Flexible glass element and method of making the same

Abstract

The object of the invention is a brittle inorganic material element which is highly flexible and has a large strength. To this end, an inorganic brittle material element (1) is provided which has two opposite sides (3, 5) and a circumferential edge (7), the element (1) comprising at least three portions, including a first portion (9) and two second portions (11, 13), the second portions adjoining the first portion such that the first portion (9) is arranged between the second portions (11, 13), the first portion (9) comprising an arrangement of openings (90) forming a passage from one side (3) of the element to the opposite side (5) such that the first portion (9) has a higher flexibility than the second portions (11, 13).

Description

TECHNICAL FIELD

[0001] The present invention relates generally to a plate-shaped glass element. In particular, the present invention relates to a glass element having high flexibility. BACKGROUND

[0002] Glass is a material that uniquely combines transparency, hardness and temperature stability. In addition, glass can withstand high pressure. On the other hand, glass is a brittle material that can accidentally break if subjected to tensile stress. Therefore, glass is not the first choice of material if high flexibility is required. However, it would be greatly beneficial for many potential applications if the superior properties of glass could be combined with high flexibility. One technical field in this respect is the development of flexible optical displays, for example for foldable smartphones.

[0003] One possibility to make glass flexible is to reduce its thickness. However, this also reduces its strength against impact. The reduction in strength can be compensated by a sandwich design that combines two or more thin glass and polymer elements. However, sandwich structures can have other drawbacks, for example being prone to delamination or reducing the light transmission due to the increased number of interfaces with a step in the refractive index. The pros and cons discussed above apply not only to glass as a material, but also to other brittle inorganic materials. SUMMARY

[0004] It is therefore an object of the present invention to provide an element of a brittle inorganic material that is both highly flexible and has high strength.

[0005] Therefore, an element of a brittle inorganic material is provided that has two opposite sides and a circumferential edge. By the opposite sides and the lower height of the edge, the element is generally flat or plate-shaped. The element has at least three portions, wherein the at least three portions comprise a first portion and two second portions, the second portions being contiguous to the first portion such that the first portion is arranged between the second portions. The first portion comprises an arrangement of openings that terminate at the two opposite sides, i.e. form a passage through the element, i.e. extend from one side of the element to the opposite side of the element. In this way, the first portion has a higher flexibility than the second portions. The openings are preferably arranged in columns side by side. Adjacent openings within each column are separated by a first web, while the openings of adjacent columns are separated by a second web. Furthermore, the first webs of adjacent columns are arranged offset from each other. In other words, the first webs are staggered from one column to the other.

[0006] In a preferred embodiment, the columns of openings are respectively straight or comprise at least a straight portion. Therefore, in this embodiment, the columns are narrow columns of openings arranged side by side. In this way, the first portion can form a hinge for the second portions.

[0007] Generally, when bending a thin glass sheet, the convex side is subjected to tensile stress. However, by introducing the cuts or openings separately, the straight connection along the bending line is interrupted and the bending moment is mainly transmitted through the webs. The first and second webs form a structure similar to a joint in bricklaying. This staggered arrangement of the first web within the second web generates torsional stress when the element is bent. However, compared to bending, torsion generates a much lower tensile stress in the material. Thus, by absorbing the bending force at least partially through the torsion of the webs, the overall tensile stress can be reduced. In this way, the element can be easily bent without breaking.

[0008] The at least one, in particular both, second portions preferably have a closed surface, i.e. do not have an opening extending through the element in the brittle material such that the opening ends at two opposite sides. Furthermore, the surface of the portion is preferably flat. However, in some embodiments, the surface can also be structured, for example by comprising at least one structure of ribs, protrusions, recesses.

[0009] In order to improve flexibility, it is preferred that the width of the web is smaller than the width of the opening in the longitudinal direction of the column of openings.

[0010] Furthermore, in order to facilitate bending of the element around the intermediate flexible portion, it is preferred that the openings are elliptical. In particular, the longitudinal direction of the openings is preferably oriented in the direction along the border line between the first and second portions.

[0011] The ratio of the web length to the element thickness increases with the length of the longitudinal opening for a given width of the second web. A large ratio is advantageous for high flexibility. However, a grid comprising webs with a high length and a low thickness can also be constructed without elliptical openings. Thus, independent of the shape of the openings, according to one embodiment of the element, the length of the second web is at least twice its thickness or the element thickness, respectively.

[0012] The most preferred material for the element is glass. However, it is also contemplated to use another brittle material, for example glass-ceramic, sapphire or a semiconductor, for example silicon, to manufacture the element.

[0013] Independent of the material used, the element can be easily bent and even folded at the flexible first portion. Thus, it is also contemplated to provide an article comprising a flat element according to the present application, whereby the flat element is bent and folded at the first portion such that the surfaces of the second portions of one of the sides face each other. Furthermore, the element can be easily bent such that the surfaces of the second portions facing each other are parallel or in an at least acute angle position.

[0014] Furthermore, the second portions can be brought close together, in particular if the flexible first portions are wide enough. If the flexible first portions have a degree of freedom to bulge outwards, the second portions can be in a position close together. Thus, according to the improvement, the flat element is folded and the mutually facing surfaces of the second portions are in a position close together, such that the first portions bulge outwards, so that the thickness of the folded flat element at the first portions is greater than at the border line between the first portions and the second portions. Also in this case, the thickness of the folded flat element at the first portions is greater than at the opposite position of the second portions.

[0015] A particularly high flexibility of the first portions can be achieved by embodiments in which the openings are oval and have a varying width along their longitudinal direction. In particular, according to this embodiment, the width measured along the longitudinal direction and starting from one end of the opening has two maxima and an intermediate minimum, the width of the intermediate minimum being smaller than the width of the maxima. In other words, the oval or elongated openings can have two width maxima spaced apart in the longitudinal direction, with an intermediate width minimum between the two maxima. Similarly, the second webs extending between the columns of openings and thus in the longitudinal direction of the openings can have a varying width. This can be the case in particular if the openings are formed as described above, i.e. the openings have an intermediate minimum of the width between the two maxima. In particular, the possible shape of the second webs has two width minima spaced apart in the longitudinal direction of the web, with an intermediate width maximum between the width minima of the web.

[0016] Generally, by structuring a portion with openings as described herein, the maximum tensile strain within a bend of the structured opening can be reduced by at least 50% of the value within a bend of an unstructured element of the same size.

[0017] Reducing the maximum tensile strain can significantly increase the flexibility of the structured part. The flexibility of the glass can generally be expressed as the broken bending gap in a 2-point bending test. According to a preferred embodiment, the flexibility of the structured part, i.e. the first part, is at least 2 times, preferably at least 3 times, most preferably at least 4 times higher compared to the non-structured part, i.e. the second part. The 2-point bending is a test to measure the bending strength or bending performance of a glass. The broken bending radius is determined by using a UTM (Universal Testing Machine) on a sample at room temperature of about 20°C and relative humidity of about 50%. The glass element is in a bending position and its opposite ends are located between two parallel plates (steel plates). Then the distance between the plates is reduced so that the bending radius of the glass element is reduced, wherein the loading speed is 60 mm / min. When the ultra-thin glass element kinks or is damaged or breaks into two or several pieces, which is determined by the signal of the UTM software, the distance between the plates is recorded. From this distance the corresponding bending radius of the glass element at the breaking is calculated. The flexibility is inversely proportional to the distance of the plates. Thus, if the flexibility of the structured part is twice the flexibility of the non-structured part, the distance of the plates can be halved before breaking. This 2-point bending test is adjustable and it is particularly suitable for ultra-thin glass elements. This method can be perfectly employed due to the flexibility of the elements described herein.

[0018] The chemical tempering of the glass can further increase the flexibility of the structured and non-structured parts.

