Detailed Description
The following detailed description is directed to certain specific embodiments of the invention. The invention may, however, be embodied in many different forms. In the description, reference is made to the drawings wherein like parts are designated with like numerals throughout. As will be apparent from the following description, the embodiments may be implemented in any device that is configured to display an image that is motion (e.g., video) or stable (e.g., still image) and text or pictures. More particularly, it is contemplated that the embodiments may be implemented or associated with various electronic devices: such as, but not limited to, mobile telephones, wireless devices, Personal Data Assistants (PDAs), hand-held or portable computers, GPS receivers/navigators, cameras, MP3 players, camcorders, game consoles, wrist watches, clocks, calculators, television monitors, flat panel displays, computer monitors, automotive displays (e.g., odometer display, etc.), cockpit controls and/or displays, display of camera views (e.g., display of a rear view camera in a vehicle), electronic photographs, electronic billboards or symbols, projectors, architectural structures, packaging, and aesthetic structures (e.g., display of images on a piece of jewelry). MEMS devices of similar structure to those described herein may also be used in non-display applications such as electronic switching devices.
One embodiment of the invention relates to a method and apparatus for regenerating a protective coating that has been deposited on an element or layer of an interferometric modulator device. In some embodiments, the protective coating can be heated to regenerate the protective coating. Heat can be applied to the device area containing the protective coating to regenerate the protective coating on a surface of the element or layer. Thus, in one embodiment, heat is used to redistribute material making up a protective coating over a surface of an interferometric modulator element or layer. The treatment allows the gap in the protective coating to be repaired as the heated protective coating fills the gap and then cools and becomes a solid layer. As will be appreciated by those skilled in the art, the heat source, heating device, or heater can be external or internal to a package containing the interferometric modulator.
As mentioned above, repeated use of an interferometric device can result in damage to the various layers of the reflective and transmissive elements or layers. This is due to bending of the elements or repeated contact between the elements. To reduce damage that occurs during failure, a protective coating may be deposited over the transmissive or reflective elements to reduce wear. The protective coating may be, for example, on a conductor layer or an insulating layer of the device. In addition, the protective coating can have other functions, such as an anti-stiction coating that prevents the components from sticking together. While the protective coating may protect the article it covers, it may also experience damage in use. Also, methods and compositions for regenerating the protective coating are provided.
In some embodiments, the heater that increases the temperature of the protective coating is a resistive heater that may be included within a sealed interferometric modulator device. In some embodiments, the heater is a heating element or filament disposed within the display device (e.g., on the substrate). In other embodiments, other circuit or wiring elements of the interferometric modulator device may be used to generate heat, for example, by shorting the ring leads of one of the reflective or transmissive elements, thereby turning that element into a heater. For example, the looped leads may comprise materials having sufficient resistive properties for use in a transmissive layer or a mechanical layer.
In other embodiments, the heater can be placed on one or more posts in an interferometric modulator device such that the heater is elevated above the substrate and located closer to the reflective element. In some embodiments, the heater is in the same plane as the reflective element. In other embodiments, a heater is disposed over the reflective element and the substrate. In some embodiments, the heater substantially covers or overlaps a surface of the reflective element.
In some embodiments, there is a reservoir of protective coating material stored within the device. In this embodiment, the material reservoir may be used to more effectively lay down a remanufactured protective coating when the rejuvenation process begins. In one embodiment, the protective coating is a single layer.
In other aspects, a method for regenerating a protective coating in an interferometric modulator device is provided. The method includes using a protective coating having a component that is temperature sensitive in state and increasing the temperature of the interferometric modulator device to allow the component to redistribute itself over the desired surface.
FIG. 1 illustrates an interferometric modulator display embodiment comprising an interferometric MEMS display element. In these devices, the pixels are in either a bright or dark state. In the bright ("on" or "open") state, the display element reflects a large portion of incident visible light to a user. When in the dark ("off" or "closed") state, the display element reflects little incident visible light to the user. According to the embodiments, the light reflectance properties of the "on" and "off" states may be reversed. MEMS pixels can be configured to reflect predominantly at selected colors, allowing for a color display in addition to black and white.
FIG. 1 is an isometric view depicting two adjacent pixels in a series of pixels of a visual display, wherein each pixel comprises a MEMS interferometric modulator. In some embodiments, an interferometric modulator display comprises a row/column array of these interferometric modulators. Each interferometric modulator includes a pair of reflective layers (also called reflective and transmissive layers) positioned at a variable and controllable distance from each other to form a resonant optical cavity with at least one variable dimension. In an embodiment, one of the reflective layers is movable between two positions. In a first position, referred to herein as the relaxed position, the movable layer is positioned at a relatively large distance from a fixed transmissive layer. In the second position, the movable layer is disposed more adjacent to the transmissive layer. Incident light that reflects from the two layers interferes constructively or destructively depending on the position of the movable reflective layer, producing a fully reflective or non-reflective state for each pixel.
The depicted portion of the pixel array in FIG. 1 includes two adjacent interferometric modulators 12a and 12 b. In the interferometric modulator 12a on the left, a movable reflective layer 14a is illustrated in a relaxed position at a predetermined distance from a fixed transmissive layer 16 a. In the interferometric modulator 12b on the right, the movable reflective (or "highly reflective") layer 14b is illustrated in an actuated position adjacent to a fixed transmissive (or "partially reflective") layer 16 b.
The fixed layers 16a, 16b are electrically conductive, partially transparent and partially reflective, and may be fabricated, for example, by depositing one or more layers each of chromium and indium tin oxide on a transparent substrate 20. The layers are patterned into parallel strips and may form row electrodes in a display device as described further below. The movable layers 14a, 14b may be formed as a series of parallel strips of a deposited metal layer or layers (orthogonal to the row electrodes 16a, 16 b) deposited on top of posts 18 and an intervening sacrificial material deposited between the posts 18. When the sacrificial material is etched away, the deformable metal layers 14a, 14b are separated from the fixed metal layers by a defined gap 19. A highly conductive reflective material such as aluminum may be used for the deformable layer, and the strips may form column electrodes in a display device.
With no applied voltage, the cavity 19 remains between the layers 14a, 16a, and the deformable layer is in a mechanically relaxed state as illustrated by the pixel 12a of FIG. 1. However, when a potential difference is applied to a selected row and column, the capacitor formed at the intersection of the row and column electrodes at the corresponding pixel becomes charged, and electrostatic forces pull the electrodes together. If the voltage is high enough, the movable layer deforms and presses against the fixed layer as illustrated by the pixel 12b on the right in FIG. 1(a dielectric material not illustrated in the figures may be deposited on the fixed layer to prevent shorting and control the separation distance). The action is the same regardless of the polarity of the applied potential difference. In this way, row/column actuation that can control the reflective vs. non-reflective pixel states is analogous in many ways to that used in conventional LCD and other display technologies.
FIGS. 2-5 illustrate an exemplary process and system for using an array of interferometric modulators in a display application.
FIG. 2 is a system block diagram illustrating one embodiment of an electronic device that may incorporate aspects of the invention. In the exemplary embodiment, the electronic device includes a processor 21, which may be any general purpose single-or multi-chip microprocessor such as an ARM, Pentium, or other microprocessor*、Pentium II*、Pentium III*、Pentium IV*、Pentium* Pro、8051、MIPS*、Power PC*、ALPHA*Or any special purpose microprocessor such as a digital signal processor, microcontroller, or programmable gate array. As is conventional in the art, the processor 21 may be configured to execute one or more software modules. In addition to executing an operating system, the processor may be configured to execute one or more software applications, including a web browser, a telephone application, an email program, or any other software application.
In one embodiment, the processor 21 is also configured to communicate with the array controller 22. In one embodiment, the array controller 22 includes a row driver circuit 24 and a column driver circuit 26 that provide signals to a display array or panel 30. The cross-section of the array illustrated in figure 1 is shown by line 1-1 in figure 2. For MEMS interferometric modulators, the row/column actuation protocol may take advantage of the hysteresis properties of these devices illustrated in FIG. 3. It may require, for example, a 10 volt potential difference to cause a movable layer to deform from the relaxed state to the actuated state. However, when the voltage is reduced from that value, the movable layer maintains its state as the voltage drops below 10 volts. In the exemplary embodiment of FIG. 3, the movable layer does not relax completely until the voltage drops below 2 volts. There is thus a voltage in the example illustrated in fig. 3 in the range of about 3V to 7V, where there exists a window of applied voltage within which the device is stable in either the relaxed or actuated state. This is referred to herein as the "hysteresis window" or "stability window". For a display array having the hysteresis characteristics of FIG. 3, the row/column actuation protocol may be designed such that during row strobing, pixels in the strobed row that are to be actuated are exposed to a voltage difference of about 10 volts, and pixels that are to be relaxed are exposed to a voltage difference of approximately 0 volts. After strobing, the pixels are exposed to a steady state voltage difference of about 5 volts such that they remain in whatever state the row strobe put them in. After writing, each pixel sees a potential difference within the "stability window" of 3-7 volts in the embodiment. This feature makes the pixel design illustrated in FIG. 1 stable in an actuated or relaxed pre-existing state under the same applied voltage conditions. Since each pixel of the interferometric modulator, whether in the actuated or relaxed state, is essentially a capacitor formed by the fixed and movable reflective layers, the stable state can be held at a voltage within the hysteresis window with little power dissipation. If the applied voltage is fixed, substantially no current flows into the pixel.
