JP2008030445A - Liquid-droplet discharge controller and its control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid-droplet discharge controller that allows to easily correct variations in characteristics of liquid droplets to be discharged among pressure chambers without deteriorating an array density of the pressure chambers and without complicating a drive-voltage setting or a driving circuit, and its control method. <P>SOLUTION: When an individual voltage value of a pressure chamber 112b is applied to an electrode 113b in the pressure chamber 112b for a period from time t1 until time t2, a partition wall 111b and a partition wall 111c are shear-deformed in a direction of separating from each other so as to allow liquid to flow into the pressure chamber 112b due to an enlargement in volume of the pressure chamber 112b. Then, when a common voltage value is applied to an electrode 113a in a pressure chamber 112a and an electrode 113c in a pressure chamber 112c that are respectively adjacent to the pressure chamber 112b for a period from the time t2 until time t3, the partition wall 111b and the partition wall 111c are shear-deformed in a direction of approaching each other so as to allow the liquid in the pressure chamber 112b to be discharged from a nozzle as a liquid-droplet due to a reduction in volume of the pressure chamber 112b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a droplet discharge control device that controls an inkjet head that discharges liquid material into droplets, and a control method therefor, and in particular, a liquid that can correct droplet discharge characteristics of a multi-nozzle share mode inkjet head. The present invention relates to a droplet discharge control device and a control method thereof.

  2. Description of the Related Art Conventionally, there is an ink jet method as one of methods for discharging a liquid, and an ink material is discharged onto a medium such as paper by using a multi-nozzle ink jet head (hereinafter simply referred to as “head”) in which a large number of nozzles are arranged. Inkjet apparatuses that perform printing at high speed are known. The share mode type ink jet head has a simple pressure chamber structure for pressurizing ink and is excellent in increasing the density of nozzles (see, for example, Patent Document 1).

  In recent years, ink jet apparatuses have been applied to industrial uses such as thin film formation. For example, it is used for manufacturing a color filter of a liquid crystal panel by separately coating red, green, and blue color materials on a glass substrate. Further, it is also applied to the formation of a light-emitting layer and an electrode thin film in the manufacturing process of an organic EL (Electro-Luminescence) panel.

  In such an industrial application, it is necessary to apply uniformly to a predetermined region, and it is necessary to suppress the amount of liquid discharged to an accuracy of several percent or less. Furthermore, for a high-definition medium, it is necessary to aim at a region where the width is only the same as that of the droplet while the inkjet head is scanned at a high speed of several hundreds m / sec, and to land the droplet. . The volume of one droplet discharged from the nozzle is several picoliters to several tens of picoliters, and the diameter of the droplets is about 20 to 30 μm.

  However, in a conventional multi-nozzle ink jet head, there is a large variation in the volume and ejection speed of the droplets ejected from each nozzle due to variation in the characteristics between the nozzles. Considering the overall profitability, it is difficult to rely only on suppressing variations in the characteristics of the head nozzles.

  Therefore, the volume of the ejected droplet and the ejection speed are corrected by individually adjusting the voltage of the drive waveform applied to the pressure chamber. For example, there is a device that generates a plurality of driving voltage waveforms of different voltages using a generating unit that generates a plurality of driving voltage waveforms, selects a driving voltage waveform for each nozzle, and supplies the driving voltage waveform to the head (for example, Patent Document 2). reference). Alternatively, a common voltage waveform is generated in the analog drive voltage generation means based on digital data that is information on the drive voltage waveform stored for each nozzle. Then, there is one that adjusts the voltage of the drive waveform for each nozzle by adjusting the opening / closing timing of a switch that determines whether or not the generated common voltage waveform is supplied to the pressure chamber (see, for example, Patent Document 3). Several other proposals have been made as means for individually adjusting the voltage of the drive waveform applied to the pressure chamber.

  However, there are the following problems when correction of variation in characteristics between nozzles by adjusting the drive voltage for each pressure chamber is applied to a share mode type inkjet. In other words, a general share mode inkjet head, that is, a head in which pressure chambers capable of ejecting droplets are continuously arranged, shares a partition that is an actuator between adjacent pressure chambers. It is not possible to drive the chambers independently, for example to discharge droplets from all pressure chambers simultaneously.

  In view of this, a method of driving the pressure chambers which are not adjacent to each other into one group and divided into two or three or more groups is employed (see, for example, Patent Document 4 and Patent Document 5). At this time, a positive voltage is applied to the pressure chamber that discharges the droplets to deform the partition as an actuator in a direction in which the volume of the pressure chamber expands, and then the positive voltage is applied to the pressure chambers adjacent to the pressure chamber. Is applied to deform the partition wall in a direction in which the volume of the pressure chamber from which the droplet is discharged is reduced. At this time, if the drive voltage is configured to be different for each pressure chamber, the drive voltage set in the adjacent pressure chamber is affected, so that the setting of the drive voltage becomes very complicated. is there. Furthermore, when driving by dividing into three or more groups, the partition wall sandwiched between the pressure chambers that do not discharge droplets is deformed by the difference between the driving voltages set in the two pressure chambers. Extra pressure waves generated by this deformation may impair the stability of droplet ejection. In addition, extra power that does not contribute to droplet ejection is consumed.

  Furthermore, in order to discharge the droplet by reducing the pressure chamber after enlarging the pressure chamber, bipolar driving in which a positive voltage and a negative voltage are alternately applied to the pressure chamber from which the droplet is discharged is performed by a drive circuit. There is a problem that it becomes complicated (see, for example, Patent Document 6).

  Furthermore, there is one that does not share a partition which is an actuator with an adjacent pressure chamber (see, for example, Patent Document 7). This is because a dummy pressure chamber is provided between the pressure chambers for ejecting droplets, so that there is a problem that the arrangement density of the pressure chambers for ejecting droplets decreases, and droplets are ejected with high precision. I can't.

JP-A-63-252750 Japanese Patent Laid-Open No. 9-11457 JP-A-2005-254211 Japanese Patent No. 3338423 JP 2002-321362 A JP 2000-141638 A Japanese Patent Laid-Open No. 5-269985

  An object of the present invention is to easily correct variations in characteristics of ejected droplets between pressure chambers without reducing the arrangement density of the pressure chambers and without complicating the drive voltage setting or the drive circuit. It is an object to provide a droplet discharge control device and a control method thereof.

The present invention forms a plurality of pressure chambers for discharging droplets by partitioning with partition walls made of a piezoelectric material, and deforms the partition walls by shear stress generated by applying an electric field to the partition walls. A droplet discharge control device that controls an inkjet head that discharges droplets by generating energy in the pressure chamber,
An electric field corresponding to each pressure chamber is individually applied to the partition walls on both sides of the pressure chamber to which the droplets are to be discharged, and no electric field is applied to the partition wall sandwiched between the pressure chambers to which the droplets should not be discharged. A droplet discharge control device including an electric field control means.

