US 6,525,704 B1Granted

Image display device to control conduction to extend the life of organic EL elements

AssigneeNEC Corporation

InventorsYuji Kondo, Atsushi Kota

Life of this patent

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Abstract

An image display device applies (M×N) data voltages in order to M rows of data lines N voltages at a time, and in synchronization with these data voltages, applies scan voltage in order to the N columns of scan lines. This scan voltage causes M rows and N columns of switching elements to turn on one column at a time, and accordingly, (M×N) data voltages that are applied from the M rows of data lines are individually held by M rows and N columns of voltage holding means. In accordance with these held voltages, M rows and N columns of drive transistors apply a drive voltage that is constantly applied to power supply electrodes to (M×N) organic EL elements. The M rows and N columns of organic EL elements are accordingly actively driven and a multiple gray-scale dot matrix image is displayed. However, conduction control elements halt the application of the drive voltage to the M organic EL elements of the nth column immediately before the scan voltage is applied to the scan line of the nth column. As a result, conduction to the organic EL elements is halted instantaneously even when an image of the same luminance is continuously displayed, thereby extending the life of the organic EL elements.

Claims17

Dependent claims

An image display device, comprising:

(M×N) organic EL (Electro-Luminescent) elements arranged two-dimensionally in M rows and N columns, where M and N are predetermined natural numbers;
M rows of data lines to which data voltages, in which the light-emission luminances of said (M×N) organic EL elements are individually set, are applied in order;
N columns of scan lines to which a scan voltage is applied in order in synchronization with data voltages that are applied to said M rows of data lines;
M rows and N columns of switching elements that are turned on one column at a time by the scan voltage that is applied in order to said N columns of scan lines;
M rows and N columns of voltage holding means for individually holding the (M×N) data voltages that are applied from said M rows of data lines in accordance with the ON state of said M rows and N columns of switching elements;
a pair of power supply electrodes to which a predetermined drive voltage is constantly applied;
M rows and N columns of drive transistors for applying said drive voltage that is constantly applied to said power supply electrodes to said (M×N) organic EL elements in accordance with each of the voltages held by said (M×N) voltage holding means;
and
conduction control elements for halting the application of the drive voltage to M said organic EL elements of the nth column immediately before a scan voltage is applied to said scan line of the nth column, where 1≦n≦N.

6 more elements

An image display device, comprising:

(M×N) organic EL elements arranged two-dimensionally in M rows and N columns;
M rows of data lines to which data voltages, in which the light-emission luminances of said (M×N) organic EL elements are individually set, are applied in order;
N columns of scan lines to which a scan voltage is applied in order in synchronization with data voltages that are applied to said M rows of data lines;
M rows and N columns of switching elements that are turned on one column at a time by the scan voltage that is applied in order to said N columns of scan lines;
M rows and N columns of voltage holding means for individually holding the (M×N) data voltages that are applied from said M rows of data lines in accordance with the ON state of said M rows and N columns of switching elements;
a pair of power supply electrodes to which a predetermined drive voltage is constantly applied;
M rows and N columns of drive transistors for applying said drive voltage that is constantly applied to said power supply electrodes to said (M×N) organic EL elements in accordance with each of the voltages held by said (M×N) voltage holding means;
and
conduction control elements for applying a reverse voltage, with the opposite polarity of the drive voltage, to M said organic elements of the nth column immediately before a scan voltage is applied to said scan line of the nth column, where 1≦n≦N.

6 more elements

Dependencies are inferred from the claim text.

Facts

Application: 09/589,283Filed 8 Jun 2000
Priority: JP 11-1624229 Jun 1999
Granted: 25 Feb 2003
Term ends: Not estimatedThe source records don’t support an estimate.

Classification7 codes

G09G 3/3233
Using an active matrix: with pixel circuitry controlling the current through the light-emitting element
G09G 2300/0842
Several active elements per pixel in active matrix panels: forming a memory circuit, e.g. a dynamic memory with one capacitor
G09G 2310/0251
Details of the generation of driving signals: precharge or discharge of pixel before applying new pixel voltage
G09G 2310/0256
Control of polarity reversal in general, other than for liquid crystal displays: with the purpose of reversing the voltage across a light emitting…