CN116635576A

CN116635576A - Black plating substrate

Info

Publication number: CN116635576A
Application number: CN202180088357.8A
Authority: CN
Inventors: B·厄兹卡亚; P·瓦赫特; M·约纳特
Original assignee: Germany Aituoteke Co ltd
Current assignee: Germany Aituoteke Co ltd
Priority date: 2020-12-11
Filing date: 2021-12-10
Publication date: 2023-08-22
Also published as: JP2023553961A; EP4259852A1; WO2022123012A1; US20240026557A1; TW202231929A; CN116583632A

Abstract

The invention relates to a black-plated substrate comprising a base substrate and a layer stack deposited thereon, wherein the layer stack comprises a black chrome plating layer comprising a conversion layer having a depth of 30nm or more on its surface, characterized in that the conversion layer comprises no metallic chrome or only up to 2 atomic% of metallic chrome, based on the total number of elemental chrome and chrome atoms in the conversion layer.

Description

Black plating substrate

Technical Field

The invention relates to a black-plated substrate comprising a base substrate and a layer stack deposited thereon, wherein the layer stack comprises a black chromium coating comprising a conversion layer having a depth of 30nm or more on its surface, characterized in that the conversion layer comprises no metallic chromium or only up to 2 at.% metallic chromium, based on the total number of elemental chromium and chromium atoms in the conversion layer.

Background

From the onset of the chrome layer, attention to the dark chrome layer was observed. Starting from a dark hexavalent chromium layer, but due to the higher environmental acceptance, the focus today shifts significantly to a trivalent chromium layer.

Typically, each chrome layer, especially the dark chrome layer, is characterized by a color value referencing an L x a x b x color space system. The value L defines the brightness (or sometimes also called brightness) and the values a and b define the color of the corresponding chrome layer. An L value of 100 defines light white (diffuse white) and an L value of 0 defines dark black. The values of a and b may be positive and negative, where a describes green (negative) and red (positive) and b describes blue (negative) and yellow (positive). Neutral gray is described in the case where the combination of a and b is 0, the lower the L value (for example, 50 or lower), the more deeply neutral black is changed.

Depending on the chemical composition of the corresponding aqueous trivalent chromium plating bath and/or its deposition parameters, a very wide variety of values of L, a, b may be produced.

Analysis has shown that the deep neutral black often requires a specific surface modification, sometimes referred to as a conversion layer or surface modification layer, especially on the outer surface of the corresponding electroplated black chrome plating.

US 2020/094526 A1 mentions blackened resin parts and a method for producing the same. It discloses a black chrome plating layer comprising the surface modification layer. US '526 discloses that the thickness of the surface modification layer is related to the amount of agent M added (see US'526, [0078 ]) and the current density applied (see [0079 ]). Furthermore, US'526 discloses a thickness of the surface modification layer of at most 37.7nm (see sample No. 1).

Our studies have shown that the higher the thickness of the conversion layer, the better the long-term stability of the black remains. It is assumed that the wear resistance of the conversion layer increases with increasing thickness of the conversion layer. This means that the black hold time is longer and is protected from e.g. physical contact, with the layer thickness having at least a sufficient minimum thickness. It is further assumed that as the thickness of the conversion layer increases, an increased hardness of this layer is obtained.

Accordingly, there is a continuing need to provide improved blackened substrates.

Object of the invention

It is therefore an object of the present invention to provide a black-plated substrate, which in particular provides a black chrome plating layer comprising a conversion layer with improved color stability and abrasion resistance, so that the visual impression retention time is longer.

Disclosure of Invention

Such objects are solved by the present invention, namely by a blackened substrate comprising a base substrate and a layer stack deposited thereon, wherein the layer stack comprises:

(a) One or more intermediate plating layers formed on the base substrate; and

(b) A black chrome plating layer formed on the one or more intermediate plating layers;

wherein the method comprises the steps of

-black chromium coating

-having an L-value of 55 or less according to the L-a-b color system;

-comprising the elements chromium, carbon and oxygen;

-comprising on its surface a conversion layer having a depth of 30nm or more measured from the surface towards the one or more intermediate plating layers; and

-having a total thickness of 100nm or more, comprising the conversion layer;

characterized in that the conversion layer contains no metallic chromium or only up to 2 at.% metallic chromium, based on the total of elemental chromium and chromium atoms in the conversion layer.

