WO2024189107A1

WO2024189107A1 - Method for making inner holes in a chemically strengthened glass sheet article

Info

Publication number: WO2024189107A1
Application number: PCT/EP2024/056720
Authority: WO
Inventors: Sylvain DRUGMAN; Jun Ito; Thomas LAMBRICHT; Tri LÊ QUANG
Original assignee: AGC Glass Europe SA
Current assignee: AGC Glass Europe SA
Priority date: 2023-03-15
Filing date: 2024-03-13
Publication date: 2024-09-19
Anticipated expiration: 2025-09-15
Also published as: CN120769835A

Abstract

The present invention relates to a method for making an inner hole (1) into a glass sheet article (10) having a thickness, T, whereby an inner portion (2) is separated from the glass sheet article along a separation line (3) The method comprising at least the following steps in the following order: a step of filamentation wherein filamentary defects are produced in the volume of the glass sheet article in the form of sub-micron hollow channels adjacently aligned along the separation line wherein the defects are produced by laser pulses of an ultrashort pulse laser, wherein the material of the glass sheet article is transparent for the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass sheet article, which causes the filamentary defects; and wherein the incidence points of the laser pulses on the glass sheet article are displaced over the surface thereof along the separation line; to introduce the filamentary defects adjacently aligned along the separation line; followed by a step of chemical strengthening of the glass sheet article; and then a separation step of the inner portion from the glass sheet article at the adjacently aligned filamentary defects along the separation line, by irradiating the inner portion with an ablation laser to ablate at least one segment (4), wherein the at least one segment has two end points located on the separation line, has substantially the thickness, T, and has a width, W, equal to or greater than 150µm (W ≥ 150µm).

Description

METHOD FOR MAKING INNER HOLES

IN A CHEMICALLY STRENGTHENED GLASS SHEET ARTICLE

1. FIELD OF THE INVENTION

[0001] The present invention relates to a laser-assisted method for making an inner hole in a chemically strengthened glass sheet article.

2. BACKGROUND OF THE INVENTION

[0002] In fields of cover glass for electronic equipment, glazing for building materials, glazing for vehicles..., high strength is often required for safety reasons and to be in line with safety rules required for such glazing. Thus, the glazing is often submitted to a chemically strengthening process to obtain a glazing or cover with high stress resistance. In the chemical strengthening treatment, alkali metal ions having an atomic diameter larger than the original atoms are introduced to the surface of the glass substrate. Therefore, a compressive stress layer is formed on the surface of the glass substrate, thereby improving the strength of the glass substrate.

[0003] Conventional methods wherein many glass items are first cut in the final shape and afterwards chemically strengthened cause a large amount of scratching and damaging if sufficient careful handling is not provided. To avoid these drawbacks, some methods have been developed such as strengthening glass having a large size before cutting glass item in its final shape.

[0004] For example, patent EP3345877B describes a method combining filamentation and chemical strengthening whereby a chemical strengthening treatment is applied to a largesized glass material in advance, and the large-sized glass material is subsequently cut by filamentation to produce chemically strengthened glass articles. WO2019/154782 proposes a method of manufacturing a coated glass article comprising the steps of filamentation for dividing a glass article from the glass substrate, then chemically strengthening the glass substrate, then a step of coating. [0005] Indeed, the filamentation technique is often used to create glass articles from a larger glass panel. The contour of the glass articles to be produced from the glass panel is shaped by filamentation separating lines. In addition, filamentation breaking lines will be further created around the contours of the glass articles to facilitate the removal of the glass articles from the glass panel. Several separation techniques are used: A typical technique is to initiate a crack with a mechanical equipment (diamond tool, cutting wheel, ...) in a controlled position so that the crack will propagate along the filamentation separating lines. It is known to create additional voids in the vicinity of the filamentation separating lines to provide a controlled crack propagation along the filamentation separating lines. A first crack initiation in a appropriated position will induce the separation of the glass articles from the initial glass panel. Despites that this technique allows to obtain glass articles without affecting its quality, this mechanical separation involves the destruction of the initial glass panel from which the glass articles are originating and therefore cannot be used to create inner holes.

[0006] Another technique would be to generate stresses in the sheet glass substrate by bending the substrate whereby the material is stretched in one half of its volume thereby creating a tensile stress in that half, while simultaneously being compressed in the other half of the volume thereby creating a compressive stress there. However, the bending of a glass substrate is not suitable for the removal of inner portions, in particular of small size.

[0007] Indeed, even if the glass has enough internal stress to start self-separation after the formation of the defect line, the geometry of the cut contour may prevent an interior glass part from releasing. This is the case for most closed or inner contours such as simple holes or slots. The interior portion of the aperture will remain in place due to the compression forces present in the glass sheet. The cracks may propagate between the perforated defects but no room exists to allow the inner piece to fall out of the mother sheet.

[0008] Mechanical separation technique could be nevertheless used to remove the glass inner portion by applying some pressure thereon. However, when using such mechanical separation technique, the edges of the inner portion and of the inner hole will rub against each other and provide edges of poor quality, not suited for the applications that demand very sharp edges. [0009] Other techniques have been designed in that art to remove the inner portion of the glass article to create such inner hole are typically based on thermal compaction. For example, US2018134606 discloses method for separating a portion from a sheet glass element having a thickness of at least 2 millimeters. The method includes producing filamentary damages along the separation lines; and heating and/or cooling the glass sheet element to cause expansion and/or contraction so that the portion detaches from the main part along the separation line.

[0010] It has been found however that separation technique based thermal compaction cannot be used to make inner holes of small sizes. Indeed such technique is based on the expansion of the main part and/orthe contraction of the portion to be removed wherein these parts change their size differently from each other. However, in the instance wherein the portion to be removed is small, the temperature differential between the glass article and the inner portion to be removed is too high to be effectively used without deteriorating even without destroying the main part.

