MXPA00011411A - Laser marking compositions and methods for producing bright oxidation resistant marks - Google Patents

Abstract

Compositions and methods for laser marking substrates such as metal, glass and ceramic are disclosed. A marking material is applied to the surface of the substrate, followed by irradiation of a portion of the marking material to form a bright, oxidation resistant marking on the substrate. The non-irradiated portion of the marking material is then removed from the substrate. The marking material comprises compounds such as metal salts and metal oxides which, upon irradiation, form oxidation resistant metallic markings. The marking method is highly versatile, can be performed quickly, and produces permanent marks of high resolution and contrast without damage to the substrate.

Description

MARKING COMPOSITIONS WITH LASER AND METHODS TO PRODUCE BRIGHT BRANDS RESISTANT TO OXIDATION FIELD OF THE INVENTION The present invention relates to the marking of substrates, and more particularly it relates to laser marking compositions and methods for producing bright and oxidation-resistant marks on various types of substrates such as metals, glasses and ceramics.

BACKGROUND INFORMATION Laser marking methods have recently been developed to mark metals, plastics, ceramics and glass. Metal laser marking typically involves a vaporization process, wherein a laser is used to remove or destroy the metal from the surface along the laser path. The resulting marking comprises engraved or meshed portions that provide three-dimensional contrast on the surface of the metal. Alternatively, metal laser marking could be performed by annealing a selected portion of the metal surface to provide areas of color contrast. In this case, instead of removing material from the surface, the laser is used to heat the surface of the metal to a Ref: 124941 annealing temperature which typically results in darkening of the annealed regions of the metal substrate. Plastics are typically marked with a laser either by changing the color of the plastic or by recording the surface of the plastic along the laser path. The color of the plastic is typically changed by localized fusion and re-solidification of the plastic. In contrast, the engraving is achieved by vaporization and removal of the plastic. Plastic laser engraving methods can be used to remove a surface layer of the plastic to reveal and highlight the contrasting color layer. Such a process is described in U.S. Pat. No. 5,601,341 to Kildal et al. Laser marking of ceramics and glass has also been investigated as a replacement for traditional etching, etching and glazing techniques as described in U.S. Pat. No. 4,327,283 to Hey an et al. and U.S. Patent No. 4,515,867 to Bleacher et al. In the methods described, two coating layers are applied to a glass substrate, and the upper layer is removed by means of the laser to reveal the contrasting sublayer. Another laser marking technique of ceramics and glasses is described in U.S. Pat. No. 4,769,310 to Gugger et al. and U.S. Patent No. 5,030,551 of Herrén et al. In this technique, a glaze having a radiation-sensitive additive containing an inorganic pigment or titanium dioxide is deposited and burned on the surface of a ceramic or glass substrate. A laser beam is then used to irradiate the burned surface layer, thereby changing the color of the surface layer in the radiation areas. Despite the marking techniques indicated above, there is still a need for a method for marking substrates such as metals, ceramics and glasses that produces permanent marks of high gloss and oxidation resistance with minimal damage or without damage to the substrate.

BRIEF DESCRIPTION OF THE INVENTION The present invention provides bright high contrast markings on a variety of substrates including metals, glasses and ceramics. A marking material containing a metallic compound is applied to the surface of the substrate and irradiated with a laser to produce a highly readable metallic mark. When marking on metal substrates, the marks are preferably based on metals that are more resistant to oxidation and corrosion than the substrates on which they are applied. One aspect of the invention is to provide a method for marking a surface of a substrate. The method includes the steps of applying a marking material containing at least one decomposable metal compound containing a salt, oxide or organometallic compound of at least one transition metal on the surface of the substrate, irradiating a portion of the marking material with a beam to adhere the irradiated marking material to the surface of the substrate and to form a metallic mark thereon, and remove a non-irradiated portion of the marking material from the substrate. Another aspect of the invention is to provide a method for marking a surface of a substrate and maintaining a readable mark after the labeled substrate has been exposed to elevated surface temperatures. The method includes the steps of applying a marking material containing at least one metal compound capable of decomposition containing a salt, oxide or organometallic compound of at least one transition metal to the surface of the substrate, irradiating a portion of the marking material. with a beam to adhere the irradiated marking material to the surface of the substrate and to form a metallic mark thereon, remove a non-irradiated portion of the marking material from the substrate, heat the labeled substrate to a service temperature of at least 300 ° C, preferably greater than 500 ° C or even higher than 800 ° C and recovering the marked substrate after exposure to the service temperature, where the mark is readable after exposure to the service temperature. A further aspect of the invention is to provide a laser marking material containing at least one metal compound capable of decomposition containing a salt, oxide or organometallic compound of at least one transition metal. Another aspect of the invention is to provide a metal laser marking containing at least one transition metal adhered to a substrate. At least a portion of the metallic laser marking is formed from a metal compound capable of decomposing irradiated containing a salt, oxide or organometallic compound of the transition metal. These and other aspects of the present invention will be more apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a partial schematic isometric view of a substrate covered with a marking material according to an embodiment of the present invention. Fig. 2 is a partial schematic isometric view of the substrate of Fig. 1 after a portion of the marking material has been irradiated with a laser. Fig. 3 is a partial schematic isometric view of the substrate of Figs. 1 and 2 after the unirradiated portion of the marking material has been red, resulting in a bright and oxidation-resistant mark on the substrate. Fig. 4 is a partial schematic isometric view of a substrate covered with a marking material according to another embodiment of the present invention. Fig. 5 is a partial schematic isometric view of the substrate of Fig. 4 after a portion of the marking material has been irradiated with a laser. Fig. 6 is a partial schematic isometric view of the substrate of Figs. 4 and 5 after the unirradiated portion of the marking material has been red, resulting in a bright and oxidation-resistant mark on the substrate. Fig. 7 is a photograph of a labeled titanium alloy substrate according to the present invention. The upper image of Fig. 7 shows the substrate after the mareadlo operation. The lower image of Fig. 7 shows a similar substrate of labeled titanium alloy after exposure to a service temperature of approximately 538 ° C (1,000 ° F).

