BENDABLE AND/OR FOLDABLE ARTICLES AND METHOD OF PROVIDING BENDABLE AND/OR FOLDABLE ARTICLES

Abstract

The present disclosure relates to bendable and/or foldable articles and uses thereof and to a method of providing bendable and/or foldable articles. The articles are of translucent and brittle material, such as glass, glass ceramic, ceramic or crystals. The articles may be used as a display cover such as a protecting cover in displays in, for example, smartphones, tablet computers, or TV devices. The articles may also be used as a substrate for electronic components, such as OLEDs or LEDs.

Claims

1. A method for providing a set of articles of translucent and brittle material, comprising: determining a plurality of parameters for individual articles of a plurality of articles, the determined plurality of parameters of each individual article comprising a fracture toughness (K.sub.Ic), a compressive stress (CS), a characteristic penetration depth (x.sub.c), and an article thickness (d); selecting a plurality of satisfactory articles from the plurality of articles, the plurality of satisfactory articles being dependent upon the plurality of parameters satisfying the following equation: $\frac{395.Math.K_{\mathrm{Ic}}}{\sqrt{m}}=\mathrm{SP}.Math.\left(\frac{}{2}-\arcsin \left(\frac{B}{4.Math.{10}^{-6}.Math.m}\right)-\frac{2}{d}.Math.\sqrt{\left(1,6.Math.{10}^{-11}.Math.m^2-B^2\right)}\right)+\mathrm{CS}.Math.\left(\left(1-\frac{x_c}{0,843.Math.d}\right).Math.\left(\frac{}{2}-\arcsin \left(\frac{B}{4.Math.{10}^{-6}.Math.m}\right)\right)-\frac{0,843.Math.\sqrt{\left(1,6.Math.{10}^{-11}.Math.m^2-B^2\right)}}{x_c}\right).Math.,.Math..Math..Math.\mathrm{wherein}.Math.$ $.Math.B=\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right).Math.$ $.Math.\mathrm{for}.Math.$ $0\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right)4.Math.{10}^{-6}.Math.,.Math..Math..Math.\mathrm{wherein}.Math..Math.B=0.Math..Math.\mathrm{for}$ $.Math.0>\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right),.Math..Math.\mathrm{wherein}.Math..Math.B=0.Math..Math.\mathrm{for}$ $.Math.\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right)>4.Math.{10}^{-6},$ wherein m=1 meter, wherein x.sub.c>0 m, and wherein SP is larger than 250 MPa; and physically separating the selected plurality of satisfactory articles from other articles of the plurality of articles.

2. The method according to claim 1, wherein the translucent and brittle material comprises a material selected from the group consisting of glass, glass ceramic, ceramic or crystals.

3. The method according to claim 1, wherein the fracture toughness K.sub.Ic is larger than 0.4 MPa.Math.m.

4. The method according to claim 1, wherein the compressive stress CS is larger than 200 MPa.

5. The method according to claim 1, wherein the characteristic penetration depth x.sub.c is at least 2 m and at most 50 m.

6. The method according to claim 1, wherein the article thickness d is in a range of from 5 m to 500 m.

7. A set of articles, consisting of: a plurality of articles comprising a translucent and brittle material, wherein each of the plurality of articles has a fracture toughness K.sub.Ic, a compressive stress CS, a characteristic penetration depth x.sub.c and an article thickness d, wherein the following equation is satisfied for each of the plurality of articles: $\frac{395.Math.K_{\mathrm{Ic}}}{\sqrt{m}}=\mathrm{SP}.Math.\left(\frac{}{2}-\arcsin \left(\frac{B}{4.Math.{10}^{-6}.Math.m}\right)-\frac{2}{d}.Math.\sqrt{\left(1,6.Math.{10}^{-11}.Math.m^2-B^2\right)}\right)+\mathrm{CS}.Math.\left(\left(1-\frac{x_c}{0,843.Math.d}\right).Math.\left(\frac{}{2}-\arcsin \left(\frac{B}{4.Math.{10}^{-6}.Math.m}\right)\right)-\frac{0,843.Math.\sqrt{\left(1,6.Math.{10}^{-11}.Math.m^2-B^2\right)}}{x_c}\right).Math.,.Math..Math..Math.\mathrm{wherein}.Math.$ $.Math.B=\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right).Math.$ $.Math.\mathrm{for}.Math.$ $0\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right)4.Math.{10}^{-6}.Math.,.Math..Math..Math.\mathrm{wherein}.Math..Math.B=0.Math..Math.\mathrm{for}$ $.Math.0>\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right),.Math..Math.\mathrm{wherein}.Math..Math.B=0.Math..Math.\mathrm{for}$ $.Math.\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right)>4.Math.{10}^{-6},$ wherein m=1 meter, wherein x.sub.c>0 m, and wherein SP is larger than 250 MPa.

