United States Patent 15
`van Kemenadeet al.
`
`[11] Patent Number:
`
`[45] Date of Patent:
`
`4,727,283
`Feb. 23, 1988
`
`[54] LOW-PRESSURE MERCURY VAPOUR
`DISCHARGE LAMP
`
`(56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`[75]
`
`Inventors:
`
`Johannes T, C. van Kemenade;
`Gerardus H. M.Siebers; Jean J.
`Heuvelmans; Johannes T. W. deHair,
`all of Eindhoven; Johannes W.ter
`Vrugt, Geldrop, all of Netherlands
`
`[73] Assignee: U.S. Philips Corporation, New York,
`N.Y.
`
`[21] Appl. No.: 883,186
`
`[22] Filed:
`
`Jul. 8, 1986
`
`Foreign Application Priority Data
`[30]
`Jul. 15, 1985 [NL] Netherlands.............ccsceseren 8502025
`
`Tint, Cbs occccceneesnnsessnseonsseenees HO1S 61/46
`[51]
`
`ee 313/487; 252/301.4 R
`(58] Field of Search............... 252/301.4 R, 582, 584,
`252/586, 301.4 P; 313/483, 486, 487, 485;
`315/57
`
`2/1976 Verstegen et al. oe 313/487
`3,937,998
`
`5/1977 Schull oo...esseeeeeee 252/301.4 R
`4,024,070
`.........eseaees 313/485
`4,177,401 12/1979 Yamaneet al.
`2/1982 Barnes .....cessesseesesees 252/301.4 R
`4,314,910
`
`.sseceseeeee 315/57
`4,383,200
`5/1983 Van Zon et al...
`
`5/1984 Kohmotoetal....
`wee 313/487
`4,447,756
`
`4,559,470 12/1985 Murakamietal. ......
`wene 313/485
`
`Primary Examiner—David K. Moore
`Assistant Examiner—Mark R. Powell
`Attorney, Agent, or Firm—John C. Fox
`
`ABSTRACT
`[57]
`"A low-pressure mercury vapor discharge lamp with a
`luminescent layer whose emission mainly lies in three
`spectral ranges and whose loading amountsto at least
`500 W per m? surface area of the luminescentlayer,is
`characterized by having an absorption layer of a lumi-
`nescent aluminate activated by trivalent cerium and
`having a garnet crystal structure. The absorption layer
`permits the obtaining of low color temperatures (down
`to 2000 K.).
`
`18 Claims, 2 Drawing Figures
`
`TCL 1029, Page 1
`TCL 1029, Page 1
`
`y q4X
`
`s
`
`HHH
`
`3qN
`
`aHH 4HNNHiA4
`
`H4N
`
`

`

`US. Patent
`
`Feb. 23, 1988
`
`
`—tlI
`
`
`
`
`F 16.1
`
`F1G.2
`
`TCL 1029, Page 2
`TCL 1029, Page 2
`
`

`

`1
`
`LOW-PRESSURE MERCURY VAPOUR
`DISCHARGE LAMP
`
`4,727,283
`
`BACKGROUND OF THE INVENTION
`
`5
`
`The invention relates to a low-pressure mercury va-
`pour discharge lamp, whose emission mainly lies in
`three spectral ranges and of which the colour tempera-
`ture of the emitted light lies in the range of 2000-3000
`K., this lamp being provided with a gas-tight discharge
`envelope transparent to radiation and having a gas fill-
`ing comprising mercury anda rare gas and with a lumi-
`nescent layer comprising luminescent materials whose
`emission mainly lies in the range of 590-630 nm and in
`the range of 520-565 nm, whilst further means are pro-
`vided for maintaining a column discharge in the gas
`filling, the power consumed by the column being at
`least 500 W/m?surface area of the luminescent layer.
