LASER-WRITEABLE FILM

Description

[0001] The present invention relates to a laser-inscribable film, designed and adapted for inscribability by means of a laser, comprising a contrast layer based on a preferably extruded polymethacrylate compound, an engraving layer based on a preferably extruded polymethacrylate compound arranged on the contrast layer, wherein the polymethacrylate compounds are based on a composition comprising 60 to 98 wt. % of at least one polymethacrylate and 2 to 40 wt. % of a coloring pigment, and wherein the contrast layer and engraving layer have different coloring pigments, as well as laser-sensitive labels produced from the film. The present invention further relates to a method for producing a laser-sensitive film.

[0002] The labeling of objects is becoming increasingly important. For example, on machinery, electrical and electronic devices, and especially in the automotive industry, conventional printed labels are being replaced by laser-engravable labels. Laser-engravable labels are used to place information and instructions such as tire pressure or fuel type on various components of motor vehicles. In addition to such instructions, laser-engravable labels can also contain security information such as chassis and vehicle identification numbers. In the event of theft or an accident, such labels allow the vehicle and its production stages to be identified. Laser-engravable labels are known from the state of the art; they can be written on quickly and allow for high-contrast inscribed characters.DE 81 30 861 U1, DE 100 48 665 A1, and DE 101 42 638 A1 disclose multilayer labels containing a thin and a thick acrylate-based lacquer layer that can be written on using a laser. In the examples mentioned, the laser-writable carrier is produced in several steps by coating several or at least two differently colored acrylate-based layers onto one another. Before each subsequent coating step, the previously coated layer is cured and thus serves as a solid substrate for the subsequent coating.

[0003] The use of special additional security features such as holograms, permanent UV imprints (footprints) on the substrate to which the label was adhered, and the targeted selection of materials for laser-markable labels serve to make it more difficult to imitate the material and to detect attempts at tampering. Tampering attempts are generally understood to mean attempts to remove the label from its original bonding position and replace it with a new label, or to reapply the removed label in a new position. One measure to prevent such tampering is the use of mechanically sensitive carrier materials. Suitable fragile carriers include paper, corresponding or modified polystyrenes (US 3,623,944 A), polyvinyl chloride, cellulose acetates (DE 34 31 239 A1), and polyesters (JP 1229042 A, US 8,530,045 B2).In addition, the use of carriers that are deliberately weakened by perforation or punching is known (US 2,845,728 A, DE 299 13 746 U1, DE 103 41 807 B1).

[0004] Given the complex manufacturing process of such security labels or tamper-evident carriers, there is a need for laser-writable carriers that can be produced quickly and variably for the production of tamper-evident labels.

[0005] The present invention is therefore based on the object of providing improved laser-writable contrast-enhancing film carriers that can be manufactured in a single production step compared to the prior art. At the same time, the chemical and UV resistance should be maintained or improved, if possible, compared to prior art labels. Chemical resistance in this sense includes, for example, resistance to hydrocarbons such as motor vehicle fuels, hydraulic fluids, and solvents with which the labels might come into contact.

[0006] JP 2017 111 344 A discloses a laser-markable film comprising a contrast layer based on a polymethacrylate compound and an engraving layer based on a polymethacrylate compound arranged on the contrast layer. Due to the addition of different pigments, the contrast layer and engraving layer have different colors. The addition of impact-modified polymethacrylate to one of the two layers is not mentioned.

[0007] The present invention achieves this object by means of a laser-inscribable film of the type mentioned at the outset in that the at least one polymethacrylate of at least one of the two layers is free of impact modifiers and the other of the two layers contains an impact-modified polymethacrylate.

[0008] Because the polymethacrylate used in at least one of the two layers - contrast layer and / or engraving layer - is free of impact modifiers, the film is particularly brittle and has a fragility that ensures that the film or a label made from the film cannot be removed non-destructively from the surface to which it is attached.

[0009] Particularly preferably, the at least one polymethacrylate or at least one of the polymethacrylates is a polymethyl methacrylate (PMMA). These exhibit particularly good brittleness properties.

