The interactive technology sector is experiencing an explosion in growth – an explosion powered by touchscreen technology.
There are many touch technologies available for interactive displays, including resistive, infrared, optical, surface acoustic wave (SAW) and surface capacitive. However, one technology stands above the rest in terms of functionality, durability, and maintenance requirements – projected capacitive touch technology or PCAP. Considered the best-in-class touch technology, PCAP is becoming more affordable and accessible too. It is also the most recognised and pervasive today as it powers the technology in our pockets – our smartphones.
However, even within PCAP, there are different varieties to consider. How can you choose which is best for your organisation? This article will guide you through the major considerations.
First, it is useful to understand the benefits of PCAP technology. PCAP allows simultaneous 10+ finger multi-touch, with fast, accurate, and extremely sensitive touch response, and optional treatments like anti-glare and anti-vandal glass. It does not register false touches with liquid and functions even with deep scratches.
Importantly, this technology allows for true-flat screen designs, where bezels have been needed for most other touchscreen technology, which makes for modern designs that are also easy to clean. It is capable of registering touch through additional cover glass 6 mm or more, with a trade-off in accuracy and number of touches, but still working beautifully for outdoor ticketing machines subject to vandalism, or as multiple touch monitors under a countertop made from a single piece of glass.
The different variations of PCAP incorporate different costs and product outcomes. To ensure the best performance and lowest maintenance and failure rates, you must match the PCAP type with the application you intend to use it for. All the variations incorporate two grids laminated in a sandwich with a glass cover layer. A high frequency electronic signal creates an electric field which projects through and above the glass.
- GF1: A passive cover glass is bonded to a one layer film sensor. Both the transmit and receive conductive traces are on the same side of the PET film (a type of plastic). This type of sensor is limited to applications with lower accuracy and smaller devices.
- GF2: A passive cover glass is bonded to a film sensor which has conductive patterns on both sides. It is lightweight, allows small border widths and single tail connection solutions. GF2 solutions are a good alternative to 2GS construction where the application is in controlled environments.
- GFF: The conductive grid is printed onto a thin PET material. The layers are stacked and laminated together with Optically Clear Adhesive (OCA). Silver nano-wires, silver metal mesh, embedded wires and ITO can all be used for the conductive substrate, and provide different levels of sensitivity. Mesh is typically used in large display sizes, 32 inch up to 70 inch or greater.
- 2GS: Virtually invisible ITO conductive coating is sputtered on to the glass surface and then patterned by etching. The patterned ITO is on the facing sides of two layers of glass which are then laminated together using an optically clear adhesive. 2GS offers pristine optical clarity, higher touch durability, and long term stability over temperature, making it ideal for non-mobile applications in sizes from 10 to 27 inches.
- OnCell, InCell: The PCAP sensor pattern is embedded in or on the LCD display layers and thus the touch sensor is incorporated. It gets expensive in larger sizes, so is best for small sensors for smartphones.
Three major factors to consider when choosing the right PCAP technology for your application are: cost; risk of breakage; and manufacturers.
From a cost perspective, remember that PCAP scales in price exponentially with size. OnCell, Incell is best suited to small devices, 2GS in midrange sizes and GFF-metal mesh for large sizes of interactive digital signage.
From a risk of breakage perspective, it is important to understand the risks of adopting plastic film PCAP technology when it is not necessary versus 2GS. One risk of film solutions like mesh or GFF PCAP is delamination of the layers over time, caused by the plastic layer reacting differently to changes in temperature and humidity by expanding and contracting while the glass layer remains stable. When the layers begin to peel apart, it is visible and requires screen replacement. Micro cracks in the ITO are another possibility, as is yellowing of the plastic material (PET) in a GFF solution due to UV exposure or heat. Using all-glass 2GS PCAP eliminates the two layers of plastic film in GFF PCAP that is the cause of all three of these potential failures – delamination, yellowing, or degradation of touch performance. 2GS touchscreens are designed to last longer than the LCD panel, and are recommended whenever possible in the midrange sizes.
From a manufacturing perspective, it is important to be aware of the proliferation of manufacturers with factories throughout China producing low cost GFF screens, which can risk cost-cutting and therefore lower quality. Most PCAP screens come with no visible label indicating the manufacturer, so it may not even be apparent if the monitor company switches unnamed touchscreen manufacturers when one can't deliver, goes out of business, or is simply cheaper. Touch monitor companies not manufacturing the PCAP technology themselves often have no clear path for issue escalation and resolution. In addition there are many small start-up companies working on conductive materials for use on film substrates. It’s important to understand their business viability and weigh the risks before choosing the material used in your system.
An informed choice
Organisations looking to incorporate touchscreen technology into their products need to weigh up these considerations and strike the right balance between cost, performance, reliability and ruggedness, according to their own needs. It is a complicated landscape, but the potential benefits are enormous.