Photocatalytically hydrophilifying and hydrophobifying material

• US 5,939,194 A
• Filed: 12/09/1997
• Issued: 08/17/1999
• Est. Priority Date: 12/09/1996
• Status: Expired due to Term

• Current Assignee: Toto Limited
• Original Assignee: Toto Limited
• Inventors: Fujishima, Akira, Hashimoto, Kazuhito, Hayakawa, Makoto, Watanabe, Toshiya, Shimohigoshi, Mitsuhide
• Primary Examiner(s): Lusignan, Michael
• Application Number:
  US08/987,670
• Time in Patent Office: 616 Days
• Field of Search: 427/299, 427/165, 427/164, 427/126.3, 134/1, 106/287.16, 428/411.1, 428/446, 428/688, 428/689
• US Class Current: 428/411.1
• CPC Class Codes: C03C 17/2456 Coating containing TiO2
• CPC Class Codes: C03C 17/256 Coating containing TiO2
• CPC Class Codes: C03C 2217/212 TiO2
• CPC Class Codes: C03C 2217/23 Mixtures
• CPC Class Codes: C03C 2217/71 Photocatalytic coatings
• CPC Class Codes: C03C 2218/113 by sol-gel processes
• CPC Class Codes: C03C 2218/151 by vacuum evaporation
• CPC Class Codes: C09K 3/18 for application to surfaces to minimize adherence of ice, mist or water thereto rendering particulate materials free flowing, in general, e.g. making them hydrophobic B01J2/30; Thawing or antifreeze materials for application to surfaces used in liquids for heat-transfer, heat-exchange or heat-storage or for the production of heat or cold other than by combustion, e.g. radiator liquids, C09K5/00
• CPC Class Codes: G02B 1/105 Protective coatings
• 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: Y10T 428/31504 Composite [nonstructural laminate]

Abstract

A method for highly hydrophilifying the surface of an article by photoexcitation of a semiconductor photocatalyst and maintaining the hydrophilicity is disclosed. A layer containing a photocatalyst is formed on a substrate. Onto the surface of the layer are fixed a hydroxyl group upon photoexcitation of the photocatalyst and a physically adsorbed water molecule in the vicinity of the hydroxyl group upon photoexcitation of the photocatalyst. Thus, the surface is highly hydrophilified. Further, this surface, simultaneously with the hydrophilification, exhibits higher hydrophobicity.

Claims

1. A process for producing a member having an amphiphilic surface, comprising the steps of:

providing a substrate; and

forming a layer, containing a photocatalyst, on the substrate.

2. A method for amphiphilifying the surface of a member, comprising the steps of:

providing a substrate;

forming a layer, containing a photocatalyst, on the substrate; and

photoexciting the photocatalyst to amphiphilify the surface of the layer.

3. A method of amphiphilifying the surface of a member as in claim 2, further comprising the step of discontinuing or substantially reducing the rate of photoexcitation before the entirety of said surface becomes hydrophilic.

4. An amphiphilic member comprising:

a substrate; and

a layer, containing a photocatalyst, provided on said substrate, wherein said photocatalyst comprises a metal oxide and oxygen atoms of said metal oxide are exposed on the surface of said layer, substantially all of said exposed oxygen atoms being oxygen atoms at bridging sites in the metal oxide.

5. The hydrophilic member according to claim 4, wherein the metal oxide is rutile titanium oxide with the (110) crystal face or (100) crystal face thereof being exposed on the surface of the layer containing a photocatalyst.

6. The hydrophilic member according to claim 4, wherein the metal oxide is anatase titanium oxide with the (001) crystal face thereof being exposed on the surface of the layer containing a photocatalyst.

7. A method for amphiphilifying the surface of a member, comprising the steps of:

providing a substrate; and

fixing a photocatalyst of a metal oxide onto the substrate so that only oxygen atoms at bridging sites in the metal oxide are substantially exposed on the surface of the layer containing a photocatalyst.

8. The method according to claim 7, wherein the metal oxide is rutile titanium oxide and the photocatalyst is fixed so that the (110) crystal face or (100) crystal face of the rutile titanium oxide is exposed on the surface of the layer containing a photocatalyst.

9. The method according to claim 7, wherein the metal oxide is anatase titanium oxide and the photocatalyst is fixed so that the (001) crystal face of the anatase titanium oxide is exposed on the surface of the layer containing a photocatalyst.

10. An amphiphilic member comprising:

a substrate; and

a layer, containing a photocatalyst, provided on the substrate, said layer having a surface, said surface having hydrophilic and hydrophobic regions, said hydrophilic regions having hydroxyl groups fixed thereto and water molecules physically adsorbed in the vicinity of said hydroxyl groups.

11. An amphiphilic member according to claim 10, wherein the total area of said surface covered by said hydrophilic regions is at least about 20% but less than 100%.

12. An amphiphilic member according to claim 10, wherein, on the surface of the layer containing a photocatalyst, said hydrophilic regions and said hydrophobic regions are present in a mosaic form.

13. An amphiphilic member according to claim 10, wherein the regions comprising the hydrophilic regions and the hydrophobic regions each have an area of about 100 to 10,000 nm².

14. An amphiphilic member according to claim 10, wherein said surface is amphiphilic such that oil deposited on said surface can be easily removed by rinsing the surface with water and water deposited on said surface can be easily removed by rinsing with oil.

15. An amphiphilic member according to any one of claims 10 and 13, wherein said surface has a contact angle with water of not more than 5°

and a contact angle with glyceride trioleate of not more than 5°

.

16. A member, selected from the group consisting of machine tools, bearings, and cutting disks, comprising:

a substrate and a layer, said layer provided on said substrate, said layer containing a photocatalyst.

17. A member according to claim 16, wherein said layer has a surface and said surface may be photoexcited such that the surface has a contact angle with water of not more than about 5°

and a contact angle with glyceride trioleate of not more than about 5°

.

18. An amphiphilic member comprising:

a substrate; and

a layer, containing a photocatalyst, provided on said substrate, said layer having a surface, and said surface having hydrophilic and hydrophobic regions,

wherein said hydrophilic regions have a contact angle with water of about 37°

or less.