  According to the present invention, a plurality of pressure chambers for discharging droplets are formed by partitioning with a partition made of a piezoelectric material, and the partition is deformed by shear stress generated by applying an electric field to the partition, When controlling the ink jet head that generates droplet discharge energy in the pressure chamber and discharges the droplet, the electric field control means separates the partition walls on both sides of the pressure chamber to which the droplet is discharged for each pressure chamber. An electric field corresponding to is applied, and no electric field is applied to the partition wall sandwiched between pressure chambers from which droplets should not be discharged.

  That is, by applying a voltage that does not apply an electric field to a partition wall that is sandwiched between pressure chambers that should not eject droplets, mutual interference that occurs in the partition wall sandwiched between pressure chambers that should not eject droplets is eliminated. Therefore, there is no need to consider mutual interference when adjusting each pressure chamber. Therefore, since it is not necessary to provide dummy pressure chambers, the pressure chamber arrangement density is reduced without reducing the arrangement density of the pressure chambers and without complicating the drive voltage setting or the drive circuit. Variations can be easily corrected.

  Further, in the present invention, the electric field control means applies an electric field for expanding the volume of the pressure chamber to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged, and subsequently reduces the volume of the pressure chamber. An electric field to be applied is applied.

  According to the present invention, after the electric field control means applies an electric field for expanding the volume of the pressure chamber to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged, the volume of the pressure chamber is subsequently changed. Since the electric field to be reduced is applied, the polarization direction of the piezoelectric body constituting the partition wall is the direction in which the volume of the pressure chamber expands when a voltage for applying an electric field is applied to the partition walls on both sides of the pressure chamber to which droplets are to be discharged. It is possible to control the inkjet head.

  Further, in the present invention, the electric field control means applies an electric field for reducing the volume of the pressure chamber to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged, and subsequently expands the volume of the pressure chamber. An electric field to be applied is applied.

  According to the present invention, after the electric field control means applies an electric field for reducing the volume of the pressure chamber to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged, the volume of the pressure chamber is subsequently reduced. Since the electric field to be expanded is applied, the direction of polarization of the piezoelectric body constituting the partition is the direction in which the volume of the pressure chamber is reduced when a voltage for applying an electric field is applied to the partition on both sides of the pressure chamber from which droplets are to be discharged. It is possible to control the inkjet head.

  In the present invention, the electric field control means applies an electric field by applying a voltage, and the voltage value of the applied voltage is a pressure so as to reduce the variation in the volume of droplets ejected from each pressure chamber. It is characterized by being adjusted in advance for each room.

  According to the present invention, an electric field is applied by applying a voltage by the electric field control means, and the voltage value of the applied voltage reduces variations in the volume of droplets ejected from each pressure chamber. Since the pressure chambers are adjusted in advance as described above, it is possible to perform correction to reduce the variation in the volume of droplets ejected from each pressure chamber.

  According to the present invention, the electric field control means applies an electric field by applying a voltage, and the voltage value of the applied voltage reduces variation in the discharge speed of the droplets discharged from each pressure chamber. The pressure chamber is adjusted in advance for each pressure chamber.

  According to the invention, an electric field is applied by applying a voltage by the electric field control means, and the voltage value of the applied voltage reduces variations in the discharge speed of droplets discharged from each pressure chamber. Thus, since the pressure chambers are adjusted in advance for each pressure chamber, it is possible to perform correction to reduce the variation in the discharge speed of the droplets discharged from each pressure chamber.

The present invention also includes a temperature detection means for detecting the temperature of the liquid stored in the pressure chamber of the inkjet head,
The previously adjusted voltage value is a temperature detection based on a predetermined temperature voltage characteristic representing a voltage value of a voltage to be applied in order to keep the volume of a droplet discharged from the pressure chamber constant with respect to a temperature change. The voltage value is corrected to a voltage value corresponding to the temperature detected by the means.

  According to the present invention, the temperature of the liquid stored in the pressure chamber of the inkjet head is detected by the temperature detecting means, and the voltage value adjusted in advance is a droplet discharged from the pressure chamber in response to a temperature change. Since the voltage value is corrected to a voltage value corresponding to the temperature detected by the temperature detecting means based on a predetermined temperature-voltage characteristic representing the voltage value of the voltage to be applied in order to keep the volume of the With the control that takes into account the correction of the variation in the volume of the liquid droplets due to the above, it is possible to apply liquid droplets without uneven application.

The present invention also includes a temperature detection means for detecting the temperature of the liquid stored in the pressure chamber of the inkjet head,
The voltage value to be adjusted in advance is based on a predetermined temperature-voltage characteristic indicating a voltage value of a voltage to be applied in order to keep a discharge speed of a droplet discharged from the pressure chamber constant with respect to a temperature change. The voltage value is corrected to a voltage value corresponding to the temperature detected by the detecting means.

  According to the present invention, the temperature of the liquid stored in the pressure chamber of the inkjet head is detected by the temperature detecting means, and the voltage value adjusted in advance is a droplet discharged from the pressure chamber in response to a temperature change. Since the voltage value is corrected to a voltage value corresponding to the temperature detected by the temperature detection means based on a predetermined temperature-voltage characteristic representing the voltage value of the voltage to be applied in order to keep the discharge speed of the ink constant, More precise landing can be achieved by controlling the variation in the ejection speed of droplets depending on temperature.

In the present invention, a plurality of pressure chambers for discharging droplets are formed by partitioning with a partition made of a piezoelectric material, and the partition is deformed by a shear stress generated by applying an electric field to the partition. A control method of a droplet discharge control device for controlling an inkjet head that discharges droplets by generating energy for discharging droplets in a pressure chamber,
An electric field corresponding to each pressure chamber is individually applied to the partition walls on both sides of the pressure chamber to which the droplets are to be discharged, and no electric field is applied to the partition wall sandwiched between the pressure chambers to which the droplets should not be discharged. A control method of a droplet discharge control device comprising an electric field control means.

  According to the present invention, a plurality of pressure chambers for discharging droplets are formed by partitioning with a partition made of a piezoelectric material, and the partition is deformed by shear stress generated by applying an electric field to the partition, When controlling the ink jet head that generates droplet discharge energy in the pressure chamber and discharges the droplet, the electric field control means separates the partition walls on both sides of the pressure chamber to which the droplet is discharged for each pressure chamber. An electric field corresponding to is applied, and no electric field is applied to the partition wall sandwiched between pressure chambers from which droplets should not be discharged.

  That is, by applying a voltage that does not apply an electric field to a partition wall that is sandwiched between pressure chambers that should not eject droplets, mutual interference that occurs in the partition wall sandwiched between pressure chambers that should not eject droplets is eliminated. Therefore, there is no need to consider mutual interference when adjusting each pressure chamber. Therefore, since it is not necessary to provide dummy pressure chambers, the pressure chamber arrangement density is reduced without reducing the arrangement density of the pressure chambers and without complicating the drive voltage setting or the drive circuit. Variations can be easily corrected.

