System and method for regionally removing the coating of a coated surface of a glass body, and regionally uncoated glass body

Abstract

The invention relates to a system for regionally removing the coating of a coated surface of a glass body, having: a laser source (4) for generating a continuous laser beam; a focusing device (8) for focusing the laser beam onto the surface of the coated glass body (6); a scan mirror arrangement (10) for the directed scanning of the laser beam on the surface of the coated glass body (6) at a scan speed of the laser beam on the surface; and a control device (18) for controlling the laser source (4) and the scan mirror arrangement (10), wherein the laser source (4), the scan mirror arrangement (10) and the control device (18) are configured to scan the continuous laser beam on the surface at a scan speed of at least 10 m / s. The invention also relates to a method and to a glass body.

Description

[0001] System and a method for the partial decoating of a coated surface of a glass body and a partial decoated glass body

[0002] The invention relates to a system and a method for the partial decoating of a coated surface of a glass body and to a partially decoated glass body.

[0003] The invention is not limited to glass bodies and can also be applied to coated surfaces of bodies made of other materials. The invention is also directed to the removal of coatings, whereby the coating is either removed as a whole or, in the case of a layered structure, only a portion of the layers is removed.

[0004] Glass bodies of the type in question here are glass bodies with a functional surface coating that improves or even enables the intended use of the glass body. Alternatively or additionally, the glass body may have a protective coating that protects the surface of the glass body. The overall structure of one or more layers is referred to below as a coating.

[0005] Glass bodies with large-area functional coatings are used, for example, to reflect infrared radiation. Such glass bodies are used in building glazing or in automotive construction. Large glass bodies, also known as raw glass, from which final formats are cut and subsequently processed, sometimes have protective coatings applied in addition to the functional coatings, which are to be at least partially removed during further processing. Large-area removal of functional coatings is necessary, for example, to achieve sufficient adhesion or sufficiently strong adhesion of adhesives or paints at the edges of the panes in building glazing, vehicles, kitchen appliances, smart devices, and other applications.

[0006] Such edge deletion or deletion of an inner region of the coating is carried out in the prior art by mechanical layer removal using grinding, in particular using rotating grinding wheels with peripheral grinding kinematics. Edge deletion is probably most widely used for insulating glazing. In the case of simple insulating glazing for a window, it is often necessary for the coating to be removed over a width of around 10 mm all the way around the final format of the pane. This usually takes place on the raw glass, i.e. before the raw glass is divided into the final formats. The coating is typically removed over a width of 20 mm, which corresponds to the width of the grinding tool. The glass is then separated in the middle of the grinding marks by scoring and breaking so that the final formats have a 10 mm wide edge.

[0007] To produce the insulating glass, the individual panes are sealed around the perimeter of the glass edge with a spacer and a primary seal, followed by a secondary seal. The resulting edge seal is usually concealed by the window frame, so quality requirements are limited to sufficient adhesive adhesion and not to visual characteristics.

[0008] However, the present invention is not limited to the removal of coatings from the edge regions of glass bodies. In addition to edge removal, the coating can also be removed from the interior regions of a coated surface of a glass body.

[0009] Achievable feed rates for mechanical decoating are up to 1400 mm / s at 20 mm width, which corresponds to a surface removal rate of approximately 28000 mm 2 / s. However, such a theoretical surface removal rate is difficult to implement only with a linear grinding track, since the back-and-forth movement requires the grinding tools to be mechanically advanced, turned, and accelerated at the ends of the grinding tracks. Ultimately, the "practical" surface removal rate always results.

[0010] The surface removal rate corresponds to the surface speed at which the tool moves across the surface and at which decoating occurs. The surface removal rate does not indicate the degree of removal leading to decoating.

[0011] Given the high theoretical surface removal rate, it must also be taken into account that the coating removal technologically takes the form of a polishing process rather than a grinding process, i.e. relatively soft peripheral grinding wheels, also known as circular decoating wheels, are used, and the glass surface essentially remains (reflective). The disadvantage of this is that the coating is not removed completely and evenly. For example, the coating can redeposit on the surface as coating material, partly due to the peripheral grinding kinematics of the polishing tools. The redeposited coating material, some of which is deposited in oxidic form on the surface, can hardly be removed later by a washing process, even due to thermal interactions during reapplication.

[0012] Vibrations or slight out-of-roundness, as well as regenerative effects from grinding tools, can also cause locally variable roughness and residual deposits on the surface of the glass body. Particularly after the edge seal has been created, these locally variable roughnesses and deposits become clearly visible in the form of discoloration and reflection effects. However, this is not important as long as the adhesive properties are sufficiently good and the edge is concealed by the window frame. In contrast to windows, the edge seal is often visible in demanding applications in glass facades such as structural glazing. Structural glazing, or structural sealant glazing, describes a type of glass facade construction in which the glass pane is held exclusively by adhesives. Pressure strips can be omitted. Mechanical loads are absorbed by the adhesive, while the dead weight of the panes is usually transferred by a concealed mechanical device.

[0013] In addition, there are demanding applications where the decoated edge is printed. Printed step-edge decoating is desirable, for example, when the visible outer pane of the insulating glass protrudes laterally beyond the inner panes, for example, to cover the frame.

[0014] In vehicle windows, kitchen appliances, or interior glazing, the outer, printed edge is often bonded all the way around to a carrier or frame. The bonded or printed edge area of ​​the glass is wider than that of window glazing. For aesthetic reasons alone, and also due to the higher safety requirements compared to window glazing, a very uniform and reproducible layer removal and a consistent roughness are required in these cases.

[0015] To ensure this using peripheral grinding kinematics, several grinding tracks are positioned next to each other, slightly overlapping. In addition, tools with a harder bond are used, so that in addition to the coating, the glass surface is also removed to a certain depth. This creates a uniform basic roughness of the surface, and due to the peripheral grinding kinematics, significantly less coating material is redeposited on the surface, also because part of the glass is removed at the surface. The increased basic roughness and the "clean" surface allow for good adhesion and a sufficiently uniform visual impression. However, with conventional grinding of the type described above, the achievable theoretical surface removal rate is on average only approximately 5000 mm. 2 / s. This is due to the significantly lower possible feed rate and the partial overlap of the grinding marks, as well as the occasional double pass over the surface. Higher surface removal rates are limited by the thermal and mechanical stress on the grinding tools and the glass itself. As the surface removal rate increases, tool wear also increases progressively, thus dramatically increasing the already very high tool costs.

[0016] The state of the art also includes surface layer removal using a pulsed laser.

[0017] The conventional approach to ablating or decoating coatings from glass bodies uses pulsed lasers with wavelengths in the near-infrared range (NIR range with wavelengths of approximately 1 pm) or shorter wavelengths. Laser pulses in the nanosecond, picosecond, or even femtosecond range are used. However, these pulsed laser systems are cost-intensive and limited in power, so the surface ablation rates are rather low.

[0018] Nanosecond lasers can be used to create fine, electrically insulating separation lines in glass coatings. Pulse lengths are typically 100 ns or shorter. Laser sources typically use 100 watts of power and a pulse repetition frequency of 100 kHz. With a focus diameter of typically 50 pm and a pulse offset of 30 pm, scan speeds of 3 m / s can be achieved.

[0019] The present invention is therefore based on the object of further improving a system and a method for stripping a portion of a coated surface of a glass body, as well as a partially stripped glass body. In particular, the object is to develop a cost-effective method and a corresponding system for surface stripping that enables a qualitatively improved removal result while simultaneously increasing productivity compared to conventional surface removal of glass coatings by grinding and compared to the use of pulsed lasers.

[0020] The above-described object is achieved according to the invention by a system having the features of claim 1, by a use of the system according to claim 9, by a method having the features of claim 10, and by a glass body having the features of claim 19. Furthermore, the object is achieved by a method according to claim 23.

[0021] The invention is not limited to applications with glass bodies and can also be applied to coated surfaces of bodies made of other materials. The invention is also directed to the removal of coatings, either by removing the entire coating or, in the case of a layered structure, by removing only a portion of the layers. Nevertheless, the invention is described with regard to the removal of coatings from glass bodies.

[0022] The system according to the invention for the regional decoating of part of a coated surface of a glass body has a structure with a laser source for generating a continuous laser beam, with a focusing device for focusing the laser beam onto the coated surface of the glass body, with a scanning mirror arrangement for directed scanning of the laser beam at a scanning speed on the surface of the coated glass body, and with a control device for controlling the laser source and the scanning mirror arrangement, wherein the laser source, the scanning mirror arrangement, and the control device are configured to scan the continuous laser beam on the surface at a scanning speed of at least 10 m / s. The scanning speed can preferably be at least 100 m / s, preferably at least 300 m / s, in particular at least 500 m / s, or preferably at least 1000 m / s.

