Transistor design for use in the construction of an electronically driven display

• US 6,545,291 B1
• Filed: 08/30/2000
• Issued: 04/08/2003
• Est. Priority Date: 08/31/1999
• Status: Expired due to Fees

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Drzaic, Paul S., Amundson, Karl R., Duthaler, Gregg
• Primary Examiner(s): Nelms, David
• Assistant Examiner(s): PHAM, LY D
• Application Number:
  US09/650,620
• Time in Patent Office: 951 Days
• Field of Search: 257/40, 257/20, 257/4, 257/59, 257/32, 257/72
• US Class Current: 257/40
• CPC Class Codes: H10K 10/462 Insulated gate field-effect transistors [IGFETs]
• CPC Class Codes: H10K 10/466 Lateral bottom-gate IGFETs comprising only a single gate
• CPC Class Codes: H10K 10/468 characterised by the gate dielectrics
• CPC Class Codes: H10K 59/00 Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
• CPC Class Codes: H10K 71/135 using ink-jet printing
• CPC Class Codes: H10K 71/60 Forming conductive regions or layers, e.g. electrodes
• CPC Class Codes: H10K 85/113 Heteroaromatic compounds comprising sulfur or selene, e.g. polythiophene
• CPC Class Codes: H10K 85/114 Poly-phenylenevinylene; Derivatives thereof

Abstract

A transistor having a channel width, W, and a channel length, L, defined by non-rectangular electrodes. The transistor is a thin film field effect transistor having an insulated gate electrode. One of a source and drain electrodes is connected to a display electrode and one is connected to a data line. The source and drain electrodes can be interdigitated to provide a desired W/L ratio. The gate is connected to a select line. An overlap region between a display electrode and a select line for another pixel defines a capacitor. The transistor is fabricated to be situated behind the display electrode so as to maximize an aperture ratio. The design enables the use of conventional printing methods, such as screen printing, ink jet printing, printing through a stencil, flexo-gravure printing and offset printing.

Claims

1. An electronic display drive circuit comprising:

a pixel electrode;

an insulator that is at least 5 micrometers thick disposed adjacent the pixel electrode; and

a transistor placed adjacent the insulator on a side thereof opposite the pixel electrode for addressing the pixel electrode, the transistor comprising a channel defined by a source electrode and a drain electrode, the channel having a length, L, defined as a distance between the source and drain electrodes, said length measuring substantially 10 micrometers or more, and a channel width, W, defined as an effective lateral length measured along the source and drain electrodes;

wherein the channel has a non-rectangular shape that allows a greater channel length than a rectangular channel between the source and drain electrodes, the pixel electrode substantially covers the channel, and the insulator insulates the source electrode and the drain electrode of the transistor from the pixel electrode except for a region of electrical contact between the source electrode of the transistor and the pixel electrode.

2. The electronic display drive circuit of claim 1 wherein the source electrode and the drain electrode are interdigitated.

3. The electronic display drive circuit of claim 1 further comprising a plurality of data lines and select lines, wherein extensions of the data lines form a plurality of drain electrodes and extensions of the select lines form a plurality of gate electrodes.

4. The electronic display drive circuit of claim 1 wherein the channel jointly defined by the source electrode and the drain electrode has a spiral shape.

5. The electronic display drive circuit of claim 1 wherein the semiconductor layer comprises an organic semiconductor layer .

6. The electronic display drive circuit of claim 5 wherein the semiconductor layer comprises a polymer chosen from regioregular poly(3-hexyl thiophene), polythiophene, poly(3-alkylthiophene), alkyl-substituted oligothiophene, polythienylenevinylene, poly(para-phenylenevinylene) and alpha-hexathienylene.

7. The electronic display drive circuit of claim 1 further comprising a storage capacitor comprising a portion of the pixel electrode and a portion of a select line.

8. The electronic display drive circuit of claim 7 wherein the storage capacitor further comprises a portion of the insulator disposed between the portion of the pixel electrode and the portion of the select line.

9. The electronic display drive circuit of claim 1 further comprising a display media comprising one of electrophoretic particles, rotating balls, suspended needles, and bichromal spheres.

10. The electronic display drive circuit of claim 1 further comprising a display media comprising liquid crystals or electroluminescent particles.

11. The electronic display drive circuit of claim 1 further comprising a light emitting diode.