Backlight module of liquid crystal display

• US 20070171186A1
• Filed: 01/26/2006
• Published: 07/26/2007
• Est. Priority Date: 01/26/2006
• Status: Active Grant

• Current Assignee: HannStar Display Corporation
• Original Assignee: HannStar Display Corporation
• Inventors: Lee, Cheng-Chung, Sun, Ching-Cherng, Chang, Chih-Li, Kao, Hung-Chen, Huang, Chi-Jen
• Granted Patent: US 7,486,354 B2
• Time in Patent Office: Days
• US Class Current: 345/107
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/133621 providing coloured light G02F1/133617, G02F1/133533 take precedence

Abstract

A cut filter is used in a backlight module or a display device and positioned over the light source to filter off a part of the light comprising an overlap of at least two of the red light, the green light, and the blue light. By filtering off the overlapping part of light emitted from the light source to obtain a purer primary color light, the display device equipped with a conventional color filter can attain an improved color gamut.

Claims

1. A backlight module of a liquid crystal display, comprising:

a housing;

a light source positioned in the housing for emitting a light comprising a red light, a green light and a blue light; and

a cut filter positioned over the light source to filter off a part of the light comprising an overlap of at least two of the red light, the green light, and the blue light.

2. The backlight module of a liquid crystal display of claim 1, wherein the overlap has a range of wavelengths between the wavelength at the half maximum intensity of the blue light and the wavelength at the half maximum intensity of the green light, both being adjacent to each other, or between the wavelength at the half maximum intensity of the green light and the wavelength at the half maximum intensity of the red light, both being adjacent to each other.

3. The backlight module of a liquid crystal display of claim 1, further comprising an optical film set.

4. The backlight module of a liquid crystal display of claim 3, wherein the cut filter is positioned between the light source and the optical film set.

5. The backlight module of a liquid crystal display of claim 3, wherein the cut filter is positioned over the optical film set.

6. The backlight module of a liquid crystal display of claim 3, wherein the optical film set comprises at least one selected from the group consisting of a diffusion plate, a prism sheet, and a light guide plate.

7. The backlight module of a liquid crystal display of claim 3, wherein the cut filter is coated on the optical film set.

8. The backlight module of a liquid crystal display of claim 1, wherein the cut filter comprises at least one metal oxide film deposited on a substrate.

9. The backlight module of a liquid crystal display of claim 8, wherein the metal oxide film has a thickness and a refraction index corresponding to the wavelength of the light to be filtered off.

10. The backlight module of a liquid crystal display of claim 1, wherein the light source comprises a cold cathode fluorescent lamp, a light emitting diode, an external electrode lamp, a field emission devices, or a flat lamp plate.

11. A display device, comprising:

a backlight module, comprising;

a housing; and

a light source positioned in the housing for emitting a light comprising a red light, a green light and a blue light;

a display panel positioned over the backlight module, comprising a TFT array substrate and a color filter substrate; and

a cut filter positioned over the backlight module to filter off a part of the light comprising an overlap of at least two of the red light, the green light, and the blue light.

12. The display device of claim 11, wherein the overlap has a range of wavelengths between the wavelength at the half maximum intensity of the blue light and the wavelength at the half maximum intensity of the green light, both being adjacent to each other, or between the wavelength at the half maximum intensity of the green light and the wavelength at the half maximum intensity of the red light, both being adjacent to each other.

13. The display device of claim 11, wherein the cut filter is positioned between the backlight module and the display panel.

14. The display device of claim 11, wherein the cut filter is positioned on the display panel.

15. The display device of claim 11, wherein the cut filter is coated on the display panel.

16. The display device of claim 11, wherein the cut filter is coated on the color filter substrate.

17. The display device of claim 11, wherein the cut filter is coated on the TFT array substrate.

18. The display device of claim 11, further comprising a polarizer positioned on the display panel, and the cut filter is coated on the polarizer.

19. The display device of claim 11, further comprising an optical film set positioned on the backlight module.

20. The display device of claim 19, wherein the optical film set comprises at least one selected from the group consisting of a diffusion plate, a prism sheet, and a light guide plate.

21. The display device of claim 19, wherein the cut filter is coated on the optical film set.

22. The display device of claim 11, wherein the cut filter comprises at least one metal oxide film deposited on a substrate.

23. The display device of claim 22, wherein the metal oxide film has a thickness and a refraction index corresponding to the wavelength of the light to be filtered off.

24. The display device of claim 11, wherein the light source comprises a cold cathode fluorescent lamp, a light emitting diode, an external electrode lamp, a field emission devices, or a flat lamp plate.

25. A method of improving color gamut of a display device comprising a light source to emit a light, a TFT array substrate and a color filter substrate to form a display panel, comprising:

obtaining a spectrum for the light emitted from the light source by a spectrometer, wherein the spectrum for the light has a first range of wavelengths for a red light, a second range of wavelengths for a green light, and a third range of wavelengths for a blue light;

determining at least a fourth range of wavelengths for the spectrum comprising an overlap of at least two of the first range of wavelengths for the red light, the second range of wavelengths for the green light, and the third range of wavelengths for the blue light; and

providing at least one cut filter to filter off the fourth range of wavelengths of the light, such that the color gamut of the display device is improved.

26. The method of claim 25, wherein the spectrum of the light is obtained after the light emitted from the light source further passes the display panel.

27. The method of claim 25, wherein the spectrum of the light is obtained by adding a first spectrum of the light emitted from the light source to a second spectrum of the display panel.

28. The method of claim 25, wherein the overlap has a range of wavelengths between the wavelength at the half maximum intensity of the blue light and the wavelength at the half maximum intensity of the green light, both being adjacent to each other, or between the wavelength at the half maximum intensity of the green light and the wavelength at the half maximum intensity of the red light, both being adjacent to each other.

29. The method of claim 25, wherein the cut filter comprises at least one metal oxide film having a thickness and a refraction index corresponding to the wavelength of the light to be filtered off.