CH711131A2 - Use of a photopolymerizable varnish composition and its method of application. - Google Patents

Abstract

The present invention relates to a use of a photopolymerizable lacquer composition for coating a timepiece, said lacquer composition comprising: a prepolymer compound comprising monomers or at least one oligomer or mixtures thereof, said monomers being selected from the group consisting of monomers comprising at least one acrylate or methacrylate function, epoxide monomers and mixtures thereof, said oligomer being selected from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins polyether acrylate resins, polysiloxane acrylate resins, epoxy acrylate resins and mixtures thereof. The invention further relates to a timepiece perhaps of a lacquer composition formed of a three-dimensional crosslinked network of monomers, oligomers, or mixtures thereof.

Description

[0001] The present invention relates to the field of watchmaking, more particularly to timepieces.

[0002] In the watch industry, watches are generally supplied to distributors with transparent plastic protective films to reduce the risk of scratches appearing on the watches during various handling operations.

[0003] The transparent protections currently supplied on the market are sorely lacking in aesthetics, which is a limiting factor as to the possibility of presenting the object with this protective element which does not sufficiently highlight the product to be sold.

[0004] In addition, the lifetime of these protections is short over time, once exposed to the surrounding environment. Indeed, it appeared that the exposure of watches equipped with current protections inevitably leads the protective film to be exposed to UV rays as well as to the heat provided by the lights used to illuminate the product displayed in the window.

[0005] This has the disadvantage that the films used are no longer able to protect the product because the film no longer adheres sufficiently, breaks or creates unsightly folds on the product. This limited aspect of the known films limits the sales potential of the product in the market which is not acceptable for shops active in the field of watchmaking.

[0006] In addition, the films currently used are not suitable for covering timepieces or even complex three-dimensional areas of watch products, which once again limits the use of such films which are ultimately not very protective. .

[0007] The films currently used in the field of watchmaking must therefore systematically be replaced, which increases the costs of using such films as well as handling costs.

[0008] Documents EP 0 889 937, WO 2013 44 289 and WO 2008 073 341 disclose compositions which make it possible to coat substrates with a view to protecting them.

[0009] Unfortunately, the disclosed compositions are not suitable for coating timepieces taking into account the aforementioned criteria, particularly at the level of the application of the composition on parts of small sizes and complex structures. In addition, the shortcomings are also at the level of the ability of the varnish obtained to be removed from the substrate on which it was applied, at the level of the transparency of the varnish, the resistance of the varnish over time as well as the duration life of this varnish.

[0010] There is therefore a real need to provide a film which can meet the demand associated with the field of watchmaking, which requires the careful transparent protection of small parts and parts with three-dimensional structures that can be complex.

[0011] Furthermore, there is also a need to provide a protective film for timepieces which has a longer duration compared to known films. Exposure of the product with its protective layer should not require short-term varnish replacement. This will have the advantage of being able to display a timepiece with a transparent and protective peelable varnish.

[0012] The aim of the invention is to coat timepieces with precision and quality by means of a photopolymerizable varnish composition which can meet the needs of the watchmaking sector.

To solve this problem, it is provided according to the invention to use a photopolymerizable varnish composition for coating a timepiece, said varnish composition comprising a prepolymer compound comprising monomers or at least one oligomer or their mixtures, said monomers being chosen from the group consisting of monomers comprising at least one acrylate or methacrylate function, epoxy monomers and mixtures thereof, said oligomer being chosen from the group consisting of polyurethane-acrylate resins, polyurethane-acrylate resins aliphatic, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and mixtures thereof.

(It has thus been observed that the application of this photopolymerizable varnish composition is easily and rapidly photopolymerized when it is exposed to UV-Vis rays. Indeed, the photopolymerization reaction makes it possible to provide a peelable varnish formed a three-dimensional network which is quickly crosslinked and which allows the user to easily remove the peelable varnish from the timepiece.

