WO2025081367A1

WO2025081367A1 - Method and device for forming locally slimmed glass and foldable plate shaped glass article manufactured therewith

Info

Publication number: WO2025081367A1
Application number: PCT/CN2023/125156
Authority: WO
Inventors: Wei Xiao; Jiahui JI; Feng He; Holger Wegener
Original assignee: Schott Glass Technologies Suzhou Co Ltd; Schott AG
Current assignee: Schott Glass Technologies Suzhou Co Ltd; Schott AG
Priority date: 2023-10-18
Filing date: 2023-10-18
Publication date: 2025-04-24
Anticipated expiration: 2026-04-18
Also published as: TW202530146A

Abstract

A method for producing a foldable glass article (1) is provided, the glass article (1) having a strip shaped section (3) with a reduced average thickness compared to adjacent sections (5, 7) so that the stiffness of the strip shaped section (3) is reduced due to the reduced average thickness so that the glass article (1) can be folded about the strip shaped section (3) without breaking, the method comprising shaping the glass (10) of a glass sheet (2) in a hot-forming step by distributing the softened glass so that the glass thickness is reduced along the strip shaped section (3).

Description

Method and device for forming locally slimmed glass and foldable plate shaped glass article manufactured therewith

Specification

Field of the invention

The invention relates to manufacturing of glass sheets in general. Specifically, the invention concerns the production of glass sheets having one or more sections with reduced thickness to facilitate bending of the glass.

Background

Foldable electronic displays make use of a front cover or carrier that is sufficiently flexible to allow for a tight bending. However, providing a both foldable and durable cover or carrier for an electronic display has been proven to be challenging. Currently, a structured metal plate is frequently used as back-plate for flexible support of the display. A tuned folding force is provided by local structuring. Typically, stainless steel or titanium with a thickness of about 0.15 mm is used for this back-plate. However, a disadvantage of metal carriers is that they are prone to fatigue due to the ductility of the material.

An alternative material for a flexible display is glass which also may provide considerable strength, particularly, if the glass is chemically strengthened. Glass, on the other hand is a brittle material and usually not suited for bending. For current foldable devices, ultrathin glass (UTG) has become the standard solution as a display cover glass. Its flexibility and foldability are key to the fold application. Still, one disadvantage of UTG is its minimal thickness and therefore low resistance to sharp impacts or scratches. To achieve a higher impact resistance the glass would have to be thicker, which negatively affects its bendability. However, a bendable glass sheet may be obtained by structuring a strip like region to reduce its stiffness. Thus, cover glasses with hinge structures or thinned folding regions have become more and more interesting for manufacturers. These cover glasses have thicker glass in the main display areas and either structured or thinned folding regions for the necessary flexibility.

Various approaches therefore are attempted. One possibility is to introduce an arrangement of holes. However, this method requires multi-step processing such as outlining the holes using a laser and subsequent etching.

Next generation foldable display devices even go beyond a single-fold design and incorporate multi-fold functionality for even bigger screens. Popular solutions are for instance the so-called S-, G-, or book-fold displays. the S-and G-type folding variant, features two folding regions with two different bending radii. Among the two variants, the S-type is particularly special, because in contrast to previous foldable devices, this display design will feature foldable cover glass also on the unprotected outside of the device when it is in folded state. In this case, also at least one folding region will be exposed on the outside of the device in an especially vulnerable state, as the glass is under tensile stress in its folded state. Additionally for these foldable displays, locally structured glasses will probably not be the best solution as cover glasses, due to their delicate structured hinge regions and the potential optical disadvantages associated with those. Hence, locally slimmed glass could be a viable solution.

So far, locally slimmed glasses are mainly being manufactured via etching from a uniformly thick preform glass. By various etching techniques, the folding regions are being thinned. These methods can include or be combined with: locally applying etching solution to the fold region, by either applying an etching paste or liquid, masking of the folding region etc., dipping of only the folding region into an etching solution, locally machining (laser or mechanical machining) the folding region with subsequent etching, or application of etching solution with local heating to increase etching speed only in the target area and other methods. What all of these methods have in common is that they are all secondary procedures that require selective post processing of a bare glass substrate with uniform thickness, which are technically difficult, and time and cost intensive.

US 2021/0107829 A1 discloses a method, wherein the glass is thinned using laser ablation. The ablation process may be carried out in the hot state of the glass ribbon. However, laser ablation requires high beam energies and typically results in narrow trench like structures as determined by the beam profile. To obtain a broader region of reduced stiffness, a multitude of parallel trenches are introduced.

It is therefore an object of the invention to facilitate fabrication of foldable glass sheets, particularly glass sheets useable as carriers for flexible electronic displays. This object is solved by the independent claims. Advantageous refinements are defined in the respective dependent claims.

Summary of the invention

Accordingly, a method for producing a foldable glass article is provided, the glass article having a strip shaped section with a reduced average thickness compared to adjacent sections so that the stiffness of the strip shaped section is reduced due to the reduced average thickness. This way, the glass sheet can be folded about the strip shaped section without breaking. The method comprises shaping the glass of a glass sheet in a hot-forming step by distributing the softened glass so that the glass thickness is reduced along the strip shaped section. A foldable glass article as disclosed herein is understood as a glass article which may be bent at the strip shaped section so that the adjacent sections change their angle from 0° to at least 90°, preferably at least 120°. If fully folded, a booklet like shape is obtained, with the adjacent sections being in opposition at an angle of or near 180° or even more than 180°, e.g. if the opposing edges are brought into contact in folded state.

The method is based on the principle that the structuring of the glass article is achieved by hot forming rather than subtractive forming methods such as ablation or cutting out holes. In particular, the glass may be distributed with the method according to this disclosure without removing glass from the glass sheet.

A device for carrying out the method as disclosed herein to produce the glass article accordingly has means to distribute glass in softened or molten state to produce a glass sheet having a strip shaped section with a reduced average thickness compared to adjacent sections so that the stiffness of the strip shaped section is reduced and the glass sheet can be folded about the strip shaped section without breaking.

Distributing or re-distributing the glass in a hot forming process with the method or device as described herein typically results in a specific shape of the locally slimmed section of the glass article. Specifically, a foldable plate shaped glass article may be obtained, having two opposed side faces and a circumferential edge and a strip shaped section with a reduced average thickness compared to adjacent sections so that the stiffness of the strip shaped section is reduced due to the reduced average thickness so that the glass sheet can be folded about the strip shaped section without breaking, the strip shaped section extending laterally along the side faces and being terminated at both of its ends by the circumferential edge. The surface profile of at least one of the side faces and/or the thickness profile within the strip shaped section is continuously curved, wherein the surface in the center of the strip shaped section is concavely curved and wherein this concave surface curvature changes into a convex surface curvature in direction from the center towards the adjacent sections so that a centered concavely curved surface portion is arranged between two convexly curved surface portions, wherein the curved surface portions form a depression. In particular, in difference to glass articles which are foldable due to an arrangement of holes, the strip shaped section may have a closed surface, i.e. is lacking of openings.

