Thermosetting Photo-Aligned Alignment Layer for Resin Substrates
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Solution Overview
Problem
Resin films used as substrates for optical elements and liquid crystal display elements have poor thermal stability, leading to deviations in alignment direction and reduced liquid crystal alignment ability due to heat-induced changes in size and shape, which deteriorate optical properties.
Innovation Solution
A thermosetting composition with a photo-alignment property is developed, comprising a copolymer with a photo-alignment constitutional unit and a thermal cross-linking constitutional unit bonded via a straight-chain alkylene group or polyethylene glycol group, allowing for low-temperature curing and improved thermal stability and solvent resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If a resin film is used as a substrate for an alignment layer, then the device achieves lightness, thinness, and flexibility, but the resin film undergoes heat-induced changes in size and shape that cause deviation in alignment direction and deteriorate optical properties
Solution Approach 1:
The patent introduces a thermosetting composition as an intermediary layer between the resin substrate and the alignment function. This composition contains cross-linkable groups that form a thermally stable network structure, mediating between the flexible resin substrate and the requirement for thermal stability during alignment layer formation and device operation.
Solution Approach 2:
The patent creates a composite material system by combining the resin substrate with a thermosetting composition containing cross-linkable functional groups. This composite structure integrates the advantages of both materials: the lightness and flexibility of the resin film with the thermal stability of the cross-linked thermosetting network.
2Reliability
If conventional thermosetting compositions are used to improve thermal stability and solvent resistance, then the alignment layer gains stability, but high curing temperatures cause heat-induced changes in the resin substrate
Solution Approach 1:
The patent changes the chemical parameters of the thermosetting composition by incorporating specific cross-linkable functional groups (carboxyl, phenolic hydroxy, hydroxymethyl, or glycidyl groups) that enable low-temperature curing. This parameter change allows the cross-linking reaction to proceed at temperatures that do not induce harmful thermal effects on the resin substrate.
Solution Approach 2:
The patent applies local quality by concentrating the cross-linking function in specific functional groups within the composition, allowing the curing reaction to occur locally at lower temperatures without requiring high-temperature treatment of the entire substrate, thus protecting the resin film from heat-induced deformation.
3Stability of the object's composition
If the alignment layer is exposed to high temperature during device use or production, then the alignment layer may maintain its structure, but the liquid crystal alignment ability is remarkably deteriorated
Solution Approach 1:
The patent performs preliminary action by forming a cross-linked thermosetting network structure in advance during the composition curing stage. This pre-formed stable network structure protects the alignment layer from thermal degradation during subsequent device operation or production processes, preserving both structural stability and liquid crystal alignment ability.
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 forms an alignment layer that inhibits heat-induced changes in the substrate, enhancing liquid crystal alignment ability and optical properties by maintaining alignment stability and optical axis deviation, while enabling energy-efficient low-temperature curing.
Implementation Method 1
an acrylic copolymer having a photo-dimerization site and a thermal cross-linking site
Implementation Method 2
a compound having a photo-alignment group and a hydroxy group
Implementation Method 3
a liquid crystal alignment agent containing a polymer component having a structure capable of a cross-inking reaction by light and a structure which cross-links by heat
Data Source
AI summary
An embodiment of the present invention provides a thermosetting composition with a photo-alignment property, including a copolymer containing a photo-alignment constitutional unit, and a thermal cross-linking constitutional unit in which a thermal cross-linking group is bonded via a straight-chain alkylene group with a carbon number of 4 to 11, or via a polyethylene glycol group with a cycle number of 2 to 5.