WO1998028663A1

WO1998028663A1 - Use for stereoscopic photolithography of a liquid composition cross-linkable by irradiation using a cation comprising a photoinitiator of the onium salts or of organometallic complex type

Info

Publication number: WO1998028663A1
Application number: PCT/FR1997/002362
Authority: WO
Inventors: Philippe Karrer
Original assignee: Rhodia Chimie
Priority date: 1996-12-24
Filing date: 1997-12-19
Publication date: 1998-07-02
Also published as: AU5565398A; FR2757530A1

Abstract

The invention concerns LASER stereoscopic photolithography (SPL) from a liquid resin precursor, cross-linkable by cationic process, under actinic activation. The aim of the invention is the improvement of known SPL resins ( decrease of volume shrinkage, lower initial viscosity for the resin, optimisation of the mechanical properties of the objects shaped by SPL). To achieve this aim, the invention proposes the use of specifically selected photoinitiators, of the onium borate type, 1) and/or oxoisothiochromanium 2) and/or monosulphonium or polysulphonium 3) and/or organometallic complexes 4) combined, for example, with polydimethylsiloxanes functionalised by groups cross-linkable by cationic process of the epoxy type, under UV LASER. These borates contain fluorosubstituted phenyls. The invention also concerns the corresponding method for making objects by SPL, as well as the liquid composition for initiating the implementation. The invention is applicable to phototype.

Description

Use for stereophotolithography of a cationic crosslinkable liquid composition comprising a photoinitiator of the onium salt or organometallic complex type

The field of the present invention is that of the (stereo) photolithography technique allowing the shaping of three-dimensional solid objects by polymerization / crosslinking, under actinic activation, of liquid precursors.

The invention relates more particularly to improvements in precursor liquid compositions comprising a polymerizable / crosslinkable raw material and a photoinitiator. The chemical mechanism underlying liquid - »solid transformations involved in StereoPhotoLithography (SPL) can be either of the polymerization / crosslinking type by radical route, or of the polymerization / crosslinking type by cationic route. The present invention is part of the cationic type SPL. SPL is a technology based on a liquid - »solid transformation localized in space and induced by actinic light, preferably produced by a UV laser source. This technology allows the construction of a three-dimensional object of determined shape, by successive solidification of slices of the targeted object, and this thanks to the repeated exposure of photocrosslinkable liquid zone corresponding to the slices, the superposition of these solidified slices and secured to each other constituting the object to be manufactured.

An actinic source - preferably LASER - scans the surface of a bath of liquid precursor over an area defined by the geometry of the edge of the object to be solidified considered. The guidance of the laser source is advantageously carried out by a computer having in memory the mathematical model of the object to be manufactured. After solidification / crosslinking of a given layer or wafer, the latter is immersed in the liquid precursor bath at a depth corresponding to the thickness of the adjacent wafer to be solidified during the light exposure to follow. The SPL is described in particular in patent US-A-4,575,330. The SPL carries promising hopes as regards its possible outlets in the field of producing prototypes of industrial parts intended for mass production. SPL is indeed an interesting alternative technique compared to conventional machining processes with numerical control or not. Such methods are restrictive in particular with regard to the wear of the tools which they generate and the limits which it comprises in the production of parts with complex topography: certain zones to be machined may not be accessible to the tools. It is therefore clear that the SPL has many advantages to assert, provided that it can best meet various technical specifications which are listed below.

Time is a crucial parameter in the industrial field. Also, the raw materials used must quickly harden by polymerization / crosslinking.

The basic liquid composition comprising the raw material (also known as resin) and the photoinitiator, must be chosen so that it leads to a reticulate capable of authorizing mutual self-adhesion of the successive solidified slices.

This basic liquid composition must have a viscosity compatible with industrial requirements for ease of use and handling, as well as storage stability.

The initiator system (photoinitiator (s) per se + possibly photosensitizer (s)) must best absorb actinic radiation, so as to improve the crosslinking yields and thus reduce the consumption of activation energy.

It is preferable that the basic liquid composition, as well as its crosslinked correspondent, is not toxic or dangerous. It is important that the basic liquid composition (raw material + initiator system) does not have too high an initial viscosity, so as not to increase the stabilization time of each slice before exposure. The stabilization time is that necessary to regain a flat surface state, after immersion of the section having just been crosslinked. It is also essential that the photocrosslinker or polymerisate has mechanical properties (hardness, elasticity, etc.) sufficient to give consistency to the three-dimensional part produced and to stabilize it in a perene manner.

Last but not least, it is necessary to insist on the specification which sins the most by default and which constitutes an obstacle to the development of SPL, namely the problem of volume shrinkage. It would indeed be desirable to have a resin leading to a shrinkage as close as possible to zero, to avoid volume deformations and tensions which distort the shape of the three-dimensional part to be produced. This volume shrinkage occurs during polymerization / crosslinking, because it is a fact that the Van der Waals bonds which prevail in the liquid formula, are characterized by greater inter-molecular distances than those induced by the covalent bonds specific to the photocrosslink /polymer. Throughout this presentation, the volume shrinkage will be defined as the density of the solid - density of the liquid being: -. liquid density

In summary, the systems implemented in the SPL must in particular meet the following conditions: * for the liquid raw material:

- the most fluid liquid state possible,

- economic,

- nontoxic,

- great stability over time; * for the polymerization / crosslinking reaction:

- photochemically primable,

- not causing or practically no volume shrinkage on the reticulate / solid polymer,

- high quantum yield of polymerization, - low exothermicity;

* for crosslinked resin:

- solid with satisfactory mechanical properties,

- insoluble in the precursor liquid raw material.

The radical polymerization / crosslinking path under UV is that in which the photoinitiator transforms into a free radical after absorption of a quantum of ultra-violet actinic radiation. The free radical thus produced is at the origin of a chain reaction involving bridging groups crosslinkable by the radical route (G ^), the latter generally being acrylates. Thus known in the SPL, diacryl 103 from AKZO CHEMISTRY, which is a bifunctional acrylate, honorable in many respects in this application, but affected by a relatively large volume shrinkage during crosslinking polymerization, namely approximately 8% ( diacryl 103 = mixture of 10% by weight of a methacrylate of low viscosity mono-functional and 90% by weight of 2,2-bis [p (ethyl methacrylate) phenyl] propane. Acrylates also have the disadvantage of being sometimes toxic and may not cure as quickly and as completely as you would like. They may also be subject to crosslinking inhibition due to oxygen in the air. Indeed, the polymer radical chain in growth can be easily terminated by molecular oxygen of a relatively stable peroxy radical. It follows that the crosslinking and therefore the hardening of the raw material is incomplete. For actinic systems with low photon flux density, nitrogen inerting is necessary (N ₂ ). This results in the use of sophisticated and therefore costly equipment, which is straining the economy of the SPL.

In addition, it is not uncommon that a post-hardening of the solids formed by SPL is necessary in the case where acrylates are used.

As regards photocrosslinking by the cationic route, which can be exploited for SPL, we are in a situation where the UV light energy of activation causes a chain reaction starting from the photoinitiator, reaction which leads to an H + cation, itself causing another polymerization chain reaction of Cationically Crosslinkable Bridging Groups (Grc) - heterocyclic group with electron donor: O, S, N and P or ethylenically unsaturated group substituted by an electron donor: vinyl ether or epoxy.

Thus, cationically, it is possible to use liquid raw materials which are precursors of solid polymers comprising Grc of ethervinyl type and / or Grc of epoxy-functional type.

