Lens Microstructures Encapsulated by Low Index Hard Coat
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Solution Overview
Problem
Existing optical articles with protruding optical elements like microlenses face a reduction in optical power and compromised abrasion resistance due to conventional abrasion-resistant coatings, which alter the surface curvature and impair the optical effects of the elements.
Innovation Solution
A protective layer with a crosslinked matrix and nanoparticles is applied, ensuring a smooth surface that maintains the original curvature of the base lens substrate, with a refractive index difference greater than 0.09 from the optical elements, providing enhanced abrasion resistance while encapsulating the optical elements without altering their power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional abrasion-resistant coating is applied to cover the microlenses, then the abrasion resistance is improved, but the optical power of the microlenses is reduced or impaired
Solution Approach 1:
The refractive index of the protective layer is specifically controlled to be lower than that of the microlenses (difference > 0.09), which compensates for the optical power reduction caused by the coating thickness. This parameter optimization allows the coating to provide abrasion resistance while maintaining the optical functionality of the microlenses.
Solution Approach 2:
The protective layer is formulated as a composite material containing crosslinked matrix and nanoparticles, which provides both mechanical durability (abrasion resistance) and controlled optical properties (refractive index < microlense index by >0.09). This composite structure enables simultaneous achievement of protection and optical performance.
2Reliability
If the thickness of the abrasion-resistant coating is reduced to minimize optical power alteration, then the optical power is better preserved, but the abrasion resistance is highly reduced
Solution Approach 1:
Instead of reducing thickness, the invention changes the refractive index parameter of the protective layer to be lower than that of the microlenses by more than 0.09. This parameter substitution allows maintaining both adequate coating thickness for abrasion resistance and preserved optical power through optical compensation.
3Reliability
If the abrasion-resistant coating reproduces the surface microstructure, then the optical effect is maintained, but the surface smoothness is compromised
Solution Approach 1:
The protective layer exhibits different properties at different locations: at the microlens apices, the layer thickness and refractive index are optimized to maintain optical power (local optical compensation), while in the inter-microlens regions, the coating provides uniform abrasion protection. This local quality differentiation resolves the conflict between optical effect preservation and surface smoothness.
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 preserves the optical power of the optical elements and provides superior abrasion resistance, allowing for the subsequent deposition of additional coatings like antireflective or anti-fogging layers, enhancing the optical article's performance and durability.
Implementation Method 1
the index nc of said protective layer is lower than the index nm of the optical elements such that the difference nm - nc is greater than 0.09
Data Source
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AI summary
The invention relates to an optical article comprising a base lens substrate having a at least one or a plurality of optical elements such as microlenses, a Fresnel structures, etc protruding from a surface thereof, and a hard coat covering encapsulating each optical elements. More particular it relates to an optical article comprising: a base lens substrate having opposing first and second lens surfaces; a protective layer having opposing first and second protective surfaces and a maximum thickness, measured in a direction perpendicular to the first protective surface between the first and second protective surfaces, the first protective surface disposed on the second lens surface; and at least one or a plurality of optical elements, each: defining a portion of one of the first protective surface and the second lens surface; having a maximum height, measured in a direction perpendicular to the second lens surface carrying them, that is less than or equal to 0.1 millimeters (mm) and a diameter that is less than or equal to 2.0 mm. wherein the protective layer is composed of a crosslinked matrix and nanoparticles and the index nc of said protective layer is lower than the index nm of the at least one or each optical element such that the difference nm - nc is greater than 0.045, preferably greater than 0.10, or even greater than 0.15; and wherein the maximum thickness of the protective layer is at least 2 times, preferably at least 5 times of the maximum height of the at least one or each of the optical elements. The invention also relates to the method for forming such optical articles, typically comprising an inkjet step.