New LCD Displays, Improved CCFL and LED Backlights
LCD Panel Technology is constantly evolving in all areas from developments in the use of different liquid crystals and improved backlight systems for better picture performance, to manufacturing processes that help improve production yield factors and therefore, reduce costs.
In this short article, we discuss the latest developments as applicable to LCD televisions; in particular we look at the constantly evolving new LED backlight technologies being introduced by TV makers in an attempt to come up with a better picture at a cheaper price.
LCD Display Technology: The fastest growing display technology in use today!
LCD is the display technology of choice in the HDTV market. This is no surprise; LCD panel technology is without doubt the fastest growing display technology in the field of home entertainment.
This is not to say that advancements are not taking place in other display technologies. Suffice to mention plasma, despite that the latest developments seems more addressed to indicate that this display technology has reached the end of the line – not because there is an immediate alternative but simply because consumers keep preferring LCD over plasma, making the latter less viable for the TV makers industry.
The New Samsung F6300 Smart LED TVC
The irony is that plasma remains the only real competitor to LCD as OLED TV Technology is still too expensive. However, developments in plasma displays, while consistent, are mainly addressed towards consolidating the technology, with new displays capable of improved picture, reduced power consumption and reduced panel profile. In this respect, 2013 plasma displays have reached the apex in picture quality.
Even if price is no issue and you still want to consider an OLED TV, keep in mind that OLED display technology has still to prove itself. In other words, the real technological break-through that literally changed the home entertainment market is LCD panel technology – mainly thanks to the developments taking place in the area of liquid crystal displays.
LCD panels today employ several variations of liquid crystal technology, including super twisted nematics (STN), dual scan twisted nematics (DSTN), ferroelectric liquid crystal (FLC) and surface stabilized ferroelectric liquid crystal (SSFLC). Use of special plastics instead of glass substrates and flexible backplanes for use in specialized applications, have also become a reality.
The truth is that development in LCD flat-panel technology is coming from all fronts and from all major display LCD panel manufactures. This is leading to larger displays panels, improved response times, higher resolution, faster refresh rates, better color freedom, and equally important to the end-customer, cheaper LCD and LED TV prices.
Price and Size issues in LCD Panels
Price and Display Size are both limited by the quality-control problems faced by display manufacturers. Increasing the display size implies adding more pixels and therefore more switching transistors, thus increasing the chance of including a few bad transistors in a display. This in turn will further increase the rejection level.
However, larger and cheaper is the way LCD HDTVs and especially LED LCD TVs are heading. The latest developments in the manufacturing processes of LCD panels mean that price is practically no longer an issue when choosing between plasma and LCD display technology for anything less than 55-inch. We have already seen 46-inch LCD HDTVs selling at a similar price to that of corresponding plasma televisions. And at 55-inch, the price difference is just marginal and more a result of the supported feature set rather than the display technology itself.
This is all thanks to the efforts invested during these last years by LCD panel manufactures in developing LCD production techniques aimed at improving yield at the larger 50 to 55-inch LCD panel size. Up to very recent, this TV screen size segment was considered the domain of plasma displays. This panel size is becoming the real favorite TV size in today’s multi-billion dollar home entertainment market.
However, 55-inch is the real maximum you can get with LCDs today in that at larger screen sizes―though readily available―plasma starts to enjoy a significant price advantage over corresponding LCD HDTVs.
There is no doubt the biggest advancements in LCD panel technology we are witnessing are taking place in the development of different backlight technologies – and in particular in LED driven backlights.
Main developments include:
– Improved Fluorescent Backlights
– LED Backlights – ‘Full-array’ and ‘Edge-Lighting’
Though CCFL LCD TVs may be seen by many as a dying breed as more TV makers are channeling their development effort towards LED TVs, CCFL LCDs still have a lot to offer. The developments that took place in CCFL before the LED TV invasion eventually served as the basis for LED LCD TVs. In particular, the use of intelligence in the control of backlights is being put to a great effect in LED backlight systems employing some form of zone dimming functionality.
It was Philips who originally employed the use of intelligence in the control of multiple high output fluorescent lamps operated in a scanning mode on some of their high-end LCD displays. This scanning principle is now being used by other TV makers like LG, Vizio, and Toshiba to generate blank frames in their 240Hz and the latest 480Hz panel refresh rates. This higher refresh rate comes into play with dejudder processing. It also helps cancel out the sample-and-hold effect, which is characteristic of conventional LCD technology; the end result is improved motion sharpness.
Similarly, actively controlling the backlight brightness level in synchronization with the picture content helps improve gray scale performance and produce deeper black levels.
