(12) United States Patent ao) Patent No.: us 6,447,934 Bi
Suzuki et al. (45) Date of Patent: Sep. 10,2002
(21) Appl. No.: 09/414,823
(22) Filed: Oct. 8, 1999
(30) Foreign Application Priority Data
Oct. 9, 1998 (JP) 10-288185
Aug. 31, 1999 (JP) 11-245939
(51) Int. CI.7 H05B 33/14
(52) U.S. CI 428/690; 428/917; 428/704;
428/212; 313/504; 313/506; 257/40; 257/103
(58) Field of Search 428/917, 690,
428/704, 212; 313/504, 506; 257/40, 103
(56) References Cited
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5,858.562 A * 1/1999 Utsugi et al 428/690
5,908,581 A * 6/1999 Chen et al 252/301.16
6,124,046 A * 9/2000 Jin et al 428/690
Primary Examiner—Cynthia H. Kelly
Assistant Examiner—Ling Xu
(74) Attorney, Agent, or Firm—Pillsbury Winthrop
An organic electroluminescent panel having two luminescent layers interposed between a pair of electrode layers emits white light or colored light. One luminescent layer is composed of a hole transport host material and a first fluorescent material doped in the host material, and the other luminescent layer is composed of an electron transport host material and a second fluorescent material doped in the host material. Both luminescent layers simultaneously emit respective lights which in turn are mixed into a white light or colored light. To realize the simultaneous light emission from both luminescent layers and to enhance energy conversion efficiency, organic materials having a solid state fluorescence spectrum peak wavelength in a range of 380 nm-510 nm are used as both host materials, and materials having a solid state fluorescence spectrum which overlaps with that of the host materials or is shifted to a longer wavelength side are used as the fluorescent materials doped in the host materials. The light color emitted from the panel is arbitrarily controlled by selecting the fluorescent dopant materials.
8 Claims, 9 Drawing Sheets