USO06969475B2 (12) United States Patent (10) Patent No.: US 6,969,475 B2 Hyland, Jr. et al. (45) Date of Patent: Nov. 29, 2005 (54) PHOTOLUMNESCENT ALKALNE EARTH 4,806,825 A 2/1989 Catherall et al. ALUMINATE AND METHOD FOR MAKING 5,273,681 A 12/1993 Srivastava THE SAME 5,376,303 A 12/1994 Royce et al. 5,424.006 A * 6/1995 Murayama et al. ... 252/301.4 R 5,644, 193 A 7/1997 Matsuda et al. (75) Inventors: Robert W. Hyland, Jr., Oakmont, PA 5,686,022 A 11/1997 Murayama et al. (US); James P. Quintenz, Henderson, 5,698.301 A 12/1997 Yonetani KY (US); Brian Tyler Dunville, 5,770, 111 A 6/1998 Moriyama et al. Sebree, KY (US); Gowri 5,811, 174 A 9/1998 Murakami Subrahmanyam, Kingston (CA) 5,879,586 A 3/1999 Kitamura et al. 5,885,483 A 3/1999 Hao et al. (73) Assignee: KB Alloys, Robards, KY (US) 6,010.644 A * 1/2000 Fu et al. ........ .... 252/301.4 R 6,117.362 A * 9/2000 Yen et al. ............. 252/301.4 R Notice: Subject to any disclaimer, the term of this 6,136,226 A 10/2000 Sakai patent is eXtended or adjusted under 35 U.S.C. 154(b) by 0 days. (Continued) FOREIGN PATENT DOCUMENTS Appl. No.: 10/717, 106 (21) EP (O) (O94 132 11/1983 (22) Filed: Nov. 19, 2003 (Continued) (65) Prior Publication Data OTHER PUBLICATIONS US 2004/0135122 A1 Jul. 15, 2004 Kinzo Nonomura, Hidetaka Higashino, and Ryuichi Murai, “Plasma Display Materials,” MRS Bulletin, Nov. 2002, pp. Related U.S. Application Data 898-902. (60) Provisional application No. 60/428,380, filed on Nov. Primary Examiner—C. Melissa Koslow 22, 2002. (74) Attorney, Agent, or Firm—Buchanan Ingersoll PC (51) Int. Cl.” ......................... C09K 11/64; CO9K 11/54 (57) ABSTRACT (52) U.S. Cl. ............................................... 252/301.4 R (58) Field of Search .................................. 252/3014 R A photoluminescent phosphorescent material for emergency lighting and the like. An alkaline earth aluminate base (56) References Cited material is alloyed with a lanthamide earth element and a transition metal element. When exposed to ambient lighting, U.S. PATENT DOCUMENTS the material of the present invention emits light in dark areas 3,294,699 A 12/1966 Lange even after the loss of electrical power. The addition of a 3,502,592 A * 3/1970 Amster ................ 252/301.4 R transition metal element such as Scandium (Sc) provides 3,595,802 A 7/1971 Blasse longer and brighter photoluminescence than is expected by 4,216,408 A 8/1980 Verstegen et al. the use of a lanthanide element alone. 4,524.300 A 6/1985 Rutten et al. 4,644223 A 2/1987 de Hair et al. 4,795,588 A 1/1989 Pet et al. 3 Claims, 4 Drawing Sheets Afterglow Performance - SrA,O, 5 1300 C Processing 10° E ????????? ttttttt 10* ... ÀW W W X W. W 1 W W W W W- M - W -M - W W W W W W - : 1 ooo - - - - - - - - - - - - - - - - - - - - - - - - - - - -; - - - - - - - - - - - - - - - - - *** å - - - - - - - - - - - - - - - - - - - - - - - $ ? 1oo -- - - - - - - - - - - - - - - - - - - - - - - - - - - -; - - - - - - - - - - - - - - - - - - - - - - - - - - - - ?i? ----------------8 g *X3. Q. i Luminance X Arbitraty Units - Eu DySc 1300C 0-7 mol% VM 10 E Eu Dy 1300C 0.7 mol% : • • • • • • • • • • • • • • • • • Eu DyGd 1 300C 0.7 mol% : EuDyScGd 1300C 0,7 mo|% 1 -- : - - - ---- ---- ---- . : 0. i ---- lili i , i i:--- 0.1 1 1 0 100 Deca y Time (min) US 6,969,475 B2 Page 2 U.S. PATENT DOCUMENTS FOREIGN PATENT DOCUMENTS 6,177,029 B1 1/2001 KaZ et al. EP 94132 * 11/1983 6,261477 B1 * 7/2001 Fu et al. ............... 252/301.4 R JP 56-152883 11/1981 6,267.911 B1 * 7/2001 Yen et al. ............. 252/301.4 R 6,280,655 B1 8/2001 Xu et al. * cited by examiner U.S. Patent Nov. 29, 2005 Sheet 1 0f 4 US 6,969,475 B2 Afterglow Performance - SrAlO, 1300 C Processing EuDySc 1300C 0.7 mo |% Eu Dy 1300C 0.7 mol% Eu DyGd 1300C 0.7 mol% Eu Dy ScGd 1300C 0.7 mol% 0.1 1 1 0 1 00 Decay Time (min) Figure 1 U.S. Patent Nov. 29, 2005 Sheet 2 0f 4 US 6,969,475 B2 Afterglow Performance - SrAl2O, 1450 C Processing 10“ » 1000 --- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 100 : : D Luminance Arbitrary Units 10 EuDy 1450C 0.67 mol% : • • • • • • • • • • • • • • • • • • • • • EuDySc 1450C 0.68 mol% : EuDyScGd 1450C 0.7 mol% 0.1 0.1 1 10 100 Decay Time (min) Figure 2 U.S. Patent Nov. 29, 2005 Sheet 3 0f 4 US 6,969,475 B2 Afterglow Performance - SrAlO4 14 25 1300 C Processin 1 0 1 000 1 00 Luminance Arb Units 1 0 E 1 O Sr4A||14O25: EU 01 E Sr4A14O25: Eu Dy Hr A Sr4A114O25: Eu DySc ÉG Sr4A14O25: Eu Dy ScGd 0.01 U - N 0.1 1 1 0 100 Decay Time (min) Figure 3 U.S. Patent Nov. 29, 2005 Sheet 4 0f 4 US 6,969,475 B2 Afterglow Performance - SrAlO, 1300 C Processing 1 000 1 0 0 - - - - - - - - - - - - - - - - - - - - - - Luminan