Author: Michael Hatcher

Although large-size LCD monitors are rare on the market, sales of LED backlight modules will continue to grow rapidly in the next two years. For LED manufacturers, the value of the possibilities they show is still unclear.

Some people think that large-size LCD screens (diagonally larger than 10") will become the next mainstream application, when high-brightness light-emitting diodes (HB LEDs) will replace more and more traditional lighting methods. Until then, almost all of these large-size LCD screens were illuminated by cold cathode fluorescent tubes (CCFLs), but the use of HB-LEDs made televisions and displays thinner and with higher energy conversion efficiency. And the profit is increased due to the improvement of color reproducibility. Of course, this is theoretically the case.

Figure 1. When the price/performance ratio of HB-LED continues to increase, the market penetration of LED backlights is also increasing. Last year, only 0.4% of large-size LCD panels were equipped with LED backlights, but this number will increase to 2.8% (12 million units) in 2009. Image source: DisplaySearch

Many HB-LED manufacturers are scaling up capacity, and they are convinced that the emerging market will be similar to the small LCD display. Driven by cellular handsets, small LCDs have become the number one killer application for HB-LEDs, and now it occupies half of the $4 billion market for such chips each year. About 300 million large-size LCD screens are being produced each year, and backlight modules account for one-third of the total cost of a large-size display. There is no doubt that there is a huge market opportunity in front of HB- LED chip and backlight module manufacturers.

So far, the transition from traditional technology to LED backlighting has been increasing. Only a few products, most of which are small-sized displays for laptops and laptops, have LED backlight modules. In fact, according to market analysts DisplaySearch's latest reports and forecasts, in 2006, only one million large-size LCD monitors equipped with LED backlight modules were sold, accounting for only 0.4% of total LCD shipments. It is estimated that 271 million LCD monitors have been shipped.

In an analysis that DisplaySearch considers "conservative," they believe that shipments of LED backlights for LCD TVs and PC monitors will triple in 2007, approaching three million units (Figure 1). In the available market for more than 300 million LCD monitors, the fast-growing segment accounts for only 0.9% of the entire market.

Steve Jurichich, director of DisplaySearch's Display Technology Division, estimates that shipments of LED backlight modules will increase to 8 million units (2.1%) in 2008 and 12 million units in 2009 (2.8% share) . Undoubtedly, this growth is fast, but in the past decade or so, in the field of mobile phones and handheld devices , LED marketing has achieved great success, others are unmatched.

The reason is simple, as always, it is still cost-effective. After all, just a few very cheap chips are enough to illuminate the screen of a mobile handheld device. But to provide backlights for TV screens on the market today, hundreds of chips are needed, and their lighting quality requirements are much higher than those required for a simple mobile phone.

According to Jurichich, DisplaySearch's forecast of LED backlight market share is relatively conservative, because there are still great uncertainties in the advantages of the new process, and manufacturers of LCD TVs and monitors should consider their costs. . Another part of the problem is for TV applications. Although LED backlights have begun to be built into very high-end models, they have not achieved much success.

Learning from Sony's lesson <br> When it comes to Sony's failure to attract early advocates to buy its LED-backlit Qualia TV in 2004, Jurichich said: "Sony's experience has made LCD TV manufacturers more conservative; Those TVs are leading the trend, but each backlight module requires 450 separate LEDs, which are quite expensive. As he said, the LCD-TV costs $13,000.

So, will LEDs be adopted as soon as possible? For the above situation, the advantages of LEDs are significant. For mobile phones, two key factors in choosing LED technology are: one is that designers want to make their phones more compact; the other is that semiconductor technology has better light conversion efficiency, which directly extends battery life. There is no doubt that notebooks and portable PCs benefit from its light weight and longer battery life, but these factors are useless in large LCD displays. Both desktop monitors and TVs are powered by wall outlets, which are more efficient than battery power. In addition, the LED can make the display slightly thinner, but its advantage is almost negligible compared to the mobile phone using HB-LED.


Figure 2. According to iSuppli's survey, if LCD panel component shipments will increase to 500 million units in 2010, TV applications will become a major growth factor for LED backlights. This is because the total area of ​​the LCD panel is dominated by the TV set, which is much larger than that of the personal computer, and the number of LED chips required will increase as the display area increases. Image source: iSuppli

iSuppli analysts are predicting the LED market , they seem to be more optimistic about the market opportunities for large-size LCD backlights. Like DisplaySearch, iSuppli analyst Paul Semenza estimates that about 300 million large-size LCDs will be shipped this year, and will increase to around 500 million in 2010 – the increased output of LCD TVs is greatly stimulating It is (Figure 2).

