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Tungsten Electrode with Emitter

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Tungsten Electrode with Emitter US 20060O87242A1 (19) United States (12) Patent Application Publication (10) Pub. No.: US 2006/0087242 A1 Scholl et al. (43) Pub. Date: Apr. 27, 2006 (54) LOW-PRESSURE GAS DISCHARGE LAMP Publication Classification WITH ELECTRON EMITTER SUBSTANCES SMILAR TO BATO3 (51) Int. Cl. HOI. I7/04 (2006.01) (76) Inventors: Robert Peter Scholl, Roetgen (DE); HOI. 6L/04 (2006.01) Rainer Hilbig, Aachen (DE); Bernd (52) U.S. Cl. ..................... 313/633; 313/311; 313/346 R Rausenberger, Aachen (DE) Correspondence Address: (57) ABSTRACT PHILIPS INTELLECTUAL PROPERTY & A low-pressure gas discharge lamp is described, which is STANDARDS equipped with a gas-discharge vessel containing an inert gas P.O. BOX 3 OO1 filling as the buffer gas and an indium, thallium and/or BRIARCLIFF MANOR, NY 10510 (US) copper halide, and with electrodes and with means for Appl. No.: 10/526,923 generating and maintaining a low-pressure gas discharge, (21) which has as the electron emitter Substance a compound (22) PCT Fed: Aug. 29, 2003 selected from the group of ABO or ABO, ACOs, or ADO, wherein: A=an alkaline earth element or a mix (86) PCT No.: PCT/BO3/O3948 ture of several different alkaline earth elements, B=cerium, titanium, Zirconium, hafnium, or a mixture of these ele (30) Foreign Application Priority Data ments, C=vanadium, niobium, tantalum, or a mixture of these elements, D=Scandium, yttrium, lanthanum, a rare Sep. 12, 2002 (DE)..................................... 102-42-241.9 earth element, or a mixture of these elements. tungsten electrode With emitter discharge chamber with InBr Or similar Substances Patent Application Publication Apr. 27, 2006 US 2006/0087242 A1 BaTiO3 coupling structure tungsten electrode With emitter Fig.2 discharge chamber with InBr or similar Substances Stick electrode Comprising Substance similar to BaTiO3 Fig3 US 2006/0O87242 A1 Apr. 27, 2006 LOW-PRESSURE GAS DISCHARGE LAMP WITH equipped with a gas-discharge vessel containing an inert gas ELECTRON EMITTER SUBSTANCES SMILAR TO filling as the buffer gas and an indium, thallium, and/or BATO3 copper halide, and with electrodes and with means for 0001. The invention relates to a low-pressure gas dis generating and maintaining a low-pressure gas discharge, in charge lamp equipped with a gas-discharge vessel contain which a compound selected from the group of ABO or ing an inert gas filling as the buffer gas and an indium, ABO. ACOs or ADO3-n is used as the electron thallium, and/or copper halide, and with electrodes and with emitter Substance, wherein: means for generating and maintaining a low-pressure gas 0010 A=an alkaline earth element or a mixture of several discharge. different alkaline earth elements 0002 The generation of light in low-pressure gas dis 0011 B=cerium, titanium, zirconium, hafnium, or a mix charge lamps is based on the fact that charge carriers, ture of these elements especially electrons but also ions, are accelerated so strongly by an electrical field between the electrodes of the lamp that, 0012 C=vanadium, niobium, tantalum, or a mixture of in the gas filling of the lamp, owing to collisions with the gas these elements atoms or molecules of the gas filling, they excite or ionize 0013 D=scandium, yttrium, lanthanum, a rare earth ele them. When the atoms or molecules of the gas filling return ment, or a mixture of these elements. to their normal state, a part of the excitation energy, which 0014 Surprisingly, it transpires that the electron emitter may be greater or Smaller, is converted into radiation. substances similar to BaTiO do not react with indium, 0003 Conventional low-pressure gas discharge lamps thallium or copper halides under lamp conditions. This has contain mercury in the gas filling, and are also equipped with been demonstrated in experiments in which BaTiO “elec a fluorescent coating internally on the gas-discharge vessel. trodes' were used in cold cathode lamps (diameter of the It is a disadvantage of mercury low-pressure gas discharge approximately 40 cm long cylindrical burner was approxi lamps that mercury vapor emits radiation primarily in the mately 3.5 mm) instead of the usual metallic electrodes as high-energy but invisible UV-C range of the electromagnetic coupling structures of the lamps (operating frequency used: spectrum, which radiation can be converted into visible either 50 kHz or 13.56 MHz). No reactions, or at least radiation, with significantly lower energy, only by using scarcely perceptible reactions, of the molecular indium, these fluorescent materials. The energy difference is hereby thallium or copper halide lamp fillings hereby occur with the converted into undesirable thermal radiation. compounds used as electron emitter substances in accor 0004 The mercury in the gas filling is also increasingly dance with the invention. regarded as an environmentally polluting and toxic Sub 0015 The compounds used as electron emitter sub stance, which should be avoided where possible in modern stances in accordance with the invention are here designated mass production owing to the environmental hazard substances similar to BaTiO for short. involved in its use, production and disposal. 