Method for producing chemically strengthened glass substrate for information recording medium
View Patent ↗Prior to conducting chemical strengthening treatment by contacting a glass with a potassium-containing chemical strengthening treating solution, oxidation treatment is conducted to iron-containing particles adhered to a surface of the glass as a pre-step, and the glass is then chemically strengthened. The oxidation treatment is a heat treatment conducted at 80-400° C. in the air. A glass substrate for an information recording medium is obtained by the method.
1. A method for producing a glass substrate for information recording medium, the method comprising the steps of:
(a) processing a plate-like glass substrate in a doughnut shape;
(b) grinding the doughnut-shaped glass substrate to smoothen a surface thereof;
(c) oxidizing metal-containing particles adhered to a surface of the glass substrate by heating in an oxidation atmosphere;
(d) adding an oxidizing agent to a potassium-containing chemical strengthening treating solution and heating the potassium-containing chemical strengthening treating solution including the oxidizing agent;
(e) oxidizing iron particles in the potassium-containing chemical strengthening treating solution by pre-heating the chemical strengthening treating solution before immersing the glass substrate in the chemical strengthening treating solution; and
(f) contacting the glass substrate with the potassium-containing chemical strengthening treating solution.
2. The method as claimed in claim 1 , wherein the oxidizing (c) is conducted by heating the glass substrate at 80-400° C.
3. The method as claimed in claim 1 , wherein the oxidizing (c) is conducted by heating the glass substrate for more than 20 minutes to 10 hours.
4. The method as claimed in claim 1 , wherein a cleaning is conducted after the chemical strengthening treatment.
5. The method as claimed in claim 4 , wherein the cleaning is conducted with a reducing agent-containing acidic solution.
6. The method as claimed in claim 5 , wherein the reducing agent is at least one selected from the group consisting of ascorbic acid and oxalic acid.
7. The method as claimed in claim 5 , wherein the acidic solution contains at least one acidic ingredient selected from the group consisting of malonic acid, nitric acid and sulfuric acid.
8. The method as claimed in claim 5 , wherein the reducing agent-containing acidic solution contains a chelating agent.
9. The method as claimed in claim 8 , wherein the chelating agent is oxalic acid or N-(2-hydroxyethyl)ethylenediaminetriacetic acid.
10. The method as claimed in claim 1 , wherein the oxidizing (c) is conducted by heating the surface of the glass substrate.
11. The method as claimed in claim 1 , wherein the oxidizing (c) comprises a treatment selected from the group consisting of ozone oxidation, ashing treatment and ultraviolet ray irradiation conducted in the presence of oxygen.
12. The method as claimed in claim 1 , wherein the oxidizing (c) is conducted in air.