Firms Show Off Foldable OLED Panels

2014/06/06 17:01
Tetsuo Nozawa, Nikkei Electronics
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Semiconductor Energy Laboratory (SEL) Co Ltd, Advanced Film Device (AFD) Inc (a subsidiary of SEL) and Nokia Corp developed a display that can be folded in two or three while displaying video.

The companies announced the display at SID 2014, an academic conference on display technologies, which runs from June 1 to 6, 2014, in San Diego, the US (lecture number 25.1, 25.2). And they showed two types of the new display in an interview.

One of the two types is a "book-type" display that can be folded in two like a book. The other is a "three-fold" display that can be folded in three. They are 5.9-inch OLED panels when unfolded. Their pixel count and resolution are 1,280 x 720 and 249ppi, respectively. They were realized by using the "WTC" structure, which combines white light-emitting OLEDs and color filter.

The display is made by forming a release layer, sealing layer and color filter layer in this order on a glass substrate. And a release layer, sealing layer, TFT layer and OLED layer are formed in this order on another glass substrate. Then, the color filter layer and OLED layer are attached to each other, and the glass substrates are peeled off and replaced with flexible substrates.

As a result, the color filter, TFT and OLED layers are sandwiched between two sets of a sealing layer and flexible substrate. The water vapor transmission rate (WVTR) of the two layers of the adhesive used to attach the sealing layer to the flexible substrate as well as the color filter to the OLED layer is as high as 7 x 10-7g/m2/day.

Both the book-type and three-fold displays can be bent up to a curvature radius of 2mm. They can be bent more than 100,000 times, SEL said.

Due to a reporting error, we inaccurately stated that the three-fold display can be bent up to a curvature radius of 4mm. In fact, it can be bent up to a curvature radius of 2mm.