Abstract:
To provide a liquid discharger and a method to discharge liquid in which lowering of the precision of the assembly and the discharge accuracy of the high-viscosity liquid caused by thermal deformation, such as thermal expansion, is suppressed when the discharge heads of the inkjet apparatus are heated to accurately discharge the high-viscosity liquid, a liquid discharger having discharge heads to pressurize functional liquid contained in cavities communicating with nozzles and discharge the functional liquid from the nozzles, a mounting plate having openings to mount the discharge heads, a tank to contain the functional liquid discharged from discharge heads, and a liquid supply channel to supply the functional liquid from the tank to the discharge heads, the discharge heads mounted to the openings of the mounting plate at a same temperature as the temperature the functional liquid is discharged from the discharge heads.

Description:
[0001]     This is a Continuation of application Ser. No. 10/827,427 filed Apr. 20, 2004, which claims the benefit of Japanese Application No. 2003-121677 filed Apr. 25, 2003. The disclosure of the prior application is hereby incorporated by reference herein in its entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a liquid discharger and a method to discharge droplets.  
         [0004]     2. Description of Related Art  
         [0005]     Inkjet printing (a method to discharge droplets) is known as a method to pattern electrical leads. Inkjet printing is a printing technology well-known through inkjet printers. In inkjet printing, ink contained in a discharge head of the inkjet apparatus (liquid discharger) is discharged as droplets from discharge heads and is applied onto a surface of a substrate. By employing inkjet printing, ink droplets can be accurately discharged onto a minute area. Thus, the ink can be applied onto desired areas without employing photolithography. Inkjet printing is an extremely practical method since ink is not wasted and production costs are lowered.  
         [0006]     An inkjet apparatus having a multi-head structure including a plurality of discharge heads serially aligned and capable of accurate inkjet drawing is already known in the related art (see Japanese Unexamined Patent Application Publication No. 2002-273869). For such a multi-head structure, accurate alignment of the discharge heads is required. A technology to assemble the discharge heads with high precision is already known (see Japanese Unexamined Patent Application Publication No. 2001-162892).  
         [0007]     Recently, inkjet apparatus to discharge high-viscosity liquid (functional liquid), such as a lubricant or a resin are known in the related art. Such an inkjet apparatus has a device to heat the parts where the functional liquid flows, e.g. the discharge heads, to lower the viscosity of the functional liquid by heat (see Japanese Unexamined Patent Application Publication No. 2003-019790).  
       SUMMARY OF THE INVENTION  
       [0008]     Although an inkjet apparatus has a precisely assembled multi-head structure as described in Japanese Unexamined Patent Application Publication No. 2001-162892, when the parts, such as the discharge heads, where high-viscosity liquid flows through, are heated, as described in Japanese Unexamined Patent Application Publication No. 2003-019790, the discharge heads and/or the portions supporting the discharge heads undergo thermal deformation, such as thermal expansion. As a result, the distance between the discharge heads changes, making it difficult to maintain the highly precise assembly. When high-viscosity liquid is discharged from discharge heads in such a condition, errors occur in the landing positions of the high-viscosity droplets. Accordingly, the high-viscosity droplets cannot be accurately discharged onto a minute area.  
         [0009]     A liquid discharger for an inkjet apparatus having a multi-head structure to discharge high-viscosity functional liquid, such as a lubricant or a resin according to an aspect of the present invention has taken into consideration such problems. The present invention provides a liquid discharger and a method to discharge liquid in which lowering of the precision of the assembly and the discharge accuracy of the high-viscosity liquid caused by thermal deformation, such as thermal expansion, is suppressed when the discharge heads of the inkjet apparatus are heated to accurately discharge the high-viscosity liquid.  
         [0010]     To achieve the above-mentioned, an aspect of the present invention adopts the following.  
         [0011]     Specifically, a liquid discharger according to an aspect of the present invention includes a plurality of discharge heads to pressurize functional liquid and discharge the functional liquid contained in cavities communicating with the nozzles from nozzles, a mounting plate having openings to mount the plurality of discharge heads, a tank containing the functional liquid to be discharged from the plurality of discharge heads, and a liquid supply channel to supply the functional liquid from the tank to the plurality of discharge heads. The plurality of discharge heads are mounted to the openings at the same temperature as that when the functional liquid is discharged from the plurality of discharge heads.  
         [0012]     Here, the term “functional liquid” refers to high-viscosity liquid, such as a lubricant, resin, or liquid crystal.  
         [0013]     The term “a plurality of discharge heads” implies the so-called multi-head structure. In an aspect of the present invention, a plurality of discharge heads are mounted to the openings of the mounting plate at an equal pitch, forming the multi-head structure.  
         [0014]     The term “discharge heads discharging functional liquid” refers to the plurality of discharge heads having a heating device to fluidize the high-viscosity functional liquid. By heating the functional liquid with the heating device, the viscosity of the functional liquid is lowered. Hence, the liquid is discharged from the nozzles without causing clogging of the discharge heads.  
