JPH11309858A - Ink jet recording head, driving method therefor and ink jet recorder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance displacement efficiency of an elastic film by increasing displacement of a piezoelectric layer. SOLUTION: The ink jet recording head includes a piezoelectric oscillator comprising an elastic film forming a part of a pressure generating chamber 12 communicating with a nozzle opening, a lower electrode 60 arranged on the elastic film, and a piezoelectric layer 70 formed on the lower electrode 60 wherein any one of the upper or lower electrode 60, 80 constituting the piezoelectric oscillator 15 patterned in a region facing the pressure generating chamber 12 and a pair of second electrodes 81, 82 are arranged on the surface of the piezoelectric layer 70 constituting the piezoelectric oscillator on the opposite sides in the breadthwise direction of the patterned electrode thus increasing displacement of the piezoelectric layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pressure generating chamber which is in communication with a nozzle opening for ejecting ink droplets, which is constituted by an elastic film. The present invention relates to an ink jet recording head that discharges ink droplets by displacement of a layer, a driving method thereof, and an ink jet recording apparatus.

[0002]

2. Description of the Related Art A part of a pressure generating chamber communicating with a nozzle opening for discharging ink droplets is formed of an elastic film, and this elastic film is deformed by a piezoelectric vibrator to pressurize ink in the pressure generating chamber to open the nozzle opening. There are two types of ink-jet recording heads that eject ink droplets from a piezoelectric vibrator, one that uses a piezoelectric vibrator that expands and contracts in the axial direction of the piezoelectric vibrator, and one that uses a piezoelectric vibrator that flexes. Has been put to practical use.

In the former method, the volume of the pressure generating chamber can be changed by bringing the end face of the piezoelectric vibrator into contact with an elastic film, so that a head suitable for high-density printing can be manufactured. A complicated process of cutting the piezoelectric vibrators into a comb-tooth shape in accordance with the arrangement pitch of the nozzle openings, and a work of positioning and fixing the separated piezoelectric vibrators in the pressure generating chambers, which complicates the manufacturing process. There is.

On the other hand, in the latter, a piezoelectric vibrator can be formed on an elastic film by a relatively simple process of sticking a green sheet of a piezoelectric material according to the shape of the pressure generating chamber and firing the green sheet. However, due to the use of flexural vibration, a certain area is required, and there is a problem 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 over the entire surface of the elastic film by a film forming technique as disclosed in Japanese Patent Application Laid-Open No. 5-286131. A proposal has been made in which this piezoelectric material layer is cut into a shape corresponding to the pressure generating chambers by lithography, and a piezoelectric vibrator is formed so as to be independent for each pressure generating chamber.

According to this, the work of attaching the piezoelectric vibrator to the elastic film becomes unnecessary, and the precision of the lithography method is eliminated.
In addition to the fact that the piezoelectric vibrator can be manufactured by a simple and simple method, there is an advantage that the thickness of the piezoelectric vibrator can be reduced and high-speed driving is possible. In this case, the piezoelectric vibrator 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 elastic film.

[0007]

However, in the above-described manufacturing method using the thin film technology and the lithography method,
When the piezoelectric vibrator is driven, there is a problem that the amount of deformation of the elastic film is small and a sufficient excluded volume cannot be obtained.

In view of such circumstances, an object of the present invention is to provide an ink jet recording head, a method of driving the same, and an ink jet recording apparatus in which the amount of displacement of the piezoelectric layer is increased and the displacement efficiency of the elastic film is improved. And

[0009]

According to a first aspect of the present invention for solving the above-mentioned problems, an elastic film constituting a part of a pressure generating chamber communicating with a nozzle opening and a lower member provided on the elastic film are provided. The piezoelectric vibrator is configured in an ink jet recording head including an electrode, a piezoelectric vibrator having a piezoelectric layer formed on the lower electrode, and an upper electrode formed on the surface of the piezoelectric layer. One of the lower electrode and the upper electrode is patterned in a region facing the pressure generating chamber, and a pair of second electrodes is formed on both sides in the width direction of the patterned electrode and on the surface of the piezoelectric layer constituting the piezoelectric vibrator. An ink jet recording head is provided with two electrodes.

