Apparatus and method for evaluating organic EL display

• US 20020047565A1
• Filed: 07/03/2001
• Published: 04/25/2002
• Est. Priority Date: 07/28/2000
• Status: Active Grant

• Current Assignee: Wintest Corp. (Wuhan Jingce Electronic Group Co., Ltd.)
• Original Assignee: Wintest Corp. (Wuhan Jingce Electronic Group Co., Ltd.)
• Inventors: Itoh, Masatoshi, Ookuma, Makoto, Nara, Shouji, Innami, Tomoharu
• Granted Patent: US 6,633,135 B2
• Time in Patent Office: Days
• US Class Current: 315/169.3
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/0295 by monitoring each display pixel
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: Y10S 345/904 Display with fail/safe testing feature

Abstract

It is an object of the present invention to provide an apparatus and method for evaluating an organic EL display, with which there is a simple drive circuit used for testing an organic EL display 10, evaluation of high reliability can be achieved, and an evaluation of the organic EL display 10 itself is performed prior to the installation of finished product drive circuits to the organic EL display 10, which makes it possible to suppress the decrease in yield caused by dealing with defective products due to the evaluation results. It was noticed that if the drive (testing) of a pixel 11 is performed during the discharge of the previous pixel 11 after the supply of drive current to that previous pixel 11, and if the difference between the drive current and discharge current values of the organic EL pixel 14 of the pixel 11 is under a specific level, then it is possible to decide that the pixels constituted by the various organic EL elements are operating normally, and the present invention is characterized in that pixel defects are detected by detecting the difference between drive current and discharge current values for every pixel 11 constituted by an organic EL element 1.

Claims

1. An apparatus for evaluating an organic EL display having organic EL elements as pixels, wherein the drive current and discharge current values are measured for each pixel constituted by an organic EL element;

and

pixel defects are detected by detecting a difference in the current values thereof.

2. The apparatus for evaluating an organic EL display according to claim 1, wherein the organic EL display has:

a constant current circuit for driving the organic EL elements; and

a switch circuit for switching the voltage in order to make the constant current produced by this constant current circuit variable.

3. The apparatus for evaluating an organic EL display according to claim 1, wherein the organic EL display has:

a constant current circuit for driving the organic EL elements; and

signal lines and selection lines for selecting the organic EL elements.

4. The apparatus for evaluating an organic EL display according to claim 1,

wherein there are provided signal lines and selection lines for selecting the organic EL elements, and

the drive current and discharge current values are measured by switching either the signal line or the selection line for each pixel constituted by an organic EL element.

5. The apparatus for evaluating an organic EL display according to claim 1,

wherein there are provided signal lines and selection lines for selecting the organic EL elements, and

the signal line or the selection line is switched for each pixel constituted by an organic EL element, so that drive current is supplied to the organic EL elements;

and

the charge stored in the organic EL elements is discharged.

6. The apparatus for evaluating an organic EL display according to claim 1,

wherein there is provided a capacitor for supplying a constant current to the organic EL elements,

drive voltage is supplied to each pixel constituted by an organic EL element, and

the charge stored in the capacitor is discharged.

7. The apparatus for evaluating an organic EL display according to claim 1, comprising:

a first transistor that performs switching for supplying a constant current to the organic EL elements; and

a second transistor that is switched by the first transistor and is connected to the organic EL elements;

wherein the first transistor is switched for each pixel constituted by an organic EL element, so that the drive current is supplied to the organic EL elements over a first specific time, and the second transistor is kept in a nonconducting state over a second specific time following this first specific time.

8. The apparatus for evaluating an organic EL display according to claim 1, comprising:

signal lines and selection lines for selecting the organic EL elements; and

voltage supply lines for supplying voltage to the organic EL elements;

wherein the signal line or the selection line is switched for each pixel constituted by an organic EL element, in a state in which this voltage supply line is ON, and

the drive current and discharge current flowing to the organic EL elements are measured.

