Inorganic thin film electroluminescent display element

Abstract

An inorganic thin film electroluminescent display element (100) with an operating layer structure (107) comprises a first conductive contact layer (101) and a second conductive contact layer (105), and a luminescent layer (103) comprising a luminescent material located between the first conductive contact layer and the second conductive contact layer. The display element includes a protective coating (108) on a side of the second conductive contact layer (105) opposite the light emitting layer, the protective coating including a nanostack (109) having alternating aluminum oxide Al2O3 and transition metal oxide TO2 sublayers (111, 110), where the nanostack includes at least two sublayers of each oxide type, and the transition metal T is hafnium Hf or zirconium Zr.

Description

Background Art

[0001] Inorganic thin film electroluminescent (TFEL) displays are considered a viable display technology, especially in applications that require rugged device configuration and reliable operation in harsh environments and extreme conditions. However, there are still some areas where improved solutions are useful.

[0002] For example, leakage currents between parts such as conductor traces, segments and / or filling areas of a transparent upper conductor layer should be prevented. One known solution is to provide an aluminium oxide protective coating on the upper transparent conductor layer, which is typically formed of indium tin oxide (ITO).

[0003] The upper conductor layer should also be protected from moisture. For example, an electroluminescent (EL) display element can be encapsulated between a substrate glass and a cover glass, which is mounted on the display element stack via an epoxy layer. However, the cover glass and epoxy are missing in the pad area for electrical contact, so an additional moisture barrier is required in this area. A known solution is to use a silicone seal encapsulation on the pad area. However, any defects in the encapsulation may cause moisture to penetrate the aluminum oxide layer and damage the ITO layer.

[0004] On the other hand, in the case where the EL display element is laminated between two glass panels to form, for example, a vehicle windshield, moisture present in the resin used in the lamination process may also cause problems if it penetrates into the upper conductor layer.

[0005] Additionally, the optical properties of the protective coating need to be addressed to ensure adequate transmission performance of the display element. Summary of the invention

[0006] This Summary is provided to introduce a selection of concepts in a simplified form that are further described in the Detailed Description below. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to limit the scope of the claimed subject matter.

[0007] According to the device aspect, an inorganic thin film electroluminescent display element can be realized, which has an operating layer structure including a first conductive contact layer and a second conductive contact layer, and a light-emitting layer including a light-emitting material located between the first conductive contact layer and the second conductive contact layer.

[0008] The display element comprises a protective coating on a layer of the second conductive contact layer opposite to the light-emitting layer, the protective coating comprising a nano-stack having alternating sub-layers of aluminum oxide Al2O3 and transition metal oxide TO2, wherein the nano-stack comprises at least two sub-layers of each oxide type, and the transition metal T is hafnium Hf or zirconium Zr.

[0009] The thickness of at least two layers (for example, five layers) of the transition metal oxide TO2 sub-layers may be greater than or equal to 0.5 nanometers.

[0010] The total thickness of the nano-stack can be greater than or equal to 25 nanometers, such as greater than or equal to 100 nanometers, or greater than or equal to 200 nanometers.

[0011] The total thickness of the nano-laminate may be less than or equal to 700 nanometers, such as less than or equal to 500 nanometers.

[0012] The nano-laminate may include more than 25 pairs of aluminum oxide and transition metal oxide sub-layers.

[0013] The total atomic ratio of aluminum to transition metal of the nanolaminate may be in the range of 20 / 80 to 95 / 5, such as 30 / 70 to 90 / 10.

[0014] The nanolaminate may have regions of different aluminum to transition metal atomic ratios through its thickness, wherein the proportion of transition metal increases toward the second dielectric layer.

[0015] The protective coating may include an aluminum oxide Al2O3 index matching layer on the side of the nano-stack opposite to the operating layer structure.

[0016] The protective coating may include a nanolaminate and possibly a transition metal oxide capping layer on the side of the index matching layer opposite to the operating layer structure. The capping layer may have a thickness of 0.5 to 5 nanometers, for example about 2 nanometers.

[0017] At least the second electrically conductive contact layer may comprise or at least essentially consist of indium tin oxide ITO.

[0018] A contact opening may be formed in the protective coating for enabling electrical contact to be formed with the second contact layer. The contact opening may be formed by laser.

[0019] Nano-laminates can be formed by atomic layer deposition (ALD).

[0020] In a second aspect, a method for manufacturing an inorganic thin film electroluminescent display element according to any embodiment of the above-mentioned device aspect can be implemented.