[0011] Hence, there remains a need to find an appropriate method to make small inner holes, having high quality edges, within chemically strengthened glass articles.

3. SUMMARY OF THE INVENTION

[0012] Other aspects and advantages of the 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 present invention relates to a method for making an inner hole into a glass sheet article having a thickness, T, whereby an inner portion is separated from the glass sheet article along a separation line. The method comprises at least the following steps in the following order: a) a step of filamentation wherein filamentary defects are produced in the volume of the glass sheet article in the form of sub-micron hollow channels adjacently aligned along the separation line wherein the defects are produced by laser pulses of an ultrashort pulse laser, wherein the material of the glass sheet article is transparent for the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass sheet article, which causes the filamentary defects; and wherein the incidence points of the laser pulses on the glass sheet article are displaced overthe surface thereof along the separation line; to introduce the filamentary defects adjacently aligned along the separation line; b) a step of chemical strengthening of the glass sheet article; e) a separation step of the inner portion from the glass sheet article at the adjacently aligned filamentary defects along the separation line, by irradiating the inner 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, has substantially the thickness, T, and has a width, W, equal to or greater than 150pm (W > 150pm).

[0014] In another embodiment, the present invention relates to a corresponding method whereby the glass sheet article having a thickness, T, and comprising an inner hole, is manufactured from a larger glass substrate. The method comprises the following steps in the following order: al) a step of filamentation for the production of the at least one glass sheet article along a separation line which divides the glass substrate into the at least one glass sheet article to be separated and, a 2) a step of filamentation for the separation an inner portion from a glass sheet article along a separation line which defines an inner portion to be separated, wherein filamentary defects are produced in the volume of the glass substrate in the form of sub-micron hollow channels adjacently aligned along the separation lines wherein the defects are produced by laser pulses of an ultrashort pulse laser, wherein the material of the glass substrate is transparent for the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass substrate, which causes the filamentary defects; and wherein the incidence points of the laser pulses on the glass substrate are displaced over the surface thereof along the separation line; to introduce the filamentary defects adjacently aligned along the separation lines; b) a step of chemical strengthening of the glass substrate; and e) el) a separation step to separate the glass sheet article from the glass substrate, e2) a separation step of the inner portion from the glass sheet article at the adjacently aligned filamentary defects along the separation line, by irradiating the inner 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, has substantially the thickness, T, and has a width W, equal to or greater than 150pm (W > 150pm).

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

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

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

[0018] The present invention further relates to glass sheet article obtained according to the methods of the present invention. The glass sheet article will preferably have a thickness of at least 0.1mm, preferably at least 0.3mm, more preferably at least 0.5mm and preferably a thickness of less than 20mm, preferably less than 10mm, more preferably less than 2mm, more preferably less than 1.5mm and more preferably less than 1mm. Preferably, the glass sheet article has a soda-lime-silicate glass composition, aluminosilicate glass composition or an alkali alumino silicate glass composition. The glass sheet article has typically CTE 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 THE DRAWINGS

[0019] Figure la shows a top view of a glass sheet article that comprises an inner hole, according to one embodiment of the present invention. Figure lb shows the same glass sheet article wherein the inner portion to be removed to create the inner hole, the separation line and the ablation segment have been illustrated.

[0020] Figure 2 shows a top view of a glass substrate comprising glass sheet articles that comprise an inner hole, according to another embodiment of the present invention.

[0021] Figure 3 illustrates several embodiments of the present invention of the inner portion to be removed with different ablation segment(s). Figure 3a shows a top view of an inner portion having a rectangular shape with an ablation segment running along 100% of the perimeter of the inner portion. Figure 3b shows a top view of an inner portion having an oval shape with an ablation segment along the longest diameter of the inner portion. Figure 3c shows a top view of an inner portion having a circular shape with two perpendicular ablation segments. Figure 3d shows a top view of an inner portion having a circular shape with an ablation segment in a moon shape, running along 50% of the perimeter of the inner portion. Figure 3e shows a top view of an inner portion having a circular shape with an ablation segment running along 100% of the perimeter of the inner portion.

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

[0023] Figure 5 is a schematic view of a method according to a second aspect of the present invention.

5. DETAILED DESCRIPTION OF THE INVENTION

[0024] The object of the present invention is to provide a chemically strengthened glass sheet article, that comprises an inner hole of high quality. Currently available manufacturing techniques do not provide the required quality and/or are not suitable to create small inner holes. It has been surprisingly found that the production methods of the present invention overcome the drawbacks of the prior art techniques.

[0025] The objective of the present invention is to allow an efficient and high quality separation of an inner portion from a chemically strengthened glass sheet article; while minimizing the risk of detrimental cracking in the remaining main part of the glass article. A further objective is to provide a simple and effective fast production method of a chemically strengthened and, optionally , glass article comprising an inner hole. By high quality, it is herein understood that the edges of the inner hole must 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 been further found that the production method of the present invention whereby such glass sheet articles are produced from a much larger glass substrate with the same steps of filamentation, chemical strengthening, potentially coating are used, is not only time and cost effective, but as well maintain the rigidity of the large glass sheet despites the presence of the high number of inner holes within the glass sheet articles and thereby greatly ease the handing and transportation.

[0027] As illustrated in Figures la and lb, the present invention in a first embodiment relates to a method for making an inner hole (1) into a glass sheet article (10) having a thickness, T, whereby an inner portion (2) is separated from the glass sheet article along a separation line (3). The separation line (3) divides the glass sheet article into an inner portion to be separated and the remaining main part of the glass sheet article.

