Method for manufacturing vehicle trims having a predefined pattern motif by laser marking

Abstract

Method for manufacturing vehicle trims having a predefined pattern motif by laser marking, wherein the vehicle trim has a trim panel comprising a three-dimensional shape and a thermoplastic composition which provides a first color, the base color; and the predefined pattern motif is formed by the combination of the first color and a second color obtained by irradiating the decorative surface of the trim panel with a laser beam in such a way that the second color obtained is visually distinguishable from the first color and uniform throughout the entire lasered area, such that the resulting vehicle trim fulfils class A surface requirements for the automotive market.

Description

[0001] A method for manufacturing vehicle linings with a predefined design motif using laser marking. Specifically, the predefined design motif is achieved through color change, i.e., through color contrast between the color of the lining panel forming the vehicle lining and the color obtained after irradiating said lining panel with a laser beam.

[0002] Background of the invention

[0003] It is common to find vehicle coverings, both on the exterior and interior of the vehicle, that have an external appearance comprising visually and / or haptically distinguishable motifs.

[0004] These motifs can serve a decorative function by having a geometric design or imitating certain designs such as wood, fabric or metal, or be a company logo; or they can provide a signaling function by displaying information about some vehicle function, such as the position of a switching area or relevant information about the use of the airbag.

[0005] Several techniques are known for creating such designs on vehicle coverings. Some of these involve adding material such as paint, ink, or even an additional layer that incorporates the design previously applied with paint or ink. Examples include documents EP4140757 and CN108891363.

[0006] Other known techniques involve altering the plastic material that forms the vehicle's coating without adding more material by applying laser energy to the surface of the vehicle's coating according to a predefined design of the corresponding motif. In this case, the laser energy is able to modify the physical and / or chemical properties of the plastic material.

[0007] In these known techniques, laser energy can produce material removal, material carbonization, foaming of the material, change of material color, or a combination of any of these. Some examples are documents JP2003312383, FR2893527, and EP2279914.

[0008] In the case of material removal, the laser energy produces the vaporization of the material irradiated by the laser.

[0009] In the case of material carbonization, the laser energy creates dark or black marks on the irradiated material caused by its melting.

[0010] In the case of foaming in the material, laser energy creates areas with a foam structure when exposed to laser energy, allowing raised marks to be created on the plastic surface of the vehicle coating.

[0011] In cases where the irradiated material changes color, the plastic forming the vehicle's coating reacts with the laser energy to produce a visible color change. To achieve this, the plastic material may contain thermochromic pigments that change color due to the temperature generated by the laser energy.

[0012] Therefore, by combining laser energy with the plastic composition that forms the vehicle coating, it is possible to selectively alter the properties of the plastic to configure the predefined design motif due to the contrast of color and / or texture.

[0013] Laser marking techniques for plastic parts offer a combination of precision, durability, versatility, recyclability, and efficiency that makes them a better option compared to traditional procedures that involve the use of additional materials.

[0014] Furthermore, the automotive market is very demanding with regard to surface quality requirements, commonly referred to as Class A surfaces.

[0015] These Class A surfaces are those aesthetic surfaces visible both on the exterior and interior of the vehicle with an exceptionally fine, continuous and imperfection-free aesthetic finish.

[0016] Taking this into account, the main objective of the present invention is a procedure for manufacturing vehicle coverings that have a predefined design motif by laser marking that meets said quality requirements.

[0017] Therefore, according to the invention, a vehicle coating having a predefined design motif of suitable quality is defined by the fact that there is no material destruction, i.e., the laser energy does not cause material removal, preserving the integrity and structural properties of the plastic part and is able to maintain the original texture of the coating panel, whether smooth or embossed, and its uniformity throughout the laser-treated area; the predefined design motif has high contrast due to the combination of the different laser-treated and non-laser-treated areas; and the laser-treated area is uniform in terms of color throughout the laser-treated area, meaning that the color and tone remain consistent (hue, saturation, brightness, etc.) and there are no differences perceptible to the human eye throughout the laser-treated area.

[0018] Therefore, and to meet the quality requirements, the present invention primarily chooses the color change effect among the different effects that laser energy can produce on a piece of plastic.

[0019] This choice helps to meet some of the quality requirements defined above, in particular it prevents the destruction of the material and allows for high contrast between the laser-treated areas and the non-laser-treated area.

[0020] However, there is still an outstanding issue regarding color uniformity in the laser-treated area.

[0021] This is because the specific color tone obtained from laser irradiation of the base color—that is, the color of the plastic part before laser irradiation—depends on the amount of energy received at each irradiated point and the composition of the plastic part at that particular point. This challenge is especially relevant when the coating part to be marked has a complex three-dimensional shape.

[0022] In this scenario, laser energy can produce an uneven effect on the plastic part due to the difficulty of achieving a homogeneous distribution of additives along the coating and due to the height variations along the surface of the coating panel to be treated with the laser energy as a consequence of its three-dimensional shape.

[0023] In view of the disadvantages mentioned above, the object of the invention is a method for manufacturing vehicle linings having a predefined design motif by laser marking, wherein the vehicle lining comprises a lining panel with a three-dimensional shape and a thermoplastic composition that provides a first color, the base color; and the predefined design motif is formed by the combination of said first color and a second color obtained by irradiating the decorative surface of the lining panel with a laser beam in such a way that the second color obtained is visually distinguishable from the first color and is uniform throughout said laser-treated area, and allows the original texture of the decorative surface to remain unaltered, such that the vehicle lining meets the requirements for Class A surfaces for the automotive market.