[0021] In this method, the nano-laminate can be formed by atomic layer deposition ALD.

[0022] In order to manufacture a display element including a contact opening formed in a protective coating layer according to the above-described device aspect embodiments, the contact opening may be formed by laser.

[0023] Many of the accompanying features will be more readily understood as the same become more apparent by reference to the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following detailed description will be helpful to better understand the present invention when read in conjunction with the accompanying drawings, in which:

[0025] Figure 1 A cross-sectional view of a horizontally limited area of ​​an inorganic thin film electroluminescent (EL) display element is shown.

[0026] Figure 2 Shows Figure 1 A cross-sectional view of a horizontal limited area of ​​the protective coating of the display element.

[0027] Figure 3 A flow chart showing a method for manufacturing an inorganic thin film electroluminescent (EL) display element.

[0028] The drawings in the figures are schematic diagrams and are not drawn to scale. DETAILED DESCRIPTION

[0029] The detailed description provided below in conjunction with the appended drawings is intended as a description of various embodiments and is not intended to represent the only forms in which such embodiments may be constructed, implemented, or utilized.

[0030] Figure 1 A side cross-sectional view of a portion of an inorganic electroluminescent (EL) display element 100 is shown.

[0031] A "display element" refers to an element that can form a complete, operable display. Alternatively, a display element can be used as one element of a complete display assembly that also includes other elements, units and / or structures.

[0032] “Display” is to be understood in a broad sense and naturally covers “ordinary”, actual displays capable of displaying various patterns, images or texts, but also covers, for example, various control panels and user interface elements which have at least one luminous area for emitting light.

[0033] The display element 100 is formed as a layered structure having a plurality of superimposed layers.

[0034] "Layer" refers to a structural entity that may extend substantially along or parallel to an imaginary substrate surface and whose thickness in a direction perpendicular to said surface is much smaller than the dimension of the layer along or parallel to said surface. Such an imaginary substrate surface may be flat. Alternatively, it may be curved in one or more directions.

[0035] exist Figure 1In the core of the EL display element 100, a light-emitting layer 103 is superimposed between a first conductive contact layer 101 and a second conductive contact layer 105. The light-emitting layer is separated from the contact layer by a first dielectric layer 102 and a second dielectric layer 104. Therefore, the light-emitting layer is located on the first dielectric layer, and the second dielectric layer is located on the light-emitting layer. Thus, the light-emitting layer is adjacent to both the first dielectric layer and the second dielectric layer.

[0036] In this specification, a layer located "on" another layer or other structure refers to a layer located "above" the other layer or structure, and the upward direction is defined in the thickness direction of the display element, from the first contact layer toward the second contact layer. The position "on" another layer or another object does not exclude the possibility that there are more intermediate layers or structures between the first layer and the other layer or structure on which it is located.

[0037] In other embodiments, the EL display element can be implemented with only one dielectric layer. Thus, the EL display element can include one or two dielectric layers. In the case where the EL display element includes only a single dielectric layer, the dielectric layer can be located between the light-emitting layer and the first contact layer or between the light-emitting layer and the second contact layer.

[0038] The dielectric layers may be formed from any suitable electrically insulating material and have any suitable thickness. They may also comprise sub-layers of different materials.

[0039] The dielectric layer may be made substantially of one single material. In other embodiments, it may include sub-layers of different material compositions.

[0040] exist Figure 1 In the example, at least the second layer, i.e. Figure 1 The upper contact layer 105 in the display element includes indium tin oxide ITO and can be substantially entirely made of indium tin oxide ITO. Since it is made of ITO, the upper contact layer can be transparent. In other embodiments, any other transparent conductive material (such as aluminum-doped zinc oxide AZO) can be used instead of ITO. In addition, the lower contact layer can also be formed of ITO, AZO or any other suitable transparent conductive material, so that the entire display element can be transparent. Alternatively, it can be formed of any suitable opaque conductive material.

[0041] The display element 100 is formed on a glass substrate 106. In other embodiments, a plastic substrate may be used. The substrate may be transparent.

[0042] The display element 100 is designed to operate substantially according to the known operating principles of inorganic thin film EL displays. The contact layers 101, 105 are used to provide electrical connections for the display element. They can be patterned into any suitable contact electrode configuration. For example, they can be patterned into segments of a segmented display element. In some other embodiments, they can be patterned into crossed electrodes of a matrix display element. In other embodiments, any other suitable contact electrode configuration can be used. Figure 1 In FIG. 1 , the patterning is shown by two regions 105a, 105b of the second contact layer separated from each other by a gap 105c.

