Optical Thermoplastic Resin with Low Birefringence
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Solution Overview
Problem
Existing optical thermoplastic resins face challenges in achieving low orientation birefringence, photoelastic birefringence, and maintaining heat stability while ensuring excellent transparency and color tone, especially in thick formed bodies like injection-formed bodies, due to issues with polymer decomposition and defects during high-temperature forming processes.
Innovation Solution
A novel optical thermoplastic resin with a specific composition of methacrylic and acrylic esters, along with a small amount of another monofunctional monomer, is developed, which has a melt viscosity reduction rate of less than 20%, orientation birefringence between -1.7 × 10^-4 and 1.7 × 10^-4, and a photoelastic constant between -3.7 × 10^-12 and 3.7 × 10^-12 Pa^-1, ensuring low birefringence and high heat stability, and is formed into a 2mm-thick body with haze of 1% or less.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional optical resins are used to form thick optical members, then the optical members can be produced with various shapes, but the resins exhibit high birefringence and poor transparency due to orientation and photoelastic birefringence
Solution Approach 1:
The patent changes the chemical composition parameters of the optical resin by incorporating fluorinated monomers (containing CF3 groups) and specific methacrylic/acrylic ester ratios to achieve low birefringence and high transparency in thick formed bodies
Solution Approach 2:
The patent creates a composite resin system combining fluorinated monomers with methacrylic and acrylic esters to achieve synergistic effects that reduce both orientation and photoelastic birefringence while maintaining excellent optical properties
2Ease of manufacture
If high-temperature forming processes are used to produce thick optical members, then various complex shapes can be achieved, but polymer decomposition occurs causing defects and poor optical properties
Solution Approach 1:
The patent modifies the thermal stability parameters of the resin by incorporating fluorinated monomers that raise the decomposition temperature, enabling high-temperature forming processes without polymer degradation while maintaining formability
Solution Approach 2:
The patent uses a carefully controlled combination of monomers with specific functional groups that provide temporary thermal stability during the forming process, preventing decomposition defects without requiring expensive additional stabilizers
3Manufacturing precision
If polymer resins with low orientation birefringence are developed, then optical isotropy is improved, but photoelastic birefringence and heat stability remain problematic
Solution Approach 1:
The patent simultaneously optimizes multiple chemical parameters including the incorporation of fluorinated monomers and specific ratios of methacrylic to acrylic esters to achieve low values for both orientation and photoelastic birefringence while maintaining heat stability
Solution Approach 2:
The patent develops a multi-component resin system where fluorinated monomers, methacrylic esters, and acrylic esters work synergistically to reduce both types of birefringence and improve overall optical performance
4Reliability
If conventional resin compositions are used to ensure heat stability, then polymer decomposition is reduced, but birefringence increases and optical properties deteriorate
Solution Approach 1:
The patent changes the chemical structure parameters by introducing fluorinated monomers and optimizing the ratio of methacrylic to acrylic esters to achieve both high heat stability and low birefringence 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 resin achieves excellent optical isotropy, transparency, and color tone with reduced thermal decomposition defects, making it suitable for optical applications with improved heat stability and minimal birefringence-related issues.
Implementation Method 1
orientation birefringence mainly caused by the orientation of main chains of the polymer
Implementation Method 2
photoelastic birefringence caused by stress
Data Source
Figure 1
Figure 2
AI summary
An object of the present invention is to provide an optical thermoplastic resin having excellent transparency and color tone, and also excellent heat stability, as well as being extremely low in both orientation birefringence and photoelastic birefringence; and a formed body made of said resin. This optical thermoplastic resin has a rate of reduction in melt viscosity of less than 20%, an orientation birefringence of -1.7 × 10-4 to 1.7 × 10-4, a photoelastic constant of -3.7 × 10-12 to 3.7 × 10-12 Pa-1, and, when formed into a 2mm-thick formed body, has a haze of 1% or less.