STORAGE MEDIUM SUBSTRATE AND STORAGE MEDIUM CONSISTING OF THE SAME

摘要

PROBLEM TO BE SOLVED: To obtain a storage medium having low gas emission and excellent surface smoothness and rigidity and made of polyphenylene sulfide resin useful for a surface recording type disk substrate. SOLUTION: The storage medium substrate consists of a thermoplastic resin composition of polyphenylene sulfide resin comprising 0.05-400 pts.wt. inorganic filler material mixed with 100 pts.wt. thermoplastic resin and having <=0.3 wt.% heating loss at 320 deg.C for 2 hrs and >=4 Gpa flexural modulus. One third or more of the overall surface area of the storage medium substrate characteristically has <=50 nm center line mean roughness Ra, >=80% image clarity (1 mm slit width), <=20 μm flatness represented by maximum waviness WCM and <=0.1% water absorption after immersion in water at 23 deg.C for 24 hrs.