In the first aspect, a tensile stress in the width direction can be applied to the piezoelectric layer by applying an electric field through the pair of second electrodes.

According to a second aspect of the present invention, in the first aspect, a voltage can be applied to the pair of second electrodes separately from the voltage application to the lower electrode and the upper electrode. Ink-jet recording head.

In the second aspect, by applying a voltage between the pair of second electrodes, a tensile stress in the width direction is applied to the piezoelectric layer, so that the piezoelectric layer is deformed in a direction opposite to a deformation direction for discharging ink. By deforming and then applying a voltage between the upper electrode and the lower electrode, the displacement of the piezoelectric layer during ink ejection is increased.

According to a third aspect of the present invention, in the first or second aspect, the pair of second electrodes are provided on both end faces in the width direction of the piezoelectric layer. In the recording head.

In the third aspect, since the pair of second electrodes face each other, it is possible to reliably apply a planar electric field to the piezoelectric layer.

According to a fourth aspect of the present invention, in any one of the first to third aspects, the piezoelectric layer constituting the piezoelectric vibrator is patterned in a region opposed to the pressure generating chamber and has a thickness. At least a part of the direction has an inclined surface patterned so that its width gradually narrows from below to above, and the pair of second electrodes are provided on the inclined surface. An ink jet recording head is characterized in that:

In the fourth aspect, the upper electrode can be easily formed by patterning the pair of second electrodes together when patterning the upper electrode.

According to a fifth aspect of the present invention, in any one of the first to fourth aspects, at least the piezoelectric layer constituting the piezoelectric vibrator is configured such that at least one of the piezoelectric vibrators extends from one end in the longitudinal direction of the piezoelectric vibrator. An ink jet recording head is provided so as to extend to an outside of a region facing the generation chamber.

According to the fifth aspect, a connection portion between the piezoelectric layer and the external wiring can be formed in a region facing the peripheral wall of the pressure generating chamber.

According to a sixth aspect of the present invention, in the fifth aspect, the upper electrode is extended on the piezoelectric layer extending to an outside of a region facing the pressure generating chamber. The feature is the ink jet recording head.

According to the sixth aspect, it is possible to connect to the external wiring via the extended upper electrode.

According to a seventh aspect of the present invention, in any one of the first to sixth aspects, a contact portion for connecting a lead electrode and the upper electrode is provided on an upper surface of the piezoelectric vibrator. Ink-jet recording head.

In the seventh aspect, the application of the voltage to the piezoelectric vibrator is performed through the contact portion.

According to an eighth aspect of the present invention, in any one of the first to seventh aspects, an insulator layer is formed on an upper surface of the piezoelectric vibrator, and a contact for connecting a lead electrode to the upper electrode is provided. The portion is formed in a contact hole formed in the insulator layer, in the ink jet recording head.

In the eighth aspect, the application of the voltage to the piezoelectric vibrator is performed through the contact portion formed through the insulator layer.

According to a ninth aspect of the present invention, in any one of the first to eighth aspects, the flow path forming substrate is formed of a silicon single crystal substrate, and the pressure generating chamber is formed by anisotropic etching. An ink jet recording head is characterized in that each layer of the piezoelectric vibrator is formed by film formation and lithography.

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

According to a tenth 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 ninth aspects.

According to the tenth aspect, it is possible to realize an ink jet recording apparatus in which the driving efficiency of the head is improved and the ink can be ejected favorably.

