Patent Publication Number: US-9409402-B2

Title: Liquid filling method, liquid filling device, and liquid container

Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to a method and a device for filling a container with a liquid maintaining the cleanness of the liquid, and to a liquid container. 
     2. Related Art 
     For example, JP-A-2005-186343 discloses a method of filling a liquid chamber unit with a liquid, the liquid chamber unit including a liquid chamber capable of containing a liquid therein and a communication port that secures communication between inside and outside of the liquid chamber. The method includes aspirating air from inside of the liquid chamber through the communication port by using a first suction unit, introducing, by using a liquid injector, the liquid stored in a liquid storage unit into the liquid chamber as cleaning liquid through the communication port, aspirating the cleaning liquid introduced into the liquid chamber through the communication port by using a second suction unit, mixing the cleaning liquid aspirated by the second suction unit and the liquid in the liquid storage unit by using a mixer, and introducing the liquid mixed by the mixer into the liquid chamber by using the liquid injector. 
     By the liquid filling method according to JP-A-2005-186343, the liquid supplied from the liquid storage unit is introduced into the liquid chamber depressurized by the first suction unit, and the liquid thus introduced is aspirated by using the second suction unit, in the manufacturing process of the liquid chamber unit. Accordingly, dust and air in the liquid chamber and the communication port are discharged together with the liquid. Then the liquid aspirated by the second suction unit is mixed with the liquid in the liquid storage unit by the mixer and introduced into the liquid chamber by the liquid injector, and therefore the aspirated liquid can be utilized as the liquid to be stored in the liquid chamber unit, without being disposed of. Such an arrangement improves the degree of deaeration and cleanness in the liquid chamber unit, and allows the liquid to be efficiently utilized in the manufacturing process of the liquid chamber unit. 
     To perform the liquid filling method according to JP-A-2005-186343, however, the cleanness of the first and the second suction unit and the liquid injector, through which the liquid passes, has to be secured in advance. The liquid to be actually filled may be employed as the cleaning liquid in order to secure the cleanness in advance, however the liquid used for cleaning is not always reusable. For example, in the case where the cleaning liquid contains an ionic impurity, the liquid may be non-reusable depending on the purpose of use of the liquid. Further, the complicated structure of the liquid filling device often brings about loss of the liquid in the aspirating process and the filling process. Therefore, especially when an expensive liquid is to be filled in the liquid chamber unit, the loss of the liquid has to be minimized as much as possible. 
     SUMMARY 
     Accordingly, the invention may be advantageously realized as the following application examples and embodiments. 
     Application Example 1 
     A first example represents a method of filling a sealable liquid container with a liquid. The method includes performing a first filling of a first liquid container with the liquid, transferring the liquid filled in the first liquid container to a second liquid container through a filter at least capable of removing a foreign matter, exchanging the second liquid container located downstream of the filter with the first liquid container, and performing a second filling of the first liquid container with the liquid through the filter. 
     By the mentioned method, the liquid filled in the first liquid container is transferred to the second liquid container. Therefore, the foreign matter existing in the first liquid container is discharged together with the liquid and then removed by the filter. In other words, the internal area of the first liquid container is cleaned with the liquid. Thereafter the second filling step follows in which the liquid is again filled in the first liquid container through the filter. Such an arrangement allows the liquid to be filled in the first liquid container, with sufficient cleanness secured inside the first liquid container. 
     In addition, the supply path for supplying the liquid therethrough is also cleaned with the liquid, through the first filling step and the transfer step. In case that the second liquid container, filled with the liquid transferred from the first liquid container through the filter, is suspected to contain an ionic impurity other than the foreign matter, the second liquid container may be disposed of. Thus, repeating the steps according to the foregoing liquid filling method enables the liquid to be filled in the liquid container constantly maintaining the cleanness inside the liquid container. 
     Application Example 2 
     In the foregoing liquid filling method, the second filling step may include connecting the second liquid container to the upstream end of the filter, connecting the first liquid container to the downstream end of the filter, and transferring the liquid transferred to the second liquid container to the first liquid container through the filter. 
     In this case, the liquid from which the foreign matter has been removed can be filled in the first liquid container cleaned through the first filling step and the transfer step, and the internal area of the second liquid container can be cleaned with the liquid, by transferring the liquid from the second liquid container to the first liquid container in the second filling step. Accordingly, the second liquid container filled with the liquid is exempted from being disposed of, and therefore loss of the liquid can be reduced in the liquid filling process. 
     Application Example 3 
     A third example represents another method of filling a sealable liquid container with a liquid. The method includes connecting a first liquid container and a second liquid container in parallel on a downstream side of a filter at least capable of removing a foreign matter, performing a first filling of the first liquid container with the liquid through the filter, transferring the liquid to the second liquid container through the filter after returning the liquid in the first liquid container to the upstream side of the filter, performing a second filling of the first liquid container with the liquid through the filter after returning the liquid transferred to the second liquid container to the upstream side of the filter, and performing a third filling of the second liquid container with the liquid after the second filling. 
