JP2001334657A - Method for driving ink jet head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for driving an ink jet head improved to suppress variation in the ink drop ejection among ink channels. SOLUTION: Depending on the depth of electrode different from ink channel to ink channel, a drive voltage being applied to each channel is varied continuously or the drive waveform is varied continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to a method for driving an ink jet head, and more particularly, to a method in which an electrode is provided in an ink channel, and pressure oscillation is generated in the ink channel to discharge ink. The present invention relates to a method of driving an ink jet head of a discharge type.

[0002]

2. Description of the Related Art In recent years, non-impact printing apparatuses such as an ink jet system suitable for colorization and multi-gradation have rapidly spread in place of impact printing apparatuses. Above all, drop-on printing that discharges the necessary ink only during printing
The demand type is attracting attention because it is advantageous for high printing efficiency, low cost, and low running cost, and the Kaiser method using a piezoelectric element and the thermal jet method are mainly used.

[0003] However, the Kaiser method has a drawback that it is difficult to reduce the size and is not suitable for high density. Although the thermal jet method is suitable for high density, heating the heater generates bubbles (bubbles) in the ink and uses the energy of the bubbles for ejection. Demands are severe, it is difficult to extend the life of the heater, and there is a problem that power consumption is also increased.

In order to solve such a drawback, an ink jet system using a shear mode of a piezoelectric material has been proposed. In this method, an electric field is applied in a direction perpendicular to the polarization direction of the piezoelectric material by applying a voltage to an electrode formed on an ink channel wall made of a piezoelectric material, and the channel wall is deformed in a shear mode, which occurs at that time. Ink droplets are ejected using pressure wave fluctuation, and are suitable for increasing the density of nozzles, reducing power consumption, and increasing driving frequency.

[0005] The structure of the ink jet head utilizing the shear mode will be described with reference to FIG.

The ink jet head comprises a base member 1 in which a plurality of grooves 4 are formed in a piezoelectric body subjected to a vertical polarization process in FIG. 12, an ink supply port 21 and a common ink chamber 22.
The ink channel 4 is formed by bonding the cover member 2 on which the nozzle holes 9 are formed and the nozzle plate 9 on which the nozzle holes 0 are formed.
Are formed. An electrode 5 for applying an electric field is formed in the upper half of the channel wall 3.

The rear end of the ink channel is formed into an R shape corresponding to the diameter of a dicing blade used for forming a groove, and a shallow groove 6 is provided at 6 as an electrode lead-out portion for supplying electricity to the outside. It is also processed by a dicing blade. The electrode formed in the shallow groove 6 is connected to an external electrode 8 such as a flexible substrate at the rear end of the shallow groove 6 by wire bonding 7.

Next, a method of manufacturing the ink jet head shown in FIG. 12 will be described with reference to FIG.

As shown in FIG. 13A, a dry resist film 11 that can be diced is laminated on a piezoelectric body 12 that has been subjected to a polarization process in the vertical direction.

Next, as shown in FIG. 13B, a groove serving as an ink channel 4 and a shallow groove 6 are processed by a dicing blade. Thereafter, the incident direction is set so that the metal serving as the electrode adheres only to the upper half of the channel wall 3, and oblique deposition is performed from the A direction and the B direction in FIG. 13B. Thereafter, by lifting off the dry resist film 11, the base member 1 as an actuator having the metal film 5 formed in the upper half of the channel wall 3 and the shallow groove 6 as shown in FIG.

The cover member 2 is formed by machining or sandblasting with the ink supply port 21 and the common ink chamber 2.
2 are provided. When performing sandblasting,
It may be applied after masking the portions other than the ink supply port 21 and the common ink chamber 22 with a resist film or a metal mask.

When the nozzle plate 9 is made of a polymer material, a nozzle hole of a predetermined size is formed by excimer laser processing. However, even if a metal material is provided with the nozzle hole by punching or the like. Good. The base member 1, the cover member 2, and the nozzle plate 9 manufactured as described above are respectively bonded to desired positions with an adhesive.

In the ink jet head thus manufactured, the ink supply port 21 is connected to an external ink storage tank (not shown), and ink is supplied to each of the plurality of ink channels 4 via the common ink chamber 22. You.
The electrodes provided in the upper half of the channel wall 3 are connected to the inside of one ink channel 4 at the R-shaped portion at the rear end of the ink channel so as to have the same potential, and are connected to the outside via the shallow groove 6. Connected to electrode 8. The electrodes formed in the respective ink channels 4 are independently connected to the external electrodes 8.

