EP3094702A1

EP3094702A1 - Method for producing a composite material containing luminescent molecules, for rendering sustainable the electromagnetic characteristics of said material

Info

Publication number: EP3094702A1
Application number: EP15703466.1A
Authority: EP
Inventors: Philippe Gravisse; Marc Schiffmann
Original assignee: Lrpl (laboratoire De Physiquedu Rayonnement Et de la Lummiere); Cascade SAS
Current assignee: Lrpl (laboratoire De Physiquedu Rayonnement Et de la Lummiere); Cascade SAS
Priority date: 2014-01-13
Filing date: 2015-01-13
Publication date: 2016-11-23
Also published as: WO2015104432A1; FR3016369B1; US20160333263A1; FR3016369A1

Abstract

The invention relates to method for rendering sustainable the electromagnetic characteristics of optically active composite materials, said method comprising: a first step of preparing doped organic compounds by mixing at least one type of optically active molecules with a protective material in order to prevent the contact thereof with photodegradation-inducing elements and the migration of the optically active molecules; a second step of producing optically active nanoparticles including said doped organic compounds; and a third step of producing optically active composite materials by incorporating the optically active nanoparticles into a polymer matrix.

Description

Process for producing a composite material containing luminescent molecules for making the electromagnetic characteristics of this material durable

The present invention relates to a method of manufacturing a composite material containing luminescent molecules to make the electromagnetic characteristics of this material durable and to a product obtained by this method.

It relates more particularly to the field of composite materials doped with luminescent molecules, further defined in what follows by the expression "optically active molecules", abbreviated MOAs.

Luminescent or optically active molecules are molecules that can emit light after passing their peripheral electrons in an excited state caused by a physical factor (light absorption), mechanical (friction) or chemical.

An excited molecule can transmit its excitation energy to another neighboring molecule in a non-radiative manner by coupling between the electronic orbitals of the two molecules. This phenomenon is called resonance energy transfer resulting from a dipole-dipole interaction between two molecules. Resonance energy transfer is possible if the emission spectrum of one molecule partially overlaps the absorption spectrum of the other molecule. This type of energy transfer, known as the Fôster type, is commonly known as FRET, an acronym for "Fôster résonance energy transfert". For the purposes of this patent, the term "light cascade" will be understood to mean the transfer of energy occurring by the combination of a series of optically active molecules (MOAs) of two distinct groups chosen in such a way that the spectrum of emission of the first group of MOAs partially overlaps the absorption spectrum of the second group of MOAs successively, each of the two groups of MOAs being defined by a re-emission wavelength different from the absorption wavelength of the group MOAs considered.

The "light cascade" within the meaning of this patent may further incorporate "Stokes type MOAs" whose retransmission wavelength is greater than the absorption wavelength and the "anti-type MOAs". - Stokes "whose retransmission wavelength is less than the absorption wavelength.

The link between the energy E and the wavelength λ is expressed by the following equation:

E = h- c / λ h is the Planck constant, c is the speed of light in vacuum.

The invention also relates to the manufacture of luminescent (or optically active) particles including luminescent (or optically active) molecules mixed in a protective material.

These optically active particles are dispersed in various types of polymers forming optically active composite materials, for example in film form, for different industrial uses.

According to the type of polymer of the film, a plurality of uses is made by these composite materials optically active. Firstly, a use such as photovoltaics (PV) can be obtained by a lamination technique - under a certain pressure and heat - with an encapsulating material such as polyethylene vinyl acetate (EVA) and all other related matrices. , or by the casting technique with polymethyl methacrylate (PMMA) and all other related matrices. In general, photovoltaic generators are manufactured in planar modules, which are integrated in buildings and greenhouses. Secondly, use as films for agricultural greenhouses is carried out by the technique of mono-extrusion or co-extrusion of low density polyethylene (LDPE), LDPE / EVA, or LLDPE for vegetable or horticultural greenhouses, for the cultivation of primeurs, salads, chews or melons, and also rigid greenhouses made of PMMA, polycarbonate, PVC, NDLR.

State of the art

[00011] The principle of light cascades is known in the prior art, which makes it possible, by doping a matrix with optically active organic or inorganic substances, in solution or in dispersion, to transfer all or part of the incident energy. , in the wavelength bands of greater sensitivities of an electromagnetic sensor, such as photovoltaic cells for example.

