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United States Patent (19) 11 Patent Number: 5,879,586 Kitamura Et Al

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United States Patent (19) 11 Patent Number: 5,879,586 Kitamura Et Al USOO587958.6A United States Patent (19) 11 Patent Number: 5,879,586 Kitamura et al. (45) Date of Patent: Mar. 9, 1999 54 METHOD FOR PRODUCING ALUMINATE 62-201989 9/1987 Japan. PHOSPHOR 2-170888 7/1990 Japan. 7-268319 10/1995 Japan. 75 Inventors: Koji Kitamura, Osaka; Shozo Oshio, 997600 2/1963 United Kingdom. Nara; Teruaki Shigeta, Osaka; Shigeru 2259095 3/1993 United Kingdom. Horii, Osaka; Takeshi Nishiura, Osaka; Tomizo Matsuoka, Osaka, all OTHER PUBLICATIONS of Japan Verstegen, “A Survey of a Group of Phosphors, Based on 73 Assignee: Matsushita Electric Industrial Co., Hexagonal Aluminate and Gallate Host Lattices”, The Jour Ltd., Osaka, Japan nal of Electrochemical Society, Vol. 121, No. 12 (1974), pp. 1623-1627. 21 Appl. No.: 721,934 22 Filed: Sep. 27, 1996 Primary Examiner Melissa Bonner Attorney, Agent, or Firm Merchant, Gould, Smith, Edell, 30 Foreign Application Priority Data Welter & Schmidt, PA. Sep. 29, 1995 JP Japan .................................... T-253917 57 ABSTRACT Mar. 29, 1996 JP Japan .................................... 8-O77126 An alkaline earth metal compound containing no fluorine 51 Int. Cl. ........................... C09K11/64; CO9K11/77; atoms in its molecules, a rare earth compound containing no C09K11/55 fluorine atoms in its molecules, and an aluminum compound 52 U.S. Cl. .................. ... 252/301.4 R 313/483 containing no fluorine atoms in its molecules are fired in a 58 Field of Search ...................... 252/301.4 R; 313/483 high-temperature reducing atmosphere ranging from 1600 to 2000 C., so that an aluminate phosphor, the particle 56) References Cited diameter and shape thereof are controlled, is provided. A U.S. PATENT DOCUMENTS mixture of 22 wt % of barium carbonate, 11 wt % of basic magnesium carbonate, 65 wt % of Spherical alpha-alumina 3.294,699 12/1966 Lange ............................... 252/301.4 R of 10 um diameter and 2 wt % of europium oxide is fired in 4,161,457 7/1979 Takahashi et al. ... ... 252/301.4 a mixed gas atmosphere consisting of gaseous hydrogen of 4,246,630 1/1981 Wolfe ............... 252/301.4 R 4,524.300 6/1985 Rutten et al. ........................... 313/487 5 volume 76 and gaseous nitrogen. The temperature is raised 4,631,144 12/1986 Beers et al. ... 252/301.4 R at 400° C./hr, and lowered at 400° C./hr after firing for two 4,795.588 1/1989 Pet et al. .......... ... 252/301.4 hours at 1700° C. As a result, a spherical aluminate phosphor 4,806,825 2/1989 Catherall et al. ....................... 313/486 of 10 um diameter, which is expressed by formula (Baoo, Euoo)MgAloO7 is obtained. FOREIGN PATENT DOCUMENTS 0 286 180 10/1988 European Pat. Off.. 24 Claims, 5 Drawing Sheets Firing temperature (C) 2OOO 18OO 17OO 16OO U.S. Patent Mar. 9, 1999 Sheet 1 of 5 5,879,586 Firing temperature (C) 2OOO 18OO 17OO 16OO 1400 1200 6 10000/T(K) F1 G. 1 U.S. Patent Mar. 9, 1999 Sheet 2 of 5 5,879,586 5 Firing temperature(C) 2OOO 18OO 17OO 1600 1400 1200 R H Sa Cs Ol --1 2 -r, Ol 3 - O. H. O.1 s 4 5 6 7 8 9 OOOO/TK) F1 G. 2 U.S. Patent Mar. 9, 1999 Sheet 3 of 5 5,879,586 F/G 3A FIG 3D 15 U.S. Patent Mar. 9, 1999 Sheet 4 of 5 5,879,586 O ast1 5 1O O O 5 10 15 2O Average particle diameter of alpha-alumina (pm) F1 G. 4 U.S. Patent Mar. 9, 1999 Sheet 5 of 5 5,879,586 F1 G. 5 A F1 G. 5 B F1 G. 5 C 5,879,586 1 2 METHOD FOR PRODUCING ALUMINATE no fluorine atoms in their molecules, the rare earth com PHOSPHOR pound is an europium compound containing no fluorine atoms in its molecules, and the aluminate phosphor com FIELD OF THE INVENTION prises the materials expressed by the following formula: This invention relates to a method for producing a phos phor used for a fluorescent lamp and a display, etc. BACKGROUND OF THE INVENTION where Aluminate phosphor for tri-band fluorescent lamps, which was developed by J. M. P. J. Verstegen and the others, has 0.03 sws 0.3, 0.8sxs 1.2, 8sys 12, and 14szs20. been commonly used with the spread of tri-band fluorescent lamps. It is preferable that the alkaline earth metal compound is Such an aluminate phosphor is produced by a method, for a magnesium compound containing no fluorine atoms in its example, taught in The Journal of Electrochemical Society 15 molecules, the rare earth compound is a cerium compound 121 (1974) p. 1623–1627. An aluminate phosphor described and a terbium compound containing no fluorine atoms in by a general formula (Baos Eulo)Mg-AlO7 is produced their molecules, and the aluminate phosphor comprises the by firing materials comprising barium carbonate, europium materials expressed by the following