DE1227590B - Alkaline earth borate phosphor - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. CL:

Number:
File number:
Registration date:
Display day:

C09c

German class: 22f-15

1227 590
N 27041IV a / 22 f
July 13, 1965
October 27, 1966

The invention relates to a phosphor, the borate contains at least one of the alkaline earth metals calcium, strontium or barium, e.g. B. for use in a cathode ray tube, gas discharge lamp, in X-ray screens and in lasers.

Phosphors, electromagnetic or corpuscular, are desirable for many applications Convert radiation into light. Depending on the application, a wide range or a range with Emission restricted to one or more wavelength ranges is preferred. For practically everyone Applications, however, always want a high conversion efficiency. Is meaningful sometimes the temperature dependence of the phosphor, under which the relationship between the Temperature of the substance and the light output is understood. In certain applications, e.g. B. at High-pressure discharge lamps, the fluorescent material is attached at a point where the temperature during operation is high, e.g. 300 to 600 ° C. It is desirable that the light emission also at these high temperatures of the fluorescent screen is large.

Many known phosphors do not meet this requirement. At room temperature they often have a good light yield, but this decreases as the temperature increases, especially as the temperature increases above 100 ° C, strongly down. This also includes the well-known green luminous phosphors, the borates contain at least one of the alkaline earth metals calcium, strontium or barium, but with magnesium and bismuth are activated. Some well-known red luminescent substances that have a good temperature dependence are fluorogermanates of magnesium activated with manganese and with manganese activated, lithium-containing arsenates of magnesium.

The phosphor according to the invention is characterized in that it is terbium and optionally activated with gadolinium, the ratio between the total amount of alkaline earth oxide and the amount of boron trioxide is between 1: 3 and 4: 1 and the total amount of activator is between 0.02 and 0.4, preferably between 0.03 and 0.3 gram atoms per mole of boron trioxide.

The luminescent borates according to the invention produce green luminescence; on closer examination it appears that the green light results from strong emissions in a number of limited wavelength ranges consists. The maxima of these limited wavelength ranges are different Wavelengths; the highest emission peak is around 545 ηιμ. As a result of this downright green Color of the emitted radiation are the alkaline earth borate phosphor

Applicant:

N.V. Philips' Gloeilampenfabrieken, Eindhoven

(Netherlands)

Representative:

Dipl.-Ing. H. Auer, patent attorney,

Hamburg 1, Mönckebergstr. 7th

Named as inventor:

Willem Lambertus Wanmaker,

Johannus Godefridus Verlijsdonk, Eindhoven

(Netherlands)

Claimed priority:

Netherlands of July 16, 1964 (6 408 082)

Phosphors according to the invention less for general lighting purposes, but they can be used in Apply a mixture with luminescent substances that are radiation in other parts of the spectrum emit, so that together with the green emission of the borates according to the invention practical white light is created. The most important applications are found where there is radiation in a very limited wavelength range is just desired. As such, the following should be mentioned: the application for light pressure lamps, lasers, plant irradiators and cathode ray tubes for the reproduction of color images.

Since the phosphors according to the invention have a particularly good temperature dependency, leave Among other things, they are advantageously used in a radiation source that consists of the combination of a High pressure mercury vapor discharge lamp and

609 7O8ßS8

a bulb surrounding this lamp with luminescent material. It is well known that a relatively large part of that of a high-pressure mercury vapor discharge lamp The electrical energy supplied is converted into heat emitted by the lamp. As a result, the temperature rises a bulb surrounding the discharge lamp. Depending on the size of this Bulb and the power consumption of the discharge lamp, this temperature is usually between 300 and 600 ° C. The smaller the piston, the higher the temperature for the same power consumption. With a smaller bulb, a phosphor with a better temperature dependency is preferred used than with a larger diameter piston.

Since the phosphors according to the invention only emit green radiation, high-pressure mercury vapor discharge lamps are used with a piston on which only a borate according to the invention is provided, generally not suitable for the usual lighting purposes. However, they are particularly suitable for collotype purposes and other special applications, e.g. B. to influence chemical reactions or for plant irradiation. In these applications in particular, the lamps are often in small rooms housed so that they easily assume a high temperature. In this case there is a good temperature dependency particularly important.

Since the phosphors according to the invention also have low melting points, they are also suitable good as laser material because they can be easily shaped into the desired shape.

The use of gadolinium has the advantage that the amount of terbium needs to be less. A large amount of terbium can lead to concentration extinction. With the addition of gadolinium further higher luminous efficacies can be achieved. The color of the emitted radiation will be practically unchanged by the use of gadolinium. Apparently the gadolinium causes a transfer of excitation energy to the terbium. An added benefit of using Gadolinium is that the cost price of the phosphors is lower, since gadolinium is substantial cheaper than terbium. Preferably the amount of gadolinium is between 0.05 and 0.25 gram atoms each Moles of boron trioxide.

