EP1279517A2 - Colour writing or marking of plastics and lacquers - Google Patents

Abstract

Surprisingly, it has been found that colored recordings or inscriptions can be made on laser markable synthetic plastic and paints when their surfaces are coated with a mixture of colorants and absorbing substances, which are partially drawn into or cover the surface. The colorant in combination with the laser light absorbing substance is drawn into the synthetic plastic or paint surface melted by laser radiation, and the inscriptions have high abrasion resistance. Independent claims are included for: (1) A process for colored inscription and colored marking of synthetic plastics and paints, in which the synthetic plastics or paint surfaces are coated with a mixture of one or more laser light absorbing substances, and this layer is partially or over the whole surface transferred partially or completely into the synthetic plastic or paint; (2) a shaped body in synthetic plastic, paint or powdered paint inscribed or marked by the process.

Description

The present invention relates to the colored inscription or marking of plastics, lacquers, including powder lacquers, a colorant being transferred into the plastics or lacquer by laser radiation with the aid of a laser light-absorbing substance.

The labeling of production goods is becoming increasingly important in almost all branches of industry. So often z. B. Production dates, expiry dates, barcodes, company logos, serial numbers, etc. can be applied to products. Currently, these markings are mainly carried out using conventional techniques such as printing, embossing, stamping and labeling. With the help of a laser beam, inscriptions can be applied to glass, metal and ceramic, especially in the infrared range. The materials from which the subsequent inscription is made are melted onto the surface. However, this method is not suitable for labeling plastics. The dark marking with lasers is becoming increasingly important for plastics. With this technique it is possible to use graphic labels such as Barcodes can be applied to a non-flat surface at high speed. Since the label is in the plastic body itself, it is permanently resistant to abrasion.

In addition to the dark marking of plastics, there is increasing interest in colored markings.

Absorber materials for the colored marking of plastics are known. Colored laser marking of a dark plastic is disclosed in EP 0 522 370 A1. For example, EP 0 684 144 B1 describes a dopant for the colored marking of plastic materials, which is characterized in that it contains a mixture of an opacifying agent and a chromogenic substance.

However, the methods known from the prior art for the colored labeling of plastics have the disadvantage that they do not enable colored marking on plastics with bright colors or that several lasers with different wavelengths are required for the colored labeling of the plastic.

It was therefore an object of the present invention to find a method which, under the action of laser light, enables colored marking with high contrast on each plastic color using only one laser or laser wavelength.

Surprisingly, it was found that plastics and paints can be labeled in color if the surface of a laser-markable plastic or varnish is coated with a mixture of colorant and absorber substance and is partially or fully entered into the surface. The colorant, in combination with the laser-absorbing substance, is introduced into the plastic or lacquer surface melted by laser radiation. Through the entry in the surface of the plastic or varnish, colored inscriptions with very high abrasion resistance can be achieved.

The invention relates to plastics and lacquers which can be labeled or marked in color, characterized in that a mixture consisting of one or more colorants and one or more laser-absorbing substances is applied to the plastic or lacquer surface.

Good marking results are achieved if the ratio of colorant / laser light-absorbing substance is 10: 1 to 1:10, preferably 95: 5 to 70:30, in particular 90:10 to 80:20.

The concentration of the colorant and the laser light-absorbing substance on the surface of the plastic or lacquer, however, depends on the plastic system or lacquer composition used and the area of the lettering.

Both organic and inorganic colorants can be used for labeling. All colorants known to the person skilled in the art which do not decompose during laser irradiation are suitable.

Suitable organic colorants are preferably those selected from the group of the organic pigments mentioned below:
Copper phthalocyanines, dioxazines, anthraquinones, monoazo and
Diazo pigments, diketopyrolopyrrole, polycyclic pigments, anthrapyrimidines, quinacridones, quinaphtalones, perinones, perylenes.

