ACQUEOUS COMPOSITION COMPRISING A CONDUCTIVE POLYMER AND USE THEREOF

Abstract

Aqueous composition comprising: from 0.5% by weight to 5% by weight, preferably from 1% by weight to 4% by weight, with respect to the total weight of said aqueous composition, of at least one conductive polymer; from 1% by weight to 100% by weight, preferably from 2% by weight to 10% by weight, more preferably from 15% by weight to 50% by weight, with respect to the total weight of said at least one conductive polymer, of at least one cellulose ether.

Said aqueous composition may advantageously be used as a printable ink or printable paste in various techniques such as, for example, screen printing, gravure printing, flexographic printing, spray coating, slot die coating, spin-coating, ink-jet printing. Preferably, said aqueous composition may advantageously be used as a printable paste for screen printing. More particularly, said aqueous composition may be used for the preparation of electrically organic conductive layers, even more particularly for the preparation of electrically organic conductive layers used in photovoltaic cells (or solar cells), in printable electronics, in organic light-emitting diodes (OLEDs), in touch screens, in antistatic coatings.

Claims

1. Aqueous composition comprising: from 0.5% by weight to 5% by weight, preferably from 1% by weight to 4% by weight, with respect to the total weight of said aqueous composition, of at least one conductive polymer; from 1% by weight to 100% by weight, preferably from 2% by weight to 10% by weight, more preferably from 15% by weight to 50% by weight, with respect to the total weight of said at least one conductive polymer, of at least one cellulose ether.

2. Aqueous composition according to claim 1, wherein said conductive polymer is selected from (co)polymers of a 3,4-dialkoxythiophene, preferably from: (co)polymers comprising repeating units having general formula (I): ##STR00002## in which R.sub.1 and R.sub.2, identical or different, represent a hydrogen atom; or are selected from C.sub.1-C.sub.4 alkyl groups; or R.sub.1 and R.sub.2 together represent a C.sub.1-C.sub.5 alkylene group or a cycloalkylene group; or (co)polymers of a 3,4-dialkoxythiophene in which the two alkoxy groups together represent an optionally substituted oxy-alkylene-oxy bridge, preferably from: poly(3,4-methylenedioxythiophene) and its derivatives, poly(3,4-ethylenedioxythiophene) and its derivatives, poly(3,4-propylenedioxythiophene) and its derivatives, poly(3,4-butylenedioxythiophene) and its derivatives, or their copolymers, or mixtures thereof; or (co)polymers of a 3,4-dialkoxythiophene in which the two alkoxy groups together represent a an oxy-alkylene-oxy bridge optionally substituted with one or more groups selected from: alkyl groups, alkoxy groups, alkyloxyalkyl groups, carboxyl groups, alkylsulphonate groups, arylsulphonate groups, ester groups; (co)polymers of a 3,4-dialkoxythiophene in which the two alkoxy groups together represent a oxy-alkylene-oxy bridge in which the alkylene group is an optionally substituted 1,2-ethylene group, a methylene group optionally substituted with at least one alkyl group, a 1,2-ethylene group optionally substituted with at least one C.sub.1-C.sub.12 alkyl group, a 1,2-ethylene group optionally substituted with at least one phenyl group, a 1,3-propylene group, a 1,2-cyclohexylene group.

3. Aqueous composition according to claim 2, wherein said (co)polymer of a 3,4-dialkoxythiophene is poly(3,4-ethylenedioxythiophene) (PEDOT).

4. Aqueous composition according to claim 2, wherein said (co)polymer of a 3,4-dialkoxythiophene is used together with a polyanion selected from polyanions of polymeric carboxylic acids such as poly(meth)acrylic acids, polymaleic acids; polyanions of polysulphonic acids such as poly(styrenesulphonic) acid; preferably, said polyanion is a polyanion of poly(styrenesulphonic) acid or a polyanion of copolymers of poly(styrenesulphonic) acid with styrene.

5. Aqueous composition according to claim 1, wherein said conductive polymer is PEDOT: PSS [poly(3,4-ethylenedioxythiophene)-polystyrene sulphonate.

6. Aqueous composition according to claim 1, wherein said cellulose ether is selected from: alkyl celluloses such as methylcellulose, ethylcellulose, propylcellulose, or mixtures thereof; hydroxyalkylcelluloses such as hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, or mixtures thereof; hydroxyalkylalkylcelluloses such as hydroxyethylmethylcellulose, hydroxypropylmethylcellulose, or mixtures thereof; or mixtures thereof; preferably said cellulose ether is methylcellulose, hydroxypropylmethylcellulose; more preferably is hydroxypropylmethylcellulose, said hydroxypropylmethylcellulose having, preferably, a methoxyl content ranging from 16.5% by weight to 30% by weight and a hydroxypropoxyl content ranging from 4% by weight to 32% by weight relative to the total weight of said hydroxypropylmethylcellulose.

