JP2001260348A - Ink jet recording head and ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording head and an ink jet recorder in which the efficiency of displacement due to driving of a piezoelectric element is enhanced. SOLUTION: The ink jet recording head comprises a diaphragm constituting a part of a pressure generating chamber 12 communicating with a nozzle opening, a lower electrode 60 constituting at least a part of the diaphragm, a piezoelectric element 300 comprising a piezoelectric layer 70 and an upper electrode 80, and a piezoelectric active part 320 serving as a substantial driving part of the piezoelectric layer 70 constituting the piezoelectric element 300 formed in a region facing the pressure generating chamber 12 wherein the neutral plane of driving through the piezoelectric active part 320 exists in the diaphragm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a part of a pressure generating chamber which communicates with a nozzle opening for discharging ink droplets, which is constituted by a vibrating plate. The present invention relates to an ink jet recording head and an ink jet recording apparatus that eject ink droplets by displacement.

[0002]

2. Description of the Related Art A part of a pressure generating chamber communicating with a nozzle opening for discharging ink droplets is constituted by a vibrating plate, and the vibrating plate is deformed by a piezoelectric element to pressurize the ink in the pressure generating chamber to pass the nozzle opening. Two types of ink jet recording heads that eject ink droplets have been commercialized, one using a longitudinal vibration mode piezoelectric actuator that expands and contracts in the axial direction of the piezoelectric element, and the other using a flexural vibration mode piezoelectric actuator. ing.

In the former method, the volume of the pressure generating chamber can be changed by bringing the end face of the piezoelectric element into contact with the diaphragm, so that a head suitable for high-density printing can be manufactured. There is a problem in that a difficult process of cutting into a comb shape in accordance with the arrangement pitch of the openings and an operation of positioning and fixing the cut piezoelectric element in the pressure generating chamber are required, and the manufacturing process is complicated.

On the other hand, in the latter, a piezoelectric element can be formed on a diaphragm by a relatively simple process of sticking a green sheet of a piezoelectric material according to the shape of a pressure generating chamber and firing the green sheet. In addition, there is a problem that a certain area is required due to the use of flexural vibration, and that high-density arrangement is difficult.

On the other hand, in order to solve the latter disadvantage of the recording head, a uniform piezoelectric material layer is formed by a thin film technique over the entire surface of the diaphragm as disclosed in Japanese Patent Application Laid-Open No. 5-286131. A proposal has been made in which the piezoelectric material layer is cut into a shape corresponding to the pressure generating chambers by a lithography method and a piezoelectric element is formed so as to be independent for each pressure generating chamber.

This eliminates the need for attaching the piezoelectric element to the vibration plate, which not only allows the piezoelectric element to be manufactured by a precise and simple method such as lithography, but also reduces the thickness of the piezoelectric element. There is an advantage that it can be made thin and can be driven at high speed. In this case, the piezoelectric element corresponding to each pressure generating chamber can be driven by providing at least only the upper electrode for each pressure generating chamber while the piezoelectric material layer is provided on the entire surface of the vibration plate.

[0007]

However, in the above-described manufacturing method using the thin film technology and the lithography method,
In general, in order to improve the piezoelectric characteristics of the piezoelectric layer, the piezoelectric layer is formed to be thicker than the diaphragm. Therefore, when the piezoelectric element is driven, the displacement efficiency is reduced because the neutral surface is located in the piezoelectric layer, and the displacement force of the piezoelectric layer itself cannot be sufficiently converted into the ink ejection force. is there.

In view of such circumstances, an object of the present invention is to provide an ink jet type recording head and an ink jet type recording apparatus in which the displacement efficiency by driving the piezoelectric element is improved.

[0009]

According to a first aspect of the present invention, which solves the above-mentioned problems, a lower electrode, a piezoelectric layer, and an upper electrode are provided via a diaphragm constituting a part of a pressure generating chamber communicating with a nozzle opening. An ink jet recording head, comprising: a piezoelectric element comprising an electrode; and a piezoelectric active section serving as a substantial driving section of the piezoelectric layer constituting the piezoelectric element in a region facing the pressure generating chamber. An ink jet recording head is characterized in that a neutral surface driven by the body active part is located in the diaphragm.

In the first aspect, since there is no neutral surface in the piezoelectric layer, only a compressive stress is applied to the piezoelectric layer during driving, and the displacement efficiency of the piezoelectric element is improved.

According to a second aspect of the present invention, in the first aspect, the product of the Young's modulus of the diaphragm and the square of the film thickness is the square of the Young's modulus and the film thickness of the upper electrode and the piezoelectric layer. The product is larger than the product of the above.

In the second aspect, the neutral surface is securely located in the diaphragm, and the displacement efficiency is improved.

According to a third aspect of the present invention, in the second aspect, the product of the Young's modulus of the diaphragm and the square of the film thickness is the square of the Young's modulus and the film thickness of the upper electrode and the piezoelectric layer. And 1 to 50 times the product of the above.

