JP7224906B2 - Module substrate cleaning method - Google Patents

Description

The present invention relates to a module substrate cleaning method for cleaning a module substrate in an ejection device that ejects an imprint material.

An imprint material ejection device that ejects an imprint material onto a substrate uses a cartridge that integrates an ejection head that ejects the imprint material from a plurality of ejection openings and a storage container that stores the imprint material. There is Such an ejection device has a maintenance mechanism that maintains and restores the ejection performance of the ejection head by eliminating clogging of the ejection ports provided on the module substrate and removing foreign matter adhering to the head surface on which the ejection ports are provided. It has

Japanese Patent Application Laid-Open No. 2002-200003 describes cleaning the inside of the ejection openings by ejecting cleaning liquid from cleaning nozzles that have an opening area larger than the opening area of the ejection openings and are provided corresponding to the ejection openings of the ejection head. ing.

Further, Japanese Patent Application Laid-Open No. 2002-200000 describes removing foreign matter in a flow path by attaching a cap to a nozzle surface, injecting a cleaning liquid from the nozzle surface into the nozzle by a pump, and sucking the cleaning liquid from the ink supply port side. ing.

JP 2012-96464 A JP-A-2005-125653

However, in the method of Patent Document 1, since only the inside of the ejection port is cleaned, foreign matter inside the ejection port can be removed, but foreign matter adhering to the head surface cannot be removed. Further, in the method of Patent Document 2, even if the foreign matter adhering to the head surface is removed, if the foreign matter is larger than the ejection port, the ejection port may be clogged with the foreign matter by suction.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a module substrate cleaning method capable of more reliably removing foreign matter in the ejection port and on the head surface.

Therefore, in the method for cleaning a module substrate of the present invention, a plurality of discharge ports provided on a first surface of a module substrate and capable of discharging a fluid, and a plurality of discharge ports provided on a second surface opposite to the first surface of the module substrate. the module substrate provided corresponding to each of the ejection ports , communicating with the ejection ports inside the module substrate, and having a plurality of supply ports having an opening area larger than the ejection ports ; a fluid discharge head having a common liquid chamber connected to a plurality of supply ports; a fluid containing portion connected to the common liquid chamber of the fluid discharge head and configured to contain a fluid; and a filling liquid contained therein. a filling liquid containing portion adjacent to the fluid containing portion via a flexible member and separated from each other by the flexible member; a second pressure control unit configured to be able to control the pressure P2 of the second space formed by the common liquid chamber and the fluid storage unit by controlling the pressure of the filling liquid storage unit. A cleaning method for cleaning the module substrate in an apparatus , wherein contact with the module substrate covers all of the plurality of discharge ports provided on the first surface, and the first surface of the module substrate is covered. a cleaning cap capable of forming a first space between ; a supply tank connected to the cleaning cap and configured to supply a fluid to the first space; and a supply tank connected to the cleaning cap to supply the fluid to the first a step of preparing a module substrate cleaning unit having a discharge tank configured to be capable of discharging from a space and a first pressure control section configured to be capable of controlling pressure P1 in the first space; a step of providing the first space by bringing the cleaning cap of the above into contact with the module substrate of the fluid ejection device; a step of filling the first space with a fluid; a first cleaning step of cleaning the second surface of the module substrate by generating a flow of fluid from the second space to the second space, and setting P1<P2 to clean the second space from the first space and a second cleaning step of cleaning the first surface of the module substrate by generating a fluid flow toward the substrate .

According to the present invention, it is possible to realize a method for cleaning a module substrate that can remove foreign matter in the ejection port and on the head surface.

