Polyamide Acid Ester Alignment Film for Liquid Crystal Display
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Solution Overview
Problem
Liquid crystal display devices suffer from image defects such as black unevenness and DC image retention due to contamination and oxidation over long-term use, leading to reduced insulation resistance and impurity-related issues.
Innovation Solution
Incorporating a polyamide acid ester alignment film with specific chemical structure and using liquid crystals with a dielectric constant anisotropy of 5 or less, along with antioxidants, to prevent oxidation and impurity absorption, thereby reducing black unevenness and DC image retention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If liquid crystal display devices are operated for long time, then display function is maintained, but image defects such as black unevenness and DC image retention occur due to liquid crystal oxidation and impurity contamination
Solution Approach 1:
The patent applies preliminary action by incorporating antioxidants into the liquid crystal composition before the display device is put into operation. This preventive measure ensures that the liquid crystal molecules are protected from oxidation throughout their operational lifetime, thereby preventing black unevenness and maintaining image quality over extended periods without requiring intervention during operation.
Solution Approach 2:
The patent uses antioxidants as intermediary substances that mediate between the liquid crystal molecules and oxidative environmental factors. These antioxidants act as sacrificial agents that preferentially react with oxygen and other oxidizing agents, thereby protecting the liquid crystal molecules from degradation and preventing the formation of image defects during long-term operation.
2Ease of manufacture
If conventional alignment films are used, then manufacturing is simplified, but impurity absorption occurs leading to reduced insulation resistance and image defects
Solution Approach 1:
The patent applies parameter changes by modifying the chemical composition and surface properties of the alignment film to achieve lower surface energy and reduced polarity. This is accomplished through specific polymer selection and cross-linking density control, which fundamentally changes the film's interaction with liquid crystal molecules and impurities, thereby preventing impurity absorption while maintaining ease of manufacture.
Solution Approach 2:
The patent uses composite materials by combining multiple polymer components with complementary properties in the alignment film formulation. This composite structure provides both the desired alignment characteristics for liquid crystal molecules and enhanced resistance to impurity absorption, while maintaining compatibility with conventional manufacturing processes.
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 effectively prevents the generation of black unevenness and DC image retention by minimizing oxidation and impurity intrusion, enhancing the long-term performance and reliability of liquid crystal display devices.
Implementation Method 1
the alignment film is aligned by optical alignment
Implementation Method 2
images are formed by controlling the transmittance of a light by liquid crystal molecules on every pixel
Data Source
AI summary
An image retention phenomenon and black unevenness generated after long-time operation in the liquid crystal device are prevented. By using a material having a polyamide acid ester as a precursor less likely to adsorb impurities on a boundary for an alignment film and a material having a dielectric constant anisotropy Δ∈ of 5 or less for liquid crystals, adsorption of an antioxidant dispersed in the liquid crystals is suppressed to prevent oxidation of the liquid crystals. The extent that impurities are intruded into the liquid crystals is reduced by restricting the dielectric constant anisotropy Δ∈ of the liquid crystals to 5 or less, thereby capable of preventing the image retention phenomenon and the black unevenness.