JP2002055287A - Electrostatic actuator, optical switching element and video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic actuator which has a two-layered structure and is low in driving voltage. SOLUTION: This electrostatic actuator is provided with a drive beam 40 for supporting an optical element 3 at one end. A fulcrum 41 in mid-way of this drive beam 40 is supported to a substrate 20 and both ends 42 and 43 of the drive beam 40 are provided with a first drive means 61 and a second drive means 62 to electrostatically drive the drive beam 40. A gap G1 or G2 of upper and lower electrodes 7a, 7b, 8a and 8b may be reduced to about half to a moving distance D of the optical element 3 and therefore the drastic reduction of the driving voltage is made possible. Accordingly, the driving with the suitable voltage is made possible even if the effective area of the electrodes is made smaller. The video display device 80 which is compact and has high resolution may be provided by using this optical switching element 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to optical communication, optical operation,
The present invention relates to an optical switching element suitable for an optical storage device, an optical printer, an image display device, and the like, an electrostatic actuator thereof, and an image display device using the same.

[0002]

2. Description of the Related Art In recent years, the size of video projectors such as data projectors and video projectors has been further reduced, and the size of video devices has been extremely reduced. For this reason, a high-resolution and small-sized video display device is required. Similarly, optical communication devices, optical operations, optical recording devices such as hologram memories, optical printers, and the like also require a small-sized image display device capable of high-speed operation with high resolution.

[0003]

FIG. 5 shows an outline of a video display device (video display device) which modulates light using an evanescent wave (evanescent light) which is being developed by the present applicant. . This image display device 90 is a device in which a plurality of optical switching elements (optical switching mechanisms) 10 are two-dimensionally arranged. Each optical switching element 10 can transmit the introduced light 2 by total reflection. The optical device 3 includes an optical element 3 that can modulate light while approaching and moving away from the light guide plate (light guide) 1, and an actuator 96 that drives the optical element 3. Then, optical elements (micro-optical elements) and actuators (micro-actuators) are manufactured in micron order or submicron order, and these are arranged two-dimensionally in an array, and the layer of the optical element 3 and the layer of the actuator 96 are formed. A semiconductor substrate 2 on which a drive circuit for driving an actuator and a digital storage circuit (storage unit) are built.
By stacking them on 0, it is possible to provide a device in which one video display device is integrated in a chip size.

[0004] The image display device 90 of the present example using evanescent light will be described in more detail. The optical switching element 10a shown on the left side of FIG. 5 is in an on state, and the optical switching element 10b shown on the right side is in an off state. The optical element 3 has a surface (contact surface or extraction surface) 3a that is in close contact with the surface (total reflection surface) 1a of the light guide plate 1 (light guide) that functions as a waveguide, and this surface 3a is the total reflection surface 1a. An evanescent wave that leaks out when closely contacted is extracted and internally reflected in a direction substantially perpendicular to the light guide plate 1.
-Shaped reflection prism (micro prism) 4 and this V
And a support structure 5 for supporting the U-shaped prism 4.

The actuator 96 is capable of electrostatically driving the optical element 3. The upper electrode 7 to which the support structure 5 of the optical element 3 is mechanically connected and the lower electrode 8 opposed to the upper electrode 7. And And the lower electrode 8
The anchor plate 9 of the upper electrode 7 is laminated on the uppermost surface 20 a of the semiconductor substrate 20. The upper electrode 7 is supported by columns 11 extending upward from the anchor plate 9, and a space is formed between the lower electrode 8 and the upper electrode 7. Therefore, for example, the upper electrode 7 is grounded via the anchor plate 9 and the drive unit 21 is connected to the lower electrode 8.
When an electric potential or electric charge is applied from above, the upper electrode 7 moves downward, and the optical element 3 moves away from the light guide plate 1 in conjunction with this (second position). On the other hand, the upper electrode 7 partially has a function as an elastic member.
When the potential or charge applied from the substrate is removed or released, the upper electrode 7 separates from the lower electrode 8 and the optical element 3 adheres to the light guide plate 1 by the elasticity of the upper electrode 7 (first position). ).

As shown in FIG. 5, illumination light 2 is supplied to the light guide plate 1 from a light source at an angle at which the illumination light 2 is totally reflected by the total reflection surface 1a. Light is repeatedly totally reflected on the side 1a facing the light switching portion 3 and on the upper surface (emission surface), and the inside of the light guide plate 1 is filled with light rays. Therefore, in this state, the illumination light 2 is macroscopically confined inside the light guide plate 1 and propagates therein without any loss. On the other hand, microscopically, in the vicinity of the surface 1a of the light guide plate 1 which is totally reflected, the illumination light 2 leaks once from the light guide plate 1 for a very small distance of about the wavelength of light, and changes its course. The phenomenon of returning to the inside of the light guide plate 1 again occurs. The light leaked from the surface 1a in this manner is generally called an evanescent wave. This evanescent wave
It can be taken out by bringing another optical member close to the total reflection surface 1a at a distance of about the wavelength of light or less. The optical switching element 10 of the present embodiment utilizes this phenomenon to modulate light transmitted through the light guide plate 1 at high speed, that is, to perform switching (on / off).