Suitable dyes are e.g. B. acridines, azo dyes, phthalocyanines, xanthenes and phenazines. The dyes can be cationic, anionic and nonionic dyes.

Suitable inorganic colorants are e.g. B. colored oxide and oxide hydroxide pigments, oxide mixed phase pigments, sulfide and sulfide selenium pigments, carbonate pigments, chromate, chromate-molybdate mixed phase pigments, complex salt pigments and silicate pigments.

The colorant can also be a mixture of two or more substances.

The laser-absorbing substances suitable for the marking are preferably based on anthracene, pentaerythritol, copper hydroxide phosphates, molybdenum disulfide, antimony (III) oxide and bismuth oxychloride, platelet-shaped, in particular transparent or semitransparent substrates made of, for example, layered silicates, such as synthetic or natural mica, talc, kaolin, glass platelet SiO ₂ platelets or synthetic carrier-free platelets. Furthermore, platelet-shaped metal oxides such. B. platelet-shaped iron oxide, aluminum oxide, titanium dioxide, silicon dioxide, LCP's (Liquid Crystal Polymers), holographic pigments, conductive pigments or coated graphite platelets.

As platelet-shaped pigments, metal platelets can also be used, which are uncoated or with one or more metal oxide layers can be covered; z. B. Al, Cr, Fe, Au, Ag and steel plates. Should corrosion-prone metal plates such. B. Al, Fe or steel plates are used uncoated, they are preferably coated with a protective polymer layer.

Particularly preferred substrates are mica flakes coated with one or more metal oxides. Colorless, highly refractive metal oxides, such as, in particular, titanium dioxide, antimony (III) oxide, zinc oxide, tin oxide and / or zirconium dioxide, and colored metal oxides such as, for example, chromium oxide, nickel oxide, copper oxide, cobalt oxide and in particular iron oxide (Fe ₂ O ₃ , Fe ₃ O ₄ ). Antimony (III) oxide is particularly preferably used alone or in combination with tin oxide as the absorber material.

These substrates are known and for the most part commercially available, e.g. B. under the brand Iriodin® LS from Merck KGaA, and / or can be prepared by standard methods known to those skilled in the art. Pigments based on transparent or semi-transparent platelet-shaped substrates are used, for. B. described in the
German patents and patent applications 14 67 468, 19 59 998, 20 09 566, 22 14 454, 22 15 191, 22 44 298, 23 13 331, 25 22 572, 31 37 808, 31 37 809, 31 51 343, 31 51 354, 31 51 355, 32 11 602, 32 35 017, 38 42 330, 44 41 223.

Coated SiO ₂ platelets are e.g. B. known from WO 93/08237 (wet chemical coating) and DE-OS 196 14 637 (CVD process).

$${\text{Glimmer + TiO}}_{\text{2}}{\text{+ SiO}}_{\text{2}}{\text{+ TiO}}_{\text{2}}{\text{/Fe}}_{\text{2}}{\text{O}}_{\text{3}}$$

$${\text{Glimmer + TiO}}_{\text{2}}{\text{+ SiO}}_{\text{2}}{\text{+ (Sn, Sb)O}}_{\text{2}}$$

$${\text{SiO}}_{\text{2}}{\text{-Plättchen + TiO}}_{\text{2}}{\text{+ SiO}}_{\text{2}}{\text{+ TiO}}_{\text{2}}$$

Multilayer pigments based on phyllosilicates are known, for example, from German published documents DE 196 18 569, DE 196 38 708, DE 197 07 806 and DE 198 03 550. Multi-layer pigments which have the following structure are particularly suitable: $${\text{Mica + TiO}}_{\text{2}}{\text{+ SiO}}_{\text{2}}{\text{+ TiO}}_{\text{2}}$$

$${\text{Mica + TiO}}_{\text{2}}{\text{+ SiO}}_{\text{2}}{\text{+ TiO}}_{\text{2}}{\text{/ Fe}}_{\text{2}}{\text{O}}_{\text{3}}$$

$${\text{Mica + TiO}}_{\text{2}}{\text{+ SiO}}_{\text{2}}{\text{+ (Sn, Sb) O}}_{\text{2}}$$

$${\text{SiO}}_{\text{2}}{\text{-Plate + TiO}}_{\text{2}}{\text{+ SiO}}_{\text{2}}{\text{+ TiO}}_{\text{2}}$$

