JP4734122B2 - Light modulation element, actuator, and driving method of actuator - Google Patents

Description

  The present invention relates to an on-demand digital exposure head used in a photolithography process, an image forming apparatus using the digital exposure head, a projection display device such as a projector, a light modulation element mounted on a micro display device such as a head-mounted display, and the like. The present invention relates to an actuator for displacing a micromachine.

  As a conventional light modulation element, for example, a movable micromirror of about 10 to 20 microns square is provided, and this micromirror is formed on an address circuit to form one pixel of an image displayed by the light modulation element array. Some of the two positions reflect incident light to the projection lens and deflect the incident light to the optical absorber at the other position.

  As said light modulation element, there exists a thing described in the following patent document 1, for example. In these light modulation elements, the mirror element supported by the yoke is deflected by the electrostatic force generated between the mirror element and the mirror address electrode, thereby deflecting the direction of the incident light to be reflected.

JP 2001-242395 A

  However, since the address electrode and the yoke are arranged on the same plane in the light modulation element disclosed in Patent Document 1, the area of each electrode is reduced, and the electrostatic force and yoke acting on the pixel mirror and the address electrode are reduced. All of the electrostatic force acting on the address electrodes is reduced, and there is room for improvement in terms of speeding up the mirror displacement drive.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide an optical modulation element, an actuator, and an actuator driving method excellent in high-speed response.

The object of the present invention is to provide a substrate,
A movable member that includes a flat plate member that rotates and displaces a beam body installed on the substrate as a rotation axis, and the upper surface of the flat plate member functions as an optically reflective mirror part ;
A pair of movable electrodes provided at positions symmetrical to the rotation axis of the flat plate member ;
A fixed electrode that is disposed outside a trajectory range in which the movable member is mechanically displaceable, and that drives the movable member to move in cooperation with the movable electrode by applying a voltage;
The movable electrode is provided with a first opposing conductive surface extending in the direction of rotational displacement of the movable member, and the fixed electrode is opposed to the first opposing conductive surface when the movable member is rotationally displaced. A second opposing conductive surface that increases the electrostatic attractive force generated on the first opposing conductive surface is provided , and the first opposing conductive surface and the second opposing conductive surface are parallel to the rotation axis. It is achieved by a light modulation element characterized in that the surface is a surface to be illuminated.

  When a voltage is applied to the fixed electrode by voltage drive control to generate a potential difference between the fixed electrode and the movable electrode provided on the movable member, the light modulation element of the present invention generates static electricity between the movable electrode and the fixed electrode. For example, a movable member having an optical function such as a mirror part having light reflectivity is displaced with respect to the substrate by using the electrostatic force as a driving force.

  Here, since the movable electrode and the fixed electrode are provided with the first opposite conductive surface and the second opposite conductive surface, respectively, the electric field is concentrated between these surfaces, and the movable electrode is placed on the fixed electrode side. Increases the electrostatic attraction force that tries to attract it. For this reason, when a voltage is applied to the fixed electrode during the displacement driving of the movable member, the driving when the movable member is displaced and driven according to the electrostatic attraction force between the first opposing conductive surface and the second opposing conductive surface. The force increases and the moving member moves faster. Therefore, the light modulation element of the present invention can improve high-speed response.

In the light modulation element, it is preferable that both the first opposing conductive surface and the second opposing conductive surface are flat surfaces.
If it carries out like this, the electrostatic force which arises on the 1st counter conductive surface and the 2nd counter conductive surface can be increased more efficiently.

The light modulation element is a curved surface in which both the first counter conductive surface and the second counter conductive surface are curved along the rotation direction of the movable member, and the second counter conductive surface is composed of a pair of conductive portions, It is preferable that the pair of conductive portions is provided side by side in the rotation direction of the movable member.
In this way, among the pair of conductive portions in each fixed electrode, by controlling the voltage drive of the conductive portions in the direction of displacement, the movable member can be displaced on both sides in the rotational direction with the beam body as the rotation axis. Since the electrostatic attraction force is applied to the movable member from both of the second opposing conductive surfaces of the fixed electrodes, a larger rotational torque can be obtained. For this reason, high-speed responsiveness can also be realized for a bidirectionally driven light modulation element. Further, after the displacement of the movable member, the static force that holds the position after the displacement of the movable member by the electrostatic attractive force acting from the second opposing conductive surface of each fixed electrode can be further increased.

In the light modulation element, it is preferable that an auxiliary electrode for applying an electrostatic force to the movable electrode is provided on the substrate.
In this way, by increasing the electrostatic attraction force applied to the movable electrode by the auxiliary electrode, the high-speed response of the light modulation element can be further improved, and the stationary force that stops the movable member after displacement is also increased. Can be made.

