Photo-Aligned Liquid Crystal Display with Oxygen Gradient Alignment Film
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Solution Overview
Problem
Photo-alignment techniques in liquid crystal display devices face challenges in achieving stable afterimage characteristics, which are crucial for maintaining high-quality display over time, especially compared to traditional rubbing methods.
Innovation Solution
A liquid crystal display device with a hydrophobic alignment film that uses a photodegradation-type photo-alignment film with a specific oxygen atom ratio gradient, where the oxygen concentration is higher on the surface than inside, and a two-layer structure with a low-resistive lower layer, to enhance alignment and prevent contamination and residual electric charge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If photo-alignment technique is used instead of rubbing method, then contamination and static electricity are reduced, but afterimage characteristics become unstable
Solution Approach 1:
The alignment film is designed with different oxygen atom ratios at different depths: the surface layer has a higher oxygen atom ratio to prevent contamination and maintain hydrophobicity, while the inner layer has a lower oxygen atom ratio to maintain stable afterimage characteristics. This spatial variation in composition resolves the contradiction between surface quality and bulk performance.
Solution Approach 2:
The alignment film is constructed as a composite structure with two distinct layers having different chemical compositions and functions. The surface layer (higher oxygen ratio) provides contamination resistance, while the inner layer (lower oxygen ratio) provides stable photo-alignment characteristics, achieving both benefits simultaneously.
2Object-affected harmful factors
If hydrophobic alignment film is used, then contamination is prevented, but alignment restraining force may be reduced
Solution Approach 1:
The alignment film exhibits different properties at different depths: the surface is made hydrophobic with high oxygen content to prevent contamination, while the inner portion maintains the photo-alignment characteristics with lower oxygen content to ensure sufficient alignment restraining force. This local differentiation resolves the contradiction between contamination resistance and alignment capability.
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 stabilizes afterimage characteristics and prevents contamination and residual electric charge, while maintaining alignment quality, even with the photo-alignment technique, thereby improving the long-term display performance.
Implementation Method 1
the alignment film is a hydrophobic material that can provide a liquid crystal alignment restraining force by irradiating polarized light
Implementation Method 2
the liquid crystal molecules are aligned in the polymer array direction using an intermolecular mutual effect by the van der Waals force of polymer chains and liquid crystal molecules at the interface
Implementation Method 3
by irradiating ultraviolet rays onto the alignment film and by performing an oxidation process for the alignment film
Data Source
AI summary
The present invention provides a liquid crystal display device in which even in the case of using a photo-alignment technique, excellent afterimage characteristics can be stably obtained.Provided is a liquid crystal display device including a TFT substrate having an alignment film, an opposed substrate which is arranged to face the TFT substrate and on which an alignment film is formed, and a liquid crystal layer sandwiched between the alignment films, wherein the alignment films are materials that can provide a liquid crystal alignment restraining force by irradiating polarized light, and the ratio of oxygen atoms on the surface of the alignment film is higher than that in the alignment film.