[0028] The making of the inner hole within the glass sheet article includes the separation of the inner portion along separation lines in the form of closed loops. The inner hole can be of any shape. When the inner hole shape comprises rectilinear lines, such lines will preferably be linked by curved angles to form the closed loop. Preferably, the inner hole will be of oval shape, more preferably of circular shape. The glass sheet article can comprise one or more inner hole(s) of the same or different shape and of the same or different sizes. [0029] The present invention is especially useful for the creation of inner hole of small size in a glass sheet article. By small size, it is understood as having a surface of typically less than less than 300 mm², preferably less than 150mm², preferably less 120mm², more preferably less than 80mm². Typically, the method of the present invention will be used to create a circular inner hole of a surface of at least 3mm², preferably of at least 5mm².

[0030] As illustrated in Figure 4, in a first embodiment, the method of the present invention comprises firstly a step of filamentation (Step a)) followed by a step of chemical strengthening (Step b) that can optionally be followed by a step of coating (Step c)) and preferably by a step of cleaving (step d)) and finally a step of separation (Step d)).

[0031] Accordingly, the method of the present invention comprises filamentation as a first step. The glass sheet article is filamented by laser pulses, that is microperforated along at least one defined separation line. Such separation line describes a closed loop and define the inner contour of the inner portion to be removed. Subsequently, a chemical strengthening step is performed on the glass sheet article. The method can optionally then comprise a step of coating. A cleaving step is then preferably performed along the separation line of the inner contour, by which the filaments are interconnected so that the inner contour separates from the main part, but without detaching from the main part.

[0032] method of the present invention comprises finally a separation step whereby the inner portion (2) is detached from the glass article (10) by irradiating the inner portion with an ablation laser to ablate at least one segment (4) of such inner portion. The ablation of a segment of the inner portion should be large enough to make the inner portion smaller and thereby release the inner portion. Thanks to this specific ablation step, the edges of the inner hole produced within the glass sheet article part can maintain the very high edge qualities that is obtained via the filamentation step. Furthermore the edges benefit from the chemical strengthening step previously operated.

Step (a) of filamentation

[0033] Laser filamentation is a technique to cut glass articles from a glass sheet. Irreversible damages in the form of filaments are caused in a glass substrate by high-energy laser pulses, and an aligned series of such damages allows to separate the glass. A filament is produced by an ultrashort laser pulse which causes self-focusing to take place inside the glass due to the Kerr effect until 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 this plasma generation site. From there, further radiation will emanate and will be subject to selffocusing and terminate in another plasma explosion. This effect is repeated several times, depending on intensity.

[0034] Hence, the first step a) of the method of making an inner hole into a glass sheet article is a step of filamentation wherein filamentary defects are produced in the volume of the glass sheet article in the form of sub-micron hollow channels adjacently aligned along the separation line wherein the defects are produced by laser pulses of an ultrashort pulse laser, wherein the material of the glass sheet article is transparent for the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass sheet article, which causes the filamentary defects; and wherein the incidence points of the laser pulses on the glass sheet article are displaced over the surface thereof along the separation line; to introduce the filamentary defects adjacently aligned along the separation line;

[0035] The details of the filamentation step of the present invention are detailed in [0037] to [0074] under step S130 and in reference to Figures 3 to Figure 7 within European patent EP3 345 877B granted to AGC Inc on 23.03.2022 and which is hereby incorporated by reference and summarized herein below:

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

[0037] Each surface void corresponds to the irradiation position of a laser on the first main surface, and has a diameter of, for example, 1 to 5 pm. The diameter of the surface void varies with a laser irradiation condition, a type of the glass material, and the like. The distance P between the centers of the adjacent surface voids may be determined based on the composition and thickness of the glass material, laser processing conditions, and the like. For example, the distance P between the centers of the adjacent surface voids may be in a range of 2 to 10 pm. The distance P between the centers of the surface voids does not have to be equal at all positions, and may be different according to places. That is, the surface voids may be arranged at irregular intervals. The shape, size, and pitch of the internal voids are not particularly specified. The void may have a shape such as a circle, an ellipse, a rectangle, a triangle, or the like when viewed from the Y direction, for example. Further, the maximum dimension of the void (typically corresponding to the length of the void along an extending direction of the internal void row) when viewed from the Y direction may, for example, be in a range of 0.1 to 1000 pm. Each of internal void rows has a corresponding one of surface voids.

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

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

[0040] In a case where an internal void row having voids sufficiently close to the second main surface is not formed by one laser application, i.e., in a case of the void closest to the second main surface being at a position sufficiently remote from the second main surface (e.g., the void closest to the second main surface has a distance equal to or less than a half of the thickness of the glass material from the first main surface), a laser may be applied twice or more to substantially the same position. Note that the "substantially the same (laser application) position" indicates not only a case where the two positions perfectly match but also indicates a case where the two positions may slightly be deviated from each other (e.g., a deviation of 3 pm at maximum). For example, a laser is applied two or more times along a first direction parallel to the first main surface of the glass material to form a first in-plane void region and a corresponding internal void row (first pass), and subsequently, a laser is applied to substantially the same direction and substantially the same position as the first pass (second pass), thereby forming a "deeper" internal void row corresponding to the first inplane void region.

[0041] The distance from the center of the void closest to the second main surface, among the voids constituting the internal void row, to the second main surface may preferably be in a range of 0 to 10 pm although such a distance may vary with the thickness of the glass material.

[0042] In particular, closely spaced micrometer hollow channels are produced, that is to say hollow channels with diameters of less than 5 micrometer. The filamentary damages produced by the laser pulses preferably have a length of at least 200 micrometers, more preferably at least 500 micrometers. For this purpose, suitable pulse energies and pulse durations are selected. The minimum lengths of filamentary damages as specified are advantageous because they promote the separation of the portion.