[0010] PMMA plastics are typically obtained by radical polymerization of mixtures containing methyl methacrylate. These mixtures generally contain at least 40 wt.%, preferably at least 60 wt.%, and particularly preferably at least 80 wt.%, based on the weight of the monomers, of methyl methacrylate. Comonomers that can be copolymerized with methyl methacrylate, such as 1-alkenes, vinyl esters, or (substituted) styrene, can also be used and are described, for example, in EP 1 963 415 A1.

[0011] The average molecular weight Mw (weight average) of such PMMA plastics is in the range of 80,000 g / mol to 180,000 g / mol, in particular 100,000 g / mol to 180,000 g / mol.

[0012] The weight-average molecular weight M w is determined by gel permeation chromatography (GPC). THF with 0.1 vol% trifluoroacetic acid is used as the eluent. The measurement is carried out at 25 °C. The precolumn used is PSS-SDV, 5 µ, 10 3 < Å, ID 8.0 mm x 50 mm. The columns used for separation are PSS-SDV, 5 µ, 10 3 < Å, 10 5 < Å, and 10 6 < Å, each with ID 8.0 mm x 300 mm. The sample concentration is 4 g / L, and the flow rate is 1.0 ml per minute. The measurement is carried out against PMMA standards (µ = µm; 1 Å = 10 -10 < m).

[0013] The brittleness of a PMMA film is directly related to the comonomer and impact modifier content. The lower the comonomer content or the impact modifier content, the more brittle the PMMA film. To achieve maximum tamper resistance, PMMA polymers with the highest possible methyl methacrylate content are preferred.

[0014] The contrast layer or the engraving layer are free of impact modifiers. According to the invention, at least one impact modifier is contained in one of the two layers. Crosslinked poly(meth)acrylates are used as impact modifiers, in particular.

[0015] An impact-modified poly(meth)acrylate plastic consists of 1 to 50 wt.% impact modifier based on the amount of PMMA matrix polymer. The elastomer particles distributed in the PMMA matrix preferably have a core with a soft elastomer phase and a bonded hard phase. The impact-modified poly(meth)acrylate plastic consists of a portion of matrix polymer and a portion of impact modifier based on crosslinked poly(meth)acrylates distributed throughout the matrix. Possibilities for increasing the impact strength of a poly(meth)acrylate plastic are described, among others, in EP 1 963 415 A.

[0016] The individual, preferably coextruded, contrast and engraving layers of laser-inscribable films according to the invention are based on a composition comprising 60 to 98 wt.% of a non-impact-modified PMMA polymer and 2 to 40 wt.% of a coloring pigment.

[0017] Preferably, the laser-inscribable film comprises a contrast layer based on an extruded polymethacrylate compound and an extruded engraving layer based on an extruded polymethacrylate compound arranged above the contrast layer.

[0018] In a preferred embodiment of the present invention, the composition of the individual layers comprises 75 to 95 wt.% PMMA polymer and preferably 5 to 25 wt.% of the coloring pigment. The amount of the coloring pigment within the composition of the preferred embodiments depends on the type of pigment used.

[0019] In the case of carbon black as the coloring pigment, for example, 2 to 7.5 wt.%, in particular 5 to 7.5 wt.%, are preferred, while in the case of TiO 2, 2 to 40 wt.%, in particular 5 to 20 wt.% and very particularly preferably 5 to 10 wt.% are preferably used.

[0020] The engraving layer is a layer arranged on top of the contrast layer that can be marked using a single laser beam or multiple laser beams. During this marking process, the engraving layer is ablated (removed by laser bombardment) at the points where a laser beam with appropriate energy is directed. With sufficient energy input, the engraving layer is completely removed locally, leaving it translucent at these points. It is also conceivable that the engraving layer is only partially ablated in some places, resulting in an opaque appearance of the engraving layer at these points.

[0021] The contrast layer of films according to the invention comprises at least one coloring pigment. Coloring pigments within the meaning of the present invention include, without limitation, all coloring pigments used as dyes and / or brighteners in paints, varnishes, and films. Suitable coloring pigments include, in particular, monoazo, disazo, laked azo pigments, azo condensation pigments, benzimidazolone, naphthol, isoindolinone, isoindoline, phthalocyanine, quinacridone, anthanthrone, perylene, perinone, thioindigo, thiazineindigo, quinophthalone, dioxazine, diketopyrrolopyrrole pigments, carbon black, nickel titanate, chromium titanate, iron oxide, ultramarine, chromium oxide, barium sulfate, zirconium dioxide, or titanium dioxide, with carbon black and titanium dioxide being particularly preferred.

