CN113613826A

CN113613826A - Method for producing an opening in a glass stack

Info

Publication number: CN113613826A
Application number: CN202180000746.0A
Authority: CN
Inventors: 叶丽雅
Original assignee: Saint Gobain Glass France SAS
Current assignee: Saint Gobain Glass France SAS; Compagnie de Saint Gobain SA
Priority date: 2020-02-05
Filing date: 2021-02-01
Publication date: 2021-11-05
Also published as: WO2021156166A1

Abstract

Method for producing an opening (6) in a horizontally supported glass sheet stack (1) by laser machining, wherein the glass sheet stack (1) comprises an upper glass sheet (3) and a lower glass sheet (4), the opening (6) passes through the total thickness of the glass sheet stack (1), and the glass sheet stack (1) has a thickness of at least 2.5mm, wherein the method comprises: a) focusing a laser (10) from above the glass sheet stack (1) through the thickness of the glass sheet stack (1) onto a lower plane, b) repeatedly moving the laser (10) along a cutting line (L), wherein the focal point of the laser (10) is in a plane arranged further above in each repetition, c) removing a glass pane (7.1,7.2) bounded by the cutting line (L) from the lower glass sheet (4) and the upper glass sheet (3) with the opening (6) exposed.

Description

Method for producing an opening in a glass stack

Technical Field

The invention relates to a method for producing an opening in a glass sheet stack by laser machining, a method for producing a composite glass sheet and the use of the method for producing a composite glass sheet.

Background

Modern glass devices are equipped with a large number of electrically controllable attached components, such as sensors, detectors, receiving or lighting units. Examples of such attached parts are, in particular, in the automotive field, camera systems, rain sensors, antennas and decorative or functional lighting elements. With the increasing popularity of various assistance systems (ADAS, advanced driving assistance system), the number of electrically controllable attached components in motor vehicles has also increased. The electrically controllable attachment component must be protected due to its sensitivity to weather influences and is usually placed behind the windshield of the motor vehicle in the passenger compartment. Some of these auxiliary systems need to be placed in openings in the sheet in order to avoid being optically obstructed by the glass in front of them. In the case of a composite sheet consisting of a plurality of individual glass sheets, it is necessary for the openings in all the glass sheets to be in exactly the same position. Otherwise, interfering edges are produced, which hinder or make difficult the installation and precise positioning of the auxiliary system or of the respective housing.

A laser separation method for dicing silicon wafers in the semiconductor industry field is described in US20070111481 a 1. The creation of openings in the stack of glass sheets is not a subject.

In WO2018085284 a method for cutting a glass sheet laminate is disclosed, in which method the edges of the laminated sheet can be processed.

In WO2019105855 a method for manufacturing a composite glass sheet with electrically attached components is disclosed, wherein the problem of a precise positioning of the through openings in the two individual glass sheets of the composite glass sheet is not addressed.

Therefore, there is a need for a method for producing openings in two glass sheets at precisely the same location.

Disclosure of Invention

The object of the invention is to provide a method for producing through-openings in a plurality of glass sheets at exactly the same location. The method should also be able to be applied in particular to three-dimensionally curved glass sheets. The object of the invention is also to provide a method for producing a composite glass sheet with through-openings.

The object of the invention is achieved according to the invention by a method for producing an opening in a stack of glass sheets according to claim 1. A method for producing a composite glass sheet and the use thereof result from the further independent claims. Preferred embodiments follow from the dependent claims.

The method involves creating openings in a horizontally supported stack of glass sheets by laser machining. The glass sheet stack comprises an upper glass sheet and a lower glass sheet. The terms "upper" and "lower" herein refer to positions in the stack of glass sheets. The upper glass sheet and the lower glass sheet are stacked in a planar manner. This means that the glass sheets are loosely stacked one above the other without a fixed connection between them, for example by means of adhesive qualities or film layers. The openings pass through the total thickness of the stack of glass sheets and thus through the upper glass sheet and through the lower glass sheet. The stack of glass sheets has a thickness of at least 2.5 mm.

The method comprises the following steps:

a) the laser light is focused from above the stack of glass sheets through the thickness of the stack of glass sheets onto a lower plane,

b) the laser is moved repeatedly along the cutting line L, wherein the focal point of the laser is in a plane arranged further up in each repetition,

c) the glass pane delimited by the cutting line is removed from the lower glass sheet and the upper glass sheet with the opening exposed.

Since the laser light is focused from above the glass sheet stack through the two glass sheets first on the lower plane and then on the plane arranged further above, it is possible to process glass sheet stacks with a thickness of more than 2.5mm with the laser light and to produce through openings. The processing in several planes from the bottom up has the advantage that the raw glass is transparent in the upper plane and the laser can be focused through the raw plane onto the plane lying therebelow. After processing by means of a laser, the glass loses transparency at the relevant location and is therefore no longer transparent to the laser. It is thereby possible to produce openings in the two glass sheets by means of a laser, which leads to an improved quality of the edges compared to conventional mechanical methods. Furthermore, machining with a laser achieves openings of arbitrary geometry even in the case of small openings spaced from one another, such as at less than 5mm spacing.

Horizontal support means that the stack is supported in such a way that its lower surface rests on a table or similar base and does not stand on one of its edges. The plane of the surface of the glass sheet is oriented here substantially parallel to the ground or at an angle of less than 45 ° relative to the ground. The floor surface is here the floor surface of the surroundings in which the method is performed, i.e. for example the floor surface of a factory workshop. The lower glass sheet is closer to the table or base than the upper glass sheet.

