JP2003011364A - Inkjet head - Google Patents

Abstract

(57) [Summary] An object of the present invention is to provide an ink jet head improved so as not to cause variation in ejection of ink droplets. SOLUTION: The ink jet head is formed at least in part of a piezoelectric material, and is provided with a plurality of grooves which are separated from each other by walls on its surface and are arranged in parallel. Base member 1 provided with
Is provided. On the base member 1 so as to cover the plurality of grooves,
Cover member 2 forming an ink channel serving as a pressure chamber
Is provided. A drive voltage is applied to the electrode 5 to cause a shear deformation on the side wall, thereby forming the ink channel 4.
Causes a pressure oscillation to cause the nozzle 10 to eject ink. The depth of each of the plurality of grooves continuously changes from the groove located at the center to both sides from the groove located at the center toward the direction in which the grooves are arranged.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to an ink jet head, and more specifically, an ink jet head improved so that variations in ink ejection between ink channels can be eliminated and printing quality can be improved. Regarding the head.

[0002]

2. Description of the Related Art Today, non-impact printers such as ink jet systems suitable for colorization and multi-gradation are rapidly becoming popular in place of impact printers. Above all, drop-on
The demand type is drawing attention because of its good printing efficiency, low cost, and low running cost, and the Kaiser method using a piezoelectric element and the thermal jet method are the mainstream.

However, the Kaiser system has a drawback that it is difficult to miniaturize and is not suitable for high density. Although the thermal jet method is suitable for high density, the heater is heated to generate bubbles in the ink, and the energy of the bubbles is used for ejection, so the durability of the ink is improved. Strict requirements for
Moreover, it is difficult to extend the life of the heater, and further, there is a problem that power consumption increases.

In order to solve such a drawback, an ink jet method utilizing a shear mode of a piezoelectric material has been proposed. This method uses an electrode formed on the ink channel wall made of a piezoelectric material to apply an electric field in a direction orthogonal to the polarization direction of the piezoelectric material to deform the channel wall in shear mode and utilize the pressure wave fluctuations that occur at that time. To eject ink droplets, and to increase the density of nozzles,
Suitable for low power consumption and high driving frequency. The structure of such an inkjet head using the shearing mode will be described with reference to FIG.

Referring to FIG. 15, the ink jet head has a base member 1 in which a plurality of grooves 4 are formed in a vertically polarized piezoelectric material, an ink supply port 21 and a common ink chamber 22. Cover member 2 and nozzle hole 10
The ink channels 4 are formed by sticking the nozzle plates 9 that have been opened.

An electrode 5 for applying an electric field is formed in the upper half of the channel wall 3. The rear end portion of the ink channel is processed into an R shape corresponding to the diameter of the dicing blade used at the time of groove processing, and a portion indicated by reference numeral 6 serves as an electrode lead-out portion for energizing with the outside. Similarly, the shallow groove portion is processed by a dicing blade. The electrode formed in the shallow groove portion 6 is connected to an external electrode 8 such as a flexible substrate by wire bonding at the rear end portion of the shallow groove portion.

Next, a method of manufacturing the ink jet head shown in FIG. 15 will be described. As shown in FIG. 16A, a dry resist film 11 capable of dicing is laminated on the piezoelectric body 12 which is vertically polarized.

Next, as shown in FIG. 16 (b), the groove portion and the shallow groove portion 6 which become the ink channels 4 are processed by a dicing blade. After that, the incident direction is set so that the metal to be the electrode adheres only to the upper half of the channel wall 3, and oblique vapor deposition is performed from the directions A and B. afterwards,
By lifting off the dry resist film 11,
The upper half of the channel wall 3 and the shallow groove 6 as shown in FIG.
The base member 1 as an actuator having the metal film 5 formed therein is produced. The cover member 2 is provided with an ink supply port 21 and a common ink chamber 22 by mechanical processing or sandblast processing.

When sandblasting is performed, it may be performed 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 having a predetermined size is drilled by excimer laser processing, but the nozzle hole may be provided in the metal material by punching or the like. The base member 1, the cover member 2, and the nozzle plate 9 manufactured in this manner are attached to desired positions with an adhesive.

