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White point compensated leds for LCD displays

A liquid crystal display and light-emitting diode technology, applied in the field of backlight, can solve problems such as waste

Active Publication Date: 2014-06-04
LUMILEDS HLDG BV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This is wasteful for those LED dies that do not match the target dominant wavelength

Method used

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  • White point compensated leds for LCD displays
  • White point compensated leds for LCD displays
  • White point compensated leds for LCD displays

Examples

Experimental program
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Embodiment Construction

[0043] The present invention can use conventional blue LED dies, such as AlInGaN blue LEDs manufactured by the assignee of the present invention. Flip-chip LED dies are used here in the examples for simplicity. The blue LED die can be the same as shown in Figure 2 with the growth substrate removed.

[0044] Examples of forming LEDs are described in US Patents 6,649,440 and 6,274,399, both assigned to Philips Lumileds Lighting and incorporated herein by reference.

[0045] Blue LEDs used in backlights for LCDs are intended to have a dominant wavelength of approximately 440 nm. However, due to the inherent nature of the LED fabrication process, the dominant wavelength is typically in the range of about 420-460 nm. Blue LED dies were energized and tested by a measurement setup to determine the dominant wavelength of each LED. The dies are then binned, either physically, or by storing the location of the LED dies on the wafer in memory after testing. Each bin may contain only ...

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PUM

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Abstract

A backlight for a color LCD includes white light LEDs formed using a blue LED die with a layer of red and green phosphors over it. The attenuation by the LCD layers of the blue light component of the white light is typically greater as the blue wavelength becomes shorter. In order to achieve a uniform blue color component across the surface of an LCD screen and achieve uniform light output from one LCD to another, the blue light leakage of the phosphor layer is tailored to the dominant or peak wavelength of the blue LED die. Therefore, the white points of the various white light LEDs in a backlight should not match when blue LED dies having different dominant or peak wavelengths are used in the backlight. The different leakage amounts through the tailored phosphor layers offset the attenuation vs. wavelength of the LCD layers.

Description

technical field [0001] The present invention relates to backlights for liquid crystal displays (LCDs), and in particular to LCD backlights using white light light emitting diodes (LEDs). Background technique [0002] Figure 1 illustrates one type of prior art color transmissive LCD. [0003] In FIG. 1, an LCD 10 includes an LED white light source 12 to provide backlighting for the upper LCD layers. The LED white light source 12 has certain advantages over using conventional fluorescent light bulbs, such as size, reliability, and avoiding the use of high voltage power supplies. [0004] For displays that are not very small, typically multiple white light LEDs are used in the backlight to more evenly distribute the light to the bottom of the LCD layer and supply the required brightness level. For small and medium LCD backlights, white light LEDs can be optically coupled to one or more edges of a transparent light guide that leaks light evenly out of its top surface. The lig...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G02F1/13357
CPCG02F1/133609G02F2001/133614G02F1/133603G02F1/133614
Inventor M·J·H·克塞尔斯W·S·斯米特G·米勒S·比尔休曾
Owner LUMILEDS HLDG BV