In the third aspect, by setting the product of the Young's modulus of the diaphragm and the square of the film thickness within a predetermined range, the efficiency of displacement is more reliably improved.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the lower electrode has a tensile stress greater than the stress of the piezoelectric layer. It is in.

In the fourth aspect, the displacement of the piezoelectric layer due to the stress of the lower electrode is prevented from being hindered.

According to a fifth aspect of the present invention, in the fourth aspect, the stress of the piezoelectric layer is a tensile stress, and the lower electrode is one to three times the tensile stress of the piezoelectric layer. An ink jet recording head is characterized in that:

[0018] In the fifth aspect, the displacement of the piezoelectric layer due to the stress of the lower electrode is more reliably prevented.

According to a sixth aspect of the present invention, in any one of the first to fifth aspects, the upper electrode has a tensile stress greater than the stress of the piezoelectric layer. It is in.

In the sixth aspect, the displacement of the piezoelectric layer due to the stress of the upper electrode is prevented from being hindered.

According to a seventh aspect of the present invention, in the sixth aspect, the stress of the piezoelectric layer is a tensile stress, and the upper electrode is one to three times the tensile stress of the piezoelectric layer. An ink jet recording head is characterized in that:

In the seventh aspect, the displacement of the piezoelectric layer due to the stress of the upper electrode is more reliably prevented.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, at least the sum of the film thicknesses of the piezoelectric layer and the upper electrode of the piezoelectric active part is equal to that of the diaphragm. An ink jet recording head is characterized in that the thickness is smaller than the sum of the thicknesses of the lower electrode and the lower electrode.

[0024] In the eighth aspect, the neutral surface is securely in the diaphragm, and the displacement efficiency is improved.

A ninth aspect of the present invention is the ink jet recording head according to any one of the first to eighth aspects, wherein the diaphragm is made of a ductile material film.

In the ninth aspect, since the diaphragm is a ductile material film suitable for tensile stress, breakage of the diaphragm due to stress at the time of displacement can be suppressed.

A tenth aspect of the present invention is the ink jet recording head according to the ninth aspect, wherein the diaphragm comprises only the lower electrode.

In the tenth aspect, since the diaphragm is composed only of the lower electrode suitable for tensile stress, destruction due to stress at the time of displacement is reliably suppressed.

According to an eleventh aspect of the present invention, in any one of the first to ninth aspects, the vibration plate includes at least one of a metal oxide film and a brittle material film, and the vibration plate is driven by driving the piezoelectric active portion. An ink jet recording head is characterized in that the upright surface is located in the metal oxide film or the brittle material film.

In the eleventh aspect, the stress acting on the diaphragm is suppressed, and breakage and deterioration of the diaphragm are prevented.

According to a twelfth aspect of the present invention, in the eleventh aspect, the diaphragm includes at least the brittle material film, the brittle material film is made of zirconium oxide, and the neutral plane is formed in the brittle material film. The ink jet recording head is characterized in that

In the twelfth aspect, by forming the brittle material film on which the neutral plane is located from a specific material, destruction due to stress at the time of displacement can be reliably suppressed.

According to an eleventh aspect of the present invention, in the ninth aspect, the vibration plate includes at least the metal oxide film, the metal oxide film is made of silicon oxide, and the neutral surface is formed in the metal oxide film. The ink jet recording head is characterized in that

In the eleventh aspect, the stress at the time of displacement is reliably suppressed by forming the metal oxide film on which the neutral plane is located with a specific material.

According to a twelfth aspect of the present invention, in any one of the first to eleventh aspects, the pressure generation chamber is formed by anisotropic etching on a silicon single crystal substrate, and each layer of the piezoelectric element is formed by film formation and etching. An ink jet recording head is formed by a lithography method.

In the twelfth aspect, an ink jet recording head having high-density nozzle openings can be manufactured in a large amount and relatively easily.

According to a thirteenth aspect of the present invention, there is provided an ink jet recording apparatus including the ink jet recording head according to any one of the first to twelfth aspects.

According to the thirteenth aspect, it is possible to realize an ink jet recording apparatus with improved head reliability.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on embodiments.

(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 cross section of one of the pressure generating chambers in the longitudinal direction. It is a figure showing a structure.

As shown in the figure, the flow path forming substrate 10 is a silicon single crystal substrate having a plane orientation (110) in this embodiment. As the flow path forming substrate 10, usually 150 to 3
A thickness of about 00 μm is used.
Those having a thickness of about 0 to 280 μm, more preferably about 220 μm are suitable. This is because the arrangement density can be increased while maintaining the rigidity of the partition wall between the adjacent pressure generating chambers.

One surface of the flow path forming substrate 10 is an opening surface, and the other surface is formed with an elastic film 50 having a thickness of 1 to 2 μm and made of silicon dioxide previously formed by thermal oxidation.

On the other hand, the silicon single crystal substrate is anisotropically etched on the opening surface of the flow path forming substrate
A nozzle opening 11 and a pressure generating chamber 12 are formed.

