NL8003443A - ULTRAVIOLET EMITTING ALUMINATE PHOSPHORUS AND TANNING FLUORESCENT LAMPS USING THEREOF. - Google Patents

Description

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Ultraviolet-emitting aluminate phosphor and fluorescent brown fluorescent lamps using them.

The invention relates to aluminate phosphors which emit in the ultraviolet region of the electromagnetic spectrum, and more particularly to such phosphors containing cerium and alkaline earth metals, and to fluorescent lamps incorporating such phosphors.

British Patent 1,452,083 describes an ultraviolet-emitting fluorescent lamp phosphor having the composition CeMgAljjOjg and the magnetoplumbite structure. British patent 1,194,014 describes a phosphor with the composition CeAlj 1018 and the magnetoplumbite structure. although

Having CaAljjOjg and CeMgAljjOjg analogous crystal structures, the incorporation of magnesium shifts the ultraviolet excited emission peak from about 460 nanometers in CeAljjOjg to about 370 nanometers in CéMgAlj.O.Q. These phosphors are self-activated by the Ce ion.

R.W. In the study of aluminates with the magnetoplumbite or B-alumina structure, Wolfe found that by partially replacing cerium with barium, strontium or calcium, the temperature dependence of the emission of the cerium magnesium aluminates could be greatly improved.

Therefore, the alkaline earth metal substituted cerium magnesium aluminates are more effective than the cerium magnesium aluminates in highly charged fluorescent lamps operating at wall temperatures within the range of 200-400 ° C. Such ceriuramagnesium alumina substituted by 800 34 43 2 alkaline earth metals are described in U.S. Pat. No. 4,088,922.

U.S. Patent 4,153,572 describes ultraviolet-emitting yttrium-substituted magnesium aluminate phosphors with optimal emissions for the treatment of psoriasis.

3+

It is known that certain ions, such as Fe and 4+

Ti, when incorporated into the soda-lime lamp glass for fluorescent lamps, effect the absorption of harmful solar radiation emitted in the UVB region, allowing the use of certain phosphors in such lamps, which would otherwise be rejected. because of their undesirably high energy yield in this area. However, such energy absorbing materials in the glass also tend to absorb energy from the UVA region, thereby diminishing the overall lamp-browning ability.

In accordance with the invention, it has been found that certain alkaline earth metal substituted cerium magnesium aluminate phosphors exhibit optimal energy yield within the UVA range and minimal energy yield within the UVB range, making these phosphors useful in fluorescent lamps for tanning applications. Such phosphors can be represented by the molecular formula C \ Ry (Mgl-BOD z ^ 1! L ° 16.5 + 3/2 (x + y) + z, "" "25 R = Ba, Sr or Ca, x = 0.80-0.95, y = 0.02-0.15, z = 0.80-1.0 and B = 0-0.5.

Lamps containing these phosphors show an improved energy yield in the UVA region and a reduced energy yield in the UVB region compared to lamps containing the known phosphorus products.

Currently, the focus is on the development of new phosphors, which exhibit maximum energy yield in the sun-tanning region of the electromagnetic spectrum, 800 34 43 ♦ 3, i.e. 315-400 nanometers, referred to as the UVA region, in in contrast to energy yields in the sunburn area below 315 nanometers, the so-called UVB area. A commercially available phosphor, currently used for 5 sun-tanning applications, is BaSi ^ O ^ iPb. However, phosphors with a higher yield in the UVA region and better lamp maintenance are desirable.

For a better understanding of the invention and for other purposes, advantages and possibilities thereof, reference is made to the description below.

The phosphors of the invention can be easily prepared by mixing the required amounts of the suitable starting materials and heating in a reducing atmosphere at an elevated temperature for a moderate period of time. The time, temperature and the reducing atmosphere are not limited, but a mixture of nitrogen and hydrogen or hydrogen is preferred, a temperature range of 1450-1750 ° C is also preferred, as well as a time period of 1- 5 hours. The special starting materials are not bound by sharp limits, but they must of course be chosen such that they give the required product during heating. Compounds which decompose to oxides upon heating, such as hydroxides, carbonates, sulfates, nitrates, etc., are acceptable. Preferred starting materials are AKOH2, 25 MgO, BaO or BaF2, CeO2 or CeF2. The presently particularly preferred product has approximately the molecular formula

Ce0,90 Ba0,05 Mgl, 0 A1ll ° 18,925 *

The invention is further illustrated but not limited by the following example.