[0023] The applicable scanning speed can therefore be adjusted over a wide range of values, taking into account various additional parameters such as the size and shape of the laser spot, the power of the laser beam, and the material properties of the coating. Thus, the parameters for applying a continuous laser beam for decoating can be adjusted over a wide range of values, or process window.

[0024] In contrast to pulsed lasers, whose laser pulses must be applied to the surface in such close succession to ensure at least a continuous scan track, according to the invention the coating removal from the surface of the glass body can be carried out with a continuous laser beam and the scanning speed can be increased as much as is possible for the energy applied by the continuous laser beam.

[0025] A surprising aspect of the described system and method is that the required surface energy for good layer removal using a continuous laser beam is only approximately 0.1 J / mm 2 lower than when using a pulsed laser for a comparable layer removal.

[0026] The advantage of continuous laser beams over pulsed lasers is the significantly lower cost per kilowatt of laser power for the same laser wavelength and the significantly higher possible laser power.

[0027] The scanning speeds, as well as the power of the laser beam generated by the continuous laser, can be variably adjusted over a wide range of values. This results in a wide working range that can be used for decoating the vitreous body.

[0028] The method for the region-wise decoating of a coated surface of a glass body comprises the method steps in which a focused laser spot of a continuous laser beam is scanned over the surface of the coated glass body at a scanning speed of at least 10 m / s and in which a coating of the surface of the glass body is decoated in the region scanned by the continuous laser beam.

[0029] Preferably, the method is carried out in which the continuous laser beam is scanned on the surface at a scanning speed of at least 100 m / s, preferably at least 300 m / s, in particular at least 500 m / s or preferably at least 1000 m / s.

[0030] With the described parameters, a virtual pulse length is achieved that corresponds to the time period over which the surface to be decoated is exposed to the laser beam. For example, the virtual pulse length is 100 ns with a scanning speed of 1000 m / s and a focus diameter of 100 pm. The goal of this approach is to bring the irradiation time, or virtual pulse length, experienced by a single point on the glass surface when scanning a continuous laser beam to the level of the pulse length of a nanosecond laser.

[0031] During surface stripping, the continuous laser beam is applied to the surface in adjacent scan tracks. The scan tracks have a scanning distance smaller than the track width, so that adjacent scan tracks partially overlap. The overlap of the scan tracks serves to even out the energy input to the surface. Furthermore, the control device is configured to operate the laser source with a power of at least 1 kW, in particular at least 3 kW, and preferably at least 5 kW. This allows the laser power to be increased up to the load limits of the scanning mirror arrangement. Different lasers can be used, or the power of a laser can be variably adjusted over a sub-range of the specified power range.

[0032] In particular, the laser beam can be scanned on the surface with a scan width of at least 10 mm, preferably of at least 50 mm, preferably of at least 200 mm, in particular of 300 mm.

[0033] On the surface of the coated glass body, the scanning speed and the scanning track spacing result in a surface removal rate of at least 2000 mm 2 / s and an applied surface energy in the range of 0.1 J / mm 2 .

[0034] The surface removal rate corresponds to a theoretical surface removal rate at which the surface is actually scanned and processed with the moving laser beam. The theoretical scanning rate does not include laser downtimes during which the surface cannot be processed.

[0035] Technical circumstances such as adjusting the glass body relative to the optics or vice versa, technical shutdown times of the continuous laser beam, or other system settings result in dead times, so that a realistic or actual surface removal rate is only a fraction, for example, approximately 35 to 90% of the theoretical surface removal rate. For example, with a theoretical surface removal rate of 5000 mm 2 / s a practical or actual surface removal rate of approx. 3500 mm 2 / s can be achieved. Depending on the adjustable parameters, the surface removal rate can also be increased so that the surface removal rate is at least 2000 mm 2 / s, preferably at least 5000 mm 2 / s, in particular at least 15000 mm 2 / s and preferably at least 25000 mm 2 / s. The surface ablation rate parameter increases with increasing scanning speed and scan track spacing, with the required energy input into the surface depending on the laser power.

[0036] The laser source can also be a single-mode laser, in particular a single-mode fiber laser, or a multi-mode laser, in particular a multi-mode fiber laser. Fiber lasers are preferred because they eliminate the need for complex beam deflections.

[0037] A standard single-mode laser has the advantage that switching the laser on and off can be performed more precisely than with a multi-mode laser. Another advantage is the better focusing properties of the single-mode laser.

[0038] A multimode laser, on the other hand, has greater laser power and a more uniform, flat beam profile than a single-mode laser. This flat beam profile is also called a top-hat profile.

[0039] Therefore, a possible increase in the theoretical area ablation rate while simultaneously further reducing costs lies in the use of continuous multimode fiber lasers instead of continuous single-mode fiber lasers. Doubling the laser power compared to a single-mode laser results in a reduction in the area energy per mm 2 and the virtual pulse length remain identical when the beam diameter, track pitch, and scan speed increase by approximately 40 percent.

[0040] The lasers mentioned above preferably work with a wavelength in the near

[0041] Infrared (NIR) range with wavelengths of approximately 1 pm. Other wavelength ranges are also possible. The wavelength range of approximately 1 pm is preferred, particularly for cost reasons and due to the laser power available in this wavelength range.

[0042] For the operation of the system, the focusing device is required to concentrate the laser power onto a small laser spot on the surface. The focusing device is designed to focus the laser beam towards the surface of the coated glass body in such a way that the focused laser beam generates a laser spot with a dimension or beam diameter of preferably less than 120 pm. The beam diameter is usually determined by the decrease in intensity to 1 / e 2of the maximum value. The cross-sectional shape of the laser spot is usually round or oval, with the beam diameter representing the largest diameter of an intensity distribution.

[0043] The focusing device is configured so that the laser power results in a desired amount of surface energy being applied. This does not necessarily mean that the laser spot coincides with the focus. The distance between the focusing device and the surface of the glass body can therefore be adjusted so that the laser spot is positioned on the surface in the focal position, just in front of the focal position, or just behind the focal position.

[0044] Furthermore, it is preferred that a device for adaptive focus position adjustment is provided. With an adaptive focus position adjustment, changes in the distance between the scanning mirror arrangement and the surface of the glass body can be adjusted on short timescales of milliseconds. For this purpose, piezo elements and associated mirror surfaces are preferably used to realize rapid adaptation of the distance. Such mirror surfaces are also suitable for higher power levels than galvano mirrors. Furthermore, it is preferred that the focusing device focuses the laser beam to a spot length transverse to the scanning direction of the laser beam that is at least 50% longer than the spot length in the scanning direction of the laser beam. Thus, the focus is stretched transversely to the scanning direction and the area exposed to the laser spot is increased. The laser power is thus distributed over a larger area compared to a round focus.If the laser power can be increased sufficiently, the scanning speed can be maintained and the surface removal rate can be further increased. For lower laser powers, the scanning speed can be reduced to achieve the same surface removal rate as with a round focus. This slows down the scanning process, facilitating overall control by the control system and potentially eliminating the need for adaptive focus position adjustment, especially with short scan paths or scan widths. This can be particularly advantageous when removing coatings from vehicle windshields.

[0045] Alternatively, the focusing device can focus the laser beam to a spot length in the scanning direction of the laser beam that is at least 50% larger than the spot length perpendicular to the scanning direction of the laser beam. This stretches the focus along the scanning direction and also increases the area exposed to the laser spot. The laser power is thus distributed over a larger area compared to a round focus. The virtual pulse length is extended, and the duration of laser power application is extended, while the track width remains the same compared to a round laser spot.

[0046] The distance between the focusing device and the surface of the glass body, as well as the strength of the focus in the scanning direction and perpendicular to the scanning direction, can also be adjusted so that the laser spot, with its spot length perpendicular to the scanning direction, is positioned on the surface in the focal position, and the laser spot, with its spot length in the scanning direction, is positioned just before or just behind the focal position. Likewise, the laser spot, with its spot length in the scanning direction, can be positioned on the surface in the focal position, and the laser spot, with its spot length perpendicular to the scanning direction, can be positioned just before or just behind the focal position.