French Patent Application No. 2,676,061 discloses compositions of polymer precursors suitable for stereophotolithography and comprising compounds with ethervinyl functions as well as compounds with epoxy function, as well as an effective amount of a cationic photoinitiator. The ethervinyl functional compounds are ethervinyl oligomers whose main chain is derived from urethane, phenol, polyester, polyether polycarbonate or polysiloxane, said main chain having pendant Grc groups of the acrylate type. The epoxide-functional compounds considered are of the type derived from phenol (bisphenol A), from novalac, from linear and / or cyclic polyaliphatic residues, from polyethylenols and from polysiloxanes, the epoxy substitutions of these compounds being located in the chain and / or at the ends of it. Polyorganosiloxanes are claimed but are not exemplified in this French patent application. The cationic photoinitiators recommended are onium salts and in particular iodonium and sulfonium salts, in which the counter anions are: BF ₄ -, PF ₆ -, SbF ₆ \ and SO ₃ CF ₃ -. Among all these counter-anions, the one which gives the most satisfaction with regard to the crosslinking performance under UV (crosslinking speed) is SbF _{6 \} but it turns out that this counteranion has the major drawback of 'be toxic. The invention described in this prior document which is based on the basic idea of associating oligomers with Grc of vinylether type and oligomers carrying Grc epoxyfunctional, as liquid precursors in a system usable in SPL, remains still perfectible, in particular with regard to the volume shrinkage and the mechanical properties (hardness of the reticulate hardened under UV laser).

In this state of knowledge, the applicant has set itself the objective of improving resins for SPL, so as to remedy the drawbacks of the radical acrylate system and of the cationic vinyl ether and / or epoxy system. The points to improve are:

- lower volume shrinkage of the reticulate,

- lower initial viscosity for the liquid raw material, - and mechanical properties of the parts crosslinked by SPL higher than those of three-dimensional objects manufactured by the known systems mentioned above.

One of the essential objectives of the invention is therefore to propose the use of a new SPL system: liquid precursor raw material + initiator system, which makes it possible to meet the technical specifications set out in the specifications above.

Another essential objective of the invention is to provide a process for manufacturing three-dimensional parts by SPL, in which a new particular basic composition (liquid precursor + initiator system) is used, which is economical, easy to implement. and which contributes to the same goals as those mentioned above with regard to the liquid precursor, the polymerization and the final crosslink obtained, in terms of volume shrinkage, toxicity, initial viscosity and mechanical properties.

Another essential objective of the invention is to provide a new liquid precursor composition, usable in SPL and having the qualities mentioned above, with reference to the new use and the new process targeted by the present invention.

The Applicant has succeeded in achieving these objectives among others, by finding, after numerous studies and experiments, that, in a completely suφrenant and unexpected manner, it was suitable for preparing a basic liquid composition for SPL, to select a photoinitiator belonging to a specific class of onium borates or organometallic complexes grouping those in which the borate counter anion comprises a boron atom linked to one or more phenyl radicals substituted by at least one electron-withdrawing group. Secondly, the Applicant has also discovered that the polyorganosiloxanes (POS) with reactive group Grc of epoxy and / or vinyl ether type are particularly suitable as a liquid raw material associated with onium borates or specific organometallic complexes.

The present invention thus relates firstly, to the use for photolithography - in particular stereophotolithography - of a composition crosslinkable by the cationic route, in particular by actinic light activation, and comprising:

D a raw material comprising at least one monomer and / or an oligomer and / or a polymer chosen from compounds comprising at least one heterocyclic group having one or more electron-donor atoms such as O, S, N and P, and among those comprising at least one ethylenically unsaturated group substituted by an electron donor atom which increases the basicity of the π system, this heterocyclic group and this ethylenically unsaturated group being groups (Grc), crosslinkable which can be crosslinked cationically; D and an effective amount of cationic initiator system comprising, as photoinitiator, a product chosen from onium borates (taken alone or as a mixture between them) of an element from groups 15 to 17 of the periodic table [Chem & Eng . News, vol.63, N ° 5, 26 of February 4, 1985] or of an organometallic complex of an element from groups 4 to 10 of the periodic table [same reference], Δ whose cationic entity is selected from: 1) onium salts of formula (I):

[(Rl) _n - A - (R2) _m ] + (I) formula in which:

• A represents an element from groups 15 to 17 such as for example: I, S, Se, P or N,

• R * represents a C6-C20 carbocyclic or heterocyclic aryl radical _. said heterocyclic radical possibly containing as heteroelements nitrogen or sulfur;

• R ^ represents R ^ or a linear or branched C1-C30 alkyl or alkenyl radical; said radicals R ^ and R ^ being optionally substituted by a C1-C25 alkoxy, C1-C25 alkyl, nitro, chloro, bromo, cyano, carboxy, ester or mercapto group; • n is an integer ranging from 1 to v + 1, v being the valence of the element A, • m is an integer ranging from 0 to v - 1 with n + m = v + 1 _>

2) The oxoisothiochromanium salts described in patent application WO 90/11303, in particular the sulfonium salt of 2-ethyl-4-oxoisothiochromanium or of 2-dodecyl-4-oxoisothio-chromanium,

3) the sulfonium salts in which the cationic entity comprises: - »3.1. At least one polysulfonium species of formula III.1.

Ar ¹ - S - Ar ³ - Ar ³ -S-Ar '(III.1)

Ar ^* Ar

in which :

- the symbols Ar ^, which may be identical or different from each other, each represent a monovalent phenyl or naphthyl radical, optionally substituted with one or more radicals chosen from: a linear or branched Cj - C12, preferably Ci, alkyl radical -Cg, a linear or branched C \ - C \ 2, preferably Cj-Cg alkoxy radical, a halogen atom, a group -OH, a group -COOH, an ester group - COO-alkyl where the part alkyl is a linear or branched residue in C \ - Ci 2, preferably in C -Cg, and a group of formula -Y ^ -Ar ^ where the symbols Y * and Ar ^ have the meanings given just below,

- the symbols Ar ^, which may be identical or different from each other or with Aχl, each represent a monovalent phenyl or naphthyl radical, optionally substituted with one or more radicals chosen from: a linear or branched Ci -Ci 2 alkyl radical of preferably in Cj -Cg, a linear or branched alkoxy radical in Ci -C 2, preferably in Cj-Cg, a halogen atom, a group -OH, a group -COOH, an ester group - COO-alkyl where the alkyl part is a linear or branched residue in Ci -C 12, preferably in C \ -Cg,

- the symbols Ar-, which may be identical or different from each other, each represent a divalent phenylene or naphthylene radical, optionally substituted with one or more radicals chosen from: a linear or branched C1-Ci2, preferably Cj, alkyl radical -Cg, a linear or branched C1-C12, preferably Cj-Cg alkoxy radical, a halogen atom, a group -OH, a group -COOH, an ester group - COO-alkyl where the alkyl part is a remains linear or branched in C 1 -C 12, preferably in Cj-Cg,

- t is an integer equal to 0 or 1, with the additional conditions that:

+ when t = 0, the symbol Y is then a monovalent radical Y ^ representing the group of formula:

Y ': - S-Ar ¹

where the symbols Ar ^ and Ar ^ have the meanings given above,

+ when t = 1:

O on the one hand, the symbol Y is then a divalent radical having the following meanings Y ^ to Y ^:

• Y ^: a group of formula:

+

* where the symbol Ar ^ has the meanings given above,

• Y ^: a simple valential link,

• Y-: a divalent residue chosen from: ι n o o a linear or branched Ci-Ci 2 alkylene residue, preferably in

Ci-Cg, and a residue of formula - Si (CH3) 2θ -, O on the other hand, in the case only where the symbol Y represents Y ^ or Y ^, the radicals Ar * and Ar ^ (terminals) have, in addition to the meanings given above, the possibility of being linked to one another by the remainder Y 'consisting in Y'1 of a simple valential link or in ^ a divalent remainder chosen from the rests cited in connection with the definition of Y ^, which is installed between the carbon atoms, facing each other, located on each aromatic cycle in position ortho with respect to the carbon atom directly connected to the cation S ⁺ ; → 3.2. and / or at least one monosulfonium species having a single cationic center S ⁺ per mole of cation and consisting, in most cases, in species of formula:

1 ⁺ 1 Ar S-Ar (HI.2)

Ar in which Ar ^ and Ar ^ have the meanings given above with regard to the formula (III.1), including the possibility of directly linking together only one of the radicals Ar ^ to Ar ^ according to the as indicated above with regard to the definition of the additional condition in force when t = 1 in formula (II), using the remainder Y *; 4) the organometallic salts of formula (IV): (L ¹ L ² L ³ M) ⁺ I (IV) formula in which:

• M represents a metal from group 4 to 10, in particular iron, manganese, chromium, cobalt ...

