Poly(Vinyl Acetal) Interlayers With Refractive Index Balancing
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Solution Overview
Problem
Existing polymer interlayers in safety glass and laminates suffer from optical defects such as mottle and high haze due to differences in refractive indices between layers, compromising clarity and impact resistance.
Innovation Solution
A resin composition comprising a first poly(vinyl acetal) resin with a refractive index of at least 1.421 and a second poly(vinyl acetal) resin with a refractive index less than 1.421, combined with a plasticizer, to form a blended poly(vinyl acetal) resin with a refractive index of at least 1.492, and optionally incorporating a refractive index balancing agent to adjust the refractive indices of the layers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayered interlayers with different glass transition temperatures are used to achieve desirable combinations of acoustic performance and impact resistance, then acoustic performance and impact resistance are improved, but optical defects such as mottle and high haze occur due to different refractive indices between layers
Solution Approach 1:
The patent changes the refractive index parameter of the polymer resins by selecting specific poly(vinyl acetal) resins with carefully controlled refractive indices (first resin: 1.48-1.52, second resin: 1.46-1.50) to minimize refractive index differences between layers, thereby reducing optical defects while maintaining the multilayer structure for acoustic and impact performance
Solution Approach 2:
The patent uses composite materials by combining different poly(vinyl acetal) resins with plasticizers in specific ratios to create a blended resin composition that achieves both the desired mechanical properties (acoustic performance and impact resistance) and optical properties (reduced haze and mottle) simultaneously
2Ease of manufacture
If different types of optically incompatible polymers and plasticizers are blended to achieve desirable property combinations, then processability and strength are improved, but high haze occurs due to light scattering at regions of different polymer materials
Solution Approach 1:
The patent controls the refractive index parameter of the blended resin composition to be within 1.49-1.53 by carefully selecting and blending poly(vinyl acetal) resins with specific refractive indices, thereby minimizing light scattering and reducing haze while maintaining processability and strength
Solution Approach 2:
The patent promotes homogeneity in the blended resin composition by ensuring compatible poly(vinyl acetal) resins are mixed with plasticizers, creating a uniform material that reduces light scattering at interfaces and minimizes haze while maintaining desirable processing characteristics
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 enhances optical properties by reducing haze and mottle, maintaining clarity and impact resistance, suitable for use in safety glass and laminates.
Implementation Method 1
Mottle is caused by small-scale surface variations at the interfaces between the soft and stiff layers wherein the individual layers have different refractive indices
Data Source
AI summary
Resin compositions, layers, and interlayers comprising two or more thermoplastic polymers and at least one RI balancing agent for adjusting the refractive index of at least one of the resins or layers is provided. Such compositions, layers, and interlayers exhibit enhanced optical properties while retaining other properties, such as impact resistance and acoustic performance.