According to an eleventh aspect of the present invention, a voltage is applied to a pair of electrodes provided on the upper and lower sides in the thickness direction of a piezoelectric layer provided on an elastic film constituting a part of a pressure generating chamber communicating with a nozzle opening. And applying a pressure to the ink in the pressure generating chamber to discharge the ink from the nozzle opening, thereby applying a pressure to the piezoelectric layer to deform the piezoelectric layer. A step of applying a voltage to a pair of second electrodes provided on both sides, and thereafter,
Applying a voltage to the pair of electrodes to apply a pressure to the ink in the pressure generating chamber to cause a flexural deformation in the piezoelectric layer. is there.

[0030] In the eleventh aspect, by applying a voltage between the pair of second electrodes, the piezoelectric layer can be deformed in a direction opposite to the bending deformation for applying pressure to the ink, The excluded volume can be improved.

According to a twelfth aspect of the present invention, in the eleventh aspect, a tensile stress is applied to the piezoelectric layer in a width direction by applying a voltage to the pair of second electrodes. Drive method of the recording head.

In the twelfth aspect, the piezoelectric layer is deformed in the direction opposite to the bending deformation for discharging ink by the tensile stress in the width direction.

The thirteenth aspect of the present invention is directed to the eleventh or twelfth aspect.
The method according to the above aspect, further comprising applying a voltage to the pair of electrodes after canceling the application of the voltage to the pair of second electrodes.

In the thirteenth aspect, since a voltage is applied to the piezoelectric layer deformed in the direction opposite to the bending deformation for discharging ink to bend and deform, the displacement of the piezoelectric layer is increased.

[0035]

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 thereof and a cross section in the longitudinal direction of one pressure generating chamber. It is a figure showing a structure.

As shown in the figure, the flow path forming substrate 10 is formed of 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, a 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, it is gradually eroded and the first (111) plane perpendicular to the (110) plane and the first (111) plane 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 entirely covers one surface of the flow path forming substrate 10 on one surface, and also serves as a reinforcing plate for protecting the silicon single crystal substrate from impact and external force. In addition, the sealing plate 20
The other surface constitutes one wall surface of the common ink chamber 31.

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 in accordance with 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 surface 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 opposite side of the opening surface of the flow path forming substrate 10 is, for example, about 0.5 μm.
A lower electrode film 60, 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 to be described later. (Piezoelectric element) 300 is constituted. Here, the piezoelectric vibrator 300 includes the lower electrode film 60, the piezoelectric film 70, and the upper electrode film 8.
Refers to the portion containing 0. Generally, one of the electrodes of the piezoelectric vibrator 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. In this case, the piezoelectric active layer 32 is constituted by one of the patterned electrodes and the piezoelectric film 70, and a portion where the piezoelectric strain is generated by applying a voltage to both electrodes is formed.
It is called 0. In the present embodiment, the lower electrode film 60 is a common electrode of the piezoelectric vibrator 300, and the upper electrode film 80 is the piezoelectric vibrator 30.
Although the number of the individual electrodes is 0, there is no problem even if this is reversed for convenience of the drive circuit and wiring. In any case, the piezoelectric active portion is formed for each pressure generating chamber. In the example described above, the elastic film 50 and the lower electrode film 6
Although 0 functions as a diaphragm, the lower electrode film may also serve as an elastic film.

As will be described later in detail, in the present embodiment, the upper electrode film 8 corresponding to each piezoelectric active portion 320 is formed.
On both sides of 0, the upper electrode film 80 is formed of the same layer, but a pair of independent second electrode films 81 and 82 are provided in parallel.

Here, a process of 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. 4B, the lower electrode film 60 is formed uniformly along the surface shape of the elastic film 50 by sputtering. Pt or the like is preferable as the material of the lower electrode film 60. This is because the piezoelectric film 70 described below, which is formed by sputtering or a sol-gel method, needs to be crystallized by baking at a temperature of about 600 to 1000 ° C. in an air atmosphere or an oxygen atmosphere after the film formation. It is. 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 PZT is used for the piezoelectric film 70, PZT
It is desirable that the change in conductivity due to the diffusion of bO is small, and Pt is preferable for these reasons.

