Abstract:
A capping apparatus including: a sealing unit that seals at least nozzle apertures of a liquid droplet ejection head that ejects liquid droplets; a heating unit that heats at least a vicinity of the nozzle apertures; and a negative pressure supplying unit that supplies an interior of the sealing unit with negative pressure that causes liquid droplets to be ejected from the nozzle apertures.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a capping unit that seals (known as “capping”) nozzle apertures in a liquid droplet ejection head and prevents drying of a liquid droplet solvent as well as clogging of the nozzle apertures, and to a method of controlling the capping unit, a liquid droplet ejection apparatus that includes the capping unit, and a device manufacturing method that uses the apparatus. 
   Priority is claimed on Japanese Patent Application No. 2003-428492, filed Dec. 25, 2003, the contents of which are incorporated herein by reference. 
   2. Description of Related Art 
   A liquid droplet ejection head is formed by a pressure generation chamber that houses a liquid droplet solvent, a piezoelectric element that pressurizes the pressure generation chamber, and nozzle apertures that are connected to the pressure generation chamber. As a result of the liquid droplet solvent in the pressure generation chamber being pressurized by the piezoelectric element, a minute quantity of liquid droplet solvent is ejected in the form of liquid droplets from nozzle apertures. In a liquid droplet ejection head having a structure such as this, if liquid droplet solvent evaporates in the vicinity of the nozzle apertures, or if an air bubble becomes blocked inside the liquid droplet ejection head, then a liquid droplet ejection malfunction occurs. Because of this, this type of liquid droplet ejection head requires a capping unit that seals the nozzle apertures so as to prevent drying of a liquid droplet solvent and also prevent blockages in the nozzle apertures. 
   Even if the nozzle apertures of a liquid droplet ejection head are sealed using a capping unit, if they are sealed for an extended period of time, then as a result of the moisture retaining properties of the liquid droplet solvent deteriorating due to evaporation of the liquid droplet solvent located on the flow path of the liquid droplet solvent and in the nozzle apertures or due to the liquid droplet solvent drying inside the capping unit, an increase in the viscosity of the liquid droplet solvent is generated and the nozzle apertures may become blocked. Because of this, the capping unit provided for the liquid droplet ejection head is one that expels liquid droplet solvent that has thickened in the vicinity of the nozzle apertures or ejects an air bubble that has become blocked in the pressure generation chamber by not only simply sealing the nozzle apertures of the liquid droplet ejection head, but by forcibly causing liquid droplet solvent to be expelled from the nozzle apertures by causing negative pressure to act on the nozzle apertures using a suction pump. 
   Note that, in addition to methods that use a capping unit, methods of clearing blockages in nozzle apertures include a method that uses a cleaning device that wipes a surface in which the nozzle apertures of the liquid droplet ejection head are formed using a wiper, and a flushing method that forcibly ejects a larger number of liquid droplets than a normal liquid droplet ejection quantity by increasing the pressure that is applied to the pressure generation chamber by the piezoelectric element. A conventional capping unit is described in detail, for example, in Japanese Unexamined Patent Application, First Publication No. H10-264402. 
   When a blockage forms in a liquid droplet ejection head, the aforementioned suctioning by a capping unit, cleaning by a cleaning device, or flushing is performed. However, if the blockage is not cleared, the suctioning, cleaning or flushing are performed a large number of times. Therefore, the problem has arisen that the ejection quantity of liquid droplet solvent from nozzle apertures where a blockage has not formed increases so that liquid droplet solvent is consumed needlessly. 
   Moreover, if the suctioning or the like is performed on a plurality of occasions, the problem arises that it takes time for a normal state (i.e., a state in which liquid droplets can be ejected from all the nozzle apertures) to be restored. In recent years, liquid droplet ejection heads have been used for the manufacture of filters used in liquid crystal display apparatuses, micro displays, as well as a variety of devices that have micro patterns. If it takes time until a normal state is restored, then a problem may arise in that throughput (i.e., the number of devices that can be manufactured in a unit time) is reduced by a corresponding amount. 
   The present invention was conceived in view of the above described circumstances, and it is an object thereof to provide a capping unit that enables blockages and the like in nozzle apertures of a liquid droplet ejection head to be cleared in a short time while restraining the needless consumption of liquid droplet solvent, as well as to a control method for the capping unit, a liquid droplet ejection apparatus that includes the capping unit, and a device manufacturing method that manufactures a device using the liquid droplet ejection apparatus. 
   SUMMARY OF THE INVENTION 
   In order to solve the above described problems, the capping apparatus of the present invention includes a sealing unit that seals at least the nozzle apertures of a liquid droplet ejection head that includes the nozzle apertures that eject liquid droplets, and includes: a heating unit that heats at least the vicinity of the nozzle apertures of the liquid droplet ejection head; and a negative pressure supplying unit that supplies an interior of the sealing unit that seals the nozzle apertures with negative pressure that causes liquid droplets to be ejected from the nozzle apertures. 
   According to this invention, by supplying the interior of the sealing unit that seals the nozzle apertures with negative pressure after heating the vicinity of the nozzle apertures of the liquid droplet ejection head, it is possible to lower the viscosity of thickened liquid droplet solvent or to melt solidified liquid droplet solvent and forcibly eject it from the nozzle apertures. As a result, it is possible to clear blockages in the nozzle apertures in a short time while restraining needless consumption of liquid droplet solvent. 
   The capping apparatus of the present invention may further include a control unit that controls a heating time of the vicinity of the nozzle apertures by the heating unit, and that controls a negative pressure supply time by the negative pressure supplying unit. 
   According to this invention, because the heating time of the vicinity of the nozzle apertures and the negative pressure supply time are controlled by the control unit, it is possible to secure a sufficient heating time that is required in order to lower the viscosity of thickened liquid droplet solvent or melt solidified liquid droplet solvent. In addition, because it is possible to secure just the sufficient expulsion time that is required to only eject the liquid droplet solvent whose viscosity has been lowered or the melted liquid droplet solvent, it is possible not only to keep the needless consumption of liquid droplet solvent to a minimum, but also to reliably clear blockages in the nozzle apertures in a short time. 
   Moreover, in the capping apparatus of the present invention, the control unit may include a time measuring unit that measures a length of time during which the nozzle apertures have been sealed by the sealing unit, and the control unit performs control to change the heating time and the negative pressure supply time in accordance with the length of time measured by the time measuring unit. 
   According to this invention, because the length of time that the nozzle apertures are sealed by the liquid droplet ejection head is measured, and the heating time and negative pressure supply time are changed in accordance with this measurement result, it is possible to set the heating time and negative pressure supply time in accordance with the extent of the increase in viscosity of the liquid droplet solvent or with the extent of the solidification of liquid droplet solvent, so that it is possible not only to keep the needless consumption of liquid droplet solvent to a minimum, but also to reliably clear blockages in the nozzle apertures in a short time. 
   Furthermore, in the capping apparatus of the present invention, there may be further provided a temperature measuring unit that measures a temperature in the vicinity of the nozzle apertures, and the heating unit adjusts the heating temperature of the vicinity of the nozzle apertures based on the temperature measured by the temperature measuring unit. 