In the light modulation element, a shield electrode that can be adjusted to the same potential as the movable electrode is preferably provided on the substrate.
In this way, it is possible to shield an unnecessary electric field around the light modulation element by the shield electrode. For example, when a light modulation element array in which the light modulation elements are arranged two-dimensionally or three-dimensionally is used, It is possible to prevent the movable member from being inappropriately displaced due to the electrostatic force from the light modulation element, and to drive the light modulation element more accurately.

In addition, the present invention can be applied to an actuator. Specifically, the invention includes a substrate and a flat plate member that rotates and displaces a beam body laid on the substrate as a rotation axis, and the upper surface of the flat plate member is optical. A movable member that functions as a reflective mirror portion , a pair of movable electrodes provided at positions symmetrical to the rotation axis of the flat plate member, and an out-of-track range in which the movable member can be mechanically displaced And a fixed electrode for driving the movable member to move in cooperation with the movable electrode by applying a voltage,
The movable electrode is provided with a first opposing conductive surface extending in the direction of rotational displacement of the movable member, and the fixed electrode is opposed to the first opposing conductive surface when the movable member is rotationally displaced. A second opposing conductive surface that increases the electrostatic attractive force generated on the first opposing conductive surface is provided , and the first opposing conductive surface and the second opposing conductive surface are parallel to the rotation axis. It is possible to provide an actuator characterized by being a surface to be operated.
By doing so, it is possible to provide an actuator with excellent high-speed response.

Furthermore, the present invention can be applied to the above-described actuator driving method, and specifically includes a substrate and a flat plate member that rotates and displaces a beam body laid on the substrate as a rotation axis. A pair of a movable member whose upper surface functions as an optically reflective mirror , a pair of movable members symmetrically with respect to the rotational axis of the flat plate member , and a pair of positions of the flat plate member symmetrical with respect to the rotational axis. And a fixed electrode that is arranged outside the trajectory range in which the movable member can be mechanically displaced and cooperates with the movable electrode by applying a voltage to drive the movable member to rotate and move. The fixed electrode is provided with a second counter conductive surface that faces the first counter conductive surface when the movable member is rotationally displaced, and the first counter conductive surface and the second counter conductive surface are provided. Surface parallel to the axis of rotation A driving method of the actuator is a surface that,
When the displacement drive of the movable member, acting between them so as to face with said first opposing conductive surface and the second opposing conductive surfaces which extend in the direction of displacement of the movable member to the movable electrode The driving method of the actuator can be characterized by increasing the electrostatic attraction force.
In this way, when the actuator is driven, the speed of the displacement operation of the actuator can be increased.

  According to the present invention, it is possible to provide an optical modulation element, an actuator, and an actuator driving method that are excellent in high-speed response.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
FIG. 1 is a perspective view showing a first embodiment of a light modulation element according to the present invention. FIG. 2 is an explanatory diagram for explaining the shape and dimensions of the light modulation element. FIG. 3 is a cross-sectional view of the light modulation element shown in FIG. FIG. 4 is a diagram illustrating a state where the light modulation element illustrated in FIG. 3 is displaced.

  The light modulation element 10 includes a substrate 11, a movable member 14 that is rotatably mounted on the substrate 11, a support portion 19 that supports the movable member 14, and fixed electrodes 12 and 13 provided on the substrate 11. And.

  The substrate 11 is a plate having a predetermined thickness, and fixed electrodes 12 and 13 having a rectangular shape are fixed to one surface (the upper surface in FIG. 1). In the light modulation element 10 of the present embodiment, the fixed electrodes 12 and 13 are provided in pairs.

  The movable member 14 is supported between the fixed electrodes 12 and 13 so as to be supported by a pair of support bodies 19 provided on the substrate 11 so as not to contact the fixed electrodes 12 and 13. The movable member 14 is a rectangular support plate 16 having a flat portion on the upper surface, and a pair of plates formed perpendicular to and parallel to each of two opposing edges of the peripheral edge of the support plate 16. It is composed of a certain movable electrode 17A, 17B and a beam 15 that passes through the center of the support plate 16 (the center of the pair of movable electrodes 17A, 17B) and projects laterally from the other two edges. Are integrally formed.

  When the conductive material is made of a metal such as aluminum, the flat portion (upper surface in FIG. 1) of the support plate 16 has optical reflectivity as an optical function and functions as the mirror portion 18.

  The movable member 14 can be mechanically displaced by applying a driving force such that the beam body 15 is used as a torsion shaft and the shaft is rotated in the direction indicated by the arrows D1 and D2 with the shaft as the rotation axis S.