It is the figure which showed the structure of the principal part of the discharge apparatus. It is a sectional view showing a discharge part. It is the figure which showed the module substrate washing|cleaning apparatus. It is the flowchart which showed the washing process. 4 is a flow chart showing a cleaning process according to this embodiment. It is a figure showing the composition of the important section of the discharge device concerning this embodiment. 4 is a flow chart showing a cleaning process according to this embodiment. It is a diagram showing a module substrate cleaning apparatus according to the present embodiment.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing the configuration of the essential parts of the ejection device 10. As shown in FIG. The discharge device 10 mainly includes a discharge section 11, a container 12, a pressure control section 13, and a circulation section 40 for circulating the discharge (fluid) inside the discharge section. A separation film 14 made of a flexible member is provided inside to separate the space inside the housing. Separation membrane 14 preferably has a thickness of 10 μm or more and 200 μm or less, and is preferably made of a material having low liquid and gas permeability. The separation membrane 14 can be formed of, for example, a film of a fluororesin material such as PFA or a composite multi-layer film of a combination of a fluororesin material and a plastic material. One accommodating portion 15 partitioned by the separation membrane 14 of the accommodating container 12 accommodates the discharge, and the other accommodating portion 16 (third space) accommodates the filling liquid. The accommodating portion 15 and the accommodating portion 16 are separated by the separation membrane 14 . The accommodation portion 16 is connected to the pressure control portion 13 by a connection pipe 17 , and the accommodation portion 15 is connected to the discharge portion 11 .

The pressure control unit 13 includes a tank of liquid to be filled, a pipe, a pressure sensor, a pump, a valve, and the like, and is configured to be able to control the pressure inside the storage unit 16 . By controlling the pressure of the filling liquid in the storage section 16 with the pressure control section 13 , the pressure of the discharged material in the storage section 15 can be controlled via the separation membrane 14 . As a result, the shape of the gas-liquid interface in the ejection section 11 can be stabilized, and the ejected material can be ejected with good reproducibility.

The circulation unit 40 has a passage 45 connected to the container 12 at both ends outside the container 12 , and a filter 41 and a pump 44 are arranged in the passage 45 . The circulation section 40 is connected to the storage section 15 of the storage container 12 , and the passage 45 communicates with the storage section 15 through a first opening 43 and a second opening 42 that open to the storage section 15 . The first opening 43 is an opening for supplying the discharge material inside the storage section 15 to the interior of the passage, and the second opening 42 is an opening for supplying the discharge material supplied from the first opening 43 to the storage section 15 . A pump 44 and a filter 41 for filtering discharge are arranged in a passage 45 connecting the first opening 43 and the second opening 42 . Considering the possibility of foreign matter being generated in the discharged matter due to dust generation from the pump 44 , the filter is positioned downstream of the pump 44 when the discharged matter flows from the first opening 43 to the second opening 42 . 41 is preferred.

Pump 44 is preferably provided within passage 45 , but may be provided outside passage 45 . When the pump 44 is driven, the discharge contained in the containing portion 15 is supplied from the first opening 43 to the passage 45 . Discharged matter supplied from the first opening 43 passes through the filter 41 inside the passage and is filtered, and then returns to the housing portion 15 via the second opening 42 . Then, it is supplied from the first opening 43 again. That is, the discharged matter in the container 15 is filtered by the filter 41 while circulating.

FIG. 2 is a cross-sectional view showing an enlarged discharge portion 11. As shown in FIG. The ejection section 11 includes a common liquid chamber 56 and a module substrate 57 . The module substrate 57 has a plurality of nozzles 54 each having a supply port 21 for supplying a discharge material to the module substrate 57 and a discharge port 19 capable of discharging the discharge material. An energy generating element 18 is provided for generating energy for generating the energy. Here, the surface of the module substrate 57 provided with the supply port 21 is referred to as a supply port side surface 59 , and the surface provided with the discharge ports 19 is referred to as a discharge port side surface 58 . The opening area of the discharge port 19 is smaller than the opening area of the supply port 21, and the cross-sectional area of the channel in the nozzle 54 is the smallest.

As the energy generating element 18, a piezoelectric element or a heating resistor can be used. It is preferable to use a piezoelectric element as the energy generating element, because a material containing a large amount of resin is often used as the ejected material. The supply port 21 communicates with the discharge port 19 inside the module substrate 57 . By controlling the energy generating element 18 with a controller, the ejected material 8 in the nozzle interior (pressure chamber) 20 between the energy generating element 18 and the ejection port 19 supplied from the supply port 21 is discharged from the ejection port 19 to the substrate. ejected upwards. The ejection section 11 is preferably an ejection head such as that used in an inkjet head or the like. Alternatively, a control valve or the like may be used to control the supply and stop of the discharge material.

