JP2010266633A - Droplet discharge device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a droplet discharge device uniformizing discharge quantity of functional fluid discharged from a plurality of droplet discharge heads arranged adjacently mutually. <P>SOLUTION: The droplet discharge device includes a plurality of droplet discharge heads 5 having a plurality of nozzles to discharge droplets and piezoelectric elements arranged in association with the respective nozzles. A plurality of droplet discharge heads 5 are disposed adjacently mutually, and electrostatic capacity of the piezoelectric element of the droplet discharge head 5 disposed on the inside is lower than that of the piezoelectric element of the droplet discharge head 5 disposed on the outside. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a droplet discharge device.

2. Description of the Related Art Conventionally, a droplet discharge head that controls the ink temperature to be highly accurate and constant to suppress fluctuations in the discharge weight and a droplet discharge device including the droplet discharge head are known (for example, see Patent Document 1).
Japanese Patent Application Laid-Open No. 2004-133867 has a problem that the weight of ink droplets ejected from the head varies due to temperature variation of the droplet ejection head (inkjet head) and the functional liquid (ink). Another problem is the discharge variation between the nozzles depending on the discharge conditions of each of the plurality of nozzles and the positional relationship with the heater.

  In Patent Document 1, in order to solve these problems, a droplet discharge head is provided with a temperature adjusting medium flow path. Then, the temperature adjusting medium is caused to flow in the flow path at a constant temperature. As a result, even if there is a temperature difference between the functional liquids corresponding to the nozzles, it is possible to exchange heat with the temperature adjusting medium, and the temperature of the functional liquid can be kept constant. become.

JP 2003-240337 A

  However, the conventional liquid droplet ejection apparatus has a problem that when a plurality of liquid droplet ejection heads are arranged adjacent to each other, a temperature difference occurs between the plurality of heads. When a plurality of droplet discharge heads are arranged adjacent to each other, heat concentrates on the droplet discharge heads arranged inside the array, resulting in a higher temperature than the droplet discharge heads arranged outside the array. Then, the viscosity of the functional liquid ejected from the droplet ejection head inside the array is lowered, and the viscosity of the functional liquid ejected between the droplet ejection heads located outside the array is varied.

  When variation occurs in the viscosity of the functional liquid ejected between the inner and outer droplet ejection heads of the array, there is a problem that variation occurs in the ejection amount of the droplets ejected from each droplet ejection head. That is, the discharge amount of the droplet discharge head that discharges the functional liquid having a low viscosity increases, and the discharge amount of the droplet discharge head that discharges the functional liquid having a high viscosity decreases. Therefore, the discharge amount of the functional liquid varies among a plurality of droplet discharge heads.

  Accordingly, the present invention provides a droplet discharge device that can uniformize the discharge amount of functional liquid discharged from a plurality of droplet discharge heads arranged adjacent to each other.

  In order to solve the above-described problems, a droplet discharge device according to the present invention includes a plurality of droplets each having a plurality of nozzles that discharge a droplet of a functional liquid and a piezoelectric element provided corresponding to each of the nozzles. A plurality of droplet discharge heads are arranged adjacent to each other, and an electrostatic capacitance of the piezoelectric element of the droplet discharge head disposed inside is disposed on the droplet discharge head disposed outside. It is smaller than the capacitance of the piezoelectric element.

  With this configuration, the amount of heat generated in the piezoelectric elements of the droplet discharge heads inside the array is less than the amount of heat generated in the piezoelectric elements of the droplet discharge heads outside the array. That is, when the heat (work) generated by the piezoelectric element is W, the capacitance of the piezoelectric element is C, and the voltage applied to the piezoelectric element is V, the following equation (1) is established.

W = CV ² (1)

