without contact. The discharge head is composed of a nozzle section with a fine orifice having an inner diameter of 10 μm to 200 μm, a pressure generating section connected to the nozzle section, a liquid chamber section that supplies liquid to the pressure generating section, and other components, and is formed with high precision. Each nozzle in a machine head can range from tens to thousands, and it is necessary to ensure that each nozzle is functioning correctly and that there are no dispensing problems (for example, no dispensing from the nozzle, dispensing in a direction not perpendicular to the nozzle surface, or dispensing droplets that do not form the desired size).

[0030] To perform such ejection failure tests, a detectable liquid is filled into the print head, and the malfunction is detected by having the print head eject the liquid. In addition, to prevent ink from leaking out and contaminating the surrounding area during repairs, it is necessary to flush out the ink inside the inkjet device. Traditionally, water alone, surfactant solutions, and solvents have been used as cleaning solutions. However, these are primarily chemical cleaning solutions, and they may not be able to clean completely, leading to problems such as poor dispensing. Functional inks, such as those used to form metal films, have been put into practical use. Metal inks include nano-inks, which disperse metal nanoparticles, and complex inks, which dissolve metal complexes. Compared to image-based inks, which contain a minimum amount of colorant necessary for identification on recording media such as paper, functional inks contain a larger amount of functional materials, which can lead to the formation of deposits where metal materials firmly adhere to the print head's flow path.

[0031] By distributing the cleaning solution and rinsing solution through the liquid dispensing device, which has a set of cleaning solution and rinsing solution, it is possible to easily remove solidified inks of various compositions, such as metal film-forming inks, which are difficult to deal with by conventional chemical cleaning, and to prevent the residue of abrasive materials.

[0032] Embodiments of the present invention will be described below with reference to the accompanying drawings. An example of a liquid discharge head related to the liquid discharge device of the present invention will be described with reference to Figures 1 and 2. Figure 1 is an external perspective view illustrating an example of a liquid discharge head in the liquid discharge device of this embodiment, and Figure 2 is a cross-sectional view in a direction perpendicular to the nozzle arrangement direction illustrating an example of the liquid discharge head shown in Figure 1. Furthermore, as described below, the "liquid" can be ink during image formation, and during cleaning, the cleaning solution and the rinsing solution can be used sequentially.

[0033] The liquid discharge head 100 is a circulating liquid discharge head, and is constructed by laminating and joining a nozzle plate 1, individual flow channel plates 2, and a diaphragm member 3 as a wall member. It is also equipped with a piezoelectric actuator 11 that displaces the vibration region (diaphragm) 30 of the diaphragm member 3, a common flow channel material 20 that also serves as the frame member of the head, and a cover 29. The nozzle plate 1 has a plurality of nozzles 4 for discharging liquid.

[0034] The flow path plate 2 has multiple pressure chambers 6 that each lead to multiple nozzles 4 via nozzle connecting passages 5, multiple individual supply flow paths 7 that also serve as fluid resistance sections and lead to each of the multiple pressure chambers 6, and intermediate supply flow paths 8 that serve as one or more liquid introduction sections and lead to two or more individual supply flow paths 7. The individual supply channel 7, similar to the embodiment described above, includes two first channels 7A and second channels 7B with a fluid resistance higher than that of the pressure chamber 6, and a third channel 7C located between the first channel 7A and the second channel 7B and having a fluid resistance lower than that of the first channel 7A and the second channel 7B. The flow path plate 2 is constructed by stacking multiple plate-shaped members 2A to 2E, but is not limited to this configuration. Furthermore, the flow channel plate 2 has multiple individual recovery channels 57 that run along the surface direction of the flow channel plate 2 and lead to multiple pressure chambers 6 via nozzle communication passages 5, and one or more intermediate recovery channels 58 that serve as liquid outlets leading to two or more individual recovery channels 57.

