Following the gray-scale response time and dynamic contrast, the focus of liquid crystal display technology will shift to the color gamut in 2008, which is the consensus of all industry insiders. However, the wide color gamut products that can be purchased on the market are still very few, and the price is relatively high. The average consumer does not know much about the color gamut.
The so-called color gamut, which determines the color richness of a display. As we all know, CRT monitors and LCD monitors are based on three primary color images. The colors displayed by the monitors are all part of the three primary colors, but there is no way to express all the colors of visible light, and the color gamut value represents the display can display Color range. The larger the color gamut, the richer the color of a color that can be displayed on the display screen, and the more vivid the color.
For liquid crystal displays, major manufacturers are working to increase the color gamut of liquid crystal displays. At present, the color gamut value of mainstream liquid crystal displays is about 70% of NTSC, while the wide color gamut liquid crystal display needs to reach NTSC more than 90%. Since the liquid crystal itself does not emit light, but the image is displayed by the light passing through the backlight, the color gamut range is mainly affected by the backlight, and the commercially available wide color gamut liquid crystal display mainly improves the fluorescent substance of the conventional CCLF. The composition (or a layer of coating) is used to achieve a higher color gamut range, making the light emitted more "white" and more stable in order to enhance the NTSC color gamut. Because the implementation of this method is not difficult, the cost will not increase too much, so it has won the support of many manufacturers. However, it must be noted that this method is not the best choice after all. With the help of this technology, the color gamut of the liquid crystal display is hard to exceed 100% of NTSC. So is there any way to solve this problem fundamentally? At present, LED is the only answer!
The best answer to the wide color gamut: LED light-emitting diodes
The current industry consensus is that the use of LED backlighting is the best way to improve the color gamut of liquid crystal displays. The so-called LED (Light Emitting Diode), which is a semiconductor solid-state light-emitting device, uses a solid semiconductor chip as a light-emitting material. When a forward voltage is applied to both ends, carriers in the semiconductor recombine to cause photon emission. Produce light. The LED can directly emit red, yellow, blue, green, cyan, orange, purple, and white light. This kind of LED backlight technology has been used in laptop screens and LCD TVs, but there is not much practice on desktop LCD monitors.
As mentioned above, the liquid crystal of the liquid crystal display itself does not emit light, but the image is displayed by the light passing through the backlight. Therefore, the backlight template of the LCD has a decisive effect on the color gamut. At present, the mainstream CCFL (cold cathode backlight) is limited by the range of illumination, and the liquid crystal display cannot reach a wide color gamut display range. Therefore, the current color range of the mainstream liquid crystal display is only about 70% of NTSC, even if an improved design is adopted. It has a larger gamut range, but the effect is not very good, and it may also have the consequence of reducing lamp life.
In view of the shortcomings of CCFL (Cold Cathode Backlight), LED light-emitting diodes have been highly anticipated. Compared with CCLF cold cathode fluorescent lamps, LED light-emitting diodes have the advantages of wide color gamut, white point adjustment, high dimming rate and long life. At present, there are mainly feedback LED backlights and combined LED backlights.
In terms of the color that everyone pays most attention to, LED backlights can be reflected by mirrors after a lightguide is dispersed to achieve a uniform brightness. In addition, the software that is carried randomly can control the backlight of the color, that is, You don't need to compensate for the shortcomings of the lamp to achieve a truly complete white light source. In addition, with the help of built-in sensors and circuit tools, users can also adjust the backlight in SpectraView according to their needs, which means that the color is more abundant and can provide the color range that ordinary LCD can not display. At present, the color gamut of LCDs using LED backlights can reach more than 110%.
LED light-emitting diodes three advantages
In addition to solving the wide color gamut problem, LED light-emitting diodes have more advantages than CCFL cold cathode backlights. The first point is environmental protection. In LCDs with CCLF cold cathode fluorescent lamps as backlights, one of the main elements that cannot be lacking is mercury, which is known as mercury, and this element is undoubtedly harmful to humans. Although the manufacturers have tried their best to reduce the mercury content in the fluorescent tubes, the completely mercury-free fluorescent tubes will bring about some new technical problems, and the prospects for realization will not be seen for the time being. The advantage of LED backlights is that they are completely free of mercury and conform to the green and fashionable fashion.
In addition to environmental protection, LED backlights are also very energy efficient, and their power consumption is lower than CCFL cold cathode backlights. LED internal driving voltage is much lower than CCFL, power consumption and safety are better than CCFL (CCFL AC voltage requirements are relatively high, starting at 1,500 ~ 1,600Vac, and then stabilized to 700 or 800Vac), and LED only needs 12 ~ It can work at 24Vdc or lower. In addition, although the luminous efficiency of the CCFL is not inferior to that of the LED, since the CCFL is scattered light, a large amount of light is wasted in the illuminating process, so that the efficiency of the LED light is higher.
In addition, LED backlights have a longer life than CCFLs. In general, the rated life of a different CCFL (semi-bright) is between 8,000 and 100,000 hours, while the LED backlight can reach about twice the CCFL. Of course, the lifetime of LED backlights is also affected by thermal management.
Status of LED backlight LCD
As the best choice to replace CCFL cold cathode fluorescent tubes, LED light-emitting diodes are currently not used in desktop liquid crystal displays. It can be said that it is in its infancy, but from the current product strategies of major manufacturers, in 2008 In the second half of the year, LED backlight LCDs will emerge in large numbers.
In terms of panels, in early 2007, Samsung Electronics announced that it will begin production of 24-inch LCD panels using LED light sources. It is said to be comparable to the high-quality TV picture quality, and the color gamut can reach 111% of the National Television System Committee (NTSC) standard, which is called the true wide color gamut. In addition to the large-screen LCD, Chi Mei also launched 19, 22-inch RGB LED backlight panels in early 2007 and shipped them to Acer and ViewSonic. Then, AUO also released a liquid crystal panel with LED backlight, which is 20.1 inches. It is believed that BenQ, which is closely related to AUO, will get the first LED panel.
In terms of products, as the promoter of wide color gamut liquid crystal display, Samsung officially released its first LCD with LED backlight in early 2007, the model is Samsung SyncMasterXL20, its color gamut range reached 114%, at the time The Hong Kong listing price is HK$15,990. Of course, this product is aimed at professional users. In addition to the Samsung SyncMasterXL20, the 19-inch Acer AL1917L (117% color gamut) was also the product of the beginning of 2007. The most noteworthy concern in the near future is that ViewSonic has launched the first 118% LED-backlit LCD monitor VLED221wm with a 118% wide color gamut. The VLED221wm is aimed at users with high color requirements, such as artists, multimedia editors and players. The product is expected to be available in February and is priced at $788. In addition, the global LCD factory AOC also said that it will release LED backlight products in the second quarter of this year.
It can be seen that major manufacturers have begun to take action on the research and development of LED backlight LCD. According to industry insiders, in the second half of 2008, LED backlight LCD will start to emerge in large numbers and become the main choice of the market.
Although LED backlight LCDs have a larger color gamut range, we must also note that consumer acceptance of wide color gamut LCDs needs to be further enhanced. From the current situation, some users are reflected in the comparison of the wide color gamut liquid crystal display and the ordinary liquid crystal display, although the color of the wide color gamut liquid crystal display is more colorful, but the feeling is rich and colorful. In addition, the price issue is also a major factor limiting the acceptance of the wide color gamut LCD. Of course, it is undeniable that as a new generation of liquid crystal display focus technology, the emergence of LED backlight will undoubtedly give us more choices and lead us into a new horizon.
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