Cyclic Olefin Copolymer Birefringence Reduction
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Solution Overview
Problem
Cyclic olefin polymers used in optical materials often exhibit orientation birefringence and stress birefringence due to molecular chain orientation during molding, which affects image quality and signal readout, and existing methods to reduce birefringence either require additive materials or compromise heat resistance and toughness.
Innovation Solution
A cyclic olefin copolymer with specific repeating structural units [A] and [B] in a predetermined molar ratio, along with optional structural unit [C], is used to suppress birefringence and stress birefringence, achieving low orientation coefficients and photoelastic constants without the need for additives, thereby maintaining transparency and toughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If cyclic olefin polymer is used for optical material, then transparency and toughness are improved, but orientation birefringence and stress birefringence occur due to molecular chain orientation during molding
Solution Approach 1:
The patent changes the chemical structure parameters of the polymer by introducing fluorine-containing groups at specific positions in the cyclic olefin copolymer structure. This structural modification alters the molecular polarizability and reduces the orientation birefringence while maintaining transparency and toughness, allowing the material to be molded without temperature or pressure limitations.
2Object-generated harmful factors
If additive materials are added to reduce birefringence, then orientation birefringence is reduced, but manufacturing complexity and process difficulty increase
Solution Approach 1:
The patent makes the polymer structure itself capable of reducing birefringence through its inherent molecular structure design with fluorine-containing groups. The material self-regulates its optical properties without requiring external additives or complex processing steps, simplifying the manufacturing process while effectively reducing orientation birefringence.
3Object-generated harmful factors
If inorganic fine particles are added to reduce birefringence, then orientation birefringence is reduced, but aggregation and size control issues arise
Solution Approach 1:
The patent eliminates the need for inorganic fine particles by designing the organic polymer structure itself to have low orientation birefringence through fluorine-containing group placement. This self-service approach avoids all issues related to additive aggregation, uniform distribution, and particle size control.
4Strength
If molding temperature and pressure are increased to improve toughness, then molecular chain orientation increases, but stress birefringence worsens
Solution Approach 1:
The patent changes the material's intrinsic optical parameters by incorporating fluorine-containing groups in the polymer structure, which reduces the photoelastic constant and orientation birefringence. This allows the material to withstand higher molding temperatures and pressures needed for toughness without developing excessive stress birefringence.
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 optical material exhibits very low birefringence and stress birefringence, ensuring high transparency and toughness without temperature or pressure limitations during molding, and results in an optical film with reduced orientation birefringence and a low photoelastic constant, making it suitable for applications like liquid crystal displays and optical lenses.
Implementation Method 1
the orientation birefringence and photoelastic constant are very low
Implementation Method 2
both of the orientation birefringence and stress birefringence are reduced
Implementation Method 3
the photoelastic constant is very low
Data Source
AI summary
Disclosed is an optical material including a cyclic olefin copolymer containing at least a repeating structural unit [A] represented by the general formula (1) and a repeating structural unit [B] represented by the general formula (2) and having a molar ratio [A]/[B] of from 95/5 to 1/99, wherein the absolute value of the ratio ΔOB/ΔF is from 0.001 to 0.250 in which ΔOB represents the amount of a change in the absolute value of the orientation birefringence calculated from the phase difference (nm) at a wavelength of 633 nm/film thickness (μm) in a stretched film obtained from the optical material, and ΔF represents the amount of a change in the absolute value of the orientation coefficient determined from the dichroic ratio of parallel light intensity I∥ to perpendicular light intensity I⊥, each relative to the orientation direction according to Raman spectroscopy.