Here, in the anisotropic etching, when a silicon single crystal substrate is immersed in an alkaline solution such as KOH, the substrate is gradually eroded, and the first (111) plane perpendicular to the (110) plane is formed. A second (1) which forms an angle of about 70 degrees with the (111) plane and forms an angle of about 35 degrees with the (110) plane.
11) plane, and the etching rate of the (111) plane is about 1/1 compared to the etching rate of the (110) plane.
This is performed using the property of being 80.
By such anisotropic etching, two first (11
Precision processing can be performed based on depth processing of a parallelogram formed by the 1) plane and two oblique second (111) planes, and the pressure generating chambers 12 can be arranged at high density. it can.

In this 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 generating chamber 12 is provided on the flow path forming substrate 1.
It is formed by etching until it reaches the elastic film 50 almost through 0. The amount of the elastic film 50 that is attacked by the alkaline solution for etching the silicon single crystal substrate is extremely small.

On the other hand, each nozzle opening 11 communicating with one end of each pressure generating chamber 12 is formed narrower and shallower than the pressure generating chamber 12. That is, the nozzle opening 11 is formed by partially etching (half-etching) the silicon single crystal substrate in the thickness direction. In addition,
Half etching is performed by adjusting the etching time.

Here, the size of the pressure generating chamber 12 for applying the ink droplet ejection pressure to the ink and the size of the nozzle opening 11 for ejecting the ink droplet depend on the amount of the ejected ink droplet, the ejection speed, and the ejection frequency. Optimized. For example,
When recording 360 ink droplets per inch, the nozzle openings 11 need to be formed with a groove width of several tens of μm with high accuracy.

Further, each pressure generating chamber 12 and a common ink chamber 31 described later are connected to each pressure generating chamber 1 of the sealing plate 20 described later.
The ink is supplied from a common ink chamber 31 through the ink supply communication port 21 formed at a position corresponding to one end of the pressure generation chamber 12. Distributed to

The sealing plate 20 is provided with an ink supply communication port 21 corresponding to each of the pressure generating chambers 12 and has a thickness of, for example, 0.1 to 1 mm and a linear expansion coefficient of 300 ° C. or less. , For example, 2.5-4.5 [× 10 ⁻⁶ / ° C.]. In addition, the ink supply communication port 21
Each of the pressure generating chambers 1 is, as shown in FIGS.
It may be one slit hole 21A crossing the vicinity of the second ink supply side end or a plurality of slit holes 21B. The sealing plate 20 is provided on one side with the flow path forming substrate 10.
, And also serves as a reinforcing plate for protecting the silicon single crystal substrate from impacts and external forces. Also, sealing plate 2
0 forms one wall surface of the common ink chamber 31 on the other surface.

The common ink chamber forming substrate 30 forms the peripheral wall of the common ink chamber 31, and is formed by punching a stainless steel plate having an appropriate thickness according to the number of nozzles and the ink droplet ejection frequency. . In the present embodiment, the thickness of the common ink chamber forming substrate 30 is 0.2 mm.

The ink chamber side plate 40 is made of a stainless steel substrate, and one surface of the ink chamber side plate 40 constitutes one wall of the common ink chamber 31. In the ink chamber side plate 40, a thin wall 41 is formed by forming a concave portion 40a by half etching on a part of the other surface, and an ink introduction port 42 for receiving ink supply from the outside is punched and formed. ing. The thin wall 41 is for absorbing pressure generated at the time of ink droplet ejection toward the side opposite to the nozzle opening 11, and is unnecessary for the other pressure generating chambers 12 via the common ink chamber 31. Prevents positive or negative pressure from being applied.
In the present embodiment, the ink chamber side plate 40 is made 0.2 mm in consideration of rigidity required at the time of connection between the ink introduction port 42 and an external ink supply means, and a part of the thickness is 0.02 mm.
The thickness of the ink chamber side plate 40 may be 0.02 mm from the beginning in order to omit the formation of the thin wall 41 by half etching.

On the other hand, the thickness of the elastic film 50 on the side opposite to the opening surface of the flow path forming substrate 10 is, for example, about 0.1 to 2
An insulating film 55 having a thickness of, for example, about 0.2 μm is formed on the insulating film 55.
0, a piezoelectric film 70 having a thickness of, for example, about 1 μm, and an upper electrode film 80 having a thickness of, for example, about 0.1 μm are formed by lamination in a process described later to form the piezoelectric element 300. I have. Here, the piezoelectric element 300 refers to a portion including the lower electrode film 60, the piezoelectric film 70, and the upper electrode film 80. Generally, one of the electrodes of the piezoelectric element 300 is used as a common electrode, and the other electrode and the piezoelectric film 70 are patterned for each of the pressure generating chambers 12. Here, a portion which is constituted by one of the patterned electrodes and the piezoelectric film 70 and in which a piezoelectric strain is generated by applying a voltage to both electrodes is referred to as a piezoelectric active portion 320. In the present embodiment, the lower electrode film 60 is used as a common electrode of the piezoelectric element 300, and the upper electrode film 80 is used as an individual electrode of the piezoelectric element 300. However, there is no problem even if the upper electrode film 80 is reversed for convenience of a drive circuit and wiring. Also,
Here, the piezoelectric element 300 and a vibration plate whose displacement is generated by driving the piezoelectric element 300 are collectively referred to as a piezoelectric actuator. In the example described above, the elastic film 50,
The insulator film 55 and the lower electrode film 60 function as a diaphragm.

