WO2008018737A1

WO2008018737A1 - Manufacturing method for flexible element using laser and flexible element

Info

Publication number: WO2008018737A1
Application number: PCT/KR2007/003792
Authority: WO
Inventors: Jong Lam Lee; Soo Young Kim
Original assignee: POSTECH Academy Industry Foundation; Pohang University of Science and Technology
Current assignee: POSTECH Academy Industry Foundation; Pohang University of Science and Technology
Priority date: 2006-08-07
Filing date: 2007-08-07
Publication date: 2008-02-14
Anticipated expiration: 2009-02-07
Also published as: KR20080013068A

Abstract

The present invention relates to a flexible element, and more particularly, to an organic light- emitting diode. A method of manufacturing the flexible element includes forming a patterned release layer on a glass substrate, forming an impurity barrier layer on the release layer, forming a transfer layer on the impurity barrier layer, attaching a plastic substrate to the transfer layer, and separating the glass substrate from the transfer layer by radiating laser onto the glass substrate to decompose the release layer. According to the present invention, it is possible to manufacture a flexible element by using all processes of an organic light-emitting diode that uses glass as a substrate. Therefore, it is possible to perform a process at high temperature, to prevent the deformation of a substrate that is caused by heat and chemicals during the manufacture of an element, and to easily align a substrate.

Description

MANUFACTURING METHOD FOR FLEXIBLE ELEMENT USING LASER AND FLEXIBLE ELEMENT

Technical Field

[1] The present invention relates to a manufacturing method for a flexible element and the flexible element. Background Art

[2] An organic light-emitting device has a laminated structure in order to obtain light- emitting efficiency as high as possible through electron-hole recombination.

[3] Glass is generally used as a material of a substrate. Indium Tin Oxide (ITO), which is transparent and has a large work function and excellent conductivity, is used as a material of an anode. Mg/ Ag or Al, which has a low work function, is used as a material of a cathode. When holes implanted from the anode and electrons implanted from the cathode are recombined with each other in an organic material layer that is a light-emitting layer, excitons are generated. While the excitons generated as described above are diffused, light corresponding to a band gap of the light-emitting layer is emitted to a transparent electrode.

[4] Since emitting light by itself, the organic light-emitting device has no problem with a viewing angle. For this reason, the organic light-emitting device can be used in small or large moving picture displays. Further, the organic light-emitting device has low power consumption, does not need a backlight, and can be manufactured at low temperature. Furthermore, since processes for manufacturing the organic light-emitting device are simple, it is possible to lower the price of the organic light-emitting device. Accordingly, it is advantageous to popularize the organic light-emitting device. In addition, since having possibility of being used as a flat panel display that is used to form a flexible display, the organic light-emitting device is in the limelight.

[5] Currently, a method using a thin glass plate, a method using a metal plate as a substrate, and a method of forming an organic light-emitting device on a flexible plastic substrate are being researched as a method of manufacturing a flexible organic light-emitting device.

[6] However, when a flexible organic light-emitting device is manufactured using a thin glass plate, there is a limitation on the bendability of a substrate due to the thin glass plate.

[7] Further, when a metal plate is used as a substrate to manufacture a flexible organic light-emitting device, the characteristics of an element deteriorate due to a substrate having rough surfaces and a conductive substrate causes cross-talk between elements. [8] When a plastic substrate is used to manufacture a flexible organic light-emitting device, an ITO anode is deposited on the plastic substrate, and a hole transport layer, a light-emitting layer, and a cathode are then sequentially laminated on the ITO anode as shown in FIG. 1. When a green organic light-emitting device is manufactured, 4'-bis [N-(l-naphtyl)-N-phenyl-amino] biphenyl (a-NPD) may be used as a material of the hole transport layer, tris( 8 -hydroxy quinoline) aluminum (AIq ) may be used as a material of the light-emitting layer, and Al may be used as a material of the cathode.

[9] Meanwhile, when the plastic substrate is used to manufacture a flexible organic light-emitting device, problems occur during a treatment using chemicals and the substrate is bent. For this reason, it is difficult to pattern or align the substrate and to produce flexible organic light-emitting devices in quantity. In particular, since the plastic substrate has low thermal stability, manufacturing processes should be performed at low temperature. Accordingly, it is difficult to decrease the resistance of the ITO, which is used as the anode of the organic light-emitting device, to 70 ohm/ square or less. As a result, an operating voltage of the organic light-emitting device is increased. Further, since processes cannot be performed at high temperature even during a sealing process or the manufacture of an electroluminescent device, the characteristics of the element deteriorate.

