Magnetic recording apparatus comprising disk with reduced thickness and reduced disk flatness

Abstract

A disk for a magnetic recording apparatus. The disk includes a substrate comprising a first surface and a second surface, wherein the substrate has a substrate thickness. The disk includes a first coating layer disposed over the first surface of the substrate, wherein the first coating layer has a first coating layer thickness. The disk includes a second coating layer disposed over the second surface of the substrate, wherein the second coating layer has a second coating layer thickness. The disk has a disk thickness, wherein the disk thickness includes the substrate thickness. The maximum thickness difference between the first coating layer thickness and the second coating layer thickness is a function of the square of the disk thickness.

What is claimed is: 
     
         1 . A disk for a magnetic recording apparatus, comprising:
 a substrate comprising a first surface and a second surface, wherein the substrate has a substrate thickness S 1 ;   a first coating layer disposed over the first surface of the substrate, wherein the first coating layer has a first coating layer thickness C 1 ; and   a second coating layer disposed over the second surface of the substrate, wherein the second coating layer has a second coating layer thickness C 2 ,   wherein the disk has a disk thickness D 1 ,   wherein the disk thickness D 1  includes the substrate thickness S 1 , and   wherein a maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of the square of the disk thickness D 1 .   
     
     
         2 . The disk of  claim 1 , wherein the disk thickness D 1  includes the substrate thickness S 1 , the first coating layer thickness C 1  and the second coating layer thickness C 2 . 
     
     
         3 . The disk of  claim 1 , wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of the square of a first ratio that includes the disk thickness D 1 . 
     
     
         4 . The disk of  claim 3 ,
 wherein a numerator of the first ratio includes the disk thickness D 1 , and   wherein a denominator of the first ratio is a thickness between 0.2 millimeter (mm) and 1 millimeter (mm).   
     
     
         5 . The disk of  claim 1 ,
 wherein the substrate has a substrate Young's modulus value E 1 , and   wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of (i) the square of a first ratio that includes the disk thickness D 1 , and (ii) a second ratio that includes the substrate Young's modulus value E 1 .   
     
     
         6 . The disk of  claim 5 ,
 wherein a numerator of the second ratio is the substrate Young's modulus value E 1 , and   wherein a denominator of the second ratio is in a range of about 60-80 gigapascals (Gpa).   
     
     
         7 . The disk of  claim 5 ,
 wherein the disk comprises a thickness of approximately  0 . 5  millimeter (mm) or less,   wherein the disk comprises a flatness of approximately 20 micrometers (μm) or less,   wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is 0.43 micrometer (μm), and   wherein the substrate Young's modulus value E 1  for the substrate is approximately 68 gigapascals (Gpa).   
     
     
         8 . The disk of  claim 5 ,
 wherein the disk comprises a thickness of approximately 0.5 millimeter (mm) or less,   wherein the disk comprises a flatness of approximately 20 micrometers (μm) or less,   wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is 0.60 micrometer (μm), and   wherein the substrate Young's modulus value E 1  for the substrate is approximately 95 gigapascals (Gpa).   
     
     
         9 . The disk of  claim 1 , wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of 
       
         
           
             
               
                 
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         wherein E 1  is a substrate Young's modulus value for the substrate, 
         wherein E 0  is a substrate Young's modulus value for a particular substrate, 
         wherein D 1  is a disk thickness for the disk, 
         wherein D 0  is a disk thickness for a particular disk comprising the particular substrate, and 
         wherein MTD 0  is a maximum thickness difference between a first particular coating layer thickness C 1   0  and a second particular coating layer thickness C 2   0  for the particular disk. 
       
     
     
         10 . The disk of  claim 9 ,
 wherein the disk thickness D 1  equals the substrate thickness S 1 , and   wherein D 0  is a disk thickness equals the substrate thickness of the particular substrate.   
     
     
         11 . The disk of  claim 1 ,
 wherein the first coating layer thickness C 1  has a thickness in a range of 12-30 micrometers (μm), and   wherein the second coating layer thickness C 2  has a thickness in a range of 12-30 micrometers (μm).   
     
     
         12 . The disk of  claim 1 , further comprising a magnetic recording layer disposed over the first coating layer, wherein the magnetic recording layer is configured to store information. 
     
     
         13 . The disk of  claim 1 , wherein the first coating layer and the second coating layer comprises nickel phosphorous (NiP). 
     
     
         14 . The disk of  claim 13 , wherein the substrate comprises glass. 
     
     
         15 . The disk of  claim 1 , wherein the substrate comprises aluminum. 
     
     
         16 . The disk of  claim 15 , wherein the substrate further comprises a material selected from the group consisting of magnesium, zinc, glass and combinations thereof. 
     