• L ^ represents 1 ligand linked to the metal M pir of the π electrons, ligand chosen from the ligands η ^ -alkyl, η5- cyclopendadienyl and η? - cycloheptratrienyl and the η ^ - aromatic compounds chosen from the ligands η "-benzene optionally substituted and the compounds having from 2 to 4 condensed cycles, each cycle being capable of contributing to the valence layer of the metal M by 3 to 8 π electrons • L ² represents a ligand linked to the metal M by π electrons, a ligand chosen from the η '-cycloheptatrienyl ligands and the η ^ - aromatic compounds chosen from the η ^ - benzene ligands optionally substituted and the compounds having from 2 to 4 condensed cycles, each cycle being capable of contributing to the valence layer of the metal M by 6 or 7 π electrons;

• L- * represents from 0 to 3 identical or different ligands linked to the metal M by σ electrons, ligand (s) chosen from CO and NO2 ^"" ; the total electronic charge q of the complex to which L ^, L ² and O contribute and the ionic charge of the metal M being positive and equal to 1 or 2;

To the borate anionic entity having the formula:

formulated in which:

- a and b are integers ranging for a from 0 to 3 and for b from 1 to 4 with a + b = 4,

- the symbols X represent:

* a halogen atom (chlorine, fluorine) with a = 0 to 3,

* an OH function with a = 0 to 2,

the symbols R are identical or different and represent:> a phenyl radical substituted by at least one electron-withdrawing group such as for example OCF3, CF3, NO2, CN, and / or by at least 2 halogen atoms (especially fluorine), when the cationic entity is an onium of an element from groups 15 to 17

> a phenyl radical substituted by at least one element or an electron-withdrawing group, in particular a halogen atom

(fluorine in particular), CF3, OCF3, NO2, CN, when the cationic entity is an organometallic complex of an element from groups 4 to 10

> an aryl radical containing at least two aromatic rings such as for example biphenyl, naphthyl, optionally substituted by at least one element or an electron-withdrawing group, in particular a halogen atom (fluorine in particular), OCF3, CF3, NO2, CN, whatever the cationic entity. It therefore appears that the invention proceeds essentially from the judicious and advantageous selection of a particular class of photoinitiators of the onium borate or borate type of organometallic complexes. Some of these photoinitiators are known moreover for other applications involving crosslinking by the cationic route, eg under UV (non-stick coatings). They did not appear a priori to be naturally transposable in the SPL application. In fact, the only systems that have had a commercial future in SPL are the acrylate systems. Furthermore, it was known that at equal amounts of actinic energy and at optical densities = equal for the liquid system, the cationic pathway is 5 times less reactive than the radical pathway. It was also known that liquid precursors, crosslinking in SPL by the radical route, have a quantum polymerization yield Φ _p (number of moles of monomers transformed per mole of absorbed photons: mol. E ^{* 1} ) much higher than their counterparts in the systems. cationically: Φ _p = 1,200 for Diacryl 103 initiated by DMPA (DimethoxyphenylAcetophenone) versus Φ _p = approximately 200, for raw materials with Grc of epoxy type primed with triphenylsulfonium hexafluoroantimonate.

Finally, the published documents relating to onium borates or of particular organometallic complexes used within the framework of the present invention, do not allude to and do not contain any incentive, as for the application of said borates in the field of SPL. Those skilled in the art therefore necessarily had to do inventive work to carry out the transposition. Within the meaning of the present invention, the activation of the polymerization / crosslinking is preferably that obtained by exposure to UV (LASER eg), but it cannot be excluded that it is possible to resort to activation by beam of electrons or thermoactivation. Liquid raw materials of monomeric and / or oligomeric and / or polymeric nature also come into play in the context of the use in accordance with the invention. These compounds carrying Grc crosslinking functional groups preferably comprise at least one siloxane, preferably a polyorganosiloxane POS, said POS being more preferably still chosen from polyorganosiloxanes which are:

→ either linear or substantially linear and consisting of units of formula (V), terminated by units of formula (VI), → or cyclic and consisting of units of formula (V):

^R3 R ³

- - Si-O- (V) Z - Si— O- (VI) I z R ³

formulas in which:

• the symbols R ³ are similar or different and represent:

either a linear or branched C -C 6 alkyl radical, optionally substituted, advantageously by one or more halogens, the preferred optionally substituted alkyl radicals being: methyl, ethyl, propyl, octyl and 3,3,3 trifluoropropyl,

- or a C 5 -C 6 cycloalkyl radical, optionally substituted,

either an aryl or aralkyl radical, optionally substituted: in particular by halogens and / or alkoxyls, the phenyl, xylyl, tolyl and dichlorophenyl radicals being very particularly selected,

- and, more preferably still, at least 60 mol% of the radicals R ³ being methyls, • the symbols Z are similar or different and represent:

- or the radical R ³ ,

either an organofunctional Grc group crosslinkable by the cationic route, preferably an epoxyfunctional or vinyloxyfunctional group, linked to silicon via a divalent radical containing, advantageously, from 2 to 20 carbon atoms comprising, optionally, a heteroatom, at least one of the symbols Z corresponding to an organofunctional group crosslinkable by the cationic route. It is clear that the quantity of Grc crosslinking functions present in the precursor liquid raw material is decisive with regard to the course of the polymerization / crosslinking and with respect to the volume shrinkage and the mechanical properties of the hardened crosslinked product obtained. after exposure under UV laser. Thus, according to a preferred arrangement of the invention, in the context of the embodiment in which at least one POS is used as a liquid precursor raw material, the title of said POS in Grc - expressed in eq of Grc per kg of POS - is greater than or equal to

0.20, preferably between 0.50 and 5, and even more preferably between

0.80 and 3.0.

The initial viscosity of the precursor liquid raw material is an important parameter for the SPL application. It follows that according to an advantageous arrangement of the invention, the raw material of POS nature has a viscosity at

25 ° C, between 10 and 3000 mPa.s preferably between 10 and 1500 mPa.s and even more preferably between 10 and 900 mPa.s.

The dynamic viscosity at 25 ° C of all the silicone polymers considered in this presentation can be measured using a BROOKFIELD viscometer, according to the AFNOR NFT 76 102 standard of February 1972.

The viscosity in question in this presentation is the dynamic viscosity at 25 ° C, called "Newtonian", that is to say the dynamic viscosity which is measured, in a manner known per se, at a speed gradient of sufficiently low shear so that the viscosity measured is independent of the speed gradient.

