WO2005033218A1

WO2005033218A1 - Pigment for laser engraving paints

Info

Publication number: WO2005033218A1
Application number: PCT/EP2004/010139
Authority: WO
Inventors: Philip Betten
Original assignee: Mankiewicz Gebr. & Co. (Gmbh & Co.Kg)
Priority date: 2003-09-18
Filing date: 2004-09-10
Publication date: 2005-04-14
Also published as: DE10343704A1

Abstract

The invention relates to a Chinese blue pigment containing a paint composition which is suitable for producing a laser engraving paint layer, which can be engraved with a laser leaving no traces of powder or residue, thereby avoiding problems arising during laser engraving, especially during painting with blue or blue tinted blackening tones. Preferably, ammonium Chinese blue having an average primary particle size of 10 - 100 nm is used. The preferred field of application is substrates made of thermoplastic synthetic material for use in automotive "day-night-design".

Description

Pigment for lacquer that can be engraved by laser

The present invention relates to a paint composition containing iron blue pigment, which is used for producing a laser-engravable paint layer. The invention also relates to the use of iron blue pigment in a lacquer composition which is suitable for producing a lacquer layer capable of laser engraving, a laser engraving method and a coated substrate which has coated and laser engraved areas. The invention further relates to the use of the coating composition in laser engraving.

Laser engraving varnishes are known. A lacquer is usually referred to as laser-engravable if the coatings produced with it can be removed from the substrate without leaving residues, with sharp contours and without traces of smoke. In general, the substrates are thermoplastic materials for "day-night design" applications in the automotive industry. The production of blue or bluish black shades of the lacquers, which are suitable for laser engraving, is problematic. The phthalocyanine pigments contained in the paints in these shades cannot be removed from the substrate without residues by the laser engraving carried out under the usual and suitable conditions. Rather, parts of the lacquer layer remain in an uncontrollable manner, which too lead to an undesirable and uncontrolled blue coloring of the substrate. Residue-free removal is only possible when high laser energy is applied, but then the substrate will be damaged. The realization of blue tones is therefore currently taking place. through a two-layer structure of the lacquer coating, the first layer being phth.alocyanine-free (sacrificial primer) and the second layer containing phthalocyanine. With laser engraving, both layers can be removed without residue. It is obvious that this two-layer structure has technical and economic disadvantages compared to a single-layer lacquer.

These described disadvantages of the prior art are particularly relevant in applications in which a lacquer, for example for the interior, such as the interior of the automobile, is applied to a transparent substrate and the lacquer is to be removed in some areas by laser engraving so that the transparent substrate, if it is illuminated from the underside, is practically completely covered in the non-laser-engraved areas and the transparency in the engraved areas, based on an unpainted substrate, is practically unchanged. Similar problems also occur when a lacquer: on an opaque or colored substrate is to be removed by laser engraving without leaving any residues.

From Holleman / Wiberg, 101st Ai flage 1995, publisher Walter D. Gruyter, Berlin, New York, it is known to use iron blue pigments in paints. Depending on the particle diameter in the range from 0.01 to 0.20 μ, the extremely strong pigments are almost black to light blue. From Römpp Chemie Lexikon, 9th edition it is known to use iron blue pigments as paints, in art painting and for the production of inks, ribbons and printing inks. turn. According to Brock / Groteklaes / Mischke, textbook on paint technology, Hanover, Vincentz Verlag, 1998, page 141, iron blue pigments were previously used in automotive top coats. Their consumption is declining today.

DE-Al-199 01 609 discloses a multilayer pearlescent pigment based on a platelet-shaped substrate. The substrate can contain organic pigments such as Berlin blue. The pigments are also intended for laser marking of plastics. The document also describes varnishes, printing inks, plastics, polymer films, etc. that are pigmented with the pigment. On a. Laser engraving is not accepted.

