Use of a storage capacitor to enhance the performance of an active matrix driven electronic display

• US 7,859,637 B2
• Filed: 12/19/2006
• Issued: 12/28/2010
• Est. Priority Date: 07/21/1999
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Drzaic, Paul S., Kazlas, Peter T., Amundson, Karl R.
• Primary Examiner(s): Dudek; James A
• Application Number:
  US11/612,509
• Publication Number:
  US 20070085818A1
• Time in Patent Office: 1,470 Days
• Field of Search: 349 38- 39
• US Class Current: 349/163
• CPC Class Codes: G02F 1/1334 based on polymer dispersed liquid crystals, e.g. microencapsulated liquid crystals
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/172 based on a suspension of orientable dipolar particles, e.g. suspended particles displays
• CPC Class Codes: G09G 2300/0809 Several active elements per pixel in active matrix panels
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2310/0262 The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167

Abstract

A system and method of use of a storage capacitor to improve the appearance and addressing characteristics of an electronically driven display. The capacitor is formed by the overlap of portions of electrodes used to address different pixels, or by the overlap of an addressing line and a conductor. An insulator layer situated between the capacitor electrodes can be the same insulator layer present in an FET transistor used to address the pixel. Methods of use of capacitors to achieve improved display addressing are disclosed.

Claims

1. An electronic display comprising:

an encapsulated display medium comprising a plurality of electrophoretic particles and a fluid dispersed as a plurality of droplets in a binder;

a plurality of transistors, each transistor having a data line, a gate electrode and a pixel electrode and comprising a layer of insulating material of the transistor situated between a first layer of conductive material of the transistor that forms the gate electrode and a second layer of conductive material of the transistor that forms the data and pixel electrodes, each transistor applying an addressing voltage to the display medium by charging the pixel electrode;

a plurality of storage capacitors, one storage capacitor being associated with each transistor, each storage capacitor comprising a layer of insulating material of the storage capacitor situated between a first layer of conductive material of the storage capacitor and a second layer of conductive material of the storage capacitor, said storage capacitor in electrical communication with the pixel addressed by the transistor for reducing the rate of voltage decay across the pixel after the addressing voltage is terminated, the first layer of conductive material and the layer of insulating material of each storage capacitor being disposed on the opposed side of the pixel electrode of its associated transistor from the display medium; and

a plurality of capacitor lines, each capacitor line being connected to the first layer of conductive material of at least one storage capacitor for applying a voltage thereto, the capacitor lines not being connected to any gate electrode.

2. An electronic display according to claim 1 further comprising a front electrode on the opposed side of the display medium from the pixel electrodes, the capacitor lines being connected to the front electrode.

3. An electronic display according to claim 1 wherein the layer of insulating material of the transistors and the layer of insulating material of the storage capacitors comprise parts of a single continuous layer of insulating material.

4. An electronic display according to claim 1 wherein the second layer of conductive material of each storage capacitor is formed by a part of the pixel electrode of its associated storage capacitor.

15. An electronic display according to claim 1 wherein the layer of insulating material of the transistors and the layer of insulating material a layer of insulating material situated between the storage capacitor electrodes and their associated pixel electrodes comprise parts of a single continuous layer of insulating material.

5. An electronic display comprising:

an encapsulated display medium comprising a plurality of electrophoretic particles and a dyed fluid in at least one capsule;

a plurality of transistors, each transistor having a data line, a gate electrode and a pixel electrode and comprising a layer of insulating material of the transistor situated between a first layer of conductive material of the transistor that forms the gate electrode and a second layer of conductive material of the transistor that forms the data and pixel electrodes, each transistor applying an addressing voltage to the display medium by charging the pixel electrode;

a plurality of storage capacitors, one storage capacitor being associated with each transistor, each storage capacitor comprising a layer of insulating material of the storage capacitor situated between a first layer of conductive material of the storage capacitor and a second layer of conductive material of the storage capacitor, said storage capacitor in electrical communication with the pixel addressed by the transistor for reducing the rate of voltage decay across the pixel after the addressing voltage is terminated, the first layer of conductive material and the layer of insulating material of each storage capacitor being disposed on the opposed side of the pixel electrode of its associated transistor from the display medium; and

a plurality of capacitor lines, each capacitor line being connected to the first layer of conductive material of at least one storage capacitor for applying a voltage thereto, the capacitor lines not being connected to any gate electrode.