In the ink jet head manufactured in this manner, 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. It
The electrodes provided on the upper half of the channel wall 3 are connected inside the ink channel 4 at the R-shaped portion at the rear end of the ink channel so as to be at the same potential, and are connected via the shallow groove 6 to the outside. It is connected to the electrode 8. The electrodes formed in each ink channel 4 are independently connected to the external electrode 8.

A predetermined ink channel is connected 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 an electric field is applied undergoes shear deformation, and as a result, pressure wave fluctuations occur in the ink channel, and ink droplets are ejected from the nozzle holes 10.

Although the electrode lead-out portion and the external electrode are connected by wire bonding in FIG. 15, a method of connecting using an anisotropic conductive film (ACF) has also been conventionally adopted.

[0013]

In a conventional ink jet head, a vertically polarized piezoelectric body is used as a base member as an actuator, and the upper half of the channel wall is deformed in order to deform the channel wall in shear mode. The electrode was formed on. On the other hand, a structure called a chevron method has been proposed in the past, in which a base member as an actuator is a composite material in which piezoelectric materials having different polarization directions in the vertical direction are laminated at a position half the height of a channel wall. Was there. In this case, since the electrodes may be formed on the entire surface of the channel wall,
It is not necessary to limit to the upper half of the channel wall, and there is a feature that an electroless plating method or the like can be used as a method of forming an electrode, but there is a problem that the manufacturing cost of a base member as an actuator becomes high. .

Therefore, at present, a method of using a single piezoelectric body vertically polarized as a base member is predominant, and electric power is obliquely vapor-deposited only in the upper half of the channel wall. Has been formed.

A conventional method for forming electrodes will be described in detail with reference to FIG. In order to form the electrode film on the upper half of the channel wall 3, the oblique vapor deposition method is used for one side, and vapor deposition is performed twice by changing the incident direction of vapor deposition particles.

FIG. 17A shows the state of the first vapor deposition, in which the channel wall has a height of 300 μm and a width of 80.
When the height of the dry resist film 11 is 30 μm and the height of the dry resist film 11 is 30 μm, vapor deposition particles are incident at an incident angle of 66 ° with respect to the normal to form an electrode in the upper half on the left side of the channel wall 3.

Next, FIG. 17 (b) shows the state of the second vapor deposition, and 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. After that, the metal film formed on the dry resist 11 is lifted off together with the dry resist 11, so that the base material 1 having the electrodes 5 formed only on the upper half of the channel wall 3 as shown in FIG. 17C.
To make. In this way, the depth of the electrode formed on the channel wall is half the channel depth.

According to Japanese Unexamined Patent Publication No. 6-238892, if the tolerance of the electrode depth is within ± 30% of the set value, the volume change of the ink channel is within ± 5%. Is disclosed. However, in the high-quality printing required for an inkjet printer in recent years, the volume of the ink droplet is small and the size is several picoliters. In order to stably eject ink droplets of such a minute size, a change of ± 5% in the volume of the ink channel is not a small value. Further, Japanese Patent Laid-Open No. 6-238892 does not describe any variation in electrode depth at the time of electrode formation, in particular, a difference in electrode depth on both sides of the channel wall, and a change in ink channel volume is It is greatly affected by the difference in electrode depth on both sides of the wall.

Japanese Unexamined Patent Publication No. 11-34317 discloses a method of widening the groove widths at both ends of an ink channel row so as to make the ejection amount constant in a channel having nozzle holes through which ink is ejected. Has been done. However,
Also in this publication, there is no description about the influence of the variation in the electrode depth on the ink ejection.

As described above, the conventionally used electrode forming method has an unavoidable problem which has not been paid attention so far, and the electrode forming height is different on both sides of the channel wall. However, there is a problem that the ink channels become non-uniform. This will be described in detail with reference to FIG.

FIG. 18 shows the positional relationship between the vapor deposition apparatus used for oblique vapor deposition and the base material 1. FIG.
Then, the vapor deposition source 15 is placed in the crucible 16 and is located at the center of the lower portion of the vapor deposition apparatus, and the substrate holder 1 is disposed above the vapor deposition apparatus.
The base member 1 is attached to the member 7 at a predetermined angle.

