Pixel structure for LCD with embedded touch screen

• US 20070176905A1
• Filed: 01/27/2006
• Published: 08/02/2007
• Est. Priority Date: 01/27/2006
• Status: Active Grant

• Current Assignee: HannStar Display Corporation
• Original Assignee: HannStar Display Corporation
• Inventors: Shih, Po-Sheng, Chen, Bo-Yang
• Granted Patent: US 7,573,459 B2
• Time in Patent Office: Days
• US Class Current: 345/173
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/134354 the sub-pixels being capacitively coupled
• CPC Class Codes: G02F 1/1362 Active matrix addressed cells G02F1/134336, G02F1/134363 take precedence
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/042 by opto-electronic means

Abstract

A pixel structure for an liquid crystal display (LCD) with an embedded touch screen is provided. The pixel structure includes a plurality of first pixels and a plurality of second pixels, each formed by intersecting two adjacent gate lines and two adjacent data lines, the first pixel including a pixel transistor having a gate electrode connected to one of the gate lines, a drain electrode connected to one of the data lines, and a source electrode; a pixel electrode connected to the source electrode of the pixel transistor; a liquid crystal capacitor C_LC formed between the pixel electrode and a common electrode; a compensation capacitor C_C formed between the pixel electrode and a compensation electrode; and the second pixel including a pixel transistor having a gate electrode connected to one of the gate lines, a drain electrode connected to one of the data lines, and a source electrode; a pixel electrode connected to the source electrode of the pixel transistor; a liquid crystal capacitor C_LC″ formed between the pixel electrode and a common electrode; a readout capacitor C_read-out between the pixel electrode and a readout line, wherein the pixel electrode is positioned above the readout line, and the pixel electrode and the readout line are overlapped.

Claims

1. A pixel structure for an liquid crystal display (LCD) with an embedded touch screen, comprising:

a plurality of first pixels and a plurality of second pixels, each formed by intersecting two adjacent gate lines and two adjacent data lines, said first pixel comprising;

a pixel transistor having a gate electrode connected to one of said gate lines, a drain electrode connected to one of said data lines, and a source electrode;

a pixel electrode connected to said source electrode of said pixel transistor;

a liquid crystal capacitor C_LC formed between said pixel electrode and a common electrode;

a compensation capacitor C_C formed between said pixel electrode and a compensation electrode; and

said second pixel comprising;

a pixel transistor having a gate electrode connected to one of said gate lines, a drain electrode connected to one of said data lines, and a source electrode;

a pixel electrode connected to said source electrode of said pixel transistor;

a liquid crystal capacitor C_LC″

formed between said pixel electrode and a common electrode;

a readout capacitor C_read-out between said pixel electrode and a readout line, wherein said pixel electrode is positioned above said readout line, and said pixel electrode and said readout line are overlapped.

2. The pixel structure as claimed in claim 1, wherein said first pixel further comprises a storage capacitor C_ST formed between said pixel electrode and a common line, and said second pixel further comprises a first storage capacitor C_ST″

formed between said pixel electrode and a common line.

3. The pixel structure as claimed in claim 2, wherein both said common electrode and said common line of said first pixel and said second pixel are connected to a common voltage source.

4. The pixel structure as claimed in claim 1, wherein said readout line of said second pixel is parallel with said data lines.

5. The pixel structure as claimed in claim 1, wherein said second pixel further comprises a photo transistor, a readout transistor, and a second storage capacitor composing an optical sensor element.

6. The pixel structure as claimed in claim 1, wherein said compensation electrode of said first pixel is said gate line that is not electrically connected to said transistor.

7. The pixel structure as claimed in claim 1, wherein said compensation electrode of said compensation capacitor is an external electrode.

8. The pixel structure as claimed in claim 7, wherein said external electrode is parallel with said data line and has a constant potential.

9. The pixel structure as claimed in claim 1, when a two-level driving method is applied to said LCD with an embedded touch screen, said capacitors of said first pixel and said second pixel have capacitances corresponding to the following equation:

C _C =Δ

C _LC +C _read-out

wherein Δ

C_LC≡

C″

_LC−

C_LC.