[0043] In addition to the electrodes, the contact layer may have any suitable number and configuration of conductor tracks to form electrical connections between the electrodes and the control electronics of the display.The contact layer may also include one or more fill regions, ie regions where conductive material is present but isolated from the rest of the contact layer.

[0044] The light emitting layer may include any suitable light emitting material, such as manganese doped zinc sulfide ZnS:Mn.

[0045] The light emitting layer may be made substantially of a single material. In other embodiments, it may include sub-layers of different material compositions.

[0046] The voltage difference between the first contact layer 101 and the second contact layer 105 provides an electric field, under the influence of which electrons move in the light-emitting layer 103, some of which excite the so-called luminescent center formed by the doping material of the light-emitting layer. When the excitation of the luminescent center relaxes, light is emitted. Therefore, the light-emitting layer can also be called an emission layer.

[0047] Thus, the contact layers 101, 105 and the light emitting layer 103 with the dielectric layers 102, 104 therebetween form the actual operating layer structure 107 of the display element. "Operating" here refers to the layers and components that are directly involved in the actual emission of light by the electroluminescent process.

[0048] The basic technology of EL displays is known and has been extensively described in, for example, Chapters 3, 5 and 8 of "Electroluminescent Displays" (Yoshimasa A. Ono, World Scientific Publishing Co., 1995 (ISBN 981-02-1920-0).

[0049] Figure 1 The display element 100 is implemented as a thin film (TF) EL display element.

[0050] The "thin film" nature of the display element refers to the total thickness of the layer structure of the operating layer structure, which is less than several tens of micrometers. The total thickness can also be significantly lower, for example in the range of 1 to 10 μm, or less than 1 μm. The thickness of the individual layers can basically be in the range of a few nanometers to tens or hundreds of nanometers or micrometers.

[0051] In addition to the operating layer structure 107, Figure 1 The display element 100 further includes a protective coating 108 formed on the second contact layer 105. Here, "on" means that the protective coating is located on a side of the second contact layer opposite to the light-emitting layer.

[0052] like Figure 1 As shown, the protective coating 108 fills the gaps between different portions of the patterned second contact layer.

[0053] Advantageously, if Figure 2 As shown in more detail, Figure 1 The protective coating 108 of the display element 100 comprises a nano-stack 109 having alternating hafnium oxide HfO 2 layers 110 and aluminum oxide Al 2 O 3 layers 111 .

[0054] In other embodiments, the other oxide may be zirconium oxide instead of hafnium oxide. Both hafnium oxide and zirconium oxide are transition metals, so the other oxide may be referred to as a transition metal oxide.

[0055] The prefix "nano" of the nanolaminate refers to the fact that the thickness of the alternating sublayers is on the nanometer scale, ie, the thickness is less than or equal to a few nanometers to tens of nanometers.

[0056] Furthermore, a nano-stack having "alternating sub-layers" of two materials means that the nano-stack includes at least two sub-layers of each of the two materials, so there are at least four sub-layers in total. Above this lower limit, the nano-stack may include any suitable number of pairs of two adjacent sub-layers of different materials. In some embodiments, it may be advantageous for the nano-stack to include more than 25 pairs of sub-layers of different oxides from the perspective of moisture protection and preventing leakage current.

[0057] exist Figure 2 In the example of FIG. 1 , the lowermost sublayer, ie, the sublayer adjacent to the second contact layer 105, is formed of hafnium oxide. In other embodiments, the lowermost sublayer may be formed of aluminum oxide.

[0058] exist Figure 2 In the example of FIG. 1 , the nano-stack 109 includes an even number of sub-layers. In other embodiments, the nano-stack may include an odd number of sub-layers, with the outermost sub-layers being the same oxide.

[0059] It may be advantageous for at least some of the hafnium oxide sublayers 110, or zirconium oxide sublayers in embodiments with zirconium as the transition metal, to be at least 0.5 nm thick. Such thicknesses ensure that the sublayers are sufficiently continuous to form a substantially uninterrupted layer, thereby enabling the formation of a true nano-laminate.

[0060] In various embodiments, the total thickness of the nano-stack can vary depending on the number and thickness of the individual sub-layers. It has been found that useful electrical and optical properties can be achieved by making the total thickness of the nano-stack at least 25 nanometers, such as at least 100 nanometers or at least 200 nanometers. The upper limit can vary, for example, between 500 nanometers and 700 nanometers. If the total thickness is too low, undesirable leakage currents may occur. On the other hand, increasing the thickness too much may reduce light transmittance and / or complicate the formation of contact openings through the protective coating.

