EP3861077A1

EP3861077A1 - Fluoropolymer ink with the rheological behavior of a yield stress fluid

Info

Publication number: EP3861077A1
Application number: EP19802240.2A
Authority: EP
Inventors: Manuel Hidalgo; Aristide LAJOUX
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2018-10-02
Filing date: 2019-09-30
Publication date: 2021-08-11
Also published as: WO2020070420A1; FR3086665A1; CN113166566A; FR3086665B1

Abstract

The invention relates to an ink having the rheological behavior of a yield stress fluid, comprising a fluoropolymer and a carrier comprising a solvent of said fluoropolymer and a non-solvent of said fluoropolymer. The invention also relates to a method for manufacturing a fluoropolymer film or an electronic device using such an ink, and also to a method for preparing such an ink.

Description

FLUORINATED POLYMER INK WITH RHEOLOGICAL BEHAVIOR OF CONSTRAINED THRESHOLD

FIELD OF THE INVENTION

The present invention relates in particular to a fluoropolymer ink exhibiting a rheological behavior of fluid at a stress threshold, the use of such an ink for the manufacture of polymer films and electronic devices, as well as a process for preparing a such ink.

TECHNICAL BACKGROUND

Fluoropolymers such as polyvinylidene fluoride (PVDF) and copolymers derived therefrom have a large number of uses, in particular in which they are deposited in the form of a film on a substrate.

Thus, it is known to manufacture electroactive copolymers based on vinylidene fluoride (VDF) and trifluoroethylene (TrFE), which may optionally contain a third monomer such as chlorotrifluoroethylene (CTFE) or 1, 1 -chlorofluoroethylene (CFE). Other copolymers, based on VDF and hexafluoropropene (HFP), have utility for the protection, planarization or passivation of substrates or electronic devices.

The deposition of such fluoropolymers in the form of a film can be carried out from a formulation called “ink”, formed by mixing fluoropolymer, and optionally additives, in a vehicle composition.

When depositing these inks on a substrate, in particular by printing techniques, it may be necessary for the ink to adopt a specific rheological behavior in order to obtain a good quality of deposit. More particularly, the rheological behavior of the string type (Newtonian or rheofluidifier with Newtonian plate) may be undesirable for certain printing processes, such as that of screen printing. In fact, the use of a solution with stringing behavior in screen printing can lead to lower productivity, clogging of the masks or less good definition of the printed patterns than with a paste type ink with a stress threshold.

Thus, the book "How to Be a Great Screen-Printer", edited by Steven Abbott, ISBN 978-0-9551220-1 -9, published by Macdermid Autotype Limited, 2008, p. 25-30, teaches that for the screen printing process, a Newtonian fluid is not very suitable, and that a shear-thinning fluid having the consistency of a non-continuous paste (fluid with stress threshold having low to high viscosities shear rate and strong at low shear rate) is better suited than a viscous shooting solution (Newtonian or Newtonian then rheofluidifying, without threshold).

However, when a fluoropolymer is dissolved in a good solvent for this polymer, the ink obtained often has a Newtonian rheological or shear thinning behavior with Newtonian plateau (depending on the molar mass and the concentration of the polymer considered).

In order to obtain compositions with rheological behavior at stress threshold from shooting compositions, one possibility consists in adding finely divided particles of silica, calcium carbonate or the like, or polymeric rheological additives such as crosslinked polymer particles which do not dissolve perfectly in the composition, but which tend to swell in the composition, in contrast to polymer chains well dissolved in the medium.

However, the presence in an ink of these rheological additives can be detrimental because it can degrade the final properties of the polymer films obtained. Thus, the films prepared from fluoropolymer inks comprising such additives may have lower (for example electro-active) properties, by simple dilution effect, or even because of negative synergies or disturbing effects provided by the additives. rheological.

There is therefore a real need to provide a fluoropolymer ink having a rheological behavior of the fluid type with stress threshold and not requiring the addition of rheological additives to obtain this behavior.

SUMMARY OF THE INVENTION

The invention relates firstly to an ink exhibiting a rheological behavior of fluid at stress threshold, comprising a fluoropolymer and a vehicle comprising a solvent for said fluoropolymer and a non-solvent for said fluoropolymer. According to embodiments, the fluoropolymer is a polymer comprising units derived from vinylidene fluoride as well as units derived from at least one other monomer of formula CXiX2 = CX3X4, in which each group Xi, X2, X3 and X ₄ is independently selected from H, Cl, F, Br, I and alkyl groups comprising from 1 to 3 carbon atoms, which are optionally partially or fully halogenated; and preferably the fluoropolymer comprises units derived from vinylidene fluoride and from at least one monomer chosen from trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, 1, 1 -chlorofluoroethylene, hexafluoropropene, 3,3,3- trifluoropropene, 1, 3,3,3-tetrafluoropropene,

2.3.3.3-tetrafluoropropene, 1-chloro-3,3,3-trifluoropropene and 2-chloro-

3.3.3-trifluoropropene; and more preferably the fluoropolymer is chosen from poly (vinylidene fluoride-co-hexafluoropropene), poly (vinylidene fluoride-co-trifluoroethylene), poly (vinylidene fluoride-ter-trifluoroethylene-ter-chlorotrifluoroethylene) and poly (vinylidene fluoride-ter-trifluoroethylene-ter-1, 1-chlorofluoroethylene).

According to embodiments, the solvent and the non-solvent are miscible.

According to embodiments, the solvent is chosen from the group consisting of ketones, esters, in particular cyclic esters, dimethylsulfoxide, phosphoric esters such as triethyl phosphate, carbonates, ethers such as tetrahydrofuran, and a mixture of these, preferably the solvent being chosen from the group consisting of ethyl acetate, gamma-butyrolactone, triethyl phosphate, cyclopentanone, monomethyl ether acetate propylene glycol and a mixture of these.

According to embodiments, the non-solvent is chosen from the group consisting of benzyl alcohol, benzaldehyde, or a mixture of these.

According to embodiments, the vehicle comprises a mass proportion of non-solvent for the fluoropolymer, in percentage, included in the range going from (the solubility limit - 50%) to the solubility limit, more preferably in the range going from (the solubility limit - 30%) to the solubility limit, more preferably in the range from (the solubility limit - 20%) to the solubility limit, even more preferably in the range from (the solubility - 15%) at the solubility limit, even more preferably in the range going from (the solubility limit - 10%) to the solubility limit, even more preferably in the range ranging from (the solubility limit - 8%) to the solubility limit; and / or the vehicle comprises a proportion by mass of solvent of the fluoropolymer, in percentage, included in the range going from (100 - the solubility limit) to (100 - (the solubility limit - 50%)), more preferably in the range going from (100 - the solubility limit) to (100 - (the solubility limit - 30%)), more preferably in the range going from (100 - the solubility limit) to (100 - (the limit of solubility - 20%)), more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 15%)), even more preferably in the range from (100 - the limit solubility) to (100 - (the solubility limit - 10%)), even more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 8%)); relative to the total weight of the vehicle comprising the solvent and the non-solvent for the fluoropolymer, the solubility limit being expressed as a percentage by mass.

According to embodiments, the ink does not include rheological additives such as silica or calcium carbonate particles, or crosslinked polymer particles and / or surfactants.

The invention also relates to a process for manufacturing a fluoropolymer film or an electronic device comprising:

- depositing an ink as defined above on a substrate;

- evaporation of the vehicle comprising the solvent and the non-solvent.

According to embodiments, the method further comprises a heat treatment of the fluoropolymer simultaneous and / or after the evaporation of the vehicle comprising the solvent and the non-solvent.

According to embodiments, the deposition of the ink is carried out by printing, in particular by screen printing, by roller printing, by flexography printing, by lithography printing, preferably by screen printing.

The invention also relates to a process for the preparation of an ink as defined above, comprising:

- the supply of a vehicle comprising a solvent for the fluoropolymer and a non-solvent for the fluoropolymer;

- The dispersion of the solid fluoropolymer in the liquid vehicle.

