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Publication numberUS3840767 A
Publication typeGrant
Publication dateOct 8, 1974
Filing dateAug 23, 1973
Priority dateAug 23, 1973
Also published asCA989463A1
Publication numberUS 3840767 A, US 3840767A, US-A-3840767, US3840767 A, US3840767A
InventorsLake W
Original AssigneeGen Electric
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Selective spectral output metal halide lamp
US 3840767 A
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Description  (OCR text may contain errors)

nited States Patent [191 Lake SELECTIVE SPECTRAL OUTPUT METAL HALIDE LAMP [75] Inventor: William H. Lake, Novelty, Ohio [73] Assignee: General Electric Company,

- Schenectady, NY.

[22] Filed: Aug. 23, 1973 [21] Appl. No.: 390,768

[52] U.S. Cl 313/184, 313/225, 313/229 [51] Int. Cl. H01j 61/18 [58] Field of Search 313/184, 225, 226, 227,

[56] References Cited UNITED STATES PATENTS 3,234,42l 2/1966 Reiling .L 313/25 Oct. 8, 1974 Primary Examiner-Eli Lieberman Attorney, Agent, or FirmErnest W. Legree; Lawrence R. Kempton; Frank L. Neuhauser [5 7] ABSTRACT 7 Claims, 3 Drawing Figures BACKGROUND OF THE INVENTION The invention relates to high pressure metal vapor lamps using an arc dischargein metal halide vapors to produce light or radiation. It is an improvement over the lamp of copending application Ser. No. 218,491, filed Jan. 17, 1972, by applicant jointly with Delmar D. Kershaw and John M. Sato, titled Selective Spectral Output Metal Halide Lamp, and assigned to the same assignee as the present invention.

In lamps intended for general lighting, the goal is gen erally to achieve the highest efficieney possible to gether with balanced white light output. However, there are other applications for electric lamps wherein emission scattered throughout the visible spectrum is undesirable. For instance in reprographie applications for making colored copies, radiation concentrated in the three primary colors, blue, green and red is desired. Likewise in some photochemical applications, high energy emission in specific regionsor bandsis required in order to promote a chemical process, and emission in other bands must be suppressed because it may inhibit the process or produce undesirable reactions.

In the above-mentioned copending application there is described and claimed a lamp sometimes referred to as a ZLT lamp containing zinc iodide, lithium iodide, and thallium iodide as the primary fill speciesfThis lamp fulfilled the needs of a reprographic process utilizing inks with photoelectric responses in three spectral energy ranges, from 440 nm to 480 nm, from 525 nm to 540 nm, and from 630 to 680 nanometers. In the ZLT lamp, the energy in the blue band was provided by a lithium line at 460 nm. Subsequent improvements in the reprographic process called for a blue band located at slightly shorter wavelengths from 400 nm to 420 nm.

' in a red band from 630 to 680 nm.

SUMMARY OF THE INVENTION In accordance with my invention, a source of radiation concentrated in the blue, green, and red bands constituting the three primary colors is a high pressure metal halide vapor are lamp having a filling comprising a limited quantity of zinc iodide serving as a buffer species which produces substantially no radiation and lithiumiodide, thallium iodide and gallium iodide serving as emitter species.

In a preferred embodiment of the invention sometimes known a's'a GZLT lamp wherein the spectral output is concentrated in the blue from 400 to 420 nm in the green from 525 to 540 nm, and in the redfrom 630 to 680 nm, the quantity of Lil is at least 0.2 milligrams per cubic centimeter of envelope volume, the quantity of Znl is from .02 to 1.5 mg/cc. the quantity of Tll is from .02 to 3 rug/cc, and the quantity 01 Gal; is from 0.1 to 1.0 mg/cc. Optionally there may be provided Hg in a quantity less than I milligram per cubic centimeter.

DESCRIPTION OF DRAWING FIG. 1 illustrates a high pressure tubular lamp embodying the invention.

FIG. 2 shows the spectral output of a preferred embodiment of the invention known as the GZLT lamp.

FIG. 3 shows the spectral output of the prior ZLT lamp to provide a basis of comparison.

