Narrow Bezel Research Articles

Dual-bootstrapping gate driver circuit design using IGZO TFTs

To promote the integration of thin-film transistor (TFT) gate driver circuit technology into high-resolution large-size display application with narrow bezel, achieving high speed is a critical challenge. This paper proposed a dual-bootstrapping TFT integrated gate driver circuit for large-size display. The over-drive voltage of the driving TFT was increased both at the rising and falling edges of the output waveforms. To validate the circuit feasibility, the proposed circuit was fabricated using amorphous indium-gallium-zinc-oxide (a-IGZO) TFT technology and measured in terms of transient response with cascaded stages and reliability tests over long operating time. Compared to conventional approaches, the proposed gate driver demonstrates a 39 % reduction in the falling time as well as compact layout. Therefore, the proposed gate driver schematic is well-suited for large-size display applications that involves heavy resistance–capacitance (RC) loadings and require high resolution above 8 K.

P‐216: The Status and Trend of Narrow‐bezel OLED Display

With the development of display technology, the terminal customer has put forward higher panel specification requirements. As a result, smart phone's panel size becomes bigger and bigger, as well as the screen ratio, which lead to sharp decrease in panel border size. While limited by the space and module structure, how to accomplish narrow bezel is always a hot topic in OLED field. During the past two years, panel makers used LIPO（Low injection pressure overmolding） technology to make border narrower, and this become standard configuration settings. However, LIPO accounts for little proportion in total panel and module border, it is the reduction for the space between the shell and module. In this paper, we analyze the trend of narrow bezel development, and introduce some new methods which may be used in future, hoping to provide some helpful reference to OLED panel narrow bezel design.

48‐3: Invited Paper: Research on Pad Bending Technology for the Extremely Narrow Bezel of Flexible OLED Screens

The bending radius of the flexible OLED down border was reduced to 0.15mm from 0.25mm by an improved bending model for the extremely narrow bezel mobile. The stability of the optimized bending model was demonstrated by simulation, and the preliminary production and environmental reliability were assessed too.

69‐2: A Novel Ultra Large Size OLED Display Base on Small‐size OLEDs

In this paper, we present the novel ultra large size OLED display with extremely narrow bezel, parallel driving of OLED, two‐time optical compensation. Using these technologies, we have designed the OLED with many units of small size OLED display, and the uniformity of brightness is more than 95%. Finally, we have successfully developed up to 256‐inch 8K OLED display.

P‐22: Scan Driver Circuit with Multiple Outputs employing Low‐temperature Polysilicon and Oxide TFTs for Mobile Displays

In this paper, we propose a scan driver circuit with two outputs employing low‐temperature polycrystalline silicon and oxide (LTPO) thin‐film transistors (TFTs). The proposed scan driver circuit can generate two types of scan signals that can drive p‐ type and n‐type switching TFTs. In addition, by using the Q[n] node bootstrapping method, the output is stably generated even in the depletion mode of the amorphous indium‐gallium‐zinc‐ oxide (a‐IGZO) TFTs. As it is a scan driver circuit that can be applied to LTPO TFT‐based pixel circuits, variable refresh rate operation is possible. Therefore, the proposed scan driver circuit can be applied to displays requiring high resolution, narrow bezel, and low power consumption.

24‐2: Facile Design of Integrated Gate Driver Circuit with Self‐aligned InGaZnO TFTs and Reliable Compensation Technology for 166 PPI WOLED Displays

In this research, we describe a facile design of white organic light emitting diode (WOLED) displays applicable to 8K4K resolution of large‐area displays. We demonstrated a 13.3‐inch diagonal size (166 pixel‐per‐inch) of WOLED display, including a self‐aligned oxide thin‐film transistors, simple pixel driving circuit, external compensation method, fast driving integrated gate driver circuit. The narrow bezel of 3.9 mm is realized when multi‐output gate driver circuit is applied. The required function for external compensation method is realized by the integrated gate driver circuit. The external compensation improved global luminance uniformity, especially at the low gray level.

25‐1: Distinguished Paper: A Novel Ultra Large Size OLED Display for Premium TVs

In this paper, we present the novel ultra large size OLED display with high image quality for premium TV using an advanced coplanar Oxide TFT backplane, MLA based OLED, small area gate driver in panel for narrow bezel, and pixel charging enhancement method with external compensation. Using these technologies, we improved the luminance efficiency about 20 %, and reduced the gate driver design area to 40%. The pixel charging ratio is more than 80% in all gray levels. Using the developed OLED display, we have successfully developed up to ultra large size 88‐inch 8K, 97‐inch 4K OLED TVs.