The present invention makes it possible to meet the need expressed above. It more particularly provides a fluoropolymer ink which is well suited to printing techniques and in particular to screen printing since it exhibits a rheological behavior of the fluid at a stress threshold, while not requiring the addition of undesirable rheological additives. Ink according to the invention thus makes it possible to obtain superior quality polymer films.

This is accomplished through the use, as the ink carrier, of a mixture of a solvent and a non-solvent for the fluoropolymer.

Without wishing to be bound by a theory, the inventors believe that the presence of non-solvent could cause local precipitation of the fluoropolymer in the form of particles of colloidal size, swollen from vehicle, which, because of their swollen particulate nature, modify the rheology of ink to create behavior at the threshold of stress.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 represents the flow curves obtained by an Anton Paar PHYSICA MCR 301 rheometer for the ink of copolymer FC-20 at 16% by weight in triethyl phosphate (curve A), the ink of copolymer FC-20 at 16% by weight in gamma-butyrolactone (curve B), PEDOT-PSS ink (curve C), Bzd / AcE 73/27 ink (curve D) and Bzd / TEP 73/27 ink (curve E) described in Example 1. The abscissa axis represents the applied shear rate (in s ^-1 ) on a logarithmic scale and the ordinate axis represents the dynamic viscosity of the ink tested (in Pa.s) on a logarithmic scale.

FIG. 2 represents the flow curves obtained by an Anton Paar PHYSICA MCR 301 rheometer for the PEDOT-PSS ink (curve C), the Bzd / TEP 73/27 ink (curve E) and the BzOH ink / gBTL 33/67 (curve F) described in Example 2. The abscissa axis represents the applied shear rate (in s ^-1 ) on a logarithmic scale and the ordinate axis represents the dynamic viscosity of the ink tested (in Pa.s) on a logarithmic scale.

FIG. 3 schematically represents a neural network that can be used for the implementation of the invention, in certain embodiments.

FIG. 4 schematically represents a computer system which can be used for the implementation of the invention, in certain embodiments.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is now described in more detail and without limitation in the description which follows. Unless otherwise indicated, all percentages for quantities are mass percentages.

In the present application, the expression "a fluoropolymer" must be understood to mean "one or more fluoropolymers". The same is true of all other species. Thus, for example, the expression "a non-solvent" should be understood to mean "one or more non-solvents".

Ink

The invention relates to an ink exhibiting a rheological behavior of a fluid at a stress threshold, at a given temperature. By "stress threshold fluid" means a fluid flowing only from a certain value of shear stress applied to the fluid (called "threshold stress"). Within the meaning of the invention, a fluid with a stress threshold is a fluid for which, when we represent in a graph the logarithm of the dynamic viscosity of the fluid as a function of the logarithm of the applied shear rate, for example using of a rheometer in cone-plane configuration, at the temperature considered, no Newtonian plateau (or plateau) is observed at low shear rates, that is to say in the range of shear rates between 0 , 1 and 10 s ^-1 . By "Newtonian plateau (or plateau)" is meant a horizontal or essentially horizontal line, that is to say that the logarithm of the viscosity is essentially constant over this range of shear rate.

In other words a stress threshold fluid can be characterized by a ratio between the dynamic viscosity value at a shear rate of 0.1 s ^-1 and the dynamic viscosity value at a shear rate of 10 s ^{- 1} greater than or equal to 2, preferably greater than or equal to 5, preferably still greater than or equal to 10, and more preferably still greater than or equal to 20, at the temperature considered. The measurement is for example carried out with an Anton Paar PHYSICA MCR 301 rheometer in cone-plane configuration.

Preferably, the ink according to the invention exhibits a rheological behavior of fluid with stress threshold at least at a temperature between 20 and 40 ° C. Preferably still, the ink according to the invention exhibits a rheological behavior of fluid with threshold temperature constraint of 20 ° C.

The ink according to the invention is preferably a homogeneous liquid dispersion. By “homogeneous dispersion” is meant a dispersion of polymer particles, more or less swollen from the vehicle, in a continuous vehicle phase. The homogeneity of the dispersion is thus a macroscopic homogeneity (that is to say that by observing it with the naked eye the dispersion is of homogeneous appearance), characterized in that the dispersion does not have any granular or macro-separated appearance. The term "homogeneous dispersion" is thus used in opposition to a "heterogeneous dispersion", that is to say a dispersion with a macroscopic partially granular appearance or having a macroscopically visible phase separation.

This ink includes a fluoropolymer.

The fluoropolymer is preferably a carbon chain polymer which comprises structural units (or units, or repeating units, or units) comprising at least one fluorine atom.

Preferably, the fluoropolymer comprises units derived from (that is to say which are obtained by polymerization of) vinylidene fluoride (VDF) monomers.

In some embodiments, the fluoropolymer is a PVDF homopolymer.

It is however preferred that the fluoropolymer is a copolymer (in the broad sense), that is to say that it comprises units derived from at least one other monomer X than VDF.

A single X monomer can be used, or several different X monomers, depending on the case.

In certain embodiments, the monomer X can be of formula CXiX2 = CX3X4, in which each group Ci, X2, X3 and X ₄ is independently chosen from H, Cl, F, Br, I and C1 alkyl groups -C3 (preferably C1 -C2), which are optionally partially or completely halogenated - this monomer X being different from VDF (that is to say that if X1 and X2 represent H, at least one of X3 and X ₄ does not represent F; and if X1 and X2 represent F, at least one of X3 and X ₄ does not represent H).

In certain embodiments, each group X1, X2, X3 and X ₄ independently represents an H, F, Cl, I or Br atom, or a methyl group optionally comprising one or more substituents chosen from F, Cl, I and Br.

In certain embodiments, each group X1, X2, X3 and X ₄ independently represents an H, F, Cl, I or Br atom. In certain embodiments, only one of the Xi, X2, X3 and X ₄ represents a Cl or I or Br atom, and the others of the groups X1, X2, X3 and X ₄ independently represent: an H or F atom or a group C1 -C3 alkyl optionally comprising one or more fluorine substituents; preferably, an H or F atom or a C1 -C2 alkyl group optionally comprising one or more fluorine substituents; and more preferably, an F1 or F atom or a methyl group optionally comprising one or more fluorine substituents.

Examples of X monomers are: vinyl fluoride (VF), trifluoroethylene (TrFE), tetrafluoroethylene (TFE), hexafluoropropene (FIFP), trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1, 3,3,3- tetrafluoropropene (in cis or preferably trans form), hexafluoroisobutylene, perfluorobutylethylene, pentafluoropropenes and in particular 1, 1, 3, 3,3-pentafluoropropene or 1, 2, 3,3,3- pentafluoropropene, perfluoroalkylvinylethers and in particular those of general formula Rf-0-CF = CF2, Rf being an alkyl group, preferably C1 to C4 (examples preferred being perfluoropropylvinylether or PPVE and perfluoromethylvinylether or PMVE).

In certain embodiments, the monomer X comprises a chlorine or bromine atom. It can in particular be chosen from bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. Chlorofluoroethylene can denote either 1-chloro-1-fluoroethylene or 1-chloro-2-fluoroethylene. The 1-chloro-1-fluoroethylene (CFE) isomer is preferred. The chlorotrifluoropropene is preferably 1-chloro-3,3,3-trifluoropropene (in cis or trans form, preferably trans) or 2-chloro-3,3,3-trifluoropropene.

In certain preferred embodiments, the fluoropolymer comprises units derived from VDF and HFP, or else is a polymer P (VDF-HFP) consisting of units derived from VDF and HFP.

The molar proportion of repeat units originating from HFP is preferably from 2 to 50%, in particular from 5 to 40%.

In certain preferred embodiments, the fluoropolymer comprises units derived from VDF and CFE, or from CTFE, or from TFE, or from TrFE. The molar proportion of repeat units originating from the monomers other than VDF is preferably less than 50%, more preferably less than 40%. In certain preferred embodiments, the fluoropolymer comprises units derived from VDF and TrFE, or else is a polymer P (VDF-TrFE) consisting of units derived from VDF and TrFE.