[0024] Description of the invention

[0025] According to a first aspect of the invention, the thermoplastic composition forming the cladding panel comprises a thermoplastic base composition and a concentrated blend or masterbatch composition that includes, among others, the base pigment, the thermochromic pigment, and the laser energy-absorbing additive.

[0026] Because both the pigments and the laser energy-absorbing additive are provided using a concentrated mixture, it is possible to obtain a homogeneous distribution throughout the material that forms the cladding panel.

[0027] This ensures uniform coloration and uniform distribution of the laser energy-absorbing additive.

[0028] First, since the second color is obtained from the first color, the more uniformly distributed the base pigment and the thermochromic pigment are, the more uniform the first color will be, and consequently the second color obtained from that first uniform color.

[0029] Secondly, the more uniformly distributed the thermochromic pigment and the laser energy-absorbing additive are, the more uniform the effect of the laser energy on the coating panel will be, and consequently, the more uniform the second color obtained will be throughout the laser-treated area.

[0030] Therefore, both colors that form the predefined design motif, i.e., the first color and the second color, are uniform throughout the cladding panel and, consequently, allow the requirements for Class A surfaces to be met.

[0031] According to another aspect of the invention, the predefined design motif is obtained by irradiating the decorative surface of the cladding panel with a laser beam.

[0032] This method of obtaining the predefined design motif has several advantages compared to those that involve adding an additional material such as paint, ink, or additional layers.In particular, laser decoration provides precise and accurate markings on plastic parts, guaranteeing consistent, high-quality results. The resulting markings are durable and resistant to fading or scratching, ensuring their visual appearance is maintained over time. It allows for a wide range of customization options, providing greater design freedom. Since it does not require the application of additional elements, it reduces material costs and environmental impact because the coating panel can be recycled as a single component. It minimizes the risk of damage to the coating panel during the application of the predefined design pattern because it does not involve physical contact with the decorative surface of the coating panel during the process. It allows for high-speed production without compromising quality or consistency.

[0033] According to another aspect of the invention, the predefined design motif is obtained particularly by changing the color, i.e., by contrasting the color between a first color of the cladding panel provided by the thermoplastic composition, and a second color of the laser-treated area obtained after irradiating the cladding panel with a laser beam.

[0034] According to this color-changing process, the plastic that forms the cladding panel reacts with laser energy to produce a visible color change. To achieve this, its composition includes a thermochromic pigment that changes color with temperature and laser energy-absorbing additives that enhance the absorption of this energy to promote a clearly perceptible color change according to a predefined color. This color change is achieved more quickly and efficiently with low-energy laser sources.

[0035] Therefore, when the temperature exceeds a predetermined value, the color of the thermochromic pigment changes.

[0036] This color-changing process involves a chemical reaction that alters the chemical bonds within the thermoplastic composition produced by laser energy. This reaction may involve the oxidation of thermochromic pigments, the modification of their crystalline structure, the modification of the amount of water in the crystals that form the thermochromic pigments, or the breaking of chemical bonds and the creation of new ones, altering the way the material absorbs and reflects light.

[0037] Furthermore, the presence of the laser energy-absorbing additive allows the color change to be promoted by irradiating with a lower energy level, thus preserving the original texture of the cladding panel.

[0038] This method of obtaining the predefined design motif through color contrast has several advantages compared to those involving the removal or simple carbonization of the plastic material.In particular, it is a non-destructive process that alters the surface color without removing material, preserving the integrity and structural properties of the plastic part and the original texture and uniformity throughout the laser-treated area; it allows for a wide range of colors and shades, offering design flexibility and customization options to suit different aesthetic preferences and achieving high-contrast and visually striking designs; it consumes less energy compared to material removal, contributing to cost savings and environmental sustainability, and avoiding the use of plastic materials that may not withstand the intensity or heat generated by such material removal procedures.

[0039] According to another aspect of the invention, the laser energy is provided by a laser equipment comprising a three-dimensionally mobile pulsed laser.

[0040] On the one hand, since pulsed lasers deliver energy in short bursts, the plastic material can cool down between pulses, reducing the risk of overheating and consequently the risk of discoloration or burning, and allowing the use of heat-sensitive materials; thanks to the high peak power of pulsed lasers, finer details and more precise markings are possible, which is especially useful for three-dimensional shapes.

[0041] According to another aspect of the invention, the laser equipment comprises a dynamically adjustable focus system that allows the laser focus to be modified or adjusted in real time during the application of the laser beam according to the three-dimensional shape of the cladding panel. This maintains a constant distance between the focusing lens and each point in the area to be treated, and consequently, a constant spot size of the laser beam at each of these points. The spot size of the laser beam refers to the diameter of the laser beam in the plane where it interacts with the material to be marked, which forms the decorative layer of the cladding panel.

[0042] This ensures that each and every laser-treated point within the corresponding treated area receives precisely the same amount of energy without interrupting the laser beam's operation. Therefore, marking accuracy is improved, enabling fine and consistent detailing on a cladding panel with a complex geometry without constant adjustments where the laser beam's operation is interrupted. This increases process efficiency by reducing the need to reposition the laser for different areas of the cladding panel according to its three-dimensional shape.

