| 摘要 |
PROBLEM TO BE SOLVED: To improve strength and reduce weight and size of a device by provid ing a light guide plate and a frame respectively with a flange portion and a flange receiving portion, both portions being of a thickness approximately half the mother plate thickness and welded together at spot-like welds on surfaces opposing and apart from each other by a predetermined gap. SOLUTION: A flange portion 31 projecting from a light glide plate 3 is of about half the thickness of the plate 3 with any one surface of the flange portion 31 being flush with top or reverse surface of the plate 3. A flange receiving portion 41 provided on a frame 4 is formed to receive the flange portion 31 without interfering with it with an appropriate gap D between mutually opposing surfaces 31c and 41a, 31b and 41b, and 31a and 41c. Either one of the surfaces 31b and 41b is provided with a plural number of welds 42 having a height of D. The light guide plate 3 and the frame 4 are made to contact each other at the welds 42 and welded together by ultrasonic welding. This improves strength and prevents deformation or breakage of a backlight device due to differences in coefficient of expansion and coefficient of water absorption. |