[0022] Specific examples of coloring pigments are titanium dioxide in the rutile modification ("TiO 2 ", for example rutile types from Kronos), carbon blacks (for example Printex types from Evonik) or other coloring pigments known to the person skilled in the art, such as those mentioned, for example, in the textbook of paints and coatings, volume 5 (Hans Kittel and Jürgen Spille, Hirzel Verlag (Stuttgart), 2003) in DE 10 2012 207 100 A1 or in DE101 02 019 A1. The coloring pigments are preferably pigments that are as weather- and UV-stable as possible. Titanium dioxide in the rutile modification is particularly preferred for the contrast layer. What is essential for the invention is not the color of the pigment or the contrast layer per se, but the resulting color difference or contrast compared to the engraved layer.The pigment used according to the invention serves to adjust the contrast that is created between the contrast layer and the engraving layer after the film has been inscribed, i.e., after the engraving layer has been ablated by laser. In addition to pigments, organic dyes such as azo or anthraquinone dyes can also be used to color the contrast or engraving layer. Suitable organic dyes that can be mixed into the PMMA base material are described in DE 101 02 019 A1 and DE 10 2005 002 072 A. In addition to mixing organic dyes into the base material, it is also possible to use organic dyes with polymerizable groups. These dyes are added during the polymerization of the PMMA base material and, due to their polymerizable groups, can be covalently incorporated into the polymer chain of the PMMA base material.Such polymerizable dyes are described in EP 0 748 853 A2 and WO 2013 / 079055 A1.

[0023] As an additional security feature, color pigments can be used that do not absorb radiation in the visible range and are therefore normally invisible. Only when the wearer is exposed to a radiation source of a suitable wavelength are the color pigments excited and emit radiation of a characteristic wavelength.

[0024] Furthermore, long-lasting (phosphorescent) or fluorescent pigments or dyes, so-called taggants, can be used. These are excited solely or predominantly by UV radiation and emit radiation in the visible range of the spectrum. Such systems are described, for example, in Ullmann's Encyclopedia of Technical Chemistry, 4th edition, 1979, Verlag Chemie.

[0025] In addition to UV-active pigments, IR-active luminescent pigments are also conceivable for use as additives in the carrier layers. Examples of such systems are described, among others, in WO 2007 / 071547 A.

[0026] In addition to IR and UV-active systems, phosphors that can be excited by electron beams, X-rays, etc. are also suitable in principle.

[0027] These dyes / pigments listed as examples are incorporated into the film formulation in at least one of the film layers in amounts of 0.01 to 50 wt. %, preferably 0.1 to 25 wt. %, and particularly preferably between 1 and 10 wt. %. Optionally, the PMMA film according to the invention can have a third extruded layer with a preferred thickness of 2 µm to 100 µm, in particular 5 µm to 50 µm. This optional third layer is located on the engraving layer. The third layer can consist of transparent PMMA, polyvinylidene fluoride (PVDF), polycarbonate (PC), or a blend of PMMA and PVDF or PC, with PMMA being particularly preferred. Such coextruded systems are described, inter alia, in WO 2008 / 074525 A or WO 2006 / 043672 A.In a particularly preferred embodiment, the third transparent outer layer contains an additional pigment which absorbs radiation in the non-visible range and is thus invisible to the human eye. Only when the carrier and thus the pigments are irradiated with a radiation source of a suitable wavelength are the color pigments excited and emit radiation with a characteristic wavelength. This emitted radiation can be in the visible or non-visible range of the spectrum. In both cases, the emitted radiation can be read and detected using a suitable spectrometer. The concentration of the pigment which absorbs radiation in the non-visible range is preferably at most 10 wt.%, more preferably at most 1 wt.%, and particularly preferably at most 0.1 wt.%. Such systems and a method for detecting such systems are described, inter alia, in WO 2011 / 098083 A1.

