Patent Publication Number: US-10310251-B1

Title: System and method for electrowetting display device with color filtering pixel walls

Description:
BACKGROUND 
     Electronic displays are found in numerous types of electronic devices including, without limitation, electronic book (“eBook”) readers, mobile phones, laptop computers, desktop computers, televisions, appliances, automotive electronics, and augmented reality devices. Electronic displays may present various types of information, such as user interfaces, device operational status, digital content items, and the like, depending on the kind and purpose of the associated device. The appearance and quality of a display may affect a user&#39;s experience with the electronic device and the content presented thereon. Accordingly, enhancing user experience and satisfaction continues to be a priority. Moreover, increased multimedia use imposes high demands on designing, packaging, and fabricating display devices, as content available for mobile use becomes more extensive and device portability continues to be a high priority to the consumer. 
     An electrowetting display includes an array of pixels individually bordered by pixel walls that retain fluid, such as an opaque oil, for example. Light transmission through each pixel is adjustable by electronically controlling a position of the fluid in the pixel. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is set forth with reference to the accompanying figures. The use of the same reference numbers in different figures indicates similar or identical items or features. 
         FIGS. 1A and 1B  illustrate cross-sectional views of a portion of an electrowetting display device. 
         FIG. 2  illustrates a top view of the electrowetting pixels of  FIGS. 1A and 1B  mostly exposed by an electrowetting fluid, according to various embodiments. 
         FIG. 3  is a block diagram of an example embodiment of an electrowetting display driving system, including a control system of the electrowetting display device. 
         FIGS. 4A and 4B  illustrate cross-sectional views of a portion of an electrowetting display device in which different pixel walls of the display device are transparent to different wavelengths of electromagnetic radiation. 
         FIG. 5  illustrates a top view of the electrowetting pixels of  FIGS. 4A and 4B  mostly exposed by an electrowetting fluid, according to various embodiments. 
         FIGS. 6 and 7  are top views of an electrowetting display device including a number of white pixels. 
         FIGS. 8A-8I  illustrate cross-sectional views of an electrowetting display device depicting steps in a photolithography process for forming pixel walls in accordance with the present disclosure. 
         FIG. 9  illustrates an example electronic device that may incorporate a display device, according to various embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     In various embodiments described herein, electronic devices include electrowetting displays for presenting content and other information. In some examples, the electronic devices may include one or more components associated with the electrowetting display, such as a touch sensor component layered atop the electrowetting display for detecting touch inputs, a front light or back light component for lighting the electrowetting display, and/or a cover layer component, which may include antiglare properties, antireflective properties, anti-fingerprint properties, anti-cracking properties, and the like. 
     An electrowetting pixel is surrounded by a number of pixel walls. The pixel walls form a structure that is configured to contain at least a portion of a first fluid, such as a black opaque oil. Light transmission through the electrowetting pixel can be controlled by an application of an electric potential to the electrowetting pixel, which results in a movement of a second fluid, such as an electrolyte solution, within the electrowetting pixel, thereby displacing the first fluid. 
     When the electrowetting pixel is in a rest state (i.e., with no electric potential applied or at an electric potential that falls below a threshold value causing the electrowetting pixel to be inactive), the opaque oil is distributed throughout the pixel. The oil absorbs light and the pixel in this condition appears black. But when the electric potential is applied, the oil is displaced to one or more sides of the pixel. Light can then enter the pixel striking a reflective surface. The light then reflects out of the pixel, causing the pixel to appear less dark (e.g., white) to an observer. If the reflective surface only reflects a portion of the spectrum of visible light or if color filters are incorporated into the pixel structure, the pixel may appear to have color. 
     In conventional display device designs, the pixel walls are constructed from a clear material. Consequently light entering one pixel within the display device can sometimes propagate through the pixel walls into other pixels. This phenomenon, referred to herein as cross-talk, can cause a shift in the colors of the image being generated by the display device. For example, cross-talk may cause color shift as pixels of one color reflect light that in fact entered differently-colored pixels of the display device. 
     Conventional display devices have included black matrix materials formed over the top of or above the pixel walls. The black matrix materials generally include light-absorbing materials and are configured to prevent light that strikes a surface of the display device at an angle nearly normal to that surface entering the display&#39;s pixels through one of the pixel walls and reflecting obliquely from a reflective surface back to a viewer, which can lead to cross-talk. But because the black matrix materials block light, such an implementation necessarily reduces the overall brightness of the display device. 
     In the present system, a pixel wall configuration is described in which the pixels walls are constructed from materials exhibiting color filtering properties. In one embodiment, each pixel in the display device is surrounded by a pixel wall arrangement having pixel walls configured to block electromagnetic radiation having wavelengths other than that reflected by the pixel. As such, electromagnetic radiation from a first pixel of a first wavelength cannot propagate through the pixel wall and enter a second pixel of a second color. Such an implementation, therefore, can reduce cross-talk between pixels of the display device. Additionally, because cross-talk is limited in the present pixel wall design, the black matrix materials of conventional devices can be avoided, thereby allowing more light to enter the display device overall, increasing the display device&#39;s brightness. In the present disclosure, the term electromagnetic radiation includes, but is not limited to light and light rays and, specifically, light rays that are at wavelengths within the visible spectrum. As used herein, the term color may refer to a perceived color of visible light or a particular wavelength or ranges of wavelengths of electromagnetic radiation. 
     A display device, such as an electrowetting display device, may be a transmissive, reflective or transflective display that generally includes an array of pixels configured to be operated by an active matrix addressing scheme. In this disclosure, a pixel may, unless otherwise specified, comprise a single sub-pixel or a pixel that includes two or more sub-pixels of an electrowetting display device. Such a pixel or sub-pixel may be the smallest light transmissive, reflective or transflective element of a display that is individually operable to directly control an amount of light transmission through and/or reflection from the element. For example, in some implementations, a pixel may be a red sub-pixel, a green sub-pixel, a blue sub-pixel or a white sub-pixel of a larger pixel or may, in some cases, include a number of sub-pixels. As such, a pixel may be a pixel that is a smallest component, e.g., the pixel does not include any sub-pixels. 
     Rows and columns of electrowetting pixels are operated by controlling voltage levels on a plurality of source lines and gate lines. In this fashion, the display device may produce an image by selecting particular pixels to transmit, reflect or block light. Pixels are addressed (e.g., selected) via rows and columns of the source lines and the gate lines that are electrically connected to transistors (e.g., used as switches) included in each pixel. The transistors take up a relatively small fraction of the area of each pixel to allow light to efficiently pass through (or reflect from) the display pixel. 
     Electrowetting displays include an array of pixels sandwiched between two support plates, such as a bottom support plate and a top support plate. For example, a bottom support plate in cooperation with a top support plate may contain pixels that include electrowetting oil, electrolyte solution and pixel walls between the support plates. Support plates may include glass, plastic (e.g., a transparent thermoplastic such as a poly(methyl methacrylate) (PMMA) or other acrylic), or other transparent material and may be made of a rigid material or a flexible material, for example. Pixels include various layers of materials built upon a bottom support plate. One example layer is a hydrophobic layer, e.g. a fluoropolymer layer, around portions of which pixel walls are built. 
