FR3041564A1 - METHOD FOR PRODUCING A DECORATIVE PATTERN ON A METALLIC SYNTHETIC POLYMER MATERIAL COMPONENT - Google Patents

Abstract

The invention relates to a method for producing a decorative pattern (7) by means of laser radiation on the surface of a component made of synthetic polymer material, which surface is previously coated with a layer of a metallic material characterized in the synthetic polymer material is transparent to said laser radiation, i.e. has a transmission coefficient of at least 25% in the wavelength of said radiation, and in that said method comprises a step of exposing at least a first area (8) of the metallized surface to a laser beam scan, the total amount of energy delivered on said surface in said at least first area (8) is at least 20% greater than that necessary to achieve the ablation of said metal layer without degradation of the surface of said material, so as to cause on the at least one first zone (8) simultaneously the disappearance of the metal layer and a change in the state of the surface of the material.

Description

METHOD FOR PRODUCING A DECORATIVE PATTERN ON A METALLIC SYNTHETIC POLYMER MATERIAL COMPONENT

Technical area

The present invention relates to a method of producing a decorative pattern on a component made of metallized synthetic polymer material.

This method is more particularly adapted to the production of decorative patterns on a component of a lighting and / or automotive signaling device, in particular on masks or pedestals for a searchlight or fire of motor vehicles.

Prior art

Very often, car manufacturers require the presence of special patterns on lighting or signaling devices. These precise and indelible motifs on certain parts such as the projector mask or the base of the fire have mostly an exclusively aesthetic purpose.

These patterns are obtained, according to a first method, by marking the manufacturing mold, thus causing a lack of flexibility and a risk of mold wear. The mold can easily wear out or be contaminated by impurities.

A second method is to use an ink deposit (screen printing) on the piece to decorate. Such a solution poses problems of resistance of the ink during the life of the piece as well as resistance to ultraviolet rays.

A third method is to add inserts such as decorative films of the type IMD (In Mold Decoration in English). Such a solution is expensive and causes problems related to the thermoforming of the film.

In the particular case of producing carbon fiber patterns, imitating the appearance of a carbon fiber weave, the first two solutions exposed do not lead to a convincing result, imitation being too coarse. One solution is then to apply on the pieces of real pieces of weaving carbon fiber, very expensive solution both for the material itself and for its implementation.

In addition, these aesthetic components of lighting devices and / or automotive signaling are generally metallized, that is to say coated with a metal layer on their surface. To achieve this metal layer, vacuum evaporation metallization machines or sputtering vacuum metallization machines are generally used. For reasons of cost and appearance, usually a layer of aluminum is deposited, usually between 30 and 200 nm thick.

If it is desired to make a decorative pattern on these metallized parts, it is therefore necessary, by a selective metallization process, to remove the layer of deposited metal or to prevent its deposition on certain selected zones by resorting to a masking during the metallization step .

Thus, it is known, for example EP1426236, to proceed to the ablation of this metal layer by laser ablation. Infrared lasers are commonly used, such as a fiber laser (1.050 μm), a CO 2 laser (1.06 μm), or an Nd: YAG or related laser (1.064 μm).

The production lines of lighting and / or signaling devices are therefore equipped with laser ablation units making it possible to produce different types of decorative patterns, by acting on the drawing of the ablation of the metallized layer which reveals the native surface. synthetic polymer material serving as a support for depositing this metallized layer.

However, an additional difficulty has been noted by the applicant: the synthetic polymer material predominantly used to make the masks and metallized bases of lighting devices and intended to be ablated is a black tinted polycarbonate which is transparent to infrared radiation, that is to say, it has a transmission coefficient of at least 25%, generally greater than 50% and advantageously greater than 85% in the wavelengths of the targeted laser radiation. This is to minimize the impact of direct exposure of the material to fiber, CO2 or Nd.YAG laser radiation. If this is particularly advantageous in the context of a method of ablation of the metal layer deposited on a black-tinted polycarbonate surface, in that it promotes the obtaining of a bare surface with a low risk, or even minimal, damaging it in case of direct exposure of the surface to the laser radiation and thus promotes the preservation of an intact appearance of the exposed surface, it is understood that this poses a problem to create a pattern on the surface released after ablation, by direct exposure to laser radiation.

One solution could be to change the type of laser, for example using an excimer laser whose wavelengths are in UV and for which the material considered has a transmission rate of less than 10%. This implies, however, to modify the laser treatment units on the production lines and the investment of an additional laser, complementary in emission wavelengths, to that deployed to perform the ablation.