Next, as shown in FIG. 4C, a piezoelectric film 70 is formed. The piezoelectric film 70 can be formed by sputtering, but 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, and further baked at a high temperature. A so-called sol-gel method for obtaining a piezoelectric film 70 made of an oxide is used. As a material for the piezoelectric film 70, a lead zirconate titanate (PZT) -based material is suitable when used in an ink jet recording head.

Next, as shown in FIG. 4D, an upper electrode film 80 is formed. The upper electrode film 80 only needs to be a material having high conductivity, and many metals such as Al, Au, Ni, and Pt, and a conductive oxide can be used. In the present embodiment, P
t 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 pressure generating chamber 12.
The patterning of the piezoelectric body active portion 320 is performed only in the region opposed to.

Next, as shown in FIG. 5C, only the upper electrode film 80 corresponding to each piezoelectric active portion 320 is patterned to remove the upper electrode film 80 in the longitudinal direction. The formation of the upper electrode film 80
The second electrode films 81 and 82 are formed on both sides in the width direction.

After patterning the lower electrode film 60 and the like as described above, preferably, the upper electrode film 80 and the second
An insulator layer 90 having electrical insulation is formed so as to cover at least the periphery of the upper surfaces of the electrode films 81 and 82 and the side surfaces of the piezoelectric film 70 and the lower electrode film 60 (see FIG. 1). The insulator layer 90 is formed of a material that can be formed by a film formation method or shaped by etching, for example, silicon oxide, silicon nitride, or an organic material, preferably photosensitive polyimide having low rigidity and excellent electrical insulation. Is preferred.

A part of the insulator layer 90 which covers the upper surface of a portion corresponding to one end of each of the upper electrode films 80 includes a part of the upper electrode film 80 for connection with a lead electrode 100 described later. A contact hole 90a exposing a portion is formed. Then, this contact hole 90a
A lead electrode 100 having one end connected to each upper electrode film 80 and the other end extending to the connection terminal portion is formed.
The lead electrode 100 is formed so as to be as narrow as possible so as to reliably supply a drive signal to the upper electrode film 80.

Also, as in the case of the upper electrode film 80, the second electrode films 81 and 82 also have contact holes 90b and 90b in the portions of the insulator layer 90 corresponding to one ends thereof.
c is formed. And this contact hole 9
Lead electrodes 100A and 100B are separately formed via Ob and 90c.

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

First, as shown in FIG. 6 (a), the upper electrode film 80, the peripheral portions of the second electrode films 81 and 82, the piezoelectric film 70
Then, an insulator layer 90 is formed so as to cover the side surface of the lower electrode film 60. Suitable materials for the insulator layer 90 are as described above, but in the present embodiment, a negative photosensitive polyimide is used.

Next, as shown in FIG. 6B, by patterning the insulator layer 90, each of the upper electrode film 80 and the second electrode films 81 and 82 on the ink supply side of the pressure generating chamber 12 is formed. A contact hole 90 is formed in a portion corresponding to the vicinity of the end.
a, 90b and 90c are formed.

The contact holes 90a, 90b,
90c may be provided at a portion corresponding to the piezoelectric active portion 320 of the pressure generating chamber 12, and may be provided at, for example, a central portion or a nozzle-side end portion. Further, in the present embodiment, the piezoelectric vibrator is provided in the region facing the pressure generating chamber 12, but is not limited thereto. For example, the piezoelectric film and the upper electrode film may be provided in the region facing the peripheral wall of the pressure generating chamber 12. It may be extended up to.

Next, for example, a lead such as Cr-Au is formed on the entire surface and then patterned to form the lead electrode 100 and the like.

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. In addition,
In the series of film formation and anisotropic etching described above, a number of chips are simultaneously formed on one wafer, and after completion of the process, each of the flow path forming substrates 10 having one chip size as shown in FIG. To divide. 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.

FIG. 7 shows a plan view and a cross section of the main part of the ink jet recording head thus formed.