     Hereinafter, example embodiments include, but are not limited to, reflective electrowetting displays that include a clear, transparent, or semi-transparent top support plate and a bottom support plate, which need not be transparent. The clear top support plate may comprise glass or any of a number of transparent materials, such as transparent plastic, quartz, and semiconductors, for example, and claimed subject matter is not limited in this respect. “Top” and “bottom” as used herein to identify the support plates of an electrowetting display do not necessarily refer to a direction referenced to gravity or to a viewing side of the electrowetting display. Also, as used herein for the sake of convenience of describing example embodiments, the top support plate is that through which viewing of pixels of a (reflective) electrowetting display occurs. 
     In some embodiments, a reflective electrowetting display comprises an array of pixels sandwiched between a bottom support plate and a top support plate. The bottom support plate may be opaque while the top support plate is transparent. Herein, describing a pixel or material as being transparent generally means that the pixel or material may transmit or enable the propagation of a relatively large fraction of the light incident upon it. For example, a transparent material or layer may transmit or propagate more than 70% or 80% of the light impinging on its surface, though claimed subject matter is not limited in this respect. In contrast, opaque generally means that the pixel or material may block or inhibit the transmission or propagation of at least a portion of the visible light spectrum incident upon it. For example, a black opaque material or layer may block, absorb, or otherwise prevent the propagation of more than 70% or 80% of the light impinging on its surface, though claimed subject matter is not limited in this respect. In the present disclosure, materials that are described as preventing the propagation of light shall be understood to prevent propagation of at least 70% of the light striking the material. Alternatively, the opaque material may be transmissive for a portion of the visible light spectrum and blocking other portions, forming a color filter. Similarly, materials that are described as being transparent or allowing propagation of light shall be understood to transmit or propagate at least 70% of the light striking the material. Within a conventional display device, the black matrix material may absorb up to 97% of electromagnetic radiation striking the black matrix material. In this description, the visible light spectrum may include light having a wavelength between 390 nanometers (nm) and 700 nm. 
     Pixel walls retain at least a first fluid which is electrically non-conductive, such as an opaque or colored oil, in the individual pixels. A cavity formed between the support plates is filled with the first fluid (e.g., retained by pixel walls) and a second fluid (e.g., considered to be an electrolyte solution) that is electrically conductive or polar and may be a water or a salt solution such as a solution of potassium chloride water. The second fluid may be transparent, but may be colored, or light-absorbing in some embodiments. The second fluid is immiscible with the first fluid. 
     Individual reflective electrowetting pixels may include a reflective layer on the bottom support plate of the electrowetting pixel, a transparent electrode layer adjacent to the reflective layer, and a hydrophobic layer on the electrode layer. Alternatively, the reflective layer may act as the pixel electrode. Pixel walls, associated with and formed around each pixel, the hydrophobic layer, and the transparent top support plate at least partially enclose a fluid region that includes an electrolyte solution and an opaque fluid, which is immiscible with the electrolyte solution. An “opaque” fluid, as described herein, is used to describe a fluid that appears black or to have color to an observer. For example, an opaque fluid appears black to an observer when it strongly absorbs a broad spectrum of wavelengths (e.g., including those of red, green and blue light) in the visible region of light or electromagnetic radiation. In some embodiments, the opaque fluid is a nonpolar electrowetting oil. 
     The opaque fluid is disposed in the fluid region. A coverage area of the opaque fluid on the bottom hydrophobic layer is electrically adjustable to affect the amount of light incident on the reflective electrowetting display that reaches the reflective material at the bottom of each pixel. 
     In addition to pixels, spacers and edge seals may also be located between the two support plates. 
     Spacers and edge seals that mechanically connect the first support plate with and opposite to the second overlying support plate, or which form a separation between the first support plate and the second support plate, contribute to the mechanical integrity of the electrowetting display. Edge seals, for example, being disposed along a periphery of an array of electrowetting pixels, may contribute to retaining fluids (e.g., the first and second fluids) between the first support plate and the second overlying support plate. Spacers can be at least partially transparent so as to not hinder throughput of light in the electrowetting display. The transparency of spacers may at least partially depend on the refractive index of the spacer material, which can be similar to or the same as the refractive indices of surrounding media. Spacers may also be chemically inert to surrounding media. 
     In some embodiments, a display device as described herein may comprise a portion of a system that includes one or more processors and one or more computer memories, which may reside on a control board, for example. Display software may be stored on the one or more memories and may be operable with the one or more processors to modulate light that is received from an outside source (e.g., ambient room light) or out-coupled from a lightguide of the display device. For example, display software may include code executable by a processor to modulate optical properties of individual pixels of the electrowetting display based, at least in part, on electronic signals representative of image and/or video data. The code may cause the processor to modulate the optical properties of pixels by controlling electrical signals (e.g., voltages, currents, and fields) on, over, and/or in layers of the electrowetting display. 
       FIG. 1A  is a cross-section of a portion of an example conventional reflective electrowetting display device  10  illustrating several electrowetting pixels  100  taken along sectional line  1 - 1  of  FIG. 2 .  FIG. 1B  shows the same cross-sectional view as  FIG. 1A  in which an electric potential has been applied to one of the electrowetting pixels  100  causing displacement of a first fluid disposed therein, as described below.  FIG. 2  shows a top view of electrowetting pixels  100  formed over a bottom support plate  104 . The view shown in  FIG. 2  is simplified and does not depict each component illustrated in  FIGS. 1A and 1B  and primarily illustrates the row and column layout of pixels  100 . 
     In  FIGS. 1A and 1B , two complete electrowetting pixels  100  and two partial electrowetting pixels  100  are illustrated. Electrowetting display device  10  may include any number (usually a very large number, such as thousands or millions) of electrowetting pixels  100 . An electrode layer  102  is formed on a bottom support plate  104 . 
     In various embodiments, electrode layer  102  consists of individual pixel electrodes  103 , each addressing an individual pixel. The individual pixel electrodes may be connected to a transistor, such as a thin film transistor (TFT) (not shown), that is switched or otherwise controlled to either select or deselect an electrowetting pixel  100  using an active matrix addressing scheme, for example. A TFT is a particular type of field-effect transistor that includes thin films of an active semiconductor layer as well as a dielectric layer and metallic contacts over a supporting (but non-conducting) substrate, which may be glass or any of a number of other suitable transparent or non-transparent materials, for example. The TFTs and corresponding data lines may be formed within electrode layer  102  or within other layers over or within support plate  104 . 
     In some embodiments, a dielectric barrier layer  106  may at least partially separate electrode layer  102  from a hydrophobic layer  107 , also formed on bottom support plate  104 . Barrier layer  106  may be formed from various materials including organic/inorganic multilayer stacks or layers. In some embodiments, hydrophobic layer  107  is an amorphous fluoropolymer layer including any suitable fluoropolymer(s), such as AF1600®, produced by DuPont, based in Wilmington, Del. Hydrophobic layer  107  may also include suitable materials that affect wettability of an adjacent material, for example. 
     Pixel walls  108  form a patterned electrowetting pixel grid on hydrophobic layer  107 . Pixel walls  108  may comprise a photoresist material such as, for example, epoxy-based negative photoresist SU-8. The patterned electrowetting pixel grid comprises rows and columns that form an array of electrowetting pixels. For example, an electrowetting pixel may have a width and a length in a range of about 50 to 500 micrometers. 
