JP2014092738A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the force required to move an MEMS shutter.SOLUTION: A display device includes a substrate, a shutter part, a beam-like first beam part connected to the substrate and having therein a first electrode, and a beam-like second beam part connected to the shutter part and having therein a second electrode. A first surface near to the second beam part of the first beam part and a second surface nearer to the first beam part of the second beam part are in contact with each other due to electrostatic attraction generated by the first electrode and the second electrode. When the first surface and the second surface are separated from each other, a distance between a first point on the first surface and a second point which is on the second surface and is brought into contact with the first point when the first surface and the second surface are in contact with each other, is monotonously increases or decreases in a direction parallel with a line of intersection between the first surface and a plane vertical to the extending direction of the first beam part.

Description

  The present invention relates to a display device, and more particularly to a display device using a microelectromechanical system for pixels.

  In recent years, a display device using a micro electro mechanical system has attracted attention. The display system of this display device is called a MEMS shutter system. A MEMS shutter type display, like a liquid crystal display device, displays an image by controlling the transmission and reflection of light such as a backlight. However, the shutter is not a liquid crystal polarization but a mechanical device using MEMS technology. It is characterized in that a shutter is used.

  In the technique disclosed in Patent Document 1, electrostatic attraction and a spring are used to move a shutter that constitutes each pixel circuit. The shutter-side beam connected to the shutter and supplied with an electric potential and the control beam connected to the substrate facing the beam and supplied with an electric potential are brought into contact with each other by electrostatic attraction, and the spring force is applied. Leave. By the movement of the shutter accompanying this, light transmission and the like are controlled.

JP 2008-197668 A

  When the beam on the shutter side and the beam on the control side come into contact with each other due to electrostatic attraction, a van der Waals force is generated at the interface between the beams. For this reason, the phenomenon that two beams adhere due to van der Waals force may occur. In order to separate the two adhered beams, it is necessary to increase the force in the direction of separating the beams by reinforcing the spring.

  However, the force generated by adhesion and the force in the direction of separating the beam are likely to vary due to manufacturing errors. For this reason, if the force in the direction of separating the two beams is increased so that the two beams are reliably separated, it is necessary to increase the electrostatic attractive force for moving the shutter, which causes an increase in power consumption. Further, if nothing is done, a dark spot (black spot), a constantly lit spot (bright spot), and a flashing bright spot will appear in the display image, and the yield rate during manufacturing will be reduced.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a MEMS capable of separating a shutter beam connected to a shutter and a control beam facing the beam with a force smaller than that of the related art. An object of the present invention is to provide a display device using a shutter.

Of the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

  (1) A substrate, a movable shutter portion, a beam-shaped first beam portion connected to the substrate and having a first electrode therein, and a beam connected to the shutter portion and having a second electrode inside A second surface of the first beam portion on the side of the second beam portion, and on the side of the first beam portion of the second beam portion. The second surface is movable by electrostatic attraction generated by the first electrode and the second electrode, and has a first state in contact with each other and a second state in which they are separated from each other. The surface and the second surface have a first end portion on the substrate side and a second end portion opposite to the first end portion, and are placed in the second state. The display device is characterized in that the distance between the first surface and the second surface is greater at the second end than at the first end.

  (2) In (1), when the first surface and the second surface are separated from each other, an intersection line between the first surface and a surface perpendicular to the extending direction of the first beam portion The display device, wherein the first line is not parallel to the second line that is the line facing the first line on the second surface.

  (3) In (2), the cross section of the first beam portion perpendicular to the direction in which the first beam portion extends has a trapezoidal shape in which two sides toward the first surface are parallel to each other. A display device with special information.

  (4) In (3), the first beam section includes the first electrode and a first dielectric film that covers the first electrode, and the first beam in the first electrode. A cross section perpendicular to the direction in which the portion extends has a trapezoidal shape in which two sides toward the first surface are parallel to each other.

  (5) In (3), the first beam section includes the first electrode and a first dielectric film covering the first electrode, and the first beam portion is oriented in a direction perpendicular to the first surface. The thickness of the dielectric film 1 monotonously increases or decreases monotonously in any direction parallel to the line of intersection of the first surface and the surface perpendicular to the direction in which the first beam portion extends. Display device.

  (6) In (2), the cross section of the second beam portion perpendicular to the direction in which the second beam portion extends has a trapezoidal shape in which two sides toward the second surface are parallel to each other. A display device.

