JP2010005544A - Inkjet head cleaning method and device using the method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet head cleaning method and a maintenance device which can ensure the stable maintenance of a discharge operation for a long time by upgrading a method of repairing a nozzle water repellent-treated film which plays an important role in forming a liquid droplet. <P>SOLUTION: Three openings of an inkjet head 1 are connected together with the help of cleaning fluid supply piping, then the normal and reverse flows of the cleaning fluid are intentionally created by combination of a liquid sending pump 19, a switching valve 18, a tank 17, etc. and thereby, a nozzle, filter, channel and the like which are apt to cause a clogging, are cleaned. Further, a nanobubble is dissolved in the cleaning fluid by a nanobubble generator, resulting in the improvement of detergency and solving a problem of the clogging. Besides, for regenerating of the water repellent-treated film, a uniform film can be formed without blocking the nozzle by a selective mist coating process. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solution channel cleaning apparatus and method for stably operating an inkjet head (hereinafter abbreviated as IJ head) which is a key device of an inkjet (hereinafter abbreviated as IJ) apparatus used for drawing and coating. .

  The IJ technology that has been developed as a printing technology is not limited to the printing technology, but has been expanded to include the electronic manufacturing field, general industrial equipment, and recently, the biotechnology field. With the expansion of application fields, printing technology and its peripheral technology have made remarkable progress. From the beginning of development to today, the major technical issue remains in the solution flow path of IJ, including nozzles. This is a problem of ejection failure due to clogging or the like. The discharge solution applied to the IJ device includes very fine solid particles, the solvent contained in the discharge solution easily evaporates under normal operating conditions, and the remaining components accelerate the curing, etc. There are various. While the IJ is being smoothly discharged, the side walls of the solution flow path including the nozzles are kept in a relatively normal state. As a result, the solid content adheres, and the droplet diameter of the discharge solution gradually decreases, eventually becoming completely clogged and being unable to discharge. If a particular nozzle is completely clogged, the row will be completely blank, creating obvious problems. Even if clogging does not occur, if the solid content adheres to the nozzle side wall or the like and the flow path is narrowed, the droplet diameter of the discharged solution decreases as a result. In particular, in the case where a thin film is formed by IJ, the variation in film thickness is increased, and this is a serious problem when a film thickness at a submicron level is targeted.

  In order to prevent these problems, an IJ head maintenance system is usually built in the apparatus in accordance with the purpose. For example, as disclosed in Patent Document 1 below, a discharge solution filling device is introduced to perform maintenance of the solution flow path and filling of the solution. In addition, a flushing operation called 'discarding' is performed, and all discharges are performed at once to maintain the solution flow path. A similar operation is also provided in a general IJ printer in which a discharge operation is performed by applying an air pressure to the solution flow path when clogging occurs.

Further, by applying a repetitive pulse at a low voltage level that does not discharge the solution to the IJ head within the rest period, the discharged solution in the flow path of the IJ head is always moved minutely to prevent the solution from solidifying. A so-called swinging (idling) method has also been proposed.
Japanese Patent Application No. 2007-197160

  The IJ method used for drawing and coating is widely used from general printers to industrial production equipment because of the simplicity of the process. Expansion to cutting-edge fields is also expected. Up to now, the problem that the IJ method has always been is the concern about reliability represented by clogging of the IJ head. In order to solve this problem, the reliability has been greatly improved in recent years by the development of the discharge solution, the development of a stable maintenance function that can always discharge in a normal state, the development of feedback technology based on the detailed inspection of the discharge result, etc. There are still concerns about clogging, depending on the characteristics and composition of the discharge solution, the discharge environment, the use conditions such as the duty difference of the nozzle, etc., and this is a major problem.

  In addition, the coating film thickness variation due to the solid volume of the discharged liquid adhering to the solution flow path, particularly the nozzle side wall, and the volume of the discharged droplets changing in time series is also a big problem. Although it becomes a big problem that the ejection becomes impossible due to clogging, it is also a fatal problem that the droplet volume fluctuates during the driving operation and as a result, the film thickness fluctuates.

  The first object of the present invention is to avoid inability to discharge due to ensuring the stability of the solution flow path. It is to develop a device that relieves the IJ head that is unfortunately clogged and has become unable to eject. To better understand the structure of the IJ head and to propose a clogging elimination method without damaging other structural parts of the IJ head.