   According to this invention, because the heating temperature of the vicinity of the nozzle apertures is adjusted based on a result of a measurement of the temperature in the vicinity of the nozzle apertures, it is possible to maintain a constant heating temperature irrespective of the surrounding temperature. The result of this is that it is possible to effectively lower the viscosity of thickened liquid droplet solvent or melt solidified liquid droplet solvent, resulting in it being possible to reliably clear blockages in the nozzle apertures in a short time. 
   In order to solve the above described problems, the present invention is directed to a method for controlling a capping apparatus including a sealing unit that seals at least the nozzle apertures of a liquid droplet ejection head that eject liquid droplets, including the steps of: heating a vicinity of the nozzle apertures of the liquid droplet ejection head; and supplying an interior of the sealing unit with negative pressure so that liquid droplets are ejected from the nozzle apertures. 
   According to this invention, by supplying the interior of the sealing unit that seals the nozzle apertures with negative pressure after heating the vicinity of the nozzle apertures of the liquid droplet ejection head, it is possible to lower the viscosity of thickened liquid droplet solvent or to melt solidified liquid droplet solvent and forcibly eject it from the nozzle apertures. As a result, it is possible to clear blockages in the nozzle apertures in a short time while restraining unnecessary consumption of the liquid droplet solvent. 
   The method for controlling a capping apparatus of the present invention may further include the steps of making a determination as to whether or not an ejection of the liquid droplets has been made from each of the nozzle apertures, and heating the vicinity of the nozzle apertures and supplying negative pressure to the interior of the sealing unit in accordance with the determination. 
   According to this invention, because a determination is made in advance as to whether or not an ejection of the liquid droplets has been made from each of the nozzle apertures, and heating of the vicinity of the nozzle apertures and supplying of negative pressure to the interior of the sealing unit that seals the nozzle apertures are performed in accordance with the determination, only when a malfunction occurs in which liquid droplets are not ejected, such as a blockage of the nozzle apertures, is an ejection of liquid droplets made in order to clear the malfunction. By performing this control, compared, for example, with when heating and supplying of negative pressure are performed regularly, there is no unnecessary ejection of liquid droplet solvent. As a result, it is possible to restrain the consumption of liquid droplet solvent and to eliminate the time required by liquid droplet ejections performed for heating or supplying negative pressure. 
   In the method for controlling a capping apparatus of the present invention, the step of heating a vicinity of the nozzle apertures of the liquid droplet ejection head and the step of supplying an interior of the sealing unit with negative pressure so that liquid droplets are ejected from the nozzle apertures may be performed at the same time. 
   According to this invention, because the heating of the vicinity of the nozzle apertures is performed at the same time as negative pressure is supplied to the interior of the sealing unit that seals the nozzle apertures, it is possible to shorten the time required for liquid droplet ejection. 
   Alternatively, in the method for controlling a capping apparatus of the present invention, the step of heating the vicinity of the nozzle apertures and the step of supplying an interior of the sealing unit with negative pressure may be performed at the same time after the vicinity of the nozzle apertures has undergone preliminary heating. 
   According to this invention, because the heating of the vicinity of the nozzle apertures and the supplying of the negative pressure to the interior of the sealing unit that seals the nozzle apertures are performed at the same time as each other and after the preliminary heating of the vicinity of the nozzle apertures, it is possible to set a longer heating time, resulting it in it being possible to effectively lower the viscosity of thickened liquid droplet solvent or to effectively melt solidified liquid droplet solvent. 
   In the method for controlling a capping apparatus of the present invention, the method may further include the steps of measuring a length of time during which the nozzle apertures have been sealed by the sealing unit, and changing a length of time during which the vicinity of the nozzle apertures is heated and a length of time during which the interior of the sealing unit is supplied with negative pressure accordance with the length of time that the nozzle apertures have been sealed measured by the sealing unit. 
   According to this invention, because the supply of negative pressure to the interior of the sealing unit that seals the nozzle apertures is performed after the preliminary heating of the nozzle apertures, it is possible to perform an ejection after sufficiently lowering the viscosity of thickened liquid droplet solvent or after sufficiently melting solidified liquid droplet solvent. 
   Moreover, the method for controlling a capping apparatus of the present invention may further include the steps of measuring a length of time during which the nozzle apertures have been sealed by the sealing unit, and changing a length of time during which the vicinity of the nozzle apertures is heated and a length of time during which the interior of the sealing unit is supplied with negative pressure accordance with the length of time that the nozzle apertures have been sealed measured by the sealing unit. 
   According to this invention, because the length of time that the nozzle apertures of the liquid droplet ejection head have been sealed is measured and the heating time and negative pressure supply time are changed in accordance with the result of this measurement, it is possible to set the heating time and negative pressure supply time in accordance with the extent of the increase in viscosity of the liquid droplet solvent or with the extent of the solidification of liquid droplet solvent, so that it is possible not only to keep the needless consumption of liquid droplet solvent to a minimum, but also to reliably clear blockages in the nozzle apertures in a short time. 
   The method for controlling a capping apparatus of the present invention may further include the step of changing a magnitude of the negative pressure that is supplied to the interior of the sealing unit. 
   According to this invention, because the size of the negative pressure that is supplied to the interior of the sealing unit that seals the nozzle apertures is changed, it is possible to control the amount of liquid droplets that are ejected per unit time, and it is possible to shorten the time in which liquid droplets are ejected. 
   In order to solve the above described problems, the liquid droplet ejection apparatus of the present invention includes: a liquid droplet ejection head including pressure generating elements that generate pressure in response to a supplied drive signal, and nozzle apertures from which are ejected liquid droplets that are pressurized by pressure generated by the pressure generating elements; a drive signal generating unit that supplies the pressure generating elements with a heating drive signal that heats a vicinity of the nozzle apertures without causing liquid droplets to be ejected from the nozzle apertures; and a capping apparatus including a sealing unit that seals the nozzle apertures and a negative pressure supplying unit that supplies an interior of the sealing unit with negative pressure that causes liquid droplets to be ejected from the nozzle apertures. 
   According to this invention, by supplying negative pressure to the interior of the sealing unit that seals the nozzle apertures after the vicinity of the nozzle apertures of the liquid droplet ejection head is heated using the pressure generating elements provided in the liquid droplet ejection head, it is possible to lower the viscosity of thickened liquid droplet solvent or melt solidified liquid droplet solvent and forcibly eject it from the nozzle apertures. As a result, it is possible to clear blockages in the nozzle apertures in a short time while restraining unnecessary consumption of liquid droplet solvent. Moreover, because the vicinity of the nozzle apertures of the liquid droplet ejection head is heated using the pressure generating elements provided in the liquid droplet ejection head, it is possible to achieve a reduction in size and a reduction in the cost of the liquid droplet ejection head compared with when a heating unit is provided separately from the pressure generating elements. 
