JP2008044068A - Actuator, optical device, optical scanner, and image formation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator, an optical device, an optical scanner, and an image formation device, which are comparatively simply and accurately driven under a desired condition. <P>SOLUTION: In the actuator 1, a voltage is applied between stationary electrodes 31, 32 and movable electrodes 41, 42, so as to generate an electrostatic attraction between them. While a beam part 43 is deformed, the movable electrodes 41, 42 are displaced in a longitudinal direction of electrode fingers 411, 422. At least one of a plurality of electrode fingers 311, 321, 411, 421 of the stationary electrodes 31, 32 and/or the movable electrodes 41, 42 has a portion whose width is gradually reduced from its tip side to a base end. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an actuator, an optical device, an optical scanner, and an image forming apparatus.

In recent years, an actuator has been proposed in which a structure for generating vibration is formed on a base portion made of silicon by a micromachining technique using a semiconductor manufacturing process (see, for example, Patent Document 1).
Conventionally, as such an actuator, for example, as disclosed in Patent Document 1, a fixed electrode fixed to a substrate, and a movable electrode supported on the substrate via an elastic portion constituted by a plurality of beams And applying an electric voltage between them to generate an electrostatic attractive force between the movable electrode and the fixed electrode, thereby displacing the movable electrode while deforming the elastic portion.

In such an actuator, each of the movable electrode and the fixed electrode has a comb shape, and is arranged so as to mesh with each other. Each of the movable electrode and the fixed electrode has a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the movable electrode is displaced in the longitudinal direction of the electrode fingers. Conventionally, each electrode finger of the movable electrode and the fixed electrode has a certain width over the entire region in the longitudinal direction. For this reason, as the amount of meshing between the movable electrode and the fixed electrode increases with the displacement of the movable electrode, the electrostatic attractive force generated between the movable electrode and the fixed electrode rapidly increases.
For this reason, when the driving voltage is relatively large, the displacement amount of the movable electrode becomes extremely large even if the driving voltage is slightly changed. Therefore, it is difficult to accurately displace the movable electrode by a desired amount. There is also a problem that the configuration of the drive circuit is complicated.

Japanese Patent Laid-Open No. 11-190635

  An object of the present invention is to provide an actuator, an optical device, an optical scanner, and an image forming apparatus that can be driven in a desired state relatively easily and with high accuracy.

Such an object is achieved by the present invention described below.
The actuator of the present invention includes a base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic part that movably supports the movable electrode with respect to the base part,
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the movable electrode is displaced in the longitudinal direction of the electrode finger while deforming the elastic portion. An actuator configured as follows:
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode It is characterized by increasing the distance.
Thereby, the raise of the ratio of the displacement amount of the movable electrode with respect to the voltage applied between a movable electrode and a fixed electrode can be suppressed. Therefore, even when the voltage applied between the movable electrode and the fixed electrode is relatively large, fine adjustment of the displacement amount of the movable electrode by changing the voltage is facilitated, and the movable electrode is relatively simple and highly accurate. The amount of displacement can be made as desired.

In the actuator of the present invention, the fixed electrode and the movable electrode are formed so that a ratio of a displacement amount of the movable electrode to a voltage applied between the fixed electrode and the movable electrode is substantially constant. Is preferred.
Thereby, the structure of the drive circuit for applying a voltage between a movable electrode and a fixed electrode can be simplified.

In the actuator of the present invention, the electrode finger on one of the fixed electrode and the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the electrode finger on the other side is in the longitudinal direction. It is preferable to have a constant width over almost the entire area.
Thereby, the design of one of the movable electrode and the fixed electrode can be simplified. As a result, the actuator design can be simplified.

In the actuator according to the present invention, the electrode finger in the fixed electrode has a portion in which the width gradually decreases from the distal end side toward the proximal end side, and the electrode finger in the movable electrode is constant over almost the entire region in the longitudinal direction. It preferably has a width.
Thereby, the design of the movable electrode can be simplified. As a result, the actuator design can be simplified.

In the actuator according to the aspect of the invention, it is preferable that the electrode finger in at least one of the fixed electrode and the movable electrode has a portion in which the width gradually decreases from the distal end side toward the proximal end side.
Thereby, a movable electrode can be displaced smoothly.
In the actuator of the present invention, it is preferable that the electrode fingers in at least one of the fixed electrode and the movable electrode have a portion whose width gradually decreases from the distal end side toward the proximal end side.
Thereby, design of a movable electrode or a fixed electrode can be simplified.

In the actuator according to the aspect of the invention, it is preferable that the electrode finger in at least one of the fixed electrode and the movable electrode has a portion whose thickness gradually decreases from the distal end side toward the proximal end side.
As a result, the difference between the maximum value and the minimum value of the width of the electrode finger is reduced, and the mechanical strength of the electrode finger is prevented from being lowered, while the movable electrode relative to the voltage applied between the movable electrode and the fixed electrode is reduced. An increase in the displacement amount ratio can be suppressed.

