Diffusion Sheet Random Convex Structures Luminance Moire
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Solution Overview
Problem
Conventional diffusion sheets used in liquid crystal display devices have insufficient luminance, which limits their performance in improving light distribution and clarity.
Innovation Solution
A diffusion sheet with randomly formed convex structures on its surface, having a specific aspect ratio and filling factor, is developed to enhance luminance and prevent moire generation, achieved through a manufacturing process involving resist layer formation, exposure, and etching to create concave portions that are then pattern-transferred to form convex structures with controlled height and distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional diffusion sheets with resin beads are used, then light diffusion is achieved, but luminance is insufficient
Solution Approach 1:
The invention uses convex lens structures with curved surfaces instead of flat or irregular resin beads. The spherical/convex shape of the lens structures enables effective light collection and directional control, improving luminance while maintaining diffusion functionality.
Solution Approach 2:
The invention optimizes specific parameters of the lens structures including aspect ratio (0.5-1.5), filling factor (60-80%), and height uniformity (standard deviation ≤10%). These parameter controls ensure both high luminance and effective light collection without the drawbacks of conventional bead-based sheets.
2Ease of manufacture
If regular patterns are used for structures, then manufacturing is easier, but moire generation occurs
Solution Approach 1:
The invention employs asymmetric random arrangement of lens structures instead of regular periodic patterns. This asymmetric distribution eliminates moire interference while the lens shapes themselves remain symmetric and manufacturable through standard molding processes.
Solution Approach 2:
Each local region contains lens structures with consistent optical properties (same aspect ratio, filling factor), but the overall arrangement is randomly distributed. This maintains local manufacturing quality while avoiding global periodicity that causes moire.
3Manufacturing precision
If structure height varies significantly, then manufacturing tolerance is relaxed, but luminance uniformity deteriorates
Solution Approach 1:
The invention implements tight control feedback for lens height during manufacturing, maintaining standard deviation within 10% of the average height. This feedback control ensures uniform light collection across all lens structures, producing consistent luminance throughout the diffusion sheet.
Solution Approach 2:
The manufacturing process is designed with built-in tolerance cushioning by specifying a relatively loose height variation limit (≤10% standard deviation) that still ensures uniform optical performance. This beforehand cushioning prevents luminance defects before they occur.
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 diffusion sheet effectively improves luminance and transferability while suppressing moire generation, leading to enhanced light collection and display quality in liquid crystal display devices.
Implementation Method 1
forming a random exposure pattern in a resist layer formed on a surface of a matrix fabrication substrate
Implementation Method 2
light incident from a light source is diffused and collected by resin beads contained in the diffusion layer
Implementation Method 3
light incident from a light source is diffused and collected by resin beads contained in the diffusion layer
Data Source
AI summary
A diffusion sheet includes: a substrate having a first principal surface and a second principal surface; and structures each in a convex shape formed randomly on the first principal surface or the second principal surface of the substrate. The structures have an identical or almost identical height. The structures have an aspect ratio h/r, where r denotes an average radius of the structures and h denotes an average height of the structures, of more than 0.85 and not more than 1.50. The structures have a filling factor of not less than 60% and not more than 80%.