In certain preferred embodiments, the fluoropolymer comprises units derived from VDF, TrFE and another monomer X as defined above, different from VDF and TrFE, or else is a polymer P (VDF-TrFE -X) consisting of units derived from VDF, TrFE and another monomer X as defined above, different from VDF and TrFE. In this case, preferably, the other monomer X is chosen from TFE, HFP, trifluoropropenes and in particular 3,3,3-trifluoropropene, tetrafluoropropenes and in particular 2,3,3,3-tetrafluoropropene or 1, 3,3,3- tetrafluoropropene (in cis or preferably trans form), bromotrifluoroethylene, chlorofluoroethylene, chlorotrifluoroethylene and chlorotrifluoropropene. CTFE or CFE are particularly preferred.

When units from VDF and T rFE are present, the proportion of units from TrFE is preferably from 5 to 95 mol.% Relative to the sum of the units from VDF and T rFE, and in particular: from 5 at 10 mol.%; or from 10 to 15 mol.%; or from 15 to 20 mol.%; or from 20 to 25 mol.%; or from 25 to 30 mol.%; or from 30 to 35 mol.%; or from 35 to 40 mol.%; or from 40 to 45 mol.%; or from 45 to 50 mol.%; or from 50 to 55 mol.%; or from 55 to 60 mol.%; or from 60 to 65 mol.%; or from 65 to 70 mol.%; or from 70 to 75 mol.%; or from 75 to 80 mol.%; or from 80 to 85 mol.%; or from 85 to 90 mol.%; or from 90 to 95 mol.%. A range of 15 to 55 mol.% Is particularly preferred.

When units from another X monomer, in addition to VDF and TrFE, are present (the X monomer being in particular CTFE or CFE), the proportion of units from this other X monomer in the fluorinated polymer (by with respect to all of the patterns) can vary for example from 0.5 to 1 mol.%; or from 1 to 2 mol.%; or from 2 to 3 mol.%; or from 3 to 4 mol.%; or from 4 to 5 mol.%; or from 5 to 6 mol.%; or from 6 to 7 mol.%; or from 7 to 8 mol.%; or from 8 to 9 mol.%; or from 9 to 10 mol.%; or from 10 to 12 mol.%; or from 12 to 15 mol.%; or from 15 to 20 mol.%; or from 20 to 25 mol.%; or from 25 to 30 mol.%; or from 30 to 40 mol.%; or from 40 to 50 mol.%. Ranges from 1 to 20 mol.%, And preferably from 2 to 15 mol.%, Are particularly suitable.

The molar composition of the units in the fluoropolymers can be determined by various means such as infrared spectroscopy or RAMAN spectroscopy. Classic methods of elemental analysis of carbon, fluorine and chlorine or bromine or iodine elements, such as spectroscopy with X-ray fluorescence, make it possible to calculate the mass composition of the polymers, from which the molar composition is deduced.

Multicore NMR techniques, in particular proton (1 H) and fluorine (19F), can also be used by analysis of a solution of the polymer in an appropriate deuterated solvent.

It is finally possible to combine elementary analysis, for example for heteroatoms such as chlorine or bromine or iodine, and NMR analysis. Thus the content of units from CTFE, in a terpolymer P (VDF-TrFE-CTFE) for example, can be determined by measuring the chlorine content by elemental analysis.

The viscosity of the fluoropolymer is preferably from 0.1 to 100 kPo (kiloPoise) by carrying out a measurement at 230 ° C and at 100 s ^-1 of shear rate (according to ASTM D4440, using a PHYSICA MCR301 device equipped two parallel plates).

The fluoropolymer is preferably random and linear.

The fluoropolymer can be homogeneous or heterogeneous. A homogeneous polymer has a uniform chain structure, the statistical distribution of the units from the different monomers practically not varying between the chains. In a heterogeneous polymer, the chains have a distribution in units derived from the various monomers of multimodal or spread type. A heterogeneous polymer therefore comprises chains richer in a given unit and chains poorer in this unit.

The ink according to the invention also comprises a liquid vehicle comprising a solvent for the fluoropolymer and a non-solvent for the fluoropolymer.

By "vehicle comprising a / the solvent for the fluoropolymer and a / the non-solvent for the fluoropolymer" is meant the combination in particular of a solvent for the fluoropolymer with a non-solvent for the fluoropolymer. This vehicle can be heterogeneous but is preferably homogeneous at the molecular level.

By "solvent of the fluoropolymer" is meant a liquid in which the fluoropolymer is capable of dissolving. By "dissolution of the fluoropolymer in a solvent" is meant the formation of a true solution, that is to say single-phase or homogeneous at the molecular level.

The term “non-solvent for the fluoropolymer” means a liquid in which the fluoropolymer is not capable of dissolving completely (or in which the fluoropolymer is not completely soluble. The addition of polymer in a non-solvent does not allow obtaining a true, single-phase or homogeneous solution at the molecular level.

The solubility of the fluoropolymer in a given liquid can be determined for example by adding an amount of fluoropolymer of 5% w / w to said liquid at room temperature (for example 25 ° C), stirring, if necessary by moderately heating to a temperature less than or equal to 60 ° C (for example at a temperature of 60 ° C), for example for 15 or 60 minutes, then allowing to cool to room temperature (for example 25 ° C) and observing visually , at this temperature, after for example 15 or 60 minutes whether or not solid polymer remains in suspension.

The solvents and non-solvents which can be used in the present invention may, in general, be any vehicle which is liquid at room temperature, and may in particular be chosen from alcohols, ethers, halogenated vehicles, alkanes, cycloalkanes, aromatic vehicles, ketones, aldehydes, esters, including cyclic esters, carbonates, phosphates, furans, amides and sulfoxides, as well as combinations thereof.

Advantageously, the solvent for the fluoropolymer and the non-solvent for the fluoropolymer are miscible.

By "miscible" is meant capable of mixing to form, in the absence of the polymer, a homogeneous mixture at the molecular level and preferably transparent, without any trace of separation of liquid / liquid phases.

As the solvent for the fluoropolymer, any liquid vehicle capable of dissolving the fluoropolymer can be used. Preferably, the solvent is chosen from the group consisting of ketones, esters, in particular cyclic esters, dimethyl sulfoxide, phosphoric esters such as triethyl phosphate, carbonates, ethers such as tetrahydrofuran, and a mixture of these. this. Low volatility solvents are particularly preferred, and in particular gamma-butyrolactone, triethyl phosphate, cyclopentanone, monomethyl ether acetate propylene glycol. Low volatility solvents allow greater ink stability. However, volatile solvents can also be used, in particular methyl ethyl ketone or ethyl acetate. The latter has the advantage of having a favorable ecotoxicological profile. The solvent for the fluoropolymer may be a mixture of two or more of the above solvents. In a particularly preferred manner, the non-solvent is benzyl alcohol, benzaldehyde, or a mixture of these. These non-solvents offer both the advantage of being low volatility, which makes it possible to maintain good stability of the ink, and the advantage of having a favorable ecotoxicological profile (non-solvents known as “green”).

Examples of combinations of solvent and non-solvent for the fluoropolymer which can be used in the invention are: ethyl acetate / benzyl alcohol; ethyl acetate / benzaldehyde; gamma-butyrolactone / benzyl alcohol; gamma-butyrolactone / benzaldehyde; triethyl phosphate / benzyl alcohol; triethyl phosphate / benzaldehyde; cyclopentanone / benzyl alcohol; cyclopentanone / benzaldehyde; monomethyl ether propylene glycol acetate / benzyl alcohol; monomethyl ether propylene glycol acetate / benzaldehyde; methyl ethyl ketone / benzyl alcohol; methyl ethyl ketone / benzaldehyde.

For a mixture comprising a given solvent and a non-solvent for the fluoropolymer, it is possible to determine a "solubility limit" (or dissolution limit) of the fluoropolymer in this mixture, at a certain temperature and at a certain concentration of polymer; within the meaning of the invention, this “solubility limit” corresponds to the mass proportion of non-solvent (relative to the total of the mixture of solvent and non-solvent) from which the fluoropolymer precipitates in a macroscopically visible manner (c (i.e. visible to the naked eye) in the mixture. This solubility limit can be defined by determining the solubility of the fluoropolymer in mixtures with increasing mass proportions of non-solvent, as described above but by adding the polymer at the concentration in question and by visually observing whether or not solid polymer remains in suspension at the temperature considered.