Preferably, the glass sheet stack consists of exactly one lower glass sheet and one upper glass sheet. Alternatively, the glass sheet stack can also comprise three or more glass sheets. In the case of exactly two glass sheets, the glass sheet stack has one glass sheet with an upper portion of the first surface (I) and the second surface (II) and one glass sheet with a lower portion of the third surface (III) and the fourth surface (IV). The first surface is here the upper surface of the stack of glass sheets and is exposed. The fourth surface is the lower surface of the glass sheet stack and is likewise exposed. During the method, the fourth surface rests, for example, on a table or a stand. The second surface of the upper glass sheet is directed towards the third surface of the lower glass sheet and is thus within the stack of glass sheets. The thickness of the stack of glass sheets corresponds to the sum of the thicknesses of the individual glass sheets.

All glass sheets of the glass sheet stack are preferably arranged congruent to each other. As a result, openings are produced in all glass sheets at precisely the same location, and in the later lamination step a single through, stepless opening is produced. Preferably, at least one of the glass sheets is curved in three dimensions. In the case of two glass sheets, the upper glass sheet and/or the lower glass sheet is bent three-dimensionally. Laser machining enables the creation of openings in a three-dimensionally curved glass sheet. In particular, in connection with three-dimensionally curved sheets it is difficult to position the holes exactly at the same location in both sheets. The method according to the invention therefore offers particular advantages in this case, since, as a result of the arrangement of the individual glass sheets in a stack during the production of the opening, the opening extends over the total thickness of the stack without undesired misalignment.

In a preferred embodiment, the upper glass sheet rests with its second surface on the third surface of the lower glass sheet, wherein preferably a separating agent is arranged between the second surface and the third surface. Suitable separating agents are known to those skilled in the art. This can be, for example, a polymer-based powdery separating agent, which is generally used for the transport and storage of glass. The separating agent prevents the sheets from adhering to one another and enables a non-destructive separation of the glass sheets after the end of the process.

In a preferred embodiment, the thickness of the stack of glass sheets is between 2.5mm and 15mm, preferably between 2.6mm and 10mm, particularly preferably between 2.7mm and 6 mm. Within the thickness range, the method provides particularly good results. The thickness of the glass sheet stack is determined by the sum of the thicknesses of the individual glass sheets in the absence of a separating agent which may be present.

The area of the opening is preferably less than 225cm²Particularly preferably less than 25cm²Especially less than 10cm². Such small gaps enable visually particularly no attachment of partsAnd (4) obvious integration.

In an advantageous embodiment, the contour of the opening has a radius of curvature of less than 2 mm. In a further advantageous embodiment, the distance between the different openings is less than 5 mm. This value is not achievable with mechanical fracture methods.

The glass sheets can be partially pre-tensioned or not.

In a preferred embodiment, the removal of the glass pane delimited by the cutting line L is effected by applying a vacuum to the glass pane. Preferably, the glass pane of the lower glass sheet, which is referred to as the lower glass pane, is first removed here. This is preferably achieved by applying a vacuum on the lower surface of the stack of glass sheets. Next, the upper glass block is removed from the upper glass sheet. This is preferably also achieved by applying a vacuum from below the stack of glass sheets. This has the advantage that the same apparatus can be used for both glass panes. Alternatively, the removal of the upper glass pane is preferably achieved by applying a vacuum to the upper surface of the stack of glass sheets. This has the advantage that the upper glass pane, when removed through the opening, does not damage the inner edges of the opening in the region of the lower glass pane. Furthermore, the removal of the upper glass pane can be carried out overlapping in time with the removal of the lower glass pane, which in turn means a time saving in the process.

In a preferred embodiment of the method according to the invention, the openings are produced by laser separation using a pulsed laser, preferably a pulsed nanosecond laser. The workpiece and the laser are moved relative to one another in such a way that a plurality of successive pulses impinge on the workpiece and melt and evaporate the material of the workpiece.

The laser beam penetrates the sheet to be processed during the separation. Thus, the wavelength of the laser radiation is preferably selected at which the glass sheet is substantially transparent. The glass sheets preferably have a transmission of at least 80%, particularly preferably at least 90%, at the laser wavelength used. For the usual glass sheets, lasers in the visible range, in the near UV range or in the IR range, for example in the range from 300nm to 2500nm, preferably from 300nm to 1100nm, particularly preferably from 300nm to 800nm, can be used. In a particularly advantageous embodiment, the laser has a wavelength of 400nm to 600nm, preferably 500nm to 550nm, for example 532 nm. This is advantageous on the one hand in terms of the transparency of the usual glass sheets and on the other hand in terms of the commercial availability of suitable and cost-effective laser systems. The laser beam is preferably emitted by a solid-state laser with quality switching (Q-switching), particularly preferably by an Nd: YAG laser.

Preferably, the laser light is first focused through the entire thickness of the glass stack onto the lower surface of the glass sheet stack upon laser separation, and laser machining is continued until the laser light is focused onto the upper surface of the glass sheet stack. In this way, a glass pane is obtained which can be detached particularly easily, which leads to a particularly well-defined inner edge of the opening.

Preferably, the distance between two successive planes in the vertical direction, that is to say perpendicular to the horizontal plane of the stack of glass sheets, during laser separation is between 20 μm and 50 μm, preferably between 25 μm and 30 μm. As a result, a particularly good separation along the cutting line L is achieved, which in turn leads to a well-defined inner edge of the opening.

The repetition rate (pulse frequency) of the laser beam at the time of separation is preferably 10kHz to 1MHz, particularly preferably 20kHz to 500kHz, preferably up to 100kHz, for example 25kHz or 100 kHz. Thereby, good results are achieved. In principle, however, it is also possible to use significantly higher pulse frequencies, for example up to 100 MHz.

The power of the laser for generating the laser beam is preferably 5W to 200W, particularly preferably 20W to 100W, at the time of separation. The pulse energy is preferably 40 to 4000 [ mu ] J, particularly preferably 80 to 1200 [ mu ] J.

