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Jan- 7, 1947-
L. R. BICKFORD, JR
2,413,940
FLUORESCENT LIGHT SOURCE
Original. Filed Jan. 1l_, 1944
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ATTORNEY
Patented Jan. 7, 1947
2,413,940
UNITED STATES ‘PATENT OFFICE‘
' ' FLUORESCENT Lron'r SOURCE
Lawrence R. Bicktord, Jr., State College, Pa., as- I
signor to Sylvania Electric Products Inc., "
Emporium, Pa.,l a corporation of Massachusetts
Original application January 11,vv 1944, Serial No.
517,806. Divided and this application March
16, 1944, Serial No. 526,768
.
(Cl. 176-122)
7 Claims.
2
This invention relates a0 ?uorescent'gl'asses
phosphate glass comprising one or several of the
and more particularly to glasses which emit
long wave ultraviolet radiation in response to
phosphates of elements of the ?rst, second and
third groups of they periodic system.
According to a feature of the invention, means
are provided including a cerium-activated phos
excitation by short wave ultraviolet radiation. ,
In some cases, it is desirable to obtain only the
long wave ultraviolet radiation from alight
phate glass, to produce visible?uorescence from
source which itself emits both, long and short
a source of short wave ultraviolet radiation by
wave ultraviolet, as, for example, a mercury arc
multiple,_frequency conversion.
lamp. The conventionalvexpedient for attain
‘
‘
A further feature of the invention relates to a
. ing this result is to use a filter glass which ab
10 ?uorescent lamp embodying a metal phosphate
sonbs the shortwave ultraviolet, while passing
glass having the optimum content of trivalent
cerium for producing improved ‘conversion of
be accomplished by making the envelope of the
short wave ultraviolet into long wave ultra
arc lamp of Corning ultraviolet transmission glass
violet radiation.
#504 or #589 or by interposing a blue corex 15
Another feature‘ of the invention‘ relates to a
glass ?lter-Corning ?lter glass #986 between a
?uorescent lamp having a cerium-activated phos
quartz mercury lamp and the object to be exposed
phate glass consisting of the phosphates of A1-,
the long wave ultraviolet radiation.
This may -
to the. long wave ultraviolet radiation.
This procedure has the disadvantage that the
short wave ultraviolet energy produced ‘by ‘the 20
light source is wasted, and is converted into heat
which may be undesirable.
'
-
‘This wasting of short wave ultraviolet energy
has so far been unavoidable in the conversion
Zn, and Ba in certain preferred proportions.
In the drawing which represents certain pre
ferred embodiments,
'
Fig. 1 ‘illustrates an experimental set-up to ex
plain the invention.
»
Fig. 2 is a simpli?ed diagram of an ultraviolet
lamp and casing according to the invention.
of ultraviolet radiation into visible light by 25 Fig. 3 is a sectional view of Fig. 1 taken along
?uorescent and phosphorescent materials which
the line 3-3 thereof.
emit visible light in response to long wave ultra
Fig. 4-is ‘a modi?cation showing the invention
violet radiation only, but have no excitation band-1 1 embodied in a ?uorescent lamp.
in the short wave ultraviolet region which is'pres
Fig. 5 is a sectional of Fig. 4, taken along the
ent in most ultraviolet light sources.
line 5-5 thereof.
to
_ It is, therefore, a principal object of the in
Fig. 6 is a modi?cation of Fig. 4.
vention to produce ?uorescent light sources which
Fig. 7 is a sectional view of Fig. 6, taken along
emit long wave ultraviolet radiation .viz., 3000 to I the line 7-’? thereof.
4000 A. in response to excitation by short wave
The cerium-activated phosphate glasses ac
ultraviolet radiation, e. g., 2537 A.
It is another object of the invention to produce
a ?uorescent lamp incorporating a cerium-ac
tivated phosphate glass.
It is a still further object of the invention to
produce ?uorescent light sources embodying a
?lter; glass which passes long wave ultraviolet
and visible radiation, and absorbs short wave
cording to the invention may be made up from
According to
35 diiferent types‘ of raw materials.