[0019] Generally, the chemical tempering is performed using a molten salt, which comprises Na + or K + ions or mixtures thereof. Commonly used salts are NaN03, KN03, NaCI, KCI, K2S04, Na2S04, Na2C03 and K2C03. Additives such as NaOH, KOH and other sodium or potassium salts can also be used during the chemical tempering to better control the speed of ion exchange, CS (compressive stress) and DoL (depth of layer). Furthermore, salt baths containing Ag + or Cu 2+ containing salt baths can be used to add antimicrobial functionality to the ultra-thin glass. The chemical tempering is not limited to a one-step process. It can also comprise multiple steps of immersing the glass sheet in salt baths with different concentrations of alkali metal ions to achieve better tempering performance. Thus, the chemically tempered glass article according to the present application can be tempered in one step or in the course of several steps, e.g. two steps.

[0020] According to some embodiments, the element can be chemically tempered to achieve a CS (i.e. compressive stress at the surface) higher than 100 MPa, preferably higher than 250 MPa, preferably higher than 400 MPa, more preferably higher than 500 MPa, more preferably higher than 600 Mpa, or even higher than 700 Mpa, or even higher than 800 MPa. However, it is preferred to limit the compressive stress to keep enough flexibility. Thus, in another embodiment, the CS is lower than 1500 MPa, preferably lower than 1300 Mpa, more preferably lower than 1200 MPa. Moreover, the element can be chemically tempered to achieve a DoL (depth of layer) greater than 1 pm, preferably greater than 3 pm, more preferably greater than 5 pm, more preferably greater than 7 pm, more preferably greater than 8 pm, more preferably greater than 10 pm, more preferably greater than 12 pm, most preferably greater than 15 pm. However, it is advantageous to limit the DoL with respect to the thickness of the glass element. Thus, according to another embodiment, the DoL is less than 0.5-t, preferably less than 0.4-t, most preferably less than 0.3-t, where t is the glass thickness. The DoL value is the depth of the compressive stress into the glass surface. It is defined as the distance from the physical surface to the point of zero stress within the glass.

[0021] The structured and non-structured parts are tempered together, thus the CS and DoL values are measured based on the non-structured part. The flexibility of the structured and non-structured parts can be improved by chemical tempering. The bending radius of the test sample can be roughly calculated as bending radius r = d / 2.4, where d is the distance between the two plates in the 2-point bending test, as measured using the 2PB bending test. According to some embodiments of the element, the chemically tempered structured first part can be bent without breaking at a bending radius smaller than 500t, preferably smaller than 300t, more preferably smaller than 100t, more preferably smaller than 50t, more preferably smaller than 40t, more preferably smaller than 30t, more preferably smaller than 25t, more preferably smaller than 20t, more preferably smaller than 15t, more preferably smaller than 10t, more preferably smaller than 7.5t, more preferably smaller than 5t, more preferably smaller than 4t, more preferably smaller than 3t, or even smaller than 2t, where t is the glass thickness. BRIEF DESCRIPTION OF DRAWINGS

[0022] The application is further illustrated below with reference to the accompanying drawings.

[0023] Figure 1 An element of brittle material is shown.

[0024] Figure 2 And Figure 3 Two different designs of the first part are shown.

[0025] Figure 4 A test apparatus for measuring the bending force on a flexure element of brittle material is shown.

[0026] Figures 5 to 12 A diagram showing the principal stress and the reaction force of a glass element versus the distance coordinate corresponding to the deflection of the glass element.

[0027] Figure 13 A cross-sectional view of an element with filled openings 90 is shown.

[0028] Figure 14 and Figure 15 An article with an element as part of a sandwich structure is shown.

[0029] Figure 16 An article with an element having a second portion with a fold is shown.

[0030] Figure 17 and Figure 18 An embodiment is shown in which the first portion 9 surrounds the second portion 11.

[0031] Figure 19 A diagram showing the force versus the distance of the plate in a 2-point bend measurement is shown.

[0032] Figure 20 A photo of a fragment of an element broken along the first portion is shown.

[0033] Figure 21 An element similar to Figure 3 is shown as well as the dimensions of the web and the opening.

[0034] Figure 22 A device for creating a laser score in a plate-like element is shown.

[0035] Figure 23 A sheet with elements 1 is shown.

[0036] Figures 24a to 24d Another embodiment of an element 1 is shown. DETAILED DESCRIPTION

[0037] Figure 1 A top view of an element 1 made of a brittle material is shown as seen from its side 3 or side 5. Preferably, the element 1 is made of glass. The element 1 can be subdivided into three portions, namely a first portion 9 having openings 90 and two second portions 11, 13 adjoining the first portion 9, such that the first portion 9 is located between the second portions 11, 13. The second portions 11, 13 preferably have closed flat surfaces and thus no openings 90. In contrast thereto, the openings 90 in the first portion 9 form a passage or through-hole from one side 3 to the opposite side 5.

[0038] Without being limited to Figure 1In the specific example shown, the openings 90 are generally arranged in an array of adjacent parallel columns 91. The columns 91 of openings are preferably arranged in parallel. In this way, the distance between the openings 90 of adjacent columns 91 remains constant. The openings 90 within a column 91 are separated by first webs 92. Furthermore, the openings 90 of adjacent columns 91 are separated by second webs 94. Thus, the first portion 9 can also generally be described as a mesh of interconnected first webs 92 and second webs 94 with openings 90 therebetween.

[0039] Due to the mesh of respective openings 90 or webs 92, 94, the first portion 9 has a high flexibility, such that the element 1 can be easily bent at the intermediate first portion 9. The flexibility is particularly high if elongated openings 90 are introduced into the element 1 to form the intermediate first portion 9. In particular, it is advantageous if the longitudinal direction of the openings extends along the longitudinal direction of the columns 91. With the shape of the webs 92, 94 and their respective dimensions, the bending force can be influenced and reduced. Generally, without being limited to the example embodiments shown, the arrangement and shape of the webs 92, 94 is designed such that the flexibility of the portion 9 with a bending axis along the longitudinal direction of the openings 90 is higher than the flexibility of the portion 9 with a bending axis perpendicular to the longitudinal direction of the openings 90. Figure 1 A preferred bending axis 95 in the direction along the longitudinal direction of the openings 91 is shown. Due to the bending axis extending along the boundary line 15 between the first portion and the second portion, the first portion 9 provides a hinge for folding the second portions 11, 13.

[0040] Furthermore, from Figure 1 It can be seen that the first webs 92 of adjacent columns 91 are arranged offset from each other. The first webs also define hanging points for the second webs 94. Due to the offset arrangement of these hanging points, the bending of the first portion 9 is partially absorbed by the torsion of the second webs 94. A very advantageous effect of the conversion of bending stress into torsional stress is that the maximum tensile stress occurring in the brittle material is reduced compared to the tensile stress occurring in a large plate that is flexed. Thus, as a general concept, an element of brittle material can also be characterized by a mesh of webs that are interconnected such that a flexure or a bend of the element causes a torsion of at least a subset of the webs. In particular, this subset comprises a plurality of second webs 94. Thus, generally, an element of inorganic brittle material is provided that has two opposite side faces 3, 5 and a circumferential edge 7, the element 1 comprises at least three portions, the at least three portions comprise a first portion 9 and two second portions 11, 13, the second portions 11, 13 adjoin the first portion 9 such that the first portion 9 is arranged between the second portions 11, 13, the first portion 9 comprises a mesh of webs 92, 94, the webs 92, 94 are interconnected to define openings 90 in the brittle material, whereby the interconnection of the webs 92, 94 is designed such that a bending of the first portion 9 causes a torsion of at least a subset of the webs. In Figure 1In the exemplary embodiment shown, the number of second webs 94 undergoing torsional strain is approximately half the total number of webs 92, 94. According to a preferred embodiment, it is generally preferred that the webs, particularly the first webs 92 and the second webs 94, form a grid, wherein the webs are interconnected such that at least a subset of the webs within the grid undergoes torsional strain when the first portion 9 flexes, wherein this subset comprises at least one-third of the total number of webs within the grid.