In the present embodiment, as shown in FIG. 7, a piezoelectric vibrator 30 having a piezoelectric film 70, an upper electrode film 80 and the like is provided.
0 is basically provided in a region facing the pressure generating chamber 12 and forms the piezoelectric active portion 320. Further, on the piezoelectric film 70 at a portion corresponding to each piezoelectric active portion 320,
The upper electrode film 80 and the second side through the groove 83 on both sides in the width direction are formed.
Of electrode films 81 and 82 are arranged in parallel.

As described above, the contact holes 90a, 90a are formed in the insulator layer 90 near one end in the longitudinal direction of each of the upper electrode film 80 and the second electrode films 81, 82, respectively.
b, 90c are formed and separate lead electrodes 100, 1
00A and 100B. In the present embodiment, a contact hole 90d is also provided in the insulator layer 90 on the lower electrode film 60, and is connected to the lead electrode 100C in the contact hole 90d like the upper electrode film 80.

Here, a method of driving the ink jet recording head of the present invention will be described.

FIG. 8 is a graph showing an example of the relationship between time and voltage applied to the piezoelectric active portion according to the first embodiment of the present invention.

First, a predetermined voltage, for example, as shown in FIG. 8, a voltage for discharging ink is applied between the second electrode films 81 and 82 on both sides of the upper electrode film 80 via the lead electrodes 100A and 100B. stands about half of the voltage V ₁ of the V _2, the piezoelectric film 7
An electric field is applied to zero. As a result, a tensile stress is generated in the piezoelectric film 70, and the piezoelectric film 70 is slightly deformed in a direction opposite to the bending deformation for discharging the ink.

Next, at the timing of ink ejection, the voltage V ₁ for applying a tensile stress is cut off, and at about the same time, a predetermined voltage V ₂ for ink ejection is applied between the upper electrode film 80 and the lower electrode film 60. An electric field is applied to the piezoelectric film 70 (t _{1 in the} figure). As a result, the piezoelectric film 70 is bent downward and convexly, and the diaphragm is deformed along with this deformation, and ink is ejected.

After a predetermined voltage is applied between the second electrode films 81 and 82, the upper electrode film 80 and the lower electrode film 6
0, the piezoelectric film 70
Can be increased.

Here, the principle that the amount of deformation of the piezoelectric film increases will be described.

FIG. 9 is a graph showing an example of the PV hysteresis loop.

The PZT used as the piezoelectric film 70 is
When a voltage is applied in the thickness direction (vertical direction), the polarization is oriented vertically, that is, becomes a compressive stress.
Has the property that when a voltage is applied, the polarization is turned sideways, that is, it becomes a tensile stress.

Further, as shown in FIG. 9, it can be seen that the polarization of the tensile stress is smaller than the polarization of the compression stress.

Further, the deformation amount of the piezoelectric film 70 is determined by the polarization (P) when the voltage (V) is applied from 0 V to a predetermined voltage.
The amount of change has a positive correlation. For example, in the hysteresis loop of the tensile stress in FIG.
Polarization (P) the amount of change upon application to ₃ is P ₃ -P _0.

By utilizing these characteristics, when the voltage for ink ejection is 0 V, a voltage is applied between the second electrode films 81 and 82 to apply a tensile stress to the piezoelectric film 70, thereby compressing the piezoelectric film 70. It should be kept to a small amount of polarization P ₀ than the amount of polarization P ₁ in the case of stress. Then, by applying a voltage V ₃ between the upper electrode film 80 and the lower electrode film 60 for ink ejection, a compressive stress is applied to the piezoelectric film 70, and the polarization amount P _{3 in} the case of a tensile stress is applied. By setting the polarization amount P ₄ to be larger, the polarization change amount becomes P ₄ −P ₀ . That is, the polarization change amount P ₃ − when no tensile stress is applied to the piezoelectric film 70.
This value is larger than P ₀ . Therefore, the displacement of the piezoelectric film 70 which is positively correlated with the polarization displacement also increases.

