Abstract:
The present invention provides applicators reducing generating bubble. Dispersion liquid is supplied while the pressure of a circulation tank on the delivery side is lower than the atmospheric pressure but higher than the pressure of the space in buffer tanks. The dispersion liquid in the discharge chambers is recovered while the pressure in a circulation tank serving as recovery destination is lower than the atmospheric pressure. Gas dissolution can be reduced because the dispersion liquid does not come into contact with gases at pressures higher than the atmospheric pressure and engulffing gas or deformation of solid microparticles can be avoided because no pump is used.

Description:
The present invention is a Continuation of International Application No. PCT/JP2006/321329 filed Oct. 26, 2006, which claims priority to Japan Patent Document No. 2005-325990, filed on Nov. 10, 2005. The entire disclosures of the prior applications are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     The present invention generally relates to inkjet spacer applicators, especially to circulating spacer applicators. 
     Recently, inkjet spacer applicators of which inkjet printer is adapted have been used to apply spacers for liquid crystal display. 
     Reference  111  in  FIG. 9(   a ) represents an example of a spacer applicator having an ink head  121  retained in a holding frame  120  above a platform  105 , and a dispersion liquid of which spacers are dispersed is discharged from the ink head  121  while the ink head  121  and substrate  107  for a liquid crystal on the platform  105  are relatively moved along a scanning direction  109 , whereby the dispersion liquid lands at a desired position on the surface of the substrate  107  and the spacer is placed there. 
       FIG. 8  is a block diagram for illustrating a system for supplying the dispersion liquid of the conventional spacer applicator  111 . 
     In this spacer applicator  111 , the ink head  121  consists of a plurality of head modules  121   a  to  121   c  each connected to a feed tank  136  placed at a lateral position with respect to the platform  105 . 
     A dispersion liquid  138  is stored in the feed tank  136  to the same height as the positions of discharge holes of the head modules  121   a  to  121   c , and when valves between the feed tank  136  and the head modules  121   a  to  121   c  are opened to connect the feed tank  136  and the head modules  121   a  to  121   c  and gas is supplied into the feed tank  136  by a pressurizer  130 , the pressure in the feed tank  136  increases so that the dispersion liquid  138  in the feed tank  136  is supplied to the head modules  121   a  to  121   c.    
     The head modules  121   a  to  121   c  are connected to a recovery tank  137  so that the dispersion liquid supplied from the feed tank  136  flow through the head modules  121   a - 121   c  and then returns to the recovery tank  137 . 
     The recovery tank  137  and the feed tank  136  are connected to each other, whereby the dispersion liquid  139  recovered in the recovery tank  137  can be returned to the feed tank  136 . These conventional art are disclosed in, for example, JPA2004-50059, JPA2002-72218 and JPA11-7028. 
     SUMMARY OF THE INVENTION 
     In the conventional applicator  111 , gases are readily dissolved in the dispersion liquid  138  because the dispersion liquid is supplied to the head modules  121   a  to  121   c  by pressurization as described above, and when the dissolved gas is reduced to bubbles in the head modules  121   a - 121   c , discharge failure may occur. 
     If the dispersion liquid is supplied by pumping, other problems (such as, engulfing of gas and deformation or damage of the spacer) occur. 
     In order to solve the problems described above, the present invention provides an applicator for allowing a dispersion liquid of which solid microparticles are dispersed to land at a desired position on a substrate by relatively moving a head module and the substrate, including a first and a second circulation tanks placed outside the head module; a buffer tank provided in the head module; a discharge chamber having an inlet connected to the buffer tank; a main line provided between the first and second circulation tanks and the buffer tank; a return line provided between an outlet of the discharge chamber and the first and second circulation tanks; a feed valve provided on the main line for connecting at least one of the first and second circulation tanks to the buffer tank; and a return valve provided on the return line for connecting at least one of the first and second circulation tanks to the head module. The first and second circulation tanks and the buffer tank are hermetically sealed and the pressure of the space above the dispersion liquid placed in each of the tanks can be controlled. 
     The present invention also provides the applicator including a gas feed/evacuation system connected to the first and second circulation tanks, wherein the gas feed/evacuation system has a structure supplying a pressurized gas to, and evacuating from a space above the liquid level of the dispersion liquid in the first and second circulation tanks. 
     The present invention also provides the applicator wherein a vacuum pump and a gas feeding system are connected to the buffer tank in order to control the pressure of the space above the liquid level of the dispersion liquid in the buffer tank. 
     The present invention also provides the applicator wherein He is supplied from the gas feeding system. 
     The present invention also provides the applicator including a transfer line provided between the first and second circulation tanks whereby the dispersion liquid can be transferred between the first and second circulation tanks without passing through the discharge chamber. 
     The present invention also provides the applicator including a filter for separating clusters provided on the transfer line, which allows the individual solid microparticles to pass and catches clusters of the solid microparticles. 
