Is Apple changing its mind on touch panel structures?

January 22, 2013 - Reports are circling around Apple’s supply chain of a potential shift in the company’s display strategy for its future iPhones and iPads — moving back to LCDs and away from touch panels — but a drastic realignment of its supply chain is probably not likely, observes DisplaySearch.

Calvin Hsieh, senior analyst at DisplaySearch, cites a report from China that Innolux has delivered "touch on display" samples for the iPhone, another China report that Innolux and AU Optronics have provided "one-glass solution" (OGS) samples for the iPad Mini, and his firm’s own analysis that the iPhone 5 uses in-cell touch technology but the iPad mini uses a glass/film dual ITO (GF2, or DITO) structure. With both those processes struggling to attain good yields, could Apple end up changing its display technology adoption midstream?

TOD is a proprietary on-cell touch technology developed by Innolux in which the sensor is located on the upper glass (the color filter substrate) beneath the top polarizer. On-cell touch combines both LCD and touch so it must meet Apple’s LCD display requirements; Hsieh notes, adding that Innolux accounted for less than 10% of iPhone 4 display shipments (3.5-in, 960×640). "If Apple were to adopt TOD, it would very likely request that Innolux share its technology, structure or even patents with Apple’s other LCD suppliers in order to ensure adequate supply," he writes," and Apple also probably would want to take over the controller IC and algorithm from any Innolux partners (e.g. Synaptics). Apple already owns DITO patents, he adds.

The OGS display technology is an even more complex problem, Hsieh points out. OGS integrates the touch ITO sensor circuits into the cover glass, via two possible methods: a piece type such as "touch on lens" (TOL) or a sheet type, each accomplished with a different process. Either way the X-Y sensor patterns are on the same side of the substrate, so it’s called a "SITO" structure or "G2." Touch panel maker TPK owns patents for the piece-type OGS method, and claim they have key SITO patents as well and are suing Nokia and Chinese panel maker O-film, Hsieh notes; whether the aforementioned Innolux-AUO partnership could produce the technology given the TPK patents is unclear, he says.

There’s more to Apple use of OGS display if it chooses that route. Sheet-type OGS has a compressive cover-glass strength of 500-6600 Mpa; Corning’s IOX-FS and Gorilla glass have 600-700 Mpa for smartphone sizes and cannot be used in sheet type, Hsieh says. Piece type has the higher CS value but are difficult to mask-stamp and align under lithography, and throughput may be low.

Among iPhone 5 panel suppliers only LG Display offers everything from in-cell touch LCD to cover glass lamination (consigned by Apple), Hsieh notes. Other in-cell touch LCD makers Japan Display and Sharp rely on partners for the cover glass. If Innolux and AUO continue with their OGS partnership, they have a choice:

  • An integrated offering of LCD, OGS sheet patterning (cover glass with SITO sensor), and lamination let Apple specify the IOX-FS glass sheet with compressive strength of Gorilla 1; "In this scenario, LG Display will never give up and must be one of the suppliers," he notes.
  • Integrate the LCD, OGS piece-type sensor patterning, and lamination, using consigned cover glass pieces from other finishers (e.g. Lens One). The challenge here is expanding tools, throughput, and yield for piece-type patterning, to be acceptable for the iPhone’s >100M unit base.

All that is somewhat speculation, though, because long-term Apple touch supplier TPK already "has excellent OGS sheet and piece-type technology, and high lamination yield rates," and is unlikely to simply hand over that business to new entrants. "Although AUO and Innolux have advantages as LCD makers and can shorten the supply chain by producing LCD and touch at the same time, TPK has strength in OGS integration from sensor patterning, cover glass finishing (for sheet type), to module lamination," Hsieh writes. "Thus, there is a good chance that TPK will once again be a key touch supplier to Apple if it decides to change touch structures."

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