Endless metal strip and coil coating process for multi-layer coating of this endless metal strip

Description

Technical area

[0001] The invention relates to an endless metal strip and a coil coating method for multi-layer coating of an endless metal strip, in which a curable polymeric primer is applied to a flat side of the metal strip by means of a roller application to form a primer layer and a curable polymeric lacquer is applied to this primer layer by means of a roller application to form a top coat layer and this primer layer and top coat layer are cured. State of the art

[0002] A continuous metal strip coating or coil coating process for the multi-layer coating of an endless metal strip in transit is known from the prior art (DE102005061319A1). In such processes, a conversion layer is usually created on a flat side of the metal strip. A curable polymer primer is then applied to this flat side using a roller application to form a primer layer. A curable polymer lacquer is then applied to this primer layer using a roller application to form a lacquer layer. Such known processes can also be used to functionalize metal strips.

[0003] EP2607950A1 discloses a method for electrochemically functionalizing a substrate, in which electrolyte segments are printed onto a pixel electrode layer.

[0004] For the electrical functionalization of a metal strip using the coil-coating process, EP2605280A1 discloses the provision of two continuous electrical conductor tracks, along with photovoltaic cells contacted to them, between an electrically insulating primer on the metal strip and a topcoat layer on the primer. The primer and topcoat are applied using a roller application. Description of the invention

[0005] Based on the prior art described above, the object of the invention is to create a coil coating process that can reproducibly ensure the stable electrochromic functionalization of a metal strip with improved electrochromic and mechanical properties. Furthermore, the coil coating process should be particularly simple and therefore cost-effective to implement.

[0006] The invention achieves the stated object by applying at least one electrochromic element between the primer layer and the topcoat layer, comprising the process steps of printing a, in particular electrically conductive, electrochromic polymer to form an electrochromic layer and / or ion storage layer and providing a solid polymer electrolyte to form an electrolyte layer, wherein the electrolyte layer and the electrochromic layer or the ion storage layer are applied wet-on-wet.

[0007] If at least one electrochromic element is applied between the primer layer and the lacquer layer, the metal strip can be given electrochromic functionality using a coil-coating process if this application includes the process steps of printing an electrochromic polymer, particularly an electrically conductive one, to form an electrochromic layer and / or ion storage layer, and providing a solid polymer electrolyte to form an electrolyte layer. Applying these layers requires particular care in the coil-coating process in order to ensure the desired electrochromic properties on the electrochromic element with comparatively high reproducibility.

[0008] To enable this reproducibility, the invention proposes that the electrolyte layer and the electrochromic layer and / or the ion storage layer be applied wet-on-wet. This ensures, for example, that the electrolyte layer is applied to an uncured electrochromic layer or uncured ion storage layer, or that the electrochromic layer or ion storage layer is applied to the uncured electrolyte layer, thereby improving the bonding of these layers at the joining surface. An electrochromic element with comparatively high mechanical strength can thus be produced reproducibly. Furthermore, the wet-on-wet application smooths out any unevenness at the interface between the layers, thus easily avoiding local stress peaks caused by unevenness at the interface.This slows down the degradation of the layers, enabling the reproducible production of an electrochromic element with a comparatively high number of switching cycles without a significant degradation of the electrochromic properties. Furthermore, such a smooth interface created by wet-on-wet application can reproducibly produce an electrochromic element with both homogeneous contrast and homogeneous switching behavior.

[0009] Generally, it is mentioned that the metal strip can be made of iron or aluminum or their alloys. This metal strip can be uncoated or coated – e.g., organic / metallic, galvanized, or alloy-galvanized. This metal strip can also be galvanized or alloy-galvanized steel strip. Generally, it is further mentioned that the respective layers can be applied wet-on-wet in such a way that flow between the two layers is permitted, at least at their common interface. This means that a wet layer is applied to a layer that is not completely dry, i.e., one that has been dried / aired off, or is not yet fully cured / uncured, to enable a "wet-on-wet" application.

[0010] The process can be further simplified if an electrochromic polymer is printed to form the electrochromic layer and the ion storage layer.

