# Patent

## Title
Actuator and method for driving the same

## Abstract

Provided is a novel actuator and a method for driving the same. The present invention is an actuator comprising a first laminate comprising a first (Bi, Na, Ba) TiO3 layer between first and second electrode layers, a second laminate comprising a second (Bi, Na, Ba) TiO3 layer between third and fourth electrode layers, and a tilt part provided between the first and second laminates. Both of the first and second (Bi, Na, Ba) TiO3 layers are preferentially oriented in a [011] crystalline axis direction. Voltages V5a, V9a, V5b, and V9b which satisfy Requirement A: V5a>V9a and V5b<V9b or Requirement B: V5a<V9a and V5b>V9b are applied to the first-fourth electrode layers so as to tilt the tilt part. One of the first edge and the second edge is moved in the [011] crystalline axis direction and the other is moved in the reverse direction thereof.

## Background
This is a continuation of International Application No. PCT/JP2013/000075, with an international filing date of Jan. 11, 2013, which claims priority of Japanese Patent Application No. 2012-004997, filed on Jan. 13, 2012, the contents of which are hereby incorporated by reference.


BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an actuator and a method for driving the same.
2. Description of the Related Art
FIG. 13 shows an actuator disclosed in Japanese Patent Laid-Open Publication No. 2009-169290.
This actuator 100 comprises a support layer 104, a first electrode layer 105, a first piezoelectric layer 106R, a second piezoelectric layer 106L, a second electrode layer 107R, and a third electrode layer 107L.
Two piezoelectric actuators 108R and 108L are formed in this actuator 100. The first piezoelectric actuator 108R is constituted with the right half 104R of the support layer 104, the right half 105R of the first electrode layer 105, the first piezoelectric layer 106R, and the second electrode layer 107R. The second piezoelectric actuator 108L is constituted with the left half 104L of the support layer 104, the left half 105L of the first electrode layer 105, the second piezoelectric layer 106L, and the third electrode layer 107L.
A torsion bar 102 is fixed to the bottom face of the support layer 104. The torsion bar 102 is interposed between the first piezoelectric actuator 108R and the second piezoelectric actuator 108L when viewed in the cross-sectional view of FIG. 13. The torsion bar 102 has a longitudinal direction perpendicular to both the lamination direction of these layers 104-107 (namely, the vertical direction in FIG. 13) and the longitudinal direction of the support layer 104 (namely, the horizontal direction in FIG. 13). A mirror 101 is provided at one end of the torsion bar 102.
A voltage of 0 volts, a negative voltage, and a positive voltage are applied to the first electrode layer 105, the second electrode layer 107R, and the third electrode layer 107L, respectively. As shown in FIG. 13, this voltage application allows the actuator 100 to be twisted so as to tilt the mirror 101.
SUMMARY OF THE INVENTION
A purpose of the present invention is to provide a novel actuator and a method for driving the same.
The present invention is a method for driving an actuator 1, the method comprising steps of:
a step (a) of preparing the actuator 1 comprising:

    
    
        a first laminate 11a; 
        a second laminate 11b; 
        a first support 13a; 
        a second support 13b; and
        a tilt part 25, wherein
    
    