     A first fluid  110 , which may have a thickness (e.g., a height) in a range of about 1 to 10 micrometers, for example, overlays hydrophobic layer  107 . First fluid  110  is partitioned by pixel walls  108  of the patterned electrowetting pixel grid. A second fluid  114 , such as an electrolyte solution, overlays first fluid  110  and pixel walls  108  of the patterned electrowetting pixel grid. First fluid  110  is immiscible with second fluid  114 . 
     Color filters  113   a ,  113   b  (collectively,  113 ) are positioned over each of pixels  100 . Each color filter  113  may be configured to be substantially transparent to particular ranges of wavelengths of light, while absorbing others. For example, color filter  113   a  may be transparent to red light having wavelengths ranging from 620 nm to 750 nm, while absorbing light having other wavelengths. Conversely, color filter  113   b  may be transparent to green light having wavelengths ranging from 495 nm to 570 nm, while absorbing light having other wavelengths. Various pixels  100  within device  10  may be associated with color filters  113  that are transparent to all wavelengths of visible light, namely white light. As used herein, visible light refers to wavelengths of electromagnetic radiation visible to the human eye. Generally, this includes electromagnetic radiation having wavelengths between about 400 nm to about 700 nm. 
     Color filters  113 , therefore, may be utilized to assign each pixel  100  a color, so that when a particular pixel  100  is in an open state, light reflected by that pixel will take on the color of the color filter  113  associated with that pixel  100 . 
     In an attempt to prevent cross-talk, device  10  includes a number of black matrix members  115  positioned over each pixel wall  108  in device  10 . Black matrix members  115  may include Chromium containing compounds like Chromium oxides, and Chromium nitrides configured to absorb all wavelengths of visible light and therefore reduce an amount of light that may enter device  10  over one pixel while exiting device  10  over a second pixel. Due to their size, in conventional device designs, black matrix member  115  may block up to 20% of the light striking device  10 . 
     A support plate  116 , in conjunction with color filters  113  and black matrix members  115 , covers second fluid  114  and spacers  118  to maintain second fluid  114  over the electrowetting pixel array. A diffuser film may be formed over or, in some cases, integrated into a portion of, support plate  116  to diffuse light striking a surface of support plate  116  and passing therethrough. 
     In one embodiment, spacers  118  extend to support plate  116  and may rest upon a top surface of one or more pixel walls  108 . Multiple spacers  118  may be interspersed throughout the array of pixels  100 . The dimensions and shape of the spacers is not restricted to pillar shape as shown in  FIG. 1A , alternative shapes include crosses, lines of spacers, or full grid spacer structures. 
     In some embodiments of device  10 , a front light component may be positioned over an edge of viewing side  120  of device  10 . In these embodiments, a light guide  117  may be positioned over device  10  to guide light generated by the front light component over viewing side  120  of device  10 . A layer  119 , e.g. glass or other material, incorporating various touch-sensitive structures may also be positioned over device  10 . 
     A voltage applied across, among other things, second fluid  114  and a pixel electrode in electrode layer  102  addressing a particular electrowetting pixel may control transmittance or reflectance of individual electrowetting pixels  100 . 
     Reflective electrowetting display device  10  has viewing side  120  on which an image formed by electrowetting display device  10  may be viewed, and an opposing rear side  122 . Support plate  116  faces viewing side  120  and bottom support plate  104  faces rear side  122 . Reflective electrowetting display device  10  may be a segmented display type in which the image is built of segments. The segments may be switched simultaneously or separately. Each segment includes one electrowetting pixel  100  or a number of electrowetting pixels  100  that may be adjacent or distant from one another. Electrowetting pixels  100  included in one segment are switched simultaneously, for example. Electrowetting display device  10  may also be an active matrix driven display type or a passive matrix driven display, for example. 
     As mentioned above, second fluid  114  is immiscible with first fluid  110 . Herein, substances are immiscible with one another if the substances do not substantially form a solution. Second fluid  114  is electrically conductive and/or polar, and may be water or a salt solution such as a solution of potassium chloride in water, for example. In certain embodiments, second fluid  114  is transparent, but may be colored or light absorbing. First fluid  110  is electrically non-conductive and may for instance be an alkane like hexadecane or (silicone) oil. 
     Hydrophobic layer  107  is arranged on bottom support plate  104  to create an electrowetting surface area. The hydrophobic character of hydrophobic layer  107  causes first fluid  110  to adhere preferentially to hydrophobic layer  107  because first fluid  110  has a higher wettability with respect to the surface of hydrophobic layer  107  than second fluid  114  in the absence of a voltage. Wettability relates to the relative affinity of a fluid for the surface of a solid. Wettability increases with increasing affinity, and it may be measured by the contact angle formed between the fluid and the solid and measured internal to the fluid of interest. For example, such a contact angle may increase from relative non-wettability of more than 90° to complete wettability at  00 , in which case the fluid tends to form a film on the surface of the solid. 
     In some embodiments, first fluid  110  absorbs light within at least a portion of the optical spectrum and so may form a color filter. The fluid may be colored by addition of pigment particles or dye, for example. Alternatively, first fluid  110  may be black (e.g., absorbing substantially all light within the optical spectrum) or reflecting. Hydrophobic layer  107  may be transparent or reflective. A reflective layer may reflect light within the entire visible spectrum, making the layer appear bright, or reflect a portion of light within the visible spectrum, making the layer have a color. 
     If a voltage is applied across an electrowetting pixel  100 , electrowetting pixel  100  will enter into an active or at least partially open state. Electrostatic forces will move second fluid  114  toward electrode layer  102  within the active pixel, thereby displacing first fluid  110  from that area of hydrophobic layer  107  to pixel walls  108  surrounding the area of hydrophobic layer  107 , to a droplet-like form. Such displacing action at least partly uncovers first fluid  110  from the surface of hydrophobic layer  107  of electrowetting pixel  100 . 
       FIG. 1B  shows one of electrowetting pixels  100  in an active state. With an electric potential applied to a pixel electrode in electrode layer  102  underneath the activated electrowetting pixel  100 , second fluid  114  is attracted towards a pixel electrode in electrode layer  102  displacing first fluid  110  within the activated electrowetting pixel  100 . 
     As second fluid  114  moves towards hydrophobic layer  107  of the activated electrowetting pixel  100 , first fluid  110  is displaced and moves towards a pixel wall  108  of the activated pixel  100  or is otherwise displaced. In the example of  FIG. 1B , first fluid  110  of pixel  100   a  has formed a droplet as a result of an electric potential being applied to pixel  100   a . After activation, when the voltage across electrowetting pixel  100   a  is returned to an inactive signal level of zero or a value near to zero, electrowetting pixel  100   a  will return to an inactive or closed state, where first fluid  110  flows back to cover hydrophobic layer  107 . In this way, first fluid  110  forms an electrically controllable optical switch in each electrowetting pixel  100 . 
     As shown in  FIG. 1B , with first fluid  110  of pixel  100   a  displaced, light ray  190  can enter pixel  100   a  through color filter  113   b , strike the reflective surface at the bottom of pixel  100   a  and reflect back out through color filter  113   b . Black matrix members  115 , however, are configured to block some of the light striking viewing side  120  of device  10 . As shown in  FIG. 1B , light ray  192 , which strikes the surface of device  10  nearly normal to viewing side  120 , is blocked by one of the black matrix members  115  and so cannot enter pixel  100   a  to be reflected therefrom. 