Deposition source 15 when the deposition source is regarded as a point source
The state of deposition of vapor deposition particles flying from the base material 1,
This will be described in detail with reference to FIG.

FIG. 19 shows a case where the vertical distance from the vapor deposition source 15 to the center of the channel row of the base material 1 is 50 cm and the horizontal distance is 20 cm. In the base material 1, the ink channels 4 are 180 DPI. 200 are formed. In this case, the ink channel will be formed over a length of about 28 mm.

In the case of FIG. 19, the base material 1 is attached to the substrate holder 17 at an angle of 45.8 ° so that the electrode formation depth at the center of the channel row is half the channel depth. After the formation of the metal film on one side of the channel wall is completed, the base material 1 is changed in direction by 180 ° and evaporated again to form the metal film on the other side. However, the channel row has a finite length, and the incident angle of vapor deposition particles is different at the end of the channel row.

This will be described in detail with reference to FIGS. 19 and 20. FIG. 19 schematically shows how vapor deposition particles enter, with the base material 1 in parallel.
When the incident angle at the center of the channel row is 66 °, the incident angles at the channel ends are 64.7 ° and 6 °.
It becomes 7.4 °. As a result, as shown in FIG. 20, the formation depth of the metal film to be the electrode 5 is 150 μm at the center of the channel row, while 138.5 μm and 162.2 μm at the end of the channel row. Becomes further,
When the metal film is deposited, the base material is rotated 180 ° and deposited twice, so that the depths of the electrodes formed on both sides of the channel wall are different at the ends of the channel row.

When the piezoelectric body is deformed in the shear mode, it can be deformed most efficiently when the electrode is formed only in the upper half of the channel wall, but when the electrode depth is different on both sides of the channel wall. The amount of deformation is reduced. This will be described in detail with reference to FIG.

FIG. 21 is a diagram schematically showing 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 (a) and when it is different on both sides (b). Is.

In FIG. 21 (a), when electrodes are formed on the upper half of the channel wall 3 made of a vertically polarized piezoelectric material, a voltage is applied from both electrodes to the upper half of the channel wall 3. An electric field is applied only in the direction orthogonal to the polarization direction, and shear strain 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, shearing strain causes the channel wall 3 to deform so as to bend at the central portion A of the channel 3 wall as indicated by the broken line.

On the other hand, in FIG. 21 (b), the electrode depth is different on both sides of the channel wall 3, and the region effectively acting to cause shear strain is the region having a shallow electrode depth. As a result, the amount of strain is reduced, and the bending point is shown in FIG.
21 (b), which is located above A in FIG. 21 (a), the volume displacement of the ink channel 4 is reduced, and the pressure change for ejecting the ink droplet from the nozzle is reduced. . As described above, in the conventional inkjet head, the depth of the electrode to which the voltage for causing the shear strain is applied changes depending on the ink channel, and the ejection speed and the ejection volume of the ink droplets ejected from the plurality of ink channels vary. There was a problem of variation.

The present invention has been made to solve such a problem, and an object of the present invention is to provide an improved ink jet head capable of reducing variations in ink droplet ejection between ink channels.

[0031]

An ink jet head according to a first aspect of the present invention is at least partially formed of a piezoelectric material, and has a plurality of grooves which are partitioned in parallel with each other on the surface and are arranged in parallel. Further, the base member is provided with an electrode on a part of the side wall of each groove. A cover member that forms an ink channel that serves as a pressure chamber is provided on the base member so as to cover the plurality of grooves. The inkjet head includes a nozzle that communicates with the ink channel. The inkjet head applies a driving voltage to the electrodes to cause shear deformation on the side walls, thereby causing pressure vibration in the ink channels and ejecting ink from the nozzles. The depth of each of the plurality of grooves continuously changes from the groove located at the center to both sides in the direction in which the grooves are arranged.

According to the present invention, 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 reduced to the above-mentioned plurality. Since the depth of the groove can be reduced by continuously changing it for each ink channel, high quality printing can be performed.

In the ink jet head according to the second aspect of the present invention, among the plurality of grooves, the depth of the groove located at the center is the smallest.