The object of the invention is now to find a pigment which on the one hand allows in an extremely thin layer of lacquer, a residue-free removal of the layer by means of laser and ^• on the other hand has a low transparency and good color properties. In particular, it is an object of the present invention to provide a coating composition which, after application even in a thin dry layer thickness, ie with a dry layer thickness of at most 120 μ, has a low transparency, ie high opacity, after curing as a single-layer lacquer with the aid of a laser can be removed without residue, without damaging the underlying substrate, results in a well-adhering lacquer layer, can be formulated in a variety of ways, for example with regard to the binder, the hue, determined in accordance with DIN 6174, can be set as flexibly as possible, i.e. the brightness on the L axis between 0 and 100 and the hue on the a axis as desired and must be arbitrarily adjustable in the negative range, preferably on the b-axis.

It has surprisingly been found that iron blue pigment can be used in the laser-engravable lacquers to solve the above-mentioned problems and to overcome the problems in the prior art.

Accordingly, the invention relates to a lacquer composition for laser engraving, which comprises a) binder polymer, b) solvent and / or dispersion medium and c) iron blue pigment u,

a lacquer layer produced therefrom can be laser-engraved with a trace of smoke and residue and meets at least one of the following parameters:

I) the lacquer layer has a reflectometer value (determined according to DIN EN ISO 2813 at a measuring angle of 60 °) of <20,

II) the lacquer layer has a characteristic value of the cross-cut test (according to DIN EN ISO 2409) of 2 or less, III) the lacquer layer has a dry layer thickness of 120 μm or less.

In preferred embodiments, two of the parameters I), II) and III) mentioned are met, in particular all three parameters are met. The simultaneous fulfillment of parameters I and II is particularly preferred. Furthermore, lacquer layers produced with preferred lacquer compositions have an adhesive peel strength (according to DIN EN ISO 4624, 2 cm stamp diameter) of> 2 MPa.

Coatings can be produced with iron-blue pigment-containing lacquers capable of being engraved, which on the one hand completely cover an underlying substrate and on the other hand can be removed without residue, the removal not requiring any laser radiation which could damage the underlying substrate.

The paint composition containing iron blue pigment means that color shades (DIN 6174) can be set in a wide range in laser-engravable paint coats. For example, the brightness on the L axis can be set between 0 and 100. The hue on the a-axis is arbitrary and on the b-axis preferably in the negative range as desired. In contrast to other blue pigments, the use of iron blue pigment also offers residue-free, smudge-free laser engraving in single-layer paints.

In DIN EN ISO 2813 it is proposed to measure at a gloss value (reflectometer value) of less than 10 at a measurement angle of 85 ° and at reflectance values between 10 and 70 at to measure a measuring angle of 60 °. In deviation from this, it is customary in the industry to also carry out the determination for matt coating systems with a reflectometer value of less than 10 at a measuring angle of 60 °. This is also how the invention is carried out.

Lacquer compositions according to the invention result in a comparatively matt lacquer layer and thus differ from the high-gloss lacquers, such as those e.g. be used outdoors in automotive engineering. In a preferred embodiment, the reflectometer value (determined in accordance with DIN EN ISO 2813 at a measurement angle of 60 °) is <15, preferably <10, in particular <8.

A preferred characteristic value of the cross-hatch test according to DIN EN ISO 2409 is 1, in particular 0, whereby at <80 μm dry layer thickness measurements are preferably made with a cutting distance of 2 mm and, in deviation from the norm, the procedure is carried out at a cutting distance of <2 mm, such as 1.5 mm or 1 mm is feasible and evaluable. The dry layer thickness of the lacquer layer (e.g. determined in accordance with DIN EN ISO 2808) is at most 120 μm, preferably <80 μm, more preferably <50 μm, and most preferably <40 μm, in particular 3 to 35 μm.

The iron blue pigments used according to the invention are M ¹ [Fe ^ Fe ¹¹¹ (CN) ₆ ] containing water of crystallization with M = Na, K and / or NH ₄ . The term iron blue pigment is defined by ISO 2495. By varying the cation and the production conditions, green to violet tones and red tones can be produced. Because of their fine particle size, iron blue pigments are very strong in color. According to the invention, ammonium (sodium) iron lukewarm pigment (which sometimes is also referred to as soluble blue) and in particular ammonium iron blue pigment is used.

