Method for producing internal holes in chemically strengthened glass sheet articles

Abstract

The invention relates to a method for producing an inner hole (1) in a glass pane (10) having a thickness T, in which an inner part (2) is separated from the glass pane along a separation line (3). The method comprises at least the following steps, carried out in the following order: a filament cutting step, in which filament-shaped defects are produced in the form of submicron hollow channels that are adjacently aligned along a separation line in the volume of the glass sheet article, in which the defects are produced by laser pulses of an ultrashort pulse laser, the material of the glass sheet article is transparent to the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass sheet article, the plasma causing the filamentous defects; and wherein the incident points of these laser pulses on the glass sheet are displaced on the surface of the glass sheet along the separation line; to introduce filamentous defects that are adjacently aligned along a separation line; followed by a step of chemically strengthening the glass sheet product; followed by a separation step of separating the inner portion from the glass sheet article at adjacently aligned filamentous defects along a separation line by irradiating the inner portion with an ablative laser to ablate at least one section (4) having two end points located on the separation line, substantially having a thickness T, and a width W equal to or greater than 150 [mu] m (W > = 150 [mu] m).

Description

1. TECHNICAL FIELD

[0001] The present invention relates to a laser-assisted method for manufacturing internal holes in a chemically strengthened glass sheet product. 2. BACKGROUND

[0002] In the field of cover glasses for electronic devices, glazing for building materials, glazing for vehicles, etc., it is often required to have high strength for safety reasons and to comply with safety specifications required for such glazing. Therefore, the glazing is often subjected to a chemical strengthening process to obtain a glazing or cover having high stress resistance. In the chemical strengthening process, alkali metal ions having an atomic diameter larger than that of the original atoms are introduced into the surface of the glass substrate. Thus, a compressive stress layer is formed on the surface of the glass substrate, thereby increasing the strength of the glass substrate.

[0003] In conventional methods, many glass pieces are first cut into a final shape, and then chemically strengthened, which can cause a large number of scratches and damage if not handled with sufficient care. In order to avoid these drawbacks, methods have been developed, such as strengthening glass having a large size before cutting the glass pieces into their final shape.

[0004] For example, patent EP 3345877 B describes a method combining filamentation cutting and chemical strengthening, in which a chemical strengthening treatment is applied beforehand to a large-size glass material, which is then cut by filamentation to produce a chemically strengthened glass product. WO 2019 / 154782 proposes a method for manufacturing a coated glass product, comprising a filamentation step for separating a glass product from a glass substrate, followed by a step of chemical strengthening of the glass substrate, followed by a coating step.

[0005] In practice, the filamentation cutting technique is generally used to create glass products from a glass panel of larger size. The profile of the glass product to be produced from the glass panel is generated by a filamentation separation line being shaped by a filamentation cutting. In addition, a filamentation breaking line will be further created around the profile of the glass product to facilitate the removal of the glass product from the glass panel. Several separation techniques are used: a typical technique is to initiate a crack at a controlled location with a mechanical device (diamond tool, cutting wheel, etc.) such that the crack will propagate along the filamentation separation line. It is known to create additional cavities in the vicinity of the filamentation separation line to provide a controlled crack propagation along the filamentation separation line. Initiating the crack for the first time at the appropriate location will cause the glass product to separate from the initial glass panel. Although this technique allows the glass product to be obtained without affecting its quality, this mechanical separation damages the initial glass panel from which the glass product originates, and thus cannot be used to create internal holes.

[0006] Another technique is to create a stress in the glass plate substrate by bending the substrate, where the material is stretched in one half of its volume, creating a tensile stress in this half, while being compressed in the other half of the volume, creating a compressive stress there. However, bending of the glass substrate is not suitable for removing internal parts, especially small size internal parts.

[0007] Indeed, even if the glass has enough internal stress to start self-separation after the defect line is formed, the geometry of the cut profile can prevent the release of the internal glass part. This is the case for most closed profiles or internal profiles, such as simple holes or slots. Due to the presence of compressive forces in the glass plate, the internal part of the hole will remain in place. The crack can propagate between the defects of the perforation, but there is no space to allow the internal part to fall off the mother sheet.

[0008] However, it is possible to use a mechanical separation technique to remove the internal part of the glass by exerting some pressure on it. However, when using such a mechanical separation technique, the edges of the internal part and the edges of the internal hole will rub against each other, resulting in poor edge quality, which is not suitable for applications requiring very sharp edges.

[0009] Other techniques for removing internal parts of a glass article to create such internal holes have been designed in the art, typically based on thermal compaction. For example, US2018134606 discloses a method for separating a portion from a glass sheet element having a thickness of at least 2 millimeters. The method comprises creating a filamentous damage along a separation line; and heating and / or cooling the glass sheet element to induce expansion and / or contraction such that the portion detaches from the body portion along the separation line.

[0010] However, it has been found that separation techniques based on thermal compaction cannot be used to manufacture small size internal holes. Indeed, such techniques are based on the expansion of the body portion and / or the contraction of the portion to be removed, where the dimensional changes of these portions are different from each other. However, in the case of small size of the portion to be removed, the temperature difference between the glass article and the internal part to be removed is too high, resulting in an ineffective use of this temperature difference without degrading the body portion, even if it is not destroyed.

[0011] Therefore, there is still a need to find an appropriate method to manufacture small size internal holes with high quality edges in a chemically strengthened glass article. 3. SUMMARY

[0012] Other aspects and advantages of embodiments will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the described embodiments.

[0013] The invention relates to a method for manufacturing an internal hole in a glass sheet product having a thickness T, wherein an internal portion is separated from the glass sheet product along a separation line. The method comprises at least the following steps performed in the following order: a) a filamentation cutting step, wherein filamentary defects are created in the volume of the glass sheet product in the form of sub-micrometric hollow channels aligned adjacently along the separation line, wherein the defects are created by laser pulses of an ultra-short pulsed laser, wherein the material of the glass sheet product is transparent to the laser pulses; wherein the laser pulses create a plasma within the volume of the glass sheet product, which plasma induces the filamentary defects; and wherein the points of incidence of the laser pulses on the glass sheet product are displaced on the surface of the glass sheet product along the separation line; to introduce filamentary defects aligned adjacently along the separation line; b) a step of chemically strengthening the glass sheet product; e) a separation step for separating the internal portion from the glass sheet product at the filamentary defects aligned adjacently along the separation line by irradiating the internal portion with an ablation laser to ablate at least one segment, wherein the at least one segment has two end points located on the separation line, substantially has the thickness T, and has a width W equal to or greater than 150 pm (W > 150 pm).

