The road to large-scale OLED panel reveals dawn (1): LG actively promotes, (2): lighting use is another driving force
Large-scale will not happen overnight
Having said that, the large-scale OLED panel still faces the difficulty of overstepping. One of them is the establishment of large-scale and low-cost mass production technologies. This is also a major reason why manufacturers have released more than 20-inch OLED TV/panels at the show to stop the prototype (Figure 5). Nowadays, the TFT and film forming processes used in small and medium-sized OLED panels cannot be directly applied to large panels. But there have been several solutions to this problem in this paper.
The biggest problem that hinders the realization of large-scale OLED panels is that the liquid crystal panels that are competitors are rapidly achieving high performance and low cost (Fig. 3). Therefore, "the original features of OLED panels such as 'high image quality' and 'ultra-thin' are difficult to form an advantage over LCD TVs" (an OLED technician).
Figure 5: OLED TVs with more than 20 inches have only prototypes. TV and panel manufacturers have exhibited large TV prototypes of more than 20 inches at the Institute and the exhibition. But the actual production of TV is only 11 inches (Sony) and 15 inches (LG).
After the large-screen, high-definition (1920×1080 pixels) development of the liquid crystal panel came to an end in 2007, high image quality and thinning will develop rapidly. The backlight source is converted from a cold cathode fluorescent tube (CCFL) to an LED, which results in a display performance that is no less than the level of the OLED panel.
For example, most LCD TVs equipped with direct-lit LED backlights achieve a contrast ratio of 1 million:1, and a color performance range of NTSC of more than 100%. Its performance is higher than the LG Electronics' 15-inch OLED TV introduced earlier. Products using edge-lit LED backlights are less than 20 mm thinner. Although OLED TVs can further achieve high image quality and thinness, the difference between the two is difficult to publicize to users.
Therefore, large OLED panels are likely to be popularized first in applications that do not compete with liquid crystal panels. Several such prototype panels were displayed at the "FPD International 2009" held in October 2009 (Figure 6). LG Display and SMD have developed a "transparent display" that can see through the panel. The display has a transparent material for the positive/negative electrodes, and a light-transmitting structure on both sides of the panel. "Imagine public use such as digital signage" (LG Display).
Figure 6: LG Display and SMD develop OLED-specific uses
LG Display and SMD are developing transparent and flexible OLED panels. It can be said that these are unique uses of OLED panels that are difficult to implement in liquid crystal panels.
In addition, LG Display has also released a "medical display" with high contrast and good visibility. SMD exhibited a flexible "IC card type display" with a thickness of 50 μm. Although the mass production period of the two has not yet been determined, the application of the characteristics of the OLED panel is just around the corner.
Large-scale and low-cost technology is steadily advancing
The development of technology to achieve large-scale OLED panels is progressing steadily. Now, each panel manufacturer is pursuing not only the display performance, but also the technology that is expected to achieve the highest yield in mass production (Korean Takashi, Senior Director of the Kodak OLED System Development Division).
The key to the large-scale is the TFT that can be applied to the OLED driver and is large-sized, and the OLED light-emitting layer film forming technology that contributes to cost reduction and enlargement (Fig. 7).
Figure 7: There are two major technical issues for large-scale and low-cost
There are many technical issues for the increase in size and cost of OLED panels. It is especially necessary to develop a TFT material for glass substrate and a OLED device lamination process technology.
The LG display, which aims to produce 40-inch products in 2012, has already set the same target for LCD panels. LG Display has proposed a long-term plan for mass production: "By 2012, using 5th to 6th generation glass substrates capable of cutting 2 to 4 40-inch panels, the material cost is 150%, and the yield is about 70%. By 2016 The 10th generation glass substrate that can cut 18 40-inch LCD panels is used to reduce the material cost to 70-80%, and the yield remains unchanged" (LG Display Kim). (To be continued, reporter: Saeki Shinya)
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