P‐2: Narrow Bezel Gate Driver Generating Positive Pulse for AMOLED Display Using LTPO Technology with Depletion Mode Oxide TFTs

We propose a novel gate driver generating positive pulse for oxide switching TFTs in AMOLED pixel circuits using low‐temperature polycrystalline silicon and oxide (LTPO) thin‐film transistors (TFTs). The proposed gate driver circuit has only five TFTs without capacitor. The proposed circuits can operate perfectly when all oxide TFTs in the circuits have threshold voltage (VTH) of ‐3.5V, depletion mode. The circuit can be easily designed for narrow bezel due to simple structures. The one stage of the circuit was designed with the size of 50 μm × 100 μm. The fabricated circuit works well with the depletion mode oxide TFTs with VTH of ‐3.5V. The circuit operated at the pulse width of 1 μs, corresponding to operating speed of 500 kHz. The proposed gate driver can be applicable for narrow bezel AMOLED display.

A novel ultra large size organic light emitting diode display for premium televisions

AbstractIn this paper, we present novel ultra large size organic light emitting diode (OLED) display technologies with high image quality for premium televisions (TVs) using an advanced coplanar oxide thin film transistor (TFT) backplane, microlens array (MLA)‐based OLED, small size gate driver in panel for narrow bezel, and pixel charging enhancement method with external compensation. Using these technologies, we improved the luminance efficiency about 20% and reduced the integrated gate driver design area to 40%. We have achieved the life time of the gate driver in panel longer than 100,000 h in reliability test. The pixel charging ratio is more than 80% in all gray levels. Using the developed OLED display, we have successfully developed up to ultra large size 88‐in. 8K and 97‐in. 4K OLED TVs.

6.3: Improving Cross Line Defects of Ultra Narrow Bezel Displays by Decreasing Foreign Matter

Cross line defects are stubborn problems which puzzles ultra narrow bezel displays for a long time. It not only seriously lower yield of ultra narrow bezel displays, but also is difficult to repair in cell processing by NRP (normal repair). In this paper we mainly describe improving cross line defects by decreasingforeign matter in the process of CVD (Chemical Vapor Deposition).

Emission Gate Driver With Five Low-Temperature Poly-Si Oxide TFTs Without Capacitor for Narrow-Bezel AMOLED Display

We report a highly simplified emission (EM) gate driver circuit for high resolution and narrow bezel active-matrix organic light emitting diode (AMOLED) display using low-temperature poly-Si oxide (LTPO) thin film transistors (TFTs). The proposed circuit consists of five TFTs, three low-temperature poly-Si (LTPS) and two oxide TFTs. The output signal can be controlled with variable pulse width by starting signal of different pulse width. The fabricated circuit operates well with depletion mode oxide TFTs having threshold voltage of -3.5 V. The output swing from 3 V to -7 V and peak to peak voltage of 10 V were used for the output measurement. The output signals with different duty ratio of 10, 50, and 90% are demonstrated. The power consumption is only 41.5 mW when the duty ratio of EM signal is 90% at refresh rate of 120 Hz for 4k (3840 × 2160) AMOLED display.

P‐5.8: Improving Cross Line Defects of Ultra Narrow Bezel Displays by Decreasing Foreign Matter

Cross line defects are stubborn problems which puzzles ultra narrow bezel displays for a long time. It not only seriously lower yield of ultra narrow bezel displays, but also is difficult to repair in cell processing by NRP (normal repair). In this paper we mainly describe improving cross line defects by decreasing foreign matter in the process of CVD (Chemical Vapor Deposition).

50.3: MPRT Enhancement Gate Driver Circuit Employing IGZO TFTs for Image‐Quality Improvement

50.3: MPRT Enhancement Gate Driver Circuit Employing IGZO TFTs for Image‐Quality Improvement

P‐7.4: Research on Ultra‐thin Narrow Bezel Technology of Liquid Crystal DisplayModule under 5G Mobile Phone

Ultra-thin narrow bezel of 5G mobile phone is very attractive, but obviously when the thickness of LGP is constant, the optical homogeneity is better when the distance from LED to visual area is bigger, so establish an optical analysis model to analyze the optical homogeneity in light emitting side in vertical direction by the relations between the distance from LED to visual area and the thickness of LGP. When the thickness of LGP is above 0.34 millimeter and the distance from LED to visual area of BLU is above 1.75 millimeters, the optical homogeneity can meet mass production by normal design. if the thickness of LGP compress from 0.34 millimeters to 0.26 millimeters and distance from LED to visual area of backlight units compress from 1.75 millimeters to 1.57 millimeters, the optical homogeneity in light-emitting side can be above 75% by the angle of LGP wedge surface is below 5 degree and the length of LGP wedge surface is between 0.35 and 0.55 millimeters, so the border of backlight units can be compressed to 2.8 millimeters based on the LED under the FPC and the thickness of liquid crystal display module can reach 0.95 millimeters. The optical effect and structural reliability of liquid crystal display module is both OK under the value of G is above 0.55 millimeters by using linear silver paste or the value of G is between 0.4 millimeters and 0.55 millimeters by using L shape silver paste based on DOE experiment.

