BENDABLE ELEMENT

Abstract

The present disclosure relates to bendable elements. The bendable elements can be used in display covers for electronic devices such as smart phones. The elements have reduced delayed elastic deformation or creep when released from the influence of persistent mechanical stresses, e.g. unfolded from a folded position. The present disclosure also relates to covers for color filters, filter printed electronics, sensors for touch control panels, fingerprint sensors, mobile electronic devices, bendable/foldable displays that include the bendable elements as substrates, or other applications where a combination of high chemical stability, temperature stability, low gas permeability, flexibility, high strength, low thickness and premium cosmetic appearance is necessary. Besides consumer and industrial electronics the present disclosure could also be used for protection applications in industrial production or metrology.

Claims

1. A bendable element having a thickness, a length and a width, and having a first and a second primary surface, wherein the element can be bent to a bending radius of 5.0 mm without failure, and wherein the element has reduced persistent deformation characterized by a total persistent deformation a.sub.0 of not more than 3.0 mm and a deformation recovery time b.sub.1 of less than 10 hours after bending the element to a bending radius of 15.0 mm for 24 hours at 25° C. and 30% relative humidity.

2. The bendable element according to claim 1, wherein the thickness is less than 800 μm.

3. The bendable element according to claim 1, wherein a.sub.0 is not more than 2.0 mm, and/or b.sub.1 is less than 5 hours.

4. The bendable element according to claim 1, wherein the length is at least 0.5 cm, and/or wherein the width is at least 0.4 cm, and wherein the length is larger than the width.

5. The bendable element according to claim 1, further comprising at least one layer, wherein the at least one layer is a polymer or a non-polymer, wherein the element has a total polymer thickness PT, a total non-polymer thickness NPT and a polymer/non-polymer thickness ratio, wherein the total polymer thickness is the sum of the thicknesses of any polymer layers in the element, wherein the total non-polymer thickness is the sum of the thicknesses of any non-polymer layers in the element, wherein the polymer/non-polymer thickness ratio is PT/NPT, and wherein at least one of the following conditions applies: PT ranges from 0.0 μm to 600 μm; NPT ranges from 20.0 μm to 200 μm; PT/NPT ranges from 0.0 to <5.0; NPT is less than 70 μm and PT/NPT ranges from 0.0 to <5.0; and NPT is at least 70 μm and PT/NPT ranges from 0.0 to <2.0.

6. The bendable element according to claim 1, further comprising one or more bendable glass layers; wherein the glass layer has at least one of the following properties: a thickness of from 20.0 μm to 200 μm; a warp of not more than 2.0 mm; a total thickness variation TTV of not more than 10 μm; a surface roughness R.sub.a of not more than 5.0 nm; a two-point bending strength of at least 700 MPa; a compressive stress of at least 100 MPa in one or both of the primary surfaces; and/or a DoL of at least 1.0 μm and up to 30.0 μm.

7. The bendable element according to claim 6, wherein the glass of the glass layer has at least one of the following properties: a Young's modulus of more than 50 GPa; a fracture toughness K.sub.IC of not more than 4.0 MPam.sup.1/2; a Poisson's ratio of less than 0.28; a Knoop hardness of at least 450 MPa; a fragility of at least 18 and/or less than 42; and a shear modulus of more than 23.5 GPa.

8. The bendable element according to claim 1, further comprising a non-polymer layer having a pen drop breakage height of at least 20.0 mm.

9. The bendable element according to claim 1, further comprising one or more coating layers on at least one of the primary surfaces.

10. The bendable element according to claim 1, further comprising one or more bendable polymer layers, wherein one or more of the polymer layers has a thickness of 1.0 μm or more.

11. The bendable element according to claim 10, wherein the one or more polymer layers has a persistent deformation factor of not more than 1.5, wherein the persistent deformation factor is the creep resistance plus tan δ of the polymer material.