[0047] The scanning mirror arrangement can be designed as a galvanically or piezoelectrically driven scanning mirror or as a polygon scanner. The use of a polygon scanner is preferred due to the higher scanning speeds that can be achieved and the very constant scanning speeds due to the constant rotation of the polygon mirror. This is because the polygon scanner can generate a scanning speed on the surface of at least 10 m / s, preferably at least 100 m / s, preferably at least 300 m / s, in particular at least 500 m / s, or preferably at least 1000 m / s. The aforementioned galvanically, galvanometrically, or piezoelectrically driven scanning mirrors are limited in their power consumption, but can in principle also be used here.

[0048] In addition, the polygon scanners can transmit power of up to 5 kW and more while maintaining a high and constant scanning speed and a large laser spot on the surface of the scanning mirrors, enabling a further increase in the theoretical surface removal rate. In this respect, the polygon scanners have an advantage over galvanically operated scanning mirror arrays. However, a similar future development for galvanically operated scanning mirror arrays cannot be ruled out.

[0049] A polygon scanner is used to deflect the incoming laser beam. A polygon wheel is provided for this purpose, which rotates around a mechanical axis at a preferably constant angular velocity. When the laser beam strikes a flat, reflective surface or facet of the polygon wheel, the laser beam is deflected over an angular range and thus scanned on a surface of the glass body. To switch between two consecutive polygon surfaces, the laser must be turned off. This ensures that only a complete laser beam is deflected at a time and that no optical interference occurs due to reflections at the edge between two polygon surfaces. Therefore, switching the laser beam on and off must be very fast and precise, and the effective duration of the laser beam being switched on is approximately 50%.In other words, the continuous laser is only switched on 50% of the time, which reduces the practical surface removal rate by half compared to the theoretical removal rate.

[0050] If, on the other hand, scanning mirrors driven by galvanic or piezo elements are used, where the scanning direction can be reversed, no or only very short laser downtimes are necessary.

[0051] The deflection results in a scan width with defined start and end points. The scan path of successive scans is directed in the same direction. The scan path and thus the scan width of the laser beam is therefore limited by the maximum possible projection of the laser beam onto the surface using a polygon area of ​​the polygon scanner and is at least 10 mm, preferably at least 50 mm, preferably at least 200 mm, in particular at least 300 mm. This allows areas of the coated surface with a width corresponding to the scan width to be decoated in one scanning process. The start and end points of each scan, i.e. the actual scan width, can also be actively controlled by deliberately switching the laser beam on and off.

[0052] Rotating polygon scanners are one-dimensional scanners that generate a single scan line. To scan a two-dimensional surface, a second movement, particularly a linear movement, must be added. The orientation of the second linear movement is preferably perpendicular to the scan line generated by the polygon scanner—as in conventional applications—and the speed of the second linear movement is matched to the rotation speed of the polygon scanner. This enables a raster scan of the surface, with the necessary synchronization provided by the control device. The second linear movement is implemented using additional scanning mirrors or a positioning device.

[0053] For this purpose, for example, galvanically or galvanometrically or piezoelectrically driven tilting mirrors can be combined with the polygon scanner so that smaller surface sections can be scanned without any relative movement of the glass body to the scanning mirror arrangement.

[0054] Alternatively or additionally, a positioning device can be provided and serves to position the glass body relative to the scanning mirror arrangement. Preferably, the positioning device moves the glass body relative to a stationary scanning mirror arrangement, thus specifying the area of ​​surface removal and the orientation of the surface relative to the scanning mirror arrangement.

[0055] However, the relative movement can also be achieved by moving a work head containing the laser source and the scanning mirror arrangement. The glass body is at rest, and the work head is designed to be mechanically adjustable, for example, by means of a robot. Such a work head can be used, for example, in the processing of curved glass panes, especially vehicle windows.

[0056] Finally, a combined movement can also be achieved by moving both the vitreous body and the working head. For example, the vitreous body can be moved in one direction while the working head is moved in another spatial direction, or in both spatial directions. Furthermore, the working head can also be rotated around one to three axes.

[0057] The relative movement between the working head with the scanning mirror assembly and the glass body creates a feed, so that the scan tracks are applied to the surface one after the other, side by side. This results in a feed rate that increases the faster the scanning speed and the larger the track spacing can be set.

[0058] The orientation of the surface relative to the scanning mirror arrangement refers, on the one hand, to the angle of incidence of the laser beam on the surface. It is preferred that the angle of incidence of the laser beam be essentially perpendicular to the surface. Alternatively, oblique angles can be set if this can improve the decoating process.

[0059] On the other hand, the scanning direction of the laser beam relative to the surface to be processed can be adjusted with respect to the side edges of the glass body. This is because the preferred application of the system and method is the removal of coatings from edge areas adjacent to side edges. The orientation of the surface relative to the scanning mirror arrangement refers to the angle of the scanning direction relative to the side edge of the surface area to be processed.

[0060] If the scanning direction is perpendicular to the side edge of the surface area to be processed, then a strip-shaped area of ​​the edge-side surface can be decoated with a width that corresponds to the length of the scan path specified by the scanning mirror arrangement.

[0061] If, however, a strip-shaped area with a width less than the length of the scan path is to be decoated, the surface of the glass body can be positioned with its side edge at an angle to the scan direction, so that the scan direction is projected onto the surface and scanned at an angle other than 90° relative to the side edge. This allows the entire scan path to be used for decoating the surface area despite the narrower width. Furthermore, the feed rate can be increased, as larger steps in the feed direction can be used to maintain the scan distance between the scan tracks.The above-mentioned method for the area-wise decoating of a coated surface of a glass body is characterized by the fact that a continuous laser beam with sufficient power at a high area removal rate introduces sufficient energy into the coating of the glass surface so that the coating is detached and removed.

[0062] The laser energy of the continuous laser beam is applied more evenly to the coating via the scan track than is the case with a pulsed scan track. This may even require less laser power to complete the decoating process.

[0063] The energy introduced by the laser beam primarily triggers thermal processes. Due to a sudden thermal expansion of the coating, the coating detaches from the glass surface or any underlying coating. The coating material is then partially vaporized, partially removed from the surface as small to tiny particles, and partially vaporized. The visual image of a decoating process of the type described above shows the development of vapor or dust, which can be extracted, blown away, or otherwise removed by the system. A blowing or suction device can be provided for this purpose to clean the treated area.

[0064] In the last-described example, the system for stripping a coated surface of a glass body can comprise a device for generating an air stream, in particular a blowing and / or suction device, which is arranged on the side of the coated surface of the glass body. The scanning mirror arrangement is arranged on the side of the glass body opposite the coated surface. Thus, the device for generating an air stream, in particular the blowing and / or suction device, and the scanning mirror arrangement are arranged on two different sides of the glass body. This has the advantage that the device for generating an air stream can be positioned closer to the coated surface and can more effectively remove the material removed by the laser beam.

[0065] The device for generating an air flow can fulfill the function of generating an air flow toward the surface of the glass body, i.e., a blowing flow, or the function of an air flow directed away from the surface, i.e., a suction flow, or just one of the two functions. A combination is preferably used so that the coating material removed by the laser beam is blown off locally by the blowing flow, preferably toward the edge of the glass body, and then sucked away with the suction flow, thus preventing contamination of the surrounding area where the coating has been removed.

[0066] The process described above can also be referred to as a thermomechanical ablation process. This process differs fundamentally from stripping with pulsed lasers, which involves extensive material changes. Depending on the layer structure, different layers can interact with the laser beam to varying degrees and can therefore be removed to varying degrees.

[0067] In a further preferred embodiment of the method, the laser beam is focused to a spot length transverse to the scanning direction of the laser beam that is at least 50% larger than the spot length in the scanning direction of the laser beam. This allows wider scan tracks to be generated, achieving equally good decoating with increased laser power at the same scanning speed, thus increasing the surface removal rate. With the same laser power compared to a round laser spot, the scanning speed can be reduced to achieve the same surface removal rate. A reduced scanning speed offers advantages for the control system for carrying out the method.

[0068] Alternatively, when performing the process, the laser beam can be focused to a spot length in the scanning direction of the laser beam that is at least 50% larger than the spot length perpendicular to the scanning direction of the laser beam. This stretches the focus along the scanning direction and also increases the area exposed to the laser spot. The laser power is thus distributed over a larger area compared to a round focus. The virtual pulse length is extended, and the duration of laser power application is extended, while the track width remains the same compared to a round laser spot.