In this structure, when a metal film to be an electrode is formed on the channel wall by oblique vapor deposition, the base material is rotated 180 ° about the center of the channel row as a rotation axis so that the electrodes are formed on both sides of the channel wall. When formed, the depth of the electrode provided on the channel wall changes continuously in accordance with the arrangement of the channel rows with the central portion of the channel row being symmetrical, and thus the ink droplets due to the variation in the volume displacement of the ink channel are formed. The variation can be reduced by continuously changing the depths of the plurality of grooves so that the depth of the groove located in the central portion of the ink channel row becomes the shallowest, so that high quality printing is performed. be able to.

In the ink jet head according to the third aspect of the present invention, the depth of the groove located at either one of the plurality of grooves is the smallest.

In this structure, when a metal film to be an electrode is formed on the channel wall by oblique vapor deposition, the base material is rotated 180 ° about one end of the channel row as the rotation axis to rotate the channel wall. When the electrodes are formed on both sides, the depth of the electrode provided on the channel wall continuously varies from one end of the channel row in accordance with the arrangement of the channel rows, which causes variations in the volume displacement of the ink channels. To reduce the variation of ink droplets caused by continuously changing the depths of the plurality of grooves so that the depth of the groove located at either end of the ink channel row becomes the smallest. Therefore, high quality printing can be performed.

In an ink jet head according to a fourth aspect of the present invention, at least a part is formed of a piezoelectric material, and a plurality of grooves arranged in parallel are provided on the surface of the ink jet head, which are separated from each other by walls. A base member having an electrode provided on a part of the side wall thereof. A cover member that forms an ink channel that serves as a pressure chamber is provided on the base member so as to cover the plurality of grooves. The inkjet head includes a nozzle that communicates with the ink channel. The inkjet head is
A drive voltage is applied to the electrodes to cause shear deformation on the side walls, thereby causing pressure vibrations in the ink channels to eject ink from the nozzles. The length of the side walls of the plurality of grooves in contact with the cover member continuously changes for each ink channel.

In this structure, the cover member is provided with the variation of the ink drop 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. Since the lengths of the side walls of the plurality of grooves in contact with each other can be reduced by continuously changing them for each ink channel, high quality printing can be performed.

In the ink jet head according to the fifth aspect of the present invention, of the plurality of side walls in contact with the cover member, the side wall located at the center of the ink channel row has the longest length or the shortest length.

In this structure, when a metal film to be an electrode is formed on the channel wall by oblique vapor deposition, the base material is rotated 180 ° about the center of the channel row as a rotation axis so that the electrodes are formed on both sides of the channel wall. When formed, the depth of the electrode provided on the channel wall changes continuously in accordance with the arrangement of the channel rows with the central portion of the channel row being symmetrical, and thus the ink droplets due to the variation in the volume displacement of the ink channel are formed. Since the variation can be reduced by continuously changing the length of the plurality of side walls located at the center of the ink channel row to be the longest or the shortest, it is possible to perform high-quality printing. You can

In the ink jet head according to the sixth aspect of the present invention, among the plurality of side walls in contact with the cover member, the side wall located at either end of the ink channel row has the longest length.

In this structure, when a metal film to be an electrode is formed on the channel wall by oblique vapor deposition, the base material is rotated 180 ° about one end of the channel row as the rotation axis to rotate the channel wall. When the electrodes are formed on both sides, the depth of the electrode provided on the channel wall continuously varies from one end of the channel row in accordance with the arrangement of the channel rows, which causes variations in the volume displacement of the ink channels. The variation of ink droplets caused by the above can be reduced by continuously changing the lengths of the plurality of side walls located at either end of the ink channel row to be the longest or the shortest. Therefore, high quality printing can be performed.

[0043]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to FIGS.

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. 1 and 2.

The ink jet head has a base member 1 in which a plurality of grooves 4 are formed in a piezoelectric body polarized in the vertical direction in FIG. 1, and a cover member 2 in which an ink supply port 21 and a common ink chamber 22 are formed. The ink channel 4 is formed by laminating the nozzle plate 9 having the nozzle holes 10 formed therein.

