Method for making a video disc

Details Method for making a video disc Method for making a video disc

1981-11-03

1983-08-09

Pavelko, Thomas P.

Plastic and nonmetallic article shaping or treating: processes

Mechanical shaping or molding to form or reform shaped article

Shaping against forming surface

264107, 26432817, 425810, B29D 1700

Patent

active

043978053

ABSTRACT:
A video disc member is described having a uniform value of birefringence over the entire information storage surface of the disc. This value of birefringence is the same at the inner information storage radius as at the outer information storage radius. The preferable composition of the video disc is a specially prepared polymethylmethacrylate, referred to as PMMA. The method of molding the improved video disc member includes an extended drying time for said composition and increasing the melting temperature. The increase in melt temperature provides a low and uniform value of birefringence. The improved drying cycle eliminates splay marks, blisters and other surface imperfections as compared to manufacturer recommended drying times.

REFERENCES:
patent: 1997572 (1935-04-01), Bren
patent: 4176104 (1979-11-01), Alsburg
patent: 4185955 (1980-01-01), Holmes
"A More Heat-Resistant Acrylate Material," British Plastics, Oct. 1943, pp. 254-257.

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