In the context of the present invention, decorative applications are emphasized. Thus, in the context of the present invention, black-plated substrate and thus black chrome plating preferably refers to decorative black-plated substrate and decorative black chrome plating, respectively. Therefore, the black chrome plating layer is preferably not a hard black chrome plating layer.

Our experiments have shown that an increased conversion layer thickness is obtained if not only the correct plating additive but also a specific amount (see examples below) is used in the corresponding electroplating bath utilized in the corresponding plating method. Furthermore, it appears that in the desired black chromium coating, the amount of metallic chromium in the conversion layer is particularly low, i.e. not more than 2 at%. As a result thereof, a relatively increased (and desired) thickness of the conversion layer is obtained, resulting in improved wear resistance and abrasion resistance, respectively. This allows the black plated substrate to have an increased lifetime with respect to visual black perception.

Drawings

Detailed Description

The black substrate comprises a black chrome plating obtained from a plating process, preferably an electrolytic plating process. This includes a black chrome plating layer obtained by a wet electroless plating process. In other words, the black-plated substrate and the black chrome plating layer are not obtained by a physical deposition method (for example, vapor deposition), respectively.

The invention relates in particular to such specifically designed blackened substrates having a corresponding black chrome plating layer comprising a conversion layer as defined above and throughout this document.

The black plating substrate of the present invention comprises a base substrate.

Preferred are the blackened substrates of the present invention wherein the base substrate preferably comprises a metallic or non-metallic base substrate, preferably a non-metallic base substrate, most preferably a plastic base substrate.

Preferred are the blackened substrates of the present invention wherein the metal base substrate is a metal base substrate comprising iron, preferably an iron base substrate, most preferably a cast iron base substrate. Preferably, the metal base substrate comprising iron comprises a brass base substrate and/or a zinc-based die-cast base substrate.

Preferred are the inventive blackened substrates wherein the nonmetallic base substrate, preferably the plastic base substrate, comprises Acrylonitrile Butadiene Styrene (ABS), acrylonitrile butadiene styrene-polycarbonate (ABS-PC), polypropylene (PP), polyamide (PA), polyurethane (PU), polyepoxide (PE), polyacrylate, polyetherimide (PEI), polyetherketone (PEK), mixtures thereof and/or composites thereof; preferably comprising Acrylonitrile Butadiene Styrene (ABS), acrylonitrile butadiene styrene-polycarbonate (ABS-PC), polyamide (PA), polyurethane (PU), polyepoxide (PE), polyacrylate, mixtures thereof and/or composites thereof. The plastic base substrates, in particular ABS and ABS-PC, are typically used for decorative applications such as automotive parts.

Furthermore, the inventive blackened substrate comprises a layer stack deposited on the base substrate. The layer stack comprises:

(a) One or more intermediate plating layers formed on the base substrate.

Preferred are the blackened substrates of the present invention wherein the one or more intermediate plating layers comprise one or more selected from the group consisting of: nickel layer, nickel alloy layer, copper layer and copper alloy layer. Preferably, it is continuous; forming a series of intermediate coatings; adjacent.

More preferably, the layer stack comprises two or more intermediate plating layers, most preferably at least one intermediate layer comprising copper and/or copper alloy and furthermore at least one intermediate layer comprising nickel and/or nickel alloy.

Thus, a layer stack is preferred, which comprises more than one intermediate coating layer consecutively located on each other.

In the context of the present invention, the term "plating" refers to deposition with and without the use of an external power source. It therefore preferably includes electroplating as well as electroless plating, for example with the aid of a reducing agent.

Preferred are the blackened substrates of the present invention wherein one or more of the intermediate plating layers formed on the base substrate comprises at least one microporous nickel plating layer (sometimes also referred to as MPS nickel plating layer). Preferably, the layer comprises non-conductive microparticles. This is most preferably applicable if the base substrate is a non-metallic base substrate, preferably a plastic base substrate. Preferably, this intermediate coating (if present) is adjacent to the black chrome coating.

Preferred are the inventive blackened substrates wherein one or more of the intermediate plating layers formed on the base substrate comprises at least one bright nickel plating layer or at least one satin nickel plating layer. This is most preferably applicable if the base substrate is a non-metallic base substrate, preferably a plastic base substrate.

