DE102010016973B4 - Method for producing a one-sided metallized control element made of plastic with backlit symbolism - Google Patents

Abstract

Method for producing a one-sided metallized control element made of plastic with backlit symbols, e.g. B. for a motor vehicle, with the following process steps: a. Generate a plastic body with i. a rear part of a non-galvanizable plastic A, and ii. a front-mounted galvanizable layer made of a galvanizable plastic B, the partial body and the galvanizable layer being produced by the injection molding process and the galvanizing layer being injection molded onto the partial body using the injection molding process, or vice versa, b. Chemical or physical deposition of an electrically conductive first metal layer on the galvanizable layer of the plastic base body, c. Structuring the first metal layer by partial removal to form the symbolism, and d. Electrochemical deposition of at least one second metal layer on the structured first metal layer.

Description

The present invention relates to a method for producing a one-sided metallized control element made of plastic with backlit symbolism, in particular for use in motor vehicles, for example, as an operating element for on-board driver information systems or for the activation of on-board functions such as interior lighting, start / stop button, controls an air conditioner, switch for Vehicle lighting etc.

Essentially, two methods for producing metallized operating elements made of plastic are known from the prior art. These are based either on the metallization of a control element made of a plastic by means of PVD method (physical vapor deposition), or on the galvanization of a control element made of plastic by means of electrochemical methods. While both methods basically allow to apply durable metal coatings on controls made of plastic, it is still problematic to date by means of PVD process control elements so that the deposited on the plastic part metal layer without additional protective layer z. B. from a transparent protective lacquer has sufficient abrasion resistance and corrosion resistance. Also, plastic parts metallized by PVD method due to the small thicknesses of the deposited metal layers do not have the often desired "cold touch" on, d. H. The feel of the metallized plastic part does not match that of a metal part.

Of the DE 102 08 674 A1 is a method for producing one-sided galvanically metallized plastic control elements refer. In particular, a method for producing a front galvanically metallized control element with backlit symbols is disclosed, wherein in the disclosed method in a first step, a base body of a transparent or translucent plastic material with a front and a back is prepared, wherein in the subsequent process step, an area Back is covered or shielded to avoid a galvanic coating in this area. Then the base body is electrically contacted with the cover or shield applied. Subsequently, the base body is chemically or optionally galvanically pretreated to produce a thin layer of metal outside the covered area. Subsequently, this first metal layer is partially removed to produce the symbol. Finally, the metallic surface coating is completed by galvanic means. In the abovementioned patent application, it is proposed to either apply a protective lacquer to the metal layer for partial removal of the metal layer and subsequently etch off the areas of the metal layer not covered by the protective lacquer. Alternatively, it is proposed to generate the symbol by means of laser ablation.

Even if that is from the DE 102 08 674 A1 previously known method has basically proven in practice, it still has the disadvantage that the invention carried out process step of partially covering the back surface of the galvanizable body makes the production of metallized controls on a large scale and therefore expensive. Also, process safety is adversely affected by the additional process step of applying a backside resist.

The EP 1 930 925 A1 discloses, for example, a method for producing a partially galvanized, transilluminable plastic component, which has a translucent symbolism in the electroplating layer. It is proposed to inject a galvanisable film with a non-galvanisable plastic, so as to form a plastic component. For the formation of the backlit symbolism, it is proposed either to cover the film on the front with a non-electroplatable layer, for. B. in screen printing. Only the uncovered areas are then galvanized. Alternatively, it is proposed to partially remove the plastic film to form the symbolism, z. B. by lasers.

Furthermore, in the EP 1 930 925 A1 proposed to inject the electroplated film with several components, z. B. with an opaque, non-galvanisable material z. B. to form a peripheral region of a control knob, as well as with a transparent, also not galvanisable material, which is arranged behind the symbolism and forms a transilluminable mechanical support for the film in the field of transilluminable symbolism.

