Patent Application
20070182335
The present invention generally relates to fluorescent lamps, and more particularly relates to techniques and structures for improving the efficiency of fluorescent lamps such as those used in liquid crystal displays.
A fluorescent lamp is any light source in which a fluorescent material transforms ultraviolet or other lower wavelength energy into visible light. Typically, fluorescent lamps include a glass or plastic tube that is filled with argon or other inert gas, along with mercury vapor or the like. When an electrical current is provided to the contents of the tube, the resulting arc causes the mercury gas within the tube to emit ultraviolet radiation, which in turn excites phosphors located on the inside lamp wall to produce visible light. Fluorescent lamps have provided lighting in numerous home, business and industrial settings for many years.
More recently, fluorescent lamps have been used as backlights in liquid crystal displays such as those used in computer displays, cockpit avionics, and the like. Such displays typically include any number of pixels arrayed in front of a relatively flat fluorescent light source. By controlling the light passing from the backlight through each pixel, color or monochrome images can be produced in a manner that is relatively efficient in terms of physical space and electrical power consumption. Despite the widespread adoption of displays and other products that incorporate fluorescent light sources, however, designers continually aspire to improve the amount of light produced by the light source, to extend the life of the light source, and/or to otherwise enhance the performance of the light source, as well as the overall performance of the display.
Accordingly, it is desirable to provide a fluorescent lamp and associated methods of building and/or operating the lamp that improve the performance and lifespan of the lamp. Other desirable features and characteristics will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.
In various embodiments, methods and apparatus are provided for increasing the efficiency of a fluorescent lamp suitable for use as a backlight in a liquid crystal display (LCD). One embodiment of a fluorescent lamp includes a light producing cavity/channel that encloses a vaporous material that produces an ultraviolet light when electrically excited. A layer of light-emitting material within the channel produces the visible light emitted from the lamp in response to the ultraviolet light, and a faceplate made up of a substantially transparent material is affixed to the cavity to confine the vaporous material. To increase the efficiency of the lamp, a coating is provided on the faceplate that reflects ultraviolet light and transmits visible light. The coating may be applied on either the internal or external surface of the faceplate as appropriate for the particular faceplate.
In another embodiment, a method of making a fluorescent lamp suitable for use in a liquid crystal display includes the broad steps of forming a layer of phosphor material within at least a portion of the channel to thereby create a light-emitting layer, preparing a faceplate comprising a substantially transparent material with a reflective coating disposed thereon, wherein the reflective coating is substantially transmissive of visible light but substantially reflective of ultraviolet light, and affixing the faceplate to the channel.
Other embodiments include other lamps or displays incorporating structures and/or techniques described herein. Additional detail about various exemplary embodiments is set forth below.
The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and
The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention.
Various techniques for improving the efficiency, lifespan or other performance aspect of a fluorescent light source are described herein. These techniques include, for example, applying a layer of ultraviolet-reflective material to the faceplate to reduce losses of UV radiation that would otherwise exit through the transparent aperture. While the various concepts and structures described herein can be combined in various ways, it is not necessary that each improvement described herein be implemented in all embodiments. Conversely, each of the various techniques and structures described herein may be readily applied to all types of fluorescent light sources, including so-called “aperture lamps”, “flat lamps” and the like.
Turning now to the drawing figures and with initial reference to
The light that is produced by backlight assembly 104/106 is appropriately blocked or passed through each of the various pixels of array 110 to produce desired imagery on the display 100. Conventionally, display 100 includes two polarizing plates or films, each located on opposite sides of pixel array 110, with axes of polarization that are twisted at an angle of approximately ninety degrees from each other. As light passes from the backlight through the first polarization layer, it takes on a polarization that would ordinarily be blocked by the opposing film. Each liquid crystal, however, is capable of adjusting the polarization of the light passing through the pixel in response to an applied electrical potential. By controlling the electrical voltages applied to each pixel, then, the polarization of the light passing through the pixel can be “twisted” to align with the second polarization layer, thereby allowing for control over the amounts and locations of light passing from backlight assembly 104/106 through pixel array 110. Most displays 100 incorporate control electronics 105 to activate, deactivate and/or adjust the electrical parameters 109 applied to each pixel. Control electronics 105 may also provide control signals 107 to activate, deactivate or otherwise control the backlight of the display. The backlight may be controlled, for example, by a switched connection between electrodes 102, 103 and appropriate power sources. While the particular operating scheme and layout shown in
Fluorescent lamp assembly 104/106 may be formed from any suitable materials and may be assembled in any manner. Substrate 104, for example, is any material capable of at least partially confining the light-producing materials present within channel 108. In various embodiments, substrate 104 is formed from ceramic, plastic, glass and/or the like. The general shape of substrate 104 may be fashioned using conventional techniques, including sawing, routing, molding and/or the like. Further, and as described more fully below, channel 108 may be formed and/or refined within substrate 104 by sandblasting in some embodiments.
Channel 108 is any cavity, indentation or other space formed within or around substrate 104 that allows for partial or entire confinement of light-producing materials. In various embodiments, lamp assembly 104/108 may be fashioned with any number of channels, each of which may be laid out in any manner. Serpentine patterns, for example, have been widely adopted to maximize the surface area of substrate 104 used to produce useful light. U.S. Pat. No. 6,876,139, for example, provides several examples of relatively complicated serpentine patterns for channel 108, although other patterns that are more or less elaborate could be adopted in many alternate embodiments.
With reference now to
An optional protective layer 204 may be provided on light-emitting layer 202 to prevent argon, mercury or other vapor molecules from diffusing into the phosphor or other light-emitting material. When used, protective layer 204 may be made up of any conventional coating material such as aluminum oxide or the like. Alternatively, various embodiments could include a protective layer 204 that includes fused silica (“quartz glass”) or a similar material to prevent mercury penetration into light emitting layer 102.
While
While
To reiterate, then, a fluorescent light source having improved luminous efficiency can be created by adding a suitable reflective layer to the faceplate or cover. Luminous material (e.g. phosphor) is applied in the channel 108 as appropriate, and a coating that is reflective of ultraviolet light yet transmissive of at least certain wavelengths of visible light is applied to the cover. This coating may comprise, for example, one or more metallic layers selected according to the desired optical characteristics of the coating, and applied on the internal and/or external face of the cover as appropriate. The faceplate assembly may then be fitted to the light source substrate by fritting, by using mechanical or chemical fasteners, and/or through any other technique.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.