The glass article 1 producible with the methods or devices described herein is useable for foldable consumer electronics such as mobile phones, tablet computers, laptops, screens (Monitors or TV's) . Additionally, foldable glasses of the present invention can also be used as back-plates for respective foldable mobile phones. Thus, in a further aspect of this disclosure, an electronic device is provided comprising a glass article as described herein. The glass article may in this regard in particular serve as a front cover, or a substrate or support for electronic components.

The invention is described in the following in more detail with reference to the accompanying figures.

Brief description of the drawings

Fig. 1 shows an orifice of a drawing apparatus.

Fig. 2 shows a drawing apparatus with an orifice as shown in Fig. 1.

Fig. 3 shows a glass article producible with the apparatus of Figs. 1, 2.

Fig. 4 is a side view of a further embodiment of a glass article.

Fig. 5 shows examples of orifices to produce glass articles with multiple folding regions.

Fig. 6 shows examples of glass articles in folded state.

Fig. 7 shows an orifice for producing a glass ribbon with multiple folding regions and oppositely arranged protrusions.

Fig. 8 shows a section of a glass ribbon with cutting lines to produce foldable glass articles therefrom.

Fig. 9 shows a further embodiment of an apparatus, having local heating means.

Fig. 10 shows a variant of a glass article with thickened transition sections between a section having reduced thickness and adjacent sections.

Figs. 11, 12 show variants of orifices having local heating means.

Fig. 13 shows parts of a float glass drawing apparatus.

Fig. 14 shows an apparatus for down drawing having various means to introduce slimmed regions transversely to the drawing direction.

Fig. 15 and Fig. 16 show an embodiment of an overflow fusion trough.

Fig. 17 illustrates method steps to produce a locally slimmed glass sheet by heating a strip-shaped region and drawing the sheet vertically to the longitudinal direction of the strip-shaped region.

Fig. 18 illustrates method steps to produce a locally slimmed glass sheet by re-drawing a glass sheet.

Fig. 19 and Fig. 20 show embodiments of glass sheets or glass articles produced by fusing glass stripes.

Fig. 21 shows a waterfall down draw apparatus.

Fig 22 shows a top view onto the device shown in Fig. 21.

Fig. 23 and Fig. 24 show an overflow-fusion device set up to combine glass melt streams.

Fig. 25 and Fig. 26 show variants of the embodiment of Figs. 23, 24 with single sided troughs.

Fig. 27 shows a down drawing apparatus with a guiding body.

Detailed description

There is a variety of means to distribute glass in softened or molten state to produce a glass sheet having a strip shaped section with a reduced average thickness compared to adjacent sections. A preferred method to distribute the glass is drawing the glass sheet from a melt or a preform. Generally, in a preferred embodiment, the method for forming the glass sheet comprises forming a glass sheet in form of a glass ribbon from a glass melt by drawing, wherein the glass is distributed before the glass of the glass ribbon cools down and solidifies. There are various methods to draw a glass ribbon from a melt, wherein preferred variants thereof are down drawing and overflow-fusion. Figs. 1 and 2 show an example of a device 30 for producing a glass sheet 2 in form of a glass ribbon 20 by down drawing. Without restriction to a particular drawing method, distributing the glass may be accomplished by at least one protrusion locally reducing or obstructing the flow of a glass melt, in particular by extending into the flow of a glass melt. The protrusion locally reduces the flow and thereby also reduces the resulting glass thickness. Of course, the protrusion 14 shown in Fig. 1 is merely an example. The shape, width and height of the protrusion 14 can be varied in many ways.

The apparatus 30 comprises an elongated orifice 12 in a duct or container 15, through which the glass melt 21 flows and is drawn into glass ribbon 20. A drawing force may be exerted by means of drawing rollers 13. Fig. 1 shows an example of an orifice 12 in top-view. Generally, without restriction to the specific example, a glass sheet 2 in form of a glass ribbon 20 is formed by down drawing the glass 10 from a slit shaped orifice 12, the orifice 12 having at least one protrusion 14 narrowing its width. This protrusion 14, which may be located on one or either sides of the orifice 12, or the corresponding narrowing of the orifice distribute the glass 10 so that the thickness of the glass ribbon 20 is lowered in a strip shaped section 3 extending downwards from the protrusion 14. Glass articles that are foldable at the strip shaped section 3 may then be cut from the glass ribbon, with the cutting direction extending transversely, in particular vertically to the longitudinal direction of the glass ribbon 20 or the strip shaped section 3, respectively.

A foldable glass article 1 which may be produced by cutting the glass ribbon 20 vertically to the drawing direction is shown in Fig. 3. The glass article 1 is generally plate shaped, having two opposed side faces 101, 102 and a circumferential edge 104. A strip-shaped section 3 where the plate shaped article 1 is locally slimmed extends along the surface of the article 1. In particular, the strip shaped section 3 extends all over one of the side faces 101 so that the strip shaped section 3 is terminated at two opposed sections of the edge 104. In other words, section 3 is terminated at both of its ends 33, 34 by the circumferential edge 104. The surface within the strip shaped section 3 is continuously curved. Further, the surface in the center of the strip shaped section 3 is concavely curved. The concave surface curvature in the center changes into a convex surface curvature in direction from the center towards sections 5, 7 which are adjacent to the strip shaped section 3. This way, a centered concavely curved surface portion 37 of strip shaped section 3 is arranged between two convexly curved surface portions 36, 38. Further, the curved surface portion forming a depression 105 which results in the local slimming or reduced average thickness, respectively. This continuously curved surface profile and/or the thickness profile of the strip shaped section 3 is achieved by the distribution of the glass during the hot forming. The smoothly rounded profile is also advantageous to achieve a high breaking strength. Generally, it is preferred to distribute the glass during hot forming so that a rather shallow depression compared to its width is formed. This is advantageous for the breaking strength and also facilitates mounting or depositing of further components as the surface may be regarded as quasi-planar. Such a smooth curvature may be achieved if the combined width of the convexly curved surface portions 36, 38 of the strip shaped section 3 is at least as large as the width of the concavely curved surface portion 37. In another alternative or additional embodiment, which is also realized in the example of Fig. 3, the width of the depression 105 is at least three times, preferably at least five times, particularly preferred at least ten times larger than the depth of the depression 105. In a preferred embodiment, the width of a strip shaped section 3 generally may be between 5 mm and 50 mm, preferably between 8 mm and 20 mm. The thickness of a glass article 1 as described herein is preferably between 50 μm and 1500 μm, preferably 70 μm to 1000 μm. A typical thickness for a glass article useable as a back plate for a smart-phone or tablet display is in the range from 60 μm to 200 μm. This thickness is referred to as the general or average thickness outside of a strip-shaped section 3, i.e. within adjacent sections 5, 7.

The minimum thickness within the strip shaped section 3 of reduced thickness is 15 μm to 150 μm. These dimensions of course also depend on the thickness of the glass article 1, i.e. its thickness outside of a strip-shaped section 3. Therefore, the above given ranges overlap, although of course the dimensions are always chosen so that the average thickness in a strip-shaped section 3 is lower than in adjacent sections 5, 7.