the first laminate 11a comprises a first electrode layer 5a, a first (Bi, Na, Ba) TiO3 layer 7a, and a second electrode layer 9a; 
the first electrode layer 5a, the first (Bi, Na, Ba) TiO3 layer 7a, and the second electrode layer 9a are laminated in such a manner that the first (Bi, Na, Ba) TiO3 layer 7a is interposed between the first electrode layer 5a and the second electrode layer 9a; 
the first (Bi, Na, Ba) TiO3 layer 7a is preferentially oriented in a [011] crystalline axis direction;
+Z direction is parallel to the [011] crystalline axis direction;
−Z direction is the reverse direction of the +Z direction;
+X direction is parallel to the longitudinal direction of the first laminate 11a; 
−X direction is the reverse direction of the +X direction;
+Y direction is perpendicular to both of the +X direction and the +Z direction in a right-handed coordinate system;
−Y direction is the reverse direction of the +Y direction;
the laminate direction of the first laminate 11a is parallel to the +Z direction;
the second laminate 11b comprises a third electrode layer 5b, a second (Bi, Na, Ba) TiO3 layer 7b, and a fourth electrode layer 9b; 
the second (Bi, Na, Ba) TiO3 layer 7b is preferentially oriented in the [011] crystalline axis direction;
the second (Bi, Na, Ba) TiO3 layer 7b is interposed between the third electrode layer 5b and the fourth electrode layer 9b along the +Z direction;
the tilt part 25 is interposed between the first laminate 11a and the second laminate 11b along the +X direction;
the tilt part 25 comprises a first edge 25a and a second edge 25b; the first edge 25a and the second edge 25b are located in the +Y side and the −Y side, respectively, in the XY plane;
one end of the first laminate 11a is fixed to the first support 13a; 
one end of the second laminate 11b is fixed to the second support 13b; and
in the XY plane, an angular degree Q formed between the +X direction and a [100] direction is more than 0 degrees and less than 90 degrees; and
a step (b) of applying the voltages V5a, V9a, V5b, and V9b which satisfy the following requirement A or B to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25 in such a manner that one of the first edge 25a and the second edge 25b is moved in the +Z direction and the other is moved in the −Z direction;
Requirement A: V5a>V9a and V5b<V9b 
Requirement B: V5a<V9a and V5b>V9b. 
In one embodiment, in the step (b), the requirement A is satisfied; and
the first edge 25a is moved in the −Z direction and the second edge 25b is moved in the +Z direction.
In one embodiment, in the step (b), the requirement B is satisfied; and
the first edge 25a is moved in the +Z direction and the second edge 25b is moved in the −Z direction.
In one embodiment, the angular degree Q is not less than 15 degrees and not more than 75 degrees.
In one embodiment, the angular degree Q is not less than 30 degrees and not more than 60 degrees.
In one embodiment, the first electrode 5a is formed integrally with the third electrode layer 5b. 
In one embodiment, the first (Bi, Na, Ba) TiO3 layer 7a is formed integrally with the second (Bi, Na, Ba) TiO3 layer 7b. 
In one embodiment, the first (Bi, Na, Ba) TiO3 layer 7a is formed of (Bi0.5Na)0.5TiO3—BaTiO3; and
the second (Bi, Na, Ba) TiO3 layer 7b is formed of (Bi0.5Na)0.5TiO3—BaTiO3.
In one embodiment, the first (Bi, Na, Ba) TiO3 layer 7a is formed of a laminate of a (1−x)(Bi0.5,Na0.5)TiO3)−x(BaTiO3) layer (0.01≦x≦0.15) and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer (0.20≦y≦0.50); and
the second (Bi, Na, Ba) TiO3 layer 7b is formed of a laminate of a (1−x)(Bi0.5,Na0.5)TiO3)−x(BaTiO3) layer (0.01≦x≦0.15) and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer (0.20≦y≦0.50)
The present invention includes the above-mentioned actuator.
The present invention provides a novel actuator and a method for driving the same.



BRIEF DESCRIPTION OF DRAWINGS
FIG. 1A shows a perspective view of an actuator 1 according to an embodiment.
FIG. 1B shows a variation of FIG. 1A.
FIG. 2 shows a cross-sectional view taken along A-A′ line included in FIG. 1.
FIG. 3 shows axes of coordinates in the embodiment.
FIG. 4 shows a method for driving the actuator 1 according to the embodiment.
FIG. 5 shows a perspective view of the actuator 1 according to the embodiment.
FIG. 6A shows a cross-sectional view taken along C1-C1′ line included in FIG. 5 while the actuator 1 is driven.
FIG. 6B shows a cross-sectional view taken along C2-C2′ line included in FIG. 5 while the actuator 1 is driven.
FIG. 6C shows a cross-sectional view taken along C3-C3′ line included in FIG. 5 while the actuator 1 is driven.
FIG. 7 shows a perspective view of another actuator 1 according to the embodiment.
FIG. 8 shows axes of coordinates in the examples 1-8 and the comparative examples 1-2.
FIG. 9A shows one step included in the method for fabricating the actuator according to the example 1.
FIG. 9B shows one step included in the method for fabricating the actuator according to the example 1, subsequently to FIG. 9A.
FIG. 9C shows one step included in the method for fabricating the actuator according to the example 1, subsequently to FIG. 9B.
FIG. 9D shows one step included in the method for fabricating the actuator according to the example 1, subsequently to FIG. 9C.
FIG. 9E shows one step included in the method for fabricating the actuator according to the example 1, subsequently to FIG. 9D.
FIG. 10 shows an X-ray diffraction profile of the piezoelectric film according to the example 1.
FIG. 11 shows a cross-sectional view taken along B-B′ line included in FIG. 7.
FIG. 12 shows axes of coordinates in the comparative example 3.
FIG. 13 shows a cross-sectional view of the actuator 100 disclosed in Japanese Patent Laid-Open Publication No. 2009-169290.



DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
An embodiment of the present invention is described below with reference to the drawings.
Embodiment 1
Step (a)
FIG. 1A shows an actuator 1 according to the embodiment. This actuator 1 comprises a first laminate 11a, a second laminate 11b, a first support 13a, a second support 13b and a tilt part 25.
FIG. 2 shows a cross-sectional view taken along A-A′ line included in FIG. 1A. The first laminate 11a comprises a first electrode layer 5a, a first (Bi, Na, Ba) TiO3 layer 7a, and a second electrode layer 9a in this order. The first electrode layer 5a is formed on a substrate 3. The first (Bi, Na, Ba) TiO3 layer 7a and the second electrode layer 9a are stacked in this order on the first electrode layer 5a. 
Similarly to this first laminate 11a, the second laminate 11b comprises a third electrode layer 5b, a second (Bi, Na, Ba) TiO3 layer 7b, and a fourth electrode layer 9b in this order.
It is desirable that the first laminate 11a and the second laminate 11b are rectangular. As shown in FIG. 1A, the longitudinal direction of the first laminate 11a is parallel to the +X direction, as described later.
The first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b are preferentially oriented in the [011] crystalline axis direction. Desirably, the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b are oriented only in the [011] crystalline axis direction. Hereinafter, “the [011] crystalline axis direction” is referred to as “the [011] direction”. When the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b are oriented in a direction other than the [011] direction, the actuator 1 fails to work. See the comparative example 3, which is described later.
(Bi, Na, Ba) TiO3 is a material known as a piezoelectric material. The (Bi, Na, Ba) TiO3 is referred to as “NBT-BT” or “BNT-BT”. A typical example of the (Bi, Na, Ba) TiO3 is (Bi0.5, Na0.5)TiO3—BaTiO3. In more detail, this is (1−x)(Bi0.5, Na0.5) TiO3−x(BaTiO3). x represents a value of not less than 0.01 and not more than 0.15.
The (Bi, Na, Ba) TiO3 may contain other metallic oxide. An example of other metallic oxide is BiFeO3. The (Bi, Na, Ba) TiO3 may contain impurities to improve the piezoelectric property. An example of the impurity is silver, niobium, tantalum or manganese.
The first (Bi, Na, Ba) TiO3 layer 7a may be formed of two or more (Bi, Na, Ba) TiO3 layers. These two or more (Bi, Na, Ba) TiO3 layers may have a different compositions. For example, the first (Bi, Na, Ba) TiO3 layer 7a may be formed of a laminate of a (1−x)(Bi0.5,Na0.5)TiO3)−x(BaTiO3) layer (0.01≦x≦0.1) and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer (0.20≦y≦0.50). See the examples 6-8, which are described later. Similarly to the first (Bi, Na, Ba) TiO3 layer 7a, the second (Bi, Na, Ba) TiO3 layer 7b may be formed of two or more (Bi, Na, Ba) TiO3 layers.
It is desirable that the first electrode layer 5a and the second electrode layer 5b are preferentially oriented in the [011] direction. The first electrode layer 5a and the second electrode layer 5b may be formed of a metallic film or an oxide conductor film. Two or more films may be used. An example of the material of the metallic film is platinum, palladium, or gold. An example of the material of the oxide conductor film is nickel oxide, ruthenium oxide, iridium oxide, strontium ruthenate, or lanthanum nickelate.
The first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b may contain a small amount of impurities such as manganese or iron to improve the piezoelectric property. The first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b can be formed by sputtering.
As shown in FIG. 1A, it is desirable that the first electrode layer 5a is formed on the substrate 3 integrally with the third electrode layer 5b. Similarly, it is desirable that the first (Bi, Na, Ba) TiO3 layer 7a is formed integrally with the second (Bi, Na, Ba) TiO3 layer 7b. An example of the material of the substrate 3 may be magnesium oxide or strontium titanate. A magnesium oxide substrate is preferable, since it is easy for the first (Bi, Na, Ba) TiO3 layer 7a to be preferentially oriented in the +Z direction.
It is necessary that the second electrode layer 9a and the fourth electrode layer 9b are insulated electrically. This is because the voltage applied to the second electrode layer 9a is different from the voltage applied to the fourth electrode layer 9b, as described later. An example of the material of the second insulating layer 9a and the fourth electrode layer 9b is gold.
It is desirable that the length along the +X direction of the second electrode layer 9a is equal to the length along the +X direction of the fourth electrode layer 9b. In other words, it is desirable that the tilt part 25 is provided at the center of the actuator 1.
Unlike in FIG. 1A, the first laminate 11a and the second laminate 11b may be formed separately. Subsequently, as shown in FIG. 1B, one end of the first laminate 11a may be joined to the one end of the second laminate 11b with epoxy resin or solder.
Here, three directions used in the present specification are defined as below.
+X direction is the direction parallel to the longitudinal direction of the first laminate 11a. 
−X direction is the reverse direction of the +X direction.
+Z direction is the direction parallel to the laminate direction of the first laminate 11a and parallel to the [011] direction. In other words, the laminate direction of the first laminate 11a is the [011] direction.