[10] Meanwhile, a conventional method of manufacturing a flexible substrate having dimensional stability has been disclosed in Korean Patent Publication No. 2004-100890. In the above-mentioned method, after a release layer made of amorphous silicon is formed on a glass substrate (first substrate) and an insulating layer made of silicon dioxide is formed on the release layer, a thin film circuit layer is formed on the insulating layer. Then, after a lyophilic treatment using plasma is performed on the thin film circuit layer and a water-soluble adhesive is applied on the thin film circuit layer, a provisional transfer substrate (second substrate) is attached to the thin film circuit layer. Subsequently, laser is radiated onto the glass substrate to allow ablation to occur in the release layer made of amorphous silicon, so that the glass substrate is separated. After that, a plastic substrate (third substrate) is attached to a portion, from which the glass substrate is separated, by using a permanent adhesive. Then, the provisional transfer substrate (second substrate) is separated in a washing process. Disclosure of Invention Technical Problem

[11] However, the above-mentioned method has a problem in that the thin film circuit layer may be damaged due to a large amount of gas generated from the release layer during the laser radiation. Further, since it is difficult to separate the amorphous silicon used as the material of the release layer, processes for attaching and detaching the provisional transfer substrate should be performed. For this reason, processes are complicated. As a result, productivity deteriorates and manufacturing cost is increased. In addition, the washing process is essential to perform the processes for attaching and detaching the provisional transfer substrate. Meanwhile, since an organic light-emitting device has a weak point against moisture, the above-mentioned process is not suitable for manufacturing an organic light-emitting device.

[12] It is difficult to manufacture a flexible element due to the problems of the conventional method of manufacturing a flexible element. Even if a flexible element can be manufactured, there is a limitation in that the characteristics of the flexible element deteriorate in comparison with those of an existing element. Technical Solution

[13] The present invention has been made to solve the above-mentioned problems, and it is an object of the present invention to provide a method of manufacturing a flexible element and a flexible element manufactured using the method. The method prevents the deformation of a substrate caused by heat and chemicals during the manufacture of an element, easily aligns a substrate, significantly reduces manufacturing cost due to the fact that existing apparatuses are used without change of the apparatuses, and easily separate a release layer, so that processes thereof are simple.

[14] According to an aspect of the present invention, a method of manufacturing a flexible element includes forming a patterned release layer on a hard substrate, forming an impurity barrier layer on the release layer, forming a transfer layer on the impurity barrier layer, attaching a plastic substrate to the transfer layer, and separating the hard substrate from the transfer layer, to which the plastic substrate is attached, by radiating laser onto the hard substrate to decompose and remove the release layer.

[15] In the method of manufacturing the flexible element according to the aspect of the present invention, the patterned release layer is used to provide paths through which gas generated from the release layer during laser radiation is discharged to the outside. Therefore, it is possible to prevent cracks from occurring in the element during the separation. Since the method allows the transfer layer attached to the plastic substrate to be easily separated from the hard substrate, it is possible to more easily manufacture a flexible element in comparison with a conventional method.

[16] Meanwhile, in the method according to the aspect of the present invention, the

"transfer layer" means a layer that excludes the plastic substrate and serves as the flexible element, and may be, for example, an organic light-emitting diode layer or an organic field-effect transistor layer.

[17] Further, in the method of manufacturing the flexible element according to the aspect of the present invention, the release layer may be preferably an oxide or a nitride that has a band gap smaller than energy corresponding to a wavelength of the laser. When the oxide or the nitride is decomposed into oxygen or nitrogen gas and a residue, a melting point of the residue may be preferably 15O⁰C or less.

[18] When laser is radiated onto the oxide or the nitride, the oxide or the nitride is thermally decomposed into metal and oxygen, or metal and nitrogen. In this case, the oxide or the nitride is separated from the substrate. For this reason, it is advantageous to use the oxide or the nitride as a material of the release layer. Further, if a melting point of the residue that is decomposed from the oxide or the nitride together with oxygen or nitrogen is higher than 15O⁰C, energy required to remove the release layer is increased, so that the plastic substrate attached to the transfer layer is deformed and cracks occur in the transfer layer due to heat. As a result, characteristics of the element may deteriorate.