0016. In the lamp in accordance with the invention, a 0005. It is already known that the spectrum of low molecular gas discharge takes place at low pressure, emit pressure gas discharge lamps can be influenced by replacing ting radiation in the visible and near UVA range of the the mercury in the gas filling with other Substances. electromagnetic spectrum. When copper halides are used, 0006 For instance, it is already known from German the radiation contains, in addition to the characteristic lines patent submissions 100 44562 and 100 44563 that a copper for copper at 325, 327, 510, 570 and 578 nm, a broad compound or an indium compound can be added to low continuum in the blue range of the electromagnetic spectrum pressure gas discharge lamps with a gas filling comprising from 400 to 550 nm. If an indium halide is used instead, a an inert gas. When standard TL electrodes (tungsten filament broad continuum in the range from 320 to 450 nm is with triple oxide emitter (BaO, SrO, CaO)) are used, it observed in addition to the characteristic lines for indium at transpires hereby, however, that, for example, the indium 410 and 451 nm. Since this is the radiation from a molecular bromide with the emitter is converted according to the discharge, the precise position of the continuum can be equation BaO+2InBr->BaBr-In-O, with the result that the controlled by means of the nature of the copper, thallium or radiant indium or indium bromide disappears from the indium halides, any further additives and the internal lamp discharge. pressure and operating temperature. 0017 Combined with fluorescent materials, the lamp in 0007) If lamps with pure tungsten electrodes without an accordance with the invention has a visual efficiency that is emitter are filled with InBr, although the InBr remains in the considerably higher than that of conventional low-pressure discharge, massive sputtering, and consequently blistering, mercury discharge lamps. The visual efficiency, expressed in occurs owing to the high work function of the tungsten. lumen/watt, is the ratio between the brightness of the radia Moreover, the efficiency of the discharge is low as the tion in a certain visible wavelength range and the generation electrode losses dominate owing to the high cathode fall. energy for the radiation. The high visual efficiency of the 0008. It was therefore the object of the invention to create lamp in accordance with the invention means that a certain a low-pressure gas discharge lamp that does not exhibit the quantity of light is realized through lower power consump stated disadvantages, wherein its radiation lies as near as tion. possible to the visible range of the electromagnetic spec 0018. In the simplest case, the gas filling comprises an trum. indium, thallium and/or copper halide in a quantity of 1 to 0009. This object is achieved in accordance with the 10 ug/cm and an inert gas. The inert gas serves as a buffer invention by means of a low-pressure gas discharge lamp gas and facilitates the ignition of the gas discharge. The US 2006/0O87242 A1 Apr. 27, 2006 preferred buffer gas is argon. Argon may be replaced, either emit in a suitable wavelength range, for example for the wholly or partially, by another inert gas Such as helium, three primary colors red, blue and green, and achieve a high neon, krypton or Xenon. fluorescence quantum yield. 0019. The efficiency can be further improved if the inter 0026. However, suitable fluorescent materials and com nal operational pressure of the lamp is optimized. The binations of fluorescent materials do not have to be applied cold-fill pressure of the buffer gas is 10 mbar max. A range to the interior of the gas discharge vessel, but may also be between 1.0 and 2.5 mbar is preferred. applied to the exterior, since the generated radiation in the 0020. A further advantageous measure to increase the UVA range is not absorbed by the normal types of glass. lumen efficiency of the low-pressure gas discharge lamp in 0027. One advantageous use for the lamp in accordance accordance with the invention has proved to be the control with the invention is its application as a UVA lamp for of the operating temperature of the lamp through Suitable Sunbeds, disinfection lamps and paint curing lamps. For design measures. The diameter and length of the lamp are general lighting purposes, the lamp is combined with appro selected such that, with an external temperature of 25°C., an priate fluorescent materials. Because the losses from the internal temperature of 170 to 285° C.
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