Electrolyte and method for the deposition of a matt metal layer

Description

[0001] This invention relates to an electrolyte as well as a method for the deposition of a matt metal layer on a substrate surface. In particular, the invention relates to an electrolyte which has a low concentration of the deposition metal and a method to deposit a matt metal layer by using such electrolytes.

[0002] In general, it is the intention when depositing metal layers on substrate surfaces to gain a plain and glossy metal layer on the substrate surface. The metal layer deposited may have functional properties, which properties can optimise the substrate surface for the later proposal, or decorative effects should be obtained. According to the intended use of the substrate, sometimes it is preferred to have a non-glossy, matt or so-called pearlbrite metal layer on the substrate surface. On one side, this intention can be based on the optical appearance of the deposit, on the other side matt or so-called pearlbrite deposits have specific technical properties, like for example to be non-glare, which properties may be desirable for technical or decorative use. The application area for such a matt or pearlbrite metal layers is, for example, jewellery industry, fitting industry, automotive industry, as well as optical or fine mechanical industry. Especially in these areas non-glare metal layers are desired. In the area of jewellery industry, the deposition of matt or pearlbrite metal layers of non-allergic or low allergic metals is requested. The same is true for the application of matt or pearlbrite metal layers in the area of kitchen machinery and kitchen implements.

[0003] In the field of optical or fine mechanical industry the deposition of matt or pearlbrite metal layers of different metals is of interest due to the different features which come along with the different metals, thus the substrate surface can be adapted to the later technical use. In this concern, for example, the ductility, the hardness, the corrosion resistance, or comparable mechanical properties of the substrate surface can be optimised.

[0004] The international patent application WO 2007/076898 discloses an electrolyte as well as a method for the deposition of matt metal layers, especially of the metals vanadium, chrome, manganese, iron, cobalt, nickel, copper, zinc, ruthenium, rhodium, palladium, silver, indium, tin, antimony, tellurium, rhenium, platinum, gold, thallium, bismuth, or alloys of these. For the deposition of these metals on a substrate surface, according to WO 2007/076898, an emulsion and/or dispersion is formed in the electrolyte by addition of an emulsion agent and/or dispersion agent, or a wetting agent.

[0005] Several other documents can be found in the patent literature which are related to electrolytic deposited metal layers from baths inter alia comprising alkylene oxides, e.g. US 3928149 A, WO 03100137 A2, GB 1236811 A, US 4119502 A, DE 2522130 B1, EP 1001054 A2, JP 2005120425 A, US 3700570 A, US 2006283715 A1, D10 WO0068464A2 and US 3839165 A.

[0006] A drawback of the electrolyte as well as the method known from the state of the art is that sometimes it is difficult to gain even deposits on the substrate surface. Thus, it is the object of this invention to optimise the electrolyte as well as the method known from the state of the art.

[0007] This object is solved by an electrolyte for the deposition of a matt metal layer of a metal of the group consisting of Co, Ni, Cu, Sn, or an alloy of these metals on a substrate surface, wherein the electrolyte comprises a substituted or unsubstituted polyalkylene oxide or a derivate of a substituted or unsubstituted polyalkylene oxide, or a wetting agent, wherein the wetting agent is fluorated or perfluorated, or is a quaternary ammonium compound substituted with a polyalkalylene oxide, for building an emulsion and/or dispersion in the electrolyte, characterised in that the electrolyte comprises at least one halogenide, sulphate, or sulfonate of an element of the group consisting of sodium, potassium, aluminium, magnesium, or boron. In an embodiment, a methanesulfonate of sodium, potassium, or magnesium is preferred. In another embodiment, aluminium sulphate and/or boron tetrafluoride is preferred.

[0008] Surprisingly it was found that the addition of soluble compounds of heavy cations, especially of an alkaline halogenide or alkaline earth halogenide, an alkaline sulphate or alkaline earth sulphate, or an alkaline sulfonate or alkaline earth sulfonate as well as aluminium sulphate, aluminium chloride, or boron tetrafluoride, alone or in combination, is capable to overcome the drawbacks known from the state of the art. These compounds can be used to increase the density of the electrolyte in the inventive way.

[0009] By increasing the density of the electrolyte, the cloud point is exceeded, which effect is to be avoided by normal plating electrolytes, but here leads to the desired matt effect of the deposited metal layer. The addition of the mentioned inert compounds which do not comprise any depositable metal cations increases the density so that a matt metal layer is deposited even at a very low concentration of plating metal in the electrolyte.

[0010] According to the invention, the electrolyte comprises a density increasing compound
within a concentration in the range of from 2 0% to 100% by weight of the concentration of
the metal to be deposited. Preferably, the alkali compound or alkaline earth compound is comprised in the inventive electrolyte in a range between 20% to 60% by weight of the concentration of the metal to be deposited.

