Flexible display stack and device including the same

Abstract

The invention provides a flexible display stack (1) comprising a display structure (3) and a cover structure (4) comprising a first cover layer (4a) and at least a second cover layer (4b). The first cover layer (4a) comprises a continuous structural element (5a) having a plurality of voids (6a) and a continuous matrix (7a) for filling the voids (6a) and at least partially surrounding the continuous structural element (5a), the structural element (5a) and the matrix (7a) comprising a material having a reflection index (R11, R12) within a first reflection index range (R1). The second cover layer (4b) comprises a continuous structural element (5b) having a plurality of voids (6b) and a continuous matrix (7b) for filling the voids (6b) and at least partially surrounding the continuous structural element (5b), the structural element (5b) and the matrix (7b) comprising a material having a reflection index (R21, R22) within a second reflection index range (R2).

Description

Technical Field

[0001] The present invention relates to a flexible display stack for an electronic device, the flexible display stack including a display structure and a cover structure superimposed on the display structure. Background Art

[0002] A truly flexible display enables bending and folding of the display of an electronic device, e.g., in response to folding of the electronic device. An OLED display stack requires layers that provide durability, user interface, and optical functions. It generally includes at least one hard coat layer, at least one cover window layer, at least one touch sensor layer, and at least one circular polarizer layer, and these layers must be laminated together using an adhesive. The hard coat layer not only determines the appearance and grade of the device, but also serves as a protective layer to protect the display stack from mechanical shock, scratches, abrasion, etc. As the name implies, the hard coat layer must be relatively hard to provide such protection, but at the same time must have sufficient flexibility to enable bending.

[0003] To provide these properties, the hard coat material is typically made of two components, one hard component and one soft component. By controlling the ratio of these components, the hardness and flexibility of the hard coat layer can be fine-tuned. However, there is always a trade-off between the mechanical properties of these two components, i.e., when the hardness increases, the flexibility decreases, and vice versa. Currently, display specifications require the hard coat layer to pass 200,000 cycles of bending (where the strain may exceed 3%), while the hard coat layer must be hard enough to pass a nail test or a standard steel wool test.

[0004] Current hard coat layers are mainly suitable for displays that fold only around one axis. Since multi-dimensional bending causes these hard coat layers to crack, these coatings cannot be applied to other types of bendable displays, e.g., slidable displays or rollable displays.

[0005] In addition, current OLED display stacks include a layer that serves as a lens to enhance the light output coupling of the light-emitting layer. However, such a lens layer causes a phenomenon called color washing effect. For example, when an RGB pixel needs to emit a certain intensity of blue light and green light but no red light, the RGB pixel is driven by a dedicated signal. However, if there is ambient light, the ambient light may be reflected from the display stack (especially from the lens layer), making it appear that the RGB pixel also emits red light, and at the same time the intensities of the green light and blue light also change. The color washing effect degrades the image quality.

[0006] To avoid the color washing effect, additional polarizing layers are typically added to the display stack. While adding such polarizing layers can solve the color washing problem, it also significantly reduces the light perception of the display pixels. To compensate for this, the display pixels must be brighter; as a result, the power consumption increases significantly and the display life is shortened. The flexibility of the polarizing layer is also poor and it cannot be used for truly flexible displays (e.g., foldable displays or rollable displays).

[0007] Accordingly, there is a need to provide an improved flexible display stack suitable for foldable electronic devices in general. Summary of the Invention

[0008] The object of the present invention is to provide an improved flexible display stack. The above and other objects are achieved by the features of the independent claims. Other implementations are apparent from the dependent claims, the description and the drawings.

[0009] According to a first aspect, there is provided a flexible display stack for an electronic device, comprising a display structure and a cover structure superimposed on the display structure. The cover structure includes a first cover layer and at least includes a second cover layer superimposed on the first cover layer. The first cover layer includes continuous structural elements, the continuous structural elements including a plurality of voids and a continuous matrix, the continuous matrix being configured to fill the voids and at least partially surround the continuous structural elements; the second cover layer also includes continuous structural elements, the continuous structural elements including a plurality of voids and a continuous matrix, the continuous matrix being configured to fill the voids and at least partially surround the continuous structural elements. The structural elements and the matrix of the first cover layer include materials having a refractive index within a first refractive index range, and the structural elements and the matrix of the second cover layer include materials having a refractive index within a second refractive index range.