Fig. 8 is a photograph of marked stainless steel substrates according to the present invention. The upper image of Fig. 8 shows the substrate after the marking operation. The lower image of Fig. 8 shows a similar substrate of marked stainless steel after exposure to a service temperature of approximately 538 ° C (1,000 ° F). Fig. 9 is a photograph of an Inconel nickel alloy substrate that was laser labeled with different types of marking material compositions and subsequently exposed to a service temperature of approximately 538 ° C (1,000 ° F). The marees made with the marking materials of the present invention remain bright and readable after exposure to the high service temperature, while the marks made with a marking material containing an elemental metal powder were illegible after exposure to the High temperature.

DETAILED DESCRIPTION Figs. 1-3 illustrate a laser marking method according to one embodiment of the present invention. In Fig. 1, a substrate 10 has a layer of marking material 12 applied thereto. Fig. 2 illustrates the substrate 10 and the marking material 12 after a portion of the marking material 12 has been irradiated by means of a laser (not shown), which traverses it and projects a beam almost perpendicular to the surface top of the marking material layer 12. The irradiated portion 14 adheres to the surface of the substrate 10 and forms a bright and oxidation-resistant mark thereon. In Fig. 3, the unirradiated portion of the marking material 12 has been washed, leaving the mark 14 on the substrate 10. Figs. 4-6 illustrate a laser marking method according to another embodiment of the present invention. In Fig. 4, a layer of marking material 22 is adhered to an adhesive sheet of reinforcing material 23. The reinforcement material could comprise paper, plastic film or the like. The marking material layer 22 and reinforcing material 23 are applied to the substrate 20. FIG. 5 illustrates the substrate 20, marking material 22 and reinforcing material 23 after a portion of the marking material 24 has been irradiated by a laser (not shown) that traverses it and projects a beam substantially perpendicular to the surface of the marking material layer 22. The irradiated portion 24 adheres to the surface of the substrate 20 and forms a bright and corrosion resistant marking in the same. In Fig. 6, the non-irradiated portion of the marking material 22 has been removed by detaching the reinforcing material 23 and the unirradiated marking material 22 is separated from the substrate 20. The irradiated mark 24 remains permanently adhered to the substrate 20. According to the present invention, marking materials are provided which are converted to glossy and oxidation-resistant markings during the laser marking operation, or in the subsequent treatment after the marking process. As used herein the term "marking material" means a metal compound capable of decomposition that includes at least one metal salt, metal oxide or organometallic compound. The metal compound capable of decomposing preferably has a decomposition temperature below the melting temperature of the transition metal of the compound. The decomposition temperature of the compound could be below 800 ° C, preferably below 600 ° C. For many applications, the decomposition temperature of the compound could be below 300 or 400 ° C. The metal component of the metal compound capable of decomposition preferably contains at least one transition metal of the Periodic Table containing Group IB or malleable metals that resist oxidation. If such metals are oxidized they can at least partially revert or be reduced to the base metal form by heating, even under oxidation conditions. The majority of Group VIII metals also exhibit this behavior. The self-reducing effect in both groups could become more pronounced for the heavier members of the groups. Other metals are useful in this invention, but may require the presence of additives to provide reduction conditions during the heat treatment step. Preferred metals or metal cations of the marking materials include silver, copper, gold, platinum, palladium, ruthenium, rhodium, rhenium, osmium and iridium. The most preferred metals are silver, copper, gold, platinum and palladium. Preferred anions of the metal compound of the marking material are carbonates, oxides and hydroxides, fluorides, chlorides and chlorates, bromides and bromates, iodides and iodates, cyanides and cyanates, nitrites and nitrates, phosphides and phosphates, sulphides, sulphites and sulphates, and thiocyanates. The most preferred anions are carbonates, oxides, hydroxides and nitrates. A preferred feature of this invention is that the metal compounds of the marking materials are broken down to the reduced form of the marking metal at temperatures well below the melting point of the purely labeled metal. The grain growth or significant film formation can be done at relatively low temperatures or short times at higher temperatures. For example, silver has a melting point of 961 ° C, while silver carbonate decomposes at about 218 ° C and silver oxide (I) decomposes at about 300 ° C. Gold labels may be made with the compositions of this invention at lower laser energy values than would be required using only metal powders as the marking material, thus avoiding or reducing thermal damage to the substrate. In one embodiment, the marking material includes metal salts that thermally decompose to simpler salts and / or the same base metal with irradiation by a laser to form the desired marks. Under appropriate conditions, thin films of the metals of such salts can be formed on the substrates. Coating a substance with a composition containing the appropriate metal salt (s) and applying a differential heat source such as a directed beam laser can generate marks, patterns or images of the applied base metal or, in some cases where the substrate is a metal, an alloy of the metal of the substrate and the metal applied. The surface of the marked area has a different composition than the surrounding substrate and consequently has an appearance, different chemical and physical properties. Mixtures of metal compounds could be used to form specific alloys. For example, silver and copper salts could be mixed to give varied forms of marks. Intermetallic compounds containing selenium and tellurium such as AuTe2, Au2Se3 and Ag2Se could also be used. Organic salts of these metals could be used. The preferred compounds are the salts of simple organic acids such as acetates, citrates, oxalates, lactates and tartrates. Also preferred are salts of fatty acids, naphthenic and resin, and amines often referred to as metal resinates. Mixed metal salts such as Ag2Cr04 are useful. In addition, complex metal salts such as phosphomolybdates and phosphotungstenatos could be used. As a particular example, the copper pyrophosphate marking material works well to produce labels on substrates of bonded tungsten carbide, Inconel