Polymer Sustained Alignment Liquid Crystal Display
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Solution Overview
Problem
Liquid crystal display devices face challenges in achieving a balance of short response time, high voltage holding ratio, low threshold voltage, large contrast ratio, and long service life, while also requiring a liquid crystal composition with high maximum temperature, low minimum temperature, small viscosity, suitable optical anisotropy, large negative dielectric anisotropy, high stability to ultraviolet light, and high stability to heat.
Innovation Solution
A polymer sustained alignment mode liquid crystal display device incorporating a liquid crystal alignment film with polyamic acid or polyamic acid ester as a main component and polyorganosiloxane as an accessory, along with a liquid crystal composition containing specific compounds that enhance dielectric anisotropy and stability, allowing for controlled alignment of liquid crystal molecules.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional liquid crystal composition is used, then the device can operate, but the response time is long and the voltage holding ratio is insufficient
Solution Approach 1:
The patent modifies the chemical composition parameters by incorporating specific compounds (cyclic carbonate compounds, compounds with ester groups, and compounds with heteroatoms) to achieve optimal balance between response time and voltage holding ratio. The composition includes compounds represented by formulas (1) and (2) with specific structural parameters that tune the liquid crystal properties.
Solution Approach 2:
The patent creates a composite liquid crystal composition by mixing multiple compounds with different functional groups and molecular structures. The composition includes cyclic carbonate compounds, ester compounds, and heteroatom-containing compounds in specific ratios to achieve synergistic effects that improve both response time and voltage holding ratio simultaneously.
2Speed
If the viscosity of the liquid crystal composition is reduced to shorten response time, then the response time improves, but the stability to ultraviolet light and heat deteriorates
Solution Approach 1:
The patent adjusts the molecular weight and structural parameters of the liquid crystal compounds to achieve low viscosity while maintaining stability. Specific compounds with formulas (1) and (2) are selected to provide the right balance between molecular mobility (for fast response) and structural stability (for UV and heat resistance).
Solution Approach 2:
The patent uses stable molecular structures that resist degradation from UV light and heat, ensuring long-term durability. The cyclic carbonate and heteroatom-containing compounds provide structural rigidity that maintains stability even at low viscosities required for fast response times.
3Illumination intensity
If the optical anisotropy is increased to improve contrast ratio, then the contrast ratio improves, but the threshold voltage increases leading to higher power consumption
Solution Approach 1:
The patent optimizes the optical anisotropy parameter by selecting compounds with specific molecular structures that provide adequate contrast ratio without excessive values. The composition balances optical properties with electrical properties to achieve energy efficiency.
Solution Approach 2:
The patent creates local variations in molecular orientation and anisotropy within the liquid crystal composition to achieve high contrast ratio in the display region while maintaining lower threshold voltage characteristics. The specific compound structures enable localized optimization of optical and electrical properties.
4Temperature
If the temperature range of the nematic phase is expanded to improve usable temperature range, then the device can operate across wider temperatures, but the viscosity characteristics at extreme temperatures worsen
Solution Approach 1:
The patent adjusts the phase transition temperature parameters by selecting compounds with specific melting points and clearing points. The cyclic carbonate and heteroatom-containing compounds are chosen to extend the nematic phase temperature range while maintaining acceptable viscosity characteristics across the expanded temperature range.
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 enables a liquid crystal display device with improved response time, voltage holding ratio, contrast ratio, and service life, while maintaining stability across various temperature ranges and environmental conditions.
Implementation Method 1
A liquid crystal composition having negative dielectric anisotropy for use in a liquid crystal display device
Implementation Method 2
a polymer sustained alignment mode liquid crystal display device
Data Source
AI summary
Provided is a liquid crystal display device having characteristics such as a short response time, a large voltage holding ratio, low threshold voltage, a large contrast ratio and a long service life. A polymer sustained alignment mode liquid crystal display device includes an electrode group formed on one or both of a pair of substrates arranged with facing each other, a plurality of active devices connected to the electrode group, liquid crystal alignment films formed on surfaces facing each other of the pair of substrates, respectively, and a liquid crystal composition interposed between the pair of substrates, in which the liquid crystal alignment film contains at least one polymer selected from polyorganosiloxane, polyamic acid, polyamic acid ester and polyimide, and the liquid crystal composition contains a specific compound having negative dielectric anisotropy as a first component.