   The liquid droplet ejection apparatus of the present invention may further include a determining unit that makes a determination as to whether or not an ejection of the liquid droplets has been made from each of the nozzle apertures; and a control unit that controls at least one of the drive signal generating unit and the negative pressure supplying unit provided in the capping apparatus in accordance with detection results of the detection unit. 
   According to this invention, because a determination is made in advance as to whether or not an ejection of the liquid droplets has been made from each of the nozzle aperture and heating of the vicinity of the nozzle apertures and supplying of negative pressure to the interior of the sealing unit that seals the nozzle apertures are performed in accordance with the determination, only when a malfunction occurs in which liquid droplets are not ejected, such as a blockage of the nozzle apertures, is an ejection of liquid droplets made in order to clear the malfunction. By performing this control, compared, for example, with when heating and supplying of negative pressure are performed regularly, there is no unnecessary ejection of liquid droplet solvent. As a result, it is possible to restrain the consumption of liquid droplet solvent and to eliminate the time required by liquid droplet ejections performed for heating or supplying negative pressure. 
   In the liquid droplet ejection apparatus of the present invention, the control unit may include a time measuring unit that measures a length of time during which the nozzle apertures of the liquid droplet ejection head have been sealed by the sealing unit, and the control unit controls a length of time during which the drive signal generating unit supplies the pressure generating elements with the heating drive signals and the length of time that the interior of the sealing unit is supplied with negative pressure in accordance with the length of time measured by the time measuring unit. 
   According to this invention, because the length of time that the nozzle apertures of the liquid droplet ejection head have been capped is measured, and the length of time of the heating by the pressure generating elements and a length of negative pressure supply time by the negative pressure supply device are changed in accordance with the results of this measurement, it is possible to set the heating time and negative pressure supply time in accordance with the extent of the increase in viscosity of the liquid droplet solvent or with the extent of the solidification of liquid droplet solvent, so that it is possible not only to keep the needless consumption of liquid droplet solvent to a minimum, but also to reliably clear blockages in the nozzle apertures in a short time. 
   In the liquid droplet ejection apparatus of the present invention, the heating drive signal may have a repetition frequency in an ultrasonic frequency band. 
   Moreover, in the liquid droplet ejection apparatus of the present invention, the repetition frequency may be 40 kHz or more. 
   Furthermore, in the liquid droplet ejection apparatus of the present invention, the amplitude of the heating drive signals may be half or less the amplitude of a drive signal that is applied to the pressure generating element when the liquid droplets are ejected from the nozzle apertures. 
   The method of manufacturing a device of the present invention is a method of manufacturing a device that includes a work piece on which is formed a pattern having functionality in a predetermined location, including the steps of: ejecting liquid droplets from the nozzle apertures that are provided in the liquid droplet ejection head using a capping apparatus described above, or using a method for controlling a capping apparatus described above, or using a liquid droplet ejection apparatus described above all; and forming the pattern by ejecting liquid droplets onto the work piece using a liquid droplet ejection head after the step of ejecting liquid droplets from the nozzle apertures has been completed. 
   According to this invention, the viscosity of thickened liquid droplet solvent is lowered or solidified liquid droplet solvent is melted and this liquid droplet solvent is then ejected using the above described capping apparatus, the method for controlling a capping apparatus, or liquid droplet ejection apparatus. Using a liquid droplet ejection head that has undergone this processing, a pattern is then formed on the work piece by ejecting liquid droplets thereon. As a result, it is possible not only to restraining unnecessary consumption of liquid droplet solvent, but also to extend the liquid droplet ejection time for forming the pattern. The result of this is that it is possible to reduce device manufacturing costs, and improve throughput. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view showing the schematic structure of a liquid droplet ejection apparatus according to an embodiment of the present invention. 
       FIG. 2  is an exploded perspective view of an ejection head  20 . 
       FIG. 3  is a perspective view showing a portion of the principal portions of the ejection head  20 . 
       FIGS. 4A  is a plan view showing the structure of a capping unit  22 . 
       FIGS. 4B  is a cross-sectional view showing the structure of a capping unit  22  taken along the arrow line A-A in  FIG. 4A . 
       FIG. 5  is a block diagram showing a structure of electric functions of the liquid droplet ejection apparatus according to an embodiment of the present invention. 
       FIGS. 6A and 6B  show waveforms of one cycle of normal drive signal and a drive signal for heating that are generated by a drive signal generating unit  54 . 
       FIG. 7  is a flowchart showing an example of a method for controlling a capping unit according to an embodiment of the present invention. 
       FIG. 8  is a cross-sectional view showing a state in which the ejection head  20  is capped by the capping unit  22 . 
       FIGS. 9A to 9C  show a relationship between a preliminary heating period and a heating period of the piezoelectric elements  150  and a suctioning time of a capping section  42 . 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   The capping unit as well as the control method for the capping unit, the liquid droplet ejection apparatus, and the device manufacturing method according to an embodiment of the present invention will now be described in detail with reference made to the drawings. 
   Liquid Droplet Ejection Apparatus 
     FIG. 1  is a perspective view showing the schematic structure of a liquid droplet ejection apparatus according to an embodiment of the present invention. Note that, in the description given below, where necessary an XYZ rectangular coordinate system is set in the drawings, and the positional relationship between each member is described with reference made to this XYZ rectangular coordinate system. In the XYZ rectangular coordinate system, the XY plane is set to a plane that is parallel with a horizontal plane, while the Z axis is set to a vertically upright direction. In addition, the direction of movement of the ejection head (i.e., the liquid droplet ejection head)  20  in the present embodiment is set to the X direction, and the direction of movement of a stage ST is set to the Y direction. 
   As shown in  FIG. 1 , a liquid droplet ejection apparatus IJ of the present embodiment is configured so as to include a base  10 , a stage ST that supports a substrate P such as a glass substrate on the base  10 , and an ejection head  20  that is supported above the stage ST (i.e., in a +Z direction), and that is able to eject predetermined liquid droplets onto the substrate P. Between the base  10  and the stage ST is provided a first moving member  12  that supports the stage ST such that it is able to move in the Y direction. A second moving member  14  that supports the ejection head  20  such that it is able to move in the X direction is provided above the stage ST. 
   A tank  16  that stores solvent of liquid droplets (i.e., liquid droplet solvent) that is ejected from the ejection head  20  via a flow path  18  is connected to the ejection head  20 . A capping unit (i.e., a capping unit)  22  and a cleaning unit  24  are also provided above the base  10 . 
   A control unit  26  controls each section of the liquid droplet ejection apparatus IJ (for example, the first moving member  12  and the second moving member  14  and the like), and controls the overall operation of the liquid droplet ejection apparatus IJ. 
   The first moving member  12  is provided on the base  10 , and is positioned in the Y axial direction. This first moving member  12  may be formed, for example, by a linear monitor, and is provided with guide rails  12   a  and with a slider  12   b  that is provided so as to be able to move along the guide rails  12   a . The slider  12   b  of this linear motor type of first moving member  12  is able to be positioned by moving in the Y axial direction along the guide rails  12   a.    