  The fixed electrodes 12 and 13 are disposed outside the track range in which the movable member 14 can be mechanically displaced, and the movable member 14 is displaced in cooperation with the movable electrodes 17A and 17B by a voltage applied by driving voltage control. Drive. The fixed electrodes 12 and 13 are provided with side surfaces 12a and 13a that are opposed to the side surfaces 17a and 17b, which are first opposing conductive surfaces, when the movable member 14 is displaced. The side surfaces 12a and 13a function as a second opposing conductive surface.

  The movable electrodes 17A and 17B are provided with side surfaces 17a and 17b erected perpendicularly to the support plate 16 from the fixed electrode 12 and 13 side ends of the support plate 16 so as to face the fixed electrodes 12 and 13, respectively. It has been. In the present embodiment, the side surfaces 17a and 17b of the movable electrodes 17A and 17B function as first opposing conductive surfaces.

  When the support portion 19 that supports the movable member 14 is formed of a conductive material, the movable member 14 and the support portion 19 are electrically connected. Therefore, when the potential of the movable member 14 is controlled, the substrate The output of a drive circuit (not shown) formed in 11 can be supplied to the movable member 14 via the support portion 19, and the structure can be simplified.

  The movable electrodes 17A and 17B may be entirely made of a conductive material, or at least a part of the movable electrodes 17A and 17b may be made of an aluminum thin film or a conductive material. Here, the side surfaces 17a and 17b are not limited to the configuration in which the side surfaces 17a and 17b are erected vertically with respect to the support plate 16 as long as they are extended in the direction in which the movable member 14 is displaced. .

  Next, a desirable shape and size of the light modulation element in this embodiment will be described with reference to FIG. FIG. 2 is an explanatory diagram for explaining the shape and dimensions of the light modulation element. As shown in FIG. 2, the center of rotation of the movable member 14 is P, and the distance from the point P to the first opposing conductive surface (the side surface 17a of the movable electrode 17A or the side surface 17b of the movable electrode 17B) is from a and P points. The horizontal distance to the second opposing conductive surface (the side surface 12a of the fixed electrode 12 or the side surface 13a of the fixed electrode 13) is b, and the side surface 12a of the fixed electrode 12 or the side surface 13a of the fixed electrode 13 is inclined with respect to the vertical line VL of the substrate 11. Let the angle be θ.

  Here, when the movable member 14 is displaced by the angle θ as shown by a broken line in FIG. 2, the gap g between the side surface 17a (first counter conductive surface) and the side surface 12a (second counter conductive surface) is ( It is calculated | required by Formula 1).

  g = b · cos θ−a (Formula 1)

  Here, in order to obtain an electrostatic force sufficient to displace the movable member 14 with a practically low driving voltage (about 5 to 50 V), the gap g is preferably set to 0.1 μm to 2.0 μm. . Furthermore, it is preferable to set it as 0.2 micrometer-1.0 micrometer practically.

  On the other hand, when the inclination angle of the side surface 12a of the fixed electrode 12 and the side surface 13a of the fixed electrode 13 is assumed to be a light modulation element that modulates light by the mirror portion 18 provided on the upper surface of the support plate 16, 1 ° to Since about 45 ° is a practically preferable value, the distance a from the point P to the first opposing conductive surface (side surfaces 17a, 17b) and the point P to the second opposing conductive surface (side surfaces 12a, 13a) The horizontal distance b is the gap g between the first opposing conductive surface (side surfaces 17a, 17b) and the second opposing conductive surface (side surfaces 12a, 13a), and the inclination angle of the side surfaces 12a, 13a of the fixed electrodes 12, 13 It is obtained by appropriately determining θ.

  If the height c of the first opposing conductive surfaces (side surfaces 17a, 17b) is increased, the area for generating electrostatic force is increased and the holding force at the time of tilt displacement is increased. The moment of inertia of 14 becomes large and the high-speed response is impaired. Accordingly, the height c of the first opposing conductive surfaces (side surfaces 17a and 17b) is appropriately determined within a range that satisfies both the holding force and the responsiveness during the tilt displacement in a well-balanced manner.

  As shown in FIG. 3, the drive electrodes V11 and V12 are electrically connected to the movable electrodes 17A and 17B, respectively, and the drive electrodes V21 and V22 are electrically connected to the fixed electrodes 12 and 13, respectively. . The light modulation element 10 according to the present embodiment controls the drive voltages of the drive electrodes V11 and V21 and / or the drive electrodes V12 and V22, so that the first counter conductive surfaces 17a and 17b and the second counter conductive surfaces 12a and 13a are controlled. And a potential difference can be generated.