[0014] In another embodiment, the invention relates to a corresponding method, wherein a glass sheet product having a thickness T and comprising an internal hole is manufactured from a glass substrate of larger dimensions. The method comprises the following steps performed in the following order: a1 ) a filamentation cutting step for creating the at least one glass sheet product along a separation line separating the glass substrate into the at least one glass sheet product to be separated, and a2) a filamentation cutting step for separating an internal portion from the glass sheet product along a separation line defining the internal portion to be separated, wherein filamentary defects are created in the volume of the glass substrate in the form of sub-micrometric hollow channels aligned adjacently along the separation lines, wherein the defects are created by laser pulses of an ultra-short pulsed laser, wherein the material of the glass substrate is transparent to the laser pulses; wherein the laser pulses create a plasma within the volume of the glass substrate, which plasma induces the filamentary defects; and wherein the points of incidence of the laser pulses on the glass substrate are displaced on the surface of the glass substrate along the separation line; to introduce filamentary defects aligned adjacently along the separation lines; b) a step of chemically strengthening the glass substrate; and e) e1 ) a separation step for separating the glass sheet product from the glass substrate, e2) a separation step of separating the inner portion from the glass sheet product at the adjacent aligned filament-like defects along the separation line by irradiating the inner portion with an ablative laser to ablate at least one segment, wherein the at least one segment has two end points lying on the separation line, has substantially a thickness T, and has a width W equal to or greater than 150 pm (W > 150 pm).

[0015] In both embodiments, the method preferably further comprises a cleaving step d) performed along the separation line, by which the filaments are interconnected, the separation step e) being performed immediately after such cleaving step. Preferably, a coating step c) of the glass sheet product or glass sheet substrate is performed after the chemical strengthening step b) and, if present, before the cleaving step d).

[0016] The surface of the inner hole created within the glass sheet product will preferably be equal to or less than 300 mm 2 (S < 300 mm 2 ); preferably equal to or less than 150 mm 2 (S < 150 mm 2 ), preferably equal to or less than 120 mm2(S < 120 mm 2 ), more preferably equal to or less than 80 mm2(S < 80 mm 2 ). The surface of the inner hole will typically be equal to or greater than 3 mm 2 (S > 3 mm2), preferably equal to or greater than 5 mm2(S > 5 mm2).

[0017] Within the separation step e1), the ablative laser will ablate at least one segment within the inner portion, the at least one segment being preferably equal to or greater than 200 pm (W > 200 pm), preferably equal to or greater than 250 pm (W > 250 pm). In one embodiment, there are at least two segments within the inner portion. In a preferred embodiment, the at least one segment extends along at least 50%, preferably at least 75%, more preferably 100% of the circumference of the inner portion.

[0018] The present application further relates to a glass sheet product obtained according to the method of the present application. The thickness of the glass sheet product will preferably be at least 0.1 mm, preferably at least 0.3 mm, more preferably at least 0.5 mm, and its thickness will preferably be less than 20 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1.5 mm, more preferably less than 1 mm. Preferably, the glass sheet product has a soda-lime silicate glass composition, an alumino-silicate glass composition or an alkali-alumino-silicate glass composition. The CTE of the glass sheet product is typically from 70 10-7 / °C to 100 10-7 / °C, preferably from 80 10-7 / °C to 95 10-7 / °C. 4. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1a A top view of a glass sheet article including an internal hole is shown according to one embodiment of the present application. Figure 1b The same glass sheet article is shown where the internal portion to be removed to create the internal hole, the separation line, and the ablation section have been illustrated.

[0020] Figure 2 A top view of a glass substrate including a glass sheet article having an internal hole is shown according to another embodiment of the present application.

[0021] Figure 3 illustrates several embodiments of the present application having internal portions to be removed with different ablation sections. Figure 3a A top view of an internal portion having a rectangular shape is shown where the ablation section of the internal portion extends along 100% of the perimeter of the internal portion. Figure 3b A top view of an internal portion having an elliptical shape is shown where the ablation section of the internal portion extends along the longest diameter of the internal portion. Figure 3c A top view of an internal portion having a circular shape is shown having two perpendicular ablation sections. Figure 3d A top view of an internal portion having a circular shape is shown where the ablation section of the internal portion is in the shape of a moon extending along 50% of the perimeter of the internal portion. Figure 3e A top view of an internal portion having a circular shape is shown where the ablation section of the internal portion extends along 100% of the perimeter of the internal portion.

[0022] Figure 4 is a schematic representation of the method according to the first aspect of the present application.

[0023] Figure 5 is a schematic representation of the method according to the second aspect of the present application. 5. DETAILED DESCRIPTION

[0024] It is an object of the present application to provide a chemically strengthened glass sheet article including an internal hole having a high quality. Current available manufacturing techniques are not able to provide the required quality and / or are not suitable for creating small size internal holes. It has been surprisingly found that the production method of the present application overcomes the drawbacks of the prior art.

[0025] It is an object of the present invention to allow an inner portion to be separated from a chemically strengthened glass sheet product with high efficiency and high quality; while minimizing the risk of detrimental cracking in the remaining bulk portion of the glass product. It is a further object to provide a simple, efficient and fast production method of chemically strengthened glass products, optionally comprising an inner hole. High quality is to be understood herein that the edge of the inner hole has to be sharp, at least partially strengthened, and free of any coating material when a coating step is added to the manufacturing process of the present invention.

[0026] It has further been found that the production method of the present invention is not only time and cost efficient, but also maintains the stiffness of large size glass sheets in case of a large number of inner holes within the glass sheet product, and thereby greatly simplifies handling and transportation, by using the same fine filiation cutting step, chemical strengthening step, possible coating step for producing such glass sheet products from much larger glass substrates.

[0027] As Figure 1a and Figure 1b shown, the present invention in a first embodiment relates to a method for manufacturing an inner hole (1) in a glass sheet product (10) having a thickness T, wherein an inner portion (2) is separated from the glass sheet product along a separation line (3). The separation line (3) separates the glass sheet product into the inner portion to be separated and the remaining bulk portion of the glass sheet product.

[0028] Manufacturing an inner hole in a glass sheet product comprises separating an inner portion along a separation line in the form of a closed loop. The inner hole can have any shape. When the inner hole shape comprises straight line segments, such straight line segments will preferably be connected by a bend angle to form a closed loop. Preferably, the inner hole will have an elliptical shape, more preferably a circular shape. The glass sheet product can comprise one or more inner holes of the same shape or different shapes and of the same size or different sizes.