12. The bendable element according to claim 6, wherein the glass layer is made of a glass having the following composition in weight percent: TABLE-US-00012 Composition (wt %) SiO.sub.2 45.0 to 75.0% Al.sub.2O.sub.3  2.5 to 25.0% Li.sub.2O  0.0 to 10.0% Na.sub.2O  5.0 to 20.0% K.sub.2O  0.0 to 10.0% MgO  0.0 to 15.0% CaO  0.0 to 10.0% P.sub.2O.sub.5  0.0 to 20.0% BaO  0.0 to 5.0%  ZnO  0.0 to 5.0%  ZrO.sub.2  0.0 to 5.0%  B.sub.2O.sub.3  0.0 to 5.0%  TiO.sub.2  0.0 to 2.5% 

13. The bendable element according to claim 1, wherein the bendable element has an initial deformation distance at a 10 mm bend radius of not more than 40 mm, wherein the initial deformation distance is the height of the deformation distance measured immediately after releasing the bendable element from a 10.0 mm bend radius after 24 hours at 25° C. and 30% relative humidity.

14. The bendable element according to claim 1, wherein the bendable element has a 40 mm-initial deformation threshold of less than 10 mm, wherein the 40 mm-initial deformation threshold is the bending radius to which the bendable element can be bent for 24 hours at 25° C. and 30% relative humidity without exceeding an initial deformation distance of 40 mm immediately after releasing the bendable element from the bend radius.

15. A bendable element comprising: a glass layer having a thickness of 70.0 μm or less; two polymer layers disposed on opposing sides of the glass layer having thicknesses of 70.0 μm or less each; and two adhesive layers disposed on opposing sides of the glass layer between glass layer and polymer layers, wherein the cumulative thickness of the glass layer, the two polymer layers and the two adhesive layers is 250.0 μm or less, and wherein the polymer layers comprise one or more polymers having a creep resistance of at least 0.65.

16. The bendable element according to claim 15, wherein the two polymer layers have a persistent deformation factor of not more than 1.5, wherein the persistent deformation factor is the creep resistance plus tan δ of the polymer material.

17. The bendable element according to claim 15, wherein the bendable element has a total persistent deformation a.sub.0 of not more than 15.0 mm and/or a deformation recovery time b.sub.1 of less than 10 hours after bending the element to a bending radius of 15.0 mm for 24 hours at 25° C. and 30% relative humidity.

18. The bendable element according to claim 15, wherein one or both of the polymer layers comprise a polymer selected from polyethylene terephthalate, polyimide, and polycarbonate, and wherein the polymer has a creep resistance of at least 0.75.

19. The bendable element according to claim 15, wherein one or both of the polymer layers comprise a polymer selected from polyethylene terephthalate, polyimide, and polycarbonate, and wherein the polymer has a tan δ of 0.01 to 0.4.

20. An electronic device having a foldable display comprising a bendable element according to claim 1, and at least one hinge allowing the display to be bent about a bending axis, wherein the electronic device is designed so that the display can be bent to a bending radius of no less than the 40 mm-initial deformation threshold of the bendable element.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0177] FIG. 1A is a schematic drawing of a bendable element within a fixture used for measuring the deformation.

[0178] FIG. 1B is a schematic drawing of a bendable element illustrating the deformation distance based on maximum deformation point and reference plane.

[0179] FIG. 2 is a schematic drawing of a bendable element of the present disclosure.

[0180] FIG. 3 is a schematic drawing of a multi-layered bendable element of the present disclosure.

[0181] FIG. 4 is a schematic drawing of a bendable element of the present disclosure in a bent state.

[0182] FIG. 5 is a schematic drawing of a multi-layered bendable element of the present disclosure in a bent state.

[0183] FIG. 6A is a plot showing the dependence of the deformation distance on time after releasing glass layers of various thicknesses from a bent state with 15 mm plate distance after 1 day at 25° C./30% relative humidity.

[0184] FIG. 6B is a plot showing the dependence of the deformation distance on time after releasing glass layers of various thicknesses from a bent state with 10 mm plate distance after 1 day at 25° C./30% relative humidity.

[0185] FIG. 6C is a plot showing the dependence of the deformation distance on time after releasing glass layers of various thicknesses from a bent state with 8 mm plate distance after 1 day at 25° C./30% relative humidity.

[0186] FIG. 7 is a plot showing the dependence of the deformation distance on time after releasing various multi-layered bendable elements from a bent state with 15 mm plate distance after 1 day at 25° C./30% relative humidity.

[0187] FIG. 8 is a plot showing the dependence of the deformation distance on time after releasing various multi-layered bendable elements from a bent state with 15 mm plate distance after 1 day at 25° C./30% relative humidity.