         [0015]     According to an aspect of the present invention, the plurality of discharge heads are mounted to the openings on the mounting plate at the same temperature as that when the functional liquid is discharged. The discharge heads are heated when they are mounted. Therefore, expansion and/or contraction of the discharge heads and/or the mounting plate caused by a temperature difference do not occur. Thus, the discharge heads and the openings are fixed in highly accurate positions relative to each other. As a result, discharge of the functional liquid while maintaining this accuracy is possible. Furthermore, since no errors occur in the landing positions of the discharged high-viscosity droplets, the high-viscosity droplets can be accurately discharged onto minute areas.  
         [0016]     The liquid discharger described above according to an aspect of the present invention includes the mounting plate having a heating device to heat the mounting plate.  
         [0017]     The heating device may be an electric heater formed of nichrome wires or a chiller including pipes with liquid, such as hot water flowing through. The heating device may be mounted on the interior or exterior of the mounting plate.  
         [0018]     According to an aspect of the present invention, the heating device mounted on the mounting plate heats the mounting plate and the discharge heads. In this way, the same effects as the above-mentioned liquid discharger are achieved. Furthermore, the mounting plate and the discharge heads are maintained at the same temperature.  
         [0019]     In addition to the above-mentioned heating device, a temperature monitoring device to monitor the temperature of the mounting plate and controlling device to control the heating device based on the results of the monitoring by the temperature monitoring device are disposed. In this way, the temperature of the mounting plate and the discharge heads can be maintained at a predetermined temperature.  
         [0020]     The above-mentioned liquid discharger according to an aspect of the present invention may include a detecting device to detect the positions of the nozzles of the discharge heads, a measuring device to measure the distance between at least two of the nozzles, a driving device to move one of the discharge heads and the mounting plate relative to each other based on the results measured by the measuring device, and an engaging device to engage the discharge heads to the openings on the mounting plate.  
         [0021]     Here, the detecting device is an imaging device, such as a CCD.  
         [0022]     The measuring device is a computer to calculate the distance between at least two nozzles by performing image processing on the image data captured by the imaging device to compute the distance between the nozzles.  
         [0023]     The driving device linearly moves one of the discharge heads by using a linear motor and/or rotationally moves one of the discharge heads by using a stepper motor or a combination of both. For example, a combination of the driving device for planar movement (in the X and Y directions) and driving device for movement in the direction perpendicular to the X-Y plane (in the Z direction) may be used.  
         [0024]     The engaging device engages the discharge heads to the openings in, for example, a direction perpendicular to the mounting plate. Each discharge head is engaged to each opening by moving the mounting plate or the discharge head.  
         [0025]     According to an aspect of the present invention, the positions of nozzles of the discharge heads are detected to measure the distance between the nozzles. Then, each discharge head is aligned and engaged with a predetermined opening of the mounting plate. In this way, the same effects as the liquid discharger described above are achieved while each discharge head is disposed with a highly accurate nozzle pitch.  
         [0026]     The above-mentioned liquid discharger according to an aspect of the present invention may include a controlling device to control the detecting device, measuring device, driving device and engaging device and to maintain an equal nozzle pitch for the discharge heads.  
         [0027]     The controlling device may be, for example, a computer.  
         [0028]     According to an aspect of the present invention, the same effects as the liquid discharger described above are achieved while mounting the discharge heads automatically and accurately to the openings of the mounting plate.  
         [0029]     In the above-mentioned liquid discharger according to an aspect of the present invention, the plurality of discharge heads are fixed to the openings of the mounting plate with an adhesive.  
         [0030]     The adhesive may be highly heat-resistant and does not expand or contract due to changes in temperature.  
         [0031]     According to an aspect of the present invention, the same effects as the liquid discharger described above are achieved while the plurality of discharge heads is fixed to the respective openings of the mounting plate. By using the adhesive, in comparison to the using fasteners, such as screws, the discharge heads and the mounting plate can be fixed together without causing deformation of the junctions between the discharge heads and the mounting plate due to torque.  
         [0032]     In a method to discharge droplets according to an aspect of the present invention, the functional liquid is supplied to the plurality of discharge heads mounted to the openings of the mounting plate, the functional liquid inside the cavities of the discharge heads is pressurized, and the functional liquid is discharged from the nozzles communicating with the cavities. Here, the plurality of discharge heads are mounted to the openings of the mounting plate at the same temperature as that when the functional liquid is discharged.  
         [0033]     According to an aspect of the present invention, the plurality of discharge heads are mounted to the openings of the mounting plate at the same temperature as that when the functional liquid is discharged. Specifically, the discharge heads are heated. Therefore, expansion and/or contraction of the discharge heads and/or the mounting plate caused by a temperature difference do not occur. Thus, the discharge heads and the openings are fixed in highly accurate positions relative to each other. As a result, the functional liquid can be discharged while maintaining this accuracy. Furthermore, since no errors occur in the landing positions of the discharged high-viscosity droplets, the high-viscosity droplet can be accurately discharged onto minute areas.  
