Dual-Layer Cholesteric Liquid Crystal Identification Medium
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Solution Overview
Problem
Existing identification media struggle to minimize the viewing angle at which reflected light shifts from the short wavelength side to the long wavelength side, making it difficult to immediately identify authenticity.
Innovation Solution
A dual-layer identification medium comprising a first cholesteric liquid crystal resin layer with high light transmittance at 400-425 nm and a second cholesteric liquid crystal resin layer, where the average light transmittance of the first layer is between 80% and 88%, allowing the color of reflected light to shift from the short wavelength side to the long side at a smaller viewing angle.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a cholesteric liquid crystal resin is used to create an identification medium with wavelength shifting properties, then the forgery prevention capability is improved, but the viewing angle required for the color shift to occur is large, delaying authentication
Solution Approach 1:
The identification medium is divided into multiple functional layers: a first cholesteric liquid crystal resin layer with specific transmittance characteristics (80-88% at 400-425 nm) and a second cholesteric liquid crystal resin layer. This segmentation allows each layer to contribute differently to the overall optical effect, enabling the color shift to occur at a smaller viewing angle while maintaining forgery prevention capability.
Solution Approach 2:
The invention uses a composite structure combining two different cholesteric liquid crystal resin layers with distinct optical properties. The first layer has high light transmittance at 400-425 nm wavelengths, while the second layer provides the primary wavelength shifting effect. This composite material approach enables simultaneous achievement of early color shift detection and reliable forgery prevention.
2Illumination intensity
If the light transmittance of the first resin layer is increased to allow more light through, then the color shift becomes more visible, but the viewing angle for the shift increases, making authentication slower
Solution Approach 1:
The invention optimizes the light transmittance parameter of the first cholesteric liquid crystal resin layer at wavelengths of 400-425 nm to be within the range of 80-88%. This specific parameter range allows sufficient light transmission for visible color shift while controlling the viewing angle to enable faster authentication. The parameter is precisely controlled to balance visibility and authentication speed.
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 dual-layer structure enhances the forgery prevention function by ensuring the color shift occurs at a smaller viewing angle, making it easier to authenticate the medium.
Implementation Method 1
A cholesteric liquid crystal resin film or a cholesteric liquid crystal resin pigment has a circular polarized light separation function to reflect one of counterclockwise and clockwise circular polarized light and transmit the other
Implementation Method 2
in such a film or pigment, the wavelength of reflected circular polarized light shifts to the short wavelength side as the viewing angle θ from the front direction increases
Data Source
Figure 1~2
Figure 3~4
AI summary
An identification medium comprising a first resin layer and a second resin layer in this order from a viewing side, wherein the first resin layer contains a first cholesteric liquid crystal resin that is a cured product of a first liquid crystal composition, and the first cholesteric liquid crystal resin selectively reflects light at a wavelength of 700 nm or longer and 900 nm or shorter, the second resin layer contains a second cholesteric liquid crystal resin that is a cured product of a second liquid crystal composition, and the second cholesteric liquid crystal resin selectively reflects light at a wavelength of 400 nm or longer and 500 nm or shorter, and the first resin layer has an average value of light transmittance at a wavelength of 400 nm or longer and 425 nm or shorter of 50% or more and 90% or less.