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Updated on May 24, 2021
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Visuel DicoValo EN

Visuel DicoValo EN

article written by Jana Darwiche and Isabelle Chéry

The Soleau envelope, named after its inventor, Eugène Soleau, is a simple and inexpensive means of proof. It is a proof of anteriority used in France to date a technical invention (a new product, an improvement to a product or process, an innovative process, a manufacturing method, etc.), an artistic work, a business or service concept, a design or model, commercial data, etc., while preserving its contents secret nature. It should be noted that the content must be sufficiently described so that it can be used either as proof of anteriority for a right of prior personal possession or to secure an exchange of confidential information with an industrialist or to date know-how or to provide proof of the date on which a copyrighted work was created. These four cases are explained in B below.
It is not useful to file a Soleau envelope on a simple idea: ideas are free to move around; thus, filing a Soleau envelope on an idea will not allow one to defend oneself if faced with one of the four cases mentioned above. Ideas are not protectable; they are not copyrightable either! A very good example is Christo Javacheff who used to package bridges (like the new bridge). The bridge he packed was protected by copyright. His permission was needed to make photographs, films, etc. of the packed bridge. But the idea of wrapping a bridge was not protected: someone else could wrap another bridge in a different way. Christo could not claim his idea, but the result of his work. Also, the Soleau envelope would have contained the photo or drawing of the wrapped bridge, not the idea of wrapping a bridge to prove the date of creation of his work. The envelope serves to record the nature of the information contained, the owner(s) and the date of possession of the information. For example, in the case of a technical creation, the Soleau envelope will describe: the technical field, the prior art, the problem posed, the technical solution, the best way of realising the invention and variants of the realisation.
The Soleau envelope can be filed at any time by anyone (inventors, creators, authors, etc.) wishing to mark the ownership and/or the anteriority of a creation.
If a public official develops a technical or artistic creation, a concept, etc., he or she must declare the invention to his or her employer (see D for Invention Declaration). Depending on the nature of the information declared and the framework in which the public official has developed his or her results, the invention or artistic creation belongs to the official’s employer. The employer will discuss with the employee how these elements can be protected, in particular by patent or by secrecy, and whether it is preferable to file a Soleau envelope.

A) What are the differences between the Soleau envelope and the patent?

The patent (P as Patent) is a key element in the innovation process: it constitutes an industrial property title and thus supports the interactions between innovation actors. Unlike the patent, the Soleau envelope does not constitute an industrial property title. It offers less protection than a patent. On the other hand, it is less costly and easier to produce.
In practice, the Soleau envelope intervenes earlier in the innovation process than a patent (see Figure I). It can be filed during the drafting of the patent's application and by another person.

B) When is it useful to file a Soleau envelope?

There are four reasons for filing a Soleau envelope:

1) To benefit from the right of prior personal possession:

The Soleau envelope does not allow its owner to oppose the exploitation of the invention by a third party. However, proof of personal possession of an invention on French territory, prior to the date of filing (or priority) of the patent application or patent filed by a third party, gives the owner of the Soleau envelope the right to continue working the invention despite this third-party patent application or patent. This exception to the patentee’s monopoly based on prior personal possession is set out in Article L 613-7 of the Intellectual Property Code. It only concerns persons acting in good faith who, being able to exploit an invention, have chosen to keep it secret. However, this right of prior personal possession does not confer any exclusive right. This exception to the right of prior personal possession only applies in France and this right can only be transferred with the business, the enterprise or the part of the enterprise it is attached to. Of course, there must be a similar technical identity between the contents of the Soleau envelope and the contents of the patent, which encourages the Soleau envelope to be drafted carefully and in detail.

2) To secure exchanges with an industrial partner before filing a patent:

Suppose that a researcher develops results that can be the subject of a patent application but that these results are not yet sufficiently developed to proceed with the filing of the patent and confidential discussions must be held with an industrial partner. If these discussions cannot be held until the patent application is filed, it may be advisable to file a Soleau envelope before starting the discussions. In this way, the number of the Soleau envelope can be indicated in the confidentiality contract signed with the industrial partner. In the event of disputes with this partner, such as fraudulent appropriation of the invention or disclosure of confidential information by the partner before the patent application is filed, the Soleau envelope will make it easier to prove the dispute before a judge.
Note: when the disclosure of a secret invention results from an abuse (note 8) such as the violation of a contractual confidentiality obligation, this does not affect the novelty of the invention if it takes place in the six months preceding the filing of the patent application (Article L611-13 of the IP Code). The Soleau envelope will make it possible to record this contractual violation and may allow the patent application to be filed.

