Window films, or heat insulation films, have undergone many generations of technological changes, such as dyed films, aluminized films, magnetron sputtering metal films, ceramic films, etc. This article is specially sorted out for aluminized film, which still has a part of the market share due to its relatively low cost and certain thermal insulation performance.
PET aluminized film, often referred to as "traditional metal film" or "plain metal film", is formed by applying evaporative coating technology to a transparent or dyed PET substrate by depositing one or more layers of cheap metal on the surface of the substrate. Aluminium is the most widely used metal for cost-effectiveness, which is why this film is widely referred to as "aluminized film".
PET vacuum aluminized solar film, picture from Foshan Cailong coating
1. Introduction to vacuum evaporation process
Vacuum coating refers to the use of various physical or chemical methods to vaporize or ionize the surface of the target under high vacuum conditions, and then deposit it on the surface of the substrate to form a thin film. Vacuum coating technology is divided into physical vapor deposition (PVD) and chemical vapor deposition (CVD). Physical vapor deposition methods are mainly divided into vacuum evaporation coating, vacuum sputtering coating, and vacuum ion coating.
Among them, the evaporation process refers to the evaporation of the plating target by means of resistance heating and electron beam bombardment under vacuum conditions, and the target molecules escape, migrate from the plating material to the surface of the substrate, and deposit to form a thin film. The main advantages are simple equipment, easy operation, fast film formation rate and high efficiency.
The main processes of vacuum evaporation coating process are: pre-plating preparation, preparation vacuum, baking, pre-melting, evaporation, post-treatment, etc.
(Schematic diagram of the principle of hot-evaporation aluminized film)
The evaporation coating equipment consists of a vacuum pumping system, a vacuum chamber and other peripheral equipment. The vacuum pumping system is composed of a high vacuum pump, a low vacuum pump, an exhaust pipe and a valve, etc.; The vacuum chamber is equipped with an evaporation source, a heating device, a substrate and other components.
Evaporation coating equipment is widely used in many fields such as optical thin films, photovoltaic cells, integrated circuits, information displays, and architectural glass.
2. Characteristics of aluminized film
PET aluminized film has excellent spectral projection performance, which can effectively isolate ultraviolet rays, and at the same time, through precise control, its light transmittance can reach more than 70%, and the efficiency of 30-40% can generally be achieved in infrared barrier.
Due to the addition of the metal layer, PET aluminized film has better performance in heat insulation than dyed film, and the aluminized layer has strong oxidation resistance, which improves the stability and service life of the film.
In addition, the PET aluminized film has a high reflectivity of visible light, and the obvious metallic luster makes the appearance characteristics particularly prominent. One of the industry's comments about the shortcomings of aluminized film is that the dense metal layer shields the transmission and reception of signals such as mobile phones and ETC in the vehicle.