  (7) In (6), the second beam section includes the second electrode and a second dielectric film covering the second electrode, and the second beam on the second electrode. A cross section perpendicular to the direction in which the portion extends has a trapezoidal shape in which two sides toward the second surface are parallel to each other.

  (8) In (6), the second beam section includes the second electrode and a second dielectric film covering the second electrode, and the second beam section is oriented in a direction perpendicular to the second surface. The thickness of the dielectric film 2 monotonously increases or decreases monotonously in any direction parallel to an intersection line between the second surface and a surface perpendicular to the extending direction of the second beam portion. Display device.

  (9) In (1) to (8), the distance between the first surface and the second surface monotonously increases in the direction from the first end to the second end. A display device characterized by that.

  According to the present invention, the shutter beam connected to the shutter and the control beam facing the beam can be separated with a force smaller than that of the conventional one.

It is a figure which shows an example of a structure of the display apparatus concerning embodiment of this invention. It is a circuit diagram which shows an example of a structure of a pixel circuit. It is a perspective view which shows an example of a structure of a shutter mechanism part and a sealing substrate. It is a top view which shows an example of a structure of a shutter mechanism part. FIG. 5 is a cross-sectional view showing an example of a cross section taken along the line AA of the shutter mechanism section shown in FIG. It is a figure which shows an example of the cross section at the time of the two beam parts shown to FIG. 5A contacting. It is a figure which shows an example of the cross section when electrostatic attraction acted on two beam parts contained in the conventional shutter mechanism part. It is a figure which shows an example of the manufacturing process of the MEMS shutter shown to FIG. 5A. It is a figure which shows an example of the manufacturing process of the MEMS shutter shown to FIG. 5A. It is sectional drawing which shows another example of the cross section in the AA cut line of the shutter mechanism part shown in FIG. It is a figure which shows an example of the cross section at the time of the two beam parts shown to FIG. 8A contacting. It is a figure which shows an example of the manufacturing process of the MEMS shutter shown to FIG. 8A. It is a figure which shows an example of the manufacturing process of the MEMS shutter shown to FIG. 8A. It is sectional drawing which shows another example of the cross section in the AA cut line of the shutter mechanism part shown in FIG. It is a figure which shows an example of the cross section at the time of the two beam parts shown to FIG. 10A contacting. It is a figure which shows an example of the manufacturing process of the MEMS shutter shown to FIG. 10A. It is a figure which shows an example of the manufacturing process of the MEMS shutter shown to FIG. 10A. It is a figure which shows an example of a portable information terminal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Of the constituent elements that appear, those having the same function are given the same reference numerals, and the description thereof is omitted.

  FIG. 1 is a diagram illustrating an example of the configuration of a MEMS shutter type display device according to an embodiment of the present invention. The MEMS shutter display device includes a plurality of pixel circuits PX arranged in a matrix, a plurality of gate lines GL, a plurality of first video signal lines DL1, a plurality of second video signal lines DL2, and a plurality of pixel circuits PX. A common signal line CL, a video signal supply circuit XDV, a gate line scanning circuit YDV, and a common potential supply circuit CS are included. In the display device shown in the example of FIG. 1, each pixel circuit PX is irradiated with red, blue, and green light output in a time-sharing manner from a backlight in which light emitting diodes of three colors are arranged. An image is displayed by displaying pixels by controlling whether or not light is transmitted using a mechanical shutter. Each of the gate lines GL is provided corresponding to one of the columns of the pixel circuits PX, and one end of the gate line GL is connected to the gate line scanning circuit YDV. The common signal line CL is connected to each pixel circuit PX, and one end is connected to the common potential supply circuit CS. The first video signal line DL1 is provided corresponding to one of the columns of the pixel circuits PX, and the second video signal line DL2 is also provided corresponding to one of the columns of the pixel circuits PX. One ends of the first video signal line DL1 and the second video signal line DL2 are connected to the video signal supply circuit XDV. Each pixel circuit PX is connected to a gate line GL, a first video signal line DL1, a second video signal line DL2, and a common signal line CL corresponding to the pixel circuit PX. Each pixel circuit PX may control light reflection using a mechanical shutter instead of controlling light transmission.

