Patentamt Europaisches |||| ||| 1 1|| ||| ||| ||| || || || ||| ||| || || || (19) J European Patent Office Office europeen des brevets (11) EP 0 788 1 40 A2 (12) EUROPEAN PATENT APPLICATION (43) Date of publication:ation: (51) |nt. CI.6: H01 J 61/16, H01 J 65/04 06.08.1997 Bulletin 1997/32 (21) Application number: 97100888.3 (22) Date of filing : 21 .01 .1 997 (84) Designated Contracting States: • Butler, Scott J. BE DE FR GB IT NL North Oxford, MA 01 537 (US) • Bochinski, Jason R. (30) Priority: 01.02.1996 US 595475 Springfield, OR 97477 (US) (71) Applicant: OSRAM SYLVANIA INC. (74) Representative: Pokorny, Gerd Danvers, MA 01 923 (US) OSRAM GmbH, Postfach 2216 34 (72) Inventors: 80506 Munchen (DE) • Lapatovich, Walter P. Marlborough, MA 01752 (US) (54) Electrodeless high intensity discharge lamp having a boron sulfide fill (57) An electrodeless high intensity discharge lamp including a sealed light-transmissive lamp envelope, a volatilizable chemical fill and inert an gas or nitrogen 12 within the envelope. The primary active component of the fill is boron sulfide. The inert gas or nitrogen within the envelope assists in starting the lamp, and is at sub- f KJ atmospheric pressure. The lamp envelope is coupled to | applicator | — rj a high frequency source to produce a light emit- \\ power ^ ting plasma discharge within the envelope. V\ \ FIG. I CM < O CO CO o Q_ LU Printed by Rank Xerox (UK) Business Services 2.14.11/3.4 1 EP 0 788 140 A2 2 Description amount of a metal halide and emitting light over a broad spectral range. CROSS-REFERENCE TO RELATED APPLICATIONS These and still further objects, features, and advan- tages of the present invention will become apparent The present application contains subject matter s upon consideration of the following description. related to U.S. Application Serial No. [Attorney's Docket No. 92-3-336], commonly assigned and filed concur- SUMMARY OF THE INVENTION rently herewith. Application [92-3-336] is incorporated herein by reference. The present invention provides an electrodeless 10 high intensity discharge lamp having a boron sulfide- BACKGROUND OF THE INVENTION based fill which may be energized by high frequency power, e.g., microwave power supplied to the lamp to The present invention relates to electrodeless dis- produce a light emitting plasma discharge without the charge light sources, and particularly to electrodeless need for mercury in the lamp. In some embodiments of lamps having a fill energized by high frequency, e.g., 15 the lamp a small amount of mercury may be included in microwave power. the lamp envelope to improve resistive heating of the Until recently, all commercially available high inten- lamp. However, an emission may be produced in the sity discharge (HID) lamps contained mercury or mer- lamp in accordance with the invention without the pres- cury salts, with other metal salts added to enhance or ence of mercury or mercury compounds. tailor the spectral output. Over the past several years, 20 In one embodiment, the invention is an electrode- environmental concerns have led to attempts to pro- less high intensity discharge lamp including a sealed duce mercury-free HID lamps. Of particular concern light-transmissive envelope, a volatilizable chemical fill has been the discarding of spent lamps, releasing mer- within the envelope, an inert gas or nitrogen within the cury into the environment. envelope to assist in starting the lamp, and means for One example of a mercury-free lamp which has 25 coupling high frequency power to the envelope to pro- been developed is a mercury-free high pressure sodium duce a light emitting plasma discharge within the enve- lamp having a fill of sodium and a high pressure (above lope. The fill includes boron sulfide as a primary active atmospheric) of an inert gas. Some examples of sodium component. The inert gas or nitrogen is at a pressure of halide and oxyhalide lamps are described in U.S. Pat- less than 760 torr at ambient temperature. In a narrower ents Nos. 4,672,267, 4,801 ,846, and 5,070,277. Like all 30 embodiment, the lamp is a mercury-free electrodeless lamps containing reactive chemical fills, these lamps high intensity discharge lamp. In another narrower are subject to wall reactions which can affect the optical embodiment, the lamp may include as a secondary properties of the arc lamp and alter the chemistry from active component an amount of a metal halide, e.g., that initial to the lamp. sodium iodide, lithium iodide, scandium iodide, or com- In another type of mercury-free lamp sulfur, sele- 35 binations thereof, within the envelope sufficient to aug- nium, or compounds thereof are included in the lamp fill, ment the emission wavelength of the fill during and are excited by electromagnetic power in excess of operation of the lamp. about 50 watts/cc, preferably in excess of 100 watts/cc. In another embodiment, the