ES2882886T3 - An aluminum alloy laminate product with intense iridescent colors - Google Patents

Abstract

An anodized decorative laminate product made from an aluminum alloy consisting, in wt%, of Mg: 0 - 1.5, Mn: 0 - 1.5, with Mg + Mn: 0.5 - 3, and where already either Mn: 0.8 - 1.5 or Mg: 0.5 - 1.1 and Mn <= 0.2, Si: <= 0.6, Fe: <= 0.8, Ti: <= 0, 1, Cu: <= 0.3, Cr: <= 0.1, Zn: <= 0.25, Zr: <= 0.1, other elements <= 0.05 each and <= 0.15 in total, the balance aluminum, where the rolled product has a porous anodic oxide film that is electrochemically or chemically colored and where the color of the decorative sheet is different when viewed at an angle of incidence of 0° and at an angle of incidence of 45° and is characterized in that the porous anodic oxide film is covered with a sol-gel coating preferably comprising silicon.

Description

DESCRIPTION

An aluminum alloy rolled product with intense iridescent colors

field of invention

The present invention relates to decorative aluminum sheet products having iridescent colors. Background of the invention

Various aluminum alloys are used in the form of rolled products for decorative applications such as cosmetic containers, automotive trim (exterior and interior), interior design, sound systems, and consumer electronics.

It is known to obtain iridescent colors in rolled aluminum products. By iridescent colors it is meant that the color changes as a function of the angle of incidence. In particular, it can be obtained on anodized aluminum having porous films of anodic oxide obtained in various electrolytes (sulfuric, phosphoric, oxalic acid, etc.). As shown in Figure 1, porous anodic oxide films consist of two layers, a thick porous outer layer 22 and an inner layer that is dense and dielectrically compact called the barrier layer 21. The iridescent phenomenon is due to interference between light reflected from the oxide surface and light reflected from a metal/oxide interface. At different angles of incidence V, as illustrated in Figure 1, different wavelengths of light have positive or negative interference resulting in the perception of different colors.

Iridescent colors can be observed in porous films of anodic oxide. In the article "Optical properties and color generation mechanism of porous anodic alumina films", Applied Surface Science, 258 (2011), 1826-1830, examples of iridescent anodic aluminum oxide films obtained on high purity aluminum sheets by anodization are provided. with phosphoric acid. The phenomenon seems to be intensified if the porous anodic oxide film is colored.

In the article "Synthesis and properties of iridescent Zn-containing anodic aluminum oxide films" - Thin Solid Films, 586 (2015), 8-12, examples of iridescent anodic aluminum oxide films obtained on high purity aluminum sheets are provided. by anodizing with phosphoric acid followed by Zn deposition.

Examples of iridescent anodic aluminum oxide films obtained by acid anodization followed Ni electrodeposition.

Patent application WO2017/013607 refers to a structural coloring method for coloring an aluminum substrate, which is exemplified by alloy 6061, which comprises forming a nanostructure of one-dimensional photonic crystals through a process of periodic anodizing by current pulses, the color obtained as a function of the time of application of the maximum and/or minimum current density of the pulse, and the color varies with the angle of observation.

In the article "Electrocolouring of anodized aluminum with copper: effect of porous and barrier oxide film thickness", G. Pastore et al., Thin Solid Films, 173 (1989), 299-308, the effect of the thickness of aluminum films is described. both porous and compact, which is exemplified by the 6063 alloy, anodized in 15% H2SO4 over the electrocoloring process using copper sulfate and magnesium sulfate solutions.

In the article "Color simulation and prediction of complex nano-structured metal oxide films Test case: Analysis and modeling of electro-coloured anodized aluminum", I. De Graeve et al., Surface and Coatings Technology, 205 (2011), 4349-4354 , an optical patterning method for predicting and patterning the color of electro-colored anodized aluminum is described which is exemplified by an AA5005 aluminum having 0.7 wt% Fe and 0.3 wt% Si.

Patent application US2016/0362808 describes a formed aluminum article, exemplified by alloys 6061 and 6063, in which the pores formed by anodic oxidation are filled with a pigment, the formed aluminum article having a suitably colored film.

Colors can be adjusted by modifying the anodizing and coloring parameters, but for typical anodizing quality, for example, high purity sheets as described in the articles mentioned or more generally in the 1XXX series alloys, the overall coloring effect remains light.

Therefore, there is a need for decorative aluminum sheet products with strong iridescent colors.