     The foregoing method allows the internal area of the first liquid container to be cleaned with the liquid, through the first filling step and the transfer step. Then through the second filling step the liquid can be again filled in the first liquid container that has been cleaned, and the internal area of the second liquid container can be cleaned with the liquid. Further, through the third filling step the liquid can be filled in the second liquid container that has been cleaned. Thus, the foregoing liquid filling method eliminates, unlike the method according to the application example 1, the need to exchange the second liquid container with the first liquid container, and allows the liquid to be filled in the liquid container with sufficient cleanness secured. 
     Application Example 4 
     In the liquid filling method arranged as above, the first liquid container and the second liquid container, both serving as the liquid container, may each include a flexible liquid bag for storing the liquid therein and a communication port that secures communication between inside and outside of the liquid bag. To transfer the liquid filled in the first liquid container or the second liquid container, a pressure may be applied to the liquid bag from outside so as to discharge the liquid from the liquid bag through the communication port. 
     By the foregoing method, the liquid is discharged by the pressure applied to the liquid bag from outside. Therefore, unlike the method according to JP-A-2005-186343 in which a suction unit is employed to discharge the liquid, the liquid is exempted from the risk of contamination by the suction unit. Further, not only the liquid bag but also the communication port can be cleaned at a time. 
     Application Example 5 
     A fifth application example represents a liquid filling device that fills a sealable liquid container with a liquid. The liquid filling device includes a supply path of the liquid, a filter connected to the supply path and at least capable of removing a foreign matter, a first on-off valve provided between the supply path and the filter, a first connector provided between the first on-off valve and the filter, a second on-off valve provided between the first connector and the filter, or downstream of the filter, a second connector provided downstream of the filter via the second on-off valve therebetween, and a first liquid container and a second liquid container respectively connected to the first connector and the second connector. The first liquid container connected to the first connector is filled with the liquid through the supply path and the first on-off valve, and the liquid thus filled is transferred to the second liquid container connected to the second connector through the second on-off valve and the filter. 
     In the foregoing liquid filling device, the liquid filled in the first liquid container connected to the first connector is transferred through the filter to the second liquid container connected to the second connector, and therefore the first liquid container connected to the first connector can be cleaned with the liquid. Then the first liquid container can be filled with the liquid with sufficient cleanness secured, by connecting the first liquid container that has been cleaned to the second connector and filling the first liquid container with the liquid through the filter. Therefore, the liquid filling device thus configured allows the liquid container to be filled with the liquid with sufficient cleanness secured. 
     Application Example 6 
     In the foregoing liquid filling device, the first and the second liquid container respectively connected to the first and the second connector may be exchanged after the liquid is transferred, and the liquid may be again transferred from the first liquid container filled with the liquid to the second liquid container not yet filled with the liquid, through the filter. 
     In this case, both the first and the second liquid container, respectively connected to the first and the second connector, can be cleaned with the liquid. 
     Application Example 7 
     A seventh application example represents another liquid filling device that fills a sealable liquid container with a liquid. The liquid filling device includes a supply path of the liquid, a filter connected to the supply path and at least capable of removing a foreign matter, a first on-off valve provided downstream of the filter, a first connector connected to the first on-off valve, a second on-off valve provided downstream of the filter parallel to the first on-off valve, a second connector connected to the second on-off valve, a first bypass route provided between the supply path upstream of the filter and the first connector, a third on-off valve provided on the first bypass route, a second bypass route provided between the supply path upstream of the filter and the second connector, and a fourth on-off valve provided on the second bypass route. A first liquid container and a second liquid container are respectively connected to the first connector and the second connector. The liquid is filled in the first liquid container connected to the first connector through the supply path, the filter, and the first on-off valve, with the second on-off valve, the third on-off valve, and the fourth on-off valve closed, and then the first on-off valve is closed and the liquid filled in the first liquid container is transferred to the second liquid container connected to the second connector through the first bypass route, the filter, and the second on-off valve. Then the second on-off valve is closed and the liquid transferred to the second liquid container is again transferred to the first liquid container connected to the first container through the second bypass route, the filter, and the first on-off valve. 
     In the foregoing liquid filling device, providing the first bypass route and the second bypass route enables the first and the second liquid container, respectively connected to the first and the second connector, to be cleaned with the liquid without the need to exchange the first liquid container and the second liquid container. Such a configuration eliminates the need to exchange the liquid containers and allows each of the liquid containers to be cleaned before being filled with the liquid. 
     Application Example 8 
     In the foregoing liquid filling device, the first on-off valve, the third on-off valve, and the fourth on-off valve may be closed and the second on-off valve may be opened, so as to again fill the second liquid container connected to the second connector through the supply path and the filter, after the liquid is again transferred to the first liquid container connected to the first connector. 
     Such a configuration allows the second liquid container, connected to the second connector and now cleaned, to be filled with the liquid from which foreign matters have been removed. 
     Application Example 9 
     In the foregoing liquid filling device, the liquid container may include a flexible liquid bag for storing the liquid therein, and a communication port that secures communication between inside and outside of the liquid bag. The liquid filling device further includes a pressurizing device that applies a pressure to the liquid bag from outside so as to discharge the liquid from the liquid bag through the communication port. 