Example

Preparation of Ce ^ BaM5 Mg] 2.330 g CeO2, 0.632 g MgO and 0.135 g BaF2 are mixed with 13.470 g AlCOH) The mixture is heated at 1550 ° C for 4 hours in a dissociated ammonia atmosphere (75 vol. % N2, 25 vol.% H2). The resulting phosphor having the above molecular 34 800 4 composition is essentially in the hexagonal magnetoplumbite phase and when incorporated into a standard 40 watt fluorescent lamp it shows an emission intensity peak at about 349 nanometers. The energy yield of the lamp after an operating time of 100 hours is as follows:

Watts yield less than 315 nm (UVB) -0.15 Watts yield between 315 and 400 nm (UVA) -11.20 100 hours hold (%) - 97.9.

The maintenance is defined as the ratio of the energy yield in the UVA region of the lamp divided by the initial energy yield of the lamp. For example, 100 hours of enforcement (%) *

Energy yield after 100 hours jqq Energy yield after 0 hours

Table A shows the lamp values for this phosphorus and for other phosphors according to the invention in comparison with known phosphorus products. All lamp values apply to low pressure mercury vapor (LPMV) lamps, the spectral transmittance of the lamp glass decreases from about 90% at about 350 nanometers to nearly 0 at about 270 nanometers.

Thus, it will be understood that a small amount of the UVA energy and a significant portion of the UVB energy of the phosphor is absorbed by the lamp glass and that the values indicated are for the lamps and not for the phosphors.

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The following is noted in connection with the values indicated in the table. First, the phosphors prepared according to the method of the invention exhibit an energy yield in the UVA region after an operating time of 100 hours ranging from comparable to superior to the high temperature phosphors of the United States U.S. Patent 4,088,922; however, the high temperature phosphors, which exhibit a comparable UVA energy yield, also exhibit an undesirably high energy yield in the UVB (sunburn) region. Second, the phosphors of the invention exhibit superior energy yield in the UVA region as compared to the remaining investigated known phosphors, including the yttrium-substituted cerium magnesium aluminate of U.S. Patent 4,153,572, the cerium magnesium aluminate of British Patent 1,452,083 and the commercially available standard lead-activated barium silicate phosphorus. Third, the phosphors of the present invention exhibit superior lamp retention after an operating time of 100 hours compared to the cerium magnesium aluminate of British Patent Specification 1,452,083 and the commercially available standard lead-activated barium silicate phosphorus.

Although preferred embodiments of the invention have been described above, it will be apparent to those skilled in the art that various changes and modifications are possible without departing from the scope of the invention.

Technical application.

The alkaline earth metal-substituted cerium magnesium aluminate phosphors of the present invention exhibit optimal energy yield in the UVA (sun tanning) region of the electromagnetic spectrum and minimal energy yield in the UVB (sunburn) region of the electromagnetic spectrum and are therefore useful in fluorescent mode! e-lamps for artificial sun-tanning applications.

35 800 34 43

Claims (4)

1. An alkaline earth metal-substituted cerium magnesium aluminate phosphorus having a hexagonal magneto-plumbite structure and having the molecular formula x = 0.80-0.95 y = 0.02-0.15, 2 = 0.80-1, 0, B = 0-0.5, 10 and wherein R is selected from Ba, Sr and Ca. Phosphorus according to claim 1, characterized in that it has the molecular formula of approximately Ce0.90Ba0.05Mgl, 0A111 ° 18.925. Fluorescent lamp containing a phosphor as defined in claims 1 or 2. 4. Phosphors and fluorescent lamps as described in the description and / or the example. 20 80034 43