LEDs for Automotive LCD Backlighting

• Example of spectral distribution of normal white Blue light + yellow phosphor

  

  | Normal White LEDs |

  Normal white LEDs achieve white light by mixing blue LED light with yellow phosphor. They feature low power consumption due to their extremely high efficiency in converting power into light, and are relatively inexpensive due to the small number of constituent materials used.On the other hand, the red light component is small, so the coloring performance of the red area when transmitted through an LCD is not high.

• Example of spectral distribution of wide gamut white Blue light + green phosphor + red phosphor

  

  | Wide Color Gamut White LED |

  White light is achieved by mixing blue LED light with green and red phosphors.The LED light component matches the LCD color filter, resulting in particularly vivid coloring around the red area, expanding the color gamut and improving the quality. On the other hand, the power consumption tends to increase due to the lower power-to-light conversion efficiency compared to normal white LEDs.

• | Normal white light |

  Normal white light with blue light + yellow phosphor has a low red component light, so red and reddish dislpay on the screen may appear dull.

• | Wide gamut white light |

  Wide gamut white light with blue light + green phosphor + red phosphor makes screen colors look more vivid than normal white light because of its high red component.

• Edge-lit/Light-guide

  

  LED light is emitted from the side to the light guide plate placed under the LCD,　and the light is extracted from the plate upward (toward the user).

  Features

  • The entire backlight emits light from the surface.
  • Relatively small number of LEDs to be used = low power consumption
  • Less uneven brightness and uniform appearance　(The backlight also emits light even in areas where there is no display.)

• Direct-lit

  

  A method in which LEDs are placed directly under the LCD display and light is directed toward the user.

  Features

  • Aggregation of area emission of each LED
  • The number of LEDs increases depending on the display size and the illumination area of each LED.
  • The brightness of the entire display can be increased according to the number of LEDs.

  Local dimming technology

  • By controlling light emission finely for each area, it is possible to light only necessary areas efficiently.
  • High-contrast and high-definition display is possible by de-illuminating areas where there is no display.

Actual display image

• 

  Edge-lit/Light-guide

  Slight light escapes from the unlettered black background, because the light guide plate behind the LCD uniformly illuminate.

• 

  Direct-lit

  The direct local dimming method allows high-contrast, clear viewing without light in areas other than the text.

Areas without lettering display a clear black color because the backlight does not emit any light.