[0043] This is very relevant as it contributes to a uniform color throughout the laser-treated area, regardless of the complex three-dimensional shape of the cladding panel.

[0044] Therefore, due to the manufacturing process of the present invention, the predefined design pattern is formed by combining a first color, the base color of the cladding panel, and a second color, the color of the corresponding laser treatment obtained after irradiation with the corresponding laser beam. Both colors are uniform across the entire decorative surface of the cladding panel, and more specifically, the second color is uniform across the entire laser-treated area. Furthermore, if the decorative surface to be irradiated has a particular textured relief, this texture remains unaltered. In this way, the manufacturing process of the invention allows compliance with the automotive Class A surface requirements in all cases.

[0045] Description of the figures

[0046] This descriptive report is supplemented by a set of figures that illustrate the preferred mode of embodiment and in no way limit the invention.

[0047] Figure 1 shows a schematic representation of the procedure for manufacturing vehicle linings having a predefined design motif by laser marking according to the invention.

[0048] Figure 2 shows a perspective view of a vehicle cladding that has a predefined design motif configured by laser marking.

[0049] Figure 3 shows a schematic representation of a predefined design motif that mimics a wood grain pattern.

[0050] Detailed description of the invention

[0051] Figure 1 shows a schematic representation of the procedure for manufacturing vehicle linings (10) comprising a predefined design motif (3) configured by laser marking on the decorative surface (2.1.1) of a lining panel (2).

[0052] The first step a) of the procedure is to provide a thermoplastic composition (1) that forms the cladding panel material (2). This thermoplastic composition (1) comprises a thermoplastic base composition and a concentrated blending composition or masterbatch.

[0053] The thermoplastic base composition comprises a weight percentage in the range of 90 to 99.5% with respect to the total weight of the thermoplastic composition (1). This may consist of a single plastic material or a combination of several plastic materials provided they are chemically compatible for recycling purposes. Some examples may be polypropylene (PP), polypropylene with 5-20% talc filler, polypropylene with 5-30% fiberglass filler, acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyamide (PA), a mixture of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS), a mixture of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS) with 5-20% fiberglass filler, a mixture of polycarbonate (PC) and acrylonitrile styrene acrylate (ASA), or a mixture of polycarbonate (PC) and acrylonitrile styrene acrylate (ASA) with 5-30% fiberglass filler.

[0054] The concentrated mixture composition comprises a weight percentage in the range of 0.5 to 10% with respect to the total weight of the thermoplastic composition (1) •

[0055] Specifically, said concentrated mixture composition comprises a concentrated mixture thermoplastic carrier, a base pigment, a thermochromic pigment, and a laser energy-absorbing additive.

[0056] Preferably, the thermoplastic carrier of the concentrated blend comprises a weight percentage in the range of 80 to 96% of the total weight of the concentrated blend composition. This may consist of a single plastic material chemically compatible with the material forming the thermoplastic base composition for recycling purposes, or of a combination of several plastic materials provided they are also chemically compatible with each other and with the thermoplastic base composition. Examples include polypropylene (PP), acrylonitrile butadiene styrene (ABS), polycarbonate (PC), polyamide (PA), a blend of polycarbonate (PC) and acrylonitrile butadiene styrene (ABS), a blend of polycarbonate (PC) and acrylonitrile styrene acrylate (ASA), or styrene acrylonitrile (SAN).

[0057] Preferably, the concentrated blend thermoplastic carrier comprises the base pigment.

[0058] Preferably, the thermochromic pigment comprises a weight percentage in the range of 2 to 10% with respect to the total weight of the concentrated mixture composition.

[0059] As mentioned earlier, this thermochromic pigment changes color when a predetermined temperature value is exceeded.

[0060] The resulting color depends on the type of thermochromic pigment used, as each pigment is formulated to change to a specific color at a predetermined temperature. The available color changes are determined by the chemical formulation of the thermochromic pigment. Therefore, the thermochromic pigment is selected according to the characteristic features of the desired pattern.

[0061] Some examples may include, among others, the thermochromic pigments marketed by the company Merck under the brand Iriotec® 8000 series.

[0062] Preferably, the laser energy-absorbing additive comprises a weight percentage in the range of 2 to 10% with respect to the total weight of the concentrated mixture composition, and preferably has an absorbance spectrum in accordance with the wavelength of the radiation provided by the laser beam to enhance energy absorption and thus promote a rapid and clearly perceptible color change of the thermochromic pigment.

[0063] According to a preferred option, the absorbance spectrum is in the near-infrared range, between 700 and 1,100 nanometers.

[0064] Optionally, the concentrated mix composition may include other additives to reach the total weight percentage of the concentrated mix composition. These additives may be UV absorbers, antioxidants, plasticizers, foaming agents, etc.

[0065] The second step b) of the procedure consists of obtaining a cladding panel ( 2 ) from the thermoplastic composition ( 1 ) of step a ).

[0066] The resulting trim panel (2) can be any trim panel forming the interior of the vehicle such as a door panel as shown in Figures 1 and 2, a pillar, an interior roof, a sunshade or a dashboard or any piece forming any of them; or it can be any trim panel forming the exterior of the vehicle such as a door panel, a pillar, a bumper or any piece forming any of them.