−Z direction is the reverse direction of the +Z direction.
+Y direction is the direction perpendicular to both the +X direction and the +Z direction.
−Y direction is the reverse direction of the +Y direction.
As shown in FIG. 1A, the tilt part 25 is interposed between the first laminate 11a and the second laminate 11b along the +X direction. In other words, the first laminate 11a and the second laminate 11b are adjacent to each other along the +X direction in such a manner that the tilt part 25 is interposed therebetween.
The shape of the tilt part 25 is not limited. It is desirable that the tilt part 25 is plate-like. In FIG. 1A, the tilt part 25 has the same width as the first laminate 11a and the second laminate 11b. Here, the “width” means the length along the +Y direction. However, as shown in FIG. 7, it is desirable that the tilt part 25 is wider than the first laminate 11a. It is desirable that the tilt part 25 has a mirror 30 on the surface thereof. The mirror 30 reflects light.
The tilt part 25 comprises a first edge 25a and a second edge 25b. In the XY plane, the first edge 25a is located in the +Y side. In the XY plane, the second edge 25b is located in the −Y side.
One end of the first laminate 11a is fixed to the first support 13a. It is desirable that the first support 13a is plate-like. In more detail, one end at the +X side of the first laminate 11a is fixed to the side of the plate-like first support 13a with epoxy resin or solder. Similarly, one end of the second laminate 11b is fixed to the second support 13b. In more detail, one end at the −X side of the second laminate 11b is fixed to the side of the second support 13b. 
As shown in FIG. 3, an angular degree Q formed between the +X direction and the [100] direction is more than zero degrees and less than 90 degrees. It is preferable that the angular degree Q is not less than 15 degrees and not more than 75 degrees, as is clear from the examples 1-5, which are described later. It is more preferable that the angular degree Q is not less than 30 degrees and not more than 60 degrees, as is clear from the examples 1-3, which are described later.
When the angular degree Q is equal to zero degrees, that is, when the +X direction is parallel to the [100] direction, the actuator fails to drive. See the comparative example 1, which is described later. Similarly, when the angular degree Q is equal to 90 degrees, that is, when the +X direction is parallel to the [01-1] direction, the actuator fails to drive. See the comparative example 2, which is described later.
Step (b)
Then, a method for driving such an actuator 1 is described below.
As shown in FIG. 4, voltages V5a, V9a, V5b, and V9b which satisfy the following requirement A are applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively.
Requirement A: V5a>V9a and V5b<V9b 
As shown in FIG. 5, FIG. 6A, FIG. 6B, FIG. 6C, and FIG. 11, this voltage application allows the first edge 25a to be moved in the −Z direction and allows the second edge 25b to be moved in the +Z direction. In this way, the actuator 1 is twisted. In other words, the tilt part 25 is tilted. The tilt angle is defined as an angular degree P. See FIG. 11. A power supply (not shown) may be used for this voltage application.
FIG. 5, FIG. 6A, FIG. 6B, and FIG. 6C are described below in more detail. FIG. 6A, FIG. 6B, and FIG. 6C show the cross-sectional views taken along C1-C1′, C2-C2′, and C3-C3′ lines included in FIG. 5, respectively. FIG. 11 shows a cross-sectional view taken along B-B′ line included in FIG. 7.
As shown in FIG. 6A, when the voltages are applied, the ends at the +Y side of the first laminate 11a and the second laminate 11b move to the −Z direction. In this way, the first edge 25a moves to the −Z direction. On the other hand, as shown in FIG. 6C, when the voltages are applied, the ends at the −Y side of the first laminate 11a and the second laminate 11b move to the +Z direction. In this way, the second edge 25b moves to the +Z direction. See also FIG. 11.
Since it is desirable that the first electrode layer 5a and the third electrode layer 5b are formed integrally, it is desirable that the value of the voltage V5a is equal to the value of the voltage V5b. More desirably, both of the values of voltages V5a and V5b are 0 volts.
It is desirable that the value of (V5a-V9a) is not more than 30 volts. In other words, the value of the voltage V9a is less than 0 volts and not less than −30 volts. Similarly, it is desirable that the value of (V9b-V5b) is not more than 30 volts. In other words, it is desirable that the value of the voltage V9b is more than 0 volts and not more than 30 volts. Desirably, the value of the voltage V9a is equal to the value of the voltage V9b. Therefore, a desirable requirement A is V9b>V5a=V5b=0 volts>V9a. 
Instead of the requirement A, the voltages V5a, V9a, V5b, and V9b which satisfy the following requirement B are applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively.
Requirement B: V5a<V9a and V5b>V9b 
This voltage application allows the first edge 25a to be moved in the +Z direction and allows the second edge 25b to be moved in the −Z direction. In this way, the actuator 1 is twisted. In other words, the tilt part 25 is tilted. See also FIG. 11.
When the voltages application is stopped, the actuator 1 restores it original shape. In other words, the tilt angle P returns to zero degrees.
EXAMPLE
The following examples describe the present invention in more detail.
Example 1