9. The apparatus for evaluating an organic EL display according to claim 1,

wherein there are provided signal lines and selection lines for selecting the organic EL elements,

the signal line or the selection line is switched for each pixel constituted by an organic EL element, and

the current supplied to the organic EL elements is controlled and the drive current and discharge current flowing to the organic EL elements are measured.

10. An apparatus for evaluating an organic EL display having:

organic EL elements as pixels;

signal lines and selection lines for selecting the organic EL elements; and

voltage supply lines for supplying voltage to the organic EL elements,

wherein said evaluation apparatus comprises;

a detection voltage generation circuit that generates a detection voltage to the signal lines, selection lines, and voltage supply lines;

a control signal generation circuit that generates a control signal for sequentially applying this detection voltage at a specific period to the signal lines, selection lines, and voltage supply lines;

a connection switching circuit for connecting this control signal to the organic EL elements via the signal lines, selection lines, and voltage supply lines;

a current detection circuit for detecting the drive current and discharge current flowing to the organic EL elements; and

a defect decision circuit that decides whether the organic EL elements are defective or non-defective based on the detected current values.

13. The apparatus for evaluating an organic EL display according to claim 10 or 11, comprising:

a current amplification circuit for amplifying the current detected by the current detection circuit; and

an A/D conversion circuit for converting this amplified current into a digital signal.

11. An apparatus for evaluating an organic EL display having organic EL elements as pixels;

and signal lines and selection lines for selecting the organic EL elements, said evaluation apparatus comprising;

a detection current generation circuit that generates a detection current to the signal lines and selection lines;

a control signal generation circuit that generates a control signal for sequentially applying this detection current at a specific period to the signal lines and selection lines;

a connection switching circuit for connecting this control signal to the organic EL elements via the signal lines and selection lines;

a current detection circuit for detecting the drive current and discharge current flowing to the organic EL elements; and

a defect decision circuit that decides whether the organic EL elements are defective or non-defective based on the detected current values.

12. The apparatus for evaluating an organic EL display according to claim 11, wherein there is provided a forward voltage drop detection circuit that measures the forward voltage drop of the organic EL elements, and

the defect decision circuit decides whether the organic EL elements are defective or non-defective based on the detected current values and on this forward voltage drop value.

14. The apparatus for evaluating an organic EL display according to claim 13,

wherein the setting of the detection voltage in the detection voltage generation circuit,

the generation of the control signal in the control signal generation circuit, and

the setting of the degree of current amplification in the current amplification circuit can be carried out as desired by means of bus data from a central control circuit.

15. The apparatus for evaluating an organic EL display according to claim 13,

wherein the setting of the detection current in the detection current generation circuit,

the generation of the control signal in the control signal generation circuit, and

the setting of the degree of current amplification in the current amplification circuit can be carried out as desired by means of bus data from a central control circuit.

16. An apparatus for evaluating an organic EL display having signal lines and selection lines arranged in a matrix;

and

organic EL elements as pixels connected to said signal lines and selection lines at the intersections between these signal lines and selection lines;

wherein the signal line or the selection line is switched for each pixel constituted by an organic EL element, so that organic EL element is driven, and the drive current and discharge current values are measured for said organic EL elements, and

pixel defects are detected by detecting a difference in the current values thereof.

17. An apparatus for evaluating an organic EL display having signal lines and selection lines arranged in a matrix;

and

organic EL elements as pixels connected to said signal lines and selection lines at the intersections between these signal lines and selection lines;

wherein the signal line or the selection line is switched for each pixel constituted by an organic EL element, and that organic EL element is driven,

a first sampling is performed for the drive current values within the drive time of the organic EL elements, and

a second sampling is performed for the discharge current values at the end of the discharge time following this drive time,

whereby the drive current and discharge current values are measured, and pixel defects are detected by detecting a difference in the current values thereof.

18. A method for evaluating an organic EL display having organic EL elements as pixels,

wherein the drive current and discharge current values are measured for each pixel constituted by an organic EL element;

and

pixel defects are detected by detecting a difference in the current values thereof.