[0010] This solution can implement a cover structure (i.e., a hard coating) suitable for displays that can be folded around an axis and other types of bendable displays, such as slidable displays or rollable displays. The cover structure has sufficient flexibility to be bent without cracking, while having sufficient hardness to provide mechanical protection for the display structure. In addition, by using several layers with different refractive indices within the cover structure, the image quality provided by the display stack is improved because destructive interference can reduce the reflections of the cover structure caused by ambient light and internal light from the display structure.

[0011] In a possible implementation of the first aspect, the covering structure includes at least one other covering layer superimposed on the second covering layer. The other covering layer includes continuous structural elements, which include a plurality of voids and a continuous matrix. The continuous matrix is used to fill the voids and at least partially surround the structural elements. The structural elements and the matrix of the other covering layer include materials having a refractive index within a third refractive index range, thereby further reducing reflections within the covering structure.

[0012] In another possible implementation of the first aspect, the display structure includes an OLED panel layer, such that the solution can be used for the currently preferred type of display panel.

[0013] In another possible implementation of the first aspect, the one or more structural elements include materials having one refractive index, and the one or more matrices include materials having another refractive index. The refractive indices are within the first refractive index range, the second refractive index range, and the third refractive index range, thereby improving the anti-glare and anti-reflection performance of the covering structure.

[0014] In another possible implementation of the first aspect, the differences between the refractive indices within the first refractive index range, the differences between the refractive indices within the second refractive index range, and the differences between the refractive indices within the third refractive index range are all ≤ 1.2%. This can prevent the display stack from being perceived as blurry or somewhat hazy. Larger differences in refractive index values may cause the structural elements to reflect and diffusely scatter light, which may be perceived as unclear.

[0015] In another possible implementation of the first aspect, the difference between the first refractive index range, the second refractive index range, and / or the other refractive index range is ≤ 18%, thereby reducing reflections when the light emitted from the display structure reaches the user of the display stack.

[0016] In another possible implementation of the first aspect, the voids of each structural element have a volume corresponding to λ / (2×R), where λ is the wavelength of the radiation, which is emitted by the display structure or is incident radiation from the outside, and R is the refractive index value representing the first refractive index range, the second refractive index range, or the third refractive index range. Such a small void size results in negligible light scattering such that the human eye cannot perceive blurriness.

[0017] In another possible implementation of the first aspect, the reflection index value of the first cover layer is one of the reflection indices of the first cover layer, the reflection index value of the second cover layer is one of the reflection indices of the second cover layer, and the reflection index value of the other cover layer is one of the reflection indices of the other cover layer; or the reflection index value is an estimated value generated from the reflection index of the first cover layer, an estimated value generated from the reflection index of the second cover layer, and an estimated value generated from the reflection index of the other cover layer. This can achieve the use of the most efficient method at that time to determine the reflection index values of different layers.

[0018] In another possible implementation of the first aspect, the covering structure includes an optically transparent material, so that the display structure is visible to the user of the device.

[0019] In another possible implementation of the first aspect, the structural element and / or the substrate includes an optically transparent material, so that the display structure is visible to the user of the device.

[0020] In another possible implementation of the first aspect, one of the structural element and the substrate includes an inorganic material, and the other of the structural element and the substrate includes an organic material. One of these materials provides hardness, while the other provides flexibility.

[0021] In another possible implementation of the first aspect, the structural element includes an inorganic material and the substrate includes an organic material. The inorganic material provides a relatively hard framework that strengthens the relatively soft and more flexible organic substrate. Accordingly, the relatively flexible organic substrate provides the flexibility required by the relatively hard inorganic framework.

[0022] In another possible implementation of the first aspect, the structural element is a three-dimensional element, and the voids are uniformly distributed in three dimensions, so that the covering element has the same hardness and the same flexibility throughout and has any suitable thickness.

[0023] In another possible implementation of the first aspect, the structural element is a skeletal framework or a grid structure. Compared with a specific impact point, this structure distributes any applied force (e.g., due to impact) over a large area, thus improving the durability of the covering structure.

