Description:

Determining the field of technology and defining the terms of marking, engraving and cutting

The invention focuses on a method of modifying metals with laser, as a result of which the processed metal is either marked, engraved or cut. These actions are not possible to carry out with metals when using lasers with low power, with a power threshold dependent on the laser wavelength - the longer the wavelength, the stronger should be the laser to induce the desired effect. This is a serious constraint of possibilities for machines for laser processing. It needs to be highlighted that marking is defined as deposition of a layer with a certain colour on the surface or changing the colour of a surface of the marked object. Engraving is defined as local removal of a part of the material from its surface or changing its texture related to e.g. local melting the surface. Cutting is defined as breaking the continuity of the material as a result of removal of the material or tearing thereof. This invention utilizes the phenomenon of cross-linking of organic silicon compounds as a result of their thermal degradation, which is induced by laser light, when it gets to the surface of metal coated with organic silicon compound or mixture containing it. This way one obtains a layer on the surface of metal which is composed of cross-linked organosilicon compound or a mixture containing such a compound. Such a layer is durable and may absorb light further, what can lead to removal of the part of metal from the surface, which ends up as either engraving or cutting of the metal.

State of the art

Currently, various methods of marking the surface of metals with laser light are known. First of all, one can use a focused laser beam with a high power of the order of 20 W and a short wavelength, e.g. 1064 nm, which leads to a change of structure of steel irradiated with such a laser. It is manifested by a change of colour of a steel object in defined spots, thanks to which one may obtain a durable pattern. Due to its simple construction and low cost, in many disciplines CO ₂ lasers are used, which have a 10 pm wavelength, which cannot induce any effect on metal object even when approximately 100 W power is used. A big popularity has been achieved by green and blue laser machines with a power of the order of 1 W, which also are not suitable for marking of metals. In the literature there are several techniques known, which allow for obtaining the effect of metal marking with e.g. CO ₂ lasers. They are based on deposition of a defined fluid on the surface of metal, which is subsequently burnt with a laser and after that a portion of the formulation which was not cured by a laser is removed, e.g. by wiping off, as a result of which on the surface of metal a desired pattern is formed. A classic example of such formulation is molybdenum disulfide, which is deposited on metal in e.g. form of suspension in isopropyl alcohol and subsequently after evaporation of the solvent it is burnt with laser. MoS ₂ undergoes local heating and melting, thanks to which it strongly adheres to the metal surface. Nevertheless, molybdenum is abundant in earth's crust in a limited quantity, which results in a low availability of MoS ₂ and its high price, which was a motor for elaboration of metal marking formulations with different principles of operation. US5866644 application presents a resin for laser marking based on polyesters with mica as a light absorbing material. However, resin was not meant for marking metals. Similar solution based on other substances were published in EP1369460 and EP2738010.

US6075223 patent discloses a method of marking metal, glass and ceramics by deposition of a mixture consisting of ground glass (glass frit) containing an additive of a substance enhancing the absorption of laser light. Thanks to the combination of those two materials a local melting of glass can be observed in spots irradiated with laser. After finishing the irradiation, the mixture which was not irradiated is removed and one can see a desired pattern on the object. It is noteworthy that in the described invention the laser induces melting of the material which is a physical transition and there are no chemical reactions.

A similar solution was described in US6852948 invention. It differs from the former in that the layer before laser irradiation is deposited on a conductive surface by electrostatic means. Moreover, instead of a mixture of a substance enhancing absorption with ground glass, one uses an energy absorbing material for the marking process.

Related solution was described in US6238847 invention. One does not deposit ground glass with absorption promoter on the object to be marked, but the precursors of the ground glass only or solely the ground glass. Laser irradiation leads then to mixing of the precursors, so e.g. SiO ₂ with AI2O3 or Na CO’,. Precursors have a higher melting point or a reaction temperature than ground glass. Therefore this solution requires longer irradiation time or using higher laser power, which is needed for mixing of the precursors or their reaction.

US6855910 application discloses a marking method, which utilizes a mixture containing an organic pigment and an absorption enhancing substance, which are deposited on a plastic substrate. Activated carbon was listed as an available absorption enhancing material. US7187396 application presents a method of marking plastics by adding to it a defined substance in a colloidal form, specifically a mixed oxide of antimony and tin.

US7204884 application shows a setup for laser marking. It consists of a spray depositing ink, a laser for local heating of the ink and adhering it to the substrate and a system for removal of the ink, which was not attached. The method focuses on glass marking process.