FIG. 3 is a diagram showing the module substrate cleaning apparatus 100. As shown in FIG. The module substrate cleaning apparatus 100 includes a discharge device 10, a supply tank 63, a supply pipe 62, a cleaning cap 61, a discharge pipe 65, a discharge tank 66, a pressure control device 64, and the like. The supply tank 63 is a tank for supplying liquid to the cleaning cap 61 , and the cleaning cap 61 and the supply tank 63 are connected by a supply pipe 62 . The liquid to be supplied to the cleaning cap 61 is preferably the same as the liquid to be discharged. Alternatively, a cleaning liquid may be used as the liquid to be supplied to the cleaning cap 61, and after using the cleaning liquid, cleaning may be performed with the same liquid as the discharge matter. At that time, purging is performed until the cleaning liquid in the flow path and the module substrate is sufficiently replaced with the same liquid as the ejected matter. As the cleaning liquid, a liquid that dissolves the organic matter adhering to the module substrate may be used. Specifically, acrylic or silicone pressure-sensitive adhesives are examples of organic substances that can adhere to the module substrate. Therefore, liquids that dissolve these organic substances include alcohols such as isopropyl alcohol and ethanol, and ethers such as propylene glycol monomethyl ether acetate (PGMEA). One of the materials contained in the ejected material may be used as the cleaning liquid. In the following, a description will be given of a case in which a discharge material is used as the liquid in the supply tank 63. FIG.

The module substrate cleaning apparatus 100 has a flow of ejected material from the ejection port 19 toward the common liquid chamber 56 (first cleaning process) and a flow of ejected material from the common liquid chamber 56 toward the ejection port 19 (second cleaning process). and are alternately generated a plurality of times to clean the module substrate 57 . In this way, by performing cleaning with different flows a plurality of times, it is possible to appropriately remove even if the foreign matter attached to the inside of the ejection port (inside the nozzle) or the head surface is larger than the ejection port 19 . A cleaning method by the module substrate cleaning apparatus 100 will be described in detail below.

The cleaning cap 61 abuts on the module substrate 57 to cover all the ejection ports 19 located on the ejection port side surface 58 (head surface) of the module substrate 57, and the ejection port side surface 58 and the cleaning cap 61 form a first contact. A space 68 is formed. The discharge tank 66 is a tank for discharging the discharge discharged from the first space 68 , and the first space 68 and the discharge tank 66 are connected by a discharge pipe 65 . A pressure control device 64 is provided in the discharge pipe 65 , and the discharge material is supplied from the supply tank 63 to the first space 68 by controlling the pressure in the first space 68 with the pressure control device 64 . As described above, the pressure inside the housing portion 15 can be controlled by the pressure control portion 13 . Since the storage portion 15 communicates with the second space 67, which is a space obtained by combining the common liquid chamber 56 inside the discharge portion 11 and the inside 55 of the storage container 12, the pressure in the second space 67 is It is controlled by the pressure controller 13 .

Here, in order to generate a flow in the module substrate 57, one of the first space 68 and the second space 67 sandwiching the module substrate 57 should be made to have a higher pressure than the other space. In other words, by providing a difference between the pressure P1 in the first space 68 and the pressure P2 in the second space 67, it is possible to generate a flow of the ejected substance inside the module substrate 57 (inside the nozzle).

When the pressure P1 is higher than the pressure P2 and the circulating unit 40 circulates the discharge inside the container 15, there are two patterns of flow. When the difference between the pressure P1 and the pressure P2 is small (P1>P2), a flow from the discharge port 19 toward the supply port 21 and a flow along the supply port side surface 59 in the common liquid chamber 56 are generated. . When the difference between the pressure P1 and the pressure P2 is large (P1>>P2), a flow from the discharge port 19 toward the supply port 21 is generated.

Conversely, when pressure P1 is less than pressure P2, there are also two patterns of flow that occur. When the difference between the pressure P1 and the pressure P2 is small (P1<P2), a flow from the supply port 21 toward the ejection port 19 and a flow along the ejection port side surface 58 of the ejected material are generated. When the difference between the pressure P1 and the pressure P2 is large (P1<<P2), a flow from the supply port 21 to the discharge port 19 is generated. By generating different flows in the module substrate 57 with such a combination of the pressure P1 and the pressure P2, the supply port side surface 59, the discharge port side surface 58, and the inside of the nozzle 20 can be cleaned with one cleaning device. becomes possible.