     The present invention also provides the applicator including a filter for removing solid microparticles provided on the transfer line, which catches the individual solid microparticles. 
     The present invention also provides the applicator wherein at least a part of the lines through which the dispersion liquid is supplied from the circulation tanks to the discharge chamber consists of a double pipe having a liquid-impermeable and gas-permeable inner pipe through which the dispersion liquid passes and a gas-impermeable outer pipe of which the inner pipe is inserted into, and a clearance between the inner pipe and the outer pipe can be evacuated. 
     The present invention also provides a method for transferring a dispersion liquid by transferring a circulating liquid in any one of the applicators described above, including when one of the first or second circulation tanks is served as a delivery source, making a pressure inside the circulation tank serving as the delivery source lower than the atmospheric pressure, and opening the feed valve to connect one of the first or second circulation tank serving as delivery source to the buffer tank in order to transfer the dispersion liquid from the circulation tank serving as delivery source to the buffer tank. 
     The present invention also provides a method for transferring a dispersion liquid by transferring a circulating liquid in any one of the applicators described above, including when one of the first or second circulation tanks is served as a recovery destination, making a pressure inside the circulation tank serving as the recovery destination lower than the atmospheric pressure, and opening the return valve to connect either one of the first or second circulation tanks serving as recovery destination to the discharge chamber in order to transfer the dispersion liquid inside the discharge chamber to the circulation tank serving as recovery destination. 
     The present invention also provides a method for transferring a dispersion liquid by transferring a circulating liquid in any one of the applicators described above, including opening the feed valve to connect either one of the first or second circulation tanks serving as delivery source to the buffer tank, opening the return valve to connect the other of the first or second circulation tanks serving as recovery destination to the discharge chamber, and transferring the dispersion liquid inside the circulation tank serving as the delivery source to the other circulation tank serving as the recovery destination through the buffer tank and the discharge chamber. 
     The present invention is constructed as described above, in which the dispersion liquid is supplied from the circulation tank to the buffer tank when the circulation tank and the buffer tank are connected while the pressure in the space above the dispersion liquid in the buffer tank (the space in the buffer tank) is lower than the pressure in the space above the dispersion liquid in the circulation tank (the space in the circulation tank). 
     When the circulation tank and the discharge chamber are connected to each other, while the force by which the circulation tank sucks the dispersion liquid in the discharge chamber is greater than the force by which the buffer tank aspirates the dispersion liquid in the discharge chamber, the dispersion liquid in the discharge chamber being aspirated into the circulation tank. 
     Gas dissolution into the dispersion liquid and bubble generating are reduced because the dispersion liquid is not contacted with gases having pressures higher than the atmospheric pressure. 
     No gas is engulfed into the dispersion liquid by pumping and generating gas can be prevented because no pump is used for transferring the dispersion liquid. 
     Microparticles dispersed in the dispersion liquid are not deformed or damaged because no pump is used. 
     No precipitation occurs because the dispersion liquid can be circulated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing the circulation system of a applicator according to an example of the present invention. 
         FIG. 2  is a diagram for illustrating a route along which a dispersion liquid flows from a first circulation tank to a second circulation tank. 
         FIG. 3  is a diagram for illustrating a route along which dispersion liquid flows from the second circulation tank to the first circulation tank. 
         FIG. 4  is a diagram for illustrating a dispersion liquid flowing through a filter for separating clusters. 
         FIG. 5  is a diagram for illustrating a dispersion liquid flowing through a filter for removing solid microparticles. 
         FIG. 6  is a diagram for illustrating the applicator that returns dispersion liquid from discharge chambers directly to buffer tanks. 
         FIG. 7  is a diagram for illustrating a deaeration unit consisting of a double pipe. 
         FIG. 8  is a diagram for illustrating the circulation pathway of a dispersion liquid in a conventional applicator. 
         FIG. 9(   a ) is a schematic illustration of the conventional applicator and  FIG. 9(   b ) is a schematic illustration of an example of the applicator of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Reference  11  in  FIG. 9(   b ) represents an example of a applicator of the present invention including a platform  5  on which a substrate  7  is mounted. 
     A holding frame  20  is provided above the platform  5 . The holding frame  20  has an ink head  21 . 
     As shown in  FIG. 1 , the ink head  21  includes a plurality of head modules  21   a ,  21   b ,  21   c . In the head modules  21   a  to  21   c , buffer tanks  41   a  to  41   c  and discharge chambers  42   a  to  42   c  are provided, respectively. 
     The applicator  11  has a circulation system supplying a dispersion liquid to the head modules  21   a  to  21   c . Reference  10  in  FIG. 1  represents the circulation system, and a first circulation tank  31 L and a second circulation tank  31 R are provided in the circulation system  10 . 
     The first and second circulation tanks  31 L,  31 R are placed at positions allowing the substrate  7  to be transported, for example, at lateral positions with respect to or below the platform  5 , and they are fixed relative to the platform  5 . 