`Low-pressure mercury vapour discharge lamps, 20
`whose emission mainly lies in three spectral ranges, also
`designated as three-band fluorescent lamps, are known
`from U.S. Pat. No. 4,176,294 and from Netherlands
`Patent Specification No. 164,697. These lamps are com-
`monly used in general illumination and have the advan- 25
`tage that they have both a good general colour rendi-
`tion (colour rendition index R(a, 8) of at least 80) and a
`high luminous efficacy (up to values of 90 Im/W and
`higher). This is possible because the emission of these
`lamps is mainiy concentrated in three comparatively 30
`narrow spectral bands. Forthis purpose the lamps con-
`tain a red luminescing material whose emission mainly
`lies in the range of 590-630 nm and a green luminescing
`material whose emission mainly lies in the range of
`520-565 nm. The required emission in the third spectral 35
`range,i.e. the range of 430-490 nm,is supplied in many
`cases by a blue luminescing material. However,, the
`visible radiation emitted by the mercury vapour dis-
`chargeitself also provides a contribution(i.e. the emis-
`sion of the 436 nm mercury line) in this spectral range. 49
`The lamps emit white light at a given colour tempera-
`ture, that is to say that the colour point (x,y in the CIE
`colour coordinate diagram) of the emitted radiationlies
`on or near the line of the black body radiators. The
`colourpoint offluorescent lamps of low colour temper- 45
`ature is generally chosen to lie preferably slightly above
`(for example about 0.010 in y coordinate) the line of the
`black body radiators.
`A desired colour temperature of the light emitted by
`a three-band fluorescent lamp is obtained by a suitable 509
`adjustmentofrelative contributions in the three spectral
`ranges to the overall emission of the lamp. As the colour
`temperature ofthe lamp is lower, the contribution in the
`blue range of 430-490 nm should be smailer. It follows
`from the aforementioned Netherlands Patent Specifica- 55
`tion No. 164,697 that the minimum attainable colour
`temperature for lamps having an inner diameter of the
`tubular discharge envelope of about 36 mm is about
`2300 K., in which event the lamp need no longer con-
`tain a blue luminescing material and all the required 60
`radiation in the blue spectral range originates from the
`blue mercury radiation. In lamps having a smaller inner
`diameter of the discharge envelope, especially a diame-
`ter of about 24 mm, the mercury vapour dischargeis
`found to be moreeffieient the relative contribution of 65
`the blue mercury line being larger. Consequently for
`these lamps, the minimumattainable colour temperature
`is found to have a highervalue, i.e. about 2500 K.
`
`2
`Three-band fluorescent lamps of the kind mentioned
`in the opening paragraph are known,for example, from
`U.S. Pat. Nos. 4,335,330; 4,199,708; and 4,374,340, and
`are generally of very compact construction and in-
`tended to replace incandescent
`lamps. Due to their
`compact construction, the luminescent layer in these
`lamps is heavily loaded, that is to say, the power con-
`sumed by the column during operation of the lampis at
`least 500 W per m?of surface area of the luminescent
`layer. This is considerably higher than the load of the
`luminescent lamp layer in the aforementioned lamps
`having an inner diameter of about 36 and 24 mm,re-
`spectively, which load has a value of the order of 300
`and 400 W/m, respectively. It has been found that in
`these heavily loaded lampsthe relative contribution of
`the blue mercury radiation is even higher, and that such
`lamps without a blue luminescing material have a col-
`our temperature of the emitted light of at least about
`2700 K. at colour points lying on the line of the black
`body radiators. Asa result ofthis, and also of their high
`R(a,8), these lampsare suitable to replace incandescent
`lamps.
`Hitherto, incandescent lamps have been mainly used
`for interior illumination. With a view to saving energy,
`it is often desirable to replace incandescent lamps with
`fluorescent lamps. A typical value of the colour temper-
`ature of an incandescent lamp is 2650 K. However,the
`use of colour lamps (for example the so-called flame
`lamps) and dimmers in interior illumination result in
`colour temperatures down to about 2000 K. A disad-
`vantage of the aforementioned heavily loaded fluores-
`cent lampsis that dueto the intense blue mercury radia-
`tion they cannot be used in the frequently desired col-
`our temperature range of about 2000 to about 2700 K.