         [0034]     In the above-mentioned method to discharge droplets according to an aspect of the present invention, the plurality of discharge heads are mounted to the respective openings of the mounting plate while the mounting plate is heated.  
         [0035]     According to an aspect of the present invention, the same effects as the method to discharge droplets described above are achieved while the mounting plate and the discharge heads are maintained at the same temperature.  
         [0036]     In addition to the above-mentioned heating of the mounting plate, by further including monitoring the temperature of the mounting plate and controlling the temperature of the heating device based on the monitoring results by the temperature monitoring device, the mounting plate and the discharge heads can be maintained at a predetermined temperature.  
         [0037]     A method to discharge droplets according to an aspect of the present invention includes detecting one of the nozzles of each discharge head, measuring the distance between the nozzles, moving one of the discharge heads relative to the mounting plate, and engaging one of the discharge heads to one of the openings of the mounting plate, the plurality of discharge heads disposed at an equal nozzle pitch.  
         [0038]     According to an aspect of the present invention, the position of one of the nozzles of each discharge head is detected, the distance between the nozzles is measured, each discharge head is aligned with the respective opening, and each discharge head is engaged with the opening of the mounting plate. In this way, the same effects as the method to discharge droplets described above are achieved while the discharge heads are disposed with an accurate nozzle pitch.  
         [0039]     A method to discharge droplets according to an aspect of the present invention includes automatically detecting the nozzles, measuring the distance between the nozzles, moving the discharge heads and the mounting plate relative to each other, and engaging the discharge heads to the openings.  
         [0040]     According to an aspect of the present invention, the same effects as the liquid discharger described above are achieved while mounting the discharge heads automatically and accurately to the openings of the mounting plate.  
         [0041]     In the above-mentioned method to discharge droplets according to an aspect of the present invention, the adhesive is applied to fix the discharge heads to the openings of the mounting plate.  
         [0042]     According to an aspect of the present invention, the same effects as the method to discharge droplets described above are achieved while the discharge heads are fixed to the openings of the mounting plate. By using the adhesive, in comparison to the using fasteners, such as screws, the discharge heads and the mounting plate can be fixed together without causing deformation of the junctions between the discharge heads and the mounting plate due to torque. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0043]      FIG. 1  is a schematic of an exemplary embodiment of a liquid discharger according to the present invention;  
         [0044]      FIG. 2  is a schematic and a cross-sectional schematic of a head unit  21 ;  
         [0045]      FIG. 3  is a schematic of an alignment device included in the liquid discharger;  
         [0046]      FIG. 4  is a schematic of the liquid discharge principle of a piezoelectric discharge method;  
         [0047]      FIG. 5  is a schematic of the main parts of a discharge head group;  
         [0048]      FIG. 6  is a cross-sectional schematic of a liquid crystal display produces by a liquid discharger;  
         [0049]      FIG. 7  is a schematic of a liquid crystal display produces by a liquid discharger;  
         [0050]      FIG. 8  is a schematic of the production process of the liquid discharger; and  
         [0051]      FIG. 9  illustrates electronic apparatus including a liquid crystal display. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0052]     Exemplary embodiments of the present invention will be described below by referring to the drawings.  
         [0053]     In  FIG. 1 , a liquid discharger  10  includes a base  112 , a substrate stage  22  on the base  112  to support a substrate  20 , a first shifter  114  disposed on the base  112  and movably supporting the substrate stage  22 , a head unit  21  capable of discharging a processing liquid to the substrate  20  supported by the substrate stage  22 , a second shifter  116  movably supporting the head unit  21 , a tank  26  containing functional liquid, such as a liquid crystal material, a liquid supply channel  27  to supply the functional liquid to the head unit  21 , a controller  23  to control the discharging of liquid by the head unit  21 , and an alignment device  100 . The liquid discharger  10  further has an electronic scale (not shown in the drawings) functioning as a weighing device disposed on the base  112 , a capping unit  25 , and a cleaning unit  24 . The movement of the liquid discharger  10  including the movement of the first shifter  114  and the second shifter  116  is controlled by the controller  23 .  
         [0054]     The first shifter  114  is disposed on the base  112  along the Y direction. The second shifter  116  is attached perpendicularly to the surface of the base  112  with braces  16 A and  16 A on the rear portion  12 A of the base  112 . The second shifter  116  moves in the X direction (a second direction) from the right to the left of the base  112 . The X direction is orthogonal to the Y direction. The first shifter  114  moves in the Y direction from the front portion  12 B to the rear portion  12 A of the base  11 . Both the X and Y directions are parallel to the base  112 . The Z direction is the direction perpendicular to the X and Y directions.  
         [0055]     The first shifter  114 , for example, includes a linear motor, guide rails  140  and  140 , and a slider  142  mounted on the guide rails  140  and  140  so that the slider  142  can move along the guide rails  140  and  140 . The slider  142  of the linear motor-driven first shifter  114  moves along the guide rails  140  and  140  in the Y direction and can be held in a predetermined position.  
