Backlight Unit Optical Sheet Dumbbell Holes Impact Resistance
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Solution Overview
Problem
Direct type backlight units in liquid crystal displays (LCDs) suffer from damage to optical sheets due to external impacts during transportation, leading to stress concentration and cracking, which degrades display quality.
Innovation Solution
The optical sheets feature first and second long holes with a dumbbell shape, where the diameter of the curved portion is larger than the width of the linear portion, allowing the first and second protrusions to distribute stress concentration points, reducing the likelihood of cracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the optical sheets are fixed using long holes with linear portions, then the optical sheets can be properly secured to the bottom cover and support sides, but stress concentration occurs at the intersection points of linear and curved portions causing cracks under external impact
Solution Approach 1:
The patent applies curvature principle by designing the long holes in the optical sheets with enlarged curved portions at both ends instead of sharp corners. This curvature design eliminates stress concentration points that would otherwise occur at the intersection of linear and curved portions, allowing the optical sheets to withstand external impacts without cracking while maintaining proper fixation to the bottom cover and support sides.
2Strength
If the diameter of curved portions is increased to distribute stress, then the optical sheets become more resistant to cracking, but the contact area with protrusions increases potentially affecting fixation stability
Solution Approach 1:
The patent applies local quality principle by selectively enlarging only the curved portions at the ends of the long holes while maintaining the linear portions' dimensions. This localized modification distributes stress concentration at the critical curved areas without unnecessarily increasing the overall contact area with the protrusions, thus improving impact resistance while maintaining fixation stability.
Data Source
AI summary
A backlight unit that minimizes damage to an optical sheet due to external impacts, and a liquid crystal display employing the backlight unit are disclosed. The backlight unit comprises a light source unit comprising a plurality of light sources; a bottom cover that receives the light source unit and comprises a first protrusion; support sides fastened to both opened shorter sides of the bottom cover to support the light source unit and comprising a second protrusion; and an optical sheet unit disposed on the light source unit and comprising a first long hole in which the first protrusion is inserted and a second long hole in which the second protrusion is inserted, wherein the first and second long holes have a dumbbell shape in which the diameter of a curved portion is larger than the width of a linear portion through which the first and second protrusions pass.