As shown in the above equation (1), the amount of heat W generated by the piezoelectric element is proportional to the capacitance C of the piezoelectric element. Therefore, the smaller the capacitance C, the less heat is generated in the piezoelectric element.
When a plurality of droplet discharge heads are arranged adjacent to each other, other droplet discharge heads are arranged adjacent to each other outside the droplet discharge heads arranged inside the array. Then, the droplet discharge head arranged on the inner side is not only difficult to dissipate heat in the atmosphere, but also affected by the heat generated by the droplet discharge head arranged on the outer side. Therefore, in a plurality of droplet discharge heads arranged adjacent to each other, the droplet discharge heads arranged on the inner side are likely to be hotter than the droplet discharge heads arranged on the outer side.
Here, in the liquid droplet ejection apparatus of the present invention, the liquid droplet ejection head arranged inside the liquid droplet ejection head arranged outside is configured to generate less heat in the piezoelectric element. Yes. For this reason, the temperature of the droplet discharge head disposed inside can be made lower than the temperature of the droplet discharge head disposed outside. As a result, even when the temperature of the droplet discharge heads arranged on the inside rises due to the heat generated by the droplet discharge heads arranged on the outside, the temperature difference between the droplet discharge heads is reduced. Can be reduced.
Thereby, the temperature of the several droplet discharge head arrange | positioned adjacently can be equalize | homogenized. When the temperature of each droplet discharge head is made uniform, the viscosity of the discharged functional liquid is made uniform. When the viscosity of the functional liquid is made uniform, the discharge amount of the functional liquid discharged from each droplet discharge head is made uniform.
Therefore, according to the droplet discharge device of the present embodiment, it is possible to make the discharge amount of the functional liquid discharged from the plurality of droplet discharge heads arranged adjacent to each other uniform.

  Further, in the droplet discharge device of the present invention, the piezoelectric element has a plurality of piezoelectric layers and conductor layers alternately stacked, and the piezoelectric element of the droplet discharge head disposed inside the piezoelectric element. Is characterized in that the area of the conductor layer is smaller than that of the piezoelectric element of the droplet discharge head disposed on the outside.

  With this configuration, the electrostatic capacitance of the piezoelectric element of the droplet discharge head disposed inside is smaller than the capacitance of the piezoelectric element of the droplet discharge head disposed outside. .

  In the droplet discharge device of the present invention, the piezoelectric element includes a plurality of piezoelectric layers and conductor layers alternately stacked, and the piezoelectric element of the droplet discharge head disposed on the inner side. Is characterized in that the thickness of the piezoelectric layer is larger than that of the piezoelectric element of the droplet discharge head disposed on the outside.

  With this configuration, the electrostatic capacitance of the piezoelectric element of the droplet discharge head disposed inside is smaller than the capacitance of the piezoelectric element of the droplet discharge head disposed outside. .

  Further, in the droplet discharge device of the present invention, the interval between the piezoelectric elements arranged adjacent to each other is different between the droplet discharge head arranged inside and the droplet discharge head arranged outside. It is characterized by.

  With this configuration, both the piezoelectric elements of the droplet discharge head arranged inside and the piezoelectric elements of the droplet discharge head arranged outside are arranged at equal pitches corresponding to the nozzles. The electrostatic capacitance of the piezoelectric element can be varied.

  In addition, the droplet discharge device of the present invention includes a plurality of carriages that hold the plurality of droplet discharge heads, and the plurality of carriages are disposed adjacent to each other, and the droplets included in the carriage disposed inside. The capacitance of the piezoelectric element of the ejection head is smaller than the capacitance of the piezoelectric element of the droplet ejection head provided in the carriage disposed on the outside.

  With this configuration, the temperature of the droplet discharge heads provided in the plurality of carriages can be made uniform, and the droplet discharge amount of the droplet discharge heads can be made uniform between the plurality of carriages.

(A) is a perspective view which shows schematic structure of the droplet discharge apparatus in embodiment of this invention, (b) is a side view of a carriage. It is sectional drawing of the droplet discharge head of the droplet discharge apparatus shown in FIG. It is the schematic which shows arrangement | positioning of the piezoelectric element of the droplet discharge head shown in FIG. 2 is a graph showing capacitance of a droplet discharge head of the droplet discharge device shown in FIG. 1. 2 is a graph showing a droplet discharge amount of a droplet discharge head of the droplet discharge apparatus shown in FIG. 1. It is a graph which shows the temperature of the droplet discharge head of the conventional droplet discharge apparatus. It is a graph which shows the discharge amount of the droplet of the droplet discharge head of the conventional droplet discharge apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the scale is appropriately changed for each member so that each member has a size that can be recognized on the drawing.
The droplet discharge device of this embodiment forms a color filter layer by discharging droplets of a color filter material liquid onto a substrate by, for example, an inkjet method.

FIG. 1A is a perspective view showing a schematic configuration of a droplet discharge device IJ in the present embodiment.
As shown in FIG. 1A, a droplet discharge device IJ includes an apparatus stand 1, a work stage (mounting table) 2, a stage moving device (driving unit) 3, a carriage 4, a droplet discharging head 5, and a carriage moving device. (Driver) 6, tube 7, first tank 8, second tank 9, third tank 10, and controller 11 are provided.