US8765855 application discloses a mixture for laser marking consisting of a marking component and a binder, while the marking component can consist of oxides of vanadium or cobalt or tungsten or zinc phosphate. According to the invention, the marking ingredients as a result of the action of laser light, undergo a chemical reaction which leads to a colour change. The layer which was not irradiated is not removed, because a trial of such removal would also cause the removal of the irradiated part.

US9205697 application shows a marking method based on pointing a laser at a metal and by this mean performing a local change of refraction coefficient. The whole operation is preceded by adjusting a chosen laser parameter. The method requires for its operation a laser with an appropriate wavelength and power so it can induce the desired effect on the metal surface and it also requires an appropriate metal type e.g. a chrome plated surface. The method does not require application of any mixture or substance on the metal surface.

WO 1996000262 application claims a composition for marking which is cured under the influence of light irradiation, which is based on a resin and a suitable dye.

However, WO1999025562 application discloses a method of marking relying on applying the marking material on an object to be marked. Subsequently, spots in which the substrate should be visible are irradiated by a laser in such a way to remove the marking material and expose the substrate. Subsequently, one bonds the remaining marking material to the substrate by e.g. melting it in a furnace.

Analogous methods based on deposition of a preparation on metal surface and then irradiating it with a laser, which would end up with an engraving or cutting effect are not known in the literature and there are no preparations on the market, which would be aimed to be used for engraving or cutting.

One can find that a crucial aspect of the this invention is cross-linking of organic silicon compounds, like silanes containing Si-C bonds or alkylsiloxanes containing both Si-C and Si-0 bonds. A presence of Si-C bond in a molecule is a key factor in this invention, because it undergoes a reaction as a result of an action of a laser. In a series of patent applications it was proven that it is possible to carry out such cross-linking which is activated by high or elevated temperature applied to the whole volume of preparation, like in US3255152, W02010028877, US8101241, US8470951, CN103864977, but not locally with a laser light.

US10471653 application reveals a method of three dimensional printing process based on placing droplets with light curable silicone in defined spots and subsequently cross-linking thereof with electromagnetic radiation, which might but does not have to be laser. Wavelength and power of the light source must be adjusted in such a way so there will be no degradation of silicone. Therefore it is necessary to use a special composition of silicone resin, which will allow for curing it at lower powers. A resin is cured on a glass or plastic substrate, but not on metal. The resin during the process does not undergo degradation, it is cured.

Defining the essence of invention

The essence of invention is a method of marking, engraving and cutting of metals utilizing crosslinking of organic silicon compounds, being substances with at least one silicon-carbon bond, which is accomplished as a result of action of laser light. Laser light affects the organic silicon compounds with silicon-carbon bonds and leads to the cross-linking thereof, which produces Si-O-Si and other bridges between adjacent molecules. The reaction may take place by the reaction of oxygen and humidity from the air with the substances being the precursors of silicones and silicagels, as well as it may be carried out as a thermal degradation of already synthesised organic silicon compounds. If we add a fine powder with a grain size below 200 pm to the organic silicon compound and the powder does not dissolve in the compound nor in other components of a composition, then we will increase the viscosity of the organic silicon compound, thanks to which it will not flow on the surface of metal during processing. Moreover, the added substance may additionally absorb light, which will accelerate the cross-linking reaction. Alternatively, the added powder may give the final layer a desired colour. Another additives available include polymer binders and solvents. After deposition of a layer containing organic silicon compound at a level of at least 1% per weight on a metal surface and after irradiating it with a laser one obtains a durable, buff and solvent resistant layer comprised of cross-linked silicon compounds and optionally auxiliary substances too. A high temperature is responsible for a strong bonding between the layer and the substrate. Metal under the irradiated preparation during the laser processing has a very high temperature. At a slow enough laser run speed or when using several laser runs it is possible to obtain laser engraving effect, because a part of the metal melts or burns out as a result of laser operation. By using even slower laser runs it is possible to obtain a metal cutting effect. In an engraving mode the metal undergoes a surface melting or a surface melting and partial removal as a result of laser operation and optionally also compressed air or gases, alternatively the metal may then also undergo bending. In a similar way cutting takes place, because the melting metal burns out or drips gravitationally or is blown with compressed air or gas. In cases of marking, engraving and cutting, it is advantageous, but not necessary, to use air assist in a form of air blow in the point of laser action, because the air will be either removing the melting metal or putting out the flame. Cutting and engraving are easier to perform on metals with low thermal conductivity, low thickness and low melting point, e.g. thin steel sheet. In a case of thicker objects cutting and engraving processes are possible under the condition of multiple repeating the operations of deposition of a preparation and laser action. Applying the same procedure of multiple applying the preparation and irradiation in case of marking may lead to a formation of a thicker layer. Strong laser irradiation may lead to bending of the metal sheet coated with the preparation.

