JP2001334658A - Inkjet head - Google Patents

Abstract

(57) [Problem] It is a main object to provide an ink jet head improved so as to be able to reduce the ejection variation of ink droplets for each ink channel. SOLUTION: A nozzle whose inertance changes continuously for each ink channel is provided according to the depth of an electrode which differs for each ink channel.

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 particularly, to a method in which an electrode is provided in an ink channel and ink is ejected by causing a pressure fluctuation in the ink channel. The present invention relates to an inkjet head.

[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 has attracted attention because it is advantageous for high printing efficiency, low cost, and low running cost.
The Kaiser method using a piezoelectric element and the thermal jet method have become mainstream.

[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, it generates bubbles in the ink by heating the heater and uses the energy of the bubbles for ejection. Requirements are severe, and it is difficult to extend the life of the heater.
Further, there is a problem that power consumption is increased.

In order to solve such disadvantages, an ink jet system utilizing 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 the ink channel wall made of the piezoelectric material,
The channel wall is deformed in a shearing mode, and ink droplets are ejected by utilizing the pressure wave fluctuation generated at that time, and is suitable for high density nozzles, low power consumption, and high driving frequency. Such a structure of the ink jet head using the shear mode will be described with reference to FIG.

The ink jet head comprises a base member 1 having a plurality of grooves 4 formed in a piezoelectric body which has been subjected to polarization processing in the vertical direction in FIG. 11, an ink supply port 21 and a common ink chamber 22.
The ink channel 4 is formed by laminating the cover member 2 in which the ink channel 4 is formed and the nozzle plate 9 having the nozzle hole 10 formed therein.
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 machined into an R shape corresponding to the diameter of the dicing blade used at the time of groove machining.
A shallow groove as an electrode lead-out portion for supplying electricity to the outside is similarly 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.

Next, a method of manufacturing the ink jet head shown in FIG. 11 will be described with reference to FIG.

As shown in FIG. 12A, 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 a vertical direction.

Next, as shown in FIG. 12B, 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 vapor deposition is performed from the A direction and the B direction in FIG. Thereafter, by lifting off the dry resist film 11, the base member 1 as an actuator having a metal film formed in the upper half of the channel wall 3 and the shallow groove 6 as shown in FIG. 11 is manufactured.

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 in this manner are respectively bonded to desired positions with an adhesive. In the ink-jet head manufactured in this manner, the ink supply port 21 has
The ink is connected to an external ink storage tank (not shown), and the ink is supplied to each of the plurality of ink channels 4 via the common ink chamber 22. The electrodes provided in the upper half of 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 externally connected via the shallow groove 6. Is connected to the electrode 8 of.

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. In addition,
In FIG. 11, the electrode lead-out portion and the external electrode are connected by wire bonding, but the anisotropic conductive film (ACF) is used.
Conventionally, a method of connecting using a method has been adopted.

[0012]

In a conventional ink jet head, a vertically polarized piezoelectric body 12 is used for a base member as an actuator. In order to deform the channel wall in a shearing mode, the upper surface of the channel wall is deformed. An electrode was formed in half. On the other hand, a so-called chevron type structure using a composite material in which a base member as an actuator is stacked at half the height of a channel wall with piezoelectric materials having different polarization directions in a vertical direction has been proposed. I was

In this case, since the electrodes need only be formed on the entire surface of the channel wall, it is not necessary to limit the formation position of the electrodes to the upper half of the channel wall.
Although there is a feature that an electroless plating method or the like can be used, there is a problem that the manufacturing cost of a base member as an actuator increases.

Therefore, at present, a method of using a single piezoelectric body which has been subjected to a polarization treatment in the vertical direction as a base member has become the mainstream, and an electrode is formed only on the upper half of the 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 deposition method is generally used, and the deposition is performed twice while changing the incident direction of the deposition particles.

FIG. 13 (a) shows a state of one evaporation, in which the height of the channel wall is 300 μm and the width is 80 μm.
m, when the height of the dry resist film is 30 μm,
In order to form an electrode on the upper left half of the channel wall 3,
The vapor deposition particles are incident at an incident angle of 66 ° with respect to the normal.

