Patent Application
20120056855
This disclosure relates to electromechanical systems and display devices.
Electromechanical systems include devices having electrical and mechanical elements, actuators, transducers, sensors, optical components (e.g., mirrors) and electronics. Electromechanical systems can be manufactured at a variety of scales including, but not limited to, microscales and nanoscales. For example, microelectromechanical systems (MEMS) devices can include structures having sizes ranging from about a micron to hundreds of microns or more. Nanoelectromechanical systems (NEMS) devices can include structures having sizes smaller than a micron including, for example, sizes smaller than several hundred nanometers. Electromechanical elements may be created using deposition, etching, lithography, and/or other micromachining processes that etch away parts of substrates and/or deposited material layers, or that add layers to form electrical and electromechanical devices.
One type of electromechanical systems device is called an interferometric modulator (IMOD). As used herein, the term interferometric modulator or interferometric light modulator refers to a device that selectively absorbs and/or reflects light using the principles of optical interference. In some implementations, an interferometric modulator may include a pair of conductive plates, one or both of which may be transparent and/or reflective, wholly or in part, and capable of relative motion upon application of an appropriate electrical signal. In an implementation, one plate may include a stationary layer deposited on a substrate and the other plate may include a reflective membrane separated from the stationary layer by an air gap. The position of one plate in relation to another can change the optical interference of light incident on the interferometric modulator. Interferometric modulator devices have a wide range of applications, and are anticipated to be used in improving existing products and creating new products, especially those with display capabilities.
The systems, methods and devices of the present disclosure each have several innovative aspects, no single one of which is solely responsible for the desirable attributes disclosed herein.
One innovative aspect of the subject matter described in this disclosure can be implemented in a display device including a first electrode, a movable layer, and a first capacitance control layer. At least a portion of the movable layer can be configured to move toward the first electrode when a first voltage is applied across the first electrode and the movable layer. An interferometric cavity can be disposed between the movable layer and the first electrode. The first capacitance control layer can be configured to decrease the magnitude of a first electric field between the movable layer and the first electrode when the voltage is applied across the movable layer and the first electrode. The first capacitance control layer can be disposed on a portion of the movable layer and positioned at least partially between the first electrode and the movable layer. The first capacitance control layer can be at least partially transmissive. The capacitance control layer can be configured to decrease the magnitude of a first electric field between the movable layer and the first electrode when the first voltage is applied across the movable layer and the first electrode. The device can also include a second electrode, with a portion of the movable layer being between the first electrode and the second electrode, and a second capacitance control layer disposed on the movable layer between the second electrode and the movable layer.
In one aspect, the first electrode can include a conductive layer and an absorber layer that is at least partially transmissive. In another aspect, the display device also can include a second electrode and a portion of the movable layer can be disposed between the first electrode and the second electrode. In some aspects, the movable layer can be configured to move toward the second electrode when a second voltage is applied between the second electrode and the movable layer and the device can further include a second capacitance control layer disposed on a portion of the movable layer. The second capacitance control layer can be positioned at least partially between the second electrode and the movable layer and can be configured to decrease the magnitude of a second electric field between the movable layer and the second electrode when the second voltage is applied across the movable layer and the second electrode. In some aspects, the first capacitance control layer can include a dielectric material, for example, silicon dioxide or silicon oxynitride. The first capacitance control layer can have a thickness dimension between about 100 nm and about 4000 nm. Additionally, the first capacitance control layer can have a thickness dimension that is about 150 nm and the first capacitance control layer and the first electrode can define an air gap therebetween having a thickness dimension between about 300 nm and about 700 nm.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a display device including an electrode, means for interferometrically modulating light, and control means for decreasing the magnitude of an electric field between the electrode and the modulating means when a voltage is applied across the modulating means and the electrode. At least a portion of the modulating means can be configured to move toward the first electrode when a voltage is applied across the first, electrode and the modulating means and an interferometric cavity can be disposed between the modulating means and the first electrode. The control means can be disposed on a portion of the modulating means and positioned at least partially between the electrode and the modulating means. The control means can be at least partially transmissive. In one aspect, the electrode includes means for absorbing light and can be at least partially transmissive. In one aspect, the control means can include a dielectric material.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a display device including a first electrode, an absorber layer disposed at least partially on the first electrode, the absorber layer being at least partially transmissive, a movable layer disposed such that at least a portion of the absorber layer is positioned between at least a portion of the movable layer and at least a portion of the first electrode, at least a portion of the movable layer can be configured to move toward the first electrode when a voltage is applied across the first electrode and the movable layer, an interferometric cavity defined between the movable layer and the absorber layer, and a first capacitance control layer configured to decrease the magnitude of a first electric field between the movable layer and the first electrode when the voltage is applied across the movable layer and the first electrode, the first capacitance control layer being disposed on a portion of the absorber layer, the first capacitance control layer being positioned at least partially between the absorber layer and the movable layer, the first capacitance control layer being at least partially transmissive. In one aspect, the device also can include a second electrode and a portion of the movable layer can be disposed between the first electrode and the second electrode. The device also can include a second capacitance control layer disposed on a portion of the second electrode and positioned at least partially between the second electrode and the movable layer.