[0028] The thickness of the total film is preferably from 40 µm to 200 µm, particularly preferably from 60 µm to 100 µm.

[0029] The engraving and / or contrast layer of the film according to the invention can contain, in addition to the aforementioned additives such as organic dyes or pigments, antiblocking agents, processing aids, or stabilizers. The engraving and / or contrast layer, and especially preferably the transparent third layer, particularly preferably contains UV stabilizers and / or UV absorbers. A combination of both systems is preferably used. The UV stabilizers are generally hindered amines (hindered amine light stabilizers; HALS compounds). The UV absorbers can be the known systems based on benzophenones, salicylic acid esters, cinnamic acid esters, oxalanilides, benzoxazinones, hydroxyphenylbenzotriazoles, triazines, benzotriazoles, or benzylidene malonates. UV absorbers based on triazines and / or benzotriazoles are preferably used.Ideally, a combination of triazines and benzotriazoles is used. In addition to blending the UV absorbers, they can also be polymerized into the matrix material using a polymerization-active group. Covalently incorporating the absorbers has the advantage that the low-molecular-weight compounds are no longer able to migrate. Suitable compounds and typical concentrations are described in EP 1 963 415 A.

[0030] When extruding film, in addition to a smooth chill roll, an embossed chill roll or an embossed pressure roller can also be used to create an embossed pattern in the extruded film. This allows additional information to be transferred from the chill roll to the film. In this case, the embossed pattern depth / height of the chill roll should be between 0.1 µm and 15 µm, preferably between 1 µm and 5 µm.

[0031] In a further embodiment of the invention, the laser-markable film according to the invention has an adhesive layer, preferably a pressure-sensitive adhesive layer, on the side of the contrast layer opposite the engraving layer. This enables simplified processing of the film, for example, in cutting or punching processes into labels, which are also the subject of the present invention. If the laser-markable film according to the invention has an adhesive layer, labels can be obtained by a punching or cutting step that can be applied directly to various substrates as such, without requiring a further coating step in the finished form.Suitable pressure-sensitive adhesives include all typical adhesives that exhibit high bond strength and tack, particularly acrylic adhesives, such as resin-modified acrylic adhesives, natural rubber adhesives, silicone adhesives, heat-activated reactive adhesives, and synthetic rubber adhesives. Suitable systems are described, among others, in patent WO 2007 / 071547 A1.

[0032] The adhesive is preferably a pressure-sensitive adhesive, i.e., a viscoelastic compound that remains permanently tacky and adhesive at room temperature when dry. Bonding occurs immediately on almost all substrates with light contact pressure.

[0033] According to the general understanding of the person skilled in the art, a "pressure-sensitive adhesive" is understood to be a viscoelastic adhesive whose cured, dry film is permanently tacky and remains adhesive at room temperature and can be bonded to a variety of substrates by applying slight contact pressure.

[0034] Pressure-sensitive adhesives have been known for decades. Adhesives that allow a permanent bond to the substrate even under relatively light pressure and can be removed from the substrate after use, leaving essentially no residue. Pressure-sensitive adhesives are permanently tacky at room temperature, meaning they have a sufficiently low viscosity and high tackiness, allowing them to wet the surface of the substrate even under light pressure. The bondability of the adhesives is based on their adhesive properties, and their removability on their cohesive properties. Various compounds can serve as the basis for pressure-sensitive adhesives. The main groups are natural rubbers, synthetic rubbers, and acrylates.

[0035] The film is particularly preferably formed by coextrusion of the two or - in the case of the additional transparent layer - three layers. This production method enables particularly simple production of the film according to the invention with a uniform layer thickness. The present invention therefore also relates to a process for producing a laser-inscribable film according to the invention, in which the layers forming the film are coextruded. An embossed chill roll or pressure roller is preferably used in the process. This makes it possible to provide the contrast and / or engraving layer with an embossing. In this way, additional information can be transferred from the chill roll to the film. The embossing depth / height of the chill roll should in the present case be between 0.1 µm and 15 µm, preferably between 1 µm and 5 µm.Following extrusion, an adhesive, preferably a pressure-sensitive adhesive, can be applied to the side of the contrast layer opposite the engraving layer. This can be covered with a release paper or a release liner.