[0188] FIG. 9 is a plot showing the dependence of the deformation distance on time after releasing various multi-layered bendable elements from a bent state with 15 mm plate distance after 1 day at 25° C./30% relative humidity.

[0189] FIG. 10 is a plot showing the dependence of the deformation distance on time after releasing various multi-layered bendable elements from a bent state with 15 mm plate distance after 1 day at 25° C./30% relative humidity.

[0190] FIG. 11 is a plot showing the dependence of the deformation distance on time after releasing various multi-layered bendable elements from a bent state with 15 mm plate distance after 1 day at 25° C./30% relative humidity.

[0191] FIG. 12 is a schematic of the pen drop test set up for unbent bendable elements.

[0192] FIG. 13 is a schematic of the pen drop test set up for bent bendable elements.

DETAILED DESCRIPTION OF THE DISCLOSURE

[0193] FIG. 1A is a schematic drawing of a top view of a bendable element 1 in a fixture after bending. The figure shows the bendable element 1 held by two cuboid jigs 10 that hold the element in a standing position. Bendable element 1 has a crease 15 extending in a vertical direction, i.e. into the image plane. The extent of crease 15 is exaggerated for illustration purposes. Bendable element 1 has an inner surface 7 and an outer surface 6. Inner surface 7 includes the concave portion of crease 15. Cuboid jigs 10 feature grooves 13 into which the vertical edges 14 of bendable element 1 are inserted. The widths of grooves 13 are larger than the thickness of bendable element 1 in order not to clamp the element within the grooves. The depths of grooves 13 are larger than inserted lengths of bendable element 1 in order not to compress the element. The element is inserted in an unbent state, i.e. the openings of grooves 13 face each other and they do not induce the bendable element 1 to curve or bend during the evaluation.

[0194] FIG. 1B is a detail view of bendable element 1 according to FIG. 1A after bending. The element has a crease 15 as a result of bending. Crease 15 has a maximum deformation point 20 on the element's inner surface 7. A reference plane may be defined as the plane that extends in a vertical direction (into the image plane) and includes two reference points 21 on inner surface 7. Reference points 21 are at a horizontal distance of 10 mm from the maximum deformation point in the direction of the first and second cuboid jigs, respectively. In other words, reference points 21 are at a horizontal distance of 10 mm from the point where a normal to the reference plane that includes the maximum deformation point meets the reference plane. The deformation height D is the shortest distance of maximum deformation point 20 to the reference plane. The deformation height shown in this FIG. 1B is exaggerated for purposes of illustration.

[0195] FIG. 2 shows a bendable element having a non-polymer layer 2. The non-polymer layer 2 can be a glass layer of 30 μm thickness. The non-polymer layer 2 is shown in an unbent state.

[0196] FIG. 3 shows a bendable element 1 in accordance with an embodiment of the disclosure. The bendable element 1 has a non-polymer layer 2 which may be a glass layer. An optional polymer layer 4 such as a PI or PET layer may be attached to the non-polymer layer 2 using an optically clear adhesive (OCA) layer 8. A further OCA layer 3 may be present for attaching a bendable element 1 to a display element of an electronic device such as a smartphone. In an embodiment, the overall thickness of OCA layer 8, polymer layer 4 and OCA layer 3 add up to about 0.1 mm, and preferably from 75 to 125 μm.

[0197] FIG. 4 shows a bendable element 1 being bent. The element has a thickness t. The outer surface 6 is under tensile stress, which is elongated due to the tension stress and facing away from the bending axis. The inner surface 7 is under compression stress and facing towards the bending axis. The figure shows a bending angle of 180°.

[0198] FIG. 5 shows a similar situation as FIG. 4, wherein an OCA layer 3 is present on the non-polymer layer 2.

[0199] FIGS. 6A to 11 show time-dependent deformation recovery for exemplary bendable elements of this disclosure.