     Additionally, because pixel walls  108  are transparent to all wavelengths of visible light, oblique light ray  194 , which entered device  10  over pixel  100  to the right of pixel  100   a , will pass through pixel wall  108 , enter pixel  100   a  and be reflected therefrom. As such, light ray  194  represents cross-talk that may diminish the performance of device  10 . 
       FIG. 3  shows a block diagram of an example embodiment of an electrowetting display driving system  300 , including a control system of the display device. Display driving system  300  can be of the so-called direct drive type and may be in the form of an integrated circuit adhered to bottom support plate  104 . Display driving system  300  includes control logic and switching logic, and is connected to the display by means of electrode signal lines  302  and a common signal line  304 . Each electrode signal line  302  connects an output from display driving system  300  to a different electrode within each pixel  100 , respectively. Common signal line  304  is connected to second fluid  114  through a common electrode, e.g. an electrode deposited over the color filter layer on the top support plate. Also included are one or more input data lines  306 , whereby display driving system  300  can be instructed with data so as to determine which pixels  100  should be in an active or open state and which pixels  100  should be in an inactive or closed state at any moment of time. In this manner, display driving system  300  can determine a target reflectance value for each pixel  100  within the display. 
     Electrowetting display driving system  300  as shown in  FIG. 3  includes a display controller  308 , e.g., a microcontroller, receiving input data from input data lines  306  relating to the image to be displayed. Display controller  308 , being in this embodiment the control system, is configured to apply a voltage to the first electrode to establish a particular display state (i.e., reflectance value) for a pixel  100 . The microcontroller controls a timing and/or a signal level of at least one signal level for a pixel  100 . 
     The output of display controller  308  is connected to the data input of a signal distributor and data output latch  310 . Signal distributor and data output latch  310  distributes incoming data over a plurality of outputs connected to the display device, via drivers in certain embodiments. Signal distributor and data output latch  310  cause data input indicating that a certain pixel  100  is to be set in a specific display state to be sent to the output connected to pixel  100 . Signal distributor and data output latch  310  may be a shift register. The input data is clocked into the shift register and at receipt of a latch pulse the content of the shift register is copied to signal distributor and data output latch  310 . Signal distributor and data output latch  310  has one or more outputs, connected to a driver assembly  312 . The outputs of signal distributor and data output latch  310  are connected to the inputs of one or more driver stages  314  within electrowetting display driving system  300 . The outputs of each driver stage  314  are connected through electrode signal lines  302  and common signal line  304  to a corresponding pixel  100 . In response to the input data, a driver stage  314  will output a voltage of the signal level set by display controller  308  to set one of pixels  100  to a corresponding display state having a target reflectance level. 
     To assist in setting a particular pixel to a target reflectance level, memory  316  may also store data that maps a particular driving voltage for a pixel to a corresponding reflectance value and vice versa. The data may be stored as one or more curves depicting the relationship between driving voltage and reflectance value, or a number of discrete data points that map a driving voltage to a reflectance value and vice versa. As such, when display controller  308  identifies a target reflectance value for a particular pixel, display controller  308  can use the data mapping driving voltage to reflectance value to identify a corresponding driving voltage. The pixel can then be driven with that driving voltage. 
     In the present display device a pixel wall configuration is presented in which the pixels walls are configured with regions arranged to filter particular wavelengths of light. By filtering particular wavelengths of light, cross-talk between pixels can be minimized, reducing overall image distortion and cross-talk related artifacts. In one embodiment, each pixel in the display device is surrounded by a pixel wall arrangement in which the pixel walls are preventing propagation of light having a wavelength other than that desired to be reflected by the pixel. For example, the pixel walls around a pixel may be configured to filter and block light in the same manner as a color filter positioned over the pixel. As such, light from a first pixel of a first wavelength cannot propagate through the pixel wall and enter a second pixel of a second color. Because cross-talk is limited in the present pixel wall design, the black matrix materials of conventional devices can be omitted, thereby allowing more light to enter the display device overall, increasing the display device&#39;s brightness. 
       FIG. 4A  is a cross-section of a portion of an example electrowetting display device  400  illustrating several electrowetting pixels  100  taken along sectional line  4 - 4  of  FIG. 5 .  FIG. 4B  shows the same cross-sectional view as  FIG. 4A  in which an electric potential has been applied to one of the electrowetting pixels  100   a  causing displacement of a first fluid disposed therein, as described below.  FIG. 5  shows a top view of electrowetting pixels  100  formed over a bottom support plate  104 . The view shown in  FIG. 5  is simplified and does not depict each component illustrated in  FIGS. 1A and 1B  and primarily illustrates the row and column layout of pixels  100 . In  FIGS. 4A, 4B, and 5 , items with the same element number as in  FIGS. 1A, 1B, and 2  are of similar construction. 
     In  FIGS. 4A and 4B , two complete electrowetting pixels  100  and two partial electrowetting pixels  100  are illustrated. Electrowetting display device  400  may include any number (usually a very large number, such as thousands or millions) of electrowetting pixels  100 . 
     Each pixel  100  is associated with a color filter  402 . Colors filters  402  (including color filters  402   a ,  402   b ,  402   c , and  402   d ) may be constructed with a generally transparent material such as a photoresist material or photo-definable polymer, including electromagnetic radiation filtering materials suspended within the material. Color filters  402   a ,  402   b ,  402   c , and  402   d  may be formed by the addition of pigments or dyes to a clear photo-definable polymer, for example. The amount of additive depends on system requirements, such as absorbance or transmission specifications. In some cases, polyacrylates are used as photoresist material. General, the organic dyes and pigments used within color filters  402   a ,  402   b ,  402   c , and  402   d  can have molecular structures containing chromophoric groups generating the color filtering properties. Some examples for chromophoric groups are azo-, anthraquinone-, methine- and phtalocyanine-groups. 
     Color filters  402  may also be formed using a dichromated gelatin doped with a photosynthesizer, dyed polyimides, resins, and the like. 
     Color filters  402  are configured to overlay each pixel  100  entirely so that the color filters  402  extend from directly over a midpoint of one pixel wall  108  on a first side of a pixel  100  to a position directly over a midpoint of another pixel wall  108  on a second side of the pixel  100 . In this configuration, no black matrix material is formed or otherwise positioned between each color filter  402 , in contrast to the device  10  configuration illustrated in  FIGS. 1A and 1B . 
     In one embodiment, device  400  includes a combination of red, blue, green, and white color filters  402 , with one color filter  402  being positioned over each pixel  100 . Using color filters  402 , each pixel  100  in device  400  can be associated with a particular wavelength of electromagnetic radiation. By controlling which pixels  100  are active within device  400 , device  400  can generate color images viewable by a user at viewing side  120 . In one embodiment, the red color filters  402  may be transparent to red light having wavelengths ranging from 620 nm to 750 nm, while being absorbing light having other wavelengths. A blue color filter  402  may be transparent to blue light having wavelengths ranging from 450 nm to 495 nm, while being absorbing to light having other wavelengths. A green color filter  402  may be transparent to green light having wavelengths ranging from 495 nm to 570 nm, while being absorbing to light having other wavelengths. A white color filter  402  may be transparent to all wavelengths of visible light. In other embodiments, different ranges of light wavelengths may be associated with the red, blue and green color filters  402 . In still other embodiments, the color filters  402  may be configured to block or transmit electromagnetic radiation of different wavelengths entirely. For example, device  400  may be configured to generate images using pixels  100  having color filters  402  configured to transmit electromagnetic radiation of the colors cyan, magenta, and yellow. In short, color filters  402  may be developed and utilized within device  400  in accordance with any display color model. 
