Reinforced window member and method of manufacturing the same

Abstract

A method of manufacturing a window member includes performing a first reinforcement operation including performing a first ion-exchange treatment on an initial window member. The first ion-exchange treatment includes applying ion salts at a temperature equal to or greater than a first temperature of about 500° C. A stress relief operation includes performing a heat treatment and/or a salt treatment on the initial window member to which the first reinforcement operation is performed. A second reinforcement operation includes performing a second ion-exchange treatment on the initial window member to which the stress relief operation is performed.

What is claimed is: 
     
         1 . A window member, comprising:
 a base comprising a first surface and a second surface facing the first surface in a first direction, the base having a thickness defined in the first direction;   first ion salts distributed in the base and each of the first ion salts having a first ion radius; and   second ion salts distributed in the base and each of the second ion salts having a second ion radius greater than the first ion radius, wherein a variation in compressive stress according to a depth increasing along the first direction from the first surface of the base forms a first plot, and the first plot comprises a point at which an absolute value of a slope is smaller than about 2 MPa/µm in a depth range in which the compressive stress is greater than about 0 MPa/µm.   
     
     
         2 . The window member of  claim 1 , wherein the thickness of the base is equal to or smaller than about 0.5 mm. 
     
     
         3 . The window member of  claim 1 , wherein the first plot has a first surface compressive stress at a point at which the depth is about 0 µm and a compressive stress of about OMPa at a point at which the depth is a first depth of compression, the first plot is divided into a first section in which the absolute value of the slope is equal to or greater than about 2 MPa/µm and a second section in which the absolute value of the slope is smaller than about 2 MPa/µm in a range in which the depth is equal to or greater than about OMPa and equal to or smaller than the first depth of compression, and the second section is defined in a depth greater than a depth in which the first section is defined. 
     
     
         4 . The window member of  claim 3 , wherein
 the first plot comprises a point at which the slope is equal to or greater than about 0 MPa/µm in the second section.   
     
     
         5 . The window member of  claim 4 , wherein the first plot has an upward convex shape in the second section. 
     
     
         6 . The window member of  claim 1 , wherein the first ion salts include sodium ions, and the second ion salts include potassium ions. 
     
     
         7 . A window member, comprising:
 a first surface; and   a second surface facing the first surface, the window member having a thickness defined in a first direction between the first surface and the second surface, the window member having a compressive stress smaller than about 150 MPa on the first surface, and having a compressive stress graph varied depending on a depth increasing along the first direction from the first surface, wherein the compressive stress graph comprises a first plot at a depth equal to or smaller than a transition point and a second plot at a depth greater than the transition point, the first plot has an average slope equal to or greater than about -200 MPa/µm and equal to or smaller than about -40 MPa/µm, the second plot has an average slope different from the first plot, and the transition point is greater than about 15 µm.   
     
     
         8 . The window member of  claim 7 , wherein an absolute value of the average slope of the second plot is smaller than an absolute value of the average slope of the first plot. 
     
     
         9 . The window member of  claim 8 , wherein the second plot comprises a section having an average slope equal to or greater than about -8 MPa/µm and equal to or smaller than about -2 MPa/µm. 
     
     
         10 . The window member of  claim 8 , wherein a depth range in which the second plot is defined comprises a depth at which the compressive stress becomes zero. 
     
     
         11 . The window member of  claim 7 , wherein the thickness is equal to or smaller than about 0.8 mm. 
     
     
         12 . The window member of  claim 11 , wherein the compressive stress graph has the compressive stress of zero when the depth is equal to or smaller than about 30 µm. 
     
     
         13 . The window member of  claim 7 , wherein the transition point is equal to or smaller than about 30 µm.