[0011] Furthermore, it was surprisingly found that the addition of a surface active wetting agent to the inventive electrolyte is possible. The addition of a surface active wetting agent supports the even deposition of metal layers further. To the electrolytes known from the state of the art the addition of surface active wetting agents was not possible since those surface active wetting agents would influence the formation of an emulsion and/or dispersion in the electrolyte, thereby influencing the matt or pearlbrite effect of the electrolyte. If surface active wetting agents were added to the electrolytes known from the state of the art, the deposited metal layers turned to be glossy instead of being non-glare.

[0012] In the inventive electrolyte, the addition of surface active wetting agents is possible without influencing the matt effect of the electrolyte.

[0013] The surface active wetting agent which can be added to the inventive electrolyte may be a wetting agent of the group consisting of alkyl sulphates, sulfosuccinic acid, and betaines.

[0014] The surface active wetting agent may be comprised in the inventive electrolyte in a concentration between 0,01 mol/l and 100 mol/l, preferably between 0,1 mol/l and 10 mol/l.

[0015] In a preferred embodiment, the density increasing compound in the inventive electrolyte is sodium sulphate, magnesium sulphate, or aluminium sulphate.

[0016] In terms of the method, the object of the invention is solved by a method for the electrolytic deposition of a matt metal layer on a substrate surface, which matt metal layer is deposited from an electrolyte forming an emulsion and/or dispersion by conducting a current between a cathodic contacted substrate surface and an anode, which method is characterised in that 10 to 50% by weight of the metal to be deposited comprised in the electrolyte is substituted by at least on density increasing halogenide, sulphate, or sulphonate of an element of the group consisting of sodium, potassium, aluminium, magnesium, or boron.

[0017] It is the inventive idea to substitute some of the concentration of the metal to be deposited in the electrolyte by a density increasing compound, thereby reducing the concentration of the metal to be deposited and increasing the density of the electrolyte.

[0018] By doing so, on one hand, due to the less amount of metal to be deposited in the electrolyte an economic benefit is gained, since less deposition metal has to be used to formulate the electrolyte. On the other hand, due to the addition of an alkali compound and/or alkaline earth compound, the density of the electrolyte is increased, which leads to a more even deposition of the metal on the substrate surface. Furthermore, it was found that due to the increased density of the electrolyte, the addition of a surface active wetting agent is possible without influencing the matt appearance of the deposited metal layer in an unintended way.

[0019] The invention is described further in terms of examples, while the subject matter of the invention is not limited to these examples.

Examples

Example 1:

[0020] From a Watts-type electrolyte comprising:

190 g/l nickel sulphate 6aq

40 g/l boric acid

30 g/l nickel chloride 6aq

5 g/l sodium saccharinate and

300 g/l magnesium sulphate 7aq

3 mg/l PEG 10.000

a matt nickel layer was deposited in 10 minutes at a temperature of 52° C and a current density of 5 A/dm². The pH-value of the electrolyte was about 4,2. The substrate to be plated was moved through the electrolyte at a speed of 2 m/min. The structure of the matt nickel layer deposited was identical to the structure of a matt nickel layer deposited from an electrolyte comprising 3 mg/l of a polyethylenglycol having an average molecular weight of 10.000 g/mol, which electrolyte comprises:

440 g/l nickel sulphate 6aq

40 g/l boric acid

30 g/l nickel chloride 6aq

5 g/l sodium saccharinate and

3 mg/l PEG 10.000

Example 2:

[0021] From a Watts-type electrolyte comprising:

190 g/l nickel sulphate 6aq

40 g/l boric acid

30 g/l nickel chloride 6aq

5 g/l sodium saccharinate and

300 g/l magnesium sulphate 7aq

3 mg/l PEG 10.000

a matt nickel layer was deposited in 10 minutes at a temperature of 52° C and a current density of 5 A/dm². The pH-value of the electrolyte was about 4,2. The substrate to be plated was moved through the electrolyte at a speed of 2 m/min. The structure of the matt nickel layer deposited was identical to the structure of a matt nickel layer deposited from an electrolyte comprising 3 mg/l of a polyethylenglycol having an average molecular weight of 10.000 g/mol, which electrolyte comprises:

440 g/l nickel sulphate 6aq

40 g/l boric acid

30 g/l nickel chloride 6aq

5 g/l sodium saccharinate and

3 mg/l PEG 10.000

Example 3:

[0022] From a Sn/Co-electrolyte comprising:

120 g/l sodium gluconate

50 g/l cobalt (II) sulphate 7aq

25 g/l tin (II) sulphate

260 g/l sodium sulphate and

1 mg/l PEG 35.000

in 5 minutes at a temperature of 45°C and a current density of 0,5 A/dm² a very fine matt layer of a tin-cobalt alloy was deposited. The pH-value of the electrolyte was about 8,4 and the substrate to be plated was moved through the electrolyte at a speed of 2 m/min. The deposited very fine matt layer was identical to a layer deposited from an electrolyte comprising

120 g/l sodium gluconate

100 g/l cobalt(II) sulphate 7aq

50 g/l tin (II) sulphate

1 mg/l PEG 35.000.

