LIQUID CRYSTAL DISPLAY DEVICE

• US 20150022501A1
• Filed: 10/09/2014
• Published: 01/22/2015
• Est. Priority Date: 05/25/2012
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Liquid Crystal Display Company Limited (Panasonic Holdings Corporation)
• Inventors: KITA, Kazuo
• Granted Patent: US 9,524,068 B2
• Time in Patent Office: Days
• US Class Current: 345/174
• CPC Class Codes: G02F 1/13338 Input devices, e.g. touch panels
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G06F 2203/04111 Cross over in capacitive digitiser, i.e. details of structures for connecting electrodes of the sensing pattern where the connections cross each other, e.g. bridge structures comprising an insulating layer, or vias through substrate
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes

Abstract

To achieve improved detection accuracy and position resolution in an in-cell type capacitive touch sensor embedded in a liquid crystal panel of a liquid crystal display device, a drive electrode of a touch sensor is formed of a transparent conductive film laminated on a surface of a TFT substrate on a liquid crystal side below a pixel electrode, and disposed in a region between gate lines. A detection electrode is formed of a transparent conductive film laminated on an outward-directed surface of the TFT substrate. A drive signal is supplied to the drive electrode to cause a voltage change, and based on the voltage change in the detection electrode caused thereby, a capacitance change in an opposing part between the drive electrode and the detection electrode is detected, to thereby detect contact of an object to a display surface near the opposing part in a liquid crystal panel.

Claims

1. A liquid crystal display device, comprising:

a liquid crystal panel in which liquid crystal is sandwiched between a front substrate and a back substrate arranged so as to oppose each other, the front substrate having an outward-directed surface as a display surface of an image,

the liquid crystal display device being configured to;

sequentially apply a selection signal to scanning wiring lines laminated on a surface of the front substrate on the liquid crystal side and respectively extended along a plurality of pixel rows forming the image, to thereby enable application of a voltage based on a video signal to each pixel electrode of corresponding one of the plurality of pixel rows; and

control alignment of the liquid crystal by an electric field generated between the pixel electrode and a common electrode, to thereby form the image; and

a capacitive touch sensor comprising;

a plurality of first electrodes formed of a transparent conductive film laminated on the surface of the front substrate on the liquid crystal side below the pixel electrode, the plurality of first electrodes being formed in regions between the scanning wiring lines;

a plurality of second electrodes formed of a transparent conductive film laminated on the outward-directed surface of the front substrate; and

a contact detection circuit configured to, when one of each of the plurality of first electrodes and each of the plurality of second electrodes is defined as a drive electrode and another thereof is defined as a detection electrode;

supply a drive signal to the drive electrode to cause a voltage change;

detect, based on the voltage change in the detection electrode caused by the supply, a change in capacitance in an opposing part between corresponding one of the plurality of first electrodes and corresponding one of the plurality of second electrodes; and

detect contact of an object to the display surface near the opposing part.

2. The liquid crystal display device according to claim 1,

wherein the common electrode is formed of a transparent conductive film laminated between the pixel electrode and the first electrodes, and

wherein the first electrodes comprise the drive electrode and cover the regions between the scanning wiring lines.

3. The liquid crystal display device according to claim 1,

wherein the contact detection circuit operates to detect the contact of the object in an effective display period of the video signal.

4. The liquid crystal display device according to claim 1,

wherein the plurality of first electrodes extends in a first direction along the display surface, and the plurality of second electrodes extends in a second direction different from the first direction along the display surface, the plurality of first electrodes and the plurality of second electrodes forming the opposing parts at a plurality of positions arrayed two-dimensionally in the display surface, and

wherein the contact detection circuit is further configured to sequentially supply the drive signal to a plurality of the drive electrodes to examine the voltage change in each of the detection electrodes, to thereby determine a position at which the object is brought into contact in the display surface.

8. The liquid crystal display device according to claim 2,

wherein the detection electrodes are formed into mesh shape.

5. A liquid crystal display device, comprising:

a liquid crystal panel in which liquid crystal is sandwiched between a front substrate and a back substrate arranged so as to oppose each other, the front substrate having an outward-directed surface as a display surface of an image,

the liquid crystal display device being configured to;

sequentially apply a selection signal to scanning wiring lines laminated on a surface of the front substrate on the liquid crystal side and respectively extended along a plurality of pixel rows forming the image, to thereby enable application of a voltage based on a video signal to each pixel electrode of corresponding one of the plurality of pixel rows; and

control alignment of the liquid crystal by an electric field generated between the pixel electrode and a common electrode, to thereby form the image; and

a capacitive touch sensor comprising;

a plurality of drive electrodes formed of a transparent conductive film laminated on the surface of the front substrate on the liquid crystal side below the pixel electrode, the plurality of drive electrodes being electrically connected to the scanning wiring lines, respectively;

a plurality of detection electrodes formed of a transparent conductive film laminated on the outward-directed surface of the front substrate; and

a contact detection circuit configured to detect a change in capacitance in an opposing part between corresponding one of the plurality of drive electrodes and corresponding one of the plurality of detection electrodes based on a voltage change in the corresponding one of the plurality of detection electrodes caused via the corresponding one of the plurality of drive electrodes when the selection signal is applied to corresponding one of the scanning wiring lines, to thereby detect contact of an object to the display surface near the opposing part.

6. The liquid crystal display device according to claim 5,

wherein the common electrode is formed of a transparent conductive film laminated on the surface of the front substrate on the liquid crystal side below the pixel electrode, and

wherein the drive electrodes cover regions between the scanning wiring lines.

7. The liquid crystal display device according to claim 5,

wherein the plurality of drive electrodes extends in a horizontal direction in the display surface, and the plurality of detection electrodes extends in a vertical direction in the display surface, the plurality of drive electrodes and the plurality of detection electrodes forming the opposing parts at a plurality of positions arrayed two-dimensionally in the display surface, and

wherein the contact detection circuit is further configured to examine the voltage change in the each of the plurality of detection electrodes when the selection signal is sequentially applied to the scanning wiring lines through vertical scanning of the image, to thereby determine a position at which the object is brought into contact in the display surface.

9. The liquid crystal display device according to claim 6,

wherein the detection electrodes are formed into mesh shape.