[0036] In addition to the direct coextrusion of a colored contrast layer and a colored engraving layer based on PMMA or other thermoplastic polymers, the colored engraving layer can also be applied via a printing process. The application of a colored engraving layer to the brittle contrast film can be achieved using conventional printing and coating processes.

[0037] The printable engraving layer is preferably a lacquer layer that can be applied by printing processes. Preferred examples of corresponding printing lacquer layers include printing lacquers based on electron-beam-curable or UV-curable acrylate lacquers. In an alternative embodiment of the invention, the engraving layer consists of a thin metal layer. The engraving layer preferably has a thickness of 1 to 30 µm, preferably 1 to 20 µm, particularly preferably 1 to 10 µm. Examples of implementation Test methods

[0038] To determine temperature resistance and tamper resistance, five labels each of the samples obtained according to Examples 1 to 9 were tested. The procedure was as follows. Temperature resistance:

[0039] The laser label is applied bubble-free to a 1 mm thick steel plate coated with a solvent-based acrylic clear coat from Kansai Paint (KINO 1210TW-2). After approximately 24 hours at room temperature, the sample is stored for 2300 hours at 150 °C.

[0040] At the end of the storage period, the sample is examined for edge lift (the separation of the edges of the label from the substrate in mm - measured from the edge of the label) and the number of tears in the label. Furthermore, the shrinkage of the samples is measured (as a percentage of the original bonded area).

[0041] The results are given as the average of five samples and are graded on a scale of 1 to 6. A value of 1, that the edge lifting is less than 0.1 mm and the shrinkage is less than 0.5%; furthermore, no cracks are visible; 2, that the edge lifting is less than 0.5 mm and the shrinkage is less than 2%; furthermore, no cracks are visible; however, edge lifting, shrinkage, and / or cracking are so pronounced that a value of "1" was not achieved; 3, that the edge lifting is less than 2.0 mm and the shrinkage is less than 5%; furthermore, a maximum of two cracks are visible; however, edge lifting, shrinkage, and / or cracking are so pronounced that a value of "2" was not achieved; 4, that the edge lifting is less than 5.0 mm and the shrinkage is less than 10%; furthermore, a maximum of five cracks are visible; however, edge lifting, shrinkage, and / or cracking are so pronounced that a value of "3" was not achieved. 5, that the label detaches completely from the substrate ("complete edge lift") and the shrinkage is 10% or more;Furthermore, up to ten cracks are visible; 6, that the label detaches completely from the substrate ("complete edge lift") and the shrinkage is 10% or more; furthermore, more than ten cracks are visible. ; Tamper-proof:

[0042] In the tamper evidence test, the brittleness of the sample is examined after bubble-free bonding to a 1 mm thick steel plate coated with a clear coat from Kansai Paint (KNIO 1210TW-2). For this purpose, an attempt is made to remove the sample from the substrate after a 24-hour waiting period following bubble-free bonding to the steel plate. The tamper resistance of the laser label material is classified into four levels ("1" to "4"). The test determines which tools can be used to remove the security label from the substrate without destruction. "Destruction" in this context refers to the breakage of the label and the formation of cracks within the contrasting layer. A value of 1, that the label cannot be removed non-destructively even using isopropanol as a solvent in combination with a sharp metal blade; in this case, the tamper resistance is rated as good. 2, that the label cannot be removed non-destructively even using a sharp metal blade as the sole additional aid; however, non-destructive removal is possible using isopropanol as a solvent in combination with a sharp metal blade; the tamper resistance is rated as sufficient; 3, that the label cannot be removed non-destructively by hand but with the help of a sharp metal blade; in this respect, the tamper resistance is also insufficient; 4, that the label can be removed non-destructively by hand without additional aid; in this respect, the tamper resistance is insufficient. Processability

[0043] When testing for processability with regard to lamination and cutting processes, the stability of the films during the further processing process is examined.

