Light emitting diode substrate, method of manufacturing the same, and liquid crystal display device using the same

Abstract

A luminance control circuit for controlling the luminance levels of different colored light sources that lends itself to easy incorporation into display devices is presented. A light emitting diode (LED) substrate includes a plurality of driving thin film transistors (TFTs) including a semiconductor layer deposited on a substrate. A plurality of LEDs for generating lights of different wavelengths is mounted respectively on the plurality of driving TFTs. A plurality of thin film sensors for sensing the luminous intensities of the plurality of LEDs is formed between the plurality of LEDs and the substrate. A luminance control circuit for controlling the driving TFTs has of a plurality of controlling TFTs including a semiconductor layer deposited on the substrate and is connected to the plurality of thin film sensors.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of an LED substrate according to an exemplary embodiment of the present invention;

FIG. 2 is an equivalent circuit diagram of the LED substrate shown in FIG. 1;

FIG. 3 is an exploded perspective view of an LCD device to which an LED substrate is applied according to an exemplary embodiment of the present invention; and

FIG. 4 is an exploded perspective view of an LCD device to which an LED substrate is applied according to another exemplary embodiment of the present invention.

Claims

1. A light emitting diode substrate, comprising: a plurality of driving thin film transistors including a semiconductor layer deposited on a substrate;a plurality of light emitting diodes mounted respectively on the plurality of driving thin film transistors, for generating lights of different wavelengths;a plurality of thin film sensors formed between the plurality of light emitting diodes and the substrate, for sensing the luminous intensities of the plurality of light emitting diodes; anda luminance control circuit having a plurality of controlling thin film transistors including a semiconductor layer deposited on the substrate and being connected to the plurality of thin film sensors to control the driving thin film transistors.

2. The light emitting diode substrate of claim 1, wherein each of the plurality of driving thin film transistors and the controlling thin film transistors of the luminance control circuit includes a semiconductor layer, a gate electrode overlapping the semiconductor layer with an insulating layer disposed therebetween, and source and drain electrodes connected to both ends of the semiconductor layer.

3. The light emitting diode substrate of claim 2, wherein the gate electrode of each of the plurality of driving thin film transistors is connected to the luminance control circuit, the source electrode is connected to one electrode of each of the light emitting diodes, and the drain electrode is connected to a driving voltage supply line for supplying a driving voltage from the exterior.

4. The light emitting diode substrate of claim 3, wherein the semiconductor layer and the plurality of thin film sensors are formed of any one of polysilicon, polysilicon-germanium, amorphous silicon, and amorphous silicon-germanium thin films.

5. The light emitting diode substrate of claim 4, wherein each of the plurality of thin film sensors is located under a through-hole penetrating one electrode of each of the light emitting diodes and is formed as a photodiode type having an anode and a cathode formed by injecting p-type and n-type impurities.

6. The light emitting diode substrate of claim 5, wherein one electrode of the anode and cathode of each of the plurality of thin film sensors is floating and the other electrode is connected through a current limiting resistor to a ground electrode, and wherein the ground electrode is connected to the other electrode of each of the light emitting diodes.

7. The light emitting diode substrate of claim 6, wherein the other electrode of each of the light emitting diodes is connected to the ground electrode through a bonding wire.

8. The light emitting diode substrate of claim 7, further comprising an organic insulating layer covering the substrate on which the plurality of light emitting diodes is mounted.

9. The light emitting diode substrate of claim 8, wherein the semiconductor layer, the gate electrode, the source electrode and the drain electrode of each of the plurality of driving thin film transistors are formed in a polygonal band or circular band shape encompassing peripheral parts of the thin film sensors.

10. The light emitting diode substrate of claim 9, wherein the plurality of light emitting diodes includes first to third light emitting diodes for respectively generating red, green and blue lights, the plurality of driving thin film transistors includes first to third driving thin film transistors for respectively driving the first to third light emitting diodes, and the plurality of thin film sensors includes first to third thin film sensors for respectively sensing the luminous intensities of the first to third light emitting diodes.

11. The light emitting diode substrate of claim 10, wherein the luminance control circuit includes: a first amplifier for controlling the third driving thin film transistor according to a luminance control signal;a first comparator for controlling the second driving thin film transistor by comparing a blue luminous sensing signal from the third thin film sensor with a green luminous sensing signal from the second thin film sensor; anda second comparator for controlling the first driving thin film transistor by comparing the blue luminous sensing signal with a red luminous sensing signal from the first thin film sensor.

12. The light emitting diode substrate according to claim 11, wherein the luminance control circuit further includes second to fourth amplifiers for amplifying the luminous sensing signals from the first to third thin film sensors, and at least one of the second to fourth amplifiers is controlled according to a relative luminance control signal.