As in the example of Fig. 1, the orifice 12 may be asymmetric in that a protrusion 14 is arranged on only one side of the orifice 12. This may result in an asymmetric profile of the glass article 1, similarly to the example of Fig. 3, wherein a depression 105 is formed in one of the side faces 101. As shown in Fig. 3, the opposite side face 102 may be flat as shown. However, depending on the viscosity of the glass while it is distributed to form the specific profile disclosed herein, due to fluid dynamics a depression may form on both sides 101, 102 of the glass article 1, even if there is a protrusion in the orifice on only one side. Fluid dynamics in the molten glass can lead to a depression also from the opposite side of the glass. Thus, according to one embodiment of the glass article 1, the surface profiles of both side faces 101, 102 and/or the thickness profile within the strip shaped section 3 are continuously curved so that the side faces 101, 102 are approximating each other towards the center of the strip shaped section 3. Such an embodiment is shown in the side view of Fig. 4.

However, if the obstructing feature such as a protrusion in the orifice contour is pronounced enough, it is possible to produce an asymmetric surface profile with the depression on one side face being more pronounced than a depression on the opposite side. This case is also realized in the example shown in Fig. 4, wherein the depression 105 is deeper than the opposite depression 106. Thus, according to one embodiment, generally, the depression 105 within the strip shaped section 3 on one of the side faces 101 has a larger depth than the depression on the opposed side face 102. In another embodiment, which may be advantageous for specific applications, the depth of the depressions 105, 106 may be similar or equal so that the surface profiles are substantially mirror symmetric.

A glass article 1 according to this disclosure and as exemplary shown in Figs. 3 and 4 is characterized by a fire polished surface, therefore having very low surface roughness, Thus, according to one aspect of this disclosure, a foldable plate shaped glass article 1, in particular producible using the method or device 30 according to this disclosure is provided, wherein the glass article 1 has two opposed side faces 101, 102 and a circumferential edge 104 and a strip shaped section 3 with a reduced average thickness compared to adjacent sections 5, 7 so that the stiffness of the strip shaped section 3 is reduced due to the reduced average thickness so that the glass sheet 1 can be folded about the strip shaped section 3 without breaking, the strip shaped section 3 extending laterally along the side faces 101, 102 and being terminated at both of its ends 33, 34 by the circumferential edge 104, wherein both side faces 101, 102 including the surface of the strip shaped section 3 have an average surface roughness of less than 0.5 nm, and/or, wherein both side faces 101, 102 including the surface of the strip shaped section 3 have a fire polished surface.

In particular, to be used as a front cover, or a back plate or substrate for a foldable electronic device such as a foldable display, it is advantageous for the breaking stability, if the glass article 1 is chemically strengthened. Chemical strengthening produces a compressive force at the side faces. However, as the thickness of the article 1 varies greatly at the strip shaped section 3, or between the strip shaped section 3 and adjacent sections 5, 7, a difference in expansion due to ion exchange between strip shaped section 3 and the adjacent sections 5, 7 may result, which may cause a wrinkle phenomenon. To counteract this, the compressive stress (CS) and/or the depth of the ion exchange layer (DoL) may be adapted to the local thickness of the glass article 1 in a way that at least one of the parameters CS, DoL is lower in the strip shaped section 3 compared to the adjacent sections 5, 7.

In the example of Figs. 1 and 2, only a single protrusion 14 is provided in the orifice 12. However, to make effective use of current ribbon widths, there may be more strip shaped thinned regions produced with respective protrusions. This may be used to produce glass articles having more than one folding region, or more than one strip shaped section 3, respectively. Fig. 5 shows three examples of orifices to produce glass articles 1 which may be folded at least twice, or, respectively, have more than one folding region or strip shaped section 3.

The orifice of example (a) has two protrusions 14 on the same side 121 of the orifice. A glass article 1 produced from a glass ribbon drawn from such an orifice may be folded in a book-fold manner with the outer sections folded inwards. Example (b) is a variant wherein one of the protrusions is wider than the other one. This leads to strip shaped foldable sections 3 of different widths. This is suitable to produce a foldable glass article where the outer sections can be folded inwardly, with one of the sections overlapping the other one. This kind of fold is generally referred to as a “G-fold” . In example (c) , the protrusions are offset along the orifice 12 as in the other examples, but arranged on opposite side of the orifice 12. This way, the depressions produced by the protrusions are on opposite sides of the glass article, so that the glass article 1 is suited for a S-shaped fold. Fig. 6 shows the respective glass articles derivable using these orifices in folded state. Example (a) shows a book-like folded article 1 which may be obtained with an orifice 12 according to Fig. 5, example (a) The article 1 comprises two laterally spaced strip shaped sections 3 of reduced average thickness and adjacent sections 5, 7, 9, wherein the section 7 is arranged between the strip shaped sections 3. The article 1 can be folded as shown with the outer sections 5, 9 folded inwards towards each other.

Example (b) is a “G-fold” article 1 which is similar to example (a) , however, with the sections 5, 7, 9 being dimensioned so that the outer sections 5, 9 overlap in folded state. As explained above, this article 1 may be produced with an orifice 12 according to example (b) of Fig. 5. Specifically, the strip shaped section 3 between adjacent sections 7, 9 may be broader than the other strip shaped section 3 to provide a larger bending radius so that the section 9 is folded on top of section 5.

A glass article 1 folded in S-shape is shown in example (c) . According to this example, the outer sections 5, 9 are folded in opposite directions so that they face opposite side faces 101, 102 of the centered section 7 arranged between the two strip shaped sections 3. Folding a glass article 1 in this manner may be facilitated if an orifice 12 according to example (c) of Fig. 5 is used, producing a glass ribbon having strip shaped sections 3 with deeper depressions on opposite side faces.

Generally, without restriction to specific examples or drawing methods, these embodiments have in common, that a glass ribbon 20 is drawn, having at least two laterally spaced strip shaped sections 3 with reduced average thickness, wherein a glass article 1 is produced, in particular cut from the glass ribbon so that the glass article 1 has at least two strip shaped sections 3 with at least three sections 5, 7, 9 foldably connected together by the strip shaped sections 3. The glass article 1 having at least two strip shaped sections 3 with at least three sections 5, 7, 9 foldably connected together by the strip shaped sections 3 may of course comprise one or more further strip shaped sections 3 and adjacent sections with substantially uniform thickness.

With the orifices 12 as exemplary shown in Fig. 1 and Fig. 5, a single glass article 1 may be obtained from a glass ribbon 20 per horizontal cut. However, the down drawing method as well as other drawing methods such as overflow-fusion drawing enable to draw glass ribbons 20 with a large width. Therefore, in a development of the method, a glass ribbon 20 with a multitude of strip like sections 3 having reduced average thickness that are laterally spaced in a direction perpendicular to the drawing direction or, respectively, to the longitudinal direction of the glass ribbon 20 is produced, wherein the glass ribbon 20 is cut along at least one cutting line 40 extending along and between two strip like sections 3 and is further cut transversely, preferably perpendicularly to the longitudinal direction of the glass ribbon 20 to obtain a multitude of glass articles 1, each having at least one strip shaped section 3 with reduced average thickness.