In the actuator of the present invention, it is preferable that each electrode finger in at least one of the fixed electrode and the movable electrode has a portion whose width gradually decreases from the distal end side toward the proximal end side.
As a result, the difference between the maximum value and the minimum value of the width of each electrode finger is reduced, and the mechanical strength of each electrode finger is prevented from being lowered, while the movable relative to the voltage applied between the movable electrode and the fixed electrode is prevented. An increase in the ratio of the displacement amount of the electrode can be suppressed more reliably.

The optical device of the present invention comprises a base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic portion for movably supporting the movable electrode with respect to the base portion;
A light reflecting portion supported by the movable electrode and having light reflectivity;
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the elastic part is deformed, and the movable electrode is displaced in the longitudinal direction of the electrode finger. , An optical device configured to change the direction of the light reflected by the light reflecting portion,
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode It is characterized by increasing the distance.
Thereby, the raise of the ratio of the displacement amount of the movable electrode with respect to the voltage applied between a movable electrode and a fixed electrode can be suppressed. Therefore, even when the voltage applied between the movable electrode and the fixed electrode is relatively large, fine adjustment of the displacement amount of the movable electrode by changing the voltage is facilitated, and the movable electrode is relatively simple and highly accurate. The amount of displacement can be made as desired. As a result, the light reflected by the light reflecting portion can be changed to a desired direction with relatively simple and high accuracy.

The optical scanner of the present invention includes a base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic portion for movably supporting the movable electrode with respect to the base portion;
A light reflecting portion supported by the movable electrode and having light reflectivity;
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the elastic part is deformed, and the movable electrode is displaced in the longitudinal direction of the electrode finger. An optical scanner configured to scan the light reflected by the light reflecting section,
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode It is characterized by increasing the distance.
Thereby, the raise of the ratio of the displacement amount of the movable electrode with respect to the voltage applied between a movable electrode and a fixed electrode can be suppressed. Therefore, even when the voltage applied between the movable electrode and the fixed electrode is relatively large, fine adjustment of the displacement amount of the movable electrode by changing the voltage is facilitated, and the movable electrode is relatively simple and highly accurate. The amount of displacement can be made as desired. As a result, it is possible to scan the light reflected by the light reflecting portion in a desired state with relatively simple and high accuracy.

An image forming apparatus of the present invention includes a base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic portion for movably supporting the movable electrode with respect to the base portion;
A light reflecting portion supported by the movable electrode and having light reflectivity;
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the elastic part is deformed, and the movable electrode is displaced in the longitudinal direction of the electrode finger. An image forming apparatus including an optical scanner configured to scan the light reflected by the light reflecting unit,
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode It is characterized by increasing the distance.
Thereby, the raise of the ratio of the displacement amount of the movable electrode with respect to the voltage applied between a movable electrode and a fixed electrode can be suppressed. Therefore, even when the voltage applied between the movable electrode and the fixed electrode is relatively large, fine adjustment of the displacement amount of the movable electrode by changing the voltage is facilitated, and the movable electrode is relatively simple and highly accurate. The amount of displacement can be made as desired. As a result, an excellent image can be formed by scanning the light reflected by the light reflecting portion in a desired state with relatively simple and high accuracy.

Hereinafter, an actuator according to the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.
<First Embodiment>
First, an actuator according to a first embodiment of the present invention will be described with reference to FIGS. In the following description, a case where the actuator of the present invention is applied to a microresonator will be described as an example.

  1 is a plan view showing a first embodiment of the actuator of the present invention, FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIG. 3 is an electrode of a movable electrode and a fixed electrode of the actuator shown in FIG. FIG. 4 is an enlarged plan view for explaining the finger, FIG. 4 is a diagram for explaining the action of the movable electrode and the fixed electrode during the operation of the actuator shown in FIG. 1, and FIG. 5 is a diagram during the operation of the actuator shown in FIG. It is a graph which shows the relationship between an applied voltage (driving voltage) and the displacement amount of a movable electrode.

As shown in FIGS. 1 and 2, the actuator 1 according to this embodiment can vibrate between a base 2, a pair of fixed electrodes 31 and 32 fixed to the base 2, and the fixed electrodes 31 and 32. And a movable part 4 provided on the surface.
The movable part 4 connects the movable electrodes 41, 42 facing the fixed electrodes 31, 32, the fixed parts 45, 46 fixed to the base 2, and the movable electrodes 41, 42 and the fixed parts 45, 46. Beam portions (elastic portions) 43, 44, and a connecting portion 47 that connects the movable electrode 41 and the movable electrode 42.

