JP2015146050A - Mems display apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the effects of stiction and improve the optical and electromechanical performance of the display apparatus.SOLUTION: This invention relates to MEMS display apparatus and methods for assembly thereof that include a plurality of light modulators having components substantially surrounded by a liquid (530) that reduces the effects of stiction and improves the optical and electromechanical performance of the display apparatus. The invention also relates to methods for aligning components of a MEMS display to establish a correspondence between the plurality of light modulators (503) and a plurality of apertures to regulate the transmission of light through the apparatus.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application claims the priority and benefits of US Provisional Patent Application No. 60 / 930,872, filed May 18, 2007, entitled "MEMS Displays and Assembled Methods". The following applications, U.S. Patent Application No. 11 / 656,307 filed January 19, 2007, entitled "Methods and Apparatus for Actuating Displays", U.S. Patent Application No. 11 filed March 30, 2007 No./731,628, title “Methods and Apparatus for Actuating Displays”, US Patent Application No. 11 / 975,398, filed Oct. 19, 2007, title “MEMS Display Apparatus” No. 11 / 975,397 filed Oct. 19, 2007, entitled “Alignment Methods in Fluid-Filled MEMS Displays”, U.S. Patent Application No. 11 / 975,411 filed Oct. 19, 2007 No., title “Methods for Manufacturing Fluid-Filled MEMS Displays”, and US patent application Ser. No. 11 / 975,622, filed Oct. 19, 2007, titled “Spaces for Maintaining Display Apart”. It is a continuation application. The entirety of each of these provisional applications and non-provisional applications is incorporated herein by reference.

  The present invention relates generally to the field of imaging display assembly, and more particularly to the assembly of mechanically operated display devices.

  Displays constructed with mechanical light modulators are an attractive alternative to displays based on liquid crystal technology. Mechanical light modulators are fast enough to display video content with good viewing angles and a wide range of colors and gray scales. Mechanical light modulators have been successful in projection display applications. Backlit displays that utilize mechanical light modulators have not yet fully demonstrated an attractive combination of brightness and low power. There is a need in the art for mechanically actuated displays that are fast, bright and low power.

  Unlike liquid crystal displays, MEMS-based displays include hundreds, thousands or even millions of moving elements. In some devices, any movement of one element creates a stiction opportunity that disables one or more elements. Furthermore, the effective operation of MEMS-based displays depends on the coupling of optical, electrical, and / or mechanical components. Such misalignment of components also leads to image quality degradation and possibly inoperability of the entire display.

  In one aspect, the invention relates to a method for manufacturing a display assembly. The method includes providing a first substrate on which a plurality of MEMS light modulators are fabricated. The first substrate may be opaque or transparent. Each light modulator has a bright state and a dark state. The method also includes providing a second substrate (preferably a transparent substrate) that includes a layer having a plurality of apertures formed therein. In one embodiment, the layer is reflective. In other embodiments, the layer is light absorbing. The first and second substrates are then aligned to set the correspondence between the respective light modulators and apertures.

  The MEMS light modulator includes a modulation element such as a shutter, an optical tap, oil, or an interferometric modulator having at least one edge. Each aperture also has an edge. In one embodiment, the first and second substrates are such that when the light modulator is in the dark state, the edge of each light modulating element overlaps the edge of its corresponding aperture by more than 0 and less than about 20 microns. Are aligned as follows. In another embodiment, the edge of the light modulator overlaps the edge of the aperture in the dark state by more than 0 microns and less than about 5 microns.

  The alignment can be maintained in many ways. The alignment can be achieved by bonding the first substrate to the second substrate with an adhesive or a heat reflowable material, or interlocking features formed on or in the first and second substrates. ) Can be maintained by connecting each other.

  The assembly process can address the manufacture of individual display assemblies or the simultaneous manufacture of multiple display assemblies. In the latter case, the plurality of MEMS modulators on the first substrate include a plurality of MEMS modulator arrays disposed on the panel. Similarly, the plurality of apertures on the second substrate may include corresponding aperture arrays. When manufacturing multiple display assemblies from a single panel, the assembly process includes singulating the display panel. Substrate singulation can occur before or after the substrate is aligned and / or sealed.

  In order to align the substrates, alignment marks can be formed on each of the first and second substrates. The substrate can be loaded into an alignment apparatus that includes a vision system that monitors misalignment between alignment marks. The alignment device also includes a motor or drive for adjusting the relative position of the two substrates. The alignment apparatus can also include a UV lamp for curing the adhesive.

  In one embodiment, the alignment method includes attaching a spacer to one of the two substrates to set a constant distance between the substrates. The spacer can be formed of a conductive material that fills the gap between the two substrates.

  Furthermore, static friction can be reduced by wetting the surface of the display component (including the front and back surfaces of the movable element) with a fluid such as a lubricant. Various fluids and gases can not only reduce static friction but also improve the optical and electromechanical performance of the display when surrounding the movable components of the MEMS light modulator.

  Thus, according to another aspect, the present invention relates to a display assembly that includes a light modulator array having elements substantially surrounded (and preferably moved therein) by a liquid, such as a lubricant. The light modulator array is formed on the first substrate. The first substrate and the second transparent substrate are sealed with an adhesive to contain the liquid surrounding the MEMS light modulator. The seal also acts to limit the relative motion between the two substrates. In one embodiment, the sealing material is formed of a polymer material.

  The liquid sealed in the display assembly has a first refractive index, and the substrate on which the aperture layer is disposed has a second refractive index. In one embodiment, the first refractive index is greater than or substantially equal to the second refractive index. The liquid is also preferably non-conductive and has a dielectric constant greater than 2.0.

  In another aspect, the invention relates to a method for manufacturing a MEMS-based display. The method includes a fluid filling step where the fluid wets the surface of the display component (including the front and back surfaces of the movable element) and acts to reduce static friction and improve the optical and electromechanical performance of the display. including. The method includes providing first and second transparent substrates. The first substrate has a plurality of MEMS light modulators formed thereon. The second substrate is transparent. In one embodiment, a reflective aperture layer is formed on the second substrate. In another embodiment, a black matrix is formed on the second substrate. The second transparent substrate is disposed adjacent to the first substrate such that the first substrate is separated from the second substrate by a certain gap. The display assembly is filled with a liquid such as a lubricant. The method also includes a display assembly sealing step in which the liquid is contained within the display assembly such that the liquid substantially surrounds the movable portion of the MEMS light modulator.

  The display sealing step includes a step of applying a sealing material along at least a part of the periphery of the display assembly. In one embodiment, the step of applying the sealing material precedes the step of filling the display. In one embodiment, the seal is cured prior to filling the assembly. In another embodiment, the sealant is cured after the display assembly is filled. The substrate may be aligned before the sealant is cured. In one embodiment, applying the sealant on the assembly includes leaving at least one filling hole unsealed. The fill hole is sealed after the step of filling the assembly with fluid to contain the fluid within the display assembly.

  In one embodiment, a single display assembly is made for each panel. In other embodiments, multiple display assemblies are made from each panel. In such an embodiment, the method includes creating a plurality of MEMS light modulator arrays on the panel and then separating them. The array can be separated before or after applying the sealant.

  In one embodiment, the substrate is placed in a vacuum chamber to fill the display. In another embodiment, the filling step includes applying a liquid to one of the substrates prior to aligning and bonding the first and second substrates.

  In another embodiment, the method includes creating a spacer on one or both of the substrates to maintain a gap between the substrates. A conductive material can be applied to fill the gap between the substrates.

  The present invention may relate to a display device having a pixel array, a substrate, and a control matrix formed on the substrate. The array can include light modulators, each corresponding to a pixel in the array. The substrate may be transparent. The control matrix may have at least one switch or cascode switch corresponding to each pixel in the array.

  According to one aspect of the present invention, a display device modulates light passing through an aperture layer from the optical waveguide, an optical waveguide that guides light toward the aperture layer, and a first substrate on which the aperture layer is formed. A plurality of MEMS optical modulators and a spacer that substantially surrounds the periphery of the optical waveguide, wherein the optical waveguide and the first substrate are separated from each other by a predetermined distance so that a gap is formed between the first substrate and the optical waveguide. For forming the spacer. The aperture layer may include a reflective aperture layer.

  In one embodiment, the spacer is between different components of the display device (first substrate, lamp for supplying light to the light guide, electrical connection for controlling one of the plurality of MEMS light modulators, A structural feature having a geometry selected to maintain alignment of at least one of the reflective layers for reflecting light toward the optical waveguide and the optical waveguide. In another embodiment, the spacer includes a structural feature having a geometry selected to limit translational movement of at least one of the optical waveguide and the first substrate. The structural feature includes a shelf on which one of the optical waveguide and the first substrate is placed. The adhesive can be disposed on a structural feature that adheres to at least one of the optical waveguide and the first substrate.

  The spacer may include a reflective surface for reflecting light into the optical waveguide. The spacer may comprise a rigid material such as polycarbonate, polyethylene, polypropylene, polyacrylate, metal, or a composite of metal and plastic. The plurality of MEMS light modulators may include a shutter-based light modulator or an electrowetting light modulator, and may be formed on the first substrate or the second substrate.

  According to another aspect of the present invention, a display device includes a first substrate on which a control matrix is formed, an optical waveguide that guides light toward the control matrix, and a plurality of light sources for modulating light from the optical waveguide. A spacer that substantially surrounds the periphery of the MEMS optical modulator and the optical waveguide, and forms a gap between the first substrate and the optical waveguide by separating the optical waveguide and the first substrate from each other by a predetermined distance. And a spacer.

  According to one aspect of the present invention, a display device includes a first substrate, a reflective aperture layer, and a plurality of MEMS light modulators. The first substrate has a front surface and a back surface. The reflective aperture layer includes a plurality of apertures disposed on the front-facing surface of the first substrate. The plurality of MEMS light modulators modulate light directed to the plurality of apertures to form an image.

  The first substrate can include an optical waveguide. Alternatively, the optical waveguide may be disposed behind the first substrate, where the reflective aperture layer can reflect light that does not pass through the plurality of apertures back to the optical waveguide. In this case, the optical waveguide may be in close contact with the first substrate.

  The plurality of MEMS light modulators can include shutter-based light modulators and / or electrowetting light modulators. The active matrix control matrix can control a plurality of MEMS light modulators, and the active matrix can include at least one switch corresponding to each MEMS light modulator. The first substrate may be transparent. The reflective aperture layer can be formed of one of a mirror, a dielectric mirror, and a metal film.

  The MEMS light modulator can be disposed on the first substrate. The first substrate may be disposed such that the reflective aperture layer is proximate to the plurality of light modulators. The plurality of apertures can correspond to respective light modulators of the plurality of light modulators.

  In one embodiment, the first substrate is positioned relative to the optical waveguide so as to form a gap between the first substrate and the optical waveguide. A fluid (which may be air) can fill the gap. The fluid may have a first refractive index and the optical waveguide may have a second refractive index. The first refractive index is less than the second refractive index.

  In another embodiment, the second substrate is placed in front of the front-facing surface of the first substrate. The plurality of MEMS light modulators can be formed on the second substrate or on the surface facing the back surface of the second substrate. A control matrix may be formed on the second substrate to control the plurality of MEMS light modulators. The second substrate may be transparent. Mechanically interlocking features and / or adhesives can maintain lateral alignment between the first and second substrates, and the relative lateral movement of the first and second substrates Can be limited to less than 5 microns in any direction. The first substrate can be disposed between the second substrate and the optical waveguide.

  The first substrate can be positioned relative to the second substrate so as to form a gap between the first substrate and the second substrate. The gap may be maintained by a spacer and / or filled with a liquid or fluid such as a lubricant. The fluid can have a first refractive index and the substrate can have a second refractive index. The first refractive index is greater than or substantially equal to the second refractive index.

  According to another aspect of the invention, the display device includes a first substrate, a second substrate, a MEMS light modulator array, and a spacer. The MEMS light modulator array is formed on one of the first and second substrates. A spacer is disposed in the array and is integrally formed or connected to the first substrate at the first end and integrally formed with the second substrate at the second end. Connected. Connecting the spacer to one of the first and second substrates may include connecting to a stack of at least one thin film deposited on the substrate. The thin film may include one of a reflective aperture layer, a light absorbing layer, and a color filter.

  The spacer may be etched from the first substrate and / or may be etched from a film deposited on the first substrate. The spacer can form an electrical connection between the electrical component on the first substrate and the electrical component on the second substrate. The spacer can be formed of a polymer, a metal, and / or an insulating material. The spacer can be fitted with an alignment element formed on the second substrate. The spacer may be between about 1 micron and about 10 microns high.

  Both the first substrate and the second substrate may be substantially rigid. Alternatively, both the first and second substrates can be substantially flexible. Alternatively, one of the first substrate and the second substrate is substantially rigid, and the other of the first substrate and the second substrate is substantially flexible. At least one of the first substrate and the second substrate is substantially transparent.

  The first substrate or the second substrate can include a front surface of the display device. The optical waveguide may be separate from the first and second substrates. The spacer and the plurality of additional spacers may be arranged in the array with a spacer density of “one spacer per four light modulators” or less. The MEMS light modulator may correspond to each display pixel, and each display pixel may include at least one spacer. The space between the first and second substrates can form a gap. This gap may be filled with a fluid such as a lubricant.

  The MEMS light modulator can be configured to selectively block the passage of light and can include a shutter-based light modulator and / or an electrowetting-based light modulator. The MEMS light modulator can selectively extract light from the optical waveguide. The spacer can limit the moving range of the component in one of the MEMS light modulators.

  According to another aspect, the present invention relates to a display device comprising two transparent substrates that are aligned to some extent by space elements formed of a thermally reflowable material such as glass, plastic or metallic material. The space element preferably also functions as an adhesive for joining two transparent substrates.

  The heat reflowable material preferably obtains a substantially liquid state at a temperature range of about 150 degrees Celsius to about 400 degrees Celsius. The heat reflowable material preferably remains in a liquid state at a temperature of at least about 400 degrees Celsius. Further, in the liquid state, the heat reflowable material wets features on or on both substrates.

  In one embodiment, one of the two transparent substrates has a plurality of light modulators, preferably MEMS light modulators formed thereon. The space elements of one embodiment are formed in the light modulator array. In another embodiment, the space elements are formed at the periphery of the array. The reflective aperture layer is formed on the same substrate or on the other of the two transparent substrates.

  In one aspect, the invention provides a plurality of apertures formed in a material layer and a shutter-based MEMS light modulator array disposed between the material layer and a desired viewer of the display device, the material layer comprising: And an array separated by a certain gap from the display device. Each aperture has at least one edge, and each light modulator includes a shutter having a light blocking portion for selectively blocking the passage of light through the corresponding one or more apertures. The shutter is shaped such that in the closed position, the light blocking portion of the shutter overlaps at least one edge of its corresponding aperture or apertures. This overlap is proportional to the gap size and is greater than or equal to the gap size.

  The overlap may be greater than about 1 micron, between about 1 micron and about 10 microns, and / or greater than about 10 microns. The shutter may include one or more shutter apertures that allow light to pass, each shutter aperture corresponding to one of the one or more apertures corresponding to the shutter. The display can include a spacer disposed between the material layer and the array to keep the shutter in the light modulator separated from the material layer by about a predetermined distance. The side of the shutter facing the material layer may be covered with a reflective material and / or a light absorbing material. The side facing away from the material layer of the shutter may be covered with a light absorbing material.

  In one embodiment, the material layer is substantially reflective and can include metal and / or dielectric mirrors. The display can include a backlight having an optical waveguide, and the material layer reflects light exiting the backlight back toward the optical waveguide. The light absorbing material can be deposited on the side facing the array of material layers. The second reflective layer may be disposed on the back side of the backlight. The array may be formed on the material layer, and the material layer may be deposited on the optical waveguide.

  In another embodiment, the display device can be a lubricant and includes a liquid disposed at least between the light modulator and the material layer. The liquid may have a refractive index greater than the refractive index of the optical waveguide and / or the refractive index of the substrate on which the material layer is formed.

  In another embodiment, the array is formed on a first substrate and the material layer is deposited on a second substrate in addition to the first substrate. The second substrate may be disposed between the first substrate and the optical waveguide. In particular, the array can be formed on the side of the first substrate facing away from the viewer. The display device may include a liquid having a refractive index greater than that of the second substrate and disposed at least between the second substrate and the light modulator.

  In another aspect, a display device includes an electrowetting-based light modulator array that transparently displays an image, and a reflective aperture layer disposed adjacent to the array, the aperture in the reflective aperture layer. A reflective aperture layer for reflecting light that does not pass through and away from the array. The image is formed by light that passes through apertures in the reflective aperture layer and is modulated by the array. The reflective aperture layer can include metal and / or dielectric mirrors.

  The backlight can be located on the opposite side of the array of reflective aperture layers. The second reflective layer can be disposed on the opposite side of the reflective aperture layer array to reflect light toward the reflective aperture layer. A layer of low refractive index material may be coupled to the optical waveguide between the backlight and the reflective aperture layer.

  In one embodiment, the electrowetting-based light modulator array includes a first electrowetting control color modulation layer and an electrowetting control black layer. The first electrowetting control color modulation layer can include a plurality of electrowetting control color modulation cells each having at least one edge. The electrowetting control black layer can include a plurality of electrowetting control light absorption cells each having at least one edge corresponding to one or more of the color modulation cells. At least one edge of each light absorbing cell may overlap with at least one edge of the corresponding one or more color modulation cells. The first electrowetting control color modulation layer can include a group of electrowetting control color modulation cells, each cell in a given group modulating a different color of light. The display device can also include second and third electrowetting control color modulation layers, each of the first, second, and third electrowetting control color modulation layers modulating light of a different color. .

  In another embodiment, the display device includes a light source for emitting light into the light guide. The light source may emit white light and / or at least three different colors of light that may be emitted sequentially. The light sources can include at least three light sources, each corresponding to one of three different colors.

  In another embodiment, the electrowetting-based light modulator array includes a plurality of electrowetting-based light modulation cells. Each cell corresponds to an aperture in the reflective aperture layer. Each of the apertures has at least one edge, and each cell includes a layer of light modulating fluid, and when inactive, the light modulating fluid of the cell overlaps at least one edge of its corresponding aperture.

  In another embodiment, the electrowetting-based light modulator includes an electrode layer. The electrode layer can be disposed between the reflective aperture layer and the light modulating fluid. The reflective aperture layer is disposed on the first substrate, and the electrode layer is disposed on a second substrate different from the first substrate. The light modulating fluid can be disposed between the reflective aperture layer and the electrode layer.

  The above discussion will be more readily understood from the following detailed description of the invention with reference to the following drawings, in which:

FIG. 3 is an isometric view of a display device according to an exemplary embodiment of the present invention. 1B is a block diagram of the display device of FIG. 1A according to an exemplary embodiment of the present invention. FIG. 1B is a perspective view of an exemplary shutter-based light modulator suitable for incorporation into the MEMS-based display of FIG. 1A, according to an exemplary embodiment of the invention. FIG. 1B is a cross-sectional view of a roller shade based light modulator suitable for incorporation into the MEMS based display of FIG. 1A according to an exemplary embodiment of the present invention. 1B is a cross-sectional view of an optical tap-based light modulator suitable for incorporation into another embodiment of the MEMS-based display of FIG. 1A, according to an exemplary embodiment of the invention. FIG. 1B is a schematic diagram of a control matrix suitable for controlling a light modulator incorporated in the MEMS-based display of FIG. 1A, according to an illustrative embodiment of the invention. FIG. FIG. 4 is a perspective view of a shutter-based light modulator array connected to the control matrix of FIG. 3 according to an exemplary embodiment of the present invention. 1 is a cross-sectional view of a display device according to an exemplary embodiment of the present invention. FIG. 9 is a plan view of the shutter assembly of FIG. 8 in an open state and a closed state, respectively, according to an exemplary embodiment of the present invention. FIG. 9 is a plan view of the shutter assembly of FIG. 8 in an open state and a closed state, respectively, according to an exemplary embodiment of the present invention. FIG. 4 is a cross-sectional view of a shutter assembly having an aperture formed in an adjacent reflective surface and a shutter that overlaps in the closed position, according to an exemplary embodiment of the present invention. FIG. 4 is a cross-sectional view of a shutter assembly having an aperture formed in an adjacent reflective surface and a shutter that overlaps in the closed position, according to an exemplary embodiment of the present invention. FIG. 4 is a cross-sectional view of a shutter assembly having an aperture formed in an adjacent reflective surface and a shutter that overlaps in the closed position, according to an exemplary embodiment of the present invention. FIG. 4 is a cross-sectional view of a shutter assembly having an aperture formed in an adjacent reflective surface and a shutter that overlaps in the closed position, according to an exemplary embodiment of the present invention. 1 is a cross-sectional view of a first electrowetting-based light modulation array according to an exemplary embodiment of the present invention. FIG. 2 is a cross-sectional view of a second electrowetting-based light modulation array according to an exemplary embodiment of the present invention. FIG. FIG. 6 is a cross-sectional view of a third electrowetting-based light modulation array according to an exemplary embodiment of the present invention. FIG. 3 is a cross-sectional view of an aperture plate according to an exemplary embodiment of the present invention. FIG. 6 is a sectional view of an aperture plate according to an exemplary embodiment of the present invention. FIG. 6 is a cross-sectional view of a display assembly according to an exemplary embodiment of the present invention. FIG. 6 is a cross-sectional view of a display assembly according to an exemplary embodiment of the present invention. FIG. 6 is a cross-sectional view of a display assembly according to an exemplary embodiment of the present invention. 2 is a perspective view of a shutter assembly in an open state and a closed state, respectively, according to an exemplary embodiment of the present invention. FIG. 2 is a perspective view of a shutter assembly in an open state and a closed state, respectively, according to an exemplary embodiment of the present invention. FIG. FIG. 6 is a cross-sectional view of a display assembly according to an exemplary embodiment of the present invention. FIG. 6 is a cross-sectional view of a display assembly according to an exemplary embodiment of the present invention. 1 is a conceptual diagram of a high precision substrate alignment apparatus according to an exemplary embodiment of the present invention. 2 is a plan view of a modulator substrate and aperture plate each including a plurality of modulators and an aperture array, according to an exemplary embodiment of the present invention. FIG. FIG. 6 is a plan view of a panel assembly after alignment according to an exemplary embodiment of the present invention. 3 is a flowchart of a cell assembly method according to an exemplary embodiment of the present invention. 1 is a conceptual diagram of a fluid filling device according to an exemplary embodiment of the present invention. 3 is a flowchart of a cell assembly method according to an exemplary embodiment of the present invention. 1 is a cross-sectional view of a liquid crystal display device according to an exemplary embodiment of the present invention. FIG. 3 is a cross-sectional view of a display module according to an exemplary embodiment of the present invention. 2 is an isometric exploded view of a display module according to an exemplary embodiment of the present invention. FIG. FIG. 3 is a cross-sectional view of a display module according to an exemplary embodiment of the present invention. FIG. 3 is a cross-sectional view of a display module according to an exemplary embodiment of the present invention.

