Liquid Crystal Media With Self-Aligning Homeotropic Orientation
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Solution Overview
Problem
Existing liquid crystal display technologies, particularly VA and VA-IPS displays, face challenges in manufacturing complexity due to the need for polyimide layers for homeotropic alignment, which can interact negatively with the liquid crystal medium, limiting material choices and increasing production costs while sacrificing switching times and viewing angle dependency.
Innovation Solution
A liquid crystal medium comprising a low-molecular-weight component and a polymerizable self-aligning mesogen that induces homeotropic alignment without the need for polyimide layers, using compounds with specific functional groups to interact with substrate surfaces, allowing for polymerization to stabilize the alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polyimide layers are used for homeotropic alignment in VA displays, then alignment is achieved, but manufacturing complexity increases and production costs rise
Solution Approach 1:
The patent removes the polyimide alignment layer from the display structure and extracts its alignment function by incorporating self-aligning mesogenic compounds directly into the liquid crystal medium. These compounds contain specific functional groups that interact with substrate surfaces to induce homeotropic alignment, eliminating the need for separate polyimide layers while maintaining the desired alignment effect.
Solution Approach 2:
The patent merges the alignment function previously performed by separate polyimide layers with the liquid crystal medium itself. By incorporating mesogenic compounds with specific functional groups (such as hydroxyl, carboxyl, or amine groups) into the LC medium, the alignment capability is integrated directly into the liquid crystal composition, simplifying the overall device structure and manufacturing process.
2Reliability
If polyimide layers are used for homeotropic alignment, then alignment is achieved, but production costs increase
Solution Approach 1:
The patent eliminates the need for expensive polyimide alignment layers by extracting their alignment function and transferring it to the liquid crystal medium through the addition of self-aligning mesogenic compounds. This reduces material costs and simplifies the manufacturing process while maintaining effective homeotropic alignment.
Solution Approach 2:
The patent employs small amounts of mesogenic compounds with specific functional groups that can be incorporated into the liquid crystal medium at low concentrations (typically 0.1-5 wt%). These compounds serve as self-aligning agents that interact with substrate surfaces to induce homeotropic alignment, providing a cost-effective alternative to polyimide layers.
3Reliability
If polyimide layers are used, then homeotropic alignment is achieved, but material choices are limited due to negative interactions
Solution Approach 1:
The patent removes the polyimide layer that imposes compatibility constraints on liquid crystal material selection. By transferring the alignment function to self-aligning mesogenic compounds within the LC medium, the invention enables broader material choices for liquid crystal components without concerns about negative interactions with polyimide layers.
Solution Approach 2:
The patent changes the chemical parameters of the liquid crystal medium by incorporating mesogenic compounds with specific functional groups (hydroxyl, carboxyl, amine groups) that provide homeotropic alignment capability. This parameter change enables compatibility with a wider range of liquid crystal materials while maintaining effective alignment.
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
Simplifies manufacturing processes, reduces production costs, and maintains fast switching times and good viewing angle dependency without the use of polyimide layers, enhancing the performance of VA and VA-IPS displays.
Implementation Method 1
polymerizable self-aligning mesogens (polymerizable self-orientation additives) that effect a homeotropic (vertical) alignment of the LCM media on a surface or the cell walls
Implementation Method 2
allowing for polymerization to stabilize the alignment
Implementation Method 3
The principle of electrically controlled birefringence, the ECB effect (electrically controlled birefringence)
Implementation Method 4
DAP effect (deformation of upright phases), was first described in 1971 (MF Schieckel and K. Fahrenschon, 'Deformation of nematic liquid crystals with vertical orientation in electrical fields'
Data Source
AI summary
The present invention relates to liquid crystal media (LCM media) with negative or positive dielectric anisotropy, comprising a low-molecular-weight component and a polymerizable component. The polymerizable component comprises self-aligning, polymerizable mesogens (polymerizable self-orientation additives) that effect a homeotropic (vertical) alignment of the LCM media on a surface or the cell walls of a liquid crystal display (LCD). The invention therefore also includes LCD displays with homeotropic alignment of the LCM medium without orientation layers. The invention discloses novel structures for self-orientation additives that exhibit a specific position of the functional groups.