The movable electrode 41 has a comb-teeth shape, and has a plurality of electrode fingers 411 arranged side by side so as to form a comb-teeth shape. Similarly, the movable electrode 42 has a comb-teeth shape, and has a plurality of electrode fingers 421 arranged side by side so as to form a comb-teeth shape.
As shown in FIG. 3, each electrode finger 411 and each electrode finger 421 have a constant width over almost the entire region in the longitudinal direction. As with electrode fingers 311 and 321 described later, each electrode finger 411 and each electrode finger 421 may have a portion whose width gradually decreases from the distal end side toward the proximal end side.

The fixing portion 45 is fixed to the upper surface of the base portion 2 via a support portion 51. Similarly, the fixing portion 46 is fixed to the upper surface of the base portion 2 via the support portion 52. Since the fixing portions 45 and 46 are thus provided, the fixing portions 45 and 46 are separated from the base portion 2 by the thickness of the support portions 51 and 52.
The beam portion 43 includes the beams 433 and 434 having the fixed portion 45 side as a fixed end as described above, and the beams 435 that connect the free ends (ends opposite to the fixed portion 45) of these beams 433 and 434. , The beam 431 connecting the beam 435 and the movable electrode 41, and the beam 432 connecting the beam 435 and the movable electrode 42. As described above, the beam portion 43 constituted by the plurality of beams 431, 432, 433, 434, and 435 can be elastically deformed along the upper surface of the base portion 2.

The beam 433 is a cantilever whose one end (fixed end) is fixed to the fixed portion 45, and has a function of bending and deforming along the surface of the base portion 2. Similarly, the beam 434 is a cantilever whose one end (fixed end) is fixed to the fixed portion 46, and has a function of bending and deforming along the surface of the base portion 2.
Each of the beams 433 and 434 has substantially the same width over the entire area in the longitudinal direction.

The beam 435 is fixed to the free ends of the beams 433 and 434 described above, and can be displaced in the vertical direction in FIG.
Each of the beams 431 and 432 is fixed to the end of the beam 435 described above, and can be displaced while being bent and deformed in the vertical direction in FIG. Further, the movable electrode 41 described above is fixed to the beam 431, and the movable electrode 42 is fixed to the beam 432.

Each of the beams 431 and 432 has substantially the same width over the entire area in the longitudinal direction.
Similar to the beam portion 43, the beam portion 44 includes beams 443 and 444 having fixed ends on the fixed portion 46 side as described above, and free ends of these beams 443 and 444 (on the opposite side to the fixed portion 46). Of the beam 445, the beam 441 connecting the beam 445 and the movable electrode 41, and the beam 442 connecting the beam 445 and the movable electrode 42. As described above, the beam portion 44 constituted by the plurality of beams 441, 442, 443, 444, and 445 can be elastically deformed along the upper surface of the base portion 2. Further, the beam portion 44 is formed so that the beam portion 43 and the beam portion 44 are symmetrical in FIG.

The connecting portion 47 that connects the movable electrode 41 and the movable electrode 42 has a function of fixing the distance between the movable electrodes 41, 42. Accordingly, the movable electrodes 41 and 42 can be displaced by the deformation of the beam portion 44 while maintaining the distance between the movable electrodes 41 and 42.
In such a movable part 4, among the parts constituting the movable part 4, the movable electrodes 41, 42, the beam parts 43, 44, and the connecting part 47 are spaced from the base 2. (Floating state).

On the other hand, the fixed electrode 31 has a comb-teeth shape, and includes a plurality of electrode fingers 311 arranged in parallel to form a comb-teeth shape, and a fixing portion 312 for supporting each electrode finger 311. ing.
The fixing portion 312 is fixed to the base portion 2 via the support portion 53. Accordingly, the plurality of electrode fingers 311 are in a state of being spaced from the base 2 (floating state). Here, the thickness of the support portion 53 is substantially the same as the thickness of each of the support portions 51 and 52 described above.

Each of the plurality of electrode fingers 311 is formed so as to protrude from the fixed portion 312 as described above along the upper surface of the base portion 2.
The plurality of electrode fingers 311 are arranged so as to mesh with the plurality of electrode fingers 411 of the movable electrode 41 described above. That is, the electrode fingers 311 and the electrode fingers 411 are arranged alternately.
As shown in FIG. 3, each electrode finger 311 has a portion 313 whose width gradually decreases from the distal end side toward the proximal end side. In the present embodiment, this portion 313 extends over substantially the entire area of the electrode finger 311 in the longitudinal direction. That is, the width of each electrode finger 311 is gradually reduced from the distal end to the proximal end. Moreover, the width | variety of the part 313 of each electrode finger 311 is changing continuously.

Similarly, the fixed electrode 32 has a plurality of electrode fingers 321 arranged side by side so as to form a comb tooth shape, and a fixing portion 322 for supporting each electrode finger 321. Here, each electrode finger 321 also has a portion whose width gradually decreases from the distal end side toward the proximal end side, like the electrode finger 311 described above.
The fixing portion 322 is fixed to the base portion 2 via the support portion 54. As a result, the plurality of electrode fingers 321 are in a state of being spaced from the base 2 (the state of being floated). Here, the thickness of the support portion 54 is substantially the same as the thickness of each of the support portions 51 and 52 described above.