[0011] A vertically arranged electrochromic element can be manufactured particularly easily if the ion storage layer, the electrolyte layer, and the electrochromic layer are applied one above the other. Printing these layers can prove particularly advantageous. It is generally stated that improved electrochromic functionality can be achieved on the electrochromic element if—as seen from the metal strip—the electrolyte layer is applied, in particular printed, to the ion storage layer and the electrochromic layer is applied, in particular, printed to the electrolyte layer.

[0012] Printing the solid polymer electrolyte can contribute to a simpler manufacturing process using the coil coating method. Preferably, a roll-to-roll process is used to ensure high line speeds.

[0013] If the electrochromic polymer is applied with at least one solvent, a sufficiently moist polymer mass can be ensured for wet-on-wet application in the coil coating process, even at comparatively high line speeds. A simple process solution is to use H2O as a solvent for this purpose.

[0014] The above-mentioned properties can also be achieved with a solid polymer electrolyte if this solid polymer electrolyte is coated with at least one solvent, particularly tetrahydrofuran. NMP (N-methyl-2-pyrrolidone) can also excel in this regard.

[0015] The manufacturing process for the electrochromic element can be further improved in the coil-coating process if the electrochromic layer and / or ion storage layer and / or the electrolyte layer are actively pre-cured before the other layer of the electrochromic element is applied. This can particularly facilitate a printing process with roll-to-roll application – and thus further increase the reproducibility of the process.

[0016] The printing of a wet layer can be ensured in a reproducible manner, in particular, if pre-curing takes place up to a viscosity in the range of 30 to 125 seconds [s], measured in DIN cup 4 according to DIN 53211 at 20°C (degrees Celsius).

[0017] A particularly easy-to-manufacture electrochromic element with excellent electrochromic properties can be created if the electrically conductive, electrochromic polymer comprises PEDOT:PSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate].

[0018] The application of the polymer electrolyte in the coil coating process can be further facilitated if the solid polymer electrolyte has PVDF-HFP [poly(vinylidene fluoride-hexafluoropropylene)] or PVC-PMMA [poly(vinyl chloride)-poly(methyl methacrylate)] as the electrolyte carrier.

[0019] If the solid polymer electrolyte contains an alkali metal salt, in particular LiCF3SO3 [lithium trifluoromethanesulfonate], as the electrolyte salt, this can further increase the reproducibility of the process.

[0020] The printed electrochromic polymer can result in a layer thickness of 50 nm to 1 µm, preferably 200 to 500 nm, and in particular 200 nm to 600 nm to improve the electrochromic functionalization of the metal ribbon.

[0021] It is also an object of the invention to provide an endless metal strip with an electrochromic element which has high mechanical and electrochromic properties.

[0022] The invention solves this problem by means of an endless metal strip having a primer layer, a top coat layer and an electrochromic element provided between the primer layer and the top coat layer, which element has a first electrode, an electrochromic layer, a solid electrolyte layer, an ion storage layer and a second electrode, wherein a first electrically conductive, electrochromic polymer forms both the first electrode and the electrochromic layer and a second electrically conductive, electrochromic polymer forms both the ion storage layer and the second electrode.

[0023] By applying the electrolyte layer and the electrochromic layer and / or the ion storage layer of the electrochromic element wet-on-wet, not only can the mechanical strength of the layers at the joint surface be improved, but the interface between these layers can also be advantageously smoothed, which improves the electrochromic properties of the electrochromic element. This leads to reduced degradation of the layers and thus an increased service life of the electrochromic element, as well as a more homogeneous contrast and switching behavior. This enables a particularly mechanically stable or improved electrochromic functionalization of a metal strip.

[0024] In general, it is mentioned that the electrolyte layer and the electrochromic layer and / or the ion storage layer can be connected, for example, via a smoothed interface formed between these layers by a wet-on-wet application.