Here, a process for forming the piezoelectric film 70 and the like on the flow path forming substrate 10 made of a silicon single crystal substrate will be described with reference to FIG.

As shown in FIG. 4A, first, a silicon single crystal substrate wafer serving as the flow path forming substrate 10 is
Thermal oxidation is performed in a diffusion furnace at 0 ° C. to form an elastic film 50 made of silicon dioxide.

Next, as shown in FIG.
On insulator 0, an insulator film 55 is formed. This insulator film 55
Is preferably formed of a material having good adhesion to the piezoelectric film 70, for example, an oxide or nitride of at least one element selected from the constituent elements of the piezoelectric film 70.
In the present embodiment, after the zirconium layer is formed on the elastic film 50, the insulating film 55 is made of zirconium dioxide by thermal oxidation in a diffusion furnace at about 1150 ° C., for example.

Next, as shown in FIG. 4C, a lower electrode film 60 is formed by sputtering. As a material of the lower electrode film 60, platinum or the like is preferable. This is because a piezoelectric film 70 to be described later, which is formed by sputtering or a sol-gel method, has a thickness of 600 to 100 in an air atmosphere or an oxygen atmosphere after the film formation.
This is because it is necessary to perform crystallization by firing at a temperature of about 0 ° C. That is, the material of the lower electrode film 60 must be able to maintain conductivity under such high temperature and oxidizing atmosphere. In particular, when the piezoelectric film 70 is made of zirconate titanate (PZT), It is desirable that the change in conductivity due to the diffusion of lead oxide is small, and for these reasons, platinum is preferred.

Next, as shown in FIG. 4D, a piezoelectric film 70 is formed. In this embodiment, a so-called sol in which a metal organic substance is dissolved and dispersed in a solvent is applied, dried, and gelled,
Further, the film was formed using a so-called sol-gel method in which a piezoelectric film 70 made of a metal oxide was obtained by firing at a high temperature. As a material of the piezoelectric film 70, a PZT-based material is suitable when used in an ink jet recording head. The method for forming the piezoelectric film 70 is not particularly limited, and may be, for example, a sputtering method.

Further, a method of forming a PZT precursor film by a sol-gel method or a sputtering method and then growing the crystal at a low temperature by a high-pressure treatment in an aqueous alkali solution may be used.

Next, as shown in FIG. 4E, an upper electrode film 80 is formed. The upper electrode film 80 only needs to be a material having high conductivity, and can use many metals such as aluminum, gold, nickel, and platinum, and a conductive oxide. In the present embodiment, platinum is formed by sputtering.

Next, as shown in FIG.
The piezoelectric film 70 and the upper electrode film 80 are patterned.

First, as shown in FIG. 5A, the lower electrode film 60, the piezoelectric film 70 and the upper electrode film 80 are etched together to pattern the entire pattern of the lower electrode film 60. Next, as shown in FIG. 5B, only the piezoelectric film 70 and the upper electrode film 80 are etched to form the piezoelectric active portion 32.
0 patterning is performed.

As described above, after the entire pattern of the lower electrode film 60 is formed, the patterning is completed by patterning the piezoelectric active portion 320.

As described above, after patterning the lower electrode film 60 and the like, preferably, an interlayer having electrical insulation is preferably provided so as to cover at least the periphery of the upper surface of each upper electrode film 80 and the side surfaces of the piezoelectric film 70. An insulating film 90 is formed (see FIG. 1).

FIG. 6 shows a process of forming such an insulator layer.
Shown in

First, as shown in FIG. 6A, an interlayer insulating film 90 is formed so as to cover the periphery of the upper electrode film 80 and the side surfaces of the piezoelectric film 70. The material of the interlayer insulating film 90 is
In this embodiment, a negative photosensitive polyimide is used.

Next, as shown in FIG. 6B, each pressure generating chamber 1 is patterned by patterning the interlayer insulating film 90.
A contact hole 90a is formed in a portion corresponding to the vicinity of the end on the ink supply side of No. 2. This contact hole 90
“a” is for connecting the lead electrode 100 and the upper electrode film 80. One end of the lead electrode 100 is connected to each upper electrode film 80 via the contact hole 90a, and the other end is extended to the connection terminal portion. The lead electrode 100 is formed so as to have a width as narrow as possible so that a drive signal can be reliably supplied to the upper electrode film 80. In the present embodiment, the contact hole 90 a is provided at a position facing the pressure generating chamber 12, but, for example, the piezoelectric film 70 and the upper electrode film 80 are extended to the peripheral wall of the pressure generating chamber 12. Thus, a contact hole 90a may be provided at a position facing the peripheral wall.