[0041] Besides bending of the element, strain can also be applied by uniaxial tensile force along the element. In this case, the web absorbs the tensile force by bending in a plane parallel to sides 3 and 5. Due to this bending, the accompanying strain can converge at the end of the opening. Figure 1 In the embodiments, for this reason, it is generally preferred to provide an opening 90 with a circular profile, particularly with circular ends. These ends are specifically located at opposite positions in the direction along column 91. A circular profile does not mean that the opening can also have a straight portion. In fact, Figure 1 One embodiment has a straight portion 93 of the profile extending along the longitudinal direction of the elliptical opening 90. In contrast, a circular profile means that the profile of the opening 90 has no sharp edges.

[0042] Figure 2 and Figure 3 Two embodiments of the grid or pattern of the opening 90 within the first part 9 are shown. Figure 2 The embodiments are similar to Figure 1 The embodiment shown. Therefore, the opening 90 is elongated and has a circular profile with straight longitudinal edges. However, Figure 3 The shapes of the opening 90 and the webs 92, 94 in the embodiment are more complex. Generally, not limited to the specific embodiment shown, the opening 90 has a varying width along its longitudinal direction. Specifically, the opening 90 has two maximum widths 17 spaced apart in the longitudinal direction, with a minimum width 18 located between the two maximum widths.

[0043] Similarly, the second web 94 has two minimum widths 19. These minimum widths 19 are spaced apart in the longitudinal direction of the web 94. Furthermore, the intermediate maximum width 20 is located between the minimum widths 19 of the second web 94.

[0044] Although the outline of the opening 90 is similar to Figure 2 The examples are more complex, but in both examples, the outline of the opening 90 or the second web 94 has at least one straight portion 93.

[0045] Specifically, and according to another embodiment, the maximum width 20 of the second web 94 is located at the midpoint of the straight portion 93. Similarly, the minimum width 18 of the opening is located along the straight portion 93. If the opposing straight portions 93 are parallel, these features produce minimum and maximum values ​​extending in the longitudinal direction, i.e., along the direction of column 91. This facilitates diffusion, thereby reducing the maximum tensile strain that may occur along the profile when bending the first portion 9.

[0046] Figure 4 A test apparatus 25 is shown for measuring the bending force required to flex an element 1 made of brittle material. The test apparatus 25 includes two grippers 26, 27, which are movably mounted relative to each other, allowing adjustment of the distance between the grippers 26, 27. The element 1, placed between the grippers 26, 27, will bend as the distance between the grippers 26, 27 decreases, as shown. To evaluate stiffness and bending behavior, the bending force applied by the element 1 is measured as a function of distance or position coordinate s. For illustration, distance s is... Figure 4 The arrow is shown in the middle. Figure 4 It also indicates that the distance coordinate s corresponds to the deflection of the glass element.

[0047] The following sections discuss three exemplary designs for glass elements that can be implemented according to... Figure 4 The device records the process of bending force. The bending force discussed here is not measured, but calculated using finite element simulation.

[0048] The sample measures 100×20mm. 2 The glass sheet. Design 1 is a comparative example consisting of a large glass plate. The glass elements according to Designs 2 and 3 have cutouts or openings 90 forming the flexible first part 9. The model of opening 90 in Design 2 corresponds to... Figure 2 Example of an embodiment. The width of the web 92 is 200 μm. Design 3 conforms to... Figure 3 The shape of opening 90 and the grid of webs 92 and 94 are shown. The width of web 94 is 50 μm at the minimum value 19, and the length of opening 90 is 3 mm. In the simulation, it is assumed that the glass has no thickness tolerance, no stress, and no chemical preload. Furthermore, it is assumed that the glass is elastic. For the calculation, it is assumed that the glass element will not break upon flexing.

[0049] Figures 5 to 12 The principal stresses S11, S22 and reaction force F of the glass element according to designs 1, 2 and 3 above are shown as functions of the distance s of the grippers 26, 27.

[0050] S22 is the principal stress in the direction perpendicular to the bending axis, S11 represents the principal stress in the direction along the bending axis 95, i.e. along the row 91 of openings 90. Typically, the component S22 is lower than the component S11 because there is no geometrical difference in the length of the segment between the lateral faces 3, 5 in the direction along the bending axis. Due to symmetry reasons, the reaction force is practically twice the one shown in the figure.

[0051] Figure 5 and Figure 6 The parameters S11, S22, F are shown for a glass element according to design 1 having a thickness of 100 μm and 200 μm, respectively. As expected, for the glass having a thickness of 200 μm, both the bending force F and the parameter S11 are quite high Figure 6 ). For the thicker glass element 1, the principal stress is roughly doubled and the reaction force is about 10 times higher.

[0052] Figure 7 and Figure 8 are graphs of the parameters S11, S22, F for a glass element 1 according to design 2, i.e. having a model of openings 90 as shown in Figure 2 The graph corresponding to Figure 7 is for a glass element 1 having a thickness of 100 μm. The length of the elongated opening 90 of the element is 1 mm. Figure 8 The example of a glass element of

[0053] The glass element according to Figure 9 is similar to the example of Figure 7 . In particular, the glass has a model of openings 90 shaped according to design 2 and has a thickness of 100 μm. However, the length of the openings is 3 mm instead of 1 mm in Figure 7 This leads to a further reduction of the reaction force, which is essentially zero for a distance value of at least 20 mm. Figure 10 are graphs of S11, S22 and F for a glass element having a thickness of 200 μm and a length of 3 mm of the openings 90.

[0054] Finally, Figure 11 and Figure 12 are graphs of S11, S22 and F for two glass elements 1 structured according to design 3. Figure 11 are shown for a value of the glass thickness of 100 μm, Figure 12 are shown for a value of the glass element thickness of 200 μm. From Figure 11 , Figure 12 it is evident from the comparison with Figures 7-10 that the design 3, having openings 90 with an intermediate minimum width, exhibits an even further reduced reaction force.

[0055] According to an example, a 200 μιη thick element of AS87 glass structured according to design 2 with 4 mm long openings 90 was chemically tempered at 390°C for 45 minutes. A DoL of 20 μιη and a CS of 700 MPa were achieved. The structured part could be bent to R3 mm without breaking.

[0056] In another example, a 100 μιη thick element of AS87 glass structured according to design 3 with 3 mm long openings 90 was chemically tempered at 390°C for 30 minutes to obtain a DoL of 15 μιη and a CS of 650 MPa. The structured part could be bent to R0.5 mm without breaking.

[0057] For designs 2 and 3, the schematic shows a sharp change in the reaction force at a distance s of about 10 mm. This occurs when the side surface of the glass element contacts the jaws 26, 27 of the device 25 at a location within the first portion 9. From this point, the length of the segment of the first portion 9 spanning the gap between the jaws decreases with distance.

[0058] The following table lists the maximum values of the parameters S11, S22 and F and the design characteristics for the examples of Figures 5 to 12 and values for other examples.

[0059]

[0060] As mentioned above, the width of the web 92 according to the example of design 2 is 200 μιη. The thickness of the glass elements listed above is either 100 μιη or 200 μιη, so that the web width does not exceed the thickness. Similarly, the minimum web width according to the example of design 3 is 50 μιη, while the plate thickness is either 100 μιη or 200 μιη, respectively. Thus, according to the embodiments also implemented in the examples discussed above, the minimum width of the second web 94 is equal to or smaller than the thickness of the element 1. More generally, it is preferred that the minimum width of the second web is equal to or smaller than twice the thickness of the element 1. If the width of the web is larger compared to the thickness of the glass element 1, the torsion of the second web 94 leads to larger tensile stresses along the web edges, thus reducing the flexibility and increasing the likelihood of failure, i.e. breaking.