The WO 2004/099460 A2 On the other hand, discloses a solution in which a layer of a galvanisable plastic or a metal is applied to a base body made of a non-galvanisable plastic. The galvanisable plastic is to be applied in particular by painting, while a metal layer can be produced for example by means of PVD process. The electroplated layer thus produced is then removed as completely as possible to form a symbolism in subregions of the surface. This is followed by galvanization, which then eliminates the symbolism created in the previous step.

Object of the present invention is to provide a method for producing a one-sided metallized plastic control element, which can be carried out at low cost even on a large scale.

This object is achieved by a method having the features of the main claim.

• a. Erzeugen eines Kunststoff-Grundkörpers mit
• i. einem rückseitig angeordneten Teilkörper aus einem nicht galvanisierbaren Kunststoff A, und
• ii. einer vorderseitig angeordneten galvanisierbaren Schicht aus einem galvanisierbaren Kunststoff B, wobei der Teilkörper und die galvanisierbare Schicht im Spritzgussverfahren hergestellt werden und die galvanisierbare Schicht an den Teilkörper im Spritzgussverfahren angespritzt wird, oder umgekehrt,
• b. Chemisches oder physikalisches Abscheiden einer elektrisch leitfähigen ersten Metallschicht auf der galvanisierbaren Schicht des Kunststoff-Grundkörpers,
• c. Strukturieren der ersten Metallschicht durch partielles Abtragen zur Ausbildung der Symbolik, und
• d. Elektrochemisches Abscheiden zumindest einer zweiten Metallschicht auf der strukturierten ersten Metallschicht.

The method according to the invention is provided for producing a front-side metallized plastic operating element with backlit symbolism, in particular for use in a motor vehicle. The method comprises at least the following method steps:

• a. Generating a plastic body with
• i. a rear side arranged part body of a non-plateable plastic A, and
• ii. a front side arranged galvanisable layer of a galvanisable plastic B, wherein the part body and the electroplatable layer are produced by injection molding and the galvanisable layer is injection-molded onto the part body by injection molding, or vice versa,
• b. Chemical or physical deposition of an electrically conductive first metal layer on the electroplatable layer of the plastic base body,
• c. Structuring the first metal layer by partial removal to form the symbolism, and
• d. Electrochemically depositing at least one second metal layer on the patterned first metal layer.

By chemical or physical deposition of the electrically conductive first metal layer on the electroplatable layer of the plastic base body in the context of the present invention, an electroless, d. H. not understood electrochemical deposition of the metal layer. By way of example, the deposition of a nickel layer from an electrolyte solution by means of a colloidal method will be described below.

As part of the abovementioned colloidal process, a layer of palladium nuclei is deposited on the electroplatable layer from an electrolyte solution in a first step. This process step is often referred to as "activating the surface" of the component to be plated. This is exemplified in the comments in the DE 102 08 674 A1 directed. It is known from the prior art, for example, that to activate the surface of the base body, palladium nuclei can be applied from a colloidal solution to the electroplatable layer, wherein these applied palladium nuclei can be protected by a tin protective colloid layer. It has proved to be advantageous if, prior to the subsequent application of the first metal layer to the activated, electroplatable layer, a tin protective colloid layer possibly covering the palladium nuclei is removed. This process, which is also referred to as "stripping", can be carried out, for example, by washing the activated electroplatable surface of the base body.

Subsequently, a first metal layer, preferably of nickel or copper, as the first metal layer is deposited on the activated surface of the basic body of the control element by chemical non-electrochemical means (ie, currentless) in a suitable metal bath (so-called "chemical nickel" or "chem. Copper").

As an alternative to the chemical deposition of the first metal layer is a deposition by physical methods available, here in particular by means of PVD method ("physical vapor deposition").