   The slider  12   b  is provided with a motor  12   c  for rotating around the Z axis (θ Z ). This motor  12   c  may, for example, be a direct drive motor, and a rotor of the motor  12   c  is fixed to the stage ST. As a result, by energizing the motor  12   c , the rotor and the stage ST rotate in the θ Z  direction, enabling the stage ST to be indexed (i.e., rotation indexed). Namely, the first moving member  12  is able to move stage ST in the Y axial direction and the θ Z  direction. The stage ST holds the substrate P, and positions it at a predetermined position. 
   The stage ST has a suction holding device (not shown), and when this suction holding device is operated, the substrate P is suctioned onto the stage ST via suction holes (not shown) that are provided in the stage ST and is held there. 
   The second moving member  14  is mounted standing upright relative to the base  10  using supporting columns  28   a , and is mounted on a rear portion  10   a  of the base  10 . The second moving member  14  is formed by a linear motor, and is supported on a column  28   b  that is fixed to the supporting columns  28   a . The second moving member  14  is provided with guide rails  14   a  that are supported on the column  28   b , and with a slider  14   b  that is supported so as to be able to move in the X axial direction along the guide rails  14   a . The slider  14   b  can be positioned by moving in the X axial direction along the guide rails  14   a . The aforementioned ejection head  20  is mounted on the slider  14   b.    
   The ejection head  20  has swinging positioning apparatuses in the form of motors  30 ,  32 ,  34 , and  36 . When the motor  30  is driven, the ejection head  20  can be moved up or down in the Z direction, enabling the ejection head  20  to be positioned at a desired position in the Z direction. When the motor  32  is driven, the ejection head  20  can be swung in the β direction around the Y axis, enabling the angle of the ejection head  20  to be adjusted. When the motor  34  is driven, the ejection head  20  can be swung in the γ direction around the X axis, enabling the angle of the ejection head  20  to be adjusted. When the motor  36  is driven, the ejection head  20  can be swung in the α direction around the Z axis, enabling the angle of the ejection head  20  to be adjusted. 
   In this manner, the ejection head  20  shown in  FIG. 1  is supported on the slider  14   b  so as to be able to move rectilinearly in the Z direction, and so as to be able to swing in the α direction, β direction, and γ direction, enabling the angle thereof to be adjusted. The position and attitude of the ejection head  20  are precisely controlled by a control unit  26  such that the position or attitude of a liquid droplet ejection surface  20   a  relative to the substrate P on the stage ST side is a predetermined position or a predetermined attitude. A plurality of nozzle apertures that eject liquid droplets are provided in the liquid droplet ejection surface  20   a  of the ejection head  20 . 
   As the liquid droplets that are ejected from the aforementioned ejection head  20 , it is possible to employ liquid droplets that contain a variety of materials such as ink containing a coloring agent, a dispersion solution containing a material such as fine metal particles, solutions containing a hole injection material such as PEDOT:PSS or organic electroluminescent (EL) material such as a light emitting material, a high viscosity functional liquid such as a liquid crystal material, a functional liquid containing material for a micro lens, and biological polymer solutions containing protein or nucleic acid or the like. 
   Here, the structure of the ejection head  20  will be described.  FIG. 2  is an exploded perspective view of the ejection head  20 .  FIG. 3  is a perspective view showing a portion of principal portions of the ejection head  20 . The ejection head  20  shown in  FIG. 2  is formed to include a nozzle plate  110 , a pressure chamber substrate  120 , a diaphragm  130 , and a housing  140 . As shown in  FIG. 2 , the pressure chamber substrate  120  is provided with a cavity  121 , a sidewall  122 , a reservoir  123 , and a supply port  124 . The cavity  121  is a pressure chamber and is formed by etching a substrate made of silicon or the like. The sidewall  122  is formed so as to divide the cavity  121 , and the reservoir  123  is formed as a common flow path that is able to supply liquid droplet solvent when each cavity  121  is being filled with the liquid droplet solvent. The supply port  124  is formed to allow liquid droplet solvent to be introduced into each cavity  121 . 
   As shown in  FIG. 3 , the diaphragm  130  is formed so as to be able to be adhered to one surface of the pressure chamber substrate  120 . A piezoelectric element  150 , which is a component of the aforementioned piezoelectric device, is provided in the diaphragm  130 . The piezoelectric element  150  is a ferroelectric crystal having a perovskite structure, and is formed in a predetermined configuration on the diaphragm  130 . The piezoelectric element  150  is configured so as to be able to generate a change in volume in response to a drive signal supplied from the control unit  26 . The nozzle plate  110  is adhered to the pressure chamber substrate  120  such that the nozzle apertures  111  thereof are placed at positions that correspond to each of the plurality of cavities (i.e., pressure chambers)  121  that are provided in the pressure chamber substrate  120 . The pressure chamber substrate  120  to which the nozzle plate  110  has been adhered is further embedded in the housing  140 , as shown in  FIG. 2 , so as to form the liquid droplet ejection head  20 . 
   In order to eject liquid droplets from the ejection head  20 , firstly, the control unit  26  supplies a drive signal for ejecting liquid droplets to the ejection head  20 . Liquid droplet solvent has been supplied to the cavities  121  of the ejection head  20 , and when a drive signal is supplied to the ejection head  20 , the piezoelectric elements  150  provided in the ejection head  20  generate a change in volume in response to that drive signal. This change in volume deforms the diaphragm  130 , and causes the volume of the cavity  121  to change. As a result, liquid droplets are ejected from the nozzle aperture  111  of that cavity  121 . The liquid droplets that had been decreased by the ejection are then refilled from the tank to the cavity  121  from which the liquid droplets were ejected. 
   By applying drive voltages in which the drive voltage and waveform (i.e., the maximum voltage and the frequency) that are applied when ejecting liquid droplets are different, the piezoelectric elements  150  that are provided in the ejection head  20  are able to heat the liquid droplet solvent inside the cavities  121  without ejecting any liquid droplets from the nozzle apertures  111 . Namely, the piezoelectric elements  150  can be used as a heating unit to heat the vicinity of the nozzle apertures  111 . Note that the ejection head described with reference to  FIG. 2  and  FIG. 3  is structured so as to eject liquid droplets by generating a volume change in a piezoelectric element, however, it may also have a head structure that ejects liquid droplets by using a heating element to apply heat to the liquid droplet solvent so that the liquid droplet solvent expands. It may also be an ejection head that ejects liquid droplets by generating a volume change by deforming the diaphragm using static electricity. 
   Returning to  FIG. 1 , as a result of the second moving member  14  moving the ejection head  20  in the X axial direction, the ejection head  20  can be selectively positioned above the cleaning unit  24  or the capping unit  22 . Namely, if, for example, the ejection head  20  is moved above the cleaning unit  24  during a device manufacturing process, the ejection head  20  can be cleaned. Moreover, if the ejection head  20  is moved above the capping unit  22 , then it is possible to perform capping on the liquid droplet ejection surface  20   a  of the ejection head  20 , or to fill the cavities  121  with liquid droplets, or to repair ejection malfunctions caused by blockages in the nozzle apertures  111 . 
