Recording medium annealing process

Abstract

Stretched surface recording disk (SD) 10 comprises an annular support 12 having raised annular ridges 42 and 28 at its inside and outside diameters 22 and 30 with a base portion 24 in between the two ridges, and an annular recording medium film 14 held in radial tension and stretched across the base portion by adhering the film to attachment surfaces 48 and 36 near the inside and outside diameters respectively. The SD is annealed twice during manufacture to relieve stress in the stretched film 14. This annealing results in SD essentially free from track anisotropy and stress distribution anisotropy in the plane of the disk. As a result, data tracks are more stable than in previous SD, track density can be greater, and the SD is generally more reliable.

What is claimed is: 
     
       1. A process for annealing a stretched surface recording disk comprising a rigid annular support, having at least two concentric raised annular reference surfaces and an annular polymeric film, having a recording layer, attached to the support and stretched between and supported by the raised annular reference surfaces, said process comprising: A. annealing a polymeric film which has been fixed in radial tension, at a temperature above its glass transition temperature for a time sufficient to obtain a substantial absence of anisotropic stress distribution in the film;   B. bonding the annealed film from step A to the annular support at or near the inside and outside diameters of the support; and   C. annealing the product of step B, at a temperature above the glass transition temperature of the polymeric film but below the temperature which would cause warping of the annular support, for a time sufficient to obtain a substantial absence of anisotropic stress distribution in the polymeric film.   
     
     
       2. The process of claim 1 wherein step B is performed by bonding the annealed film to the annular support using a thermosetting adhesive. 
     
     
       3. The process of claim 1 wherein step B is performed by using an adhesive selected from the group consisting of acrylate and methacrylate functional adhesives which are curable by radiation, said adhesive being applied inbetween the polymeric film and the annular support, and curing said adhesive by exposing it to electron beam radiation. 
     
     
       4. The process of claim 3 wherein the adhesive is selected from the group consisting of acrylated epoxy resins, acrylated bisphenol A resins, polyester acrylate resins, acrylated urethane .[.resina.]. .Iadd.resins .Iaddend.and alkyd acrylates. 
     
     
       5. The process of claim 3 wherein the electron beam irradiation process of step B is performed using an inert atmosphere having less than 60 ppm oxygen, and the annealed film and annular support are exposed to no more than about 10 Mrad of radiation. 
     
     
       6. The process of claim 1 wherein step A is carried out at conditions selected from: 16 hours of annealing at 66° C. or 3 minutes of annealing at 166° C. 
     
     
       7. The process of claim 1 wherein step C is carried out at conditions selected from: 4 minutes of annealing at 93° C. or 36 hours of .[.anneling.]. .Iadd.annealing .Iaddend.at 66° C. 
     
     
       8. A process for annealing a stretched surface recording disk comprising a rigid annular support, having at least two concentric raised annular reference surfaces and an annular polymeric film, having a recording layer, attached to the support and stretched between and supported by the raised annular reference surfaces, said process comprising: A. annealing a polymeric film which has been fixed in radial tension, at a temperature above its glass transition temperature for a time sufficient to obtain a substantial absence of anisotropic .[.stree.]. .Iadd.stress .Iaddend.distribution in the film;   B. bonding the annealed film from step A to the annular support at or near the inside and outside diameters of the support; and   C. annealing the product of step B in an oven by placing the product of step B within a temperature dampening chamber within an oven, said temperature dampening chamber consisting essentially of a container larger than the annular support and a holding means for holding the product of step B, and maintaining temperature above the glass transition temperature of the polymeric film but below the temperature which would cause warping of the annular support, for a time sufficient to obtain a substantial absence of anisotropic stress distribution in the polymeric film. .Iadd.   
     
     
       9.  A process for producing a magnetic disc comprising (1) bonding a recording medium film disc comprising a biaxially oriented flexible polyethylene terephthalate film substrate having a magnetic layer coated thereon to at least one side of an annular support wherein a gap is formed between the back surface of the recording medium film and the annular support and, then, (2) annealing the magnetic disc at a temperature in the range of 66° C. to 93° C. for 4 minutes to 36 hours. .Iaddend. .Iadd.10. The process of claim 9 wherein at least one air hole is provided between said gap and the atmosphere. .Iaddend.