DE2261424A1 - LUMINAIRE - Google Patents

Description

PHN.6077. .ever / bos s / evh

DIpL-In ₀ -H ^ RST AUER

Applicant: Κ. V.? I; .Li.-y & LGi.LÄiiPtKFABHIEKEII

File: PHF- 6077
Registration from 14 "'T) 6Z" 1? 72

Luminescent screen

The invention relates to a luminescent screen which is activated with a luminescent, bivalent manganese Gallat is provided. The invention also relates to low-pressure mercury vapor discharge lamps and cathode ray tubes provided with such a phosphor screen, and that luminescent gallate itself.

A luminescent magnesium gallate activated with divalent manganese is known from US Pat. No. 3,407,325. The basic lattice of this phosphor can be represented by the formula MgGa ₂ (V and has a spinel crystal structure. When excited with short-wave ultraviolet radiation or with electrons, the known gallate has an intense green emission with a maximum in the spectrum at

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a wavelength of about 510 nm. The most important area of application of this substance are mercury vapor discharge lamps, lamps intended in particular for blueprint apparatuses. In German patent specification 1 302 782 there is a

Lura-escent magnesium gallate activated with bivalent manganese with a spinel structure in which the gallium is partially replaced by aluminum. This substitution has a beneficial influence on the properties of the Luminescent substance, namely the temperature dependence of the Luminous flux when excited with ultraviolet radiation.

Although the known gallates mentioned are in the Proven in practice, many studies aim to create new phosphors with which higher luminous fluxes can be achieved in the wavelength range around 500 nm.

The luminescent screen according to the invention contains a luminescent gallate activated with divalent manganese and is characterized in that the gallate has a magnetopium bit crystal structure and of the formula

corresponds to where B is at least one of the elements Al and Sc and where C is at least one substance from the group consisting of Mg, Zn and Li _n e-Ga-. _R is and the following conditions are satisfied

0 ^: χ + ρ ^ i _f o

0 ^ y + ρ ^ η » 0 ^ ζ + ρ <1.0

0 <: r ^ 1.0

0.0005 ^ p ^: 0.10

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The luminescent screen according to the invention contains a strontium gallate activated with bivalent manganese, the basic lattice of which can be represented _{by the formula SrGa 13} O _19. This basic lattice has a magnetoplumbite crystal structure. Various substitutions can be made in this strontium gallate, but the magnetoplumbite structure is always retained. First and foremost, some of the strontium is replaced by the manganese activator, although it is assumed that manganese and strontium do not occupy the same place in the crystal lattice. Apart from the part replaced by the activator, the strontium can be completely or partially replaced by barium and / or calcium. If comparatively large amounts of strontium are replaced by calcium (for example at values of y which are greater than 0.25), 30 it is generally desirable to use a proportionally large substitution of gallium by aluminum, otherwise the magnetoplumbite phase will not occur occurs »It is possible, for example, _{to produce the compound CaGa ^ -AIgO 19} with a magnetoplumbite structure. It is also possible to completely or partially replace strontium with lanthanum. When replacing a certain amount of the divalent strontium with the trivalent lanthanum, it is desirable to replace an almost equal amount of the trivalent gallium with a divalent metal in order to achieve charge balance. Magnesium and zinc and also the combination of equiatomic amounts of lithium and gallium (Li _{n K} ^Ga r »κ) come ^into consideration as divalent metals. It is also possible to use the gallium in the gallate according to the invention

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to be partially replaced by aluminum and / or scandium « The aluminum and / or scandium content q must not be greater than 11, otherwise the values of q, that are larger than 11, substances with a brightness that is too low for practical applications can be obtained

The luminescent gallates according to the invention can be excited well with ultraviolet radiation, in particular with short-wave ultraviolet radiation. The absorption of ultraviolet radiation with a wavelength of 2 $ k nm is * tw4? 0-! F> $ ^. Furthermore, the gallates according to the invention can be excited well with electrons. The gallates have a very intense emission in a narrow band with a maximum in the spectrum at 500-515 nm. The half-width of the emission band has a value between about 20 and 35 nm.

High luminous fluxes are achieved with the luminescent gallates according to the invention, in which ζ is almost equal to r. Then, namely, an almost complete charge equalization takes place. Replacing strontium with calcium does not offer any additional advantages, in particular with regard to the luminous flux of the luminescent gallates. This also applies to the replacement of strontium by BarIuH, if the barlum content is χ greater than 0.50. Therefore, according to the invention, luminescent screens are preferred which contain a gallate for which ζ is almost equal to r, for which 0 £ χέ0.50 and γ m 0.