  FIG. 2 is a circuit diagram showing an example of the configuration of the pixel circuit PX. Each pixel circuit PX includes two pixel switches T1 and T2, two capacitances C1 and C2, and a shutter mechanism unit M. Each of the pixel switches T1 and T2 is a thin film transistor including a gate electrode, a drain electrode, and a source electrode. The gate electrodes of the pixel switches T1 and T2 are connected to the gate line GL. The drain electrode of the pixel switch T1 is connected to the first video signal line DL1, and the source electrode is connected to the shutter mechanism unit M. One end of the capacitance C1 is connected to the source electrode of the pixel switch T1, and the other end is connected to a wiring for supplying a constant potential such as a ground wiring. Similarly, the drain electrode of the pixel switch T2 is connected to the second video signal line DL2, and the source electrode is connected to the shutter mechanism unit M. One end of the capacitance C2 is connected to the source electrode of the pixel switch T2, and the other end is connected to a ground wiring or the like. The common signal line CL is connected to the shutter mechanism unit M. When the gate line scanning circuit YDV supplies a pulse having a high level potential to the gate line GL, the pixel switches T1 and T2 are turned on. Then, a video signal is sent from the first video signal line DL1 to the shutter mechanism unit M, and the potential of the video signal is held even when the pixel switch T1 is turned off due to a potential difference stored in the capacitance C1. Further, a video signal is sent from the second video signal line DL2 to the shutter mechanism unit M, and the potential of the video signal is held even when the pixel switch T2 is turned off due to a potential difference stored in the capacitance C2. Note that since the thin film transistor has no polarity, the connection destination of the source electrode and the drain electrode may be opposite to that described above.

  FIG. 3 is a perspective view showing an example of the configuration of one pixel circuit PX. FIG. 4 is a plan view showing an example of the configuration of the shutter mechanism M. As shown in FIG. The array substrate SUBM and the sealing substrate SUBS face each other, and each pixel circuit PX is formed in a rectangular region (hereinafter referred to as a pixel region) on the array substrate SUBM. The shutter mechanism M is formed in the upper layer (the side closest to the sealing substrate SUBS) of the array substrate SUBM. The shutter mechanism unit M includes a shutter unit MS, a first actuator unit AC1, and a second actuator unit AC2. A shutter unit MS is provided in the center of the pixel region in the left-right direction in FIG. The shutter part MS is substantially rectangular in plan view, and the shutter part MS is provided with a rectangular shutter opening SH. In the shutter part MS and the shutter opening part SH, the direction in which the long side extends (long side direction) and the direction in which the short side extend (short side direction) coincide. The shutter unit MS moves in the short side direction of the shutter unit MS. A light shielding film is formed on the surface of the sealing substrate SUBS on the array substrate SUBM side. The light shielding film is provided with a light shielding film opening BH having the same shape as the shutter opening SH. The light shielding film opening BH is provided so as to substantially coincide with the shutter opening SH in a plan view when the shutter part MS is moved to the full side in either of the short sides. A dielectric liquid (for example, silicon oil) is filled between the sealing substrate SUBS and the array substrate SUBM facing the array substrate SUBM in order to increase electrostatic attraction. Note that dry nitrogen may be enclosed instead of the dielectric liquid.

  The first actuator portion AC1 and the second actuator portion AC2 are provided so as to face each other with the shutter portion MS interposed therebetween in the left-right direction in FIG. As shown in FIG. 4, the first actuator portion AC1 and the second actuator portion AC2 are provided on the left side and the right side of the pixel region, respectively. Each of the first actuator unit AC1 and the second actuator unit AC2 includes two shutter side anchors SA, two shutter side drive units SM, a control side anchor CA, and two control side drive units CM. . The two shutter-side anchors SA included in the first actuator unit AC1 are fixed to the left end of the pixel region at a position on the array substrate SUBM that faces each other with the control-side anchor CA interposed therebetween in the vertical direction. One shutter-side drive unit SM corresponds to each of the two shutter-side anchors SA included in the first actuator unit AC1. Each of the shutter side anchors SA is connected to the vicinity of the central portion of the shutter unit MS on the first actuator unit AC1 side via the corresponding shutter side drive unit SM. In plan view, each of the shutter-side drive units SM extends outward in the left-right direction from a point where it is connected to the shutter unit MS, changes its direction and extends outward in the vertical direction (this portion is referred to as a shutter-side beam unit SB). Further, it extends to the corner of the pixel area on the outer side in the left-right direction, and bends and connects to the corresponding shutter-side anchor SA. One control side drive unit CM is provided corresponding to each of the shutter side beam units SB. The control-side drive unit CM extends slightly inward in the left-right direction from the control-side anchor CA, and then extends while slightly bending toward a position adjacent to the outer end of the corresponding shutter-side beam unit SB (this portion is controlled on the control side). Called the beam portion CB). Then, it is bent from the adjacent position to the opposite side of the shutter side beam portion SB, extends toward the control side anchor CA, and is connected to the control side anchor CA. The details of the structure of the second actuator unit AC2 are the same except that the second actuator unit AC2 is symmetrical with respect to the shutter unit MS, that is, the left and right directions are opposite.