The speed of movement of the laser along the cutting line (contour of the through-opening) is preferably from 500mm/s to 5000mm/s, preferably from 1000mm/s to 4500 mm/s.

The laser beam is preferably focused onto the glass surface by means of an optical element or system. The extension of the focus perpendicular to the radiation direction can be less than or equal to 50 μm, preferably less than or equal to 30 μm, for example 10 μm or less.

In a preferred embodiment, the laser machining is performed by laser separation, and the inner edge K of the opening is inclined. This means that the upper boundary Ko of the inner edge in the upper surface region of the stack of glass sheets is offset by 100 μm to 500 μm, preferably by 150 μm to 350 μm, compared to the lower boundary Ku of the inner edge in the lower surface region of the stack of glass sheets towards the inside of the opening. The opening is here greater in the region of the lower surface of the glass sheet stack than in the region of the upper surface of the glass sheet stack. This has the advantage that the lower glass pane and the upper glass pane fall out of the opening under the influence of gravity. This can be supported by applying a vacuum. In this case, an advantageous inclination of the inner edge of the opening is achieved, which can also be used for fixing the subsequent attachment part.

In a preferred embodiment, the laser machining is performed by laser separation and the openings are arranged entirely within the plane of the stack of glass sheets. That is, the opening has a hole shape and passes through all the sheets stacked. The cross-section of the opening/hole can have any geometrical shape, such as circular, oval, polygonal, rectangular, trapezoidal or square. In connection with laser separation, this design is particularly advantageous, since only small stresses occur in the region of the opening, which can lead to damage to the surrounding glass in the selection of other methods of introducing thermal stresses.

In a further preferred embodiment, the laser machining is carried out by laser separation and the opening is implemented in the form of a lateral recess at the edge of the sheet.

In a further preferred embodiment of the method according to the invention, the laser machining is performed with a first laser and a second laser. Here, steps (a) and (b) are carried out with a pulsed first laser having a pulse length of less than 100ps for producing the filaments, wherein in step (c) the second laser is moved along the cutting line L in a continuous wave run at a wavelength of 1 μm to 20 μm for heating the glass sheet. Preferably, in step (c), the stack of glass sheets is cooled along the cutting line. Alternatively, the glass sheet stack is preferably not cooled along the cutting line L. This simplifies the method and the required equipment. The advantage of the method is that the cutting can be performed without a machining step, such as breaking by mechanical pressure. Here, the removal of the glass pane can also be supported by applying a vacuum. The method is also well suited for automated processing. Cooling creates stresses in the glass so that ejection of the glass block functions particularly well. Since no mechanical pressure has to be applied with a suitable tool in order to break the glass, a very small radius of curvature of the opening can be achieved. It has been shown that radii of curvature of less than 2mm can be produced without problems, which cannot be reliably achieved in the case of mechanical fractures. It is also possible to realize a plurality of openings with only small mutual distances.

In the method according to the invention, first of all a pulsed laser is used to generate an internal material change in the glass sheet. Such material variations are known as so-called filaments. The individual filaments are arranged along the cutting line and are preferably spaced apart from one another. This is related to the mechanism of filament generation, and the inventors have assumed that self-focusing of the laser beam occurs due to the nonlinear kerr effect, thereby achieving higher power densities. With such high power densities, the filaments are produced as a result of multiphoton ionization, field ionization, and electron impact ionization. The resulting electron plasma in turn causes defocusing as a balance for self-focusing. The interaction of focusing and defocusing as the laser radiation passes through the glass layer to produce the filaments results in each filament structure having an array of alternating focused and defocused locations, which extend in the radiation direction of the laser beam, preferably perpendicular to the surface of the glass layer. For a more detailed discussion of the envisaged mechanisms, reference is made to US2013/0126573a1, especially paragraphs [0043] to [0048 ].

The material change produced by the first laser comprises, in particular, local regions of increased density, which are produced by the described self-focusing of the laser radiation.

The first laser is moved along the desired cutting line. The first laser beam produces a material weakening along the cutting line, which forms a theoretical breaking point for further processing. Preferably, here the upper surface of the glass sheet stack and the lower surface of the glass sheet stack are undamaged, i.e. not provided with scratches, nicks or the like. The first laser preferably does not cause material removal at the upper and lower surfaces. Instead, the laser produces a row of microstructured material variations, so-called "filaments", inside the glass sheet, next to each other along a cutting line. Each of these filaments is generated by a row of laser pulses. By appropriate control of the laser radiation, such multiple rows of laser pulses are output onto the glass layer at suitable, usually periodic intervals during the movement of the laser along the cutting line. Such a line of laser pulses is also commonly referred to as a pulse train or pulse train. Each pulse train produces a filament in the glass layer. Thereby, a row of wires next to each other is constructed along the cutting line, wherein adjacent wires have a distance to each other. Methods for generating such spaced-apart pulse trains are known to the person skilled in the art, for example by means of so-called Burst generators (Burst generators). By the movement of the pulsed laser radiation, such a trajectory of the filaments spaced apart from one another is produced along the cutting line, thereby producing a theoretical breaking line. The glass sheets are perforated to some extent by the filaments. The material variation can be seen as a local density increase, with a consequent different refractive index.

In a preferred embodiment, the focal point of the first laser is first positioned in the plane of the lower part between the lower surface of the stack of glass sheets and the upper surface of the stack of glass sheets, and the first laser is then moved along the cutting line. The focal point of the first laser is then positioned in the upper plane between the upper surface and the lower plane and then moved along the cutting line. The individual planes need not be centered in the thickness of the glass sheets. Preferably, the focal plane of the laser is located in each glass sheet of the stack of glass sheets one time each. This results in a particularly good separation of the lower glass pane from the upper glass pane.