Due to this, a method of modifying metals providing an effect of laser marking or engraving or cutting is based on applying on metal the organic silicon compounds being substances with siliconcarbon bond or a mixture containing them with a content of at least 1% per weight. Apart from organic silicon compounds the preparation may contain powders absorbing light, powders increasing viscosity, polymer binder or solvents facilitating application. After deposition of a thin layer of the preparation a stage of laser curing thereof in desired spots takes place. After the process the mixture which was not irradiated is removed, e.g. by wiping, however, in particular cases it may be favourable to leave it. The irradiated preparation then is cured and thanks to this is resistant to wiping. Engraving requires using slower laser runs or a higher power or a higher number of runs than marking. Cutting requires utilizing slower laser runs or a higher power or a higher number of runs than engraving. In case of marking or engraving or cutting it may be desired to use a higher number of operations of applying the preparation and subsequent burning it with a laser.

The preparation for applying to the metal surface should contain at least one organic silicon compound being a substance with silicon-carbon bond with a content of at least 1% per weight in a form i.a. tetramethyl silane or tetraethyl silane or tetrapropylsilane or tetrabutylsilane or triethoxymethylsilane or tri ethoxybutyl silane or triethoxyoctylsilane or dimethyldichlorosilane or diacetoxydimethylsilane or triacetoxymethylsilane or triacetoxyethylsilane or polimethylsiloxanes or other alkylsilanes or alkylsiloxanes or alkylsilanols or oligoalkylsiloxanes or polyalkylsiloxanes or polydimethylsiloxanes or halogensilanes or carboxysilanes or other substances with siliconcarbon bond. Among the aforementioned substances one can distinguish reactive substances, like e.g. diacetoxydimethylsilane, as well as non-reactive substances, like e.g. polydimethylsiloxanes. This means that in both cases the mechanism of cross-linking with laser light may be different. In case of reactive compounds reactions with oxygen or water from the air are possible, as well as decomposition of silicon substituent. As a result of this, chains or a network of O-Si-O and C-Si-C bonds are formed. In case of non-reactive substances simple detachment of substituents is not possible, because of which cross-linking is carried out on the basis of degradation of those compounds, which results in formation of Si-O-Si or other bridges between adjacent molecules. Of course in both cases formation of bridges different than oxygen based is possible with utilization of silicon substituents. It is noteworthy that the aforementioned silicon organic compounds in their absorption spectra have spots with higher and lower absorption of light for different wavelengths. However in the range of wavelengths belonging to the infrared, visible and ultraviolet parts of spectrum practically there are no places with a totally zero absorption. This means that the implementation of invention requires using a laser emitting light within a range of infrared, visible or ultraviolet light.

Apart from the organic silicon compounds the composition may contain also additional substances, like absorption promoters, substances increasing viscosity, binders and solvents. The examples of the absorption promoters are substances absorbing laser radiation in a form of carbon or activated carbon or soot or graphite or oxides of iron or copper or tin or nickel or manganese or silver or chromium or sulfides of iron or copper or lead or silver or other substances absorbing the light of used laser with a content from 1% to 95% per weight. Examples of the substances increasing the viscosity are silica or alumina or kaolin or talc or powdered clays or glass frit or plaster or cement or calcium carbonate or magnesium carbonate or boric acid or borax or bauxite or dolomite with a grain size below 200 pm and with a content from 1% to 95% per weight of the mixture. The examples of binders are poly(methyl metacrylate) or other polymetacrylates or poly(vinyl acetate) or poly(vinyl alcohol) or poly(vinyl chloride) or polystyrene or acrylonitrile-butadiene-styrene copolymer or polyamides or polyethylene or polypropylene or polyethylene oxide) or polyoxymethylene or polytetrafluoroethylene or poly(vinylidene chloride) or epoxy resins or polyester resins or unsaturated polyester resins or polyurethane resins or natural or synthetic rubbers or other polymers or oligomers which are added with a content from 1% to 95% per weight. Thanks to the binder, the layer of preparation is quite durable after applying it to metal and evaporation of solvent, moreover after the irradiation thanks to the utilization of binder it is possible to achieve thicker layers. It is beneficial when the binder is dissolved in a solvent or organic silicon compound, but it is not necessary. It is noteworthy that the given substance may play more than one role in a composition. For instance, a powder of iron sulfide with a grain size of 100 pm increases the viscosity as well as it absorbs light. It is important to highlight that different substances may be the light absorbing substances, which depends on the laser wavelength. For example, carbon may absorb the light of CO2 laser as well as Nd: YAG laser, while glass frit may only absorb the light of CO ₂ laser. The mixture applied to metal, apart from the aforementioned additives, may also contain at least one solvent being an organic compound, liquid at room temperature, in a form of aliphatic or aromatic hydrocarbons or alcohols or esters or amides or amines or ethers or ketones or halogenoalkanes with a content from 1% to 95% per weight. The addition of solvent, as well as other additives, is not necessary, but it may be beneficial in some cases. The role of the solvent is to facilitate the operation of deposition of layer of preparation and also levelling it and controlling its thickness. Utilized organic silicon compound should dissolve in the solvent or form an emulsion with it.