[0035] The individual recovery channel 57 includes two first channel 57A and second channel 57B, which have a higher fluid resistance than the pressure chamber 6, and a third channel 57C located between the first channel 57A and the second channel 57B, which has a lower fluid resistance than the first channel 57A and the second channel 57B. The channel 57D of the individual recovery channel 57, which is downstream of the second channel 57B in the circulation direction, has the same channel width as the third channel 57C.

[0036] The common flow channel material 20 forms a common supply channel 10 and a common recovery channel 50 that lead to multiple pressure chambers 6. In this embodiment, the common supply channel 10 is composed of a channel portion 10A that is aligned with the common recovery channel 50 in the nozzle arrangement direction and a channel portion 10B that is not aligned with the common recovery channel 50.

[0037] The common supply channel 10 communicates with the intermediate supply channel 8, which serves as the liquid introduction section, through an opening 9 provided in the diaphragm member 3, and connects to the individual supply channels 7 via the intermediate supply channel 8. The common recovery channel 50 communicates with the intermediate recovery channel 58, which serves as the liquid discharge section, through an opening 59 provided in the diaphragm member 3, and connects to the individual recovery channels 57 via the intermediate recovery channel 58. Furthermore, the common supply channel 10 leads to the supply port 71, and the common recovery channel 50 leads to the recovery port 72.

[0038] The diaphragm member 3 has a plurality of displaceable diaphragms (vibration regions) 30 that form the wall surface of the pressure chamber 6 of the flow channel plate 2. Here, the diaphragm member 3 has a two-layer structure (not limited to this), consisting of a first layer 3A that forms a thin-walled portion from the flow channel plate 2 side and a second layer 3B that forms a thick-walled portion. A deformable vibration region 30 is formed in the thin-walled first layer 3A in the portion corresponding to the pressure chamber 6. Within the vibration region 30, a convex portion 30a is formed in the thick-walled second layer 3B, which connects to the piezoelectric actuator 11.

[0039] On the side of the diaphragm member 3 opposite the pressure chamber 6, a piezoelectric actuator 11 is positioned, which includes an electromechanical conversion element as a driving means (actuator means, pressure generating means) for deforming the vibration region 30 of the diaphragm member 3. This piezoelectric actuator 11 has a piezoelectric member joined to a base member 13, grooves formed by half-cut dicing, and a required number of columnar piezoelectric elements 12 are formed in a comb-like pattern at predetermined intervals in the nozzle arrangement direction. The piezoelectric elements 12 are then joined to a convex portion 30a, which is a thickened portion formed in the vibration region 30 of the diaphragm member 3. This piezoelectric element 12 is constructed by alternately stacking piezoelectric layers and internal electrodes. Each internal electrode is brought out to its end face and connected to an external electrode (end face electrode), and a flexible wiring member 15 is connected to the external electrode.

[0040] In this liquid discharge head 100, the piezoelectric element 12 is extended in the stacking direction, and the vibration region 30 of the diaphragm member 3 is deformed toward the nozzle 4, thereby contracting the volume of the pressure chamber 6. As a result, the liquid in the pressure chamber 6 is pressurized and the liquid is discharged from the nozzle 4. Furthermore, any liquid that is not discharged from nozzle 4 passes through nozzle 4 and is recovered from individual recovery channels 57 to a common recovery channel 50, and then supplied again from the common recovery channel 50 to the common supply channel 10 via an external circulation channel. Also, even when liquid is not being discharged from nozzle 4, liquid circulates from the common supply channel 10 through the pressure chamber 6 to the common recovery channel 50, and is supplied again to the common supply channel 10 via an external circulation channel. In this embodiment, with a simple configuration, pressure fluctuations associated with liquid discharge can be attenuated and their propagation to the common supply channel 10 and common recovery channel 50 can be suppressed.