  To assist in a comprehensive understanding of the present invention, certain exemplary embodiments are described below, including devices and methods for displaying images. However, the systems and methods described herein can be adapted and modified to be appropriate for the application being addressed, the systems and methods described herein can be utilized in other suitable applications, and It will be appreciated by those skilled in the art that such other additions and modifications do not depart from the scope of this specification.

  FIG. 1A is a schematic diagram of a direct-view MEMS-based display device 100 according to an exemplary embodiment of the present invention. Display device 100 includes a plurality of light modulators 102a-102d (generally referred to as "light modulators 102") arranged in rows and columns. In the display device 100, the light modulators 102a and 102d are in an open state that allows light to pass therethrough. The light modulators 102b and 102c are in a closed state that obstructs the passage of light. By selectively setting the states of the light modulators 102a-102d, the display device 100 can be used to form a backlight display image 104 when illuminated by one or more lamps 105. it can. In another embodiment, the device 100 may be imaged by reflection of ambient light coming from the front of the device. In another embodiment, the device 100 can form an image by reflection of light from one or more lamps placed in front of the display (ie, by utilizing front light). In the closed or open state, the light modulator 102 is in the optical path, for example and without limitation, by blocking, reflecting, absorbing, filtering, polarizing, diffracting light, or by changing the characteristics or path of light. Interferes with the light.

  In the display device 100, each light modulator 102 corresponds to a pixel 106 in the image 104. In other embodiments, the display device 100 can utilize multiple light modulators to form the pixels 106 in the image 104. For example, the display device 100 may include three specific color light modulators 102. By selectively opening one or more specific color light modulators 102 corresponding to specific pixels 106, display device 100 can generate color pixels 106 in image 104. In another embodiment, display device 100 includes two or more light modulators 102 for each pixel 106 to provide a gray scale in image 104. With respect to images, the term “pixel” corresponds to the smallest picture element defined by the image resolution. With respect to the structural components of display device 100, the term “pixel” refers to a combination of mechanical and electrical components that are utilized to modulate the light that forms a single pixel of an image.

  The display device 100 is a direct view type display in that an imaging optical system is not required. The user views the image by directly viewing the display device 100. In another embodiment, the display device 100 is incorporated into a projection display. In such embodiments, the display forms an image by projecting light onto a screen or wall. In a projection application, the display device 100 is substantially smaller than the projected image 104.

  Direct view displays can operate in either transmissive or reflective modes. In a transmissive display, the light modulator filters or selectively blocks light coming from one or more lamps located behind the display. The light from the lamp is optionally injected into the optical waveguide, or “backlit”. Transparent direct view display embodiments are often built on transparent or glass substrates to facilitate sandwich assembly arrangements in which a single substrate containing a light modulator is placed directly on the backlight. In some transmissive display embodiments, a specific color light modulator is made by associating a color filter material with each modulator 102. In other transmissive display embodiments, colors may be generated by utilizing a field sequential color method by alternately illuminating lamps having different primary colors, as described below. it can.

  Each light modulator 102 includes a shutter 108 and an aperture 109. In order to illuminate the pixels 106 in the image 104, the shutter 108 is arranged to allow light to pass through the aperture 109 towards the viewer. In order to keep the pixel 106 unlit, the shutter 108 is positioned to block the passage of light through the aperture 109. Aperture 109 is defined by an aperture patterned with a reflective or light absorbing material.

The display device also includes a control matrix for controlling the movement of the shutter connected to the substrate and the light modulator. The control matrix includes a series of electrical wires (eg, wires 110, 112, 114) that include at least one write enable wire 110 (also referred to as a “scan line wire”) for each row of pixels, and one data for each column of pixels. The wiring 112 includes a common wiring 114 that supplies a common voltage to all pixels or at least to pixels from both the plurality of columns and the plurality of rows in the display device 100. In response to application of an appropriate voltage ("write enable voltage, _Vwe "), the write enable wiring 110 of a given row of pixels prepares the pixel in that row for receiving a new shutter movement command. The data line 112 transmits a new movement command in the form of data voltage pulses. The data voltage pulse applied to the data line 112 directly contributes to the electrostatic movement of the shutter in some embodiments. In other embodiments, the data voltage pulse controls a switch, such as a transistor or other non-linear circuit element, that controls the application of another operating voltage (usually greater than the data voltage) to the light modulator 102. Application of these actuation voltages then results in electrostatic drive movement of the shutter 108.

  FIG. 1B is a block diagram 150 of the display device 100. Referring to FIGS. 1A and 1B, in addition to the elements of display device 100 described above, as shown in block diagram 150, display device 100 includes a plurality of scan drivers 152 (also referred to as “write permission power supplies”) and a plurality of data. A driver 154 (also referred to as “data power supply”) is included. The scan driver 152 applies a write permission voltage to the scan line wiring 110. The data driver 154 applies a data voltage to the data line 112. In some embodiments of the display device, the data driver 154 is configured to provide an analog data voltage to the light modulator, particularly when the gray scale of the image 104 is generated in an analog manner. In analog operation, when a range of intermediate voltages is applied via the data line 112, a range of intermediate open states at the shutter 108, and thus a range of intermediate illumination states (ie, gray scale) within the image 104. In addition, the optical modulator 102 is designed.

  In other cases, the data driver 154 is configured to apply only a reduced set of two, three, or four digital voltage levels to the control matrix. These voltage levels are designed to set each shutter 108 in either an open state or a closed state in a digital manner.

  The scan driver 152 and the data driver 154 are connected to a digital control circuit 156 (also referred to as “controller 156”). The controller 156 includes an input processing module 158. The input processing module 158 processes the input image signal 157 and converts it to a digital image format suitable for the spatial addressing and gray scale function of the display device 100. The pixel location and grayscale data of each image is stored in the frame buffer 159 so that the data is supplied to the data driver 154 as needed. Data is sent to the data driver 154 in a primarily serial manner organized in a predetermined sequence grouped by rows and image frames. Data driver 154 includes a serial to parallel data converter, a level shifter, and for some applications a digital analog voltage converter.

  Display 100 optionally includes a set of common drivers 153 (also referred to as a common power source). In some embodiments, the common driver 153 supplies a DC common potential to all the light modulators in the light modulator array 103, for example, by supplying a voltage to a series of common wires 114. In other embodiments, the common driver 153 drives and / or initiates the simultaneous activation of all light modulators in multiple rows and columns of the array 103 in accordance with instructions from the controller 156. A global actuation pulse) that can be transmitted to the light modulator array 103.

  Drivers for different display functions (for example, the scan driver 152, the data driver 154, and the common driver 153) are all time synchronized by the timing control module 160 in the controller 156. Timing instructions from module 160 include illumination of red, green, blue, and white lamps (162, 164, 166, and 167, respectively) via lamp driver 168, and write permission and order for specific rows in pixel array 103. And adjusting the voltage output from the data driver 154 and the voltage output resulting in the operation of the light modulator.

  The controller 156 establishes a sequencing or addressing scheme in which each shutter 108 in the array 103 can be reset to an appropriate illumination level for the new image 104. Details of suitable addressing, imaging, and gray scale techniques can be found in US patent application Ser. No. 11 / 326,696 and US patent application Ser. No. 11 / 643,404, which are incorporated herein by reference. This is incorporated herein. New images 104 can be set at periodic intervals. For example, in a video display, the video color image 104 or frame is refreshed at a frequency in the range of 10 to 300 hertz. In some embodiments, setting the image frame to the array 103 includes lighting the lamps 162, 164, 166 such that the alternating image frame is illuminated with an alternating series of colors such as red, green, blue, etc. Be synchronized. Each color image frame is referred to as a color sub-frame. In this method (called a field sequential color method), when the color sub-frames are alternated at a frequency exceeding 20 Hz, the human brain averages the alternating frame images as an image having a wide continuous range of colors. recognize. In another embodiment, four or more lamps including three primary colors of red, green, and blue can be used in the display device 100 by using primary colors other than red, green, and blue.

  In some embodiments where the display device 100 is designed to be digitally switched between the open and closed states of the shutter 108, the controller 156 may generate the image 104 with the appropriate gray scale. Determine the addressing sequence and / or the time interval between image frames. The process of generating various levels of gray scale by controlling the amount of time that the shutter 108 is opened in a particular frame is called time division gray scale. In one embodiment of time division grayscale, the controller 156 determines a time interval or a portion of that time within each frame that the shutter 108 can remain open according to the desired illumination level or grayscale of the pixel. To do. In other embodiments, for each image frame, controller 156 sets a plurality of subframe images in a plurality of rows and columns of array 103, and the controller includes each subframe image within a coded word with respect to grayscale. The duration of illumination is changed in proportion to the gray scale value or weight value used in the. For example, the illumination time of a series of sub-frame images is represented by binary coded sequences 1, 2, 4, 8,. . . Can be changed in proportion to The shutter 108 for each pixel in the array 103 is set to either the open state or the closed state in the sub-frame image according to the value of the corresponding position in the pixel's binary encoded word relative to the gray scale level.

  In other embodiments, the controller changes the intensity of light from lamps 162, 164, 166 in proportion to the gray scale value desired for a particular subframe image. Many composite techniques are also available for forming color and gray scale from the shutter array 108. For example, the time division technique described above can be combined with using multiple shutters 108 per pixel, or the grayscale value for a particular subframe image can be set by combining both subframe timing and lamp intensity. can do. Details of these and other embodiments can be found in the above referenced US patent application Ser. No. 11 / 643,404.

  In some embodiments, image state 104 data is loaded into the modulator array 103 by the controller 156 by sequentially addressing individual rows (also referred to as scan lines). For each row or scan line in the addressing sequence, the scan driver 152 applies a write enable voltage to the write enable wiring 110 of that row of the array 103, after which the data driver 154 performs a desired operation for each column in the selected row. A data voltage corresponding to the shutter state is supplied. This process is repeated until the data has been loaded into every row in the array. In some embodiments, the sequence of rows selected for data loading is linear and proceeds from top to bottom in the array. In other embodiments, the sequence of selected rows is pseudo-randomized to minimize visible artifacts. And in other embodiments, the sequence is organized in blocks. Here, for a block, only a specific part of the image state 104 is loaded into the array, for example by addressing only every fifth row of the array in sequence.

  In some embodiments, the process of loading image data into the array 103 is separated in time from the process of operating the shutter 108. In these embodiments, the modulator array 103 may include a data storage element for each pixel in the array 103, and the control matrix may initiate a common driver 153 that initiates simultaneous operation of the shutter 108 in accordance with the data stored in the storage element. Global actuation wiring can be included to carry trigger signals from Various addressing sequences, many of which are described in US patent application Ser. No. 11 / 643,042, can be coordinated by the timing control module 160.

  In another embodiment, the pixel array 103 and the control matrix that controls the pixels can be arranged in configurations other than rectangular rows and columns. For example, the pixels can be arranged in a hexagonal array or curvilinear rows and columns. In general, as used herein, the term “scan line” is intended to refer to any plurality of pixels that share a write enable line.

  The display apparatus 100 includes a plurality of functional blocks including a timing control module 160, a frame buffer 159, a scan driver 152, a data driver 154, and drivers 153 and 168. Each block may be understood to represent either an identifiable hardware circuit and / or an executable code module. In some embodiments, the functional blocks are provided as individual chips or as circuits connected together by circuit boards and / or cables. Alternatively, many of these circuits can be fabricated with the pixel array 103 on the same glass or plastic substrate. In other embodiments, multiple circuits, drivers, processors, and / or control functions of block diagram 150 can be integrated together in a single silicon chip. The silicon chip is directly bonded to the transparent substrate holding the pixel array 103.

  The controller 156 includes a program link 180 that allows the addressing, color, and / or grayscale algorithms implemented within the controller 156 to be modified according to the needs of a particular application. In some embodiments, program link 180 obtains information from environmental sensors, such as ambient light sensors or temperature sensors, so that controller 156 can adjust the imaging mode or backlight power in response to environmental conditions. introduce. The controller 156 also includes a power input 182 that supplies the necessary power to the lamp as well as the operation of the light modulator. If necessary, the drivers 152, 153, 154, and / or 168 may convert the input voltage 182 into various voltages sufficient to operate the shutter 108 or to illuminate a lamp such as the lamps 162, 164, 166, 167. A DC converter may be included, or a DC-DC converter may be attached.

  2A is a perspective view of an exemplary shutter-based light modulator 200 suitable for incorporation into the MEMS-based display device 100 of FIG. 1A, according to an exemplary embodiment of the invention. Shutter-based light modulator 200 (also referred to as shutter assembly 200) includes a shutter 202 coupled to an actuator 204. As described in US patent application Ser. No. 11 / 251,035 filed Oct. 14, 2005, the actuator 204 is comprised of two separate elastic electrode beam actuators 205 (hereinafter “actuators 205”). It is formed. The shutter 202 is connected to the actuator 205 on one side. Actuator 205 moves shutter 202 laterally above surface 203 in a plane of motion substantially parallel to surface 203. The opposite side of the shutter 202 is connected to a spring 207 that provides a restoring force against the force applied by the actuator 204.

  Each actuator 205 includes an elastic load beam 206 that connects the shutter 202 to a load anchor 208. A load anchor 208 along with the elastic load beam 206 functions as a mechanical support and keeps the shutter 202 suspended in the vicinity of the surface 203. The load anchor 208 physically connects the elastic load beam 206 and the shutter 202 to the surface 203 and electrically connects the load beam 206 to a bias voltage (sometimes to ground).

  Each actuator 205 also includes a resilient drive beam 216 disposed adjacent to each load beam 206. The drive beam 216 is connected at one end to a drive beam anchor 218 shared between the drive beams 216. The other end of each drive beam 216 can move freely. Each drive beam 216 is curved to be closest to the load beam 206 near the free end of the drive beam 216 and the anchor end of the load beam 206.

  Surface 203 includes one or more apertures 211 that allow light to pass therethrough. When the shutter assembly 200 is formed on an opaque substrate made of, for example, silicon, the surface 203 is the surface of the substrate, and the aperture 211 is formed by etching a hole array through the substrate. When the shutter assembly 200 is formed on a transparent substrate made of glass or plastic, for example, the surface 203 is the surface of a light blocking layer deposited on the substrate, and the aperture 211 etches the surface 203 into the hole array. It is formed by. The shape of the aperture 211 may generally be circular, elliptical, polygonal, serpentine, or irregular.

  During operation, the display device incorporating the light modulator 200 applies a potential to the drive beam 216 via the drive beam anchor 218. A second potential can be applied to the load beam 206. The potential difference created between drive beam 216 and load beam 206 pulls the free end of drive beam 216 toward the anchor end of load beam 206 and pulls the shutter end of load beam 206 toward the anchor end of drive beam 216. Thus, the shutter 202 is driven laterally toward the drive anchor 218. The elastic member 206 acts as a spring, and when the voltage between the beams 206 and 216 is removed, the load beam 206 pushes the shutter 202 back to its initial position by releasing the stress stored in the load beam 206.

  Shutter assembly 200 (also referred to as an elastic shutter assembly) incorporates a passive restoring force such as a spring to return the shutter to its resting or relaxed position after the voltage is removed. Many elastic restoring mechanisms and various electrostatic couplers can be designed to be electrostatic actuators (the elastic beam illustrated in shutter assembly 200 is just one example) or in combination with electrostatic actuators. it can. Other examples are described in US patent application Ser. No. 11 / 251,035 and US patent application Ser. No. 11 / 326,696, which are hereby incorporated by reference. For example, a highly non-linear voltage displacement response can be provided that supports abrupt transitions between the “open” and “closed” states of operation and often provides the shutter assembly with bistable or hysteresis operating characteristics. Other electrostatic actuators with more incremental voltage-displacement response and significantly reduced hysteresis can be designed that would be preferable for analog grayscale operation.

  The actuator 205 in the elastic shutter assembly is considered to operate in the closed or actuated position and the relaxed position. However, the designer ensures that whenever the actuator 205 is in its relaxed position, the shutter assembly 200 is either in the “open” state (ie, allows light to pass) or “closed” (ie, blocks light). Installation of the aperture 211 can be selected. For illustrative purposes, the following assumes that the elastic shutter assembly described herein is designed to be open in its relaxed state.

  In many cases, a duplex set of “open” actuators and “closed” actuators are provided as part of the shutter assembly so that the control electronics can electrostatically drive the shutters in the open and closed states, respectively. It is preferable.

  In another embodiment, display device 100 includes a light modulator other than a transverse shutter-based light modulator, such as shutter assembly 200 described above. For example, FIG. 2B is a cross-sectional view of a rolling actuator shutter-based light modulator 220 suitable for incorporation into another embodiment of the MEMS-based display device 100 of FIG. 1A, according to an illustrative embodiment of the invention. Further in US Pat. No. 5,233,459, entitled “Electric Display Device” and US Pat. No. 5,784,189, entitled “Spatial Light Modulator”, which is incorporated herein by reference in its entirety. As described, a rolling actuator shutter-based light modulator is a movable electrode located on the opposite side of a fixed electrode that is biased to move in a preferred direction when an electric field is applied to produce a shutter. Movable electrode. In one embodiment, the light modulator 220 includes a planar electrode 226 disposed between the substrate 228 and the insulating layer 224 and a movable electrode 222 having a fixed end 230 attached to the insulating layer 224. In the absence of any applied voltage, the movable end 232 of the movable electrode 222 is free to rotate toward the fixed end 230 to form a rolled state. When a voltage is applied between the electrodes 222 and 226, the movable electrode 222 is unfolded and placed flat against the insulating layer 224, whereby the movable electrode 222 acts as a shutter that blocks light propagating through the substrate 228. After the voltage is removed, the movable electrode 222 returns to the state wound by the elastic restoring force. The urging to the rolled state can be realized by manufacturing the movable electrode 222 so as to include an anisotropic stress state.

  FIG. 2C is a cross-sectional view of an exemplary non-shutter-based MEMS light modulator 250. The optical tap modulator 250 is suitable for incorporation into another embodiment of the MEMS-based display device 100 of FIG. 1A, according to an illustrative embodiment of the invention. As further described in US Pat. No. 5,771,321, entitled “Micromechanical Optical Switch and Flat Panel Display”, which is incorporated herein by reference in its entirety, optical taps are leaked total internal reflection. It works according to the principle of total internal reflection. That is, the light 252 is guided into the optical waveguide 254. Without interfering within the optical waveguide 254, most of the light 252 cannot escape the optical waveguide 254 through its front or back because of total internal reflection. In the optical tap 250, in response to the tap element 256 coming into contact with the optical waveguide 254, the light 252 hitting the surface of the optical waveguide 254 adjacent to the tap element 256 escapes from the optical waveguide 254 to the viewer through the tap element 256. Includes a tap element 256 having a sufficiently high refractive index to contribute to image formation.

  In one embodiment, tap element 256 is formed as part of beam 258 of flexible transparent material. Electrode 260 covers a portion of one side of beam 258. The counter electrode 260 is disposed on the optical waveguide 254. By applying a voltage to both ends of the electrode 260, the position of the tap element 256 relative to the optical waveguide 254 can be controlled so as to selectively extract the light 252 from the optical waveguide 254.

  Roller-based light modulator 220 and light tap modulator 250 are not the only examples of MEMS light modulators suitable for inclusion in various embodiments of the present invention. It will be understood that other MEMS light modulators exist and can be incorporated into the present invention.

  US patent application Ser. No. 11 / 251,035 and US patent application Ser. No. 11 / 326,696 are subject to a control matrix to generate an image (often a video) with the appropriate gray scale. Various ways in which the shutter array can be controlled are described. In some cases, control is achieved by a passive matrix array of row and column wiring connected to the drive circuitry at the periphery of the display. In other cases, including switching elements and / or data storage elements within each pixel of the array (so-called active matrix) to improve either display speed, grayscale, and / or power consumption performance Is appropriate.

  FIG. 3 is a schematic diagram of a control matrix 300 suitable for controlling a light modulator incorporated in the MEMS-based display device 100 of FIG. 1A, according to an illustrative embodiment of the invention. FIG. 4 is a perspective view of a shutter-based light modulator array 320 connected to the control matrix 300 of FIG. 3, according to an illustrative embodiment of the invention. The control matrix 300 can address a pixel array 320 (hereinafter simply referred to as “array 320”). Each pixel 301 includes a resilient shutter assembly 302 such as the shutter assembly 200 of FIG. Each pixel also includes an aperture layer 322 that includes an aperture 324. Additional electrical and mechanical descriptions of shutter assemblies such as shutter assembly 302 and variations thereof can be found in US patent application Ser. No. 11 / 251,035 and US patent application Ser. No. 11 / 326,696. Can do. A description of another control matrix can also be found in US patent application Ser. No. 11 / 607,715.

The control matrix 300 is fabricated as an electrical circuit that is diffused or thin film deposited on the surface of the substrate 304 on which the shutter assembly 302 is formed. The control matrix 300 includes a scan line wiring 306 for each row of pixels 301 in the control matrix 300 and a data wiring 308 for each column of pixels 301 in the control matrix 300. Each scan line wiring 306 electrically connects the write enable power supply 307 to the pixels 301 in the corresponding row of pixels 301. Each data line 308 electrically connects a data power supply (“ _Vd power supply”) 309 to the pixels 301 in the corresponding column of pixels 301. In the control matrix 300, the data voltage V _d provides most of the energy required to operate the shutter assembly 302. Therefore, the data voltage 309 also functions as an operating power source.

  With reference to FIGS. 3 and 4, for each pixel 301 or shutter assembly 302 in the pixel array 320, the control matrix 300 includes a transistor 310 and a capacitor 312. The gate of each transistor 310 is electrically connected to the scan line wiring 306 of the row in the array 320 in which the pixel 301 is disposed. The source of each transistor 310 is electrically connected to its corresponding data line 308. The actuator 303 of each shutter assembly 302 includes two electrodes. The drain of each transistor 310 is electrically connected in parallel to one electrode of the corresponding capacitor 312 and one of the electrodes of the corresponding actuator 303. The other electrode of the capacitor 312 in the shutter assembly 302 and the other electrode of the actuator 303 are connected to a common potential or a ground potential. In another embodiment, transistor 310 may be replaced with a semiconductor diode and / or a metal-insulator-metal sandwich switching element.

In operation, in order to form an image, the control matrix 300 allows each row in the array 320 to be written sequentially by applying V _we to each scan line wire 306 in turn. In a writable row, applying V _we to the gate of transistor 310 of pixel 301 in the row allows a current flow through data wire 308 and through transistor 310 to apply a potential to actuator 303 of shutter assembly 302. become. While the row is being writable, data voltages V _d are selectively applied to the data line 308. In embodiments providing an analog gray scale, the data voltage applied to each data line 308 is related to the desired brightness of the pixel 301 located at the intersection of the scan line line 306 and the data line 308 enabled for writing. be changed. In embodiments that implement a digital control scheme, the data voltage is selected to be a relatively small voltage (ie, a voltage near ground potential) or greater than V _at (actuation threshold voltage). In response to the application of _{V at} to a data interconnect 308, the corresponding actuator 303 in shutter assembly 302 to open the shutter in the shutter assembly 302 to operate them. The voltage applied to the data line 308 remains stored in the capacitor 312 of the pixel 301 even after the control matrix 300 stops applying _Vwe to the row. Thus, it is not necessary to wait long enough for the shutter assembly 302 to operate and maintain the voltage _Vwe on the row. That is, such an operation can be continued even after the write enable voltage is removed from the row. Capacitor 312 also functions as a storage element in array 320 and stores the operating instructions for a period of time that requires illumination of the image frame.

