Polymerizable Liquid Crystal Compound for Reverse Wavelength Dispersion
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Solution Overview
Problem
Current phase retarders, particularly those used in liquid crystal display devices, face challenges in achieving stable reverse wavelength dispersion and are often thick, making them unsuitable for thin-layer applications, and their production is complex and costly due to the need for laminating multiple optically anisotropic layers.
Innovation Solution
A polymerizable liquid crystal compound with specific mesogen groups and linkers that exhibit normal wavelength dispersion characteristics, allowing for the creation of thin, optically anisotropic bodies with stable reverse wavelength dispersion, even when used with a photo-alignment layer, by incorporating polymerizable groups for crosslinking and improved solubility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a laminate-type phase retarder is used to achieve reverse wavelength dispersion, then the phase difference can be maintained across a wide wavelength band, but the production process becomes complicated and costly due to the need to laminate multiple optically anisotropic layers
Solution Approach 1:
The patent merges multiple optically anisotropic layers into a single integrated layer by incorporating multiple mesogen groups with different wavelength dispersion characteristics into one liquid crystal composition. This allows the composition to exhibit composite optical properties (reverse wavelength dispersion) without requiring physical lamination of separate films, thus simplifying the production process while maintaining phase difference stability across wide wavelength bands
Solution Approach 2:
The patent uses a composite liquid crystal composition containing multiple types of mesogen groups (first, second, third, and fourth mesogen groups) with different optical anisotropy characteristics. This composite approach enables the single layer to achieve reverse wavelength dispersion that would otherwise require multiple laminated layers, resolving the contradiction between optical performance and production complexity
2Ease of manufacture
If film drawing is used to induce reverse dispersion in a single phase retarder, then the production process is simplified, but the plate thickness becomes 100 μm or more, making it unsuitable for thin-layer liquid crystal display devices
Solution Approach 1:
The patent changes the fundamental approach from mechanical film drawing to chemical composition design by selecting specific mesogen group combinations and ratios. This allows reverse wavelength dispersion to be achieved through molecular arrangement and optical properties rather than physical stretching, enabling thin film formation (suitable for LCD devices) while maintaining production simplicity
Solution Approach 2:
The patent achieves reverse wavelength dispersion locally within the liquid crystal molecules through specific mesogen group configurations rather than requiring global film structure modification like drawing. This allows the thin film to exhibit reverse dispersion properties inherent to its molecular composition, eliminating the need for thick plates
3Reliability
If non-liquid crystal materials are added to induce reverse wavelength dispersion, then reverse dispersion can be achieved, but the liquid crystalline characteristics are lost when the mixing ratio is high
Solution Approach 1:
The patent changes the approach from adding non-liquid crystal materials to using liquid crystal materials with specific mesogen group structures that inherently provide reverse wavelength dispersion. By selecting mesogen groups with appropriate aromatic rings and structural characteristics, the composition maintains liquid crystalline properties while achieving the desired optical dispersion, eliminating the need for high concentrations of non-LC additives
4Ease of manufacture
If common resin films are used for phase retarders, then the production is simple, but they show normal wavelength dispersion instead of reverse wavelength dispersion
Solution Approach 1:
The patent develops a composite liquid crystal composition with specifically designed mesogen group combinations that inherently exhibit reverse wavelength dispersion. This composition can be processed into films using simple coating methods similar to common resin films, thus maintaining production simplicity while achieving the required reverse dispersion optical characteristic
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 polymerizable liquid crystal compound enables the production of thin, optically anisotropic films with stable reverse wavelength dispersion, enhancing processability and solubility, and effectively realizing reverse wavelength dispersion, suitable for various optical and electronic devices.
Implementation Method 1
a) A polymerizable liquid crystal composition is coated on a substrate, b) The coated substrate is irradiated with UV light to perform UV-curing, thereby producing an optically anisotropic body
Implementation Method 2
When a light passes through an electromagnetic phase retarder, the polarization direction (direction of electric field vector) becomes a sum of two elements (an ordinary ray and an extraordinary ray) parallel or perpendicular to the optic axis
Data Source
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AI summary
The present description relates to a polymerizable liquid crystal compound, a polymerizable liquid crystal composition including the same, and an optically anisotropic body. The polymerizable liquid crystal compound includes a radical derived from the first liquid crystal molecule including a mesogen group having a non-aromatic ring; a radical derived from the second liquid crystal molecule including a mesogen group that has a structure different from said mesogen group having a non-aromatic ring and includes a ring containing a double bond; and a linker that has a specific structure and links the sp3-hybridized carbon in the non-aromatic ring of the radical derived from the first liquid crystal molecule and the sp2-hybridized carbon in the mesogen group of the radical derived from the second liquid crystal molecule, wherein at least one of the radicals derived from the first and the second liquid crystal molecules may include one or more polymerizable groups which are connected to the mesogen group directly or via spacer groups. Such polymerizable liquid crystal compound makes it possible to exhibit stable reverse wavelength dispersion solely or by being mixed with other liquid crystal materials.