[0023] The above embodiments clearly show that the inventive addition of an alkali compound or alkaline earth compound to an electrolyte composition known from the state of the art enables the reduction of the plating metal concentration in the electrolyte, without influencing the plating result. This enables plating electrolytes having a very low concentration of plating metal which gives great economic benefit.

Example 4:

[0024] From a Ni-electrolyte comprising:

225 g/l nickel sulphate 7aq

50 g/l nickel chloride

40g/l boric acid

225 g/l magnesium sulphate 7aq

2,6 g/l sodium benzoic acid sulphonimide

1,5 mg/l polyethylenglycol-methylether and

1,8 mg/l sodium-2-propen-sulphonate

on a substrate surface a matt nickel layer was deposited in 10 min. at a current density of 5 A/dm² and a temperature of 55°C, which layer has the same properties than a layer deposited under the same conditions by from an electrolyte comprising 550 g/l nickel sulphate and no magnesium sulphate.

Example 5:

[0025] From a Sn/Co-electrolyte comprising:

120 g/l sodium gluconate

50 g/l cobalt (II) sulphate 7aq

25 g/l tin (II) sulphate

120 g/l aluminium sulphate and

1 mg/l PEG 35.000

in 5 minutes at a temperature of 45°C and a current density of 0,5 A/dm² a very fine matt layer of a tin-cobalt alloy was deposited. The pH-value of the electrolyte was about 8,4 and the substrate to be plated was moved through the electrolyte at a speed of 2 m/min. The deposited very fine matt layer was identical to a layer deposited from an electrolyte comprising

120 g/l sodium gluconate

100 g/l cobalt(II) sulphate 7aq

50 g/l tin (II) sulphate

1 mg/l PEG 35.000.

[0026] The above embodiments clearly show that the inventive addition of a density increasing compound to an electrolyte composition known from the state of the art enables the reduction of the plating metal concentration in the electrolyte, without influencing the plating result. This enables plating electrolytes having a very low concentration of plating metal which gives great economic benefit.

Claims

1. Method for the electrolytic deposition of a matt layer of a metal of the group consisting of Co, Ni, Cu, Sn or an alloy of these metals on a substrate surface from an electrolyte forming an emulsion and/or dispersion, by conducting a current between a cathodic contacted substrate and an anode, the method comprising the steps of

a) selecting a first composition for an electrolyte capable to deposit a matt metal layer of a metal of the aforementioned group on the substrate surface, said composition having a concentration of the metal to be deposited and wherein the composition comprises a substituted or unsubstituted polyalkylene oxide or derivate of an substituted or unsubstituted polyakylene oxide, or a wetting agent to form an elmulsion and/or dispersion, wherein the wetting agent is a fluorated or perfluorated wetting agent or a quaternary ammonium compound substituted with the polyalkylene oxide;

b) preparing a plating electrolyte based on the first composition, wherein between 10 to 50% by weight of the metal to be deposited according to the first composition is substituted by at least one density increasing halogenide, sulphate, or sulphonate of an element of the group consisting of sodium, potassium, aluminum, magnesium, or boron to reduce the concentration of the metal to be deposited in comparison to the first composition and wherein the concentration of the density increasing compound is in the range from between 20% to 100% by weight of the concentration of the metal to be deposited;

c) contacting the substrate surface with the plating electrolyte resulting from step b) and applying the current.

2. The method according to claim 1, wherein the composition selected in step a) comprises a surface active wetting agent in a concentration within the range of 0.01 mol/L and 100mol/L, said surface active wetting agent is selected from the group consisting of alkyl sulphates, sulfosuccinic acid, and betaines.

3. The method according to claim 1 or 2, wherein the electrolyte according to step b) comprises at least one compound of the group consisting of sodium methanesulfonate, potassium methanesulfonate, magnesium methanesulfonate, aluminum sulphate, or boron tetrafluoride.