Another innovative aspect of the subject matter described in this disclosure can be implemented in a display device including an electrode, a movable layer, and a capacitance control layer configured to decrease the magnitude of an electric field between the movable layer and the electrode when a voltage is applied across the movable layer and the electrode. At least a portion of the movable layer can be configured to move toward the electrode when a voltage is applied across the first electrode and the movable layer and an interferometric cavity can be defined between the first electrode and the movable layer. The movable layer can include a first portion, a second portion that is offset from the first portion, and a step between the first portion and the second portion. The capacitance control layer can be disposed on the second portion of the movable layer and positioned at least partially between the electrode and the movable layer. In one aspect, the capacitance control layer includes a dielectric material and the capacitance control layer can be at least partially transmissive.
One innovative aspect of the subject matter described in this disclosure can be implemented in a method of manufacturing a display device. The method can include providing a first electrode, forming a first sacrificial layer over the first electrode, forming a first capacitance control layer over the sacrificial layer, and forming a movable layer over the first sacrificial layer. In some implementations, the method can include forming a first protective layer between the first sacrificial layer and the first capacitance control layer. In another implementation, the method can include forming a second sacrificial layer over the movable layer, positioning a second electrode over the second sacrificial layer, and removing the first and second sacrificial layers. In some aspects, the method can include forming a second capacitance control layer between the movable layer and the second sacrificial layer and forming a second protective layer between the second capacitance control layer and the second sacrificial layer.
Details of one or more implementations of the subject matter described in this specification are set forth in the accompanying drawings and the description below. Other features, aspects, and advantages will become apparent from the description, the drawings, and the claims. Note that the relative dimensions of the following figures may not be drawn to scale.
Like reference numbers and designations in the various drawings indicate like elements.
The following detailed description is directed to certain implementations for the purposes of describing the innovative aspects. However, the teachings herein can be applied in a multitude of different ways. The described implementations may be implemented in any device that is configured to display an image, whether in motion (e.g., video) or stationary (e.g., still image), and whether textual, graphical or pictorial. More particularly, it is contemplated that the implementations may be implemented in or associated with a variety of electronic devices such as, but not limited to, mobile telephones, multimedia Internet enabled cellular telephones, mobile television receivers, wireless devices, smartphones, bluetooth devices, personal data assistants (PDAs), wireless electronic mail receivers, hand-held or portable computers, netbooks, notebooks, smartbooks, printers, copiers, scanners, facsimile devices, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, electronic reading devices (e.g., e-readers), computer monitors, auto displays (e.g., odometer display, etc.), cockpit controls and/or displays, camera view displays (e.g., display of a rear view camera in a vehicle), electronic photographs, electronic billboards or signs, projectors, architectural structures, microwaves, refrigerators, stereo systems, cassette recorders or players, DVD players, CD players, VCRs, radios, portable memory chips, washers, dryers, washer/dryers, parking meters, packaging (e.g., MEMS and non-MEMS), aesthetic structures (e.g., display of images on a piece of jewelry) and a variety of electromechanical systems devices. The teachings herein also can be used in non-display applications such as, but not limited to, electronic switching devices, radio frequency filters, sensors, accelerometers, gyroscopes, motion-sensing devices, magnetometers, inertial components for consumer electronics, parts of consumer electronics products, varactors, liquid crystal devices, electrophoretic devices, drive schemes, manufacturing processes, electronic test equipment. Thus, the teachings are not intended to be limited to the implementations depicted solely in the Figures, but instead have wide applicability as will be readily apparent to one having ordinary skill in the art.
Some implementations of interferometric modulator (IMOD) display devices can include a movable reflective layer that is configured to move through a cavity so the movable layer is positioned relative to one or more partially reflective/partially transmissive layers to change an optical characteristic of the display device. In some interferometric modulator displays (for example, analog displays) it can be desirable for the movable layer to move to various selected positions relative to a partially reflective/partially transmissive layer, each position placing the modulator into a particular “state” which has certain light reflectance properties such that the modulator can reflect light selectively over a wide range of the optical spectrum. For example, an analog interferometric modulator display can be configured to change between a red state, a green state, a blue state, a black state, and a white state by moving the movable layer into certain positions, each of the red, green, blue, black and white colored states corresponding to a perceivable color reflective state of the display device. As the drive voltage on the interferometric modulator device is increased, the movable layer moves closer to a partially reflective/partially transmissive layer due to electrostatic forces. As the movable layer moves closer to the partially reflective/partially transmissive layer, the strength of the electrostatic force between the movable layer and the partially reflective and partially transmissive layer increases faster than the mechanical restoration force of the movable layer increases. As the drive voltage on the interferometric device is varied incrementally, the movable layer moves to a new position and the electrical and mechanical restoring forces balance one another. In some implementations, once the deflection of the movable layer crosses a certain e.g., predefined, threshold, the electrical force can be unconditionally greater than the mechanical restoring force, which can result in causing the movable layer to move in close proximity to the partially reflective and partially transmissive layer. In some implementations, interferometric modulator displays can become unstable once the deflection of the movable layer crosses this threshold. Accordingly, it can be desirable to maximize the distance that a movable layer can move through the cavity. As used herein “stably move” or “stable movement” refers to the movement of a movable layer when the mechanical restoration force of the movable layer has not been overcome by an electrostatic force.