A predetermined ink channel is selected according to print data, and a voltage is applied from an external electrode 8 so that an electric field is applied in a direction perpendicular to the polarization direction of the channel wall 3. The channel wall 3 to which the electric field is applied undergoes shear deformation, and as a result, a pressure wave fluctuation occurs in the ink channel, and an ink droplet is ejected from the nozzle hole 10. In addition,
In FIG. 12, although the electrode lead-out portion and the external electrode are connected by wire bonding 7, the anisotropic conductive film (AC
The connection method using F) has also been conventionally employed.

[0015]

In a conventional ink jet head, a vertically polarized piezoelectric body 12 is used as a base member as an actuator. In order to deform the channel wall in a shearing mode, the channel wall is deformed. The electrode 5 was formed on the upper half.

On the other hand, there is also a so-called chevron type structure in which a base material as an actuator is a composite material in which piezoelectric materials having different polarization directions in the vertical direction are stacked at a position half the height of the channel wall. It has been conventionally proposed. In this case, since the electrode may be formed on the entire surface of the channel wall, it is not necessary to limit the electrode formation position to the upper half of the channel wall, and an electroless plating method or the like can be used as a method for forming the electrode. However, there is a problem that the manufacturing cost of the base member as the actuator increases.

Therefore, at present, a method of using a single piezoelectric body which has been subjected to a polarization treatment in a vertical direction as a base member has become the mainstream, and an electrode is formed on only an upper half of a channel wall by oblique evaporation. Is formed.

A conventional method for forming an electrode will be described in detail with reference to FIG. In order to form an electrode film on the upper half of the channel wall 3, an oblique evaporation method is generally used, and evaporation is performed twice while changing the incident direction of evaporation particles.

FIG. 14A shows the state of the first evaporation, in which the channel wall has a height of 300 μm and a width of 80 μm.
When the height of the dry resist film is 30 μm and the height of the dry resist film is 30 μm, vapor-deposited particles are incident at an incident angle of 66 ° with respect to the normal in order to form an electrode on the upper left half of the channel wall 3.

Next, FIG. 14B shows the state of the second vapor deposition. In order to form an electrode on the upper right half of the channel wall 3, the incident angle is also 66 ° with respect to the normal line. Inject vapor deposition particles.

Thereafter, the metal film formed on the dry resist 11 is lifted off together with the dry resist 11, thereby forming the channel wall 3 as shown in FIG.
Base member 1 having electrode 5 formed only on the upper half side wall
Is prepared. Thus, the depth of the electrode formed on the channel wall 3 is formed to be half the channel depth.

Japanese Patent Application Laid-Open No. Hei 6-238892 discloses that if the tolerance of the depth of the electrode is within ± 30% with respect to the set position, the change in the volume of the ink channel is within ± 5%. ing. However, in the high quality printing required for the ink jet printer in recent years, the volume of the ink droplet is small, and is several picoliters. In order to stably eject such minute ink droplets, the change of the ink channel volume of ± 5% is not a small value.

Japanese Unexamined Patent Publication No. Hei 6-238892 does not disclose any variation in electrode depth at the time of forming an electrode, particularly the difference in electrode depth on both sides of a channel wall. Is greatly affected by the difference in electrode depth on both sides of the channel wall.

Conventionally used electrode forming methods include:
There is an unavoidable problem that has not been focused on heretofore, and there has been a problem that the formation height of the electrodes differs on both sides of the channel wall and becomes uneven depending on the ink channel.

This will be described in detail with reference to FIG. FIG. 15 shows the positional relationship between the vapor deposition device used for oblique vapor deposition and the base member 1. In FIG. 15, the deposition source 15 is placed in a crucible 16 and is positioned at the center below the deposition apparatus, and the base member 1 is attached to the substrate holder 17 above the deposition apparatus at a predetermined angle. . FIG. 16 shows a state in which vapor deposition particles flying from the vapor deposition source 15 enter the base member 1 when the vapor deposition source is regarded as a point source.
This will be described in detail with reference to FIG.

FIG. 16 shows a case where the vertical distance from the evaporation source 15 to the center of the channel row of the base member 1 is 50 cm and the horizontal distance is 20 cm. 200 are formed. In this case, the ink channel 4 has a width of about 2
8 mm (= 25.4 [inch / mm] / 180 [do
t / inch] * 200 [dot]).

