Patent Application
20070290600
In the drawings, identical reference numbers identify similar elements. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale.
In the following description, numerous specific details are given to provide a thorough understanding of various embodiments of the invention. The invention, with equivalent structures and methods to those shown and described, can be practiced without one or more of the specific details, or with other methods, components, materials, etc. Well-known structures, materials, or operations are not shown or described in detail which are within the scope of the art and do not form part of this invention.
In one embodiment, the lamp 1 comprises a top plate 2 and the bottom plate 4. The top and bottom plates 2 and 4, respectively, are connected to electrically insulating sidewalls 6 (collectively referenced as 6 and individually referenced as 6a, 6b) and end walls 5 at the peripheral edges 8 of the top and bottom plates 2 and 4, respectively, forming a hermetically sealed chamber. A plurality of electrically insulating partitions 10 extend between the top and bottom plates 2, 4 forming the plurality of discharge channels 12.
The inner surfaces of one or both of the top plate 2 or bottom plate 4 are coated with a photoluminescent material 14. Additionally or alternatively, the surfaces of the electrically insulating partitions 10 may also be coated with the photoluminescent material 14. The photoluminescent material 14 may be, for example, a phosphor layer or any suitable layer for generating visible light energy in response to excitation by ultraviolet (UV) radiation, as is well known in the art.
The hermetic chamber includes an ultraviolet emissive gas. While mercury vapor is commonly used in fluorescent lamps, it is possible to use other gases and chemical vapors to provide the UV energy such as, for example, xenon, krypton, neon, helium, and or with argon, xenon, a mixture of inert halogen gases and the like, either alone or in combination to produce the desired spectral characteristics, all of which are known to those skilled in the art. The ultraviolet emissive gas used in the lamp 1 emits ultraviolet radiation when the gas is electrically excited. The lamp pressure is selected to provide the desired spectral characteristics of the lamp 1 for a given gas or gas and vapor combination, as is known in the art. Accordingly, the embodiments described herein are not limited by the lamp pressure, the type of photoluminescent material 14, the type of gas or gas and vapor combination used to fill the lamp 1.
The lamp 1 of
Power is supplied to the electrode plates 16a, 16b to create electrical discharge paths within the gas of each channel 12. In some embodiments, a pulsed AC power supply 18 may power the electrodes 16 while in other embodiments a pulsed DC waveform may be converted from low voltage DC power or a continuous wave form is used.
In one embodiment, the carrier waveform is about 20 khz and is pulsed at between 20-400 hertz as required. The secondary of a transformer is a center point ground type. With the center point ground electrically connected to the lamp ground plane and the aluminum heat sink all connected to system ground.
In another embodiment the lamp 1 is pulsed on and off, in relation to the LCD scan rate and aids in reducing blurring artifacts in motion displayed images on the LCD.
According to further embodiments, first and second electrodes (not shown) are disposed along an exterior of the first and second planar plates 2, 4 to create a uniform electric field along each of the plurality of chambers 12 by capacitive coupling through the first and second planar plates 2, 4.
According to some embodiments, the gas permeable passage 20 is positioned between adjacent channels 12 to permit a passage of gas molecules and/or vapor between the adjacent channels 12 while blocking an electrical discharge 19 (
For example, the lamp 1 may be positioned in an upright position during use, thereby causing a temperature gradient between the plurality of channels 12 due to the difference in elevation between channels 12. Since heat rises, channels 12 positioned at a higher elevation than others may have a significantly higher internal temperature. In such an upright position, the temperature in each channel 12 is greater than the underlying channel 12, thus forming a temperature gradient as the channels 12 increase in height from sidewall 6a to sidewall 6b (For example, if sidewall 6a is positioned at a lower height than sidewall 6b).