In some implementations, an interferometric display device can include one or more capacitance control layers disposed between a movable layer and an electrode (used for driving the movable layer) to decrease the magnitude of the electric field therebetween. Decreasing the magnitude of the electric field between a movable layer and a driving electrode can decrease the magnitude of a resulting electrostatic force and can allow the movable layer to move closer to the electrode in a controllable manner. In some implementations, without the effect of the two opposite forces, the mechanical restoration force and the electrostatic driving force can become uncontrollable or unstable. The decreased electric field facilitates the movable layer moving in a controlled manner a greater distance through the cavity and through more states (positions relative to a corresponding reflective layer of the device), which can allow reflectance over a wider range of the optical spectrum. In some implementations, the capacitance control layers can include one or more layers of dielectric materials having dielectric constants that decrease the magnitude of an electric field within the volume of the material.
Particular implementations of the subject matter described in this disclosure can be implemented to realize one or more of the following potential advantages. Some implementations described herein provide interferometric modulators with one or more capacitance control layers that decrease the magnitude of an electric field between a movable layer and an electrode. Decreasing the magnitude of an electric field between a movable layer and an electrode can increase the stability of the interferometric display. For example, decreasing the magnitude of the electric field can allow the movable layer to move closer to the electrode without an electrostatic force acting on the movable layer to overcome a mechanical restoration force of the movable layer. Additionally, increasing the stable range of motion of a movable layer can result in reflectance from the interferometric display over a wider range of the optical spectrum.
An example of a suitable MEMS device, to which the described implementations may apply, is a reflective display device. Reflective display devices can incorporate interferometric modulators (IMODs) to selectively absorb and/or reflect light incident thereon using principles of optical interference. IMODs can include an absorber, a reflector that is movable with respect to the absorber, and an optical resonant cavity defined between the absorber and the reflector. The reflector can be moved to two or more different positions, which can change the size of the optical resonant cavity and thereby affect the reflectance of the interferometric modulator. The reflectance spectrums of IMODs can create fairly broad spectral bands which can be shifted across the visible wavelengths to generate different colors. The position of the spectral band can be adjusted by changing the height of the optical resonant cavity, i.e., by changing the position of the reflector.
The IMOD display device can include a row/column array of IMODs. Each IMOD can include a pair of reflective layers, i.e., a movable reflective layer and a fixed partially reflective layer, positioned at a variable and controllable distance from each other to form an air gap (also referred to as an optical gap or cavity). The movable reflective layer may be moved between at least two positions. In a first position, i.e., a relaxed position, the movable reflective layer can be positioned at a relatively large distance from the fixed partially reflective layer. In a second position, i.e., an actuated position, the movable reflective layer can be positioned more closely to the partially reflective layer. Incident light that reflects from the two layers can interfere constructively or destructively depending on the position of the movable reflective layer, producing either an overall reflective or non-reflective state for each pixel. In some implementations, the IMOD may be in a reflective state when unactuated, reflecting light within the visible spectrum, and may be in a dark state when unactuated, reflecting light outside of the visible range (e.g., infrared light). In some other implementations, however, an IMOD may be in a dark state when unactuated, and in a reflective state when actuated. In some implementations, the introduction of an applied voltage can drive the pixels to change states. In some other implementations, an applied charge can drive the pixels to change states.
The depicted portion of the pixel array in
In
The optical stack 16 can include a single layer or several layers. The layer(s) can include one or more of an electrode layer, a partially reflective and partially transmissive layer and a transparent dielectric layer. In some implementations, the optical stack 16 is electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more of the above layers onto a transparent substrate 20. The electrode layer can be formed from a variety of materials, such as various metals, for example indium tin oxide (ITO). The partially reflective layer can be formed from a variety of materials that are partially reflective, such as various metals, e.g., chromium (Cr), semiconductors, and dielectrics. The partially reflective layer can be formed of one or more layers of materials, and each of the layers can be formed of a single material or a combination of materials. In some implementations, the optical stack 16 can include a single semi-transparent thickness of metal or semiconductor which serves as both an optical absorber and conductor, while different, more conductive layers or portions (e.g., of the optical stack 16 or of other structures of the IMOD) can serve to bus signals between IMOD pixels. The optical stack 16 also can include one or more insulating or dielectric layers covering one or more conductive layers or a conductive/absorptive layer.
In some implementations, the layer(s) of the optical stack 16 can be patterned into parallel strips, and may form row electrodes in a display device as described further below. As will be understood by one having skill in the art, the term “patterned” is used herein to refer to masking as well as etching processes. In some implementations, a highly conductive and reflective material, such as aluminum (Al), may be used for the movable reflective layer 14, and these strips may form column electrodes in a display device. The movable reflective layer 14 may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes of the optical stack 16) to form columns deposited on top of posts 18 and an intervening sacrificial material deposited between the posts 18. When the sacrificial material is etched away, a defined gap 19, or optical cavity, can be formed between the movable reflective layer 14 and the optical stack 16. In some implementations, the spacing between posts 18 may be approximately 1-1000 um, while the gap 19 may be less than 10,000 Angstroms (Å).
