Plastic Lens UV Absorption Yellowing Prevention
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Solution Overview
Problem
Existing methods for producing plastic lenses with ultraviolet ray absorbents often result in yellowing, which compromises transparency, especially during heat treatment processes.
Innovation Solution
Incorporating specific anthraquinone compounds with particular structures during the polymerization of monomer compositions, such as those represented by formulas (1) and (2), which include chlorine and hydrogen atoms, and alkyl groups, to prevent yellowing while maintaining transparency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If an ultraviolet ray absorbent is added in production of a plastic lens, then the ultraviolet ray absorbing power is improved, but the plastic lens yellowing occurs
Solution Approach 1:
The patent introduces a specific anthraquinone compound as an intermediary substance that mediates between the ultraviolet ray absorbent and the plastic lens material. This compound acts as a protective agent that prevents the yellowing reaction while allowing the ultraviolet absorbent to function, thus resolving the contradiction between UV protection and color stability.
Solution Approach 2:
The patent changes the chemical parameters by selecting a specific anthraquinone compound with particular structural characteristics (formula (1)) that has optimal properties for preventing yellowing. By adjusting the chemical composition parameters - specifically the type and concentration of the anthraquinone compound - the patent achieves both UV absorption and color stability.
2Object-generated harmful factors
If a bluing agent or blue dye is added in the production process, then the yellowing is compensated, but the solubility is poor and discoloration occurs during polymerization
Solution Approach 1:
Instead of using conventional blue dyes that require high concentrations and suffer from solubility issues, the patent employs a small amount of anthraquinone compound that provides sustained protection throughout the polymerization process and beyond. This compound acts as a long-lasting protective agent that eliminates the need for conventional bluing agents.
Solution Approach 2:
The patent changes the approach from adding blue dyes (which have poor solubility) to adding a specific anthraquinone compound with optimized solubility parameters. The compound of formula (1) is specifically selected for its ability to dissolve properly in the monomer composition and remain stable during polymerization, thus improving manufacturability.
3Manufacturing precision
If heat treatment is applied in production process, then the lens properties are improved, but the yellowing of plastic lens occurs
Solution Approach 1:
The patent applies the principle of beforehand cushioning by incorporating the anthraquinone compound into the monomer composition before polymerization and heat treatment. This compound provides preemptive protection against yellowing that may occur during subsequent heat treatment processes, allowing the lens to undergo necessary thermal processing without developing yellow discoloration.
Solution Approach 2:
The anthraquinone compound serves as a protective intermediary between the heat treatment process and the plastic lens material. It absorbs or neutralizes the harmful effects of heat that would otherwise cause yellowing, while permitting the beneficial thermal processing to proceed, thus enabling improved lens properties without yellowing.
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 method effectively produces plastic lenses that remain colorless and transparent, even with the addition of ultraviolet ray absorbents and heat treatment, ensuring optimal transparency and preventing yellowing.
Implementation Method 1
A spectacle lens is demanded to have an ultraviolet ray absorbing power for protecting eyes from a harmful ultraviolet ray, and an ultraviolet ray absorbent may be added in production of a spectacle lens formed of a plastic material
Implementation Method 2
it has been found that the addition of an anthraquinone compound having a particular structure may provide a plastic lens that is extremely close to colorless and transparent without yellowing even though the plastic lens is produced through a process including addition of an ultraviolet ray absorbent and a heat treatment
Data Source
AI summary
The present invention is a method for producing a plastic lens, containing polymerizing a monomer composition, at least one compound selected from a compound represented by the following formula (1) and a compound represented by the following formula (2) being added in polymerization of the monomer composition: wherein in the formulae (1) and (2), one of X1 and X2 represents a chlorine atom, and the other thereof represents a hydrogen atom; and R1 and R2 each independently represent a hydrogen atom or a group selected from an alkyl group having from 1 to 8 carbon atoms.