[0044] To assess processability, at least 100 meters of each film sample (220 mm wide) are laminated with a transfer compound. After lamination, the film samples are cut in half using an S-cut, resulting in two 110 mm wide roll samples. The processability of the materials is rated on four levels ("1" to "4"). It is checked whether film tears occur during the lamination and cutting process, and whether perforation of the cut edges occurs during the cutting process. 1. No film tears occur during the lamination process. Subsequent cutting does not cause film tears or perforation of the film edges. 2. No film tears occur during the lamination process. Subsequent cutting results in perforation of the film edges. 3. One film tear occurs during the lamination process. Subsequent roll cutting results in one film tear and perforation of the film edges. 4. Multiple film tears occur during the lamination process. Subsequent cutting results in multiple film tears and perforation of the film edges. Identification of taggants

[0045] To identify the taggants, an emission spectrum is recorded using a handheld device. The handheld device contains both the emission source (LED UV emitter 250 to 550 nm) and the spectrometer. The recorded emission spectrum is compared with the corresponding data set stored on the handheld reader. If a match is found, the identity of the corresponding taggant is displayed.

[0046] The identifiability of the sample is divided into three evaluation levels ("1" to "3") 1, the sample is correctly identified on the first identification attempt; 2, between two and five attempts are required before the sample is identified; 3, the sample is not identified after at least five attempts. Production of masterbatch from PMMA and taggant

[0047] A mixture of 90 parts PMMA molding compound and 10 parts inorganic taggant (Tailor-Safe®) from Tailorlux was processed into a masterbatch using a twin-screw extruder (Coperion ZSK 26). The extrusion temperatures were 90 °C for the feed zone, 150 °C for the plasticizing zone, and 250 °C for the shear zone. The extruded hot masterbatch strand was cooled to near room temperature in a water bath and granulated into granules using a granulator. Printing on a brittle PMMA contrast film

[0048] To produce samples of laser-markable printed films, in Examples 8 and 9 below, a 50 µm-thick colored PMMA film was printed on an SMB UV flexographic printing unit at a web speed of 15 m / min using Flexocure Gemini (black) from Flint to produce an engraving layer, resulting in a print height between 2 and 5 µm. The resulting coating was then UV-cured to produce the engraving layer using an E 70-2 (4)x1 BLK-2-SLC mercury lamp from IST Metz GmbH. The lamp output of the lamp tube was 80 W / cm. Lamination of an adhesive

[0049] The extruded multilayer PMMA film, consisting of an engraving layer and a contrast layer, was applied to a 40 µm thick acrylic pressure-sensitive adhesive coated on one side with a release liner. The pressure-sensitive adhesive used was a resin-modified acrylic adhesive consisting of 80 wt.% acrylate copolymer and 20 wt.% terpene-phenol resin. The copolymer was obtained by polymerizing 47.5 wt.% n-butyl acrylate, 47.5 wt.% 2-ethylhexyl acrylate, 2 wt.% glycidyl methacrylate, and 1 wt.% acrylic acid. Lasers

[0050] The resulting film was laser-labeled with a test lettering and a barcode using a Rofin Nd:YAG solid-state laser 50D and cut into 3 x 8 cm labels using this laser. General description of the extrusion parameters

[0051] An extrusion chill-roll process was used to produce the two-layer colored films. The extrusion system used for this purpose consisted of two (optionally three) single-screw extruders and a multi-layer die (wide slot extrusion die with two, optionally three distribution channels). The overall setup, comprising the chill-roll and additional rolling mill, had an L-configuration. Furthermore, a rubberized pressure roll was installed at an angle of 90° to the polymer melt and at an angle of 180° to the chill-roll, which could optionally be used to press the polymer melt against the chill-roll. The PMMA molding compounds blended with a white masterbatch were used in the first single-screw extruder (A) to produce the thicker contrast layer. The molding compounds blended with a black masterbatch were used in the second single-screw extruder (B) to produce the outer, thinner engraved layer.The extrusion temperatures for the non-impact-modified PMMA molding compounds were 90 °C for the feed zone, 150 °C for the plasticizing zone, 250 °C for the shear zone, and 250 °C for the die. For the impact-modified PMMA-Resist ®< molding compounds, the temperatures for the feed zone were 90 °C, 150 °C for the plasticizing zone, 250 °C for the shear zone, and 230 °C for the die. The chill roll was positioned centrally at a distance of approximately 20 mm from the outlet opening of the multilayer die. The chill roll temperature was set between 70 °C and 130 °C, preferably between 90 °C and 100 °C. The temperature of the melt stream at the nozzle exit was approximately 250 °C and 230 °C, respectively. The inner layer of the polymer melt film adhered almost tangentially to the chill roll, wrapping it at an angle of approximately 90°. After wrapping the remaining post-cooling rolls, the film was wound up.The thickness ratio of the thicker contrast layer to the thinner engraving layer was always chosen at 4 to 1. The total thickness of Examples 1, 3, and 4 was 125 µm, and that of Example 2 was 75 µm. Extrusion was carried out at a speed of 4 m / min. Comparison example 1 (brittle / brittle) -

