Prepolymer-Based Polyurethane for Holographic Media Brightness
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Solution Overview
Problem
Existing polyurethane compositions for holographic media have low achievable brightness due to a low relative difference in refractive indices between the polyurethane matrix and monomer, limiting their optical applications beyond digital data storage, and require modifications that maintain compatibility with other components while simplifying mixing and delivery.
Innovation Solution
Incorporating specific prepolymers with primary NCO groups based on difunctional polyols in the isocyanate component, using allophanates from HDI or TMDI and difunctional polyether polyols with number average molar masses between 1000 and 8200 g/mol, along with isocyanate-reactive polymers, free radical stabilizers, photoinitiators, and optional catalysts and additives, to enhance the curing and optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional polyurethane formulations with secondary isocyanate groups are used, then compatibility with Schreibmonomer and other components is maintained, but the hardening rate is insufficient
Solution Approach 1:
The patent changes the functional group parameter from secondary isocyanate groups to primary isocyanate groups in the prepolymer structure. This parameter change increases the hardening rate while the specific prepolymer structure (allophanates from HDI or TMDI with difunctional polyether polyols) maintains compatibility with Schreibmonomer and other formulation components.
2Illumination intensity
If the refractive index difference between polyurethane matrix and Schreibmonomer is increased, then brightness of stored holograms is improved, but compatibility and processing simplicity are compromised
Solution Approach 1:
The patent optimizes the refractive index parameter by selecting specific difunctional polyether polyols with number average molar masses of 1000-8200 g/mol, which achieve a higher refractive index difference (improved brightness) while maintaining formulation simplicity and component compatibility through the standardized prepolymer structure.
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 significantly improves the brightness and optical performance of holographic media, allowing for broader optical applications by optimizing the refractive index difference and ensuring compatibility and ease of processing.
Implementation Method 1
compounds which contain (on exposure to actinic radiation with ethylenically unsaturated compounds by polymerization-reacting groups radiation-curing groups)
Implementation Method 2
NCO-functional prepolymers allophanates from HDI or TMDI and difunctional polyether polyols
Data Source
AI summary
The present invention relates to novel polyurethane compositions advantageously suited for producing holographic media for, among others, data storage, but also for a variety of optical applications.