WO2013007711A1

WO2013007711A1 - Device comprising polymer layer

Info

Publication number: WO2013007711A1
Application number: PCT/EP2012/063454
Authority: WO
Inventors: Olivier Lhost
Original assignee: Total Petrochemicals Research Feluy
Priority date: 2011-07-12
Filing date: 2012-07-10
Publication date: 2013-01-17

Abstract

The present invention relates to a device comprising at least one conductive or semiconductive layer, and at least one additional layer, said additional layer having a composition comprising polylactic acid (PLA) and at least one coated metal oxide particle.

Description

DEVICE COMPRISING POLYMER LAYER

FIELD OF THE INVENTION

The invention relates to a device comprising at least one conductive or semiconductive layer and further comprising at least one additional polymer layer.

BACKGROUND OF THE INVENTION

Organic semiconductors and organic conductors are increasingly used in the development of photovoltaic cells, light-emitting diodes, flat panel displays, polymer field effect transistors, and the like. Such devices usually correspond to a multilayer structure: the "active" part of the structure is constituted by an organic layer, which may be sandwiched between two conductive layers. Additional layers are often introduced as support, barrier layers, adhesive layers, or the like.

For durable applications, it becomes increasingly important to avoid degradation of the organic components of the devices. UV-light in particular is often responsible for degradation of the organic component, and thus reduces the life time of the device. The problem of UV degradation is a common problem in many products exposed to sunlight. Continuous exposure is a more serious problem than intermittent exposure, since attack is dependent on the extent and degree of exposure, making UV degradation a particularly serious problem for photovoltaic cells, and even more so for organic photovoltaic cells. Organic photovoltaic devices currently have a shelf life of several years (typically between 1 and 5 years). They can thus not compete in terms of shelf life to silicon-based devices, which are known to have a much higher shelf life (typically of at least 25 years). Therefore, there is a need for organic photovoltaic devices to improve their shelf life, or they will remain limited to niche applications..

For flexible solar cells and films in particular, such a UV-protective layer needs to be also flexible, as thin as possible and as cheap as possible. Furthermore, such a UV-protective layer needs to block UV-C (with a wavelength of approximately 100-280 nm) and UV-B (280-315 nm) parts of the spectrum, which may be achieved by using for example a PET layer. Improvement has mainly to be done to block UV-A (315-400 nm) rays which may nevertheless be passed through the protective layer.

There is therefore a need to improve the devices of the prior art in terms of efficient UV- light filtration, without significant loss of transparency in the visible part of the spectrum. It is accordingly one of the objects of the present invention to overcome or ameliorate at least one of the disadvantages of the prior art, or to provide a useful alternative. SUMMARY OF THE INVENTION

The present inventors have now found that one or more of these objects can be obtained by using a device comprising a composition as presently claimed.

A first aspect of the present invention concerns the use of a composition comprising polylactic acid (PLA) and at least one coated metal oxide particle, as a UV filter for a device comprising at least one conductive or semiconductive layer. In a preferred embodiment of the present invention, said composition is used as a UV-A filter for a device comprising at least one conductive or semiconductive layer.

The inventors have surprisingly found that a polylactic acid (PLA) composition comprising metal oxide particles, whereby the particles are coated to prevent degradation of the PLA, can provide optimal UV absorption for an electric, an electronic, an optic, a photoelectric or a photovoltaic device, while minimizing loss of mechanical and thermal properties which is otherwise due to intensive degradation of the polymer matrix. Furthermore, the UV absorption can be tailored to include strong absorption in the UV range of the spectrum, as well as strong absorption in the UV-A sub-range of the spectrum, but only limited absorption in the visible range of the spectrum.

According to a second aspect, the present invention also encompasses a device comprising at least one conductive or semiconductive layer, and at least one additional layer, said additional layer having a composition comprising polylactic acid (PLA) and at least one coated metal oxide particle.

The layer composition comprising polylactic acid (PLA) and at least one coated metal oxide particle has the advantages of blocking most of all UV light with a wave length up to about 400 nm, and hardly blocking any light with a wavelength in the visible part of the spectrum. This composition is particularly useful for devices comprising conductive or semiconductive layers.

Preferably, the device is selected from the group comprising an electric, an electronic, an optic, a photoelectric and a photovoltaic module or device. More preferably, the device is selected from the group comprising a photovoltaic cell, a light-emitting diode, a fuel cell, a battery, a sensor, a field effect transistor and a display, preferably wherein the device is a photovoltaic cell. Preferably, the device is an organic photovoltaic cell.

Preferred embodiments of the invention are disclosed in the detailed description and appended claims. In the following passages different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 represents a graph plotting the transmission (T) of UV-visible spectra as a function of the wavelength for the films of examples 2 to 5.

DETAILED DESCRIPTION OF THE INVENTION

When describing the invention, the terms used are to be construed in accordance with the following definitions, unless a context dictates otherwise.

Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art.

The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of", "consists" and "consists of". As used in the specification and the appended claims, the singular forms "a", "an," and "the" include plural referents unless the context clearly dictates otherwise. By way of example, "a layer" means one layer or more than one layer.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as is commonly understood by one of skill in the art. All publications referenced herein are incorporated by reference thereto.

Throughout this application, the term 'about' is used to indicate that a value includes the standard deviation of error for the device or method being employed to determine the value.

The recitation of numerical ranges by endpoints includes all integer numbers and, where appropriate, fractions subsumed within that range (e.g. 1 to 5 can include 1 , 2, 3, 4 when referring to, for example, a number of elements, and can also include 1.5, 2, 2.75 and 3.80, when referring to, for example, measurements). The recitation of end points also includes the end point values themselves (e.g. from 1.0 to 5.0 includes both 1.0 and 5.0). Any numerical range recited herein is intended to include all sub-ranges subsumed therein.

According to a first aspect, the present invention concerns the use of a composition comprising a PLA polymer and at least one coated metal oxide particle, as a UV filter for a device, said device comprising at least one conductive or semiconductive layer. In a preferred embodiment of the present invention, said composition is used as a UV-A filter in a device comprising at least one conductive or semiconductive layer.