  Below, as shown to Fig.1 (a), an XYZ rectangular coordinate system is set, and each member is demonstrated, referring this XYZ rectangular coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the holding surface 2 a that holds the substrate P of the work stage 2. The Z axis is set in a direction perpendicular to the holding surface 2a. Here, the work stage 2 is provided so that the holding surface 2a is parallel to the horizontal plane. That is, the X axis and the Y axis are parallel to the horizontal plane, and the Z axis is parallel to the vertical direction.

The apparatus base 1 is a support base that supports the work stage 2 and the stage moving device 3.
The work stage 2 is provided on the apparatus base 1 and is configured to be movable in the X-axis direction by a stage moving device 3. The work stage 2 is provided so that the substrate P transported from an upstream transport device (not shown) is held on the holding surface 2a by a vacuum suction mechanism.

The stage moving device 3 includes a bearing mechanism such as a ball screw or a linear guide, and moves the work stage 2 in the X-axis direction based on a control signal input from the control unit 11.
The carriage 4 is provided so as to hold a plurality of droplet discharge heads 5 and is provided so as to be movable in the Y-axis direction and the Z-axis direction by the carriage moving device 6.

FIG. 1B is a side view of the carriage 4.
As shown in FIG. 1B, a plurality of droplet discharge heads 5 are arranged adjacent to the carriage 4 in the X-axis direction. In the present embodiment, the six droplet discharge heads 5 from the first droplet discharge head 51 to the sixth droplet discharge head 56 are arranged adjacent to each other in the X-axis direction. Although not shown, a plurality of droplet discharge heads 5 are arranged adjacent to each other in the Y-axis direction.

Each droplet discharge head 5 is provided corresponding to each material liquid of R (red), G (green), and B (blue). As shown in FIG. 1A, a tube 7 is connected to each droplet discharge head 5 via a carriage 4. A tube 7 connected to the droplet discharge head 5 corresponding to R (red) is connected to a first tank 8 that stores a material liquid for R (red). A tube 7 connected to the droplet discharge head 5 corresponding to G (green) is connected to a second tank 9 that stores a material liquid for G (green). A tube 7 connected to the droplet discharge head 5 corresponding to B (blue) is connected to a third tank 10 that stores a material liquid for B (blue).
As a result, the tube 7 from each of the first tank 8, the second tank 9, and the third tank 10 is attached to each of the droplet discharge heads 5 corresponding to R (red), G (green), and B (blue). The material liquids of R (red), G (green), and B (blue) are supplied through the respective parts.

FIG. 2 is a cross-sectional view of the droplet discharge head 5.
As shown in FIG. 2, the droplet discharge head 5 includes a head body 5 </ b> A, a flow path unit 20, and an actuator unit 30.
The head main body 5A is a hollow box-shaped member, and a flow path 5B and a storage chamber 5C are formed inside the head main body 5A.

  The flow path 5B is formed so as to penetrate the head body 5A in the height direction. The upper end of the flow path 5B is connected to the tube 7 shown in FIG. 1A via a packing, an introduction needle unit, etc. (not shown). The lower end of the flow path 5B communicates with the common ink chamber 25 in the flow path unit 20 so that the functional liquid such as ink introduced from the introduction needle unit is supplied to the flow path unit 20 through the flow path 5B. It has become.

The flow path unit 20 includes a nozzle plate 21, a flow path substrate 23 and a vibration plate 24. The nozzle plate 21, the flow path substrate 23, and the vibration plate 24 are stacked in this order, and are joined and integrated with an adhesive (not shown).
On the lower end surface (nozzle surface 21 a) of the flow path unit 20, a plurality of nozzles 22 that discharge the functional liquid supplied to the flow path unit 20 are arrayed along the Y-axis direction.
The nozzle plate 21 is provided at the lower end of the droplet discharge head 5 so as to close the lower portion of the flow path substrate 23. The nozzles 22 are provided so as to penetrate the nozzle plate 21 and are opened in the nozzle surface 21a on the lower surface.

