COLORED ELECTROPHORETIC DISPLAYS

• US 20140340430A1
• Filed: 05/14/2014
• Published: 11/20/2014
• Est. Priority Date: 05/14/2013
• Status: Active Grant

• Current Assignee: E Ink Holdings Incorporated
• Original Assignee: E Ink Holdings Incorporated
• Inventors: Telfer, Stephen J., Bouchard, Alain, Ladavac, Kosta, Lattes, Ana L., Paolini, Richard J. Jr., Yezek, Lee, Crounse, Kenneth R., Kruse, J. Ryan, Feick, Jason D., Bull, Stephen, Herb, Craig A. Jr., Morrison, Jennifer M., Regan, Michael Thomas, Slominski, Luke M., Hoogeboom, Christopher L., Miller, David Darrell
• Granted Patent: US 9,697,778 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G02F 1/167 by electrophoresis
• CPC Class Codes: G02F 1/1685 Operation of cells; Circuit arrangements affecting the entire cell
• CPC Class Codes: G02F 2001/1678 characterised by the composition or particle type
• CPC Class Codes: G09G 2310/06 Details of flat display driving waveforms
• CPC Class Codes: G09G 2310/068 Application of pulses of alternating polarity prior to the drive pulse in electrophoretic displays
• 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

An electrophoretic medium comprises a fluid and at least one species of particles disposed, When a first addressing impulse is applied to the medium, the first species of particles move in one direction relative to the electric field, but when a second addressing impulse, larger than the first addressing impulse, is applied to the medium, the first species of particles move in the opposed direction relative to the electric field.

Claims

1. An electrophoretic medium comprising a fluid and at least a first species of particles disposed in the fluid, the first species of particles being such that when a first addressing impulse is applied to the medium, the first species of particles move in one direction relative to the electric field, but when a second addressing impulse larger than the first addressing impulse but having the same polarity, is applied to the medium, the first species of particles move in the opposed direction relative to the electric field.

2. An electrophoretic medium according to claim 1 wherein the fluid is colored and the electrophoretic medium comprises a second species of particles having a color different from the first species of particles and moving in the same direction relative to the electric field under both the first and second addressing impulses.

3. An electrophoretic medium according to claim 2 wherein the second species of particles move in the opposed direction from the first species of particles under the first addressing impulse and in the same direction as the first species of particles under the second addressing impulse.

4. An electrophoretic medium according to claim 2 wherein one of the dyed fluid and the two species of particles has one of the additive primary colors and another of the dyed fluid and the two species of particles has the complementary subtractive primary color.

5. An electrophoretic medium according to claim 4 wherein the first species of particles is white, one of the dyed fluid and the second species of particles has one of the additive primary colors and the other of the dyed fluid and the second species of particles has the complementary subtractive primary color.

6. An electrophoretic medium according to claim 1 wherein the electrophoretic medium comprises second and third species of particles having colors different from the first species of particles and from each other, the second and third species of particles bearing charges of opposite polarities and the first species of particles bearing a charge of the same polarity as the third species of particles, such that when the first addressing impulse is applied in one direction, one surface of the electrophoretic medium displays the color of the third species of particle, when the first addressing impulse is applied in the opposed direction, said one surface of the display displays a mixture of the colors of the first and second particles, while when the second addressing impulse is applied in said one direction, said one surface displays a mixture of the colors of the first and third particles, and when the second addressing impulse is applied in the opposed direction, said one surface displays the color of the second particles.

7. An electrophoretic medium according to claim 6 wherein the fluid is uncolored.

8. An electrophoretic medium according to claim 7 wherein the second and third species of particles are white and black.

9. An electrophoretic medium according to claim 6 wherein, upon application of a third addressing impulse greater than the second addressing impulse, the first, second and third particles all travel in the same direction relative to the electric field.

10. An electrophoretic medium according to claim 9 wherein the fluid is colored with a color different from the colors of the first, second and third species of particles.

