Polyether Polyurethane Holographic Media Brightness
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Solution Overview
Problem
Existing polyurethane-based systems for holographic media suffer from low brightness of stored holograms due to a small relative difference in refractive indices between the matrix polymer and the writing monomer, limiting the achievable contrast ratio and brightness without compromising compatibility and ease of formulation.
Innovation Solution
The use of special polyether polyols with number-average molecular weights over 1000 g/mol, containing oxyalkylene units, in combination with a polyisocyanate component, radiation-curable groups, free-radical stabilizers, photoinitiators, and optional catalysts and additives, to form polyurethane compositions that enhance the contrast ratio and brightness of holograms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyether polyols with low molar mass (Mn≦1000 g/mol) or mixtures with poly(THF) are used to form the matrix polymer, then the formulation is easier to process and components are more compatible, but the brightness and contrast ratio of the stored holograms become too low
Solution Approach 1:
The patent changes the molecular weight parameter of the polyether polyol from low (Mn≦1000 g/mol) to high (Mn>1000 g/mol), specifically using polyols with Mn of 1500-5000 g/mol. This parameter change increases the refractive index of the matrix polymer, thereby improving the brightness and contrast ratio of holograms while maintaining formulation feasibility
Solution Approach 2:
The patent creates a composite polyurethane system by combining polyether polyols with specific molecular weights (Mn>1000 g/mol) containing oxyalkylene units (ethylene oxide, propylene oxide, butylene oxide) with polyisocyanates. This composite approach optimizes both the optical properties (brightness) and the compatibility of components in the formulation
2Illumination intensity
If the refractive index difference between the matrix polymer and the writing monomer is increased to improve brightness, then the brightness and contrast ratio improve, but the compatibility between matrix polymer and writing monomer may be compromised
Solution Approach 1:
The patent modifies the chemical structure parameters of the polyether polyol by specifying the inclusion of oxyalkylene units (ethylene oxide, propylene oxide, butylene oxide) with specific ratios. These structural changes adjust the refractive index of the matrix polymer to achieve optimal brightness while preserving compatibility with writing monomers through appropriate functional group interactions
Solution Approach 2:
The polyether polyol with Mn>1000 g/mol acts as an intermediary material that bridges the optical property requirements (high refractive index for brightness) and the compatibility requirements (chemical compatibility with writing monomer). The specific oxyalkylene structure serves as a mediator that achieves both objectives simultaneously
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 proposed polyurethane compositions achieve improved brightness and contrast ratio of holograms, maintaining compatibility with the matrix polymer and writing monomer, and facilitating easy formulation and processing.
Implementation Method 1
Compounds which have groups which react with ethylenically unsaturated compounds to polymerize under the action of actinic radiation (radiation-curing groups)
Implementation Method 2
photoinitiators
Implementation Method 3
Its production starts from isocyanate-functional materials which are crosslinked with polyols such as polyethers or polyesters to form urethanes
Data Source
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AI summary
The present invention relates to novel polyurethane compositions which are advantageously suitable for the production of holographic media, including for data storage, but also for various types of optical applications.