Next, the order of parts to be cleaned will be described. In the present invention, first, the supply port side surface 59 and the discharge port side surface 58 are washed, and then the inside of the nozzle 20 is washed. The reason for this is that if the inside of the nozzle 20 is washed first, foreign matter adhering to the supply port side surface 59 and the discharge port side surface 58 may enter the nozzle inside 20 from the supply port 21 and the discharge port 19 . If the foreign matter that has entered is large, it may cause clogging of the nozzle 54, so the surface 59 on the supply port side and the surface 58 on the discharge port side are cleaned first.

FIG. 4 is a flow chart showing the cleaning process in this embodiment. The processing of the cleaning step in this embodiment will be described below using this flow chart. When the cleaning process is started while the cleaning cap 61 is in contact with the discharge part 11, in S1, prior to cleaning the module substrate, the first space 68 of the cleaning cap 61 of the module substrate cleaning apparatus 100, the supply pipe 62, and the discharge pipe are removed. The pipe 65 is filled with the discharge material. Therefore, the pressure P1 of the pressure control device 64 is lowered from 0 kPa to a negative value. As a result, the pressure in the first space 68 is reduced to generate a flow of discharge from the supply tank 63 to the discharge tank 66 via the first space 68, thereby discharging the first space 68, the supply pipe 62, and the discharge pipe 65. fill with things However, this process alone may not fill the upper portion of the first space 68 with the discharge. Therefore, the pressure P2 in the second space 67 is then increased from 0 kPa to a positive value by the pressure control unit 13 to satisfy the pressure P2>pressure P1 (P1<0 kPa, P2>0 kPa). A flow of discharge towards the space 68 is produced. As a result, the upper portion of the first space 68 is filled with the discharge substance, and the entire first space 68 is filled with the discharge substance.

Thereafter, in S2, the supply port side surface (supply port surface) 59 is washed (supply port surface cleaning). Here, first, the pressure control unit 13 lowers the pressure P2 in the second space 67 to make the pressure P2 in the second space 67 lower than the pressure P1 in the first space 68 (P1>P2, P1<0 kPa, P2< 0 kPa). As a result, a flow of the ejected material from the ejection port 19 toward the supply port 21 is generated within the module substrate 57 . Furthermore, by circulating the discharged matter inside the housing portion 15 by the circulation portion 40, the discharged matter is induced to flow along the supply port side surface 59, and the foreign matter adhering to the supply port side surface 59 is removed.

Then, in S3, the ejection port side surface (ejection port surface) 58 is washed (ejection port surface cleaning). The pressure control unit 13 increases the pressure P2 in the second space 67 to make the pressure P2 in the second space 67 higher than the pressure P1 in the first space 68 (P1<P2, P1<0 kPa, P2>0 kPa). As a result, a flow of ejected material from the supply port 21 toward the ejection port 19 is generated within the module substrate 57, and foreign matter adhering to the ejection port side surface 58 is removed.

After that, in S4, the inside of the nozzle is washed A for flowing the ejected matter from the ejection port 19 to the supply port 21. As shown in FIG. Here, the pressure control unit 13 lowers the pressure P2 in the second space 67 to make the pressure P2 in the second space 67 lower than the pressure P1 in the first space 68 (P2<<P1, P1<0 kPa, P2< 0 kPa). As a result, a flow of the ejected material from the ejection port 19 to the supply port 21 is generated, so that the foreign matter adhering to the wall of the nozzle interior 20 is flushed out from the supply port 21 . At that time, it is preferable to clean while driving the energy generating element 18 at the same time. Here, it is conceivable that foreign matter that has flowed out of the supply port 21 in S4 adheres to the surface 59 on the supply port side. Therefore, in S5, a flow along the supply port side surface 59 is generated.

In S5, the pressure control unit 13 increases the pressure P2 in the second space 67 to make the pressure P2 in the second space 67 lower than the pressure P1 in the first space 68 (P2<P1, P1<0kPa, P2<0kPa ). As a result, a flow of the ejected matter from the ejection port 19 toward the supply port 21 is generated, and a flow of the ejected matter along the supply port side surface 59 is induced to remove foreign matter from the supply port side surface 59 . At the same time, the circulating portion 40 circulates the discharged matter inside the housing portion 15 , and the filter 41 filters foreign matter separated from the supply port side surface 59 .