[00012] French patent FR2792460 describing a photovoltaic generator comprising at least one photovoltaic cell and a transparent matrix deposited with at least one optically active material having a wavelength are known in the prior art. absorption lambda _a and lambda retransmission wavelength _r, the optically active material being selected such that _lambda corresponds to a range of lesser sensitivity of the photovoltaic cell as lambda _r, the matrix having a reflective coating.

US Patent US4952442 describes a light cascade doped film for agricultural greenhouses so that the light is enriched in the frequency bands favorable to photosynthesis and the yield of plants is significantly improved.

The patent application FR1000696 discloses a photovoltaic module for a greenhouse comprising a front plate intended to be in contact with sunlight, a rear substrate and a set of photovoltaic cells disposed between the front plate and the rear substrate. The photovoltaic module has an expansion coefficient substantially between 0.2 and 0.8 and comprises at least one layer of a light-cascade doped dopant material promoting photosynthesis capable of absorbing sunlight in at least one range of lengths. wave to re-emit in at least a second range of wavelengths favorable for photosynthesis of at least one plant species.

FR7808150 French patent describes a polymer matrix based on a homogeneous mixture of rare earth-type optically active crystals capable of generating a light cascade, which emits photons in the infrared region. This polymeric matrix displaces incident light close to the highest sensitivity of a photocell. Disadvantages of prior art

The solutions of the prior art have problems stabilizing optically active molecules. Although the various doped polymeric organic matrices of organic or inorganic optically active molecules give interesting energy conversion efficiencies, the aging effect of these doped matrices is significant and the light fastness is insufficient.

One possible cause is the photo-oxidation of optically active molecules, which is related to the high permeability of polymers to gases, especially oxygen or ozone. These polymers are commonly used for photovoltaics, for example, of the EVA family and for agricultural green films, for example, of the PE family. This aging effect is accelerated by electromagnetic radiation, such as UV rays. Oxygen and UV radiation - a component of solar energy - produce a conjugated effect on MOAs, which causes a rise in temperature leading to greater sensitivity to photooxidation.

In order to solve this problem, adjuvants Antioxidant, Anti-UV, HALS - heat and light stabilization - phosphite, phosphorite, antistatic type are generally added in the polymer films such as EVA, PE. However, despite the decrease in aging, the number of actual charges - MOAs - per unit volume, is substantially limited.

The other cause of the aging of the films is the migration of the optically active molecules in the PE / EVA type matrices, which exude with the PE / EVA plasticizers and create localized overconcentration. This aggregation leads to a phenomenon of self-extinction due to a high local concentration of optically active molecules. In other organic polymer matrices doped with rare earths, the aging effect is limited. However, the energy conversion efficiencies are too low to allow industrial and commercial use. Another difficulty comes from the shift in the absorption and emission spectrum of the MOAs, when they are found in the presence of a solvent. A number of environmental parameters in the solvent can modify the spectra of these molecules: the pH, the presence of organic solutes, the temperature and the polarity of the solvent. The effects of these parameters vary from one type of MOA to another type. The more the solvent is polar, the more the effect is marked. Such a type of effect also occurs on molecules with a large dipole. Solution provided by the invention

The invention aims to solve the problems of the state of the art, in particular to ensure an interesting energy conversion efficiency, while delaying the aging of the optically active molecules. To do this, it is proposed to overcome the effects of migrations, photo-oxidation and photo-degradation of MOAs in α-polar polymers, which has a low gas permeability.

For this purpose, the present invention provides an improvement of the morphology of the support matrices with respect to doping optically active molecules. For this purpose, the subject of the present invention is a method for making the electromagnetic characteristics of optically active composite materials durable, comprising: a first step of preparation of the doped organic compounds by mixing at least one type of optically active molecules with a protective material to prevent their contact with elements inducing photodegradation and migration of optically active molecules,

a second step of manufacturing optically active nanoparticles including said doped organic compounds,

and a third step of producing optically active composite materials by integrating the optically active nanoparticles into a polymer matrix.

According to the characteristics of the invention, said protective material consists of at least one type of polar polymer and crosslinked in three dimensions, and which has a low gas permeability.

According to advantageous features, the invention provides optically active nanoparticles have a diameter of between 1.10 ^"8 meter and 2.10 ^{" 6} meter.