The present invention also encompasses the use of such a composition for preparing a device comprising at least one conductive or semiconductive layer, and at least one additional layer having a composition as described in the first aspect of the invention. In a preferred embodiment, said additional layer is a UV filter. In an even more preferred embodiment, said additional layer is a UV-A filter.

The present invention also encompasses a device comprising at least one conductive or semiconductive layer, and at least one additional layer, said additional layer having a composition comprising polylactic acid (PLA) and at least one coated metal oxide particle. The present invention also encompasses a device comprising at least one conductive or semiconductive layer, and at least one UV filter, preferably a UV-A filter, said filter having a composition comprising polylactic acid (PLA) and at least one coated metal oxide particle. As used herein, the terms "polylactic acid" or "polylactide" or "PLA" are used interchangeably and refers to poly (lactic acid) polymers containing repeat units derived from lactic acid.

PLA suitable for the present invention can be prepared according to any method known in the state of the art. The PLA can be prepared by ring-opening polymerization of raw materials having required structures selected from lactide, which is a cyclic dimer of lactic acid, glycolide, which is a cyclic dimer of glycolic acid, and caprolactone and the like. Lactide includes L-lactide, which is a cyclic dimer of L-lactic acid, D-lactide, which is a cyclic dimer of D-lactic acid, meso-lactide, which is a cyclic dimer of D-lactic acid and L- lactic acid, and DL-lactide, which is a racemate of D-lactide and L-lactide. The PLA polymers used in the present invention can be derived from D-lactic acid, L-lactic acid, or a mixture thereof. A mixture of two or more PLA polymers can be used.

The PLA for use in the present invention may comprise the product of polymerization reaction of a racemic mixture of L-lactides and D-lactides, also known as poly-DL-lactide (PDLLA). The PLA for use in the present invention may comprise the product of polymerization reaction of mainly D-lactides, also known as poly-D-lactide (PDLA). Preferably, The PLA for use in the present invention may comprise the product of polymerization reaction of mainly L-lactides (or L, L-lactides), also known as poly-L-lactide (PLLA). Other suitable PLA can be copolymers of PLLA with some D lactic acid units. PLLA-PDLA stereocomplexes can also be used.

Copolymeric components other than lactic acid may be used and include dicarboxylic acid, polyhydric alcohol, hydroxycarboxylic acid, lactone, or the like, which have two or more functional groups each capable of forming an ester bonding. These are, for example, polyester, polyether, polycarbonate, or the like which have the two or more unreacted functional groups in a molecule. The hydroxycarboxylic acids may be selected from the list comprising glycolic acid, hydroxybutyric acid, hydroxy valeric acid, hydroxypentanoic acid, hydroxycaproic acid, and hydroxyheptanoic acid.

Other examples of copolymers include poly-ester-urethanes, as disclosed in US 2010/01 13734 A1 , which is hereby incorporated by reference in its entirety, or lactide - amino-acid comonomers. PLLA-PDLA stereocomplexes or copolymer stereocomplexes like poly-ester-urethane stereocomplexes can also be used in the present invention. Examples of suitable copolymers can be polylactide-urethane copolymers, which are the reaction products that can be obtained by a process comprising the step of contacting: a polylactide having terminal hydroxyl groups, produced by contacting at least one lactide monomer with a diol or a diamine of general formula ¹(A)₂ wherein A is -OH or -IM H2 and R¹ is a substituted or an unsubstituted C1-20 alkylene or C_6-2o arylene group in the presence of a catalytic system under polymerization conditions, with - a diisocyanate compound of general formula 0=C=N-R²-N=C=0 wherein R² is a substituted or unsubstituted C1-20 alkylene or C_6-2o arylene group, optionally in the presence of a second diol or diamine of general formula R³(A)₂ wherein A is -OH or -NH₂ and R³ is a substituted or an unsubstituted C1-20 alkylene or C_6-2o arylene group in the presence of a catalytic system under polymerization conditions. Preferably, the polylactide and the polylactide-urethane copolymers can be produced by reactive extrusion.

Preferably, R¹, R² and R³ are an alkylene or an arylene group containing from 3 to 20 carbon atoms, preferably from 3 to 13 carbon atoms, more preferably from 6 to 13 carbon atoms. The alkyl or the aryl group may be substituted or not. The alkyl group may be linear, cyclic, saturated or unsaturated. Preferably, R¹, R² and R³ are an arylene group. Examples of suitable diamines include 1 ,4-butanediamine, 1 ,6-hexanediamine, 1 ,4- cyclohexanediamine, 1 ,4-phenyldiamine, 4,4'-diaminodiphenylmethane, preferably 1 ,4- phenyldiamine or 4,4'-diaminodiphenylmethane. Examples of suitable diols include 1 ,3- propandiol, 1 ,3-butanediol, 1 ,4-butanediol, 1 ,6-hexanediol, 1 ,7-heptanediol, 1 ,8- octanediol, and preferably xylene glycol. For example, the lactide used to obtain a polylactide-urethane copolymer can be a compound formed by the cyclic dimerization of the lactic acid. The lactide may exist in a variety of isomeric forms such as L, L-lactide, D, D-lactide and D, L-lactide. Preferably, L, L-lactide can be used. Examples of suitable diisocyanates include 1 ,6-hexamethylene diisocyanate (HMDI), 4,4'-dicyclohexylmethane diisocyanate, 4,4'-methylene diphenylisocyanate (MDI), toluene diisocyanate (TDI), and p-phenylene diisocyanate. Preferably, 4,4'-methylene diphenylisocyanate can be used.

In a preferred embodiment, the PLA for use in the present invention comprises PLLA. In an embodiment, the PLA for use in the present invention can comprise a physical polymer blend of PLA and at least one other polymer. In a preferred embodiment, the at least one other polymer is poly(methyl methacrylate) (PMMA). Therefore, the invention also encompasses a device wherein the composition further comprises poly(methyl methacrylate) (PMMA).

