Reflective film display device that is electromechanically...

Computer graphics processing and selective visual display system – Single display system having stacked superimposed display...

Reexamination Certificate

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C345S001100

Reexamination Certificate

active

06738029

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-192759, filed Jun. 27, 2000, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a reflective film display device that is electromechanically actuated, the method of manufacturing the same, and a method of manufacturing a cantilever for display for the reflective film display device, particularly, to an electromechanically actuated reflective film display device forming a plurality of black, white or colored tabs that engender text and images, in which a large number of electromechanically actuated film devices are two dimensionally arranged to form a grid or matrix, the manufacturing method thereof, and a method of manufacturing a cantilever for display for the reflective film display device.
These display devices, called “actuated film displays” (AFD or AFD's), offer features such as a paper-like white appearance, low power consumption, quick response and good color performance.
Display manufacturers have long aspired to supply customers with large hang-on-the-wall televisions and electronic information boards at affordable prices. Various technologies that offer excellent optical properties are already available on the market but most of these are limited in size and none is yet able to satisfy the low cost requirements. The present invention is intended to make possible the fabrication of thin and light displays in any size and at low cost, without compromising on highly desirable qualities such as a high contrast ratio, an excellent color gamut, a wide viewing angle, quick response and low energy consumption.
Before describing the present invention, we will briefly discuss the advantages and problems associated with other well-known type of display.
A liquid crystal display (LCD) is a panel technology which is, by far, the most widely used to create thin and light reflective as well as transmissive display devices. Most reflective LCD's tend to produce dark images due to the inclusion of polarizers and can only offer faded colors due to a low contrast ratio. They are therefore used in a variety of applications, such as watches, portable phones, game consoles or electric appliances, where brightness and color quality are sacrificed in order reduce manufacturing costs as much as possible and increase mobility and battery life. Applications that require much higher quality images and extended viewing periods of time and where costs are not crucial will rather include transmissive LCD's. They have completely dominated the portable notebook computer market for several years already and have even started to penetrate the desktop display market as manufacturing yields have improved and prices have gone down. The most common LCD device usually comprises a glass cell confining a layer of liquid crystal in the twisted nematic (TN) configuration. LCD's can, without a doubt, claim to offer the near-perfect solution for notebook computers due to their light weight, thin frame, wide range of colors, high resolution and crisp text quality. Current TFT LCD's are still relatively expensive when compared to cathode ray tubes (CRT's) due to the large number of TFT manufacturing processes involved and yield consideration. Despite this, they are in great demand since they allow complete mobility. It remains doubtful however if they will ever become a viable solution for very large displays since manufacturing defects are far more likely to appear in larger cells (the larger the surface, the higher the probability of various deficiencies to appear), therefore causing production yields to decrease significantly and costs to sky-rocket. While it can be expected that very large LCD's will find a niche in the corporate market, radically inexpensive manufacturing processes will have to be developed in order for them to compete with large CRT's. Efforts have been made to assemble a series of smaller and cheaper LCD's to form a larger one by using seamless technology (the edge of each display is rendered invisible) but with limited success so far.
While size may be considered as the most pressing problem to be solved in the near future, it is certainly not the only hurdle limiting the range of LCD applications. The response time of the most commonly used liquid crystals, i.e., the liquid crystals that offer the best optical performance, also tends to be rather slow. This means that when movies or television broadcasts are shown, ghost-like halos trail moving objects and details of continuously changing images become blurred. Therefore, new cell structures and liquid crystals suitable for fast switching (while maintaining current optical properties) need to be developed.
The second most widely manufactured flat panel display technology, albeit in much smaller volumes than LCD's, is of the plasma display. These can be fabricated in large sizes and offer ideal optical properties such as a wide range of colors, a high contrast, a wide viewing angle as well as a quick response. Plasma displays consumes a lot of power, however, in order to provide sufficient luminance. They are also considerably heavier and bulkier than equivalent-sized LCD's, characteristics that are fatal problems as far as the notebook computer market is concerned. As for large-sized displays, production costs are still extremely high and they are not expected to be a serious rival to CRTs for many years to come.
The field emissive display (FED) is considered by many to be the technology that has the best chance of replacing all CRT's with thin and light displays offering superior optical properties. FED's basically includes a glass panel supporting an array of microscopic conically shaped tip electrodes which can be induced to emit electrons when submitted to an intense electric field. In a process that greatly resembles the techniques used in common cathode ray tubes of televisions, the emitted electrons then serve to bombard patterned phosphors which in turn emit red, green or blue light. Displays of a small size have been fabricated successfully but it is still unclear if manufacturers will be able to fabricate large displays at affordable price.
Further, the present inventor has already proposed a novel movable film type display device in Japanese Patent Disclosure (Kokai) No. 8-271933. The movable film type display device of the noble construction comprises a movable cantilever supporting a tab (display piece) and fixed at one end portion with the other end portion made movable and a stationary electrode. A gap is formed between the movable cantilever and the stationary electrode in this display device. The movable cantilever is moved within the gap by the electrostatic force generated between the movable cantilever and the stationary electrode so as to allow the background of the tab (folded piece) supported by the movable cantilever to perform the function of the display region. To be more specific, when the tab is moved to expose the background of the tab to the outside, the background can be seen from the outside, thereby allowing it to perform the function of the display region. In the movable film type display device of this type, the structures described above are arranged in the row and column directions and each tab is moved independently so as to make it possible to display an image.
In the movable film type display device in which a large number of electromechanically movable members are arranged, it is necessary to stack the electromechanically movable structures one upon the other. For the arrangement of the electromechanically movable structures, an accurate alignment is required. Therefore, proposals of the structure adapted for the manufacture and novel manufacturing method and apparatus are awaited.
As described above, thin and lightweight display devices having good optical characteristics are already available on the

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