Hoya Corporation

Toray Plastics (America), Inc.

Hirokazu Tajima

Tamaki Horisaka

Hiromi Nakano

Nao Yokota

Roberto Siu

Carlos Hinton

Biaxially oriented polyester films including polyester polymer, a carbodiimide hydrolysis stabilizer, and a UV absorber are described. The polyester films have a carboxyl end group concentration of 5-20 equivalents per ton, and a haze value of 2% or less. The films exhibit superior transparency and possess stable light transmission characteristics. Methods of making the films and articles produced from the films are also described.

Optically clear UV and hydrolysis resistant polyester film

A polishing pad is used when a surface of a glass workpiece is polished for manufacturing a glass substrate of information recording medium. The polishing pad has a nap layer. The nap layer includes an inner layer that contains a plurality of closed cells, and an outer layer. A plurality of pores are formed on the surface of the outer layer. The sizes of the pores are minute compared to those of the closed cells.

Glass substrate for data recording medium, manufacturing method thereof and polishing pad used in the method

A polishing pad used for precise polishing of the surface of a lapped glass workpiece when a glass substrate for use in data recording media is manufactured from a glass workpiece. The polishing pad comprises a base and a polishing portion laminated on the base and contacting the surface of the glass workpiece at the time of polishing. The polishing portion is formed of a foam made of a synthetic resin having a 100% modulus of 11.8 MPa or less. A type of parameter representing the surface roughness of the polishing portion, namely, the maximum height (Rmax), is 70 &#x3bc;m or less.

Polishing pad, method of manufacturing glass substrate for use in data recording medium using the pad, and glass substrate for use in data recording medium obtained by using the method

A glass substrate for a data recording medium is manufactured by using a tabular carrier with circular holes formed therein, housing disk-shaped glass workpieces in the circular holes of this carrier, sliding polishing pads over the surface of the carrier and the principal surfaces of the glass workpieces and polishing the glass workpieces until the height (NRa) of micro-waviness on the principal surfaces of the glass workpieces is reduced to a predetermined value or less. The height (NRa) of micro-waviness of the principal surfaces is a value dependent on the surface roughness of the polishing pad and the surface roughness of this polishing pad is a value dependent on the surface roughness of the carrier. A glass substrate for a data recording medium is manufactured by reducing the surface roughness (Ra) of the carrier to 0.08 &#x3bc;m or less and polishing the glass workpieces until the height (NRa) of micro-waviness on the principal surfaces measured using a three-dimensional surface structure analysis microscope whose measuring wavelength (&#x3bb;) is set to 0.2 to 1.4 mm is reduced to 0.12 nm or less.

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Osaka, Japan

Hirokazu Tajima