JP6353249B2 - Display element and display device - Google Patents

Description

  The present invention relates to a display element and a display device, and more particularly to a display element and a display device using a micro electrical mechanical system (MEMS) element using a piezoelectric material as a driving material.

  Currently, flat panel displays such as liquid crystal displays and PDPs have become the mainstream of society, replacing CRT displays that have been the main players for a long time. Is widely used as a display for many devices such as mobile phones, tablets, and portable audio players. Among flat panel displays, the main role of the current display is a liquid crystal display, but it requires polarized illumination light as a major limitation in operation. In general, the amount of light is significantly attenuated by the polarization of illumination light, thereby lowering the brightness of the display. Increasing the brightness increases power consumption and requires relatively expensive optical components. For this reason, the contrast ratio of the liquid crystal display is generally low, which lowers the clarity of the display image and the quality of the entire display image. In particular, when the display is used outdoors, there is a big problem that it is difficult to see because the luminance is low. If the brightness is increased, the power consumption increases, which is a major drawback for mobile devices using batteries. In addition, there is a problem that a complicated and expensive component structure and a difficult manufacturing process are generally required.

  In order to solve the above-mentioned problems such as low screen brightness, low contrast ratio, large power consumption, and complicated structure, a display element and a display device using a micro electrical mechanical system (MEMS) are provided. Proposed.

  Patent Document 1 (Japanese Patent Application Laid-Open No. 2003-270589) has an electrostatic MEMS actuator in which an aperture corresponding to each pixel of a display and a reflection plate are formed, and light that is reflected by the reflection plate is reflected. Has a mechanism for using the display for display through the aperture. The electrostatic MEMS actuator is a cantilever type actuator. When the electrostatic MEMS actuator is deformed by an electrostatic force when it is energized, the angle of the reflection plate changes due to the change in the angle of the reflector. As a result, the operation principle is such that the amount of light passing through the aperture changes. However, the displacement of the reflector is small for the large area occupied by the electrostatic MEMS actuator for each pixel. In addition, since the aperture area is small, the amount of light passing therethrough is small, and the shape of the electrostatic MEMS actuator is small. Since it is large, the pixel becomes large and high definition is difficult. In addition, since the electrostatic actuator is driven at a high voltage, the power consumption is large, and since the electrostatic MEMS actuator is large, there is a disadvantage that the configured device becomes large.

  Patent Document 2 (Japanese Patent Laid-Open No. 2008-197668) and Patent Document 3 (Japanese Patent Laid-Open No. 2011-039534) are displays of electrostatic MEMS actuators, and electrostatic that drives an aperture and a shutter corresponding to each pixel. A display is constructed by controlling the amount of incoming light by opening and closing the aperture with the shutter by driving the shutter by deforming the electrostatic MEMS actuator by energizing a high voltage. An electrostatic MEMS actuator is two cantilever actuators. However, the area occupied by the electrostatic MEMS actuator is larger than the area of the pixel. As a result, the aperture area through which the light passes is small, so that the amount of light passing therethrough is small. In addition, the electrostatic actuator requires a high voltage drive and has a disadvantage that power consumption increases.

  As described above, since the electrostatic MEMS display employs electrostatic force as a driving force, the driving voltage is high, the driving force is small, and a large actuator is required to drive a reflector, a shutter, and the like. I need it. As a result, the area occupied by the actuator increases with respect to the area of the pixel. As a result, the aperture area becomes small, and the amount of light that can be controlled decreases, making it difficult to realize a highly efficient and bright display. In addition, it is difficult to increase the definition of the display due to the need for an actuator having a large shape, and in addition, the power consumption is high due to the need for a high voltage.

  On the other hand, Patent Document 4 (Japanese Patent Application Laid-Open No. 2001-356281) uses an organic piezoelectric material as a shutter actuator material and employs a cantilever type actuator as the actuator shape, so that the drive voltage can be lowered. , Power consumption can be reduced. In addition, since the actuator material is organic, the range of motion is large, the shape of the shutter actuator can be relatively small, and the display device can have high definition. However, the organic piezoelectric material has a large elastic constant and a temperature characteristic of the piezoelectric constant, a change in the shutter operation increases due to a change in environmental temperature, and a characteristic of the organic piezoelectric material changes due to a change with time. That is, there is a problem that operations of the display element and the display device become unstable.