     Pixel walls  404 , including separate regions  404   a ,  404   b ,  404   c , and  404   d  are formed about each pixel  100 . Accordingly, each pixel wall  404  is associated with one or more of pixels  100 . Each region  404   a ,  404   b ,  404   c , and  404   d  of pixel walls  404  are configured to transmit and block different wavelengths of electromagnetic radiation. Within device  400 , the regions of pixel walls  404  immediately surrounding each pixel  100  will be configured to block and transmit wavelengths of electromagnetic radiation in the same manner as the color filter  402  associated with pixel  100 . For example, with reference to  FIGS. 4A and 4B , if color filter  402   b  is configured to transmit red light, but block other wavelengths of electromagnetic radiation, region  404   b  of pixel wall  404  is configured to also transmit red light, while blocking other wavelengths of electromagnetic radiation. 
     In  FIGS. 4A and 4B , pixel  100   a  and pixel  100   b  are adjacent pixels within the display device. Pixels  100  are adjacent when they are next to one another in the display device with no intervening pixel  100  between. A pixel wall  404  is formed between pixel  100   a  and pixel  100   b  so that a region  404   b  of the pixel wall  404  between pixel  100   a  and  100   b  runs along a boundary between pixel  100   a  and pixel  100   b . Similarly, region  404   c  of the pixel wall  404  between pixel  100   a  and  100   b  runs along the same boundary between pixel  100   a  and pixel  100   b.    
     The different regions  404   a ,  404   b ,  404   c , and  404   d  of pixel walls  404  may be formed in a multi-step photolithography process, as described below, or may be formed together as part of a unitary pixel wall  404  structure. In some cases, a reflective material may be deposited at the interface between regions  404   a ,  404   b ,  404   c , and  404   d  of pixel walls  404 . The materials making up pixel walls  404  and, particularly, the different color filter regions  404   a ,  404   b ,  404   c , and  404   d  of pixel walls  404  may be similar or, in fact, the same as the materials making up color filters  402 . In some embodiments, however, the amount of color filter material formed within regions  404   a ,  404   b ,  404   c , and  404   d  of pixel walls  404  may be different than that of the color filters  402  so that regions  404   a ,  404   b ,  404   c , and  404   d  may be more or less transparent to electromagnetic radiation of a particular wavelength than corresponding color filter  402 . 
     In this arrangement, not only do color filters  402  play a role in controlling the wavelengths of electromagnetic radiation outputted by each pixel  100 , but pixel walls  404  also play a role. With reference to  FIG. 1B , for example, light ray  406  can enter the open pixel  100   a  and be reflected out through color filter  402   b . If, for example, color filter  402   b  is configured to transmit red light, while blocking other wavelengths of electromagnetic radiation, only the red portion of light ray  406  will enter pixel  100   a  and be reflected out. Other wavelengths of electromagnetic radiation within light ray  406  will be blocked by color filter  402   b.    
     Light ray  408  can also enter pixel  100   a  and be reflected out through color filter  402   b . This is the case even though light ray  408  enters device  400  at a location above pixel wall  404 . In a conventional device (see, for example,  FIGS. 1A and 1B ), a black matrix material is positioned over the device&#39;s pixel walls and would have blocked light ray  408 . The configuration of device  400  illustrated in  FIGS. 4A and 4B , therefore, allows more light to enter device  400  in contrast to conventional configurations, thereby increasing the overall brightness of device  400 . In one embodiment, for example, where pixels  100  each have a length of 120 micrometers and a width of 60 micrometers, and where the black matrix material in a conventional device has a width of 12 microns, the brightness in the present device  400  may increase over the conventional design by up to approximately 20%. 
     The configuration of pixel walls  404  may also operate to prevent or minimize cross-talk within device  400 . In one example, light ray  410  strikes viewing side  120  of device  400  at a sufficiently small angle θ that it might enter device  400  over pixel  100   b  (a green pixel), but pass into pixel  100   a  (a red pixel). The angle θ at which light ray  410  would pass from one pixel  100  to another may depend upon the dimensions of pixels  100 , the total thickness of the fluid layers between the bottom and top support plate and the height of fluid  110  within pixels  100 . For example, in some devices  440  the total thickness of the fluid layers between the bottom and top support plate may ranges from 20-50 micrometers, pixel  100  wall  404  height may range from 1-10 micrometers, and pixel  100  widths and lengths may ranges from 50-500 micrometers. Instead, however, light ray  410  strikes color filter  402   c , which only allows particular wavelengths of electromagnetic radiation to pass. As such, color filter  402   c  only allows the green portion of light ray  410  to pass. The green portion of light ray  410  then enters the pixel wall  404  as depicted. In a conventional design, in which the pixel walls are constructed from transparent materials, the green portion of light ray  410  would be free to enter the red pixel  100   a . In this example, however, the pixel wall  404  configuration prevents cross-talk. In this example, the green portion of light ray  410  passes through region  404   c  of pixel wall  404 , which is configured to transmit green light. But the green portion of light ray  410  is blocked by region  404   b  of pixel wall  404 , which is configured to only transmit red light, while absorbing green light. Accordingly, the green portion of light ray  410  is terminated at the pixel wall  404  and does not enter pixel  100   a.    
     In many embodiments, a particular pixel  100  of device  400  is associated with a particular color or wavelengths of electromagnetic radiation, so that both the color filter  402  over a particular pixel  100 , as well as the pixel walls  404  surrounding the pixel  100  are all of the same color—that is, they transmit the same wavelengths of electromagnetic radiation, while inhibiting the transmission of other wavelengths of electromagnetic radiation. In the case of a white pixel  100 —a pixel that is configured to reflect white light—that may mean that the color filter  402  over the pixel is transparent to all wavelengths of electromagnetic radiation (in some cases, no color filter may be used). Similarly, the regions of the pixel walls  404  surrounding a white pixel  100  may also be transparent to all wavelengths of electromagnetic radiation. This arrangement is illustrated in  FIG. 5  in which white pixel  502  is surrounded by transparent pixel wall  404  regions  504 . 
     In other configurations, however, white pixels  100  within device  400  may be surrounded by pixel wall regions  404  that are transparent to a number of different wavelengths of electromagnetic radiation.  FIG. 6 , for example, shows a top view of a pixel configuration in which the pixel walls  604   a ,  604   b ,  604   c , and  604   d  surrounding the device&#39;s white pixel  602  are configured to filter light in the same manner as the neighboring pixels. In other words, the pixel wall structures surrounding each white pixel  602  is an extension of the pixel walls defining the neighboring pixels. With reference to a particular white pixel  602  depicted in  FIG. 6 , the pixel wall defining the left side of the white pixel  602  is configured to transmit the same wavelengths of electromagnetic radiation as the pixel to the left of the white pixel; the pixel wall defining the right side of the white pixel  602  is configured to transmit the same wavelengths of electromagnetic radiation as the pixel to the right of the white pixel; the pixel wall defining the top side of the white pixel  602  is configured to transmit the same wavelengths of electromagnetic radiation as the pixel to the top of the white pixel; and the pixel wall defining the bottom side of the white pixel  602  is configured to transmit the same wavelengths of electromagnetic radiation as the pixel to the bottom of the white pixel. 
