Patent Publication Number: US-8529031-B2

Title: Liquid discharge device and liquid discharge method

Description:
TECHNICAL FIELD 
     The present invention relates to liquid discharge devices and liquid discharge methods for discharging droplets of a liquid, and in particular relates to a liquid discharge device and liquid discharge method in which liquids containing dispersed solid matter and high viscosity liquids can be used and in which the amount of liquid that is discharged can be accurately controlled. 
     BACKGROUND ART 
     One conventional printing technique includes an ink jetting technique of discharging droplets of ink in precise locations to print an image on a piece of paper. In recent years, this ink jetting technique has been used in manufacturing processes for all sorts of devices to form patterns and thin, uniform films, for example. 
     Furthermore, a liquid discharge device capable of discharging a variety of liquids is required for this ink jetting technique to be used widely in fields other than print and graphics. For example, in order for a blue light emitting diode (LED) to emit a white light, a clear resin layer dispersed with fine-grained phosphor must be deposited on the surface of the LED. To deposit such a layer, a liquid discharge device for discharging a liquid containing solid matter is required. Moreover, in order to discharge the high viscosity thermo setting resin required in the semiconductor device manufacturing process, a liquid discharge device capable of discharging an accurate amount of a high viscosity liquid is required. 
     An example of a device capable of discharging various types of liquids is disclosed in Patent Literature (PTL) 1. The liquid discharge device disclosed in PTL 1 includes a storage chamber, which stores a liquid to be discharged, having a variable volumetric capacity provided such that a supply hole for supplying the liquid leads to a discharge hole for discharging the liquid. The liquid is discharged from the discharge hole by reducing the volumetric capacity of the storage chamber for a short period of time. 
     With a liquid discharge device having this structure, no damage is incurred by the solid matter contained in the liquid seeping between the rigid parts and causing friction. Moreover, it is possible to discharge a high viscosity liquid since the force that reduces the volumetric capacity of the storage chamber is great. 
     CITATION LIST 
     Patent Literature 
     
         
         [PTL 1] Japanese Unexamined Patent Application Publication No. 2008-307466 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     However, with the above-described structure of the liquid discharge device, while it is possible to accurately discharge a definite amount of liquid by filling a discharge hole to the brim with the liquid, a problem arises in that it takes a long time to fill the whole discharge hole with the liquid because the discharge hole is filled with the liquid by surface tension. Moreover, if the volumetric capacity of the discharge hole is increased for the purpose of increasing the amount of liquid discharged, the time it takes to fill the discharge hole with the liquid increases even further, meaning discharging a large volume of liquid within a given period of time becomes problematic. 
     Furthermore, with the above-mentioned liquid discharge device having a structure which is in series between supply hole and the discharge hole via the storage chamber, when pressure is applied to the liquid to increase the filling speed and the supply of liquid is forced, there is a hazard that the liquid could leak from the discharge hole due to the pressure applied to the liquid to be supplied, making it difficult to yield a high discharge rate while maintaining stability. 
     However, the inventor has found, through research and repeated experiments, that rapid filling is possible while reducing factors that adversely affect accuracy and while avoiding problems such as leakage, by stopping the application of pressure to the liquid under a suitable condition even when the pressure applied to the liquid to be supplied to the storage chamber or the discharge hole is increased. 
     The present invention is based on the above knowledge, and aims to provide a liquid discharge device and a liquid discharge method capable of discharging an accurate amount of liquid at high speed. 
     Solution to Problem 
     In order to achieve the above-describe objective, a liquid discharge device includes a discharge unit configured to discharge a droplet of a liquid including: an elastic discharge part including a storage chamber at least partially formed of an elastic component, a supply hole which leads to the storage chamber and through which the liquid is supplied to the storage chamber, and a discharge hole through which the liquid stored in the storage chamber is discharged; and an actuating unit configured to vary a volumetric capacity of the storage chamber, and the liquid discharge device further including: a pressurizing unit configured to pressurize the liquid to be supplied to the storage chamber to a pressure within a stable range; a supply control unit configured to control whether the pressurized liquid is supplied to the storage chamber; and an actuation control unit configured to control operation of the actuating unit. 
     With this, it is possible to rapidly fill the storage chamber and the discharge hole with the liquid while reducing factors that adversely accuracy because the liquid can be supplied to the storage chamber while pressurized. Moreover, even when the viscosity of the liquid is high, it is possible to rapidly fill the storage chamber and such while reducing factors that adversely accuracy. Furthermore, by controlling the discharge timing of the liquid with the actuation control unit while also controlling the timing of the supply of the pressurized liquid (hereinafter also referred to as pressurized supply liquid) to the storage chamber with the supply control unit, it is possible to suitably adjust the amount of liquid to be discharged. 
     Consequently, it is possible to discharge an accurate amount of liquid regardless of the viscosity and discharge liquid at high speed while reducing factors that adversely accuracy. 
     Furthermore, because the liquid is pressurized to within a stable range by the pressurizing unit, the liquid will not inadvertently leak from the discharge hole even if there is a slight error in the control timing by the supply control unit or the actuation control unit. 
     It is difficult to demarcate the “stable range” since it is dependent on the viscosity and surface tension of the liquid as well as the diameter and length of the discharge hole. 