and stainless steel. In addition, many of the precious metals suitable for use in the present marking materials are available as complexes based on organic ligands or chelating groups which often contain oxygen, sulfur, nitrogen and / or halogen atoms. An example is tetramine platinum (II) chloride, (Pt (NH3) 4) C12 «H20. Metal powders such as silver, copper, zinc, bronze, tin, indium, lead, bismuth, cadmium, etc. it could optionally be added to the metal salts to form alloys. Such metal powders could contain up to about 80 weight percent of the marking material, depending on the particular marking application. Even additions of small amounts of such metal powder to the marking materials could help with the wetting of the substrate, and could help reduce the amount of material that could otherwise be vaporized or released by the laser. Preferred amounts of metal additions are from about 0.1 to 50 weight percent of the marking material powder for many applications. However, when "gold" marks are desired, for example, on glass or porcelain substrates, or when electrically conductive silver or copper marks are desired on non-conductive substrates, the amount of elemental metal powder contained in the substrate may be increased. marking material, eg, 70 or 80 percent by weight. Liquid colloids of precious metals, which are finely divided forms of metals, e.g., less than 1 miera, could be easier to melt than larger metal powders. For example, a mixture that includes liquid gold colloid and tin hydrate could produce marks similar to bright gold. According to one embodiment of the invention, safety and / or trace problems could be addressed by adding additives to the main metal of the marking material with small but distinct amounts of other metals. The trace metal could preferably comprise 0.01 to 10 weight percent of the final metallic mark. For example, to a marking material based on silver carbonate, 0.1% rhodium and 0.2% platinum could be added. This would not be visually detectable, but if the origin of the marked object comes into question, the X-ray analysis could determine the specific adjuvants and the amounts of such adjuvants. Preferred adjunct metals include noble metals such as gold, platinum, palladium, rhodium, rhenium, ruthenium, iridium and osmium, refractory metals such as titanium, zirconium, hydrogen, tantalum and tungsten, and rare earth metals such as lanthanum, cerium, praseodymium, neodymium, europium and the like. The adjuvant metals could be provided as part of a metal compound capable of decomposition, and / or they could be provided in the form of an elemental powder. Such traces could be used for various applications such as aircraft engine parts, art objects, precious metal ingots and semiconductors. Traces could be used, for example when traces of a particular item are needed, or when there is concern of falsification. The addition of streams could produce preferred materials. Flows such as ammonia and / or metal halides or transition metal salts of organic acids could help the marking material to wet the surface of the substrate and alter the surface tension of the hot metal, this could give smoother texture marks with better adhesion . Some of these flows could be tagging materials at their own convenience, e.g., AgCl added to Ag20. Silver and copper phosphates with suitable labeling materials when used alone could be useful flow agents when used in combination with other compositions. Flow agents may also function as grain refiners for the marking material Additions of refractory fillers such as rare earth oxides, Group IIIB and IVB metal oxides, nitrides, carbides, borides and silicates may improve mechanical properties such as hardness and abrasion resistance of the markings, and could also serve as fine grain refiners for marking materials.The quantities of such refractory fillers could be tailored to the measurement of the marking material for specific applications. when refractory fillers are used for grain refining purposes, from about 0.01 to 5 weight percent, more preferably from about 0.05 to about 3 weight percent could be used.Additions of substances could be used to increase the laser absorption or produce reduction atmospheres during the heat treatment process, such as carbonaceous materials, rare earth compounds, pigments, inks or reducing agents such as ureas and sugars. 1 The marking materials could be provided in the form of loose powder, they could be dispersed in various types of vehicles or they could be covered with flexible substrates to form ribbons or bars. The use of tapes could provide uniformity of the film, easy to clean and the ability to recover the precious metal components of the marking material. When the marking material is dispersed in a vehicle, non-water based media and / or essentially water-insoluble salts, e.g., less than 1 percent solubility, are desirable to avoid spontaneous metal deposition reactions with certain combinations. For example, silver nitrate, solubility 122 g per 100 ml at 0 ° C, is not as versatile as Ag2Co3, solubility 0.0032 g per 100 at 20 ° C. Suitable carriers include water and organic solvents such as alcohols, ketones, hydrocarbons, chlorinated hydrocarbons, and the like. Organic resin solutions are preferred in these solvents because the material is given more mechanical durability before the laser action facilitates handling. Inorganic film formers such as natural and modified clays, silicates and phosphates dispersed or solubilized in water also cause the preferred vehicles that are without organic material to burn completely in the laser action process. 1 In accordance with the present invention, various substrate materials can be labeled. For example, the present method could be used to mark substrates of metal, glass, ceramic, composite metal, brick, stone and plastic. High temperature substrates having melting points above, e.g., 300 ° C could be marked according to one embodiment of the invention. For example, substrates at high temperature could have melting points above 500 or 800 ° C, or higher. Suitable metal substrates include both pure metal and alloys. Examples include iron, aluminum, titanium, tantalum and common alloys such as steel, stainless steel, brass and bronze. Steel for tools and plated steel such as aluminized, tin plating, chrome plating, galvanizing and tin and lead plated steel are suitable substrates. In addition, reactive and refractory metals such as titanium, niobium, tantalum and zirconium alloys could be used as a substrate. Alloys of high performance properties such as alloys of Inconel, Hastelloy, Haynes, Monel, Incoloy and Nimonic are especially suitable. Glass substrates include clear and colored soda-lime and borosilicate glass, as well as specialized glass and materials such as fused quartz and lead crystal. Ceramic substrates include fired clay, alumina, mulita, and white fine china, as they are and as glazes.