  Pixels 301 as well as control matrix 300 of array 320 are formed on substrate 304. The array includes an aperture layer 322 disposed on the substrate 304. Aperture layer 322 includes a set of apertures 324 for each pixel 301 in array 320. The aperture 324 is aligned with the shutter assembly 302 within each pixel. In one embodiment, the substrate 304 is made of a transparent material such as glass or plastic. In another embodiment, the substrate 304 is made of an opaque material and holes are formed in the substrate 304 to form apertures 324.

  The components of the shutter assembly 302 are processed simultaneously with the control matrix 300 or in subsequent processing steps on the same substrate. The electrical components in the control matrix 300 are made by using many thin film technologies that are common with the manufacture of thin film transistor arrays for liquid crystal displays. Available techniques are described in Den Boer, Active Matrix Liquid Crystal Displays (Elsevier, Amsterdam, 2005) and are incorporated herein by reference. The shutter assembly is fabricated by using techniques similar to micromachining techniques or micromechanical (ie MEMS) device manufacturing techniques. Many applicable thin film MEMS technologies are described in Rai-Chudhury, ed. , Handbook of Microlithography, Micromachining & Microfabrication (SPIE Optical Engineering Press, Bellingham, Wash. 1997), which is incorporated herein by reference. Manufacturing techniques specific to MEMS light modulators formed on glass substrates can be found in US patent application Ser. Nos. 11 / 361,785 and 11 / 731,628, which are incorporated by reference. This is incorporated herein. For example, as described in these applications, the shutter assembly 302 can be formed of a thin film of amorphous silicon deposited by a chemical vapor deposition process.

  The shutter assembly 302 along with the actuator 303 can be bistable. That is, the shutter can be in at least two equilibrium positions (eg, open and closed positions) that require little or no power to hold the shutter in either position. Specifically, the shutter assembly 302 may be mechanically bistable. Once the shutter of shutter assembly 302 is set to the proper position, no electrical energy or holding voltage is required to maintain that position. Mechanical stress on the physical elements of the shutter assembly 302 can hold the shutter in place.

  The shutter assembly 302 along with the actuator 303 can also be electrically bistable. In an electrically bistable shutter assembly, there is a voltage range that is lower than the operating voltage of the shutter assembly. When this voltage is applied to a closed actuator (shutter is open or closed), the shutter assembly closes the actuator and holds the shutter in place even if a reaction force is applied to the shutter. . The reaction force may be applied by a spring, such as the spring 207 in the shutter-based light modulator 200, or by an opposing actuator, such as an “open” or “closed” actuator.

  The light modulator array 320 is depicted as having a single MEMS light modulator per pixel. Other embodiments are possible that provide more than a simple binary “on” or “off” optical state of each pixel by providing multiple MEMS light modulators within each pixel. A particular type of coded area division gray scale, in which a plurality of MEMS light modulators within a pixel are provided, and the apertures 324 associated with each of the light modulators have non-uniform areas. Is possible.

  In other embodiments, roller-based light modulators 220 or light taps 250 as well as other MEMS-based light modulators can be substituted for the shutter assemblies 302 in the light modulator array 320.

  FIG. 5 is a cross-sectional view of a display device 500 incorporating a shutter-based light modulator (shutter assembly) 502, according to an illustrative embodiment of the invention. Each shutter assembly incorporates a shutter 503 and an anchor 505. The elastic beam actuator that assists in suspending the shutter at a short distance above the substrate surface when connected between the anchor 505 and the shutter 503 is not shown. The shutter assembly 502 is disposed on a transparent substrate 504, preferably made of plastic or glass. The back-facing reflective layer (reflective film 506) disposed on the substrate 504 defines a plurality of surface apertures 508 positioned below the closed position of the shutter 503 of the shutter assembly 502. The reflective film 506 reflects light that does not pass through the front surface aperture 508 and returns it to the back surface of the display device 500. The reflective aperture layer 506 may be a particulate metal film free of inclusions formed into a thin film by a number of deposition techniques including sputtering, evaporation, ion plating, laser cutting, or chemical vapor deposition. In another embodiment, the back-facing reflective layer 506 can be formed of a mirror such as a dielectric mirror. The dielectric mirror is manufactured as a stack of dielectric thin films in which a material having a high refractive index and a material having a low refractive index are repeated. The vertical gap separating the shutter 503 from the reflective film 506 (in which the shutter can move freely) is in the range of 0.5 to 10 microns. The size of the vertical gap is preferably smaller than the lateral overlap between the edge of the shutter 503 and the edge of the aperture 508 in the closed state.

  The display device 500 includes an optional diffuser 512 and / or an optional brightness enhancement film 514 that separates the substrate 504 from the planar light guide 516. The optical waveguide is made of a transparent material, ie glass or plastic material. The light guide 516 is illuminated by one or more light sources 518 forming a backlight. The light source 518 may be, for example and without limitation, an incandescent lamp, a fluorescent lamp, a laser, or a light emitting diode (LED). Reflector 519 helps direct light from lamp 518 toward light guide 516. The front-facing reflective film 520 is disposed on the back surface of the backlight 516 and reflects light toward the shutter assembly 502. Rays such as ray 521 from the backlight that do not pass through one of the shutter assemblies 502 are returned to the backlight and reflected again by the film 520. In this way, initially the light that failed to leave the display to form an image can be reused and made available to transmit through other open apertures in the array of shutter assemblies 502. Become. It has been shown that such light recycling increases the illumination efficiency of the display.

  The light guide 516 includes a set of geometric light redirectors or prisms 517 that redirect the light from the lamp 518 towards the aperture 508 and thus towards the front of the display. The optical redirector may be molded into the plastic body of the optical waveguide 516, whose cross section may be triangular, trapezoidal, or curved. The density of prism 517 generally increases with distance from lamp 518.

  In another embodiment, the aperture layer 506 can be made of a light absorbing material, and in another embodiment, the surface of the shutter 503 can be covered with a light absorbing or light reflecting material. In another embodiment, the aperture layer 506 can be deposited directly on the surface of the optical waveguide 516. In another embodiment, the aperture layer 506 need not be located on the same substrate as the shutter 503 and anchor 505 (see MEMS down configuration below). These and other embodiments for display lighting systems are described in detail in US patent application Ser. No. 11 / 218,690 and US patent application Ser. No. 11 / 528,191, which are incorporated herein by reference. This is incorporated herein.

  In one embodiment, the light source 518 can include lamps of different colors, such as red, green, and blue. Color images can be formed by sequentially illuminating the images with different colored lamps at a rate sufficient to allow the human brain to average different color images into a single multicolor image. Various color-specific images are formed by using the shutter assembly array 502. In another embodiment, light source 518 includes a lamp having four or more different colors. For example, the light source 518 may include a red, green, blue, white lamp, or a red, green, blue, yellow lamp.

  The cover plate 522 forms the front surface of the display device 500. The back side of the cover plate 522 can be covered with a black matrix 524 to enhance contrast. In another embodiment, the cover plate includes color filters (eg, individual red, green and blue filters corresponding to different colors of the shutter assembly 502). The cover plate 522 is supported a predetermined distance away from the shutter assembly 502 that forms the gap 526. The gap 526 is maintained by a mechanical support or spacer 527 and / or by an adhesive seal 528 that attaches the cover plate 522 to the substrate 504.

  Sealant 528 can be formed of a polymer adhesive such as epoxy, acrylate, or silicon material. Adhesive seal 528 should preferably have a cure temperature lower than 200 ° C., preferably should have a coefficient of thermal expansion of less than about 50 ppm / ° C., and must be moisture resistant. . An exemplary sealant 528 is available from Epoxy Technology, Inc. It is EPO-TEK B9021-1 sold more. In another embodiment, the adhesive is formed of a heat reflowable material such as a solder metal or glass frit compound.

Adhesive seal 528 seals working fluid 530. The working fluid 530 is preferably designed with a viscosity of less than about 10 centipoise, a dielectric constant preferably greater than about 2.0, and a breakdown strength greater than about 10 ⁴ V / cm. The working fluid 530 can also function as a lubricant. In another embodiment, the working fluid 530 has a refractive index that is greater than or less than the refractive index of the substrate 504. In one embodiment, the working fluid has a refractive index greater than 2.0. Suitable working fluids 530 include, but are not limited to, ion-removed water, methanol, ethanol, silicone oil, silicone oil fluoride, dimethylsiloxane, polydimethylsiloxane, hexamethyldisiloxane, and diethylbenzene.

  In another embodiment, the working fluid 530 is a hydrophobic liquid with high surface wetting performance. This wetting performance is preferably sufficient to wet not only the back surface but also the front surface of the shutter assembly 502. The hydrophobic liquid can remove water from the surface of the shutter assembly 502. In another embodiment, the working fluid 530 comprises a suspension of particles having a diameter in the range of 0.5-20 microns. Such particles scatter light and widen the viewing angle of the display. In another embodiment, the working fluid 530 includes dye molecules in the solution that absorb some or all of the visible light frequency to increase the contrast of the display.

  A sheet metal or molded plastic assembly bracket 532 holds the cover plate 522, substrate 504, backlight 516, and other components together around the edges. The assembly bracket 532 is fixed with screws or indent tabs to increase the rigidity of the combined display device 500. In some embodiments, the light source 518 is molded in place with an epoxy embedding resin. The reflector 536 helps light that leaks from the edge of the light guide 516 back into the light guide. Electrical wiring that supplies not only power but also control signals to the shutter assembly 502 and lamp 518 is not shown in FIG.

  Further details and alternative configurations (and thus manufacturing methods) of the display device 500 can be found in US patent application Ser. No. 11 / 361,785 and US patent application Ser. No. 11 / 731,628, These are incorporated herein by reference.

  Display device 500 is referred to as a MEMS up configuration. In this configuration, the MEMS-based light modulator is formed on the front surface of the substrate 504 (ie, the surface facing the viewer). The shutter assembly 502 is built directly on the reflective aperture layer 506. In another embodiment of the invention, referred to as a MEMS down configuration, the shutter assembly is disposed on a substrate separate from the substrate on which the reflective aperture layer is formed. A substrate on which a reflective aperture layer is formed and that defines a plurality of apertures is referred to herein as an aperture plate. In the MEMS down configuration, the substrate on which the MEMS-based light modulator is mounted replaces the cover plate 522 of the display device 500. This substrate is oriented so that the MEMS-based light modulator is placed on the back surface of the upper substrate (ie, the surface facing the backlight 516 away from the viewer). This places the MEMS-based light modulator on the opposite side of the reflective aperture layer and with a certain gap from the reflective aperture layer. The gap can be maintained by a series of spacer posts that connect the aperture plate and the substrate on which the MEMS modulator is formed. In some embodiments, the spacer is located within or between each pixel in the array. The gap or distance separating the MEMS light modulator from its corresponding aperture is preferably less than 10 microns or less than the overlap between the shutter and aperture.

  Further details and alternative embodiments of the MEMS down display configuration can be found in the above referenced US patent application Ser. Nos. 11 / 361,785 and 11 / 528,191. .

  In other embodiments, roller-based light modulators 220 or light taps 250 as well as other MEMS-based light modulators can be substituted for the shutter assembly 502 in the display assembly 500.

  FIGS. 6A and 6B illustrate another shutter-based light modulator (shutter assembly) 2200 suitable for inclusion in various embodiments of the present invention. The light modulator 2200 is an example of a dual actuator shutter assembly and is shown in the open state in FIG. 6A. FIG. 6B is a diagram of the dual actuator shutter assembly 2200 in the closed state. The shutter assembly 2200 is described in further detail in US patent application Ser. No. 11 / 251,035, referenced above. In contrast to shutter assembly 200, shutter assembly 2200 includes actuators 2208 and 2210 on one side of shutter 2202. Each actuator 2210 and 2208 is controlled independently. The first actuator (shutter opening actuator 2210) functions to open the shutter 2202. A second opposing actuator (shutter closing actuator 2208) functions to close the shutter 2202. Both actuators 2210 and 2208 are elastic beam electrode actuators. Actuators 2210 and 2208 open and close shutter 2202 by driving shutter 2202 in a plane substantially parallel to aperture layer 2204 on which the shutter is suspended. The shutter 2202 is suspended at a distance from the top of the aperture layer 2204 by an anchor 2206 attached to the actuators 2210 and 2208. Inclusion of supports attached to the ends of the shutter along the axis of motion of the shutter 2202 reduces the out-of-plane motion of the shutter 2202 and substantially restricts its motion to a plane parallel to the substrate. By analogy with the control matrix 300 of FIG. 3, a suitable control matrix for use with the shutter assembly 2200 includes one transistor and one capacitor for each of the opposing shutter open and shutter close actuators 2210 and 2208. It would be fine.

  The shutter 2202 includes three shutter apertures 2212 through which light can pass. The remaining part of the shutter 2202 obstructs the passage of light. In various embodiments, the side of the shutter 2202 facing the reflective aperture layer 2204 is covered with a light absorbing material or reflective material to absorb or reflect light that has been blocked from passing, respectively.

  The reflective aperture layer 2204 is deposited on a transparent substrate, preferably formed of plastic or glass. The reflective aperture layer 2204 can be formed of a metal film deposited on the substrate, a dielectric mirror, or other highly reflective material or combination of materials. The reflective aperture layer 2204 is formed with a set of apertures 2214 that allow light to pass through the apertures from the transparent substrate toward the shutter 2202. The reflective aperture layer 2204 has one aperture corresponding to each shutter aperture 2212. For example, in a light modulator array that includes a shutter assembly 2200, the reflective aperture layer includes three apertures 2214 for each shutter assembly 2200. Each aperture has at least one edge at its periphery. For example, the rectangular aperture 2214 has four edges. In another embodiment, a circular, oval, oval, or other curved aperture is formed in the reflective aperture layer 2204. Each aperture may have only a single edge. In other embodiments, the apertures are separated, i.e. need not be non-identical in a mathematical sense, but the apertures can be connected to each other. That is, a portion or shaped portion of the aperture can have a corresponding relationship with each shutter, some of which are connected such that a single continuous periphery of the aperture is shared by multiple shutters. Good.

  In FIG. 6A, the shutter assembly 2200 is in an open state. Actuator 2208 is in the open position and actuator 2210 is in the folded position. The aperture 2214 can be viewed through the shutter aperture 2212. As can be seen, the shutter aperture 2212 has a larger area than the aperture 2214 formed in the reflective aperture layer 2204. This dimensional difference increases the range of angles over which light can pass through the shutter aperture 2212 toward the desired viewer.

  In various embodiments, it is advantageous that the shutter used in the shutter assembly overlaps the corresponding aperture when the shutter is in the closed position.

  In FIG. 6B, the shutter assembly is in the closed state. Actuator 2208 is in the folded position and actuator 2210 is in the open position. The light blocking portion of the shutter 2202 covers the aperture 2214 of the reflective aperture layer 2204. The light blocking portion of the shutter 2202 overlaps the edge of the aperture 2214 of the reflective aperture layer 2204 by a predetermined overlap 2216. In some embodiments, some light may leak through the aperture 2214 at an angle away from the axis normal to the shutter 2202 even when the shutter is in the closed state. The overlap included in the shutter assembly 2200 reduces or eliminates this light leakage. The light blocking portion of the shutter 2202 overlaps with all four edges of the aperture as shown in FIG. 6B, but light leakage is reduced by overlapping the light blocking portion of the shutter 2202 with one of the edges.

  7A-7C are cross-sectional views of various configurations of the shutter assembly 2200 with respect to the transparent substrate on which the reflective aperture layer 2204 is formed. The cross-sectional view corresponds to the B-B 'line of FIGS. 6A and 6B. For illustration, the shutter 2202 is illustrated in FIGS. 7A-7C as having only a single shutter aperture 2323 and two light blocking portions 2324.

  7A is a first configuration of a display device 2300 including a shutter assembly 2301 similar to that shown in FIG. 6 in the closed state, taken along line BB, according to an exemplary embodiment of the present invention. It is a cross section. In the first configuration, the shutter assembly 2301 is formed on the reflective aperture layer 2302. The reflective aperture layer 2302 is formed of a thin metal film deposited on the transparent substrate 2304. Alternatively, the reflective aperture layer 2302 can be formed of a dielectric mirror, or other highly reflective material or combination of materials. The reflective aperture layer 2302 is patterned to form the aperture 2306. The transparent substrate 2304 is disposed in the vicinity of the optical waveguide 2308. The transparent substrate 2304 and the optical waveguide 2308 are separated by a gap 2309 filled with a fluid such as air. The refractive index of the fluid is preferably smaller than the optical waveguide 2308. A suitable light guide 2308 for display device 2300 is further described in US patent application Ser. No. 11 / 528,191, which is incorporated herein by reference in its entirety. Display device 2300 also includes a front-facing back reflective layer 2310 disposed adjacent to the back side of light guide 2308.

  Shutter assembly 2301 includes a shutter 2314 supported in close proximity to reflective aperture layer 2302 by anchors 2316 via portions of opposing actuators 2318 and 2320. Anchor 2316 and actuators 2318 and 2320 suspend shutter 2314 at approximately a fixed distance H1 (measured from the bottom of shutter 2314) from above reflective aperture layer 2302. Further, the display device 2300 includes a cover plate 2311 supported on the transparent substrate 2304 by spacer posts 2312. The spacer post 2312 holds the cover plate away from the top of the shutter 2314 by about a second distance H2. Substrates 2304 and 2311 can be made of a substantially rigid material such as glass. In this case, a relatively low density spacer 2312 can be used to maintain the desired spacing H2. For example, with a rigid substrate, display device 2300 includes one spacer 2312 for every four pixels in one embodiment. However, other higher or lower densities can also be utilized. In another embodiment, either substrate 2304 or 2311 can be made of a flexible material such as plastic. In this case, it is preferable to have a higher density of spacers 2312 (eg, one spacer 2312 within or between each pixel in the array).

  The gap between the cover plate 2311 and the transparent substrate 2304 is filled with a working fluid 2322 such as the working fluid 530 described above. The working fluid 2322 preferably has a higher refractive index than the transparent substrate 2304. In another embodiment, the working fluid has a refractive index greater than 2.0. In another embodiment, the working fluid 2322 has a refractive index that is less than the refractive index of the transparent substrate 2304.

  As indicated above, the shutter assembly 2301 is in a closed state. The light blocking portion 2324 of the shutter 2314 overlaps the edge of the aperture 2306 formed in the reflective aperture layer 2302. When the gap between the shutter and the aperture (that is, the distance H1) is made as small as possible, the light blocking characteristics of the shutter 2314 are improved. In one embodiment, H1 is less than about 100 μm. In another embodiment, H1 is less than about 10 μm. In yet another embodiment, H1 is about 1 μm. In another embodiment, the distance H1 exceeds 0.5 mm but is still smaller than the display pitch. The display pitch is defined as the distance between pixels (measured between centers) and is often set as the distance between apertures (measured between centers), such as the aperture 2306 of the reflective layer 2302 facing the back. The

  The size of the overlap W1 is preferably proportional to the distance H1. The overlap W1 may be smaller, but is preferably equal to or longer than the distance H1. In one embodiment, the overlap W1 is 1 micron or greater. In another embodiment, the overlap W1 is between about 1 micron and 10 microns. In another embodiment, the overlap W1 is greater than 10 microns. In one particular embodiment, the shutter 2314 is about 4 μm thick. H1 is about 2 μm, H2 is about 2 μm, and W1> = 2 μm. By making the overlap W1 greater than or equal to H1, most of the light having an angle sufficient to exit the light guide 2308 through the aperture 2306 when the shutter assembly 2301 is in the closed state as shown in FIG. 7A. Since it hits the light blocking unit 2324 of 2314, the contrast ratio of the display device 2300 is improved.

  H2 is preferably approximately the same distance as H1. The spacer posts 2312 are preferably formed of a polymeric material that is lithographically patterned, developed, and / or etched into a cylinder. The height of the spacer is determined by the thickness of the cured polymer material. Methods and materials for the formation of spacers 2312 are disclosed in co-owned US patent application Ser. No. 11 / 361,785 filed on Feb. 23, 2006, which is incorporated herein by reference. In another embodiment, the spacers 2312 can be formed of a metal that is electrochemically deposited in a mold of sacrificial material.

  7B is a cross-section of a second configuration of display device 2340 that includes a shutter assembly 2341 similar to that shown in FIG. 6 in the closed state, according to an illustrative embodiment of the invention. This second configuration is referred to as a MEMS down configuration. Here, the reflective aperture layer 2344 is formed on a transparent substrate called an aperture plate 2346 (separate from the light modulator substrate 2342 to which the shutter assembly 2341 is locked). The shutter assembly includes a shutter 2354 having a light blocking portion 2362 and a shutter aperture 2363 formed therein. Similar to the aperture plate 2346, the light modulator substrate 2342 is also transparent. The two substrates 2342 and 2346 are separated by a gap. As shown in FIG. 6, when the shutter is in the closed position, the two substrates 2342 and 2346 are arranged between each of the apertures 2347 and each of the light blocking portions 2362 of the shutter 2354 and / or the shutter is in the open position. In some cases, alignment is done during assembly such that there is a one-to-one correspondence between aperture 2347 and shutter aperture 2363. In another embodiment, the correspondence between the aperture and either the light blocker 2362 or the shutter aperture 2363 of the shutter 2354 is one-to-many or many-to-one.

  In the MEMS down display device 2340, the shutter assembly 2341 is formed on the surface facing the back surface of the optical modulator substrate 2342, that is, on the side facing the optical waveguide 2348. In the display device 2340, the aperture plate 2346 is disposed between the light modulator substrate 2342 and the optical waveguide 2348. The reflective aperture layer 2344 is formed of a thin metal film deposited on the front facing surface of the transparent aperture plate 2346. The reflective aperture layer 2344 is patterned to form the aperture 2347. In another embodiment, the reflective layer 2344 can be formed of a mirror, such as a dielectric mirror. The dielectric mirror is manufactured by stacking dielectric thin films having different refractive indexes or a combination of a metal layer and a dielectric layer.

  The aperture plate 2346 is disposed in proximity to the backlight or optical waveguide 2348. The aperture plate 2346 is separated from the optical waveguide 2348 by a gap 2349 filled with a fluid such as air. The refractive index of the fluid is preferably smaller than the optical waveguide 2348. A suitable backlight 2348 for display device 2340 is further described in US patent application Ser. No. 11 / 528,191, which is incorporated herein by reference in its entirety. Display device 2340 also includes a front-facing back side reflective layer 2350 disposed adjacent to the back side of backlight 2348. The front-facing reflective layer 2350 in combination with the back-facing reflective layer 2344 forms an optical resonator that facilitates the reuse of light rays that do not initially pass through the aperture 2347. The shutter assembly 2341 includes a shutter 2354 supported in close proximity to the transparent substrate 2342 by anchors 2356 via portions of opposing actuators 2358 and 2360. Anchor 2356 and actuators 2358 and 2360 suspend shutter 2354 below light modulator substrate 2342 at an approximately constant distance H4 (measured from the top of shutter 2354). Further, the display device includes a spacer post 2357 that supports the light modulator substrate 2342 on the aperture plate 2346. The spacer post 2357 holds the light modulator substrate 2342 at a distance of about a second constant distance H5 from the aperture plate 2346, so that the bottom surface of the shutter 2354 is positioned above the reflective aperture layer 2344 and about a third constant distance H6. Hold in place. The spacer post 2357 is formed in the same manner as the spacer 2312.