  The flow path substrate 23 has a common ink chamber 25, a functional liquid supply port 26, and a pressure chamber 27 formed therein. The common ink chamber 25 is provided in common to the plurality of nozzles 22 and stores the functional liquid supplied from the flow path 5B. Further, the common ink chamber 25 supplies the functional liquid to each of the pressure chambers 27 that communicate with each other via the functional liquid supply port 26. The pressure chamber 27 is divided for each nozzle 22, and the internal pressure is changed by the vibration of the vibration plate 24.

  The diaphragm 24 is a composite plate material having a double structure in which an elastic film is laminated on a metal support plate such as stainless steel. At a portion corresponding to the pressure chamber 27 of the vibration plate 24, an island portion 28 to which the front end surface of the piezoelectric element 31 is joined is formed by removing the support plate in an annular shape by etching or the like. This island part 28 functions as a diaphragm part.

  The diaphragm 24 is configured such that the elastic film around the island portion 28 is elastically deformed in accordance with the operation of the piezoelectric element 31. One opening surface of the flow path substrate 23 is sealed to function as the compliance portion 29. In the portion corresponding to the compliance portion 29, the support plate is removed by etching or the like as in the diaphragm portion, and only the elastic film remains.

  The actuator unit 30 includes a piezoelectric element 31, a fixed plate 32 to which the piezoelectric element 31 is joined, and a flexible cable 33 that supplies a drive signal from the control unit 11 to the piezoelectric element 31. The actuator unit 30 is fixed in the storage chamber 5C by bonding a fixing plate 32 to the inner wall surface of the storage chamber 5C.

  One end of the piezoelectric element 31 is joined to the fixed plate 32, and the other end protrudes from the front end surface of the fixed plate 32, and is fixed to the island portion 28 of the diaphragm 24. The piezoelectric elements 31 are provided corresponding to the respective nozzles 22 and the pressure chambers 27, and a plurality of the piezoelectric elements 31 are arranged in the arrangement direction (Y-axis direction) of the nozzles 22.

FIG. 3 is a perspective view showing the arrangement and schematic configuration of the piezoelectric elements 31 in the droplet discharge head 5.
As shown in FIG. 3, the piezoelectric elements 31 are arranged at an interval d equal to the arrangement direction (Y-axis direction) of the nozzles 22. The piezoelectric element 31 has a plurality of piezoelectric layers 31a and conductor layers 31b that are alternately stacked in the X-axis direction. The piezoelectric layer 31a is formed of a dielectric material (piezoelectric material) such as PZT. The conductor layer 31b is formed of a conductor such as a metal plate, for example.

  In the following description, the dimension of the piezoelectric element 31 in the X-axis direction (direction orthogonal to the arrangement direction of the nozzles 22) is the thickness T, the dimension in the Y-axis direction (the arrangement direction of the nozzles 22) is the width w, and the Z-axis direction (longitudinal) The direction) is the length l. In the present embodiment, the interval between the nozzles 22 and the length l of the piezoelectric element 31 shown in FIG.

  As shown in FIG. 1B, the width w and interval d of the piezoelectric elements 31 shown in FIG. 3 differ between the plurality of droplet discharge heads 5 arranged adjacent to each other depending on their positions. Therefore, the area of each surface 31c (vertical surface parallel to the arrangement direction of the nozzles 22) parallel to the YZ plane of the piezoelectric element 31 differs depending on the position of each droplet discharge head 5. Thereby, the area of the conductor layer 31b varies depending on the position of each droplet discharge head 5.

  Specifically, as shown in FIG. 1B, among the plurality of droplet discharge heads 5 arranged in the X-axis direction, the piezoelectric element 31 of the first droplet discharge head 51 arranged on the outermost side. The width w is larger than the width w of the piezoelectric element 31 of the second droplet discharge head 52 disposed inside the width w. Therefore, the area of the surface 31 c of the piezoelectric element 31 of the first droplet discharge head 51 is larger than the area of the surface 31 c of the piezoelectric element 31 of the second droplet discharge head 52. Thereby, the area S of the conductor layer 31b of the piezoelectric element 31 is smaller in the second droplet discharge head 52 disposed on the inner side than in the first droplet discharge head 51 disposed on the outer side. .

  In general, the capacitance C of the piezoelectric element 31 is expressed by the following formula (A) using the thickness t of the piezoelectric layer 31a, the dielectric constant ε of the piezoelectric layer 31a, and the area S of the conductor layer 31b.