Therefore, in the optical switching element 10a, since the optical element 3 is at the first position in contact with the total reflection surface 1a of the light guide plate 1, evanescent waves can be extracted by the surface 3a of the optical element 3. For this reason, the light 2 extracted by the microprism 4 of the optical element 3 is changed in angle and becomes the output light 2a. On the other hand, the optical switching element 10
In b, voltages having different polarities are applied to the upper and lower electrodes 7 and 8 by the drive unit 21, and these electrodes 7 and 8 are applied.
The optical element 3 is moved to the second position apart from the light guide plate 1 by the electrostatic force acting during the period. Therefore, the evanescent wave is not extracted by the optical element 3, and the light 2 does not exit from the inside of the light guide plate 1.

An optical switching element using an evanescent wave functions as a device that can switch light by itself, but as shown in FIG. 5, they are arranged in one-dimensional or two-dimensional direction, and furthermore, arranged in three-dimensional. It is configured to be able to. In particular, by arranging them two-dimensionally in a matrix or array, it is possible to provide a video display device 90 capable of displaying a planar image in the same manner as a liquid crystal or DMD. In the image display device 90 using the evanescent light, since the moving distance of the optical element 3 is on the order of submicron, it can be used as a light modulator having a response speed one digit or more faster than that of the liquid crystal.
It is possible to provide a projector or a direct-view video display device using this. Further, the optical switching element 10 using evanescent light can turn on and off the light by almost 100% with a movement on the order of submicrons, and can express an image with a very high contrast. Therefore, it is easy to increase the temporal resolution, and a high-contrast image display device can be provided.

It is required that the image display device be reduced in size, further increased in resolution, and reduced in power consumption. For example, a high-resolution liquid crystal panel (LC
If the size is reduced to the same extent as D), the size per pixel (pixel pitch), which is a unit constituting the screen, becomes smaller,
For example, it is subdivided to a pitch of about 14 microns.
Therefore, in the device (video display device) 90 using the electrostatic actuator 96, the effective area of the electrodes constituting the electrostatic actuator 96 also becomes small. As the effective area S of the electrode (the area where the upper electrode and the lower electrode overlap) S decreases, the drive voltage Ve increases. That is, as shown in FIG. 6, as the pixel pitch becomes smaller, the area occupied by the actuator per pixel becomes smaller, and in order to secure the spring elasticity, the area occupied by the spring 97 supporting the upper electrode 7 is increased. Is relatively large. Therefore, the electrode area is reduced, and a sufficient driving force cannot be obtained unless the driving voltage is increased.

Actuator 96 driven by electrostatic force Fs
Then, the drive voltage Ve, the effective area S of the electrode, and the displacement x of the spring
The following equation (1) is established between. The moving distance to the first and second positions shown in FIG. 5 is d,
The difference between the moving distance and the displacement x of the spring is the gap G between the electrodes. In particular, the voltage generated when no voltage is applied to the electrode, that is, when the displacement x is 0, is the maximum value of the drive voltage. Fs is a proportionality constant.

Ve = Fs × (d−x) ² / S = Fs × G ² / S (1) As can be seen from the equation (1), when the effective area S of the electrode becomes small, it becomes inversely proportional thereto. As a result, the driving voltage Ve increases.

In order to suppress the rise of the drive voltage Ve, it is conceivable to lower the spring elasticity and decrease the proportionality constant Fs. One is a method of increasing the length of the spring. When the length of the spring is increased, the electrode area is reduced in a limited area, and when the occupied area of the actuator is reduced,
Further, the electrode area is reduced. Therefore, the drive voltage Ve cannot be reduced. On the other hand, it is possible to reduce the spring elasticity by reducing the width of the spring.However, when the actuator is to be miniaturized, further narrowing the width of the spring exceeds the limit of the minimum width that can be manufactured. This makes production difficult.

Therefore, the most effective means for lowering the drive voltage Ve is to reduce the gap G between the electrodes. However, if the moving distance d of the switching element is reduced in order to reduce the gap G, it is difficult to obtain the contrast by turning on and off the light. Therefore,
The gap G cannot simply be reduced. When a stopper is provided to avoid contact between the electrodes, the gap G tends to widen as shown in the following equation (2) when the height is m. Therefore, it is not easy to reduce the drive voltage Ve by reducing the gap G.

G = d + m (2) However, the electrodes of the electrodes, that is, the lower electrode (fixed), the intermediate electrode (movable) and the upper electrode (fixed) are sequentially stacked, and the voltage is applied to the upper electrode and the lower electrode. Are alternately added, and the intermediate electrode is moved up and down, the gap G between the electrodes can be reduced to about half while the moving distance d of the switching element is secured, and the driving voltage Ve can be reduced. It is possible.

However, in the electrostatic actuator provided with these three electrodes, the number of structural layers is increased by one, and in order to form this one layer, the number of manufacturing steps is increased by about five. First, a step (deposition) of forming a sacrificial layer on the second structural layer, a step of patterning the sacrificial layer, a third step of forming a stopper structure of the upper electrode, First, a step (deposition) of forming a structural layer constituting the upper electrode and fifth, a step of patterning the structural layer are required. As described above, in order to form an electrode having a three-layer structure, the labor is greatly increased, and the yield is significantly reduced accordingly. For this reason, the manufacturing cost increases, which is not practical.

Accordingly, an object of the present invention is to provide an electrostatic actuator having a two-layer structure and capable of lowering a driving voltage. It is still another object of the present invention to provide a compact power saving type optical switching element using such an electrostatic actuator, and to further provide a small, high resolution, and low power consumption video display device. .

