`
`ieamSearotcae
`Volume 6/Number 2—_January aee
`
`hy)gotafee
`
`“ieatee i
`fyagpehale
`hier
`
`3
`
`25
`
`TCL 1021, Pe
`
`_ Of theIlluminating Engineering Society
`
`oe
`ie a
`
`Lighting in the logging and sawmill industries
`Technical Committee Report
`
`Ultraviolet radiation—considerationsin interior lighting design
`R. E. Levin, G. R. Spears, G. W. Clark and E. D. Bickford
`
`Improved color rendition in high pressure mercury vapor lamps
`Mary V. Hoffman
`
`The design of safety-colors
`W. A. Thornton
`
`Tungsten-halogen lamp dosed with tin tetraiodide
`A. D. Kulkarni, J. Martin and H. G. Sell
`
`An automated high-speed photometer
`L. C. Snyder and P. E. Westlake
`
`Recommendedpractice for the specification of an ESI rating in
`interior spaces when specific task locations are unknown
`Technical Committee Report
`
`Discussion of previously published papers
`
`67
`
`80
`
`89
`
`92
`
`100
`
`105
`
`111
`
`124
`
`ished quarterly in the United States of America by the Illuminating Engineering Society of North America, 345
`‘47th St., New York, N.Y. 10017. Copyright, Illuminating Engineering Society of North America, 1977. Sec-
`class postage paid at New York, N.Y. and additional mailing offices. This publication is indexed regularly
`ingineering Index, Inc., and is available on microfilm from University Microfilm, Ann Arbor, Mich. 48106.
`scription rates: $25.00 for four annual issues, plus extra postage to all countries in which second-class postage
`s do not apply. Single copies: $2.50 to members; $6.25 to nonmembers.Editorial Office, 345 East 47th St.,
`'York, N.Y. 10017. Printing Office, Easton, Pa.
`
`
`
`Clifford L. Forbes Jr. Editor
`
`Jack F. Christensen Associate Editor
`John E. Kaufman Technical Director
`
`Howard Haynes Engineering Assistant
`
`C. L. Crouch Director of Research JERI
`
`TCL 1021, Page 1
`
`

`

` Improved color rendition
`
`in high pressure mercury vapor lamps
`
`Mary V. Hoffman
`
`The addition of Y;Al;0;2:Ce to the group of phosphors suitable for color
`correcting the mercury discharge lampprovides for improving the color
`rendering index without a lumen loss. By altering the cerium contentin the
`formulation, the absorption and brightness can be adjusted to its optimum
`value in the lamp.
`
`430
`
`TCL 1021, Page 2
`
`this substitution. Combinations of these two phos-
`phors can beused,as described by Rokosz,et al.*
`We have found another phosphor, cerium-acti-
`vated yttrium aluminate garnet (YAG:Ce) whichis
`useful in improving color rendition by absorbing the
`blue Hg radiation andalso addsto the total emission
`of the lamp by converting this blue radiation into
`emission centered at 560 nanometers. It can be
`combined with the Y(VP)O4:Eu emission, effectively
`changingthecolor of the lamp.
`Lampsprepared with blends of YAG:Ce and YVP
`phosphorsshowtheshift in color points from below
`the black bodyto, on, or above the locus, depending
`on the proportions used. Typical color points are
`shown in Fig. 1 for a warm color corrected lamp. The
`
`Figure 1. Color shifts with increasing YAG:Ce in Y(VP)
`O,:Eu.
`
`Theideal in color rendition of a high pressure mer-
`cury discharge lamp has been the subject of several
`recent papers, in which simulated spectral distribu-
`tions have been created by the addition or subtrac-
`tion of spectral energy.!? This can be done to obtain
`lamps of selected color temperatures, with various
`combinations of real and simulated phosphor emis-
`sions. The optimization of the luminousefficiency
`can be calculated in the same manner. One study has
`shown that the addition of emission at 620 nanome-
`ters to the Hg discharge is near the optimum for color
`rendition, but that for lamps with color temperature
`of 4000 to 3000 kelvins, it is necessary to remove some
`of the Hg dischargein the blue. For luminosity, ad-
`aition of emission near 590 nanometers is need-
`ed.?:
`Amongthe existing phosphors meeting the tem-
`perature and stability requirements of the mercury
`discharge lamps, only Y VO4:Eu and Y(VP)O4:Eu
`phosphors (YVP) supply emission at the necessary
`spectral region, with the main peak at 618 nanome-
`ters. They do not provide absorption of the blue Hg
`lines in sufficient amount or emission in the high
`luminous region.Filtering of the blue can be obtained
`by the addition of a pigment or of a phosphor which
`also acts as a pigment. The phosphor magnesium
`fluogermanate activated with manganese (MG)is the
`only suitable red emitter with appreciable absorption
`of the blue lines, but since the emission is at 650 to
`660 nanometers, the luminosity is not enhanced by
`A paper presented at the Annual IES Conference, August 29
`through September 2, 1976, Cleveland, Ohio. AUTHOR: General
`Electric Company, Cleveland, Ohio.
`
`
`
`
`.390
`
`-410
`
`-400
`
`A410
`
`420
`
`