[0061] Furthermore, the length of the second web 94 of the examples listed above is at least twice the thickness of the element 1 with the large cut length of the openings.

[0062] However, while long openings and thin webs are advantageous for achieving high flexibility, the mesh of the webs 92, 94 in the first portion 9 can still be designed such that the surface is mainly formed by the brittle material. In other words, according to an embodiment, the surface portion of the brittle material is larger than the surface portion of the openings 90 within the first portion. This is especially advantageous for connecting the laminate to other elements, among others.

[0063] The element 1 is preferably made of glass, which can be easily structured to introduce the openings 90 and which remains sufficiently stable after structuring.

[0064] According to a first embodiment of the composition, the glass of the element comprises the following components in % by weight:

[0065]

[0066] According to a second embodiment of the composition, the glass of the element comprises the following components in % by weight:

[0067]

[0068]

[0069] According to a third embodiment of the composition, the glass of the element is substantially free of alkali metal oxides. The glass comprises the following components in % by weight:

[0070]

[0071] Preferably, in the composition of this glass, the total content of MgO, CaO and BaO is in the range of 8 to 18% by weight.

[0072] In a fourth embodiment, the glass composition comprises the following components in % by weight:

[0073]

[0074] Furthermore, the glass can comprise 0 to 1% by weight of P2O5, SrO, BaO; 0 to 1% by weight of a fining agent, preferably SnO2, CeO2or As2O3.

[0075] According to an embodiment, the element 1 is chemically tempered to increase the mechanical strength. Chemical tempering involves ion exchange within the glass as a brittle material, wherein the ions of the glass in the region of the glass adjacent to the surface are exchanged for larger ions, so that the larger ions exert a compressive stress on the glass. Typically, alkali ions are exchanged to achieve tempering. Thus, as long as the above listed glasses contain alkali ions in sufficient amounts, they are suitable for chemical tempering. Furthermore, the glass can also be tempered (temper) to provide a compressive stress region at the surface. Tempering or thermal tempering comprises heating the glass until it softens and then rapidly cooling the glass element, so that the surface shrinks stronger than the glass in the volume of the element. Thermal tempering is particularly effective for thicker glass elements. It is preferred that the depth of the compressive stress region achieved by tempering is less than half of the smallest web width of the first web 92 and the second web 94. If the compression region is deeper than half the web width, the compressive stress region extending into the glass from the edge of the web will join in the center of the respective web, thereby reducing the tempering effect. In the case of chemical tempering, the compressive stress region is essentially defined by the ion exchange depth. Thus, it is preferred that the ion exchange depth (also referred to as DoL = "depth of layer") is less than half of the web width.

[0076] For some applications, it is desirable that the closed surface of the element 1. To this end, the openings 90 can be filled with an organic material, i.e. a plastic, a rubber or an adhesive. Figure 13 A cross-sectional view showing an example of the openings 90 filled with a plastic 30 is shown. It can also be useful to leave some of the openings 90 open, depending on the application. Thus, generally and without being limited to the specific examples shown, an element 1 is provided, wherein at least a subset or a portion of the number of openings 90 is filled with a plastic 30. Preferably and as shown, the openings 90 are closed by the filler. However, it is also possible to provide a filler to one or more openings, e.g. openings forming a fine channel.

[0077] According to a refinement of the embodiment in which the openings 90 are filled with a plastic, it is intended that the plastic is chosen and adjusted such that the counterforce due to a deflection of the element is changed by at most 30%, preferably at most 20%, in particular at most 10%, particularly preferably at most 1%. This change is measured relative to a configuration with open openings 90, i.e. without plastic in the openings 90. In practice, this property can be easily demonstrated by measuring the counterforce when the element 1 is deflected while the openings 90 are filled, then removing the plastic 30 and repeating the measurement. Generally, without being limited to the above counterforce conditions, the plastic can be or at least contain an elastomer. This allows the plastic filler to remain sufficiently flexible to avoid a significant increase in rigidity.

[0078] According to a further refinement, the plastic 30 is transparent. In particular, the plastic 30 can have a refractive index that matches the refractive index of the brittle material of the element 1. It can not be necessary to achieve a perfect match. Rather, in the present application, a match of the refractive indices of the plastic 30 and the brittle material is understood to mean that the difference in refractive indices is less than 0.3, preferably less than 0.2, more preferably less than 0.15, more preferably less than 0.1, more preferably less than 0.05, more preferably less than 0.02, or less than 0.01, or less than 0.005, or even less than 0.002.

[0079] A suitable plastic can comprise a silicone as a polymer. Silicones are particularly suitable for combination with silicon-containing inorganic brittle materials, such as most suitable glasses. Likewise, silicones can be both elastomers and transparent plastics.

[0080] In a further embodiment, within the first portion 9, the surface of the element 1 is formed in part by the plastic 30. Depending on the application, this can be disadvantageous for the application of the element 1. For example, the plastic 30 can provide less adhesion for a component or layer to be applied to one of the side faces 3, 5 than the inorganic brittle material of the element 1. For this purpose, an optional inorganic layer can be deposited to at least one of the side faces 3, 5. According to an embodiment, silicon oxide is deposited as the inorganic layer. The layer 33 can be deposited, for example, by chemical vapor deposition (CVD) or by flame lysis. If the layer 33 spans both the brittle material and the plastic 33, uniform surface properties can be achieved despite the different materials of the element 1.

[0081] The element 1 as described herein can be used as a component of a variety of articles. An article comprising the flat element 1 as described herein can be, for example, a flexible, in particular foldable, display. Typically, the high flexibility of the element 1 due to the structuring of the first portion is imparted to the article comprising the element 1, which has at least two portions or components that are movable relative to each other.

[0082] According to an embodiment, the article 2 comprising the element 1 of brittle material comprises a sandwich structure, wherein the element 1 forms one layer of the sandwich structure. Figure 14 and Figure 15 An example of an article 2 is shown, wherein the element 1 forms one layer of a sandwich structure.

[0083] Typically, the sandwich structure can comprise a laminate. In a preferred embodiment, the laminate can comprise an organic layer 35, in particular a polymer or plastic layer, laminated to a side face of the element 1. The organic layer can also comprise or consist of a silicone. Likewise and as Figure 14As shown, the organic layer 35, in particular the plastic or polymer layer 35, can be laminated to both sides 3, 5 of the element 1. Thus, with the lamination of at least one side 3, 5 of the element 1 to an organic layer, such as a polymer layer 35, a sandwich structure is obtained which combines the high hardness of a brittle material, such as glass, with high flexibility. The polymer layer 35 can be laminated to the element 1 by means of an adhesive, i.e. an optically transparent adhesive, thereby forming a further organic layer, or the polymer layer 35 can be applied to the surface of the element 1 without glue. The protective layer is applied, for example, by chemical vapor deposition (CVD), dip coating, spin coating, inkjet, casting, screen printing, spray painting and spraying. However, the present application is not limited to these processes. Suitable materials are also known in the art. For example, suitable materials can include a hard plastic reactive resin which is a polymer selected from the group consisting of phenolic plastic, phenol formaldehyde resin, aminoplastic, urea formaldehyde resin, melamine formaldehyde resin, epoxy resin, unsaturated polyester resin, vinyl ester resin, styrene acrylate resin, phthalic acid diacrylate resin, silicone resin, cross-linked polyurethane resin, polymethacrylate reactive resin and polyacrylate reactive resin.