Particularly preferred laser light-absorbing substances are anthracene, pentaerythritol, copper hydroxide phosphates, molybdenum disulfide, antimony (III) oxide and bismuth oxychloride.

The laser light absorbing substance can also be a mixture of two or more components.

All known thermoplastics as well as Duraplast, e.g. in Ullmann, vol. 15, pp. 457 ff., publisher VCH, can be permanently and abrasion-resistant inscribed using a laser using the method according to the invention. Suitable plastics are in particular polyethylene, polypropylene, polyamides, polyesters, polyester esters, polyether esters, polyphenylene ethers, polyacetal, polybutylene terephthalate, polymethyl methacrylate, polyvinyl acetal, polystyrene, acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-acrylic esters (ASA), polycarbonate, polyethersulfone and polyether ketones and their copolymers and / or mixture.

Lacquers are understood to be all lacquers known to the person skilled in the art, such as, for B. car paints, industrial paints, refinish paints, powder coatings.

Particularly suitable powder coatings are based on polyester, epoxy resins, polyester epoxy resins (mixed powder), polyurethanes, acrylates, fluidized bed powders (polyamide base).

So-called carrier substances of the colorant / absorber component can be added to improve the color input into the matrix of the plastic or the powder coating. These significantly improve the entry into the surface of the plastic or powder coating, but are not retained as a component in the marking.

Suitable carriers are e.g. B. mineral oils, waxes, paraffins and nitrocellulose varnishes.

The proportion of carrier substance based on the colorant / absorber component is 0.1 to 99.9% by weight, preferably 10 to 90% by weight, in particular 25 to 75% by weight.

In a special embodiment, the colored marking of the plastics and powder coatings becomes even more high-contrast if the plastic or coating system to be labeled is additionally doped with one or more laser light-absorbing substances. The entry of the colorant into the surface of the system to be marked is then significantly improved.

The dopant in the plastic or in the lacquer can be the same or different with the laser light-absorbing substance of the colorant / absorber component. Suitable laser-absorbing substances in plastic or lacquer are in particular platelet-shaped transparent or semi-transparent substrates which are coated with one or more colored or colorless metal oxides. Dopants based on mica substrates are particularly preferred. These platelet-shaped pigments are known and are commercially available under the brand Iriodin® LS from Merck KGaA.

The marking of plastics and powder coatings is simple and easy to use. The colored marking takes place predominantly in the plastic or powder coating matrix, ie not by melting another plastic or coating component. For application, the colorant / absorber component can be applied directly to the plastic or lacquer to be labeled. The colorant / absorber component is applied to the surface of the system to be marked by customary techniques, such as brushing, brushing, printing, spraying, knife coating. The layer thickness is generally 0.1 to 10000 nm, preferably 10 to 5000 nm, in particular 50 to 3000 nm. The entry into the plastic surface is made directly by the laser beam focused on the plastic or lacquer surface. Depending on the colorant / absorber combinations used, lasers with different wavelengths can be used, but preferably CO ₂ lasers at a wavelength of 10.6 μm, and Nd: YAG lasers at 1064 nm by simply wiping the surface of the marked system from the unused colorant / absorber component.