Fig. 7 shows an orifice for producing a glass ribbon with multiple folding regions and oppositely arranged protrusions to carry out the embodiment of the method as explained above. As can be seen, the orifice 12 has a multitude of protrusions 14. In this example, the orifice 12 is symmetric, having opposed protrusions 14 on both sides 120, 121. This arrangement will produce symmetric depressions along the strip shaped sections 3. For example, to produce glass articles 1 each having two strip shaped slimmed sections 3 as in Fig. 6, the glass ribbon produced with the orifice 12 may be longitudinally cut between every second pair of sections 3. The cutting positions are shown by hatched lines. Fig. 8 schematically shows a section of a glass ribbon 20 producible with an orifice 12 according to Fig. 7. The vertical cutting lines 40 extend along the drawing direction and correspond to the hatched lines shown in Fig. 7. The cutting lines 41 extend transversely, in particular perpendicularly to cutting lines 40 and may be referred to as horizontal cutting lines. If the glass ribbon 20 is cut along both lines 40 and lines 41, a multitude of foldable glass articles 1, or at least intermediate products thereof are obtained. Of course, other cutting patterns may be applied. In the example as shown, each foldable glass article 1 has two laterally spaced strip shaped section 3. However, glass articles having a single strip shaped section 3 similarly to the examples of Fig. 3 and Fig. 4 may be produced as well.

Drawing a glass article 2 in form of a glass-ribbon 20 with one or more strip-shaped sections 3 with reduced average thickness can be somewhat challenging regarding controlling the cooling of such ribbons. as the differences in thickness will lead to different cooling speeds of the respective sections. The thin sections will cool down much more rapidly than the thicker sections and may therefore become rigid, while adjacent sections are still soft and deformable. A thickness control of the individual sections is therefore complicated and stress may build up in the ribbon, which can lead to breakage of the ribbon upon bending into the horizontal transport direction at the cold end of the melting tank or during separation of individual sheets. One possibility to avoid building up of strains and achieve homogeneous cooling is to apply a local temperature control. For example, local heaters could be used to adapt the temperature in the one or more thinned strip-shaped sections 3 to adjacent sections. Thus, as also shown in Fig. 2, local heating means 25 may be provided to elevate the temperature within the one or more strip-shaped sections 3 to adapt the temperature therein to adjacent sections 5, 7, wherein the heating means 25 are in particular located or arranged so that elevating the heating to the respective strip-shaped section 3 is applied at a position, where the glass of the adjacent sections 5, 7 is still softened or formable, respectively.

On the other hand, local heating may also be used to control the thickness of the glass ribbon 20. In other words, the means to distribute glass in softened or molten state to produce a glass sheet 2 having a strip shaped section 3 with a reduced average thickness compared to adjacent sections 5, 7 may comprise local heating means. In this regard, without restriction to specific examples, in a further embodiment, a glass sheet 2 in form of a glass ribbon 20 is formed by drawing, wherein the glass 10 while still in a soft state is locally heated to a higher temperature along a strip shaped region 16 compared to adjacent regions of the glass ribbon 20 so that its viscosity along this region 16 is lower than in adjacent regions, wherein the glass thickness is lowered along the strip shaped region 16 due to the drawing. As shown, the strip shaped region 16, i.e. its longitudinal direction generally extends parallel to the drawing direction, or parallel to the longitudinal direction of the glass ribbon. As in the example of Fig. 9, the local heating may be performed using a laser beam 251 from a laser 250 as local heating means. Alternatively, other heating means such as coil heaters may be employed. In the example, two laser beams 251 are used so that two laterally spaced strip-shaped regions 16 are formed extending along the longitudinal direction of glass-ribbon 20. Due to the elevated temperature within the strip-shaped region 16, the viscosity of the glass is locally reduced. This way, these regions are drawn out thinner, compared to untreated regions. Accordingly, a strip-shaped section 3 having a reduced average thickness is formed along the region 16. In difference to the example of the apparatus 30 as shown, heating can be done from both sides of the glass as well, leading to uniform thinning of the glass on either side. Also, heating with different heat source can be combined, like for instance precise laser heating at certain spots with a broader treatment zone of a coil heater. This can for instance be relevant to smooth out transition areas from the thinned region into the thicker areas of the glass. One possible feature of this method, however, is that the glass is distributed so that it moves out of the heated region 16 to form thickened transition sections between the strip-shaped section 3 and the adjacent sections 5, 7, having substantial constant thickness. Fig. 10 shows such a variant of a glass article 1 with thickened transition sections 50, 70 between a strip-shaped section 3 having reduced thickness and adjacent sections 5, 7. The transition sections 50, 70 may be advantageous for the stability and breaking strength of the glass article 1.

Preferably a lateral component of the drawing force can be applied in combination with the local heating, e.g. by the drawing rollers to stretch the rippon transversely to the drawing direction. Thus, a drawing force is applied having a component perpendicular to the drawing direction. For example, the drawing rollers 13, might be oriented slightly inclined against the longitudinal direction of the glass ribbon 20, applying not only a force in a vertical drawing direction but as well a lateral component, that stretches the glass ribbon 20 and thereby reduces its thickness at the region of lowest viscosity. In this embodiment the formation of thickened transition sections between the strip-shaped section 3 and the adjacent sections 5, 7, having substantial constant thickness, can be reduced or completely avoided.

In an alternative or additional solution, applying a secondary heating in the forming region or below, can be achieved by a locally heated down draw orifice in form of either a straight slid or a slid with constrictions, or a protrusion 12, respectively. Fig. 11 shows an orifice 12 with a local heating means 25, e.g. a coil heater 252 to locally elevate the temperature of the glass melt passing the orifice 12 to a temperature above adjacent regions of the glass ribbon 20 to be formed. This way, a strip like region 16 in the glass ribbon 20 with elevated temperature and extending along the longitudinal direction of the glass ribbon 20 is formed similarly to the example of Fig. 9.

Fig. 12 shows a variant of the embodiment of Fig. 11. In this variant, the orifice 12 has at least one protrusion 14 similar to the embodiment of Fig. 1. In the embodiment of Fig. 12, local heating means 25, e.g. a coil heater 252 are provided in or at the orifice 12 to heat the glass melt passing the constriction, or protrusion 14, respectively, to elevate its temperature compared to adjacent regions. In the shown embodiment, the local heating means 25 is arranged at the side 121 of the orifice 12 with the protrusion 14. In Alternatively or additionally, the heating means 25 may be arranged on the opposite side 120 of the orifice. In both cases, a strip shaped region 16 with elevated temperature is formed along the glass ribbon 20. If these local areas at constrictions or protrusions 14 in the orifice 12 are hotter than the rest of the slid, the hotter glass can be drawn out thinner than the relatively colder glass passing through the rest of the orifice 12. Another beneficial effect of a combination of a protrusion 14 with local heating means 25 is that a faster cooling of the thinned strip-shaped section 3 along the glass ribbon 20 may at least partly be compensated. This also holds for other local heating means 25, such as a laser 250 according to the embodiment of Fig. 9.

