JP4243341B2 - Inkjet head - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to an inkjet head.
[0002]
[Prior art]
In general, as an ink jet head mounted on an ink jet recording apparatus used in an image recording apparatus (including an image forming apparatus) such as a printer, a facsimile machine, a copying apparatus, and a plotter, a nozzle for ejecting ink droplets and an ink communicating with the nozzle A liquid chamber (also referred to as a discharge chamber, an ink flow path, an ink chamber, a pressure chamber, a pressurizing chamber, a pressurized liquid chamber, etc.), and a vibration plate that also serves as a first electrode that forms the wall surface of the ink liquid chamber; There is known an electrostatic ink-jet head that includes an electrode (second electrode) opposed to this and deforms a diaphragm with an electrostatic force to eject ink droplets from a nozzle.
[0003]
In such an electrostatic ink jet head, the distance (gap) between the diaphragm and the electrode is set in a range of 0.05 to 2.0 μm in order to achieve low voltage driving. When the gap between the diaphragm and the electrode is small, the air pressure in the vibration chamber formed by the diaphragm and the electrode rises when the diaphragm is deformed, and the deformation of the diaphragm is hindered and a desired displacement amount cannot be obtained. The so-called air damper effect occurs.
[0004]
Therefore, in a conventional electrostatic ink jet head, for example, as described in JP-A-7-299908, an actuator including at least a vibration chamber formed by a diaphragm and an electrode is hermetically configured. It has been proposed that the ratio of the volume V to the volume ΔV excluded by the diaphragm be in the range of 2 ≦ V / ΔV ≦ 8.
[0005]
Further, as described in Japanese Patent Application Laid-Open No. 11-34319, the gap between the diaphragm substrate other than directly below the diaphragm and the electrode substrate is made larger than the interval immediately below the diaphragm, or communicated with each vibration chamber to open the atmosphere. It has been proposed to provide an opening to reduce the air damper effect.
[0006]
On the other hand, such a minute gap between the diaphragm and the electrode needs to be shielded from dust and moisture from the outside in order to perform normal operation of the diaphragm. Therefore, JP-A-6-71882 discloses a method of sealing a gap with an epoxy adhesive, JP-A-10-264381 discloses a method of sealing a gap using a low-melting glass, Japanese Patent Application Laid-Open No. 11-286109 discloses a method for compensating for a change in atmospheric pressure of a sealed gap.
[0007]
[Problems to be solved by the invention]
However, when the experiment was repeated, as the actuator volume V, only the volume immediately below the diaphragm exerted a great effect on reducing the air damper effect, and even if the volume other than just below the diaphragm was increased, the effect of reducing the air damper effect was small. It has been found.
[0008]
Therefore, when the ratio of the actuator volume V and the volume ΔV excluded by the diaphragm is limited to the range of 2 ≦ V / ΔV ≦ 8 as in the conventional inkjet head described above, in an actual inkjet head, The effect of reducing the air damper effect is not obtained.
[0009]
In addition, the air damper effect can be sufficiently reduced simply by making the gap between the diaphragm substrate and the electrode substrate other than directly below the diaphragm larger than the gap directly below the diaphragm, or by providing openings that communicate with each vibration chamber and open to the atmosphere. I can't.
[0010]
In addition, when the opening of the vibration chamber is sealed with epoxy adhesive or low melting glass, the pressure in the gap changes due to changes in atmospheric pressure or temperature, and the displacement characteristics of the vibration plate fluctuate. There is a problem that displacement cannot be obtained.
[0011]
The present invention has been made in view of the above problems, and has as its object to effectively reduce the air damper effect and further to prevent fluctuations in diaphragm displacement characteristics due to changes in atmospheric pressure and temperature.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, an ink jet head according to the present invention includes a first air chamber communicating with a vibration chamber formed by a diaphragm and an electrode on an electrode substrate, and one end having a plurality of first chambers. A second air chamber is provided which communicates in common with the air chamber and whose other end communicates with the atmosphere.
[0013]
Here, the second air chamber communicates in common with the plurality of odd-numbered and even-numbered first air chambers corresponding to the two nozzle rows, one end of which is arranged in a staggered manner, and the other end. Is preferably in communication with the atmosphere. In addition, it is preferable that one end of the second air chamber communicates with the plurality of first air chambers in common and the other end communicates with the atmosphere through a plurality of openings.