[0015] It has been found that the use of the varnish composition according to the invention makes it possible to provide a peelable varnish which is transparent and therefore complies with the requirements of the field of watchmaking.

[0016] By applying the photopolymerizable varnish composition to timepieces, it is possible to manipulate the part as desired without risking losing the varnish or scratching timepieces.

To date, the formulations of varnish photopolymerizable by UV-Vis radiation are simply used in coatings, paints, inks, composites, adhesives or else in electronics.

Advantageously, said prepolymer compound consists of monomers comprising at least one acrylate or methacrylate function and optionally of oligomers chosen from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether acrylate resins, polysiloxane acrylate resins, epoxy acrylate resins, and mixtures thereof.

[0019] Preferably, said prepolymer compound comprises an oligomer having the following formula:

[0020] More preferably, the prepolymer compound comprises at least one radical, cationic or hybrid photoinitiator for respectively initiating a radical, cationic or hybrid polymerization reaction.

Advantageously, the radical photoinitiator is chosen from the group consisting of acetophenone derivatives or phosphine oxide derivatives, 2-hyrdoxy-2-methylpropiophenone, benzophenone, 2,4,6- trimethylbenzophenone, methyl benzophenone, alpha-phenylacetophenone, 1-hydroxy-cyclohexyl-phenyl-ketone and mixtures thereof.

[0022] According to a particular embodiment of the invention, said prepolymer compound comprises at least one additive comprising an anti-bubble agent or an oil such as soya lecithin or a mixture of anti-foam polymers without silicone or mixtures thereof.

[0023] According to a preferred embodiment of the invention, said prepolymer compound comprises at least one photosensitizing agent such as benzotriazoles, triazines, preferably hydroxyphenyl-triazine.

Preferably, the prepolymer compound comprises at least one UV absorber and / or a light stabilizer chosen from the group consisting of 2-hydroxy-benzophenones, 2-hydroxy-benzotriazoles, hydroxy-benzoates, cyanoacrylar. es and aryl esters.

Advantageously, the UV absorber and / or the light stabilizer can be the product Tinuvin <®> 292 and / or the product Tinuvin <®> 400.

Advantageously, the light stabilizer is 2- [2 ́-hydroxy-3 ́, 5 ́-di (α, α-dimethylbenzyl) phenyl] benzotriazole.

[0027] Even more advantageously, said prepolymer compound comprises a diluting agent, such as hexanediol diacrylate, ethyl-diethylene glycol acrylate or isobornyl-acrylate.

[0028] Preferably, said prepolymer compound comprises a pigment.

[0029] In an advantageous embodiment according to the invention, said prepolymer compound comprises: said monomers or said at least one oligomer or their mixtures in an amount ranging from 30 and 70 parts by weight, said photoinitiator in an amount ranging from 2 to 6 parts by weight, optionally, said diluting agent in an amount ranging from 30 to 70 parts by weight, optionally said absorber in an amount ranging from 0.3 to 1 part by weight, and optionally said pigment in an amount of less than 5 parts by weight, said parts by weight being expressed relative to the total weight of said prepolymer compound.

[0030] Preferably, said oligomer has a molecular mass of between 300 and 100,000 g / mol.

More preferably, said monomers comprising at least one acrylate or methacrylate function have a molecular mass of less than 1000 g / mol.

Advantageously, the prepolymer compound has a viscosity greater than 3000 mPa.s at 20 ° C, preferably greater than 5000 mPa.s at 20 ° C, more preferably greater than 8000 mPa.s at 20 ° C.

[0033] Other embodiments of the use according to the invention are indicated in the appended claims.

[0034] The subject of the invention is also a process for coating a timepiece with a peelable varnish comprising the steps of: provision of a prepolymer compound comprising monomers or at least one oligomer or mixtures thereof, said monomers being selected from the group consisting of monomers comprising at least one acrylate function, epoxy monomers and mixtures thereof, said oligomer being chosen from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and mixtures thereof, addition of at least one photoinitiator to said compound to form a photopolymerizable varnish composition, application of said photopolymerizable varnish composition to a timepiece, exposure to UV-Visible rays of said timepiece on which said photopolymerizable varnish composition has been applied, obtaining a peelable varnish formed from a three-dimensional network of polymers based on acrylate or epoxy on said timepiece.