In an embodiment of the invention, the composition comprises at least 50 wt% of PLA based on the total weight of the composition. In a preferred embodiment of the invention, the composition comprises at least 80 wt% of PLA based on the total weight of the composition. In a more preferred embodiment of the invention, the composition comprises at least 90 wt% of PLA based on the total weight of the composition.

In an embodiment of the invention, the PLA for use in the invention has a mean molecular weight Mn higher than 20000 Da, preferably higher than 50000, more preferably higher than 100000 Da, more preferably higher than 200000 Da.

As used herein, the term "UV" refers to the band of electro-magnetic radiation with a wavelength of 100 nm to 400 nm. As used herein, the term "visible light" refers to the band of electro-magnetic radiation with wavelengths approximately in the 400 nm to 750 nm range.

As used herein, the term "UV-A", also referred to as UVA, Ultraviolet A, long wave, or black light, refers to the band of electro-magnetic radiation with a wavelength of 315 nm to 400 nm. As used herein, the term "UV-B", also referred to as UVB, Ultraviolet B, or medium wave, refers to the band of electro-magnetic radiation with a wavelength of 280 nm to 315 nm. As used herein, the term "UV-C", also referred to as UVC, Ultraviolet C, short wave, or germicidal, refers to the band of electro-magnetic radiation with a wavelength of 100 nm to 280 nm.

As used herein, the term "UV filter" refers to a substance which is able to absorb ultraviolet rays and give off the absorbed energy again in the form of longer-wave radiation, e.g. heat. The term "light transmittance" as used herein, refers to the amount of light that is transmitted or passes through a substance or product, expressed as a percentage.

In one embodiment, UV light transmittance of the UV filter suitable for use in the invention is less than 30%. In preferred embodiment of the invention, the UV light transmittance of the UV filter is less than 20%. In a more preferred embodiment of the invention, the UV light transmittance of the UV filter is less than 10%. In an even more preferred embodiment of the invention, the UV light transmittance of the UV filter is less than 5%.

In one embodiment, UV-A light transmittance of the UV-A filter suitable for use in the invention is less than 30%. In preferred embodiment of the invention, the UV-A light transmittance of the UV-A filter is less than 20%. In a more preferred embodiment of the invention, the UV-A light transmittance of the UV-A filter is less than 10%. In an even more preferred embodiment of the invention, the UV-A light transmittance of the UV-A filter is less than 5%.

Preferably, the UV filter or UV-A filter has limited absorption for light in the visible range of the spectrum. In one embodiment, the UV filter or the UV-A filter suitable for use in the present invention has a visible light transmittance of about 50% or greater. In a preferred embodiment, the UV filter or the UV-A filter has a visible light transmittance of about 60% or greater. In a more preferred embodiment, the UV filter or the UV-A filter has a visible light transmittance of about 70% or greater. In an even more preferred embodiment, the UV filter or the UV-A filter has a visible light transmittance of 75% or greater.

As used herein, the term "metal oxide" refers to a solid compound that contains a metal cation and an oxide anion.

In an embodiment of the invention, the metal can be selected from the group comprising Ca, Mg, Ni, Cu, Ag, Si, Ti and Zn, and combinations thereof. In a preferred embodiment of the invention, the metal is selected from the group comprising Ca, Mg, or Zn.

In a preferred embodiment, the at least one metal oxide particle is a zinc oxide (ZnO) particle.

In an embodiment of the invention, the composition comprises between 0.01 wt% and 10 wt% of metal oxide based on the total weight of the composition, preferably between 0.5 wt% and 3 wt% based on the total weight of the composition, more preferably between 0.5 wt% and 1 .5 wt% based on the total weight of the composition. Preferably the composition can comprises between 0.01 wt% and 10 wt% of zinc oxide based on the total weight of the composition, preferably between 0.5 wt% and 3 wt% based on the total weight of the composition, more preferably between 0.5 wt% and 1.5 wt% based on the total weight of the composition.

Nano-sized particles are preferred in order to obtain the best available dispersion with the lowest total amount of product. It thus allows optimizing other relevant properties of the material such as optical and/or mechanical properties. As also used throughout this application, "nano-particles" or "nano-sized particles" are particles having at least one of its average dimensions (diameter, width, thickness or length) ranging between 1 nanometer and 300 nanometers. In a preferred embodiment, the nano-particles have an average particle size of between 1 nanometer and 300 nanometers.

In an embodiment of the invention, the at least one metal oxide particle has an average particle size smaller than or equal to 30 μηη, preferably smaller than or equal to 3 μηη, preferably smaller or equal to 300 nm, preferably smaller than or equal to 100 nm, more preferably smaller than or equal to 50 nm, more preferably smaller than or equal to 40 nm, more preferably smaller than or equal to 30 nm.

Preferably, the at least one metal oxide particle, preferably the zinc oxide particle, has a maximum particle size (D99) of less than 100 μηη, preferably of less than 30 μηη, preferably of less than 20 μηη, preferably of less then 17 μηη, preferably of less than 15 μηη, preferably of less than 10 μηη, preferably of less than 5 μηη, for example of less than 3 μηη, for example of less than 2 μηη, preferably smaller or equal to 300 nm, preferably smaller than or equal to 100 nm, more preferably smaller than or equal to 50 nm, more preferably smaller than or equal to 40 nm, more preferably smaller than or equal to 30 nm.

As used herein, particle average size may be expressed as "Dxx" where the "xx" is the volume percent of that particle having a size equal to or less than the Dxx. The D99 is defined as the particle size for which ninety nine percent by volume of the particles has a size lower than the D99. The D99 can be measured by sieving, by BET surface measurement, or by laser diffraction analysis, for example using a Malvern analyzer.