     The buffer tanks  41   a  to  41   c  are placed above the discharge chambers  42   a  to  42   c , and dispersion liquid  48   a  to  48   c  of which solid microparticles are dispersed is stored in the buffer tanks  41   a  to  41   c . The dispersion liquid  48   a  to  48   c  is contained in the buffer tanks  41   a  to  41   c  to the extent that a space is formed above the liquid level of the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c.    
     A vacuum pump  58  is connected to the ceilings or upper positions of the wall surfaces of each of the buffer tanks  41   a  to  41   c . The vacuum pump is connected to the each buffer tank  41   a  to  41   c  at positions above the liquid level of the dispersion liquid in the buffer tanks  41   a  to  41   c  so that the pressure of the space above the liquid level of the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c  can be decreased by evacuating the space. 
     A gas feeding system  57  is also connected to the ceilings or upper positions of the wall surfaces of the buffer tanks  41   a  to  41   c . The gas feeding system  57  is connected to the buffer tanks  41   a  to  41   c  at positions above the liquid level of the dispersion liquid in the buffer tanks  41   a  to  41   c  so that the pressure in the space above the liquid level of the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c  can be increased by supplying this space with a pressurized gas less soluble for the dispersion liquid. 
     The buffer tanks  41   a  to  41   c  have feed ports at positions below the liquid level of the dispersion liquid at, for example, bottom portions or lower parts of the wall surfaces thereof, and the discharge chambers  42   a  to  42   c  have inlets on their wall surfaces or ceilings. 
     The feed ports of the buffer tanks  41   a  to  41   c  are connected to the inlets of the discharge chambers  42   a  to  42   c , respectively, so that the dispersion liquid in the buffer tanks  41   a  to  41   c  can be transferred to the discharge chambers  42   a  to  42   c.    
     The discharge chambers  42   a  to  42   c  are located at such positions that their bottoms face the substrate mounted on the platform  5 . The discharge chambers  42   a  to  42   c  have a number of discharge holes at their bottoms through which the dispersion liquid in the discharge chambers  42   a  to  42   c  are in contact with the atmosphere. 
     When the pressure P B  of the space in the buffer tanks  41   a  to  41   c  is negative pressure (P B &lt;(atmospheric pressure)) and the suction force of the negative pressure is balanced the weight of the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c , the dispersion liquid in the discharge chambers  42   a  to  42   c  does not drop from the discharge holes; and therefore, the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c  is not transferred to the discharge chambers  42   a  to  42   c.    
     Each discharge chamber  42   a - 42   c  has cells corresponding to the discharge holes, and each cell has a piezoelectric element. 
     When a voltage is applied to the piezoelectric element, the piezoelectric element expands and contracts by the piezoelectric effect, whereby the dispersion liquid in each cell is pressurized and discharged from the discharge hole of the cell toward the surface of the substrate  7 . 
     When the dispersion liquid in the discharge chamber  42   a  to  42   c  is discharged, the dispersion liquid is drawn from the buffer tank  41   a  to  41   c  in order to supply to the discharge chamber  42   a  to  42   c  with the amount of the dispersion liquid  48   a  to  48   c  discharged. 
     If the liquid level of the dispersion liquid in the buffer tanks  41   a  to  41   c  drops, a pressurized gas is introduced into the buffer tanks  41   a  to  41   c  from the gas feeding system  57  or the dispersion liquid is supplied from the first circulation tank  31 L, or the second circulation tank  31 R as described later so that the pressure of the space in the buffer tanks  41   a  to  41   c  remains constant. 
     The transfer of the dispersion liquid from the first or second circulation tanks  31 L,  31 R to the buffer tanks  41   a  to  41   c  is performed by the weight of the dispersion liquid  23 L in the first circulation tank  31 L or the dispersion liquid  23 R in the second circulation tank  31 R and the force of difference between the pressure in the first or second circulation tank  31 L,  31 R and the pressure in the buffer tanks  41   a  to  41   c.    
     The substrate  7  and the holding frame  20  are arranged in such a manner that either one or both of them may move along a scanning direction  9 . The substrate  7  may be stationary while the holding frame  20  may move along the scanning direction  9 , or the holding frame  20  may be stationary while the substrate  7  may move along the scanning direction  9 . The substrate  7  and the holding frame  20  may move in the same direction or opposite directions along the scanning direction  9 . In any case, the ink head  21  moves with the holding frame  20 . 
     As a result, the substrate  7  can move relative to the ink head  21 , i.e., relative to the buffer tanks  41   a  to  41   c  and the discharge chambers  42   a  to  42   c.    
     When the substrate  7  and the ink head  21  are relatively moved until the ink head  21  reaches a desired position on the substrate  7 , and then a voltage is applied to the piezoelectric element to discharge the dispersion liquid from the discharge hole, the discharged dispersion liquid lands at the desired position on the surface of the substrate  7 . 