At higher channel 12 temperatures the mercury vapor is driven down toward the cooler regions which reduce the pressure. This increases the pressure in lower channels and substantially equalizes the pressure throughout the lamp 1. With such self regulating vapor pressure means, a minimum quantity of mercury liquid is required in the hermetically sealed lamp 1. Absent a means for allowing the passage of gas and vapor between the channels, those channels 12 with the higher internal temperature would emit more light than channels 12 positioned at a lower height and having a relatively lower internal temperature. This would result in a non-uniform light distribution across the lamp 1.
The gas permeable passage 20 allows for the gas and vapor pressure to appropriately compensate for the temperature gradient across the lamp 1. For example, the gas molecules from a hot channel 12 may diffuse into the cold channel 12 to compensate for the temperature gradient and resulting non-uniformity in light emission between the channels 12. This establishes uniform light emission throughout the lamp 1.
In another embodiment, a thermoelectric device (not shown) may be coupled to the center of the coldest cold channel 12, proximate the sidewall 6a, by heating the cold channel 12 and effectively increasing the internal temperature, thereby raising the vapor pressure and providing light emission comparable to the warmer channels 12. The thermoelectric device may be placed at the center of the bottom channel, (also known as the cold spot of the lamp—the area where the mercury vapor would condense back to the liquid state). If the lamp has ran for a period of time, the mercury vapor will reach equilibrium and condense at the cold spot of a particular lamp. By the heating of the thermoelectric heater, the mercury vapor is flashed into the lamp raising the vapor pressure up through the permeable passage. This allows the lamp 1 to initially start up with uniform illumination without the delay associated with the gradual raise in vapor pressure associated with the plasma discharge heating only.
Once desired vapor gas pressure and uniform light is achieved throughout the lamp 1, the thermoelectric device may function to control the gas pressure and associated light emission by functioning interchangeably as a cooler as well as a heater.
As a further example, when a fluorescent lamp ages, the vapor pressure may be reduced vary slightly as mercury is lost into the lamp coatings or glass walls on the chamber. Also, the gas pressure may become reduced at the cathode area from being trapped between the walls of the chamber and a thin sputtered film associated with cathode operation. If a plurality of channels are adjacent to each other and are hermetically isolated, over time, the vapor and gas pressure in each will gradually change at different rates, thus causing the light emitted to vary. If the channels are adjacent to each other, even minor variations in light emission may be apparent to an observer. Such variations would create dark or light areas in the back light of an LCD and thus would be undesirable in the displayed images.
As described above, one of the applications of the lamp 1, such as a backlight for a flat screen display (shown in
In the event that the lamp 1 is used for low light applications it may be beneficial to neutralize the electric fields near the electrodes 16a, 16b. Since the electric fields near the electrodes 16a, 16b are higher than at other portions of the channel 12, there may be a noticeably higher illumination near the areas of high electric field (e.g., near the electrodes 16a, 16b) and thus non-uniform light emission across the channel 12. In order to substantially eliminate such non uniformity, the electric field near the electrodes 16a, 16b may be neutralized by having a grounded conductive layer 32 disposed along at least portions of the backside of the bottom plate 4 that correspond to the electrode 16a, 16b. The conductive layer 32 is at least aligned with the electrode 16a, 16b and blocks the electric field from influencing the light emission within the channel 12. An insulator 13 encapsulates at least a portion of the conductive layer 32 that is positioned within the extruding coverings 30a, 30b. The insulator 13 prevents the gas from contacting the grounded conductive layer 32. The insulator 13 may be of electrically insulating material that is similar to the insulating material comprising the lamp 1. The grounded conductive plane 32 may be positioned on the front of the lamp in an alternate design by using a transparent conductor film or grid.
