Compositions – Inorganic luminescent compositions – Compositions containing halogen; e.g. – halides and oxyhalides
Reexamination Certificate
2000-10-03
2003-05-20
Koslow, C. Melissa (Department: 1755)
Compositions
Inorganic luminescent compositions
Compositions containing halogen; e.g., halides and oxyhalides
Reexamination Certificate
active
06565771
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present relates to a method for producing an aluminate-based phosphor. More particularly, the present invention relates to a method for producing an aluminate-based phosphor having extremely uniform cation composition, used for various displays of emitting type such as a plasma display panel (PDP) and the like.
Further, the present invention relates to a method for producing a luminescent aluminate-based phosphor. More particularly, the present invention relates to a method for producing a luminescent aluminate-based phosphor used for a luminous material which is excited by ultraviolet and visible lights to show afterglow property for a long period of time, and the like.
BACKGROUND OF THE INVENTION
Recently, there are investigations of an aluminate-based phosphor which is excited by a vacuum ultraviolet ray and the like radiated by rare gas discharge, to emit lights. For example, there are known BaMgAl
10
O
17
:Eu, BaMgAl
14
O
23
:Eu and the like as a blue light emitting phosphor, and BaAl
12
O
19
:Mn, BaMgAl
14
O
23
:Mn and the like as a green light emitting phosphor.
For example, a blue phosphor (BaMgAl
10
O
17
:Eu, BaMgAl
14
O
23
:Eu and the like) can be produced by preparing a mixture of 1) a barium compound, 2) an europium compound, 3) a magnesium compound and 4) an aluminum compound as raw materials and calcining, in a weak reductive atmosphere, the mixture as a precursor.
In this method, however, solid compounds of respective constituent ions are used as raw materials and mixing thereof is conducted by physical mixing such as ball mixing and the like, this precursor obtained by physical mixing such as ball milling and the like reveals poor dispersion of constituent ions, barium ion, europium ion, magnesium ion, aluminum ion and the like, and a blue phosphor after calcination does not easily obtain uniform composition. When dispersion of constituent ion is poor, particularly when dispersion of an europium ion acting as light emitting center is poor, portions of higher concentration of europium emerge locally, causing reduction in emitting brilliance which is called concentration quench.
Consequently, for obtaining a phosphor having excellent emitting efficiency, it has been desired to obtain a phosphor precursor in which dispersion of constituent ions is more excellent and to produce a phosphor having a uniform composition from said precursor.
On the other hand, there are conventionally used, as a luminescent phosphor, self emitting nocturnally luminous paints obtained by adding a radioative substance to a phosphor, for a night display or a nocturnal clock. Recently, there are wide investigations on application of a luminescent phosphor containing no radioative substance which shows afterglow property for a long period of time. As the luminescent phosphor, for example, europium-activated strontium aluminate (SrAl
2
O
4
:Eu and the like) is mainly investigated.
It is well known that the property of a phosphor is influenced by dispersibility of constituent ions of the phosphor, and the light emitting efficiency becomes higher when dispersibility of constituent ions of the phosphor is more excellent, particularly, when dispersibility of an activating agent and co-activating agent is more excellent. It is said that also in a luminescent phosphor, afterglow brilliance becomes higher when dispersibility of constituent ions is more excellent.
Further, it is well known that the light emitting property of a phosphor is significantly influenced by a trace impurity. Therefore, for obtaining aluminate which is substrate of a luminescent aluminate-based phosphor, there are used as the main raw material, a high purity aluminum compound powder and the like such as highly purified &agr;-alumina or high purity &ggr;-alumina, high purity aluminum hydroxide and the like.
As the aluminum compound, there is often used alumina such as &agr;-alumina or &ggr;-alumina and the like mainly, and it is known that, if alumina is used, high temperature calcination at 1600° C. or more is required for obtaining a luminescent aluminate-based phosphor in single-phase in which dispersion of constituent ions is excellent. In this case, members of apparatuses such as a calcinations furnace and the like required are limited to expensive materials.
Therefore, for obtaining a luminescent aluminate-based phosphor having excellent light emitting efficiency and afterglow brilliance, it has been desired to produce a luminescent aluminate-based phosphor in which dispersion of constituent ions is more excellent.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a method which can easily produce an aluminate-based phosphor which has excellent light emitting efficiency and in which dispersion of constituent ions is excellent.
Another object of the present invention is to provide a method which can easily produce a luminescent aluminate-based phosphor which has excellent light emitting efficiency and higher afterglow brilliance and in which dispersion of constituent ions is excellent.
Under such conditions, the present inventors have intensively studied and found that a method by which an aluminate-based phosphor in which dispersion of constituent ions is extremely excellent can be produced easily when a specific aluminum compound is used as a raw material.
Further, the present inventors have also found that a method by which a luminescent aluminate-based phosphor in which dispersion of constituent ions is extremely excellent can be produced easily when specific aluminum compound is used as a raw material, and have completed the present invention.
Namely, the present invention provides a method for producing an aluminate-based phosphor comprising calcining an aluminum compound having a BET specific surface area of 100 m
2
/g or more.
The present invention also provides a method for producing an aluminate-based phosphor comprising the steps of;
mixing an aluminum compound with an organic acid using an organic solvent to obtain a slurry,
mixing the slurry with an aqueous solution of at least one cation selected from the group consisting of Ba, Mg, Eu, Mn, Sr, Ca, Tb, Ce and Zn to obtain a slurry of the mixture,
precipitating the cation in the form of an organic acid salt around the aluminum compound to obtain a precursor,
separating and drying the precursor, and
calcining the precursor at a temperature of from 1000° C. or more to 1700° C. or less, to produce an aluminate-based phosphor.
The present invention further provides a method for producing a luminescent aluminate-based phosphor comprising calcining an aluminum compound having a BET specific surface area of 100 m
2
/g or more.
The present invention further provides a method for producing a luminescent aluminate-based phosphor comprising the steps of,
mixing an aluminum compound with an organic acid using an organic solvent to obtain a slurry,
mixing the slurry with an aqueous with an aqueous solution of at least one cation selected from the group consisting of Eu, Dy, Nd, Sr, Ca, Pb, Zn and Bi to obtain a slurry of the mixture,
precipitating the cation in the form of an organic acid salt around aluminum hydroxide to obtain a precursor,
separating and drying the precursor, and
calcining the precursor at a temperature of from 1000° C. or more to 1700° C. or less.
DETAILED DESCRIPTION OF THE INVENTION
In the present invention the aluminum compound used for obtaining a precursor of an aluminate-based phosphor is not particularly restricted providing it is a solid material containing aluminum, and examples thereof include aluminum hydroxide, aluminum oxide, aluminum sulfate and the like.
As the calcinations raw material used for obtaining an aluminate-based phosphor, there is used an aluminum compound having a BET specific surface area of 100 m
2
/g or more, and aluminum hydroxide or aluminum oxide having a BET specific surface area of 100 m
2
/g or more is preferable, aluminum hydroxide having a BET specific surface area of 100 m
2
/g or more is more preferable, aluminum hydroxide having a BET specific surf
Miyazaki Susumu
Ono Keiji
Koslow C. Melissa
Sumitomo Chemical Company Limited
LandOfFree
Process for producing aluminate-based phosphor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for producing aluminate-based phosphor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for producing aluminate-based phosphor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3006935