JP2014192417A - Piezoelectric/electrostrictive device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a piezoelectric/electrostrictive device capable of improving operation stability.SOLUTION: An actuator 100 includes: a piezoelectric/electrostrictive element 10 having a diaphragm 11; a junction layer 20 disposed on a surface of the diaphragm 11; and a plurality of supports 30 each of which is bitten into the junction layer. A joint length L between each support 30 and the junction layer 20 is within ±25% of an average value M of the joint lengths.

Description

  The present invention relates to a piezoelectric / electrostrictive device including a piezoelectric / electrostrictive element and a manufacturing method thereof.

  Conventionally, a piezoelectric / electrostrictive device including a piezoelectric / electrostrictive element, a flow path unit including a plurality of supports, and a bonding layer formed between the piezoelectric / electrostrictive element and the flow path unit is known. (For example, refer to Patent Document 1). Each support is bonded to the piezoelectric / electrostrictive element via a bonding layer.

JP 2008-230052 A

  However, in the piezoelectric / electrostrictive device of Patent Document 1, when the surface of the piezoelectric / electrostrictive element has waviness or warpage, the support strength of each support by the bonding layer varies, and the operation of the piezoelectric / electrostrictive device May become unstable.

  The present invention has been made in view of the above situation, and an object thereof is to provide a piezoelectric / electrostrictive device capable of improving operational stability.

  A piezoelectric / electrostrictive device according to the present invention includes a piezoelectric / electrostrictive element having a vibration plate, a bonding layer disposed on the surface of the vibration plate, and a plurality of supports that respectively bite into the bonding layer. The bonding layer is made of resin. In the cross section perpendicular to the surface of the diaphragm, the bonding length between each of the plurality of supports and the bonding layer is within ± 25% of the average value of the bonding lengths.

  According to the present invention, a piezoelectric / electrostrictive device capable of improving operational stability is provided.

Plan view showing the configuration of the actuator XX sectional view of FIG. Partial enlarged view of FIG. Diagram for explaining the manufacturing method of the actuator Diagram for explaining the manufacturing method of the actuator Diagram for explaining the manufacturing method of the actuator

  Hereinafter, an actuator for an ink jet head will be described as an example of a piezoelectric / electrostrictive device according to the present invention with reference to the drawings. However, the piezoelectric / electrostrictive device according to the present invention can be applied to various applications such as a gyro sensor, an oscillator, or an actuator for an injector.

  In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. The drawings are schematic, and the ratio of each dimension may be different from the actual one. Accordingly, specific dimensions and the like should be determined in consideration of the following description.

(Configuration of actuator 100)
The configuration of the actuator 100 will be described with reference to the drawings. FIG. 1 is a plan view showing the configuration of the actuator 100. FIG. 2 is a sectional view taken along line XX in FIG. In the following description, as shown in FIG. 1, the direction in which the support 30 extends is referred to as “length direction”, and the direction orthogonal to the length direction is referred to as “width direction”. Further, as shown in FIG. 2, a direction orthogonal to the length direction and the width direction is referred to as a “thickness direction”.

  The actuator 100 includes a piezoelectric / electrostrictive element 10, a bonding layer 20, and a plurality of supports 30.

1. Piezoelectric / electrostrictive element 10
The piezoelectric / electrostrictive element 10 includes a vibration plate 11, a plurality of piezoelectric bodies 12, and a plurality of upper electrodes 13.

  The diaphragm 11 vibrates (displaces) in the thickness direction according to the expansion and contraction of each piezoelectric body 12. The diaphragm 11 also functions as a lower electrode. As shown in FIG. 2, the diaphragm 11 may have swell and warp. The swell and warp of the diaphragm 11 are caused by the swell and warp of a large piezoelectric body 12a (see FIG. 4A) described later.

  The diaphragm 11 has a first main surface 11S and a second main surface 11T. A plurality of piezoelectric bodies 12 are arranged on the first main surface 11S. The bonding layer 20 is disposed on the second main surface 11T.

  In the present embodiment, the diaphragm 11 includes a main body film 11a and a barrier film 11b.

  The main body film 11a is a thin film formed by plating, vapor deposition, or sputtering. The main body film 11a can be made of a metal such as nickel, platinum, palladium, rhodium, gold, silver, tungsten, or an alloy containing these as a main component. In particular, nickel, which has a stress relieving action and is difficult to recrystallize by heating, is suitable. The film thickness of the main body film 11a can be 0.1 μm to 50 μm.