  Next, the second object is to propose a repair method other than catastrophic damage in the process of repairing the IJ head. As a specific example, there is a method for forming a water-repellent treatment film of a nozzle plate that plays an important role in droplet formation in IJ.

  With the above consideration, it is an object to provide an apparatus and a method capable of realizing stable drawing and coating by improving the reliability of the IJ head in the IJ method.

  The present invention is a film forming apparatus that discharges and applies a coating solution onto a substrate by using an IJ head. A droplet discharged by narrowing of a solution flow path due to clogging of a nozzle of an IJ head that occurs during operation or solidification of a coating solution. The present invention relates to an in-line type cleaning apparatus that is built in without an IJ coating apparatus, and a cleaning apparatus that removes an IJ head from the coating apparatus and repairs it offline.

  In general, solid or gel-like substances adhering to the side walls of the solution flow path of the IJ head cause the solid content contained in the coating solution to precipitate, or the resin component such as the binder constituting the coating solution to be semi-cured. Often. These change to stable substances over time, so monitor changes in the volume of liquid droplets over time, clogging, etc., to grasp the change in state and introduce maintenance processes as appropriate. Therefore, it is necessary to always maintain stable discharge.

  In order to solve this problem, in the first aspect, fine bubbles are generated in the cleaning liquid, dissolved in the cleaning liquid, and injected and circulated into the solution flow path of the IJ head. In general, a solution that can dissolve a solidified or gelled coating substance is desirable as the cleaning liquid, but on the other hand, the structure of the IJ head is often composed of an adhesive structure based on an organic material. The cleaning solution must not damage the parts. When activated, the nanobubbles dissolved in the cleaning agent have a much higher dissolving ability than the cleaning liquid alone, and have a strong effect on solidified precipitates in fine areas and gel substances.

  Next, fine bubbles are likely to be generated in water, but in a solution centered on a solvent, the bubble diameter may increase. The nozzle diameter of the IJ head is usually about 10 to 50 microns, and if the bubble diameter becomes too large, the bubbles are combined to form a huge bubble, which obstructs smooth liquid feeding. In order to eliminate clogging of the nozzle, a method has been proposed in which a rigid fine metal wire is precisely positioned and passed through the nozzle position. Since it has a great influence on droplet formation, it is a method that should be avoided if possible. The method of using nanobubbles wipes out the concern. In claim 2, the method of defining the average diameter of the generated bubbles is used.

  The third aspect considers a mechanism for cleaning the details of the IJ head by circulating the cleaning liquid from both the injection port of the coating solution of the IJ head and the nozzle as the final outlet by the pressurizing means. Naturally, the dissolved solidified substance or the gelled deposit is filtered by a mesh filter placed in the middle of the circulation path when it leaves the solution flow path of the IJ head, and cleaning is performed by a mechanism in which only the cleaning liquid is circulated.

  The main purpose of the present invention is to repair an IJ head that has stopped functioning due to clogging or the like. However, there is an indication of clogging or the volume of a droplet (specifically, the dot volume after landing on the substrate). If it is monitored in time series, it is convenient to take countermeasures before the catastrophic failure is revealed. According to claim 4, from this viewpoint, if a circulation path for cleaning is created in advance in the IJ head mounted on the IJ coating apparatus and a sign of clogging is detected by monitoring dots or the like. The cleaning operation is performed by switching the operation.

  To repair the IJ head, it is not sufficient to clean the solution flow path such as clogging, and it is also necessary to recover the wear of the water repellent film on the nozzle plate that plays an important role in the formation of the meniscus of the droplets. is there. Claim 5 is based on the intention. Usually, a nozzle opening is formed on the nozzle plate, and particularly, the water repellent treatment at the end of the nozzle opening is severely worn. If the water-repellent treatment is left worn, the 'wetting' between the discharged solution and the nozzle plate becomes sufficient, resulting in a significant hindrance to droplet formation. Therefore, it is necessary to repair the water-repellent film on the entire nozzle plate including the nozzle mouth end. If application is simply performed on the nozzle plate, the nozzle opening may be clogged, and the mist application of the super water-repellent material is realized in claim 5.