[0029] The present invention is particularly useful for creating small size inner holes in a glass sheet product. Small size is to be understood as having a surface typically less than 300 mm 2 , preferably less than 150 mm 2 , preferably less than 120 mm 2 , more preferably less than 80 mm 2 . Typically, the method of the present invention will be used to create a circular inner hole having a surface of at least 3 mm 2 , preferably at least 5 mm 2 .

[0030] As Figure 4As shown, in the first embodiment, the method of the present application first comprises a filigree cutting step (step a)), followed by a chemical strengthening step (step b), optionally can be followed by a coating step (step c)) and preferably a cleaving step (step d)), and finally a separation step (step d)).

[0031] Correspondingly, the method of the present application comprises a filigree cutting as a first step. The glass sheet product is filigree cut by laser pulses, i.e. micro-perforations are made along at least one defined separation line. This separation line delineates a closed loop and defines an inner contour of an inner portion to be removed. Subsequently, a chemical strengthening step is performed on the glass sheet product. The method can then optionally comprise a coating step. Then, a cleaving step is performed, preferably along the separation line of the inner contour, by which the filaments are interconnected such that the inner contour is separated from the main portion, but not detached from the main portion.

[0032] The method of the present application finally comprises a separation step, wherein the inner portion (2) is separated from the glass product (10) by irradiating the inner portion with an ablating laser to ablate at least one segment (4) of this inner portion. The ablation of the segment of the inner portion should be large enough to make the inner portion smaller, thereby releasing the inner portion. Due to this specific ablation step, the edges of the inner hole generated within the glass sheet product portion can maintain the very high edge quality obtained via the filigree cutting step. Moreover, the edges benefit from the chemical strengthening step of the previous operation. Filamentation cutting step (a)

[0033] Laser filigree cutting is a technique to cut out a glass product from a glass sheet. Irreversible damage in the form of filaments is induced in the glass substrate by high-energy laser pulses, and a series of aligned such damages will allow the separation of the glass. The filaments are generated by ultra-short laser pulses which due to the Kerr effect cause self-focusing to occur inside the glass until the energy density becomes so high at some point that a plasma is ignited. A plasma explosion occurs during which the glass undergoes irreversible damage around the plasma generation site. From this, further radiation will be emitted and will again experience self-focusing and end in another plasma explosion. This effect repeats several times depending on the intensity.

[0034] Accordingly, the first step a) of the method of manufacturing internal holes in a glass sheet product is a filamentation cutting step, wherein filament-like defects in the form of sub-micron hollow channels aligned adjacently along a separation line are created in the volume of the glass sheet product, wherein these defects are created by laser pulses of an ultra-short pulsed laser, wherein the material of the glass sheet product is transparent to said laser pulses; wherein these laser pulses create a plasma within the volume of the glass sheet product, which plasma causes these filament-like defects; and wherein the points of incidence of these laser pulses on the glass sheet product are displaced on the surface of the glass sheet product along the separation line; to introduce filament-like defects aligned adjacently along a separation line;

[0035] Details of the filamentation cutting step of the present invention are summarized in the following with reference to paragraphs

[0037] to

[0074] of European patent EP3 345 877 B granted to AGC Inc. on 23 March 2022 regarding step S130 and referring to figures 3 to 7, which is incorporated herein by reference and is summarized as follows:

[0036] A glass material is irradiated with a laser to form an in-plane hole region on a first main surface of the glass material. Two or more internal hole rows are formed from the in-plane hole region toward a second main surface. The "in-plane hole region" indicates two or more surface holes formed in a predetermined arrangement. In addition, the "internal hole row" indicates a linear region having one hole or two or more holes formed inside the glass material from the first main surface toward the second main surface.

[0037] Each surface hole corresponds to a position of irradiation of the laser on the first main surface, and has a diameter of, for example, 1 to 5 pm. The diameter of the surface hole varies depending on the laser irradiation conditions, the type of the glass material, and the like. The distance P between the centers of adjacent surface holes can be determined based on the composition and thickness of the glass material, the laser processing conditions, and the like. For example, the distance P between the centers of adjacent surface holes can be in the range of 2 to 10 pm. The distance P between the centers of the surface holes does not necessarily have to be equal at all positions, and can differ depending on the position. That is, the surface holes can be arranged at irregular intervals. The shape, size, and pitch of the internal holes are not particularly specified. For example, the shape of the hole can be, for example, circular, elliptical, rectangular, triangular, or the like when viewed from the Y direction. Further, the maximum dimension of the hole (typically corresponding to the length of the hole in the direction of extension along the internal hole row) can be, for example, in the range of 0.1 to 1000 pm when viewed from the Y direction. Each internal hole row has a corresponding one of the surface holes.

[0038] As understood from the foregoing, the in-plane void region represents a region that is not actually formed as a continuous "line" but a virtual linear region formed by connecting the respective surface voids. Similarly, the inner void row represents a region that is not actually formed as a continuous "line" but a virtual linear region formed by connecting the respective voids.

[0039] The in-plane void region and the inner void row as described above can be formed by irradiating the first major surface of the glass material with a laser. More specifically, first, the laser is applied to a first position of the first major surface of the glass material to form a first inner void row including surface voids from the first major surface to the second major surface. Next, the laser application position with respect to the glass material is changed so that the laser is applied to a second position of the first major surface of the glass material to form a second inner void row including second surface voids from the first major surface to the second major surface. The in-plane void region and the corresponding inner void row can be formed by repeating this operation.

[0040] In a case where the inner void row having a void sufficiently close to the second major surface is not formed by one laser application, that is, in a case where the void closest to the second major surface is at a position sufficiently away from the second major surface (for example, the distance of the void closest to the second major surface from the first major surface is equal to or less than half the thickness of the glass material), two or more laser applications can be performed to substantially the same position. Note that the "substantially the same (laser application) position" indicates not only a case where the two positions match exactly but also a case where the two positions can slightly deviate from each other (for example, the maximum deviation is 3 μm). For example, two or more laser applications are performed along a first direction parallel to the first major surface of the glass material to form a first in-plane void region and a corresponding inner void row (first pass), and then the laser is applied to substantially the same direction and substantially the same position as the first pass (second pass), thereby forming a "deeper" inner void row corresponding to the first in-plane void region.

[0041] In the voids constituting the inner void row, the distance from the center of the void closest to the second major surface to the second major surface can preferably be in the range of 0 to 10 μm, but this distance can vary with the thickness of the glass material.