According to a first variant embodiment, the optically active nanoparticles are inorganic.

According to a second variant, the optically active nanoparticles are organic, in one embodiment, the organic nanoparticles are made colloidal latex from methyl methacrylate, in another embodiment, the organic nanoparticles are produced by mechanical micronization. According to a preferred embodiment of the invention, only one type of optically active molecules is mixed with a protective material and doped in the nanoparticles to obtain the optically active nanoparticles doped unitarily.

Preferably, a set of said optically active nanoparticles doped unitarily are associated according to an optimized concentration rule to achieve the light cascade effect and integrated in the polymers to form an optically active composite material.

According to a particularly advantageous embodiment, a plurality of types of optically active molecules associated according to a concentration rule optimized for the light cascade effect are mixed in at least one type of protective and doped materials in the nanoparticles. to obtain optically active nanoparticles doped in light cascade. Preferably, said optically active nanoparticles doped in light cascade are integrated in the polymers to form an optically active composite material.

[00034] Several of said optically active composite materials of different functions are stacked at the time of coextrusion of the matrix films.

In one embodiment, the emission spectrum of one type of MOA partially overlaps the absorption spectrum of another type of MOA successively forming a luminous cascade, and the ratio C ₂ / C ₁ between the concentration of the first type with respect to the concentration C ₂ of the second type is between 0.13 and 0.26. More particularly, the optically active composite materials include at least one type of optically active Stokes molecules whose retransmission wavelength is greater than the absorption wavelength and / or at least one type of the molecules optically. anti-Stokes actives whose retransmission wavelength is less than the absorption wavelength.

According to another embodiment, optically active molecules of the organic fluorophore type having a remanence of less than 10 ns are associated with the optically active crystals of the inorganic ZnS.Ag type having a remanence greater than 10 ns, the lengths of which are emission and absorption waves respond to the light cascade effect.

The optically active composite materials having according to the invention perennial optoelectro-magnetic characteristics, include optically active nanoparticles doped optically active molecules, which are mixed with the protective materials.

The invention also relates to an application of said optically active composite material for industrial uses such as photovoltaics or agricultural greenhouses films.

The protective material is often a polar type organic polymer and crosslinked in three dimensions, which has a low oxygen permeability. These features help to resist aging and increase the light fastness of organic matrices doped with MOAs to avoid photo-degradations and MOA migration in the PE, EVA matrix families. [00041] The nanoparticles have important interfacial surfaces and high cross sections. Indeed, a uniform dispersion of the active particles of submicron size leads to a consequent increase in the adsorption rate of the organic compounds doped with MOAs for a given charge mass. So a significant increase in the number of MOAs per unit volume for a given volume fraction.

The invention thus relates to: · A method of manufacturing a luminescent composite material intended to make durable the electromagnetic characteristics of this material comprising:

A first step of preparing an organic compound with protected light-emitting molecules by mixing at least a first group of light-emitting molecules with a protective material to avoid their contact with elements inducing the photo-degradation and the migration of the luminescent molecules,

A second step of manufacturing luminescent particles having a diameter of between 1. 10 ^"8 meters and 2 ^" 10 ^"6 meters including said organic compounds,

And a third step of producing a luminescent composite material by integrating the luminescent particles into a polymer matrix.

• According to this process

the protective material consists of at least one polar polymer compatible with the luminescent molecules, preferably physico-chemically stable. the step of manufacturing said luminescent particles consists of grinding the organic compound by grinding.

the step of manufacturing said light-emitting particles consists, during the production of the organic compound, of initially introducing the at least first group of light-emitting molecules into a monomer to form a luminescent polymer, to integrate this polymer with an inorganic particle, then to evaporating the polymer leaving the luminescent molecules fixed on the inorganic support so as to form the luminescent particles.

the step of manufacturing said luminescent particles consists in producing organic particles and dissolving the at least first group of light-emitting molecules in the organic particles formed so as to form the luminescent particles,

the organic nanoparticles are made colloidally latex from methyl methacrylate.

each luminescent particle comprises the same type of luminescent molecules, and which are capable of reacting in light cascade with a second type of luminescent molecule of a second group of luminescent particles or each luminescent particle comprises different types of luminescent molecules capable of reacting two to two in cascade light,

the concentrations of the different types of luminescent molecules of the different groups of luminescent particles are optimized to achieve the light cascade effect. The polymer matrix is in the form of a film.

