GATE DRIVER AND DISPLAY DEVICE USING THE SAME

• US 20180122323A1
• Filed: 10/31/2017
• Published: 05/03/2018
• Est. Priority Date: 10/31/2016
• Status: Active Grant

• Current Assignee: LG Display Co., Ltd.
• Original Assignee: LG Display Co., Ltd.
• Inventors: PARK, Yongseok, JI, Hyelim
• Granted Patent: US 10,210,836 B2
• Time in Patent Office: Days
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/133512 Light shielding layers, e.g. black matrix G02F1/136209 takes precedence
• CPC Class Codes: G02F 1/133514 Colour filters
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2202/104 poly-Si
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2310/0286 Details of a shift registers arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• CPC Class Codes: G09G 3/3688 suitable for active matrices only
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 27/1248 with a particular composition or shape of the interlayer dielectric specially adapted to the circuit arrangement
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H01L 29/78696 : characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621

Abstract

A gate driver and a display device using the same are disclosed. The gate driver includes a first transistor configured to pre-charge a Q node, a second transistor configured to raise the output voltage depending on a voltage of the Q node, a third transistor configured to charge a QB node, a fourth transistor configured to lower the output voltage depending on a voltage of the QB node, and a capacitor connected between a gate and a source in at least one of the second transistor and the third transistor. The capacitor has a capacitance greater than a capacitance between the gate and a drain of the transistor to which the capacitor is connected. The capacitor includes an upper capacitor disposed on an organic passivation layer covering the transistors.

Claims

1. A gate driver comprising:

a plurality of stages to which a shift clock is applied through a clock wiring and which are connected in a cascade connection manner through a carry signal and sequentially generate an output voltage through each output terminal,

each of the stages includes;

a first transistor configured to pre-charge a Q node;

a second transistor configured to raise the output voltage depending on a voltage of the Q node;

a third transistor configured to charge a QB node;

a fourth transistor configured to lower the output voltage depending on a voltage of the QB node; and

a first capacitor connected between a gate and one of a source or a drain in at least one of the second transistor and the third transistor,

wherein the first capacitor has a capacitance greater than a capacitance between the gate and the other one of the source or the drain of the transistor to which the first capacitor is connected, and

wherein the first capacitor includes an upper capacitor disposed on an organic passivation layer overlaying the transistors.

2. The gate driver of claim 1, wherein the upper capacitor includes a first electrode and a second electrode opposite to each other with an inorganic passivation layer interposed therebetween.

3. The gate driver of claim 2, wherein the first capacitor further includes a lower capacitor disposed under the organic passivation layer and at least partially overlapped in projection with the upper capacitor, and

wherein the lower capacitor includes a third electrode and a fourth electrode opposing each other with a gate insulating layer interposed therebetween.

4. The gate driver of claim 3, wherein a thickness of the inorganic passivation layer is less than that of the gate insulating layer.

5. The gate driver of claim 1, further comprising:

a fifth transistor connected between a gate and a drain of the first transistor,

wherein the fifth transistor includes;

a gate connected to the gate of the first transistor;

a drain to which a gate-on voltage is applied; and

a source connected to the drain of the first transistor,

wherein a carry signal is applied to the gates of the first and fifth transistors.

6. The gate driver of claim 5, further comprising:

a second capacitor connected between the gate and the source of the fifth transistor,

wherein the second capacitor has a capacitance greater than a capacitance between the gate and the drain of the fifth transistor, and

wherein the second capacitor includes an upper capacitor disposed on the organic passivation layer.

7. The gate driver of claim 6, wherein the upper capacitor of the second capacitor includes a first electrode and a second electrode opposite to each other with an inorganic passivation layer interposed therebetween.

8. The gate driver of claim 7, wherein the second capacitor further includes a lower capacitor disposed under the organic passivation layer and at least partially overlapped in projection with the upper capacitor, and

wherein the lower capacitor includes a third electrode and a fourth electrode at least partially overlapped with each other with a gate insulating layer interposed therebetween.