     Such a configuration allows the liquid to be discharged by the pressure applied by the pressurizing device to the liquid bag from outside. Therefore, unlike the arrangement according to JP-A-2005-186343 in which a suction unit is employed to discharge the liquid, the liquid is exempted from the risk of contamination by the suction unit. Further, not only the liquid bag but also the communication port can be cleaned at a time. 
     Application Example 10 
     In the foregoing liquid filling device, preferably, the filter may be configured so as to discharge an air bubble in the liquid. 
     Such a configuration allows the liquid container to be filled with the liquid from which foreign matters and air bubbles have been removed. 
     Application Example 11 
     An eleventh application example represents a liquid container configured to be filled with a liquid by the liquid filling method according to the foregoing application examples. 
     Application Example 12 
     A twelfth application example represents a liquid container configured to be filled with a liquid by the liquid filling device according to the foregoing application examples. 
     The liquid container thus configured can have the internal area cleaned, and be filled with a liquid from which foreign matters have been removed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements. 
         FIG. 1  is a schematic perspective view showing a configuration of a dispensing device. 
         FIG. 2  is a schematic perspective view showing a configuration of a dispensing head. 
         FIG. 3  is a schematic perspective view showing a configuration of an ink pack serving as a liquid container. 
         FIG. 4  is a schematic drawing showing a configuration of a liquid filling device according to a first embodiment. 
         FIG. 5  is a schematic cross-sectional view showing a configuration of a filter. 
         FIG. 6  is a schematic drawing showing a configuration of a pressurizing device for the ink pack. 
         FIGS. 7A to 7C  are schematic drawings for explaining a liquid filling method according to the first embodiment. 
         FIG. 8  is a schematic drawing showing a configuration of a liquid filling device according to a second embodiment. 
         FIGS. 9A to 9D  are schematic drawings for explaining a liquid filling method according to the second embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     Hereafter, embodiments of the invention will be described referring to the drawings. For the sake of better visual recognition, components shown in the drawings may be enlarged or minified as the case may be. 
     The embodiments represent a liquid container that stores therein a functional liquid containing a functional material (hereinafter, liquid or ink) and a liquid filling device that fills the liquid container with the functional liquid, to be used in a dispensing device that dispenses the functional liquid onto a workpiece to thereby form a functional film containing the functional material on the workpiece. 
     First Embodiment 
     Dispensing Device 
     Referring first to  FIGS. 1 to 3 , the dispensing device and the liquid container will be described.  FIG. 1  is a schematic perspective view showing a configuration of the dispensing device,  FIG. 2  is a schematic perspective view showing a configuration of a dispensing head, and  FIG. 3  is a schematic perspective view showing a configuration of an ink pack serving as the liquid container. 
     As shown in  FIG. 1 , the dispensing device  1  includes a stage  7  on which a substrate W exemplifying the workpiece is to be placed, and a dispensing head  50  that dispenses a functional liquid in the form of liquid droplets onto the substrate W placed on the stage  7 . The functional liquid is supplied to the dispensing head  50  from an ink cartridge  11  including therein an ink pack  20  (see  FIG. 3 ), exemplifying the liquid container, filled with the functional liquid, through a tube  27 . 
     The dispensing device  1  includes an x-direction guide shaft  3  for driving a carriage  10  on which the dispensing head  50  is mounted in a sub scanning direction (X-direction), an X-axis driving motor  2  that rotates the X-direction guide shaft  3 , a Y-direction guide shaft  4  for driving the stage  7  in a main scanning direction (Y-direction) orthogonal to the sub scanning direction (X-direction), and a Y-axis driving motor  5  that rotates the Y-direction guide shaft  4 . The dispensing device  1  also includes a base table  9  on which the X-direction guide shaft  3  and the Y-direction guide shaft  4  are mounted, and a control unit  15  provided under the base table  9 . The X-direction guide shaft  3 , the X-axis driving motor  2 , the Y-direction guide shaft  4  and the Y-axis driving motor  5  constitute a moving mechanism that relatively moves the stage  7  in the main scanning direction (Y-direction) and the sub scanning direction (X-direction) with respect to the dispensing head  50 , with the stage  7  disposed so as to oppose the dispensing head  50 . 
     Further, the dispensing device  1  includes a cleaning mechanism  8  that cleans (restores) the dispensing head  50 . The cleaning mechanism  8  also includes a Y-axis driving motor  6 . 
     The dispensing head  50  is mounted on the carriage  10  such that a nozzle surface  58   a  (see  FIG. 2 ) is opposed to the stage  7 . The dispensing head  50  is configured to vary the amount of the droplet of the functional liquid to be dispensed therefrom (dispensing amount) according to a voltage supplied by the control unit  15 . 
     The X-axis driving motor  2  may be, for example, a stepping motor that rotates the X-direction guide shaft  3  upon receipt of an X-direction driving pulse signal from the control unit  15 , to thereby move the dispensing head  50  engaged with the X-direction guide shaft  3  in the X-direction. 
     Likewise, the Y-axis driving motors  5 ,  6  may each be, for example, a stepping motor that rotates the Y-direction guide shaft  4  upon receipt of a Y-direction driving pulse signal from the control unit  15 , to thereby move the stage  7  and the cleaning mechanism  8  in the Y-direction. 