Preferably, the ink comprises a proportion by mass of non-solvent of the fluoropolymer, in percentage, included in the range going from (the solubility limit - 50%) to the solubility limit, more preferably in the range going from ( the solubility limit - 40%) to the solubility limit, more preferably in the range from (the solubility limit - 30%) to the solubility limit, even more preferably in the range from (the solubility limit - 20%) at the solubility limit, even more preferably in the range from (the solubility limit - 15%) to the solubility limit, even more preferably in the range from (the solubility limit - 10%) to the solubility limit, even more preferably in the range from (the solubility limit - 8%) to the solubility limit, relative to the total weight of the solvent and non-solvent mixture of the fluoropolymer, the solubility limit being expressed as a percentage by mass and as defined in the preceding paragraph.

Preferably, the ink comprises a proportion by mass of solvent of the fluoropolymer, in percentage, included in the range going from (100

- the solubility limit) to (100 - (the solubility limit - 50%)), more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 40%)) , more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 30%)), more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 20%)), more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 15%)), even more preferably in the range from ( 100 - the solubility limit) to (100 - (the solubility limit - 10%)), even more preferably in the range from (100 - the solubility limit) to (100

- (the solubility limit - 8%)), relative to the total weight of the mixture of solvent and non-solvent of the fluoropolymer, the solubility limit being expressed in mass percentage.

In other embodiments, the ink comprises from 0.1 to 5%, or from 5 to 10%, or from 10 to 20%, or from 20 to 30%, or from 30 to 40%, or from 40 to 50%, or 50 to 60%, or 60 to 70%, or 70% to 80%, or 80 to 90%, or 90 to 95%, or 95 to 99.9%, by weight of solvent for the fluorinated polymer, relative to the total weight of liquid vehicle.

In embodiments, the ink comprises from 0.1 to 5%, or from 5 to 10%, or from 10 to 20%, or from 20 to 30%, or from 30 to 40%, or from 40 to 50%, or 50 to 60%, or 60 to 70%, or 70% to 80%, or 80 to 90%, or 90 to 95%, or 95 to 99.9%, by weight of non-solvent for the fluorinated polymer, relative to the total weight of liquid vehicle.

The ink may contain from 0.1 to 60%, preferably from 0.5 to 30%, more preferably from 1 to 25%, more preferably from 3 to 20% by weight of polymer, relative to the total weight ink. The polymer may consist of the above fluoropolymer, or may include said fluoropolymer and one or more additional polymers. The ink preferably comprises from 0.1 to 60%, more preferably from 0.5 to 30%, more preferably from 1 to 25%, even more preferably from 3 to 20%, by weight of the fluoropolymer, relative to the total weight of the ink.

The ink may optionally include one or more additives, in particular chosen from rheology modifying agents, agents modifiers of aging resistance, adhesion modifiers, pigments or dyes, fillers (including nanofillers). The ink may also contain one or more additives having served for the synthesis of the polymer (s).

However, in a particularly preferred manner, the ink does not comprise rheology modifying agents (also called “rheological additives”), in particular the silica particles, the calcium carbonate particles, and / or the crosslinked polymer particles. . Preferably, the ink does not include agents that modify surface or interfacial tension, such as surfactants.

In certain embodiments in which it is desired to crosslink the polymers after deposition of the composition, the ink comprises at least one additive for crosslinking aid preferably chosen from radical initiators, photoinitiators, co-agents such as bifunctional or polyfunctional molecules in terms of reactive double bonds, basic crosslinking agents such as di-amines, and combinations thereof.

In other embodiments, no crosslinking aid additive, such as a photoinitiator or a crosslinking agent, is present in the ink.

The total content of additives is preferably less than 20% by weight, more preferably less than 10% by weight, relative to the total of the polymers and additives.

The ink preferably has a non-volatile dry matter content of 0.1 to 60%, preferably of 0.5 to 30%, more preferably of 1 to 25%, more preferably of 3 to 20% by weight .

Applications

The ink described above can be deposited on a substrate. The substrate may be a surface of a metal, whether or not coated with an oxide or nitride layer of said metal or of another metal, of a plastic material, of wood, of paper, of concrete, of mortar. or grout, glass, plaster, woven or nonwoven fabric, leather, etc. Preferably, the substrate is a surface of glass, or silicon, whether or not coated with silicon nitride or oxides of silicon, or quartz, or of polymer material (in particular polyethylene terephthalate or polyethylene naphthalate), or of a metal other than silicon, or a mixed surface made up of several different materials, coated or not with passivating layers of oxides or nitrides metallic. The application of the ink may include spreading by discrete or continuous means. The deposition can be carried out in particular by coating by centrifugation (“spin-coating”), by spraying or atomization (“spray coating”), by coating in particular with a bar or a film puller (“bar coating”), by coating with a slot-die coating, by dip coating, by roll-to-roll printing, by screen-printing, flexographic printing, by lithographic printing. In a particularly preferred manner, the ink is deposited by printing (in particular roller printing, in screen printing, in flexography, in lithography) and even more advantageously, by printing in screen printing.

The vehicle comprising the solvent and the non-solvent for the fluoropolymer can be evaporated after deposition. The fluoropolymer layer (which may also optionally include one or more other polymers and / or additives) then solidifies to form a continuous film, by inter-diffusion of the polymer molecules. Evaporation can be carried out at room temperature and / or by heating at a temperature preferably ranging from 30 to 200 ° C, more preferably from 30 to 180 ° C, more preferably from 80 to 160 ° C. The layer can be subjected to ventilation to facilitate evaporation. The duration of the evaporation can for example be from 1 minute to 24 hours, preferably from 5 minutes to 5 hours, more preferably from 10 minutes to 2 hours.

An annealing step can be carried out after evaporation of the vehicle, for example to allow or increase the crystallization of the polymer. Annealing can in particular be carried out by subjecting the deposited layer to a temperature of 50 to 200 ° C, preferably from 80 to 180 ° C, more preferably from 100 to 160 ° C, in particular from 120 to 150 ° C.

The application of a heat treatment to the fluoropolymer simultaneous and / or subsequent to the evaporation of the vehicle, as described above, can make it possible to improve the continuity of the film.

The fluoropolymer layer thus formed may in particular have a thickness of 50 nm to 100 μm, preferably from 200 nm to 50 μm, and more preferably from 500 nm to 20 μm.

In certain embodiments, a crosslinking step can be carried out by subjecting the layer to radiation, such as X, gamma, UV radiation or by thermal activation if the annealing step is not sufficient. The fluoropolymer film can be used as an electro-active layer and / or as a dielectric layer in an electronic device, and in particular when the fluoropolymer is a P (VDF-TrFE) or P (VDF-TrFE-CFE) copolymer ) or P (VDF-TrFE-CTFE) as described above.

One or more additional layers can be deposited on the substrate provided with the fluoropolymer film, for example one or more layers of polymers, semiconductor materials, or metals, in a manner known per se.

By electronic device is meant either a single electronic component, or a set of electronic components, capable of performing one or more functions in an electrical or electronic circuit.

According to certain variations, the electronic device is more particularly an optoelectronic device, that is to say capable of emitting, detecting or controlling electromagnetic radiation.

Examples of electronic devices, or if appropriate optoelectronic, concerned by the present invention are ferroelectric memories, transistors (in particular field effect), chips, batteries, electrodes, photovoltaic cells, light emitting diodes (LEDs) ), organic light emitting diodes (OLEDs), sensors, actuators, transformers, haptics, electromechanical microsystems (MEMS) and detectors.

Electronic and optoelectronic devices are used and integrated in many electronic devices, equipment or sub-assemblies and in many objects and applications such as televisions, computers, mobile phones, rigid or flexible screens, photovoltaic modules with layers thin, light sources, energy sensors and converters, medical devices, floors and walls, roofs and ceilings, etc.