  According to the present invention, in the head structure in which the partition which is an actuator is shared between the pressure chambers, the mutual voltage generated by adjusting the voltage to be applied to the partition on both sides of the pressure chamber to which droplets are to be discharged is adjusted for each pressure chamber. Since interference can be eliminated, it is not necessary to consider mutual interference when adjusting each pressure chamber, and the adjustment of the characteristics of the droplets discharged for each pressure chamber can be simplified.

  Further, according to the present invention, the polarization direction of the piezoelectric body constituting the partition wall is a direction in which the volume of the pressure chamber expands when a voltage for applying an electric field is applied to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged. Since the ink jet head can be controlled, the present invention can be applied to a cantilever type head structure in which, for example, a piezoelectric material constituting a partition wall, for example, a piezoelectric material has an upward polarization direction and an electrode is formed on the upper half.

  Further, according to the present invention, the polarization direction of the piezoelectric body constituting the partition wall is a direction in which the volume of the pressure chamber is reduced when a voltage for applying an electric field is applied to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged. Since the inkjet head can be controlled, it can be applied to, for example, a cantilever type head structure in which the piezoelectric material constituting the partition wall, for example, a piezoelectric material has a downward polarization direction and an electrode is formed on the upper half.

  In addition, according to the present invention, it is possible to perform correction to reduce the variation in volume of droplets ejected from each pressure chamber, so that it is possible to apply droplets without coating unevenness.

  Further, according to the present invention, it is possible to perform correction to reduce the variation in the ejection speed of the droplets ejected from each pressure chamber, so that the landing position accuracy of the droplets can be improved, and the high-definition medium can be obtained. Discharging becomes possible.

  In addition, according to the present invention, it is possible to apply droplets with less unevenness of application by controlling the correction of variation in droplet volume depending on temperature. Therefore, in addition to correcting variations in the pressure chambers, by correcting fluctuations in the amount of ejected ink due to temperature, it is possible to realize both prevention of coating unevenness and high ink droplet ejection stability.

  In addition, according to the present invention, it is possible to land with higher accuracy by the control in consideration of the variation correction of the droplet discharge speed depending on the temperature. Therefore, in addition to correcting variations in the pressure chambers, it is possible to realize both high ink droplet landing accuracy and high ink droplet discharge stability by correcting fluctuations in the discharge speed due to temperature.

  Further, according to the present invention, in the head structure in which the partition walls serving as actuators are shared between the pressure chambers, the voltage applied to the partition walls on both sides of the pressure chambers from which droplets are to be ejected is generated for each pressure chamber. Since mutual interference can be eliminated, it is not necessary to consider mutual interference when adjusting each pressure chamber, and the adjustment of the characteristics of the droplets ejected for each pressure chamber can be simplified.

  FIG. 1 is a perspective view schematically showing an external configuration of an inkjet apparatus 1 according to an embodiment of the present invention. An ink jet apparatus 1 that is a droplet discharge control apparatus includes a suction plate 2, a main scanning direction driving unit 3, a carriage 4, a sub scanning direction driving unit 5, a maintenance unit 6, and a surface plate 7. The control method of the droplet discharge control apparatus according to the present invention is processed by the ink jet apparatus 1.

  The suction disk 2 sucks and holds, for example, a glass substrate 20 that is a recording medium. The main scanning direction driving means 3 moves the suction disk 2 in the main scanning direction 8. The carriage 4 includes an inkjet head 10 (described later) that performs recording by discharging droplets from nozzles and a liquid storage tank (not shown) that stores liquid to be discharged. The sub scanning direction driving means 5 is a gantry (gate structure) type driving means for moving the carriage 4 in the sub scanning direction 9. The maintenance unit 6 maintains the inkjet head 10 built in the carriage 5. The surface plate 7 holds the main scanning direction driving unit 3, the sub scanning direction driving unit 5, and the maintenance unit 6 on one surface.

  The suction plate 2 is formed with a plurality of holes that open on the surface on which the glass substrate 20 is placed, and a suction device (not shown) that constitutes a suction device (not shown) is formed on the opposite side of the openings of the plurality of holes. Is connected. By the suction operation of the suction device, the glass substrate 20 placed on the suction plate 2 is sucked and held, and the glass substrate 20 moves integrally with the suction plate 2.

  The main scanning direction driving means 3 includes a pair of main scanning direction slide mechanisms 31 provided in parallel on the surface plate 7, a linear servo motor (not shown) built in the main scanning direction slide mechanism 31, and the main scanning direction slide mechanism 31. A linear encoder (not shown) for detecting the position state of the linear servo motor, and a main scanning drive control unit (not shown) for controlling the driving operation of the linear servo motor. Since the main scanning direction driving unit 3 includes a linear encoder, the moving position and moving speed of the suction plate 2, that is, the glass substrate 20, can be detected and controlled with high accuracy. The movement position detection accuracy in the main scanning direction 8 by this linear encoder can be set to a minimum of 1 μm.

  The sub-scanning direction driving means 5 includes a gantry 51 provided so as to straddle the suction plate 2 and the glass substrate 20 perpendicular to the main scanning direction 8, a sub-scanning direction slide mechanism 52 provided on the beam portion 51a of the gantry 51, A linear servo motor (not shown) that moves the carriage 4 engaged with the sub-scanning direction slide mechanism 52 in the sub-scanning direction 9 and a sub-scanning drive control unit (not shown) that controls the driving operation of the linear servo motor are configured. .

  FIG. 2 is a perspective view showing the external appearance of the main components of the inkjet head 10 included in the carriage 4 shown in FIG. 1 before assembly. The ink jet head 10 is a share mode type ink jet head, and a cover plate 12 is placed on the upper surface of a substrate 11 made of a piezoelectric material such as PZT (lead zirconate titanate), and a filter 14 is further provided thereon. And the nozzle plate 13 on which the plurality of nozzles 131 are formed is fixed to the front surface of the substrate 11. The nozzle 131 of the nozzle plate 13 is provided at a position facing each pressure chamber 112 formed on the substrate 11. Each pressure chamber 112 is supplied with a liquid to be discharged from a tank (not shown) via a filter 121 and a hole 121 formed in the cover plate 12.

  FIG. 3 is a perspective view showing an appearance of the substrate 11 shown in FIG. A plurality of groove-shaped pressure chambers 112 are formed in parallel on the upper portion of the substrate 11 with a partition wall 111 interposed therebetween by cutting using a diamond blade or the like. On both surfaces of the partition wall 111 exposed to the pressure chamber 112, metal electrodes 113 are formed on the upper half by sputtering or the like. Each pressure chamber 112 has a shallow groove on the back side, that is, on the side opposite to the side where the nozzle plate 13 is fixed, and the bottom surface of the pressure chamber has a shallow groove. An electrode 113 is formed and connected to the electrode 113 in the same pressure chamber formed in the upper half of the partition wall 111. This bottom surface portion becomes an electrical connection portion with the outside, and is connected to a drive circuit described later by wire bonding or the like. A driving pulse is individually applied to the electrodes 113 of each pressure chamber for each pressure chamber 112 by a driving circuit.

