JP2004034417A - Liquid ejection head and liquid ejector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid ejection head and a liquid ejector capable of ejecting liquid with uniform characteristics by preventing crosstalk caused by a tension of a diaphragm. <P>SOLUTION: The liquid ejection head comprises a channel forming board 10 in which pressure chambers 12 communicating with nozzle openings are defined, and a piezoelectric element 300 provided on one side of the channel forming board 10 through a diaphragm and comprising a lower electrode 60, a piezoelectric layer 70 and an upper electrode 80. The diaphragm includes at least one layer of compressive film 50 having compressive stress and at least one layer of tensile film 55, 60 having tensile stress. Difference of tension between the compressive film 50 and the tensile film 55, 60 is set within 20% of the higher one of tensions of the compressive film 50 and the tensile film 55, 60 thus preventing crosstalk caused by the tension of the diaphragm. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a liquid ejecting head and a liquid ejecting apparatus that eject a liquid to be ejected, and in particular, pressurizes ink supplied to a pressure generating chamber that communicates with a nozzle opening that ejects ink droplets via a piezoelectric element or a heating element. The present invention relates to an ink jet recording head and an ink jet recording apparatus that eject ink droplets from nozzle openings.
[0002]
[Prior art]
A part of the pressure generation chamber communicating with the nozzle opening for discharging ink droplets is constituted by a vibration plate, and the vibration plate is deformed by a piezoelectric element to pressurize the ink in the pressure generation chamber to discharge ink droplets from the nozzle opening. Two types of ink jet recording heads have been put into practical use, one using a piezoelectric actuator in a longitudinal vibration mode in which a piezoelectric element extends and contracts in the axial direction and one using a piezoelectric element in a flexural vibration mode.
[0003]
The former can change the volume of the pressure generation chamber by bringing the end face of the piezoelectric element into contact with the vibration plate, and it is possible to manufacture a head suitable for high-density printing, while the piezoelectric element is arranged in an array of nozzle openings. There is a problem that the manufacturing process is complicated because a difficult process of matching the pitch into a comb-like shape and an operation of positioning and fixing the cut piezoelectric element in the pressure generating chamber are necessary.
[0004]
On the other hand, the latter can flexibly vibrate, although a piezoelectric element can be built on the diaphragm by a relatively simple process of sticking a green sheet of piezoelectric material according to the shape of the pressure generation chamber and firing it. There is a problem that a certain amount of area is required for the use of, and high-density arrangement is difficult.
[0005]
On the other hand, in order to eliminate the inconvenience of the latter recording head, a uniform piezoelectric material layer is formed by a film forming technique over the entire surface of the diaphragm as seen in Japanese Patent Laid-Open No. 5-286131. A material in which a piezoelectric layer is formed so that a material layer is cut into a shape corresponding to a pressure generation chamber by a lithography method and is independent for each pressure generation chamber has been proposed.
[0006]
This eliminates the need to affix the piezoelectric element to the diaphragm, so that not only can the piezoelectric element be created by a precise and simple technique called lithography, but also the thickness of the piezoelectric element can be reduced. There is an advantage that high-speed driving is possible.
[0007]
[Problems to be solved by the invention]
However, in the ink jet recording head in which the nozzle openings are arranged at high density in this way, the rigidity of the partition walls partitioning each pressure generating chamber is lowered, so that the partition walls are easily influenced by the tension of the diaphragm, and this vibration There is a problem that crosstalk due to the tension of the plate occurs.
[0008]
That is, there is a problem that the amount of displacement of the diaphragm in the region facing each pressure generating chamber changes depending on the number of piezoelectric elements to be driven, and the ink ejection characteristics are not stable.
[0009]
Such a problem exists not only in an ink jet recording head that ejects ink, but also in other liquid ejecting heads that eject liquid other than ink.
[0010]
In view of such circumstances, it is an object of the present invention to provide a liquid ejecting head and a liquid ejecting apparatus that can eject liquid with uniform characteristics by preventing crosstalk caused by tension of a diaphragm.