  The control side beam unit CB included in the first actuator unit AC1 is electrically connected to the source electrode of the pixel switch T1 via the control side anchor CA, and the control side beam unit CB included in the second actuator unit AC2 is It is electrically connected to the source electrode of the pixel switch T2 via the control side anchor CA. The shutter side beam unit SB included in the first actuator unit AC1 and the second actuator unit AC2 is connected to the common signal line CL via the shutter side anchor SA. To move the shutter unit MS, for example, a potential higher than the potential of the common signal line CL is applied to the control side beam unit CB included in the first actuator unit AC1, and the control side beam unit CB included in the second actuator unit AC2 is applied. The same potential as that of the common signal line CL is applied. Then, an electrostatic attractive force is generated between the control side beam unit CB and the shutter side beam unit SB of the first actuator unit AC1, and the shutter unit MS moves to the first actuator unit AC1 side. When the shutter unit MS moves toward the first actuator unit AC1, the electrostatic attractive force is proportional to the square of the distance. Therefore, first, the shutter side beam unit SB and the control side beam unit CB are located on the outer side in the long side direction of the closest rectangle. The portions are attracted to and in contact with each other, and thereafter, the inner portion gradually contacts with the movement of the shutter side beam unit SB and the deformation of the control side driving unit CM. Eventually, most of the shutter side beam portion SB and the control side beam portion CB come into contact with each other by electrostatic attraction. At that time, if the shutter opening SH and the light shielding film opening BH overlap, light is transmitted, and if not, the light is blocked. Hereinafter, regarding the surface that contacts when the shutter side beam unit SB and the control side beam unit CB come into contact, the SB side of the control side beam unit is the first contact surface, and the CB side of the shutter side beam unit is the second contact. It is described as a surface. When the shutter side beam portion SB and the control side beam portion CB are in contact, the first contact surface and the second contact surface are in contact. Further, hereinafter, the shutter side beam unit SB and the control side beam unit CB are collectively referred to as two beam units.

  When the two beam parts of the first actuator part AC1 are in contact with each other, the two beam parts of the second actuator part AC2 are separated from each other, so that a potential is simply applied to the control-side beam part CB included in the second actuator part AC2. However, the shutter part MS does not move only by applying the electrostatic attractive force Fe. First, the electrostatic attractive force Fe is prevented from acting between the two beam portions of the first actuator portion AC1, and the shutter portion MS returns to the center by the spring force Fs due to the elasticity of the shutter side drive portion SM, and then the second The electrostatic attractive force Fe works between the two beam portions of the two actuator portions AC2 by the same mechanism as that described for the first actuator portion AC1, and the shutter portion MS moves toward the second actuator portion AC2.

  The shutter-side beam part SB and the control-side beam part CB have a quadrangular cross section and are beam-like structures extending along the array substrate SUBM. Further, regarding the shutter side beam unit SB and the control side beam unit CB, the length in the direction (height direction) perpendicular to the substrate is larger than the length in the direction perpendicular to the extending direction and perpendicular to the height direction. Here, the direction in which the shutter-side beam unit SB and the control-side beam unit CB extend indicates the direction from the starting point to the end point if the shutter-side beam unit SB and the control-side beam unit CB are straight lines in a plan view, If so, it refers to the tangential direction.

  5A is a cross-sectional view showing an example of a cross section taken along the line AA of the shutter mechanism portion M shown in FIG. Here, the AA cutting line passes through a point where the shutter side beam part SB and the control side beam part CB come into contact with each other. That is, the cross section shown in FIG. 5A shows the positional relationship between the points where the two beam portions are in contact with each other when the two beam portions are in contact with each other. The direction of the cross section is a direction perpendicular to the extending direction of each of the two beam portions. The cross section of the control side beam portion CB is a trapezoid in which two sides extending in the direction along the array substrate SUBM are parallel to the two sides toward the first contact surface. The cross section of the shutter side beam portion SB has a trapezoidal shape in which two sides extending in the direction along the array substrate SUBM are parallel to the two sides toward the second contact surface.

