Luminescent material

Luminescent material may be fabricated of silicon dioxide containing as activators approximately up to 1% monovalent copper together with up to approximately 15% aluminum. The material may be in powder form, it may be in glass form or it may be produced by electrolytic ingredient transfer. The material is luminescent in the blue range from 380-580 nanometers.

DESCRIPTION 
1. Technical Field 
The technical field of the invention is that of materials that convert 
light energy at one frequency to light energy at another frequency. Such 
materials have come to be known in the art as luminescent materials or 
phosphors. In the presence of a background light of a certain frequency 
the emitted light from such materials will be of a different frequency and 
will be predominantly of one wavelength. The performance of luminescent 
materials is usually influenced by the presence of materials serving as 
activators. 
2. Background Art 
Luminescent materials have been used in a variety of applications in the 
art. One principal example is in displays where the luminescent materials 
with various physical property-imparting activators are stimulated by 
energy sources such as electron beams. 
For display purposes, as described in U.S. Pat. No. 2,876,129, a metal 
coating was deposited on and annealed into a glass envelope to provide 
fluorescent properties to a television screen. 
Copper has been known as a phosphor activator in U.S. Pat. No. 2,570,136 
and copper doped aluminosilicate phosphors have been known and described 
in the Journal of The Electrochemical Society, Vol. 98, No. 2, October 
1951, pp. 409-413. 
Luminescence in the blue range from about 420-570 nanometers is desirable 
for a variety of applications. Such luminescence has been achieved using 
lanthanides as the phosphor activator. The lanthanide activated materials, 
however, have been found to require close control on the purity of the 
ingredients, to give narrow band emission and the luminescent output 
diminishes above 300.degree. C. 
Weak blue luminescence, further has been observed in natural, somewhat 
impure, quartz that has been melted to silica glass. 
DISCLOSURE OF INVENTION 
Luminescent materials may be fabricated with the principal ingredient being 
silicon dioxide and, as activators both monovalent copper and aluminum 
additives are simultaneously present. The additives are present as 
Cu.sup.+ and Al.sup.+++ ions. The luminescent output is intense and 
extends over a range from the vicinity of 380-570 nanometers with a peak 
in the blue color range. 
Significant luminescent intensity occurs when the copper ingredient is in 
the vicinity of 0.08% to 0.85% Cu.sub.2 O at the same time the Al.sub.2 
O.sub.3 ingredient is in the vicinity of 1.2% to 15%. The luminescent 
material is not sensitive to ingredient purity within 1% and maintains 
light output until the temperature exceeds 500.degree. C. The luminescent 
material may be in powder form. It may be in the form of a clear glass or 
it may be in the form of an electrolytically converted commercial glass. 
BEST MODE FOR CARRYING OUT INVENTION 
In accordance with the invention, blue luminescent material is made by 
adding finally divided silicic acid and quantities of cupric nitrate and 
aluminum nitrate to provide concentrations of cuprous oxide within the 
range 0.08 to 0.85 Mole % and aluminum oxide in the range of 1.2 to 15 
Mole %. 
The relative concentrations in Mole % of the critical ingredients and the 
corresponding relative visual intensity are shown for a number of examples 
in Table I. 
TABLE I 
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POWDERS INTENSITY 
COMPOSITION MOLE % % Compared With 
Cu.sub.2 O 
Al.sub.2 O.sub.3 
SiO.sub.2 
ZnO 
______________________________________ 
.08 .19 99.73 15 
.12 .12 99.76 19 
.12 1.2 98.68 24 
.2 4.0 95.8 25 
.34 2.4 97.26 27 
.34 3.0 96.6 31 
.42 1.2 98.38 33 
.42 3.8 95.78 34 
.42 10.0 89.58 30 
.42 12. 87.58 24 
.65 2.4 95.95 20 
.85 4.0 95.15 15 
0 4 96 &lt;1 
0.42 0 99.58 &lt;1 
0.4 15 84.6 15 
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Visual intensity is measured relative to an intensity value of 100 
exhibited by commercially available zinc oxide luminescent material under 
245 nanometer mercury light using a photocell and a voltmeter. The 
commercially available zinc oxide material is manufactured by Sylvania 
Electric Products, Inc. and is available commercially under the 
designation P-15. 
From Table I it may be seen that the intensity peaks where the range of 
cuprous oxide is from 0.34 to 0.42% and where the range of aluminum is 1.2 
to 10%. Intensities of 15 and above may be considered useful.

The luminescent material may be prepared as is set forth in the following 
examples. 
