Abstract:
A device grows sapphire ingots by dipping a sapphire seed into molten aluminum oxide and lifting and spinning the sapphire seed from the molten aluminum oxide to cause the molten aluminum oxide adhering to the sapphire. Meanwhile, the device controls temperature such that the molten aluminum oxide is crystallized on the sapphire seed which is gradually cooled down to a room temperature. The device also includes a housing and air controller for providing desire air conditions for growing the sapphire ingot.

Description:
BACKGROUND 
       [0001]    1. Technical Field 
         [0002]    The present disclosure relates to sapphire growing technologies and, particularly, to a device for growing a sapphire ingot at a high speed and a cover glass made of sapphire and having excellent optical properties. 
         [0003]    2. Description of Related Art 
         [0004]    Due to excellent mechanical and optical properties, sapphires are one of preferred materials for cover glasses of lens modules. The sapphire is typically made by a kyropoulos method with a low crystallization rate, and increases cost of the sapphire and the cover glass. In addition, a transmissivity of the sapphire at visible light wavelengths is often less than satisfactory (&lt;86%), which degrades the optical quality of the cover glass. 
         [0005]    Therefore, it is desirable to provide a device for growing a sapphire ingot and a cover glass, which can overcome the above-mentioned problems. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    Many aspects of the present disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present disclosure. 
           [0007]      FIG. 1  is a schematic view of a device for growing a sapphire ingot, according to an embodiment, which is in a first state. 
           [0008]      FIG. 2  is similar to  FIG. 1 , but showing the device in a second state. 
           [0009]      FIG. 3  is similar to  FIG. 1 , but showing the device in a third state. 
           [0010]      FIG. 4  is a schematic view of a cover glass, according to another embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Embodiments of the present disclosure will now be described in detail with reference to the drawings. 
         [0012]    Referring to  FIGS. 1-3 , a device  10  for growing a sapphire ingot  16   a,  according to an embodiment, includes a crucible  11 , an aluminum oxide material  12 , a heater  13 , a temperature controller  14 , a heat preservation shell  15 , a sapphire seed assembly  16 , a driver  17 , a post-heating device  18 , a housing  19 , and an air controller  20 . 
         [0013]    The aluminum oxide material  12  is received in the crucible  11 . Sapphire is a gemstone variety of the mineral corundum, and has a hexagonal crystal structure. The main chemical component of sapphire is aluminum oxide. Therefore, the aluminum oxide material  12  is used as the raw material of the sapphire ingot  16   a.  The crucible  11  can be made of tungsten which can withstand a relative high temperature. Specifically, a melting point of tungsten is higher than a melting point of aluminum oxide which is about 2050 degrees Celsius. 
         [0014]    The heater  13  includes a coil  131  winding the crucible  11 . The temperature controller  14  is configured for controlling the heater  13  to heat the crucible  11  utilizing the electromagnetic induction effect of the coil  131  such that the aluminum oxide material  12  is molten into a liquid  12   a  and a temperature above the liquid  12   a  is lower than a melting point of the aluminum oxide material  12  and gradually decreases from the liquid  12   a  to a top of the crucible  11 . In the embodiment, the temperature controller  14  includes a thermometer  141  and a controller  142 . The thermometer  141  is configured for measuring the temperature in the crucible  11 . The controller  142  is configured for controlling the heater  13  to heat the crucible  11  based upon measuring results of the thermometer  141 . The controller  142  can apply electric currents of different levels of power to different parts of the coil  131  to heat the different parts of the crucible  11  at different levels to obtain desired temperatures of the different parts of the crucible  11 . 
         [0015]    The heat perseveration shell  15  encloses the crucible  11  configured for maintaining a constant temperature filed in the crucible  11 . In addition, the heat preservation shell  15  is made of non-radiation material and thus can provide shielding against electromagnetic interference. 
         [0016]    The sapphire seed assembly  16  includes a sapphire seed  161  and a holder  162  holding the sapphire seed  161 . The holder  162  is a rod arranged substantially perpendicular to a top surface of the liquid  12   a  and holds the sapphire seed  161  at an end that is adjacent to the liquid  12   a.  A growing axis of the sapphire seed  161  can be the a axis (11   2   0), c axis (0001), or m axis (10   1   0). 
         [0017]    The driver  17  is configured for driving the sapphire seed assembly  16  to move such that the sapphire seed  161  dips into the liquid  12   a,  and then lifts out of the liquid  12   a  and the crucible  11  and spins at predetermined speeds. As such, the liquid  12   a  adhering to the sapphire seed  16  is shaped cylinder-like and is crystallized as the sapphire seed  161  ascends and the temperature gradually decreases to form the sapphire ingot  16   a.  In the embodiment, the driver  17  can be installed within the housing  19 . For example, the driver  17  can be suspended to the ceiling of the housing  19  and can include a linear motor (or cylinder) and a rotational motor for driving the holder  162  to move linearly and spin. 