If a nickel or a copper layer is deposited chemically or physically, it typically has a layer thickness between 100 nanometers and 5 micrometers, preferably between 500 nanometers and two micrometers, and particularly preferably about 1 micrometer. The minimum layer thickness is essentially dependent on the layer thickness from which a sufficient electrical conductivity of the first metal layer is formed. Also, the minimum layer thickness is determined by the current carrying capacity of the first metal layer, which is required for the subsequent electroplating steps. The maximum layer thickness is determined primarily by the deposition rate of the chemical or physical process used to electrolessly deposit the first metal layer. If the residence time in the corresponding process step is too long, the entire process becomes uneconomical.

Preferably, at least the process steps "activating the surface", "applying the first metal layer (chemically nickel / chemically copper)" and "structuring the first metal layer to form the symbolism" in less than 24 h to undergo a passivation of the reactive surface of the chemical To avoid nickel / chemical copper.

As mentioned, the chemically or physically deposited first metal layer typically has a thickness of one micrometer or less. This first metal layer can then, for example, by means of laser ablation or by lithography, ie by means of structured applied protective lacquer and subsequent etching of the metal layer and washing the protective varnish are structured.

If the electroless deposited first metal layer actually has only a low current carrying capacity, which would be detrimental to the subsequent electrochemical process steps, optionally at low currents, a first metal layer z. Example, of copper or nickel by electrodeposition on the first metal layer are deposited (so-called. "Pre-copper" or "pre-nickel"), which is possible both before and after the structuring of the first metal layer.

In order to complete the metallized operating element, the thickness of the first, now structured metal layer, which is possibly still covered with a thin layer of precursor or nickel, is subsequently determined by means of a galvanic, d. H. increased electrochemical process. As a rule, a first intermediate layer of copper is deposited on the first metal layer for this purpose, which forms a bridge between the plastic base body, which has a high elasticity, and a decorative layer deposited on the surface of the operating element in a subsequent process step on account of its high ductility a hard decorative metal such as chrome or nickel. This first intermediate layer of copper may have a layer thickness of 10 to 40 micrometers and above. As a rule, the electroplating process for depositing the first intermediate layer of copper is adjusted so that a layer thickness of this first intermediate layer of at least 20 micrometres is ensured on all operating elements coated at the same time in the electroplating bath.

Often, a second intermediate metal layer is deposited on the first intermediate layer of copper in order to increase the corrosion resistance of the metal coating. This second intermediate layer can also increase the adhesion of the decorative layer applied to the surface of the operating element to the first intermediate layer. Finally, the appearance of the decorative layer can be selectively influenced by a suitable choice of the material of the second intermediate layer. The application of a second intermediate layer of nickel has proven particularly useful. In this case, this second intermediate layer may in particular consist of cracked nickel, matt nickel, semi-bright nickel or bright nickel and in turn be subdivided into intermediate layers. So has in mechanically particularly stressed controls such. As the shift knob of the gear selector lever of a transmission, or controls that are particularly exposed to the attack of corrosive media such as hand perspiration, a layer structure proven consisting of an applied to the first intermediate layer of copper layer of semi-bright nickel and deposited on the surface layer of matt nickel , on whose surface finally a layer of cracked nickel is applied. The cracked nickel layer contributes to a substantial increase in the corrosion resistance of the entire layer structure, which is considered to be the cause of a controlled corrosion attack on the cracked nickel layer. But the adhesion of the decorative layer is increased by this intermediate layer again. The layer thickness of the second intermediate layer is typically between 5 and 30 micrometers, preferably 10 micrometers and above, in particular with a second intermediate layer of nickel.

Subsequently, a layer of a decorative metal is deposited on the first intermediate layer of copper or the optional second intermediate layer of nickel, which may, for example, be chromium or nickel. Here, recourse is had to the processes known per se for the formation of a semi-gloss or matt nickel layer (aluminum design), a cracked nickel layer or a bright chrome layer. Typical layer thicknesses of this decorative layer are i. A. between 100 nanometers and a few microns, in the case of chromium preferably at least 300 nanometers.