EXAMPLE A 
Luminescent Powder 
Phosphor powders may be made with silicic acid, cupric nitrate, aluminum 
nitrate and an additive boric acid. These are mixed with water, alcohol 
and acetic acid. A ball mill or magnetic stirring can be used. The mixture 
is poured into shallow dishes to dry at approximately 120.degree. C. The 
dried cake is then broken, placed in refractory boats or crucibles and 
heated approximately 1150.degree. C. for from 5 to 30 minutes. Luminescent 
activity becomes apparent at 600.degree. C. and is fully developed by 
1150.degree. C. The heating is done in the presence of wet nitrogen 
containing from 0 to 2% of hydrogen in order to keep the copper 
monovalent. The product of firing is then cooled rapidly to avoid 
oxidation of the copper. The cooled material may be shaped, spread on a 
substrate or preferably ground to powder form. The resulting powder when 
measured under mercury light at 245 nanometer wavelength by photocell and 
voltmeter instrumentation is equal in brightness to commercially available 
zinc silicate or zinc oxide luminescent materials. The zinc silicate 
material is produced by Sylvania Electric Products, Inc. and is designated 
P-39. The zinc oxide material is prepared by Sylvania Electric Products 
and is designated P15. 
The luminescent powder further has been found to emit light over a band 
from 380 to 570 nanometers. The luminescent cavity is retained to higher 
temperatures. Useful light is obtained to 550.degree. C. 
EXAMPLE B 
Luminescent Powders 
The addition of boron has been found to produce the brightest phosphor 
powders. 
Luminescent powder in accordance with the invention may be provided with 
the following starting ingredients. 
Place: 
______________________________________ 
Cu.sup.+ Al.sup.+++ SiO.sub.2 B.sub.2 O.sub.3 
in the form of oxides, carbonates, hydroxides or nitrates. 
______________________________________ 
By 
Mole 0.5 5.5 85.8 8.2 
By 
WT % Cu(NO.sub.2).sub.2 
Al(NO.sub.3).sub.3 . 9 H.sub.2 O 
SiO.sub.2 .times. H.sub.2 O 
H.sub.3 BO.sub.3 
.BHorizBrace. 
.BHorizBrace. 
.BHorizBrace. 
gms 0.56 8 16 2 
In: 
21cc H.sub.2 O, 
5cc methanol, 
3cc acetic acid 
______________________________________ 
And: 
ball mill for 20 minutes, dry in a shallow glass dish then fire at 
1150.degree. C. for 12 minutes in an ambient of wet nitrogen 98% gas with 
1-2% hydrogen. Thereafter, grind the material to a powder. 
The light output is comparable to that exhibited by commercial zinc 
silicate and zinc oxide when stimulated under 245 nm Hg light. The 
luminescent powder further has been found to emit light over a band from 
380-570 nanometers. 
TABLE II indicates examples of concentrations for intensity ranges. 
TABLE II 
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INTENSITY 
% Compared With ZnO 
COMPOSITION MOLE % 
Furnace Gas Furnace Gas 
Cu.sub.2 O 
Al.sub.2 O.sub.3 
SiO.sub.2 
B.sub.2 O.sub.3 
Wet Nitrogen 
Air 
______________________________________ 
.34 3 96.5 0 31 
.47 4 93.53 2 45 
.4 3 94.1 2.5 79 
.4 4 93.6 3 98 
.6 6 89.9 4.5 100 
.6 6 87.4 6 94 
.5 5.5 85.8 8.2 100 
.66 10 80.34 9 98 
.55 4 86.45 9 104 60 
.55 8 82.45 9 104 55 
.5 8 81.5 10 70 
.5 4 82.3 12 79 
.7 4 92.3 3 79 
.5 15 86.5 8 57 
.85 4 91.15 4 70 
.2 4 91.8 4 61 
0 4 92.0 4 &lt;1 
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It may be noted from TABLE II that substitution of Air for Wet Nitrogen 
results in loss of intensity illustrating the requirement that the copper 
be monovalent. 
EXAMPLE C 
Luminescent Glass 
Where a glass article is the desired form of the luminescent material there 
must be added an alkali metal oxide to adjust the viscosity to be within 
the range that permits bubbles to be eliminated in melting. Lithium sodium 
or potassium oxides may be employed. Lithium is found to be preferred 
because it produces brighter luminescent materials than sodium or 
potassium. 
Luminescent glasses in accordance with the invention may be provided with 
the following starting ingredients. 
Place: 
______________________________________ 
Cu.sup.+ 
Al.sup.+++ 
SiO.sub.2 
Li.sub.2 O 
B.sub.2 O.sub.3 
in the form of oxides, carbonates, hydroxides or carbonates. 