         [0056]     The slider  142  has a motor  144  that rotates on the Z axis (θZ). The motor  144  is, for example, a direct drive motor, and the rotor of the motor  144  is fixed to the substrate stage  22 . In this way, by supplying electricity to the motor  114 , the rotor and the substrate stage  22  can rotate on the Z axis to index the substrate stage  22 . For example, the first shifter  114  can move the substrate stage  22  in the Y direction (first direction) and the OZ direction.  
         [0057]     The substrate stage  22  supports the substrate  20  and holds it in a predetermined position. The substrate stage  22  has a suction device not shown in the drawing. By activating the suction device, the substrate  20  is sucked towards the substrate stage  22  through a hole  46 A of the substrate stage  22 .  
         [0058]     The second shifter  116  has a linear motor, a column  16 B fixed to the braces  16 A and  16 A, guide rails  62 A and  62 A supported by the column  16 B, and a slider  160  supported by the guide rails  62 A and  62 A so that it can move in the X direction. The slider  160  moves along the guide rails  62 A and  62 A in the X direction and can be held at a predetermined position. The head unit  21  is attached to the slider  160 .  
         [0059]     The head unit  21  has motors  62 ,  64 ,  67 , and  68  as oscillating positioning devices. By activating the motor  62 , the head unit  21  moves vertically along the Z axis and can be held at a predetermined position. The Z axis is orthogonal to the X and Y axes. By activating the motor  64 , the head unit  21  oscillates in the β direction around the Y axis and can be held at a predetermined position. By activating the motor  67 , the head unit  21  oscillates in the γ direction around the X axis and can be held at a predetermined position.  
         [0060]     By activating the motor  68 , the head unit  21  oscillates in the α direction around the Z axis and can be held at a predetermined position. For example, the second shifter  116  supports the head unit  21  so that it can move in the X (first) and Z directions and the θX, θY, and θZ directions.  
         [0061]     As described above, the head unit  21  illustrated in  FIG. 1  can be held at a predetermined position by moving linearly along the Z axis on the slider  160  and oscillating in the α, β, and γ directions. The position and/or orientation of a liquid discharge surface  11 P of the head unit  21  can be accurately controlled with respect to the surface of the substrate  20  on the substrate stage  22 .  
         [0062]      FIG. 2   a  is a schematic of the head unit  21  viewed from the substrate  20  illustrated in  FIG. 1 . For example,  FIG. 2   a  illustrates the bottom surface of a discharge head group  50  including a plurality of discharge heads  34 .  FIG. 2   b  is a cross-sectional schematic of  FIG. 2   a  taken along an arbitrary plane in  FIG. 2   a,  illustrating the cross-sectional schematics of a mounting plate  51  and one of the discharge heads  34 .  
         [0063]     As shown in  FIG. 2   a,  the head unit  21  according to this exemplary embodiment includes the rectangular mounting plate  51  and the discharge head group  50  of two rows of six discharge heads  34 , i.e., a total of 12 discharge heads  34 , fixed to the mounting plate  51 . The discharge heads  34  are positioned at a predetermined angle so that the apparent pitch between nozzles is decreased. In this way, the distance between the discharged droplets becomes small, enhancing the discharge accuracy. Since the discharge head group  50  has a large area suitable to discharge onto a large-size substrate, in principle, the discharge head group  50  does not move in the X direction in  FIG. 1 , and only the substrate  20  moves in the Y direction in  FIG. 1 . However, if the substrate is larger than the width of the discharge head group  50 , the discharge head group  50  also moves in the X direction for line feed.  
         [0064]     As shown in  FIG. 2   b,  one of the discharge heads  34  is partly engaged with a respective opening  51  a of the mounting plate  51 . The discharge heads  34  are fixed to the mounting plate  51  with an adhesive  52 . A head heater  34   a  covers the discharge head  34  to heat the discharge head  34  when a high-viscosity liquid is discharged. By heating the high-viscosity liquid, the viscosity is lowered and the liquid is fluidized. The mounting plate  51  has a heater (heating device)  53 . The heater  53  receives electricity from a heater power supply  54  and heats the mounting plate  51 . Furthermore, the mounting plate  51  has a temperature sensor (temperature monitoring device)  55  to measure the temperature of the mounting plate  51 . The temperature sensor  55  is connected to the controller (controlling device)  23 . Specifically, the controller  23  controls the power supplied from the heater power supply  54  to the heater  53  in accordance with the results detected by the temperature sensor  55 .  
         [0065]      FIG. 3  is a schematic of the alignment device  100 , which is apart of the liquid discharger illustrated in  FIG. 1 . The alignment device  100  engages one of the discharge heads  34  to one of the openings  5  la of the mounting plate  51  and adjusts the position of the discharge head  34 .  
         [0066]     The alignment device  100  has an imaging device (detecting device)  56 , a measuring device (measuring device)  57 , a driving device (driving means)  58 , and an engagement mechanism (engaging device)  59 .  