[0061] like Figure 2 As shown, different types of sublayers 110, 111 of the nano-stack 109 may have different thicknesses. This may affect the ratio of aluminum to transition metal oxide in the nano-stack. It may be advantageous for the total ratio of aluminum to transition metal in the nano-stack to be in the range of 20 / 80 to 95 / 5, or, for example, in the range of 30 / 70 to 90 / 10.

[0062] Surprisingly, the nano-layers described above can provide good electrical, moisture-proof and optical properties. First, the protective coating including the nano-laminate can reduce leakage current between different regions of the upper contact layer (i.e., the second contact layer). The nano-laminate can also prevent or inhibit the diffusion of moisture, thereby protecting the second contact layer and the layers below it from the adverse effects of moisture. In addition, the nano-laminate can also be used as an optical intermediate layer to improve the light transmittance of the display element.

[0063] exist Figure 1 and Figure 2 In the example of , the nanolaminate includes regions with different ratios of aluminum to transition metal atoms in the thickness direction thereof. This is achieved by making the thickness of the sublayers different between different regions. In the first or lowermost region 112 adjacent to the second contact layer 105, the thickness of the aluminum oxide sublayer relative to the transition metal sublayer is thinner than in the last or uppermost region 113 farthest from the second contact layer. This means that the ratio of aluminum to transition metal atoms in the last region is higher than in the first region. Therefore, the proportion of transition metal in the nanolaminate increases towards the second dielectric layer.

[0064] There can be any number of other regions between the first region and the last region, so that the above principle of increasing the proportion of transition metal toward the second dielectric layer can be met. In this arrangement, the ratio of aluminum to transition metal atoms and the ratio of aluminum to transition layer gradually change in the thickness direction of the nano-stack.

[0065] The change in the atomic ratio can also change the effective refractive index of the nano-stack 109 .

[0066] The “effective” refractive index means that, because the thickness of the sublayers is on the nanometer scale, far below the wavelength of hundreds of nanometers, light waves do not see the nanolayer stack as separate sublayers with the refractive index of their bulk material, but rather as a single material with an effective refractive index between the refractive indices of the two materials.

[0067] The effective refractive index varies with the proportional thickness of the different sub-layer types and with the atomic ratio of aluminum to transition metal between different regions. The effective refractive index of the nano-laminate can then be varied gradually in the direction of the thickness of the nano-laminate by appropriate adjustment of the sub-layer thicknesses. In this way, in embodiments where the display element is laminated between two glass sheets, the nano-laminate can act as an effective anti-reflection coating to minimize reflection losses between the operating layers of the display element and the cover glass or upper glass.

[0068] Therefore, the thickness of the different types of sublayers can be adjusted in the first region to produce an effective refractive index close to the bulk refractive index of the second contact layer at a relevant wavelength. For example, the "relevant wavelength" can refer to the wavelength of the light emitted by the light-emitting layer, or can refer to the entire visible light wavelength range of about 400-700 nanometers. For example, for ZnS:Mn as the light-emitting layer material, the relevant wavelength can be, for example, the emission peak wavelength of 580 nanometers. For example, in the case of ITO as the second contact layer material, the effective refractive index of the first region can be close to the bulk refractive index of ITO at a nanometer wavelength of 580nm. For example, it can be about 1.90.

[0069] As Figure 1 and Figure 2 As part of the optical optimization of the protective coating, there is an additional aluminum oxide Al2O3 refractive index matching layer 114 on the nano stack 109. This additional aluminum oxide layer can be thicker than the sub-layers of the nano stack. If the thickness is sufficient, the layer can be optically operated as a bulk aluminum oxide. For example, at a wavelength of 580 nanometers, the refractive index of aluminum oxide can be about 1.6, which can be close to the refractive index of the epoxy or other adhesive used to mount the cover glass to the display element layer stack at said wavelength. Therefore, the refractive index matching layer can be used to optically match the outermost layer or upper portion of the protective coating to the adhesive layer.

[0070] Accordingly, in embodiments where the display element is laminated between two glass panels, an aluminum oxide index matching layer may be used to optically match the protective coating to the laminating polymer, such as polyvinyl butyral (PVB) or thermoplastic polyurethane (TPU).

