On the strength of this expansion as “one of the major European sources, we can offer the different bonding processes inhouse, matching the particular application and choice of components”, points out Kaminski, head of product marketing Data Modul. Depending on product configuration and application, the processes currently in use are LOCA (liquid optical clear adhesive), OCA (optical clear adhesive), and/or gel bonding. When it comes to touch technology the situation is basically that for new projects nearly all customers want PCAP (projected capacitive). In less common cases, as a factor of application or price, there are still projects using resistive touch.
In displays up to 32 inches for every second project a display with touch is ordered, the dominating entry system that is increasingly taking the place of classical keys. For larger display diagonals upwards of 42 inches “touch tends to be rare”, he says, “but will become the basis of the interactive information monitor because of strong growth of signage markets.” To be prepared for this, Data Modul was continuously expanding its bonding capacity to produce medium and large volumes.
Hy-Line Computer Components currently outsources bonding — joining the touch sensor to the cover glass, and joining the cover glass (together with the touch sensor) to the display — in Asia or Germany, reports Rudolf Sosnowsky, head of marketing and application. But was considering its own involvement in manufacturing at a later date. It aims to bring the entire expertise inhouse. The advantages are improved handling by elimination of transportation, and higher value added through vertical range of manufacture.
As far as bonding is concerned, the emphasis is on two processes: vacuum bonding, where a kind of flexible film, tailored to the size of the display, is laid between the display and the touchscreen, and adhered on the inside by withdrawing air. And the liquid process, where a bonding layer with a material produced from two components cures, creating the mechanical and optical connection. In concrete terms Hy-Line uses the proven OCA process for sensor bonding, “we only bond glass sensors with liquid components.” In display bonding two-component bonding came first — also because of the display diagonals. Vacuum bonding is for applications with large batches, allowing automation for small diagonals.
In touch technology PCAP holds a share of 80 percent at Hy-Line, “with a very marked trend.” PCAP is used almost alone for small diagonals of 2.4 to 10.1 inches. The reasons: the extra price for a solution without touchscreen is still minimal because there is more than enough capacity in China. And with its relatively sensitive surface the display needs protection against scratches anyway. For medium-sized diagonals in HMI applications in industrial automation PCAP is almost 100 percent standard. In the gaming segment one could see that large diagonals are migrating from S-CAP to PCAP.
In digital signage the share is about 50 percent and growing. Resistive 5-wire touch still figures about 20 percent at Hy-Line, with quantities remaining pleasantly stable. Other technologies only play a subordinate role for special areas: infrared touch is very much dropping off, and SAW (surface acoustic wave) is used where there is a call for resistance to vandalism (like with automated teller machines), a requirement met by hardened glass.
Selected market sectors where ruggedness and longterm availability are called for are the focus of Densitron. That includes the broadcast segment, says Marc Corrigan, managing director Germany. “Here you want haptic feedback, as realistic as possible, to approach the tactile features of mechanical keys or buttons.” Bonding is “important for us but needn’t necessarily be implemented inhouse.” In the meantime there were good specialists in the Far East who could be relied on as a manufacturing partner. No longer taking care of the bonding yourself, you could choose the technology best suited to the application, and the right partner. In new developments some 50 percent of displays feature touch, of which in Europe 80 to 90 percent go to PCAP. PCAP has “many advantages and no longer any drawbacks to speak of.” Operation wearing gloves had been well solved, so that you only found resistive touch in niche applications.
Bonding is a mixed business for Kyocera. “We bond ourselves for direct clients and largish volume”, says Eberhard Schill, manager marketing & distribution at Kyocera Display Europe. That means customers from the automobile sector and other industries. “For standard products and smaller volume our contracting distributors are very well set up in the meantime.” That way an optimal bonding process could be offered matching the application.