When cyclic polyorganosiloxanes are involved, these consist of units (D) which may be, for example, of the dialkylsiloxy or alkylarylsiloxy type. These cyclic polyorganosiloxanes have a viscosity of the order of 1 to 5000 mPa.s, at 25 ° C. To come to more precise chemical composition characteristics of the preferred POS precursors according to the invention, the following examples may be mentioned of epoxyfunctional Grc crosslinking groups:

- (0 ^) ₃ O-CHj— CH—; CH ₂ ; - ₍ CH _j ) ₃ - C — CH CH _j

O With regard to Grc groups of the vinyl ether type, it may be mentioned, e. g., those contained in the following formulas:

- (CH _j J _j _-O-CH≈CK,;

• with R ^ =

- linear or branched C1-C12 alkylene, optionally substituted,

- or arylene, preferably phenylene, optionally substituted, preferably by one to three C 1 -C 6 alkyl groups; • with R ^ = linear or branched C _j -C ₆ alkyl;

The preferred epoxy or vinyloxyfunctional polyorganosiloxanes are described in particular in patents DE-A-4,009,889; EP-A-0 396 130; EP-A-0 355

381; EP-A-0 105 341; FR-A-2 1 10 115; FR-A-2 526 800.

The epoxy-functional polyorganosiloxanes can be prepared by hydrosilylation reaction between oils with Si-H units and epoxyfunctional compounds, such as 4-vinylcyclohexeneoxide, allylglycidylether ...

The vinyloxyfunctional polyorganosiloxanes can be prepared by hydrosilylation reaction between oils with Si-H units and vinyloxyfunctional compounds, such as allyl viny! ether, allyl-vinyloxyethoxybenzene, etc. The POSs which appear to be particularly suitable for use according to the invention are linear oligomers, the siloxy ends M of which carry at least one group Y = Grc (eg epoxy or vinyl ether, preferably epoxy), said oligomers whether or not containing pendant Y = Grc groups in the chain. According to a variant of the invention, the monomers and / or oligomers and / or polymers forming the raw material belong to at least one of the following species: cycloaliphatic epoxides (A) or not (B), alkenyl ethers (C) , linear or cyclic, the species A, B, C listed below being preferred: - A corresponding to the cycloaliphatic epoxides, taken alone or as a mixture between them, the epoxides of the 3,4-epoxycyclo- type hexylmethyl-3,4-epoxycyclohexane carboxylate or Bis (3,4-epoxycyclohexyl) adipate being particularly preferred; - B corresponding to the other non-cycloaliphatic epoxides, taken alone or as a mixture with one another, epoxides of the type of those resulting from the condensation of bisphenol A and of epichlorohydrin and of the type:

> di and triglycidyl ethers of alkoxylated Bisphenol A, of 1,6 hexane diol, of glycerol, of neopentyl glycol and of propane trimethylol,> diglycidyl ethers of Bisphenol A,> or alpha-olefin epoxides, NOVOLAC epoxides, soya oil and linseed epoxides, epoxidized polybutadiene, being particularly preferred;

- C corresponding to alkenyl ethers, linear or cyclic, taken alone or as a mixture between them, • vinyl ethers, in particular the triethyl ether of divinyl glycol the ether of 1,4-cyclohexanedimethanol divinyl the vinyl ethers cyclic or tetramers and / or dimers of acroleins • propenyl ethers

• and butenyl ethers being especially preferred. Without being limiting, more details are given below as to the subclasses of onium borate and organometallic salt borate more particularly preferred in the context of the use in accordance with the invention.

Thus, as regards the borate anionic entity, the species which are particularly suitable are the following:

[B (C ₆ F ₅ ) ₄ ] - [B (C ₆ H ₄ CF ₃ ) ₄ ] - [B (CgF ₄ OCF3) 4] - [B (C ₆ F ₄₀ CF ₃ ) ₄ ] -

[(CgF5) ₂ BF ₂ ] - [CgF ₅ BF ₃ ] - [B (CgH ₃ F2) ₄ ] - As regards the cationic entity of the photoinitiator, we distinguish:

- 1) the onium salts of formula (I)

- 2) the oxoisothiochromanium salts of formula (II)

- 3) the mono and / or polysylfonium salts of formula (III.1) and / or (III.2)

- 4) the organometallic salts of formula (IV). The first 1) are described in numerous documents, particularly in patents US-A-4,026,705, US-A-4,032,673, US-A-4,069,056, US-A-4,136,102, TJS-A- 4 173476. Among these, the following cations will be particularly favored: [() 2ll ⁺ [C ₈ H ₁₇ -O-Φ-I-Φ] ⁺ [(Φ-CH ₃ ) ₂ 1] ⁺ [C12 H ₂₅ -Φ-I-Φ] ⁺ [(C ₈ H ₁₇ -O-Φ) ₂ 1] ⁺ [(C ₈ H ₁₇ -O-Φ- I-Φ)] +

[(Φ) ₃ S] ⁺ [(Φ) ₂ -S-Φ-OC ₈ H ₁₇ ] ⁺ [(CH ₃ -Φ-I-Φ-CH (CH ₃ ) ₂ ] ⁺

[Φ-S-Φ-S- (Φ) ₂ ] ⁺ [(Cι ₂ H ₂₅ -Φ) 2 1] ⁺ [(CH ₃ -Φ-I-Φ-OC ₂ H ₅ ] ⁺

As regards the second family of cationic entities of formula (II) and of the oxoisothiochromanium type, it preferably comprises cations corresponding to the structure D _j which is defined on page 14 of application WO-A-90/11303 and has the formula (II):

where the radical R ⁶ has the meaning given in this WO application in connection with the symbol R ¹ ; a cationic entity of this type which is more preferred is that where R ⁶ represents an alkyl radical, linear or branched, C ^ C ^. As oxoisothiochromanium salts which are particularly suitable, mention will be made in particular of the sulfonium salt of 2-ethyl-4-oxoisothiochromanium or of 2-dodecyl-4-oxoisothiochromanium. As regards the cationic polysulfonium entities (III.1), it will be specified that the cationic polysulfonium entity preferably comprises a species or a mixture of species of formula (III.1) in which:

- the Ar ^ radicals, identical or different from each other, each represent a phenyl radical, optionally substituted by a linear or branched Cι-C ₄ alkyl radical or by the group of formula:

- the radicals Ar ² , identical or different from each other and with Ar, each represent a phenyl radical, optionally substituted by a linear or branched C i -C ₄ alkyl radical, - the radicals Ar ³ each represent a non-phenylene para-radical substituted, - t is 0 or 1, with the additional conditions that:

+ when t = 0, Y = Y ^J = - S ⁺ - Ar ¹

Ar ² where the radicals Ar * and Ar ² have the preferred meanings given just above in this paragraph; + when t = 1:

O on the one hand, Y = Y ² to Y ⁴ with: • Y2 =

Ar where the radical Ar ² has the preferred meaning given just above in this paragraph,

• γ3 = a valential link,

. Y ⁴ = - O— or —S—, and

O on the other hand, when Y = Y ³ or Y ⁴ and when we then wish to use radicals Ar and Ar ² (terminals) linked together, we install a bond Y 'consisting of a valential bond or the rest - O -. The mono-sulfonium species, when there are any, which fall within the framework of this preferential modality are the species of formula (IV) in which the symbols Arl and Ar ² have the preferred meanings indicated above in the preceding paragraph , including, when these radicals are directly linked together by a remainder Y ', the installation of a valential link or the rest - O -. As examples of cationic sulfonium entities, particular mention may be made of:

mixtures, in variable quantities, of species 5 + 2 + possibly 3_, mixtures, in variable quantities, of species 5 with the species iO of formula

The borate anionic entity is preferably chosen from the anions of formula [BX _to RJ- in which:

- the symbols X represent a fluorine atom,

the symbols R, which are identical or different, represent a phenyl radical substituted by at least one electron-attracting group chosen from OCF3, CF3, NO and CN, and / or by at least two fluorine atoms.