As the substrate 11, a CMOS circuit (not shown) is formed on a Si substrate, and an insulating film made of SiO ₂ or the like is formed on the circuit. After the surface is planarized by CMP or the like, contact holes for connecting the output of the drive circuit to each electrode of the element are formed. When the support portion 19 that supports the movable member 14 is formed of a conductive material, the drive voltage can be moved via the support portion 19 by forming the drive electrodes V11 and V12 on the substrate 11. The member 14 can be supplied.

Next, an operation when the light modulation element of this embodiment is displaced will be described.
In the light modulation element 10, when the movable member 14 is movably driven and displaced in the directions indicated by the arrows d1 and d2 in FIG. 3, the side surface 17b, which is the first opposing conductive surface, is applied by voltage application of the drive electrodes V12 and V22. A potential difference with the side surface 13a which is the second opposing conductive surface is generated, and an electrostatic force is generated between them. Then, an electrostatic attraction force that is attracted toward the second opposing conductive surface 13a of the fixed electrode 13 is generated on the movable electrode 17B of the movable member 14 by using an electrostatic force as a driving force. Thus, the movable member 14 is driven in the direction indicated by the arrows d1 and d2 in FIG. 3 with the torsion axis S of the beam body 15 as the rotation axis, and the first opposing conductive surface 17b and the second opposing conductive surface 13a are driven. Stop at the position where the electrostatic force between them becomes maximum. As a result, as shown in FIG. 4, the position of the movable member 14 having the mirror portion 18 formed on the upper surface is displaced as an optical function. For this reason, the reflection direction of the incident light L applied to the mirror unit 18 can be deflected.

  The displaced position of the movable member 14 can be reliably held by the electrostatic force between the side surface 17b that is the first opposing conductive surface and the side surface 13a that is the second opposing conductive surface.

  Further, in order to return the movable member 14 to the original position before the displacement, the voltage application to the drive electrodes V12 and V22 is stopped and the side surface 17b which is the first counter conductive surface and the side surface 13a which is the second counter conductive surface. By eliminating the potential difference between the two, the electrostatic force between the two disappears. Then, the movable member 14 is mechanically displaced in the directions indicated by arrows d3 and d4 in FIG. Become almost parallel.

  On the other hand, in the light modulation element 10, when the movable member 14 is movably driven and displaced in the directions indicated by the arrows d3 and d4 in FIG. 3, the side surface that is the first opposing conductive surface is applied by voltage application of the drive electrodes V11 and V21. A potential difference is generated between the side surface 12a, which is the second opposing conductive surface, and an electrostatic force is generated between the two. Then, an electrostatic attraction force that is attracted toward the second opposing conductive surface 12a of the fixed electrode 12 is generated on the movable electrode 17A of the movable member 14 by using an electrostatic force as a driving force. Thus, the movable member 14 is driven in the direction indicated by the arrows d3 and d4 in FIG. 3 with the torsion axis S of the beam body 15 as the rotation axis, and the direction in which the incident light L applied to the mirror portion 18 is reflected is deflected. Will be able to. Similarly, in order to return the movable member 14 to the original position before displacement, voltage application to the drive electrodes V11 and V21 is stopped and the side surface 17a which is the first counter conductive surface and the side surface which is the second counter conductive surface. By eliminating the potential difference from 12a, the movable member 14 is mechanically displaced in the directions indicated by the arrows d1 and d2 in FIG. 3, and the support plate 16 becomes substantially parallel to the surface of the substrate 11 as originally.

  As in the above embodiment, the light modulation element 10 according to the present invention applies voltage to the fixed electrodes 12 and 13 by voltage drive control, and the movable electrodes 17A and 17A provided on the fixed electrodes 12 and 13 and the movable member 14 are provided. When a potential difference from 17B is generated, an electrostatic force is generated between the movable electrodes 17A and 17B and the fixed electrodes 12 and 13, and the movable member 14 uses the electrostatic force as a driving force so that the substrate 11 together with the mirror portion 18 is driven. It is the structure displaced with respect to.

  Here, the movable electrodes 17A and 17B and the fixed electrodes 12 and 13 are provided with the first opposing conductive surfaces 17a and 17b and the second opposing conductive surfaces 12a and 13a, respectively. The concentration of the electric field occurs, and the electrostatic attractive force that tries to attract the movable electrodes 17A and 17B to the fixed electrodes 12 and 13 side increases. For this reason, when a voltage is applied to the fixed electrodes 12 and 13 during the displacement driving of the movable member 14, the electrostatic attractive force between the first opposing conductive surfaces 17a and 17b and the second opposing conductive surfaces 12a and 13a is determined. Thus, the driving force when the movable member 14 is displaced is increased, and the moving speed of the movable member 14 is increased. Therefore, the light modulation element 10 of the present invention can improve high-speed response.