Alternatively, the fluoropolymer layer can be used as a protective coating (or encapsulation) for an electronic device, and in particular when the fluoropolymer is a P copolymer (VDF-HFP) as described above. Such a protective coating can be used alone or in combination with other protective films.

In this case, the electronic device may in particular comprise a substrate and electronic elements supported thereon, which may include layers of conductive material, semiconductor material and the like. The electronic elements are preferably on one side of the substrate but in certain embodiments they can be on both sides of the substrate. The layer can cover all or part of the electronic elements, and all or part of the substrate. Preferably, the layer covers at least part of the substrate and at least part of the electronic elements, and fulfills a planarizing function. The layer may cover only one of the two faces of the substrate (preferably the face which comprises the electronic elements), in whole or in part, or alternatively the two faces of the substrate, in whole or in part.

When the layer is used as a protective coating for an electronic device, the electronic device can be of the same type as above.

Ink preparation process

The invention also relates to a method for preparing an ink as described above.

The ink can then be prepared by dispersing the fluoropolymer, in solid form, (and optionally the other polymers) in the vehicle comprising the solvent and the non-solvent for the fluoropolymer, and, preferably, by mixing.

The temperature applied during the preparation is preferably from 0 to 100 ° C, more preferably from 10 to 75 ° C, more preferably from 15 to 60 ° C, and ideally from 20 to 30 ° C. In some embodiments, the preparation is carried out at room temperature. Advantageously, the preparation is carried out with moderate stirring.

The vehicle comprising the solvent and the non-solvent for the fluoropolymer can be prepared by mixing the solvent for the fluoropolymer with the non-solvent for the fluoropolymer. This mixture can be prepared before, during or after the incorporation of the fluoropolymer (and / or any other polymers), that is to say that the fluoropolymer can be dispersed in the solvent and the non-solvent already mixed. , or the fluoropolymer, the solvent and the non-solvent can be added at the same time, or the fluoropolymer can be added in the solvent or in the non-solvent, the non-solvent or the solvent being subsequently added.

When additives must be added to form the ink according to the invention, they can be added before, during or after the dispersion of the polymers in the liquid vehicle.

The solvent and the non-solvent for the fluoropolymer can be a known solvent or non-solvent for the fluoropolymer. Alternatively, the solubility of the fluoropolymer can be evaluated in a given liquid vehicle, so that determine whether this vehicle is a solvent or a non-solvent for the fluoropolymer, for example as described above.

According to other embodiments, the solubility of the fluoropolymer in a given liquid vehicle can be determined by a process implemented by computer. This method is based on a function configured to associate a probability of solubility of the fluoropolymer with solubility parameters of a vehicle composition, for example determined by learning.

Function determined by learning

Preferably, the above function is determined by a method implemented by computer.

The determination of this function can be based on the formation of a training data set and then the training of the function on the basis of the training data set.

The training data set includes, for several respective vehicle compositions:

- a plurality of solubility parameters of the vehicle composition;

- in combination with information on the solubility of the fluoropolymer in the vehicle composition in question.

By "association" is meant here that there is a link between the data in question, for each composition of vehicle. Thus, the solubility parameters and the solubility information can be included in a relational database. For example, the solubility parameters and the solubility information can be entered in respective fields of the same database.

The information on the solubility of the fluoropolymer is preferably binary information of the yes / no type, that is to say soluble or insoluble. It can thus for example be coded in the form of a 0 or a 1. This information can be determined if necessary by an experimental test for each vehicle composition of the training data set, for example by adding a certain quantity of fluoropolymer to the vehicle composition, by stirring, if necessary by moderately heating (for example at a temperature less than or equal to 60 ° C, or less than or equal to 50 ° C, or less than or equal to 40 ° C) but preferably at room temperature, and by observing visually after for example 15 or 60 minutes whether or not solid polymer remains in suspension. The amount of fluoropolymer used in the test can be in particular from 1 to 10% w / w, preferably around 5% w / w.

The solubility parameters of the vehicle composition can in particular be two in number, or preferably three in number.

It is in particular preferred to choose the solubility parameters from the Hansen solubility parameters.

The Hansen solubility parameters are as follows:

- 5d: dispersive component (energy linked to the dispersion forces between the molecules of the composition);

- d _R : polar component (energy linked to the intermolecular dipole forces between the molecules of the composition); and

- 5h: hydrogen component (energy linked to hydrogen bonds between the molecules of the composition).

Preferably, all of the Hansen solubility parameters are supplied at the same reference temperature, for example 25 ° C.

The solubility parameters used in the training data set can thus be 5d and d _R ; or ôd and ôh; or d _R and ôh; or particularly preferably ôd, d _R and ôh.

The Hansen solubility parameters can be given in MPa ^1/2 or in any other unit (for example in (cal / cm ³ ) ^1/2 ).

The solubility parameters can be determined by experimental tests combined with theoretical considerations (semi-empirical methods). For example, Hoy determined the components ôd, d _R and ôh in a semi-empirical way using (Handbook of Solubility Parameters, and Other Cohesion Parameters, 1983 edition, page 59):

1. The experimental evaluation of the Hildebrand solubility parameter expressed as ôt (Hildebrand solubility parameter) = (ôd ² + ô _P ² + ôh ² ) ^1/2 (vapor enthalpy measurements and use of equations d 'state).

2. The estimation of oh from an aggregation number obtained from an equation resulting from the regression of the molar volume as a function of the ratio Tb / Tc (boiling temperature, crystallization temperature), the molecular mass and density.

3. The calculation of the parameter d _R by a method of contribution of groups to the molar attraction.

4. The deduction of the parameter ôd, by difference, from the expression of the Hildebrand solubility parameter (point 1). Preferably, the solubility parameters come from one or more pre-existing reference tables. By “reference table” is meant a compilation of data relating to the cohesive energy (which ultimately translates into the solubility parameters) of different vehicle compositions, these data being obtained from experimental or semi-empirical work carried out according to the same methodology, and preferably with the same equipment and by the same team.

In some embodiments, all the solubility parameters of the training data set come from the same reference table. In other embodiments, the solubility parameters of the training data set come from two or more of two different reference tables. It was surprisingly found that the use of data from at least two different reference tables leads to the determination of a reliable function. Using at least two different reference tables can be advantageous as it can minimize the risk of bias or error in the training data. It is thus possible to integrate into the training data set a first set of solubility parameters for a given vehicle composition, coming from a first reference table, and a second set of solubility parameters for the same given vehicle composition, from a second reference table. It is also possible to do this for several given vehicle compositions or for all vehicle compositions.

For example, the solubility parameters can be taken from a reference table contained in the CRC Handbook of Solubility Parameters and Other Cohesion Parameters, by Allan FM Barton, 2 ^nd edition (1991), and for example from Table 2 of chapter 7 and / or of table 5 of chapter 8 of this work.

The vehicle compositions of the training data set can be pure substances and / or mixtures of substances. The term "pure substance" is used as opposed to "mixture of substances". A pure substance thus preferably has a mass purity greater than or equal to 98%, or 99%, or 99.5%, or 99.9%. It is understood that a pure substance within the meaning of the present application may contain small amounts of impurities.

When mixtures of substances are taken into account, the solubility parameters can be determined by experimental or semi-empirical tests, or preferably be calculated as linear combination from the solubility parameters of pure substances in mixture. In such a linear combination, the weighting coefficients applied preferably correspond to the volume proportions of each of the substances.

The training data set can be divided into a training data set and a test data set. The learning can then be implemented by carrying out sequences of a training phase (on the training data set) and of a test phase (on the test data set), and until the test phase gives a positive result (i.e. until the test phase meets a validation criterion). Alternatively, the training data set may be entirely made up of the training data set, and no test phase is carried out, or the test phase is carried out on additional data.

It is also possible to provide that the training data set is successively divided N times in different ways into a training data set and a test data set. Each time, the training phase and test phase sequences are performed as described above. This results in N different models. The model with the best statistical validation (smallest error) is chosen as the final model for the function.

This method is particularly suitable when the training data set is small, because it offers efficient use of a limited amount of data.

The learning can be carried out by machine learning, using any technique known to those skilled in the art.