In an advantageous embodiment, the first laser is a pulsed laser with a pulse length of less than 10ps, preferably less than 1ps, particularly preferably less than 500 fs. Such short pulses are particularly advantageous in terms of self-focusing of the radiation.

Since it is important for the generation of the internal material change to penetrate the glass sheet with the laser radiation, it is preferable to select a wavelength of the laser radiation at which the glass sheet is substantially transparent. The glass sheets preferably have a transmission of at least 80%, particularly preferably at least 90%, at the laser wavelength used. For the usual glass sheets, lasers in the visible range, in the near UV range or in the IR range, for example lasers in the range from 300nm to 2500nm, preferably from 300nm to 1200nm, particularly preferably from 350nm to 1100nm, for example 1064nm, can be used. This is advantageous on the one hand in terms of the transparency of the usual glass sheets and on the other hand in terms of the commercial availability of suitable and cost-effective laser systems. The first laser beam is preferably generated by a solid-state laser with quality switching (Q-switching).

The repetition rate (pulse frequency) of the first laser is preferably 10kHz to 1MHz, particularly preferably 20kHz to 500kHz, for example 25kHz or 100 kHz. Thereby, good results are achieved. In principle, however, it is also possible to use significantly higher pulse frequencies, for example up to 100 MHz.

The power of the first laser is preferably 5W to 200W, particularly preferably 20W to 100W. The pulse energy is preferably 4 to 500 [ mu ] J.

The selection of the pulse frequency and power can influence the material depth to which the filaments extend. Preferably, starting from the surface of the glass layer through which the laser radiation penetrates into the glass layer, the filaments should extend over at least 40%, particularly preferably at least 50%, and very particularly preferably at least 60% of the thickness of the glass layer. The theoretical fracture site is advantageously highlighted and the subsequent material separation is efficient.

Preferably, the distance between two successive focal planes of the first laser in the vertical direction in steps (a) and (b) is between 1mm and 3mm, preferably between 1.5mm and 2.5 mm. Thereby, a particularly efficient material separation is achieved and the glass pane can be easily removed.

Preferably, a plurality of rows of laser pulses (pulse trains) occurring periodically, wherein each row produces one filament, are output at a repetition rate of preferably less than 1kHz, for example in the range of 200Hz to 800 Hz. Each pulse train preferably consists of at least 5 pulses, for example in the range of 5 to 15 pulses.

The speed of movement of the first laser along the cutting line is preferably from 100mm/s to 1500mm/s, for example from 500mm/s to 1200 mm/s.

The first laser beam is preferably focused onto the glass surface by means of an optical element or system. The extension of the focal spot perpendicular to the radiation direction can be, for example, 10 μm or less.

After the theoretical fracture line is created with the first laser, the actual fracture of the glass sheet is induced with the second laser. The second laser is moved on the first surface along the cutting line, which causes the glass sheet to be heated in the region of the cutting line and subsequently causes the glass sheet to break along the cutting line L. The glass sheet stack is preferably cooled along the cutting line, wherein the glass sheets break along the cutting line due to the generated thermal stress. The combination of the second laser and cooling creates stress to particularly easily dislodge the glass block from the stack of glass sheets.

The chronological order of the method steps is not to be understood in such a way that the irradiation with the first laser along the entire cutting line has to be ended before the irradiation with the second laser is started, or the irradiation with the second laser along the entire cutting line has to be ended before the optional step of cooling is started. Conversely, during the movement of the first laser beam still along the cutting line, it is already possible to begin irradiating with the second laser beam the region of the cutting line which has already been swept over by the first laser beam. Even during the movement of the second laser beam still over the cutting line, it is already possible to start cooling the region of the cutting line which has already been swept over by the second laser beam. In particular, this last-mentioned variant is advantageous because no excessive time can elapse between heating by the second laser beam and rapid cooling in order to generate the required thermal stress. Preferably, the means for cooling (device) is arranged after the second laser beam in the direction of movement, and the second laser beam and the means for cooling are moved along the cutting line at the same speed. Particularly preferably, the second laser beam is moved simultaneously with the cooling device along the cutting line L, wherein the second laser beam and the cooling device are aligned at the same position at the surface of the glass sheet stack. The thermal stress is generated particularly effectively by simultaneous heating and cooling, which leads to a smooth fracture along the cutting line L.

The second laser light is preferably moved once along the cutting line L in the focal plane of the lower surface of the glass sheet stack and once again along the cutting line L in the focal plane of the upper surface of the glass sheet stack. Preferably, the second laser is moved first in the region of the lower surface and then in the region of the upper surface, so that the lower glass pane is detached first and then the upper glass pane is detached. In a preferred embodiment, two lasers of the second laser type are used, wherein the second laser is focused onto the upper surface from above the glass sheet stack and a further laser of the second laser type is focused onto the lower surface of the glass sheet stack, so that the heating is particularly effective over the entire glass sheet stack. If two lasers of the second laser type are moved simultaneously along the cutting line L, the process time can advantageously be reduced.

The glass sheet stack is heated along the cutting line by laser irradiation of a second laser. Laser radiation is therefore suitable, in particular, with a wavelength for which the glass sheets have a high absorption coefficient. For this reason, laser radiation in the middle infrared range is particularly suitable. The second laser has a wavelength of, for example, 800nm to 20 μm, preferably 1 μm to 20 μm, particularly preferably 5 μm to 15 μm. CO 2₂Lasers are particularly suitable, CO₂The laser is typically at a wavelength of 9.4 μm or 10.6 μm. Good results are for example also obtained with Nd: YAG laser. But it is also possible to use, for example, diode lasers or solid-state lasers.

The laser for generating the second laser beam is preferably operated in continuous wave operation (CW). It has been shown that a good heating of the glass layer is thereby achieved. Furthermore, continuous wave operation is technically easier to achieve than pulsed operation.