[0041] Figure 3 is a schematic diagram illustrating an example of a liquid dispensing device of this embodiment. The liquid dispensing device in Figure 2 has a liquid dispensing head 100 and a stage 110 that can be heated up to, for example, 200°C. The object to be coated 120 is fixedly placed on the stage 110 and is transported in the direction of the arrow while ink is applied. The inner diameter of the discharge port (nozzle diameter of the nozzle section) that contributes to discharge in the flow path of the liquid discharge head 100 is determined by the resolution and droplet size. For a liquid discharge head capable of discharging droplets of 7 pL, the inner diameter of the discharge port was 26 μm. Furthermore, liquid dispensing devices also include larger dispensing devices compared to inkjet printers, such as jet dispensers. The inner diameter of the dispensing port of a jet dispenser is, for example, 100 μm to 200 μm.

[0042] Figures 4 and 5 show examples of liquid dispensing devices that have a circulation channel as a mechanism for circulating liquids such as ink, while Figure 6 shows an example of a liquid dispensing device that does not have a circulation channel and circulates liquid in one direction. As shown in Figure 4, the inkjet device 200 has an ink tank 201, an inkjet head as an ejection unit 202, and a circulation channel 203 inside. The circulation channel 203 includes a buffer tank 203A and a pump 203B. However, as shown in the inkjet device 300 in Figure 5, the circulation channel 303 does not necessarily have to include a buffer tank and a pump, but may include an ink tank 301, a discharge unit 302, and the circulation channel 303. Furthermore, as shown in Figure 6, the inkjet device 400 may not have a circulation channel and instead have an ink tank 401, an inkjet head as an ejection unit 402, and a channel 403 through which liquid flows in one direction from the ink tank 401 to the ejection unit 402. Such devices have been widely used for some time.

[0043] As shown in Figure 4, the inkjet device 200 preferably has a buffer tank 203A and a pump 203B within the circulation channel 203. Ink is normally stored in liquid form in the ink tank 201. Ink is dispensed from the dispensing unit 202. The dispensing unit 202 has a nozzle. The dispensing unit 202 is connected to the ink tank 201. The ink tank 201 and the dispensing unit 202 are connected via a flow path. One end of the circulation flow path 203 is connected to the dispensing unit 202, and the other end is connected to the ink tank 201. Ink flows through the inside of the circulation flow path 203.

[0044] If a buffer tank 203A or a pump 203B is provided, it is preferable that the buffer tank 203A and the pump 203B are positioned between the dispensing unit 202 and the ink tank 201, respectively. The buffer tank 203A is positioned closer to the dispensing unit 202 than the pump 203B. The pump 203B is positioned closer to the ink tank 201 than the buffer tank 203A. Ink is temporarily stored in the buffer tank 203A. Examples of ejection units 202, 302, and 402 include thermal, bubble jet, electromagnetic valve, or piezo-type inkjet heads.

[0045] Ink can be circulated using its own weight or by using a pump to create pressure changes. These methods may be used in combination. To improve circulation efficiency, it is preferable to have a pump in the circulation channel 203 to transfer the ink. At the discharge port of the discharge section 202, it is preferable to maintain an appropriate pressure and minimize pressure fluctuations. When using a pump or the like, it is preferable to provide a buffer tank or damper between the pump and the discharge section to suppress pump pulsation. In the ink coating process, within the inkjet device 200, ink is moved from the ink tank 201 to the ejection unit 202, and any ink that was not ejected from the ejection unit 202 is then moved back to the ink tank 201 through the circulation channel 203. This allows the ink to be circulated during the coating process.

[0046] (Cleaning method and cleaning mode in liquid dispensing device) The cleaning method of the present invention is a cleaning method for cleaning the flow path and outlet of a liquid discharge device using the above-described set of cleaning solution and rinsing solution of the present invention, and preferably includes a cleaning step and a rinsing step, and further includes a cleaning degree determination step, and may include other steps as necessary. The liquid dispensing device of the present invention preferably includes a washing means, a rinsing means, and a cleaning degree determination means, and further includes other means as necessary. As for the set of cleaning solution and rinsing solution, the items described above in the set of cleaning solution and rinsing solution of the present invention can be appropriately selected.