As used herein, the term "coated" or "coating" refers to the fact that the at least one metal oxide particle has undergone one or more surface treatments of chemical, electronic, mechanochemical and/or mechanical nature with compounds such as amino acids, beeswax, fatty acids, fatty alcohols, anionic surfactants, lecithins, sodium, potassium, zinc, iron or aluminum salts of fatty acids, metal (e.g. titanium or aluminum) alkoxides, polyethylene, silicones, proteins (collagen or elastin), alkanolamines, silicon oxides, metal oxides, sodium hexa-metaphosphate, alumina, glycerol, silanes, tiophenes or citrates or combination thereof. Such a surface treatment results in a coating of the metal oxide particle. Said coating can result in partial or complete encapsulation of the metal oxide particle. In an embodiment of the invention, the at least one metal oxide particle is coated with at least one compound selected from the group comprising silanes, tiophenes, citrates, or combinations thereof.

In a preferred embodiment of the invention, said at least one compound is a silane compound. In an even more preferred embodiment of the invention said at least one compound is an alkoxysilane compound.

The present inventors have surprisingly found that the use of uncoated metal oxide particles into PLA composition can lead to significant loss of the thermo-mechanical performances. The present inventors have found that composition comprising coated metal oxide, on the other hand, can prevent or diminish such a reduction in thermo- mechanical performances, whereas good dispersion/distribution of metal oxide remains possible. Moreover, such composition can be easily extruded into films. In addition the present composition shows very effective anti-UV action, as well as antibacterial protection. In an embodiment of the invention, the silane compound can be selected from the group comprising alkoxysilanes, silazanes and siloxanes.

Non-limiting examples of silazane compound can be hexamethyldisilazane (HMDS or Bis(trimethylsilyl)amine). Non-limiting examples of siloxane compound can be selected from polydimethylsiloxane (PDMS) and octamethylcyclotetrasiloxane.

In a preferred embodiment of the invention, the silane compound is an alkoxysilane. As used herein, the term "alkoxysilane" refers to a compound that comprises a silicon atom, at least one alkoxy group and at least one other organic group, wherein said silicon atom is bonded with said organic group by covalent bond. Preferably, the alkoxysilane is selected from the group comprising alkylsilanes; acryl-based silanes; vinyl-based silanes; aromatic silanes; epoxy-based silanes; amino-based silanes and amines that possess - NH₂, -NHCH₃ or -N(CH₃)₂; ureide-based silanes; mercapto-based silanes; and, in addition alkoxysilanes which have a hydroxyl group (i.e., -OH). An acryl-based silane may be selected from the group comprising [beta]-acryloxyethyl trimethoxysilane; [beta]- acryloxypropyl trimethoxysilane; [gamma]-acryloxyethyl trimethoxysilane; [gamma]- acryloxypropyl trimethoxysilane; [beta]-acryloxyethyl triethoxysilane; [beta]-acryloxypropyl triethoxysilane; [gamma]-acryloxyethyl triethoxysilane; [gamma]-acryloxypropyl triethoxysilane; [beta]-methacryloxyethyl trimethoxysilane; [beta]-methacryloxypropyl trimethoxysilane; [gamma]-methacryloxyethyl trimethoxysilane; [gamma]- methacryloxypropyl trimethoxysilane; [beta]-methacryloxyethyl triethoxysilane; [beta]- methacryloxypropyl triethoxysilane; [gamma]-methacryloxyethyl triethoxysilane; [gamma]- methacryloxypropyl triethoxysilane; 3-methacryloxypropylmethyl diethoxysilane. A vinyl- based silane may be selected from the group comprising vinyl trimethoxysilane; vinyl triethoxysilane; p-styryl trimethoxysilane, methylvinyldimethoxysilane, vinyldimethylmethoxysilane, divinyldimethoxysilane, vinyltris(2-methoxyethoxy)silane, and vinylbenzylethylenediaminopropyltrimethoxysilane. An aromatic silane may be selected from phenyltrimethoxysilane and phenyltriethoxysilane. An epoxy-based silane may be selected from the group comprising 3-glycydoxypropyl trimethoxysilane; 3- glycydoxypropylmethyl diethoxysilane; 3-glycydoxypropyl triethoxysilane; 2-(3,4- epoxycyclohexyl)ethyl trimethoxysilane, and glycidyloxypropylmethyldimethoxysilane. An amino-based silane may be selected from the group comprising 3-aminopropyl triethoxysilane; 3-aminopropyl trimethoxysilane; 3-aminopropyldimethyl ethoxysilane; 3- aminopropylmethyldiethoxysilane; 4-aminobutyltriethoxysilane; 3-aminopropyldiisopropyl ethoxysilane; 1 -amino-2-(dimethylethoxysilyl)propane; (aminoethylamino)-3- isobutyldimethyl methoxysilane; N-(2-aminoethyl)-3-aminoisobutylmethyl dimethoxysilane; (aminoethylaminomethyl)phenetyl trimethoxysilane; N-(2-aminoethyl)-3- aminopropylmethyl dimethoxysilane; N-(2-aminoethyl)-3-aminopropyl trimethoxysilane; N- (2-aminoethyl)-3-aminopropyl triethoxysilane; N-(6-aminohexyl)aminomethyl trimethoxysilane; N-(6-aminohexyl)aminomethyl trimethoxysilane; N-(6- aminohexyl)aminopropyl trimethoxysilane; N-(2-aminoethyl)-1 1 -aminoundecyl trimethoxysilane; 1 1 -aminoundecyl triethoxysilane; 3-(m-aminophenoxy)propyl trimethoxysilane; m-aminophenyl trimethoxysilane; p-aminophenyl trimethoxysilane; (3- trimethoxysilylpropyl)diethylenetriamine; N-methylaminopropylmethyl dimehoxysilane; N- methylaminopropyl trimethoxysilane; dimethylaminomethyl ethoxysilane; (N,N- dimethylaminopropyl)trimethoxysilane; (N-acetylglycysil)-3-aminopropyl trimetoxysilane, N-phenyl-3-aminopropyltrimethoxysilane, N-phenyl-3-aminopropyltriethoxysilane, phenylaminopropyltrimethoxysilane, aminoethylaminopropyltrimethoxysilane, and aminoethylaminopropylmethyldimethoxysilane. An ureide-based silane may be 3- ureidepropyl triethoxysilane. A mercapto-based silane may be selected from the group comprising 3-mercaptopropylmethyl dimethoxysilane, 3-mercaptopropyl trimethoxysilane, and 3-mercaptopropyl triethoxysilane. An alkoxysilane having a hydroxyl group may be selected from the group comprising hydroxymethyl triethoxysilane; N-(hydroxyethyl)-N- methylaminopropyl trimethoxysilane; bis(2-hydroxyethyl)-3-aminopropyl triethoxysilane; N-(3-triethoxysilylpropyl)-4-hydroxy butylamide; 1 1 -(triethoxysilyl)undecanol; triethoxysilyl undecanol; ethylene glycol acetal; and N-(3-ethoxysilylpropyl)gluconamide.