formula: oxide, magnesium carbonate and alumina in a hydrogen reducing atmosphere at 1200° C. (CelTb) Mg,Al,O. A fluorine compound like aluminum fluoride or magne sium fluoride is added to the materials So that the crystal where linity of the aluminate phosphor is improved, So as not to deteriorate during a heating treatment when the aluminate phosphor is coated on a device Such as a fluorescent lamp or 25 0.03 sws 0.6,0.8sxs 1.2, 9sys13, and 152s23. a display. The quantity of the fluorine compound is varied to It is also preferable that the alkaline earth metal com control the particle diameter and the shape of the aluminate pound is a Strontium compound containing no fluorine atoms phosphor, So that the phosphor can be coated on the device in its molecules, the rare earth compound is an europium more uniformly. compound containing no fluorine atoms in its molecules, In a conventional method for producing an aluminate and the aluminate phosphor comprises the materials phosphor, a fluorine compound Such as aluminum fluoride is expressed by the following formula: added to improve its crystallinity and to control the diameter and the shape. (Sra(1-1) Euan) AlO. The method, however, costs more than the material cost 35 because of the Sublimation characteristics of the added where fluorine compound. Furthermore, the firing furnace will be corroded and damaged because of the corrosiveness of the fluorine compound. On the other hand, the crystallinity of 0.01 sws 0.6, 11 sixs 17, and 20sys30. the aluminate phosphor does not improve and controlling of 40 It is further preferable that the particle diameter of the the particle diameter and the shape cannot be conducted if aluminum compound containing no fluorine atoms in its the fluorine compound is not added. molecules is the same or Substantially the same as that of the desired aluminate phosphor. SUMMARY OF THE INVENTION It is still preferable that the particle diameter of the In order to solve these and other problems, this invention 45 aluminum compound containing no fluorine atoms in its aims to provide a method for producing an aluminate molecules ranges from 1 to 20 lim. phosphor. According to this method, the crystallinity is It is also preferable that the particle shape of the alumi improved and the diameter and shape of the particles are num compound containing no fluorine atoms in its mol controlled, without adding any fluorine compounds Such as ecules is the same or Substantially the Same as that of the aluminum fluoride. 50 desired aluminate phosphor. In order to achieve the above-mentioned purpose, the It is preferable that the aluminum compound is spherical method for producing an aluminate phosphor of this inven or Substantially Spherical. tion fires an alkaline earth metal compound, a rare earth It is further preferable that the alkaline earth metal com compound, and an aluminum compound in a reducing pound containing no fluorine atoms in its molecules is at atmosphere at a temperature from 1600 to 2000 C. The 55 least one Selected from the group consisting of oxide, carbonate, basic carbonate, nitrate and chloride of an alkali compounds do not contain fluorine atoms in their molecules. earth metal. It is preferable that the reducing atmosphere is a mixture It is also preferable that the rare earth compound contain of gaseous hydrogen and gaseous nitrogen. ing no fluorine atoms in its molecules is at least one Selected It is also preferable that the concentration of the gaseous 60 from the group consisting of oxide, carbonate, basic Salt, hydrogen ranges from 0.1 to 10 volume 7% of the reducing nitrate and chloride of a rare earth element. atmosphere consisting of the mixture of gaseous hydrogen It is also preferable that the aluminum compound con and gaseous nitrogen. taining no fluorine atoms in its molecules is at least one It is further preferable that the firing time is at least five Selected from the group consisting of oxide, chloride, minutes. 65 nitrate, Sulfate and alkoxide of aluminum. It is preferable that the alkaline earth metal compound is In the method for producing an aluminate phosphor of this a barium compound and a magnesium compound containing invention, an alkaline earth metal compound containing no 5,879,586 3 fluorine atoms in its molecules, a rare earth compound containing no fluorine atoms in its molecules, and an alu minum compound containing no fluorine atoms in its mol (Sr.4(1-Eu 1)AlOy ecules are fired in a high-temperature reducing atmosphere ranging from 1600 to 2000 C., so that the reaction is where promoted and the crystallinity can be improved without using any fluorine compounds. As a result, the crystallinity can be improved without using any fluorine compounds that 0.01 sws 0.6, 11 sixs 17, 20sys30.
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