In-Cell Retardation Layer Polymerization for Voltage Holding Ratio Stability
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Solution Overview
Problem
Liquid crystal display devices with in-cell retardation layers face issues of reduced voltage holding ratio and increased ion density, leading to defects like white spots, uneven alignment, and image-sticking due to impurities in the retardation layer affecting the liquid crystal layer.
Innovation Solution
Incorporating a liquid crystal composition with specific compounds in the liquid crystal layer and an optically anisotropic body formed through polymerization of a polymerizable liquid crystal composition with specific compounds in the retardation layer to prevent impurity-related issues, ensuring the liquid crystal display device maintains a stable voltage holding ratio and reduces defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a retardation layer is disposed inside the liquid crystal cell (in-cell type) to enhance productivity and reduce thickness, then manufacturing efficiency is improved and device thickness is reduced, but impurities in the retardation layer affect the liquid crystal layer causing reduced voltage holding ratio and increased ion density
Solution Approach 1:
The patent changes the chemical composition parameters of the liquid crystal material used in the retardation layer, specifically using liquid crystal compounds with specific molecular structures (formulae 1-6) that have low impurity content and high chemical stability. This parameter change allows the retardation layer to maintain its optical functions while preventing impurity migration to the liquid crystal layer, thus resolving the contradiction between manufacturing efficiency and voltage holding ratio.
Solution Approach 2:
The patent employs composite material design by combining multiple liquid crystal compounds with specific properties in the retardation layer. The composite composition includes compounds from formulae (1)-(6) with specific ratios, creating a material that simultaneously provides the necessary optical anisotropy for retardation function while maintaining low impurity content and high stability, preventing degradation of the liquid crystal layer.
2Device complexity
If a retardation layer is disposed inside the liquid crystal cell to eliminate attachment steps, then manufacturing complexity is reduced, but defective display such as white spots and uneven alignment occurs due to impurity migration
Solution Approach 1:
The patent modifies the chemical parameters of the retardation layer material by selecting liquid crystal compounds with specific molecular structures (formulae 1-6) that exhibit high chemical stability and low impurity generation. This parameter change ensures that even though the retardation layer is integrated inside the cell simplifying manufacturing, the display quality is maintained by preventing impurity-related defects such as white spots and uneven alignment.
3Device complexity
If the liquid crystal layer and retardation layer are not completely separated, then device structure is simplified, but impurities from the retardation layer migrate to the liquid crystal layer causing image-sticking and defective display
Solution Approach 1:
The patent converts the potential harm of close contact between the retardation layer and liquid crystal layer into a benefit by selecting liquid crystal compounds with specific structures (formulae 1-6) that have inherently low impurity content and high stability. Instead of using complex separation structures, the patent makes the material itself resistant to impurity migration, thus simplifying the device structure while preventing image-sticking and defective display.
Solution Approach 2:
The patent changes the chemical composition parameters of the retardation layer material to use liquid crystal compounds with specific molecular structures (formulae 1-6) that exhibit superior chemical stability and low impurity generation. This parameter change eliminates impurity migration issues without requiring complete separation between layers, maintaining structural simplicity while preventing harmful effects.
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 effectively prevents reductions in voltage holding ratio and ion density, eliminating defects such as white spots and uneven alignment, thereby enhancing the display quality of the liquid crystal display device.
Implementation Method 1
an optically anisotropic body formed through polymerization of a polymerizable liquid crystal composition containing 25 weight % or more of a liquid crystal compound having at least two polymerizable functional groups
Implementation Method 2
Liquid crystal display devices have a view angle dependency attributed to the birefringence properties of the liquid crystal molecules
Data Source
AI summary
The present invention provides a liquid crystal display device that is free from a reduction in the voltage holding ratio (VHR) of the liquid crystal layer and an increase in ion density (ID) and that enables problems of defective display, such as white spots, uneven alignment, and image-sticking, to be eliminated. In particular, the present invention provides a liquid crystal display device in which a liquid crystal composition containing a liquid crystal compound having a specific structure is used in the liquid crystal layer and in which an optically anisotropic body formed through polymerization of a polymerizable liquid crystal composition containing a specific amount of a polymerizable liquid crystal compound having a specific structure is used as an in-cell retardation layer.