The method according to the invention has the advantage of using a crosslinking polymerization reaction which calls for the use of UV-Vis rays to obtain the hardening of the composition in order to obtain the peelable varnish and transparent.

The method according to the invention has the advantage that it does not require the use of organic solvents and therefore does not produce volatile organic compounds (VOCs) in the atmosphere, which is advantageous from a point of view from an environmental perspective.

[0037] The application of such a process is therefore ecological and respectful of the environment.

[0038] Thus the prepolymer compound can be in the form of a liquid ready to be polymerized by UV-Vis rays.

After hardening of the varnish composition, the peelable varnish obtained on the timepiece has a longer lifespan compared to known varnishes, an ability to be easily removed, transparency and hold adapted to the related needs. to the watchmaking sector, which makes the invention particularly attractive for this field of application which requires precision and thoroughness in order to sufficiently protect said parts.

[0040] According to a preferred embodiment of the present invention, said prepolymer compound consists of monomers comprising at least one acrylate or methacrylate function and optionally of oligomers chosen from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins , polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins, and mixtures thereof.

[0041] Preferably, said prepolymer compound comprises an oligomer having the following formula:

Advantageously, said at least one photoinitiator is chosen from the group consisting of radical, cationic or hybrid photoinitiators to respectively initiate a radical, cationic or hybrid polymerization reaction.

[0043] According to a preferred embodiment, the radical photoinitiators are chosen from the group consisting of acetophenone derivatives or derivatives of phosphine oxide, benzophenone and mixtures thereof.

[0044] Advantageously, the method according to the invention further comprises a step of adding to said compound at least one additive which comprises an anti-bubble agent or an oil such as soya lecithin or else a mixture of silicone-free antifoaming polymers or mixtures thereof.

[0045] More preferably, the method according to the present invention comprises a step of adding to said at least one photosensitizing agent such as benzotriazoles, triazines, preferably hydroxyphenyl-triazine.

According to an advantageous embodiment of the invention, the method also comprises a step of adding at least one UV absorber and / or a light stabilizing agent chosen from the group consisting of 2-hydroxy-benzophenones, 2- hydroxy-benzotriazoles, hydroxy-benzoates, cyanoacrylaf.es and aryl esters.

Advantageously, the UV absorber and / or the light stabilizer can be the product Tinuvin <®> 292 and / or the product Tlnuvin <®> 400.

Advantageously, said light stabilizer is 2- [2 ́-hydroxy-3 ́, 5 ́-di (α, α-dimethylbenzyl) phenyl] benzotriazole.

More advantageously, the method also comprises a step of adding a diluting agent, such as hexanediol diacrylate ethyl-diethylene glycol acrylate - butyl-acrylate or hexanediol diacrylate ethyl-diethylene, glycol acrylate, isobomyl -acrylate.

[0050] Preferably, the method according to the present invention comprises a step of adding a pigment.

[0051] Other embodiments of the process according to the invention are indicated in the appended claims.

The present invention also relates to a timepiece coated with a peelable varnish composition formed from a three-dimensional crosslinked network of monomers or oligomers or their mixtures, said monomers being chosen from the group consisting of monomers comprising at least one acrylate function, epoxy monomers and mixtures thereof, said oligomers being chosen from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether resins. acrylate, polysiloxane-acrylate resins, epoxy-acrylate resins and mixtures thereof.

[0053] Other embodiments of the timepiece coated with a peelable varnish composition according to the invention are indicated in the appended claims.