[0014]
In addition, the openings of the plurality of vibration chambers are sealed with the first sealing material, and the atmosphere openings of the second air chamber communicating with the plurality of first air chambers are sealed with the second sealing material. It is preferable to seal.
[0015]
In addition, the openings of the plurality of vibration chambers are sealed with the first sealing material, and the atmosphere openings of the second air chamber communicating with the plurality of first air chambers are sealed through elastic members. It is preferable to do. In this case, the elastic member that seals the atmospheric opening of the second air chamber preferably has an elastic modulus smaller than that of the diaphragm. No .
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the overall configuration of a first embodiment of an inkjet head according to the present invention will be described with reference to FIGS. 1 is an exploded perspective view of the head, FIG. 2 is a cross-sectional view of the head along the longitudinal direction of the diaphragm, and FIG. 3 is an enlarged cross-sectional view of essential parts of the head along the longitudinal direction of the diaphragm. FIG. 3 is an enlarged cross-sectional view of a main part along the diaphragm short side direction of the head.
[0019]
The inkjet head includes a flow path substrate (vibration plate substrate) 1 that is a first substrate using a silicon substrate such as a single crystal silicon substrate or an SOI substrate, and a silicon substrate provided below the flow path substrate 1 or A nozzle 4 that discharges ink droplets is provided with an electrode substrate 2 that is a second substrate using a Pyrex glass substrate or a ceramic substrate, and a nozzle plate 3 that is a third substrate provided above the flow path substrate 1. A discharge chamber 6 that is an ink liquid chamber, a common liquid chamber 8 that communicates with each discharge chamber 6 via a fluid resistance portion 7 that also serves as an ink supply path, and the like are formed.
[0020]
The flow path substrate 1 is formed with a plurality of discharge chambers 6 with which the nozzles 4 communicate with each other and concave portions that form a vibration plate 10 (also serving as an electrode) that forms the bottom of the wall of the discharge chamber 6. Forms a hole for forming the nozzle 4 and a groove for forming the fluid resistance portion 7, and a through-hole for forming the common liquid chamber 8 is formed in the flow path substrate 1 and the electrode substrate 2.
[0021]
Here, for example, when a single crystal silicon substrate is used as the flow path substrate 1, after boron is injected into the diaphragm thickness in advance to form a high-concentration boron layer serving as an etching stop layer and bonded to the electrode substrate 2. Then, the recess 10 serving as the discharge chamber 6 is anisotropically etched using an etching solution such as a KOH aqueous solution, and at this time, the high-concentration boron layer becomes an etching stop layer, and the diaphragm 10 is formed with high accuracy.
[0022]
As the flow path substrate 1, an SOI (Silicon On Insulator) substrate in which a base substrate that is a silicon substrate and an active layer substrate are bonded via an oxide film can also be used. In this case, a silicon active layer having a thickness of about 1 to 3 μm is used for the diaphragm 10.
[0023]
In addition, although the electrode film which becomes a 1st electrode may be separately formed in the diaphragm 10, as above-mentioned, the diaphragm is made to serve as an electrode using the silicon substrate. An insulating film can also be formed on the surface of the vibration plate 10 on the electrode substrate 2 side. This insulating film is SiO ₂ Oxide-based insulating film such as Si _Three N _Four Nitride-based insulating films such as those can be used. The insulating film can be formed by thermally oxidizing the vibration plate surface to form an oxide film or using a film forming method.
[0024]
Further, a p-type or n-type single crystal silicon substrate is used as the electrode substrate 2, an oxide film 2 a is formed by a thermal oxidation method or the like, and a recess 14 for forming a vibration chamber 16 is formed in the oxide layer 2 a. Then, an electrode 15 is provided on the bottom surface of the recess 14 to face the diaphragm 10 with a predetermined gap therebetween, and the diaphragm 10 and the electrode 15 constitute an electrostatic actuator unit. The electrode substrate 2 is formed with an air chamber or the like communicating with the vibration chamber 16, details of which will be described later.
[0025]
The surface of the electrode 15 is SiO. ₂ Oxide-based insulating films such as films, Si _Three N ₄ A dielectric insulating film 17 made of a nitride insulating film such as a film is formed. As described above, the insulating film 17 can be formed on the vibration plate 10 side without forming the insulating film 17 on the surface of the electrode 15. Furthermore, as the electrode 15, gold, a metal material such as Al, Cr, or Ni generally used in a process for forming a semiconductor element, or a refractory metal such as Ti, TiN, or W can be used. .
