Polycarbonate Spectacle Lens UV Absorber Composition
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Solution Overview
Problem
Polycarbonate resin spectacle lenses face challenges in maintaining transparency and impact resistance while providing adequate ultraviolet protection, as existing methods often result in yellowing and mold contamination due to the use of ultraviolet light absorbers, and suffer from unsatisfactory molding heat resistance and releasability.
Innovation Solution
A polycarbonate resin composition incorporating specific ultraviolet light absorbers, a full ester of an aliphatic polyhydric alcohol and aliphatic carboxylic acid as a release agent, and a phosphorus-based heat stabilizer, which together enhance ultraviolet absorption, prevent yellowing, and improve molding heat resistance and releasability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a large amount of ultraviolet light absorber is added to absorb ultraviolet radiation having a wavelength longer than 375 nm, then ultraviolet absorptivity is improved, but the ultraviolet light absorber sublimes and contaminates the mirror surface of a mold during injection molding
Solution Approach 1:
The patent changes the chemical structure parameters of the ultraviolet light absorber by using a benzotriazole compound with specific substituents (tert-butyl group at position 3, methyl group at position 5, and chlorine atom at position 7). This structural modification reduces the sublimation tendency while maintaining ultraviolet absorption capability at wavelengths longer than 375 nm, thereby preventing mold contamination.
Solution Approach 2:
The patent creates a composite resin composition by combining polycarbonate resin with a specific benzotriazole-type ultraviolet light absorber and a phosphorus-based heat stabilizer. This composite formulation achieves synergistic effects where the heat stabilizer further suppresses degradation and sublimation, allowing effective ultraviolet protection without mold contamination.
2Object-affected harmful factors
If a long wavelength absorbing ultraviolet light absorber is added to absorb ultraviolet radiation having a wavelength longer than 375 nm, then ultraviolet absorptivity is improved, but the polycarbonate resin yellows markedly
Solution Approach 1:
The patent modifies the chemical structure of the ultraviolet light absorber by introducing a chlorine atom at the 7-position of the benzotriazole ring, along with specific alkyl groups. This structural parameter change shifts the absorption maximum to longer wavelengths (380-420 nm) while reducing the yellowing effect on the polycarbonate resin, achieving a balance between ultraviolet protection and color stability.
Solution Approach 2:
The patent introduces a phosphorus-based heat stabilizer as an intermediary substance that mediates between the ultraviolet light absorber and the polycarbonate resin. This heat stabilizer suppresses the yellowing effect caused by the long-wavelength ultraviolet absorber, allowing the resin to maintain its optical properties while providing effective ultraviolet protection.
3Reliability
If 0.1 to 20 parts by weight of an oligomer type ultraviolet light absorber is added to provide weatherability, then weatherability is improved, but transparency is impaired and luminous transmittance is greatly reduced
Solution Approach 1:
The patent changes the molecular weight and structural parameters of the ultraviolet light absorber by using a monomeric or low-polymerized benzotriazole compound rather than an oligomer. This parameter change reduces the concentration required for effective ultraviolet absorption, thereby maintaining high luminous transmittance and transparency while providing adequate weatherability.
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 solution achieves high transparency, complete absorption of ultraviolet radiation, and maintains impact resistance, with minimal yellowing and excellent releasability, even under heat history, thus addressing the limitations of existing technologies.
Implementation Method 1
it absorbs ultraviolet radiation having a wavelength of 385 nm or more
Implementation Method 2
excellent releasability at the time of molding
Implementation Method 3
excellent molding heat resistance and is so superior in reproduction property
Data Source
AI summary
A spectacle lens made of a polycarbonate resin composition which comprises (1) 100 parts by weight of a polycarbonate resin, (2) 0.05 to 0.5 part by weight of (A) at least one ultraviolet light absorber selected from the group consisting of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole and 2-(2′-hydroxy-5′-tert-octylphenyl)benzotriazole, (3) 0.01 to 0.3 part by weight of (B) at least one ultraviolet light absorber selected from the group consisting of 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole, 2,2′-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotraizole)-2-ylphenol] and 2-[2-hydroxy-3,5-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, and (4) 0.01 to 0.5 part by weight of (C) a full ester of a tetravalent to octavalent aliphatic polyhydric alcohol having 5 to 30 carbon atoms and an aliphatic carboxylic acid having 10 to 22 carbon atoms, having an acid value of 4 to 20.According to the present invention, the spectacle lens made of the above polycarbonate resin composition has molding heat resistance which enables it to be kept at a high temperature for a long time when the lens is formed by extrusion compression molding, a small change in hue when heat history such as re-extrusion is applied so as to recycle product waste and excellent releasability.