Previous articles in this Journal have described the importance of patents as a key source of technical and commercial intelligence (1, 2). The use of patent mapping to visualise large sets of patent data and to identify trends contained within that data has also been demonstrated (2). The present paper further develops these themes by examining the patent literature on pgms published since 1983, in particular that on the minor metals iridium and ruthenium.

Searching – What and Where?

I will begin by thinking about search strategy. In this case, the initial objective is to create a large set of patents relating to the pgms, which will later be analysed and refined. The choice of keywords is therefore straightforward: platinum, palladium, rhodium, iridium, osmium and ruthenium. In the patent literature it is unlikely that the names of these metals would be used in other contexts. However, this might be a difficult problem if we were searching the news or business press, where the names of the pgms are associated with many brand names – for example there would probably be many hits on topics such as platinum credit cards or iridium satellite communication systems, and strategies for removing such material would need to be found.

Perhaps a more important question to ask is which patent collections to use to search for these words? The software package used at the Johnson Matthey Technology Centre is Aureka^® (a product available from Thomson Reuters) (3), which includes patent data sets from the Patent Cooperation Treaty (PCT) and European Patent offices, plus a range of national patent collections including those of the U.S.A., Japan, the U.K., France and Germany. With the exception of Japan, these collections contain full-text patent documents, available either as PDF or HTML files. In the case of Japanese patents, a text version of the English-language title, abstract and other front page details is available, together with a PDF file of the full specification in Japanese.

It must be borne in mind that using the French and German collections would require us to search in French or German respectively, and of course the results obtained would also be in French or German. The patent collections of other countries, for example China and India, are not currently available in Aureka. However at this stage we are looking for the big picture. The detail can follow later if necessary, for example by adding Chinese patent documents retrieved from other patent databases.

We also need to think about where in the patent document we might wish to search for information on pgms. This is an important question and to understand the various possibilities and their implications we first need to think about the structure of a typical patent:

Then, depending on the particular country, there may also be sections on:

Now let us suppose we are searching for patents in which a new pgm chemical or material is disclosed, or in which the use of a pgm is a key part of the invention. In this case restricting the search to terms in the title or abstract, and possibly also the claims, will be adequate. Clearly if the word ‘platinum’ appears in any of these sections then it is likely to be a very important part of the invention.

But what about the case when the name of the pgm appears somewhere in the rest of the patent, but not in the title, abstract or claims? Can these patents safely be ignored? An example of such patents might be the use of a standard palladium on carbon hydrogenation catalyst in a multi-stage organic synthesis route. The novelty is in the end-product, not the catalyst used, and therefore the term ‘palladium’ is unlikely to occur in the title, abstract or claims. However it may well come up in the examples. While we can probably ignore such patents for the purpose of identifying key new application areas, important information may nevertheless be obtained from them. For example, they may provide valuable intelligence on sales opportunities for suppliers of catalysts, the customer being the owner of the patent.

Table I illustrates the wide variation in the number of retrieved patents obtained according to where in the patent the search is performed. The table clearly shows that choosing which part of the patent document to search is critical. If we search in the patent title, abstract and claims then we retrieve over five times as many patents as exactly the same search restricted to just title and abstract. If we search in the full text of the patent then we retrieve five times as many again.

Table II shows the top fifteen assignees for each set of results in Table I. It shows that we might expect to obtain quite different results for the various searches, even though the keyword is the same in each case. Apart from Micron Technology Inc, which heads up each list, there are some very significant differences. Engelhard (now BASF Catalysts) comes in at number five in the ‘title or abstract’ search but does not appear in the ‘title, abstract or claims’ or full-text searches. On the other hand, the Semiconductor Energy Laboratory, while it does not appear in the ‘title or abstract’ search, and only reaches number twelve in the ‘title, abstract or claims’ search, comes in at number two in the full-text search.

Pfizer is another good example. Like Semiconductor Energy Laboratory, this company only appears in the top assignees from the full-text search. One would expect Pfizer's main interest in platinum to be as a user of catalysts in pharmaceutical manufacturing, rather than as a developer of new pgm-based technologies. Manual inspection of selected Pfizer patents confirms this to be the case.

The Results List and Initial Analysis

For the remainder of this paper we will be considering the results of searches based on the names of the pgms in the patent title or abstract. We have undertaken the search in the U.S., European and PCT patent collections, for patent applications or granted patents published in the period from 1st January 1983 to 31st December 2007. The search results have then been ‘deduplicated’ to exclude patent family members filed in different geographical regions, to leave one patent per invention. The final document list contains just over 13,540 patents.

Figure 1 shows a basic breakdown of these patents by metal and by five-year timeslices. Overall growth in pgm patents in the period from 1983 to 2007 is about 6% per annum. In the last seven years, this growth rate has been nearly 13%. However, growth in the number of patents by individual metal is not completely uniform. There has been somewhat higher growth for platinum, ruthenium and iridium patents, and slightly lower growth for palladium and rhodium, as shown in Table III.