The present invention also relates to a device for applying a photopolymerizable mixture to a timepiece designed to be placed on a support, said device comprising: a photopolymerizable mixture tank composed of prepolymers comprising monomers or at least one oligomer or their mixtures and further comprising a photoinitiator, said monomers being chosen from the group consisting of monomers comprising at least one acrylate function, epoxy monomers and of mixtures thereof, said oligomer being selected from the group consisting of polyurethane-acrylate resins, aliphatic polyurethane-acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and their mixtures, a printing station having an inkjet printing head connected to said reservoir and being arranged to distribute said photopolymerizable mixture on said timepiece, a source of UV-VIS radiation placed a short distance above the support to uniformly irradiate said mixture in order to obtain a peelable varnish on said timepiece.

[0055] It is thus possible to print predefined patterns on the timepiece, said patterns being peelable and transparent.

[0056] Other characteristics, details and advantages of the invention will emerge from the description given below, without limitation and with reference to the accompanying drawings.

In the context of the present invention, the term “timepieces” should be understood to mean any part belonging to the watchmaking sector such as the watch crystal, the elements constituting a watch or a clock, a watch case. watch, ... or even a watch or a clock as such.

[0058] The present invention thus relates to a specific use of a polymerizable varnish composition as described in the present application in order to protect timepieces.

The method according to the present invention thus makes it possible to coat a timepiece with a peelable varnish.

To carry out the process according to the invention, it is necessary to have available a prepolymer compound which comprises monomers or at least one oligomer or their mixtures.

[0061] The monomers according to the present invention are chosen from the group consisting of monomers comprising at least one acrylate function, epoxy monomers and mixtures thereof.

The oligomer is for its part chosen from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy resins -acrylate and mixtures thereof.

The crosslinking polymerization reaction of the monomers or oligomers or of their mixtures makes it possible to provide a peelable varnish.

[0064] Advantageously, the monomers and oligomers can be crosslinked according to different reactions such as a radical, cationic or hybrid reaction. A hybrid type reaction corresponds both to a radical reaction and to a cationic reaction which ultimately makes it possible to form networks of interpenetrating polymers, known as “IPN”.

The treatments making it possible to carry out the crosslinking reaction can also consist of a method which has both a thermal and photochemical character (Dual-Cure).

The photopolymerizable varnish compositions used according to the present invention comprise monomers and oligomers of the polyurethane acrylate type and / or of the epoxy type.

For the varnish compositions crosslinked by the radical route, the monomers containing an acrylate or methacrylate function will be preferred optionally in admixture with oligomers containing an acrylate or (meth) acrylate function.

In this particular embodiment, the varnish composition according to the invention is flexible and has a viscosity greater than 5000 mPa.s at 20 ° C, preferably greater than 8000 mPa.s at 20 ° C.

The acrylate or methacrylate oligomers used are advantageously modified with epoxy, polyesters, polyethers, polyurethanes and / or silicone groups.

The acrylate and / or (meth) acrylate oligomers modified are polymers of variable molecular weights, namely from 300 to 1,000,000.

Advantageously, the peelable varnish compositions according to the invention were obtained using oligomers of the polyurethane acrylate and / or aliphatic methacrylate type, with viscosities greater than 3000 mPa.s at 20 ° C.

The acrylate and / or (meth) acrylate monomers used are preferably molecules of molecular masses (less than 1000 g / mol). It appeared that the use of such polymers preferably makes it possible to obtain viscosity values of less than 500 mPa.s at 20 ° C. Such monomers have functional groups ranging from 1 to 6. In the case of dendrimers, the number of functional groups can be greater than 6.

The present invention can also make use of oligomers of the type of esters 1,3-butadiene, 2-methyl maleate and homopolymerized, 2 - [(2-methyl-1-oxo-2-propenyl) oxy] ethyl, such as shown below:

Preferably, the oligomeric acrylate resins used in the context of the present invention can be resins that are fluid at room temperature, the fluidity being determined in the absence of solvent.

Advantageously, the prepolymer compound comprises polymers of the polyurethane type and epoxy polymers in a polyurethane polymer / epoxy polymer ratio of between 0.5 and 1.5.