Each of the plurality of electrode fingers 321 is formed so as to protrude from the fixed portion 322 as described above along the upper surface of the base portion 2.
The plurality of electrode fingers 321 are arranged so as to mesh with the plurality of electrode fingers 421 of the movable electrode 42 described above. That is, the electrode fingers 321 and the electrode fingers 421 are arranged so as to be alternately positioned.

In such an actuator 1, when a voltage is applied between the fixed electrode 31 and the movable electrode 41, an electrostatic attractive force is generated between the electrodes 31 and 41, and the movable electrode 41 moves so as to approach the fixed electrode 31. To do.
On the other hand, when a voltage is applied between the fixed electrode 32 and the movable electrode 42, an electrostatic attractive force is generated between the electrodes 32 and 42, and the movable electrode 42 moves toward the fixed electrode 32.

Therefore, by alternately applying a voltage between the fixed electrode 31 and the movable electrode 41 and between the fixed electrode 32 and the movable electrode 42, the movable electrodes 41 and 42 reciprocate (vibrate). At this time, the distance between the movable electrodes 41 and 42 is kept constant by the connecting portion 47, and the movable electrodes 41 and 42 reciprocate in the longitudinal direction of the connecting portion 47.
In such an actuator 1, the amount of engagement between the movable electrode 41 and the fixed electrode 31 according to the voltage applied between the movable electrode 42 and the fixed electrode 32 (hereinafter also simply referred to as “applied voltage”), and The meshing amount of the movable electrode 42 and the fixed electrode 32 changes.
And if the vibration frequency is made into the resonant frequency of the movable part 4, the movable part 4 can be vibrated efficiently. At this time, the resonance frequency is determined by the restoring force against the displacement determined by the mass of the movable portion 4 (mainly the total mass of the movable electrodes 41 and 42 and the connecting portion 47) and the spring constant of the beam portions 43 and 44.

  Here, the operation of the fixed electrodes 31 and 32 and the movable electrodes 41 and 42 will be described in detail with reference to FIG. In the following, the operations of the fixed electrode 31 and the movable electrode 41 will be described representatively, and the operations of the fixed electrode 32 and the movable electrode 42 are the same as the operations of the fixed electrode 31 and the movable electrode 41. Omitted. In the following description, two electrode fingers 311 adjacent to each other among the plurality of electrode fingers 311 of the fixed electrode 31 and electrodes disposed between the two electrode fingers 311 among the plurality of electrode fingers 411 of the movable electrode 41 will be described. The finger 411 will be described representatively.

When the actuator 1 is in a non-driven state, that is, when no voltage is applied between the movable electrode 41 and the fixed electrode 31 and between the movable electrode 42 and the fixed electrode 32, the electrode finger 411 and the electrode finger 311 amount of overlap, i.e., engagement of the movable electrode 41 and the fixed electrode 31, as shown in FIG. 4 (a), an L _1. The distance between the tip of the electrode fingers 411 of the movable electrode 41 and the electrode fingers 311 of the fixed electrode 31 is _{D 1.} Further, the distance between the movable electrode 41 and the fixed electrode 31 is gradually reduced toward the tip of the electrode finger 311.

  When a voltage is applied between the fixed electrode 31 and the movable electrode 41 in such a state, an electrostatic attractive force is generated between them, but mainly the tip of the electrode finger 411 of the movable electrode 41 and the fixed electrode 31 Due to the electrostatic attraction generated between the electrode finger 311 and the electrostatic attraction generated between the tip of the electrode finger 311 of the fixed electrode 31 and the electrode finger 411 of the movable electrode 41, the electrode finger 411 is displaced in the direction of the tip. To do. Thereby, the amount of engagement between the movable electrode 41 and the fixed electrode 31 increases.

When the meshing amount of the movable electrode 41 and the fixed electrode 31 increases and the meshing amount becomes L ₂ (L ₂ > L ₁ ) as shown in FIG. 4B, the electrode finger of the movable electrode 41 the distance between the tip 411 and the electrode fingers 311 of the fixed electrode 31 becomes larger _{D 2} than _{D 1.} In the present embodiment, the distance between the tip of the electrode finger 311 of the fixed electrode 31 and the electrode finger 411 of the movable electrode 41 does not change.

Further, when the meshing amount of the movable electrode 41 and the fixed electrode 31 is further increased and the meshing amount becomes L ₃ (L ₃ > L ₂ ) as shown in FIG. The distance between the tip of the electrode finger 411 and the electrode finger 311 of the fixed electrode 31 is D ₃ which is larger than D ₂ . In the present embodiment, the distance between the tip of the electrode finger 311 of the fixed electrode 31 and the electrode finger 411 of the movable electrode 41 does not change.