A particularly advantageous embodiment of the fluorescent screen according to the invention contains a luminescent one Gallat, in which the value of the lanthanum content ζ so chosen

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is that the condition 0.2 ^. ζ ί- ρ ^ 1 is sufficient. These gallates have a very favorable temperature dependence of the luminous flux. The maximum quantum efficiency of these substances is achieved at temperatures between room temperature and about 180 ^° C. This property makes such gallates according to the invention for use in highly stressed low-pressure mercury vapor discharge lamps for blueprint

t

machines particularly suitable »The current density in the lamps can be increased even further than was previously the case for such lamps heavily loaded lamps was common, so that a very high luminous flux emitted by the lamps is possible. that the highest efficiency of the discharge in a normal low-pressure coke silver vapor discharge lamp at one temperature the lamp wall of about 40 ° C is reached. The above Said property of the lanthanum-containing gallates according to the invention can therefore only be used advantageously if when the optimum operating temperature of the low-pressure mercury vapor discharge lamp is increased. Many measures are known to achieve the latter.

As a divalent element C, which is part of the gallium replaced in a luminescent GaIlat according to the invention, Magnesium is preferably used to balance the charges when strontium is substituted by lanthanum. Then the highest luminous fluxes are achieved.

Aluminum is preferably chosen as element B, since this element is cheaper than scandium.

Experiments have shown that a particular embodiment of the fluorescent screen according to the invention is obtained when

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In strontium gallate (in which the above-mentioned Substitutions are made) up to a maximum of 5 atoms of gallium is replaced by lithium, with no charge equalization is made. From X-ray diffraction analyzes it can be seen that this gallate also has a magnetoplumbite structure to have"

When excited with ultraviolet radiation, the highest values of the luminous flux are those according to the invention luminescent gallates that are not barren only contain little aluminum and / or scandium and for which the manganese content ρ is between 0.002 and 0.01. When applied In a low-pressure mercury vapor discharge lamp, a fluorescent screen according to the invention is therefore preferred for the 0 <. q <1, 5 and 0.002 << ρ $ 0.01 applies.

Apart from the already mentioned application in low-pressure mercury vapor discharge lamps, the luminescent gallates according to the invention can also be used in cathode ray tubes, since they have a high degree of energy conversion efficiency when excited by electrons. Here gallate are preferred in which the AIuminium- and / or scandium q between the values 0 and 6, and the manganese content ρ between the limits 0.002 to 0.05. Such an invention & sse cathode ray tube has the advantage that the emitted radiation has a very saturated green color, which is desirable for applications vl tie.

The invention is explained in more detail using a production example, a few tables and a figure.

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In the figure, the spectral energy distribution of the emitted radiation of a gallate according to the invention is shown in a graph. Manufacturing example

A mixture is produced

0.685 g of SrCO ₃

5.623 g Ga ₂ ° 3

0.0023g MnC0 "

This mixture is heated in an oven in air at a temperature of 1400 ° C. three times for 2 hours each time. After each heating, the reaction product is distributed and, if necessary, sieved. The product obtained in this way is then heated for one hour at a temperature of 1300 ^° C. in a slightly reducing atmosphere * This atmosphere can be achieved by passing a stream of nitrogen containing a few percent hydrogen into the furnace. After cooling after the last heating, the luminescent gallate obtained is ground and, if necessary, sieved, and it is then ready for brewing. The luminescent gallate complies with the formula

^{from Ho>} ntgendiffraktions-

analyzes emerges, Magn © toplumbit-Kr ± itAi, lAt * uktikr; r- With -excitation with short-wave ultraviolet radiation (essentially 25 ^ nm) the quantum efficiency is about 65 $ The maximum of the spectral distribution of the emitted radiation is 502 nm and the half-width of the spectral Distribution is about 23 nm. When excited with ultraviolet radiation, the relative luminous flux and the peak value are

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the spectral distribution of this gallate according to the invention 11 k or 140. An activated with bivalent manganese Magnesiumgallats both set equal to 100 ■ *> dug, in which the gallium is partly replaced by aluminum, corresponding to the formula Mg (Ga _Q q A1 _q -i J ₂ ⁰ - It is current as a scale of the light and the peak value Ji * M * ¹ (spinel crystal structure; see German patent specification 1 302 782). The maximum of the spectral distribution of this comparison substance is 504 nm and the half-width is 28 nm.