         [0067]     The imaging device  56  includes a sensor, such as a DDC or a CMOS, and captures images of the opening  51   a  from above the mounting plate  51 .  
         [0068]     The measuring device  57  processes the image data captured by the imaging device  56  to compute the distance between the nozzles on the discharge head.  
         [0069]     The driving device  58  positions the engagement mechanism  59  by relatively moving the engagement mechanism  59  and the mounting plate  51 . The driving device  58  includes an X axis drive  58 X to move the discharge head  34  linearly in the X direction, a Y axis drive  58 Y to move the discharge head  34  linearly in the Y direction, and a θZ drive  58 θZ to rotate the discharge head  34  around the Z axis.  
         [0070]     The engagement mechanism  59  is retractable in the Z direction, and the discharge head  34  on the engagement mechanism  59  is engaged with one of the openings  51   a  on the mounting plate  51 .  
         [0071]     The measuring device  57 , the driving device  58 , and the engagement mechanism  59  are controlled by the controller  23 . The discharge head  34  is engaged with one of the opening  51   a  in a predetermined position based on the image data captured by the imaging device  56 .  
         [0072]     Furthermore, the alignment device  100  has an adhesive applying mechanism  52   a  to apply the adhesive  52  to the area near the border of the opening  51  a and the discharge head  34 . The adhesive applying mechanism  52   a  applies the adhesive  52  through an adhesive applying nozzle  52   b  to a predetermined area.  
         [0073]     Referring back to  FIG. 1 , the head unit  21  (discharge head group  50 ) discharges liquid, such as liquid crystal (functional liquid) from nozzles by employing a so-called liquid discharge method. As the liquid discharge method, suitable methods may be employed, such as a piezoelectric method in which ink is discharged by piezoelectric elements or a method in which a liquid is discharged by generating a bubble by heating the liquid. The piezoelectric method is advantageous in that the liquid is not heated and the composition of the liquid is not affected. In this exemplary embodiment, the piezoelectric method is used.  
         [0074]      FIG. 4  illustrates the liquid discharge principle of the piezoelectric method. In  FIG. 4 , a liquid chamber (cavity)  31  containing liquid is disposed adjacent to a piezoelectric element  32 . The liquid chamber  31  receives liquid through a liquid supplying system  35  including a tank containing the liquid. The piezoelectric element  32  is connected to a driving circuit  33 . A voltage is applied to the piezoelectric element  32  via the driving circuit  33 . The deformation of the piezoelectric element  32  causes the liquid chamber  31  to deform. As a result, liquid is discharged from a nozzle  30 . By changing the value of the voltage applied, the deformation of the piezoelectric element  32  is controlled, and by changing the frequency of the voltage applied, the deformation rate of the piezoelectric element  32  is controlled. Specifically, in the head unit  21 , the liquid discharged from the nozzle  30  is controlled by controlling the voltage applied to the piezoelectric element  32 .  
         [0075]     In this exemplary embodiment, the head heater  34   a  to lower the viscosity of the high-viscosity liquid, such as liquid crystal is disposed on the periphery of the discharge head  34 .  
         [0076]     Referring back to  FIG. 1 , the electronic scale (not shown in the drawing) receives, for example, 5,000 droplets from one of the nozzles of the head unit  21  to measure and control the weight of one droplet discharged from the nozzle. The electronic scale divides the total weight of the 5,000 droplets by 5,000 to accurately define the weight of a droplet. Based on the weight of a droplet, the volume of the droplet discharged from the head unit  21  can be optimally controlled.  
         [0077]     The cleaning unit  24  cleans the nozzles of the head unit  21  regularly or on demand during the operation or stand-by of the liquid discharger. The capping unit  25  caps the liquid discharge surface  11 P of the head unit  21  when not in operation or during stand-by so that the liquid discharge surface  11 P does not dry out.  
         [0078]     The second shifter  116  moves the head unit  21  in the X direction to position the head unit  21  selectively above the electronic scale, the cleaning unit  24 , or the capping unit  25 . For example, even if the liquid discharger is in operation, the droplets may be weighed by moving the head unit  21  to the electronic scale. By moving the head unit  21  to the cleaning unit  24 , the head unit  21  can be cleaned. By moving the head unit  21  to the capping unit  25 , the liquid discharge surface  11 P of the head unit  21  is capped. This helps to prevent drying out.  
         [0079]     The electronic scale, cleaning unit  24 , and the capping unit  25  are positioned on the rear edge of the base  112  directly under the moving path of the head unit  21  apart from the substrate stage  22 . Since the substrate  20  is supplied to or removed from the substrate stage  22  at the front edge of the base  112 , the supplying or removal of the substrate  20  is not interfered by the electronic scale, the cleaning unit  24 , or the capping unit  25 .  