Finally, the metallized surface of the control element can still be provided with a suitable protective and / or decorative paint on the decorative layer of the decorative metal such. As chrome is applied and increases the corrosion resistance of the entire applied to the control panel structure again.

• a. Erzeugen eines nicht galvanisierbaren Teilkörpers aus einem nicht galvanisierbaren Kunststoff A, und
• b. Aufbringen einer galvanisierbaren Schicht aus einem galvanisierbaren Kunststoff B vorderseitig des Teilkörpers.

In a first preferred embodiment of the method according to the invention, the following special procedure for the production of the main body is used:

• a. Producing a non-galvanisable body part of a non-plateable plastic A, and
• b. Applying a galvanisable layer of an electroplatable plastic B on the front side of the part body.

In an alternative process management, the sequence of the production of the electroplatable layer made of an electroplatable plastic B and of the non-electroplatable partial body made of a non-plateable plastic A is reversed on the back of the electroplatable layer.

In both preferred embodiments mentioned above, the base body may be a so-called 2-component component, which is produced by means of suitable injection molding methods from two different plastic components. Preferably, such a sequence is maintained in the production of the two components of the base body, in which first that plastic component is injected, the plastic material must be processed at a higher temperature, ie i. A. has the higher melting point, and in a subsequent process step, the second plastic component to be processed at a lower temperature to the preferably already completely solidified first plastic component is molded.

Furthermore, the injection molding process known as injection molding decoration (IMD) has also proved to be suitable for producing the base body to be used according to the invention. In the context of such an IMD process, a film made of an electroplatable plastic B is placed in an injection mold and subsequently back-injected with a non-plateable plastic A. Depending on the shape of the main body or material properties of the film, it is also conceivable to insert a non-electroplatable plastic A film in an injection mold for the formation of the non-galvanisable back of the body and to inject them with a galvanisable plastic B, wherein from the Plastic B existing component in the finished body forms the galvanisierbare surface of the body. The latter variant of the method has the advantage that the surface of an injection-molded plastic part is to be metallized, for which there are considerably more empirical values in the prior art than for the metallization of plastic films.

As a particularly suitable plastic A for the formation of non-galvanisable body part has proven polycarbonate. In addition to the fact that it practically does not participate in the subsequent process steps, this material has the advantage that it is particularly suitable as a light guide. In addition, PC can be doped well with light-scattering particles, which can be achieved in the control element, a particularly homogeneous light distribution. This can be advantageous, in particular when using only one light source, in order to achieve a homogeneous illumination of the symbolism, in particular if this light source is approximately punctiform.

On the other hand, the materials polyamide, ABS or an ABS / polycarbonate blend have proved to be particularly suitable plastics B for forming the electroplatable layer. A highly resilient mechanical connection of the part body with the electroplatable layer is obtained if the electroplatable layer consists of an ABS / polycarbonate blend and the partial body of polycarbonate. If a polyamide is used for the electroplatable layer, it has proved to be advantageous if, for example, by means of suitable shaping of the electroplatable layer and of the partial body, additional mechanical interlocking is effected between the two. All plastics used A and B are preferably transparent or at least translucent.

If ABS or an ABS / polycarbonate blend is used for the electroplatable layer, a particularly good adhesion of the metal layer electrodeposited on the electroplatable layer can be achieved if the electroplatable layer is subjected to an additional chemical treatment prior to the metallization, which the Roughness of the surface increased. For example, it has proved to be advantageous if the butadiene portions of the ABS plastic are at least partially dissolved out of the surface of the electroplatable layer. This can be done, for example, by means of a chemical treatment of at least the electroplatable layer, but preferably of the entire base body, for. B. be carried out by means of a pickling in a chromosulfuric acid bath. If, on the other hand, use is made of an electrodepositable layer of polyamide, then the surface roughness can be increased before applying the metallization by chemically pretreating at least the electroplatable layer of polyamide, but preferably in turn the entire base body, in order to swell the polyamide layer to effect. Details can be found, for example, the chapter "Pretreatment and chemical metallization" of the technical publication "Plastic Metallization - Manual for Theory and Practice", published in Eugen G. Leuze Verlag, which is hereby added to the disclosure of the present application.