[0042] In particular, closely spaced micron-scale hollow channels, that is, hollow channels having a diameter of less than 5 microns, are produced. The length of the filament-like damage produced by the laser pulses is preferably at least 200 microns, more preferably at least 500 microns. For this purpose, a suitable pulse energy and pulse duration are chosen. The specified minimum length of the filament-like damage is advantageous because they facilitate the separation of the part.

[0043] It is particularly advantageous for producing long filament-like lesions to operate the ultra-short pulsed laser in so-called burst mode. In this mode of operation, the laser pulses are not emitted as single pulses, but as a sequence of pulses emitted in rapid succession, which together form a burst, i.e. a so-called pulse burst. Accordingly, one embodiment of the present application envisages the ultra-short pulsed laser to be operated in the form of temporally successive laser pulses, i.e. in the form of pulse bursts, wherein each of these pulse bursts preferably produces a respective one filament-like lesion. The energy of such a pulse burst is typically slightly higher than the single pulse in the conventional single-shot operation. However, the pulses of the pulse burst contain significantly less energy than the single pulse. Moreover, the pulse energy of the pulses typically decreases within the pulse burst.

[0044] A suitable laser source according to the present application is a neodymium-doped yttrium aluminum garnet laser with a wavelength of 1064 nanometers. The laser source is in particular operated with a repetition rate between 10 kHz and 1 MHz, preferably between 30 kHz and 300 kHz, most preferably between 35 kHz and 200 kHz. The scan rate can preferably be chosen such that the spacing between adjacent filament-like lesions will be in the range of 2 micrometers to 10 micrometers, depending on the repetition rate.

[0045] In this case, a suitable pulse duration of the laser pulses is in the range of less than 100 picoseconds, preferably less than 100 picoseconds. The pulse duration can even be less than 30 picoseconds. Most advantageously, the laser source is operated at a typical power in the range of from 30 to 500 watts. According to one advantageous embodiment of the present application, a pulse energy of more than 200 microjoules is applied in the pulse burst, further advantageously a total pulse burst energy of more than 400 microjoules is applied in order to achieve the filament-like lesion.

[0046] In case the ultra-short pulsed laser is operated in burst mode, the repetition rate is the frequency of the repeated burst emission. The pulse duration is essentially independent of whether the laser is operated in single-pulse mode or in burst mode. The pulses within the burst typically have a similar pulse length as the pulses in the single-pulse mode.

[0047] During the micro-perforation employed in the present application, no material is removed from the separation slit except for an extremely small amount of material. When the filament-like lesion has been introduced, the two parts to be separated will still be essentially connected to each other. Once the micro-perforation has been completed, a predetermined breaking line exists in the material along the separation line, along which the material has not yet been separated, but can easily be separated if a suitable stress is induced in the material. In particular, a cleaving step is suitable for this purpose.

[0048] Due to the precise separation process by the filigree cutting step a), a very high edge quality is achieved at the cutting edge. Since the quality of the glass edge is of great importance for the bending strength of the glass element, the high edge quality also increases the bending strength of the main body portion of the glass article. In fact, the possible cleanest glass edge with as little and as small chipping, notching and other unevennesses and preferably without chipping, notching and other unevennesses helps to reduce the risk of glass breakage. In particular, these edges are distinguished by a chipping of less than 10 micrometers, more preferably less than 5 micrometers, and a roughness Rz value of less than 30 micrometers, preferably 20 micrometers, more preferably 10 micrometers. Chemical strengthening step - step (b)

[0049] The method for manufacturing an internal hole in a glass article of the present invention will further comprise a chemical strengthening step b) immediately after the filigree cutting step a) and before the separation step e) and, if present, also before the coating step c) and / or the cleaving step d).

[0050] Details of the preferred chemical strengthening step of the present invention are found in the paragraphs

[0075] to

[0089] regarding step S120 in European patent EP 3 345 877 B to AGC Inc. granted on 23 March 2022, which is incorporated herein by reference.

[0051] The conditions of the chemical strengthening treatment are not particularly limited. The chemical strengthening can be performed, for example, by immersing the glass sheet article, on which at least one separation line defining a contour line of at least one glass article is defined, in a molten salt of 380°C to 500°C for 1 minute to 72 hours.

[0052] As the molten salt, a nitrate salt can be used. For example, when replacing lithium ions contained in the glass sheet article with larger alkali metal ions, a molten salt containing at least one of sodium nitrate, potassium nitrate, rubidium nitrate, and cesium nitrate can be used. Further, in the case of replacing sodium ions contained in the glass sheet article with larger alkali metal ions, a molten salt containing at least one of potassium nitrate, rubidium nitrate, and cesium nitrate can be used. Furthermore, when replacing potassium ions contained in the glass sheet article with larger alkali metal ions, a molten salt containing at least one of rubidium nitrate and cesium nitrate can be used. In addition, one or more salts such as potassium carbonate can be further added to the molten salt. In this case, a low-density layer having a thickness of 10 nm to 1 pm can be formed on the surface of the glass sheet article.

[0053] By subjecting the glass sheet product, on which at least one separation line defining a contour line of the inner portion is defined, to a chemical strengthening treatment, a compressive stress layer can be formed on both surfaces of the glass sheet product and on the edge of the inner hole. The thickness of the compressive stress layer corresponds to the penetration depth of the alkali metal ions used for the substitution. For example, in the case of using potassium nitrate to replace sodium ions with potassium ions, the thickness of the compressive stress layer can be 8 pm to 27 pm for soda-lime glass and 10 pm to 100 pm for aluminosilicate glass. In the case of aluminosilicate glass, the penetration depth of the alkali metal ions is preferably 10 pm or more, more preferably 20 pm or more.

[0054] Thus, since the glass sheet product has been chemically strengthened, it is easier to ensure the scratch-free appearance and the strength of the manufactured glass sheet product compared to conventional manufacturing methods. Therefore, the manufacturing yield can be improved. Moreover and more particularly, after separating the inner portion by the separation line, the edge of the glass product having the inner hole is also chemically enhanced. Thus, the glass product obtains sufficient strength. Therefore, the quality of the chemical strengthening on the edge of the inner hole is improved, thereby reducing the loss level, more particularly the edge effect. Optional but preferred coating step c)

[0055] In a preferred embodiment of the present application, the method will comprise an additional coating step c) after the chemical strengthening step b) and before the separation step e) and, if present, also before the cleaving step d).