     
         17 . A magnetic storage device configured to store information, comprising:
 a disk comprising:
 a substrate comprising a first surface and a second surface, wherein the substrate has a substrate thickness S 1 , 
 a first coating layer disposed over the first surface of the substrate, wherein the first coating layer has a first coating layer thickness C 1 ; and 
 a second coating layer disposed over the second surface of the substrate, wherein the second coating layer has a second coating layer thickness C 2 , 
 wherein the disk has a disk thickness D 1 , 
 wherein the disk thickness D 1  includes the substrate thickness S 1 , and 
 wherein a maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of the square of the disk thickness D 1 , and 
   a slider configured to glide over a surface of the disk.   
     
     
         18 . The magnetic storage device of  claim 17 , wherein the disk thickness D 1  includes the substrate thickness S 1 , the first coating layer thickness C 1  and the second coating layer thickness C 2 . 
     
     
         19 . The magnetic storage device of  claim 17 , wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of the square of a first ratio that includes the disk thickness D 1 . 
     
     
         20 . The magnetic storage device of  claim 17 , wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of 
       
         
           
             
               
                 
                   MTD 
                   0 
                 
                 × 
                 
                   
                     ( 
                     
                       
                         D 
                          
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                     E 
                      
                     1 
                   
                   
                     E 
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               , 
             
           
         
         wherein E 1  is a substrate Young's modulus value for the substrate, 
         wherein E 0  is a substrate Young's modulus value for a particular substrate, 
         wherein D 1  is a disk thickness for the disk, 
         wherein D 0  is a disk thickness for a particular disk comprising the particular substrate, and 
         wherein MTD 0  is a maximum thickness difference between a first particular coating layer thickness C 1   0  and a second particular coating layer thickness C 2   0  for the particular disk. 
       
     
     
         21 . The magnetic storage device of  claim 17 ,
 wherein the disk thickness D 1  equals the substrate thickness S 1 , and   wherein D 0  is a disk thickness equals the substrate thickness of the particular substrate.   
     
     
         22 . A method for fabricating a disk for a magnetic recording apparatus, comprising:
 providing a substrate comprising a first surface and a second surface, wherein the substrate has a substrate thickness S 1 ,   forming a first coating layer over the first surface of the substrate, wherein the first coating layer has a first coating layer thickness C 1 ; and   forming a second coating layer over the second surface of the substrate, wherein the second coating layer has a second coating layer thickness C 2 ,   wherein the disk is fabricated such that the disk has a disk thickness D 1 ,   wherein the disk thickness D 1  includes the substrate thickness S 1 , and   wherein the second coating layer is formed over the second surface such that a maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of the square of the disk thickness D 1 .   
     
     
         23 . The method of  claim 22 , wherein the disk thickness D 1  includes the substrate thickness S 1 , the first coating layer thickness C 1  and the second coating layer thickness C 2 . 
     
     
         24 . The method of  claim 22 , wherein the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of the square of a first ratio that includes the disk thickness D 1 . 
     
     
         25 . The method of  claim 24 ,
 wherein a numerator of the first ratio includes the disk thickness D 1 , and   wherein a denominator of the first ratio is a thickness between 1 millimeter (mm) and 0.2 millimeter (mm).   
     
     
         26 . The method of  claim 22 ,
 wherein the substrate has a substrate Young's modulus value E 1 , and   wherein the second coating layer is formed over the second surface such that the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of (i) the square of the first ratio that includes the disk thickness D 1 , and (ii) a second ratio that includes the substrate Young's modulus value E 1 .   
     
     
         27 . The method of  claim 26 ,
 wherein a numerator of the second ratio is the substrate Young's modulus value E 1 , and   wherein a denominator of the second ratio is in a range of about 60-80 gigapascals (Gpa).   
     
     
         28 . The method of  claim 22 , wherein the second coating layer is formed over the second surface such that the maximum thickness difference between the first coating layer thickness C 1  and the second coating layer thickness C 2  is a function of 
       
         
           
             
               
                 
                   MTD 
                   0 
                 
                 × 
                 
                   
                     ( 
                     
                       
                         D 
                          
                         1 
                       
                       
                         D 
                          
                         0 
                       
                     
                     ) 
                   
                   2 
                 
                 × 
                 
                   
                     E 
                      
                     1 
                   
                   
                     E 
                      
                     0 
                   
                 
               
               , 
             
           
         
         wherein E 1  is a substrate Young's modulus value for the substrate, 
         wherein E 0  is a substrate Young's modulus value for a particular substrate, 
         wherein D 1  is a disk thickness for the disk, 
         wherein D 0  is a disk thickness for a particular disk comprising the particular substrate, and 
         wherein MTD 0  is a maximum thickness difference between a first particular coating layer thickness C 1   0  and a second particular coating layer thickness C 2   0  for the particular disk. 
       
     
     
         29 . The method of  claim 28 ,
 wherein the disk thickness D 1  equals the substrate thickness S 1 , and   wherein D 0  is a disk thickness equals the substrate thickness of the particular substrate.   
     
     
         30 . The method of  claim 22 , further comprising forming a magnetic recording layer over the first coating layer, wherein the magnetic recording layer is configured to store information.