Aromatic Polycarbonate Polarizing Lens Shape Precision
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Solution Overview
Problem
Aromatic polycarbonate polarizing lenses using one-side stretched polycarbonate sheets face challenges in achieving desired surface shape precision due to variations in processing conditions, leading to issues with base curve anisotropy and resolution, which affects their ability to be fixed to frames and meets American Standard ANSI-Z87.1 requirements.
Innovation Solution
A polarizing lens formed by laminating aromatic polycarbonate through an adhesive layer on polarizing films, curving to create spherical or aspherical surfaces, and injecting aromatic polycarbonate with specific retardation values and stretch axis orientations to achieve precise surface shapes, ensuring base curve anisotropy of 0.25 or less and resolution of 20 or more.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a curving process is applied to provide spherical or aspherical shape, then the lens obtains desired surface shape, but coloring interference stripe occurs due to high photoelastic constant of aromatic polycarbonate
Solution Approach 1:
The aromatic polycarbonate sheet is subjected to a stretching process in advance to cause large retardation before the curving process. This preliminary action creates a pre-stretched state that compensates for the photoelastic effects during subsequent curving, preventing coloring interference stripes from appearing in the final lens product
2Strength
If aromatic polycarbonate is injected to improve impact resistance, then impact resistance is improved, but unevenness of thickness becomes visible causing poor appearance
Solution Approach 1:
The patent changes the physical state and flow characteristics of the aromatic polycarbonate by controlling injection parameters (temperature, pressure, injection rate) to achieve uniform filling of the mold cavity. This ensures that the injected polycarbonate layer uniformly covers the polarizing sheet without creating visible thickness variations or surface defects
3Manufacturing precision
If surface shape of mold is adjusted to compensate for volume contraction, then lens thickness precision is improved, but device complexity increases
Solution Approach 1:
The mold surface shapes are pre-adjusted during mold design to compensate for the predictable volume contraction that occurs during resin solidification. By incorporating these compensatory features into the mold design before production, the patent achieves precise lens thickness control without requiring complex real-time adjustments during the injection process
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
Stably provides high shape precision and meets ANSI-Z87.1 standards for polarizing lenses, ensuring accurate surface shape and resolution, even after heat treatment, thereby improving the lens's fit and protective capabilities.
Implementation Method 1
since aromatic polycarbonate has a high photoelastic constant, when a curving process is applied to a spherical or aspherical shape of sunglasses, goggles or the like, a coloring interference stripe tends to easily occur due to retardation
Implementation Method 2
formed by laminating an aromatic polycarbonate sheet as a protection layer through an adhesive layer to each surface of a polarizing film
Data Source
AI summary
Provided is a polarizing lens which is excellent especially in terms of impact resistance, appearance, and prevention of eye strain and which has high precision of the surface shape. The polarizing lens is formed by laminating a sheet of an aromatic polycarbonate through an adhesive layer to each surface of a film having polarizing properties, curving the resultant laminate so as to impart spherical or aspherical surfaces thereto to obtain a polarizing sheet, inserting the polarizing sheet into a mold, and injecting an aromatic polycarbonate, wherein the polarizing sheet is obtained through the laminating so that the stretch axis of one of the aromatic-polycarbonate sheets is perpendicular to the absorption axis of the film having the polarizing properties.