Abstract:
A method for strengthening glass substrate includes: preheating a glass substrate; spraying a molted salt onto the substrate to form a ion exchange layer; forming a titanium dioxide layer on the ion exchange layer. The ion exchange layer infills some microcracks. The titanium dioxide layer reinforces the infilling of microcracks and applying further toughness. An article manufactured by the method is also provided.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to a method for strengthening glass substrate and articles manufactured by the method. 
         [0003]    2. Description of Related Art 
         [0004]    Glass substrates may be used as cover sheets and/or touch screens for LCD and LED displays incorporated in mobile telephones, GPS devices, display devices such as televisions and computer monitors and other electronic devices. However, the toughness of the basic glass substrate is low and the substrate is susceptible to damage. 
         [0005]    To enhance the toughness, a chemical strengthening process is widely used to treat glass substrates. Traditionally, the chemical strengthening process is carried out by dipping the glass substrate in a molten salt solution containing potassium ions, which forms an ion exchange layer having a thickness of about 8 μm to about 12 μm in the glass substrate. However, when the thickness of the glass substrate is thicker than 1.5 mm, the ion exchange layer cannot completely fill in all the micro cracks on the outer surface of glass substrate. Additionally, during the chemical strengthening process, the corners of the glass substrate have fewer potassium ions aggregated thereon compared to the expanse of the glass substrate. Consequently, the corners of the glass substrate do not have the same strengthening effect as the rest of the substrate. 
         [0006]    Therefore, there is room for improvement within the art. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0007]    Many aspects of the disclosure can be better understood with reference to the following figures. The components in the figures are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views. 
           [0008]      FIG. 1  is a cross-sectional view of an exemplary embodiment of an article. 
           [0009]      FIG. 2  is a schematic view of an exemplary embodiment of a strengthening treatment device. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    Referring to  FIG. 1 , an exemplary method for strengthening glass substrate may include at least the following steps: 
         [0011]    (1) A glass substrate  11  is provided. 
         [0012]    The glass substrate  11  is a sodium silicate glass substrate. The thickness of the glass substrate  11  is about 0.5 mm to about 3 mm. The glass substrate may have a plurality of micro cracks (not shown) defined on the surface of the glass substrate  11  caused by the annealing process during the manufacturing of the glass substrate or other causes. The glass substrate  11  may be a plain glass or a glass having a three-dimensional structure. 
         [0013]    In the embodiment, the glass substrate  11  having a three-dimensional structure is made from a plain glass by hot bending treatment. 
         [0014]    (2) The glass substrate  11  is polished to smoothen the inside and outside surfaces of the glass substrate  11 . 
         [0015]    (3) The glass substrate  11  is strengthened to form an ion exchange layer  13 . 
         [0016]    Referring to  FIG. 2 , a strengthening treatment device  300  is provided. The device  300  includes a strengthening furnace  310 , a bath  330  retained in the furnace  310 , and a horn-shaped spraying element  350  inserted into the bath  330 . The bath  330  contains salt solution  370 . 
         [0017]    The strengthening process is carried out by the following steps: firstly, the glass substrate  11  is placed in the device  300  above the spraying element  350 , and the internal temperature of the furnace  310  is heated to about 200° C.-450° C. at a rate of about 2° C./min-12° C./min to pre-heat the glass substrate  11 ; secondly, the internal temperature of the furnace  310  and the salt solution  370  is heated to about 450° C.-550° C. at a rate of about 5° C./min-10° C./min, thus melting the salt solution  370 ; thirdly, the melted salt solution  370  is sprayed on the glass substrate  11  for about 90 min-240 min by the spraying element  350 , which facilitates an ion exchange between potassium ions included in the glass substrate  11  and potassium ions included in the salt solution  370 ; fourthly, the internal temperature of the furnace  310  is decreased to room temperature at a rate of about 1° C./min-2° C./min. 