[0056] Indeed, in a preferred embodiment of the present application, the glass sheet product is subjected to a coating treatment before separating the inner portion from the glass sheet product by the at least one separation line. Indeed, it has been found that when such a coating step is performed before separating the inner portion of the glass sheet product from the remaining portion, it allows coating the remaining portion of the glass sheet up to the separation line while avoiding the dripping of the coating along the edge of the inner hole which would occur in case the inner hole has been created prior to the coating step. The method of the present application not only can provide very sharp and neat edges, partially enhanced edges in a very efficient, simplified and fast production process, but also can provide a very neat coated surface.

[0057] According to one embodiment of the present application, the glass sheet product is coated with at least one thin layer which is transparent and conductive. The transparent and conductive thin layer according to the present application can for example be a layer based on Sn02:F, Sn02:Sb or ITO (Indium Tin Oxide), ZnO:Al or also ZnO:Ga.

[0058] According to another advantageous embodiment of the application, the glass sheet product is coated with at least one anti-reflective layer. The anti-reflective layer according to the application can for example be a layer based on porous silica with a low refractive index, or it can consist of several layers (stack), in particular of a stack of layers with alternating dielectric material layers with a low refractive index and a high refractive index and terminating with a layer with a low refractive index. It is also possible to use a textured glass sheet product. It is also possible to use etching techniques or coating techniques to avoid reflections.

[0059] According to another embodiment, the glass sheet product is coated with at least one anti-fingerprint layer or has been treated in order to reduce or prevent fingerprints. Such a layer or such a treatment can be combined with a transparent and conductive thin layer deposited on the opposite face. Such a layer can be combined with an anti-reflective layer deposited on the same face, the anti-fingerprint layer being on the outside of the stack and thus covering the anti-reflective layer.

[0060] According to another embodiment, the glass sheet product is a digital or screen-printed product, an etched product.

[0061] According to another embodiment, the glass sheet product is coated with a paint / enamel, an antibacterial glass coating, etc. According to the application, the term "coated / coating" can be a coating itself, but also a paint, but also a surface treatment able to modify the properties of the glass surface (mechanical properties, chemical properties, light energy properties, biological properties, electrical properties, aesthetic properties, etc.) by addition, removal or physical-chemical modification of the surface material (at "glass visible" temperatures below its Tg).

[0062] According to another embodiment, the glass sheet product is coated with a coating chosen from the following non-exhaustive list of coatings: low-emissivity coatings, solar control coatings, diamond-like coatings, self-cleaning coatings (Tio2, etc.), ion-implanted coatings, lacquer coatings (of the Lacobel type), silver or dielectric coatings, conductive inks, infrared transparent inks, translucent inks, fluorescent or up-conversion materials, "reticulated structure" depositions (silver nanowires, carbon nanotubes), (nano)laser structuring treatments of the surface, security films, double-sided adhesive, sol-gel coatings (with all their functionalities, i.e. colour modification, enzyme integration, etc.), solar-type coatings and thin films, etc., acid etching, sandblasting, engraving, etc. of the surface.

[0063] The coating(s) can be provided on one and / or both surfaces of the glass sheet product, according to the application and / or properties desired. Moreover, a combination of several coatings can be deposited on one and / or the other face of the glass sheet product, as a screen-printing and as a coating itself.

[0064] According to a preferred embodiment of the application, the glass sheet product is provided with an anti-glare coating, an anti-reflective coating and an anti-fingerprint coating in face 1 (a term well known to the skilled person) and with a multi-color screen printing and a security film in face 2. Optional but preferred cleaving step (d)

[0065] In a preferred embodiment, the method of the application further comprises a cracking step d). The cracking occurs once the filigree-like damages are introduced adjacent along the separation line. The point of incidence of the laser radiation (preferably of a carbon dioxide laser) is displaced along the separation line on the surface of the glass product so that a local tensile stress is induced in the glass along the separation line in order to form a crack between the adjacent filigree-like damages. This cracking method step can also be facilitated by a local cooling after heating in order to increase the tensile stress generated in the material. The cracking step serves for a preliminary separation. This makes it possible to initiate the formation of a crack connecting the filigree-like damages along the separation line in order to induce a fracture along the separation line at least in a section of the separation line, but generally not to detach this part from the main part. Both the filigree structure itself and the additional cracks in the material induced by the cracking step are preliminary damages in the material extending along the separation line. Abrasion step e)

[0066] The final required step of the method of the application is the separation of the inner part (2) from the glass sheet product (10) at the adjacent aligned filigree-like defects along the separation line (3), as shown in Figure 1b The separation is achieved by irradiation with an ablative laser to ablate at least one section (4) within the inner part (2). This section has 2 end points located on the separation line (3). The thickness T of this section is substantially the same as the glass sheet product and the width is equal to or greater than (>) 150 pm so that the inner part is separated from the main part at the adjacent aligned filigree-like defects along the separation line.

[0067] The glass sheet product extends along a plane P defined by a longitudinal axis X and a vertical axis Y. The thickness is measured in a direction perpendicular to the plane P. The width is measured along the plane P. In a preferred embodiment, the width of the section (4) is equal to or greater than 200 pm (W > 200 pm), preferably equal to or greater than 250 pm (W > 250 pm). It is conceivable that the section does not have the same width along its length, such as in a moon shape. In this case, the minimum width of the ablation section needs to be equal to or greater than 150 pm. Typically, the width of the section will be equal to or less than 500 pm (W < 500 pm), preferably equal to or less than 450 pm (W < 450 pm), more preferably less than or equal to 400 pm (W < 400 pm). It is generally accepted that the greater the width of the section, the more time the separation step takes.

[0068] The purpose of the ablation step of the method of the present application is to reduce the volume of the inner portion to counteract the compressive forces between the remaining portion of the glass sheet product and the inner portion. In practice, even if the glass has sufficient internal stress to start to separate after the defect line is formed, the geometry of the cut profile can prevent the inner portion from releasing. This is the case for most closed profiles or inner profiles such as simple holes or slots. Due to the presence of compressive forces in the glass sheet, the inner portion of the hole will remain in place. A crack can propagate between the defects of the perforation, but there is no space to allow the inner piece to fall off the glass sheet product.

[0069] Depending on the shape of the inner portion to be removed, several embodiments for the section to be ablated can be considered to further improve the speed and ease of removing the inner portion. For example, more than one section spanning the inner portion can be considered. In another embodiment, the ablation section can extend along at least 50%, preferably at least 75%, more preferably at least 100% of the circumference of the inner portion.

