Thin glass composite and method for storing a thin glass film

Abstract

The invention relates to a rolled up thin glass composite comprising a thin glass film and at least one further layer (10, 11, 20, 30) applied over the surface of one side of the thin glass film, wherein the at least one further layer (10, 11, 20, 30) is applied to a radially outer side of the rolled up thin glass film and the at least one further layer (10, 11, 20, 30) contains a desiccant which protects the thin glass film against stress corrosion cracking. The invention also relates to a method for storing a thin glass film by providing a thin glass film, applying at least one further layer (10, 11, 20, 30) over the surface of at least one side of the thin glass film, wherein a desiccant which protects the thin glass film against stress corrosion cracking is added to the at least one further layer (10, 11, 20, 30) and a thin glass composite composed of the thin glass film and the at least one further layer (10, 11, 20, 30) is rolled up in such a way that the at least one further layer (10, 11, 20, 30) is applied to a radially outer side of the rolled up thin glass film.

Claims

1. A rolled up thin glass composite comprising a thin glass film having a thickness of 15 to 200 m, and at least one further layer applied over the surface of one side of the thin glass film, wherein the at least one further layer is present on the radially outer side of the rolled up thin glass film, and the at least one further layer comprises a desiccant which is adapted to protect the thin glass film against stress corrosion cracking, which dessicant is selected from: salts, selected from the group consisting of: group cobalt chloride, calcium chloride, calcium bromide, lithium chloride, lithium bromide, magnesium chloride, barium perchlorate, magnesium perchlorate, zinc chloride, zinc bromide, aluminum sulfate, calcium sulfate, copper sulfate, barium sulfate, magnesium sulfate, lithium sulfate, sodium sulfate, cobalt sulfate, titanium sulfate, sodium dithionite, sodium carbonate, sodium sulfate, potassium disulfite, potassium carbonate, magnesium carbonate; phyllosilicates, selected from the group consisting of: montmorillonite and bentonite; metal oxides, selected from the group consisting of: barium oxide, calcium oxide, iron oxide, magnesium oxide, sodium oxide, potassium oxide, strontium oxide, aluminum oxide (activated alumina), and titanium dioxide; carbon nanotubes; activated carbon; phosphorus pentoxide; oxidizable metals selected from iron, calcium, sodium, and magnesium; metal hydrides, selected from the group consisting of: calcium hydride, barium hydride, strontium hydride, sodium hydride, and lithium aluminum hydride; hydroxides, selected from the group consisting of: potassium hydroxide and sodium hydroxide; metal complexes, selected from the group consisting of: aluminum acetylacetonate: silicas, selected from the group consisting of: silica gel, kieselguhr; zeolites; anhydrides of single and multiple carboxylic acids, selected from the group consisting of: acetic anhydride, propionic anhydride, butyric anhydride or methyltetrahydrophthalic anhydride; hybrid polymers used combination with catalysts; carbodiimides; organic absorbers selected from the group consisting of: weakly crosslinked polyacrylic acid, polyvinyl alcohol, ascorbates, glucose, gallic acid, and unsaturated fats and oils; and, mixtures of two or more of the above substances.

2. The rolled up thin glass composite according to claim 1, wherein the at least one further layer comprises a layer of adhesive and/or a carrier material layer.

3. The rolled up thin glass composite according to claim 2, which comprises the thin glass film, a carrier material layer, and an adhesive layer between the thin glass film and the carrier material layer.

4. The rolled up thin glass composite according to claim 1; wherein, over the entire extent of the thin glass film, an adhesive layer is present over the full area directly to the thin glass film, and a carrier material layer is present over the full area directly to the adhesive layer.

5. The rolled up thin glass composite according to claim 1, wherein the at least one further layer comprises an autoadhesive.

6. The rolled up thin glass composite according to claim 1, wherein a layer of adhesive present upon the thin glass film is a reversible layer of pressure-sensitive adhesive.

7. The rolled up thin glass composite according to claim 1, wherein the at least one further layer is a layer of adhesive comprising a repair material adapted for the repair of glass microcracks.

8. The rolled up thin glass composite according to claim 7, wherein the repair material comprises a hydrophobic silane.

9. The rolled up thin glass composite according to claim 1, wherein the at least one further layer comprises a barrier layer.