  According to the present invention, when drawing or coating is performed by the IJ method, the droplet volume of the IJ head, which is the most important issue in terms of reliability, is reduced due to clogging of the IJ head or narrowing of the solution flow path due to solidification of the discharge solution. The present invention provides a method and apparatus for cleaning an IJ head that is effective in suppressing fluctuations. By applying the present invention to an actual process, it is possible to maintain a stable ejection state at all times. As a result, it is possible to prevent drawing defects in drawing, prevent thin film defects in film coating, and maintain and reduce film thickness variations. it can. On the other hand, up to now, it is treated as a consumable, clogging is considered as one of the lifetimes, and the expensive IJ head that has been discarded can be revived, and there are many places to gain in terms of equipment cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  First, the structure of the target IJ head will be described. The IJ head is manufactured by a miniaturization process similar to that of a semiconductor. In general, liquid feeding, droplet formation, and ejection are performed by deformation of a piezoelectric element device using a piezoelectric element as a drive source. Depending on the deformation mode of the piezoelectric element, it can be divided into a direct acting type, a diaphragm type (out-of-plane deformation type), and a shearing type. In the former two cases, the discharge solution (ink) is fixed, the load for discharge is almost constant, and it is frequently used when it is small, and high definition is also possible. On the other hand, the latter is used for various types of thin film formation, and is often compatible with many varied discharge solutions, and requires a relatively wide tolerance for fluid properties such as viscosity and surface tension. Has been. Here, FIG. 1 shows an outline of a shearing type IJ head used for general industry that requires much higher reliability than a general printer. The IJ head 1 is usually provided with an inlet 2 for supplying a discharge solution from a container and a discharge port 3 having a function of expelling air remaining in the discharge solution or inside the IJ head, which is the most downstream of IJ coating. It can be seen that it has a nozzle opening 4 and a total of three openings.

  Furthermore, the solution flow path of the IJ head 1 is schematically shown in FIG. The discharge solution entered from the injection port 2 first proceeds to the manifold 5 and is supplied to the channel 7 with electrodes through the filter 6, and the flow path member is formed of a piezoelectric material. 8 is a mechanism for discharging from a nozzle port 4 opened at 8. The filter 6 is disposed in the preceding stage as a preventive measure against clogging of the nozzle 4 and the channel 7, and generally a filter having mesh numbers # 1450 to # 2400 is used. In the course of the discharge operation, the nozzle 4 is most likely to be clogged, and even if the nozzle 4 does not become completely clogged, the droplet volume is likely to change due to the reduction in the nozzle diameter. As mentioned above, the filter mesh 6 is originally arranged for the purpose of preventing clogging, but it can remove coarse solids and dust here, but it contains a resin binder that is easy to solidify. In the case of a solution, it is known from experimental results that gelation tends to proceed around the mesh when the discharge operation is stopped. Once the gelled product adheres to this part, the flow resistance becomes large and affects the pressure head difference. That is, when the adhesion is mottled, it directly leads to a change in the volume of the ejected droplets, resulting in unevenness in the formed coating film. Moreover, the solidified product or gelled material of the discharge solution may also adhere to the side walls of each channel 7, which causes an increase in piping resistance. The present invention solves these problems.

  Next, the portion of the IJ head that is worn out for a long time is the water repellent film 9 applied to the surface of the nozzle plate 8 including the nozzles 4. This film has an important role of controlling the shape of the droplet (meniscus) at the tip of the nozzle where ejection is performed and generating the droplet as a droplet. However, after long-time operation, the function is considerably deteriorated due to wear damage due to minute solids contained in the discharged solution and mechanical damage due to wiping operation (wiping operation) of the nozzle plate. Therefore, it is the role of the present invention to remove the obstacle solidifying substance and gelling substance accumulated in the solution flow path, and to return the water repellent film on the nozzle surface for controlling the droplets to the initial state. .

  A first embodiment will be described. FIG. 3 shows a system diagram of an IJ head cleaning maintenance system according to the present invention. This system is composed of three units, a nozzle cleaning unit, a filter cleaning unit, and a nano bubble generation unit, and is an apparatus for cleaning and repairing an IJ head alone offline.

