Molecular devices activated by an electric field for electronic ink and other visual display

• US 20020075420A1
• Filed: 08/17/2001
• Published: 06/20/2002
• Est. Priority Date: 12/14/2000
• Status: Active Grant

• Current Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Original Assignee: Hewlett-Packard Development Company, L.P. (HP Inc.)
• Inventors: Chen, Yong, Williams, R. Stanley, Bratkovski, Alexandre, Vincent, Kent D., Zhang, Xiao-An
• Granted Patent: US 6,805,817 B2
• Time in Patent Office: Days
• US Class Current: 349/41
• CPC Class Codes: B82Y 10/00 Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
• CPC Class Codes: C09D 11/03 characterised by features other than the chemical nature of the binder
• CPC Class Codes: C09D 11/50 Sympathetic, colour changing or similar inks
• CPC Class Codes: C09K 9/02 Organic tenebrescent materials
• CPC Class Codes: G02B 26/026 based on the rotation of particles under the influence of an external field, e.g. gyricons, twisting ball displays based on orientable dipolar particles G02F1/172; based on electrophoresis G02F1/167
• CPC Class Codes: G02F 1/1516 comprising organic material
• CPC Class Codes: G02F 1/174 based on absorption band-shift, e.g. Stark - or Franz-Keldysh effect G02F1/015, G02F1/178 take precedence
• CPC Class Codes: G11C 13/0014 comprising cells based on organic memory material
• CPC Class Codes: G11C 13/02 using elements whose operation depends upon chemical change G11C13/0009 takes precedence
• CPC Class Codes: G11C 13/04 using optical elements ; using other beam accessed elements, e.g. electron or ion beam
• CPC Class Codes: G11C 2213/14 Use of different molecule structures as storage states, e.g. part of molecule being rotated
• CPC Class Codes: G11C 2213/77 Array wherein the memory element being directly connected to the bit lines and word lines without any access device being used
• CPC Class Codes: G11C 23/00 Digital stores characterised by movement of mechanical parts to effect storage, e.g. using balls; Storage elements therefor

Abstract

An electric field activated molecular system, preferably bi-stable, configured within an electric field generated by a pair of electrodes is provided for use, e.g., as electronic ink or other visual displays. The molecular system has an electric field induced band gap change that occurs via a change (reversible or irreversible) of the extent of the electron conjugation via chemical bonding change to change the band gap, wherein in a first state, there is substantial conjugation throughout the molecular system, resulting in a relatively smaller band gap, and wherein in a second state, the substantial conjugation is destroyed, resulting in a relatively larger band gap. The changing of substantial conjugation may be accomplished in one of the following ways: (1) charge separation or recombination accompanied by increasing or decreasing electron localization in the molecule; or (2) change of substantial conjugation via charge separation or recombination and π-bond breaking or making. A primary advantage of the molecular system is improved contrast. Because the colorant of the present invention is molecular and thus effectively monoplanar, there should be no backside reflection or excessive scattering from the colorant. A second advantage of the present invention is improved resolution. Finally, each molecule of the present invention will latch to stabilize one or the other of its color states.

Claims

1. A switchable medium for a visual display comprising an electric field activated molecular system configured within an electric field generated by a pair of electrodes, said molecular system having an electric field induced band gap change that occurs via a reversible or irreversible change of extent of the electron conjugation in the molecule via chemical bonding change to change the band gap, wherein in a first state, there is substantial conjugation throughout the molecular system, resulting in a relatively smaller band gap, and wherein in a second state, the substantial conjugation is destroyed, resulting in a relatively larger band gap.

2. The switchable medium of claim 1 wherein said change of substantial conjugation is accomplished by charge separation or recombination accompanied by increasing or decreasing molecular electronic state localization.

3. The switchable medium of claim 2 wherein said molecular system comprises

4. The switchable medium of claim 2 wherein said molecular system comprises

5. The switchable medium of claim 1 wherein said change of substantial conjugation is accomplished by change of extent of the conjugation of the molecular electronic states via charge separation or recombination and π

-bond breaking or making.

6. The switchable medium of claim 5 wherein said molecular system includes a C—

O bond of a lactone that is labile enough and can undergo a bond breaking or making in the presence of an applied electric field, thereby inducing said change of the electron conjugation via chemical bonding change to change the band gap.

7. The switchable medium of claim 6 wherein said molecular system comprises

8. The switchable medium of claim 6 wherein said molecular system comprises

9. The switchable medium of claim 6 wherein said molecular system comprises

10. The switchable medium of claim 6 wherein said molecular system comprises

11. The switchable medium of claim 1 wherein said molecular system is bi-stable, which provides a non-volatile component.

12. The switchable medium of claim 1 wherein said molecular system has essentially a low activation barrier between different states to provide a fast, but volatile, switch.

13. The switchable medium of claim 1 wherein said molecular system has more than two switchable states, such that optical properties of said molecular system can be tuned by either continuously by application of a decreasing or increasing electric field to form a volatile switch or the color is changed abruptly by the application of voltage pulses to a switch with at least one activation barrier.

14. The switchable medium of claim 1 wherein said molecular system changes between a transparent state and a colored state.

15. The switchable medium of claim 1 wherein said molecular system changes between one colored state and another colored state.

17. The electronic ink of claim 16 wherein said change of substantial conjugation is accomplished by charge separation or recombination accompanied by increasing or decreasing molecular electronic state localization.

19. The electronic ink of claim 17 wherein said molecular system comprises

20. The switchable medium of claim 16 wherein said change of substantial conjugation is accomplished by change of extent of the conjugation of the molecular electronic states via charge separation or recombination and π

-bond breaking or making.

21. The switchable medium of claim 20 wherein said molecular system includes a C—

O bond of a lactone that is labile enough and can undergo a bond breaking or making in the presence of an applied electric field, thereby inducing said change of the electron conjugation via chemical bonding change to change the band gap.

22. The switchable medium of claim 21 wherein said molecular system comprises

23. The electronic ink of claim 21 wherein said molecular system comprises

24. The electronic ink of claim 21 wherein said molecular system comprises

25. The electronic ink of claim 21 wherein said molecular system comprises

26. The electronic ink of claim 16 wherein said molecular system is bi-stable, which provides a non-volatile component.

27. The electronic ink of claim 16 wherein said molecular system has essentially a low activation barrier between different states to provide a fast, but volatile, switch.

28. The electronic ink of claim 16 wherein said molecular system has more than two switchable states, such that optical properties of said molecular system can be tuned by either continuously by application of a decreasing or increasing electric field to form a volatile switch or the color is changed abruptly by the application of voltage pulses to a switch with at least one activation barrier.

29. The electronic ink of claim 16 wherein said molecular system changes between a transparent state and a colored state.

30. The electronic ink of claim 16 wherein said molecular system changes between one colored state and another colored state.

16. An electronic ink including an electric field activated molecular system configured within an electric field generated by a pair of electrodes, said molecular system having an electric field induced band gap change that occurs via a reversible or irreversible change of extent of the electron conjugation in the molecule via chemical bonding change to change the band gap, wherein in a first state, there is substantial conjugation throughout the molecular system, resulting in a relatively smaller band gap, and wherein in a second state, the substantial conjugation is destroyed, resulting in a relatively larger band gap.

18. The electronic ink of 17 wherein said molecular system comprises