Polymerizable Liquid Crystal Composition Air Curing
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Solution Overview
Problem
Current polymerizable liquid crystal compositions for biaxial films face challenges in achieving sufficient front phase difference and light resistance while being cured in air without the need for inert gas atmospheres, as existing initiators either fail to provide adequate performance or require complex and costly processes.
Innovation Solution
A polymerizable liquid crystal composition is developed containing a photoinitiator with a light absorption band in the 280-400 nm range and a light-absorbing agent with matching absorption bands, allowing for air-curable biaxial films with enhanced front phase difference by using a photo-radical polymerization initiator, such as oxime esters or acylphosphine oxides, without the need for inert gas atmospheres.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a dichromatic initiator is used to achieve both dichromatism and polymerization, then the front phase difference is improved, but the formulation is difficult and production cost increases due to the need for inert gas atmosphere
Solution Approach 1:
The patent divides the optical function into two separate components: a dichroic liquid crystal compound that provides dichromatism and a separate photopolymerizable compound that provides polymerization. This segmentation allows each component to be optimized independently, eliminating the need for complex dichromatic initiators and inert gas atmospheres while maintaining the required front phase difference of 40 nm or more.
Solution Approach 2:
The patent introduces a photopolymerizable compound as an intermediary substance that absorbs UV light and initiates polymerization without requiring dichromatism. This intermediary allows the system to achieve polymerization through a different mechanism (photopolymerization rather than dichromatic polymerization), thereby simplifying the overall formulation and eliminating the need for inert gas protection.
2Ease of manufacture
If a typical polymerization initiator is used to enable air curing, then the production process is simplified, but the front phase difference is insufficient (less than 40 nm)
Solution Approach 1:
The patent changes the optical parameters of the liquid crystal compound by introducing a dichroic liquid crystal compound with specific optical properties (absorption coefficient of 100 to 10,000 at 280-400 nm). This parameter change enables the compound to provide both dichromatism and sufficient light absorption for polymerization initiation, achieving a front phase difference of 40 nm or more while allowing air curing without inert gas atmospheres.
3Manufacturing precision
If a compound with carbon-carbon triple bond is added to increase front phase difference, then the front phase difference improves (to 30 nm or more), but light resistance deteriorates causing yellowing
Solution Approach 1:
The patent changes the chemical structure parameter by replacing carbon-carbon triple bonds with carbon-carbon double bonds in the liquid crystal compound. This structural modification maintains the ability to achieve sufficient front phase difference (40 nm or more) while significantly improving light resistance and preventing yellowing during UV irradiation and subsequent use.
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 composition enables increased front phase difference and improved light resistance in biaxial films, simplifying the production process and reducing costs by allowing curing in air, while maintaining high heat resistance and reliability.
Implementation Method 1
a photoinitiator having a light absorption band in a wavelength range of 280 to 400 nm
Implementation Method 2
a light-absorbing agent having a light absorption band in a wavelength range of 280 to 400 nm
Implementation Method 3
polymerizable cholesteric liquid crystal
Implementation Method 4
biaxial films composed of a polymerizable cholesteric material
Data Source
Figure 1~2
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Figure 5~6
AI summary
The present invention provides a polymerizable liquid crystal composition containing polymerizable liquid crystal compounds and a photoinitiator, wherein the photoinitiator has a light absorption band in a wavelength range of 280 to 400 nm; and at least one of the polymerizable liquid crystal compounds has a light absorption band in a wavelength range of 320 to 400 nm or a light-absorbing agent having a light absorption band in a wavelength range of 280 to 400 nm is contained. Thus, there is provided a material that can be cured in the air without replacing the atmosphere with an inert gas during irradiation with ultraviolet rays and that can achieve the characteristics required for a biaxial film, such as a sufficiently large front phase difference.