Bum-Sik Kim

Novel technologies for commercialized 55-inch WRGB OLED TV

World’s first commercialized 55-inch WRGB OLED TV has been developed and launched recently. Large-sized OLED displays require novel technologies to realize mass production. We will introduce commercialized 55-inch WRGB OLED TV and its novel technologies including oxide TFT, WOLED, solid phase encapsulation, and compensation technologies.

11.1: Invited Paper: 15inch RGBW Panel Using TwoStacked White OLED and Color Filter for LargeSized Display Applications

We have developed a twostacked white OLED based on bottomemission structure for largesized display. It consists of one unit emitting fluorescent blue and the other unit emitting phosphorescent yellow twodopant of red and green in a host layer. In order to improve the performance of the WOLED, we adopted new noncabazole compound as a hole transporting layer with high triplet energy level and akali—metal doped charge generation layer. In addition, we employed new greenish yellow dopant instead of previous green dopant to enhance the lifetime of the phosphorescent stack. The resulting device exhibits 61.3 cd/A of current efficiency, 30 lm/W of power efficiency, and 6.4 V of driving voltage of at 1000 nit where its CIE coordinate is 0.340, 0.334. Halflifetime T50 of the device is estimated more than 130,000 hrs at 1000 nit. We also fabricated 15inch HD panel employing the twostacked WOLED and color filter.

Depletion Mode Oxide TFT Shift Register for Variable Frame Rate AMOLED Displays

This letter demonstrates a shift register circuit at the backplane of depletion mode oxide thin-film transistors (TFTs), which can cover variable frame rates for low-power active matrix organic light emitting diode (AMOLED) displays. The proposed scheme focuses on the stable gate control of a pull-up TFT by securing the charging and discharging paths at the wide operating frequency range. In a prototype high-definition (HD: 1366 × 768) AMOLED panel, it is ensured that fabricated shift registers operate at the wide frame frequency range from 1 to 240 Hz. The measured current consumptions are 30, 4, 6, and 5.8 mA for four clock signals, VGH of 24 V, VGL1 of -6 V, and VGL2 of -14 V at a frame rate of 120 Hz.

27.2: 31_inch FHD AMOLED 3‐D TV using Emission‐Switch Control Method

31_inch FHD AMOLED 3-D TV using the Emission-Switch Control for 3-D driving was developed. The Emission-Switch Control used here is that EM switches of each pixel are controlled simultaneously so that all pixels are emission and non-emission at the same time. In order to use this control method, we developed and adopted EM driver which have 2-D/3-D switch-able block between shift register and buffer. By using this method, we fabricated and demonstrated 31_inch AMOLED TV that achieved great viewing angle and on-off 3-D Cross-talk with 0.39 % level. Also, compared to Active Voltage Control this method helps reducing the load on the system.

42.2: Time Division Analog Driving Method to Display High Gray-scale of OLED Display

To raise gray-scale, the size of DAC should be increased on driver ICs at LCD or OLED display using an analog driving method. This factor makes problems such as size and costs of a driver IC. To overcome these obstacles, this paper proposes method to display high gray-scale without changing driver IC size. This method has a feature which is combined a digital driving technique and an analog driving technique. To implement this method, a frame should be divided into two sub-frames which have different roles. The first sub-frame displays an image and the second one displays additional gray-scale which can not be displayed on the first sub-frame. Also each sub-frame has different gamma voltages to implement high gray-scale.