Advantageously, the borate anionic entity of formula [BX..R - is chosen from the following anions: [B (CF ₅ ) ₄ ] - [B (CgH4CF ₃ ) ₄ ] - [B {CgH ₃ (CF ₃ ) 2 } ₄ ] - the '3' 5 '

[(CgF5) 2BF ₂ ] - [B (CgF ₄ OCF ₃ ) ₄ ] - [B (CgH ₃ F2) ₄ ] -

2 '4' 6 '

The new polysulfonium borates which will be used very preferably are the salts formed by the association of the following cations and anions:

Cation Anion

5 V

5 y

5 mixes 5 + __ V mixes 5 + 10 mixes 5 + 10 4 '

These polysulfonium borates can be prepared by exchange reaction between a salt of the cationic entity (halide such as for example chloride, iodide) with an alkali metal salt (sodium, lithium, potassium) of the anionic entity. The operating conditions (respective quantities of reagents, choice of solvents, duration, temperature, stirring) are within the reach of those skilled in the art; these must make it possible to recover the desired polysulfonium borate in solid form by filtration of the precipitate formed or in oily form by extraction using an appropriate solvent.

The procedures for the synthesis of halides of cationic entities of formula (III.1) are described in particular in: "Polymer Bulletin (Berlin)", vol. 14, pages 279-286 (1985) and US-A-4400 541.

According to an alternative concerning the preparation of polysulfonium borates, the latter can be prepared directly by reaction between a diarylsulfoxide and a diarylsulfide according to the teaching described in: "J; Org. Chem.", Vol. 55, pages 4222 - 4225 (1990).

These new polysulfonium borates can be used, as they are obtained at the end of their preparation process, for example in solid or liquid form or in solution in an appropriate solvent, in monomer / oligomer / polymer compositions which are intended to be polymerized and / or crosslinked cationically and under activation, for example UV.

The mono-sulfonium species (III.2) mentioned above may be in particular the co-products which are formed at the time of the preparation of the polysulfonium cations and whose presence can be more or less avoided.

Up to 99%, more generally up to 90% and even more generally up to 50 mol% (of cation) of the polysulfonium species of formula (in.1) can be replaced by monosulfonium species (III.2) .

As regards the fourth type of cationic entity, it is described in US patent A-4,973,722, US-A-4,992,572, European patent applications EP-A-203,829, EP-A- 323 584 and EP-A-354 181. The organometallic salts more readily used in practice are in particular:

. (η ^ - cyclopentadienyl) (η ^ - toluene) Fe ⁺ . (η ^ - cyclopentadienyl) (η ^ - methyl-1-naphthalene) Fe ⁺ . (η ^ - cyclopentadienyl) (η ^ - cumene) Fe ⁺

. bis (η - mesitylene) Fe ⁺ . bis (η ⁶ - benzene) Cr ⁺ It follows from the above that the preferred photoinitiators according to the invention are those corresponding to the following formulas: [(Φ) ₂ 1] ⁺ , [B (C ₆ F ₅ ) ₄ ] - [(C ₈ H ₁₇ ) -O-Φ-I-Φ)] ⁺ , [B (C ₆ F ₅ ) ₄ ] -

[Cι ₂ H ₂₅ -Φ-I-Φ] ⁺ , [B (CgF ₅ ) ₄ ] - [(C ₈ Hι ₇ -O-Φ) ₂ I] ⁺ , [B (C ₆ F ₅ ) ₄ ] - [(C ₈ H ₁₇ ) -O-Φ-I-Φ)] ⁺ , [B (CgF ₅ ) ₄ ] - [(Φ) ₃ S] ⁺ , [B (CgF ₅ ) ₄ ] -

[(Φ) ₂ S-Φ-OC ₈ H ₁₇ ] +, [B (C ₆ H4CF ₃ ) ₄ ] - [(C ₁₂ H ₂₅ -Φ) ₂ I] ⁺ , [B (CgF ₅ ) ₄ ] - [(Φ) ₃ S] ⁺ , [B (CgF ₄ OCF ₃ ) ₄ ] - [(Φ-CH ₃ ) ₂ I] ⁺ , [B (CgF ₅ ) ₄ ] -

[(Φ-CH ₃ ) ₂ I] + [B (C ₆ F ₄ OCF ₃ ) ₄ ] -. (η ⁵ - cyclopentadienyl) (η ⁶ - toluene) Fe ⁺ , [B (CgF5)] "

. (η5 - cyclopentadienyl) (η ^ - methyll-naphthalene) Fe ⁺ , [B (CgF5) ₄ ] ^_ • Cπ ^ - cyclopentadienyl) (η ^ - cumene) Fe ⁺ , [B (C F5) ₄ ] ^_

As another literary reference to define the onium borates 1) and 2) and the organometallic salt borates 4), selected as photoinitiator in the context of SPL use according to the invention, mention may be made of the entire content of the applications for European patent N ° 0 562 897 and 0 562 922. This content is fully incorporated by reference in the present presentation.

The initiating salts of type 1) and 2) used in the context of the use according to the present invention can be prepared by exchange reaction between a salt of the cationic entity (halide such as chloride, iodide ... , hexafluorophosphate, tetrafluoroborate, tosylate ...) with an alkali metal salt

(sodium, lithium, potassium) of the anionic entity.

The operating conditions (respective quantities of reagents, choice of solvents, duration, temperature, stirring, etc.) are within the reach of those skilled in the art; these must make it possible to recover the initiating salt sought in solid form by filtration of the precipitate formed or in oily form by extraction using a suitable solvent.

The alkali metal salts of the anionic entity can be prepared in a known manner, by an exchange reaction between a haloborinated compound and an organometallic compound (magnesian, lithian, stannic, etc.) carrying the desired hydrocarbon groups, in stoichiometric quantity, optionally followed by hydrolysis using an aqueous alkali metal halide solution; this type of synthesis is for example described in "J. of organometallic Chemistry" vol 178, p. 1- 4, 1979; "J.A.C.S" 82, 1960, 5298; "Anal. Chem, Acta" 44, 1969, 175-183; US-A-4 139681 and DE-A-2091 367; "Zh. Org. Khim." Vol. 25, No. 5 - pages 1099 - 1102, May 1989.

The preparative mode of the salts of the cationic entity 4) of formula (IV) is described in particular in D. ASTRUC, Tetrahedron Letters, 36, p.3437 (1973); D.

ASTRUC, Bull. Soc. Chim. Fr, 1-2, p. 228 (1976); D. ASTRUC, Bull. Soc. Chim. Fr, 11-12, p. 2571 (1975); D. ASTRUC, CR Acad. Se. Paris, series C, 272, p. 1337

(1971); AN NESMEYANOV et al., Izves, Akad. Nauk SSSR, ser. Khim., 7, p. 1524 (1969); YEAR. NESMEYANOV et al. Dokl. Akad. Nausk SSSR, 160 (6), p. 1327

(1965); A.N. NESMEYANOV et al. Dokl. Akad. Nausk SSSR, 149 (3), p. 615

(1963).

It has been observed that the photoinitiators onium borate and borate of organometallic salts selected in accordance with the invention are very good quantum effective initiators. They only need a few photons to trigger crosslinking and therefore the hardening of the liquid precursor raw material.

This efficiency is linked to their absorbance A which is given by the formula: A = εχ. 1. C, in which ε ^ is the molar extinction coefficient of the photoinitiator at the wavelength _λ , C its concentration and 1 the length of the optical path.

In practice, one works for example by fixing ε ^ .C = 10, which determines a depth of polymerization / crosslinking varying from I to a few millimeters. This variation is explained taking into account the variation of the initial optical density which is a function of the conversion rate of the photoinitiator under the effect of the irradiation.

Advantageously, we therefore work with a constant product ε.C for given wavelengths.

The use of a laser makes it possible to obtain a discrete wavelength and to provide high energy exposure radiation. The wavelengths used can be included in the ultraviolet and visible range, for example.