       FIG. 7  shows a top view of a pixel configuration depicting another alternative white pixel configuration in which each pixel wall  704   a ,  704   b ,  704   c , and  704   d  of white pixel  702  is configured to transmit different wavelengths of electromagnetic radiation. Although this embodiment may allow colored light from the neighboring pixels to enter white pixel  702 , the colored light from the neighboring pixels will mix, resulting in an output of white light from white pixel  702 . 
     The pixel walls of the present disclosure may be fabricated using any suitable process for forming and shaping pixel wall structures that are transparent to particular wavelengths of electromagnetic radiation, while absorbing other wavelengths. Example processes for forming the pixel walls include, without limitation, lithography, embossing, imprinting and electroforming. In one example manufacturing process,  FIGS. 8A-8I  illustrate cross-sectional views of device  800  depicting steps in a photolithography process for forming pixel walls in accordance with the present disclosure. In a first step depicted in  FIG. 8A , a multilayer stack  802  is first formed. The multilayer stack includes a first conductive layer deposited on a first support plate. In one embodiment, the first conductive layer is indium tin oxide (ITO), although in alternative embodiments the first conductive layer may be another suitable material. Deposition techniques include, for example, chemical vapor deposition (CVD), physical vapor deposition (PVD), molecular beam epitaxy (MBE), and sputtering. The first support plate may be the same as or similar to support plate  104  illustrated in  FIGS. 1A and 1B . 
     The multilayer stack includes a first dielectric layer deposited on the first conductive layer of multilayer stack  802 . The first dielectric layer may comprise SiN, SiON, SiO, or TaO, for example. Any suitable deposition technique may be used, such as CVD, PVD, MBE, and a sputtering, for example. A hydrophobic layer (e.g., hydrophobic layer  107 , illustrated in  FIGS. 1A and 1B ) may be deposited over the patterned first dielectric layer. The pixel walls may be formed as illustrated in  FIGS. 8A-8I  before or after the application of the hydrophobic layer to the multilayer stack. 
     Photoresist material  804 , such as epoxy-based negative photoresist SU-8, is deposited over multilayer stack  802 . Photoresist material  804  is configured to be transparent to first wavelengths of electromagnetic radiation (e.g., blue), while preventing propagation of other wavelengths of electromagnetic radiation. This behavior may be achieved by adding pigments or dyes to the photoresist material. The amount of pigments or dyes determines the transparency of the final pixel wall portion to a specific wavelength or wavelength regime and the absorption of the other wavelengths of electromagnetic radiation. The color of the pixel wall portion is determined by the type and concentration of pigments or dye materials used. The pixel walls may include similar amounts of dye or pigment materials so as to provide the same color-filtering properties as color filters that may be positioned over the filters. In other embodiments, however, the pixel walls may include a greater or lesser amount or density of dye or pigment materials. 
     Referring to  FIG. 8B , mask  806  is placed over photoresist material  804 . Photoresist material  804  is then exposed to light through the gaps in mask  806  to pattern photoresist material  804 . The portions of photoresist material  804  exposed to light through mask  806  cure or harden. Mask  806  and the non-cured portions of photoresist material  804  can then be removed to form a first set of pixel walls  808  as illustrated in  FIG. 8C . Although the present example is described in terms of a negative photoresist material  804 , it should be understood that in order fabrication processes positive-type photoresist materials could be used instead. In that case, the portion of the photoresist material exposed to light becomes soluble in the developer material and is removed during fabrication. The mask used for both types of materials may include different patterns. 
     Turning to  FIG. 8D , photoresist material  810 , such as epoxy-based negative photoresist SU-8, is deposited over multilayer stack  802  and around pixel walls  808 . Photoresist material  810  is configured to be transparent to second wavelengths of electromagnetic radiation (e.g., red), while being absorbing to other wavelengths of electromagnetic radiation. 
     Turning to  FIG. 8E , mask  812  is placed over photoresist material  810 . Photoresist material  810  is then exposed to light through the gaps in mask  812  to pattern photoresist material  810 . The portions of photoresist material  810  exposed to light through mask  812  cure or harden. Mask  812  and the non-cured portions of photoresist material  810  can then be removed to form a second set of pixel walls  814  as illustrated in  FIG. 8F . 
     Turning to  FIG. 8G , photoresist material  816 , such as epoxy-based negative photoresist SU-8, is deposited over multilayer stack  802  and around pixel walls  808  and  814 . Photoresist material  816  is configured to be transparent to third wavelengths of electromagnetic radiation (e.g., green), while absorbing other wavelengths of electromagnetic radiation. 
     Turning to  FIG. 8H , mask  818  is placed over photoresist material  816 . Photoresist material  816  is then exposed to light through the gaps in mask  818  to pattern photoresist material  816 . The portions of photoresist material  816  exposed to light through mask  818  cure or harden. Mask  818  and the non-cured portions of photoresist material  816  can then be removed to form a third set of pixel walls  820  as illustrated in  FIG. 8I . As shown in  FIG. 8I , pixel walls  808 ,  814 , and  820  are formed so that portions of the pixel walls may be in contact with one another. 
     With the pixel walls formed as illustrated in  FIGS. 8A-8I , the first and second fluid can be positioned over multilayer stack  802  and a second support plate can be mounted over the fluid and multilayer stack  802  parallel to multilayer stack  802 . 
     In various manufacturing steps various combinations of pixel walls can be combined, wherein different portions of the pixel walls may be configured to be transparent to particular wavelengths of electromagnetic radiation while blocking other wavelengths of electromagnetic radiation. The various pixel wall configurations may include pixel walls or portions of pixel walls that are transparent to all wavelengths of electromagnetic radiation. 
       FIG. 9  illustrates an example electronic device  1400  that may incorporate any of the display devices discussed above. Electronic device  1400  may comprise any type of electronic device having a display. For instance, electronic device  1400  may be a mobile electronic device (e.g., an electronic book reader, a tablet computing device, a laptop computer, a smart phone or other multifunction communication device, a portable digital assistant, a wearable computing device, or an automotive display). Alternatively, electronic device  1400  may be a non-mobile electronic device (e.g., a computer display or a television). In addition, while  FIG. 9  illustrates several example components of electronic device  1400 , it is to be appreciated that electronic device  1400  may also include other conventional components, such as an operating system, system busses, input/output components, and the like. Further, in other embodiments, such as in the case of a television or computer monitor, electronic device  1400  may only include a subset of the components illustrated. 
     Regardless of the specific implementation of electronic device  1400 , electronic device  1400  includes a display  1402  and a corresponding display controller  1404 . The display  1402  may represent a reflective or transmissive display in some instances or, alternatively, a transflective display (partially transmissive and partially reflective). 
