LAYER COMPOSITIONS WITH IMPROVED ELECTRICAL PARAMETERS COMPRISING PEDOT/PSS AND A STABILIZER

Abstract

The present invention relates to a process for the production of a layer composition (10) with an electrically conductive layer (11), comprising the process steps: a) provision of a substrate (12) with a substrate surface (13); b) formation of a polymer layer (14) comprising an electrically conductive polymer (15) on at least a part of the substrate surface (13); c) application of a liquid stabilizer phase, comprising a stabilizer and a liquid phase, to the polymer layer (14) from process step b), wherein the stabilizer phase comprises less than 0.2 wt. %, based on the stabilizer phase, of the electrically conductive polymer,

wherein the stabilizer is an aromatic compound with at least two OH groups, and a layer composition (10) and uses thereof.

Claims

1-21. (canceled)

22. A capacitor which comprises a layer composition, the layer composition comprising S1. a substrate with a substrate surface, wherein the substrate comprises an electrode body of an electrode material, the surface of this electrode material being at least partly covered by a dielectric; S2. a polymer layer following the substrate surface and serving as a layer of a solid electrolyte, the polymer layer comprising an electrically conductive polymer; S3. a stabilizer layer following the polymer layer, comprising a stabilizer which is an aromatic compound with at least two OH groups.

23. The capacitor according to claim 22, wherein the electrically conductive polymer comprises at least one polythiophene, polypyrrole or polyaniline or one of their derivatives or a mixture of at least two of these.

24. The capacitor according to claim 22, wherein the electrically conductive polymer comprises at least one polythiophene with recurring units chosen from the group consisting of the general formula (I), the general formula (II) or the general formula (III) or a combination of at least two of these ##STR00002## wherein A represents an optionally substituted C.sub.1-C.sub.5-alkylene radical, R represents a linear or branched, optionally substituted C.sub.1-C.sub.18-alkyl radical, an optionally substituted C.sub.5-C.sub.12-cycloalkyl radical, an optionally substituted C.sub.6-C.sub.14-aryl radical, an optionally substituted C.sub.7-C.sub.18-aralkyl radical, an optionally substituted C.sub.1-C.sub.4-hydroxyalkyl radical or a hydroxyl radical, x represents an integer from 0 to 8 and in the case where several radicals R are bonded to A, these can be identical or different.

25. The capacitor according to claim 22, wherein the electrically conductive polymer is poly(3,4-ethylenedioxythiophene).

26. The capacitor according to claim 22, wherein the electrically conductive polymer additionally comprises at least one polymeric anion.

27. The capacitor according to claim 26, wherein the polymeric anion is polystyrenesulphonic acid.

28. The capacitor according to claim 22, wherein the electrode material is a valve metal or NbO.

29. The capacitor according to claim 22, wherein the electrode material is aluminium.

30. The capacitor according to claim 22, wherein the stabilizer is at least one compound selected from the group consisting of 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 2,3-dihydroxybenzene, dihydroxyalkylbenzene, trihydroxybenzene, dihydroxynaphthalene and derivatives thereof.

31. The capacitor according to claim 30, wherein the stabilizer is a gallic acid ester.

32. The capacitor according to claim 31, wherein the gallic acid ester is a tannin.

33. A process for the production of a layer composition with an electrically conductive layer, comprising the process steps: a) providing a substrate with a substrate surface; b) forming a polymer layer comprising an electrically conductive polymer on at least a part of the substrate surface; c) application of a liquid stabilizer phase, comprising a stabilizer and a liquid phase, onto the polymer layer from process step b), wherein the stabilizer phase comprises less than 0.2 wt. %, based on the stabilizer phase, of the electrically conductive polymer, wherein the stabilizer is an aromatic compound with at least two OH groups, wherein the layer composition is a capacitor and wherein the substrate comprises an electrode body of an electrode material, and a dielectric at least partly covers a surface of this electrode material.

34. The process according to claim 33, wherein after application of the stabilizer phase in process step c) the liquid phase is at least partly removed in a further process step d).

35. The process according to claim 33, wherein the stabilizer is at least one compound selected from the group consisting of 1,3-dihydroxybenzene, 1,4-dihydroxybenzene, 2,3-dihydroxybenzene, dihydroxyalkylbenzene, trihydroxybenzene, dihydroxynaphthalene and derivatives thereof.