The laser inscription is such that the sample body is brought into the beam path of a pulsed laser, preferably a CO ₂ or Nd: YAG laser. Labeling with an excimer laser, for example using a mask technique, is also possible. However, the desired results can also be achieved with other conventional laser types which have a wavelength in a high absorption range of the laser light-absorbing substance used. The marking obtained is determined by the irradiation time (or the number of pulses in the case of pulse lasers) and the irradiation power of the laser and the plastic system or coating system used. The power of the lasers used depends on the respective application and can be easily determined by a specialist in individual cases.

The laser used generally has a wavelength in the range from 157 nm to 10.6 μm, preferably in the range from 532 nm to 10.6 μm. For example, CO ₂ lasers (10.6 µm) and Nd: YAG lasers (1064 or 532 nm) or pulsed UV lasers may be mentioned here. The excimer lasers have the following wavelengths: F ₂ excimer laser (157 nm), ArF excimer laser (193 nm), KrCI excimer laser (222 nm), KrF excimer laser (248 nm), XeCl excimer laser (308 nm), XeF excimer laser (351 nm), frequency multiplied Nd: YAG laser with wavelengths of 355 nm (frequency tripled) or 265 nm (frequency quadrupled). Nd: YAG lasers (1064 or 532 nm) and CO ₂ lasers are particularly preferably used. The energy densities of the lasers used are generally in the range from 0.3 mJ / cm ² to 50 J / cm ² , preferably 0.3 mJ / cm ² to 10 J / cm ² .

When using pulsed lasers, the pulse frequency is generally in the range from 1 to 30 kHz. Corresponding lasers that can be used in the method according to the invention are commercially available.

The plastic or varnish according to the invention can be used in all fields where previously customary printing processes have been used for labeling plastics. For example, moldings made from the plastic according to the invention can be used in the electrical, electronics and motor vehicle industries. The marking and labeling of e.g. Cables, lines, moldings or functional parts in the heating, ventilation and cooling area or switches, plugs, levers and handles, which consist of the plastic according to the invention, can be marked with the aid of laser light even in hard-to-reach places. Furthermore, the plastic system according to the invention can be used in packaging in the food sector or in the toy sector. The markings on the packaging are characterized by the fact that they are smudge-proof and scratch-resistant, stable during subsequent sterilization processes, and can be applied hygienically during the marking process. Complete label images can be permanently applied to the packaging for a reusable system. Another important area of application for laser marking is plastic tags for the individual identification of animals, so-called cattle tags or ear tags. The information that is specific to the animal is stored via a barcode system. If necessary, these can be called up again using a scanner. The lettering has to be very durable, because the mark remains on the animals for several years.

The paints and powder coatings of the invention can be used in the identification of functional parts in the automotive and industrial sectors, in the electrical sector and in levers, handles, tools, metal plates, pipes, ceramic plates, packaging, plugs, grids, developer parts.

The following examples are intended to illustrate the invention without, however, limiting it. The percentages given are percentages by weight.

Examples example 1

Injection molded bodies are made from a thermoplastic polypropylene (type: PPH 10 from DSM, Geelen), which is 1% titanium dioxide (Kronos, from Kronos) and 0.2% Iriodin® LS 825 (coated with (Sn, Sb) O ₂ ) Mica from Merck KGaA, Darmstadt) included.

The additives are added in the form of polypropylene concentrates before the spraying process. The injection molded bodies show a white body color under daylight. Using a commercially available airbrush gun, a mixture of a blue color pigment (PV real blue, from Clariant) and a tin-antimony mixed oxide (Zelec ECP-3010-XC, from Dupont Chemicals) is applied to the surface of the injection molded body at a mixing ratio of 2: 8 applied. For use in the airbrush gun, the mixture is mixed in a ratio of 1: 1 with a mineral oil (Energol WM6 from BP Lubricant GmbH). The uniform color layer of colorant and laser absorber obtained after spraying is applied to the surface with a commercially available Nd: YAG laser (type Starkmark, from Baasel Lasertechnik). Then the surface is removed by simply wiping off the color layer that has not been entered. What remains are blue, high-contrast lettering, which is characterized by a high surface quality and very good abrasion resistance.