Preferably, alkylsilane suitable for the invention can be expressed with a general formula: R_nSi(OR')₄-_n wherein: n is 1 , 2 or 3; R is a Ci_-2oalkyl; and R' is an Ci_-2oalkyl.

The term "alkyl" by itself or as part of another substituent, refers to a straight or branched or cyclic saturated hydrocarbon group joined by single carbon-carbon bonds having 1 to 20 carbon atoms, for example 1 to 10 carbon atoms, for example 1 to 8 carbon atoms, preferably 1 to 6 carbon atoms. When a subscript is used herein following a carbon atom, the subscript refers to the number of carbon atoms that the named group may contain. Thus, for example, Ci_-6alkyl means an alkyl of one to six carbon atoms. Examples of alkyl groups are methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, ie f-butyl, 2- methylbutyl, pentyl iso-amyl and its isomers, hexyl and its isomers, heptyl and its isomers, octyl and its isomer, decyl and its isomer, dodecyl and its isomers.

The term "C₂-₂oalkenyl" by itself or as part of another substituent, refers to an unsaturated hydrocarbyl group, which may be linear, or branched, comprising one or more carbon- carbon double bonds having 2 to 20 carbon atoms. Examples of C_2-6alkenyl groups are ethenyl, 2-propenyl, 2-butenyl, 3-butenyl, 2-pentenyl and its isomers, 2-hexenyl and its isomers, 2,4-pentadienyl and the like.

An alkylsilane may be selected from the group comprising methyltrimethoxysilane; methyltriethoxysilane; ethyltrimethoxysilane; ethyltriethoxysilane; propyltrimethoxysilane; propyltriethoxysilane; hexyltrimethoxysilane; hexyltriethoxysilane; octyltrimethoxysilane; octyltriethoxysilane; decyltrimethoxysilane; decyltriethoxysilane; dodecyltrimethoxysilane: dodecyltriethoxysilane; tridecyltrimethoxysilane; dodecyltriethoxysilane; hexadecyltrimethoxysilane; hexadecyltriethoxysilane; octadecyltrimethoxysilane; octadecyltriethoxysilane, trimethylmethoxysilane, methylhydrodimethoxysilane, dimethyldimethoxysilane, diisopropyldimethoxysilane, diisobutyldimethoxysilane, isobutyltrimethoxysilane, n-butyltrimethoxysilane, n-butylmethyldimethoxysilane, phenyltrimethoxysilane, phenyltrimethoxysilane, phenylmethyldimethoxysilane, triphenylsilanol, n-hexyltrimethoxysilane, n-octyltrimethoxysilane, isooctyltrimethoxysilane, decyltrimethoxysilane, hexadecyltrimethoxysilane, cyclohexylmethyldimethoxysilane, cyclohexylethyldimethoxysilane, dicyclopentyldimethoxysilane, tert-butylethyldimethoxysilane, tert- butylpropyldimethoxysilane, dicyclohexyldimethoxysilane.

In a preferred embodiment of the invention, the silane compound is an alkylsilane. Preferably, said silane compound is selected from triethoxyoctylsilane, trimethoxyoctylsilane or combinations thereof.

In a particularly preferred embodiment of the invention, the coated metal oxide particle is a zinc oxide particle coated with a silane. In a particularly preferred embodiment of the invention, the coated metal oxide particle is a zinc oxide particle coated with an alkylsilane. In a particularly preferred embodiment of the invention, the coated metal oxide particle is a zinc oxide particle coated with octyltrimethoxysilane. In a particularly preferred embodiment of the invention, the coated metal oxide particle is a zinc oxide particle coated with octyltriethoxysilane.

The composition may further comprise at least one additive. The invention therefore also encompasses the use as described herein or the device as described herein wherein the composition comprises from 0% to 10 wt% of at least one additive based on the total weight of the composition. In a preferred embodiment, said composition comprises less than 5 wt% of additive based on the total weight of the composition, for example 0.1 to 3 wt% of additive based on the total weight of the composition. Said additive may be selected from the group comprising an epoxy-functional styrene acrylic resin, an antioxidant, a thermal stabilizer, an antiacid, a UV-stabilizing agent, a solvent, a weather resistant agent, or an antistatic agent.

Suitable antioxidants include, for example, organophosphites such as bis(2,4-di-t- butylphenyl)pentaerythritoldiphosphite, tris(nonylphenyl)phosphite, tris(2,4-di-t- butylphenyl)phosphite, (2,4,6-tri-tert-butylphenyl)(2-butyl-2-ethyl-l,3- propanediol)phosphite, distearyl pentaerythritol diphosphite or the like; alkylated monophenols or polyphenols; alkylated reaction products of polyphenols with dienes, such as tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane, or the like; butylated reaction products of para-cresol or dicyclopentadiene; alkylated hydroquinones; hydroxylated thiodiphenyl ethers; alkylidene-bisphenols; benzyl compounds; acylaminophenols; esters of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)- propionic acid with monohydric or polyhydric alcohols; esters of beta-(5-tert-butyl-4- hydroxy-3-methylphenyl)- propionic acid with monohydric or polyhydric alcohols; esters of thioalkyl or thioaryl compounds such as distearylthiopropionate, dilaurylthiopropionate, ditridecylthiodipropionate, octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate or the like; amides of beta-(3,5-di-tert-butyl-4-hydroxyphenyl)-propionic acid or the like, or combinations comprising at least one of the foregoing antioxidants. Preferred antioxidant is ((bis(2,4-di- t-butylphenyl) pentaerythritol diphosphite) (know under the tradename (Ultranox®, 626). Antioxidants are generally used in amounts of about 0.1 to about 5 parts by weight, based on 100 parts by weight of the composition .

