PPG's Photosol® photochromic dyes reversibly alter their color upon exposure to ultraviolet sources. Full color changes appear with exposure to UV light; this exposure ranges from milliseconds using a flash gun to 20 to 60 seconds in the sunlight.
When sunlight or ultraviolet (UV) radiation is applied, a Photosol photochromic dye becomes excited and the molecular structure is changed, allowing a color to appear. When the stimulus (sunlight/UV) is removed, the dye will return to a state of rest, which is its colorless form. The photochromics can be activated by UV light ranging from 300 to 360 nanometers. PPG's Photosol photochromic dyes are supplied as a crystalline organic dye.
The proprietary organic materials come in various base colors such as: blue, yellow, burgundy and red. When combined, additional colors can be produced.
By using a base UV transparent color, you can produce additional photochromic color effects (e.g., base pink plus blue photochromic used in sunlight will give a purple color.)
Photosol photochromics dyes can be used in various paints, inks and plastics such as PVC, PVB, PP, CAB, EVA, urethanes, and acrylics. The dyes are soluble in most organic solvents.
Technical Overview
A common feature of the photochromic is a colorless isomer that contains a carbon-oxygen bond which dissociates with UV activation.
The colorless isomer contains two localized pi systems that absorb only in the UV part of the spectrum. Hence, the molecule appears colorless. After the carbon-oxygen bond dissociates, the two pi systems change into a single delocalized pi system which absorbs in the visible part of the spectrum, causing color formulation.
The life of photochromic material depends on the amount of photochromic compound used, the stabilizers used and the material in which it is used. Generally, it is suggested that 0.1 gram per square foot be used to provide an adequate reservoir of photochromic compound.
The use of ultraviolet absorbers will also extend the life of the photochromic, but will reduce the color intensity.
Photosol is a registered trademark of PPG Industries, Inc.
Statements and methods presented are based upon the best available information and practices known to PPG Industries, Inc., as of March 1, 1994, but are not representations or warranties of performance, results or comprehensiveness, nor do they imply any recommendations to infringe any patent or an offer of license under any patent.
The products mentioned herein can be hazardous if not used properly. Any health hazard and safety information contained herein should be passed on to your customers or employees, as the case may be. PPG Industries also recommends that, before use, anyone using or handling this product thoroughly read and understand the information and precautions on the label, as well as in other product safety publications such as the Material Safety Data Sheet.
Like all potentially hazardous materials, this product must be kept out of the reach of children.