In particular, learning can be based on a neural network model.

The neural network can be binary response (perceptron network) or gradual response, giving a probability for example in the form of any value between 0 and 1 (sigmoid neural network for example).

The neural network has an input layer, one or more intermediate layers, or hidden layers, and an output layer.

The input layer contains part of the training data. It feeds a single intermediate or hidden layer, or else a succession of intermediate or hidden layers, which feed (s) itself (s) the output layer. Each intermediate layer performs a digital operation from the data from the previous layer, the digital operation involving variable parameters. The result of the digital operation feeds the next layer.

The output layer also performs a digital operation from data from the previous layer, the digital operation involving variable parameters. The result of the numerical operation provides an estimate of the probability of solubility.

An error function is then calculated from this estimated probability of solubility and the corresponding solubility information from the training data set. The variable parameters of the intermediate layer or layers and of the output layer are optimized so as to minimize the error function. The network can, in certain cases, feed back with calculation results (outputs) becoming inputs for neurons of the layer considered or of the previous layers. Preferably, a network without feedback is used.

By way of example, and with reference to FIG. 3, the solubility parameters 1, 2, 3 can be supplied as input to three neurons 4, 5, 6 of a single intermediate layer, which themselves supply a output layer 7.

Each of the intermediate neurons 4, 5, 6 calculates a digital function from the solubility parameters 1, 2, 3. The digital function can for example comprise a linear or refined combination of the solubility parameters 1, 2, 3, the coefficients ( weight) of the linear or affine combination corresponding to variable parameters as described above; the numerical function can also include the application of another mathematical function to such a linear or affine combination, for example the application of a hyperbolic tangent function.

The output layer 7 calculates a digital function from the values from the intermediate neurons 4, 5, 6.

In certain embodiments, a threshold can be associated with each intermediate neuron 4, 5, 6. Each intermediate neuron 4, 5, 6 is therefore activated or not with respect to the output layer 7, that is to say that is to say feeds the output layer 7 or not, depending on whether the value of the calculated digital function fulfills a defined condition with respect to the threshold or not. The threshold, like the weights, represents a variable parameter as described above. The digital function of the output layer 7 can for example comprise a linear or affine combination of values from intermediate neurons 4, 5, 6, the coefficients of the linear or affine combination corresponding to variable parameters as described above; the numerical function can also include the application of another mathematical function to such a linear or affine combination, for example the application of a tangent hyperbolic function or any other exponential function or combination of exponential functions.

When the neural network has a binary response, the value resulting from the digital function of the output layer 7 is compared with a predetermined threshold, to give a yes / no response, which can for example be coded as d 'a 0 or a 1.

When the neural network has a gradual response, the value resulting from the digital function of the output layer 7 is for example any value between 0 and 1, indicating a probability of solubility of the fluoropolymer in the vehicle composition.

In either case, the value resulting from the numerical function of the output layer 7 is compared with the information on the solubility of the polymer (for example coded in the form of a 0 or a 1). and an error function is calculated.

The above steps are repeated a number of times, both by varying the variable parameters (weight, threshold) of the intermediate neurons 4, 5, 6 and the output layer 7, and by varying the data from of the training data set, so as to minimize the error function.

At the end of the process, a function configured to associate a probability of solubility of the fluoropolymer with a vehicle composition is obtained. This function is determined according to the values of the variable parameters (weight, threshold) optimized by the previous process.

Selection of substances or mixtures of substances

The function configured to associate a probability of solubility of a fluoropolymer with a vehicle composition can be used in a computer-implemented method for selecting the solvent for the fluoropolymer and / or the non-solvent for the fluoropolymer and / or the proportions of solvent and non-solvent for the fluoropolymer in the vehicle comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer. Thus, in general, the function can be used to obtain a probability of solubility of the fluoropolymer for a vehicle composition to be tested, which is not included in the training data set.

This function is then applied to the solubility parameters of the vehicle composition to be tested.

The probability of solubility obtained by application of the function represents an estimate of the ability of the fluoropolymer to be dissolved in the vehicle composition. This estimate can be obtained either in binary form (yes / no answer), or in the form of any probability (for example any value from 0 to 1). In this second case, the probability is compared with a threshold value in order to define whether the fluoropolymer is estimated to be soluble or insoluble in the vehicle composition.

Depending on the result of the test, the vehicle composition to be tested may or may not be used.

In certain embodiments, the function is applied successively to a plurality of vehicle compositions to be tested, so as to select one or more of these compositions.

The vehicle compositions to be tested can be pure substances or mixtures of substances.

In the case of pure substances, the solubility parameters to which the function is applied can be determined by experimental or semi-empirical tests, as exemplified above, or preferably come from one or more reference tables preexisting, as described above.

In the case of mixtures, the solubility parameters to which the function is applied can be determined by experimental or semi-empirical tests or preferably be calculated as a linear combination from the solubility parameters of pure substances in mixture . In such a linear combination, the weighting coefficients applied preferably correspond to the volume proportions of each of the solvents.

The selection function and / or method described above can be used to select a solvent for the fluoropolymer; a solvent is then retained if the fluoropolymer is estimated to be soluble in it.

The selection function and / or method described above can also be used to select a non-solvent for the fluoropolymer; we then retains a non-solvent if the fluoropolymer is considered insoluble therein.

The selection function and / or method described above can also be applied to select the proportions of solvent for the fluoropolymer and non-solvent for the fluoropolymer in the vehicle used for the preparation of the ink.

In this case, the vehicle composition to be tested, at the solubility parameters to which the function is applied, is a mixture comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer.

In preferred embodiments, the function is applied successively to a plurality of vehicle compositions to be tested, all consisting of a mixture comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer, the proportion of solvent for the fluoropolymer and / or of the non-solvent for the fluoropolymer varying in the different compositions to be tested, so as to select one or more of these compositions.

One can then select a vehicle composition (consisting of a mixture comprising the solvent of the fluoropolymer and the non-solvent of the fluoropolymer) if the fluoropolymer is estimated to be soluble in it.

When the function is applied successively to a plurality of mixtures comprising an increasing proportion of non-solvent for the fluoropolymer, the method can make it possible to determine a range of proportions of non-solvent for the fluoropolymer within which the solubility limit is estimated to lie. .

Thus, the solvent for the fluoropolymer and / or the non-solvent for the fluoropolymer and / or the proportions of solvent and for non-solvent in the vehicle comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer can be chosen according to a selection process implemented by computer and comprising:

a) the provision of a function configured to associate a probability of solubility of the fluoropolymer with solubility parameters of a vehicle composition, for example a function determined by learning as described above;

b) providing solubility parameters associated with at least one vehicle composition (this vehicle composition being a mixture in the case of the selection of the proportions of solvent and of non-solvent);

c) applying the function provided in step a) to the solubility parameters provided in step b), so as to obtain a probability of solubility of the fluoropolymer associated with each respective vehicle composition;

d) as appropriate:

selecting a composition as a solvent for the fluoropolymer, in which the fluoropolymer is considered soluble, or selecting a composition as a non-solvent for the fluoropolymer, in which the fluoropolymer is considered insoluble, or

the selection of a vehicle composition as a mixture comprising the solvent for the fluoropolymer and the non-solvent for the fluoropolymer, in which the mass proportion of non-solvent is estimated to be less than the solubility limit, and preferably is estimated to be in one of the ranges mentioned above, relative to the solubility limit, according to a predetermined test.

Such a method allows efficient, reliable, easy and rapid selection since it does not necessarily require carrying out multiple dissolution experiments.

The selected vehicle composition can then be used to make an ink by dispersing the fluoropolymer in said vehicle composition.

One (or more) rheological test (s) can be carried out on the ink thus produced in order to determine its rheological behavior. For example, the dynamic viscosity of the ink can be measured as a function of the shear rate applied, over a given range of shear rate, for example from 0.01 to 1000 s ^-1 , or from 0.1 to 1000 s ¹ . This measurement then makes it possible to draw a rheometric curve of the ink tested, called "flow curve". The measurement (as well as the drawing of the curve) can be carried out using a rheometer, for example in cone-plane configuration, at the temperature considered. These rheological measurements have the advantage of being quick and easy to perform.