In the example 1, the actuator 1 shown in FIG. 7 was fabricated. In the example 1, the angular degree Q was set at 45 degrees.
The first laminate 11a had an X-direction length of 8 millimeters and a Y-direction length of 2 millimeters. The substrate 3 was an MgO single crystalline substrate having a thickness of 50 micrometers. The tilt part 25 had an X-direction length of 2 millimeters and a Y-direction length of 4 millimeters.
The actuator 1 was fabricated in accordance with the procedure shown in FIGS. 9A-9E.
An MgO single crystalline substrate 3 was prepared. This MgO single crystalline substrate 3 had a normal direction of only a [001] direction, and had no other axis direction. The MgO single crystalline substrate 3 had a thickness of 0.5 millimeters.
The first electrode layer 5a and the third electrode layer 5b both of which are formed of platinum were formed integrally on the surface of this MgO single crystalline substrate 3 by an RF magnetron sputtering method. The first electrode layer 5a and the third electrode layer 5b had the [011] axial direction. In other words, the normal directions of the first electrode layer 5a and the third electrode layer 5b were the [011] direction. Each of the first electrode layer 5a and the third electrode layer 5b had a thickness of 250 nanometers.
The condition of the RF magnetron sputtering method is described below.
Target: Metal platinum
Atmosphere: Argon gas
RF power: 15 W
Substrate temperature: 300 Celsius degrees
Then, a (Bi, Na, Ba) TiO3 layer having a thickness of 2.7 micrometers was deposited on the surfaces of the first electrode layer 5a and the third electrode layer 5b by an RF magnetron sputtering method so as to form the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b integrally.
The condition of the RF magnetron sputtering method is described below.
Target: Above-mentioned composition
Atmosphere: Gaseous mixture of argon and oxygen (Ar/O2 flow ratio: 50/50)
RF power: 170 W
Substrate temperature: 650 Celsius degrees
The crystalline structures of the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b were analyzed by an X-ray diffraction method. FIG. 10 shows the result of the X-ray diffraction profile.
The intensity of the reflection peak was a very high value of 255,956 cps. The profile shown in FIG. 10 means that the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b according to the example 1 were oriented strongly in the crystalline axis direction, namely, in the +Z direction.
Then, a mask layer 71 was formed on the surfaces of the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b. The mask layer 71 was formed by an RF magnetron sputtering method. The mask layer 71 was formed of a chrome layer having a thickness of 0.3 micrometers.
The condition of the RF magnetron sputtering method is described below.
Target: Metal chrome
Atmosphere: Argon gas
RF power: 150 W
Substrate temperature: Room temperature
A resist was applied on the mask layer 71 to form a resist pattern 73 through exposure and development. See FIG. 9A.
The mask layer 71 was dry-etched using the resist pattern 73 as a mask.
The condition of the dry etching is described below.
Etching gas: Gaseous mixture of chlorine and oxygen (Cl2/O2 flow ratio: 40/20)
RF power: 600 W
Bias power: 100 W
The resist pattern 73 was removed by ashing treatment using oxygen plasma. Subsequently, a mask pattern 75 was formed as shown in FIG. 9B. As shown in FIG. 8, the angular degree Q was set at 45 degrees.
Using this mask pattern 75, an unnecessary parts of the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b were dry-etched.
The condition of the dry etching is described below.
Etching gas: Gaseous mixture of tetrafluoromethane and argon (CF4/Ar flow ratio: 30/70)
RF power: 1,000 W
Bias power: 100 W
Then, using the mask pattern 75 again, an unnecessary part of the first electrode layer 5a and the third electrode layer 5b were dry-etched.
The condition of the dry etching is described below.
Etching gas: Argon
RF power: 800 W
Bias power: 100 W
Subsequently, the mask pattern 75 was removed by wet etching using diammonium cerium (IV) nitrate.
As shown in FIG. 9C, a resist film 77 was formed on the reverse surface of the MgO single crystalline substrate 3.
As shown in FIG. 9D, the MgO single crystalline substrate 3 was patterned by wet etching using hot phosphoric acid. The resist film 77 was then removed afterwards by ashing treatment with oxygen plasma.
Finally, as shown in FIG. 9E, the second electrode layer 9a and the fourth electrode layer 9b were formed on the obverse surface of the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b, respectively, using a shadow mask (not shown) by an evaporation method. Each of the second electrode layer 9a and the fourth electrode layer 9b were formed of a gold film having a thickness of 100 nanometers. Similarly, the mirror machine 30 was formed on the tilt part 25. This mirror 30 was also formed of a gold film having a thickness of 100 nanometers. In this way, the actuator 1 was fabricated.
The actuator 1 thus obtained was driven as below.
First, the tilt part 25 was irradiated with laser beam. This laser beam was reflected by the mirror 30. The reflected light was projected on a screen disposed away from the actuator 1.
Then, voltages shown in Table 1 were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b to tilt the tilt part 25. The tilt angular degree P was calculated on the basis of the movement distance of the reflected light projected on the screen.











