Optical Coatings
Optical coatings for architecture, TV screens and data displays
Glass is used extensively in various
applications as a result of its outstanding properties. Glass is an extremely stable material and is relatively scratch resistant. Importantly for optical applications it also has high transparency for the visible
electromagnetic spectrum. These properties have led to the widespread use of glass in
architecture and modern information and communication
technologies such as TV screens and data
displays.
However glass is not a perfect material particularly
for architectural use. It has low reflectance for the far
infrared (room temperature radiation) resulting in the loss of thermal
energy from buildings and its high transmission of the near infrared (solar radiation)
increases the energy necessary for cooling buildings.
Also in the visible region of the electromagnetic spectrum a glass pane will reflect
8.4% of the light impinging its surface (4.2% per side). This reflection can not be allowed for certain applications such as optical lenses.
Optical coatings on glass can solve all these problems
Since the end of the 1970s the use of vacuum coating technologies to deposit optical coatings on large scale glass substrates has increased steadily. In the last 10 years the capacity of the annual worldwide production
of vacuum coating systems for architectural and
automotive glass has more than doubled to approximately 120 million square metres. The main applications areas are in the
areas of low emissivity and solar control coatings.
Since the end of the 1980s new applications have surfaced such as coatings for the flat panel display industry and transparent and
conductive ITO layers for liquid crystal
displays.
New applications are always under development for example electrochromic coatings for solar cells.
All of these optical applications require fast and stable deposition of metal and
metal oxide/metal nitride layers with reproducibility and
uniformity over large area substrates (up to 3.2 m×6 m).
As a result of the high plasma density, uniform plasma distribution in the
longitudinal direction and high deposition rate magnetron sputtering is the leading process for large area coating.
Anti-reflective (AR) optical coatings for spectacles and sun glasses
Anti-reflection “AR” coatings are used extensively to reduce reflection and glare for spectacles and sun glasses. Magnetron sputtering systems are used throughout the optical industry to deposit these AR coatings. Small batch, fast turnaround coating systems are used to supply retail opticians and small laboratories with optical coatings and optical lens manufacturers use industrial scale sputtering systems to deposit AR coatings on stock lenses. Magnetron sputtering has become a key optical coating technology as the coating technique is more energetic than conventional electron beam evaporation and therefore produces denser and more durable optical coatings.
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