FFS Liquid Crystal Display Element with Negative Dielectric Anisotropy
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Solution Overview
Problem
Existing liquid crystal display elements, particularly those in the FFS mode, face challenges in achieving high transmittance and power efficiency due to the large potential difference gradient caused by the small inter-electrode distance, leading to issues like flicker and burn-in, which are difficult to predict and mitigate with conventional n-type liquid crystal compositions.
Innovation Solution
A liquid crystal display element is designed with a specific n-type liquid crystal composition having negative dielectric anisotropy, a nematic phase-isotropic transition temperature of 60° C. or more, and a dielectric anisotropy of 1.5 or higher, optimized for use in FFS mode with a configuration that includes a transparent insulating substrate, a liquid crystal layer, and electrodes satisfying specific voltage and inter-electrode distance relationships to minimize flicker and enhance display characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the inter-electrode distance is reduced to improve opening ratio and transmittance, then the opening ratio and transmittance are improved, but the potential difference gradient becomes very large causing display defects like flicker and burn-in
Solution Approach 1:
The patent changes the dielectric anisotropy parameter of the liquid crystal composition from positive to negative, and optimizes other parameters such as viscosity and refractive index anisotropy, to enable stable operation under high potential difference gradient conditions while maintaining high transmittance
Solution Approach 2:
The patent uses a composite liquid crystal composition containing multiple components including compounds of formula (I) and (II) in specific ratios, along with additives, to achieve optimized overall properties that balance high transmittance with resistance to display defects under large potential difference gradient
2Use of energy by moving object
If p-type liquid crystal composition is used in FFS mode, then the voltage is easily lowered, but the fringe electric field causes liquid crystal molecules to tilt and transmittance deteriorates
Solution Approach 1:
The patent inverts the conventional approach by using n-type liquid crystal composition with negative dielectric anisotropy instead of p-type with positive dielectric anisotropy. This inversion causes liquid crystal molecules to align with their major axis parallel to the electrode surface while responding to the fringe electric field in a way that maintains transmittance
3Reliability
If n-type liquid crystal composition for VA mode is used, then the material properties are optimized for VA, but the large potential difference gradient in FFS mode causes unpredictable effects like drip mark and burn-in
Solution Approach 1:
The patent optimizes specific parameters of the n-type liquid crystal composition including dielectric anisotropy (Δε ≤ -1.5), viscosity (η ≤ 200 mPa·s), and refractive index anisotropy (Δn ≥ 0.08) to ensure stable performance under the high potential difference gradient conditions of FFS mode, preventing display defects
Solution Approach 2:
The patent ensures the liquid crystal composition has appropriate dynamic properties including response time and rotational viscosity that allow the liquid crystal molecules to respond quickly and stably to the high potential difference gradient, preventing flicker and other time-dependent display defects
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 high-speed responsive liquid crystal display element with reduced display defects like flickering, offering excellent display characteristics suitable for applications such as liquid crystal TVs and monitors, while also improving power efficiency and suppressing drip marks.
Implementation Method 1
a liquid crystal composition having negative dielectric anisotropy... in the case of using the n-type liquid crystal composition, since the polarization direction of the n-type composition is the minor axis direction of the molecules, the influence of the fringe electric field simply rotates the liquid crystal molecules along the major axis and the major axis of the molecule is maintained in a parallel arrangement
Implementation Method 2
a transition temperature of the nematic phase-isotropic liquid of 60° C. or more
Data Source
AI summary
The present invention provides a liquid crystal display element that exhibits a large potential-difference gradient due to inter-electrode distance in FFS mode or the like and contains one or more compounds selected from the group of compounds represented by General Formula (I) and one or more compounds selected from the group of compounds represented by General Formula (II). The liquid crystal display element of the present invention provides a liquid crystal display element which uses a liquid crystal composition with negative dielectric anisotropy and makes it possible to realize excellent display characteristics such as flicker when used in a liquid crystal display element that exhibits a large potential-difference gradient due to inter-electrode distance in FFS mode or the like, without deteriorating the burn-in characteristics of the display element or various liquid crystal-display-element characteristics such as dielectric anisotropy, viscosity, maximum nematic-phase temperature, nematic-phase stability at low temperatures, or γ1.