The composite material comprises several films each incorporating luminescent particles, these films being stacked together to combine the effects of the luminescent particles they contain. the film stacking is performed at the time of a film coextrusion step. the luminescent molecules (MOAs), whose emission spectrum of one type of MOAs partially overlaps the absorption spectrum of another type of MOAs successively forming a luminous cascade, respect the C ₂ / C ₁ ratio between the concentration of a first type with respect to the C ₂ concentration of a second type between 0.13 and 0.26. the luminescent molecules include at least one type of Stokes-type molecules whose retransmission wavelength is greater than the absorption wavelength and / or at least one type of the optically active anti-Stokes molecules whose length is greater than The retransmission wave is less than the absorption wavelength.

the molecules the luminescent molecules include at least organic fluorophore-like molecules having a remanence of less than 10 ns are associated with optically active crystals of inorganic ZnS.Ag type having a remanence greater than 10 ns, the wavelengths of which emission and absorption respond to the light cascade effect. The invention relates to a material obtained according to the method above.

As well as a material comprising PMMA luminescent particles doped with colloidal latex-based luminescent molecules from MMA monomers.

And the use of the material according to the preceding claim as a photovoltaic element or film of agricultural greenhouses.

Detailed description of a nonlimiting example of embodiment

The invention will be better understood and other features and advantages will appear more clearly on reading the description which follows, with reference to the accompanying drawings in which - FIG. 1 represents the emission spectra of the doped PMMA microsphere samples. of the formula P004NP obtained under the excitation of UV light with a wavelength of 365 nm,

FIG. 2 shows the comparison of emission spectra of samples made in different ways, obtained under the excitation of UV light with a wavelength of 365 nm.

Non-limiting description of exemplary embodiments

Other features and advantages of the invention will emerge on reading the description given hereinabove. after particular embodiments of the invention, given by way of indication but not limiting.

In order to achieve the "light cascade" effect between several distinct groups of MOAs, it is necessary to fulfill three conditions between two groups of MOAs in order to obtain the "Foister resonance energy transfer" phenomenon, abbreviated to FRET:

• The emission spectrum of a molecule of a first group partially overlaps the absorption spectrum of a molecule of the second group,

• The distance separating the two molecules respectively from the two groups is less than 1.8 × R ₀ , R ₀ is the distance between the two molecules respectively of the two groups for which the efficiency of the energy transfer is 50%,

• The relative orientation between the two molecules respectively of the two groups makes it possible to define a dipole.

The structure of the molecule and the number of nuclei can determine the wavelengths of absorption and emission of molecules. The optically active molecules of a first group are selected such that the emission ranges of these molecules correspond to the absorption ranges of the molecules of the second group, in order to fulfill the first criterion.

According to one embodiment of the invention, the optically active molecules are of the organic phosphon scintillator type with N + 1, N + 2, N + 3, N + x nuclei phi chosen from: aromatic cyclics, Anthracene, naphthacene, penthacene, hexacene, rhodamine, oxazine, diphenyloxazol and dimethyloxazol. [00047] According to another embodiment, the MOAs include at least one group of MOAs stokes and at least one group of anti-Stokes MOAs. In this case, it is possible to use molecules including rare earth atoms such as anti-Stokes MOAs. They can form, when combined with organic polymer matrices, organic polymer matrices that are luminescent because they are doped with rare earths, which give a good path for exploiting the anti-Stokes effects. Indeed, the optically active crystals that can form organic polymer matrices doped with rare earths, are generally capable of performing a reverse light cascade. For example, a two-photon absorbing molecule in the infrared region is capable of emitting a photon in the visible region. This is the case, for example, with anti-Stokes luminescences of three Ln202S: Er (sup 3 +), Yb (sup 3 +), which are phosphors incorporated into triplexes under the excitation of IR sources in the different ranges of 0.93, 1.53, and 1.59 micrometers. More details are given in the table below:

In a third particularly advantageous embodiment, a first group of optically active molecules (MOAs) of organic fluorophore type having a remanence <10 ns is associated with a second group of MOAs of inorganic photoluminescent type / optically active crystals (series ZnS doped Ag or Cu) having a remanence> 10 ns, the molecules of the two groups respectively having lengths emission and absorption waves responding to the light cascade effect. The remanence of the light cascade becomes longer (> 10 ns) and the effect of energy re-emission by the fluorophores then takes place over a longer time.

