Controlled Melt Fracture in Polymer Interlayers for Optical Clarity
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Solution Overview
Problem
Multiple layer interlayers with a soft inner layer and stiff outer layers face optical distortion issues during lamination due to the transfer of surface topography from outer layers to inner layers, which is not effectively addressed by conventional embossing methods.
Innovation Solution
Controlled melt fracture is introduced to the outer surfaces of the interlayer during formation, creating specific surface topography that prevents optical distortion during lamination, allowing for the use of multiple layer interlayers in glass panels without compromising optical quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If multiple layer interlayers with soft inner layer and stiff outer layers are used to improve acoustic dampening, then sound transmission reduction is improved, but optical distortion occurs during lamination due to surface topography transfer
Solution Approach 1:
Instead of trying to prevent surface topography formation or remove it after formation, the invention inverts the approach by intentionally creating controlled surface topography through melt fracture that does not transfer to the inner layer. The outer layers are designed with surface irregularities that remain on the outer surfaces only, while the inner layer maintains optical quality by not receiving transferred topography.
Solution Approach 2:
The invention applies different properties to different parts of the interlayer structure. The outer layers have controlled surface topography for acoustic dampening, while the inner layer maintains smooth surfaces for optical quality. This local differentiation allows each layer to fulfill its specific function without compromising the other.
2Ease of operation
If embossing is used to facilitate deairing during lamination, then ease of operation is improved, but optical distortion is caused by transfer of surface topography to inner layers
Solution Approach 1:
The invention segments the deairing function from the optical quality function by placing textured surfaces only on the outer layers that contact the glass substrates. The inner layer remains smooth and optically clear, while the outer layers provide the necessary surface irregularities for air evacuation during lamination without transferring distortion to the inner layer.
3Ease of manufacture
If conventional embossing is applied to outer layers of three layer interlayer, then surface topography is created for deairing, but unacceptable optical distortion is transferred to the softer inner layer
Solution Approach 1:
The outer layers act as intermediaries that absorb the deairing function through their textured surfaces. These outer layers protect the inner layer from direct contact with embossing tools, preventing topography transfer to the softer inner layer while still providing the necessary surface irregularities for air evacuation during the lamination process.
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 controlled surface topography enables the lamination of multiple layer interlayers without optical distortion, improving sound transmission reduction by up to 8 decibels and maintaining the differential plasticizer content between layers, making them suitable for applications like windshields and architectural windows.
Implementation Method 1
Multiple layer interlayers of the present invention have surface topography that is formed by controlling the melt fracture that occurs at the exposed surface of the interlayer, or individual layers of the multiple layer interlayer, during formation of the interlayer.
Data Source
Figure 1
AI summary
The present invention provides multiple layer interlayers having a soft inner polymer layer and relatively stiff outer layers that can be laminated without unacceptable optical distortion and used in various multiple layer glass panel type applications. Multiple layer interlayers of the present invention have surface topography that is formed by controlling the melt fracture that occurs at the exposed surface of the interlayer, or individual layers of the multiple layer interlayer, during formation of the interlayer. By precisely controlling the surface topography of the interlayer, lamination of the interlayer with a rigid substrate does not lead to unacceptable optical distortion caused by the transfer of the surface topography through outer, stiffer layers into softer, internal layers of the interlayer.