[0017]

For this reason, in the present invention, a drive beam for supporting a switching portion at one end is provided, electrodes are provided at both ends of the drive beam, and an actuator structure for moving the electrodes mutually is provided. Thus, an electrostatic actuator having a small gap between electrodes (gap) and a low driving voltage can be realized with a two-layer structure.

That is, the electrostatic actuator of the present invention that drives the switching portion that can move to the first position and the second position that is distant from the first position has the following structure. Extending in a direction substantially perpendicular to the direction,
A driving beam supporting the switching unit at one end, a first driving unit driving one end of the driving beam,
Second driving means for driving the other end of the driving beam, wherein the first driving means includes a first electrode provided at or near one end of the driving beam, and the first electrode A second electrode provided on the substrate at a position opposed to the third electrode. The second driving means includes a third electrode provided at or near the other end of the driving beam, and a third electrode provided at the other end. And a fourth electrode provided on the substrate at a position opposed to the first electrode. Further, the fourth electrode is provided so that the drive beam can rotate in the directions of the first position and the second position. And a support portion that supports the substrate with the middle point as a fulcrum.

In the electrostatic actuator of the present invention, a driving beam for supporting the switching portion at one end is provided, and the switching portion is supported rotatably by the supporting portion. The first provided
The driving beam moves like a seesaw by mutually driving the second driving unit and the second driving unit, and the switching unit can be moved to the first position and the second position. Accordingly, based on the intermediate state (intermediate position) of the stable posture of the drive beam, the distance (displacement) by which the first and second drive means drives the drive beam is determined by the first and second distances at which the switching unit moves. About half of the distance (displacement) of the position. Therefore, the distance between the electrodes constituting the first and second driving means, that is, the distance (gap) between the first and second electrodes and the third and fourth electrodes is determined by the displacement of the switching unit. It can be reduced to half or less. Further, since the electrodes forming the first and second driving means are the first and second electrodes and the third and fourth electrodes, respectively, the electrostatic actuator of the present invention is realized with a two-layer structure. it can. For this reason, a state in which the driving voltage can be reduced similarly to the three-layered actuator having the above-described intermediate electrode can be realized by a two-layered structure which can be manufactured with high yield and low cost by using the current technology.

Therefore, by using the electrostatic actuator of the present invention, an optical switching element having a switching portion supported at one end of the driving beam and turning on and off light at the first position and the second position is provided. An optical switching element with a small driving voltage can be provided. For this reason, the optical switching element can be miniaturized, the occupied area can be reduced, and the optical switching element can be operated at a low voltage without increasing the drive voltage even if the electrode area is reduced.

Therefore, by arranging such optical switching elements in an array, it is possible to provide an image display device that requires a high resolution and a fine structure and can be driven at a low voltage. A small, high-resolution video display device that can be driven at low voltage has low power consumption and
It can be directly driven by a semiconductor integrated circuit device operating at a low voltage such as a CMOS circuit, and the degree of integration including the drive circuit can be increased. Therefore, a small-sized video device with low power consumption can be provided.

The support can also be connected directly to the drive beam. However, by providing an elastic support beam extending in a direction orthogonal to the drive beam and a column supporting both ends of the support beam from the substrate, the support beam exerting the spring elasticity can be made thinner and longer, and the elastic coefficient is increased. Can be reduced. Accordingly, the spring elastic force for moving the drive beam to the intermediate position, which is a force opposing the first and second drive units, which are electrostatic drive units, can be reduced, so that the voltage for driving the drive beam can be further reduced. it can.

The drive beam may have the same (symmetrical) distance from a fulcrum provided in the middle to both ends. However, the distance between one end to which the switching unit is connected and the fulcrum is given by:
It is desirable that the distance between the other end where the second driving means for driving the switching unit to the first position is provided and the fulcrum is short. This makes it possible to reduce the displacement of the other end driven by the second drive means with respect to the displacement of the switching unit, so that the distance between the third and fourth electrodes constituting the second drive means can be further reduced. . Therefore, the driving voltage for driving the second driving means can be further reduced.

Further, the drive beam is formed with a recess along the longitudinal direction, so that the drive beam is partially provided with rigidity to obtain strength. Therefore, durability can be improved and a highly reliable electrostatic actuator can be provided.

Furthermore, in the optical switching element, it is desirable that the attitude of the switching unit be kept parallel at the first position which is the ON position. In particular, as in an optical switching element that turns on and off the evanescent light, the switching unit includes an optical element that can change the direction of light emitted from the light introduction unit by contacting the bottom surface of the light introduction unit at the first position. In such a case, it is desirable that the optical element be in close contact with the bottom surface of the light introducing section. For this purpose, it is desirable that the drive beam has high rigidity, and it is desirable that the drive beam be formed with a depression along the longitudinal direction so as not to bend. The depression is desirably formed so as to be convex in the direction of the second electrode, and can have a function as a stopper for preventing the first electrode from adhering to the second electrode.
Further, when a stopper is provided so that the fourth electrode does not adhere to the third electrode, the depression of the drive beam can be formed in the step of forming the stopper, so that the manufacturing can be easily performed without increasing the number of steps. Even if the drive beam is provided with a depression to increase rigidity, the spring elasticity can be secured by the support beam of the support portion.

