TECHNICAL FIELD [0001] Embodiments of the present disclosure relate to layer systems adapted for use in electro-optical devices and methods for manufacturing such layer systems in a continuous roll-to-roll process. In particular, embodiments of the present disclosure relate to layer systems including a stack of layers deposited on a flexible substrate. More specifically, embodiments of the present disclosure relate to layer systems which are manufactured by a continuous roll-to-roll vacuum deposition process.

BACKGROUND

[0002] Processing of flexible substrates, such as plastic films or foils, is in high demand in the packaging industry, semiconductor industries and other industries. Processing may consist of coating a flexible substrate with a desired material, such as a metal, in particular aluminum, semiconductors and dielectric materials, etching and other processing actions conducted on a substrate for the desired applications. Systems performing this task typically include a process drum, e.g., a cylindrical roller, coupled to a processing system for transporting the substrate, and on which at least a portion of the substrate is processed. Accordingly, roll-to-roll (R2R) coating systems can provide a high throughput system.

[0003] Typically, a process, e.g. a physical vapor deposition (PVD) process, a chemical vapor deposition (CVD) process, and a plasma enhanced chemical vapor deposition (PECVD) process, can be utilized for depositing thin layers of metals which can be coated onto flexible substrates. In particular, roll-to-roll deposition systems are experiencing a large increase in demand in the display industry and the photovoltaic (PV) industry.

[0004] Examples of products made of a coated flexible substrate are touch panels or organic light emitting diode (OLED) displays, which have received significant interest recently in display applications in view of their faster response times, larger viewing angles, higher contrast, lighter weight, lower power, and amenability to flexible substrates, as compared to liquid crystal displays (LCD). [0005] Therefore, over the years, electro-optical devices, e.g. display devices or touch panels, have evolved into multiple layer systems in which different layers have different functions. However, the quality of conventional multilayer systems still need to be improved, for instance with respect to structural stability and product durability. [0006] In light of the foregoing, there is a need to provide layer systems adapted for use in electro-optical devices and methods for manufacturing such layer systems that overcome at least some of the problems in the art.

SUMMARY

[0007] In light of the above, a layer system and a method for manufacturing a layer system according to the independent claims are provided. Further aspects, benefits, and features of the present disclosure are apparent from the claims, the description, and the accompanying drawings.

[0008] According to an aspect of the present disclosure, a layer system adapted for use in an electro-optical device is provided. The layer system includes a flexible substrate, a planarization layer provided on the flexible substrate, and a transparent conductive oxide layer provided on the planarization layer. The planarization layer is configured to encapsulate defects on the flexible substrate. Further, the planarization layer is configured to covalently bind to the surface of the flexible substrate.

[0009] According to another aspect of the present disclosure, a layer system adapted for use in an electro-optical device is provided. The layer system includes a flexible substrate, a planarization layer provided on the flexible substrate, and a transparent conductive oxide layer provided on the planarization layer. The planarization layer is configured to encapsulate defects on the flexible substrate. Further, the planarization layer is configured to covalently bind to the surface of the flexible substrate and to promote adhesion of the transparent conductive oxide layer to the planarization layer. In particular, the planarization layer has a thickness T _PL of 100 nm < Tp _L < 800 nm and consists of silicon oxycarbide SiO _x C _y . Further, the transparent conductive oxide layer has a thickness T _TC0 of 5 nm < T _TC0 ≤ 10 nm and consists of silicon oxide SiO _x or niobium oxide NbO _x .

[0010] According to a further aspect of the present disclosure, an electro- optical device having a layer system according to any embodiments described herein is provided.

