113005786665». United States Patent [191 [11] Patent Number: 5,786,665 Ohtsuki et a]. [45] Date of Patent: Jul. 28, 1998

[54] PLANE-SHAPED LIGHTING DEVICE AND A 5,408,388 4/1995 Kobayashi et a1. .. 362/27 X DISPLAY USING SUCH A DEVICE 5,641,219 6/1997 Mizobe ...... 362/31 [75] Inventors: Terukazu Ohtsuki. lkoma-gun; FOREIGN PATENT DOCUMENTS Masahiko Kimoto. lkoma; Hiroshi 60-152185 10/1985 . Minematsu. ; Nobuynki 485588 7/1990 Japan . Tominaga. ; Takahiro 6152867 11/1992 Japan . Fnnakoshi. Fujiidera; Yasuhiro Watla. ; Hitoshi Azuma. Primary Examiner-Ashok Patel Tondabayashi. all of Japan [57] ABSTRACT [73] Assignee: Sharp Kabnshiki Kaisha. Osaka. Japan A plane-shaped lighting device has a light-directing plate and a light source that is placed in contact with or in the [21] Appl. No.: 652,304 proximity of the light-incident surface of the light-directing [22] Filed: May 23, 1996 plate. and the light source is constituted of a plurality of LED lamps each of which has an LED chip for emitting light and [30] Foreign Application Priority Data a semispherical lens for directing the light from the LED chip into the light-directing plate. Here. the distance from May 23, 1995 [JP] Japan ...... 7-123878 the LED chip to the top of the semispherical lens is set to be [51] Int. (:1.6 ...... F21V 7/00 1.8 times as long as the radius of curvature of the semi— [52] us. (:1...... 313/512; 313/113; 362/27; spherical lens. This arrangement allows the light emitted 362/31; 362/800; 362/812 from the LED chip to be e?iciently incident on the light [58] Field of Search ...... 313/512. 113. incident surface of the light-directing plate. thereby improv 313/114; 362/257. 247. 296. 310. 341. ing the light-incidence ef?ciency to the light-directing plate. 362. 27. 31. 800. 812; 40/546 Further. the application of this plane-shaped lighting device to display devices makes it possible to improve the chi [56] References Cited ciency of light utilization. and consequently to provide thinner display devices with high visibility. U.S. PATENT DOCUMENTS

4,473,866 9/1984 Davis ...... 313/362 24 Claims, 44 Drawing Sheets

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