[0011]
[Means for Solving the Problems]
According to a first aspect of the present invention for solving the above-described problem, a flow path forming substrate in which a pressure generation chamber communicating with a nozzle opening is defined, and a flow path forming substrate is provided on one surface via a diaphragm, and In the liquid ejecting head including at least the lower electrode, the piezoelectric layer, and the piezoelectric element having the upper electrode, the diaphragm includes at least one compressive film having compressive stress and at least one tensile film having tensile stress. In the liquid ejecting head, the difference between the tension of the compression film and the tension of the tension film is within 20% of the larger one of the tension of the compression film and the tension film.
[0012]
In the first aspect, the resultant force of each layer constituting the diaphragm can be kept relatively small, and crosstalk caused by the tension of the diaphragm can be prevented. Therefore, the first aspect is always uniform regardless of the number of driven piezoelectric elements. Ink ejection characteristics can be obtained.
[0013]
According to a second aspect of the invention, in the liquid jet head according to the first aspect, the compression film includes a film made of silicon dioxide.
[0014]
In the second aspect, by using a predetermined material, a compressed film having a compressive stress can be reliably formed.
[0015]
According to a third aspect of the present invention, in the liquid jet head according to the first or second aspect, the tensile film includes a film made of zirconium dioxide.
[0016]
In the third aspect, a tensile film having a tensile stress can be reliably formed by using a predetermined material.
[0017]
According to a fourth aspect of the present invention, in any one of the first to third aspects, the lower electrode is provided so as to cover a region facing the plurality of pressure generation chambers, and constitutes a part of the diaphragm. In the liquid ejecting head, the liquid ejecting head is provided.
[0018]
In the fourth aspect, the tension of the diaphragm can be adjusted relatively easily.
[0019]
According to a fifth aspect of the present invention, in the liquid jet head according to the fourth aspect, the lower electrode constitutes a part of the tensile film.
[0020]
In the fifth aspect, the tensile film can be formed relatively easily, and the tension of the diaphragm can be adjusted relatively easily.
[0021]
According to a sixth aspect of the present invention, in any one of the first to fifth aspects, a protective film that protects the inner surface of the pressure generating chamber is provided on the inner surface of the pressure generating chamber, and the protective film is the diaphragm. The liquid jet head is characterized by constituting a part of the liquid jet head.
[0022]
In the sixth aspect, corrosion of the flow path forming substrate and the like due to ink can be prevented and the number of layers constituting the diaphragm is increased, so that the tension of the diaphragm can be more easily adjusted.
[0023]
According to a seventh aspect of the present invention, in the liquid jet head according to the sixth aspect, the protective film forms a part of the compression film.
[0024]
In the seventh aspect, the compression film can be formed relatively easily, and the tension of the diaphragm can be adjusted relatively easily.
[0025]
According to an eighth aspect of the present invention, in the liquid jet head according to the sixth aspect, the protective film constitutes a part of the tensile film.
[0026]
In the eighth aspect, the tension of the diaphragm can be adjusted relatively easily by adjusting the thickness of the protective film.
[0027]
According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the pressure generating chamber is formed on a silicon single crystal substrate by anisotropic etching, and each layer of the piezoelectric element is formed by film formation and lithography. In the liquid ejecting head, the liquid ejecting head is formed.
[0028]
In the ninth aspect, a large number of liquid jet heads having high-density nozzle openings can be manufactured relatively easily.
[0029]
A tenth aspect of the present invention is a liquid ejecting apparatus including the liquid ejecting head according to any one of the first to ninth aspects.
[0030]
In the tenth aspect, a liquid ejecting apparatus with improved print quality can be realized.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments.
[0032]
(Embodiment 1)
FIG. 1 is an exploded perspective view showing an ink jet recording head according to Embodiment 1 of the present invention, and FIG. 2 is a plan view and a sectional view thereof.
[0033]
As shown in the figure, the flow path forming substrate 10 is made of a silicon single crystal substrate having a plane orientation (110) in this embodiment, and an elastic film 50 made of silicon dioxide previously formed by thermal oxidation is formed on one surface thereof. ing.