10. The rolled up thin glass composite according to claim 9, wherein there is present a metal layer or an organic coating or a sol-gel coating as a barrier layer between the thin glass film and the layer of adhesive or as a barrier layer between the carrier material layer and the layer of adhesive.

11. The rolled up thin glass composite according to claim 1, wherein the thin glass film has a thickness of 20-100 m.

12. The rolled up thin glass composite according to claim 11, wherein the thin glass film has a thickness of 25 to 75 m.

13. The rolled up thin glass composite according to claim 1, wherein the dessicant is selected from group consisting of: cobalt chloride, calcium chloride, calcium bromide, lithium chloride, lithium bromide, magnesium chloride, barium perchlorate, magnesium perchlorate, zinc chloride, zinc bromide, aluminum sulfate, calcium sulfate, copper sulfate, barium sulfate, magnesium sulfate, lithium sulfate, sodium sulfate, cobalt sulfate, titanium sulfate, sodium carbonate, sodium sulfate, potassium carbonate, zeolites, calcium, magnesium, barium oxide, calcium oxide, magnesium oxide, sodium oxide, potassium oxide, strontium oxide, activated carbon, phosphorus pentoxide, calcium hydride, barium hydride, strontium hydride, sodium hydride, and lithium aluminum hydride, potassium hydroxide, sodium hydroxide, acetic anhydride, propionic anhydride, butyric anhydride, methyltetrahydrophthalic anhydride, and carbodiimides, and also mixtures of two or more of the above substances.

14. The rolled up thin glass composite according to claim 1, wherein the dessicant is selected from group consisting of: barium, calcium, calcium sulfate, calcium chloride, calcium oxide, sodium sulfate, potassium carbonate, copper sulfate, magnesium perchlorate, magnesium sulfate, lithium chloride, and zeolites, and also mixtures of two or more of the above substances.

15. The rolled up thin glass composite according to claim 1, wherein the dessicant is selected from group consisting of: calcium oxide, calcium sulfate, calcium chloride, fumed silicas, and zeolites, and also mixtures of two or more of the above substances.

16. The rolled up thin glass composite according to claim 1, wherein the dessicant is selected from group consisting of: calcium oxide, calcium, barium, lithium chloride, and cobalt chloride.

Description

(1) The invention is described using exemplary embodiments in five figures. In the figures:

(2) FIG. 1 shows a sectional view of a schematic construction of an inventive adhesive tape for a thin glass composite,

(3) FIG. 2 shows a schematic view of a second embodiment of an inventive adhesive tape for a thin glass composite,

(4) FIG. 3a shows a representative drawing of the bent thin glass composite in a two-point bending test,

(5) FIG. 3b shows a schematic view of the strain gauges arranged on the thin glass composite,

(6) FIG. 3c shows a schematic side view of the bent thin glass.

(7) Described first of all is the production of different layers of adhesive, which are then investigated for their water vapor permeation rate and peel adhesion to float glass.

(8) For the production of layers of adhesive, different adhesives were applied from a solvent to a Silphan S75 M371 liner from Siliconature by means of a laboratory coater, and then dried.

(9) Reported in table 4 in each case is the thickness of the layer of adhesive after drying. It is 50 m.

(10) Drying took place in each case at 120 C. for 30 minutes in a laboratory dryer.

(11) TABLE-US-00001 K1: Pressure-sensitive adhesive 100 parts Tuftec P 1500 SBBS, a partly hydrogenated styrene-butadiene-styrene block copolymer (SBS), with 30 wt % block polystyrene content, from Asahi. The SBBS contains about 68 wt % diblock content. 100 parts Escorez 5600 Hydrogenated HC resin having a softening point of 100 C., from Exxon 25 parts Ondina 917 White oil comprising paraffinic and naphthenic fractions, from Shell The solvent used was a mixture of toluene and acetone in a ratio of 2:1.

(12) TABLE-US-00002 K2: Reversible pressure-sensitive adhesive 90 parts Butyl 100 Butyl rubber from Bayer, isoprene content 0.9 mol % 10 parts Hyvis 200 Polybutene from BP Chemical The solvent used was special-boiling-point spirit.

(13) TABLE-US-00003 K3: Reversible pressure-sensitive adhesive 80 parts Butyl 100 Butyl rubber from Lanxess, isoprene content 0.9 mol % 10 parts Oppanol B 150 Polyisobutylene (PIB) from BASF, Mn = 425 000 g/mol 10 parts Regalite R 1100 Hydrogenated hydrocarbon resin from Eastman with a softening point of 100 C. The solvent used was special-boiling-point spirit.