A preferred thermal stabilizer is Biomax Thermal 300 modifier from DuPont or a blend with poly(methyl methacrylate) (PMMA). Thermal stabilizers are generally used in amounts of about 0.1 to about 5 parts by weight, based on 100 parts by weight of the composition.

Non-limiting examples of the heat stabilizer and the antioxidant include hindered phenols, hindered amines, sulfur compounds, copper compounds and halides of alkali metals. In an embodiment, the composition comprises bis(2,4-di-t-butylphenyl)pentaerythritol diphosphite (Ultranox®, such as Ultranox626A). In an embodiment, the composition comprises 1 ,3,5-tris(3,5-di-t-butyl-4-hydroxybenzyl) isocyanurate.

Suitable UV-stabilizing agents include for example, hydroxybenzophenones; hydroxybenzotriazoles; hydroxybenzotriazines; cyanoacrylates; oxanilides; benzoxazinones; 2-(2H-benzotriazol-2-yl)-4-(1 ,1 ,3,3-tetramethylbutyl)-phenol (CYASORB 541 1 ); 2-hydroxy-4-n-octyloxybenzophenone (CYASORB 531 ); 2-[4,6-bis(2,4- dimethylphenyl)- 1 ,3,5-triazin-2-yl]- 5-(octyloxy)-phenol (CYASORB 1 164); 2,2'-(1 ,4- phenylene)bis(4H-3,1 -benzoxazin-4-one) (CYASORB UV- 3638); 1 ,3-bis[(2-cyano-3,3- diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane (UVINUL 3030);2,2'-(1 ,4-phenylene) bis(4H-3,1 -benzoxazin-4-one); 1 ,3-bis[(2-cyano-3,3- diphenylacryloyl)oxy]-2,2-bis[[(2-cyano-3,3-diphenylacryloyl)oxy]methyl]propane; nano- size inorganic materials such as titanium oxide, cerium oxide, and zinc oxide, all with particle size less than about 100 nanometers; or the like, or combinations comprising at least one of the foregoing U-stabilizing agents. UV-stabilizing agents are generally used in amounts of about 0.5 to about 20 parts by weight, based on 100 parts by weight of the composition.

Examples of antistatic agents include glycerol monostearate, glycerol distearate, glycerol tristearate, ethoxylated amines, primary, secondary and tertiary amines, ethoxylated alcohols, alkyl sulfates, alkylarylsulfates, alkylphosphates, alkylaminesulfates, alkyl sulfonate salts such as sodium stearyl sulfonate, sodium dodecylbenzenesulfonate or the like, quaternary ammonium salts, quaternary ammonium resins, imidazoline derivatives, sorbitan esters, ethanolamides, betaines, polyesteramides polyether-polyamide (polyetheramide) block copolymers, polyetheresteramide block copolymers, polyetheresters, or polyurethanes, each containing polyalkylene glycol moieties polyalkylene oxide units such as polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like. Such polymeric antistatic agents are commercially available, for example Pelestat 6321 (Sanyo) or Pebax MH1657 (Atofina), Irgastat P18 and P22 (Ciba-Geigy). Antistatic agents are generally used in amounts of about 0.05 to about 20 parts by weight, based on 100 parts by weight of the composition.

Non-limiting examples of suitable solvents include chloro-subsituted alkanes (such as dichloro methane and trichloro methane), alkyl acetates (such as ethyl-, propyl- and n- butyl acetate), ethers (such as diethyl ether and tetrahydrofuran), alcohols (such as methanol and ethanol), ketones (such as acetone, methyl ethyl ketone and methyl isobutyl ketone), cyclic hydrocarbons (such as hexane) and aromatic hydrocarbons (such as toluene, o-dichlorobenzene and o-, m-, or p-xylene) or acetonitrile. In an embodiment of the invention, the solvent is dichloro methane.

The present invention also encompasses the use of said composition for the preparation of a film. The present invention also encompasses a device wherein the at least one additional layer is a film. In an embodiment of the invention, the film has a thickness between 1 μηη and 0.5 mm, preferably between 4 μηη and 150 μηη, more preferably between 30 μηη and 50 μηη.

The PLA composition may optionally include other additives known in the art to improve processing and application of polymer films, e.g., antiblock additives, slip additives and viscosity enhancers. When used to enhance the production of polymer films, it should be noted that these additives are not essential for blowing the PLA films per se, but may be preferentially employed to enhance the processing, performance and look of the final product. In an embodiment , the PLA composition comprises a slip agent, preferably erucamide. In an embodiment , the PLA composition comprises an antiblock additive, preferably talc or other silica-based products.

The composition comprising PLA and metal oxide particles can be readily prepared by any method known in the art. For example, the components of the composition can be blended together by melt extrusion or can be admixed together on a conventional mixing machine such as an extruder, a kneader or a continuous mixer.

The composition of the present invention can be formed into film using any technique known in the art such as a cast method or blown film method or coating method. The present invention includes a blown film process wherein an extruder having an annular die is used for extruding the composition for use in the present invention. Air is blown in through the extruder die to form a bubble of the composition. After a cooling air stream cures, the film is wound onto rolls. More particularly, a composition as defined hereinabove is introduced into the feed hopper of an extruder that is resistance heated. The film can extruded through the die into a film that is cooled by blowing air onto the surface of the film in a blowing manner. The film can be drawn from the die typically forming a cylindrical film that is cooled, collapsed, optionally slit, and wound to form a roll of film.

