Method for driving an organic electroluminescent display device

• US 7,218,293 B2
• Filed: 02/10/2004
• Issued: 05/15/2007
• Est. Priority Date: 02/10/2003
• Status: Expired due to Fees

• Current Assignee: Optrex Corporation (Kyocera Corporation)
• Original Assignee: Optrex Corporation (Kyocera Corporation)
• Inventors: Kato, Naoki
• Primary Examiner(s): CHOW, DOON Y
• Application Number:
  US10/774,382
• Publication Number:
  US 20040217926A1
• Time in Patent Office: 1,190 Days
• Field of Search: 345 76- 83, 315/169.3
• US Class Current: 345/76
• CPC Class Codes: G09G 2310/0251 Precharge or discharge of pixel before applying new pixel voltage
• CPC Class Codes: G09G 2320/0209 Crosstalk reduction, i.e. to reduce direct or indirect influences of signals directed to a certain pixel of the displayed image on other pixels of said image, inclusive of influences affecting pixels in different frames or fields or sub-images which constitute a same image, e.g. left and right images of a stereoscopic display
• CPC Class Codes: G09G 2320/0223 Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2320/041 Temperature compensation
• CPC Class Codes: G09G 3/2014 by modulation of the duration of a single pulse during which the logic level remains constant
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3283 in which the data driver supplies a variable data current for setting the current through, or the voltage across, the light-emitting elements

Abstract

When the ambient temperature of an organic electroluminescent display device is a low temperature, a capacitive charge driving method is performed to supply a constant current to a column electrode after performing capacitance charge and then apply a constant voltage to the column electrode to turn off a pixel; and when the ambient temperature is room temperature or a high temperature, an electric charge control driving method is performed to supply a constant current to the data electrode and then place the column electrode in a high impedance state. In the electric charge control driving method, a driving section is set in a selection period so as to be shorter than the selection period, and the amount of electric charges supplied to the pixel in the driving section is controlled depending on a required luminance.

Claims

1. A method for driving an organic electroluminescent display device, which has a set of row electrodes and a set of column electrodes provided in a matrix pattern, and an organic electroluminescent element sandwiched between both sets;

comprising;

driving the organic electroluminescent element by an electric charge control driving method when an ambient temperature is higher than a prescribed temperature, the electric charge control driving method comprising supplying electric charges to a column electrode in the set of column electrodes and then placing an output from a driving circuit to the column electrode in the set of column electrodes in a high impedance state;

driving the organic electroluminescent element by the electric charge control driving method when the ambient temperature is not higher than the prescribed temperature and when a light-emission luminance in a maximum gray scale is a relatively low luminance; and

driving the organic electroluminescent element by a capacitive charge driving method when the ambient temperature is not higher than the prescribed temperature and when the light-emission luminance in the maximum gray scale is a relatively high luminance, the capacitive charge driving method comprising supplying a constant current to the column electrode in the set of column electrodes after performing the capacitance charge, and then applying a constant voltage to the column electrode in the set of column electrodes to turn off a pixel.

2. The method according to claim 1, wherein when the ambient temperature is not higher than the prescribed temperature and when a rated luminance is defined as 100%, a light-emission luminance when switching between both driving methods has a value of 40% to 60% of the rated luminance.

3. The method according to claim 1, wherein the prescribed temperature is in a temperature range of from −

10°

C. to +10°

C.

4. The method according to claim 1, wherein a maximum voltage of a supply voltage of the driving circuit is not higher than 25 V.