Photoluminescent electrophoretic display

• US 7,015,893 B2
• Filed: 01/31/2003
• Issued: 03/21/2006
• Est. Priority Date: 01/31/2003
• Status: Expired due to Fees

• Current Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Coleman, Zane, Li, Zili
• Primary Examiner(s): YANG, RYAN R
• Application Number:
  US10/356,003
• Publication Number:
  US 20040150613A1
• Time in Patent Office: 1,145 Days
• Field of Search: 345/107, 359/296, 250/458.1, 250/461.1, 430/32
• US Class Current: 345/107
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1677 Structural association of cells with optical devices, e.g. reflectors or illuminating devices
• 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

Electrophoretic displays (100, 400) comprise suspensions in one or more bodies of liquid (116, 418, 426) of reflective particles (118, 420), and photoluminescent particles (120, 422). The one or more bodies of liquid are located between a front wall (104, 402) and a back wall (102, 404). Electrodes (128, 129, 410, 412) and optionally a transparent ground plane layer (124) are provided for applying electric fields to the suspensions according to image information. The reflective particles and the photoluminescent particles are characterized by the electrophoretic mobilities of the same sign, and therefore move in the same direction in response to applied fields. A source of radiation (140, 428) capable of exciting photoluminescence of the photoluminescent particles is optically coupled to the liquid suspensions. An optical filter layer is optionally located at the front of the displays. The display is capable of operating under a wide range of ambient light conditions.

Claims

1. An electrophoretic display comprising:

a first wall; and

a second light transmissive wall spaced from the first wall;

one or more bodies of liquid located between the first wall and the second wall;

a plurality of first cohesive bodies that are light reflective and are characterized by electrophoretic mobility of a particular sign suspended In at least a subset of the one or more bodies of liquid;

a plurality of second cohesive bodies that are photoluminescent and are characterized by electrophoretic mobility of the particular sign suspended in at least a subset of the one or more bodies of liquid;

one or more electrodes located proximate the one or more bodies of liquid for imagewise application of electric fields to the one or more bodies of liquid; and

a source of radiation capable of exciting photoluminescence of the plurality of second cohesive bodies optically coupled to the plurality of second cohesive bodies,

wherein the liquid is transmissive of radiation capable of exciting photoluminescence of the second cohesive bodies, and blocks radiation emitted by photoluminescence of the second cohesive bodies, and

wherein the liquid comprises nigrosin.

2. An electrophoretic display comprising:

a first wall; and

a second light transmissive wall spaced from the first wall;

one or more bodies of liquid located between the first wall and the second wall;

a plurality of first cohesive bodies that are light reflective and are characterized by electrophoretic mobility of a particular sign suspended in at least a subset of the one or more bodies of liquid;

a plurality of second cohesive bodies that are photoluminescent and are characterized by electrophoretic mobility of the particular sign suspended in at least a subset of the one or more bodies of liquid;

one or more electrodes located proximate the one or more bodies of liquid for imagewise application of electric fields to the one or more bodies of liquid; and

a source of radiation capable of exciting photoluminescence of the plurality of second cohesive bodies optically coupled to the plurality of second cohesive bodies,

wherein the one or more electrodes comprise an array of electrodes that are transmissive of radiation capable of exciting photoluminescence of the second cohesive bodies, and

wherein the source of radiation is optically coupled to the second plurality of cohesive bodies through the array of electrodes.

3. The electrophoretic display according to claim 2 wherein:

the array of electrodes comprise indium tin oxide.

4. The electrophoretic display according to claim 2 wherein:

the array of electrodes comprises a transparent conductive polymer.

5. The electrophoretic display according to claim 2 wherein:

the source of radiation comprises an emitting diode that emits radiation in the range of 370 to 405 nanometers;

and the second cohesive bodies comprise one or more phosphors selected from the group consisting of;

(Ba_1-x-y-z,Ca_X,Sr_Y,Eu_Z)₂(Mg_1-w,Zn_W)Si₂O₇,

wherein

X+Y+Z<

=1;

Z>

0; and

0.05<

=W<

=0.50;

(Sr_X,Ba_Y,Ca_Z)₅(PO₄)₃Cl;

Eu^2+;

wherein;

X+Y+Z=1; and

Y₂O₃;

Eu³⁺,Bi³⁺.