In some implementations, each pixel of the IMOD, whether in the actuated or relaxed state, is essentially a capacitor formed by the fixed and moving reflective layers. When no voltage is applied, the movable reflective layer 14 remains in a mechanically relaxed state, as illustrated by the pixel 12 on the left in
The processor 21 can be configured to communicate with an array driver 22. The array driver 22 can include a row driver circuit 24 and a column driver circuit 26 that provide signals to, e.g., a display array or panel 30. The cross section of the IMOD display device illustrated in
In some implementations, a frame of an image may be created by applying data signals in the form of “segment” voltages along the set of column electrodes, in accordance with the desired change (if any) to the state of the pixels in a given row. Each row of the array can be addressed in turn, such that the frame is written one row at a time. To write the desired data to the pixels in a first row, segment voltages corresponding to the desired state of the pixels in the first row can be applied on the column electrodes, and a first row pulse in the form of a specific “common” voltage or signal can be applied to the first row electrode. The set of segment voltages can then be changed to correspond to the desired change (if any) to the state of the pixels in the second row, and a second common voltage can be applied to the second row electrode. In some implementations, the pixels in the first row are unaffected by the change in the segment voltages applied along the column electrodes, and remain in the state they were set to during the first common voltage row pulse. This process may be repeated for the entire series of rows, or alternatively, columns, in a sequential fashion to produce the image frame. The frames can be refreshed and/or updated with new image data by continually repeating this process at some desired number of frames per second.
The combination of segment and common signals applied across each pixel (that is, the potential difference across each pixel) determines the resulting state of each pixel.
As illustrated in
When a hold voltage is applied on a common line, such as a high hold voltage VCHOLD
When an addressing, or actuation, voltage is applied on a common line, such as a high addressing voltage VCADD
In some implementations, hold voltages, address voltages, and segment voltages may be used which always produce the same polarity potential difference across the modulators. In some other implementations, signals can be used which alternate the polarity of the potential difference of the modulators. Alternation of the polarity across the modulators (that is, alternation of the polarity of write procedures) may reduce or inhibit charge accumulation which could occur after repeated write operations of a single polarity.
During the first line time 60a: a release voltage 70 is applied on common line 1; the voltage applied on common line 2 begins at a high hold voltage 72 and moves to a release voltage 70; and a low hold voltage 76 is applied along common line 3. Thus, the modulators (common 1, segment 1), (1,2) and (1,3) along common line 1 remain in a relaxed, or unactuated, state for the duration of the first line time 60a, the modulators (2,1), (2,2) and (2,3) along common line 2 will move to a relaxed state, and the modulators (3,1), (3,2) and (3,3) along common line 3 will remain in their previous state. With reference to
During the second line time 60b, the voltage on common line 1 moves to a high hold voltage 72, and all modulators along common line 1 remain in a relaxed state regardless of the segment voltage applied because no addressing, or actuation, voltage was applied on the common line 1. The modulators along common line 2 remain in a relaxed state due to the application of the release voltage 70, and the modulators (3,1), (3,2) and (3,3) along common line 3 will relax when the voltage along common line 3 moves to a release voltage 70.
During the third line time 60c, common line 1 is addressed by applying a high address voltage 74 on common line 1. Because a low segment voltage 64 is applied along segment lines 1 and 2 during the application of this address voltage, the pixel voltage across modulators (1,1) and (1,2) is greater than the high end of the positive stability window (i.e., the voltage differential exceeded a predefined threshold) of the modulators, and the modulators (1,1) and (1,2) are actuated. Conversely, because a high segment voltage 62 is applied along segment line 3, the pixel voltage across modulator (1,3) is less than that of modulators (1,1) and (1,2), and remains within the positive stability window of the modulator; modulator (1,3) thus remains relaxed. Also during line time 60c, the voltage along common line 2 decreases to a low hold voltage 76, and the voltage along common line 3 remains at a release voltage 70, leaving the modulators along common lines 2 and 3 in a relaxed position.
During the fourth line time 60d, the voltage on common line 1 returns to a high hold voltage 72, leaving the modulators along common line 1 in their respective addressed states. The voltage on common line 2 is decreased to a low address voltage 78. Because a high segment voltage 62 is applied along segment line 2, the pixel voltage across modulator (2,2) is below the lower end of the negative stability window of the modulator, causing the modulator (2,2) to actuate. Conversely, because a low segment voltage 64 is applied along segment lines 1 and 3, the modulators (2,1) and (2,3) remain in a relaxed position. The voltage on common line 3 increases to a high hold voltage 72, leaving the modulators along common line 3 in a relaxed state.