[0026]
These flow path substrate 1 and electrode substrate 2 are bonded by direct bonding of silicon.
[0027]
In the nozzle plate 3, a large number of nozzles 4 are formed, and a groove portion for forming a fluid resistance portion 7 for communicating the common liquid chamber 8 and the discharge chamber 6 is formed. Here, a water-repellent film is formed on the ink ejection surface (nozzle surface side). This nozzle plate 3 uses a stainless steel substrate, but in addition to this, a nickel plated film by electroforming (electroforming) method, excimer laser processing on a resin such as polyimide, and punching a metal plate by pressing. It can also be used.
[0028]
The water-repellent film can be formed by a plating film by electrolytic or electroless nickel eutectoid plating (PTFE-Ni eutectoid plating) in which polytetrafluoroethylene fine particles, which are fluororesin fine particles, are dispersed.
[0029]
In this ink jet head, nozzles 4 are arranged in two rows (nozzle rows 4A and 4B), and discharge chamber 6, diaphragm 10 and electrode 15 are arranged in two rows corresponding to each nozzle row 4A, 4B. The common liquid chamber 8 is disposed in the central portion of the nozzle and the ink is supplied to the left and right ejection chambers 6. Thus, a multi-nozzle head having a large number of nozzles can be configured with a simple head configuration.
[0030]
The electrode 15 is extended to the outside to form a connection portion (electrode pad portion) 15a, and an FPC cable 21 on which a driver IC 20 as a head drive circuit is mounted by wire bonding is connected via an anisotropic conductive film or the like. is doing.
[0031]
Further, the entire inkjet head is bonded onto the frame member 25 with an adhesive. An ink supply hole 26 for supplying ink from the outside to the common liquid chamber 8 of the ink jet head is formed in the frame member 25, and the FPC cable 21 and the like are accommodated in a hole portion 27 formed in the frame member 25. The
[0032]
The frame member 25 and the nozzle plate 3 are sealed with a gap sealant 28 using an adhesive such as an epoxy resin, and the ink on the surface of the nozzle plate 3 having water repellency is transferred to the electrode substrate 2 or the FPC cable 21. To prevent it from going around.
[0033]
A joint member 30 with an ink cartridge is connected to the frame member 25 of the head, and ink is supplied from the ink cartridge to the common liquid chamber 8 through the ink supply hole 26 through a filter 31 thermally fused to the frame member 25. Supplied.
[0034]
In the ink jet head configured as described above, the diaphragm 10 is used as a common electrode, the electrode 15 is used as an individual electrode, and a drive waveform is applied between the diaphragm 10 and the electrode 15, whereby the diaphragm 10 and the electrode 15 are separated. An electrostatic force (electrostatic attractive force) is generated in the meantime, and the diaphragm 10 is deformed and displaced toward the electrode 15. As a result, the internal volume of the discharge chamber 6 is expanded and the internal pressure is lowered, so that the discharge chamber 6 is filled with ink from the common liquid chamber 8 via the fluid resistance portion 7.
[0035]
Next, when the voltage application to the electrode 15 is cut off, the electrostatic force stops working, and the diaphragm 10 is restored by its own elasticity. With this operation, the internal pressure of the discharge chamber 6 increases, and ink droplets are discharged from the nozzle 5. When a voltage is applied to the electrode again, the diaphragm is again pulled toward the electrode by electrostatic attraction.
[0036]
Therefore, the configuration of the ink jet head according to the present invention will be described in detail with reference to FIGS. 5 and 6 in addition to FIG. FIG. 5 is a top view of the electrode substrate of the head, and FIG. 6 is a plan view of the main part of the head.
As shown in FIGS. 4 and 5, the electrode substrate 2 is provided with a first air chamber 41 communicating with the vibration chamber 16 formed by the diaphragm 10 and the electrode 15 through the slit 40 and at one end. Is provided in common with a plurality of first air chambers 41, and a second air chamber 42 with the other end communicating with the atmosphere is provided. By forming the air chamber 41 on the lower side of the electrode 15 of the electrode substrate 2 in this way, there is no significant increase in the process, and the increase in the chip size of the head due to the provision of the air chamber 41 is accompanied by this. The increase in cost can be suppressed.
