Optical Recording

The first CDs

In the spring of 1981, Herbert von Karajan, conductor of the Berlin Philharmonic orchestra, was one of the first outsiders to be allowed to listen to the CD at Philips.

He instantly fell in love with the quality of the new medium. In April of that year, during the Salzburger Festspiele, Von Karajan decided to play the new sound at a press conference. "This is a technological advance that is comparable with the changeover from gas lamps to electric light," he told his audience.

Von Karajan’s enthusiasm was however not sufficient to win over the record companies for the new medium. PolyGram, a Philips subsidiary, only changed its track when Jan Timmer (later president of Philips) took over the helm. He announced a 500-day program to develop CD presses and to take the market by storm one and a half years later with half a million CDs.

Very precise equipment is required for the production of a CD. It starts with the production of one CD, the master. A powerful laser writes the information on a light-sensitive layer. The parts exposed to laser light are etched away, thus giving rise to the pit pattern. This positive master is used to make a negative die from nickel. This ‘stamper’ has bumps at the places where pits are to be made in the CD.

When the stamper is ready, it is installed in the core of the CD press. The negative die forms a part of the mould which is used to cast the CD. The CD is cast by heating plastic (polycarbonate) and injecting it into the mould. When the plastic has cooled, it leaves a disc in the mould which has a precise imprint of the pit pattern. This disc then passes to the following station in the machine to be given a reflective aluminum layer on the side with the pit pattern. This layer causes the laser light to be reflected when the CD is played. In the following process step the aluminum layer is coated in a protective transparent lacquer. The lacquer prevents the aluminum from oxidising and ensures that the CD remains antistatic. In most cases a label is then printed on the CD in the same machine.

All of this must be carried out with great precision. A single particle of dust can potentially cause irregularities and subsequently lead to hitches in the music. In the early days expensive cleanrooms were required to allow the equipment to operate unhindered and, because every person carries a lot of dust with them, the specialist technologists were dressed like astronauts so as to prevent any risk of contamination.

The extremely short development time for a CD factory could only be achieved using concurrent engineering, at that time a new way of carrying out large-scale production. Various technical aspects of the presses were not developed one after the other, but in parallel by separate teams. This meant that work was being carried out simultaneously on the processes for the presses, the application of a reflective metallic layer, the protective transparent coating, the printing of a label and the design of a factory.

This parallel method of working requires that the development teams are exceptionally well geared to one another. The manner in which the reflective layer had to be applied, for example, was very much dependent on the temperature during pressing or on the properties of the protective coating. A change in one process had consequences for another.

The PolyGram engineers did not know whether or not the result would be favorable until just before they were to commence building the factory. Then a prototype CD player became available with an audio output, with which the music could be made audible. Until that point in time, the test pressings could only be assessed by means of measuring instruments.

In August 1982 the real pressing was ready to begin in the new factory, not far from the place where Emil Berliner had produced his first gramophone record 93 years earlier. (Deutsche Grammophon, Berliner’s company, had by now become a part of PolyGram). The first CD that was pressed in Hanover was a recording of Herbert von Karajan conducting the Alpine Symphony by Richard Strauß. In January 1983, 500 working days after the start of production, half a million CDs had been made. The demand from Japan in particular was overwhelming.