Photochromic phenomenon is a kind of chemical physics, contains organic, inorganic, biological, polymer light induced by chemical and physical reactions.
This kind of phenomenon is a compound under a certain wavelengths of light under the irradiation of a specific chemical reaction, can be obtained, or get a different color, in another wavelength of light or heat, and to restore to its original form, namely the original color.
In the light of reversible color change can occur under the action of compounds, called photochromic materials.
Photochromic can be used in optical storage, optical switch, optical lenses, etc. , as well as a variety of security certificate authentication marks.
After 1955, military and commercial interest prompted the people light discoloration phenomenon research, then people to explore and develop the photochromic materials, this special materials are widely used in various fields, photochromic materials over the years has been the inorganic, organic and material chemists pay attention to and research hot spot, is recognized to be the application prospect of functional materials.
Practical application of photochromic material is the most important characteristics of a deceptive body must have enough thermal stability and fatigue resistance.
Now development of photochromic materials can be roughly divided into organic and inorganic photochromic materials of two kinds of photochromic materials.
Different types of photochromic materials with different mechanism of color change, especially the color mechanism of inorganic photochromic lens material and organic material is a significant difference between the system of typical inorganic photochromic effect with reversible oxidation, namely the reduction reaction.
Typical photochromic effect of inorganic materials with good reversibility and fatigue resistance.
System of organic photochromic also is often accompanied by many associated with photochemical reaction process, thereby resulting in the molecular structure of some kind of change.
As the basic principle of photochromic lenses is enough color materials under the influence of ultraviolet (uv) radiation color darker, colorless state to recover by ultraviolet (uv) radiation to disappear;
While under the influence of high temperature surrounding color becomes weak, the two processes are reversible, the phenomenon is by activating material of photochromic material mix molecules.
Reversible reaction is an important standard of photochromic, irreversible reaction occur under the action of light, also can cause the change of the colors, but only belong to the category of general photochemical, not belong to the category of photochromic.
Namely: in two different between the absorption spectra of the isomers of a reversible photoinduced lens is photochromic lens shift performance.
This lens under strong sunlight irradiation can quickly become dark, the light transmittance of the lens is reduced greatly, the stronger the light, the color of the lens is more deep, can protect the eyes from strong light stimulus, enter indoor or outside light, color will be lighter, back to the original state of transparent, to ensure the normal observation of scenery.
The photochromic lenses is a reversible chemical reaction, it is generally believed into two categories: one is positive photochromic, refers to by the color of the light material colorless or light into the dark;
Another is confusion photochromic, refers to the color of the material under light colorless or from dark to light color.