[0069] To achieve the most uniform stripping possible, adjacent scan tracks of the laser scan are applied overlappingly on the surface. It is preferable to create adjacent scan tracks with a track spacing of no more than 50% of the focal length of the laser spot perpendicular to the scanning direction. For example, with a focal length of the laser spot perpendicular to the scanning direction of 90 μm, the scan tracks are applied with a distance between the centers of the scan tracks of 40 μm. The track spacing is determined between the center lines of two adjacent scan tracks.

[0070] During the partial stripping of the coated surface, slight contamination may occur in the already stripped areas. This is because the stripped or evaporated coating material partially condenses and redeposits to a small extent on the surface. Therefore, after stripping a portion of the surface of the coated glass body, it is preferable to mechanically remove deposits of the stripped material. Various mechanical methods such as blowing, vacuuming, wiping, washing, or other dry or wet methods can be used.

[0071] This also ensures that the material is not deposited but is removed. In addition, the removal process can be supported by blowing off the decoated material. The described method can be carried out from two sides of the glass body. Firstly, the laser beam can be applied to the coated surface of the glass body. This results in the laser beam having a direct effect on the coating and the glass material arranged below the coating in the direction of the beam is only slightly affected or not at all. Secondly, the laser beam can be applied to the surface opposite the coated surface, which is usually an uncoated surface. The laser beam first passes through the material of the glass body and then hits the coating from below for decoating.The radiation pressure directed away from the surface of the vitreous body supports the detachment and decoating process.

[0072] Common coatings on glass bodies serve to reflect infrared radiation, thus improving the thermal performance of the glass body or glass pane. These coatings are also known as low-e coatings or solar control coatings and can be made of reflective metals such as metals and their oxides, such as gold, silver, copper, nickel-chromium, stainless steel, titanium, etc., or their oxides. These materials possess high transmittance in the visible spectral range and high reflectivity in the infrared range.

[0073] Such or other coatings are applied using, for example, high-vacuum magnetron processes, physical vapor deposition (PVD), chemical vapor deposition (CVD), and sol-gel processes. In high-vacuum magnetron processes, thin metal or metal oxide layers are applied or sputtered in an electromagnetic process under high vacuum. In PVD processes, a thin layer is created on the glass body by condensation from a vapor phase. In the CVD process, a thin layer is deposited from a vacuum, and the sol-gel process is a wet-chemical process. The described process can also be used for laminated glass, in which at least two glass panes are bonded together by a film. The parameters can be adjusted so that the film within the laminated glass is not damaged.

[0074] Furthermore, to improve the adhesion of the aforementioned coating materials, a primer layer can be placed between the glass body and the actual coating. During decoating, the goal may be to remove the primer layer along with the coating, or to at least partially retain the primer layer and not decoat it. Barrier layers and / or ceramic-like protective layers can also be applied.

[0075] A coating on a glass body, which can also be stripped of a coating in sections using the described method, can also consist of an applied or printed ink layer. The ink layer can be stripped of a coating in sections using the continuous laser beam in the manner described, creating a desired pattern or a flat structure consisting of coated areas, i.e., areas containing the ink layer, and stripped areas. The coating or ink layer patterned or structured in this way is then fixed and / or cured, for example, by means of heat treatment in an oven. One application is the production of front panels for kitchen appliances.

[0076] With the described method, it is possible to remove at least 95%, preferably at least 99% of the coating material by scanning the area of ​​the glass surface to be decoated once.

[0077] In the case of multi-layer coatings, for example with an adhesion promoter layer, it is also possible for the adhesion promoter layer to remain intact, but for at least 95%, preferably at least 99%, of the coating material to be removed from the layer structure above it. For carrying out the process, there is at least one parameter range in which good stripping of the surface is achieved. There is a lower threshold for the surface energy above which sufficient stripping is only achieved. However, the parameter range is also upper limited, since excessive surface energy applied can damage the glass surface beneath the coating or another layer underneath. On the other hand, processing of the glass surface may be desired in order to achieve a certain surface roughness, but even in this case, the surface energy to be applied is upper limited.If the surface energy is too high, thermally induced surface damage and / or fractures in the glass body can occur, for example, due to decoating.

[0078] The process window, i.e., the possible combinations of the various parameter ranges with possible settings, is very large for the previously described processes. Thus, decoating can be adjusted with a variety of possible combinations of laser power, scan speed, scan width, angle of the scan direction relative to the side edge of the glass body, and / or spot lengths perpendicular to the scan direction and in the scan direction.

[0079] The object indicated above is also achieved by a glass body having a structure with a base body made of a glass material, wherein the base body has a surface with a first surface region and with a second surface region, wherein the first surface region has a coating, and wherein in the second surface region the coating is at least partially stripped of its coating by processing, and wherein the stripped region has a plurality of adjacent continuous scanning tracks.

[0080] The scan tracks of a glass body according to the invention are located adjacent to and overlap each other. Furthermore, the scan tracks are continuous in the sense that the continuous laser beam processes each scan track with the same laser power throughout. Thus, only a few and slight differences in the coating removal occur along the scan tracks, so that the scan tracks are characterized by a uniform, i.e., continuous, geometric progression.

[0081] Thus, the continuous scan tracks can be distinguished from scan tracks created with a pulsed laser in the second area of ​​a glass surface. The scan tracks created with a pulsed laser have distinct and preferably predominantly overlapping points along the scan track.

[0082] Another characteristic of a glass surface stripped with a continuous laser is that the boundary between the first and second regions exhibits an irregularity on the order of magnitude of the distance between the scan tracks. This structure is caused by the property of a continuous laser that the laser can only be switched on and off with limited temporal accuracy. This property is also called jitter. Thus, due to the high scanning speeds, the start or end points of a laser track on the surface cannot be precisely positioned along a boundary line. This creates an irregular characteristic boundary or boundary line.

[0083] The boundary line becomes flatter, i.e. more regular, along the boundary, the greater the angle at which the laser beam is scanned over the surface.

[0084] Preferably, at least 95%, preferably at least 99%, of the coating material in the area of ​​the stripped surface is removed in the second surface region. Furthermore, a small proportion of particulate material from the at least partially removed coating can be present in the second surface region. This is because the stripped and possibly evaporated material can condense again and redeposit a small portion on the surface. This characteristic deposition of the material can be used to determine the stripping effect.

[0085] The object indicated above is also achieved by a method for the region-wise decoating of a coated surface of a glass body, in which a focused laser beam is scanned over the surface of the coated glass body and in which a coating of the surface of the glass body is decoated in the area scanned by the laser beam and in which the scanning direction of the laser beam is set to an angle different from 90° relative to the surface to be processed with respect to side edges of the glass body.

[0086] This process can be carried out with both continuous lasers and pulsed lasers and is therefore independent of the previously described solutions to the problem.

[0087] For both continuous-wave lasers and pulsed lasers, the previously described advantages for decoating areas of a coated surface arise when the laser beam is scanned at an angle other than 90° to the side edge. Particularly when the scan width is longer than the width of the area to be decoated, a larger portion or even the entire scan width of the laser track on the surface can be used for decoating by guiding the laser beam at an angle other than 90°.

[0088] Here too, the boundary line along the border between the decoated area and the still coated area becomes flatter, i.e. more regular, the larger the angle, i.e. the more diagonally, at which the laser beam is scanned over the surface.

[0089] The invention is explained in more detail below using exemplary embodiments. The drawing shows

[0090] Fig. 1 a system for the partial decoating of a coated surface of a glass body,

[0091] Fig. 2 is a schematic representation of the scanning paths during the implementation of a method for the partial decoating of a coated surface of a glass body in a first variant,

[0092] Fig. 3 is a schematic representation of the scanning paths during the execution of a method for the partial decoating of a coated surface of a glass body in a second variant,

[0093] Fig. 4a-b photographic representations of decoated areas of surfaces of glass bodies with decoating by means of a pulsed laser (aj) and with a continuous laser (b),

[0094] Fig. 5 is a schematic representation of the boundary line between decoated and coated areas of the surface of a glass body,

[0095] Fig.6a-c Examples of different geometries of focused laser spots on the surface of a glass body,

[0096] Fig. 7 shows a further system for the partial decoating of a coated surface of a glass body and Fig. 8a-d shows a schematic representation of the scanning of the laser beam with a resonant scanning mirror arrangement as well as diagrams for explanation.

[0097] The invention is described below using exemplary embodiments for the decoating of glass bodies. However, the invention is fundamentally not limited to application to glass bodies and can also be applied to coated surfaces of bodies made of other materials. The invention is also directed to decoating coatings, whereby the coating is either decoated as a whole or, in the case of a layered structure, only a portion of the layers is decoated. Nevertheless, the invention is described with regard to the decoating of glass bodies.

