Winding core and magnetic recording medium producing method

Abstract

A winding core 10 according to the present invention has a cylindrical outer peripheral surface and arranged in a manner that when a web is wound around the outer peripheral surface and so a predetermined pressure acts on the outer peripheral surface, the deformation distortion γ(=ΔR/R) of the outer peripheral surface along the radial direction thereof is equal to or less than 0.001. In this case, ΔR represents the maximum deformation amount along the radial direction of the outer peripheral surface of the winding core and R the diameter of the outer peripheral surface of the winding core upon no occurrence of deformation.

What is claimed is:  
     
         1 . A winding core comprising 
 a cylindrical outer peripheral surface for winding a web,    wherein when a predetermined pressure acts on said outer peripheral surface by winding web, deformation distortion γ of said outer peripheral surface along radial direction thereof satisfies following expressions:   γ=Δ R/R≦ 0.001,   and   γ≦0.001,   wherein ΔR represents a maximum deformation amount along said radial direction of said outer peripheral surface of said winding core and R represents a diameter of said outer peripheral surface of said winding core upon no occurrence of deformation.    
     
     
         2 . A winding core comprising 
 a cylindrical outer peripheral surface for winding a web,    wherein when a pressure acts on said outer peripheral surface by winding said web, deformation coefficient β of said winding core satisfies following expressions:   β=Δ R×P/R   2     and,   β≦6.0×10 −11 ,   wherein ΔR represents a maximum deformation amount (m) along a radial direction of said outer peripheral surface of said winding core, P represents a pressure (N/m 2 ) acting on said outer peripheral surface of said winding core and R represents a diameter (m) of said outer peripheral surface of said winding core upon no occurrence of deformation.    
     
     
         3 . The winding core according to    claim 1   , comprising a supporting portion which fits an outer surface thereof fits to an inner surface of said winding core.  
     
     
         4 . A method for producing a magnetic recording medium comprising a step of winding a web around a winding core, 
 wherein when a predetermined pressure acts on an outer peripheral surface of said winding core by winding said web, a following expression is satisfied at said outer peripheral surface:   Δ R/R≦ 0.001,   wherein ΔR represents a maximum deformation amount along a radial direction of said outer peripheral surface and R represents a diameter of said outer peripheral surface of said winding core upon no occurrence of deformation.    
     
     
         5 . A method for producing a magnetic recording medium comprising a step of winding a web around a winding core, 
 wherein a following expression is satisfied at an outer peripheral surface of said winding core:   Δ R×P/R   2 ≦6.0×10 −11 ,   wherein ΔR represents a maximum deformation amount (m) along a radial direction of an outer peripheral surface, P represents a pressure (N/m 2 ) acting on said outer peripheral surface of said winding core and R represents a diameter (m) of said outer peripheral surface of said winding core upon no occurrence of deformation.