The table below describes the various possible electronic transitions of the molecules.

A transition is often made between the excited state of the first level and the ground state.

In order to fulfill the second criterion, it is necessary to reach a certain concentration of MOAs. By way of example, the table below represents two examples of formulas, composition and concentration of MOAs in gr / kg or in percentage: the first formula P004NP dosed at 21 gr / kg, the second formula 2013F dosed at 5 gr / kg.

PPO Compounds Uvitex OB LFR305 // GG

OR610 reference 2,5 2,5 Di Hostasol diphenyl thiophene perylene red oxazole C32H16

C26H26N202S C23H120S

C15H11NO

Formula 15,4gr 3,85gr 0,8744gr 0,8744gr

P004NP

73.33% 18.33% 4.166% 4.166%

Formula 3,657gr 0,942gr 0,401gr

2013F 73, 14% 18.84% 8.02%

The doped organic compounds are obtained by a mixture of a protective polymethyl methacrylate (PMMA) material, which is physico-chemical stable, and optically active molecules. PMMA is polar because it effectively aligns dipole molecules and produces a CL effect statistically more prominent than isotopic materials. However, the absence of spectrum shift should be regularly monitored.

In doped organic compounds, the polymethyl methacrylate type protective material may be replaced by another type of protective material: other polar polymers (or made polar by electron bombardment or functionalization of the polymer molecules) and compatible with the molecules optically active, for example, polyesters, methylenebut-3-en-1-ol (IOH), polycarbonate (PC), silicone, and methyl methacrylate (MMA).

A protective material suitable for the production of organic compounds with protected luminescent molecules is physico-chemically stable, polar and compatible with the luminescent molecules considered, that is to say it prevents the exudation, migration, photooxidation and photodegradation of this MOA.

These doped organic compounds are then grafted into nanoparticles of the type explained hereinafter having high cross sections forming optically active nanoparticles (NOAs).

[00055] A large interfacial surface associated with micro or nanometric dimensions is the main element that differentiates nanoparticles, traditional fillers. The specific surfaces of certain loads can reach values between 500 and 1000 m ² / g in the case of lamellar charges (montmorillonite). The adsorption rate related to the interface is then all the more important. To produce the optically active composite materials, the optically active nanoparticles are integrated into the polymers of industrial use, which are chosen from:

- polymethyl methacrylate (PMMA), - polyethylene vinyl acetate (EVA),

- Polyvinyl chloride (PVC),

- Polycarbonate (PC), Low density polyethylene (LDPE),

- Polyvinylidene fluoride (PVDF).

The above paragraphs generally describe the process for producing optically active composite materials, while the following paragraphs relate in particular to the different embodiments of the optically active nanoparticles.

1. inorganic nanoparticles According to a first embodiment, the optically active nanoparticles are inorganic, and made for example, in alumino silicate, mesoporous silica, alumino zeolite, aluminosilicates. It is interesting in this case to be able to prepare the choice:

(a) a first type of nanoparticles each doped only with the same first group of MOAs, and a second type of doped nanoparticles of the same second group of MOAs capable of operating in Cascade

Bright with the MOAs of the first type of nanoparticles, or

(b) nanoparticles each individually doped with two groups of MOAs capable of reacting together in a luminous cascade.

1. a) inorganic nanoparticles doped with a single type of MOAs

An embodiment of nanoparticles doped solely with the same first group of MOAs is described below:

According to a first step, a first doped solution of a first group of MOAs is produced by operating the dissolution of optically active molecules (MOAs) of a first group in an ad hoc ligand or MMAs which connect the MOA to the zeolite. The MOAs of this first group may for example be chosen from polycyclic aromatic hydrocarbons N Phi nuclei (Anthracene or Benzenic series):

• polycyclic aromatic hydrocarbon 3 phi,

• polycyclic aromatic hydrocarbon 4 phi, • polycyclic aromatic hydrocarbon 5 phi ...

The same method is used to produce other doped solutions of other groups of MOAs than those characterizing the first group above, by choosing the MOAs of the solution prepared according to their capacity to create a luminous cascade effect with the MOAs of the first solution.

