Magnetic tape and magnetic tape cartridge

Abstract

A magnetic recording medium comprising a non-magnetic support; at least one lower magnetic layer containing magnetic powder and a binder resin, which is formed on one side of the non-magnetic support with or without a non-magnetic primer layer interposed between the non-magnetic support and the lower magnetic layer; at least one non-magnetic intermediate layer containing non-magnetic powder and a binder resin, which is formed on the lower magnetic layer; at least one upper magnetic layer containing magnetic powder and a binder resin, which is formed on the non-magnetic intermediate layer; and a back layer which is formed on the other side of the non-magnetic support, characterized in that the magnetic powder contained in the uppermost magnetic layer of the upper magnetic layer is iron type magnetic powder which comprises substantially spherical or ellipsoidal particles with a number-average particle diameter of 5 to 50 nm and an average axial ratio of 1 to 2, each of said particles containing iron or containing iron as a main component and a transition element; and that the total thickness of the magnetic recording medium is 6 μm or less. This magnetic recording medium has electromagnetic conversion, characteristics which cannot be achieved by any of conventional magnetic recording media, and also is expected to have excellent magnetic serve characteristics.

1 . A magnetic recording medium comprising 
 a non-magnetic support,    at least one primer layer containing non-magnetic powder and a binder resin, which is formed on one side of the non-magnetic support, and    at least one magnetic: layer containing magnetic powder and a binder resin, which is formed on said primer layer,    wherein said magnetic powder contained in the uppermost magnetic layer is iron-containing magnetic powder comprising substantially spherical or ellipsoidal particles which have a number-average particle diameter of 5 to 50 nm and an iron nitride phase in which 0 to 40 atomic % of iron elements are replaced with a transition metal, and wherein the uppermost magnetic layer has a thickness of 0.89 μm or less, and a coercive force of 200 to 400 kA/m.    
     
     
         2 . The magnetic recording medium according to  claim 1 , wherein the iron-containing magnetic powder contained in the uppermost magnetic layer comprises at least, one element selected from the group consisting of rare earth elements, aluminum and silicon.  
     
     
         3 . The magnetic recording medium according to  claim 1 , wherein said iron nitride phase is an iron nitride phase represented by Fe 16 N 2 .  
     
     
         4 . The magnetic recording medium according to  claim 1 , wherein a total thickness of the magnetic recording medium is less than 6 μm.  
     
     
         5 . A magnetic recording cartridge comprising a box-shaped casing body and a reel onto which, the magnetic recording medium claimed in  claim 1  is wound, disposed in the box-shaped casing body, 
 characterized in that magnetically recorded data signals on the uppermost magnetic layer of the medium are reproduced with a magnetoresistance magnetic head.    
     
     
         6 . A magnetic recording medium comprising 
 a non-magnetic support,    at least one primer layer containing non-magnetic powder and a binder resin, which is formed on one side of the non-magnetic support, and    at least one magnetic layer containing magnetic powder and a binder resin, which is formed on said, primer layer,    wherein said magnetic powder contained in the uppermost magnetic layer is iron-containing magnetic powder comprising substantially spherical or ellipsoidal, particles which have a number-average particle diameter of 5 to 50 nm and an iron nitride phase in which 0 to 40 atomic % of iron elements are replaced with a transition metal, and a product (Br·δ) of a residual magnetic flux density (Br) and a thickness (δ) of the uppermost magnetic layer is 0.0018 to 0.05 μTm, and wherein the uppermost magnetic layer has a coercive force of 200 to 400 kA/m.    
     
     
         7 . The magnetic recording medium according to  claim 6 , wherein the iron-containing magnetic powder contained in the uppermost magnetic layer comprises at least, one element, selected from the group consisting of rare earth elements, aluminum and silicon.  
     
     
         8 . The magnetic recording medium according to  claim 6 , wherein said iron nitride phrase is an iron nitride phase represented by Fe 16 N 2 .  
     
     
         9 . The magnetic recording medium according to:  claim 6 , wherein, a total thickness of the magnetic recording medium is less than 6 μm.  
     
     
         10 . A magnetic recording cartridge comprising a box-shaped casing body and a reel onto which the magnetic recording medium claimed in  claim 5  is wound, disposed in the box-shaped casing body, 
 characterized in that magnetically recorded data signals on the uppermost magnetic layer of the medium are reproduced with magnetoresistance magnetic head.    
     
     
         11 . A magnetic recording medium comprising 
 a non-magnetic support,    at least one primer layer containing non-magnetic powder and a binder resin, which is formed on one side of the non-magnetic support, and    at least one magnetic layer containing magnetic powder and a binder resin, which is formed on said primer layer,    wherein said magnetic powder contained in the uppermost magnetic layer is iron-containing magnetic powder comprising substantially spherical or ellipsoidal particles which have a number-average particle diameter of 5 to 50 nm and an iron nitride phase in which 0; to 40 atomic % of iron elements are replaced with a transition metal, and wherein the uppermost magnetic layer has an anisotropic magnetic field, distribution (Ha) of 0.51 or less and a coercive force of 200 to 400 kA/m.    
     
     
         12 . The magnetic recording medium according to  claim 11 , wherein the iron-containing magnetic powder contained in the uppermost magnetic layer comprises at least one element selected from the group consisting of rare earth elements, aluminum and silicon.  
     
     
         13 . The magnetic recording medium according to  claim 11 , wherein said iron nitride phase is an iron nitride phase represented by Fe 16 N 2 .  
     
     
         14 . The magnetic recording medium according to  claim 11 , wherein a total thickness of the magnetic recording medium is less than 6 μm.  
     
     
         15 . A magnetic recording cartridge comprising a box-shaped casing body and a reel once which the magnetic recording medium claimed in  claim 11  is wound, disposed in the box-shaped casing body, 
 characterized in that magnetically recorded data signals on the uppermost magnetic layer of the medium are reproduced with a magnetoresistance magnetic head.