[0200] FIG. 12 shows the pen drop set up for unbent bendable elements. A bendable element includes a non-polymer layer 2 and a polymer layer 4. The polymer layer 4 is indirectly attached to the non-polymer layer 2 by intermediate layers, namely an additional adhesive layer in the form of OCA layer 8. The polymer layer 4 is attached to a steel plate 11, resembling a display element for the pen drop test. A ball-point pen drop is performed. To simplify the results, a 0.5 mm thick steel plate 11 is used to simulate the display element. The weight of the ball-point pen is around 5 g. The ball of the pen 12 made of tungsten carbide has a radius of 0.35 mm. The pen drop starts from a height of 10 mm. The height is increased until the bendable element breaks. The greatest height at which the bendable element does not break after pen drop is the pen drop height. 30 pieces of the bendable element are tested and the average pen drop height is recorded.

[0201] FIG. 13 shows the pen drop set up for bent elements. A bendable element includes a non-polymer layer 2 and an OCA layer 3. The OCA layer 3 is fixed to the non-polymer layer 2. The OCA layer 3 is attached to a steel plate 11. A ball-point pen drop is performed. To simplify the results, a 0.5 mm thick steel plate 11 is used to simulate a display element. The weight of the ball-point pen is around 5 g. The ball of the pen 12 made of tungsten carbide has a radius of 0.35 mm. The bending radius is 4 mm. The pen drop starts from a height of 5 mm. The height is increased until the bendable element breaks. The greatest height at which the non-polymer layer 2 does not break after pen drop is the pen drop height. 30 pieces of the bendable element are tested and the average pen drop height is recorded.

Examples

1. Glass Articles

[0202] Table 1 shows the compositions of glass articles obtainable by direct hot-forming or chemical slimming. The glasses can be chemically toughened.

TABLE-US-00002 TABLE 1 Composition (wt %) Type 1 Type 2 Type 3 SiO.sub.2 61 62 68.3 Al.sub.2O.sub.3 17 18 4.8 Li.sub.2O — 5 — Na.sub.2O 12 9.4 15.8 K.sub.2O 4 0.1 — MgO 4 9.0 CaO — 0.7 1.6 ZrO.sub.2 2 3.6 — B.sub.2O.sub.3 — 0.7 — Others 0.5 0.5

[0203] Glass articles of the different glass types were produced in a down draw process or chemical slimming process. The glass articles had very low thicknesses ranging from 30 μm to 100 μm. The articles were chemically toughened to form chemically toughened glass articles.

[0204] Each glass article has two major surfaces. In these embodiments, each sample represents a glass article toughened on both sides, generating a compressive stress region with a certain depth (DoL) on each side of the glass article.

2. Polymer Layers

[0205] Polymer layers were prepared. Each layer measured about 40 mm×100 mm. The polymers were polyimide (PI) and polyethylene terephthalate (PET). Each polymer was prepared in thicknesses of 30 μm, 50 μm, 80 μm and 100 μm layer thickness. Some of the layers were covered with a hard coating of 10 μm thickness. A deformation test was performed on the specimen.

[0206] The used PI had a creep resistance of about 0.8, and the used PET had a creep resistance of about 0.75.

[0207] The used PI had a tan δ of about 0.04, as measured by DMA according to ISO 6721-6:2019, determined at a temperature of 25° C. The used PET had a tan δ of about 0.03, as measured by DMA according to ISO 6721-6:2019, determined at a temperature of 25° C.

[0208] The creep modulus of the polymers has been determined at 25° C. and 30% relative humidity, at an initial tension of 10, 20 and 40 MPa.

[0209] The test samples were prepared as follows: The films were bent to 180° between two parallel Bakelite plates with distances of 15 mm, 10 mm and 8 mm, and held for a duration of 1 day at 25° C. and a humidity of 30%. Then, the films were taken out, put on a polished steel plate and the deformation at the bending region was checked with a CCD camera. The deformation distance was recorded over time.

TABLE-US-00003 TABLE 2 Distance of PET PI Thickness/μm the two plates 30 50 80 100 30 50 80 100 initial D = 15 mm 4.8 2.5 2.1 1.8 10.2 7.4 5.2 4.1 deformation D = 10 mm 8.4 6.9 6.3 6.0 14.2 12.1 10.1 9.5 distance/mm D = 8 mm  10.3 8.6 7.5 7.1 16.7 14.6 13.7 12.4

TABLE-US-00004 TABLE 3 Distance of PET + HC PI + HC Thickness/μm the two plates 30 + 10 50 + 10 80 + 10 100 + 10 30 + 10 50 + 10 80 + 10 100 + 10 initial D = 15 mm 8.7 6.5 5.1 4.0 37.2 30.7 21.0 16.6 deformation D = 10 mm 14.2 12.8 11.0 9.5 43.1 35.4 26.7 20.4 distance/mm D = 8 mm  16.9 15.7 14.3 12.9 46.7 37.8 30.1 23.6

3. Glass and Polymer Stack Assemblies

[0210] Laminates of alumosilicate glass and polymer were examined. Table 4 shows the layers of the laminates and summarizes their behavior after bending for 480 h at 85° C./85% between plates of 10.5 mm distance.