[0084] In the case of lamination, the polymer material can be selected, for example, from the group consisting of silicone polymers, sol-gel polymers, polycarbonate (PC), polyether sulfone, polyacrylate, polyimide (PI), inorganic silica / polymer hybrid, cyclic olefin copolymer, polyolefin, silicone resin, polyethylene (PE), polypropylene, polypropylene polyvinyl chloride, polystyrene, styrene-acrylonitrile copolymer, polymethyl methacrylate (PMMA), ethylene-vinyl acetate copolymer, polyethylene terephthalate (PET), polybutylene terephthalate, polyamide (PA), polyacetal, polyphenylene ether, polyphenylene sulfide, fluorinated polymer, chlorinated polymer, ethylene tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polyvinylidene chloride (PVDC), polyvinylidene fluoride (PVDF), polyethylene naphthalate (PEN), terpolymer made of tetrafluoroethylene, terpolymer made of hexafluoropropylene and terpolymer made of vinylidene fluoride (THV) or polyurethane or mixtures thereof. The polymer layer can be applied to the element 1 by any known method.

[0085] Figure 15 An example based on an embodiment of the article 2, wherein a glass sheet 37 is laminated to the element 1. In particular, the glass sheet 37 can be laminated to the element 1 by means of an intermediate organic layer 35, preferably a plastic layer. The glass sheet 37 can be a thin glass with a thickness not exceeding the thickness of the element 1. The thickness of the glass sheet 37 is preferably less than 220 pm, preferably less than 160 pm. The glass sheet 37 can form a substrate for a light-emitting or light-transmitting structure of a display, which can be folded at the flexible first portion 9. The glass sheet 37 can also be chemically tempered.

[0086] In Figure 14 and Figure 15 the examples, the openings 90 are not filled as in the example of Figure 13 However, these examples can also be combined.

[0087] If the columns 91 of openings 90 are parallel and straight as in the example of Figure 1 , the first portion 9 can provide a hinge between adjacent second portions 11, 13. The hinge can be flexible so that the element can be folded together to bring the second portions 11, 13 against each other. Furthermore, as shown in Figure 16 , if the positions of the second portions 11, 13 against each other are so close that the first portion 9 bulges out so that the thickness W2 of the folded element 1 at the first portion 9 is larger than at the border line 12 between the first portion 9 and the second portions 11, 13, a very compact arrangement of the article 2 can be achieved. As shown, the thickness Wl of the folded element 1 at the position of the opposite border line 15 is smaller than the thickness W2 at the outwardly bulging first portion 9. A reduced thickness can also be present at any position where the second portions 11, 13 are opposite. From Figure 16 It is apparent that the element 1 is folded like a booklet.

[0088] Due to the folding and the outward bulging of the first portion 9, generally, two concave curved portions 40 of the first portion 9 are formed with an intermediate convex portion. The concave curved portions 40 adjoin the border lines 15 between the first portion 9 and the second portions 11, 13.

[0089] In the presently described embodiment, the flexible first portion 9 forms a continuous band between the second portions 11, 13 in order to provide a hinge joint between the second portions 11, 13. In another embodiment, the first portion 9 is also arranged between the second portions 11, 13. However, according to this embodiment, the first portion 9 encloses one of the second portions. An example of this embodiment is shown in Figure 17 . The further second portion 13 encloses the first portion. According to a refinement, the first portion 9 is closed loop-shaped as in the shown example. Preferably, the columns 91 of openings 90 are concentrically closed columns. Figure 17 Also shown is an example where the columns 91 of openings 90 are not straight. Rather, the columns 91 are closed and circular. Figure 18 Another embodiment is shown where the first portion is ring-shaped and encloses the second portion 11. However, in contrast to Figure 17 , the inner second portion 11 is rectangular. Likewise, the first portion has a rectangular frame shape. Furthermore, the columns 91 of openings 90 are straight in cross-section.

[0090] In embodiments where the first flexible portion surrounds the second part, the first part 9 can effectively function as a spring. When the first part is stretched, the inner second part can deflect in a direction perpendicular to the sides 3, 5. The reaction force of the first part then generates a force on the inner second part 11, which drives the inner second part 11 back to a position coplanar with the outer second part 13. This configuration can be used, for example, to provide a push-button switch. Therefore, according to another embodiment, an article 2 with a push-button switch is provided, wherein the button of the push-button switch is formed by one of the second parts 11, 13.

[0091] Figure 17 and Figure 18 The examples are merely illustrative; of course, many other configurations, such as those in Part 1, 9 and Parts 2, 11 and 13, are possible.

[0092] According to another aspect of the invention, the brittle material element 1 can be structured in a very advantageous manner in terms of its fracture behavior. If a sheet of brittle material is bent until it breaks, a large number of fragments are typically obtained. However, by properly structuring the first portion 9, the fracture can be controlled, resulting in only two large fragments. There may eventually be other fragments of the brittle material, but if this is the case, their size is very small compared to the two main fragments. Therefore, according to one embodiment, the first portion of the element is structured such that bending the first portion 9 about the bending axis until fracture causes the element to break into two fragments. Since there are no other larger fragments, typically the total weight of the two fragments is at least 95% of the original element weight. This fracture behavior is advantageous because a large number of small fragments increases the risk of injury. This is especially true for brittle materials, such as glass, which typically fracture into sharp-edged fragments.

[0093] Figure 19 It shows the use of Figure 4 This diagram illustrates the force relative to the plate distance *s* during a two-point bending test performed using the measuring equipment shown. The structured glass element being tested has a thickness of 300 μm. The element is similar. Figure 2 The embodiment was structured, with an elongated opening 90 having a straight edge portion 93. Three samples with a section width of 200 μm (curve group (c)) and three other samples with a section width of 300 μm (curve group (b)) were tested. For comparison, additional bending measurements of an unstructured continuous glass sheet with a thickness of 70 μm are shown (curve (a)). All glass elements were made of AS87 type glass.

[0094] The joint width is the width of the second web 94, which is constant along the straight section. The sample is bent until it breaks. Figure 19The shown curves indicate that the flexibility of the glass elements described herein is greatly increased compared to unstructured glass sheets. Furthermore, the flexibility of the samples with a pitch of 200 μιη is much higher than the flexibility of the samples with a pitch of 300 μιη. All samples were tempered under the same tempering conditions to reach a CS of about 700 MPa and a DoL of about 20 μιη. The following table lists the plate distance at which the structured samples broke:

[0095] 200 μm pitch 300 μm pitch 1.20 2.44 0.94 2.94 1.10 2.74

[0096] The breakage usually occurs in the direction of the rows 91 along the openings 90 and in the middle of the first web 92.

[0097] From Figure 19 It is further apparent that the suitable structuring of the openings 90 in the first portion significantly reduces the force required for bending the element 1 compared to unstructured glass sheets. Even in the example of Figure 19 a thickness of 200 μιη, the structured element shows a reduction of the bending force (curves (b) and (c)) of more than 50% compared to the unstructured element (curve (a)). Thus, according to an embodiment, the first portion 9 is structured such that the stress generated by bending at the surface (stress is proportional to the force required for bending) is reduced by at least 50% compared to an unstructured element of the same thickness. This property can be verified in various ways. One possibility is to use finite element analysis to compare the stress of a model of a structured and an unstructured element. Another possibility is to compare the bending force of the element bent at the structured first portion and bent at an unstructured second portion. Furthermore, a large number of samples with and without a structured first portion 9 can be tested until the samples break using the two-point bending method described with respect to Figure 4

[0098] In another embodiment, the element 1 or the first portion 9, respectively, is structured such that the stress at the surface of the first portion is almost independent of the thickness of the element 1. This is especially true if the structure is scaled with the thickness of the element 1. That is, if the thickness of the element is doubled together with the dimensions of the structuring, i.e. the openings 90 and the webs 92, 94, the stress does not change significantly. Specifically, an element 1 is provided having a first portion 9 structured such that the stress at the surface of the first portion due to bending varies by at most 10% over a range of element thicknesses from 200 μιη to 2 mm. Again, this property can be verified by finite element analysis or by performing 2-point bending tests until breakage on samples of different thickness and comparing the Weibull parameters.