FIG. 13 (b) shows the state of two evaporations. In order to form an electrode in the upper right half of the channel wall 3, the electrode is also formed at an incident angle of 66 ° with respect to the normal line. The deposition particles are incident. After that, the metal film formed on the dry resist 11 is lifted off together with the dry resist 11, so that the base 5 on which the electrode 5 is formed only on the upper half of the side wall of the channel wall 3 as shown in FIG. The member 1 is manufactured. As described above, the depth of the electrode formed on the channel wall 3 is formed such that the channel depth becomes half.

Japanese Patent Application Laid-Open No. 6-28892 discloses that if the intersection of the electrode depths is within ± 30% of a set value, the change in volume of the ink channel will be 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, a change in the volume of the ink channel of ± 5% is not a small value.

The publication also does not disclose any variation in electrode depth during electrode formation, particularly the difference in electrode depth on both sides of the channel wall. Is greatly affected by the difference in electrode depth on both sides.

Conventional 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. 14 shows the positional relationship between the vapor deposition device used for oblique vapor deposition and the base member 1. In FIG. 14, a deposition source 15 is placed in a crucible 16 and positioned at the center below the deposition apparatus, and a base member 1 is attached to a substrate holder 17 above the deposition apparatus at a predetermined angle. FIG. 14 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. 14 shows a case where the vertical distance from the vapor deposition source 15 to the center of the channel row of the base member 1 is 50 cm and the horizontal distance is 20 cm. dot / in
ch) are formed. In this case, the ink channel 4 has a width of about 28 mm (= 25.4 [inch / inch).
mm] / 180 [dot / inch] * 200 [do
t]).

In the case of FIG. 14, 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 angle of incidence on the deposition particles differs at the end of the channel row. This will be described in detail with reference to FIG.

FIG. 15 schematically shows the incident state of the deposition particles when the base member 1 is parallel. When the incident angle at the center of the channel row is 66 °, the incident angles at the end of the channel are 64.7 ° and 67.4 °, respectively.

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 becomes larger than the incident angle at the central portion, and 0.4 ° The incident angle at the end of the channel row farther from the vapor deposition source 15 is 64.7 °, which is smaller than the incident angle at the center.

As a result, as shown in FIG. 16, the formation depth of the metal film serving as the electrode 5 is 1 at the center of the channel row.
In contrast to 50 μm, they are 138.5 μm and 162.2 μm at the end of the channel row, 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 deformed most efficiently if the electrode is formed only in the upper half of the channel wall. The amount decreases. This will be described in detail with reference to FIG.

FIG. 17A shows the case where the depth of the electrode is formed in the upper half of the channel wall 3 and FIG.
(B) is a diagram schematically showing the deformation mode of the channel wall 3 when different on both sides.

In FIG. 17 (a), when electrodes are 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 perpendicular 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, the channel wall 3 is caused to shear by the shear strain, as shown by a broken line.
Is deformed so as to be bent at the central portion A of.

On the other hand, in FIG. 17 (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 'above A in FIG. 7A, the volume displacement of the ink channel 4 becomes small, and the pressure change for discharging the ink droplet from the nozzle becomes small. As described above, in the conventional inkjet head, the depth of the electrode to which a voltage for causing shear strain is applied changes depending on the ink channel, and the ejection speed and ejection volume of the ink droplet ejected 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 an ink jet head which can reduce variation in ejection of ink droplets for each ink channel.

[0033]

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

In the ink jet head 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 a part of a side wall of each groove is provided. A base member provided with an electrode, 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; A drive voltage is applied to the ink channel to generate a shear deformation on the side wall, thereby generating a pressure vibration in the ink channel and discharging ink from the nozzle.

The inertance of the nozzle is continuously changed for each ink channel.

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

The ink jet head according to the second aspect of the present invention is characterized in that the inertance of the nozzle whose inertance changes continuously is the largest at the nozzle located at the center of the row of the plurality of ink channels. .

