When a light beam is focussed on an optically clear surface, a part of the light gets absorbed by the surface, some of it gets scattered and the remaining gets transmitted through the material. Optical transmission refers to the proportion of light that is transmitted through an optically clear medium. Applications such as fiber-optic communications, opto-electronic sensors and photonics require the highest levels of transmission.
Typically, optical components need to be bonded or coated using adhesives, without affecting their transmission properties. The adhesive needs to provide superior protection at elevated temperatures and harsh environmental conditions, while retaining its transparency. In order to measure the adhesive’s optical properties, a thin film is coated on a reference material such as glass. The transmission spectra of the coated substrate is then compared with that of the reference to determine the level of radiation absorption by the adhesive. Kohesi Bond has successfully developed phenomenal optical adhesives that offer over 97% transmission, from 350 nm through the IR (infrared) range.
Apart from transparency, another important aspect to be considered for optical applications is refractive index (RI). Refractive index is a measurement of how light propagates or refracts while entering a medium. It is calculated by measuring the ratio of velocity of light in vacuum to the velocity of light through a particular medium. Through persistent research and development, Kohesi Bond has developed first-rate epoxy and sodium silicate based bonding and coating systems that offer refractive indices in the range of 1.50 – 1.57. This is a highly favorable range of refractive index for optical applications.
In addition to optical transmittance and ideal refractive indices, our products are capable of passing NASA standards for low outgassing, resists extremely high as well as cryogenic temperatures, withstand harsh chemicals and offer a varying degree of hardness. Specialized products also offer excellent non-yellowing properties. Kohesi Bond’s optical adhesives are widely used in LEDs, display devices, LCDs, lasers and similar applications.
PRODUCT | REFRACTIVE INDEX | HIGHLIGHT |
KB 1040 | 1.56 | Low Viscosity Superior Mechanical Strength |
KB 1039 CRLP | 1.53 | Cryogenic Serviceability NASA Low Outgassing (ASTM E-595) |
KB 10473 FL | 1.51 | Highly Flexible Very Low Exotherm |
