Japanese manufacturers survey consumers, most of them think that 50mm thick LCD TVs are not attractive, while 30mm products can be favored by consumers. In order to produce attractive products, side-light white LEDs will turn from NB to LCD. TV.
It is generally believed that side-lit LEDs are mostly used in displays of portable devices or backlights for notebook computers (NB). Currently, TFT LCD related companies are designing towards ultra-thin LCD TV/panels, while side-lit white LED backlights are on the side. Optical cold cathode fluorescent lamps (CCFL) and RGB LEDs, as well as direct-lit CCFLs and LEDs have this advantage, so related applications are gaining attention.
The thinnest part of the edge-lit white LED backlight module design
Hitachi will be the world's first manufacturer of ultra-thin LCD TVs. It will begin selling 32-inch LCD TVs with a thickness of only 35mm in December 2007. The model uses CCFL backlights and sells for 230,000. Japanese yen (about $2,116).
Hitachi has recently conducted a survey on 60 LCD TVs with a thickness of 50mm and 30mm for respondents. Only 1.6% of respondents believe that LCD TVs with 50mm thickness are attractive, up to 55.6. % of respondents indicated that the 30mm LCD TV is attractive, showing that ultra-thin LCD TV is one of the design trends of the future TV.
Due to its low cost and high reliability, CCFL is the preferred and marketed backlight in ultra-thin LCD TVs. However, in terms of “thicknessâ€, LED backlights are more “slim†than CCFLs. Advantage.
Among the ultra-thin TV LCD panels released by various manufacturers in recent days, the 40-inch LCD panel exhibited by Samsung Electronics in late October is the thinnest, and it uses a side-light white LED backlight, which is expected to begin in mid-2008. Mass production, Samsung Electronics launch time is more than half a year later than Hitachi, but its thickness is comparable to OLED TV (Sony 27å‹ OLED TV thickness is 9mm).
Although Sony's recently launched OLED TVs are only 11 inches in size, the future OLED size will grow to 40 degrees. Take Samsung SDI as an example for the future OLED size planning blueprint. It will mass produce 42-inch OLED panels in 2010. Therefore, if the LCD camp can be closer to OLED TV in ultra-thin TV thickness, priority should be given to side lighting. The LED backlight is introduced into the LCD panel for TV.
Sidelight white LED saves power and saves space
If the LCD TV is to be thin, there are two main deciding factors, namely the backlight module and the power substrate thickness. However, the entire area of ​​the backlight module is similar to that of the LCD panel, and the power substrate only occupies the LCD TV area, in other words. The thickness of the thinnest part of the LCD TV has a great relationship with the backlight module.
The side-lit LED is applied to the LCD backlight module for TV, and its thickness is thinner than the CCFL type direct-type and side-light type, and the LED direct type. The backlight is used for the LCD panel of Samsung Electronics 40å‹ and thickness 10mm TV. The module thickness is only about 5mm.
Why is the thickness of the backlight module designed to be straight down? The reason is that if the light source (whether CCFL or LED) is too close to the upper optical film, it is easy to produce Mura (light unevenness), so between the backlight and the optical film. It is necessary to maintain a certain distance; if the RGB LED is a direct-lit backlight, a longer mixing space is required.
In the edge-lit CCFL type backlight module, since the diameter of the CCFL lamp tube is higher than that of the LED package, the thickness of the LCD panel of the side-lit LED backlight can be made thinner than the CCFL side light type.
Although the thickness of the backlight module of the side-light RGB LED and the white LED type can be made very thin, the ultra-thin LCD TV is also designed to be low in power consumption. Among them, the white LED light source can meet the requirements of lower power consumption. The reason is that white LEDs have better luminous efficiency than RGB LEDs. Therefore, in LCD panels of the same size, such as 40-inch TV, the latter uses about 1 times more power and power consumption than the former.
Side-light white LED backlight application in LCD TV shortcomings
Although the above mentioned side-light white LEDs are used in the advantages of LCD TV backlights, there are some problems that cannot be ignored in the design. For example, it is impossible to make regional control, the number of used and the power consumption is higher than that of direct-lit white LEDs. Problems such as light board development.
One of the biggest advantages of direct-lit LED backlights (whether RGB or white LEDs) is that because the LED is a point source, it can be used for area control. This feature allows the brightness of the LCD TV screen to be adjusted to be bright and dark, and the dynamic contrast value is greatly increased to several. 100,000 to 1 or more, power consumption can be lower than CCFL backlight, and dynamic image quality is better. The above is a function that CCFL backlights are difficult to achieve.
However, since the side-light LED is composed of a point source to form a line source, rather than being distributed by the point source to the entire area of ​​the LCD LCD panel, the area control function cannot be performed, and thus the dynamic contrast value and the dynamic image quality improvement are not helpful; Furthermore, the edge-lit LEDs are used to evenly distribute the light energy to the LCD panel for the entire TV. Therefore, the optical density and the luminous flux are required to be high. Therefore, in the same size, the side-light white LEDs are slightly smaller than the direct-lit white LEDs. In addition, because the edge-lit LED light source is in the fully bright state, the power consumption is higher than the area-controlled direct-lit LED backlight.
The ultra-thin light guide plate is still used in LED backlight NB. The cost is still high. It is a challenge to make a large area of ​​40 å‹ or more. It is not only to prevent the large-area chipping problem of the ultra-thin light guide plate, but how to distribute the side light source evenly. To the other end, the microstructure design of the light guide plate is also tested.
Because each backlight has different advantages in the LCD backlight for TV, and has a mutual replacement relationship in different requirements or designs, such as requiring better color rendering, the RGB LED backlight is used, but the cost and power consumption are the highest; Considering the cost factor, CCFL is the best choice in recent years; similarly, if only the thinness problem is considered, the edge-light white LED is the best design for the ultra-thin LCD TV, but it needs to be in the direct-lit LED backlight area. The characteristics of control. In order to provide consumers with a variety of choices for LCD TVs, although none of the backlights can satisfy all designs, at least the side-lit white LEDs have been used in display applications of portable products in the past, and have gradually emerged in LCD TV backlights.
Edit; Nizi
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