(14) TABLE-US-00004 K4: Reversible pressure-sensitive adhesive 100 parts Levapren 700 Polyethylene-vinyl acetate, manufacturer Bayer, vinyl acetate fraction 70 wt % 30 parts Levapren 800 Polyethylene-vinyl acetate, manufacturer Bayer, vinyl acetate fraction 80 wt % 25 parts Levapren 450 Polyethylene-vinyl acetate, manufacturer Bayer, vinyl acetate fraction 45 wt % The solvent used was methyl ethyl ketone.

(15) TABLE-US-00005 K5: Radiation-activatedly reversible pressure-sensitive adhesive 59 parts Acrylate copolymer consisting of 56 wt % butyl acrylate, 40 wt % methyl acrylate, 2 wt % acrylic acid, and 2 wt % benzoin acrylate, prepared in radical polymerization by the method disclosed in DE 195 20 238 02 (example 1) 0.4 part Aluminum acetylacetonate 28 parts Ebecryl 220 Hexafunctional, aromatic urethane-acrylate oligomer from Cytec 12 parts PETIA Pentaerythritoltri-tetraacrylates from Cytec with a tri-tetra ratio of about 1:1

(16) TABLE-US-00006 K6: Reversible pressure-sensitive adhesive 85 parts Oppanol B 150 PIB from BASF, Mn = 425 000 g/mol 15 parts Oppanol B 50 PIB from BASF, Mn = 120 000 g/mol The solvent used was special-boiling-point spirit.

(17) The water vapor permeation rate (WVTR) of the layers of pressure-sensitive adhesive was measured at 38 C. and 90% relative humidity in accordance with ASTM F-1249. ASTM F-1249 is a standard test method for determining the water vapor permeation rate (ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohokecken, Pa. 19428-2959, USA according to the presently valid version of 22 Jun. 2006). The WVTR value reported in table 1 is an average value from two measurements in each case. The value reported is standardized for a layer thickness of 50 m.

(18) The peel adhesion was determined on float glass in analogy to ISO 29862 (method 3) at 23 C. and 50% relative humidity, with a peel rate of 300 mm/min and a peel angle of 180. The reinforcing film used, to which the respective layer of adhesive was applied, was the polyester film F1 indicated further below. The polyester film was first laminated to the dried adhesive strips. The bonding of the measurement strip, this being the film with the layer of adhesive agent, was performed using a roll-on machine at a temperature of 23 C. The adhesive tapes were peeled under the conditions stated above after 24 hours of storage. The value reported is the average value from three measurements.

(19) TABLE-US-00007 TABLE 1 WVTR Peel adhesion/glass Identification [g/m.sup.2 d] [N/cm] K1 (not reversible) 68 6.9 K2 44 1.5 K3 18 2.0 K4 155 1.2 K5 569 1.7 before/0.2 after UV K6 6 0.9

(20) On determination of the peel adhesion, the desiccants were not yet present in the layer of adhesive.

(21) First of all it is clearly apparent that adhesive K1 is a nonreversible pressure-sensitive adhesive, while adhesives K2 to K6 are reversible pressure-sensitive adhesives. Reversible pressure-sensitive adhesives can easily be peeled by hand, since they have a peel adhesion of less than 3 N/cm, preferably of less than 2.2 N/cm.

(22) For the production of the layers of adhesive of the invention comprising desiccants, the solutions of the pressure-sensitive adhesives are admixed with a desiccant. These desiccants are incorporated into the solutions of adhesive by means of a high-speed dispersing disk of a laboratory stirring apparatus. The solutions of adhesive are dried beforehand using zeolite beads with a size of approximately 1 mm, which are filtered out again prior to coating.

(23) Drying materials used were as follows:

(24) TABLE-US-00008 TABLE 2 Identification Description Trade name Supplier G1 Calcium oxide Calcium oxide Sigma-Aldrich nanopower G2 Zeolite 3A Purmol 3 STH Zeochem

(25) As carrier material layer 30 for the adhesive tapes, two films were used, a polyester film F1 and also a polyester film with inorganic barrier layer F2, which are set out below:

(26) TABLE-US-00009 TABLE 3 Thick- Identi- ness WVTR fication Description Trade name Supplier [m] [g/m.sup.2 d] F1 Polyester film Melinex 723 Dupon- 36 64 Teijin-Films F2 Polyester film GX-P-F Toppan 30 0.13 with inorganic Printing barrier layer

(27) The adhesive tapes were produced in different ways depending on the carrier material.