[0047] <Cleaning process, cleaning means> The cleaning step involves circulating the cleaning solution through the flow path and the discharge port, and can be suitably carried out by the cleaning means. The cleaning means is a means for circulating the cleaning liquid through the flow path and the discharge port. By using the cleaning liquid as a liquid instead of ink, it can be circulated through the flow path and the discharge port of the liquid dispensing device. The cleaning process involves, for example, circulating (preferably recirculating) the cleaning solution through the flow path and discharge port at a predetermined flow rate. For setting the cleaning time and evaluating the cleaning effect, for example, the cleaning solution can be discharged from the discharge port every 60 seconds, and the point at which no more detached pieces of the adhering material are observed can be defined as the required cleaning time (recovery time).

[0048] There are no particular restrictions on the flow rate of the cleaning solution, and it can be appropriately selected according to the purpose. It may be the flow rate used when circulating ink, and the flow rate may be increased by pressurizing. There are no particular restrictions on the pressure of the pressurization, and it can be appropriately selected according to the purpose, but it is preferably 0.01 MPa or more and 0.2 MPa or less, and more preferably 0.02 MPa or more and 0.1 MPa or less. Furthermore, to enhance the delamination effect of the adhering material, turbulence may be created during the flow of the cleaning solution, and ultrasonic treatment may be performed by applying ultrasound.

[0049] <Rinsing process, rinsing methods> The rinsing step is a step of removing the cleaning solution by circulating the rinsing liquid through the flow path and discharge port, and can be suitably carried out by the rinsing means. The rinsing means is a means of removing the cleaning solution by circulating the rinsing liquid through the flow path and discharge port. By using the rinsing liquid as a liquid instead of ink, it can be circulated through the flow path and discharge port of the liquid dispensing device. The rinsing process involves, for example, circulating the rinsing liquid through the flow path and discharge port at a predetermined flow rate. The rinsing liquid may be circulated within the liquid discharge device and then discharged into the discharge port or rinsing liquid container after circulating for a certain period of time, or it may be circulated in one direction to the discharge port.

[0050] There are no particular restrictions on the number of rinsing steps, and they can be appropriately selected depending on the purpose. However, it is preferable to perform multiple rinsing steps (two or more, three or more, four or more, etc.) using fresh rinsing solution. The number of rinsing cycles, the setting of rinsing time, and the evaluation of rinsing effectiveness can be set and evaluated using indicators such as the absence of detached fragments of adhering material in the rinsing liquid discharged from the outlet, and electrical conductivity, as determined by the cleaning degree determination process described later.

[0051] <Cleaning degree determination process, cleaning degree determination means> The cleaning degree determination step is a step of determining the cleaning degree by measuring the electrical conductivity of the rinsing liquid that has flowed through the flow path, and can be suitably carried out by the cleaning degree determination means. The cleaning degree determination means is a means for determining the cleaning degree by measuring the electrical conductivity of the rinsing liquid that has flowed through the flow path. The cleaning degree determination step can be performed if the particles dissolve and ionize in the rinsing solution. The rinsing solution is preferably water or carbonated water.

[0052] If the electrical conductivity is 400 μs / cm or less, it can be determined that the electrical conductivity is as low as that of tap water, which has an electrical conductivity of approximately 400 μs / cm or less, and that the dissolved particles have been sufficiently removed by the rinsing process.

[0053] <Other processes, other means> The aforementioned other steps and means are not particularly limited, and known steps and means used in liquid dispensing devices can be appropriately selected according to the purpose. [Examples]

[0054] The present invention will be described more specifically below based on examples, but the present invention is not limited to the following examples.

[0055] The following inks 1-4 were prepared as functional inks for metal film formation.