Curing of the layer of the preparation requires a focused beam of high power light, which can be quickly turned on and off. The most suitable source of this type are lasers. Because of the used substances, organic silicon compounds in particular or radiation absorbers too, it is the most suitable to use lasers emitting light within a range of infrared, visible and ultraviolet light. It is noteworthy that during marking, engraving or cutting processes the coherence of laser beam is not used, so theoretically one could use non-laser radiation sources for the purpose of implementation of the invention, however using them would be limited due to a low power of focused beam and a lack of possibility of quick turning on and off. Implementation of the invention can be conveniently carried out with lasers of various types, like CO ₂ laser, Nd: YAG laser, optical fiber laser or lasers emitting light from the visible range of wavelengths. Beam power should not be too low, because then the process of cross-linking of organic silicon compounds could be too slow or even impossible. Because of this the laser power should be equal to 1 W or higher. There are no upper limits of power, because while using very strong lasers, obtaining desired effects of marking, engraving and cutting is possible if the speed of laser head movement is increased, so the irradiated point would not receive too high dose of energy. The speed of laser movement should be adjusted in reference to the laser wavelength and its power. In case of blue lasers with a power of approximately 5 W, fiber lasers with a power of approximately 20 W, Nd:YAG lasers with a power of approximately 20 W and CO ₂ lasers with a power of approximately 80 W, laser run speeds optimal for marking according to the described invention reside within a range between 5 and 200 mm/s. Engraving may be achieved for the same power of lasers in a range of run speeds up to 40 mm/s, while it may turn out that for this purpose one may need to carry out several laser runs at such a speed. Cutting may be carried out at velocities of up to 10 mm/s and one may take multiple runs if needed. It is possible to use weaker or stronger lasers in an analogous way for marking, engraving and cutting, it is then needed to increase or decrease the speed of laser movement and also to change the number of runs if needed. Alternatively, instead of doing many runs for engraving and cutting it is also possible to use a single, slower run. If the object to be cut is thick, then after using the laser it may be necessary to deposit the preparation again and to perform another laser processing to achieve the assumed result. Cutting and engraving are faster when the thickness of the processed element is lower or when the heat conductivity of the processed metal is lower or when the melting point of metal is lower.

The described invention is different from the solutions published before in a significant way. Majority of the solutions focused on marking metals utilized a process of melting glass or glass precursors or MoS ₂ or mixtures of these. In some cases the process used was the process of forming glass by means of chemical reaction from glass precursors. There is no information about the possibility of marking, engraving or cutting metals by cross-linking of organic silicon compounds. There is a known process of engraving metals with a use of laser carried out by deposition of a protective lacquer on metal, burning it and subsequent chemical or electrolytical etching of metal in places stripped of lacquer. However, due to a huge level of complexity and low repeatability of results, this process has not found broader application.

Beneficial effects of the invention

The invention is linked to a whole series of beneficial effects. It provides a possibility of carrying out metal marking with a use of simple lasers, like CO ₂ laser or a blue laser, which have achieved a high popularity in processing of non-metal materials due to simple construction and low cost. Currently on the market there are preparations for marking metals which utilize hard to get, complicated or expensive materials, like MoS ₂ or special phosphorous compounds. It is worth highlighting that due to a lack of possibility of marking metals with CO ₂ laser, a whole branch of industry evolved which is focused on manufacturing plastic plates coated with a metal resembling foil. Because a plastic of an appropriate high thickness is necessary to use to keep the usable conditions and also due to a complexity of manufacturing process, the price of such plastic plates is high. Using a preparation for marking steel or aluminium sheets would mean multiple savings in reference to using such plastic plates. What is more, the durability of marking according to the invention is much higher than the durability of those coated plastic plates and the strength of metal sheets is higher than the strength of plastic plates. Another group of beneficial effects of the invention is the possibility of engraving and cutting metals with the use of lasers, which normally would not be able to do that, like the aforementioned CO ₂ lasers with power below 200 W without gas assist and lasers emitting visible light with a power below 20 W, which due to a simple construction have found a broad range of applications in processing of non-metal materials. Currently there are no alternative solutions in a form of a preparation to deposit on metal, which would allow for engraving and cutting metals while using such lasers.

