Display device with thin film transistor (TFT) and organic semiconductor film in a luminescent element

• US 6,194,837 B1
• Filed: 02/26/1999
• Issued: 02/27/2001
• Est. Priority Date: 07/02/1997
• Status: Expired due to Term

• Current Assignee: Intellectual Keystone Technology LLC
• Original Assignee: Seiko Epson Corporation (Seiko Group)
• Inventors: Ozawa, Tokuroh
• Primary Examiner(s): VU, DAVID HUNG
• Application Number:
  US09/242,927
• Time in Patent Office: 732 Days
• Field of Search: 315/169.1, 315/169.3, 313/495, 313/505, 313/506
• US Class Current: 315/169.1
• CPC Class Codes: G09G 2300/0417 Special arrangements specific to the use of low carrier mobility technology
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0439 Pixel structures
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0876 Supplementary capacities in pixels having special driving circuits and electrodes instead of being connected to common electrode or ground; Use of additional capacitively coupled compensation electrodes
• 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 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 3/3225 using an active matrix
• CPC Class Codes: H10K 2102/351 Thickness
• CPC Class Codes: H10K 50/865 comprising light absorbing layers, e.g. light-blocking layers
• CPC Class Codes: H10K 59/121 characterised by the geometry or disposition of pixel elements
• CPC Class Codes: H10K 59/122 Pixel-defining structures or layers, e.g. banks
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/8792 comprising light absorbing layers, e.g. black layers

Abstract

The invention provides a display device in which parasitic capacitance associated with data lines and driving circuits is prevented using a bank layer whose primary purpose is to define areas on a substrate in which an organic semiconductor film is formed. When the organic semiconductor film for forming a luminescent element such as an electroluminescent element or an LED is formed is formed in pixel regions (7), the organic semiconductor film is formed in the areas surrounded by the bank layer (bank) formed of a black resist. The bank layer (bank) is also formed between an opposite electrode (op) and data lines (sig) for supplying an image signal to first TFTs (20) and holding capacitors (cap) in the pixel regions (7) thereby preventing parasitic capacitance associated with the data lines (sig).

Claims

1. A display device comprising elements formed on a substrate, said elements including:

a plurality of scanning lines;

a plurality of data lines extending in a direction crossing a direction in which said scanning lines extend;

a plurality of common power supply lines extending in a direction parallel to said data lines; and

pixel regions formed in the shape of a matrix defined by said data lines and said scanning lines, each of said pixel regions including;

a first thin film transistor having a first gate electrode to which a scanning signal is supplied via one of the scanning lines;

a holding capacitor for holding an image signal supplied from a corresponding data line via said first thin film transistor;

a second thin film transistor having a second gate electrode to which said image signal held by said holding capacitor is supplied; and

a luminescent element including an organic semiconductor film formed between a pixel electrode provided in each of said pixel regions and an opposite electrode extending across the data lines such that said opposite electrode faces the plurality of pixel electrodes, said luminescent element being adapted to emit light when said organic semiconductor film is driven by a driving current which flows between said pixel electrode and said opposite electrode when said pixel electrode is electrically connected to a corresponding common power supply line via said second thin film transistor,

light emitting areas of said organic semiconductor film being surrounded by a bank layer made up of an insulating film having a thickness greater than that of said organic semiconductor film, said bank layer being formed such that said data lines are, at least partly, covered with said bank layer.

2. The display device according to claim 1, further comprising at least one of a first driving circuit for outputting said image signal over said data lines and a second driving circuit for outputting said scanning signal over said scanning lines, and said at least one of said driving circuits being covered with said bank layer.

3. The display device according to claim 1, said organic semiconductor film being formed by means of an ink-jet technique in the areas surrounded by said bank layer, and said bank layer being a water repellent film.

4. The display device according to claim 1, said organic semiconductor film being formed by means of an ink-jet technique in the areas surrounded by said bank layer, and said bank layer having a thickness equal to or greater than 1 μ

m.

5. The display device according to claim 1, an area of each said pixel electrode overlapping the corresponding first thin film transistor or second thin film transistor being covered with said bank layer.

6. The display device according to claim 1, said bank layer being formed of a black resist film.

7. The display device according to claim 1, a resistance of said common power supply lines per unit length being smaller than a resistance of said data lines per unit length.

8. The display device according to claim 1, said common power supply lines and said data lines being made of a same material and having a same thickness and a width of said common power supply lines being greater than a width of said data lines.

9. The display device according to claim 1, pixel regions located at both sides of each of said common power supply lines being supplied with said driving current via said respective common power supply line, and data lines extending over said pixel regions on the respective sides of said common power supply line.

10. The display device according to claim 9, further comprising an interconnection layer formed between the two data lines extending, across said pixel regions, on the sides of each of said common power supply lines.

11. The display device according to claim 1, a center-to-center pitch of the organic semiconductor film areas being equal in any of the pixel regions located along a direction parallel to a direction in which said scanning lines extend.

12. A display device comprising elements formed on a substrate, said elements including:

a plurality of scanning lines;

a plurality of data lines extending in a direction perpendicular to a direction in which said scanning lines extend;

a plurality of common power supply lines extending in a direction parallel to said data lines;

at least one of a first driving circuit for outputting an image signal over said data lines and a second driving circuit for outputting a scanning signal over said scanning lines; and

pixel regions formed in the shape of a matrix defined by said data lines and said scanning lines, each of said pixel regions including;

a first thin film transistor having a first gate electrode to which the scanning signal is supplied via one of the scanning lines;

a holding capacitor for holding the image signal supplied from a corresponding data line via said first thin film transistor;

a second thin film transistor having a second gate electrode to which said image signal held by said holding capacitor is supplied; and

a luminescent element including an organic semiconductor film formed between a pixel electrode provided in each of said pixel regions and an opposite electrode extending across the data lines such that said opposite electrode faces the plurality of pixel electrodes, said luminescent element being adapted to emit light when said organic semiconductor film is driven by a driving current which flows between said pixel electrode and said opposite electrode when said pixel electrode is electrically connected to a corresponding common power supply line via said second thin film transistor,

light emitting areas of said organic semiconductor film being surrounded by a bank layer made up of an insulating film having a thickness greater than that of said organic semiconductor film, said bank layer being formed such that said at least one of said driving circuits are covered with said bank layer.

13. The display device according to claim 12, said organic semiconductor film being formed by means of an ink-jet technique in the areas surrounded by said bank layer, and said bank layer being a water repellent film.

14. The display device according to claim 12, said organic semiconductor film being formed by means of an ink-jet technique in the areas surrounded by said bank layer, and said bank layer having a thickness equal to or greater than 1 μ

m.

15. The display device according to claim 12, an area of each said pixel electrode overlapping the corresponding first thin film transistor or second thin film transistor being covered with said bank layer.

16. The display device according to claim 12, said bank layer being formed of a black resist film.

17. The display device according to claim 12, a resistance of said common power supply lines per unit length being smaller than a resistance of said data lines per unit length.

18. The display device according to claim 12, said common power supply lines and said data lines being made of a same material and having a same thickness and a width of said common power supply lines being greater than a width of said data lines.

19. The display device according to claim 12, pixel regions located at both sides of each of said common power supply lines being supplied with said driving current via said respective common power supply line, and data lines extending over said pixel regions on the respective sides of said common power supply line.

20. The display device according to claim 19, further comprising an interconnection layer formed between the two data lines extending, across said pixel regions, on the sides of each of said common power supply lines.

21. The display device according to claim 12, a center-to-center pitch of the organic semiconductor film areas being equal in any of the pixel regions located along a direction parallel to a direction in which said scanning lines extend.