Professor Young
78 Professor Young was asked to give his opinion, based upon his knowledge on or before June 1998, as to which metal or metals he would have advised prior to June 1998 to be most suitable to use to comprise the reflective layer in a recordable CD and, specifically:
'(a) if the metallic coating was composed of 100% silver whether all of the specifications in relation to the reflective layer set out [below] would be satisfied;
(b) if the metallic coating was composed of 100% gold whether all of the specifications in relation to the reflective layer set out [below] would be satisfied; and
(c) if neither 100% silver nor 100% gold satisfies all of the specifications set out [below], then please provide your expert opinion as to suitable alternatives for the composition of the metallic coating; ie what metal or metals we could use to form the reflective layer so that all of the characteristics set out [below] above are satisfied.
79 Professor Young was given the following specifications:
(a) The metallic coating should be as reflective as possible and at least 95% reflective at the required wavelength of light.
(b) The metal or metals comprising the metallic reflective layer should be able to be deposited using deposition methods that were commonly used as at June 1998 (eg evaporation or sputtering).
(c) The metal or metals comprising the metallic reflective layer should be stable, that is not corrode or otherwise change its physical properties when being exposed to sunlight, heat, normal atmospheric conditions and other environmental conditions to which CDs or DVDs may typically be exposed. Optical recording media optimally has a life span of around 30 years.
(d) The metal or metals comprising the reflective layer should be as economical as possible, as the discs are to be commercialised.
80 Professor Young was given a series of assumptions. In the absence of evidence to the contrary, I accept that those assumptions represent the information he would have been given by Dr Day of the notional team.
81 In accordance with the given assumption, Professor Young first considered whether reflective layers comprising 100% silver and 100% gold would meet the required specifications. He concluded that neither 100% silver or 100% gold would meet the required specifications.
82 Professor Young then set out his evidence in great detail. He referred to reference books which he had in his possession and which he states were commonly known and used in the materials science/metallurgist field and kept in university libraries. He gave his reason for referring to each book, for example, to ascertain the percentage reflectivity of a metal. He explained the techniques of which he was aware prior to the priority date, such as sputtering and those he had used prior to the priority date, such as deposition methods. He also explained problems that were well-known to him and to other metallurgists and materials scientists prior to the priority date, such as corrosion and the susceptibility to corrosion of silver.
83 Professor Young had taught the strategies of alloying metals to counteract corrosion to undergraduate university students since at least 1980 and had carried out research on alloying for corrosion since 1971. He was also aware of the cost of various metals such as gold, silver and platinum.
84 Prior to June 1998, he was aware that permutations of differing amounts of constituents in any one kind of alloy could be expressed in suitable ranges. For example, an iron chromium alloy containing from 12 to 25 percentage weight chromium can be specified by the atomic formula Fe(a) Cr(b) where 0.74£ a £ 0.87 and 0.13 £b £0.26. The values of (a) and (b) specify the fractions of the atoms in the alloy which are, respectively, iron and chromium. Prior to June 1998, this was a commonly used method of expressing ranges of constituents in alloys and was one that he frequently used.
85 For reasons that he gives, Professor Young's evidence is that, prior to the priority date he would, by a process of logic, have concluded that gold would be sufficiently stable to use in the reflective layer of recordable CDs but that silver would not be sufficiently stable because of its susceptibility to tarnishing in typical urban atmospheres and to corrosion in the presence of halogen ions in the organic dye. He would not have considered gold appropriate on economic grounds.
86 Professor Young says that, as silver was satisfactory save for its susceptibility to corrosion, he would have considered metal alloys. As the silver alloy was to be designed for corrosion resistance, he would have chosen the dilution method for alloying silver and he would have alloyed the silver with palladium, rejecting his first consideration of platinum for cost reasons. He gave reasons for the choice of palladium on the basis of characteristics of that metal that were part of common general knowledge. He would have kept the palladium content in the silver palladium alloy sufficiently low to meet the reflectivity requirements, as palladium has a relatively low reflectivity compared with silver and gold, but at a high enough level to counteract the silver tarnishing. He would have started with a range of palladium being 1% to 20% by weight. When described in atomic fractions, this is Ag(a)Pd(b) where 0.80 £ 0.99 and 0.01 £ 0.20. It would have been customary to provide a number of appropriate ranges for the respective amounts of silver and palladium present in the alloy and to determine those by routine accelerated exposure testing.
87 Prior to June 1998, having considered an appropriate starting range for the amount of palladium comprising the silver palladium alloy, Professor Young would have then run accelerated exposure tests on reflective layers, starting at the lower limits of the range (1 atomic percent palladium). Such tests were routinely used to test materials for their relative ability to resist corrosion.
88 The upper threshold limit of the suitable amount of palladium would be determined by whether the silver palladium alloy was at least 95% reflective, as required.
89 In recommending the amounts of silver and palladium to be used in the alloy, he would have provided a number of appropriate ranges for the amounts. He says that it was customary for metallurgists and materials scientists to do so prior to June 1998 as it is now.
90 If asked to continue to recommend suitable alloys, Professor Young would have, for reasons which he gave based on well-known brazing alloys, recommended silver palladium copper alloys. In order to bond two metals, a brazing alloy is melted and used as a "glue" to join the two metals. He would have started with 23 atomic percent of copper. It was commonly known that these alloys could be deposited using routine methods such as evaporation or sputtering.
91 Professor Young would also have considered other inert metals which had properties similar to palladium and, in particular platinum and rhodium. They could be added in small amounts to silver palladium and to silver palladium copper alloys.
92 Professor Young selected the proportions of the metals by reference to a set of known and desirable criteria and by reference to textbooks that formed part of common general knowledge.
93 The evidence is that a silver-based alloy was an obvious choice because it was well known that silver has high optical reflectivity. It was also well known that corrosion was a problem, so that any metals combined with silver would need to assist in corrosion resistance.
94 Professor Young's evidence is that the qualities of various metals were matters of ordinary knowledge by metallurgists or materials scientists. Such persons armed with knowledge of the requirements of optical storage media as specified by a designer of reflective layers for optical storage media would have chosen the alloys claimed.
95 Professor Young's evidence represents the mental logic that would have been applied by him, had be been consulted prior to the priority date to recommend metals for use in an optical storage medium with the properties required. He would have chosen silver palladium alloys and the addition of precious metals. He also explains how and why particular proportions and ranges would have been chosen. The way in which his evidence was obtained, without knowledge of the patent and in response to questions which asked for recommendations based upon the required properties that would have been specified by Dr Day, satisfies me that his evidence does not reflect a hindsight analysis with knowledge of the subject matter of the claims.