Japan NanoOpto developed a so-called "cover glass integrated touch panel," which is made by forming electrodes of capacitive touch sensors on a chemically-strengthened glass plate that covers the surface of a smartphone or tablet computer.
The company calls the panel "All-in-one Touch Panel." It will start volume production of the panel in August 2012.
The new touch panel enables to reduce the number of components of a display unit from three (cover glass, touch panel and LCD panel) to two (the new panel and LCD panel). Compared with a case where an external touch panel using a glass substrate is used, it is possible to reduce thickness by 0.5mm and weight by about 40%.
This time, Japan NanoOpto employed the "sheet process," which cuts and processes a large-size glass substrate after chemically strengthening it by ion exchange, forming external patterns and sensor electrodes and processing the surface. The sheet process is more productive than the "cell process," which first cuts a large-size glass substrate, forms it into the shape of a mobile device and polishes it and, then, chemically strengthens the glass by ion exchange and forms external patterns and sensor electrodes on it, the company said.
The problems of the sheet process are that it is difficult to cut a chemically-strengthened glass substrate and that the strength of the substrate lowers due to cracks after the cutting. To address the problem, Japan NanoOpto made changes to the conditions of the chemical strengthening, the process after the cutting, etc.
Though Japan NanoOpto did not disclose the details, the company said that, for the process after the cutting, it developed a new polishing apparatus using ceric oxide (CeO2) as an abrasive. In the case of the 4.3-inch model of the All-in-one Touch Panel, its yield ratio is 90% or higher, and the strength measured in a four-point bending test is 800MPa or higher, the company said.