Photo-alignment Monomer Retardation Layer for LCD Contrast
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Solution Overview
Problem
Conventional methods for forming retardation layers in liquid crystal display devices face issues such as insufficient alignability, thermal stability, and increased randomness of reactive monomers, leading to reduced contrast ratios and retardation, especially under bright conditions like natural light.
Innovation Solution
The use of photo-alignment monomers, represented by a specific formula, which are aligned and polymerized using polarized light, forming a retardation layer with improved alignability and thermal stability, eliminating the need for an alignment layer and reducing scattering-induced contrast ratio decreases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional reactive monomers are used with alignment layer treatment, then the retardation layer can be formed, but the alignability deteriorates and randomness increases
Solution Approach 1:
The patent replaces the mechanical rubbing treatment system with a photo-alignment system using polarized light. Instead of using mechanical friction to align monomers, the invention uses optical fields (polarized light) to induce alignment through photo-responsive groups in the monomer molecules, thereby improving alignability and thermal stability simultaneously
Solution Approach 2:
The patent changes the chemical parameters of the monomer by introducing photo-responsive groups (such as cinnamate, coumarin, or styryl groups) that can respond to polarized light. This parameter change enables the monomer to undergo photo-alignment, transforming the alignment mechanism from mechanical to optical, which resolves the contradiction between alignability and thermal stability
2Force
If alignment layer is used for monomer alignment, then alignment control is achieved, but the alignment control force is insufficient for thick films
Solution Approach 1:
The patent replaces the weak mechanical alignment control from the alignment layer with a strong optical alignment field. The photo-alignment mechanism using polarized light provides sufficient alignment control force throughout the entire film thickness, eliminating the limitation of insufficient control force in thick films
Solution Approach 2:
The patent introduces a new dimension of control by using optical fields (electromagnetic radiation) instead of relying solely on surface-level mechanical alignment. This allows alignment control to penetrate through the entire thickness of the film, providing uniform alignment control force from surface to bulk
3Manufacturing precision
If rubbing treatment is applied to alignment layer, then alignment is achieved, but pre-tilt angle increases causing insufficient retardation
Solution Approach 1:
The patent replaces the rubbing treatment mechanism with photo-alignment using polarized light. This substitution eliminates the pre-tilt angle issue caused by mechanical rubbing, as the optical alignment method can achieve planar alignment with minimal or zero pre-tilt, thereby maintaining sufficient retardation performance
Solution Approach 2:
The patent changes the alignment mechanism parameter from mechanical contact (rubbing) to optical interaction (photo-alignment). This parameter change allows precise control of the alignment angle and minimizes pre-tilt, resolving the contradiction between alignment precision and retardation performance
4Manufacturing precision
If photo-alignment treatment is used on alignment layer, then alignment is achieved, but alignment control force is weak reducing retardation over time
Solution Approach 1:
The patent replaces the weak photo-alignment treatment on the alignment layer with direct photo-alignment of the monomer itself. By incorporating photo-responsive groups into the monomer structure, the alignment is achieved directly during polymerization, providing strong and stable alignment control that maintains retardation performance over long periods
Solution Approach 2:
The patent performs preliminary alignment of the monomer molecules through photo-alignment before polymerization occurs. This preliminary alignment is locked in during the polymerization process, ensuring that the alignment structure is established early and maintained stably over time, preventing degradation of retardation performance
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 enhanced thermal stability and suppressed contrast ratio degradation, ensuring clear visibility even in bright environments by achieving uniform alignment and stable retardation.
Implementation Method 1
irradiating the film with polarized light to align and polymerize molecules of the photo-alignment monomer
Implementation Method 2
aligned and polymerized using polarized light, forming a retardation layer with improved alignability
Data Source
AI summary
The present invention provides a liquid crystal display device that includes a retardation layer with excellent thermal stability and suppresses a decrease in contrast ratio caused by scattering even when the retardation layer has been formed by polymerizing reactive monomers. The liquid crystal display device includes a pair of substrates and a liquid crystal layer held between the substrates. At least one of the substrates includes a retardation layer that contains a polymer of at least one type of monomer. The at least one type of monomer includes a photo-alignment monomer represented by a certain formula.