invention is a mercury- Other known electrodeless lamps containing metal hali- free electrodeless high intensity discharge lamp includ- des or oxyhalides have good color rendering properties 40 ing a sealed light-transmissive envelope, a volatilizable and high lumen output. However, most of these also chemical fill within the light-transmissive envelope, include mercury. xenon gas within the light transmissive envelope to Accordingly, it is an object of the present invention assist in starting the lamp, and means for coupling high to provide an electrodeless high intensity discharge frequency power at about 13 - 6000 MHz to the light lamp that overcomes the disadvantages of prior art 45 transmissive envelope to produce a light emitting lamps. plasma discharge within the light transmissive enve- It is another object of the present invention to pro- lope. The fill includes boron sulfide as a primary active vide an electrodeless high intensity discharge lamp hav- component, the amount of the primary active compo- ing a boron sulfide-based fill. nent being about 1 - 10 mg for each cm3 of volume It is yet another object of the invention to provide an so within the light transmissive envelope. The xenon gas is electrodeless high intensity discharge lamp having a at a pressure of about 20 - 200 torr at ambient tempera- boron sulfide-based fill which is free of mercury. ture. In a narrower embodiment, the fill further includes It is still another object of the invention to provide an a secondary active component selected from sodium electrodeless high intensity discharge lamp having a iodide, lithium iodide, scandium iodide, and combina- boron sulfide-based fill which is free of both mercury ss tions thereof. and metal halides. It is a further object of the invention to provide a BRIEF DESCRIPTION OF THE DRAWINGS mercury-free electrodeless high intensity discharge lamp having a boron sulfide-based fill including a small For a better understanding of the present invention, 2 3 EP 0 788 140 A2 4 together with other objects, advantages, and capabili- duce a light emitting plasma discharge within the ties thereof, reference is made to the following Descrip- envelope. tion and appended Claims, together with the Drawing in In this embodiment, no mercury or mercury com- which: pounds are introduced to the lamp envelope. In other 5 embodiments a small amount of mercury may be added Figure 1 is a cross-sectional schematic elevation to improve resistive heating of the lamp, typically about view of a spherical electrodeless high intensity dis- 1 - 35 mg/cm3 of volume of the light transmissive enve- charge lamp capsule in accordance with one lope. However, the presence of mercury or mercury embodiment of the present invention; compounds is not required to produce an emission in Figure 2 is an emission spectrum for a boron sulfide to the lamps described herein. fill for a lamp in accordance with another embodi- The inert gas or nitrogen mentioned above is ment of the present invention. present within the envelope at subatmospheric pres- sure (less than 760 torr at ambient temperature) to facil- DETAILED DESCRIPTION OF THE PREFERRED itate starting of the lamp, i.e., establishing the light EMBODIMENTS 75 emitting plasma discharge within the envelope. These gases may be any of the Group VIII inert gas elements, An exemplary embodiment of the electrodeless HID nitrogen, or a combination of these. The preferred inert lamp in accordance with the present invention is a mer- gas is argon, krypton, or xenon; most preferred is cury-free electrodeless HID lamp including a volatiliza- xenon. The preferred pressure for the inert gas is about ble chemical fill and an inert gas or nitrogen sealed 20 1 - 700 torr, more preferred is about 20 - 700 torr, most within a light-transmissive envelope. The primary active preferred is about 20 - 200 torr. At 20 - 200 torr, the inert component of the fill is boron sulfide. By the term "active gas is readily ionized by the available high frequency component" is meant a volatilizable light emitting com- power, and rapidly transits to a thermal arc. At lower ponent, the primary active component being the compo- pressure the inert gas is easier to ionize, but transition nent having the most predominant spectral emission. 25 to the thermal arc is slower and the lamp requires a Also included in the term "active component", as used longer warm-up time. At higher pressure the inert gas is herein, are precursors of the desired active component, more difficult to ionize, requiring a higher power applica- e.g., boron sulfide compound. The precursors are intro- tion to establish the thermal arc. duced to the lamp envelope to produce, e.g., the The amount of volatilizable active fill components desired boron sulfide compound by chemical reaction 30 within the envelope depends on the volume of the enve- during operation of the lamp.