UVR Defense Tech, Ltd.
The Science behind UVRC

To create a camouflage that could be applied either in the factory or in the field on differing types of fabric while retaining the desirable visible and NIR characteristics of the fabric, UVR Defense Tech looked to the science of thin-film optical filters and nanoparticles. The principles of thin-film optical filtering of light suggested that discrete wavelengths of light, in this case the near ultraviolet range from 320nm to 400nm, could be selectively reflected from the fabric while permitting visible and NIR wavelengths - 410nm to 1150nm - to pass back and forth through the coating, transparently.

In order for a thin film to be transparent to some wavelengths of light while reflecting other wavelengths the proper reflective "pigment" must be chosen and it must be created or milled to a thickness less than one-quarter the wavelength of the light to be reflected. In the case of ultraviolet light with a wavelength of 330nm-400nm, very specific reflective materials are required. These materials needed to possess the following properties:

  • Known reflectance in the near ultraviolet range
  • Available in a consistent diameter of less than 100nm (the average human hair is 100,000nm thick)
  • Acceptable aggregate size
  • Stable, non-oxidizing, non-catalytic
  • Non-flammable
  • Non-toxic
  • Odorless

The class of materials that met most of the criteria above is that known as Technical Ceramics. Some could be quickly discarded - such as compounds of lead, barium, lithium, strontium - because of possible health hazards. Others could be eliminated because of odor, e.g., sulphur, while others were reactive with the film material chosen. Agglomeration - particles clumping together - was a significant problem with some chemicals. The pigments which fit all our general needs were in the class of Oxide Ceramics which includes Aluminum Oxide, Cerium Oxide, Zirconium Oxide, Zinc Oxide, etc..

Publication of the UVA diffuse reflectance spectra of ceramics is spotty. UVR had to test for themselves the near-UV reflectance of many compounds, hoping that pigments with all the other positive properties would also have usable UV reflectivity and high visible light transmission. In some cases the reflectivity of the dry powder was excellent, but when mixed with the organic film base and applied to a fabric, the reflectivity was not in a usable range. As well, the diffuse reflectance was found to increase with a decrease in the mean particle size; that is, the more finely ground nano-particles were more reflective. However, there was a point of diminishing returns; when the particles were too small in the aggregate, their Infrared reflectivity increased. Since the object was to maintain both visible and NIR characteristics of the underlying camouflage, sometimes optimum UV reflectivity was sacrificed.

When using a thin film in optical filtering on a glass substrate, the exact thickness of the film can be controlled. This is not true when applying a film to a fabric. The weave of the fabric - coarse or fine; the absorbency of the fabric - highly absorbent or treated to repel water; and the depth of the fabric - from fleece to canvas; all these make application of a coherent thin film difficult. The carriers, solvents, film agents, dispersants, and pigments chosen had to produce a consistent level of UV-reflectance, no matter what the underlying fabric was.

As difficult as it was to choose reflective particles, the choice of film agent was perhaps equally difficult. The criteria such an agent had to meet were many and varied:

  • A minimal effect on underlying visible and NIR camouflage
  • No increase in noise of treated apparel
  • No increase in specular reflection (shine, gloss) in any wavelength
  • Convenient application method(s)
  • Quick-drying
  • Heat-tolerant
  • Flexible
  • Thin
  • Odor-free
  • Sweat-proof
  • Non-allergenic
  • Water-resistant
  • Non-toxic
  • Non-flammable
  • May be applied to any fabric without degrading foundation material or dyes
  • Fabric breathability is retained
  • Fungus-resistant

After many false starts, UVR was able to find film agents that met the specifications. Then, the combinations and permutations of film and pigment were created and tested. Since each pigment has an optimum UV reflectivity based upon its chemistry and size, different pigments and proportions were required for each of the different products.

UVRC is the only camouflage system designed for the near-ultraviolet spectrum.

"UVRC", "UVRC-P", and "UVRC-A" are trademarks of UVR Defense Tech, Ltd.
"MultiCam" is a registered trademark of Crye Precision LLC.
Copyright © 2010-2012 UVR Defense Tech, Ltd.