Liquid Crystal Display Photoalignment Film Anchoring Energy
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Solution Overview
Problem
Liquid crystal display devices face challenges in achieving a balance between short response time, high voltage holding ratio, low threshold voltage, large contrast ratio, long service life, and minimizing flicker, particularly due to limitations in the photoalignment method's anchoring energy and potential decreases in voltage holding ratio and light transmittance.
Innovation Solution
A liquid crystal display device incorporating a liquid crystal photoalignment film with a polymer having a photoreactive group and a composition including compounds represented by specific formulas, which enhances dielectric anisotropy, reduces viscosity, and improves the stability of liquid crystal molecules, thereby addressing the limitations of the photoalignment method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the photoalignment method is used to improve alignment precision, then manufacturing precision is improved, but the anchoring energy is insufficient which causes reliability to deteriorate
Solution Approach 1:
The patent uses a composite alignment film structure comprising a polyimide film layer and an organic solvent-soluble polyimide layer. This composite structure combines the advantages of both materials: the polyimide film provides strong anchoring energy and thermal stability, while the organic solvent-soluble polyimide layer enables precise photoalignment. The synergistic combination resolves the contradiction between alignment precision and anchoring energy by distributing these functions across different material layers.
Solution Approach 2:
The patent changes the chemical and physical parameters of the alignment film by selecting specific polyimide compounds with appropriate molecular weights, glass transition temperatures, and photo sensitivity. By optimizing these parameters, the film achieves both high anchoring energy (through strong liquid crystal interaction) and precise photoalignment (through controlled photoreaction), thereby resolving the contradiction between reliability and manufacturing precision.
2Manufacturing precision
If the photoalignment method is used to improve alignment precision, then manufacturing precision is improved, but voltage holding ratio decreases
Solution Approach 1:
The composite alignment film structure addresses the voltage holding ratio issue by using the polyimide film base layer to provide electrical stability and strong anchoring, while the organic solvent-soluble polyimide top layer provides precise photoalignment. This division of functional responsibilities ensures that the alignment precision improvement does not come at the cost of voltage holding ratio degradation.
Solution Approach 2:
The patent applies local quality by giving different regions of the alignment film different properties: the polyimide film layer provides strong anchoring and electrical stability in the bulk, while the organic solvent-soluble polyimide layer provides precise optical alignment at the surface. This localized functional differentiation resolves the contradiction between alignment precision and voltage holding ratio.
3Manufacturing precision
If the photoalignment method is used to improve alignment precision, then manufacturing precision is improved, but light transmittance decreases
Solution Approach 1:
The patent optimizes the thickness and composition parameters of the alignment film to minimize light absorption. By controlling the film thickness to be as thin as possible while maintaining sufficient anchoring energy, and by selecting polyimide compounds with appropriate optical transparency, the film achieves precise photoalignment without significantly compromising light transmittance.
4Speed
If liquid crystal composition is optimized to reduce viscosity for short response time, then response time is improved, but voltage holding ratio may deteriorate
Solution Approach 1:
The patent changes the physical parameters of the liquid crystal composition by selecting compounds with appropriate viscosity, dielectric anisotropy, and elastic constants. By optimizing these parameters within specific ranges, the composition achieves fast response time (low viscosity) while maintaining sufficient voltage holding ratio (adequate dielectric anisotropy and elastic properties), thereby resolving the contradiction between speed and reliability.
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 results in a liquid crystal display device with improved characteristics such as short response time, high voltage holding ratio, low threshold voltage, large contrast ratio, and reduced flicker, while maintaining long service life and high light transmittance.
Implementation Method 1
the composition is irradiated with ultraviolet light, while a voltage is applied between the substrates of this device. The polymerizable compound is polymerized to give a network structure of a polymer in the composition
Implementation Method 2
The optical anisotropy of the composition relates to the contrast ratio of the device. A large optical anisotropy or a small optical anisotropy, namely a suitable optical anisotropy, is necessary depending on the mode of the device
Implementation Method 3
A large dielectric anisotropy of the composition contributes to a low threshold voltage, low power consumption and a large contrast ratio of the device
Data Source
AI summary
Subject The subject is to provide a liquid crystal display device that has characteristics such as a short response time, a large voltage holding ratio, a low threshold voltage, a large contrast ratio, a long service life and a small flicker rate. Means for solution The invention relates to a liquid crystal display device including an electrode group formed on one or both of a pair of substrates that are opposed to each other, and a plurality of active devices connected to the electrode group, and a liquid crystal alignment film formed on the opposing surfaces of the pair of substrates, and a liquid crystal composition sandwiched in between the pair of substrates, and the liquid crystal composition includes at least one compound selected from the group of compounds represented by formula (1) as a first component, and relates to the liquid crystal composition included in the device and the liquid crystal alignment film included in the device: in formula (1), R1 is alkyl having 1 to 12 carbons or the like; ring A is 1,4-cyclohexylene, 1,4-phenylene or the like; Z1 is a single bond or the like; X1 and X2 are hydrogen or fluorine; Y1 is fluorine or the like; and a is 1, 2, 3 or 4.