         [0018]    In the embodiment, the salt solution  370  contains potassium nitrate, auxiliary substances (see below for description) and water, wherein the mass percentage of the potassium nitrate is about 54% to about 72%, the mass percentage of the auxiliary substances is about 4% to about 10%, the mass percentage of water is about 2.3% to about 7.5%. The auxiliary substances include corundum powder, potassium silicate and diatomite, wherein the mass percentage of the corundum powder is about 25% to about 35%, the mass percentage of the potassium silicate is about 25% to about 40%, and the mass percentage of diatomite is about 25% to about 50%. 
         [0019]    During the strengthening process, sodium ions from the glass substrate  11  are exchanged with potassium ions included in the salt solution  370  to form an ion exchange layer  13 . Some of the micro cracks are filled and smoothed over by potassium ions, because the diameter of each potassium ion is larger than the diameter of the sodium ion. The ion exchange layer  13  has a thickness of about 10 μm to about 30 μm. 
         [0020]    During the strengthening process, melted salt solution  370  is sprayed evenly on the surface of the glass substrate  11 , which makes the glass substrate  11  have a three-dimensional structure that is uniform in strength. Additionally, less of the salt solution  370  is consumed by the method compared to the consumption in the traditional chemical strengthening process. 
         [0021]    (4) A titanium dioxide layer  15  is formed on the ion exchange layer  13  by thermal spraying. 
         [0022]    A spraying solution is provided. The spraying solution includes carbon tetrachloride and organic solution, wherein the mass percentage of the carbon tetrachloride is about 58% to about 80%, and the mass percentage of the organic solution is about 20% to about 42%. The organic solution is an alcohol, such as ethanol or methanol. 
         [0023]    The glass substrate  11  is positioned in a sealed chamber (not shown). The internal temperature of the chamber is heated to about 500° C.-700° C. The spraying solution is sprayed on the ion exchange layer  13 . Meanwhile, the carbon tetrachloride decomposes into titanium dioxide as a result of the high internal temperature of the chamber (500° C.-700° C)., which forms a titanium dioxide layer  15  on the ion exchange layer  13 . The titanium dioxide layer  15  consists of titanium dioxide. The thickness of the titanium dioxide layer  15  is about 15 μm-30 μm. 
         [0024]    The titanium dioxide layer  15  is formed on the ion exchange layer  13 . Some of the titanium dioxide included in the titanium dioxide layer  15  is embedded in the micro cracks which are left unfilled by the potassium ions. 
         [0025]    The above method not only strengthens the glass substrate  11  having a thickness less than 1.5 mm, but also strengthens the glass substrate  11  having a thickness about 1.5 mm to about 3 mm. 
         [0026]    An article  10  manufactured by the above method is also provided. The article  10  includes a glass substrate  11 , an ion exchange layer  13  formed on the glass substrate  11 , and a titanium dioxide layer  15  formed on the ion exchange layer  13 . 
         [0027]    The glass substrate  11  defines a plurality of micro cracks. The thickness of the glass substrate  11  is about 0.5 mm to about 3 mm. 
         [0028]    The ion exchange layer  13  has sodium ions and potassium ions. Potassium ions are embedded in the glass substrate, partly filling any micro cracks. The ion exchange layer  13  has a thickness of about 10 μm to about 30 μm. 
         [0029]    The titanium dioxide layer  15  is formed on the ion exchange layer  13 . Some of titanium dioxide included in the titanium dioxide layer  15  embeds in the micro cracks which are left unfilled by potassium ions. The titanium dioxide layer  15  consists of titanium dioxide. The thickness of the titanium dioxide layer  15  is about 15 μm-30 μm. 
         [0030]    The ion exchanging layer  13  and the titanium oxide layer  15  are resistant to the propagation of existing micro cracks and the formation of new micro cracks due to impacts, thus improving the strength and toughness of the glass substrate  11 . Additionally, the titanium oxide layer  15  provides an enhanced resistance to abrasions and scratches. 
         [0031]    It is believed that the exemplary embodiment and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its advantages, the examples hereinbefore described merely being preferred or exemplary embodiment of the disclosure.