  The barrier film 11b is a thin film formed by plating, vapor deposition, or sputtering. The barrier film 11b is made of a metal material having resistance to the etching solution for the piezoelectric body 12. The film thickness of the barrier film 11b can be 1 μm to 1 μm.

  The piezoelectric body 12 is disposed on the first main surface 11S of the diaphragm 11. The piezoelectric body 12 is a thin plate-like fired body. When a voltage is applied to the diaphragm 11 and the upper electrode 13, the piezoelectric body 12 expands and contracts in a direction perpendicular to the thickness direction. Due to the expansion and contraction of the piezoelectric body 12, the vibration plate 11 vibrates in the thickness direction. The size of the piezoelectric body 12 can be, for example, a length of 10 μm to 50 mm, a width of 10 μm to 50 mm, and a thickness of 0.1 μm to 1 mm. In particular, in this embodiment, a case where the thickness of the piezoelectric body 12 is 10 μm or less is assumed.

  The piezoelectric body 12 can be constituted by a conventionally used ceramic material for a piezoelectric body. Examples of such ceramic materials include lead zirconate, lead titanate, lead magnesium niobate, lead nickel niobate, lead zinc niobate, lead manganate niobate, lead antimony stannate, lead manganese tungstate, cobalt niobate Lead, barium titanate, sodium bismuth titanate, potassium sodium niobate, strontium bismuth tantalate, and mixtures thereof. Ceramic materials include lanthanum, calcium, strontium, molybdenum, tungsten, barium, niobium, zinc, nickel, manganese, cerium, cadmium, chromium, cobalt, antimony, iron, yttrium, tantalum, lithium, bismuth, tin, etc. An oxide may be added.

  The upper electrode 13 is disposed on the piezoelectric body 12. The upper electrode 13 is a thin plate formed by firing a conductive material. The upper electrode 13 may be a thin film formed by a plating method or a vapor deposition method. The upper electrode 13 can be made of an acid-resistant conductive material. Examples of such conductive materials include noble metals such as gold, silver, platinum, and copper, and alloys thereof.

2. Bonding layer 20
The bonding layer 20 is disposed on the second main surface 11T of the diaphragm 11. The upper end portion of each support body 30 bites into the bonding layer 20. The bonding layer 20 fixes the support 30 to the piezoelectric / electrostrictive element 10.

  The bonding layer 20 is made of an organic resin such as a thermosetting resin or a light (ultraviolet) curable resin. Examples of such an organic resin include an epoxy resin and a polyimide resin. The bonding layer 20 is formed in two steps as will be described later.

3. Support 30
The support 30 is formed in a rod shape. As shown in FIG. 2, the support 30 has a trapezoidal cross section, but may be a square or a rectangle. The upper end portion of the support body 30 bites into the bonding layer 20, and the lower end portion of the support body 30 is fixed to a base plate (not shown). A pressure chamber 31 is formed between the two supports 30. The pressure chamber 31 stores ink injected from the ink introduction port. The ink stored in the pressure chamber 31 is ejected from the ejection nozzle according to the vibration of the diaphragm 11.

  The size of one support 30 can be, for example, 10 μm to 50 mm in length, 1 μm to 49 mm in width, and 1 μm to 10 mm in thickness. The sizes of the supports 30 are the same as each other.

(Bonding of bonding layer 20 and support 30)
Next, the joining of the joining layer 20 and the support 30 will be described with reference to the drawings. FIG. 3 is a partially enlarged view of FIG.

  The support 30 has an upper surface 30S, a first side surface 30T, and a second side surface 30U. The upper surface 30S faces the second main surface 11T of the diaphragm 11. The upper surface 30S is entirely embedded in the bonding layer 20. The first side surface 30T and the second side surface 30U are continuous with the upper surface 30S. Upper end portions of the first side surface 30T and the second side surface 30U are embedded in the bonding layer 20.

  Thus, the support 30 is bonded to the bonding layer 20 on the upper surface 30S, the first side surface 30T, and the second side surface 30U. The total length L of the region where the support 30 is bonded to the bonding layer 20 (hereinafter referred to as “bonding length L”) is the length L1 at which the upper surface 30S is bonded to the bonding layer 20 and the first side surface 30T is bonded. This is the total value of the length L2 that joins the layer 20 and the length L3 that the second side face 30U joins the joining layer 20. The joining length L is equal to the interface length between the joining layer 20 and the support 30 in a cross section perpendicular to the length direction.