In practice, the onium borates preferred in the SPL application are the sulfonium borates. Preferably, it is provided in accordance with the use according to the invention that the initiator system comprising the photoinitiator, is used in solution in an organic solvent (accelerator), preferably. iύ among the proton donors and more preferably still from the following group: isopropyl alcohol, benzyl alcohol, diacetonalcohol, butyl lactate and mixtures thereof. In practice, the initiators according to the invention are very simply prepared by dissolving the borate which is in solid form (powder), in the accelerator (liquid).

According to an alternative concerning the borate, the latter can be prepared directly in the accelerator, starting from a salt (eg chloride) of the cation eg (iodonium) and a salt (for example of potassium) of the borate anion. In addition to the specific photoinitiator (s) of borate type 1) to 4), the initiator system can comprise, according to an advantageous variant, at least one photosensitizer selected from (poly) aromatic products - possibly metallic - and heterocyclic products, and preferably in the following product list: phenothiazine, tetracene, perylene, anthracene, diphenyl-9-10-anthracene, thioxanthone, benzophenone, acetophenone, xanthone, fluorenone, anthraquinone, 9, 10-dimethylanthracene, 2-ethyl-9, 10-dimethyloxyanthracene, 2,6-dimethylnaphthalene, 2,5-diphenyl-1-3 ~ 4-oxadiazole, xanthopinacol, 1,2-benzanthracene, 9-nitro-anthracene, and mixtures thereof. By effective amount of initiator system is meant in the sense of the invention, the amount sufficient to initiate crosslinking.

Preferably this effective amount corresponding to 1.10- ^4-1, preferably from 1.10 ^-3 to 1.10 ^-1 and even more preferably from 1.10 ° to 1.10- ² mol of photoinitiator per 1 mol of Grc. If a photosensitizer is used, the appropriate concentration ranges for the latter are: Δ 1.10 " ⁴ to 1.10- ¹ mole / mole of Grc Δ preferably from 1.10 ^-4 to 1.10- ² mole / mole of Grc Δ and more preferably still from 1.10 ^-4 to 1.10- ³ mole / mole of Grc. According to another of these aspects, the present invention relates to a method of manufacturing by SPL of a three-dimensional object from a raw material liquid which can be polymerized and / or crosslinkable by the cationic route, in particular by actinic light activation, in the presence of at least one photoinitiator, said process consisting essentially: - of implementing a bath comprising the raw material and the initiator system,

- exposing part of the surface of this bath to at least one actinic beam, said exposed surface part having a geometry corresponding to a slice of the object to be manufactured, for a time sufficient to allow the solidification of the corresponding surface layer to said object slice,

- immersing this solidified layer in the bath,

- and to repeat these operations of actinic exposure and immersion so as to obtain successive solid layers supeφosed and linked together, to form the targeted object, characterized in that the selected composition is used in the context of the use as defined above.

In the SPL process, the radiation used is either in the UV range whose wavelength is between 200 and 400 nanometers, or in the visible range whose wavelength is between 400 and 800 nm.

The actinic source used is e.g. a LASER, the beam of which moves peφendicularly on the surface of the bath, the irradiation time depends on the scanning speed and the size of the LASER beam. The crosslinking carried out is excellent, even in the absence of any heating. Of course, the coupling of photoactivation to thermoactivation, e.g. by heating between 25 and 100 ° C, is not excluded from the invention.

Another subject of the invention relates to a composition which can be polymerized and / or crosslinkable by the cationic route, in particular by actinic activation, usable in (stereo) photolithography, characterized in that it comprises:

- a raw material as defined above,

- at least one initiating system as defined above,

- And optionally at least one additive chosen from those generally known in liquid stereophotolithography precursors. The specific additives of SPL and capable of entering into the composition according to the invention are for example: mineral fillers, organic fillers and / or pigments, such as ground synthetic or natural fibers (polymers), calcium carbonate , talc, clay, titanium dioxide or fumed silica. These additives can in particular make it possible to improve e.g. the mechanical characteristics of the final materials.

Soluble dyes, oxidation inhibitors, and / or any other material which does not interfere with the catalytic activity of the photoinitiator and does not absorb in the wavelength range chosen for photoactivation, can also be added to the composition or used in the context of the process according to the invention.

These compositions according to the invention are prepared, without distinction, before (or even long before) or even immediately before use. It should be noted that these compositions are particularly stable on storage and that, in accordance with the process of the invention, they offer rapid crosslinking kinetics. In addition, their uncrosslinked state, before exposure to activation light radiation, offers great ease of handling. The compositions according to the invention can be used as such, in particular in SPL.

The present invention also relates to the three-dimensional parts obtained by SPL in accordance with the invention.

The following examples are given by way of illustration and cannot be considered as limiting the scope and spirit of the invention.

EXAMPLES: EXAMPLE 1:

Composition of the photosensitive system:

- POS silicone oil functionalized (UV resin) with Z (formula (V)) = Grc = 3-ethyl-1,2-epoxycyclohexene. RHONE POULENC poly 200 SBLCOLEASE oil - η (25 ° C) = 270 mPa.s. [epoxy] = 0.95 eq / kg.

(1,2-epoxy-4-ethyl- cγclohexyl) -polydimethylsiloxanes of formula:

primer

concentration: 0.043 mol / 1 or 45.0 g / 1 of Poly 200 (from a 20% solution by mass in butyl lactate).

- irradiation source: ionized argon laser brand Spectra-Physics model 2025/03 emitting 80% of its power at 351, 1 nm and 20% at 363.8 nn. The molar extinction coefficients of the initiator in the Poly 200 at 351, 1 and at 363.8 nm are respectively 275 and 77 l.cnr'.moF.

The laser beam, with a UV power of 40 mW, travels peφendicularly on the surface of a container containing the photosensitive system at a speed of 2.5 mm / s. The system polymerizes just where the laser beam passes and over a width equal to the diameter of the beam, ie 1 mm. Under these conditions, the system polymerizes to a depth of 5 mm, i.e. an energy consumption of 3.2 mJ / mm ³ . By adding several layers of the photosensitive system, as described in the introduction, it was possible to build a room.

EXAMPLE 2:

Composition of the photosensitive system:

- Poly 200 oil as described in Example 1.

- initiator: concentration: 5.10 - ³ mol / 1 or 4.3 g / 1 of Poly 200 (from a 20% solution by mass in butyl lactate).

- photosensitizer: benzo [alpha] pyrene at 5.71.10 " ⁴ mol / 1 or 0.144 g / 1 of Poly 200. The molar extinction coefficients of benzo [alpha] pyrene in Poly 200 at 351, 1 and 363.8 nm are 1120 and 25180 l.cπv'.mol- ^{1 respectively} .

- isopropanol: 5% by mass / Poly 200.

- source of irradiation: identical to that of Example 1.

For there to be polymerization with the same beam scanning speed as in Example 1, the beam power must be approximately three times higher or

120 mW. Due to the high absorbance of the system, polymerization is only carried out under these conditions to a depth of 1 mm.

EXAMPLE 3:

Composition of the photosensitive system:

- silicone oil of formula:

b = 32.8 viscosity = 28 mPa.s at 25 ° C; [epoxide] = 1.5 eq / kg. - initiator:

- source of irradiation: identical to that of Example 1.

20 mW. The polymerization depth is identical to that obtained in the example

1 is approximately 5 mm. The energy consumption is 1.6 mJ / mm ³ .

EXAMPLE 4: MEASUREMENT OF THE REMOVAL OF THE OILS USED IN THE EXAMPLES

The Poly 200 oil of Example 1 and the oil of Example 3 are polymerized in the form of cubes 10 mm side by irradiation under a medium-pressure mercury vapor lamp in the presence of iodonium salt used in example 2

concentrated at 2 g / l for the Poly 200 of example 1 and 1 g / 1 for the oil of example 3. These polymerizations are carried out in the absence of photosensitizer. The densities of the oils are measured by arnometry.