Suitable composite metal substrates include metallic ceramics such as cobalt bonded to tungsten carbide, nickel bonded to tungsten carbide, and the like. Typical plastic substrates include thermoplastics and relatively high temperature thermosetting resins such as polyamide, polycarbonate, ABS, silicone, epoxy, polyurethane and phenolic resins. The types of substrate that could be marked according to the present invention include automotive parts, automotive glasses, aerospace parts, medical devices, electronic devices, cutting tools, consumer products, packaging, glass bottles, metal cans, metal labels , bricks, earthenware, electrical and construction articles for plumbing, lighting with decorative ceramics, art objects, gold ingots, precious stones, parts of machines and the like. Various methods could be used to apply the marking material to the surface of the substrate. The surface of the substrate can be covered with marking material powders or, preferably, it can be covered with a dispersion of the powders in a suitable vehicle. Water-based media are preferred because of their minimal environmental impact, but solvent-based media can also be used to control the drying rate, dispersion or moisture sensitivity of certain marking materials. According to one embodiment, colloidal gel materials could be used to apply the marking material to the substrate. When dispersions are used, the deposited layer can be dried before the irradiation step, however it is not necessary. The marking material in a water or solvent dispersion can be applied on the surface of the substrate by various methods, such as printing, brushing, atomizing, roller coating, dipping, flow coating, electrostatic application and cleaning blade. The marking materials can also be dispersed in high temperature waxes or polymers and applied to a substrate surface of a hot melt, or by rubbing the surface of the substrate with such material. Alternatively, the marking material layer could be applied in the form of a tape, bar or decal, and may be on the surface thereof or dispersed therein. The marking material is typically applied to the substrate in a thickness of from about 1 to about 500 microns, more preferably from about 5 to about 200 microns. After the marking material is applied to the surface of the substrate, a selected portion of the marking material is irradiated with a beam to adhere the marking material irradiated to the substrate and to form a permanent mark thereon. For many types of markings, the selected portion of the marking material could comprise from about 1 to about 99 percent of the total surface area of the marking material layer, typically from about 5 to about 95 percent. A laser is preferably used to selectively irradiate the marking material. However, other forms of concentrated energy could be used in accordance with the present invention. Irradiation could be achieved by moving a laser beam onto a stationary substrate using conventional directed beam laser methods, moving the substrate relative to the laser beam and / or masking the substrate. Laser irradiation is typically performed by directing the beam directly against the layer of marking material, but it could also be done by directing the beam through a sufficiently transparent substrate. Lasers suitable for use in accordance with the present invention include neodymium lasers: yttrium aluminum garnet (Nd: YAG), carbon dioxide lasers (C02), diode lasers, excimer lasers and the like. Typical YAG lasers emit light in the near-infrared spectrum at 1064 nm wavelengths. Such lasers typically have continuous power outputs of about 1 to about 50 watts, and can be operated in a pulse fashion at typical power peaks of about 1 watt to about 45 kilowatts. For pulse operation mode, frequencies of approximately 1 to approximately 64,000 pulses / second could be used. Typical C02 lasers emit light in the far infrared region of the spectrum, with peaks of intensity at wavelengths of 9.8 to 10.6 microns. Such C02 lasers typically operate at a continuous power output of about 1 to about 40 watts. In accordance with the present invention, the size of the light spot incident on the marking material is typically greater than 0.1 microns in diameter, preferably from about 40 to about 500 microns, and more preferably from about 50 to about 125 microns. The speed at which the laser beam travels the surface of the marking material is preferably in the range from 0 to about 250 centimeters / second (up to about 100 inches / second), more preferably from about 2.5 or 5 to about 50 cm / second (approximately 1 or 2 to 20 inches / second) for most thicknesses and marking material compositions. The laser beam could be projected with an overlap of the union from 0 to 100 percent, preferably from about 10 to about 90 percent for many applications. The laser parameters are controlled to provide sufficient localized heating of the marking material, while preventing unwanted damage to the substrate. For many laser marking operations, a Lumonics LightWriter Spe YAG laser that operates under the following parameters is suitable. Typically, marks on a glass substrate could be made using pulse or continuous wave, lamp currents from about 30 to about 38 amps, power levels from about 100 watts / second2 to about 5 megawatts / cm2 during continuous wave operation , marking speeds of approximately 2.5 to approximately 50 cm / second (approximately 1 to 20 inches / second), laser spot sizes of approximately 50 to approximately 250 microns (approximately 0.002 and 0.01 inches), and binding overlaps of approximately 25 to approximately 50 percent. Laser marking is typically done with the beam in focus, but it could also be done with the beam out of focus. Lamp currents of approximately 28.5 to approximately 30 amps and writing speeds of approximately 5 to approximately 12.7 cm / second (approximately 2 to 5 inches / second) are particularly advantageous for many applications. The laser beam, the movement of which can be controlled by a computer, could be used to create discrete symbols or designs or, alternatively, could be indexed serially across the surface