PC lenses (polycarbonate lenses) are widely used in the eyewear industry due to their advantages such as lightness and strong impact resistance. However, their surface hardness is low and they are easily scratched, so they need to be hardened to improve their wear resistance. The following is a detailed analysis of the PC lens hardening process:

1. The core principle of the hardening process

Base treatment: Clean the lens surface by chemical or physical methods to remove grease and impurities and enhance the adhesion of the hardened layer.

Hard coating: Coat the lens surface with a high hardness material (such as silicone resin) and form a wear-resistant layer through curing.

Curing technology: UV curing or thermal curing is commonly used to make the coating tightly bonded to the PC substrate.

2. Main hardening methods

(1) Dip coating

Process: Immerse the lens in the hardening liquid → Pull at a constant speed to control the thickness → UV/thermal curing.

Advantages: The coating is uniform and suitable for mass production.

Key points: Hardening liquid formula (including nano-silica and other ingredients) and curing conditions (UV intensity, temperature).

(2) Spin Coating
Process: The lens is fixed on a rotating table, hard liquid is added → high-speed rotation and evenly mixed → solidification.
Advantages: Controllable thickness, suitable for high-precision requirements.
Disadvantages: Large amount of material waste.
(3) Vacuum Coating
Technology: Inorganic hard films such as SiO₂ are deposited on the surface through PVD (physical vapor deposition).
Features: Extremely high hardness (close to glass), but high cost and special equipment required.
(4) Plasma Treatment
Function: Cleans the surface and activates molecules through plasma to improve coating adhesion.
Application: Often used as a pre-treatment or in combination with the dipping method.
3. Materials for Hard Coating
Silicone resin: mainstream choice, forming a cross-linked network through UV curing.
Nanocomposite materials: such as nano-SiO₂ and Al₂O₃ dispersed in the resin, significantly improving hardness.
Polyurethane acrylate: good flexibility and strong impact resistance.
4. Key Process Parameters
Curing Conditions: UV wavelength (typically 365nm), energy (500-1000mJ/cm²), temperature (60-80°C).

Coating Thickness: Generally 2-5μm. Thicker coatings are prone to cracking, while thinner coatings may lack abrasion resistance.

Environmental Control: Dust-free room (ISO Class 7 or higher), humidity 40-60%.

5. Quality Inspection Standards
Abrasion Resistance: Taber Abrasion Test (CS-10 grinding wheel, 500g load, haze change ≤5% after 1000 cycles).

Adhesion: Grid Knife Test (ASTM D3359, 4B or higher).

Hardness: Pencil Hardness Test (≥3H is acceptable).

Weather Resistance: UV Aging Test (no cracking or yellowing after 500 hours).

6. Common Problems and Solutions
Coating Delamination: Optimize surface treatment (such as plasma activation) or adjust curing parameters.

Surface orange peel: Caused by excessive viscosity of the hardening solution or uneven spin coating speed; formulation or process adjustments are required.

Bubbles: Vacuum degassing or reducing the pull/spin speed.

7. Industry Trends
Nanocomposite coatings: Nanomaterials (such as graphene) are used to further enhance hardness while maintaining light transmittance.

Environmentally friendly processes: Water-based hardening solutions replace solvent-based solutions, reducing VOC emissions.

Multifunctional coatings: Integrate blue light protection, anti-fog, and anti-static properties.