Micro-Wrinkled Cholesteric Liquid Crystal Film for Angle-Independent Color
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Solution Overview
Problem
Existing methods for forming micro-wrinkled structures on substrates face challenges in stability, spacing, height uniformity, and angle-dependent wavelength reflection, particularly in cholesteric liquid crystal films, limiting their flexibility and color consistency across viewing angles.
Innovation Solution
A method involving an elastic polymer substrate with an interpenetrating polymer network structure is used to form micro-wrinkles, followed by shear-coating cholesteric liquid crystal monomers, stabilizing the layer through photopolymerization, and transferring the structure to create an angle-independent photonic crystal film.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If alloy plate mold is used for embossing to create micro-wrinkled structure, then large-area surface wrinkle film can be manufactured, but thermal expansion of metal components at high embossing temperature limits wrinkle size to micrometer level
Solution Approach 1:
The patent changes the material parameter from metal to polymer, and changes the operating temperature parameter from high (metal embossing) to low (polymer embossing). This allows maintaining large-area manufacturing capability while achieving precise wrinkle size control through the lower thermal expansion of polymer materials at reduced embossing temperatures
Solution Approach 2:
The patent replaces expensive, heat-sensitive metal alloy plates with cheaper polymer materials that can be embossed at lower temperatures. The polymer substrate can be easily formed and discarded or reused without the thermal expansion constraints of metal, enabling precise micrometer-level wrinkle control
2Reliability
If conventional cholesteric liquid crystal film is used, then selective light reflection is achieved, but reflected wavelength varies significantly with viewing angle
Solution Approach 1:
The patent introduces a micro-wrinkled (curved) structure on the film surface that creates multiple reflection angles. The undulating topography causes light to reflect at various angles simultaneously, making the reflected wavelength appear consistent across different viewing angles by averaging out the angle-dependent wavelength variations
Solution Approach 2:
The patent transfers the micro-wrinkled structure pattern from a template substrate to the cholesteric liquid crystal film. This copied surface topology enables the film to maintain color consistency across viewing angles without requiring changes to the liquid crystal material composition
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 resulting cholesteric liquid crystal film maintains consistent color appearance across various viewing angles due to its micro-wrinkled structure, enabling a wide viewing angle and reduced angle dependence of reflected wavelength.
Implementation Method 1
a step of preparing a micro-wrinkle-structured substrate by stretching the elastic polymer substrate in one direction and removing the stretching force
Implementation Method 2
stabilizing the layer through photopolymerization
Implementation Method 3
The resulting cholesteric liquid crystal film maintains consistent color appearance across various viewing angles due to its micro-wrinkled structure, enabling a wide viewing angle and reduced angle dependence of reflected wavelength
Data Source
AI summary
In a method for manufacturing a cholesteric liquid crystal film, an elastic polymer substrate is prepared by impregnating, on one or both sides of a first polymer film, a second polymer having a modulus different from that of the first polymer, a micro-wrinkle-structured substrate is prepared by stretching the elastic polymer substrate in one direction and removing the stretching force, and a micro-wrinkle-structured cholesteric liquid crystal film is prepared by transferring a cholesteric liquid crystal monomer mixture onto one side of the micro-wrinkle-structured substrate. The cholesteric liquid crystal film manufactured is induced to have a micro-wrinkled structure and, thus, has the advantage of appearing as the same color even when observed at various angles.