To improve the dispersibility, the iron blue pigment can be surface-treated in a conventional manner (e.g. surface-coated).

A typical average primary particle size of the iron blue pigment is approximately 33 nm (arithmetic mean DN), particle sizes of 10 jois 100 nm being preferred, in particular 20 to 90 nm, according to the invention. Incidentally, reference is made to H. Endriss, Current Inorganic Colored Pigments (Vincentz- Verlag, Hanover, 1997).

The polymer of the coating composition serving as a binder is preferably selected from polyurethane, acrylate, polyurethane-acrylate hybrid, polyol, polyalcohol, urethane acrylate, polyester, unsaturated polyester, dendritic polymer, epoxy resin, polycarbonate, melamine resin, phenolic resin, acrylic-polyurethane Hybrid and mixtures thereof. The polymers mentioned can contain functional groups (for example OH groups, amine functionalities or blocked isocyanate groups) as well as non-functional polymers. The polymers mentioned can be contained in the lacl composition according to the invention both in the form of a solution and of a dispersion. The amount of binder is preferably 15 to 60% by weight, more preferably 20 to 45% by weight, in particular 25 to 40% by weight (based on the coating composition). The coating system can be both aqueous and solvent-based or solvent-based or a high-solid system. In a preferred embodiment, the solvent and / or dispersion medium is selected from water, ketones, esters, aliphatic hydrocarbons, aromatic hydrocarbons, glycols and glycol derivatives, N-methylpyrrolidone, alcohols, ethers and glycol ethers and mixtures thereof. The amount of solvent and / or dispersion medium is preferably 10 to 75% by weight, more preferably 15 to 65% by weight, in particular 20 to 60% by weight, based on the coating composition.

In addition to the iron blue pigment, the coating composition can further comprise one or more inorganic pigments, organic pigments, effect pigments and / or fillers. Preferred inorganic pigments are titanium dioxide, carbon black, chromium oxide, ultramarine, molybdate red, chrome yellow, cobalt blue, mixed oxide pigment, iron oxides (such as iron oxide red, iron oxide yellow, iron oxide black), bismuth vanadate, chromium titanium yellow and nickel titanium yellow, with carbon black being used particularly frequently. Preferred organic pigments are, for example, azo pigments, diazo pigments, polycyclic pigments, quinacridone pigments, dioxazine pigments, perylene pigments, diketo-pyrrolo pigments and isoindoline pigments. For example, aluminum flake pigments and pearlescent pigments are preferred as effect pigments.

The amount of pigmentation in the paint composition must be less than or equal to the critical pigment volume concentration (KPVK). Preferred total amounts of pigment (including iron blue pigment), based on the coating composition, are less than 20% by weight, more preferably less than 15% by weight, in particular less than 10% by weight. The amount of iron blue pigment is drew on the paint composition. preferably 0.1 to 10% by weight, more preferably 1 to 5% by weight, in particular 2 to 4% by weight. The amount of additional pigment (especially carbon black), based on the coating composition, is generally 0.1-10%, preferably 2 to 10%, in particular 3 to 8%.

The pigments are in their powdered form in the agglomerated state. In the production of the paint composition, the agglomerated pigments are broken up and dispersed, for example, by stirrers, dissolvers, agitator ball mills, ball mills, colloid mills, three-roll mills or high-pressure homogenizers, so that a granularity, measured using the grinder according to DIN EN ISO 1524, generally less than 120 μm, preferably less than 50 μm, in particular less than 30 μm, is achieved.

Furthermore, the paint composition according to the invention can include one or more customary additives selected from defoamers, deaerators, wetting dispersants, surface additives (such as leveling and slip additives), wax dispersions, waxes, matting agents (silicates or polyamide powder, polymer powder), theological additives (thickeners , Associative thickener or thixotropic agent), aerosils, layered silicates, adhesion promoters, substrate wetting agents, catalysts, accelerators, photoiniators, dyes, biocides and mixtures thereof. Preferred amounts of matting agent, based on the coating composition, are generally less than 30% by weight, preferably less than 20% by weight, in particular less than 15% by weight. The invention further relates to a laser engraving method in which

a) a coating composition according to the invention is applied to a substrate,

b) the lacquer composition is cured - and thus a lacquer layer is produced and

c) at least part of the lacquer layer is removed by means of a laser.