So far, drawing processes which may be employed for the method according to this disclosure have been described on the basis of down drawing a glass ribbon 20 from an orifice 12. However, other drawing processes may be used as well. Another drawing process is the float process. In the float process, the glass melt is drawn while floating on a liquid metal bath. Fig. 13 shows an example of a device 30 for producing a glass article 1 with a float bath 45 on which a glass sheet in form of a glass ribbon 20 is formed by means of a float process. Further, generally and without restriction to the specific drawing process, distributing the softened glass 10 so that the glass thickness is reduced along a strip shaped section 3 may also comprise blowing a gas jet 49 onto the softened glass 10 or glass melt 21. This embodiment is also realized in the example of Fig. 13. A gas nozzle 47 is provided to blow the gas jet 49 onto the still molten or softened glass ribbon 20. The gas jet 49 displaces the glass 10 outwardly, so that in combination with the movement in drawing direction as indicated by the arrow, a strip-shaped section 3 having reduced average thickness is formed. The gas jet 49 may also be used to locally heat the glass 10. Of course, a multitude of nozzles 47 may be arranged in spaced apart relationship to introduce a multitude of spaced apart sections 3 into the glass ribbon 20.

In the examples describes above, where one or more slimmed sections 3 are introduced into a glass ribbon 20, the longitudinal direction of the strip shaped sections 3 extend in longitudinal direction of the glass ribbon 20, or the drawing direction, respectively. According to further embodiments, however, a glass sheet 2 in form of a glass ribbon 20 is formed by drawing, wherein a multitude of strip shaped sections 3 with a reduced average thickness compared to adjacent sections 5, 7 are formed in the drawing process, with the longitudinal direction of the strip shaped sections 3 extending transversely, preferably perpendicular to the drawing direction.

This structuring of the glass ribbon 20 may in particular be achieved by at least one of

- varying the drawing speed,

- varying the temperature so that strip-shaped regions extending transversely to the drawing direction have an elevated temperature compared to adjacent regions.

Fig. 14 shows an apparatus 30 set up for down drawing a glass ribbon 20 and having various means to produce slimmed strip shaped sections 3 oriented transversely to the drawing direction. These means may be employed alternatively or in combination.

To vary the temperature, it is possible to either adjust the temperature of the drawing tank or the orifice in an oscillating manner. For this purpose, appropriate heating means 25 may be integrated into the container 15 or the orifice 12 as shown. Again, coil heaters 252 or other electrical heating elements may be used. As well, heating means 25 such as coil heaters 252 that have a sufficiently fast response to produce narrow, well-defined regions of elevated temperature may be arranged below the orifice 12, as also shown. Further, heat energy may be deposited onto the glass ribbon 20 by a confined radiation source such as a laser 250, whose laser beam 251 may be swept in a direction transversally to the drawing direction to produce the strip shaped sections of elevated temperature. Due to the elevated temperature of this regions, the glass is softer than in intermediate regions, causing the regions with elevated temperature to expand under the applied drawing force, thereby reducing their thickness so that the strip-shaped sections 3 with reduced thickness are obtained.

Yet another additional or alternative possibility is to control and alternate the drawing speed or drawing force. For this purpose, either the speed of the drawing rollers 13 can be changed in an oscillating fashion, or rollers 13 with non-circular, e.g. elliptical shape, and/or eccentrically arranged rotation axis can be used. In the example as shown, the drawing rollers 13 have elliptical shape and have an eccentrical rotation axis to oscillate the drawing speed and/or drawing force.

As mentioned, a variety of drawing principles may be used to carry out the method as described herein. So far, examples for down drawing and floating to produce glass ribbons 20 with one or more stripe shaped sections 3 having reduced thickness have been shown.

Similar to using an altered contour of a down draw orifice 12, the shape of an overflow fusion supply trough can be adapted as well to vary the flow of molten glass at different locations to obtain the desired thickness profile. Figs 15 shows a cross section of an overflow-fusion trough 18 in operation and Fig. 16 shows a top view onto the trough 18. The glass melt 21 is constantly fed into channel 19 of the trough 18 so that the glass melt 21 overflows the trough 18 and runs down its side walls 180, 182. According to one embodiment, a glass sheet 2 in form of a glass ribbon 20 is formed by overflow-fusion from a trough 18 having a protrusion 14 on at least one of its sides, in particular on at least one of its side walls 180, 182, as also realized in the shown example. A protrusion may alternatively be also on top of the channel one or both of the sides to reduce the glass flow. In the example, protrusions are provided on both opposite side walls 180, 182. However, it is also feasible to arrange a protrusion 14 on only one of the side walls 180, 182 so that an effect similarly to a down draw with an orifice 12 with a protrusion on only one side (e.g. as shown in Fig. 1) is achieved. Thus, such a design may be used to obtain a thinned section 3 with asymmetric profile as schematically shown in Figs. 3, 4. Depending on the ribbon width and the design of the final application, there may of course multiple thinned sections 3 similar to the example of Fig. 8 by providing multiple protrusions 14 on the trough 18.

Alternatively or in addition to the above described embodiments, a convenient approach is glass redrawing which is also a drawing process. Process steps according to one embodiment based on re-drawing are shown in Fig. 17. Specifically, a glass sheet 2 of preferably uniform thickness is provided and may be locally heated along a strip shaped region 16, so that the glass in the strip shaped region 16 softens, and wherein the glass sheet 2 is then drawn in a direction transversely to the strip shaped region 16 so that the strip shaped region 16 is expanded and the glass thickness within the strip shaped region 16 is lowered. This way, a strip-shaped section 3 of reduced average thickness is produced. Heating may be accomplished by appropriate local heating means 25, in particular as already described with respect to embodiments of Figs. 9 and 14. Preferably, the glass of the glass sheet 2 is in a cold or at least rigid state so that only the glass within the strip shaped region 16 is softened. In a variant to this embodiment, the glass sheet 2 is already in a hot state and may even be soft, wherein the glass in the strip shaped region 16 is further heated and softened so that its viscosity is relatively lower compared to adjacent regions. Fig. 17 (a) shows a glass sheet 2 and local heating means 25 arranged on top of one of the side faces 101. A strip shaped region 16 below the local heating means 25 is heated until the glass softens. With the local temperature close to or above the softening point, the regions intended to be slimmed will have a much lower viscosity. Therefore, these regions will deform/elongate much more significantly comparing to the non-heated regions, when a force is applied transversely to the longitudinal direction of the strip shaped region 16. The applied force is shown by arrows in Fig. 17 (a) . Typically, as the total volume of glass is constant, a larger thickness difference between a thinned section 3 and adjacent sections 5, 7 will always lead to a wider slimmed section 3. Fig. 17, chart (b) shows the glass sheet 2 after drawing. The heated region 16 is widened and thinned, now forming a strip-shaped section 3 having a reduced average thickness with respect to adjacent sections 5, 7.

The added width due to the drawing is typically relatively smaller when the initial thickness of the glass is bigger when targeting a same thickness difference. Furthermore, typically, there will be some constriction taking place at the edges of the thinned/drawn out section 3. Thus, advantageously, the processed glass sheet will be cut to size to obtain the glass article 1. However, in some cases it might also be advantageous to have the thinned areas recessed from the main edge to protect the slimmed section 3.

