How would it feel if one could wear clothes that will change colors like a garden chameleon?
dyes have renewed interest in the field of dye chemistry, and the fields
closely related to its applications. A type of dye can change color all by itself
once they are exposed to sunlight. Photochromic dyes changes the color of
clothes, giving them a dramatic effect. When clothes are exposed under
sunlight and absorb the ultra violet radiation, they change colors. When the
radiation is removed, the dyes resume their original shade.
Photochromic means 'ability to change color when exposed to sunlight'. Photochromic dyes generate dynamic reversible color change under the sunlight or ultra violet (UV) light in the range of 300 to 360 nanometers. When kept under the sunlight, or ultra violet rays, the molecular structure changes allowing the photochromic compound to turn into a dark color. The effect is reversed when the light fades. The speed at which the dyes fade back to become colorless depends on the ambient temperature, and chemical structure of the dye.
An optical medium contains one or more dyes and polymer which forms liquid crystalline phases. Information is written in the liquid crystalline polymer layer through a laser. The polymer gets heated up above a phase transition temperature. After observing the energy of sunlight or ultra violet rays, the molecular structure is changed, causing its absorbed wavelength to be changed allowing the color to spread. When it is cooled, the change is frozen in a glass state. It reverts back to its original molecule structure and shade when the light is blocked. The material posses high contrast storage, high sensitivity, good stability and resolution. When not exposed to sunlight or UV radiation, these dyes are off-white. It gains color when exposed to sunlight or UV light.
Photochromic dyes can be mixed together to make an assortment of shades. These dyes can be applied to fabrics through conventional printing, dyeing, extrusion and spraying methods. It can also be used in a variety of other applications:
- Photochromic dyes can be used on garments to print brand name or logo to prevent its duplication.
- These dyes can be used in making fashionable materials like footwear, furnishings etc.
- They can be used for security devices that can be observed spectroscopically or by specialized instruments.
- It can be used in packaging industries.
- It can also be used to make ophthalmic lens that change its clear color to become dark outdoors.