     However, the inventor has found, through repeated experiments, that the stable range is a range of the supply liquid pressure in which, under specific conditions that the length of time that the pressurized supply liquid is supplied is constant and that the volumetric capacity of the storage chamber is decreased in order to discharge the liquid, the flying speed of the discharged droplet (hereinafter also referred to as droplet velocity; strictly speaking, since the speed of the droplet decreases due to air resistance and rebound force when a column of the discharged liquid is severed as the liquid becomes a droplet, flying speed indicates an average speed within a given period) becomes constant when the pressure of the pressurized supply liquid is changed. 
     Moreover, the constant flying speed of the droplet confirms that the volume of the droplet discharged by the liquid discharge device will be constant. 
     Furthermore, the inventor has confirmed that when the supply liquid pressure is set within the stable range, the flying speed of the droplet will remain constant and the liquid will not inadvertently leak from the discharge hole even if there is a slight difference in the control timing by the supply control unit and the actuation control unit. 
     Furthermore, the liquid discharge device may include a negative pressurizing unit configured to apply a negative pressure to the liquid in the storage chamber to equalize a pressure of the liquid with the atmospheric pressure. 
     With this, since the pressure of the liquid in the storage chamber (including the discharge hole) after supply of the liquid can be made a constant value (for example, atmospheric pressure or in the vicinity thereof), it is possible to maintain the state of the surface of the liquid (the state of the convex or concave surface of the liquid inside a tube, caused by surface tension, that is, meniscus) and the position of the surface of the liquid inside the discharge hole (or in the vicinity of the outer edge of the opening of the discharge hole) at a constant level. 
     This is particularly advantageous in a situation in which the pressure inside the storage chamber fluctuates as a result of the height of the surface of the liquid to be supplied, such as when the supply source is positioned higher than the opening of the discharge hole, or in a situation in which a variation occurs in the atmospheric pressure in the area of the liquid discharge device. 
     Furthermore, the liquid discharge device may include a supply source including a syringe and a plunger, the supply source holding, in the syringe, the liquid to be supplied to the storage chamber, wherein the plunger includes a flexible portion that is flexible in a moving direction of the plunger, the syringe includes a sealed pressure regulating chamber on a side of the plunger opposite to a holding chamber which holds the liquid, and the negative pressurizing unit may be configured to apply a negative pressure to the liquid by transporting gas from inside the pressure regulating chamber to outside the pressure regulating chamber. 
     With this, it is possible to avoid complications in accurately adjusting the pressure of the liquid due to the frictional resistance between the plunger and the syringe when making the pressure of the liquid equal to or in the vicinity of the atmospheric pressure by causing the negative pressurizing unit to adjust the pressure inside the pressure regulating chamber. 
     That is to say, since the flexible portion included in the plunger flexes with the change in pressure in the pressure regulating chamber irrespective of frictional resistance between the plunger and the syringe, the pressure inside the pressure regulating chamber acts directly on the liquid, and the pressure of the liquid can be accurately adjusted. 
     In this sense, it is preferable that the flexible portion flex under a force less than the force of the frictional resistance between the plunger and the syringe. 
     Moreover, in order to achieve the above-describe objective, a liquid discharge method for discharging a liquid as a droplet using a discharge unit including: an elastic discharge part including a storage chamber at least partially formed of an elastic component, a supply hole which leads to the storage chamber and through which the liquid is supplied to the storage chamber, and a discharge hole through which the liquid stored in the storage chamber is discharged; and an actuating unit which varies a volumetric capacity of the storage chamber, the liquid discharge method including: pressurizing the liquid to be supplied to the storage chamber to a pressure within a stable range; controlling whether the pressurized liquid is supplied to the storage chamber using the supply control unit; and discharging the liquid by controlling operation of the actuating unit using the actuation control unit. 
     Consequently, it is possible to discharge an accurate amount of liquid regardless of the viscosity and discharge liquid at high speed while reducing factors that adversely accuracy. 
     It is to be noted that implementation of the present invention as a computer program for causing a computer to execute each process included in the liquid discharge method is intended to be included in an embodiment of the present invention. A non-transitory computer-readable recording medium for use in a computer containing said program is also intended to be included in an embodiment of the present invention. 
     Advantageous Effects of Invention 
     With the present invention, it is possible to discharge a wide variety of liquids, discharge an accurate amount of liquid, and discharge liquid at high speed. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a perspective view of the liquid discharge device framework. 
         FIG. 2  is a perspective exploded view illustrating the framework of the parts of the liquid discharge device related to the discharging of liquid. 
         FIG. 3  is a perspective external view illustrating the framework of the parts of the liquid discharge device related to the discharging of liquid. 
         FIG. 4  illustrates a partial cross-section of the framework of the parts of the liquid discharge device related to the discharging of liquid. 
         FIG. 5  is a block diagram showing the functional configuration of the parts of the liquid discharge device related to the discharging of liquid. 
         FIG. 6  is a cross-sectional view illustrating a liquid discharging operation of the discharge unit when in (a) a pre-discharge state and (b) a post-discharge state. 
         FIG. 7  is a timing chart showing shifts in operations of the liquid discharge device. 
         FIG. 8  is a graph illustrating an example of actual experiment results. 
         FIG. 9  is a timing chart showing shifts in operations of the liquid discharge device. 
