Classifications

• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D17/00—Constructional parts, or assemblies thereof, of cells for electrolytic coating
  • C25D17/10—Electrodes, e.g. composition, counter electrode
  • C25D17/12—Shape or form
• • C—CHEMISTRY; METALLURGY
  • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
  • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
  • C25D21/00—Processes for servicing or operating cells for electrolytic coating
  • C25D21/12—Process control or regulation

Definitions

• Electrodes and methods are described with the aid of which it is possible to electrochemically deposit thin layers with a largely homogeneous layer thickness on large-area substrates with relatively high electrical resistances.
• the thin layers to be deposited must have a high degree of homogeneity of their properties, which is usually only achieved by a homogeneous layer thickness distribution.
• These thin layers are, for example, electro-optically, opto-electrically or electromagnetically active layers (for example electrochromic layers, layers for photovoltaics, magnetic storage layers, but also metallizations of semiconductors).
• Vacuum processes have a number of disadvantages, for example they are comparatively cost-intensive and, in principle, various thin layers cannot be produced by vacuum processes (for example complex compounds or conductive polymers).
• Electrochemical deposition is cheaper to implement and also enables materials such as complex compounds and conductive polymers to be deposited.
• the homogeneous deposition of thin layers on electrically conductive substrates by electrochemical deposition is state of the art and possible without any problems if the substrates to be coated are metals and consequently have a sufficiently high electrical conductivity.
• the specific resistance of the metals is in the range between 1.5 x 10 "6 ⁇ cm and 5 x 10 " 5 ⁇ cm. Some characteristic specific resistances of metals are mentioned below: silver 1.49 x 10 "6 ⁇ cm, copper: 1.55 x 10 " 6 ⁇ cm, aluminum: 2.41 x 10 "6 ⁇ cm, nickel 6.05 x 10 " 6 ⁇ cm, lead 1.88 x 10 "5 ⁇ cm and titanium: 4.35 x 10 " 5 ⁇ cm.
• the workpieces to be coated have a conductivity that is significantly below that of the metals, this is often so high Voltage drop from the contacting of the workpiece, that as the distance from this contacting increases, the deposited layer thickness becomes smaller and smaller, so that the inexpensive and well-controlled electrochemical deposition cannot be used with such materials and then often due to much more complicated and usually also more expensive processes, such as must be replaced by vacuum coating processes.
• Materials with such lower resistances are primarily the semiconductor materials which are widely used in microelectronics, such as germanium, silicon, gallium arsenide or indium phosphide.
• the specific resistances of these semiconductor materials are in the range of 10 3 ⁇ cm for so-called semi-insulating material and up to 10 "4 ⁇ cm for highly doped variants.
• electrically conductive, optically transparent materials for example as control electrodes for liquid crystal displays, organic LED systems and electrochromic arrangements Used have significantly lower electrical conductivities than metals, such as tin-doped indium oxide, also called ITO (from ITO ...
• indium tin oxide fluorine- or antimony-doped tin dioxide or aluminum-doped zinc oxide
• these transparent conductive materials are usually applied to glass or plastic substrates in layer thicknesses of less than 1 ⁇ m, resulting in surface resistances that are usually significantly greater than 1 D is.
• the use of thin metal films on nonconducting substrates despite the low resistivity of the metals due to the low layer thickness of a high voltage drop may occur.
• the greater the specific electrical resistance of such materials the smaller their layer thickness, the higher the current densities to be used for electrochemical deposition and the larger the surfaces to be coated, the greater the voltage drop on the substrate to be coated.
• With increasing voltage drop the homogeneity of the deposited layers becomes worse and worse. Particularly great demands are placed on the homogeneity of such electrochemically deposited layers optically active layers, for example in the case of electrochromic or photochromic layers.
• US Pat. No. 6,136,587 specifies various possibilities for improving the homogeneity of the metal deposition on semiconductor wafers. Among other things, this is achieved by increasing the electrolyte resistance between the counterelectrode and the workpiece to be coated by reducing the ionic conductivity of the electrolyte, by increasing the electrode spacing or by introducing a porous separator. Also the use of a smaller counter electrode and the Periodic current reversal (change of polarity) should lead to an improvement in the homogeneity of the deposition. However, all of these measures only lead to a substantial improvement in the deposition homogeneity in the case of relatively small-area substrates and are therefore not applicable to the present task.