     In one embodiment, display  1402  comprises an electrowetting display that employs an applied voltage to change the surface tension of a fluid in relation to a surface. For example, such an electrowetting display may include the array of pixels  100  illustrated in  FIG. 1 , though claimed subject matter is not limited in this respect. By applying a voltage across a portion of an electrowetting pixel of an electrowetting display, wetting properties of a surface may be modified so that the surface becomes increasingly hydrophilic. As one example of an electrowetting display, the modification of the surface tension acts as an optical switch by displacing a colored oil film if a voltage is applied to individual pixels of the display. If the voltage is absent, the colored oil forms a continuous film within a pixel, and the color may thus be visible to a user. On the other hand, if the voltage is applied to the pixel, the colored oil is displaced and the pixel becomes transparent. If multiple pixels of the display are independently activated, display  1402  may present a color or grayscale image. The pixels may form the basis for a transmissive, reflective, or transmissive/reflective (transreflective) display. Further, the pixels may be responsive to high switching speeds (e.g., on the order of several milliseconds), while employing small pixel dimensions. Accordingly, the electrowetting displays herein may be suitable for applications such as displaying video or other animated content. 
     Of course, while several different examples have been given, it is to be appreciated that while some of the examples described above are discussed as rendering black, white, and varying shades of gray, it is to be appreciated that the described techniques apply equally to reflective displays capable of rendering color pixels. As such, the terms “white,” “gray,” and “black” may refer to varying degrees of color in implementations utilizing color displays. For instance, where a pixel includes a red color filter, a “gray” value of the pixel may correspond to a shade of pink while a “white” value of the pixel may correspond to a brightest red of the color filter. Furthermore, while some examples herein are described in the environment of a reflective display, in other examples, display  1402  may represent a backlit display, examples of which are mentioned above. 
     In addition to including display  1402 ,  FIG. 9  illustrates that some examples of electronic device  1400  may include a touch sensor component  1406  and a touch controller  1408 . In some instances, at least one touch sensor component  1406  resides with, or is stacked on, display  1402  to form a touch-sensitive display. Thus, display  1402  may be capable of both accepting user touch input and rendering content in response to or corresponding to the touch input. As several examples, touch sensor component  1406  may comprise a capacitive touch sensor, a force sensitive resistance (FSR), an interpolating force sensitive resistance (IFSR) sensor, or any other type of touch sensor. In some instances, touch sensor component  1406  is capable of detecting touches as well as determining an amount of pressure or force of these touches. 
       FIG. 9  further illustrates that electronic device  1400  may include one or more processors  1410  and one or more computer-readable media  1412 , as well as a front light component  1414  (which may alternatively be a backlight component in the case of a backlit display) for lighting display  1402 , a cover layer component  1416 , such as a cover glass or cover sheet, one or more communication interfaces  1418  and one or more power sources  1420 . The communication interfaces  1418  may support both wired and wireless connection to various networks, such as cellular networks, radio, WiFi networks, short range networks (e.g., Bluetooth® technology), and infrared (IR) networks, for example. 
     Depending on the configuration of electronic device  1400 , computer-readable media  1412  (and other computer-readable media described throughout) is an example of computer storage media and may include volatile and nonvolatile memory. Thus, computer-readable media  1412  may include, without limitation, RAM, ROM, EEPROM, flash memory, and/or other memory technology, and/or any other suitable medium that may be used to store computer-readable instructions, programs, applications, media items, and/or data which may be accessed by electronic device  1400 . 
     Computer-readable media  1412  may be used to store any number of functional components that are executable on processor  1410 , as well as content items  1422  and applications  1424 . Thus, computer-readable media  1412  may include an operating system and a storage database to store one or more content items  1422 , such as eBooks, audio books, songs, videos, still images, and the like. Computer-readable media  1412  of electronic device  1400  may also store one or more content presentation applications to render content items on electronic device  1400 . These content presentation applications may be implemented as various applications  1424  depending upon content items  1422 . For instance, the content presentation application may be an electronic book reader application for rending textual electronic books, an audio player for playing audio books or songs, or a video player for playing video. 
     In some instances, electronic device  1400  may couple to a cover (not illustrated in  FIG. 9 ) to protect the display  1402  (and other components in the display stack or display assembly) of electronic device  1400 . In one example, the cover may include a back flap that covers a back portion of electronic device  1400  and a front flap that covers display  1402  and the other components in the stack. Electronic device  1400  and/or the cover may include a sensor (e.g., a Hall effect sensor) to detect whether the cover is open (i.e., if the front flap is not atop display  1402  and other components). The sensor may send a signal to front light component  1414  if the cover is open and, in response, front light component  1414  may illuminate display  1402 . If the cover is closed, meanwhile, front light component  1414  may receive a signal indicating that the cover has closed and, in response, front light component  1414  may turn off. 
     Furthermore, the amount of light emitted by front light component  1414  may vary. For instance, upon a user opening the cover, the light from the front light may gradually increase to its full illumination. In some instances, electronic device  1400  includes an ambient light sensor (not illustrated in  FIG. 9 ) and the amount of illumination of front light component  1414  may be based at least in part on the amount of ambient light detected by the ambient light sensor. For example, front light component  1414  may be dimmer if the ambient light sensor detects relatively little ambient light, such as in a dark room; may be brighter if the ambient light sensor detects ambient light within a particular range; and may be dimmer or turned off if the ambient light sensor detects a relatively large amount of ambient light, such as direct sunlight. 
     In addition, the settings of display  1402  may vary depending on whether front light component  1414  is on or off, or based on the amount of light provided by front light component  1414 . For instance, electronic device  1400  may implement a larger default font or a greater contrast when the light is off compared to when the light is on. In some embodiments, electronic device  1400  maintains, if the light is on, a contrast ratio for display  1402  that is within a certain defined percentage of the contrast ratio if the light is off. 
     As described above, touch sensor component  1406  may comprise a capacitive touch sensor that resides atop display  1402 . In some examples, touch sensor component  1406  may be formed on or integrated with cover layer component  1416 . In other examples, touch sensor component  1406  may be a separate component in the stack of the display assembly. Front light component  1414  may reside atop or below touch sensor component  1406 . In some instances, either touch sensor component  1406  or front light component  1414  is coupled to a top surface of a protective sheet  1426  of display  1402 . As one example, front light component  1414  may include a lightguide sheet and a light source (not illustrated in  FIG. 9 ). The lightguide sheet may comprise a substrate (e.g., a transparent thermoplastic such as PMMA or other acrylic), a layer of lacquer and multiple grating elements formed in the layer of lacquer that function to propagate light from the light source towards display  1402 ; thus, illuminating display  1402 . 
     Cover layer component  1416  may include a transparent substrate or sheet having an outer layer that functions to reduce at least one of glare or reflection of ambient light incident on electronic device  1400 . In some instances, cover layer component  1416  may comprise a hard-coated polyester and/or polycarbonate film, including a base polyester or a polycarbonate, that results in a chemically bonded UV-cured hard surface coating that is scratch resistant. In some instances, the film may be manufactured with additives such that the resulting film includes a hardness rating that is greater than a predefined threshold (e.g., at least a hardness rating that is resistant to a 3h pencil). Without such scratch resistance, a device may be more easily scratched and a user may perceive the scratches from the light that is dispersed over the top of the reflective display. In some examples, protective sheet  1426  may include a similar UV-cured hard coating on the outer surface. Cover layer component  1416  may couple to another component or to protective sheet  1426  of display  1402 . Cover layer component  1416  may, in some instances, also include a UV filter, a UV-absorbing dye, or the like, for protecting components lower in the stack from UV light incident on electronic device  1400 . In still other examples, cover layer component  1416  may include a sheet of high-strength glass having an antiglare and/or antireflective coating. 
