High density electrochromic display

• US 5,847,860 A
• Filed: 07/17/1996
• Issued: 12/08/1998
• Est. Priority Date: 07/17/1996
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Hougham, Gareth Geoffrey, Lowe, Anthony Cyril
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): BEY, DAWN MARIE
• Application Number:
  US08/684,767
• Time in Patent Office: 874 Days
• Field of Search: 359/267, 359/274, 359/270
• US Class Current: 359/267
• CPC Class Codes: G02F 1/1506 caused by electrodeposition, e.g. electrolytic deposition of an inorganic material on or close to an electrode
• CPC Class Codes: G02F 1/157 Structural association of cells with optical devices, e.g. reflectors or illuminating devices
• CPC Class Codes: G02F 2001/1552 Inner electrode, e.g. the electrochromic layer being sandwiched between the inner electrode and the support substrate

Abstract

An electrochromic display and a method for making thereof are disclosed. The display has isolated and perforated reflectors separating an electrolyte confined between two electrodes. The front electrode is transparent. The reflector eliminates the need to include pigment particles in the electrolyte to mask the black rear electrode and to provide a desired color background. The pigment free electrolyte is thinner than a pigmented electrolyte. The reflector reflects light back to the transparent electrode thus masking the rear electrode and providing a background color other than black. When the rear electrode is driven by a drive circuit, ions of the electrolyte and current pass through the reflector towards the front electrode, where a coloration reaction occurs to form an image. The electrochromic display is thin, has high resolution, and does not exhibit image spreading and distortion.

Claims

1. A method for forming a display comprising the steps of:

(a) forming a counter electrode on a rear display;

(b) forming a first layer of electrolyte on said counter electrode;

(c) forming a reflector on said first layer of electrolyte;

(d) forming a second layer of electrolyte, said second layer of electrolyte stressing said reflector to form voids therein; and

(e) forming a front electrode on said second layer of electrolyte.

2. The method of claim 1, further comprising, after said step (e), the step of forming a diffuser over said front electrode.

3. The method of claim 1, further comprising, after said step (b), the step of dehydrating said first layer of electrolyte.

4. The method of claim 1, further comprising, after said step (d), the steps of:

forming a second reflector over said second layer of electrolyte;

forming voids in said second reflector, said second reflector voids being offset from said first reflector void; and

forming a third layer of electrolytes over said second reflector.

5. The method of claim 1, further comprising, after said step (d), the steps of:

forming a mask over said reflector;

patterning said mask to expose portions of said reflector;

etching said exposed portions of said reflectors to form holes therein; and

removing said patterned mask.

6. The method of claim 1, further comprising, after said step (d), the step of etching holes through said reflector.

7. A display comprising:

an electrode which is substantially transparent;

a counter electrode spaced transversely and separated from said electrode by a predetermined distance;

a reflector located between said electrode and counter electrode, said reflector being electrically isolated and ion permeable; and

an electrolyte having ions and being interposed between said electrode and counter electrode,

said predetermined distance being approximately between 50 microns to 100 microns to prevent image spreading from said counter electrode to said electrode.

8. A display comprising:

an electrode which is substantially transparent;

a counter electrode spaced transversely and separated from said electrode by a predetermined distance;

a reflector located between said electrode and counter electrode, said reflector being electrically isolated and being ion permeable due to one of cracks formed under tensile stress and holes etched therein; and

an electrolyte having ions and being interposed between said electrode and counter electrode,

said predetermined distance being selected to prevent image spreading from said counter electrode to said electrode.

9. A display comprising:

an electrode which is substantially transparent;

a counter electrode spaced transversely and separated from said electrode by a predetermined distance;

a reflector located between said electrode and counter electrode, said reflector being electrically isolated and ion permeable, and having a plurality of first voids for ion movement therethrough;

a second reflector having a plurality of second voids which are offset from said first voids to increase reflectivity, said second reflector being located between said electrode and counter electrode; and

an electrolyte having ions and being interposed between said electrode and counter electrode,

said predetermined distance being selected to prevent image spreading from said counter electrode to said electrode.

10. A display comprising:

an electrode which is substantially transparent;

a diffuser located over said electrode;

a counter electrode spaced transversely and separated from said electrode by a predetermined distance;

a reflector located between said electrode and counter electrode, said reflector being electrically isolated and ion permeable; and

an electrolyte having ions and being interposed between said electrode and counter electrode,

said predetermined distance being selected to prevent image spreading from said counter electrode to said electrode.

11. The display of claim 10, wherein said diffuser is a holographic diffuser which diffuses light incident thereon.

12. A display comprising:

an electrode which is substantially transparent;

a counter electrode spaced transversely and separated from said electrode by a Predetermined distance;

a reflector located between said electrode and counter electrode, said reflector being electrically isolated and ion permeable;

an electrolyte having ions and being interposed between said electrode and counter electrode; and

inter-pixel isolation barriers interposed between said electrode and counter electrode, said barriers confining said electrolyte between said electrode and counter electrode, and said predetermined distance being selected to prevent image spreading from said counter electrode to said electrode.