The laser beam of the second laser is preferably focused onto a plane surface by means of an optical element or system, wherein a circular beam profile is preferably produced. The diameter of the beam profile in the focal plane is preferably 1mm to 10 mm.

Other beam profiles, for example elongated, for example elliptical, beam profiles, can also be used.

The second laser is preferably moved over the glass surface at a speed of from 1m/min to 30m/min, particularly preferably from 5m/min to 20m/min, very particularly preferably from 10m/min to 15 m/min. Particularly good results are thereby achieved.

The power (output power) of the second laser beam is preferably 30W to 1kW, for example, 50W to 100W. With this power, sufficient heating of the glass layer can be achieved. But also significantly higher powers can be used.

The movement of the first and second laser beam and the cooling device along the cutting line can in principle be achieved by a movement of the glass sheet stack and/or by a movement of the laser and/or the cooling device.

Laser scanning devices known per se, which in the simplest case are one or more tiltable mirrors, are suitable for moving the laser beam over the stack of (in particular positionally fixed) glass sheets. The laser radiation can also be moved, for example, by moving an optical waveguide, for example, a glass fiber, over the stack of glass sheets. It can be simpler and therefore preferred to fix the position of the first and second laser beam and the cooling device and to move only the glass sheet stack.

The surface of the stack of glass sheets is preferably cooled after or during heating. By heating and cooling, thermal stresses are generated along the cutting line, which cause the desired fracture. The removal of the glass pane from the opening can additionally be supported by the application of a vacuum. The cooling is preferably effected by loading the glass surface with a coolant in gaseous form along the cutting line. The present invention is not limited to a specific coolant. The preferred coolant is cooled gas, since this cooling can be achieved simply and is cost-effective. Suitable gases are, for example, carbon dioxide or nitrogen or conventional compressed air.

The coolant is preferably brought onto the glass surface along a section line by means of a nozzle. The nozzle is preferably moved at the same speed and at the same position or immediately after the second laser over the glass surface. The time difference between the heating of the glass sheet stack by means of laser radiation and the cooling ("chilling") of the glass sheet stack is preferably 0ms to 500 ms. As a result, particularly suitable thermal stresses are generated which lead to effective fractures with clean fracture edges.

Preferably, the openings are positioned at the edges of the sheet, so that they correspond to the lateral recesses. Thereby, the thermal stress generated during the two-stage method can be conducted out to one side and the fracture of the glass pane can occur independently. Otherwise, in the case of an opening surrounded by glass, thermal stresses may lead to damage of the glass sheet.

The glass sheets can be thermally or chemically pre-tensioned, partially pre-tensioned or not pre-tensioned.

The type of glass sheet is not limited to a particular glass type. On the contrary, the method according to the invention can be applied to glass sheets of essentially any composition. The glass sheet comprises, for example, soda lime glass or borosilicate glass.

The invention also includes a method for making a composite glass sheet with through openings. The method comprises the following steps:

d) two glass sheets are stacked one on top of the other congruent so as to form a glass sheet stack consisting of an upper glass sheet and a lower glass sheet,

e) by means of the method according to the invention for producing an opening in a stack of glass sheets at least one through-going opening is produced in the upper and lower glass sheets,

f) two glass sheets are laminated into a composite sheet with a thermoplastic interlayer sandwiched between them.

Preferably, one of the glass sheets of the composite glass is subjected to a bending process prior to lamination. In a preferred embodiment, two glass sheets are subjected to a bending process. This is advantageous in particular in the case of strong bending in a plurality of directions in space (so-called three-dimensional bending).

Alternatively, one of the glass sheets is not pre-bent. This is advantageous in particular in the case of glass sheets with a very small thickness, since they have a film-like flexibility and can thus be adapted to the pre-bent glass sheet without having to be pre-bent on their own.

The glass sheets can be bent individually. Preferably, the glass sheets are bent congruently (i.e. simultaneously and by the same tool) together, since the shape of the individual sheets is thereby optimally matched to one another for the subsequent lamination.

The bending of the sheet is preferably performed before the laser machining in step e). If a conductive layer should be applied on the sheet, it is deposited on the desired sheet surface before bending. For example, the upper glass sheet and/or the lower glass sheet is first provided with an electrically conductive layer, for example by means of magnetron sputtering. In a next step, the two glass sheets are jointly bent congruent and provided according to step d). The laser machining according to step e) is not carried out until then. Since the sheet has achieved its final curvature, a 3D laser process is applied here. This has the advantage that the opening can be produced in its final size and the effect of the bending method on the opening does not have to be taken into account. In this way, manufacturing tolerances can be maintained significantly more precisely.

The thermoplastic intermediate layer is preferably provided as a film. The production of composite glass by lamination is effected by means of customary methods known per se to the person skilled in the art, for example autoclave methods, vacuum bag methods, vacuum ring methods, calendering methods, vacuum laminators or combinations thereof. The joining of the two glass sheets is usually effected here under the influence of heat, vacuum and/or pressure.

When the method for manufacturing a composite sheet is applied to the automotive field, the thickness of the sheet provided as an inner sheet is generally in the range of 0.3mm to 2.5mm, and the thickness of the sheet provided as an outer sheet is generally in the range of 0.8mm to 2.5 mm. In a preferred embodiment, the composite sheet is a wind-shielding sheet, wherein the thickness of the outer sheet is between 1.4mm and 2.1mm and the thickness of the inner sheet is between 0.8mm and 1.8 mm.

The invention also comprises the use of the composite sheet according to the invention with electrically attached components integrated in the interspace as a vehicle glazing, in particular a windshield, roof, side or rear window sheet.