[001 1] According to yet another aspect of the present disclosure, a method for manufacturing a layer system in a continuous roll-to-roll process is provided. The method includes providing a flexible substrate to at least one first processing zone and at least one second processing zone without breaking vacuum. Further, the method includes depositing a planarization layer on the flexible substrate in the at least one first processing zone such that defects on the flexible substrate are encapsulated by the planarization layer. Additionally, the method includes depositing a transparent conductive oxide layer on the planarization layer in the at least one second processing zone. In particular, depositing the planarization layer includes forming covalent bonds between the flexible substrate and the planarization layer. [0012] Embodiments are also directed at apparatuses for carrying out the disclosed methods and include apparatus parts for performing each described method aspect. These method aspects may be performed by way of hardware components, a computer programmed by appropriate software, by any combination of the two or in any other manner. Furthermore, embodiments according to the disclosure are also directed at methods for operating the described apparatus. The methods for operating the described apparatus include method aspects for carrying out every function of the apparatus. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] So that the manner in which the above recited features of the present disclosure can be understood in detail, a more particular description of the disclosure, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to embodiments of the disclosure and are described in the following:

FIG. 1 shows a schematic view of a layer system according to embodiments described herein;

FIGS. 2 and 3 show detailed views of a portion of a layer system according to embodiments described herein illustrating the function of the planarization layer;

FIGS. 4 A to 4C show schematic views of a layer system according to yet further embodiments described herein;

FIG. 5 shows a schematic view of a processing system for manufacturing a layer system according to embodiments described herein; FIG. 6 shows a schematic view of an electro-optical device having a layer system according to embodiments described herein; and

FIG. 7 shows a flow chart illustrating a method for manufacturing a layer system in a continuous roll-to-roll process according to embodiments described herein.

DETAILED DESCRIPTION OF EMBODIMENTS

[0014] Reference will now be made in detail to the various embodiments, one or more examples of which are illustrated in each figure. Each example is provided by way of explanation and is not meant as a limitation. For example, features illustrated or described as part of one embodiment can be used on or in conjunction with any other embodiment to yield yet a further embodiment. It is intended that the present disclosure includes such modifications and variations. [0015] Within the following description of the drawings, the same reference numbers refer to the same or to similar components. Generally, only the differences with respect to the individual embodiments are described. Unless specified otherwise, the description of a part or aspect in one embodiment can apply to a corresponding part or aspect in another embodiment as well.

[0016] Before various embodiments of the present disclosure are described in more detail, some aspects with respect to some terms and expressions used herein are explained.

[0017] In the present disclosure, a "layer system" is to be understood as a stack of layers. In particular, a layer system as described herein can be understood as a stack of layers having at least two layers of different material composition. In particular, a layer system as described herein can be transparent. The term "transparent" as used herein can particularly include the capability of a structure to transmit light with relatively low scattering, so that, for example, light transmitted therethrough can be seen in a substantially clear manner.

[0018] In the present disclosure, a "flexible substrate" may be characterized in that the substrate is bendable. For example, the flexible substrate may be a foil. In particular, it is to be understood that a flexible substrate as described herein can be processed in a continuous roll-to-roll process as described herein, for instance in a roll-to-roll processing system as described herein. In particular, the flexible substrate as described herein is suitable for manufacturing coatings or electronic devices on the flexible substrate. In particular, a flexible substrate as described herein can be transparent, e.g. the flexible substrate may be made of a transparent polymer material. More specifically, a flexible substrate as described herein may include materials like polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), polyimide (PI), polyurethane (PU), poly(methacrylic acid methyl ester), triacetyl cellulose, cellulose triacetate (TaC), cyclo olefin polymer, poly(ethylene naphthalate), one or more metals, paper, combinations thereof, and already coated substrates like Hard Coated PET (HC-PET) or Hard Coated TAC (HC-TAC) and the like. [0019] In the present disclosure, a "planarization layer" is to be understood as a layer which is configured to encapsulate defects and fill scratches of the substrate or layer onto which the planarization layer is deposited. Accordingly, a planarization layer is to be understood as a layer configured for providing a significantly smoothened surface for a subsequent processing action, particularly a subsequent layer deposition on the planarization layer. In particular, a planarization layer as described herein can be transparent. Further, the planarization layer can be configured to improve adhesion to the substrate or layer onto which the planarization layer is deposited. For instance, the planarization layer can be configured to chemically bind, e.g. by covalent bonds, to the surface of the substrate or to the surface of the layer onto which the planarization layer is deposited. Typically, the planarization layer as described herein is deposited by using a CVD process, for instance a PECVD process or a HWCVD (Hot Wire Chemical Vapor Deposition) process. Further, the mechanical properties of the planarization layer as described herein can be adapted to the mechanical properties of the flexible substrate as described herein. For example, the flexibility, e.g. the E-modulus, of the planarization layer can be adapted to the mechanical properties of the flexible substrate.