(28) For the production of a construction according to FIG. 2, using carrier material F1, the solutions are coated directly onto the carrier material 30 and dried to eliminate solvent. The dried layers 11 of desiccant-comprising adhesive were furnished temporarily with a liner after drying in each case.

(29) For the production of a construction according to FIG. 2, using carrier material F2, the solutions are coated onto the above-stated liner and dried to eliminate solvent. The dried layers 11 of desiccant-comprising adhesive were laminated immediately after drying in each case at further elevated temperature (about 60 C.) to the carrier material 2, using a laboratory roll laminator.

(30) In the embodiment according to FIG. 1, the construction according to FIG. 2 has its liner removed, and an outer layer 10 of adhesive, which lies directly on the glass film, is laminated onto the now exposed side of the desiccant-comprising layer 20, using a laboratory roll laminator. The layer 10 of adhesive contains no drying material and was produced as described above by means of coating on the stated liner.

(31) Table 4 shows, in an overview, adhesive tapes produced according to the second embodiment in FIG. 2, and also according to the first embodiment as per FIG. 1. According to the second embodiment, the adhesive tapes T1 to T8 and T10 to T16 are produced. The adhesives K1, K4, and K5 here have a WVTR of more than 50 g/m.sup.2d (per square meter per day).

(32) Only adhesive tape T9 was produced according to FIG. 1, with the desiccant being dispersed in adhesive K1 and used as layer comprising drying material 20 in a thickness of 40 m. The reversible adhesive K4 was used as layer 10 of adhesive.

(33) As a comparative example (C1), an adhesive tape was produced in which the adhesive contains no drying material at all; the adhesive has a water vapor permeation rate of more than 50 g/m.sup.2d, and the carrier material layer 30 has a water vapor permeation rate of more than 10 g/m.sup.2d. (C1).

(34) Further adhesive tapes without drying material were also produced (C2, C3, C4), their adhesive having a water vapor permeation rate, when adhesive K1 was used, of more than 50 g/m.sup.2d, or less than 50 g/m.sup.2d, namely when adhesive K6 was used. The carrier material layer 30 either has a water vapor permeation rate of more than 10 g/m.sup.2d, when carrier film F1 is used, or of less than 10 g/m.sup.2d, when carrier film F2 is used.

(35) TABLE-US-00010 TABLE 4 Thickness of Fraction layer of Getter of getter adhesive Identification Adhesive material [wt %] [m] Carrier T1 K2 G1 5 50 F2 T2 K3 G1 5 50 F1 T3 K3 G1 5 50 F2 T4 K4 G1 5 50 F2 T5 K5 G1 5 50 F2 T6 K2 G2 10 50 F2 T7 K3 G2 10 50 F1 T8 K3 G2 10 50 F2 T9 K4 G2 10 50 F2 T10 K5 G2 10 50 F2 T11 K1/K4 G2 in K1 10 K1: 40; K2: 10 F2 T12 K1 G2 10 50 F2 T13 K6 G2 10 50 F1 T14 K6 G2 10 50 F2 T15* K6 G2 10 50 F2 T16 K5 G2 10 50 F2 C3 K6 0 50 F1 C4 K6 0 50 F2 C2 K1 0 50 F2 C1 K1 0 50 F1 *Adhesive K6 in example T15 contained additionally 5% of tetraethoxysilane, which was added to the solution after the addition of the desiccant.

(36) Before being laminated to the thin glass, the adhesive tapes of the invention are stored temporarily in a permeation-proof packaging, by being welded into a composite aluminum foil. The specimens for determining the water content were taken after 14 days of storage.

(37) Table 5 shows the determination of the water content after 14 days of storage (fourth column from right). The water content is determined by means of DIN 53715 (Karl Fischer titration). The measurement takes place in a Karl Fischer Coulometer 851 in conjunction with an oven sampler (oven temperature 140 C.). With an initial mass of approximately 0.3 g, a triple determination was carried out in each case. The water content reported is the arithmetic mean of the measurement.

