Protective Coating / Hard Coating
Custom Fabrication
Custom Fabrication
Any question you want to know, just to contact email: cusoptics@micquartz.com.
What is Protective Coating / Hard Coating?
Protective coating is a transparent and hard thin film applied to the outermost surface of optical components or functional film layers. Its core purpose is not to directly change the optical performance, but to act as a “transparent armor”, providing physical protection and chemical isolation for the delicate surface below, thereby ensuring the long-term performance stability and durability of optical components.
You can understand it as applying a transparent, superhard protective paint to precious artworks.
Why do we need Protective Coating / Hard Coating? ——Defense and Durability
Optical components face various threats in use:
Physical scratching: Cleaning, installation, touching, and dust particles can all scratch the surface.
Chemical corrosion: Moisture, salt spray, and acidic or alkaline substances can corrode the film layer and substrate.
Environmental oxidation: Oxygen and water in the air can cause the metal film layer to lose its luster and deteriorate its performance.
Mold growth: In humid and hot environments, mold on glass surfaces can damage optical surfaces.
How does Protective Coating / Hard Coating work?
The protective coating mainly works through physical shielding and chemical passivation.
Material selection: The protective film itself must be an extremely stable and hard inert material. The most commonly used ones are silicon dioxide (SiO ₂) and aluminum oxide (Al ₂ O3). They have high hardness, high density, low stress, and excellent chemical resistance.
Forming a barrier: This dense film can effectively isolate water vapor, corrosive ions, and pollutants from contact with the underlying material, preventing electrochemical corrosion and oxidation.
Enduring wear and tear: Its high hardness (usually close to or exceeding glass) means it can withstand friction and scratching, leaving mechanical damage on its own surface, thereby protecting softer functional film layers (such as metal reflective films) or substrate materials (such as plastic lenses) underneath.
Types & Features of Protective Coating / Hard Coating (Protected Object)
| Type | Features | Advantage |
|---|---|---|
| Metal reflective coating (such as aluminum mirrors, silver mirrors) | Aluminum, silver and other metals are very soft and easily oxidized, resulting in blackening and failure. | The most important application. Providing physical wear resistance and chemical isolation to prevent oxidation and scratches is a prerequisite for the practical application of metal reflectors |
| Anti reflective film (AR) and other functional films | Although multi-layer dielectric films are harder, they are still inferior to glass, and frequent cleaning can lead to wear and tear. | Improve the mechanical strength and chemical resistance of the overall membrane system, and extend its service life. |
| Plastic optical components (such as PC, PMMA lenses) | The surface of plastic is extremely soft, easily scratched, and not resistant to solvents. | Providing a surface with ultra-high hardness, enabling it to achieve wear resistance close to glass, widely used in eyeglass lenses, car headlight covers, and safety goggles. |
| Infrared materials (such as germanium Ge, zinc sulfide ZnS) | Many infrared materials have a soft texture and are easily hygroscopic (they decompose when exposed to water). | Provide wear-resistant protection and moisture-proof sealing, enabling them to be used in harsh environments. |
The advantages of Protective Coating / Hard Coating
High hardness and wear resistance: Usually tested using pencil hardness (such as 9H) or friction tests (such as steel wool or rubber friction).
Strong adhesion: The film layer must be tightly bonded to the substrate and not easily detached. Commonly used tape stripping method for testing.
Chemical stability: It must be resistant to water, salt spray, and solvents. Commonly used methods include immersion steaming, salt spray testing, etc. to verify.
Environmental durability: High and low temperature cycling, wet heat testing, etc. are required to ensure that it does not rupture or fail under changes in temperature.
Optical neutrality: The ideal protective film itself should not change the optical properties (transmittance, reflectivity) of the underlying components.
Application
Consumer electronics: anti fingerprint (AF), anti glare (AG), and wear-resistant (HC) films on smartphone camera lenses and AR/VR lenses.
Automotive industry: car headlight protection cover, interior display cover, sensor window.
Aerospace and Defense: Airborne electro-optical pod windows, submarine periscopes, laser protective goggles, need to withstand extreme environments.
Medical equipment: Endoscope lenses, surgical microscope lenses, require repeated cleaning and disinfection.
Energy sector: Solar cell cover plates need to withstand long-term wind and sand wear.
Daily necessities: Almost all resin eyeglass lenses are coated with superhard protective film.Consumer electronics: anti fingerprint (AF), anti glare (AG), and wear-resistant (HC) films on smartphone camera lenses and AR/VR lenses.
Automotive industry: car headlight protection cover, interior display cover, sensor window.
Aerospace and Defense: Airborne electro-optical pod windows, submarine periscopes, laser protective goggles, need to withstand extreme environments.
Medical equipment: Endoscope lenses, surgical microscope lenses, require repeated cleaning and disinfection.
Energy sector: Solar cell cover plates need to withstand long-term wind and sand wear.
Daily necessities: Almost all resin eyeglass lenses are coated with superhard protective film.
Send Us A Message