[0043] Particularly advantageous for the generation of long filamentary damages is an operation of the ultrashort pulse laser in the so-called burst mode. In this operation mode, the laser pulse is not emitted as a single pulse, but as a sequence of pulses emitted in quick succession, which together form a pulse packet, a so-called burst. Accordingly, one embodiment of the invention contemplates an operation of the ultrashort pulse laser in the form of an emission of laser pulses in time succession, in the form of bursts or pulse packets, wherein each of such bursts preferably generates a respective one of the filamentary damages. Such a pulse packet generally has a slightly higher energy than a single pulse in the conventional single-shot operation. However, the pulses of a burst contain significantly less energy than a single pulse. Furthermore, the pulse energies of the pulses typically decrease within a burst. [0044] A suitable laser source according to the present invention is a neodymium-doped yttrium-aluminum-garnet laser having a wavelength of 1064 nanometers. The laser source in particular operates at a repetition rate between 10 kHz and 1 MHz, preferably between 30 kHz and 300 kHz, and most preferably between 35 kHz and 200 kHz. The scan rate can preferably be chosen such that, depending on the repetition rate, the spacing between adjacent filamentary damages will be in a range from 2 micrometers to 10 micrometers.

[0045] In this case, the suitable pulse duration of a laser pulse is in a range of less than 100 picoseconds, preferably less than 100 picoseconds. The pulse duration may even be less than 30 picosecond. Most favorably, the laser source is operated at a typical power in a range from 30 to 500 watts. According to one advantageous embodiment of the invention, a pulse energy of more than 200 microjoules is applied in the burst, and furthermore advantageously a total burst energy of more than 400 microjoules, in order to achieve the filamentary damages.

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

[0047] Apart from tiny amounts, no material is removed from the separation seam during the microperforation employed for the invention. When the filamentary damages have been introduced, both parts to be separated will still be substantially connected to each other. Once the microperforation has been accomplished, a predetermined breaking line is existing in the material along the separation line, along which the material is not yet separated, but can be easily separated if a suitable stress is induced in the material. In particular a cleaving step is suitable for this purpose.

[0048] Due to the precision separation process by filamentation step a), a very high edge quality is achieved at the cut edges. Since the quality of the glass edge is of great importance for the flexural strength of a glass element, high edge quality also leads to increased flexural strength of the main part of the glass article. Indeed, a neatest possible glass edge with the fewest and smallest possible and preferably no chipping, notches, and other unevenness contributes to a reduction of the risk of glass breakage. In particular the edges are distinguished by chipping of less than 10 micrometers, more preferably less than 5 micrometers, and by a roughness with an Rz value of less than 30 micrometers, preferably 20 micrometers, more preferably 10 micrometers.

Step of chemical strengthening - Step (b)

[0049] The method of making an inner hole into a glass article of the present invention will further comprise a step b) of chemical strengthening right after the filamentation step a) and before the separation step e) and if present, before the coating step c) and/or cleaving step d).

[0050] The details of the preferred step of chemical strengthening of the present invention are provided in [0075] to [0089] under step S120 within European patent EP3 345 877B granted to AGC Inc on 23.03.2022 and which is hereby incorporated by reference.

[0051] The conditions of the chemical strengthening treatment are not particularly limited. Chemical strengthening may be carried out, for example, by dipping the glass sheet article on which the at least one separating line defining contour lines of the at least one glass article in molten salt at 380 °C to 500 °C for 1 minute to 72 hours.

[0052] As the molten salt, nitrate may be used. For example, when replacing the lithium ions contained in the glass sheet article with a larger alkali metal ion, a molten salt containing at least one of sodium nitrate, potassium nitrate, rubidium nitrate, and cesium nitrate may be used. Further, in the case of replacing the sodium ions contained in the glass sheet article with a larger alkali metal ion, a molten salt containing at least one of potassium nitrate, rubidium nitrate, and cesium nitrate may be used. Furthermore, when replacing the potassium ion contained in the glass sheet article with a larger alkali metal ion, a molten salt containing at least one of rubidium nitrate and cesium nitrate may be used. In addition, one or more kinds of salts such as potassium carbonate may be further added to the molten salt. In this case, a low density layer having a thickness of lOnm to 1pm can be formed on the surface of the glass sheet article. [0053] By subjecting the glass sheet article on which the at least one separating line defining contour lines of the inner portion to a chemical strengthening treatment, a compression stress layer can be formed on both surfaces of the glass sheet article and on edges of inner hole. The thickness of the compressive stress layer corresponds to the penetration depth of alkali metal ions for substitution. For example, in the case of replacing sodium ions with potassium ions using potassium nitrate, the thickness of the compressive stress layer can be 8pm to 27pm for soda-lime glass, and the thickness of the compression stress layer for aluminosilicate glass is 10pm to 100pm. In the case of aluminosilicate glass, the penetration depth of alkali metal ions is preferably 10pm or more, more preferably 20pm or more.

[0054] Therefore, since the glass sheet article has been chemically strengthened, it is easier to secure scratch-free appearance and strength of the glass sheet article to be manufactured as compared with the conventional manufacturing method. Thus, the manufacturing yield may be increased. Furthermore and more particularly, the glass article with its inner hole, after separation of the inner portion through separating lines, has edges that are also chemically reinforced. Thus, a sufficient strength is be obtained for the glass article. Thus, the quality of the chemically strengthening is improved on the inner hole edge reducing the level of loss and more particularly the edge effects.