[0037]
In this case, the second air chamber 42 has a plurality of odd-numbered and even-numbered first air chambers 41 corresponding to the two nozzle rows 4A and 4B in which the nozzles 4 are arranged in a staggered manner at one end. It communicates in common and the other end communicates with the atmosphere. In this case, for each nozzle row 4A, 4B, a second air chamber 42 having an air opening 42a whose one end communicates with the first air chamber 41 and whose other end opens to the atmosphere is provided independently. You can also In addition, as shown in FIG. 7, a plurality of atmospheric openings 42 a of the second air chamber 42 can be formed on the same end side of the electrode substrate 2.
[0038]
The opening 16 a of each vibration chamber 16 is sealed with a first sealing material 46. As the sealing material 46, a material excellent in gas barrier properties, for example, an epoxy adhesive (for example, 342-3 manufactured by Able Bond Co., Ltd.) is used. When sealing with the first sealing material 46, a minute gas may be generated from the sealing material 46. When performing the first sealing, the slit 40 and the first air are used. Since the atmosphere opening side (second air chamber 42) communicating with the vibration chamber 16 through the chamber 41 is not sealed, deformation of the diaphragm 10 due to gas generation can be avoided.
[0039]
The atmospheric opening 42 a of the second air chamber 42 is sealed with a second sealing material 47. At this time, the air opening 42 a is sealed through an elastic member 48 having a smaller elastic modulus than that of the diaphragm 10. As a result, gas generation when sealed with the second sealing material 47, changes in pressure after being hermetically sealed, pressure changes associated with temperature changes, etc. can be absorbed by the elastic member 48 having a low elastic modulus. In addition, deformation of the diaphragm 10 due to pressure change or the like can be prevented, and variation in vibration characteristics can be prevented.
[0040]
The elastic member 48 is preferably made of a material having excellent gas barrier properties, and a laminated member obtained by sandwiching an ethylene vinyl alcohol copolymer resin with a high-density polyethylene resin having a low elastic modulus is particularly preferable. By providing a plurality of atmospheric openings 42 a in the second air chamber 42, the area of the elastic member 48 is increased when the pressure change accompanying the change in atmospheric pressure and temperature is absorbed by the elastic member 48, and the absorption effect is increased. To do.
[0041]
Therefore, the action of reducing the air damper effect in this ink jet head will be described with reference to FIG.
First, the volume V of the vibration chamber 16 which is a gap space formed between the vibration plate 10 and the electrode 15 is defined as “a” for the short direction length of the vibration plate 10, “b” for the long direction length, and “δ” for the gap length. V = a × b × δ. On the other hand, the excluded volume ΔV when the diaphragm 10 is deformed is ΔV = 8 × a × b × δ / 15. Here, δ is adopted as the displacement amount of the vibration plate 10, but this is because the so-called contact driving method in which the vibration plate 10 is driven by contacting the electrode 15 reduces the voltage and discharges ink droplets. This is because it is excellent in terms of uniform amount.
[0042]
By the way, in the case of such a contact driving method, when the bottom surface of the recess 14 is made flat without providing the first air chamber 41 (example in FIG. 8), the volume (actuator volume) V of the vibration chamber 16 is excluded. The ratio V / ΔV of the volume ΔV is approximately V / ΔV = 15/8 and is a value of 2 or less. Here, as a result of repeating the experiment, as the air damper effect, as the actuator volume V, only an increase in the volume of the vibration chamber directly under the diaphragm exerts a large effect, and the effect of reducing the air damper effect on the volume increase other than directly under the diaphragm Turned out to be small.
[0043]
Therefore, as in this embodiment, the vibration chamber 16 is provided through a slit 40 facing the vibration chamber 16 in a portion substantially facing the vibration plate 10 of the electrode substrate 2, that is, in this case, a portion where the electrode 15 on the bottom surface of the recess 14 is not formed. By providing the first air chamber 41 communicating with the air chamber, the effective vibration chamber volume V can be increased, the value of V / ΔV can be increased, the air damper effect can be reduced, and stable with low voltage drive The obtained diaphragm displacement can be obtained.
[0044]
In this case, by providing the first air chamber 41 inside the electrode substrate 2 and communicating with the vibration chamber 16 through the slit 40, the area of the electrode formation surface (the bottom surface of the recess 14) is reduced and the electrode formation area is reduced. It can be avoided that the electrostatic force decreases due to the decrease. The first air chamber 41 having a large volume can be secured by making the width of the first air chamber 41 wider than the width of the slit 40.
