Microstructured Optical Lens Molding With Pre-Drying for Stable Power
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Solution Overview
Problem
Existing injection molding processes for optical microstructures in corrective lenses suffer from issues such as residual stress, dimensional instability, and variability in optical properties due to moisture content and post-molding effects, leading to inconsistent replication and increased production costs.
Innovation Solution
A method involving a pre-drying step to reduce moisture content in the first optical functional element to below 500 PPM, followed by injection molding and overmolding with a second material to form a composite structure, ensuring dimensional stability and consistent optical properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If injection molding is performed directly without pre-drying the first optical functional element, then the manufacturing process is simpler and faster, but the moisture content causes residual stress and dimensional instability leading to inconsistent optical properties
Solution Approach 1:
The first optical functional element is pre-dried to reduce moisture content to below 500 PPM before the injection molding of the second material. This preliminary action eliminates moisture-induced residual stress and dimensional instability, ensuring consistent optical properties in the final composite lens without requiring complex post-processing adjustments.
2Reliability
If a pre-drying step is added to reduce moisture content below 500 PPM, then residual stress and dimensional instability are reduced, but the manufacturing time and process complexity increase
Solution Approach 1:
The drying process parameters (temperature, humidity, time) are optimized to achieve the critical threshold of below 500 PPM moisture content in the first optical functional element. By controlling these parameters efficiently, the process achieves reliable dimensional stability while minimizing the time penalty of the drying step, making the additional process time worthwhile for the quality improvement.
3Manufacturing precision
If multiple concept loops are performed to compensate for coating-induced shape changes, then the optical microstructure design is optimized, but the development time and cost increase significantly
Solution Approach 1:
The harmful effect of moisture-induced shape changes during coating is eliminated by extracting the moisture from the first optical functional element through pre-drying to below 500 PPM. This removes the need for multiple iterative concept loops to compensate for coating-induced deformations, significantly reducing development time and cost while maintaining microstructure shape accuracy.
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 achieves consistent replication of optical microstructures with reduced residual stress and improved accuracy of global average power, enhancing the reliability and efficiency of myopia control lenses.
Implementation Method 1
drying the first optical functional element A, said drying step being adapted to or configured to obtain the first optical functional element A that has a moisture content lower than or equal to 500 PPM
Implementation Method 2
producing a first optical functional element A having a first refractive index, named hereafter nA, by injecting into a mold of an injection molding device at least a first material A1
Implementation Method 3
The optical article thus formed comprises a substrate having a composite structure (thin upper part/main lower part) that adhered through thermomechanical fusing
Data Source
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AI summary
The invention relates to a process for manufacturing an optical article comprising at least the following successive steps: (a) producing a first optical functional element A having a first refractive index, named hereafter nA, by injecting in a mold of an injection molding device at least a first material A1, the first optical functional element A having at least a first main face and a second main face, said first main face including a pattern of optical microstructures, (b) coating directly onto said first main face of the first optical functional element A, a second optical functional element B via a first main face of said second optical functional element, having a second refractive index, named hereafter nB, that is distinct from nA, by injecting into said mold at least a second material B1, characterized in that before performing the step (b), the process further comprises (a1) drying the first optical functional element A, said drying step is adapted to or configured to obtain a first optical functional element A having a moisture content lower than or equal to 500 PPM. The invention also relates to an optical article obtained according to the above-mentioned process and its use for myopia control and/or prevention.