An electrode 5 for applying an electric field is formed on the channel wall 3. The rear end portion of the ink channel 4 is processed into an R shape corresponding to the diameter of the dicing blade used at the time of groove processing, and a portion indicated by reference numeral 6 serves as an electrode lead-out portion for energizing with the outside. Similarly, the shallow groove portion is processed by a dicing blade. The electrode formed in the shallow groove portion 6 is connected to an external electrode 8 such as a flexible substrate by wire bonding at the rear end portion of the shallow groove portion.

The electrodes provided on the channel wall 3 are connected to each other inside the ink channel 4 at the R-shaped portion at the rear end of the ink channel so as to have the same potential, and through the shallow groove 6 to the outside. It is connected to the electrode 8. The electrodes formed in each ink channel 4 are independently connected to the external electrode 8. The specified ink channel is selected according to the print data,
A voltage is applied from the 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 an electric field is applied undergoes shear deformation, and as a result, pressure wave fluctuations occur in the ink channel, and ink droplets are ejected from the nozzle holes 10. In FIG. 1, the electrode lead portion and the external electrode are connected by wire bonding, but they may be connected by using an anisotropic conductive film (ACF).

In the present embodiment, the case where the electrodes are formed on the channel walls 3 by obliquely vapor-depositing the base material 1 twice by rotating the base material 1 by 180 ° about the center of the channel row as a rotation axis will be described. To do.

FIG. 2 shows a sectional view of a channel row. In FIG. 2, the electrode 5 provided on the channel wall 3
Are formed in the central part of the channel row in the range of 150 μm, which is the upper half with equal 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 oblique vapor deposition, and the electrode row is formed shallower than the central portion and deeper than the end portion. The channel array continuously changes from the center to the end.

FIG. 3 is a diagram showing the depth of each electrode formed on the left and right sides of the channel wall when the number of channels is 200, with the horizontal axis representing the arrangement of channel rows. In this figure, the groove depth is the same for all channels for the sake of explanation.

From FIG. 3, the left and right electrode depths are equal at the center of the channel wall, but the left and right electrode depths change symmetrically continuously toward the end of the channel row. Recognize. When an inkjet head with such an electrode depth has the same groove depth for all channels, the displacement of the channel wall at the center of the channel row becomes the largest, and , The displacement amount will decrease continuously.

In the present embodiment, such a change in the displacement amount due to the uneven power source depth for each channel is set so that the groove depth of the central portion of the channel row is the shallowest and the end portion of the channel row is reduced. The solution is to make it deeper continuously as you go.

FIG. 4 is a diagram showing the groove depth according to the present embodiment, with the horizontal axis representing the channel rows. As shown in FIG. 4, the groove depth at the center of the channel row is the smallest, and the groove depth is continuously increased toward both ends of the channel row.

FIG. 5 is a sectional view of an ink jet head according to this embodiment. By forming channels with such a groove depth, 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. You can

In this embodiment, the groove depth at the center of the channel row is 300 μm, the electrode depth at the center of the channel row is 150 μm, and the groove depth at both ends of the channel row is 320 μm. Although the value is changed, the value may be adjusted according to the degree of variation in ink ejection according to the depth of the electrode for each channel, and it is not always necessary to change it linearly.

If the groove depth at both ends of the channel row is too deep, the rigidity of the channel wall is reduced and the pressure for ejecting ink is reduced. It is preferable that the depth is not more than 20%.

Second Embodiment In the present embodiment, the structure of the ink jet head is similar to that described in the first embodiment, and therefore the description thereof will not be repeated.

In the present embodiment, referring to FIG. 6, for forming electrodes on the channel walls 3, the base material 1 is rotated 180 ° about the end of the channel row as a rotation axis, and oblique deposition is performed twice. The case of forming by this will be described.

FIG. 6 shows a sectional view of the channel array. In FIG. 6, the electrode 5 provided on the channel wall 3
Are formed in the range of 150 μm, which is the upper half at the same depth on both sides of the channel wall 3 at the end of the channel row. 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 oblique deposition, and the depth is continuously shallow on one side of the channel wall and continuous on the other side. Is deeply formed.

FIG. 7 is a diagram showing the depth of the electrodes formed on both the left and right sides of the channel wall when the number of channels is 200, with the horizontal axis representing the arrangement of channel rows.