[0045]
Here, a specific example of the ink jet head according to this embodiment will be described including the manufacturing process. As the electrode substrate 2, a silicon substrate having a crystal plane orientation (100) was used, and an oxide film 2a having a thickness of 2 μm was formed by thermal oxidation. And the recessed part 14 used as the vibration chamber 16 was formed in the thermal oxide film 2a by the dry etching method with the depth of 0.6 micrometer. An electrode 15 made of TiN having a thickness of 0.15 μm was formed on the bottom surface of the recess 14 by sputtering and patterned by dry etching. SiO as electrode protective film 17 ₂ Was formed by P-CVD so as to have a thickness of 0.15 μm, and was patterned by dry etching.
[0046]
Next, a thermal oxide film 2a of the silicon substrate (electrode substrate 2) is formed by dry etching a notch (slit 40) having a width of 4 μm and a vibration plate length of 1 mm around the electrode 15 on the bottom surface of the recess 14. It was formed to a depth that reached no region. Thereafter, a resist pattern is formed to expose only the notch and dry etching is performed to form a first air chamber 41 having substantially the same shape as that obtained by isotropic etching inside the electrode substrate 2. did.
[0047]
At this time, the size of the first air chamber 41 can be changed by the etching time. When the shape of the first air chamber 41 is approximated by a trapezoid, the upper side length is 16 μm, the lower side length is 6 μm, and the depth is 12 μm. The first air chamber 41 was used. Even when the volume of the notched portion (slit 40) of the thermal oxide film 2a was removed, the ratio W / ΔV of the entire volume W of the first air chamber 41 to the excluded volume ΔV was a value exceeding “12”.
[0048]
On the other hand, as the flow path substrate 1, an SOI substrate in which a silicon substrate is bonded via a thermal oxide film is used, and after directly bonding the SOI substrate and the electrode substrate 2 at a temperature of 900 ° C., the plane orientation of the SOI substrate. Si of (110) was etched by wet etching to form a recess to be the discharge chamber 6 and the like, and at the same time, a diaphragm 10 having a plate thickness of 3 μm was formed.
[0049]
Then, the opening of the vibration chamber 16 was sealed with an epoxy adhesive as the first sealing material 46. Thereafter, the atmospheric opening 42 a of the second air chamber 42 was sealed with the second sealing material 47 via the elastic member 48.
[0050]
Further, as a comparative example, an ink jet head in which the first air chamber 41 and the slit 40 were not formed as shown in FIG.
[0051]
And the vibration displacement amount of the actuator of each ink jet head was measured with a laser Doppler meter. As a result, the voltage at which the diaphragm 10 starts to come into contact with the protective film 17 on the surface of the electrode 15 is about 6 V lower when the first air chamber 41 is provided, and the first air chamber 41 is substantially reduced. Also functioned as the vibration chamber 16, and it was confirmed that the effect was large.
[0052]
In the case of an actuator without the first air chamber 41, it has been confirmed that the displacement of the diaphragm 10 becomes unstable when the drive frequency is set to 20 KHz or more. However, when the first air chamber 21 is provided, It was confirmed that there was no instability phenomenon of vibration displacement with respect to such frequency change.
[0053]
Further, the nozzle plate 3 is formed of a transparent glass plate, and after sealing with the first sealing material 46 and the second sealing material 47, the diaphragm 10 The deformation of was measured with a laser Doppler meter. As a result, it was confirmed that the displacement amount of the diaphragm 10 was substantially constant with respect to the temperature change, and the elastic member 48 absorbed the pressure.
[0054]
Next, a second embodiment of the inkjet head according to the present invention will be described with reference to FIGS. 9 is an explanatory cross-sectional view of the head along the transverse direction of the diaphragm, FIG. 10 is an explanatory top view of the electrode substrate of the head, and FIG. 11 is an explanatory plan view of the head.
In this ink jet head, an air chamber 51 communicating with the vibration chamber 16 is formed on the electrode substrate 2 through a slit 50 formed at the center of the electrode 15, and the air chamber 51 is placed on the back side of the electrode substrate 2 in the atmosphere. An air opening 52 communicating with the air is formed.
[0055]
Here, the atmospheric openings 52 of the electrode substrate 2 are shown in a plurality of odd-numbered and even-numbered air chambers 51 corresponding to the two nozzle rows 4A and 4B arranged in a staggered manner as shown in FIG. As shown in FIG. In addition, the opening of the vibration chamber 16 is sealed with the first sealing material 46 described above, and the atmosphere opening 52 of the electrode substrate 2 is sealed with a second sealing material (not shown) via the elastic member 53. The same as the second sealing material 47).