As described above, on the piezoelectric film 70 in the region corresponding to the piezoelectric vibrator 300, the upper electrode film 80 which is independent in the width direction and the second electrode films 81 and 82 are provided on both sides thereof. By applying a voltage between the electrode films 81 and 82,
By applying a voltage between the upper electrode film 80 and the lower electrode film 60 after applying a tensile stress to the piezoelectric film 70, the amount of deformation of the piezoelectric film 70 can be increased, and the displacement of the diaphragm can be increased. The amount can be increased, that is, the displacement efficiency can be improved.

The driving method is not limited to the above. For example, by applying a voltage to the second electrode films 81 and 82 to deform the piezoelectric film 70 in a direction opposite to the ejection direction, and then releasing the voltage, the piezoelectric film 70 is released.
Can be deformed in the ejection direction, thereby ejecting ink droplets. In this case, the ink droplet is relatively smaller than the ink droplet ejected by applying a voltage to the upper electrode film 80 and the lower electrode film 60. Accordingly, the case where a voltage is applied between the second electrode films 81 and 82 and the case where
The case where the ink is ejected only by applying a voltage between the first electrode film 60 and the lower electrode film 60, and the case where both the second electrode films 81 and 82 and the upper electrode film 80 and the lower electrode film 60 As described above, the ink droplets having different sizes can be ejected in the case where the voltage is applied in coordination. In this case, the size of the ink droplet can be changed by changing the size of the upper electrode film 80 and the second electrode films 81 and 82, or changing the driving waveform.

(Embodiment 2) FIG. 10 shows the shapes of a piezoelectric active portion and a pressure generating chamber of an ink jet recording head according to Embodiment 2 of the present invention.

In the present embodiment, as shown in FIG. 10, both side surfaces of the piezoelectric film 70 constituting a part of the piezoelectric active portion 320 are patterned so as to gradually narrow from bottom to top. The two side surfaces in the width direction of the piezoelectric film 70 are inclined surfaces 70a.
The second embodiment is the same as the first embodiment except that an upper electrode film 80 and second electrode films 81 and 82 are provided on the upper surface and both inclined surfaces of the piezoelectric film 70, respectively.

The method of manufacturing such a piezoelectric active portion 320 is not particularly limited. For example, the piezoelectric active portion 320 can be manufactured by the following method.

FIG. 11 is a view showing a thin film manufacturing process according to the second embodiment.

As shown in the first embodiment, the lower electrode film 60
After laminating the piezoelectric film 70 thereon (FIG. 4 (c)), the piezoelectric film 70 is then patterned as shown in FIG. The body film 70 is removed. At this time, the piezoelectric film 70 is patterned so that both side surfaces in the width direction become gradually narrower from bottom to top, thereby forming an inclined surface 70a.

Next, as shown in FIG. 11B, the upper electrode film 80 is uniformly laminated, and then, as shown in FIG. Room 1
The piezoelectric active portion 320 is formed in a region facing the second piezoelectric element 2. At this time, as in the first embodiment, the upper electrode film 80 is located on the upper surface of the piezoelectric film 70 in a region corresponding to the piezoelectric active portion 320, and the upper electrode film 80 is located on the portion corresponding to the inclined surface 70a on both sides in the width direction. The upper electrode film 80 is patterned so that the second electrode films 81 and 82 are located.

Thereafter, similarly to the first embodiment, an insulating layer, a lead electrode and the like are sequentially formed to form the ink jet recording head of the present embodiment.

In such a configuration, similarly to the first embodiment, the amount of deformation of the piezoelectric film 70 is increased, and the displacement efficiency of the diaphragm can be improved. Further, in the present embodiment, the piezoelectric film 7 provided with the second electrode films 81 and 82 is provided.
Since the zero inclined surface 70a is inclined in a direction in which the second electrode films 81 and 82 are opposed to each other, a voltage can be reliably applied between the two and the piezoelectric film 70 can reliably apply a tensile stress. Can be given.