[0098] Fig. 1 shows a system 2 for the partial decoating of a coated surface of a glass body 4 with a coating 5. The following explains how the system 2 is designed to remove the coating 5 from a part of the surface of the glass body 4, i.e. to decoat a region of the surface.

[0099] The system 2 initially has a laser source 6 for generating a continuous laser beam, i.e. the laser source is a cw laser source, where cw stands for continuous wave.

[0100] The system 2 also includes a focusing device 8 for focusing the laser beam onto the surface of the glass body 4, whereby the focused laser beam creates a laser spot on the surface of the glass body. The focusing device 8 includes a conventional arrangement of lenses that focus the laser beam. A lens 8a is shown symbolically.

[0101] A scanning mirror arrangement 10 for directed scanning of the laser beam on the surface of the glass body 4 is provided in order to scan the laser beam on the surface of the glass body 4 at a predetermined scanning speed of the laser beam and a predetermined scanning path with a scanning width according to the arrow 12.

[0102] In the present case, the scanning mirror arrangement 10 is designed as a polygon scanner and has a polygon wheel 10a that rotates at a preferably constant angular velocity around a mechanical axis (see arrow 13). When the laser beam strikes a flat, reflective surface or facet 10b of the polygon wheel 10a, the laser beam is deflected over an angular range and thus scanned on the surface of the coated glass body 4. The scanning direction therefore depends on the direction of rotation of the polygon scanner 10.

[0103] Furthermore, a positioning device 14 is provided for positioning the glass body 4 by linear and rotating movements relative to the scanning mirror arrangement 10. The positioning device 14 moves the glass body 6 in two directions of movement perpendicular to the incident laser beam, which is symbolized by crossed arrows 16a in Fig. 1. The rotating movement is symbolized by arrow 16b, whereby rotation about up to three axes can be enabled. The positioning device 14 can also be configured to move the glass body 6 in a direction of movement parallel to the alignment of the laser beam. This is particularly advantageous when the system 2 is used for curved surfaces of glass bodies 6, for example, curved vehicle windows, or for adjusting distance fluctuations.

[0104] The laser 6, the focusing device 8, and the positioning device 10 are combined in a working head 11, which can be moved as a single unit. The working head 11 can be moved in two directions perpendicular to the incident laser beam, as symbolized by crossed arrows 17a in Fig. 1. A rotating movement is also possible, symbolized by a rotating arrow 17b. This rotating movement can also occur around up to three axes. Furthermore, at least one movable mirror can be arranged between the laser 6 and the polygon scanner 10 or between the polygon scanner 10 and the glass body 4 to enable an additional movement component for scanning the laser beam on the surface. Such a movable mirror is not shown in Fig. 1 for reasons of clarity.

[0105] A control device 18, shown schematically in Fig. 1, is provided for controlling the laser source 6, the scanning mirror arrangement 10, and the positioning device 16. The connecting lines between the components are shown with dashed double arrows.

[0106] The laser source 6, the scanning mirror arrangement 10, and the control device 18 are configured to scan the surface with the continuous laser beam at a scanning speed of at least 10 m / s. Preferably, the laser beam is scanned at a scanning speed of at least 100 m / s, preferably at least 300 m / s, in particular at least 500 m / s, or preferably at least 1000 m / s. The advantage of an increased scanning speed is increased productivity.

[0107] The laser source 6 can be operated with a power of at least 1 kW, in particular at least 3 kW and preferably at least 5 kW.

[0108] This creates a working window for decoating the surface of the glass body 4 with a range of possible scanning speeds and a range of usable laser powers, allowing the decoating process to be adjusted depending on the properties of the coating 5, such as material, thickness, and hardness. Other adjustable parameters that influence the decoating process include the scan width and track pitch.

[0109] By scanning the laser beam, a theoretical surface removal rate of at least 2000 mm can be achieved on the surface of the glass body 4 with the coating 5, which can be calculated from the scanning speed and the track distance. 2 / s. The surface removal rate can also be at least 5000 mm 2 / s, in particular at least 15000 mm 2 / s and preferably at least 25000 mm 2 / s.

[0110] The surface energy applied to the surface of the coating 5 is, for example, in the range of 0.1 J / mm 2 .

[0111] The laser source 6 is designed as a single-mode laser or as a multi-mode laser and generates a laser beam with a wavelength in the range of 1 pm, i.e. in the near infrared range (NIR).

[0112] The focusing device 8 is configured to focus the laser beam onto the surface 5 of the glass body 4, so that the focused laser beam generates a laser spot with a dimension of less than 120 pm in the scanning direction.

[0113] Due to the design of the polygon mirror 10 and its rotation at a constant angular velocity, the maximum possible scan width of the laser beam is fixed by projecting the laser beam onto the surface using a respective polygon surface 10b of the polygon scanner 10 and is determined by the distance of the polygon scanner 10 from the coated surface. The scan width is, for example, at least 10 mm, preferably at least 50 mm, preferably at least 200 mm, in particular at least 300 mm.

[0114] In Fig. 1, the scan width is indicated by the length of the arrow 12 on the coating 5 and is also shown by arrow lengths in Figs. 2 and 3 considered below.

[0115] Fig. 2 schematically shows a glass body 4 with a top view of the surface with the coating 5. This illustration is intended to explain the decoating process using the method according to the invention. The first surface region 5a of the coating is to remain after decoating, while the surrounding second surface region 5b, as an edge region in which a plurality of arrows are drawn, is to be decoated. The second surface region 5b is delimited outwardly by the side edges of the glass body.

[0116] The method according to the invention for the region-wise decoating of a coated surface 5 of a glass body 4 comprises the steps of scanning a focused continuous laser beam over the surface 5 of the coated glass body 4 at a scanning speed of at least 10 m / s and decoating a coating of the surface of the glass body in the region scanned by the continuous laser beam.

[0117] This allows the coated surface of the glass body to be removed with a theoretical surface removal rate of at least 2000 mm, which results from the scanning speed and the track width. 2 / s and an applied surface energy of about 0.1 J / mm 2 be scanned.

[0118] The scanning movement of the laser beam on the surface is represented by the arrows 12. The length of the arrows corresponds to the scan path or the scan width, which results from the geometry of the polygon mirror 10 and the distance between the polygon mirror 10 and the glass body 4. The length of the scan path is marked A in the top right of Fig. 2. In general, scanning can be performed from the outside in or from the inside out. However, when decoating a glass body 4, it is preferred to scan all side edges from the outside in or from the inside out.

[0119] In Fig. 2 and also in Fig. 3 discussed below, the track spacings are not drawn to scale, but are drawn much too large. This serves to improve visualization and comparability. The scan path is adjusted so that, in a real application, the scan track begins or ends a few millimeters outside the edge of the glass due to positioning and dimensional tolerances of the glass body, positioning tolerances of the scanning mirror arrangement, and tolerances of the scan path.

[0120] First, the decoating of the upper edge area is described. A first scan 12a is performed on the left side edge of the upper second surface area 5b, starting from the top to the end of the scan path, represented by the arrowhead, and the coating material is decoated. The laser beam on the surface has a defined scanning speed and a defined width transverse to the scanning direction, as well as a defined length in the scanning direction of the laser spot. The scanning direction is essentially perpendicular to the side edge.

[0121] The relative position of the glass body 4 is then changed by one track spacing by adjusting it in the feed direction, indicated by arrow B. The track spacing is marked on the upper side with the letter C and is oversized in Fig. 2 and not shown to scale. The adjustment can be performed intermittently so that all adjacent scan tracks are applied while the glass body is stationary relative to the polygon scanner. Alternatively, the glass body can be continuously moved relative to the polygon scanner so that equidistant scan tracks are also applied. This causes the scan tracks to run at a slight angle to the side edge of the glass body 4.

[0122] The coating is then removed by a subsequent scan along arrow 12b, and the adjustment and scanning continue until the final scan along arrow 12c is performed at the right edge. Thus, the coating material has been removed across the entire upper second surface area 5b by equidistant scan tracks. The width D of the second surface area 5b essentially corresponds to the length A of the scan paths of the laser beam. Adjacent scan tracks 12a, 12b, etc. are generated with a track spacing of a maximum of 50% of the width of the laser spot transverse to the scan direction. The track spacing is measured, for example, between the center of track 12a and the center of track 12b.

