1. Technical characteristics
(1) The first generation of anti-wear film technology
The anti-wear film began in the early 1970s, when it was believed that optical lenses were not easy to grind because of their high hardness, while organic lenses were too soft to wear easily. Therefore, the quartz material is coated on the surface of the organic lens under vacuum to form a very hard anti-wear film, but due to the mismatch of its thermal expansion coefficient and the base material, it is easy to peel off and the film layer is brittle, so it is resistant to The wear effect is not ideal.
(2) Second-generation anti-wear film technology
After the 1980s, researchers theoretically found that the mechanism of wear is not only related to hardness, the film material has the dual characteristics of "hardness/deformation", that is, some materials have higher hardness, but less deformation, and some The hardness of the material is low, but the deformation is large. The second-generation anti-wear film technology is to plate a material with high hardness and not easy to be brittle by immersion process.
(3) The third generation anti-wear film technology
The third generation of anti-wear film technology was developed after the 1990s, mainly to solve the problem of wear resistance of organic lenses coated with anti-reflection coatings. Because the hardness of the base of the organic lens and the hardness of the anti-reflection film layer are very different, the new theory believes that there is a layer of anti-wear film between the two, so that the lens can play a buffer role when it is rubbed by grit, and It is not prone to scratches. The hardness of the third-generation anti-wear film material is between the hardness of the anti-reflection film and the lens base. Its friction coefficient is low and it is not easy to crack.
(4) The fourth-generation anti-wear film technology
The fourth generation of anti-film technology is the use of silicon atoms. For example, the French Essilor Company’s TITUS hardening fluid contains both an organic matrix and inorganic ultra-fine particles including silicon elements to make the anti-wear film It has toughness while increasing hardness. The most important modern anti-wear film coating technology is the immersion method, that is, the lens is immersed in the hardening liquid after multiple cleanings, and after a certain time, it is lifted at a certain speed. This speed is related to the viscosity of the hardening fluid and plays a decisive role in the thickness of the anti-wear film. After lifting, it is polymerized in an oven at about 100°C for 4-5 hours, and the thickness of the coating is about 3-5 microns.
Second, the test method
The most basic method to judge and test the wear resistance of the anti-wear film is clinical use, let the wearer wear it for a period of time, and then observe and compare the wear of the lens with a microscope. Of course, this is usually the method adopted before this new technology is officially launched. At present, the more rapid and intuitive test methods we commonly use are:
(1) Frosted test
Place the lens in the propaganda product containing the gravel (the grain size and hardness of the gravel are specified), and rub it back and forth under certain control. After the end, use a haze meter to test the amount of light diffuse reflection before and after lens rubbing, and compare with the standard lens.
(2) Steel wool test
With a specified steel wool, under a certain pressure and speed, rub the surface of the lens a number of times, then use a haze meter to test the amount of light diffuse reflection before and after the lens is rubbed, and compare it with the standard lens. Of course, we can also operate manually, rub the two lenses with the same pressure the same number of times, and then observe and compare with the naked eye.
The results of the above two test methods are close to the clinical results of long-term wearers wearing glasses.
(3) Relationship between anti-reflection film and anti-wear film
The anti-reflection coating on the lens surface is a very thin inorganic metal oxide material (thickness less than 1 micron), which is hard and brittle. When coated on the optical lens, because the base is hard, the gravel is scratched on it, and the film layer is relatively not easy to produce scratches; but when the anti-reflection film is coated on the organic lens, because the base is soft, the gravel is on the film The layer is scratched, and the film layer is prone to scratches.
Therefore, the optical lens must be coated with an anti-wear film before the anti-reflection coating, and the hardness of the two film layers must match.