  4 is a cross-sectional view of the inkjet head 10 in which the substrate 11 and the cover plate 13 shown in FIG. 2 are assembled. Each pressure chamber 112 is formed in parallel with the upper part of the substrate 11 between two partition walls 111. The piezoelectric material constituting the substrate 11 is polarized in the thickness direction of the substrate 11, for example, the upward direction in FIG. 4. In each pressure chamber 112, the electrodes 113 are arranged so as to face each other on the upper half of the side surface of the partition wall 111 in the pressure chambers, and these electrodes 113 are formed on the bottom portion where the depth of the groove is shallow. The same drive pulse is applied via the electrode portions connected to these electrodes 113.

  FIG. 5 schematically shows the connection between the electrode 113 and the drive circuit 114 shown in FIG. The drive circuit 114 is a circuit that generates drive pulses, and is a commonly used pulse generation circuit. In FIG. 5, a drive circuit is represented by a symbol representing a drive pulse. The drive circuit 114 is provided for each pressure chamber 112 and is connected to the electrode 113 of each pressure chamber 112. The drive pulse applied to the electrode 113 of each pressure chamber 112 by the drive circuit 114 is a pulse of an individual voltage value adjusted in advance for each pressure chamber 112 or a pulse of a common voltage value adjusted in advance for all pressure chambers. .

  FIG. 6 shows an example of the voltage waveform of the drive pulse generated by the drive circuit 114 shown in FIG. 6A shows the voltage waveform of the first drive pulse P1 generated by the drive circuit 114. FIG. The discharge period is a predetermined period, for example, a period of a period of time from time ts to time te. The first drive pulse P1 is a pulse that changes from 0 V to an individual voltage value adjusted in advance for each pressure chamber at time t1, and changes from the individual voltage value to 0 V at time t2 after the time AL has elapsed. FIG. 6B shows a voltage waveform of the second drive pulse P <b> 2 generated by the drive circuit 114. The second drive pulse P2 is a pulse that changes from 0V to a common voltage value that is adjusted in advance for all the pressure chambers at time t2, and changes from the common voltage value to 0V at time t3 after time 2AL has elapsed. .

  FIG. 7 is a cross-sectional view of the inkjet head 10 for explaining the deformation of the partition walls when the droplets are ejected using the drive pulse shown in FIG. An example in which droplets are ejected from the central pressure chamber 112b by focusing on three consecutive pressure chambers 112a to 112c among the pressure chambers formed on the substrate 11 will be described. In FIG. 7A, no voltage is applied to the electrode of any pressure chamber, and none of the partition walls is deformed.

  FIG. 7B shows a state in which the volume of the pressure chamber 112b is enlarged. The state during the application time AL of the first drive pulse P1 shown in FIG. 6A, that is, the period from time t1 to time t2 when the individual voltage value of the pressure chamber 112b is applied to the electrode 113b of the pressure chamber 112b. It is a state. The partition wall 111b and the partition wall 111c forming the pressure chamber 112b are sheared and deformed in a direction away from each other, and the volume of the pressure chamber 112b is expanded, so that the liquid flows into the pressure chamber 112b.

  FIG. 7C shows a state in which the volume of the pressure chamber 112b is reduced. In the state of the application time 2AL of the second drive pulse P2 shown in FIG. 6B, the time t2 to the time t3 when the common voltage value is applied to the electrode 113a of the pressure chamber 112a and the electrode 113c of the pressure chamber 112c. It is the state of the period until. The partition wall 111b and the partition wall 111c forming the pressure chamber 112b are sheared and deformed in a direction approaching each other, and the volume of the pressure chamber 112b is reduced, whereby the liquid in the pressure chamber 112b is discharged as a droplet from the nozzle.

  At this time, the application time AL of the first drive pulse P1 is a time until the pressure wave caused by the liquid flowing into the pressure chamber 112b whose volume has expanded propagates through the entire pressure chamber 112b and reaches the nozzle. The application time AL is obtained by dividing the length of the pressure chamber 112b, that is, the length from the ink inlet to the nozzle by the speed of sound in the liquid. By setting the application time AL of the first drive pulse P1 in this way, the pressure wave generated by the inflow of the liquid can be efficiently used for discharging the droplet. The application time 2AL of the second drive pulse P2 is a time for the pressure wave generated when the volume of the pressure chamber 112b is reduced to propagate back and forth in the pressure chamber 112b. By setting the application time 2AL of the second drive pulse P2 in this way, the residual vibration after droplet ejection can be efficiently canceled by the negative pressure when the contracted pressure chamber 112b is restored. Furthermore, the rising timing of the second driving pulse P2 is made coincident with the falling timing of the first driving pulse P1, so that the pressure wave generated when the pressure chamber 112b contracts is efficiently used for discharging the droplets. I am doing so.

  As described above, the pressure wave due to the shear deformation in the expansion direction generated in the partition 111 due to the rise of the first drive pulse P1, the reduction direction generated in the partition 111 due to the fall of the first drive pulse P1 and the rise of the second drive pulse P2. The liquid droplets in the pressure chamber 112 are discharged by the sum of the pressure wave caused by the shear deformation.

  FIG. 8 shows an example of a time chart when the drive pulse shown in FIG. 6 is applied to nine adjacent pressure chambers. FIG. 9 schematically shows a change state of the partition to which the drive pulse shown in FIG. 8 is applied. FIG. 8 is also a time chart showing a method for controlling the inkjet apparatus 1 according to another embodiment of the present invention. This shows a case where nine pressure chambers Ch1 to Ch9 arranged in parallel are divided into two groups and driven. That is, the case where the three-phase driving is performed by dividing into an A-phase group, a B-phase group, and a C-phase group is shown for three ejection periods. The pressure chambers Ch1, Ch4 and Ch7 belong to the A phase group, the pressure chambers Ch2, Ch5 and Ch8 belong to the B phase group, and the pressure chambers Ch3, Ch6 and Ch9 belong to the C phase group. belong to.

  In the example shown in FIGS. 8 and 9, first, the pressure chambers belonging to the B phase group perform the discharge operation, then the pressure chambers belonging to the A phase group perform the discharge operation, and finally belong to the C phase group. The pressure chamber performs the discharge operation. The state shown in FIG. 9A is a state at time t0, and each pressure chamber is in an initial state. The states shown in FIGS. 9B to 9D are states at time tB, time tA, and time tC, respectively, and pressure chambers belonging to the B phase group, pressure chambers belonging to the A phase group, In addition, the pressure chambers belonging to the C phase group are contracted.

  In the discharge operation, after the voltage of the individual voltage value of the first drive pulse P1 adjusted individually for each pressure chamber is applied to the pressure chamber for discharging the droplets, the pressure chambers on both sides of the pressure chamber for discharging the droplets A voltage having a common voltage value of the second drive pulse P2 common to the pressure chambers is applied. When the voltage of the individual voltage value of the first drive pulse P1 is applied to the pressure chamber that ejects the droplet, the volume of the pressure chamber that ejects the droplet expands, and the pressure chambers on both sides of the pressure chamber that ejects the droplet When the voltage of the common voltage value of the second drive pulse P2 is applied to the second chamber, the volume of the pressure chamber that ejects the droplet is reduced.