[0056] (Ink 1) The Ag complex ink (Ink 1) was prepared by mixing 2-methylacetoacetate silver, an amine solvent, and acetylene alcohol in a mass ratio of 25:74:1, based on the "Low-temperature wiring formation technology using β-ketocarboxylic acid silver salt ink" published in the IEICE Transactions on Electronics, Information and Communication Engineers, Vol. J95-C No. 11, pp. 394-399. The functional material, i.e., Ag content was 2% by volume, and the viscosity was 13 mPa·s. The thermal conductivity of the film formed using ink 1 was 84 W / m·K, and the volume resistivity was 7.1 μΩcm.

[0057] (Ink 2) The Ag nanoparticle dispersion ink has a particle size of 50 nm for the Ag particles, an Ag content of 17 volume%, and a viscosity of 10 mPa·s. The thermal conductivity of the film formed using ink 2 was 70 W / m·K, and the volume resistivity was 8.0 μΩcm.

[0058] (Ink 3) The Cu complex ink (Ink 3) was obtained by dissolving copper formate tetrahydrate in a mixture of ethanol and diamine in a Cu:NH2 molar ratio of 1:4, based on Journal of Materials Chemistry C, 2018, 6, 6406, and then filtering the solution. The Cu content of the Cu complex ink was 2 vol% and the viscosity was 13 mPa·s. The thermal conductivity of the film formed using ink 3 was 88 W / m·K, and the volume resistivity was 6.9 μΩcm.

[0059] (Ink 4) The Cu nanoparticle dispersion ink had a Cu particle size of 50 nm, a Cu content of 12 volume%, and a viscosity of 8 mPa·s. The thermal conductivity of the film formed using ink 4 was 62 W / m·K, and the volume resistivity was 8.5 μΩcm.

[0060] [Formation of functional membranes] As shown in Figures 1-3, a printing apparatus 500 equipped with a liquid ejection head 100 (industrial inkjet head MH5420, manufactured by Ricoh Co., Ltd.) was used to apply ink to electronic components to be coated, which were fixedly placed on a transport belt 412 capable of being heated up to 200°C, while being transported in the sub-scanning direction. The liquid ejection head 100 was positioned with a 2 mm gap from the top surface of the object to be coated. The ejection drive waveform of the liquid ejection head was adjusted so that the ejected droplet size could be drawn at 7 pL. Each ink was ejected at an ejection frequency of 2 kHz. The inner diameter of the nozzle (discharge port), which is the most important part of the liquid discharge flow path, was 26 μm.

[0061] Both inks require heating of the stage, and 100cm 3 ~200cm 3 As a result of the ink ejection process, ejection failures occurred in 5 to 10 of the 320 x 4 rows (i.e., a total of 1280 channels) nozzles. Upon disassembling and observing these heads, as shown in Figure 7, which is an enlarged view of the liquid discharge head's flow path (nozzle communication passage 5) and discharge port (nozzle 4) shown in Figure 2, solidified material containing the same metal as the main component of the ink was found in the nozzle or the flow path near the nozzle.

[0062] [Mohs hardness measurement of adhered materials] The Mohs hardness of the metal films of each ink (1-4) was measured using the standard minerals shown in Table 1. The results showed that the silver films formed with silver complex ink or silver nanoparticle dispersion ink all had a Mohs hardness of 2, while the copper films formed with copper complex ink or copper nanoparticle dispersion ink all had a Mohs hardness of 3.

[0063] [Mohs hardness measurement of major materials in a flow channel] The inkjet head (MH5420, manufactured by Ricoh Co., Ltd.) uses stainless steel (SUS) in its flow path. When the Mohs hardness of various SUS materials, including SUS304, SUS316, and SUS430, was measured, all were found to have a Mohs hardness of 4. On the other hand, when the Mohs hardness of the silicon constituting the flow channels of an inkjet head manufactured by a silicon process (TH6310F, manufactured by Ricoh Co., Ltd., 100 channels x 8 rows x 2 modules (i.e., a total of 1,600 channels)) was measured, it was found to be 7.