In the case of FIG. 16, the base member 1 is attached to the substrate holder 17 at an angle of 45.8 ° in order to make the electrode formation depth at the center of the channel row half the channel depth. After the formation of the metal film on one side of the channel wall is completed, the base member 1 is turned 180 ° and deposited again to form a metal film on the remaining one side.

By the way, the channel row has a finite length, and the incident angle of the vapor deposition particles differs at the end of the channel row.

This will be described in detail with reference to FIGS. FIG. 16 schematically shows the incident state of the vapor deposition particles when the base member 1 is parallel. When the incident angle at the center of the channel row is 66 °, the incident angle at the end of the channel is 64.
7 ° and 67.4 °. That is, referring to FIG. 15, when the vapor deposition source 15 is regarded as a point source, the incident angle at the end of the channel row closer to the vapor deposition source 15 is larger than the incident angle at the center, and is 67.4. °, the angle of incidence at the end of the channel row farther from the deposition source 15 is smaller than the angle of incidence at the center, 64.7.
°.

As a result, as shown in FIG. 17, the formation depth of the metal film serving as the electrode 5 is:
Whereas at the end of the channel row,
They are 138.5 μm and 160.2 μm, respectively.

Further, when the metal film is deposited, the base member is
Rotating by 80 ° and depositing twice results in different depths of the electrodes formed on both sides of the channel wall at the end of the channel row. When the piezoelectric body is deformed in the shear mode, the electrode can be formed most efficiently when the electrode is formed only in the upper half of the channel wall. Decrease.

This will be described in detail with reference to FIG. FIG. 18A schematically shows the deformation mode of the channel wall 3 when the depth of the electrode is formed in the upper half of the channel wall 3, and FIG. FIG.

In FIG. 18A, when an electrode is formed on the upper half of the channel wall 3 made of a vertically polarized piezoelectric material, when a voltage is applied from both electrodes, the upper half of the channel wall 3 is formed. An electric field is applied only in the direction orthogonal to the polarization direction, and shear distortion occurs in the piezoelectric body to which the electric field is applied.
Since the upper and lower sides of the channel wall 3 are fixed, the channel wall 3 is deformed by the shear strain so as to be bent at the center portion A of the channel wall 3 as shown by a broken line.

On the other hand, in FIG. 18 (b), the electrode depth is different on both sides of the channel wall 3, and the region which works effectively to cause shear strain is a region where the electrode depth is shallow. As a result, the amount of distortion is reduced, and the bending point is reduced as shown in FIG.
As a result, the ink channel 4 moves to A ', which is higher than A in FIG. 8A, so that the volume displacement of the ink channel 4 is reduced, and the pressure change for discharging the ink droplet from the nozzle is reduced. As described above, in the conventional inkjet head, the depth of the electrode for applying the voltage for causing the shear distortion changes depending on the ink channel, and the discharge speed and the discharge volume of the ink droplets discharged from the plurality of ink channels are reduced. There was a problem of variation.

The present invention has been made in order to solve such a problem, and an object of the present invention is to provide a method of driving an ink-jet head which can reduce variation in ejection of ink droplets for each ink channel.

[0036]

The present invention has the following arrangement as means for solving the above problems.

In the method according to the first aspect of the present invention, at least a portion is formed of a piezoelectric material, and a plurality of grooves are provided in parallel with the surface thereof, and further, an electrode is formed on a part of a side wall of the groove. A base member provided, a cover member provided to cover the plurality of grooves of the base member and constituting an ink channel serving as a pressure chamber, and a nozzle communicating with the ink channel; The present invention relates to a method for driving an ink jet head that applies a voltage to cause a shear deformation on the side wall to generate pressure vibration in the ink channel and discharge ink from the nozzle. The voltage applied to the electrode is applied so as to change continuously according to the arrangement of the ink channel rows.

In this configuration, the variation of the ink droplets caused by the variation of the volume displacement of the ink channel due to the depth of the electrode provided on the channel wall continuously changing in accordance with the arrangement of the channel rows is applied to the electrode. Since the voltage can be reduced by continuously changing the applied voltage, high-quality printing can be performed.

In the ink jet head driving method according to the second aspect of the present invention, the voltage applied to the electrodes is the smallest applied to the ink channel located at the center of the plurality of ink channel rows.