[19] As long as a material satisfies the above-mentioned conditions, any material may be used as a material of the release layer. However, GaN, ITO, or GaO , of which residue decomposed from the oxide or the nitride together with oxygen or nitrogen has a low melting point, may be preferably used as a material of the release layer. Since a melting point of gallium (Ga) is very low (29.78⁰C), GaN or GaO among them is easily melted even though laser having low energy is radiated. Therefore, it is possible to easily separate the transfer layer, to which the plastic substrate is attached, from the hard substrate without the damage of the transfer layer or the plastic substrate.

[20] Accordingly, it is not necessary that a separate second provisional transfer substrate be used or an adhesive be removed in the washing process like the above-mentioned conventional method. For this reason, the method according to the aspect of the present invention is particularly suitable to form an element that has a weak point against moisture, such as an organic light-emitting diode, by using a flexible element.

[21] Further, it is preferable that the release layer be patterned to discharge gas generated during the decomposition of the release layer, and it is more preferable that the patterns have cell structures.

[22] Furthermore, it is preferable that each of the cell structures have a size of 1 cm x 1 cm or less. The reason for this is as follows: if each of the cell structures has a size of 1 cm x 1 cm or more, even though the release layer is patterned, it is not possible to sufficiently provide paths through which gas generated during the decomposition of the release layer is discharged to the outside. Accordingly, cracks may occur in the transfer layer.

[23] In addition, it is preferable that a distance between patterns of the patterned release layer be 1 D or more in order to discharge gas generated during the decomposition of the release layer. It is more preferable that the distance between the patterns of the patterned release layer be 30 D or more. Further, if the distance between the patterns is excessively large, the cathode may be affected during the laser radiation. Accordingly, it is preferable that the distance between the patterns be 60 D or less.

[24] The impurity barrier layer may be preferably made of an oxide, a nitride, or a mixture where an oxide and a nitride are alternately laminated. Specifically, it is preferable that the oxide be at least one selected from a group consisting of SiO, AlO, MgO, NiO, ZnO, TiO, CoO, BeO, RuO, IrO, and ZrO. It is preferable that the nitride be at least one selected from a group consisting of SiN, BN, and AlN.

[25] Further, a heat barrier layer, which is made of metal, such as Ag, Cu, Au, Al, W,

Rh, Ir, Mo, Ru, Zn, Co, Cd, Ni, Pd, or Pt, may be formed on the impurity barrier layer, under the impurity barrier layer, or in the impurity barrier layer in order to prevent thermal diffusion.

[26] Glass or quartz may be used as a material of the hard substrate.

[27] Meanwhile, gas laser, such as ArF laser, KrCl laser, KrF laser, XeCl laser, or XeF laser, which has energy larger than a band gap of a material of the release layer, may be preferably used as the laser. The energy of the laser may be preferably in the range that does not cause organic materials to be damaged and can cause laser separation. It is preferable that the wavelength of the laser be in the range of 200 to 400 nm.

[28] In addition, another aspect of the present invention provides a flexible element that is manufactured by the above-mentioned method of manufacturing the flexible element.

Advantageous Effects

[29] As described above, according to the present invention, a patterned release layer is formed on a glass substrate, a transfer layer is laminated on the release layer, a plastic substrate is attached, and the transfer layer is separated from the glass substrate at an interface therebetween by using laser, thereby manufacturing a flexible element. Accordingly, it is possible to obtain the following effects.

[30] First, existing apparatuses, which use glass as a material of the substrate, can be used without the change of the apparatuses. Therefore, it is possible to reduce manufacturing cost.

[31] Further, since the temperature of processes for manufacturing an element is not limited, it is possible to manufacture an element that has more excellent performance in comparison with a flexible element formed in a plastic substrate.

[32] Since a glass substrate is used, it is possible to prevent the deformation of the substrate that is caused by heat and chemicals during the manufacture of the element and to easily align the substrate.

[33] Since patterns are formed on the release layer, it is possible to prevent cracks, which are caused by gas generated during the decomposition of the release layer, from occurring in a transfer layer. [34] Since an oxide or a nitride of a material having a low melting point of 15O⁰C or less is used in the method of manufacturing the flexible element according to the aspect of the present invention, it is possible to very easily and simply separate the glass substrate and to prevent the damage of the transfer layer or the plastic substrate that is caused by heat.