36. The process according to claim 35, wherein the stabilizer is a gallic acid ester.35

37. The process according to claim 36, wherein the gallic acid ester is a tannine.

38. The process according to claim 33, wherein the liquid phase in process step c) comprises water or an alcohol or a mixture thereof.

39. The process according to claim 33, wherein the stabilizer phase in process step c) comprises the stabilizer in a concentration in a range of from 0.1 to 50 wt. %, based on the stabilizer phase.

40. The process according to claim 33, wherein the electrically conductive polymer comprises at least one polythiophene, polypyrrole or polyaniline or one of their derivatives or a mixture of at least two of these.

41. The process according to claim 33, wherein the electrically conductive polymer comprises at least one polythiophene with recurring units chosen from the group consisting of the general formula (I), the general formula (II) or the general formula (III) or a combination of at least two of these ##STR00003## wherein A represents an optionally substituted C.sub.1-C.sub.5-alkylene radical, R represents a linear or branched, optionally substituted C.sub.1-C.sub.18-alkyl radical, an optionally substituted C.sub.5-C.sub.12-cycloalkyl radical, an optionally substituted C.sub.6-C.sub.14-aryl radical, an optionally substituted C.sub.7-C.sub.18-aralkyl radical, an optionally substituted C.sub.1-C.sub.4-hydroxyalkyl radical or a hydroxyl radical, x represents an integer from 0 to 8 and in the case where several radicals R are bonded to A, these can be identical or different.

42. The process according to claim 41, wherein the electrically conductive polymer is poly(3,4-ethylenedioxythiophene).

43. The process according to claim 33, wherein the electrically conductive polymer additionally comprises at least one polymeric anion.

44. The process according to claim 43, wherein the polymeric anion is polystyrenesulphonic acid.

45. The process according to claim 33, wherein the formation of a polymer layer in process step b) is carried out by application of a dispersion containing particles of an electrically conductive polymer and a dispersing agent and the at least partial removal of this dispersing agent.

46. The process according to claim 45, wherein the particles of the dispersion in process step b) have a size (d.sub.50) of 70 nm and less.

47. The process according to claim 46, wherein the dispersion containing particles of an electrically conductive polymer in process step b) comprises organic solvents, water or mixtures of an organic solvent and water as the dispersing agent.

48. The process according to claim 33, wherein the electrode material is a valve metal or NbO.

49. The process according to claim 33, wherein the electrode material is aluminium.

Description

EXAMPLES

Example 1

Preparation of a Dispersion of Conductive Polymers

[0131] 868 g of deionized water, 330 g of an aqueous polystyrenesulphonic acid solution with an average molecular weight of 70,000 and a solids content of 3.8 wt. % were initially introduced into a 2 l three-necked flask with a stirrer and internal thermometer. The reaction temperature was kept between 20 and 25 C. 5.1 g of 3,4-ethylenedioxythiophene were added, while stirring. The solution was stirred for 30 minutes. 0.03 g of iron(III) sulphate and 9.5 g of sodium persulphate were then added and the solution was stirred for a further 24 h.

[0132] After the reaction had ended, for removal of inorganic salts 100 ml of a strongly acid cation exchanger (Lewatit S100, Lanxess AG) and 250 ml of a weakly basic anion exchanger (Lewatit MP62, Lanxess AG) were added arid the solution was stirred for a further 2 h. The ion exchanger was filtered off.

Example 2

Preparation of a Formulation of Conductive Polymers

[0133] 100 g of the dispersion from Example 1 and 4 g of dimethylsulphoxide (DMSO) were stirred intensively in a glass beaker with a stirrer.

Example 3

Preparation of a Homogenized Dispersion of Conductive Polymers

[0134] The poly(3,4-ethylenedioxythiophene)/polystyrenesulphonate dispersion from Example 1 was homogenized with a high pressure homogenizer five times under a pressure of 1,500 bar. The dispersion was subsequently concentrated in a rotary evaporator to a solids content of 2.5% and then additionally homogenized with the high pressure homogenizer another five times under a pressure of 1,500 bar.

Example 4

Preparation of a Formulation of Conductive Polymers

[0135] 44 g of the dispersion from Example 3, 52 g of distilled water and 4 g of dimethylsulphoxide (DMSO) were stirred intensively in a glass beaker with a stirrer.

Example 5

Preparation of a Formulation of Conductive Polymers

[0136] 100 g of the dispersion from Example 3 and 10 g of ethylene glycol were stirred intensively in a glass beaker with a stirrer and thereafter adjusted to a pH of 3 with aqueous ammonia.