If structuring by means of laser ablation is used to form the symbolism in the metal layer, then this is preferably carried out on the first metal layer, the thickness of which is advantageously between 100 nanometers and 2 micrometers, in particular approximately one micrometer. As mentioned, the minimum layer thickness is essentially determined by the layer thickness at which the metal used has sufficient electrical conductivity and also current carrying capacity for the subsequent galvanization. The maximum layer thickness is - in addition to the limitation of a still economically to be represented residence time in the metal bath - essentially determined by the fact that the metal layer must be partially removed by laser ablation, without that such an energy input is required that the lying below the first metal layer Plastic layer is significantly affected, in particular, for example, is melted.

In the case of laser structuring, it is particularly advantageous if a laser whose wavelength experiences only a low absorption at least in the electroplatable layer of the plastic B, but preferably also in the underlying layer of the non-plateable plastic A, is of particular advantage In this context, the use of IR lasers such as Nd: YAG or CO ₂ lasers has proven particularly useful, which are preferably operated in pulsed mode.

If large-scale symbols are to be formed in the metallized surface of the control element, this may be u. a. by means of large-scale laser ablation, which will be discussed in more detail below. However, it has been found that large-area symbols can advantageously also be produced by structuring the first metal layer with a narrow line width, such that islands are produced in the first metal layer that are electrically insulated from the surrounding regions of the first metal layer. In the electrochemical electroplating steps following the patterning step, this electrically isolated island does not participate in the electrodeposition. Rather, the deposited there first metal layer dissolves in the galvanic bath, so that here the galvanisierbare surface of the control element is exposed. The mentioned fine structures can be produced in a particularly simple manner by means of laser structuring in the first metal layer, for example by laser inscription with a sharply focused laser beam which is preferably pulsed and only has a low power.

• a. Freiräumen der von der Kontur der Symbolik umschlossenen Fläche, und
• b. Schreiben der Kontur der Symbolik.

In a particularly advantageous process management, the following steps for the formation of the symbolism are carried out by means of laser ablation:

• a. Free space of the area enclosed by the contour of the symbolism, and
• b. Writing the contour of the symbolism.

In principle, the order of the method steps is freely selectable, and it has proven to be advantageous in practical testing first to clear the surface of the symbolism and then to trace the contour of the symbolism. Both process guides lead to a sharp transition between the free plastic surface and the first metal layer, which has an advantageous effect on the further metal layers forming in the subsequent electroplating steps. Thus, it has been found that the metallization of controls in which the first metal layer has been structured to form the symbolism as described above has only slight overgrowths in the area of the symbolism to be screened. Since overgrowths in these areas are practically not associated with the surface of the plastic operating element, minimizing overgrowths has directly beneficial effects on the adhesion of the metallization on the surface of the control element at the edge of the symbolism and on the tightness of the applied metallic layer structure. While the former improves the mechanical strength of the control element, the latter leads to a significant increase in the corrosion resistance of the metallization.

In order to clear the area enclosed by the contour of the symbol, the ablating laser beam is advantageously operated pulsed and z. B. performed in the form of hatching over the surface to be cleared. Feed, travel, pulse repetition rate, focus size and pulse energy are set in such a way that the laser spots forming on the operating element surface, i. H. the areas in which ablation occurs have sufficient mutual coverage to clear the total area of the symbology in the sum.