[0064] [Selection of particles, cleaning solution, and rinsing solution] In selecting the particles, we considered the relationship between the Mohs hardness of the particles, the Mohs hardness of the adhering material, and the Mohs hardness of the main material in the flow path, as well as selecting substances with a large difference in solubility / insolubility in the cleaning liquid and rinsing liquid. The combinations used are shown in Tables 2-1 and 2-2.

[0065] [Implementation of cleaning method] The maximum particle size was limited using filters with predetermined pore sizes (syringe filter, manufactured by Membrane Solutions, pore size: 3 μm; and filter wire mesh, manufactured by Flon Chemical, pore sizes: 5, 7, 8, and 10 μm). Using the apparatus shown in Figures 1-3, a cleaning process was performed in which cleaning solution was injected from the ink injection side and circulated at a flow rate of 1 mL / s to 4 mL / s while simultaneously being discharged from the nozzles. Discharge from the nozzles was evaluated every 60 seconds by particle observation, and the recovery time at which discharge occurred from all nozzles and the discharge angle was within ±10° was evaluated with n3. The measured recovery times and their averages are shown in Table 2-3. Here, "particle observation" refers to a method of observing the repeated discharge state of the liquid as if it were stationary particles by using a camera that observes the nozzle from the side and flashing an LED or other light source opposite it in accordance with the discharge frequency.

[0066] For the rinsing process, five rinse cycles were performed in which rinsing solution was circulated at a flow rate of 1 mL / s to 4 mL / s, and the solution was drained from the nozzle and ink outlet port. For the examples and comparative examples where the rinsing solution was water or carbonated water, the degree of cleaning was determined by measuring the ionization resistance of the fifth rinsing solution. If the electrical conductivity is 400 μs / cm or less, it can be determined that the electrical conductivity is as low as that of tap water, which has an electrical conductivity of approximately 400 μs / cm or less, and that the dissolved particles have been sufficiently removed by the rinsing process. The measured recovery times and their averages are shown in Table 2-3.

[0067] [evaluation] The print head's ejection performance after rinsing was confirmed by ejecting ink again. Furthermore, the inkjet print head was disassembled, and the presence of scratches, deposits, and residual particles inside the flow path was checked using a microscope. Table 2-2 shows the results for the examples and comparative examples.

[0068] [Table 2-1]

[0069] [Table 2-2]

[0070] [Table 2-3]

[0071] [Table 2-4]

[0072] In the examples, the adhering material was efficiently removed by a cleaning solution containing particles with a maximum particle size of 1 / 3 or less of the inner diameter of the discharge port. When the Mohs hardness of the particles was the same as or higher than the Mohs hardness of the adhering material, the adhering material was efficiently removed. Since the particles were soluble in the rinsing solution, the particles were reliably removed during the rinsing process, and no residual particles were observed after rinsing. When the ink discharge performance, which is affected by the generation of adhering material, was evaluated, all examples showed good ink discharge performance due to the removal of the adhering material. Furthermore, in the examples, since the Mohs hardness of the particles was the same as or lower than the Mohs hardness of the main material in the flow channel, no damage was observed inside the flow channel. Furthermore, as shown in Examples 3-2 and 4-2, it was found that when the particle size exceeds 1 / 3 of the nozzle diameter, the cleaning efficiency decreases and the recovery time required for cleaning increases, but cleaning is still performed well.

[0073] On the other hand, as shown in Comparative Examples 1, 2, 3-1, 4-1, and 5, when the rinsing solution could not dissolve the particles, residual particles were observed after rinsing, indicating that the rinsing process could not efficiently remove the particles. As shown in Comparative Examples 6 and 7, it was found that if the Mohs hardness of the particles is higher than that of the head material (SUS), it causes damage to the inside of the flow path, resulting in malfunctions. On the other hand, using a head material made of silicon, which has a higher Mohs hardness, prevents damage to the inside of the flow path. In Comparative Examples 6 and 7, the particles could not be removed with the rinsing solution, so particles remained after rinsing.

