Substrate for magnetic recording medium and method for manufacturing same

Abstract

Provided is a surface-treated substrate in which the roughness of the surface of the substrate is controlled. The surface-treated substrate can form a magnetic recording medium in which head flying stability is maintained and which has a magnetic film that can achieve high recording densities. Also provided is a method for roughening the surface of the substrate. More specifically, provided is a surface-treated silicon substrate for a magnetic recording medium in which a surface used for forming a recording layer has 40 to 1000 protrusions per 1 μm 2 with a maximum height of 10 nm or less and an average roughness of 0.3 to 2.0 nm, and in which there are no defects or spots on any of the surface. Furthermore, provided is a method for manufacturing the surface-treated silicon substrate for the magnetic recording medium, comprising a step of etching a surface of a silicon substrate, wherein ultrasound is applied to the surface of the silicon substrate with the substrate shaken or rotated. Also provided is a magnetic recording medium, comprising the silicon substrate.

1 . A method for manufacturing a surface-treated silicon substrate for a magnetic recording medium, the method comprising:
 a step of etching a surface of a silicon substrate wherein ultrasound is applied to the surface of the silicon substrate with the silicon substrate shaken or rotated.   
   
   
       2 . The method for manufacturing a surface-treated silicon substrate for a magnetic recording medium according to  claim 1 , wherein said ultrasound has a frequency of 20 to 3000 kHz. 
   
   
       3 . The method for manufacturing a surface-treated silicon substrate for a magnetic recording medium according to  claim 1 , wherein the substrate is shaken or rotated 1 to 80 times per minute in said step of etching. 
   
   
       4 . The method for manufacturing a surface-treated silicon substrate for a magnetic recording medium according to  claim 1 , wherein said step of etching comprises use of an etching agent comprising an alkaline salt and a surfactant, and having pH of 10 to 13. 
   
   
       5 . The method for manufacturing a surface-treated silicon substrate for a magnetic recording medium according to  claim 4 , wherein said surfactant is one or more selected from the group consisting of polyoxyalkylene alkyl ether, polyoxyalkylene alkyl phenyl ether, alkylbenzenesulfonic acid and salts thereof, alkyl phosphate, polyoxyalkylene alkyl phenyl ether sulfonic acid and salts thereof, polyoxyalkylene alkyl ether sulfonic acid and salts thereof, fluorine-based surfactant, salts of high amine and halogenated acid, halogenated alkylpyridinium and tertiary ammonium salts. 
   
   
       6 . The method for manufacturing a surface-treated silicon substrate for a magnetic recording medium according to  claim 4 , wherein said alkaline salt is one or more selected from the group consisting of potassium hydroxide, sodium hydroxide, sodium carbonate, sodium hydrogencarbonate, ammonium hydroxide, potassium carbonate and potassium hydrogencarbonate. 
   
   
       7 . The method for manufacturing a surface-treated silicon substrate for a magnetic recording medium according to  claim 4 , wherein said etching agent comprises said surfactant at a concentration of 0.01 to 10% by weight. 
   
   
       8 . The method for manufacturing a surface-treated silicon substrate for a magnetic recording medium according to  claim 1 , wherein temperature of said etching agent is 20 to 90° C.