The above is the film forming process. After forming the film in this manner, as shown in FIG. 6C, the silicon single crystal substrate is subjected to anisotropic etching with the above-described alkali solution to form the pressure generating chamber 12 and the like.

The configuration of the wiring for driving the piezoelectric active section 320 is not particularly limited. That is, in the above-described example, the lower electrode film 60 is formed over the entire surface, and the piezoelectric film 70 and the upper electrode film 80 are patterned in a region facing the pressure generating chamber 12. 70 and the upper electrode film 80, for example,
The contact hole may be omitted by drawing out from the end of the contact hole. Further, the lower electrode film 60 is connected to the pressure generating chamber 1.
Patterning can also be performed in the region facing 2 and the configuration of such a wiring is completely free.

In the above-described series of film formation and anisotropic etching, a number of chips are simultaneously formed on one wafer, and after the process is completed, a flow path having one chip size as shown in FIG. It is divided for each forming substrate 10. Further, the divided flow path forming substrate 10 is sequentially adhered and integrated with the sealing plate 20, the common ink chamber forming substrate 30, and the ink chamber side plate 40 to form an ink jet recording head.

The ink jet head thus configured takes in ink from an ink inlet 42 connected to an external ink supply means (not shown), fills the interior from the common ink chamber 31 to the nozzle opening 11 with ink, and
According to a recording signal from an external drive circuit (not shown), a voltage is applied between the lower electrode film 60 and the upper electrode film 80 via the lead electrode 100, and the elastic film 50, the insulator film 55, the lower electrode film 60, By flexing and deforming the piezoelectric film 70, the pressure in the pressure generating chamber 12 increases, and ink droplets are ejected from the nozzle openings 11.

FIG. 7 is a plan view and a cross-sectional view showing a main part of such an ink jet recording head of this embodiment.

As shown in FIG. 7 (a) and FIG. 7 (b), which is a cross-sectional view taken along the line BB 'of FIG. 7 (a), a piezoelectric film comprising a lower electrode film 60, a piezoelectric film 70, and an upper electrode film 80. Element 300
In the present embodiment, the piezoelectric active portion 320 is provided in a region facing the pressure generating chamber 12. Also,
The upper electrode film 80 and the lead electrode 1 are disposed in the vicinity of the longitudinal end of the piezoelectric active portion 320 through the contact hole 90a of the interlayer insulating film 90 provided on the piezoelectric active portion 320.
00 is connected.

In the present embodiment, as described above, the lower electrode film 60 which is one electrode of the piezoelectric active portion 320 is used.
An insulator film 55 made of zirconium oxide is formed over the entire surface between the elastic film 50 and the elastic film 50, and the elastic film 50, the insulator film 55, and the lower electrode film 60 function as a diaphragm. . Then, the thickness of the vibration plate is formed so as to be larger than the thicknesses of the piezoelectric film 70 and the upper electrode film 80 constituting the piezoelectric active portion 320, and the piezoelectric active portion 320 is formed.
When driving the diaphragm, the neutral plane is located in the diaphragm. That is, for example, in the present embodiment, as shown by a dotted line in the figure, when driving the piezoelectric active portion 320, each layer constituting the diaphragm so that the neutral plane y ₀ is in the insulator film 55. Was adjusted in thickness.

Here, the neutral plane y ₀ is expressed by the following equation (1) with reference to the boundary between the diaphragm (lower electrode film 60) and the piezoelectric film 70.

[0075]

(Equation 1)

E _f : Young's modulus of piezoelectric film and upper electrode film
E _s : Young's modulus of diaphragm ν _f : Poisson's ratio of piezoelectric film and upper electrode film ν _s : Poisson's ratio of diaphragm d: Film thickness of piezoelectric film and upper electrode film D: Film thickness of diaphragm

From this equation, if the thickness of each layer is determined according to characteristics such as Young's modulus and Poisson's ratio of each layer so that the relationship of y ₀ <0 is satisfied, the neutral plane is located in the diaphragm. Will be. Further, the Young's modulus and Poisson's ratio of the diaphragm and the piezoelectric film are about 0.2 to 0.3, and the denominator is always a positive value. Therefore, according to the characteristics of each layer of the piezoelectric element and the diaphragm, If each thickness is set to a value that satisfies the relationship of the following equation (2), the neutral plane can be inside the diaphragm.

[0078]

(Equation 2)

That is, the thickness of each layer is determined so that the product of the Young's modulus of the diaphragm and the square of the film thickness is larger than the product of the Young's modulus of the upper electrode film 80 and the piezoelectric film 70 and the square of the film thickness. do it. The product of the Young's modulus of the diaphragm and the square of the film thickness is preferably 1 to 50 times the product of the Young's modulus of the upper electrode film 80 and the piezoelectric film 70 and the square of the film thickness. . Thereby, the deformation efficiency of the diaphragm by driving the piezoelectric element is improved.

When the piezoelectric film 70 is deformed by applying a voltage, the piezoelectric film 70 becomes harder with this deformation,
Although the apparent Young's modulus becomes large, it is preferable to determine the thickness of each layer according to the characteristics of each layer so as to satisfy the relationship of the above expression 2 also at this time.