(38) The thin glass used was D263 T glass from Schott, Mainz, with a thickness of 70 m and a length of 100 mm, and the width likewise of 100 mm. A thin glass of this type was laminated over virtually the full area with the respective adhesive tape at room temperature, using a laboratory roll laminator, with just a strip approximately 9 mm wide being left free at the edges transversely to the flexural axis. In order to rule out edge effects, a stabilizing strip of adhesive tape tesa 50575 (80 m aluminum foil with pressure-sensitive acrylate adhesive) approximately 10 mm wide was bonded along both edges of the thin glass film, transversely to the flexural axis, thus protruding approximately 1 mm beyond the glass edge. In the course of the flexural test, these aluminum strips come to lie on the outside of the radius of flexure, and ensure that the glass edge is held under compressive stress, thereby significantly reducing the risk of cracks originating from the edge.

(39) Subsequently, a minimum radius of flexure R without storage was ascertained (second column from right in table 5).

(40) Assemblies of thin glass and adhesive tape, produced equivalently, were further stored over 28 days at 60 C. in 90% relative humidity with a radius of flexure of 100 mm, with the side of the glass protected by the adhesive tape lying on the outside of the radius and hence being exposed substantially to a tensile stress. This was followed by determination of the minimum radius of flexure after storage (far right column in table 5).

(41) Table 5 shows the comparison of the radii of flexure before and after storage in the two right-hand columns. Additionally, an assessment was made of the reversibility of the adhesives, subjectively, on detachment of the adhesive tape from the thin glass. For this purpose, the assembly with its glass side was adhered, using a strongly adhering adhesive tape Tesa 4972, to a steel plate, and the protective film was peeled off using the adhered grip tab, starting from one corner. Specimens with the adhesive K5 were crosslinked beforehand with a UV-C dose of 80 mJ/cm.sup.3 in the 250 to 260 nm band, using a UV-Cube from Hoenle, to produce the reversibility. Table 5 shows the results:

(42) TABLE-US-00011 TABLE 5 Reversibility ++ very easily detachable + easily Water detachable Radius of Radius of content of o detachable flexure flexure adhesive with some force without after Adhesive tape detachable storage storage tape [ppm] with high force [mm] [mm] T1 68 + 31 33 T2 14 + 29 38 T3 10 + 32 31 T4 7 + 29 33 T5 19 ++ 28 32 T6 18 + 31 31 T7 8 + 33 39 T8 6 + 33 31 T9 13 + 32 31 T10 16 ++ 29 32 T11 10 + 34 33 T12 8 29 34 T13 18 ++ 30 38 T14 17 ++ 30 29 T15 29 + 32 29 T16 21 ++ 34 35 C3 1588 ++ 31 39 C4 1521 ++ 33 36 C2 1966 34 37 C1 2004 29 41

(43) The results show that thin glass can be effectively protected by the method of the invention. In particular, the embodiments with the film F2 are suitable for the adhesive tape, since this film considerably reduces the inward diffusion of moisture into the assembly.

(44) The use of permeation-inhibiting adhesives K2, K3, and K6 likewise brings advantages relative to more permeable adhesives. Adhesive tapes without drying material, with a carrier material layer 30 comprising the film F2 (C2, C4), also still show a protective effect, although when using the film F1 (C1, C3) as carrier material layer 30, this effect subsides significantly, since under the harsh test conditions, the moisture is able very easily to diffuse into the assembly.

(45) The use of the silane as crack repair agent shows a clear effect, since there is a more significant decrease in the maximum radius of flexure than could be assigned to the random scatterings alone.

(46) The minimum radius of flexure is determined using the two-point bending test. The test method is based on the published Corning method of S. T. Gulati and patent WO 2011/084323 A1 (Gulati et al., ID Symposium Digest of Technical Papers Vol 42, Issue 1, pages 652 to 654, June 2011).

(47) The flexibility of the glass/protective film laminate can be characterized by the two-point bending test. In this test, the minimum radius of flexure is measured and calculated in millimeters shortly before or exactly at the moment of fracture. The laminate lies with its protective film side upward, and is fixed on one side. The other side is displaced at a rate of 10 mm/min in the direction of the fixed end. The resulting radius of flexure is measured or calculated from the displacement. The test setup for the two-point bending test is shown in FIG. 3a. A dotted line 31 represents the position and the length of the thin glass composite prior to flexure. The solid line shows the position of the thin glass composite on minimum flexure at the moment of the first crack occurring transverse to the direction of movement.

