Display apparatus and method of measuring liquid crystal capacitance

1. A display apparatus comprising:

a first substrate comprising a display area, on which an image is displayed, and a peripheral area surrounding at least a portion of the display area, wherein the first substrate further comprises:

a plurality of pixel electrodes arranged in the display area; and

a plurality of dummy pixel electrodes arranged in the peripheral area;

a second substrate disposed opposite to and coupled to the first substrate, wherein the second substrate comprises:

a reference electrode facing the pixel electrodes in the display area and facing the dummy pixel electrodes in the peripheral area; and

a liquid crystal layer interposed between the first substrate and the second substrate,

wherein the first substrate further comprises:

a test line electrically connected to the dummy pixel electrodes;

a first pad electrode configured to apply a test voltage to the test line to measure a liquid crystal capacitance;

a reference voltage line configured to receive a reference voltage from an external source; and

a second pad electrode configured to apply the reference voltage to the reference voltage line to measure the liquid crystal capacitance.

2. The display apparatus of claim 1 , wherein

the first substrate further comprises a pad area which is an elongated portion of the first substrate outwardly from the peripheral area, and

the first and second pad electrodes are disposed in the pad area.

3. The display apparatus of claim 2 , further comprising:

an insulating layer interposed between the first pad electrode and the test line, and between second pad and the reference voltage line,

wherein

the first pad electrode overlaps the test line,

the second pad electrode overlaps the reference voltage line, and

the first pad electrode and the second pad electrode are configured to be electrically connected to the test line and the reference electrode, respectively, to measure the liquid crystal capacitance.

4. The display apparatus of claim 2 , further comprising:

a flexible film attached to the pad area of the first substrate; and

a printed circuit board which applies a control signal to the flexible film.

5. The display apparatus of claim 4 , wherein

the printed circuit board comprises:

a first test pad electrically connected to the first pad electrode; and

a second test pad electrically connected to the second pad electrode, and

the first and second test pads are electrically connected to the first and second pad electrodes, respectively, by the flexible film.

6. The display apparatus of claim 4 , further comprising:

a driving chip configured to apply a driving signal to the first substrate in response to the control signal.

7. The display apparatus of claim 6 , wherein the driving chip is disposed on the flexible film.

8. The display apparatus of claim 1 , further comprising:

a coupling member interposed between the first substrate and the second substrate and disposed in the peripheral area,

wherein the coupling member couples the first and second substrates to each other.

9. The display apparatus of claim 8 , wherein a distance between the coupling member and the dummy pixel electrode is equal to or greater than about 0.4 millimeter when viewed from a top view.

10. A method of measuring a liquid crystal capacitance of a display apparatus, the method comprising:

preparing a first substrate comprising a display area, in which an image is displayed, and a peripheral area surrounding at least a portion of the display area, wherein the first substrate further comprises a plurality of pixels arranged in the display area, and a plurality of dummy pixel electrodes arranged in the peripheral area;

preparing a second substrate including a reference electrode facing the pixel electrodes in the display area and facing the dummy pixel electrodes in the peripheral area;

providing a liquid crystal layer between the first and second substrates;

applying a reference voltage and a test voltage to the reference electrode and the dummy pixel electrodes, respectively, to measure the liquid crystal capacitance; and

controlling a voltage level of the reference voltage based on the measured liquid crystal capacitance.

11. The method of claim 10 , wherein the first substrate further comprises:

a test line electrically connected to the dummy pixel electrodes;

a first pad electrode configured to apply the test voltage to the test line to measure the liquid crystal capacitance;

a reference voltage line which receives the reference voltage from an external source; and

a second pad electrode configured to apply the reference voltage to the reference voltage line to measure the liquid crystal capacitance.

12. The method of claim 11 , wherein

the first substrate further comprises a pad area in an elongated portion of the first substrate outwardly from the peripheral area, and

the first and second pad electrodes are arranged in the pad area.

13. The method of claim 11 , further comprising:

providing an insulating layer between the first pad electrode and the test line, and between second pad and the reference voltage line, wherein the first pad electrode overlaps the test line, and the second pad electrode overlaps the reference voltage line; and

electrically connecting the first pad electrode and the second pad electrode to the test line and the reference electrode, respectively, by irradiating a laser beam onto the first and second pad electrodes to measure the liquid crystal capacitance.

14. The method of claim 10 , further comprising:

providing a coupling member between the first and second substrates in the peripheral area to couple the first and second substrates to each other.

15. The method of claim 14 , wherein a distance between the coupling member and the dummy pixel electrode is equal to or greater than about 0.4 millimeter when viewed from a top view.

16. The display apparatus of claim 1 , wherein the reference electrode and the pixel electrode define a liquid crystal capacitor with the liquid crystal layer interposed therebetween.

17. The method of claim 10 , wherein the reference electrode and the pixel electrode define a liquid crystal capacitor with the liquid crystal layer interposed therebetween.