  The gap between the light modulator substrate 2342 and the aperture plate 2346 is filled with a working fluid 2352 such as the working fluid 530 described above. The working fluid 2352 preferably has a higher refractive index than the transparent aperture plate 2346. In another embodiment, the working fluid has a refractive index greater than 2.0. In another embodiment, the working fluid 2352 preferably has a refractive index that is less than or equal to the refractive index of the aperture plate 2346.

  As indicated above, the shutter assembly 2341 is in a closed state. The light blocking portion 2362 of the shutter 2354 overlaps the edge of the aperture 2347 formed in the reflective aperture layer 2344. The size of the overlap W2 is preferably proportional to the distance H6. The overlap W2 may be even smaller, but is preferably a distance H6 or more. In one embodiment, H6 is less than about 100 μm. In another embodiment, H6 is less than about 10 μm. In yet another embodiment, H6 is about 1 μm. In another embodiment, the distance H6 exceeds 0.5 mm but is still smaller than the display pitch. The display pitch is defined as the distance between pixels (measured between the centers) and is often set as the distance between the centers of the apertures of the reflective layer facing the back, such as the aperture 2347. H4 is preferably approximately the same distance as H6. In one particular embodiment, shutter 2354 is about 4 μm thick, H6 is about 2 μm, H4 is about 2 μm, H5 is about 8 μm, and W2> = 2 μm. By making the overlap W2 greater than or equal to H6, when the shutter assembly 2341 is in the closed state as shown in FIG. Since it hits the light blocking part 2362 of 2354, the contrast ratio of the display device 2340 is improved.

  FIG. 7C is a cross section of a third configuration of display device 2370 including a shutter assembly 2371 similar to that shown in FIG. 6 in a closed state, according to an illustrative embodiment of the invention. In comparison with the second configuration of the display device 2340 described above, the display device 2370 has a light modulator substrate 2372 (similar to the light modulator substrate 2342) on which the shutter assembly 2371 is formed and a reflective aperture layer 2376 deposited. Is designed in consideration of minor misalignment that may occur during alignment and bonding with the aperture plate 2374 (similar to the aperture plate 2346). To address this potential problem, display device 2370 includes an additional layer 2377 of light absorbing material deposited on light modulator substrate 2372. The light absorbing material 2377 may be a part of the black mask, but at least a part of the light absorbing material 2377 is preferably disposed inside the pixel to which the shutter assembly 2371 corresponds. The light absorbing material 2377 absorbs light 2378 that otherwise passes through the light modulator substrate 2372 while the shutter 2382 is in the closed state. Additional light absorbing material 2377 can be deposited on the front side of the reflective aperture layer 2376 to absorb light (eg, light 2380 deflected from the shutter 2382).

  7D is a cross-section of a fourth configuration of display device 2390 that includes a shutter assembly 2385 similar to that shown in FIG. 6 in a closed state, according to an illustrative embodiment of the invention. In comparison with the second configuration of shutter assembly 2354 described above, the shutter assembly 2385 is made according to a different process, so that some of its members have different cross-sectional thicknesses. The generated shutter 2393 is referred to herein as a waveform shutter. However, it is preferable that the design guidelines for the gap distance (for example, H8, H10) and the overlap parameter W4 are not changed from the corresponding gap distance and the overlap parameter. Display device 2390 includes a transparent light modulator substrate 2386 (based on a MEMS down configuration) to which a shutter assembly 2385 is attached. Display device 2390 also includes a transparent aperture plate 2387 on which a back-facing reflective aperture layer 2388 is deposited. Display device 2390 includes fluid 2389 that fills the gap between substrates 2386 and 2387. The fluid 2389 preferably has a higher refractive index than the aperture plate 2387. The display device also includes a backlight 2348 along with a front facing reflective layer 2350.

  Shutter assembly 2385 is in a closed state. The light blocking portion 2391 of the waveform shutter 2393 overlaps the edge of the aperture 2394 formed in the reflective aperture layer 2388. The corrugated shutter 2393 is composed of two connected flat plate portions (that is, a horizontally oriented portion 2391 and a vertically oriented portion 2392). Each flat plate portion 2391 and 2392 is made of a thin film material having a thickness in the range of 0.2 to 2.0 μm. In a particular embodiment, the horizontal portion 2391 has a thickness of 0.5 μm. Longitudinal section 2392 provides corrugated shutter 2393 with rigidity and height to match actuator 2358 without requiring deposition of bulk material thicker than about 2 μm. Methods and materials for the formation of shutters having corrugated and / or three-dimensional structures are disclosed in commonly-owned US patent application Ser. No. 11 / 361,785 filed on Feb. 23, 2006, by reference. This is incorporated herein.

  Similar to the dimensions described for display device 2340, in certain embodiments, the dimensions of H8, H9, and H10 of display device 2390 may be 2 μm, 8 μm, and 2 μm, respectively. The overlap W4 is preferably not less than the distance H10. In another embodiment, the distance H10 and the overlap W4 may be 1 μm or more. However, by using the present material and method for the corrugated shutter 2393, the thickness of the portion 2391 can be reduced to about 0.5 μm. By making the overlap W4 greater than or equal to H10, most of the light having an angle sufficient to exit the backlight 2348 through the aperture 2394 when the shutter assembly 2385 is in the closed state as shown in FIG. Since it hits the light blocking portion 2391 of 2393, the contrast ratio of the display device 2390 is improved.

  FIG. 8 is a cross-sectional view of a first electrowetting-based light modulation array 2400, according to an illustrative embodiment of the invention. Light modulation array 2400 includes a plurality of electrowetting-based light modulation cells 2402a-2402d (generally referred to as "cells 2402") formed on optical resonator 2404. The light modulation array 2400 also includes a set of color filters 2406 corresponding to the cells 2402.

  Each cell 2402 includes a layer 2408 of water (or other transparent conductive or polar fluid), a layer 2410 of light absorbing oil, a transparent electrode 2412 (eg, made of indium tin oxide), and a layer of light absorbing oil. 2410 and an insulating layer 2414 disposed between the transparent electrodes 2412. An exemplary embodiment of such a cell is further described in US Patent Application Publication No. 2005/0104804, published May 19, 2005, entitled “Display Device”, which is incorporated herein by reference. Incorporated into. In the embodiment described herein, the transparent electrode 2412 occupies only a portion of the back surface of the cell 2402.

  The remaining portion of the back surface of the cell 2402 is formed by a reflective aperture layer 2416 that forms the front surface of the optical resonator 2404. The back-facing reflective layer 2416 is patterned to form an aperture. The aperture coincides with the transparent electrode 2412 in the cell 2402 embodiment. Preferably, when in the closed position, the layer of light absorbing oil 2410 overlaps a portion of one or more edges of its corresponding aperture in the reflective aperture layer 2416. The reflective aperture layer 2416 is formed of a reflective material such as a reflective metal or a stack of thin films that form a dielectric mirror. In each cell 2402, an aperture is formed in the reflective aperture layer 2416 so that light can pass through. In another embodiment, the cell electrode 2412 is deposited in the aperture and on the material forming the reflective aperture layer 2416 and separated by another dielectric layer.

  The remaining portion of the optical resonator 2404 includes an optical waveguide 2418 disposed proximate to the reflective aperture layer 2416 and a second reflective layer 2420 opposite to the reflective aperture layer 2416 of the optical waveguide 2418. A series of optical redirectors 2421 are formed on the back surface of the optical waveguide adjacent to the second reflective layer. The light redirector 2421 may be a diffusive or specular mirror. One or more light sources 2422 inject light 2424 into the optical waveguide 2418.

  In another embodiment, the light source 2422 can include lamps of different colors (eg, red, green, blue). Color images can be formed by sequentially illuminating images with different colored lamps at a rate sufficient to allow the human brain to average different color images into a single multicolor image. Various color specific images are formed by using the electrowetting modulation cell array 2402. In another embodiment, light source 2422 includes a lamp having four or more different colors. For example, the light source 2422 may include a red, green, blue, white lamp, or a red, green, blue, yellow lamp.

  In another embodiment, cell 2402 and reflective aperture layer 2416 are separate from light guide 2418 and are formed on an additional light modulator substrate separated by a gap (eg, the light modulation of FIG. 9). (See instrument board 2513). In yet another embodiment, a material layer having a lower refractive index than the optical waveguide 2418 is inserted between the reflective aperture layer 2416 and the optical waveguide 2418. A material layer having a small refractive index helps to improve the uniformity of the light emitted from the optical waveguide 2418.

  During operation, a voltage is applied to electrode 2412 of a cell (eg, cell 2402b or 2402c), causing light absorbing oil 2410 in the cell to accumulate in a portion of cell 2402. As a result, the light absorbing oil 2410 no longer interferes with the passage of light through the aperture formed in the reflective aperture layer 2416 (see, for example, cells 2402b and 2402c). The light that escapes the backlight at the aperture then passes through the cell and through a corresponding color (eg, red, green, or blue) filter in a set of color filters 2406 to form a color pixel in the image. can do. When electrode 2412 is grounded, light absorbing oil 2410 covers the aperture of reflective aperture layer 2416 and absorbs any light 2424 that attempts to pass through it (see, for example, cell 2402a).

  The area where oil 2410 accumulates when voltage is applied to cell 2402 constitutes a useless space for image formation. Regardless of whether a voltage is applied to this region, light cannot pass therethrough. Thus, this region will absorb light that would otherwise have been available to contribute to the formation of the image if it did not include the reflective portion of the reflective aperture layer 2416. However, if the reflective aperture layer 2416 is included, this light that would otherwise have been absorbed is reflected back into the light guide 2420 for future escape through the different apertures.

  FIG. 9 is a cross-sectional view of a second electrowetting-based light modulation array 2500, according to an illustrative embodiment of the invention. The second electrowetting-based light modulation array 2500 includes three subarrays 2501a, 2501b, 2501c of color electrowetting-based light modulation cells 2502 (generally referred to as “cells 2502”) disposed one above the other. . Each cell 2502 includes a transparent electrode 2504 and a color oil 2506 separated by an insulator 2508. In one embodiment, oil 2506 in cell 2502 of subarray 2501a is cyan, oil 2506 in cell 2502 of subarray 2501b is yellow, and oil 2506 in cell 2502 of subarray 2501c is magenta. It is done. Cells 2502 in subarray 2501a and cells 2502 in subarray 2501b share a common water layer 2520. The cell 2502 of the subarray 2501c includes its own water layer 2520.

  The electrowetting-based light modulation array 2500 includes an optical reusable optical resonator 2510 coupled to three subarrays 2501a to 2501c. The optical resonator 2510 includes an optical waveguide 2512 and an optical modulator substrate 2513 separated from the optical waveguide 2512 by a gap 2515. The front surface of the light modulator substrate 2513 includes a back facing reflective aperture layer 2514. The reflective aperture layer 2514 is formed of a metal layer or a stack of thin films that form a dielectric mirror. Aperture 2516 is patterned into a reflective aperture layer below cells 2502 of subarrays 2501a-2501c, allowing light to escape the optical waveguide and pass through subarrays 2501a-2501c to form an image. The transparent electrode 2504 of the cell 2502 is formed above the reflective aperture layer 2514.

  The substrates (ie, optical waveguide 2512 and modulator substrate 2513) are separated by a gap 2515 filled with a fluid such as air. The refractive index of the fluid is smaller than the optical waveguide 2512. The front-facing reflective layer 2518 is formed on the opposite side of the optical waveguide 2512 or in the vicinity thereof. The light modulation array 2500 includes at least one light source 2522 for injecting light into the light guide 2512. A suitable light guide 2618 for display device 2600 is further described in US patent application Ser. No. 11 / 528,191, which is hereby incorporated by reference in its entirety.

  FIG. 10 is a cross-sectional view of a third electrowetting-based light modulation array 2600, according to an illustrative embodiment of the invention. The light modulation array 2600 includes a plurality of electrowetting-based light modulation cells 2602 a-2602 c (generally referred to as “cells 2602”) formed on an optical resonator 2604. The light modulation array 2600 also includes a set of color filters 2606 corresponding to the cells 2602.

  Array 2400 is considered an example of an array in a MEMS up configuration, while array 2600 is an example of an electrowetting-based array assembled in a MEMS down configuration. Each cell 2602 includes a layer of water (or other transparent conductive or polar fluid) 2608, a layer of light absorbing oil 2610, a transparent electrode 2612 (eg, made of indium tin oxide), and a layer of light absorbing oil. 2610 and an insulating layer 2614 disposed between the transparent electrodes 2612. However, in the MEMS down configuration of the light modulator array 2600, both the insulating layer 2614 and the transparent electrode 2612 are disposed on a light modulator substrate 2630 separate from the aperture plate 2632. Similar to the light modulator substrate 2630, the aperture plate 2632 is also a transparent substrate. Light modulator substrate 2630 is the top substrate and is oriented so that control electrodes such as transparent electrode 2612 are disposed on the back surface of substrate 2630 (ie, the surface facing the optical waveguide away from the viewer). . In addition to the transparent electrode 2612, the back side of the light modulator substrate 2630 provides other common components of the switching matrix or control matrix for the modulator array (including but not limited to row electrodes, column electrodes, transistors per pixel, pixels And a capacitor). The electrodes and switching components formed on the light modulator substrate 2630 that manages the operation of the light modulators in the array are on the opposite side of the reflective aperture layer 2616 disposed on the front facing surface of the aperture plate 2632. Alternatively, it is disposed with a gap 2636 therebetween. The gap 2636 is filled with water 2608 and oil 2610 which are electrowetting fluid components.

  A reflective aperture layer 2616 is deposited on a transparent substrate 2632 which is preferably formed of plastic or glass. The reflective aperture layer 2616 can be formed of a metal film deposited on the substrate, a dielectric mirror, or other highly reflective material or combination of materials. The reflective aperture layer 2616 is a reflective layer facing the back surface, and forms the front surface of the optical resonator 2604. The reflective aperture layer 2616 is formed with a set of apertures 2617 that allow light to travel through the apertures toward the electrowetting fluid components 2608 and 2610. Optionally, the aperture plate 2632 includes a set of color filters 2606 deposited on the top surface of the reflective aperture 2616 and filling the aperture 2617.

  The aperture plate 2632 is disposed between the optical modulator substrate 2630 and the optical waveguide 2618. Substrates 2632 and 2618 are separated from each other by a gap 2634 filled with a fluid such as air. The refractive index of the fluid is smaller than the optical waveguide 2618. A suitable light guide 2618 for display device 2600 is further described in US patent application Ser. No. 11 / 528,191, which is hereby incorporated by reference in its entirety. The optical resonator 2604 also includes substrates 2632 and 2618 and a front-facing back side reflective layer 2620 disposed adjacent to the back side of the optical waveguide 2618. One or more light sources 2622 inject light into the light guide 2618.

  The reflective aperture layer 2616 has one aperture 2617 corresponding to each light modulator cell 2602 in the array 2600. Similarly, the light modulator substrate 2630 has one transparent electrode 2612 or a set of pixel transistors and capacitors for each light modulator cell 2602. Substrates 2630 and 2632 are assembled to ensure that their corresponding apertures 2617 are positioned where light is not obstructed by oil 2610 when the cell is activated or held open (eg, cell 2602b). Aligned inside.

Aperture Plate Fabrication The aperture plate 2700 of FIG. 11 illustrates the detailed structure of one embodiment of an aperture plate, such as an aperture plate 2346, 2374, 2387, or 2632, according to an exemplary embodiment of the present invention. The aperture plate 2700 includes a substrate 2702, a dielectric enhanced metal mirror 2704, a light absorption layer 2706, and a spacer post 2708. The dielectric reinforced metal mirror and the light absorbing layer are patterned into an aperture 2709.

The substrate 2702 is preferably a transparent material (eg, glass or plastic). Dielectric reinforced metal mirror 2704 includes Si ₃ N ₄ thin film 2710, SiO ₂ thin film 2712, another Si ₃ N ₄ thin film 2710, another SiO ₂ thin film 2712 in order from the substrate to the top, It is composed of five layers of materials including an aluminum thin film 2714. The relative thicknesses and preferred refractive indices of these layers are shown in Table 1.

The light absorption layer 2706 can be formed of an oxide film or a thin film of black chrome which is a composite of metal chromium particles suspended in a nitride matrix. Examples thereof include Cr particulate matter in a Cr ₂ O ₃ matrix or Cr particulate matter in a SiO ₂ matrix. In other embodiments, the black chromium can be formed of a thin metal film of chromium on which a thin film of CrOx (chromium oxide) has been grown or deposited. The preferred thickness of black chrome is 150 nm.

  Aperture window 2709 can be patterned from a thin film stack of materials 2704 and 2706 by processes known in the art such as photolithography and etching, or by photolithography and lift-off. In the etching process, a photoresist layer is added on top of the thin film stack and then exposed to UV light through a mask. After developing the aperture pattern in the exposed photoresist layer, the entire stack is etched down to the substrate 2702 in the aperture region 2709. Such etching can be performed by immersion in a wet drug, dry plasma or ion beam etching, or any combination of the above. In the lift-off process, a photoresist layer developed into an inverted pattern of the etching mask pattern is added to the glass before deposition of the thin film stack. The thin film stack is then deposited on the photoresist so that the thin film stack contacts the glass everywhere except the aperture region 2709. After the deposition of the thin film stack is complete, the substrate is immersed in a chemical bath that dissolves or lifts off the photoresist as well as any thin film material deposited on the photoresist.

  The spacer posts 2708 are formed of a photosensitive polymer such as a photosensitive epoxy (particularly novolak epoxy) or a photosensitive polyimide material. Other polymer families that can be prepared in photosensitive form and useful for the present application include polyarylene, parylene, benzocyclobutane, perfluorocyclobutane, silsesquioxane, silicon polymers. A specific photosensitive resist useful for spacer applications is Nano SU-8 material available from Microchem Corporation, headquartered in Newton, Massachusetts.

  The polymer spacer material is first deposited as a thick film on the thin film stack 2704 and 2706 after the aperture 2709 is patterned. Next, the photosensitive polymer is exposed to UV light through a mask. The alignment mark helps to ensure that the generated spacer 2708 is correctly positioned with respect to the aperture 2709. For example, alignment criteria can be formed at the periphery of the display during the process of etching the aperture 2709. These references are aligned with a corresponding set of references on the exposure mask to ensure correct placement of the spacers 2708. As a result, the development process is effectively performed when removing all the polymer other than the place exposed to UV light. In an alternative method, the features on the exposure mask can be directly aligned with the display features on the substrate 2702, such as the aperture 2709.

  In the particular embodiment described with respect to display device 2340, the spacer posts may be 8 microns high. In other embodiments, the spacer height may range from about 2 microns to about 50 microns. When cut in the plane of the substrate 2702, the spacer may take a general shape such as a cylinder or rectangle having a width in the range of 2 to 50 microns. Alternatively, the spacer may have a complex irregular cross section designed to fit between other structures on the substrate, such as aperture 2709, and to maximize the contact area of the spacer. In a preferred embodiment, the size, shape, and placement of the spacer are determined such that the spacer does not interfere with the movement of a shutter, such as shutter 2354, or the movement of other MEMS components, such as actuator 2358 of display device 2340.

  In another embodiment, the spacer post 2708 is not provided as a polymeric material, but instead comprises a thermally reflowable adhesive such as a solder alloy. Exemplary heat reflowable materials are described below with respect to FIG. 13B. The solder alloy goes through a melting or reflow process that allows the solder alloy to wet or bond to the mating surface on the counter substrate. Thus, the solder alloy performs an additional function as an adhesive between an aperture plate such as aperture plate 2346 and a modulator substrate such as substrate 2342. Due to the reflow process, the solder alloy is usually relaxed into an eccentric shape (referred to as solder bump). The predetermined spacing between the substrates can be maintained by controlling the average volume of the solder bump material. The solder bumps can be applied to the aperture plate 2700 by thin film deposition, thick film deposition through a stencil mask, or electroplating.

  In another embodiment, the aperture plate 2700 can be sandblasted after the process of forming the optical layers 2704 and 2708. Sandblasting has an effect of selectively roughening the substrate surface of the aperture region 2709. The rough surface at aperture 2709 acts as an optical diffuser that can give the display the advantage of a wide viewing angle. In another embodiment, the diffusing surface in aperture 2709 is provided by an etching process in which etching is selectively performed in aperture region 2709 after exposure of the photomask photoresist. The etch pit or etch trench can be formed by a suitable design of the photomask, and the sidewall angle or depth of the pit or trench can be controlled by a wet or dry etching process. In this way, an optical structure in which the degree of diffusion spread is controlled can be formed. In this way, an anisotropic diffuser can be formed on the substrate surface that deflects light along the preferred optical axis to form elliptical and / or multi-directional cone-shaped radiation.

  In another embodiment, etch trenches may be provided in the substrate 2702 that substantially surrounds the display along the periphery of the aperture array 2709 (ie, the periphery of the active display area). The etch trench operates as a mechanical positioning structure to limit the movement or flow of adhesive, such as adhesive 528, used to seal aperture plate 2700 to the opposing substrate.

  Further details regarding the materials and processes described above can be found in US patent application Ser. No. 11 / 361,785 filed Feb. 23, 2006, which is incorporated herein by reference. For example, the application includes additional materials and processing methodologies for forming dielectric reinforced metal mirrors with apertures, light absorbing layers, and spacer posts. Although dielectric mirrors and spacers are described in this application in the context of an integrated (eg, MEMS up configuration) display design, similar processing should be adapted to make aperture plates such as aperture plate 2700. It will be understood that

  In some embodiments of the aperture plate 2700, it is desirable to utilize a transparent plastic material for the substrate 2702. Applicable plastics include, but are not limited to, polymethyl methacrylate (PMMA) and polycarbonate. If a plastic material is used, it may be possible to use an injection molding or stamping process to form the spacer posts 2708. In such a process, the spacer posts are first formed with a mold or stamper prior to application of the dielectric reinforced metal mirror 2704. At this time, all layers of the dielectric reinforced metal mirror 2704 are sequentially deposited on the substrate including the spacer posts 2708 in advance. A light absorbing layer 2706 is deposited on the dielectric mirror 2704. To pattern the aperture window 2709, a special photoresist is applied that uniformly covers the surface of the thin film without being disturbed by the presence of the spacer posts 2708. Suitable photoresists include spray-on photoresist and electroplated photoresist. Alternatively, a spin-on resist is applied, followed by a reflow process in which a uniform resist film thickness is provided over the entire surface of the thin film in the aperture region 2709. Next, resist exposure, development, and thin film layer etching proceed as described above. After removal of the photoresist, the process is complete. A lift-off process can also be utilized to pattern the dielectric reinforced mirror as described above. To reduce the material cost required to make the aperture plate 2700, it is helpful to use a molding or stamping process to form the spacer posts 2708.