[0099] Figure 20 ​A photograph of a sample fractured along the structured first portion 9 is shown. The element 1 is placed on a substrate having a printed grid visible as bright lines. The pitch of the sample shown, i.e. the width of the second web 94, is 200 pm. It can be seen that a single fracture 9 extends linearly along the first portion 9, dividing the element 1 into only two large fragments.

[0100] In the following, the influence of various dimensions of the openings 90 and the webs 92, 94 on the principal stresses S11, S22 is further detailed. To this end, finite element analysis is used to study the features of the basic design and some variations thereof. Figure 21 A first portion 9 of the basic design with the respective dimensions is shown. Thus, the length of the first web 92 is 0.1 mm and the minimum width of the second web 94 is 0.05 mm. The length of the opening 90 is 3 mm and the width varies between 0.1 mm and 0.2 mm. The thickness of the reference element 1 is 100 pm.

[0101] In a first analysis, different lengths of the first web 92 are investigated. The lengths are 50 pm, 100 pm (reference), 200 pm, 300 pm. The finite element analysis shows that the S11 component of the strain remains almost constant at 50 MPa for the bending radius. However, the S22 component decreases significantly with increasing length of the first web 92. Specifically, for a bending radius of 3 mm, S22 drops from 180 MPa for a 50 pm web length to 50 MPa for a 300 pm web length. Thus, according to an embodiment, the length of the first web 92 is at least as large as the thickness of the element, preferably at least twice the thickness of the element, to reduce the overall bending stress.

[0102] In a second analysis, different lengths of the opening 90 are investigated. Specifically, openings of 2 mm and 3 mm length are compared. The analysis shows that the length of the opening 90 has little influence on the principal strains. The following table lists the maximum principal strains S11 最大 , S22 最大 :

[0103] Length of opening 90 2 mm 3 mm

[0011] 最大 ]]> 67 MPa 49 MPa <S22 最大 ]]> 122 MPa 104 MPa

[0104] For the embodiment with a length of 3 mm, the strain values are slightly better. Thus, according to another embodiment, the opening 90 preferably has a length that is at least 25 times the thickness of the element. However, if the length is too large, the stability against pressure on one of the side faces decreases. Thus, it is preferred to limit the length of the opening to at most 100 times the thickness of the element.

[0105] In a third analysis, the minimum width of the second web 94 is varied. Specifically, in addition to the reference model with a minimum width of 50 pm, other widths of 25 pm, 35 pm and 70 pm are investigated.

[0106] For a bending radius of 3 mm, the maximum values of the principal strains are listed in the following table:

[0107] Minimum width of web 94 70 μm 50 μm 35 μm 25 μm

[0011] S11 最大 ]] 50 MPa 50 MPa 50 MPa 21 MPa <S22 最大 ]]> 200 MPa 100 MPa 60 MPa 9 Mpa

[0108] Thus, while the reduction of the minimum web width has a small effect on the S11 component, the S22 component is significantly reduced. However, on the other hand, a small web width leads to a very fragile structure which is prone to breakage. Therefore, according to a further embodiment, the minimum width of the second web 92 is preferably smaller than the thickness of the element 1 and more preferably in the range of 0.3 to 0.6 times the thickness of the element 1.

[0109] In a fourth analysis, the thickness of the element 1 was varied. Specifically, in addition to the reference value of 100 pm, elements with a thickness of 200 pm and 300 pm were analyzed.

[0110] The maximum value of the S11 component varied from 50 MPa to 150 MPa. This variation is proportional to the thickness of the element 1 with a factor of 3. The S22 component showed a smaller variation in the range from 80 MPa to 100 MPa. A further model with a minimum width of the second web 94 of 35 pm was analyzed. The maximum value of S11 was similar, ranging from 51 MPa to 146 MPa. The S11 component varied between 60 MPa and 76 MPa. The element 1 as described herein can be manufactured with a method as described in DE 10 2018 100 299 A1 or PCT / CN2019 / 086830. A method was employed in which a laser pre-scribes the openings 90 in the element. The pre-scribed element is then etched to create the openings.

[0111] Specifically, a method can be employed which has the following steps:

[0112] - providing a plate-like element 1 of a brittle material;

[0113] - directing and focusing a laser beam of an ultra-short pulsed laser onto the element 1, the laser beam 50 having a wavelength at which the brittle material of the element 1 is transparent such that the laser beam 50 can penetrate into the element 1;

[0114] - focusing the laser beam to create an elongated focal point 52 within the element, the intensity of the laser beam 50 being sufficient to create a filamentous damage region 57 within the element 1 along the focal point 52;

[0115] - moving the laser beam 50 relative to the element to introduce a plurality of filamentous damage regions 57 side-by-side along a plurality of annular or closed paths;

[0116] - by etching by exposing the element to an etchant, which penetrates into the filamentous damage regions 57, so that the filamentous damage regions 57 widen to form a channel which, due to the widening, joins, thereby separating the part of the element enclosed by the annular path and creating an opening 90, thereby forming at least three parts, which comprise a first part 9 and two second parts 11, 13, the second parts adjoining the first part, so that the first part 9 is arranged between the second parts 11, 13, the first part 9 comprising the opening 90, so that the first part 9 has a higher flexibility than the second parts 11, 13.

[0117] According to a refinement, after etching, the element 1 can be subjected to chemical tempering.

[0118] Figure 22 An apparatus for producing laser marks in a plate-like element 1 as described above is shown. As Figure 22 is shown, a laser beam 50 of an ultrashort pulse laser 49 is directed and focused onto the element 1, which is preferably made of glass. The laser beam 50 has a wavelength at which the material of the element 1 is transparent. Thus, the laser beam 50 can pass through the element 1. By means of a lens 51, the laser beam 50 is focused to produce an elongated focal point 52 within the element 1. A suitable lens is a so-called axicon lens. This lens has a substantially conical refractive surface such that parallel rays are refracted into a direction with constant polar angle. However, alternatively or additionally, other focusing means producing an elongated focal point can be used.

[0119] The laser beam 50 is strong enough to produce a damage region within the brittle material. In particular, the damage region can be due to optical breakdown and / or plasma formation within the material. Ideally, the damage region 57 extends from one side 3 through the element to the opposite side 5.

[0120] The laser beam 50 is moved relative to the element 1 to produce a series of damage regions 57. The movement also follows an annular path as Figure 1 is shown, so that a plurality of damage regions 57 encircle a region of the element 1, which forms the contour of one of the openings 90 to be produced. Then, the element 1 is exposed to an etchant. The etchant does not only etch the surface of the sheet. In particular, the etchant, preferably an aqueous etching solution, can penetrate into the damage regions 57, so that the brittle material is etched along these regions. Thus, the damage regions 57 widen by etching to form a channel across the element 1.

[0121] According to a further embodiment, a sheet 2 of brittle material is provided, wherein a plurality of elements 1 is manufactured with the method as defined above, and wherein the contour of the elements 1 is produced in the sheet 2 by laser scribing and etchant in the same way. One example of this embodiment is shown in Figure 23 .

[0122] In this way, by etching the sheet 2, the element 1 is separated from the larger sheet 2 and the inner part of the opening 90 is separated from the element. In another embodiment, at least some of the damaged areas 57 of the profile 45 of the element 1 have a pitch such that, after etching, the element 1 remains connected to the sheet 2, with the web bridging the annular opening along the profile 45 of the element 1.