Preferred are the blackened substrates of the present invention wherein one or more of the intermediate plating layers formed on the base substrate comprises at least one semi-bright nickel plating layer. This is most preferably applicable if the base substrate is a non-metallic base substrate, preferably a plastic base substrate. More preferred is the black plated substrate of the present invention, wherein the semi-bright nickel plating layer is additionally present in addition to the bright nickel plating layer or satin nickel plating layer.

Preferred are the blackened substrates of the present invention wherein one or more of the intermediate plating layers formed on the base substrate comprises at least one nickel alloy plating layer, preferably adjacent to (i.e., directly on) the base substrate. This is most preferably applicable if the base substrate is a non-metallic base substrate, preferably a plastic base substrate.

Preferred are the blackened substrates of the present invention wherein one or more of the intermediate plating layers formed on the base substrate comprises at least one copper plating layer, preferably adjacent to (i.e., directly on) the aforementioned at least one nickel alloy plating layer. This is most preferably applicable if the base substrate is a non-metallic base substrate, preferably a plastic base substrate.

Very preferred is a blackened substrate of the present invention comprising:

a non-metallic base substrate, preferably a plastic base substrate, most preferably a plastic base substrate as previously described as preferred;

-a layer stack deposited on the nonmetallic base substrate (or on a preferred base substrate as defined previously as preferred), the layer stack comprising, in succession starting from the nonmetallic base substrate:

-optionally, a nickel or nickel alloy coating, preferably an electrodeless nickel alloy coating;

-a copper plating, preferably an electrolytic copper plating;

-optionally, a semi-bright nickel coating;

-a bright nickel coating or satin nickel layer;

-optionally, a microporous nickel coating;

-a black chrome plating as defined throughout the present invention;

optionally, a passivation layer and/or an anti-fingerprint layer.

Preferably, the features and preferred features with respect to the individual layers mentioned also apply equally to the individual layers in this very preferred blackened substrate of the present invention. Furthermore, additional layers in the layer stack, such as an activation layer comprising palladium, are not excluded and may also be one of the one or more intermediate plating layers.

Preferably, the black chrome plating (including the conversion layer) or passivation layer (if present and deposited on top of the black chrome plating) is the outermost layer of the layer stack.

Preferably, the optional passivation layer comprises trivalent chromium phosphate and/or (preferably) manganese species. Most preferably, the optional passivation layer has no significant effect on the visual appearance of the black chrome plating, most particularly with respect to the values of L, a and b of the black chrome plating.

The layer stack further includes a black chrome plating formed on the one or more intermediate plating layers. Generally, the black plated substrate of the present invention is preferred wherein the black chrome plating is adjacent to the outermost intermediate plating. The black chrome plating is preferably an electroplated black chrome plating.

In the context of the present invention, the chrome plating is black. This black is preferably perceived visually as dark black. Most preferably, the entire blackened substrate is perceived in this way.

Most preferred is the black plated substrate of the invention wherein the black chrome plating is obtained from a trivalent chromium plating bath. This means that the source of chromium in the black chromium deposit is chromium in the trivalent state and is not derived from hexavalent chromium.

Preferred are black plated substrates of the present invention wherein the black chrome plating has an L-x value of 53 or less, preferably 51 or less, more preferably 50 or less, even more preferably 49 or less, yet even more preferably 47 or less, most preferably 45 or less, yet even most preferably 43 or less. This most preferably applies equally to the entire blackened substrate.

More preferred is the black plated substrate of the invention, wherein the black chrome plating has an L-x value in the range of 30 to 55, preferably 32 to 53, more preferably 34 to 51, even more preferably 36 to 49, most preferably 38 to 47, even most preferably 40 to 45. This most preferably applies equally to the entire blackened substrate.

More preferred is a dark black visual perception with reduced or no visual perception of another color, such as pale yellow, pale brown, pale blue, etc. This means that the dark visual perception is most preferably a neutral dark visual perception.

Therefore, preferred is a black plated substrate of the present invention, wherein the black chrome plating layer has a b-value of +7 or less, +6 or less, more preferably +5 or less, even more preferably +4 or less, most preferably +3 or less, according to the L-a-b color system. This most preferably applies equally to the entire blackened substrate.

More preferred is the black plated substrate of the invention, wherein the black chrome plating has a b-x value in the range of-6 to +6, preferably-5 to +5, more preferably-4 to +4, even more preferably-3 to +3, most preferably-2 to +2, even most preferably-1 to +1. This most preferably applies equally to the entire blackened substrate.