  C = εS / t (A)

  From the above formula (A), it can be seen that the capacitance C is proportional to the area S of the conductor layer 31b. Therefore, if the thickness t of the piezoelectric layer 31a is equal, the electrostatic capacitance C of the piezoelectric element 31 of the second droplet discharge head 52 disposed on the inside is equal to the first droplet discharge head 51 disposed on the outside. It becomes smaller than the electrostatic capacitance C of the piezoelectric element 31.

  Here, the interval between the nozzles 22 of the first droplet ejection head 51 and the second droplet ejection head 52 is equal, and the piezoelectric elements 31 are provided corresponding to the nozzles 22 respectively. The first droplet discharge head 51 has a width w of the piezoelectric element 31 larger than that of the second droplet discharge head 52. Therefore, the distance d between the piezoelectric elements 31 is smaller in the first droplet discharge head 51 than in the second droplet discharge head 52 inside. Thus, in a state where both the piezoelectric element 31 of the droplet discharge head 52 disposed on the inside and the piezoelectric element 31 of the droplet discharge head 51 disposed on the outside are disposed corresponding to the nozzles 22, these The electrostatic capacitance C can be varied.

  Similarly, the third droplet discharge head 53 disposed inside the second droplet discharge head 52 shown in FIG. 1B has a width w of the piezoelectric element 31 shown in FIG. It is getting smaller. For this reason, the area of the surface 31 c of the piezoelectric element 31 and the area of the conductor layer 31 b are smaller in the third droplet ejection head 53 than in the second droplet ejection head 52. Thereby, the electrostatic capacity C of the piezoelectric element 31 of the third droplet discharge head 53 disposed on the inner side is larger than the electrostatic capacity C of the piezoelectric element 31 of the second droplet discharge head 52 disposed on the outer side. Is also getting smaller.

  In addition, the second droplet discharge head 52 has a width w of the piezoelectric element 31 larger than that of the third droplet discharge head 53. For this reason, the distance d between the piezoelectric elements 31 and 31 is smaller in the second droplet discharge head 52 than in the third droplet discharge head 53 inside. As a result, both the piezoelectric element 31 of the droplet discharge head 53 arranged on the inner side and the piezoelectric element 31 of the droplet discharge head 52 arranged on the outer side are arranged corresponding to the nozzles 22. The electrostatic capacitance C can be made different.

  In the present embodiment, the first droplet discharge head 51 and the sixth droplet discharge head 56 arranged on the outermost side in the X-axis direction have the same configuration, and the electrostatic capacitances C of the piezoelectric elements 31 are equal. ing. In addition, the second droplet discharge head 52 and the fifth droplet discharge head 55 arranged on the inside thereof have the same configuration, and the capacitance C of the piezoelectric element 31 is equal. In addition, the third droplet discharge head 53 and the fourth droplet discharge head 54 arranged on the inside thereof have the same configuration, and the electrostatic capacitances C of the piezoelectric elements 31 are equal.

  FIG. 4 is a graph showing the magnitude relationship of the capacitance C of the first droplet discharge head 51 to the sixth droplet discharge head 56 shown in FIG. In FIG. 4, the vertical axis represents the capacitance C, and the numbers from 1 to 6 on the horizontal axis correspond to the first droplet discharge head 51 to the sixth droplet discharge head 56, respectively.

  As shown in FIG. 4, the electrostatic capacitance C of the first droplet discharge head 51 and the sixth droplet discharge head 56 arranged on the outermost side is the largest. The electrostatic capacities C of the second droplet discharge head 52 and the fifth droplet discharge head 55 arranged on the inner side are the first droplet discharge head 51 and the sixth liquid arranged on the outside. The capacitance is smaller than the electrostatic capacitance C of the droplet discharge head 56. In addition, the electrostatic capacitance C of the third droplet discharge head 53 and the fourth droplet discharge head 54 arranged on the inner side thereof is equal to the second droplet discharge head 52 and the fifth liquid arranged on the outer side. It is smaller than the electrostatic capacitance C of the droplet discharge head 55.

  The plurality of droplet discharge heads 5 arranged adjacent to each other in the Y-axis direction are also provided in the same manner as the plurality of droplet discharge heads 5 arranged adjacent to each other in the X-axis direction. In other words, the plurality of droplet discharge heads 5 arranged adjacent to each other in the Y-axis direction has a capacitance C of the piezoelectric element 31 of the droplet discharge head 5 disposed on the inner side and the droplet discharge disposed on the outer side. The piezoelectric element 31 of the head 5 is configured to be smaller than the capacitance C.

