|Publication number||US20050285816 A1|
|Application number||US 11/217,038|
|Publication date||Dec 29, 2005|
|Filing date||Aug 31, 2005|
|Priority date||Feb 26, 1999|
|Also published as||US7167156|
|Publication number||11217038, 217038, US 2005/0285816 A1, US 2005/285816 A1, US 20050285816 A1, US 20050285816A1, US 2005285816 A1, US 2005285816A1, US-A1-20050285816, US-A1-2005285816, US2005/0285816A1, US2005/285816A1, US20050285816 A1, US20050285816A1, US2005285816 A1, US2005285816A1|
|Original Assignee||Micron Technology, Inc.|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (6), Referenced by (29), Classifications (10)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is a Divisional of U.S. application Ser. No. 09/258,743, filed Feb. 26, 1999, which is incorporated herein by reference,
The invention relates generally to an electronic display apparatus, and specifically to use of electrowetting to actuate pixels in a display.
A number of display types exist for the purpose of physically displaying a representation of an image formed electronically, such as on a computer. Standard Cathode-Ray Tube (CRT) displays are the most common, but are supplemented by technologies such as Liquid Crystal Display (LCD) and gas plasma display when space is a concern. Each of these display types has characteristics that are advantageous for certain applications, but all share certain characteristics that limit the use of electronic displays to certain applications.
A standard CRT display used with most personal computer systems receives three signals of varying intensity, each representing one of the colors red, green, and blue. The strength of each signal controls the intensity of an electron stream produced by an electron gun within the CRT. The electron streams are focused and aimed by a magnetic deflection apparatus, which receives signals from the video source that control the deflection apparatus to sweep each electron beam from side to side in a pattern that crosses and moves down the screen. The beams pass through a shadow mask, a metal plate comprising a number of small holes or slots, used to keep the electron beams precisely focused on the target. The beams then strike phosphor which coats the inside of the screen, and create a visible image. Separate phosphors exist for each of the three colors, and glow with intensity proportional to the intensity of the striking electron beam. This CRT apparatus is well-understood and relatively inexpensive, but is physically large in size, and its resolution is limited by the slot mask and screen phosphor geometry.
A popular alternative is a Liquid Crystal Display (LCD). Such a display operates by first generating light from a fluorescent panel near the back of the display. A polarizing filter in front of the light panel passes only those light waves that are vibrating in or near a particular plane, most commonly horizontal. The polarized light then passes through a layer of liquid crystal cells. Each of the cells may be electronically activated by varying voltages, such that a cell receiving no voltage has no twist in the crystal structure of the liquid crystal cell, while a cell receiving a high voltage has about 90 degrees of twist in the crystal structure of the liquid crystal cell. Polarized light entering the rear of the cells follows the structure of the liquid crystal, turning up to 90 degrees in orientation with the twist in the crystal structure. The light then passes through a color filter that is either red, blue, or green, and through a second polarizing filter oriented at 90 degrees rotated from the first polarizing filter. Light that is not oriented essentially in the same plane as the second polarizing filter is attenuated, and light that vibrates at 90 degrees from the orientation of the second filter is blocked almost completely. Therefore, by varying the voltage applied to the liquid crystal cell, the light transmitted through the display is varied proportionately, and an array of such devices is used to produce an image. Such a display can be quite flat, but resolution is again limited by the physical size of the polarizing and color filters, and the liquid crystal cell.
Other display mechanisms exist, but most have some physical attribute that limits the resolution displayable by the apparatus. What is needed is a display apparatus that allows real-time creation of very high-resolution images.
The present invention comprises construction of a display from display elements that are actuated using the physical principle of electrowetting. In one embodiment, pores within porous silicon are filled with an ionic and an optically reflective electronic conductor, and actuated by application of an electric potential across the pore. An image is then formed on an array of such pores by applying an appropriate voltage to each pore of the array to create an optical image in the light reflected off the electronic conductors. Such a display may be constructed to have very high resolution, making it desirable for creating real-time holographic images, or for creating high-resolution mask images for use in photolithography.
In the following detailed description of sample embodiments of the invention, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific sample embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical, and other changes may be made without departing from the spirit or scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the invention is defined only by the appended claims.
The present invention comprises use of electrowetting principles in porous silicon to create a display apparatus. The display apparatus is controlled by an electronic control matrix, which creates an electric potential across selected silicon pores to actuate the display elements. Each display element contains an electronic conductive liquid and an ionic conductive liquid, such that electrowetting principles cause the electronic conductive liquid to shift from end to end in the pore when a potential gradient is present across the pore.
Electrowetting is a physical phenomena in which an applied electrical potential introduces interfacial surface tension change in a liquid, causing the liquid to flow. In one embodiment, a mercury slug serves as the electronic conductive liquid and saltwater serves as the ionic conductive liquid, and a potential gradient between the ends of a cylindrical pore in silicon causes actuation and movement of the mercury slug. The exact composition of the saltwater is not critical, but should be sufficient to facilitate movement in a potential field.
To increase surface resistance of the pore, the interior surface of the pore can be lightly oxidized. Alternatively, the substrate can be comprised of polysilicon, or other nonconductive material. The insulating substrate contains a number of cylindrical pores 102, each of which are injected with an ionic conductor fluid 103 and a reflective electronic conductor 104. In one embodiment, the electronic conductor 104 is mercury and the ionic conductor 103 is saltwater. The pore containing the ionic and electronic conductors is sealed with a transparent seal 105, which may be a transparent metallic conductive composition such as Indium tin oxide. An external light source (not shown) can be employed in one embodiment to provide light which reflects off the reflective electronic conductor of each display element. Alternatively, ambient light from the operating environment of the display is reflected off the reflective electronic conductor of each display element to form an image.
In operation, a voltage applied at one end of a display element as pictured in
This effect is known as electrowetting, and is used in one embodiment to move reflective mercury slugs serving as electronic conductors within a number of display elements as shown in
Alternatively, the pores may be constructed as shown in
One possible circuit for altering the potential of the bottom cap of each display element pore is shown in
In a further embodiment, a selected voltage may be applied to each of several column select lines 404 while a single row select line 403 is energized, allowing an entire row of pores to be actuated at the same time, each to an independently selected position. Because a different voltage may be applied to each of the column select lines simultaneously while a voltage is applied to a single row select line, each element activated by the energized row select line 403 and switched transistor 401 is independently actuated.
An array of electrowetting display elements as pictured in
Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. This application is intended to cover any adaptations or variations of the invention. It is intended that this invention be limited only by the claims, and the full scope of equivalents thereof.
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|International Classification||G09G3/28, G02B26/02, G09G3/34|
|Cooperative Classification||G09G2310/0262, G09G3/3433, G02B26/005|
|European Classification||G02B26/00L1, G02B26/00L, G09G3/34E|