     Display  1402  includes protective sheet  1426  overlying an image-displaying component  1428 . For example, display  1402  may be preassembled to have protective sheet  1426  as an outer surface on the upper or image-viewing side of display  1402 . Accordingly, protective sheet  1426  may be integral with and may overlay image-displaying component  1428 . Protective sheet  1426  may be optically transparent to enable a user to view, through protective sheet  1426 , an image presented on image-displaying component  1428  of display  1402 . 
     In some examples, protective sheet  1426  may be a transparent polymer film in the range of 25 to 200 micrometers in thickness. As several examples, protective sheet  1426  may be a transparent polyester, such as polyethylene terephthalate (PET) or polyethylene naphthalate (PEN), or other suitable transparent polymer film or sheet, such as a polycarbonate or an acrylic. In some examples, the outer surface of protective sheet  1426  may include a coating, such as the hard coating described above. For instance, the hard coating may be applied to the outer surface of protective sheet  1426  before or after assembly of protective sheet  1426  with image-displaying component  1428  of display  1402 . In some examples, the hard coating may include a photoinitiator or other reactive species in its composition, such as for curing the hard coating on protective sheet  1426 . Furthermore, in some examples, protective sheet  1426  may be dyed with a UV-light-absorbing dye, or may be treated with other UV-absorbing treatment. For example, protective sheet  1426  may be treated to have a specified UV cutoff such that UV light below a cutoff or threshold wavelength is at least partially absorbed by protective sheet  1426 , thereby protecting image-displaying component  1428  from UV light. 
     According to some embodiments herein, one or more of the components discussed above may be coupled to display  1402  using fluid optically-clear adhesive (LOCA). For example, the lightguide portion of front light component  1414  may be coupled to display  1402  by placing LOCA on the outer or upper surface of protective sheet  1426 . If the LOCA reaches the corner(s) and/or at least a portion of the perimeter of protective sheet  1426 , UV-curing may be performed on the LOCA at the corners and/or the portion of the perimeter. Thereafter, the remaining LOCA may be UV-cured and front light component  1414  may be coupled to the LOCA. By first curing the corner(s) and/or the perimeter, the techniques effectively create a barrier for the remaining LOCA and also prevent the formation of air gaps in the LOCA layer, thereby increasing the efficacy of front light component  1414 . In other embodiments, the LOCA may be placed near a center of protective sheet  1426 , and pressed outwards towards a perimeter of the top surface of protective sheet  1426  by placing front light component  1414  on top of the LOCA. The LOCA may then be cured by directing UV light through front light component  1414 . As discussed above, and as discussed additionally below, various techniques, such as surface treatment of the protective sheet, may be used to prevent discoloration of the LOCA and/or protective sheet  1426 . 
     While  FIG. 9  illustrates a few example components, electronic device  1400  may have additional features or functionality. For example, electronic device  1400  may also include additional data storage devices (removable and/or non-removable) such as, for example, magnetic disks, optical disks, or tape. The additional data storage media, which may reside in a control board, may include volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. In addition, some or all of the functionality described as residing within electronic device  1400  may reside remotely from electronic device  1400  in some implementations. In these implementations, electronic device  1400  may utilize communication interfaces  1418  to communicate with and utilize this functionality. 
     In an embodiment, an electrowetting display device includes a first support plate and a second support plate. The electrowetting display device includes a first fluid and a second fluid that is immiscible with the first fluid. The first fluid and the second fluid are between the first support plate and the second support plate. The electrowetting display device includes a plurality of pixel walls over the first support plate. The plurality of pixel walls are associated with an electrowetting pixel and allow propagation of visible light of a first color and prevent propagation of visible light of a second color. The second color is different from the first color. The electrowetting display device includes a color filter over the electrowetting pixel. The color filter allows propagation of visible light of the first color and prevents propagation of visible light of the second color. The electrowetting display device includes a pixel electrode over the first support plate and a common electrode coupled to the second fluid for applying a voltage within the electrowetting pixel to cause relative displacement of the first fluid and the second fluid. 
     In another embodiment, a display device includes a first support plate, and a wall over the first support plate. The wall is associated with an electrowetting pixel. The wall allows propagation of light having a wavelength within a first range of wavelengths and prevents propagation of light having a second wavelength in a second range of wavelengths. The display device includes a color filter over the electrowetting pixel. The color filter allows propagation of light having the wavelength within the first range of wavelengths and prevents propagation of light having the second wavelength within the second range of wavelengths. 
     In another embodiment, a method for fabricating at least a portion of an electrowetting display device includes depositing a first photoresist over a surface of a support plate. The first photoresist is transparent to a first color of visible light and absorbing a second color of visible light. The method includes patterning the first photoresist through a first mask to cure a first portion of the first photoresist into a first pixel wall that is transparent to the first color of visible light and absorbing the second color of visible light, and depositing a second photoresist over the surface of the support plate. The second photoresist being transparent to the second color of visible light and absorbing the first color of visible light. The method includes patterning the second photoresist through a second mask to cure a second portion of the second photoresist into a second pixel wall that is transparent to the second color of visible light and absorbing the first color of visible light. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described. Rather, the specific features and acts are disclosed as illustrative forms of implementing the claims. 
     One skilled in the art will realize that a virtually unlimited number of variations to the above descriptions are possible, and that the examples and the accompanying figures are merely to illustrate one or more examples of implementations. 
     It will be understood by those skilled in the art that various other modifications may be made, and equivalents may be substituted, without departing from claimed subject matter. Additionally, many modifications may be made to adapt a particular situation to the teachings of claimed subject matter without departing from the central concept described herein. Therefore, it is intended that claimed subject matter not be limited to the particular embodiments disclosed, but that such claimed subject matter may also include all embodiments falling within the scope of the appended claims, and equivalents thereof. 
     In the detailed description above, numerous specific details are set forth to provide a thorough understanding of claimed subject matter. However, it will be understood by those skilled in the art that claimed subject matter may be practiced without these specific details. In other instances, methods, apparatuses, or systems that would be known by one of ordinary skill have not been described in detail so as not to obscure claimed subject matter. 
     Reference throughout this specification to “one embodiment” or “an embodiment” may mean that a particular feature, structure, or characteristic described in connection with a particular embodiment may be included in at least one embodiment of claimed subject matter. Thus, appearances of the phrase “in one embodiment” or “an embodiment” in various places throughout this specification is not necessarily intended to refer to the same embodiment or to any one particular embodiment described. Furthermore, it is to be understood that particular features, structures, or characteristics described may be combined in various ways in one or more embodiments. In general, of course, these and other issues may vary with the particular context of usage. Therefore, the particular context of the description or the usage of these terms may provide helpful guidance regarding inferences to be drawn for that context.