   Namely, the cleaning unit  24  and the capping unit  22  are placed apart from the stage ST directly below the movement path of the ejection head  20  on the rear portion  10   a  side on top of the base  10 . Because the tasks of transporting the substrate P onto the stage ST and removing the substrate P from the stage ST are carried out on the front portion  10   b  side of the base  10 , these tasks are not obstructed by the cleaning unit  24  or the capping unit  22 . 
   The cleaning unit  24  is able to clean the nozzle apertures  111  and the like of the ejection head  20  either regularly or at any time during a device manufacturing process or during a standby period. The capping unit  22  may cap the liquid droplet ejection surface  20   a  during a standby period when no device is being manufactured such that the liquid droplet ejection surface  20   a  of the ejection head  20  does not dry out, or may be used when the cavities  121  are being filled with liquid droplets, or may repair the ejection head  20  when a ejection malfunction occurs. 
   Capping Unit 
   Next, the capping unit  22  will be described in detail.  FIGS. 4A and 4B  are views showing the structure of the capping unit  22 .  FIG. 4A  is a plan view of the capping unit  22  as seen from the ejection head  20  side, while  FIG. 4B  is a cross-sectional view taken along the arrow line A-A in  FIG. 4A . As shown in  FIGS. 4A and 4B , the capping unit  22  is configured so as to include a body  40 , a capping section  42  (i.e., a sealing section), a connecting tube  44 , and a pump (i.e., a negative pressure supply device)  46 . 
   The capping section  42  is provided with a wetting member  42   b  that is fitted in an internal portion of a concave portion  42   a  that is formed in the body  40 , and a protruding portion  42   c  that protrudes from a top surface  40   a  of the body  40 . The connecting tube  44  that penetrates a bottom surface  40   b  of the body  40  is connected to a bottom surface of a concave portion  42   a . Here, the wetting member  42   b  is formed by a material such as, for example, a sponge that has excellent properties of absorbing liquid droplets ejected from the ejection head  20  and that maintains this wet state when the liquid droplets are absorbed. The pump  46  suctions and depressurizes (i.e., supplies negative pressure to) the capping section  42  via the communicating tube  44 . The pump  46  is electrically connected to the control unit  26 , and the driving of the pump  46  is controlled by the control unit  26 . 
   Returning to  FIG. 1 , a liquid droplet ejection apparatus IJ of the present embodiment is provided with a ejection detection unit  38  that determines whether or not there is a nozzle aperture  111  that is not ejecting liquid droplets (i.e., whether there are missing dots) from among the plurality of nozzle apertures  111  provided in the liquid droplet ejection surface  20   a  of the ejection head  20 . The ejection detection unit  38  may be formed, for example, by a laser light source and a photodetector that detects laser light from the laser light source. The laser light source and the photodetector are placed so as to sandwich a trajectory of the liquid droplets that are ejected from each of the nozzle apertures  111  when the position of the ejection head  20  in the X direction is positioned at a predetermined position. The laser light source and photodetector detect whether or not there are missing dots based on whether or not there is a change in the amount of light that is detected by the photodetector when liquid droplets are ejected in sequence from each of the nozzle apertures  111 . 
   The ejection detection unit  38  may also be formed by a printing unit on which the liquid droplets from each of the nozzle apertures  111  are printed and that is formed such that a printing surface thereof can be cleaned by a wiper or the like, and by an image pickup element such as a charge coupled device (CCD) that is set so as to be optically coupled with the printing unit by an optical lens or the like. When the ejection detection unit  38  is formed using this structure, the printing surface is printed by ejecting liquid droplets from each of the nozzle apertures  111 . Image processing is then performed on image signals that are obtained by an image pickup of the printed surface by the image pickup element, which then enables a detection to be made as to whether or not there are any missing dots. 
   Next, a description will be given of the structure of the electrical functions of the liquid droplet ejection apparatus IJ of the present embodiment.  FIG. 5  is a block diagram showing the structure of the electrical functions of the liquid droplet ejection apparatus according to an embodiment of the present intention. Note that, in  FIG. 5 , the same reference symbols are allocated to blocks that correspond to members shown in  FIGS. 1 to 4B . As shown in  FIG. 5 , the electrical structure that controls the liquid droplet ejection apparatus IJ is configured so as to include a control computer  50 , the control unit  26 , and a drive integrated circuit  60 . 
   The control computer  50  may be formed so as to include, for example, a central processing unit (CPU), an internal storage such as random access memory (RAM) and read-only memory (ROM), a hard disk, an external storage such as a CD-ROM, and a display apparatus such as a liquid crystal display apparatus or a cathode ray tube (CRT). The control computer  50  outputs control signals that control operations of the liquid droplet ejection apparatus IJ in accordance with a program stored in ROM or on a hard disk. This control computer  50  is connected to the control unit  26  that is provided in the liquid droplet ejection apparatus IJ shown in  FIG. 1  using, for example, a cable or the like. 
   The control unit  26  is configured so as to include a calculation control unit  52 , a drive signal generation unit  54 , and a timer unit  56 . The calculation control unit  52  drives the first moving member  12 , the second moving member  14 , and the motors  30  to  36  and also controls the operation of the pump  46  that is provided in the capping unit  22  based on control signals that are input from the control computer  50  and on a control program that is stored internally in advance. 
   The calculation control unit  52  also outputs a variety of data (i.e., drive signal generation data) that is used to generate various drive signals that drive the plurality of piezoelectric elements  150  that are provided in the ejection head  20 . Based on the aforementioned control program, the calculation control unit  52  also generates selection data and outputs this to a switching signal generating unit  62  that is provided in the drive integrated circuit  60 . This selection data is made up of nozzle selection data that is used to specify the piezoelectric elements  150  to which the drive signals are to be applied, and waveform selection data that is used to specify the drive signals that are applied to the piezoelectric elements  150 . 
   In addition, the calculation control unit  52  uses the timer unit  56  to measure the length of time that the ejection head  20  has been capped (i.e., sealed) using the capping unit  22 , and also controls the length of time that the vicinity of the nozzle apertures  111  has been heated using the piezoelectric elements  150  and the length of time that the pump  46  has been driven. Based on detection results from the ejection detection unit  38 , the calculation control unit  52  also controls the capping or cleaning of the ejection head  20 . 
   The drive signal generation unit  54  generates a variety of drive signals having predetermined configurations, namely, normal drive signals or heating drive signals based on the aforementioned drive signal generation data, and outputs them to a switching circuit  64 . The timer unit  56 , for example, receives the input of a time measurement start signal and a measurement time that are output from the calculation control unit  52 , and outputs a time measurement completion signal when the measurement time has passed since the starting of the time measurement. 
