Light Control Device Silane Coupling Adhesion
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Solution Overview
Problem
The existing polymer/liquid crystal composite materials used in light control devices, such as those described in Japanese Patent No. 4630954 and Japanese Patent No. 5386630, face issues with low tensile modulus leading to deformation and unevenness, poor adhesive strength between layers, and sensitivity to UV polymerization temperature, resulting in suboptimal performance and durability in applications like window glass and partitions.
Innovation Solution
A light control device is developed using a polymer/liquid crystal composite material with an increased content of acrylic monomer and the application of a silane coupling agent to ITO surfaces, enhancing the adhesive strength and robustness, and reducing sensitivity to UV polymerization temperature by forming a silane coupling agent layer between the polymer/liquid crystal composite material and ITO layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a urethane-based diacrylate soft oligomer is used in the polymer/liquid crystal composite material, then the material has high viscosity that enables uniform composite film formation and high tackiness to base material, but the tensile modulus becomes too low (70-690 Mpa) causing local unevenness and partial transparency due to stress and bending
Solution Approach 1:
The patent changes the chemical composition parameters of the polymerizable composition by replacing urethane-based diacrylate soft oligomer with acrylic monomers (such as polyfunctional acrylic monomers and monofunctional acrylic monomers) to achieve both high tensile modulus (2200-3200 Mpa) and adequate viscosity for film formation
Solution Approach 2:
The patent creates a composite polymer network by combining multiple acrylic monomers with different functional groups and molecular weights to achieve synergistic effects, where the polyfunctional acrylic monomer provides crosslinking for strength while the monofunctional acrylic monomer maintains viscosity and processability
2Ease of operation
If a polymer/liquid crystal composite material with low tensile modulus is used, then the material is softer and more pliable, but it deforms under external stress causing liquid crystal to align in fixed direction and locally occur unevenness in transmittance and transparency
Solution Approach 1:
The patent changes the mechanical properties parameters by selecting acrylic monomers that form a polymer network with tensile modulus of 2200-3200 Mpa, which is sufficiently rigid to maintain dimensional stability and prevent liquid crystal misalignment under stress while still allowing for large-area application
3Strength
If indium tin oxide (ITO) and polymer are used in direct contact, then the adhesive strength between layers is insufficient, but increasing adhesive strength requires additional processing steps that increase manufacturing complexity
Solution Approach 1:
The patent introduces a silane coupling agent as an intermediary substance between the ITO electrode and the acrylic polymer network. The silane coupling agent forms chemical bonds with both the ITO surface and the polymer matrix, significantly enhancing interfacial adhesion and preventing delamination without requiring additional complex processing steps
Solution Approach 2:
The patent modifies the chemical composition of the polymerizable composition by incorporating silane coupling agents, which change the interfacial chemical properties between ITO and polymer, enabling strong adhesion through chemical bonding rather than relying on physical adhesion alone
4Reliability
If the cell gap is increased to ensure shielding properties when electric field is turned off, then shielding performance improves, but the viewing angle when electric field is turned on becomes very poor
Solution Approach 1:
The patent changes the polymer network composition and crosslinking density to achieve optimal cell gap dimensions. By adjusting the polymerizable composition parameters, the patent enables sufficient shielding performance at reduced cell gap thickness, which in turn improves viewing angle characteristics when the electric field is activated
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 improved mechanical strength, increased adhesive strength, and enhanced durability, ensuring the light control device maintains transparency and shielding properties even under stress and UV exposure, with improved viewing angles and reduced liquid crystal bleeding.
Implementation Method 1
application of a silane coupling agent to ITO surfaces, enhancing the adhesive strength and robustness, and reducing sensitivity to UV polymerization temperature by forming a silane coupling agent layer between the polymer/liquid crystal composite material and ITO layers
Implementation Method 2
forming a polymer network by UV polymerization
Data Source
AI summary
There is provided a light control device that solves various practical problems, including the adhesive strength between layers, of a light control device comprising a polymer/liquid crystal composite derived from a polymerizable composition comprising an acrylic monomer and ITO layers. In the light control device, ITO layers are respectively bonded to both surfaces of a polymer/liquid crystal composite material layer in which a liquid crystal material is dispersed in a polymer material obtained by polymerizing an acrylic monomer, an amount of the acrylic monomer is in the range of 30 to 45% by weight based on a total amount of the acrylic monomer and the liquid crystal material, and silane coupling agent layers are respectively interposed between the polymer/liquid crystal composite material layer and the ITO layers.