`The invention has for its object to obviate the said
`disadvantage and in general to provide meansforshift-
`ing the colour point of heavily loaded three-band fluo-
`rescent lamps and for reducing the colour temperature,
`while substantially maintaining the good general colour
`rendition and the high relative luminousflux.
`
`SUMMARYOF THE INVENTION
`
`A low-pressure mercury vapour discharge lamp of
`the kind described in the opening paragraph is charac-
`terized according to the invention in that the lampis
`provided with an absorption layer comprising an alumi-
`nate activated by trivalent cerium and having a garnet
`crystal structure.
`The said garnet is a known luminescent material (See
`for example J.O.S.A., 59, No. 1, 60, 1969), which ab-
`sorbs short-wave ultraviolet radiation, but especially
`absorbs radiation having a wavelength between about
`400 and 480 nm and convertsit into radiation in a wide
`emission band (half-value width of about 110 nm) with
`a maximum at about 560 nm.It has been found that the
`use of such a luminescent garnet in an absorption layer
`for three-band fluorescent lamps leads to a shift of the
`colour point of the radiation emitted by the lamp and
`allows for a reduction of the colour temperature of the
`lamp.
`A reduction of the colour temperaturein itself could
`be attained with any yellow pigment absorbing blue
`radiation. However, a yellow pigmentleads to a reduc-
`tion (unacceptable for this lamp type) of the relative
`luminous flux so that it cannot be used.
`Theuse of the luminescent garnet in lamps according
`to the invention has the advantage that the absorbed
`radiation is no lost, but is converted with a high effi-
`
`.
`
`TCL 1029, Page 3
`TCL 1029, Page 3
`
`

`

`4,727,283
`
`4
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Embodiments of lamps according to the invention
`will now be described more fully with reference to the
`drawing in which:
`FIG.1 showsin elevation and partly broken away a
`low-pressure mercury vapour discharge lamp compris-
`ing two parallel tube portions interconnected by a cou-
`pling tube, and
`FIG. 2 shows diagrammatically a low-pressure mer-
`cury vapour discharge lamp capped on one end, which
`is suitable to replace incandescent lamps.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENTS
`
`3
`ciency into visible radiation so that high relative lumi-
`nousfluxes are obtained. In addition, the lamps accord-
`ing to the invention have high values of R(a, 8), which
`could not be expected because it is known for three-
`band fluorescent lamps that radiation in the range of 5
`565-590 nm, in which a comparatively large part of the
`emission of the garnet is found,
`is detrimental to the
`colour rendition properties.
`A preferred lamp according to the inventionis char-
`acterized in that the luminescent aluminate having a
`garnet structure corresponds to the formula Ln3.,Cex.
`Als.p.gGapScgO12, in which Ln is at least one of the
`elements yttrium, gadolinium, lanthanum and lutetium
`and in which
`0.01 3x30.15
`The lamp shown in FIG. 1 comprises a glass dis-
`0Sp33 and
`charge envelope 1 sealed in a gas-tight manner and
`0Sq=1.
`comprising two parallel tube portions 2 and 3 intercon-
`in the
`As appears from the formula and conditions,
`nected by a coupling tube 4. The discharge envelope 1
`garnet one or more of the elements Y, Gd, La and Lu
`contains a small quantity of mercury and argon at a
`may be used as the cation Ln and the aluminium may be
`pressure of 400 Pa andis further provided at its inner
`partly replaced within the aforementioned limits by
`surface with a luminescent layer 5. The layer 5 com-
`gallium and/or scandium. The Ce activator replaces
`prises a red luminescing yttrium oxide activated by
`part of the Ln andis present in a concentration x of0.01
`trivalent europium and a green luminescing terbium-
`to 0.15. Ce contents lower than 0.01 lead to materials 45
`activated cerium magnesium aluminate. An electrode
`having an insufficient blue absorption, while for Ce
`(not shown in the drawing) is arranged at each of the
`contents higher than 0.15 the garnet is formed insuffi-
`ends of the tube portions 2 and 3 remote from the cou-
`ciently and undesired subphases may be obtained.