Preferably, the prepolymer compound comprises oligomers of polyurethane type and polymers of epoxy type in a ratio of oligomers of polyurethane type / polymers of epoxy type of between 0.5 and 1.5.

[0077] When applying the process according to the invention, it is further necessary to add to said prepolymer compound at least one photoinitiator to form a photopolymerizable varnish composition.

[0078] The initiator makes it possible to initiate the photopolymerization reaction.

After this step, a varnish composition is obtained which can be applied directly to a timepiece.

[0080] Preferably, it is possible to heat the timepiece prior to applying the varnish composition thereon. This particular case will be preferred when the timepiece is a watch crystal.

Once the photopolymerizable varnish composition has been applied to the timepiece, exposure to UV-visible rays of said timepiece makes it possible to obtain a peelable varnish formed of a three-dimensional network of polymers with acrylate or epoxy base on said timepiece.

In the context of the present invention, the following commercial oligomer products are preferred: Desmolux <®> XP 2491 (Bayer), EBECRYL <®> 8402 (Allnex), CN966H90 (sartomer), Ebecryl <®> < > 230 (Arkema), 6148J75 (ethercure), CN965 urethane diacrylate oligomer based on acrylate polyester (Arkema).

Example 1

[0083] A photopolymerizable prepolymer compound is prepared by mixing 40 parts by weight of a polyester with 3 parts by weight of a photoinitiator, 56 parts by weight of a reaction diluent and 1 part by weight of UV absorber. Said amounts being expressed relative to the total weight of the prepolymer compound.

[0084] Application of the prepolymer compound to a timepiece and exposure of said part comprising the compound to UV-Visible rays to carry out photopolymerization in order to obtain a peelable varnish on said part. The varnish is formed of a three-dimensional crosslinked network which is physically and chemically stable over time.

Example 2

A photopolymerizable prepolymer compound is prepared by mixing a polyester with a polyurethane in an amount between 30 and 70 parts by weight, a photoinitiator in an amount between 2 and 6 parts by weight, a reaction diluent in an amount of between 30 and 70 parts by weight and a UV absorber in an amount of between 0.3 and 1 part by weight. Said amounts being expressed relative to the total weight of the prepolymer compound.

Heating a watch crystal and application of the prepolymer compound ready to be crosslinked on the watch crystal and exposure of said part comprising the compound to UV-Visible rays to carry out photopolymerization in order to obtain a peelable varnish on said watch crystal.

[0087] The varnish being formed of a crosslinked three-dimensional network which is physically and chemically stable over time.

Example 3

[0088] A prepolymer compound is prepared using 50 parts by weight of the compound having the following formulation:

To this compound is then added 5 parts by weight of an acetophenone derivative, 0.5 parts by weight of 2- [2 ́-hydroxy-3 ́, 5 ́-di (α, α-dimethylbenzyle ) phenyl] benzotriazole, and 44.5 parts by weight of hexanediol diacrylate.

Example 4

A prepolymer compound is prepared by mixing the Desmolux <®> XP 2491 product with the EBECRYL <®> 8402 oligomer in a Desmolux <®> XP 2491 / EBECRYL <®> 8402 proportion of 92/5% by weight based on the total weight of the prepolymer compound.

The remaining 3% by weight corresponding to the amount of photoinitiator and optionally of additive (s), relative to the total weight of the composition.

Example 5

A prepolymer compound is prepared by mixing the Desmolux <®> XP 2491 product with the EBECRYL <®> 8402 oligomer in a Desmolux <®> XP 2491 / EBECRYL <®> 8402 proportion of 87/10% by weight based on the total weight of the prepolymer compound.

The remaining 3% by weight corresponding to the amount of photoinitiator and optionally additives), relative to the total weight of the composition.

Example 6

A prepolymer compound is prepared by mixing the product CN966H90 with the oligomer EBECRYL <®> 8402 in a proportion CN966H907 EBECRYL <®> 8402 of 90/5% by weight relative to the total weight of the prepolymer compound.