Drawings

The invention is explained in more detail with the aid of the figures. The figures are schematic and not to scale. The drawings in no way limit the invention. In the drawings:

fig. 1a shows a top view of a stack of glass sheets, which is provided with an opening by means of the method according to the invention,

figure 1b shows a cross-section of one possible stack of glass sheets in figure 1a along the line a-a',

figure 1c shows a cross-section of one possible stack of glass sheets in figure 1a along the line a-a',

figure 2 shows an embodiment of the method according to the invention by means of three cross sections of the stack of glass sheets along the line a-a' in figure 1a during the method,

figure 3 shows another embodiment of the method according to the invention by means of three cross sections of the stack of glass sheets along the line B-B' in figure 1a during the method,

FIG. 4a shows a plan view of a composite glass sheet produced by means of the method according to the invention, and

FIG. 4b shows a cross-section of the composite glass sheet of FIG. 4a along line C-C'.

Detailed Description

Fig. 1a shows a top view of a glass sheet stack 1 consisting of a lower glass sheet 4 and an upper glass sheet 3, which are made of soda-lime glass. The opening 6 passes through both

glass sheets

3 and 4. The

glass sheets

3 and 4 are arranged one above the other so that the opening 6 is located in both

glass sheets

3 and 4 at exactly the same location. The contour of the opening 6 is predetermined by the cutting line L and corresponds to the shape of an equilateral trapezoid, wherein the base and the waist of the trapezoid have a length of 1.5cm and the side of the trapezoid opposite the base has a length of 0.7 cm. As can be seen in the figure, the openings 6 are arranged in the middle in the

glass sheets

3 and 4 of the glass sheet stack 1 and not in the form of lateral recesses at the edges of the sheets, as shown in fig. 4 a. The opening 6 has the shape of a hole which passes through all the sheets of the stack 1 and which is trapezoidal in cross-section. Fig. 1b and 1c show different embodiment variants of the basic structure of the glass stack 1 according to fig. 1a in detail.

Fig. 1b shows a possible cross section along the section line a-a' according to the basic configuration of fig. 1 a. The glass sheet stack 1 has an upper surface I and a lower surface IV. The upper glass sheet 3 has an upper surface I and a lower surface II, which is the same as the upper surface of the glass sheet stack 1. The lower glass sheet has an upper surface III and a lower surface IV which is identical to the lower surface of the glass sheet stack. Between the

glass sheets

3 and 4 is a separating agent 12 in the form of a polymethyl methacrylate-based powder. The separating agent 12 prevents the

glass sheets

3 and 4 from adhering to each other so strongly that they cannot then be separated. The separating agent 12 does not interfere with the method according to the invention. The thickness of the separating agent layer is shown strongly exaggerated for the sake of clarity. The lower glass sheet 4 has a thickness of 1.6mm and the upper glass sheet 3 has a thickness of 2.1 mm. Thus, the glass sheet stack 1 has a thickness of 3.7mm, since the separating agent 12 is not considered here.

The opening 6 is produced, for example, by a two-stage laser method, as shown in fig. 3. The opening has an inner edge K which extends along the cutting line L and through the total thickness of the glass sheet stack 1. The inner edge K is completely free of steps and is particularly smooth owing to the production by means of a laser method, so that no subsequent grinding or polishing is necessary. The opening 6 has an upper boundary Ko of the inner edge, which is in the plane of the upper surface I of the glass sheet stack, and a lower boundary Ku of the inner edge, which is in the plane of the lower surface IV of the glass sheet stack. The upper boundary Ko of the inner edge and the lower boundary Ku of the inner edge are arranged without offset, i.e. the opening 6 is equally large in the region of the upper surface I of the glass sheet stack and in the region of the lower surface IV of the glass sheet stack. A suitable housing with a straight outer edge for attaching components can be inserted perfectly into the opening 6.

Fig. 1c shows another possible cross section along the section line a-a' according to the basic configuration of fig. 1 a. This construction is essentially implemented as in fig. 1 b. The design differs from this in the embodiment of the inner edge K of the opening 6, which in this example is embodied at an angle. The variant shown is preferably produced by a laser separation method, as described, for example, in fig. 2. In this case, the upper boundary Ko of the inner edge is offset by 250 μm in the region of the upper surface I of the stack of glass sheets compared to the lower boundary Ku of the inner edge. The offset s between the upper limit of the inner edge and the lower limit of the inner edge is 250 μm, so that the opening 6 is greater in the region of the lower surface IV of the glass sheet stack than in the region of the upper surface I of the glass sheet stack. This achieves that the glass panes 7.1 and 7.2 are more easily detached downwards during manufacture. Furthermore, the inclined opening of the inner edge can also be used for later fixing of the housing for attaching the component.

Fig. 2 shows three cross sections of the stack of glass sheets in fig. 1a along the line a-a' during a possible embodiment of the method according to the invention. In contrast to fig. 1a, the opening 6 in fig. 2 has not yet been completely produced. Cross sections a), b1) and b2) are method steps a) and b) of the method according to the invention. Method step c) is not shown in this illustration. The method is performed at a glass sheet stack 1 as shown in fig. 1 b. In fig. 1b a completed glass sheet stack 1 with an opening 6 is shown.