Summary of the invention

An object of the invention is an anodized decorative laminate product made of an aluminum alloy consisting, in % by weight,

Mg: 0 - 1.5,

Min: 0 - 1.5,

With MgMn: 0.5 - 3

and wherein either Mn: 0.8 - 1.5 or Mg: 0.5 - 1.1 and Mn < 0.2,

If: < 0.6,

Faith: < 0.8,

Ti: < 0.1,

Cu: < 0.3,

Cr: <0.1,

Zn: < 0.25,

Zr: < 0.1,

other elements < 0.05 each and < 0.15 in total, the rest aluminum,

wherein the laminate has a porous anodic oxide film that is electrochemically or chemically colored and wherein the color of the decorative sheet is different when viewed at a 0° angle of incidence and at a 45° angle of incidence and wherein the porous anodic oxide film is covered with a sol-gel coating preferably comprising silicon.

Another object of the invention is a method for manufacturing an anodized decorative laminate product according to the invention comprising the steps of

- casting an aluminum alloy according to the invention to form an ingot;

- reheat and/or homogenize the ingot preferably at a temperature of 460 °C to 560 °C,

- hot rolling the ingot to a final hot rolling thickness, preferably at a temperature of 350 to 500 °C,

- cold rolling to obtain a cold rolled product, with a preferred final thickness of 0.2 to 2 mm and preferably 0.5 to 0.8 mm,

- optionally annealing said cold-rolled product preferably at a temperature of 200 to 300 °C, - cleaning said cold-rolled product, preferably with a solvent or an aqueous cleaner containing surfactants,

- optionally provide a matt or glossy appearance, for example by satin matte etching or by chemical/electrochemical polishing,

- anodizing said cold-rolled product in sulfuric acid, phosphoric acid or oxalic acid or a combination thereof to obtain a porous film of anodic oxide,

- coloring said porous film of anodic oxide by electrochemical deposition preferably of at least one of Zn, Ni, Sn, Co, Cu, Ag or chemical deposition preferably of at least one dye among an azo dye, an anthraquinone dye, an indigo dye ,

- rinse with deionized water,

- optionally sealing the porous anodic oxide film by hydrothermal sealing, cold sealing or a combination thereof,

- dry off,

- coating the porous anodic oxide film by deposition of a sol-gel precursor followed by evaporation and/or curing.

Description of the figures

Figure 1: Interference between light reflected at the oxide surface and light reflected at a metal/oxide interface, for a porous anodic alumina on an aluminum surface.

Description of the invention

All aluminum alloys mentioned below are designated by using the rules and designations defined by the Aluminum Association in the Series of Records of Registration that it publishes regularly, unless otherwise indicated.

Unless otherwise stated, all statements relating to the chemical composition of alloys are expressed as mass percent by weight based on the total weight of the alloy. In the formula Mg Cu, Mg and Cu mean the percentage by weight of Mg and Cu, respectively.

The metallurgical temples referred to are designated by using the European standard EN-515.

The inventors have discovered that by using alloys having a specific composition, and in particular including additions of Mg and/or Mn, it is possible to obtain decorative aluminum laminates with strong iridescent colors.

According to the invention, an anodized decorative laminate product with strong iridescent colors can be obtained with a laminate product made of an aluminum alloy consisting, in % by weight,

Mg: 0 - 1.5,

Min: 0 - 1.5,

with MgMn: 0.5 - 3

and wherein either Mn: 0.8 - 1.5 or Mg: 0.5 - 1.1 and Mn < 0.2,

If: < 0.6,

Faith: < 0.8,

Ti: < 0.1,

Cu: < 0.3,

Cr: <0.1,

Zn: < 0.25,

Zr: < 0.1,

other elements < 0.05 each and < 0.15 in total, the rest aluminum,

wherein the laminate has a porous anodic oxide film that is electrochemically or chemically colored and wherein the color of the decorative sheet is different when viewed at a 0° angle of incidence and at a 45° angle of incidence and wherein the porous anodic oxide film is covered with a sol-gel coating preferably comprising silicon.

The presence of Mn and/or Mg containing precipitates in the alloy surprisingly enhances the colors and iridescent properties.

The presence of Si further enhances the strength of the colors in some cases. Advantageously, the Si content is at least 0.03% by weight. However, excessive Si content can be detrimental to formability. Preferably, the Si content is at most 0.3% by weight and preferably at most 0.25% by weight and more preferably at most 0.2% by weight.

Similarly, the presence of Fe further enhances the strength of colors in some cases. Advantageously, the Fe content is at least 0.02% by weight. However, excessive Fe content can be detrimental to formability. Preferably, the Fe content is at most 0.5% by weight, more preferably at most 0.4% by weight and preferably at most 0.2% by weight. Preferably, Fe is at most 0.5% by weight and Si is at most 0.3% by weight. The other elements having a content of <0.05% by weight each and <0.15% by weight in total are undesirable impurities.