Preferred are the black plated substrates of the present invention wherein the black chrome plating has an a-value of +5 or less, more preferably +4 or less, even more preferably +3 or less, even more preferably +2 or less, most preferably +1 or less, according to the L-a-b color system. This most preferably applies equally to the entire blackened substrate.

More preferred is the black plated substrate of the invention, wherein the black chrome plating has an a-x value in the range of-5 to +5, preferably-4 to +4, more preferably-3 to +3, most preferably-2 to +2, even most preferably-1 to +1. This most preferably applies equally to the entire blackened substrate.

The black chrome plating typically comprises chrome, which is preferably predominantly metallic.

Therefore, preferred is the black-plated substrate of the present invention, wherein the black chromium plating layer contains chromium in a total amount ranging from 20 atomic% to 70 atomic%, preferably from 25 atomic% to 63 atomic%, more preferably from 29 atomic% to 56 atomic%, even more preferably from 33 atomic% to 51 atomic%, most preferably from 35 atomic% to 47 atomic%, even most preferably from 38 atomic% to 43 atomic%, based on the total amount of atoms in the black chromium plating layer including the conversion layer.

As mentioned above, the source of chromium in the black chromium deposit is preferably derived from chromium in the trivalent state. This typically includes complexing agents for use in the corresponding electroplating bath to complex the corresponding trivalent chromium ions. Typically and in comparison to hexavalent chromium sources, this results in a certain carbon content in the black chromium deposit compared to chromium deposits derived from hexavalent chromium sources.

Therefore, preferred is the black-plated substrate of the present invention, wherein the black chromium plating layer contains carbon in a total amount ranging from 5 atomic% to 40 atomic%, preferably from 6 atomic% to 33 atomic%, more preferably from 7 atomic% to 28 atomic%, even more preferably from 8 atomic% to 24 atomic%, most preferably from 9 atomic% to 20 atomic%, even most preferably from 10 atomic% to 16 atomic%, based on the total amount of atoms in the black chromium plating layer including the conversion layer.

Preferred is the black plated substrate of the present invention, wherein the black chromium plating layer contains oxygen in a total amount ranging from 12 atomic% to 40 atomic%, preferably from 14 atomic% to 38 atomic%, more preferably from 16 atomic% to 36 atomic%, even more preferably from 18 atomic% to 34 atomic%, most preferably from 20 atomic% to 31 atomic%, even most preferably from 22 atomic% to 28 atomic%, based on the total amount of atoms in the black chromium plating layer including the conversion layer.

In order to obtain a black-plated substrate, in particular a black chrome plating layer, it is preferred to use a blackening agent typically in the corresponding electroplating bath to deposit the black chrome plating layer. In some cases, organic and/or inorganic blackening agents are preferred. Highly preferred inorganic blackening agents comprise iron-containing compounds, preferably iron ions, most preferably iron (II) ions; cobalt-containing compounds, preferably cobalt ions, most preferably cobalt (II) ions; thiocyanate and/or salts thereof. Preferred organic blackening compounds comprise methionine and/or salts thereof. Preferably, an inorganic blackening agent, most preferably the iron-and cobalt-containing compound is incorporated into the black chrome plating.

Preferred is the black plated substrate of the present invention, wherein the black chromium plating layer contains iron in a total amount of preferably in a range of 5 atomic% to 23 atomic%, preferably 6 atomic% to 21 atomic%, more preferably 7 atomic% to 19 atomic%, even more preferably 8 atomic% to 17 atomic%, most preferably 9 atomic% to 15 atomic%, even most preferably 10 atomic% to 13 atomic%, based on the total amount of atoms in the black chromium plating layer including the conversion layer.

Preferred is the black plated substrate of the present invention, wherein the black chromium plating layer comprises cobalt in a total amount of preferably in the range of 5 to 23 atomic%, preferably 6 to 21 atomic%, more preferably 7 to 19 atomic%, even more preferably 8 to 17 atomic%, most preferably 9 to 15 atomic%, even most preferably 10 to 13 atomic%, in place of or in addition to the iron (preferably in addition to) based on the total amount of atoms in the black chromium plating layer comprising the conversion layer.