Claims

CLAIMS:

1 - Use for photolithography - in particular stereophotolithography - of a composition crosslinkable by the cationic route, in particular by actinic activation, and comprising: D a raw material comprising at least one monomer and / or an oligomer and / or a polymer chosen from compounds comprising at least one heterocyclic group having one or more electron donor atoms such as O, S, N and P, and among those comprising at least one ethylenically unsaturated group substituted by an electron donor atom which increases the basicity of the π system, this heterocyclic group and this ethylenically unsaturated group being (Grc) bridging groups which can be crosslinked cationically;

D and an effective amount of cationic initiator (system) comprising, as photoinitiator, a product chosen from onium borates of an element from groups 15 to 17 of the periodic classification [Chem & Eng. News, vol.63, N ° 5, 26 of February 4, 1985] or of an organometallic complex of an element from groups 4 to 10 of the periodic table [same reference], Δ whose cationic entity is selected from: 1) onium salts of formula (I):

[(Rl) _n - A - (R) _m ] + (I) formula in which:

• A represents an element from groups 15 to 17 such as for example, I, S, Se, P, or N, • Ri represents a carbocyclic or heterocyclic aryl radical in

Cg-C o, said heterocyclic radical possibly containing nitrogen or sulfur as heteroelements;

• R ² represents R ^ or a linear or branched C ₁ -C ₃ alkyl or alkenyl radical; said radicals R 1 and R ² being optionally substituted by a C1-C25 alkoxy, C1-C25 alkyl, nitro, chloro, bromo, cyano, carboxy, ester or mercapto group,

• n is an integer ranging from 1 to v + 1, v being the valence of the element A,

• m is an integer ranging from 0 to v - 1 with n + m = v + 1, 2) The oxoisothiochromanium salts, in particular the sulfonium salt of 2-ethyl-4-oxoisothiochromanium or 2-dodecyl-4 -oxoisothio-chromanium, 3) the sulfonium salts in which the cationic entity comprises: → 3.1. at least one polysulfonium species of formula III.1.

Ar ¹ (III.1)

in which: - the symbols Ar ^, which may be identical or different from each other, each represent a monovalent phenyl or naphthyl radical, optionally substituted with one or more radicals chosen from: a linear or branched Ci-Ci 2 alkyl radical _. preferably in C1-C, a linear or branched alkoxy radical in C - C 2, preferably in C _j -Cg, a halogen atom, a group -OH, a group -COOH, an ester group -

COO-alkyl where the alkyl part is a linear or branched residue in Cj - Ci 2, preferably in Ci-Cg, and a group of formula -Y ⁴ -Ar ² where the symbols Y ⁴ and Ar ² have the meanings given just below,

the symbols Ar ² , which may be identical or different from each other or with Ar, each represent a monovalent phenyl or naphthyl radical, optionally substituted with one or more radicals chosen from: a linear or branched C1-C 2 alkyl radical, of preferably in C 1 -C, a linear or branched C 1 -C 2 alkoxy radical, preferably in C 1 -C 6, a halogen atom, a group -OH, a group -COOH, an ester group - COO-alkyl where the alkyl part is a linear or branched residue in Ci -Ci 2, preferably in C -Cg,

- the symbols Ar ^, which may be identical or different from each other, each represent a divalent phenylene or naphthylene radical, optionally substituted with one or more radicals chosen from: a linear or branched C1-C 2, preferably Cj, alkyl radical -Cg, a linear or branched C -Cι ₂ alkoxy radical, preferably Cj-Cg, a halogen atom, a group -OH, a group -COOH, an ester group - COO-alkyl where the alkyl part is a linear or branched residue in Cι-C _{j 2} , preferably in Cj-Cg, - t is an integer equal to 0 or 1, with the additional conditions according to which:

+ when t = 0, the symbol Y is then a monovalent radical Y * representing the group of formula: Y ': —S-Ar "

where the symbols Ar ^ and Ar ² have the meanings given above, + when t = 1:

O on the one hand, the symbol Y is then a divalent radical having the following meanings Y ² to Y ⁴ :

• Y ² : a grouping of formula:

+

where the symbol Ar ² has the meanings given above,

• Y-: a simple valential link, • Y ⁴ : a divalent remainder chosen from:

oo a linear or branched alkylene residue in Ci -Ci 2, preferably in Cj-Cg, and a residue of formula - Si (CH ₃ ) 2θ -, O on the other hand, in the case only where the symbol Y represents Y ^ or Y ⁴ , the radicals Ar * and Ar ² (terminals) have, in addition to the meanings given above, the possibility of being linked together by the remainder Y 'consisting in Y' a simple valential link or in Y ' ² a divalent residue chosen from the residues cited in connection with the definition of Y ⁴ , which is installed between the carbon atoms, facing each other, located on each aromatic cycle in position ortho with respect to the carbon atom directly connected to the S ⁺ cation; - »3.2. and / or at least one monosulfonium species having a single cationic center S ⁺ per mole of cation and consisting, in most cases, in species of formula:

Ar 'S-Ar ¹ (HI.2)

Ar in which Ar ^ and Ar ² have the meanings given above with regard to the formula (III.1), including the possibility of directly linking together only one of the radicals Ar ^ to Ar ² in the manner indicated above about the definition of the additional condition in force when t = 1 in formula (II), calling on the remainder Y '; 4) the organometallic salts of formula (IV): (L ^ VMJ + I (IV) formula in which:

• L * represents 1 ligand linked to the metal M by π electrons, a ligand chosen from the ligands η ^ -alkyl, η ^ "cyclopendadienyl and η? - cycloheptratrienyl and the η ^ - aromatic compounds chosen from the ligands η ^ -benzene substituted and the compounds having from 2 to 4 condensed cycles, each cycle being able to contribute to the valence layer of the metal M by 3 to 8 π electrons;

• L ² represents a ligand linked to the metal M by π electrons, a ligand chosen from the η '-cycloheptatrienyl ligands and the η6- aromatic compounds chosen from the η ^ - benzene ligands optionally substituted and the compounds having from 2 to 4 condensed rings , each cycle being capable of contributing to the valence layer of the metal M by 6 or 7 π electrons;

• L- represents from 0 to 3 identical or different ligands linked to the metal M by σ electrons, ligand (s) chosen from CO and NO2 ⁺ ; the total electronic charge q of the complex to which L ^, L ² and L- contribute and the ionic charge of the metal M being positive and equal to 1 or 2; Δ the anionic borate entity having the formula:

[BX _a Rbl ^' formula in which:

- the symbols X represent:

* a halogen atom (chlorine, fluorine) with a = 0 to 3, * an OH function with a = 0 to 2,

- the symbols R are identical or different and represent:

> a phenyl radical substituted by at least one electron-withdrawing group such as for example OCF ₃ , CF, NO2, CN, and / or by at least 2 halogen atoms (especially fluorine), and this when the cationic entity is a onium of an element from groups 15 to 17 > a phenyl radical substituted by at least one element or an electron-withdrawing group, in particular a halogen atom (especially fluorine), CF ₃ , OCF ₃ , NO2, CN, and this when the cationic entity is an organometallic complex of an element groups 4 to 10

> an aryl radical containing at least two aromatic rings such as for example biphenyl, naphthyl, optionally substituted by at least one element or an electron-withdrawing group, in particular a halogen atom (fluorine in particular), OCF ₃ , CF, NO2, CN , whatever the cationic entity.

