JP2000105345A - Actuator, optical switching element, and picture display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simply structured actuator used as a driving source of an optical switching element capable of operating at a speed higher than that of a liquid crystal. SOLUTION: An operation space 32 capable of almost sealing up an operation liquid 33 is arranged, so that the operation liquid 33 can partially be warmed with a heater 36 in contact with the operation liquid 33. In this actuator 30, the operation liquid 33 is heated up and forms an air bubble 39 to raise the inner pressure, therefore, a displaceable thin film 35 is displaced upward to drive a switching part 11. Therefore, it is possible to provide a switching element 10 capable of operating at a high speed with a simple structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator usable for a micro machine, an optical switching element using the same, and an image display device.

[0002]

2. Description of the Related Art As an optical switching element capable of controlling on / off of light, an element using liquid crystal is widely used.
Optical switching elements are used in many applications such as optical communication, optical operation, optical storage devices, and optical printers, and image display devices are also one of important applications. As an image display device using liquid crystal, there is a device that displays an image on a liquid crystal panel in which liquid crystal cells are arranged two-dimensionally, or a projector that projects and displays an image.

[0003]

However, an optical switching element using a liquid crystal does not have such a high response speed, and has a response speed of several milliseconds. Therefore, it is difficult to apply the present invention to an optical storage device such as an optical communication device, an optical operation device, a hologram memory, etc., which requires a high-speed response, an optical printer, or a digitally driven image display device. Further, there still remains a problem that the use efficiency of light decreases due to a polarizing plate necessary for displaying an image on a liquid crystal panel. In recent years, higher quality image quality has been demanded, and an optical switching element with more accurate gradation expression than liquid crystal has been demanded.

[0004] Therefore, an optical switching element capable of modulating light at high speed by mechanically moving a switching element capable of controlling light has been developed. One is a micromirror device, which supports the mirror pivotally with a yoke,
The light is modulated by changing the angle of the mirror by an actuator.

Further, an optical switching element has been developed which modulates incident light by moving a switching element having a reflection function or a transmission function in parallel. An optical switching element using evanescent light, filed by the present applicant, is one of them. In this optical switching element, a switching element provided with an extraction surface is brought into contact with a total reflection surface of a light guide portion capable of transmitting light by total reflection, and evanescent light leaked from the total reflection surface is extracted. The light is modulated. Therefore, light can be modulated by moving the switching element by a small distance of about one wavelength or less, so that high-speed operation is possible. In addition, a switching element having a high on / off contrast can be realized only by moving a minute distance, and an optical switching element capable of accurately expressing a gradation can be provided because there is no absorption of light by a polarizing plate.

However, actuators that can be employed in the optical switching element using these micromechanisms are mainly electrostatic actuators utilizing electrostatic force, and piezo actuators can be used in others. The actuators used in these conventional micro machines have a problem that the structure is complicated and difficult to make. For example, for an electrostatic actuator,
It is necessary to prepare two sets of electrodes in order to move the switching element to the two positions of on and off, or to prepare one set of electrodes and an elastic body capable of driving the switching element in opposition thereto. If the elastic force and electrostatic force are not properly adjusted, the optical switching element cannot be operated at high speed, or the contrast may be reduced without accurately moving the switching element to the on or off position. is there.

Accordingly, an object of the present invention is to provide an actuator which has a simple structure and can respond at high speed to a conventional actuator for a micro machine. An object of the present invention is to provide an optical switching element which can be driven digitally, operates at high speed, and has high contrast by using this actuator. Further, it is another object of the present invention to provide an image display device having accurate gradation characteristics.

[0008]

SUMMARY OF THE INVENTION Accordingly, in the present invention, an actuator for a micro machine utilizing a liquid expansion phenomenon is provided. That is,
The actuator according to the present invention includes at least one working section filled with liquid, heating means capable of rapidly increasing the temperature of at least a part of a surface in contact with the liquid in the working section, and a liquid in the working section. An actuating portion that is displaced in a predetermined direction when inflated. The control method using the expansion of the liquid by heat is used for control of ejecting ink of a printer, and a response speed of several microseconds to several tens of microseconds is realized. Therefore, an actuator having a high response speed can be realized.