[0034]
The flow path forming substrate 10 is formed with a pressure generating chamber 12 partitioned by a plurality of partition walls 11 by anisotropic etching from the other side. In addition, the pressure generation chambers 12 of each row communicate with the reservoir section 31 provided on the reservoir formation substrate 30 (described later) through a communication hole 51 on the outer side in the longitudinal direction, thereby forming a common ink chamber for the pressure generation chambers 12. A communication portion 13 constituting the reservoir 100 is formed. The communication portion 13 is in communication with one end portion in the longitudinal direction of each pressure generating chamber 12 through the ink supply path 14.
[0035]
Here, the anisotropic etching is performed by utilizing the difference in etching rate of the silicon single crystal substrate. For example, in this embodiment, when a silicon single crystal substrate is immersed in an alkaline solution such as KOH, the first (111) plane perpendicular to the (110) plane is gradually eroded, and the first (111) plane. And a second (111) plane that forms an angle of about 70 degrees with the (110) plane and an angle of about 35 degrees appears, and the (111) plane is compared with the etching rate of the (110) plane. This is performed using the property that the etching rate is about 1/180. By this anisotropic etching, precision processing can be performed based on the parallelogram depth processing formed by two first (111) surfaces and two oblique second (111) surfaces. The pressure generating chambers 12 can be arranged with high density.
[0036]
In the present embodiment, the long side of each pressure generating chamber 12 is formed by the first (111) plane and the short side is formed by the second (111) plane. The pressure generation chamber 12 is formed by etching until it substantially passes through the flow path forming substrate 10 and reaches the elastic film 50. Here, the amount of the elastic film 50 that is affected by the alkaline solution for etching the silicon single crystal substrate is extremely small. In addition, each ink supply path 14 communicating with one end of each pressure generation chamber 12 is formed shallower than the pressure generation chamber 12, and the flow path resistance of the ink flowing into the pressure generation chamber 12 is kept constant. That is, the ink supply path 14 is formed by etching the silicon single crystal substrate halfway in the thickness direction (half etching). Half etching is performed by adjusting the etching time.
[0037]
The thickness of the flow path forming substrate 10 may be selected as the optimum thickness according to the arrangement density of the pressure generating chambers 12, and the arrangement density of the pressure generating chambers 12 is, for example, 180 per inch ( If it is about 180 dpi), the thickness of the flow path forming substrate 10 may be about 220 μm. However, for example, when arranged at a relatively high density of 200 dpi or more, the thickness of the flow path forming substrate 10 is It is preferable to make it relatively thin as 100 μm or less. This is because the arrangement density can be increased while maintaining the rigidity of the partition wall 11 between the adjacent pressure generation chambers 12.
[0038]
Further, a nozzle plate 20 having a nozzle opening 21 communicating with the side opposite to the ink supply path 14 of each pressure generating chamber 12 on the opening surface side of the flow path forming substrate 10 is an adhesive, a heat-welded film, or the like. It is fixed through. The nozzle plate 20 has a thickness of, for example, 0.05 to 1 mm, a linear expansion coefficient of 300 ° C. or less, for example, 2.5 to 4.5 [× 10 ^-6 / ° C] glass ceramics or non-rust steel. The nozzle plate 20 entirely covers one surface of the flow path forming substrate 10 on one surface, and also serves as a reinforcing plate that protects the silicon single crystal substrate from impact and external force. Further, the nozzle plate 20 may be formed of a material having substantially the same thermal expansion coefficient as that of the flow path forming substrate 10. In this case, since the deformation by heat of the flow path forming substrate 10 and the nozzle plate 20 is substantially the same, it can be easily joined using a thermosetting adhesive or the like.
[0039]
Here, the size of the pressure generation chamber 12 that applies ink droplet discharge pressure to the ink and the size of the nozzle opening 21 that discharges the ink droplet are optimized according to the amount of ink droplet to be discharged, the discharge speed, and the discharge frequency. The For example, when recording 360 ink droplets per inch, the nozzle opening 21 needs to be accurately formed with a diameter of several tens of μm.