[0067] In particular, the objective of this stage is to obtain a cladding panel (2) comprising a first color Ci provided by a homogeneous distribution of the concentrated mixture and the thermoplastic base composition and having a three-dimensional shape.

[0068] According to the invention, the three-dimensional form refers to a cladding panel that not only has width, length, and thickness like a simple uniform plate, but incorporates surfaces with variable elevations, i.e., it includes regions with different heights along the surface to be treated with the laser.

[0069] As mentioned above, the use of a concentrated mixture to provide the base pigment and the thermochromic pigment allows for a homogeneous distribution and consequently a uniform color throughout the cladding panel (2).

[0070] The first Ci color is provided primarily by the combination of the thermoplastic base color with the base pigment colors and the thermochromic pigment that forms the thermoplastic composition (1). This first Ci color is also called the base color because it is the color of the coating panel (2) before its surface is irradiated with the laser.

[0071] There may be several options for obtaining the cladding panel (2), in particular and according to a preferred option of step b) the cladding panel (2) is manufactured entirely by the thermoplastic composition (1) of step a).

[0072] This means that the cladding panel (2) comprises a single layer that simultaneously serves a decorative and a support function.

[0073] According to this option, step b) can be carried out using any tooling (4) and process such as injection molding, extrusion molding or steam chamber molding.

[0074] According to another option, the cladding panel (2) is partially manufactured using the thermoplastic composition (1) of step a), in particular the decorative layer (2.1) that forms the visible surface of the cladding panel (2) is the one comprising said composition (1).

[0075] Therefore, in this case the cladding panel (2) comprises at least two layers, the decorative layer (2.1) mentioned above, which performs the decorative function, and a carrier substrate (2.2) which performs a support function.

[0076] According to this option, the invention considers several variants for manufacturing the cladding panel (2).

[0077] One variant may comprise manufacturing the decorative layer (2.1) beforehand, for example, by extrusion molding. This decorative layer (2.1) may then be laminated with the carrier substrate (2.2), which preferably comprises a material chemically compatible with the thermoplastic composition (1) of step a).

[0078] Optionally, the decorative layer (2.1) obtained according to this variant can be preformed to adopt a three-dimensional shape, before being laminated with the carrier substrate (2.2).

[0079] The lamination process can be carried out in several ways. According to a first method, the carrier substrate (2.2) can also be pre-fabricated, for example by injection molding, and then both the decorative layer (2.1) and the carrier substrate (2.2) are laminated using adhesive means to form the cladding panel (2).

[0080] According to a second method, the decorative layer (2.1) can be introduced into an injection mold, and then the carrier substrate (2.2) can be formed inside the injection mold directly onto the decorative layer (2.1). Therefore, in this case, the lamination takes place inside the injection mold. According to this second method, the decorative layer (2.1) can be preformed into a three-dimensional shape before being introduced into the injection mold, or this three-dimensional shape can be acquired directly inside the injection mold, for example, by vacuum.

[0081] According to a third method, the decorative layer (2.1) and the carrier substrate (2.2) can be laminated within the same injection mold by overmolding, i.e., both layers are manufactured within the same mold by injection molding to obtain the cladding panel (2).

[0082] Additionally, and in accordance with any variant described in this stage b) the decorative surface (2.1.1) of the cladding panel (2) obtained may comprise a decorative texture that can be provided inside the tooling (4) used to manufacture the cladding panel (2) or the decorative layer (2.1) that forms the cladding panel (2) depending on the particular manufacturing process chosen.

[0083] Finally, the third stage c) of the procedure comprises obtaining a predefined design motif (3) visible on the decorative surface (2.1.1) of the cladding panel (2) obtained in stage b) due to a visual contrast between the first color Ci and a second color C2.

[0084] The predefined design motif (3) comprises a visible mark whose design is predefined. It can serve a decorative or signaling function. The second color C2 forming the predefined design motif (3) is obtained by irradiating a first area of ​​the decorative surface (2.1.1) of the cladding panel (2) with a first laser beam providing a first laser energy, thereby creating a first laser-treated area having said second color C2.

[0085] Since the color change occurs due to the effect of laser energy, starting from the first color Ci, that is, the base color of the cladding panel (2), it is possible to obtain different colors by adjusting the laser energy provided in each case.

[0086] To create the first laser-treated area, the first laser beam is applied using a laser device (5) comprising a three-dimensionally movable pulsed laser (5.1) and a worktable comprising a support surface (5.2) extending in an XY plane and configured to support the cladding panel (2) during the marking process. The laser (5.1) further comprises a head (5.1.1) housing a focusing lens for concentrating the laser beam onto a specific point on the decorative surface (2.1.1) of the cladding panel (2) to be treated.

[0087] Preferably, the laser equipment (5) may comprise a solid-state laser such as a fiber laser, an Nd:YAG laser, or an Nd:YV04 laser because they provide high laser beam quality and efficiency.

[0088] Preferably, said laser equipment (5) provides a laser beam with a wavelength in the near-infrared range between 700 and 1,100 nm.

[0089] Preferably, the laser equipment (5) has a power in the range between 10 and 50 W. Preferably, said laser equipment (5) provides each pulse to create individual points to form the laser-treated area.

