Blue or bluish green aluminum silicate luminous storage material and its manufacturing method

#The present invention relates to a blue or bluish green aluminum silicate luminous storage material and its manufacturing method. Specifically, the present invention relates to an aluminum silicate luminous storage material. The material comprises an emitter that emits a blue or bluish green light indoors, outdoors, underwater, or in other dark places when excited by electron beams, ultraviolet rays, and/or visible radiation. The material also has a long-lasting blue afterglow after excitation is stopped. The luminous storage material is mainly activated by Eu.sup.2+, is thermally stable, and exhibits excellent chemical stability in an oxidizing or reducing atmosphere. The present invention also relates to a manufacturing method for this material.

#Phosphor emits light when excited by certain external stimuli such as grain energy, electrons, or light. A persistent luminous material that can maintain emission after excitation is stopped is called a luminous storage material. Due to the needs for various types of displays and advanced functions for dark places, there is a demand for luminous storage that can handle multiple colors and maintain emissions over a long period of time. In addition, greater weather resistance is also now needed.

#In conventional luminous storage material, a very small number of materials are available, the number of colors of light and afterglow are limited, the afterglow time is short, and weather resistance is insufficient. Inorganic materials include sulfide or oxyacid-salt (such as strontiumaluminate) luminous material due to their storage capability. Sulfide phosphors include, for example, (Ca, Sr) S:Bi.sup.3+ phosphors emitting a blue light, ZnS:Cu.sup.2+ phosphors emitting a yellowish green light; and (Zn, Cd) S:Cu phosphors emitting a red light. Oxyacid salt phosphors include, for example, alkali earth metal aluminate which has been activated by europium and which is expressed by the chemical formula MAl.sub.2 O.sub.4. In this case, M is alkali earth metal of magnesium, calcium, or strontium. In particular, an SrAl.sub.2 O.sub.4 :Eu.sup.2+ phosphor having a stuffed tridymite structure and reported in Journal of Electrochemical Society, Vol. 118, pp. 930 (1971) is known to have relatively high persistence. These phosphors, however, are not good enough luminous storage or have poor weather resistance.

#FIG. 1 is a diagram showing a powder X-ray diffraction chart of a luminous storage material having a chemical composition according to Embodiment 1.

#FIG. 2 is a diagram showing a powder X-ray diffraction chart of SrAl.sub.2 O.sub.4 for comparison.

#FIG. 3 is a diagram showing as (a) to (f) emission spectra (excitation: 360 nm) of a luminous storage material according to Embodiments 1 to 6 of this invention.

#This invention is described below in more detail by showing embodiments and comparative examples. Theoretically, the composition formula is as shown in Formula (1) or (2), but is adjusted to the following formula according to the embodiments. In the composition,

#(M.sub.l-n-m M*.sub.n Eu.sub.m)(Al.sub.1-x Si.sub.x).sub.2 O.sub.4

#or