Spin coating of TiO2 and SiO2 layers on curved CRT screens to form antireflex coatings.

Abstract

Reflections from a CRT screen are very annoying for the viewer. They hamper the recognition of the image displayed on the screen and can even make it disappear completely. A reduction in reflection is possible by applying an antireflex coating on the outer surface of the screen. This has already been demonstrated on CRT's using evaporation as the deposition technique for the antireflex layers [1,2]. Another, and possibly cheaper, way to deposit antireflex layers is by spin coating them from sol-gel solutions [3 – 7]. In these studies the spin coating has been performed on relatively small substrates which were completely flat, without paying much attention to the thickness homogeneity of the layers on the substrates. For application of spin coating on CRT's, however, the substrate is the relatively large (14" diameter and up) curved outer surface of the screen, while the thickness uniformity of the coating over the entire screen has to be high. In order to see whether spin coating can be used to produce antireflex coatings on CRT's with a high thickness uniformity, both single TiO2 and SiO2 layers were spin coated on 14" CRT screens. In this paper, the thickness uniformity of these spin coated layers will be discussed. It will be shown that layers having less than 2% thickness variation over the entire screen can be made in this way.