  FIG. 8 shows drive pulse waveforms in which the individual voltage values of the pressure chambers Ch1 to Ch9 are Vch1 to Vch9 and the common voltage value is Vcom, respectively. For example, first, in order to discharge droplets from the pressure chambers Ch2, Ch5, and Ch8 belonging to the B phase group, the individual voltage value Vch2 in the pressure chamber Ch2, the individual voltage value Vch5 in the pressure chamber Ch5, and the individual voltage in the pressure chamber Ch8. After the value Vch8 is applied, the pressure chamber Ch1 and the pressure chamber Ch3 on both sides of the pressure chamber Ch2, the pressure chamber Ch4 and the pressure chamber Ch6 on both sides of the pressure chamber Ch5, and the pressure chamber Ch7 and the pressure chamber Ch9 on both sides of the pressure chamber Ch8. Is applied with a common voltage value Vcom.

  Next, in order to discharge droplets from the pressure chambers Ch1, Ch4, and Ch7 belonging to the A phase group, the individual voltage value Vch1 is stored in the pressure chamber Ch1, the individual voltage value Vch4 is stored in the pressure chamber Ch4, and the individual voltage is stored in the pressure chamber Ch6. After the value Vch6 is applied, the pressure chamber Ch2 adjacent to the pressure chamber Ch1, the pressure chamber Ch3 and pressure chamber Ch5 adjacent to the pressure chamber Ch4, the pressure chamber Ch6 and pressure chamber Ch8 adjacent to the pressure chamber Ch7, and the pressure chamber Ch9. Is applied with a common voltage value Vcom.

  Further, in order to discharge droplets from the pressure chambers Ch3, Ch6, and Ch9 belonging to the C phase group, the individual voltage value Vch3 is stored in the pressure chamber Ch3, the individual voltage value Vch6 is stored in the pressure chamber Ch6, and the individual voltage value is stored in the pressure chamber Ch9. After Vch9 is applied, the pressure chamber Ch2 and the pressure chamber Ch4 adjacent to the pressure chamber Ch3, the pressure chamber Ch5 and the pressure chamber Ch7 adjacent to the pressure chamber Ch6, the pressure chamber Ch8 adjacent to the pressure chamber Ch9, and the pressure chamber Ch1 are applied. A common voltage value Vcom is applied.

  In this way, the individual voltage value applied to the pressure chamber electrodes for discharging droplets can be adjusted and applied for each pressure chamber, so according to the voltage value applied to each pressure chamber electrode, The ejection characteristics, for example, the volume of the ejected droplets or the ejection speed can be adjusted. At this time, the volume or discharge speed of the discharged droplet is determined by the individual voltage value adjusted for each pressure chamber discharging the droplet and the common voltage value adjusted for all the pressure chambers. It is not affected by the individual voltage value set in the pressure chamber adjacent to the pressure chamber to be discharged. That is, the voltage of each pressure chamber can be adjusted without receiving mutual interference.

  Furthermore, between pressure chambers that do not discharge droplets, for example, in the case of three-phase driving, formed on both surfaces of the partition wall between two pressure chambers between two adjacent pressure chambers among the pressure chambers that simultaneously discharge droplets Since the potentials of the formed electrodes are the same, the partition between the pressure chambers is not deformed. Therefore, when the pressure chambers do not have the same potential, it is possible to eliminate the instability of droplet discharge due to an extra pressure wave that may have been caused by the deformation of the partition wall. In addition, the power that would have been required for the deformation of the partition wall that does not contribute to the discharge of the droplets is not consumed.

  FIG. 10 shows an example of a time chart when a driving pulse according to the prior art is applied to nine adjacent pressure chambers. In the example shown in FIG. 8, the drive pulse having the common voltage value common to the pressure chambers is applied to the pressure chambers adjacent to the pressure chambers for discharging the droplets. In the example shown in FIG. Instead of a value driving pulse, a driving pulse of an individual voltage value of each pressure chamber is applied.

  FIG. 11 schematically shows a change state of the partition walls to which the drive pulse shown in FIG. 10 is applied. The state shown in FIG. 11A is a state at time t0, and each pressure chamber is in an initial state. The states shown in FIGS. 11B to 11D are states at time tB, time tA, and time tC, respectively, and pressure chambers belonging to the B phase group, pressure chambers belonging to the A phase group, In addition, the pressure chambers belonging to the C phase group are contracted.

  However, for example, at time tB, the partition wall 111a that separates the pressure chamber Ch3 and the pressure chamber Ch4 that has not been deformed in FIG. 9B, and the partition wall 111b that partitions the pressure chamber Ch6 and the pressure chamber Ch7 are shown in FIG. ) Is deformed. This occurs because the voltage value applied to the electrodes of these pressure chambers is not the common voltage value but the individual voltage value of each pressure chamber at time tB. That is, since a potential difference is generated in the voltage applied to the electrodes on both sides of the partition wall 111a, that is, the voltage Vch3 is applied to the electrode of the pressure chamber Ch3 and the voltage Vch4 is applied to the electrode of the pressure chamber Ch4. Since the potential difference of the difference from the voltage Vch4 is generated, the partition wall 111a is deformed. Similarly, since a potential difference is generated in the voltage applied to the electrodes on both sides of the partition wall 111b, the partition wall 111b is deformed. Further, in FIG. 11C, the partition wall 111c that partitions the pressure chamber Ch2 and the pressure chamber Ch3, the partition wall 111d that partitions the pressure chamber Ch5 and the pressure chamber Ch6, and the partition wall 111e that partitions the pressure chamber Ch8 and the pressure chamber Ch9 are deformed. is doing. In FIG. 11D, the partition 111f that partitions the pressure chamber Ch4 and the pressure chamber Ch5 and the partition 111g that partitions the pressure chamber Ch7 and the pressure chamber Ch8 are deformed.

  In the example shown in FIGS. 10 and 11, although the individual voltage value of the drive pulse is adjusted for each pressure chamber for the purpose of adjusting the volume or the discharge speed of the droplets discharged from each pressure chamber, the common voltage Value drive pulse is not used. In the example shown in FIG. 10 and FIG. 11, in order to expand the volume of the pressure chamber that ejects droplets, a voltage having an individual voltage value adjusted for the pressure chamber is applied to the pressure chamber that ejects droplets. In order to reduce the volume of the pressure chamber that ejects droplets, the individual voltage values adjusted for the respective pressure chambers are applied to the pressure chambers adjacent to the pressure chamber that ejects droplets. That is, the individual voltage value adjusted for each pressure chamber is not only used for expanding each pressure chamber, but also used for reducing adjacent pressure chambers. However, the droplet discharge characteristics are affected by the individual voltage value applied to the pressure chamber for discharging the droplet and the individual voltage values applied to the pressure chambers adjacent to the pressure chamber for discharging the droplet. The Therefore, in order to finally adjust the ejection characteristics, for example, the volume of the ejected droplets or the ejection speed, the operation of determining the individual voltage value of each pressure chamber becomes very complicated.