P‐138: High Torque Hinge for Large Size Foldable Device

In order to expand the mobile foldable technology to large size IT device, we have developed a folding hinge having high torque value. It has stress‐free folding characteristics by virtual axis structure and compact dimension by the parallel arrangement of a folding part and a torque part. Therefore, we can make a large size foldable device which is slim and narrow bezel. It has the torque value of 14 kgf·cm on device and free‐stop function. By the enlargement of friction area by the change of CAM concept and the structural optimization we can reduce abrasion of hinge CAM surface, and the torque reduction by 70k folding lifetime test is less than 20% of its initial value. It is very important progress in the foldable technology.

P‐24: Distinguished Student Poster: Gate Driver with LTPO‐TFT Circuits for Low Power Consumption and Narrow Bezel AMOLED Displays

We propose a novel gate driver circuit using low‐temperature polycrystalline silicon and oxide (LTPO) thin‐film transistors (TFTs). The proposed circuit operates well when oxide TFTs have VTH of −7.5 V, which is very depletion mode. In addition, by utilizing extremely low off‐state current of oxide TFTs, ultra‐low power consumption can be achieved. The proposed circuit consists of only six TFTs, four p‐type LTPS and two n‐type a‐IGZO TFTs, without capacitor. The fabricated circuit operates with a pulse width of 1 μs corresponding to operating speed of 500 kHz with very small pitch. The proposed circuit can be applied to ultra‐high definition (UHD) and narrow bezel AMOLED display.

32‐3: 1.5‐inch, 3207‐ppi Side‐by‐Side OLED Display Capable of 32‐Division Driving with OSLSI/SiLSI Structure Fabricated by Photolithography

In this paper, we fabricate a 1.50‐inch, 3207‐ppi prototype OLED display with drivers capable of 32‐division driving, which is achieved by monolithically stacking CAAC‐OS FETs over SiFETs. This structure enables a narrow bezel and two‐dimensional driver arrangement, leading to independent driving of 32 pixel arrays with divided source and gate lines.

62‐3: Distinguished Paper: High Precise Laser Glass Cutting for Future Display

As one of the various attempts to reduce the size of display bezel, high‐precision glass cutting process is required to be developed for future displays. In this study, the Bessel‐beam Laser Cutting (BLC) process has been studied, which is capable of minimizing the thermal deformation of the black matrix (BM) material on glass. In an experimental setup composed of IR ps laser with bessel‐beam optics, the smallest thermal degradation of BM and the highest cutting precision are achieved as 40μm and 10μm, respectively. When reducing thermal effects caused by high‐order beams without sacrificing glass breaking strength, effective heat affected zone (HAZ) could be reduced nearby 30um width from the cutting line. This high precision cutting technology will contribute to realize extremely narrow bezel display near future.

P‐44: MPRT Enhancement Gate Driver Circuit Employing IGZO TFTs for Image‐Quality Improvement

We present a novel gate driver circuit using IGZO TFTs which can decrease the MPRT (Motion Picture Response Time) value from 6.8ms to 3.4ms at the frequency of 120Hz. And this means the OLED panels’ image quality can be greatly improved through motion blur reduction. The MPRT enhancement GOA (Gate driver on array) can output three kinds of waveforms for normal display, black data insertion and external compensation within one frame. We save 14 TFTs and 2 capacitors through sharing sense input and hold unit, black data inserting input unit and leakage prevention unit between two adjacent rows which greatly simplify our multifunction GOA structure. This circuit is verified at high temperature (50℃) companied with high humidity (80% RH) during 500 hours with no problem through 15.6 inch experiment panels which resolution is 768 columns by 2160 rows. Besides, the proposed structure can make our future 30inch 4K2K panel to achieve a narrow bezel smaller than 7mm.

Gate driver with low‐temperature polycrystalline silicon and oxide thin‐film‐transistor circuits for low power consumption and narrow bezel AMOLED displays

AbstractWe propose a novel gate driver circuit using low‐temperature polycrystalline silicon and oxide (LTPO) thin‐film transistors (TFTs). The proposed circuit consists of only six TFTs, four p‐type LTPS, and two n‐type a‐IGZO TFTs, without capacitor. The proposed circuit operates well when oxide TFTs have threshold voltage (VTH) of −7.5 V, which is very depletion mode. Without bootstrapping, low gate bias stress occurs on TFTs in the proposed circuit. With dual gate (DG) structure of oxide TFTs, the stability of the proposed circuit is improved. In addition, by utilizing extremely low off‐state current of oxide TFTs, ultra‐low power consumption can be achieved. The total power consumption of the proposed gate driver is less than 100 mW under a‐IGZO TFT's VTH of −6 V at 120 Hz 4k (3,840 × 2,160) resolution display. The fabricated circuit works perfectly at a pulse width of 1 μs equivalent to operating speed of 500 kHz. The proposed circuit can be applied to ultra‐high definition (UHD) and narrow bezel AMOLED display.