Smart Window Film Laminate With PVB Layer to Prevent LC Mura
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Solution Overview
Problem
Conventional transmittance variable optical laminates experience liquid crystal mura due to uneven pressure distribution during glass bonding, especially when a polarizing plate and conductive layer are in direct contact without a substrate, leading to poor appearance and quality issues.
Innovation Solution
Incorporating a low-temperature curable polyvinyl butyral (PVB) surface protective layer with optimal thickness and a gap layer at the ends of the optical laminate, along with a two-step bonding process to minimize pressure on the liquid crystal layer during glass bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If glass bonding is performed on a conventional optical laminate without additional protective layers, then the bonding process is simple and quick, but uneven pressure is applied to the liquid crystal layer causing liquid crystal mura
Solution Approach 1:
A surface protective layer made of low-temperature curable PVB film is introduced as an intermediary between the glass and the optical laminate. This protective layer has optimal thickness (0.01-0.35mm) and mechanical properties that allow it to absorb and distribute bonding pressure uniformly, preventing direct transmission of uneven pressure to the liquid crystal layer while maintaining bonding effectiveness
Solution Approach 2:
The bonding process is segmented into multiple stages: initial bonding at room temperature or low temperature, followed by gradual heating to curing temperature (90°C or lower). This segmented approach allows the PVB film to progressively adjust its mechanical properties, starting from a compliant state that accommodates pressure distribution, then transitioning to a cured state that provides structural stability
2Quantity of substance
If a separate substrate is used to form the conductive layer, then the conductive layer has good electrical properties, but the overall laminate thickness increases
Solution Approach 1:
The conductive layer is merged directly with the polarizing plate by forming it on the polarizing plate's surface, eliminating the need for a separate substrate. This integration maintains the electrical conductivity function while significantly reducing the overall laminate thickness, as the conductive layer becomes part of the existing polarizing plate structure rather than adding a separate component
Solution Approach 2:
The PVB surface protective layer is implemented as an ultra-thin film (0.01-0.35mm) that provides necessary mechanical protection and pressure distribution functionality without adding significant thickness. This thin film approach allows the laminate to maintain compact dimensions while still incorporating the protective function
3Stress or pressure
If the PVB film thickness is increased to improve pressure distribution, then pressure uniformity improves, but the risk of liquid crystal mura increases due to excessive pressure absorption
Solution Approach 1:
The thickness of the PVB film is precisely controlled within the range of 0.01-0.35mm, and its mechanical properties are optimized through selection of appropriate polymerization degree and saponification degree. These parameter optimizations ensure the film has sufficient compliance to distribute pressure uniformly during bonding, while preventing excessive pressure absorption that would cause liquid crystal mura
Solution Approach 2:
The PVB film is formulated as a composite material with specific polymerization degree (100-2,000) and saponification degree (70-90%), creating a material that balances compliance and structural integrity. This composite structure allows the film to provide optimal pressure distribution while maintaining dimensional stability and preventing liquid crystal displacement
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
Prevents liquid crystal mura by dispersing pressure and maintaining the laminate's appearance, while reducing thickness by eliminating the need for a separate substrate for the conductive layer.
Implementation Method 1
the surface protective layer may minimize (disperse) the pressure applied to a liquid crystal layer during glass bonding
Implementation Method 2
the surface protective layer is a low-temperature curable polyvinyl butyral (PVB) film that is cured at a temperature of 90° C. or lower
Data Source
AI summary
Disclosed are a film laminate, a smart window including the same, and a method for manufacturing the same. The film laminate includes: an optical laminate; and a surface protective layer laminated on at least one of the upper and lower surfaces of the optical laminate, wherein the surface protective layer is a low-temperature curable polyvinyl butyral (PVB) film that is cured at a temperature of 90° C. or lower, has a thickness of 0.01 mm to 0.35 mm, and has a total area larger than the area of the optical laminate that is in contact with the surface protective layer.