Electro-optic displays

• US 20010030637A1
• Filed: 06/19/2001
• Published: 10/18/2001
• Est. Priority Date: 04/28/1995
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Company (HP Inc.)
• Inventors: Geisow, Adrian Derek, Rudin, John Christopher
• Granted Patent: US 6,590,558 B2
• Time in Patent Office: Days
• US Class Current: 345/97
• CPC Class Codes: G02F 1/134336 Matrix
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 2203/30 Gray scale

Abstract

An electro optic display (10) provides an electrode configuration adjacent each pixel which allows a non-uniform electrical field to be applied across the pixel (22) so that the optical output varies in the direction transverse to the pixel thickness. This allows only part of the pixel to be turned ON, or for shading within the pixel, depending on the characteristics of the electro-optic material. In a preferred embodiment the row and column electrodes (14, 17) are each made up of a group of conductive tracks (12, 18) connected into groups by impedance elements (13, 19). Voltage ramps are applied across the electrodes via input electrodes 15 and 20. A multiphase drive scheme is described for ferro-electric and similar materials in which a number of different voltage ramps are applied to a row in succession, and at each phase the appropriate ramps are applied simultaneously to the column electrodes to build up the required pixel shape over a number of phases.

Claims

1. A display comprising:

a first substrate having thereon a plurality of row electrode means,

a second substrate having thereon a plurality of column electrode means,

a layer of electro-optic material disposed between said first and said second substrate,

row drive means associated with said first substrate for applying a respective selected voltage profile across each row electrode means in a direction transverse to the thickness of said layer,

column drive means associated with said second substrate for applying a respective selected voltage profile across each column electrode means in a direction transverse to the thickness of said layer,

whereby the electrical field in each pixel in the direction transverse to the thickness of the electro-optic layer may be selected to provide a non-uniform optical output.

2. A display according to

claim 1

, wherein each one of said row electrode means and said column electrode means comprises a group of generally parallel electrically conductive tracks.

3. A display according to

claim 2

, wherein each of said row electrode means includes impedance means coupling together the electrically conductive tracks making up said group, and each of said column electrode means includes impedance means coupling together the electrically conducting tracks making up said group.

4. A display according to

claim 3

, wherein each of said impedance means comprises an electrically resistive element contacting each of said electrically conductive tracks.

5. A display according to

claim 3

, wherein a selected adjustable voltage ramp is applied across opposite end regions of each of said impedance means.

6. A display according to any of

claim 3

to 5, wherein the row electrode impedance means are provided on said first substrate and the column electrode impedance means are provided on said second substrate.

7. A display according to any of

claims 3

to

5

, wherein the row electrode impedance means and said column electrode impedance means are provided on respective further substrate means disposed in electrical contact with said first and second substrates respectively.

8. A display according to

claim 3

, wherein each of said impedance means comprises an electrically resistive element contacting at least several groups of conductive tracks, and includes input electrode means intermediate each group.

9. A display according to

claim 1

, wherein said row drive means is inductively or capacitatively coupled to each of said column groups.

10. Apparatus according to any preceding claim, comprising display controller means responsive to image input data to cause said row drive means to apply to each row electrode means in successive phases each of a series of predetermined voltage profiles, and to cause said column drive means to apply to said column electrodes selected voltage profiles to create the desired non-uniform pixel.

11. A display comprising,

first and second substrate means provided to either side of a layer of electro-optic material,

the first substrate having thereon at least one electrically resistive surface,

electrode means for applying selected voltages to respective points or regions across said resistive surface, and

drive means for applying selected voltages to said group or groups to provide across a pixel an electrical field whose magnitude varies in at least one direction transverse to the thickness of the layer of electro-optic material, thereby to provide a non-uniform optical output across said pixel.

12. A display according to

claim 11

, wherein said first substrate has thereon an array of discrete electrically resistive surface elements each defining a pixel, each surface element having associated therewith electrode means comprising a group of at least three electrodes.

13. A display according to

claim 12

, wherein each of said resistive surface elements is generally rectangular, with the electrodes of the group located in the corner regions thereof.

14. A display according to

claim 11

, wherein said first substrate has a continuous electrically resistive surface, and said electrode means comprises a plurality of electrodes for applying selected voltages to respective points or regions on said resistive surface.

15. A display according to

claim 14

, wherein said plurality of electrodes comprises an array of point electrodes at spaced locations across the electrically resistive surface.