According to the invention it is possible to provide substrates of any material with a resist layer lasergravierfahigen where ^¬ when the substrate is preferably made of metal and / or consists of plastic. The substrate may be, for example, from thermoplastic material (such as polycarbonate, Polymethacrylmethacrylat, polyamide, acrylonitrile / butadiene / styrene, polybutylene terephthalate, Po ^¬ lystyrol, polyethylene, polypropylene, or thermoplastic elastomers). Acrylonitrile / butadiene / styrene, acrylonitrile / butadiene / styrene-polycatalyst, polycarbonate and polyamide are preferred as plastics. The thermoplastic can be transparent, opaque or colored, for example white.

In addition, the use of substrates made of thermosets or polyurethanes is possible, such as hard or soft foams or integral foams. As metals come e.g. Steels or metal sheets, iron sheets or aluminum sheets in question.

The plastics and metals mentioned are generally not colored black and are preferably too black in one contrasting color, or are uncolored, opaque or transparent substrates.

All manual or automatic application methods that are customary for paints are suitable as application methods. Exemplary methods are in A. Goldschmidt, H-J. Streitberger, BASF Handbook of Painting Technology, Vincentz Verlag Hannover, 2002. These include e.g. Spray applications such as pneumatic atomization or electrostatically assisted pneumatic atomization, mist-reduced pneumatic atomization (HVLP), high-speed atomization, hydraulic atomization (airless), pneumatically assisted hydraulic atomization, whereby all atomization methods can also be used electrostatically assisted, or other application methods such as e.g. Rolling, casting, painting, dipping, drumming, winding or printing.

In a typical manual application process, the paint composition according to the invention is first applied by pneumatic spray application. A preferred spray application method is characterized, for example, by the following parameters:

For example, spray application is possible with a nozzle diameter of 0.8 mm, an atomizing air pressure of 4 bar, a material pressure of 0.5 bar at 22 ° C ambient temperature and 60% relative air humidity. The paint composition is then allowed to flash off at 22 ° C. ambient temperature and 60% relative atmospheric humidity for 10 minutes, dried at 80 ° C. for 30 minutes and then aged at 60 ° C. for 48 hours.

It is possible to apply several paint compositions according to the invention or one paint composition according to the invention to apply several times. This procedure is encompassed by the term "one layer".

When carrying out the method according to the invention, it is possible to apply the coating composition according to the invention as a single layer to the substrate. This means that un ^¬ indirectly applied no other lasergravierfähige lacquer layer on the substrate (s) than the resist layer of the inventive coating composition comprising the iron-blue pigment. Alternatively, it is possible to put on a body (for example made of plastic or metal)

1) apply a white (or colored) primer, which is preferably not laser-engravable,

2) to apply and harden the coating composition according to the invention on the substrate as a topcoat and

3) to remove the lacquer layer according to the invention by laser engraving.

The substrate is not changed by the laser engraving and accordingly forms the visible surface in the laser-engraved areas. Before the coating composition is applied, the substrate can be surface-treated in a conventional manner.

The curing processes include oxidative curing, curing at room temperature, forced curing at higher temperatures, UV curing, amine curing and reactive crosslinking, for example with isocyanates (for example tolylene diisocyanate, TDI, hexamethylene diisocyanate, HDI, isophorone diisocyanate, IPDI, methylene phenylene diisocyanate, MD or Polyisocyanate) possible. One-component systems, for example based on blocked isocyanates, can also be used.

Laser engraving processes which remove a layer of lacquer, which has been produced by applying and curing a lacquer composition according to the invention, without smoke and residues are known to those skilled in the art. The amount of energy that is applied to a certain area of the lacquer layer in a certain period of time and that removes the lacquer layer without damaging the substrate is usually determined in a preliminary test. It has been found according to the invention that removal of a blue pigment-coated lacquer layer without smoke and residues is possible if the lacquer composition used to produce the lacquer layer comprises iron blue pigment.

