Liquid Crystal Composition for Active Matrix Displays
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing liquid crystal compositions for active matrix devices lack sufficient high upper limit temperature, low lower limit temperature, small viscosity, large optical anisotropy, large dielectric anisotropy, high stability to ultraviolet light, and high stability to heat, which are essential for achieving short response times, large voltage holding ratios, and long service life in liquid crystal display devices.
Innovation Solution
A liquid crystal composition comprising specific compounds expressed by general formulas (I), (II), (III), (IV), and (V), with weight ratios that enhance optical anisotropy, dielectric anisotropy, and thermal stability, including type I monomers with high refractivity, type II compounds with low viscosity, type III compounds with high polarity, and type V compounds with high clearing points, to create a balanced composition for improved performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional liquid crystal compositions are used, then the device can operate, but the upper limit temperature of the nematic phase is insufficient and the lower limit temperature is too high
Solution Approach 1:
The patent uses a composite liquid crystal composition containing five different types of compounds (formulas I-V) with specific weight ratios. Each compound type contributes different properties: type I provides high refractivity and dielectric anisotropy, type II provides low viscosity and low melting point, type III provides high polarity and dielectric anisotropy, type IV provides low viscosity and high upper limit temperature, and type V provides high clearing point. The synergistic combination of these five compound types resolves the temperature range limitation of conventional single-type compositions.
Solution Approach 2:
The patent optimizes the weight ratios of the five compound types to achieve desired temperature characteristics. Specifically, the composition contains 8-50% of compound (I), 10-70% of compound (II), 5-50% of compound (III), 0-20% of compound (IV), and 0-15% of compound (V). By adjusting these parameters within specified ranges, the patent achieves a nematic phase temperature range with upper limit of 70°C or more and lower limit of -10°C or less, thereby expanding the usable temperature range.
2Reliability
If liquid crystal composition with high viscosity is used, then the composition is stable, but the response time of the device becomes long
Solution Approach 1:
The patent combines compounds with different viscosity characteristics to achieve optimal balance. Type II compounds (10-70% by weight) provide low viscosity and low melting point properties that reduce overall composition viscosity and improve response time. Type IV compounds (0-20% by weight) also contribute low viscosity while providing high upper limit temperature. This composite approach maintains composition stability while achieving short response times suitable for moving image display.
3Device complexity
If liquid crystal composition with small optical anisotropy is used, then the composition is simple, but the contrast ratio of the device becomes small
Solution Approach 1:
The patent uses a composite composition with five compound types, where type I compounds (8-50% by weight) provide high refractivity and large optical anisotropy, directly improving contrast ratio. Type III compounds (5-50% by weight) provide high polarity and dielectric anisotropy that also contribute to optical performance. The synergistic combination of these compound types achieves large contrast ratio while maintaining reasonable composition complexity through systematic design.
4Use of energy by moving object
If liquid crystal composition with small dielectric anisotropy is used, then the threshold voltage is high and power consumption is large, but the composition structure is simple
Solution Approach 1:
The patent combines compounds with different dielectric properties to achieve large dielectric anisotropy. Type I compounds provide large dielectric anisotropy, and type III compounds also provide high dielectric anisotropy due to their high polarity. The composite composition containing 8-50% of compound (I) and 5-50% of compound (III) achieves large dielectric anisotropy that reduces threshold voltage and power consumption, while the systematic design maintains compositional simplicity.
5Reliability
If liquid crystal composition with low specific resistance is used, then the voltage holding ratio is low and contrast ratio is small, but the manufacturing is easier
Solution Approach 1:
The patent uses a composite composition with five compound types that collectively provide high specific resistance at both room temperature and high temperature. This is achieved through the molecular structures of the compounds, particularly type I, III, and V compounds which have structures that inhibit ion mobility. The systematic combination of these compounds achieves high voltage holding ratio and contrast ratio while maintaining ease of manufacture through a straightforward mixing process without complex synthesis steps.
6Reliability
If liquid crystal composition with insufficient UV and heat stability is used, then the service life is short, but the composition can be simplified
Solution Approach 1:
The patent combines compounds with different stability characteristics to achieve high UV and heat stability. Type V compounds provide high clearing point and thermal stability, while the fluorinated structures in types I, II, and III compounds provide UV resistance. The composite composition systematically combines these stable compound types in specific ratios (8-50% of I, 10-70% of II, 5-50% of III, 0-20% of IV, 0-15% of V) to achieve long service life while maintaining compositional simplicity through a well-defined formulation approach.
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 achieves a wider usable temperature range, shorter response times, higher contrast ratios, lower threshold voltage, and increased service life, while maintaining stability under UV light and heat, thereby enhancing the performance of active matrix devices.
Implementation Method 1
The optical anisotropy of the composition relates to the contrast ratio of the device. A large optical anisotropy is desirable for a device having a small thickness of the liquid crystal layer.
Implementation Method 2
A large dielectric anisotropy of 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 temperature range of a nematic phase relates to the working temperature range of the device. A desirable upper limit temperature of the nematic phase is 70°C or more, and a desirable lower limit temperature of the nematic phase is -10°C or less.
Data Source
Figure 1A
Figure 1B
Figure 2
AI summary
The present invention provides a liquid crystal composition applicable to an active matrix (AM) device and having a nematic phase and positive dielectric anisotropy, and an AM liquid crystal display device comprising the liquid crystal composition. By the total weight of the liquid crystal composition, the liquid crystal composition comporises 8%-50% of compound expressed by a general formula (I), 10%-70% (by weight) of compound expressed by a general formula (II), and 5%-50% (by weight) of compound expressed by a general formula (III).