         FIG. 10  shows a cross-section of another embodiment of the discharge unit. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Next, an embodiment of the liquid discharge device and liquid discharge method according to the present invention will be discussed with reference to the Drawings. It is to be noted that the following embodiments are merely an example of the liquid discharge device and liquid discharge method according to the present invention. As such, the scope of the present invention is demarcated by the scope of the language in the Claims using the below embodiments as a reference, and is not intended to be limited merely by the following embodiments. 
       FIG. 1  is a perspective view of the liquid discharge device framework. 
     A liquid discharge device  100  according to this embodiment is a device which can form a pattern by discharging a liquid  201  onto a desired location on an object to be coated  204 , and includes a head  221  and a stage  231  which holds the object to be coated  204 . 
     The head  221  is provided with one or more discharge units  101  (to be described later), and reciprocates in a main scanning direction (x axis direction in  FIG. 1 ) along a head transporter  202  supported by a work base  206 . The stage  231  similarly reciprocates in a vertical scanning direction (y axis direction in  FIG. 1 ) along a stage transporter  203  supported by the work base  206 . 
     With this configuration, the liquid discharge device  100  discharges the liquid  201  in a direction facing the object to be coated  204  from the discharge unit  101  which includes the head  221  while relatively moving the head  221  and the object to be coated  204  secured above the stage  231  to form a desired pattern or a uniform film on the object to be coated  204 . 
       FIG. 2  is a perspective exploded view illustrating the framework of the parts of the liquid discharge device related to the discharging of liquid. 
       FIG. 3  is a perspective external view illustrating the framework of the parts of the liquid discharge device related to the discharging of liquid. 
       FIG. 4  illustrates a partial cross-section of the framework of the parts of the liquid discharge device related to the discharging of liquid. 
       FIG. 5  is a block diagram showing the functional configuration of the parts of the liquid discharge device related to the discharging of liquid. 
     As is shown in these Drawings, the liquid discharge device  100  is a device which can discharge no more or less than a given amount of a desired liquid  201  as a droplet, and includes the discharge unit  101 , a pressurizing unit  102 , a supply control unit  103 , an actuation control unit  104 , and a supply source  210 . 
     The discharge unit  101  includes an elastic discharge part  105  and an actuating unit  114 , and can discharge the liquid  201  filling a storage chamber  110 , which is formed inside the elastic discharge part  105 , as a droplet by reducing the volumetric capacity of the storage chamber  110  for a short period of time. In this embodiment, the elastic discharge part  105  includes a first component  111 , a second component  112 , and an elastic component  113 . 
     The first component  111  is a part of the elastic discharge part  105 , and forms part of the storage chamber  110 . The first component  111  is a tube which functions as a supply path  115  for the liquid  201 . An indented portion having a conical shape (tapered shape) is formed at a tip portion of the first component  111 , the surface area of which gradually increases in a direction towards the tip surface (the end towards the second component  112  in the z axis direction). The indented portion forms one portion (one component) of the storage chamber  110 . Moreover, a supply hole  116 , which is an orifice which opens to the supply path  115  and the storage chamber  110 , is provided at a portion corresponding to the apex of the conical indented portion. The first component  111  is a component which compresses the elastic component  113  with the second component  112 , and compared to the elastic component  113 , is made of a highly rigid material. The first component  111  is, for example, made of stainless steel. 
     The second component  112  forms another portion (other component) of the storage chamber  110 , and provides a discharge hole  117  for discharging the liquid  201  in the storage chamber  110 . In this embodiment, the second component  112  is provided with an indented portion having a tapered shape whose surface area gradually increases in a direction from the discharge hole  117  towards the first component  111 . The storage chamber  110  is formed by positioning the indented portion of the first component  111  and the indented portion of the second component  112  to face each other. The second component  112  is a component which compresses the elastic component  113  with the first component  111 , and compared to the elastic component  113 , is made of a highly rigid material. The second component  112  is, for example, made of stainless steel. 
     The elastic component  113  is disposed between the first component  111  and the second component  112  and provided for varying the volumetric capacity of the storage chamber  110 . In this embodiment, the elastic component  113  is formed in the shape of a thin plate, and a portion of the elastic component  113  that is sandwiched between the two indented portions (that is, between the first component  111  and the second component  112 ) is provided with a through hole extending in a thickness direction (z axis direction) shaped to correspond with the two indented portions. In detail, the elastic component  113  is formed of fluorine rubber or silicone rubber, for example, and has an elastic characteristic that allows for the distance between the first component  111  and the second component  112  to be reduced by the actuating unit  114 , a sealing characteristic that allows for the prevention of leaking from the surface between the first component  111  and the second component  112  forming the storage chamber  110 , the strength to resist the pressure of the liquid  201  in the storage chamber  110 , and a shape restoration characteristic that allows for the discharging of the liquid  201  to occur multiple times. Moreover, the function of the elastic component  113  is not based in these material properties alone, but also in the shape (for example, ring shaped in the XY plane) of the elastic component  113 . For example, by forming the elastic component  113  to have a thickness between 100 μm and 300 μm (inclusive), preferably in the shape of a thin plate approximately 200 μm thick centrally provided with a loop-shaped component having through hole in a thickness direction with an inner diameter of approximately 1000 μm, the elastic component  113  realizes its function interdependently of its material properties. 