As shown in FIG. 7, 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. I understand. When an inkjet head having such an electrode depth has the same groove depth for all channels, the displacement of the channel wall at the end of the channel row where the electrode depth is the same is the largest, The amount of displacement continuously decreases toward the other end of the.

In the present embodiment, such a change in the amount of displacement due to the nonuniformity of the electrode depth as described above is minimized at the groove depth at the end where the electrode depths of the channel rows are equal. Towards the other end of the row of channels,
The solution is to make it deeper continuously.

FIG. 8 is a view showing the groove depth of the channel according to the present embodiment, with the abscissa showing the channel row arrangement.

As shown in FIG. 8, the groove depth of the channel at the end where the electrode depth of the channel line is the same is the smallest, and the depth is continuously deeper toward the other end of the channel line. By forming channels with such a groove depth, 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. You can

In the present embodiment, the groove depth at the end where the electrodes of the channel rows are equal is 300 μm, the electrode depth is 150 μm, and the groove depth at the end of the other channel row is 330 μm. Although it is changed linearly, the value may be adjusted according to the degree of dispersion of ink ejection according to the depth of the electrode for each channel, and it is not always necessary to change linearly. If the groove depth at the end where the electrodes of the channel rows are not equal is too deep, the rigidity of the channel wall is reduced and the pressure for ink ejection is reduced. It is preferably not more than 20% deeper than the depth of the center of the row.

Embodiment 3 In this embodiment, electrodes are formed on the channel walls 3 by using the base material 1 for 180 times with the center of the channel row as the axis of rotation.
A case of forming by performing oblique evaporation twice by rotating by ° will be described.

Since the structure of the ink jet head and the depth of the electrodes are the same as those in the first embodiment, detailed description will be omitted. In the present embodiment, the length of the channel wall in contact with the cover member is continuously changing.

FIG. 9 is a diagram schematically showing the drive waveform applied to the channel and the deformation of the channel wall at that time.

In FIG. 9, a voltage for expanding the volume of the ink channel is applied to the electrode for time T1, and then a voltage for narrowing the volume of the ink channel is applied for time T2. The voltages applied at the times T1 and T2 have the same magnitude and opposite directions.

The positive / negative of the voltage applied to T1 and T2 is uniquely determined by the polarization direction of the base material 1.

The time T1 affects the ink droplet ejection speed, and the time T1 at which the ejection speed is maximized is determined by the length of the ink channel and the ink channel determined by the length in contact with the cover member of the channel wall. Determined by compliance and velocity of pressure wave propagation. That is, the discharge speed is
It can be controlled by the time T1, which means that if the time T1 is fixed, the ejection speed can be controlled by the length of the ink channel.

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, it may be set to a value 3 to 4 times the time T1.

In FIG. 10, the ink channel width 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 the result of measuring the ejection speed of the ink droplets with the time T1 as a parameter under the same applied voltage of 25V.

From FIG. 10, when the time T1 is 2.25 μs, the ejection speed has a peak, and the time T1 is 2.2.
Whether it is longer or shorter than 5 μs, the ejection speed of ink droplets decreases.

Subsequently, in FIG. 11, the time T1 is 2.25.
It is the result of measuring the ink ejection speed with the length of the ink channel as a parameter, while fixing to μs.

When the ink channel length is 1 mm, the ejection speed becomes maximum, and the ink channel length is 1 m.
The ejection speed is reduced regardless of whether it is longer or shorter than m. This is equivalent to the case where the length of the ink channel is fixed and the time T1 is increased or decreased from the optimum value.

In the present embodiment, the length of the ink channels at both ends is set to 1 mm so that the ejection speed from the channels at both ends of the channel row where the depths of the electrodes differ most on both sides of the channel wall becomes maximum. The length of the central ink channel is 1.2 mm.

FIG. 12 shows the length of the ink channel used in this embodiment for each channel. In FIG. 12, the ink channel length is 1.0 mm at both ends of the channel row and 1.2 at the center of the channel row.
It changes continuously with mm.