- I one method, the raw batch comprises P205 and
compounds in the form of salts of elements of
the ?rst, second and third groups of the periodic
system, which transform into the metal oxides
40 during
melting of the raw batch. To the raw
batch-is added up to 10% of a cerium salt (e. g.,
C6203, CeOz, Ce(N03)4. Ce(N03)a and a reducing
agent, such as AS203, red phosphorus, aluminum
According to another object of the‘ invention,
‘
means are provided for increasing the luminous 45 powder, or cream of tartar.
According to another method, the raw batch
e?icien'cy of ?uorescent lamps and the like.
ultraviolet without-transforming it intoheat.
Another principal object of the invention re
consists of one or a mixture of several meta
,phosphate's of the elements of the second and
third ‘groups of the periodic system, c. g.,
lamp which consists of two layers of ?uorescent
glass, the inner layer being made of cerium 50 Zn(PO3)2; BaCPOsh; A1(PO3)3. To this raw
activated phosphate glass; the outer of a mate
batch are added cerium salts and reducing agents
rial emitting visible light primarily in response
as in the ?rst method. Preferred mixing ratios
to long‘wave ultraviolet radiation.
of the three metaphosphates for making my
An additional object of the invention is to pro
cerium-activated phosphate glasses are given
vide a ?uorescent lamp with a cerium-activated 55 in table.
.
.
lates to an envelope for a gas or vapor discharge
2,413,940
5
3
able
‘
.
source S into long wave ultraviolet radiation.
}
‘
An added amount of long wave ultraviolet radi
m
"(2)
(35
(4)
>
2110,03)‘, ______________________________
50
B11008), ____________ __
“(Pom ----------------- --' ------ "' ---- --
o
25
0
so
25
45
m
50
50
40
__
'ation, emitted by glass plate P, passes therefore
_,
through ?lter F, and increases the visible light
1'5 5 emission of glass plate G in the region A as. com
pared with that emitted on side B.
Taking advantage of this phenomenon, I have
1
built two types of lamps.
Cerium-activated phosphate glasses‘ having
The ?rst type shown
in Figs. 2 and 3 consists of a combination of an
similar proportions as those made up from the 10 ordinary “black light" ultraviolet lamp I, (which
metaphosphates, but made up of the raw materials according to the ?rst-mentioned method,
'
viz., starting from P205 and either ZnO, BaO.
A1203 or 2Zn(COa).3Zn(OH)z or B8.(C0a) are, of
consists of a mercury arc lamp built into a ?x
ture having an outer casing or window 3 made
of “red-purple Corex A" glass (or “Corning
#986”) with a second cerium-activated phos
course, equivalent to the preferred glasses ac- 15 phate glass plate or wall 2 interposed between
cording to the table.
'
,
'
4
-
the are lamp. and the “Corex A” glass filter.
I have found that the addition of 2% to ‘4% '. This newJamp delivers a larger amount of long
cerium to mixture (4) of table,'introduced pref- ywave ultraviolet radiation from any given are
erably in the form of C8203 or of cemomerno,
lamp than the conventional “black light lamps.” '
with further addition of an appropriate amount 20‘ and is therefore of higher e?iciency in the long
- of any of the above described reducing agents
wave ultraviolet region than are the commercial
yields a glass with a relatively high conversion
lamps of this type- Incidentally, the "COreX A"
of shortwave ultraviolet radiation, e. g.,'2537 A.
_ ?lter 3 is not as hot during operation, because
into long wave ultraviolet radiation between
3000 and 4000 A_
v
Of the fact that the short wave ultraviolet radi
25 ation is not absorbed and transformed into heat.
According to the invention, these new phos-
8.5 is the case with the conventional lambs. For
phate glasses are used as light ?lters and for
multiple frequency conversion equipment in new
a detailed disclosure of a device such as lamp I,
reference may be had to U. S. Patent No
combinations with gas and vapor‘ arc lamps in .
2.383.189.