In typical applications, a display frame may be created by determining the set of column electrodes based on the desired set of actuated pixels in the first row. A row pulse is then applied to the row 1 electrode, actuating the pixels corresponding to the asserted column lines. The determined set of column electrodes is then changed to correspond to the desired set of actuated pixels in the second row. A pulse is then applied to the row 2 electrode, actuating the appropriate pixels in row 2 in accordance with the asserted column electrodes. The row 1 pixels are unaffected by the row 2 pulse, and remain in the state they were set to during the row 1 pulse. The above may be repeated for the entire row in a sequential manner to produce a frame. Generally, the frames are refreshed and/or updated with new display data by continually repeating the process at some desired number of frames per second. A variety of protocols for driving row and column electrodes of pixel arrays to produce display frames are also well known and may be used in conjunction with the present invention.
Fig. 4 and 5 illustrate one possible actuation protocol for generating display frames on the 3 x3 array of fig. 2. Figure 4 illustrates a possible set of column and row voltage levels that may be used for pixels exhibiting the hysteresis curves of figure 3. In the FIG. 4 embodiment, actuating a pixel involves setting the appropriate column to-VBias voltageAnd the appropriate row is set to + av, which may correspond to-5 volts and +5 volts, respectively. Relaxing the pixelBy setting the appropriate column to + VBias voltageAnd the appropriate row is set to the same + av, producing a 0 volt potential difference across the pixel. In a row in which the row voltage is held at 0 volts, regardless of whether the column is at + VBias voltageOr is-VBias voltageThe pixel is stable in the state it was in. As also illustrated in FIG. 4, it will be appreciated that voltages of opposite polarity than those described above can be used, e.g., actuating a pixel can include setting the appropriate column to + VBias voltageAnd sets the appropriate row to-av. In this embodiment, releasing the pixel is accomplished by setting the appropriate column to-VBias voltageAnd the appropriate row is set to the same-av, producing a 0 volt potential difference across the pixel.
FIG. 5B is a timing diagram showing a series of row and column signals applied to the 3X 3 array of FIG. 2 which will result in the display arrangement illustrated in FIG. 5A, where actuating pixels is non-reflective. Prior to writing the frame illustrated in FIG. 5A, the pixels can be in any state, and in this example, all the rows are 0 volts and all the columns are +5 volts. At these applied voltages, all pixels are stable in their existing actuated or relaxed states.
In the fig. 5A frame, pixels (1, 1), (1, 2), (2, 2), (3, 2) and (3, 3) are actuated. To accomplish this, during a "line time" for row 1, columns 1 and 2 are set to-5 volts, and column 3 is set to +5 volts. This does not change the state of any pixels because all pixels remain in the 3-7 volt stability window. Row 1 is then strobed with a pulse that goes from 0 volts, up to 5 volts, and back to 0 volts. This actuates the (1, 1) and (1, 2) pixels and relaxes the (1, 3) pixel. The other pixels in the array are unaffected. To set row 2 as desired, column 2 is set to-5 volts, and columns 1 and 3 are set to +5 volts. The same strobe applied to row 2 will then actuate pixel (2, 2) and relax pixels (2, 1) and (2, 3). Also, other pixels of the array are unaffected. Row 3 is similarly set by setting columns 2 and 3 to-5 volts, and column 1 to +5 volts. The row 3 strobe sets the row 3 pixels as shown in FIG. 5A. After writing the frame, the row potential is 0, and the column potential can remain at either +5 or-5 volts, and then the display is stable in the arrangement of FIG. 5A. It will be appreciated that the same procedure can be used for tens or hundreds of rows and columns arrays. It will also be appreciated that the timing, sequence, and levels of voltages used to perform row and column actuation can be varied widely within the general principles outlined above, and the above example is exemplary only, and any actuation voltage method can be used with the systems and methods described herein.
Fig. 6A and 6B are system block diagrams illustrating an embodiment of a display device 40. The display device 40 may be, for example, a cellular or mobile telephone. However, the same components of display device 40, or slight variations thereof, are also illustrative of different types of display devices such as televisions and portable media players.
The display device 40 includes a housing 41, a display 30, an antenna 43, a speaker 44, an input device 48, and a microphone 46. The housing 41 is generally formed from any of a variety of manufacturing processes including injection molding and vacuum forming, as is well known to those skilled in the art. Additionally, 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 combinations thereof. In one embodiment, the housing 41 includes removable portions (not shown) that may be interchanged with other removable portions of different color, or containing different logos, pictures, or symbols.
As described herein, the display 30 of exemplary display device 40 may be any of a variety of displays, including a bi-stable display. In other embodiments, as described above, the display 30 comprises a flat panel display, such as a plasma, EL, OLED, STN LCD, or TFT LCD, or a non-flat panel display, such as a CRT or other tube device, as is known to those of skill in the art. However, for purposes of describing the present embodiment, the display 30 as described herein comprises an interferometric modulator display.
The components of one embodiment of exemplary display device 40 are schematically illustrated in FIG. 6B. The illustrated exemplary display device 40 includes a housing 41 and may include additional components at least partially enclosed therein. For example, in one embodiment, the exemplary display device 40 includes a network interface 27 that includes an antenna 43 coupled to a transceiver 47. The transceiver 47 is connected to a processor 21 which is connected to conditioning hardware 52. The conditioning hardware 52 may be configured to condition a signal (e.g., filter a signal). The conditioning hardware 52 is connected to a speaker 44 and a microphone 46. The processor 21 is also connected to an input device 48 and a driver controller 29. The driver controller 29 is coupled to a frame buffer 28 and to an array driver 22, which array driver 22 is in turn coupled to a display array 30. A power supply 50 provides power to all components as required by the particular exemplary display device 40 design.
The network interface 27 includes the antenna 43 and the transceiver 47 so that the exemplary display device 40 can communicate with one or more devices over a network. In one embodiment, the network interface 27 may also have some processing capabilities to reduce the requirements of the processor 21. The antenna 43 is any antenna known to those skilled in the art for transmitting and receiving signals. In one embodiment, the antenna transmits and receives RF signals according to the IEEE 802.11 standard, including IEEE 802.11(a), (b), or (g). In another embodiment, the antenna transmits and receives RF signals according to the bluetooth standard. In the case of a cellular telephone, the antenna is designed to receive CDMA, GSM, AMPS or other known signals that are used to communicate within a wireless mobile telephone network. The transceiver 47 pre-processes the signals received from the antenna 43 so that they may be received by and further operated on by the processor 21. The transceiver 47 also processes signals received from the processor 21 so that they may be transmitted from the exemplary display device 40 via the antenna 43.
In an alternative embodiment, the transceiver 47 can be replaced by a receiver. In another alternative embodiment, network interface 27 can be replaced by an image source, which can store or generate image data to be sent to the processor 21. For example, the image source can be a Digital Video Disk (DVD) or a hard-disk drive that contains image data, or a software module that generates image data.
The processor 21 generally controls the overall operation of the exemplary 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 then sends the processed data to the driver controller 29 or to frame buffer 28 for storage. Raw data generally refers to information that identifies the image characteristics of each location within an image. For example, the image characteristics may include color, saturation, and gray-scale level.
In one embodiment, the processor 21 includes a microcontroller, CPU, or logic unit to control operation of the exemplary display device 40. Conditioning hardware 52 generally includes amplifiers or filters for sending signals to the speaker 44 and receiving signals from the microphone 46. Conditioning hardware 52 may be discrete components within the exemplary display device 40, or may be incorporated within the processor 21 or other components.
The driver controller 29 takes the raw image data generated by the processor 21 either directly from the processor 21 or from the frame buffer 28 and reformats the raw image data appropriately for high speed transmission to the array driver 22. In particular, the driver controller 29 reformats 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. The driver controller 29 then sends the formatted information to the array driver 22. Although a driver controller 29, such as an LCD controller, is typically associated with the system processor 21 as a stand-alone Integrated Circuit (IC), the controller may be implemented in a variety of ways. It 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.
Typically, the array driver 22 receives the formatted information from the driver controller 29 and reformats the video data into a parallel set of waveforms that are applied many times per second to the hundreds and sometimes thousands of leads coming from the display's x-y matrix of pixels.
In one embodiment, the driver controller 29, array driver 22, and display array 30 are appropriate for any of the types of displays described herein. For example, in one embodiment, the driver controller 29 is a conventional display controller or a bi-stable display controller (e.g., an interferometric modulator controller). In another embodiment, the array driver 22 is a conventional driver or a bi-stable display driver (e.g., an interferometric modulator display). In one embodiment, a driver controller 29 is integral with the array driver 22. The embodiments are common in highly integrated systems such as cellular phones, watches, and other small area displays. In another embodiment, the display array 30 is a typical display array or a bi-stable display array (e.g., a display including an array of interferometric modulators).