Further, it is desirable that the connecting portion between the driving beam and the first electrode and / or the third electrode is formed more flexibly than other portions of the driving beam. This allows
When the drive beam turns upward or downward, the drive beam turns around the fulcrum, while the electrodes connected to both ends of the drive beam deform so as to face the opposing electrode, and the effective area of the electrode Can be secured. Also, when the optical element of the switching unit placed on the electrode contacts the bottom surface of the light introducing unit, along the bottom surface,
Or adhere closely. Therefore, it is possible to increase the efficiency of extracting light from the bottom surface of the light introducing portion to the optical element, and to increase the efficiency of using light. Therefore, it is possible to provide a bright optical switching element having a large contrast and a video display device using the same.

In the optical switching element, it is desirable that a connecting portion between the switching unit and the drive beam is provided at a position close to the center of gravity of the switching unit. By supporting the center of gravity of the optical switching unit with the driving beam, the switching unit can be moved in a well-balanced manner, the optical elements can be moved in parallel, and the optical element of the switching unit supported by the driving beam can be moved. When it comes into contact with the bottom surface of the light introducing section, it is easy to adhere along or following the bottom surface. Therefore, it is possible to increase the efficiency of extracting light from the bottom surface of the light introducing portion to the optical element, and to increase the efficiency of using light. Therefore, it is possible to provide a bright optical switching element having a large contrast and a video display device using the same.

Further, in the electrostatic actuator of the present invention, when no voltage is applied to each electrode, that is, when there is no potential difference between the electrodes and the electrodes are maintained at the same potential, both ends of the drive beam are connected to these electrodes. Is in the middle position. Therefore, the switching unit is not at the first position, which is the ON position, but at an intermediate position between the first and second positions. Therefore, in the video display device using the optical switching element of the present invention, the screen is erased without applying the driving voltage, and it is not necessary to forcibly apply the voltage for erasing the image.

[0029]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be further described below with reference to the drawings. FIG. 1 shows an outline of an image display device 80 for modulating light using an evanescent wave (evanescent light) according to the present invention. This video display device 80
Similar to the image display device described with reference to FIG. 5, a light guide plate (light guide) capable of totally transmitting the introduced light 2 and transmitting the light.
The optical switching device 10 includes an optical element 3 capable of extracting evanescent light by approaching and moving away from the total reflection surface 1a of the first optical element 1 and an optical switching element 10 on which an electrostatic actuator 6 for driving the optical element 3 is stacked. The elements are arranged two-dimensionally. The optical element 3 serving as a switching section is moved by the electrostatic actuator 6 to a first position in close contact with the total reflection surface 1a of the light guide 1 as shown by a switching element 10a on the left side of FIG. Reflective surface 1a
An evanescent wave is extracted from the surface (contact surface or extraction surface) 3a which is in close contact with the surface. The optical element 3 of the present example also includes a V-shaped reflecting prism (microprism) 4 that reflects the extracted light in a direction substantially perpendicular to the light guide plate 1, and changes the direction of light propagating through the light guide 1. And output as outgoing light 2a.

On the other hand, the optical element 3 is
When the light guide 1 is moved to a second position away from the total reflection surface 1a of the light guide 1 as shown in the right switching element 10b of FIG.
The light is totally reflected at a and is not extracted outside. As described above, the optical switching element 1 constituting the video display device 80 of the present embodiment
0 also moves in the same manner as the above-described optical switching element when the optical element 3 is driven by the actuator 6.
Therefore, similarly to the above-described image display device, evanescent light is extracted by the optical switching element, and an image can be displayed using light propagating inside the light guide 1.

The electrostatic actuator 6 of this embodiment is an actuator that moves like a seesaw as a whole, and the substrate 20 is moved in the direction perpendicular to the direction in which the optical element 3 moves up and down, that is, in the first and second directions. Or total reflection surface 1a
And a drive beam 40 extending substantially in parallel with. The drive beam 40 is rotatably supported by the support unit 50 on the substrate 20 with the middle as a fulcrum 41, and the optical element 3, which is a switching unit, at one end (left side in the drawing) 42 via the support unit 5. You can turn while supporting. An upper electrode 7a serving as a first electrode is formed at one end 42 of the drive beam 40, and a lower electrode 8a serving as a second electrode is disposed on the upper surface of the substrate 20 facing the upper electrode 7a. Therefore, the first drive means 61 for driving the one end 42 of the drive beam 40 by pairing the upper electrode 7a and the lower electrode 8a constitutes.

On the other hand, an upper electrode 7b serving as a third electrode is also formed at the other end 43 of the drive beam 40, and a lower electrode 8b serving as a fourth electrode is disposed on the upper surface of the substrate 20 facing the upper electrode 7b. ing. Therefore, the upper electrode 7b and the lower electrode 8b are paired to form a second driving means 62 for driving the other end 43 of the driving beam 40.

FIG. 2 schematically shows the optical switching elements 10 constituting the video display device 80 viewed from above in order to sequentially explain the structure thereof. In the upper row,
FIG. 6 shows a state in which the optical element 3 is arranged. In the middle part, a structure of a second layer including a drive beam 40 located below the optical element 3, a support beam 51 constituting the support unit 50, and upper electrodes 7a and 7b. Are indicated by hatching. Further, in the lower part, the lower electrodes 8a and 8b arranged below them, that is, the lower electrodes 8a and 8b arranged on the substrate 20 are indicated by hatching.

FIG. 3 shows the structure of the second layer having the drive beam 40, the support beam 51 and the upper electrodes 7a and 7b in an enlarged manner. In FIG. It is shown by a cross section along the drive beam 40. Hereinafter, further description will be made with reference to these drawings.