Optional but preferred coating step c)

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

[0056] Indeed, in one preferred embodiment of the present invention, before the inner portion is separated from the glass sheet article through the at least one separating line, the glass sheet article is submitted to a coating treatment. Indeed, it has been found that when such coating step is performed before the separation of the inner portion from the remaining part of the glass sheet article, it allows to coat the remaining part of the glass sheet up to the separation line while avoiding the coating to drip along the edges of the inner hole, would the inner hole have been created before the coating step. The method of the present invention not only can provide very sharp and neat edges, partially reinforced edges but as well very neat coated surface in very efficient, simplified and fast production process. [0057] According to one embodiment of the invention, the glass sheet article is coated with at least one transparent and electrically conducting thin layer. A transparent and conducting thin layer according to the invention can, for example, be a layer based on SnO2:F, SnO2:Sb or ITO (indium tin oxide), ZnO:AI or also ZnO:Ga.

[0058] According to another advantageous embodiment of the invention, the glass sheet article is coated with at least one antireflection layer. An antireflection layer according to the invention may, for example, be a layer based on porous silica having a low refractive index or it may be composed of several layers (stack), in particular a stack of layers of dielectric material alternating layers having low and high refractive indexes and terminating in a layer having a low refractive index. A textured glass sheet article may be also used. Etching or coating techniques may as well be used in order to avoid reflection.

[0059] According to another embodiment, the glass sheet article is coated with at least one anti- fingerprint layer or has been treated so as to reduce or prevent fingerprints. Such a layer or such a treatment may be combined with a transparent and electrically conducting thin layer deposited on the opposite face. Such a layer may be combined with an antireflection layer deposited on the same face, the anti- fingerprint layer being on the outside of the stack and thus covering the antireflection layer.

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

[0061] According to another embodiment, the glass sheet article is coated with a paint/enamel, an anti-bacterial glass coating.... According to the present invention, the term "coated/coating" may be a coating as such can be a coating as such as well as a paint or a surface treatment capable of modifying the properties of surface of the glass (mechanical, chemical, opto-energetical, biological, electrical, esthetical properties...) by addition or deletion, modification physico-chemical of the surface material (at a temperature 'visible for the glass' lower than its Tg). [0062] According to another embodiment, the glass sheet article is coated with a coating chosen amongst the following list of non-exhaustive coatings: low- e coating, solar control coating, diamond like coatings, self-cleaning coatings (Tio2, ...), ion implantation coating, lacquer painting (Lacobel type), silver or dielectric coating, conductive inks, infrared transparent inks, semi-transparent inks, fluorescent or up-conversion materials, deposition of 'mesh' (silver nanowires, carbon nanotubes), (nano) laser structuration of the surface, a safety film, a double-sided adhesive, a sol-gel coating (with all their functions ie modification of the color, integration of enzymes, ... ), solar type coatings and thin film etc, the acid attacks, the sanding, the engravings of surface...,

[0063] According to the applications and/or properties desired, the coating may be provided on one and/or both surfaces of the glass sheet article. Also, a combination of several coating may be deposited on one and/or the other face of the glass sheet article as a serigraphy and a coating as such...

[0064] According to one preferred embodiment of the present invention, the glass sheet article is provided with in face 1 (term well known forthe skilled person) an anti-glare, an anti- reflective and an anti- fingerprint coatings and a multicolored serigraphy a safety film in face 2.

Optional but preferred cleaving step (d)

[0065] In a preferred embodiment, the method of the present invention further comprises a cleaving step d). Cleaving occurs once the filamentary damages adjacently aligned along the separation line have been introduced. A point of incidence of laser radiation, preferably of a carbon dioxide laser, is displaced over the surface of the glass article along the separation line so that local tensile stresses are caused in the glass along the separation line in order to cause crack formation between adjacent filamentary damages. This cleaving method step may also be promoted by local cooling following the heating in order to increase the tensile stresses generated in the material. The cleaving step is used for preliminary separation. This makes it possible to initiate formation of cracks connecting the filamentary damages along the separation line so as to cause severing along the separation line at least in sections thereof, but usually without the portion detaching from the main part. Both the filament structures per se and additional cracks in the material as caused by a cleaving step are preliminary damages in the material that extends along the separation line.

Ablation step e)

[0066] The final required step of the method of the present invention is the separation of the inner portion (2) from the glass sheet article (10) at the adjacently aligned filamentary defects along the separation line (3) as illustrated in Figure lb. Separation is achieved by irradiating with an ablation laser to ablate at least one segment (4) within the inner portion (2). The segment has 2 end points located on the separation line (3). It has substantially the same thickness, T, than the glass sheet article and has a width equal to or greater than of > 150pm so that the inner portion detaches from the main part at the adjacently aligned filamentary defects along the separation line.

[0067] The glass sheet article extends long a plane, P, defined by a longitudinal axis, X, and a vertical axis, Y. The thicknesses are measured in the direction normal to the plane, P. The width is measured along the plane, P. In a preferred embodiment the segment (4) has a width equal to or greater than 200pm (W > 200pm), preferably equal to or greater than 250pm (W > 250pm). It can be contemplated that the segment does not have the same width along its length such as in a moon shape. In this instance, it is required that the minimal width of the ablation segment is equal to or greater than 150pm. Typically, the segment will have a width equal to or less than 500pm (W < 500pm), preferably equal to or less than 450pm (W < 450pm), more preferably less than equal to or 400pm(W < 400pm). It is recognized that the larger is the width of the segment, the more time takes the separation step.

[0068] The objective of the ablation step of the process of the present invention is to reduce the volume of the inner portion to counteract the compression forces between the remaining part of the glass sheet article and the inner portion. Indeed, even if the glass has enough internal stress to start self-separation after the formation of the defect line, the geometry of the cut contour may prevent an inner portion from releasing. This is the case for most closed or inner contours, such as simple holes or slots. The inner portion of the hole will remain in place due to the compression forces present in the glass sheet. The cracks may propagate between the perforated defects, but no room exists to allow the piece to fall out of the glass sheet article. [0069] Depending on the shape of the inner portion to be removed, several embodiments for the segment to be ablated can be considered to increase further the speed and ease of the removal of the inner portion. For example, more than one segment across the inner portion can be considered. In another embodiment, the ablated segment can run along at least 50%, preferably at least 75%, more preferably at least 100% of the perimeter of the inner portion.