According to a second step, each solution prepared with the same type of MOAs is introduced into functionalized zeolite-type inorganic nanoparticles with a magnetic stirrer at a temperature of 45 degrees Celsius in order to obtain the different groups of NOAs (optically nanoparticles). active) doped CL (Light Cascade). Then the ad hoc ligand or MMA is evaporated to obtain different groups of optically active nanoparticles each doped with the same type of MOAs attached to the inorganic nanoparticles. Finally, these CL doped NOAs are dried and integrated into the polymer encapsulation matrices.

According to a third step, each type of doped inorganic NOAs of 3, 4, 5 or N phi respectively are associated with a polymer matrix, in concentrations optimized to produce the light cascade effect, the most adapted to the intended application:

PV - photovoltaic - or PS - photosynthesis -.

[00065] This produces the reinforcing effects of

light fastness and resistance to aging. 1. b) inorganic nanoparticles doped with several types of MOAs

An embodiment of nanoparticles each individually doped with at least two groups of MOAs capable of reacting two by two in a luminous cascade is described below.

According to another embodiment of the invention, several types of MOAs at concentrations and proportions optimized for the desired light cascade effect are introduced into a ligand or MMA for example, to form a solution of light cascade (CL).

Then, this solution is introduced into the inorganic nanoparticles of the zeolite type in a magnetic stirrer at a temperature of 45 degrees.

Celsius in order to obtain the NOAs doped CL (luminous Cascade). Then the ad hoc ligand or MMA is evaporated. Finally, these CL doped NOAs are dried and integrated into the encapsulation matrices.

There are effects of photon scattering, strengthening of light fastness, resistance to aging.

The process for producing inorganic nanoparticles is known to those skilled in the art. For example, French Patent EP1335879 describes the manufacture of a zeolite material loaded with dye. The publication in the scientific journal "microporous and mesoporous materials" (volume 145, issues 1-3, November 2011, pages 157-164) describes the adsorption behavior of methylenen blue on the modified clinoptilolite. [00071] 2) organic nanoparticles

[00072] According to a second variant embodiment, the optically active nanoparticles are organic. The techniques for manufacturing organic nanoparticles historically fall within the context of colloidal chemistry and involve conventional sol-gel processes, or other aggregation methods.

[00073] These wet chemistry techniques currently offer nanoparticles of better quality.

It is known to produce the organic nanoparticles from polymethyl methacrylate (PMMA) in a colloidal solution by latex starting from the MMA (monomer PMMA) by different methods. For example, in the scientific journal

"Macromoleccular rapid communications", it is described the synthesis of poly nanometric (methyl methacrylate) initiated by 2, 2-azoisobutyronitrile by differential microemulsion polymerization; in the scientific journal "polymer" (volumn 49, issue 26, December 8, 2008, pages 5636-556), poly (methyl methacrylate) and silica nanocomposites produced by "graft through" are described using reversible by addition-fragmentation transfer of polymerization chain.

[00076] 2) a) organic nanoparticles doped with a single type of MOA

In a first step, the optically active molecules (MOAs) are dissolved in a colloidal solution by latex starting from the PMMA monomer. With a magnetic stirrer and at a temperature of 45 degrees Celsius, NOAs of a few tens to a few hundred nm are obtained. Each type of unitary NOA includes only one type of MOA. According to a second step, several groups of organic NOAs doped respectively with several different types of MOAs, each NOA having the same type of MOA, are mixed in a twin-screw extruder with LDPE / EVA compounds, according to a rule of optimized concentration to obtain the desired cascade effect.

2) b) organic nanoparticles doped by several types of MOA

According to another embodiment of the invention, a plurality of types of MOAs, for example, phosphors of HAP type 2, 3, 4, N phi at concentrations and proportions optimized for the light cascade effect. , are introduced into a colloidal latex solution starting from the MMA (PMMA monomer), with a magnetic stirrer and at a temperature of 45 degrees Celsius in order to obtain the CL doped NOAs. These CL doped NOAs are then mixed with the PMMA polymer or the PEBD / EVA compounds in a twin-screw extruder. By this method of producing doped NOAs CL, were obtained NOAs of 500 nm and 2 micrometers doped according to the formula P004NP to CL, whose analysis results are represented in FIG. 1.