     The cleaning mechanism  8  is moved to a position close to the dispensing head  50 , and serves to aspirate an excess of the functional liquid in close contact with the nozzle surface  58   a  (in  FIG. 2 ) of the dispensing head  50  (capping), wipe the nozzle surface  58   a  to which the functional liquid is stuck (wiping), dispense the functional liquid through all nozzles  51  of the dispensing head  50  (preliminary dispensation), and receive residual functional liquid to discharge the same (restoration). 
     The entirety of the dispensing device  1  is enclosed in a clean booth  16 . Cleaned air is introduced into the clean booth  16  through a HEPA unit  17  located on the ceiling of the clean booth  16 . Accordingly, cleanness is secured inside the clean booth  16 , to keep a foreign matter from sticking to the surface of the substrate W before the functional liquid is dispensed onto the surface of the substrate W. 
     As shown in  FIG. 2 , the dispensing head  50  is of a dual type including an introduction chamber  53  of the functional liquid having a pair of connection needles  54 , a head substrate  55  stacked on the introduction chamber  53 , and a head main body  56  mounted on the head substrate  55  and including an in-head flow path for the functional liquid. The connection needles  54  are each connected to the ink cartridge  11  through the tube  27 , so that the functional liquid is introduced into the in-head flow path through the connection needles  54 . The head substrate  55  includes a pair of connectors  59  connected to a head driving circuit through a flexible flat cable. 
     The head main body  56  includes a pressure unit  57  having a cavity in which an actuator such as a piezoelectric element is provided, and a nozzle plate  58  including a pair of nozzle rows  52 ,  52  formed in parallel on the nozzle surface  58   a.    
     The nozzle rows  52 ,  52  each include a plurality (in this embodiment, 180) of nozzles  51  aligned on the nozzle plate  58  at generally regular intervals, such that the nozzles on one of the rows are shifted by half a pitch from the nozzles of the other row. The nozzle pitch in this embodiment is approximately 140 μm. Accordingly, 360 nozzles  51  are aligned at intervals of approximately 70 μm, when viewed in the direction orthogonal to the nozzle rows  52 . 
     In the dispensing head  50 , an electrical signal representing a driving waveform applied to the actuator from the head driving circuit causes a change in volume of the cavities respectively associated with the nozzles  51  of the pressure unit  57 , so that a pressure is applied owing to a pumping effect to the functional liquid filled in the cavity, and thus the functional liquid is dispensed through the nozzle  51  communicating with the cavity, in the form of a droplet. 
     The dispensing head  50  may be what is known as an ink jet head, and the actuator may be, without limitation to the piezoelectric element, an electrothermal converter such as a heater that heats the functional liquid so as to be dispensed through the nozzle  51 , or an electromechanical converter that electrostatically deforms a vibrating plate constituting the cavity. 
     Liquid Container 
     As shown in  FIG. 3 , the ink pack  20  exemplifying the liquid container in the invention includes a liquid bag  21  and a communication port  25  for communication between inside and outside of the liquid bag  21 . The liquid bag  21  is composed of two flexible rectangular films  22 ,  23  of the same size superposed on each other, and formed into a bag shape by thermal bonding of the periphery of the four sides. In addition, the communication port  25  is interposed between the films  22 ,  23  on one of the sides  24  of the liquid bag  21 . Accordingly, the internal space of the liquid bag  21  is sealed, to be filled with the functional liquid. 
     The films  22 ,  23  have a multilayer structure composed of thermoplastic resin layers, such as polyethylene, and a gas barrier layer such as aluminum vapor-deposited between the resin layers. The communication port  25  is formed of a resin that can be thermally bonded with the thermoplastic resin layers of the films  22 ,  23 . Thus, the functional liquid is introduced into the liquid bag  21  through the communication port  25 . Upon closing the communication port  25 , the ink pack  20  filled with the functional liquid can be tightly sealed. The capacity of the ink pack  20  serving as the liquid container is, for example, 500 ml. 
     The ink pack  20  is filled with the functional liquid by using the liquid filling device to be subsequently described, and therefore the functional liquid can be retained in the ink pack  20  in which cleanness is secured free from foreign matters. Accordingly, upon dispensing the functional liquid in the ink pack  20  thus prepared onto the substrate W through the dispensing head  50  of the dispensing device  1 , the functional film free from foreign matters can be stably formed on the substrate W. Here, the foreign matters to be removed in this embodiment include those intruding from the working environment such as metal powder and fibers, and a part of the functional liquid that has turned into gel. 
     Further, a plurality of dispensing heads  50  may be mounted on the carriage  10  of the dispensing device  1  instead of one, according to the type of the functional liquid to be dispensed. In this case, the same number of ink cartridges  11 , each including the ink pack  20 , as that of the types of the functional liquid are to be provided. 
     An example of the functional liquid (ink) to be filled in the ink pack  20  is one that contains a material that forms a light emitting layer, employed for forming a light emitting layer of an organic electroluminescence (EL) element through a liquid-phase process. The material for forming a light emitting layer contains a low- or high-molecular organic semiconductor material, and the functional liquid contains a material that disperses or dissolves the semiconductor material, for example an organic solvent. It is essential that such a functional liquid be free from foreign matters and ionic impurities, in order to secure a desired emission characteristic and life span of the light emitting layer. 
