The history of the photochromic lenses

The evolution of the photochromic lens has experienced a series of changes, from the beginning of the photochromic glass lenses to subsequent photochromic resin lenses, and complex photochromic lenses, made by leaps and bounds development in recent years. In 1962 the first generation of photochromic lens glass material, then be modified to improve performance continuously, it is mainly in glass material joined the silver halide crystals, the crystals under ultraviolet (uv) radiation on chemical reaction, make the color of the lens. The first generation of photochromic lens material change color is silver atoms and an electronic exchange between chlorine atom, by silver chloride and the surrounding environment. In 1964, the United States Corning ( Corning) Company developed color glass lenses, on the market in 1966 launched the first in the world of silver halide, a series of copper halide photochromic glass lenses. Photochromic lenses for the first generation of raw materials is specially designed for general frame, main bag out the tongue plate frames and metal frames, with its ground of tonal and downy, there are mainly two gray, and tan colors. The second generation of raw materials has good tensile strength, can be up to 25 kg, the second generation except for plate frame and metal raw materials, also applies to his rimless frames ( Accounted for 20% of the whole frame market) 。 The second generation of raw material is made from a kind of super light weight materials, it has the existing of refraction ( O multiples) Have reliable properties, has better tensile strength at the same time, IOO % against uva rays, UVA) And narrow wave ultraviolet ray ( UVB) , relative to the first generation of raw materials is more suitable for the design of his rimless glasses. The second generation of the raw material with pure grey and light brown, in the lens of the whole life to keep color stability, long service life. Photochromic materials are mostly gray and brown, commonly known as gray change and tea, its characteristic is can be both used vision correction lenses, and can do the sun glasses, suitable for field workers to wear. There is the main reason for the change of tea and grey color change is the additive in the lens is different, which leads to the lens color is different, the color of the other changes can also be achieved through special process. Become tea in addition to joining can change color of silver halide, also joined the silica, alumina and boron oxide, cobalt, nickel, manganese, etc. , dark brown is suitable for the wearer is more sensitive to light, because tea color can enhance the contrast. Grey mainly of silica, aluminum hydroxide, boric acid, zirconium oxide, silver nitrate, cobalt oxide, cerium oxide, nickel oxide, etc. , gray can produce excellent restore the color of the object, the object color is more vivid image. Now, people and made all sorts of color glass oxides of rare earth elements, such as: join the oxidation of rubidium glass, glows purple under sunlight, after fluorescent lights are purple, some colorful color lenses on the market today, the principle and the photochromic lens, just different additives, relative change dark brown and gray, colorful color color is relatively stable. Photochromic glass lenses with high refractive index and excellent optical performance, photochromic glass lens is relatively hard, durable, wear-resisting performance is very good, but fragile and for high refractive power of lenses will produce certain negative effect, because the lens is thicker, the lower light transmittance. The color concentration of photochromic lenses followed the thickness of the lens and 6 different change. Highly negative edge of the lens is thicker than the middle, then the color density and therefore increase the edge and in this case, there will be a high refractive power lens center color shallow phenomenon, and has a very deep around the ribbon. For the lens on the contrary, the influence of middle area very deep color, and the surrounding color light. Photochromic glass lenses appear this kind of color difference not only caused a very bad lens appearance, but also brought the inconvenience of visual impact, especially serious high myopia, there will be a glare. In 1991, the United States Transitions company launched the first generation of resin lenses, before this, all color piece are glass color piece, after the company launched resin color piece, photochromic lenses market ushered in the new growth point. With the successful development of photochromic materials, the first generation of photopolymer resin lenses, successful development has obtained certain result, in 1990 the first generation of the whole line of sight glasses, photochromic resin lenses in the true sense begin to popularize. Resin photochromic patches of light effect in the lens material is joined to a mixture of light and, in the role of special wavelength of ultraviolet radiation, the photosensitive material structure changed, thus changing the absorption ability of the material itself. The combination of the mixture and materials by the two methods: one kind is mixed with liquid monomers before polymerization, one kind is after polymerization permeability of materials. In 1993, a new kind of photochromic resin lenses on the market, this new type of resin lens is made of osmosis in convex lens, the layer of photochromic material, then an abrasion resistant layer on the membrane, protect and wear-resisting function, all of this for the photochromic lenses have laid a good foundation.