of the marking material, to create multiple symbols or designs at the same time. weather. For example, a word could be created by separately making each letter of the word with the laser, or by making the laser lattice through the entire word to form all the letters at the same time. During the irradiation step, the surface of the substrate could be exposed to any type of desired atmosphere. For example, the atmosphere could contain air at atmospheric, sub-atmospheric or superatmospheric pressures. In addition, the atmosphere could contain an inert gas such as nitrogen, argon or carbon dioxide, an oxidizing atmosphere such as air or oxygen, a reducing atmosphere such as hydrogen or carbon monoxide, or a vacuum. Oxidizing and reducing gases can be used in combination with inert gases. It is also possible to control the atmosphere at the surface of the substrate through the type of medium in which the marking material is dispersed. The atmosphere to which the surface of the substrate is exposed could affect the color and quality of the brand. A simple laser beam could be used for marking according to the present invention. Alternatively, two or more laser beams could be used. For example, a first laser beam could be used to preheat the marking material and substrate, followed by a second laser that is used to adhere the marking material to the preheated substrate. This is particularly advantageous for marking glass because the preheating could help reduce the internal stress and micro cracking that can result from the laser marking op- eration. After the selected portion of the marking material has been irradiated, the unirradiated portion of the marking material is removed from the substrate. In the embodiment shown in Figs. 1-3, the non-irradiated portion of the marking material could be removed by methods such as washing, rubbing, vacuum cleaning, subliming or blowing the surface. In the embodiment shown in Figs. 4-6, the non-irradiated portion of the marking material remains adhered to the adhesive sheet 23, and could be removed from the substrate 20 by peeling off the adhesive sheet and the non-irradiated layer of the material to separate them from the substrate. In accordance with the present invention, a selected portion of the marking material adheres to the substrate in the irradiation or in the subsequent treatment, as used herein, the term "adhering" is used to designate any substantially permanent means of bonding the material of labeled irradiated to the substrate. For example, the irradiated marking material could adhere to the surface of the substrate by sintering the marking material to the substrate, melting the marking material on the surface of the substrate, diffusing at least a portion of the marking material on the substrate, reacting the marking material with the substrate and the like. The marking material could also be adhered to the substrate by subsequent heat treatment after irradiation. The labels produced in accordance with the present invention could be entangled in the substrate, but in some preferred applications they have a thickness of from 0 to about 200 microns which is measured from the surface of the substrate, preferably from about 0.05 to about 50 microns. The thicker marks could be preferred when the mark is used as an electrically conductive pattern. Under the preferred labeling conditions, substantially no indentation or removal of the substrate is observed. In many applications, it is preferable to avoid removing the material from the substrate because the indentations tend to weaken the substrate. When metal marking is to be used to conduct electric current, a resistance of less than 10 ohms / square, more preferably less than 1 ohm / square, is preferably present. For some applications, an electrical resistance of less than 0.1 ohm / square, more preferably less than 0.01 ohm / square, is preferred. In irradiation, the resulting metallic label contains the transition metal, or an alloy thereof, which originated from the metal compound capable of decomposition. In many applications, the transition metal contains at least 20 weight percent of the metallic brand, typically at least 50 weight percent. In many applications where the transition metal contains, e.g., silver, copper, gold, platinum or palladium, at least 80 percent of the metallic mark contains such transition metals, more preferably at least 90 weight percent for some applications. Relatively high levels of transition metals are often desired in metallic markings to be used as electrically conductive standards, or for many applications where the marked substrate is subsequently exposed to high service temperatures. Relatively low levels of transition metals could be present in some types of metallic markings, for example, when metal markings are subjected to extensive wear or abrasion, in this case extensively wear-resistant fillers could be used extensively. Various types of marks could be produced in accordance with the present invention. For example, the markings could comprise cylindrical symbols, graphs, logos, designs, decorations, serial registers, bar codes, two-dimensional matrices and the like using conventional laser controlled with computer elements and programming elements, the markings of the present The invention could be varied rapidly from operation to operation for applications such as serial records, beirra codes, manufacturing quality control and automated manufacturing. The bright and oxidation-resistant marks are preferably formed with high contrast and high resolution. The resolution of the mark is determined mainly by the size of the laser beam and the particle size of the marking material. The contrast / color of the mark is typically determined by the composition of the marking material. The following examples illustrate various aspects of the present invention and are not intended to limit the scope of the invention. In the following examples, a 5% hydroxypropyl cellulose medium sold under the designation of Klucel E by Hercules, Inc. was dissolved in ethanol to make a vehicle for the metal salt of the marking material powders.