[0025] The mechanical stability and electrochromic functionalization can be further improved if the electrically conductive, electrochromic polymer comprises PEDOT:PSS and / or the solid polymer electrolyte comprises PVDF-HFP or PVC-PMMA as the electrolyte carrier. This can be further enhanced if the solid polymer electrolyte comprises an alkali metal salt, particularly LiCF 3 SO 3 , as the electrolyte salt. Short description of the drawings

[0026] The figures show, for example, the subject matter of the invention in more detail using several embodiments. Fig. 1a schematic view of a device for a coil coating process, Fig. 1a an alternative embodiment of the Fig. 1 shown device, Fig. 2 a cut-away and torn-open plan view of an endless metal belt according to a first embodiment - manufactured according to Fig. 1 shown coil coating process, Fig. 3 a sectional view according to III-III of the Fig. 2 and Fig. 4 a sectional view of another endless metal belt according to a second embodiment. Ways to implement the invention

[0027] According to Fig. 1 a device 1 for carrying out the coil coating process according to the invention is shown, in which an endless metal strip 2, for example a steel strip (galvanized / non-galvanized), is unwound from a coil 3 and continuously coated with a multi-layer coating 4 as it passes through the strip (see the Figuren 3 ).

[0028] Using a roller 5 of a coater (not shown), a curable polymeric primer 7 is applied to a flat side 6 of the metal strip 2 to create a primer layer 7.1 on this flat side 6. The primer 7 can, for example, be polyester-based. This is known to increase the adhesion to and / or corrosion protection of the metal strip 2.

[0029] A curable polymeric lacquer 8, which also has a polyester base, for example, is then applied to the primer layer 7.1 on the flat side 6 of the metal strip 2 to form a topcoat layer 8.1. This application is carried out—similar to the primer application—using a roller 9 of a coater (not shown). The applied primer 7 and the applied lacquer 8 are each cured by a dryer 10, 11 and / or cured by chemical crosslinking.

[0030] Before applying the primer layer 7.1 on the upper flat side 6 of the metal strip 2, it is conceivable that a sol-gel 12 is sprayed on to create a conversion layer.

[0031] According to the invention, the metal strip 2 is electrochromically functionalized. For this purpose, an electrochromic element 13 is applied between the primer layer 7.1 and the topcoat layer 8.1 using the coil-coating process. Specifically, an electrically conductive, electrochromic polymer 14 and a solid polymer electrolyte 15 are applied using the coil-coating process.

[0032] Here, the electrically conductive, electrochromic polymer 14 is printed using a printer 17 (e.g., by digital printing, screen printing, gravure printing, etc.). The electrically conductive, electrochromic polymer 14 forms an electrochromic layer 14.1 or ion storage layer 14.2 on the metal strip 2, each with a layer thickness of 400 nm. Likewise, the solid polymer electrolyte 15 is printed onto the metal strip 2 using a coil-coating process—specifically, using a coater (not shown) that uses a roller 16 to create an electrolyte layer 15.1 on the metal strip 2 using a roll-to-roll process.

[0033] The electrically conductive, electrochromic polymer 14 comprises PEDOT:PSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate] and optionally also a solvent (e.g., H2O and / or isopropanol-based). The printability of such an electrically conductive, electrochromic polymer 14 can be improved if PEDOT:PSS is applied as an aqueous and / or isopropanol-based dispersion.

[0034] The solid polymer electrolyte 15 is made from a mixture of PVC-PMMA [poly(vinyl chloride)-poly(methyl methacrylate)] as electrolyte carrier and LiCF 3 SO 3 [lithium trifluoromethanesulfonate] as electrolyte salt with 18 weight percent PVC, 42 weight percent PMMA, and 40 weight percent LiCF 3 SO 3. This mixture is dissolved in THF (tetrahydrofuran) at a ratio of 1 to 9.

[0035] A mixture of PVDF-HFP [poly(vinylidene fluoride-hexafluoropropylene)] as the electrolyte carrier and LiCF 3 SO 3 [lithium trifluoromethanesulfonate] as the electrolyte salt, with 77 weight percent electrolyte carrier and 23 weight percent electrolyte salt, is also conceivable as the solid polymer electrolyte 15. This mixture, containing 1.3 g, can be dissolved in 6 g of NMP (N-methyl-2-pyrrolidone). The applied solid polymer electrolyte 15 results in a layer thickness in the range between 2.7 and 13.5 µm.