  In some display embodiments, the aperture plate 2346 is combined with the light guide 2348 into a single solid body (referred to herein as a single backlight or a composite backlight), the details of which are described in US patent application. No. 11 / 218,690 and US patent application Ser. No. 11 / 528,191, respectively. Both applications are incorporated herein by reference. All of the processes described above for the formation of the dielectric reinforced metal mirror 2704, the light absorbing layer 2706, and / or the spacer post 2708 can be similarly applied to the substrates to be joined or to the substrates that are indistinguishable from the optical waveguide. it can. The surface of a single backlight to which the thin film is deposited may be glass or plastic (including plastics molded to form spacer posts such as spacer posts 2357).

  In one embodiment, spacer posts 2708 are formed or attached to aperture plate 2700 before the aperture plate is aligned to a modulator substrate, such as modulator substrate 2342. In another embodiment of display device 2340, spacer posts 2357 are made on and as part of the modulator substrate 2342 before the modulator substrate is aligned to the aperture plate 2346. Such an embodiment has been described with respect to FIG. 20 of the aforementioned US patent application Ser. No. 11 / 361,785.

  FIG. 12 is a cross-sectional view of a display according to an exemplary embodiment of the present invention. Display assembly 2800 includes a modulator substrate 2802 and an aperture plate 2804. Display assembly 2800 also includes a set of shutter assemblies 2806 and a reflective aperture layer 2808. The reflective aperture layer 2805 includes an aperture 2810. A predetermined gap or separation H12 between the substrates 2802 and 2804 is maintained by a pair of opposing spacers 2812 and 2814. The spacer 2812 is formed on or as part of the modulator substrate 2802. Spacer 2814 is formed on or as part of aperture plate 2804. During assembly, the two substrates 2802 and 2804 are aligned such that the spacers 2812 on the modulator substrate 2802 are in contact with the respective spacers 2814.

  In this example, the separation or distance H12 is 8 microns. To set this separation, spacer 2812 is 2 microns high and spacer 2814 is 6 microns high. Alternatively, both spacers 2812 and 2814 may be 4 microns high. Alternatively, spacer 2812 may be 6 microns in height while spacer 2814 may be 2 microns in height. In fact, any combination of spacer heights can be employed as long as their total height sets the desired separation H12.

  The placement of spacers on both substrates 2802 and 2804 (which are then aligned or fitted during assembly) has advantages with respect to material and processing costs. Since a relatively long time is required for curing, exposing and developing the photosensitive polymer, installation of a spacer (such as 8 microns) having a considerably high height (such as spacer 2708) can be expensive. By using mating spacers as in display assembly 2800, a thinner polymer coating is available on each substrate.

  In another embodiment, the spacer 2812 formed on the modulator substrate 2802 can be formed with the same material and patterning process used to form the shutter assembly 2806. For example, an anchor used in shutter assembly 2806 (similar to anchor 2356) can also perform a function similar to spacer 2812. In this embodiment, a separate application of polymeric material to form the spacer is not required, and a separate exposure mask for the spacer may not be required.

  The display assembly 2900 of FIG. 13A illustrates one method for alignment of the modulator substrate and aperture plate, according to an illustrative embodiment of the invention. Display assembly 2900 includes a modulator substrate 2902 and an aperture plate 2904. Display assembly 2900 also includes a set of shutter assemblies 2906 and a reflective aperture layer 2908 that includes apertures 2910. A predetermined gap or separation between the substrates 2902 and 2904 is maintained by the spacer 2912. The spacer 2912 is formed on or as part of the aperture plate 2904. Display assembly 2900 also includes a set of alignment guides 2914. These alignment guides are formed on or as part of the modulator substrate 2902. When assembling the modulator substrate 2902 and aperture plate 2904, the gap between the alignment guide 2914 and the spacer 2912 is intimate and in some cases less than 1 micron. By incorporating the spacer posts between the dense alignment guides, the lateral movement between the modulator substrate 2902 and the aperture plate 2904 is limited, thereby maintaining the alignment between the shutter 2906 and the aperture 2910.

  In various embodiments, the alignment guide 2914 is ring-shaped or donut-shaped. In other embodiments, the alignment guide 2914 is a simple slot that incorporates a wall-like shape from the aperture plate 2904. The alignment slot may be oriented parallel to one or both edges of the modulator substrate 2903. Including alignment slots with different (and preferably vertical) orientations helps prevent movement in any direction parallel to the plane of the substrate 2902. However, other orientations may be employed. Alignment guides 2914 may be placed between the pixels, within the pixels, or outside the pixel array along the periphery of the display.

  Alternative means of maintaining the alignment between the modulator substrate and the aperture plate are possible. In one embodiment, an adhesive such as adhesive 528 of FIG. 5 is provided to hold the two substrates together during lateral alignment. In this embodiment, an alignment device (eg, a mechanical platform equipped with a translational motor drive and an alignment camera) is suitable for two substrates while an adhesive such as adhesive 528 is dried or cured in place. Used to hold in a proper orientation. Epoxy resins that are partially or fully cured by UV radiation are particularly useful as adhesives in this embodiment. In embodiments where the adhesive is applied at the periphery of the display assembly, this is referred to as an edge seal or gasket seal. In some embodiments, the edge sealant comprises a glass or polymer bead that acts as a spacer to maintain a predetermined gap or spacing between opposing substrates.

  The display assembly 2950 of FIG. 13B illustrates another means for aligning the modulator substrate to the aperture plate, according to an illustrative embodiment of the invention. Display assembly 2950 includes a modulator substrate 2952 and an aperture plate 2954. Display assembly 2950 also includes a set of shutter assemblies 2956 and a reflective aperture layer 2958 that includes apertures 2960. A predetermined gap or separation between the substrates 2952 and 2954 is maintained by a pair of opposing spacers 2962 and 2964. Spacers 2962 are formed on or as part of the modulator substrate 2952. The spacer 2964 is formed on or as part of the aperture plate 2954.

  Spacers 2962 and 2964 are made of different materials. In an embodiment of display assembly 2950, spacer 2962 is made of a thermally reflowable material such as solder, while spacer 2964 is made of a material that is substantially solid or has a melting or softening point that is significantly higher than spacer 2962. . The materials used for the substantially solid spacer 2964 are those of the materials described with respect to the spacer post 2708, including those listed in US patent application Ser. No. 11 / 361,785, incorporated herein by reference. Any of the materials described below with respect to the conductive spacer 3112 may be used.

  Spacers 2962 (also referred to as solder bumps) can be made of a variety of metals or alloys commonly used for soldering electrical connections. Exemplary alloys include, but are not limited to, Pb—Sn alloys, Pb—In alloys, In—Sn alloys, In—Cu—Sn alloys, Au—Sn alloys, Bi—Sn alloys, or substantially pure metals, In, Sn, Ga, or Bi can be given. Such alloys are designed to liquefy or reflow at temperatures in the range of 150 to 400 degrees Celsius and to wet the surfaces of two opposing contact materials. After cooling and solidification, the solder material joins (and optionally electrically connects) two opposing contact materials and acts as an adhesive. In the application illustrated by display assembly 2950, solder material 2962 serves as an adhesive link between spacer post 2964 and modulator substrate 2952. Non-metallic reflow materials are also applicable for use as the spacer 2962. These materials include glass frit materials such as barium silicate or lead silicate glass, or mixtures of thermoplastic polymers such as polyethylene, polystyrene, or polypropylene, and / or natural such as carnauba wax, paraffin or olefin wax. And synthetic waxes.

  The assembly process for display 2950 will proceed as follows. Initially, spacer materials 2962 and 2964 will be fabricated on each substrate. The two substrates 2952 and 2954 will then be combined with a generally appropriate lateral alignment. The two substrates will then be heated to liquefy or reflow solder material 2962. Once melted, the material 2962 will be substantially solid and will wet the surface of the opposing spacer post 2964. At the same time, the surface tension of the current liquid feed 2962 serves to minimize its surface area. The resulting capillary force has the effect of pulling or sliding the two substrates 2952 and 2954 laterally for a more complete alignment. After cooling and solidification, the two substrates are locked into alignment by the adhesion of the solder material 2962.

  In another embodiment, a substantially solid material can be made on the modulator substrate, while a heat reflowable material is made on the aperture plate. In another embodiment, both the solid material and the reflow material are sequentially formed on one or the other of the modulator substrate or aperture plate. In this embodiment, the solder material is designed to wet and bond to the bonding pads located on the counter substrate.

  There are other adhesive arrangements that can use thermally reflowable materials to ensure alignment between opposing substrates. In one embodiment, solder bumps are made on both substrates, and bumps or beads of solder material are bonded or bonded during the reflow process. In this embodiment, a substantially solid spacer material such as spacer 2964 is not used. The gap between the two substrates is determined by the average solder bump volume after solidification. The average solder bump volume can be controlled by the size of the solder bumps produced before assembly. In another embodiment, the spacer post 2964 is replaced with a detent or solder receptacle structure such as a ring or square frame formed on one of the two substrates having a central recess. Molten solder tends to wet and fill the gap in the center of the ring, thereby pulling the opposing substrates into alignment. A similar process for semiconductor package alignment is described in more detail in US Pat. No. 5,477,086, which is hereby incorporated by reference in its entirety.

  In some embodiments, the thermally reflowable material is disposed within or between each pixel in the array. In other embodiments, pairs of reflow material and corresponding posts, receptacles, or connection pads on the opposing substrate can be placed at the periphery of the display or at the outer corner of the display assembly. When the reflow material is disposed at the periphery of the display, the reflow material may serve another purpose similar to epoxy 528 (see FIG. 5) as a sealant or gasket material in some embodiments.

  14A and 14B are top views of a display assembly 3000 similar to the shutter assembly 2200 of FIGS. 6A and 6B in an open position and a closed position, respectively, according to an illustrative embodiment of the invention. Display assembly 3000 includes a shutter assembly (including shutter 3002) supported above reflective aperture layer 3004. The shutter assembly also includes portions of opposing actuators 3008 and 3010. In display assembly 3000, the shutter is connected to a modulator substrate (not shown) such as modulator substrate 2342 via actuators 3008 and 3010 and anchors 3006 and 3007. The reflective aperture layer 3004 is formed on a separate substrate such as the aperture plate 2346. The shutter assembly 3001 is suitable for inclusion in a light modulator array included in a display device.

  The shutter 3002 includes three shutter apertures 3012 through which light can pass. The remaining part of the shutter 3002 obstructs the passage of light. The reflective aperture layer 3004 also includes an aperture 3014 that allows light to pass therethrough. In FIG. 14A with the shutter in the open position, apertures 3012 and 3014 are aligned to allow light to pass. In FIG. 14B with the shutter in the closed position, shutter 3002 blocks the passage of light through aperture 3014.

  Display device 3000 includes spacer posts 3020 that function similarly to spacer posts 2357 of display device 2340 that maintain a predetermined gap or spacing between opposing substrates. However, the spacer post 3020 provides an additional function that ensures proper alignment between the shutter 3002 and the aperture 3014 by fitting between the detents 3022 that are solid extensions of the shutter 3002. When in the open position, the shutter 3002 is in firm contact with the spacer post 3020 through a set of detents. When in the closed position, the shutter 3002 contacts the spacer post 3020 again via another set of detents 3022. The amount of momentum allowed for the shutter 3002 between each stop position ranges from about 5 microns to about 50 microns in various embodiments.

  The alignment control method of the display assembly 3000 is such that both the aperture 3014 and the spacer post 3020 are attached to one substrate (for example, the aperture plate), and the shutter 3002 is attached to another substrate (for example, the modulator substrate) by the anchor 3007. It is effective. In such an embodiment, proper alignment between the shutter 3002 and the aperture 3014 can be achieved even with as little as 5 microns or 10 microns misalignment during assembly of the two substrates. Thus, a narrow shutter / aperture overlap of about 1 micron (for example, the overlap W1 in the display device 2300) can be maintained.

  FIG. 15 is a cross-sectional view of a display assembly 3100 according to another exemplary embodiment of the present invention. Display assembly 3100 includes a modulator substrate 3102 and an aperture plate 3104. The display assembly 3100 also includes a set of shutter assemblies 3106 and a reflective aperture layer 3108. Further, the aperture plate 3104 includes a dielectric insulating layer 3114 and conductive wiring 3116. The cross-sectional view of FIG. 15 is taken along a line in the reflective layer 3108 where no aperture hole exists. A predetermined gap or separation between the substrates 3102 and 3104 is maintained by a set of spacers 3112.

  The spacer 3112 of the display assembly 3100 includes a conductive material. For example, the spacer 3112 can be formed using a metal post formed by an electroplating process, an etching process, or a lift-off process. Without limitation, copper, nickel, aluminum, gold, or titanium metal is useful for this application. Alternatively, post 3112 can be formed of a composite material, such as a polymer or epoxy material impregnated with metal particles to provide electrical conductivity. Alternatively, the post 3112 can be formed of a polymer material covered with a thin metal film so that the surface is conductive.

  The conductive spacer 3112 is arranged to provide an electrical connection between one electrode of the shutter assembly 3106 and the conductive wiring 3116. For example, as shown in FIG. 15, the wiring 3116 can be patterned as a metal wiring parallel to one of the rows or columns in the display. The spacer 3112 and the wiring 3116 then provide a common electrical connection between the electrodes in all the shutter assemblies 3106 in a given row or column. In this way, a portion of the metal layer used to form the addressing or control matrix of a display such as display device 2340 is fabricated on the aperture plate 3104 rather than on the modulator substrate 3102. Can do. The spacers 3112 can be configured to provide individual electrical connections between the light modulators 3106 in each pixel in the array to electrical circuits on the opposing substrate. In the extreme case, each electrode of each shutter assembly is conductive so that the entire control circuit (including transistors and capacitors) is formed on a substrate separate from the light modulator, ie on a substrate remote from the light modulator. It may be connected to a circuit on the opposite substrate by a spacer post.

  The conductive spacer posts 3112 can be formed on the modulator substrate 3102 or the aperture plate 3104 prior to the assembly process. In one embodiment, the conductive spacers are formed of gold alloy studs that are individually placed and bonded by machine on one or the other of the substrates 3102 or 3104 as part of the assembly process. In another embodiment, the spacers are formed with solder bumps that are electroplated or tensled on one or the other or both of the substrates 3102 or 3104 as part of the assembly process. Any of the above solder materials for the solder bumps 2962 can be used for the spacer posts 3112.

  The processing of alignment or electrical connection between the spacer posts and the land areas on the counter substrate may include a reflow process such as interdiffusion or soldering so that a good electrical connection is made between the two surfaces.

  Although the display assembly 3100 is illustrated as part of a MEMS down configuration, similar uses for conductive spacer posts can be found in the MEMS up configuration as well as the display device 2300, for example. In the MEMS up configuration, both the light modulator and the reflective aperture layer are formed on the same substrate, and the conductive wiring such as the wiring 3116 is formed on a counter substrate such as a cover plate. At this time, a conductive spacer, such as spacer 3112, will form an electrical connection between the modulator substrate and the cover plate. The present invention is particularly useful for applications where the cover plate also acts as a touch screen input device. In particular, an electrical connection between substrates in which a connection is provided for each pixel in the array is useful for providing an electrical connection between the touch screen sensor array and another substrate that includes a control matrix for the pixel array. .

  FIG. 16 is a cross-sectional view of another display assembly 3200 according to an exemplary embodiment of the present invention. Display assembly 3200 includes a modulator substrate 3202 and an aperture plate 3204. The display assembly 3200 also includes a set of electrical wirings 3210 formed on the modulator substrate and a set of electrical wirings 3212 formed on the aperture plate 3204. The two substrates electrically connect the wirings 3210 and 3212 with an anisotropic conductive adhesive 3214. The aperture plate also includes a dielectric insulating layer 3211 and a reflective aperture layer 3208. Since this cross-sectional view is taken along a line near the periphery of the display outside the pixel array, the shutter assembly formed on the substrate 3202 or any aperture window in the reflective layer 3208 is not shown in this view.

  Anisotropic conductive adhesive (or “ACA”) 3214 is a polymer adhesive impregnated with solid conductive ball group 3216. When the two substrates 3202 and 3204 are pressed against each other, the conductive sphere is trapped between the contact surfaces of the wirings 3210 and 3212. As a result, electrical connection between the wirings 3210 and 3212 on the counter substrate is set. The electrical connection is locked in place after the ACA polymer matrix is cured or polymerized. The conductive sphere 3216 may have a size in the range of 5 to 50 microns in diameter. The conductive sphere 3216 can be made of a metal such as nickel or an alloy such as Ni—Au, Ni—Ag, or Cr—Au. Nickel has sufficient hardness to maintain its geometric shape under compressive loading. The conductive sphere can also be made of a dielectric material such as glass or polymer and covered with a conductive layer such as gold. In another embodiment, a metal sphere such as nickel can be covered with another metal having higher conductivity and oxidation resistance, such as gold, to reduce contact resistance.

  When the conductive spheres are selected to have a uniform diameter, the contacts 3210 and 3212 are crushed into the conductive spheres 3216 to set a constant spacing or gap between the contacts. Accordingly, the conductive sphere 3216 can perform the same function as the spacer 2312 or 2357.

  The conductive sphere does not form a continuous contact along an axis parallel to the substrate plane. As a result, electrical connections are typically not established between adjacent conductor 3210 pairs or conductor 3212 pairs. Thus, a single application of ACA 3214 is considered sufficient to make multiple independent electrical connections between independent sets of wires 3210 or 3212. This particular wiring medium is referred to as an anisotropic conductive medium.

  ACA 3214 is typically attached across multiple independent electrical contacts by a tape or needle dispenser. The ACA 3214 is particularly useful for making multiple connections along the periphery of the display. For example, ACA 3214 can connect a series of row wirings on one substrate together to a set of parallel row wirings on another substrate. This is probably useful when the driver chip is attached to a set of parallel wires on the aperture plate 3204 and the control matrix is built on the modulator substrate 3202. The functions of the substrates 3202 and 3206 may be reversed so that the modulator substrate is on the bottom closest to the backlight and the substrate opposite the ACA 3214 functions as a cover plate.

  Conductive spacers 3112 in display assembly 3100 are preferably used in all pixels in the array, but may be attached to the periphery of the array. Conductive spheres 3216 (which are also spacers) in display assembly 3200 are preferably attached along the periphery of the pixel array. The spacer 3020 (which functions as a detent) of the display assembly 3100 is preferably used at every pixel in the array. The spacers 2312 or 2357 of the display devices 2300 and 2340, respectively, can be placed within or between each pixel of the array. Similarly, the spacers shown in FIGS. 20 and 21 of US patent application Ser. No. 11 / 361,785 may also be included in every pixel in the array.

  However, it is not necessary to associate spacers with all pixels in order to maintain the desired gap between the substrates. The spacer may be associated with, for example, each group of 4 pixels or each group of 16 pixels. In other embodiments, the spacer could be limited to the periphery of the display. Alternatively, as shown in display assembly 3000, the display assembly may include multiple spacers per pixel.

  The spacer 2357 in the display device 2340 plays a role of maintaining the aperture at a shutter interval H6 (which may be about 1 micron), for example. A high density spacer arrangement is particularly useful when the display resolution exceeds 200 pixels per row or column or when the display diagonal exceeds 2 inches. The dense spacer array also helps to maintain a uniform pressure in the display device 2300, for example on the lubricating fluid 2322 applied to the front of the display (otherwise it can be disturbed by local pressure such as finger pressure). .

  The spacers described with respect to the present invention are usefully applied to maintain a gap between substrates in an electrowetting display such as display device 2500 or 2600. Any display that utilizes a MEMS-based light modulator can in fact benefit from spacers applied inside the light modulator array. Examples of alternative MEMS-based light modulators include a digital mirror device (DMD), an interferometric modulation display (IMOD), a light tap display, or an attenuated total reflection display (frustrated display). reflection display).

Alignment Device and Alignment Technique As shown in the discussion of display devices 2300 and 2340 and shutter assembly 2200, the alignment of the shutter assembly and its corresponding aperture is an important design feature of a MEMS light modulator. The overlap shown as overlap 2216 or overlap W1 and W2 reduces or eliminates light leakage while the MEMS light modulator is in the closed state (also referred to as the light blocking state or dark state). In the MEMS down display device 2340, the overlap W2 is set during the cell assembly process where the two substrates 2342 and 2346 are aligned and mechanically attached to each other. In the display device 2340, the aperture 2347 is formed on the aperture plate 2346, and the shutter assembly 2341 is formed on or supported by the modulator substrate 2342. If a means for accurate alignment of the two substrates 2342 and 2346 can be provided, an appropriate spatial relationship between the aperture 2347 and the shutter assembly 2341 can be achieved with high accuracy. One method for alignment of two substrates according to an exemplary embodiment of the present invention is possible with alignment apparatus 3300 as illustrated in FIG.

  The alignment device 3300 includes a fixed chuck 3302, a set of translational drives or motors 3304, a vision system 3305, and a set of UV exposure lamps 3306. The modulator substrate 3308 is firmly attached to the chuck 3302. The aperture plate 3310 is held at a predetermined position and is guided by the motor 3304. The motor 3304 translates the substrate 3310 in three translational directions, eg, along the x and y coordinates in the plane of the substrate 3310 and further along the z coordinate to set and change the distance between the two substrates 3308 and 3310. Give the ability to. Further, although not shown in FIG. 17, it is possible to provide an additional and optional set of three rotary motors that ensure both the coplanarity of the substrates 3308 and 3310 and their proper rotational relationship in the xy plane. it can. Although all the translation motors 3304 are shown attached to the aperture plate 3310, in other embodiments the motors may be arranged differently between the two substrates. For example, an xy translation motor may be attached to the aperture plate 3310, and a Z-axis translation motor and a theta rotation motor (centered on the Z-axis) may be attached to the chuck 3302.

  Various types of motors can be used for the motor 3304. These motors may be digitally controlled stepping motors in some embodiments, in some cases linear screw drives, and in other cases magnetically driven solenoid drives. . The motor need not be arranged to move a substrate, such as substrate 3310, directly. Instead, the motor may be designed to move a stage or platter onto which the product or substrate 3310 being processed is rigidly attached. The use of a moving stage is advantageous because an additional optical measurement system (in some cases a laser interference system) can be provided on the stage that can continuously measure its translational position with a high accuracy of less than 1 μm. At this time, feedback electronic circuitry can be utilized between the motor 3304 and the optical measurement system to improve both the accuracy and stability of the stage position.

  In some embodiments of the apparatus 3300, both the chuck 3302 and the optional translation stage may include heaters and / or temperature control elements to ensure a uniform temperature across the substrates 3308 and 3310. Especially for substrates whose diagonal exceeds about 20 centimeters, the uniform temperature helps to ensure proper alignment between the patterns on the two substrates.

