Light Diffusing Sheet Surface Profile for Uniform Luminance
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Solution Overview
Problem
Conventional light diffusing sheets fail to achieve high front luminance while maintaining adequate diffusibility, especially when used with high brightness LEDs, leading to non-uniform brightness distribution in liquid crystal displays.
Innovation Solution
A light diffusing sheet with a specific surface profile of the diffusion layer, characterized by kurtosis (Rku) not less than 3.0, arithmetic mean roughness (Ra) not more than 1.5 μm, and a ratio of mean length (RSm) to mean height (Rc) of roughness curve elements not less than 7.0, which enhances light diffusion and luminance uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the content of diffusing agent in light diffusing sheet is increased to improve diffusibility, then light diffusion is enhanced, but front luminance deteriorates
Solution Approach 1:
The invention changes the geometric parameters of the diffusion layer surface profile, specifically controlling Rku (kurtosis) ≥ 3.0, Ra (arithmetic mean roughness) ≤ 1.5 μm, and RSm/Rc (ratio of mean length to mean height of roughness elements) ≥ 7.0. These parameter changes optimize the balance between light diffusion and front luminance without requiring increased diffusing agent content
Solution Approach 2:
The invention transitions from controlling diffusion primarily through material composition (diffusing agent content) to controlling it through surface geometry (three-dimensional surface profile parameters). This dimensional shift from chemical to physical control enables simultaneous achievement of high diffusibility and front luminance
2Illumination intensity
If high brightness LED is used as light source to improve luminance, then brightness is increased, but brightness distribution uniformity deteriorates
Solution Approach 1:
The invention uses specific surface profile parameters (Rku ≥ 3.0, Ra ≤ 1.5 μm, RSm/Rc ≥ 7.0) to control and uniformize light distribution across the display surface, compensating for the non-uniform emission characteristics of high brightness LEDs
3Measurement precision
If liquid crystal pixel size is reduced to improve resolution, then image quality is enhanced, but light transmittance deteriorates
Solution Approach 1:
The invention optimizes surface profile parameters to enhance light extraction efficiency, compensating for the reduced light transmittance caused by smaller pixel sizes in high-resolution displays
Solution Approach 2:
The invention utilizes curved surface features (roughness elements with specific RSm/Rc ratio ≥ 7.0) to redirect and distribute light more effectively, improving light utilization in high-resolution displays with reduced pixel transmittance
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 high front luminance and uniform brightness distribution, even when used with high brightness LEDs, while maintaining diffusibility, and is suitable for thin liquid crystal displays.
Implementation Method 1
a light diffusing sheet which is capable of exhibiting high front luminance and diffusibility
Data Source
AI summary
A light diffusing sheet can include a diffusion layer. The diffusion layer has a surface profile that satisfies certain conditions.