Thus, in the actuator 1, the electrode finger 311 in the fixed electrode 31 has the portion 313 whose width gradually decreases from the distal end side toward the proximal end side. As the amount of meshing increases, the distance between the tip of the electrode finger 411 of the movable electrode 41 and the electrode finger 311 of the fixed electrode 31 increases.
Thereby, an increase in the ratio of the displacement amount of the movable electrode 41 to the voltage applied between the movable electrode 41 and the fixed electrode 31 can be suppressed. Therefore, even when the voltage applied between the movable electrode 41 and the fixed electrode 31 is relatively large, fine adjustment of the displacement amount of the movable electrode 41 by changing the voltage is facilitated, and it is relatively simple and highly accurate. The displacement amount of the movable electrode 41 can be set to a desired value.

  Here, as shown in FIG. 5, it is preferable that the fixed electrode 31 and the movable electrode 41 are formed so that the ratio of the displacement amount of the movable electrodes 41 and 42 to the applied voltage is substantially constant. Thereby, the structure of the drive circuit (power supply circuit) for generating the applied voltage can be simplified. For example, a drive circuit that can generate a voltage having the same voltage waveform as that of a commercial power supply can be used. Even in this case, the displacement amount of the movable electrodes 41 and 42 can be easily finely adjusted simply by changing the voltage value. can do. That is, it is possible to easily control the applied voltage.

In particular, in the present embodiment, as described above, the electrode finger 311 in the fixed electrode 31 has a portion in which the width gradually decreases from the distal end side toward the proximal end side, and the electrode finger 411 in the movable electrode 41 has its longitudinal length. Since it has a constant width in almost the entire region in the direction, the design of the movable electrode 41 can be simplified. As a result, the design of the actuator 1 can be simplified.
In addition, if the electrode finger in at least one of the fixed electrode 31 and the movable electrode 41 has a portion whose width gradually decreases from the distal end side to the proximal end side, the effect of the present invention can be obtained. The electrode finger in one of the fixed electrode 31 and the movable electrode 41 has a portion in which the width gradually decreases from the distal end side to the proximal end side, and the electrode finger in the other is constant over almost the entire area in the longitudinal direction. With this width, one design of the movable electrode 41 and the fixed electrode 31 can be simplified. As a result, the design of the actuator 1 can be simplified.

In addition, since the width of the portion 313 of the electrode finger 311 in the fixed electrode 31 continuously decreases gradually from the distal end side to the proximal end side, the distance between the movable electrode 41 and the fixed electrode 31 accompanying the displacement of the movable electrode 41 is reduced. The amount of increase in electrostatic attraction (with displacement) can be made constant. As a result, the movable electrode 41 can be displaced smoothly.
In the present embodiment, each electrode finger 311 in the fixed electrode 31 has a portion 313 in which the width gradually decreases from the distal end side toward the proximal end side, so that the maximum value and the minimum value of the width of each electrode finger 311 The increase in the ratio of the displacement amount of the movable electrode 41 to the voltage applied between the movable electrode 41 and the fixed electrode 31 is further reduced while the mechanical strength of each electrode finger 311 is prevented from decreasing. It can be surely suppressed.

Moreover, it is preferable that the electrode finger in at least one of the fixed electrode 31 and the movable electrode 41 has a portion where the thickness gradually decreases from the distal end side toward the proximal end side. Thereby, the difference between the maximum value and the minimum value of the width of the electrode finger is reduced, and the mechanical strength of the electrode finger is prevented from being lowered, and the movable relative to the voltage applied between the movable electrode 41 and the fixed electrode 31 is prevented. An increase in the displacement amount ratio of the electrode 41 can be suppressed.
The actuator 1 as described above can be driven in a desired state with relatively simple and high accuracy.

<Actuator manufacturing method>
Next, an example of manufacturing the actuator 1 described above will be described with reference to FIG.
FIG. 6 is a diagram for explaining a method of manufacturing the actuator shown in FIGS. 1 and 2. FIG. 6 shows a cross section corresponding to the cross section taken along line AA in FIG.

In the following description, the upper side in FIG. 6 is referred to as “upper” and the lower side is referred to as “lower”.
The manufacturing method of the actuator 1 of this embodiment includes [1] a step of preparing a three-layer substrate, [2] a step of etching the first layer of the substrate (first etching), and [3] the substrate. And etching the second layer (second etching). Hereinafter, each process is demonstrated one by one.

[1] Preparation of Substrate First, as shown in FIG. 6A, a second layer 102 that is not substantially etched by the first etching described later and the first etching are etched on the base 101. A substrate 10 having a three-layer structure in which the first layer 103 is laminated in this order is prepared.
Of the layers constituting the substrate 10, the first layer 103 is the movable portion 4 and the fixed electrodes 31 and 32 of the actuator 1, and the second layer 102 is the support portions 51, 52, 53, and so on. 54, and the base 101 is a part that becomes the base 2.