TABLE-US-00005 TABLE 4 A B C 5.sup.th layer 50 μm PI 50 μm PI 4.sup.th layer 50 μm OCA 25 μm OCA 3.sup.rd layer 75 μm glass 75 μm glass 75 μm glass 2.sup.nd layer 50 μm OCA 50 μm OCA 50 μm OCA 1.sup.st layer 100 μm PET 100 μm PET 100 μm PET total thickness 225 μm 325 μm 300 μm initial deformation  48 mm  47 mm  46 mm distance deformation distance  34 mm  40 mm  42 mm after 168 h relaxation

4. Bendable Element Comprising Glass Layer Type 1

[0211] Glass type 1 was prepared in small thicknesses of 30 μm, 50 μm, 70 μm and 100 μm by a slot down draw method and cut to 150 mm×100 mm sheets. All the sheets were immersed into pure KNO.sub.3 for ion exchanging. CS and DoL of the glass dies were measured with FSM 6000.

[0212] The glass sheets were placed between the parallel Bakelite plates as described above. For the deformation, test samples of glass articles are prepared as follows: five cut and toughened glass articles were placed between two parallel Bakelite plate with a distance of 15 mm, 10 mm and 8 mm. Then, the sheets were held at 25° C. with a humidity of 30% for 1 day. Afterwards, the glass sheets were released and checked for deformation at the bending part with a CCD camera. The deformation distance was recorded via time. The initial deformation distance was recorded via CCD camera, and the deformation recovery time b.sub.1 and total persistent deformation a.sub.0 were calculated via formula (2).

[0213] The results are shown in FIGS. 6A to C. Table 5 summarizes the values.

TABLE-US-00006 TABLE 5 30 μm Glass type 1 50 μm Glass type 1 70 μm Glass type 1 100 μm Glass type 1 (CS = 643 MPa, (CS = 681 MPa, (CS = 735M Pa, (CS = 763 MPa, DoL = 6.1 μm) DoL = 10.4 μm) DoL = 13.7 μm) DoL = 17.7 μm) a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h D = 15 mm 0.83 4.77 0.47 3.58 0.79  3.98 0.08 4.82 D = 10 mm 0.53 7.35 0.12 9.30 0.01 10.53 — — D = 8 mm  0.01 5.63 0.18 3.59 — — — —

5. Bendable Element Comprising Coated Glass Layer Type 1

[0214] Glass type 1 was drawn to a thickness of 50 μm using a slot down draw method. The glass was cut to sheets of size 150 mm×100 mm. All the glass sheets were immersed into pure KNO.sub.3 for ion-exchanging. CS and DoL of the glass sheets were measured with FSM 6000.

[0215] A first set of elements was single-coated with a 20 μm thick acrylic-based resin hard coating (HC), which structure is referred to as “glass+HC”. The coated elements were placed between parallel Bakelite plates with the hard coating bent inwards as described above.

[0216] A second set of elements was single-coated with a 40 μm thick colorless polyamide (CPI) layer, which structure is referred to as “glass+CPI”. The coated elements were placed between parallel Bakelite plates with the surface of PI bent inwards as described above.

[0217] A third set of elements was coated with a 40 μm thick colorless polyamide (CPI) and then coated with a 10 μm thick acrylic-based resin hard coating (HC), which structure is referred to as “glass+CPI+HC”. The coated elements were placed between parallel Bakelite plates with the hard coating bent inwards as described above.

[0218] For the deformation test, samples of elements were prepared as follows: five elements were placed between two parallel Bakelite plates at a distance of 15 mm and held at 25° C. with a humidity of 30% for 1 day. Then, the elements were released and the deformation at the bending region was evaluated with a CCD camera. The deformation distance was recorded over time. The initial deformation distance was recorded with a CCD camera, and the deformation recovery time b.sub.1 and total persistent deformation a.sub.0 were calculated using formula (2).