Examples of implementation of the invention

Example 1

A mixture of tri ethoxy methyl silane and SiO ₂ is prepared, while the contents per weight are 60% and 40% respectively. Subsequently it is applied in a form of a layer on a copper object. The layer is irradiated with a 450 nm wavelength laser at 5 W power by doing 1 run at a speed of 100 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 2

A mixture of tetraethylsilane and Ag ₂ S is prepared, while the contents per weight are 80% and 20% respectively. Subsequently it is applied in a form of a layer on a zinc object. The layer is irradiated with Nd:YAG laser at 20 W power by doing 1 run at a speed of 150 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 3

Diacetoxydimethylsilane is deposited on a sheet made of an alloy of nickel and copper with 63% per weight of nickel. The layer is irradiated with a CO ₂ laser at 30 W power by doing 1 run at a speed of 30 mm/s, during which the laser light burns the desired pattern. After the process the sheet is wiped to remove part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 4

A mixture of triacetoxymethylsilane, talc and dodecane is prepared, while the contents per weight are 20%, 40% and 40% respectively. Subsequently it is applied in a form of a layer on an aluminium sheet. The layer is irradiated with a CO ₂ laser at 40 W power by doing 1 run at a speed of 50 mm/s, during which the laser light burns the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 5

A mixture of diacetoxydimethylsilane, kaolin, polystyrene and dodecane is prepared, while the contents per weight are 20%, 20%, 10% and 50% respectively. Subsequently it is applied in a form of a layer on an aluminium object and then it is necessary to wait 72 hours until the solvent evaporates and the mixture undergoes an initial cross-linking as a result of a reaction with air humidity. The layer is irradiated with a CO ₂ laser at 40 W power by doing 1 run at a speed of 50 mm/s, during which the laser light bums the desired pattern. After the process the sheet is not wiped, as a result of which a burnt black pattern with a black background is left on the metal, whereas the pattern and the background exhibit different textures and reflectivity coefficients, which is an example of marking.

Example 6

A galvanized sheet is coated with polydimethylsiloxane in a liquid form. The layer is irradiated with a CO ₂ laser at 80 W power by doing 1 run at a speed of 100 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking. Example 7

A mixture of liquid polydimethylsiloxane and activated carbon is prepared, while the contents per weight are 90% and 10% respectively. Subsequently it is applied in a form of a layer on a steel object. The layer is irradiated with a CO2 laser at 80 W power by doing 1 run at a speed of 50 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 8

A mixture of liquid polydimethylsiloxane and activated carbon is prepared, while the contents per weight are 90% and 10% respectively. Subsequently it is applied in a form of a layer on a steel object. The layer is irradiated with a CO ₂ laser at 80 W power by doing 2 runs at a speed of 100 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 9

A mixture of liquid polydimethylsiloxane and activated carbon is prepared, while the contents per weight are 90% and 10% respectively. Subsequently it is applied in a form of a layer on a steel object. The layer is irradiated with a CO ₂ laser at 80 W power by doing 1 run at a speed of 50 mm/s, during which the laser light burns the desired pattern. Subsequently, polydimethylsiloxane and activated carbon mixture is again deposited on the steel element and is processed with laser the same way as it was before. Later the same actions are carried out for the third time. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 10

A mixture of liquid polydimethylsiloxane, activated carbon, silica, poly(methyl metacrylate) and toluene is prepared, while the contents per weight are 30%, 10%, 20%, 10% and 30% respectively. Subsequently it is applied in a form of a layer on a steel object. The layer is irradiated with a CO ₂ laser at 80 W power by doing 1 run at a speed of 50 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 11

A mixture of triacetoxyethylsilane and glass frit is prepared, while the contents per weight are 80% and 20% respectively. Subsequently it is applied in a form of a layer on a stainless steel object. The layer is irradiated with a 450 nm wavelength laser at 5 W power by doing 4 runs at a speed of 20 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove residues of the mixture, as a result of which a deeply engraved pattern is left on the metal.