With a relatively large initial thickness, a second redraw process could be done in the direction of the strip shaped section 3 to further reduce the thickness of the whole glass sheet to the desired dimensions. Here a preform with an already pre-shaped thin and thick regions can be drawn out to the target thickness. Typically, the thickness of different regions will be reduced by a same ratio by this process. So, the initial thickness profile shall be well designed to reach a desired final thickness profile. This step may be used with a glass article not only obtained with the process as described with respect to Fig. 17 but with all method variants producing a locally slimmed glass sheet, such as down drawing or overflow fusion. Thus, generally, according to one embodiment, a glass sheet 2 with a strip-shaped section 3 with reduced average thickness is provided and heated so that the glass 10 of the glass sheet 2 softens, and wherein the glass sheet 2 is drawn in a direction along the longitudinal direction of the strip-shaped section 3 to reduce the thickness of the glass sheet 2. This process of re-drawing a locally slimmed glass sheet is illustrated in Fig. 18. Preferably, as shown in chart (a) , a strip-shaped region 16 is heated using local heating means 25. This region extends transverse, in particular vertically to the longitudinal direction of strip-shaped section 3 At the same time, a drawing force is applied in direction along the strip-shaped section 3 is applied as indicated by the arrow. This causes a re-drawing of the heated region which expands along the drawing direction and at the same time reduces its thickness. Chart (b) of Fig. 18 shows the re-drawn glass article 2 having a smaller thickness and higher length than the initial glass sheet 2.

In another alternative or additional embodiment, the glass sheet 2 having a strip-shaped section 3 of reduced average thickness may be subjected to an etching medium. This will uniformly reduce the thickness of the glass sheet. Thus, the average thickness of the strip shaped section 3 is further reduced by etching the glass sheet 2. A similar effect may be achieved with other glass removing methods, such as abrasive methods. Thus, generally, without restriction to a specific type of process, a glass sheet 2 is provided having a strip-shaped section 3 of reduced average thickness, wherein the ratio of the thickness D of the glass sheet 2, which is the thickness of the sections 5, 7 adjacent to the strip-shaped section 3, to the minimum thickness D_min at the strip-shaped section 3 is enlarged by uniformly removing glass from at least one of the side faces 101, 102 of the glass sheet 2. For illustration, the thickness D and the minimum thickness D_min are indicated in chart (a) of Fig. 18.

Etching, in particular for reducing the thickness of the glass article 1 also typically results in a specific surface quality. In particular, in comparison to glass substrates having a folding region formed by laser structuring and etching, a very homogeneous surface quality may be achieved. Thus, according to a further aspect of this disclosure, a foldable plate shaped glass article 1, in particular producible using the method or device 30 according to this disclosure is provided, wherein the glass article 1 has two opposed side faces 101, 102 and a circumferential edge 104 and a strip shaped section 3 with a reduced average thickness compared to adjacent sections 5, 7 so that the stiffness of the strip shaped section 3 is reduced due to the reduced average thickness so that the glass sheet 1 can be folded about the strip shaped section 3 without breaking, the strip shaped section 3 extending laterally along the side faces 101, 102 and being terminated at both of its ends 33, 34 by the circumferential edge 104, wherein the combined surface of both side faces 101, 102 including the surface of the strip shaped section 3 has a roughness homogeneity of more than 90%.

The embodiments presented so far are based on distributing the glass away from a region which is intended to be slimmed. However, it is also possible to feed additional glass to sections adjacent to the slimmed section 3. Thus, instead of diverting or obstructing melt streams to produce a thinned section, the adjacent sections may be thickened by distributing, specifically by adding melt streams. Obviously, this also can result in a glass article having a strip-shaped section 3 of reduced average thickness. Accordingly, in further embodiments, a method is provided, comprising combining and fusing glass melt streams or softened glass stripes having different widths to produce a glass ribbon in which the glass stripes or glass melt streams are arranged so that at least one strip shaped section 3 with reduced average thickness is produced.

Fig. 19 and Fig. 20 show embodiments of glass sheets 2 or glass articles 1 produced therefrom (e.g. simply by cutting the glass sheet 2 to size) produced according to the aforementioned embodiment of the method. In both cases, generally, a glass sheet 27 is fused together with narrower glass stripes 29 so that a gap 22 remains between the glass stripes 29 that is bridged by glass sheet 27. Due to the gap, a strip shaped section 3 is formed having a reduced thickness compared to sections 5, 7, 9 having the combined thickness of the fused glass elements 27, 29. In the variant of Fig. 19, a single strip-shaped section 3 is formed between glass stripes 5, 7, whereas Fig. 20 shows an embodiment with three spaced glass stripes 29, forming two strip-shaped sections 3, and thereby two folding areas between. The glass element 27 and the glass stripes 29 may be fused, e.g. after re-heating until the glass softens. However, this kind of distributing glass may instead be achieved by combining stripes of a glass melt, or glass melt streams, respectively.

In another embodiment, the glass sheet 27 and glass stripes 29 are combined by gluing or, more generally, by a method other than fusing in softened state, i.e. by fixing them together below softening temperature. Thus, generally and without restriction to a specific method of fixing the glass parts together, a method for producing a foldable glass article 1 is contemplated, wherein the glass article 1 has a strip shaped section 3 with a reduced average thickness compared to adjacent sections 5, 7 so that the stiffness of the strip shaped section 3 is reduced due to the reduced average thickness so that the glass sheet 1 can be folded about the strip shaped section 3 without breaking, wherein a glass sheet 27 is connected to narrower glass stripes 29 so that the glass stripes 29 are laterally spaced apart with a gap 22 therebetween, so that a strip shaped section 3 having a reduced average thickness is formed along the gap 3. As mentioned above, fixing the stripes 29 to the glass sheet 27 may be performed by glueing and/or at a temperature, where the glass is not softened but rigid, e.g. at room temperature.

In a refinement of this embodiment, the glass body formed by combining and fixing the glass stripes to the glass sheet 27 may then be drawn out to reduce the thickness.

In one embodiment, a glass-ribbon 20 is formed by a waterfall down draw method. This apparatus as well as other devices discussed herein may have means to combine melt streams of different widths to produce a glass-ribbon 20 with at least one strip-shaped section 3 of reduced average thickness. A device 30 for producing a glass article 1 using the waterfall down draw method is shown in Fig. 21 and the top view onto the device shows Fig. 22. Without restriction to the specific example as shown, The device 30 may comprise a container 15 containing a glass melt 21, the container 15 having a slit 52 through which the glass melt flows out in a melt stream 23 and is guided over a lip 54, wherein this melt stream 23 preferably extends over the full width of the glass-ribbon 20 to be formed, and wherein a second container 16 with a second glass-melt 21 is provided, wherein the glass melt is released through laterally spaced slits 52 out of this second container 16 and guided over a lip 54, wherein the lip 54 of the second container 16 is arranged so that the glass melt streams 24 released from the lip 54 fall onto the glass melt stream 23 on the lip 54 of the first container 15 and combine or fuse with the melt stream 23. The combined melt streams are released from the lip 54 of the first container 15, thereby forming the glass-ribbon 20 which is drawn by pairs of drawing rollers 13.

The glass melt streams 24 from the second container 16 have a gap 22 in between so that a thinned strip-shaped section 3 is formed in longitudinal direction of the glass-ribbon 20.

Alternatively or additionally, a waterfall down draw device may also have means to distribute the glass melt analogously to the down draw device as described with respect to Fig. 1 and Fig. 2. This means that in addition or in alternative to adding melt streams 24, one or more protrusions 14 may be provided at the slit or on the lip to locally reduce the thickness of melt stream 23.