Depending on the flow curve obtained (representing the logarithm of the dynamic viscosity, as a function of the logarithm of the shear rate), the rheological behavior of the ink can be determined.

The fluid (that is to say the ink in the context of the present invention) exhibits a "Newtonian" type behavior when its viscosity does not depend on the shear rate at which the viscosity is measured. The curve flow is therefore of the horizontal line type (or essentially horizontal).

The fluid exhibits a behavior of “shear thinning with Newtonian plateau” when its viscosity at low shear rate follows Newtonian behavior (that is to say that it remains constant), then begins to decrease from a certain shear rate. This leads to a flow curve with a Newtonian plateau (horizontal line) at low shear rate, followed, when the shear rate increases, a negative slope (representing a drop in viscosity, called shear thinning). If the shear rate tested is high enough, a new plateau may appear after rheofluidification giving rise to a flow curve with two plateaus (high and low shear rate).

A fluid having a “stress threshold” type behavior is as defined above.

When a fluid has a Newtonian type behavior or a shear thinning type with Newtonian plateau, it has a threading type behavior, as opposed to a pasty or creamy type behavior.

It is then possible to select an ink exhibiting a rheological behavior of fluid at a stress threshold.

IT system

When it comes to a computer-implemented process, it is understood that all or almost all of the process steps are performed by a computer or a set of computers. The steps can be performed completely automatically, or partially automatically. In certain embodiments, the triggering of certain steps can be performed in response to an interaction with a user. The degree of automation envisaged can be predefined and / or defined by the user.

For example, the distribution of the training data set between a training data set and a test data set can be decided by the user, or can be determined automatically.

The learning is carried out automatically, according to any learning technique known to those skilled in the art. In particular, the error function is preferably automated according to any variant known to those skilled in the art. Referring to Figure 4, an example system that can be used to execute the above-described computer-implemented methods, via a computer program, is provided. In this example, the system is a computer, for example a workstation.

The computer thus comprises a processor unit 1010 connected to a computer bus 1000, and a random access memory 1070 (RAM) also connected to the computer bus 1000. The computer further comprises a graphics processor unit 1 1 10 which is associated with a video random access memory 1,100 connected to the computer bus. A mass storage device controller 1020 manages access to a mass storage device, such as a hard drive 1030. The mass storage devices 1040 adapted to tangibly represent computer program instructions and data includes all forms of non-volatile memory, including, for example, semiconductor memory devices such as EPROM, EEPROM and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical discs, and CD-ROM discs. These can also be supplemented by or incorporated into specific ASICs (application-specific integrated circuits). A 1050 network adapter manages access to a 1060 network. The computer can also include a 1090 haptic device such as a cursor control device, a keyboard or the like. A cursor control device is used to allow the user to selectively position a cursor at any location on the 1080 display. In addition, the cursor control device allows the user to select various commands and signals input control. The cursor control device includes signal generation devices for system input control signals. Typically it can be a mouse, the mouse button being used to generate the signals. The computer system may also include a touch screen and / or a touch pad.

The computer program can include instructions executable by a computer, the instructions including means for driving the above system to implement the method. The program can be saved on any data medium, including system memory. The program can for example be implemented in digital electronic circuits, or in computer hardware, firmware or software, or combinations thereof. The program can be implemented as a device, for example a product represented in a way tangible in a memory device that can be read by a machine to be executed by a programmable processor. Process steps can be performed by a programmable processor executing an instruction program to perform process functions by processing input data and generating outputs. The processor can thus be programmable and coupled to receive data and instructions from, and to transmit data and instructions to, a memory device, at least one input device and at least one output device. The program can be implemented in a high procedural or object oriented programming language, or in a machine or assembler language. Language can be compiled or interpreted. The program can be a full installation program or an update program. Applying the program to the system leads to instructions for performing the process.

EXAMPLES

The following examples illustrate the invention without limiting it.

In the examples below, the model used is constructed as follows.

A set of learning data has been compiled from the following table:

In this table, the Hansen solubility parameters are given in MPa ^1/2 . The notations (2) or (5) indicate that these Hansen solubility parameters come either from Table 2 in Chapter 7 or from Table 5 to Chapter 8 of the CRC Handbook of Solubility Parameters and Other Cohesion Parameters, by Allan FM Barton, 2 ^nd edition (1991).

The information relating to the solubility was obtained experimentally with a copolymer P (VDF-TrFE) comprising 80% of VDF units and 20% of TrFE units (in molar proportions).

JMP 13.0.0 software from SAS was used to provide a neural network as shown schematically in Figure 3.

20 rows of the table were used for learning the model and 6 for validation. The success rate obtained is 100%.

The "KFold" validation method was used. This method, as explained in the software manual, divides the data into K subgroups. Each of the K subgroups is then used to validate the fit or model created with the rest of the data not included in the K subgroup, which makes it possible to obtain K different models. The model with the best statistical validation (smallest error) is chosen as the final model.

From this modeling the following prediction model was obtained.

Functions of the three neurons of the (hidden) intermediate layer:

- H1 = tan h (0.5 x (0.288078 x 5d + 0.029058 xd _R + 0.092642 x bu - 4.79788));

- H2 = tan h (0.5 x (0.131723 x 5d - 0.16692 xd _R - 0.03299 x - 0.05098));

- H3 = tan h (0.5 x (0.399484 x bd - 0.1 1 103x d _R - 0.05299 x bu - 4.13038)).

In the above, the Hansen solubility parameters are expressed in MPa ^1/2 . Function of the output neuron: S = exp (201, 3275 x H1 + 192.4403 x H2 - 156.203 x H3 - 82.431 1).

The probability of non-solubility (or non-dissolution) is equal to S / (1 + S) and the probability of solubility is equal to 1 - probability of non-solubility.

The model thus obtained can be applied to any new vehicle composition not present in the previous learning table.

Example 1

Ethyl acetate is a known solvent for electroactive fluorinated copolymers based on VDF and TrFE. Benzaldehyde has been evaluated as a non-solvent for a copolymer P (VDF-TrFE) comprising 80% of VDF units and 20% of TrFE units (in molar proportions).

Using the model described above, the probability of dissolution (or solubility) of a copolymer P (VDF-T rFE) comprising 80% of VDF units and 20% of TrFE units (in molar proportions) (copolymer "FC-20") in different mixtures of ethyl acetate and benzaldehyde, is estimated. These dissolution probabilities are given in the table below (the first two columns of the table represent the mass proportion of the substance in the mixture evaluated).

The stability limit (corresponding to the solubility limit) given by the model is between approximately 73% and approximately 82% by weight of benzaldehyde: in fact, according to the model, the copolymer is soluble in this mixing up to, at least, a composition by weight of the mixture of 27% ethyl acetate and 73% benzaldehyde. At concentrations by weight of benzaldehyde greater than 73%, the risk of precipitation is high.

Thus, a mixture of 27% ethyl acetate and 73% benzaldehyde is selected for the preparation of an ink, for the performance of rheological tests. The presence of the non-solvent gives the ink a homogeneous, translucent macroscopic appearance, not completely transparent, and the dispersion, that is to say here the ink, is stable.

Different inks are prepared:

- a solution of copolymer FC-20 at 16% by weight in triethyl phosphate (triethyl phosphate being a solvent for FC-20);

- a solution of FC-20 copolymer at 16% by weight in gamma-butyrolactone (gamma-butyrolactone being a solvent for FC-20);

- a paste formulated from a PEDOT-PSS semiconductor polymer blend (blend of poly (3,4-ethylenedioxythiophene) (PEDOT) and sodium polystyrene sulfonate (PSS)), as an example of ink having rheological behavior of the fluid at the stress threshold (non-continuous paste);

an ink at 10% by weight of FC-20 in a mixture of 73% by weight of benzaldehyde (non-solvent for FC-20) and 27% by weight of ethyl acetate (solvent for FC-20) ( "Bzd / AcE 73/27" ink);

an ink containing 11% by weight of FC-20 in a mixture of 73% by weight of benzaldehyde (non-solvent for FC-20) and 27% by weight of triethyl phosphate (solvent for FC-20) (ink “ Bzd / TEP 73/27 ”);

Rheological tests are carried out at room temperature on the inks using an Anton Paar PHYSICA MCR 301 rheometer in cone-plane configuration. A shear rate sweep is performed between 0.1 and 1000 s ^-1 of shear rate. At least three scans are carried out to check the repeatability of the measurement, preferably in the order 1000 to 0.1 s ¹ , 0.1 to 1000 S ¹ and 1000 to 0.1 s ¹ .