[0123] Subsequently, the other edges of the coated surface 5 of the glass body 4 can be decoated.

[0124] When stripping one of the second surface regions 5b, the scanning tracks can be applied either starting from the side edge toward the inner coated first surface region 5a or starting from the inner coated first surface region 5a outward to the side edge. Since the scanning paths are precisely defined and have the same length, essentially smooth edges are created for the stripped regions, especially at the inner edges.

[0125] The example in Fig. 2 shows the decoating of edge regions with a width corresponding to the length of the scan path of each individual scan of the laser beam across the surface, for example, 20 mm or 30 mm. However, if edge regions with a smaller width D are to be decoated with the same scan paths A, a portion of the scan path remains unused if the scan direction is essentially perpendicular to the side edge.

[0126] Fig. 3 shows a solution to this problem in that the scanning direction of the laser beam is adjusted relative to the surface 5 to be processed with respect to the side edges of the glass body 4. In Fig. 3, the scanning direction runs obliquely at a defined angle of approximately 80° to the side edge. This angle allows the scanning path, which is represented by the length of the arrows 12 in the same way as in Fig. 2, to be completely applied to the coating 5. The length of the scanning path is again marked A, the adjustment direction for decoating the upper edge region is marked B, and the track spacing is marked C. The width D of the edge region D to be decoated is significantly smaller than the scanning path A.

[0127] Due to the 80° angle of the scanning direction relative to the side edge, not only is the entire scan path utilized, but the advance of the glass body 4 relative to the scanning mirror arrangement and thus the decoating of the second surface region 5b can be faster because fewer laser scans are required, which also results directly from the different number of arrows 12 in Figs. 2 and 3. Thus, the advance speed is faster by the quotient of the narrowing of the edge decoating. For example, the advance speed can be increased from 1.75 m / min x 300 mm / 52 mm to 10 m / min. Likewise, the width of the transition region between the decoated region and the coated region can be reduced by the same quotient.

[0128] The method shown in Fig. 3 for removing coatings from a coated surface of a glass body can, on the one hand, be carried out with a continuously operating laser, as described with reference to Fig. 2. The method can also be carried out with a pulsed laser and is therefore independent of the application with a continuous laser.

[0129] Figures 4a and 4b show photographic representations of decoated areas of surfaces of glass bodies with decoating by means of a pulsed laser (a) and with a continuous laser (b).

[0130] In Fig. 4a, scan tracks 12' can be seen on the surface of the glass body 4. These tracks visibly consist of individual dots that were introduced successively along the scanning direction (from left to right). Fig. 4b, in contrast, shows a stripped area of ​​a glass body 4 that was stripped using a continuous laser. The scan tracks 12 are continuous and form a continuous pattern. The boundary lines between the adjacent scan tracks 12 can be seen as bright lines that have been highlighted by contrast enhancement of the image.

[0131] Fig. 5 shows another property of a glass surface stripped with a continuous laser. It shows a section of the surface of a glass body 4 with a first surface region 5a (top) and a second surface region 5b (bottom). The second surface region 5b has been stripped with a continuous laser, with the scan tracks 12 applied running from bottom to top. For clarity, the scan tracks are shown alternately with a solid line and a dashed line. The boundary line 14, in contrast, is shown as a solid line.

[0132] The boundary or boundary line 14 between the first region 5a and the second region 5b exhibits an irregularity of an order of magnitude equal to the distance between the scan tracks. This structure is caused by the property of a continuous laser 6 (see Fig. 1) that the laser can only be switched on and off with limited temporal accuracy. This property is also called jitter. Thus, due to the high scanning speeds, the starting or end points of a laser track 12 on the surface cannot be precisely positioned along a straight boundary line 14. This creates an irregular but characteristic boundary or boundary line 14.

[0133] The boundary line 14 is shown schematically as a solid line in Fig. 5. In a real application, the boundary line 14 will not be so clearly visible, since a transition region with decreasing degree of decoating occurs when the continuous laser beam is switched on and off and the applied scanning speed. At a scanning speed of 1000 m / s, for example, the laser 6 (see Fig. 1) would have to be switched off with a temporal accuracy of + / - 0.5 ps in order to maintain an accuracy in the range of + / - 50 pm, on the order of magnitude of the track pitch, when scanning perpendicular to the side edge of the glass body 4. If the scanning direction is set at an angle of 80° to the side edge, the accuracy improves to + / - 9 pm.

[0134] For these reasons, the two surface areas 5a and 5b show a characteristic course at their boundary lines 14, as shown in Fig. 5.

[0135] The boundary line 14 shown is typical for decoating with a continuous laser 6. When using a pulsed laser, the timing can be carried out much more precisely due to the design, so that a straight boundary line can be expected.

[0136] Examples of decoating processes according to the prior art and according to the present invention are discussed below.

[0137] Figs. 6a to 6c show various geometric shapes of the focused laser spot 20 on the surface, with the dashed lines indicating the different widths of the scan tracks. Fig. 6a shows a substantially round laser spot 20 in which the laser beam has a spot length transverse to the scanning direction of the laser beam that is equal to the spot length in the scanning direction of the laser beam.

[0138] Fig. 6b shows a configuration of the laser spot 20 in which the spot length transverse to the scanning direction of the laser beam is 50% longer than the spot length in the scanning direction of the laser beam. Fig. 6c shows a configuration of the laser spot 20 in which the spot length transverse to the scanning direction of the laser beam is 200% longer than the spot length in the scanning direction of the laser beam.

[0139] The focusing device 8 has an arrangement of at least one cylindrical or otherwise non-rotationally symmetric lens 8a for generating the different spot lengths.

[0140] By using different laser spots with different spot lengths perpendicular to the scanning direction, the scanning speed can be reduced while maintaining the same surface ablation rate. The scanning speeds are shown in Figs. 6a to 6c with arrows of different lengths. This schematically illustrates that the wider the focus perpendicular to the scanning direction, the slower the scanning speed can be to achieve the same surface ablation rate at approximately the same surface energy. The laser power is adjusted to ensure that sufficient surface energy is introduced into the coating. This is, for example, approximately 0.1 J / mm 2 .

[0141] Fig. 7 shows an embodiment of a system 2 for the region-by-region decoating of a coated surface of a glass body 4. A laser source (not shown) generates a laser beam that is focused onto the surface of the coated glass body 4 by a focusing device 8. A scanning mirror arrangement 10' in the form of a galvanically, galvanometrically, or piezoelectrically driven scanning mirror scans the laser beam at a predetermined scanning speed on the surface of the coated glass body 4. The design of the scanning mirror arrangement 10' in the form of an acousto-optical modulator is also possible.

[0142] In contrast to the illustration in Fig. 1, the scanning mirror arrangement according to Fig. 7 is arranged on the side 4a of the glass body 4 opposite the coated surface. The laser beam is scanned vertically in Fig. 7 and first passes through the glass body 4 before the laser power acts on the coating to be removed.

[0143] The coating is located on side 4b of the glass body 4 and is shown with a thicker line.

[0144] Furthermore, a device for generating an air flow in the form of a suction device 30 is arranged on side 4b of the coated surface of the glass body 4. The suction device 30 is shown only schematically and is intended to ensure that a large portion of the detached coating material, preferably almost all of the detached material, is suctioned away so that this material does not redeposit on the surface of the glass body 4. Instead of the suction device 30 shown, a blowing device can also be used.

[0145] The illustration shows a partial decoating of the upper section of side 4b, with the decoated area indicated by a thinner line. The area exposed to the suction device 30 is sufficiently large to ensure sufficient suction power at least across the scanning width of the laser beam.

[0146] Alternatively or in addition to the suction device 30, a blowing device (not shown here) can also be provided, which generates an air stream directed toward the area of ​​the surface exposed to the laser beam and detaches and transports detached material from the surface. It is preferred that the blowing device generates an air stream directed toward the upper edge.

[0147] Figs. 8a-d show a schematic representation of the scanning movement of the laser beam on the coating 5 of the glass body 4 with concrete dimensions that represent a specific example. The specified values ​​are purely exemplary and do not restrict the decoating process to these values. The laser used is a 4 kW single-mode cw laser. As already explained in connection with Fig. 7, a scanning mirror arrangement 10' in the form of a galvanically, galvanometrically, or piezoelectrically driven scanning mirror can be used. The use of such a scanning mirror arrangement has the advantage that the deflection of the laser beam by the scanning mirror 10' enables a back-and-forth movement along one direction. Typically, the scanning mirrors 10' are operated in resonance, and the oscillating movement corresponds to a sine curve as shown in the diagram in Fig. 8b. The scanning frequency is 1,857 Hz.