The organic blackening agent is typically incorporated into the black chrome plating by its sulphur atoms. Therefore, preferred is the black-plated substrate of the present invention, wherein the total amount of the black chromium plating layer containing sulfur is preferably in the range of 0.1 atom% to 10 atom%, preferably 0.3 atom% to 9 atom%, more preferably 0.5 atom% to 8 atom%, even more preferably 0.7 atom% to 7 atom%, most preferably 1 atom% to 6 atom%, even most preferably 1.3 atom% to 5 atom%, based on the total amount of atoms in the black chromium plating layer including the conversion layer.

Preferred is the black plated substrate of the present invention, wherein the total amount of nitrogen contained in the black chromium plating layer is preferably in the range of 0.1 atomic% to 10 atomic%, preferably 0.5 atomic% to 9 atomic%, more preferably 1 atomic% to 8 atomic%, even more preferably 1.5 atomic% to 7 atomic%, most preferably 2 atomic% to 6 atomic%, even most preferably 2.5 atomic% to 5 atomic%, based on the total amount of atoms in the black chromium plating layer including the conversion layer.

The black chrome plating layer includes a conversion layer on a surface thereof. In the context of the present invention, the depth (or thickness) of the conversion layer is at least 30nm. This is believed to provide the minimum required abrasion resistance and abrasion resistance, respectively, to maintain a useful minimum depth (or thickness) of the relatively long visual life of the blackened substrate.

Preferred are the black plated substrates of the present invention wherein the depth of the conversion layer is 32nm or more, preferably 35nm or more, more preferably 38nm or more, even more preferably 41nm or more, yet even more preferably 44nm or more, most preferably 48nm or more, even most preferably 51nm or more.

Preferred are the black plated substrates of the present invention wherein the maximum depth of the conversion layer is 90nm or less, preferably 80nm or less, more preferably 70nm or less, even more preferably 66nm or less, yet even more preferably 62nm or less, most preferably 60nm or less.

More preferred is the black plated substrate of the present invention, wherein the depth of the conversion layer is in the range of 30nm to 90nm, preferably 32nm to 85nm, more preferably 35nm to 80nm, even more preferably 38nm to 70nm, yet even more preferably 41nm to 66nm, most preferably 44nm to 62nm, even most preferably 48nm to 60 nm.

In the black plating substrate, the thickness of the black chrome plating layer excluding the conversion layer is preferably higher than the depth (or thickness) of the conversion layer. Preferably, the black chrome plating layer excluding the conversion layer is at least twice, preferably at least 3 times, more preferably at least 4 to 5 times, even more preferably at least 6 to 7 times, most preferably at least 8 to 9 times, even most preferably at least 10 times thicker than the conversion layer.

Preferably, the depth or thickness of the conversion layer is determined according to b.r.s. Luo Meier (b.r.strohmeier), surface and interface analysis (Surface and Interface Analysis), volume 15, pages 51 to 56 (1990).

Preferred is a black plated substrate of the present invention, wherein the total thickness of the black chrome plating layer including the conversion layer is 130nm or more, preferably 160nm or more, more preferably 190nm or more, even more preferably 220nm or more, still even more preferably 250nm or more, most preferably 275nm or more, even most preferably 300nm or more.

More preferred is the black plated substrate of the invention, wherein the total thickness of the black chrome plating layer is in the range of 100nm to 1000nm, preferably 130nm to 900nm, more preferably 160nm to 800nm, even more preferably 190nm to 700nm, yet even more preferably 220nm to 600nm, most preferably 250nm to 500nm, even most preferably 275nm to 400 nm. The total thickness typically provides excellent color stability over the typical lifetime of a corresponding blackened substrate, even if the substrate is often touched and/or sometimes cleaned by wiping.

Furthermore, in the context of the present invention, it is necessary to have no metallic chromium or only a very small amount of metallic chromium in the conversion layer. The depth of the conversion layer has been shown to be related to the amount of metallic chromium in the conversion layer and it appears that the depth increases with decreasing amount of metallic chromium. Without wishing to be bound by theory, it appears that this is the result of a combination of specific blackening agents in specific amounts (see examples).

Preferred are the inventive blackened substrates wherein the conversion layer contains no metallic chromium or only up to 1.7 at% metallic chromium, preferably no metallic chromium or only up to 1.5 at% metallic chromium, more preferably no metallic chromium or only up to 1.2 at% metallic chromium, even more preferably no metallic chromium or only up to 1 at% metallic chromium, even more preferably no metallic chromium or only up to 0.8 at% metallic chromium, most preferably no metallic chromium or only up to 0.5 at% metallic chromium, and most preferably no metallic chromium or only up to 0.3 at% metallic chromium, based on the total number of elemental chromium and chromium atoms in the conversion layer.