In the laser engraving method according to the invention, customary lasers are used with which the lacquer is removed without damaging the substrate. With phthalocyanine (e.g. copper phthalocyanine blue) varnishes containing blue, if the substrate is not to be damaged, blue residues remain visibly. The opacity of the coated areas is assessed visually by holding a lamp under the substrate. The transparency of the laser-engraved areas and the edge sharpness between the coated area and the laser-engraved area are also assessed visually.

A typical laser engraving process uses a neodymium YAG laser with a wavelength of 1064 nm. Such lasers with an output of 50 watts in continuous operation are suitable, for example. In practice, predominantly one Combination of continuous and pulsed operation applied, with higher performance occurring in the short term.

The invention further relates to a coated substrate, with

a) at least one coated area which is provided with at least one lacquer layer which comprises iron blue pigment, the area meeting at least one of the above-mentioned parameters I), II) and III), and

b) at least one laser-engraved area in which the substrate located under the lacquer layer is essentially completely exposed.

In a typical application, the laser-engravable lacquer layer is produced on a component in the interior of the automobile that is backlit ("day-night design"). A special application of the invention is the production of consoles for car radios and control and switching buttons in the automotive interior.

The invention further relates to the use of the above-mentioned lacquer composition in a laser engraving process.

Similarly, the invention is also suitable for the decorative field such as Lampshades. In addition, the invention can be used in the tampon print area and in the heat seal area (in each case without backlighting).

The use of iron blue pigments in laser lacquers according to the invention enables laser-engraved removal of the residue-free, sharp-contoured and smear-free traces of the resultant provided coatings. Due to the replacement of the phthalocyanine pigments by iron blue pigments, laser coatings that can be used in one layer can be formulated. The advantage of the iron blue pigments is that the color tones of the laser lacquers on the b-axis in the CIELAB color space can be set as desired, especially in the negative range, regardless of the intrinsic color tone of the binders. The laser lacquers according to the invention can be applied in one layer and can also be laser-engraved without residue without sacrificial primer.

The standards mentioned in the description of the invention are the currently applicable standards. The cross-cut test was carried out in accordance with DIN EN ISO 2409. The dry layer thickness was determined in accordance with DIN EN ISO 2808. The reflectometer value was determined in accordance with DIN EN ISO 2813.

Examples

Example 1:

Production of a black pigmented laser varnish:

200 g of commercially available polyurethane dispersion (with a non-volatile content of 40% and an OH content based on the resin of 0.5%) were placed in a plastic beaker with a stirrer and then 5 g of commercially available dispersant (for example a modified styrene-methacrylate copoly- mer), 5 g of commercially available pigment black and 5 g of commercially available HEUR (hydrophobically modified, ethoxylated polyurethane) associative thickener with stirring. The pH was raised by adding about 1 g of 2-amino-2-methyl-propanol (90% in water) The pH was adjusted to 8 and the mill base viscosity was regulated with approx. 8 g of fully deionized water. The mixture thus obtained was ground to a grain size of 5 μm (measurement by grindometer lift) in a bead mill. 50 g of commercially available silicate matting agent, 50 g of butyl glycol and a further 100 g of the above-mentioned polyurethane dispersion were then added, and the mixture was dispersed for 20 minutes using a dissolver. After adding 390 g of the above-mentioned polyurethane dispersion, the mixture was finished by adding about 175 c of deionized water so that the finished mixture had a non-volatile content of 35%. The paint was adjusted to pH = 8 with 2-amino-2-methyl-propanol (90% in water) and the viscosity was adjusted to a suitable impurity viscosity of 45 seconds at 20 ° by adding approx. 11 g HEUR associative thickener C measured with a cup set according to the previous standard DIN B4.

A 75% solution of a commercially available polyisocyanate (e.g. based on a hydrophilized HDI and an isocyanate content of approx. 17%) in methoxypropyl acetate was used as the hardener.

