Many inventions, particularly in the chemical field, are defined by ‘parameters’ rather than structural features. Parameters are measurable physical or chemical properties used to define an invention where using structural features would not be possible or would be too limiting. For example, a new gold nanoparticle may be defined by its size to differentiate it from other gold nanoparticles of widely differing sizes to establish patentability.
But how much detail should you include about these parameters in your European patent application? Here are some tips to help you navigate the European Patent Office's (EPO) approach to parameters for the best chance of success in Europe.
Key points
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In Europe, the method for measuring a parameter (or at least a reference thereto) should be included in the claim to avoid a lack of clarity.
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Particular care should be taken when the value of the parameter can vary according to the measurement conditions.
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If a measurement method is not included in the application as filed, there are certain circumstances where the lack of clarity can be overcome by argument.
Practice points
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When drafting patent applications with a parameter for Europe, include a clearly defined method of measurement, drafted such that it can be introduced into the relevant claim.
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When amending claims during opposition, be careful not to introduce a lack of clarity.
How much detail about a parameter should I include in my patent application?
The EPO generally permits the use of parameters to define an invention, provided that clarity requirements are met (governed by Article 84 EPC). However, one of the quirks of European patent law is that for a claim to be considered clear, typically the method for measuring a parameter (or at least a reference thereto) must appear completely in the claim itself (T 1851/06).
In some instances, a reference to an internationally recognised standard (e.g. an ISO standard) might be enough, but where there is no standard method then a complete description of the measurement method should be provided. Particular care should be taken when the value of the parameter can vary according to the measurement conditions. For example, viscosity is dependent on the temperature at which it is measured and so a measurement method for viscosity must specify the temperature in order to be deemed clear (T 0869/20).
Fixing issues: What if I’ve omitted details about a measurement method?
If no measurement method for a parameter is included in the application as filed, it may still be possible to meet the EPO’s requirements for clarity if it can be successfully shown that:
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the measurement method belongs to the skilled person's common general knowledge, e.g. because there is only one method, or because a particular method is commonly used; or
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all the measurement methodologies known in the relevant technical field for determining this parameter yield the same result within the appropriate limit of measurement accuracy.
For example, in EPO Board of Appeal decision T 148/91, the claims referred to a particulate material having a specific surface area, but the patent lacked any measurement method to measure this property. The Board concluded that measuring specific surface area is so apparent that a skilled person would be able to measure this reliably without undue burden using their common general knowledge, such that the omission of a measurement method was not an issue.
In T 307/06, the claim related to a polymer with a glass transition temperature (Tg) of less than 25°C. The Board concluded this feature was unclear because there are different methods for determining Tg, yielding different results for the same material.
Beware the inescapable trap
Due to the strict approach adopted by the EPO in their assessment of added subject-matter (i.e., whether an amendment to a patent application introduces content extending beyond what was originally disclosed in the application as filed, Article 123(2) EPC), it is often difficult to remove an offending parameter without causing further issues.
This is especially true if the offending parameter is described in the application as being essential to the invention, but no measurement method is provided. The applicant can end up in a situation where their patent cannot be granted because the claim includes a parameter that is unclear, but also cannot be granted without it, because removing the parameter from the claim would add subject-matter (see Figure 1).
Oppositions and a lack of sufficiency
While lack of clarity is not a ground for opposition at the EPO, a lack of sufficiency is a ground for opposition. If a parameter is not described in enough detail in the application as filed, this could not only lead to a lack of clarity, but also a lack of sufficiency. For a patent to be sufficient it must “disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art” (Article 83 EPC). The distinction between a lack of clarity and a lack of sufficiency is an important one, as opponents may try to disguise clarity objections as sufficiency attacks (T 1627/17).
A number of EPO Board of Appeal decisions have considered the relationship between clarity and sufficiency and the requirements for each ground. In T 593/09 the Board concluded that where there is an insufficient disclosure due to an ill-defined parameter in a claim, the claim would also lack clarity, since establishing the exact scope of the claim would then be impossible. However, this does not mean that the reverse conclusion can be drawn.
The Board in T 608/07 considered the situation where there was ambiguity in a particular parameter. The Board held that although an ambiguity may lead to a lack of sufficiency, it is fundamentally a clarity issue. For a lack of sufficiency to be present “it is not enough to show that an ambiguity exists, e.g., at the edges of the claims. It will normally be necessary to show that the ambiguity deprives the person skilled in the art of the promise of the invention.”
In T 59/08, the claim related to a polyethylene composition which was defined by various molecular weight values, but no description of the measurement methods were provided. It was accepted that alternative methods were available which would provide different results. However, this uncertainty did not result in a lack of sufficiency. The Board considered that the claims covered compositions that met the claimed molecular weight values measured using any method in the art.
Care has to be taken when amending claims during opposition and appeal proceedings, particularly when introducing new parameters into the claims. Although clarity is not a ground for opposition, objections of lack of clarity are allowed against post-grant amendments that introduce subject-matter not present in the claims of the patent as granted (G 3/14).
Summary
Parameters can be a useful way of defining inventions. When drafting patent applications for Europe, ensure that all parameters have a specified method of measurement, complete with as much detail as possible: relying on the common general knowledge should only be a last resort.
For more information, please contact Faysal Farah, Tom Hailes, Benjamin Heller, Jessica Smart, or your usual Kilburn & Strode advisor.