The lamp 1 is preferably formed by high speed extruding the hot glass into a channeled flat ribbon having channel detail corresponding to the desired channels 12 in the lamp 1, as shown in
The three sets of holes 29 may be formed using the torch or the laser or hot pressing when the glass is hot or by drilling or water jet cutting or sandblasting the holes 29 when the glass is at ambient temperature. The holes 29 may be manufactured according to any suitable technique known in the art. The lamp 1 is then internally coated with the photoluminescent material 14 and baked. The coverings 30 are sealed onto the bottom plate 4 using the torch or low-melting point frit. Covering 30c is left with one unsealed opening, which is inserted with the pumping tube for extracting air from the lamp 1 by means of vacuum pumping. Following the vacuum pumping, the pumping tube fills the lamp 1 with the desired gas and mercury source. As the pumping tube is sealed-off from the opening of the covering 30c, the tip-off 25 is formed, as is practiced in the industry.
According to one embodiment, the top and bottom plates 2, 4, the insulating partitions 10, the sidewalls 6, and the end walls 5 comprise one unit of glass, hereinafter referred to as the unitary structure 15. As illustrated in
The lamp 1 of
The lamp 1 allows for mass production by having two sets of holes 29a, 29b formed through the bottom plate 4 with the gas permeable passage 20 formed by the removal of at least the photoluminescent material 14 underlying each of the electrically insulating partitions 10 at a position along a region 21 (described in detail in
Extruding coverings 30a and 30b have electrode plates 16a and 16b, respectively, disposed along the outside or inside (not shown) of the extruding covering 30a, 30b along the directional axis perpendicular to the channels 12. The insulating dividers 31 are disposed within the coverings 30a, 30b to electrically divide the electrode plates 16a, 16b so that each channel 12 is electrically isolated from the other.
The production of the lamp 1 of
The sets of holes 29a, 29b may be formed using the torch or a laser when the bottom plate 4 is hot, by drilling when the bottom plate 4 is cold, or by other suitable techniques known in the art. The gas permeable passage 20 may be formed using any suitable masking technique. A mask may be applied prior to deposition of the photoluminescent material 14 so that only the desired portions of the bottom plate 4 are covered with the photoluminescent material 14. Alternatively, mechanically scraping or removing the photoluminescent material 14 from the desired portions of the bottom plate 4 may form the passage 20. The coverings 30a, 30b are sealed onto the bottom plate 4 using the torch or low-melting point frit. One of the sidewalls 6a, 6b has at least one unsealed opening adjacent the passage 20, which is inserted with a pumping tube for extracting air from the lamp 1 by means of vacuum pumping. Following the vacuum pumping, the pumping tube fills the lamp 1 with the desired gas. As the pumping tube is removed from the sidewall 6a, 6b opening, the tip-off tube 25 is formed.
Power is supplied to the electrodes 16a, 16b (collectively referenced as 16 and individually referenced as 16a, 16b) disposed adjacent each of the plurality of channels 12 and at opposite ends of the channels 12 to create respective electrical discharge paths within the gas of each channel 12. In some embodiments, the electrodes 16 are disposed adjacent the channels 12 on the backside of the lamp 1 while in other embodiments, alternatively or additionally, the electrodes 16 are disposed within the channel 12. The electrodes 16 may be anodes/cathodes, filaments (e.g., heated electrodes or hot cathodes as shown in
The powered electrodes 16 create the electrical discharge 19 within each of the channels 12 when the voltage across the channel 12 rises above a threshold value, called the breakdown voltage. Electrons are generated and emitted from each of the electrodes 16 within the channels 12, thereby forming the electrical discharge 19. The electrical discharge 19 is sustained by a flow of electrons generated by electrodes 16a, 16b, which operate alternatively as cathode and anode during AC operation. Since the electrical discharge 19 are on opposed sides of the channel 12 and flowing in opposite directions, there exists at least a portion of the region 21 within each of the channels 12 where the electrical energy is of minimal electrical energy in comparison to other locations within the channel 12. The phenomena known as space charge effect produces a voltage drop across the plurality of channels 12 within the lamp 1 causing the atmosphere in the chamber to conduct, which accelerates electrons, thus changing the electrical energy into kinetic energy and forming a plasma gas. The excitation of the plasma gas, which includes the ultraviolet emissive gas, causes the gas to emit ultraviolet radiation, which illuminates the photoluminescent material 14.
