METHOD OF REDUCING THE THICKNESS OF A SAPPHIRE LAYER
A method of removing material from a sapphire article is described. In particular, the method comprises the step of providing an initial sapphire layer and reducing the thickness of the layer while not significantly increasing the surface roughness of the layer. Cover plates for electronic device and methods of preparing them are also disclosed, along with a method of analyzing a sapphire article produced by the present method.
1 . A method of producing a sapphire layer comprising the steps of:
i) providing an initial sapphire layer having a thickness and at least one surface, the surface of the initial sapphire layer having an average surface roughness value of Ra I ; and
ii) reducing the thickness of the initial sapphire layer by contacting the surface with a reagent solution to produce the sapphire layer,
wherein the sapphire layer has a thickness that is less than the thickness of the initial sapphire layer and further has a final surface having an average surface roughness value of Ra F , wherein (Ra F −Ra I )/Ra I is less than or equal to 0.2.
2 . The method of claim 1 , wherein the initial sapphire layer has a thickness of from about 0.4 mm to about 0.8 mm.
3 . The method of claim 1 , wherein the sapphire layer has a thickness of from about 0.35 mm to about 0.75 mm.
4 . The method of claim 1 , wherein the thickness of the initial sapphire layer is reduced at a rate of greater than or equal to about 30 microns/hour.
5 . The method of claim 1 , wherein the thickness of the initial sapphire layer is reduced at a temperature of from about 250° C. to about 350° C.
6 . The method of claim 1 , wherein the reagent solution comprises sulfuric acid.
7 . The method of claim 1 , wherein the reagent solution comprises phosphoric acid.
8 . The method of claim 6 , wherein the reagent solution comprises phosphoric acid.
9 . The method of claim 1 , wherein (Ra F −Ra I )/Ra I is less than or equal to 0.1.
10 . The method of claim 1 , wherein the initial sapphire layer has c-axis orientation in a direction perpendicular to the surface.
11 . The method of claim 1 , wherein the initial sapphire layer has an a-axis orientation in a direction perpendicular to the surface.
12 . The method of claim 1 , wherein the method further comprises the step of polishing the final surface.
13 . The method of claim 1 , wherein the initial sapphire layer comprises single crystal sapphire prepared in a crystal growth furnace.
14 . The method of claim 13 , where the crystal growth furnace is a heat exchanger method furnace.
15 . The method of claim 1 , wherein the initial sapphire layer is prepared by a method comprising the steps of:
i) providing a donor body of sapphire comprising a top surface;
ii) implanting through the top surface of the donor body with an ion dosage to form a cleave plane beneath the top surface; and
iii) exfoliating the initial sapphire layer from the donor body along the cleave plane.
16 . The electronic device of claim 15 , wherein the ion dosage comprises hydrogen ions.
17 . The electronic device of claim 15 , wherein the ion dosage comprises helium ions.
18 . A method of preparing a cover plate configured for use with an electronic device and having at least one transparent display region, the cover plate comprising one or more sapphire layers, wherein the method comprises the steps of:
i) providing an initial sapphire layer having a thickness and at least one surface, the surface of the initial sapphire layer having an average surface roughness value of Ra I ; and
ii) reducing the thickness of the initial sapphire layer by contacting the surface with a reagent solution to produce the sapphire layer, wherein the sapphire layer has a thickness that is less than the thickness of the initial sapphire layer and further has a final surface having an average surface roughness value of Ra F , wherein (Ra F −Ra I )/Ra I is less than or equal to 0.2; and
iii) forming the cover plate comprising the sapphire layer.
19 . The method of claim 18 , wherein the step of forming the cover plate comprises combining the sapphire layer with at least one additional layer.
20 . The method of claim 19 , wherein the sapphire layer is an exterior layer of the cover plate.
21 . The method of claim 20 , wherein final surface of the sapphire layer faces outwardly.
22 . The method of claim 19 , wherein the additional layer is a transparent layer.
23 . The method of claim 22 , wherein the transparent layer is a subsurface layer having a front surface, and wherein the sapphire layer is affixed to the front surface of the subsurface layer.
24 . The method of claim 22 , wherein the transparent layer is an exterior surface coating layer.
25 . The method, of claim 18 , wherein the electronic device is an electronic media player, a mobile telephone, a personal data assistant, a pager, a tablet, a laptop computer, or an electronic notebook.