The film can be obtained using a cast film process, wherein a flat die extruder is used for extruding the composition for use in the present invention. The film is then cast on a chill roll where cooling quenches it. The film can be obtained by extrusion coating process, wherein a flat die extruder is used for extruding the composition for use in the present invention. The film is then cast on a support.

According to an embodiment of the invention, the film can be co-extruded with one or more other polymer compositions to form a multi-layered film. The film can also be used in a lamination process. The film can be used as a substrate in production processes used for production of multilayer devices with at least one organic UV-sensitive layer. Such processes can include, for example, spin coating, vacuum thermal evaporation, vapor phase deposition, printing technologies or coating.

The film generally has a higher impact strength and a higher gloss than the neat PLA. The film is particularly useful for the preparation of a device comprising at least one at least one conductive or semiconductive layer.

The role of this layer or film having a composition as described herein can be multiple: it can serve as a support for the whole structure. It can be used as a barrier layer for example to prevent migration of water, gas, and the like. This layer can be used as external layer, and can provide a very high gloss to the structure. In particular this layer has the advantage of being a UV barrier.

Preferably, the present invention encompasses a device comprising at least one conductive or semiconductive layer, and at least one film having a composition comprising polylactic acid (PLA) and at least one coated metal oxide particle.

As used herein, the term "conductive layer" refers to a layer comprising a conductive material, i.e. a material that does not have a band gap or that has a very small band gap. As used herein, the term "semiconductive layer" refers to a layer comprising a semiconductive material, i.e. a material with a band gap smaller than 5 eV. In a preferred embodiment of the invention, the band gap of the semiconductive material is smaller than 3 eV. In a more preferred embodiment of the invention, the band gap of the semiconductive material is between 1 and 2 eV.

In an embodiment of the invention, the at least one conductive or semiconductive layer is organic or semi-organic. Preferably, the conductive or semiconductive layer comprises an organic conductor or semiconductor. More preferably the conductive or semiconductive layer comprises a polymeric organic conductor or semiconductor.

In an embodiment of the invention, the polymeric organic conductor or semiconductor is selected from the list comprising poly(fluorene), polyphenylene, polypyrene, polyazulene, polynaphthalene, poly(pyrrole) (PPY), polycarbazole, polyindole, polyazepine, polyaniline (PANI), poly(thiophene) (PT), poly(3-hexylthiophene), poly(3,4-ethylenedioxythiophene) (PEDOT), poly(dioctyl-bithiophene) (PDOT), poly(p-phenylene sulfide) (PPS), poly(p- phenylene vinylene) (PPV), poly(acetylene) (PAC) and their derivatives. Conductive and semiconductive polymers are lighter, more flexible, and less expensive than inorganic conductors. This makes them a desirable alternative in many applications. It also creates the possibility of new applications that would be impossible using copper or silicon.

In a preferred embodiment, the organic conductor or semiconductor is a polythiophene derivative, particularly poly (3 hexyl thiophene). In a more preferred embodiment , the polythiophene derivative is the "donor" component, combined with fullerene based compound, such as, for example, [6,6]-phenyl-C₆rbutyric acid methyl ester (PC[60]BM), or a carbon nanotube (CNT) based compound as the "acceptor" component.

In an embodiment of the invention, the device is selected from the group comprising an electric, an electronic, an optic, a photoelectric and a photovoltaic module or device.

In an embodiment of the invention, the device is selected from the group comprising a photovoltaic cell, a light-emitting diode, a fuel cell, a battery, a sensor, a field effect transistor and a display. In a particularly preferred embodiment, the device is a photovoltaic cell.

In a preferred embodiment, the device is flexible. In a preferred embodiment, the device is an organic electronic device. As used herein, the term "organic electronic device" does not only include devices based on organic semiconductors, but also devices comprising organic dielectrics, conductors and light emitters. Examples of organic electronic devices include organic field-effect transistors (OFET), organic light-emitting diodes (OLED) and organic photovoltaic cell (OPVC).

In a particularly preferred embodiment, the device is an organic photovoltaic cell (OPVC). In a preferred embodiment, the additional layer is used as a support in organic multilayer photovoltaic devices.

The organic photovoltaic cell according to an embodiment of the invention can comprise a planar heterojunction (PHJ), a bulk heterojunction (BHJ) or an ordered heterojunction (OHJ). An organic photovoltaic cell according to an embodiment of the invention can be manufactured by any technique known in the art. Preferably, the photovoltaic cell is manufactured by laminated multiple layers onto a support.

In an embodiment, the organic photovoltaic cell can comprise multiple layers: a substrate or support layer, a transparent first electrode layer, optionally an interlayer, an active layer and a second electrode layer. In a preferred embodiment, the substrate layer or support layer comprises a composition comprising PLA and at least one coated metal oxide particle.

As the skilled person will understand, any transparent electrode is suitable such as one formed from a layer of transparent conductive oxide, such as indium tin oxide (ITO).

In a preferred embodiment, the interlayer comprises a conductive organic material, such as poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (also known as PEDOT:PSS). The interlayer may further comprise any conjugated families, compounds, their derivatives, moieties etc, for example: polyfluorene, polyphenylenevinylene, poly(methyl methacrylate), polyvinylcarbazol (PVK) thiophene and their derivatives which include cross-linkable forms. The interlayer can be arranged between the electrodes and the active layer.

The active layer can comprise any electron accepting material, such as a fullerene, and any electron donating material, such as an active polymer, for example polythiophene.

The skilled person will understand that the second electrode can comprise any metal, such as aluminium or silver, or a combination of two or more metals, such as calcium and aluminium or calcium and silver or lithium fluoride and aluminium or lithium fluoride and silver.

The composition is thus an improved UV-filter, and provides an improved shelf-life of the active organic layer in a photovoltaic device.

EXAMPLES

Unless otherwise indicated, all parts and all percentages in the following examples, as well as throughout the specification, are parts by weight or percentages by weight respectively.