• the patent US4818352 describes a method for depositing electrochromic layers, in particular Prussian blue layers on large-area substrates with relatively high electrical resistances, such as thin ITO or thin doped tin dioxide layers on glass.
• An improvement in the homogeneity is achieved in that the glass pane to be coated is contacted not only on one side on one edge, but all around on all edges. This all-round contacting can improve the homogeneity of the electrochemical deposition somewhat, since the voltage drop is now no longer only from one contact point over the entire surface to be coated, but from all 4 sides over the surface. If the area contacted in this way exceeds a certain size, however, the inhomogeneity of the electrochemical deposition resulting from the voltage drop is again too large for technical use of the product.
• the invention is therefore based on the object of specifying a device and a method with which it is possible to provide large-area substrates with comparatively high electrical resistances by means of electrochemical deposition with thin layers of largely homogeneous layer thickness.
• the large-area electrochemical deposition of electro-optical and opto-electrical thin layers, preferably electrochromic or photochromic layers should also be possible, the quality of which makes particularly high demands.
• the invention should in particular also be suitable for electrochemically providing areas larger than 1 m 2 , for example heat-insulating glass for insulating glass windows with sizes of 1.20 mx 2.00 m, so that the products thus produced can be used in building glazing.
• the object is achieved in that the counterelectrode is divided into a plurality of electrode segments and different voltages can be applied between each individual electrode segment and the substrate to be coated.
• a counterelectrode segmented in this way essentially from each electrode segment coated the opposite parts of the large-area substrate. This ensures that a largely homogeneous current density distribution is achieved over the entire substrate to be coated. This current density distribution is the prerequisite for good homogeneity of the deposited layers.
• possible embodiment variants are shown schematically on the basis of two figures.
• FIG. 1 shows an example of the segmented counter electrode according to the invention.
• FIG. 2 shows an electrolysis cell with the substrate to be coated and segmented counterelectrode.
• the individual segmented counter electrodes can preferably all be positioned in the electrolyte at the same distance from the substrate to be coated.
• they can, for example, be attached to a plastic plate, as is shown schematically in FIG. 1 denotes the plastic plate on which the electrode strips 2 are fixed by means of fastening screws 3.
• Metal rails 4, for example made of titanium, are used for contacting and are guided upwards on the rear side of the plastic plate 1 and are connected to the respective electrode strips 2 using metal screws 5, which can also be made of titanium.
• the number and size of the electrode strips can be dimensioned differently, depending on the size of the substrate to be coated and on the voltage drops occurring in it.
• Activated titanium electrodes, graphite electrodes or other materials customary in the prior art can be used as electrode materials.
• FIG. 2 shows a section through an electrolysis cell with the segmented counterelectrode according to the invention, with 6 denoting the electrolysis vessel, 7 the large-area substrate to be coated with comparatively high resistance, 8 the contacting of the substrate and 9 the top edge of the electrolyte liquid.
• the shapes shown in the figures represent examples of the segmentation of the counterelectrode according to the invention.
• Other variants can also be used to design the segmentation, for example by attaching the segments directly to the wall of the electrolysis vessel or by creating a segment structure on a glass or plastic surface by vapor deposition.
• each of these counter-electrode segments is controlled by its own voltage source, one pole of this voltage source being connected to the corresponding counter-electrode segment and the other pole of each voltage source being connected to the substrate to be coated.
• an individual voltage of its own can be applied between each counter electrode segment and the substrate.
• the voltage When realizing a homogeneous current density across the substrate, the voltage generally increases from the uppermost segment electrode to the lowest segment electrode.
• all counter-electrode segments are controlled by a voltage source, and a suitable electrical resistance which is adapted with regard to the electrical parameters is connected between this voltage source and each individual segment counter-electrode.
• rectifiers are used as voltage sources.
• the use of rectifiers is the easiest way to provide the necessary individual voltages. With rectifiers, self-regulating electrolysis operation is possible, in which the currents specified for the individual segments are realized by the different voltages that arise at the rectifiers.
• electrochemical voltage sources can also be used as voltage sources. Also by using electrochemical voltage sources, such as batteries or accumulators, the voltage and power supply of the device according to the invention can take place.
• the individual electrode segments of the counterelectrode have a uniform size and geometric shape. Such an embodiment is shown in FIG. 1 and was used in the exemplary embodiments described below.
• the total current required to achieve the desired layer is divided evenly between the individual counter electrode segments. With the same current intensity at each counter electrode segment, a different voltage results for each of these counter electrode segments.
