Replacement of an essential feature in the claim may result in an extension beyond the content of the application as filed

Patents Case Law

In T1099/21, a decision of the Opposition Division (OD) to reject the opposition against European patent application no. 1 834 524 was appealed by the opponent (O). Said patent related to a coating composition comprising a microencapsulated biocide and a free (i.e., not microencapsulated) isothiazolone biocide or antifouling agent. In the appeal proceedings, O argued that the subject matter of the claims extended beyond the content of the application as filed because an essential feature of the claims as originally filed had been replaced by a non-equivalent feature. The patent proprietor (P) disagreed and presented several arguments as to why the replacement should be deemed allowable. In particular, P believed that, because the replacement of the feature was made during the examination phase in order to address the examining division’s clarity objections under Articles 83 and 84 EPC, replacement of the feature was allowed. The Board of Appeal (the Board) disagreed with the P and ruled that any unclarity that may arise from an ambiguity in an application as filed was to the detriment of a patent proprietor.

The fact that a feature in the application as filed is unclear cannot justify or excuse the complete deletion of the unclear feature or its replacement by another feature if this replacement is not directly and unambiguously derivable from the application as filed. In such case, the replacement results in an extension beyond the content of the application as filed and will prejudice the maintenance of the patent as granted;
What prompted a patent proprietor to make a particular amendment to the claims cannot have any influence on the outcome of the assessment of the ground for opposition under Article 100(c) EPC.

Background

European patent no. 1 834 524 essentially related to a coating composition comprising a microencapsulated biocide and a free (i.e., not microencapsulated) isothiazolone biocide or antifouling agent. Claim 1 of the application as filed read as follows:

"1. A coating composition comprising:

a) a microencapsulated biocide comprising an isothiazolone biocide or antifouling agent as a core material encapsulated in a wall material that is essentially impermeable to xylene and from which water can leach the biocide from the wall material;
b). free isothiazolone biocide or antifouling agent;
c) a film forming polymer or binder; and
d) one or more solvents;

wherein the concentration of free isothiazolone biocide or antifouling agent is from 0.25 percent, by weight of the composition, up to a concentration that does not reduce the glass transition temperature of the film forming polymer by more than 20 °C."

The upper concentration limit of the free isothiazolone biocide or antifouling agent was defined functionally in terms of a result to be achieved ("up to a concentration that does not reduce the glass transition temperature of the film forming polymer by more than 20 °C"). In the application as filed, this functional feature was disclosed as an essential feature of the invention and did not merely relate to a preferred embodiment.

However, the functionally defined upper limit of the concentration range for the free isothiazolone biocide had been deleted in claim 1 of the main request, and had instead been replaced by an upper limited defined numerically:

“1. A coating composition comprising:

a) a microencapsulated biocide comprising an isothiazolone biocide as a core material encapsulated in a wall material, wherein less than 20 percent of the encapsulated biocide is released when contacted with xylene for a period of 90 days at 45°C and from which water can leach the biocide from the wall material;
b) free isothiazolone biocide;
c) a film forming polymer or binder solids; and
d) one or more solvents;

[…] wherein the concentration of free isothiazolone biocide is from 0.25 percent to 15 percent of the weight of the film forming polymer or binder solids;

The Appeal

According to O, the functional feature in claim 1 as originally filed could not be deleted or replaced by a different non-equivalent feature such as the numerical upper limit in claim 1 of the main request. This was because the question of whether or not the glass transition temperature of the film forming polymer was reduced by more than 20 °C depended on the coating composition under consideration and in particular the actual film forming polymer contained in it. Hence, the subject-matter of claim 1 of the main request extended beyond the content of the application as originally filed.

In response, P stated that the application as filed only disclosed one quantitative teaching of a particular biocide (i.e., “the free DCOIT [author’s note: the particular biocide] is added in an amount of from 0.25% to 15% of the weight of the film forming polymer or the binder solids”). Thus, this quantitative was applicable to the invention of claim 1 as filed.

However, any unclarity that may arise from an ambiguity in an application as filed is to the detriment of a patent proprietor, who is ultimately responsible for the drafting of the application as filed and its claims

Even assuming that the quantitative teaching of the specific biocide could be generalised to all isothiazolone biocides, as was done in claim 1 of the main request, the Board did not follow P’s reasoning because the application as filed did not disclose that the numerical upper limit of 15% was meant to be the same as the functionally defined upper limit of claim 1 as filed.

In this context, P submitted that the effect of lowering the glass transition temperature of polymeric binders of certain biocides such as DCOIT on film forming polymers was well-known to the skilled person. The wording of claim 1 of the main request stated the concentration of the free isothiazolone biocide in relation to the weight of the film forming or binder solids. This was a pointer to the skilled person that the coating composition of claim 1 of the main request should not contain too much free isothiazolone biocide, depending on the film forming polymer actually used. For this reason, compositions in which, for example, concentrations of 15% of free isothiazolone biocide caused a glass transition temperature reduction of more than 20 °C precisely did not fall within the subject matter of claim 1.

The Board considered that the latter argument ultimately means reading into claim 1 of the main request a lower possible concentration for the free isothiazolone biocide precisely when concentrations close or identical to the numerical upper limit of 15% led to a glass transition temperature decrease of more than 20 °C. As a result, the Board rejected P’s argument again and stated that the subject-matter of a claim was determined by its wording, which in the present case provided for an explicit upper limit of 15% for any film forming polymer.

Finally, P argued that the functional feature in claim 1 as filed could not be meaningfully interpreted by the skilled person as defining a boundary. The replacement of the functional feature in claim 1 as filed by the numerical upper limit in claim 1 of the main request was made to address the examining division's objections in this respect under Articles 83 and 84 EPC and should be considered allowable.

Once again, the Board did not agree with P. According to the Board, it was already clear from the wording of the functional feature that it was intended to define an upper limit for the concentration of the free isothiazolone biocide in the coating composition. The fact that claim 1 as filed did not define an exact numerical upper limit may be due to the fact that the actual upper limit depended on the composition under consideration. However, any unclarity that may arise from an ambiguity in an application as filed is to the detriment of a patent proprietor, who is ultimately responsible for the drafting of the application as filed and its claims. The fact that a feature in the application as filed was unclear cannot justify or excuse the complete deletion of the unclear feature or its replacement by another feature if this resulted in an extension beyond the content of the application as filed. In fact, what prompted a patent proprietor to make a particular amendment to the claims (in this case to address the examining division's objections) cannot have any influence on the outcome of the assessment of the ground for opposition under Article 100(c) EPC.

Decision of the Board (of Appeal)

The Board decided that the subject matter of claim 1 extended beyond the content of the application as filed and that the ground for opposition under Article 100(c) EPC prejudiced the maintenance of the patent as granted. As a result, the patent was revoked.

Summary written by the NLO EPO Case Law Team

More about this case:

T1099/21

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