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 variation in the ink droplets caused by the variation in the volume displacement of the ink channel due to the depth of the electrode provided on the channel wall being continuously changed in accordance with the arrangement of the channel rows with the center of the channel row being symmetrical, Since the inertance of the nozzle at the center of the channel row can be reduced by making it the largest and continuously changing it, high-quality printing can be performed.

In the ink jet head according to the third aspect of the present invention, the inertance of the nozzle whose inertance continuously changes is the largest at the nozzle located at either one end of the plurality of ink channel rows. It is characterized by.

In this configuration, when a metal film to be an electrode is formed on the channel wall by oblique vapor deposition, the base member is rotated by 180 ° C. about one end 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 due to this can be reduced by making the inertance of the nozzle at one end of the channel row the largest and continuously changing it, so that high quality printing can be performed. it can.

An ink jet head according to a fourth aspect of the present invention is characterized in that, in the above-mentioned nozzle whose inertance changes continuously, the taper angle of the nozzle hole changes continuously for each channel.

In this configuration, the variation of the ink droplets caused by the variation of the volume displacement of the ink channel due to the continuous change of the depth of the electrode provided on the channel wall in accordance with the arrangement of the channel rows is eliminated. By continuously changing the taper angle of the nozzles, the inertance of the nozzles can be reduced by continuously changing the nozzles, so that the variation of ink droplets ejected from each nozzle can be reduced, and high quality can be achieved. Can be printed.

In the ink-jet head according to the fifth aspect of the present invention, the nozzle whose taper angle changes continuously, the nozzle located at the center of the plurality of ink channel rows has the smallest taper angle. I do.

In this configuration, when a metal film to be an electrode is formed on the channel wall by oblique evaporation, the base member is rotated 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. The variation can be continuously changed by making the taper angle of the nozzle at the center of the channel row the smallest, thereby reducing the inertance of the nozzle by continuously changing it. The variation in ink droplets to be used can be reduced, and high quality printing can be performed.

In the ink jet head according to the sixth aspect of the present invention, the nozzle having the continuously changing taper angle has the smallest taper angle at the nozzle located at one end of the plurality of ink channel rows. It is characterized by the following.

In this configuration, when a metal film to be an electrode is formed on the channel wall by oblique evaporation, the base member is rotated by 180 ° with one end 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. The variation of the resulting ink droplets is continuously changed by minimizing the taper angle of the nozzle at one end of the channel row, thereby continuously changing the inertance of the nozzle to reduce it. Therefore, variations in ink droplets ejected from each nozzle can be reduced, and high quality printing can be performed. That.

In the ink-jet head according to the seventh aspect of the present invention, in the above-mentioned nozzle having a continuously changing inertance, both the opening diameter of the nozzle on the ink discharge side and the opening diameter of the ink channel side are continuous for each channel. Characteristically change.

In this configuration, variations in ink droplets due to variations in the volume displacement of the ink channels due to the depth of the electrodes provided on the channel walls continuously changing in accordance with the arrangement of the channel rows are eliminated. By continuously changing both the opening diameter on the ink ejection side and the opening diameter on the ink channel side, it is possible to reduce the inertance of the nozzle by continuously changing it. Droplet variation can be reduced, and high quality printing can be performed.

In the ink jet head according to the eighth aspect of the present invention, a plurality of ink channel arrays are formed by the nozzles in which both the opening diameter on the ink discharge side and the opening diameter on the ink channel side change continuously for each channel. Is characterized in that the opening diameter on the ink ejection side and the opening diameter on the ink channel side of the nozzle located at the center of the nozzle are the smallest.

In this configuration, when a metal film to be an electrode is formed on the channel wall by oblique evaporation, 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. The variation is continuously changed by minimizing both the opening diameter on the ink ejection side, the opening diameter on the ink channel side, and the opening diameter on the ink channel side of the nozzle at the center of the channel row,
Since the inertance of the nozzles can be reduced by continuously changing them, variations in ink droplets ejected from each nozzle can be reduced, and high quality printing can be performed.