10. The pixel structure as claimed in claim 2, when a two-level driving method is applied to said LCD with an embedded touch screen, said capacitors of said first pixel and said second pixel have capacitances corresponding to the following equation:

C _ST +C _C =Δ

C _LC +C″

_ST +C _read-out

wherein Δ

C_LC≡

C″

<sub>LC−

CLC</sub>.

11. The pixel structure as claimed in claim 3, when a row-inversion driving method with said common voltage modulation is applied to said LCD with an embedded touch screen, said capacitors of said first pixel and said second pixel have capacitances corresponding to the following two equations:

$\frac{C_{\mathrm{LC}}^{\mathrm{″<br><br>}}+C_{\mathrm{ST}}^{\mathrm{″<br><br>}}}{C_{\mathrm{LC}}^{\mathrm{″<br><br>}}+C_{\mathrm{ST}}^{\mathrm{″<br><br>}}+C_{\mathrm{read}<br><br>\text{-}<br><br>\mathrm{out}}+C_{\mathrm{GS}}}=\frac{C_{\mathrm{LC}}+C_{\mathrm{ST}}}{C_{\mathrm{LC}}+C_{\mathrm{ST}}+C_C+C_{\mathrm{GS}}}$ $\mathrm{and}$ $\frac{C_{\mathrm{LC}}+C_{\mathrm{ST}}}{C_{\mathrm{LC}}^{\mathrm{″<br><br>}}+C_{\mathrm{ST}}^{\mathrm{″<br><br>}}}\cong <br><br>1$

where C_GS is a parasitic capacitor formed between said gate electrode and said source electrode of said pixel transistor.

12. The pixel structure as claimed in claim 1, wherein said second pixel is a readout pixel.

13. A pixel structure for an liquid crystal display (LCD) with an embedded touch screen, comprising:

a plurality of first pixels and a plurality of second pixels, each formed by intersecting two adjacent gate lines and two adjacent data lines, said first pixel comprising;

a pixel transistor having a gate electrode connected to one of said gate lines, a drain electrode connected to one of said data lines, and a source electrode;

a pixel electrode connected to said source electrode of said pixel transistor;

a liquid crystal capacitor C_LC formed between said pixel electrode and a common electrode;

a storage capacitor C_ST formed between said pixel electrode and a common line; and

said second pixel comprising;

a pixel transistor having a gate electrode connected to one of said gate lines, a drain electrode connected to one of said data lines, and a source electrode;

a pixel electrode connected to said source electrode of said pixel transistor;

a liquid crystal capacitor C_LC″

formed between said pixel electrode and a common electrode;

a readout capacitor C_read-out between said pixel electrode and a readout line, wherein said pixel electrode is positioned above said readout line, and said pixel electrode and said readout line are overlapped.

14. The pixel structure as claimed in claim 13, wherein said second pixel further comprises a first storage capacitor C_ST″

formed between said pixel electrode and a common line.

15. The pixel structure as claimed in claim 13, wherein said readout line of said second pixel is parallel with said data lines.

16. The pixel structure as claimed in claim 13, wherein said second pixel further comprises a photo transistor, a readout transistor, and a second storage capacitor composing an optical sensor element.

17. The pixel structure as claimed in claim 13, when a two-level driving method is applied to said LCD with an embedded touch screen, said capacitors of said first pixel and said second pixel have capacitances corresponding to the following equation:

C _ST =Δ

C _LC +C _read-out

wherein Δ

C_LC≡

C″

_LC−

C_LC.

18. The pixel structure as claimed in claim 14, when a two-level driving method is applied to said LCD with an embedded touch screen, said capacitors of said first pixel and said second pixel have capacitances corresponding to the following equation:

C _ST Δ

C _LC +C″

_ST +C _read-out

wherein Δ

C_LC≡

C″

_LC−

C_LC.

19. The pixel structure as claimed in claim 13, wherein said second pixel is a readout pixel.