Optical Article Hard Coating Thickness Control
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Solution Overview
Problem
Plastic optical substrates, such as spectacle lenses, face challenges with interference fringes due to refractive index differences and nonuniform thickness of hard coating layers, leading to aesthetic issues and increased manufacturing complexity, especially with high refractive index materials.
Innovation Solution
A functional layer with a thickness within specific ranges (e.g., 6.5dn+4.0≦T≦100) is applied to the optical substrate, allowing refractive index differences at the interface while increasing the thickness to suppress interference fringes, which are then made imperceptible by ensuring the layer's surface accuracy and minimizing color differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a hard coating layer is formed on a plastic substrate with high refractive index to protect against scratches, then abrasion resistance is improved, but interference fringes are formed due to refractive index difference and nonuniform thickness
Solution Approach 1:
The patent changes the thickness parameter of the hard coating layer to a specific range (5-50 μm) to suppress interference fringes. This parameter change allows the coating to maintain sufficient thickness for protection while eliminating the optical interference effects that occur with thinner coatings on high refractive index substrates.
Solution Approach 2:
The patent ensures uniform thickness distribution across the hard coating layer to minimize local variations in refractive index path length. By controlling thickness uniformity, the patent reduces the formation of interference fringes while maintaining the protective function throughout the entire coating surface.
2Reliability
If the refractive index of the hard coating layer is adjusted to match the plastic substrate to reduce reflectance, then optical performance is improved, but manufacturing complexity increases due to the need for special coatings for each substrate
Solution Approach 1:
The patent develops a universal hard coating formulation and application method that works across multiple plastic substrate types with different refractive indices. By using a coating composition with specific refractive index characteristics (1.50-1.55) and controlling thickness within 5-50 μm, the same coating system can be applied to various substrates without requiring substrate-specific coating designs, thereby simplifying manufacturing.
3Object-generated harmful factors
If the thickness of the hard coating layer is increased to suppress interference fringes, then appearance quality is improved, but surface accuracy may be compromised
Solution Approach 1:
The patent identifies an optimal thickness range (5-50 μm) for the hard coating layer that balances interference fringe suppression with surface accuracy maintenance. This parameter optimization ensures that the coating is thick enough to eliminate optical interference effects while remaining thin enough to preserve surface flatness and optical precision.
Solution Approach 2:
The patent applies a moderate thickness increase to the hard coating layer rather than using excessive thickness. By selecting a controlled thickness range (5-50 μm) rather than maximizing thickness, the patent achieves sufficient interference fringe suppression while avoiding the negative effects of overly thick coatings on surface accuracy and manufacturing feasibility.
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 solution effectively reduces the visibility of interference fringes, maintaining surface accuracy and simplifying manufacturing by allowing a common coating system for various refractive index substrates, thereby enhancing the commercial value and production efficiency of plastic lenses.
Implementation Method 1
interference fringes are formed due to the difference in refractive index and nonuniformity in the thickness of the film
Data Source
AI summary
An optical article includes: an optical substrate, and a functional layer laminated on the surface of the optical substrate, the functional layer having a thickness T μm that satisfies the following condition:6.5dn+4.0≦T≦100wherein the thickness T is larger than 5 μm, and dn is the refractive index difference at the boundary of the optical substrate and the functional layer and satisfies the following condition:0.06≦dn≦0.4.