In the present embodiment, the thickness of each layer constituting the diaphragm is adjusted so that the neutral plane is located in the diaphragm. However, the method is not particularly limited. With the body film formed, the film thickness of the upper electrode film 80 may be determined in accordance with the physical properties, film thickness, etc. of each layer. Thus, the neutral surface can be easily and reliably set in the diaphragm. At this time, if the insulator film 55 made of zirconium oxide is formed relatively thick or hard, the thickness of the upper electrode film 80 can be easily adjusted.

Even if the insulator film 55 is made hard or its thickness is increased, it does not significantly affect the deformation of the diaphragm due to the driving of the piezoelectric element within the range of actual use. Also, by increasing the thickness of the diaphragm,
When the rigidity of the diaphragm increases and the amount of displacement decreases, the width of the pressure generating chamber 12 can be increased to cope with the problem.

Further, by appropriately setting the cross-sectional shape of the piezoelectric film 70, the neutral plane can be accommodated in the diaphragm. That is, the physical property value, the film thickness, or the cross-sectional shape of each film is set within the scope of the invention of the present application. As a result, it is within the scope of the present invention that the neutral plane is driven by the driving of the piezoelectric active part in the diaphragm. Becomes

Also, at least one of the electrodes formed on the surface of the piezoelectric film 70, for example, the lower electrode film 60 is
It is preferable that the piezoelectric film 70 has a tensile stress larger than the stress of the piezoelectric film 70. In particular, when the piezoelectric film 70 has a tensile stress, the tensile stress of the lower electrode film 60 is one of the tensile stress of the piezoelectric film 70. It is preferably up to 3 times. Similarly, it is preferable that the upper electrode film 80 also has a tensile stress larger than the stress of the piezoelectric film 70, and in particular, when the piezoelectric film 70 has a tensile stress, the tensile stress of the upper electrode film 80 is The tensile stress is preferably 1 to 3 times the tensile stress of the piezoelectric film 70, respectively. This can prevent the deformation of the piezoelectric film 70 from being hindered, and as a result, the piezoelectric film 7
The displacement efficiency of 0 can be improved.

When a voltage is applied to the piezoelectric active portion 320 of the ink jet type recording head having such a configuration and the piezoelectric active portion 320 is driven, the upper electrode film of each layer of the diaphragm and the piezoelectric active portion 320 is bounded by the neutral plane y _0. Compressive stress is applied to the 80 side,
On the other hand, a tensile stress is applied to the elastic film 50 side. Therefore, if the neutral plane y ₀ is located in the diaphragm as in the present embodiment, only the compressive stress is applied to the piezoelectric film 70 when the piezoelectric active portion 320 is driven, and the piezoelectric film 70 It can sufficiently convert its own displacement force into ink ejection force,
The driving voltage can be reduced.

Further, in the present embodiment, particularly, the neutral plane y ₀
In the insulator film 55 made of a brittle material.
That is, since the insulating film 55 made of a brittle material is located at the place where the stress concentration is least, the stress applied to the diaphragm when the piezoelectric active part 320 is driven is suppressed, and the destruction and deterioration of the diaphragm are performed. Etc. can also be prevented.

Of course, the present invention is not limited to the present embodiment. For example, the diaphragm can be constituted only by the lower electrode film 60. In this case, the diaphragm can be made suitable for tensile stress by forming the lower electrode film 60 with a ductile material such as platinum.

On the other hand, as in the prior art, the neutral surface is
8, the compressive stress is applied to the piezoelectric film 70a on the upper electrode film 80 side from the neutral plane y ₀ , but the piezoelectric film 70b on the elastic film 50 side is applied to the piezoelectric film 70b as shown in FIG. A tensile stress is applied. Therefore, the displacement force of the piezoelectric film 70 itself cannot be sufficiently converted into the ink ejection force, and the displacement efficiency is reduced.

Here, a specific example of the ink jet recording head of the present embodiment as described above will be described.

(Examples and Test Examples) In this example, each layer of the vibration plate and the piezoelectric element was formed with the physical properties and film thickness shown in Table 1 below so as to satisfy the relationship of the above equation 2, and the neutral plane was formed. y ₀
Formed an ink jet recording head located in the diaphragm.

As a comparative example, each layer of the diaphragm and the piezoelectric element was made to have the physical properties and thickness shown in Table 1 below, and the other conditions were the same as in the example, and the neutral plane y ₀ was positioned outside the diaphragm. Thus, an ink jet recording head was prepared.

[0092]

[Table 1]

[0093]

(Equation 3)

Further, in the ink jet recording heads of these Examples and Comparative Examples, the amount of deformation and the deformation efficiency of the diaphragm when the piezoelectric element was driven by applying a voltage of 25 V (per unit when a voltage of 25 V was applied). Displacement energy) was measured. Note that Comparative Example 1 is an example in which the film thickness is changed while keeping the strain and Young's modulus constant, and Comparative Example 2 is an example in which the film thickness and the strain are kept constant and the Young's modulus is changed. Table 2 shows the results.

