LIQUID CRYSTAL DISPLAY DEVICE

• US 20120081648A1
• Filed: 10/03/2011
• Published: 04/05/2012
• Est. Priority Date: 10/05/2010
• Status: Active Grant

• Current Assignee: Japan Display Incorporated
• Original Assignee: Hitachi Displays Limited (Japan Display Incorporated)
• Inventors: NAGAMI, Takahiro
• Granted Patent: US 8,908,114 B2
• Time in Patent Office: Days
• US Class Current: 349/139
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/134372 for fringe field switching [FFS] where the common electrode is not patterned
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/13624 having more than one switching element per pixel
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/13629 Multilayer wirings
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence

Abstract

An IPS liquid crystal display device with a reduced number of layers, in which the variation of pixel electrode potential due to ON/OFF operation of a gate voltage is suppressed. A pixel electrode is formed on a TFT substrate formed of glass. A gate insulating film is formed to cover the pixel electrode, an inorganic passivation film is formed on the gate insulating film, and a common electrode is formed on the passivation film.

A liquid crystal molecule is driven with an electric line of force in a slit formed in the common electrode. A capacitive electrode, which is connected to the common electrode, is formed on the gate insulating film. The capacitive electrode forms an added capacitance with the pixel electrode via the gate insulating layer. The variation of pixel electrode potential due to ON/OFF operation of a gate voltage is suppressed with the added capacitance.

Claims

1. A liquid crystal display device having a TFT substrate, an opposite substrate, and a liquid crystal held between the TFT substrate and the opposite substrate,

wherein in the TFT substrate, a scan line extends in a first direction and arranged in a second direction, a video signal line extends in the second direction and arranged in the first direction, and a pixel is formed between the scan line and the video signal line,

wherein a pixel electrode is formed on the TFT substrate, a gate insulating film is formed on the pixel electrode, an inorganic passivation film is formed on the gate insulating film, a common electrode having a slit is formed on the inorganic passivation film, the liquid crystal is driven by supply of a video signal to the pixel electrode,

wherein a capacitive electrode formed of metal or alloy is formed on the gate insulating film and under the inorganic passivation film, to be opposite to the pixel electrode, and

wherein the pixel electrode is connected to the TFT, the capacitive electrode is connected to the common electrode, and the capacitive electrode and the pixel electrode form the added capacitance.

2. The liquid crystal display device according to claim 1, wherein the pixel is arranged in an in-line shape in the second direction.

3. The liquid crystal display device according to claim 1, wherein the pixel is arranged in a delta arrangement.

4. The liquid crystal display device according to claim 1, wherein a film thickness of the gate insulating film in the TFT is thicker than a film thickness of the gate insulating film in the added capacitance.

5. A liquid crystal display device having a TFT substrate, an opposite substrate, and a liquid crystal held between the TFT substrate and the opposite substrate,

wherein in the TFT substrate, a pair of scan lines having a first scan line and a second scan line extends in a first direction and arranged in a second direction, a video signal line extends in the second direction and arranged in the first direction, and first pixel and second pixel are formed in the first direction between the pair of scan lines and the video signal line,

wherein the first pixel is driven with the first scan line, and the second pixel is driven with the second scan line,

wherein a first TFT is formed in correspondence with the first pixel, and a second TFT is formed in correspondence with the second pixel,

wherein in the first pixel and the second pixel, a first pixel electrode and a second pixel electrode are respectively formed on the TFT substrate, a gate insulating film is formed on the pixel electrode, an inorganic passivation film is formed on the gate insulating film, a common electrode having a slit is formed on the inorganic passivation film, and the liquid crystal is driven by supply of a video signal to the pixel electrode,

wherein a first capacitive electrode formed of metal or alloy is formed on the gate insulating film and under the inorganic passivation film, to be opposite to the first pixel electrode,

wherein a second capacitive electrode formed of metal or alloy is formed on the gate insulating film and under the inorganic passivation film, to be opposite to the second pixel electrode,

wherein the first capacitive electrode is connected to the common electrode, to form first added capacitance with the first capacitive electrode and the first pixel electrode, and

wherein the second capacitive electrode is connected to the common electrode, and the second capacitive electrode and the second pixel electrode form second added capacitance.

6. The liquid crystal display device according to claim 5, wherein the first pixel and the second pixel are arranged in an in-line arrangement in the second direction.

7. The liquid crystal display device according to claim 5, wherein the first pixel and the second pixel are arranged in a delta arrangement.

8. The liquid crystal display device according to claim 5, wherein the first capacitive electrode and the second capacitive electrode are continuous.

9. The liquid crystal display device according to claim 5, wherein a film thickness of the gate insulating film in the first TFT and the second TFT is thicker than a film thickness of the gate insulating film in the first added capacitance and the second added capacitance.