  Patent Document 5 (Japanese Patent Publication No. 2002-512701) uses an inorganic piezoelectric material such as PZT or PLZT as a shutter actuator material, and basically employs a cantilever type actuator as the actuator shape. In addition, the drive voltage can be lowered and the power consumption can be reduced. The inorganic piezoelectric material has small elastic constants and temperature characteristics of the piezoelectric constant, and the operation of the display element and the display device is stable against changes in environmental temperature. However, since the actuator material is inorganic, the movable range is small, the shape of the shutter actuator is larger than that of Patent Document 4, and it is difficult to increase the definition of the display device.

  As described above, since the piezoelectric MEMS display employs piezoelectric power as a driving force as an actuator, the driving voltage is low and the driving force is large. Therefore, an actuator smaller than the electrostatic type may be used to drive the reflecting plate and the shutter. As a result, the area occupied by the actuator is reduced with respect to the area of the pixel, the area of the aperture is increased, and the amount of light that can be controlled from the electrostatic type is increased. However, high definition corresponding to future high definition is still difficult. The reason for this is that the piezoelectric actuator is a simple operation of a cantilever structure and a sufficient movable region cannot be realized, and therefore sufficient size reduction cannot be achieved.

JP 2003-270589 A JP 2008-197668 A JP 2011-039534 A JP 2001-356281 A Japanese translation of PCT publication No. 2002-512701

  An object of the present invention is to provide a display element and a display device that can reduce the size of a shutter actuator to cope with high definition, have low power consumption, high contrast, high brightness, simple structure, and high reliability. It is to provide.

  The present invention relates to a shielding plate that does not transmit light, an aperture that is provided on the shielding plate and transmits light, a shutter that opens and closes the aperture, and a piezoelectric that uses a micro-electrical mechanical system element that uses a piezoelectric material as a driving material. A display element having a drive unit, comprising a square bar part in contact with a shutter, forming a piezoelectric drive part near both ends of the square bar part, and applying an alternating voltage to the piezoelectric drive part The display element controls the light passing through the aperture by exciting an elastic traveling wave and moving the shutter to open and close the aperture.

  In the present invention, an AC voltage is applied to the piezoelectric driving units installed on both sides of the square bar portion to excite the elastic traveling wave, and the shutter is moved by repeatedly driving the elastic traveling wave. The shutter actuator can be reduced in size as compared with a single operation actuator having a simple structure such as a structure.

  The present invention also utilizes a shielding plate that does not transmit light, an aperture that is provided on the shielding plate to allow light to pass through, a shutter that opens and closes the aperture, and a micro-electrical mechanical system element that uses a piezoelectric material as a driving material. A display element having a piezoelectric drive unit configured to form a protrusion that is inclined and in contact with a shutter, and the piezoelectric drive unit is formed on the protrusion, and an AC voltage is applied to the piezoelectric drive unit to generate an elastic standing wave. Is a display element that constitutes a piezoelectric drive unit that controls light passing through the aperture by opening and closing the aperture by moving the shutter.

  In the present invention, the shutter is moved by repeatedly driving the bumps by applying an AC voltage to the piezoelectric driving unit installed on the protruding portion to excite the elastic standing wave. The shutter actuator can be reduced in size as compared with a single-operation actuator having a structure.

  The display device of the present invention includes the display element.

  SUMMARY OF THE INVENTION An object of the present invention is to realize a display device and a display that realizes downsizing of a shutter actuator and can cope with high definition, and has low power consumption, high contrast, high brightness, simple structure, and high reliability. An apparatus can be provided.

3 is a plan view of the display element of Embodiment 1. FIG. (A) thru | or (D) are the top views of one unit of the display element of Embodiment 1. FIG. 6 is a partial diagram illustrating an operation of the display element of Embodiment 1. FIG. FIG. 10 is another partial view for explaining the operation of the display element of the first embodiment. 6 is a plan view of a display element according to Embodiment 2. FIG. (A) thru | or (D) are the top views of one unit of the display element of Embodiment 2. FIG. (A) And (B) is a partial figure explaining operation | movement of the display element of Embodiment 1. FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment 1)
FIG. 1 is a plan view of a display element 100 constituting a display device of the present invention. In the figure, reference numeral 101 denotes a thin plate such as silicon or glass plate that can be easily processed precisely, and is a shielding plate whose surface is covered with a metal thin film, a ceramic thin film or the like so that light is not transmitted when the material is transparent. The shielding plate 101 has apertures (windows) 102a1, 102a2,..., 102b1, 102b2,..., 102c1, 102c2,. 103a1, 103a2,..., 103b1, 103b2,..., 103c1, 103c2,... Are actually shutters and are not visible because they exist behind the shielding plate 101. Therefore, it is displayed transparently. 104 a 1-1, 104 a 1-2, 104 a 1-3, 104 a 1-4,. Part. Here, the symbols are written only in the portions surrounding the aperture 102a1 and the shutter 103a1, but the symbols are also given to the portions surrounding the aperture 103a2 and the shutter 103a2, the aperture 103b1, the shutter 103b1,. The aperture 102a1, the shutter 103a1, and the piezoelectric driving units 104a1-1, 104a1-2, 104a1-3, and 104a1-4 constitute one unit (display element), and this unit corresponds to a pixel of the display device. That is, as many units as the number of pixels of the display device are formed on the shielding plate 101. 105 a 1, 105 b 1, etc. are slits for vibration isolation. In FIG. 1, only a part is given a sign for easy understanding, and the vertical units shown in FIG. ing.