The flow curves obtained are presented in Figure 1.

It can be seen that the two FC-20 inks in triethyl phosphate alone and in gamma-butyrolactone alone (curves A and B respectively) are both inks whose rheological behavior is that of a true solution, homogeneous at the molecular level ; this behavior is, thus, of Newtonian type, then shear-thinning from a certain rate of shearing. These two inks have a continuous character. The Bzd / AcE 73/27 ink of FC-20 in the benzaldehyde / ethyl acetate mixture (73% / 27% w / w) (curve D) exhibits a rheological behavior without a Newtonian plateau, specific to that of a fluid with stress threshold.

The Bzd / TEP 73/27 ink of FC-20 in the benzaldehyde / triethyl phosphate mixture (73% / 27% w / w) (curve E) exhibits Newtonian behavior up to a shear rate of 100 s ¹ .

The Bzd / AcE 73/27 ink corresponds to an ink according to the invention, the other inks correspond to counterexamples or witnesses.

Bzd / AcE 73/27 ink is less stringy than Bzd / TEP 73/27 ink.

This could be explained by the fact that triethyl phosphate is a better solvent for FC-20 than ethyl acetate. The probabilities of dissolution of FC-20 in mixtures of benzaldehyde / triethyl phosphate given by the model described above are as follows:

The solubility limit given by the model, in the benzaldehyde / triethyl phosphate mixture, is between a proportion of approximately 80% and a proportion of approximately 90% by weight of benzaldehyde, while it is between a proportion of about 73% and a proportion of about 82% by weight of benzaldehyde for the benzaldehyde / ethyl acetate mixture. The model therefore predicts that more benzaldehyde is needed in the mixture to make it precipitating with respect to FC-20, in the case of the benzaldehyde / triethyl phosphate mixture than in that of the benzaldehyde / ethyl acetate mixture: triethyl phosphate is therefore a better solvent for the FC-20 copolymer than ethyl acetate. This could explain that at 73% by weight of benzaldehyde for the two mixtures, in one case (Bzd ink / TEP 73/27) the rheological profile remains that of a shooting solution, while in the other (Bzd ink / AcE 73/27) a rheological behavior of the fluid at the stress threshold (two-phase system or dispersion) is obtained. Example 2

In this example, a mixture of gamma-butyrolactone / benzyl alcohol is evaluated. As noted above, gamma-butyrolactone is a solvent for FC-20. Benzyl alcohol is a non-solvent for the FC-20 copolymer.

The model described above is used to give the following solubility probabilities:

The solubility limit (switching from a non-precipitating to precipitating mixture) is between a proportion of approximately 58% and a proportion of approximately 68% by weight of benzyl alcohol (i.e. at a lower non-solvent level to that of the mixtures of Example 1). An ink consisting of 15% by weight of copolymer FC-20 dispersed in a mixture of 33% by weight of benzyl alcohol and 67% by weight of gamma-butyrolactone is prepared (“BzOH / gBTL 33/67” ink).

This ink is compared with the PEDOT-PSS and Bzd / TEP 73/27 inks described in Example 1.

The inks are subjected to rheological tests as described in Example 1 and the flow curves obtained are presented in Figure 2.

The BzOH / gBTL 33/67 ink (curve F) presents a rheological profile of the fluid at the stress threshold and does not spin.

The ink BzOH / gBTL 33/67 is an ink according to the invention while the other two inks correspond to comparative examples or controls.

Claims

1. An ink exhibiting a rheological behavior of fluid at stress threshold, comprising a fluoropolymer and a vehicle comprising a solvent for said fluoropolymer and a non-solvent for said fluoropolymer.

2. The ink as claimed in claim 1, in which the fluoropolymer is a polymer comprising units derived from vinylidene fluoride as well as units derived from at least one other monomer of formula CXiX2 = CX3X4, in which each group Xi, X2, X3 and X ₄ is independently selected from H, Cl, F, Br, I and alkyl groups comprising from 1 to 3 carbon atoms, which are optionally partially or fully halogenated; and preferably the fluoropolymer comprises units derived from vinylidene fluoride and from at least one monomer chosen from trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, 1, 1 - chlorofluoroethylene, hexafluoropropene, 3,3,3- trifluoropropene, 1, 3,3,3-tetrafluoropropene, 2, 3,3,3-tetrafluoropropene, 1-chloro-3,3,3-trifluoropropene and 2-chloro-3,3,3-trifluoropropene; and more preferably the fluoropolymer is chosen from poly (vinylidene fluoride-co-hexafluoropropene), poly (vinylidene fluoride-co-trifluoroethylene), poly (vinylidene fluoride-ter-trifluoroethylene-ter-chlorotrifluoroethylene) and poly (vinylidene fluoride-ter-trifluoroethylene-ter-1, 1-chlorofluoroethylene).

3. The ink of claim 1 or 2, wherein the solvent and the non-solvent are miscible.

4. Ink according to one of claims 1 to 3, in which the solvent is chosen from the group consisting of ketones, esters, in particular cyclic esters, dimethyl sulfoxide, phosphoric esters such as triethyl phosphate, carbonates, ethers such as tetrahydrofuran, and a mixture thereof, preferably the solvent being selected from the group consisting of ethyl acetate, gamma-butyrolactone, triethyl phosphate, cyclopentanone, monomethyl ether propylene glycol acetate and a mixture thereof. Ink according to one of claims 1 to 4, in which the non-solvent is chosen from the group consisting of benzyl alcohol, benzaldehyde, or a mixture of these. Ink according to one of claims 1 to 5, in which the vehicle comprises a mass proportion of non-solvent for the fluoropolymer, in percentage, ranging from (the solubility limit - 50%) to the solubility limit , more preferably in the range from (the solubility limit

- 30%) at the solubility limit, more preferably in the range going from (the solubility limit - 20%) to the solubility limit; even more preferably in the range from (the solubility limit - 15%) to the solubility limit, even more preferably in the range from (the solubility limit - 10%) to the solubility limit, even more preferably in the range from (the solubility limit

- 8%) at the solubility limit;

and / or the vehicle comprises a proportion by mass of solvent of the fluoropolymer, in percentage, included in the range going from (100 - the solubility limit) to (100 - (the solubility limit - 50%)), more preferably in the range from (100 - solubility limit) to (100 - (solubility limit - 30%)), even more preferably in the range from (100 - solubility limit) to (100 - (limit solubility - 20%)); more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 15%)), even more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 10%)), even more preferably in the range from (100 - the solubility limit) to (100 - (the solubility limit - 8%)); relative to the total weight of the vehicle comprising the solvent and the non-solvent for the fluoropolymer; the solubility limit being expressed as a percentage by mass.

7. Ink according to one of claims 1 to 6, not comprising rheological additives such as silica or calcium carbonate particles, or crosslinked polymer particles and / or surfactants.

8. Method for manufacturing a fluoropolymer film or an electronic device comprising:

- depositing an ink according to one of claims 1 to 7 on a substrate;

- evaporation of the vehicle comprising the solvent and the non-solvent.

9. The method of claim 8, further comprising a heat treatment of the fluoropolymer simultaneous and / or subsequent to the evaporation of the vehicle comprising the solvent and the non-solvent.

10. The method of claim 8 or 9, wherein the deposition of the ink is carried out by printing, in particular by screen printing, by roller printing, by flexography printing, by lithography printing, preferably by printing in screen printing.

11. Method for preparing an ink according to one of claims 1 to 7, comprising:

- The dispersion of the solid fluoropolymer in the liquid vehicle.