[0071] Figure 1 and Figure 2 The protective coating 108 also includes a HfO 2 capping layer 115 located on the nano-stack 109 and an additional refractive index matching Al 2 O 3 layer 114 .

[0072] In other embodiments, especially those using zirconium oxide ZrO2 as the transition metal oxide of the nano-laminated layer, the capping layer may be formed of zirconium oxide ZrO2. In the embodiment using zirconium oxide ZrO2 as the transition metal oxide of the nano-laminated layer, an HfO2 capping layer may also be used, and vice versa.

[0073] In other embodiments, the protective coating may be achieved without the use of an Al2O3 index matching layer. However, a capping layer of HfO2 or ZrO2 may be present on the nano-stack.

[0074] Embodiments without any covering layer are also possible.

[0075] The HfO2 capping layer 115 can form an effective moisture barrier to prevent moisture from penetrating into the nano-stack and further into the operating layers of the display element, thereby advantageously improving the protective coating performance.

[0076] Figure 1 The cover layer of the display element has a thickness of about 2 nanometers. In other embodiments, a cover layer thickness in the range of, for example, 0.5 to 5 nanometers may be used.

[0077] As mentioned above, in Figure 1 In the display element 100, a cover glass 116 is mounted on the protective coating 108 via an epoxy resin layer 117 or some other suitable adhesive with suitable optical properties. Figure 1 The display element 100 is encapsulated between a glass substrate 106 and a cover glass 116 .

[0078] exist Figure 1 In the example of FIG. 1 , there is a pad area 118 in the display element layout for forming an electrical connection between the upper contact layer or the second contact layer 105 and control electronics (not shown) configured to drive the display element.

[0079] In the pad area 118, the cover glass 116 is missing. In addition, a contact opening 119 is formed in the protective coating 108 to expose the second contact layer 105. Subsequently, the protective coating can be removed by laser to form the contact opening. By means of a laser, the protective coating material can be removed by ablation. Using laser ablation, the formation of the contact opening can be precisely controlled in the horizontal and vertical directions (i.e., in the direction along the substrate surface of the layer and sub-layer and in the thickness direction thereof).

[0080] In addition to the pad areas, other contact openings formed by laser or other means may also exist at other locations where connections need to be made through the protective coating.

[0081] Conductor trace 120 is formed on protection layer 108 to extend to pad region 118 and contact second contact layer 105 location exposed by contact opening 119. Conductor trace 120 may be formed of, for example, any suitable metal (eg, copper) or any other suitable material having suitable conductivity.

[0082] It should be noted that Figure 1 and Figure 2 A limited portion of the display element (100) and the protective coating (108) in the horizontal direction (i.e., in the direction of the substrate surface of the virtual layer) is shown, respectively. Therefore, in the horizontal direction, the display element and the nano-stack may extend further than shown in the figures.

[0083] The nano-stacked layers of any of the above embodiments may be formed by atomic layer deposition (ALD, atomic layer deposition).

[0084] ALD refers to a thin film technology that can produce thin film coatings with nanometer thickness accurately and in a well-controlled manner. ALD can also be called atomic layer epitaxy ALE. In the ALD process, the substrate is exposed to at least two precursors alternately, one at a time, and a coating is formed on the substrate by alternating and repeating the essentially self-limiting surface reaction between the substrate surface (in the subsequent stage, naturally, the coating surface already formed on the substrate) and the precursors. As a result, the deposited material "grows" on the substrate one molecular layer at a time.

[0085] It may be preferred to use ALD not only in the formation of the nano-stack, but also in the formation of the handle layer, possible Al2O3 index matching layer and / or possible HfO2 capping layer.

[0086] ALD provides a well-controlled process by which designed layer and sub-layer thicknesses can be produced with high precision and high material quality.

[0087] Referenced above Figure 1 Any of the display elements discussed may be used with reference to Figure 3 On the other hand, those display elements discussed above represent examples of display elements that can be manufactured by the methods discussed below. The details, definitions and advantages of the display elements discussed above also apply to the display elements discussed below in the context of the manufacturing methods.

[0088] Figure 1The method 300 begins at stage 310 by forming operating layers of an EL display element on a glass or plastic substrate.

[0089] At stage 320, a protective coating is formed on the handle layer, in effect on the second contact layer.

[0090] First, in sub-operation 321, a protective coating is formed to include a nano-laminate having alternating aluminum oxide Al2O3 and transition metal oxide TO2 sub-layers, wherein the nano-laminate includes at least two sub-layers of each oxide type, and the transition metal T is hafnium Hf or zirconium Zr.