After that, in S6, the inside of the nozzle is washed B for flowing the ejected matter from the supply port 21 to the ejection port 19. FIG. The pressure control unit 13 increases the pressure P2 in the second space 67 to make the pressure P2 in the second space 67 higher than the pressure P1 in the first space 68 (P2>>P1, P1<0 kPa, P2>0 kPa). As a result, the discharge material flows from the supply port 21 to the discharge port 19 , so that the foreign matter adhering to the wall of the nozzle interior 20 is flushed out from the discharge port 19 . At that time, it is preferable to clean while driving the energy generating element 18 at the same time. By driving the energy generating element 18 , vibration is applied to the ejected matter, and foreign matter is flowed out from the ejection port 19 . Here, it is conceivable that foreign matter that has flowed out of the ejection port 19 in S6 adheres to the ejection port side surface 58 . Therefore, in S7, a flow along the outlet side surface 58 is generated.

In S7, the pressure control unit 13 reduces the pressure P2 in the second space 67 to make the pressure P2 in the second space 67 higher than the pressure P1 in the first space 68 (P2>P1, P1<0 kPa, P2>0 kPa ). As a result, a flow of the discharge material is generated from the supply port 21 toward the discharge port 19 , and a flow of the discharge material along the discharge port side surface 58 is induced to remove foreign matter from the discharge port side surface 58 .

After that, in S8, it is determined whether the processing from S4 to S7 has been repeated N (N>0) times, and if not repeated, the process returns to S4. In S8, if the processes from S4 to S7 have been completed N times, the cleaning process is completed.

The means for judging the end of the cleaning process (termination judgment) may use the ejection evaluation result (ejection result) using the ejection device, or may use the particle measurement result using the particle measurement device. FIGS. 5 and 7 are flow charts showing the cleaning process in this embodiment, which is the same as FIG. 4 from S1 to S7, but differs in the process of determining whether to end the cleaning process. 5, the flow chart in FIG. 7 is used to determine the end of the cleaning process based on the ejection evaluation result using the ejection evaluation device. will be described.

In FIG. 5, in S8, a process (S8-1) for performing ejection evaluation and a process (S8-2) for determining whether or not the ejection evaluation result is good are performed. FIG. 6 shows an example of the ejection device used in S8-1. The ejection detection mechanism 71 shown in FIG. 6 detects the ejection 8 . The ejection detection mechanism 71 is located at a location where information on the ejection material 8 ejected from the ejection device 10 can be obtained. Information about the ejected material 8 may be obtained by processing an image acquired by a camera or the like, or by detecting light emitted from an irradiation unit (not shown) and determining whether or not the ejected droplets have passed through the emitted light. It may be one that detects whether In S8-2, based on the information obtained by the ejection detection mechanism 71, for example, it is confirmed that the liquid has been ejected from the ejection holes at a desired speed and volume, and it is determined that the ejection evaluation result is good. , ending the washing process.

In FIG. 7, in S8, a process of evaluating particles (S8-1) and a process of determining whether the result of particle measurement is good (S8-2) are performed. FIG. 8 shows an example of a particle measuring device used in S8-1. A particle measurement device 72 shown in FIG. 8 measures particles in the cleaning liquid. In S8-2, it is confirmed that the particle measurement result is 0.1 particles/ml or less, and the cleaning process is completed by judging that the particle measurement result is good. As the cleaning liquid for particle measurement, in addition to liquids that dissolve organic substances, water, which generally has high particle measurement sensitivity, may be used.

Here, in the cleaning of the inside of the nozzle 20 in the cleaning process described above, the process (S4) is performed by generating a flow from the supply port 21 to the supply port 21 to generate a flow from the supply port 21 to the discharge port 19. The reason why this is performed prior to the process (S6) will be explained. The discharge port 19 has the smallest cross-sectional area in the flow path through which the discharge material flows. Therefore, when the flow from the supply port 21 to the discharge port 19 is first induced, if foreign matter having a size larger than the opening area of the discharge port 19 adheres to the wall of the nozzle interior 20, the discharge port 19 may be clogged. have a nature. Therefore, in the present embodiment, a process for generating a flow from the ejection port 19 to the supply port 21 is performed in advance, so that the foreign matter adhering to the wall of the nozzle interior 20 is discharged from the supply port 21 and the ejection port 19 is discharged. prevent clogging in the

In this manner, the module substrate is cleaned by alternately generating a flow from the discharge port to the supply port and a flow from the supply port to the discharge port. As a result, it is possible to realize a method for cleaning a module substrate that can more reliably remove foreign matter in the ejection port and on the head surface.