Example 12

A mixture of diacetoxydimethylsilane and activated carbon is prepared, while the contents per weight are 80% and 20% respectively. Subsequently it is applied in a form of a layer on a stainless steel object. The layer is irradiated with a 450 nm wavelength laser at 5 W power by doing 1 run at a speed of 5 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove residues of the mixture, as a result of which a deeply engraved pattern is left on the metal.

Example 13

A mixture of diacetoxydimethylsilane, activated carbon, poly(methyl metacrylate) and acetone is prepared, while the contents per weight are 40%, 20%, 10% and 30% respectively. Subsequently it is applied in a form of a layer on an aluminium object and then it is necessary to wait 72 hours for initial curing of the layer. The layer is irradiated with a 450 nm wavelength laser at 5 W power by doing 1 run at a speed of 5 mm/s, during which the laser light burns the desired pattern. After the process the sheet is not wiped to remove residues of the mixture, as a result of which a deeply engraved pattern is left on the metal, while the background is black. Example 14

A mixture of liquid polydimethylsiloxane, poly(methyl metacrylate) and ethyl acetate is prepared, while the contents per weight are 30%, 20% and 50% respectively. Subsequently it is applied in a form of a layer on a zinc coated steel sheet. The layer is irradiated with a CO2 laser at 60 W power by doing 1 run at a speed of 4 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove residues of the mixture, as a result of which a deeply engraved pattern is left on the metal.

Example 15

A mixture of liquid polydimethylsiloxane, iron sulfide, plaster, poly(methyl metacrylate) and ethyl acetate is prepared, while the contents per weight are 30%, 10%, 10%, 10% and 40% respectively. Subsequently it is applied in a form of a layer on a brass sheet. The layer is irradiated with a CO ₂ laser at 60 W power by doing 1 run at a speed of 20 mm/s, during which the laser light bums the desired pattern. After the process the sheet is wiped to remove residues of the mixture, as a result of which a deeply engraved pattern is left on the metal.

Example 16

A mixture of diacetoxydimethylsilane and iron(II, III) oxide is prepared, while the contents per weight are 80% and 20% respectively. Subsequently it is applied in a form of a layer on a stainless steel sheet. The layer is irradiated with a 450 nm wavelength laser at 5 W power by doing 2 runs at a speed of 15 mm/s, during which the laser light bums the desired pattern. The operations of deposition of the mixture and burning the pattern with a laser are repeated 2 more times. After the process the sheet is wiped to remove residues of the mixture, as a result of which a deeply engraved pattern is left on the metal.

Example 17

A mixture of liquid polydimethylsiloxane, activated carbon and octyl acetate is prepared, while the contents per weight are 40%, 40% and 20% respectively. Subsequently it is applied in a form of a layer on a 0.1 mm thick brass sheet. The layer is irradiated with a CO ₂ laser at 80 W power by doing

3 runs at a speed of 1 mm/s, during which the laser light bums the desired pattern. After the process the sheet is cut according to the laser run lines.

Example 18

A mixture of liquid polydimethylsiloxane and activated carbon is prepared, while the contents per weight are 70% and 30% respectively. Subsequently it is applied in a form of a layer on a 0.1 mm thick stainless steel sheet. The layer is irradiated with a CO2 laser at 100 W power by doing 1 run at a speed of 2 mm/s, during which the laser light bums the desired pattern. After the process the sheet is cut according to the laser run lines.

Example 19

A mixture of liquid polydimethylsiloxane and activated carbon is prepared, while the contents per weight are 70% and 30% respectively. Subsequently it is applied in a form of a layer on a 1 mm thick stainless steel sheet. The layer is irradiated with a CO2 laser at 100 W power by doing 1 run at a speed of 2 mm/s, during which the laser light bums the desired pattern. The procedure of deposition of the mixture and burning it with a laser is carried out 20 times. After the process the sheet is cut according to the laser run lines.

Example 20

A mixture of diacetoxydimethylsilane and iron(II) sulfide is prepared, while the contents per weight are 70% and 30% respectively. Subsequently it is applied in a form of a layer on a 0.1 mm thick stainless steel sheet. The layer is irradiated with a 450 nm wavelength laser at 5 W power by doing

4 runs at a speed of 1 mm/s, during which the laser light bums the desired pattern. After the process the sheet is cut according to the laser run lines.