The input device 48 allows a user to control the operation of the exemplary display device 40. In one embodiment, input device 48 includes a keypad, such as a QWERTY keyboard or a telephone keypad, a button, a switch, a touch-sensitive screen, a pressure-or heat-sensitive membrane. In one embodiment, the microphone 46 is an input device for the exemplary display device 40. When the microphone 46 is used to input data to the device, a user may provide voice commands to control the operation of the exemplary display device 40.
As is well known in the art, the power supply 50 may include a variety of energy storage devices. For example, in one embodiment, power source 50 is a rechargeable battery, such as a nickel cadmium battery or a lithium ion battery. In another embodiment, power source 50 is a renewable energy source, a capacitor, or a solar cell including a plastic solar cell and solar-cell paint. In another embodiment, power supply 50 is configured to receive power from a wall outlet.
In some embodiments, control programmability resides, as described above, in a driver controller that can be located in several places in the electronic display system. In some cases, control programmability resides in the array driver 22. Those skilled in the art will recognize that the above-described optimization may be implemented in any number of hardware and/or software components and in various configurations.
The details of the structure of interferometric modulators that operate in accordance with the principles set forth above may vary widely. For example, FIGS. 7A-7C illustrate three different embodiments of moving mirror structures. Fig. 7A is a cross-section of the embodiment of fig. 1, wherein a strip of metallic material 14 is deposited on orthogonally extending supports 18. In FIG. 7B, the moveable reflective material 14 is attached only at the corners of the supports, on tethers 32. In FIG. 7C, the moveable reflective material 14 is suspended from a deformable layer 34. This embodiment is beneficial because the structural design and materials used for the reflective material 14 can be optimized with respect to the optical properties, and the structural design and materials used for the deformable layer 34 can be optimized with respect to desired mechanical properties. The production of various types of interferometric devices is described in various published documents, including, for example, U.S. published application 2004/0051929. A variety of known techniques may be used to produce the above-described structures, including a series of material deposition, patterning, and etching steps.
The interferometric modulator devices described above may be enclosed together in a package. Various packages are contemplated and those skilled in the art will recognize that the particular characteristics of the packages may depend on the particular use for the interferometric modulator device.
FIGS. 8A-8C are schematic diagrams of the basic package structure of an interferometric modulator. As shown in fig. 8A, the basic package structure 40 includes a transparent substrate 41 (e.g., glass) and a back plate or "lid" 42. 8A-8C, an array of interferometric light modulators 43 is encapsulated within the package structure 40. The backplate 42 may be formed of any suitable material, such as glass, metal, foil, polymer, plastic, ceramic, or a semiconductor material (e.g., silicon).
An encapsulant 44 is typically provided to join the transparent substrate 41 and the backplane 42 to form the package structure 40. According to the embodiment, the seal 44 may be a non-hermetic, semi-hermetic, or hermetic seal. One example of a hermetic sealing process is disclosed in U.S. patent No. 6,589,625.
In one embodiment, a desiccant 46 is provided within the package structure 40 to reduce humidity within the package structure 40. In one embodiment, the desiccant is located between the array 43 and the backplate 42. Desiccants may be used in packages having hermetic or semi-hermetic seals. Suitable desiccant materials include, but are not limited to, zeolites, molecular sieves, surface adsorbents, bulk adsorbents, and chemical reactants. The desiccant 46 may also be referred to as a getter material or may be used in addition to a getter material that removes other materials such as oxygen or particulates. In an embodiment, the amount of desiccant used within the package 40 is selected to absorb water vapor that permeates the seal 44 during the useful life of the device 40.
Generally, the encapsulation process may be accomplished in a vacuum, a pressure between up to and including ambient pressure, or a pressure above ambient pressure. The encapsulation process may also be accomplished in various and controlled high or low pressure environments during the sealing process.
FIG. 8B illustrates the flow of water vapor into the package 40 and the absorption of the permeated water vapor by the desiccant 46. Referring to fig. 8B, the desiccant 46 absorbs water or water vapor that is present inside the package 40 when the package is sealed. The desiccant 46 also absorbs water or water vapor 47 that has penetrated into the interior of the package 40 after the package is sealed as shown in fig. 8B.
In one embodiment, as shown in FIG. 8C, the package structure 50 may eliminate the need for a desiccant. In this embodiment, the seal 44 is preferably a hermetic seal to prevent or minimize the passage of moisture from the atmosphere into the interior of the enclosure 50. In another embodiment, instead of sealing a separate backplate 42 to the transparent substrate 41, a thin film (not shown) is deposited on the transparent substrate 41 to seal the array 43 within the package structure 50. Thus, the function of the backsheet may be fulfilled by the sealing layer.
As will be appreciated by those skilled in the art, the presence of a desiccant is beneficial for reducing the amount of water vapor in the package, which in turn results in less water between the transmissive and reflective layers. The reduction of water may be advantageous because it helps to reduce the stiction force formed between the transmissive and reflective layers. However, alternative ways of reducing static friction also exist. For example, as will be described in greater detail below, the purpose of the protective coating may not only serve as an anti-stiction coating, but also to provide structural integrity to other layers associated with the reflective and transmissive layers. The protective coating will be discussed in more detail below.
FIG. 9 is a detailed side view of an interferometric light modulating device 80 that includes a light modulating cavity 108 in which optical resonance occurs between a fixed transmissive layer 102 and a movable reflective layer 106. The transmissive layer 102 transmits light and may be partially reflective. The movable reflective layer 106 reflects light and may be partially transmissive. As will be appreciated by those skilled in the art, various terms may be used to describe the two layers. The main factor to consider is that the device should act as an interferometric modulator and the description of "reflection" or "transmission" between the two layers is relevant. Alternative terms that may indicate a transmissive layer may include a fixed layer, a partially reflective layer, a transmissive element, and a primary conductor. Alternative terms that may indicate a reflective layer may include a movable or deformable highly reflective layer, a reflective element, and a secondary conductor.
The transmissive layer 102 is layered over a transparent substrate 100, which transparent substrate 100 may be any transparent substrate capable of having thin film MEMS devices fabricated thereon. Including, but not limited to, glass, plastic, and transparent polymers. The reflective layer 102, depicted here as a thin film stack of sublayers, typically includes an electrode sublayer 110 and a primary mirror sublayer (or transmissive sublayer) 120. The primary mirror sublayer 120 may be made of a metal film. In some embodiments, the insulating sublayer 130 is disposed over the primary mirror sublayer 120 and acts as an insulator and also enhances reflection from the transmissive layer 102. The movable reflective layer 106, depicted here as a membrane of sublayers, typically includes a secondary mirror sublayer 140 and an electrode sublayer 150. The secondary mirror sublayer 140 may be made of a thin metal film. Supports 104 are formed to support the movable reflective layer 106. In one embodiment, the support 104 is an insulator. The electrode layers 110 and 150 are connected to a voltage source (V) shown in fig. 1 so that a voltage (V) can be applied to the two layers 102 and 106. Other interferometric modulator configurations and modes of operation are disclosed in U.S. Pat. No. 5,835,255.
As used herein, the terms reflective layer and transmissive layer are to be given their broadest ordinary meaning. A reflective layer is at least one layer that reflects light and is partially transmissive to light. The term reflective layer may refer to, but is not limited to, the layers described herein as reflective layer 106 or secondary mirror sublayer 140. A transmissive layer is at least one layer that transmits light and partially reflects light. The term transmissive layer may refer to, but is not limited to, the layers described herein as transmissive layer 102 or primary mirror sublayer 120. When the term "element" is employed, it is generally meant to indicate a larger or partially larger portion of the device that relates to one of the layers. Thus, as shown in FIG. 9, 106 may be referred to as a reflective element. The term "layer" as in "reflective layer" in FIG. 9 can be used to describe the entire reflective layer 106 or a particular layer (secondary mirror or sublayer) 140 that is reflective. The term "sublayer" or "subelement" generally refers to a particular layer (e.g., article 140) having particular properties.
Referring to FIG. 9, in a driven state of an interferometric light modulating device 80, the reflective layer 106, depicted herein as a film, may be in contact with the transmissive layer 102, depicted herein as a thin film stack. When a potential difference is applied to the layers 102 and 106, a capacitor is formed between the two layers that creates an electrostatic force that pulls the reflective layer 106 toward the transmissive layer 102. This results in the cavity 108 being destroyed. If the voltage is high enough, the reflective layer 106 may deform and press against the transmissive layer 102 to completely destroy the cavity 108. However, when no potential difference is applied, the mechanical restoring force of the reflective layer 106 and its surrounding structures can return the layer 106 to its original position, thereby restoring the cavity 108. But even in the undriven state, layers 106 and 102 are close to each other, e.g., about 0.2 μm. Thus, the mechanical restoring force of the movable highly reflective layer 106 should be exactly equal to the electrostatic force generated between the layer 106 and the transmissive layer 102 to ensure proper operation and responsiveness of the interferometric light modulating device 80.
Protective coating
Over time, the different layers will start to experience imperfections due to wear and general use. To reduce the risk that one layer (e.g., the insulating layer) experiences failure, a protective coating may be applied to the surface of the insulating layer on the transmissive layer or to the surface of the reflective layer.
