Electrochromic device having a self-cleaning hydrophilic coating

• US 6,789,906 B2
• Filed: 09/09/2002
• Issued: 09/14/2004
• Est. Priority Date: 06/25/1999
• Status: Expired due to Fees

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Cammenga, David J., Tonar, William L., Anderson, John S.
• Primary Examiner(s): SIKDER, MOHAMMAD YUNUS
• Application Number:
  US10/238,015
• Publication Number:
  US 20030048538A1
• Time in Patent Office: 736 Days
• Field of Search: 359/604, 359/601-603, 359/265-267, 359/272-275, 359/582, 359/586, 359/602, 359/587, 359/589, 359/883, 428/325, 428/326
• US Class Current: 359/604
• CPC Class Codes: B60R 1/0602 comprising means for cleaning or deicing
• CPC Class Codes: B60R 1/088 using a cell of electrically changeable optical characteristic, e.g. liquid-crystal or electrochromic mirrors
• CPC Class Codes: G02B 1/18 Coatings for keeping optical surfaces clean, e.g. hydrophobic or photo-catalytic films G02B1/16 takes precedence
• CPC Class Codes: G02B 27/0006 with means to keep optical surfaces clean, e.g. by preventing or removing dirt, stains, contamination, condensation G02B1/18 takes precedence; cleaning in general B08B
• CPC Class Codes: G02F 1/157 Structural association of cells with optical devices, e.g. reflectors or illuminating devices

Abstract

An electrochromic device is disclosed having a self-cleaning, hydrophilic optical coating. The electrochromic device preferably forms an external rearview mirror for a vehicle The coating preferably includes alternating layers of a photocatalytic material having a high index of refraction and a hydrophilic material having a low refractive index More specifically, the coating includes a first layer having a high refractive index, a second layer having a low refractive index, a third layer of titanium dioxide, and a fourth layer of silicon dioxide provided as an outermost layer. The disclosed optical coating exhibits a reflectance at the front surface of the reflective element that is less than about 20 percent, and has sufficient hydrophilic properties such that water droplets on a front surface of the optical coating exhibit a contact angle of less than about 20°.

Claims

1. An electrochromic device, comprising:

a first substantially transparent element having a front surface and a rear surface, wherein a self-cleaning, hydrophilic coating is applied to at least a portion of the front surface, and further wherein an electrically conductive material is applied to at least a portion of the rear surface;

a second element having a front surface and a rear surface, wherein an electrically conductive material is applied to at least a portion of the front surface;

an electrochromic medium contained within a chamber positioned between the first and second elements; and

wherein the electrochromic device exhibits a C* value of less than approximately 20 in both a high reflectance state and a low reflectance state.

2. The electrochromic device according to claim 1, wherein the electrochromic medium comprises at least one solvent, an anodic material, and a cathodic material.

3. The electrochromic device according to claim 1, wherein the self-cleaning, hydrophilic coating is sufficiently hydrophilic such that water droplets on a front surface of the self-cleaning, hydrophilic coating exhibit a contact angle of less than about 30 degrees.

4. The electrochromic device according to claim 1, wherein the self-cleaning, hydrophilic coating is sufficiently hydrophilic such that water droplets on a front surface of the self-cleaning, hydrophilic coating exhibit a contact angle of less than about 20 degrees.

5. The electrochromic device according to claim 1, wherein the self-cleaning, hydrophilic coating is sufficiently hydrophilic such that water droplets on a front surface of the self-cleaning, hydrophilic coating exhibit a contact angle of less than about 10 degrees.

6. The electrochromic device according to claim 5, wherein the self-cleaning, hydrophilic coating includes at least one layer of photocatalytic material having a thickness of less than approximately 300 angstroms.

7. The electrochromic device according to claim 5, wherein the self-cleaning, hydrophilic coating includes at least one layer of photocatalytic material having a thickness of less than approximately 500 angstroms.

8. An electrochromic device, comprising:

a first substantially transparent element having a front surface and a rear surface, wherein a self-cleaning, hydrophilic coating is applied to at least a portion of the front surface, and further wherein an electrically conductive material is applied to at least a portion of the rear surface;

a second element having a front surface and a rear surface, wherein an electrically conductive material is applied to at least a portion of the front surface;

an electrochromic medium contained within a chamber positioned between the first and second elements; and

wherein the electrochromic device exhibits a C* value of less than approximately 25 in both a high reflectance state and a low reflectance state.

9. The electrochromic device according to claim 8, wherein the electrochromic medium comprises at least one solvent, an anodic material, and a cathodic material.

10. The electrochromic device according to claim 8, wherein the self-cleaning, hydrophilic coating is sufficiently hydrophilic such that water droplets on a front surface of the self-cleaning, hydrophilic coating exhibit a contact angle of less than about 30 degrees.

11. The electrochromic device according to claim 8, wherein the self-cleaning, hydrophilic coating is sufficiently hydrophilic such that water droplets on a front surface of the self-cleaning, hydrophilic coating exhibit a contact angle of less than about 20 degrees.

12. The electrochromic device according to claim 8, wherein the self-cleaning, hydrophilic coating is sufficiently hydrophilic such that water droplets on a front surface of the self-cleaning, hydrophilic coating exhibit a contact angle of less than about 10 degrees.

13. The electrochromic device according to claim 12, wherein the self-cleaning, hydrophilic coating includes at least one layer of photocatalytic material having a thickness of less than approximately 300 angstroms.

14. The electrochromic device according to claim 12, wherein the self-cleaning, hydrophilic coating includes at least one layer of photocatalytic material having a thickness of less than approximately 500 angstroms.