SENSORS
FEAT
ATURE
SUBHEAD
Journey to the centre of the system
As a rigid, transparent and scratch resistant substrate, glass is a fundamental element in touchscreen displays. Ian Crosby, sales and marketing director at Zytronic can be transformed from a simple sheet into a sophisticated touch sensor
A
t Zytronic, sheets of gl ass, in th e required thickness, are cut to various shapes and sizes, up t o around 90 inches (2.28m) on the diagonal. CNC machines can then cut holes and slots into the screens so that peripheral devices can be mount ed behind t he finished touch sensor. Other surface features, such as dimples, grooves or raised markings may also be added. For aesthetics or safety, the edges can be grounded , profiled o r polished. Zytronic also has dedicated ovens that bend the glass to specific radii, matching the latest curved displays. There are also various types of glas s coat ings available. For example, for interactive mirror applications, a reflective but semi-transparent metal oxide layer is used. In strongly lit indoor and outdoor applications, anti-reflective coatings help reduce light reflected from the surface by around 75 per cent. In outdoor applications, chemically et ched anti-glare glass is used, enabling a user to view information on the displ ay i n strong sunlight.
In addit ion t o its transparency, glass is a far stronger material than you may
/ ELECTR ONICS
Various thicknesses, design features and
visual finishes are taken into consideration when preparing the glass
imagine, and can manufacture touch sensors in thicknesses up to around 30mm. As a result, touchscreens can be produced that can pass impact t ests for industry standards such as UL60950, IK10 and UL22. Zytronic regularly designs touch sensors for extreme applications , such as the control panels used in mines, oil rigs and petrochemical facilities. More commonly , glass with a thickness of 3mm or more is strengthened by thermal toughening. This involve s heating to just above its strain point (500 – 600 degrees Celsius) and then rapidly cooling it back to ambient temperature. The resulting toughene d glass - often referred to as being vandal resistant - is around five t imes stronger than annealed glass. Zytronic thermal ly toughens and tests all its glas s i n accordance with BSI/ISO 12150.
For glass less than 3mm thick, or for applications requiring even great er levels of impact resistance, Zy tronic can produce touch sensors using chemically strengthened glass. As in thermal toughening, this proce ss create s compressive forces in the surface of the glass, which make it up to around eight times stronger than annealed glass . However, if shattered, it tends to break into large pieces: system designers need to keep this failure mode in mind when designing touch systems for public use. The glass screens are then move d into one of Zy tronic’s ISO Class 5 clean rooms for inspection, before beginning the final steps in their journey. Copper touch detection electrodes are applie d directly t o an optically clear adhesive film, laminated to t he rear of the glass. With a diameter of just ten microns, these electrodes are barely visible. Once the matrix of copper electrodes have
As a rigid, transparent and scratch resistant substrate, glass is a fundamental element in touchscreen displays. Ian Crosby, sales and marketing director at Zytronic, explains how it can be transformed from a simple sheet into a sophisticated touch sensor
been encapsulated by laminated film, thin, flexible connectors are fixed to the terminating copper electrodes at th e edge, enabling the touch sensor to be linked to the touch control electronics - the exa ct type determined by whether the application requires single, dual or multi-touch functionality .
Zy t ronic’s touch controllers are suitable for use within operating sys tems, and software supporting
complex touches such as pinches, zooms and swipes, delivering functionality th at is smartphone-like, but on a far larger scale. All Zytronic controllers are designed for compliance with the Human Interface Device (HID) protocol, allowing USB plug-and-play operat ion with all current MS Windows operating sys tems and suitable versions of Linux and Android; other available interface protocols include serial, SPI and I2 C. As all of Zytronic’s projected capacitive technolo gy (P CT and MPCT) touchscreen s are made at its ISO9001:2015 accredited UK facility , the company t akes full
ownership of the products’ performance. As such, all of Zytronic’s touch sensors are bar coded and scanned throughout their manufacture, ensuring traceability. The design options available are wide- ranging, and the inherent flexibility of the technology means t hat, often, there is little or no investment in special tooling to produce a one-off design. This benefit is passed along to t he cust omer through low tooling fees (in many cases , no tooling fee) and no minimum order quantit y, making the design of new, touchscreen enabled systems quicker and easier to develop than ever before.
Zytronic
www.zytronic.co.uk ELECTRONI CS | APRIL 2020 27
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