Diffusion Sheet with Random Convex Structures and Rough Flat Portions
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Solution Overview
Problem
The existing diffusion sheets in liquid crystal display apparatuses do not adequately enhance light diffusion functions while maintaining low luminance unevenness, particularly in thinned display devices, where higher haze values are desired to reduce thickness and prevent moire generation.
Innovation Solution
A diffusion sheet with a light-transmissive substrate featuring randomly formed convex structures on one main surface and a flat portion with a surface roughness of at least 0.9 μm, which also has a lower frictional force on the opposing surface to prevent damage, is developed. This sheet is produced using a method involving random exposure patterns, etching, and blast processing to achieve the desired surface roughness and structure distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the diffusion sheet thickness is reduced to meet thinned liquid crystal display apparatus requirements, then the overall device thickness is reduced, but the light diffusion function deteriorates and luminance unevenness increases
Solution Approach 1:
The patent applies local quality by creating distinct regions on the diffusion sheet surface: convex-shaped structures in certain areas for light collection and diffusion, and flat portions with specific surface roughness (Ra ≥ 0.9 μm) in other areas for enhanced light diffusion. This localized functional differentiation allows the thin diffusion sheet to maintain effective light diffusion performance despite reduced overall thickness.
2Reliability
If the haze value is increased to enhance light diffusion function, then the light diffusion performance is improved, but the luminance is reduced and the image quality deteriorates
Solution Approach 1:
The patent employs local quality by distributing convex-shaped structures and flat portions with specific surface roughness across different areas of the diffusion sheet. The convex structures have higher refractive index differences that enhance light diffusion locally, while the flat portions with controlled roughness (Ra ≥ 0.9 μm) provide diffusion in other regions, achieving overall high haze without uniform luminance reduction across the entire sheet.
Solution Approach 2:
The diffusion sheet is segmented into multiple functional elements: numerous convex-shaped structures and flat portions with specific surface roughness. This segmentation allows different regions to contribute differently to light diffusion, enabling the sheet to achieve high overall haze while maintaining acceptable luminance through the combined effect of multiple segmented elements rather than uniform diffusion across the entire surface.
3Reliability
If convex-shaped structures are formed on the diffusion sheet surface, then the light collection function is enhanced, but the moire generation increases due to regular patterns
Solution Approach 1:
The patent applies asymmetry by using convex-shaped structures with asymmetric or irregular shapes rather than perfect circles or uniform geometric forms. The asymmetric shapes disrupt regular light diffraction patterns that would otherwise create moire effects, while still maintaining the light collection and diffusion functionality of the convex structures.
Solution Approach 2:
The patent uses local quality by creating flat portions with specific surface roughness (Ra ≥ 0.9 μm) interspersed among the convex-shaped structures. These flat portions with controlled roughness provide localized light diffusion that helps break up regular patterns formed by the convex structures, thereby suppressing moire generation while the convex structures maintain their light collection function in their respective local areas.
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 significantly enhances light diffusion and collection functions, suppresses moire generation, and maintains high luminance by adjusting the surface roughness of both main surfaces, allowing for thinner backlight and liquid crystal display apparatus designs with reduced luminance unevenness.
Implementation Method 1
The structures have a function of diffusing light transmitting through the substrate
Implementation Method 2
the flat portion formed among the structures on the first main surface has a surface roughness (Ra: arithmetic average surface roughness) of no less than 0.9 μm, and hence it is possible to obtain a high light diffusion effect
Data Source
AI summary
A diffusion sheet includes a light-transmissive substrate, a plurality of structures, and a flat portion. The light-transmissive substrate includes a first main surface, and a second main surface. The plurality of structures have convex shapes and are randomly formed on the first main surface. The flat portion is formed among the plurality of structures on the first main surface and has a surface roughness (Ra) of no less than 0.9 μm.