[0052] 100 µm / 25 µm Contrast layer 83 For you PMMA H7 Brittle PMMA molding compound from Evonik 15 For you Renol White, PMMA H7 TiO 2 color masterbatch from Clariant Engraving layer 90 For you PMMA H7 Brittle PMMA molding compound from Evonik 10 For you Renol Black, PMMA H7 Carbon Black color masterbatch from Clariant Comparison example 2 (brittle / brittle) -

[0053] 60 µm / 15 µm thinner version that breaks more easily Contrast layer 80 For you PMMA H7 Brittle PMMA molding compound from Evonik 20 For you Renol White, PMMA H7 TiO 2 color masterbatch from Clariant Engraving layer 85 For you PMMA H7 Brittle PMMA molding compound from Evonik 15 For you Renol Black, PMMA H7 Carbon Black color masterbatch from Clariant Example 3 (brittle / impact modified) -

[0054] 100 µm / 25 µm Contrast layer 85 For you PMMA H7 Brittle PMMA molding compound from Evonik 15 For you Renol White, PMMA H7 TiO 2 color masterbatch from Clariant Engraving layer 90 For you PMMA Resist ®< 100 Impact modified PMMA molding compound from Evonik 10 For you Renol Black, PMMA Resist 100 Carbon Black color masterbatch from Clariant Example 4 (impact modified / brittle) -

[0055] Comparison example (because it can be removed without damage) 100 µm / 25 µm Contrast layer 85 For you PMMA Resist ®< 100 Impact modified PMMA molding compound from Evonik 15 For you Renol Weiss, PMMA Resist 100 TiO 2 color masterbatch from Clariant Engraving layer 90 For you PMMA H7 Brittle PMMA molding compound from Evonik 10 For you Renol Black, PMMA H7 Carbon Black color masterbatch from Clariant Comparison example 5 (brittle / brittle / brittle) -

[0056] 60 µm / 15 µm / 15 µm thinner version that breaks more easily + Taggant 80 For you PMMA H7 Brittle PMMA molding compound from Evonik 20 For you Renol White, PMMA H7 TiO 2 color masterbatch from Clariant Engraving layer 85 For you PMMA H7 Brittle PMMA molding compound from Evonik 15 For you Renol Black, PMMA H7 Carbon Black color masterbatch from Clariant Taggant-marked layer 99 For you PMMA H7 Brittle PMMA molding compound from Evonik 1 parts PMMA H7 Taggant masterbatch made from brittle PMMA molding compound from Evonik and Taggant from Tailorlux Comparison example 6 (brittle / brittle / brittle) -

[0057] Comparative example 60 µm / 15 µm / 15 µm thinner variant that breaks more easily + taggant in the black layer (no detection) Contrast layer 80 For you PMMA H7 Brittle PMMA molding compound from Evonik 20 For you Renol White, PMMA H7 TiO 2 color masterbatch from Clariant Engraving layer 84 For you PMMA H7 Brittle PMMA molding compound from Evonik 15 For you Renol Black, PMMA H7 Carbon Black color masterbatch from Clariant 1 For you PMMA H7 Taggant masterbatch made from brittle PMMA molding compound from Evonik and Taggant from Tailorlux Transparent outer layer 99 For you PMMA H7 Brittle PMMA molding compound from Evonik Comparison example 7 (impact modified / impact modified) -