In this configuration, when the metal film serving as the electrode of the channel wall is formed by oblique deposition, the base member is rotated by 180 ° about the center of the channel row as a rotation axis to connect the electrodes on both sides of the channel wall. When formed, the depth of the electrode provided on the channel wall is changed symmetrically with respect to the center of the channel row, and continuously changes according to the arrangement of the channel row. Variations can be reduced by continuously changing the voltage applied to the electrodes, so that high-quality printing can be performed.

In the method of driving an ink jet head according to the third aspect of the present invention, the voltage applied to the electrodes is such that the voltage applied to the ink channel located at one end of the plurality of ink channel rows is the smallest. It is characterized by.

In this configuration, when a metal film to be an electrode is formed on the channel wall by oblique deposition, the base member is rotated by 180 ° about one of the ends of the channel row as a rotation axis, and the base member is rotated by 180 °. When electrodes are formed on both sides, the depth of the electrode provided on the channel wall varies from one end of the channel row continuously according to the arrangement of the channel row, and the variation in the volume displacement of the ink channel is reduced. Variations in ink droplets caused by the change can be reduced by continuously changing the voltage applied to the electrodes, so that high-quality printing can be performed.

The method according to the fourth aspect of the present invention is the method according to the fourth aspect, wherein at least a part is formed of a piezoelectric material, and a plurality of grooves are provided in parallel on a surface of the piezoelectric material. A base member provided with a cover member that is provided so as to cover the plurality of grooves of the base member and constitutes an ink channel serving as a pressure chamber; and a nozzle that communicates with the ink channel. The present invention relates to a method for driving an ink jet head that applies a driving voltage to cause shear deformation on the side wall to generate pressure vibration in the ink channel and discharge ink from the nozzle. The voltage applied to the electrode is applied for a predetermined time in a direction to increase the volume of the ink channel, and is subsequently applied for a predetermined time in a direction to decrease the volume of the ink channel. Is characterized in that the time during which a voltage is applied to the ink channel continuously changes in accordance with the arrangement of the ink channel rows.

In this configuration, variations in ink droplets due to variations in volume displacement of the ink channel due to the depth of the electrode provided on the channel wall continuously changing in accordance with the arrangement of the channel rows are eliminated. Since it can be reduced by continuously changing the time during which the voltage is applied in the direction of increasing the volume,
Variations in ink droplets ejected from each nozzle can be reduced, and high quality printing can be performed.

In the method of driving an ink jet head according to a fifth aspect of the present invention, the ink channels positioned at both ends of the plurality of ink channel rows are controlled by applying a voltage in a direction to increase the volume of the ink channel. Is set so that the ejection speed of the ink droplets is maximized, and continuously changes.

In this configuration, when a metal film to be an electrode is formed on the channel wall by oblique deposition, the base member is rotated by 180 ° about the center of the channel row as a rotation axis, and electrodes are provided on both sides of the channel wall. When formed, the depth of the electrode provided on the channel wall is changed symmetrically with respect to the center of the channel row, and continuously changes according to the arrangement of the channel row. Variations are set such that the time applied to the ink channels located at both ends of the channel row is set so that the ejection speed of the ink droplets is maximized, and the center of the channel row is symmetrical and continuous according to the arrangement of the channel rows. The variation of the ink droplets ejected from each nozzle. Can, it is possible to perform the printing of high quality.

In the ink jet head driving method according to the sixth aspect of the present invention, the voltage is applied to the ink channel in a direction of increasing the volume of the ink channel, and the voltage is applied to one end of the plurality of ink channel rows. It is characterized in that the time applied to the located ink channel is set so that the ejection speed of the ink droplet is maximized and changes continuously.

In this configuration, when a metal film to be an electrode is formed on the channel wall by oblique deposition, the base member is rotated by 180 ° about one end of the channel row as a rotation axis, and the channel wall is rotated. When electrodes are formed on both sides of the channel, the depth of the electrode provided on the channel wall is
The variation of ink droplets caused by the variation of the volume displacement of the ink channel due to the continuous change according to the arrangement of the channel rows from either end of the channel row is applied to one end of the channel row. Time is set so that the ink droplets and the ejection speed are maximized, and can be reduced by continuously changing the ink droplets in accordance with the arrangement of the channel rows, thereby reducing variations in the ink droplets ejected from each nozzle. And high quality printing can be performed.