In addition to the physical protection of the layer, there are other uses and benefits associated with a protective coating. For example, there are additional attractive forces that can upset the balance of the forces described above. These additional attractive forces may be van der waals forces due to water condensation on each device or holding the two layers together. During the lifetime of an interferometric light modulating device, water vapor (or water) may continually permeate the interior of the device (as depicted in FIG. 8B), and the permeated water vapor may be present on the surface of each of the layers 102 and 106. Due to the water condensation, the water vapor may cause the two layers 102 and 106 to have an additional attractive capillary force between them. Furthermore, van der waals forces that result in a short range of forces for adjacent materials to become attractive at the molecular level may cause layers 102 and 106 to have an additional attractive force between them. In an interferometric light modulating device 80, the movable reflective layer 106 (including the secondary mirror sublayer 140) moves toward and away from the fixed transmissive layer 102, including the primary mirror sublayer 120, depending on the operating conditions. If there is additional attraction between layers 102 and 106, device 80 may not function properly, even to the point where the layers may adhere together. Thus, in embodiments of the present invention, the means for reducing the attractive forces between the layers 102 and 106 comprises a protective coating applied to one or more layer surfaces (or sublayer surfaces) of an interferometric light modulating device 80 such that additional attractive forces between adjacent surfaces can be minimized or eliminated due to, for example, capillary water condensation or van der Waals forces.
As used herein, the term "protective" coating is to be given its broadest ordinary meaning, including (but not limited to) materials that reduce attractive forces between surfaces and/or materials that reduce failure of the layers that it covers. The term protective coating can refer to, but is not limited to, a self-aligned monolayer ("SAM" also known as self-assembled monolayer). In some embodiments, examples of a protective coating include (but are not limited to) a self-aligned monolayer such as one or more of the following: fluorosilane, fluorochlorosilane, methoxysilane, trichlorosilane, perfluorodecanoic acid, Octadecyltrichlorosilane (OTS) or dichlorodimethylsilane. In some embodiments, examples of protective coatings include (but are not limited to) polymeric materials such as one or more of the following: polytetrafluoroethylene, silicone, polystyrene, polyurethane (standard and uv curable), a block copolymer containing a hydrophobic component (e.g., polymethyl methacrylate), or polysilazane (especially with polysiloxane). In some embodiments, an example of a protective coating includes (but is not limited to) inorganic materials such as one or more of the following: graphite, Diamond Like Carbon (DLC), silicon carbide (SiC), a hydrogenated diamond coating, or fluorinated DLC.
In some embodiments, the protective coating does not significantly adversely affect the optical response or characteristics of the optical cavity 108, such as the optical response and/or characteristics of the layers 102 or 106. In any event, changes in the optical cavity characteristics due to the presence of the protective coating may be compensated for by adjusting the parameters of the layers and sublayers. As will be appreciated by those skilled in the art, not all protective coatings are as easily renewable as other protective coatings. Exemplary materials for the regenerative protective coating include, for example, self-aligned monolayers such as Polytetrafluoroethylene (PTFE), Octadecyltrichlorosilane (OTS), and perfluorodecanoic acid, although alternatives will also be ascertainable by those of skill in the art in light of the present disclosure. In some embodiments, a material that can act as a renewable protective coating is one that is self-limiting and self-aligning in its deposition such that a monolayer of the material is deposited over an exposed area to be covered. In addition, since the regeneration process may be temperature dependent, those materials that change state from solid to liquid or gaseous at sufficiently low temperatures may also be desirable.
FIG. 10 illustrates an interferometric light modulating device 80 having portions of layers 102 and 106 within a light modulating cavity 108 coated with protective coatings 160 and 170, respectively, according to an embodiment of the invention. In other embodiments, at least a portion of all surfaces within the light modulation cavity 108 (including the supports 104) are coated with a protective material. In another embodiment, only one surface of the device is coated with a protective coating. As will be appreciated by those skilled in the art, many benefits can be achieved by covering only one surface.
As described above, an insulator layer can be formed on the conductor layer, and the protective coating (e.g., self-aligned monolayer) can be formed on the insulator layer. However, since the insulator layer can be patterned in detail during the general fabrication of the interferometric modulator, the insulator layer can be selectively removed from any desired layer. Therefore, in the following description, when the protective coating is most conveniently and efficiently located on the conductor layer, this will be assumed to be the case. This will be assumed to be the case when the protective coating is most conveniently and effectively located on the insulator layer. However, those skilled in the art will also recognize that other variations are possible. When the protective coating is on an "element" or a "layer," the coating can be on any layer associated with the layer or element (e.g., insulator, conductor, primary protective coating, etc.). When the protective coating is on a sublayer or "directly" on a layer, the coating is then immediately placed against the specified specific layer.
FIG. 11 illustrates an alternative embodiment of an interferometric light modulating device 80 having layers 102 and 106 coated with a protective material in accordance with another embodiment of the invention. In this embodiment, protective coatings 160 and 170 are formed on the surfaces of layers 106 and 102 inside cavity 108. In this embodiment, the movable reflective layer 106 includes its own vertical support mechanism via a hemisphere, unlike the embodiment of FIG. 10 where there is a separate support post 104 formed between the two layers 106 and 102. Although fig. 10 and 11 depict protective coatings 160 and 170 as covering the entire surfaces of layers 102 and 106 within light modulation cavity 108, coating 102 and/or portions of layer 106 are encompassed by the present invention. For example, in one embodiment, only a portion of layer 102 comprises a protective coating. In another embodiment, only a portion of layer 106 comprises a protective coating. The reflective layer can take other shapes (e.g., other than hemispherical), as will be appreciated by those skilled in the art. For example, a multi-radius (multi-radius) shape or a curved corner (curved corner) shape may also be used. The claimed device need not be limited by the shape of the reflective layer.
FIGS. 12A, 12B, and 12C illustrate an interferometric light modulating device 80 having a selective coating of one or more layers in accordance with an embodiment of the invention. In FIG. 12A, a protective coating 160 is provided on the surface of the movable reflective layer 106 and not on the fixed transmissive layer 102. In contrast, in fig. 12B, protective coating 107 is provided on the surface of layer 102 and not on layer 106. In some embodiments, the protective layer is selectively provided on a specific material. In other embodiments, the protective layer is provided on all materials that are adjacent to and coplanar with a particular layer. In other embodiments, the protective layer is applied entirely within the package of the device. In some embodiments, multiple layers of a protective coating are located on a reflective or transmissive layer. For example, there may be two protective coatings on a reflective layer. In some embodiments, it may be more difficult to obtain the desired substance to adhere to a desired surface. In this case, a single layer of "adhesion promoter" can be laid down (put down) to modify the surface and then the anti-stiction or protective coating is laid down.
As depicted in fig. 12C, one way to accomplish the selective coating illustrated in fig. 12A and 12C is to use a cover element 175. During the coating process, the surface not to be covered, depicted herein as the fixed transmissive layer 102, may be covered by the cover element 175 as a sacrificial material such that the protective coating is not formed on the surface covered by the cover element 175. In other embodiments, the cover element 175 can be provided on any surface within the cavity 108 that does not require a protective coating, such as the surface of the post 104 within the cavity 108.
FIGS. 13A and 13B illustrate an interferometric light modulating device package 85 having a layer 102 and a layer 106 coated with a protective material according to another embodiment of the invention. In these embodiments, layers 102 and 106 are sealed within package 85, and the application of the protective coating is performed after package 85 is manufactured. In one embodiment, the backplate 42 is a recessed or shaped structure, but this is not required if the amount of desiccant (not shown in FIGS. 13A and 13B) in the package 85 is reduced or eliminated. In such an embodiment, the need for a recess depth may be reduced or eliminated. In one embodiment, the use of protective coatings 160 and 170 (e.g., self-aligned monolayers) may allow for changes in the lid (backplate) design to reduce the necessary recession compared to the recession required if a desiccant is used.
In the embodiment depicted in fig. 13A and 13B, the aperture 176 is defined in the package, such as in the seal 44 shown in fig. 13A or 13B. In these embodiments, the protective coating material may be supplied into the interior of the package 85 via the hole 176. In another embodiment, as shown in FIG. 13B, two holes 176 and 177 are created in the package 85 (e.g., in the seals 44 and 45) for the transfer of protective material. In another embodiment, more than two holes (not shown) may be defined in the package 85 and the protective coating material supplied into the interior of the package 20 through the holes. In other embodiments, the holes may be formed in the substrate 100 or the backplate 42. It is therefore within the scope of the present invention to have holes in the seal 44, substrate 100 and/or backplate 42 for the transfer of protective coatings.
In these embodiments, the holes formed in the package 85 may also be used to remove water vapor from the interior of the package 85. After the hole is no longer needed, it may be plugged, welded or sealed depending on the nature of the hole.
FIG. 14 illustrates a protective coating system for an interferometric light modulating device 80 in accordance with one embodiment of the invention. Referring to fig. 14, the system 180 includes a chamber 181, a coating material container 182, a valve 184, and a carrier gas reservoir 186. Those skilled in the art will appreciate that system 180 is merely exemplary and that other coating systems may be used that may exclude some of the elements or layers of system 180 and/or include additional elements. In one embodiment, the system 180 may perform a protective coating for the fabricated package as shown in fig. 12A, 12B, and 12C.