2 - Use according to claim 1, characterized in that the raw material comprises at least one siloxane, preferably a polyorganosiloxane (POS), carrying Grc groups and more preferably still chosen from polyorganosiloxanes which are: → either linear or substantially linear and consisting of units of formula (V), terminated by units of formula (VI), → either cyclic and consisting of units of formula (V):

R ³ _R 3

-Si-O -) - (V) Z— SI i— O- (VI) ZR ^J

formulas in which:

• the symbols R- are similar or different and represent:

either a linear or branched C 1 -C 6 alkyl radical, optionally substituted, advantageously by one or more halogens, the preferred optionally substituted alkyl radicals being: methyl, ethyl, propyl, octyl and 3,3,3 trifluoropropyl,

- either a C5-C cycloalkyl radical, optionally substituted,

- or an aryl or aralkyl radical, optionally substituted: in particular by halogens and / or alkoxyls,. the phenyl, xylyl, tolyl and dichlorophenyl radicals being very particularly selected,

- and, more preferably still, at least 60 mol% of the radicals R- * being methyls,

• the symbols Z are similar or different and represent: - either the radical R ^,

- Either an organofunctional Grc group crosslinkable by the cationic route, preferably an epoxyfunctional or vinyloxyfunctional group, linked to silicon via a divalent radical containing, advantageously, from 2 to 20 carbon atoms comprising, optionally, a heteroatom, l '' at least Z symbols corresponding to an organofunctional group crosslinkable cationically.

3 - Use according to claim 1 or claim 2, characterized in that the POS forming the raw material has a title in Grc - expressed in eq of Grc per kg of POS, greater than or equal to 0.2, preferably between 0.5 and 5.0 and more preferably still between 0.8 and 3.0.

4 - Use according to claim 2 or 3, characterized in that the raw material of POS nature has a viscosity at 25 ° C, between 10 and 3000 mPa.s, preferably between 10 and 1500 mPa.s and more preferably still between 10 and 900 mPa.s.

5 - Use according to claim 1, characterized in that the monomers and / or oligomers and / or polymers forming the raw material belong to at least one of the following species: cycloaliphatic epoxides (A) or not (B), alkenyl- ethers (C), linear or cyclic, the species A, B, C listed below being preferred:

- A corresponding to cycloaliphatic epoxides, taken alone or as a mixture with one another, epoxides of the 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane carboxylate or Bis (3,4-epoxycyclohexyl) adipate type being particularly preferred;

- B corresponding to other non-cycloaliphatic epoxides, taken alone or as a mixture with one another, epoxides of the type of those resulting from the condensation of Bisphenol A and of epichlorohydrin and of the type:> di and triglycidyl ethers of alkoxylated Bisphenol A, of 1,6 hexane diol, glycerol, neopentylglycol and propane trimethylol, diglycidyl ethers of bisphenol A, t> or alpha-olefin epoxides, NOVOLAC epoxides, epoxidized soybean and linseed oil, epoxidized polybutadiene; - C corresponding to alkenyl ethers, linear or cyclic, taken alone or as a mixture between them,

• vinyl ethers, in particular triethylene glycol divinyl ether 1,4-cyclohexanedimethanol divinyl ether, cyclic vinyl ethers or acrolein tetramers and / or dimers

• propenyl ethers

• and butenyl ethers being especially preferred.

6 - Use according to any one of claims 1 to 5, characterized in that the anionic entity of the photoinitiator is one of those set out below:

[B (CgF ₅ ) ₄ ] - [B (C H4CF ₃ ) ₄ ] - [B (CgF ₄ OCF ₃ ) ₄ ] "[B (CgF ₄₀ CF ₃ ) ₄ ]" [(CgF ₅ ) 2BF ₂ ] - [CgF ₅ BF ₃ ] - [B (C ₆ H ₃ F ₂ ) ₄ ] "

7 - Use according to any one of claims 1 to 6, characterized in that the cationic entity of the photoinitiator is chosen from the following list: t (Φ) 2l] ⁺ [C ₈ H ₁₇ -O-Φ-I- Φ] ⁺ [(Φ-CH ₃ ) ₂ 1] ⁺ [Cπ H ₂₅ -Φ-I-Φ] ⁺ [(C ₈ Hι ₇ -O-Φ) ₂ 1] ⁺ [(C ₈ H -O-Φ - I-Φ)] ⁺ [(Φ) ₃ S] ⁺ [(Φ) ₂ -S-Φ-OC ₈ Hι ₇ ] ⁺

[Φ-S-Φ-S- (Φ) ₂ ] ⁺ [(Cι ₂ H ₂₅ -Φ) 2 1] ⁺

. (η * - cyclopentadienyl) (η ^ - toluene) Fe ⁺ . (η ^ - cyclopentadienyl) (η ^ - methyl-1-naphthalene) Fe ⁺ . (η ^ - cyclopentadienyl) (η ^ - cumene) Fe ⁺ . bis (η ^ - mesitylene) Fe ⁺ . bis (η ^ - benzene) Cr ⁺

8 - Use according to any one of claims 1 to 7, characterized in that the photoinitiator corresponds to at least one of the following formulas:

[(Φ) ₂ I] ⁺ , [B (CgF ₅ ) ₄ ] - [(C ₈ H ₁₇ ) -O-Φ-I-Φ)] +, [B (CgF ₅ ) ₄ ] -

[Cι ₂ H ₂₅ -Φ-I-Φ] ⁺ , [B (CgF ₅ ) ₄ ] - [(C ₈ H ₁₇ -O-Φ) ₂ I] ⁺ , [B (CgF ₅ ) ₄ ] -

[(C ₈ H ₁₇ ) -O-Φ-I-Φ)] ⁺ , [B (CgF ₅ ) ₄ ] - [(Φ) ₃ S] ⁺ , [B (C ₆ F ₅ ) ₄ ] - [( Φ) ₂ S-Φ-OC ₈ Hι ₇ ] ⁺ , [B (C ₆ H4CF ₃ ) ₄ ] - [(Cι ₂ H ₂ 5-Φ) ₂ I] ⁺ , [B (CgF ₅ ) ₄ ] - [ (Φ) ₃ S] ⁺ , [B (CgF ₄ OCF ₃ ) ₄ ] - [(Φ-CH ₃ ) ₂ I] ⁺ , [B (CgF ₅ ) ₄ ] - [(Φ-CH ₃ ) ₂ I] ⁺ , [B (CgF ₄ OCF ₃ ) ₄ ] -

. (η ⁵ - cyclopentadienyl) (η ⁶ - toluene) Fe ⁺ , [B (CgF5) ₄ ] "

. (η5. cyclopentadienyl) (η ^ - methyll-naphthalene) Fe ⁺ , [B (CgF5)] ^~

. (η ^ - cyclopentadienyl) (η ^ - cumene) Fe ⁺ , B (C Εζ) _ \] ~

9 - Use according to any one of claims 1 to 8, characterized in that the effective amount of photoinitiator corresponds to I. IO- ⁴ to 1, preferably of I. IO " ³ to I. IO" ¹ and more preferably still from I. IO- ³ to I. IO- ² moles of photoinitiator for 1 mole of Grc.

10 - Process for manufacturing a three-dimensional object from a liquid polymerizable and / or crosslinkable liquid raw material by cationic route, in particular by actinic activation, in the presence of at least one photoinitiator, said process essentially consisting in implementing a bath comprising the raw material and the initiator system, to expose a part of the surface of this bath to at least one actinic beam, said exposed surface part having a geometry corresponding to a slice of the object to be manufactured, for a sufficient time to allow the solidification of the surface layer corresponding to said slice of object, to immerse this solidified layer in the bath, and to repeat these actinic exposure and immersion operations so as to obtain successive solid layers supeφosed and bonded between them, to form the targeted object, characterized in that the composition selected in l is used e scope of use according to any one of claims 1 to 9.

11 - Composition which can be polymerized and / or crosslinked cationically, in particular by actinic activation, usable in (stereo) photolithography, characterized in that it comprises:

- a raw material as defined in claims 1 to 5,

- at least one initiator system as defined in claims l, 6 to 9, - and optionally at least one additive chosen from those generally known in liquid stereophotolithography precursors.