Optical Diffusive Layer for Wavelength-Selective Light Scattering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional optical diffusers scatter both visible and infrared light, making them unsuitable for applications like fingerprint detection in liquid crystal displays where minimal scattering of infrared light is required.
Innovation Solution
An optical film or stack with an optically diffusive layer containing nanoparticles dispersed in a polymeric material, forming aggregates and voids, which provides higher specular transmittance in the infrared range than in the visible range, minimizing infrared light scattering while maintaining effective diffusion of visible light.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If traditional optical diffusers are used to diffuse visible light, then uniformity and hot spot reduction are improved, but infrared light scattering increases making them unsuitable for fingerprint detection
Solution Approach 1:
The patent applies local quality by creating an optically diffusive layer with spatially varying nanoparticle aggregates that selectively diffuse visible light while transmitting infrared light. The nanoparticle aggregates (50-500 nm size) are distributed throughout the polymer matrix to provide wavelength-dependent optical properties, with the aggregate size and distribution optimized to affect visible wavelengths (400-700 nm) differently from infrared wavelengths (700-1000 nm).
Solution Approach 2:
The patent employs parameter changes by controlling the nanoparticle aggregate size (50-500 nm), concentration (5-50 wt%), and distribution within the polymer matrix to achieve wavelength-selective optical diffusion. The aggregate size parameter is specifically tuned to resonate with visible light wavelengths while being transparent to infrared wavelengths, and the polymer matrix composition is adjusted to maintain appropriate refractive index differences for visible light scattering.
2Illumination intensity
If nanoparticle aggregates with high void occupancy are used to increase visible light diffusion, then optical diffusion performance is improved, but the structural integrity and flexibility of the optically diffusive layer deteriorates
Solution Approach 1:
The patent utilizes porous materials by incorporating nanoparticle aggregates with internal voids (10-50 nm pores) within the polymer matrix. These porous aggregate structures increase the surface area and scattering centers for visible light diffusion while the polymer matrix provides structural continuity and mechanical strength. The void occupancy is controlled at 10-50% to balance optical performance with structural integrity.
Solution Approach 2:
The patent applies composite materials by combining nanoparticle aggregates (silica, titania, zirconia, or alumina) with a polymer matrix (polyester, polyacrylic, or polyvinylidene fluoride). This composite structure allows the inorganic nanoparticle aggregates to provide optical diffusion functionality while the organic polymer matrix provides mechanical flexibility and structural support, creating a synergistic material system that achieves both optical performance and structural integrity.
3Ease of operation
If the optically diffusive layer is made thin to maintain flexibility, then bendability is improved, but the optical diffusion effectiveness decreases
Solution Approach 1:
The patent applies dimensionality change by transitioning from traditional thick bulk diffusers to a thin-film optically diffusive layer (1-10 micrometers thick) with vertically distributed nanoparticle aggregates. The three-dimensional distribution of aggregates throughout the thin film thickness provides sufficient optical path length for effective diffusion while maintaining overall film thinness for flexibility. The aggregate size (50-500 nm) is optimized to maximize scattering cross-section within the constrained thin-film geometry.
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 ensures minimal scattering of infrared light while achieving desired optical diffusion of visible light, making it suitable for applications like fingerprint detection without compromising on light transmission.
Implementation Method 1
Traditional optical diffusers scatter both visible and infrared light... provides higher specular transmittance in the infrared range than in the visible range, minimizing infrared light scattering while maintaining effective diffusion of visible light
Implementation Method 2
The optically diffusive layer includes a polymeric material bonding the nanoparticles to each other to form a plurality of nanoparticle aggregates
Data Source
AI summary
Optical films and stacks include at least one optically diffusive layer. The optically diffusive layer can include a plurality of nanoparticles and a polymeric material bonding the nanoparticles to each other to form a plurality of nanoparticle aggregates defining a plurality of voids therebetween. For substantially normally incident light and a visible wavelength range from about 450 nm to about 650 nm and an infrared wavelength range from about 930 nm to about 970 nm: in the visible wavelength range, the optical film or optically diffusive layer has an average specular transmittance Vs; and in the infrared wavelength range, the optical film or optically diffusive layer has an average total transmittance It and an average specular transmittance Is, Is/It≥0.6, Is/Vs≥2.5.