  The nanobubble generation unit, which is the greatest feature of this apparatus, will be described. In general, microbubbles and nanobubbles do not have a definite boundary. However, the average diameter (defined as the bubble diameter with a generation probability of 50% in the number distribution) is determined based on the size of the filter mesh to be cleaned and the nozzle diameter. ) Is considered as an object to consider 1 micron or less, and this region is expressed here as nanobubbles. Since there is a distribution of bubble generation, naturally there are bubbles of 1 micron or more, but large bubbles inevitably disappear in the washing liquid tank and inevitably disappear. There is a fixed relationship between the bubble diameter and the rising speed (disappearance time), and it is possible to set the bubble diameter to a certain value or less by controlling the residence time of the cleaning liquid tank. There are various ways to create bubbles. The diffuser plate method is a method of creating bubbles by ventilating countless fine holes. The ejector method is a method in which gas is dissolved in a liquid by vigorous gas-liquid mixing, and bubbles are formed by shearing. The stirring and mixing method is a method in which a gas is sheared into bubbles by stirring in a liquid. Next, in the pressure dissolution method, gas is blown and dissolved in the liquid sent to the pressure dissolution tank by a pump to create pressurized water, and the excess dissolved gas becomes bubbles by reducing the pressure. To be deposited. Finally, in the pump suction system, a gas-liquid pump is pushed into an accumulator to dissolve the gas in the liquid, and the excess dissolved gas is deposited as bubbles.

  In the embodiment, a method in which a pump suction method and a pressure dissolution method are combined is adopted. In the nano-bubble generating unit of FIG. 3, the circulating pressure pump 10 takes in the cleaning liquid and air and pressurizes them, and sends them to the pressurized dissolution tank 11 where the air is sufficiently dissolved in the cleaning liquid, and the bubble generating nozzle 12 reduces the pressure. Then, it is discharged into the bubble pool 13. If this is circulated, nanobubbles can be generated in the cleaning liquid.

  Next, the nozzle cleaning unit and the filter cleaning unit will be described. In order to clean the solution flow path of the IJ head 1, the three openings of the injection solution injection port 2, the discharge port 3, and the nozzle port 4 are effectively connected. The pressure cleaning cap 14 and the circulation cleaning cap 15 are attached to the nozzle plate along the circulation path from the IJ head 1 removed from the apparatus. The circulation path is one path in which a cleaning liquid containing nanobubbles is introduced from the injection solution injection port 2 of the IJ head and is discharged to the nozzle port 4 and the discharge port 3, and the injection port 2 and the discharge port 3 are inserted from the nozzle port 4. Two cleaning routes are assumed, starting from The former is suitable for cleaning the filter and the manifold 5 because most of the flow rate is concentrated on the route from the inlet 2 to the outlet 3. On the other hand, the latter is a path suitable for cleaning the nozzle 4 and the flow path 7 because the cleaning liquid is directly passed from the nozzle plate 8 to the channel 7 made of the piezoelectric element of the IJ head. In these two paths, the resistance when the cleaning liquid is pushed into the inside is considerably different, so that the bracket 16 fixing the IJ head can be rotated upside down as shown in FIG. When the cleaning liquid is introduced from the inlet 2, the nozzle plate 8 is directed downward and when the nozzle plate 8 is directed upward when the nozzle plate 8 is directed upward, as in the case of the IJ head operation, no extra load is applied. Therefore, the damage to the IJ head can be minimized. Circulation of the cleaning liquid is circulated by the liquid feed pump 19 around the cleaning liquid tank 17 directly connected to the nanobubble generating unit according to the set flow path of the switching valve 18. In the middle of this flow path, pressure is applied everywhere so as not to damage the filter 20 for removing the solidified substance and the gelled substance separated from the IJ head by washing and the channel 7 and the nozzle 4 in the IJ head. A sensor 21 is arranged to circulate. These controls are performed by a sequencer (PLC) 22 and fully automatic operation is possible.

  Next, the bubble diameter of nanobubbles used for cleaning will be mentioned. The cleaning liquid is usually an organic solvent such as ethyl alcohol or acetone. Since the hydrodynamic characteristics such as viscosity and surface tension of these solvents are significantly different from those of water, the bubble diameter and dissolution rate differ. Therefore, an additive etc. may be added and a physical property value may be approximated. It is the nozzle diameter that defines the size of the bubble. In particular, the problem of reliability such as clogging is not a general printer, but a coating apparatus used for manufacturing a thin film of an electronic device. The nozzle diameter of the IJ head used in this field is about 10 to 50 microns, and bubbles having a diameter larger than this cannot pass. In addition, in order to exert the cleaning effect, it is necessary to have a free stroke of about 10 times the average diameter of the bubbles. This suggests that it is necessary to suppress the bubble diameter to about 1/10 of the nozzle diameter.