  FIG. 2 is a plan view of one unit of the display element 100 of FIG. 1, and the symbols in the figure are the same as those in FIG. In FIG. 2, small slits 106a1 and 106b1 are provided in the shielding plate 101, and the shutter 103b1 is fitted into the slits 106a1 and 106b1, and is configured to move in the horizontal direction parallel to the paper surface along the slits 106a1 and 106b1. ing. The slit 105a1 and the slit 106a1 form a square bar portion that is elastically separated, and the slit 105b1 and the slit 106b1 also form a square bar portion that is elastically separated. Piezoelectric drive units 104a1-1, 104a1-2, 104a1-3, and 104a1-4 are formed in the vicinity of both ends of these square bar portions. In FIG. 2, two square bar portions are provided. However, if the shutter 103b1 is stably moved in the horizontal direction in parallel to the paper surface, either one may be provided. FIG. 2A shows a state in which the shutter 103b1 is completely opened.

  Here, when a driving AC voltage is applied to the piezoelectric driving units 104b1-1 and 104b1-2 made of a piezoelectric thin film, an elastic traveling wave is generated between the slit 105a1 and the slit 106a1 as indicated by an arrow in FIG. The rod portion and the square rod portion between the slit 105b1 and the slit 106b1 advance from left to right. The two elastic traveling waves drive the shutter 103b1, and the shutter 103b1 moves from the left to the right as shown in FIG. 2B, and closes the aperture 102b1. Here, if the drive voltage applied to the piezoelectric drive units 104b1-1 and 104b1-2 is an asymmetric voltage waveform such as a sawtooth wave, drive efficiency can be increased. Further, if the piezoelectric thin films 104b1-3 and 104b1-4 are terminated with an impedance in the vicinity of the matching impedance, the traveling elastic wave can be absorbed and the driving efficiency can be increased. FIG. 2C shows a state in which the aperture 102b1 is completely closed by the shutter 103b1.

  Conversely, when a driving AC voltage is applied to the piezoelectric driving units 104b1-3 and 104b1-4, as shown by arrows in FIG. 2D, elastic traveling waves are generated from the square bar portions between the slits 105a1 and 106a1, and The square bar portion between the slit 105b1 and the slit 106b1 advances in the opposite direction (from right to left) as shown in FIG. Similarly, the elastic traveling wave drives the shutter 103b1, and the shutter 103b1 travels from the right to the left as shown in FIG. 2D, and opens the aperture 102b1. As a result, the aperture 102b1 can be opened and closed by driving the piezoelectric thin films 104b1-1 and 104b1-2 or the piezoelectric thin films 104b1-3 and 104b1-4 with an alternating voltage.