In a first embodiment, the alloy contains 0.8 to 1.5% by weight of Mn and is preferably an alloy of the 3XXX series. The preferred alloys in this first embodiment are AA3103, AA3104 and AA3005. Preferably, in the first embodiment, the Mg content is at most 1.3% by weight and preferably at most 0.6% by weight.

In a second embodiment, the Mn content is at most 0.2% by weight and the Mg content is 0.5 to 1.1% by weight. In this second embodiment, the alloy is preferably a 5XXX series alloy. This second embodiment is also advantageously combined with an Si content of at most 0.2% by weight, preferably at most 0.1% by weight and most preferably at most 0.04% by weight. This second embodiment is also advantageously combined with an Fe content of at most 0.2% by weight, preferably at most 0.1% by weight and most preferably at most 0.06% by weight. The preferred alloys in this second embodiment are AA5005, AA5505 and AA5657.

The method for manufacturing an anodized decorative laminate product according to the invention comprises the steps of

- casting an aluminum alloy according to the invention to form an ingot;

- reheat and/or homogenize the ingot preferably at a temperature of 460 °C to 560 °C,

- hot rolling the ingot to a final hot rolling thickness, preferably at a temperature of 350 to 500 °C,

- cold rolling to obtain a cold rolled product, with a preferred final thickness of 0.2 to 2 mm and preferably 0.5 to 0.8 mm,

- optionally annealing said cold-rolled product preferably at a temperature of 200 to 300 °C, - cleaning said cold-rolled product, preferably with a solvent or an aqueous cleaner containing surfactants,

- optionally provide a matt or glossy appearance, for example by satin matte etching or by chemical/electrochemical polishing,

- anodizing said cold-rolled product in sulfuric acid, phosphoric acid or oxalic acid or a combination thereof to obtain a porous film of anodic oxide,

- coloring said porous film of anodic oxide by electrochemical deposition preferably of at least one of Zn, Ni, Sn, Co, Cu, Ag or chemical deposition preferably of at least one dye among an azo dye, an anthraquinone dye, an indigo dye ,

- rinse with deionized water,

- optionally sealing said porous anodic oxide film by hydrothermal sealing, cold sealing or a combination thereof,

- dry off,

- coating the porous anodic oxide film by deposition of a sol-gel precursor followed by evaporation and/or curing.

Typical surfactants are anionic such as carboxylates or sulfonates, nonionic such as ethoxylated aliphatic alcohols, cationic such as quaternary ammonium salts, or amphoteric such as aliphatic aminocarboxylic acid salts.

The porous outer layer obtained from acid anodizing can be schematically represented as a closed packed matrix of hexagonally arranged cells containing pores at each cell center. Figure 1 illustrates a cross section of a porous anodic oxide film 2 on aluminum and an aluminum substrate 1, comprising a barrier layer 21 and a porous outer layer 22. The porous anodic oxide film is characterized by given parameters such as the diameter of the pores, the distance between the pores (cell diameter) of the porous outer layer and the thickness of the barrier layer. The porous anodic oxide film of the products according to the invention has a barrier layer advantageously 15 to 25 nm thick, in order to obtain the desired iridescent colors. The total thickness of the porous anodic oxide film is advantageously between 1 and 10 |_im.

Sulfuric anodizing can usually be achieved at 1-1.5A/dm2 at 20°C, providing a barrier layer of approximately 21nm thickness, the anodizing time is adjusted to vary the coloration effect.

The dye concentration can vary from 0.1 to 10 g/L, depending on the color and darkness required. The temperature is usually in the range of 50 to 60 °C, with some exceptions working at lower temperatures.

According to the invention, the porous anodic oxide film is coated by deposition of a sol-gel precursor followed by evaporation and/or curing to obtain a sol-gel coating. The present inventors surprisingly found that the sol-gel coating does not alter the iridescent appearance, probably due to its specific optical properties. The sol-gel coating protects the porous anodic film from scratches, fingerprints and other surface defects. In contrast, conventional coatings such as clear lacquer do not allow the iridescent appearance to be maintained.