     It is to be noted that the size (volumetric capacity) and shape of the storage chamber  110 , the supply hole  116 , and the discharge hole  117  can be designed to suit the type of liquid  201  to be discharged and the volume of the droplet to be discharged. For example, when the cubic volume of the discharged droplet is a few nanoliters (for example, 3 nl), the discharge hole  117  is 85 μm in diameter and approximately 70 μm in length, the vicinity of the elastic component  113  in the storage chamber  110  is a cylindrical shape approximately 1000 μm in diameter, the supply hole  116  is 110 μm in diameter and approximately 700 μm in length. Moreover, when the cubic volume of the discharged droplet is several nl (for example, 20 nl), the discharge hole  117  is 100 μm in diameter and approximately 100 μm in length, and the vicinity of the elastic component  113  in the storage chamber  110  is a cylindrical shape approximately 1500 μm in diameter. 
     Here, the supply hole  116  (orifice) which supplies the liquid  201 , the storage chamber  110 , and the discharge hole  117  are positioned in a straight line to reduce resistance to the liquid  201 . This makes it easier to rapidly fill the storage chamber  110  and the discharge hole  117  with the liquid  201 . 
     Moreover, at least one of the first component  111  and the second component  112  (second component  112  in this embodiment) is provided with a recessed portion in which the elastic component  113  is fitted to box in the outer surface of the elastic component  113 . This restricts the elastic component  113  from deforming outward with respect to the storage chamber  110  when elastic deformation of the elastic component  113  occurs in the thickness direction. This is to keep the pressure of the liquid  201  inside the storage chamber  110  from decreasing as a result of the elastic component  113  expanding in an intersecting direction of the thickness direction thereof. 
     The actuating unit  114  is an actuator which exerts power to extend the storage chamber  110  in the z axis direction and increase the volumetric capacity thereof (see  FIG. 6  ( a )) under normal circumstances (a normal basis in which supply of the liquid  201  to the storage chamber  110  is possible), and exerts power to relatively reduce the distance between the first component  111  and the second component  112  (see  FIG. 6  ( b )) by compressing the elastic component  113  and reducing the volumetric capacity of the storage chamber  110  in order to discharge the liquid  201 . Here, a unit which operates the first component  111  and the second component using air pressure or magnetism can be used as the actuating unit  114 , but taking into consideration the size of the apparatus and responsivity, a piezoelectric element is preferable. In particular, a stacked piezoelectric body is preferable for the actuating unit  114 . In this embodiment, one end (upper end) of the actuating unit  114  in the lengthwise direction (z axis direction) is rigidly connected to the outer surface of the first component  111  with an adhesive, and the other end (lower end) is connected to a portion of the second component  112  via the elastic component  113 . Under voltage supply, the actuating unit  114  exerts power to extend the distance between the first component  111  and the second component  112  in the lengthwise direction (z axis direction). It is to be noted that in this embodiment, the other end (lower end) of the actuating unit  114  is connected to a portion of the second component  112  supported by a housing  119  (to be described later) via the elastic component  113 , and is not rigidly connected using an adhesive, for example. 
     It is to be noted that the portion in which the other end (lower end) of the actuating unit  114  and a portion of the second component  112  are in direct contact may be fixed together with an adhesive in order to prevent the relative follow-up timing of the second component  112  from being off in the z axis direction with respect to the other end (lower end) of the actuating unit  114  when the actuating unit  114  contracts in the z axis direction (in order to ensure stable discharge of the liquid  201  droplet and prevent leaking between the contact surfaces of the other end (lower end) of the actuating unit  114  and the second component). This configuration is, however, not intended to be limiting. For example, a fixed configuration of a separable, mechanical structure achieved by increasing the elastic force (biasing force) of the biasing unit  120  is acceptable. 
     Specifically, the actuating unit  114  expands in the z axis direction, as is shown in  FIG. 6  ( a ), as a result of voltage being applied to an electrode  118 , and contracts in the z axis direction, as is shown in  FIG. 6  ( b ), as a result of releasing the application of voltage, thereby causing the discharge of the liquid  201 . 
     Moreover, the stacked piezoelectric body used as the actuating unit  114  is arranged to encompass the perimeter of the cylindrical first component  111 . That is, the stacked piezoelectric body used as the actuating unit  114  is provided with a through-hole in which the first component  111  can be inserted with room to maneuver. By forming the actuating unit  114  to have this kind of shape, the elastic component  113  interposed between the first component  111  and the second component  112  can contract and expand relatively uniformly in the z axis direction. 
     In this embodiment, the discharge unit  101  is further provided with the housing  119  and the biasing unit  120 . 
     The housing  119  is a separable structure arranged to sandwich the elastic component  113  between the second component  112  and the actuating unit  114  as well as the first component  111  rigidly connected to the actuating unit  114 . 
     The biasing unit  120  has a biasing force in a direction pushing the actuating unit  114  into the second component  112  via the housing  119 . In this embodiment, the biasing unit  120  is a disc spring. 
     Since, for example, by taking apart the housing  119  it is possible to separate the first component  111  from the actuating unit  114  and the actuating unit  114  from the second component  112 , and possible to easily exchange or clean the second component  112  when the discharge hole  117  is clogged, the maintenance capability of the discharge unit  101  is improved with this kind of structure. Moreover, by preparing multiple second components  112  having different discharge holes  117  and indented portions, the second component  112  can be easily changed out to suit the type of liquid  201  to be used. 