7. Aqueous composition according to claim 1, wherein said aqueous composition comprises at least one compound selected from: sulphoxides; aprotic liquids having a dielectric constant greater than 15; diols; sugars; or mixtures thereof; preferably, sulphoxides; and/or: said sulphoxides are selected from: alkyl sulphoxides such as dimethyl sulphoxide (DMSO), diethyl sulphoxide, di-n-propyl sulphoxide, di-n-butyl sulphoxide, di-iso-amyl sulphoxide, or mixtures thereof; aryl sulphoxides such as benzyl phenyl sulphoxide, diphenyl sulphoxide, methyl phenyl sulphoxide, dibenzyl sulphoxide, di-p-tolyl sulphoxide, or mixtures thereof; or mixtures thereof; preferably dimethyl sulphoxide (DMSO); and/or said aprotic liquids having a dielectric constant greater than 15 are selected from: N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, 2-pyrrolidone, N,N,N′,N′-tetramethylurea, formamide, N,N-dimethylformamide, N-methylacetamide, N,N-dimethylacetamide, tetramethylsulphoneurea, or mixtures thereof; and/or said diols are selected from: diethylene glycol, propylene glycol, or mixtures thereof; and/or said sugars are selected from: sorbitol, mannitol, sucrose, fructose, or mixtures thereof; and/or said compound selected from sulphoxides, aprotic liquids having a dielectric constant greater than 15, diols, sugars, being preferably used in an amount ranging from 2% by weight to 20% by weight, preferably ranging from 3% by weight to 8% by weight, with respect to the total weight of said aqueous composition.

8. Aqueous composition according to claim 1, wherein said aqueous composition comprises at least one organic solvent miscible with water, said organic solvent being preferably selected from: alcohols such as methyl alcohol, ethyl alcohol, iso-propyl alcohol, or mixtures thereof; acetic acid esters such as methyl acetate, ethyl acetate, n-propyl acetate, iso-propyl acetate, or mixtures thereof; ketones such as acetone, methyl ethyl ketone, methyl iso-butyl ketone, cyclohexanone, or mixtures thereof; or mixtures thereof; preferably is iso-propyl alcohol; said organic solvent being preferably used in an amount ranging from 0.1% by weight to 70% by weight, preferably ranging from 10% by weight to 60% by weight, relative to the total weight of said aqueous composition.

9. Aqueous composition according to claim 1, wherein said aqueous composition has a viscosity, at 25° C., ranging from 1 mPa×s to 10.sup.5 mPa×s, preferably ranging from 5 mPa×s to 1000 mPa×s, more preferably ranging from 1000 mPa×s to 10.sup.5 mPa.

10. Printable ink or printable paste, preferably printable paste, comprising the aqueous composition as claimed in claim 1.

11. Method for the preparation of electrically organic conductive layers even more particularly for the preparation of electrically organic conductive layers usable in photovoltaic cells (or solar cells), in printable electronics, in organic light-emitting diodes (OLEDs), in touch screens, and in antistatic coatings, comprising applying the aqueous composition of claim 1 to a surface.

12. The method of claim 11, wherein the aqueous composition of claim 2 is applied to the surface.

13. The method of claim 11, wherein the aqueous composition of claim 3 is applied to the surface.

14. The method of claim 11, wherein the aqueous composition of claim 4 is applied to the surface.

15. The method of claim 11, wherein the aqueous composition of claim 5 is applied to a surface.

16. The method of claim 11, wherein the aqueous composition of claim 6 is applied to a surface.

17. The method of claim 11, wherein the aqueous composition of claim 7 is applied to a surface.

18. The method of claim 11, wherein the aqueous composition of claim 8 is applied to a surface.

19. The method of claim 11, wherein the aqueous composition of claim 9 is applied to a surface.

Description

EXAMPLE 1

[0059] Into a 10 ml vial, fitted with a plug, were loaded 2 ml of poly(3,4-ethylenedioxythiophene)-polystyrenesulphonate (PEDOT:PSS) (Clevios™ PH 1000 from Heraeus) (1.3% by weight with respect to the total weight of the aqueous composition), 0.19 g of a 5% aqueous solution of hydroxypropylmethylcellulose (Methocel® 90 HG from Sigma Aldrich) (approximately 37% by weight with respect to the total weight of PEDOT:PSS) and 0.09 ml dimethyl sulphoxide (DMSO) (“ACS reagent”, purity ≥99.9%, from Sigma Aldrich): the whole was left, at 25° C., under stirring at 200 rpm, for 20 minutes. The paste thus obtained had a viscosity >10.sup.4 mPa×s as measured at 25° C., at a shear rate of 1 s.sup.−1 by way of a plate-cone measurement system using the MCR 302 rheometer from Anton-Paar.

[0060] The paste was subsequently printed using a polyester fabric screen having 55 filaments per cm (Estal® mono from Sefar) to give a 1 cm.sup.2×0.5 cm.sup.2 coating layer, and dried at 140° C., for 5 minutes. The coating layer had a surface resistivity of 360 Ω/sq as measured using a 4-point probe as described by L. J. van der Pauw, “A method of measuring specific resistivity and Hall effect of discs of arbitrary shape”, “Philips Research Reports” (1958), Vol. 13, pp. 1-9.

[0061] Whilst operating as described above, a commercial ink, i.e. 5% by weight poly(3,4-ethylenedioxythiophene)-polystyrenesulphonate (PEDOT:PSS) (product No. 76865 from Sigma Aldrich), was printed for the purpose of comparison, obtaining a coating layer which had a surface resistivity, measured as described above, of 320 Ω/sq.

[0062] From the data set out above, it can be seen how the paste obtained in accordance with the present invention has a surface resistivity entirely similar to that of the reference commercial ink.