Liquid Crystal Display Vertical Alignment via Monomer Polymerization
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Solution Overview
Problem
Conventional liquid crystal display devices without alignment films face issues with insufficient controllability of liquid crystal molecule alignment, leading to display failures such as bright spots or blight lines, and reduced voltage holding ratio (VHR) due to the use of monofunctional and polyfunctional monomers under specific irradiation conditions.
Innovation Solution
A liquid crystal display device is developed using a combination of a monofunctional monomer with a biphenyl skeleton and a polyfunctional monomer that generates radicals by annealing and photoirradiation at wavelengths of not less than 340 nm, eliminating the need for an alignment film and enhancing the vertical alignment and VHR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an alignment control layer is formed by polymerizing monomers in a liquid crystal composition, then the need for an alignment film is eliminated, but the controllability of liquid crystal molecule alignment becomes insufficient
Solution Approach 1:
The patent changes the chemical structure parameters of the monomers used in the alignment control layer. Specifically, it employs monomers with particular molecular structures (such as acrylate groups combined with specific aromatic rings or alkyl chains) that can induce vertical alignment of liquid crystal molecules through photo-polymerization, thereby achieving sufficient alignment controllability without requiring an alignment film.
Solution Approach 2:
The patent uses composite monomer systems combining different functional monomers (e.g., acrylate monomers with specific aromatic or aliphatic structures) to create an alignment control layer that achieves both the elimination of alignment film and sufficient alignment controllability. The composite approach allows synergistic effects where different monomer components contribute to both alignment induction and polymerization efficiency.
2Reliability
If conventional monomers are used in the alignment control layer, then polymerization can occur, but display failures such as bright spots or bright lines occur due to defective alignment
Solution Approach 1:
The patent modifies the molecular structure parameters of the monomers to achieve proper vertical alignment of liquid crystal molecules. By selecting monomers with specific structures (such as certain aromatic rings, alkyl chain lengths, or functional group configurations), the patent ensures that the alignment control layer induces the correct molecular orientation, preventing display defects like bright spots or lines while maintaining reliable display quality.
3Object-affected harmful factors
If an alignment film is formed, then alignment treatment is needed, but this generates static electricity and dusts by rubbing
Solution Approach 1:
The patent extracts and eliminates the alignment film component from the liquid crystal display structure. Instead of using a separate alignment film that requires rubbing treatment, the patent integrates alignment functionality directly into the liquid crystal composition through photo-polymerizable monomers that form an alignment control layer, thereby removing the source of static electricity and dust generation while simplifying the alignment process.
Solution Approach 2:
The patent replaces the mechanical rubbing process with a photochemical polymerization process. Instead of mechanically rubbing an alignment film to induce alignment, the patent uses light irradiation to trigger polymerization of monomers in the alignment control layer, which then chemically induces vertical alignment of liquid crystal molecules without any mechanical contact, thereby eliminating static electricity and dust generation.
4Productivity
If the alignment film is not formed, then production steps are reduced, but the film thickness nonuniformity and contamination issues remain
Solution Approach 1:
The patent extracts and eliminates the alignment film from the production process. By using photo-polymerizable monomers that form an alignment control layer directly within the liquid crystal composition, the patent removes the separate alignment film formation step, thereby reducing production steps and improving productivity while avoiding the film thickness nonuniformity and contamination issues associated with conventional alignment films.
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 significantly reduces the occurrence of display failures, maintains high VHR, and improves light resistance in aging, providing a reliable and efficient liquid crystal display device without the need for an alignment film.
Implementation Method 1
a polyfunctional monomer that generates radicals by annealing and photoirradiation at wavelengths of not less than 340 nm
Implementation Method 2
the alignment control layer being formed by polymerizing a monofunctional monomer and a polyfunctional monomer
Data Source
AI summary
The present invention provides a liquid crystal display device that is less likely to have display failures and has high reliability and excellent light resistance in aging. The present invention relates to a liquid crystal display device, including: a pair of substrates; a liquid crystal layer containing liquid crystal molecules and interposed between the pair of substrates; and an alignment control layer for perpendicularly aligning the liquid crystal molecules, the alignment control layer being formed by polymerizing a monofunctional monomer and a polyfunctional monomer in a liquid crystal composition containing the liquid crystal molecules, the monofunctional monomer, and the polyfunctional monomer, the polyfunctional monomer generating a radical by annealing and irradiation with light at not less than 340 nm, the monofunctional monomer having a biphenyl skeleton as a core and a polymerizable group bonded to the biphenyl skeleton directly or indirectly via a spacer.