[0020] In the present disclosure, a "transparent conductive oxide layer" is to be understood as a layer of optically transparent and electrically conductive material.

[0021] FIG. 1 shows a schematic view of a layer system 100 according to embodiments described herein. According to embodiments which can be combined with any other embodiments described herein, the layer system 100 is adapted for use in an electro-optical device. In particular, the layer system 100 includes a flexible substrate 101, a planarization layer 110 provided on the flexible substrate 101, and a transparent conductive oxide layer 120 provided on the planarization layer 110. For example, the flexible substrate 101 can include a polymer material selected from the group consisting of: polycarbonate, polyethylene terephthalate, poly(methacrylic acid methyl ester), triacetyl cellulose, cyclo olefin polymer, and poly(ethylene naphthalate). Typically, the planarization layer 110 is configured to encapsulate defects on the flexible substrate 101. Further, the planarization layer is configured to covalently bind to the surface of the flexible substrate.

[0022] Accordingly, a layer system is provided which has an improved structural stability compared to conventional layer systems. Further, the quality of the layer system as described herein is improved since the planarization layer is configured to encapsulate defects and fill scratches of the substrate onto which the planarization layer is deposited. Accordingly, a significantly smoothened surface for a subsequent processing action, particularly for a subsequent layer deposition process, can be obtained. Thus, by employing embodiments of the layer system as described herein in electro-optical devices, e.g. display devices or touch panels, the quality as well as the product durability of the electro-optical devices can be improved.

[0023] With exemplary reference to FIG. 1, according to embodiments which can be combined with any other embodiments described herein, the planarization layer 110 can have a thickness T _PL of 100 nm < T _PL < 800 nm. For instance, the thickness T _PL of the planarization layer 110 can be selected from a range having a lower limit of 100 nm, particularly a lower limit of 200 nm, more particularly a lower limit of 300 nm and an upper limit of 600 nm, particularly an upper limit of 700 nm, more particularly an upper limit of 800 nm. Accordingly, by providing a layer system with a planarization layer having a thickness T _PL as described herein, the overall layer system quality can be improved. For instance, as the thickness T _PL of the planarization layer is increased, defects on the substrate (e.g. scratches or particles) can be smoothened out more effectively.

[0024] According to embodiments which can be combined with any other embodiment described herein, the mechanical properties of the planarization layer can be adapted to the mechanical properties of the flexible substrate.

For example, the flexibility, e.g. the E-modulus, of the planarization layer can be adapted to the mechanical properties of the flexible substrate.

Accordingly, the structural stability of the layer system as described herein can be improved, since the planarization layer can follow a deformation of the flexible substrate.

[0025] FIGS. 2 and 3 show detailed views of a portion of a layer system 100 according to embodiments described herein for illustrating the function of the planarization layer 110. In particular, FIG. 2 shows a layer system including a defect structure D on the surface of the flexible substrate 101 and FIG. 3 shows a layer system having a particle P on the surface of the flexible substrate 101.

[0026] With exemplary reference to FIG. 2, according to embodiments which can be combined with any other embodiments described herein, the thickness T _PL of the planarization layer 110 is selected according to the equation: T _PL [ran] = (1- T _TC o/hd) ^x 100, wherein T _TC o is a thickness of the transparent conductive oxide layer, and wherein h _d is a height of a defect on the substrate.

[0027] Accordingly, by selecting the thickness T _PL of the planarization layer according to the equation T _PL [nm] = (1- (T _TC0 /h _d ) ^x the overall layer system quality can be improved. In particular, defects (e.g. scratches or particles) can be smoothened out more effectively.

[0028] According to embodiments which can be combined with any other embodiments described herein, a thickness T _TC0 of the transparent conductive oxide layer 120 can be 5 nm < T _T co≤ 100 nm. For instance, the thickness T _T co of the transparent conductive oxide layer 120 can be selected from a range having a lower limit of 5 nm, particularly a lower limit of 10 nm, particularly a lower limit of 20 nm, more particularly a lower limit of 40 nm and an upper limit of 60 nm, particularly an upper limit of 80 nm, more particularly an upper limit of 100 nm.