A comparison between the pgm patent picture and that for a number of other metals (gold, silver, nickel and cobalt) is shown in Figure 2. The number of patents on all these metals has increased. However the rate of increase for pgms and gold is considerably higher than that for nickel, cobalt and silver. This is illustrated in Table IV by looking at the earliest (1983–1987) and latest (2003–2007) time periods.

Figure 3 shows the importance of these metals in selected technology areas. The analysis was based on selected International Patent Classification (IPC) codes (4).

Patent Mapping

The Aureka ThemeScape™ tool (3) was used to create a visualisation of the pgm document list described above. The results are shown in Figure 4. The resulting map looks like a mountainous island surrounded by sea. The visualisation is helpful because ThemeScape groups together similar documents and labels these groups according to frequently used key terms found within those groups. The more documents contained within each group, the higher the ‘mountain’ appears. The automatic labelling sometimes produces meaningful headings (e.g. silicone, rubber, polysiloxane), but sometimes these are less obviously meaningful (compounds, preparation, reaction). Where necessary these can be edited following an inspection of documents contained within the groups.

The grey dots represent sample documents – in this set of 13,540 documents only a small proportion are shown in this view, but more (or all) documents will be shown when specific areas are magnified. Clicking on specific dots will display the original document. The contour lines enclosing particular areas can be used to select groups of documents for inspection or further analysis.

In Figure 5, we have further processed the basic map shown in Figure 4 in two ways. Firstly, to create a timeslice covering documents published only in the period January 2003 to December 2007; secondly, to show patents on platinum as red dots and patents on palladium as green dots. Where specific documents cover both platinum and palladium, these are shown as white dots.

The reason for this exercise is to show the relative importance of particular metals in specific technology areas. For example, the ‘silicone, rubber, organopolysiloxane’ and ‘fuel cell, fuel, electrode’ areas are dominated by red dots, indicating that platinum is the preferred metal in these applications. The ‘plating, deposited, substrate’ region is dominated by green dots, confirming the importance of palladium in electronic applications. The ‘exhaust, engine, oxide’ area contains many red, green and white dots, indicating that both metals may be used in emission control applications.

Figure 6 is a similar image showing the minor metals rhodium, ruthenium, iridium and osmium. Of particular interest here are the two boxed areas, the first just left of centre, the second centre right. These contain a cluster of mainly light blue dots (ruthenium) and dark blue dots (iridium), respectively. Comparison of the number of dots with the same areas in Figure 7, covering the 1993 to 1997 timeslice, shows a marked increase in the numbers of iridium and ruthenium patents published in 2003–2007. These are examples of emerging technologies. Magnification of one of these areas (see Figure 8) shows that this area includes many patents on organic light emitting diodes (OLEDs), which is an important potential new application for iridium-based fluorescent or phosphorescent dopants. OLEDs (see also References (5, 6)) are solid-state devices composed of thin films of organic molecules that create light with the application of an electric current. Compared with conventional light-emitting diodes (LEDs) or liquid crystal displays (LCDs), OLEDs provide brighter, crisper displays which require less power. It has been discovered that in some iridium complexes, strong spin-orbit coupling leads to singlet-triplet mixing, ideal for highly efficient electrophosphorescence required for future OLEDs. Companies with pgm patents in the OLED area currently include DuPont (U.S.A.), Samsung (Korea), LG Electronics (Korea), Idemitsu Kosan (Japan) and Konica Minolta (Japan).

Further analysis of the map shows that ruthenium-based interconnects and electrodes, iridium-based capacitor materials, new magnetic materials containing iridium or ruthenium, ruthenium-based metathesis catalysts (for example Grubbs' catalyst) and the application of ruthenium in silane production are other emerging technology areas.

The Non-Patent Literature

While patents are an extremely important source of technical and commercial intelligence, there is also a huge amount of non-patent literature covering the pgms. This is illustrated in Figure 9, which compares the size of the patent literature on ruthenium with that of the non-patent scientific literature on the uses of this metal in chemistry-related areas. The top ten uses for ruthenium in the non-patent literature, based on controlled index terms used in the Chemical Abstracts database, are shown in Table V. Specialised software tools such as STN^® AnaVist™ (7) are now available to assist with the analysis of non-patent (as well as patent) literature, similar to that described above for the patent data.

Conclusions

The patent literature is an extensive and detailed source of information on existing and potential new applications for the pgms. At the time of writing, there are in the region of 13,540 inventions, covering the period from January 1983, in which the use of one or more pgms is a key part of the inventive step. There are many others in which pgms may be used, for example as part of a complex organic synthesis route. Growth of this literature is expected to continue to increase at a rate slightly higher than that of certain base metals.

Patent mapping tools can be used to identify key areas of development and ‘hot spots’ of activity which may lead to future volume applications. ‘Hot spot’ areas for the minor metals ruthenium and iridium currently include iridium in organic light emitting diodes (OLEDs), ruthenium-based interconnects and electrodes, iridium-based capacitor materials, new magnetic materials containing iridium and/or ruthenium, and the application of ruthenium in silane production.