Nowadays, we are required to use coated lenses for eyeglasses. For ophthalmic resin lenses, the main optical films are hardening film, anti-reflective film (transmittance enhancement film), anti-fouling film (waterproof film), anti-radiation film, polarising film, anti-fogging film, and spectrophotometric film. Do you know the characteristics of each film layer for lens coating?

1, hardening film. The hardness of resin lenses is low, and the surface of the lenses is easy to produce scratches. In order to improve the anti-wear ability of the lens, it is necessary to plating hard film on the surface of the lens. At present, silicon atoms are mostly used for hardening treatment, i.e., the hardening solution containing organic matrix and inorganic super particles including silicon elements is used to make the hard film have toughness and hardness at the same time. Modern hardcoat plating technology mainly adopts the immersion method. The hardcoat layer is thicker, about 3 to 5 μm, and the hardcoated resin lenses can be identified by the sound of tabletop tapping and the colour brightness of the lenses. The lens with crisp sound and bright edge is hardened.

2. Anti-reflection film. Reflection-reducing film is the use of the principle of interference, so that the light through the film layer to offset each other to achieve the purpose of reducing reflection. Reflection-reducing film can reduce the reflection loss of light energy on the surface of the lens to improve the imaging intensity and resolution. In order to meet the requirements of low reflection over a wide spectral range, it is necessary to use three or more layers of reflection-reducing films. The thickness of the current multi-layer anti-reflection film is about 0.3μm, and it is mostly made of high-purity metal oxide materials such as titanium oxide and zirconium oxide, which are plated on the surface of resin lenses by evaporation process to achieve good anti-reflection effect. There will be a residual colour after the anti-reflection coating, which is mainly green. For lenses that need to be hardened, they should be hardened first and then plated with anti-reflection film.

3. Anti-fouling film. Lenses coated with anti-reflective film are particularly susceptible to stains, which can damage the effect of anti-reflective film and reduce the transmission of light. Under the microscope, the porous structure of the film makes it easy for oil and dirt to infiltrate the film. It is possible to coat a layer of anti-oil and water resistant film on top of the anti-reflective film layer, which will not change the optical properties of the anti-reflective film. The material of anti-fouling film is mainly fluoride, which can cover the porous layer of the anti-reflective film, and can reduce the contact area of water and oil with the lens, so that the oil and water droplets are not easy to adhere to the surface of the lens, and is therefore also known as waterproof film. Anti-fouling film is plated by vacuum coating method. The film layer is thin, about 0.005～0.01μm.

4. Anti-radiation film. Anti-radiation lens is based on the principle of electromagnetic interference shielding using special coating process, after special electrical conductor film processing, so that the lens has the function of anti-electromagnetic radiation. The anti-radiation substance is a metal compound, forming a barrier on the surface of the lens, reflecting and absorbing the low-frequency radiation and microwave, effectively filtering out electromagnetic radiation waves.

5. Polarising film. Polarised lenses are made of polarising film and ordinary lenses glued together. Polarising film is the use of material to two perpendicular vibration of polarised light selective absorption characteristics and made. Natural light can be broken down into horizontal and vertical linearly polarised light with mutually perpendicular vectors, equal sizes and unrelated phases. When natural light is incident on an interface at a specific angle (i.e., the Brewster angle), the reflected light becomes linearly polarised with light vectors vibrating perpendicular to the incident surface. The glare reflected from a smooth interface is polarised light. A polarising film can be used to block the stronger horizontal component of this blinding glare. There are two types of polarising films used in ophthalmic lenses. One is a relatively thick polarising film glued to the middle of the lens, which makes the edge of the lens appear as a clear "sandwich". One is attached to the surface of the lens thickness of the new thin polarising film, such lenses are more beautiful.

6, anti-UV film: can block the sun's harmful ultraviolet rays.