[0090] Preferably, the laser equipment (5) provides a spot size diameter in the range between 20 and 100 pm.

[0091] Furthermore, the laser equipment (5) allows various parameters to be configured to provide the necessary laser energy in each case to obtain a specific color through the base color or first color Ci as described below.

[0092] Additionally, the laser equipment (5) may comprise control software where the predefined design of the motif is loaded, to adjust the design parameters according to the shape of the cladding panel (2) to be marked; to configure the laser parameters in order to provide a particular laser energy to obtain a particular color according to the predefined design; and to adjust the laser focus in real time according to the three-dimensional shape of the cladding panel (2).

[0093] In particular, the first laser energy to create the first laser-treated area is defined by a first laser energy density, and is obtained by setting first laser parameters.

[0094] Laser energy density, measured in joules per square centimeter, refers to the amount of energy delivered per unit area of ​​the surface to be treated with a laser.

[0095] This laser energy density is defined on the basis of the thermoplastic composition (1) of step a) to modify the chemical structure of said composition (1) without removing material and to obtain a particular color.

[0096] Therefore, to obtain the second color C2, the first laser energy density is defined on the basis of the thermoplastic composition ( 1 ).

[0097] To promote the color change effect according to the composition (1), this laser energy density is preferably in the range between 3 and 20 J / cm² 2 .

[0098] In particular, to obtain the laser energy density, several laser parameters can be controlled, such as the pulse frequency or repetition rate, measured in hertz, defined as the number of pulses emitted per unit of time; the exposure time or pulse duration, measured in seconds; the scanning speed, measured in millimeters per second, i.e., the speed at which the laser beam moves; the laser power, i.e., the percentage of the maximum laser power used; the maximum pulse power, i.e., the maximum power reached during the duration of a single laser pulse; the laser defocus, i.e., the adjustment of the focal point of the laser beam with respect to the surface to be treated to control the energy density; and the line density, i.e., the number of laser lines applied per unit area.

[0099] Depending on the laser equipment used, these parameters can be set directly or indirectly since they may in turn depend on other parameters.

[0100] Optionally, the predefined design pattern (3) can be obtained through the visual contrast between the first color Ci, the second color C2, and a third color C3. This third color C3 is obtained by irradiating a second area of ​​the decorative surface (2.1.1) of the cladding panel (2) with a second laser beam, which provides a second laser energy, thereby creating a second laser-treated area that has this third color C3. Preferably, the second area is different from the first area.

[0101] To create this second laser-treated area, the laser parameters (5) set to configure the first area are readjusted, i.e., set according to different values ​​with respect to the first laser parameters to provide a second laser energy defined by a second laser energy density to obtain a third color C3 different from the second color C2 and the first color Ci.

[0102] Therefore, said second laser energy density is different from the first laser energy density and is defined on the basis of the thermoplastic composition (1) of step a) to modify the chemical structure of said composition (1) without removing material and with the aim of obtaining the third color C3.

[0103] The predefined design motif (3) can be achieved through the visual contrast provided by combining as many colors as necessary to configure the particular design of the predefined motif. For example, if the predefined design motif (3) comprises a wood grain design as shown in Figure 3, the combination of several different colors Ci, C2, C3, C4, C5, C may be required. n obtained each of them by adjusting the laser parameters (5) accordingly.

[0104] To obtain each of the different colors Ci, C2, C3, C4, C5, the three-dimensionally moving pulsed laser ( 5 . 1 ) performs as many laser sweeps as there are different colors needed to configure the predefined design pattern ( 3 ).

[0105] The period of time during which the laser beam irradiates the cladding panel (2) according to certain preselected laser parameters, and where these parameters are kept unchanged to provide a particular laser energy density to obtain a particular color, is called a laser scan. Thus, according to a first laser scan, a second color C2 is obtained by means of a first laser beam whose first laser energy density is defined by some first laser parameters; according to a second laser scan, a third color C3 is obtained by means of a second laser beam whose second laser energy density is defined by some second laser parameters; and so on.

[0106] According to one variant of the invention, the laser-treated areas (first, second, third, etc.) may, in addition to changing color, exhibit a relief due to local foaming of the thermoplastic composition. This foaming may also lighten the color obtained from the thermochromic pigment after being irradiated by the laser beam. This effect is intentional and therefore not incompatible with the process preserving the original texture of the cladding panel.

[0107] Foaming can occur due to the effect of laser energy itself; therefore, this effect can be achieved by controlling the laser parameters to provide a particular laser energy density.

[0108] Additionally, this foaming effect can occur due to the fact that the thermoplastic composition (1) also comprises a foaming agent. The weight percentage of the foaming agent can range from 0.1 to 3% with respect to the concentrated mixture composition.

[0109] According to one variant of the invention, the laser-treated areas (first, second, third, etc.), in addition to changing color and, optionally and intentionally, the relief due to local foaming of the thermoplastic composition, may undergo a slight degree of carbonization if the target color is too dark to be achieved solely through color change. Therefore, this effect can be used to darken the color obtained from the thermochromic pigment after irradiation by the laser beam.

[0110] This carbonization effect can be produced by the effect of laser energy itself.