______________________________________ 
By 
Mole % 0.3 5.1 64.0 20.6 10.0 
______________________________________ 
Mix in: 
100 cc methanol, 12 cc NH.sub.4 OH, 16 cc acetic acid and stir for 20 
minutes, dry, and melt in a platinum crucible for 1 hour at 1300.degree. 
C. in a wet nitrogen ambient. The material may then be poured or 
fabricated into a desired shape. 
The glass is clear, luminesces over a range from 380 nanometer to 570 
nanometers with a peak at 520 nanometers with an intensity when in powder 
form that is 12% compared with zinc silicate or zinc oxide when stimulated 
with a mercury light at 245 nanometers. 
TABLE III indicates examples of concentrations for intensity ranges. 
TABLE III 
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COMPOSITION MOLE % INTENSITY 
GLASSES In Powder Form - 
Cu.sub.2 O 
Al.sub.2 O.sub.3 
SiO.sub.2 
B.sub.2 O.sub.3 
Li.sub.2 O 
% Compared With ZnO 
______________________________________ 
0.30 5.1 64.0 10 20.6 12 
0.4 5.0 75.2 7.5 11.0 9 
0.8 5.0 53.2 19.0 22.0 10 
0.42 4.2 71.1 6.7 16.6 9 
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It is also possible to provide the luminescent material of the invention by 
electrolytically altering the ingredients in existing commercially 
available glasses. The alteration can operate to remove an ingredient or 
to replace an ingredient with another. 
EXAMPLE D 
Electrolytically altered commercially available glass 
There is a heat resistant glass that contains approximately 96% SiO.sub.2, 
approximately 4% B.sub.2 O.sub.3 and in the vicinity of less than 1% of 
Na.sub.2 and of Al.sub.2 O.sub.3. The glass is commercially available 
under the "Vycor" trademark of the Corning Glass Company. It is possible 
to replace the sodium in such a glass with the Cu.sup.+ of the invention 
by electrolysis at 700.degree.-800.degree. C. This is done by providing an 
electrode system containing the ingredient to be electrolytically 
transferred. A lead borosilicate glass electrode system is provided 
containing approximately 1-5 Mole % of Cu.sub.2 O, approximately 45 Mole % 
of PbO, approximately 45% B.sub.2 O.sub.3 and approximately 5% to 
SiO.sub.2. A "Vycor" glass disk is positioned having on opposing sides 
thereof a powder layer of the lead borosilicate electrode system. 
Electrical wire connections of nichrome are held in contact with this 
electrode system and while the assembly is maintained at 730.degree. C., 
500 V d.c. is applied for about 5 to 15 minutes. 
Upon cooling, the lead borosilicate electrode system is removed with nitric 
acid. 
The resulting luminescent glass exhibits a bright blue luminescent property 
of 30% intensity compared with P-15 as measured by photocell and voltmeter 
instrumentation. 
The electrolytically altered glass has a composition of 96% SiO.sub.2, 4% 
B.sub.2 O.sub.3 and less than 1% CuO and Al.sub.2 O.sub.3. The glass 
withstands a temperature of 800.degree. C., is resistant to heat shock and 
has a low coefficient of expansion. The luminescent activity is retained 
to a 550.degree. C. temperature. 
What has been described is a luminescent material or phosphor of of 
SiO.sub.2 with approximately 0.08 to 0.85 Mole % cuprous oxide providing 
monovalent copper and from approximately 1.2 to 15 Mole % aluminum oxide, 
that luminesces in a broad blue band from about 380 to 520 nanometer 
wavelength with a maximum intensity using an addition of boron. It may be 
produced from inexpensive ingredients, is not sensitive as to precise 
ingredient compositions and presence of other ingredients and is active to 
high temperatures. Such material may be provided in powder form, glass 
form and altered commercial glass form. In powder form it is responsive to 
ultraviolet stimulation for lighting purposes, cathode ray stimulation for 
display purposes and X-ray stimulation for medical and special 
applications. In glass form it can be stimulated by photo, electron 
bombardment or by X-rays. Since the glass can be fabricated in a desired 
shape and other property imparting dopants can be included, a stimulated 
emission of radiation device such as a neodymium laser may be fabricated. 
Further, in laser type applications, the providing of the material of the 
invention by the electrolytic transfer of ingredients permits glasses that 
have a low thermal coefficient of expansion and that will support higher 
energy detuning or will prevent bursting from heat shock. The glasses of 
the invention are useful as light sources when photo stimulated by a short 
wavelength light such as a mercury vapor lamp. They may be applied as a 
coating or inactive glasses.