6. The electrophoretic display according to claim 2 further wherein:

the army of electrodes is located proximate the first wall; and

the electrophoretic display further comprises;

an optical filter layer that transmits light in the visible portion of the spectrum; and

blocks radiation capable of exciting photoluminescence of the second cohesive bodies said optical filter layer located proximate the second light transmissive wall.

12. The electrophoretic display according to claim 2, wherein the plurality of second cohesive bodies comprise core particles that are coated with photoluminescent material.

13. The electrophoretic display according to claim 2, wherein a ratio of the surface area of the plurality of first cohesive bodies to the surface area of the plurality of second cohesive bodies is at least one to one.

14. The electrophoretic display according to claim 2, wherein the source of radiation comprises an electroluminescent lamp.

15. The electrophoretic display according to claim 2, wherein the liquid is transmissive of radiation capable of exciting photoluminescence of the second cohesive bodies, and blocks radiation emitted by photoluminescence of the second cohesive bodies.

16. The electrophoretic display according to claim 2, wherein the source of radiation comprises an emitting diode that emits radiation in the range of 320 to 405 nanometers.

17. The electrophoretic display according to claim 2, wherein the first wall transmits ultraviolet light.

18. The electrophoretic display according to claim 2, wherein the second wall substantially blocks ultraviolet light.

19. The electrophoretic display according to claim 2, wherein the plurality of second cohesive particles comprise core particles that are reflective in the visible spectrum.

20. The electrophoretic display according to claim 19, wherein the first cohesive particles and the core particles comprise titanium oxide.

7. An electrophoretic display comprising:

a first wall; and

a second light transmissive wall spaced from the first wall;

one or more bodies of liquid located between the first wall and the second wall;

a plurality of visible light reflecting, photoluminescent cohesive bodies suspended in the one or more bodies of liquid, said reflecting, photoluminescent cohesive bodies comprising reflective phosphor particles;

one or more electrodes located proximate the one or more bodies of liquid for imagewise application of electric fields to the one or more bodies of liquid; and

a source of radiation capable of exciting photoluminescence of the plurality of visible light reflecting, photoluminescent cohesive bodies optically coupled to the plurality of visible light reflecting, photoluminescent cohesive bodies; and

an optical filter layer that transmits light in the visible portion of the spectrum; and

blocks radiation capable of exciting photoluminescence of the light reflecting, photoluminescent cohesive bodies said optical filter layer located proximate the second light transmissive wall.

8. An electrophoretic display comprising:

a first wall; and

a second light transmissive wall spaced from the first wall;

one or more bodies of liquid located between the first wall and the second wall;

plurality of visible light reflecting, photoluminescent cohesive bodies suspended in the one or more bodies of liquid, said reflecting, photoluminescent cohesive bodies comprising reflective phosphor particles;

one or more electrodes located proximate the one or more bodies of liquid for imagewise application of electric fields to the one or more bodies of liquid; and

a source of radiation capable of exciting photoluminescence of the plurality of visible light reflecting, photoluminescent cohesive bodies optically coupled to the plurality of visible light reflecting, photoluminescent cohesive bodies,

wherein the liquid is transmissive of radiation capable of exciting photoluminescence of the light reflecting, photoluminescent cohesive bodies, and blocks radiation emitted by photoluminescence of the light reflecting, photoluminescent cohesive bodies, and

wherein the liquid comprises nigrosin.

9. An electrophoretic display comprising:

a first wall; and

a second light transmissive wall spaced from the first wall;

one or more bodies of liquid located between the first wall and the second wall;

a plurality of visible light reflecting, photoluminescent cohesive bodies suspended in the one or more bodies of liquid, said reflecting, photoluminescent cohesive bodies comprising reflective phosphor particles;

one or more electrodes located proximate the one or more bodies of liquid for imagewise application of electric fields to the one or more bodies of liquid; and

a source of radiation capable of exciting photoluminescence of the plurality of visible light reflecting, photoluminescent cohesive bodies optically coupled to the plurality of visible light reflecting, photoluminescent cohesive bodies,

wherein the one or more electrodes comprise an array of electrodes that are transmissive of radiation capable of exciting photoluminescence of the light reflecting, photoluminescent cohesive bodies; and

the source of radiation is optically coupled to the light reflecting, photoluminescent cohesive bodies through the array of electrodes.

10. The electrophoretic display according to claim 9 wherein:

the array of electrodes comprise indium tin oxide.

11. The electrophoretic display according to claim 9 wherein:

the array of electrodes comprises a transparent conductive polymer.