[0040]
On the other hand, as described above, the elastic film 50 having a thickness of, for example, 0.5 μm is provided on the surface of the flow path forming substrate 10 opposite to the opening surface. For example, an insulating film 55 of about 0.4 μm is provided. Further, on the insulating film 55, a lower electrode film 60 having a thickness of, for example, about 0.2 μm, a piezoelectric layer 70 having a thickness of, for example, about 0.5 to 5 μm, and a thickness of, for example, about The upper electrode film 80 having a thickness of 0.1 μm is laminated by a process described later to constitute the piezoelectric element 300. Here, the piezoelectric element 300 refers to a portion including the lower electrode film 60, the piezoelectric layer 70, and the upper electrode film 80. In general, one electrode of the piezoelectric element 300 is used as a common electrode, and the other electrode and the piezoelectric layer 70 are patterned for each pressure generating chamber 12. In addition, here, a portion that is configured by any one of the patterned electrodes and the piezoelectric layer 70 and in which piezoelectric distortion is generated by applying a voltage to both electrodes is referred to as a piezoelectric active portion. In this embodiment, the lower electrode film 60 is a common electrode of the piezoelectric element 300, and the upper electrode film 80 is an individual electrode of the piezoelectric element 300. However, there is no problem even if this is reversed for the convenience of the drive circuit and wiring. In either case, a piezoelectric active part is formed for each pressure generating chamber. Further, here, the piezoelectric element 300 and the vibration plate that is displaced by driving the piezoelectric element 300 are collectively referred to as a piezoelectric actuator.
[0041]
A lead electrode 90 made of, for example, gold (Au) or the like is connected to the vicinity of one end in the longitudinal direction of the upper electrode film 80 of the piezoelectric element 300, and this lead electrode 90 is near the end of the flow path forming substrate 10. Has been pulled out. Although not shown, the vicinity of the end portion of the lead electrode 90 is connected to a driving IC for driving the piezoelectric element 300 by wire bonding.
[0042]
Here, in the present invention, the diaphragm that is displaced by the driving of the piezoelectric element 300 includes a compression film having a compression stress and a tension film having a tensile stress, and the tension of the compression film and the tension of the tension film. Is less than 20% of the larger of the tension of the compression film or the tension film. Here, the tension is a value obtained by multiplying the internal stress of each film by the film thickness.
[0043]
For example, in the present embodiment, as shown in FIG. 3, the lower electrode film 60 constituting the piezoelectric element 300 is continuously provided over a region facing the plurality of pressure generation chambers 12, so that the elastic film 50, the insulating film 55, and the lower electrode film 60 function as a diaphragm. Among these, the elastic film 50 has a compressive stress, and the insulating film 55 and the lower electrode film 60 have a tensile stress. Since the tension of the diaphragm in the region where the pressure generating chamber 12 is formed is released, the compressive stress of the elastic film 50 pulls the diaphragm to the outside of the pressure generating chamber 12 as shown in FIG. The tensile stress of the insulating film 55 and the lower electrode film 60 becomes a force in the direction of compressing the diaphragm.
[0044]
In this embodiment, the elastic film 50, which is a compression film, is made of, for example, silicon dioxide and has a thickness of about 0.5 μm, so that the tension is about 110 N / m. On the other hand, the insulating film 55 which is a tensile film is made of, for example, zirconium dioxide and has a thickness of about 0.4 μm, and the lower electrode film 60 is made of, for example, platinum and has a thickness of about 0.2 μm. Is about 100 N / m. Therefore, the difference between the tension of the elastic film 50 and the sum of the tensions of the insulating film 55 and the lower electrode film 60 is about 10 N / m, and in this embodiment, whichever is larger, the tension of the compression film or the tension film, It is 20% or less of the tension of the elastic film 50. The difference between the tension of the elastic film 50 and the sum of the tensions of the insulating film 55 and the lower electrode film 60 is preferably as small as possible, and is preferably zero.
[0045]
As described above, in this embodiment, the difference between the tension of the compression film (elastic film 50) constituting the diaphragm and the tension of the tension film (insulating film 55 and lower electrode film 60) is relatively small. The deflection amount (initial deflection amount) of the diaphragm in the state where 300 is not driven is suppressed to be extremely small. If the difference between the tension of the elastic film 50 and the sum of the tensions of the insulating film 55 and the lower electrode film 60 is zero, the initial deflection of the diaphragm is substantially eliminated.