   The drive signal integrated circuit  60  is provided inside the ejection head  20  and is configured so as to include the switching signal generating unit  62  and the switching circuit  64 . The switching signal generating unit  62  generates switching signals that command that a drive signal be supplied to or not supplied to the respective piezoelectric elements  150  based on selection data that is output from the calculation control unit  52 , and outputs these switching signals to the switching circuit  64 . A switching circuit  64  is provided in each piezoelectric element  150 , and outputs the drive signal that is instructed by the switching signal to the piezoelectric element  150 . 
   Here, a description will be given of an example of a drive signal generated by the drive signal generation unit  54 .  FIGS. 6A to 6B  are exemplary diagrams showing a waveform of one cycle of a normal drive signal and a drive signal for heating that are generated by a drive signal generating unit  54 .  FIG. 6A  shows the waveform of a normal drive signal ND, while  FIG. 6B  shows the waveform of a heating drive signal HD. As shown in  FIG. 6A , a repetition frequency “f” of the normal drive signal ND is set to 10 kHz, while, as shown in  FIG. 6B , a repetition frequency “f” of the heating drive signal HD is set to 100 kHz. Note that, here, a description is given using as an example a case in which the repetition frequency “f” of the heating drive signal HD is set to 100 kHz, however, a frequency in the ultrasonic region of 40 kHz or more is preferable for the repetition frequency “f” of the heating drive signal HD. 
   A repetition frequency “f” in the vicinity of 100 kHz enables the piezoelectric elements  150  to be driven (i.e., mechanically deformed) sufficiently while, at the same time, this frequency generates operating heat with excellent response by driving the piezoelectric elements  150  at high speed. The amplitude of the heating drive signal HD is set to a size whereby the liquid droplets are not ejected from the nozzle apertures  111 , for example, half (i.e., 50%) the amplitude VHN of the normal drive signals ND. Note that, here, a description is given using as an example of a case in which the amplitude of the heating drive signals HD is set to half the amplitude VHN of the normal drive signals ND. However, it is preferable that the amplitude of the heating drive signals HD is half or less the amplitude VHN of the normal drive signals ND. 
   Liquid Droplet Ejection Method and Capping Unit Control Method 
   Next, a method of forming a micro array on the substrate P using the liquid droplet ejection apparatus IJ having the above described structure will be described. In addition, a method for controlling a capping unit that is performed when the micro array is formed will be described.  FIG. 7  is a flowchart showing an example of a capping unit control method according to an embodiment of the present invention. 
   In the flowchart shown in  FIG. 7 , when the routine is started, a determination is made in the calculation control unit  52  as to whether or not a missing dot detection command is present (step S 11 ). A missing dot detection command is output from the control computer  50  when the power of the liquid droplet ejection apparatus IJ is turned on, or is output from a program of the calculation control unit  52  when a liquid droplet ejection is started or when the substrate P is replaced. This missing dot detection command is also be output from the control computer  50  when an operator of the control computer  50  issues a manual command to the control computer  50 . If there is no missing dot detection command (i.e., if the result of the determination is NO), the processing of step S 11  is repeated until a missing dot detection command is present. 
   If, however, in step S 11 , a missing dot detection command is present (i.e., if the result of the determination is YES), the calculation control unit  52  moves and positions the ejection head  20  so as to drive the second moving member  14  so that the nozzle apertures  111  are placed above (i.e., in the +Z direction) the ejection detection unit  38 . When the positioning of the ejection head  20  is completed, the calculation control unit  52  outputs drive signal generation data to the drive signal generation unit  54  so as to generate a normal drive signal ND, and outputs selection data to the switching signal generating unit  62 . 
   Based on the selection data sent from the calculation control unit  52 , a switching signal that commands that a drive signal either be supplied or not be supplied to the respective piezoelectric elements  150  is generated in the switching signal generating unit  62 , and a normal drive signal ND that is specified by the switching signal is then output to the piezoelectric element  150  by the switching circuit  64 . As a result, liquid droplets are ejected from the plurality of nozzle apertures of the ejection head  20  to the ejection detection unit  38 , and missing dot detection is performed by the ejection detection unit  38  (step S 12 ). 
   When the missing dot detection is completed, the result of the detection is output to the calculation control unit  52 , and whether or not any missing dots are present is determined by the calculation control unit  52  (step S 13 ). If it is determined that there are no missing dots (i.e., if the result of the determination is NO), then a normal ejection of liquid droplets is performed (step S 14 ). Namely, the calculation control unit  52  controls the first moving member  12  so that the object P is moved to a movement starting position, and controls the second moving member  14  and the like such that the ejection head  20  is moved to a ejection starting position. The drive signal generation data and the selection data are then output respectively to the drive signal generation unit  54  and the switching signal generating unit  62 , and normal drive signals ND are then supplied to the piezoelectric elements  150  so that an ejection of liquid droplets onto the substrate P is started. 
   Once the ejection of liquid droplets has started, the calculation control unit  52  ejects liquid droplets at a predetermined width from predetermined nozzles of the ejection head  20  onto the substrate P while relatively moving (i.e., scanning) the ejection head  20  and the substrate P in the X axial direction, so as to form a micro array on the substrate P. In the present embodiment, the ejection operation is performed while the ejection head  20  moves in the +X direction relative to the substrate P. When one relative movement (i.e. scan) of the ejection head  20  and the substrate P has ended, the stage ST that is supporting the substrate P performs a step movement of a predetermined distance in the Y axial direction relative to the ejection head  20 . The calculation control unit  52  then performs a ejection operation while relatively moving (i.e., scanning) for a second time the ejection head  20  relative to the substrate P in, for example, the −X direction. By repeating this operation of plurality of times, the ejection head  20  ejects liquid droplets onto the substrate P based on the control of the calculation control unit  52  so as to form a micro array. 
   When a micro array has been formed on the substrate P as a result of the above described operation being performed, the calculation control unit  52  controls the first moving member  12  so that the substrate P on which the liquid droplets have been ejected is moved to the unload position. The suction holding by the stage ST is then released, and the substrate P is unloaded from the stage ST by an unloading device (not shown). Next, while the substrate P is being unloaded from the stage ST, the calculation control unit  52  controls the second moving member  14  so that the ejection head  20  is moved in the X axial direction and is positioned above the capping unit  22 . The ejection head  20  is then further moved in the Z axial direction, and is placed in contact with the capping unit  22  so that capping of the ejection head  20  is performed (step S 15 ). Once the capping of the ejection head  20  has started, a counter Tc that shows the capping time is reset, and once again measurement of the capping time is started using the timer unit  56 . As a result of the above operation, an operation to eject liquid droplets onto one substrate P is completed. 
   If, however, in step S 13 , it is determined that missing dots are present (i.e., if the result of the determination is YES), the calculation control unit  52  determines whether or not dots are missing for 2% or more of the nozzle apertures out of all of the nozzle apertures  111  (step S 16 ). If less than 2% of the nozzle apertures have missing dots (i.e., if the result of the determination is NO), the calculation control unit  52  sets the value of a counter Tp that shows the time of the suctioning of the capping section  42  by the pump  46  (i.e., the time that negative pressure is supplied to the capping section  42 ) to “2” so that the suctioning time is set to two seconds (step S 17 ). 
