Light Diffusion Sheet Ridge Curvature for Scratch-Resistant Uniformity
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Solution Overview
Problem
Existing direct type backlights in liquid crystal displays suffer from insufficient protection of light diffusion plates and optical films, leading to damage during transportation and vibration, which affects luminance uniformity.
Innovation Solution
A light diffusion sheet with recesses in a substantially inverted polygon or truncated polygon pyramid shape, featuring a recessed ridge between intersections, with controlled height differences and arrangement pitches, enhancing scratch resistance and luminance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the light diffusion sheet is layered with other optical sheets, then luminance uniformity is improved, but wear and damage occur at the ridge portions
Solution Approach 1:
The ridge portion is formed with a curved surface (circular arc, parabolic arc, or elliptic arc) instead of a sharp edge, reducing stress concentration and preventing wear when layered with other optical sheets. The curvature radius is specifically controlled to balance luminance uniformity and scratch resistance.
Solution Approach 2:
Different portions of the recess structure have different functional characteristics: the curved ridge portion provides scratch resistance, while the inverted polygon pyramid shape provides luminance uniformity. This local differentiation resolves the contradiction between the two requirements.
2Reliability
If the ridge is recessed to improve scratch resistance, then wear is reduced, but luminance uniformity drops
Solution Approach 1:
The curvature radius of the ridge is optimized within a specific range (0.01-0.5mm) to achieve the best balance between scratch resistance and luminance uniformity. This parameter optimization allows both requirements to be satisfied simultaneously.
Solution Approach 2:
The ridge is recessed only partially (forming a curved surface) rather than completely flattening it, which is sufficient to reduce wear while maintaining the structural integrity needed for luminance uniformity.
3Reliability
If the maximum height difference is increased to improve scratch resistance, then wear resistance improves, but luminance uniformity deteriorates
Solution Approach 1:
The maximum height difference of the curved surface is controlled within a specific range (0.003-0.05 times the recess depth) to optimize both scratch resistance and luminance uniformity. This parameter control resolves the contradiction between the two performance aspects.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a light diffusion sheet that minimizes damage and maintains luminance uniformity even when layered with other optical sheets, improving scratch resistance and reducing wear.
Implementation Method 1
a light diffusion member (a light diffusion plate, a light diffusion sheet, or a light diffusion film) is used to avoid making the light sources themselves such as light emitting diodes (LEDs) traceable through a light-emitting surface and improving uniformity of in-plane luminance
Data Source
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AI summary
Alight diffusion sheet 43 includes, at least in its first surface 43a, a plurality of recesses 22 formed in a substantially inverted polygon pyramid or in a substantially inverted truncated polygon pyramid. The ridge 23 parting the plurality of recesses 22 has a recessed shape between the intersections 23a, with respect to a straight line connecting the intersections 23a of the ridge 23. Where P is the arrangement pitch of the plurality of recesses 22 and Wr is the dimension occupied by a curved portion at the top portion of the ridge 23 in the arrangement direction of the plurality of recesses 22, a ratio Wr/P is 0.3 or less. The maximum height difference d between the ridge 23 and the straight line connecting the intersections 23a of the ridge 23 is 1 µm or more and 10 µm or less.