The conversion layer contains chromium hydroxide and chromium oxide in addition to a very small amount of metallic chromium (or no chromium). Most preferably, the chromium is present only in the form of metallic chromium, chromium hydroxide and chromium oxide up to 2 atomic% (including zero atomic%). More preferably, therefore, the conversion layer consists of the above-described form, based on chromium species in the conversion layer.

Preferred is a black plated substrate of the present invention, wherein the conversion layer comprises chromium in the form of chromium hydroxide, the total amount of which is preferably in the range of 40 to 75 atomic%, preferably 46 to 70 atomic%, more preferably 50 to 66 atomic%, most preferably 54 to 62 atomic%, based on the total amount of elemental chromium and chromium atoms in the conversion layer.

Preferred is a black plated substrate of the invention, wherein the conversion layer comprises chromium in the form of chromium oxide, preferably in a total amount in the range of 25 to 55 atomic%, preferably 29 to 51 atomic%, more preferably 32 to 48 atomic%, most preferably 35 to 45 atomic%, based on the total amount of elemental chromium and chromium atoms in the conversion layer.

More preferably, the conversion layer comprises chromium oxide and chromium hydroxide, wherein the total amount of chromium hydroxide is higher than that of chromium oxide. Our experiments have shown that this is also a very preferred feature of the blackened substrate according to the invention (see examples below).

Preferred are inventive black-plated substrates in which the atomic ratio of elemental chromium to elemental oxygen in the conversion layer is less than 1 and/or (preferably and) in black-chrome plating without conversion layer the atomic ratio of elemental chromium to elemental oxygen is greater than 1.

In some cases, the black-plated substrate of the present invention is preferred, wherein the black chrome plating comprises particles, preferably nanoparticles. Preferred particles comprise one or more than one chemical element selected from the group consisting of: silicon, aluminum and carbon, preferably silicon and aluminum, most preferably aluminum.

Preferably, the particle size of the particles is below 1000nm, preferably below 500nm, more preferably at least 90% of the particles have a particle size below 500nm, most preferably at least 90% of the particles have a particle size below 150nm.

Preferably, the average particle diameter D of the particles is by volume ₅₀ Is 100nm or less, preferably 80nm or less, more preferably 60nm or less, even more preferably 50nm or less, most preferably 40nm or less, most preferably 30nm or less, even most preferably 25nm or less.

Most preferably, the particles comprise alumina, preferably alumina particles.

Preferred are the black-plated substrates of the invention wherein the black chrome plating is substantially free, preferably free, of zinc. More preferably, the entire layer stack is substantially free, preferably free of zinc.

Preferred are the black-plated substrates of the present invention wherein the black chrome plating is substantially free, preferably free of fluorine. More preferably, the entire layer stack is substantially free, preferably free of fluorine.

Preferred are the black-plated substrates of the present invention wherein the black chrome plating is substantially free, preferably free, of aluminum. More preferably, the entire layer stack is substantially free, preferably free of aluminum.

The spirit of the invention is further illustrated in the following examples without limiting the scope of the invention as defined in the claims herein.

Examples

An ABS sheet was used as a substrate, which was pretreated prior to deposition of the black chrome plating as follows:

in a first step, an ABS sheet is used at 50 DEG C151 (An Meite (Atotech) product) for 5 minutes.

In the second step, the cleaned substrate is subjected to a chrome-sulfuric acid etch at about 70 ℃ for about 10 minutes. In a subsequent step, the etched substrate is activated by means of colloidal palladium.

In the third step, the activated substrate is subjected to an electroless nickel plating step (10 minutes, 40 ℃) followed by a 10% by volume sulfuric acid dipping step and an electroless copper plating step.

