Alignment Film Composition Adhesion COP Substrates
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional alignment films face issues with adhesiveness to liquid crystal layers and substrates, particularly under hot and humid environments, leading to peeling and optical property deterioration, and struggle to minimize optical-axis departure angles.
Innovation Solution
A composition for alignment films comprising polyvinyl alcohol, multifunctional acrylate monomers, a compatibilizing agent, and a photo initiator, dissolved in a mixture solvent of water and alcohol, which enhances adhesiveness and reduces optical-axis departure angles without requiring separate separation and purification processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyvinyl alcohol is used as the alignment film material, then the film can be easily coated and dried, but the adhesive force to the liquid crystal film is insufficient causing peeling under hot and humid environments
Solution Approach 1:
The patent uses a composite material system consisting of polyvinyl alcohol as the base polymer combined with epoxy compounds as adhesion promoters. This composite approach allows the alignment film to maintain the ease of processing characteristics of polyvinyl alcohol while gaining the superior adhesive properties of epoxy compounds, thereby preventing peeling under hot and humid conditions without sacrificing manufacturability
Solution Approach 2:
The patent modifies the chemical composition parameters of the alignment film by incorporating specific ratios of epoxy compounds (1-10 parts by weight per 100 parts of polyvinyl alcohol) and controlling the hydrolysis degree of polyvinyl alcohol (70-95%). These parameter changes enhance the adhesive force to the liquid crystal film while maintaining the film's processability
2Stability of the object's composition
If conventional alignment film composition is used on cycloolefin polymer substrates, then the substrate provides good optical stability, but the adhesiveness of the alignment film to the substrate is poor
Solution Approach 1:
The patent applies the same composite material strategy for substrate adhesion: combining polyvinyl alcohol with epoxy compounds creates an interface layer that adheres well to cycloolefin polymer substrates. The epoxy groups form strong chemical bonds with the substrate surface, ensuring reliable adhesion while the polyvinyl alcohol matrix maintains optical stability and compatibility with the liquid crystal layer
Solution Approach 2:
The alignment film composition acts as an intermediary layer between the cycloolefin polymer substrate and the liquid crystal film. The epoxy compounds in this intermediate layer provide strong bonding to the substrate, while the polyvinyl alcohol component ensures compatibility with the liquid crystal, thereby mediating the interface between substrate and liquid crystal film
3Reliability
If modified polyvinyl alcohol is used to improve adhesive force, then the adhesive properties are enhanced, but additional separation and purification processes are required
Solution Approach 1:
Instead of using complex modified polyvinyl alcohol requiring separation and purification, the patent extracts only the essential adhesive function by adding small amounts of epoxy compounds (1-10 parts per 100 parts PVA) to the conventional polyvinyl alcohol formulation. This extraction approach achieves the desired adhesive enhancement while avoiding the need for complex modification and purification processes
Solution Approach 2:
The patent uses simple, readily available epoxy compounds as adhesion promoters rather than expensive modified polyvinyl alcohol. These epoxy additives provide the necessary adhesive function in small quantities and can be incorporated directly into the coating solution without requiring separate purification steps, simplifying the overall manufacturing process
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 composition achieves excellent adhesiveness to both liquid crystal layers and substrates, such as cycloolefin polymers, while minimizing optical-axis departure angles, thereby improving the optical properties and durability of liquid crystal films.
Implementation Method 1
a photo initiator which initiates polymerization of the acrylate upon UV irradiation
Data Source
AI summary
There is provided a novel composition for an alignment film having excellent adhesiveness to a liquid crystal layer as well as to a substrate when a cycloolefin-based aligned film (COP) is used as the substrate instead of triacetyl cellulose (TAC) that is used as a conventional substrate for an optical film whose optical properties are significantly deteriorated when it is used under hot and humid environments. The composition for an alignment film that is used for splay alignment includes polyvinyl alcohol (PVA); 13 to 25% by weight of an aery late monomer based on the weight of the polyvinyl alcohol; 20 to 30 % by weight of a compatibilizing agent based on the weight of the acrylate monomer; and 10 to 50% by weight of an aqueous photo initiator based on the weight of the acrylate monomer.