The same principle of combining glass melt streams 23, 24 may be used in other drawing devices as well. Fig. 23 and Fig. 24 show an overflow-fusion device set up to combine glass melt streams 23, 24. Fig. 23 shows a cross section and Fig. 24 a side view of the device 30. Generally, without restriction to the specific set-up as shown in Figs. 23, 24 and also the variant shown in Fig. 25, and analogously to the waterfall down draw device described above, the embodiments are based on an overflow-fusion device 30 having at least two troughs arranged on top of each other, wherein the troughs are set up to release glass melt streams having different widths and are combined to produce a glass ribbon having a strip-shaped section of reduced average thickness formed by a gap between two laterally spaced glass melt streams. In the shown example, the top trough 185 releases two melt streams 24 laterally spaced with a gap on each side. For example, the upper edges of the trough 185 may have protrusions 14 as seen in Fig. 24 to divide the overflowing glass melt 21 into the laterally spaced glass melt streams 24. The lower trough 18 produces glass melt streams 23 flowing down at its side walls 180, 182, the glass melt streams 23 having a larger width which defines the width of the glass ribbon 20 to be produced. All glass melt streams 23, 24 combine at the lower end of the lower trough 18 to form the glass ribbon 20. Due to the gap between the glass melt streams 24, the thickness of the glass ribbon 20 is locally reduced, thereby producing a strip-shaped section 3 having reduced average thickness. Several variants of the shown example are possible. Instead of a single upper trough 185, a series of troughs could be provided to produce the laterally spaced glass melt streams 24. Further, the position of the troughs 18, 185 could be reversed, so that the lower trough releases the laterally spaced glass melt streams 24 having a reduced width and a gap therebetween. Further, at least one of the troughs could be asymmetric so that a glass melt stream is only released on one side thereof. An inverse configuration is also possible, wherein the lower trough may have a protrusion as, e.g. in the examples of Figs. 15 and 16 and the top trough applies a uniform, wide ribbon on top of the separated or locally thinned lower ribbon.

Fig. 25 shows such a variant with two single sided troughs 18, 185. Such asymmetric arrangements may be used to produce glass articles with an asymmetric thickness profile such as shown in Fig. 3 or Fig. 4. The glass melt streams 23, 24 in this embodiment are only released to one side of the troughs 18, 185 and only flow along one of the side walls 182 of the lower trough. Again, several variants are possible. As in the embodiment of Fig. 24, a protrusion 14 on the upper edge of one of the troughs 18, 185 may be provided to produce laterally spaced glass melt streams 24 having a reduced width to achieve at least one strip-shaped section 3 having reduced average thickness. Optionally, a rotating cylinder 56 may be arranged under the lower end of the lower trough for guiding the combined glass melt streams 23, 24, as shown in the variant of Fig. 26.

In yet another embodiment of joining multiple glass flows into one ribbon, or distributing the glass by combining glass melt flows, respectively, comprises producing a glass sheet in the form of a glass ribbon by updrawing. It is possible to produce glass laminates, wherein a first ribbon is drawn through a Fourcault orifice, while infusing a second glass flow into a reservoir on top of the same Fourcault orifice, which is then drawn upwards with the first ribbon. A glass ribbon 20 and a glass article 1 cut therefrom, having a strip-shaped section 3 may be produced by using two or more second glass flows for the thicker sections of the glass ribbon. Typically, updrawing is less suited to produce very thin glasses. However, such a process may be combined with a redrawing, such as explained with respect to Fig. 18. Further, an updrawing process and device may be used with a Fourcault orifice having a protrusion 14, i.e., being shaped as explained with reference to Figs. 1 and 5. Hence, in one embodiment, a device 30 is provided comprising an updrawing apparatus with a Fourcault orifice having a least one protrusion 14 to produce a glass ribbon 20 having a strip-shaped section 3 of reduced average thickness.

A variant of the down drawing method and device makes use of a guiding body protruding downwards from the orifice. This variant may as well be employed for the method and device according to this disclosure. Fig. 27 shows a schematic example of a device 30 comprising a down drawing apparatus with a guiding body 58. Without restriction to the specific example as shown, one embodiment of this variant bases on providing a first glass melt flow 23 through an orifice 12 that flows down on a guiding body 58 arranged within and protruding downwards from the orifice 12, and providing second glass melt flows 24 having a width smaller than the first glass melt flow 23 and being laterally spaced apart with a gap in between, wherein the first glass melt flow 23 and the second glass melt flows 24 are combined on the guiding body 58, wherein the combined glass melt flows 23, 24 strip from the guiding body 58 at its lower end and are drawn to a glass ribbon 20, wherein the gap 22 between the second glass melt flows produces a strip-shaped section 3 on the glass ribbon 20 having a reduced average thickness with respect to adjacent sections. Preferably, as shown, the glass melt flows 23, 24 are combined at a position on the guiding body 58 below the orifice 12. In the cross-sectional view, only one of the second glass melt flows 24 is visible. However, a side view shows a similar configuration of the glass melt flows with a gap 22 as shown, e.g, in Fig. 22. The arrangement of the device of Fig. 27 is asymmetric in that the second glass melt streams are provided to only one side of the guiding body 58. However, feeding the glass melt streams 24 from both sides is possible as well. Further, the second glass melt streams 24 are provided from a separate container 16. However, the glass melt streams 23, 24 could also be fed from a single container 15 via appropriate ducts.

List of reference signs
1                  glass article
2, 27              glass sheet
3                  strip shaped section
5, 7, 9            sections adjacent to strip shaped section 3
10                 glass
12                 orifice
13                 drawing roller
14                 protrusion
15, 17             container
16                 heated strip shaped region
18, 185            overflow-fusion trough
19                 channel
20                 glass ribbon
21                 glass melt
22                 gap
23, 24             glass melt stream
25                 local heating means
29                 glass stripe
30                 device for producing a glass article 1
33, 34             ends of strip shaped section 3
36, 38             convexly curved surface portion of section 3
37                 concavely curved surface portion of section 3
40                 vertical cutting line
42                 horizontal cutting line
45             float bath
47                nozzle
49                gas jet
50, 70            transition section
52                slit
54                lip
56                cylinder
58                guiding body
101, 102          side face of 1
104               circumferential edge of 1
105, 106          depression
120, 121          sides of 12
250               laser
251               laser beam
252               coil heater