In the ink jet head according to the ninth aspect of the present invention, a plurality of ink channel arrays are formed by the nozzles in which both the opening diameter on the ink discharge side and the opening diameter on the ink channel side change continuously for each channel. The opening diameter on the ink ejection side and the opening diameter on the ink channel side of the nozzle located at one of the ends are the smallest.

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 by 180 °. 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 symmetrical one end of the channel row and the continuous change according to the arrangement of the channel row is reduced to the one end of the channel row. By making both the opening diameter of the nozzle on the ink ejection side and the opening diameter on the ink channel side of the portion the smallest and changing them continuously, the inertance of the nozzles can be changed continuously and reduced. In addition, variations in ink droplets ejected from each nozzle can be reduced, and high quality printing can be performed.

[0053]

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 which has been subjected to polarization processing 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.

PZT as base member 1, cover member 2
As the PTZ, non-polarized PTZ was used. The nozzle plate 9 is provided with a nozzle hole 10 by excimer laser processing using a polyimide film having a thickness of 50 μm. A 1 μm thick A1 is formed on the channel wall 3 by oblique evaporation as an electrode 5 for applying an electric field.

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. A shallow groove 6 is provided at 6 as an electrode lead-out part 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 by wire bonding at the rear end of the shallow groove 6.

The shallow groove 6 has a channel wall 3
Al is simultaneously formed as an electrode when the electrode 5 is formed. The electrode 5 provided on the channel wall 3
In each of the ink channels 4, the ink channels 4 are connected 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 external electrode 8 via the shallow groove 6. 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 voltage 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 FIG. 1, the electrode lead portion and the external electrode are connected by wire bonding 7, but they may be connected by using an anisotropic conductive film (ACF).

In this 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. .

FIG. 2 is a cross-sectional view of a channel row produced by the vapor deposition method. In FIG. 2, the electrode 5 provided on the channel wall 3 is formed at the center of the channel row in a range of 150 μm, which is an 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. It changes continuously from the center of the row to the end.

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. From FIG. 3, at the center of the channel wall (near channel column number 100), the left and right electrode depths are equal, but at the end of the channel column (channel column numbers 0 and 2).
It can be seen that the left and right electrode depths continuously change symmetrically as the position moves toward 00). 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 center of the channel row becomes the largest, and the displacement is continuously increased toward the end of the channel row. Thus, the displacement amount is reduced. As a result, when the same voltage is applied, if the nozzle plate 9 provided with the nozzle holes of the same shape is used,
The ejection speed and the ejection volume of the ink ejected for each nozzle change.

In this embodiment, the change in the ink discharge speed and the discharge volume for each channel due to such non-uniform electrode depth is minimized by minimizing the taper angle of the nozzle hole provided at the center of the channel row. The problem is solved by increasing the taper angle continuously toward the end of the channel row.

FIG. 4 is a diagram showing the taper angles of the nozzle holes according to the present embodiment, with the channel axis arranged along the horizontal axis.

FIG. 5A is a cross-sectional view of the nozzle hole at the center of the channel row, and FIG. 5B is a cross-sectional view of the nozzle hole at the end of the channel row. As shown in FIG. 4, the nozzle array is manufactured such that the taper angle of the nozzle hole at the center of the channel array is the smallest and continuously increases toward both ends of the channel array. That is, FIG.
As shown in FIG. 7, since the taper angle of the nozzle hole at the center of the channel row where the displacement amount of the channel wall 3 is the largest is the smallest, the inertance of this nozzle becomes the largest,
The resistance of the nozzle holes to ink ejection is maximized.
Also, as shown in FIG. 5B, the taper angle of the nozzle hole increases toward the end of the channel row,
The inertance of the nozzle is also reduced, and the resistance to ink ejection is also reduced.