     Furthermore, since the elastic component  113  is also separable it can easily be changed out in the case of deterioration, for example, thereby improving the longevity of the discharge unit  101  as a whole. 
     The supply source  210  holds the liquid  201  to be supplied to the storage chamber  110 , and in the case of this embodiment, includes a syringe  211  and a plunger  212 . 
     The syringe  211  is a cylindrical container which holds the liquid  201  internally, and can supply the liquid  201  to the storage chamber  110  at a constant pressure by moving the plunger  212 . The syringe  211  includes a holding chamber  213  which holds the liquid  201 , and a sealed pressure regulating chamber  214  on a side of the plunger  212  opposite to the holding chamber  213 . 
     The plunger  212  is positioned inside the syringe  211  to slide independently of the syringe  211  and is a piston which can push out the liquid  201  from inside the syringe  211 . In this embodiment, a flexible portion  215 , which is flexible in the direction in which the plunger  212  slides, is provided in a portion of the plunger  212 . In this embodiment, the flexible portion  215  is a film which blocks one end of a hole penetrating the plunger  212  in the direction in which the plunger  212  slides. 
     It is to be noted that the entire plunger  212  itself may be flexible and function as the flexible portion  215 . 
     The above-described aspect of the supply source  210  is preferable because, compared to a pump, for instance, pulsation does not occur. 
     The pressurizing unit  102  pressurizes the liquid  201  to be supplied to the storage chamber  110  to a pressure greater than the atmospheric pressure. In this embodiment, since the supply source  210  is configured of the syringe  211  and the plunger  212 , the pressurizing unit  102  can inject pressurized air into the pressure regulating chamber  214  of the supply source  210 . By injecting pressurized air into the pressure regulating chamber  214 , the pressurizing unit  102  can move the plunger  212  relative to the syringe  211  and pressurize the liquid  201 . 
     It is to be noted that the pressurizing unit  102  is not limited to a device such as an air compressor which generates pressurized air, but may be a device which mechanically moves the plunger  212  relative to the syringe  211 , such as a device using a biasing unit such as a spring to apply a constant force to the plunger  212 . The pressurizing unit  102  may also be a pump having the functions of the pressurizing unit  102  that can pressurize and supply the liquid  201  at the same time, such as a tube pump, for example. Moreover, an industrial air source, such as one found in a manufacturing facility, may also be used. 
     Furthermore, when the liquid  201  does not include a volatile element, the pressurizing unit  102  may be a device which supplies the liquid  201  to the storage chamber  110  of the elastic discharge part  105  by directly pressurizing the liquid  201  with air, for example, without the use of a plunger. 
     The supply control unit  103  controls whether or not the pressurized liquid  201  is supplied to the storage chamber  110 . In this embodiment, the supply control unit  103  includes a first valve  131  and a supply control unit  132  (see  FIG. 4  and  FIG. 5 ). 
     The first valve  131  is provided along an air pathway connecting the pressurizing unit  102  (air compressor, industrial air source, etc.) and the pressure regulating chamber  214 , and controls whether to let in or block pressured air to the pressure regulating chamber  214  by opening or closing, respectively. 
     In this embodiment, the first valve  131  is a three-port valve (see  FIG. 4 ). That is to say, when the first valve  131  is closed, pressurized air from the pressurizing unit  102  is blocked from being supplied to the pressure regulating chamber  214  and the pressure regulating chamber  214  is switched to open to a different path. The “different path” is a path connected to a second valve  181  (to be described later). Furthermore, the second valve  181  is a three-port valve just like the first valve  131  is, and can selectively connect to a negative-pressure source  107  (to be described later), the atmosphere, and the different path. It is to be noted that the different path may simply be a path that opens to the atmospheric pressure. 
     With the above configuration, when the air path is switched from being open to the pressurizing unit  102  to being open to the negative-pressure source  107 , the path between the pressure regulating chamber  214  and the negative-pressure source  107  is open. Here, when the first valve switches to the different path, it is possible to reduce (remove) residual pressure in the pressure regulating chamber  214  pressurized by the pressurizing unit  102  in a minimal amount of time by opening the pressure regulating chamber  214  to the atmospheric pressure using the second valve  181 . Here, “minimal amount of time” is between 10 and 20 msec (not shown in  FIG. 7  or  FIG. 9 ). With this, the pressure added to the liquid  201  is stopped and the supply of the liquid to the storage chamber  110  is stopped. 
     The supply control unit  132  is a processing unit realized from a main control apparatus  109 , such as a computer, included in the liquid discharge device  100 , and controls the opening and closing of the first valve  131 . 
     It is to be noted that when the pressurizing unit  102  is, for example, a pump, the supply control unit  103  may control the supply of the liquid  201  by controlling the operation and non-operation of the pump instead of controlling the supply of the liquid  201  by opening and closing the valve. 
     The actuation control unit  104  is a processing unit which controls the actuating unit  114 . In this embodiment, since the actuating unit  114  is made of a piezoelectric element, the operation of the actuating unit  114  is controlled by controlling the application of voltage to two electrodes  118  included in the actuating unit  114 . It is to be noted that the actuation control unit  104  may control the operation of the actuating unit  114  by adjusting the voltage applied to the actuating unit  114 . 