         [0018]    The post-heating device  18  is configured for heating the sapphire ingot  16   a  out of the crucible  11  such that the sapphire ingot  16   a  can be gradually cooled down to the room temperature. The post-heating device  18  can be positioned above the crucible  11  and can be made of metal oxide having a high melting point, such as aluminum oxide or ceramic, or can be a multi-layer metal reflector made of molybdenum or platinum. The controller  142  is also connected to the post-heating device  18  and can control the post-heating device  18 . 
         [0019]    The housing  19  encloses the heat preservation shell  15  and is configured for providing air conditions and electromagnetic interference shielding for growing the sapphire ingot  16   a.  The housing  19  defines an air outlet  191  and an air inlet  192 . The air outlet  191  is positioned close to a bottom of the housing  19  and the air inlet  192  is positioned close to a top of the housing  19 . 
         [0020]    The air controller  20  is configured for vacuumizing the housing  19  and introducing desired gases into the housing  19  to control air conditions within the housing  19 . The air controller  20  includes an air pump system  201  and an air introducer  202 . 
         [0021]    The air pump system  201  includes a mechanical pump  2011 , a turbine pump  2012 , and a first pipe system  2013 . The first pipe system  2013  communicates the housing  19  with the mechanical pump  2011  and the turbine pump  2012  via the air outlet  191  and has a number of air valves  203 . The air valves  203  are configured for individually connecting or disconnecting the housing  19  to the air pump  2011  and the turbine pump  2012 . In operation, the air valves  203  are operated such that the housing  19  is connected to the mechanical pump  2011 , but disconnected from the turbine pump  2012 . Then the housing  19  is vacuumized by the mechanical pump  2011 . Next, the air valves  203  are operated such that the housing  19  is connected to the turbine pump  2012 , but disconnected from the mechanical pump  2011 . The housing  19  is further vacuumized by the turbine pump  2012 . Finally, the air valves  203  are operated such that the housing  19  is disconnected from both the mechanical pump  2011  and the turbine pump  2012 . 
         [0022]    The air introducer  202  includes a number of gas sources  2021  and a second pipe system  2022 . The gas sources  2021  are configured for providing gases for growing the sapphire ingot  16   a , such as argon and/or helium. The second pipe system  2022  communicates the housing  19  with the gas sources  2021  via the air inlet  192  and also has a number of air valves  203 . The air valves  203  are configured for selectively connecting or disconnecting the air sources  2021  with the housing  19 . The air introducer  202  can further includes a mass flow controller  2023  installed at the second pipe system  2022 , which is configured for control the flow of the gases. 
         [0023]    The device  10  also includes a camera  21  and a residual gas analyzer  22 . The camera  21  is configured for monitoring the growing of the sapphire ingot  16   a.  The residual gas analyzer  22  is configured for analyzing the components of the gases in the housing  19 . 
         [0024]    Referring to  FIG. 4 , a cover glass  30 , according to an embodiment, includes a substrate  31  and an anti-reflection film  32  coated on the substrate  31 . The substrate  31  is made of the sapphire ingot  16   a.  The anti-reflection film  32  includes a number of high refractive layers  321  and a number of low refractive layers  322  alternately stacked on the substrate  31 . A structure of the anti-reflection layer  32  can be represented by (xHyL) n , which indicates that the anti-reflection film  32  has “n” repetitions of (xHyL), wherein n is a positive inter and satisfies the condition: 4≦n≦8. Each repetition of (xHyL) has the high refractive layer xH of an optical thickness “xλ/4” and the low index layer yL of an optical thickness “yλ/4”, wherein x and y satisfy the conditions: 1&lt;x&lt;2 and 1&lt;y&lt;2, and λ is a central working wavelength of the anti-reflection film  32 . The first high refractive layer  321  is in contact with the substrate  31  and the first low refractive layer  322  is in contact with the first high refractive layer  321 . 
         [0025]    The high refractive layers  321  can be made from titanium dioxide with a refractive index of about 2.705. The low refractive layers  322  can be made from silicon dioxide with a refractive index of about 1.499. 
         [0026]    A crystallization rate of the sapphire ingot  16   a  grown in the device  10  greatly increases, as compared to a kyropoulos method. By employing the anti-reflection film  32 , a transmissivity of the cover glass  30  can be enhanced to about 99.5%. 
         [0027]    It will be understood that the above particular embodiments are shown and described by way of illustration only. The principles and the features of the present disclosure may be employed in various and numerous embodiment thereof without departing from the scope of the disclosure as claimed. The above-described embodiments illustrate the possible scope of the disclosure but do not restrict the scope of the disclosure.