Display device capable of controlling viewing angle and driving method thereof

1. A viewing angle controllable display device comprising:

an image mixing unit generating a mixed image data signal by mixing an original image data signal, or a gray-adjusted original image data signal, with a protection image data signal that disturbs recognition of the original image;

an output image selecting unit receiving both the original image data signal and the mixed image data signal and optionally selecting one of the original image data signal and the mixed image data signal for output to a display panel; and

a display panel responding to gate signals sequentially transmitted from a gate driver, and receiving a data voltage corresponding to the original image data signal or the mixed image data signal selected from the output image selecting unit through a data driver, and displaying an original image or a mixed image,

the protection image data signal having a gray value modulated within a gray range adjusted based on panel gray data that resides within a memory and used by the display device to indicate an acceptable range of gray values to process.

2. The display device of claim 1 , wherein a viewing angle of the mixed image is narrower than that of the original image.

3. The display device of claim 1 , wherein the display panel displaying the mixed image has a limit of readability in a side-viewed image.

4. The display device of claim 1 , wherein the mixed image data signal is generated by mixing the original image data signal, or the gray-adjusted original image data signal, with the protection image data signal for each pixel unit or each sub-pixel unit.

5. The display device of claim 1 , wherein the image mixing unit comprises:

a gray adjusting unit adjusting a gray value of the original image data signal or the protection image data signal, within a gray-adjusted gray range based on panel gray data; and

an image combining unit generating the mixed image data signal by mixing the gray-adjusted protection image data signal having a gray value adjusted by the gray adjusting unit with the original image data signal, or with the gray-adjusted original image data signal having a gray value adjusted by the gray adjusting unit.

6. The display device of claim 5 , wherein the image combining unit generates the mixed image data signal by combining the protection image data signal with the original image data signal, or with the gray-adjusted original image data signal for each pixel unit or each sub-pixel unit.

7. The display device of claim 5 , wherein the image mixing unit further comprises a storage unit storing data of an original image data signal, data of the gray-adjusted original image data signal, data of the protection image data signal, and data of the gray-adjusted protection image data signal.

8. The display device of claim 1 , wherein the display panel is a liquid crystal display panel or a flat display panel.

9. The display device of claim 1 , further comprising a controller generating and transmitting an image selection control signal that controls selection of an image data signal to be displayed on the display panel to the output image selecting unit.

10. A driving method of a viewing angle controllable display device, comprising:

storing panel gray data for gray-adjusting to a memory unit;

generating a mixed image data signal by mixing an original image data signal, or a gray-adjusted original image data signal modulated based on the panel gray data, with a protection image data signal that disturbs recognition of the original image;

applying both the original image data signal and the mixed image data signal to a selecting unit and selecting an output image data signal corresponding to an image output on the display panel among the original image data signal and the mixed image data signal; and

displaying an image according to the selected output image data signal on the display panel,

the protection image data signal having a gray value modulated within a gray range modulated based on the panel gray data stored in the memory unit and used by the display device to indicate an acceptable range of gray values to process.

11. The driving method of claim 10 , wherein, when the mixed image data signal is selected as the output image data signal, a viewing angle of a mixed image displayed according to the mixed image data signal is limited.

12. The driving method of claim 11 , wherein the mixed image displayed according to the mixed image data signal has a limit of readability in a side-viewed image.

13. The driving method of claim 11 , wherein a viewing angle of the mixed image displayed according to the mixed image data signal is narrower than that of an original image.

14. The driving method of claim 10 , wherein the mixed image data signal is generated by combining the original image data signal or the gray-adjusted original image data signal, with the protection image data signal for each pixel unit or each sub-pixel unit.

15. The driving method of claim 10 , further comprising, before the generating the mixed image data signal, adjusting a gray value of the original image data signal or the protection image data signal within a gray range adjusted based on the panel gray data.