Brief Description of the Drawings [35] FIG. 1 is a cross-sectional view of a conventional organic light-emitting device, which is manufactured using a plastic substrate. [36] FIG. 2 is a cross-sectional view illustrating a method of manufacturing an organic light-emitting device according to a first embodiment of the present invention. [37] FIG. 3 is a cross-sectional view illustrating a method of manufacturing an organic light-emitting device according to a second embodiment of the present invention. [38] FIG. 4 is a cross-sectional view illustrating a method of manufacturing an organic light-emitting device according to a comparative example. [39] FIG. 5A is a cross-sectional view illustrating a method of testing the separation caused by laser radiation. [40] FIG. 5B is a view showing a result of a measurement that is performed on a portion of a transfer layer separated from a glass substrate by using an energy depressive X-ray after laser radiation. [41] FIG. 5C is a view showing a result of a measurement that is performed on a glass substrate separated from a portion of a transfer layer by using an energy dispersive X- ray after laser radiation. [42] FIG. 6A is a photograph, which is taken by an optical microscope, of a transfer layer manufactured by the method according to the first embodiment of the present invention. [43] FIG. 6B is a photograph, which is taken by an optical microscope, of a transfer layer manufactured by the method according to the second embodiment of the present invention. [44] FIG. 6C is a photograph, which is taken by an optical microscope, of a transfer layer manufactured by the method according to the comparative example. [45] FIG. 7 is a cross-sectional view of an organic light-emitting device that is manufactured by the method of manufacturing the flexible element according to the present invention.

Best Mode for Carrying Out the Invention [46] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it should be understood that the following embodiments are not limitative, but illustrative in all aspects.

[47] [First Embodiment]

[48] As shown in FIG. 2, a patterned release layer capable of absorbing laser, an impurity barrier layer, and a transfer layer are sequentially deposited on a glass substrate. The transfer layer includes an anode, a hole transport layer, a light-emitting layer, and a cathode. Then, after a plastic substrate is attached to the transfer layer, laser is radiated onto the glass substrate to decompose a material of the release layer. As a result, the impurity barrier layer is separated from the glass substrate.

[49] The release layer is a layer for separating the glass substrate from the transfer layer.

A band gap of the release layer should be smaller than a band gap corresponding to a wavelength of laser to be used so that the release layer can absorb the laser. Since KrF laser having a wavelength of 248 nm is used in the first embodiment of the present invention, GaO having a band gap of 4.8 eV or ITO having a band gap of 3.7 eV is used as a material of the release layer.

[50] The impurity barrier layer prevents impurities such as moisture and oxygen, which are generated when the release layer is decomposed due to the laser radiation, from being implanted into an element, that is, the transfer layer. Silicon oxide is used as a material of the impurity barrier layer. In addition to silicon oxide, the material of the impurity barrier layer may include silicon nitride, and other oxides or nitrides.

[51] The transfer layer includes an anode, a hole transport layer, a light-emitting layer, and a cathode, which are sequentially disposed in this order. ITO is used as a material of the anode, and 4'-bis [N-(l-naphtyl)-N-phenyl-amino] biphenyl(a-NPD) is used as a material of the hole transport layer. Further, tris(8-hydroxyquinoline) aluminum (AIq ) is used as a material of the light-emitting layer, and Al is used as a material of the cathode.

[52] After the transfer layer is deposited, a plastic substrate is attached to the transfer layer. Then, laser is radiated onto the glass substrate to decompose the material of the release layer. As a result, the impurity barrier layer is separated from the glass substrate.

[53] Meanwhile, according to the first embodiment of the present invention, the release layer is patterned to have the shape of a cell so that the impurity barrier layer is easily separated from the glass substrate during the laser radiation. When laser is radiated onto the glass substrate, a GaO layer used as the release layer is decomposed and oxygen is generated. If the release layer is patterned to have the shape of a cell as described above, oxygen generated due to the decomposition of the GaO layer can pass through paths formed between cells. As a result, it is possible to prevent cracks, which are caused by gas generated during the decomposition of the release layer, from occurring in the transfer layer. [54] The patterned release layer has a size of 300 D x 300 D, and a distance between patterns is in the range of 30 to 60 D.