The present invention aims to provide a method of producing a decorative pattern on a synthetic polymer component and in particular a component of a lighting device and / or automotive signaling allowing the realization of low-cost precise patterns on parts such as masks or pedestals without using a mold with a particular marking, marking ink or inserts such as films or pieces of carbon fiber fabrics. Summary of the invention

The present invention proposes for this purpose a method of producing a decorative pattern by means of laser radiation on the surface of a component made of synthetic polymer material, which surface is previously coated with a layer of a metallic material.

This method is remarkable in that the synthetic polymeric material is transparent to said laser radiation, i.e. has a transmission coefficient of at least 25% in the wavelength of said radiation, and in that said method comprises a step of exposing at least a first zone of the metallized surface to a laser beam scan, the amount of total energy delivered on said surface in said at least first zone is at least 20% greater than that necessary to achieve the ablation of said metal layer without degradation of the surface of said material, so as to cause on the at least one first zone simultaneously the disappearance of the metal layer and a change in the state of the surface of the material.

Thus, by applying a quantity of energy that is less than 20% greater than that required to obtain the strict ablation of the metal layer, a thermal effect is generated which is strong enough to obtain a significant heating of the underlying surface. to the metal layer before evaporation of said layer and thus a modification of the surface state, in particular by burning of the material with texturing related to the formation of boiling microbubbles, corresponding to a foaming effect, or even a superficial melting of the material. Depending on the amount of energy applied, there will be a more or less pronounced surface effect, up to color changes.

Preferably, the amount of energy applied is at least 25% higher, advantageously at least 33% higher, preferably at least 50%, preferably at least 75%, more preferably at least 90%.

According to another characteristic, the method comprises an additional step of exposing at least a portion of the at least first zone previously devoid of its metal layer to a second laser scanning, so as to generate at least a second textured zone , different in appearance from the first zone. It will be understood that the first scan having modified the surface state of the material, it also modifies the absorption properties of the laser radiation used on the surface, which makes it possible to create additional texturing on the altered surface areas.

Depending on the scanning parameters, different effects can be obtained, including a matte, non-smooth and non-glossy surface. The application of a second scan on the exposed and textured surface by the first scan makes it possible to give a marked grain to the surface thus treated. In addition, it will also be possible to modify the perceived color, for example creating zones in shades of gray when the native color of the synthetic polymer is black.

According to one variant, the parameters of the first scan on a first zone of the surface when it is followed by a second scan are different from the parameters of said first scan when only the step of the first scan is performed on a first given zone. This provides more varied texture effects and adapted to the decorative pattern that is desired.

According to another characteristic, the method comprises a step of ablation of the metallized surface by exposure to a laser beam scan, in order to generate at least a third zone on the surface of the material. The decorative pattern can thus have surface areas laid bare and smooth, without texturing.

Preferably, the ablation step is performed after the steps of producing the at least one first zone and / or at least one second zone. This avoids any material projections related to the first scan on adjacent areas that have previously been exposed. However, if the parameters of the second scan and those of the ablation scan are identical, then the ablation step can be performed concomitantly with that of the second scan of the creation of the second zones.

According to another characteristic, at least one fourth metallized zone is preserved on the surface of the material. It is thus possible to create an even larger variety of patterns.

According to a variant, the laser scanning is performed with a laser emitting radiation in the infrared.

Thus, the laser is preferentially taken from: fiber laser, Nd: YAG laser or a related laser, CO2 laser.

According to this variant, the synthetic polymer material is a translucent polymer colored by an organic dye such that the transmission coefficient is at least 25% for wavelengths greater than 800 nm, the synthetic polymer material being taken from: a polycarbonate, modified polycarbonate, polycarbonate copolymer or polyamide 6.

Advantageously, the organic dye comprises an anthraquinone.

According to another characteristic, the metal layer is a layer of a metal selected from the following group: aluminum, copper, stainless steel, chrome, gold, silver. Preferably and advantageously for application to lighting and / or signaling devices of a motor vehicle, the metal is aluminum.

According to another characteristic, the decorative pattern is a raster pattern reproducing the appearance of a weave, resulting from a combination of at least a plurality of second areas and third areas of rectangular shape.

Advantageously, the raster pattern reproducing the appearance of a weave results from a combination of at least a plurality of first zones, second zones and third zones.