[0046]
Thereby, it is possible to prevent the displacement amount of the diaphragm from changing between when one piezoelectric element 300 is driven and when a plurality of piezoelectric elements 300 are driven simultaneously. That is, since the partition wall 11 is not deformed by the tension of the diaphragm, even if the plurality of piezoelectric elements 300 are driven at the same time, the partition wall 11 is not changed, and crosstalk caused by the tension of the diaphragm is generated. Can be suppressed. Therefore, regardless of the number of piezoelectric elements 300 to be driven, the displacement amount of the diaphragm is constant, and uniform ink ejection characteristics can always be obtained.
[0047]
Note that the tensions of the elastic film 50, the insulating film 55, and the lower electrode film 60 can be adjusted by the respective film thicknesses, and each film thickness may be determined in consideration of the tension balance of the entire diaphragm.
[0048]
The stress state of the diaphragm, that is, the degree of compressive stress or tensile stress of the entire diaphragm can be determined by observing a cross section of the diaphragm with an electron microscope or the like, for example. The determination can also be made by removing the piezoelectric element 300 and observing the bending state of the diaphragm.
[0049]
A reservoir having a reservoir portion 31 constituting at least a part of the reservoir 100 serving as a common ink chamber of each pressure generating chamber 12 is provided on such a diaphragm, that is, on the piezoelectric element 300 side of the flow path forming substrate 10. The formation substrate 30 is bonded. In this embodiment, the reservoir portion 31 is formed through the reservoir forming substrate 30 in the thickness direction and across the width direction of the pressure generating chamber 12, and a through hole 51 provided through the diaphragm. The reservoir 100 is configured to communicate with the communication portion 13 of the flow path forming substrate 10 through the first and second pressure generation chambers 12 and serve as a common ink chamber.
[0050]
As the reservoir forming substrate 30, it is preferable to use a material substantially the same as the coefficient of thermal expansion of the flow path forming substrate 10, for example, glass, ceramic material, etc. In this embodiment, the same material as the flow path forming substrate 10 is used. It was formed using a silicon single crystal substrate.
[0051]
Further, in a region facing the piezoelectric element 300 of the reservoir forming substrate 30, a piezoelectric element holding portion 32 capable of sealing the space is provided in a state where a space that does not hinder the movement of the piezoelectric element 300 is secured. The element 300 is sealed in the piezoelectric element holding portion 32.
[0052]
Further, a compliance substrate 40 including a sealing film 41 and a fixing plate 42 is bonded onto the reservoir forming substrate 30. Here, the sealing film 41 is made of a material having low rigidity and flexibility (for example, a polyphenylene sulfide (PPS) film having a thickness of 6 μm), and the sealing film 41 seals one surface of the reservoir portion 31. It has been stopped. The fixing plate 42 is made of a hard material such as metal (for example, stainless steel (SUS) having a thickness of 30 μm). Since the region of the fixing plate 42 facing the reservoir 100 is an opening 43 that is completely removed in the thickness direction, one surface of the reservoir 100 is sealed only with a flexible sealing film 41. Has been.
[0053]
Although not shown, the reservoir forming substrate 30 and the compliance substrate 40 are formed with ink introduction ports that allow the reservoir 100 to communicate with the outside, and ink is supplied into the reservoir 100 from the ink introduction ports.
[0054]
The ink jet recording head according to this embodiment takes in ink from an external ink supply unit (not shown) through an ink introduction port, fills the interior from the reservoir 100 to the nozzle opening 21, and then A voltage is applied between the lower electrode film 60 and the upper electrode film 80 corresponding to the pressure generation chamber 12 in accordance with a recording signal from the driving IC that does not, and the elastic film 50, the insulating film 55, the lower electrode film 60, and the piezoelectric film. By flexing and deforming the body layer 70, the pressure in each pressure generating chamber 12 increases and ink droplets are ejected from the nozzle openings 21.
[0055]
Hereinafter, the manufacturing process of the ink jet recording head of the present embodiment, particularly the process of forming each layer constituting the diaphragm and the piezoelectric element 300 will be described with reference to FIGS.
[0056]
First, as shown in FIG. 4A, a silicon single crystal substrate wafer to be the flow path forming substrate 10 is thermally oxidized in a diffusion furnace at about 1100 ° C. to form an elastic film 50 made of silicon dioxide and having a compressive stress. To do.