Preferably, the sol-gel precursor is prepared from a mixture of a polysiloxane, preferably prepared from an alcoholic silane solution, more preferably from an alcoholic alkoxysilane solution and an aqueous colloidal silica solution. The sol-gel precursor is advantageously prepared from two solutions A and B, solution A is an alcoholic solution of one or more alkoxysilanes, the alcohol used as solvent is methanol, ethanol, propanol, preferably isopropanol, butanol or a combination of the same, the alkoxysilanes are described by the general formula XnSi(OR)4-n where "R" is a simple alkyl, preferably chosen from the group consisting of methyl, ethyl, propyl and butyl and "X" is also a alkyl, preferably selected from the group consisting of methyl, ethyl, propyl, and butyl; solution B is a solution of colloidal silica dissolved in water. Advantageously, the alkoxysilanes belong to the group comprising tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMOS). Preferably, solution A contains 25-35% by weight of TEOS and 15-25% by weight of MTMOS, both dissolved in 40-60% by weight of isopropyl alcohol. Advantageously, solution B is fixed with an acid, preferably nitric acid (HNO3), at a pH value between 2.0 and 4, preferably between 2.5 and 3.0 and more preferably close to 2.7. Advantageously, the alkali content of the silica is less than 0.04% by weight of Na2O.

Preferably, the deposition of the sol-gel precursor is carried out by immersion. Advantageously, the thickness of the sol-gel coating is between 2 and 4 |_im. Preferably, the sol-gel coating contains a small amount of organic compounds, for example, the carbon content of the coating measured by XPS (X-ray photoelectron spectrometry) is less than 10 atomic % measured by the concentration profile through the sol-gel coating. Preferably, the curing of the sol-gel is carried out at a temperature between 150 and 250 °C for 30 to 60 seconds.

The product of the invention is particularly useful for decorative applications such as cosmetic packaging, automotive trim (exterior and interior), interior design, sound system, and consumer electronics.

Example

Example 1 (reference example)

In this example, color anodizing of rolled products made from various alloys has been tested.

The composition of the alloys is given in Table 1

Table 1, Typical Alloy Composition in Weight %

The products received surface treatment as follows:

- Solvent cleaning with Methyl-Ethyl-Ketone on flat samples

- Rinse with deionized water

- Anodizing with 180 g/L sulfuric acid, at 20 °C, for 1 to 2 min under a continuous current of 1 A/dm2 - Rinsing with deionized water

- Electrolytic dye: with nickel sulfate 30 g/L, boric acid 30 g/L, ammonium sulfate 15 g/L, 35 °C, 2 min current 19 V AC or chemical dye with a chrome complex azo dye: Sanodal ® Black 2LW (1 g/L), with an azo dye copper complex: Sanodure® Fast Gold L (3 g/L), and with an anthraquinone dye: Sanodye® Blue 2LW (3 g/L) at 60 ° C for 2 min,

- Rinse with deionized water

- drying

The resulting samples were observed at different angles of incidence. The intensity of the colors was classified by comparison with reference samples and was scaled from 1: light to 3: strong.

The results are provided in Table 2

Table 2 - Results obtained

Coloring with alloys according to the invention makes it possible to obtain strong iridescent colors, ranging from 2 to 3.

Example 2

The example 1 sample made of 5657 alloy is protected by a sol-gel coating.

The sol-gel solution applied by immersion consists of a mixture of a solution A and a solution B.

Anhydrous solution A comprises a mixture of siloxanes and unhydrolyzed alcohols:

50% by weight of isopropanol

30% by weight of tetraethylorthosilicate (TEOS)

20% by weight of trimethoxymethylsilane (MTMOS)

The aqueous solution B comprises: 25 % by weight of colloidal silica and 75 % by weight of water.

The pH of solution B is changed to 2.5 by adding an acid such as HNO3. The silica should have the lowest possible alkaline content, preferably less than 0.04 mass% Na2O. Solution A is mixed with solution B in the presence of nitric acid with continuous stirring and leads to a hydrolysis and condensation reaction that brings the mixture to a gel state. Solutions A and B are mixed in a weight ratio of preferably 7:3. The mixture is preferably maintained at a pH value between 2 and 4, preferably between 2.5 and 3.0 and most preferably at 2.7. The pH value is corrected by adding acid, preferably nitric acid.

After mixing solutions A and B for 6 hours, the resulting solution is filtered. Filtration can be done, for example, by using polypropylene filters with a mesh size of 1 micron. Before use, the solution is allowed to stand for 12 to 22 hours before being applied to the substrate to form the protective deposit.

The deposit is baked at a temperature of 150 to 250 °C for 30 to 60 seconds. The thickness of the deposit is preferably 2 to 4 µm and contains only very few organic compounds (less than 10% at, measured by XPS depth profile).

The strong iridescent coloration of the alloy according to the invention is not modified by the solgel coating, which is surprising because the iridescence is based on interference phenomena and the addition of a thin coating is expected to affect the coloration. Furthermore, the surface is well protected mechanically by the sol-gel coating.