  FIG. 4 shows an example of the measurement result of the bubble diameter when the solution is water. The bubble generation number distribution is shown, and the average bubble diameter is defined with a generation probability of 50%. It is necessary to collect such data under the actual cleaning agent and generate nanobubbles. FIG. 5 shows the relationship between the bubble diameter and the bubble rising speed. This data is for water, but as the bubble diameter increases, the ascent rate increases. That is, the disappearance speed is increased. If the bubble pool 13 is designed using this principle, bubbles having relatively uniform diameters can be obtained. Claim 2 is based on this idea.

  In addition, due to the optimization of the cleaning liquid, there may be a case where a sufficient cleaning effect can be expected without using the power of nanobubbles. An example of a mechanism for cleaning only by circulating the cleaning liquid is shown in FIG. Since the nanobubble generation unit occupies a considerable volume, it is possible to reduce the size and to build in the coating apparatus. Since the details have been described in the description of FIG. 3, although omitted here, the basic idea is based on claim 3.

  Next, a second embodiment will be described. FIG. 7 shows a perspective view of the IJ coating apparatus. The coating device comprises an IJ head 1, an IJ head support structure 23, a tank 24, a supply pipe 25, a substrate transport table 26, a table driving actuator 27, a guide rail 28, a position detection means 29, a pedestal 30 and a control device 31. IJ is applied onto the substrate 32 in a non-contact manner. The IJ head 1 is a device that receives supply of a discharge solution and branches and discharges it to a plurality of nozzles 4. The IJ head support structure 23 is a frame for supporting the IJ head 1 above the substrate transport table 26 and is mounted with the nozzle surface facing down. The tank 24 is a container for storing the discharge solution, and supplies the discharge solution to the IJ head 1 through the supply pipe 25. The substrate transport table 26 is a table that moves horizontally relative to the IJ head 1 along the guide rail 28 by a table driving actuator 27. A substrate 32 is held on the upper surface of the table by an electrostatic chuck or the like. The table driving actuator 27 is a driving device installed on the lower side of the substrate transfer table 26 and is usually placed on the guide rail 28. The guide rail 28 is a linear track laid on the pedestal 30. The above is a mechanism of a coating apparatus called a table moving type, but there is also a method of coating while fixing a table on which a substrate is placed and moving a structure including an IJ head. Further, the position detection means 29 detects the position of the substrate transport table 26 with a sensor, and feedback-controls the table driving actuator 27 so that the speed of the substrate transport table 26 is appropriate. The pedestal 30 is a foundation that supports the whole. Finally, the control device 31 is a device that controls operations such as movement speed and ejection timing of the IJ head 1 and the table driving actuator 27 by a computer or the like, and is a control tower of the entire system.

  The normal IJ coating device as shown here is equipped with a maintenance system for starting the air, filling the discharge solution, preventing drying, etc., but it is unstable and appears as a sign of preventing clogging. There is no mechanism to prevent or prevent discharge. Therefore, the simplest mechanism is to replace the discharge solution with the cleaning solution, put it through the injection port 2 of the IJ head, cover the nozzle plate 8 with the cleaning cap 33, and circulate in the same direction as during the discharge operation in FIG. Show. By only having this device, the ejection stability increases and normal application can be realized. This is the fourth aspect.

  Finally, a third embodiment will be described. As previously indicated, in order to maintain a stable discharge operation, not only clogging and narrowing of the nozzles and filters, which are the solution flow paths, but also the formation of droplets of the discharge solution It is important to recover the damage of the water repellent film 9 formed on the nozzle plate 8 that plays an important role. While repeating the discharge operation, the wall surface of the nozzle is severely worn due to the influence of fine solids contained in the discharge solution, and the water repellent film 9 formed on the nozzle plate 8 is also It may be damaged by a mechanical load during wiping operation (wiping) or filling suction operation (sucking), and stable droplets may not be formed. FIG. 9 schematically shows the meniscus shape of the discharge solution with respect to the nozzle cross section. In FIG. 6A, the water repellent treatment layer 9 is healthy, and ideal voltage droplets are formed when a voltage pulse for extruding is applied in this state. On the other hand, FIG. 5B shows a case where the water-repellent film is damaged, and it becomes easy to “wet” the discharge solution and the nozzle plate. Drops are difficult to form and even if formed, they become unstable. Therefore, the regeneration of the water repellent film is an extremely important matter for realizing stable ejection.