[0036] Excellent electrochromic and mechanical properties of the electrochromic element 13 are ensured by applying the electrolyte layer 15.1 and the electrochromic layer 14.1 or the ion storage layer 14.2 wet-on-wet. To achieve this, one of these layers 14.1, 14.2, or 15.1 is still moist or wet and thus not fully cured—to which the other wet layer 14.1, 14.2, or 15.1 is applied. This allows for flow of at least those layers to which the wet layer is applied, smoothing out any unevenness and ensuring a smooth interface 18.1 or 18.2 between the respective layers 14.1, 14.2, or 15.1. This reduces the degradation of the electrochromic element 13, resulting in a comparatively large number of switching cycles without any significant deterioration of the electrochromic properties.This also enables a homogeneous contrast and a homogeneous switching behavior on the electrochromic element 13 - whereby this type of material-to-material joining at the interface 18.1 or 18.2 and thus also the joining surface ensures a high adhesive strength and leads to a high stability on the electrochromic element 13.

[0037] As particularly in Fig. 1 As can be seen, one electrochromic polymer 14 is printed for each of the electrochromic layers 14.1 and the ion storage layer 14.2. It is conceivable that only one printer 17 is used to print the two layers 14.1, 14.2. Since the electrochromic polymer 14 is also electrically conductive, the electrochromic layer 14.1 and the ion storage layer 14.2 simultaneously form the electrodes, or rather the first electrode 22.1 and second electrode 22.2, of the electrochromic element 13 - as shown in Fig. 2 can be seen.

[0038] The Fig. 3 It can be seen that the electrochromic layer 14.1 and the ion storage layer 14.2 are provided side by side on the metal strip 2. The electrolyte layer 15.1 is applied wet to these two layers 14.1, 14.2, with the electrochromic layer 14.1 and the ion storage layer 14.2 still wet in order to ensure the advantages according to the invention at both boundary layers 18.1, 18.2 or joining surfaces.

[0039] The solid polymer electrolyte 15 also contains a solvent, namely tetrahydrofuran.

[0040] Electrochromic layer 14.1, ion storage layer 14.2 and solid electrolyte layer 15.1 can be pre-cured as done by the dryers 19, 20 in the Figuren 1 und 1a is indicated.

[0041] Pre-curing the electrochromic layer 14.1 and / or ion storage layer 14.2 can facilitate the application / printing of the electrolyte layer 15.1 (cf. Fig. 1 ).

[0042] In addition, pre-curing the electrolyte layer 15.1 can facilitate the application / printing of the electrochromic layer 14.1 or ion storage layer 14.2 (cf. Fig. 1a ).

[0043] Layers 14.1, 14.2, or 15.1 are precured prior to the wet application of the other layers 14.1, 14.2, or 15.1, respectively, such that this precured layer has a viscosity measured in a DIN cup 4 according to DIN 53211 in the range of 30 to 125 seconds [s] at 20°C. This ensures reproducible wet-on-wet application of the respective layers—and, in particular, further optimizes the influence of the interface between the wet-on-wet layers. Furthermore, it is possible to reproducibly enable wet printing of the other layers (electrochromic layer 14.1, ion storage layer 14.2, and solid electrolyte layer 15.1).

[0044] In the Fig. 4 An alternative embodiment of an electrochromic element 21 is disclosed: This electrochromic element 21 is applied to the metal strip 2 by means of a device 1, which device 1 is electrochromically functionalized according to Fig. 1a In contrast to the Fig. 1 The electrochromic functionalization shown is carried out according to Fig. 1a the application of the electrolyte layer 15.1 in the strip passage between the application of the ion storage layer 14.2 and the electrochromic layer 14.1.

[0045] Through this design change to the device or through this process change, the electrochromic element 21 can be Fig. 4 This vertical structure of the electrochromic element 21 is shown in Fig. 4This can be seen from the fact that, as seen from the metal strip 2, the electrolyte layer 15.1 is applied or printed onto the ion storage layer 14.2 and the electrochromic layer 14.1 is applied or printed onto the electrolyte layer 15.1.

[0046] Preferably, both the ion storage layer 14.2 and the electrolyte layer 15.1 as well as the electrolyte layer 15.1 and the electrochromic layer 14.1 are applied or printed wet-on-wet.