[0056]
In this case, when sealing with the first sealing material 46, a minute gas may be generated from the sealing material 46, but when performing the first sealing, through the slit 50 and the air chamber 51. Since the atmospheric opening 52 communicating with the vibration chamber 16 is not sealed, deformation of the vibration plate 10 due to gas generation can be avoided.
[0057]
In addition, the elastic member 53 sealing the atmospheric opening 52 of the electrode substrate 2 has a lower elastic modulus than that of the diaphragm 10, and a resin material having a high gas barrier property is replaced with a resin material having a low elastic modulus. It is a laminated resin material. For example, as described above, a laminated member in which an ethylene vinyl alcohol copolymer resin is sandwiched with a high-density polyethylene resin having a low elastic modulus is particularly preferable.
[0058]
Here, a specific example of the ink jet head according to this embodiment will be described including the manufacturing process. Similar to the first embodiment, a silicon substrate having a crystal plane orientation (100) was used as the electrode substrate 2, and an oxide film 2a having a thickness of 2 μm was formed by thermal oxidation. And the recessed part 14 used as the vibration chamber 16 was formed in the thermal oxide film 2a by the dry etching method with the depth of 0.6 micrometer. An electrode 15 made of TiN having a thickness of 0.15 μm was formed on the bottom surface of the recess 14 by sputtering and patterned by dry etching. SiO as electrode protective film 17 ₂ Was formed by P-CVD so as to have a thickness of 0.15 μm, and was patterned by dry etching.
[0059]
Next, a silicon substrate (electrode substrate 2) is thermally oxidized by dry etching a notch (slit 50) having a width of 4 μm at the center of the electrode 15 on the bottom of the recess 14 and a length of 1.1 mm with respect to the diaphragm length of 1 mm. The film was formed to a depth reaching a region where the film 2a was not present. Thereafter, a resist pattern was formed to expose only the notch, and dry etching was performed to form an air chamber 51 having a shape substantially the same as that obtained by isotropic etching immediately below the electrode 15.
[0060]
At this time, the size of the air chamber 51 can be changed by the etching time. When the shape of the air chamber 51 is approximated by a trapezoid, the air chamber 51 has an upper side length of 16 μm, a lower side length of 6 μm, and a depth of 12 μm. .
[0061]
Furthermore, isotropic etching with KOH was performed from the back surface of the electrode substrate 2 to form an air opening 52 on the back surface side of the electrode substrate communicating with each air chamber 51.
[0062]
In this case as well, an SOI substrate in which a silicon substrate is bonded via a thermal oxide film is used as the flow path substrate 1, and the SOI substrate and the electrode substrate 2 are directly bonded at a temperature of 900 ° C., and then the SOI substrate. The Si having the surface orientation (110) was etched by wet etching to form a recess to be the discharge chamber 6 and the like, and at the same time, the diaphragm 10 having a thickness of 3 μm was formed.
[0063]
Then, the opening of the vibration chamber 16 was sealed with an epoxy adhesive as the first sealing material 46. Thereafter, the atmospheric opening 52 on the back surface of the electrode substrate was sealed through the elastic member 53 using the second sealing material 47.
[0064]
Next, a third embodiment of the inkjet head according to the present invention will be described with reference to FIGS.
Also in this ink jet head, an air chamber 51 communicating with the vibration chamber 16 is formed in the electrode substrate 2 through the central portion of the electrode 15 and the slit 50 formed in the oxide film 2a. One end of each of the slit 50 and the air chamber 51 communicates in common with each vibration chamber 16 and further with a row of the vibration chambers 16 arranged in a staggered manner. Further, the bottom of the lead portion 55 through which the slit 50 and the air chamber 51 are drawn in common is open to the atmosphere through an air opening 56 formed on the back side of the electrode substrate 2.
[0065]
Here, the opening of the vibration chamber 16 is sealed with the first sealing material 46 described above, and the atmospheric opening 56 of the electrode substrate 2 is interposed via the elastic member (the same as the elastic member 53 described above). The second sealing material (same as the second sealing material 47 described above) is used.
[0066]
Therefore, the vibration displacement amount of the actuators of the second and third embodiments was measured with a laser Doppler meter. As a result, the voltage at which the diaphragm 10 starts to contact the electrode substrate 2 is lower by about 6 Volts when the air chamber 51 is provided, and the air chamber 51 functions as a vibration chamber, and it is confirmed that the effect is large. It was done. Further, in the case of an actuator without the air chamber 51, it was confirmed that the vibration displacement becomes unstable when the drive frequency is set to 20 KHz or more. However, when the air chamber 51 is provided, the vibration displacement with respect to such a frequency change is reduced. It was confirmed that there was no instability phenomenon.