  The alignment device 3300 includes a vision system 3305 for detecting the relative positions of the two substrates 3308 and 3310. In a preferred embodiment, alignment marks are patterned into a thin film on each of substrates 3308 and 3310 (see, eg, alignment marks 3408 and 3412 in FIG. 18). The vision system can image the alignment marks on each of the two substrates simultaneously, even though the marks are located on different surfaces, i.e. on the z-axis.

  In the illustrated embodiment, the vision system 3305 incorporates two imaging lenses 3312 and 3313 and either a microscope capable of split field imaging or two cameras 3314 and 3315. Accordingly, the vision system 3305 can image two sets of separate alignment marks substantially simultaneously. The two sets of alignment marks are preferably located on the far side or corner of the modulator array or panel.

  In operation, the operator uses the vision system 3305 to see the relative position of alignment marks such as marks 3408 and 3412, thereby determining the direction and extent of misalignment between the two substrates. At this time, the operator can adjust the alignment between the substrates 3308 and 3310 using the drive motor 3304 until the alignment marks on the two substrates show a misalignment that is less than or equal to an allowable error. After sufficiently reducing misalignment, the operator turns on the Z-axis motor until the spacer on substrate 3308 or 3310 (either spacer 2357, 2708, or 2812 and 2814) is in contact with counter substrate 3308 or 3310 or counter spacer. To drive. In many cases, the misalignment or non-planarity of the substrate requires the operator to constantly fine tune the xy alignment between the substrates as the Z-axis distance between the two substrates decreases. In some embodiments, final x, y and theta corrections can be made even after connections are set up between boards. After being connected, the adhesive 3318 also makes a connection between the two substrates. In some embodiments, as a final step in method 3301, the adhesive is at least partially cured while alignment device 3300 holds the two substrates in place. A UV exposure lamp 3306 can be used to initiate or accelerate the curing of the adhesive, thereby bonding the two substrates together. In some embodiments, the substrate stage or chuck 3302 includes a heater for thermally curing the adhesive 3318. Alignment marks such as marks 3408 and 3412 are typically patterned and etched simultaneously and printed with the same photomask as the mask used to pattern the aperture, such as aperture 2347, and the shutter assembly, such as shutter assembly 2341, respectively. Therefore, the alignment mark is designed for the reference function. That is, an operator who achieves sufficient alignment between alignment marks is reliable that the shutters and apertures in adjacent arrays are also properly aligned.

  According to the consideration of the display device 2340, the overlap W2 is preferably 2 μm or more. In practice, the overlap W2 that is reliably realized during manufacture is determined by the safety margin designed in the mask and by the alignment accuracy or tolerance. The accuracy or achievable tolerances are based on process variables such as alignment device 3300 design, alignment mark design, temperature, pressure, sealant viscosity or plasticity. Two examples of acceptable tolerance designs are given below. In a first example that withstands relatively wide variations in alignment during manufacturing, the shutter and aperture array is designed with a nominal 22 μm overlap, ie, when fully aligned, the shutter overlaps the aperture by 22 μm. Designed. At this time, if the device 3300 allows +/− 20 μm alignment repeatability, the designer will have all of the shutters (or 99.99% depending on how reliability is specified) at least 2 μm. It is guaranteed that they have an overlap. However, for high density pixel arrays or high resolution displays, there is usually no margin available in 22 μm overlapping array designs. Therefore, more accurate alignment capability is desired.

  In the second example, a nominally only 1 μm overlap is provided in the mask and the device 3300 is designed to provide an alignment accuracy within +/− 1 μm between the patterns on the first and second substrates. To achieve this accuracy, a) the vision system 3305 has a resolution of less than 1 μm, and b) the motor 3304 (or the associated translation stage) is stable to discriminate position differences with a resolution of less than 1 μm. C) The alignment mark is patterned and etched with precise edges, dimensions and / or placement with a resolution of less than 1 μm. Automatic alignment devices with sub-micron accuracy are now available for semiconductor mask alignment, optoelectronic assembly, and micromedical device purposes. Representative suppliers of these systems include Automation Tooling Systems Corp. of Cambridge, Ontario, Canada and the Physik Instrument LP of Karlsruhe, Germany.

  In general, if attention is paid to the design of the vision system and the drive motor, and the design of the alignment mark, the alignment device 3300 and the alignment that can guarantee an overlap W2 of more than 0 μm and less than 20 μm between the shutter 2341 and the aperture 2347 It is possible to provide a method. In a preferred design, the alignment method can guarantee an overlap W2 of greater than 0 μm and less than 2 μm.

  The alignment method is provided as an example of an alignment method that assigns active control of the motor 3304 to a human operator. In other methods, no operator intervention is required to achieve alignment. A device that can measure not only the amount of misalignment between the references on the two substrates but also the direction, and can automatically drive the motor 3304 until the measured misalignment is below a predetermined level. An intelligent vision (machine vision) system for 3300 (ie, a system that includes a digital camera and computer image processing) is available, for example, from the vendors listed above.

  The alignment marks or references utilized in apparatus 3300 can take many forms other than those shown or discussed with respect to FIG. 18 below. In some embodiments, an operator or machine vision system can recognize a particular functional pattern on the substrate, such as the shape of a shutter assembly (eg, shutter 2202) or aperture (eg, aperture 2214). This allows the vision system to directly measure and minimize misalignment between the shutter and the aperture. In another embodiment, the edge of the display is cut or diced to an exact location relative to the shutter and aperture positions. This causes the vision system to measure and minimize misalignment between the edges of the two substrates.

  A UV exposure lamp 3306 can be used to at least partially cure the adhesive 3318 after a human operator or automatic alignment device aligns the substrates and establishes a connection between the two substrates. The adhesive 3318 prevents relative movement between the substrates 3308 and 3310 after alignment is achieved in the device 3300. Alternative means are available for maintaining alignment between the two substrates after alignment. These alternatives include the use of alignment guides such as alignment guide 2914 and thermally reflowable spacer materials such as spacer 2962.

  Although the functionality of the alignment device 3300 has been with respect to the example of a display 2340 in a MEMS down configuration, similar alignment techniques are useful when applied to a MEMS up configuration as illustrated by the display device 500. In display assembly 500, shutter assembly 502 is formed on substrate 504 and black matrix and associated aperture 524 are formed on substrate 522. By using the alignment device 3300 such that there is an overlap between at least one edge of the shutter 503 and the edge of the corresponding aperture in the black matrix 524, the two substrates 504 and 522 can be aligned. The alignment device 3300 ensures an overlap between 0-20 micron edges. In a preferred design, this alignment method ensures an overlap that is greater than 0 microns and less than 5 microns, or in some cases less than 2 microns.

  Although the functionality of the alignment device 3300 has been described with respect to a display incorporating a transverse shutter-based light modulator such as the shutter assembly 2341, the alignment device 3300 and alignment method can be usefully applied to alternative MEMS light modulator technologies. It will be understood. For example, if the aperture plate 2632 is aligned with the modulator substrate 2630 such that the overlap is set between the edge of the oil 2610 and the edge 2617 in the light blocking, filtering, or dark state, the electrowetting modulator The array 2600 has advantages. Similarly, a rolling actuator light modulator such as light modulator 220 (overlapping between the light blocking edge of the roller actuator modulator on the first substrate and the edge of the patterned corresponding aperture on the second substrate). Can be prepared and aligned in a similar manner.

  Other non-shutter based modulators can benefit from the alignment apparatus 3300 and method described above. For example, a MEMS interferometric modulator or MEMS optical tap modulator, such as optical modulator 250 made on a first substrate, can be aligned to the edge of a black matrix made on a second substrate. Details of these light modulators can be found in US Pat. No. 6,674,562 and US Pat. No. 5,771,321, which are hereby incorporated by reference.

Panel fabrication process Manufacturing productivity can always be improved if modulator arrays for multiple displays can be built in parallel on the same glass or plastic substrate. Large glass substrates, called panels, and their associated fabrication equipment are available today in dimensions up to 2 meters square. FIG. 18 illustrates how multiple MEMS light modulator arrays can be formed on one large modulator substrate 3402 while multiple aperture hole arrays are formed on a large aperture plate 3404 in accordance with an exemplary embodiment of the present invention. Show if you can. Panel 3402 includes a set 3406 of four modulator alignment marks in addition to a set 3406 of six modulator arrays. Panel 3404 includes a set 3410 of six aperture arrays in addition to a set 3412 of four aperture alignment marks. Each of the modulator arrays 3406 of the aperture array 3410 is such that when the panels 3402 and 3404 are aligned and sealed, each of their corresponding modulator array-aperture array pairs form a display assembly (also referred to as a cell assembly). Designed to accommodate one. Thus, a single alignment and sealing operation between the substrates 3402 and 3404 is sufficient to simultaneously align and seal the six cell assemblies. In the example shown in FIG. 18, glass panels 3402 and 3704 will be 30 cm diagonal, and each cell assembly or display area will be 10 cm diagonal. In other embodiments, 50 cm diagonal panels or more can be utilized to make up to 25 10 cm diagonal displays per panel.

  Also shown are epoxy adhesive 3414 lines (a type of sealing material) and spacer posts 3416 added to each of the arrays on the aperture plate 3404. Various spacers are applied to the interior of each array on the aperture plate 3404 as described with respect to the display assemblies 2340, 2700, 2800, 2900, 3000, 3100, 3200. The process of applying the adhesive will be described later with respect to the cell assembly step 3614.

  FIG. 19 illustrates a panel assembly 3500 after alignment and sealing of the panels 3402, 3404, according to an exemplary embodiment of the present invention. Successful alignment of the two substrates is indicated by the nesting of the modulator alignment mark 3408 within the aperture alignment mark 3412. The alignment mark may be designed such that a nominal 1 μm gap is allowed between the inner edge of mark 3412 and the outer edge of mark 3408 (the size of these gaps is exaggerated in FIG. 19 for purposes of illustration). . In this alignment design, the operator and / or the automatic alignment device allows the substrate to remain in place until the appropriate gap is visible in both the x and y directions of the nested alignment mark (eg, until none of the lines cross or touch). The relative position is adjusted with the tool 3300. If the appropriate gap is visible, the alignment is considered successful (ie, misalignment has been reduced to within tolerances and the expected overlap between the modulators and apertures in each of the arrays 3406, 3410 has been achieved). The nominal gap between alignment marks can be designed to meet the expected accuracy of the alignment process. For example, the gap is 10 microns, 2 microns, or 1 micron depending on the desired alignment accuracy. In an alternative design, one alignment mark is a circular dot and the other mark is formed as a ring. A gap can be designed between the dot and the ring that corresponds to the desired alignment accuracy. In some alignment mechanical designs, gaps between alignment marks are not required, but instead the machine uses a digital camera to estimate the center points of both the dots and rings. At this time, the alignment software tries to align the center points of the dot and ring.

  The two panels 3402 and 3404 are bonded in place with an adhesive. This curing of the adhesive is described below with respect to the cell assembly process 3620.

  FIG. 19 also illustrates a set of dicing lines 3502 overlaid on the panel assembly 3500. Dicing lines 3502 mark the lines along which the panel is cut so that individual arrays (also referred to as displays or cell assemblies) are cut from the panel. The separation step, also referred to as unification, can be performed by a scribe and break method. In this process, a diamond tip or carbide tip is used to scratch the line 3502 along the surface of the glass panel. At this time, a simple bending process can be used to break the panel along the scribe line. In another embodiment, the separation or singulation process is performed by a dicing saw. Both substrates 3402 and 3408 need not be cut along the same dicing line. It is often advantageous that the modulator substrate be diced to a wider peripheral width than that defined for the aperture substrate. This provides a space for driver chip bonding on the edge of the modulator substrate after cell assembly is complete.

FIG. 20 illustrates a first method 3600 (also referred to as a cell assembly method 3600) for assembling a display device incorporating a MEMS light modulator, according to an exemplary embodiment of the present invention. Illustrate. The method 3600 begins with providing two substrates (steps 3602, 3604) on which display components are to be fabricated (steps 3606, 3608, 3610). The method continues to apply a spacer (step 3612) and a sealant (step 3614) to one or both of the two substrates. At this time, the substrates are aligned and bonded to each other. The method includes separating or singulating individual displays from the large panel assembly (step 3622) and filling the gap between the two substrates with a fluid or lubricant (step 3624). Finally, the filling hole is sealed (step 3626).

  A first embodiment of the method 3600 will be described with respect to a MEMS down display assembly as illustrated by display device 2340 or 2600. A second embodiment for the assembly of a MEMS up configuration display will be described later.

  The cell assembly method 3600 for MEM down display begins by providing two substrates at steps 3602 and 3604. Both of these substrates are transparent and made of glass or plastic. The assembly method continues with the creation of the control matrix at step 3606 and the fabrication of the MEMS modulator array at step 3608. In a preferred embodiment, both the control matrix and the modulator array are fabricated on a first substrate called the modulator substrate. Examples of this include the substrates 2342 and 2630 of FIGS. 7 and 10, respectively. However, as discussed with respect to display assembly 3100, there are embodiments in which the control matrix can be fabricated on a substrate separate from the modulator substrate, and the control matrix can be connected to the modulator substrate by a conductive spacer. To do. Further details regarding the fabrication of this modulator substrate can be found in US patent application Ser. No. 11 / 361,785 referenced above.

  The MEMS down assembly method 3600 proceeds to step 3610 which includes creating an aperture layer. The aperture layer is preferably made of a transparent material (eg plastic or glass) and is made on the second substrate. In the MEMS down configuration, the second substrate is called an aperture plate. Exemplary useful plates include the aperture plate 2346 or 2632 of FIGS. In other MEMS down embodiments, the second substrate on which the aperture layer is made is also used as an optical waveguide. In some embodiments, the aperture layer consists of a light absorbing material that is patterned into a series of apertures. In the preferred embodiment described with respect to aperture plate 2700, the aperture layer is designed to reflect light incident from the substrate back to the substrate. Exemplary reflective aperture layers include the reflective aperture layers 2616 or 2704 of FIGS. 10 and 11, respectively.

  The method 3600 continues at step 3612 including applying a spacer. All of the spacers exemplified by spacers 2357, 2708, 2812, 2814, 2912, 2914, 2962, 2964, 3020, or 3112 (and thus including the fabrication methods described) can be incorporated at step 3612. The spacer may be formed on either or both of the first and second substrates.

  The method 3600 continues at step 3614 including applying a sealant, such as an epoxy sealant 528. The sealant may be applied to either or both of the first and second substrates used in method 3600. The sealing material is an adhesive that maintains the positions of the first and second substrates after the alignment process. The seal is also used to contain fluid (added at step 3624) in the gap between the two substrates. The applicable sealing material may be a polymer material such as an epoxy, acrylate, or silicon material, or the sealing material may be formed of a thermally reflowable solder metal such as a solder bump 2962. In some embodiments, the sealing material may be a composite material such as anisotropic conductive adhesive 3214. The sealant can be dispensed from nozzles that move along the respective periphery of the modulator or aperture array, as shown with respect to the display panel 3404 of FIG. The sealant 3414 does not completely surround the periphery of each display area on the display panel 3404. A gap 3418, referred to as a fill hole, is intentionally left in the peripheral seal to accommodate the fluid filling of the cell in step 3624.

  After the distribution, the sealing material becomes relatively strong through a curing process. As part of step 3614, the sealant may be partially cured, but in many embodiments, final curing is not performed until one of the subsequent steps 3618 or 3620. The sealant can be formulated to allow many other types of curing, including dehydration curing, UV or ultraviolet curing, thermal curing, or microwave curing. When using an alignment tool such as apparatus 3300, a UV curable epoxy resin may be preferred.

  As shown in FIGS. 18 and 19, the processes for the fabrication of the control matrix 3606, the fabrication of the MEMS modulator 3608, the fabrication of the aperture layer 3610, the coating of the spacer 3612, and the coating of the sealant 3614 are all performed by a plurality of displays. Can be done at the panel level, where they are made simultaneously on large glass or plastic panels. Alternatively, these steps may be performed for each individual display on a small substrate. Further details of the fabrication of assembly steps 3606, 3608, 3610, 3612 can be found in US patent application Ser. No. 11 / 361,785 referenced above.

  Method 3600 continues at step 3616 with optional dispensing of conductive adhesive. If the spacer or sealant added at steps 3612 and 3614 does not have conductive properties, it is often advantageous to add additional adhesive with this property. The conductive adhesive added at step 3616 allows electrical connection between the control matrix on the first substrate and the aperture layer on the second substrate. The adhesive added at step 3616 is typically placed at several points along the periphery of the display area.

  The method 3600 continues at step 3618, which includes aligning the first and second substrates as described with respect to the alignment apparatus 3300 of FIG. Alignment apparatus 3300 includes a camera and / or microscope system for confirming that the alignment is accurate to within tolerances. The first and second substrates are connected by spacers as part of the alignment step 3618.

  As part of the alignment step 3618, the adhesive is at least partially cured to bond the two substrates or maintain their relative positions. Alignment apparatus 3300 includes a heater and / or UV exposure lamp that provides curing of the adhesive. In some embodiments, the entire peripheral seal, such as seal 3414, is at least partially cured as part of step 3618. In other embodiments, a plurality of UV curable adhesive dots are provided on the substrate prior to alignment in addition to the thermosetting sealant 3414. In this embodiment, only the epoxy dots are cured as part of the alignment step 3618 and the remainder of the sealant is cured in a later step 3620.

  Method 3600 continues to step 3620, which includes curing the sealant. In many embodiments, proper alignment between the first and second substrates can be maintained only when the sealant acts as a relatively hard adhesive. The adhesive is cured in step 3620 to ensure the rigidity of the sealant. Curing at step 3620 can be performed as thermal curing, UV curing, or microwave curing. In some embodiments, the sealant is cured in step 3620 by placing the assembly in an oven or by UV or microwave exposure system under pressure or between plates of a press. Pressing helps to minimize bending or warping of the substrate while the adhesive is cured. Pressurization helps to ensure that a gap, such as gap H5 or H9 (shown with respect to display assemblies 2340, 2390), is maintained by ensuring a firm contact of each substrate to the spacer (such as spacer 2357).

  The method 3600 continues at step 3622 including optionally separating individual display arrays from a large panel that includes a plurality of arrays. Such separation is only required if the cell assembly process has progressed to this point according to the large panel process as described in FIGS. If the modulation substrate and aperture plate are made as individual displays in steps 3606-3614, no singulation or separation steps are necessary. This separation can be realized by a scribe and break process or a dicing saw.

  The method 3600 continues at step 3624 with filling the display assembly with fluid. As shown in the discussion of display devices 500 and 2340, the two substrates of the display device are preferably separated by a gap, such as gap H5, which is filled with a fluid, such as working fluid 530 or 2352. In many displays, the fluid acts as a lubricant that substantially surrounds the MEMS light modulator. This fluid also defines the electrical and optical properties as discussed above.

  In many applications, it is desirable to fill the display assembly with liquid while avoiding air bubbles entering the gap formed between the two substrates. Bubbles formed on the surface of the MEMS light modulator interfere with the operation of these modulators. The bubble-free filling process can be performed by utilizing a vacuum atmosphere at some point during the fluid filling process.

  Details of the fluid filling process (step 3624) are described with respect to the fluid filling device 3700 illustrated in FIG. 21 according to an exemplary embodiment of the invention. The fluid filling device is formed by a vacuum chamber 3702 that is partially filled with a reservoir of working fluid 3704. An aligned and partially sealed cell assembly or panel assembly, such as panel assembly 3500, is suspended over a fluid reservoir by a wand 3706 or by a movable platter. A port 3708 leading to the vacuum pump and a port 3710 used to vent the vacuum chamber to atmospheric pressure are attached to the vacuum chamber. Although not shown in FIG. 21, a valve is coupled to each of ports 3708 and 3710.

  In operation, filling the gap between substrates in a panel assembly such as assembly 3500 is a two-step process. First, air or other gas is removed from between the two plates and then the gap is filled with fluid. When the valve to the vacuum pump is opened, air is removed from between the plates and the entire chamber 3702 is reduced to a pressure substantially below 1 Torr. The vacuum valve is then closed and the wand 3706 is used to immerse the panel assembly 3500 in the working fluid reservoir 3704. Once soaked, the vent valve is opened to the atmosphere or opened to remove nitrogen or argon gas from the bottle. Returned air brings the pressure on all fluids to atmospheric pressure (or pressure above 600 Torr). Under pressure, the working fluid is then introduced into the gap between the substrates of the cell assembly 3500. When the cell assembly is removed from the chamber 3702, the cell assembly is filled with fluid, thus completing the assembly process 3624.

  In an alternative design, panel assembly 3500 need not be suspended by a movable wand such as wand 3706. Alternatively, the panel assembly can be secured in place and the lubricant 3705 can be moved into or out of the vacuum chamber 3702 by a series of valves. The chamber is evacuated until fluid is almost gone from the chamber. After evacuation, the fluid level in the chamber is increased by flowing additional fluid through the chamber. The fluid is added until the assembly 3500 is immersed in the fluid. After immersing the panel in fluid, the system is vented to atmospheric pressure to fill the gap with fluid.

  In another embodiment, chamber 3702 is not filled with a liquid, such as liquid 3704, but instead chamber 3702 is backfilled with gas after being evacuated. Examples of gas to be refilled include an inert gas (argon, nitrogen), a gas phase lubricant, a specific reactive gas, or any combination of the above. The reactive gas is a gas that can react with the moving surface of the MEMS modulator or a gas that can be deposited thereon. The reactive gas can chemically reduce or reduce the adhesiveness of the moving surface by reducing the interfacial energy. Examples include, but are not limited to, dimethyldichlorosilane (DDM), tridecafluoro-1,1,2,2-tetrahydrooctyltrichlorosilane (FOTS), heptadecafluoro-1,1,2,2- Tetrahydrodecyltrichlorosilane (FDTS) is mentioned. Vapor phase lubricants are gases that remain substantially in the gas phase throughout the operation of the device and can similarly soften the surface. Examples include, but are not limited to, sulfur hexafluoride and methanol, ethanol, acetone, ethylene glycol, glycerin, silicone oil, fluorinated silicone oil, dimethylsiloxane, polydimethylsiloxane, hexamethyldisiloxane, and diethylbenzene. Gas phase form, or any mixture of the above.

  The fluid filling process in chamber 3702 may be performed at the cell level or the panel level. In the assembly process 3600, the unification process 3622 precedes the fluid filling process 3624. This means that cell assemblies for individual displays are loaded into the vacuum chamber 3702 for fluid filling. The vacuum chamber 3702 can include platters that can hold and immerse multiple individual displays in a single pump-down operation such that multiple displays are filled with fluid simultaneously. Alternatively, the order of these steps can be reversed to load a complete panel assembly, such as assembly 3500, into the vacuum chamber. At this time, the gaps in each of the displays on the panel are simultaneously evacuated and filled. Next, after the fluid filling step 3624 is complete, a dicing or singulation process 3622 begins.