Example 21

A mixture containing organic silicon compounds, viscosity increasing substances, light absorbing substances, binder and solvent is prepared.

The mixture contains 20% per weight of organic silicon compounds, namely equal quantities per weight of: tetramethylsilane, tetraethyl silane, tetrapropylsilane, tetrabutylsilane, triethoxymethylsilane, triethoxybutylsilane, triethoxyoctylsilane, dimethyldichlorosilane, diacetoxydimethylsilane, triacetoxymethylsilane, trimethylsilanol, triethylsilanol, octamethylcyclotetrasiloxane, polydimethylsiloxane, trimethylchlorosilane, trimethylsilane, methyltrimethyl silyl ether.

Moreover, the mixture contains 20% per weight of substances increasing viscosity, namely equal quantities per weight of: silica, alumina, kaolin, talc, powdered clays, glass frit, plaster, cement, calcium carbonate, magnesium carbonate, boric acid, borax, bauxite, dolomite. All the viscosity increasing substances have a form of powders with a grain size below 200 pm.

Apart from that the mixture contains 20% per weight of light absorbing substances, namely equal quantities per weight of: carbon, activated carbon, soot, graphite, oxides of iron (II), (II, III) and (III), oxides of copper (I) and (II), oxides of tin (II) and (IV), nickel(II) oxide, manganese(IV) oxide, silver(I) oxide, chromium(III) and (IV) oxides, iron(II) suflide, sulfides of copper (I) and (II), lead(II) sulfide, silver(I) sulfide. All the absorbing substances occur in a form of powders.

Apart from that the mixture contains 20% per weight of binder, which is constituted of equal quantities per weight of: poly(methyl metacrylate), poly(butyl metacrylate), poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl chloride), polystyrene, acrylonitrile-butadiene-styrene copolymer, polyamide, polyethylene, polypropylene, polyethylene oxide), polyoxymethylene, polytetrafluoroethylene, poly(vinylidene chloride), epoxy resin, polyester resin, unsaturated polyester resin, polyurethane resin, natural rubber, synthetic rubber. Binder is prepared by mixing all the aforementioned substances in forms of powders or liquids and then grinding them as a result of which a powder is formed.

Apart from the above mentioned, the mixture contains 20% per weight of a solvent, which is made of equal quantities per weight of: decane, toluene, o-xylene, ethylbenzene, butanol, butyl acetate, chlorobenzene, dimethylformamide, ethanolamine, diethyl ether, butanone, cyclohexanone.

The mixture is formed by placing all the ingredients in one vessel and then mixing them, as a result of which a product with a consistency of a paste is formed. The paste may be conveniently applied on metal surfaces and it does not flow due to the laser action.

Subsequently it is applied in a form of a layer on a stainless steel object. The layer is irradiated with a CO ₂ laser at 70 W power by doing 1 run at a speed of 40 mm/s, during which the laser light burns the desired pattern. After the process the sheet is wiped to remove the part of the mixture, which did not bond to the substrate, as a result of which a burnt black pattern is left on the metal, which is an example of marking.

Example 22

A mixture containing organic silicon compounds, viscosity increasing substances, light absorbing substances, binder and solvent is prepared.

The mixture contains 20% per weight of organic silicon compounds, namely equal quantities per weight of: tetramethylsilane, tetraethyl silane, tetrapropylsilane, tetrabutylsilane, triethoxymethylsilane, triethoxybutylsilane, triethoxyoctylsilane, dimethyldichlorosilane, diacetoxydimethylsilane, triacetoxymethylsilane, trimethylsilanol, triethylsilanol, octamethylcyclotetrasiloxane, polydimethylsiloxane, trimethylchlorosilane, trimethylsilane, methyltrimethyl silyl ether.

Moreover, the mixture contains 20% per weight of substances increasing viscosity, namely equal quantities per weight of: silica, alumina, kaolin, talc, powdered clays, glass frit, plaster, cement, calcium carbonate, magnesium carbonate, boric acid, borax, bauxite, dolomite. All the viscosity increasing substances have a form of powders with a grain size below 200 pm.

Apart from that the mixture contains 20% per weight of light absorbing substances, namely equal quantities per weight of: carbon, activated carbon, soot, graphite, oxides of iron (II), (II, III) and (III), oxides of copper (I) and (II), oxides of tin (II) and (IV), nickel(II) oxide, manganese(IV) oxide, silver(I) oxide, chromium(III) and (IV) oxides, iron(II) suflide, sulfides of copper (I) and (II), lead(II) sulfide, silver(I) sulfide. All the absorbing substances occur in form of powders.