The remaining 5% by weight corresponding to the amount of photoinitiator and optionally of additive (s), relative to the total weight of the composition.

Preferably, the proportion of CN966H90 / EBECRYL <®> 8402 can be 70/20% by weight, more preferably 87/5% by weight, advantageously 68/29% by weight, even more advantageously still of 87/10 relative to the total weight of the composition.

Example 7

A prepolymer compound is prepared by mixing the product Ebecryl <®> 230 with the oligomer EBECRYL <®> 8402 in a proportion Ebecryl <®> 230 / EBECRYL <®> 8402 of 90/5% by weight relative to to the total weight of the prepolymer compound.

The remaining 5% by weight corresponding to the amount of photoinitiator and optionally of additive (s), relative to the total weight of the composition.

It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made thereto without departing from the scope of the appended claims.

Claims (28)

1. Use of a photopolymerizable varnish composition for coating a timepiece, said varnish composition comprising: A prepolymer compound comprising monomers or at least one oligomer or their mixtures, said monomers being chosen from the group consisting of monomers comprising at least one acrylate or methacrylate function, epoxy monomers and mixtures thereof, said oligomer being chosen from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins, and mixtures thereof. 2. Use according to claim 1, wherein said prepolymer compound consists of monomers comprising at least one acrylate or methacrylate function and optionally oligomers selected from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and mixtures thereof. 3. Use according to claim 1 or 2, wherein said prepolymer compound further comprises an oligomer having the following formula: 4. Use according to one of the preceding claims, in which the prepolymer compound comprises at least one radical, cationic or hybrid photoinitiator for respectively initiating a radical, cationic or hybrid polymerization reaction. 5. Use according to claim 4, wherein the free radical photoinitiator is selected from the group consisting of acetophenone derivatives or derivatives of phosphine oxide, benzophenone and mixtures thereof. 6. Use according to one of the preceding claims, wherein said prepolymer compound comprises at least one additive which comprises an anti-bubble agent or an oil such as soya lecithin or else a mixture of anti-foam polymers without silicone or their mixtures. . 7. Use according to one of the preceding claims, wherein said prepolymer compound comprises at least one photosensitizer such as benzotriazoles, triazines, preferably hydroxyphenyl-triazine. 8. Use according to one of the preceding claims, wherein the prepolymer compound comprises at least one UV absorber and / or a light stabilizer chosen from the group consisting of 2-hydroxy-benzophenones, 2-hydroxy-benzotriazoles, hydroxy-benzoates, cyanoacrylates and aryl esters. 9. Use according to claim 8, wherein the light stabilizer is 2- [2 ́-hydroxy-3 ́, 5 ́-di (α, α-dimethylbenzyl) phenyl] benzotriazole. 10. Use according to one of the preceding claims, wherein said prepolymer compound comprises a diluting agent, such as hexanediol diacrylate ethyl-diethylene glycol acrylate -isobomyl-acry late. 11. Use according to one of the preceding claims, wherein said prepolymer compound comprises a pigment. 12. Use according to one of the preceding claims, wherein said prepolymer compound comprises: - Said monomers or said at least one oligomer or their mixtures in an amount ranging from 30 and 70 parts by weight, - said photoinitiator in an amount ranging from 2 to 6 parts by weight, - optionally, said diluting agent in an amount ranging from 30 to 70 parts by weight, - optionally said absorber in an amount ranging from 0.3 to 1 part by weight, and - optionally said pigment in an amount less than 5 parts by weight, said parts by weight being expressed relative to the total weight of said prepolymer compound. 