Blue backlight and phosphor layer for a color LCD

• US 20020145685A1
• Filed: 04/04/2001
• Published: 10/10/2002
• Est. Priority Date: 04/04/2001
• Status: Active Grant

• Current Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Original Assignee: Lumileds Lighting US LLC (Apollo Global Management, Inc.)
• Inventors: Mueller-Mach, Regina, Mueller, Gerd O.
• Granted Patent: US 6,844,903 B2
• Time in Patent Office: Days
• US Class Current: 349/61
• CPC Class Codes: G02F 1/133617 Illumination with ultraviolet light; Luminescent elements or materials associated to the cell
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence

Abstract

A color, transmissive LCD uses a backlight that supplies a uniform blue light to the back of the liquid crystal layer in an LCD. The blue light, after being modulated by the liquid crystal layer, is then incident on the back surface of phosphor material located above the liquid crystal layer. A first phosphor material, when irradiated with the blue light, generates red light for the red pixel areas of the display, and a second phosphor material, when irradiated with the blue light, generates green light for the green pixel areas of the display. No phosphor is deposited over the blue pixel areas.

Claims

1. A color liquid display comprising:

a backlight for outputting blue light;

a plurality of layers including a liquid crystal layer being intersected by said blue light, said liquid crystal layer for modulating said blue light;

a first phosphor material being irradiated by said blue light modulated by said liquid crystal layer, said first phosphor material, when irradiated by said blue light, generating red light, said first phosphor material being located in first areas overlying said plurality of layers constituting red pixels of said display;

a second phosphor material being irradiated by said blue light modulated by said liquid crystal layer, said second phosphor material, when irradiated by said blue light, generating green light, said second phosphor material being located in second areas overlying said plurality of layers constituting green pixels of said display; and

third areas overlying said plurality of layers, constituting blue pixels, having no phosphor material to allow modulated blue light to pass.

2. The device of claim 1 further comprising at least one blue light emitting diode (LED) being optically coupled to said backlight.

3. The device of claim 1 wherein said plurality of layers comprises a polarizing filter overlying said liquid crystal layer, said first phosphor material and said second phosphor material overlying said polarizing layer.

4. The device of claim 1 wherein said plurality of layers comprises a thin film transistor array layer.

5. The device of claim 1 further comprising a diffusing material in said third areas.

6. The device of claim 1 wherein said backlight comprises a light guide having surface deformities to reflect light out of said light guide through a surface of said light guide.

7. The device of claim 1 wherein said backlight comprises a light guide having a first surface for emanating light and a side surface optically coupled to a blue light source.

8. The device of claim 1 wherein said blue light source is a blue LED.

9. The device of claim 1 wherein said first phosphor comprises SrS:

Eu²⁺.

10. The device of claim 1 wherein said second phosphor comprises SrGa₂S₄:

Eu²⁺.

11. The device of claim 1 wherein said first phosphor material and said second phosphor material are arranged in strips to constitute said red pixels and said green pixels, respectively.

13. The method of claim 12 further comprising polarizing light, using a polarizing filter, modulated by said liquid crystal layer, said first phosphor material and said second phosphor material overlying said polarizing layer.

14. The method of claim 12 further comprising diffusing blue light in said third areas.

15. The method of claim 12 wherein said irradiating said first phosphor material and irradiating said second phosphor material comprise irradiating strips of said first phosphor material and said second phosphor material constituting said red pixels and said green pixels, respectively.

12. A method for displaying color images comprising:

energizing at least one blue light emitting diode (LED) to output blue light from a backlight;

modulating said blue light by selectively controlling a liquid crystal layer intersected by said blue light;

irradiating a first phosphor material by said blue light modulated by said liquid crystal layer, said first phosphor material, when irradiated by said blue light, generating red light, said first phosphor material being located in first areas overlying said liquid crystal layer constituting red pixels of said display;

irradiating a second phosphor material by said blue light modulated by said liquid crystal layer, said second phosphor material, when irradiated by said blue light, generating green light, said second phosphor material being located in second areas overlying said liquid crystal layer constituting green pixels of said display; and

allowing said blue light modulated by said liquid crystal layer to pass through third areas, constituting blue pixels, overlying said liquid crystal layer, said third areas having no phosphor material.