  FIG. 3 is a partial view of the square bar portion for explaining in detail the operation of driving the shutter 103b1 by the elastic traveling wave. The square bar portion between the slit 105a1 and the slit 106a1 of the shielding plate 101 is enlarged. The portion shown in FIG. 3 is elastically separated by the slit 105a1 and the slit 106a1, and can be regarded as an almost independent square bar in terms of elastic vibration. Piezoelectric materials such as PZT and PLZT are formed at both ends of the square bar portion 110 as piezoelectric drive portions (piezoelectric thin films) 104b1-1 and 104b1-3 by a method such as sputtering, CVD, or sol-gel. For example, when an AC voltage is applied to the piezoelectric drive unit 104b1-1, the piezoelectric drive unit 104b1-1 starts elastic vibration due to the piezoelectric effect, and this piezoelectric vibration (elastic wave) causes the square bar unit 110 to move as indicated by the arrow in FIG. Proceed in the direction. Since the piezoelectric vibration traveling wave is reflected by the piezoelectric drive unit 104b1-3 and becomes a standing wave component, the piezoelectric drive unit 104b1-3 is electrically short-circuited with a resistance close to the matching impedance, and the square bar unit 110 is connected. The traveling acoustic wave that has traveled is converted to a voltage by the piezoelectric drive unit 104b1-3 and lost by resistance, thereby obtaining an traveling acoustic wave having a small standing wave component. Both the elastic traveling wave and the elastic traveling wave of the square bar portion between the slit 105b1 and the slit 106b1 of the shielding plate 101 drive the shutter 103b1, and move the shutter 103b1 in the traveling direction of the elastic traveling wave. Although the figure shows a case where the shutter 103b1 is driven from the left to the right of the page, the same applies to the case where the shutter 103b1 is driven from the right to the left of the page.

  FIG. 4 is a partial view of another square bar portion for explaining in detail the operation of driving the shutter 103b1 by the elastic traveling wave. Similar to FIG. 3, the portion between the slit 105a1 and the slit 106a1 of the shielding plate 101 is shown. It has expanded. In the description of FIG. 3, since the piezoelectric vibration is only driven by the AC voltage to the piezoelectric drive unit 104b1-1, the piezoelectric vibration proceeds to both sides of the piezoelectric drive unit 104b1-1, so that about half of the vibration energy is wasted. However, in FIG. 4, since the notch portions 111 are formed on both sides of the piezoelectric drive units 104b1-1 and 104b1-3, the piezoelectric vibration mainly proceeds to the right side of the piezoelectric drive unit 104b1-1. Elastic traveling waves can be obtained with high efficiency, and the shutter 103b1 can be driven with higher efficiency.

  A transmissive display device can be configured by installing a light source on one side of the display element 100 described above, opening and closing the aperture 102 with a shutter 103, and viewing from the other side, and installing a mirror on one side of the display element 100 Alternatively, a reflective display device can be configured by configuring a mirror in the shutter 103 and opening and closing the aperture 102 with the shutter 103 and viewing from the same side as the light. If the mirror is a half mirror, a display device having both a transmission type and a reflection type function can be configured.

(Embodiment 2)
FIG. 5 is a plan view of a display element 200 used to constitute another display device of the present invention. In the figure, reference numeral 201 denotes a thin plate such as silicon or glass plate that can be processed precisely. In the case of a material that transmits light, 201 is a shielding plate whose surface is covered with a metal thin film, a ceramic thin film, or the like so as not to transmit light. Apertures (windows) 202a1, 202a2,..., 202b1, 202b2,..., 202c1, 202c2,... Are opened in the shielding plate 201, and light passes through these apertures. 203a1, 203a2,..., 203b1, 203b2,..., 203c1, 203c2... Shutters open and close the aperture. Although the shutter is actually not visible because it is behind the shielding plate 201, it is shown here in a transparent manner for easy understanding of the operation. 204a1-1, 204a1-2, 204a1-3, 204a1-4,... Are PZT and PLZT formed on the protrusions 205a1-1, 205a1-2, 205a1-3, 205a1-4,. , PLT, ZnO, etc., a piezoelectric drive unit formed of a piezoelectric thin film. Here, symbols are given only to a part for easy viewing of the figure. Aperture 202a1, shutter 203a1, protrusions 205a1-1, 205a1-2, 205a1-3, 205a1-4 and piezoelectric driving units 204a1-1, 204a1-2, 204a1-3, 204a1-4 constitute one unit, This unit corresponds to a pixel of a display element or a display device. That is, as many units as the number of pixels of the display device are formed on the shielding plate 201.

  6 is a plan view of one unit of the display device 200 of FIG. 5, and the symbols in the figure are the same as those in FIG. FIG. 6A shows a state in which the shutter 203a1 is completely opened.

  Here, when a driving AC voltage is applied to the piezoelectric driving units 204a1-1 and 204a1-2 made of piezoelectric thin films, as shown in FIG. 6B, the protrusions 205a1-1 and 205a1-2 are in the direction of the white arrow. Since the protrusions 205a1-1 and 205a1-2 and the shutter 203a1 are tilted due to elastic vibration, both the protrusions 205a1-1 and 205a1-2 push the shutter 203a1 and drive the shutter 203a1. As shown in (A), the sheet moves from the left to the right of the page, and the aperture 202b1 is closed. Here, if the drive AC voltage applied to the piezoelectric thin films 204a1-1 and 204a1-2 is a frequency near the resonance of the protrusions 205a1-1 and 205a1-2, the drive efficiency can be increased. FIG. 6C shows a state in which the aperture 202a1 is completely closed by the shutter 203a1.