In this embodiment, both side surfaces of the piezoelectric film 70 are inclined surfaces 70a, and the second electrode films 81 and 82 are provided on the inclined surfaces 70a. May be provided perpendicular to the surface of the lower electrode film 60, and the second electrode films may be respectively provided on both perpendicular surfaces.

In the present embodiment, the entire side surfaces of the piezoelectric film 70 are formed as the inclined surfaces 70a. However, the present invention is not limited to this.
For example, an inclined surface may be provided in a part of the thickness direction.

Further, the upper electrode film 80 and the second electrode film 8
Although the patterns 1 and 82 are patterned from the same film, they may be formed from films separately laminated.

(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 addition to the sealing plate 20, the common ink chamber forming plate 30 may be made of glass ceramic, and the thin film 41 may be made of glass ceramic as a separate member. Changes are free.

Further, in the above embodiment, the nozzle opening is formed on the end face of the flow path forming substrate 10, but a nozzle opening projecting in a direction perpendicular to the surface may be formed.

FIG. 12 is an exploded perspective view of the embodiment configured as described above, and FIG. 13 is a cross-sectional view of the flow path. In this embodiment, the nozzle openings 11 are drilled in the nozzle substrate 120 opposite to the piezoelectric vibrator, and these nozzle openings 11
A nozzle communication port 22 for communicating the pressure generating chamber 12 with the pressure generating chamber 12 is provided so as to penetrate the sealing plate 20, the common ink chamber forming plate 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 above-described embodiment except that the ink chamber side plate 40A and the ink chamber side plate 40A are separate members, and the opening is formed in the ink chamber side plate 40. Is omitted.

In this embodiment, as in the above-described embodiment, the upper electrode film and the second electrode film are provided on the piezoelectric film, and the diaphragm is deformed by the above-described driving method. The displacement efficiency of the diaphragm can be improved.

Of course, it is needless to say that the above-described embodiments can be more effective when implemented in combination as appropriate.

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 body may be formed by laminating substrates to form a pressure generating chamber, or by forming a piezoelectric film by attaching a green sheet or by screen printing, or by attaching a bulk ceramic. The present invention can be applied to ink jet recording heads having various structures, such as those that form a film.

Further, the example in which the insulator layer is provided between the piezoelectric vibrator and the lead electrode has been described. However, the present invention is not limited to this. The conductive film may be thermally welded, and the anisotropic conductive film may be connected to the 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 the gist of the present invention is not contradicted.

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. 14, recording head units 1A and 1B having an ink jet recording head are
Cartridges 2A and 2B constituting ink supply means are provided detachably, 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 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, the apparatus main 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 wound around the platen 8. It is designed to be transported.

[0107]

As described above, according to the present invention, the second electrode films are juxtaposed on both sides of the upper electrode film on the piezoelectric film in the region corresponding to the piezoelectric vibrator. By applying a voltage between the films, a tensile stress is applied to the piezoelectric film, and the piezoelectric film is deformed in a direction opposite to the deformation for discharging ink. Thereafter, by applying a voltage between the upper electrode film and the lower electrode film to deform the piezoelectric film and ejecting ink, the amount of deformation of the piezoelectric film can be increased. Therefore, the amount of displacement of the elastic film due to the deformation of the piezoelectric film also increases, and the displacement efficiency can be improved.

[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 view showing a modification of the sealing plate of FIG. 1;

FIG. 4 is a diagram showing a thin film manufacturing process according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating a thin film manufacturing process according to the first embodiment of the present invention.

FIG. 6 is a view showing 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 illustrating Embodiment 1 of the present invention.

FIG. 8 is a graph showing an example of a voltage applied to a piezoelectric vibrator.

FIG. 9 is a graph showing an example of a PV hysteresis loop of the piezoelectric layer.

FIG. 10 is a sectional view illustrating Embodiment 2 of the present invention.

FIG. 11 is a diagram showing a thin film manufacturing process according to a second embodiment of the present invention.