         [0080]     As shown in  FIG. 1 , on the substrate stage  22 , except for the part that supports the substrate  20 , a preliminary discharge area  152  for the head unit  21  to perform trial discharge and preliminary discharge is disposed apart from the cleaning unit  24 . The preliminary discharge area  152 , as shown in  FIG. 1 , is disposed in the X direction along the rear edge of the substrate stage  22 . The preliminary discharge area  152  is fixed to the substrate stage  22 . The preliminary discharge area  152  has a U-shaped cross-sectional view with an opening on the upper part and has a replaceable absorber to absorb the discharged liquid set inside the recess of the receiver.  
         [0081]     The tank  26  and the liquid supply channel  27  have a heating device. The heating device preheats and then retains the heat of the functional liquid, such as liquid crystal, to be discharged from the discharge head  34 . In this way, the functional liquid, such as liquid crystal, flows to the discharge head  34  with its viscosity lowered to a preferable degree.  
         [0082]     The substrate  20  may be composed of various materials, such as glass, silicon, quartz, ceramic, metal, plastic, or plastic film. The substrate composed of one of these materials may have a base layer composed of a material, such as a semiconductor film, a metal film, a dielectric film, or an organic film disposed on its surface. The plastic used to compose the substrate may be, for example, polyolefin, polyester, polyacrylate, polycarbonate, polyether sulphone, or polyetherketone.  
         [0083]     The liquid is liquid crystal and, may be, nematic liquid crystal.  
         [0084]     In this exemplary embodiment, a case in which the liquid discharger  10  is used to discharge liquid crystal is described. It, however, is possible to employ the present invention when high-viscosity liquid, such as a lubricant or a resin, is used as the liquid.  
         [0085]     Next, a method to discharge droplets according to an aspect of the present invention is described.  
         [0086]     In this exemplary embodiment, before discharging droplets to the substrate  20 , engaging and fixing the discharge heads  34  to the openings  51  a of the mounting plate  51  is performed to form a head unit having a multi-head structure.  
         [0087]     First, the mounting plate  51  is heated to a predetermined temperature.  
         [0088]     The predetermined temperature is preset by the controller  23 , which is equal to the temperature of the discharge head  34  when it discharges droplets in a later step.  
         [0089]     As shown in  FIG. 2   b,  the temperature of the mounting plate  51  is controlled by the controller  23  so that the temperature of the mounting plate  51  complies with the preset temperature. When the temperature detected by the temperature sensor  55  is lower than the preset temperature, the heater power supply  54  is turned on. Electricity is supplied to the heater  53  and the heater generates heat, causing the temperature of the mounting plate  51  to increase. When the temperature detected by the temperature sensor  55  is higher than the preset temperature, the heater power supply  54  is turned off, causing the temperature of the mounting plate  51  to decrease. In this way, the temperature of the mounting plate  51  is controlled so as to be equal to the preset temperature.  
         [0090]     In this exemplary embodiment, the controller  23  controls the heater power supply  54  by turning it on and off. The method to control the heater power supply  54  is not limited to this. The temperature of the mounting plate  51  may be controlled by regulating the electrical current of the heater power supply  54 .  
         [0091]     Subsequently, while the temperature of the mounting plate  51  being set, a first discharge head  34  is engaged to one of the openings  51  a.  
         [0092]     Specifically, the discharge head  34  is set on the engagement mechanism  59  of the alignment device  100 , as shown in  FIG. 3 . Moreover, the imaging device  56  captures an image of the discharge head  34 . Then, according to the captured image data, the driving device  58  moves the discharge head  34  disposed on the engagement mechanism  59  and the mounting plate  51  relative to each other to align the engagement mechanism  59  to the lower portion of the opening  51   a.  The engagement mechanism  59  extends in the Z direction to engage the discharge head  34  disposed on the engagement mechanism  59  with the opening  51   a.  Then, the adhesive applying mechanism  52   a  applies the adhesive  52  through the adhesive applying nozzle  52   b  to fix the first discharge head  34  inside the opening  51   a.    
         [0093]     Subsequently, while the temperature of the mounting plate  51  being set, a second and then a third discharge head  34  are engaged with the respective openings  51  a. Then, the adhesive  52  is applied.  
         [0094]     By using the alignment device  100  as described above, the second and third discharge heads  34  are each engaged with one of the openings  51   a.  Accordingly, the distance between the discharge heads of the discharge head group  50  including the first, second, and third discharge heads  34  is maintained highly accurately.  
         [0095]     A method to fix the discharge head  34  is described in detail below by referring to  FIG. 5 .  
         [0096]      FIG. 5  is a plan view of a first discharge head  34   f,  a second discharge head  34   g,  and a third discharge head  34   h  representing the discharge heads  34  of the discharge head group  50 .  
         [0097]     Each discharge head  34   f,    34   g,  and  34   h  has a nozzle group N which includes a reference nozzle N 1  to position the nozzle group N on the mounting plate  51 . When the second and third discharge heads  34   g  and  34   h  are fixed to the mounting plate  51 , the image of each reference nozzle N 1  is captured by the imaging device  56 . Then, the second and third discharge heads  34   g  and  34   h  are fixed to the opening  51   a  so that the distance t, which is measured by the measuring device  57 , between each reference nozzle N 1  is equal.  
