Display device

• US 20030071772A1
• Filed: 12/18/2002
• Published: 04/17/2003
• Est. Priority Date: 08/28/1997
• Status: Active Grant

• Current Assignee: Intellectual Keystone Technology LLC
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Kimura, Mutsumi
• Granted Patent: US 7,236,164 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0852 being a dynamic memory with more than one capacitor
• CPC Class Codes: G09G 2310/027 Details of drivers for data electrodes, the drivers handling digital grey scale data, e.g. use of D/A converters
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/2074 using sub-pixels
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

In a display device in accordance with the present invention, each pixel includes a plurality of luminescent elements having different luminous intensities to represent gray scales by controlling the turning ON/OFF of the luminescent elements. A digital signal is transmitted to each pixel to carry out control by thin film transistors connected in series with the luminescent elements. The luminous intensities of the luminescent elements are the geometric progressions of a common ratio of 2. The ON resistance of the thin film transistors is set to be lower than the ON resistance of the luminescent elements, while the OFF resistance of the thin film transistors is set to be higher than the OFF resistance of the luminescent elements. These features have reduced the nonuniformity in the luminous intensities of the luminescent elements caused by the nonuniformity in the conductance of the transistors, thus achieving improved image quality.

Claims

1. A display element comprising a plurality of scanning lines, a plurality of signal lines, and a pixel formed in a matrix pattern by the scanning lines and the signal lines, a plurality of thin film transistors and a plurality of luminescent elements being formed in the pixel;

wherein the thin film transistors and the luminescent elements are respectively connected in series, and the luminous intensities of the respective luminescent elements are different.

2. A display device according to claim 1, wherein the turning ON/OFF of the luminescent elements is controlled by a digital signal.

3. A display device according to claim 1, wherein luminous intensities of the luminescent elements are geometric progressions of a common ratio of 2.

4. A display device according to claim 1, wherein ON resistance of the thin film transistors is lower than ON resistance of the luminescent elements, while OFF resistance of the thin film transistors is higher than the OFF resistance of the luminescent elements.

5. A display device according to claim 1, wherein the thin film transistors are polycrystalline silicon thin film transistors produced at a low temperature process at 600 degrees Celsius or below.

6. A display device according to claim 1, wherein the luminescent elements are organic electroluminescent elements produced by an ink-jet process.