[0024] In another possible implementation of the first aspect, the substrate includes an incompressible material, so that forces from impacts, etc. can be distributed over the cover layer.

[0025] In another possible implementation of the first aspect, the structural element includes a porous membrane, so that the covering structure can be manufactured simply and efficiently, and thus the display stack can be manufactured.

[0026] In another possible implementation of the first aspect, the structural element includes silicon dioxide, titanium dioxide, aluminum oxide, silicon nitride, silicon oxynitride, and / or silicon oxycarbide, so that the most suitable material can be selected based on individual prerequisites and objectives.

[0027] In another possible implementation of the first aspect, the matrix includes an organic monomer or polymer, and the matrix provides flexibility to the display stack while facilitating simple manufacturing.

[0028] In another possible implementation of the first aspect, the matrix includes a thermoplastic polyurethane-based, a silicone-based elastomer, or a perylene-based polymer, and the matrix provides flexibility to the display stack while facilitating simple manufacturing.

[0029] In another possible implementation of the first aspect, at least one of the matrices includes at least one of the following materials: scratch-resistant material, self-healing material, fingerprint-proof material, and anti-glare material, so as to further improve the durability of the covering structure while also providing multiple characteristics to the display stack.

[0030] In another possible implementation of the first aspect, the flexible display stack includes an antiviral material, and the antiviral material is a separate layer superimposed on the second covering layer or the other covering layer; or the antiviral material is included in the second covering layer or the other covering layer, so that a virus-free display stack can be always maintained, or at least the amount of virus on the surface of the display stack can be reduced.

[0031] According to the second aspect, an electronic device is provided, including the flexible display stack as described above, and the covering structure of the flexible display stack forms the peripheral surface of the electronic device. Such a device has a covering structure (i.e., a hard coating) suitable for different types of bendable displays, such as a slidable display or a rollable display. The covering structure has sufficient flexibility to be bent without cracking, and at the same time has sufficient hardness to provide mechanical protection for the display structure.

[0032] According to a third aspect, a method of manufacturing a flexible display stack is provided, the method comprising the steps of: generating a first cover layer by performing the following operations: depositing a porous and continuous inorganic structural element, coating the structural element with an organic monomer matrix, and curing the matrix; generating a second cover layer by performing the following operations: depositing a porous and continuous inorganic structural element on the first cover layer, coating the structural element with an organic monomer matrix, and curing the matrix.

[0033] The method can manufacture a flexible display stack simply, reliably and efficiently, wherein the inorganic material provides a relatively hard framework that strengthens the relatively soft and more flexible organic matrix. Correspondingly, the relatively flexible organic matrix provides the flexibility required for the relatively hard inorganic framework.

[0034] In a possible implementation of the third aspect, the method further comprises the steps of: generating at least one other cover layer by performing the following operations: depositing a porous and continuous inorganic structural element on the second cover layer, coating the structural element with an organic monomer matrix, and curing the matrix. Using several layers improves the image quality since reflection caused by ambient light as well as internal light from the display structure can be reduced by destructive interference.

[0035] In another possible implementation of the third aspect, the matrix is configured to shrink by ≤2% upon curing such that the shape and volume of the cover structure are not affected and / or do not suffer from internal stress.

[0036] In another possible implementation of the third aspect, the structural element is deposited by a physical deposition method or a chemical deposition method, which are cost-effective and simple.

[0037] In another possible implementation of the third aspect, the deposition method is one of the following methods: pulsed laser deposition, EB deposition, resistive or arc evaporation, sputtering, CVD, PE-CVD, MOCVD, sol-gel and spray pyrolysis, so that the flexible display stack can be manufactured using a series of methods.

[0038] In another possible implementation of the third aspect, the organic monomer matrix is coated onto the structural element by spin coating, slot coating, dipping or vapor phase infiltration, so that the flexible display stack can be manufactured using a series of methods.

[0039] In another possible implementation of the third aspect, the method further comprises the steps of: pretreating the structural element with an adhesion-promoting additive before coating the structural element with the organic monomer matrix, thereby promoting the penetration of the matrix into the voids of the structural element.

[0040] In another possible implementation of the third aspect, the adhesion-promoting additive is a silane, preferably an amino-silane. This additive enhances the wettability of the structural element by forming a nano-layer, thereby improving the coating and leveling properties of other polymers.

