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Патент USA US2113973

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.April 12, 1938.,
2,113,973
N. W. H. ADDINK _
RED FLUORESCENT LAYER
Original Filed Oct. 22, 1936
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2,113,973
Patented Apr. 12, 1938 _.
OFFICE
UNITED STATES
2,113,973
RED FLUOBESCEN'E LAYEB
Nicolaas Willem‘ Hendrik Addink, Eindhoven,
Netherlands, assignm- to N. V. Philips’ Gloei
lampeniabrieken, Eindhoven, Netherlands
Application October 22, 1936, Serial No. 107,107.
Renewed March ‘I, 1938. In Germany October,
25, 1935
7 Claims. (Cl. 88-1)
My invention relates to red ?uorescent layers, dyestu?’ without depriving this layer of its red
and more particularly to layers containing a red
?uorescent rhodamine dyestufi.
On highways illuminated by metal vapor dis
5 charge tubes it is advantageous to use signals
provided with a layer of red ?uorescent dyestu?,
as the usual dyestuffs when illuminated for ex
ample, by mercury vapor or sodium-vapor dis
charge tubes produce either an undesired color
10 or no color at all. While red ?uorescent rhoda
mine dyestu?s, produce a distinct red color when
radiated by such light, they have the drawback
that they are poorly resistant to the action of
light and are photochemically decomposed.
15
Although such photochemical decomposition
was generally believed to be due to the action of
ultra-violet light, I have found that this dyestu?
intensely absorbs a band of light in the visible
portion of the spectrum, and that it is the ab
sorption of this light which causes, to a large
degree, the decomposition.
While it would appear that this drawback could
be overcome in a simple manner by using a light
?uorescence capacity.
More particularly, in accordance with the in
vention I provide the layer containing the red
fluorescent rhodamine dyestu? with an orange- 5
colored light ?lter which absorbs only a portion
of the light having wave lengths within ‘the range
of the rhodamine dyestu? absorption band lying
in the visible part of the spectrum, and which
transmits red light. Preferably, the material of 10
the orange-colored ?lter itself should be capable
of resisting photochemical decomposition.
The use of such a ?lter has the great advan
tage that a red ?uorescent layer of rhodamine
dyestu? is rendered much more resistant to the 15'
action of daylight, particularly sunlight, while at
the same time it produces the desired red-?uo
rescence when illuminated either by daylight or
by arti?cial light, for example the light of the
above-mentioned metal-vapor discharge tubes.
In order that my invention may be clearly
understood and readily carried into effect, I shall
describe same more fully in connection with the
?lter to ?lter out light of the wave-length range ' accompanying drawing, in which:
of the absorption band- or bands of the rhodamine
dyestuff, this is'not the case, as with such a dye
stu? the light ?lter would absorb light necessary
for the generation of the red ?uorescence and
thus render the layer of rhodamine dyestuif in
30 capable of producing the desired color. To over
come this difficulty quite different methods have
been proposed for example, the red ?uorescent
dyestu? has been dispersed in a condensation
product obtained from phthalic acid and a poly—
35 valent alcohol, or from symmetrical diamethyl
glycol and citric acid. Such methods, however,
had the disadvantage that the resistance to the
action of light is not satisfying in such a degree
as preferred in practice.
40
Figure l is a view of a signal according to the 25
invention;
FlFig. 2 is a sectional view along lines 2—2 of
g- 1;
.
,
Fig. 3 is a graph giving light-absorption curves;
Fig. 4 is a graph giving the light-transmission 30
curve of the ?ltering layer of Figs. 1 and" 2.
The signal shown in Figs. _1 and 2 comprises a
metal disc carrying an indicating arrow 2 con
sisting of a ?uorescent layer 3 and a ?ltering
layer 4, each layer having a thickness of about
1 mm.
The ?uorescent layer 3 is formed by applying
to disc I in an acetone solution, a dispersion of
rhodamine B in a condensation product obtained
The object of my invention is to overcome the
from symmetrical dlmethylglycol and citric acid;
layer which is'protected against photochemical
tive_ to the condensation product being 0.25%.
To increase the ?uorescence e?ect the dispersion
may also ‘contain a quantity of lead chromate
not exceeding 3%, computed on the condensation
product. The ?ltering layer 4 covers the layer 3
and is applied thereto by means of an acetone
above di?iculties and to provide a red ?uorescent , the concentration of the rhodamine dyestu? rela
decomposition while at the same time it radiates
light of the desired color, when illuminated with
45 either natural light or the light of metal-vapor
discharge tubes.
'
.
My invention, which utilizes the ?ltering prin
ciple, is based upon the fact that the light of
all wave lengths within the range of the rhoda
50 mine dyestu? absorption band lying in the vis
ible portion of the spectrum, is capable of gen
erating the red light of ?uorescence. Thus, theo
retically, any light ?lter that does not absorb all
the wave lengths in the above-mentioned range
55 could be combined with a layer of rhodamine
solution containing equal quantities by weight of
the above-mentioned condensation product and
acetone, and 0.2 kilogram per 100 liters of the
dyestu? known as methasolaurine A. S.
Instead of methasolaurine A. S., the dyestuff
known as orange G may be used; a concentration
of 21/2 kilograms of this dyestuff per 100 litre of
the above-described solution giving with other
5
2
8,118,978
conditions the same-a 5-fold increase in light
durability. In addition, the well-known commer-.
cial dyestu?' Sudan-orange G may be used as
?ltering dyestu?'s.
_
Instead of the above-mentioned dispersion me
diums, synthetic resins may also be used, for ex
ample condensation products obtained from
Dhthalic acid or citric acid with glycerine.