  In the light modulation element 10 of the present embodiment, the movable electrodes 17A and 17B and the fixed electrodes 12 and 13 include the first opposing conductive surfaces 17a and 17b and the second opposing conductive surfaces 12a and 13a when the movable member 14 is displaced. Therefore, the electrostatic force generated by the first opposing conductive surfaces 17a and 17b and the second opposing conductive surfaces 12a and 13a can be increased more efficiently.

  Next, a method for producing the above-described light modulation element will be described with reference to FIG. FIG. 5 is a schematic view for explaining the process of producing the light modulation element from (a) to (h).

As shown in FIG. 5 (a), the substrate 11 forms a CMOS drive circuit (not shown) on the Si substrate 61, to form a first Si0 ₂ insulating film (not shown) thereon After the surface is flattened by CMP (chemical mechanical polishing) or the like, contact holes (not shown) for connecting the output of the CMOS drive circuit to the fixed electrodes 12, 13 and the movable electrodes 17A, 17B are formed. Configured. Aluminum (preferably an aluminum alloy containing a refractory metal) as the first conductive film 62 is formed on the Si substrate 61 by sputtering.

  Next, as shown in FIG. 5B, a positive resist film is applied, and a first resist structure 63 having a desired shape is formed by photolithography using a gray scale photomask. The first resist structure 63 is a structure similar to the shape of the lower half of the pair of fixed electrodes 12 and 13 having a desired inclination on the inner side and the support portion 19 that supports the beam body 15.

  Next, as shown in FIG. 5C, a first conductive film 62 having a desired inclination is formed inside the side surface of the first conductive film by RIE dry etching using a chlorine-based gas. That is, the first resist structure 63 is transferred to the structure of the first conductive film 62. Here, the first conductive film 62 is separated into the left and right fixed electrodes 12 and 13, which are connected to the drive electrodes V21 and V22 on the Si substrate 61 side via contact holes (not shown). .

  Next, as shown in FIG. 5D, a positive resist film is applied as the sacrificial layer 64 and hard-baked. Hard baking is performed at a temperature exceeding 200 ° C. while irradiating with Deep UV. As a result, the shape is maintained even in a high-temperature process as a subsequent step, and becomes insoluble in the resist stripping solvent. In addition, due to the reflow effect at the time of baking, the resist surface becomes substantially flat regardless of the level difference of the base film, but the upper surface of the resist is made the same as the height of the first conductive film 62 by using etch back or polishing method. The sacrificial layer 64 is removed in a process described later. Accordingly, the resist film thickness determines the gap between the upper surface of the substrate 11 and the lower surface of the support plate 16 in the future. As the sacrificial layer 64, photosensitive polyimide can be used instead of the resist.

  Then, as shown in FIG. 5E, a second aluminum thin film (preferably an aluminum alloy containing a refractory metal) is formed as the second conductive film 65 by sputtering.

  Next, as shown in FIG. 5F, a positive resist is applied, and a second resist structure 66 having a desired shape is formed by photolithography using a gray scale photomask. The second resist structure 66 includes an upper half of a pair of fixed electrodes 12 and 13 having a desired inclination inside, a movable portion 14 having a pair of counter electrode surfaces 17a and 17b, and the shape of the beam body 15. It is a similar structure.

  Then, as shown in FIG. 5 (g), the upper half of the pair of fixed electrodes 12 and 13 having a desired inclination inside the side surface of the second conductive film and the pair of opposing layers by RIE dry etching using a chlorine-based gas. The movable part 14 having the electrode surfaces 17a and 17b and the beam body 15 are formed. That is, the second resist structure 66 is transferred to the structure of the second conductive film 65.

Finally, as shown in FIG. 5 (h), the resist layer, which is the sacrificial layer 64, is removed by plasma etching (ashing) of an oxygen-based gas to form a gap C, thereby forming a light modulation element having a desired structure. .
Note that the structure, material, and process are not limited to those described above as long as they conform to the gist of the present invention.

(Second Embodiment)
6, 7 and 8 show a second embodiment according to the present invention. In the embodiments described below, members having the same configuration / action as those already described are denoted by the same or corresponding reference numerals in the drawings, and description thereof is simplified or omitted. Here, FIG. 6 is a perspective view showing a second embodiment of the light modulation element according to the present invention. 7 is a cross-sectional view of the light modulation element shown in FIG. FIG. 8 is a diagram illustrating a state in which the light modulation element illustrated in FIG. 7 is displaced.