[0070] FIG3 illustrates different embodiments of the glass sheet article of the present invention wherein the inner portion is of different shape and of different ablation segments shapes and sizes. All Figures should be considered for illustrative purposes only. In particular, Fig. IB and FIG.3 are very schematic to illustrate the separation line, the inner portion and the segment.

[0071] FIG3a illustrates a glass sheet article with an inner portion having a rectangular shape with curved angles and with an ablation segment running along 100% of the perimeter of the inner portion. FIG.3b illustrates a glass sheet article with an inner portion having an oval shape and a single ablation segment along the longest diameter of the inner portion. FIG.3cde illustrates 3 different embodiments of a glass sheet article with an inner portion having a circular shape. FIG.3c illustrates the embodiment with 2 ablation segments running along 2 diameters of the circular inner portion. In this instance, the 2 segments are perpendicular to each other but any angle between the segments can be herein contemplated. FIG.X3d illustrates the embodiment with a single ablation segment running along the 50% of perimeter of the circular inner portion and wherein the ablation segment has a moon shape. In this instance, the ablation segment does not have the same width along it length. FIG.3e illustrates the embodiment with a single ablation segment running along the entire perimeter of the circular inner portion.

[0072] Glass ablation by laser is a process in which a laser is used to remove material from a glass surface. The laser heats up the glass to a high temperature and vaporizes it, removing small amounts of material at a time. The ablation is achieved with a laser beam with intensity high enough to cause rapid melting, leading to evaporation of the glass. The ablation process is done by layer by layer until the thickness T is removed. Typically, the ablation laser system has a wavelength within the range 193nm - 1070nm, pulse duration below Ips, ideally below 100ns. The average power of the laser system is in general of a few hundred watts. The laser can operate at a repetition frequency above 100Hz and with the laser spot diameter at the glass surface below 100pm. The scanning speed of the laser system is typically above 50mm/s.

Production of the glass sheet article from a glass substrate

[0073] The glass sheet article can be manufactured by any known method in the art. However, it is preferred that the glass sheet article is produced from a glass substrate by a similar manufacturing method using filamentation / chemical strengthening / separation whereby typically a large number of glass sheet articles can be manufactured from a large glass substrate.

[0074] Therefore, in a second embodiment, the present invention relates to a method for manufacturing at least one glass sheet article (10) having a thickness, T, and comprising an inner hole (1) from a glass substrate (20). As illustrated in Figure 5, such manufacturing method comprises, firstly a step of filamentation (Step a)) followed by a step of chemical strengthening (Step b) that can optionally be followed by a step of coating (Step c)) and preferably by a step of cleaving (step d)) and finally a step of separation (Step d)). The description of the different steps that have been described above in reference to the glass sheet article apply herein mutatis mutandis to the glass substrate.

[0075] It has been indeed found that when inner holes are created in the glass sheet articles before the glass substrate is subjected to chemically strengthening, it decreases the rigidity of the glass substrate and increases significantly the risk of breakage during all following processing steps such as chemical strengthening coating, handling and transportation. Therefore, the second embodiment of the present invention avoids these drawbacks and provide an efficient method for the manufacture of high quality glass sheet articles comprising an inner hole.

[0076] The filamentation process of step a) is the same step as described above in reference to the method for the making of the inner hole within the glass sheet article. This step comprises a sub-step of filamentation al) for the manufacture of the at least one glass sheet article along an intended separation line which divides the glass substrate into the at least one glass sheet article to be separated and a substrate remaining part. This step also comprise a sub-step of filamentation a2) for the separation an inner portion (2) from a glass sheet article along an intended separation line (3) which defines an inner portion to be separated. For process efficiency, it is preferred that the separation lines dividing the glass sheet articles from the glass substrates and the separation lines for the separation of the inner portion are performed at the same time. It can be contemplated however that the sub-steps al) and a2) are performed separately in any order.

[0077] As described above, a step b) of chemical strengt he riing is performed on the surface of the glass substrate. By subjecting the glass substrate on which the separation lines which divides the glass substrate into the at least one glass sheet article to be separated and the separation line which defines an inner portion to be separated, to a chemical strengthening treatment, a compression stress layer can be formed on both surfaces of the glass sheet article and on edges of the glass sheet articles and on the edges of the inner hole.

[0078] A third, optional but preferred^ coating step c) step can be performed on the surface of the glass substrate. It has been found that when such coating step is performed before the separation of the inner portion from the remaining part of the glass sheet article and before the separation of the different glass sheet articles from the glass substrate, it allows the coating of the glass sheet article around its edges and around the edges of the inner hole up to the separation line while avoiding the coating to drip along the edges of the glass sheet article / inner hole, would the glass sheet article / inner hole have been created before the coating step. Hence, the method of the present invention not only can provide very sharp and neat edges, partially reinforced edges but as well very neat coated surface in very efficient, simplified and fast production process.

[0079] A fourth, optional but preferred, step is the cleaving step d) comprising the cleaving step dl) of the separation lines (3) forming the glass sheet articles (10) (Step dl)) and the cleaving step d2) of the separation lines (3) forming the inner hole (1) within the glass sheet articles (10). For process efficiency, it is preferred that the separation lines dividing the glass sheet articles (10) from the glass substrate (20) and the intended separation lines for the separation of the inner portion are performed at the same time. It can be contemplated however that the sub-steps dl) and d2) are performed separately in any order. The same techniques described above in relation to the cleaving step d) apply herein. [0080] The final step of the method of the second embodiment of the present invention is the separation step e) that comprises a separation step el) to separate the glass sheet article (10) from the glass substrate (20). Any separation technique can be used. Separation step d) further comprise a separation step e2) of the inner portion (2) from the glass sheet article (10) at the adjacently aligned filamentary defects along the separation line (3), by irradiating with an ablation laser to ablate at least one segment within the inner portion, wherein the at least one segment has two end points located on the separation line, has substantially the thickness, T, and has a width, W, equal to or greater than 150pm (W > 150pm). Depending on the separation technique used to separate the glass sheet articles from the glass substrate, steps el) and e2) can be performed at the same time or sequentially in any order.