Example 1 Copper (II) pyrophosphate, Cu2P207 »3H20, (Alpha AESAR) was dispersed in a sufficient amount of the vehicle to make a brushable paste. The mixture was painted on a black cobalt cutting tool bonded to tungsten carbide and allowed to dry. A C02 laser of 35 watts was used to mark bright copper colored letters on the tool. The rest of the marking material was washed without image.

Example 2 Silver carbonate, Ag2C03, (Copper Chemical) was dispersed in the vehicle. The mixture was painted on black cobalt cutting tools bonded to tungsten carbide, and heels of Inconel 718, Ti-6-2-2-4 and 410 stainless steel, and allowed to dry. A 35-watt C02 laser made brilliant silver marks on all substrates. Similar results were obtained with a 50 watt Nd: YAG laser. The tungsten carbide marks had high contrast compared to the relatively dark substrate. The marks on the semi-glossy gray metallic substrates were also highly legible. The marks on the substrates of Ti-6-2-2-4 and stainless steel 410 are shown in the upper images of Figs. 7 and 8, respectively. Some of the substrates labeled Ti-6-2-2-4 and 410 stainless steel were heated to 538 ° C. After heating, the marks were still highly legible, as shown in the lower images of Figs. 7 and 8, respectively. When the labeled Inconel substrate was subsequently heated to 538 ° C to simulate a temperature service cycle, the Inconel substrate was substantially obscured but the area marked with the silver carbonate marking material remained as bright silver colored with high contrast as shown in the photograph of Fig. 9.