`pling tube 4 and these electrodes constitute the means
`Preferably, such a lamp according to the inventionis
`for maintaining a column discharge in the gas filling.
`characterized in that in the garnet Ln is yttrium and in
`The endsof the tube portions 2 and 3 located near the
`that the garnet does not contain Ga and Sc(p=q=0).
`electrodes are connected to a lamp base 6, which carries
`Such materials in fact have the most favourable absorp-
`two current-supply pins 7 and 8 and in which a glow
`tion properties and supply the highest luminous fluxes.
`starter (not shown)is arranged. The discharge envelope
`In an embodimentof a lamp according to the inven-
`1 is coated throughout its outer surface with a thin
`tion, the absorption layer is disposed on the outer sur- 35
`absorption layer 9 of yttrium aluminate activated by
`face of the discharge envelope. This has the advantage
`trivalent cerium having a garnet structure. The inner
`that the mercury resonance radiation produced in the
`diameter of the tube portions 2 and 3 is 10 mm and the
`lampis utilized to the optimum andthe absorption layer
`length of the U-shaped discharge path is about 200 mm.
`only absorbs the undesired blue radiation and converts
`During operation, the lamp comsumes a power of 9 W
`it into visible radiation. In general, such a lamp will be
`and the load of the luminescentlayer5, i.e. the power
`provided with protection, for example an outer bulb, or
`consumed by the column divided by the surface area of
`will be used in a closed luminaire.
`the luminescent layer 5, is about 1350 W/m2.
`Another embodiment of a lamp according io the
`The lamp of FIG. 2 has an envelope 1 comprising a
`invention is characterized in that the absorption layeris
`glass outer bulb 2 and a bottom portion 3, which is
`disposed on the inner surface of the discharge envelope
`connected to the bulb and is provided with a cap in the
`and in that the luminescentlayer is disposed on the side
`form of an E 27 lamp base 4. In the envelope 1 are
`of the absorption layer facing the discharge. In this
`arranged a discharge bulb 5, a ballast unit 6 and an
`lamp, the mercury resonanceradiation will mainly be ~
`ignition unit (not shownin the drawing) provided in the
`absorbed by the luminescent layer. The use of an outer
`bottom portion 3. The discharge bulb 5 comprises a
`bulb or a closed luminaireis not necessary for this lamp.
`glass tube having an inner diameter of 9.5 mm,this tube
`Another embodiment of a lamp according to the
`being bent into the shape of a hook comprising four
`invention is characterized in that the garnet activated
`adjacent parallel extending tube portions intercon-
`by trivalent cerium is mixed with the luminescent mate-
`nected by three curved tube portions. The discharge
`rials of the luminescent layer so that the luminescent 55
`bulb 5 contains a small quantity of mercury and an
`layer is at the same time the absorption layer. Such a
`amalgam and a mixture of argon and neonat a pressure
`lamp can in fact be manufactured in a simple manner
`of 300 Pa. Electrodes 7 and8, respectively, are arranged
`because the absorption layer and the luminescent layer
`at the ends of the bulb 5 andthe inner surface of the bulb
`can be introduced into the lamp in a single operation.