The driving beam 40, the supporting beam 51 constituting the supporting portion 50, and the second having the upper electrodes 7a and 7b
The layer is formed of a conductive thin film material which can obtain appropriate elasticity with a thin film, for example, an Al film or the like. The support portion 50 supporting the drive beam 40 includes an elastic support beam 51 extending from the fulcrum 41 of the drive beam 40 in a direction perpendicular to the drive beam 40 in parallel with the substrate 20, and both ends 51 a of the support beam 51. And supporting columns (posts) 11 extending upward to support the substrate 20 from the substrate 20. This pillar 1
1 is further connected to the anchor plate 9 laminated on the uppermost surface of the semiconductor substrate 20, and has a configuration capable of holding the drive beam 40 with sufficient strength to the substrate 20. The support beam 51 is a portion that provides spring elasticity for holding the drive beam 40 at an intermediate position, and does not cause much resistance to the first and second drive units 61 and 62. Further, it is designed such that an elastic force capable of obtaining a force enough to hold the drive beam 40 at the intermediate position can be exerted. Further, a second driving circuit 21 formed on the semiconductor substrate 20 via the anchor plate 9
The potential of the layer can be set.

As shown in FIGS. 2 and 3, one end 42 of the drive beam 40 extends in a direction parallel to the substrate 20 and is substantially symmetrical left and right (up and down in the figure) about the drive beam 40. It serves as the upper electrode 7a of the first driving means 61 having a flat rectangular surface. The support structure 5 of the optical element 3 is connected to the upper electrode 7a in an area 44 indicated by a broken line. The connecting portion 46 between the drive beam 40 and the upper electrode 7a is narrowly narrowed and has a flexible shape, but the upper electrode 7a connected left and right from the connecting portion 46 almost reaches the support beam 51. An electrode which is wide and has a large area is formed.

On the other hand, the other end 43 of the drive beam 40 also
The driving beam 40 extends in a direction parallel to the substrate 20.
The upper electrode 7b of the second drive means 62 has a substantially flat rectangular surface formed symmetrically left and right (up and down in the figure) with the center as the center. The upper electrode 7b also extends almost until it reaches the support beam 51, and an electrode having a large area is formed. As described above, these upper electrodes 7a and 7b are connected to the support 11 via the support beam 51, and are all at the same potential.

At the other end 43 of the drive beam 40, a stopper 45 for preventing suction between the electrodes constituting the second drive means 62 is provided.
Are formed so as to protrude in the direction of the lower electrode 8b. Further, the drive beam 40 includes electrodes 7a and 7b
A recess 48 is formed along the longitudinal direction so as to increase the rigidity except for the connection parts 46 and 47 with the connection. The depression 48 is recessed so as to protrude toward the lower electrodes 8a and 8b, that is, toward the substrate 20, as shown in FIG. Are formed continuously along the longitudinal direction with the fulcrum 41 intersecting with the support beam 51 of the first embodiment. Since the depression 48 protrudes in the same direction as the stopper 45 formed at the other end 43, the depression 48 can be formed by the same process, and the depression 48 constitutes the first driving means 61. It also functions as a stopper to prevent suction between. The ends (both ends) 48a and 48 of the depression 48
b extends to a position before connecting portions 46 and 47 between the upper electrodes 7a and 7b and the drive beam 40, but the connecting portions 46 and 47 are not formed with a depression 48. Therefore, the connection portions 46 and 47 have a flexible structure, and the upper electrodes 7a and 7b can be moved in parallel with the substrate 20, and the extraction surface 3a of the optical element 3 can be brought into close contact with the total reflection surface 1a.

Therefore, the optical switching element 10 of the present embodiment has an appropriate voltage between the upper electrode 7b and the lower electrode 8b constituting the second driving means 62, as shown in the optical switching element 10a on the left side of FIG. Is applied to generate a potential difference, these electrodes attract each other and the right end (the other end) 43 of the drive beam 40 is lowered, pivots around the fulcrum 41, and moves to the left end (one end) 42 of the drive beam 40. The mounted optical element 3 rises and moves to the first position. And
When the upper surface (extraction surface) 3a of the microprism 4 of the optical element 3 comes into contact with the lower surface (total reflection surface) 1a of the light guide 1 so as to follow, the light 2 of the light guide 1 is extracted. The outgoing light 2a is output in the vertical direction and is turned on.

On the other hand, the optical switching element 1 on the right side of FIG.
As shown in FIG. 0b, when an appropriate voltage is applied between the upper electrode 7a and the lower electrode 8a constituting the first driving means 61 to generate a potential difference, these electrodes attract each other and one of the driving beams 40 End 42 descends and pivots about fulcrum 41, leaving the other end 43 of drive beam 40 apart. Then, the optical element 3 mounted on one end 42 moves down and moves to a second position below and away from the light guide 1. Therefore, since the extraction surface 3a of the optical element 3 is separated from the total reflection surface 1a, evanescent light cannot be extracted, and the light 2 of the light guide 1 is not emitted. Therefore, the optical switching element 1
0b is off.

