As myopic frequent occurrence, all sorts of myopic glasses emerge in endlessly, so how did the color change myopic glasses become the problem that everybody cares most. Because discoloration myopia glasses look good, so it is the choice of a lot of myopic patients, below for discoloration myopia glasses how to introduce in detail for you.
The photochromic lens are made by adding appropriate amount of silver bromide and copper oxide micrograins into ordinary glass. When exposed to strong light, silver bromide breaks down into silver and bromine. The tiny grains of silver that decompose give the glass a dark brown color. When the light dimmed, the silver and bromine were catalyzed by copper oxide to form silver bromide again. As a result, the color of the lenses became lighter again.
Extremely stylish “photochromic lens” and “Polarized sun lenses”
Suitable for all people, including short-sighted people
First, the lens is made of discolored glass
Glass that changes colour when irradiated by light of an appropriate wavelength and restores its original colour when the source of light is removed. Also known as photochromic glass or light color glass. Color changing glass is made by adding light color material into the glass raw material. This material has two different molecules or electronic structure state, in the visible light region there are two different absorption coefficient, in under the action of light, can shift from one structure to another kind of structure, cause of reversible color change, common containing silver halide color glass, aluminum in sodium borate glass to add a small amount of silver halide (AgX) as a sensitizer, After adding a trace of copper and cadmium ions as sensitizer, the glass is fused and heat treated at appropriate temperature to make the silver halide concentrate into particles. When it is irradiated by ultraviolet light or short wave of visible light, silver ions are reduced to silver atoms, and a number of silver atoms gather into colloid to make the glass color; When the light stops, the silver atoms become silver ions and fade under the irradiation of thermal radiation or long-wave light (red or infrared).
Silver halide color-changing glass is not easy to fatigue, after more than 300,000 changes in light and shade, still does not fail, is a common material for making color-changing glasses. The color changing glass can also be used for information storage and display, image conversion, light intensity control and adjustment.
Two, the color change principle
Glasses in which the lens automatically changes color as ambient light changes. Full name photochromic glasses, also known as light color glasses. The color of the lens becomes darker and the light transmittance decreases when the lens is irradiated by ultraviolet and short-wave visible light under sunlight. In indoor or dark lens light transmittance increases, fade to restore vision. The photochromism of the lens is automatic and reversible. The color changing glasses can adjust the light transmittance through the lens color change, so that the human eye can adapt to the change of environmental light, reduce visual fatigue, protect the eyes. Chromic lens chromic before divided without a base color and light color has two kinds of base color; The color after discoloration basically has gray, tawny two kinds.
1964 Corning Glass Company invented photochromic glass. At present, the world’s main manufacturers of discolored glass lens blank are the United States and France corning glass company, Germany Schott Group special glass company and The UK Chance Pilkington company. Beijing, China, and other manufacturers produce color – changing lenses.
The chromic lens contains silver halide (silver chloride, silver bromide) microcrystals. When exposed to the activated light such as ultraviolet light or short wavelength visible light, the halide ion emits electrons, which are captured by the silver ion, and the following reactions occur:
The colorless silver halide breaks down into opaque silver atoms and transparent halogen atoms, which absorb light and make the lens less transparent. Since the halogen in the discoloration lens does not escape, reversible reactions can occur. After the activation light is removed, the silver and halogen are recombined to restore the lens to its original clear, colorless or light-colored state. The content of silver halide micrograins is about 4×1015 /cm3, the diameter is about 80 ~ 150, and the average distance between particles is about 600. The photochromic properties of the discoloration lenses are described by the darkening – restoring characteristic curve (see figure). TO is the original transmittance of the lens glass before exposure, and TD is the transmittance of the lens at 550nm wavelength after exposure TO 5× 104Lx xenon lamp for 15 minutes. THF is the half recovery time, that is, the time required for the transmittance of the discolored lens to recover after the stop. High quality color changing lens should be transparent, do not contain emulsifying color and lustre, half recovery time is short, rapid recovery. The original transmittance of chromic lenses without primary color is about 90%. The original transmittance of chromatic lenses with primary color can be as low as 60 ~ 70%. The transmittance of general sunglass type color changing lens decreases to 20 ~ 30% after light discoloration. Comfortable type of discoloration lens discoloration is shallow, light discoloration after the transmittance of about 40 ~ 50%.
Three, production process
Discoloration glasses using discoloration glass according to composition is divided into borosilicate discoloration glass and aluminum phosphate discoloration glass. China, the United States, Germany and other borosilicate glass, the United Kingdom uses aluminum phosphate glass.
The production of color changing lens glass blank includes preparation of compound, glass melting, pressing molding and heat treatment. The continuous melting process is used in the melting of discolored glass in the world, and there are two methods of single platinum crucible melting and continuous melting in China. After the color changing lens is pressed into shape, heat treatment must be carried out under strict temperature control to make the glass phase split and controlled to generate a large number of dispersed and fine silver halide microcrystals, which gives the lens photochromism.
Four, the production of materials
The glass containing silver bromide (or silver chloride) and trace copper oxide is a kind of discoloration glass, when subjected to sunlight or ultraviolet radiation, the silver bromide occurs decomposition, silver atoms (AgBr==Ag+Br), silver atomic energy to attract visible light, when the silver atoms are gathered to a certain number, the bright part on the glass is absorbed, Originally colorless transparent glass becomes a film at this moment, when the glass into the dark, after color change under the catalysis of copper oxide, silver and bromine atoms can combine into a silver bromide (Ag + Br = = AgBr), because silver ions do not absorb visible light, so the glass will become colorless, transparent, this is the basic principle of color glass discoloration.
Make window glass with change color glass, can make the light that passes under scorching sun becomes downy and have cool feeling, change color glass also can be used to make sun lens, became change color eyeglasses from this.
Under normal circumstances, only photometric test is matched accurately will not cause harm to the eye, but because each person’s use of the eye is not the same, so do not represent you with glasses after the diopter will not increase. The market color of the myopic lens is mainly film layer discoloration and film base discoloration two kinds, the difference is that the film changes the reaction speed is fast, no color difference, the price is slightly expensive. The speed of the substrate is slower, if the degree of the left and right will not appear color difference, but affordable, longer use time. If it is stained, it is not recommended for long-term wear.
Change color myopic glasses are used more convenient, do not need special sunglasses, it is the sunglasses of myopic patient. However, it takes time to change color, which is not suitable for environments where light changes quickly and can not be changed permanently. Height myopia and the person with big difference of degree of two eye eyesight should not match change color piece.
How about discoloration myopia glasses? Actually change color myopic glasses and colorless same, won’t make eye degree deepens because of taking color, wear glasses to want to pay attention to those details more only, do not lie for instance read a book, watch TV and use computer as far as possible do not rely on too close, otherwise myopic degree also is able to deepen slowly.
Saw above to “change color myopia glasses how” introduce, believe you have understood somewhat to change color myopia glasses. Remind you, with myopia glasses must go to the regular optometry department, so as not to make mistakes.
Post time: Aug-04-2021