`5 is provided with a luminescent layer 9 comprising red
`In a particularly advantageous embodiment a lamp
`and green luminescing materials of the type mentioned
`according to the invention comprises a discharge enve-
`in FIG. 1. The bulb5is arranged withits free ends in a
`lope, a ballast unit and an ignition unit, and optional
`bottom plate 10, which is secured in the bottom portion
`reflectors, all in a common envelope consisting of a
`3. The bottom plate 10 and the ballast unit 6 are coated
`bottom portion comprising a cap and an outer bulb
`with thin absorption layers 11 and 12, respectively, of
`transparent to radiation, and is characterized in that an 65
`cerium-activated yttrium aluminate. The lamp con-
`absorptionlayer is disposed on at least parts of the sur-
`sumes during operation a powerof 18 W. The length of
`face ofthe ballast unit and/or ignition unit and/or ofthe
`the curved discharge path is about 390 mm and the
`bottom portion and/or the reflectors.
`power consumed by the column divided by the surface
`
`30
`
`TCL 1029, Page 4
`TCL 1029, Page 4
`
`

`

`5
`area of the luminescent layer 9 has a value of 1250
`W/m2.
`
`4,727,283
`
`EXAMPLES 1 TO 4
`
`6
`TABLE II
`L 1000 (Im)
`Ly (im)
`y
`R (a8)
`x
`ex. A (mg)
`502
`564
`0.411
`82
`0.457
`a
`0
`502
`573
`0.423
`8t
`0.466
`5
`25
`Four lamps (designated 1 through 4) of the type de-
`
`
`
`6 0.475=0.43650 81 566 505
`
`
`scribed with reference to FIG. 1 (9 W) were provided
`7
`75
`0.480
`0.444
`80
`566
`513
`with a thin uniform absorption layer of cerium-
`activated garnet according to the formula Y2.9Cep;Al-
`sO12, which layer was disposed on the outer surface of
`the discharge bulb. For each lamp a different
`layer
`thickness was used. In the following Table I, the overall
`mass of the garnet used in the absorption layer (A in
`mg), the colour point (x,y) of the light emitted by the
`lamp and the luminous flux obtained (L in lumen) are
`indicated for each of these lamps. For comparison, (x,
`y) and L were measured on a lamp designated a) with-
`out an absorption layer, but otherwise identical to the
`lamps 1-4. These value also indicated.
`TABLEI
`
`It is again seen that the absorption layer leads to a shift
`of the colour point by about Ay=1.5Ax. The lamps5,6,
`and 7 all had a luminescent layer with the sameratio of
`the quantity of red luminescing material to that of the
`green luminescing material as the lamp a, which has a
`colour temperature of about 2750 K. A small enlarge-
`mentofthis ratio yields for the lamp 5 a colour point
`near the line of the black body radiators, in which event
`the colour temperature is about 2500 K. In a corre-
`sponding manner, even lower colour
`temperatures
`(downto about 2000 K.) can beattained for the lamps 6
`and 7.
`
`— 0
`
`_ 5
`
`20
`
`L dm)
`y
`x
`A (mg)
`example
`564
`0.411
`0.457
`0
`a
`558
`0.429
`0.468
`59
`1
`542
`0.434
`0.470
`72
`2
`$42
`0.439
`0.473
`80
`3
`
`
`
`
`150 0.483 0.4504 536
`
`It clearly appears that with increasing thickness of the
`absorption layer an increasing shift of the colour point
`occurs, where total Ay=1.5Ax. The colour temperature
`of the light emitted by the lamp a is about 2750 K and
`the colour pointlies substantially on theline of the black
`body radiators.
`If now in the luminescent layer of the lamps 1-4 the
`ratio of the quantity of red luminescing material to the
`quantity of the green luminescing material is enlarged
`(this ratio must be larger as the absorption layer is
`_ thicker) so that the colour point of the lamp shifts to an
`area on or near the line of the black bodyradiators, a
`colour temperatureis attained of about 2400, 2340, 2200
`and 2000 K for the lamps 1-4, respectively.
`EXAMPLES5 TO 7
`
`Three lamps (5, 6 and 7) of the kind shown in FIG.1
`(9 W), but without an outer absorption layer, were
`coated on the inner side of the discharge bulb with
`varying thicknesses of an absorption layer of cerium-
`activated garnet according to the formula Y2,9Cep |Al-
`
`EXAMPLE8
`
`25
`
`w0
`
`A lamp (8) of the kind described with reference to
`FIG. 2 (18 W) was provided with a Y29Ceo,; AlsO}2-
`containing absorption layer disposed on the bottom
`plate on the ballast unit and onthe side of the upright
`edge of the bottom portion facing the discharge bulb.