[0081] Separation of the glass sheet article from the glass substrate is preferably achieved by a process of filamentation of releasing lines created around the contours of the glass sheet article. Filamentation step of the releasing lines a3) can occur separately or during the filamentation step al) for the production of the at least one glass sheet article along a separation line which divides the glass substrate into the at least one glass sheet article to be separated and/or during step a 2) for the separation an inner portion from a glass sheet article along a separation line (3) which defines an inner portion to be separated. Indeed, filamentation steps al), a2) and/or a3) can be performed at the same time or sequentially in any order. In a preferred embodiment, filamentation step al) and step a2) are performed simultaneously in a single step which is followed by filamentation step a 3 ) before the step of chemical strengthening. Alternatively the filamentation step of the releasing lines a 3) can be performed just before or after the separation step el) of the inner portion from the glass article.

[0082] Thanks to the proposed method of the second embodiment, a chemically strengthened, preferably coated glass sheet article with an inner hole may be produced from a simple method wherein the chemically strengthening and the optional coating processes can be consecutively applied directly on a larger glass substrate. The glass sheet articles, following separating lines determined in function of the required size and shape of the glass article, are then separated from the large sized glass. The inner portion, following separation lines determined in function of the required size and shape of the inner hole are separated as per the ablation separation step e2). Thus, the strengthening, the preferred coating and the separation of the glass articles are better controlled. Also, the coating deposition - when used, by this method is much more easy as it is performed on a large sized glass panel. Therefore, the production yield are increased and manufacturing costs are reduced. Thanks to this method, a coating and painting deposition edge-to-edge is easily manufacturable. Furthermore, the inventive method provides a mean for substantially saving consumption of coating material and glass substrate.

[0083] Furthermore, the inventive method provides a mean for obtaining a chemically strengthened coated glass article that can be cold bent. The method according to the present inventive is less expensive and more efficient than conventional method for manufacturing a coated chemically strengthened glass. As the name indicates, cold bending is performed with the factory's natural temperature. The process starts by putting the glass into a frame that mechanically bends the glass into the desired frame shape. In the frame installation process, the glass is glued or screwed directly into the frame. The frame is then ready for installation into a vehicle or a building. The thinner the glass, the easier it is to bend from a mechanical perspective. The shape, however, can also have a twisted design. By this method, the cold bending performances are enhanced because the end faces of the glass article are strong thanks to the ion exchange.

[0084] The cold bending is particularly appreciated for bending glass article for interior and exterior glazing part for automotive such as glass console, dashboard, trim element for door, pillars, windshields, side windows, back windows, sun roofs, separation walls, ... According to the present invention, after the strengthening and preferably the coating, the level of potassium on the surface of the glass article is higher than the level of potassium presents on the edges on the glass article and of the inner hole. The level of potassium in the end faces of glass article is increased during the chemical strengthening. Therefore, the glass article's end faces are more resistant to external load / stress. Thus, faces of the glass articles that can be stressed in tension are better reinforced (in particular in cold bending) and the compression is limited in places where there is no need of compression 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, GET, is comprised between 70x10-7 /°C and 100x10-7 /°C (70xl0-7/°C < GET < 100 10-7/°C); preferably between 80x10-7 /°C and 95x10-7 /°C (80x10- 7/°C < GET < 95 10-7/°C). The thermal expansion coefficient of a glass is a parameter that indicates how the dimensions of a corresponding glass element will change by expansion or contraction as a result of a change in temperature. Thermal expansion coefficient refers to the coefficient of linear thermal expansion -=(1/L) (AL/AT), wherein AT denotes the temperature difference and AL the change along a linear dimension relative to the original length L.

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

Glass sheet article

[0087] The present invention concerns also a glass article obtained by the methods described above. The glass article may be used for example, in fields of cover glass for electronic equipment, glazing for building materials, glazing for vehicles..., for which high strength is often required for safety reasons and to be in line with safety rules required for such glazing.

[0088] In particular, the present invention proposes a decorative panel fora vehicle's interior. A decorative panel according to the invention is mounted on any part in the vehicle's interior in orderto provide a better aesthetic orto secure or protect some part of the vehicle's interior. Such decorative panel can be mounted to cover (either fully or partially) doors, door handles contours, parts of the dashboard or the center console (where the center console means the console between the front passengers' seats, which can extend towards the dashboard), back of seats (including headrest's back), roofs, armrests, ... A vehicle refers to any kind of vehicles such as (but not restricted to) a car, a van, a lorry, a motorbike, a bus, a tram, a train, a drone, an airplane, an helicopter and the like.

Example

[0089] 45 glass articles comprising each 2 inner holes were made by the following method. A glass substrate made of aluminosilicate glass having a length of 1000mm, a width of 1000mm, and a thickness of 1.3mm was prepared. The inner holes have a surface of 20mm2. The glass substrate has the following composition expressed in percentage by weight of total composition:

Filamentation step a)

[0090] The inner holes within the glass sheet article and the glass sheet articles within the glass substrate were created by a single filamentation step. The glass substrate was irradiated with a laser in the direction of the main surface side to form two or more in-plane void regions in the vertical direction and the horizontal direction. The laser, Hyper Rapid NX produced by Coherent (Germany), which is capable of emitting a short pulsed-laser of picosecond order, was used. The frequency of one burst of the laser was 80 kHz, the pulse width was 9 picoseconds. Laser irradiation was achieved only once in each in-plane void region (accordingly, 1-pass laser irradiation). In each in-plane void region, the center-to-center distance between the centers of the surface voids was set to 5 pm. The separation lines of the glass sheet articles within the glass substrate and the separation lines of the inner hole within the glass sheet article were created at the same time. Chemical strengthening step b)

[0091] The 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 no pre-splitting in the glass substrate.