Samsung was the first to introduce the use of flat fluorescent lamp (FFL) instead of the standard cold cathode fluorescent tubular lights to power some of their flat-panel CCFL LCD HDTVs. The main advantage is that FFLs have a paper-thin form factor that produces light from its entire surface, thus rendering greater picture uniformity, better brightness, and a higher contrast ratio.
Sharp is also utilizing improved CCFL technology in their LCD panels. Of particular interest here is the use of enhanced color filtering at the sub-pixel level used by Sharp Quattron technology. The latter use a fourth color—yellow—in addition to the standard red, green, and blue; the main benefit is a wider color gamut, and therefore, more true to life colors.
Surely, one of the main developments in backlight technology is the use of light emitting diodes or LEDs as a backlight source in LCD panels. As we will explain further on in this article, LED LCD TVs use one of two main backlight systems—edge-lit or full array with local dimming. However, since 2010, we started seeing a hybrid of these two technologies that aims at enjoying the benefits of both.
LED backlights in LCD panels offer a few significant advantages over conventional CCFL backlight systems, like reduced power consumption and the ability to dim the backlight in synchronization with the average brightness level of the content being displayed on the screen; the latter is partly the reason behind the much touted mega contrast ratio levels by LED TV makers.
LG, Samsung, and Sony were the first LCD TV makers to come up with mass-market attempts at using LED backlit technology for their LCD HDTVs. In particular, both Samsung and Sony did leave their mark when in late 2008, both released the first LED TVs using full LED array backlights with local dimming. These LED LCD TV sets proved capable of superior black levels that are unsurpassed by a CCFL-based LCD sets, to the point that when displaying dark content in a completely darkened room, these sets literally disappear in the background.
As expected, new technology does not come cheap and full array LED backlights in LCD panels has so far proved to be expensive to manufacture. For this reason, some TV makers started moving away from ‘full LED array with local dimming technology and instead focus on the use of a hybrid LED technology; the latter uses zone dimming with edge-lit LED backlighting. In 2010, Samsung referred to this backlight technology as ‘precision’ dimming’ technology; since then, this has changed terminology a number of times, from micro-dimming to precision dimming and so on.
Despite the name, precision dimming—or micro-dimming—is not superior to backlight systems using full LED array with local dimming; but it is definitely better than standard edge-lit LED backlight technology as it introduces the ability to dim selected picture zones for improved black level performance over standard edge-lit LED TVs.
This is possible thanks to:
 An LED edge lighting that is divided into different segments which can be dimmed independent of each other and in line with the average brightness level of the picture content within the respective screen segments they control, and
 The use of a special diffusion layer technology behind the LCD panel that directs light from the respective edge LED sections to selected segments on the screen surface.
Samsung does not divulge how many unique screen segments this new technology can address. But there is no doubt the latest Samsung edge-lit LED backlight with zone dimming technology results in improved picture performance while still retaining the main advantages of edge-lit LED backlights, namely reduced power consumption, slimmer panel profile, and affordability.
The latest micro-dimming seems to have gone a step further in its ability to produce more precise zone control in LCD panels than previous versions; in this respect, this year Samsung UNF8000 is definitely capable of one of the very best TV pictures for the price.
Samsung’s micro-dimming is not the only innovation in LED backlight technology. In 2011, LG came with an improved LED TV technology for its high-end 55-inch 55LW9800 LED TV using full array LED backlight with local dimming. Termed Nano LED technology, this resulted in improved local-dimming LED technology in an ultra slim profile. In fact, LG Nano LED TVs came with a panel thickness that is more associated with edge-lit LED TVs than full array LED backlights with local dimming technology. It also delivered improved picture quality with deeper localized blacks than that possible with an edge-lit LED backlight.
Nano LED used an extremely thin film printed with a proprietary light dispersion pattern combined with a full array of LEDs. This thin film incorporated tiny nano-size holes. It was capable of a TV picture that was brighter and with significantly more uniform image brightness across the entire screen.
LG’s Nano LED technology was a derivative of the integrated optical plate (IOP) LED system introduced by LG in 2010 where LEDs were placed behind a special optical layer to enabled local dimming. The aim was to create a slimmer LCD panel with full array of LEDs using local dimming technology. The result in 2010 was a relatively slim TV but not as slim as edge-lit LED TVs and the latest LG Nano LED TV.
LG’s Nano LED technology advantage was not just the ultra slim LCD panel and improved brightness uniformity; it also supported a larger number of local dimming zones for improve picture quality and reduce blooming. The 2011 LG 55LW9800 utilized 2,304 LEDs supporting 288 independent local dimming zones. In comparison, 2010 IOP 47-inch and 55-inch LED TVs used 864 and 1200 LEDs supporting 216 and 240 independently dimmable zones respectively.