     In the dispersion liquid, solid particles (such as, spacer or pigment) are dispersed. After the dispersion solvent included in the landed dispersion liquid is evaporated, the solid particles are fixed on the substrate  7 . 
     Besides the circulation system  10 , a dispersion liquid feeding system  28  is provided, and the first and second circulation tanks  31 L,  31 R are connected to the dispersion liquid feeding system  28 . 
     Valves v 1 , v 2  are provided on the midway of lines connecting the first and second circulation tanks  31 L,  31 R and the dispersion liquid feeding system  28 . When the valves v 1 , v 2  are opened, the dispersion liquid of which the solid microparticles are dispersed is supplied from the dispersion liquid feeding system  28  to the first and second circulation tanks  31 L,  31 R. 
       FIG. 1  and the other drawings described later show open valves in white and closed valves in black; and therefore,  FIG. 1  shows that the valve v 1  connected to the first circulation tank  31 L is at an open state as shown by white while the valve v 2  connected to the second circulation tank  31 R is at a closed state as shown by black. 
     A gas feed/evacuation system  24  is connected to the first and second circulation tanks  31 L,  31 R via switches  22 L,  22 R. The gas feed/evacuation system  24  includes a gas feeding system  44  and a vacuum pump (or evacuation system)  45  so that the first and second circulation tanks  31 L,  31 R can be independently connected to the gas feeding system  44  and the vacuum pump  45  by switching valves in the switches  22 L,  22 R. It is also possible to connect one to the gas feeding system  44  and the other to the vacuum pump  45 . 
     The first and second circulation tanks  31 L,  31 R are connected to the gas feed/evacuation system  24  at their ceilings or upper parts of the wall surfaces above the liquid level of the dispersion liquid  23 L,  23 R in the first and second circulation tanks  31 L,  31 R. 
     The first and second circulation tanks  31 L,  31 R are hermetically sealed and when they are connected to the gas feeding system  44  via the switches  22 L,  22 R to supply a pressurized gas from the gas feeding system  44 , the pressure of the space in the first and second circulation tanks  31 L,  31 R increases. 
     When the first and second circulation tanks  31 L,  31 R are connected to the vacuum pump  45  via the switches  22 L,  22 R to evacuate the space above the liquid level of the dispersion liquid  23 L,  23 R by the vacuum pump  45 , the pressure of the space above the liquid level decreases. 
     The first and second circulation tanks  31 L,  31 R have feed ports at or near bottom portions thereof below the liquid level of the dispersion liquid  23 L,  23 R. 
     Each buffer tank  41   a  to  41   c  has an inlet, which is connected to the feed ports of the first and second circulation tanks  31 L,  31 R via the main line  37 . In the figure, the feed ports are the ends of the main lines. 
     A first feed valve vs L  and a second feed valve vs R  are provided on the pathway of the main line  37  near the feed ports of the first and second circulation tanks  31 L,  31 R and inlet valves vi a -vi c  are provided at positions nearer to the inlets of the buffer tanks  41   a  to  41   c  than the first and second feed valves vs L , vs R . When either one of the first and second feed valves vs L , vs R  is opened while the other is closed and the inlet valve vi a -vi c  of the head module  21   a  to  21   c  to be fed is opened, the first or second circulation tank  31 L,  31 R connected to the opened first or second feed valve vs L , vs R  serves as delivery source and the buffer tank  41   a  to  41   c  connected to the opened inlet valve vi a -vi c  serves as delivery destination so that the delivery source and the delivery destination are connected. 
     The pressure P S  of the space in the first and second circulation tanks  31 L,  31 R can be controlled by supplying a pressurized gas, and if the pressure P s  of the space in the first or second circulation tank  31 L,  31 R serving as delivery source has been preliminarily increased higher than the pressure P B  of the space in the buffer tank  41   a  to  41   c  (P B &lt;P S ), the dispersion liquid  23 L,  23 R in the first or second circulation tank  31 L,  31 R serving as delivery source flows into the buffer tank  41   a  to  41   c  serving as delivery destination via the main line  37 . 
     Once a predetermined amount of the dispersion liquid  48   a  to  48   c  has been stored in the buffer tank  41   a  to  41   c , the buffer tank  41   a  to  41   c  is ready to supply the dispersion liquid to the discharge chamber  42   a  to  42   c.    
     Even if the pressurized gas is supplied to the first or second circulation tanks  31 L,  31 R, the inside pressure P s  is not higher than the atmospheric pressure (P s ≦atmospheric pressure); as a result, the pressurized gas is not dissolved into the dispersion liquid. 
     When the discharge chamber  42   a  to  42   c  is filled with the dispersion liquid, it is possible to discharge the dispersion liquid onto the surface of the substrate  7 . 
     Next, downstream side from the discharge chambers  42   a  to  42   c  will be explained. 
