Sharp Corp. has developed a LED device for backlight in LCD panels and expanded color gamut by 25% without lowering the screen’s brightness, according to a Tech-On article. Using the LED device, the LCD panels can now reach 90% color gamut on NTSC (CIE1931) standards without making any changes to liquid crystal cells.

Top Photo: A comparison between colors displayed by Sharp's new LED device (right) compared with the old (left). Bottom Photo: Colors displayed by Sharp's new LED device (top) compared to old LED device (bottom). (Photo Courtesy of Tech-On article)

The company has developed four LED device models, two for small and mid-sized LD panels (0.4 and 0.6 mm in thickness) and two for large-size panels (edge-and direct-type backlights). The samples cost 40 Japanese Yen (US$ 0.39 including tax). Sharp has plans of releasing samples on Christmas Eve (Dec. 24, 2013) and start mass production in April 2014. 

The company’s new LED device combines blue LED chip with red and green phosphors made from new materials to reach 90% color gamut on NTSC (CIE1931) standards and high brightness. For 0.4mm-thick model for small-mid sized LCD panels, it is possible to ensure screen brightness is only 3 percent less than LCD panels using yellow phosphors. The wider gamut enables video displayed to appear stereoscopic. 

Color Gamut with the new technology. (Photo Courtesy of Tech-On)

Sharp commented that the wider color gamut LCD panels was possible because the company developed red and green phosphors with new materials that now have high wavelength conversion efficiencies. The red phosphor was developed by a phosphor maker, while the green phosphor was developed through a partnership between Sharp and a phosphor maker. 

In addition, the new device increases peak intensity of the spectrum of red light and decreases peak width, resulting in a spectral distribution where the red and green light peaks have few overlaps. As a result, color gamut was expanded from 83% to 90% on NTSC (CIE1931) standards.

Previously, Sharp had been mainly using blue LED chips and yellow phosphors in its LED device for LCD panels backlights. The company’s panels using this backlight method reached 72% color gamut on NTSC (CIE1931) standards. For some of the wide color gamut LCD panels, the company used a LED device that combined blue LED chips and red and green phosphors to meet 83% color gamut on NTSC (CIE1931) standards. However, screen brightness was down 20% compared to using LCD panels with yellow phosphors.