  Further, at time tB, time tA, and time tC, between the pressure chambers that do not discharge droplets, for example, in the case of three-phase driving, between two adjacent pressure chambers among the pressure chambers that simultaneously discharge droplets. Since the potentials of the electrodes formed on both surfaces of the partition wall between the two pressure chambers are not necessarily the same potential, the partition wall between the pressure chambers may be deformed. Therefore, an excessive pressure wave generated by the deformation of the partition wall may impair stable droplet discharge. In addition, power required for deformation of the partition wall that does not contribute to droplet discharge is consumed.

  In the embodiment described above, the polarization direction of the piezoelectric material forming the partition walls is one direction, for example, the upward direction in the example shown in FIG. 4, and the cantilever type head structure is provided with electrodes on the upper half of the partition wall side surfaces. However, the present invention is not limited to this, and the polarization direction of the piezoelectric material is reversed, and the voltage of the common voltage value of the second drive pulse P2 is applied to the pressure chambers on both sides of the pressure chamber that discharges the droplets. Thereafter, the voltage of the individual voltage value of the first drive pulse P1 may be applied to the pressure chamber that ejects the droplet.

  Alternatively, it may be a chevron type head structure in which the polarization direction of the piezoelectric material forming the partition wall is substantially opposed to or opposite to the center of the partition wall height, and electrodes are provided on the entire surface in the height direction of the partition wall.

  Furthermore, in the above-described embodiment, the pressure chamber is divided into three groups every two groups and driven, that is, in the case of three-phase driving, an arbitrary value of three or more natural numbers is shown. May be divided into n (n + 1) groups and driven.

  FIG. 12 schematically shows the state of the partition walls to which the three-phase drive pulses shown in FIG. 8 are applied. That is, the partition of “electric field = 0” in the case of driving by dividing the pressure chamber into every third group, that is, in the case of three-phase driving, is shown at time tB shown in FIG. In FIG. 12, the partition 111e and the partition 111f are partitions with “electric field = 0”. A common voltage value Vcom is applied to the electrodes of the pressure chamber Ch3 and the pressure chamber Ch4 so as not to apply an electric field to the partition wall sandwiched between the pressure chambers that do not discharge droplets, for example, the partition wall 111e sandwiched between the pressure chamber Ch3 and the pressure chamber Ch4. To do. Therefore, a voltage having a potential difference of 0 V is applied to the partition wall 111e, and no electric field is applied. The same applies to the partition 111f sandwiched between the pressure chamber Ch6 and the pressure chamber Ch7.

  FIG. 13 schematically shows a state of the partition wall to which a four-phase driving pulse is applied instead of the three-phase driving pulse shown in FIG. That is, the partition wall of “electric field = 0” in the case where the pressure chamber is driven by being divided into four groups every three groups, that is, in the case of four-phase driving is shown. In FIG. 13, the partition 111g, the partition 111h, the partition 111j, and the partition 111k are partitions with “electric field = 0”. A common voltage is applied to the electrodes of the pressure chamber Ch3 to the pressure chamber Ch5 so as not to apply an electric field to the partition wall sandwiched between the pressure chambers that do not discharge droplets, for example, the partition wall 111g sandwiched between the pressure chamber Ch3 to the pressure chamber Ch5. Apply the value Vcom. Accordingly, a voltage having a potential difference of 0 V is applied to the partition 111g and the partition 111h, and no electric field is applied. The same applies to the partition 111j and the partition 111k sandwiched between the pressure chambers Ch7 to Ch9. In addition, even in the case of five-phase driving or more, an electric field is applied to the partition wall sandwiched between the pressure chambers that do not discharge droplets, even for a driving method for any number of partition walls sandwiched between pressure chambers that do not discharge droplets. In order to prevent this, the common voltage value Vcom is applied to the electrode of the pressure chamber that does not eject droplets.

  The common voltage value Vcom applied to the electrodes so as not to apply an electric field is the voltage value of the second drive pulse for returning the original volume after reducing the volume of the pressure chamber that discharges the droplet, or the droplet This is the voltage value of the second drive pulse for returning the original volume after expanding the volume of the pressure chamber to be discharged. When the common voltage value Vcom is higher than the individual voltage value Vch, that is, when Vcom> Vch, when the common voltage value Vcom is lower than the individual voltage value Vch, that is, when Vcom <Vch, and when the common voltage value Vcom is the individual voltage In the case where the value Vch is not the same, that is, in any case where Vcom ≠ Vch, a potential sufficient to restore the original volume after reducing or expanding the volume of the pressure chamber for discharging the droplets Since the timings for driving the pressure all coincide with each other, the vibration modes of the pressure waves generated in the respective pressure chambers are the same and can be driven in the same manner.

  FIG. 14 shows a temperature-voltage characteristic that keeps the droplet discharge speed constant with respect to temperature change for a viscosity of 7 cp (centipoise). The graph of the temperature-voltage characteristic shown in FIG. 14 shows the voltage to be applied to the electrode 113 shown in FIG. 4 in order to keep the droplet discharge speed constant even when the temperature of the droplet changes. Measured at a viscosity of 7 cp for 7.5 m / s, 8.0 m / s, and 8.5 m / s. For example, it is reduced to about 28 V at a temperature of 5 ° C., about 20 V at a temperature of 15 ° C., about 17 V at a temperature of 25 ° C., and about 15 V at a temperature of 35 ° C. Table 1 shows the voltage to be applied in order to keep the droplet discharge speed constant even when the temperature of the droplet changes, the droplet discharge speeds 7.5 m / s, 8.0 m / s, and 8.5 m. The data measured about / s is shown, and is the original data of the graph shown in FIG.

  FIG. 15 shows a temperature-voltage characteristic for a viscosity of 4 cp that keeps the droplet discharge speed constant with respect to a temperature change. The graph of the temperature-voltage characteristic shown in FIG. 15 shows the voltage to be applied to the electrode 113 shown in FIG. 4 in order to keep the droplet discharge speed constant even when the temperature of the droplet changes. It is measured at a viscosity of 4 cp for 7.5 m / s, 8.0 m / s, and 8.5 m / s. For example, it is reduced to about 18 V at a temperature of 5 ° C., about 16 V at a temperature of 15 ° C., about 15 V at a temperature of 25 ° C., and about 13 V at a temperature of 35 ° C. Table 2 shows the voltage to be applied to keep the droplet discharge speed constant even when the temperature of the droplet changes, the droplet discharge speeds 7.5 m / s, 8.0 m / s, and 8.5 m. The data measured about / s is shown, and is the original data of the graph shown in FIG.