The resulting symbolism in the first metal layer may have a "frayed" border, depending on the chosen process parameters, which reflects the spacing and dimensions of the laser spots used to clear the surface. It has therefore been found to be advantageous if, in a further method step, the contour of the symbolism is again traced with the ablating laser beam. Here, the ablation parameters such. B. Pulse repetition rate and energy and feed are selectively changed so that the contour consists of smaller laser spots with a smaller distance and thus has finer structure sizes. This leads to a sharp contouring of the symbolism formed in the first metal layer, from which the advantages described above result.

Furthermore, when clearing the surface of the symbolism, the risk of damage to the plastic surface can be minimized if the travel path of the laser beam used for clearing does not intersect as much as possible on the surface lying within the contour. In this way, a double action of the ablating laser can be avoided on a position of the surface of the plastic control element, whereby laser-induced damage in the surface can be minimized.

When clearing the surface of the symbolism and also when writing the contour, the risk of laser-induced damage to the plastic part can be further reduced by ablating in a two-step process. In this case, in a first ablation step more than 75% of the layer thickness of the first metal layer and, in a subsequent second ablation step, the layer thickness is further reduced to less than 5% of the original layer thickness, preferably to less than 2%. In general, in the second ablation step, the layer thickness is reduced to such an extent that any remaining residues of the first metal layer are reduced in thickness such that the first metal layer locally no longer has sufficient electrical conductivity and / or current carrying capacity for an electrochemical deposition of further metal layers having. If this condition is met, then this part of the surface of the control element no longer participates in the subsequent galvanic metallization. Even with this special procedure, it is advantageous to avoid laser-induced damage if the travel paths of the laser beam in the first and in the second ablation step do not substantially overlap.

In principle, it is also possible to structure the first metal layer by means of lithographic methods for the formation of the symbolism. For this purpose, it is provided in a suitable manner with a protective varnish, which is either applied directly structured or structured in a separate process step, for example, photolithographically, whereby the surface of the first metal layer is exposed. Subsequently, an etching step is carried out in which the first metal layer is removed where its surface is not covered by the protective lacquer. Finally, in a further method step, the protective lacquer is removed again from the surface of the first metal layer, so that the uncovered, but now structured first metal layer remains, which is subsequently subjected to the electroplating process.

The following is based on the attached 1 an advantageous embodiment of the method according to the invention explained in more detail.

In the process step 1 In an injection mold, a partial body made of a non-plateable plastic A (for example polycarbonate) is produced by means of injection molding.

In the process step 2 An electroformable layer made of an electroplatable plastic B (eg ABS / polycarbonate blend) is injection-molded onto this partial body on the front side, as a result of which the main body of the operating element according to the invention designed as a two-component (2K) component is formed.

In the subsequent process step 3 At least the surface of the electroplatable layer of the operating element is subjected to a pickling process in which the Butadienanteile be dissolved out of the surface of the ABS plastic portion. This process step is preferably carried out in a chromosulfuric acid bath. In addition to the roughening of the galvanisable surface of the plastic operating element, contaminants are removed from the electroplatable surface, in particular possibly adhering organic contaminants.

In the process step 4 the galvanisable surface of the body is activated, ie it is germinated on colloidal solution from the prior art, the surface with palladium nuclei, the palladium nuclei are preferably covered by a tin protective colloid. The tin protective colloid is removed by washing to form a surface with active palladium.

In the process step 5 is applied chemically, that is, without application of a Galvanisierungsstroms, an electrically conductive first metal layer on the activated surface of the body. For this purpose, the base body is introduced into a suitable nickel bath, from which nickel is deposited on the activated surface of the base body (so-called "chemical nickel"). The resulting thin nickel layer ("first metal layer") has a thickness of about one micron.

In an alternative process procedure is in the process step 4a activates the electroplatable surface of the body, ie the surface is germinated from colloidal solution with palladium nuclei, wherein the palladium nuclei are preferably covered by a tin protective colloid. This is replaced by copper in a process step, not shown, in an alkaline solution. The resulting copper layer offers a sufficiently high coverage and thus electrical conductivity in order to be able to be electrochemically electroplated without further intermediate steps (such as, for example, the deposition of chemical nickel / chemical copper). This process is also referred to as direct metallization.