[0148] Scanning the surface using laterally offset scan tracks requires either a relative movement of the glass body 4 to the scanning mirror arrangement 10' or an additional second scanner perpendicular to the first scanning movement, for example, in the form of a galvanically, galvanometrically, or piezoelectrically driven scanner. In Fig. 8a, the scan tracks are shown parallel to each other, which requires a stepwise movement of the glass body 4 relative to the scanning direction. Alternatively, a continuous movement of the glass body 4 relative to the scanning direction can be generated, so that the adjacent scan tracks form a small angle to each other.

[0149] The top right of Fig. 8 shows the movement of the laser beam on the surface of the glass body 4, with only a small section of the glass body 4 being shown. The upper section in Fig. 8a shows the path of the back-and-forth movement of the laser beam, which led to a removal of the coating, so that the coating 5 is still present only below the solid line 5'.

[0150] In the direction of the vertical arrows, the laser beam is switched on, as shown by solid lines. During the reversal movement at the upper and lower ends, the glass body 5 is moved further relative to the scanning mirror arrangement 10' by a scan track pitch of 46.2 pm. During the reversal movement, the laser beam's power is reduced below an excitation threshold or switched off, as shown by dashed and curved lines. This creates a de-layered area with a scan width of 80 mm, while the entire area, including the reversal movement, has a width of 98.9 mm.

[0151] Fig. 8b shows the sinusoidal oscillation path in a path-time diagram. Parallel dashed lines establish a reference to the representation in Fig. 8a. The two inner dashed lines indicate the region in which the laser beam is switched on, so that in this region the line in the path-time diagram is shown as a solid line. Between the two outer dashed parallel lines in the path-time diagram, the reversal movement takes place, during which the laser beam's power is reduced or switched off. In the path-time diagram, the line in these regions is shown as a dashed line.

[0152] Fig. 8c shows a scan speed-time diagram whose horizontal time axis corresponds to the time axis of Fig. 8b. Thus, the time periods in which the laser beam is switched on are shown with a solid line, and the time periods in which the laser beam is reduced in power or switched off are shown with dashed lines.

[0153] The two arrows in Fig. 8c mark point A of the curve shown with a maximum scanning speed of 577 m / sec and point B with a minimum scanning speed of 342 m / sec. Thus, in the reversal range during the sinusoidal scanning motion, the laser beam's power can be reduced or switched off, and the laser beam is not used for decoating during the slow scanning speed.

[0154] In addition, Fig. 8c shows the durations and time fractions of laser on (Laser ON) at 60% and off (Laser Off) at 40%. Taking the different scanning speeds into account, this results in a duty cycle of 51.5%. During the on-times, the laser power can be kept constant.

[0155] If the introduced surface energy is to be kept constant in the resonant scanner shown, the laser power must be varied depending on the scanning speed.

[0156] Fig. 8d then shows an acceleration-time diagram, also with a matching time axis. The accelerations are relatively large; for example, the accelerations of a scanning mirror with a diameter of 40 mm at the edge are several hundred gravitational accelerations g.

[0157] With the specific values ​​of this embodiment, the average feed of the glass body relative to the scanning mirror arrangement 10' with a value of

[0158] 2 x 1857 Hz x 46.2 pm = 171.5 mm / sec. This results in a surface removal rate of

[0159] 2 x 1857Hz x 46.2pm x 80mm = 137.2cm 2 / sec reached.

[0160] In the following, the possible parameter ranges for carrying out the method according to the invention with a continuous laser beam, which are used in the examples, are first given.

[0161] The laser beam can be reduced to a focus diameter of less than 120 pm.

[0162] The polygon scanner 10 can generate a scanning speed on the surface of at least 100 m / s, preferably at least 350 m / s, in particular at least 500 m / s and in particular at least 1000 m / s.

[0163] The surface removal rate is at least 2000 mm 2 / s, preferably at least 5000 mm 2 / s, in particular at least 15000 mm 2 / s and preferably at least 25000 mm 2 / s. The laser source 6 can be operated with a power of at least 1 kW, in particular at least 3 kW and preferably at least 5 kW.

[0164] The applied surface energy is in the range of 0.1 J / mm 2 .

[0165] The laser beam can be scanned on the surface with a scan width of at least 10 mm, preferably at least 50 mm, preferably at least 200 mm, preferably 300 mm.

[0166] The off-time values ​​include, among other things, the time required for adjusting the laser beam between adjacent tracks, as well as for accelerating, decelerating, and rotating the mirror scanner at the side edges of the glass body. This off-time is multiplied by the laser's temporary off time corresponding to a relative duty cycle (in percent) to calculate the practical area removal rate from the theoretical area removal rate. Additionally, the reduction in laser power at the ends of the scan tracks can also be taken into account.

[0167] As a reference, the coating removal process is based on conventional grinding of the surface. With conventional grinding, a theoretical surface removal rate of approximately 8000 mm 2 / s and a practical surface removal rate of approx. 4000 mm 2 / s can be reached.

[0168] Examples 1 and 2 concern applications of pulsed lasers for comparison with Examples 3 to 5 with continuous lasers.

[0169] Example 1: pulsed single-mode fiber laser with galvano scanner average laser power 50 W pulse length 100 ns pulse frequency 100 kHz with pulse spacing of 10 ps spot length in scanning direction on surface 50 pm spot length across scanning direction on surface 50 pm

[0170] Lane spacing 25 pm

[0171] Scanning speed 2.5 m / s

[0172] Laser duty cycle 100%

[0173] Time out 10%

[0174] Surface treatment

[0175] Scan width 100 mm

[0176] Feed rate 0.6 mm / s theoretical surface removal rate 63 mm 2 / s practical surface removal rate 56 mm 2 / s Surface energy 0.8 J / mm 2

[0177] Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 0.8% practical surface removal rate: 1.4%

[0178] Example 1 shows that a pulsed laser with low laser power has a very low surface removal rate compared to mechanical decoating.

[0179] Example 2: pulsed single-mode fiber laser with polygon scanner, average laser power 1 kW, pulse length 60 ns

[0180] Pulse frequency 4 MHz with pulse spacing of 250 ns

[0181] Spot length in scanning direction on surface 60 pm Spot length across scanning direction on surface 60 pm Track pitch 30 pm

[0182] Scanning speed 120 m / s

[0183] Laser duty cycle 50%

[0184] Time out 30% surface treatment

[0185] Scan width 300 mm

[0186] Feed rate 6 mm / s theoretical surface removal rate 3600 mm 2 / s practical surface removal rate 1260 mm 2 / s Surface energy 0.28 J / mm 2

[0187] Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 23% practical surface removal rate: 32%

[0188] With increased laser power of the pulsed laser according to Example 2, higher ablation rates are achieved, but these are still far below the mechanically achievable values.

[0189] Examples 1 and 2 demonstrate applications of pulsed lasers that can achieve homogeneous ablation of a coating. However, the surface ablation rates are low and lie below 2000 mm 2 / s.

[0190] Example 3: continuous single-mode fiber laser with polygon scanner

[0191] Laser power 2 kW

[0192] Spot length in scanning direction on surface 90 pm

[0193] Spot length across the scanning direction on surface 90 pm

[0194] Lane spacing 50 pm

[0195] Scan speed 350 m / s virtual pulse length 257 ns laser on time 50% off time 30%

[0196] Surface treatment

[0197] Scan width 300 mm

[0198] Feed rate 29 mm / s theoretical surface removal rate 17325 mm 2 / s practical surface removal rate 6064 mm 2 / s Surface energy 0.115 J / mm 2

[0199] Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 108% practical surface removal rate: 152%

[0200] Even with the moderate laser power of a standard continuous-wave laser, significantly higher surface removal rates can be achieved than with a more powerful pulsed laser, particularly due to the lower surface energy required. The theoretical surface removal rate is in the range of mechanical decoating processes, although the practical surface removal rate is significantly higher than with mechanical processes.