     Here, the organic EL element is composed of an anode, a cathode, and a functional layer including the light emitting layer interposed between the anode and the cathode. The functional layer includes, in addition to the light emitting layer, thin-film layers such as a hole injection layer, a hole transport layer, an electron transport layer, and an electron injection layer. These thin-film layers can also be formed through a liquid-phase process. Therefore, for example a functional liquid containing a material for forming the hole injection layer, or a functional liquid containing a material for forming the hole transport layer may be involved in the filling and dispensing process. The manufacturing process of such functional liquids themselves is performed in an environment where, for example, the cleanness corresponding to Class 10 to 100 is secured. 
     Liquid Filling Device 
     Referring now to  FIGS. 4 to 6 , the liquid filling device according to this embodiment will be described hereunder.  FIG. 4  is a schematic drawing showing a configuration of the liquid filling device according to the first embodiment,  FIG. 5  is a schematic cross-sectional view showing a configuration of a filter, and  FIG. 6  is a schematic drawing showing a configuration of a pressurizing device for the ink pack. 
     As shown in  FIG. 4 , the liquid filling device  100  according to this embodiment includes an ink tank  110  to store therein the functional liquid L, and a first connector  141  and a second connector  142  both connected to a filter  120  and respectively connected to the ink packs  20  ( 20 A,  20 B). 
     The ink tank  110  is a sealed tank, and an inlet tube  111  and an inlet valve  112  for the functional liquid L are provided above the ink tank  110 . In addition, a gas inlet tube  113  is provided above the ink tank  110  for introducing a gas for pressurizing the inside of the ink tank  110 . A supply tube  114 , exemplifying the supply path in the invention, is connected to the ink tank  110 , and an end portion of the supply tube  114  extends as far as the vicinity of the inner bottom of the ink tank  110 . The other end portion of the supply tube  114  is connected to the first connector  141  and the filter  120 . The second connector  142  is located downstream of the filter  120 . A first on-off valve  131  is provided in a portion of the supply tube  114  upstream of the filter  120 . A second on-off valve  132  is provided between the filter  120  and the second connector  142 . Alternatively, the second on-off valve  132  may be located upstream of the filter  120  at a position close thereto. Further, in the case where the liquid filling device  100  is configured so as to change the flowing direction of the functional liquid L, a three-way on-off valve having the functions of both the first on-off valve  131  and the second on-off valve  132  may be employed. 
     The liquid filling device  100  is configured to supply the functional liquid L to the first connector  141  and the filter  120  through the supply tube  114 , by pressurizing the ink tank  110  filled with the functional liquid L with an inert gas such as nitrogen through the gas inlet tube  113 . 
     As shown in  FIG. 5 , the filter  120  is of a capsule type and includes a cylindrical casing  121  and an upper lid  123  that covers the casing  121 . A bottomed cylindrical filter element  125  is attached to the upper lid  123  at a generally central position thereof. The upper lid  123  includes a liquid inlet  124  communicating with the internal space  122  of the casing  121 , a liquid outlet  126  communicating with the filter element  125 , and a gas discharge port  127  communicating with the internal space  122  of the casing  121 , and through which a gas is discharged as shown in  FIG. 5 . 
     In the filter  120 , the filter element  125  removes foreign matters from the liquid introduced into the internal space  122  through the liquid inlet  124 , and the liquid is discharged through the liquid outlet  126 . At the same time, the gas contained in the liquid is released through the gas discharge port  127 . Thus, the filter  120  is capable of removing foreign matters, as well as separating a gas in the liquid and discharging the gas. 
     The filter element  125  is a mesh filter formed of a fluorine-based resin such as tetrafluoroethylene perfluoroalkylvinylether copolymer (PFA) or polytetrafluoroethylene (PTFE), polypropylene (PP), polyethylene (PE), or the like. The mesh size may be in a range of 0.1 μm to 0.2 μm, and may be selected according to the size of the foreign matter to be removed. 
     As shown in  FIG. 6 , the liquid filling device  100  includes a pressurizing device  150  that applies a pressure to the ink pack  20  connected to the first connector  141 . 
     The pressurizing device  150  includes a pair of pressure rollers  151  opposed to each other with a predetermined gap therebetween. The pressurizing device  150  is configured to hold the end portion of the liquid bag  21  opposite to the communication port  25  between the pressure rollers  151 , and to sequentially pressurize the liquid bag  21  toward the communication port  25  by rotating the pressure roller  151 , thus to discharge the functional liquid L in the ink pack  20  through the communication port  25 . 
     Without limitation to the above, the pressurizing device  150  may include a support member that supports one of the sides of the liquid bag  21  of the ink pack  20 , and a pressing member that presses the liquid bag  21  held between the support member and the pressing member. Alternatively, the pressurizing device  150  may include a sealed container in which the liquid bag  21  can be accommodated and a pressure unit that supplies a fluid (liquid or gas) into the sealed container. 
     In place of the pressurizing device  150 , further, a pressure difference mechanism may be provided that makes a pressure difference between the ink pack  20 A and the ink pack  20 B so as to transfer the functional liquid L filled in the ink pack  20 A to the ink pack  20 B by means of the pressure difference. 