[0058] Comparison example (because it can be removed without damage) 100 µm / 25 µm Contrast layer 85 For you PMMA Resist ®< 100 Impact modified PMMA molding compound from Evonik 15 For you Renol Weiss, PMMA Resist 100 TiO 2 color masterbatch from Clariant Engraving layer 90 For you PMMA Resist ®< 100 Brittle PMMA molding compound from Evonik 10 For you Renol Black, PMMA Resist ®< 100 Carbon Black color masterbatch from Clariant Comparison example 8 (brittle white foil / black with laser label varnish printed) -

[0059] 50 µm / 5 µm Contrast layer 80 For you PMMA H7 Brittle PMMA molding compound from Evonik 20 For you Renol White, PMMA H7 TiO 2 color masterbatch from Clariant Engraving layer 5 µm Flexocure Gemini (black) Comparison example 9 (impact modified white foil / black with laser label varnish printed) -

[0060] 50 µm / 4 µm comparison example (because it can be removed without damage) Contrast layer 85 For you PMMA Resist ®< 100 Impact modified PMMA molding compound from Evonik 15 For you Renol Weiss, PMMA Resist 100 TiO 2 color masterbatch from Clariant Engraving layer 5 µm Flexocure Gemini (black) Results

[0061] Comparison example 1 Comparison example 2 Example 3 Example 4 Comparison example 5 Comparison example 6 Comparison example 7 Temperature resistance 2 2 1 1 1 1 2 Tamper-proof 2 1 3 3 1 1 4 Processability 1 1 1 1 1 1 1 Detectability of taggants - - - - 1 3 - Comparison example 8 Comparison example 9 Temperature resistance 2 2 Tamper-proof 1 4 Processability 1 1 Detectability of taggants - -

Claims

1. Laser-writable film, configured and adapted for writability by means of a laser, comprising - a contrast layer based on a polymethacrylate compound, preferably extruded, - an engraving layer, preferably extruded, disposed on the contrast layer and based on a preferably extruded polymethacrylate compound, wherein the polymethacrylate compounds are based on a composition comprising ∘ 60% to 98% by weight of at least one polymethacrylate ∘ and 2% to 40% by weight of a colouring pigment and wherein contrast layer and engraving layer have different colouring pigments from each other, characterized in that the at least one polymethacrylate of at least one of the two layers is free of impact modifiers and the other of the two layers contains an impact-modified polymethacrylate.

2. Laser-writable film according to Claim 1, characterized in that the at least one polymethacrylate is a polymethyl methacrylate.

3. Laser-writable film according to one of Claims 1 or 2, characterized in that the contrast layer contains TiO2 as colouring pigment and the engraving layer contains carbon black as colouring pigment.

4. Laser-writable film according to Claim 3, characterized in that the contrast layer contains at least 5% by weight, preferably at least 10% by weight, of TiO2.

5. Laser-writable film according to Claim 3 or 4, characterized in that the engraving layer contains at least 5% by weight, preferably at least 7.5% by weight, of carbon black.

6. Laser-writable film according to at least one of the preceding claims, characterized in that it additionally has an extruded transparent third layer disposed on the engraving layer.

7. Laser-writable film according to Claim 6, characterized in that the transparent third layer consists of a poly(meth)acrylate.

8. Laser-writable film according to Claim 6 or 7, characterized in that the transparent third layer contains a pigment that absorbs radiation in the non-visible range.

9. Laser-writable film according to Claim 8, characterized in that the concentration of the pigment that absorbs radiation in the non-visible range is at most 10% by weight, preferably at most 1% by weight and more preferably at most 0.1% by weight.

10. Laser-writable film according to at least one of the preceding claims, characterized in that the film has a layer thickness of 40 µm to 200 µm.

11. Laser-writable film according to at least one of the preceding claims, characterized in that on the opposite side of the contrast layer from the engraving layer, a layer of adhesive, more particularly a layer of pressure-sensitive adhesive, is disposed.

12. Laser-writable film according to at least one of the preceding claims, characterized in that the layers are formed by coextrusion.

13. Laser-writable label, produced from a portion of the laser-writable film according to at least one of the preceding claims.

14. Method for producing a laser-writable film according to at least one of Claims 1 to 12, characterized in that the layers forming the film are coextruded.

15. Use of the laser-writable film according to any of Claims 1 to 12 or of the laser-writable label according to Claim 13 for marking vehicles or vehicle parts.