`The lamp had a colour point of the emitted radiation
`x=0.465 and y=0.417, which is very close to the de-
`sired point (x=0.468 and y=0.418). An identical lamp,
`but without an absorption layer, had a colour point
`x=0.461 and y=0.412.
`EXAMPLES9 TO 11
`
`Three lamps (9, 10 and 11)of the kind described with
`reference to FIG. 2 (18 W) were provided with a lumi-
`nescentlayer consisting of a mixture of green luminesc-
`ing terbium-activated cerium magnesium aluminate
`(CAT), red luminescing yttrium oxide activated by
`trivalent europium (YOX) and cerium-activated garnet
`(YAG) according to the formula Y2,9Cep,AlsO1. In
`these lamps, the luminescent layer therefore also ful-
`filled the function of absorption layer. In the following
`Table III, the composition of the luminescent layer (in
`% by weight) of the colour point (x, y), the colour
`temperature (T; in K.), luminousefficacy (7 in 1 m/W)
`and the general colour rendition index R (a, 8) are indi-
`cated for these lamps.
`
`TABLE IMI
`
`CAT
`n
`Te
`YAG
`YOX
`example % by weight
`
`
`% by weight % by weight (im/W)|R {a,8)x y (K)
`
`
`9
`30.8
`66.5
`2.7
`0.477 0.414 2500
`49.0
`80
`10
`26.8
`67.9
`5.3
`0.493 0.415
`2325
`48.4
`82
`i
`23.0
`68.1
`8.9
`0.508 0.415
`2175
`47.6
`83
`
`5012. On this absorption layer, a luminescent layer con-
`sisting of a mixture of red luminescing Y203-Eu3+ and
`green luminescing CeMgAl11019-Tb is provided. In the
`following Table II, for each lamp the mass of the ab-
`sorption layer (A in mg), the colour point (x, y), the
`general colour rendering index R (a, 8), the luminous
`flux at 0 hours (Lo in | m) and the luminousflux after
`1000 operating hours (Liooo in 1 m) are indicated. For
`comparison,these valuesarealso indicated for the lamp
`a without an absorption layer.
`
`65
`
`Finally, it should be noted that the luminescent layer
`of a lamp according to the invention may comprise
`besides a red luminescing and a green luminescing mate-
`rial also a small quantity of a blue luminescing material,
`as is also the case in three-band fluorescent lamps hav-
`ing a high colour temperature. In the present heavily
`loaded lamps, this can afford advantages because the
`blue luminescing material provides an additional degree
`of freedom for reaching a desired value of the colour
`point of the lamp.
`Whatis claimed is:
`
`TCL 1029, Page 5
`TCL 1029, Page 5
`
`

`

`4,727,283
`
`— 0
`
`m 5
`
`25
`
`8
`7
`9. A lamp as claimed in claim 1, characterized in that
`1. A low-pressure mercury vapour discharge lamp,
`the absorption layer is disposed on the outer surface of
`whose emission mainly lies in three spectral ranges and
`the discharge envelope.
`whose colour temperature of emission lies in the range
`10. A lampas claimed in claim 2, characterized in that
`of 2000-3000 K., the lamp comprising a gas-tight dis-
`the absorption layer is disposed on the inner surface of
`charge envelope transparent to radiation and having a
`the discharge envelope andin that the luminescent layer
`gas filling comprising mercury andarare gas, a lumines-
`cent
`layer comprising luminescent materials whose
`is disposed ontheside of the absorption layer facing the
`emission mainly lies in the ranges of 590-630 nm and
`discharge.