     In addition to the configuration shown in  FIG. 4 , the liquid filling device  100  may include a meter that monitors the amount and density of the functional liquid L in the ink tank  110 , a heating device such as a heater for lowering the viscosity of the functional liquid L, a meter that detects the pressure at the front and rear of the filter  120  to thereby monitor the life span of the filter  120  on the basis of the pressure difference (pressure loss), a meter that monitors the size and amount of particles (foreign matters) contained in the functional liquid L, or a degassing module that removes a gas dissolved in the functional liquid L. 
     Liquid Filling Method 
     Referring now to  FIGS. 7A to 7C , a liquid filling method performed by using the liquid filling device  100  will be described hereunder.  FIGS. 7A to 7C  are schematic drawings for explaining the liquid filling method according to the first embodiment. The ink tank  110  and the pressurizing device  150  are excluded from  FIGS. 7A to 7C  for the sake of clarity. 
     The method of filling the ink pack  20 , corresponding to the liquid container in the invention, with the functional liquid L by using the liquid filling device  100  according to this embodiment includes a connection step, a first filling step, a transfer step, and a second filling step. 
     In the connection step, the ink packs  20 A and  20 B, which are empty at this point, are respectively connected to the first connector  141  and the second connector  142 . The ink pack  20 A connected to the first connector  141  corresponds to the first liquid container in the invention, and the ink pack  20 B connected to the second connector  142  corresponds to the second liquid container in the invention. Here, gas (air) in the empty ink packs  20 A,  20 B is discharged by pressurizing the liquid bag  21 , before these ink packs are connected to the first connector  141  and the second connector  142 . 
     In the first filling step, the functional liquid L is introduced into the ink pack  20 A connected to the first connector  141  through the supply tube  114  as shown in  FIG. 7A , with the first on-off valve  131  opened and the second on-off valve  132  closed. As already stated, the functional liquid L can be introduced into the ink pack  20 A through the supply tube  114  by pressurizing the inside of the ink tank  110  in which the functional liquid L is stored. 
     In the transfer step, the pressurizing device  150  applies a pressure to the ink pack  20 A now filled with the functional liquid L, with the first on-off valve  131  closed and the second on-off valve  132  opened. Accordingly, the functional liquid L in the ink pack  20 A is transferred to the ink pack  20 B connected to the second connector  142  through the filter  120  and the second on-off valve  132 , as shown in  FIG. 7B . By discharging the functional liquid L from the ink pack  20 A at the transfer step, foreign matters in the ink pack  20 A, if any, are discharged together with the functional liquid L and then removed by the filter  120 . Thus, the inside of the ink pack  20 A and the communication port  25  are cleaned with the functional liquid L. 
     In the second filling step, the ink pack  20 A and the ink pack  20 B are exchanged as shown in  FIG. 7C . To be more detailed, the ink pack  20 B now filled with the functional liquid L is connected to the first connector  141 , and the ink pack  20 A that has been cleaned with the functional liquid L is connected to the second connector  142 . Then the pressurizing device  150  applies a pressure to the ink pack  20 B connected to the first connector  141  to thereby transfer the functional liquid L in the ink pack  20 B to the ink pack  20 A connected to the second connector  142  through the filter  120  and the second on-off valve  132 , thus to again fill the ink pack  20 A with the functional liquid L. 
     With the liquid filling device  100  and the liquid filling method thereby performed according to this embodiment, the ink pack  20 A connected to the first connector  141  can be cleaned by using the functional liquid L, through the first filling step and the transfer step. At the same time, the supply path of the functional liquid L (including the supply tube  114 ) can also be cleaned. Then through the second filling step, in which the ink pack  20 B is connected to the first connector  141  and the ink pack  20 A that has been cleaned is connected to the second connector  142  located downstream of the filter  120  so as to again fill the ink pack  20 A with the functional liquid L, the ink pack  20 A can be filled, with the cleanness maintained therein, with the functional liquid L from which foreign matters and air bubbles have been removed. 
     After the second filling step, foreign matters in the ink pack  20 B, if any, are discharged together with the functional liquid L, and therefore the ink pack  20 B can also be cleaned with the functional liquid L. Upon connecting the cleaned ink pack  20 B again to the second connector  142  located downstream of the filter  120 , the ink pack  20 B can be filled with the functional liquid L, with the cleanness maintained therein. The ink pack  20 B can be refilled with the functional liquid L by connecting a third ink pack  20  to the first connector  141  and filling it with the functional liquid L, and then transferring the functional liquid L in the third ink pack  20  to the ink pack  20 B that has been cleaned. 
     Thus, the ink packs  20 A,  20 B can be cleaned with the functional liquid L, and filled with the functional liquid L from which foreign matters and air bubbles have been removed, by repeating the filling step and the transfer step of the functional liquid L. 
     The supply path of the functional liquid L is cleaned through the first session of the first filling step and the transfer step, and therefore the ink pack  20 B filled with the functional liquid L for the first time is free from foreign matters. However, the ink pack  20 B may contain an ionic impurity, and in case that the ink pack  20 B is suspected to be inappropriate for use with the functional liquid L, the ink pack  20 B may be disposed of. In the case where the ink pack  20 B is decided to be usable the functional liquid L can be refilled therein as described above, and thus the loss of the functional liquid L arising from the filling and transferring thereof can be minimized. 
