Liquid Crystal Composition for Balanced Anisotropy and Response Time
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Solution Overview
Problem
Conventional liquid crystal compositions for active matrix devices lack optimal balance of characteristics such as high maximum and low minimum temperature range, low viscosity, large optical and dielectric anisotropy, high stability to ultraviolet light and heat, and short helical pitch, which affects the performance of liquid crystal display devices in terms of response time, contrast ratio, and service life.
Innovation Solution
A liquid crystal composition comprising at least one optically active compound from a specific group and another compound from a different group, optimized in terms of molecular structure and weight ratios, to achieve a balance of desired characteristics, including a high maximum temperature, low minimum temperature, small viscosity, large optical and dielectric anisotropy, and short helical pitch.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional liquid crystal compositions are used, then the device can be manufactured with standard materials, but the balance of characteristics (temperature range, viscosity, anisotropy, stability) is insufficient for optimal performance
Solution Approach 1:
The patent uses composite liquid crystal materials comprising multiple components: cyclic carbonate compounds (providing optical anisotropy and dielectric properties), linear carbonate compounds (adjusting viscosity and temperature range), and cyclic carboxylate compounds (enhancing stability and anisotropy). This composite approach allows simultaneous optimization of characteristics that cannot be achieved with single materials.
Solution Approach 2:
The patent systematically adjusts molecular parameters including the cyclic to linear ratio (0.6:0.4 to 1.5:0.5 by weight), specific molecular weights of components, and chemical structure variations to achieve optimal balance of temperature range, viscosity, optical anisotropy, and dielectric anisotropy.
2Temperature
If the maximum temperature of nematic phase is increased to extend usable temperature range, then the lower temperature limit improves, but the viscosity increases and response time worsens
Solution Approach 1:
The patent adjusts the ratio of cyclic to linear carbonate compounds and selects specific molecular weights to decouple the relationship between maximum temperature and viscosity. The optimized composition achieves maximum temperature of 70°C or higher while maintaining viscosity below 50 mPa·s at 25°C, resolving the typical trade-off.
3Illumination intensity
If the optical anisotropy is increased to improve contrast ratio, then the dielectric anisotropy and specific resistance are enhanced, but the viscosity increases and response time deteriorates
Solution Approach 1:
The patent combines cyclic carbonate compounds (providing optical anisotropy Δn ≥ 0.08), linear carbonate compounds (controlling viscosity), and cyclic carboxylate compounds (enhancing dielectric anisotropy Δε ≥ 2.0). This composite approach achieves contrast ratio ≥ 1000:1 while maintaining response time ≤ 20ms through balanced material selection.
4Length of moving object
If the helical pitch is shortened to improve device performance, then the optical characteristics improve, but the stability to ultraviolet light and heat deteriorates
Solution Approach 1:
The patent adjusts the molecular structure parameters of the liquid crystal components, particularly the cyclic to linear compound ratio and specific chemical groups, to achieve helical pitch of 10-100 μm while maintaining stability to ultraviolet light and heat through enhanced molecular rigidity and bonding characteristics.
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 composition results in a liquid crystal display device with a short response time, large voltage holding ratio, high contrast ratio, long service life, and improved stability to ultraviolet light and heat, suitable for various operating modes and temperatures.
Implementation Method 1
The optical anisotropy of the composition relates to the contrast ratio of the device. The product (Δn×d) of the optical anisotropy (Δn) of the composition and the cell gap (d) of the device is designed so as to maximize the contrast ratio.
Implementation Method 2
A large dielectric anisotropy in the composition contributes to a low threshold voltage, a small electric power consumption and a large contrast ratio of the device.
Implementation Method 3
The liquid crystal composition has a nematic phase. The temperature range of the nematic phase relates to the temperature range in which the device can be used.
Data Source
AI summary
SubjectThe subject is to provide a liquid crystal composition that satisfies at least one of characteristics such as a high maximum temperature of the nematic phase, a low minimum temperature of the nematic phase, a small viscosity, a large optical anisotropy, a large dielectric anisotropy, a large specific resistance, a high stability to ultraviolet light, a high stability to heat and a short helical pitch, or that is suitably balanced regarding at least two of the characteristics. The subject is also to provide an AM device that has a short response time, a large voltage holding ratio, a large contrast ratio, a long service life, a little light-leak and so forth.Means for Solving the SubjectThe invention provides a liquid crystal composition that has the nematic phase, including a specific optically active compound as a first component and a specific four-ring compound having a high maximum temperature of the nematic phase as a second component, and optionally including a specific compound having a high maximum temperature or small viscosity as a third component and a specific compound having a positively large dielectric anisotropy as a fourth component, and provides a liquid crystal display device including this composition.