Furthermore, it is known that the sequence of the process steps, not shown in the figure, sources of the plastic (ABS, ABS-PC, PC, PES, PEI, PEEK, etc.), pickling in an oxidizing solution (chromic acid, potassium permanganate, etc.). Activating in a metal complex-containing solution, crosslinking by formation of metal sulfides in an alkaline sulfide solution, and finally electrochemical plating in a metal bath allows to dispense with a time-consuming electroless deposition of chemical nickel or chemical copper.

In the optional process step 6 For example, the layer thickness of the thin nickel layer is increased by several 100 nanometers by means of electrochemical deposition of nickel or copper at low current to increase the conductivity and / or current carrying capacity of the first metal layer ("pre-nickel", "precursor").

In the next process step, which is not shown, the base body covered on the electroplatable surface with the first metal layer (that is to say a thin nickel layer and possibly a layer of nickel or precursor) is taken from the electroplating process, washed and dried.

In the next process step 7 For example, the first metal layer is structured by means of an IR labeling laser to form the symbolism. For this purpose, for. B. 8 or 16 controls placed on a holder and with a repeatability of a 10th of a millimeter or better relative to the beam of the marking laser, z. As a Nd: YAG or a CO ₂ laser positioned. Subsequently, the laser ablation is performed while holding the position of the holder. For this purpose, the laser beam of the inscription laser is guided successively over the surface to be structured of the controls located in the holder, ie the controls are lasered one after the other. The processing time required for the complete formation of the symbolism is typically a few seconds. The beam guidance is carried out automatically by means of suitable actuating means. For the formation of the symbolism, the two-step method described in the general part is used, ie in a first stage, the area enclosed by the contour of the symbolism is cleared, and subsequently, with changed laser parameters, the contour of the symbolism is rewritten. In order to avoid unwanted reflections of the marking laser, the holder can be locally cut free in the areas in which the symbolism is formed on the surface of the held, at least translucent, operating elements. Alternatively, the holder may be made of a non-reflective (plastic) material such as polyoxymethylene (POM) or provided with a non-reflective coating.

Subsequently, the main body are now supplied with structured first metal layer the electroplating process. This will be in the next step 8th in a first (if Vorkupfer or Vornickel was applied: second) electrochemical electroplating step, a first metallic intermediate layer electrodeposited. This is usually made of copper and has a thickness of typically between 10 and 40 microns. This electroplating step is preferably carried out in such a way that a minimum layer thickness of the first copper intermediate layer of 20 micrometers is achieved, regardless of the position of a control element on the holder.

In the following process steps 9 and 10 On the first intermediate layer of copper, a second intermediate layer of nickel is electrodeposited. This can, for. B. be designed as a single-layer of matte nickel with a thickness of at least 10 microns. Alternatively, the second intermediate layer may also be formed as a layer sequence of bright nickel, semi-bright nickel, matt nickel, microporous nickel and / or cracked nickel. Proven in practice, for example, has a layer structure of about 5 micrometers semigloss nickel, on which subsequently a layer with a thickness of about 5 microns of matt nickel or bright nickel (depending on the desired appearance of the finished metallized surface) is applied. This layer structure has a high corrosion resistance due to the positive properties of semi-bright nickel. If the metallized operating elements are intended for use in a highly corrosive environment, then it has proven useful to use at least one intermediate layer of cracked nickel, in particular to use a layer sequence of semi-bright nickel, bright or matt nickel and cracked nickel for the second intermediate layer.

Finally, in the process step 11 On the second intermediate layer of nickel, a layer of a decorative metal is deposited galvanically, which may, for example, be chromium. Typical layer thicknesses of this decorative layer are i. A. between 100 nanometers and a few microns, in the case of chromium preferably at least 300 nanometers.