[55] [Second Embodiment]

[56] As shown in FIG. 3, according to a second embodiment, like the first embodiment, a patterned release layer, an impurity barrier layer, and a transfer layer are sequentially deposited on a glass substrate. The transfer layer includes an anode, a hole transport layer, a light-emitting layer, and a cathode. Then, after a plastic substrate is attached to the transfer layer, laser is radiated onto the glass substrate to decompose a material of the release layer. As a result, the impurity barrier layer is separated from the glass substrate.

[57] However, according to the second embodiment, a heat barrier layer is further formed in the impurity barrier layer. It is preferable that the heat barrier layer be made of metal having high thermal conductivity, such as Ag, Cu, Au, Al, W, Rh, Ir, Mo, Ru, Zn, Co, Cd, Ni, Pd, or Pt.

[58] The heat barrier layer allows heat generated during the laser radiation to be radiated to the outside, and prevents laser from affecting the transfer layer. The heat barrier layer may be formed on the impurity barrier layer or under the impurity barrier layer in addition to in the impurity barrier layer.

[59] [Comparative Example]

[60] As shown in FIG. 4, according to a comparative example, like the first embodiment of the present invention, a release layer capable of absorbing laser, an impurity barrier layer, and a transfer layer are sequentially deposited on a glass substrate. The transfer layer includes an anode, a hole transport layer, a light-emitting layer, and a cathode. T hen, after a plastic substrate is attached to the transfer layer, laser is radiated onto the glass substrate to decompose a material of the release layer. As a result, the impurity barrier layer is separated from the glass substrate. However, the comparative example is different from the first embodiment in that the release layer does not have patterns, and is formed on the entire surface of the glass substrate.

[61] [Separation Test]

[62] Next, when laser is radiated onto the release layer, whether the transfer layer is easily separated from the glass substrate is tested.

[63] FIG. 5A is a cross-sectional view illustrating a method of testing the separation caused by laser radiation. FIG. 5B is a view showing a result of a measurement that is performed on a portion of the transfer layer separated from the glass substrate by using an energy dispersive X-ray after laser radiation. FIG. 5C is a view showing a result of a measurement that is performed on the glass substrate separated from the portion of the transfer layer by using an energy dispersive X-ray after laser radiation.

[64] As shown in FIG. 5 A, a sample used in the test is obtained as follows: a GaO layer, which is used as a release layer and has a thickness of 0.5 D, is formed on the glass substrate. A Silicon oxide layer, which is used as an impurity barrier layer, is deposited on the release layer. Then, a plastic substrate is attached to the impurity barrier layer. [65] In the case of a patterned sample, patterns are formed of an optical resistor on a glass substrate at intervals of 300 to 1000 D, and a GaO layer is then deposited on the entire surface of the patterned sample to have a thickness of 0.5 D by using an electron- beam deposition device. If the thickness of the GaO layer is in the range of 0.2 to 5 D, laser can be radiated. However, it is preferable that the thickness of the GaO layer be as small as possible. The optical resistor is removed using acetone after the deposition. As a result, it is possible to obtain a release layer that includes GaO patterns separated from each other. A silicon oxide layer is deposited on the release layer.

[66] While He gas flows at a flow rate of 80 seem, SiH gas flows at a flow rate of 6 seem, N gas flows at a flow rate of 80 seem, and N O gas flows at a flow rate of 90 seem, a silicon oxide layer is deposited using an induced plasma-chemical beam deposition method at a temperature of 25O⁰C and a pressure of 800 mTorr. Deposition rate is 0.05 D/min. Subsequently, a plastic substrate is attached to the silicon oxide layer by using an epoxy resin. Then, KrF laser is radiated so that the transfer layer is separated from the glass substrate.

[67] As a result of the separation of the transfer layer, it is understood from Ga peaks shown in FIGS. 5B and 5C that a large amount of GaO remains at a lower portion of the transfer layer onto which laser is radiated and a little GaO remains on the surface of the glass substrate separated from the transfer layer due to the laser radiation. That is, it can be understood that the separation occur at an interface between the glass substrate and the GaO layer due to the decomposition of the release layer if laser is radiated onto the sample.