According to another characteristic, the decorative pattern is a pattern reproducing the appearance of a grained leather, resulting from a combination of a plurality of second zones and third zones in the form of dots. The subject of the invention is also a device for lighting and / or signaling a motor vehicle that is remarkable in that it comprises a component made of synthetic polymer material that is transparent to infrared radiation and that has at least traces of metallization of its surface, said component being coated with a decorative pattern obtained according to the method of the invention as described above.

Preferably, said component is a mask or a base.

BRIEF DESCRIPTION OF THE FIGURES: Other advantages and characteristics of the invention will become apparent in the light of the description of an embodiment of the invention given below, by way of illustration and without limitation, with reference to the appended drawings in which: FIG. 1 is a schematic view of a vehicle headlamp comprising a mask having decorative motifs produced according to the method according to the invention; - FIG. 2 is an optical microscope view of a first embodiment of a pattern according to FIG. 3 is an enlarged view of FIG. 2, FIG. 4 is a scanning optical microscope view of FIG. 3, FIG. 5 is a detailed view of FIG. 4, FIG. FIG. 6 is an optical microscope view of a second exemplary embodiment of a pattern according to the invention; FIG. 7 is an enlargement of the view of FIG. 6; FIG. 8 is a detail view under a microscope. op scan tick of Figure 7.

Detailed description of the invention

Figure 1 schematically shows a projector 1 which is an automotive lighting device comprising a component which is a mask 4 having decorative patterns 7 obtained by the method according to the invention.

The projector 1 comprises in particular a housing 2, a protective glass 3, said mask 4, elliptical lighting module lenses 5. The mask 4 has two orifices 6 for the elliptical lighting module lenses 5.

The housing 2, the protective glass 3 and the mask 4 are made of thermoplastic synthetic polymer material by injection.

The mask 4 includes three surfaces having a decorative pattern 7. The mask 4 is obtained by injection of a black mass-dyed thermoplastic material. The mask 4 is then entirely metallized by an aluminum layer. For example, vacuum deposition metallization will be carried out.

The decorative patterns are then produced by exposing certain areas of the surface of the mask material 4 to laser radiation, the remainder of the surface remaining metallized.

According to the invention, the synthetic polymer material of the mask 4 is transparent to said laser radiation, that is to say has a transmission coefficient of at least 25% in the wavelength of said radiation. Advantageously, the transmission coefficient is greater than 50%, preferably 85%.

According to another characteristic, the laser scanning is performed with a laser emitting radiation in the infrared. For this purpose, the laser is taken from: fiber laser, CO2 laser, Nd: YAG laser or related laser.

For the exemplary embodiments of patterns as illustrated in FIGS. 2 to 8, the laser used is a Q-Switch Nd: YV04 pulse laser, adjusted to 10W of average power.

The material used is a Lexan HF1110R black stained polycarbonate, color 71257 (Sabic). The transmission curve of this black-tinted polymer has a band-pass profile, with a zero transmission coefficient in the wavelength region of the visible range and then a sudden, almost vertical transition between 700 and 750 nm to reach a plateau. at over 85% transmission, close to 90% in the 1000-1100 nm zone.

Small rectangular sample plates (approximately 3cm by 12cm) were made of this material and then metallized under vacuum in order to coat them with an aluminum layer.

Finally, they were subjected to a controlled laser scanning to achieve a predefined pattern, combining different surface aspects of the material.

For example, the defined pattern is converted into a grayscale image to which a surface state is assigned among the four types of surface state zones according to the invention: a first zone on which a first scan whose quantity delivered total energy is at least 20% greater than that required to achieve conventional ablation of the metal layer, that is to say without degradation of the surface of the material; - A second zone which corresponds to a first zone on which a second scan is performed, in order to confer an additional textured appearance; - A third zone where the scanning applied is that of a conventional ablation of the metal layer, without degradation of the coated surface; - A fourth zone where the metal coating is left intact and where the laser is thus extinguished.

The decorative patterns made according to the invention may combine: first and second zones; first and third zones; first and fourth zones; second and third zones; second and fourth zones; first and second and third zones; first and second and fourth zones; first and third and fourth zones; second and third and fourth zones; finally, the four types of zones.

With reference to FIGS. 2 and 3, a first pattern 7 that can be produced by the process according to the invention is a woven pattern, in particular of the carbon fiber type.

This pattern consists of series of second zones in the form of rectangle 9 arranged diagonally and offset, each diagonal series being connected by strips 8 corresponding to the first zones. The rectangles 9 and the strips 8 enclose series of third zones which take the form of series of rectangles 10 exposing the native surface of the support material, oriented perpendicularly to the rectangles 9 of the second zones, so as to form mixed chevrons with a branch formed of a rectangle 9 and the other branch of a rectangle 10.