[0137] The particle size d.sub.10 of 16 nm, particle size d.sub.50 of 20 nm and particle size d.sub.90 of 36 nm were determined from the dispersion obtained in this way. The conductivity of the dispersion determined by the above method was 455 S/cm.

Comparison Example 1

Preparation of a Dispersion of Conductive Polymers with Tannin

[0138] 0.5 wt. %, 1 wt. % and 2 wt. % of tannin (AldrichCAS no. 1401-55-4) were added to in each case 10 g of the dispersion from Example 4 in a glass beaker, with intensive stirring. The viscosities of these dispersions and that of the dispersion from Example 4 were determined (viscosity before storage). Thereafter, all 4 dispersions were stored in a closed glass beaker at 40 C. for 21 days and the viscosity of the dispersions was then determined again (viscosity after storage). The viscosities are to be found in Table 1.

TABLE-US-00001 TABLE 1 Viscosity Viscosity Ratio of viscosity Tannin addition before storage after storage before storage/ [wt. %] [mPas] [mPas] viscosity after storage 0 17 17 1 0.5 17 28 1.65 1 17 43 2.53 2 17 64 3.76

[0139] The viscosity of the dispersion without addition of stabilizer does not change due to the storage. On the other hand, the viscosities of the dispersions with addition of stabilizer increase significantly during storage. Comparison. Example 1 shows that the addition of even a relatively small amount of stabilizer leads to a significantly reduced storage stability of the dispersion.

Example 6

Production of Layer Compositions

[0140] A portion of the dispersion from Example 2 was knife-coated on to a piece of polyester film 1520 cm.sup.2 in size with a spiral bar (Erichson K HAND COATER 620 K bar no. 6). The coating was dried in a circulating air drying cabinet at 130 C. for 20 minutes. The coated polyester films were then each immersed in a solution of a stabilizer for 1 min and thereafter dried in a circulating air drying cabinet at 130 C. for 20 min. The stabilizer solutions used (all Aldrich) are to be found in Table 2. The stabilizer solutions were prepared by addition of the stabilizer to the corresponding solvent with intensive stirring. The surface resistance of the coatings was determined before and after storage, which took place in air at 150 C. for 192 hours. The surface resistances before storage and the increase in the surface resistance after storage, i.e. the ratio of surface resistance after storage to surface resistance before storage, are to be found in Table 2.

Comparison Example 2

Production of Layer Compositions

[0141] Coatings were produced from dispersions analogously to Example 6 and measured, but without an immersion in a stabilizer solution. The results are to be found in Table 2.

Comparison Example 3

Production of Layer Compositions

[0142] 0.1 g of tannin (AldrichCAS no. 1401-55-4) was added to 10 g of the dispersion from Example 2 with intensive stirring. Coatings were produced from this dispersion obtained in this way, analogously to Example 6, and measured, but without an impregnation in a stabilizer solution. The results are to be found in Table 2.

TABLE-US-00002 TABLE 2 Surface Increase in Concentration resistance surface of stabilizer before resistance [wt. %] and storage after Stabilizer solvent (/square] storage Example 6-1 1,4- 5%, water 66 4.6 dihydroxy- benzene Example 6-2 1,2,3- 5%, water 65 7.2 trihydroxy- benzene Example 6-3 propyl .sup.5%, ethanol 66 6.7 gallate Example 6-4 methyl .sup.5%, ethanol 67 4.2 gallate Example 6-5 tannin 1%, water 62 1.5 Example 6-6 tannin 5%, water 65 1.4 Example 6-7 tannin 10%, water 67 1.4 Comparison none 65 11.8 Example 2 Comparison tannin 66 2.6 Example 3 dispersion

[0143] As the results from the table show, the post-treatment with stabilizer leads to a significant increase in the heat stability of the surface resistance (Example 6-1 to 6-7) compared with the untreated sample (Comparison Example 2). Comparison of Example 6-5 with Comparison Example 3 moreover shows that the heat stability increases more due to the post-treatment with stabilizer than due to addition of the stabilizer to the dispersion.

Example 7

Production of Layers by Means of in situ Polymerization

[0144] A solution consisting of 0.5 g of 3,4-ethylenedioxythiophene (3.5 mmol), 4.5 g of Fe(III) tosylate (7.9 mmol) and 6.75 g of butanol (91 mmol) was prepared and a portion of the solution was spin-coated on to two glass microscope slides by means of a spin-coater at 2,000 rpm for 5 seconds. The samples were dried at 130 C. for 15 min and then washed in water for 15 min. After drying, two opposite edges of the microscope slide were coated with conductive silver. After the conductive silver had dried, the two silver strips were contacted. The coated microscope slides were then each immersed in a 5 wt. % aqueous tannin solution for 1 min and thereafter dried at 130 C. for 15 min.

