Shaping tool for information carrier disc blanks

A method for production of information-carrying disk blanks of polymethacrylate plastic by injection molding or compression molding in an apparatus comprising two mold parts, wherein one mold part contains a female die with the information data and together with the second mold part forms a cavity for the one information-carrying disk blank, a sprue bushing for a sprue piece with a centrally positioned gate, and an impact cylinder for shearing the sprue piece in the apparatus and an ejector pin are also provided, wherein the injection gap between the gate of the sprue piece and the information-carrying disk blank is smaller than 0.3 mm and the cutting gap between the rim of the impact cylinder and the information-carrying disk blank is smaller than 0.2 mm, in which method the polymethacrylate plastic in molten condition is injected via a nozzle at high pressure through the sprue bushing into the apparatus, the polymethacrylate plastic solidifies in the apparatus, the sprue piece is sheared off inside the apparatus, at gate, by means of the impact cylinder, the sprue piece is ejected by means of the ejector pin, and the information-carrying disk blank is removed after the apparatus has been opened, wherein the polymethacrylate plastic is used in the form of a granulated polymethacrylate molding compound

• comprising 85 to 97 wt % of methyl methacrylate and 15 to 3 wt % of methyl acrylate, ethyl acrylate or n-butyl acrylate
• with a melt-flow index of 5.5 to 30 ml/10 minutes at 230° C./3.8 kg (ISO 1133)
• thermal stability of at least 320° C. (TD value for 2% weight loss, measured in a thermal gravimetric analysis balance at a heating rate of 5° C./minute under nitrogen atmosphere)
• a modulus of elasticity of 2800 to 3300 MPa (ISO 527)
• a fines proportion in the granules of less than 0.5 wt %, determined by sieve analysis (1.6 mm mesh openings).

An information-carrying disk blank of polymethacrylate plastic, obtainable in a method for production of information-carrying disk blanks of polymethacrylate plastic by injection molding or compression molding in an apparatus comprising two mold parts, wherein one mold part contains a female die with the information data and together with the second mold part forms a cavity for the one information-carrying disk blank, a sprue bushing for a sprue piece with a centrally positioned gate, and an impact cylinder for shearing the sprue piece in the apparatus and an ejector pin are also provided, wherein the injection gap between the gate of the sprue piece and the information-carrying disk blank is smaller than 0.3 mm and the cutting gap between the rim of the impact cylinder and the information-carrying disk blank is smaller than 0.2 mm, in which method the polymethacrylate plastic in molten condition is injected via a nozzle at high pressure through the sprue bushing into the apparatus, the polymethacrylate plastic solidifies in the apparatus, the sprue piece is sheared off inside the apparatus, at gate, by means of the impact cylinder, the sprue piece is ejected by means of the ejector pin, and the information-carrying disk blank is removed after the apparatus has been opened, wherein a roughened zone due to removal of the gate is disposed centrally at the rim of the hole of the information-carrying disk.