Valve 184 controls the injection of coating material into chamber 181. In one embodiment, valve 184 is controlled by a computing device. In one embodiment, valve 184 may be a valve suitable for use in the described protective coating process. In another embodiment, valve 184 may be used to mix the carrier gas with a carrier gas such as XeF2And adjusting the carrier gas with the etching gas.
The container 182 contains a protective coating material. In various embodiments, as discussed above, examples of a protective coating may include (but are not limited to) the following: self-aligned (or self-assembled) monolayers such as OTS, dichlorodimethylsilane, and the like; other polymeric materials such as polytetrafluoroethylene, polystyrene, and the like; or other inorganic materials such as graphite, DLC, etc. In another embodiment, the coating material comprises any protective material that does not significantly adversely affect the optical response or properties of the optical cavity 108, such as the optical response and/or properties of layers 102 or 106. In a preferred embodiment, the protective coating material comprises a self-assembled monolayer having a relatively low melting or vaporization point. This may allow the protective coating to be regenerated after a device containing the interferometric modulator device has been assembled at relatively low temperatures.
In one embodiment, the carrier gas reservoir 186 contains a gas such as nitrogen (N)2) Or argon, for delivering the protective material to chamber 181 by a known pumping mechanism. In another embodiment, the carrier gas may incorporate other types of gettering materials or chemicals as long as the performance of the interferometric light modulating device 80 is not significantly adversely affected. In another embodiment, the carrier gas may be used in combination with the released etchant gas XeF2The chemical substances of (a) are integrated.
FIG. 15 is a schematic flow chart illustrating a protective coating process according to one embodiment of the present invention. Those of skill in the art will appreciate that additional steps may be added, other steps removed, or the order of the steps changed according to the embodiments. Fig. 15 demonstrates the protective coating procedure according to an embodiment of the present invention and as shown in fig. 8-13.
A protective coating material is provided in step 90. In step 92, the surface to be coated, such as layers 102 and/or 106, interferometric light modulating device 80 is placed in a force 181. A protective coating is applied to the surface to be coated in step 94. In one embodiment, the surface of layers 102 and/or 106, such as a mirror surface or an insulator surface, may be heated such that water vapor present on the surface to be coated is removed prior to performing the protective coating. In an embodiment, the insulating sub-layer 130 is not provided and the protective coating is formed on the surface of the primary mirror sub-layer 120 (depicted in FIG. 9). In another embodiment, the protective coating is formed on the surface of the secondary mirror sublayer 140 (depicted in FIG. 9). In another embodiment, the protective coating is formed on the surfaces of the insulating sublayer 130 and the secondary mirror sublayer 140 (depicted in FIG. 9).
In one embodiment of the protective coating process, the protective coating is formed during an interferometric light modulating device manufacturing process. For example, the protective coating may incorporate a "release" treatment. In the release process, for example, XeF is used2Etches away a sacrificial layer 175 (depicted in fig. 12C) of the interferometric light modulating device 80. In one embodiment, the protective coating material can be pumped with XeF2Into the chamber 181. In another embodiment, XeF may be completed2The protective coating is applied after etching. Typically, the release process is performed by a MEMS etching system, such as the X3 series Xetch available from XACIX, USA and MEMS ETCHER available from Penta Vacuum, Singapore.
In another embodiment of the protective coating process, the protective coating is uniform in thickness. In another embodiment, the protective coating is non-uniform in thickness. Generally speaking, even if the protective coating is not uniform, a protective coating such as a self-aligned monolayer is a thin film coating and therefore it does not significantly affect the optical properties (or response) of the layers 102 or 106, including the mirror surfaces 120 and 140 (depicted in FIG. 9).
In one embodiment, the protective coating is performed using a process such as disclosed in "dichlormethicilline as an Anti-sticking Monolayer for MEMS" from March.2001, Vol.1, J.10 MEMS and U.S. Pat. No. 6,335,224. In another embodiment, the protective coating is performed using a deposition process such as chemical vapor deposition or physical vapor deposition. In another embodiment, any suitable protective coating method on the surface of a mirror or insulator that is known or to be developed in the future may be used. The protective coating process is then completed in step 96 and the interferometric light modulating device 80 is removed from the chamber 181 in step 98.
FIG. 16 is a flow chart describing a method for applying a protective coating for an interferometric light modulating device according to one embodiment of the invention. The figure illustrates another method for reducing attractive forces between layers within a light modulation device. According to the method, interferometric light modulating devices described in this disclosure, including the devices described with reference to FIGS. 8-13, can be fabricated. In this manner, a transmissive element is provided in step 200. The transmissive element may be provided by layering a transmissive layer on a substrate. The transmissive element may be, for example, the entire fixed transmissive element 102 or any of its sublayers, such as the primary mirror sublayer (transmissive sublayer) 120, the insulating sublayer 130, or the electrode sublayer 110 depicted in fig. 9. In step 210, a reflective element is provided. The reflective element may be provided by forming a thin film stack over the transmissive element. The reflective element can be, for example, the movable reflective layer 106 or any of its sublayers, such as the secondary mirror sublayer 140 or the electrode sublayer 150 depicted in FIG. 9. A protective coating is then provided in step 220, wherein the protective coating is positioned between at least a portion of the reflective layer and the transmissive layer. A protective coating can be provided as described herein with reference to fig. 12-15. Those skilled in the art will appreciate that the method depicted in fig. 16 is merely exemplary, and that other coating methods may be used that may exclude some elements or steps in the depicted method and/or include additional elements, layers, or steps.
For example, in other embodiments, the reflective element may be provided before the transmissive element is provided. Also in other embodiments, the protective coating is provided after the reflective or transmissive element is provided. Also in other embodiments, a cover element, such as a sacrificial layer, may be applied to the portion of the interferometric light modulating device where the protective coating is needed. Then, if desired, after providing the protective coating, other elements can be contacted with the coated cover element, thereby providing a protective coating by transfer contact. The cover element and/or sacrificial layer may then be etched. In other embodiments, a sacrificial layer is provided between the reflective and transmissive elements and then etched before the protective coating is provided. In other embodiments, the transmissive and reflective elements are packaged in an interferometric light modulating device package as depicted in FIGS. 13A and 13B before the protective coating is provided. In other embodiments, the protective coating is provided before the encapsulation.
Regeneration of protective coatings
FIG. 17 shows a simplified and enlarged side view of another embodiment of a transmissive element or layer 102 that may be used in a MEMS configuration. The transmissive element has a protective coating 908, such as a single layer, deposited over an insulator layer 904. The insulator layer 904 is located on a transmissive layer 902 on a substrate 900. For example, there may be an electrode layer between layer 902 and substrate 900 as shown in fig. 9. If aluminum is used, the insulating layer 904 can be formed, for example, by oxidation in an oxygen plasma; thus, a thin layer of aluminum oxide is formed.
FIG. 18A is a side view illustrating an embodiment of a package structure 340 for an array of interferometric modulators that may contain the transmissive elements 102 depicted in FIG. 17. Similar to the structure described above, the package structure 340 includes an array of interferometric modulators 342 formed on a substantially transparent substrate (e.g., glass) 344, and a backplane cover or "lid" 346 that encloses the array. The package structure 340 may further have a seal 348 formed or applied between the facing surface of the backplate 346 and the substrate 344. In one embodiment, primary seal 348 is a non-hermetic seal, such as a conventional epoxy-based adhesive. The various packaging systems described above and other systems may also be employed. Unlike the packaging system described above, the device of FIG. 18A further contains an optical heater 350 that can be used to regenerate the protective coating as described in detail below.
Fig. 18B is a plan view illustrating the package structure 340 of fig. 18A. As illustrated in FIG. 18B, a plurality of conductive leads 352 (partially shown) may be located on the substrate 344 and configured to provide electrical connection of a driver circuit (not shown) to the elements of the interferometric modulator array 342. The package structure 340 may include conductive leads 352 formed on more than one side of a substrate 344, and the conductive leads are illustrated on only one side of the substrate and in the configuration shown for convenience.
The drive circuitry is configured to control the operation of the elements of the interferometric modulator array 342. As will be appreciated by those skilled in the art, the conductive leads 352 may be located on the substrate 344 in a plurality of configurations, and the illustrated configuration is exemplary in nature. In some embodiments, the drive circuit is configured to control the heater. In other embodiments, a separate device or element is used to control the heater.
The drive circuits may be located in different areas of the package, as will be appreciated by those skilled in the art. In some embodiments, the driver circuit 353 is located on the substrate as shown in fig. 18C. In this embodiment, the drive circuit can be used to control the heater without difficulty, particularly if the heater is located on the substrate. As will be appreciated by those skilled in the art, in some embodiments, the heater is controlled by a device other than a drive circuit. For example, in embodiments where the heater or heater leads are off the substrate, other discrete components may be used to control the heater. For example, a power transistor (power transistor) may be used to control the heater. Given the present disclosure, one of ordinary skill in the art is readily able to identify alternative means for providing power to or controlling a heater.