Examples of the substrate 10 include various types of combinations of the layers 101, 102, and 103. In particular, a second layer mainly made of SiO ₂ and mainly a base 101 made mainly of Si, and mainly An SOI substrate in which a first layer (active layer) 103 made of Si is laminated in this order is preferable. Hereinafter, a case where an SOI substrate is used as the substrate 10 will be described as an example.

  By using an SOI substrate as the substrate 10, a substrate having a relatively thick first layer 103 can be manufactured. For this reason, since the thickness of each electrode finger 311, 321, 411, 421 to be formed can be increased, the sectional area of each electrode finger 311, 321, 411, 421 (in a direction perpendicular to the longitudinal direction) Can be increased. Thereby, in the actuator 1, an electrostatic capacity can be enlarged, As a result, the displacement amount of the movable part 4 with respect to an applied voltage can be increased.

  Moreover, since the thickness of each electrode finger 311, 321, 411, 421 can be set large, the width | variety can be made small, ensuring the required cross-sectional area. As a result, the fixed electrodes 31, 32, 41, 42 can be reduced in size, and the actuator 1 as a whole can be reduced in size. Moreover, the highly accurate actuator 1 can be obtained simply.

  The thickness (average) of the first layer 103 is not particularly limited, but is preferably about 0.2 to 100 μm, and more preferably about 20 to 60 μm. If the thickness of the first layer 103 is too thin, depending on the constituent material of the first layer 103, it may be difficult for the actuator 1 to sufficiently increase the amount of displacement of the movable portion 4 with respect to the applied voltage. On the other hand, even if the thickness of the first layer 103 is increased beyond the upper limit, not only an increase in the effect cannot be expected, but it becomes difficult to perform the etching deeply and vertically.

[2] First Etching Next, as shown in FIG. 6B, the movable portion 4 is formed on the substrate 10 as described above.
Specifically, first, in the etching region on the first layer 103 (opposite side of the second layer 102) of the substrate 10, the movable part (structure) 4 is handled by using, for example, a photolithography method. A mask having a shape to be formed is formed.

Next, the first layer 103 is etched using the formed mask. At this time, the second layer 102 is not substantially etched by the first etching, and functions as a stop layer that prevents the invasion during the first etching.
For the first etching, for example, reactive ion etching, plasma etching, beam etching, dry etching such as optically assisted etching, wet etching, etc. can be used alone or in combination of two or more. It is preferable to use dry etching, particularly reactive ion etching.

By using dry etching as the first etching, the first layer 103 can be patterned with high dimensional accuracy. In particular, highly reactive etching can be performed on the first layer 103 by using reactive ion etching as the first etching.
By this step [2], the first layer 103 is patterned (processed) into a shape corresponding to the mask described above, and the movable portion 4 and the fixed electrodes 31 and 32 are formed.

Next, the aforementioned mask is removed. By removing the mask prior to the second etching, when wet etching is used in step [3] to be described later, contamination of the etching solution due to dissolution of the mask material (resist material or metal material) is prevented. Or it can be suppressed.
As a method for removing the mask, for example, when the mask is made of a resist material, a resist stripping solution is used. When the mask is made of a metal material, a metal stripping solution such as a phosphoric acid solution is used. be able to.

[3] Second Etching Next, as shown in FIG. 6C, the first layer 103 is not substantially etched with respect to the second layer 102, and the second layer 102 can be etched. Second etching is performed. Thereby, a part of the second layer 102 is removed.
For the second etching, for example, one or more of reactive ion etching, plasma etching, beam etching, dry etching such as light-assisted etching, wet etching, and the like can be used. It is preferable to use wet etching.

By using wet etching as the second etching, the second layer 102 can be isotropically etched. Therefore, the second layer 102 immediately below the first layer 103 processed and remaining in the step [2] can also be efficiently removed.
As an etchant used for this wet etching, for example, hydrofluoric acid or the like can be given.
When the substrate 10 is immersed in such an etchant, first, the etching of the second layer 102 not covered by the remaining first layer 103 (the movable portion 4 and the fixed electrodes 31 and 32) starts from the upper surface. Etching proceeds isotropically.

Next, the second layer 102 immediately below the movable portion 4 and the fixed electrodes 31 and 32 is also gradually removed by etching from the exposed side surfaces.
Then, by removing the second layer 102, a gap is formed between the base 101 and the first layer 103.
Here, each of the fixed portions 45 and 46 is set to have an area larger than the area (maximum) of the belt-shaped body constituting each of the movable electrodes 41 and 42 and each of the beam portions 43 and 44 in plan view. For this reason, at the time when the second layer 102 directly under the portions other than the fixed portions 45 and 46 (the movable electrodes 41 and 42 and the beam portions 43 and 44) is almost completely removed due to the difference in area. In this state, a part of the second layer 102 immediately below the fixing portions 45 and 46 remains.

