This case, which recently published, is an example of how things can go very wrong for a patent proprietor when claims directed to compositions which contain both open language (comprising) and generic terms of the "Markush type" have to be amended.
To refresh the memory, Article 123(3) EPC reads:
"The European patent may not be amended in such a way as to extend the protection it confers."
In this particular case claim 1 as granted reads:
"A hair dye composition which
comprises
(A) an acid dye and
(B)
an alkylene carbonate having 3-5 carbon atoms in total,
wherein the content of (B) is 0.5-50 % by weight
[..]"
During opposition this claim was amended to read :
"A hair dye composition which
comprises
(A) an acid dye and
(B)
an alkylene carbonate having 3-5 carbon atoms in total,
wherein the content of (B) is 0.5-50 % by weight,
the alkylene carbonate being propylene carbonate
[..]"
At first sight such a claim seems acceptable. However, the opponent and the Board further examined the case and found that by limiting the claim to a species of the genus
"carbonate" at the same time maintaining the
"comprising" language the scope of protection was in fact not limited but extended. The Board basically reasons that because of the
"comprising" nature of the claim the hair dye may still contain carbonates falling within the genus
"carbonate having 3-5 carbon atoms in total". As the amount of these further carbonates is not defined in the claim, one may end up with a total of
"carbonate" well over 50%. This would result in a broader protection than the protection conferred by the claim as granted.
The Board of Appeal formulated the following headnote :
A composition which is specified in a claim to comprise a component in an amount which is defined by a numerical range of values is subject to an implicit proviso excluding the presence of that component in an amount outside of that range.
An amendment restricting the breadth of that component, for instance by narrowing down a generic class or a list of chemical compounds defining that component, has the consequence of limiting the scope of this implicit proviso.
A composition which is defined as comprising the components indicated in the claim is open to the presence of any further components, unless otherwise specified. In a claim directed to such an openly defined composition, the restriction of the breadth of a component present therein may have the effect of broadening the scope of protection of that claim, with the consequence that in opposition/appeal proceedings such amended claim may extend the protection conferred by the granted patent (Article 123(3) EPC).
To me the decision makes sense, but at the same time I have to admit that this is a scenario I have never considered before when drafting claims.
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