81-E Transparent-Electrically Conducting and Infra-Red Reflecting Coatings

This coating is produced primarily for glass optical elements that must not be appreciably changed by processing or heating operations.

*When the coated element is used at angles other than normal, curve peaks will shift toward shorter wave lengths (down scale). This variation is dependent on degree of angularity from normal incidence.

Properties of 81-E electrically conducting coatings:

1. A resistivity of approximately 7 ohms per square area. This can be changed to some degree. Such change will also change light transmission.
2. Visible light transmission of approximately 78% when applied to commercial plate glass.
3. Visible light reflection from either surface is less than from plate glass.
4. Appreciably no color.
5. The coating is free of haze.
6. No optical strain, distortion, or optical resolution loss occurs when the plates are heated by the electrical current.
7. Application of the coating to an optical part does not change its flatness or optical resolution, and does not introduce any strain.
8. Excellent adhesion.
9. Excellent weather resistance.
10. Good abrasion resistance. Since the coating is very thin, it should be cleaned with a liquid non-abrasive cleaner.
11. Non-inductive, static dissipating, and radio frequency shielding. Can be used to produce electrical space charges and fields.
12. Highly conductive, dependable, excellently adhered, durable, water resistant bus bars to which leads can be clamped or soldered. Soldering technique is available.
13. Electrical resistance and transmission can be changed within limits.
14. Voltages necessary in heating applications are low for a given power due to the very low resistance of IR-81-E. Voltages may be determined by V = R x P x A where V equals voltage necessary, R equals resistance of the piece, P is the desired watts per square foot, and A is the piece area in square feet. The resistance of a given piece may be visualized as the result of squares in parallel or series circuit but the location of the bus bars must be defined.
15. For defogging or deicing of optical and instrument faces and windows, prisms, lenses, and other optical elements in instruments at low or no air speed, 75 to 125 watts per square foot are generally sufficient.
    For heating glass in still air at room temperature, 1.25 watts per square foot are required for each 1° F of desired temperature rise. Under these conditions, operation must be at less than 200 watts per square foot when the coating is on ordinary glass to avoid excessive thermal strain and breakage. For high temperatures and higher wattages in still air, use of heat resisting glass is indicated.
16. Necessary power inputs increase rapidly with air speed. Airplane windows require for defogging, 150 watts per square foot, and for deicing, 600 to 800 watts per square foot. In such uses, small controlling thermostats, placed on the coating, are available to provide continuous on-and-off power to maintain the glass at the desired temperature, regardless of the variation in air speed and air temperature. Note: One watt is equal to 3.41 b.t.u. per hour.
17. Where the glass is continuously cooled, power of 2000 watts per square foot may be safely applied.

Most applications of IR-81-E have to be specifically engineered.