Colored Polarizing Lens Dyeing and Curving Process
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Solution Overview
Problem
Conventional polarizing films for sunglasses face challenges in maintaining desired total light transmittance and polarization levels with minimal color tone changes, especially during the curving process to form spherical or aspherical surfaces, leading to variations in product quality due to dye degradation and uneven thickness.
Innovation Solution
A method involving a polyvinyl alcohol film that is swollen, uniaxially stretched, and dyed with a combination of dichroic organic azo dyes and coloration organic dyes, where the dichroic dyes maintain a high dichroic ratio for polarization and the coloration dyes provide desired colors with minimal transmittance reduction, using an aqueous solution and specific dye concentrations to control the film's properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If aromatic polycarbonate is curved to make spherical or aspherical surfaces, then impact resistance and heat resistance are improved, but interference fringes in coloration arise due to large photoelastic constant and retardation
Solution Approach 1:
The harmful photoelastic property is extracted and relocated to the polycarbonate protective layer, which is intentionally designed with high photoelastic constant. This separates the polarization function (in PVA film with minimal photoelasticity) from the protective function (in polycarbonate layer with high photoelasticity), preventing interference fringes in the polarizing film while maintaining impact resistance in the protective layer.
Solution Approach 2:
Different layers are assigned different photoelastic properties: the PVA polarizing film has minimal photoelastic constant to avoid interference fringes, while the polycarbonate protective layer has large photoelastic constant to absorb stress-induced optical effects. This local differentiation resolves the contradiction between protection and optical quality.
2Reliability
If dichroic dyes are used to achieve high degree of polarization, then polarization performance is improved, but color tone selection is limited and transmittance is reduced
Solution Approach 1:
The dyeing function is segmented into two independent systems: dichroic dyes for polarization performance and coloration dyes for color tone control. This allows optimization of each function separately - dichroic dyes maximize polarization while coloration dyes provide versatile color selection without compromising transmittance.
Solution Approach 2:
The patent uses a composite dye system combining dichroic dyes (for polarization) and coloration dyes (for color and transmittance control). This composite approach allows simultaneous achievement of high polarization degree and desired color tone with controlled transmittance, resolving the trade-off between polarization performance and color versatility.
3Strength
If aromatic polycarbonate is injected into curved polarizing sheet to produce aromatic polycarbonate polarizing lens, then impact resistance and thickness uniformity are improved, but color tone changes during heat-curving process
Solution Approach 1:
The polarizing film is pre-dyed with dichroic and coloration dyes before curving and injection processes. This preliminary dyeing ensures that the polarization and color properties are established early, and subsequent processing steps (curving, injection) are designed to minimize further color changes, maintaining color tone stability while achieving high impact resistance.
4Adaptability or versatility
If polarizing film is dyed to achieve desired color tone, then color selection is improved, but transmittance is reduced
Solution Approach 1:
The patent independently controls multiple parameters: dichroic dye concentration for polarization degree, coloration dye concentration for color tone, and their combination for transmittance control. By adjusting these parameters separately, the invention achieves desired color tone and transmittance without compromising polarization performance.
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 approach allows for a wider selection of colors and reduced color tone changes during the molding process, particularly the heat-curving process, resulting in polarizing films, sheets, and lenses with consistent transmittance and polarization properties.
Implementation Method 1
the dichroic organic dye composition comprises a combination of three or more dichroic organic azo dyes having a dichroic ratio of 13 or higher
Implementation Method 2
the coloration organic dye composition comprises a combination of dyes having an extremely low dichroic ratio of 4 or less or substantially having no dichroic ratio, used in an amount yielding a desired dyed color
Data Source
AI summary
[Problem to be solved] A polarizing film for sunglasses having a color that can be more freely selected and that shows smaller changes in color tone and a colored polarizing sheet using the film and a colored polarizing lens using the polarizing sheet are provided. [Solution] A polarizing film that is produced by swelling a polyvinyl alcohol film with water, uniaxially stretching it, dyeing it with an organic dichroic dye, and drying it, wherein the dichroic organic dye is made by using a dichroic organic dye composition and a coloration organic dye composition, wherein the dichroic organic dye composition comprises a combination of organic dyes having a dichroic ratio of 13 or higher used in an amount to keep the degree of polarization at 90% or more, and wherein the coloration dye composition comprises a combination of dyes having extremely low dichroic ratios of 4 or less or substantially having no dichroic ratio, laminating at least one layer of a transparent plastic sheet onto at least both sides of the polarizing film, which is obtained by using an amount of coloration organic dye composition to yield the desired color, to obtain a polarizing sheet; curving the polarizing sheet so as to impart spherical or aspherical surfaces thereto to obtain a polarizing lens or curving the polarizing sheet so as to impart spherical or aspherical surfaces thereto and injecting a transparent resin to the concave surface of the curved polarizing sheet to obtain an injection polarizing lens, wherein the transparent resin is an aromatic polycarbonate, wherein the surface of the one side of the polarizing sheet is an aromatic polycarbonate and that side is curved to make the concave surface.