Antireflection Stack with Four-Layer Refractive Index Profile
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Solution Overview
Problem
Conventional antireflection stacks with high refractive index and low refractive index oxide layers alternately stacked face challenges in achieving low reflectance and maintaining a moderate chromatic color, especially when layer thicknesses fluctuate due to production variations, leading to excessive reflectance and multicolorization.
Innovation Solution
A four-layer antireflection stack with specific refractive index ranges for each layer (1.70 to 1.85, 2.25 to 2.45, 2.10 to 2.3, and 1.25 to 1.5) and thickness ratios, formed using metal oxides and hollow silica particles, to reduce reflectance and prevent multicolorization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional high refractive index and low refractive index oxide layers are alternately stacked, then the reflectance is reduced, but the reflected color becomes excessively chromatic and multicolorization occurs
Solution Approach 1:
The patent applies parameter changes by precisely controlling the refractive indices within specific ranges (1.74-1.88, 1.9-2.1, ≤1.48) and thicknesses (45-65 nm, 90-110 nm, 80-110 nm) for each layer. This systematic adjustment of optical parameters achieves reflectance reduction below 0.7% while maintaining moderate chromatic color and suppressing multicolorization, resolving the contradiction between energy loss reduction and harmful optical effects.
Solution Approach 2:
The patent employs composite materials by stacking multiple oxide layers with different refractive index characteristics. The combination of high refractive index oxide layers (e.g., TiO2, Nb2O5), intermediate refractive index oxide layers (e.g., SiO2, In2O3), and low refractive index oxide layers (e.g., MgF2, SiO2) creates a composite structure that simultaneously achieves low reflectance and controlled chromatic properties through constructive and destructive interference of light waves.
2Object-affected harmful factors
If the thicknesses of oxide layers are adjusted to achieve moderate chromatic color, then the reflected color is improved, but the production conditions cause thickness fluctuations leading to quality inconsistency
Solution Approach 1:
The patent establishes robust parameter ranges for layer thicknesses (45-65 nm, 90-110 nm, 80-110 nm) that provide a buffer zone for manufacturing variations. By designing the antireflection stack with these optimized thickness ranges rather than single precise values, the system maintains moderate chromatic color and suppresses multicolorization even when thickness fluctuations occur during production, thereby improving quality consistency.
Solution Approach 2:
The patent implements beforehand cushioning by designing thickness ranges with built-in margins that accommodate expected manufacturing variations. The specified thickness ranges (45-65 nm, 90-110 nm, 80-110 nm) are wider than minimum requirements, creating a cushion that absorbs thickness fluctuations without compromising the optical performance, thus ensuring consistent quality despite production condition variations.
3Loss of energy
If more oxide layers are stacked to reduce reflectance further, then the reflectance decreases, but the device complexity and production difficulty increase
Solution Approach 1:
The patent achieves optimal reflectance reduction with a balanced four-layer structure by carefully adjusting the refractive indices and thicknesses of each layer. This parameter optimization allows the system to reach reflectance below 0.7% without requiring excessive numbers of layers, thereby maintaining reasonable device complexity and production feasibility while achieving the desired optical performance.
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 effectively reduces reflectance to less than 0.2% and maintains a moderate chromatic color across varying incident angles, even with slight layer thickness fluctuations, enhancing the appearance and functionality of image display devices.
Implementation Method 1
an antireflection stack such as an antireflection film on the image display surface... one having a high refractive index oxide layer and a low refractive index oxide layer stacked alternately
Implementation Method 2
a first oxide layer, a second oxide layer and a third oxide layer formed on a substrate, wherein the first oxide layer has a refractive index of from 1.74 to 1.88... the second oxide layer has a refractive index of from 1.9 to 2.1... the third oxide layer has a refractive index of at most 1.48
Data Source
Figure 1~2
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Figure 5~6
AI summary
To provide an antireflection stack, whereby a reflected color is moderate, and a multicolorization is suppressed. The antireflection stack 1 comprises a substrate 2 and an antireflection layer 3 stacked on the substrate 2. The antireflection layer 3 has a four-layer structure and comprises, sequentially from the substrate side, a first layer 31, a second layer 32, a third layer 33 and a fourth layer 34. Further, the first layer 31 has a refractive index of from 1.6 to 1.9, the second layer 32 has a refractive index of from 2.2 to 2.5, the third layer 33 has a refractive index of from 2.0 to 2.3, the fourth layer 34 has a refractive index of from 1.2 to 1.5, and the refractive index of the second layer 32 is larger than that of the third layer 33.