Further, when no voltage is applied, that is, the upper electrode 7a and the lower electrode 8a forming the first driving means 61 are set to the same potential, and the upper electrode 7b and the lower electrode 8b forming the second driving means 62 are formed. Are the same potential, as shown in the optical switching element 10c in the center of FIG.
Does not work, and the elastic force of the support beam 51 causes the intermediate state to be substantially horizontal. Therefore, the driving beam 40
The extraction surface 3a of the optical element 3 mounted on one end 42 of the light guide 1 is located at a position distant from the total reflection surface 1a of the light guide 1, and the light 2 is hardly extracted from the light guide 1 and is almost off.

As described above, in the electrostatic actuator 6, the drive beam 40 turns around the fulcrum 41, and moves the optical element 3 as the switching unit in the directions of the first position and the second position in the vertical direction. It has a seesaw structure. Therefore, as shown in FIG.
That is, when the distance (movement amount) D between the first position and the second position is the movement amount d1 and the movement amount d2 of the first and second driving units 61 and 62 that drive the drive beam 40, Considering the intermediate state as a reference, it is about half of the movement amount D. That is, in the optical switching element shown in FIG. 5, the movement amount of the optical element portion and the movement amount of the actuator were almost equal, whereas in the actuator 6 of the present example, the movement amounts d1 and d2 were approximately half.
Thus, it is possible to move from the first position where it is turned on to the second position where it is turned off. Therefore, the gap (gap) G1 between the electrodes 7a and 8a constituting the first driving means 61 and the second
The distance (gap) G2 between the electrodes 7b and 8b constituting the driving means 62 can be reduced to almost half of the two-layered actuator shown in FIG.

Since the drive voltage Ve is proportional to the square of the gap G as described above with reference to the equation (1), the gap G is halved. The voltage Ve can be reduced to approximately 1/4. Therefore, the electrostatic actuator 6 of the present example can be driven with a drive voltage of about １ ／ of the conventional drive voltage.

Further, in the electrostatic actuator 6 of this embodiment, the position of the fulcrum 42 for supporting the drive beam 40 is determined by the distance L1 between one end 42 for supporting the optical element 3 and the fulcrum 41.
In contrast, the distance L2 between the fulcrum 41 for driving the optical element 3 in the ON direction and the other end 43 is reduced. That is, the distance L1 (left side in the figure) from the connection portion 46 of the upper electrode 7a of the drive beam 40 to the support beam 51 is smaller.
It is longer than the distance L2 from the connection portion 47 of the upper electrode 7b to the support beam 51. Therefore, when the second driving means 62 is displaced by the movement amount d2, the optical element 3 moves largely by L1 / L2 times. That is, the electrode 7 constituting the second driving means 62 with respect to the movement of the optical element 3
The gap G2 between b and 8b can be further reduced. Therefore, in the actuator 6 of this example, the optical element 3 can be driven with a drive voltage Ve that is １ ／ or less of that of the actuator shown in FIG.

The actual gap G1 between the electrodes 7a and 8a and the gap G2 between the electrodes 7b and 8b are as follows in consideration of the height m1 of the depression 48 of the drive beam 40 serving as a stopper and the height m2 of the stopper 45. And the following is given with respect to the movement amount D of the optical element 3.

D1 = G1-m1 d2 = G2-m2 D = d1 + (L1 / L2) × d2 (3) Since the gaps G1 and G2 are widened by the heights m1 and m2 of the stopper, the gaps G1 and G2 are actually increased. Gap G1 and G2
Is difficult to reduce to half or less than that of the conventional actuator, but it can be reduced to about half, and considering that the drive voltage Ve is proportional to the square of the gap G, Actuator 6
The effect of suppressing the drive voltage by adopting the method is very large. For example, while the drive voltage is about 20 V in the conventional two-layer actuator, the drive voltage Ve can be reduced to about 5 V in the actuator 6 of the present embodiment, and the drive voltage is set to about 5 V. CM
Since the level is the same as the drive voltage of the OS circuit, the CMOS
The first driving means 61 and the second driving means 6
2 can also be applied with a voltage.

Further, since the gap G is reduced and the drive voltage Ve can be reduced, the drive voltage Ve does not need to be increased even if the electrode area S is reduced, or the drive voltage Ve depends on the degree of reduction of the electrode area S. It is also possible to lower. Therefore, it is possible to provide the optical switching element 10 which is more compact and has a lower driving voltage than before. Further, in the video display device 80 using the optical switching element 10 of the present embodiment, the size of the optical switching element 10 can be reduced, so that a high-density and high-resolution image can be obtained. Can be provided. Further, since the driving voltage can be reduced, it is possible to directly drive from the CMOS circuit, and a driver circuit for applying a high voltage is not required.
The video display device integrated with the OS circuit can be formed very compact. Further, since the driving voltage is reduced, the power consumption is reduced, and it is not necessary to generate a high voltage for driving, so that the loss for that can be reduced.
Therefore, it is possible to provide a high-resolution video display device 80 which is compact with low power consumption.

As described above, an actuator capable of reducing the drive voltage by reducing the amount of movement from the intermediate position can be realized by providing an intermediate electrode driven between the upper and lower electrodes. However, as described above, the actuator of the three-layer structure provided with the intermediate electrode requires a very large number of steps, so that the yield is remarkably reduced, which is not practical. In contrast, the actuator 6 of the present example
Has the same two-layer structure as that of the related art, including upper electrodes 7a and 7b and lower electrodes 8a and 8b. Therefore, it is possible to manufacture low-cost, high-quality products without increasing the number of steps and without reducing the yield.