[0111] According to the invention, step c) in addition to setting the laser parameters mentioned above to obtain a particular laser energy density responsible for obtaining a particular color from the first color Ci or base color, further carries out an adjustment of the focus of the three-dimensionally moving pulsed laser (5.1) in real time during the application of the corresponding laser beam according to the three-dimensional shape of the coating panel (2) obtained in step b).

[0112] This adjustment is made to maintain a constant distance between the focusing lens and each point of the corresponding area to be treated with the laser, in order to maintain a constant spot size of the corresponding laser beam at each of these points. More specifically, in the case of the first laser beam, this applies across the entire first area to be treated; in the case of a second laser beam, it applies across the entire second area to be treated; and so on.

[0113] This dynamic focus adjustment comprises the continuous and automatic movement in the Z direction of the focusing lens located in the head (5.1.1) based on the height variations of the decorative surface (2.1.1) in said Z direction as a result of its three-dimensional shape, so that the distance between said focusing lens and the corresponding point of the area to be treated is always the same throughout the corresponding area to be treated.

[0114] This allows the spot size of the corresponding laser beam at each of the points that make up the corresponding area to be treated with said laser beam to remain constant throughout it, thus ensuring that each of the points that make it up always receives the same amount of energy.

[0115] The Z direction is the direction perpendicular to the support surface (5.2) of the laser equipment worktable where the cladding panel (2) to be treated is supported.

[0116] Depending on the laser equipment used, the Z-axis movement of the focusing lens may vary. In the case of the invention, a laser equipment has been chosen that allows a Z-axis movement of the focusing lens with an amplitude of up to 100 mm.

[0117] However, depending on the equipment chosen, this Z-shaped movement could have a greater amplitude.

[0118] It should be noted that the cladding panels (2) typically subjected to this process mainly exhibit height variations, which would be compensated for by a focusing lens with Z-axis movement capability within that range, with larger height variations being less common. Therefore, from a cycle time perspective, this dynamic focus adjustment is very advantageous.

[0119] For larger height variations, the entire laser head (5.1.1) moves in the Z direction. During this adjustment, unlike that carried out with dynamic focusing, the laser beam stops, i.e., it ceases to work.

[0120] The information relating to the height variation corresponding to the three-dimensional shape of the cladding panel (2) to be treated, is processed by the control software of the three-dimensionally mobile pulsed laser (5) to calculate the corresponding adjustments of the focusing lens to maintain a constant distance between it and each of the points of the area to be treated.

[0121] On the one hand, such height variation information can be acquired, for example, using a scanning system comprising a distance sensor to scan the decorative surface (2.1.1) that measures the height variations along the surface to be treated with a laser.

[0122] The system can then create a height map, identifying any height variations that need to be compensated for during the marking process.

[0123] Furthermore, the laser control software (5) can directly import the CAD (computer-aided design) model of the cladding panel (2) to obtain the height variation information. This allows the control software to pre-program the necessary focus adjustments across the entire surface to be laser-treated during the marking process. This option eliminates the need for additional hardware to measure height variations.

[0124] Once the information regarding the height variation has been acquired, the laser parameters will be adjusted to obtain the corresponding color change as described above. Next, the laser head (5.1.1) will be positioned at an initial height in the Z direction defined by a reference plane, which could be, for example, a plane parallel to the XY plane defined by the support surface of the cladding panel (2) and containing the highest point of the cladding panel (2), i.e., the point closest to the focusing lens of the laser head (5.1.1). Then, the corresponding laser sweep or pass will be initiated, in which, thanks to the dynamic focus adjustment, the focusing lens will move in the Z direction according to the corresponding height variations as the laser head (5.1.1) moves in the XY plane according to the three-dimensional shape of the surface to be treated with the laser beam.As described above, according to the equipment chosen in the present invention, the focusing lens could be moved in the Z direction up to 100 mm from the initial height.

[0125] Thus, the dynamic focus adjustment is performed in real time during the corresponding laser scan by adjusting the position of the focusing lens in the Z direction, ensuring that the laser beam remains correctly focused on each point that forms the decorative surface (2.1.1) to be laser treated, regardless of variations in the height of the cladding panel (2). Therefore, as the corresponding laser beam moves through points with different heights, the focusing lens is continuously adjusted to maintain the spot size of the laser beam unchanged throughout the treated area, thereby ensuring a constant energy application without interrupting its operation.

[0126] This dynamic adjustment of focus is key to ensuring that the color obtained due to the laser energy density provided by the corresponding laser beam defined by particular laser parameters (first laser beam, second laser beam, etc.) remains unchanged throughout the laser-treated area despite changes in the geometry of the cladding panel (2) due to its three-dimensional shape.

[0127] Therefore, according to the manufacturing procedure of the invention, all steps a), b) and c) are carried out so that the second color C2, optionally other colors, obtained are visually distinguishable from the first color Ci and uniform throughout the corresponding laser-treated area, i.e., the second color C2 is uniform throughout the first laser-treated area, the third color C3 is uniform throughout the second laser-treated area and so on, and all colors Ci, C2, C3, etc., are visually distinguishable from each other.

[0128] The following examples describe selected embodiments relating to the composition (1) and the controlled laser parameters for obtaining the laser energy density provided to promote the color-changing effect from the first color Ci, i.e., the base color of the cladding panel (2), to the colors obtained after laser irradiation. These are provided for illustrative purposes. The scope of the invention is defined solely by the claims.