[0219] The results are shown in FIG. 7. Table 6 summarizes the values.

TABLE-US-00007 TABLE 6 50 μm Glass type 1 with 50 μm Glass type 1 with 50 μm Glass type 1 with 20 μm HC 40 μm CPI 40 μm CPI and 10 μm HC (CS = 681 MPa, DoL = 10.4 μm) (CS = 681 MPa, DoL = 10.4 μm) (CS = 681 MPa, DoL = 10.4 μm) a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h D = 15 mm 1.24 3.62 1.17 4.97 1.07 1.79

6. Bendable Element Comprising Glass Layer Type 1 and Polymer Layer (Outwards)

[0220] Glass type 1 was drawn to a thickness of 70 μm by a slot down draw method. The sheets were cut to a size of 150 mm×100 mm. All the sheets were immersed into pure KNO.sub.3 for ion-exchanging. CS and DoL of the glass sheets were measured with FSM 6000.

[0221] Two laminates were prepared by using PET and CPI (manufactured by Kolon). The first laminate was the glass sheet laminated with 25 μm PSA and 50 μm PET. The PSA is Flexcon® classic plus 20092, which has an adhesive force around 4.0 N/cm. The first laminate was placed between the parallel Bakelite plates with the surface of PET bent outwards as described above.

[0222] The second laminate was the glass sheet laminated with 25 μm PSA and 50 μm CPI. The PSA was the same as that used for the first laminate. The second laminate was placed between parallel Bakelite plates with the surface of CPI bent outwards as described above.

[0223] For the deformation test, samples of the elements were prepared as follows: five cut and toughened elements were placed between two parallel Bakelite plates with a distance of 15 mm and held for 1 day at 25° C. with a humidity of 30%. Then, the elements were taken out and the deformation at the bending region was evaluated with a CCD camera. The deformation distance was recorded via time.

[0224] The initial deformation distance was recorded via CCD camera, and the deformation recovery time b.sub.1 and total persistent deformation a.sub.0 were calculated via formula (2).

[0225] It was found that the elements either laminated with PET or CPI had a very high initial deformation distance after releasing from the two parallel Bakelite immediately and then quickly dropped into a small value in 1 h. Therefore, the deformation distance after 1 h were used for simulation by formula (2).

[0226] The results are shown in FIG. 8. Table 7 summarizes the values.

TABLE-US-00008 TABLE 7 First laminate (CS = 735 MPa, Second laminate DoL = 13.7 μm) (CS = 735 MPa, DoL = 13.7 μm) a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h D = 15 mm 1.17 0.48 1.37 0.30

7. Bendable Element Comprising Glass Layer Type 1 and Polymer Layer (Inwards)

[0227] Glass type 1 was drawn to a thickness of 70 μm by a slot down draw method. The sheets were cut to a size of 150 mm×100 mm. All the sheets were immersed into pure KNO.sub.3 for ion-exchanging. CS and DoL of the glass sheets were measured with FSM 6000.

[0228] Two laminates were prepared by using PET and CPI. The first laminate was the glass sheet laminated with 25 μm PSA and 50 μm PET. The first laminate was placed between the parallel Bakelite plates with the surface of PET bent inwards as described above.

[0229] The second laminate was the glass sheet laminated with 25 μm PSA and 50 μm CPI. The second laminate was placed between parallel Bakelite plates with the surface of CPI bent inwards as described above.

[0230] For the deformation test, samples of elements were prepared as follows: five cut and toughened elements were placed between two parallel Bakelite plates with a distance of 15 mm and held for 1 day at 25° C. with a humidity of 30%. Then, the elements were taken out and the deformation at the bending part was evaluated with a CCD camera. The deformation distance was recorded via time.

[0231] The initial deformation distance was recorded via CCD camera, and the deformation recovery time b.sub.1 and total persistent deformation a.sub.0 were calculated via formula (2).

[0232] It was found that the elements either laminated with PET or CPI had a very high initial deformation distance after releasing from the two parallel Bakelite immediately and then quickly dropped into a small value in 1 h. Therefore, the deformation distance after 1 h were used for simulation by formula (2).

[0233] The results are shown in FIG. 9. Table 8 summarizes the values.

