Magnetic tape

Abstract

A magnetic tape favorably employable for recording computer data, comprising a support web, a magnetic layer and a back-coat layer and having a thickness of 3 to 10 μm, should have a curl having a radius of curvature of greater than 10 mm in its longitudinal direction and a curl having a radius of curvature of greater than 40 mm in its width direction, wherein the curl in the width direction gives a convex surface on the side of the magnetic layer.

What is claimed is:  
     
         1 . A magnetic tape having a thickness of 3 to 10 μm, which comprises a support web, a magnetic layer which is placed on a surface on one side of the support web and comprises a ferromagnetic powder and a binder, and a back-coat layer which is placed on a surface on another side of the support web and comprises carbon black and a binder, which shows a curl having a radius of curvature of greater than 10 mm in its longitudinal direction and a curl having a radius of curvature of greater than 40 mm in its width direction, said curl in the width direction giving a convex surface on the side of the magnetic layer.  
     
     
         2 . The magnetic tape of  claim 1 , wherein the support web has a Young's modulus of 750 to 950 kg/mm 2  in its longitudinal direction and a less Young's modulus in its width direction, the ratio of the former Young's modulus to the latter Young's modulus being in the range of 1.1 to 1.8.  
     
     
         3 . The magnetic tape of  claim 1 , wherein the support web has a thickness in the range of 3.0 to 7.0 μm.  
     
     
         4 . The magnetic tape of  claim 1 , wherein the back-coat layer has a thickness in the range of 0.3 to 0.6 μm.  
     
     
         5 . The magnetic tape of  claim 1 , wherein the binder of the back-coat layer comprises at least one of nitrocellulose resin, vinyl chloride resin, and a phenoxy resin.  
     
     
         6 . The magnetic tape of  claim 1 , wherein the carbon black of the back-coat layer comprises one carbon black having an average diameter of 10 to 20 mμ and another carbon black having an average diameter of 230 to 300 mμ.  
     
     
         7 . A magnetic tape having a thickness of 3 to 10 μm, which comprises a support web, a non-magnetic layer which is placed on a surface on one side of the support web, has a thickness of 0.3 to 2.5 μm and comprises a non-magnetic powder and a binder, a magnetic layer which is placed on the non-magnetic layer, has a thickness of 0.05 to 1.0 μm and comprises a ferromagnetic powder and a binder, and a back-coat layer which is placed on a surface on another side of the support web which comprises carbon black and a binder, which shows a curl having a radius of curvature of greater than 10 mm in its longitudinal direction and a curl having a radius of curvature of greater than 40 mm in its width direction, said curl in the width direction giving a convex surface on the side of the magnetic layer.  
     
     
         8 . The magnetic tape of  claim 7 , wherein the support web has a Young's modulus of 750 to 950 kg/mm 2  in its longitudinal direction and a less Young's modulus in its width direction, the ratio of the former Young's modulus to the latter Young's modulus being in the range of 1.1 to 1.8.  
     
     
         9 . The magnetic tape of  claim 7 , wherein the support web has a thickness in the range of 3.0 to 7.0 μm.  
     
     
         10 . The magnetic tape of  claim 7 , wherein the back-coat layer has a thickness in the range of 0.3 to 0.6 μm.  
     
     
         11 . The magnetic tape of  claim 7 , wherein the binder of the back-coat layer comprises at least one of nitrocellulose resin, vinyl chloride resin, and a phenoxy resin.  
     
     
         12 . The magnetic tape of  claim 7 , wherein the carbon black of the back-coat layer comprises one carbon black having an average diameter of 10 to 20 mμ and another carbon black having an average diameter of 230 to 300 mμ.