Protective overlayer material and electro-optical coating using same

• US 5,530,581 A
• Filed: 05/31/1995
• Issued: 06/25/1996
• Est. Priority Date: 05/31/1995
• Status: Expired due to Fees

• Current Assignee: EIC Laboratories, Inc.
• Original Assignee: EIC Laboratories, Inc.
• Inventors: Cogan, Stuart F.
• Primary Examiner(s): Epps, Georgia Y.
• Assistant Examiner(s): BEY, DAWN MARIE
• Application Number:
  US08/456,268
• Time in Patent Office: 391 Days
• Field of Search: 359/265, 359/274, 359/275, 359/359, 359/245, 359/273
• US Class Current: 359/265
• CPC Class Codes: G02F 1/1533 structural features not otherwise provided for
• CPC Class Codes: G02F 2001/1536 additional, e.g. protective, layer inside the cell

Abstract

An electro-optical device comprising a series of thin films with an electrically controllable optical state provided with a protective overlayer that has a high optical transmittance and high resistance to penetration by H₂ O. The protective overlayer is a film of amorphous silicon oxycarbide (a-SiOC:H) having an O to C ratio such that the optical absorption edge of the a-SiOC:H is 3 eV or greater and the H₂ O transport through a 500 nm thick film of a-SiOC:H is 10¹² molecules/cm² -s or less.

Claims

1. An electro-optical device comprising;

a substrate;

an electrochromic coating comprising at least one thin electrochromic film, said thin electrochromic film having an electrically controllable optical state, disposed on said substrate,

and a protective overlayer disposed on said electrochromic coating, said protective overlayer comprising at least one thin-film of a-SiOC;

H having an oxygen to carbon ratio such that the optical absorption edge of said amorphous a-SiOC;

H is at least 3 eV and the water transport is less than 10¹² molecules/sec-cm² through a 500 nm thick film of said a-SiOC;

H.

2. The electro-optical device of claim 1, wherein said a-SiOC:

H thin-film contains nitrogen as an impurity, the concentration of said nitrogen impurity being less than an amount necessary to shift the optical absorption edge of said a-SiOC;

H to less than 3 eV.

3. The electro-optical device of claim 1, wherein said protective overlayer acts as multilayer interference filter, the indices of refraction and thickness of the a-SiOC:

H and other thin-films in said protective overlayer being chosen to increase the maximum transmittance of said electro-optic device in one or more wavelength ranges in the solar spectrum.

4. The electro-optical device of claim 1, wherein said electrochromic coating comprises at least two reduction-oxidation active layers chosen singly or as a mixture from the group of electrochromic materials consisting of WO₃, MoO₃, Li_y CrO_2+x, V₂ O₅, Nb₂ O₅, TiO₂, and mixed-oxides of Cr and V and wherein a quantity of electro-active lithium is distributed between said reduction-oxidation active layers.

5. The electro-optical device of claim 1, wherein said electrochromic coating comprises at least two reduction-oxidation active layers chosen singly or as a mixture from the group WO₃, MoO₃, IrO₂, and NiO, wherein one or more of said reduction-oxidation active layers is partially reduced.

6. The electro-optical device of claim 1, wherein said electrochromic coating comprises;

a first electronic contact disposed over said substrate,

a layer comprised of a first electrochromic material that colors on oxidation;

a layer comprised of a second electrochromic material that colors on reduction;

an ion conducting layer disposed between said first and second electrochromic layers;

said first and second electrochromic material being disposed over said first electronic contact; and

a second electronic contact disposed over said previous layers.

7. The electro-optical device of claim 1, wherein said protective overlayer comprises one or more layers of said a-SiOC:

H and one or more layers of zirconium dioxide.

8. A method for making an electro-optical device comprising a substrate;

at least one electrochromic coating comprising at least one thin electrochromic film, wherein each of said films has an electrically controllable optical state, and a protective overlayer disposed on said electrochromic coating comprising the steps of;

providing a substrate with at least one electrochromic layer disposed on said substrate to a vacuum of less than about 20 millitorr;

maintaining a temperature of said substrate of at least about 100 degrees Celsius;

providing a reactive gas mixture comprising at least silane, methane, and nitrous oxide at a pressure of about 200 millitorr to 1 torr;

providing an RF field at about 50 kHz to 13.56 MHz at a power density of about 0.1 to 1 watt/cm² of substrate area for a time sufficient to provide an a-SiOC;

H coating having an oxygen to carbon ratio such that the optical absorption edge of said a-SiOC;

H is at least 3 eV and the water transport is less than 10¹² molecules/sec-cm² through a 500 nm thick film of said a-SiOC;

H.