The electrical discharge 19 through the channels 12 excite the ultraviolet emissive gas molecules within the respective channels 12, thereby forming plasma gas. To ensure that the electrical discharge 19 is maintained within each channel 12 without flowing into an adjacent channel 12, the passage 20 is situated along the region 21 of least electrical energy for each of the plurality of channels 12, thereby ensuring that the path of least resistance is through the individual channel 12, namely, between the electrodes 16a and 16b, and not through adjacent channels 12, namely, not between the adjacent electrodes 16b and 16b. Therefore, the passage 20 atmospherically connects each of the plurality of chambers 12 along the region 21 of least electrical energy or high resistance while blocking the electrical discharge 19 between adjacent chambers 12.
Referring jointly to
The lamp 1 of
The inner surface of the bottom plate 4 is coated with the photoluminescent coatings 14, as is known in the fluorescent tubular lamp industry. The electrodes 16a, 16b are disposed on the backside of the bottom plate 4 at opposite ends of each of the channels 12 in order to form the discharge path within the channel 12. The electrodes 16a, 16b are separate electrode entities that extend along a portion of each one of the channels 12. The electrical discharge 19 is blocked between the channels 12 while the channels 12 are atmospherically connected along the region 21 of least electrical energy via the gas permeable passage 20.
According to the embodiments illustrated in
Embodiments of the fluorescent lamp 1 may comprise electrically insulating partitions 10 of various shapes and sizes. Examples of such embodiments are shown in
The lamp 1 is similar in some respects to the lamp 1 of
The lamp 1 comprises the top plate 2 and the bottom plate 4, the bottom plate 4 shaped to include the partitions 10 and the sidewalls 6 as a portion of the bottom plate 4.
According to some embodiments, the gas permeable passage 20 may take the form of a plurality of apertures 22 in the plurality of partitions 10. The apertures 22 may be openings or windows of various shapes and sizes within the electrically insulating partitions 10 and positioned between adjacent channels 12. The apertures 22 permit the passage of gas molecules and/or vapor between the adjacent channels 12 while the electrical discharge 19 between the channels 12 is blocked. Similarly to the passage 20 discussed above in
The gas pressure throughout the channels 12 may become equalized while the vapor pressure (e.g., mercury vapor pressure) varies between the channels 12. Since the conductivity of the channels 12 are affected by the vapor pressure and cathodes, one channel 12 may have higher conductivity and electrical discharge 19 than another channel 12. Thus, a ballasting capacitor C is connected in series between each of the electrodes 16b and the power supply 18. Each capacitor C limits the amount of current or electrical discharge 19 that may flow within the associated channel 12, thereby assuring uniform illumination between the plurality of channels 12.
The embodiments of the fluorescent lamp 1 may comprise electrically insulating partitions 10 of various shapes and sizes. Examples of such embodiments are shown in
As discussed above, the electrically insulating partitions 10 may be of various shapes and sizes. Each of the plurality of gas permeable membranes 23 is disposed to cover the aperture 22 between adjacent channels 12. The membranes 23 serve as a selective passageway allowing gas molecules and the like to pass, while blocking other components from passing through the membrane 23. The plurality of gas permeable membranes 23 covering the apertures 22 serve a similar function as a selective gas permeable passage 20. The membrane 23 can be on the wall of partitions 10, to cover the aperture 22, or can be within the apertures 22.
The gas permeable membranes 23 are electrically insulating, thus ensuring that the electrical discharge 19 is maintained within each of the channels 12 and does not pass through the membranes 23 and into adjacent channels 12. Accordingly, the membranes 23 may be located at various positions between the channels 12 and need not be arranged along the region 21 of least electrical energy. In some embodiments, the membranes 23 are gas permeable and do not pass vapor (e.g., mercury vapor), while in other embodiments, the membranes 23 pass both gas and vapor (e.g., mercury vapor).
