Coated Glass

This is industrially produced glass on whose surface metallic oxides are powdered so as to obtain a very thin layer (from 0.01 to 0.8 micro-metres).
This brings about a change of the behaviour of the glass in relation to sunrays, both visible and infrared.

It is used for the production of shields which can meet the needs, at the same time, in relation to:
- Solar energy control;
- Luminosity control;
- Aesthetics;
- Economy both for heating and cooling of the air (low compliance glass).

The applied layer consists of several superimposed films (up to 15):
- One film which ensures adhesion to the glass;
- One of more films which gives the glass the required characteristics;
- One chemical and mechanical protection film.

The versatility of coating production plants allows a wide possibility of variations of optical and thermal properties of the sheets and allows us to satisfy the requirements of designers and construction workers.
Coating technologies can be either chemical or physical.
Chemical processes are mainly used to obtain oxide coatings characterised by very stable connections with the glass sheet. Also, some of these permit on-line coating, that is, directly onto the glass strip in the intermediate stage between production and annealing.

This technique produces a metallic oxide coating by thermal decomposition in contact with the surface of the glass at a high temperature (about 600°C).
It can be carried out in three ways:
- In a liquid phase: a solution containing metallic salts is sputtered, in the form of an aerosol, on the surface of the glass
- In a solid phase: involves coating the glass with powdered metallic oxide by means of a gas
- In a steam phase: the constituents of a gas or steam, upon contact with the hot surface of the glass, react chemically and form the coating.

This is a technique to obtain glass in a thin layer at a low temperature (about 400°C).
The sheet is immersed in an organic solution of metallic salts (sol); the rate of extraction determines the thickness of the layer that is deposited on the surface which is then heated and vitrified.
Thin films can be obtained with different characteristics (mechanical, optical etc.).

Physical methods are used especially for the production of coatings of noble metals and necessarily require the cut of the sheet and putting it into a vacuum chamber. Amongst these, we list cathode sputtering.
This sputtering method is the consequence of bombarding cathode ions which brings about the discharge of metal atoms, of which the electrode is made of, which condense on the front surface.

Coatings, with their various applications, have undergone considerable developments in the last 30 years. And the evolution is still continuing: self-cleaning glass has recently been put on the market. This glass is coated with titanium oxide which, acting as a catalyser under the effects of ultraviolet rays, breaks down organic composts (fats, for example) which store the atmospheric particles in the surface of the glass.