  In the light modulation element 20 of the present embodiment, the movable member 24 supported by the support portion 19 has the torsion axis S of the beam body 25 as the rotation axis at each of the fixed electrode 22 and 23 side edges of the support plate 26. The movable electrodes 27A and 27B curved so as to follow the rotating direction are attached. In the present embodiment, the curved side surfaces 27a and 27b of the movable electrodes 27A and 27B facing the fixed electrodes 22 and 23 function as the first opposing conductive surface.

  In the fixed electrodes 22 and 23, the side surfaces facing each other are curved surfaces formed so as to be recessed toward the opposite side surfaces. A pair of conductive portions 22A, 22B, 23A, and 23B are fixed on these curved surfaces along the direction in which the movable member 24 is displaced. The conductive portions 22A, 22B, 23A, and 23B are plate-like members that are curved along the curved surface, and the curved surfaces 22a, 22b, 23a, and 23b on the movable member 24 side function as second opposing conductive surfaces.

  As shown in FIG. 7, the driving electrode V31 is electrically connected to the fixed electrodes 22B and 23A, and the driving electrode V32 is electrically connected to the fixed electrodes 22A and 23B. The drive electrode V33 is electrically connected to the movable electrodes 27A and 27B of the movable member 24. By controlling the voltage of these drive electrodes V31, V32 and V33, a potential difference is formed between the first opposing conductive surfaces 27a and 27b and the second opposing conductive surfaces 22a, 22b, 23a and 23b, and electrostatic force It is the structure which can generate | occur | produce.

  Note that, on the condition that a potential difference can be formed by voltage drive control, separate drive electrodes may be connected to the fixed electrodes 22B and 23A, and separate drive electrodes may be connected to the fixed electrodes 22A and 23B. An electrode may be connected. Furthermore, separate drive electrodes may be connected to the movable electrodes 27A and 27B, respectively.

Next, an operation when the light modulation element of this embodiment is displaced will be described.
In the light modulation element 20, when the movable member 24 is movably driven and displaced in the directions indicated by the arrows d1 and d2 in FIG. 7, the side surface 27a, which is the first opposing conductive surface, is applied by voltage application of the drive electrodes V32 and V33. A potential difference is generated between the side surface 22a that is the second counter conductive surface and a potential difference between the side surface 27b that is the first counter conductive surface and the side surface 23b that is the second counter conductive surface. Then, between the side surface 27a which is the first counter conductive surface and the side surface 22a which is the second counter conductive surface, and the side surface 27b which is the first counter conductive surface and the side surface 23b which is the second counter conductive surface. Electrostatic force is generated between Then, an electrostatic attraction force that is attracted toward the second opposing conductive surface 22a of the fixed electrode 12 using the electrostatic force as a driving force is generated in the movable electrode 27A of the movable member 24, and the movable electrode 27B of the movable member 24 is electrostatically charged. An electrostatic attractive force that is attracted toward the second opposing conductive surface 23b of the fixed electrode 13 is generated using the force as a driving force. Thus, the movable member 24 is driven in the direction indicated by the arrows d1 and d2 in FIG. 7 with the torsion axis S of the beam body 25 as the rotation axis, and is the second opposing conductive surface 22a and the first opposing conductive surface. It stops at the position where the electrostatic force between the side surface 27a and the second opposing conductive surface 23b and the side surface 27b which is the first opposing conductive surface is maximized.
As a result, as shown in FIG. 8, the position of the movable member 24 having the mirror portion 28 formed on the upper surface is displaced as an optical function. For this reason, the direction in which the incident light L applied to the mirror portion 28 is reflected can be deflected.

  Further, in order to return the movable member 24 to the original position before the displacement, voltage application to the drive electrodes V32 and V33 is stopped, and the side surface 27a that is the first opposing conductive surface and the side surface that is the second opposing conductive surface. The potential difference between 22a and the potential difference between the side surface 27b which is the first counter conductive surface and the side surface 23b which is the second counter conductive surface is eliminated. Then, the electrostatic force between the two disappears, and the movable member 24 is mechanically displaced in the directions indicated by the arrows d3 and d4 in FIG. The support plate 26 returns to a position that is substantially parallel to the surface of the substrate 21.

  That is, in the light modulation element 20 of the present embodiment, the first opposing conductive surfaces 27a and 27b and the second opposing conductive surfaces 22a, 22b, 23a, and 23b are both curved surfaces that are curved along the rotation direction of the movable member 24. The second opposing conductive surfaces 22a, 22b, 23a, and 23b are formed of a pair of conductive portions 22A, 22B, 23A, and 23B, and the pair of conductive portions 22A, 22B, 23A, and 23B is the rotational direction of the movable member. Are arranged side by side.