[0029] According to embodiments which can be combined with any other embodiments described herein, the planarization layer 110 is further configured to promote adhesion of the transparent conductive oxide layer 120 to the planarization layer 110. In particular, a configuration of the planarization layer for promoting adhesion to the transparent conductive oxide layer can be obtained by a planarization layer having a material composition as described herein.

[0030] According to embodiments which can be combined with any other embodiments described herein, the transparent conductive oxide layer 120 may include at least one material selected from the group consisting of silicon oxide SiO _x , niobium oxide NbO _x and indium tin oxide ITO. In particular, the transparent conductive oxide layer 120 may consist of at least one material selected from the group consisting of silicon oxide SiO _x , niobium oxide NbO _x and indium tin oxide ITO.

[0031] According to embodiments which can be combined with any other embodiments described herein, the planarization layer 110 includes silicon oxycarbide SiO _x C _y . In particular, the planarization layer 110 consists of silicon oxycarbide SiO _x C _y . Accordingly, by employing a planarization layer having a material composition as described herein, the planarization layer is configured to covalently bind to the surface of the flexible substrate as described herein, which is beneficial for improving the structural stability of the layer system. Further, a planarization layer including silicon oxycarbide SiO _x C _y can be beneficial for promoting adhesion to the transparent conductive oxide layer deposited on the planarization layer.

[0032] With exemplary reference to FIG. 4A, according to embodiments which can be combined with any other embodiments described herein, the layer system further comprises a layer stack 130 provided on the planarization layer 110. Typically, the layer stack 130 comprises a first layer 131 of niobium oxide (NbO _x ), a second layer 132 of silicon oxide (SiO _x ) and a third layer 133 of indium tin oxide (ITO), as exemplarily shown in FIG. 4B. In particular, the first layer 131 may consist of niobium oxide (NbO _x ), the second layer 132 may consist of silicon oxide (SiO _x ) and the third layer 133 may consist of indium tin oxide (ITO). [0033] For instance, the first layer 131 may have a thickness T ₁ of 5 nm < T ₁ < 10 nm. For instance, the thickness T ₁ of the first layer 131 can be selected from a range having a lower limit of 5 nm, particularly a lower limit of 6 nm, more particularly a lower limit of 7 nm and an upper limit of 8 nm, particularly an upper limit of 9 nm, more particularly an upper limit of lO nm. [0034] The second layer 132 may have a thickness T ₂ of 40 nm < T ₂ < 80 nm. For instance, the thickness T ₂ of the second layer 132 can be selected from a range having a lower limit of 40 nm, particularly a lower limit of 45 nm, more particularly a lower limit of 50 nm and an upper limit of 60 nm, particularly an upper limit of 70 nm, more particularly an upper limit of 80 nm.

[0035] The third layer 133 may have a thickness T ₃ of 20 nm < T ₃ < 60 nm. For instance, the thickness T ₃ of the third layer 133 can be selected from a range having a lower limit of 20 nm, particularly a lower limit of 25 nm, more particularly a lower limit of 30 nm and an upper limit of 40 nm, particularly an upper limit of 50 nm, more particularly an upper limit of 60 nm.

[0036] With exemplary reference to FIG. 4C, according to embodiments which can be combined with any other embodiments described herein, the layer stack 130 may include a fourth layer 134 provided between the flexible substrate 101 and the first layer 131. In particular, the fourth layer 134 may have a thickness T ₄ of 5 nm < T ₂ < 10 nm. For instance, the thickness T ₄ of the fourth layer 134 can be selected from a range having a lower limit of 5 nm, particularly a lower limit of 6 nm, more particularly a lower limit of 7 nm and an upper limit of 8 nm, particularly an upper limit of 9 nm, more particularly an upper limit of 10 nm. For example, the fourth layer can consist of silicon oxide SiO _x .