When the second etching is completed at this time (state), the remaining second layer 102 becomes the support portions 51 and 52, and the movable portion 4 is connected to each fixed portion via the support portions 51 and 52. 45 and 46 are fixed to the base 101 (base 2), respectively. On the other hand, the other part of the movable part 4 is in a state of floating from the base part 101.
Thereafter, the mass of the movable part 4 and the spring constant are adjusted by removing a part of the movable part 4 or adding a material to the movable part 4 as necessary.
The actuator 1 is manufactured through the steps as described above.

<Second Embodiment>
Next, a second embodiment of the actuator of the present invention will be described.
FIG. 7 is a partially enlarged plan view showing a second embodiment of the actuator of the present invention, and FIG. 8 is a diagram for explaining the operation of the fixed electrode and the movable electrode of the actuator shown in FIG.
Hereinafter, the actuator of the second embodiment will be described focusing on the differences from the actuator of the first embodiment described above, and the description of the same matters will be omitted.
As shown in FIG. 7, the actuator of the second embodiment is substantially the same as the actuator 1 of the first embodiment except that the shape of the electrode fingers of the fixed electrode is different.
As shown in FIG. 7, the actuator of the second embodiment has an electrode finger 311 </ b> A instead of the electrode finger 311 in the first embodiment described above.

The electrode finger 311A has a portion 313A in which the width gradually decreases from the distal end side toward the proximal end side. When the width of the electrode finger 311A is thus changed stepwise, the design of the fixed electrode 31 can be simplified. In FIG. 7, the width of the electrode finger 311A changes in two steps, but it may be three or more.
In such a actuator, when the actuator 1 is in a non-driven state, the amount of overlap between the electrode fingers 411 and the electrode fingers 311A, as shown in FIG. 8 (a), an L _1. The distance between the tip of the electrode fingers 411 and the electrode fingers 311A is _{D 1.}

When the overlap amount between the electrode finger 411 and the electrode finger 311A is increased to L ₂ (L ₂ > L ₁ ) as shown in FIG. 8B, that is, the change in the overlap amount from the non-driven state. when is small, the distance between the tip of the electrode fingers 411 and the electrode fingers 311A remains _{D 1.}
Further, when the amount of overlap between the electrode finger 411 and the electrode finger 311A is further increased to L ₃ (L ₃ > L ₂ ) as shown in FIG. 8C, that is, the overlap from the non-driven state. When the change in the amount becomes large to some extent, the distance between the tip of the electrode finger 411 of the movable electrode 41 and the electrode finger 311 of the fixed electrode 31 becomes D ₃ which is larger than D ₁ .

The actuator according to the second embodiment as described above can be driven in a desired state relatively easily and with high accuracy, like the actuator 1 according to the first embodiment described above.
The microresonator (actuator) according to the above-described embodiment is, for example, an ink jet type ejection device (for example, an ink jet printer), a laptop type in addition to a personal computer (mobile type personal computer), a mobile phone, and a digital still camera. Personal computers, TVs, video cameras, video tape recorders, car navigation devices, pagers, electronic notebooks (including those with communication functions), electronic dictionaries, calculators, electronic game machines, word processors, workstations, video phones, security TV monitors, Electronic binoculars, POS terminal, medical equipment (eg electronic thermometer, blood pressure meter, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments (eg, vehicle, aircraft) Ship total S), can be applied to electronic equipment such as a flight simulator.

The actuator of the present invention is not limited to the above-described microresonator, but various vibrators such as sensors (pressure, acceleration, angular velocity, attitude) for MEMS application, optical devices such as optical scanners, optical switches, optical attenuators, etc. Can be applied to.
Here, the movable electrode of the actuator according to the present invention as described above supports a light reflecting portion having light reflectivity, and is configured to change the direction of light reflected by the light reflecting portion, that is, The optical device according to the present invention can change the light reflected by the light reflecting portion to a desired direction with relatively simple and high accuracy.

Further, a light reflecting portion having light reflectivity is supported on the movable electrode of the actuator according to the present invention as described above, and configured to scan the light reflected by the light reflecting portion, that is, according to the present invention. Such an optical scanner can scan the light reflected by the light reflecting portion in a desired state with relatively simple and high accuracy.
Such an optical scanner can be suitably applied to an image forming apparatus such as a laser printer, a barcode reader, a scanning confocal laser microscope, and an imaging display.

An image forming apparatus including such an optical scanner can form an excellent image by scanning light reflected by the light reflecting portion in a desired state with relatively simple and high accuracy.
Although the actuator of the present invention has been described above, the present invention is not limited to these.
For example, each unit constituting the actuator of the present invention can be replaced with any one that exhibits the same function, or other configurations can be added.