  By doing this, voltage drive control is performed on the conductive portions 22A, 23B (or 22B, 23A) in the displacing direction among the pair of conductive portions 22A, 22B, 23A, 23B in the fixed electrodes 22, 23, respectively. The movable member 24 can be displaced to both sides in the rotational direction with the beam body 25 as a rotation axis, and the movable member 24 has second opposing conductive surfaces 22a and 23b (or 22b and 23a) of the fixed electrodes 22 and 23. The electrostatic attraction force is applied from both. As a result, the movable member 24 can obtain a larger rotational torque. For this reason, with the configuration of the present embodiment, high-speed responsiveness can also be realized for a bidirectionally-modulated light modulation element. Further, after the movable member 24 is displaced, the movable member 24 is displaced by the electrostatic attraction force acting from both the second opposing conductive surfaces 22a and 23b (or 22b and 23a) of the fixed electrodes 22 and 23. The stationary force that holds the position can be further increased.

(Third embodiment)
FIG. 9 is a cross-sectional view for explaining a third embodiment of the light modulation element according to the present invention. The basic configuration of this embodiment is the same as that of the first embodiment shown in FIGS.
The light modulation element 40 of the present embodiment is an upper surface of the substrate 41, and the auxiliary electrodes 42 </ b> A, 43A is provided.

  According to the light modulation element 40 of the present embodiment, the high speed responsiveness of the light modulation element 40 can be further improved by increasing the electrostatic attractive force applied to the movable electrodes 47A and 47B by the auxiliary electrodes 42A and 43A. In addition, it is possible to increase the static force that stops the movable member 44 after the displacement.

  In the light modulation element 40 of the present embodiment, the positions where the auxiliary electrodes 42A and 43A are provided are merely examples, and other positions are within a range in which the electrostatic attractive force can be applied to the movable electrodes 47A and 47B. The same effect can be obtained even if it is provided.

(Fourth embodiment)
FIG. 10 is a sectional view for explaining a fourth embodiment of the light modulation element according to the present invention. The basic configuration of this embodiment is the same as that of the first embodiment shown in FIGS.
In the light modulation element 50 of this embodiment, a shield electrode 52 s is provided on the upper surface of the substrate 51 and below the support plate 56 of the movable member 54. The shield electrode 52s is made of a metal thin film such as aluminum or Cr.

  The light modulation element 50 according to the present embodiment can shield static electricity exerted from a charged body outside the light modulation element 50 by the shield electrode 52s, and the light modulation element 50 is arranged two-dimensionally or three-dimensionally. In this case, the static electricity exerted from the other light modulation elements is shielded by the shield electrode 52s and does not affect the movable electrodes 57A and 57B. Inappropriate displacement can be prevented, and the light modulator 50 can be driven more accurately.

  In each of the above-described embodiments, the example of the mirror has been described as the optical function provided in the movable portion. However, the present invention is not limited to this. For example, an optical interference film made of a dielectric multilayer film or a diffraction grating may be used as an optical function. When these are rotationally displaced, they can also be applied to light modulation elements that utilize the incident angle dependency.

The present invention extends to an actuator having the configuration of the light modulation element of the above embodiment and a driving method of the actuator.
As such an actuator, it can be set as the structure which abbreviate | omitted the mirror part. Specifically, the substrate, a movable member installed on the substrate so as to be displaceable, a movable electrode provided on the movable member, and disposed outside the trajectory range in which the movable member can be mechanically displaced, The movable electrode is provided with a fixed electrode that cooperates with the movable electrode by voltage application to drive the movable member. The movable electrode is provided with a first opposing conductive surface that extends in the direction in which the movable member is displaced. A second opposing conductive surface is provided that increases the electrostatic attractive force generated on the first opposing conductive surface while facing the first opposing conductive surface during displacement driving of the member.
If it carries out like this, the drive of a movable member can be sped up and an actuator excellent in high-speed response can be provided.

  In addition, the actuator driving method according to the present invention includes a substrate, a movable member that can be displaced on the substrate, a movable electrode provided on the movable member, and a mechanical displacement of the movable member. A driving method of an actuator provided with a fixed electrode that is arranged outside a trajectory range and is driven to displace the movable member in cooperation with the movable electrode by applying a voltage, and the movable member is moved to the movable electrode during the displacement driving of the movable member. The electrostatic attraction force acting between the first opposing conductive surface extending in the direction in which the first opposing conductive surface and the second opposing conductive surface provided on the fixed electrode are opposed to each other is increased. And

In addition, this invention is not limited to embodiment mentioned above, A suitable deformation | transformation, improvement, etc. are possible.
For example, the method of displacing the movable member by the electrode wiring and the drive voltage control in the light modulation element of the above embodiment is an example, and is not limited to this.