8. The set of articles according to claim 7, wherein the translucent and brittle material comprises a material selected from the group consisting of glass, glass ceramic, ceramic or crystals.

9. The set of articles according to claim 7, wherein the fracture toughness K.sub.Ic is larger than 0.4 MPa.Math.m.

10. The set of articles according to claim 7, wherein the compressive stress CS is larger than 200 MPa.

11. The set of articles according to claim 7, wherein the characteristic penetration depth x.sub.c is at least 2 m and at most 50 m.

12. The set of articles according to claim 7, wherein the article thickness is in a range of from 5 m to 500 m.

13. The set of articles according to claim 7, further comprising a further material attached to at least one side of at least one of the plurality of articles to form a composite, wherein a Young's modulus of the further material is larger than 10 GPa.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0080] The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:

[0081] FIG. 1 illustrates the correlation between measured bending radii (characteristic value according to Weibull statistics) and the calculated SP-values (secondary y-axis) using an exemplary glass with d=100 m, K.sub.Ic=0.7 MPa.Math.m and CS=960 MPa; the two reference values indicate the bending radius or the SP-value of a non-toughened glass, respectively.

[0082] FIG. 2 illustrates the correlation between measured bending radii (characteristic value according to Weibull statistics) and the calculated SP-values (secondary y-axis) using a further exemplary glass with d=100 m, K.sub.Ic=0.7 MPa.Math.m and CS=960 MPa; the two reference values indicate the bending radius or the SP-value of a non-toughened glass, respectively.

[0083] FIG. 3 illustrates SP-values depending on the bending radius; the two data points having low SP-values below 200 MPa are the reference values of a non-toughened glass.

[0084] FIG. 4 illustrates SP-values depending on the breaking stress; the two data points having low SP-values below 200 MPa are the reference values of a non-toughened glass.

[0085] FIG. 5 illustrates SP-values depending on x.sub.c for three glasses that differ with respect to the com-pressive stress CS.

[0086] FIG. 6 illustrates SP-values depending on x.sub.c for four glasses that differ with respect to their thickness d.

[0087] FIG. 7 illustrates SP-values depending on x.sub.c for four glasses that differ with respect to their thickness d.

[0088] FIG. 8 illustrates SP-values depending on x.sub.c for three glasses that differ with respect to their fracture toughness K.sub.Ic.

[0089] FIG. 9 illustrates SP-values depending on x.sub.c for three glasses that differ with respect to their fracture toughness K.sub.Ic.

[0090] Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0091] A plurality of articles of different production batches are provided. Fracture toughness K.sub.Ic, compressive stress CS, characteristic penetration depth x.sub.c and article thickness d of the individual articles are determined. The determination of the indicated parameters of the individual articles is done for each production batch using ten reference articles, which are representative for the respective batch. Based on the determination of the parameters, those articles are selected for which the following equation is satisfied:

[00007]$\frac{395.Math.K_{\mathrm{Ic}}}{\sqrt{m}}=\mathrm{SP}.Math.\left(\frac{}{2}-\arcsin \left(\frac{B}{4.Math.{10}^{-6}.Math.m}\right)-\frac{2}{d}.Math.\sqrt{\left(1,6.Math.{10}^{-11}.Math.m^2-B^2\right)}\right)+\mathrm{CS}.Math.\left(\left(1-\frac{x_c}{0,843.Math.d}\right).Math.\left(\frac{}{2}-\arcsin \left(\frac{B}{4.Math.{10}^{-6}.Math.m}\right)\right)-\frac{0,843.Math.\sqrt{\left(1,6.Math.{10}^{-11}.Math.m^2-B^2\right)}}{x_c}\right).Math.,.Math..Math..Math.\mathrm{wherein}.Math.$$.Math.B=\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right).Math.$$.Math.\mathrm{for}.Math.$$0\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right)4.Math.{10}^{-6}.Math.,.Math..Math..Math.\mathrm{wherein}.Math..Math.B=0.Math..Math.\mathrm{for}$$.Math.0>\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right),.Math..Math.\mathrm{wherein}.Math..Math.B=0.Math..Math.\mathrm{for}$$.Math.\frac{x_c}{0,843}.Math.\left(\frac{d}{\mathrm{CS}.Math.d+2,37.Math.\mathrm{SP}.Math.x_c}\right).Math.\left(\mathrm{SP}+\mathrm{CS}-\frac{\mathrm{CS}.Math.x_c}{0,843.Math.d}\right)>4.Math.{10}^{-6},$

[0092] wherein m=1 meter, wherein x.sub.c>0 m, and wherein SP is larger than 250 MPa.

[0093] In particular, those articles are not selected for which SP is not larger than 250 MPa. The selected articles are separated from the remaining articles and put together as a set of articles in accordance with the present disclosure.

[0094] Surprisingly, it was found that glass having a higher SP can be bent to a lower bending radius before it breaks.

[0095] FIG. 1 illustrates the correlation between measured bending radii (characteristic value according to Weibull statistics) and the calculated SP-values (secondary y-axis) using an exemplary glass. The two reference values indicate the bending radius or the SP-value of a non-toughened glass, respectively. It can be seen that the SP-value is highest for the lowest bending radii. This means that low bending radii can be achieved at high SP-values. It was measured using 2-point-bending. (see also Matthewson and Kurkjian (J. Am. Ceram. Soc., 69 [11], pages 815-821 (1986))). In this diagram, half of the distance of the plates at breakage of the glass was set as bending radius of the 2-point-bending.

[0096] FIG. 2 shows a comparable diagram once more for another exemplary glass having a pre-stress of only 440 MPa (see diagram title). As can be seen, the achievable bending radii are considerably higher and the SP-graph is considerably lower as compared to the exemplary glass having CS=960 MPa, which is illustrated in FIG. 1. Thus, lower bending radii can be achieved with higher pre-stress. These measurements were done with a stepped roll as described in DE 10 2014 110 855 A1. The bending radius in the diagram is the radius of the roll on which the glass broke.

[0097] If the data for both exemplary glasses are shown in one diagram, this results in the two diagrams shown in FIGS. 3 and 4 having SP as a function of bending radius or as a function of breaking stress (the higher the stress, the lower the bending radius), respectively. It can be seen that lower bending radii can be achieved with higher SP-values. Higher SP-values are related with a higher breaking stress. The two data points with the low SP-values below 200 MPa are the reference values and are also representative for glasses that cannot be toughened or that have only very low CS-values.

[0098] FIGS. 5 to 9 show diagrams in which the survival parameter is shown as function of the other parameters. The x-axis is always taken by x.sub.c. Two further parameters are kept fixed and the third is varied by the graphs. Which parameters are fixed with which value is indicated in the title of each diagram.

[0099] FIG. 5 shows that the survival parameter SP is increased at higher pre-stress CS. FIG. 6 and FIG. 7 show that a higher article thickness is correlated with higher SP-values. In FIGS. 8 and 9, it can be seen that a higher fracture toughness K.sub.Ic correlates with higher SP-values.

[0100] While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice hi the art to which this invention pertains and which fall within the limits of the appended claims.