     Each discharge chamber  42   a  to  42   c  has an outlet, and each of first and second circulation tanks  31 L,  31 R has an inlet. A return line  38  is provided between the outlet of the discharge chamber  42  and the inlets of the first and second circulation tanks  31 L,  31 R. In the figure, the inlets are the ends of the return line  38 . 
     The return line  38  has outlet valves vo a -vo c  near the outlets of the discharge chambers  42   a  to  42   c , respectively, and a first return valve vr L  and a second return valve vr R  positioned nearer to the outlets of the first and second circulation tanks  31 L,  31 R than the outlet valves vo a -vo c . 
     The return valves vr L , vr R  are valves for connecting at least one of the first and second circulation tanks to the head modules  21   a  to  21   c . When either one of the first and second feed valves vs L , vs R  is opened and the other is closed, the first or second circulation tank  31 L,  31 R connected to the closed feed valve vs L  or vs R  serves as recovery destination, and when the return valve vr L  or vr R  of the first or second circulation tank  31 L,  31 R serving as recovery destination is opened and the desired outlet valve vo a  to vo c  is opened, the discharge chamber  42   a ,  42   b  or  42   c  connected to the opened outlet valve vo a , Vo b  or vo c  serves as return source so that the discharge chamber  42   a ,  42   b  or  42   c  serving as return source and the first or second circulation tank  31 L,  31 R serving as recovery destination are connected. If all of the outlet valves vo a -vo c  are opened, each discharge chamber  42   a  to  42   c  serves as return source. 
     In this situation, if the dispersion liquid in each discharge chamber  42   a  to  42   c  is in contact with the atmosphere in the discharge holes, the dispersion liquid in the discharge chamber  42   a  to  42   c  serving as return source can be transferred to the first or second circulation tank  31 L,  31 R serving as recovery destination by decreasing the pressure P R  in the first or second circulation tank  31 L,  31 R serving as recovery destination below the atmospheric pressure (P R &lt;(atmospheric pressure)). 
     The dispersion liquid can be made to flow from the inlet to the outlet in the discharge chamber  42   a  to  42   c  and then, the dispersion liquid can be transferred to the circulation tank  31 L,  31 R serving as recovery destination by decreasing the pressure of the first or second circulation tank  31 L,  31 R serving as recovery destination lower than the pressure in the buffer tank  41   a  to  41   c  and decreasing the pressure at the outlet of the discharge chamber  42   a  to  42   c  lower than the pressure at the inlet of the discharge chamber  42   a  to  42   c.    
     The outlet valves vo a -vo c  are three-way valves, so that the outlet valves vo a -vo c  can connect not only the discharge chamber  42   a  to  42   c  to the first or second circulation tank  31 L,  31 R but also the discharge chamber  42   a  to  42   c  to drains. 
     The applicator  11  of the present invention has a level sensor detecting the height of the liquid level of the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c  and a pressure sensor measuring the pressure in the space above the liquid level of the dispersion liquid  48   a  to  48   c  in the buffer tanks. Any change in the liquid level in the buffer tanks  41   a  to  41   c  or any change of the pressure in the space above the liquid level is detected so that the dispersion liquid is added from the first or second circulation tank  31 L,  31 R in order to maintain a constant liquid level, or a pressurized gas is introduced from the gas feeding system  57 , or the buffer tank  41   a  to  41   c  is evacuated by the vacuum pump  58  in order to maintain a constant pressure, whereby the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c  is prevented from dropping from the discharge holes of the discharge chambers  42   a  to  42   c.    
     When a part or all of the dispersion liquid in the discharge chambers  42   a  to  42   c  is transferred to the first or second circulation tank  31 L,  31 R serving as recovery destination, the dispersion liquid in the buffer tanks  41   a  to  41   c  is transferred to the discharge chambers  42   a  to  42   c . In this case, the liquid level of the dispersion liquid  48   a  to  48   c  in the buffer tanks  41   a  to  41   c  is lowered and the pressure in the space in the buffer tanks  41   a  to  41   c  decrease. 
     In this case, since the dispersion liquid in the first or second circulation tank  31 L,  31 R serving as delivery source can be transferred to the buffer tanks  41   a  to  41   c , then the dispersion liquid can be transferred from the first or second circulation tank  31 L or  31 R serving as delivery source to the first or second circulation tank  31 L or  31 R serving as recovery destination through the buffer tanks  41   a  to  41   c  and discharge chamber  42   a  to  42   c.    
     During this operation, the pressure of the inner space in the buffer tanks  41   a  to  41   c  can be maintained at a predetermined value. 
       FIG. 2  shows the state in which the dispersion liquid flows from the first circulation tank  31 L serving as delivery source to the second circulation tank  31 R serving as recovery destination (i.e., the first feed valve vs L  and the second return valve vr R  are opened and the second feed valve vs R  and the first return valve vr L  are closed). The dispersion liquid flows from the first circulation tank  31 L to the second circulation tank  32 R. 
