Liquid Crystal Display Device with Polymer Network for Off-Response Speed
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Solution Overview
Problem
Liquid crystal display devices face challenges in achieving a high off-response speed while maintaining a good balance between drive voltage and transmittance, stability over time, and a high voltage holding ratio, especially when subjected to curving or external forces.
Innovation Solution
A liquid crystal display device with a polymer component that focuses on dynamic viscoelasticity, specifically a loss tangent range of 0.1 to 1, to enhance off-response speed and stability, and a polymer network structure that supports alignment on curved surfaces and reduces alignment variations under pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If polymer concentration is increased to improve off-response speed, then off-response speed increases, but device characteristics (drive voltage, transmittance) become unstable and vary with production conditions
Solution Approach 1:
The patent changes the parameter of polymer concentration from high (1-40% by mass) to low (0.01-5% by mass), and introduces a specific viscosity parameter (100-10,000 mPa·s) to control the polymer's flow and relaxation behavior. This parameter optimization resolves the contradiction by achieving sufficient off-response speed while maintaining characteristic stability.
Solution Approach 2:
The patent creates a composite liquid crystal composition combining liquid crystal molecules with polymer components in specific ratios, where the polymer provides anchoring force for off-response while the liquid crystal maintains optical properties. This composite approach balances off-response speed with stable drive voltage and transmittance characteristics.
2Reliability
If ultraviolet radiation amount is increased to ensure complete polymerization, then off-response characteristics are maintained, but liquid crystal material degrades and voltage holding ratio decreases
Solution Approach 1:
The patent optimizes ultraviolet radiation parameters by specifying irradiation energy density (1-100 mJ/cm²) and using photopolymerization initiators with specific absorption characteristics. This controlled parameter approach ensures complete polymerization for stable off-response while preventing liquid crystal degradation and maintaining high voltage holding ratio.
3Speed
If polymer concentration is increased to improve off-response, then off-response speed increases, but drive voltage and transmittance balance deteriorates
Solution Approach 1:
The patent optimizes polymer concentration to 0.01-5% by mass and controls polymer viscosity at 100-10,000 mPa·s, creating optimal anchoring force without excessive polymer content. This parameter control achieves improved off-response speed while maintaining good drive voltage and transmittance balance.
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 provides a liquid crystal display device with improved off-response speed, balanced drive voltage and transmittance, and high voltage holding ratio, while maintaining stability and resistance to curving and external forces.
Implementation Method 1
the polymerizable compound is polymerized by UV radiation to form a polymer layer on an alignment film
Implementation Method 2
the attractive interaction between the polymer and liquid crystal molecules is utilized to facilitate the relaxation to the initial alignment state during the switching off response
Implementation Method 3
the liquid crystal layer has a loss tangent in the range of 0.1 to 1 at a measurement frequency of 1 Hz
Data Source
AI summary
To provide a liquid crystal display device that has a high off-response speed and a good balance between drive voltage and transmittance, is stable over time, and also has a high voltage holding ratio. A liquid crystal display device in which a liquid crystal layer containing a polymer network (A) and a liquid crystal composition (B) is disposed between two substrates having an electrode on at least one side thereof and having transparent properties on at least one side thereof, and the loss factor (tan δ) (loss modulus/storage modulus) of the liquid crystal layer calculated from the storage modulus (Pa) and the loss modulus (Pa) in a sinusoidal vibration measured with a rheometer at 25° C. and at a measurement frequency of 1 Hz ranges from 0.1 to 1.