Multilayer UV-Blocking Material with Steep Filtration Front
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Solution Overview
Problem
Current UV-screening agents, such as TiO2 and ZnO, have limited efficiency in blocking UV-A rays and require high concentrations to achieve high SPF values, leading to whitening effects and unpleasant skin sensations, while existing multilayer pigments lack a steep filtration front and high transparency in visible wavelengths.
Innovation Solution
A multilayer material with an odd number of layers, alternated with different refractive indices, specifically designed to have a narrow filtration front and high transmittance in visible wavelengths, using materials like TiO2 and SiO2 to effectively block UV rays without significant visible light transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If large amounts of UV-screening agents (TiO2, ZnO) are used to achieve high SPF values, then UV protection efficiency is improved, but whitening effects and unpleasant skin sensations occur
Solution Approach 1:
The patent divides the UV-screening function into multiple thin alternating layers of materials with different refractive indices (e.g., TiO2 and SiO2). This segmentation creates a multilayer structure that achieves superior UV blocking per unit thickness compared to bulk mineral agents, thereby reducing the total amount of screening agent needed and eliminating whitening effects.
Solution Approach 2:
The invention uses composite multilayer structures combining materials with different optical properties (TiO2 with high refractive index and SiO2 with lower refractive index). This composite approach creates constructive and destructive interference patterns that enhance UV absorption while maintaining transparency in the visible range, providing efficient protection without the drawbacks of conventional high-concentration mineral sunscreens.
2Reliability
If existing multilayer pigments are used to block UV rays, then UV screening is achieved, but the filtration front is not steep and transparency in visible wavelengths is insufficient
Solution Approach 1:
The patent optimizes the local optical properties of each layer in the multilayer structure. By carefully selecting the thickness and refractive index of individual layers (e.g., varying TiO2 and SiO2 layer thicknesses), the structure creates a steep filtration front that sharply transitions from UV blocking to visible transparency, achieving both superior UV screening and excellent visible light transmission.
Solution Approach 2:
The invention systematically varies critical parameters including layer thickness (ranging from 10-100 nm), refractive index differences between adjacent layers, and the number of alternating layers. These parameter optimizations create resonant conditions that produce a steep cut-off wavelength, enabling the material to block UV rays effectively while remaining highly transparent in the visible spectrum.
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 multilayer material provides enhanced UV protection, particularly in the UVA range, with a well-defined cut-off and high transparency in visible wavelengths, reducing UV transmission while maintaining excellent visible light transmission.
Implementation Method 1
successive layers of which are alternated and in which the adjacent layers have different refractive indices
Implementation Method 2
multilayer material... with a narrow filtration front and high transmittance in visible wavelengths
Data Source
AI summary
The invention relates to i) a multilayer material; ii) a process for preparing said multilayer materials; iii) a cosmetic composition comprising one or more multilayer materials; iv) a process for treating keratin materials, notably human keratin materials such as the skin; v) the use of multilayer material for screening out ultraviolet (UV) rays. Said multilayer material has an odd number N of layers: ▪comprising at least three layers, each layer of which consists of a material A or of a material B different from A, said successive layers A and B being alternated and two adjacent layers having different refractive indices; ▪for which the thickness of each layer obeys the mathematical formula (I) below: [x/y/(αx/y)a/x] in which formula (I): x is the thickness of the inner and outer layer; y is the thickness of the layer adjacent to the inner layer αx or the outer layer x; α is an integer or fraction and α=2±0 to 15%, preferably α=2±0 to 10%, more preferentially α=2±0 to 5%, the intermediate odd layers (αx) have a double thickness±0 to 15% of the thickness of said outer layers x; and a represents an integer greater than or equal to 0, connected to the number of alternated layers N such that a=(N−3)/2; it being understood that: ▪preferably, x has a different thickness from y; ▪when several layers are of thickness x, this means that each layer has a thickness x±0 to 15%, preferably±0 to 10%, more preferentially±0 to 5%; ▪when several layers are of thickness y, this means that each layer has a thickness y±0 to 15%, preferably±0 to 10%, more preferentially±0 to 5%; and ▪when several layers are of thickness α x, this means that each layer has a thickness α x±0 to 15%, preferably±0 to 10%, more preferentially±0 to 5%.