The development of friction modifying back coats for optical tapes

For many years magnetic tapes and discs have been the standard method of storing large amounts of information, and increasingly optical discs are being used for some archive operations where high density storage is required. Optical Tape is the next logical step in the media storage market, offering increasingly higher data storage capacities at lower cost per byte of information than other storage methods. Information is written onto optical discs and tapes by use of a focussed laser. Writing a pattern of pits that are recognised as 1s and 0s by the computer, thus storing information using binary code as does magnetic media. Optical Tape, unlike magnetic media, has a very smooth sensitive active layer, this is where information is written. The speed at which the tape moves through the tape drive necessitates a back coat to modify the frictional properties of the tape. This programme of work investigates the development of back coats for two different optical tapes, from the point where it was realised that a backcoat would be required to the production of a development grade material. It was discovered that there was a fine balance between the degree of surface roughness required for good handling with appropriate frictional properties and prevention of damage to the sensitive active layers, either during tape handling or when the tapes are archived for long periods.