[0067]
Further, in order to facilitate the observation of the deformation of the vibration plate 10, the nozzle plate was made of a glass plate, and the vibration displacement was measured. After performing the first and second sealing, the deformation of the diaphragm 10 was measured with a laser Doppler meter while changing the temperature in the high-temperature tank. As a result, it was confirmed that the displacement amount of the diaphragm 10 was substantially constant with respect to the temperature change, and the elastic member effectively absorbed the pressure.
[0068]
In the above embodiment, the present invention is applied to the side shooter type inkjet head in which the vibration plate displacement direction and the ink droplet ejection direction are the same, but the edge shooter method orthogonal to the vibration plate displacement direction and the ink droplet ejection direction. The same can be applied to the inkjet head. Furthermore, the present invention can be applied not only to an ink jet head but also to a droplet discharge head that discharges a liquid resist or the like. Further, although the diaphragm and the liquid chamber substrate are formed from the same substrate, the diaphragm and the liquid chamber substrate can be joined separately.
[0069]
【The invention's effect】
As described above, according to the ink jet head according to the present invention, the first air chamber communicating with the vibration chamber formed by the diaphragm and the electrode, and one end common to the plurality of first air chambers. Since the second air chamber that communicates and the other end communicates with the atmosphere is provided, the effective vibration chamber volume increases, and the ratio to the volume that is eliminated when the diaphragm is deformed increases, resulting in an air-damper effect. Can be significantly reduced, and a stable diaphragm displacement can be obtained by low-voltage driving.
[0070]
Here, the second air chamber communicates in common with the plurality of odd-numbered and even-numbered first air chambers corresponding to the two nozzle rows, one end of which is arranged in a staggered manner, and the other end. By communicating with the atmosphere, the air-damper effect can be significantly reduced while increasing the nozzle density. The second air chamber has one end commonly connected to the plurality of first air chambers, and the other end communicated to the atmosphere through a plurality of openings, thereby opening the elastic member. When sealing through, the area in contact with the opening of the elastic member is increased, and the effect of absorbing pressure fluctuation is increased.
[0071]
In addition, the openings of the plurality of vibration chambers are sealed with the first sealing material, and the atmosphere openings of the second air chamber communicating with the plurality of first air chambers are sealed with the second sealing material. By sealing, it is possible to prevent the intrusion of dust and moisture into the vibration chamber and to prevent fluctuations in the diaphragm displacement characteristics.
[0072]
In addition, the openings of the plurality of vibration chambers are sealed with the first sealing material, and the atmosphere openings of the second air chamber communicating with the plurality of first air chambers are sealed through elastic members. By doing so, it is possible to prevent the diaphragm from being deformed due to environmental changes such as temperature and pressure after sealing.
[0073]
In this case, the elastic member that seals the atmospheric opening of the second air chamber has an elastic modulus smaller than that of the diaphragm, so that the elastic member is resistant to environmental changes such as temperature and pressure after sealing. Is deformed first, and the deformation of the diaphragm can be prevented more reliably. In addition, the elastic member that seals the air opening of the second air chamber is a resin material obtained by laminating a resin material having a high gas barrier property with a resin material having a low elastic modulus. Intrusion of outside air, etc. can be reliably prevented.
[0074]
According to the ink jet head of the present invention, an air chamber that communicates with a vibration chamber formed by a diaphragm and an electrode is provided in the electrode substrate, and an air opening that communicates the air chamber with the atmosphere is provided on the back side of the electrode substrate. As a result, the effective volume of the vibration chamber increases, the ratio to the volume that is eliminated when the diaphragm is deformed, the air-damper effect can be significantly reduced, and a stable diaphragm displacement is obtained with low voltage drive. be able to.
[0075]
Here, the atmosphere openings of the electrode substrate communicate with a plurality of odd-numbered and even-numbered air chambers corresponding to the two nozzle rows arranged in a staggered manner, thereby increasing the nozzle density. However, the air damper effect can be significantly reduced.