In the fourth step, furthermore, the copper-plated substrate was subjected to an electrolytic copper plating step (25 ℃ C., 50 minutes, 4A/dm) ² )。

In the fifth step, the electrolytic copper-plated substrate was subjected to a semi-bright nickel plating step (55 ℃ C., 15 minutes, 4A/dm) ² ) Then a bright nickel plating step (55 ℃,25 minutes, 4A/dm) ² )。

In the sixth step, the bright nickel plating substrate was subjected to a microporous nickel layer plating step (55 ℃ C., 4 minutes, 3A/dm) ² )。

In a seventh step, a black chrome plating layer is deposited using the following aqueous (i.e., water as the only solvent) trivalent chromium plating bath:

about 20g/L to 25g/L Cr ³⁺ Ions (provided in the form of basic chromium sulphate),

about 30g/L to 45g/L formic acid,

about 60g/L of boric acid,

table 1 the potassium thiocyanate salt was used,

table 1 the amino acid methionine is used,

about 10g/L of ammonium bromide,

about 100g/L of ammonium chloride,

about 100g/L potassium chloride, and

FeSO at about 0.5g/L ₄ ·7H ₂ O

The electroplating bath further comprises a minor amount (up to 4 g/L) of saccharin and between 5g/L and 50g/L of an S-containing glycol.

The pH was adjusted to 3.2.

In a subsequent step, electroplating was carried out for about 3 minutes and with a current density of about 10A/dm ² . The temperature of the corresponding plating bath was about 35 ℃. By air stirringAgitation is achieved dynamically. Thus, a uniformly distributed black chromium deposit is deposited.

In addition, the substrate coated with the black chrome plating is subjected to a passivation composition comprising a permanganate.

In the eighth step, the substrate was immersed in hot water (80 ℃) for 10 minutes in the rinsing step. This applies to examples E and CE1, while for example CE2 the immersion is not performed.

Then, the L.a.b.values (Konica Minolta) CM-700D spectrophotometry, CIE standard illuminant D65 and 10 ° standard observer) were determined from the L.a.b color space system. Calibration of the spectrophotometer was performed with black and white standards.

Furthermore, HAXPES measurements (photon energy: 6000eV; analyser: european (scientific) EW4000; peak resolution is performed as outlined in US 2020/094526 A1, [0070 ]) were performed on Berlin's Beschin synchrotron (BESSY synchrotron, berlin). The results are summarized in table 1 below.

Table 1: summary of results

In table 1, "E" refers to an example according to the present invention, wherein "CE" refers to a comparative example.

Table 1 shows that the overall reduction of methionine and potassium thiocyanate contents (435 mmol/L of E to 251mmol/L of CE 2) leads to a corresponding reduction of the layer thickness of the conversion layer (55 nm of E to 25nm of CE 2).

In contrast, an increase in the relative amount of chromium metal results in a decrease in the layer thickness of the conversion layer.

Comparative example CE2 was not subjected to immersion in hot water at 80 ℃, whereas comparative example CE1 was subjected to this immersion. As can be seen from table 1, it appears that mainly the combined total amount of methionine and potassium thiocyanate has a significant effect on the conversion layer thickness.

Furthermore, only example E according to the invention shows that the relative total amount of chromium hydroxide is higher than that of chromium oxide.

Thus, the above examples demonstrate that particularly high conversion layer thicknesses are associated with significantly lower amounts of chromium metal in the conversion layer.

In other tests, the black chrome plating of example E, which was subjected to adequate cleaning, was protected from undesirable wear for a longer period of time and therefore better dark color stability than the black chrome plating of comparative examples CE1 and CE 2. It was observed that if the conversion layer was at least almost removed from the black chrome plating, a brighter black color appeared under the conversion layer.

Claims

1. A black plated substrate comprising a base substrate and a layer stack deposited thereon, wherein the layer stack comprises:

(a) One or more intermediate plating layers formed on the base substrate; and

wherein the method comprises the steps of

-said black chrome coating

-having an L-value of 55 or less according to the L-a-b color system;

-comprising the elements chromium, carbon and oxygen;

-comprising on its surface a conversion layer having a depth of 30nm or more measured from said surface towards said one or more intermediate plating layers; and

-having a total thickness of 100nm or more, comprising the conversion layer;

characterized in that the conversion layer contains no metallic chromium or only up to 2 at.% metallic chromium, based on the total of the elemental chromium and the chromium atoms in the conversion layer.

2. The blackout substrate according to claim 1, wherein the base substrate is a metallic or non-metallic base substrate, preferably a non-metallic base substrate, most preferably a plastic base substrate.

3. The blackout substrate of claim 1 or 2, wherein the one or more intermediate plating layers comprise one or more selected from the group consisting of: nickel layer, nickel alloy layer, copper layer and copper alloy layer.

4. A black plated substrate according to any of claims 1 to 3, wherein the black chrome plating has an L-value of 53 or less, preferably 51 or less, more preferably 50 or less, even more preferably 49 or less, yet even more preferably 47 or less, most preferably 45 or less, yet even most preferably 43 or less.