[0123] In an example, a sheet 2 of AS87 eco-glass having dimensions of 520*380 mm and a thickness of 200 pm was processed to obtain elements 1 having openings 90 of 4 mm length. The design was similar to Figure 2 The illustrated embodiment, the openings have straight portions. The glass sheet 2 was pre-scribed with a laser to form elements 1 of rectangular dimensions of 120 mm*80 mm with rounded corners of a radius of 0.1 mm. The pre-scribed structured glass master sheet 2 was etched with a 5% NH4HF2solution for 5 minutes and then chemically tempered at 390 °C for 45 minutes to obtain a DoL of 20 pm and a CS of 700 MPa. After tempering, the AS87 elements 1 of 120*80*0.2 mm could be manually broken off the master sheet 2. A post-etching with 5% NH4HF2was performed for 5 minutes. The elements 1 thus obtained could be bent to a bending radius of 3 mm without breaking.

[0124] In another embodiment, LAS glass of a larger thickness (0.55 mm - 0.7 mm) was used. Elements of LAS80 glass of 550 pm having a design as illustrated in Figure 3 and openings 90 of 3 mm length were chemically tempered in a 50 wt.% KNO3+ 50 wt.% NaNO3salt bath at a temperature of 395 °C for 3 hours and then tempered in a 92 wt.% KNO3+ 8 wt.% NaNO3salt bath at a temperature of 380 °C for 3 hours. For Na + and K + , the CS and DoL of the LAS80 elements 1 of 550 pm were measured with SLP 1000 and FSM600, respectively. The CS and DoL of the K + were 630 MPa and 3.8 pm, respectively. The CS of the Na + was 85 MPa at the DoL position, and the DoL of the Na + was 98 pm. The structured parts could be bent to R 3 mm without breaking.

[0125] According to a further embodiment, schematically depicted but not drawn to scale in Fig. 24, the element 1 comprises at least five portions, the at least five portions comprising three second portions 11, 12, 13 and two first portions 9a, 9b, the first portions 9a, 9b being arranged between two second portions 11, 12, 13, respectively, such that the first portions 9a, 9b form a hinge for the second portions 11, 12, 13, and wherein the first portions 9a, 9b are preferably formed differently. Figure 24a Such an element 1 is depicted in Fig. 24, wherein the first portions 9a, 9b are indicated to be formed differently by using differently oriented hatching. In the exemplary embodiment of Fig. 24, the first portion 9a is arranged between the second portions 11 and 12, while the first portion 9b is arranged between the second portions 12 and 13. Generally, not being limited to the exemplary embodiment of the element 1 schematically depicted but not drawn to scale in Fig. 24, the element 1 can comprise more than five portions, e.g. seven portions, wherein four of the seven portions are formed as second portions, while three portions are formed as first portions, which can act as hinges between the second portions.

[0126] In case of such an element 1, the element 1 can be folded into an S-shape or zigzag, e.g. as Figure 24b schematically but not drawn to scale in Fig. 24. I.e. in the exemplary embodiment depicted here, the element 1 is adapted for a double fold, wherein preferably, once folded, one of the first portions, e.g. the first portion 9a, is formed as an "in-fold", while the other first portion, e.g. the first portion 9b, is formed as an "out-fold". The in-fold and the out-fold are understood here with respect to the side faces 3, 5 of the element 1, wherein the side face 3 is understood here to point towards the device, e.g. a mobile phone or the like, and wherein the side face 5 is understood here to point away from the device. In that case, the in-fold area and the out-fold area can have different bending angles, and thus, preferably, the first portions 9a, 9b are formed differently. For example, the minimum radius of curvature of the out-fold can be larger than the minimum radius of the in-fold.

[0127] For example, once folded, the first portion forming the out-fold, i.e. Figure 24b The first portion 9b in the example shown can be optimized for such a larger minimum radius of curvature, thereby having a larger mechanical strength.

[0128] For example, such an element 1 comprising differently formed first portions 9a, 9b can be obtained by careful adjustment of the structuring parameters, such that the structures formed in the portions 9a, 9b are different from each other, e.g. the width and / or length of the structures or the openings 90 (not depicted here) formed within the element 9 are different.

[0129] However, it is also possible and even preferred that both elements 1 can be configured such that two first portions 9a, 9b are produced which can be bent in the same direction, for example, so that two inner folds can be obtained. In Figure 24c Such an element 1 is schematically but not to scale depicted in Fig. 1. This configuration of the element 1 can be preferred because in that case, particularly if the first portions 9a, 9b are configured to form inner folds, the display of the device is always protected because the side 5 folds over itself. It is also preferred here that the portions 9a, 9b are formed differently because one portion, for example, portion 9a, can be adapted to form a "first inner fold" with a smaller minimum radius of curvature, because the other first portion 9b is adapted to form a "second inner fold", which requires a larger minimum radius of curvature and thus can be formed with a larger mechanical strength. However, it is also possible that both first portions 9a, 9b are formed identically. In this way, the second portions 11, 13 can be folded inwardly such that they cover the side 5 of the portion 12 in a door-like manner, i.e. as wings of a door, as Figure 24d schematically but not to scale in Fig. 2.

[0130] List of reference signs

[0131] 1 plate-like element

[0132] 3, 5 side of 1

[0133] 7 edge of 1

[0134] 9, 9a, 9b first portion of 1

[0135] 11, 12, 13 second portion of 1

[0136] 15 boundary line between 9 and 11, 9 and 13

[0137] 17 maximum width of opening 90

[0138] 18 minimum width of opening 90 in the middle

[0139] 19 minimum width of web 94

[0140] 20 maximum width of web 94 in the middle

[0141] 25 test device

[0142] 26, 27 clamping jaws

[0143] 30 plastic

[0144] 33 inorganic layer

[0145] 35 organic layer

[0146] 37 glass sheet

[0147] 40 concave portion

[0148] 42 convex portion

[0149] 45 profile of element 1

[0150] 49 laser

[0151] 50 laser beam

[0152] 51 lens

[0153] 52 focal point of laser beam 50

[0154] 57 damage area

[0155] 90 opening in 9

[0156] 91 row of openings 90

[0157] 92, 94 web

[0158] 95 bend axis

[0159] 93 straight portion

[0160] 95 break mark

Claims

1. An inorganic brittle material element (1) having two opposite sides (3, 5) and a circumferential edge (7), the element (1) comprising at least three portions, the at least three portions comprising a first portion (9) and two second portions (11, 13), the second portions being contiguous with the first portion, such that the first portion (9) is arranged between the second portions (11, 13), the first portion (9) comprising an arrangement of openings (90) forming a passage from one side (3) to the opposite side (5) of the element, such that the first portion (9) has a higher flexibility than the second portions (11, 13), wherein the openings (90) have a varying width along their longitudinal direction, wherein, The openings (90) have two width maxima (17) spaced apart in the longitudinal direction, with a width minimum (18) in between the two maxima.

2. The element (1) according to claim 1, wherein The openings (90) are arranged in side-by-side rows (91), adjacent openings (90) within each row are separated by first webs (92), and openings (90) of adjacent rows (91) are separated by second webs (94), and wherein the first webs (92) of adjacent rows (91) are arranged offset from each other.

3. The element (1) according to claim 1 or 2, wherein The flexibility of the first portion (9) is at least 2 times higher than the flexibility of the second portions (11, 13).

4. The element (1) according to claim 1 or 2, wherein The flexibility of the first portion (9) is at least 3 times higher than the flexibility of the second portions (11, 13).

5. The element (1) according to claim 1 or 2, wherein The flexibility of the first portion (9) is at least 4 times higher than the flexibility of the second portions (11, 13).

6. Element (1) according to claim 1 or 2, having at least one of the following features: - the rows (91) of openings (90) are straight, - the first portion (9) forms a hinge for the second portions (11, 13), - the longitudinal direction of the openings (90) is oriented in the direction of a border line (15) between the first portion (9) and a second portion (13).

