Projected capacitive, the predominant touch screen technology, has many different structures. Over the next few years, these structures will be simplified as sensor substrate layers are reduced, according to DisplaySearch. These simpler touch panel structures will bring the benefit of thinner and lighter devices.

"Two approaches are emerging to simplify projected capacitive sensor designs," said Jennifer Colegrove, vice president of Emerging Display Technologies for DisplaySearch. "One is sensor-on-cover and the other is in/on-cell."

In-cell and on-cell sensors are typically integrated during the display manufacturing process, whereas sensor-on-cover involves coordination between touch sensor and cover glass makers. While Apple products use glass-based sensors with ITO (indium tin oxide, the typical transparent conductor) layers on both sides, most sensors use one or two layers of ITO on the same side of the glass; this is required for sensor-on-cover because the outer side is the exterior of the product.

As projected capacitive touch screen shipments grow by more than 100% on-year, cover glass has become a key component in touch screens. Regardless of the type used-sensor-on-cover or in/on-cell-cover glass is a must for projected capacitive touch for both cosmetic and protection purposes. Cover glass finishing is very labor-intensive and, depending on the processes required and specifications, has yield rates in the 70% range. Process challenges will be an increasingly strategic issue for the industry. Depending on the technology and supply chain, cover glass finishers and touch module makers will be working together by contract or informal relationship, while tier-one touch module makers are integrating and expanding their in-house cover glass finishing capacities. 

Source:digitimes