  FIG. 10 shows a schematic view of an apparatus for regenerating the water repellent film formed on the nozzle plate 8 of the IJ head. The supplied water repellent material is sprayed from the tank 34 containing the water repellent material from the two-fluid spray nozzle 35 toward a mist conveying fan (cross-flow fan) 36 that is a certain distance ahead. Among the fine particles of the water repellent material, relatively heavy ones are dropped and collected before reaching the once-through fan 36. Only what reaches the cross-flow fan 36 changes direction and accumulates on the nozzle plate of the IJ head. At this time, it is important that the water repellent film is uniformly regenerated and the nozzle is not filled. Therefore, it is preferable to form a film with as small particles as possible while avoiding heavy particles. Thereafter, the film moves to the drying chamber 37 and is dried by the heater 38, so that the water repellent film can be regenerated.

It is a general-view figure of the industrial inkjet head used as the object of the present invention. It is the figure which showed typically the solution flow path in the industrial inkjet head used as the object of this invention. 1 is a system diagram of an inkjet head cleaning maintenance system according to an embodiment of the present invention. FIG. It is an example of a measurement related to the distribution of the bubble diameter of nanobubbles related to the present invention. It is the figure which showed the relationship between the bubble diameter of the nanobubble relevant to this invention, and the rising speed. 1 shows an example of a system for cleaning an ink jet head only by circulation of a cleaning liquid according to an embodiment of the present invention. 1 is a perspective view of an ink jet coating apparatus according to the present invention. The example of a piping system at the time of incorporating a washing | cleaning system into the inkjet coating device which is one Example of this invention is shown. It is the figure which showed typically the meniscus shape just before droplet formation in the nozzle part of an inkjet head. (A) When the water repellent film is healthy (b) When the water repellent film is worn 1 shows a configuration and a perspective view of an apparatus for repairing a water repellent film in an embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet head 2 Solution injection port of inkjet head 3 Solution discharge port of inkjet head 4 Nozzle (mouth) of inkjet head
5 Manifold 6 Mesh filter 7 Electrode channel (flow path in inkjet head)
8 Nozzle plate 9 Water repellent treatment film 10 Circulating pressure pump 11 Pressurizing dissolution tank 12 Bubble generating nozzle 13 Bubble pool 14 Pressure cleaning cap 15 Circulating cleaning cap 16 Inkjet head fixing bracket 17 Cleaning liquid tank 18 Switching valve 19 Liquid feeding pump 20 Intermediate filter 21 Pressure sensor 22 Control sequencer (PLC)
23 Head support structure 24 Tank 25 Supply pipe 26 Substrate transport table 27 Table drive actuator 28 Guide rail 29 Position detection means 30 Base 31 Controller 32 Substrate 33 Cleaning cap 34 Water repellent material storage tank 35 Two-fluid spray nozzle 36 Mist transport Fan (through-flow fan)
37 Drying room 38 Heater

Claims (5)

  Nano-bubble generation mechanism in an inkjet head cleaning device for maintaining a stable ejection application for a long period of time without causing clogging of the inkjet head / nozzle in a film forming apparatus for ejecting and applying a coating solution onto a substrate using an inkjet head An apparatus and method for cleaning an ink jet head solution flow path by dissolving nanobubbles in a cleaning liquid.   2. The cleaning apparatus and method according to claim 1, wherein the average diameter of the generated nanobubbles is 1 micron or less.   Having a cleaning cap that can alternately inject the cleaning liquid from the inlet upstream of the coating solution of the inkjet head and the nozzle surface downstream, and equipped with a pressurized liquid feeding means that allows the cleaning liquid to circulate An inkjet head cleaning apparatus and method.   The cleaning solution piping is directly connected to the coating solution piping directly connected to the inlet and outlet of the inkjet head constituting the inkjet coating apparatus through a switching valve, and the opening and closing of the three openings of the inlet, outlet and nozzle are combined. Thus, an inkjet coating apparatus and method comprising a mechanism capable of in-line cleaning of the interior of the inkjet head, such as a filter surface of the inkjet head, a solution flow path sidewall, and a nozzle surface, by circulating the cleaning liquid. In inkjet coating, the water-repellent film on the nozzle surface, which has a large effect on the formation of droplets of the discharge solution, is subject to wear and tear due to long-term operation and damage caused by the discharge solution filling process and nozzle plate wiping process. An apparatus and method for forming a water-repellent layer using fine mist, wherein the film is formed without clogging the nozzle opening for repair.