       FIG. 2  and  FIGS. 3 to 5 , described later, are diagrams for illustrating the flow of the dispersion liquid, in which the lines through which the dispersion liquid flow are shown by solid lines while the other lines are shown by dashed lines. 
     In contrast to  FIG. 2 ,  FIG. 3  shows the state in which the dispersion liquid flows from the second circulation tank  31 R serving as delivery source to the first circulation tank  31 L serving as recovery destination when the first feed valve vs L  and the second return valve vr R  are closed and the second feed valve vs R  and the first return valve vr L  are opened. 
     Next, the pathway along which the dispersion liquid is directly transferred between the first and second circulation tanks  31 L,  31 R is explained. 
     The first and second circulation tanks  31 L,  31 R have first and second transfer ports at positions below the liquid level of the dispersion liquid  23 L,  23 R in the first and second circulation tanks  31 L,  31 R. 
     Since the first and second transfer ports are connected to each other by a transfer line  39 , which is distinct from the main line  37  and the return line  38 , the inside of the first and second circulation tanks are connected by the transfer line  39 . In this example, the first and second transfer ports consist of the end of the transfer line  39 . 
     The valves provided on the main line  37  or return line  38  are closed to cut off the connection between the first and second circulation tanks  31 L,  31 R and the buffer tanks  41   a  to  41   c  via the main line  37  or the connection between the first and second circulation tanks  31 L,  31 R and the discharge chambers  42   a  to  42   c  via the return line  38 . 
     Open-close valves  26  are provided on the transfer line  39 , and the open-close valves  26  are closed to provide a pressure difference between the inside of the first circulation tank  31 L and the inside of the second circulation tank  31 R by the gas feed/evacuation system  24 . The first or second circulation tank  31 L,  31 R on the higher pressure side serves as transfer source and the first or second circulation tank  31 L,  31 R on the lower pressure side serves as transfer destination, and then the open-close valves  26  are opened, whereby the dispersion liquid flows from the first or second circulation tank  31 L,  31 R serving as transfer source toward the first or second circulation tank  31 L,  31 R serving as transfer destination. 
     A filter system  25  is provided on the halfway of the transfer line  39 . The filter system  25  includes a filter for separating clusters  47  and a filter for removing solid microparticles  49 . The filter for separating clusters  47  and the filter for removing solid microparticles  49  are in parallel between the first and second circulation tanks  31 L,  31 R so that the dispersion liquid can be transferred between the first and second circulation tanks  31 L,  31 R through either one of filters ( 47  or  49 ) or both filters ( 47 ,  49 ). 
     Solid microparticles dispersed in the dispersion liquid may gather to form clusters having large particle sizes during circulation in lines or storage in tanks (such as, the circulation tanks  31 L,  31 R), but the clusters are caught on the filter for separating clusters  47  and removed when the dispersion liquid passes through the filter for separating clusters  47  because the filter for separating clusters  47  has a mesh size larger than the solid microparticles but smaller than the clusters of the solid microparticles. 
     The filter for separating clusters  47  is also connected to an ultrasonic wave generator  46  that applies ultrasonic waves to the filter for separating clusters  47 . 
     When ultrasonic waves are applied to the filter for separating clusters  47 , the clusters caught on the filter for separating clusters  47  separate into individual solid microparticles and pass through the filter for separating clusters  47 , whereby the dispersion liquid is regenerated during circulation in the transfer line  39  because the clusters are decomposed. 
       FIG. 4  shows the state in which the dispersion liquid flows through the filter for separating clusters  47  in the transfer line  39  from the second circulation tank  31 R toward the first circulation tank  31 L. The dispersion liquid recovered by the first or second circulation tank  31 L,  31 R serving as recovery destination can be returned to the first or second circulation tank  31 L,  31 R serving as delivery source while it is reclaimed. 
     The dispersion liquid flowing through the transfer line  39  can also pass through the filter for removing solid microparticles  49  in parallel to the filter for separating clusters  47  instead of passing through the filter for separating clusters  47  by manipulating the open-close valves  26  on the transfer line  39 . 
       FIG. 5  shows the state in which the dispersion liquid flows through the filter for removing solid microparticles  49  in the transfer line  39  from the second circulation tank  31 R toward the first circulation tank  31 L. 
     Solid microparticles contained in the dispersion liquid cannot pass through the filter for removing solid microparticles  49  because the filter for removing solid microparticles  49  has a mesh size smaller than the microparticles. Thus, the solid microparticles are totally caught on the filter for removing solid microparticles  49  when the dispersion liquid passes through the filter for removing solid microparticles  49 . 
     The applicator  11  should be adaptable to multiple types of dispersion liquids, such as, dispersion liquids of which microparticles of different materials are dispersed or dispersion liquids of which microparticles of different particle sizes are dispersed. 