REFERENCE SIGNS LIST 13 Pressure control unit 19 Discharge port 21 Supply port 57 Module substrate 58 Discharge port side surface 59 Supply port side surface 67 Second space 68 First space 100 Module substrate cleaning device

Claims (13)

a plurality of discharge ports provided on a first surface of a module substrate and capable of discharging a fluid; and a second surface of the module substrate opposite to the first surface provided corresponding to each of the plurality of discharge ports , a module substrate including a plurality of supply ports communicating with the ejection ports inside the module substrate and having an opening area larger than the ejection ports; and a common liquid chamber connected to the plurality of supply ports. a fluid ejection head having
a fluid containing portion connected to the common liquid chamber of the fluid ejection head and capable of containing a fluid;
a filling liquid storage section configured to be able to store a filling liquid therein, adjacent to the fluid storage section via a flexible member, and arranged separated from each other by the flexible member;
A second space configured to be connected to the filling liquid storage section and control the pressure of the filling liquid storage section to control the pressure P2 of the second space formed by the common liquid chamber and the fluid storage section. a pressure control unit of
A cleaning method for cleaning the module substrate in a fluid ejection device comprising :
a cleaning cap capable of covering all of the plurality of ejection ports provided on the first surface by coming into contact with the module substrate and forming a first space with the first surface of the module substrate; a supply tank connected to a cleaning cap and configured to supply fluid to the first space; a discharge tank connected to the cleaning cap and configured to discharge fluid from the first space; a first pressure control unit configured to be able to control the pressure P1 of the space;
providing a module substrate cleaning unit having
providing the first space by bringing the cleaning cap of the module substrate cleaning unit into contact with the module substrate of the fluid ejection device;
filling the first space with a fluid;
a first cleaning step of cleaning the second surface of the module substrate by generating a fluid flow from the first space toward the second space by setting P1>P2 ;
a second cleaning step of cleaning the first surface of the module substrate by causing a fluid flow from the second space toward the first space by satisfying P1<P2;
A method for cleaning a module substrate, comprising: 2. The module substrate cleaning method according to claim 1, wherein in at least one of the first cleaning step and the second cleaning step, vibration is applied to the fluid by using a mechanism for ejecting the fluid of the module substrate . . 3. The module substrate cleaning method according to claim 1, wherein the fluid is a liquid that dissolves organic matter adhering to the module substrate. 4. The module substrate cleaning method according to claim 3, wherein the liquid is alcohol or ether. 5. The module substrate cleaning method according to claim 1, wherein the second cleaning step is performed after performing the first cleaning step. 6. The module substrate cleaning method according to claim 1, wherein the first cleaning step and the second cleaning step are performed multiple times. 7. The module substrate cleaning method according to any one of claims 1 to 6, wherein the termination of the first cleaning step and the second cleaning step is determined based on the result of fluid ejection from the ejection port. 8. The method according to any one of claims 1 to 7, wherein the end of the first cleaning step and the second cleaning step is determined based on particle measurement results of the fluid filling the first space and the second space. module substrate cleaning method. In the first cleaning step, the pressure in the second space is controlled by the second pressure control unit capable of controlling the pressure in the second space, thereby causing the fluid to flow from the discharge port to the supply port. The module substrate cleaning method according to any one of claims 1 to 8. 10. The method of cleaning a module substrate according to claim 9, wherein in the second cleaning step, the pressure in the second space is controlled by the second pressure control unit to cause the fluid to flow from the supply port to the discharge port. . The first cleaning step and the second cleaning step are performed by controlling the pressure in the filling liquid storage portion separated by the second space and the flexible member by the second pressure control portion. 11. The method for cleaning a module substrate according to 10. 12. The module substrate cleaning method according to any one of claims 1 to 11, further comprising a circulation step of circulating the fluid in the second space. 13. The method of cleaning a module substrate according to claim 12 , wherein the circulating fluid is filtered in the circulating step.

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