11. An electrophoretic medium according to claim 10 wherein one of the species of particles is white and the colors of the other two species of particles and the fluid are selected from yellow, cyan and magenta, in any order.

12. An electrophoretic medium according to claim 1 wherein the particles and the fluid are confined within a plurality of capsules or microcells.

13. An electrophoretic medium according to claim 1 wherein the particles and the fluid are present as a plurality of discrete droplets surrounded by a continuous phase comprising a polymeric material.

14. A front plane laminate, double release sheet, inverted front plane laminate or electrophoretic display comprising an electrophoretic medium according to claim 1.

15. An electrophoretic display comprising an electrophoretic medium according to claim 1 and at least one electrode arranged to apply an electric field to the electrophoretic medium.

16. An electronic book reader, portable computer, tablet computer, cellular telephone, smart card, sign, watch, shelf label or flash drive incorporating an electrophoretic medium according to claim 15.

17. A method of driving an electrophoretic medium comprising a fluid and at least a first species of particles disposed in the fluid, the method comprising:

(a) applying a first addressing impulse to the medium, thereby causing the first species of particles to move in one direction relative to the electric field; and

(b) applying a second addressing impulse, larger than the first addressing impulse but having the same polarity, to the medium, thereby causing the first species of particles to move in the opposed direction relative to the electric field.

18. A method according to claim 17 wherein the fluid is colored and the electrophoretic medium comprises a second species of particles having a color different from the first species of particles, and wherein the second species of particles move in the same direction relative to the electric field under both the first and second addressing impulses.

19. A method according to claim 17 wherein the electrophoretic medium comprises second and third species of particles having colors different from the first species of particles and from each other, the second and third species of particles bearing charges of opposite polarities and the first species of particles bearing a charge of the same polarity as the third species of particles, the method comprising:

(a) applying the first addressing impulse in one direction, thereby causing one surface of the electrophoretic medium displays the color of the third species of particle;

(b) applying first addressing impulse in the opposed direction, thereby causing said one surface of the display to display a mixture of the colors of the first and second particles;

(c) applying the second addressing impulse in said one direction, thereby causing said one surface to display a mixture of the colors of the first and third particles; and

(d) applying the second addressing impulse in the opposed direction, thereby causing said one surface to display the color of the second particles.

20. A method according to claim 19 further comprising applying to the medium a third addressing impulse greater than the second addressing impulse, thereby causing the first, second and third particles all to travel in the same direction relative to the electric field.

21. A method according to claim 19 wherein step (b) is effected by applying to electrophoretic medium a waveform comprising a series of short voltage pulses of one polarity, each except the last of the short voltage pulses being followed by a longer voltage pulse of the opposite polarity.

22. An electrophoretic display capable of rendering multiple different colors, the display comprising an electrophoretic medium comprising a fluid and a plurality of particles disposed in the fluid, the display further comprising first and second electrodes disposed on opposed sides of the electrophoretic medium, wherein upon application of a first addressing impulse to the electrophoretic medium the particles move towards the first electrode, but upon application of a second addressing impulse, larger than, but of the same polarity as, the first addressing impulse, the particles move towards the second electrode.

23. An electrophoretic display according to claim 22 wherein, upon application of the first addressing impulse the particles move towards the more positive electrode but upon application of the second addressing impulse the particles move towards the more negative electrode.

24. An electrophoretic display according to claim 23 further comprising a second type of particles which have a color different from the first type of particles and which move towards the more negative electrode upon application of either the first or second addressing impulse.

25. An electrophoretic medium comprising a fluid and first, second and third species of particles disposed in the fluid, the first species of particles bearing charges of one polarity, and the second and third species of particles bearing charges of the opposite polarity, such that when a first addressing impulse is applied to the electrophoretic medium, the first and third species of particles move in one direction relative to the electric field and the second species of particles move in the opposed direction relative to the electric field, but when a second addressing impulse, larger than the first addressing impulse but of the same polarity, is applied to the electrophoretic medium, the first species of particles move in said one direction relative to the electric field, while the second and third species of particles move in said opposed direction relative to the electric field.