Claims (14)

1. An anodized decorative laminate product made from an aluminum alloy consisting, in % by weight, Mg: 0 - 1.5, Min: 0 - 1.5, with MgMn: 0.5 - 3, and where either Mn: 0.8 - 1.5 or Mg: 0.5 - 1.1 and Mn < 0.2, If: < 0.6, Faith: < 0.8, Ti: < 0.1, Cu: < 0.3, Cr: <0.1, Zn: < 0.25, Zr: < 0.1, other elements < 0.05 each and < 0.15 in total, the rest aluminum, wherein the laminate has a porous anodic oxide film that is electrochemically or chemically colored and wherein the color of the decorative sheet is different when viewed at a 0° angle of incidence and at a 45° angle of incidence and it is characterized in that the porous anodic oxide film is covered with a sol-gel coating preferably comprising silicon. 2. A product according to claim 1, wherein Fe is at most 0.5% by weight and Si is at most 0.3% by weight. 3. A product according to claim 1 or claim 2, wherein Mn is at most 0.2% by weight, Si is at most 0.1% by weight and Fe is at most 0.2% by weight. 4. A product according to claim 1 or claim 2, wherein Mn: 0.8 - 1.5% by weight and where the content of Mg is at most 1.3% by weight and preferably at most 0.6% by weight. 5. A product according to any of claims 1 to 4, wherein the Si content is at least 0.03% by weight. 6. A product according to any of claims 1 to 5, wherein the Fe content is at least 0.02% by weight. 7. A product according to any of claims 1 to 6, wherein the barrier layer of the porous anodic oxide film has a thickness of 15 to 25 nm. 8. A product according to any of claims 1 to 7, wherein the porous anodic oxide film comprises at least one of Zn, Ni, Sn, Co, Cu, Ag. 9. A product according to any of claims 1 to 7, wherein the porous anodic oxide film comprises at least one dye among an azo dye, an anthraquinone dye, an indigo dye. 10. A method for manufacturing an anodized decorative laminate product according to any of claims 1 to 9, comprising the steps of - casting an aluminum alloy according to any of claims 1 to 6 to form an ingot; - reheat and/or homogenize the ingot preferably at a temperature of 460 °C to 560 °C, - hot rolling the ingot to a final hot rolling thickness, preferably at a temperature of 350 to 500 °C, - cold rolling to obtain a cold rolled product, with a preferred final thickness of 0.2 to 2 mm and preferably 0.5 to 0.8 mm, - optionally annealing said cold rolled product preferably at a temperature of 200 to 300 °C, - cleaning said cold rolled product, preferably with a solvent or an aqueous cleaner containing surfactants, - optionally provide a matt or glossy appearance, for example by satin matte etching or by chemical/electrochemical polishing, - anodizing said cold rolled product in sulfuric acid, phosphoric acid or oxalic acid or a combination thereof to obtain a porous film of anodic oxide, - coloring said porous film of anodic oxide by electrochemical deposition preferably of at least one of Zn, Ni, Sn, Co, Cu, Ag or chemical deposition preferably of at least one dye among an azo dye, an anthraquinone dye, an indigo dye , - rinse with deionized water, - optionally sealing the porous anodic oxide film by hydrothermal sealing, cold sealing or a combination thereof, - dry off, - coating the porous anodic oxide film by deposition of a sol-gel precursor followed by evaporation and/or curing. 11. A method according to claim 10, wherein the sol-gel precursor is prepared from a mixture of a polysiloxane, preferably prepared from an alcoholic silane solution, more preferably from an alcoholic solution of an alkoxysilane and an aqueous solution of colloidal silica. 12. A method according to claim 11, wherein the sol-gel precursor is prepared from two solutions A and B, solution A is an alcoholic solution of one or more alkoxysilanes, the alcohol used as solvent is methanol , ethanol, propanol, preferably isopropanol, butanol or a combination thereof, the alkoxysilanes are described by the general formula XnSi(OR)4-n where "R" is a simple alkyl, preferably chosen from the group consisting of methyl, ethyl, propyl and butyl and "X" is also an alkyl, preferably selected from the group consisting of methyl, ethyl, propyl and butyl; solution B is a solution of colloidal silica dissolved in water. 13. A method according to claim 12, wherein said alkoxysilanes belong to the group comprising tetramethoxysilane (TMOS), tetraethoxysilane (TEOS) and methyltrimethoxysilane (MTMOS). A method according to claim 13, wherein solution A contains 25-35 wt% TEOS and 15-25 wt% MTMOS, both dissolved in 40-60 wt% isopropyl alcohol.