13. A method of manufacturing a light emitting diode substrate, comprising: forming a plurality of driving thin film transistors including a semiconductor layer deposited on a substrate;mounting a plurality of light emitting diodes generating lights of different wavelengths on the plurality of driving thin film transistors;forming a plurality of thin film sensors sensing the luminous intensities of the plurality of light emitting diodes between the plurality of light emitting diodes and the substrate; andforming a luminance control circuit that has a plurality of controlling thin film transistors including a semiconductor layer deposited on the substrate and is connected to the plurality of thin film sensors and the plurality of driving thin film transistors.

14. The method of claim 13, wherein each of the plurality of driving thin film transistors and the controlling thin film transistors of the luminance control circuit includes a semiconductor layer, a gate electrode overlapping the semiconductor layer with an insulating layer disposed therebetween, and source and drain electrodes connected to both ends of the semiconductor layer.

15. The method of claim 14, wherein the gate electrode of each of the plurality of driving thin film transistors is connected to the luminance control circuit, the source electrode is connected to one electrode of each of the light emitting diodes, the drain electrode is connected to a driving voltage supply line for supplying a driving voltage from the exterior, and the other electrode of each of the light emitting diodes is connected to a ground electrode through a bonding wire.

16. The method of claim 15, wherein the semiconductor layer and the plurality of thin film sensors are formed of any one of polysilicon, polysilicon-germanium, amorphous silicon, and amorphous silicon-germanium thin films.

17. The method of claim 16, wherein p-type and n-type impurities are injected into both terminals of each of the plurality of thin film sensors to form an anode and a cathode, and wherein one electrode of the anode and cathode of each of the plurality of thin film sensors is floating and the other electrode is connected to the ground electrode through a current limiting resistor.

18. The method of claim 17, further comprising forming an organic insulating layer on the substrate on which the plurality of light emitting diodes is mounted.

19. The method of claim 18, wherein the semiconductor layer, the gate electrode, the source electrode and the drain electrode of each of the plurality of driving thin film transistors are formed in a polygonal band or circular band shape encompassing peripheral parts of the thin film sensors.

20. A liquid crystal display device, comprising: a light source including: a plurality of driving thin film transistors formed on a substrate,a plurality of light emitting diodes mounted respectively on the plurality of driving thin film transistors for generating lights of different wavelengths,a plurality of thin film sensors formed between the plurality of light emitting diodes and the substrate for sensing the luminous intensities of the plurality of light emitting diodes, anda luminance control circuit that has a plurality of controlling thin film transistors formed on the substrate and is connected to the plurality of thin film sensors and the plurality of driving thin film transistors; anda liquid crystal display panel for displaying an image by using light generated from the light source.

21. The liquid crystal display device of claim 20, wherein each of the plurality of driving thin film transistors and the controlling thin film transistors of the luminance control circuit includes a semiconductor layer, a gate electrode overlapping the semiconductor layer with an insulating layer disposed therebetween, and source and drain electrodes connected to both ends of the semiconductor layer, and wherein the gate electrode of each of the plurality of driving thin film transistors is connected to the luminance control circuit, the source electrode is connected to one electrode of each of the light emitting diodes, and the drain electrode is connected to a driving voltage supply line for receiving a driving voltage.

22. The liquid crystal display device of claim 21, wherein the semiconductor layer and the plurality of thin film sensors are formed of any one of polysilicon, polysilicon-germanium, amorphous silicon, and amorphous silicon-germanium thin films, and wherein each of the plurality of thin film sensors is located under a through-hole penetrating one electrode of each of the light emitting diodes and is formed as a photodiode type having an anode and a cathode formed by injection of p-type and n-type impurities.

23. The liquid crystal display device of claim 22, wherein one electrode of the anode and cathode of each of the plurality of thin film sensors is floating and the other electrode is connected through a current limiting resistor to a ground electrode that is connected to the other electrode of each of the light emitting diodes, through a bonding wire.

24. The liquid crystal display device of claim 23, further comprising an organic insulating layer covering the substrate on which the plurality of light emitting diodes is mounted.

25. The liquid crystal display device of claim 24, wherein the plurality of light emitting diodes includes first to third light emitting diodes for respectively generating red, green and blue lights, the plurality of driving thin film transistors includes first to third driving thin film transistors for respectively driving the first to third light emitting diodes, and the plurality of thin film sensors includes first to third thin film sensors for respectively sensing the luminous intensities of the first to third light emitting diodes.

26. The liquid crystal display device of claim 25, wherein the luminance control circuit includes: a first amplifier for controlling the third driving thin film transistor according to a luminance control signal;a first comparator for controlling the second driving thin film transistor by comparing a blue luminous sensing signal from the third thin film sensor with a green luminous sensing signal from the second thin film sensor;a second comparator for controlling the first driving thin film transistor by comparing the blue luminous sensing signal with a red luminous sensing signal from the first thin film sensor; andsecond to fourth amplifiers for amplifying the luminous sensing signals from the first to third thin film sensors,wherein at least one of the second to fourth amplifiers is controlled according to a relative luminance control signal.