   When the value of the counter Tp has been set, the calculation control unit  52  controls the second moving member  14  so as to move the ejection head  20  and position it above the capping unit  22 . The ejection head  20  is then further moved in the Z axial direction, and is placed in contact with the capping unit  22  so that capping of the ejection head  20  is performed.  FIG. 8  is a cross-sectional view showing a state in which the ejection head  20  is capped by the capping unit  22 . As shown in  FIG. 8 , the liquid droplet ejection surface  20   a  of the ejection head  20  is placed in front of the wetting member  42   b  of the capping section  42 . In addition, the liquid droplet ejection surface  20   a  of the ejection head  20  is engaged with the protruding portion  42   c  and capping is performed. 
   While capping of the ejection head  20  is being performed by the capping unit  22 , the calculation control unit  52  outputs a control signal to the pump  46  so that suctioning is performed by supplying negative pressure to the capping section  42  for the time that was set in the counter Tp (in this example, 2 seconds) (step S 18 ). In step S 17 , because the value of only the counter Tp that indicates the suctioning time of the capping section  42  is set, here, suctioning only is performed. Once the two seconds of suction have ended, the processing returns to step S 11 . 
   If however, in step S 16 , dots are missing from 2% or more of the nozzle apertures (i.e., if the result of the determination is YES), the calculation control unit  52  determines whether or not the value of the counter Tc that indicates the length of time of the most recent capping time is a value indicating  24  hours or more (step S 19 ). If the value of the counter Tc is less than a value indicating  24  hours (i.e., if the result of the determination is NO), the calculation control unit  52  sets the value of a counter Ty that indicates the preliminary heating time by the piezoelectric elements  150  to “20,” so that the preliminary heating time is set to 20 seconds. 
   Moreover, with the value of the counter Tp that indicates the suctioning time of the capping section  42  by the pump  46  and the value of a counter Tk that indicates the heating time by the piezoelectric elements  150  set to “2,” the suctioning time and heating time are set to 2 seconds (step S 20 ). Note that the preliminary heating is advance heating that is performed by the piezoelectric elements  150  prior to the suctioning of the capping section  42 . The heating is heating that is performed by the piezoelectric elements  150  together with the suctioning of the capping section  42 . 
   When the values of the counters Ty, Tp, and Tk have been set, the calculation control unit  52  controls the second moving member  14  so that the ejection head  20  is moved and is positioned above the capping unit  22 . The calculation control unit  52  then further moves the ejection head  20  in the Z axial direction so that it is placed in contact with the capping unit  22  and the ejection head  20  is capped. As a result, the ejection head  20  is capped in the same manner as shown in  FIG. 8 . 
   While the capping of the ejection head  20  by the capping unit  22  is performed, the calculation control unit  52  firstly outputs a heating drive signal HD to the ejection head  20 , and performs preliminary heating of the vicinity of the nozzle apertures  111  (i.e., of the liquid droplet solvent inside the cavities  121 ) for the length of time that is set in the counter Ty (in this example, 20 seconds). When the preliminary heating ends, a heating drive signal HD is output to the ejection head  20  for the length of time that is set in the counter Tk (in this example, 2 seconds), and the vicinity of the nozzle apertures  111  is heated. At the same time as this, negative pressure is supplied to the capping section  42  for the length of time that is set in the counter TP (in this example, 2 seconds), and suctioning is performed (step S 18 ). Once the above described operations have ended, the processing returns to step S 11 . 
   In the processing when step S 18  is performed via step S 16  and step S 17 , only two seconds of suctioning are conducted because the number of missing dots is small. However, in the processing when step S 18  is performed via step S 19  and step  20 , because the number of missing dots is large, preliminary heating is performed so that the viscosity of the liquid droplet solvent that has become thicker in the vicinity of the nozzle apertures  111  is lowered, or so that solidified liquid droplet solvent is melted, and after this the heating and suction are performed. 
   Here, a description will be given of the heating period by the piezoelectric elements  150  and of the suction period of the capping section  42 .  FIGS. 9A to 9C  are views showing the relationship between a preliminary heating period and a heating period of the piezoelectric elements  150  and a suctioning time of a capping section  42 . As shown in  FIG. 9A , there are provided a first period T 1  and a second period T 2 , and a heating drive signal HD whose repetition frequency “f” is 100 kHz is supplied to the piezoelectric elements  150  during these periods, so that the vicinity of the nozzle apertures  111  is heated. 
   In the first period T 1 , a heating drive signal HD is supplied to the piezoelectric elements  150 , however, the suctioning of the capping section  42  is not performed. In contrast to this, in the second period T 2 , a heating drive signal HD is supplied to the piezoelectric elements  150  and suctioning of the capping section  42  is also performed. As is described above, because the preliminary heating is advance heating that is performed by the piezoelectric elements  150  prior to the suctioning of the capping section  42 , the above first period T 1  is the preliminary heating period, and the second period T 2  is the heating period and suctioning period. Namely, in the present embodiment, the heating period and the suctioning period are set as the same period. 
   Returning to  FIG. 7 , if, in step  19 , the value of the counter Tc is a value indicating 24 hours or more (i.e., if the result of the determination is YES), the calculation control unit  52  determines whether or not the value of the counter Tc that shows the length of time of the most recent capping time is a value indicating 120 hours or more (step S 21 ). If the value of the counter Tc is less than a value indicating 120 hours (i.e., if the result of the determination is NO), the calculation control unit  52  sets the value of a counter Ty that shows the preliminary heating time by the piezoelectric elements  150  to “20,” so that the preliminary heating time is set to 20 seconds. Moreover, with the value of the counter Tp that indicates the suctioning time of the capping section  42  by the pump  46  and the value of a counter Tk that indicates the heating time by the piezoelectric elements  150  set to “5,” the suctioning time and heating time are set to 5 seconds (step S 22 ). 
   When the values of the counters Ty, Tp, and Tk have been set, the calculation control unit  52  controls the second moving member  14  so that the ejection head  20  is moved and is positioned above the capping unit  22 . The calculation control unit  52  also moves the ejection head  20  in the Z axial direction so that it is placed in contact with the capping unit  22  and the ejection head  20  is capped in the same manner As shown in  FIG. 8 . While the capping of the ejection head  20  is performed by the capping unit  22 , the calculation control unit  52  firstly outputs a heating drive signal HD to the ejection head  20 , and performs preliminary heating of the vicinity of the nozzle apertures  111  (i.e., of the liquid droplet solvent inside the cavities  121 ) for the length of time that is set in the counter Ty (in this example, 20 seconds). 
   When the preliminary heating has ended, a heating drive signal HD is output to the ejection head  20  for the length of time that is set in the counter Tk (in this example, 5 seconds), and the vicinity of the nozzle apertures  111  is heated. At the same time as this, negative pressure is supplied to the capping section  42  for the length of time that is set in the counter TP (in this example, 5 seconds), and suctioning is performed (step S 18 ). Once the above described operations have ended, the processing returns to step S 11 . 