FIG. 12 is an exploded perspective view of an ink jet recording head according to another embodiment of the present invention.

FIG. 13 is a cross-sectional view illustrating an ink jet recording head according to another embodiment of the present invention.

FIG. 14 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 11 nozzle opening 12 pressure generating chamber 50 elastic film 60 lower electrode film 70 piezoelectric film 70a inclined surface 80 upper electrode film 81, 82 second electrode film 83 groove 90 insulating layer 90a, 90b, 90c, 90d Contact hole 100, 100A, 100B, 100C Lead electrode 300 Piezoelectric vibrator 320 Piezoelectric active part

Claims (13)

[Claims] An elastic film forming a part of a pressure generating chamber communicating with a nozzle opening; a lower electrode provided on the elastic film; a piezoelectric layer formed on the lower electrode; In an ink jet type recording head including a piezoelectric vibrator having an upper electrode formed on the surface of a body layer, one of the lower electrode and the upper electrode constituting the piezoelectric vibrator faces the pressure generating chamber. An ink jet recording head, wherein a pair of second electrodes are provided on both sides of the patterned electrode in the width direction and on the surface of a piezoelectric layer constituting the piezoelectric vibrator. 2. The ink jet recording head according to claim 1, wherein a voltage can be applied to the pair of second electrodes separately from a voltage application to the lower electrode and the upper electrode. 3. The ink jet recording head according to claim 1, wherein the pair of second electrodes are provided on both end surfaces of the piezoelectric layer in the width direction. 4. The piezoelectric vibrator according to claim 1, wherein the piezoelectric layer constituting the piezoelectric vibrator is patterned in a region facing the pressure generating chamber, and has at least a part thereof in a thickness direction. An ink-jet recording head having an inclined surface patterned so that a width gradually decreases from bottom to top, and wherein the pair of second electrodes are provided on the inclined surface; . 5. The piezoelectric vibrator according to claim 1, wherein at least the piezoelectric layer constituting the piezoelectric vibrator extends from one end in the longitudinal direction of the piezoelectric vibrator to an outside of a region facing the pressure generating chamber. An ink jet recording head which is extended. 6. The ink jet recording head according to claim 5, wherein the upper electrode extends on the piezoelectric layer extending to a region outside the region facing the pressure generating chamber. 7. The ink jet recording head according to claim 1, wherein a contact portion for connecting a lead electrode and the upper electrode is provided on an upper surface of the piezoelectric vibrator. 8. An insulating layer according to claim 1, wherein an insulating layer is formed on an upper surface of said piezoelectric vibrator, and a contact portion for connecting a lead electrode and said upper electrode is formed on said insulating layer. An ink jet recording head formed in the formed contact hole. 9. The piezoelectric vibrator according to claim 1, wherein the flow path forming substrate is formed of a silicon single crystal substrate, the pressure generating chamber is formed by anisotropic etching, and each layer of the piezoelectric vibrator is formed. And an ink jet recording head formed by a lithography method. 10. An ink jet recording apparatus comprising the ink jet recording head according to claim 1. 11. A piezoelectric device according to claim 1, wherein a voltage is applied to a pair of electrodes provided on upper and lower sides in a thickness direction of a piezoelectric layer provided on an elastic film constituting a part of the pressure generating chamber communicating with the nozzle opening. A method of driving an ink jet recording head that flexes and deforms a body layer to apply pressure to ink in the pressure generating chamber and ejects ink from the nozzle openings. Applying a voltage to the two electrodes, and thereafter, applying a voltage to the pair of electrodes to cause the piezoelectric layer to bend and deform to apply pressure to the ink in the pressure generating chamber. A method of driving an ink jet recording head. 12. The method according to claim 11, wherein the pair of second
Applying a voltage to the electrodes to apply a tensile stress to the piezoelectric layer in the width direction. 13. The method according to claim 11, wherein a voltage is applied to the pair of electrodes after the voltage application to the pair of second electrodes is released.