[0037] Providing a layer system with a layer stack 130 as described herein, can be beneficial for enhancing the optical performance of the layer system compared to conventional layer structures, particularly for use in electro-optical devices such as OLED displays. For instance, the layer stack as described herein, can be beneficial for optical matching of the layers of the layer system, e.g. for obtaining a layer system with antireflective properties. [0038] According to some embodiments which can be combined with other embodiments described herein, the first layer 131 and/or the second layer 132 and/or the third layer 133 and/or the fourth layer 134 can be deposited using a physical vapor deposition (PVD) process. [0039] According to an example which can be combined with other embodiments described herein, the layer system 100 adapted for use in an electro-optical device includes a flexible substrate 101, a planarization layer 110 provided on the flexible substrate 101, and a transparent conductive oxide layer 120 provided on the planarization layer 110. The planarization layer is configured to encapsulate defects on the flexible substrate. Further, the planarization layer is configured to covalently bind to the surface of the flexible substrate and to promote adhesion of the transparent conductive oxide layer to the planarization layer. In particular, the planarization layer has a thickness T _PL of 100 nm < T _PL < 800 nm and consists of silicon oxycarbide SiO _x C _y . Further, the transparent conductive oxide layer has a thickness T _TC o of 5 nm < T _TC o≤ 10 nm and consists of silicon oxide SiOx or niobium oxide NbO _x .

[0040] Accordingly, in view of the embodiments of the layer system as described herein, it is to be understood that the layer system is well suited for being manufactured in a continuous roll-to-roll process, particularly a continuous vacuum deposition roll-to-roll process.

[0041] As an example, a schematic view of a processing system 300 for manufacturing a layer system according to embodiments described herein is shown in FIG. 5. In particular, FIG. 5 shows a roll-to-roll processing system configured for carrying out a method for manufacturing a layer system in a continuous roll-to-roll process as exemplarily described in more detail with reference to FIG. 7.

[0042] As exemplarily shown in FIG. 5, the processing system 300 can include at least three chamber portions, such as a first chamber portion 302 A, a second chamber portion 302B and a third chamber portion 302C. At the third chamber portion 302C, one or more deposition sources 630 and optionally an etching station 430 can be provided as processing tools. A substrate, e.g. a flexible substrate 101 as described herein, is provided on a first roll 764, e.g. having a winding shaft. The flexible substrate is unwound from the first roll 764 as indicated by the substrate movement direction shown by arrow 108. A separation wall 701 is provided for separation of the first chamber portion 302 A and the second chamber portion 302B. The separation wall 701 can further be provided with gap sluices 740 to allow the flexible substrate 101 to pass therethrough. A vacuum flange 312 provided between the second chamber portion 302B and the third chamber portion 302C can be provided with openings to take up at least some processing tools.

[0043] The flexible substrate 101 is moved through the deposition areas provided at a coating drum 710 and corresponding to positions of the deposition sources 630. During operation, the coating drum 710 rotates around an axis such that the flexible substrate 101 moves in the direction of arrow 108. According to some embodiments, the flexible substrate 101 is guided via one, two or more rollers from the first roll 764 to the coating drum 710 and from the coating drum 710 to the second roll 764', e.g. having a winding shaft, on which the flexible substrate 101 is wound after processing thereof.

[0044] According to some embodiments, the deposition sources 630 can be configured for depositing the layers as described herein. As an example, at least one deposition source can be adapted for deposition of the planarization layer 110 and at least one deposition source can be adapted for deposition of the transparent conductive oxide layer 120. Further, deposition sources may be provided for depositing a layer stack 130 as described herein. [0045] In some implementations, the first chamber portion 302A is separated in an interleaf chamber portion unit 302A1 and a substrate chamber portion unit 302A2. For instance, interleaf rolls 766/766' and interleaf rollers 305 can be provided as a modular element of the processing system 300. The processing system 300 can further include a pre-heating unit 394 to heat the flexible substrate. Further, additionally or alternatively a pre-treatment plasma source 392, e.g. an RF (radio frequency) plasma source can be provided to treat the substrate with a plasma prior to entering the third chamber portion 302C. [0046] According to yet further embodiments, which can be combined with other embodiments described herein, optionally also an optical measurement unit 494 for evaluating the result of the substrate processing and/or one or more ionization units 492 for adapting the charge on the substrate can be provided. [0047] According to some embodiments, the deposition material may be chosen according to the deposition process and the later application of the coated substrate. For instance, the deposition material of the deposition sources may be selected according to the respective material of the planarization layer, transparent conductive oxide layer, and the individual layers of the layer stack as described herein.

