Sunglass Lens Materials and Coatings

Sunglass Lens Materials

Glass Lenses

Advantages: 

• Exceptional scratch resistance (you don’t need a scratch-resistant coating).
• Excellent optical clarity.
• The anti-reflective (AR) coating adheres to glass very well.

Disadvantages:

• At least twice the weight of plastic or polycarbonate lenses.
• About 25 to 40 percent thicker than polycarbonate and high index plastic lenses.
• Can shatter or chip easier than lenses made of other materials.
• Require a special coating to provide 100% UV protection.

Plastic Lenses

Advantages:

• Lightweight: About half the weight of glass lenses.
• Plastic lenses accept tints easily.
• More shatter-resistant than glass lenses.

Disadvantages:

• About 20 to 35 percent thicker than polycarbonate or high-index plastic lenses
• Require a scratch-resistant coating for added durability.
• Require a special coating to provide 100% UV protection.

Polycarbonate Lenses 

Advantages:

• Safest lens material – 10 times more impact resistant than other lenses.
• Thin: About 20 to 25 percent thinner than plastic or glass lenses.
• Lightweight: About 20 percent lighter than plastic lenses.
• It blocks 100 percent of UV rays without needing a special coating.

Disadvantages:

• Requires a scratch-resistant coating for durability.
• Peripheral vision may be slightly less clear with strong prescription powers.
• More lens reflections than glass or plastic lenses (AR coating is recommended).

High Index Plastic Lenses

Advantages:

• Lightweight: between plastic and polycarbonate lenses in weight.
• Thin: About 15 to 30 percent thinner than plastic lenses.
• Better peripheral optics than polycarbonate lenses (for prescription sunglasses).

Disadvantages:

• Requires scratch-resistant coating for durability.
• More lens reflections than glass or plastic lenses (AR coating is recommended).

Sunglass Lens Coatings

UV Coating

• UV coating is a nearly clear lens treatment that blocks ultraviolet (UV) rays from the sun.
• To provide 100% UV protection, glass and plastic lenses must have UV coating applied.
• Polycarbonate and most high-index plastic lens materials block 100 percent UV without the need for added coatings.

Scratch-Resistant Coating

• All lightweight lens materials (plastic, polycarbonate, and high-index plastics) have a relatively soft surface. These materials require a scratch-resistant coating (SRC) to be applied to both sides of the lens.
• Most lenses with scratch-resistant coatings include a 1-year warranty. Ask your optician for details.
• Glass lenses do not require a scratch-resistant coating. Because of its natural hardness, glass is even more scratch-resistant than most lightweight lenses with SRC applied.

Anti-reflective coating

• Anti-reflective (AR) coating eliminates lens reflections from the backside of sunglasses that can be distracting and interfere with comfortable vision.
• The application process for anti-reflective coating is highly sophisticated. AR coating is microscopically thin and is applied with vacuum coating technology.
• AR coating is a good idea for all sunglass lenses, regardless of material. It is particularly helpful on polycarbonate and high-index plastic lenses since these lenses reflect slightly more light than glass or plastic lenses.

Mirror Coatings

• Mirror coatings reduce the amount of light passing through them by reflecting light. 
• Mirror coatings are applied to the front surface of the lenses only. They are typically applied in combination with an underlying sunglass tint.
• The density of the mirror coating determines how much light it reflects. Half-silvered mirror coatings have an even coating of reflective particles across the surface of the lens, but the particles are spaced so about half of the light striking the lens surface hits a coating particle and is reflected.  The remaining 50 percent of visible light striking the lens passes between the reflective particles.  Some of this light is absorbed by the underlying lens tint. The remainder passes through the lens to the eye.
• Mirror coatings are sometimes applied as a gradient coating, being the densest at the top of the lens and then fading to nothing in the middle of the lens. This type of coating provides maximum shading of overhead sunlight while allowing more light to pass through the middle and lower parts of the lens.
• Mirror coatings are also available in a double-gradient style, in which the coating is quite dense at the top and bottom of the lens and less dense in the center of the lens. Double-gradient mirror coatings are an excellent choice for snow skiing and other winter activities because they provide excellent protection from both overhead sunlight and light reflecting off snow on the ground.