Further, the electrostatic actuator 6 of this embodiment employs several structures capable of securely extracting the evanescent light by bringing the optical element (switching portion) 3 into close contact with the light guide 1. First, the drive beam 40 is applied to the electrode 7a.
A recess 48 is formed so as to increase rigidity except for connection portions 46 and 47 to the connection portions 7 and 7b. Accordingly, when the other end 43 of the drive beam 40 is driven by the second drive means 62, the drive beam 40 is prevented from bending, and
Can be efficiently transmitted to one end 42 on which the optical element 3 is mounted. For this reason,
The extraction surface 3a of the optical element 3 can be pressed against the total reflection surface 1a with a sufficient force, and the light use efficiency can be improved.

As described above, the vicinity of the center of the drive beam 40, which is a beam, is reinforced, and the connection portions 46 and 47 to the electrodes 7a and 7b are not reinforced. . As shown in FIG. 1, the tips 42 and 43 of the drive beam 40 make a circular motion about the fulcrum 41, so that if they have a rigid structure, the electrodes 7a and 7b and the optical element 3 will be placed on the total reflection surface 1a or the substrate 20. Tilt and not parallel. Therefore, the electrodes 7a and 7b
In this case, a large gap is opened between the electrodes 8a and 8b facing each other. In particular, in the second driving means 62, a force for pressing the optical element 3 against the light guide 1 cannot be obtained. In the optical element 3, the light extraction surface 3 a and the total reflection surface 1 a
Since a does not adhere, the light extraction efficiency decreases, and the contrast decreases.

On the other hand, if the connecting portions 46 and 47 of the both ends 42 and 43 of the drive beam 40 are made relatively flexible so as to be easily bent, the electrodes 7a and 7b move closer to the opposing electrodes 8a and 8b. Parallel to the electrodes 8a and 8b, and can approach the minimum distance secured by the stopper. Therefore, a strong driving force can be obtained, and in particular, the second driving means 62
In, a sufficient force for pressing the optical element 3 against the light guide 1 can be obtained. Also, in the optical element 3, when the extraction surface 3a approaches the total reflection surface 1a, the extraction surface 3a
Is bent in such a manner that the surface becomes parallel to the total reflection surface 1a, and the extraction surface 3 closely adheres to the total reflection surface 1a. Therefore, the evanescent light can be efficiently extracted, the light use efficiency can be increased, and the optical switching element 10 and the image display device 80 with high contrast can be provided.

In particular, it is desirable to provide an appropriate interval H between the terminal end 48b of the depression 48 for increasing the rigidity of the drive beam 40 and the connection portion 47. By providing an appropriate interval H, when the upper electrode 7b approaches the lower electrode 8b and a certain or more force is generated by the second driving means 62, the portion of the interval H near the connection portion 47 bends, and When the electrode 7b and the lower electrode 8b try to be in a parallel state, the upper electrode 7a on the opposite side of the fulcrum 41 is largely pushed upward. Therefore, by bending the distance H between the connection portions 47 and turning the drive beam 40 largely, the optical element portion 3 is turned on at the first position which is the ON position.
Can be reliably brought into close contact with the bottom surface (total reflection surface) 1a of the light guide 1. Further, an appropriate interval H
Is set in advance, the drive beam 40 is turned on at the on position.
Of the light guide 1 and the substrate 20 can be sufficiently absorbed even when the dimensional tolerance between the light guide 1 and the substrate 20 is relatively large, and the extraction surface 3 can be secured.
a can be brought into close contact with the total reflection surface 1a.

Further, in this embodiment, the connecting portion 46 of the one end 42 of the drive beam 40 supporting the optical element 3 and the upper electrode 7a is connected to the center of gravity 3g of the optical element 3 as a switching section.
And very close to the center of gravity 3g on the vertical line. Therefore, the optical element 3 can be moved by the drive beam 40 while maintaining the balance. For this reason, the extraction surface 3a of the optical element 3 becomes the total reflection surface 1a.
The optical element 3 can be smoothly brought into close contact with the light guide 1 without being unnecessarily tilted when it comes into contact with the light guide 1. As described above, in the electrostatic actuator 6 of the present embodiment, the optical element 3 driven thereby is brought into close contact with the light guide 1 so that the light 2 can be emitted efficiently. Therefore, it is possible to provide the light switching element 10 and the image display device 80 that have high light use efficiency, are bright, and have high contrast.

Further, as shown by the optical switching element 10c in the center of FIG. 1, the electrostatic actuator 6 of this embodiment is supported when no voltage is applied to the first driving means 61 and the second driving means 62. Due to the elasticity of the beam 51, the drive beam 40 is maintained in a substantially horizontal intermediate state. Therefore, the optical element 3 is located at a position distant from the first position where light is output to be in the ON state. Therefore, the image display device 8
At 0, when erasing the screen, the voltages of the optical switching elements 10 constituting all the pixels may be simply turned off. On the other hand, in the video display device 50 using the actuator shown in FIG. 5, it is necessary to apply a voltage for erasing the screen to forcibly separate the optical element 3 from the light guide 1. Therefore, the video display device 80 using the optical switching element 10 of the present invention does not need to supply power when the video display device is in the off state where no video is displayed, and power can be saved also in this regard.

