Radiation imagery chemistry: process – composition – or product th – Radiation sensitive product – Identified backing or protective layer containing
Reexamination Certificate
1999-11-04
2001-12-25
Ashton, Rosemary (Department: 1756)
Radiation imagery chemistry: process, composition, or product th
Radiation sensitive product
Identified backing or protective layer containing
C430S527000, C250S503100, C427S398100
Reexamination Certificate
active
06333145
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method for producing a polymeric conductive layer on an object. This invention relates especially to a method for producing a polymeric conductive layer of polythiophene and derivatives.
BACKGROUND OF THE INVENTION
The production and the use of electronically conductive polymers are well known in the art. In DE-A-41 32 614 the production of film-forming, electronically conductive polymers by anodic oxidation of pyrroles, thiophenes, furans or aromatic amines (or their derivatives.) is effected with a sulphone compound present in the electrolyte solution. In U.S. Pat. No. 5,254,648 the preparation of electrically-conducting polythiophenes are described. In U.S. Pat. No. 5,236,627 a method for the preparation of polypyrrole is described. There are several uses for such polymers, they can be used as electrodes in capacitors, as disclosed in, e.g., EP-A-803 886, they are useful as a replacement for metal conductors in electrostatic discharge elimination and electromagnetic shielding as disclosed in, e.g., WO-A-96/266355. The layers of electrically-conductive polymers can be shaped into “wires” or channels using conventional photolithographic techniques and can then be used as interconnects for microchip fabrication, in devices requiring controlled resistance of resistive “channels”, in non-linear optics, etc. Such shaping of electrically-conductive polymers into “wires” or channels has been disclosed in U.S. Pat. No. 5,561,030. Also in WO-A-97/18944 methods for patterning electrically-conductive polymer layers are disclosed.
Many of the electrically conductive polymers can not be applied to an object from an aqueous solution but have to be applied from a composition with organic solvents, e.g. polyaniline is frequently processed from solutions in cresol. In the light of ecological needs, the need to use organic solvents is a drawback and can hamper the widespread use of electrically conductive polymers. In EP-A-440 957 a method for preparing polythiophene in an aqueous environment and applying polythiophene from an aqueous solution has been described. Such a solution is up until now mostly be used in photographic materials as disclosed in, e.g., U.S. Pat. Nos. 5,312,681, 5,354,613 and 5,391,472.
An other limiting factor in the use of electrically-conducting polymers is the fact that, when the polymer is applied in an amount leading to good conductivity, the layers are frequently coloured, which is undesired when these polymer layers are to be used as transparent electrode in LCD or electroluminescent devices. Therefore much efforts have be done to increase the conductivity of the polymers without increasing the coloration so that thin, almost colourless layers of electrically-conductive polymers can be applied having high conductivity.
In EP-A-686 662 it has been disclosed that layers of polythiophene coated from an aqueous composition could be made with high conductivity. Therefore the aqueous composition of the polythiophene comprises further a di- or polyhydroxy compound and after coating said composition and drying the layer, the layer has to be treated at temperatures between 150 and 250° C. in a separate production step. Although the layers disclosed in EP-A-686 662 have a low resistivity of about 300 &OHgr;/square and lower, there is still a need for a method wherein the low resistivity can be reached at lower temperature and without the need of a separate annealing step.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of the invention to provide a method for producing highly conductive layers of electrically-conducting polymers on an object without needing an additional annealing step at elevated temperatures.
It is an other object of the invention to provide an aqueous composition of an electrically conductive polymer that can be used to provide a highly conductive layer on an object.
It is a further object of the invention to provide a polymeric film carrying a highly conductive layer of an electrically conductive polymer, which can be used as electrodes in displays, e.g., LCD's, electroluminescent devices, capacitors, etc.
The objects of this invention are realised by providing a method for producing a polymeric conductive layer on an object comprising the steps of:
providing an aqueous composition containing:
a polythiophene,
a polyanion compound and
an aprotic compound with a dielectric constant, &egr;, ≧15,
applying said composition to said object forming a layer and drying said layer to form a conductive polymeric layer on said object, characterised in that said object and said layer are kept at a temperature below 100° C. and said conductive polymeric layer has a resistivity of at most 2 k&OHgr;/square.
Preferably said polythiophene has formula
in which, each of R
1
and R
2
independently represents hydrogen or a C1-4 alkyl group or together represent an optionally substituted C1-4 alkylene group or a cycloalkylene group, preferably an ethylene group, an optionally alkyl-substituted methylene group, an optionally C1-12 alkyl- or phenyl-substituted 1,2-ethylene group, a 1,3-propylene group or a 1,2-cyclohexylene group,
The objects of the invention are further realised by providing an aqueous composition containing:
a polythiophene with formula
in which, each of R
1
and R
2
independently represents hydrogen or a C1-4 alkyl group or together represent an optionally substituted C1-4 alkylene group or a cycloalkylene group, preferably an ethylene group, an optionally alkyl-substituted methylene group, an optionally C1-12 alkyl- or phenyl-substituted 1,2-ethylene group, a 1,3-propylene group or a 1,2-cyclohexylene group,
a polyanion compound and
an aprotic compound with dielectric constant, &egr;, ≧15 selected from the group consisting of sulphones, sulphoxides, organic phosphate esters, organic phosphonates, organic phosphamides, urea, derivatives of urea and mixtures thereof.
DETAILED DESCRIPTION OF THE INVENTION
It was found after experimentation that the annealing step, necessary to enhance the conductivity of a layer containing polythiophene and a di- or polyhydroxy compound could be omitted. When instead of such a di- or polyhydroxy compound, an aprotic compound (in this document aprotic is used to indicate compounds not carrying hydroxyl or carboxyl groups) with a dielectric constant, &egr;≧15 was used, a layer of polythiophene applied to an object having a resistivity of lower than 2 k&OHgr;/square could be prepared by applying an aqueous composition with a polythiophene and said aprotic compound (Further on Compound A) to the object and simply drying it at a temperature lower than 100° C., or more preferably below 90° C. Even when the drying proceeded at a temperature lower than 50° C. a very low resistivity could be achieved. It was possible to prepare layers with a resistivity below 500 &OHgr;/square by simply drying the layer at a temperature lower than 50° C. Thus no special, separate annealing step was necessary which is advantageous since it simplifies the production process of polymeric conductive layers and makes it both less expensive and more ecological since, in the method of this invention, less calories have to be used to form the conductive layer. Furthermore the absence of an annealing step at high temperature makes it possible to use the method of this invention for applying conductive layers on stretched polymeric films, e.g. stretched polyester, that risk to shrink and curl when treated at temperatures above 120 or 150° C. Thus the method of this invention can also be used for applying conductive polymer layers on non-heat stable polymeric objects.
All resistivities in this document are measured according to the following method: A strip of the substrate coated with the conductive polymer is taken. This strip has a length of 27.5 cm and a width of 35 mm. Over the width of the strip electrodes are applied at a distance of 10 cm of each other. The electrodes are made of a conductive polymer, ECCOCOAT CC-2 available from Emerson & Cumming Speciality polymers. Over said ele
Andriessen Hieronymus
Cloots Tom
Loccufier Johan
Louwet Frank
AGFA-GEVAERT
Ashton Rosemary
Breiner & Breiner L.L.C.
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