However, unlike DisplaySearch, Semenza also predicts the potential value of the large-size LCD backlight market for LED chip manufacturers. He said that with the beginning of 2006, the sales of LED backlight modules in the year can be neglected, but for the LED chip market for large-size LCD applications, it will increase from 100 million US dollars in 2007 to 1 billion US dollars in 2009. The growth rate is exponential.
This year seems to be a crucial year, and the average selling price of LED backlight modules is expected to fall by a third to reach $200. Even at this price, it is almost twice the price of CCFL.

LED backlight module
The DisplaySearch report did not predict the impact of large-size LCD backlights on the HB-LED market. The reason is that when DisplaySearch analysts consider changes in various factors (such as a large number of backlight designs, including many custom), they believe that such predictions may be speculated. Larger screens require brighter chips, some use RGB sources, others use phosphor-based white LEDs, and the efficiency and price of the chip will continue to change over the next few years as the process increases. Production is more precise.

Market share <br> For LED manufacturers targeting large LCD backlight modules, more efficient and reliable displays may be infiltrating the market for different LCD applications. The DisplaySearch and iSuppli reports agree on this total market share. For 2009, Displayrich's Jurichich showed that 2.8% of the total LCD display will use LED backlight modules; while iSuppli's Semenza thinks it is only 2.5%.

Semenza said: "Oversized (over 40") TV panels have the highest share of 13%; but for standard notebooks and monitors it is below 1%. More than 40" panels will use many LEDs in each backlight module, and the average price of LEDs in each panel of the LCD TV is $140 compared to a $50 notebook or monitor panel." He added. "The share of LEDs will increase significantly after 2009, which will validate our vision; by 2011 its market share will increase significantly to 10% (total share)."

However, as Jurichich warned, CCFL manufacturers will not sit down and watch their products become yesterday's yellow flowers. Now they are developing color reproduction technology. Jurichich said: "They are already in a good position."

As a result, LED backlight developers (including Cree, Lumileds, and Osram Opto Semiconductors) may have to focus on other advantages of solid-state lighting technology. For example, LEDs do not require a high startup voltage. This means that the backlight module will use a smaller amount of capacitance. Another advantage of RGB LEDs over CCFLs is their fast switching speed and the ability to achieve high quality images for simultaneous transmission without the need for color filters.

For a long time, this may be a favorable factor for LEDs, because the color filter is the most expensive part of the LCD TV's relay backlight source. For a typical 40" display, its cost accounts for the entire component cost. 19%. Jurichich believes that although it may take five years to fully develop this technology, it is this advantage that will eventually inspire LEDs to penetrate the wider market.

The crux of the problem <br> Currently, for LED and LED backlight manufacturers, the main focus is on how to increase the cost per lumen of LED. For a 23" TV, by properly increasing the luminous efficiency of the LED to 60 lm/W, we can reduce the number of LEDs required for the backlight module by about one-third, from 309 to 234. Jurichich On this basis, manufacturers may be more likely to accept the additional cost of backlighting, as well as consumers.

Reference reading
DisplaySearch's 832 slide TFT LCD Materials Report is now available. See for details. At the Photonics West 2007 conference held in January this year, iSuppli's Paul Semenza made a detailed report on the HB-LED market forecast.

LED backlight assembly overview
● LED backlights are very useful in the mobile field because they consume much less battery energy than traditional cold cathode fluorescent backlights (CCFLs), such as LED backlighting on a long airplane journey, which can significantly extend a notebook Computer working hours.
● Since 2005, laptop displays have used LED backlights, including Sony's 11-inch Vaio, Fujitsu-Siemens' 10.6-inch handheld, and Toshiba's Libretto (the first laptop with LED backlighting).
● In the TV market, the quality of the colors produced on the display is very important, which means that a single red, green and blue (RGB) launch tube is better. But for laptops, color reproduction is no longer a problem, and phosphor-based white light tubes provide the desired color for most applications.
● RGB LED backlights in TV applications provide more color reproducibility than CCFLs, and are especially noteworthy for red images. This is because the red light excited by the CCFL is significantly weaker than the blue-green portion of its own emission spectrum. But now CCFL manufacturers are developing products with better color reproducibility.
● LCD TVs will increasingly control all LCD markets. This is mainly because TV screens tend to be much larger than the size of personal computer screens, and it is clear that consumers have a tendency to buy larger TVs – as the evolution of e-commerce will be evidence.
● The number of LED tubes required for an LCD panel depends on its size. iSuppli estimates that 50 phosphor-based white light tubes are sufficient for a 17" notebook display, but for a 46" LCD TV, about 450 separate tubes (180 red) are required. And green, 90 blue).

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