According to one embodiment, the lamp 1 comprises the plurality of discharge channels 12 in the form of a plurality of individual fluorescent phosphor coated or colored glass tubes 24. For example, each three tubes could be respectively coated with red, green and blue phosphor or wavelength filtered by the glass itself, as is known in the art. Each of the tubes 24 is an individual chamber with an inner coating of photoluminescent material 14 such as, for example, phosphor that generates visible light energy in response to excitation via ultraviolet radiation. The plurality of tubes 24 are of electrically insulating material similar to that of the electrically insulating partitions 10 and may be spaced from each other or may be in direct contact with the adjacent tube 24.
Each of the tubes 24 includes the ultra violet emissive gas such as, for example, mercury vapor. As described above, while mercury vapor is commonly used in fluorescent lamps, it is possible to use other materials and gases such as, for example, krypton, argon, xenon, a mixture of inert halogen gases and the like, either alone or in combination to produce the desired spectral characteristics, all of which are known to those skilled in the art. Similarly to
Power is supplied to the plurality of electrodes 16 disposed adjacent each of the tubes 24 to create electrical discharge 19 within the gas of each tube 24. The electrodes 16 may be anodes/cathodes, filaments or a combination of the two. In some embodiments, the AC power supply 18 may power the electrodes 16 while in other embodiments the DC power supply may be converted to AC power at a selected frequency. The powered electrodes 16 create the electrical discharge 19 within each of the tubes 24 when the voltage across the tube 24 rises above a threshold value. The electrical discharge 19 and the region 21 of least electrical energy are as described in detail above.
According to one embodiment, the gas permeable passage 20 takes the form of a plurality of vias 26 linking the plurality of tubes 24. The via 26 permits the passage of gas molecules and/or vapor between adjacent tubes 24 while the electrical discharge 19 between the tubes 24 is blocked. The electrical discharge 19 within each individual tube 24 excites the ultraviolet emissive gas molecules within the tube 24, thereby forming the plasma in the gas. To ensure that the electrical discharge 19 within each tube 24 flows throughout the tube 24 without flowing through the via 26 and into an adjacent tube 24, the vias 26 are situated at locations along the region 21 of least electrical energy for each of the plurality of tubes 24, thereby ensuring that the path of least resistance is through the individual tube 24 (e.g., between the electrodes 16a and 16b) and not through adjacent tubes 24 (e.g., between the electrodes 16a and 16a). Thus, the plurality of vias 26 atmospherically connect each of the tubes 24 along the region 21 of least electrical energy or high resistance while blocking the electrical discharge 19 between adjacent tubes 24.
Embodiments of the lamp 1 may comprise electrically insulating partitions 10 in the form of the plurality of tubes 24, which may take the form of various shapes and sizes. An example of such is shown in
Therefore in conclusion, the fluorescent lamp 1 with its plurality of individual discharge channels 12 provides shorter paths for electrical discharge 19 in comparison to the prior art (serpentine structure). Shorter paths for electrical discharge 19 require lower electrode voltages to ionize the ultraviolet emissive gas. The fluorescent lamp 1 is scaleable to larger sizes without having to dramatically increase the voltage across the long channels 12, simply by adding more discharge channels 12 with electrodes 16 disposed on opposite ends. Thus, the lamp 1 may be specifically sized to function as a backlight for a variety of LCD television sets, as shown in
The fluorescent lamp 1 further includes a means for allowing the passage of plasma gas molecules between the plurality of channels 12 to permit uniform gas pressure throughout the plurality of channels 12 while maintaining separate electrical discharge 19 within each channel 12. Uniform gas pressure throughout all channels 12 comprising the lamp 1 provides a uniform display across the entire lamp 1, which is essential in many display applications such as, for example, flat-screen televisions.
All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety.
From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.
