A novel measuring method of testing ITO protective coatings for use in mobile phone LCD's

Abstract

In liquid crystal displays (LCD's) for mobile phones various functional coatings are used. Besides optimized for the function they are applied for, these coatings need to fulfill reliability requirements. To avoid unexpected problems during lifetime, insight in the behavior of the materials is obtained using model studies. Important aspects to study are the interactions of the materials with other ambient materials and the protective function under influence of temperature and humidity. The advantage of model studies is that a specific aspect can be investigated and side effects can be excluded. More statistically sounded conclusions can be drawn and interactions, which occur at a low frequency, can be studied. An interesting aspect is the translation of the model studies to effects occurring on module level and in the application like a mobile phone. A typical example of a functional coating is a protection layer applied on the tin-doped indium oxide (ITO) tracks outside the active area of the display. Effects of humidity condensation and temperature play an important role in the functionality of the material whereas also interactions with other materials to which the protection layer is in contact are essential parameters. In this article we have investigated a new measuring method to shorten the evaluation time of the protective coatings at various ambient conditions.