Magnesium barium thioaluminate and related phosphor materials

Abstract

A phosphor and a method of deposition. The phosphor comprises a composition of the formula M'aBa1-aM''2M'''4':RE, where M' is at least one element selected from magnesium and calcium, M'' is at least one element selected from aluminum, gallium and indium, M''' is at least one element selected from sulphur, selenium and tellurium, RE is at least one rare earth element, especially europium or cerium, and 0<a<1. Deposition is preferably by dual source electron beam deposition. The phosphor may be annealed. The phosphor provides a high luminosity blue emission that does not require an optical filter to achieve acceptable colour coordinates for the blue sub-pixel element for a full colour thin film or thick film electroluminescent display. The blue sub-pixel pixel performance meets the luminosity and colour temperature specifications for current generation cathode ray tube displays.

Description

[0001] The present invention relates to a high luminosity blue phosphor. In particular, the present invention relates to a blue phosphor that may be used without an optical filter to provide acceptable colour coordinates for the blue sub-pixel element of a full-colour electroluminescent display. In preferred embodiments, the electroluminescent displays employ thick film dielectric layers with a high dielectric constant. In embodiments, the phosphor is M'.sub.aBa.sub.1-aM".sub.2M'".sub.4.RE, where M' is selected from magnesium and calcium, M" is selected from aluminum, gallium and indium, M'" is selected from sulphur, selenium and tellurium, and RE is a rare earth element, especially europium and cerium.BACKGROUND TO THE INVENTION[0002] Thin film electroluminescent (TFEL) displays are known and are typically fabricated on glass substrates. Electroluminescent displays with thin film phosphors employing thick film dielectric layers fabricated on ceramic substrates, as exemplified by U....

AI Technical Summary

Problems solved by technology

For displays with high resolution, however, the shadow mask technique does not provide adequate accuracy, and photolithographic methods must be employed.

Some phosphor materials, for example strontium sulphide are susceptible to hydrolysis, and water and aprotic solvents may degrade the properties of the phosphor materials.

However, such a design modification demands increased performance from the phosphor materials used for the red and green phosphor materials, and requires the use of higher display operating voltages.

The higher operating voltages increase the power consumption of the display, decrease the reliability and increase the cost of operating the electronics of the display.

However, even with the enhanced luminosity that is obtained, thick film electroluminescent displays have not achieved the phosphor luminance and colour coordinates needed to be fully competitive with cathode ray tube (CRT) displays.

The filter substantially attenuates the luminosity of the phosphor, and it is therefore difficult to achieve adequate display luminosity.

These include cerium-activated alkaline earth thiogallate compounds, which give good blue colour coordinates, but have relatively poor luminosity and stability.

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