Polycarbonate Resin Composition for Low-Birefringence Optical Materials
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Solution Overview
Problem
Polycarbonate resins with low-birefringence and excellent environmental resistance properties are needed for optical materials, but existing solutions suffer from issues such as high cost, insufficient chemical resistance, and birefringence, making them unsuitable for applications requiring these properties.
Innovation Solution
A polycarbonate resin composition is developed by blending polycarbonate resin (A) formed from a dihydroxy compound with a diester carbonate and polycarbonate resin (B) formed from 2,2-bis(4-hydroxyphenyl)propane, optimized in molecular weight and glass-transition temperature to achieve low-birefringence and environmental resistance, with specific ratios and production methods to ensure compatibility and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polycarbonate resin formed of 2,2-bis(4-hydroxyphenyl)propane is used, then transparency, heat resistance, and mechanical characteristics are improved, but birefringence increases making it unsuitable for low-birefringence applications
Solution Approach 1:
The invention uses a composite resin system combining polycarbonate resin (A) with specific molecular weight (20,000-200,000) and glass transition temperature (80-150°C) with polycarbonate resin (B) formed of 2,2-bis(4-hydroxyphenyl)propane. This composite approach allows the mixture to exhibit lower birefringence than resin (B) alone while maintaining mechanical strength, transparency, and heat resistance. The synergistic effect of the two resins resolves the contradiction between mechanical performance and low birefringence.
2Object-affected harmful factors
If acrylic resins or noncrystalline polyolefins are used for low-birefringence applications, then birefringence is reduced, but water absorption increases and dimension stability decreases
Solution Approach 1:
The invention employs a composite of two polycarbonate resins where resin (A) with controlled molecular weight and glass transition temperature contributes to low birefringence, while resin (B) formed of 2,2-bis(4-hydroxyphenyl)propane provides excellent dimension stability, low water absorption, and chemical resistance. The composite achieves dimension stability of 0.05% or less in change of molded article dimension, outperforming acrylic resins and noncrystalline polyolefins while maintaining low birefringence.
Solution Approach 2:
The invention controls the molecular weight of resin (A) within 20,000-200,000 and glass transition temperature within 80-150°C to optimize the balance between birefringence reduction and dimension stability. By adjusting these parameters, the composite achieves both low birefringence and high dimension stability, resolving the contradiction between these two properties.
3Object-affected harmful factors
If copolymerization-polycarbonate resins derived from 9,9-bis(3-methyl-4-hydroxyphenyl)fluorene are used, then low-birefringence is achieved, but chemical resistance and environmental stability become insufficient
Solution Approach 1:
The invention combines polycarbonate resin (A) with specific molecular weight and glass transition temperature with polycarbonate resin (B) formed of 2,2-bis(4-hydroxyphenyl)propane. This composite provides both low birefringence and excellent environmental stability with yellowing index change of 10 or less after weathering tests, chemical resistance, and oil resistance. The synergistic combination resolves the contradiction between low birefringence and environmental reliability.
Data Source
AI summary
To provide a polycarbonate resin composition excellent in low-birefringence and environment resistance properties to be used for optical materials such as lenses, films or sheets. Disclosed is a polycarbonate resin composition comprising a polycarbonate resin (A) prepared by forming carbonate bonds in a dihydroxy compound represented by formula (1) with a diester carbonate, and a polycarbonate resin (B) prepared by forming carbonate bonds in 2,2-bis (4-hydroxyphenyl)propane with a diester carbonate or phosgene. In the formula, R1 and R2 each independently represent a hydrogen atom or methyl.