`

`color shift is due largely to the absorption of the 436
`nanometer Hg line, which is filtered by about 40
`percent with 15 percent YAG in the blend. Thelu-
`minosity of the lamps remains about the same for
`four lamp colors shown. This is due to the efficient
`conversion of the 436 Hgline into visible emission.
`These data are summarized in TableI.
`Theactual color points obtained can be varied by
`the amount of phosphor used on the Jamp as well as
`the proportion of YAG:Ce in theblend.It can also be
`
`varied by using the blend over a pre-coat, as de-
`scribed by Rokosz, et al.4 The pre-coat acts as a re-
`flector for both ultraviolet and the blue radiation,
`allowing better utilization of the Hg radiation by the
`phosphors. With the YAG:Cepresent,the reflection
`of the blue radiation increases its effect both as a
`pigment and as a phosphor.
`The YAG:Ce phosphor, which was developed for
`its emission characteristics under cathoderay exci-
`tation®* is strongly absorbing in the blue, as shown
`
`10
`
`og
`
`lu
`2 08
`<
`Lee
`ine
`ya OT
`ul
`iva
`wy 08
`wn
`g
`i O05
`[=
`
`04
`
`o3
`
`ake
`B
`Zz
`i
`e
`=
`w
`=
`=
`a
`in
`iW
`
`330 340 350 360
`nm
`
`
`
`TCL 1021, Page 3
`
`
`
`|
`
`
`300
`
`600
`500
`400
`WAVELENGTH, nm
`Figure 2. Diffuse Reflectance curve,
`(Yo925 Céo.075)3
`Als04>.
`
`700
`
`Figure 4. Emission curve: excitation wavelength—436
`nanometers.
`
`420
`
`470 480
`430 440 450 460
`WAVELENGTH,nm
`Figure 3. Excitation curve: detected wavelength—511
`nanometers.
`
`Figure 5. Emission intensity vs cerium content, measured
`at 25° C and 300° C. Excitation wavelength—436 nm.
`
`>
`5
`im
`iJ
`5
`—_—
`ia
`>
`q_!
`re}
`x
`
`at 25°C
`
`480
`
`600 640 680
`520 560
`WAVELENGTH, nm
`
`na
`
`ws Ae
`ese
`o
`f-—aot 25°C
`
`100
`
`/
`|
`|
`>
`[:
`FE
`:
`wn
`||
`Zz 90
`I
`WW
`hi
`S
`J
`= —— at 300*'C
`
`Ope ea eer,
`x
`
`8020
`
`720
`
`90
`
`JOURNAL OF IES / JANUARY 1977
`TCL 1021, Page 3
`
`