         [0098]     The production of the head unit  21  is completed by disposing the discharge heads  34  (discharge head group  50 ) to the mounting plate  51 .  
         [0099]     In this exemplary embodiment, the first, second, and third discharge heads  34   f,    34   g,  and  34   h  were referred to as representatives of the discharge heads  34  in the description. Other discharge heads, also, are fixed to each of the openings  51   a  with an equal distance t.  
         [0100]     Next, the head unit  21  is set on the liquid discharger  10  to perform the discharging of the droplets.  
         [0101]     In the discharging of the droplets, liquid crystal contained in the tank  26  is discharged from the discharge head  34  through the liquid supply channel  27 . The liquid crystal is heated to a predetermined temperature by the heating device included in the tank  26  and the liquid supply channel  27 . Then the liquid crystal is further heated by the head heater  34   a  for the discharge heads  34 . In this way, the viscosity of the liquid crystal is lowered to a degree that facilitates discharge. While being heated, the liquid crystal is discharged onto the substrate  20  by the above-mentioned piezoelectric method according to the pattern of the electronic data set by the liquid discharger  10 . Since the discharging of the droplets is performed by the head unit  21  having the plurality of discharge heads  34 , the liquid crystal droplets are discharged with a predetermined pitch. The pitch of the liquid crystal droplets are determined by the distance between each of the discharge heads  34  of the discharge head group  50 . In this case, the distance between each of the discharge heads  34  is equal, and, thus, the distance between the liquid crystal droplets is also equal.  
         [0102]     As described above, on the liquid discharger  10 , the discharge heads  34  are mounted to the openings  51   a  of the mounting plate  51  as they are heated to the temperature equal to the temperature the liquid crystal is heated to lower the viscosity. Therefore, when the liquid crystal is discharged, the discharge heads  34  do not undergo expansion and/or contraction caused by a temperature change. Accordingly, the discharge heads  34  and the openings  51   a  are kept in highly accurate positions relative to each other. These positions are maintained while the liquid crystal is discharged. Moreover, the liquid crystal droplets can be discharged accurately onto minute areas since there is no error in the droplet landing positions.  
         [0103]     Moreover, the mounting plate  51  has the heater  53  to heat both the mounting plate  51  and the discharge heads  34 .  
         [0104]     Since the liquid discharger  10  has the alignment device  100 , the plurality of discharge heads  34  can be disposed so that the distance between the reference nozzles N 1  are equal.  
         [0105]     Since the controller  23  automatically controls the engagement of the discharge heads  34  with the openings  51   a  and the temperature setting of the mounting plate  51 , manual operation is unnecessary and the efficiency of the process is promoted.  
         [0106]     By using the adhesive  52 , the discharge heads  34  and the openings  51   a  are fixed together. In this way, no torque is applied compared to a case in which fasteners, such as screws are used. Therefore, the discharge heads  34  and the openings  51   a  can be fixed together without any distortion.  
         [0107]     A method to make a liquid crystal display using the above-mentioned liquid discharger  10  is described below.  
         [0108]      FIG. 6  is a cross-sectional schematic of the overview of layer structure of a liquid crystal display (hereinafter referred to as “a liquid panel”) produced by using the liquid discharger  10 .  FIG. 7  is a schematic of the overview of the liquid crystal panel viewed from the display surface. Elements, such as polarization plates and retardation plates, not referred to in the description of the present invention are omitted. The actual liquid crystal device, however, includes polarization plates and retardation plates. The size and the number of each component do not express the actual proportions.  
         [0109]     In the description below, for convenience, the method to drive the liquid crystal is a passive matrix method. The method, however, may be other methods, such as an active matrix method.  
         [0110]     As shown in  FIGS. 6 and 7 , the liquid crystal panel is basically formed of a pair of opposing glass substrates, i.e., a first substrate  210  and a second substrate  220 , bonded together by a sealing material  230 . Liquid crystal  241  is disposed inside a cell  240 . The sealing material  230  surrounds the area that becomes a display area which is interposed between the pair of substrates  210  and  220 . The liquid crystal  241  is discharged onto the substrate by the above-mentioned liquid discharger  10 .  
         [0111]     On the inner surface of the first substrate  210 , first electrodes  212  composed of a transparent conductive film, such as indium tin oxide (ITO), and then an alignment film  211  composed of polyimide resin are disposed. One of the ends of the first electrodes  212  extends beyond the sealing material  230  on the substrate to form connecting terminals. On the first electrodes  212 , an alignment film  211  composed of a polyimide resin is disposed. The alignment film  211  is processed to have a predetermined alignment direction.  
