Liquid Crystal Display Alignment Film Suppressing Flicker
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Solution Overview
Problem
Liquid crystal display devices with reflective electrodes face issues of flicker and image sticking due to long-term use, caused by the reduction in Voltage Holding Ratio (VHR) and increase in residual DC voltage, particularly when using conductive materials like Al, Ag, or Cu.
Innovation Solution
Incorporating a polymer with a salicylic acid derivative functional group in the side chain of the alignment film, which forms a complex with metal ions such as Al3+, thereby suppressing oxidation-reduction reactions and reducing the generation of ions in the liquid crystal layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a reflective electrode made of highly ionizable metal (Al, Ag, Zn, Cu) is used to eliminate backlight illumination, then power consumption is reduced and the device achieves reflective display capability, but long-term use causes reduction in VHR and increase in residual DC voltage leading to flicker and image sticking
Solution Approach 1:
The patent introduces a protective film made of specific polymer materials (polyimide, polyacrylonitrile, polyacrylic acid, or their copolymers) as an intermediary layer between the reflective electrode and the liquid crystal layer. This protective film mediates the interaction by preventing direct contact between metal ions and the liquid crystal, thereby eliminating the harmful oxidation-reduction reactions while maintaining the reflective display's low power consumption advantage
Solution Approach 2:
The patent changes the chemical composition parameters of the alignment film by selecting specific polymer types with particular functional groups (amide, nitrile, carboxyl). This parameter change in material composition enables the film to form complexes with metal ions, fundamentally altering the chemical environment at the electrode-liquid crystal interface to prevent degradation reactions
2Manufacturing precision
If the number of conductive lines and area of black matrix are increased to improve display quality, then image contrast and definition are enhanced, but irregularities on substrate surfaces increase making rubbing alignment uneven
Solution Approach 1:
The patent replaces the mechanical rubbing alignment method with a photo-alignment method. By irradiating the alignment film with polarized light, the liquid crystal molecules achieve uniform alignment without physical contact. This substitution eliminates the problem of uneven rubbing caused by substrate irregularities while maintaining high alignment precision required for displays with increased conductive lines and black matrix area
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
This approach effectively suppresses flicker and image sticking by maintaining a high VHR and low residual DC voltage even after long-term use, enhancing the reliability of the liquid crystal display device.
Implementation Method 1
a complex is formed between a metal ion such as Al3+ and the salicylic acid derivative functional group
Data Source
AI summary
The present invention provides a liquid crystal display device in which flicker and image sticking caused by long-term use are suppressed. The liquid crystal display device includes, in the following order: a first substrate; a liquid crystal layer; and a second substrate, the liquid crystal display device including an alignment film including a polymer containing a salicylic acid derivative functional group in a side chain on the liquid crystal layer side of at least one of the first substrate and the second substrate, the salicylic acid derivative functional group having a structure represented by the following formula (Z):