     The procedure for changing the dispersion liquid using the filter for removing solid microparticles  49  is explained as follows. In order to change the dispersion liquid circulated in the applicator  11  and discharged from the ink head  21 , it is necessary to first remove the dispersion liquid in the lines  37  to  39  and the dispersion liquid in the tanks  31 L,  31 R,  41   a  to  41   c  from drains or the like and wash the lines  37 - 39  and each tanks  31 L,  31 R,  41   a  to  41   c , and then supply another type of dispersion liquid from the dispersion liquid feeding system  28  to the first and second circulation tanks  31 L,  31 R. 
     In this applicator  11 , the solvent feeding system  29  is connected to either one or both of the first and second circulation tanks  31 L,  31 R. In this example, it is connected to the first circulation tank  31 L, and the valve between the solvent feeding system  29  and the first circulation tank  31 L is opened to supply a washing liquid to the first circulation tank  31 L from the solvent feeding system  29  after the dispersion liquid in the each tanks  31 L,  31 R,  41   a  to  41   c  and head modules  21   a  to  21   c  and lines  37 - 39  has been discharged into drains and before another dispersion liquid is placed in the first and second circulation tanks  31 L,  31 R, whereby the washing liquid is transferred instead of the dispersion liquid to the second circulation tank  31 R via the buffer tanks  41   a  to  41   c  and head modules  21   a  to  21   c , and the washing liquid is returned from the second circulation tank  31 R to the first circulation tank  31 L via the transfer line  39 . 
     Thus, the inside of the tanks  31 L,  31 R,  41   a  to  41   c  and lines  37  to  39  are washed and microparticles are removed by supplying a washing liquid (solvent) to either one of the first or second circulation tank  31 L,  31 R or both and circulating it in the same manner as the dispersion liquid. 
     After the washing liquid has been discharged from drains, a fresh dispersion liquid is placed in the first and second circulation tanks  31 L,  31 R so that the solid microparticles in the previous dispersion liquid cannot mix the fresh dispersion liquid. 
     Before the dispersion liquid is discharged into drains and replaced with a washing liquid, microparticles in the dispersion liquid to be replaced are removed by the filter  49  for removing solid microparticles, and the dispersion liquid solvent is circulated, whereby the inside of the lines is first washed with the dispersion liquid solvent of the dispersion liquid. Then, the dispersion liquid solvent is discharged followed by washing with a washing liquid, whereby the washing liquid can be saved. 
     In this example, a bypass line  40  connecting the first and second circulation tanks  31 L,  31 R by detouring around the filter system  25  is provided in parallel to the transfer line  39  of which the filter system  25  is provided midway its line. 
     The bypass line  40  has an open-close valve  27 . When the open-close valve  27  is closed, the dispersion liquid does not flow through the bypass line  40 , and when the open-close valve  27  on the bypass line  40  is opened while the open-close valves  26  on the transfer line  39  are closed, the dispersion liquid flows through the bypass line  40  under a pressure difference in the space in the first and second circulation tanks  31 L,  31 R. Each bypass port provided in the first and second circular tanks  31 L and  31 R, which are connected to the bypass line  40 , is arranged below the liquid level of the first and second circulation tanks  31 L,  31 R. 
     A washer  6  is provided at a lateral position with respect to the platform  5 , and a washing liquid or dispersion liquid solvent can also be circulated while the discharge holes are blocked with the washer  6  by moving the ink head  21  from a position above the substrate  7  to a position above the washer  6 . 
     A gas feeding system  57  is connected to the buffer tanks  41   a  to  41   c  via valves. When the ink head  21  is moved from a position above the substrate  7  to the washer  6  and then the outlet valves vo a  to vo c  on the return line  38  are closed, and valves provided between the gas feeding system  57  and the buffer tanks  41   a  to  41   c  are opened and purge gas is introduced into buffer tanks  41   a  to  41   c  while the discharge holes are opened, the pressure inside the buffer tanks  41   a  to  41   c  are introduced at atmospheric pressure or higher than atmospheric pressure. Consequently, the dispersion liquid or washing liquid in the buffer tanks  41   a  to  41   c  can be discharged from the discharge holes of the head modules  21   a  to  21   c  into the washer  6 . 
     As explained above, in the applicator  11  of the present invention, when one of the first and second circulation tanks  31 L,  31 R is served as the delivery source and the other of the first or second circulation tank  31 L,  31 R is served as recovery destination, flowing from the first or second circulation tanks  31 L,  31 R serving as delivery source to the other of the first or second circulation tanks  31 L,  31 R serving as recovery destination, further returning to the first or second circulation tank serving as the delivery source, the dispersion liquid can flow through the buffer tanks  41   a  to  41   c  and the discharge chamber  42   a  to  42   c . Consequently, it is possible to prevent sinking of solid microparticles in the discharge chamber  42   a  to  42   c  or inside of lines. 
