Compositions – Inorganic luminescent compositions – Compositions containing halogen; e.g. – halides and oxyhalides
Patent
1996-11-26
1998-06-23
Bonner, Melissa
Compositions
Inorganic luminescent compositions
Compositions containing halogen; e.g., halides and oxyhalides
2523014F, C09K 1180, C09K 1164
Patent
active
057701113
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a phosphor or fluorescent substance having afterglow characteristics and adapted for example for use in luminous paint and the like.
BACKGROUND ART
In the past, there has been the occurrence of a so-called "afterglow phenomenon" as a characteristic of a phosphor or fluorescent substance. For instance, in the case of zinc silicate (Zn.SiO.sub.4 :Mn.sup.20+)-type phospor, the occurrence of such "afterglow phenomenon" will be caused depending on the selection of its composition, firing conditions, etc. Also, "afterglow phenomenon" occurs not only in the case of zinc silicate (ZnSiO.sub.4 :Eu.sup.2+) type but also in the case of strontium aluminate type SAE (4SrO.7Al.sub.2 O.sub.3 :Eu.sup.2+), etc.
However, the duration times of their afterglow are merely on the order of several seconds at the most, and also it is recognized that as regards the characteristics of the phospor, generally the possession of afterglow characteristics is not desirable and rather tends to deteriorate the fluorescence characteristics.
Then, in addition to the above-mentioned SAE (490 nm), suchsubstances as 2SrO.3Al.sub.2 O.sub.3 (SAL: 460 nm) are also known as the so-called strontium aluminate phosphor. It has been reported that not only these phosphors are different in the emission peaking but also they are different compounds in terms of the crystal structure (B. Smets, J. Rutten, G. Hocks and J. Verlijsdonk; J. Electrochem. Soc. 136, 2119, 1989).
However, while the investigations have been vigorously conducted on the strontium aluminates having emission wavelengths of "blue" or "blue green" as light emitting phosphors for lamps, such investigations as aimed toward improving the afterglow phenomenon as in the case of the so-called "luminous paints" have been practically unknown.
Recently, phosphors have been proposed which have long afterglow characteristics by virtue of the addition of dysprosium (Dy) or the like (JP-A-7-11250, EP-A-0 622 440, U.S. Pat. No. 5,424,006). Such phosphor is represented in terms of a compound MAl.sub.2 O.sub.4, and more particularly it is a compound in the form of a mother crystal in which M represents at least one metal element selected from the group consisting of calcium, strontium and barium and which contains europium (Eu) as an activator in an amount of not less than 0.001% and not greater than 10% in terms of mol % relative to the metal element represented by M and also, as a co-activator, at least one element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, samarium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, manganese, tin and bismuth in an amount of not less than 0.001% and not greater than 10% in terms of mol % relative to the metal element represented by M. It is to be noted that the afterglow of this proposed phosphor is the emission of light having a greenish color tone.
DISCLOSURE OF INVENTION
The inventors have made earnest efforts in the production of a phosphor having more intense and longer afterglow characteristics by utilizing one of the previously mentioned compounds MAl.sub.2 O.sub.4, more particularly a phosphor (SrO.Al.sub.2 O.sub.3 :Eu.sup.2+ Dy.sup.2+) in which strontium and aluminate are added in the same mol with each other as a reference sample.
As a result, the inventors have succeeded in the production of phosphors having more intense and longer afterglow characteristics by utilizing as matrices the phosphor SrO.yAl.sub.2 O.sub.3 :Eu.sup.2+ containing strontium and aluminate in varying proportions. In addition, the production of a phosphor having more intense and longer afterglow characteristics has been succeeded by adding a trace amount of a novel additive element to the previously mentioned compound MAl.sub.2 O.sub.4.
In other words, it is the primary object of the present invention to provide a phosphor having more intense and longer afterglow characteristics, and more particularly, it is another object of the present invention to provide a phos
REFERENCES:
patent: 5424006 (1995-06-01), Murayama et al.
patent: 5424066 (1995-06-01), Murayama et al.
B. Smets et al, Two New Blue-Emitting Phosphors, J. Electrochem. Soc., vol. 136, No. 7, pp. 2119-2123, Jul. 1989.
Goto Teruo
Moriyama Hirofumi
Moriyama Tomofumi
Bonner Melissa
Kabushiki Kaisha Tokyo Kagaku Kenkyusho
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