In the present embodiment, the electrodes are formed on the channel walls 3 by oblique vapor deposition twice with the center of the channel row as the rotation axis. The electrode depths are different on both sides of the wall 3, and the left and right electrode depths are equal in the central portion of the channel wall, but the left and right electrode depths continuously change symmetrically toward the ends of the channel row. ing. for that reason,
In the central part of the channel wall, when driven with the same voltage, the displacement of the channel wall is the largest, and the ejection speed of ink droplets is the highest.

In the present embodiment, the ink channel length is set to 1 m so that the ink droplet ejection speed is maximized at both ends of the channel row where the ink droplet ejection speed is low.
m, and the length of the ink channel is 1.2 mm at the center of the channel row. As a result, even if an inkjet head having different depths of electrodes for each channel is used, it is possible to reduce variations in the ejection speed of ink droplets for each channel, and it is possible to perform high-quality printing.

In this embodiment, the ink channel length at the center of the channel row is 1.2 mm,
As is clear from FIG. 11, it is possible to take a value shorter than 1.0 mm at which the ejection speed of the ink droplet becomes maximum.

Since the length of the ink channel that maximizes the ink droplet ejection speed is determined by the width of the ink channel, the depth of the ink channel, the size of the nozzle, the ink characteristics, etc., the dimensional specifications of the ink jet head. If is different, the optimum value may be used for each.

The length of the ink channel can be arbitrarily changed depending on the shape of the common ink chamber of the cover member. This will be described with reference to FIG.

FIG. 13 is a plan view of an ink jet head in which the ink channel length at the center of the channel row is 1.2 mm and the ink channel length at both ends is 1.0 mm. The common ink chamber 22 of the cover member 2 is shown in FIG. Figure 1
The feature is that the length A of 3 is processed so as to be continuously changed. As described above, the length of the ink channel is determined by the length of contact between the upper surface of the channel wall and the cover member, and thus can be easily changed by processing the cover member into a desired shape.

Fourth Embodiment In the present embodiment, the electrode is formed on the channel wall 3 with the base material 1 at 180 ° with the end of the channel row as the rotation axis.
A case of forming by rotating and performing oblique vapor deposition twice will be described.

Since the structure of the ink jet head and the depth of the electrodes are the same as those in the third embodiment, detailed description will be omitted.

In FIG. 14, the ink channel length continuously changes to 1.0 mm at one end of the channel row and 1.3 mm at the other end of the channel row.

In the present embodiment, the electrode is formed on the channel wall 3 by obliquely vapor depositing twice with the end of the channel row as the axis of rotation. The electrode depths are different on both sides of 3, and the left and right electrode depths are the same at one end of the channel wall, but as it goes to the other end of the channel row,
The left and right electrode depths are continuously changed symmetrically.

Therefore, at one end of the channel wall, when driven at the same voltage, the displacement of the channel wall is the largest, and the ink droplet ejection speed is the highest.

In the present embodiment, the ink channel length is set to 1 mm so that the ink droplet ejection speed is maximized at one end of the channel row where the ink droplet ejection speed is low. At the other end, the length of the ink channel is 1.3 mm. As a result, even if an inkjet head having different depths of electrodes for each channel is used, it is possible to reduce variations in the ejection speed of ink droplets for each channel, and it is possible to perform high-quality printing.

In the present embodiment, the ink channel length at one end of the channel row is set to 1.3 mm, but as is clear from FIG. 11, the maximum ink droplet ejection speed is 1. It is also possible to take a value shorter than 0 mm.

The length of the ink channel that maximizes the ink droplet ejection speed is determined by the width of the ink channel, the depth of the ink channel, the size of the nozzle, the ink characteristics, etc. If is different, the optimum value may be used for each.

The method of arbitrarily changing the length of the ink channel depending on the shape of the common ink chamber of the cover member is the same as that of the third embodiment, and the detailed description thereof will be omitted.

The embodiments disclosed this time are to be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description but by the claims, and is intended to include meanings equivalent to the claims and all modifications within the scope.

[0096]

As described above, the ink jet head according to the present invention is in contact with the groove depth of the ink channel or the cover member of the ink channel according to the depth of the electrode which is different for each ink channel. Since the length is continuously changed, it is possible to reduce variations in the ejection of ink droplets for each ink channel, and it is possible to obtain high-quality printing.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of an inkjet head according to the present invention.