FIG. 1 contains the emission spectra of PMMA microsphere samples doped according to the formula

P004NP under excitation of UV light of wavelength 365 nm. The PMMA microspheres doped here are performed colloidally latex from the MMA as explained in the previous paragraphs. The X axis represents the wavelength in nanometers, one hundred nanometers per scale, while the Y axis represents the intensity in the arbitrary unit. The solid line represents the lot3 sample of microspheres of size 2 micrometers, while the dotted line represents the lot5 sample of microspheres of size 500 nanometers.

The following table shows the intensities of the peak in the light region of red and blue, respectively. This table makes it easy to classify productions in terms of energy conversion efficiency.

Lot 3 is the most efficient for Photovoltaics.

Lot 5 can be considered for agricultural applications, because it is very effective in the blue while being significant in the retransmission in the red.

[00085] Optically active molecules grafted into optically active nanoparticles made of PMMA have increased light fastness and good UV and 1Ό2 resistance.

3. nanoparticles resulting from the grinding of doped PMMA

According to a third variant embodiment, a CL-doped PMMA matrix is micronized by grinding to form an organic pigment. The matrix is constituted by a rigid or flexible organic material, or is in the form of an applicable coating under the form of a resin. The organic material is polymethyl methacrylate (PMMA) for example.

The PMMA matrices doped CL are micronized by grinding at 40/50 micrometers. It is a "top-down" method that reduces particle size by ball mills or planetary mills.

[00088] The optically active dopants are organic pigments with 2, 3, 4, N + 1 phi nuclei of aromatic cyclic type, or of anthracene, naphthacene, penthacene, hexacene, rhodamine, oxazine, diphenyloxazol or dimethyloxazol type. The particles thus obtained are called organic pigments.

[00089] FIG. 2 shows the comparison between the emission spectra of the samples made in different ways under the excitation of the UV light of wavelength at

365nm. The first type is the doped PMMA compound of the 2013F formula before the micronization process; the second type is the doped PMMA compound of the 2013F formula after the cryomilling type micronization process; while the third type is the lot3 sample (the microspheres doped with the P004NP formula of size 2 micrometer).

The X axis represents the wavelength in nanometers, one hundred nanometers per graduation, while the Y axis represents the relative intensity in arbitrary units. The solid line represents the doped PMMA compounds, the dashed line represents PMMA grinding-cryo compounds, while the dotted-pull line represents the sample lot 3 - the microspheres in 2 microns.

In blue, the intensity of the emission peak microspheres 2 micrometer lot 3 is 27% lower than the cryo-crushed PMMA peak. In the red, the intensity of the emission peaks is of the same order for the doped PMMA compound 2013F, the cryo-milled 2013F doped PMMA compound and the micrometers 2 micrometers lot 3 (doped P004NP). However, a slight shift exists in the wavelength of the peaks between the three:

• the doped PMMA compound 2013F: 634 nm,

• the cryo-milled 2013F doped PMMA compound: 617 nm,

Microspheres 2 micrometers lot 3: 628 nm.

The organic pigments thus obtained are associated with the polymer matrices of use in the industrial applications concerned: films for agricultural greenhouses or in the polyvinyl chloride (PVC) sheets, polyethylene vinyl acetate (EVA) or polycarbonate (PC).

[00093] The new aging retardation performance of the doped PMMA CL in the EVA matrix is measured by the durability using the "Suntest XLS + Atlas" machine under the following applied test conditions:

• 60W / m ² and 300-400 nm;

• the light continues;

• 102 min dry, 18 min rainy;

• Temperature: 65 +/- 2 ° C.

The materials are exposed under these conditions up to 1500 hours and no degradation appears. Therefore, the equivalent durability in natural conditions is estimated to be greater than 10 years, whereas without the invention it lasts only one month in EVA or PE doped CL with MOAs. The effect of delaying aging is therefore verified.

It is possible to produce the final composite material which includes the optically active nanoparticles or luminescent particles described in the paragraphs.

1) to 3) above, and a polymer matrix type PMMA, EVA, PVC, LDPE, PVDF, by extrusion.

The nanoparticles of the above type and the polymer matrix monomers are introduced into the extruder in order to obtain an extruded film at the outlet.