As described above, the resistance to ink ejection can be continuously changed by the taper angle of the nozzle hole according to the ink ejection force. By using the nozzle plate 9 provided with the nozzle holes 10 having such a tapered angle, variations in ink droplets ejected from the nozzles can be reduced, and high-quality printing can be performed.

In the present embodiment, the opening diameter of the nozzle hole 10 on the ink ejection side is fixed at 25 μm and the taper angle is continuously changed from 10 ° to 15 °. , Depending on the variation of the electrode depth,
What is necessary is just to set a taper angle. Alternatively, the taper angle may be changed by keeping the opening diameter of the nozzle hole 10 on the ink supply side constant. In addition, during excimer laser processing, the taper angle of the nozzle hole can be changed by changing conditions such as a reduction ratio of laser light, laser power, and irradiation time. In this embodiment, the laser power and the irradiation time are kept constant,
By changing the reduction ratio from 3 to 4, the energy density of the laser beam incident on the nozzle plate was changed, and the taper angle was changed.

<Embodiment 2> A second embodiment according to 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. 6 is a cross-sectional view of a channel row produced by the vapor deposition method. In FIG. 6, the electrode 5 provided on the channel wall 3 is formed at the end of the channel row (the leftmost channel in the drawing) in the range of 150 μm, which is the same depth on both sides of the channel wall 3 and becomes the upper half. I have. On the other hand, at the other end of the channel row (the rightmost channel in the drawing), 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 it is continuously shallow on one side of the channel wall. It is formed continuously deep on another side.

FIG. 7 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 row of channels arranged along the horizontal axis. From FIG. 7, at the end of the channel wall (near channel row number 0), the left and right electrode depths are equal, but the other end of the channel row (channel row number 200).
It can be seen that the depths of the left and right electrodes are continuously changing as going toward. 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. As a result, when the same voltage is applied,
If a nozzle plate 9 provided with nozzle holes of the same shape is used, the discharge speed and the discharge volume of the ink discharged for each nozzle will change.

In this embodiment, the change in the ink discharge speed and the discharge volume for each channel due to such non-uniform electrode depth is determined by the taper angle of the nozzle hole provided at one end of the channel row. Is minimized, and the taper angle increases continuously toward the other end of the channel row.

FIG. 8 is a diagram showing the taper angles of the nozzle holes according to the present embodiment, with the horizontal axis representing the channel array. As shown in FIG. 8, the taper angle of the nozzle hole at the end of the channel row (channel row 1) is the smallest and continuously increases toward the other end of the channel row (channel row 200). In other words, since the taper angle of the nozzle hole at the end of the channel row (channel row 1) where the amount of displacement of the channel wall 3 is largest is the smallest, the inertance of this nozzle is the largest, and the resistance of the nozzle hole to ink ejection is the largest. growing. Also, the other end of the channel row (channel row 20)
Toward 0), the taper angle of the nozzle hole increases, the inertance of the nozzle decreases, and the resistance to ink ejection decreases. As described above, the resistance to ink ejection can be continuously changed by the taper angle of the nozzle hole according to the ink ejection force. By using the nozzle plate 9 provided with the nozzle holes 10 having such a tapered angle, variations in ink droplets ejected from the nozzles can be reduced, and high-quality printing can be performed.

In this embodiment, the opening diameter of the nozzle hole 10 on the ink discharge side is fixed at 25 μm and the taper angle is continuously changed from 10 ° to 18 °. , Depending on the variation of the electrode depth,
What is necessary is just to set a taper angle. Alternatively, the taper angle may be changed by keeping the opening diameter of the nozzle hole 10 on the ink supply side constant. Further, the taper angle of the nozzle hole can be changed by changing conditions such as the reduction ratio of laser light, laser power, and irradiation time during excimer laser processing. In the present embodiment, the laser power and the irradiation time are kept constant, and the reduction ratio is changed from 3 to 4, thereby changing the energy density of the laser light incident on the nozzle plate and changing the taper angle.

<Embodiment 3> A third embodiment according to 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 case will be described in which the opening diameter of the nozzle hole 10 on the ink discharge side and the opening diameter on the ink supply side both change continuously.