TABLE-US-00009 TABLE 8 First laminate Second laminate (CS = 735 MPa, (CS = 735 MPa, DoL = 13.7 μm) DoL = 13.7 μm) a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h D = 15 mm 0.95 1.73 2.67 3.48

8. Bendable Element Comprising Glass Layer Type 3 and Polymer Layers

[0234] Glass articles of glass type 3 cut to sheets of 150 mm×100 mm and slimmed down to a thickness of 33 μm. All the sheets were immersed into pure KNO.sub.3 for ion-exchanging. CS and DoL of the glass sheets were measured with FSM 6000.

[0235] A first set of elements was double-coated on both primary surfaces with 10 μm thick acrylic-based resin hard coatings (HC), which structure is referred to as “HC+glass+HC”. The coated elements were placed between parallel Bakelite plates and bent as described above.

[0236] A second set of elements was double-coated on both primary surfaces with 20 μm thick polyimide (PI) coatings, which structure is referred to as “PI+glass+PI”. The coated elements were placed between parallel Bakelite plates and bent as described above.

[0237] A third set of elements was double-coated on both primary surfaces with 20 μm thick polyamide (PI) coatings and then double-coated with 10 μm thick acrylic-based resin hard coatings (HC). The structure is referred to as “HC+PI+glass+PI+HC”. The coated elements were placed between parallel Bakelite plates and bent as described above.

[0238] For the deformation test, samples of elements were prepared as follows: five cut and toughened elements were placed between two parallel Bakelite plates with a distance of 4 mm and held at 85° C. with a humidity of 85% for 10 days. Then, the elements were taken out and the deformation at the bending region was evaluated with a CCD camera. The deformation distance was recorded via time. The initial deformation distance was recorded via CCD camera, and the deformation recovery time b.sub.1 and total persistent deformation a.sub.0 were calculated via formula (2).

[0239] The results are shown in FIG. 10. Table 9 summarizes the values.

TABLE-US-00010 TABLE 9 First set of elements Second set of elements Third set of elements (CS = 538 MPa, (CS = 538 MPa, (CS = 538 MPa, DoL = 6.1 μm) DoL = 6.1 μm) DoL = 6.1 μm) a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h a.sub.0/mm b.sub.1/h D = 4 mm 0.47 4.29 0.43 3.75 1.58 8.74

9. Bendable Element Comprising Glass Layer Type 1, OCA, and Polymer Layer Laminate (Outwards)

[0240] Glass type 1 was drawn to a thickness of 70 μm by a slot down draw method. The sheets were cut to a size of 150 mm×100 mm. All the sheets were immersed into pure KNO.sub.3 for ion-exchanging. CS and DoL of the glass sheets were measured with FSM 6000.

[0241] A laminate was prepared by using colorless PI (CPI). The first laminate was the glass sheet laminated with 25 μm PSA and 50 μm colorless PI with 10 μm hard coating. The PSA is Flexcon® classic plus 20092, which has an adhesive force around 4.0 N/cm. The first laminate was placed between the parallel Bakelite plates with the surface of CPI bent outwards as described above.

[0242] For the deformation test, samples of bendable elements were prepared as follows: five cut and toughened elements were placed between two parallel Bakelite plates with a distance of 10 mm and held for 1 day at 25° C. with a humidity of 30%. Then, the sheets were taken out and the deformation at the bending part was evaluated with a CCD camera. The deformation distance was recorded via time.

[0243] The initial deformation distance was recorded via CCD camera, and the deformation recovery time b.sub.1 and total persistent deformation a.sub.0 were calculated via formula (2).

[0244] The results are shown in FIG. 11. Table 10 summarizes the values.

TABLE-US-00011 TABLE 10 Laminate @ 25° C./30% (CS = 735 MPa, DoL = 13.7 μm) a.sub.0/mm b.sub.1/h D = 10 mm 2.26 0.33

[0245] While the present disclosure has been described with reference to one or more exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the present disclosure. In addition, many modifications can be made to adapt a particular situation or material to the teachings of the disclosure without departing from the scope thereof. Therefore, it is intended that the present disclosure is not limited to the particular embodiment(s) disclosed as the best mode contemplated, but that the disclosure will include all embodiments falling within the scope of the appended claims.