  Conversely, when a driving AC voltage is applied to the piezoelectric thin films 204a1-3 and 204a1-4, as shown in FIG. 6D, the protrusions 205a1-3 and 205a1-4 are deformed in the direction of the arrow, and the shutter 203a1 is moved. As a result, the shutter 203a1 moves from the right to the left as shown in FIG. 6D to open the aperture 202a1. That is, the aperture 202a1 can be opened and closed by applying a driving AC voltage to the piezoelectric thin films 204a1-1 and 204a1-2 or the piezoelectric thin films 204a1-3 and 204a1-4. Here, the protrusions are installed on both sides of the shutter, but may be installed only on one side if the shutter moves smoothly.

  FIG. 7 is a partial view for explaining in detail the operation of pushing and driving the shutter 203a1 by the elastic standing wave of the protrusion, and the upper half of the unit of FIG. 6 is drawn. On the protrusions 205a1-3 and 205a1-3, piezoelectric materials such as PZT and PLZT are formed as piezoelectric driving portions (piezoelectric thin films) 204a1-1 and 204a1-3 by a method such as sputtering, CVD, or sol-gel. Yes. For example, in FIG. 6A, when an AC voltage is applied to the piezoelectric drive unit 204b1-1, the protrusion 204a1-1 starts elastic vibration in the direction of the white arrow in the figure due to the piezoelectric effect. Since the protrusion 204a1-1 is installed in contact with the shutter 203a1, the protrusion 204a1-1 hits the shutter 203a1 and moves the shutter 203a1 in the direction of the arrow (from the left to the right of the page). FIG. 6B shows a case where the shutter 203a1 is driven from the right to the left of the drawing.

  If a light source is installed on one side of the display element 200 described above, the aperture 202 is opened and closed by the shutter 203, and viewed from the other side, a transmissive display device can be configured, and a mirror is installed on one side of the display element 200. When the shutter 203 is configured with a mirror and the aperture 202 is opened and closed by the shutter 203 and viewed from the direction of light, a reflective display device can be configured. If the mirror is a half mirror, a display device having both a transmission type and a reflection type function can be configured.

  The present invention relates to a display element and a display device, and more particularly to a display element and a display device using a micro electrical mechanical system (MEMS) element using a piezoelectric material as a driving force. The display element and the display device of the present invention have a high contrast ratio, high clarity of the display image, high quality of the entire display image, and low power consumption. Therefore, it can be widely used as a monitor of a TV or a personal computer with a large screen and as a display of many devices such as a mobile phone, a tablet, and a portable audio player with a small screen.

DESCRIPTION OF SYMBOLS 100 Display element 101 Shielding plate 102a1, 102a2, ... Aperture (window)
103a1, 103a2, ... Shutter 104a1-1, 104a1-2, ... Piezoelectric thin film 105a1, 104b1, ... Slit 110 Square bar part 111 Notch part 200 Display element 201 Shielding plate 202a1, 202a2, ... Aperture (window)
203a1, 203a2, ... Shutter 204a1-1, 204a1-2, ... Piezoelectric thin film 205a1-1, 205a1-2, ... Projection

Claims (5)

A shielding plate that does not transmit light;
An aperture provided on the shielding plate to allow light to pass through;
A shutter for opening and closing the aperture;
A display element having a piezoelectric drive unit using a micro-electrical mechanical system element using a piezoelectric material as a drive material,
Consists of a protrusion that touches the shutter at an angle,
The piezoelectric driving unit excites an elastic standing wave by applying an alternating voltage to the protrusion, opens and closes the aperture by moving the shutter by the elastic standing wave, and passes through the aperture. A display element configured to control light. 2. The display element according to claim 1 , wherein at least two of the protrusions are in contact with only one side of the shutter, or at least four of the two sides on both sides. The display element according to claim 1 , wherein the protrusion is configured to contact one side of the shutter, and a driving AC voltage is applied to one side of the piezoelectric driving unit. The protrusion configured to contact with both sides of the shutter, according to claim 1, characterized in that applying two AC driving voltage to one side of the piezoelectric driving unit on the same side of the moving direction of the shutter Display element. A display device comprising the display element according to claim 1, 2, 3 or 4 .

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