The openings 6 are produced in this example by laser separation. The laser light 10 is first focused in step a) of the method from above the glass sheet stack 1 through a total thickness of 3.7mm onto the lower surface IV of the glass sheet stack. Focusing from above through the stack downwards enables a stepped processing with laser light because transparency in the laser-treated plane is lost. In this way, it is possible to machine a relatively thick stack of glass sheets with a laser and in one single method to produce openings precisely at the same location in both glass sheets. The lower surface of the stack of glass sheets corresponds to the plane E1 of the lower part. The laser is a pulsed nanosecond laser with a wavelength of 532nm, such as Nd: YAG laser. The laser 10 is first focused in the lower plane E1 and moved along the cutting line L. In step b1), it is shown how the laser is then focused in the plane E2 lying above it, which is arranged further above. The distance d in the vertical direction between two successive planes E1 and E2 is 25 μm. The distance d between two successive planes is preferably constant throughout the entire process involving stacking of glass sheets. This provides a particularly uniform edge and simplifies the method. Shown in step b2), the laser light 10 is focused in the plane of the upper surface I of the glass sheet stack. Thereby, the laser 10 passes through the total thickness of the glass sheet stack 1 along the cutting line L. Focusing on the lower surface IV in the first step and on the upper surface I in the last step provides glass panes 7.1 and 7.2 which can be detached particularly well. After the illustrated step b2), the lower glass pane 7.1 is first detached by applying a vacuum and the upper glass pane 7.2 is likewise detached by applying a vacuum. The edges K are embodied in a straight line in this example, i.e. the glass panes 7.1 and 7.2 can also be simultaneously released upwards and downwards by applying a vacuum, which reduces the production time. After detachment, no further post-treatment of the opening edges is required, so that the

sheets

3 and 4 can be directly further processed to form composite sheets.

Fig. 3 shows three cross sections of the stack of glass sheets in fig. 1a along the line B-B' during a possible embodiment of the method according to the invention. In contrast to fig. 1a, the opening 6 in fig. 3 has not yet been completely produced. The cross sections a), b1) and c) are method steps a), b) and c) of the method according to the invention. The method is performed at a glass sheet stack 1 as shown in fig. 1b along line a-a'. In fig. 1b a completed glass sheet stack 1 with an opening 6 is shown.

The opening 6 is produced in this example by a two-stage laser method. First the first laser light 10 focused inside the glass sheet stack 1 is moved along the desired cutting line L at a speed v1=1 m/s. The arrows shown in the figure indicate the direction of movement of the laser. The first laser light 10 is first focused in step a) onto the lower plane E1 inside the lower glass sheet 4. The first laser 10 is a pulsed laser with a pulse length of, for example, 10ps, a pulse train frequency of, for example, 25kHz, a power of, for example, 50W, and a wavelength of, for example, 1064 nm. Suitable lasers are, for example, switched-quality solid-state lasers, in particular diode-triggered (diodengepumpter) solid-state lasers. The

glass sheets

3 and 4 are transparent to the greatest extent at the wavelength of the first laser light. However, the highly concentrated laser radiation causes internal changes in the glass material, so-called "filaments". The variations are confined to the inside of the glass, which do not alter or damage the surface of the stack of glass sheets I, IV. The material variations are arranged along the cutting line L. The local weakening of the glass layer with material change defines the cutting line L as a theoretical breaking point. Each filament is produced by a pulse train of the first laser 10. The pulse trains separated from one another each contain, for example, 5 pulses and are generated using what are known as burst generators.

In a subsequent step, as shown in b1), the first laser light 10 is focused onto the plane E2 lying above it. The material change which has taken place in the plane E1 lying below it changes the transparency of the

glass sheets

3,4 to the first laser light 10. Therefore, processing in the vertical direction from the bottom to the top occurs. The spacing between two planes lying one above the other is approximately 2 mm. Thus, the first laser 10 need only move within the glass sheet stack 1 along the cutting line L in the two planes E1 and E2. The planes E1 and E2 are arranged in the lower glass sheet or in the upper glass sheet. Thereby, a particularly good separation of the two

glass sheets

3,4 is achieved.

In a subsequent step c), the second laser 11 is moved along the cutting line L at a speed v2=1 m/s. The second laser 11 is, for example, CO having a wavelength of 10.6 [ mu ] m and a power of 50W₂The beam of the laser in continuous wave operation. The second laser 11 is in a circleIs focused onto the glass surface I. On the glass surface I, the profile has a diameter of 5mm, for example. The second laser 11 is then focused onto the lower glass surface IV so that the two

glass sheets

3 and 4 are heated by the second laser 11, thereby heating the entire glass sheet stack 1 along the cutting line L. Alternatively, it is also possible to focus further laser light having the same characteristics as the second laser light 11 onto the lower surface IV from below the glass sheet stack 1. In this case, the process time can be shortened when the second laser 11 and the further laser are moved simultaneously along the cutting line.

Immediately after the second laser 11 or at the same location as the laser 11, the nozzle 13 moves along the cutting line L and is aligned with the surface of the glass sheet stack. The second laser 11 and the nozzle 13 are here moved at the same speed. The stack of glass sheets is loaded with a coolant, for example with compressed air, by means of the nozzle 13. Preferably, the laser 11 and the nozzle 13 are aligned at the same position at the surface. The rapid cooling of the

heated glass sheets

3,4 causes thermal stresses which cause the

glass sheets

3 and 4 to break along the cutting line L. The areas that have cooled are shown in the figure by dark shading. As already explained, the breaking of the glass layer occurs independently as a result of thermal stress. Thus, active fracturing by applying pressure can be dispensed with. This enables a small radius of curvature to be achieved and material scrap to be reduced. Furthermore, the method leads to smooth cut edges without disturbing damage, such as microcracks. Only one nozzle 13 is shown in the figure, which cools the upper surface of the stack of glass sheets. The further nozzles 13 are preferably aligned with the lower surface IV of the glass sheet stack from below the glass sheet stack 1.