  The ink jet device 1 includes a temperature detection device such as a thermistor (not shown), and can detect the temperature of the liquid supplied from the tank to the pressure chamber. The drive circuit 114 changes the voltage applied to the electrode 113 according to the temperature detected by the temperature detection device based on the measurement data shown in FIG. 14 or FIG. To compensate for fluctuations. The variation in droplet discharge speed in each pressure chamber is thought to be due to variations in processing accuracy in each pressure chamber, and the degree of variation in droplet discharge speed between the pressure chambers is constant even when the temperature changes. It is considered that Therefore, the voltage of the first drive pulse determined by the individual voltage value for each pressure chamber corresponding to the temperature of the liquid supplied to the pressure chamber is applied while keeping the difference in variation in droplet velocity for each pressure chamber constant. This makes it possible to land with high accuracy. Further, by using the driving voltage data with respect to the temperature corresponding to the viscosity condition of the liquid to be used, that is, the ink, for example, the temperature voltage characteristic data shown in FIGS. It becomes possible.

  14 and FIG. 15 was measured by changing the temperature of the voltage applied to the electrode 113 shown in FIG. 4 in order to keep the droplet discharge speed constant with respect to the temperature change. Although it is data, similarly, the voltage applied to the electrode 113 in order to keep the volume of the ejected droplet constant with respect to the temperature change is measured by changing the temperature. Then, by controlling the voltage applied to the electrode 113 based on the measurement data, it is possible to correct the change in the volume of the droplet accompanying the temperature change. That is, the variation in the volume of droplets discharged from each pressure chamber is considered to be due to the variation in processing accuracy of each pressure chamber, and the degree of variation in the volume of droplets between the pressure chambers varies with temperature. However, it is thought that it is held constant. Therefore, the voltage of the first drive pulse determined by the individual voltage value for each pressure chamber corresponding to the temperature of the liquid supplied to the pressure chamber is applied while keeping the difference in the volume variation of the droplets for each pressure chamber constant. By doing so, it is possible to apply droplets without application unevenness.

  In this way, for example, the pressure chamber 112 which is a plurality of pressure chambers for discharging droplets is formed by partitioning with the partition wall 111 which is a piezoelectric material, for example, a partition made of a piezoelectric material, and an electric field is applied to the partition wall. In controlling the inkjet head 10, for example, an electric field control means for controlling the inkjet head 10, which is an inkjet head that deforms the partition wall by the shear stress generated by the application and generates energy in the pressure chamber to eject the droplet. For example, the drive circuit 114 applies an electric field individually corresponding to each pressure chamber to the partition walls on both sides of the pressure chamber to which droplets are to be discharged, and the partition walls sandwiched between the pressure chambers to which droplets are not to be discharged. No electric field is applied.

  That is, by applying a voltage that does not apply an electric field to a partition wall that is sandwiched between pressure chambers that should not eject droplets, mutual interference that occurs in the partition wall sandwiched between pressure chambers that should not eject droplets is eliminated. Therefore, there is no need to consider mutual interference when adjusting each pressure chamber. Therefore, since it is not necessary to provide dummy pressure chambers, the pressure chamber arrangement density is reduced without reducing the arrangement density of the pressure chambers and without complicating the drive voltage setting or the drive circuit. Variations can be easily corrected. In other words, in the head structure in which the partition walls, which are actuators, are shared between the pressure chambers, the mutual interference caused by adjusting the voltage applied to the partition walls on both sides of the pressure chambers from which droplets are to be discharged is eliminated. Therefore, it is not necessary to consider mutual interference when adjusting each pressure chamber, and the adjustment of the characteristics of the droplets discharged for each pressure chamber can be simplified.

  Furthermore, after an electric field for expanding the volume of the pressure chamber is applied to the partition walls on both sides of the pressure chamber to which droplets are to be discharged by the electric field control means voltage, an electric field for subsequently reducing the volume of the pressure chamber is applied. Therefore, the polarization direction of the piezoelectric body constituting the partition wall is the direction in which the volume of the pressure chamber expands when a voltage for applying an electric field is applied to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged. The head can be controlled. Therefore, for example, the present invention can be applied to a cantilever type head structure in which the polarization direction of a piezoelectric body, for example, a piezoelectric material constituting a partition wall is upward and an electrode is formed on the upper half.

  Furthermore, after the electric field control means applies an electric field for reducing the volume of the pressure chamber to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged, an electric field for subsequently expanding the volume of the pressure chamber. Therefore, the polarization direction of the piezoelectric body constituting the partition wall is a direction in which the volume of the pressure chamber is reduced when a voltage for applying an electric field is applied to the partition walls on both sides of the pressure chamber to which the droplet is to be discharged. The head can be controlled. Therefore, for example, the present invention can be applied to a cantilever type head structure in which the polarization direction of a piezoelectric body, for example, a piezoelectric material that constitutes a partition wall is a downward direction and an electrode is formed on the upper half.

  Further, an electric field is applied by applying a voltage by the electric field control means, and the voltage value of the applied voltage is a pressure chamber so as to reduce variations in the volume of droplets ejected from each pressure chamber. Since the adjustment is performed every time, it is possible to perform correction to reduce the variation in the volume of the droplets discharged from each pressure chamber. Accordingly, it is possible to apply droplets without application unevenness.

  Furthermore, an electric field is applied by applying a voltage by the electric field control means, and the voltage value of the applied voltage is such that variations in the discharge speed of the droplets discharged from each pressure chamber are reduced. Since adjustment is performed in advance for each pressure chamber, it is possible to perform correction to reduce variation in the ejection speed of the droplets ejected from each pressure chamber. Accordingly, it is possible to improve the landing position accuracy of the droplets, and it is possible to discharge onto a high-definition medium.

  Furthermore, the temperature of the liquid stored in the pressure chamber of the ink jet head is detected by the temperature detecting means, and the voltage value adjusted in advance maintains the volume of the liquid droplets ejected from the pressure chamber with respect to the temperature change. Since the voltage value is corrected to a voltage value corresponding to the temperature detected by the temperature detecting means based on a predetermined temperature voltage characteristic representing the voltage value of the voltage to be applied to maintain the voltage, The liquid droplet application without application unevenness can be performed by the control in consideration of the volume variation correction. Therefore, in addition to correcting variations in the pressure chambers, by correcting fluctuations in the amount of ejected ink due to temperature, it is possible to realize both prevention of coating unevenness and high ink droplet ejection stability.

  Furthermore, the temperature detection means detects the temperature of the liquid stored in the pressure chamber of the inkjet head, and the voltage value adjusted in advance is the discharge speed of the liquid droplets discharged from the pressure chamber in response to a temperature change. Since the voltage value is corrected to a voltage value corresponding to the temperature detected by the temperature detecting means based on a predetermined temperature-voltage characteristic representing the voltage value of the voltage to be applied in order to keep the voltage constant, More precise landing can be achieved by controlling the dispersion of the droplet discharge speed. Therefore, in addition to correcting variations in the pressure chambers, it is possible to realize both high ink droplet landing accuracy and high ink droplet discharge stability by correcting fluctuations in the discharge speed due to temperature.