Optionally, after removal of the main body from the electroplating, followed by a cleaning and a drying step (not shown in the figure), in a further process step, not shown, a coloring of the metallized surface by means of PVD method. Here, between 100 nanometers and a few micrometers thick metal layer z. B. applied from gold. Here is a wide range of colors can be achieved.

Finally, in a final process step (not shown), a lacquer layer can be applied which, for example, can change or improve the appearance of the metal layer applied on the front side or its corrosion resistance.

Claims (20)

Method for producing a one-sided metallized control element made of plastic with backlit symbolism, z. For a motor vehicle, with the following process steps: a. Generating a plastic body with i. a rear side arranged part body of a non-plateable plastic A, and ii. a front side arranged galvanisable layer of an electroplatable plastic B, wherein the part body and the electroplatable layer are produced by injection molding and the electroplatable layer is injection-molded onto the part body by injection molding, or vice versa, b. Chemical or physical deposition of an electrically conductive first metal layer on the electroplatable layer of the plastic base body, c. Patterning the first metal layer by partial ablation to form the symbology, and d. Electrochemically depositing at least one second metal layer on the patterned first metal layer. A method according to claim 1, characterized in that for the chemical deposition of the electrically conductive first metal layer, a layer of palladium nuclei on the electroplated layer is applied. A method according to claim 2, characterized in that the applied palladium nuclei are protected by a tin protective colloid layer. A method according to claim 3, characterized in that before the chemical deposition of the first metal layer, the tin protective colloid layer is removed. A method according to claim 1, characterized in that before depositing the first metal layer, the surface to be plated of the electroplatable layer is roughened, z. B. by chemical treatment. A method according to claim 1, characterized in that for producing the plastic base body, the following method steps are carried out: a. Producing a non-galvanisable part body made of a non-plateable plastic A, b. Applying a galvanisable layer of an electroplatable plastic B on the front side of the part body. A method according to claim 1, characterized in that for producing the plastic base body, the following method steps are carried out: a. Producing a galvanisable layer of an electroplatable plastic B, and b. Applying a non-galvanisable part body made of a non-plateable plastic A on the back of the electroplatable layer. A method according to claim 1, characterized in that the plastic B is a transparent or translucent polyamide, ABS or ABS / polycarbonate blend. A method according to claim 1, characterized in that the plastic A is a polycarbonate. A method according to claim 1, characterized in that the partial removal of the first metal layer by means of laser ablation. A method according to claim 10, characterized in that a pulsed laser is used for the laser ablation. A method according to claim 10, characterized in that for the laser ablation, a laser is used whose wavelength undergoes a low absorption in the plastic A and / or in the plastic B. A method according to claim 10, characterized in that a Nd: YAG, a CO ₂ - or a UV laser is used. A method according to claim 10, characterized in that to form the symbolism, the following steps are performed: a. Clear the area enclosed by the contour of the symbolism, and b. Writing the contour of the symbolism. A method according to claim 14, characterized in that for clearing the area enclosed by the contour of the symbolism: a. in a first ablation step, more than 75% of the layer thickness of the first metal layer is removed, and b. in a subsequent second ablation step, the layer thickness within the contour is reduced to less than 5% of the original layer thickness. A method according to claim 14 or 15, characterized in that when clearing the surface of the travel path of the laser beam used on the surface lying within the contour substantially does not intersect within an ablation step itself. A method according to claim 16, characterized in that when clearing the surface, the travel paths of the laser beam in the first and in the second Ablationsschritt do not substantially overlap. A method according to claim 11 and 14, characterized in that the laser spots used to clear the surface have a higher distance from each other than the laser spots used to write the contour. Method according to claim 1, characterized in that at least one island, which is insulated electrically relative to the surrounding metal layer, is produced in the metal layer by the partial removal of the first metal layer. A method according to claim 19, characterized in that the isolated island is washed off in a subsequent electroplating step.

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