     Moreover, in this embodiment, as  FIG. 4  and  FIG. 5  show, the liquid discharge device  100  includes the negative pressurizing unit  180 , and the main control apparatus  109  includes a synchronizing unit  191 . In this embodiment, the negative pressurizing unit  180  includes the negative-pressure source  107  and a negative-pressure supply control unit  108 . 
     the negative pressurizing unit  180  applies negative pressure to the liquid  201  in the storage chamber  110  to provide pressure equalization between the liquid  201  and the atmosphere. For example, when the supply source  210  is configured of the syringe  211  and the plunger  212 , such as the case with this embodiment, the negative-pressure source  107  can expel a gas (air) from the pressure regulating chamber  214  in the supply source  210  (such as an exhaust pump, a vacuum pump, an industrial vacuum, or a vacuum tank). Moreover, the negative-pressure source  107  may be the atmosphere (may be exposed to the atmosphere by an open end). Moreover, the negative-pressure supply control unit  108  includes the second valve  181  and a negative-pressure control unit  182 . As described above, the negative-pressure supply control unit  108  controls the second valve  181  via the negative-pressure control unit  182  to make the path between the negative-pressure source  107  and the pressure regulating chamber  214  open and expel the gas from the pressure regulating chamber  214 : This makes it possible to equalize the pressure of the liquid  201  with the atmospheric pressure, which is the pressure of the gas outside the syringe  211  and the storage chamber  110 . 
     It is to be noted that here (see  FIG. 4 ), the path between the negative-pressure source  107  and the pressure regulating chamber  214  can be opened via both the first valve  131  and the second valve  181 , but the present invention is not limited to this configuration. The pressure regulating chamber  214  may be opened to via each of the first valve  131  and the second valve  181 , for example. In this case, the first valve  131  and the second valve  181  do not need to be three-port valves. However, with this configuration, the pressurizing unit  102  and the negative-pressure source  107  cannot be open to the pressure regulating chamber  214  at the same time, and caution must be given with regard to keeping the control of the pressure regulating chamber  214  from becoming unstable. 
     With this, it is possible to proactively keep the pressure of the liquid inside the storage chamber  110  and the discharge hole  117  at a constant valve (for example, atmospheric pressure or a value in the vicinity thereof), and possible to maintain a constant position (height) of the surface of the liquid and meniscus. Consequently, the cubic volume of the liquid  201  held in the storage chamber  110  and the discharge hole  117  can be kept constant, making it possible to achieve an extremely accurate discharge volume in which droplets of the liquid  201  are discharged having a constant volume (cubic volume). 
     With this embodiment in particular, since the plunger  212  includes the flexible portion  215 , even a slight change in pressure in the pressure regulating chamber  214  can be acutely translated to the liquid  201 , making it possible to finely adjust the pressure of the liquid  201  to equalize it with the atmospheric pressure. 
     It is to be noted that there are instances in which it is acceptable that the negative pressurizing unit  180  does not include a negative-pressure source  107  which actively discharges the gas from the pressure regulating chamber  114 , such as a vacuum pump. For example, the negative pressurizing unit  180  may be an apparatus which can change the position of the height of the supply source  210  and adjust the heightwise (z axis direction) positional relationship between the storage chamber  110  and the surface of the liquid  201  stored in the supply source  210 , and equalizes the pressure of the liquid  201  in the storage chamber  110  with the atmospheric pressure by, for example, lowering the surface of the liquid  201  stored in the supply source  210  to a height lower than the storage chamber  110  to keep the hydraulic head pressure of the liquid  201  in the supply source  210  applied to the storage chamber  110  from exceeding the necessary amount. 
     The synchronizing unit  191  is a processing unit which adjusts the discharge timing of the liquid  201  from the discharge hole  117  in the elastic discharge part  105  and the supply timing of the pressurized liquid  201  to the storage chamber  110  by receiving information from each of the actuation control unit  104  and the supply control unit  132 . In this embodiment, the synchronizing unit  191  also adjusts the negative pressure application timing by receiving information between the negative-pressure control unit  182  as well. 
     Next, the operation of the above-described liquid discharge device  100  will be explained. 
       FIG. 7  is a timing chart showing shifts in operations of the liquid discharge device. 
     First, the actuation control unit  104  causes the actuating unit  114  to extend in the z axis direction and increase the volumetric capacity of the storage chamber  110  (see  FIG. 6  ( a )) by applying a predetermined voltage (for example, 20 V) to the actuating unit  114 . Next, the actuation control unit  104  fills the discharge hole  117  and the increased volumetric capacity storage chamber  110  with the liquid  201  via the supply hole  116 , whose channel diameter is temporarily narrowed just before the liquid  201  enters the storage chamber  110 , which is the supply mouth for the liquid  201 . Next, the actuation control unit  104  releases the voltage applied to the actuating unit  114  for an extremely short period of time (for example, between 10 μsec and 10 msec). This causes the actuating unit  114  to contract for an instant in the z axis direction (the condition shown in  FIG. 6  ( b )). 
     Since the first component  111  and the second component  112  deform such that their relative positions become closer together a result of the upper portion of the actuating unit  114  being connected to the first component  111  in a fixed manner and the contraction of the actuating unit  114  being pressed towards the second component  112  by the biasing unit  120 , the elastic component  113  sandwiched between the first component  111  and the second component  112  deforms and contracts, thereby relatively reducing the space in the storage chamber  110  in the z axis direction and applying pressure to the liquid  201  in the storage chamber  110 . 
