Monomers of selected colour numbers and capacitors prepared therefrom

1. A monomer having the general formula (I):

wherein R 1 and R 2 each independently represent for hydrogen, for an optionally substituted C 1 -C 20 -alkyl group or C 1 -C 20 -oxyalkyl group, optionally interrupted by 1 to 5 oxygen atoms and/or sulfur atoms, or jointly for an optionally substituted C 1 -C 20 -dioxyalkylene group or C 6 -C 20 -dioxyarylene group,

wherein the monomer has a colour in a range of

a Hazen colour number determined according to test method described herein of at least 20,

to

a Gardner colour number determined according to test method described herein of not more than 5.

2. The monomer according to claim 1 , wherein the thiophene derivative monomers are those having the general formula (II)

in which

A stands for an optionally substituted C 1 -C 5 -alkylene residue or a C 6 -C 14 -arylene residue,

R stands for a linear or branched, optionally substituted C 1 -C 18 -alkyl residue, preferably a linear or branched, optionally substituted C 1 -C 14 -alkyl residue, an optionally substituted C 5 -C 12 -cycloalkyl residue, an optionally substituted C 6 -C 14 -aryl residue, an optionally substituted C 7 -C 18 -aralkyl residue, an optionally substituted C1-C4-hydroxyalkyl residue, or a hydroxyl residue,

x stands for an integer from 0 to 8 and

in the case where several residues R are bonded to A, these may be the same or different.

3. The monomer according to claim 1 , wherein the thiophene derivative monomers are those having the general formula (IIa)

in which R and x have the significance stated in claim 1 .

4. The monomer according to claim 1 , wherein the thiophene derivative monomer is 3,4-ethylenedioxythiophene.

5. The monomer according to claim 1 , wherein the range is from a Hazen colour number determined according to the test method described herein of at least 25 to a Gardner colour number determined according to the test method described herein of not more than 4.

6. The monomer according to claim 1 ,

wherein the range is from a Hazen colour number determined according to the test method described herein of at least 30 to a Gardner colour number determined according the test method described herein of not more than 3.

7. The monomer according to claim 1 , wherein the range is from Hazen colour number determined according to the test method described herein of at least 30 to a Gardner colour number determined according to the test method described herein of not more than 2.

8. The monomer according to claim 1 , wherein the range is from Hazen colour number determined according to the test method described herein of at least 30 to a Gardner colour number determined according to the test method described herein of not more than 1.

9. The monomer according to claim 1 , wherein the range is form a Hazen colour number determined according to the test method described herein of at least 50 to of not more than 200.

10. A method for the manufacture of a capacitor comprising

forming an anode of a valve metal;

forming a precursor comprising said anode and a dielectric;

adding an intrinsically conductive polymer on said precursor, wherein said intrinsically conductive polymer is based on the monomer as defined in claim 1 .

11. The method according to claim 10 , wherein said adding comprises

coating said precursor with said monomer;

polymerizing said monomer such that the intrinsically conductive polymer is obtained.

12. A capacitor, obtainable by the method according to claim 11 .

13. Use of a monomer as defined in claim 1 for the manufacture of a capacitor.

14. The monomer according to claim 1 , wherein the thiophene derivative monomers are those having the general formula (II)

in which

A stands for an optionally substituted C 1 -C 5 -alkylene residue or a an optionally substituted C 2 -C 3 - alkylene residue,

R stands for a linear or branched, optionally substituted C 1 -C 14 -alkyl residue, preferably a linear or branched, optionally substituted C 1 -C 14 -alkyl residue, an optionally substituted C 5 -C 12 -cycloalkyl residue, an optionally substituted C 6 -C 14 -aryl residue, an optionally substituted C 7 -C 18 -aralkyl residue, an optionally substituted C 1 -C 2 -hydroxyalkyl residue, or a hydroxyl residue,

x stands for an integer from 0 to 6, and in the case where several residues R are bonded to A, these may be the same or different.

15. The monomer according to claim 14 , wherein x stands for an integer 0 or 1.

16. A process for the manufacture of a capacitor which comprises utilizing the monomer as defined in claim 1 .