[0070] Figure 3 illustrates different embodiments of the glass sheet product of the present application with inner portions having different shapes and with different ablation section shapes and sizes. All figures should be considered only for illustrative purposes. In particular, Figures IB and 3 illustrate very schematically the separation line, the inner portion and the section.

[0071] Figure 3a A glass sheet product with an inner portion having a rectangular shape with a curved corner and with an ablation section extending along 100% of the circumference of the inner portion is illustrated. Figure 3b A glass sheet product with an inner portion having an elliptical shape and a single ablation section extending along the longest diameter of the inner portion is illustrated. Figure 3c de Three different embodiments of a glass sheet product with an inner portion having a circular shape are illustrated. Figure 3c An embodiment with two ablation sections extending along two diameters of a circular inner portion is illustrated. In this case, the two sections are perpendicular to each other, but any angle between the sections can be envisaged herein. Figure X3d illustrates an embodiment with a single ablation section extending along 50% of the circumference of the circular inner portion and wherein the ablation section has a moon shape. In this case, the ablation section does not have the same width along its length. Figure 3e An embodiment with a single ablation section extending along the entire circumference of a circular inner portion is illustrated.

[0072] Glass ablation by laser is a process using a laser to remove material from the surface of a glass. The laser heats the glass to a high temperature and vaporizes it, removing a small amount of material at a time. Ablation is achieved with a high intensity laser beam, strong enough to cause rapid melting, thus causing the glass to evaporate. The ablation process is done layer by layer until the thickness T is removed. Typically, the wavelength of the ablation laser system is in the range 193 nm to 1070 nm, the pulse duration is below 1 μs, ideally below 100 ns. The average power of the laser system is usually several hundred watts. The laser can operate at a repetition rate above 100 Hz and the laser spot diameter at the glass surface is below 100 μm. The scanning speed of the laser system is typically above 50 mm / s. Producing a glass sheet article from a glass substrate

[0073] The glass sheet product can be manufactured by any method known in the art. However, it is preferred that the glass sheet product is produced from a glass substrate by a similar manufacturing method using thinning cutting / chemical strengthening / separation, wherein typically a large number of glass sheet products can be manufactured from a large size glass substrate.

[0074] Thus, in a second embodiment, the present invention relates to a method for manufacturing at least one glass sheet product (10) having a thickness T and comprising an internal hole (1) from a glass substrate (20). As shown in Figure 5 This manufacturing method comprises first a thinning cutting step (step a)), followed by a chemical strengthening step (step b), optionally can be followed by a coating step (step c)) and preferably a cleaving step (step d)), and finally a separation step (step d)). The description of the different steps already described above with reference to the glass sheet product applies mutatis mutandis to the glass substrate.

[0075] Indeed, it has been found that when creating an internal hole in a glass sheet product before the glass substrate is subjected to chemical strengthening, the stiffness of the glass substrate is reduced and the risk of breakage during all subsequent processing steps, such as chemical strengthening, coating, handling and transportation, is significantly increased. Thus, the second embodiment of the present invention avoids these drawbacks and provides an efficient method for manufacturing high quality glass sheet products comprising an internal hole.

[0076] The filigree cutting process of step a) is the same step as described above with reference to the method for manufacturing an internal hole within a glass sheet product. This step comprises a filigree cutting sub-step al) for manufacturing at least one glass sheet product along an intended separation line separating the glass substrate into the at least one glass sheet product to be separated and a remaining part of the substrate. This step further comprises a filigree cutting sub-step a2) for separating an internal portion (2) from the glass sheet product along an intended separation line (3) defining the internal portion to be separated. For process efficiency, it is preferred to simultaneously form the separation line separating the glass sheet product from the glass substrate and the separation line for separating the internal portion. However, it is conceivable that sub-step al) and sub-step a2) are performed separately in any order.

[0077] As mentioned above, the chemical strengthening step b) is performed on the surface of the glass substrate. By subjecting the glass substrate (on which there is a separation line separating the glass substrate into at least one glass sheet product to be separated and a separation line defining an internal portion to be separated) to a chemical strengthening treatment, a compressive stress layer can be formed on both surfaces of the glass sheet product, on the edges of the glass sheet product and on the edges of the internal hole.

[0078] A third optional but preferred coating step c) can be performed on the surface of the glass substrate. It has been found that when this coating step is performed before the separation of the internal portion from the remaining portion of the glass sheet product and before the separation of the different glass sheet products from the glass substrate, it allows coating the glass sheet product up to the separation line around the edges of the glass sheet product and of the internal hole, while avoiding the dripping of the coating along the edges of the glass sheet product / internal hole, which would occur if the coating step was performed after the creation of the glass sheet product / internal hole. Thus, the method of the present invention not only provides very sharp and neat edges, partially reinforced edges in a very efficient, simplified and fast production process, but also provides a very neat coated surface.

[0079] A fourth optional but preferred step is the cleaving step d) comprising a cleaving step dl) of the separation line (3) forming a glass sheet product (10) (step dl)) and a cleaving step d2) of the separation line (3) forming an internal hole (1) within the glass sheet product (10). For process efficiency, it is preferred to simultaneously perform the separation line separating the glass sheet product (10) from the glass substrate (20) and the intended separation line for separating the internal portion. However, it is conceivable that sub-step dl) and sub-step d2) are performed separately in any order. The same techniques described above in relation to the cleaving step d) apply here as well.

[0080] The last step of the method of the second embodiment of the present invention is a separation step e) comprising a separation step el) of separating the glass pane article (10) from the glass substrate (20). Any separation technique can be used. The separation step d) further comprises a separation step e2) of separating the inner portion (2) from the glass pane article (10) at the adjacent aligned filament-like defects along the separation line (3) by irradiation with an ablative laser to ablate at least one segment within the inner portion, wherein the at least one segment has two end points lying on the separation line, essentially has a thickness T, and has a width W equal to or greater than 150 pm (W > 150 pm). Depending on the separation technique used to separate the glass pane article from the glass substrate, the step el) and the step e2) can be performed simultaneously or sequentially in any order.

[0081] The separation of the glass pane article from the glass substrate is preferably achieved by a filamentation cutting process through a release line created around the contour of the glass pane article. The filamentation cutting step a3) of the release line can be performed separately or during the filamentation cutting step al) for producing at least one glass pane article along a separation line separating the glass substrate into at least one glass pane article to be separated, and / or during the step a2) for separating the inner portion from the glass pane article along the separation line (3) defining the inner portion to be separated. In fact, the filamentation cutting steps al), a2) and / or a3) can be performed simultaneously or sequentially in any order. In a preferred embodiment, the filamentation cutting steps al) and a2) are performed simultaneously in a single step, followed by the filamentation cutting step a3) and then the chemical strengthening step. Alternatively, the filamentation cutting step of the release line a3) can be performed immediately before or after the separation step el) of separating the inner portion from the glass article.