7. The element (1) according to claim 1 or 2, wherein The element (1) comprises at least five portions, the at least five portions comprising three second portions (11, 12, 13) and two first portions (9a, 9b), the first portions (9a, 9b) being arranged between two second portions (11, 12, 13), respectively, such that the first portions (9a, 9b) form a hinge for the second portions (11, 12, 13).

8. The element (1) according to claim 7, wherein The first portions (9a, 9b) are formed differently.

9. The element (1) according to claim 2, wherein In the longitudinal direction of the rows (91) of openings (90), the width of the first webs (92) is smaller than the width of the openings (90).

10. The element (1) according to claim 1, wherein The first portion (9) encloses one of the second portions (11), while the other second portion (13) encloses the first portion (9).

11. Element (1) according to claim 2 or 9, characterized in that The first webs (92) and the second webs (94) form a grid, wherein the first webs (92) and the second webs (94) are connected to each other such that at least a subset of the first webs (92) and the second webs (94) within the grid experiences a torsional strain upon flexure of the first portion (9), wherein the subset comprises at least one third of the total number of the first webs (92) and the second webs (94) within the grid.

12. The element (1) according to claim 1 or 2, wherein The element (1) comprises glass as the brittle material.

13. The element (1) according to claim 1 or 2, wherein The first portion (9) of the element (1) is structured such that bending of the first portion (9) about a bending axis until fracture divides the element (1) into two fragments, the total weight of the two fragments being at least 95% of the weight of the element (1).

14. Element (1) according to claim 12, characterized in that The glass composition of the element (1) comprises the following components in wt% according to one of the following embodiments: - first embodiment: SiO2 30 to 85, B2O3 3 to 20, Al2O3 0 to 15, Na2O 3 to 15, K2O 3 to 15, ZnO 0 to 12, TiO20.5 to 10, CaO 0 to 0.1 ; - Second embodiment: SiO2 55 to 75, Na2O 0 to 15, K2O 2 to 14, Al2O3 0 to 15, MgO 0 to 4, CaO 3 to 12, BaO 0 to 15, ZnO 0 to 5, TiO20 to 2; - Third embodiment: SiO2 58 to 65, B2O3 6 to 10.5, Al2O3 14 to 25, MgO 0 to 3, CaO 0 to 9, BaO 3 to 8, ZnO 0 to 2, - Fourth embodiment: SiO2 50 to 65, Al2O3 15 to 20, B2O3 0 to 6, Li2O 0 to 6, Na2O 8 to 17, K2O 0 to 5, MgO 0 to 5, CaO 0 to 7, ZnO 0 to 4, ZrO2 0 to 4, TiO20 to 1.

15. The element (1) according to claim 14, wherein According to the third embodiment, the glass is substantially free of alkali metal oxides.

16. The element (1) according to claim 14, wherein According to the fourth embodiment, the content of CaO is 0 to 1 in weight % and the content of ZnO is 0 to 1 in weight %.

17. The element (1) according to claim 14 or 16, wherein According to the fourth embodiment, the glass is substantially free of TiO2.

18. The element (1) according to claim 2, wherein The opening (90) is elongated and wherein the element (1) is characterized by having at least one of the following features: - the second web (94) has two minimum width values (19) spaced apart in the longitudinal direction of the web (94), with an intermediate maximum width value (20) between the minimum width values (19) of the second web (94), - the profile of the opening (90) or the second web (94) has at least one straight portion (93), - the minimum width of the second web (94) is equal to or less than twice the thickness of the element (1), - the length of the second web (94) is at least twice the thickness of the element (1), - the element (1) is chemically or thermally tempered, - the depth of the compressive stress zone created by tempering is less than half the minimum web width of the first web (92) and second web (94).

19. The element (1) according to claim 1 or 2, characterized in that At least a portion of the number of openings (90) are filled with plastic.

20. Element (1) according to claim 19, characterized in that The element (1) comprises at least one of the following features: - the reaction force due to the deflection of the element (1) is modified by at most 30% relative to the element (1) in which there is no plastic in the opening (90), - the plastic (30) is transparent, - the plastic (30) matches the refractive index of the brittle material of the element (1), - the plastic (30) comprises an elastomer.

21. The element (1) according to claim 19, characterized in that The plastic (30) comprises a silicone.

22. The element according to claim 1 or 2, wherein The element is chemically tempered and has at least one of the following features: - the compressive stress of the element is higher than 100 MPa, - the compressive stress of the element is lower than 1500 MPa, - the DoL is greater than 1 pm, - the DoL is less than 0.4 t, - the structured first portion of the chemical tempering can be bent with a bending radius of less than 500 t without breaking, where t is the thickness of the glass.

23. The element according to claim 1 or 2, wherein - the element is chemically tempered and has at least one of the following characteristics: - the compressive stress of the element is higher than 250 MPa, - the compressive stress of the element is lower than 1300 MPa, - the DoL is greater than 3 pm, - the DoL is less than 0.3t, - the chemically tempered structured first portion is bendable without breakage with a bending radius of less than 30t, where t is the glass thickness.

24. The element according to claim 1 or 2, characterized by - the first portion (9) is structured such that the stress generated at the surface due to bending is reduced by at least 50% compared to a non-structured element of the same thickness, - the first portion (9) is structured such that the stress generated at the surface of the first portion due to bending varies at most by 10% over a thickness range of the element from 200 pm to 2 mm.

25. An article (2) comprising the element (1) according to any one of claims 1 to 24, the element (1) comprising at least two portions movable relative to each other. The element (1) is bent and folded at the first portion such that the surfaces of the second portions (11, 13) of one of the side faces (3, 5) face each other.

26. The article of claim 25, wherein, The article comprises at least one of the following characteristics:

27. The article of claim 26, wherein, - the element (1) is bent such that the surfaces of the second portions (11, 13) facing each other are positioned in parallel or at an acute angle, - the surfaces of the second portions (11, 13) facing each other are positioned close together such that the first portion (9) bulges outwards, thereby making the thickness of the folded element at the first portion (9) greater than the thickness at the dividing line (15) between the first portion (9) and the second portions (11, 13) or greater than the thickness at the location where the second portions (11, 13) are opposite each other, - the element (1) forms one layer of a sandwich structure, - at least one side face (3, 5) of the element (1) is laminated to an organic layer, - the laminate comprises a glass sheet (37) laminated to the element (1), - the article (2) is a foldable display, - the article (2) has a press switch, wherein the button of the press switch is formed by one of the second portions (11, 13). At least one side face (3, 5) of the element (1) is laminated to a plastic layer (35).

28. The article of claim 26, wherein, 29. A method for manufacturing an element (1) of inorganic brittle material according to any one of claims 1 to 24, comprising the following steps: - providing a plate-like element (1) of brittle material, - directing and focusing a laser beam of an ultra-short pulsed laser (49) onto the element (1), the laser beam (50) having a wavelength at which the brittle material of the element (1) is transparent such that the laser beam (50) can penetrate into the element (1), - focusing the laser beam (50) to create an elongated focal point (52) within the element (1), the laser beam (50) being strong enough to create a filamentous damage region (57) along the focal point (52) within the element (1), - moving the element (1) relative to the focal point (52) to create a plurality of elongated damage regions (57) within the element (1), - Move the laser beam (50) relative to the element to introduce multiple filamentary damage regions (57) side by side along multiple annular paths. - By exposing the element to an etchant for etching, the etchant penetrates the filamentary damage region (57), causing the filamentary damage region (57) to widen to form a channel that is joined due to the widening, thereby separating the portion of the element surrounded by the annular path and creating an opening (90), thereby forming at least three parts, including a first part (9) and two second parts (11, 13), the second parts being adjacent to the first parts, such that the first part (9) is arranged between the second parts (11, 13), the first part (9) including the opening (90), such that the first part (9) has greater flexibility than the second parts (11, 13).

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