  Furthermore, a plurality of pressure chambers for ejecting droplets are formed by partitioning with partition walls made of piezoelectric material, and the partition walls are deformed by shear stress generated by applying an electric field to the partition walls, and the droplets are ejected. In controlling the inkjet head that discharges droplets by generating energy in the pressure chambers, the electric field control means uses the electric field control means to separate the electric fields corresponding to each pressure chamber in the partition walls on both sides of the pressure chambers. And an electric field is not applied to the partition wall sandwiched between the pressure chambers from which droplets should not be discharged.

  That is, by applying a voltage that does not apply an electric field to a partition wall that is sandwiched between pressure chambers that should not eject droplets, mutual interference that occurs in the partition wall sandwiched between pressure chambers that should not eject droplets is eliminated. Therefore, there is no need to consider mutual interference when adjusting each pressure chamber. Therefore, since it is not necessary to provide dummy pressure chambers, the pressure chamber arrangement density is reduced without reducing the arrangement density of the pressure chambers and without complicating the drive voltage setting or the drive circuit. Variations can be easily corrected. In other words, in the head structure in which the partition walls, which are actuators, are shared between the pressure chambers, the mutual interference caused by adjusting the voltage applied to the partition walls on both sides of the pressure chambers from which droplets are to be discharged is eliminated. Therefore, it is not necessary to consider mutual interference when adjusting each pressure chamber, and the adjustment of the characteristics of the droplets discharged for each pressure chamber can be simplified.

1 is a perspective view schematically showing an external configuration of an inkjet apparatus 1 according to an embodiment of the present invention. FIG. 2 is a perspective view showing an external appearance of main components of an inkjet head 10 included in the carriage 4 shown in FIG. 1 before assembly. It is a perspective view which shows the external appearance of the board | substrate 11 shown in FIG. FIG. 3 is a cross-sectional view of an inkjet head 10 in which a substrate 11 and a cover plate 13 shown in FIG. 2 are assembled. A connection between the electrode 113 and the drive circuit 114 shown in FIG. 4 is schematically shown. 6 shows an example of a voltage waveform of a drive pulse generated by the drive circuit 114 shown in FIG. It is sectional drawing of the inkjet head 10 for demonstrating a deformation | transformation of the partition at the time of discharging a droplet using the drive pulse shown in FIG. An example of the time chart in the case of applying the drive pulse shown in FIG. 6 to nine adjacent pressure chambers is shown. The state of the change of the partition to which the drive pulse shown in FIG. 8 is applied is schematically shown. An example of the time chart in the case of applying the drive pulse by a prior art to nine adjacent pressure chambers is shown. The state of the change of the partition to which the drive pulse shown in FIG. 10 is applied is schematically shown. FIG. 9 schematically shows the state of the partition walls to which the three-phase drive pulse shown in FIG. 8 is applied. FIG. 9 schematically shows a state of a partition wall to which a four-phase drive pulse is applied instead of the three-phase drive pulse shown in FIG. 8. A temperature-voltage characteristic for keeping the droplet discharge speed constant with respect to temperature change is shown for a viscosity of 7 cp. A temperature voltage characteristic for keeping the droplet discharge speed constant with respect to a temperature change is shown for a viscosity of 4 cp.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inkjet apparatus 2 Suction board 3 Main scanning direction drive means 4 Carriage 5 Sub scanning direction drive means 6 Maintenance part 7 Surface plate 10 Inkjet head 11 Substrate 12 Cover plate 13 Nozzle plate 14 Filter 20 Glass substrate 31 Main scanning direction slide mechanism 51 Gantry 52 Sub-scanning direction sliding mechanism 111 Bulkhead 112 Pressure chamber 113 Electrode 114 Drive circuit

Claims (8)

By partitioning with a partition made of piezoelectric material, a plurality of pressure chambers are formed to eject droplets, and the partition walls are deformed by the shear stress generated by applying an electric field to the partition, and the energy for ejecting the droplets Is a droplet discharge control device that controls an inkjet head that generates droplets in a pressure chamber and discharges droplets,
An electric field corresponding to each pressure chamber is individually applied to the partition walls on both sides of the pressure chamber to which the droplets are to be discharged, and no electric field is applied to the partition wall sandwiched between the pressure chambers to which the droplets should not be discharged. A droplet discharge control device comprising an electric field control means.   The electric field control means applies an electric field that expands the volume of the pressure chamber to the partition walls on both sides of the pressure chamber to which droplets are to be discharged, and then applies an electric field that reduces the volume of the pressure chamber. The droplet discharge control device according to claim 1.   The electric field control means applies an electric field for reducing the volume of the pressure chamber to the partition walls on both sides of the pressure chamber to which the liquid droplets are to be discharged, and subsequently applies an electric field for expanding the volume of the pressure chamber. The droplet discharge control device according to claim 1.   The electric field control means applies an electric field by applying a voltage, and the voltage value of the applied voltage is adjusted in advance for each pressure chamber so as to reduce variations in the volume of droplets discharged from each pressure chamber. The droplet discharge control device according to any one of claims 1 to 3, wherein   The electric field control means applies an electric field by applying a voltage, and the voltage value of the applied voltage is previously set for each pressure chamber so as to reduce variations in the discharge speed of droplets discharged from each pressure chamber. The droplet discharge control device according to claim 1, wherein the droplet discharge control device is adjusted. Temperature detecting means for detecting the temperature of the liquid stored in the pressure chamber of the inkjet head,
The previously adjusted voltage value is a temperature detection based on a predetermined temperature voltage characteristic representing a voltage value of a voltage to be applied in order to keep the volume of a droplet discharged from the pressure chamber constant with respect to a temperature change. The droplet discharge control device according to claim 4, wherein the droplet discharge control device is a voltage value corrected to a voltage value corresponding to the temperature detected by the means. Temperature detecting means for detecting the temperature of the liquid stored in the pressure chamber of the inkjet head,
The voltage value to be adjusted in advance is based on a predetermined temperature-voltage characteristic indicating a voltage value of a voltage to be applied in order to keep a discharge speed of a droplet discharged from the pressure chamber constant with respect to a temperature change. 6. The droplet discharge control apparatus according to claim 5, wherein the droplet discharge control device is a voltage value corrected to a voltage value corresponding to the temperature detected by the detection means. By partitioning with a partition made of piezoelectric material, a plurality of pressure chambers are formed to eject droplets, and the partition walls are deformed by the shear stress generated by applying an electric field to the partition, and the energy for ejecting the droplets Is a control method of a droplet discharge control device for controlling an inkjet head that generates droplets in a pressure chamber and discharges droplets,
An electric field corresponding to each pressure chamber is individually applied to the partition walls on both sides of the pressure chamber to which the droplets are to be discharged, and no electric field is applied to the partition wall sandwiched between the pressure chambers to which the droplets should not be discharged. A control method for a droplet discharge control device, comprising an electric field control means.

Images