[68] FIG. 6A is a photograph, which is taken by an optical microscope, of a transfer layer according to the first embodiment of the present invention. FIG. 6B is a photograph, which is taken by an optical microscope, of a transfer layer according to the second embodiment of the present invention. FIG. 6C is a photograph, which is taken by an optical microscope, of a transfer layer according to the comparative example.

[69] It can be understood that the transfer layer is clearly separated from the glass substrate as shown in FIG. 6A if a patterned release layer is formed to have a size of 300 D x 300 D and laser is radiated onto the release layer like the first embodiment. The reason for this is that patterns are formed on the GaO release layer and serve as paths through which oxygen generated during the decomposition of the release layer passes.

[70] Further, like the second embodiment, if a heat barrier layer is formed in the release layer that is patterned to have a size of 1000 D x 1000 D and laser is then radiated like the second embodiment, the transfer layer is clearly separated from the glass substrate as shown in FIG. 6B. Furthermore, the heat barrier layer prevents the effect on the transfer layer that may be caused by the laser radiation, for example, the occurrence of cracks in the cathode.

[71] Meanwhile, it can be understood that cracks occur in the transfer layer as shown in

FIG. 6C if a release layer is not patterned on a glass substrate and formed on the entire of the glass substrate and laser is then radiated like the comparative example. The reason for this is presumed as follows: when the release layer is decomposed due to the laser radiation, gas is generated. Since the transfer layer does not have paths through which the gas passes, cracks occur due to the pressure of the gas.

[72] FIG. 7 is a cross-sectional view of an organic light-emitting device that is manufactured by the method of manufacturing a flexible element according to the present invention.

[73] According to the present invention, a release layer, an impurity barrier layer, and a transfer layer are sequentially laminated on a glass substrate. Then, a plastic substrate is attached to the transfer layer by using an epoxy resin. Subsequently, if laser is radiated onto the glass substrate, the release layer is decomposed and the transfer layer is separated from the glass substrate. After that, a plastic substrate is attached to a separation surface of the transfer layer by using an epoxy resin, so that a flexible element having a cross-section shown in FIG. 7 is obtained.

Claims

[I] A method of manufacturing a flexible element, the method comprising: forming a patterned release layer on a hard substrate; forming an impurity barrier layer on the release layer; forming a transfer layer on the impurity barrier layer; attaching a plastic substrate to the transfer layer; and separating the hard substrate from the transfer layer, to which the plastic substrate is attached, by radiating laser onto the hard substrate to decompose and remove the release layer.

[2] The method according to claim 1, wherein the release layer is made of an oxide or a nitride that has a band gap smaller than energy corresponding to a wavelength of the laser, and when the oxide or the nitride is decomposed into oxygen or nitrogen gas and a residue, a melting point of the residue is 15O⁰C or less.

[3] The method according to claim 1, wherein the release layer is made of at least one selected from a group consisting of GaN, ITO, and GaO .

[4] The method according to claim 1, wherein the release layer is made of GaO .

[5] The method according to any one of claims 1 to 4, wherein the patterns have cell structures. [6] The method according to claim 5, wherein each of the cell structures has a size of

1 cm x 1 cm or less. [7] The method according to any one of claims 1 to 4, wherein a distance between patterns of the patterned release layer is 1 D or more. [8] The method according to any one of claims 1 to 4, wherein the impurity barrier layer is made of an oxide, a nitride, or a mixture where an oxide and a nitride are alternately laminated. [9] The method according to claim 8, wherein the oxide is at least one selected from a group consisting of SiO, AlO, MgO, NiO, ZnO, TiO, CoO, BeO, RuO, IrO, and ZrO, and the nitride is at least one selected from a group consisting of SiN,

BN, and AlN. [10] The method according to any one of claims 1 to 4, further comprising: forming a heat barrier layer on the impurity barrier layer, under the impurity barrier layer, or in the impurity barrier layer.

[I I] The method according to claim 10, wherein the heat barrier layer is made of at least one selected from a group consisting of Ag, Cu, Au, Al, W, Rh, Ir, Mo, Ru, Zn, Co, Cd, Ni, Pd, and Pt.

[12] The method according to any one of claims 1 to 4, wherein the transfer layer is an organic light-emitting diode or an organic field effect transistor element. [13] The method according to any one of claims 1 to 4, wherein the hard substrate is a glass substrate.

[14] A flexible element manufactured by the method according to any one of claims 1 to 4.