• These different voltages are realized by the voltage source belonging in each case to the corresponding counter electrode segment or, if only one voltage source is used, by different resistors connected between the voltage source and the counter electrode segment.
• the material additionally deposited there without using the auxiliary electrode according to the invention is now practically exclusively deposited on the auxiliary electrode and can be removed from the latter if necessary.
• Such an auxiliary electrode is shown in FIG. 2 (10).
• the thin layers electrochemically deposited using the device according to the invention and the method according to the invention are preferably optically active layers.
• the novel method of electrochemical deposition of thin layers is particularly advantageous for the production of optically active layers, since particularly high demands are placed on such layers with regard to the homogeneity of the layer thickness distribution.
• the optically active layers are, in particular, electro-optically or opto-electrically active layers.
• Optoelectrically active layers are used, for example, in thin-film solar cells. This preferably concerns materials such as cadmium telluride, copper indium diselenide or copper indium disulfide. These can be deposited electrochemically homogeneously on thin metal or metal oxide layers using the method and the device according to the invention.
• the thin layers also include electromagnetically active layers. Electromagnetically active layers are used, for example, as information storage layers.
• the thin layers also include metal or metal oxide layers.
• the solderable metal layers on semiconductor components. The contacting of semiconductor components usually takes place at these solderable metal layers.
• thin layers are also semiconductor layers. These include the compound semiconductors cadmium telluride, copper indium diselenide and copper indium disulfide already mentioned, but also sensor-active oxides.
• metal oxides, complex compounds or conductive polymers are also deposited as thin layers. In the latter two cases, the use of the method and the device according to the invention is particularly advantageous and also necessary, since thin layers of these materials cannot be produced using the known vacuum technologies.
• Such thin layers are particularly suitable for electrochromic elements, as is also demonstrated in the exemplary embodiments described below.
• Components for organic electroluminescence can also be interposed by conductive organic polymers according to the invention Method and be deposited with the device according to the invention, are significantly improved in terms of their efficiency and optical quality.
• the optically active layers are electrochromic and / or photochromic layers.
• Electrochromic layers are layers whose electro-optical properties can be changed by oxidation or reduction. This includes layers made of the following materials: metal oxides, conductive polymers and complex compounds.
• Photochromic layers are layers whose electro-optical properties can be changed by exposure to light.
• Typical examples of the electrochromic layers according to the invention are tungsten oxide, nickel oxide, Prussian blue or polyaniline.
• Tungsten oxide is a cathodic electrochromic material, which means that it is colored in the case of cathodic reduction (blue) and decolorized in the case of anodic oxidation. Color changes from transparent to colored with anodic oxidation are possible on the basis of nickel oxide, Prussian blue and polyaniline.
• semiconductors or semiconductor layers are used as large-area electrically conductive substrates with relatively high resistances due to their comparatively high electrical resistance.
• the large-area electrically conductive substrates with relatively high resistances are thin metal layers on non-conductive substrates. Although metals have a low specific resistance, the resistance in thin metal films can become so high due to the small layer thickness that homogeneous thin layers can only be electrochemically deposited on the large-area thin metal films with the device and the method according to the invention.
• the large-area electrically conductive substrates with relatively high resistances are transparent conductive oxide layers on transparent substrates.
• Transparent conductive oxide layers are, for example, tin-doped indium oxide, antimony or fluorine-doped tin dioxide or aluminum-doped zinc oxide.
• Transparent substrates can be, for example, glass or plastic substrates. Polycarbonates, for example, can be used as plastic substrates. embodiments
• a doped tin dioxide layer with a fluoro-4 mm thick glass plate coated (K-glass from Pilkington) of the size 30 x 50 cm 2 was the deposition of a tungsten oxide film.
• the surface resistance of the substrate was 17 ⁇ / T.
• the deposition took place from a 0.05 molar aqueous peroxy tungstic acid solution. This solution was prepared by dissolving the appropriate amount of tungsten in an excess amount of hydrogen peroxide and then diluting it. Hydrogen peroxide which was not used in the production was catalytically decomposed by immersing a platinized titanium electrode in the solution.
• the conductivity of the electrolyte was approximately 6 mS / cm.
• the glass pane to be coated was placed in the container such that a 1 cm wide strip protruded from the solution.
• a copper conductive tape (tape 1181 from 3M) was glued to these strips for contacting over the full width of 50 cm.
• Each of the 6 electrode strips was 50 cm long corresponding to the width of the glass plate to be coated and 4 cm wide. The distance between the individual strips was 0.7 cm.
