Optical Article Front Interferential Coating Abrasion Resistance
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Solution Overview
Problem
Existing optical articles with reflective coatings, such as solar lenses, suffer from inadequate abrasion and scratch resistance, particularly on their mirror-facing surfaces, which can lead to reduced vision quality and aesthetic issues, as well as potential exposure to harmful light due to scratches.
Innovation Solution
A novel optical article design featuring a substrate with a front interferential coating comprising low and high refractive index layers, where an external abrasion-resistant coating is directly applied over the interferential coating, providing enhanced mechanical properties and thermal stability without compromising optical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a reflective interferential coating is applied to provide mirror effect and reduce light transmission, then optical performance is improved, but abrasion and scratch resistance deteriorates
Solution Approach 1:
The patent applies a composite coating structure consisting of multiple layers with different properties: a first hard coat layer providing abrasion resistance, a second hard coat layer with different mechanical properties, and an interferential coating providing reflective properties. This composite structure allows the final coating to simultaneously achieve both optical performance (mirror effect) and mechanical durability (scratch resistance) by combining materials with complementary characteristics.
Solution Approach 2:
The reflective coating is divided into multiple distinct layers rather than being a single homogeneous coating. Each layer serves a specific function: the first hard coat layer provides foundational abrasion resistance, the second hard coat layer enhances mechanical properties, and the interferential coating provides the mirror effect. This segmentation allows optimization of each layer for its specific purpose while achieving overall system performance.
2Device complexity
If the interferential coating is made thinner to reduce manufacturing complexity, then device complexity is reduced, but abrasion resistance worsens
Solution Approach 1:
Instead of using a single thick interferential coating, the patent employs a composite structure with multiple thinner layers. This approach maintains or improves scratch resistance because each layer can be optimized for its specific function, and the cumulative effect of multiple layers provides better mechanical interlocking and distribution of stress compared to a single thick layer.
3Reliability
If a thick external hard coat is applied to improve abrasion resistance, then scratch resistance is improved, but optical clarity and colorimetric properties deteriorate
Solution Approach 1:
The hard coat functionality is segmented into two separate layers rather than being contained in a single thick layer. The first hard coat layer provides the primary abrasion resistance, while the second hard coat layer, being thinner, minimizes impact on optical clarity. This segmentation allows the system to achieve sufficient scratch protection without compromising visual quality.
Solution Approach 2:
Different layers are assigned different thicknesses and material compositions based on their specific functions. The first hard coat layer can be thicker and more abrasion-resistant, while the second hard coat layer and interferential coating are optimized for optical properties. This local optimization of properties at different positions in the coating stack allows simultaneous achievement of mechanical durability and optical clarity.
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 significantly improves abrasion and scratch resistance, maintains optical clarity, and enhances thermal stability, reducing the visibility of scratches and protecting against harmful light transmission.
Implementation Method 1
Reflective coatings usually consist of interferential thin layers... designed so as to confer to the surface of an optical article they coat, a mean light reflection factor in the visible region
Implementation Method 2
said front interferential coating comprising at least one layer having a low refractive index and at least one layer having a high refractive index
Data Source
Figure 1~3
AI summary
The invention relates to an optical article (OA) having a front main face and a rear main face, comprising at least: - one base element having a front main surface and a rear main surface; at least one front interferential coating deposited to the front main surface of the base element, said front interferential coating comprising at least one layer having a low refractive index which is lower than 1.55, defined as "LI layer", and at least one layer having a high refractive index which is equal to or higher than 1.55, defined as "HI layer", characterized in that an external abrasion-resistant coating is coated directly onto said front interferential coating so that the front interferential coating is positioned between the base element and the external abrasion-resistant coating, said external abrasion-resistant coating having a physical thickness ranging from 1 µm to 5 µm; and wherein the optical article has, on its front main face, a mean light reflection factor in the visible region Rv (front face OA) that is higher than or equal to 5 % for an angle of incidence of 15°.