FIG. 2 is a cross-sectional view of a channel row according to the first embodiment.

FIG. 3 is a diagram of electrode depth in the inkjet head according to the first embodiment.

FIG. 4 is a diagram showing a groove depth of the inkjet head according to the first embodiment.

FIG. 5 is a sectional view of the inkjet head according to the first embodiment.

FIG. 6 is a cross-sectional view of an inkjet head according to a second embodiment.

FIG. 7 is a diagram showing the electrode depth of the inkjet head according to the second embodiment.

FIG. 8 is a diagram showing the groove depth of the inkjet head according to the second embodiment.

FIG. 9 is a drive schematic diagram of drive waveforms and channel drive of an inkjet head according to the related art and the present invention.

FIG. 10 is a diagram showing the relationship between the drive waveform time T1 and the ink ejection speed of the inkjet head according to the third embodiment.

FIG. 11 is a diagram showing the relationship between the channel length and the ink ejection speed of the inkjet head according to the third embodiment.

FIG. 12 is a diagram showing a channel length for each channel row of the inkjet head according to the third embodiment.

FIG. 13 is a plan view of an inkjet head according to a third embodiment.

FIG. 14 is a diagram showing a channel length for each channel row of the inkjet head according to the fourth embodiment.

FIG. 15 is a perspective view showing a conventional inkjet head.

FIG. 16 is a diagram showing a conventional method for manufacturing an inkjet head.

FIG. 17 is a cross-sectional view showing a conventional method for forming electrodes of an inkjet head.

FIG. 18 is a diagram showing a conventional electrode forming apparatus for an inkjet head.

FIG. 19 is a cross-sectional view showing a conventional method for forming electrodes of an inkjet head.

FIG. 20 is a cross-sectional view showing a conventional inkjet head.

FIG. 21 is a cross-sectional view showing how a channel of a conventional inkjet head is driven.

[Explanation of symbols]

1 base member, 2 cover member, 3 channel wall,
4 ink channels, 5 electrodes (metal film), 6 shallow groove parts, 7 bonding wires, 8 external electrodes, 9 nozzle plates, 10 nozzle holes, 11 dry resist film, 12 piezoelectric bodies, 21 ink supply ports, 22 common ink chamber.

Claims (6)

[Claims] 1. A piezoelectric material, at least a part of which is formed,
Further, a plurality of grooves are provided on the surface thereof, which are separated from each other by walls, and are arranged in parallel, and further, a base member provided with an electrode on a part of a sidewall of each groove, and the base so as to cover the plurality of grooves A cover member that is provided on the member and that forms an ink channel that serves as a pressure chamber; and a nozzle that communicates with the ink channel, and apply a drive voltage to the electrode to cause shear deformation in the side wall. In an inkjet head that causes pressure vibration in the ink channel to eject ink from the nozzles, the depth of each of the plurality of grooves is the direction in which the grooves are arranged on both sides of the groove located in the central portion. An ink jet head characterized by continuously changing toward. 2. The ink jet head according to claim 1, wherein among the plurality of grooves, the depth of the groove located at the center is the smallest. 3. The ink jet head according to claim 1, wherein the depth of the groove located at either one of the plurality of grooves is the smallest. 4. At least a portion formed of a piezoelectric material,
Further, a plurality of grooves are provided on the surface thereof, which are separated from each other by walls, and are arranged in parallel, and further, a base member provided with an electrode on a part of a side wall of each groove, and the base so as to cover the plurality of grooves. A cover member that is provided on the member and forms an ink channel that serves as a pressure chamber; and a nozzle that communicates with the ink channel, and applies a drive voltage to the electrode to cause shear deformation in the side wall. Thus, in the ink jet head in which pressure vibration is generated in the ink channels to eject ink from the nozzles, the lengths of the side walls of the plurality of grooves in contact with the cover member continuously change for each ink channel. An inkjet head characterized in that. 5. The ink jet head according to claim 4, wherein among the side walls of the plurality of grooves in contact with the cover member, the side wall located at the center of the ink channel row has the longest length or the shortest length. 6. The ink jet head according to claim 4, wherein among the plurality of side walls in contact with the cover member, the side wall located at either end of the ink channel row has the longest length.