Example 2:

Production of a blue-black pigmented laser varnish:

200 g of commercially available polyurethane dispersion (with a non-volatile content of 40% and an OH content based on 100% resin of 0.5%) were placed in a plastic beaker with a stirrer and then 5 g of commercially available dispersant (for example a modified styrene-methacrylate copoly - er), 3 g of commercially available pigment black, 2 g of iron blue pigment and 5 g of commercially available HEUR association thicker with stirring. give. By adding about 1 g of 2-amino-2-methyl-propanol (90% in water), the pH was adjusted to pH = 8 and the millbase viscosity was regulated with about 8 g of fully deionized water. The mixture obtained in this way was ground in a bead mill to a granularity of 5 μm (measurement by grinder meter elevator). 50 g of commercially available silicate matting agent, 50 g of butyl glycol and a further 100 g of the above-mentioned polyurethane dispersion were then added, and the mixture was dispersed for 20 minutes using a dissolver. After adding 390 g of the above-mentioned polyurethane dispersion, the mixture was finished by adding about 175 g of deionized water so that the finished mixture had a non-volatile content of 35%. The paint was adjusted to pH = 8 with 2-amino-2-methyl-propanol (90% in water) and the viscosity was measured by adding about 11 g of HEUR associative thickener to a suitable processing viscosity of 45 seconds at 20 ° C adjusted with a cup according to the previous standard DIN B4.

Example 3:

Production of a blue-black pigmented laser varnish:

200 g of commercially available polyurethane dispersion (with a non-volatile content of 40% and an OH content based on the resin of 0.5%) were placed in a plastic beaker with a stirrer and then 5 g of commercially available dispersant (for example a modified styrene-methacrylate copolymer). mer), 3 g commercial pigment black, 2 g commercial phthalate Locyanin pigment (eg Cu phthalocyanine blue) and 5 g of commercially available HEUR associative thickeners are added with stirring. By adding about 1 g of 2-amino-2-methyl-propanol (90% in water), the pH was adjusted to pH 8 and the millbase viscosity was regulated with about 8 g of deionized water. The mixture thus obtained was ground in a bead mill to a grain size of 5 μm (measurement by grindometer lift). 50 g of commercially available silicate matting agent, 50 g of butyl glycol and a further 100 g of the above-mentioned polyurethane dispersion were then added, and the mixture was dispersed for 20 minutes using a dissolver. After adding 390 g of the above-mentioned polyurethane dispersion, the mixture was finished by adding about 175 g of deionized water so that the finished mixture had a non-volatile content of 35%. The lacquer was adjusted to pH = 8 with 2-amino-2-methyl-propanol (90% in water) and the viscosity was measured by adding approx. 11 g HEUR associative thickener to a suitable processing viscosity of 45 seconds at 20 ° C adjusted with a cup according to the previous standard DIN B4.

Example 4:

Production of a laser-engravable coating:

The laser lacquers previously described in Examples 1-3 were applied to a plastic plate made of polycarbonate (PC) with the dimensions 200 × 100 mm × 3 mm, so that a dry layer thickness of 35 μm was obtained. After a flash off time of The coating was dried at 80 ° C for 10 minutes at 22 ° C for 30 minutes and aged at 60 ° C for 48 hours.

Production of the Lase engravings:

Small test areas measuring 4 x 4 mm were engraved in the coated plates with a laser. In order to find the optimal settings of the laser engraver, both pulse frequencies and energy input were varied discontinuously.

Rating:

The lacquers of Examples 1-3 cannot be completely removed if the laser's energy input is too low.

Paints 1 and 2 can be completely removed from the substrate with optimal energy input without the substrate being charred or damaged. A sharply contoured laser engraving is obtained. If the energy input is too high, the plastic substrate becomes charred or damaged.

Lacquer 3 cannot be laser engraved in such a way that the lacquer is completely removed and the substrate is not damaged. There are always clearly visible blue or colored residues of the paint in the engraved area or the plastic substrate is charred.

