Multi-Layer Optical Sheet for LCD Brightness Uniformity
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Solution Overview
Problem
LCD devices with existing optical sheets suffer from optical loss and non-uniform brightness due to abrasion of prism ridges, which degrades their optical efficiency.
Innovation Solution
An optical sheet comprising layers with different refractive indices and a refractive pattern of ridges and furrows that refract light at least three times to condense and diffuse light, minimizing optical loss and enhancing brightness uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a prism sheet with ridges and furrows is used to enhance optical characteristics, then brightness uniformity and front brightness are improved, but optical loss increases due to abrasion of the ridges
Solution Approach 1:
The optical sheet is divided into multiple layers (first layer, second layer, and third layer) with different refractive indices. The refractive pattern is segmented across these layers, with each layer contributing to the overall light modulation function. This segmentation distributes the optical stress and reduces abrasion on any single layer while maintaining the brightness uniformity enhancement.
Solution Approach 2:
The optical sheet uses composite material structure with at least three layers having different refractive indices (first layer with refractive index n1, second layer with refractive index n2, third layer with refractive index n3). This composite structure enables multiple refraction events that work together to achieve uniform brightness while reducing optical loss compared to single-material prism sheets.
2Productivity
If a single-layer prism sheet is used to condense light, then optical efficiency is improved, but non-uniform brightness is caused by abrasion of ridges
Solution Approach 1:
The single-layer structure is segmented into multiple layers with different refractive indices. Each layer performs a portion of the light condensation function, which distributes the mechanical stress and abrasion across multiple layers rather than concentrating it in one layer, thereby maintaining brightness uniformity while preserving optical efficiency.
Solution Approach 2:
Each layer of the optical sheet has different local optical properties (different refractive indices). The first layer, second layer, and third layer are optimized for different aspects of light modulation, creating local quality variations that collectively achieve both high optical efficiency and uniform brightness without the abrasion problems of single-layer designs.
3Illumination intensity
If optical sheets are used to enhance optical characteristics, then brightness uniformity is improved, but optical loss degrades optical efficiency
Solution Approach 1:
The patent converts the potentially harmful effect of multiple refraction interfaces (which could cause optical loss) into a beneficial structure. By carefully designing the refractive indices of the three layers, the multiple refraction events work together to achieve superior brightness uniformity and front brightness enhancement, with the overall optical efficiency being maintained or improved despite the additional interfaces.
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 significantly increases optical efficiency and prevents defects caused by prism ridge abrasion, achieving higher peak luminance compared to traditional prism sheets.
Implementation Method 1
The refractive pattern is disposed at a boundary surface between the first layer and the second layer and includes ridges and furrows that change a traveling path of light. The optical sheet refracts light at least three times to condense the light in a direction perpendicular to a light-exiting surface.
Data Source
AI summary
Provided are an optical sheet, a backlight unit and an LCD device having the same. The backlight unit includes a first layer, a second layer, and a refractive pattern. The first layer has a larger refractivity than an air layer, and the second layer has a larger refractivity than the first layer. The refractive pattern is disposed at a boundary surface between the first layer and the second layer and has ridges and furrows that change a traveling path of light. The optical sheet refracts light at least three times to condense the light in a direction perpendicular to a light-exiting surface.