Transmittance-Variable Film Bubble Suppression via Tan Delta Control
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Solution Overview
Problem
Transmittance-variable films with single or double-cell structures face challenges in suppressing bubble formation within the liquid crystal layer or at the interface between the base film and pressure-sensitive adhesive layer under high-temperature and high-humidity conditions, leading to visual defects and reliability issues.
Innovation Solution
A transmittance-variable film with a double-cell or single-cell structure is designed, featuring a liquid crystal cell with a pressure-sensitive adhesive layer that controls the tangent delta (tan δ) value of the adhesive to prevent bubble generation, where the tan δ value of the adhesive is optimized between 0.25 and 0.5 to balance elasticity and viscosity, ensuring effective bubble suppression.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a pressure-sensitive adhesive is used to attach optical functional films or liquid crystal cells, then the transmittance-variable film can be assembled, but air bubbles may be generated inside the liquid crystal layer or at the interface between the base film and pressure-sensitive adhesive under high-temperature and high-humidity conditions
Solution Approach 1:
The patent changes the physical-chemical parameters of the pressure-sensitive adhesive by controlling its tan δ value within the specific range of 0.25 to 0.5. This parameter optimization allows the adhesive to maintain appropriate elasticity and viscosity balance, enabling it to effectively suppress air bubble generation from the base film while maintaining assembly capability.
Solution Approach 2:
The patent applies different tan δ value requirements to different regions of the pressure-sensitive adhesive layer. The adhesive needs to have specific tan δ characteristics at the interface with the base film to suppress bubble generation, while maintaining appropriate adhesive properties for bonding. This localized quality control addresses the bubble issue without compromising overall assembly functionality.
2Stability of the object's composition
If the tan δ value of the pressure-sensitive adhesive is too low, then the adhesive has high elasticity but may not provide sufficient viscosity to suppress air bubble movement, leading to bubble formation inside the liquid crystal layer
Solution Approach 1:
The patent optimizes the tan δ value parameter of the pressure-sensitive adhesive to fall within the specific range of 0.25 to 0.5. This parameter change ensures the adhesive has the right balance between elasticity (for stability) and viscosity (for bubble suppression), resolving the contradiction between these two properties.
3Reliability
If the tan δ value of the pressure-sensitive adhesive is too high, then the adhesive has high viscosity but may generate internal stress under high-temperature and high-humidity conditions, leading to bubble formation at the interface
Solution Approach 1:
The patent controls the tan δ value of the pressure-sensitive adhesive to be within 0.25 to 0.5, which optimizes the balance between viscosity (for bubble suppression) and elasticity (for stress relief). This parameter optimization prevents excessive internal stress accumulation under high-temperature and high-humidity conditions while maintaining effective bubble suppression.
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 optimized pressure-sensitive adhesive layer effectively suppresses bubble formation under high-temperature and high-humidity conditions, maintaining the film's reliability and appearance by preventing bubbles larger than 10 µm from forming within the liquid crystal layer.
Implementation Method 1
the tan δ value of the adhesive is optimized between 0.25 and 0.5 to balance elasticity and viscosity, ensuring effective bubble suppression
Implementation Method 2
the liquid crystals are oriented depending on whether or not a voltage is applied and the dichroic dye is simultaneously oriented, so that the transmittance can be varied
Implementation Method 3
a liquid crystal layer including liquid crystals and a dichroic dye
Data Source
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AI summary
The present application relates to a transmittance-variable film and a use thereof. The present application can provide a transmittance-variable film having a double-cell structure or a single-cell structure capable of suppressing formation of bubbles inside a liquid crystal layer or at the interface between a base film and a pressure-sensitive adhesive layer under high-temperature and high-humidity reliability conditions. An exemplary transmittance-variable film can be applied to various applications, including various construction or automotive materials that require control of transmittance, or eyewear, such as augmented reality experience or sports goggles, sunglasses or helmets.