Claims

claims

1. Lacquer composition for laser engraving, which comprises a) binder polymer, b) solvent and / or dispersing agent and c) iron blue pigment, it being possible to laser-engrave a lacquer layer produced therefrom with a laser free of traces of smoke and residues and fulfilling at least one of the following parameters :

I) the lacquer layer has a reflector value (determined according to DIN EN ISO 2813 at a measuring angle of 60 °) of <20,

II) the lacquer layer has a characteristic value of the cross-cut test (according to DIN EN ISO 2409) of 2 or less,

III) the lacquer layer has a dry layer thickness of 120 μm or less.

2. Lacquer composition according to claim 1, in which two, preferably three of said parameters I), II) and III) are satisfied.

3. Lacquer composition according to claim 1 or 2, wherein the iron blue pigment is ammonium iron blue pigment.

4. Lacquer composition according to one of the preceding claims, wherein the iron blue pigment has a medium primary part size (arithmetic mean DN) of 10 to 100 nm, preferably 20 to 90 nm.

5. Lacquer composition according to one of the preceding claims, in which the binder polymer is selected from polyurethane, polycarbonate, acrylate, polyurethane-acrylate hybrid, polyol, polyalcohol, urethane acrylate, polyester, unsaturated polyester, dendritic polymer, epoxy resin, melamine resin, phenolic resin, acrylic Polyurethane hybrid and mixtures thereof.

6. - Lacquer composition according to one of the preceding claims,. Wherein the solvent and / or dispersion medium is selected from water, ketones, esters, aliphatic hydrocarbons, aromatic hydrocarbons, glycols and glycol derivatives, N-methylpyrrolidone, alcohols, ethers, glycol - ethers and mixtures thereof.

7. Lacquer composition according to one of the preceding claims, which additionally comprises one or more inorganic pigments, organic pigments, effect pigments, and / or fillers.

8. Lacquer composition according to claim 7, in which the inorganic pigment is selected from the group consisting of titanium dioxide, carbon black, chromium oxide, ultramarine, molybdate red, chromium yellow, cobalt blue, oxidic mixed-phase pigments, iron oxides such as iron oxide red, iron oxide yellow, iron oxide black, bismuth vanadate, chromium titanium yellow, nickel titanium yellow and Mixtures of these, with carbon black being particularly preferred.

9. A coating composition according to claim 7 or 8, in which the organic pigment is selected from the group consisting of azo pigment, diazo pigment, polycyclic pigment, quinacrodone pigment, dioxazine pigment, perylene pigment, diketo-pyrrolo pigment, isoindoline pigment and mixtures thereof.

10. Lacquer composition according to one of claims 7 to 9, wherein the effect pigment is selected from aluminum flake pigments and pearlescent pigments.

11. Use of iron blue pigment in a lacquer composition for producing a residue-free laser-engravable lacquer layer, the lacquer layer fulfilling at least one, preferably two, in particular all three of the parameters I), II and III) mentioned in claim 1.

12. Laser engraving method, in which a) a lacquer composition according to one of claims 1 to 10 is applied to a substrate, b) the lacquer composition is cured and thus a lacquer layer is produced and c) at least a part of the lacquer layer is removed by means of a laser.

13. The method according to claim 12, in which a neodymium YAG laser with a wavelength of 1064 mm is used.

14. The method according to claim 12 or 13, wherein the substrate consists of metal and / or plastic.

15. The method of claim 14, wherein the plastic is selected from acrylonitrile / butadiene / styrene, acrylonitrile / butadiene / styrene polycarbonate, polycarbonate and polyamide.

16. The method according to any one of claims 12 to 15, in which the lacquer composition is applied in such an amount that the dry layer thickness of the lacquer layer (determined according to DIN EN ISO 2808) <120 μm, preferably <80 μm, more preferably <50 μm, in particular 3 is up to 35 μm.

17. Coated substrate which is obtainable by the process according to one of claims 12 to 16.

18. Coated substrate, with a) at least one coated area which is provided with at least one lacquer layer comprising iron blue pigment, the area meeting at least one of the parameters I), II) and III) mentioned in claim 1, and b ) at least one laser-engraved area in which the substrate located under the lacquer layer is essentially completely exposed.

19. Use of the coating composition according to one of claims 1 to 10 in a laser engraving process.