[0095]

[Table 2]

As is clear from Table 2, in the example in which the neutral plane is located in the diaphragm, the displacement amount and the displacement energy are remarkably improved as compared with the comparative example. That is, if the neutral surface is located in the diaphragm, the displacement efficiency of the diaphragm by driving the piezoelectric element can be significantly improved.

(Other Embodiments) The embodiments of the present invention have been described above, but the basic configuration of the ink jet recording head is not limited to the above.

For example, in the above-described embodiment, the neutral surface is located within the insulator film 55 of the diaphragm. However, the present invention is not limited to this. For example, as shown in FIG. The thickness may be adjusted so that the neutral plane y ₀ is in the elastic film 50 as shown by a dotted line in the figure. Further, needless to say, the neutral plane y ₀ may be provided in the lower electrode film 60. In any case, if the neutral plane y ₀ is located in the diaphragm,
As in the above embodiment, the displacement efficiency can be improved.

For example, in addition to the sealing plate 20 described above,
The common ink chamber forming substrate 30 may be made of glass ceramic, and further, the thin film 41 may be made of glass ceramic as a separate member, and the material, structure, and the like can be freely changed.

In the above-described embodiment, the nozzle openings are formed on the end face of the flow path forming substrate 10. However, the nozzle openings may be formed to project in a direction perpendicular to the surface.

FIG. 10 is an exploded perspective view of the embodiment configured as described above, and FIG. 11 is a cross-sectional view of the flow path. In this embodiment, the nozzle opening 11 is formed in the nozzle substrate 120 opposite to the piezoelectric element, and the nozzle communication port 22 that connects the nozzle opening 11 and the pressure generating chamber 12 is formed with the sealing plate 20 and the common ink chamber. It is arranged so as to penetrate the formation substrate 30, the thin plate 41A, and the ink chamber side plate 40A.

The present embodiment is different from the first embodiment in that
A is basically the same as the first embodiment except that the ink chamber side plate 40A and the ink chamber side plate 40A are formed as separate members, and the opening is formed in the ink chamber side plate 40A. Description is omitted.

Further, needless to say, the present invention can be similarly applied to an ink jet recording head of a type in which a common ink chamber is formed in a flow path forming substrate.

In each of the embodiments described above, a thin-film type ink jet recording head which can be manufactured by applying a film forming and lithography process is described as an example.
Of course, the present invention is not limited to this. For example, a piezoelectric film is formed by laminating substrates to form a pressure generating chamber, or a piezoelectric film is formed by attaching a green sheet or by screen printing, or a piezoelectric film formed by crystal growth. The present invention can be applied to ink jet recording heads having various structures, such as those that form a recording medium.

Further, an example in which an interlayer insulating film is provided between the piezoelectric element and the lead electrode has been described. However, the present invention is not limited to this. For example, an anisotropic conductive film may be provided on each upper electrode without providing an interlayer insulating film. The film may be thermally welded, and the anisotropic conductive film may be connected to a lead electrode, or may be connected using various bonding techniques such as wire bonding.

As described above, the present invention can be applied to ink jet recording heads having various structures, as long as it does not violate the gist of the present invention.

The ink jet recording head of each of these embodiments constitutes a part of a recording head unit having an ink flow path communicating with an ink cartridge and the like, and is mounted on an ink jet recording apparatus. FIG.
FIG. 1 is a schematic view showing an example of the ink jet recording apparatus.

As shown in FIG. 12, recording head units 1A and 1B having an ink jet recording head are
Cartridges 2A and 2B constituting ink supply means are detachably provided. 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 main body 4 so as to be movable in the axial direction. I have. The recording head units 1A and 1B are, for example,
Each of them ejects a black ink composition and a color ink composition.

The driving force of the driving motor 6 is transmitted to the carriage 3 via a plurality of gears and a timing belt 7 (not shown), so that the carriage 3 on which the recording head units 1A and 1B are mounted moves along the carriage shaft 5. Moved. On the other hand, a platen 8 is provided on the apparatus main body 4 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 wound around the platen 8. It is designed to be transported.

[0110]

As described above, according to the present invention, when the piezoelectric element is driven, the neutral plane is not in the piezoelectric film, so that the displacement efficiency of the piezoelectric film can be improved. As a result, the ejection efficiency of the ink can be improved. Therefore, the driving voltage of the piezoelectric element can be reduced. In particular, when the neutral surface of the piezoelectric element during driving is in the brittle material, breakage and deterioration of the brittle material due to driving of the piezoelectric element can be prevented.

[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.

FIG. 2 is a plan view and a cross-sectional view of the inkjet recording head according to the first embodiment of the present invention, showing the same.

FIG. 3 is a perspective view showing a modification of the sealing plate of FIG. 1;

FIG. 4 is a cross-sectional view illustrating a thin-film manufacturing process according to the first embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a thin-film manufacturing process according to the first embodiment of the present invention.