While the protective coatings discussed above have many possible advantages, it has been recognized that the protective coating 160, 170, or 908 may be wiped or cut off during operation of the interferometric modulator element due to repeated contact with the transmissive and reflective elements. The rubbing or cutting may or may not be uniform over the surface of the coating. The protective coating may flake off of the insulator layer over a period of time. Thus, it may be advantageous to occasionally repair the protective coating during use of the device. Different methods for how the protective coating can be regenerated are disclosed below.
One embodiment of a method for regenerating or redistributing a protective coating (e.g., a self-aligned monolayer) such as the illustrated protective coating 908, 170, or 160 comprises: the temperature of the protective coating 908, 170, or 160 is increased to a temperature at which the protective coating material changes from a solid to a liquid, vapor, or vapor pressure is increased significantly such that the protective coating material is redistributed over the layer it was originally applied in a substantially uniform configuration. This allows the protective coating to be repaired and regenerated even though it is still contained within a package (e.g., fig. 13A, 13B, 18A, or 18B). This can be achieved by different means. For example, as shown in FIG. 18A, an optical heater 350 may be included in the package.
FIG. 18D depicts an embodiment of the method. First, 300, an interferometric modulator device having a protective coating, preferably a coating that has been damaged or is suspected of being damaged, is provided. Then 310, the temperature of the protective coating material is raised so that the protective coating can redistribute itself on a surface. The heated protective coating material can be the material of the protective coating (i.e., the coating on the reflective or transmissive element) itself or it can be a reservoir from the protective coating material. Once the temperature has been increased over a period of time to allow redistribution of the material of the protective coating, the device 320 is allowed to cool, which allows solidification of the protective coating; thus, the protective coating is regenerated. As will be appreciated by those skilled in the art, if the method depicted in fig. 18D is helpful in initially establishing a monolayer, it may be performed after the method depicted in fig. 15 or 16, or even during an early procedure.
As will be appreciated by those skilled in the art, the increase in temperature in a device may be measured in different ways, for example, at the temperature of the heating element or at some point of the device to be heated. When the upper limit of temperature is discussed, it is generally with respect to the temperature of the item to be heated, rather than the heating element itself. One skilled in the art will recognize that the heating element itself may generally be heated in some embodiments, and the device may not be heated to substantially higher temperatures. In a preferred embodiment, the desired amount of heat is obtained by running a particular heater for a known current for a known time. Given the present disclosure, the current and time can be determined by routine experimentation.
In some aspects, the present invention uses a material as a protective coating that can allow for the regeneration of the protective coating after assembly of the device. Thus, in one embodiment, protective coatings are contemplated that are predominantly solid at relatively low temperatures and exhibit relatively high volatility at high temperatures and thus can be redistributed in a system upon heating. For example, protective coating materials that redistribute themselves when heated to temperatures greater than 22-50, 50-85, 85-100, 100-. As will be appreciated by those skilled in the art, protective coatings having higher stability at lower temperatures may be advantageous for typical operating conditions because the protective coating should maintain a relatively solid form during typical use of the device.
Various protective coatings have been discussed above. In a preferred embodiment, the material used for the protective coating may form a self-assembled monolayer (SAM). Preferably, materials that are solid at standard operating conditions are susceptible to melting or vaporization with the addition of energy (e.g., heat). Thus, particularly preferred materials are those that form SAMs, that can be decomposed and regenerated at various temperatures, and that do not damage the interferometric modulator device, the package, and/or the elements of the device in which they are contained. Exemplary materials for the regenerative protective coating include, for example, self-aligned monolayers, such as Polytetrafluoroethylene (PTFE) and Octadecyltrichlorosilane (OTS).
The material further comprises, for example, a compound of the formula F3C(CF2)XLong chain aliphatic halogenated polar compounds of perfluoroalkanoic acids (perfluorodecanoic acids) of COOH, wherein X is preferably 10 or greater (e.g., perfluorodecanoic acid), such as 10, 12, 14, 16 or 18. The COOH moiety provides a better "anchoring" to the surface of the transmissive or reflective element, while the free end or residue of each molecule provides a low surface energy that prevents the two elements from adhering. The attachment of the COOH moiety can be enhanced by appropriate pre-treatment of the surface of the reflective or transmissive layer. As discussed herein, these molecules are selected based on being able to form a stable protective coating under typical operating conditions, but are sufficiently volatile when heated to allow the protective coating to move and regenerate. Those skilled in the art will recognize how to select or modify such a single layer, given the present disclosure. For example, the number of carbons in a long chain or the number of double bonds in a long chain may change the stability of the protective coating produced. Additionally, additives may be added to further adjust the melting point of the protective coating.
In some embodiments, multiple types of protective coating materials may be used simultaneously. In some embodiments, a relatively difficult to regenerate initial protective coating (e.g., teflon) is establishedTM) And also adding a second type of easily recyclable protective coating material to the device. In some embodiments, the second type of protective coating material is selected such that it will preferentially bond to teflonTMAny gaps in the coating thus reestablish a complete protective coating. In some embodiments, the "lower" coating may be chosen to adjust other parameters such as adhesion and temperature dependence.
Although the embodiments discussed herein focus on methods and compositions using a heat source internal to the package, in some embodiments, the heat or energy source may be located external to the package 85. Thus, in some embodiments, an external heat source may heat a portion of the entire package or device (e.g., only the reflective and/or transmissive elements). This can be done in a number of ways, for example using radiation such as a laser, or heating the atmosphere surrounding the device. The heating may be dictated by the substrate 344 or, for example, by the back plate 346. The heating may be governed by radiation, conduction or convection.
FIG. 19 is a flow diagram illustrating another embodiment of a system 354 for regenerating a protective coating formed on the surface of an interferometric modulator array 342. The system illustrated in FIG. 19 includes a heater, such as a heater element 355 located adjacent to the interferometric modulator array 342. The heater element 355 may be fabricated by photolithographic patterning of one or more metal layers deposited during fabrication of the interferometric modulator structure. The heater elements 355 are configured to emit heat in response to current generated by application of current defined at the conductive leads 356A and 356B, wherein the amount of heat emitted by the heater elements 355 is sufficient to raise the temperature of the protective coating (e.g., a self-aligned monolayer) such that the coating redistributes over the conductor layer.
The application of a current to the conductive leads 356A and 356B can be controlled, for example, by the driver circuit (not shown) which is also configured to control the operation of the elements of the interferometric modulator array 342 via the conductive leads 352. When the interferometric modulator array 342 is implemented in an electronic device, the drive circuitry may be configured to apply a predetermined current to the heater elements 355 on a fixed periodic basis during its lifetime. In other embodiments, the application of a predetermined voltage is used. The drive circuit itself may be located on the glass, as will be appreciated by those skilled in the art. However, in some embodiments, such as when the heater is not on the glass, the drive circuitry need not be located on the glass. In some embodiments, the drive circuit is not used to control the heater and uses another current/voltage source.
In one embodiment, heater element 355 is located on substrate 344. In other embodiments, multiple heater elements can be implemented, for example, adjacent to each edge of the interferometric modulator array 342. As will be appreciated by those skilled in the art, the configuration of the heater element 355 is not limited to that shown or described, and additional configurations are contemplated. The actual configuration and arrangement of the heaters may vary depending on the desired application, and one of ordinary skill in the art will be able to determine the appropriate arrangement and configuration in light of this disclosure. For example, the amount of space available, the proximity of the heating element to other heat sensitive devices, the level of heating required to substantially vaporize or regenerate the protective coating, the volatility of the protective coating material to be heated, the composition of the heating element and the composition of the electrical resistance and the substrate, to name a few factors.
The terms "heater," "heater device," "heater element," and other similar terms are interchangeable as appropriate. Generally speaking, a "heater element" indicates the actual substance heated by an electric current or other means, while a heater may indicate a more general concept of the entire heating device or the element itself.
In another embodiment, the heater is not located on the substrate but is located elsewhere in the device. For example, the heater may be located on the back plate or cover 346. For example, in one embodiment, the article 350 in FIG. 18A is a heater; thus, in some embodiments the heater may be attached to the backing plate.
As will be appreciated by those skilled in the art, the number of heats required and the duration of heat application can be determined in a variety of ways. For example, in a given package containing a damaged protective coating (which may be intentionally damaged for testing purposes), a large amount of heat is applied to the device and the device is allowed to cool. After this, the surface and consistency of the protective coating can be checked, for example, functionally or directly via a microscope. The process may be repeated in the same or different devices to determine the duration and amount of current required to adequately regenerate a protective coating to generate sufficient heat for a particular heater in a particular package. Regeneration of surfaces that return to their original covered state by different amounts of regeneration, such as 1-10, 10-20, 20-30, 30-40, 40-50, 50-60, 60-70, 70-80, 80-90, 90-99, and 99-100 percent, is contemplated. In some embodiments, the maximum current that lasts the longest is used. In a preferred embodiment, data from the above can be used to generate a heating protocol in which a predetermined current is passed through the heating device for a predetermined period of time to regenerate the layer. In a preferred embodiment, the integrity of the layer need not be checked.