   Comparing the processing when step S 18  is performed via step S 16  and step S 17  with processing when step S 18  is performed via step S 19  to step S 21  and S 22 , the times of the counter Tk that indicates the heating time and of the counter Tp that indicates the suctioning time are longer. If the time that the ejection head  20  has been capped by the capping unit  22  is one day (i.e., 24 hours) or more and less than five days (i.e., 120 hours), there is a possibility that the liquid droplet solvent will have thickened due to evaporation, therefore the heating time and suctioning time that are required to reliably clear up blockages of the nozzle apertures  111  and the like are lengthened. 
   If, however, in step S 21 , the value of the counter Tc is a value indicating 120 hours or more (i.e., if the result of the determination is YES), the calculation control unit  52  sets the value of the counter Ty that shows the preliminary heating time by the piezoelectric elements  150  to “20,” so that the preliminary heating time is set to 20 seconds. Moreover, with the value of the counter Tp that indicates the suctioning time of the capping section  42  by the pump  46  and the value of a counter Tk that indicates the heating time by the piezoelectric elements  150  set to “8,” the suctioning time and heating time are set to 8 seconds (step S 23 ). 
   When the values of the counters Ty, Tp, and Tk have been set, the calculation control unit  52  performs capping on the ejection head  20  in the same way As shown in  FIG. 8 . While the capping is performed, the calculation control unit  52  firstly outputs a heating drive signal HD to the ejection head  20 , and performs preliminary heating of the vicinity of the nozzle apertures  111  (i.e., of the liquid droplet solvent inside the cavities  121 ) for the length of time that is set in the counter Ty (in this example, 20 seconds). When the preliminary heating has ended, a heating drive signal HD is output to the ejection head  20  for the length of time that is set in the counter Tk (in this example, 8 seconds), and the vicinity of the nozzle apertures  111  is heated. At the same time as this, negative pressure is supplied to the capping section  42  for the length of time that is set in the counter TP (in this example, 8 seconds), and suctioning is performed (step S 18 ). Once the above described operations have ended, the processing returns to step S 11 . 
   In this manner, if the time that the ejection head  20  has been capped by the capping unit  22  is five days (i.e., 120 hours) or more, there is an extremely strong possibility that the liquid droplet solvent will have thickened, therefore the heating time and suctioning time are lengthened even more so that the ejection amount of liquid droplet is increased, thereby reliably clearing up blockages of the nozzle apertures  111  and the like. As has been described above, in the present embodiment, because the heating time and suctioning time are changed in accordance with the capping time of the ejection head  20 , unnecessary consumption of liquid droplet solvent can be considerably reduced in accordance with the extent of the solidification or the extent of the thickening of the liquid droplet solvent, and it is possible to reliably clear up blockages of the nozzle apertures in a short time span. 
   Note that, in the above described embodiment, because the vicinities of the nozzle apertures  111  are heated by applying a heating drive signal HD to the piezoelectric elements  150 , a structure in which a temperature sensor that detects the temperature in the vicinity of the nozzle apertures  111  of the piezoelectric elements  150  is provided inside the ejection head  20  is desirable. If the heating drive signals HD are supplied to the piezoelectric elements  150 , it is preferable that the piezoelectric elements are driven by performing feedback on the detection results from the temperature sensor. By performing driving such as this, it is possible to keep the heating temperature constant irrespective of the surrounding temperature, and it is possible to effectively lower the viscosity of liquid droplet solvent that has thickened or melt solidified liquid droplet solvent, resulting in it becoming possible to reliably clear blockages of the nozzle apertures in a short time span. 
   Moreover, in the above described embodiment, the piezoelectric elements  150  are used as a heating unit to heat the vicinity of the nozzle apertures  111 , however, it is also possible to provide a heater separately from the piezoelectric elements  150 . If a heater is used, then it is possible to heat not only the nozzle apertures  111 , but also the entire ejection head  20  and also the tank  16  and flow passages  18 . It also becomes possible to more effectively lower the viscosity of thickened liquid droplet solvent, or to more effectively melt solidified liquid droplet solvent. 
   Furthermore, in the flowchart shown in  FIG. 7 , either the suctioning by the pump  46  only is performed, or else the suctioning is performed while heating is applied after the preliminary heating. However, As shown in  FIG. 9B , it is also possible to perform the suctioning while applying heating without the preliminary heating having been performed, or, As shown in  FIG. 9C , it is possible to perform the suctioning without applying heating after having applied the preliminary heating. Provided that blockages in the nozzle apertures  111  and the like are reliably cleared, then it is desirable to perform the suctioning while applying heating after the preliminary heating has been applied, as in the above described embodiment. 
   Moreover, in the above described embodiment, the length of time for which the suctioning is performed together with the heating is changed in accordance with the length of time of the most recent capping time of the ejection head  20 , however, this assumes that the suctioning force of the pump  46  is constant. If it is possible to vary the suctioning force of the pump  46 , then it is also possible to vary the quantity ejected from the nozzle apertures  111  by changing the suctioning force (i.e., by changing the size of the negative pressure). Note that when changing the suctioning force, the suctioning time may be either constant or may be changed together with the suctioning force. 
   Device Manufacturing Methods and Electronic Instrument 
   A description has been given above of a capping unit according to an embodiment of the present invention, as well as to a control method for this capping unit and a liquid droplet ejection apparatus. This liquid droplet ejection apparatus can be used as a film forming apparatus that forms a film, a wiring apparatus that forms wiring such as metal wiring, or as a device manufacturing apparatus to manufacture devices such as a micro lens array, a liquid crystal display apparatus, an organic EL device, a plasma display device, and a field emission display (FED). 
   Using the above described liquid droplet ejection apparatus, after the viscosity of liquid droplet solvent that has thickened has been lowered or after solidified liquid droplet solvent has been melted, it is ejected. Using an ejection head  20  that has finished undergoing this processing, a pattern is formed on a substrate P by ejecting liquid droplets. As a result, it is possible to restrain unnecessary consumption of liquid droplet solvent, and also lengthen the liquid droplet ejection time for forming patterns. Consequently, it is possible to reduce device manufacturing costs and improve throughput. 
   Devices such as the above described liquid crystal device, organic EL device, plasma display device, and FED are provided in electronic apparatuses such as notebook computers and mobile telephones. However, the electronic apparatuses are not limited to these notebook computers and mobile telephones, and the present invention may be applied to a variety of electronic apparatuses. For example, the present invention can be applied to electronic apparatuses such as liquid crystal projectors, personal computers (PC) and engineering workstations (EWS) for multimedia applications, pagers, word processors, televisions, viewfinder type or direct monitor view type video recorders, electronic organizers, electronic desk calculators, car navigation devices, POS terminals, and apparatuses that are provided with touch panels. 
   While preferred embodiments of the invention have been described and illustrated above, it should be understood that these are exemplary of the invention and are not to be considered as limiting. Additions, omissions, substitutions, and other modifications can be made without departing from the spirit or scope of the present invention. Accordingly, the invention is not to be considered as limited by the foregoing description and is only limited by the scope of the appended claims.