Flat Diffusing Structure for LCD Backlight Homogeneity
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Solution Overview
Problem
Existing backlighting systems for liquid crystal displays (LCDs) with a 'Direct Light' structure face issues of non-homogeneous light emission and high costs due to the need for high-quality diffusers that are sensitive to heat and suffer from light recycling losses.
Innovation Solution
A planar diffusing structure comprising a transparent first element and a diffusing second element, with a low-index interposed element between them, which limits the angle of light rays and enhances luminance efficiency by reducing absorption and increasing the outgoing luminous flux, using materials like glass or plastic with a refractive index difference greater than 0.1 and a thickness of at least 100 nm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If plastic diffusing means are used to homogenize light, then light homogeneity is improved, but structural deformation occurs due to heat sensitivity leading to luminance heterogeneity
Solution Approach 1:
The patent replaces expensive, heat-sensitive plastic diffusers with a more reliable glass substrate-based diffusing structure that can withstand thermal conditions without deforming, thereby maintaining both light homogeneity and structural stability
Solution Approach 2:
The patent changes the material parameter from plastic to glass substrate, which has superior thermal stability. The glass substrate with deposited diffusing layer maintains its structural integrity under heat while still achieving the required light homogenization function
2Loss of energy
If extra-clear glass substrate is used to reduce light absorption, then luminance efficiency is improved, but manufacturing cost increases
Solution Approach 1:
The patent introduces a dielectric layer as an intermediary between the glass substrate and the external environment. This layer optimizes optical coupling and reduces reflection losses, allowing the use of standard clear glass instead of expensive extra-clear glass while maintaining high luminance efficiency
Solution Approach 2:
The patent creates a composite structure combining glass substrate with a dielectric coating layer. This composite approach achieves superior optical performance comparable to extra-clear glass but using more cost-effective base materials and coating processes
3Illumination intensity
If conventional diffusing structure is used, then light diffusion is achieved, but light recycling losses occur due to multiple reflections at interfaces
Solution Approach 1:
The dielectric layer acts as an optical intermediary that manages reflections at the glass-air interface. By optimizing the refractive index matching, it reduces parasitic reflections that would otherwise cause light to bounce back and forth, minimizing energy loss while preserving the desired light diffusion effect
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 improved optical performance and cost-effectiveness by maintaining luminance while reducing structural deformation and light losses, allowing for the use of less expensive materials without compromising the total outgoing luminous flux.
Implementation Method 1
the low index element, interposed between the first transparent element and the second diffusing element, limits the angle of the rays entering the first element by retroreflecting them
Implementation Method 2
most of the rays entering the first element are directly refracted outwards
Data Source
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AI summary
The present invention relates to a flat multilayer diffusing structure (20) comprising: a first substrate element (23) which has a refractive index n1 in the visible, chosen from a glass, a plastic or a titanium oxide; a second element (21) which is diffusing and is on a first main face of the first element; and a low-index layer (22) placed between the first element and the second element and at least in optical contact with the first and second elements, the low-index element being largely transparent, with a thickness equal to or greater than 100 nm, and having a refractive index n2 in the visible, the difference n1-n2 being equal to or greater than 0.1. The second element either takes the form of a continuous layer with a variable thickness or a discontinuous layer. The invention also relates to its manufacturing process and to its applications.