[0145] The surface resistance was determined with a Keithley 199 Multimeter before and after storage, which took place in air at 130 C. for 93 hours. The surface resistances before storage and the increase in the surface resistance after storage, i.e. the ratio of surface resistance after storage to surface resistance before storage, are to be found in Table 3.

Comparison Example 4

Production of Layers by Means of in situ Polymerization

[0146] Coatings were produced analogously to Example 7 and measured, but without an impregnation in the tannin solution. The results are to be found in Table 3.

Comparison Example 5

Production of Layers by Means of in situ Polymerization

[0147] A solution consisting of 0.5 g of 3,4-ethylenedioxythiophene (3.5 mmol), 4.5 g of Fe(III) tosylate (7.9 mmol), 6.75 g of butanol (91 mmol) and 0.05 g of tannin (Aldrich) was prepared. Precipitates occurred immediately in the solution, and this was therefore not suitable for production of coatings.

TABLE-US-00003 TABLE 3 Surface resistance before Increase in surface storage (/square] resistance after storage Example 7 235 1.9 Comparison 241 3.4 Example 4

[0148] The results in Table 3 show that the in situ layers post-treated with stabilizer are significantly more heat-stable than untreated layers. By means of Comparison Example 5 it becomes clear that an addition of stabilizer to the reactive in situ solution to increase the heat stability of the layers produced from the solution is not possible.

Example 8

Capacitors

8.1. Production of Oxidized Electrode Bodies:

[0149] A porous aluminium foil with dimensions of 170 mm5 mm (anode foil) was oxidized with a forming voltage of 92 V in a 9% aqueous solution of ammonium adipate. The anode foil and a porous aluminium foil with dimensions of 200 mm5 mm (cathode foil) were each provided with a contact wire and were then wound up together with two cellulose separator papers and fixed with an adhesive tape. 5 of these oxidized electrode bodies were produced. The separator papers of the oxidized electrode bodies were then carbonized in an oven at 300 C.

8.2 Production of the Solid Electrolyte

[0150] The oxidized electrode bodies from 8.1 were immersed in the dispersion from Example 5 for 15 min. Thereafter, drying was carried out at 120 C. for 20 min, at 150 C. for 20 min and finally at 260 C. for 3 min. The capacitors were then impregnated in an aqueous solution containing 5 wt. % of tannin (Aldrich) for 15 minutes. Thereafter, drying was carried out at 120 C. for 20 min and at 150 C. for 20 min.

[0151] The electrical values of the 5 capacitors produced in the preceding manner were measured after production of the solid electrolyte and after storage in air in a drying cabinet at 125 C. for 576 hours. The mean electrical values and the relative change in the values (quotient of values after storage for 492 hours and starting values) are to be found in Table 4.

Comparison Example 6

Capacitors

[0152] Capacitors were produced as in Example 8 and measured, but no impregnation in a tannin solution was carried out during the production of the solid electrolyte. The mean electrical values of the 5 capacitors and the relative changes after storage for 576 hours are to be found in Table 4.

TABLE-US-00004 TABLE 4 Capac- Change itance in capac- ESR Change DF Change (F) itance (m) in ESR (%) in DF Example 8 60 0.95 36 1.4 2.4 2.1 Comparison 60 0.76 36 2.8 3.4 5.6 Example 6

[0153] The capacitors from Example 8 produced according to the invention have a significantly higher stability of their electrical values on storage under elevated temperature than the capacitors from Comparison Example 6. A post-treatment of the solid electrolyte with a stabilizer consequently significantly increases the heat stability of the capacitors.

LIST OF REFERENCE SYMBOLS

[0154] 1 Electrode body

[0155] 2 Electrode material

[0156] 3 Dielectric

[0157] 4 Electrode surface of anode body

[0158] 5 Solid electrolyte

[0159] 6 Capacitor body

[0160] 7 Stabilizer

[0161] 8 Pores

[0162] 9 Layer composition

[0163] 10 Conductive layer

[0164] 11 Substrate

[0165] 12 Substrate surface

[0166] 13 Polymer layer

[0167] 14 Electrically conductive polymer

[0168] 15 Stabilizer layer