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PPG's Photosol® photochromic dyes reversibly alter their color upon exposure to ultraviolet sources. These chameleon-like dyes respond to natural solar irradiation as well as artificial sources such as 365 nanometer "black light." When sunlight or ultraviolet (UV) radiation is applied, the Photosol photochromic dye becomes excited and the molecular structure is changed allowing a color to appear. When the stimulus (sunlight/UV radiation) is removed, the dye will return to a state of rest, which is its colorless form. Photochromic molecules are not reactive in their crystalline state and need to be dissolved in a solvent or polymer to function.
These proprietary organic materials come in various activated colors such as blue, yellow, burgundy and red. When combined, additional colors such as green, brown and gray can be produced. By further adjusting the ratios or combinations of Photosol photochromic dyes, various additional color shades can be achieved. It is possible to combine both fluorescent and/or organic pigments with reversible photochromics to produce permanent colors indoors and, by the color additive effect, different colors outdoors. This allows thousands of additional color possibilities.
The range of applications is only limited by the imagination. Existing products include textiles that evolve new patterns upon exposure to sunlight/UV radiation; security devices that are observable spectroscopically or by specialized instruments; inks for screen printing; and laminate, automotive, industrial and aerospace coatings. The largest single commercial photochromic product is an ophthalmic lens that changes from clear indoors to dark outdoors.
Photosol photochromic dyes can be used to develop products that are suitable for printing, spraying, exhaust dyeing and extrusion applications. While these photochromics are insoluble in water, they can be treated like other water insoluble materials and "tricked" into water-based systems. Photosol photochromic dyes are soluble in organic materials and most organic polymers.
With more than 15 years of experience in the area of organic photochromic research and development, PPG's staff of researchers is ready to work with you to meet your product development needs. |