Ce Arb UnitS 1 0 O STA||4O7:EU SrA|4O7:Eu Dy A SrA|4O7: Eu DySc - - - - - - - - - - - - - : - - - - - - - - - - - - - - - - - - - - - - - - - - A SrA|4O7: Eu DyScGd : SrA|4O7:Eu DyScGd III 0.1 1 1 0 1 0 0 Decay Time (min) Figure 4 US 6,969,475 B2 1 2 PHOTOLUMNESCENT ALKALNE EARTH It has become common practice to chemically identify ALUMINATE AND METHOD FOR MAKING optically active inorganic materials Such as the AE alumi THE SAME nates that have been doped by indicating the stoichiometry of the oxide phase followed by the dopant chemical identity. This Application claims priority from Provisional Patent Thus, the above-mentioned materials are denoted in the Ser. No. 60/428,380 filed Nov. 22, 2002. literature as SrAl2O4:Eu,Dy or SrAl2O4:Eu, Dy, Pr, etc. Where indicated, these additional dopants serve as co BACKGROUND OF THE INVENTION activators and in certain specific formulations they have been found to enhance the photoluminescence behavior of 1. Field of the Invention 1 O the base Eu activated strontium aluminate or SrAl2O4:Eu The present invention relates to a phosphorescent mate and several other Sr aluminates. rial, and more particularly to a photoluminescent phospho The precise quantum mechanical mechanisms that govern rescent material containing an alkaline earth aluminate and this behavior in the AE aluminates have not been completely method for making the same. and unambiguously identified at this time. However, there is 15 Sufficient experimental and theoretical evidence to indicate 2. Description of the Prior Art that the process of electron/hole trapping of photostimulated Photoluminescent materials are well known in the art. carriers due to the presence of dopant species gives rise to They provide substance in material whereby items “glow in the long decay time phosphorescence observed in these the dark” after having been exposed to light, either natural materials. or artificial. These items range in use from watch faces, 20 For example, the photoemission extinction time that novelty items and the like to safety features Such as lighted marks the cessation of afterglow phosphorescence was exit signs. An important feature of Such materials is their found to increase by a factor of 10 to 15 for SrAl2O4, that is decay time, or resident time that will remain luminescent co-doped with about 1.5 mol % of Eu and Dy or Eu and one and visible when the Surroundings that the material is used ore more of the rare earth elements mentioned above. The in become dark. 25 extinction time is commonly defined as the time required for In recent years, it has become important to use Such the afterglow photoemission to diminish to 0.032 millican materials in exit way lighting, Such that an emergency exit dela per Square meter (mcd/m). This value, though Some way can remain lighted even after electrical power has been what arbitrary, is approximately 100 times the commonly cut. With this type of material, the exit lighting absorbs light accepted limiting light intensity that can be detected by the energy or radiation from the ambient lighting within a 30 human eye. stairwell, for example, and can remain photoluminescent for long periods of time after the electricity has been cut. Very SUMMARY OF THE INVENTION bright materials generally comprise phosphorescent materi als such that the ambient light that they provide is very It has been discovered that Small additions of Scandium bright for an eXtended period of time, Such as 12—24 hours. 35 (Sc) in the form of Sc2O3 incorporated as a ternary or Historically, there has been considerable commercial quaternary co-activator to SrAl2O4: Eu, Dy, REM result in a interest in the optical properties of rare earth activated photoluminescent oxide material that possesses an improved alkaline earth (AE) aluminates due to their suitability in a persistent afterglow intensity relative to both traditional ZnS variety of applications. Significant growth has taken place in and certain formulations of strontium aluminate Such as markets such as opto-electronics, telecommunications and 40 SrAl2O4:Eu,Dy at long extinction times (in the range 1—3 optically active commercial products including architectural hours after optical excitation). Persistent phosphorescence lighting, building products and way-finding Systems. With may also be obtained in applying the invention to other Eu respect to the applications in the artificial lighting and and Dy doped oxide compositions within the SrO—Al2O3 illuminated display technology areas, AE aluminate mate system Such as SrAl2O7: Eu, Dy, SrAl2O4: Eu,Dy, rials have recently become important due to their greatly 45 SrAlO2, and mixtures thereof.