[0041] These and other aspects will be apparent in one or more of the embodiments described below. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In the following detailed description of the present invention, various aspects, embodiments, and implementations are explained in more detail with reference to the exemplary embodiments shown in the accompanying drawings, in which:

[0043] Figure 1 A schematic side view of an example of a flexible display stack according to an embodiment of the present invention is shown;

[0044] Figure 2 A schematic side view of a cover structure of an example of a flexible display stack according to an embodiment of the present invention is shown;

[0045] Figure 3a A schematic perspective view of a cover structure of an example of a flexible display stack according to an embodiment of the present invention is shown;

[0046] Figure 3b Shown in more detail Figure 3a A portion of the example shown in

[0047] Figure 4 a to Figure 4 f show schematic side views of method steps for manufacturing a flexible display stack according to an example of an embodiment of the present invention. DETAILED DESCRIPTION

[0048] The present invention relates to an electronic device 2, including a flexible display stack 1 described in further detail below, wherein the cover structure 4 of the flexible display stack 1 forms the peripheral surface of the electronic device 2, i.e., the outer surface that the user contacts by means such as touch. The electronic device 2 can be a smart phone, a wearable device, a tablet computer, a screen for a television or a computer, or any type of electronic device 2 that requires a non-reflective display.

[0049] In addition to the flexible display stack 1, the electronic device 2 may further include a housing (not shown). The flexible display stack 1 may be slidable or rollable relative to the housing, such that the bent portion of the flexible display stack 1 moves in response to the sliding or rolling of the flexible display stack 1 relative to the housing. The housing may include two or more interconnected housing parts, which are interconnected by a hinge, or one housing part is slidably disposed relative to another housing part, such that one housing part slides into and out of another housing part.

[0050] The flexible display stack 1 includes a display structure 3 and a cover structure 4 superimposed on the display structure 3. The cover structure 4 includes a first cover layer 4a and at least a second cover layer 4b superimposed on the first cover layer 4a. The first cover layer 4a includes a continuous structural element 5a, and the continuous structural element 5a includes a plurality of voids 6a and a continuous matrix 7a. The continuous matrix 7a is used to fill the voids 6a and at least partially surround the continuous structural element 5a. The second cover layer 4b includes a continuous structural element 5b, and the continuous structural element 5b includes a plurality of voids 6b and a continuous matrix 7b. The continuous matrix 7b is used to fill the voids 6b and at least partially surround the continuous structural element 5b. The structural element 5a and the matrix 7a of the first cover layer 4a include materials having refractive indices R11, R12 within a first refractive index range R1, and the structural element 5b and the matrix 7b of the second cover layer 4b include materials having refractive indices R21, R22 within a second refractive index range R2.

[0051] As Figure 1 shown, the flexible display stack 1 includes a display structure 3 and a cover structure 4 superimposed on the display structure 3.

[0052] The display structure 3 may include a plurality of discrete layers superimposed (i.e., stacked) on one another, as Figure 1 schematically shown in. For example, the display structure 3 may include an OLED panel layer, a flexible substrate, a polarization layer, and a touch sensor layer.

[0053] The cover structure 4 includes a first cover layer 4a and at least a second cover layer 4b superimposed on the first cover layer 4a. The cover structure 4 may further include at least one other cover layer 4c superimposed on the second cover layer 4b, i.e., the cover structure 4 may include one or several other cover layers 4c superimposed on one another.

[0054] The first cover layer 4a includes a continuous structural element 5a, and the continuous structural element 5a includes a plurality of voids 6a and a continuous matrix 7a. The matrix is a material for encapsulating or embedding something therein (for protection or research). The matrix 7a is used to fill the voids 6a formed within the continuous structural element 5a and at least partially surround the continuous structural element 5a. Correspondingly, the second cover layer 4b also includes a continuous structural element 5b, and the continuous structural element 5b includes a plurality of voids 6b and a continuous matrix 7b. The continuous matrix 7b is used to fill the voids 6b and at least partially surround the continuous structural element 5b. This is schematically shown in Figure 2 in Figure 3a and Figure 3bis shown in more detail in. Similarly, any other overlay 4c includes a continuous structural element 5c, which includes a plurality of voids 6c and a continuous matrix 7c for filling the voids 6c and at least partially surrounding the structural element 5c.