• the electrode strips consisted of 1 mm thick ruthenium oxide coated titanium.
• This strip served as an auxiliary electrode.
• 6 rectifiers with a maximum of 40 V and 3 A of the type PS-2403D (Conrad) were used for the electrolytic tungsten deposition.
• the negative poles of all 6 rectifiers were connected to the glass plate to be coated and the auxiliary electrode, while each positive pole of the 6 different rectifiers was connected to a different one of the 6 individual counter electrode segments was connected.
• a current of 80 mA was set on each of the 6 rectifiers, so that the total current of the deposition was 480 mA.
• the voltage required could be self-regulating on each rectifier.
• a 10-minute cathodic deposition of the tungsten oxide layer from the tungsten peroxyacid solution was carried out under these conditions.
• a tungsten oxide layer with great homogeneity of the layer thickness of 180 nm was obtained.
• Deviations in optical homogeneity were less than 5%.
• layers were obtained which had significantly higher layer thicknesses of up to 225 nm in an upper approximately 4 cm wide strip. The deviations in the optical homogeneity were up to 25%.
• a doped tin dioxide layer with a fluorine-coated 4 mm thick glass plate (K-glass from Pilkington) of the size 30 x 50 cm 2 was the deposition of a Prussian blue film.
• the surface resistance of the substrate was 17 ⁇ / D.
• the deposition was carried out from an aqueous solution which contained 0.5 mol / l potassium hydrogen sulfate, 0.005 mol / l iron (III) sulfate and 0.005 mol / l potassium hexacyanoferrate (III).
• the conductivity of this solution was approximately 114 mS / cm.
• the glass pane to be coated was placed in the container such that a 1 cm wide strip protruded from the solution.
• a copper conductive tape (tape 1181 from 3M) was glued to these strips for contacting over the full width of 50 cm.
• the deposition was carried out in an arrangement with 6 counter electrode segments, as described in exemplary embodiment 1.
• 6 rectifiers were also used for the electrolytic Prussian-Blue deposition, the negative poles of which were all connected to the glass plate to be coated and the auxiliary electrode, while each positive pole of the 6 different rectifiers was connected to another of the 6 individual counter electrodes.
• a current of 3.5 mA was set on each of the 6 rectifiers, so that the total current of the deposition was 21 mA. The required voltage was able to adjust itself to every rectifier.
• a glass plate (K glass from Pilkington) of size 80 ⁇ 120 cm 2 was used to deposit a tungsten oxide film.
• the surface resistance of the substrate was 17 ⁇ / D.
• the deposition was carried out from a solution as described in Example 1.
• the glass pane to be coated was placed in the coating bath in such a way that a 1 cm wide strip protruded from the solution.
• a copper conductive tape (tape 1181 from 3M) was glued to these strips for contacting over the full width of 120 cm.
• the electrode strips consisted of 1 mm thick iridium oxide coated titanium.
• a 1 mm thick platinum-coated titanium strip with a length of 120 cm and a width of 4 cm was attached to the upper part of the glass plate to be coated and immersed approximately 0.5 cm deep in the electrolyte solution.
• This strip served as an auxiliary electrode.
• 17 rectifiers were used for the electrolytic tungsten deposition. The negative poles of all 17 rectifiers were connected to the glass plate to be coated and the auxiliary electrode, while each positive pole of the 17 different rectifiers was connected to another of the 17 individual counter electrodes. There was one on each of the 17 rectifiers Current of 190 mA set, so that the total current of the deposition was 3.23 A. The voltage required could be self-regulating on each rectifier.
• a tungsten oxide layer was cathodically deposited for 10 minutes under these conditions. A tungsten oxide layer with a layer thickness of 180 nm was obtained. Deviations in optical homogeneity were less than 5%.

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• 2001
  • 2001-01-04 DE DE10100297A patent/DE10100297A1/de not_active Withdrawn
  • 2001-09-24 WO PCT/DE2001/003676 patent/WO2002053806A2/fr not_active Ceased
  • 2001-09-24 DE DE50112278T patent/DE50112278D1/de not_active Expired - Lifetime
  • 2001-09-24 AT AT01272605T patent/ATE358194T1/de active
  • 2001-09-24 AU AU2002223435A patent/AU2002223435A1/en not_active Abandoned
  • 2001-09-24 EP EP01272605A patent/EP1534880B1/fr not_active Expired - Lifetime
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