[0048] With exemplary reference to FIG. 6, according to one aspect of the present disclosure, an electro-optical device 150 having a layer system 100 according to any embodiments described herein is provided. Accordingly, it is to be understood that layer systems as described herein can beneficially be used in optical applications, for instance for OLEDs, in order to improve the structural stability of the electro-optical device in which the layer system as described herein is employed.

[0049] With exemplary reference to FIG. 7, embodiments of a method 200 for manufacturing a layer system in a continuous roll-to-roll process is described. According to embodiments which can be combined with any other embodiments described herein, the method 200 includes providing (see block 210) a flexible substrate to at least one first processing zone and at least one second processing zone without breaking vacuum. Further, the method 200 includes depositing (see block 220) a planarization layer on the flexible substrate in the at least one first processing zone such that defects on the flexible substrate are encapsulated by the planarization layer. Additionally, the method 200 includes depositing (see block 230) a transparent conductive oxide layer on the planarization layer in the at least one second processing zone. In particular, depositing the planarization layer includes forming covalent bonds between the flexible substrate and the planarization layer.

[0050] According to embodiments of the method which can be combined with any other embodiments described herein, depositing (block 220) the planarization layer and depositing (block 230) the transparent conductive oxide layer includes using a PECVD process and/or a HWCVD process. For instance, the planarization layer and/or the transparent conductive oxide layer and/or the layer stack as described herein may be deposited using a low temperature microwave PECVD process. [0051] According to embodiments of the method which can be combined with any other embodiments described herein, depositing (block 220) the planarization layer can include using at least one precursor selected from the group consisting of: HMDSO Hexamethyldisiloxane; TOMCAT Tetramethyl Cyclotetrasiloxane (C ₄ Hi ₆ 0 ₄ Si ₄ ); HMDSN Hexamethyldisilazane ([(CH ₃ ) ₃ Si] ₂ NH); and TEOS Tetraethyl Orthosilicate (Si(OC ₂ H ₅ ) ₄ ).

[0052] Further, depositing (block 230) the transparent conductive oxide layer may also include using at least one precursor selected from the group consisting of: HMDSO Hexamethyldisiloxane; TOMCAT Tetramethyl Cyclotetrasiloxane (C ₄ H ₁₆ 0 ₄ Si ₄ ); HMDSN Hexamethyldisilazane ([(CH ₃ ) ₃ Si] ₂ NH); and TEOS Tetraethyl Orthosilicate (Si(OC ₂ H ₅ ) ₄ ). In particular, depositing (block 220) the planarization layer and depositing (block 230) the transparent conductive oxide layer can include using the same precursor. [0053] In particular, depositing the planarization layer can further include using at least one agent selected from the group consisting of: peroxides as initiators, particularly TBPO (tert-butyl peroxide); acrylate monomers, particularly ethyl-hexyl acrylate; and a crosslinking agent, particularly BDDA (butanediol-diacrylate). Accordingly, the structural stability of the layer system as described herein can be improved.

[0054] In light of the foregoing, it is to be understood that embodiments described herein provide for an improved layer system as well as for methods for manufacturing such an improved layer system, particularly for use in electro-optical devices. [0055] While the foregoing is directed to embodiments of the disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

[0056] In particular, this written description uses examples to disclose the disclosure, including the best mode, and also to enable any person skilled in the art to practice the described subject-matter, including making and using any devices or systems and performing any incorporated methods. While various specific embodiments have been disclosed in the foregoing, mutually non-exclusive features of the embodiments described above may be combined with each other. The patentable scope is defined by the claims, and other examples are intended to be within the scope of the claims if the claims have structural elements that do not differ from the literal language of the claims, or if the claims include equivalent structural elements with insubstantial differences from the literal language of the claims.