Claims

1. Coil-coating process for the multilayer coating of an endless metal strip (2), in which a curable polymeric primer (7) for forming a primer layer (7.1) is applied to a flat side (6) of the metal strip (2) by means of a roller application and a curable polymeric lacquer (8) for forming a topcoat layer (8.1) is applied to this primer layer (7.1) by means of a roller application to form a topcoat layer (8.1) and this primer layer (7.1) and topcoat layer (8.1) are cured, characterized in that at least one electrochromic element (13, 21) is applied between the primer layer (7.1) and topcoat layer (8.1), comprising the process steps of printing an, more particularly electrically conductive, electrochromic polymer (14) to form an electrochromic layer (14.1) and / or ion storage layer (14.2) and providing a solid polymer electrolyte (15) to form an electrolyte layer (15.1), wherein the electrolyte layer (15.1) and the electrochromic layer (14.1) or the ion storage layer (14.2) are applied wet-on-wet.

2. Coil-coating process according to claim 1, characterized in that an electrochromic polymer (14) is printed in each case to form the electrochromic layer (14.1) and the ion storage layer (14.2).

3. Coil-coating process according to claim 1 or 2, characterized in that the ion storage layer (14.2), the electrolyte layer (15.1) and the electrochromic layer (14.1) are applied, more particularly printed, on top of one another.

4. Coil-coating process according to claim 1, 2 or 3, characterized in that the solid polymer electrolyte (15) is printed, more particularly using a roll-to-roll process.

5. Coil-coating process according to one of claims 1 to 4, characterized in that the electrochromic polymer (14) is applied with at least one solvent, more particularly H2O.

6. Coil-coating process according to one of claims 1 to 5, characterized in that the solid polymer electrolyte (15) is applied with at least one solvent, more particularly THF (tetrahydrofuran) or NMP (N-methyl-2-pyrrolidone).

7. Coil-coating process according to claim 5 or 6, characterized in that the electrochromic layer (14.1) and / or ion storage layer (14.2) and / or the electrolyte layer (15.1) are actively pre-cured before the respective other layer of the electrochromic element (13, 21) is applied.

8. Coil-coating process according to claim 7, characterized in that pre-curing is carried out up to a viscosity in the range from 30 to 125 seconds [s], measured in DIN cup 4 according to DIN 53211.

9. Coil-coating process according to one of claims 1 to 8, characterized in that the electrically conductive, electrochromic polymer (14) comprises PEDOT: PSS.

10. Coil-coating process according to one of claims 1 to 9, characterized in that the solid polymer electrolyte (15) comprises PVDF-HFP or PVC-PMMA as electrolyte carrier.

11. Coil-coating process according to claim 10, characterized in that the solid polymer electrolyte (15) has an alkali metal salt, more particularly LiCF3SO3, as electrolyte salt.

12. Coil-coating process according to one of claims 1 to 11, characterized in that the printed electrochromic polymer (14) results in a layer thickness of 50 nm to 1 µm, preferably 200 to 500 nm, and more particularly 200 nm to 600 nm.

13. Endless metal strip produced by a process according to one of claims 1 to 12 having a primer layer (7.1), having a topcoat layer (8.1) and having an electrochromic element (13, 21) provided between the primer layer (7.1) and the topcoat layer (8.1), which comprises a first electrode (22.1), an electrochromic layer (14.1), a solid electrolyte layer (15.1), an ion storage layer (14.2) and a second electrode (22.2), wherein a first electrically conductive, electrochromic polymer (14) forms both the first electrode (22.1) and the electrochromic layer (14.1) and a second electrically conductive, electrochromic polymer (14) forms both the ion storage layer (14.2) and the second electrode (22.2).

14. Endless metal strip according to claim 13, characterized in that the electrically conductive, electrochromic polymer (14) comprises PEDOT:PSS.

15. Endless metal strip according to claim 13 or 14, characterized in that the solid polymer electrolyte (15) comprises PVDF-HFP or PVC-PMMA as electrolyte carrier.

16. Endless metal strip according to claim 15, characterized in that the solid polymer electrolyte (15) has an alkali metal salt, more particularly LiCF3SO3, as electrolyte salt.