A novel edge-light backlight unit using an optically patterned film (OPF backlight unit) for liquid crystal displays (LCDs) is composed of a light guide plate bonded to the top of fine lenses formed on the OPF, a diffusive sheet, a reflective sheet and a light source. A viewing-angle-dependent luminance distribution of the OPF backlight unit was controllable by changing the shape of a fine lens used for the extraction of light propagating through a light guide plate and the direction control of radiating light, and a luminance distribution in a radiation plane suitable for LCDs was realized by adjusting the interval between lenses. Moreover, the extraction efficiency of the OPF backlight unit was greater than that of a conventional backlight unit. Thus, the OPF backlight unit was shown to be promising for the realization of a brighter, lower power consumption, slimmer and lighter LCD than conventional LCDs.
We have constructed an edge‐lit backlight by using a blue‐emitting laser diode, an optical fiber and a YAG‐based phosphor. White light output was obtained from the backlight surface. We discuss some design issues and expect a high efficiency and a wide gamut for such a backlight.
In an edge-light backlight unit using an optically patterned film (OPF backlight unit) with plural light-emitting diodes (LEDs) placed on the side as a light source, dark areas are easily generated between LEDs, because the OPF backlight unit mainly uses the total reflection induced by optical patterns formed on the OPF. Such dark areas were eliminated by narrowing the interval between optical patterns between LEDs and widening it near LEDs. By adjusting the interval between optical patterns across the entire area additionally, a luminance distribution in a radiation plane suitable for liquid crystal displays (LCDs) was realized. Moreover, viewing-angle-dependent luminance distribution can be narrowed by adjusting the shape of the lens-shaped optical pattern. Thus, the OPF backlight unit using plural LEDs was shown to be suitable for small-area LCDs.
Color filters have been used for a variety of applications such as liquid crystal displays (LCDs). Conventional color filters produce color by absorbing unnecessary wavelengths, which cause energy loss. Additionally, as an important optical element in the LCDs, polarization filters are required since liquid crystals have polarization dependency. We propose hybrid plasmonic-dielectric subwavelength grating (SWG) filters, which have both functions of wavelength-and polarization-selectivities in one filter. The SWG filter consists of a three-layered one-dimensional SWG, in which a plasmonic layer, a buffer layer, and a dielectric layer are stacked on a substrate. Using rigorous coupled-wave analysis, three kinds of the SWG filters with periods of 300, 380, and 500 nm are designed to produce blue, green, and red colors, respectively. For transverse-magnetic polarized light, each SWG filter shows high transmittance in each color region with good wavelength selectivity, which functions as a color filter. Maximum transmittances of 72.4%, 72.6%, and 73.5% are obtained at wavelengths of 445, 540, and 650 nm for the blue, green, and red filters, respectively. For transverse-electric polarized light, each SWG filter shows high reflectance in the whole visible region, which functions as a broadband band-stop filter.
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