Example 2

Analogous to Example 1, but with a red color pigment (PV Echtrot, from Clariant) and a tin-antimony mixed oxide (Zelec ECP-3010-XC, from Dupont Chemicals), the mixing ratio being 3: 7. It shows red, high-contrast lettering, which are characterized by a high surface quality and very good abrasion resistance.

Example 3

Analogous to Example 2, but with a yellow color pigment (PV real yellow, from Clariant) and a tin-antimony mixed oxide (Zelec ECP-3010-XC, from Dupont Chemicals), the mixing ratio being 1: 9. It shows yellow, high-contrast lettering, which are characterized by a high surface quality and very good abrasion resistance.

Example 4

Injection moldings are produced from a thermoplastic polyamide (type Schulamid, from Schulmann) which contain 0.8% Iriodin® LS 835 (mica coated with Fe ₃ O _{4 from} Merck KGaA, Darmstadt). The additives are added in the form of concentrates in polyamide before the spraying process. The injection molded bodies show a black body color under daylight. The laser marking is carried out analogously to Example 1. You get blue, high-contrast lettering, which is characterized by a high surface quality and very good abrasion resistance.

Example 5

Metal bodies are powder-coated with a powder coating based on polyester, the powder coating containing 2% Iriodin® LS 820 (Merck KGaA). The laser marking is carried out analogously to Example 1. You get blue, high-contrast lettering, which is characterized by a high surface quality and very good abrasion resistance.

Claims (10)

Plastics and lacquers that can be labeled or marked in color, characterized in that a mixture consisting of one or more colorants and one or more laser-absorbing substances is applied to the plastic or lacquer surface. Plastics or lacquers which can be written on or marked in color according to Claim 1, characterized in that the colorant: laser light-absorbing substance ratio is 10: 1 to 1:10. Plastics or lacquers which can be labeled or marked in color according to Claim 1 or 2, characterized in that the colorant is a dye and / or an organic or an inorganic pigment. Plastic or lacquers which can be written on or marked in accordance with claim 3, characterized in that the colorant is selected from the group of copper phthalocyanines, dioxazines, anthraquinones, monoazo and diazo pigments, diketopyrolopyrrole, polycyclic pigments, anthrapyrimidines, quinacridones, quinaphthalones, perinones, perylenes, acrylenes , Azo dyes, phthalocyanines, xanthenes and phenazines, colored oxide and oxide hydroxide pigments, oxide mixed-phase pigments, sulfide and sulfide-selenium pigments, carbonate pigments, chromate, chromate-molybdate mixed-phase pigments, complex salt pigments and silicate pigments. Plastics which can be labeled or marked in color according to one of Claims 1 to 4, characterized in that the plastics material is a thermoplastic or a thermoset. Plastics which can be labeled or marked in color according to claim 6, characterized in that the plastics material is made of polyethylene, polypropylene, polyamide, polyester, polyester ester, polyether ester, Polyphenylene ether, polyacetal, polybutylene terephthalate, polymethyl methacrylate, polyvinyl acetal, polystyrene, acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylic ester (ASA), polycarbonate, polyether sulfones and polyether ketones and their copolymers and / or mixture. Plastics and powder coatings which can be labeled or marked in color according to one of claims 1 to 6, characterized in that the plastic or the coating itself contains one or more laser light-absorbing substances. Process for the colored labeling and colored marking of plastics and paints, characterized in that the plastic or lacquer surface is covered with a mixture consisting of one or more colorants and one or more laser light-absorbing substances, and this layer is partially or completely covered with laser light completely or partially the plastic or the lacquer is transferred. Process for the colored inscription and colored marking of plastics and paints according to claim 8, characterized in that one uses a CO ₂ - or Nd: YAG laser. Shaped bodies made of plastic, lacquers and powder lacquers colored or marked in accordance with the method of claim 8.