A coverlens, sometimes known as a cover-glass, is bonded onto the top of a P-CAP touch screen for both cosmetics and protection. It allows designers to make the touch-screen flush with the surface of their product, imparting an iPad type look and feel. It can also carry graphics, logos, colour masks, P-CAP buttons and LED light guides.
While the coverlens protects the touch screen, its presence also reduces its sensitivity. Sensitivity can be improved by reducing the coverlens thickness, or by increasing its dielectric constant. Plastic (PMMA) can be used in place of glass, however, it has a lower dielectric constant so must be half its thickness to achieve the same performance.
Cover-glass is typically 0.55 mm, 0.75 mm or 1.1 mm thick for mobile devices, and up to 20 mm for industrial and kiosk applications. Some designers use chemical strengthening to reduce the chance of breakage. Float glass or soda-lime and alumina silicate are the most commonly used glass types. Chemically treatment roughly halves the likelihood of float glass breaking and reduces that of alumina silicate breaking by over a third.
Gorilla Glass and Dragontrail are popular commercially available solutions. Gorilla Glass 3 is claimed to be up to three times more damage resistant than Gorilla Glass 2. It owes its toughness to its atomic configuration as well as its chemical strengthening. Dragontrail is promoted as an innovative glass with qualities superior to glass and plastic in all areas of strength, scratch resistance and texture.