In the same way as in the above Production Example described, a large number of gallates were made according to the invention. As starting materials you can use the oxides of the desired metals or compounds which, when heated, form these oxides. It is possible at small deviations in the production of the gallates according to the invention from the stoichiometry to allow. It is known that a small excess of one or more of the metals can die Promote educational response. Those used in excess Elements remain in addition to the luminescent phase and generally do not interfere. The temperature at which the If heating can occur, one can choose between wide limits, and in general it depends on the reactivity of the starting mixture. In general, this reactivity is also decisive for the number of heatings. One Heating in a reducing atmosphere is necessary in most cases to turn the manganese activator into divalent To move state.

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In the following Table I measurements on a number of strontium gallates according to the invention with different manganese contents ρ are listed. The spinel mentioned in the preparation example was used as a comparison substance in these measurements. The influence of the activator content can be derived from the measurements of the light flux »LO and the peak value of the spectral distribution PH when excited with ultraviolet radiation. The last column also shows the efficiency of the energy conversion / Υ] with electron excitation (20 kV).

TABLE I (Sr ₁ Mn

P. LO PH in $> 0.001 87 106 - Q, 0O2 111 135 4th 0.004 114 i4o 4th 0.005 112 138 5 0.020 85 105 7th

Table II below shows the results of measurements of the luminous flux LO and the peak value PH some gallates in which various substitutions are made are listed. In these measurements the In the preparation example mentioned reference substance used.

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TABLE II

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Ex. Basic grid P. LO PH 1 ^Sr O, 7 ^Ba O, 3 ^Ga 12 ° 19 0.003 108 130 2 ^{Sr o.5 Ba o.5 Ga} i2 ° i9 0.003 104 127 3 ^Sr O, 3 ^Ba O _t 7 ^Ga 12 ° 19 0.003 98 115 4th ^Sr O _f 9 ^Ca O, 1 ^Ga 12 ° 19 0.003 93 110 5 ^Sr o _f 25 ^La o, 75 ^Ga ii, 25 ^Me o, 75 ° 19 0.007 107 103 6th ^Sr o _t 25 ^La o _f 75 ^Ga ii »25 ^Me o _f 75 ^O 19 0.010 90 84 7th ^{SrGa 10.8 Al} 1.2 ° 19 o, oo4 92 106 8th ^SrGa 10.8 ^Sc 1.2 ° 19 o, oo4 92 102 9 *) ^SrGa 11.9 ^Li O, 1 ° 18.9 0.004 108 130 10 *) ^SrGa 11.7 ^Ll O, 3 ° i8,7 0.004 95 113

In these gallates a substitution of gallium was made Lithium carried out without doing a charge equalization was made.

The lanthanum-containing gallates according to the invention have, as already mentioned, a very favorable temperature dependence of the luminous flux. This is illustrated in Table III below, which shows the results of measurements shows a number of examples of lanthanum-containing gallates. The table leads next to the luminous flare LO and the peak value PH, measured at room temperature, furthermore the maximum peak value PH and the temperature T,

^r max max

at which this maximum peak value is reached.

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TABLE III

Example, Basic grid _ — __—
P.
LO PH PH
Max T
Max
in ° C 11 ^Sr o.75 ^La o, 25 ^Ga 1ι, 75 ^Me o, 25 ° 19 0.004 108 119 128 60 12th ^Sr o.5O ^La o, 5o ^Ga ii, 5O ^Mg o, 5Q ^o i9 0.004 101 90 137 88 13th ^Sr o, 25 ^La 0, 75 ^Ga 1 1, 25 ^Mg 0.2 5 1 9 ° o ₉ oo4 ". 94 72 144 93 14th LaGa ₁₁ MgO ₁₉ 0.003 63 48 100 90 15th ^Sr 0.8 ^La 0.2 ^Ga 11.9 ^Li 0.1 ° 19 o, oo4 106 107 120 67 16 Sr _{Of | for} La _{o> 6} Ga ₁₁₇ Li _{o> 3} O _1Q 0.004 81 68 106 90 17th ^Ba o, 25 ^La o, 75 ^Ga ii _i 25 ^Mg O.75 ^O i9 0.004 100 81 98 75 18th ^Sr 0.25 ^La 0.75 ^Ga i 0.05 ^Mg 0.75 ^Al 1.2 ⁰ ₁₉ o, oo4 67 65 81 150 19th ^{Sr o.25 La} o.75 ^Ga i 0.05 ^Zn 0.75 ^A1 1.2 ° ", ₉ o, oo4 65 48 100 147 20th ^Sr o, 25 ^La o, 75 ^Ga i 1.25 ^Zn o, 75 ° 19 0.004 lh 51 77 110

The strontium gallate activated with manganese according to the invention and also the aluminum-containing gallates have upon stimulation with electrons a höh® brightness. This is illustrated in Table IV, which shows the results of Measurements of the brightness H of a number of Gallaten lists. The excitation takes place by electrons with an energy of 5 KeV in these measurements a green luminescent zinc oxide is used, the brightness of which is set equal to 100.