Here, the bonding length L is preferably within ± 25% of the average value S _L from the average value S _L of the bonding lengths. In other words, the difference between the average value S _L and the junction length L is preferably within ± 25% of mean values S _L. Mean value S _L of the plurality of supports 30 each junction length L can be 3μm or 30μm or less. In this case, the standard deviation of the joining length L of each of the plurality of supports 30 is preferably 1.01 μm or less.

Further, the bonding area M is the product of the length of the junction between the length L support 30 is preferably an average value S _M of the joint area M is within ± 22% of the average value S _M. That is, the difference between the bonding area M and the average value S _M is preferably within ± 25% of the average value S _M. Mean value _{S M} of the bonding area M of the plurality of supports 30 each may be a 0.005 mm ² or more 0.045 mm ² or less. In this case, the standard deviation of the bonding area M of each of the plurality of supports 30 is preferably 0.002 mm ² or less.

  As described above, by limiting the variation in the bonding length L and the bonding area M to a predetermined range, the support strength of each support 30 by the bonding layer 20 is made uniform.

(Manufacturing method of actuator 100)
Next, a method for manufacturing the actuator 100 will be described with reference to the drawings.

  First, a green sheet is prepared by molding a slurry containing a ceramic material for a piezoelectric body. The thickness of the green sheet can be 1 μm to 80 μm.

  Next, as shown in FIG. 4A, the large size piezoelectric body 12a is manufactured by firing the green sheet under a predetermined condition (1200 ° C., 2 hours). In the present embodiment, since it is assumed that the piezoelectric body 12a is extremely thin with a thickness of 10 μm or less, the large piezoelectric body 12a may be swelled or warped.

  Next, as shown in FIG. 4B, an organic metal compound is applied on the surface of the piezoelectric body 12a and fired, or a metal is sputtered on the surface of the piezoelectric body 12a. The upper electrode 13a is produced.

  Next, as shown in FIG. 4C, the barrier film 11b and the main body film 11a are sequentially formed on the back surface of the piezoelectric body 12a by using a plating method, a vapor deposition method, or a sputtering method, so that the diaphragm 11 is formed. Thus, the piezoelectric / electrostrictive element 10 is manufactured.

  Next, as shown to Fig.5 (a), the 1st soft resin layer 20a is formed by apply | coating or printing on the 2nd main surface 11T of the diaphragm 11 with organic resin. The hardness of the first soft resin layer 20a can be set to 10 GPa to 100 GPa, for example.

  Next, as shown in FIG. 5B, the first hard resin layer 20a ′ is formed by temporarily curing the first soft resin layer 20a at a predetermined temperature (a temperature lower than the curing temperature of the organic resin). . The hardness of the first hard resin layer 20a 'can be set to 100 GPa to 500 GPa, for example.

  Next, as illustrated in FIG. 5C, the second soft resin layer 20 b is formed by applying or printing an organic resin on the first hard resin layer 20 a ′. The second soft resin layer 20b can be made of the same or different organic resin as the first soft resin layer 20a. The hardness of the second soft resin layer 20b can be set to 10 GPa to 100 GPa, for example.

  Next, the plurality of supports 30 are set on the jig, and as shown in FIG. 6A, the plurality of supports 30 until the upper surfaces 30S of the plurality of supports 30 come into contact with the first hard resin layer 20a ′. Is inserted into the second soft resin layer 20b. At this time, the support 30 may be pressed against the first hard resin layer 20a 'so that substantially the entire upper surface 30S of the support 30 is in contact with the first hard resin layer 20a'.

  Next, as shown in FIG. 6B, the first hard resin layer 20a ′ and the second soft resin layer 20b are subjected to main curing at a predetermined temperature (a temperature equal to or higher than the curing temperature of each organic resin) to thereby form a bonding layer. 20 is formed. By this main curing, the first hard resin layer 20a 'and the second soft resin layer 20b are integrated.

  Next, after a photoresist film having a predetermined pattern is formed on the upper electrode 13a, the upper electrode 13a is patterned by etching the upper electrode 13a with an etchant as shown in FIG. 6C.

  Next, after covering the upper electrode 13a with a photoresist film having a predetermined pattern, the piezoelectric body 12a is patterned by etching as shown in FIG. 6D. Thus, the actuator 100 is completed.

