Wavelength-Selective Reflection Layer for Optical Elements
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Solution Overview
Problem
Conventional heat-ray shading films with multi-layer films on flat plates cause changes in color tones due to variations in refractive index and incident light angles, leading to issues like increased heat island phenomena and reduced lawn growth around buildings.
Innovation Solution
An optical element with a concave-convex surface, a five-layer wavelength-selective reflection layer alternately stacked with high-refractive-index and metal layers, where specific ratios of layer thicknesses are optimized to suppress color tone changes by controlling the geometric film thickness and layer arrangements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a multi-layer film is formed on a flat plate to shade near infrared rays, then the heat-shading function is improved, but color tone changes occur due to variations in refractive index and incident light angles
Solution Approach 1:
The patent applies a concave-convex surface structure to the multi-layer film, transforming the flat surface into a curved micro-structure. This curvature causes incident light rays to be reflected in multiple directions rather than following regular reflection laws, thereby suppressing color tone changes that occur with varying incident angles while maintaining the heat-shading function through selective wavelength reflection.
2Illumination intensity
If a reflection layer is formed on flat window glass to reflect solar light, then the transparency in visible light region is improved, but reflected light causes heat island phenomena and suppresses lawn growth
Solution Approach 1:
The concave-convex surface structure transforms regular reflection into diffuse reflection, scattering reflected light in multiple directions. This prevents concentrated reflected light from causing heat island phenomena and suppresses harmful effects on surrounding vegetation while maintaining visible light transparency through optimized layer thickness ratios.
Solution Approach 2:
The patent employs a five-layer structure with alternating high-refractive-index and metal layers, where each layer has specific thickness ratios (α and β parameters). This local optimization of layer properties enables selective reflection of near-infrared rays while transmitting visible light, achieving both transparency and heat-shading functions simultaneously.
3Ease of manufacture
If the layer thickness ratios in the wavelength-selective reflection layer are not optimized, then the manufacturing process is simplified, but color tone changes and performance deviation occur
Solution Approach 1:
The patent establishes specific parameter ranges for layer thickness ratios (α = db/da and β = d3/d1) that define optimal performance regions. By controlling these dimensionless parameters within specified ranges, the invention ensures consistent optical performance across different manufacturing conditions while providing clear manufacturing guidelines that balance simplicity and precision.
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 maintains transparency in the visible light region while shading near-infrared rays, preventing color tone changes and reducing heat island effects by optimizing the layer thickness ratios and arrangements.
Implementation Method 1
a wavelength-selective reflection layer formed on the concave-convex surface
Implementation Method 2
a layer for absorbing or reflecting one portion of solar light... an optical element having a high transmittance in the near infrared ray region
Implementation Method 3
a first optical layer having a concave-convex surface... since such a reflection layer is formed on a flat-shaped film or a window glass, it is only possible to regularly reflect incident solar light
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3C
AI summary
An optical element is provided with a wavelength-selective reflection layer having a five-layer configuration in which high-refractive-index layers and metal layers are alternately stacked. The present invention is designed so that the ratio α of an optical film thickness db of the entire metal layer relative to an optical film thickness da of the high-refractive-index layers as a whole, and the ratio β (= d3/d1) of an optical film thickness d3 of the third high-refractive-index layer with respect to the optical film thickness d1 of the first high-refractive-index layer as viewed from either the first optical layer side or the second optical layer side are included within a predetermined range.