TABLE 1





First
Second
Third
Fourth



electrode
electrode
electrode
electrode


layer 5a
layer 9a
layer 5b
layer 9b


(Voltage:
(Voltage:
(voltage:
(voltage:
Tilt angular


V5a)
V9a)
V5b)
V9b)
degree P



















0
−30
0
+30
0.56


0
−15
0
+15
0.28


0
0
0
0
0


0
+15
0
−15
−0.28


0
+30
0
−15
+0.56









As is clear from Table 1, the tilt part 25 was tilted.
Example 2
An actuator similar to the actuator according to the example 1 was fabricated except that the angular degree Q was set at 30 degrees. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volt were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 2.
Example 3
An actuator similar to the actuator according to the example 1 was fabricated except that the angular degree Q was set at 15 degrees. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volt were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 2.
Example 4
An actuator similar to the actuator according to the example 1 was fabricated except that the angular degree Q was set at 60 degrees. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volt were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 2.
Example 5
An actuator similar to the actuator according to the example 1 was fabricated except that the angular degree Q was set at 75 degrees. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volt were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 2.
Comparative Example 1
An actuator similar to the actuator according to the example 1 was fabricated except that the angular degree Q was set at 0 degrees. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volt were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 2.
Comparative Example 2
An actuator similar to the actuator according to the example 1 was fabricated except that the angular degree Q was set at 90 degrees. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volts were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 2.
Comparative Example 3
An actuator similar to the actuator according to the example 1 was fabricated except that the +Z direction is the [001] direction. FIG. 12 shows the axes of coordinate in the comparative example 3. In the comparative example 3, the angular degree Q was set at 45 degrees. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volts were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 2.










TABLE 2







Angular
Tilt angular



degree Q
degree P




















Comparative
0
0



example 1



Example 3
15
0.31



Example 2
30
0.48



Example 1
45
0.56



Example 4
60
0.48



Example 5
75
0.28



Comparative
90
0



example 2



Comparative
45
0



example 3










As is clear from Table 2, it is necessary that the angular degree Q is more than zero degrees and less than 90 degrees. It is preferable that the angular degree Q is not less than 15 degrees and not more than 75 degrees. It is more preferable that the angular degree Q is not less than 30 degrees and not more than 60 degrees.
As is clear from the comparative example 3, it is necessary that the (Bi,Na,Ba)TiO3 layer is preferentially oriented in the [011] direction. It is more preferable that the (Bi,Na,Ba)TiO3 layer is oriented only in the [011] direction.
Example 6
An actuator similar to the actuator according to the example 1 was fabricated except that each of the first (Bi, Na, Ba) TiO3 layer 7a and the second (Bi, Na, Ba) TiO3 layer 7b was substituted with a laminate of a (Bi, Na, Ba) TiO3 layer and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volt were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 3.
The (Bi, Na, Ba) TiO3 layer and the (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer were formed as below.
First, a (Bi, Na, Ba) TiO3 layer was deposited on the surface of the first electrode layer 5a and the third electrode layer 5b by an RF magnetron sputtering method. This (Bi, Na, Ba) TiO3 layer had a thickness of 1.35 micrometers.
The condition of the RF magnetron sputtering method is described below.
Target: Above-mentioned composition
Atmosphere: Gaseous mixture of argon and oxygen (Ar/O2 flow ratio: 50/50)
RF power: 170 W
Substrate temperature: 650 Celsius degrees
Then, the (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 (y=0.3) layer was deposited on the surface of the (Bi, Na, Ba) TiO3 layer by an RF magnetron sputtering method. This (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 (y=0.3) layer had a thickness of 1.35 micrometers.
The condition of the RF magnetron sputtering method is described below.
Target: Above-mentioned composition
Atmosphere: Gaseous mixture of argon and oxygen (Ar/O2 flow ratio: 50/50)
RF power: 170 W
Substrate temperature: 650 Celsius degrees
Example 7
An actuator similar to the actuator according to the example 6 was fabricated except that the (Bi, Na, Ba) TiO3 layer had a thickness of 1.6 micrometers and except that (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 (y=0.3) layer had a thickness of 1.1 micrometers. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volts were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 3.
Example 8
An actuator similar to the actuator according to the example 6 was fabricated except that the (Bi, Na, Ba) TiO3 layer had a thickness of 1.1 micrometers and except that (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 (y=0.3) layer had a thickness of 1.6 micrometers. Similarly to the example 1, the voltages of 0 volts, −30 volts, 0 volts, and +30 volts were applied to the first electrode layer 5a, the second electrode layer 9a, the third electrode layer 5b, and the fourth electrode layer 9b, respectively, so as to tilt the tilt part 25. The tilt angular degree P is shown in Table 3.