[0049]

1 to 10 show an embodiment according to the present invention.
This will be described in detail with reference to FIG.

<Embodiment 1> The structure of an ink-jet head using the driving method according to the present invention will be described with reference to FIGS.

The ink jet head has a base member 1 in which a plurality of grooves 4 are formed in a piezoelectric body subjected to a polarization process in FIG. 1 and a cover member 2 in which an ink supply port 21 and a common ink chamber 22 are formed. And a nozzle plate 9 having a nozzle hole 10 formed therein, whereby the ink channel 4 is formed.
Are formed.

An electrode 5 for applying an electric field is formed on the channel wall 3. The rear end of the ink channel 4 is machined into an R shape corresponding to the diameter of the dicing blade used at the time of machining the groove, and a shallow groove 6 serving as an electrode lead-out portion for energizing with the outside is formed in 6. It is processed by a dicing blade. The electrode formed in the shallow groove 6 is connected to an external electrode 8 such as a flexible substrate by a bonding wire 7 at the rear end of the shallow groove 6. The electrodes provided on the channel wall 3 are connected at the R-shaped portion at the rear end of the ink channel so as to have the same potential inside one ink channel 4, and are connected to the external electrode 8 via the shallow groove 6. Connected. The electrodes formed in the respective ink channels 4 are independently connected to the external electrodes 8. A predetermined ink channel is selected according to the print data, and a voltage is applied from an external electrode 8 so that an electric field is applied in a direction orthogonal to the polarization direction of the channel wall 3. The channel wall 3 to which the electric field is applied undergoes shear deformation, and as a result, a pressure wave fluctuation occurs in the ink channel, and an ink droplet is ejected from the nozzle hole 10. FIG.
In the above, the electrode lead portion and the external electrode are connected by wire bonding, but may be connected by using an anisotropic conductive film (ACF).

In this embodiment, an explanation will be given of a case where the electrodes are formed on the channel wall 3 by performing the oblique deposition twice by rotating the base member 1 by 180 ° about the center of the channel row as a rotation axis. .

FIG. 2 is a cross-sectional view of a channel row. In FIG. 2, the electrode 5 provided on the channel wall 3
Is formed at the center of the channel row in the range of 150 μm, which is the upper half at the same depth on both sides of the channel wall 3.

On the other hand, at the end of the channel row, the electrode depth is different on both sides of the channel wall 3 due to the difference in the incident angle of the oblique deposition, and the depth is formed shallower than the center of the channel row and deeper than the end. And changes continuously from the center to the end of the channel row.

FIG. 3 is a diagram showing, when the number of channels is 200, the depth of each electrode formed on the left and right sides of the channel wall, with the row of channels arranged along the horizontal axis. FIG. 3 shows that the left and right electrode depths are equal at the center of the channel wall, but the left and right electrode depths continuously change symmetrically toward the end of the channel row.

When the same voltage is applied to all the channels in the ink jet head having such an electrode depth, the displacement of the channel wall at the center of the channel row becomes the largest, and the displacement toward the end of the channel row. Thus, the displacement amount continuously decreases. like this. In the present embodiment, the change in the amount of displacement caused by the non-uniform electrode depth for each channel is the lowest applied to the center of the channel row, and is applied continuously toward the end of the channel row. The problem is solved by increasing the voltage.

FIG. 4 is a diagram showing the applied voltage according to the present embodiment, with the abscissa plotting the channel row.
As shown in FIG. 4, the voltage applied to the channel wall at the center of the channel row is the smallest, and continuously increases toward both ends of the channel row. By adopting such a driving voltage application method, the amount of displacement of the channel wall for each channel becomes equal, the variation of ink droplets ejected from the nozzles can be reduced, and high quality printing can be performed. it can.

In this embodiment, the voltage applied to the center of the channel wall is set to 20 V and the voltage applied to the end is set to 25 V, and is linearly changed. The value may be adjusted according to the degree of variation in ink ejection, and may be a step-like or quadratic curve, and need not necessarily be changed linearly.

For example, five channels are regarded as one block, and the same applied voltage is applied in the same block. On the other hand, the applied voltage of the block to which the channel belongs is set closer to the end of the channel. Higher than the applied voltage. In this case, the number of blocks is 40 (200
/ 5). Further, the variation of the applied voltage in each block does not need to be constant, and the variation in the applied voltage may be increased as the end channel is reached. As described above, by blocking the applied voltage, the types of applied voltage can be greatly reduced, and the burden on the driver IC can be reduced and the cost can be suppressed.