[0091] As part of forming the protective coating, an aluminum oxide index matching layer and a hafnium oxide capping layer may be formed on the nano-laminate in optional sub-operations 322 and 323, respectively.

[0092] In the above operations, at least the nano-stack (possibly all layers) is formed using atomic layer deposition ALD. During deposition, precursors and process parameters (such as temperature) known in the art may be used.

[0093] In order to be able to form an electrical contact with the second contact layer, a contact opening is formed in the protective coating to expose the second contact film layer in sub-operation 324. Preferably, the opening is formed by laser ablation.

[0094] Any suitable further sub-operations may be performed between any of the sub-operations discussed above. Therefore, the above sub-operations do not necessarily have to be performed immediately one after another.

[0095] It should be noted that the EL display element and the method for manufacturing the same are not limited to the above-described embodiments and examples. Instead, the embodiments can be freely varied within the scope of the claims.

[0096] It should be understood that the benefits and advantages described above may relate to one embodiment or example, or may relate to several embodiments or examples. The embodiments and examples are not limited to those that solve any or all of the problems described, nor are they limited to those that have any or all of the benefits and advantages described. It is further understood that reference to "an" item refers to one or more of these items.

[0097] The term "comprising" as used in this specification means including the following features, but does not exclude the presence of one or more additional features.

Claims

1. An inorganic thin film electroluminescent display element (100) having an operating layer structure (107), comprising: - a first conductive contact layer (101) and a second conductive contact layer (105), and - a light emitting layer (103) comprising a light emitting material, located between the first conductive contact layer and the second conductive contact layer, The display element (100) is characterized in that it includes a protective coating (108) on the side of the second conductive contact layer (105) opposite to the light-emitting layer (103), the protective coating including a nano-stack (109) having alternating aluminum oxide Al2O3 and transition metal oxide TO2 sub-layers (111, 110), wherein the nano-stack includes at least two sub-layers of each oxide type, and the transition metal T is hafnium Hf or zirconium Zr.

2. The inorganic thin film electroluminescent display element (100) according to claim 1, wherein: At least two of the transition metal oxide TO2 sub-layers, for example five sub-layers, have a thickness greater than or equal to 0.5 nanometers.

3. The inorganic thin film electroluminescent display element (100) according to claim 1 or 2, wherein: The total thickness of the nano-stack is greater than or equal to 25 nanometers, such as greater than or equal to 100 nanometers, or greater than or equal to 200 nanometers.

4. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 3, wherein: The total thickness of the nano-laminate is less than or equal to 700 nanometers, for example, less than or equal to 500 nanometers.

5. The inorganic thin film electroluminescent display element (100) according to claim 1 or 2, wherein: The nano-laminate includes more than 25 pairs of aluminum oxide and transition metal oxide sub-layers.

6. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 5, wherein: The total atomic ratio of aluminum to transition metal of the nanolaminate is in the range of 20 / 80 to 95 / 5, such as 30 / 70 to 90 / 10.

7. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 6, wherein: The nano-stack has regions with different atomic ratios of aluminum to transition metal in a thickness direction, with the ratio of transition metal increasing toward the second dielectric layer.

8. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 9, wherein: The protective coating includes an aluminum oxide Al2O3 refractive index matching layer (114) on the side of the nano-stack opposite to the operating layer structure (107).

9. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 7, wherein: The protective coating includes a transition metal oxide capping layer (115) on the side of the nano-stack opposite the operating layer structure (107).

10. The inorganic thin film electroluminescent display element (100) according to claim 8, wherein: The thickness of the capping layer is 0.5 to 5 nanometers, for example about 2 nanometers.

11. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 10, wherein: At least the second electrically conductive contact layer comprises indium tin oxide ITO.

12. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 11, wherein: A contact opening is formed in the protective coating for enabling electrical contact to be made with the second contact layer.

13. The inorganic thin film electroluminescent display element (100) according to claim 12, wherein: The contact openings are formed by laser.

14. The inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 13, wherein: The nano-stacks are formed by atomic layer deposition (ALD).

15. A method for manufacturing the inorganic thin film electroluminescent display element (100) according to any one of claims 1 to 14.

16. The method according to claim 15, wherein: The nano-stacks are formed by atomic layer deposition (ALD).

17. The method for manufacturing the inorganic thin film electroluminescent display element (100) according to claim 12 according to claim 15 or 16, wherein: The contact openings are formed by laser.

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