Further, the actuator according to the present invention has a very simple structure including an operating section, a heating means, and an operating portion, and can be realized at low cost by using a photolithography technique or the like. In the actuator of the present invention, the liquid in the working section partially expands due to the heating means,
In particular, when the phase changes and bubbles are formed, the internal pressure increases, so that the operating portion moves in a spreading direction. On the other hand, when the heating is stopped, the surrounding liquid absorbs the heat, so that the bubbles rapidly contract and the internal pressure decreases. For this reason, the working part moves in the direction of narrowing. Therefore, the switching section capable of modulating light can be moved to the on and off positions only by the actuator of the present invention, and an optical switching element that operates at high speed with a simple structure can be provided.

Further, when the liquid in the working compartment is phase-changed to form bubbles by utilizing the film boiling phenomenon, the volume changes by about 1000 times depending on the type of liquid. For this reason, it is possible to provide an actuator having a small displacement even though the actuator is small.

In an actuator having a plurality of working sections, the working spaces may be connected by a narrow flow path and connected so that the liquid flows so as not to hinder the movement of the working portion in a predetermined direction. desirable. By connecting the working spaces, it is possible to easily fill the liquid when manufacturing the actuator.

In addition, a plurality of operating sections are arranged two-dimensionally,
If each operating part is configured to be displaced in the same direction, it is possible to realize an image display device that operates at a high speed by moving the switching part by the operating parts. of course,
By arranging one-dimensionally or three-dimensionally, an optical switching element suitable for other uses such as optical communication, optical operation, an optical storage device, or an optical printer can be realized.

In an optical switching element using an evanescent wave, an optical switching unit is driven by an actuator with respect to a total reflection surface of a light guide unit having a total reflection surface capable of transmitting the reflected light by total reflection. By making contact with the total reflection surface, evanescent light leaked from the total reflection surface can be extracted. By arranging a plurality of optical switching elements two-dimensionally, it is possible to provide an image display device that can operate at high speed, has high contrast, and has a simple structure.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a schematic configuration of an image display device according to the present invention and its operation using a cross-sectional view. The image display device 1 according to the present embodiment includes a transparent light guide 4 that totally reflects incident light 2 on a total reflection surface 3 and transmits the light, and a plurality of switching units 1 for the total reflection surface 3 of the light guide 4.
The switching layers 12 are two-dimensionally arranged at intervals of about 0.5 μm, and an actuator 30 for moving these switching units 11 is sequentially laminated from above. The light guide 4, the switching unit 11, and the actuator 30 constitute the switching element 10 according to the present invention, and the image display device 1 has a plurality of switching elements 10 arranged two-dimensionally. ing.

The switching unit 11 includes an actuator 30
When it is displaced upward, it comes into close contact with the total reflection surface 3 and extracts an evanescent wave leaking from the total reflection surface 3, and reflects the extracted light upward. V that emits light from the exit surface 5 of the light guide
A prism 14 having a character shape and a support 15 for supporting the prism 14 are provided.

The actuator 30 for driving the switching unit 11 up and down has a silicon substrate 31 and a plurality of operating sections 32 formed on the substrate 31 by etching or the like. Each of the working sections 32 has an opening at an upper part, is filled with a working liquid 33, and the upper opening is sealed with a thin film 35 of elastic silicon or the like. A heating element 36 is provided on the bottom surface 34 of the operation section 32, and power can be supplied to the heating elements 36 of the individual operation sections 32 by the electrodes 37 and 38.