Apart from that the mixture contains 20% per weight of binder, which is constituted of equal quantities per weight of: poly(methyl metacrylate), poly(butyl metacrylate), poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl chloride), polystyrene, acrylonitrile-butadiene-styrene copolymer, polyamide, polyethylene, polypropylene, polyethylene oxide), polyoxymethylene, polytetrafluoroethylene, poly(vinylidene chloride), epoxy resin, polyester resin, unsaturated polyester resin, polyurethane resin, natural rubber, synthetic rubber. Binder is prepared by mixing all the aforementioned substances in forms of powders or liquids and then grinding them as a result of which a powder is formed.

Apart from the above mentioned, the mixture contains 20% per weight of a solvent, which is made of equal quantities per weight of: decane, toluene, o-xylene, ethylbenzene, butanol, butyl acetate, chlorobenzene, dimethylformamide, ethanolamine, diethyl ether, butanone, cyclohexanone.

The mixture is formed by placing all the ingredients in one vessel and then mixing them, as a result of which a product with a consistency of a paste is formed. The paste may be conveniently applied on metal surfaces and it does not flow due to the laser action.

Subsequently it is applied in a form of a layer on a stainless steel object. The layer is irradiated with a CO2 laser at 50 W power by doing 1 run at a speed of 8 mm/s, during which the laser light burns the desired pattern. After the process the sheet is wiped to remove residues of the mixture, as a result of which a deeply engraved pattern is left on the metal.

Example 23

A mixture containing organic silicon compounds, viscosity increasing substances, light absorbing substances, binder and solvent is prepared.

The mixture contains 20% per weight of organic silicon compounds, namely equal quantities per weight of: tetramethylsilane, tetraethyl silane, tetrapropylsilane, tetrabutylsilane, triethoxymethylsilane, triethoxybutylsilane, triethoxyoctylsilane, dimethyldichlorosilane, diacetoxydimethylsilane, triacetoxymethylsilane, trimethylsilanol, triethylsilanol, octamethylcyclotetrasiloxane, polydimethylsiloxane, trimethylchlorosilane, trimethylsilane, methyltrimethyl silyl ether.

Moreover, the mixture contains 20% per weight of substances increasing viscosity, namely equal quantities per weight of: silica, alumina, kaolin, talc, powdered clays, glass frit, plaster, cement, calcium carbonate, magnesium carbonate, boric acid, borax, bauxite, dolomite. All the viscosity increasing substances have a form of powders with a grain size below 200 pm.

Apart from that the mixture contains 20% per weight of light absorbing substances, namely equal quantities per weight of: carbon, activated carbon, soot, graphite, oxides of iron (II), (II, III) and (III), oxides of copper (I) and (II), oxides of tin (II) and (IV), nickel(II) oxide, manganese(IV) oxide, silver(I) oxide, chromium(III) and (IV) oxides, iron(II) suflide, sulfides of copper (I) and (II), lead(II) sulfide, silver(I) sulfide. All the absorbing substances occur in form of powders.

Apart from that the mixture contains 20% per weight of binder, which is constituted of equal quantities per weight of: poly(methyl metacrylate), poly(butyl metacrylate), poly(vinyl acetate), poly(vinyl alcohol), poly(vinyl chloride), polystyrene, acrylonitrile-butadiene-styrene copolymer, polyamide, polyethylene, polypropylene, polyethylene oxide), polyoxymethylene, polytetrafluoroethylene, poly(vinylidene chloride), epoxy resin, polyester resin, unsaturated polyester resin, polyurethane resin, natural rubber, synthetic rubber. Binder is prepared by mixing all the aforementioned substances in forms of powders or liquids and then grinding them as a result of which a powder is formed.

Apart from the above mentioned, the mixture contains 20% per weight of a solvent, which is made of equal quantities per weight of: decane, toluene, o-xylene, ethylbenzene, butanol, butyl acetate, chlorobenzene, dimethylformamide, ethanolamine, diethyl ether, butanone, cyclohexanone.

The mixture is formed by placing all the ingredients in one vessel and then mixing them, as a result of which a product with a consistency of a paste is formed. The paste may be conveniently applied on metal surfaces and it does not flow due to the laser action.

Subsequently it is applied in a form of a layer on a 0.1 mm thick stainless steel sheet. The layer is irradiated with a CO2 laser at 100 W power by doing 1 run at a speed of 2 mm/s, during which the laser light burns the desired pattern. After the process the sheet is cut according to the laser run lines.