  The control side drive unit CM including the control side beam unit CB includes the first electrode E1 and the first dielectric film DF1 covering the first electrode E1, and includes the shutter side beam unit SB. The part SM includes a second electrode E2 and a second dielectric film DF2 that covers the second electrode E2. The cross section of the first electrode E1 has a trapezoidal shape in which two sides extending in the direction along the array substrate SUBM are parallel to the two sides toward the first contact surface. The cross section of the second electrode E2 is a trapezoid in which two sides extending in a direction along the array substrate SUBM are parallel to the two sides toward the second contact surface. Further, the thickness of the portion of the first dielectric film DF1 between the first contact surface and the first electrode E1 is constant, and the second contact surface of the second dielectric film DF2 The thickness between the two electrodes E2 is constant. Further, a first line that is an intersection line (a right side of the cross section of the control side beam portion CB in FIG. 5A) between the first contact surface and a plane perpendicular to the extending direction of the control side beam portion CB; The second line that is on the second contact surface and is in contact with the first line when the first contact surface and the second contact surface are in contact with each other is not parallel. This is because a distance between a point on the first contact surface and a point on the second contact surface that are in contact with each other when the first contact surface and the second contact surface are in contact with each other is measured. This indicates that the point (second point) increases or decreases monotonously by moving in the direction parallel to the intersection line of the cross section and the first contact surface (second contact surface). In the example of FIG. 5A, if the array substrate SUBM is a flat surface, the above-mentioned distance monotonously increases as the array substrate SUBM moves away from the array substrate SUBM.

  FIG. 5B is a diagram illustrating an example of a cross section when the two beam portions illustrated in FIG. 5A are in contact with each other. When the two beam portions having the cross section shown in FIG. 5A are in contact with each other by the electrostatic attractive force Fe, the lower end where the first contact surface and the second contact surface are in contact (the distance is minimum) due to the change in the distance described above. Each of the two beam portions is rotated with a fulcrum FP as the fulcrum FP. The rotation causes the connecting portion between the control side beam portion CB and the control side anchor CA and the shutter side beam portion SB and the portion of the shutter side driving portion SM connected thereto to rotate in the opposite direction due to a twisting force or the like. A rotational force Ft is generated. This works in the same direction as the spring force Fs generated in the direction of separating the two beam portions due to the elastic force of the shutter side drive unit SM. Since the rotational force Ft acts as a force against the van der Waals force Fv in addition to the spring force Fs, the two beam portions can be separated even when the van der Waals force Fv cannot be opposed only by the spring force Fs. . The van der Waals force Fv is inversely proportional to the sixth power of the distance. Then, the decrease in the van der Waals force Fv is larger than the decrease in the rotational force Ft associated with the separation of the first contact surface of the control side beam portion CB and the second contact surface of the shutter side beam portion SB. For this reason, after the rotational force Ft is reduced, the two beam portions can be separated by only the spring force Fs. Further, since the rotational force Ft works only when the two beam portions are in contact with each other, the two beam portions can be brought into contact with each other even with an electrostatic attractive force Fe that has not been strengthened conventionally. The electrostatic attraction force Fe is most required before the two beam portions are in contact with each other, and therefore the rotational force Ft does not interfere with the contact between the two beam portions. It is also important that the rotation shown in FIG. 5B occurs in a cross section perpendicular to the direction in which the two beam portions extend. This is because the fulcrum FP and the place where the rotational force Ft should be transmitted are close to each other, so that the possibility that the force is attenuated by the deflection is low.

  FIG. 6 is a diagram illustrating an example of a cross section when electrostatic attraction Fe is applied to two beam portions included in a conventional shutter mechanism portion M. Conventionally, even if the first contact surface of the control-side beam unit CB and the second contact surface of the shutter-side beam unit SB are in contact with each other, no rotation occurs when viewed in a cross section perpendicular to the direction in which the two beam units extend. Therefore, no rotational force Ft is generated, and the spring force Fs that opposes the van der Waals force Fv must be stronger.

  Further, as shown in FIG. 5A, if the first contact surface or the second contact surface has a predetermined angle with respect to the traveling direction of the control-side beam unit CB and the shutter-side beam unit SB, the control-side beam unit CB. Further, the flow of the medium generated by the movement of the shutter side beam portion SB becomes smooth. Thereby, the moving speed of the shutter part MS is also improved. In order not to reflect the variation in the opening time due to the variation in the operation of the shutter unit MS in the display gradation, it is desirable to perform control not to irradiate light from the backlight while the shutter unit MS moves. In the case of performing this control, it is possible to improve the luminance by using the shortened moving time of the shutter unit MS for the light emission period.