In some embodiments, it is useful to have additional reservoirs of protective coating material available in the package. This may be particularly useful where the protective coating is a single layer. In some embodiments, both the exposed surface of the reflective layer and the exposed surface of the transmissive layer are covered with a protective coating. In some embodiments, there is a reservoir of protective coating material in the package, in addition to the amount already on the transmissive and reflective layers. In some embodiments, the reservoir is thicker than a monolayer. The reservoir layer may be dispensed on the package such that an excess protective coating is available on the package and surrounds the array of interferometric modulator devices. The reservoir may be located on top of or near the heating element. Thus, in some embodiments, very low levels of heat need to be applied in order to have a protective coating material that is capable of self-redistributing the reservoir. In some embodiments, the reservoir layer is present with only more protective coating material than is required to coat a surface of the transmissive or reflective layer.
As will be appreciated by those skilled in the art, in embodiments where a reservoir is used, any structure in the package or interferometric modulator device may be used as a surface for the reservoir to which the packaging material is added, including various posts, supports, and package surfaces. As will be appreciated by those skilled in the art, the addition of a protective coating by blowing it into the package or onto the interferometric modulator device may necessarily result in excess protective coating material in the package or on the interferometric modulator device, thus creating a reservoir. In one embodiment, where the protective coating has been added by blowing protective coating material through an aperture in the package, the protective coating material may be located on different surfaces of the package. In embodiments where the protective coating is blown onto the interferometric modulator device prior to enclosing the device within the package, only the interferometric modulator device may be coated with the protective coating. As will be appreciated by those skilled in the art, not every type of protective coating can adhere to every surface that is available. The type of protective coating can be selected based on the previously mentioned characteristics and where and how much of the protective coating is needed in the final device. In some embodiments, additional protective material is added to the device after the device has been used. In some embodiments, the protective coating is established prior to first using the device for its intended purpose. In other embodiments, the heating or heater described herein is employed when first establishing the protective coating to help establish a uniform coating of the protective coating.
In some embodiments, the regeneration assembly and method are used with an interferometric modulator device having an getter or desiccant. As will be appreciated by those skilled in the art, the temperature of the getter should generally not be raised to the point of losing the absorbed water. This can be achieved by thermally isolating the getter from the heater system or maintaining the temperature of the heater below a certain temperature. In some embodiments, a desiccant or getter is not employed when a heater is employed.
In some embodiments, only one protective coating is needed between the transmissive and reflective layers. Thus, when more than one surface area is covered, the additional material may be considered a reservoir. As will be appreciated by those skilled in the art, heating the device can cause the protective coating to move from one layer to another when the reservoir is a supplemental layer. One layer may be allowed to loosen the protective coating so that the other layer can regenerate its protective coating.
As will be appreciated by those skilled in the art, in some embodiments, the protective coating is not "fully" regenerated. Rather, in some embodiments, a damaged portion of the coating is regenerated while another portion of the coating is exposed. This can occur without adversely affecting the operation of the device when the portion from which the protective coating material is taken is from a portion of a layer that does not contact another layer. This may include, for example, a portion of reflective layer 14b located between support 18 and where reflective layer 14b contacts transmissive layer 16 b. It will be appreciated by those skilled in the art to some extent that repositioning of the protective coating material will occur due to the fact that the location of damage to the protective coating will be where contact between the two layers occurs, for example, thus creating a relatively lower concentration of material therein, and randomly redistributing the protective coating will result in an increase in the protective coating material at the damaged location and a decrease in the concentration at the undamaged location. This can be achieved without difficulty by using a self-assembled monolayer whose molecules redistribute themselves on one layer. Thus, in some embodiments, only the contact area of the protective coating (the area where one element contacts another element) is regenerated or partially regenerated.
FIG. 20A shows another embodiment of a system 362 for regenerating a protective coating for an interferometric modulator array 342. In this embodiment, reusable conductive leads 352 are present to emit sufficient heat to redistribute the protective coating in response to a predetermined voltage. In one embodiment, elements or layers already in the interferometric modulator device are reused as a heater.
Typically, the conductive leads extend from the driver circuit through the array of interferometric modulators and terminate at a distal opening of the array. In some embodiments, a plurality of these conductive leads may be routed back or "looped" to drive circuitry around the periphery of the array. During normal operation, the looped lead is isolated from ground potential by a transistor switch internal to the driver circuit, for example. When redistribution of the protective coating is desired, the transistor switches are actuated to short the ring leads to ground potential, and application of a predetermined current or voltage will cause one or more ring leads to emit sufficient heat to redistribute the protective coating of the interferometric modulator array 342. In some embodiments, a current limiting resistor is in the loop between the lead and ground.
In one embodiment, the heat generating current is looped through the transmissive layer. In a preferred embodiment, the heat generating current is looped through a circuit having a relatively high resistance so that a desired amount of heat can be generated. As mentioned above, the transmissive layer may comprise a relatively high resistance material, such as chromium. In embodiments where the protective coating is directly or indirectly attached to the transmissive layer, this may be advantageous as heat will be generated on the surface that requires the protective material of the additional coating or redistribution thereof. In another embodiment, the heat generating current is looped through another conductive layer with a relatively high electrical resistance (such as a layer with chromium or nickel therein), such as the mechanical layer (or movable layer) 34 in the device.
As will be appreciated by those skilled in the art, in some embodiments, any substance or portion of an interferometric modulator device or package that will emit heat when a current is passed may be used. As will be appreciated by those skilled in the art, the interferometric modulator device need not be operable during the regeneration step, so even devices or elements that may be typically required for operating the interferometric modulator device may be used as heaters. As will be appreciated by those skilled in the art, it may be desirable to have a relatively large amount of space above the surface to be repaired, as it will allow a more efficient regeneration process to occur. Thus, in some embodiments, the reflective and transmissive elements are positioned relatively far from each other during the regeneration process.
In some embodiments, as illustrated in fig. 20A, the isolation switch used in the above embodiments may be implemented on a substrate as a MEMS switch 365, where the MEMS switch is coupled to a common ground connection in a driver or elsewhere. Fig. 20B is a perspective view illustrating an exemplary MEMS switch 366. MEMS switch 366 includes a substrate 370 having a primary conductor layer 372 formed thereon. An insulator layer may be formed on the primary conductor layer 372. However, the insulator layers are not illustrated in fig. 20B for convenience, and reference to the primary conductor layer 372 should be understood to include the combination of the conductor layer 372 and the insulator layers formed thereon.
Similar to the reflective layer (or conductor layer) 14b illustrated in fig. 1, the MEMS switch 366 further includes a secondary conductor layer 374 configured to deform into a primary conductor layer 372 in response to application of a voltage. The MEMS switch 366 can be fabricated, for example, as described in detail in U.S. Pat. No. 5,835,255 and with reference to FIGS. 26A-K. The MEMS switch 366 also includes one or more switch conductors 376 formed on the primary conductor layer 372. During operation, the secondary conductor layer 374 deforms into the primary conductor layer 372 in response to application of a voltage V (see fig. 1, for example). When the secondary conductor layer 374 contacts the switch conductor 376, the MEMS switch 366 allows current to flow between the conductors 376. Accordingly, the MEMS switch 366 may be actuated in response to a predetermined voltage applied to the primary 372 and secondary 374 conductors.
In some embodiments, the heater or heater element is located relatively close to the reflective layer. This can be achieved in a number of ways. For example, as discussed above, the heater may be located on a back plate of a package.
FIG. 21A is another embodiment in which the heater is located relatively close to the reflective layer. FIG. 21A is an illustration of a side view of another embodiment of a system 380 for regenerating a self-aligned monolayer for an array of interferometric modulators. Similar to the interferometric modulator element illustrated in FIG. 1, the system 380 comprises a transmissive layer 502 formed on a substrate 500, and a reflective layer 506 supported by insulating supports 504. An insulator layer 382 similar to insulator layer 904 (fig. 17) is formed on transmissive layer 502, and a protective coating 384 such as a self-aligned monolayer (similar to protective coating 908 in fig. 17) is also present, which is formed on insulator layer 382. In some embodiments, the protective coating is dispensed over a plurality of surfaces and is not limited to being formed on top of the insulating layer 382.
As illustrated in FIG. 21A, the system 380 may further include one or more support posts 386 formed on the insulator layer 384 between adjacent reflective layers 506 (see FIG. 21B). The support posts 386 extend away from the insulator layer 384 and may extend beyond the height of the reflective layer 506. The support posts 386 are configured to support a heater grid 388 or individual heating elements. The heater grid 388 is configured to emit heat in response to a predetermined voltage or current. The emitted heat is sufficient to raise the temperature of the protective coating such that the protective coating or additional protective coating is substantially evenly redistributed over the insulator layer 382 or any layer covered by the protective coating. In one embodiment, the protective coating is redistributed while not heating layer 384 to any great extent. For example, an additional amount of protective coating material may be located on the heater grid; and therefore, the heater grid need only be heated to any effective number of degrees.
Fig. 21B is a plan view illustration of the system 380 of fig. 21A. The top of the posts 386 are shown for illustrative purposes only. The substrate 500 may include conductive leads (not shown) for connection between the heater grid 388 and drive circuitry (not shown) for the interferometric modulator array. The drive circuit is configured to control a current or voltage applied to the heater grid 388, thereby controlling regeneration of the protective coating 384. As will be appreciated by those skilled in the art, the current required to be provided by the driver IC and other voltage/current sources may be used for these heaters. When the heater leads are off the glass, the voltage/current can be supplied by an alternative voltage/current source without difficulty.