9. The gate driver of claim 6, wherein each of the first and fifth transistors has a semiconductor channel of a single length structure.

10. A display device comprising:

a display panel in which data lines and gate lines intersect, pixels are arranged in a matrix form; and

a display driver configured to write data of an input image to the pixels, the display driver including a shift register configured to sequentially supply a gate pulse to the gate lines, the shift register including;

a plurality of stages to which a shift clock is applied through a clock wiring and which are connected in a cascade connection manner through a carry signal and sequentially generate an output voltage through each output terminal,

wherein each of the stages includes;

a first transistor configured to pre-charge a Q node;

a second transistor configured to raise the output voltage depending on a voltage of the Q node;

a third transistor configured to charge a QB node;

a fourth transistor configured to lower the output voltage depending on a voltage of the QB node; and

a first capacitor connected between a gate and one of a source or a drain in at least one of the second transistor and the third transistor,

wherein the first capacitor has a capacitance greater than a capacitance between the gate and another one of the source or the drain of the transistor to which the first capacitor is connected, and

wherein the first capacitor includes an upper capacitor disposed on an organic passivation layer overlaying the transistors.

11. The display device of claim 10, wherein the first capacitor further includes a lower capacitor disposed under the organic passivation layer and overlapped with the upper capacitor, and

wherein the lower capacitor includes a third electrode and a fourth electrode at least partially overlapped with each other with a gate insulating layer interposed therebetween.

12. The display device of claim 10, further comprising:

a fifth transistor connected between a gate and a drain of the first transistor,

wherein the fifth transistor includes;

a gate connected to the gate of the first transistor;

a drain to which a gate-on voltage is applied; and

a source connected to the drain of the first transistor,

wherein a carry signal is applied to the gates of the first and fifth transistors.

13. The display device of claim 12, further comprising:

a second capacitor connected between the gate and the source of the fifth transistor,

wherein the second capacitor has a capacitance greater than a capacitance between the gate and the drain of the fifth transistor, and

wherein the second capacitor includes the upper capacitor disposed on the organic passivation layer.

14. The display device of claim 13, wherein the upper capacitor includes a first electrode and a second electrode opposite to each other with an inorganic passivation layer interposed therebetween.

15. The display device of claim 14, wherein the second capacitor further includes a lower capacitor disposed under the organic passivation layer and at least partially overlapped in projection with the upper capacitor, and

wherein the lower capacitor includes a third electrode and a fourth electrode at least partially overlapped with each other with a gate insulating layer interposed therebetween.

16. The display device of claim 15, wherein a thickness of the inorganic passivation layer is less than that of the gate insulating layer.

17. The display device of claim 13, wherein each of the first and fifth transistors has a semiconductor channel of a single length structure.

18. A structure comprising:

a first metal layer overlying a substrate;

an insulation layer overlying the first metal layer;

a first aperture in the insulation layer exposing the first metal layer;

a second metal layer overlying the insulation layer and the first metal layer to create a lower capacitive element;

a first passivation layer overlying the second metal layer,

a second aperture in the first passivation layer exposing the second metal layer;

a third metal layer overlying the first passivation layer, the first metal layer, the insulation layer and the second metal layer;

a second passivation layer overlying the third metal layer;

a third aperture in the second passivation layer exposing the third metal layer;

a fourth metal layer overlying the third metal layer and the second passivation layer to create an upper capacitive element;

a metal connection extending from the first aperture to the third aperture that electrically connects the first metal layer of the lower capacitive element to the third metal layer of the upper capacitive element; and

a metal connection extending from the second aperture to the fourth metal layer that electrically connects the second metal layer to the fourth metal layer of the upper capacitive element.

19. The structure of claim 18, wherein the upper capacitive element and the lower capacitive element at least partially overlap one another in plan projection.

20. The structure of claim 19, wherein the second passivation layer is greater than five times thicker than the insulation layer to reduce the capacitive coupling between the second and third metal layers relative to the capacitive coupling between the first and second metal layers.