-
‘a manner about to be described,
7
30
A second type of lamp according to the inven
Fig. 1 shows in diagrammatic form, an ex-. ' @1011. as Shown in Figs- 4 and 5, consists of ai
perimental arrangement illustrating the.princi-_
Suitable envelope 4 which contains the usual
ples of the invention. A plate of any glass (G) -_
mixture of gas and vapor ?lling as customarily \
capable of emitting ‘visible ?uorescence onexei-
employed in commercial ?uorescent‘ lamps
tation by long waveultraviolet radiation (as are as Mounted at opposite ends of the envelope. which
most manganese_activated phosphate qr ‘Silicate
ends are of course sealed, there are the usual
electrodes 5 and .5, either 01' both of Which may
duced by an ultraviolet source s, from‘which the
be of the thermionic or of the ?eld-emission type.
short wave and visible radiation haslbeen'?ltered
It Will be understood 01' course‘; that the elec
out by a Corex black ?lter F, made-of a glass com- 40 trodes 5 and 6 are connected in'circuit with any
merciauy kngwn as “Coming #936301. “red_
well-known starting control arrangement such as
glasses) -is exposed to the radiation originally pro
purple Col-ex. A" Between the light sources
wh1ch maybe of ‘any weh_known type, 'such for
is ordinarily employed in commercial ?uorescent
lamps. In accordance with the present inven
example as Shown in U_ 3. Patent No_ 2’283’189,
tion, envelope 4 is made of a cerium-activated
and the ?lter F is placed a glass sheet p com 45 phosphate glass as above described. In accord
sisting of one of the new phosphate glasses acance with the invention also, the exterior sur
cording to the invention, and covering about one
' face of envelope‘ ‘ 15 Provided with a coating 7
half of the area of Corex ?lter F, in the region
of one of the well-known ?uorescent materials
marked A in the drawing In the right half’
which emit visible light more readily in response
marked B in the drawing, the radiation from 50 to long wave ultraviolet radiation than they do
light source 5 passes only the ?lter F before
to short wave ultraviolet radiation. This coating
striking, glass plate G’ i‘ e" no phosphate glass
1 may for example be of zinc sul?de. For a de
is interposed between light source, S and ?lter F‘
tailed disclosure of the construction of such a
The striking phenomenon observed with this
lamp to which the coating can be applied’ ref‘
arrangement is, that the glass plate G remains 65 erence is hereby made to U‘ 8' Patent NO' 21283"
comparatively dark on the side marked 13’ while
189. the disclosure of which is incorporated here
it emits a large amount of visible light on the
in expressly since in the type of lamp shown
side marked A, where the phosphate glass P has
in Figs. 4 and 5, the'actual ?uorescent coating is
been interposed between the source S and the'
applied externally of the envelope 4' it 15 p05‘
?lter F_ The result is striking and unexpected 60 sible to use for illumination purposes, sul?des
for any one not familiar with the new ?uoresSuch as 'zns; Zncds; 01' Cas- These sul?des
cent glass because the expected interpretation of
°°u1d_n°t be used successfully“! this Particular
the glass plate P would be that ofan additional
?eld "1 the Past, because when they are applied
?lter, i. e., of a partly transparent shield which
as a’ coating internally of the envelope 4' they
absorbs part of the radiation from light source 65 are destroyed by the are 0' Vapor discharge be‘
s_ The usual observer would’ therefore’ expect
H tween the electrodes 5 and 8. It will be under
that
the side
the marked
visible ?uorescence
A could only
of be
glass
weaker’
plate or on
at
Stood
to any01'particular
course, kind
theofinvention
?uorescent
is nOt
coating 1.
best‘ just as good, as on side B_
If desired. other ?uorescent materials which
The explanation of the fact that glass plate 70 emit visible radiation preferably in response to
G emits more visible radiation on the side where
10118 Wave ultlfa-vi?lell excitation may be used as
the phosphate glass P has been interposed bean external coating- Examples 01 Such mate
tween the light source S and the?lter F is, of
,rials are organic ?uorescent materials such as
course, the property of my new glass to convert
the rhodamlnes, or U-activated CaFz, CaO, or
the short wave ultraviolet radiation of the light 76 z‘inc vanadate.
‘
'
auaeso
5
.
In another embodiment of this type of ?uo
rescent lamp, and as shown in Figs. 6 and ‘I, the
envelope may consist of an-internal evacuated
and sealed tube 8, carrying at ‘opposite ends the
usual electrodes 9 and ill, for‘ sustaining an ultra
violetproducing. discharge within the cavity of ‘
the tube 8 which cavity contains the usual ?ll
ing of metallic vapor such as mercury vapor and
‘means to generate ultraviolet radiation having
long and‘ short ultraviolet wavelength compo
' nents, means mainly responsive to excitation only
by long wave ultraviolet to produce visible ?uo
rescence, and means including a cerium-acti
vated phosphate glass’ located between said gen
erator means and said responsive means to con
vert said short wavelength components into long
wavelength components whereby visible light is
a small percentage of a gas such as argon, helium
and the like as describedior example in said 10 produced in response both to said long wave
components and to said short wave components.
