Polymerizable liquid crystal material and polymerized liquid crystal film
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Solution Overview
Problem
Current methods for producing multilayer cholesteric polymer films face challenges such as high temperature requirements for uniform alignment, limited material choices due to differing glass transition temperatures, and issues with dewetting and haze, particularly when using polymers with high glass temperatures or surfactants.
Innovation Solution
A polymerizable LC material comprising reactive mesogenic compounds, chiral compounds, and a block copolymer with a polyfluorooxetane block bonded to a polyether block, which allows for improved birefringence, solubility, and resistance to UV light yellowing, and facilitates better dewetting behavior and alignment without the need for surfactants.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high glass transition temperature polymers are used to achieve good thermal stability, then alignment uniformity deteriorates due to dewetting and haze
Solution Approach 1:
A surfactant is introduced as an intermediary substance between the polymer and the liquid crystal mixture. The surfactant modifies the surface properties and interfacial tension, preventing dewetting and haze formation even when using high glass transition temperature polymers, thus maintaining both thermal stability and alignment uniformity
Solution Approach 2:
The glass transition temperature of the polymer is modified by incorporating surfactant molecules that alter the polymer chain mobility and intermolecular forces. This parameter change allows the polymer to maintain thermal stability while reducing dewetting tendency and improving alignment uniformity
2Manufacturing precision
If surfactants are added to prevent dewetting, then alignment improves, but material complexity increases
Solution Approach 1:
The surfactant serves multiple functions simultaneously: it acts as a dewetting prevention agent, an alignment promoter, and a haze reducer. This multi-functionality reduces material complexity by eliminating the need for separate additives for each function
3Illumination intensity
If tolane groups are incorporated to increase birefringence, then optical properties improve, but UV light resistance deteriorates due to yellowing
Solution Approach 1:
The patent creates a composite material system combining polymer, liquid crystal mixture, and surfactant. This composite structure allows the polymer matrix to provide UV stability while the liquid crystal mixture maintains high birefringence, achieving both optical performance and UV light resistance
4Illumination intensity
If high birefringence materials are used to broaden reflection bandwidth, then optical properties improve, but solubility deteriorates
Solution Approach 1:
The surfactant creates local microenvironments with modified solvation properties. These local quality changes at the molecular level allow high birefringence materials to dissolve uniformly in the liquid crystal mixture, maintaining both optical properties and solubility
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 production of polymer films with enhanced optical properties, improved alignment, and reduced haze, allowing for broader reflection bandwidths and easier multilayer stacking, suitable for applications in displays and security devices.
Implementation Method 1
The manufacture of RM film products with high birefringence is of high importance for manufacturing optical components
Implementation Method 2
Cholesteric liquid crystal (CLC) materials, when formed into thin layers with planar alignment, exhibit the well-known effect of selective reflection of light
Implementation Method 3
mesogenic tolane derivatives are known for example from U.S. Pat. No. 6,514,578 B1... Generally tolane groups are relatively reactive and are mostly unsuited to light exposure, making them difficult to utilize in many optical applications due to yellowing or other degradation effects
Data Source
AI summary
A polymerizable LC material comprising one or more reactive mesogenic compounds, one or more chiral compounds and a block copolymer that comprises at least one polyfluorooxetane block bonded to a polyether block, said polyfluorooxetane block having a repeating unit of the formulaFurther, a method for its preparation, a polymer film obtainable from a corresponding polymerizable LC material, a method of preparation of such polymer film, and the use of such polymer film and said polymerizable LC material in optical, electro-optical, decorative or security devices.