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TABLE IV

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Ex. Basic grid P. H 21 SrGa ₁₂ O ₁₉ 0.004 22nd SrGa ₁₂ O ₁₉ 0.010 133 23 SrGa ₁₂ O ₁₉ 0.020 Ui Zk ^SrGa 10 _f 8 ^Al 1 _t 2 ° 19 0.003 116 25th ^SrGa 9.6 ^Al 2A ° 19 0.007 129 26th ^SrGa 8.4 ^Al 3.6 ° 19 0.007 113 27 ^SrGa 8.4 ^Al 3.6 ° 19 0.010 116 28 ^SrGa 7.2 ^Al lf _f 8 ° 19 0.007 101 29 SrGa ₈ Al ₄ O ₁₉ 0.010 139 30th BaGaAl ₁₁ O ₁₉ 0.050 86 31 CaGaAl ₁₁ O ₁₉ 0.050 41 32 CaGa ₆ Al ₆ O ₁₉ 0.010 123 33 ^SrGa 11.9 ^Li O, 1 ° 18.9 0.004 103

In the figure is the spectral energy distribution

of the gallate according to the formula Sr

₀ oo4 ^Ga 12 ° 19 *

which is achieved with a method according to the above production example, reproduced in a graphic representation. The wavelength Λ is on the horizontal axis. i _{n au nm} and the vertical axis f the radiation energy E per constant applied Wellenllngenintervall in arbitrary units. The excitation is carried out by short-wave ultraviolet radiation. For comparison, the dashed curve shows the spectral energy distribution of the well-known gallate with spinel structure (MgGa _{1 a} Al _n -0 iMn)

1.0 O, 2 * l

specified.

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Claims (1)

- 13 - PHN.6077. 226H24 PATENT CLAIMS t 1 · Fluorescent screen with a luminescent, with bivalent manganese activated GaIlat is provided, thereby characterized in that the gallate has magnetoplumbite crystal structure and the formula (^ ixyzp ^ V ^ V [ ^Ga 12-q-rVrl corresponds, in which B represents at least one of the elements Al and Sc and in which C is at least one substance from the group Mg, Zn and Li _{n K} 6a « _R , and where the the following conditions are met ι ο ^ y + ρ 41.0 0 ^ ζ + p ^ 1.0 0 t £ q ^ 11 0 ^ r ■ 4 1.0 0.0005 ^ P 4 0.10 2. Luminous screen according to claim 1, characterized in that that ζ is almost equal to r, and that 0 ^ x ^ .0.50 and y » 3 »luminescent screen according to claim 1 or 2, characterized in that 0.2 ^ z + P4 1. k. Luminescent screen according to claim 1, 2 or 3, characterized in that C is magnesium 5. Luminescent screen according to claim 1, 2, 3 or k _t, characterized in that B is aluminum 6. luminescent screen according to claim 1, 2, 3, h or 5, characterized in that up to a maximum of 5 atom # des in the gallate 309828/0725 - 1> - PHN.6077. 226U24 Gallium is replaced by lithium, with no charge equalization has been made. 7 · Luminescent screen according to one or more of the preceding claims, characterized in that O <q £ 1 | 5 and 0.002 £ ρ ^ O.01. 8. Low pressure mercury vapor discharge lamp with one Luminescent screen according to one or more of the preceding claims 9 * luminescent screen according to claim 1, 2, 3, k _t 5 or 6 »characterized in that · $ 0 q £ 6 and 0.002 ^ ρ £ .0.05. 10. Cathode ray tube with a fluorescent screen according to claim 1, 2, 3, k _t 51 6 or 9. 11. Luminescent activated with divalent manganese Gallate, which has magnetoplumbite crystal structure and which formula (Sr ₁ -XV- ^ _x Ca _x La ₁ Mn ₁ ,) L ^ -q-rV r) ⁰ I ₉ * where B represents at least one of the elements Al and Sc and where C is at least one substance from the group Mg, Zn and Li _ng 6a _ft _ and where the following conditions are satisfied j O ^ χ + ρζ.1, 0 11 0.0005 - C 0.10. 309828/0725