(48) L is the length of the thin glass composite 31, s the distance traveled by one end of the thin glass composite during the flexing process up to the point of fracture. The thickness of the laminate is given in abbreviated form as d. is the contact angle, which is needed in order to calculate the flexural stress. As the contact angle goes down, in other words as the radius R reduces, there is an increase in the stress on the glass.

(49) The radius R is measured during the test or calculated by the formula below. The flexural elongation , which is necessary in order to calculate the radius R of flexure, is determined by means of a strain gauge or calculated.

(50) FIG. 3b shows the arrangement of the strain gauge in the center of the thin glass composite.

(51) The radius R of flexure is calculated from the measured flexural elongation as follows:

(52) $\frac{R}{R+\frac{d}{2}}=\frac{L}{L+L}$$\frac{R}{R+\frac{d}{2}}=\frac{1}{1+\frac{L}{L}}=\frac{1}{1+\mathrm{.Math.}}$$R+R\mathrm{.Math.}=R+\frac{d}{2}$$R=\frac{d}{2\mathrm{.Math.}}$ with the flexural elongation =L/L, L: original length and length of the middle phase of the thin glass composite with radius R, and L corresponds to the change in length of the outer phase of the thin glass composite with radius

(53) $R+\frac{d}{2}$
in FIG. 3c.

(54) The minimum radius R of flexure reported in table 5 is the median value from fifteen measurements.

(55) Measurement Methods

(56) Molecular Weight:

(57) The molecular weight determinations of the number-average molecular weights M.sub.n and the weight-average molecular weights M.sub.w (or the other molecular weights) took place by means of gel permeation chromatography (GPC). The eluent used was THF (tetrahydrofuran) with 0.1 vol % of trifluoroacetic acid. The measurement was made at 25 C. The pre-column used was PSS-SDV, 5, 10.sup.3 , ID 8.0 mm50 mm. Separation took place using the columns PSS-SDV, 5, 10.sup.3 and also 10.sup.5 and 10.sup.6 each with ID 8.0 mm300 mm. The sample concentration was 4 g/l, the flow rate 1.0 ml per minute. Measurement was made against polystyrene standards.

(58) Tackifier Resin Softening Temperature:

(59) The tackifier resin softening temperature is carried out according to the relevant methodology, which is known as ring and ball and is standardized according to ASTM E28.

(60) The tackifier resin softening temperature of the resins is determined using an automatic ring and ball device HRB 754 from Herzog. Resin specimens are first of all finely mortared. The resulting powder is placed into a brass cylinder with an opening of the base (internal diameter at the top part of the cylinder 20 mm, diameter of the base opening in the cylinder 16 mm, height of the cylinder 6 mm) and melted on a hot plate. The amount introduced is selected such that the resin after melting fully fills the cylinder without protruding. The resulting specimen, including the cylinder, is inserted into the sample mount of the HRB 754. Glycerol is used to fill the conditioning bath, provided the tackifier resin softening temperature is between 50 C. and 150 C. For lower tackifier resin softening temperatures, it is also possible to operate using a water bath. The test balls have a diameter of 9.5 mm and weigh 3.5 g. In accordance with the HRB 754 procedure, the ball is arranged above the specimen in the conditioning bath, and is laid down on the specimen. At a distance of 25 mm beneath the base of the cylinder there is a catch plate, with a light barrier 2 mm above it. During the measuring operation, the temperature is increased at 5 C./min. In the temperature range of the tackifier resin softening temperature, the ball begins to move through the base opening in the cylinder, before finally coming to rest on the catch plate. In this position it is detected by the light barrier, and at this instant the temperature of the conditioning bath is recorded. A duplicate determination is made. The tackifier resin softening temperature is the average value from the two individual measurements.

LIST OF REFERENCE SYMBOLS

(61) 10 Outer layer of adhesive

(62) 11 Desiccant-comprising layer of adhesive

(63) 20 Desiccant-comprising layer of adhesive

(64) 30 Carrier material layer

(65) 31 Thin glass composite prior to flexure

(66) d Thickness of thin glass composite

(67) s Displacement of thin glass composite

(68) L Length of thin glass composite

(69) R Radius/radius of flexure

(70) Contact angle

(71) Flexural stress

(72) Flexural elongation