Method of manufacturing flexible cover window and flexible cover window manufactured using same
Proposed is a flexible cover window manufacturing method capable of simultaneously reinforcing a plane part and a folding part by using alkali-based metal ions having an ionic radius smaller than that of alkali-based metal ions contained in a glass. A flexible cover window manufactured using the same method is also proposed. The plane part and the folding part are simultaneously reinforced using alkali-based metal ions having a smaller ionic radius than alkali-based metal ions included in a glass to simplify the process, and the flexible cover window ensures strength and folding characteristics by controlling tensile stress of the entire part of the flexible cover window.
1. A method of manufacturing a flexible glass cover window, the glass cover window comprising a plane part and a folding part, said method comprising:
an etching step for etching a glass substrate to form the folding part of the glass cover window wherein the folding part of the glass cover window has a thinner thickness than the plane part of the glass cover window,
following the etching step, a first reinforcing step of immersing, simultaneously, the plane part and the folding part of the glass cover window comprising sodium ions in a first molten salt comprising potassium ions and lithium ions such that surfaces of the plane part and the folding part of the glass cover window directly contact with the first molten salt comprising potassium ions and lithium ions, thereby decreasing amounts of lengths of the plane part and the folding part, and
subsequent to said first reinforcing step, a second reinforcing step of immersing, simultaneously, the plane part and the folding part of the glass cover window in a second molten salt comprising potassium ions such that the surfaces of the plane part and the folding part of the glass cover window directly contact with the second molten salt comprising potassium ions, thereby increasing the lengths of the plane part and the folding part and thus offsetting the decreases in the amounts of the lengths of the plane part and the folding part that occurred in the first reinforcing step,
wherein the first molten salt used in the first reinforcing step comprises KNO 3 , NaNO 3 , and LiNO 3 ,
wherein in the first reinforcing step, the content of KNO 3 is 20 to 70 parts by weight, based on a total weight of the first molten salt in the first reinforcing step, and the content of LiNO 3 is 1 to 5 parts by weight, based on the total weight of the first molten salt in the first reinforcing step,
wherein, by using the first molten salt, the first reinforcing step is configured to reduce the length of the folding part having a relatively thin thickness to a relatively large extent, and to reduce the length of the plane part having a relatively thick thickness to a relatively small extent,
wherein, by using the second molten salt, the second reinforcing step is configured to increase the length of the folding part having the relatively thin thickness to a relatively large extent, and to increase the length of the plane part having the relatively thick thickness to a relatively small extent, and
wherein the first reinforcing step and the second reinforcing step are configured to combine to reduce deformation or bending in an entire area of the folding part and the plane part while reinforcing the folding part and the plane part simultaneously.
2. The method of claim 1 , wherein the second molten salt used in the second reinforcing step comprises KNO 3 and any one or both of LiNO 3 and NaNO 3 .
3. The method of claim 2 , wherein the amount of LiNO 3 used in the second reinforcing step is equal to or less than the amount of LiNO 3 used in the first reinforcing step.
4. The method of claim 3 , wherein in the second reinforcing step the content of LiNO 3 in the second total molten salt is 0.1 to 2 parts by weight, based on the total weight of the molten salt.
5. The method of claim 1 , wherein the plane part has a thickness of 30 μm-300 μm, and the folding part has a thickness of 10 μm-100 μm.
6. The method of claim 1 , wherein the second molten salt of the second reinforcing step consists of KNO 3 .
7. The method of claim 1 , wherein the method does not include a step of masking to provide partial chemical reinforcing.
8. The method of claim 1 , wherein the first reinforcement step is carried out for a duration of 5 minutes to 10 hours.
9. The method of claim 1 , wherein the second reinforcement step is carried out for a duration of from 1 minute to 1 hour.