  Further, in the present embodiment, in the plurality of droplet discharge heads 5 arranged adjacent to each other in the X-axis direction and the Y-axis direction, the piezoelectric elements 31 of the droplet discharge heads 5 arranged on the inner side are arranged on the outer side. The thickness t of the piezoelectric layer 31 a shown in FIG. 3 is larger than that of the piezoelectric element 31 of the droplet discharge head 5. From the above formula (A), it can be seen that the capacitance C is inversely proportional to the thickness t of the piezoelectric layer 31a.

  Therefore, when the area S of the conductor layer 31b is constant, the capacitance C decreases as the thickness t (distance between the conductor layers 31b) of the piezoelectric element 31 increases. In the present embodiment, in the plurality of droplet discharge heads 5 arranged adjacent to each other in the X-axis direction and the Y-axis direction, the area of the conductor layer 31b becomes smaller as the droplet discharge heads 5 arranged on the inner side. Yes. Accordingly, the capacitance C of the inner droplet discharge head 5 can be further reduced, and the difference in the capacitance C between the inner and outer droplet discharge heads 5 can be further increased.

  As shown in FIG. 1A, the carriage moving device 6 has a bridge structure straddling the device mount 1, and includes a bearing mechanism such as a ball screw or a linear guide in the Y-axis direction and the Z-axis direction. The carriage moving device 6 moves the carriage 4 in the Y-axis direction and the Z-axis direction based on a control signal input from the control unit 11.

  The controller 11 controls the droplet discharge head 5, the stage moving device 3, and the carriage moving device 6. The control unit 11 is configured to output a stage position indicating the X coordinate of the work stage 2 to the stage moving device 3 as a control signal. In addition, a carriage position indicating the Y coordinate and Z coordinate of the carriage 4 is output to the carriage moving device 6. In addition, drawing data and a drive control signal are output to a drive circuit board (not shown) of the droplet discharge head 5.

  With the above configuration, the droplet discharge device IJ drives the stage moving device 3 by the control unit 11 to move the droplet discharge head 5 relative to the substrate P held on the work stage 2 in the X-axis direction. Be able to. In addition, by driving the carriage moving device 6 by the control unit 11, the droplet discharge head 5 can be moved relative to the substrate P on the work stage 2 in the Y-axis direction and the Z-axis direction. Yes.

Next, the operation of the droplet discharge device IJ of this embodiment will be described.
As shown in FIG. 1A, when film formation is performed on the substrate P held on the holding surface 2 a of the work stage 2, the stage moving device 3 and the carriage moving device 6 are driven by the control unit 11. Then, while moving the carriage 4 relative to the substrate P, a functional liquid such as a color filter material liquid is intermittently discharged from the nozzles 22 of the droplet discharge head 5. As a result, the color filter can be deposited by disposing the color filter material liquid in a predetermined region on the substrate P.

When the functional liquid is ejected from the nozzle 22 of the droplet ejection head 5 shown in FIG. 2, a predetermined voltage waveform is applied to each piezoelectric element 31 via the flexible cable 33 by the control unit 11. Thereby, each piezoelectric element 31 expands and contracts according to the voltage waveform, and the diaphragm 24 vibrates and the volume of the pressure chamber 27 changes. A change in volume of the pressure chamber 27 causes a pressure change in the pressure chamber 27. By increasing or decreasing the pressure of the functional liquid in each pressure chamber 27 due to this pressure change, the functional liquid droplet D is discharged from each nozzle 22.
When a voltage waveform is applied to the piezoelectric element 31 to expand and contract, heat is generated in the piezoelectric element 31 and the temperature of the droplet discharge head 5 rises.

  Here, in this embodiment, as shown in FIG. 1B, a plurality of droplet discharge heads 5 are arranged adjacent to each other. In this case, the outer surfaces of the first droplet discharge head 51 and the sixth droplet discharge head 56 disposed on the outside are exposed. Therefore, the heat generated in these is easily radiated to an atmosphere such as air.

  However, the second droplet discharge head 52 and the fifth droplet discharge head 55 arranged on the inside thereof are adjacent to the first droplet discharge head 51 and the sixth droplet discharge head 56 on the outside thereof. Are arranged. Therefore, the heat generated in these is less likely to be dissipated than the first droplet discharge head 51 and the sixth droplet discharge head 56. Further, it is affected by heat generated by the first droplet discharge head 51 and the sixth droplet discharge head 56 disposed on the outside. Therefore, the second droplet discharge head 52 and the fifth droplet discharge head 55 are likely to have a higher temperature than the first droplet discharge head 51 and the sixth droplet discharge head 56 disposed on the outside thereof. .