Coating step c)

[0092] After washing, two layers of silk screen printing were performed on one side of the glass substrate. Ink was a black organic. Curing condition was 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-reflective coating was added inside a vacuum chamber by digital spattering process of the anti-reflective functional layer and an anti-fingerprint organic material was deposited on the top of the anti- reflective functionals layer by evaporation.

Additional step

[0093] After chemical strengthening and coating surface treatments, additional release lines for the separation step el) were created by the same laser and condition than described above. These additional release lines were self-cleaved by central tension of chemical tempered glass.

Cleaving step d)

[0094] The separation lines of the glass sheet articles within the glass substrate and the separation lines of the inner holes within the glass sheet article were interconnected by CO2 laser which is Diamond J5 produced by Coherent. CO2 laser was irradiated from anti-reflective and anti-fingerprint coated side. Average power was 25W, estimated focus diameter was 5mm.

Separation step e)

[0095] The glass sheet articles were firstly separated from the glass substrate by mechanical breaking of the releasing lines created in the above step.

[0096] For the separation of the inner holes within the glass sheet article, a segment of the inner portions was ablated by ablation laser. A nano-second pulsed green laser irradiated a segment of 150pm thick around 100% of the perimeter of the inner portion to create space for the inner portion to fall out of the glass sheet article and create the inner hole. The laser average power was 50W and its estimated focus diameter was 30 urn.

Claims

1. A method for making an inner hole (1) into a glass sheet article (10) having a thickness, T, whereby an inner portion (2) is separated from the glass sheet article along a separation line (3); the method comprising at least the following steps in the following order: c) a step of filamentation wherein filamentary defects are produced in the volume of the glass sheet article in the form of sub-micron hollow channels adjacently aligned along the separation line wherein the defects are produced by laser pulses of an ultrashort pulse laser, wherein the material of the glass sheet article is transparent for the laser pulses; wherein the laser pulses generate a plasma within the volume of the glass sheet article, which causes the filamentary defects; and wherein the incidence points of the laser pulses on the glass sheet article are displaced over the surface thereof along the separation line; to introduce the filamentary defects adjacently aligned along the separation line; d) a step of chemical strengthening of the glass sheet article; f) a separation step of the inner portion from the glass sheet article at the adjacently aligned filamentary defects along the separation line, by irradiating the inner portion with an ablation laser to ablate at least one segment (4), wherein the at least one segment has two end points located on the separation line, has substantially the thickness, T, and has a width, W, equal to or greater than 150pm (W > 150pm).

2. A method for manufacturing at least one glass sheet article (10) having a thickness, T, and comprising an inner hole (1), from a glass substrate (20); the method comprising the following steps in the following order: al) a step of filamentation for the production of the at least one glass sheet article along a separation line which divides the glass substrate into the at least one glass sheet article to be separated, and a 2) a step of filamentation for the separation an inner portion (2) from the glass sheet article along a separation line (3) which defines an inner portion to be separated, wherein filamentary defects are produced in the volume of the glass substrate in the form of sub-micron hollow channels adjacently aligned along the separation lines wherein the defects are produced by laser pulses of an ultrashort pulse laser, wherein the material of the glass substrate is transparent forthe laser pulses; wherein the laser pulses generate a plasma within the volume of the glass substrate, which causes the filamentary defects; and wherein the incidence points of the laser pulses on the glass substrate are displaced overthe surface thereof along the separation line; to introduce the filamentary defects adjacently aligned along the separation lines; c) a step of chemical strengthening of the glass substrate (20); and f) el) a separation step to separate the glass sheet article (10) from the glass substrate (20), e2) a separation step of the inner portion (2) from the glass sheet article at the adjacently aligned filamentary defects along the separation line (3), by irradiating the inner 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, has substantially the thickness, T, and has a width W, equal to or greater than 150pm (W > 150pm).

3. A method according to any one of claims 1 and 2 further comprising a cleaving step d) performed along the separation line(s), by which the filaments are interconnected, such cleaving step being performed just before the separation step e).

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

5. A method according to any one of the preceding claims wherein the inner hole has a surface equal to or less than 300mm² (S < 300mm²) ; preferably equal to or less than 150mm² (S < 150mm²), preferably equal to or less than 120mm²(S < 120mm²), more preferably equal to or less than 80mm² (S < 80mm²).

6. A method according to any one of the preceding claims wherein the inner hole has a surface equal to or greater than 3mm² (S > 3mm²), preferably equal to or greater than 5mm² (S > 5mm²).

7. A method according to any one of the preceding claims wherein the at least one segment within the inner portion, has width equal to or greater than 200pm (W > 200pm), preferably equal to or greater than 250pm (W > 250pm).

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

9. A method according to any one of the preceding claims 1 to 8 wherein the at least one segment runs along at least 50%, preferably at least 75%, more preferably along 100% of the perimeter of the inner portion.

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

11. A glass sheet article obtained according to the any one of the method claims 1 to 10.

12. A glass sheet article according to claim 11 having a soda-lime-silicate glass composition, aluminosilicate glass composition or an alkali alumino silicate glass composition.

13. A glass sheet article according to any one of claims 11 to 12 wherein the glass article has a CTE from 70 10’⁷/°C to 100 10’⁷/°C, preferably from 80 10’⁷/°C to 95 10’⁷/°C.