(Function and effect)
(1) The actuator 100 according to the embodiment includes a piezoelectric / electrostrictive element 10 having a vibration plate 11, a bonding layer 20 disposed on the surface of the vibration plate 11, and a plurality of supports respectively inserted in the bonding layer. 30. The difference between the joining length L and the mean value S _L of joining lengths is within ± 25% of the mean value S _L.

  Therefore, since the support strength of each support 30 by the bonding layer 20 can be made uniform, the operational stability of the actuator 100 can be improved.

  (2) The manufacturing method of the actuator 100 according to the embodiment includes the step of inserting the support 30 into the second soft resin layer 20b until it contacts the first hard resin layer 20a ′, the first hard resin layer 20a ′ and the first hard resin layer 20a ′. And a step of fully curing the two soft resin layers 20b.

  Therefore, the distance between the support bodies 30 with respect to the diaphragm 11 is made uniform via the first hard resin layer 20a ', so that the support strength of the support bodies 30 by the bonding layer 20 can be made uniform. As a result, the operation stability of the actuator 100 can be improved.

(Other embodiments)
The present invention is not limited to the embodiment described above, and various modifications or changes can be made without departing from the scope of the present invention.

(A) In the above embodiment, the piezoelectric / electrostrictive element 10 includes the diaphragm 11 that also functions as the lower electrode, but the present invention is not limited to this. The piezoelectric / electrostrictive element 10 may include a lower electrode formed between the diaphragm 11 and the piezoelectric body 12 separately from the diaphragm 11. In this case, since the diaphragm 11 does not need to have conductivity, Si, SiO ₂ , SiN, a ceramic material (such as zirconia or alumina), glass, or the like can be used as a constituent material of the diaphragm 11. .

  (B) Although the case where the actuator 100 includes a plurality of support bodies 30 has been described in the above embodiment, the actuator 100 only needs to include at least two support bodies 30. Even in this case, according to the manufacturing method described above, the distance between each of the two supports 30 and the diaphragm 11 can be made uniform with high accuracy.

  (C) In the above embodiment, in the manufacturing process of the actuator 100, the support 30 is inserted into the second soft resin layer 20b until it contacts the first hard resin layer 20a ′. The second soft resin layer 20b may be formed after contacting the first hard resin layer 20a ′. Even in this case, the distance between the support bodies 30 with respect to the diaphragm 11 can be made uniform via the first hard resin layer 20a '.

  Examples according to the present invention will be described below. However, the present invention is not limited to the examples described below.

(Preparation of actuator according to example)
First, a green sheet was produced by molding a slurry containing zirconate titanate (PZT), Pb (Ni _1/3 Nb _2/3 ) O ₃ powder, an organic binder, a dispersant and a plasticizer.

  Next, the green sheet was fired at 1200 ° C. for 2 hours to produce a large piezoelectric body (length 1 mm, width 100 μm, thickness 5 μm).

  Next, a large-sized upper electrode was fabricated by sputtering gold on the surface of the piezoelectric body using a sputtering method.

  Next, using a plating method, a barrier film and a main body film were sequentially formed by plating nickel on the back surface of the piezoelectric body, thereby forming a diaphragm functioning as a lower electrode.

  Next, the first soft resin layer (thickness 2 μm) was formed by applying a polyimide resin on the diaphragm using a spin coater method. The hardness of the first soft resin layer was 30 GPa.

  Next, the first hard resin layer was formed by heating the first soft resin layer at 150 ° C. The hardness of the first hard resin layer was 200 GPa.

  Next, a second soft resin layer (thickness 2 μm) was formed by applying a polyimide resin on the first hard resin layer using a spin coater method. The hardness of the second soft resin layer was 30 GPa.

  Next, 400 supports were set on the jig and inserted into the second soft resin layer until the upper surface of the support was in contact with the first hard resin layer.

  Next, the 1st hard resin layer and the 2nd soft resin layer were heated at 280 degreeC, and were hardened, and the joining layer was formed. Thereafter, the upper electrode and the piezoelectric body were sequentially patterned using a photoresist.

(Production of actuator according to comparative example)
First, a diaphragm was formed in the same manner as in the example.

  Next, a single soft resin layer (thickness 4 μm) was formed by applying a polyimide resin on the diaphragm using a spin coater method.