6. An electronic display according to claim 5 further comprising a front electrode on the opposed side of the display medium from the pixel electrodes, the capacitor lines being connected to the front electrode.

7. An electronic display according to claim 5 wherein the layer of insulating material of the transistors and the layer of insulating material of the storage capacitors comprise parts of a single continuous layer of insulating material.

8. An electronic display according to claim 5 wherein the second layer of conductive material of each storage capacitor is formed by a part of the pixel electrode of its associated storage capacitor.

9. An electronic display comprising:

an encapsulated display medium comprising a first set of electrophoretic particles and a second set of electrophoretic particles, the first and second sets of electrophoretic particles having contrasting optical properties and differing electrophoretic mobilities, the first and second sets of particles being disposed in a substantially clear fluid in at least one capsule;

a plurality of transistors, each transistor having a data line, a gate electrode and a pixel electrode and comprising a layer of insulating material of the transistor situated between a first layer of conductive material of the transistor that forms the gate electrode and a second layer of conductive material of the transistor that forms the data and pixel electrodes, each transistor applying an addressing voltage to the display medium by charging the pixel electrode;

a plurality of storage capacitors, one storage capacitor being associated with each transistor, each storage capacitor comprising a layer of insulating material of the storage capacitor situated between a first layer of conductive material of the storage capacitor and a second layer of conductive material of the storage capacitor, said storage capacitor in electrical communication with the pixel addressed by the transistor for reducing the rate of voltage decay across the pixel after the addressing voltage is terminated, the first layer of conductive material and the layer of insulating material of each storage capacitor being disposed on the opposed side of the pixel electrode of its associated transistor from the display medium; and

a plurality of capacitor lines, each capacitor line being connected to the first layer of conductive material of at least one storage capacitor for applying a voltage thereto, the capacitor lines not being connected to any gate electrode.

10. An electronic display according to claim 9 further comprising a front electrode on the opposed side of the display medium from the pixel electrodes, the capacitor lines being connected to the front electrode.

11. An electronic display according to claim 9 wherein the layer of insulating material of the transistors and the layer of insulating material of the storage capacitors comprise parts of a single continuous layer of insulating material.

12. An electronic display according to claim 9 wherein the second layer of conductive material of each storage capacitor is formed by a part of the pixel electrode of its associated storage capacitor.

13. An electronic display comprising:

an encapsulated display medium;

a plurality of transistors, each transistor having a data line, a gate electrode and a pixel electrode and comprising a layer of insulating material of the transistor situated between a first layer of conductive material of the transistor that forms the gate electrode and a second layer of conductive material of the transistor that forms the data and pixel electrodes, each transistor applying an addressing voltage to the display medium by charging the pixel electrode;

a plurality of storage capacitor electrodes, one storage capacitor electrode being associated with each transistor, each storage capacitor electrode forming a capacitor with the pixel electrode of its associated transistor with a layer of insulating material being situated between the storage capacitor electrode and its associated pixel electrode, said storage capacitor serving to reduce the rate of voltage decay across the pixel after the addressing voltage is terminated, a portion of the pixel electrode being disposed between its associated storage capacitor electrode and the encapsulated display medium; and

a plurality of capacitor lines, each capacitor line being connected to at least one storage capacitor electrode for applying a voltage thereto, the capacitor lines not being connected to any gate electrode.

14. An electronic display according to claim 13 further comprising a front electrode on the opposed side of the display medium from the pixel electrodes, the capacitor lines being connected to the front electrode.