INSTRUMENTATION • ELECTRONICSSECTION TITLE
ENHANCING DISPLAYS
as an expensive luxury for top of the range products, but as manufacturing issues have been ironed out and new innovations have been made available to nullify some of their drawbacks, their performance has improved almost as fast as their price has dropped. Displays provide the easiest method of viewing relevant and often complex information about the status of applications and equipment. In some cases, they also allow us to control the application through touch. One of the most appealing things about LCD displays is their fl exibility. T ey can be produced in almost any size and shape to fi t the required application and this fl exibility allows them to be used in many diff erent situations and environments.
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OPTICAL GLASS CHOICES LCD displays are very fragile and normally require a cover lens to be added in front of the display to protect it from damage and ensure that the data on display can be seen as clearly as possible. Cover lenses are usually fabricated from glass. However, not all glass is equal and there are diff erent treatments that can complicate the decision process. T e two main types of glass used
iquid crystal display (LCD) screens seem to be incorporated in almost every electronic product imaginable these days. Initially they were seen
Alexander Pang explains how to get the best out of your LCD with the right coverlens
to manufacture cover lens each have their own properties and are used for diff erent applications. Soda-lime is the most well- known type of glass and makes up around 90% of the glass used in the world. As would be expected from its popularity, it off ers a well-balanced list of specifi cations that includes good mechanical strength, optical parameters and temperature resistance. As it is easy to manufacture, it is very aff ordable. T e main alternative to soda-lime glass is aluminosilicate glass, which off ers better performance than its competitor, but is much harder to produce and therefore can be up to 6 times more expensive. Because of its cost, it is usually only found in higher-end and niche applications where
additional strength and protection is paramount, such as smart phones and AR/ AV devices. T e main features that make aluminosilicate glass attractive for cover lens use are its resistance to high temperature and chemical exposure, and its ability to withstand scratching.
STRENGTHENING Both types of cover lens glass are strengthened before use. T ere are two ways that glass is normally strengthened, and each has its own pros and cons. Chemical strengthening involves soaking the glass in a KNO3
solution at a temperature of
420°C. T e sodium ions are replaced by larger potassium ions on the surface of the glass. T e larger surface ions are squeezed together to form a stress layer. After toughening, aluminosilicate glass has a typical strength of 600 megapascals (mpa) compared to soda-lime glass, which is generally in the region of 450 mpa. Aluminosilicate glass also keeps its shape and doesn’t bend after chemical strengthening, unlike soda-lime glass where its curve allows it some room to fl ex if the glass is pressurised. Chemically strengthened glass is the method seen in
Strengthening impact on glass breakage
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