LG 60-inch 60LA7400 3D LED TV
With LG, we no longer have Nano LED technology. Instead, for 2012 and 2013, LG has come up with the term LED Plus with local dimming.
This is the latest derivative of edge-lit LED backlight with zone dimming technology from LG. It is a cheaper alternative to LG’s Nano LED, yet it is still capable of very good picture quality performance.
LED Backlight Technology Explained
Full-array LED with Local Dimming
So far we have referred to LED local dimming without actually explaining why this is the best LED backlight technology ever produced so far for LCD panels. The best way to do so is to refer to the first LED backlights produced by Samsung and Sony in 2008; these were ‘simpler’ in their implementation than the derivatives that followed later.
Local dimming technology provide more precise control thanks to the use of hundreds of LED modules placed behind the screen to replace the standard CCFL backlight used in LCD panels. Individual groups of LEDs are dimmed or switched off depending on the image content.
Local dimming LED backlight technology can achieve superior contrast performance to any other LCD backlight in use today.
LCD panel manufacturers using this technology have so far employed different backlight setups – with the most common being a full array of white LED lamps as used on some Samsung and LG LED HDTVs.
Instead, Sony had originally made use of the Sony Triluminos Technology on its first LED TVs in 2008 whereby the basic LED backlight module consisted of three colors – using two green and one of each red and blue LEDs. According to Sony, this produces a wider color gamut with improved color purity.
Sony did not continue using this three-color LED backlight philosophy as it turned too expensive to development with respect to what the competition was doing. However, five years down the line, Sony’s Triluminous technology has re-surfaced once again on the new 2013 W900 series LED TV. Now, it does not make use of red, green, and blue LEDs but instead Sony’s new Triluminous LED TVs make use of ‘pure blue light’ emitting LEDs placed behind a filter formed from two types of ‘Quantum Dots’ that are tuned to reproduce pure green and pure red light once these are energized with pure blue light. The result is more intense white light for a brighter image while ensuring accurate yet well-saturated colors that are more true to life than with standard backlighting.
The new Sony Triluminous backlight technology is used its W850/W900 series LED TVs and the X850/X900 Ultra HD sets.
Edge-Lit LED TV Backlight Technology:
The majority of LED TVs released during these last years use LED edge-lit LCD panel technology, a less complex derivative of LED lighting technology than local dimming. Simplistically speaking, these inch-thick edge-lit LED TV sets are nothing more than standard LCD TVs with LED (light emitting diodes) as their light source instead of CCFL. This partly explains why edge-lit LED backlights does not really add anything to the TV picture quality but it definitely has its pros at well—in particular with respect to their inch-thick profile and ultra-low power consumption.
Sony’s W900Series LED TV
Edge-lit LED TVs—including Samsung’s latest micro-dimming—can never deliver the same level of picture quality as full array LED local dimming technology. Screen brightness uniformity and side viewing discoloring due to a restricted viewing angle are the main culprits here even though we have to admit that the latest LED TVs have shown significant improvements in these picture quality areas.
LED backlighting enjoys a number of advantages over LCD panels using cold-cathode fluorescent lamps (CCFL), with the most significant being:
– Improved picture performance that is similar to CRTs and plasma TVs when it comes to displaying deep blacks thanks to their impressive dynamic contrast ratings.
– Reduced power consumption
– Longer life that is typical twice that of CCFL based models;
– Generally improved color rendering that is more true to life thanks to the finer control possible over the light frequencies generated by the LED backlight
Nothing is perfect! Most LED TVs suffer from a more noticeable deterioration in picture quality from off-angle than standard CCFL-based LCD TVs; move slightly away from the best seat and colors start to appear washed-out.
In addition, with LCD panels using full array local dimming LED backlights, other picture artifacts come into play. The way full array local dimming LED backlight LCD panel technology is implemented means that the 1000 or so individual LEDs used in these backlight systems are far from enough to correspond to the individual pixels forming the image.
This means that local dimming LED light technology—no matter how selective it is—can never correspond to the exact requirements of the individual pixels forming the image. In other words, local dimming, while responsible for the extreme black levels of some of the top LED LCD TVs, it also produces a sort of a subtle halo effect instead of pure blackness in dark areas adjacent to bright parts of an image.
This is due to light spilling over from light to adjacent dark areas in the image. This halo effect worsens with off-angle viewing; this picture artifact is referred to this as ‘blooming’ as a result of the way dark pixels at the edges of a dark object adjacent to bright objects appear brightened as well.