5. The black plated substrate according to any one of claims 1 to 4, wherein the black chrome plating layer has a b-value of +7 or less, more preferably +6 or less, even more preferably +5 or less, even more preferably +4 or less, most preferably +3 or less according to the L-a-b color system.

6. The black plated substrate according to any one of claims 1 to 5, wherein the black chrome plating layer comprises a total amount of chrome in the range of 20 to 70 atomic%, preferably 25 to 63 atomic%, more preferably 29 to 56 atomic%, even more preferably 33 to 51 atomic%, most preferably 35 to 47 atomic%, even most preferably 38 to 43 atomic%, based on the total amount of atoms in the black chrome plating layer comprising the conversion layer.

7. The black plated substrate according to any one of claims 1 to 6, wherein the black chrome plating layer comprises carbon in a total amount ranging from 5 to 40 atomic%, preferably from 6 to 33 atomic%, more preferably from 7 to 28 atomic%, even more preferably from 8 to 24 atomic%, most preferably from 9 to 20 atomic%, even most preferably from 10 to 16 atomic%, based on the total amount of atoms in the black chrome plating layer comprising the conversion layer.

8. The black plated substrate according to any one of claims 1 to 7, wherein the black chrome plating layer comprises oxygen in a total amount ranging from 12 to 40 atomic%, preferably from 14 to 38 atomic%, more preferably from 16 to 36 atomic%, even more preferably from 18 to 34 atomic%, most preferably from 20 to 31 atomic%, even most preferably from 22 to 28 atomic%, based on the total amount of atoms in the black chrome plating layer comprising the conversion layer.

9. The black plated substrate according to any one of claims 1 to 8, wherein the black chrome plating layer comprises iron in a total amount of preferably in the range of 5 to 23 atomic%, preferably 6 to 21 atomic%, more preferably 7 to 19 atomic%, even more preferably 8 to 17 atomic%, most preferably 9 to 15 atomic%, even most preferably 10 to 13 atomic%, based on the total amount of atoms in the black chrome plating layer comprising the conversion layer.

10. The blackout substrate according to any one of claims 1 to 9, wherein the depth of the conversion layer is 32nm or more, preferably 35nm or more, more preferably 38nm or more, even more preferably 41nm or more, yet even more preferably 44nm or more, most preferably 48nm or more, even most preferably 51nm or more.

11. The blackout substrate according to any one of claims 1 to 10, wherein the maximum depth of the conversion layer is 90nm or less, preferably 80nm or less, more preferably 70nm or less, even more preferably 66nm or less, yet even more preferably 62nm or less, most preferably 60nm or less.

12. The black plated substrate according to any one of claims 1 to 11, wherein the total thickness of the black chrome plating layer comprising the conversion layer is 130nm or more, preferably 160nm or more, more preferably 190nm or more, even more preferably 220nm or more, yet even more preferably 250nm or more, most preferably 275nm or more, even most preferably 300nm or more.

13. The blackout substrate according to any one of claims 1 to 12, wherein the conversion layer comprises no metallic chromium or comprises only up to 1.7 at% metallic chromium, preferably no metallic chromium or comprises only up to 1.5 at% metallic chromium, more preferably no metallic chromium or comprises only up to 1.2 at% metallic chromium, even more preferably no metallic chromium or comprises only up to 1 at% metallic chromium, even more preferably no metallic chromium or comprises only up to 0.8 at% metallic chromium, most preferably no metallic chromium or comprises only up to 0.5 at% metallic chromium, and most preferably no metallic chromium or comprises only up to 0.3 at% metallic chromium, based on the total number of elemental chromium and chromium atoms in the conversion layer.

14. The blackout substrate of any one of claims 1 to 13, wherein the conversion layer comprises chromium in the form of chromium hydroxide, preferably in a total amount in the range of 40 to 75 atomic%, preferably 46 to 70 atomic%, more preferably 50 to 66 atomic%, most preferably 54 to 62 atomic%, based on the total number of elemental chromium and chromium atoms in the conversion layer.

15. The blackout substrate of any one of claims 1-14, wherein an atomic ratio of the elemental chromium to elemental oxygen in the conversion layer is less than 1 and/or an atomic ratio of the elemental chromium to the elemental oxygen in the black chrome plating without the conversion layer is greater than 1.