<Embodiment 2> A driving method according to a second embodiment of the present invention will be described. The structure of the ink jet head is the same as that described in the first embodiment, and a detailed description thereof will be omitted. In the present embodiment, a case will be described in which electrodes are formed on the channel walls 3 by rotating the base member 1 by 180 ° with the end of the channel row as a rotation axis and performing oblique deposition twice.

FIG. 5 is a sectional view of a channel row. In FIG. 5, the electrode 5 provided on the channel wall 3
Is formed at the end of the channel row in the range of 150 μm, which is the upper half at the same depth on both sides of the channel wall 3. On the other hand, at the other end of the channel row, the electrode depth is different on both sides of the channel wall 3 due to the difference in the incident angle of the oblique deposition, and is continuously shallow on one side of the channel wall and continuously on the other side. It is deeply formed.

FIG. 6 is a diagram showing the depth of each of the electrodes formed on the left and right sides of the channel wall when the number of channels is 200, with the row of channels arranged along the horizontal axis. From FIG. 6, it can be seen that the left and right electrode depths are equal at the end of the channel wall, but the left and right electrode depths continuously change toward the other end of the channel row. When the same voltage is applied to all the channels of an inkjet head having such an electrode depth, the displacement of the channel wall at the end of the channel row having the same electrode depth becomes the largest, and the other end of the channel row becomes the largest. The displacement amount continuously decreases toward one end. In the present embodiment, such a change in the amount of displacement due to non-uniformity of the electrode depth for each channel is considered as follows. The applied voltage is continuously increased toward the other end.

FIG. 7 is a diagram showing applied voltages according to the present embodiment, with the horizontal axis representing the arrangement of channels.
As shown in FIG. 7, the voltage applied to the channel wall at the end where the electrodes of the channel row have the same depth is the smallest, and continuously increases toward the other end of the channel row. By adopting such a driving voltage application method, the amount of displacement of the channel wall for each channel becomes equal, the variation of ink droplets ejected from the nozzles can be reduced, and high quality printing can be performed. . In this embodiment, the voltage applied to the end of the channel wall having the same electrode depth is 20 V, and the voltage applied to the other end is 30 V. In accordance with the depth of the electrode, the value may be adjusted according to the degree of variation in ink ejection, and may be a step-like or quadratic curve, and may be linear, as described in the above embodiment. Need not be changed to

<Embodiment 3> A driving method according to a third embodiment of the present invention will be described. In the present embodiment, a case will be described in which electrodes are formed on the channel wall 3 by rotating the base member 1 by 180 ° about the center of the channel row as a rotation axis and performing oblique deposition twice. Note that the structure of the ink jet head and the depth of the electrodes are the same as those in the first embodiment, and a detailed description thereof will be omitted. In the present embodiment, a driving method for changing a driving waveform while keeping a voltage applied to a channel constant will be described.

FIG. 8 is a diagram schematically showing the drive waveform applied to the channel and the deformation of the channel wall at that time. A voltage for increasing the volume of the ink channel is applied to the electrode 5 for a time T1, and then a voltage for reducing the volume of the ink channel is applied for a time T2.
The voltages applied for the times T1 and T2 are equal in magnitude and opposite in direction. The sign of the voltage applied to T1 and T2 is uniquely determined by the polarization direction of the base member 1.

The time T1 affects the ejection speed of the ink droplet, and the time at which the ejection speed is maximized is determined by the length of the ink channel, the compliance of the ink channel, the propagation speed of the pressure wave, and the like. That is, the discharge speed is T
It can be controlled by one time.

The time T2 is set to an optimum value in relation to the residual vibration of the ink channel and the ejection cycle, and generally may be set to a value three to four times the time T1.

FIG. 9 shows that the width of the ink channel is 80 μm.
m, depth 300 μm, length 1 mm, nozzle diameter φ42 μm on the ink channel side, φ25 μm on the ejection side,
With an inkjet head with a nozzle plate thickness of 50 μm,
This is a result of measuring the ejection speed of the ink droplet under the same applied voltage of 25 V and using the time of T1 as a parameter. From FIG. 9, it can be seen that the ejection speed has a peak when the time T1 is 2.25 μs, and the ejection speed of the ink drops decreases even if the time T1 is longer or shorter than 2.25 μs.
In the present embodiment, the drive waveforms applied to both ends are set so that the ejection speed from the channels at both ends of the channel row in which the depth of the electrodes is the most different on both sides of the channel wall is maximized.