3) To keep secret, with a view to commercial exploitation by a third party, an invention that does not meet all the criteria for patentability.

Depending on the invention characteristics, it may be decided to prefer a know-how (secret) to the filing of a patent either for strategic reasons of keeping the secret (the patent being published within 18 months of filing), or because the filing of a patent is not feasible (the invention does not meet all the patentability criteria). The owner of the invention then proceeds to file the Soleau envelope. This makes it possible to describe the know-how, which can then be exploited by a company under the cover of the signature of a transfer contract, called a know-how communication contract. The know-how communication contract then cites the number of the Soleau envelope in order to clearly identify the object of the transfer and the information that must be kept secret.
Information: know-how is defined as a body of unpatented practical or technical knowledge. It must be secret, substantial, i.e., it must have an economic utility (and not necessarily a technical utility) and it must be identified, i.e., sufficiently described for someone else to be able to implement it and finally it must be transferable, i.e., it must be reproducible.
Note: if the know-how is not transferred to the operating company, it may be difficult for it to justify the right of prior possession (B 1) which can only be transferred together with the business, undertaking or part of the undertaking to which it is attached.

4) To prove the date on which a copyright work was created

In the case of a work protected by copyright (texts, works, art, music, photography, etc.), protection is acquired without formalities, by the very fact of the work creation. The creation is therefore protected from the day the author made it. However, in the event of a dispute, the author must be able to prove the date on which his work was created. The Soleau envelope is a means of proof.

C) What does it look like?

In its paper version, the Soleau envelope is made up of two compartments, each of which contains an identical description of the invention or creation, diagrams, drawings, photos, etc. The first part is kept by the INPI (Institut National de la Propriété Industrielle) for five years; the second is returned to the applicant.
Once completed with the applicant’s name, first name and address, the envelope must be folded, sealed and sent to the INPI. The INPI registers it and punches a hole in it to date it. Care must be taken to ensure that the envelope does not contain any hard material such as cardboard, rubber, CDs, plastic, etc. The INPI returns one of the two compartments to the inventor, who must keep it carefully.

Soleau: what it looks like

Figure 2: Soleau envelope (INRS)
Since 15 November 2016, INPI has switched to digital service. The advantages are threefold. Firstly, the filing is immediate. There is no delay between the filing on the INPI platform and its proof. Secondly, the documents volume is no longer limited to the 7 sheets of the paper version but offers, on the contrary, a large filing capacity (up to 300Mb). Thirdly, filing is accompanied by document archiving security. Filing is done via the online service e-soleau. At the end of this process, a receipt is issued by e-mail mentioning the date of filing, the list of registered documents and their respective fingerprints. It will allow you to prove that you filed your documents at the INPI on a certain date and that they have not been modified.
In terms of price, the paper envelope costs €15 each. For the digital version, the rates are adjusted according to volume: €15 for 10 MB, then €10 per additional €10 MB.
Note: The Soleau envelope deposit can be replaced, notably for reasons of volume, by depositing a sealed envelope containing a description of the invention with a bailiff or a notary, or with an author’s society such as the Société des gens de Lettres (SGDL).

D) How to obtain a Soleau envelope?

Yoann Miccoli (, your intellectual property officer at Grenoble INP, will be able to advise you and help you with your procedures.
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Date of update May 24, 2021

Grenoble INP Institut d’ingénierie et de management, Université Grenoble Alpes
Grenoble INP, Graduate schools of Engineering and Management
Université Grenoble Alpes

(Institut polytechnique de Grenoble)
46 avenue Félix Viallet
F38031 Grenoble Cedex 1 - France
Tel. : +33 4 76 57 45 00 - Fax. : +33 4 76 57 45 01
Université Grenoble Alpes