[0076]
In addition, the opening portion of the vibration chamber is sealed with the first sealing material, and the atmospheric opening portion of the electrode substrate is sealed with the second sealing material via the elastic member. The vibration characteristics of the diaphragm can be prevented from fluctuating due to intrusion of dust and outside air, etc., and pressure fluctuations due to environmental changes such as atmospheric pressure and temperature can be absorbed by the elastic member. Variation can be suppressed.
[0077]
In this case, the elastic member that seals the atmospheric opening of the electrode substrate has an elastic modulus smaller than that of the diaphragm, so that the elastic member is first in response to environmental changes such as temperature and pressure after sealing. It is possible to prevent deformation of the diaphragm more reliably. In addition, the elastic member that seals the air opening of the electrode substrate is made of a resin material having a high gas barrier property and laminated with a resin material having a low elastic modulus, so that the outside air to the second air chamber, etc. Can be surely prevented.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view showing a first embodiment of an inkjet head according to the invention.
FIG. 2 is an explanatory cross-sectional view of the head along the longitudinal direction of the diaphragm.
FIG. 3 is an enlarged sectional explanatory view of a main part along the longitudinal direction of the diaphragm of the head.
FIG. 4 is an explanatory cross-sectional view of the head along the transverse direction of the diaphragm.
FIG. 5 is a top view of the electrode substrate of the head.
FIG. 6 is an explanatory plan view of the head.
FIG. 7 is an upper surface explanatory view of an electrode substrate for explaining another example of the second air chamber of the head.
FIG. 8 is a cross-sectional explanatory view of the head of a comparative example taken along the lateral direction of the diaphragm for explaining the operation of the head.
FIG. 9 is an explanatory cross-sectional view along the transversal direction of the diaphragm, showing a second embodiment of an inkjet head according to the present invention.
FIG. 10 is a top view of the electrode substrate of the head.
FIG. 11 is an explanatory plan view of the head.
FIG. 12 is a cross-sectional explanatory view along the transversal direction of the diaphragm showing a third embodiment of an inkjet head according to the present invention.
FIG. 13 is a top view of the electrode substrate of the head.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Channel substrate, 2 ... Electrode substrate, 3 ... Nozzle plate, 4 ... Nozzle, 6 ... Discharge chamber, 7 ... Fluid resistance part, 8 ... Common liquid chamber, 10 ... Vibration plate, 14 ... Recessed part, 15 ... Electrode, DESCRIPTION OF SYMBOLS 16 ... Vibration chamber, 40 ... Slit, 41 ... 1st air chamber, 42 ... 2nd air chamber, 46 ... 1st sealing material, 47 ... 2nd sealing material, 48 ... Elastic member, 50 ... Slit, 51 ... air chamber, 52 ... atmospheric opening, 53 ... elastic member.

Claims (6)

A nozzle, an ink liquid chamber communicating with the nozzle, a diaphragm that forms part of the wall surface of the ink liquid chamber, and an electrode that is disposed opposite the diaphragm and formed on the electrode substrate In an inkjet head that ejects ink droplets from the nozzles by deforming the diaphragm with an electrostatic force generated between the diaphragm and the electrode ,
A first air chamber communicating with a vibration chamber formed by a diaphragm and an electrode is provided in the electrode substrate,
2. An ink jet head, comprising: a second air chamber having one end communicating with the plurality of first air chambers in common and the other end communicating with the atmosphere.   2. The inkjet head according to claim 1, wherein the second air chamber is a plurality of odd-numbered and even-numbered first air chambers corresponding to two nozzle rows arranged at one end in a staggered manner. An inkjet head characterized in that it communicates in common and the other end communicates with the atmosphere.   3. The inkjet head according to claim 1, wherein one end of the second air chamber communicates in common with the plurality of first air chambers, and the other end communicates with the atmosphere through a plurality of openings. An ink jet head characterized by the above. 4. The inkjet head according to claim 1, wherein the plurality of vibration chambers open through an opening formed between the vibration plate and the electrode substrate, and the openings of the plurality of vibration chambers are formed. An inkjet head characterized in that the air opening of the second air chamber that is sealed with the first sealing material and communicates with the plurality of first air chambers is sealed with the second sealing material. .   4. The second air according to claim 1, wherein the openings of the plurality of vibration chambers are sealed with a first sealing material and communicated with the plurality of first air chambers. An ink jet head, wherein an atmospheric opening of a chamber is sealed with an elastic member.   6. The ink jet head according to claim 5, wherein the elastic member for sealing the atmospheric opening of the second air chamber has an elastic modulus smaller than that of the diaphragm.

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