With reference to FIG. 3, the third zones that are the rectangles 10 are black, the second zones formed by the rectangles 9 are ash gray and the first remaining zones formed by the strips 8 are of a darker matt gray.

To carry out the conventional ablation of the metal layer, and to obtain the third zones 10, the laser has been parameterized according to a hatched sweep, with a spacing spacing of 70 micrometers. The beam diameter is about 100 micrometers.

The first ablation scan according to the invention which makes it possible to obtain the first zones 8, which emerge dull gray, has for essential modification of parameterization a reduction of the scanning speed by a factor greater than 10, for example of approximately 13. A slight decrease (about 10%) of the average power of the laser and a 50% increase in pulse frequency were also applied. It has been estimated that this parameter change leads to delivering a total energy amount more than 15 times greater than that delivered for conventional ablation.

For the realization of the second zones 9, the first scan differs essentially from that applied for conventional ablation in that the scanning is performed at a resolution of 600 dots per inch (DPI) instead of hatching. A moderate drop (about 25%) of the average laser power was also performed. It has been evaluated that this parameter change leads to a total energy quantity approximately 2 times greater than that delivered for conventional ablation. The second scan was performed with the same parameters as those of conventional ablation.

An examination of the surface with a scanning electron microscope also makes it possible to differentiate the roughness of the different zones: with reference to FIG. 4, where the magnification is 25 ×, the ablated zones 10 appear smooth, the first zones 8 emerge matte with a slight texturing and the second zones 9 present a marked relief. Figure 5 is a close-up magnification at 400x of a second zone 9: there are clearly distinguishable patterns of melting-type and craters 11, whose size varies between 5 and 30 pm in diameter.

Referring to Figure 6, a second pattern 7 achievable by the method according to the invention is a pattern of grained leather type.

As is apparent from FIG. 7, which is a detail view of FIG. 6, with a magnification of 40 ×, this pattern is obtained by a non-repetitive distribution of points corresponding to second 9 or third zones 10.

In the scanning electron microscope, the second areas emerge as circular spots about 60 μm in diameter with a fused ring, while the surface of the third ablated areas is smooth.

Another interesting characteristic emerges from an observation of the surface of a material treated according to the invention with a scanning electron microscope (SEM) equipped with a system of microanalysis with energy dispersion, making it possible to detect the chemical elements at from the Bore. In fact, in the first and third zones, traces of aluminum are still detected, with a very diffuse distribution whereas the latter has almost disappeared in the second zones; in these, it is the carbon element which predominates clearly. The distribution contrast C-AI between the second zones on which a second scan has been made and the other zones is very marked.

The exemplary embodiments were carried out on a black tinted polycarbonate matrix. The product is available under the trade name Lexan HF1110R, color 71257 (Sabic). Other grades of polycarbonate containing this dye are available. The transmission curve of this tinted polymer exhibits a band-pass type profile, with a zero transmission coefficient in the wavelength region of the visible range and then a sudden, almost vertical transition between 700 and 750 nm to reach a plateau. more than 85%, close to 90% in the 1000-1100 nm zone.

In the context of the present invention, it will be possible to use other translucent polymers which are stained with a dye such as all of the light in the visible spectral range up to a lambdaco exclusion wavelength in the region. limit interval between the spectral range of visible light and the spectral range of the near infrared and only a part of the light in the spectral range of the near and intermediate infrared upwardly from the exclusion wavelength The aforementioned lambdaco are absorbed by the colored polymer.

In particular, the translucent polymer is polycarbonate or a modified polycarbonate or a polycarbonate copolymer or a polyamide 6.

For example, to prepare a colored polymer at the exclusion wavelength lambdaco = 700 nm, a perinone having a color index C.I. will be used as dyes, in combination with one of the translucent polymers listed above. 564 120, Solvent Red 135, at a concentration in the range of 0.05% by weight to 1% by weight, preferably 0.08 to 0.25% by weight, and an anthraquinone having a color index C.I. 61,565, Solvent Green 3, has a concentration ranging from 0.05% by weight to 1% by weight, preferably from 0.08 to 0.25% by weight.