Finally, during the fifth line time 60e, the voltage on common line 1 remains at high hold voltage 72, and the voltage on common line 2 remains at a low hold voltage 76, leaving the modulators along common lines 1 and 2 in their respective addressed states. The voltage on common line 3 increases to a high address voltage 74 to address the modulators along common line 3. As a low segment voltage 64 is applied on segment lines 2 and 3, the modulators (3,2) and (3,3) actuate, while the high segment voltage 62 applied along segment line 1 causes modulator (3,1) to remain in a relaxed position. Thus, at the end of the fifth line time 60e, the 3×3 pixel array is in the state shown in
In the timing diagram of
The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example,
As illustrated in
In such interferometric stack black mask structures 23, the conductive absorbers can be used to transmit or bus signals between lower, stationary electrodes in the optical stack 16 of each row or column. In some implementations, a spacer layer 35 can serve to generally electrically isolate the absorber layer 16a from the conductive layers in the black mask 23.
In implementations such as those shown in
The process 80 continues at block 84 with the formation of a sacrificial layer 25 over the optical stack 16. The sacrificial layer 25 is later removed (e.g., at block 90) to form the cavity 19 and thus the sacrificial layer 25 is not shown in the resulting interferometric modulators 12 illustrated in
The process 80 continues at block 86 with the formation of a support structure e.g., a post 18 as illustrated in
The process 80 continues at block 88 with the formation of a movable reflective layer or membrane such as the movable reflective layer 14 illustrated in
The process 80 continues at block 90 with the formation of a cavity, e.g., cavity 19 as illustrated in
The interferometric modulators described in reference to
The movable layer 806a illustrated in
The upper electrode 802a, lower electrode 810a, and movable layer 806a each form a terminal of the interferometric modulator 800a. The three terminals are separated by and electrically insulated by posts 804a, the posts supporting the movable layer 806a between the electrodes 802a, 810a. At least a portion of the movable layer 806a is configured to move in the cavity (or space) between the upper electrode 802a and the lower electrode 810a.
In
The movable layer 806a can be driven between the upper and lower electrodes 802a, 810a using various circuit configurations. As illustrated in
Still referring to
Still referring to
In some implementations, the first and second control circuits 850a, 852a can be configured to apply voltages simultaneously or separately to control the movement of the movable layer 806a. For example, the first control circuit 850a can apply a first voltage across the upper electrode 802a and the movable layer 806a and the second control circuit 852a can simultaneously apply a second voltage across the lower electrode 810a and the movable layer 806a. In such an example, movement of the movable layer 806a will be determined by the magnitude of the two voltages applied by the first and second control circuits 850a, 852a. In other implementations, the first and second control circuits 850a, 852a do not apply voltages simultaneously to the movable layer 806a.
A control circuit 850b is configured to apply a voltage across the upper electrode 802b and the lower electrode 810b. A second control circuit 852b is configured to selectively apply an amount of charge to the movable layer 806b. In some implementations second control circuit 852b includes charge pump or a current source that is turned on for a specific amount of time. In some implementations, second control circuit 852b can use one or more switching devices to control the connection of voltages to a capacitor. In one implementation, the second control circuit 852b can be configured to apply a charge between about 1 pC to about 20 pC to the movable layer 806b, however, other charges also can be applied. Using the control circuits 850b, 852b, electrostatic actuation of the movable layer 806b is achieved. When connected, i.e., when switch 833b contacts the movable layer 806b, the second control circuit 852b delivers an amount of positive charge to the movable layer 806b . The charged movable layer 806b then, interacts with the electric field created by the application of a voltage by control circuit 850b between upper electrode 802b and lower electrode 810b. The interaction of the charged movable layer 806b and the electric field causes the movable layer 806b to move between electrodes 802b, 810b. The movable layer 806b can be moved to various positions by varying the voltage applied by the control circuit 850b. For example, a voltage Vc (“positive” as indicated in
A switch 833b can be used to selectively connect or disconnect the movable layer 806b from the second control circuit 852b. Those having ordinary skill in the art will understand that other methods known in the art besides a switch 833b may be used to selectively connect or disconnect the movable layer 806b from the second control circuit 852b. For example, a thin film semiconductor, a fuse, or an anti fuse, also can be used.
The switch 833b can be configured to open and close to deliver a specific amount of charge to the movable layer 806b by a control circuit (not shown). The charge level can be chosen based on the desired electrostatic force. Further, the control circuit can be configured to reapply a charge over time as an applied charge may leak away or dissipate from the movable layer 806b. In some implementations, a charge can be reapplied to the movable layer 806b according to a specified time interval. In one implementation, the specific time interval ranges between about 10 ms and about 100 ms.
