Laser Dyeing of High-Index Plastic Lenses Without Yellowing
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Solution Overview
Problem
Conventional methods for dyeing high refractive index plastic lenses, such as those with refractive indices of 1.74 or more, face issues like yellow discoloration due to increased heating temperatures and times, and struggle to achieve desired color density without heating the entire lens, leading to inefficient dyeing processes.
Innovation Solution
A dyeing method using a laser beam with wavelengths in the infrared or ultraviolet region to heat the surface of the plastic lens without melting it, allowing the dye to be dispersed into the lens while minimizing heat absorption by the dye, thus preventing sublimation and maintaining color tone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the heating temperature and heating time are increased to fix sublimable dyes on high refractive index lenses, then the dye fixation is improved, but the lens turns yellow due to chemical changes
Solution Approach 1:
The patent applies local quality by using a laser beam to heat only the surface layer of the lens where the dye is applied, rather than heating the entire lens. This localized heating approach allows sufficient dye fixation at the surface while preventing the bulk material from reaching temperatures that cause yellow discoloration. The laser energy is concentrated in a specific depth range (100-200 µm) to achieve this selective heating effect.
Solution Approach 2:
The patent replaces the conventional thermal convection heating system (oven) with a laser beam heating system. This substitution allows for precise control of heating depth and temperature distribution, enabling surface-level dye fixation without heating the entire lens volume, thereby avoiding yellow discoloration while maintaining effective dye bonding.
2Productivity
If the entire lens is heated to fix dyes efficiently, then the dye fixation speed is improved, but the yellow discoloration problem worsens
Solution Approach 1:
The laser beam heating method applies local quality by concentrating thermal energy in the surface region where dye fixation is needed, rather than heating the entire lens. This enables rapid dye fixation at the surface level while keeping the bulk lens temperature low, thus achieving high productivity without causing yellow discoloration throughout the lens.
Solution Approach 2:
The heating process is segmented into different depth zones: the surface layer (100-200 µm) receives high temperature for rapid dye fixation, while the interior remains at lower temperature to avoid yellow discoloration. This spatial segmentation of temperature zones allows simultaneous achievement of fast processing and color stability.
3Productivity
If the laser beam directly heats the dye, then the dye fixation efficiency is improved, but the dye sublimates and desired color density cannot be obtained
Solution Approach 1:
The patent uses local quality by selecting a laser wavelength that is absorbed by the lens material but not by the dye molecules. This creates a localized heating zone within the lens substrate that indirectly heats the dye through thermal conduction, rather than directly irradiating the dye. The result is efficient dye fixation without excessive dye sublimation, preserving color density.
Solution Approach 2:
The lens material acts as an intermediary that absorbs the laser energy and converts it to thermal energy, which then transfers to the dye through conduction. This indirect heating mechanism via the lens substrate as intermediary prevents direct laser-dye interaction that would cause excessive sublimation, while still achieving effective dye fixation.
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
This method efficiently fixes dyes on the surface of high refractive index plastic lenses in a short time, preventing yellow discoloration and ensuring uniform color density without altering the lens's tone, even when the surface is heated to a depth of 100-200 µm, while the interior remains unheated.
Implementation Method 1
irradiating a laser beam having a wavelength in an infrared region or an ultraviolet region toward the transparent resin body to heat the dye through the transparent resin body and heat the transparent resin body
Implementation Method 2
irradiating a laser beam having a wavelength in an infrared region or an ultraviolet region
Implementation Method 3
heat the transparent resin body to a temperature that does not melt the surface of the transparent resin body and that causes the heated dye to be dispersed into the transparent resin body
Data Source
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AI summary
Disclosed is a dyeing method using a laser beam. The method can dye transparent resins such as plastic lens well. Also disclosed is a dyeing apparatus. The dyeing method comprises heating a plastic lens (10) having a dye-coated surface to fix the dye on the surface of the plastic lens (10). The method comprises the step of applying a laser beam with a wavelength, which is less likely to be absorbed in the dye but it absorbed in the plastic lens (10), onto the surface of the plastic lens (10) through the dye.