TABLE 3







Tilt angular



degree P



















Example 6
0.62



Example 7
0.60



Example 8
0.60










INDUSTRIAL APPLICABILITY
The actuator according to the embodiment may be used for a laser scanner.
REFERENCE SIGNS LIST


    1: actuator
    5a: first electrode layer
    5b: third electrode layer
    7a: first (Bi, Na, Ba) TiO3 layer
    7b: second (Bi, Na, Ba) TiO3 layer
    9a: second electrode layer
    9b: fourth electrode layer
    11a: first laminate
    11b: second laminate
    13a: first support
    13b: second support
    25: tilt part
    25a: first edge
    25b: second edge
    Q: angular degree formed between the [100] direction and the longitudinal direction of the first laminate 11, namely, the +X direction
    P: tilt angular degree

## Claims

1. A method for driving an actuator, the method comprising steps of:
a step (a) of preparing the actuator comprising:
a first laminate;
a second laminate;
a first support;
a second support; and
a tilt part, wherein

the first laminate comprises a first electrode layer, a first (Bi, Na, Ba) TiO3 layer, and a second electrode layer,
the first electrode layer, the first (Bi, Na, Ba) TiO3 layer, and the second electrode layer are laminated in such a manner that the first (Bi, Na, Ba) TiO3 layer is interposed between the first electrode layer and the second electrode layer,
the first (Bi, Na, Ba) TiO3 layer is preferentially oriented in a [011] crystalline axis direction,
+Z direction is parallel to the [011] crystalline axis direction,
−Z direction is the reverse direction of the +Z direction,
+X direction is parallel to the longitudinal direction of the first laminate,
−X direction is the reverse direction of the +X direction,
+Y direction is perpendicular to both of the +X direction and the +Z direction in a right-handed coordinate system,
−Y direction is the reverse direction of the +Y direction,
the laminate direction of the first laminate is parallel to the +Z direction,
the second laminate comprises a third electrode layer, a second (Bi, Na, Ba) TiO3 layer, and a fourth electrode layer,
the second (Bi, Na, Ba) TiO3 layer is preferentially oriented in the [011] crystalline axis direction,
the second (Bi, Na, Ba) TiO3 layer is interposed between the third electrode layer and the fourth electrode layer along the +Z direction,
the tilt part is interposed between the first laminate and the second laminate along the +X direction,
the tilt part comprises a first edge and a second edge,
the first edge and the second edge are located in the +Y side and the −Y side, respectively, in the XY plane,
one end of the first laminate is fixed to the first support,
one end of the second laminate is fixed to the second support, and
in the XY plane, an angular degree Q formed between the +X direction and a [100] direction is more than 0 degrees and less than 90 degrees, and
a step (b) of applying the voltages V5a, V9a, V5b, and V9b which satisfy the following requirement A or B to the first electrode layer, the second electrode layer, the third electrode layer, and the fourth electrode layer, respectively, so as to tilt the tilt part in such a manner that one of the first edge and the second edge is moved in the +Z direction and the other is moved in the −Z direction;
Requirement A: V5a>V9a and V5b<V9b 
Requirement B: V5a<V9a and V5b>V9b.

2. The method according to claim 1, wherein
in the step (b), the requirement A is satisfied; and
the first edge is moved in the −Z direction and the second edge is moved in the +Z direction.

