At Touch Taiwan show last week, I saw display vendors mired in the battle over ever-narrowing bezels, and the never-ending pixel-per-inch war. As I examined the proliferation of display technologies, I found myself getting lost in the weeds.
AUO, alone, is spreading its resources wide and thin as it works on four different display technologies, ranging from amorphous silicon (a-Si) and low temperature Polycrystalline Silicon (LTPS) to oxide TFT and OLED.
So many panels on display at the show were breathtakingly beautiful. Does a narrow bezel matter? Absolutely. Do consumers want more PPI? You bet.
Nonetheless, I couldn’t help but roll my eyes when the discussion kept coming back to whether a 1mm border is really that much worse than 0.7 mm for a 5-inch full HD high resolution smartphone panel.
I understand that specs are life-or-death for engineers. But all this "specmanship" is killing Taiwan’s display vendors. To make matters worse, the fierce price competition just keeps escalating. Vendors are scrambling to devise new (and possibly more simplified) manufacturing processes, while staying constantly on the lookout out for new materials.
Display vendors, in general, are also clobbered by rapidly changing market trends. Declining e-reader demands worldwide, for example, have affected E-Ink. (However, I was pleasantly surprised to see E-Ink displays smartly designed into some of the most inventive smartphones featuring dual screens.)
Meanwhile, the growing education market for media pads and electronic whiteboards is asking for larger touch screens — where pupils can use a pen instead of a finger. The logic is intuitive: Teaching kids how to write on a touch screen that only recognizes fingers must be tough.
Sharp, although a latecomer to the touch screen market, demonstrated a large-screen projected capacitance technology that can also respond to a passive stylus. Sharp is leveraging a new analog front-end IC it developed to improve the signal-to-noise ratio. It’s specifically designed for a large-surface multi-capacitance touch screen.
Although it’s too early to predict the end of an era for touch screens, it was interesting to hear Tetsuya Hayashi, one of the keynote speakers, talking about development activities around post-touch screen technology in Japan. Hayashi, deputy director of Nikkei BP ICT Innovation Research Institute, illustrated the future of display technology as “ambient,” “free-form,” and “wearable.” Images, he foresaw, will be projected on any surface or in the air, instead of being constrained to a rigid, bulky box.
In the following pages, I’ll offer a few highlights of my exploration at this year’s Touch Taiwan.
Any surface for touch
The whole point of a “touch screen” is that the screen responds to human touch. But what if you could touch any surface — your clothes, your desk or in the air — to make your device respond to the movement of your hands?
Called “Anywhere Surface Touch,” the new technology uses any surface as an input area with a wearable device. It turns any flat or curved surface within reach into an input area. The interface uses a single small camera and a contact microphone to recognize numerous interactions between the fingers of the user and the surface.
The system recognizes which fingers are interacting and in which direction the fingers are moving. Additionally, the fusion of vision and sound allows the system to distinguish contact conditions between the fingers and the surface. The Ishikawa Watanabe Laboratory at the University of Tokyo is working on this.
Sharp’s high SNR projective capacitive touch panel
Sharp unveiled a capacitive touch panel system, which it says could be applied to a very large screen. The picture above shows a 70-inch touch panel. The limitation of touch-screen size is attributed to conventional sequential drive controllers, because as the number of sensor channels increases, the SNRs degrade.
Sharp, as revealed in its ISSCC paper earlier this year, resolved the issue by driving the sensor channels in parallel. Although the parallel drive methodology tends to mix the signals from multiple channels, Sharp engineers have figured out a way to reconstruct the original signals.
Amorphous silicon (a-Si) TFT LCD coming to smartphones?
Now, AUO says it plans to launch a 5-inch full HD smartphone panel by using an a-Si TFT LCD. The 5-inch panel on display, with 443 ppi pixel density, comes with a 1mm border. AUO described it as the narrowest border achieved by using a-Si technology.
LTPS rules in resolution and slim border
AUO also showcased a 5.5-inch WQHD panel (1,440 x 2,560) for smartphone displays created by using a Low Temperature Polycrystalline Silicon (LTPS) process. It has raised the pixel density to 538 PPI. The new display also features a border as narrow as 0.7 mm.
In-cell touch is the way of the future?
Integrating display and touch sensor into one module seems to be the way of the future. AUO’s 5.5-inch AMOLED panel (403ppi) is using an in-cell touch panel, while employing Low Temperature Polycrystalline Silicon (LTPS) process production. Its bottom line? Panel thickness is less than 0.45 mm.
The in-cell touch technology enables thinner and light panels, while it achieves better anti-glare performance, according to AUO.
AUO showed off a 5.5-inch full HD panel (1080 x 1920) based on oxide TFT technology. Featuring 403 ppi pixel density, 500cd/m2 brightness and 1000:1 contrast ratio, its claim to fame is low power consumption enabled by low refresh rate design (1Hz).
— Junko Yoshida, Chief International Correspondent, EE Times
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