In another example, to prepare a colored polymer at the exclusion wavelength lambdaco = 800 nm, a perinone having a color index C.I. will be used as dyes, in combination with one of the translucent polymers listed above. 564 120, Solvent Red 135, at a concentration in the range of 0.05% by weight to 1% by weight, preferably 0.1% by weight to 0.25% by weight and a phthalocyanine having a color number Cl 74 260, Pigment Green 7, at a concentration in the range of from 0.05% by weight to 1% by weight, preferably 0.1% by weight to 0.25% by weight and an anthraquinone having a Cl color 615 290, Solvent Blue 97, at a concentration in the range of 0.05% by weight to 1% by weight, preferably 0.1% by weight to 0.25% by weight are used as colorants in the preparation of colored polymer at the exclusion wavelength lambdaco = 800 nm.

Such material compositions are described in EP1529081. In the infrared spectral range of 700 nm (or 800 nm respectively) at 3000 nm, these material compositions absorb less than 60% and transmit at least 25% incident light flux.

It is understood that the reasons given by way of illustration are only non-limiting examples of the design possibilities of the method according to the invention.

Industrial application

The present invention makes it possible in particular to produce masks, pedestals or screens that are metallized and decorated, in particular for equipping lighting and / or signaling devices for motor vehicles.

Claims (16)

1. A method of producing a decorative pattern (7) by means of laser radiation on the surface of a component made of synthetic polymer material, a surface previously coated with a layer of a metallic material, characterized in that the synthetic polymeric material is transparent to said laser radiation, i.e. has a transmission coefficient of at least 25% in the wavelength of said radiation, and in that said method comprises an exposure step of at least a first zone (8) of the metallized surface to a laser beam scan, the total amount of energy delivered on said surface in said at least first zone (8) is at least 20% greater than that required for performing ablation of said metal layer without degradation of the surface of said material, so as to cause on the at least one first zone (8) simultaneously the disappearance of the metal layer ue and a change in the state of the surface of the material. 2. Method according to claim 1 characterized in that it comprises an additional step of exposing at least a portion of the at least first zone previously devoid of its metal layer to a second scan by laser radiation, so as to generate at least one second zone (9) textured, different in appearance from the first zone (8). 3. Method according to the preceding claim characterized in that the parameters of the first scan on a first area of the surface when followed by a second scan are different from the parameters of said first scan when only the step of the first scan is performed. on a given first area. 4. Method according to one of the preceding claim characterized in that it comprises a step of ablation of the metallized surface by exposure to a scanning laser beam, to generate at least a third zone (10) on the surface of the material. 5. Method according to the preceding claim characterized in that the ablation step is performed after the steps of producing the at least a first zone and / or at least a second zone. 6. Method according to any one of the preceding claims characterized in that at least a fourth metallized zone is preserved on the surface of the material. 7. Method according to any one of the preceding claims, characterized in that the laser scanning is performed with a laser emitting radiation in the infrared. 8. Method according to the preceding claim, characterized in that the laser is taken from: fiber laser, Nd: YAG laser or cognate laser CO2. 9. Method according to claim 7 or 8, characterized in that the synthetic polymer material is a translucent polymer colored by an organic dye such that the transmission coefficient is at least 25% for wavelengths greater than 800 nm. the synthetic polymer material being selected from: polycarbonate, modified polycarbonate, polycarbonate copolymer or polyamide 6. 10. Method according to the preceding claim, characterized in that the organic dye comprises an anthraquinone. 11. Method according to any one of the preceding claims, characterized in that the metal layer is a layer of a metal selected from the following group: aluminum, copper, stainless steel, chromium, gold, silver. 12. Method according to any one of claims 4 to 11, characterized in that the decorative pattern (7) is a raster pattern reproducing the appearance of a weaving, resulting from a combination of at least a plurality of second zones ( 9) and third zones (10) of rectangular shape. 13. Method according to the preceding claim, characterized in that the raster pattern reproducing the appearance of a weaving, resulting from a combination of at least a plurality of first zones (8), second zones (9) and third zones ( 10). A method according to any one of claims 4 to 11, characterized in that the decorative pattern (7) is a pattern reproducing the appearance of a grained leather, resulting from a combination of a plurality of second zones (9). and third zones (10) in the form of dots. 15. Device (1) for lighting and / or signaling of a motor vehicle characterized in that it comprises a component of synthetic polymer material transparent to infrared radiation and having at least traces of metallization of its surface, said component being coated with a decorative pattern (7) obtained according to the method according to any one of the preceding claims. 16. Apparatus (1) for lighting and / or signaling of a motor vehicle according to the preceding claim characterized in that said component is a mask (4) or a base.