Aryl Silsesquioxane Polysiloxane Films for High Refractive Index
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Solution Overview
Problem
Polymethylsiloxanes are not suitable as light-guide materials due to their high cost and low refractive index, and existing polysiloxane compositions struggle to form optically smooth films with sufficient stiffness and refractive index for efficient light transmission, especially when cured in open air at elevated temperatures.
Innovation Solution
A curable polysiloxane composition comprising vinyl functional M-capped aryl silsesquioxane resin, vinyl functional disiloxane, and silicon-hydride functional M-capped silsesquioxane resin, combined with a platinum hydrosilylation catalyst, which can be cast and cured to form films with a refractive index greater than 1.50, surface roughness less than 25 nanometers, and stiffness greater than 15 dN*m, even when exposed to air at temperatures above 100°C.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If polymethylsiloxanes are used as light-guide material, then thermal stability is improved, but refractive index is insufficient (lower than 1.50)
Solution Approach 1:
The patent uses a composite polysiloxane composition containing multiple components: vinyl-functional M-capped aryl silsesquioxane resin, silicon-hydride-functional M-capped silsesquioxane resin, and vinyl-functional disiloxane. This composite approach combines materials with different properties to achieve both high refractive index (>1.50) and thermal stability, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent changes the chemical composition parameters by incorporating aryl groups (such as phenyl groups) into the polysiloxane structure through the use of aryl silsesquioxane resins. This chemical parameter change increases the refractive index from the typical 1.4 of polymethylsiloxanes to greater than 1.50, while maintaining the thermal stability characteristic of polysiloxanes.
2Productivity
If polysiloxane composition is cured at elevated temperatures in open air, then curing speed is improved, but surface roughness increases (Ra greater than 25 nanometers)
Solution Approach 1:
The patent introduces a specific catalyst system (platinum catalyst) as an intermediary to mediate the curing reaction. This catalyst enables the composition to cure at elevated temperatures in open air while maintaining optically smooth surfaces (Ra < 25 nm), resolving the contradiction between curing speed and surface quality by controlling the reaction kinetics.
Solution Approach 2:
The patent changes the curing parameters by optimizing the composition to cure at temperatures above 100°C in open air conditions. This parameter change allows rapid curing while preventing surface roughening, achieving both high productivity and manufacturing precision simultaneously.
3Volume of moving object
If film thickness is reduced to 25-500 micrometers, then flexibility and thinness are improved, but optical smoothness becomes more difficult to achieve
Solution Approach 1:
The patent changes the physical and chemical parameters of the composition to enable curing of thin films (25-500 micrometers) while maintaining optical smoothness. The composition formulation and curing conditions are optimized specifically for thin film applications, allowing the film to be both thin and optically smooth (Ra < 25 nm).
4Strength
If composition cures to high stiffness (>15 dN*m), then handleability is improved, but working time at 25°C may be reduced
Solution Approach 1:
The patent creates a dynamic curing process where the composition maintains a working time of at least one hour at 25°C for easy handling and processing, then cures to achieve high stiffness (>15 dN*m). The composition and curing conditions are designed to provide this time-dependent property change, resolving the contradiction between initial workability and final mechanical strength.
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 composition achieves optically smooth films with enhanced refractive index and stiffness, enabling efficient light transmission and handling, while maintaining a working time of at least one hour at 25°C, addressing the limitations of existing polysiloxane compositions.
Implementation Method 1
A curable polysiloxane composition comprising vinyl functional M-capped aryl silsesquioxane resin, vinyl functional disiloxane, and silicon-hydride functional M-capped silsesquioxane resin, combined with a platinum hydrosilylation catalyst
Data Source
AI summary
A curable composition contains: (a) 15 to 73 weight-percent of a vinyl functional M-capped aryl silsesquioxane resin: (b) 0.5 to 5 weight-percent of a vinyl functional disiloxane: (c) 2 to 25 wt % of a silicon-hydride functional M-capped silsesquioxane resin; and (d) 1 to 10 weight parts per million weight parts of platinum from a platinum hydrosilylation catalyst: wherein the sum of the concentration of (a) and (b) is at least 35 weight-percent: weight-percent values are relative to weight of curable composition; and the curable composition is free of acetylenic alcohol hydrosilylation inhibitors.