[0129] Example 1

[0130] The vehicle coating (10) comprises a predefined design motif (3) obtained by laser marking comprising two colors, a first color Ci or black base color and provided mainly by the combination of the thermoplastic base color with the base pigment colors and the thermochromic pigment that forms the thermoplastic composition, and a second color C2 that is white and is obtained after laser irradiation according to a first laser energy density defined by first laser parameters.

[0131] The thermoplastic composition (1) comprises a thermoplastic base composition formed from polypropylene (PP) and comprising 98% by weight of the thermoplastic composition (1), and a concentrated blend composition comprising 2% by weight of the thermoplastic composition (1). In particular, the concentrated blend composition consists of a concentrated blend thermoplastic carrier formed from a low-viscosity polypropylene and comprising 90% by weight of the concentrated blend composition, further including a base pigment, particularly a black pigment; the thermochromic pigment being a white thermochromic pigment and comprising 5% by weight of the concentrated blend composition; and a laser energy-absorbing additive comprising 5% by weight of the total weight of the concentrated blend composition.

[0132] The vehicle lining (1) is manufactured entirely from the thermoplastic composition of step a) by injection molding, i.e., it comprises a single layer that simultaneously performs a decorative function and a support function.

[0133] To promote the color change from the first color C1 which is black to the second color which is white, a first area of ​​the decorative surface (2.1.1) is irradiated with a first laser beam applied with a three-dimensionally mobile pulsed laser (5) which is a solid-state fiber laser having a laser power of 40 W and having a wavelength of 1030 nm and comprising a focusing lens with a movement amplitude in the Z direction of 100 mm.

[0134] The first laser beam provides a first energy defined by a first laser energy density of 6.63 J / cm² 2The first laser parameters established to obtain this first laser energy density are a maximum pulse power of 6.6 kW, a pulse frequency of 100 Hz, a scan speed of 4000 mm / s and a spot size diameter of 70 pm.

[0135] Additionally, the focus of the three-dimensionally moving pulsed laser (5) is modified in real time during the application of the first laser beam according to the three-dimensional shape of the cladding panel (2) of step b) to maintain a spot size of 70 µm throughout the first laser-treated area. The first laser-treated area comprises height variations of up to 55 mm with respect to a reference plane defined by a plane parallel to the support surface (5.2) of the laser equipment worktable containing the point of the cladding panel (2) closest to the focusing lens.

[0136] Example 2

[0137] The vehicle coating (10) comprises a predefined design motif (3) obtained by laser marking comprising three colors, a first color Ci or base color which is gray and is provided mainly by the combination of the color of the thermoplastic base with the color of the thermochromic pigment that forms the thermoplastic composition, a second color C2 which is dark gray and is obtained after laser irradiation according to a first laser energy density defined by first laser parameters, a third color C3 which is black and is obtained after laser irradiation according to a second laser energy density defined by second laser parameters.

[0138] The thermoplastic composition (1) comprises a thermoplastic base composition made of polycarbonate / acrylonitrile butadiene styrene (PC-ABS) comprising a weight percentage of 96% with respect to the thermoplastic composition (1) and a concentrated blend composition comprising a weight percentage of 4% with respect to the thermoplastic composition (1).In particular, the concentrated mixture composition consists of a concentrated mixture thermoplastic carrier formed from a low viscosity styrene acrylonitrile (SAN) resin comprising 95% by weight of the concentrated mixture composition, and further includes a base pigment, particularly a white pigment; the thermochromic pigment being a thermochromic black pigment comprising 2.5% by weight of the concentrated mixture composition; and a laser energy-absorbing additive comprising 2.5% by weight of the total weight of the concentrated mixture composition.

[0139] The vehicle lining (1) is manufactured entirely from the thermoplastic composition of step a) by injection molding, i.e., it comprises a single layer that simultaneously performs a decorative function and a support function.

[0140] To promote the color change from the first color Ci which is gray to the second color C2 which is dark gray, a first area of ​​the decorative surface (2.1.1) is irradiated with a first laser beam applied with a three-dimensionally mobile pulsed laser (5) which is a solid-state fiber laser having a laser power of 40 W and having a wavelength of 1030 nm and comprising a focusing lens with a movement amplitude in the Z direction of 100 mm.

[0141] The first laser beam provides a first energy defined by a first laser energy density of 4.03 J / cm² 2 The first laser parameters established to obtain this first laser energy density are a maximum pulse power of 4.013 kW, a pulse frequency of 100 Hz, a scan speed of 6600 mm / s and a spot size diameter of 70 pm.

[0142] To promote the color change from the first color Ci which is gray to the third color C3 which is black, a second area of ​​the decorative surface (2.1.1) is irradiated with a second laser beam applied with a three-dimensionally mobile pulsed laser (5) which is a solid-state fiber laser having a laser power of 40 W and having a wavelength of 1030 nm.

[0143] The second laser beam provides a second energy defined by a second laser energy density of 12.72 J / cm² 2 The second laser parameters set to obtain this second laser energy density are a maximum pulse power of 14.95 kW, a pulse frequency of 85 Hz, a scan speed of 5950 mm / s and a spot size diameter of 70 pm.