[0082] Thanks to the proposed method of the second embodiment, a chemically strengthened, preferably coated, glass pane article with an inner hole can be produced by a simple method, wherein the chemical strengthening process and optionally the coating process can be applied directly on a large glass substrate in succession. Then, the glass pane article is separated from the large size glass according to a separation line determined according to the required size and shape of the glass article. According to the ablation separation step e2), the inner portion is separated according to a separation line determined according to the required size and shape of the inner hole. Thus, the strengthening, preferably coating, and separation of the glass article are better controlled. Moreover, when used by this method, the coating deposition is much easier as it is performed on a large size glass panel. Thus, the production yield is improved and the manufacturing cost is reduced. Thanks to this method, edge-to-edge coating and painting deposition can be easily manufactured. Furthermore, the method of the present invention provides a means for significantly saving the consumption of coating material and glass substrate.

[0083] Furthermore, the method of the present application provides a means for obtaining chemically strengthened coated glass articles that can be cold-bent. The method according to the present application is cheaper and more efficient than traditional methods for manufacturing coated chemically strengthened glass. As the name implies, cold-bending is performed at the natural temperature of the factory. The process begins with the placement of the glass into a frame that mechanically bends the glass into the desired frame shape. During the frame mounting process, the glass is glued or twisted directly into the frame. The frame is then ready to be installed into a vehicle or building. From a mechanical point of view, the thinner the glass, the easier it is to bend. However, its shape can also have a twisted design. With this method, the cold-bending performance is enhanced because the end faces of the glass article are strong due to ion exchange.

[0084] Cold-bending is understood in particular as bending glass articles for interior and exterior glazing parts of automobiles, such as glass consoles, instrument panels, decorative elements for vehicle doors, pillars, windshields, side windows, rear windows, sunroofs, partition glass, etc. According to the present application, the potassium content on the surface of the glass article is higher than the potassium content present on the edges of the glass article and on the edges of the internal holes after the strengthening and preferably the coating. During the chemical strengthening, the potassium content in the end faces of the glass article is increased. Thus, the end faces of the glass article are more resistant to external loads / stresses. Therefore, the faces of the glass article that can be stressed in tension are better strengthened (in particular in cold-bending), and where there is no need for compressive stress, the compressive stress should be limited to limit the central tension. Glass properties

[0085] In a preferred embodiment, the glass sheet article and the glass substrate have a coefficient of thermal expansion CET comprised between 70 x 10-7 / °C and 100 x 10-7 / °C (70 x 10-7 / °C < CET < 100 10-7 / °C); preferably between 80 x 10-7 / °C and 95 x 10-7 / °C (80 x 10-7 / °C < CET < 95 10-7 / °C). The coefficient of thermal expansion of a glass is a parameter that indicates how the dimensions of the corresponding glass element will change by expansion or contraction due to a change in temperature. The coefficient of thermal expansion refers to the linear coefficient of thermal expansion a = (1 / L)(AL / AT), where AT represents the temperature difference and AL represents the change along the linear dimension relative to the original length L.

[0086] Typically, the thickness of the glass sheet product / glass substrate is at least 0.1 mm (T > 0.1 mm), preferably at least 0.3 mm (T > 0.3 mm), more preferably at least 0.5 mm (T > 0.5 mm). Typically, the thickness of the glass sheet product / glass substrate is equal to or less than 20.0 mm (T < 20.0 mm), preferably equal to or less than 10.0 mm (T < 10.0 mm), more preferably equal to or less than 2 mm (T < 2.0 mm), more preferably equal to or less than 1.5 mm (T < 1.5 mm), more preferably equal to or less than 1 mm (T < 1 mm). The method for laser-assisted separation of a portion from a glass sheet element of the present application is particularly suitable for sheet-like elements having the above-mentioned thicknesses. Indeed, it has been found that the thinner the glass sheet product, the faster the process. It has further been found that the thinner the glass product, the smaller the internal hole that can be achieved. Glass sheet article

[0087] The present application also relates to a glass product obtained by the above-mentioned method. This glass product can be used, for example, in the field of cover glasses for electronic devices, glazing for building materials, glazing for vehicles, etc. For safety reasons and in order to comply with the safety specifications required for such glazing, it is generally required that the glass product has a high strength.

[0088] In particular, the present application proposes a decorative panel for the interior of a vehicle. The decorative panel according to the present application is mounted on any part of the interior of a vehicle in order to provide better aesthetics or to secure or protect certain parts of the vehicle interior. Such a decorative panel can be mounted to (completely or partially) cover a door, a door handle profile, a part of a dashboard or a center console (where the center console refers to the console between the front passenger seats which can extend towards the dashboard), a seat backrest (including the back of a headrest), a roof, an armrest, etc. The vehicle refers to any kind of vehicle such as (but not limited to) a car, a van, a truck, a motorcycle, a bus, a tram, a train, a drone, an airplane, a helicopter, etc. Examples

[0089] Forty-five glass products each comprising two internal holes were manufactured by the following method. A glass substrate made of aluminosilicate glass having a length of 1000 mm, a width of 1000 mm and a thickness of 1.3 mm was prepared. The surface of the internal hole was 20 mm2. The glass substrate had the following composition expressed in weight percentage of the total composition: SiO2 66.5 Al2O3 5.8 Na2O 15.7 CaO 0.9 MgO 9.5 K2O 1.1 Fe2O3 <100 ppm Minor constituents Supplement to 100% Filamentation cutting step a)

[0090] An internal hole within the glass sheet product and a glass sheet product within the glass substrate were created by a single filigree cutting step. The glass substrate was irradiated with a laser in the direction of the main surface side to form two or more in-plane hole regions in the vertical direction and the horizontal direction. A Hyper Rapid NX laser produced by Coherent (Germany) was used, which is capable of emitting a short pulse laser of the order of picoseconds. The frequency of one pulse train of the laser was 80 kHz, and the pulse width was 9 picoseconds. Laser irradiation was implemented only once (correspondingly, 1 pass of laser irradiation) in each in-plane hole region. In each in-plane hole region, the center-to-center distance between the centers of the surface holes was set to 5 pm. The separation line of the glass sheet product within the glass substrate and the separation line of the internal hole within the glass sheet product were created simultaneously. Chemical strengthening step b)