The modulator 900 can selectively reflect certain wavelengths of light depending on the configuration of the modulator. In some implementations, the distance between the upper electrode 902 and the movable layer 906 changes the interferometric properties of the modulator 900. In some implementations, the upper electrode 902 can act as, or include, an absorbing layer. For example, the modulator 900 can be configured to be viewed through the substrate 912 side of the modulator. In this example, light enters the modulator 900 through the substrate 912. Depending on the position of the movable layer 906, different wavelengths of light are reflected from the movable layer 906 back through the substrate 912, which gives the appearance of different colors. For example, in position 930, a red (R) wavelength of light is reflected while other colors are absorbed. Accordingly, the interferometric modulator 900 can be considered in a red state when the movable layer 906 is in position 930. When the movable layer 906 moves to position 932, the modulator 900 is in a green state and green (G) light is reflected through the substrate 912. When the movable layer 906 moves to position 934, the modulator 900 is in a blue state and blue (B) light is reflected, and when the movable layer 906 moves to position 936, the modulator is in a white state and all the wavelengths of light in the visible spectrum are reflected (e.g., a white (W) color is reflected). In one implementation, when the movable layer 906 is in the white state the distance between the movable layer and the upper electrode 902 is very small, for example, approximately less than about 10 nm, in some implementations about 0-5 nm, and in other implementations about 0-1 nm. In one implementation, when the movable layer 906 is in the red state the distance between the movable layer and the upper electrode 902 is about 350 nm. In one implementation, when the movable layer 906 is in the green state the distance between the movable layer and the upper electrode 902 is about 250 nm. In one implementation, when the movable layer 906 is in the blue state the distance between the movable layer and the upper electrode 902 is about 200 nm. In one implementation, when the movable layer 906 is in the black state the distance between the movable layer and the upper electrode 902 is about 100 nm. One having ordinary skill in the art will recognize that the modulator 900 can take on other states and selectively reflect other wavelengths of light or combinations of wavelengths of light depending on the materials used in the construction of the modulator 900 and on the position of the movable layer 906. Therefore, in some implementations, it is desirable to maximize the distance through which the movable layer 906 can move while maintaining the stability of the modulator 900.
E=V/(δ1) (1)
where:
E is the electric field due to a voltage V applied by a control circuit; and
δ1 is the effective distance between the upper electrode 1002a and the movable layer 1006a.
Similarly, the electric field induced by a voltage applied between the lower electrode 1010a and the movable layer 1006a can be defined as follows:
E=V/(δ2) (2)
where:
E is the electric field due to voltage V applied by a control circuit; and
δ2 is the effective distance between the lower electrode 1010a and the movable layer 1006a.
Effective distance takes into account both the actual distance (e.g., d1 and d2) between the two electrodes and the effect of the capacitance control layer 1080a. Therefore, δ1=d1+dε/ε and δ2=d2+dε/ε. In the illustrated implementation, δ2=d2 because there is not a capacitance control layer disposed between the movable layer 1006a and the lower electrode 1010a. In some implementations, the capacitance control layer 1080a works to increase the effective distance and the effective distance of the capacitance control layer itself is calculated as dε/ε where dε is the thickness of the capacitance control layer and ε is the dielectric constant of the capacitance control layer 1080a. When materials with high dielectric constants are placed in an electric field, the magnitude of that electric field will be measurably reduced within the volume of the dielectric material. On the other hand, the capacitance control layer 1080a increases the effective distance between the upper electrode 1002a and the movable layer 1006a by decreasing the electric field and electrostatic force between the electrode 1002a and the movable layer 1006a. Capacitance control layers can have different thicknesses and can be formed of various materials. For example, capacitance control layers can have thicknesses between about 100 nm and 3000 nm. In some implementations, capacitance control layers can include dielectric materials, for example, silicon oxy-nitride having a dielectric constant of about 5 or silicon dioxide having a dielectric constant of about 4. The capacitance control layers can be formed of a single layer of material or a composite stack of materials.
Still referring to
F
S
=−Kx (3)
where:
K=the composite spring constant of the movable layer; and
x=the position of the movable layer 1006a relative to the equilibrium or relaxed position of the movable layer 1006a when no voltage is applied by a control circuit.
Thus, the point of instability for the modulator 1000a can be determined by balancing the mechanical restoration force of the movable layer 1006a with the electrostatic forces applied to the movable layer. The electrostatic forces acting on the movable layer 1006a are related to electric fields between the upper electrode 1002a and the movable layer 1006a and between the lower electrode 1010a and the movable layer 1006a. Accordingly, the overall distance the movable layer 1006a can move between the upper electrode 1002a and the lower electrode 1010a while remaining stable can be determined by calculating the range of x where the mechanical restoration force of the movable layer 1006a is greater than the electrostatic forces applied to the movable layer. This distance or stable range of movement can be increased by increasing the effective distances between the electrodes and the movable layer 1006a.
Still referring to
Still referring to
In
Method 1100 includes the block of providing a first electrode as illustrated in block 1101. As described above with reference to
Method 1100 further includes the block of forming a first sacrificial layer over the first electrode as illustrated in block 1103. The first sacrificial layer is later removed as discussed below to form a gap or space between the first electrode and the capacitance control layer. The formation of the first sacrificial layer over the first electrode can include a deposition block. Additionally, the first sacrificial layer can include more than one layer, or include a layer of varying thickness, to aid in the formation of a display device having a multitude of resonant optical gaps. For an interferometric modulator array, each gap size can represent a different reflected color. In some implementations, the sacrificial layer may be patterned to form vias so as to aid in the formation of support posts.
