Display device

• US 20070216610A1
• Filed: 01/24/2005
• Published: 09/20/2007
• Est. Priority Date: 01/30/2004
• Status: Active Grant

• Current Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Original Assignee: Cambridge Display Technology Limited (Sumitomo Chemical Company Limited)
• Inventors: Smith, Euan
• Granted Patent: US 7,956,531 B2
• Time in Patent Office: Days
• US Class Current: 345/76
• CPC Class Codes: G09G 2300/0452 Details of colour pixel setup, e.g. pixel composed of a red, a blue and two green components
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3216 using a passive matrix
• CPC Class Codes: G09G 3/3225 using an active matrix
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• CPC Class Codes: H10K 59/12 Active-matrix OLED [AMOLED] displays
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/352 the areas of the RGB subpixels being different
• CPC Class Codes: H10K 59/353 characterised by the geometrical arrangement of the RGB subpixels
• CPC Class Codes: H10K 59/86 Series electrical configurations of multiple OLEDs
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An organic light emitting diode (OLED) display device is described, the display device having a plurality of pixels each comprising at least two sub-pixels of different types, a first sub-pixel type comprising an OLED device including a first type of OLED material and a second sub-pixel type comprising an OLED device including a second type of OLED material, and wherein at least one of said first and second types of sub-pixel comprises a plurality of series-connected OLED devices. Employing series-connected sub-pixels where different types of OLED material are used for a display such as a color, active matrix OLED display facilitates balancing sub-pixel drive voltages and hence enables the production of display devices with improved efficiency.

Claims

1. An organic light emitting diode (OLED) display device, the display device having a plurality of pixels each comprising at least two sub-pixels of different types, a first sub-pixel type comprising an OLED device including a first type of OLED material and a second sub-pixel type comprising an OLED device including a second type of OLED material, and wherein at least one of said first and second types of sub-pixel comprises a plurality of series-connected OLED devices.

2. An OLED display device as claimed in claim 1 wherein a said pixel has a common power supply line for supplying power to said at least two sub-pixels.

3. An OLED display device as claimed in claim 2 wherein an OLED device including said first type of OLED material has a lower drive voltage than an OLED device including said second type of OLED material, and wherein at least said first type of sub-pixel comprises series connected devices.

4. An OLED display device as claimed in claim 1 wherein each of said plurality of series connected devices has substantially the same light emissive area.

5. An OLED display device as claimed in claim 1 wherein said first and second types of OLED material have different peak emission wavelengths.

6. An OLED display device as claimed in claim 1 wherein a said pixel comprises three sub-pixels of different types, a said pixel including a third sub-pixel type comprising an OLED device including a third type of OLED material.

7. An OLED display device as claimed in claim 6 wherein at least two of said sub-pixel types comprise a plurality of series-connected OLED devices.

8. An OLED display device as claimed in claim 1 further comprising a drive transistor associated with each sub-pixel.

9. An OLED display device as claimed in claim 1 wherein a series-connection configuration of OLED devices of said first and second sub-pixel types is determined by a supply or operating voltage for which the display device is designed.

10. An OLED display device as claimed in claim 1 wherein said first type of OLED material comprises a fluorescent material.

11. An OLED display device as claimed in claim 10 wherein said second type of OLED material comprises a phosphorescent OLED material.

12. An OLED display device as claimed in claim 1 wherein said first type of OLED material comprises a polymer material.

13. An OLED display device as claimed in claim 12 wherein said second type of OLED material comprises a dendrimer OLED material or small molecule OLED material.

14. An active matrix color display incorporating the display device of claim 1.

15. A color active matrix OLED display having a plurality of pixels, each pixel comprising a red sub-pixel, a green sub-pixel, and a blue sub-pixel powered from a common supply line and having an associated sub-pixel driver transistor, at least one of said red, green and blue sub-pixels comprising two or more series connected organic light emitting diodes (OLEDs).

16. A color active matrix OLED display as claimed in claim 15 wherein power requirements of said red, green and blue sub-pixels are balanced such that a power requirement of a said pixel including said associated sub-pixel driver transistors, with said red, green and blue sub-pixels illuminated, is less than a power requirement a said pixel would have for substantially the same perceived brightness were none of said sub-pixels to comprise series-connected OLEDs.

17. A method of designing an organic light emitting diode (OLED) display device, the display device having a plurality of pixels each comprising at least two sub-pixels of different types, a first sub-pixel type comprising an OLED device including a first type of OLED material and a second sub-pixel type comprising an OLED device including a second type of OLED material, and wherein at least one of said first and second types of sub-pixel comprises a plurality of series-connected OLED devices, the method comprising selecting whether said first and second types of sub-pixel comprise series-connected OLED devices dependent upon a drive voltage for a said OLED device of a said sub-pixel.