13. Use according to one of the preceding claims, wherein said oligomer has a molecular mass of between 300 and 100,000 g / mol. 14. Use according to one of the preceding claims, wherein said monomers comprising at least one acrylate or methacrylate function have a molecular weight of less than 1000 g / mol. 15. Use according to one of the preceding claims, in which the prepolymer compound has a viscosity greater than 3000 mPa.s at 20 ° C, preferably greater than 5000 mPa.s at 20 ° C, more preferably greater than 8000 mPa. .s at 20 ° C. 16. Process for coating a timepiece with a peelable varnish comprising the steps of: - provision of a prepolymer compound comprising monomers or at least one oligomer or their mixtures, said monomers being chosen from the group consisting of monomers comprising at least one acrylate function, epoxy monomers and their mixtures, said oligomer being chosen from the group consisting of polyurethane-acrylate resins, aliphatic polyurethane-acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and mixtures thereof, - addition of at least one photoinitiator to said compound to form a photopolymerizable varnish composition, - application of said photopolymerizable varnish composition to a timepiece, - exposure to UV-Visible rays of said timepiece on which said photopolymerizable varnish composition has been applied, - obtaining a peelable varnish formed from a three-dimensional network of polymers based on acrylate or epoxy on said timepiece. 17. The method of claim 16, wherein said prepolymer compound consists of monomers comprising at least one acrylate or methacrylate function and optionally oligomers selected from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and mixtures thereof. 18. The method of claim 16 or 17, wherein said prepolymer compound further comprises an oligomer having the following formula: 19. Method according to one of the preceding claims, wherein said at least one photoinitiator is selected from the group consisting of radical, cationic or hybrid photoinitiators to respectively initiate a radical, cationic or hybrid polymerization reaction. 20. Process according to one of the preceding claims, in which the free radical photoinitiators are chosen from the group consisting of acetophenone derivatives or phosphine oxide derivatives, benzophenones and mixtures thereof. 21. Method according to one of the preceding claims, comprising a step of adding at least one additive comprising an anti-bubble agent or an oil such as soya lecithin or a mixture of anti-foam polymers without silicone or their mixtures. . 22. Method according to one of the preceding claims, comprising a step of adding to said at least one photosensitizing agent such as benzotriazoies, triazines, preferably hydroxyphenyl-triazine. 23. Method according to one of the preceding claims, comprising a step of adding at least one UV absorber and / or a light stabilizer chosen from the group consisting of 2-hydroxy-benzophenones, 2-hydroxy-benzotriazoles, hydroxy-benzoates, cyanoacrylates and aryl esters. 24. A method according to any preceding claim, wherein said light stabilizer is 2- [2 ́-hydroxy-3 ́, 5 ́-di (α, α-dimethylbenzyl) phenyl] benzotriazole. 25. Method according to one of the preceding claims, comprising a step of adding a diluting agent, such as hexanediol, ethyl-diethylene glycol diacrylate, acrylate-isobornyl-acrylate. 26. Method according to one of the preceding claims, comprising a step of adding a pigment. 27. Timepiece coated with a peelable varnish composition formed of a three-dimensional crosslinked network of monomers or oligomers or their mixtures, said monomers being chosen from the group consisting of monomers comprising at least one acrylate function, epoxy monomers and mixtures thereof, said oligomers being selected from the group consisting of polyurethane-acrylate resins, aliphatic polyurethane-acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and mixtures thereof. 28. Device for applying a photopolymerizable mixture to a timepiece arranged to be placed on a support, said device comprising: A photopolymerizable mixture reservoir composed of prepolymers comprising monomers or at least one oligomer or their mixtures and further comprising a photoinitiator, said monomers being chosen from the group consisting of monomers comprising at least one acrylate function, epoxy monomers and mixtures thereof, said oligomer being selected from the group consisting of polyurethane-acrylate resins, polyurethane-aliphatic acrylate resins, polyester-acrylate resins, polyether-acrylate resins, polysiloxane-acrylate resins, epoxy-acrylate resins and their mixtures, - a printing station having an inkjet printing head connected to said reservoir and being arranged to distribute said photopolymerizable mixture on said timepiece, - a radiation source placed a short distance above the support to uniformly irradiate said mixture in order to obtain a peelable varnish on said timepiece.