  Hereinafter, an example of a manufacturing process of the MEMS shutter illustrated in FIG. 5A will be described. First, a circuit including a thin film transistor and the like is formed on the array substrate SUBM, and an insulating passivation layer is provided thereon. Next, a photosensitive resin such as a photoresist is patterned by lithography and cured with ultraviolet rays or the like to form an electrode processing sacrificial layer RG. The electrode processing sacrificial layer RG and the passivation layer have holes in portions corresponding to the shutter-side anchor SA and the control-side anchor CA. Next, the first electrode E1, the second electrode E2, the shutter part MS, and the like are formed on the electrode processing sacrificial layer RG. These are formed of amorphous Si doped with impurities, and their shapes are processed by anisotropic etching (see FIG. 7A). Next, an ashing process is performed from above. In the ashing process, the reaction proceeds preferentially from above containing a large amount of reactive groups, so that the cross section of the electrode can be processed into a trapezoid as shown in FIG. 7B. Subsequently, if the sacrificial layer RG for electrode processing is removed and an alumina dielectric film is formed on the processed first electrode E1 or the like by using an ALD (Atomic Layer Deposition) method, the two beam portions shown in FIG. A MEMS shutter is formed. Note that the first electrode E1 and the like may be other conductors such as metal, and the dielectric may be a dielectric other than alumina.

  The structures of the shutter side beam unit SB and the control side beam unit CB may be different from those described above. 8A is a cross-sectional view showing another example of a cross section taken along the line AA of the shutter mechanism portion M shown in FIG. Similarly to the example of FIG. 5A, the cross section of the control side beam portion CB has a trapezoidal shape in which two sides extending in the direction along the array substrate SUBM are parallel to the two sides toward the first contact surface. The cross section of the shutter side beam portion SB has a trapezoidal shape in which two sides extending in the direction along the array substrate SUBM are parallel to the two sides toward the second contact surface. Similarly to the example of FIG. 5A, the control-side drive unit CM including the control-side beam unit CB includes a first electrode E1 and a first dielectric film DF1 that covers the first electrode E1, The shutter-side drive unit SM including the shutter-side beam unit SB includes a second electrode E2 and a second dielectric film DF2 that covers the second electrode E2.

  Unlike the example of FIG. 5A, the cross section of the first electrode E1 and the second electrode E2 is a rectangle that is long in the direction perpendicular to the array substrate SUBM, and the cross section of the first electrode E1 and the second electrode E2 Inner sides are parallel. On the other hand, the thickness of the portion of the first dielectric film DF1 between the first contact surface and the first electrode E1 is perpendicular to the extending direction of the control side beam portion CB. As it moves in either direction parallel to the line of intersection of the surface and the first contact surface, it increases or decreases monotonously. In the example of FIG. 8A, the above-mentioned thickness increases monotonously as the distance from the array substrate SUBM increases. As a result, the first line which is an intersection line between the first contact surface and the surface perpendicular to the extending direction of the control side beam portion CB, the first contact surface and the second line on the second contact surface. The second line that is a line in contact with the first line when contacting the contact surface is not parallel.

  FIG. 8B is a diagram illustrating an example of a cross section when the two beam portions illustrated in FIG. 8A are in contact with each other. When the two beam portions having the cross section shown in FIG. 8A are in contact with each other by the electrostatic attractive force Fe, due to the cross-sectional shape described above, the first contact surface and the upper end where the second contact surface is in contact (the distance is minimum). Each of the two beam portions rotates with a fulcrum FP as a fulcrum FP. Due to the rotation, a rotation force Ft is generated in a direction in which the two beam portions are separated by the rotation on the opposite side to the case shown in FIG. 5B. As in the example shown in FIG. 5B, the rotational force Ft allows the two beam portions to be separated even when the van der Waals force Fv cannot be countered only by the spring force Fs.

  Next, an example of a manufacturing process of the MEMS shutter shown in FIG. 8A will be described. The process until the first electrode E1, the second electrode E2, and the like are formed on the electrode processing sacrificial layer RG is the same as the manufacturing process of the MEMS shutter shown in FIG. 5A. After the first electrode E1, the second electrode E2, and the like are processed by anisotropic etching, the electrode processing sacrificial layer RG is removed (see FIG. 9A). Next, plasma CVD treatment is performed on the Si nitride so that the film thickness is different between the upper side and the lower side. By controlling the radical supply rate-limiting condition during the plasma CVD process, a Si nitride film is preferentially formed on the top (see FIG. 9B). Thereby, a MEMS shutter having two beam portions shown in FIG. 8A can be formed.

