Method for manufacturing ultra-thin glass substrate

1. A method for manufacturing an ultra-thin glass substrate, the method comprising:

a feeding step of feeding a preform for a glass substrate, previously wound on a cylindrical first winding roll, to a production line by unwinding the preform from the cylindrical first winding roll;

a heating step of heating the preform fed from the feeding step to a temperature around a softening point thereof; and

a drawing step of drawing the preform that has softened in the heating step to form an ultra-thin glass substrate.

2. The method for manufacturing an ultra-thin glass substrate according to claim 1 , wherein the preform has been wound on the first winding roll together with a first protective sheet having a thickness of 10 μm to 1,000 μm superposed on one or each surface of the preform, and

the method further comprises a protective-sheet peeling step of peeling the first protective sheet from the perform before introducing the preform into the heating step.

3. The method for manufacturing an ultra-thin glass substrate according to claim 1 , wherein the drawing step is a step in which drawing is conducted with one or a pair of drawing rolls, and

the ultra-thin glass substrate which has undergone the heating step is pulled while keeping the ultra-thin glass substrate in contact with the one drawing roll, or the ultra-thin glass substrate which has undergone the heating step is pulled while gripping the ultra-thin glass substrate with the pair of drawing rolls.

4. The method for manufacturing an ultra-thin glass substrate according to claim 1 , wherein, in the heating step, both width-direction ends of the preform that has softened are gripped with gripping rolls.

5. The method for manufacturing an ultra-thin glass substrate according to claim 1 , further comprising, after the drawing step,

a winding step of winding the ultra-thin glass substrate on a cylindrical second winding roll having a roll diameter of 50 mm to 2,000 mm.

6. The method for manufacturing an ultra-thin glass substrate according to claim 3 , wherein, in the drawing step, a second protective sheet having a thickness of 10 μm to 1,000 μm is inserted between the drawing roll and the ultra-thin glass substrate.

7. The method for manufacturing an ultra-thin glass substrate according to claim 5 , wherein, after the drawing step, a third protective sheet having a thickness of 10 μm to 1,000 μm is supplied to one or each surface of the ultra-thin glass substrate, and the ultra-thin glass substrate and the third protective sheet are superposed together and wound on the second winding roll.

8. A method for manufacturing an ultra-thin glass substrate, the method comprising:

a feeding step of feeding a preform for a glass substrate, previously wound on a cylindrical first winding roll, to a production line by unwinding the preform from the cylindrical first winding roll;

a heating step of heating the preform fed from the feeding step to a temperature around a softening point thereof; and

a drawing step of drawing the preform that has softened in the heating step to form an ultra-thin glass substrate,

wherein the cylindrical first winding roll has a roll diameter of 100 mm to 1,500 mm, a thickness Tp of 20 μm to 250 μm, a width Wp of 10 mm to 2,000 mm, and a length of 1 m to 5,000 m,

the ultra-thin glass substrate produced by the drawing step has a thickness Tg of 2 μm to 50 μm, a width Wg of 0.3 mm to 500 mm, and a length of 5 m to 500,000 m, and

when a thickness-direction reduction ratio and a width-direction reduction ratio in which the preform is drawn in the drawing step are expressed by Tg/Tp and Wg/Wp, respectively, then the Tg/Tp is from 1/125 to ½ and the Wg/Wp is from 1/125 to 1.

9. The method for manufacturing an ultra-thin glass substrate according to claim 8 , wherein the preform has been wound on the first winding roll together with a first protective sheet having a thickness of 10 μm to 1,000 μm superposed on one or each surface of the preform, and

the method further comprises a protective-sheet peeling step of peeling the first protective sheet from the perform before introducing the preform into the heating step.

10. The method for manufacturing an ultra-thin glass substrate according to claim 8 , wherein the drawing step is a step in which drawing is conducted with one or a pair of drawing rolls, and

the ultra-thin glass substrate which has undergone the heating step is pulled while keeping the ultra-thin glass substrate in contact with the one drawing roll, or the ultra-thin glass substrate which has undergone the heating step is pulled while gripping the ultra-thin glass substrate with the pair of drawing rolls.

11. The method for manufacturing an ultra-thin glass substrate according to claim 8 , wherein, in the heating step, both width-direction ends of the preform that has softened are gripped with gripping rolls.

12. The method for manufacturing an ultra-thin glass substrate according to claim 8 , further comprising, after the drawing step,

a winding step of winding the ultra-thin glass substrate on a cylindrical second winding roll having a roll diameter of 50 mm to 2,000 mm.

13. The method for manufacturing an ultra-thin glass substrate according to claim 10 , wherein, in the drawing step, a second protective sheet having a thickness of 10 μm to 1,000 μm is inserted between the drawing roll and the ultra-thin glass substrate.

14. The method for manufacturing an ultra-thin glass substrate according to claim 12 , wherein, after the drawing step, a third protective sheet having a thickness of 10 μm to 1,000 μm is supplied to one or each surface of the ultra-thin glass substrate, and the ultra-thin glass substrate and the third protective sheet are superposed together and wound on the second winding roll.