Multilayer Interlayer Film for Laminated Glass with Surface Roughness Control
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Solution Overview
Problem
Laminated glass with multiple resin layers experiences optical distortion due to residual stress from the rolling process during production, which affects the surface roughness and deaeration properties.
Innovation Solution
The interlayer film features a multilayer structure with minute recesses and projections on its surface, arranged in a specific pattern to reduce residual stress and enhance deaeration, achieved by controlling the surface roughness (Rz) and embossing conditions, ensuring the recesses have a continuous bottom and are regularly arranged.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an interlayer film includes a laminate of two or more resin layers to provide various properties, then functional performance is improved, but optical distortion occurs due to residual stress from rolling
Solution Approach 1:
The patent applies local quality by creating specific surface structures (recesses and protrusions) only on certain surfaces of the interlayer film, while maintaining different resin layers with distinct properties throughout the laminate. This allows the film to have varied functional characteristics in different regions and layers without causing uniform optical distortion across the entire structure.
Solution Approach 2:
The patent employs asymmetry by forming recesses and protrusions with specific geometric characteristics (groove shape with continuous bottom, regular arrangement) on the surface. This asymmetric surface structure helps distribute and reduce residual stress unevenly, preventing the uniform optical distortion that would occur with symmetric or flat surfaces in multilayer laminates.
2Adaptability or versatility
If the interlayer film is extended with heat to follow curved glass surfaces, then adaptability to glass shapes is improved, but optical distortion becomes more pronounced
Solution Approach 1:
The patent applies parameter changes by modifying the surface roughness parameters through controlled embossing to create specific recess and protrusion geometries. This changes the physical parameters of the interlayer film surface, allowing it to better accommodate thermal extension and curved glass shapes while the structured surface helps manage stress distribution to reduce optical distortion during heating and forming processes.
3Productivity
If the surface has minute recesses and protrusions to improve deaeration, then deaeration properties are enhanced, but surface roughness increases affecting optical quality
Solution Approach 1:
The patent applies the porous materials principle by creating a surface structure with minute recesses and protrusions that form a controlled porous-like topology. This surface morphology enhances deaeration by providing pathways for air evacuation during lamination, while the specific geometry (groove shape with continuous bottom) and scale of these features are controlled to maintain acceptable optical quality and surface roughness parameters.
Data Source
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AI summary
The present invention aims to provide an interlayer film for laminated glass having small optical distortion while having a multilayer structure of two or more layers, and a laminated glass including the interlayer film for laminated glass. The present invention relates to an interlayer film for laminated glass including at least two resin layers laminated together, the interlayer film having a large number of minute recesses and a large number of minute projections on at least one surface, the at least two resin layers including a first surface layer and a second surface layer and each containing a thermoplastic resin and a plasticizer, wherein, provided that the interlayer film is allowed to stand at 23°C and a humidity of 30%RH for three hours, and cut with a microtome at 23°C and a humidity of 30%RH in the horizontal direction of the interlayer film at a portion of 80 to 90 µm distant on the first surface layer side from the interface between the first surface layer and a resin layer contacting the interior side of the first surface layer and then at a portion of 50 µm distant from the cut face on the second surface layer side to prepare a resin film 1 having a thickness of 50µm, the resin film 1 after standing at a temperature of 23°C and a humidity of 30%RH for three hours has a surface roughness (Rz) measured by a method in conformity with JIS B-0601 (1994) of less than 2.5 µm.