FIG. 10 shows the time T1 for each channel of the drive waveform used in this embodiment.

In FIG. 10, the time T1 of the drive waveform applied to both ends of the channel row is 2.25 μs, the time T1 of the drive waveform applied to the center channel of the channel row is 1.8 μs, It is changing continuously. In this embodiment, the electrodes are formed on the channel wall 3 by oblique vapor deposition twice using the center of the channel row as the rotation axis. In the center of the channel wall, the left and right electrode depths are equal, but the left and right electrode depths continuously change symmetrically toward the end of the channel row. Therefore, in the center of the channel wall,
When driven by the same voltage, the displacement of the channel wall is the largest, and the ejection speed of the ink droplet is high.

In this embodiment, a driving waveform of T1 = 2.25 μs at which the ejection speed of the ink droplet becomes maximum is applied to both ends of the channel array where the ejection speed of the ink droplet is small. A drive waveform of T1 = 1.8 μs is used. As a result, even if an ink jet head having a different electrode depth for each channel is used, it is possible to reduce variations in the ink droplet ejection speed for each channel,
High quality printing can be performed.

In this embodiment, the driving waveform T1 applied to the center of the channel row is set to 1.8 μs.
As is clear from FIG. 9, it is possible to take a value larger than 2.25 μs at which the ejection speed of the ink droplet becomes maximum.
Further, the value of T1 that maximizes the ejection speed of ink droplets is determined by the dimensions of the ink channel, the dimensions of the nozzles, the ink characteristics, and so on. It may be used.

<Embodiment 4> A driving method according to a fourth embodiment of the present invention will be described. In the present embodiment, a case will be described in which electrodes are formed on the channel walls 3 by rotating the base member 1 by 180 ° with the end of the channel row as a rotation axis and performing oblique deposition twice. Note that the structure of the ink jet head and the depth of the electrodes are the same as those in the second embodiment, and thus detailed description is omitted.

FIG. 11 shows the time T1 for each channel of the drive waveform used in this embodiment. In FIG. 11, the end of the channel row (200 of the channel row)
Is 2.25 μs, and the T1 time of the drive waveform applied to the other end of the channel row (1 in the channel row) is 1.6 μs, and continuously changes. ing.

In this embodiment, the electrodes are formed on the channel wall 3 by obliquely depositing the base member 1 twice by rotating the base member 1 by 180 ° about the end of the channel row (channel row 1) as a rotation axis. Therefore, the electrode depth differs on both sides of the channel wall 3 due to the difference in the incident angle of the oblique deposition, and the left and right electrode depths are equal at the end of the rotation center of the channel wall during the oblique deposition. The left and right electrode depths are continuously changing toward the other end of the row. Therefore, at the end of the channel wall, which is the center of rotation during oblique deposition, when the channel wall is driven at the same voltage, the displacement of the channel wall is the largest, and the ejection speed of the ink droplet is high.

In this embodiment, a driving waveform of T1 = 2.25 μs at which the ejection speed of the ink droplet is maximized is given at one end of the channel row where the ejection speed of the ink droplet is small.
At the other end of the channel row, T1 = 1.6 μs
Is used. As a result, even when an ink jet head having a different electrode depth for each channel is used, it is possible to reduce variations in the ejection speed of ink droplets for each channel and to perform high quality printing.

In this embodiment, the drive waveform T applied to the end serving as the rotation center during the oblique vapor deposition of the channel row is used.
Although 1 is set to 1.6 μs, as can be seen from FIG. 9, it can be set to a value larger than 2.25 μs at which the ejection speed of the ink droplet becomes maximum. Further, the value of T1 that maximizes the ejection speed of ink droplets is determined by the dimensions of the ink channel, the dimensions of the nozzles, the ink characteristics, and so on. It may be used.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0080]

As described above, in the method of driving an ink jet head according to the present invention, the drive voltage applied to each ink channel is continuously changed according to the depth of the electrode which differs for each ink channel. Alternatively, since the driving waveform is continuously changed, it is possible to reduce the variation in the ejection of ink droplets for each ink channel, and to obtain high-quality printing.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an ink jet head of the present invention.

FIG. 2 is a sectional view showing a first embodiment of the ink jet head of the present invention.

