Method for preparing a cross-linked fluorinated polymer film
A process for preparing a crosslinked fluoropolymer film, including the successive steps of: (1) formulating an ink containing: (a) the product of the reaction of triethylamine with at least one fluorinated copolymer obtained by radical copolymerization of monomers including: (i) vinylidene fluoride (VDF), (ii) trifluoroethylene (TrFE), (iii) at least one chlorinated monomer of formula —CXCl═CX 1 X 2 where X, X 1 and X 2 independently denote H, F or CF 3 , wherein at most one of X, X 1 and X 2 denotes CF 3 ; (b) at least one crosslinking agent; (c) at least one photoinitiator; and (d) at least one organic solvent; (2) applying said ink in film form to a substrate; and (3) UV-irradiating said film. Also, the film capable of being obtained according to this process, and also to the uses thereof, in particular in the manufacture of (opto)electronic devices and more particularly in the manufacture of a gate dielectric layer in a field-effect transistor.
1. A process for preparing a crosslinked fluoropolymer film, comprising the successive steps of:
(1) formulating an ink comprising:
(a) a product of a partial reaction of triethylamine with at least one fluorinated copolymer, the fluorinated copolymer being a result of a radical copolymerization of monomers comprising:
(i) vinylidene fluoride (VDF),
(ii) trifluoroethylene (TrFE), and
(iii) at least one chlorinated monomer of formula —CXCl═CX 1 X 2 where X, X 1 and X 2 independently denote H, F or CF 3 , wherein at most one of X, X 1 and X 2 denotes CF 3 ,
wherein the partial reaction with triethylamine retains some —CXCl—CH 2 units in the fluorinated copolymer at the end of the partial reaction;
(b) at least one crosslinking agent;
(c) at least one photoinitiator; and
(d) at least one organic solvent;
(2) applying said ink in film form to a substrate; and
(3) UV-irradiating said film.
2. The process as claimed in claim 1 , wherein the chlorinated monomer is chlorotrifluoroethylene (CTFE) or chlorofluoroethylene (CFE).
3. The process as claimed in claim 1 , wherein the proportion of units derived from TrFE ranges from 5 to 95 mol %, relative to the sum of the units derived from VDF and TrFE.
4. The process as claimed in claim 1 , wherein the proportion of units derived from the chlorinated monomer varies from 1 to 20 mol %, relative to all of the units.
5. The process as claimed in claim 1 , wherein the at least one fluorinated copolymer optionally contains an additional monomer, the units derived from the optional additional monomer represent from 0 to 20 mol %, relative to all of the units of the fluorinated copolymer.
6. The process as claimed in claim 1 , wherein the crosslinking agent is chosen from monomers or oligomers bearing at least two (meth)acrylic functions that are reactive in radical polymerization, which may optionally further comprise at least one other function chosen from hydroxyl, ester, ether, urethane, epoxy, cyanurate or isocyanurate functions.
7. The process as claimed in claim 1 , wherein the organic solvent is chosen from: esters; alkyl phosphates; alkyl carbonates; ketones; sulfur-containing solvents; halogenated solvents; and mixtures thereof.
8. A crosslinked fluoropolymer film capable of being obtained according to the process as claimed in claim 1 .
9. A device comprising the film as claimed in claim 8 , wherein the device is selected from (opto)electronic devices; haptic devices; actuators; microelectromechanical systems (MEMS); sensors; steerable catheters; Braille keyboards; acoustic devices; electrocaloric devices; and energy recovery devices.
10. A gate dielectric layer in a field-effect transistor comprising the film as claimed in claim 8 .