  Further, the third droplet discharge head 53 and the fourth droplet discharge head 54 arranged on the inner side thereof are constituted by the second droplet discharge head 52 and the fifth droplet discharge head 55 arranged on the outside thereof. Difficult to dissipate heat. In addition, the second droplet discharge head 52 and the fifth liquid are affected by the heat generated by them and the heat of the first droplet discharge head 51 and the sixth droplet discharge head 56 on the outside thereof. The temperature tends to be higher than that of the droplet discharge head 55.

  Here, in the droplet discharge device IJ of the present embodiment, the electrostatic capacitance C of the piezoelectric element 31 of the droplet discharge head 5 disposed on the inner side of the piezoelectric element 31 of the droplet discharge head 5 disposed on the outer side. The capacitance is smaller than the capacitance C.

  When the amount of heat (work) generated by the piezoelectric element 31 is W and the voltage applied to the piezoelectric element 31 is V, the relationship of the following equation (1) is established between the piezoelectric element 31 and the capacitance C.

W = CV ² (1)

  As shown in the above formula (1), the amount of heat W generated by the piezoelectric element 31 is proportional to the capacitance C of the piezoelectric element 31. Therefore, the smaller the capacitance C, the less heat generated in the piezoelectric element 31.

  Therefore, as shown in FIG. 1B, the amount of heat generated in the piezoelectric elements 31 of the droplet discharge heads 53 and 54 inside the array is generated in the piezoelectric elements 31 of the droplet discharge heads 52 and 55 outside the array. Less than the amount of heat to be. Further, the amount of heat generated in the piezoelectric elements 31 of the droplet discharge heads 52 and 55 is smaller than the amount of heat generated in the piezoelectric elements 31 of the droplet discharge heads 51 and 56 on the outer side.

  Therefore, even when the temperature of the droplet discharge heads 52 and 55 arranged on the inside rises due to the influence of the heat generated by the droplet discharge heads 51 and 56 arranged on the outside, each droplet discharge The temperature difference of the head 5 can be reduced. Similarly, even when the temperature of the droplet discharge heads 53 and 54 arranged on the inside rises due to the influence of heat generated by the droplet discharge heads 51, 52, 55 and 56 arranged on the outside. The temperature difference between the droplet discharge heads 5 can be reduced. Similarly, the temperature difference can be reduced in each droplet discharge head 5 arranged adjacent to the Y-axis direction.

  Thereby, the temperature of the several droplet discharge head 5 arrange | positioned adjacently can be equalize | homogenized. When the temperature of each droplet discharge head 5 is made uniform, the viscosity of the discharged functional liquid is made uniform. When the viscosity of the functional liquid is made uniform, the discharge amount of the functional liquid discharged from each droplet discharge head 5 is made uniform.

FIG. 5 is a graph showing the discharge amount of the droplet discharge heads 5 arranged adjacent to each other in the X-axis direction as shown in FIG. In FIG. 5, the vertical axis represents the discharge amount (g) of the functional liquid, and the numbers from 1 to 6 on the horizontal axis correspond to the first droplet discharge head 51 to the sixth droplet discharge head 56, respectively. Yes.
As the temperature of the first droplet discharge head 51 to the sixth droplet discharge head 56 is made uniform and the viscosity of the functional liquid to be discharged is made uniform, as shown in FIG. It can be seen that the discharge amount is uniform.

Here, for comparison with the droplet discharge device IJ of the present embodiment, a conventional droplet discharge device will be described with reference to FIGS. 6 and 7 with reference to FIG.
The conventional droplet discharge device described in the present embodiment is similar to the droplet discharge device IJ of the present embodiment shown in FIG. 1B, and is adjacent to first to sixth droplet discharge heads. It has. However, unlike the droplet discharge device IJ of the present embodiment, the electrostatic capacitances of the piezoelectric elements included in each droplet discharge head are all equal.