FIG. 6 is a cross-sectional view illustrating a thin-film manufacturing process according to the first embodiment of the present invention.

FIG. 7 is a plan view and a cross-sectional view of the inkjet recording head according to the first embodiment of the invention.

FIG. 8 is a cross-sectional view illustrating a neutral surface driven by driving a piezoelectric active portion according to a conventional technique.

FIG. 9 is a cross-sectional view of an ink jet recording head according to another embodiment of the present invention.

FIG. 10 is an exploded perspective view showing an ink jet recording head according to another embodiment of the present invention.

FIG. 11 is a cross-sectional view showing an ink jet recording head according to another embodiment of the present invention.

FIG. 12 is a schematic view of an ink jet recording apparatus according to an embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 flow path forming substrate 12 pressure generating chamber 50 elastic film 55 insulating film 60 lower electrode film 70 piezoelectric film 80 upper electrode film 90 interlayer insulating film 100 lead electrode 300 piezoelectric element 320 piezoelectric active part

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[Procedure amendment]

[Submission date] April 18, 2000 (2004.1.
8)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0033

[Correction method] Change

[Correction contents]

According to a thirteenth aspect of the present invention, in the eleventh aspect, the vibration plate includes at least the metal oxide film, the metal oxide film is made of silicon oxide, and the neutral surface is formed in the metal oxide film. The ink jet recording head is characterized in that

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0034

[Correction method] Change

[Correction contents]

In the thirteenth aspect, the stress at the time of displacement is reliably suppressed by forming the metal oxide film on which the neutral plane is located with a specific material.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0035

[Correction method] Change

[Correction contents]

According to a fourteenth aspect of the present invention, in any one of the first to thirteenth 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. An ink jet recording head is formed by a lithography method.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0036

[Correction method] Change

[Correction contents]

In the fourteenth aspect, an ink jet recording head having high-density nozzle openings can be manufactured in a large amount and relatively easily.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0037

[Correction method] Change

[Correction contents]

According to a fifteenth aspect of the present invention, there is provided an ink jet recording apparatus comprising the ink jet recording head according to any one of the first to fourteenth aspects.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction contents]

According to the fifteenth aspect, it is possible to realize an ink jet recording apparatus with improved head reliability.

Claims (15)

[Claims] 1. A diaphragm comprising a part of a pressure generating chamber communicating with a nozzle opening, and a piezoelectric element comprising at least a part of the diaphragm, a lower electrode, a piezoelectric layer and an upper electrode, and In an ink jet type recording head comprising a piezoelectric active part serving as a substantial driving part of the piezoelectric layer constituting the piezoelectric element in a region facing the pressure generating chamber, a neutral state is obtained by driving the piezoelectric active part. An ink jet recording head having a surface in the diaphragm. 2. The method according to claim 1, wherein the product of the Young's modulus of the diaphragm and the square of the film thickness is larger than the product of the Young's modulus of the upper electrode and the piezoelectric layer and the square of the film thickness. Characteristic inkjet recording head. 3. The product according to claim 2, wherein the product of the Young's modulus of the diaphragm and the square of the film thickness is 1 to 50 times the product of the Young's modulus of the upper electrode and the piezoelectric layer and the square of the film thickness. An ink jet recording head, characterized in that: 4. The ink jet recording head according to claim 1, wherein the lower electrode has a tensile stress greater than a stress of the piezoelectric layer. 5. The ink jet recording head according to claim 4, wherein the stress of the piezoelectric layer is a tensile stress, and the lower electrode is one to three times the tensile stress of the piezoelectric layer. . 6. The ink jet recording head according to claim 1, wherein the upper electrode has a tensile stress greater than a stress of the piezoelectric layer. 7. The ink-jet recording head according to claim 6, wherein the stress of the piezoelectric layer is a tensile stress, and the upper electrode is one to three times the tensile stress of the piezoelectric layer. . 8. The method according to claim 1, wherein at least the sum of the thicknesses of the piezoelectric layer and the upper electrode of the piezoelectric active portion is smaller than the thickness of the diaphragm. Inkjet recording head. 9. An ink jet recording head according to claim 1, wherein said diaphragm is made of a ductile material film. 10. An ink jet recording head according to claim 9, wherein said diaphragm comprises only said lower electrode. 11. The vibration plate according to claim 1, wherein the vibration plate includes at least one of a metal oxide film and a brittle material film, and a neutral surface formed by driving the piezoelectric active part is the metal oxide film or the brittle material film. An ink jet recording head which is located in a brittle material film. 12. The device according to claim 11, wherein the diaphragm includes at least the brittle material film, the brittle material film is made of zirconium oxide, and the neutral plane is located in the brittle material film. Ink jet recording head. 13. The method according to claim 11, wherein the diaphragm includes at least the metal oxide film, the metal oxide film is made of silicon oxide, and the neutral plane is located in the metal oxide film. Ink jet recording head. 14. The pressure generating chamber according to claim 1, wherein 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 a lithography method. An ink jet recording head, comprising: 15. An ink jet recording apparatus comprising the ink jet recording head according to claim 1.