[0057]
Next, as shown in FIG. 4B, an insulating film 55 is formed on the elastic film 50. As a material of the insulating film 55, a material having a predetermined strength and a film having a tensile stress, for example, zirconium dioxide is preferably used.
[0058]
In the insulating film 55 of this embodiment, after forming a zirconium layer on the elastic film 50 by sputtering, the insulating film 55 made of zirconium dioxide having tensile stress was formed by thermal oxidation treatment in a diffusion furnace at about 900 ° C. .
[0059]
Next, as shown in FIG. 4C, after the lower electrode film 60 is formed on the entire surface of the insulating film 55 by sputtering, the lower electrode film 60 is patterned to form an entire pattern. As a material of the lower electrode film 60, platinum (Pt) is suitable. This is because a piezoelectric layer 70 described later formed by sputtering or sol-gel method needs to be crystallized by firing at a temperature of about 600 to 1000 ° C. in an air atmosphere or an oxygen atmosphere after the film formation. Because. That is, the material of the lower electrode film 60 must be able to maintain conductivity at such a high temperature and in an oxidizing atmosphere, particularly when lead zirconate titanate (PZT) is used as the piezoelectric layer 70. It is desirable that the change in conductivity due to diffusion of lead oxide is small, and platinum is preferable for these reasons.
[0060]
Next, as shown in FIG. 4D, the piezoelectric layer 70 is formed. The piezoelectric layer 70 preferably has crystals oriented. For example, in the present embodiment, a so-called sol-gel method is obtained in which a so-called sol in which a metal organic material is dissolved and dispersed in a catalyst is applied and dried to be gelled, and further baked at a high temperature to obtain a piezoelectric layer 70 made of a metal oxide. Thus, the piezoelectric layer 70 in which the crystals are oriented is obtained. As a material of the piezoelectric layer 70, a lead zirconate titanate-based material is suitable when used for an ink jet recording head. In addition, the film-forming method of this piezoelectric material layer 70 is not specifically limited, For example, you may form by sputtering method.
[0061]
Furthermore, after forming a lead zirconate titanate precursor film by a sol-gel method or a sputtering method, a method of crystal growth at a low temperature by a high-pressure treatment method in an alkaline aqueous solution may be used.
[0062]
In any case, the piezoelectric layer 70 thus formed has crystals preferentially oriented unlike the bulk piezoelectric body, and in this embodiment, the piezoelectric layer 70 is formed in a columnar shape. Has been. Note that the preferential orientation refers to a state in which the orientation direction of the crystal is not disordered and a specific crystal plane is oriented in a substantially constant direction. A columnar thin film refers to a state in which substantially cylindrical crystals are aggregated over the surface direction with the central axis substantially coincided with the thickness direction to form a thin film. Of course, it may be a thin film formed of preferentially oriented granular crystals. Note that the thickness of the piezoelectric layer manufactured in this way in the thin film process is generally 0.2 to 5 μm.
[0063]
Next, as shown in FIG. 5A, an upper electrode film 80 is formed. The upper electrode film 80 may be made of a highly conductive material, and many metals such as aluminum, gold, nickel, platinum, and iridium, conductive oxides, and the like can be used. In this embodiment, iridium is formed by sputtering.
[0064]
Next, as shown in FIG. 5B, the piezoelectric element 300 is patterned by etching only the piezoelectric layer 70 and the upper electrode film 80.
[0065]
Next, as shown in FIG. 5C, lead electrodes 90 are formed. Specifically, for example, a lead electrode 90 made of gold (Au) or the like is formed over the entire surface of the flow path forming substrate 10 and patterned for each piezoelectric element 300.
[0066]
The above is the film forming process. After forming the film in this manner, the anisotropic etching of the silicon single crystal substrate with the alkali solution described above is performed, and as shown in FIG. 5D, the pressure generating chamber 12, the communication portion 13, and the ink supply path 14 etc. are formed.
[0067]
In practice, a large number of chips are simultaneously formed on a single wafer by the above-described series of film formation and anisotropic etching, and after the process is completed, a single chip-sized flow path is formed as shown in FIG. Divide each substrate 10. Then, the reservoir forming substrate 30 and the compliance substrate 40 are sequentially bonded and integrated with the divided flow path forming substrate 10 to form an ink jet recording head.