3. The method according to claim 1, wherein
in the step (b), the requirement B is satisfied; and
the first edge is moved in the +Z direction and the second edge is moved in the −Z direction.

4. The method according to claim 1, wherein
the angular degree Q is not less than 15 degrees and not more than 75 degrees.

5. The method according to claim 1, wherein
the angular degree Q is not less than 30 degrees and not more than 60 degrees.

6. The method according to claim 1, wherein
the first electrode layer is formed integrally with the third electrode layer.

7. The method according to claim 1, wherein
the first (Bi, Na, Ba) TiO3 layer is formed integrally with the second (Bi, Na, Ba) TiO3 layer.

8. The method according to claim 1, wherein
the first (Bi, Na, Ba) TiO3 layer is formed of (Bi0.5Na)0.5TiO3—BaTiO3; and
the second (Bi, Na, Ba) TiO3 layer is formed of (Bi0.5Na)0.5TiO3—BaTiO3.

9. The method according to claim 1, wherein
the first (Bi, Na, Ba) TiO3 layer is formed of a laminate of a (1−x)(Bi0.5,Na0.5)TiO3)−x(BaTiO3) layer (0.01≦x≦0.15) and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer (0.20≦y≦0.50); and
the second (Bi, Na, Ba) TiO3 layer is formed of a laminate of a (1−x)(Bi0.5,Na0.5)TiO3)−x(BaTiO3) layer (0.01≦x≦0.15) and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer (0.20≦y≦0.50).

10. An actuator comprising:
a first laminate;
a second laminate;
a first support;
a second support; and
a tilt part, wherein
the first laminate comprises a first electrode layer, a first (Bi, Na, Ba) TiO3 layer, and a second electrode layer;
the first electrode layer, the first (Bi, Na, Ba) TiO3 layer, and the second electrode layer are laminated in such a manner that the first (Bi, Na, Ba) TiO3 layer is interposed between the first electrode layer and the second electrode layer;
the first (Bi, Na, Ba) TiO3 layer is preferentially oriented in a [011] crystalline axis direction;
+Z direction is parallel to the [011] crystalline axis direction;
−Z direction is the reverse direction of the +Z direction;
+X direction is parallel to the longitudinal direction of the first laminate;
−X direction is the reverse direction of the +X direction;
+Y direction is perpendicular to both of the +X direction and the +Z direction in a right-handed coordinate system;
−Y direction is the reverse direction of the +Y direction;
the laminate direction of the first laminate is parallel to the +Z direction;
the second laminate comprises a third electrode layer, a second (Bi, Na, Ba) TiO3 layer, and a fourth electrode layer;
the second (Bi, Na, Ba) TiO3 layer is preferentially oriented in the [011] crystalline axis direction;
the second (Bi, Na, Ba) TiO3 layer is interposed between the third electrode layer and the fourth electrode layer along the +Z direction;
the tilt part is interposed between the first laminate and the second laminate along the +X direction;
the tilt part comprises a first edge and a second edge;
the first edge and the second edge are located in the +Y side and the −Y side, respectively, in the XY plane;
one end of the first laminate is fixed to the first support;
one end of the second laminate is fixed to the second support and;
in the XY plane, an angular degree Q formed between the +X direction and a [100] direction is more than 0 degrees and less than 90 degrees.

11. The actuator according to claim 10, wherein
the angular degree Q is not less than 15 degrees and not more than 75 degrees.

12. The actuator according to claim 10, wherein
the angular degree Q is not less than 30 degrees and not more than 60 degrees.

13. The actuator according to claim 10, wherein
the first electrode layer is formed integrally with the third electrode layer.

14. The actuator according to claim 10, wherein
the first (Bi, Na, Ba) TiO3 layer is formed integrally with the second (Bi, Na, Ba) TiO3 layer.

15. The actuator according to claim 10, wherein
the first (Bi, Na, Ba) TiO3 layer is formed of (Bi0.5Na)0.5TiO3—BaTiO3; and
the second (Bi, Na, Ba) TiO3 layer is formed of (Bi0.5Na)0.5TiO3—BaTiO3.

16. The actuator according to claim 10, wherein
the first (Bi, Na, Ba) TiO3 layer is formed of a laminate of a (1−y)(Bi0.5,Na0.5)TiO3)−x(BaTiO3) layer (0.01≦x≦0.15) and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer (0.20≦y≦0.50); and
the second (Bi, Na, Ba) TiO3 layer is formed of a laminate of a (1−y)(Bi0.5,Na0.5)TiO3)−x(BaTiO3) layer (0.01≦x≦0.15) and a (1−y)[(Bi,Na,Ba)TiO3]−yBiFeO3 layer (0.20≦y≦0.50).