     With this, the liquid  201  is discharged toward the object to be coated  204  as a droplet from the discharge hole  117 , which has lower back pressure resistance (discharge resistance on the discharge hole  117  side) than the supply hole  116  which is the supply mouth for the liquid  201  in the storage chamber  110 . The droplet adheres as a dot to the upper surface of the object to be coated  204 . 
     Next, the first valve  131  is opened by the supply control unit  132  in order to supply the liquid  201  to the storage chamber  110  as a result of the synchronizing unit  191  transmitting, to the supply control unit  132 , information on the voltage applied to the actuating unit  114  by the actuation control unit  104 . 
     With this, the pressurized liquid  201  travels from the supply source  210  and passes through the supply path  115  of the first component  111 , and fills the storage chamber  110  rapidly and without comprising accuracy via the supply hole  116  smaller in diameter than the supply path  115  and the storage chamber  110 . It is to be noted that at this point, the first component  111  has shifted due to the actuating unit  114  expanding in the z axis direction as a result of a voltage application thereto, causing the space in the storage chamber  110  in the z axis direction to expand, returning the storage chamber  110  its original state (original volumetric capacity). 
     The supply control unit  132  accurately controls the length of time that the first valve  131 , which is a positive pressure valve that pressure supplies the liquid  201  to the storage chamber  110 , remains open. For example, when the cubic volume of the discharged droplet of the liquid  201  is a few nanoliters, the first valve  131  is made to remain open for approximately 50 msec. 
     Here, the pressure applied to the liquid by the pressurizing unit  102  may be a pressure selected from a stable range. The stable range is a range of the air pressure injected into the pressure regulating chamber  214  by the pressurizing unit  201 . The stable range differs depending on the amount of the liquid  102  discharged and the size and shape of the storage chamber  110  and the discharge hole  117 . For example, when the cubic volume of the discharged droplet of the liquid  201  is a few nanoliters, the stable range is between 10 kPa and 30 kPa, inclusive. 
     Moreover, a fixed stable range for the liquid discharge device  100  can be determined with the following experimental test. An average speed (droplet flying speed) and a volume of the discharged liquid  201  droplet in a predetermined period can be measured by changing the supply pressure of the liquid  201  via the pressurizing unit  102  in multiple stages and discharging the liquid  201  in each of the stages, as  FIG. 8  shows. As a result, even if the supply pressure which supplies the liquid to the storage chamber  110  is changed, a range can be selected in which the speed and volume of the droplet does not greatly vary. This range may be set as the stable range. 
     Similarly, regarding the supply time of the liquid  201  to the storage chamber  110  and the discharge hole  117 , in this embodiment, the amount of time that the supply control unit  132  keeps the first valve  131  open can be set in advance. For example, an average speed and a volume of the discharged liquid  201  droplet in a predetermined period can be measured by changing the supply time in multiple stages and discharging the liquid  201  in each of the stages. As a result, even if the supply time is changed, a range can be selected in which the speed and volume of the droplet does not greatly vary. This range may also be set as the stable range for the supply time. Consequently, a shorter time from the stable range may be selected when one wishes to increase the discharge cycle of the liquid  201 . 
     Next, the second valve  181  is opened by the negative-pressure control unit  182  as a result of the synchronizing unit  191  transmitting, to the negative-pressure control unit  182 , information regarding the ending of the opening of the first valve  131  (the closing of the first valve  131 ) by the supply control unit  132 . With this, the liquid  201  filling the storage chamber  110  and the discharge hole  117  is drawn into a stable condition by negative pressure. That is to say, the state of the meniscus, which is the surface made by the liquid  201  in the narrow tube (discharge hole  117 ), is stabilized due to the surface tension of the liquid  201  in the discharge hole  117 , and the amount of the liquid  201  filling the storage chamber  110  and the discharge hole  117  is stabilized. With this, leakage of the liquid  201  from the discharge hole  117  can be kept under control. 
     By the actuation control unit  104  once again releasing the application of the voltage to the piezoelectric element configured of the actuating unit  114  and shrinking the actuating unit  114 , it is possible to once again discharge a droplet of approximately the same volume that was previously discharged. 
     Here, “approximately the same volume” refers to within a margin of error of 1% when the volume of the discharged droplet is a few nanoliters. At this point in time, the margin of error for the droplet volume is smaller than can actually be measured, and is believed to be 0.01% or less. As a comparison, the droplet volume margin of error in a conventional apparatus is approximately 3%. 
     It is to be noted that in  FIG. 7 , while the second valve  181  is set to be open for an interval of 50 msec, the time is not intended to be limited thereto. In the case that one wishes to shorten the discharge cycle, the interval time may be shortened. 
     With this, after discharge of the liquid  201 , the storage chamber  110  and the discharge hole  117  can be filled in an extremely short period of time (in milliseconds or a lower magnitude of order) by supplying the liquid  201  pressurized to within the stable range. Moreover, since the stable range is sufficiently high relative to the atmospheric pressure, the storage chamber  110  and the discharge hole  117  can be filled with a constant amount of the liquid  201  each time, even if the atmospheric pressure were to change. 