Example 3 Silver oxide, Ag20, was used in place of silver carbonate to label an Inconel 718 substrate in a manner similar to Example 2. The resulting labels were very similar to those made in the Inconel 718 substrate of Example 2, and they were highly readable in the irradiation and subsequent heating of the labeled substrate. The labeled Inconel 718 substrate, after exposure to the service temperature of 538 ° C, is shown in Fig. 9.

Example 4 Silver metal was used instead of silver carbonate in an attempt to label an Inconel 718 substrate in a manner similar to Example 2. The resulting marks were not legible. After exposure to the service temperature of 538 ° C, the marks remained illegible, as shown in Fig. 9.

Example 5 A mixture of 25 weight percent Ag20 and 75 weight percent Ag metal powder was used instead of silver carbonate to mark an Inconel 718 substrate, in a similar manner to Example 2. The marks The results were defined vividly, but were thicker than those produced in Example 2.

Example 6 A platinum-based composition containing platinum resinate and auxiliaries sold under the designation GP 500 Bright Platinum by Cerdee was painted on an Inconel 718 substrate and allowed to dry. A C02 laser of 35 watts produced smooth dark marks and a 50 watt Nd: YAG laser in a 40 kHz pulse mode gave bright metallic marks. Both brands had good contrast after the Inconel substrate darkened when heated to 538 ° C (1000 ° F).

Example 7 A composition containing 5 parts of copper (II) pyrophosphate, 10 parts of silver powder (Degussa), 5 parts of silver oxide (I) (Degussa), 10 parts of Bronze powder 5890 (Acupowder International, LLC), Tin powder 301 (Acupowder), and 10 parts of the Klucel vehicle in ethanol were mixed and applied to both soda-lime glass and glazed ceramic kitchenware. A 50 watt Nd: YAG laser in continuous wave mode gave bright colored gold marks. When operated in the 40 kHz pulse mode the same laser gave very bright, almost mirror-like, colored gold marks.

Example 8 A composition containing 10 parts of silver powder (Degussa), 5 parts of silver oxide (I) (Degussa), 3 parts of silver orthophosphate (Alfa-AESAR), 5 parts of Tin powder 301 (Acupowder ), 2 parts of Ultrox 1000W zirconium silicate powder (Elf Atochem), and 5 parts of the Klucel vehicle in ethanol were mixed and applied to soda-lime glass and glazed ceramic kitchenware. A 50 watt Nd: YAG laser in continuous wave mode gave bright silver or platinum colored markings. When operated in the 40 kHz pulse mode the same laser gave very bright silver or platinum colored marks.

Example 9 A composition containing 10 parts of silver powder (Degussa), 3 parts of silver oxide (I) (Degussa), 2 parts of 2% Laponite RD (Laporte synthetic clay) in water were mixed and thinned with enough water to apply a 20 mil wet film to soda-lime car glasses. After drying a 50-watt Nd: YAG laser that operated with a lamp current of 33 amps and writing at 25 cm / sec (10 in / sec) produced a line pattern of 0.8 mm in width, with a resistance Electricity of approximately 0.004 ohms / square. This value of the resistance is in the range of conventional conductive coatings of silver for ceramics. While the particular embodiments of this invention have been described above for purposes of illustration, it will be apparent to those skilled in the art that numerous variations of the details of the present invention could be made without departing from the invention as defined in the rei appended indications. .

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (26)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. A method for marking a surface of a substrate, characterized in that it comprises: applying a marking material containing at least one metal compound capable of decomposition containing a salt, oxide or organometallic compound of at least one transition metal on the surface of the substrate; irradiating a portion of the marking material with a beam to adhere the irradiated marking material to the surface of the substrate and to form a metallic mark thereon; and 'removing a non-irradiated portion of the marking material from the substrate.

The method of claim 1, characterized in that the transition metal contains at least one metal of groups IB and VIII of the Periodic Table.

The method of claim 1, characterized in that the transition metal contains at least one metal selected from silver, copper, gold, platinum, palladium, ruthenium, rhodium, rhenium, osmium and iridium.

The method of claim 1, characterized in that the metal compound capable of decomposing contains at least carbonate, oxide, hydroxide, fluoride, chloride, chlorate, bromide, bromate, iodide, iodate, cyanide, cyanate, nitride, nitrate, phosphide, phosphate, pyrophosphate, sulfur, sulfate or thiocyanate of the transition metal.