[0201] Example 4: continuous single-mode fiber laser with polygon scanner

[0202] Laser power 3 kW

[0203] Spot length in scanning direction on surface 90 pm

[0204] Spot length across the scanning direction on surface 90 pm

[0205] Lane spacing 45 pm

[0206] Scanning speed 500 m / s Virtual pulse length 180 ns Scanner duty cycle 50% Off time 30%

[0207] Surface treatment

[0208] Scan width 300 mm

[0209] Feed rate 34 mm / s theoretical surface removal rate 20250 mm 2 / s practical surface removal rate 7090 mm 2 / s Surface energy 0.148 J / mm 2

[0210] Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 127% practical surface removal rate: 177%

[0211] Example 5: continuous multimode fiber laser with polygon scanner Laser power 5 kW

[0212] Spot length in scanning direction on surface 105 pm

[0213] Spot length across the scanning direction on surface 105 pm

[0214] Lane spacing 55 pm

[0215] Scanning speed 650 m / s Virtual pulse length 162 ns Scanner duty cycle 50% Off time 30%

[0216] Surface treatment

[0217] Scan width 300 mm

[0218] Feed rate 57 mm / s theoretical surface removal rate 34125 mm 2 / s practical surface removal rate 11945 mm 2 / s Surface energy 0.147 J / mm 2

[0219] Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 213% practical surface removal rate: 299%

[0220] Examples 3 to 5 demonstrate applications according to the invention with continuous laser beams, which can achieve a very homogeneous removal of the coating compared to pulsed lasers. With the improved surface removal, high surface removal rates of over 2000 mm are also possible. 2 / s and sometimes well above 5000 mm 2 / s while simultaneously achieving comparatively lower surface energies. The remaining examples 6 to 8 correspond to examples 3 to 5, except that the laser spot has been widened transversely to the scanning direction, allowing the surface ablation rates to be further increased. Furthermore, the scan width is 50 mm instead of the previous 300 mm. However, the feed rates can be selected significantly higher.

[0221] Example 6: continuous single-mode fiber laser with polygon scanner, laser power 2 kW

[0222] Spot length in scanning direction on surface 90 pm

[0223] Spot length across the scanning direction on surface 315 pm

[0224] Lane spacing 170 pm

[0225] Scan speed 100 m / s virtual pulse length 900 ns laser on time 50% off time 30%

[0226] Surface treatment

[0227] Scan width 50 mm

[0228] Feed rate 173 mm / s theoretical surface removal rate 17325 mm 2 / s practical surface removal rate 6064 mm 2 / s Surface energy 0.115 J / mm 2

[0229] Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 108% practical surface removal rate: 152%

[0230] Example 7: continuous single-mode fiber laser with polygon scanner, laser power 3 kW

[0231] Spot length in scanning direction on surface 90 pm Spot length across scanning direction on surface 450 pm Track pitch 245 pm

[0232] Scanning speed 100 m / s Virtual pulse length 900 ns Scanner duty cycle 50% Off time 30%

[0233] Surface treatment

[0234] Scan width 50 mm

[0235] Feed rate 341 mm / s theoretical surface removal rate 20250 mm 2 / s practical surface removal rate 7090 mm 2 / s Surface energy 0.148 J / mm 2

[0236] Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 127% practical surface removal rate: 177%

[0237] Example 8: continuous multimode fiber laser with polygon scanner laser power 5 kW

[0238] Spot length in scanning direction on surface 105 pm

[0239] Spot length across the scanning direction on surface 683 pm Track pitch 341 pm

[0240] Scanning speed 100 m / s Virtual pulse length 1050 ns Scanner duty cycle 50% Off time 30%

[0241] Surface treatment

[0242] Scan width 50 mm

[0243] Feed rate 341 mm / s theoretical surface removal rate 34125 mm 2 / s practical surface removal rate 11945 mm 2 / s Surface energy 0.147 J / mm 2Relationship to the surface removal rate in conventional grinding: theoretical surface removal rate: 213% practical surface removal rate: 299%

Claims

Patent claims 1. System for the region-wise decoating of a coated surface of a glass body, with a laser source (6) for generating a continuous laser beam, with a focusing device (8) for focusing the laser beam onto the surface of the coated glass body (4), with a scanning mirror arrangement (10) for directed scanning of the laser beam at a scanning speed on the surface of the coated glass body (4) and with a control device (18) for controlling the laser source (6) and the scanning mirror arrangement (10), wherein the laser source (6), the scanning mirror arrangement (10) and the control device (18) are configured to scan the continuous laser beam at a scanning speed of at least 10 m / s on the surface.

2. System according to claim 1, characterized in that the scanning speed is at least 100 m / s, preferably at least 300 m / s, in particular at least 500 m / s or preferably at least 1000 m / s.

3. System according to claim 1 or 2, characterized in that the control device (18) is designed to operate the laser source (6) with a power of at least 1 kW, in particular at least 3 kW and preferably at least 5 kW.

4. System according to one of claims 1 to 3, characterized in that the scanning mirror arrangement comprises a polygon scanner (10) or a galvanically or galvanometrically or piezoelectrically driven scanning mirror (10').

5. System according to claim 4, characterized in that the scan width by projecting the laser beam onto the surface by means of a respective polygon surface of the polygon scanner is at least 10 mm, preferably at least 50 mm, preferably at least 200 mm, in particular at least 300 mm.

6. System according to one of claims 1 to 5, characterized in that the scanning direction of the laser beam relative to the surface to be processed can be adjusted to an angle other than 90° with respect to side edges of the glass body.

7. System according to one of claims 1 to 6, characterized in that the focusing device (8) focuses the laser beam to a spot length transverse to the scanning direction of the laser beam which is at least 50% greater than the spot length in the scanning direction of the laser beam.

8. System according to one of claims 1 to 7, characterized in that the scanning mirror arrangement (10, 10') is arranged on the side (4a) of the glass body (4) opposite the coated surface and that a device for generating an air flow, in particular a blowing and / or suction device (30) is arranged on the side (4b) of the coated surface of the glass body (4).

9. Use of a system according to one of claims 1 to 8 for the partial decoating of a coated surface of a glass body.

10. A method for the region-by-region decoating of a coated surface of a glass body, in which a focused laser spot of a continuous laser beam is scanned over the surface of the coated glass body at a scanning speed of at least 10 m / s and in which a coating of the surface of the glass body is decoated in the region scanned by the continuous laser beam.

11. The method according to claim 10, wherein the continuous laser beam is scanned on the surface at a scanning speed of at least 100 m / s, preferably at least 300 m / s, in particular at least 500 m / s or preferably at least 1000 m / s.

12. The method according to claim 10 or 11, wherein a laser beam with a power of at least 1 kW, in particular at least 3 kW and preferably at least 5 kW is used.

13. Method according to one of claims 10 to 12, wherein the laser beam is scanned on the surface with a scan width of at least 10 mm, preferably of at least 50 mm, preferably of at least 200 mm, in particular of 300 mm.

14. A method according to any one of claims 10 to 13, wherein a theoretical surface removal rate of at least 2000 mm 2 / s, preferably at least 5000 mm 2 / s, in particular at least 15000 mm 2 / s and preferably at least 25000 mm 2 / s is reached.

15. The method according to any one of claims 10 to 14, wherein the scanning direction of the laser beam relative to the surface to be processed is set to an angle other than 90° with respect to side edges of the glass body.

16. The method according to any one of claims 10 to 15, wherein the laser beam is focused to a spot length transverse to the scanning direction of the laser beam which is at least 50% greater than the spot length in the scanning direction of the laser beam.

17. Method according to one of claims 10 to 16, in which adjacent scanning tracks are generated with a track pitch of less than 50% of the diameter of the laser beam.

18. A method according to any one of claims 10 to 17, wherein, after decoating a portion of the surface of the coated glass body, deposits of the decoated material are mechanically removed.

19. Glass body with a base body (4) made of a glass material, wherein the base body (4) has a surface with a first surface area (5a) and with a second surface area (5b), wherein the first surface area (5a) has a coating, and wherein in the second surface area (5b) the coating is at least partially stripped by processing and wherein the decoated area has a plurality of adjacent continuous scanning tracks.

20. A glass body according to claim 19, characterized in that the boundary between the first region and the second region has an irregularity of an order of magnitude equal to the distance between the scanning tracks.

21. Glass body according to claim 19 or 20, characterized in that in the second surface region (5b) at least 95%, preferably at least 98% of the coating is removed.

22. Glass body according to one of claims 19 to 21, characterized in that a small proportion of particulate material of the at least partially removed coating is arranged in the second surface region (5b).

23. A method for the region-by-region decoating of a coated surface of a glass body, in which a focused laser beam is scanned over the surface of the coated glass body and in which a coating of the surface of the glass body is decoated in the region scanned by the laser beam and in which the scanning direction of the laser beam is set to an angle other than 90° relative to the surface to be treated with respect to side edges of the glass body.

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