  In the example shown in FIG. 8A, since the thicknesses of the first electrode E1 and the second electrode E2 do not change in the vertical direction, the electric resistance can be easily controlled to be constant. This makes it easier to keep a constant time constant determined by the capacitance generated between the control side drive unit CM and the shutter side drive unit SM and the electrical resistance. This time constant needs to be kept at a constant value in order to operate the shutter unit MS reliably.

  Only one cross section of the shutter side beam part SB and the control side beam part CB may be trapezoidal. 10A is a cross-sectional view showing another example of a cross section taken along the line AA of the shutter mechanism portion M shown in FIG. Unlike FIG. 5A, the cross section of the control side beam portion CB is a rectangle with a long side in a direction perpendicular to the direction in which the control side beam portion CB moves. The cross section of the shutter side beam portion SB has a trapezoidal shape in which two sides in the direction along the array substrate SUBM are parallel to the two sides toward the second contact surface. Similarly to the example of FIG. 5A, the control-side drive unit CM including the control-side beam unit CB includes a first electrode E1 and a first dielectric film DF1 that covers the first electrode E1, The shutter-side drive unit SM including the shutter-side beam unit SB includes a second electrode E2 and a second dielectric film DF2 that covers the second electrode E2.

  The cross section of the first electrode E1 is a rectangle that is long in the direction perpendicular to the substrate. The cross section of the second electrode E2 is a trapezoid in which two sides extending in a direction along the array substrate SUBM are parallel to the two sides toward the second contact surface. Further, the thickness of the portion of the first dielectric film DF1 between the first contact surface and the first electrode E1 is constant, and the second contact surface of the second dielectric film DF2 The thickness between the two electrodes E2 is constant. In addition, a first line that is an intersection line between the first contact surface and a surface perpendicular to the extending direction of the control side beam portion CB, and the first contact surface and the second contact that are on the second contact surface. The second line, which is a line in contact with the first line when contacting the surface, is not parallel.

  FIG. 10B is a diagram illustrating an example of a cross section when the two beam portions illustrated in FIG. 10A are in contact with each other. When the two beam portions having the cross section shown in FIG. 10A are in contact with each other by the electrostatic attractive force Fe, the first contact surface and the lower end where the second contact surface is in contact (the distance is minimum) due to the above-described cross-sectional shape. Each of the two beam portions rotates with a fulcrum FP as a fulcrum FP. Due to the rotation, a rotation force Ft is generated in the direction in which the two beam portions are separated by the rotation in the same direction as that shown in FIG. 5B. As in the example shown in FIG. 5B, the rotational force Ft allows the two beam portions to be separated even when the van der Waals force Fv cannot be countered only by the spring force Fs.

  Next, an example of a manufacturing process of the MEMS shutter illustrated in FIG. 10A will be described. The process until the first electrode E1, the second electrode E2, etc. are formed on the sacrificial layer RG for electrode processing is the same as the manufacturing process of the MEMS shutter shown in FIG. 5A (see FIG. 11A). Of the first electrode E1 and the second electrode E2 subjected to anisotropic etching, the first electrode E1 whose cross section does not have a trapezoidal shape and other members are covered with the protective resist film RGS, and then an ashing process is performed from above. Is done. By the ashing process, the second electrode E2 not covered with the protective resist film RGS is processed into a trapezoidal shape, and the first electrode E1 and the like are not processed as a rectangle (see FIG. 11B). Subsequently, the protective resist film RGS and the electrode processing sacrificial layer RG are removed, and an alumina dielectric film is formed on the processed first electrode E1 or the like using an ALD (Atomic Layer Deposition) method. A MEMS shutter having the two beam portions shown is formed.

  Since the tip side of the control side beam portion CB is bent more greatly, it is desirable to avoid a decrease or variation in the spring stress of the control side beam portion CB. Therefore, a more stable operation can be performed by avoiding a decrease or variation in spring stress due to the processing of the first electrode E1. In addition, since the above-described manufacturing method can process only necessary portions of the two beam portions, there is an advantage that the characteristics of other members can be easily optimized.