As will be appreciated by those skilled in the art, in accordance with the present disclosure, the heaters or heater grids 388 may be located at different stages. For example, when the heater grid 388 is shown above the reflective layer or element 506, it may also be located in the same plane as the reflective layer or element, below or partially below the reflective layer or element 506. In addition, the position of the protective coating can be changed, or a protective coating can be applied to the entire interferometric modulator device or the entire package. As will be appreciated by those skilled in the art, placing a protective coating on the reflective layer 506 that is in the embodiment proximate to the heater grid 388 may allow a lower amount of heat from the heater grid sufficient to redistribute the protective coating over the layer.
In some embodiments, the different embodiments described above are combined. For example, in some embodiments, multiple types of heaters are combined, or multiple methods of heating and regenerating the device are performed simultaneously. For example, an external source of heat may be applied while using an internal heater, which may allow more efficient regeneration to occur.
In some embodiments, a bus system similar to that shown in FIG. 22 above the reflective element can be reused to heat the protective coating. In this embodiment, the interferometric modulator device 600 is similar to other interferometric modulator devices in that it has a cavity 660 and reflective and transmissive layers, but it further has a bus structure 671 on top of the support. The bus structure (e.g., a particular MEMS switch or transistor) may be reused as described above. One advantage of the structure is that the heater or heating element does not occupy additional space of the interferometric modulator device; thus, the resolution of the device is not lost. In addition, since the bus structure 671 is located on top of the support of the reflective layer, no additional support needs to be added to the device to support the heater. A detailed description of a bus structure and how to manufacture the bus structure is disclosed in U.S. patent application No. 10/644,312, filed on 8/19/2003.
The foregoing description details certain embodiments of the invention. However, it should be appreciated that no matter how detailed the foregoing appears in text, the invention can be practiced in many ways. It should also be noted that no particular terminology used when describing certain features or aspects of the invention should be taken to imply that the terminology is being redefined herein to be restricted to including any specific characteristics of the features or aspects of the invention with which that terminology is associated.
23A and 23B are system block diagrams illustrating an embodiment of a display device 2040. The display device 2040 may be, for example, a cellular or mobile telephone. However, the same components of display device 2040 or slightly different variations thereof are also illustrative for different types of display devices, such as televisions and portable media players. .
The display device 2040 includes a housing 2041, a display 2030, an antenna 2043, a speaker 2045, an input device 2048, and a microphone 2046. The housing 2041 is generally formed from any of a variety of manufacturing processes well known to those skilled in the art, including injection molding and vacuum molding. Additionally, the housing 2041 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. In one embodiment, the housing 2041 includes removable portions (not shown) that are interchangeable with other removable portions of different color or containing different logos, pictures, or symbols.
As described herein, the display 2030 of the exemplary display device 2040 may be any of a variety of displays, including a bi-stable display. In other embodiments, the display 2030 comprises a flat panel display, such as plasma, EL, OLED, STN LCD, or TFT LCD, as described above, or a non-flat panel display, such as a CRT or other line set, as is well known to those of skill in the art. However, for purposes of describing the present embodiment, the display 2030 includes an interferometric modulator display, as described herein.
The components of one embodiment of exemplary display device 2040 are schematically illustrated in figure 23B. The illustrated exemplary display device 2040 includes a housing 2041 and can include additional components at least partially enclosed therein. For example, in one embodiment, the exemplary display device 2040 includes a network interface 2027 that includes an antenna 2043 coupled to a transceiver 2047. The transceiver 2047 is connected to a processor 2021 which is connected to conditioning hardware 2052. The conditioning hardware 2052 may be configured to condition a signal (e.g., filter a signal). Conditioning hardware 2052 is coupled to a speaker 2045 and a microphone 2046. The processor 2021 is in turn connected to an input device 2048 and a driver controller 2029. The driver controller 2029 is coupled to a frame buffer 2028 and to an array driver 2022, which array driver 2022 is in turn coupled to a display array 2030. A power supply 2050 provides power to all components as required by the design of the particular exemplary display device 2040. The network interface 2027 includes the antenna 2043 and the transceiver 2047 so that the exemplary display device 2040 can communicate with one or more devices over a network. In one embodiment, the network interface 2027 may also have some processing capabilities to relieve requirements of the processor 2021. The antenna 2043 is any antenna known to those skilled in the art for sending and receiving signals. In one embodiment, the antenna transmits and receives RF signals according to the IEEE 802.11 standard, including IEEE 802.11(a), (b), or (g). In another embodiment, the antenna transmits and receives RF signals according to the BLUETOOTH standard. In the case of a cellular telephone, the antenna is designed to receive CDMA, GSM, AMPS or other known signals that are used to communicate within a wireless mobile telephone network. The transceiver 2047 pre-processes signals received from the antenna 2043 so that they may be received by and further manipulated by the processor 2021. The transceiver 2047 likewise processes signals received from the processor 2021 so that they may be sent from the exemplary display device 2040 via the antenna 2043.
In an alternative embodiment, the transceiver 2047 may be replaced by a receiver. In another alternative embodiment, the network interface 2027 may be replaced by an image source, which may store or generate image data to be sent to the processor 2021. For example, the image source can be a Digital Video Disc (DVD) or a hard-disc drive that contains image data, or a software module that generates image data.
The processor 2021 generally controls the overall operation of the exemplary display device 2040. The processor 2021 receives data, such as compressed image data from the network interface 2027 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 2021 then sends the processed data to the driver controller 2029 or to a frame buffer 2028 for storage. Raw data generally refers to information that identifies image characteristics at each location within an image. For example, the image characteristics may include color, saturation, and gray-scale level.
In one embodiment, the processor 2021 includes a microcontroller, CPU, or logic unit to control operation of the exemplary display device 2040. Conditioning hardware 2052 typically includes amplifiers and filters for transmitting signals to the speaker 2045, and for receiving signals from the microphone 2046. Conditioning hardware 2052 may be discrete components within the exemplary display device 2040, or may be incorporated within the processor 2021 or other components.
The driver controller 2029 takes the raw image data generated by the processor 2021 either directly from the processor 2021 or from the frame buffer 2028 and reformats the raw image data appropriately for high speed sending to the array driver 2022. In particular, the driver controller 2029 reformats the raw image data into a data flow having a raster-like format (raster-like format) such that it has a time order suitable for scanning across the display array 2030. The driver controller 2029 then sends the formatted information to the array driver 2022. Although a driver controller 2029, such as an LCD controller, is typically associated with the system processor 2021 as a stand-alone Integrated Circuit (IC), the controller may be implemented in a number of ways. They may be embedded in the processor 2021 as hardware, embedded in the processor 2021 as software, or may be fully integrated within the hardware with the array driver 2022.
Typically, the array driver 2022 receives the formatted information from the driver controller 2029 and reformats the video data into a parallel set of waveforms that are applied many times per second to the hundreds and sometimes thousands of leads coming from the display's x-y matrix of pixels.
In an embodiment, the driver controller 2029, array driver 2022, and display array 2030 are appropriate for any of the types of displays described herein. For example, in one embodiment, the driver controller 2029 is a conventional display controller or a bi-stable display controller (e.g., an interferometric modulator controller). In another embodiment, the array driver 2022 is a conventional driver or a bi-stable display driver (e.g., an interferometric modulator display). In one embodiment, a driver controller 2029 is integrated with the array driver 2022. The embodiments are ubiquitous in highly integrated systems such as cellular phones, watches, and other small area displays. In another embodiment, the display array 2030 is a typical display array or a bi-stable display array (e.g., a display including an array of interferometric modulators).
The input device 2048 allows a user to control the operation of the exemplary display device 2040. In one embodiment, input device 2048 includes a keypad (such as a QWERTY keyboard or a telephone keypad), a button, a switch, a touch-sensitive screen, a pressure-sensitive or heat-sensitive membrane. In one embodiment, microphone 2046 is an input device for exemplary display device 2040. When the microphone 2046 is used to input data to the device, voice commands may be provided by a user to control the operation of the exemplary display device 2040.
The power supply 2050 may include various energy storage devices, as is well known in the art. For example, in one embodiment, power supply 2050 is a rechargeable battery, such as a nickel-cadmium battery or a lithium ion battery. In another embodiment, power supply 2050 is a renewable energy source, a capacitor, or a solar cell including a plastic solar cell and solar-cell paint. In another embodiment, power supply 2050 is configured to receive power from a wall outlet.
In some implementations, control programmability resides, as described above, in a driver controller that can be located in several places in the electronic display system. In some cases, control programmability exists for the array driver 2022. Those skilled in the art will recognize that the above-described optimization scenario may be implemented in any number of hardware and/or software components and in various configurations.
While the above detailed description has shown, described, and pointed out novel features of the invention as applied to various embodiments, it will be understood that various omissions, substitutions, and changes in the form and details of the device or process illustrated may be made by those skilled in the art without departing from the spirit of the invention. It will be recognized that the present invention may be embodied within a form that does not provide all of the features and benefits set forth herein, as some features may be used or practiced separately from others.