The working liquid 3 filled in the working compartment 32
Reference numeral 3 denotes a substance that is liquid at room temperature, such as water, alcohol, oil, or a mixture thereof. Therefore, as shown in FIG. 2, when power is supplied to the heating element 36 via the electrodes 37 and 38 and a part of the working liquid 33 in contact with the heating element 36 is rapidly heated, the part is film-boiling. Then, the phase changes to form bubbles 39. For this reason, the internal pressure of the working section 32 rises, and the working liquid 33 expands while pushing the deformable thin film 35 upward. Therefore, the thin film 3
5 is an operating portion, which displaces the switching portion 11 attached to the thin film 35 upward. As a result, the extraction surface 13 of the switching unit 11 is brought into close contact with the total reflection surface 3 and can extract an evanescent wave. The extracted evanescent wave is reflected by the microprism 14 in the direction of the emission surface 5, so that the switching element 10 is turned on.

On the other hand, when the power supply to the heating element 36 is stopped, the heat is taken away by the surrounding working liquid 33, so that the gas changes phase and becomes a liquid, and the bubbles 39 disappear naturally.
As a result, the internal pressure of the working section 32 decreases, and the working liquid 33
Shrinks. Therefore, the thin film 35 is displaced downward. At this time, a force that returns the thin film 35 to the initial position by the elastic force can be expected. Therefore, when the power supply to the heating element 36 is stopped, the thin film 35 is displaced downward in a short time,
The switching unit 11 attached to the thin film 35 is also displaced downward. For this reason, since the extraction surface 13 is separated from the total reflection surface 3, the evanescent wave is not extracted, and the switching element 10 is turned off.

As described above, the actuator 30 of the present embodiment
Is a working chamber 32 filled with a working liquid 33 in a substantially closed state. When a part of the working section 32 is heated, the thin film 35 serving as the working part is slightly displaced by utilizing a volume change in which the working liquid 33 expands. I can do it. In particular, the heating element 36 in contact with the working liquid 33 is applied for several microseconds or several
Power is rapidly supplied by a pulse of about 0 microsecond,
It is known in ink ejection control that film boiling can be caused by rapidly increasing the surface temperature. In the actuator of this example, it is also possible to cause the film to boil, and when the working liquid 33 in contact with the heating element 36 undergoes a phase change to become bubbles 39 of an appropriate size, the expansion coefficient of that portion is about 1000 times. become. For this reason, even if the volume of the operation section 32 is small, the thin film 35 can be sufficiently displaced. Further, the bubble 39 can be formed by a pulse of about 10 microseconds, and an actuator having a high response speed can be realized. Therefore, the optical switching element 10 of this example can be driven by a digital signal,
A much faster response speed than liquid crystal can be obtained.

The internal pressure at which the bubbles 39 are generated is 1
As high as about 5 atm, a sufficient force to move the switching unit 11 up and down can be obtained. Further, since the inside of the bubble 39 is a compressive gas, the switching unit 11 comes into contact with the total reflection surface 3 and when the thin film 35 cannot be displaced upward, the thin film and the bubble are deformed into an appropriate shape, or The internal pressure rises instead of volume expansion. Therefore, after the switching unit 11 comes into contact with the total reflection surface 3, a force for pressing the extraction surface 13 of the switching unit 11 against the total reflection surface 3 is obtained by the actuator 30. For this reason, an evanescent wave can be efficiently extracted, and an optical switching element with high contrast can be provided. In addition, since the actuator itself is not displaced after the switching unit 11 comes into contact with the total reflection surface 3, a highly reliable optical switching element can be realized without causing mechanical destruction.

Further, the actuator 30 of this embodiment has an extremely simple configuration including the operating section 32, the operating liquid 33, the heating element 36, and the thin film 35 serving as an operating portion, and can be compactly assembled. Further, since the working section 32, the heating element 36, the electric wires 37 and 38, and the like can be manufactured by a known photolithography technique, they can be supplied at low cost. As described above, with the thermal control type actuator of the present embodiment, an optical switching element that has high contrast at high speed and can be digitally driven can be supplied at low cost. In addition, by arranging the optical switching elements 10 two-dimensionally, it is possible to provide the image display device 1 having a faster response speed and a more accurate gradation characteristic than liquid crystal. Further, a projection type image display device can be provided by placing a projection lens and a screen in front of the emission surface 5 of the light guide.