It is also possible to coextrude different films each including particular functionalities using the corresponding MOAs: according to the desired applications, it is possible to alternate at the time of the coextrusion of the matrix films, the functionalities of the outer, inner films (central core ) and inside. For example, in a greenhouse, we will choose an anti UV and anti 02 function in external film, MOAs cascade light in the central core, anti-fogging function in the inner film. Light scattering, IR reflector and film thicknesses can also be broken down by application.

At the time of coextrusion of the matrix films

4. Composite material derived from a copolymer of which one is doped

According to a fourth variant embodiment, a composite material consists of a PMMA copolymer - PE / EVA, where PMMA is the polar polymer doped with MOAs, forming a light cascade.

This type of material is the addition of two different polymers, one technical and functional and forming an agricultural film or one PE / EVA photovoltaic encapsulation, the other optically active, such as PMMA doped with MOAs. micronized.

[000100] Any other type of matrix associated with any other type of organic pigment, such as IOH or PC is compatible.

Claims

claims

A method of manufacturing a luminescent composite material for rendering durable the electromagnetic characteristics of this light-emitting material comprising:

a first step of preparing an organic compound with protected light-emitting molecules by mixing at least a first group of luminescent molecules with a protective material to prevent their contact with elements inducing the photo-degradation and the migration of the luminescent molecules,

a second luminescent particles manufacturing step having a diameter of between 1.10 ^"and 2.10 ⁸ ^{meter" 6} meter including said organic compounds,

2. Method according to claim 1, characterized in that the protective material consists of at least one polar polymer compatible with the luminescent molecules, preferably physico-chemically stable.

3. Method according to claim 1 or 2, characterized in that the step of manufacturing said luminescent particles comprises micronize by grinding the organic compound.

4. Method according to claim 1 or 2, characterized in that the step of manufacturing said light-emitting particles consists, during the manufacture of the organic compound, in initially introducing the at least first group of luminescent molecules into a monomer to form a luminescent polymer, to integrate this polymer with an inorganic particle, then evaporate the polymer leaving the luminescent molecules fixed on the inorganic support so as to form the luminescent particles.

5. Method according to claim 1 or 2, characterized in that the step of manufacturing said luminescent particles consists of producing organic particles and dissolving the at least first group of luminescent molecules in the organic particles formed to form the luminescent particles.

6. Method according to claim 6, characterized in that the organic nanoparticles are made colloidally latex from methyl methacrylate.

7. Method according to one of the preceding claims, characterized in that each luminescent particle comprises the same type of luminescent molecules, and which are capable of reacting in light cascade with a second type of luminescent molecule of a second group of luminescent particles. or each luminescent particle comprises different types of luminescent molecules capable of reacting two by two in light cascade.

8. Method according to claim 7, characterized in that the concentrations of the different types of luminescent molecules of the different groups of luminescent particles are optimized to achieve the light cascade effect.

9. Method according to one of the preceding claims, characterized in that the polymer matrix is in the form of a film.

10. Method according to claim 9, characterized in that the composite material comprises several films each incorporating luminescent particles, these films being stacked to each other to combine the effects of the luminescent particles they contain.

11. Process according to Claim 10, characterized in that the stack of films is produced at the time of a coextrusion step of the films.

12. Method according to one of the preceding claims, characterized in that the luminescent molecules (MOAs), the emission spectrum of one type of MOAs partially overlaps the absorption spectrum of another type of MOAs successively forming a cascade luminous, respect the ratio C ₂ / C ₁ between the concentration of a first type with respect to the concentration C ₂ of a second type between 0.13 and 0.26.

13. Method according to one of the preceding claims, characterized in that the luminescent molecules include at least one type of Stokes-type molecules whose retransmission wavelength is greater than the absorption wavelength and / or at least a type of anti-Stokes optically active molecules whose retransmission wavelength is less than the absorption wavelength.

14. Method according to one of the preceding claims, characterized in that the molecules the luminescent molecules include at least organic fluorophore-type molecules having a remanence of less than 10 ns are associated with the optically active crystals of the inorganic ZnS.Ag type having a remanence greater than 10 ns, whose emission and absorption wavelengths respond to the light cascade effect.

15. Material obtained according to the process according to any one of the preceding claims.

16. Material comprising PMMA luminescent particles doped with colloidal latex-based luminescent molecules from MMA monomers.

17. Use of the material according to the preceding claim as a photovoltaic element or film of agricultural greenhouses.