Fig. 4a and 4b show a top view and a cross section of a possible embodiment of a composite sheet 2 with a through-opening 6, in which a housing 5 for electrical attachment components is inserted. Fig. 4a shows a top view of a composite sheet 2 comprising an upper sheet 3 and a lower sheet 4, which are laminated to each other via a thermoplastic intermediate layer 9. The composite sheet 2 is used as a wind shielding sheet for an automobile. The upper sheet 3 is provided as an outer sheet 3 and the lower sheet 4 is provided as an inner sheet. Both sheets are made of soda-lime glass. The thermoplastic interlayer 9 is a polyvinyl butyral film having a thickness of 0.76mm measured prior to the lamination process. The composite sheet 2 has an opening 6 in which a housing 5 for electrical attachment means is embedded. The opening has the shape of a lateral recess. The housing is a polymer housing and can be inserted into the opening 6. In this example, the polymer housing ends flush with the outer sheet 3. This is not necessarily required and can also be implemented such that the polymer housing protrudes beyond the outer sheet 3.

List of reference numerals

(1) Glass sheet stack

(2) Composite sheet

(3) Upper glass sheet

(4) Lower glass sheet

(5) Housing for electrically attached components

(6) Opening of the container

(7.1,7.2) lower or upper glass pane delimited by cutting lines

(8) Electrical attachment component

(9) Thermoplastic intermediate layer

(10) Laser, first laser

(11) Second laser

(12) Separating agent

(13) A nozzle for cooling; cooling device

L-shaped cutting line

K-opening inner edge

Upper boundary of Ko inner edge

Lower boundary of Ku inner edge

v₁Speed of movement of the first laser

v₂Speed of movement of the second laser

I upper surface of glass sheet stack 1, upper surface of upper glass sheet 3

II lower surface of upper glass sheet 3

Upper surface of lower glass sheet 4

Lower surface of IV glass sheet stack 1

Claims

1. Method for producing an opening (6) in a horizontally supported glass sheet stack (1) by laser machining,

wherein the glass sheet stack (1) comprises an upper glass sheet (3) and a lower glass sheet (4), the opening (6) passes through the total thickness of the glass sheet stack (1), and the glass sheet stack (1) has a thickness of at least 2.5mm,

wherein the method comprises the following steps:

a) focusing a laser light (10) from above the glass sheet stack (1) through the thickness of the glass sheet stack (1) onto a lower plane,

b) repeatedly moving the laser (10) along a cutting line (L), wherein the focal point of the laser (10) is in a plane arranged further up in each repetition,

c) removing the glass panes (7.1,7.2) delimited by the cutting lines (L) from the lower glass sheet (4) and the upper glass sheet (3) while exposing the opening (6).

2. Method according to claim 1, wherein the upper glass sheet (3) and the lower glass sheet (4) are arranged congruent to each other and wherein the upper glass sheet (3) and/or the lower glass sheet (4) are curved in three dimensions.

3. Method according to one of claims 1 to 2, wherein the removal of the glass panes (7.1,7.2) delimited by the cutting line (L) is effected by applying a vacuum to the glass panes (7.1,7.2), wherein preferably a lower glass pane (7.1) is first removed from the lower glass sheet (4) and then an upper glass pane (7.2) is removed from the upper glass sheet (3).

4. A method according to any one of claims 1 to 3, wherein the opening (6) has the shape of a hole.

5. The method according to any of claims 1 to 4, wherein the laser machining is performed by laser separation with pulsed nanosecond laser light (10) and a wavelength of 300 to 800 nm.

6. The method according to claim 5, wherein the laser light (10) is first focused through the thickness of the entire glass stack (1) onto the lower surface of the glass sheet stack (1) and the laser machining is continued until the laser light (10) is focused onto the upper surface of the glass sheet stack (1).

7. Method according to any one of claims 5 to 6, wherein the inner edge (K) of the opening (6) is inclined such that the upper limit (Ko) of the inner edge in the area of the upper surface (I) of the stack of glass sheets is staggered by 100 to 500 [ mu ] m, preferably by 150 to 350 [ mu ] m, compared to the lower limit (Ku) of the inner edge in the area of the lower surface (IV) of the stack of glass sheets.

8. The method according to any one of claims 1 to 4, wherein the laser machining is performed with a first laser (10) and a second laser (11), wherein the steps (a) and (b) are performed with a pulsed first laser (10) having a pulse length of less than 100ps for generating filaments, wherein in step (c) the second laser (11) is moved along the cutting line (L) in a continuous wave run at a wavelength of 1 μm to 20 μm for heating the glass sheets (3,4), and preferably cooling the stack of glass sheets (1) along the cutting line (L).

9. Method according to claim 8, wherein the spacing in the vertical direction between two planes following one another in steps (a) and (b) is between 1mm and 3mm, preferably between 1.5mm and 2.5 mm.

10. The method according to any of claims 8 or 9, wherein the second laser light (11) is focused once onto the lower surface (IV) of the glass sheet stack and once onto the upper surface (I) of the glass sheet stack.

11. The method according to any one of claims 8 to 10, wherein the first laser light (10) has a wavelength between 300nm and 1200nm, preferably between 350nm and 1100 nm.

12. The method according to any one of claims 8 to 11, wherein the second laser (11) is CO₂And (4) laser.

13. Method for producing a composite glass sheet (2) with through-openings (6), wherein,

d) two glass sheets (3,4) are stacked one on top of the other congruent on top of the other in a glass sheet stack (1) consisting of an upper glass sheet (3) and a lower glass sheet (4),

e) -creating at least one through opening (6) in the upper glass sheet (3) and the lower glass sheet (4) by means of the method according to any one of claims 1 to 12,

f) the two glass sheets (3,4) are laminated to form a composite sheet (2) with a thermoplastic intermediate layer (9) interposed therebetween.

14. Method according to claim 13, wherein a housing (5) for an electrical attachment means (8) is integrated in the through-opening (6), wherein this is done before or after step (f).

15. Use of the composite sheet (2) manufactured in the method according to any one of claims 13 or 14 as a vehicle glazing, in particular as a windscreen sheet, a roof sheet, a side sheet or a rear window sheet.