FIG. 6 is a graph showing the temperature of a droplet discharge head in a conventional droplet discharge apparatus. In FIG. 6, the vertical axis represents temperature, and the numbers 1 to 6 on the horizontal axis correspond to the first to sixth droplet discharge heads arranged adjacent to each other.
As shown in FIG. 6, in the conventional droplet discharge device, the temperature of the third and fourth droplet discharge heads arranged on the innermost side is the highest. Next, the temperature of the second and fifth droplet discharge heads arranged outside thereof is high, and the temperature of the first and sixth droplet discharge heads arranged outside thereof is lowest.

  When such a temperature difference occurs between a plurality of droplet discharge heads, the viscosity of the functional liquid discharged from each droplet discharge head becomes non-uniform. Specifically, the higher the temperature, the lower the viscosity of the functional liquid, and the lower the temperature, the higher the functional liquid viscosity.

FIG. 7 is a graph showing the droplet discharge amount of each droplet discharge head in the conventional droplet discharge apparatus. In FIG. 7, the vertical axis represents the discharge amount (g) of the functional liquid, and the numbers 1 to 6 on the horizontal axis correspond to the first droplet discharge head 51 to the sixth droplet discharge head 56, respectively. .
In the conventional droplet discharge device, the temperature of the first to sixth droplet discharge heads is non-uniform, and the viscosity of the functional liquid to be discharged is non-uniform, so as shown in FIG. The discharge amount of the discharge head is uneven.

  On the other hand, in the droplet discharge device IJ of the present embodiment, the electrostatic capacitance C of the piezoelectric element 31 of each droplet discharge head 5 is made different according to the position of the droplet discharge head 5 as described above. . Thereby, the discharge amount of the functional liquid discharged from the plurality of droplet discharge heads 5 arranged adjacent to each other can be made uniform.

  As described above, according to the droplet discharge device IJ of the present embodiment, the discharge amount of the functional liquid discharged from the plurality of droplet discharge heads 5 arranged adjacent to each other can be made uniform.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention. For example, in the above-described embodiment, the configuration in which a plurality of droplet discharge heads are held in one carriage has been described. However, the droplet discharge apparatus of the present invention has a plurality of carriages that hold a plurality of droplet discharge heads. It is good also as a structure provided with. In this case, the plurality of carriages are arranged adjacent to each other, and the electrostatic capacity of the piezoelectric element of the droplet discharge head included in the carriage disposed on the inner side is equal to that of the piezoelectric element of the droplet discharge head included in the carriage disposed on the outer side. Make it smaller than the capacitance. With this configuration, the temperature of the droplet discharge heads provided in the plurality of carriages can be made uniform, and the droplet discharge amount of the droplet discharge heads can be made uniform between the plurality of carriages.

4 Carriage, 5, 51, 52, 53, 54, 55, 56 Droplet ejection head, 22 nozzles, 31 Piezoelectric element, 31a Piezoelectric layer, 31b Conductor layer, C capacitance, d interval, IJ droplet ejection Equipment, S area, t thickness

Claims (5)

A plurality of droplet discharge heads having a plurality of nozzles for discharging droplets and piezoelectric elements provided corresponding to each of the nozzles;
The plurality of droplet discharge heads are disposed adjacent to each other;
A droplet discharge device characterized in that an electrostatic capacitance of the piezoelectric element of the droplet discharge head disposed inside is smaller than a capacitance of the piezoelectric element of the droplet discharge head disposed outside. . The piezoelectric element has a plurality of piezoelectric layers and conductor layers alternately stacked,
The piezoelectric element of the droplet discharge head arranged on the inner side has a smaller area of the conductor layer than the piezoelectric element of the droplet discharge head arranged on the outer side. 2. The droplet discharge device according to 1. The piezoelectric element has a plurality of piezoelectric layers and conductor layers alternately stacked,
The piezoelectric element of the droplet discharge head disposed on the inside has a thickness of the piezoelectric layer larger than that of the piezoelectric element of the droplet discharge head disposed on the outside. The droplet discharge device according to claim 1. The interval between the piezoelectric elements arranged adjacent to each other is different between the liquid droplet ejection head arranged on the inner side and the liquid droplet ejection head arranged on the outer side. The droplet discharge device according to any one of the above. A plurality of carriages for holding the plurality of droplet discharge heads;
The plurality of carriages are arranged adjacent to each other;
The electrostatic capacity of the piezoelectric element of the droplet discharge head included in the carriage disposed inside is smaller than the electrostatic capacity of the piezoelectric element of the droplet discharge head included in the carriage disposed outside. The droplet discharge device according to any one of claims 1 to 4, wherein

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