     Second Embodiment 
     Liquid Filling Device 
     Hereunder, a second embodiment of the liquid filling device will be described referring to  FIG. 8 .  FIG. 8  is a schematic drawing showing a configuration of the liquid filling device according to the second embodiment. 
     As shown in  FIG. 8 , the liquid filling device  200  according to this embodiment includes an ink tank  210  to store therein the functional liquid L, a filter  220 , and a first connector  241  and a second connector  242  to which a pair of ink packs  20  ( 20 A,  20 B) are respectively connected. In addition, the liquid filling device  200  also includes the pressurizing device  150  that applies a pressure to the ink packs  20  connected to the first connector  241  and the second connector  242  as in the first embodiment, though not shown in  FIG. 8 . 
     Like the ink tank  110  according to the first embodiment, the ink tank  210  is a sealed tank, and an inlet tube  211  and an inlet valve  212  for the functional liquid L are provided above the ink tank  210 . In addition, a gas inlet tube  213  is provided above the ink tank  210  for introducing a gas for pressurizing the inside of the ink tank  210 . A supply tube  214 , exemplifying the supply path in the invention, is connected to the ink tank  210 , and an end portion of the supply tube  114  extends as far as the vicinity of the inner bottom of the ink tank  210 . A liquid supply valve  215  that controls the supply of the functional liquid L is provided on the supply tube  214 . 
     The other end portion of the supply tube  214  is connected to a manifold  255 . The manifold  255  is configured to accept four tubes. In addition to the supply tube  214 , a tube  256  connected to the filter  220 , a tube  251  corresponding to the first bypass route in the invention, and a tube  252  corresponding to the second bypass route in the invention are connected to the manifold  255 . 
     A tube  257  is connected to the downstream end of the filter  220 , and the first connector  241  and the second connector  242  are connected in parallel to the tube  257 . The tube  251  corresponding to the first bypass route, connected to the manifold  255  via an end portion, is connected to the first connector  241  via the other end portion. Likewise, the tube  252  corresponding to the second bypass route, connected to the manifold  255  via an end portion, is connected to the second connector  242  via the other end portion. 
     A first on-off valve  231  is provided on a tube located between the tube  257  downstream of the filter  220  and the first connector  241 . Likewise, a second on-off valve  232  is provided on a tube located between the tube  257  downstream of the filter  220  and the second connector  242 . A third on-off valve  253  is provided on the tube  251  between the manifold  255  and the first connector  241 . Likewise, a fourth on-off valve  254  is provided on the tube  252  between the manifold  255  and the second connector  242 . 
     In the case where the liquid filling device  200  is configured so as to change the flowing direction of the functional liquid L, a three-way on-off valve having the functions of both the first on-off valve  231  and the second on-off valve  232  may be employed. Likewise, a three-way on-off valve having the functions of both the third on-off valve  253  and the fourth on-off valve  254  may be employed. 
     The filter  220  is of a capsule type, and capable of removing foreign matters as well as removing air bubbles from the functional liquid L, as in the first embodiment. 
     The liquid filling device  200  is configured to supply the functional liquid L to the first connector  241 , the second connector  242 , and the filter  220  through the supply tube  214 , by pressurizing the ink tank  210  filled with the functional liquid L with an inert gas such as nitrogen through the gas inlet tube  213 . 
     As stated referring to the first embodiment, the liquid filling device  200  may also include a meter that monitors the amount and density of the functional liquid L in the ink tank  210 , a heating device such as a heater for lowering the viscosity of the functional liquid L, a meter that detects the pressure at the front and rear of the filter  220  to thereby monitor the life span of the filter  220  on the basis of the pressure difference (pressure loss), a meter that monitors the size and amount of particles (foreign matters) contained in the functional liquid L, or a degassing module that removes a gas dissolved in the functional liquid L. 
     Liquid Filling Method 
     Referring now to  FIGS. 9A to 9D , a liquid filling method to be performed by using the liquid filling device  200  will be described hereunder.  FIGS. 9A to 9D  are schematic drawings for explaining the liquid filling method according to the second embodiment. The ink tank  210  and the pressurizing device  150  are excluded from  FIGS. 9A to 9D  for the sake of clarity. 
     The method of filling the ink pack  20 , corresponding to the liquid container in the invention, with the functional liquid L by using the liquid filling device  200  according to this embodiment includes a connection step, a first filling step, a transfer step, a second filling step, and a third filling step. 
     In the connection step, the ink packs  20 A and  20 B, which are empty at this point, are respectively connected to the first connector  241  and the second connector  242 , as in the first embodiment. The ink pack  20 A connected to the first connector  241  corresponds to the first liquid container in the invention, and the ink pack  20 B connected to the second connector  242  corresponds to the second liquid container in the invention. Here, gas (air) in the empty ink packs  20 A,  20 B is discharged by pressurizing the liquid bag  21 , before these ink packs are connected to the first connector  241  and the second connector  242 . 