FIG. 3 is a diagram of an electrode depth showing a first embodiment of the ink jet head of the present invention.

FIG. 4 is an applied voltage illustrating the first embodiment of the ink jet head of the present invention.

FIG. 5 is a sectional view showing a second embodiment of the ink jet head of the present invention.

FIG. 6 is a diagram of an electrode depth showing a second embodiment of the ink jet head of the present invention.

FIG. 7 is an applied voltage illustrating the second embodiment of the ink jet head of the present invention.

FIG. 8 is a schematic diagram of driving waveforms and channels showing a third embodiment of the ink jet head of the present invention.

FIG. 9 shows a time T1 of a drive waveform and an ink ejection speed in a third embodiment of the inkjet head of the present invention.

FIG. 10 is a time T1 of a drive waveform for each channel row in the third embodiment of the ink jet head of the present invention.

FIG. 11 shows a drive waveform time T1 for each channel row in a fourth embodiment of the inkjet head of the present invention.

FIG. 12 is a perspective view showing a conventional inkjet head.

FIG. 13 is a diagram showing a conventional method for manufacturing an ink jet head.

FIG. 14 is a cross-sectional view illustrating a conventional method for forming an electrode of an inkjet head.

FIG. 15 is a view showing a conventional electrode forming apparatus for an ink jet head.

FIG. 16 is a cross-sectional view illustrating a conventional method for forming an electrode of an inkjet head.

FIG. 17 is a cross-sectional view showing a conventional inkjet head.

FIG. 18 is a cross-sectional view showing a state of driving a channel of a conventional inkjet head.

[Explanation of symbols]

1 base member, 2 cover members, 3 channel walls,
4 ink channel, 5 electrode (metal film), 6 shallow groove, 7 bonding wire, 8 external electrode, 9 nozzle plate, 10 nozzle hole, 11 dry resist film, 12 piezoelectric body, 21 ink supply port, 22 common ink chamber.

Claims (6)

[Claims] At least a portion is formed of a piezoelectric material,
And a plurality of grooves are provided in parallel on the surface thereof, and a base member provided with an electrode on a part of a side wall of each of the grooves, and a base member provided to cover the plurality of grooves of the base member. A cover member constituting an ink channel serving as a pressure chamber; and a nozzle communicating with the ink channel. A drive voltage is applied to the electrode to generate a shear deformation on the side wall, thereby causing pressure vibration on the ink channel. Wherein the voltage applied to the electrodes is applied so as to be continuously changed in accordance with the arrangement of the ink channel rows. Drive method. 2. The ink jet head driving method according to claim 1, wherein a voltage applied to the ink channel located at the center of the plurality of ink channel rows is the smallest among the voltages applied to the electrodes. 3. The method according to claim 1, wherein a voltage applied to the ink channel located at one end of the plurality of ink channel rows is the smallest among the voltages applied to the electrodes.
A method for driving an ink jet head according to claim 1. 4. At least a portion is formed of a piezoelectric material,
And a plurality of grooves are provided in parallel on the surface thereof, and a base member provided with an electrode on a part of a side wall of each of the grooves, and a base member provided to cover the plurality of grooves of the base member. A cover member constituting an ink channel serving as a pressure chamber; and a nozzle communicating with the ink channel. A drive voltage is applied to the electrode to generate a shear deformation on the side wall, thereby causing pressure vibration on the ink channel. In the method of driving an ink jet head that causes ink to be ejected from the nozzles, a voltage applied to the electrode is applied for a predetermined time in a direction to increase the volume of the ink channel, and subsequently, a direction to decrease the volume of the ink channel. Is applied for a predetermined time, and the time during which the voltage is applied in the direction of increasing the volume of the ink channel is A method for driving an ink-jet head, wherein the method continuously changes according to the arrangement of ink channel rows. 5. The time when a voltage is applied in a direction to increase the volume of the ink channel, and the time when the voltage is applied to the ink channels located at both ends of the plurality of ink channel rows is the time when the ink droplet ejection speed is the highest. The method for driving an ink jet head according to claim 4, wherein the ink jet head is set to be large and changes continuously. 6. The time when a voltage is applied in a direction to increase the volume of the ink channel, and the time when a voltage is applied to an ink channel located at one end of a plurality of ink channel rows is a time when an ink droplet is applied. 5. The method according to claim 4, wherein the ejection speed is set to be maximum and changes continuously.