  FIG. 12 is a diagram illustrating an example of a portable information terminal WT using the display device according to the embodiment of the present invention. The portable information terminal WT includes a display device DISP having the same configuration as the display device shown in FIG. 1, a display controller CTL, a memory MEM, a microprocessor MPU, an input / output circuit IO, a wireless communication circuit WL, a power supply Circuit PWR. The microprocessor MPU controls communication and display using the input / output circuit IO and the display controller CTL based on a program stored in the memory MEM. The wireless communication circuit WL exchanges data with the outside by wireless communication, and the data received by the wireless communication circuit WL is input and stored in the memory MEM via the input / output circuit IO. The power supply circuit PWR is composed of a secondary battery or the like and supplies power to each part. When browsing information on the Internet, for example, the wireless communication circuit WL takes in image data compressed from the outside under the control of the microprocessor MPU and transfers it to the microprocessor MPU and the memory MEM via the input / output circuit IO. To do. Then, the microprocessor MPU decodes the compressed image data and performs signal processing based on a user instruction, and stores the display data in the memory MEM. Further, in accordance with an instruction from the microprocessor MPU, the display controller CTL acquires the display data and causes the display device DISP to display an image indicated by the display data. According to the present invention, the performance of the display device DISP can be improved, the cost of the portable information terminal WT can be reduced, and the performance such as the battery duration can be improved.

  CL common signal line, CS common potential supply circuit, DL1 first video signal line, DL2 second video signal line, GL gate line, PX pixel circuit, XDV video signal supply circuit, YDV gate line scanning circuit, T1, T2 Pixel switch, C1, C2 capacitance, M shutter mechanism, AC1 first actuator, AC2 second actuator, BH light shielding film opening, CA control side anchor, CB control side beam, CM control side drive, MS shutter part, SA shutter side anchor, SB shutter side beam part, SH shutter opening part, SM shutter side drive part, SUBS sealing substrate, SUBM array substrate, DF1 first dielectric film, DF2 second dielectric film, E1 1st electrode, E2 2nd electrode, FP fulcrum, Fe electrostatic attraction, Fs spring force, Ft rotational force, Fv Anderuwarusu force, RG electrode processing sacrificial layer, RGS protective resist film, CTL display controller, DISP display device, IO output circuit, MEM a memory, MPU microprocessor, PWR power supply circuit, WL wireless communication circuit, WT portable information terminal.

Claims (9)

A substrate,
A movable shutter;
A beam-shaped first beam portion connected to the substrate and having a first electrode therein;
A beam-like second beam portion connected to the shutter portion and having a second electrode therein;
Including
The first surface of the first beam portion on the second beam portion side and the second surface of the second beam portion on the first beam portion side are the first electrode. And is movable by electrostatic attraction generated by the second electrode, and has a first state in contact with each other and a second state in which they are separated from each other,
The first surface and the second surface have a first end portion on the substrate side and a second end portion opposite to the first end portion,
In the second state, the distance between the first surface and the second surface is larger at the second end than at the first end. . When the first surface and the second surface are separated from each other, a first line that is an intersection line of the first surface and a surface perpendicular to the extending direction of the first beam portion; A second line that is opposite to the first line on the second surface is not parallel to the first line;
The display device according to claim 1. The cross section of the first beam portion perpendicular to the direction in which the first beam portion extends is a trapezoid in which two sides toward the first surface are parallel to each other.
The display device according to claim 2. The first beam portion has the first electrode and a first dielectric film covering the first electrode,
The cross section of the first electrode perpendicular to the direction in which the first beam portion extends is a trapezoid whose two sides toward the first surface are parallel.
The display device according to claim 3. The first beam portion has the first electrode and a first dielectric film covering the first electrode,
The thickness of the first dielectric film in the direction perpendicular to the first surface is any direction parallel to the intersection line of the first surface and the surface perpendicular to the extending direction of the first beam portion. Monotonically increasing or decreasing monotonically,
The display device according to claim 3. The cross section perpendicular to the direction in which the second beam portion extends in the second beam portion is a trapezoidal shape in which two sides toward the second surface are parallel.
The display device according to claim 2. The second beam portion includes the second electrode and a second dielectric film covering the second electrode,
The cross section of the second electrode perpendicular to the direction in which the second beam portion extends is a trapezoid in which two sides toward the second surface are parallel.
The display device according to claim 6. The second beam portion includes the second electrode and a second dielectric film covering the second electrode,
The thickness of the second dielectric film in the direction perpendicular to the second surface is any direction parallel to the intersection line of the second surface and the surface perpendicular to the extending direction of the second beam portion. Monotonically increasing or decreasing monotonically,
The display device according to claim 6. The distance between the first surface and the second surface monotonously increases in a direction from the first end portion to the second end portion. The display device according to any one of the above.

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