U. 8. Patent No. 2,283,189. Surrounding the
2. A ?uorescent lamp comprising a sealed en
tube 8 and in spaced relation thereto, is another
velope containing an ionizable medium for pro
glass tube II. In accordance with the inven
ducing ultraviolet radiation including long and
tion, the envelope 8 is composed of one of the
» above-described
cerium-activated phosphate 15 short wave length components. the envelope be
ing 01' a glass which has the property‘oi usefully
glasses, while the outer casing’ ll consists of
converting a substantial. part of the short wave
manganese-activated phosphate glass. When a
components ‘into long_wave ‘components, and
gaseous discharge is maintained between. the
fluorescent means carried by said envelope and .
electrodes 9 and ill in the well-known manner,
there is emitted both long and short wave’ ultra 20 responsive to the original long wave components
and '_ to said converted components to produce
violet radiation. The long wave radiation passes
substantially freely through the wall of member
a and excites the member II to visible ?uo
resence. At the same time,c,the short wave radia
_ tion from the discharge is converted by member 25
I to long wave ultraviolet radiation which sup
plements the excitation‘of the member ll, thus
visible ?uorescence.
I
3. A ?uorescent lamp according to claim 2 in
which the glass of the envelope is of the cerium
activated phosphate type.
_
'
‘ 4. A ?uorescent lamp according to claim 2 in
which said ?uorescent means is in the form of a
‘ stratum on the exterior 01' said envelope.
increasing the overall ?uorescent e?lciency oi
5. ‘A ?uorescent lamp comprising a pair of
the device. The ?rst factor causing this in
crease of e?lciency is-the pre-converslon of short 30 spaced glass casings, one of which has means to
support on its interior a discharge for producing
wave ultraviolet radiation into long wave ultra
ultraviolet radiations containing long and short
violet radiation by means of the member 8 as
wave lengths and being oi.’ a glass which has the
described above. The second factor is the low
ering'oi temperature of the visible ?uorescent '
property 01’ usefully converting short ultraviolet
layer which may be either directly in the mem 35 wave lengths into long ultraviolet wave lengths,‘v
and ?uorescent means responsive to said long
ber II or in the form oi’ a ?uorescent coating
which may be applled'to the external or to the
internal surface of member II. This lowering
of temperature causes increasede?iciency be
ultraviolet wave lengths and to said converted
wave lengths and carried by the other or said
casings.
6. A ?uorescent lamp according to claim 5 in
cause the short wave ultraviolet radiation is not 40
which the casings surround each other, the inner
dissipated as heat but is converted into a long
casing being of cerium-activated phosphate glass,
wave ultraviolet radiation. The visible ?uo
and the outer glass casing being of manganese
rescent sheath carried by- member Ii or incor
porated in member ii itself, is a greater distance
activated ?uorescent glass.
from the hot discharge path within member 8; 45 '7. A ?uorescent lamp comprising an enclosing.
glass envelope having means to produce an elec
and ?nally the larger external area of the device
' provides a greater heat radiating surface.
tric discharge therein, which discharge produces
It will be understood of course that the in
long wave length ultra-violet and a substantial
vention is not limited to the particular struc
portion of short wave length ultra-violet, a signal
tures. shapes. or materials herein mentioned, but 50 ?uorescent coating on the wall of said envelope
and responsive substantially entirely to long wave
_ that various changes and modi?cations may be
made therein without departing from the spirit
length ultra-violet; and means incorporated in
and scope of the invention.
.
said glass for converting the short wave length
This application is a ~division of application
ultra-violet from said discharge into long wave
Serial No. 517,806, ?ied January 11, 1944. 55 length ultra-violet before acting on said ?uores
What is claimed is:
cent coating.
l. A ?uorescent light source comprising.
.
LAWRENCE R. BICKFORD, Ja.‘
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