[0091] Chemical strengthening was performed by immersing the glass substrate in a molten salt at 450 °C for 2 hours. The result of the chemical strengthening treatment indicated that there was no pre-cracking phenomenon in the glass substrate. Coating step c)

[0092] After washing, double screen printing was performed on one side of the glass substrate. The ink was black organic matter. The curing conditions were 100 °C for 15 min as pre-curing, 150 °C for 20 min as final curing. On the other side of the glass substrate, an anti-fingerprint organic material was deposited on top of the anti-reflective functional layer by evaporation, and an anti-reflective coating was added inside the vacuum chamber by a digital sputtering process of the anti-reflective functional layer. Additional steps

[0093] After chemical strengthening and coating surface treatment, additional release lines for the separation step e1) were created by the same laser and conditions as described above. These additional release lines were opened by the central tension of the chemically tempered glass. Cleaving step d)

[0094] The separation line of the glass sheet product within the glass substrate and the separation line of the internal hole within the glass sheet product were interconnected by a CO2 laser, which was a Diamond J5 laser produced by Coherent Inc. The CO2 laser irradiated from the side that was coated with anti-reflective and anti-fingerprint. The average power was 25 W, and the estimated focal diameter was 5 mm. Separation step e)

[0095] The glass sheet product was first separated from the glass substrate by mechanically breaking the release lines created in the above steps.

[0096] To separate the internal hole within the glass sheet article, a section of the internal portion was ablated by an ablative laser. A nanosecond pulsed green laser was directed at a section around 100% of the perimeter of the internal portion with a thickness of 150 pm to create a space for the internal portion to fall from the glass sheet article and create an internal hole. The laser average power was 50 W and its estimated focal spot diameter was 30 pm. 10 Glass sheet article 20 Glass substrate 1 Inner hole 2 Inner portion 3 Separation line 4 Abrasion section

Claims

1. A method for producing an internal hole (1) in a glass sheet product (10) having a thickness T, wherein: The inner portion (2) is separated from the glass sheet product along a separation line (3); the method comprising at least the following steps performed in the following order: c) a filigree cutting step, wherein filigree defects are generated in the volume of the glass sheet article in the form of submicron hollow channels adjacently aligned along the separation line, wherein the defects are generated by laser pulses of an ultrashort pulse laser, wherein the material of the glass sheet article is transparent to the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass sheet article, wherein the plasma causes the filigree defects; and wherein the point of incidence of the laser pulses on the glass sheet article is displaced on the surface of the glass sheet article along the separation line to introduce the filigree defects adjacently aligned along the separation line; d) chemically strengthening the glass sheet product; f) a separation step of separating the inner portion from the glass sheet product at adjacently aligned hairline defects along the separation line by irradiating the inner portion with an ablative laser to ablate at least one segment (4), wherein the at least one segment has two end points located on the separation line, substantially has a thickness T, and has a width W equal to or greater than 150 μm (W ≥ 150 μm).

2. A method for producing at least one glass sheet product (10) having a thickness T and comprising an internal hole (1) from a glass substrate (20), The method comprises the following steps performed in the following order: a1) a filigree cutting step for producing the at least one glass sheet product along a separation line separating the glass substrate into the at least one glass sheet product to be separated, and a2) a filigree cutting step for separating the inner portion (2) from the glass sheet product along a separation line (3) defining the inner portion to be separated, in, generating filamentary defects in the volume of the glass substrate in the form of submicron hollow channels adjacently aligned along the separation line, wherein the defects are generated by laser pulses of an ultrashort pulse laser, wherein the material of the glass substrate is transparent to the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass substrate, the plasma causing the filamentary defects; and wherein the point of incidence of the laser pulses on the glass substrate is displaced on the surface of the glass substrate along the separation line to introduce the filamentary defects adjacently aligned along the separation line; c) chemically strengthening the glass substrate (20); and f) e1) a separation step for separating the glass sheet product (10) from the glass substrate (20), e2) a separation step of separating the inner portion (2) from the glass sheet product at adjacently aligned hairline defects along the separation line (3) by irradiating the inner portion with an ablative laser to ablate at least one segment, wherein the at least one segment has two end points located on the separation line, substantially has a thickness T, and has a width W equal to or greater than 150 μm (W ≥ 150 μm).

3. The method according to any one of claims 1 and 2, further comprising a splitting step d) performed along the separation line, by which the filaments are interconnected, and immediately after the splitting step, the separation step e) is performed.

4. The method according to any one of the preceding claims, further comprising performing a coating step c) of the glass sheet product or glass sheet substrate after the chemical strengthening step b) and before the cleaving step d) if present.

5. A method according to any one of the preceding claims, wherein The surface of the internal hole is equal to or less than 300mm 2 (S≤300mm 2 ); preferably equal to or less than 150mm 2 (S≤150mm 2 ), preferably equal to or less than 120 mm 2 (S≤120mm 2 ), more preferably equal to or less than 80 mm 2 (S≤80mm 2 ).

6. A method according to any one of the preceding claims, wherein The surface of the internal hole is equal to or greater than 3mm 2 (S≥3mm 2 ), preferably equal to or greater than 5mm 2 (S≥5mm 2 ).

7. A method according to any one of the preceding claims, wherein The width of the at least one section within the inner portion is equal to or greater than 200 μm (W≧200 μm), preferably equal to or greater than 250 μm (W≧250 μm).

8. A method according to any one of the preceding claims, wherein There are at least two sections within the inner portion.

9. The method according to any one of the preceding claims 1 to 8, wherein The at least one section extends along at least 50%, preferably at least 75%, more preferably 100% of the circumference of the inner portion.

10. A method according to any one of the preceding claims, wherein The glass sheet product has a thickness of at least 0.1 mm, preferably at least 0.3 mm, more preferably at least 0.5 mm, and a thickness of less than 20 mm, preferably less than 10 mm, more preferably less than 2 mm, more preferably less than 1.5 mm, more preferably less than 1 mm.

11. A glass sheet product obtainable by the method according to any one of claims 1 to 10.

12. The glass sheet product of claim 11, having a soda-lime-silicate glass composition, an aluminosilicate glass composition, or an alkali-aluminosilicate glass composition.

13. The glass sheet product according to any one of claims 11 to 12, wherein: The CTE of the glass product is 7010 -7 / ℃ to 100 10 -7 / ℃, preferably 80 10 -7 / ℃ to 95 10 -7 / ℃.

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