1 is a perspective view showing a first embodiment of a light modulation element according to the present invention. It is explanatory drawing for demonstrating the shape and dimension of the light modulation element shown in FIG. It is sectional drawing in the AA arrow line view of the light modulation element shown in FIG. It is a figure which shows the state which displaced the light modulation element shown in FIG. It is the schematic explaining the creation process of a light modulation element from (a) to (h). It is a perspective view which shows 2nd Embodiment of the light modulation element concerning this invention. It is sectional drawing in the BB arrow line view of the light modulation element shown in FIG. It is a figure which shows the state which displaced the light modulation element shown in FIG. It is a figure explaining 3rd Embodiment of the light modulation element concerning this invention. It is a figure explaining 4th Embodiment of the light modulation element concerning this invention.

Explanation of symbols

10, 20, 40, 50 Light modulation elements 11, 21, 41, 51 Substrate 12, 13, 22, 23, 42, 43, 52, 53 Fixed electrodes 14, 24, 44, 54 Movable members 17a, 17b, 27a, 27b, 47a, 47b, 57a, 57b First opposing conductive surface (side surface of movable member)
12a, 13a, 22a, 22b, 23a, 23b, 42a, 43a, 52a, 53a Second opposing conductive surface (side surface of fixed electrode)

Claims (7)

A substrate,
A movable member that includes a flat plate member that rotates and displaces a beam body installed on the substrate as a rotation axis, and the upper surface of the flat plate member functions as an optically reflective mirror part ;
A pair of movable electrodes provided at positions symmetrical to the rotation axis of the flat plate member ;
A fixed electrode that is disposed outside a trajectory range in which the movable member is mechanically displaceable, and that drives the movable member to move in cooperation with the movable electrode by applying a voltage;
The movable electrode is provided with a first opposing conductive surface extending in the direction of rotational displacement of the movable member, and the fixed electrode is opposed to the first opposing conductive surface when the movable member is rotationally displaced. A second opposing conductive surface that increases the electrostatic attractive force generated on the first opposing conductive surface is provided , and the first opposing conductive surface and the second opposing conductive surface are parallel to the rotation axis. A light modulation element characterized in that the light modulation element. 2. The light modulation element according to claim 1 , wherein both the first opposing conductive surface and the second opposing conductive surface are flat surfaces. The first opposing conductive surface and the second opposing conductive surface are both curved surfaces that are curved along the rotation direction of the movable member, and the second opposing conductive surface is composed of a pair of conductive portions, The light modulation element according to claim 1 , wherein the conductive portions are arranged side by side in the rotation direction of the movable member. The light modulation element according to any one of claims 1 to 3 , wherein an auxiliary electrode for applying an electrostatic force to the movable electrode is provided on the substrate. Wherein the substrate, the optical modulation device according to claim 1, any one of 3, characterized in that adjustable shield electrode is provided on the movable electrode at the same potential. A plate member that includes a substrate, a flat plate member that pivots and displaces with a beam mounted on the substrate as a rotation axis, a movable member whose upper surface functions as an optically reflective mirror portion, and the rotation of the flat plate member. A pair of movable electrodes provided at positions symmetrical to the moving axis, and the movable member are disposed outside the trajectory range in which the movable member can be mechanically displaced, and the movable member is displaced in cooperation with the movable electrode by applying a voltage. A fixed electrode to be driven,
The movable electrode is provided with a first opposing conductive surface extending in the direction of rotational displacement of the movable member, and the fixed electrode is opposed to the first opposing conductive surface when the movable member is rotationally displaced. A second opposing conductive surface that increases the electrostatic attractive force generated on the first opposing conductive surface is provided , and the first opposing conductive surface and the second opposing conductive surface are parallel to the rotation axis. Actuator characterized by being a surface to perform. A plate member that includes a substrate, a flat plate member that pivots and displaces with a beam mounted on the substrate as a rotation axis, a movable member whose upper surface functions as an optically reflective mirror portion, and the rotation of the flat plate member. A pair of movable members symmetric with respect to the moving axis, a pair of movable electrodes symmetric with respect to the rotational axis of the flat plate member, and an out of orbit range where the movable member can be mechanically displaced. A fixed electrode that is disposed and cooperates with the movable electrode by voltage application to drive the movable member to be rotationally displaced , and the fixed electrode has the first opposing conductive surface when the movable member is rotationally displaced. A second opposing conductive surface facing the actuator, wherein the first opposing conductive surface and the second opposing conductive surface are surfaces parallel to the rotation axis ,
When the displacement drive of the movable member, acting between them so as to face with said first opposing conductive surface and the second opposing conductive surfaces which extend in the direction of displacement of the movable member to the movable electrode An actuator driving method characterized by increasing an electrostatic attraction force.

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