It is a top view which shows 1st Embodiment of the actuator of this invention. It is the sectional view on the AA line in FIG. It is an enlarged plan view for demonstrating the movable electrode of the actuator shown in FIG. 1, and the electrode finger of a fixed electrode. It is a figure for demonstrating the effect | action of a movable electrode and a fixed electrode at the time of operation | movement of the actuator shown in FIG. 2 is a graph showing a relationship between an applied voltage (drive voltage) and an amount of displacement of a movable electrode during operation of the actuator shown in FIG. It is a figure for demonstrating the manufacturing method of the actuator shown in FIG. 1 and FIG. It is a partial enlarged plan view which shows 2nd Embodiment of the actuator of this invention. It is a figure for demonstrating the effect | action of a movable electrode and a fixed electrode at the time of operation | movement of the actuator shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Actuator 2 ... Base 31, 32 ... Fixed electrode 311, 311A, 321 ... Electrode finger 312, 322 ... Fixed part 313, 313A ... Part 4 ... Movable part 41, 42 ... Movable electrode 411 , 421... Electrode fingers 43 and 44... Beam portions 431, 432, 433, 434, 435, 441, 442, 443, 444, 445... Beams 45 and 46. , 53, 54... Supporting part 10... Substrate 101... Base part 102... Etching stopper (second layer) 103 .. Etched layer (first layer)

Claims (11)

The base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic part that movably supports the movable electrode with respect to the base part,
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the movable electrode is displaced in the longitudinal direction of the electrode finger while deforming the elastic portion. An actuator configured as follows:
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode An actuator characterized by increasing the distance.   The actuator according to claim 1, wherein the fixed electrode and the movable electrode are formed so that a ratio of a displacement amount of the movable electrode to a voltage applied between the fixed electrode and the movable electrode is substantially constant. .   Of the fixed electrode and the movable electrode, one of the electrode fingers has a portion whose width gradually decreases from the distal end side to the proximal end side, and the electrode finger on the other side is constant over almost the entire area in the longitudinal direction. The actuator according to claim 1, wherein the actuator has a width.   The electrode finger in the fixed electrode has a portion in which the width gradually decreases from the distal end side toward the proximal end side, and the electrode finger in the movable electrode has a constant width in almost the entire region in the longitudinal direction. The actuator described in 1.   5. The actuator according to claim 1, wherein an electrode finger in at least one of the fixed electrode and the movable electrode has a portion in which a width gradually decreases from the distal end side toward the proximal end side.   5. The actuator according to claim 1, wherein an electrode finger in at least one of the fixed electrode and the movable electrode has a portion whose width gradually decreases from the distal end side toward the proximal end side.   The actuator according to any one of claims 1 to 6, wherein an electrode finger in at least one of the fixed electrode and the movable electrode has a portion whose thickness gradually decreases from the distal end side toward the proximal end side.   The actuator according to claim 1, wherein each electrode finger in at least one of the fixed electrode and the movable electrode has a portion whose width gradually decreases from the distal end side toward the proximal end side. The base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic portion for movably supporting the movable electrode with respect to the base portion;
A light reflecting portion supported by the movable electrode and having light reflectivity;
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the elastic part is deformed, and the movable electrode is displaced in the longitudinal direction of the electrode finger. , An optical device configured to change the direction of the light reflected by the light reflecting portion,
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode An optical device characterized by increasing the distance. The base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic portion for movably supporting the movable electrode with respect to the base portion;
A light reflecting portion supported by the movable electrode and having light reflectivity;
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the elastic part is deformed, and the movable electrode is displaced in the longitudinal direction of the electrode finger. An optical scanner configured to scan the light reflected by the light reflecting section,
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode An optical scanner characterized by increasing the distance. The base,
At least one fixed electrode fixed to the base;
A movable electrode provided corresponding to each of the fixed electrodes and displaceable with respect to the base;
An elastically deformable elastic portion for movably supporting the movable electrode with respect to the base portion;
A light reflecting portion supported by the movable electrode and having light reflectivity;
Each of the movable electrode and the fixed electrode includes a plurality of electrode fingers arranged in parallel so as to form a comb-tooth shape, and the plurality of electrode fingers of the movable electrode and the plurality of electrode fingers of the fixed electrode mesh with each other. Are arranged as follows,
By applying a voltage between the fixed electrode and the movable electrode, an electrostatic attractive force is generated between them, and the elastic part is deformed, and the movable electrode is displaced in the longitudinal direction of the electrode finger. An image forming apparatus including an optical scanner configured to scan the light reflected by the light reflecting unit,
At least one of the plurality of electrode fingers in the fixed electrode and / or the movable electrode has a portion whose width gradually decreases from the distal end side to the proximal end side, and the fixed electrode, the movable electrode, As the amount of engagement increases, the distance between the tip of the electrode finger of the fixed electrode and the electrode finger of the movable electrode and / or the tip of the electrode finger of the movable electrode and the electrode finger of the fixed electrode An image forming apparatus characterized in that the distance is increased.

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