LG Display’s Kwon Se-Yeol senior researcher introduced the 77-inch transparent flexible OLED which had been introduced in June at IMID 2017 held in BEXCO, Busan on Aug. 30, and announced the applied technologies to realize this.
Kwon Se-Yeol senior researcher mentioned, “OLED is self-luminous, so it can be manufactured with a thin thickness because it does not need a back light unit. The thinner the thickness, the more flexible the OLED can be so that it is easy to implement flexible displays with OLEDs.” and forecasted. “It can be used in various fields such as signage and smart desk.”
The 77-inch transparent flexible OLED which is released this time is a top emission type for improved luminance. The transparent thin film encapsulation layer is applied, different from the conventional OLED TV or large flexible OLED, and two polyimide substrates are used.
Kwon Se-Yeol senior researcher said “We applied a transparent thin-film encapsulation layer instead of the existing metal encapsulation layer for the top emission method ” and explained “A white OLED light emitting layer and a color filter layer were formed on two polyimide substrates and cemented together. A barrier film and a multi-barrier were applied to the top and bottom of the polyimide substrates to prevent moisture and oxygen penetration.”
The Kwon Se-Yeol senior researcher then states that “flexural rigidity of the panel is mainly affected by the thickness of the polarizer and the encapsulant layer, so it is necessary to reduce the thickness in order to improve the flexibility”, and emphasized “By reducing the thickness of the encapsulant layer from 100 μm to 20 μm, we can reduce the strain on the OLED module from 0.36% to 0.21%, along with improved flexibility”.
In addition, he mentioned that surface reflection due to polyimide birefringence phenomenon, laser wavelength selection according to polyimide properties in LLO (laser lift off) process, and use of flexible OLED module are all covered, and technical development is continuing.
Meanwhile, LG Display has developed the world’s first 77-inch transparent flexible OLED with UHD (3840 × 2160) resolution, transmittance of 40%, and radius of curvature of 80R as part of the national project.