[0074] In Examples 1-3 and 5, it was found that the removal of particulate components after rinsing can be confirmed by measuring the electrical conductivity of the rinse solution after rinsing, since the particles ionize in the rinse solution. Figures 8A to 8C show how the cleaning method of this embodiment is used to clean the solidified material in the liquid discharge head's flow path and discharge port, as can be inferred from these results. Specifically, by washing with a cleaning solution containing particles p, the adhering material a is detached and removed from the nozzle plate 1 and other components that form the flow path 5 by contact with the particles p (see Figure 8A). Next, the particles p are dissolved and removed by rinsing with a rinsing solution capable of dissolving the particles p (see Figure 8B). Through this washing and rinsing, the adhering material a is detached and removed, and the particles p and residual particles r are also removed, resulting in a clean flow path and discharge port of the liquid discharge device (see Figure 8C).

[0075] Examples of the present invention are as follows: <1> It includes a washing solution and a rinsing solution. The cleaning solution comprises particles and a liquid that does not dissolve the particles. The set of a washing solution and a rinsing solution is characterized in that the rinsing solution contains a liquid capable of dissolving the particles. <2> A set of cleaning solution and rinsing solution for cleaning the flow path and outlet of a liquid dispensing device, The maximum particle size of the aforementioned particles is 1 / 3 or less of the inner diameter of the discharge port. <1> This is a set of cleaning solution and rinsing solution as described. <3> The maximum particle size of the aforementioned particles is 100 μm or less. <1> This is a set of cleaning solution and rinsing solution as described. <4> The maximum particle size of the aforementioned particles is 10 μm or less. <2> or <3> This is a set of cleaning solution and rinsing solution as described. <5> The aforementioned <1> from <4> A cleaning method for cleaning the flow path and outlet of a liquid dispensing device using a set of cleaning solution and rinsing solution described in any of the above, A step of flowing the cleaning liquid through the flow path and the discharge port, A step of flowing the rinsing liquid through the flow path and discharge port to remove the cleaning liquid, This cleaning method is characterized by including [a specific ingredient / method]. <6> The Mohs hardness of the aforementioned particles is the same as or lower than the Mohs hardness of the main material in the flow channel. <5> This is the cleaning method described in [the document]. <7> The Mohs hardness of the aforementioned particles is the same as or higher than the Mohs hardness of the deposits fixed in the flow channel. <5> or <6> This is the cleaning method described in [the document]. <8> The aforementioned particles are particles that dissolve and ionize in the rinsing solution, The process further includes measuring the electrical conductivity of the rinsing liquid that has flowed through the aforementioned channel to determine the degree of cleaning. <5> from <7> The cleaning method is as described in one of the following. <9> The aforementioned <1> from <4> A set of cleaning solution and rinsing solution as described in any of the following, A container for holding liquid, A flow path through which the aforementioned liquid can flow, A liquid dispensing head having a dispensing port for dispensing droplets of the aforementioned liquid, This liquid dispensing device is characterized in that it can distribute each of the aforementioned cleaning solution and rinsing solution as liquids. <10> The flow path is a flow path through which the liquid can circulate, The cleaning solution and the rinsing solution can each be circulated as the liquid. <9> This is the liquid dispensing device described in [reference]. <11> Means for circulating the cleaning liquid through the flow path, A means for circulating the rinse liquid through the flow path to remove the cleaning liquid, The foregoing <9> or <10> This is the liquid dispensing device described in [reference]. <12> The aforementioned particles are particles that dissolve and ionize in the rinsing solution, The means further comprises measuring the electrical conductivity of the rinsing liquid that has flowed through the aforementioned flow path to determine the degree of cleaning. <9> from <11> It is a liquid dispensing device as described in any of the above. <13> A cleaning solution container containing the aforementioned cleaning solution, The system further comprises a rinse liquid container containing the rinse liquid, The washing liquid container and the rinsing liquid container are each detachable from the liquid dispensing device. <9> from <12> It is a liquid dispensing device as described in any of the above.