  The cell assembly is completed at step 3626 of method 3600 including sealing the fill hole. The fluid entered or was introduced into the space between the substrates in step 3624 through the fill hole 3418 left in the peripheral seal at step 3614. This hole is filled with an adhesive at the end of the assembly process to prevent fluid leakage from the display assembly. As part of step 3626 and prior to sealing the filler hole, pressure can be applied to the cell via a pressurizer. In the pressurization, two substrates are pressed, and a spacer manufactured on one substrate is brought into close contact with the other substrate. This sets a uniform gap or spacing between the two substrates. The fill hole 3418 is then sealed with an adhesive prior to removing pressure from the display. Once sealed, the sealed and fluid filled chamber within the cell prevents the substrate from separating under ambient conditions. The adhesive used in step 3626 may be a polymer adhesive that is cured by using thermal curing, UV curing, or microwave curing. The final process of assembling the display after the end of method 3600 is often referred to generally as the module assembly process. Module assembly includes attaching one or more silicon chips including control and drive circuits directly to the glass substrate, bonding flexible circuitry to interconnect the display and external devices, and bonding optical films such as contrast filters. A step of attaching a backlight, and a step of mounting the display in a support structure or a housing. The flexible circuit may consist of simple wiring or may include additional electrical elements such as resistors, capacitors, inductors, transistors, or integrated circuits.

  The cell assembly method 3600 applied to the MEMS up-display configuration is scrutinized below. An example of that is given by the display assemblies 500 and 2400 of FIGS. In the MEMS up-display configuration, both the control matrix and the MEMS modulator array are fabricated on the first substrate at steps 3606 and 3608. This embodiment is provided as a modulator substrate 504 or 2418. An aperture layer is deposited on the second substrate at step 3610.

  As discussed with respect to the display assembly 3100, there are embodiments in which the control matrix can be fabricated on a second substrate while the MEMS modulator array is fabricated on the first substrate. The two substrates are in electrical communication with a conductive spacer.

  In the MEMS up display configuration, the second substrate is referred to as a cover plate (such as a cover plate 522). The aperture layer produced in step 3610 is called a black matrix layer (such as black matrix 524) and is patterned into an aperture array. The black matrix layer is preferably composed of a light absorbing material in order to improve the peripheral contrast of the display. After assembly, the black matrix aperture preferably overlaps the MEMS light modulator disposed on the modulator substrate.

  In the MEMS up display assembly method 3600, the cover plate, ie the second substrate provided in step 3604, is preferably made of a transparent material, ie plastic or glass. However, in the MEMS up-assembly method, the modulator substrate provided in step 3602 can be made of an opaque material such as silicon. For example, in a reflective MEMS up display, the first substrate (eg, silicon) can be covered with a reflective layer in step 3606 or 3608. In a transmissive MEMS up display, the opaque material used for the first substrate can be etched using a through-hole array of aperture locations, such as aperture 508.

  In MEMS up-display assembly 3600, the spacer is applied at step 3612 and the sealant is applied to the first or second substrate (ie, modulator substrate or cover plate) at step 3614.

  Subsequent steps in the MEMS up-display assembly method 3600 are the same as those in the MEMS down-display assembly method 3600, and include an alignment step 3618, a sealant curing step 3620, a step 3622 of separating individual displays from the panel, and a fluid filling step 3624. Including.

  As described with respect to alignment apparatus 3600, MEMS up or MEMS down assembly method 3600 is applicable to many alternative MEMS light modulator technologies, including electrowetting displays and rolling actuator displays. The MEMS up-display assembly method 3600 is particularly applicable to interferometric modulator displays and MEMS optical tap modulator displays.

  FIG. 22 illustrates an alternative method for assembling a display device incorporating a MEMS light modulator. The method 3800 may be employed to assemble a display in either the MEMS down configuration or the MEMS up configuration described with respect to the method 3600. Similar to method 3600, assembly method 3800 begins with providing two substrates (steps 3802 and 3804) from which display components are fabricated (steps 3806, 3608, 3810). The method 3800 continues with applying a spacer (step 3812) and a sealant (step 3814) to one or both of the two substrates. The method 3800 also includes filling a gap in the display assembly with a fluid (step 3118). However, in contrast to method 3600, the order of fluid filling (step 3818) and display assembly (steps 3820, 3822, 3824) is reversed. The assembly method 3800 is sometimes referred to as a one-drop fill method.

  The assembly method 3800 begins with providing first and second substrates (steps 3802 and 3804), creating a control matrix (step 3806), making a MEMS modulator array (step 3808), and making an aperture layer (step). 3810), followed by fabrication of the spacer (step 3812). These steps include substantially the same assembly steps used for the corresponding steps in assembly method 3600.

  The method 3800 continues to step 3814, which includes applying a sealant. As used in the sealing material application step 3612, a similar dispensing method and similar dispensing method can be applied in step 3814. However, at step 3814, no gaps or filling holes are left in the seal at the periphery of the active area of the display.

  An optional conductive adhesive application step 3816 follows similar to the adhesive application step 3616.

  The method 3800 continues at step 3818 with application of a liquid. Applicable liquids including lubricity and other electrical, mechanical and optical properties have already been described with respect to display device 500. In the liquid filling step (step 3800), a vacuum filling device such as the device 3700 is not necessary. An appropriate amount of fluid can be dispensed directly onto one open surface of the first or second substrate. Since this substrate generally does not have a MEMS component that includes a cavity or recessed surface where air bubbles may accumulate, it is preferred that the fluid be distributed onto the second substrate on which the aperture layer is formed. If the substrate is a large panel containing multiple displays, such as panel 3404, an appropriate amount of fluid is dispensed into the active area of each array. In general, the fluid spreads across the surface of the substrate until it is limited by the periphery of the sealant 3414. The appropriate amount of fluid completely fills the cavity defined by the peripheral seal. In some embodiments, an optical measurement tool is used to determine the exact volume per cavity prior to filling by measuring the actual peripheral dimensions of individual arrays on the panel.

  The method 3800 continues at step 3820 with the alignment of the two substrates. Since the lubricating fluid has already been applied to one of the substrates, the alignment apparatus required for step 3800 is different from that shown by apparatus 3300. As a fundamental difference, this alignment operation is preferably performed under reduced pressure or vacuum. This means that many of the moving and visual system components provided for alignment, as well as the first and second substrates, are now processed in a vacuum chamber (referred to as the alignment chamber). To do.

  In operation, the two substrates will be directed to the alignment chamber and the chamber will be evacuated. In order to prevent evaporation of the fluid (already dispensed at step 3818), the chamber may be refilled to the equilibrium vapor pressure of the lubricating fluid. After the two substrates are aligned and bonded, the lubricating fluid contacts the respective surfaces of the two substrates and substantially surrounds each of the moving parts of the MEMS light modulator. After the substrates are contacted and the fluid wets its entire surface, the alignment chamber is vented and returned to atmospheric pressure (step 3822). A partial curing process may also be applied to the adhesive after the substrates are bonded together. The adhesive can be cured by thermal means or a UV lamp installed in a vacuum chamber.

  In some embodiments where the lubricating fluid has a high vapor pressure, i.e., the lubricating fluid evaporates immediately at ambient temperature, it may not be practical to dispense the fluid in step 3818 before the panel is directed into the alignment chamber. unknown. In this embodiment, after the alignment chamber is evacuated and refilled with the vapor pressure of the lubricant, a nozzle can be provided to distribute the lubricating fluid onto one of the substrates just prior to the alignment process of the two substrates.

  If the sealant was not completely cured during the alignment operation at step 3820, another curing step is applied at step 3824. The curing of step 3824 may be performed as either thermal curing, UV curing, or microwave curing.

  The method 3800 is completed at step 3826, which optionally includes separating the individual display arrays from a large panel containing a plurality of arrays. Such separation is only required if the cell assembly process has progressed to this point according to the large panel process as described in FIGS. If the modulation substrate and aperture plate are made in the form of individual displays in steps 3806-3814, a final separation step is not necessary. This separation can be realized by a scribe and break process or by using a dicing saw.

  The final process of assembling the display after the end of method 3600 is often referred to generally as the module assembly process. Module assembly includes attaching one or more silicon chips including control and drive circuits directly to the glass substrate, bonding flexible circuitry to interconnect the display and external devices, and bonding optical films such as contrast filters. A step of attaching a backlight, and a step of mounting the display in a support structure or a housing. The flexible circuit may consist of simple wiring or may include additional electrical elements such as resistors, capacitors, inductors, transistors, or integrated circuits.

  FIG. 23 is a cross-sectional view of a display device 600 incorporating a liquid crystal light modulator 602, according to an illustrative embodiment of the invention. The display device includes a liquid crystal material 604 sandwiched between two transparent substrates 606 and 608. Electrode arrays 610 and 612 for adjusting the voltage applied across the liquid crystal material are formed on each of the two substrates. The display device 600 modulates the light by changing the polarization characteristics of the light passing through the liquid crystal material 604 depending on the voltage selected at the electrodes 610 and 612.

  The back-facing reflective layer (reflective film 614) disposed on the substrate 606 defines a plurality of surface apertures 616 located below the liquid crystal light modulator 602. The reflective film 614 reflects light that does not pass through the front surface aperture 616 and returns the light toward the back surface of the display device 600. The reflective aperture layer 614 may be a particulate metal film free of inclusions formed into a thin film by a number of deposition techniques including sputtering, evaporation, ion plating, laser cutting, or chemical vapor deposition. In another embodiment, the back-facing reflective layer 614 can be formed of a mirror, such as a dielectric mirror. The dielectric mirror is manufactured as a stack of dielectric thin films in which a material having a high refractive index and a material having a low refractive index are repeated.

  The liquid crystal display device 600 includes an optional diffuser 622 and / or an optional brightness enhancement film 624 that separates the substrate 606 from the planar light guide 616. The optical waveguide is made of a transparent material, ie glass or plastic material. The light guide 616 is illuminated by one or more light sources 618 that form a backlight. A reflector 619 helps direct light from the lamp 618 towards the light guide 616. A front-facing reflective film 620 is disposed on the back surface of the optical waveguide 616 and reflects light toward the liquid crystal modulator 602. Light rays from the backlight that do not pass through one of the shutter liquid crystal modulators 602 are returned to the backlight and reflected again by the film 620. In this way, the light that originally failed to leave the display to form an image can be reused and made available to transmit through other open apertures in the array of liquid crystal modulators 602. become.

  The light guide 616 includes a set of geometric light redirectors or prisms 617 that redirect the light from the lamp 618 towards the aperture 616 and thus towards the front of the display. The optical redirector may be molded into the plastic body of the optical waveguide 616, whose cross section may be triangular, trapezoidal, or curved. The density of prism 617 typically increases with distance from lamp 618.

  A sheet metal or molded plastic assembly bracket 632 holds the cover plate 608, the substrate 606, the backlight 616, and other components together around the edges. The assembly bracket 632 is secured with screws or indent tabs to increase the rigidity of the combined display device 600. The reflector 636 helps light that leaks from the edge of the light guide 616 back into the light guide.

  FIG. 24A provides a cross-sectional view of a display module assembly 700 in a MEMS up configuration, according to an illustrative embodiment of the invention. FIG. 24B provides an exploded isometric view of the display assembly 700. The module assembly includes one or more lamps 702, an optical waveguide 704, a MEMS modulator substrate 706, a cover plate 708, a drive circuit 710, a module spacer 712, assembly brackets 713 and 714, and flexible electrical wiring 716 and 718. Similar to that illustrated with respect to display device 500, module assembly 700 also includes a working fluid 720, cell spacers (not shown in FIG. 23), and sealant 722. The module assembly also includes an electrical connection 724 between the substrates 706 and 708. The assembly includes a front facing reflector film 728.

  The combination of MEMS modulator substrate 706, cover plate 708, cell spacer, working fluid 720, and seal 722 is often referred to as cell assembly 705. Techniques for cell assembly alignment, fluid filling, and sealing have already been described in US patent application Ser. No. 11 / 731,628 and US provisional patent application No. 60 / 930,872. The entirety of which is incorporated herein by reference.

  After uniting the cell assembly parts, the module 700 assembly process proceeds as follows. First, the drive circuit 710 is attached to the cell assembly 705. The drive circuit 710 may be a silicon chip that includes any or all of the functional blocks (including timing adjustment circuit, buffer memory, scan driver, data driver, and common driver) illustrated as part of the block diagram 150. . Electrical connection is made between the drive circuit 710 and the wiring on the substrate 706 by an anisotropic conductive adhesive 726. In the second step of module assembly, flexible electrical wiring 716 is also affixed to cell assembly 705 with an anisotropic conductive adhesive. In the optional third step of module assembly, one or more lamps 702 are attached to the light guide 704. The lamp is also attached to flexible electrical wiring 718. In the optional fourth step of assembly, a front facing reflector 728 is attached to the bottom surface of the module spacer 712. In the fifth step of assembly, the module spacer 712 is inserted into the assembly bracket 714. In the sixth step of assembly, all the remaining parts including the optical waveguide are attached on the module spacer 712 or at predetermined positions therein. In the final assembly process, the assembly bracket 713 is attached to a predetermined position above the cell assembly 705.

  The assembly bracket 713 includes an indent tab that completes the housing of the display module by firmly connecting the bracket 713 to the bracket 714. Module spacer 712 includes a number of features to facilitate and maintain mechanical alignment between the components of the module. For example, the positioning surfaces 730 and 732 help limit the movement of the ramp 702 after assembly. Such a plane in spacer 712 helps to maintain proper xy alignment between lamp 702 and light guide 704. By appropriately designing such positioning surfaces (sometimes referred to as storage pockets) within the module spacer 712, a high degree of alignment between the parts can be maintained even when the parts are to be assembled by hand. Similarly, xy alignment between the optical waveguide 704 and the MEMS modulator substrate 706 is ensured to some extent by the positioning surfaces 734 and 736, respectively.

  Longitudinal alignment between the parts of the assembly 700 is also maintained by a positioning surface designed in the module spacer 712. The MEMS modulator substrate 706 is placed on a shelf formed by the positioning surface 740, for example. The substrate 706 is supported by the positioning surface 740 at several points on the periphery of the substrate 706. Similarly, the optical waveguide 704 is placed on the positioning surface 742. An air gap 744 was set between the optical waveguide 704 and the MEMS modulator substrate 706. This air gap is maintained because the vertical distance between the positioning surfaces 740 and 742 is intentionally greater than the thickness of the optical waveguide 704. The air gap 744 performs a useful function because it allows total internal reflection to be utilized at the top surface of the light guide 704 that disperses light within the light guide. In addition, the air gap is between the two reflective surfaces of the display's optical resonator (eg, formed between the reflective film 506 and the front-facing reflector film 520), such as the light beam 521 in the display 500. Do not disturb the bounce.

  In the module assembly 700, the positioning surface 742 supports the optical waveguide 704 only along the periphery of the optical waveguide. An open area remains in the module spacer 712 below the optical waveguide 704 in the display area of the display. Module spacer 712 also includes a positioning surface 746 along the periphery of the surface opposite the surface 742. The front-facing reflector 728 is attached to the positioning surface 746 with an adhesive. In this way, an air gap is also provided between the front-facing reflector 728 and the light guide 704. In an alternative embodiment, the front-facing reflector 728 is glued directly to the assembly bracket 714.

  The module spacer 712 can be made of plastic or metal material. The polished metal material is useful because its surface reflects light that escapes from the optical waveguide 704 back into the optical resonator. In a particular embodiment of module 700, spacer 712 is made by injection molding of polycarbonate. Polycarbonate is dyed white and its edges are smooth to enhance the reflection of light returning into the optical resonator. Other plastic materials applicable to this part include, but are not limited to, polyethylene, polypropylene, acrylic resin, or epoxy material. These materials can be molded by using either thermoplastic or thermosetting. In some embodiments, the module spacer can be formed of a conductive polymer or polymer composite to protect against electromagnetic interference.

  Module spacer 712 typically supports optical waveguide 704 and MEMS modulator substrate 706 only along the periphery of the substrate. However, assembly brackets 713 and 714 are designed to completely surround the module along the bottom, sides, and also the invisible portions of the top surface. A gap for accommodating the flexible electrical wires 716 and 718 is left on the side surface of the assembly bracket. When connected by indent tabs, assembly brackets 713 and 714 provide mechanical rigidity to the display module. When formed of sheet metal, the assembly bracket also provides electronic shielding of the display and protection from electromagnetic interference. In some embodiments, the functions of the module spacer 712 and the assembly bracket 714 can be combined in a composite structure. In such a composite structure, the plastic part is molded on or around the base made of sheet metal and is permanently bonded to the base. After the plastic molding is complete, all sheet metal protrusions can be further bent or folded back to form part of the interlock housing.

  In some embodiments, an adhesive is applied along the periphery of the cell assembly and / or the light guide 704 to prevent movement of parts along respective positioning surfaces on the module spacer 712. In other embodiments, an elastic material (synthetic sponge or rubber material) is inserted between the components, eg, between the optical waveguide 704 and the modulator substrate 706 and / or between the cover plate 708 and the assembly bracket 714. The elastic material can be compressed after surrounding the assembly brackets 713 and 714, thereby preventing further movement of the parts. The elastic material also protects the display component from mechanical shocks. In some embodiments, a protrusion is provided in spacer 712 that aligns with an indent or tab in assembly bracket 713 or 714. These position detection protrusions prevent the spacer 712 within the assembly bracket 714 from moving.

  In a preferred embodiment, the MEMS modulator substrate 706 includes a shutter-based MEMS modulator array, such as light modulators 200 and 220, but a substrate including a non-shutter-based MEMS light modulator is effectively utilized in the present invention. Can do. Applicable non-shutter based modulators that can be arranged on the substrate 706 include an optical tap 250 and an electrowetting based optical modulator 2400.

  In an alternative embodiment, the cell component of the display device 600 can be replaced with a MEMS light modulator in the display device 700. For example, the substrate 606 can be replaced with a MEMS modulator substrate 706, and the substrate 608 can be replaced with a cover plate 708. In the liquid crystal embodiment of the present invention, fluid 720 can be replaced with liquid crystal material 604. Similar advantages obtained by the design of the module spacer 712 also apply when the module spacer 712 is used in the liquid crystal display device 600.

  FIG. 25 provides a detailed view of the display module assembly 800 in a MEMS up configuration, according to an illustrative embodiment of the invention. The module assembly includes one or more lamps 802, an optical waveguide 804, a modulator substrate 806, a cover plate 808, a drive circuit 810, a module spacer 812, a front-facing reflector 828, assembly brackets 813 and 814, and flexible electrical wiring. 816 and 818.

  Longitudinal alignment between the parts of the assembly 800 is also maintained by a positioning surface designed in the module spacer 812. For example, the MEMS modulator substrate 806 is placed on a shelf formed by the positioning surface 836. The substrate 806 is supported by the positioning surface 836 at several points on the periphery of the substrate 806. Similarly, the optical waveguide 804 rests on the positioning surface 840 located on the opposite side of the positioning surface 836 on the module spacer 812. The air gap 844 was set between the optical waveguide 804 and the MEMS modulator substrate 806 by inserting a module spacer 812 between the substrates along the periphery of the display. The shape of the module spacer 812 was designed such that the spacer material was placed between the two substrates at several points along the periphery of the substrates 804 and 806.

  Module assembly 800 also includes resilient inserts 850 and 852. The elastic insert 850 is disposed between the cover plate and the assembly bracket 813. The elastic insert 852 is disposed between the optical waveguide 804 and the assembly bracket 814. The elastic insert is constructed of an elastic material (synthetic sponge or rubber material) so that it can be compressed during encapsulation of the brackets 813 and 814. The elastic insert ensures that the optical waveguide 804 and the modulator substrate 806 are pressed directly against the positioning surfaces 840 and 836, respectively. The elastic material also protects the display component from mechanical shocks. In some embodiments, the front-facing reflector 828 is bonded directly to the light guide 804 such that the elastic insert 852 is positioned between the assembly bracket 814 and the reflector 828.

  FIG. 26 provides a detailed view of the display module assembly 900 in a MEMS down configuration, according to an illustrative embodiment of the invention. The module assembly includes one or more lamps 902, an optical waveguide 904, an aperture plate 906, a modulator board 908, a drive circuit 910, a module spacer 912, a front-facing reflector 928, assembly brackets 913 and 914, and flexible electrical wiring. 916 and 918 are included.

  The combination of MEMS modulator substrate 908, aperture plate 906, cell spacer, working fluid 920, and seal 922 is referred to as cell assembly 905. However, in the MEMS down configuration, the MEMS shutter assembly array is fabricated on the side of the substrate 908 that faces the light guide 904 and away from the viewer. As a result, the drive circuit 910 is also mounted on the bottom surface of the modulator substrate 908.

  Module spacer 912 includes a number of features to facilitate and maintain mechanical alignment between the components of the module. For example, the spacer 912 includes positioning surfaces 930 and 932 that help ensure proper positioning of the ramp 902. In a similar shape, the xy alignment between the optical waveguide 904 and the MEMS aperture plate 906 is guaranteed to some extent by the positioning surfaces 934 and 936, respectively.

  Longitudinal alignment between the parts of the assembly 900 is also maintained by a positioning surface designed in the module spacer 912. The aperture plate 906 is placed on a shelf formed by the positioning surface 940, for example. The substrate 906 is supported by the positioning surface 940 at several points on the periphery of the substrate 906. Similarly, the optical waveguide 904 is placed on the positioning surface 942. The air gap 944 was set between the optical waveguide 904 and the aperture plate 906. This air gap is maintained because the vertical distance between the positioning surfaces 940 and 942 is intentionally greater than the thickness of the optical waveguide 904. The air gap 944 performs a useful function because it allows total internal reflection to be utilized on the top surface of the light guide 904 that disperses light within the light guide. In addition, the air gap is between the two reflective surfaces of the display's optical resonator (eg, formed between the reflective film 506 and the front-facing reflector film 520), such as the light beam 521 in the display 500. Do not disturb the bounce.

  In the module assembly 900, the positioning surface 942 supports the optical waveguide 904 only along the periphery of the optical waveguide. An open area is left in the module spacer 912 under the optical waveguide 904 in the display area of the display. Module spacer 912 also includes a positioning surface 946 along the periphery of the surface opposite the surface 942. The front-facing reflector 928 is attached to the positioning surface 946 with an adhesive. In this way, an air gap is also provided between the front-facing reflector 928 and the optical waveguide 904. In an alternative embodiment, the front facing reflector 928 is glued directly to the assembly bracket 914.

  The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. Accordingly, the foregoing embodiments are to be considered in all respects only as illustrative and not restrictive.

