Optical Sheet Light Diffusion Layer Sparkle Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Liquid crystal display apparatuses experience sparkle or fine luminance unevenness due to interference between the uneven surface of the overlying light diffusion sheet and the liquid crystal panel, particularly exacerbated by reduced cell array pitch in higher definition panels.
Innovation Solution
The optical sheet features a light diffusion layer with resin beads of 2 μm or less in particle diameter, uniformly dispersed to prevent bead aggregation, resulting in a surface with an arithmetic average roughness of 0.6 μm or less and a peak count of 16 or more, which effectively suppresses sparkle contrast to 4% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If resin beads are used to create surface unevenness for light diffusion, then light diffusion function is improved, but sparkle contrast increases due to surface unevenness
Solution Approach 1:
The patent applies parameter changes by precisely controlling the particle diameter of resin beads to 7 μm or less, and controlling the arithmetic average roughness Ra of the surface to 0.6 μm or less. These specific parameter thresholds transform the surface unevenness from a sparkle-causing defect into a controlled light diffusion mechanism that maintains display quality.
Solution Approach 2:
The patent implements local quality by creating specific surface characteristics in the light diffusion layer - namely, controlling the distribution and size of resin beads to produce localized minute convex portions with specific roughness parameters. This localized control of surface topology enables light diffusion while preventing sparkle interference with the liquid crystal panel.
2Measurement precision
If cell array pitch is reduced for higher definition, then display resolution is improved, but sparkle occurs more easily due to increased sensitivity to surface unevenness
Solution Approach 1:
The patent applies preliminary anti-action by pre-controlling the surface properties of the optical sheet before it interacts with the high-definition liquid crystal panel. By establishing specific roughness parameters (Ra ≤ 0.6 μm) and bead size constraints (≤ 7 μm) in advance, the patent prevents sparkle from occurring when the reduced pitch panel is used, rather than attempting to correct it afterward.
3Illumination intensity
If resin beads are aggregated to form surface unevenness, then light diffusion is enhanced, but non-damage giving properties deteriorate
Solution Approach 1:
The patent resolves this contradiction through parameter changes by shifting from aggregated bead structures to uniformly dispersed sub-7 μm beads. This parameter transformation maintains light diffusion effectiveness while eliminating the aggregation-induced damage risks, thereby improving both optical performance and reliability.
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
This configuration stabilizes sparkle reduction on display screens by ensuring uniform, dense minute convex portions on the optical sheet surface, further reducing sparkle contrast to 3% or less when optimized, and improves non-damage giving properties and haze values.
Implementation Method 1
a light diffusion layer (12) provided on the base layer (11), the light diffusion layer including a resin matrix (13) and resin beads (14) dispersed in the resin matrix
Data Source
AI summary
An optical sheet 5 is an optical sheet, at least a first surface of the optical sheet has unevenness. A sparkle contrast of the first surface measured in conformity with JIS C 1006: 2019 is 4% or less. An arithmetic average roughness Ra of the first surface measured in conformity with JIS B 0601: 2001 (with an assessment length set to 290 μm) may be 0.6 μm or less. A peak count RPc of the first surface measured in conformity with JIS B 0601: 2001 (with an assessment length set to 290 μm) may be 16 or more.