[0068]
(Embodiment 2)
FIG. 6 is a cross-sectional view of a main part of the ink jet recording head according to the second embodiment.
[0069]
In the present embodiment, as shown in FIG. 6, after the pressure generation chamber 12 is formed, the protective film 110 is formed on the inner surface of the pressure generation chamber 12 including the lower surface side formed by the elastic film 50, and the elastic film 50 is insulated. This embodiment is the same as the first embodiment except that the diaphragm is constituted by the protective film 110 in addition to the film 55 and the lower electrode film 60.
[0070]
This protective film 110 is for preventing corrosion by the ink in the pressure generating chamber 12 and suppressing the generation of bubbles. For example, in the present embodiment, the protective film 110 is formed of silicon dioxide like the elastic film 50. Therefore, the protective film 110 has a compressive stress like the elastic film 50. In this embodiment, by adjusting the film thickness of the elastic film 50 and the protective film 110, the sum of the tensions of the elastic film 50 and the protective film 110 and the sum of the tensions of the insulating film 55 and the lower electrode film 60 are obtained. Of the elastic film 50 and the protective film 110 is set to be 20% or less of the total tension.
[0071]
The protective film 110 may be formed by any method that can be formed at a relatively low temperature that does not adversely affect the piezoelectric element 300 and the like. For example, a CVD method using TEOS (tetraethyl orthosilicate) is used. be able to.
[0072]
Even in such a configuration, of course, as in the first embodiment, it is possible to prevent crosstalk due to the tension of the diaphragm, and the ink ejection characteristics are always uniform regardless of the number of piezoelectric elements 300 to be driven. Can be obtained.
[0073]
In the present embodiment, the protective film 110 has a compressive stress, but may of course have a tensile stress. In this case, the film thicknesses of the insulating film 55 and the lower electrode film 60 that are tensile films may be adjusted. In any case, if the respective film thicknesses are appropriately determined such that the difference between the tension of the compression film and the tension of the tension film is 20% or less of the larger of the tension of the compression film or the tension film. Good.
[0074]
(Other embodiments)
While the embodiments of the present invention have been described above, the basic configuration of the ink jet recording head is not limited to that described above.
[0075]
For example, in the above-described embodiment, the lower electrode film 60 constitutes a part of the diaphragm. However, the present invention is not limited to this, and the lower electrode film 60 may be patterned for each piezoelectric element 300. In this case, the elastic film 50 and the insulating film 55 or the elastic film 50, the insulating film 55, and the protective film 110 act as a vibration plate.
[0076]
Further, in the above-described embodiment, the thin film type ink jet recording head that can be manufactured by applying the film forming and lithography processes is exemplified. However, the present invention is not limited to this. For example, the substrate is laminated. The present invention can be applied to ink jet recording heads of various structures, such as those that form a pressure generating chamber, or those that form a piezoelectric layer by attaching a green sheet or screen printing.
[0077]
As described above, the present invention can be applied to ink jet recording heads having various structures as long as the gist of the invention is not contradicted.
[0078]
In addition, the ink jet recording heads of these embodiments constitute a part of a recording head unit having an ink flow path communicating with an ink cartridge or the like, and are mounted on the ink jet recording apparatus. FIG. 7 is a schematic view showing an example of the ink jet recording apparatus.
[0079]
As shown in FIG. 7, in the recording head units 1A and 1B having the ink jet recording head, cartridges 2A and 2B constituting ink supply means are detachably provided, and a carriage 3 on which the recording head units 1A and 1B are mounted. Is provided on a carriage shaft 5 attached to the apparatus body 4 so as to be movable in the axial direction. The recording head units 1A and 1B, for example, are configured to eject a black ink composition and a color ink composition, respectively.
[0080]
The driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and timing belt 7 (not shown), so that the carriage 3 on which the recording head units 1A and 1B are mounted is moved along the carriage shaft 5. The On the other hand, the apparatus body 4 is provided with a platen 8 along the carriage shaft 5, and a recording sheet S, which is a recording medium such as paper fed by a paper feed roller (not shown), is conveyed on the platen 8. It is like that.