Claims

A method for producing a foldable glass article (1) , the glass article (1) having a strip shaped section (3) with a reduced average thickness compared to adjacent sections (5, 7) so that the stiffness of the strip shaped section (3) is reduced due to the reduced average thickness so that the glass sheet (1) can be folded about the strip shaped section (3) without breaking, the method comprising shaping the glass (10) of a glass sheet (2) in a hot-forming step by distributing the softened glass so that the glass thickness is reduced along the strip shaped section (3) .
The method according to claim 1, wherein the glass is distributed without removing glass (10) from the glass sheet (2) .
The method according to claim 1, the method comprising forming a glass sheet in form of a glass ribbon (20) from a glass melt (21) by drawing, wherein the glass (10) is distributed before the glass (10) of the glass ribbon (20) cools down and solidifies.
The method according to claim 1, wherein distributing the glass (10) is accomplished by a protrusion (14) , locally reducing the flow of a glass melt (21) , particularly extending into the flow of a glass melt (21) .
The method according to claim 4, wherein a glass sheet (2) in form of a glass ribbon (20) is formed by down drawing the glass (10) from a slit shaped orifice (12) , the orifice (12) having a protrusion (14) narrowing its width.
The method according to claim 4, wherein a glass sheet (2) in form of a glass ribbon (20) is formed by overflow-fusion from a trough (18) having a protrusion (14) on at least one of its sides.
The method according to claim 1, wherein a glass ribbon (20) with a multitude of strip shaped sections (3) having reduced average thickness that are laterally spaced in a direction perpendicular to the longitudinal direction of the glass ribbon (20) is produced, wherein the glass ribbon (20) is cut along at least one cutting line extending along and between two strip like sections (3) , and is further cut perpendicularly to the longitudinal direction of the glass ribbon (20) to obtain a multitude of glass articles (1) , each having at least one strip shaped section (3) with reduced average thickness.
The method according to claim 1, wherein a glass sheet (2) in form of a glass ribbon (20) is formed by drawing, wherein the glass (10) while still in a soft state is locally heated to a higher temperature along a strip shaped region (16) compared to adjacent regions of the glass ribbon (20) so that its viscosity along this region (16) is lower than in adjacent regions, wherein the strip shaped region (16) extends parallel to the drawing direction, and wherein a drawing force is applied having a component perpendicular to the drawing direction so that the glass thickness is lowered along the strip shaped region (16) due to the drawing.
The method according to claim 1, wherein a glass sheet (2) is provided, that preferably has a homogenous thickness, and is locally heated along a strip shaped region (16) , so that the glass (10) in the strip shaped region (16) softens, and wherein the glass sheet (2) is drawn in a direction transversely to the strip shaped region (16) so that the strip shaped region (16) is expanded and the glass thickness within the strip shaped region (16) is lowered.
The method according to claim 1, wherein a glass sheet (2) with a strip-shaped section (3) with reduced average thickness is provided and heated so that the glass (10) of the glass sheet (2) softens and wherein the glass sheet (2) is drawn in a direction along the longitudinal direction of the strip-shaped section (3) to reduce the thickness of the glass sheet (2) .
The method according to claim 1, wherein a glass sheet (2) in form of a glass ribbon (20) is formed by drawing, and wherein a multitude of strip shaped sections (3) with a reduced average thickness compared to adjacent sections (5, 7) are formed in the drawing process, with the longitudinal direction of the strip shaped sections (3) extending transversely, preferably perpendicular to the drawing direction.
The method according to the preceding claim, wherein forming a multitude of strip shaped sections (3) with a reduced average thickness comprises at least one of the following steps:

- varying the drawing speed,

- varying the temperature so that strip shaped regions extending transversely to the drawing direction have an elevated temperature compared to adjacent regions.
The method according to claim 1, wherein distributing the softened glass so that the glass thickness is reduced along a strip shaped section (3) comprises at least one of the following features:

- combining and fusing glass melt streams (23, 24) or softened glass stripes (27, 29) having different widths to produce a glass ribbon (20) in which the glass stripes (27, 29) or glass melt streams (23, 24) are arranged so that at least one strip shaped section (3) with reduced average thickness is produced,

- blowing a gas jet (49) onto the softened glass (10) or glass melt (21) .
The method according to claim 1, wherein the average thickness of the strip shaped section (3) is further reduced by etching the glass sheet (2) .
The method according to claim 1, wherein the ratio of the thickness D of the glass sheet (2) to the minimum thickness Dmin at the strip-shaped section (3) is enlarged by uniformly removing glass from at least one of the side faces (101, 102) of the glass sheet (2) .
The method according to claim 1, wherein a glass ribbon (20) is drawn, having at least two laterally spaced strip shaped sections (3) with reduced average thickness, wherein a glass article (1) is cut from the glass ribbon (20) so that the glass article (1) has at least two strip shaped sections 3 with at least three sections (5, 7, 9) foldably connected together by the strip shaped sections (3) .
A device (30) for carrying out a method according to one of the preceding claims to produce a glass article (1) , the device (30) having means to distribute glass in softened or molten state to produce a glass sheet having a strip shaped section (3) with a reduced average thickness compared to adjacent sections (5, 7) so that the stiffness of the strip shaped section (3) is reduced and the glass sheet (1) can be folded about the strip shaped section (3) without breaking.
The device (30) according to the preceding claim, wherein the means to distribute glass in softened or molten state comprise at least one of:

- a protrusion (14) in an orifice (12) for drawing a glass-ribbon (20) ,

- local heating means (25) .
A foldable plate shaped glass article (1) , in particular producible using a method or device (30) according to one of the preceding claims, the glass article (1) having two opposed side faces (101, 102) and a circumferential edge (104) and a strip shaped section (3) with a reduced average thickness compared to adjacent sections (5, 7) so that the stiffness of the strip shaped section (3) is reduced due to the reduced average thickness so that the glass sheet (1) can be folded about the strip shaped section (3) without breaking, the strip shaped section (3) extending laterally along the side faces (101, 102) and being terminated at both of its ends (33, 34) by the circumferential edge (104) , wherein the surface profile of at least one of the side faces (101, 102) and/or the thickness profile within the strip shaped section (3) is continuously curved, wherein the surface in the center of the strip shaped section (3) is concavely curved and wherein this concave surface curvature changes into a convex surface curvature in direction from the center towards the adjacent sections (5, 7) so that a centered concavely curved surface portion (37) is arranged between two convexly curved surface portions (36, 38) , the curved surface portions forming a depression (104, 105) .
The plate shaped glass article (1) according to the preceding claim, comprising at least one of the following features:

- the combined width of the convexly curved surface portions (36, 38) of the strip shaped section (3) is at least as large as the width of the concavely curved surface portion (37) ,

- the width of the depression (105) is at least three times, preferably at least five times larger than the depth of the depression (105) ,

- the glass article (1) comprises thickened transition sections (50, 70) between the strip-shaped section (3) and the adjacent sections (5, 7) having constant thickness.
The plate shaped glass article (1) according to claim 19, wherein the surface profiles of both side faces (101, 102) and/or the thickness profile within the strip shaped section (3) are continuously curved so that the side faces (101, 102) are approximating each other towards the center of the strip shaped section (3) .
The plate shaped glass article (1) according to the preceding claim, wherein the depression within the strip shaped section (3) on one of the side faces (101) has a larger depth than the depression on the opposed side face (102) .
The plate shaped article according to claim 19, having at least one of the following features:

- both side faces (101, 102) including the surface of the strip shaped section (3) have an average surface roughness of less than 0.5 nm,

- both side faces (101, 102) including the surface of the strip shaped section (3) have a fire polished surface

- the combined surface of both side faces (101, 102) including the surface of the strip shaped section 3 has a roughness homogeneity of more than 90%.
The plate shaped article (1) according to claim 19, wherein the glass article (1) is chemically strengthened.
The plate shaped article (1) according to the preceding claim, wherein at least one of the parameters compressive stress (CS) and depth of the ion exchange layer (DoL) is lower in the strip shaped section (3) compared to the adjacent sections (5, 7) .
An electronic device comprising a glass article (1) according to claim 19.