Each of the pure Epolight™ dyes has peak absorption at a specific wavelength. To block a given segment of the spectrum it is often necessary to combine two or more dyes. Each dye will block the specific wavelength on both the higher (bathochromic) and lower (hypsochronic) sides of the peak.
The wavelength span of an individual dye is determined by the concentration of the dye and its innate optical properties. For example, some dyes are broader in their absorption than others at the same concentration. It has also been found that the use of 2 or more dyes to block a given wavelength span works more effectively than using one dye at a much higher concentration.
Blocking UV and visible light
Epolight dyes in the 7276 group are designed to block the entire visible light spectrum from 400 to 700 nm. For certain applications it may be necessary to expand this blocking to include higher wave lengths.
Epolight 7276C blocks up to 650 nm, Epolight 7276B up to 700 nm, Epolight 7276A up to 800 nm, Epolight 7276F up to 850 nm and Epolight 7276E extends this to 950 nm.
Blocking the near infrared (NIR)
Dye combinations also block very large segments of the near infrared spectrum as well.
In certain applications the benefit of a broader wavelength block of the near infrared must be balanced against what one expects to see in visible light transmission. Also consider the blocking intensity demanded in the near infrared. The higher the optical density achieved in the near infrared, the greater the loss in transmission in other parts of the spectrum.
Blocking both the NIR and the visible spectrum
In many applications it is necessary to block a specific wave length from a laser that emits in the near infrared and at the same time block a harmonic of that laser in the visible. An example of such a formulation is Epolight™ 7541 which protects against the Neodymium YAG laser which has a primary emission at 1064 nm with a harmonic at 532 nm.
General considerations in using the Epolight 7000 dye mixture series
The requirements of blocking range, the optical density over this range and the way one intends to apply the dyes are important considerations. Each application whether it is for a coating, injection molding, extrusion or cell casting, requires an intimate knowledge of dye properties and behavior. For this reason we illustrate only a few formulations in this section. In most instances, knowing the special requirements of the customer, we can develop a formulation that closely meets his or her requirements.
The formulations shown in the website were evaluated in solution at low concentration through a long light path (10 mm). The data, while accurate, was obtained at high dilution and must be accepted with some reservation.
Some dyes have poor solubility in coating solvents and resins yet can be successfully used for injection molding applications because the high molding temperatures improve the solubility of the dyes. Other dye mixtures may not be suitable for molding due do dye and/or polymer interaction at high temperatures. Check with Epolin for your particular requirements.