         [0112]     On the inner surface of the second substrate  220 , color filters  223  disposed in a sequence of red (R), green (G), and blue (B) in correspondence to the pixel areas are disposed. Then, with a cell gap between the color filters  223 , second electrodes  222 , composed of strips of transparent conductive material such as ITO, are disposed orthogonally to the first electrodes  212 . Then, an alignment film  221  is disposed on the second electrodes  222 . One of the ends of the second electrodes  222 , extends beyond the sealing material  230  on the substrate to form connecting terminals. The alignment film  221  is processed to have a predetermined alignment direction.  
         [0113]     Moreover, spacers  24  are distributed inside the cell  240  to maintain a constant cell gap.  
         [0114]     In this liquid crystal panel, a retardation plate and a polarization plate cover the entire outer surface of the first substrate. These plates, however, are omitted in the drawing.  
         [0115]     In general, the liquid crystal panel is produced by following the steps illustrated in FIGS.  8 ( a ) to  8 ( e ).  
         [0116]     Forming the alignment film, as shown in  FIG. 8   a,  strips of the first electrode  212 ,  212  are formed by photolithography on one side of the first substrate  210 . Then, the alignment film  211  is disposed on the area that will be the display area in a predetermined alignment direction. One of the ends of the first electrodes  212  is extended beyond the sealing material  230  on the substrate to form connecting terminals.  
         [0117]     Subsequently, as shown in  FIG. 8   b,  disposing the sealing material, distributing the spacers, and discharging the liquid crystal are performed.  
         [0118]     In disposing the sealing material, the uncured sealing material  230  of photo-curable resin ink is disposed around the alignment film  211 .  
         [0119]     In distributing the spacers, the spacers  242  are distributed on the alignment film  211 .  
         [0120]     In discharging the liquid crystal, the liquid crystal  241  is discharged by the above-mentioned liquid discharger  10 . The viscosity of the liquid crystal  241  is lowered by heating the discharge heads  34 . As a result, the liquid crystal  241  is discharged without clogging. Moreover, the discharge heads  34  are fixed to the openings  51   a  of the mounting plate  51  by the alignment device  100  at the same temperature as the temperature the liquid crystal  241  is discharged. For this reason, errors caused by heat expansion of the discharge heads  34  do not occur, and the liquid crystal  241  is discharged with high accuracy. Therefore, even when the liquid crystal  241  is discharged in the vicinity of the uncured sealing material  230 , it does not contact the sealing material  230 .  
         [0121]     On the other hand, as shown in  FIG. 8   c,  the color filters  223  (details are omitted in the drawing) are formed on one side of the second substrate  220 . On the color filters  223 ,  223 , the second electrodes  222  are disposed. Then, in the step of forming an alignment film, an alignment film  221  is disposed on the second electrodes  222  in a predetermined alignment direction. One of the ends of the second electrodes  222  extends beyond the sealing material  230  on the first substrate to form connecting terminals.  
         [0122]     The bonding of the layers together is shown in  FIG. 8   d.  The first substrate  210  is turned over and bonded with the second substrate  220  so that the alignment films  211  and  221  are disposed on the inner sides of the substrates.  
         [0123]     However, the second substrate  220  may be turned over and bonded with the first substrate  210 .  
         [0124]     The curing of the sealing material is shown in  FIG. 8   e.  The uncured sealing material  230  is cured by being irradiated with ultraviolet light emitted from an ultrahigh pressure mercury lamp through a filter F 1  disposed on the outer surface of the first substrate  210 , which becomes the display surface. In this case, by simultaneously exposing the sealing material  230  to light and heat, the curing process is accelerated and the sealing material  230  cures completely in a short period of time.  
         [0125]     As described above, the liquid crystal  241  is discharged by the liquid discharger, achieving the same effects as the above-mentioned liquid discharger.  
         [0126]     Exemplary embodiments of electronic apparatus having the liquid crystal panel are described by referring to  FIG. 9 .  
         [0127]      FIG. 9   a  is a schematic of an exemplary embodiment of a cellular phone. In  FIG. 9   a,  the reference numeral  1000  indicates a cellular phone body and the reference numeral  1001  indicates a liquid display.  
         [0128]      FIG. 9   b  is a perspective view of an exemplary embodiment of an electronic watch. In  FIG. 9   b,  the reference numeral  1100  indicates a watch body and the reference numeral  1101  indicates a liquid display.  
         [0129]      FIG. 9   c  is a perspective view of an exemplary embodiment of an electronic portable information processor, such as a word processor or a personal computer. In  FIG. 9   c,  the reference numeral  1200  indicates an information processor, the reference numeral  1201  indicates an input device, such as a keyboard, the reference numeral  1202  indicates a display including a liquid crystal display, and the reference numeral  1203  indicates an information processor body.  
         [0130]     The electronic apparatus illustrated in  FIGS. 9   a  to  9   c  each have a display including a liquid crystal display according to a exemplary embodiment described above. Thus, the same effects as the above-mentioned exemplary embodiment are achieved.  
         [0131]     These electronic apparatus are produced by incorporating the liquid crystal display according to a exemplary embodiment described above into the display of various electronic apparatus, such as a cellular phone, a portable information processor, or an electronic watch.