Method 1100 also can optionally include forming a protective layer over the first sacrificial layer as illustrated in block 1105 and forming a capacitance control layer over the protective layer as illustrated in block 1107a. A movable layer can be formed over the first sacrificial layer. As discussed above, in some implementations, the movable layer can include a single optically reflective and electrically conductive layer and in other implementations, the movable layer includes a reflective layer, a conductive layer, and a membrane layer disposed at least partially between the reflective layer and the conductive layer. The reflective layer is disposed between the first capacitance control layer and the conductive layer as illustrated in block 1107b. In one implementation, the membrane layer is a dielectric layer, for example, SiON. The reflective layer and the conductive layer can include various materials, for example, metals.
As illustrated in block 1109, the method 1100 can further include forming a second sacrificial layer over the movable layer. The second sacrificial layer is typically later removed to form a gap or space between the movable layer and the second electrode. The formation of the second sacrificial layer over the movable layer can include a deposition block. Additionally, the second sacrificial layer can be selected to include more than one layer, or include a layer of varying thickness, to aid in the formation of a display device having a multitude of resonant optical gaps. A second electrode can be positioned over the second sacrificial layer as illustrated in block 1111. Lastly, the method 1100 can include removing the first and second sacrificial layers as illustrated in block 1113. The sacrificial layers can be removed using a variety of methods, for example, using an XeF2 dry etch process. After removal, the movable layer can move through the cavities and deflect towards the first electrode and/or second electrode. A person having ordinary skill in the art will understand that additional blocks may be included in a method of manufacturing an interferometric modulator and that blocks may be altered or added in order to make any of the implementations illustrated in
As discussed above, analog interferometric modulators can include three-terminal configurations.
The display device 40 includes a housing 41, a display 30, an antenna 43, a speaker 45, an input device 48, and a microphone 46. The housing 41 can be formed from any of a variety of manufacturing processes, including injection molding, and vacuum forming. In addition, the housing 41 may be made from any of a variety of materials, including, but not limited to: plastic, metal, glass, rubber, and ceramic, or a combination thereof. The housing 41 can include removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.
The display 30 may be any of a variety of displays, including a bi-stable or analog display, as described herein. The display 30 also can be configured to include a flat-panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat-panel display, such as a CRT or other tube device. In addition, the display 30 can include an interferometric modulator display, as described herein.
The components of the display device 40 are schematically illustrated in
The network interface 27 includes the antenna 43 and the transceiver 47 so that the display device 40 can communicate with one or more devices over a network. The network interface 27 also may have some processing capabilities to relieve, e.g., data processing requirements of the processor 21. The antenna 43 can transmit and receive signals. In some implementations, the antenna 43 transmits and receives RF signals according to the IEEE 16.11 standard, including IEEE 16.11(a), (b), or (g), or the IEEE 802.11 standard, including IEEE 802.11a, b, g or n. In some other implementations, the antenna 43 transmits and receives RF signals according to the BLUETOOTH standard. In the case of a cellular telephone, the antenna 43 is designed to receive code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), Global System for Mobile communications (GSM), GSM/General Packet Radio Service (GPRS), Enhanced Data GSM Environment (EDGE), Terrestrial Trunked Radio (TETRA), Wideband-CDMA (W-CDMA), Evolution Data Optimized (EV-DO), 1xEV-DO, EV-DO Rev A, EV-DO Rev B, High Speed Packet Access (HSPA), High Speed Downlink Packet Access (HSDPA), High Speed Uplink Packet Access (HSUPA), Evolved High Speed Packet Access (HSPA+), Long Term Evolution (LTE), AMPS, or other known signals that are used to communicate within a wireless network, such as a system utilizing 3G or 4G technology. The transceiver 47 can pre-process the signals received from the antenna 43 so that they may be received by and further manipulated by the processor 21. The transceiver 47 also can process signals received from the processor 21 so that they may be transmitted from the display device 40 via the antenna 43.
In some implementations, the transceiver 47 can be replaced by a receiver. In addition, the network interface 27 can be replaced by an image source, which can store or generate image data to be sent to the processor 21. The processor 21 can control the overall operation of the display device 40. The processor 21 receives data, such as compressed image data from the network interface 27 or an image source, and processes the data into raw image data or into a format that is readily processed into raw image data. The processor 21 can send the processed data to the driver controller 29 or to the frame buffer 28 for storage. Raw data typically refers to the information that identifies the image characteristics at each location within an image. For example, such image characteristics can include color, saturation, and gray-scale level.
The processor 21 can include a microcontroller, CPU, or logic unit to control operation of the display device 40. The conditioning hardware 52 may include amplifiers and filters for transmitting signals to the speaker 45, and for receiving signals from the microphone 46. The conditioning hardware 52 may be discrete components within the display device 40, or may be incorporated within the processor 21 or other components.