     If the dispersion liquid in the first or second circulation tank  31 L,  31 R serving as recovery destination has increased, the first or second circulation tank  31 L,  31 R can be in turn used as delivery source to circulate the dispersion liquid via the buffer tanks  41   a  to  41   c  to the discharge chambers  42   a  to  42   c  and the dispersion liquid can be returned to the first or second circulation tank  31 L,  31 R serving as delivery source through the filter for separating clusters  47 . 
     The first and second circulation tanks  31 L,  31 R include ultrasonic wave oscillators  33 L,  33 R, respectively. When ultrasonic waves are applied from ultrasonic wave generators  34 L,  34 R to the ultrasonic wave oscillator  33 L,  33 R to allow them to ultrasonically oscillate, the dispersion liquid in the first and second circulation tanks  31 L,  31 R ultrasonically oscillates; thereby, preventing clustering of solid microparticles and dispersing clusters that have already formed. 
     The first and second circulation tanks  31 L,  31 R also include rotors  35 L,  35 R each having a magnet. Below the bottom portions of the first and second circulation tanks  31 L,  31 R, stirrers  36 L,  36 R magnetically linked to the rotors  35 L,  35 R are provided. When the stirrers  36 L,  36 R are actuated, the rotors  35 L,  35 R rotate at a desired speed to stir the dispersion liquid in the first and second circulation tanks  31 L,  31 R. It is possible to prevent precipitation of solid microparticles. 
     The part of each line  37 - 40  described above, especially of the main line  37  where the dispersion liquid is supplied from the first and second circulation tanks  31 L,  31 R to the discharge chambers  42   a  to  42   c  can totally or partially consist of a double pipe in order to degas the dispersion liquid flowing through the double pipe. The double pipe is desirably placed immediately before the position where the dispersion liquid is discharged, i.e., between the buffer chambers  41   a  to  41   c  and the discharge chambers  42   a  to  42   c.    
     Reference number  60  in  FIG. 7  represents the double pipe for degassing. This double pipe  60  has an inner pipe  61  and an outer pipe  62  placed around the inner pipe  61  to surround the periphery of the inner pipe  61 . The inner pipe  61  is inserted into the outer pipe  62 . 
     The inner pipe  61  is made of a gas-permeable and liquid-impermeable resin (such as PTFA, etc.), and the outer pipe  62  is a pipe made of a gas-impermeable and liquid-impermeable metal (SUS). The inner and outer pipes  61 ,  62  are flexible and can be bent. 
     Connecting members  69   1 ,  69   2  for connecting to other lines are provided between the ends of the inner pipe  61  and the ends of the outer pipe  62 , and the clearance  63  between the inner pipe  61  and outer pipe  62  is blocked by the connecting members  69   1 ,  69   2  at both ends of the inner pipe  61  and therefore hermetically sealed. 
     The outer pipe  62  has an exhaust port  64 , which is connected to a vacuum pump  68  so that the clearance  63  can be evacuated. 
     When the clearance  63  is evacuated during circulation of the dispersion liquid from one to the other of both ends  66   1 ,  66   2  of the inner pipe  61 , the gases dissolved in the dispersion liquid are sucked into the clearance  63  through the inner pipe  61  so that gasses are removed from the dispersion liquid. 
     He gas is used as the pressurized gas described above and the low solubility of He gas reduces generating bubble. 
     Although two feed valves vs L , vs R  are provided in the foregoing description, the number of the valves may be one or more than two as long as either one or both of the first and second circulation tanks  31 L, 31 R can be connected to the main line  37 . 
     Similarly, the number of return valves vr L , vr R  is not limited to two, but any number of the valves may be used so far as either one or both of the first and second circulation tanks  31 L, 31 R can be connected to the return line  38 . 
     As shown in  FIG. 6 , when pumps which do not engulf gas are connected between the return line  38  at the downstream from the discharge chamber  42   a  to  42   c  and main line  37  positioned between the buffer tanks  42   a  to  42   c  and the first or second circulation tanks  31 L,  31 R, and the dispersion liquid that has passed through the discharge chamber  42   a  to  42   c  and drained from the discharge chamber  42   a  to  42   c  is returned from the return line  38  to the main line  37 , the dispersion liquid discharged from the discharge chamber  41   a  to  42   c  can be returned to the buffer tanks  41   a  to  42   c.    
     The present invention can be applied to applicators discharging solutions (such as, pigment dispersion liquid inks for forming color filter, spacer dispersion liquids for forming spacers, solutions of which various functional solids such as conductive, dielectric, semiconductor, luminescent and electron-emitting materials, etc.). They can be used to coat the overall surfaces or discharge the solutions onto only predetermined positions to form patterns. 
     Applicators discharging spacers can also be used as spacer arrangement systems for placing a spacer between a color filter substrate and an array substrate of a liquid crystal display.