Ansprüche

1. Verfahren zum elektrolytischen Abscheiden einer matten Schicht aus einem Metall aus der Gruppe bestehend aus Co, Ni, Cu, Sn oder einer Legierung dieser Metalle auf einer Substratoberfläche von einem Elektrolyt, der eine Emulsion und/oder Dispersion bildet, durch Leiten eines Stroms zwischen einem kathodisch kontaktierten Substrat und einer Anode, wobei das Verfahren die Schritte aufweist:

a) Auswählen einer ersten Zusammensetzung für einen Elektrolyten, die dazu geeignet ist, eine matte Metallschicht eines Metalls der vorstehend erwähnten Gruppe auf der Substratoberfläche abzuscheiden, wobei die Zusammensetzung eine Konzentration des abzuscheidenden Metalls aufweist, und wobei die Zusammensetzung ein substituiertes oder unsubstituiertes Polyalkylenoxid oder ein Derivat eines substituierten oder unsubstituierten Polyalkylenoxids oder ein Benetzungsmittel aufweist, um eine Emulsion und/oder Dispersion zu bilden, wobei das Benetzungsmittel ein fluoriertes oder perfluoriertes Benetzungsmittel oder eine mit dem Polyalkylenoxid substituierte quaternäre Ammoniumverbindung ist;

b) Herstellen eines auf der ersten Zusammensetzung basierenden Metallisierungselektrolyts, wobei 10 bis 50 Gew.-% des gemäß der ersten Zusammensetzung abzuscheidenden Metalls durch mindestens ein die Dichte erhöhendes Halogenid, Sulfat oder Sulfonat eines Elements der Gruppe bestehend aus Natrium, Kalium, Aluminium, Magnesium oder Bor ersetzt ist, um die Konzentration des abzuscheidenden Metalls im Vergleich zur ersten Zusammensetzung zu reduzieren, und wobei die Konzentration der die Dichte erhöhenden Verbindung im Bereich zwischen 20 Gew.-% und 100 Gew.-% der Konzentration des abzuscheidenden Metalls beträgt; und

c) Inkontaktbringen der Substratoberfläche mit dem in Schritt b) erhaltenen Metallisierungselektrolyt und Zuführen des Stroms.

2. Verfahren nach Anspruch 1, wobei die in Schritt a) ausgewählte Zusammensetzung ein oberflächenaktives Benetzungsmittel in einer Konzentration innerhalb des Bereichs von 0,01 Mol/l und 100 Mol/l aufweist, wobei das oberflächenaktive Benetzungsmittel ausgewählt ist aus der Gruppe bestehend aus Alkylsulfaten, Sulfobernsteinsäure und Betainen.

3. Verfahren nach Anspruch 1 oder 2, wobei der Elektrolyt gemäß Schritt b) mindestens eine Verbindung der Gruppe bestehend aus Methansulfonat, Kaliummethansulfonat, Magnesiummethansulfonat, Aluminiumsulfat oder Bortetrafluorid aufweist.

Revendications

1. Procédé de dépôt électrolytique d'un couche mate d'un métal du groupe constitué de Co, Ni, Cu, Sn ou d'un alliage de ces métaux, sur une surface de substrat, à partir d'un électrolyte formant une émulsion et/ou une dispersion, en faisant passer un courant entre un substrat en contact de manière cathodique et une anode, le procédé comprenant les étapes de

a) sélection d'une première composition pour un électrolyte capable de déposer une couche de métal mate d'un métal du groupe mentionné auparavant sur la surface du substrat, ladite composition ayant une concentration du métal devant être déposé et où la composition comprend un oxyde de polyalkylène substitué ou non substitué, ou un dérivé d'un oxyde de polyalkylène substitué ou non substitué, ou un agent mouillant pour former une émulsion et/ou une dispersion, où l'agent mouillant est un agent mouillant fluoré ou perfluoré ou un composé d'ammonium quaternaire substitué avec de l'oxyde de polyalkylène ;

b) préparation d'un électrolyte de placage basé sur la première composition, où entre 10 et 50 % en poids de métal devant être déposé selon la première composition sont substitués par au moins un composé augmentant la densité de type halogénure, sulfate ou sulfonate d'un élément du groupe constitué du sodium, du potassium, de l'aluminium, du magnésium, ou du bore pour réduire la concentration du métal devant être déposé en comparaison à la première composition et où la concentration du composé augmentant la densité est dans la gamme entre 20 % et 100 % en poids de la concentration du métal devant être déposé ;

c) mise en contact de la surface du substrat avec l'électrolyte de placage résultant de l'étape b) et application du courant.

2. Procédé selon la revendication 1, dans lequel la composition sélectionnée dans l'étape a) comprend un agent mouillant tensioactif dans une concentration dans la gamme de 0,01 mol/l et 100 mol/l, ledit agent mouillant tensioactif est choisi dans le groupe constitué des alkylsulfates, de l'acide sulfosuccinique et de bétaïnes.

3. Procédé selon l'une des revendications 1 ou 2, dans lequel l'électrolyte selon l'étape b) comprend au moins un composé du groupe constitué par du méthanesulfonate de sodium, du méthanesulfonate de potassium, du méthanesulfonate de magnésium, du sulfate d'aluminium, ou du tétrafluorure de bore.