Electro-optic device having a self-cleaning hydrophilic coating

• US 6,991,339 B2
• Filed: 02/20/2004
• Issued: 01/31/2006
• 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): Shafer, Ricky D.
• Application Number:
  US10/783,099
• Publication Number:
  US 20040233552A1
• Time in Patent Office: 711 Days
• Field of Search: 359/265, 359/267, 359/273, 359/512, 359/603, 359/884, 359/507
• US Class Current: 359/507
• 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 1/105 Protective coatings
• CPC Class Codes: G02B 1/14 Protective coatings, e.g. hard coatings
• 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 electro-optic device is disclosed having a self-cleaning, hydrophilic optical coating. The electro-optic device preferably forms an external rearview mirror for a vehicle. The optical coating preferably includes photocatalytic layer(s), a hydrophilic layer, and a color suppression coating. The electro-optic device is preferably an electrochromic mirror. 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°. The mirror exhibits a C* value of less than 25.

Claims

1. A variable reflectance rearview mirror for a vehicle, comprising:

a variable reflectance mirror element having a reflectivity that varies in response to an applied potential so as to exhibit at least a high reflectance state and a low reflectance state;

a hydrophilic coating applied to a front surface of said mirror element;

wherein the variable reflectance rearview mirror exhibits a high reflectance state to a low reflectance state ratio of greater than approximately 2.5;

1.0; and

wherein said mirror exhibits a C* value of less than about 25 or wherein said mirror exhibits a C* value of greater than approximately 20 in one or more of the high reflectance state and the low reflectance state when b* contributes to at least approximately 50% of the C* value.

2. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a high reflectance state to a low reflectance state ratio of greater than approximately 3.2:

1.0.

3. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a high reflectance state to a low reflectance state ratio of greater than approximately 3.3:

1.0.

4. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a high reflectance state to a low reflectance state ratio of greater than approximately 4.3:

1.0.

5. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a high reflectance state to a low reflectance state ratio of greater than approximately 5.0:

1.0.

6. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a high reflectance state to a low reflectance state ratio of greater than approximately 6.5:

1.0.

7. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a C* value of less than about 20.

8. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a C* value of less than about 15.

9. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a C* value of less than about 10.

10. The variable reflectance rearview mirror according to claim 1, wherein said mirror exhibits a C* value of greater than approximately 20 in one or more of the high reflectance state and the low reflectance state when b* contributes to at least approximately 75% of the C* value.

11. The variable reflectance rearview mirror according to claim 1, wherein said hydrophilic coating includes a layer of a photocatalytic material.

12. The variable reflectance rearview mirror according to claim 11, wherein said photocatalytic layer comprises TiO₂.

13. The variable reflectance rearview mirror according to claim 1, wherein said hydrophilic coating comprises a layer of SiO₂.

14. The variable reflectance rearview mirror according to claim 1, wherein said hydrophilic coating comprises a color suppression coating.

15. The variable reflectance rearview mirror according to claim 14, wherein said color suppression coating comprises at least one of TiO₂, SiO₂, tin oxide, and tin doped indium oxide.