Patent Application
20070182306
The present invention generally relates to fluorescent lamps, and more particularly relates to techniques and structures for improving the life and/or 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, a fluorescent lamp includes a glass 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 coating the inside lamp wall to produce visible light. Fluorescent lamps have provided lighting for 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 life of a fluorescent lamp suitable for use as a backlight in an avionics or other liquid crystal display (LCD). The apparatus includes a channel configured confine a vaporous material that produces an ultra-violet light when electrically excited. A layer of light-emitting material is disposed within at least a portion of the channel is responsive to the ultra-violet light to produce the visible light emitted from the lamp. An electrode assembly that electrically excites the vaporous material includes a first post, a second post, a conductive filament suspended between the first post and the second post and having a tail portion extending therebeyond, and a benign insulating material such as glass frit substantially covering the tail portion to prevent radio frequency (RF) emissions from the tail portion of the filament.
In another embodiment, a method of forming an electrode assembly suitable for use in a fluorescent light source suitably includes the broad steps of suspending the filament between two conductive posts, trimming the filament, and subsequently applying glass frit or another appropriate insulating material over the tails of the filament that remain after trimming.
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, luminescence and/or other performance aspect of a fluorescent light source are described herein. For example, a technique for reducing RF emissions emanating from unkempt wires protruding from light source filaments is described below. Each of the various techniques and structures described herein may be independently applied to any and all types of fluorescent light sources, including so-called “aperture lamps”, “flat lamps”, fluorescent bulbs, 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.
Channel 108 is appropriately formed in substrate 104 by milling, molding or the like, and light-emitting material is applied though spraying or any other conventional technique. Light-emitting material found within channel 108 is typically a phosphorescent compound capable of producing visible light in response to “pump” energy (e.g. ultraviolet light) emitted by vaporous materials confined within channel 108. Various phosphors used in fluorescent lamps include any presently known or subsequently developed light-emitting materials, which may be individually or collectively employed in a wide array of alternate embodiments. Light emitting materials may be applied or otherwise formed in channel 108 using any technique, such as conventional spraying or the like. In various embodiments, an optional protective layer may be provided to prevent argon, mercury or other vapor molecules from diffusing into the light-emitting material. When used, such a protective layer may be made up of any conventional coating material such as aluminum oxide or the like. Alternatively, various embodiments could include a protective layer that includes fused silica (“quartz glass”) or a similar material to prevent mercury penetration.
Turning now to
Lamp 602 is any bulb or other light source capable of producing fluorescent light resulting from electrical excitation of vaporous materials residing within channel 108, as described above. In various embodiments, lamp 602 suitably includes two or more electrode assemblies 604A-B that provide an interface between external sources of electrical energy and the gas or plasma residing within channel 108. In a conventional implementation, electrode assemblies 604A-B each include two or more electrode posts 612A-B, 614A-B interconnected by one or more filaments 610A-B. In the exemplary embodiment of
In many conventional lamps 602, filaments 610A-B are extended between holes or other gaps in electrode posts 612A-B and 614A-B. Filaments 610A-B may be suspended, for example, between two posts made of nickel or other conductive material. Frequently, after the filaments are stretched between the conductive posts during construction of the lamp, a small segment or “tail” 612A-B, 614A-B remains on the outer portion of electrodes 612A-B, 614A-B (respectively). Because the voltage difference between the ends of the lamp can be significant in some embodiments (e.g. on the order of a kilovolt or more), tails 612A-B, 614A-B can have adverse effects on the performance or life of lamp 602 if left untreated. If the filament tails 612A-B, 614A-B have sharp end points, for example, and are allowed to remain relatively close to the wall of lamp 602, field emission can result in sputtering of the material at the tail, as well as significant radio frequency (RF) emission. Even if the tails 612A-B, 614A-B are trimmed closer to the posts, RF emission can still occur. To prevent such effects, various embodiments provide a benign insulating material 616A-B, 618A-B such as glass frit or the like over the filament tails 612A-B, 614A-B (respectively). In such embodiments, glass frit can be effectively fired on the filament ends 616A-B, 618A-B after trimming, but before processing and installation in lamp 602. Insulating material 616A-B, 618A-B may be any equivalent material capable of affixing to electrode posts 606, 608 and of insulating or otherwise preventing RF emissions from tails 612, 614. Other embodiments may therefore provide alternate insulating materials other than glass frit as appropriate.
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. The techniques described with primary respect to a fluorescent light bulb, for example, could be readily implemented in any sort of flat lamp, aperture lamp or other light source. 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.
