Display device and electric apparatus using the same

• US 20070040982A1
• Filed: 10/25/2006
• Published: 02/22/2007
• Est. Priority Date: 01/13/2005
• Status: Active Grant

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Nakano, Shinichi, Teranishi, Tomoko, Miyata, Akio, Niwano, Hiroko
• Granted Patent: US 7,839,555 B2
• Time in Patent Office: Days
• US Class Current: 349/149
• CPC Class Codes: G02B 26/005 based on electrowetting

Abstract

In a display device that includes a display space provided on a display surface side and a liquid sealed inside the display space so as to be operable and is constituted so as to be able to change a display color on the display surface side according to an application of an electric field to the liquid, the liquid is an ionic liquid containing an ambient temperature molten salt combining a cation and an anion. Further, an amount of water blended in the liquid is 0 to 10 parts by weight with respect to 100 parts by weight of the ionic liquid. This makes it possible both to reduce a voltage to be applied to the liquid so as to allow driving at a low voltage and to improve an operation performance.

Claims

1. A display device comprising:

a display space provided on a display surface side; and

a liquid sealed inside the display space so as to be operable;

the display device being constituted so as to be able to change a display color on the display surface side according to an application of an electric field to the liquid;

wherein the liquid is an ionic liquid containing an ambient temperature molten salt combining a cation and an anion, and

an amount of water blended in the liquid is 0 to 10 parts by weight with respect to 100 parts by weight of the ionic liquid.

2. The display device according to claim 1, wherein the liquid is colored in a predetermined color,

a transparent upper layer provided on the display surface side and a light-scattering layer provided such that the display space is formed between the upper layer and the light-scattering layer are provided, and

the display color on the display surface side is changed selectively between the predetermined color resulting from the liquid and white resulting from the light-scattering layer.

3. The display device according to claim 2, comprising a lower layer provided on a non-display surface side of the light-scattering layer,

wherein an upper space constituting the display space is formed between the upper layer and the light-scattering layer, and a lower space that is in communication with the upper space via a communication space provided so as to penetrate through the light-scattering layer is provided between the light-scattering layer and the lower layer, and

the display device comprises

a transparent upper electrode provided on a surface side opposed to the upper space in at least one of the upper layer and the light-scattering layer,

a common electrode provided in the light-scattering layer so as to surround the communication space,

a lower electrode provided on a surface side opposed to the lower space in at least one of the light-scattering layer and the lower layer, and

a driving portion that comprises an upper switch connected between the upper electrode and the common electrode, a lower switch connected between the lower electrode and the common electrode and a power supply and changes the display color on the display surface side by moving the liquid toward the upper space or the lower space according to an operation of opening/dosing the upper switch and the lower switch.

4. The display device according to claim 3, wherein a dielectric layer is layered on surfaces of the upper electrode and the lower electrode.

5. The display device according to claim 2, wherein the light-scattering layer is provided with a liquid storage space whose one end is in communication with the display space, and

the display device comprises

a transparent first electrode provided on a surface side opposed to the display space in at least one of the upper layer and the light-scattering layer,

a second electrode provided in the light-scattering layer so as to surround the liquid storage space, and

a driving portion that has a switch and a power supply connected between the first electrode and the second electrode and changes the display color on the display surface side by moving the liquid toward the display space or the liquid storage space according to an operation of closing/opening the switch.

6. The display device according to claim 5, wherein a dielectric layer is layered on a surface of the first electrode or the second electrode.

7. The display device according to claim 1, wherein the liquid is an ionic liquid that is a nonaqueous solution containing no water.

8. The display device according to claim 1, wherein an electrolyte of the ionic liquid is formed of a 1-1 salt obtained by combining one kind of the cation that is monovalent and one kind of the anion that is monovalent.

9. The display device according to claim 1, wherein the cation is selected from the group consisting of 1,3-dialkylimidazolium cation, N-alkylpyridinium cation, tetraalkylammonium cation and tetraalkylphosphonium cation.

10. The display device according to claim 1, wherein the anion is selected from the group consisting of (AlCl₃)nCl⁻

, (AlBr₃)nBr⁻

, Cl⁻

, Br⁻

, I⁻

, (HF)nF⁻

, (HF)₂F₃⁻

, BF₄⁻

, AlF₄⁻

, PF₆⁻

, AsF₆⁻

, SbF₆⁻

, NbF₆⁻

, TaF₆⁻

, CH₃SO₃⁻

, WF₇⁻

, NO₃⁻

, NO₂⁻

, VOCl₄⁻

, CF₃SO₃⁻

, (CF₃SO₂)₂N⁻

, (CF₃SO₂)₃C⁻

, C₄H₉SO₃⁻

, (CF₃CF₂SO₂)N⁻

, CF₃CO₂⁻

, CF₃CF₂CF₂CO⁻

, CF₃CF₂CF₂SO₃⁻

, (CN)₂N⁻

and CH₃CO₂⁻

,

where n is an integer.

11. The display device according to claim 1, wherein the ionic liquid contains a chemical species selected from the group consisting of chemical compounds represented by the structural formulae below.

12. The display device according to claim 1, wherein the ionic liquid has an ionic conductivity (s/cm) at 25°

C. of equal to or greater than 0.1×

10<sup>−

3</sup>.

13. The display device according to claim 1, wherein the ionic liquid has a viscosity at 25°

C. of equal to or smaller than 300 cp.

14. The display device according to claim 1, wherein the ionic liquid has a melting point ranging from −

4°

C. to −

90°

C.

15. The display device according to claim 1, wherein an insulating fluid that does not mix with the liquid is sealed inside the display space.

16. The display device according to claim 1, wherein a plurality of the display spaces are provided respectively for a plurality of colors allowing a full color display on the display surface side.

17. An electric apparatus comprising:

a display portion for displaying information containing a character and an image;

wherein the display portion is a display device that comprises a display space provided on a display surface side and a liquid sealed inside the display space so as to be operable and is constituted so as to be able to change a display color on the display surface side according to an application of an electric field to the liquid,

the liquid is an ionic liquid containing an ambient temperature molten salt combining a cation and an anion, and

an amount of water blended in the liquid is 0 to 10 parts by weight with respect to 100 parts by weight of the ionic liquid.