FIG. 3 shows an operating section 32 formed on the surface of a silicon substrate 31 to constitute the actuator 30.
An example is shown. In the example shown in FIG. 3, rectangular projections (lands) 41 are formed intermittently on the surface of the silicon substrate 31 in the vertical and horizontal directions, and a substantially square section surrounded by the lands 41 on four sides is an operation section 32. It has become. And
A heating element 36 is provided substantially at the center of the working section 32. A narrow flow path 42 is formed between the lands 41 surrounding four sides of the operation section 32, and the lands 41 intermittently arranged.
Is connected to the surrounding operation section 32 through the gap. Since the working section 32 thus formed is almost entirely surrounded by the land 41, the working section 32 is substantially sealed. Therefore, when the internal pressure of the liquid sealed in the operation section 32 increases due to rapid heating by the heating element 36, the operation liquid 33 hardly moves due to the large resistance in the narrow flow path 42, and the displaceable upper thin film 35 is displaced. Press to expand.

On the other hand, the plurality of working sections 32 are formed in a narrow channel 42.
When the actuators 30 are connected to each other, the actuator 30 can be easily manufactured. That is, first, the thin film 35 is adhered to the silicon substrate 31 on which the working section 32 has been etched to form a substantially sealed working section 32, and then the working liquid 33 is supplied to each working section through a thin channel 42 by capillary action. 32 can be filled. Therefore, the labor for manufacturing the actuator 30 can be omitted, and the actuator 30 can be supplied at low cost.

FIG. 4 shows a different example in which the plurality of operating sections 32 are formed as a space almost in a closed state and are connected to each other via a narrow flow path 42. In this example, a square-shaped land 43 is formed in order to form the almost closed working section 32, and the land 43 is formed.
A narrow flow path 42 is formed lacking one portion. A buffer area 4 is provided around each operation section 32.
4 are provided, and the direction of the narrow flow path 42 connecting the buffer area 44 and each working section 32 is as follows.
The working sections 32 adjacent in the vertical and horizontal directions are different, and are arranged such that the flow paths 42 do not face each other.

Therefore, in the actuator 30 having the working compartments 32 arranged as shown in this figure, even if the pressure in a certain working compartment 32 rises and the pressure propagates from the flow path 42, it is absorbed in the buffer area 44, Further, since the directions of the flow paths 42 are different from each other, the possibility that the pressure propagates to the adjacent working section 32 via the flow path 42 is very small. Therefore, the pressure is hardly affected by the adjacent working section 32. Therefore, it is possible to realize the image display device 1 in which the crosstalk between the pixels constituted by the adjacent optical switching elements 10 hardly occurs.

Also, as described above, the flow path 42 is
Even if an arrangement having only one is adopted, the working liquid 33 can be smoothly filled by injecting the liquid after the working section 32 is almost evacuated.

The arrangement of the working sections 32 shown in FIG. 5 is an example in which each working section 32 is independently and completely sealed by lands 45 that are continuous in the vertical and horizontal directions. With such an arrangement, since there is no flow path connecting the operation sections 32, there is no possibility that pressure will propagate to the adjacent operation sections 32, and an image display device with almost no crosstalk can be realized. Further, since the pressure does not escape through the flow path, it is possible to provide an actuator having a large displacement amount of the thin film 35 which is an operating portion. However, since the working compartment 32 here needs to be filled with the working liquid 33,
The manufacturing cost is higher than the actuator described above.

As described above, the actuator 30 of the present embodiment
Is designed to be able to drive a switching unit and the like by using a volume change due to heat of a sealed liquid, particularly a volume change due to a phase change, and can be realized with a very simple configuration.
In addition, the thin film, which is the operating part, can be displaced only by supplying a short drive pulse to rapidly heat the heating element. early. Furthermore, the actuator 30 of the present example supplies power only when the working liquid is expanded, and returns to the original state when the power is stopped. Therefore, it is sufficient to supply energy only when the actuator 30 is moved in one direction. Therefore, the actuator has high energy efficiency. Further, since the volume rapidly expands due to the phase change, an actuator having a small displacement and a large displacement can be realized with a simple configuration. As described above, the actuator of the present example is an actuator that is optimal as a driving source of a micro machine.