`11. A lamp as claimedin claim 1, characterized in that
`520-565 nm, means for maintaining a column discharge
`the absorption layer is disposed on the inner surface of
`in the gas filling, the power consumed by the column
`being at least 500 W per m?surface area ofthe lumines-
`the discharge envelope andin that the luminescentlayer
`is disposed on the side of the absorption layer facing the
`cent layer,
`characterized in that the lamp is provided with an
`discharge.
`12, A lamp as claimed in claim 2, characterized in that
`absorption layer comprising a luminescent alumi-
`the garnet activated by trivalent cerium is mixed with
`nate activated by trivalent cerium and having a
`the luminescent materials of the luminescent layer and
`garnet crystal structure.
`2. A lampas claimed in claim 1, characterized in that
`in that the luminescent layer also is the absorption layer.
`the luminescent aluminate having a garnet structure
`13. A lamp as claimedin claim 1, characterized in that
`corresponds to the formula Ln3.,Ce,Als.p.gGapSe,O12,
`the garnet activated by trivalent cerium is mixed with
`the luminescent materials of the luminescent layer and
`in which Ln is at least one of the elements yttrium,
`gadolinium, lanthanum and lutetium and in which
`in that the luminescentlayer also is the absorption layer.
`0.013x350.15
`14. A lampas claimed in claim 2, including a ballast
`unit and an ignition unit, which are arranged together
`0=p33
`with the discharge envelope in a common envelope
`0=q=1.
`3. A lampas claimed in claim 2, characterized in that
`consisting of a bottom portion comprising a cap and of
`Lnis yttrium and p=q=0.
`an outer bulb transparent to radiation, characterized in
`4, A lamp as claimed in claim 3, characterized in that
`that the absorption layer is disposed on at least parts of
`the absorption layer is disposed on the outer surface of
`the surface of one or more ofthe ballast unit, the igni-
`tion unit and the bottom portion.
`the discharge envelope.
`5. A lamp as claimed in claim 3, characterized in that
`15. A lampas claimed in claim 1, including a ballast
`unit and an ignition unit, which are arranged together
`the absorption layer is disposed on the inner surface of
`the discharge envelope andin that the luminescentlayer
`with the discharge envelope in a common envelope
`is disposed on the side of the absorption layer facing the
`consisting of a bottom portion comprising a cap and of
`an outer bulb transparent to radiation, characterized in
`discharge.
`that the absorption layer is disposed onatleast parts of
`6. A lamp as claimed in claim 3, characterized in that
`the garnet activated by trivalent cerium is mixed with
`the surface of one or more ofthe ballast unit, the igni-
`the luminescent materials of the luminescent
`layer
`tion unit and the bottom portion.
`whereby the luminescent layer also is the absorption
`16. A lamp as claimed in claim 7, including at least
`layer.
`one reflector arranged within the envelope, character-
`7. A lamp as claimed in claim 3, including a ballast
`ized in that the adsorption layer is disposed on atleast a
`unit and an ignition unit, which are arranged together
`portion of the surface ofthe reflector.
`with the discharge envelope in a common envelope
`17. A lamp as claimed in claim 14, including at least
`consisting of a bottom portion comprising a cap and of
`one reflector arranged within the envelope, character-
`an outer bulb transparent to radiation, characterized in
`ized in that the absorption layer is disposed on at least a
`that the absorption layer is disposed on at least parts of
`portion of the surface of the reflector.
`the surface of one or moreof the ballast unit, the igni-
`18. A lamp as claimed in claim 15, including at least
`tion unit and the bottom portion.
`one reflector arranged within the envelope, character-
`8. A lampas claimed in claim 2, characterized in that
`ized in that the absorption layer is disposed on at least a
`the absorption layer is disposed on the outer surface of
`portion of the surface of the reflector.
`s
`*£
`*
`*€£©
`*
`the discharge envelope.
`
`40
`
`45
`
`50
`
`55
`
`65
`
`TCL 1029, Page 6
`TCL 1029, Page 6
`
`