DESCRIPTION OF PREFERRED EMBODIMENT Referring to FIG. 1, a lamp embodying the invention in preferred form comprises an arc tube 1 of quartz or fused silica about 8 millimeters inside diameter and I0 millimeters outside diameter having sealed therein at opposite ends a pair of arcing electrodes 2, 2' defining an arc gap of about 34 centimeters. The lamp is shown with a central portion cut out for ease of illustration; its internal volume is about 17 cc and its overall length is about 41 centimeters. The electrode inleads 3, 3 have intermediate thin molybdenum foil sections 4 hermetically sealed through pinch seals 5 of known l-beam cross section at the ends of the tube. The electrodes each comprise a double layer tungsten wire helix 6 wrapped around a tungsten core wire 7, and may be conventionally activated by thorium oxide applied as a coating on the turns of the helix or filling the interstices between turns. However the same electrodes may also be used without activating material of any kind in order to reduce segregation of species and variation in output along the length of the lamp, as taughtin the earlier mentioned copending application.

In the ZLT lamp which was designed to radiate in the blue from 440 to 480 nm, in the green from 525 to 540 nm and in the red from 630 to 680 'nm and with energy levels within these bands in the approximate ratio 122:2, the following filling was used:

Znl, 0.02 to [.5 mg/cc Lil 0.2 to 2 mg/cc Tll 0.02 to 3 mg/cc Hg Not over 1.0 mg/cc Znl as buffer, the power which may be delivered to the lamp before envelope limiting. temperature is reached is almost twice as much as when Hg is used for the buffer. The thallium iodide content also reduces the arc temperature and is a factor in permitting higher input power. Mercury in an amount not exceeding about 0.25 mg/cc, may be added to reduce the reignition voltage by a large factor, as much as threefold, without introducing any substantial characteristic mercury radiation. A somewhat higher proportion of mercury, up to about I mg/ec. may be added to decrease thermal losses to the wall and increase the lifetime of charge carriers in order to improve lamp power factor. reduce current, and lower electrode losses at the same power input.

Inmodifying the ZLT lamp by adding other metal iodides to provide specific spectral responses, the prob lem is to avoid upsetting the balance and high efficiency already present. A suitable emitter must be selected, but the ultimate choice of materials for buffer or emitter species must take into account the ionization potentials and the lowest significant excitation potential (LSEP). Unless the LSEP of the buffer exceeds by at least approximately 2 volts the excitation level of the desired radiation, the buffer radiation will be substantial and if it is outside the desired region, it will reduce lamp efficiency. Only a limited number of metals have primary radiation in the desired region. Of these many have so-called picket fence radiation, that is spectral lines scattered throughout the visible range and are not suitable. The iodides of others have too low a vapor pressure to provide sufficient radiation.

l have discovered that gallium iodide may be used as an effective emitter in combination with zinc iodide as buffer and lithium iodide and thallium iodide as emitters. This means that gallium iodide may be added to the ZLT lamp filling to shift its blue band radiation to a shorter wavelength while leaving the green band and red band radiation substantially unaffected. The principal line radiation of gallium occurs at 417.2 nm and it has another line of about 60% of the amplitude of the principal line at 403.3 nm, as may be seen in FIG. 2. The addition of gallium has the beneficial effect of adding these two lines to the spectrum without appreciably affecting the thallium line at 535 nm in the green band or the lithium line at 670 nm in the red band, as may be seen by comparing the spectral curve of FIG. 2 with that of FIG. 3.

The quantity of gallium iodide added to the lamp should be from 0.1 to 1.0 milligrams per cubic centimeter of lamp volume. Below 0.1 mg/cc, the radiation from the gallium is insignificant. As the quantity of gallium is increased, the radiation output at 417.2 nm, which is its principal line, saturates rather quickly and at a level of about 0.5 mg per cc of lamp volume, the continuum radiation begins to rise. This sets a practical limit of about 1 mg per cc on the quantity of gallium desirable.