In the above description, an example in which the actuator according to the present invention is applied to an optical switching element using an evanescent wave has been described.
Of course, it can be used as a driving source for a mirror of a micromirror device. Further, these optical switching elements can be used not only in image display devices but also in fields such as optical communication and optical operation that require high-speed digital control. Further, the actuator of the present invention can be used not only as a driving source of an optical switching element but also as a driving source of a micro robot or other micro machines. Therefore, the specific configuration of the actuator is not limited to the above. For example, it is possible to employ a piston or a rod instead of a thin film as the operating portion. In the actuator of this example, a plurality of operation sections are arranged two-dimensionally so that a two-dimensional image can be displayed, and the operation portions move in the same direction. However, the operation section is one-dimensional or three-dimensional. It is also possible to arrange in. Furthermore, the shape of the operation section and the installation position of the heating element are not limited to those in the present embodiment, and those suitable for the object to be driven can be adopted.

[0030]

As described above, the actuator of the present invention drives the operating part by utilizing a large volume change due to the expansion of the liquid, especially the phase change, and is high speed, energy efficient and An actuator having a simple structure can be provided. For this reason, the actuator of the present invention
By applying the present invention to an optical switching element using an evanescent wave, an optical switching element having a simple structure with a high speed and a high contrast can be realized.

Further, by arranging the optical switching element of the present invention two-dimensionally and applying it to an image display device, it is possible to provide an image display device with good energy efficiency and accurate gradation expression.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a schematic configuration of an image display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the image display device shown in FIG. 1, showing a state where an optical switching element is turned on.

FIG. 3 is a diagram showing an arrangement of operation sections constituting an actuator of the image display device shown in FIG. 1;

FIG. 4 is a view showing an arrangement of an operation section different from that of FIG. 3;

FIG. 5 shows a further different arrangement of the working compartments.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Image display apparatus 2 Incident light 3 Total reflection surface 4 Light guide 5 Outgoing surface 10 Optical switching element 11 Switching part 12 Switching layer 13 Extraction surface 14 Micro prism 15 Support 30 Actuator 31 Silicon substrate 32 Working section 33 Working liquid 34 Working section Bottom surface 35 Thin film (operating part) 36 Heating element 37, 38 Electric wire 39 Bubble 41, 43, 45 Land for sealing the working section 42 Narrow flow path 44 Buffer area

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 2H041 AA04 AB26 AB40 AC02 AC07 3H082 AA17 AA22 CC05 DB04 DD12 DE05 EE20 5C094 AA06 AA13 AA15 AA22 AA45 AA48 AA53 BA66 BA73 BA96 CA18 CA20 DA20 EA10 ED10 ED10 ED10

Claims (8)

[Claims] At least one working section filled with a liquid, heating means capable of rapidly increasing the temperature of at least a part of a surface in contact with the liquid in the working section, and a liquid in the working section An actuating portion that displaces in a predetermined direction when inflated. 2. The actuator according to claim 1, comprising a plurality of the operation sections and a narrow flow path connecting the operation sections. 3. The actuator according to claim 2, wherein the plurality of operation sections are arranged two-dimensionally, and each of the operation portions is displaced in the same direction. 4. An optical switching element comprising: the actuator according to claim 1; and a switching unit that is displaced by the operating part and can modulate light. 5. A light guide according to claim 4, further comprising: a light guide section having a total reflection surface capable of transmitting the reflected light by total reflection, wherein said light switching section is in contact with said total reflection surface and said total reflection is performed. An optical switching element that can extract evanescent light leaked from the surface. 6. An image display device wherein the plurality of optical switching elements according to claim 4 are two-dimensionally arranged. 7. The image display device according to claim 6, further comprising a narrow flow path connecting the plurality of operation sections so that a liquid flows. 8. A light guide according to claim 6, further comprising a light guide section provided with a total reflection surface capable of transmitting the reflected light by total reflection, wherein said light switching section is in contact with said total reflection surface, and said total reflection is performed. An image display device that can extract evanescent light leaked from the surface.