[0144] Additionally, the position of the focusing lens in the Z direction is modified in real time during the application of the first laser beam according to the three-dimensional shape of the coating panel (2) of stage b) to maintain a spot size of 70 pm throughout the first and second laser-treated areas. Both laser-treated areas comprise height variations of up to 70 mm with respect to a reference plane defined by a plane parallel to the support surface (5.2) of the laser equipment worktable that contains the nearest point of the coating panel (2) to the focusing lens.

Claims

CLAIMS 1. A method for manufacturing vehicle coverings (10) having a predefined design motif by laser marking, comprising the following steps: a) Providing a thermoplastic composition (1) comprising: • a thermoplastic base composition comprising a weight percentage in the range of 90 to 99.5% with respect to the thermoplastic composition, • a concentrated blend composition comprising a weight percentage in the range of 0.5 to 10% with respect to the thermoplastic composition, wherein the concentrated blend composition comprises a concentrated blend thermoplastic carrier, a base pigment, a thermochromic pigment and a laser energy-absorbing additive, and wherein the concentrated blend thermoplastic carrier is chemically compatible with the thermoplastic base, b) Obtaining a cladding panel (2) having a decorative surface (2.1.1) from the thermoplastic composition (1) of step a) comprising a first color C1 provided by a homogeneous distribution of the concentrated blend and the thermoplastic base composition and having a three-dimensional shape, c) Obtaining a predefined design motif (3) visible on the decorative surface (2.1.1) of the cladding panel (2) obtained in stage b) due to a visual contrast between the first color Ci and a second color C2 in which the second color C2 is obtained by irradiating. a first area of ​​the decorative surface (2.1.1) with a first laser beam providing a first energy defined by a first laser energy density, thereby creating a first laser-treated area having a second color C2, wherein the first laser beam is applied with a laser apparatus (5) comprising a three-dimensionally movable pulsed laser (5.1) comprising a head (5.1.1) comprising a focusing lens and a support surface (5.2) extending in an XY plane and configured to support the cladding panel (2), wherein said first laser energy density is defined according to the composition (1) of step a) to modify the chemical structure of said thermoplastic composition without removing material to obtain the second color C2, wherein the position of the focusing lens is modified in real time during the application of the first laser beam with respect to a Z direction perpendicular to the support surface (5).2) in accordance with the three-dimensional shape of the coating panel (2) of step b) to keep the distance between the focusing lens and each corresponding point of the first area constant and thus keep a constant spot size of said first laser beam throughout the entire first area, all steps a), b) and c) carried out so that the second color C2 obtained is visually distinguishable from the first color (2.1) and uniform throughout said first laser-treated area.

2. Method for manufacturing vehicle coverings (10) having a predefined design motif (3) by laser marking in accordance with the claim 1, wherein step c) further comprises irradiating a second area of ​​the decorative surface (2.1.1) with a second laser beam applied with the laser equipment (5), said second laser beam providing a second energy defined by a second laser energy density thereby creating a second laser-treated area having a third color C3 such that the predefined design motif (3) is visible on the decorative surface (2.1.1) due to a visual contrast between the first color Ci, the second color C2 and the third color C3, said second laser energy density is defined according to the composition (1) of step a) to modify the chemical structure of said thermoplastic composition (1) without removing material to obtain the third color C3, wherein the position of the focusing lens is modified in real time during the application of the second laser beam with respect to the Z direction according to the three-dimensional shape of the coating panel (2) of step b) to keep constant the distance between the focusing lens and each corresponding point of the second area and thus keep a constant spot size of said second laser beam throughout the entire second area, all steps a), b) and c) carried out so that the third color C3 obtained is visually distinguishable from the first color Ci and the second color C2 and uniform throughout said second laser-treated area.

3. A method for manufacturing vehicle coverings (10) having a predefined design motif (3) by laser marking according to claim 1 or 2, wherein the first treated area with laser and / or the second laser-treated area comprise a relief due to the foaming of the thermoplastic composition (1).

4. A method for manufacturing vehicle linings (10) having a predefined design motif (3) by laser marking according to claim 3, wherein foaming occurs because the thermoplastic composition (1) further comprises a foaming agent.

5. Method for manufacturing vehicle coatings (10) having a predefined design motif (3) by laser marking according to claim 1, wherein the wavelength of the first laser beam and / or the second laser beam is within the near-infrared spectrum range.

6. Method for manufacturing vehicle coverings (10) having a predefined design motif (3) by laser marking according to claim 1, wherein the covering panel obtained in step b) comprises a single layer.

7. A method for manufacturing vehicle linings (10) having a predefined design motif (3) by laser marking according to claim 6, wherein step b) is carried out by injection molding, by extrusion molding or by vapor chamber molding.

8. A method for manufacturing vehicle coverings (10) having a predefined design motif (3) by laser marking according to claim 1, wherein the covering panel (2) obtained in step b) comprises two layers, a decorative layer (2.1) manufactured by composition thermoplastic (1) of step a) and a carrier substrate (2.2) .

9. Method for manufacturing vehicle coatings (10) having a predefined design motif (3) by laser marking according to claim 8, wherein the decorative layer (2.1) is manufactured by extrusion molding or by injection molding.

10. Method for manufacturing vehicle coatings (10) having a predefined design motif (3) by laser marking according to claim 1, wherein the focusing lens is moved along the Z direction with an amplitude of 100 mm.

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