Some examples of various phosphors are given in Tables I to VI below. In The first column of the tables shows the alkaline earth metal oxides used and their ratio to boron trioxide specified. The tables also show the amount of activator used, the relative amount Light output at room temperature and the light output at 400 and 500 ° C as a percentage of the Light output at room temperature. The light output at room temperature was given by reference on a standard fluorescent powder made of calcium halophosphate activated with manganese and antimony in such a mixture with calcium carbonate measured that to increase the measurement accuracy the light output is reduced to 54% of the original light output of the calcium halophosphate became. For comparison, it should be mentioned that the well-known red luminescent magnesium arsenate, the one with manganese is activated, has a luminous efficacy of 87% compared to this standard. All measurements were made carried out upon excitation of the luminescent borates with a radiation of a wavelength of 253.7 ηιμ.

Table I relationship
CaO: B ₂ O ₃ lot lot Relative Light output at Terbium
in atoms
per mole linium
in atoms light in the 500 ⁰ C B ₂ O ₃ per mole
B ₂ O ₃ yield
at
room Light output
at room
temperature 59 3: 1 tempe at 54 3: 1 0.06 . . rature 400 ⁰ C 63 3: 1 0.12 0.12 42 64 90 3: 1 0.06 0.06 64 106 83 3: 1 0.06 0.12 76 102 0.06 0.24 78 96 68 93

Table II relationship
SrO: B ₂ O ₀ 1 lot lot Relative Light output at 1 Terbium
in atoms
per mole VJdUU "
linium
in atoms light in the 500 ° C 1 B ₂ O ₃ JC IYHJl
BoO, yield
at
room Light output
at room
temperature 17th 3 1 tempe at 22nd 0.12 _ rature 400 ° C 30th 3 0.12 0.12 141 64 125 1 0.06 0.06 52 75 0.12 - 100 68 76 121

ι lot Table III Relative Light output at 1 Terbium
in atoms
per mole light in the 500 ° C 2 B ₂ O ₃ Jvlenge yield
at
room Light output
at room
temperature 126 linium
in atoms
per mole tempe at 157 0.06 2 3 rature 400 ⁰ C 126 0.06 . . 57 120 relationship
BaO: B ₂ O ₃ 0.06 0.12 26th 155 - 34 116 1 1 1

Table IV

relationship

(V ₂ CaO +

V ₂ SrO):

B ₂ O ₃

: 1

lot

Terbium

in atoms

per mole

B ₂ O ₃

0.06

lot
Gadolinium
in atoms
per mole
B ₂ O ₃

Relative
Light output

at

Room temperature
rature

0.12

Table V

Luminous efficiency in% of

Light output at room temperature

at 400 ^° C

85

relationship

(V ₂ BaO +

V ₂ SrO):

B ₂ O ₃

: 1
: 1

lot

Terbium

in atoms

per mole

B ₂ O ₃

0.06
0.06

lot
Gadolinium
in atoms
per mole
B ₂ O ₃

0.12
0.12

Relative
Light output

at

Room temperature
rature

83 54

Light output

in% of the light output at room temperature

at 400 ^° C

71 116

Table VI relationship lot lot Relative Light output at (V ₃ CaO + Terbium UaAlU-
linium light in the 500 ° C V ₃ BaO + in atoms in atoms yield Light output 121 V ₃ SrO): per mole JC IVX (Ji
B "O. at at room B ₂ O ₃ B ₂ O ₃ ■ ^L »2 ^v - ' ₃ room temperature tempe at 1: 1 0.06 rature 400 ° C 60 117

10

The tables show that certain phosphors have a higher luminous efficacy at higher temperatures than at room temperature. From the tables it can also be seen that the light output of certain phosphors decreases relatively sharply at higher temperatures; there some Phosphors have a very high relative luminous efficacy at room temperature, this needs a strong one Relapse not to be bothersome. The product of the light fallback and the relative luminous efficacy at Room temperature is decisive for every application. Because the light output at room temperature can often be increased by an improved manufacturing process, the possibility is not excluded that the borates according to the invention can provide a much higher light yield than the values given in the tables.

For example, below is a method for preparing a substance according to the invention for calcium borate, which is activated with terbium, which is indicated in the first line of Table I.

example

A mixture of 5.70 gmol CaCO ₃ , 2.50 gmol H ₃ BO ₃ and 0.23 gmol TbP _{7 is} prepared. This mixture is heated to a temperature of 600 to 700 ° C. in a crucible made of ceramic material until the water has been removed from the H ₃ BO ₃ . This is followed by further heating in air for 2 hours, during which the phosphor is formed. In certain cases it is desirable to finely grind the product obtained after sintering and to reheat it in air for 2 hours. If necessary, this treatment is repeated. The heating is preferably to a temperature just below the melting point of the borates.

The borates of the other alkaline earth metals or mixtures thereof with those given in the tables Compositions can be prepared in a corresponding manner. The quantities in grams can be calculate from the molar ratios in the tables.

Claims (2)

Patent claims: 1. Phosphor, the borate of at least one of the alkaline earth metals calcium, strontium or Contains barium, characterized in that it is combined with terbium and optionally activated with gadolinium, the ratio between the total amount of alkaline earth oxide and the amount of boron trioxide is between 1: 3 and 4: 1 and the total amount of activator is between 0.02 and 0.4, preferably between 0.03 and 0.3 gram atoms per mole of boron trioxide. 2. phosphor according to claim 1, characterized in that the amount of gadolinium between 0.05 and 0.25 gram atoms per mole of boron trioxide Hegt. Considered publications:
U.S. Patent No. 2,920,046. 609 708B58 10. 66 © Bundesdruckerei Berlin