  Next, 400 supports were set on the jig, and the supports were inserted into a single soft resin layer. At this time, the upper surface of the support was adjusted so as not to contact the diaphragm as much as possible.

  Next, the bonding layer was formed by heating the soft resin layer at 280 ° C. to perform main curing. Thereafter, the upper electrode and the piezoelectric body were sequentially patterned using a photoresist.

(Measurement of joining length and joining area)
The actuators according to Examples and Comparative Examples were cut in the thickness direction, and the cross sections thereof were observed with an electron microscope, thereby measuring the joining lengths of 13 supports and joining layers. Table 1 summarizes the measurement results of the joint length, the average value, the maximum and minimum values, the standard deviation, and the maximum variation ratio from the average value. Note that the maximum variation ratio from the average value is the ratio of the difference between the maximum value and the average value or the larger value between the minimum value and the average value to the average value.
Further, the joining area was calculated by multiplying the joining length by the length of the support. Table 1 summarizes the calculation results, average value, maximum / minimum value, standard deviation, and maximum variation ratio from the average value of the bonding area.

  As shown in Table 1, in the actuator according to the comparative example, the maximum variation ratio from the average value of the joining length was a large value of 81.5%. This is because the vibration plate is distorted in accordance with the undulation or warping of the piezoelectric body, and the intervals between the support members with respect to the vibration plate are irregular. As a result, the bonding strengths of the supports varied widely, and the operation of the actuator according to the comparative example was unstable.

  In the actuator according to the comparative example, the standard deviation of the joint length was a large value of 3.91, and the standard deviation of the joint area was a large value of 0.006.

  On the other hand, in the actuator according to the example, the maximum variation ratio from the average value of the joining length was a small value of 24.6%. This is because the first hard resin layer and the second soft resin layer are fully cured after the upper surface of the support is brought into contact with the first hard resin layer, so that the distance between the supports relative to the vibration plate is independent of the distortion of the vibration plate. This is due to the fact that it was made constant. As a result, it was confirmed that the bonding strength of each support was uniform, and the operation of the actuator according to the example was stable. Therefore, it was found that the operation of the actuator can be stabilized by limiting the joining length to within ± 25% from the average joining length.

  In the actuator according to the example, the standard deviation of the joining length was a small value of 1.01, and the standard deviation of the joining area was a small value of 0.002.

10 Piezoelectric / electrostrictive element 11 Diaphragm (lower electrode)
11S 1st main surface 11T 2nd main surface 11a Main body film 11b Barrier film 12 Piezoelectric body 13 Upper electrode 20 Bonding layer 20a 1st soft resin layer 20a '1st hard resin layer 20b 2nd soft resin layer 30 Support body 30S Upper surface 30T First side 30U Second side

Claims (5)

A piezoelectric / electrostrictive element having a diaphragm;
A bonding layer disposed on the surface of the diaphragm and made of resin;
A plurality of supports each biting into the bonding layer;
With
In a cross section perpendicular to the surface, the bonding length between each of the plurality of supports and the bonding layer is within ± 25% of the average value of the bonding lengths.
Piezoelectric / electrostrictive device. Each of the plurality of supports has an upper surface facing the diaphragm, and a pair of side surfaces connected to the upper surface.
The bonding layer is bonded to the upper surface and the side surface,
The piezoelectric / electrostrictive device according to claim 1. The piezoelectric / electrostrictive element has a plurality of piezoelectric bodies disposed on the first main surface of the diaphragm, and a plurality of upper electrodes disposed on the plurality of piezoelectric bodies,
The bonding layer is disposed on the second main surface of the diaphragm.
The piezoelectric / electrostrictive device according to claim 1 or 2. Forming a first resin layer on the surface of the diaphragm of the piezoelectric / electrostrictive element;
Pre-curing the first resin layer;
Forming a second resin layer on the first resin layer;
Inserting a plurality of supports into the second resin layer until contacting the first resin layer;
Curing the first resin layer and the second resin layer;
A method for manufacturing a piezoelectric / electrostrictive device comprising: Forming a first resin layer on the surface of the diaphragm of the piezoelectric / electrostrictive element;
Pre-curing the first resin layer;
Contacting a plurality of supports with the first resin layer;
Forming a second resin layer on the first resin layer;
Curing the first resin layer and the second resin layer;
A method for manufacturing a piezoelectric / electrostrictive device comprising:

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