[0055]

As described above, in the electrostatic actuator of the present invention, the switching section is supported at one end of the drive beam rotating around the fulcrum, and both ends of the drive beam are first and second. It is electrostatically driven by the driving means. Therefore, the amount of movement of the switching unit
In addition, the distance between the electrodes constituting the second driving means can be reduced to about half. For this reason, it is possible to reduce the voltage for driving the first and second driving means to about 1/4, to drive the electrostatic actuator with low voltage and low power consumption, an optical switching element using the same, and Can provide a video display device. further,
The electrostatic actuator of the present invention has a two-layer structure because the first and second driving means can be constituted by a combination of upper and lower electrodes. Therefore, unlike a three-layer structure in which an intermediate electrode is arranged between upper and lower electrodes, the number of manufacturing steps is small, and manufacturing can be performed with a sufficiently high yield. Therefore, the present invention can provide an electrostatic actuator that can be mass-produced and that can be driven at a low voltage. Since the driving voltage can be greatly reduced by this electrostatic actuator, the electrode area can be reduced, and the optical switching element for turning on and off light using evanescent light can be compactly driven at low voltage. Furthermore, a high-contrast, high-resolution and compact video display device using evanescent light can be actually provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an outline of a video display device provided with an optical switching element using evanescent light using an electrostatic actuator according to the present invention.

FIG. 2 is a plan view showing the configuration of each layer constituting the optical switching element and the electrostatic actuator in order to explain the configuration of the electrostatic actuator and the optical switching element shown in FIG. 1;

FIG. 3 is a view showing a structure of a second layer constituting the electrostatic actuator shown in FIG. 2;

FIG. 4 is a view of the electrostatic actuator shown in FIG. 3 cut along a cross section along a drive beam.

FIG. 5 is a diagram schematically illustrating an image display device including an optical switching element using evanescent light.

FIG. 6 is a diagram schematically showing a state where the electrostatic actuator shown in FIG. 5 is viewed from a substrate side.

[Explanation of symbols]

 Reference Signs List 1 light guide plate (light guide) 2 incident light 3 optical element (switching part) 4 microprism 5 support 6, 96 electrostatic actuator 7a first electrode (upper electrode) 7b third electrode (upper electrode) 8a second Electrode (lower electrode) 8b Fourth electrode (lower electrode) 10 Optical switching element 11 Post (post) 20 Semiconductor substrate 40 Drive beam 41 Support point 42 One end of drive beam 43 The other end of drive beam 44 Connection part with switching part (Area) 45 Stopper 46, 47 Connection part 48 Depression 50 Support part 51 Support beam 61 First drive means 62 Second drive means 80 Image display device

Claims (15)

[Claims] 1. An electrostatic actuator for driving a switching portion movable to a first position and a second position distant from the first position, the electrostatic actuator comprising: A drive beam extending in a direction substantially perpendicular to the direction and supporting the switching unit at one end; a first drive unit for driving the one end of the drive beam; and a second drive unit for driving the other end of the drive beam. A second driving unit for driving, the first driving unit includes a first electrode provided at or near one end of the driving beam, and a first electrode provided at a position facing the first electrode. A second electrode provided on a substrate, wherein the second drive means includes a third electrode provided at or near the other end of the drive beam, and the third electrode A second substrate provided on the substrate at a position facing the second substrate; And a supporting portion that supports the substrate with the drive beam at a midpoint as a fulcrum so that the drive beam can pivot in the directions of the first position and the second position. An electrostatic actuator having: 2. The static electricity storage device according to claim 1, wherein the support portion includes an elastic support beam extending in a direction perpendicular to the drive beam, and a column supporting both ends of the support beam from the substrate. Electric actuator. 3. The driving beam according to claim 1, wherein
An electrostatic actuator wherein the distance between the fulcrum and the other end is shorter than the distance between the one end and the fulcrum. 4. The electrostatic actuator according to claim 1, wherein the drive beam has a depression formed in the direction of the second electrode along a longitudinal direction thereof. 5. The electrostatic actuator according to claim 1, wherein a connecting portion between the first electrode and / or the third electrode and the driving beam is more flexible than other portions of the driving beam. 6. The electrostatic actuator according to claim 1, further comprising: a switching unit supported at one end of the drive beam, wherein the switching unit is configured to emit light at the first position and the second position. An optical switching element that can be turned on and off. 7. The switching unit according to claim 6, wherein the switching unit includes an optical element that can change a direction of light emitted from the light introduction unit by contacting a bottom surface of the light introduction unit at the first position. Optical switching element. 8. The optical switching element according to claim 6, wherein the first electrode of the first driving means moves integrally with the switching section. 9. The light according to claim 6, wherein the support portion includes an elastic support beam extending in a direction orthogonal to the drive beam, and a support for supporting both ends of the support beam from the substrate. Switching element. 10. The optical switching element according to claim 6, wherein a distance between the fulcrum and the other end is shorter than a distance between the one end and the fulcrum. 11. The optical switching element according to claim 6, wherein the driving beam has a depression formed in the direction of the second electrode along a longitudinal direction thereof. 12. The optical switching element according to claim 6, wherein a connection portion between the first electrode and / or the third electrode and the drive beam is more flexible than another portion of the drive beam. 13. The optical switching element according to claim 6, wherein a connection portion between the switching unit and the drive beam is located near a center of gravity of the switching unit. 14. The optical switching element according to claim 6, wherein when no voltage is applied to the electrode, the switching unit is located farther from the bottom surface. 15. An image display device in which the optical switching elements according to claim 6 are arranged in an array.