26. An electrophoretic medium according to claim 25 wherein the second species of particles bears a polymeric surface treatment and the third species of particles bears either no polymeric surface treatment or a a polymeric surface treatment having a lower mass coverage per unit area of the particle surface than the second species of particles.

27. An electrophoretic display capable of rendering multiple different colors, the display comprising an electrophoretic medium and first and second electrodes disposed on opposed sides of the electrophoretic medium, the electrophoretic medium comprising a fluid and a plurality of a first species of particles having a negative charge, a plurality of a second species of particles having a positive charge, and a plurality of a third species of particles having a positive charge, wherein the particle pair interactions, both Coulombic and attractive non-Coulombic, are less between the first species of particles and the second species of particles than between the first species of particles and the third species of particles, such that with a first addressing impulse the particles of the first and third species move towards the more positive electrode and the particles of the second species move towards the more negative electrode, but with a second addressing impulse larger than the first addressing impulse, the particles of the first species move towards the more positive electrode or remain in the vicinity of the more positive electrode and the particles of the third species move towards the more negative electrode, while the particles of the second species remain in the vicinity of the more negative electrode.

28. An electrophoretic medium comprising a fluid, dyed a first color, and first, second and third species of particles disposed in the fluid, the first species of particles being light-scattering, and bearing charges of one polarity, while the second and third species of particles are non-light scattering, are of second and third colors respectively different from the first color and from each other, and bear charges of the opposite polarity, the characteristics of the first, second and third species of particles being such that the particle-particle interactions are less between the particles of the first species and the particles of the second species than between the particles of the first species and the particles of the third species, such that when a first addressing impulse is applied to the electrophoretic medium, the first and third species of particles move in one direction relative to the electric field and the second species of particles move in the opposed direction relative to the electric field, but when a second addressing impulse, larger than the first addressing impulse but of the same polarity is applied to the electrophoretic medium, the first species of particles move in said one direction relative to the electric field, while the second and third species of particles move in said opposed direction relative to the electric field, and when a third addressing impulse, larger than the second addressing impulse but of the same polarity is applied to the electrophoretic medium, the first species of particles move in said opposed direction relative to the electric field, while the second and third species of particles continue to move in said opposed direction relative to the electric field.

29. An electrophoretic display capable of rendering multiple different colors, the display comprising an electrophoretic medium and first and second electrodes disposed on opposed sides of the electrophoretic medium, the electrophoretic medium comprising a fluid dyed a first color;

a plurality of a first species of light-scattering particles having a negative charge;

a plurality of a second species of non-light scattering particles having a second color and a positive charge; and

a plurality of a third species of non-light-scattering particles having a third color and a positive charge, the particle pair interactions, both Coulombic and attractive non-Coulombic, being less between the first species of particles and the second species of particles than between the first species of particles and the third species of particles, such that when a first addressing impulse is applied to the display, the first and third species of particles move towards the more positive electrode and the pigment particles of the second type move towards the more negative electrode, but when a second addressing impulse, larger than the first addressing impulse, is applied to the display, the first species of particles move towards the more positive electrode or remain in the vicinity of the more positive electrode and the third species of particles move towards the more negative electrode, while the second species of particles remain in the vicinity of the more negative electrode, and when a third addressing impulse, larger than the second addressing impulse, is applied to the display, the first species of particles move towards the more negative electrode.

30. An electrophoretic medium comprising a fluid and at least one type of charged particle disposed in the fluid and capable of moving through the fluid when an electric field is applied to the medium, the medium further comprising a charge-control adjuvant capable of imparting a more positive charge to the charged particles, wherein the charge-control adjuvant is a metal salt of a carboxylic acid, wherein the metal is chosen from the group consisting of lithium, magnesium, calcium, strontium, rubidium, barium, zinc, copper, tin, titanium, manganese, iron, vanadium, and aluminum.