Claims (194)

A display assembly manufacturing method comprising:
Providing a first substrate on which a plurality of MEMS light modulators each having a bright state and a dark state are fabricated;
Providing a second transparent substrate on which a layer including a plurality of apertures is formed;
Aligning the first substrate and the second transparent substrate to set the correspondence between each MEMS light modulator and the aperture. The method of claim 1, wherein each MEMS light modulator includes a modulation element having an edge, and each aperture includes at least one edge,
The step of aligning the first and second substrates is such that, in the dark state, the edge of the modulation element of the MEMS light modulator overlaps the edge of its corresponding aperture by more than 0 microns and less than about 20 microns. Aligning a first substrate and the second substrate.   The method of claim 2, wherein the first substrate is substantially transparent.   The method of claim 2, comprising maintaining the alignment by bonding the first substrate to the second substrate with an adhesive.   The method of claim 2, comprising maintaining alignment by connecting the first substrate to the second substrate by a mechanical interlock feature.   The method of claim 2, comprising maintaining alignment by connecting the first substrate to the second substrate with a thermally reflowable material.   3. The method of claim 2, wherein the plurality of MEMS light modulators on the first substrate includes a plurality of light modulator arrays, and the plurality of apertures on the second substrate includes a plurality of aperture arrays. A method comprising the step of unifying the first and second substrates.   8. The method of claim 7, wherein the first and second substrates are singulated prior to their alignment.   The method of claim 7, wherein the first and second substrates are singulated after alignment.   The method of claim 2, comprising forming alignment marks on the first and second substrates.   The step of aligning the first and second substrates includes loading the first and second substrates into an alignment apparatus that includes a vision system for monitoring the degree of misalignment between alignment marks. Item 11. The method according to Item 10.   The method of claim 11, wherein the alignment apparatus includes a motor for adjusting a relative position of the two substrates.   The method of claim 11, wherein the alignment apparatus includes a UV lamp for curing the adhesive.   The method according to claim 2, further comprising attaching a spacer for setting a constant separation distance between the first and second substrates.   The method of claim 1, wherein in the bright state, the light modulator locally obstructs total internal reflection of light reflected at one of the first and second substrates.   The method of claim 1, wherein the light modulator is an electrowetting modulator.   The method of claim 1, wherein the layer formed on the second substrate comprises a reflective material.   The method of claim 1, wherein the layer formed on the second substrate comprises a light absorbing material.   3. The method of claim 2, wherein in the dark state, the edge of the modulation element of the MEMS light modulator overlaps its corresponding edge of the aperture by more than 0 and less than about 5 microns.   The method of claim 1, comprising applying a conductive material that fills a gap between the first and second transparent substrates. A MEMS light modulator array formed on the first substrate;
A second transparent substrate separated from the first substrate by a certain gap;
A liquid disposed between the first and second substrates substantially surrounding a movable part of the MEMS light modulator;
A display assembly including an adhesive seal surrounding the MEMS modulator array for containing the liquid between the two substrates and limiting relative movement between the two substrates.   The display assembly of claim 21, wherein the liquid comprises a lubricant.   The display assembly of claim 21, further comprising a reflective aperture layer disposed on one of the first and second substrates.   The liquid has a first refractive index, the substrate on which the reflective aperture layer is disposed has a second refractive index, and the first refractive index is greater than the second refractive index, or 24. The display assembly of claim 23, wherein the display assembly is substantially equal.   The display assembly of claim 21, wherein the liquid is non-conductive.   The display assembly of claim 21, wherein the liquid has a dielectric constant greater than 2.0.   The display assembly of claim 21, wherein the liquid wets a surface of the MEMS modulator in the MEMS modulator array.   28. The display assembly of claim 27, wherein each of the MEMS light modulators includes a front surface and a back surface, and the liquid wets both the front and back surfaces of the MEMS light modulator.   The display assembly of claim 21, wherein the adhesive seal comprises a polymeric material.   The display assembly of claim 21, wherein each of the MEMS light modulators includes components that controllably move through the liquid.   The display assembly of claim 21, wherein the liquid comprises a single liquid. A method of manufacturing a display assembly including first and second transparent substrates, comprising:
Providing a MEMS light modulator array on the first transparent substrate;
Disposing the second transparent substrate adjacent to the first substrate such that the first transparent substrate is separated from the second transparent substrate by a certain gap;
Applying a sealant along at least a portion of the periphery of the display assembly;
Filling the display assembly with a fluid such that the fluid substantially surrounds a movable portion of the MEMS light modulator;
Curing the sealant after filling the display assembly with a fluid.   34. The method of claim 32, wherein the fluid is a liquid.   The method of claim 32, wherein the fluid is a gas.   The method of claim 32, wherein the fluid is a lubricant.   33. The method of claim 32, wherein the step of applying the sealant precedes the step of filling the display.   The method of claim 32, further comprising aligning the first and second transparent substrates prior to the step of curing the sealant.   The step of filling the display assembly with a fluid includes applying the liquid to one of the first and second transparent substrates prior to aligning the first and second transparent substrates. 34. The method according to 33.   35. The method of claim 32, wherein filling the display assembly with the fluid comprises lowering an air pressure surrounding the display assembly to a pressure below atmospheric pressure.   35. The method of claim 32, further comprising fabricating at least one additional MEMS light modulator array on the first transparent substrate while fabricating the MEMS light modulator array.   41. The method of claim 40, further comprising the step of separating the MEMS light modulator array from the at least one additional MEMS light modulator array after applying the sealant.   36. The method of claim 32, further comprising creating a spacer on at least one of the first and second transparent substrates to maintain a gap between the two substrates.   33. The method of claim 32, further comprising providing a conductive material that fills the gap between the first and second transparent substrates. A method of manufacturing a display assembly including first and second transparent substrates, comprising:
Providing a MEMS light modulator array on the first transparent substrate;
Disposing the second transparent substrate adjacent to the first substrate such that the first transparent substrate is separated from the second transparent substrate by a certain gap;
Applying a sealant along at least a portion of the periphery of the display assembly;
Curing the sealing material to connect the first and second transparent substrates;
Filling the display assembly with the fluid after curing the sealing material such that a fluid substantially surrounds a movable part of the MEMS light modulator.   45. The method of claim 44, wherein the fluid is a liquid.   45. The method of claim 44, wherein the fluid is a gas.   45. The method of claim 44, wherein the fluid is a lubricant.   45. The method of claim 44, further comprising aligning the first and second transparent substrates prior to the step of curing the sealant.   45. The method of claim 44, further comprising fabricating at least one additional MEMS light modulator array on the first transparent substrate while fabricating the MEMS light modulator array.   50. The method of claim 49, further comprising the step of separating the MEMS light modulator array from the at least one additional MEMS light modulator array after applying the sealant.   45. The method of claim 44, further comprising creating a spacer on at least one of the first and second transparent substrates to maintain a gap between the two substrates.   45. The method of claim 44, further comprising providing a conductive material that fills the gap between the first and second transparent substrates.   45. The method of claim 44, wherein affixing the sealant to the display assembly includes leaving at least one filling hole unsealed.   45. The method of claim 44, wherein filling the display assembly includes lowering an air pressure surrounding the display assembly to a pressure below atmospheric pressure.   54. The method of claim 53, further comprising sealing the at least one filling hole after filling the display assembly to contain the fluid in the display assembly. A first substrate on which an aperture layer is formed;
An optical waveguide for directing light toward the aperture layer;
A plurality of MEMS light modulators for modulating light passing through the aperture layer from the optical waveguide;
A spacer that substantially surrounds the periphery of the optical waveguide, wherein a gap is formed between the first substrate and the optical waveguide by separating the optical waveguide and the first substrate from each other by a predetermined distance; Display device.   57. The display device of claim 56, wherein the spacer includes a reflective surface for reflecting light into the optical waveguide.   57. The display device of claim 56, wherein the spacer includes a structural feature having a geometry selected to maintain alignment between the light guide and a lamp for supplying light to the light guide.   The spacer includes a structural feature having a geometry selected to maintain alignment between the optical waveguide and electrical connections for controlling one of the plurality of MEMS light modulators. Item 56. The display device according to item 56.   57. The display device of claim 56, wherein the spacer includes a structural feature having a geometry selected to maintain alignment between the optical waveguide and the first substrate.   57. The display device according to claim 56, wherein the spacer includes a shelf on which one of the optical waveguide and the first substrate is placed.   57. The display device of claim 56, wherein the spacer includes a structural feature having a geometry selected to limit translational movement of at least one of the optical waveguide and the first substrate.   57. The display device of claim 56, further comprising an adhesive disposed on the spacer for adhering to at least one of the optical waveguide and the first substrate.   57. The display device according to claim 56, wherein the spacer is disposed between the optical waveguide and the first substrate.   57. The display device of claim 56, wherein the spacer includes a rigid material.   The display device of claim 65, wherein the spacer comprises at least one of polycarbonate, polyethylene, polypropylene, and polyacrylate.   66. The display device of claim 65, wherein the spacer comprises a metal.   66. The display device of claim 65, wherein the spacer comprises a composite of metal and plastic.   57. The display device of claim 56, wherein the MEMS light modulator comprises a shutter-based light modulator.   57. The display device of claim 56, wherein the MEMS light modulator comprises an electrowetting light modulator.   The spacer includes a structural feature having a geometry selected to maintain alignment between the optical waveguide and a reflective layer for reflecting light toward the optical waveguide. A display device according to 1.   57. A display device according to claim 56, wherein the aperture layer comprises a reflective aperture layer.   57. The display device according to claim 56, wherein the plurality of MEMS light modulators are disposed on the first substrate.   57. The display device according to claim 56, wherein the plurality of MEMS light modulators are disposed on a second substrate. A plurality of MEMS light modulators;
A first substrate on which a control matrix for controlling the plurality of MEMS optical modulators is formed;
An optical waveguide for directing light toward the first substrate;
A spacer that substantially surrounds the periphery of the optical waveguide, wherein a gap is formed between the first substrate and the optical waveguide by separating the optical waveguide and the first substrate from each other by a predetermined distance; Display device.   The spacer of claim 75, wherein the spacer includes a structural feature having a geometry selected to maintain alignment between the light guide and a lamp for supplying light to the light guide. Display device.   The display apparatus according to claim 75, wherein the spacer includes a reflective surface for reflecting light into the optical waveguide.   The display device of claim 75, wherein the spacer includes a structural feature having a geometry selected to maintain alignment between the optical waveguide and the first substrate.   The display device of claim 75, wherein the spacer includes a structural feature having a geometry selected to limit translational movement of at least one of the optical waveguide and the first substrate.   The display device according to claim 75, wherein the spacer includes a shelf on which one of the optical waveguide and the first substrate is placed. A first substrate having a front facing surface and a back facing surface;
A reflective aperture layer including a plurality of apertures disposed on the front-facing surface of the first substrate;
And a plurality of MEMS light modulators that modulate light directed to the plurality of apertures to form an image.   The display device of claim 81, wherein the first substrate includes an optical waveguide.   The display apparatus of claim 81, wherein the plurality of MEMS light modulators comprise shutter-based light modulators.   The display apparatus according to claim 81, wherein the plurality of MEMS light modulators include electrowetting light modulators.   The display apparatus according to claim 81, wherein the MEMS light modulator is disposed on the first substrate.   82. A display device according to claim 81, wherein the first substrate is transparent. 82. The display device of claim 81, comprising an optical waveguide located behind the first substrate,
The display device, wherein the reflective aperture layer reflects light that does not pass through the plurality of apertures included in the reflective aperture layer and returns the light toward the optical waveguide.   The display device according to claim 87, wherein the first substrate is in close contact with the optical waveguide.   The display apparatus of claim 81, wherein the reflective aperture layer is formed of one of a mirror, a dielectric mirror, and a metal film.   The display apparatus according to claim 81, wherein the plurality of apertures correspond to respective light modulators of the plurality of light modulators.   The display apparatus according to claim 81, wherein the first substrate is disposed such that the reflective aperture layer is adjacent to the plurality of light modulators.   The display apparatus according to claim 81, wherein the first substrate is positioned with respect to the optical waveguide so as to form a gap between the first substrate and the optical waveguide.   94. A display device according to claim 92, comprising a fluid filling the gap.   94. A display device according to claim 93, wherein the fluid is air.   94. The display device of claim 93, wherein the fluid has a first refractive index, the optical waveguide has a second refractive index, and the first refractive index is less than the second refractive index. The display apparatus of claim 81, comprising an active matrix control matrix for controlling the plurality of MEMS light modulators,
The display device, wherein the active matrix includes at least one switch corresponding to each MEMS light modulator.   82. A display device according to claim 81, comprising a second substrate disposed in front of the front-facing surface of the first substrate.   98. The display device of claim 97, wherein the plurality of MEMS light modulators are formed on the second substrate.   The display apparatus according to claim 97, wherein the plurality of MEMS light modulators are formed on a surface facing the back surface of the second substrate.   98. A display device according to claim 97, comprising a control matrix formed on the second substrate for controlling the plurality of MEMS light modulators.   98. A display device according to claim 97, wherein the second substrate is transparent.   98. The display device of claim 97, further comprising a mechanical interlock feature for maintaining a lateral alignment between the first and second substrates.   103. The display device of claim 102, wherein the mechanical interlock feature limits relative lateral movement of the first and second substrates to less than 5 microns in any direction.   98. A display device according to claim 97, comprising an adhesive for maintaining a lateral alignment between the first and second substrates.   105. The display device of claim 104, wherein the adhesive limits relative lateral movement of the first and second substrates to less than 5 microns in any direction.   The display apparatus according to claim 97, wherein the first substrate is disposed between an optical waveguide and the second substrate.   98. The display device of claim 97, wherein the first substrate is positioned relative to the second substrate so as to form a gap between the first substrate and the second substrate.   108. The display device of claim 107, comprising a spacer for maintaining the gap.   109. A display device according to claim 108, comprising a fluid filling the gap.   110. A display device according to claim 109, comprising a liquid filling the gap.   110. A display device according to claim 109, wherein the fluid is a lubricant.   110. The fluid of claim 109, wherein the fluid has a first index of refraction, the substrate has a second index of refraction, and the first index of refraction is greater than or substantially equal to the second index of refraction. The display device described. A first substrate;
A second substrate;
A MEMS light modulator array formed on one of the first and second substrates;
A spacer installed in the array, formed or connected to the first substrate at a first end and connected to the second substrate at a second end. And a spacer.   114. The display device of claim 113, wherein the connection of the spacer to one of the first and second substrates includes a connection to a stack of at least one thin film deposited on the substrate.   115. The display device of claim 114, wherein the thin film includes one of a reflective aperture layer, a light absorption layer, and a color filter.   114. The display device of claim 113, wherein the spacer is etched from the first substrate.   114. The display device of claim 113, wherein the spacer is etched from a film deposited on the first substrate.   114. The display device of claim 113, wherein the first substrate and the second substrate are substantially rigid.   114. The display device of claim 113, wherein the first substrate and the second substrate are substantially flexible.   114. One of the first substrate and the second substrate is substantially rigid, and the other of the first substrate and the second substrate is substantially flexible. Display device.   114. The display device of claim 113, wherein the spacer is made of an insulating material.   114. The display device of claim 113, wherein the first substrate includes a front surface of the display device.   114. The display device of claim 113, wherein the second substrate includes a front surface of the display device.   114. The display device of claim 113, wherein the first and second substrates include separate optical waveguides. 114. The display device of claim 113, comprising a plurality of additional spacers,
The display device, wherein the spacer and the plurality of additional spacers are arranged in the array with a spacer density of “one spacer per four light modulators” or less. 114. The display device of claim 113, comprising a plurality of additional spacers,
The display device, wherein the MEMS light modulator corresponds to a respective display pixel, and each of the respective display pixels includes at least one spacer.   114. The display device of claim 113, wherein the spacer forms an electrical connection between an electrical component on the first substrate and an electrical component on the second substrate.   114. The display device of claim 113, wherein the spacer is formed of a polymer.   114. The display device of claim 113, wherein the spacer is made of metal.   114. The display device of claim 113, wherein the MEMS light modulator is configured to selectively obstruct light passage.   135. The display device of claim 130, wherein the MEMS light modulator comprises a shutter-based light modulator.   131. The display device of claim 130, wherein the MEMS light modulator comprises an electrowetting based light modulator.   114. The display device of claim 113, wherein the MEMS light modulator selectively extracts light from an optical waveguide.   114. The display device of claim 113, wherein the spacer limits a moving range of components in one of the MEMS light modulators.   114. The display device according to claim 113, wherein the spacer is fitted with an alignment element formed on the second substrate.   114. The display device of claim 113, comprising a fluid that fills a gap between the first substrate and the second substrate.   137. The display device of claim 136, wherein the fluid includes a lubricant.   114. The display device of claim 113, wherein at least one of the first substrate and the second substrate is substantially transparent.   114. The display device of claim 113, wherein the spacer is between about 1 micron and about 10 microns high. A first transparent substrate;
A second transparent substrate on which the array light modulator is formed;
A display device comprising: a space element formed of a heat reflowable material for aligning the first transparent substrate and the second transparent substrate.   143. The display device of claim 140, wherein the thermally reflowable material obtains a substantially liquid state between about 150 degrees Celsius and about 400 degrees Celsius.   141. The display device according to claim 140, wherein the space element functions as an adhesive that joins the first transparent substrate to the second transparent substrate.   141. The display device of claim 140, comprising a reflective aperture layer formed on one of the first transparent substrate and the second transparent substrate.   141. The display device of claim 140, wherein the light modulator comprises a MEMS light modulator.   141. The display device of claim 140, wherein the space element is disposed at a periphery of the light modulator array.   141. A display device according to claim 140, wherein the space elements are arranged in the light modulator array.   141. The display device of claim 140, wherein the thermally reflowable material comprises one of metal, plastic, and glass.   141. The display device of claim 140, wherein the thermally reflowable material wets a feature surface on both the first transparent substrate and the second transparent substrate when in a substantially liquid state.   105. The display device of claim 104, wherein the adhesive comprises a heat reflowable material. A plurality of apertures formed in the material layer, each having at least one edge;
A shutter-based MEMS light modulator array disposed between the material layer and a desired viewer of the display device;
Each light modulator including a shutter having a light blocking portion for selectively blocking the passage of light through the corresponding one or more apertures, comprising:
The shutter is shaped such that, in the closed position, the light blocking portion of the shutter overlaps at least one edge of its corresponding aperture or apertures;
The array is separated from the material layer by a certain gap;
The display device, wherein the overlap is proportional to the size of the gap and greater than or equal to the size of the gap.   The display device of claim 150, wherein the overlap is greater than or equal to about 1 micron.   The display device of claim 150, wherein the overlap is between about 1 micron and about 10 microns.   The display device of claim 150, wherein the overlap is greater than about 10 microns.   161. The display of claim 150, wherein the shutter includes one or more shutter apertures that allow light to pass through, each shutter aperture corresponding to one of the one or more apertures corresponding to the shutter. apparatus.   The display device of claim 150, wherein the material layer is substantially reflective.   The display apparatus of claim 155, wherein the material layer comprises a metal.   The display apparatus of claim 155, wherein the material layer includes a dielectric mirror. The display apparatus of claim 155, comprising an optical waveguide,
The display device, wherein the material layer reflects light returning from a backlight and returns the light toward the optical waveguide.   166. The display device of claim 155, comprising a light absorbing material deposited on the side of the material layer facing the array.   160. The display device of claim 159, comprising a second reflective layer disposed on the back side of the backlight.   The display device of claim 150, wherein the array is formed on the material layer.   The display apparatus of claim 161, wherein the material layer is deposited on an optical waveguide.   161. The display device of claim 150, wherein the array is formed on the first substrate and the material layer is deposited on a second substrate other than the first substrate.   166. The display device of claim 163, wherein the array is formed on a side of the first substrate facing away from the viewer. 164. The display device of claim 163, comprising an optical waveguide,
The display device, wherein the second substrate is disposed between the first substrate and the optical waveguide.   165. The display device of claim 150, comprising a spacer disposed between the material layer and the array for keeping a shutter in the light modulator at a predetermined distance from the material layer.   The display device of claim 150, comprising a liquid disposed at least between the light modulator and the material layer.   166. The display device of claim 167, wherein the liquid is a lubricant.   166. The display device of claim 167, wherein the liquid has a refractive index greater than that of a substrate on which the material layer is formed. 166. The display device of claim 167, comprising an optical waveguide,
The display device, wherein the liquid has a refractive index greater than that of the optical waveguide. 166. The display apparatus of claim 163, comprising an optical waveguide having a refractive index greater than that of the second substrate and a liquid.
The display device, wherein the second substrate is disposed between the first substrate and the optical waveguide, and the liquid is disposed at least between the second substrate and the optical modulator.   The display device of claim 150, wherein a side of the shutter facing the material layer is covered with a reflective material.   The display device according to claim 150, wherein a side of the shutter facing the material layer is covered with a light absorbing material.   The display device according to claim 150, wherein a side of the shutter facing outward from the material layer is covered with a light absorbing material. An electrowetting-based light modulator array for transparently displaying images;
A reflective aperture layer disposed adjacent to the array, the reflective aperture layer configured to reflect light that does not pass through the apertures in the reflective aperture layer and away from the array; There,
The display device, wherein the image is formed of light that passes through the aperture in the reflective aperture layer and is modulated by the array.   175. The display device of claim 175, comprising a backlight disposed on the opposite side of the reflective aperture layer from the array.   175. The display device of claim 175, comprising a second reflective layer disposed on the opposite side of the reflective aperture layer from the array to reflect light toward the reflective aperture layer.   178. The display device of claim 175, comprising a layer of low refractive index material coupled to the optical waveguide between the backlight and the reflective aperture layer.   178. The display device of claim 175, wherein the electrowetting-based light modulator array includes a first electrowetting control color modulation layer and an electrowetting control black layer. The first electrowetting control color modulation layer includes a plurality of electrowetting control color modulation cells each having at least one edge;
The electrowetting control black layer includes a plurality of electrowetting control light absorption cells each having at least one edge corresponding to one or more of the color modulation cells;
180. The display device of claim 179, wherein at least one edge of each light absorbing cell overlaps at least one edge of a corresponding one or more color modulation cells.   179. The display apparatus of claim 179, wherein the first electrowetting control color modulation layer comprises a group of electrowetting control color modulation cells, and each cell in a given group modulates a different color of light. 180. The display device of claim 179, comprising second and third electrowetting control color modulation layers.
The display device, wherein each of the first, second, and third electrowetting control color modulation layers modulates light of different colors.   177. The display device of claim 176, comprising a light source for emitting light to the backlight.   187. The display device of claim 183, wherein the light source emits white light.   187. The display device of claim 183, wherein the light source emits at least three different colors of light sequentially.   186. The display device of claim 185, wherein the light sources include at least three light sources each corresponding to one of the three different colors.   178. The display device of claim 175, wherein the reflective aperture layer comprises a metal.   The display apparatus of claim 175, wherein the reflective aperture layer comprises a dielectric mirror.   175. The display device of claim 175, wherein the electrowetting-based light modulator array includes a plurality of electrowetting light modulation cells, each of the cells corresponding to an aperture in the reflective aperture layer.   Each of the apertures has at least one edge, and each cell includes a layer of light modulating fluid, and when inactive, the light modulating fluid of the cell is at the edge of the corresponding aperture. 189. The display device of claim 189, which overlaps a portion.   178. The display device of claim 175, wherein the electrowetting-based light modulator includes an electrode layer.   The display apparatus of claim 191, wherein the electrode layer is disposed between the reflective aperture layer and the light modulating fluid.   The display apparatus according to claim 191, wherein the reflective aperture layer is disposed on a first substrate, and the electrode layer is disposed on a second substrate different from the first substrate.   191. The display device of claim 191, wherein a light modulating fluid is disposed between the reflective aperture layer and the electrode layer.

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