`

` Table |—Lampdata: YAG:Ce with Y(VP)O, :Eu
`
`Information for authors
`
`to the review of the Papers Committee of the IES.
`
`The JOURNAL OF THEIESis published quarterly by the Illuminating Engi-
`neering Society of North America. Manuscripts should be sent to the editor,
`345 East 47th Street, New York, N. Y. 10017. All manuscripts are subject
`
`JOURNAL OF IES / JANUARY 1977
`
`Percent
`100-hour
`
`YAG:Ce
`im/w
`x
`Y
`
`0
`5
`10
`15
`
`§1.5
`52.1
`50.7
`BLS
`
`408
`411
`420
`426
`
`384
`.394
`.403
`AY)
`
`CRI
`
`45
`—
`=
`51
`
`4. F. Rokosz, J. W. Sausville, and J. Van Broekhoven, “Incan-
`descent lampcolor with high-intensity discharge lamps,” JOUR-
`NAL OF THE ILLUMINATING ENGINEERING SOCIETY,Vol. 3, No.
`1, October 1973, p. 95.
`5. G. Blasse and A.Bril, “A new phosphorfor flying-spot cath-
`ode-ray tubesfor colortelevision: yellow-emitting Y3Al;Oj2:Ce,”
`Applied Physics Letters, Vol. IL, No. 2, July 15, 1967,p. 53.
`6. W. W. Holloway,Jr. and M.Kestigian, “Optical properties of
`cerium-activated garnet crystals,” Journalof the Optical Society
`of America, Vol. 59, No. 1, January 1969, p. 60.
`
`by the diffuse reflectance curve (see Fig. 2), and is
`also excited by this radiation. This absorption is into
`the 5d state of the cerium, which in this crystal
`structure, lies in an unusual position. Cerium usually
`absorbsin the ultraviolet and emits inthe near ul-
`traviolet or in the blue. The YAG:Ce phosphoris not
`excited by 254 nanometers and only weakly by 365
`nanometers from the Hgarc. The excitation spectra
`(See Fig. 3) shows the very strong dependenceof-the
`emission intensity on the 436-nm Hgradiation.
`Theemission of the phosphoris in a band peaking
`at about 540 nanometers at 25 ° C shifting to about
`560 nanometersat 300° C (See Fig. 4). This is at the
`maximum eyesensitivity and close to the calculated
`peak of 590 nm for good lumen output in the sys-
`tem.
`As with most phosphors, the specific conditions of
`the lamp determineits applicability, and the com-
`position can often be altered accordingto its use. In
`the YAG:Ce phosphor, the cerium concentrationis
`the critical factor. Both the absorption at 436 na-
`nometers and the emission intensity increase with
`the cerium concentration with the brightness
`reaching a maximum at about one- to two-atom
`percent and the absorption at about three-atom
`percent when measured at 25° C. At the temperature
`of operation of the lamp, the phosphoris less effi-
`cient, and brightness measurements madeat 300° C
`show that lower cerium concentrationsare desirable.
`As shown in Fig. 5, a rather narrow range of cerium
`content must be maintained for the best conversion
`of 436 radiation to emission at 560 nm in the lamp.
`
`References
`
`1. J. J. Opstelten, D. Radielovié and W. L. Wanmaker, “The
`choice and evaluation of phosphorsfor application to lamps with
`improved color rendition,” Journal of the Electrochemical So-
`ciety, Vol. 120, No. 10, October 1973, p. 1400.
`2, T. F. Soules and M.A. Maier, “Optimized spectral powerdis-
`tributions for mercury vapor lamps,” Journal of the Electro-
`chemical Society, Vol. 121, No. 3, March 1974, p. 407.
`3. H. Ivey, “Color and efficiency of fluorescent and fluoro-
`rescent-mercury lamps,” Journal of the Optical Society of
`America, Vol. 62, 1972, p. 814.
`
`DISCUSSION
`
`Thehigh pressure mercury vapor lamp is
`W.A.THORNTON:*
`in need ofall the kindly attentionit can get. This welcome paper
`brings better lamp performancecloser. It performs a service by
`bringing another useful phosphorinto the very limited line-up of
`luminescent materials that can endure the operating conditions
`in this lamp. The new phosphorhasthe useful property of con-
`verting undesired blue-violet arc emission to desired green light,
`which tends to improve both color rendering and output. Does the
`increase in Color Rendering Index (CRI), as 15 percent of the new
`phosphoris added, represent a real visual improvementin color
`rendering of real objects and scenes? As to the proposed addition
`of yellow wavelengths near 590 nanoeters “for good lumen output
`in the lamp system,” we believe that such addition would harm
`color rendering more than it would improve lumen output. The
`usefulness of the new YAG:Ce phosphoris, we believe, due to the
`fact (see Fig. 4) that it contributes green light and redlight; that
`it also contributes yellow light is a disadvantage. The Soules and
`Maier study (see Reference 2) makes clear that peak lumen output
`by use of yellow light is accompanied by color rendering index of
`—20. Reference 1 ascribes poor color rendering to yellow emitting
`phosphors. Has the author any prospectof an efficient phosphor
`emitting a narrow band near 490 nanometers, which, according
`to the same references, can help raise CRI further?
`
`Thetrue test of improved color rendition always rests
`AUTHOR:*
`on a subjective visual evaluation, especially in a system suchas this
`one, with about ten percent calculated change in CRI. No sys-
`tematic evaluation of this lamp system has been made, but the
`general appearances have been favorable.
`The emission contribution of YAG:Ce(if present as the only
`phosphor) would definitely result in a lower CRI. The Soules and
`Maier paperpoints to a system that closely approximates a pure
`YAG:Ce lamp.It has a CRI of 23. The usefulness of the YAG:Ce
`lies in its ability to absorb the 436-nm Hgline to the extentsuffi-
`cient to improve the CRI, and supply enough emission to con-
`tribute to the lumenlevel, at a relatively low weight percent.
`The Soules and Maier paperascribes the CRI of —20 to a system
`containing a narrow band emission at 580 nanometers, when
`combined with bluer line emission, but shows that when Eut®
`emission is present the CRI cannotfall that low.
`* Westinghouse Electric Corporation, Bloomfield,New Jersey.
`+ The author wishes to acknowledge the help of Dr. T. F. Soules
`for numerous discussions and E. Homonnayfor the testing in
`lamps.
`
`aeeeeeae: eeeeeeemeee
`
`eeeeee
`
`S41
`TCL 1021, Page 4
`TCL 1021,
`
`

`

`
`
`TCL 1021, Page 5
`TCL 1021, Page 5
`
`

`

`Shoah
`OT|
`
`aa Cae steae"
`
`ra)
`
`OCT. 1975-
`
`TCL 1021, Page 6
`
`a &F
`
`MaNICe
`ents
`
`
`
`HINiNT9814 il
`6i18
`
`
`
`
`TTSB
`
`
`
`
`eeeseaeeSeeeeeeeeeekoeee
`
`4
`|
`
`