The dyestuffs mentioned above are identi?ed
10 by 'the following index numbers as given in the
well-known "Farbsto?'tabellen’f by Schulz 1931:
Dyestuif
Rhodamine B
Index number
__ 864
Methasolaurine A. S ________ _; __________ __ 843
Orange G
39
Sudan orangeG
33
The functioning of the signal shown in Figs. 1
and 2 will'be described in connection with Figs. 3
20 and 4 in which curve I shows the variation in the
absorption of light in the visible portions of the
spectrum by the rhodamine B dyestuif contained
in layer 3, if the layer 4 were not present, and
curve 2 shows the variation in light-absorption
of the rhodamine B dyestu? with the layer 4 in
place. Curve 3 indicates the transparency to
light of the visible portion of the spectrum of the
methasolaurine A. S. having the concentration
given for layer 4.
30
When irradiating the signal by monochromatic
light of wave length 550 mg, a portion of this light
is absorbed by layer 4 ‘before reaching layer 3.
As seen from Fig. 4, approximately 70% of this
light is transmitted through layer 4, and thus
whereas the light durability was found experi
mentally to have been increased three times.
While ‘I have described my invention in con
nection with speci?c applications and examples, I
do not wish to be limited thereto, but desire the
appended claims to be construed as broadly as
permissible in view of the prior art.
.
What I claim is:
1. A body having red ?uorescent properties
comprising a ?uorescent layer containing a red 10
?uorescent rhodamine dyestu? and a ?ltering
layer containing an orange-colored ?lteringsub
stance having the properties of transmitting red
light and of absorbing a portion of the light whose
wave lengths are within the range of the rhoda
mine dyestufi' absorption band lying within the
15
visible portion of the spectrum.
4 2. A body having red ?uorescent properties
comprising a ?uorescent layer containing a red
?uorescent rhodamine. dyestu?', and a‘ ?ltering 20
layer containing methasolaurine A. S. dyestu?’.
3. A body having red ?uorescent properties
comprising a ?uorescent layer containing a red
?uorescent rhodamine dyestu? and a ?ltering
layer containing an orange-colored ?ltering sub 25
stance having the properties of transmitting red
light and of absorbing a portion of the light whose
wave lengths are within the range of the rhoda
mine dyestuii' absorption band lying within the
visible portion of the spectrum, the area enclosed 30
by the light-absorption curve of said dyestu?'
being more than twice the area enclosed by a
curve obtained'by multiplying the ordinates of
said light-absorption curve by the ordinates of
layer 3 receives about 70% of the original quan - the light-transmission curve of the ?ltering layer.
35
tity of this light. This is indicated in Figure 3
4. In combination, a red ?uorescent layer con
by the point B, which lies at aboutv70% of the taining
a red ?uorescent rhodamine dyestu?, and
height of the point A. Thus curve 2 is obtained a ?ltering layer containing an orange-colored
by multiplying each ordinate of the curve I by the ?ltering substance having the properties of trans
40 transmission as given by curve 3 for the corre
mitting red light and of absorbing a portion of
sponding wave length. In the case of irradia
the light whose wave lengths are within the range
tion by daylight or sunlight, the absorption curve of ‘the rhodamine dyestuif absorbing band lying
_2 consequently applies for this system. The de
within the visible portion of the spectrum.
crease in'absorption of layer 3 for light having
5. A red ?uorescent indicating body adapted to
45 wave lengths lying within the visible portion of
be radiated by the light of a mercury-vapor dis 45
the spectrum is indicated by the hatched area 6, charge tube comprising a ?uorescent layer con
which is the diiference between the area enclosed taining a red ?uorescent rhodamine dyestu?’, and
by curve I and the area enclosed by curve 2, and I a ?ltering layer containing an orange-colored
have found that the durability of the system is ?ltering substance having the properties of trans
50 increased accordingly.
mitting red light and of absorbing a portion of
When irradiating the signal with the light of a the light whose wave lengths are within the range 50
sodium-vapor discharge tube or a mercury-vapor of the rhodamine dyestu? absorption band lying
discharge tube, however, the desired red ?uores
within the visible portion of the spectrum.
cence is not decreased to any appreciable degree
6. A red ?uorescent body adapted to be radiated
55 because a very large portion of the light emitted
by the light of a sodium vapor discharge tube
by these tubes at 590 my. and 540 in,“ respectively comprising a ?uorescent layer containing a red »
is still absorbed by the layer 3 to cause same to ?uorescent rhodamine dyestu? and a ?ltering
emit a large quantity of red-?uorescent light, layer containing an orange-colored ?ltering sub
which passes through the orange-colored ?ltering stance having the properties of transmitting red
60 layer 4 practically unhampered. For the same
light and of absorbing a portion of the light
reason, the red color of the system of the two whose wave lengths are within the range of the
layers remains practically unvaried in daylight.
rhodamine dyestu? absorption band lying within
In the example illustrated, the ratio of the area the visible portion of the spectrum.
enclosed by curve 2 to the area enclosed by curve
7. A body having red ?uorescent properties
65 I is about 1:2 and upon measurement. the light
comprising a ?uorescent layer containing a red
durability of the system of layers was found to ?uorescent
rhodamine dyestu?', and a ?ltering
have been doubled. When, with the other condi
layer containing an orange-colored ?ltering dye
tions remaining the same, the methasolaurine stu? selected from the group consisting of meth
A. S. dyestu? was used in a concentration of 0.7 asolaurine A. 8., orange G, and Sudan-orange G.
10 kilogram per 100 litre, the above ratio became 1:3,
NICOLAAS WILLEM HENDRIK ADDINK.
70
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