     In the first filling step, the functional liquid L is introduced into the ink pack  20 A connected to the first connector  241  through the supply tube  214  and the filter  220  as shown in  FIG. 9A , with the liquid supply valve  215  and the first on-off valve  231  opened and the second on-off valve  232 , the third on-off valve  253 , and the fourth on-off valve  254  closed. 
     In the transfer step, the liquid supply valve  215 , the first on-off valve  231 , and the fourth on-off valve  254  are closed, and the second on-off valve  232  and the third on-off valve  253  are opened. Under such setting, the functional liquid L in the ink pack  20 A is transferred to the ink pack  20 B connected to the second connector  242 , through the tube  251  and the filter  220 , as shown in  FIG. 9B . To transfer the functional liquid L, the pressurizing device  150  applies a pressure to the liquid bag  21  of the ink pack  20 A. 
     Through the first filling step and the transfer step, the ink pack  20 A is cleaned with the functional liquid L. At the same time, the supply tube  214 , the tubes  251 ,  256 , and  257  are also cleaned with the functional liquid L. 
     In the second filling step, the pressurizing device  150  applies a pressure to the ink pack  20 B connected to the second connector  242 , with the first on-off valve  231  and the fourth on-off valve  254  opened and the second on-off valve  232  and the third on-off valve  253  closed, to thereby transfer the functional liquid L in the ink pack  20 B to the ink pack  20 A connected to the first connector  241  through the tube  252  and the filter  220  as shown in  FIG. 9C , thus to again fill the ink pack  20 A with the functional liquid L. 
     Upon performing the second filling step, the ink pack  20 B is cleaned with the functional liquid L. At the same time, the tube  252  is also cleaned with the functional liquid L. Further, the ink pack  20 A cleaned through the first filling step and the transfer step is again filled with the functional liquid L through the filter  220 . Thus, the ink pack  20 A in which sufficient cleanness is secured can be filled with the functional liquid L from which foreign matters and air bubbles have been removed. 
     In the third filling step, the liquid supply valve  215  and the second on-off valve  232  are opened and the first on-off valve  231 , the third on-off valve  253 , and the fourth on-off valve  254  are closed. Under such setting, the ink pack  20 B connected to the second connector  242  is filled with the functional liquid L, through the supply tube  214  and the filter  220 , as shown in  FIG. 9D . 
     Upon performing the third filling step, the ink pack  20 B in which sufficient cleanness is secured can be filled with the functional liquid L from which foreign matters and air bubbles have been removed. 
     With the liquid filling method to be performed by using the liquid filling device  200  according to the second embodiment, both of the ink packs  20 A,  20 B can be cleaned by using the functional liquid L, and the ink packs  20 A,  20 B thus cleaned can be efficiently filled with the with the functional liquid L from which foreign matters and air bubbles have been removed, without the need to remove or exchange the ink packs  20 A,  20 B respectively connected to the first connector  241  and the second connector  242 , halfway of the filling process. 
     The liquid filling devices  100 ,  200  according to the first and the second embodiment do not employ a suction unit to discharge the functional liquid L from the ink pack  20 , unlike the technique according to JP-A-2005-186343. Therefore, the functional liquid L is exempted from the risk of contamination by the suction unit. In addition, the liquid filling devices  100 ,  200  have a simpler configuration compared with that of JP-A-2005-186343, and therefore loss of the functional liquid L can be minimized in the filling and transferring process. 
     It is to be understood that the invention is in no way limited to the foregoing embodiments, but may be modified as desired within the scope and spirit of the invention set forth in the appended claims. Liquid filling methods and liquid filling devices that reflect such modification, as well as liquid containers to which any of the liquid filling methods and liquid filling devices are applied, are included in the technical scope of the invention. To cite a few examples, the foregoing embodiments may be modified as under. 
     Variation 1 
     In the liquid filling device  100  according to the first embodiment, two or more filters may be provided in the supply path of the functional liquid L. For example, another filter of a larger mesh size than the filter  120  may be provided in the supply tube  114  serving as the supply path. In this case, foreign matters can be removed in stages according to the size thereof, and therefore the life span of the filter  120  can be prolonged. Such a configuration of the filter is also applicable to the liquid filling device  200  according to the second embodiment. 
     Variation 2 
     In the liquid filling device  200  according to the second embodiment, three or more ink packs  20  may be provided to be filled with the functional liquid L. For example, in the case where one or more additional connectors are connected in parallel to the supply tube  214  in addition to the first connector  241  and the second connector  242 , three or more ink packs  20  can be connected for more efficient filling of the functional liquid L. 
     Variation 3 
     The functional liquid L to be filled in the ink pack  20 , corresponding to the liquid container in the invention, is not limited to the one employed for forming a functional layer of an organic EL element through a liquid-phase process. The functional liquid L may be a chemical for medical use. In the case of filling the ink pack  20  with a chemical liquid for medical use by using the liquid filling device  100  or  200 , it is preferable that the liquid filling device  100  or  200  include a sterilizer such as a UV irradiator that kills microorganisms contained in the liquid. 
     The entire disclosure of Japanese Patent Application No. 2013-038465, filed Feb. 28, 2013 is expressly incorporated by reference herein.