By way of example of a GZLT lamp constituting a preferred example of the invention, an envelope such as illustrated in FIG. 1 and previously described was provided with the following fill and gave the spectral curve of FIG. 2.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A high intensity lamp providing radiation concentrated in selected blue, green, and red spectral bands comprising:

a hermetically sealed light-transmissive envelope;

a pair of arc electrodes sealed therein and defining an arc gap;

an inert starting gas at a pressure of a few torr therein;

and a charge therein comprising per cubic centimeter of envelope volume from about .02 to 1.5 milligrams of Znl from about 0.2 to 2.0 milligrams of Lil, from about .02 to 3.0 milligrams of Tll, and from about 0.1 to 1.0 milligrams of GaI 2. A lamp as in claim 1 comprising in addition not over about 0.25 milligrams of mercury per cubic centimeter of envelope volume 3. A lamp as in claim 1 containing in addition not over about 1 milligram of mercury per cubic centimeterofenvelope volume. i

4. A high intensity lamp providing radiation concentrated in the blue spectral band from 400 to 420 nm, in the green spectral band from 525 to 540 nm and in the red spectral band from 630 to 680 nm comprising:

a tubular elongated sealed light-transmissive envelope; a pair of arc electrodes sealed therein and defining an arc gap; an inert starting gas at a pressure of a few torr therein; and a charge therein comprising per cubic centimeter of envelope volume from about .02 to'l.5 milligrams of Znl from about 0.2 to 2.0 milligrams of Lil, from about .02 to 3.0 milligrams of Tll, and m t .-.Q.!. l @ms9 G aa 5. A lamp as in claim 4 containing in addition not over about 0.25 milligrams of mercury per cubic centimeter of envelope volume.

6. A lamp as in claim 4 containing in addition not over about 1 milligram of mercury per cubic centimeter of envelope volume.

7. A lamp as in claim 4 containing per cubic centimeter of envelope volume about 0.29 mg of Znl about 0.42 mg of Lil, about 0.42 mg of Tll, about 0.33 mg of Gal and about 0.08 mg of Hg.

Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4850918 *Oct 28, 1988Jul 25, 1989Gte Products CorporationPulsed metal halide source
US4992700 *Mar 10, 1989Feb 12, 1991General Electric CompanyMetal halide electric arc
US5013968 *Mar 10, 1989May 7, 1991General Electric CompanyReprographic metal halide lamps having long life and maintenance
US5698948 *Apr 6, 1995Dec 16, 1997U.S. Philips CorporationMetal halide lamp with ceramic discharge vessel and magnesium in the fill to improve lumen maintenance
US6005346 *Apr 8, 1996Dec 21, 1999Ilc Technology, Inc.Color lamp comprises a glass envelope with a krypton arc doped with lithium iodide to produce red light, thallium iodide to produce green light
US6353289 *May 29, 1998Mar 5, 2002Harison Toshiba Lighting Corp.Metal halide discharge lamp, lighting device for metal halide discharge lamp, and illuminating apparatus using metal halide discharge lamp
US6528946Oct 16, 2001Mar 4, 2003Harison Toshiba Lighting Corp.Compact-type metal halide discharge lamp
US6873109Dec 19, 2002Mar 29, 2005Harison Toshiba Lighting CorporationMetal halide discharge lamp, lighting device for metal halide discharge lamp, and illuminating apparatus using metal halide discharge lamp
US7057349Feb 18, 2005Jun 6, 2006Harison Toshiba Lighting CorporationLightening device for metal halide discharge lamp
US7388333 *Oct 7, 2004Jun 17, 2008Koninklijke Philips Electronics, N.V.High pressure discharge lamp having emission matching an absorption spectrum of green plant
USRE42181 *May 3, 2007Mar 1, 2011Ushio America, Inc.Metal halide lamp for curing adhesives
CN100571650CJun 13, 2006Dec 23, 2009皇家飞利浦电子股份有限公司Apparatus for cosmetic skin rejuvenation treatment
EP0320933A2 *Dec 15, 1988Jun 21, 1989Gte Products CorporationPulsed metal halide light source
EP0386602A2 *Feb 28, 1990Sep 12, 1990General Electric CompanyReprographic metal halide lamps having high blue emission
EP1733691A1 *Jun 14, 2005Dec 20, 2006Philips Electronics N.V.Apparatus for cosmetic skin rejuvenation treatment
WO2006134555A1 *Jun 13, 2006Dec 21, 2006Koninkl Philips Electronics NvApparatus for cosmetic skin rejuvenation treatment
Classifications
U.S. Classification313/639, 313/637, 313/572
International ClassificationH01J61/12, H01J61/18
Cooperative ClassificationH01J61/18
European ClassificationH01J61/18