The method of claim 1, characterized in that the metal compound capable of decomposition contains at least one metal salt of an organic acid or a metal resinate.

The method of claim 1, characterized in that the marking material further comprises up to about 80% by weight of at least one metal powder selected from the group comprising silver, copper, zinc, bronze, tin, indium, lead, bismuth and cadmium.

The method of claim 1, characterized in that the metal compound capable of decomposition has a decomposition temperature below the melting temperature of the transition metal.

The method of claim 1, characterized in that the marking material is applied to the surface of the substrate with a thickness of about 1 to about 500 microns.

The method of claim 1, characterized in that the marking material adheres to the reinforcing material.

The method of claim 1, characterized in that the portion of the marking material is irradiated with a laser.

The method of claim 1, characterized in that the metallic label contains at least 20% by weight of the transition metal of the metal compound capable of decomposing.

The method of claim 1, characterized in that the metal label contains at least 0.01% by weight of a refractory filler and / or from about 0.01 to about 5% by weight of at least one grain refiner.

The method of claim 1, characterized in that the metallic marking has an electrical resistance of less than 10 ohms / square.

The method of claim 1, characterized in that the substrate is selected from the group comprising metals, glasses, ceramics and metallic ceramics.

The method of claim 1, characterized in that it further comprises: heating the labeled substrate to a high service temperature; and recovering the labeled substrate after exposure to the service temperature, wherein the metallic marking is readable after exposure to the service temperature.

16. A method for marking a surface of a substrate at high temperature, characterized in that it comprises: applying a marking material containing at least one metal compound capable of decomposition containing a salt, oxide or organometallic compound of at least one transition metal in the surface of the substrate; irradiate a portion of the marking material with a beam to adhere the irradiated marking material to the surface of the substrate and to form a metallic mark thereon; removing a non-irradiated portion of the marking material from the substrate; heating the labeled substrate to a service temperature of at least 300 ° C; and recovering the labeled substrate after exposure to the service temperature, wherein the metallic marking is readable after exposure to the service temperature.

17. The method of claim 16, characterized in that the service temperature is greater than 500 ° C.

The method of claim 16, characterized in that the metal compound capable of decomposition has a decomposition temperature below the melting temperature of the transition metal.

19. A laser marking material, characterized in that it comprises at least one metal compound capable of decomposition containing at least one salt, oxide or organometallic compound of at least one transition metal.

20. The laser marking material of claim 19, characterized in that at least one metal compound capable of decomposition contains at least carbonate, oxide, hydroxide, fluoride, chloride, chlorate, bromide, bromate, iodide, iodate, cyanide, cyanate, nitride, nitrate, phosphide, phosphate, pyrophosphate, sulfide, sulfite, sulfate, thiocyanate or salt of an organic acid or transition metal resinate of groups IB and VIII of the Periodic Table.

21. The laser marking material of claim 19, characterized in that the transition metal contains at least one metal selected from silver, copper, gold, platinum, palladium, ruthenium, rhodium, rhenium, osmium and iridium.

22. The laser marking material of claim 19, characterized in that the marking material further contains at least one metal powder, preferably selected from silver, copper, zinc, bronze, tin, indium and lead.

23. The laser marking material of claim 19, characterized in that it further comprises at least 0.01% by weight of a refractory filler and / or from about 0.01 to about 5% by weight of at least one grain refiner.

24. The laser marking material of claim 19, characterized in that the metal compound capable of decomposition is dispersed in a liquid vehicle.

25. The laser marking material of claim 19, characterized in that the metal compound capable of decomposition is adhered to a reinforcing material.

26. A metal mark made with laser, characterized in that it comprises at least one transition metal adhered to a substrate, wherein at least a portion of the laser-made metal mark is formed from a metal compound capable of decomposing irradiated which contains a salt, oxide or organometallic compound of at least one transition metal. , - * MARKING COMPOSITIONS WITH LASER AND METHODS TO PRODUCE BRIGHT BRANDS RESISTANT TO OXIDATION SUMMARY OF THE INVENTION 5 Compositions and methods are described for laser marking substrates such as metal, glass and ceramics. A marking material is applied to the surface of the substrate, followed by irradiation of a portion of the marking material to form a bright mark and 10 resistant to oxidation in the substrate. The non-irradiated portion of the marking material is removed after the substrate. The marking material contains compounds such as metal salts and metal oxides which, in the irradiation, form metallic marks resistant to 15 oxidation. The marking method is highly versatile, can be done quickly, and produces permanent high resolution and contrast markings without damaging the substrate.