FIG. 9 is a diagram showing the opening diameter of the nozzle holes on the ink discharge side and the opening diameter on the ink supply side of the nozzle hole according to the present embodiment, with the channel axis arranged on the horizontal axis. As shown in FIG. 9, the opening diameter on the ink ejection side and the opening diameter on the ink supply side of the nozzle hole at the center of the channel row are the smallest, and continuously increase toward both ends of the channel row. That is, since the opening diameter on the ink ejection side and the opening diameter on the ink supply side of the nozzle hole at the center of the channel row where the amount of displacement of the channel wall 3 is the largest, the inertance of this nozzle becomes the largest, The resistance to ink ejection is highest.

Further, as approaching the end of the channel row, the opening diameter of the nozzle hole on the ink discharge side and the opening diameter on the ink supply side increase, the inertance of the nozzle decreases, and the resistance to ink discharge decreases. As described above, by changing the opening diameter of the nozzle hole on the ink discharging side and the opening diameter of the ink supply side according to the ink discharging force, the resistance to ink discharging can be continuously changed. By using the nozzle plate 9 provided with the nozzle holes 10 having such an opening diameter, variations in ink droplets ejected from the nozzles can be reduced, and high-quality printing can be performed. In this embodiment,
The opening diameter of the nozzle hole 10 at the center of the channel row on the ink ejection side is φ20 μm, and the opening diameter on the ink supply side is φ40 μm.
m, the opening diameter on the ink ejection side of the nozzle hole 10 at the end of the channel row is φ23 μm, and the opening diameter on the ink supply side is φ43.
Although it was continuously changed in μm, the diameter of each opening may be set according to the variation in the depth of the electrode.

The diameter of the nozzle hole can be changed by changing conditions such as the reduction ratio of laser light, laser power, and irradiation time during excimer laser processing.

In this embodiment, the laser power is kept constant,
By changing the irradiation time from 1 to 4 seconds and the reduction ratio from 3 to 4, the energy density of the laser beam incident on the nozzle plate was changed, and the taper angle was changed.

<Embodiment 4> A fourth embodiment according to 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.

Since the structure of the ink jet head and the depth of the electrodes are the same as those in the second embodiment, detailed description will be omitted. In the present embodiment, a case will be described in which the opening diameter of the nozzle hole 10 on the ink discharge side and the opening diameter on the ink supply side both change continuously. FIG. 10 is a diagram showing the opening diameter of the nozzle hole on the ink discharge side and the opening diameter of the ink supply side of the nozzle hole according to the present embodiment, with the channel axis arranged along the horizontal axis.

As shown in FIG. 10, the opening diameter on the ink discharge side and the opening diameter on the ink supply side of the nozzle hole at the end (channel 1) of the channel row are the smallest, and the other end (channel 200). That is, since the opening diameter on the ink ejection side and the opening diameter on the ink supply side of the nozzle hole at the end (channel 1) of the channel row where the displacement amount of the channel wall 3 is the largest, the nozzle inertance becomes the largest. In addition, the resistance of the nozzle hole to ink ejection becomes highest. Further, as the nozzle hole approaches the other end (channel 200), the opening diameter of the nozzle hole on the ink discharge side and the opening diameter on the ink supply side increase, the inertance of the nozzle decreases, and the resistance to ink discharge decreases. Become smaller. As described above, by changing the opening diameter of the nozzle hole on the ink discharging side and the opening diameter of the ink supply side according to the ink discharging force, the resistance to ink discharging can be continuously changed.

By using the nozzle plate 9 provided with the nozzle holes 10 having such an opening diameter, variations in ink droplets ejected from the nozzles can be reduced, and high quality printing can be performed. .

In this embodiment, the opening diameter of the nozzle hole 10 at the end of the channel row (channel 1) on the ink ejection side is φ20 μm, the opening diameter on the ink supply side is φ40 μm, and
The opening diameter of the nozzle hole 10 at the end of the channel row on the ink ejection side is φ25 μm, and the opening diameter on the ink supply side is φ45 μm.
, But each opening diameter may be set according to the variation in the depth of the electrode.