     Consequently, the discharge cycle, which is the span that the liquid  201  is discharged, can be shortened and a large number of droplets of the liquid  201  can be discharged in a short period of time. Moreover, since the amount of the liquid  201  up to the discharge hole  117  is a stabilized amount, the amount of liquid  201  discharged is a constant amount, and the object to be coated  204  can be coated with an accurate amount of the liquid  201 . 
     Furthermore, with the above-described pressurized supply of the liquid  201 , it is possible to rapidly fill the storage chamber  110  and the discharge hole  117  with the liquid  201  while reducing factors that adversely accuracy. As such, it is possible to increase the capacity of the storage chamber  110  and the discharge hole  117 , supply the liquid  201  while controlling the pressurized supply so that the condition of the meniscus remains stable in the discharge hole  117 , and discharge the liquid  201  pressurized by the actuating unit  114 . In turn, this makes it possible to accurately discharge an even larger amount of the liquid. 
     Moreover, since the discharge unit  101  does not include components having rigid parts which slide or come into contact with the parts through with the liquid  201  passes, the liquid  201  can be discharged in a stable manner even when it contains solid matter dispersed therein. 
     It is to be noted that the present invention is not limited to the above embodiment. For example, embodiments resulting from arbitrary combinations of constituent elements recited in the present invention or embodiments in which some constituent elements are left out may also be embodiments of the present invention. The present invention also includes variations of the embodiments conceived by those skilled in the art unless they depart from the spirit and scope of the present invention, that is, the wording in the claims. 
     For example, as  FIG. 9  shows, when the first valve  131  is opened by the supply control unit  132  and the liquid  201  is being supplied to the storage chamber  110  and the discharge hole  117 , the actuation control unit  104  may operate the actuating unit  114  once or multiple times to discharge the liquid  201 . 
     In this case, by making the discharge span of the liquid  201  constant, a substantially accurate amount of the liquid  201  can be discharged. This is effective when multiple droplets of the liquid are to be discharged in one location on the object to be coated  204  because it is possible to apply an amount of the liquid  201  exceeding one droplet the liquid  201  to a single location. 
     It is to be noted that the shape of the elastic discharge part  105  is not limited to the above embodiment. For example, as  FIG. 10  shows, a elastic discharge part  105  in which at least one surface of the rectangular box-shaped elastic discharge part  105  is formed of the elastic component  113  (two of the surfaces are formed of the elastic component  113  in  FIG. 10 ) is acceptable. In this case, the actuating unit  114  disposed between the housing  119  and the elastic component  113  may directly distort the elastic component  113  to increase the volumetric capacity of the storage chamber  110 , whereby the liquid  201  fills the storage chamber  110  and the discharge hole  117  from the supply path  115  via the supply hole  116  and is discharged. 
     Moreover, the pressurizing unit  102  may include a regulator, for example, for regulating pressure (positive pressure), and the negative pressurizing unit  180  may include a regulator, for example, for regulating pressure (negative pressure). 
     Moreover, the elastic discharge part may include: a first component which forms a portion of the storage chamber; and a second component in which the discharge hole is provided, and the elastic component may be disposed between the first component and the second component. 
     Furthermore, the liquid discharge device may include a synchronizing unit configured to synchronize control for starting the supply of the liquid by the supply control unit and control for discharging the liquid by the actuation control unit.
         With this, it is possible to rapidly fill the storage chamber and the discharge hole since the liquid is supplied under pressure directly after being pressurized.       

     Furthermore, the liquid discharge method may include discharging the liquid in a supply period for supplying the pressurized liquid, the discharge being performed by the actuating unit under control of the actuation control unit. 
     With this, it is possible to discharge an adequate amount of liquid even if the discharge interval is shortened by supplying the pressurized liquid while the liquid is being discharged, and therefore the a relatively large amount of liquid can be accurately supplied. 
     INDUSTRIAL APPLICABILITY 
     The present invention is capable of accurately controlling the volume of and rapidly discharging a droplet, regardless of the type of liquid. As such, the present invention is applicable in forming thin, even films with various patterns in the manufacturing of various devices such as liquid crystal display panels, circuit boards, or LED elements. Moreover, the present invention is applicable in forming films which produce white light from monochromatic luminous bodies by discharging thereon a liquid dispersed with phosphor solid matter in phosphor coating processes for LED elements, for example. 
     REFERENCE SIGNS LIST 
     
         
           100  liquid discharge device 
           101  discharge unit 
           102  pressurizing unit 
           103  supply control unit 
           104  actuation control unit 
           105  elastic discharge part 
           107  negative-pressure source 
           108  negative-pressure supply control unit 
           109  main control apparatus 
           110  storage chamber 
           111  first component 
           112  second component 
           113  elastic component 
           114  actuating unit 
           115  supply path 
           116  supply hole 
           117  discharge hole 
           118  electrode 
           119  housing 
           120  biasing unit 
           131  first valve 
           132  supply control unit 
           180  negative pressurizing unit 
           181  second valve 
           182  negative-pressure control unit 
           191  synchronizing unit 
           201  liquid 
           202  head transporter 
           203  stage transporter 
           204  object to be coated 
           206  work base 
           210  supply source 
           211  syringe 
           212  plunger 
           213  holding chamber 
           214  pressure regulating chamber 
           215  flexible portion 
           221  head 
           231  stage