Helical Polymer Network in PDLC Display for Low Voltage Scattering
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Solution Overview
Problem
Reverse-type polymer dispersed liquid crystal display devices face challenges in achieving sufficient scattering while maintaining low drive voltage, as existing technologies require high drive voltages to achieve the desired scattering state and often result in high transmittance when a voltage is applied.
Innovation Solution
A polymer dispersed liquid crystal display device with a composite layer comprising a photopolymerizable liquid crystal compound and a polymer network with a helical structure, where the thickness and twisting pitch of the polymer network satisfy specific relational expressions, and a refractive index anisotropy of the liquid crystal component is within a certain range, allowing for sufficient scattering at reduced drive voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a voltage is applied to achieve the scattering state, then the scattering performance is improved, but the drive voltage becomes excessively high
Solution Approach 1:
The patent changes the fundamental alignment parameter from planar (horizontal) to homeotropic (vertical) alignment. This parameter change modifies the refractive index matching conditions, enabling effective scattering at lower drive voltages by creating a different optical anisotropy state that responds to lower electric fields
Solution Approach 2:
The patent uses a composite system combining liquid crystal components with specific refractive index characteristics and a polymer network. This composite material system creates enhanced light scattering through the interaction between the liquid crystal phase and polymer matrix, achieving better scattering performance without requiring excessively high voltages
2Illumination intensity
If the liquid crystal component and polymer network are fully aligned horizontally, then the transparent state is achieved, but the drive voltage becomes large
Solution Approach 1:
The patent inverts the conventional alignment approach by using homeotropic (vertical) alignment instead of planar (horizontal) alignment. This inversion changes the optical response characteristics, allowing the device to achieve both transparent and scattering states with lower drive voltages by exploiting vertical orientation effects rather than horizontal alignment
3Reliability
If one type of polarized light does not sense the refractive index difference, then the scattering efficiency is reduced, but changing the alignment state is required
Solution Approach 1:
The patent changes the alignment parameter from planar to homeotropic, which modifies how polarized light interacts with the liquid crystal-polymer composite. This parameter change ensures that both types of polarized light can sense the refractive index difference, improving scattering efficiency without requiring complex multi-layer alignment structures
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 enables the display device to achieve low transmittance and high scattering when a voltage is applied, while maintaining high transmittance and low drive voltage, effectively addressing the limitations of existing technologies.
Implementation Method 1
a polymer network having a helical structure with a number of turns of from one to less than eight in the composite layer
Implementation Method 2
the refractive indexes of the liquid crystal component and the polymer network match, and therefore the reverse-type polymer dispersed liquid crystal display device achieves a transparent state
Data Source
AI summary
Provided is a polymer dispersed liquid crystal display device including: a pair of substrates including an electrode on at least one substrate; and a composite layer disposed between the pair of substrates. The composite layer includes a liquid crystal component and a polymer network constituted by a cured product of a photopolymerizable liquid crystal compound, and is in a transparent state when no voltage is applied and in a scattering state when a voltage is applied, and the polymer network has a helical structure with a number of turns of from one to less than eight in the composite layer.