[0081]
In the above-described embodiment, an example of an ink jet recording head that prints a predetermined image or character on a print medium has been described as an example of a liquid ejecting head, but the present invention is not limited to this. For example, color material ejection heads used in the production of color filters such as liquid crystal displays, organic EL displays, electrode material ejection heads used in the formation of electrodes such as FEDs (surface emitting displays), and bio-organic matter ejections used in the production of biochips The present invention can also be applied to other liquid jet heads such as a head. In the color material ejecting head, a liquid in which RGB (Red, Green, Blue) color material is dissolved, in an electrode material ejecting head, a liquid in which an electrode material is dissolved, and in a biological organic matter ejecting head, a liquid in which an organic substance is dissolved is used. Use each instead.
[0082]
【The invention's effect】
As described above, in the present invention, the diaphragm has a compression film having a compressive stress and a tensile film having a tensile stress, and the difference between the tension of the compression film and the tension of the tension film is the compression film or the tension film. Therefore, even if a large number of piezoelectric elements are driven simultaneously, the occurrence of crosstalk due to the tension of the diaphragm can be prevented. Therefore, regardless of the number of piezoelectric elements to be driven, the amount of displacement of the diaphragm due to the driving of the piezoelectric elements is substantially constant, and there is an effect that liquid can be ejected with uniform characteristics at all times.
[Brief description of the drawings]
FIG. 1 is an exploded perspective view of an ink jet recording head according to an embodiment of the present invention.
2A and 2B are diagrams illustrating an ink jet recording head according to the first embodiment of the invention, and are a plan view and a cross-sectional view of FIG.
FIG. 3 is a cross-sectional view showing a stress state of a diaphragm constituting the ink jet recording head according to the first embodiment of the invention.
FIG. 4 is a cross-sectional view showing a thin film manufacturing process according to the first embodiment of the present invention.
FIG. 5 is a cross-sectional view showing a thin film manufacturing process according to the first embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a stress state of a diaphragm constituting an ink jet recording head according to a second embodiment of the invention.
FIG. 7 is a schematic view of an ink jet recording apparatus according to an embodiment of the present invention.
[Explanation of symbols]
10 Channel formation substrate
11 Bulkhead
12 Pressure generation chamber
50 Elastic membrane
55 Insulating film
60 Lower electrode membrane
70 Piezoelectric layer
80 Upper electrode film
90 Lead electrode
100 reservoir
110 Protective film
300 Piezoelectric element

Claims (10)

A flow path forming substrate in which a pressure generating chamber communicating with a nozzle opening is defined, and a piezoelectric element that is provided on one surface of the flow path forming substrate via a vibration plate and has at least a lower electrode, a piezoelectric layer, and an upper electrode In a liquid jet head comprising:
The diaphragm includes at least one compression film having a compressive stress and at least one tensile film having a tensile stress, and a difference between a tension of the compression film and a tension of the tension film is the compression film or the tension film. A liquid jet head characterized by being within 20% of the larger tension of the tensile film. The liquid ejecting head according to claim 1, wherein the compression film includes a film made of silicon dioxide. The liquid ejecting head according to claim 1, wherein the tensile film includes a film made of zirconium dioxide. The liquid ejecting head according to claim 1, wherein the lower electrode is provided so as to cover a region facing the plurality of pressure generating chambers and constitutes a part of the diaphragm. The liquid ejecting head according to claim 4, wherein the lower electrode forms part of the tensile film. In any one of Claims 1-5, the protective film which protects the inner surface of the said pressure generation chamber is provided in the inner surface of the said pressure generation chamber, and this protective film comprises a part of said diaphragm. A liquid ejecting head. The liquid ejecting head according to claim 6, wherein the protective film constitutes a part of the compression film. The liquid ejecting head according to claim 6, wherein the protective film forms part of the tensile film. The pressure generation chamber according to any one of claims 1 to 8, wherein the pressure generation chamber is formed on a silicon single crystal substrate by anisotropic etching, and each layer of the piezoelectric element is formed by film formation and lithography. Liquid ejecting head. A liquid ejecting apparatus comprising the liquid ejecting head according to claim 1.

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