The diameter of the nozzle hole can be changed by changing conditions such as the reduction ratio of laser light, laser power, and irradiation time during excimer laser processing. In this embodiment, the laser power is kept constant, the irradiation time is changed from 1 to 4 seconds, and the reduction rate is changed from 3 to 4, thereby changing the energy density of the laser light incident on the nozzle plate and changing the taper angle. Was.

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.

[0086]

As described above, the ink jet head according to the present invention continuously changes the inertance of the nozzle for each ink channel according to the electrode depth which differs for each ink channel. It is possible to reduce the variation in the ejection of the ink droplets from each other, 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 a diagram of a taper angle of a nozzle hole showing a first embodiment of the ink jet head of the present invention.

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

FIG. 6 is a sectional view showing a second embodiment of the ink jet head of the present invention.

FIG. 7 is a diagram of an electrode depth showing a second embodiment of the ink jet head of the present invention.

FIG. 8 is a view of a taper angle of a nozzle hole showing a second embodiment of the ink jet head of the present invention.

FIG. 9 is a view of the opening diameter of a nozzle hole showing a third embodiment of the ink jet head of the present invention.

FIG. 10 is a view of the opening diameter of a nozzle hole showing a fourth embodiment of the ink jet head of the present invention.

FIG. 11 is a perspective view showing a conventional inkjet head.

FIG. 12 is a view illustrating a method for manufacturing a conventional inkjet head.

FIG. 13 is a cross-sectional view illustrating a conventional method for forming an electrode of an inkjet head.

FIG. 14 is a diagram showing a conventional electrode forming apparatus for an inkjet head.

FIG. 15 is a cross-sectional view illustrating a conventional method for forming an electrode of an inkjet head.

FIG. 16 is a cross-sectional view showing a conventional inkjet head.

FIG. 17 is a cross-sectional view showing how a channel of a conventional inkjet head is driven.

[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 (9)

[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 further, a base member provided with an electrode on a part of a side wall of each groove, and provided so as to cover the plurality of grooves of the base member. A cover member forming 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 a pressure oscillation on the ink channel. Wherein the inertance of the nozzle is continuously changed for each ink channel. 2. The ink jet head according to claim 1, wherein the inertance of the nozzle having the continuously changing inertance is the largest in the nozzle located at the center of the row of the plurality of ink channels. 3. The ink jet head according to claim 1, wherein the inertance of the nozzle at which one of the plurality of rows of the ink channels is located at one end is the largest among the nozzles whose inertance changes continuously. . 4. The ink jet head according to claim 1, wherein the taper angle of the nozzle hole changes continuously for each channel in the nozzle in which the inertance changes continuously. 5. The ink-jet head according to claim 4, wherein the nozzle at which the taper angle changes continuously has the smallest taper angle at the nozzle located at the center of the plurality of ink channel rows. 6. The nozzle according to claim 4, wherein in the nozzle whose taper angle changes continuously, the nozzle located at one end of each of the plurality of ink channels has the smallest taper angle. Inkjet head. 7. The nozzle whose inertance changes continuously, wherein both the opening diameter of the nozzle on the ink discharge side and the opening diameter of the ink channel side change continuously for each channel. 2. The inkjet head according to 1. 8. The nozzle in which both the opening diameter on the ink ejection side and the opening diameter on the ink channel side continuously change for each channel, and the ink ejection side of a nozzle located at the center of a plurality of ink channel rows. The ink jet head according to claim 7, wherein the opening diameter of the ink channel and the opening diameter of the ink channel side are the smallest. 9. The nozzle in which both the opening diameter on the ink ejection side and the opening diameter on the ink channel side change continuously for each channel, and the nozzle located at one end of a plurality of ink channel rows. 8. The ink jet head according to claim 7, wherein the opening diameter on the ink ejection side and the opening diameter on the ink channel side are the smallest.