The driver controller 29 can take the raw image data generated by the processor 21 either directly from the processor 21 or from the frame buffer 28 and can re-format the raw image data appropriately for high speed transmission to the array driver 22. In some implementations, the driver controller 29 can re-format the raw image data into a data flow having a raster-like format, such that it has a time order suitable for scanning across the display array 30. Then the driver controller 29 sends the formatted information to the array driver 22. Although a driver controller 29, such as an LCD controller, is often associated with the system processor 21 as a stand-alone Integrated Circuit (IC), such controllers may be implemented in many ways. For example, controllers may be embedded in the processor 21 as hardware, embedded in the processor 21 as software, or fully integrated in hardware with the array driver 22.
The array driver 22 can receive the formatted information from the driver controller 29 and can re-format the video data into a parallel set of waveforms that are applied many times per second to the hundreds, and sometimes thousands (or more), of leads coming from the display's x-y matrix of pixels.
In some implementations, the driver controller 29, the array driver 22, and the display array 30 are appropriate for any of the types of displays described herein. For example, the driver controller 29 can be a conventional display controller or a bi-stable display controller (e.g., an IMOD controller). Additionally, the array driver 22 can be a conventional driver or a bi-stable display driver (e.g., an IMOD display driver). Moreover, the display array 30 can be a conventional display array or a bi-stable display array (e.g., a display including an array of IMODs). In some implementations, the driver controller 29 can be integrated with the array driver 22. Such an implementation is common in highly integrated systems such as cellular phones, watches and other small-area displays.
In some implementations, the input device 48 can be configured to allow, e.g., a user to control the operation of the display device 40. The input device 48 can include a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a rocker, a touch-sensitive screen, or a pressure- or heat-sensitive membrane. The microphone 46 can be configured as an input device for the display device 40. In some implementations, voice commands through the microphone 46 can be used for controlling operations of the display device 40.
The power supply 50 can include a variety of energy storage devices as are well known in the art. For example, the power supply 50 can be a rechargeable battery, such as a nickel-cadmium battery or a lithium-ion battery. The power supply 50 also can be a renewable energy source, a capacitor, or a solar cell, including a plastic solar cell or solar-cell paint. The power supply 50 also can be configured to receive power from a wall outlet.
In some implementations, control programmability resides in the driver controller 29 which can be located in several places in the electronic display system. In some other implementations, control programmability resides in the array driver 22. The above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.
The various illustrative logics, logical blocks, modules, circuits and algorithm steps described in connection with the implementations disclosed herein may be implemented as electronic hardware, computer software, or combinations of both. The interchangeability of hardware and software has been described generally, in terms of functionality, and illustrated in the various illustrative components, blocks, modules, circuits and steps described above. Whether such functionality is implemented in hardware or software depends upon the particular application and design constraints imposed on the overall system.
The hardware and data processing apparatus used to implement the various illustrative logics, logical blocks, modules and circuits described in connection with the aspects disclosed herein may be implemented or performed with a general purpose single- or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, or, any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration. In some implementations, particular steps and methods may be performed by circuitry that is specific to a given function.
In one or more aspects, the functions described may be implemented in hardware, digital electronic circuitry, computer software, firmware, including the structures disclosed in this specification and their structural equivalents thereof, or in any combination thereof. Implementations of the subject matter described in this specification also can be implemented as one or more computer programs, i.e., one or more modules of computer program instructions, encoded on a computer storage media for execution by, or to control the operation of, data processing apparatus.
Various modifications to the implementations described in this disclosure may be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other implementations without departing from the spirit or scope of this disclosure. Thus, the disclosure is not intended to be limited to the implementations shown herein, but is to be accorded the widest scope consistent with the claims, the principles and the novel features disclosed herein. The word “exemplary” is used exclusively herein to mean “serving as an example, instance, or illustration.” Any implementation described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other implementations. Additionally, a person having ordinary skill in the art will readily appreciate, the terms “upper” and “lower” are sometimes used for ease of describing the figures, and indicate relative positions corresponding to the orientation of the figure on a properly oriented page, and may not reflect the proper orientation of the IMOD as implemented.
Certain features that are described in this specification in the context of separate implementations also can be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation also can be implemented in multiple implementations separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination.
Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Further, the drawings may schematically depict one more example processes in the form of a flow diagram. However, other operations that are not depicted can be incorporated in the example processes that are schematically illustrated. For example, one or more additional operations can be performed before, after, simultaneously, or between any of the illustrated operations. In certain circumstances, multitasking and parallel processing may be advantageous. Moreover, the separation of various system components in the implementations described above should not be understood as requiring such separation in all implementations, and it should be understood that the described program components and systems can generally be integrated together in a single software product or packaged into multiple software products. Additionally, other implementations are within the scope of the following claims. In some cases, the actions recited in the claims can be performed in a different order and still achieve desirable results.
This disclosure claims priority to U.S. Provisional Patent Application No. 61/379,910, filed Sep. 3, 2010, entitled “INTERFEROMETRIC DISPLAY DEVICE,” and assigned to the assignee hereof. The disclosure of the prior application is considered part of, and is incorporated by reference in, this disclosure.
| Number | Date | Country | |
|---|---|---|---|
| 61379910 | Sep 2010 | US |