Example 1 : Preparation of a PLA layer for use in the device according to an embodiment of the invention

A film was prepared using a composition comprising PLA (Mn = 80000 daltons, Mw/Mn = 1 .9, D isomer - 1 .4 %) and 0.5% of Zano20 (ZnO particles coated with triethoxy caprylylsilane), commercialized by Umicore Zinc Chemicals (Belgium). 0.3 wt % of Ultranox 626 (bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite) supplied by GE Specialty Chemicals was further added to the composition.

The Zano20, Ultranox 626 and dried-PLA pellets were first mixed in a Brabender twin screw extruder TSE20 (L/D = 40) at 190 °C, 80 rpm equipped with a 4 mm diameter strand die. The strand was cooled in a water bath and cut with a pelletizer. Pellets with the appropriate final compositions were thus produced.

Dried polymer pellets were then introduced in a Brabender single screw extruder (19 mm diameter - L/D = 25 - heated at 210 C - throughput = 1 .5 kg/h) equipped, at the output, with a blown film die (25 mm diameter - gap 0.5 mm). The blow-up ratio was 2.5 - 3. Rolling system speed was adjusted to obtain a 40 μηη thickness film.

The following characteristics considering the UV-visible spectrum were obtained for this film:

- the transmittance was smaller than 5 % for all wavelengths smaller than 375 nm

- above 450 nm at least until 800 nm, the highest considered wavelength, all transmittance was higher than 75 %.

The film can thus be used as a substrate e.g. for the production of a photovoltaic organic device.

Example 2: Preparation of a PLA layer for use in the device according to an embodiment of the invention

A film was prepared using a composition comprising PLA (Ingeo™ 4042D commercially available at NatureWorks LLC) and 0.1 % of Zano20 plus (ZnO particles coated with triethoxy caprylylsilane), commercialized by Umicore Zinc Chemicals (Belgium). 0.3 wt% of Ultranox 626 (bis(2,4-di-t-butylphenyl) pentaerythritol diphosphite) supplied by GE Specialty Chemicals was further added to the composition.

The Zano20 plus, Ultranox 626 and dried-PLA pellets were first mixed in a Brabender twin screw extruder TSE20 (L/D = 40) at 190°C, 80 rpm equipped with a 4 mm diameter strand die. The strand was cooled in a water bath and cut with a pelletizer. Pellets with the appropriate final compositions were thus produced.

Dried polymer pellets were then introduced in a Brabender single screw extruder (19 mm diameter - L/D = 25 - heated at 210°C - throughput = 1 .5 kg/h) equipped, at the output, with a cast film die (length = 10 cm, thickness = 0.8 mm). The film was cooled on a chill roll, with imposed temperature = 30°C. The thickness of the obtained film was close to 100 m.

The UV-visible spectrum obtained for this film is illustrated in Figure 1 (b) and compared to the UV-visible spectrum of the same film without Zano20 plus in Figure 1 (a). The film with the Znano20 plus can thus be used as a substrate e.g. for the production of a photovoltaic organic device.

Example 3: Preparation of a PLA layer for use in the device according to an embodiment of the invention

The same experiment as the one described in example 2 was reproduced but with 0.1 % of Zano20 plus. The UV-visible spectrum obtained for this film is illustrated in Figure 1 (c).

Example 4: Preparation of a PLA layer for use in the device according to an embodiment of the invention

The same experiment as the one described in example 2 has been reproduced but with 0.5% of Zano20 plus. The UV-visible spectrum obtained for this film is illustrated in Figure 1 (d).

Example 5: Preparation of a PLA layer for use in the device according to an embodiment of the invention

The same experiment as the one described in example 2 has been reproduced but with 1 % of Zano20 plus. The UV-visible spectrum obtained for this film is illustrated in Figure 1 (e).

The films of examples 3-5 can thus be used as a substrate, e.g. for the production of a photovoltaic organic device.

Claims

I . A device comprising at least one conductive or semiconductive layer, and at least one additional layer, said additional layer having a composition comprising polylactic acid (PLA) and at least one coated metal oxide particle.

2. The device according to claim 1 , wherein the metal is selected from the group comprising Ca, Mg, Ni, Cu, Ag, Si, Ti and Zn, and combinations thereof.

3. The device according to claim 1 or 2, wherein the metal oxide is zinc oxide.

4. The device according to any of claims 1 to 3, wherein said metal oxide is coated with at least one compound selected from the group comprising silanes, tiophenes, citrates, or combinations thereof.

5. The device according to claim 4, wherein said at least one compound is a silane compound, preferably an alkoxysilane compound.

6. The device according to any of claims 1 to 5, wherein the composition comprises at least 80 wt% of polylactic acid based on the total weight of the composition.

7. The device according to any of claims 1 to 6, wherein the composition comprises between 0.01 wt% and 10 wt% of metal oxide based on the total weight of the composition.

8. The device according to any of claims 1 to 7, wherein the at least one metal oxide particle has a average particle size smaller than or equal to 30 μηη, preferably smaller than or equal to 3 μηη, preferably smaller than or equal to 300 nm, preferably smaller than or equal to 100 nm, more preferably smaller than or equal to 50 nm.

9. The device according to any of claims 1 to 8, wherein the at least one additional layer is a film.

10. The device according to claim 9, wherein the film has a thickness between 1 μηη and 0.5 mm, preferably between 4 μηη and 150 μηη, more preferably between 30 μηη and

50 μηη.

I I . The device according to any of claims 1 to 10, wherein the device is selected from the group comprising an electric, an electronic, an optic, a photoelectric and a photovoltaic module or device.

12. The device according to any of claims 1 to 1 1 , wherein the device is selected from the group comprising a photovoltaic cell, a light-emitting diode, a fuel cell, a battery, a sensor, a field effect transistor and a display, preferably wherein the device is a photovoltaic cell.

13. The device according to any of claims 1 to 12, wherein the at least one conductive or semiconductive layer is organic.

14. The device according to any of claims 1 to 13, wherein the composition further comprises poly(methyl methacrylate) (PMMA).

15. The device according to any of claims 1 to 14, wherein the at least one conductive or semiconductive layer comprises a polythiophene derivative.