[0076] The aforementioned <1> from <4> A set of cleaning solution and rinsing solution as described in any of the above, <5> from <8> The cleaning method described in any of the above, and the <9> from <13> A liquid dispensing device described in any of the above can solve the aforementioned problems of the conventional invention and achieve the objectives of the present invention. [Explanation of symbols]

[0077] 100 liquid dispensing heads 200, 300, 400 Inkjet Printers (Liquid Dispensing Devices) 1 Nozzle plate 2 Flow channel plate 3. Diaphragm component 4 Nozzles (discharge ports) 5. Nozzle connection passage (flow path) a. Adhered material p particle r Residue (residual particles) [Prior art documents] [Patent Documents]

[0078] [Patent Document 1] Japanese Patent Publication No. 2011-140556 [Patent Document 2] Patent No. 3103404

Claims

1. It includes a washing solution and a rinsing solution. The cleaning solution comprises particles and a liquid that does not dissolve the particles. A set of a cleaning solution and a rinsing solution, characterized in that the rinsing solution contains a liquid capable of dissolving the particles.

2. A set of cleaning solution and rinsing solution for cleaning the flow path and outlet of a liquid dispensing device, The set of cleaning solution and rinsing solution according to claim 1, wherein the maximum particle size of the aforementioned particles is 1 / 3 or less of the inner diameter of the discharge port.

3. The set of washing solution and rinsing solution according to claim 1, wherein the maximum particle size of the aforementioned particles is 100 μm or less.

4. The set of washing solution and rinsing solution according to claim 2 or 3, wherein the maximum particle size of the aforementioned particles is 10 μm or less.

5. A cleaning method for cleaning the flow path and outlet of a liquid dispensing device using the set of cleaning solution and rinsing solution described in claim 1 or 2, A step of flowing the cleaning liquid through the flow path and the discharge port, A step of flowing the rinsing liquid through the flow path and discharge port to remove the cleaning liquid, A cleaning method characterized by including [a certain component].

6. The cleaning method according to claim 5, wherein the Mohs hardness of the particles is the same as or lower than the Mohs hardness of the main material in the flow path.

7. The cleaning method according to claim 5, wherein the Mohs hardness of the particles is the same as or higher than the Mohs hardness of the deposits fixed in the flow path.

8. The aforementioned particles are particles that dissolve and ionize in the rinsing solution, The cleaning method according to claim 5, further comprising the step of determining the degree of cleaning by measuring the electrical conductivity of the rinsing liquid that has flowed through the channel.

9. A set of cleaning solution and rinsing solution according to claim 1 or 2, A container for holding liquid, A flow path through which the aforementioned liquid can flow, A liquid dispensing head having a dispensing port for dispensing droplets of the aforementioned liquid, A liquid dispensing device characterized in that the washing solution and the rinsing solution can each be circulated as the liquid.

10. The flow path is a flow path through which the liquid can circulate, The liquid dispensing device according to claim 9, wherein each of the washing liquid and the rinsing liquid can be circulated as the liquid.

11. Means for circulating the cleaning liquid through the flow path, A means for circulating the rinse liquid through the flow path to remove the cleaning liquid, A liquid dispensing device according to claim 9, having the following features.

12. The aforementioned particles are particles that dissolve and ionize in the rinsing solution, The liquid dispensing device according to claim 9, further comprising means for determining the degree of cleaning by measuring the electrical conductivity of the rinsing liquid that has flowed through the aforementioned flow path.

13. A cleaning solution container containing the aforementioned cleaning solution, The system further comprises a rinse liquid container containing the rinse liquid, The liquid dispensing device according to claim 9, wherein each of the washing liquid container and the rinsing liquid container is detachable from the liquid dispensing device.

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