[0055] As Figures 2 to 3b shown, the structural elements 5a, 5b, 5c can be a skeletal framework, or in other words, a grid structure. The structural elements 5a, 5b, 5c are three-dimensional elements, and the voids 6a, 6b, 6c are uniformly distributed in three dimensions and interconnected. The structural elements 5a, 5b, 5c can include a porous membrane.

[0056] The continuous matrices 7a, 7b, 7c are for filling the voids 6a, 6b, 6c and at least partially surrounding the structural elements 5a, 5b, 5c, such that not only are the voids 6a, 6b, 6c filled by the matrices 7a, 7b, 7c, but at least a portion of the outer surfaces of the structural elements 5a, 5b, 5c can be covered by the matrices 7a, 7b, 7c. In other words, the entire structural elements 5a, 5b, 5c can be covered by the matrices 7a, 7b, 7c. The matrices 7a, 7b, 7c are continuous such that all of the matrix material is interconnected as a single entity, even though it surrounds the structural elements 5a, 5b, 5c. The total volume of any defects within the matrices 7a, 7b, 7c can be less than or equal to (≤) 1% of the total volume of the matrices 7a, 7b, 7c, such that the major portion of the matrix is in direct contact with the structural elements 5a, 5b, 5c. Any contact gaps (i.e., defects in the form of air bubbles) would reduce the durability of the overlay.

[0057] The overlay structure 4 can include an optically transparent material. The structural elements 5a, 5b, 5c and / or the matrices 7a, 7b, 7c of the overlay structure 4 can include an optically transparent material. The structural elements 5a, 5b, 5c can include a first material, while the matrices 7a, 7b, 7c can include a second material different from the first material. For each overlay 4a, 4b, 4c, one of the structural elements 5a, 5b, 5c and the matrices 7a, 7b, 7c can include an inorganic material, while the other of the structural elements 5a, 5b, 5c and the matrices 7a, 7b, 7c can include an organic material. In one example, the structural elements 5a, 5b, 5c include an inorganic material, while the matrices 7a, 7b, 7c include an organic material.

[0058] The structural elements 5a, 5b, 5c can include silica, titanium dioxide, alumina, silicon nitride, silicon oxynitride, and / or silicon oxycarbide, or any suitable material that can improve wear resistance.

[0059] The matrices 7a, 7b, 7c may include incompressible materials, and / or the matrices 7a, 7b, 7c may include organic monomers or polymers. More specifically, the matrices 7a, 7b, 7c may include thermoplastic polyurethanes, silicone-based elastomers, or perylene-based polymers. For example, the matrices 7a, 7b, 7c may include silanes or fluorosilanes that provide an anti-fingerprint effect, and a refractive index adjustable resin that provides flexibility and optical properties. The matrices 7a, 7b, 7c may be low-viscosity solutions that do not contain reactive solvents.

[0060] For example, matrices 7a, 7b, 7c that include cellulose nanocrystals (CNC) can form a transparent CNC film when used in combination with structural elements 5a, 5b, 5c that include titanium dioxide. The CNC film may also have a thin layer of titanium dioxide distributed on the top surface.

[0061] In addition, at least one of the matrices 7a, 7b, 7c may include at least one of the following materials: scratch-resistant materials, self-healing materials, anti-fingerprint materials, and anti-glare materials. Preferably, the matrices 7b, 7c of at least the outermost cover layers 4b, 4c include such materials.

[0062] In other words, the matrices 7a, 7b, 7c can be used to restore their initial shape after being scratched or damaged. The scratch-resistant material can be a high tensile modulus polymer. The self-healing material is usually soft and vulnerable to scratching. However, combining such a material with the harder structural elements 5a, 5b, 5c can make the covering structure 4 have sufficient hardness and sufficient flexibility. In addition, the matrices 7a, 7b, 7c can be used to resist stains and reduce reflections.

[0063] In addition, the flexible display stack 1 may include an antiviral material, which is a separate layer superimposed on the second cover layer 4b or other cover layers 4c. In addition, the antiviral material may be included within the second cover layer 4b or other cover layers 4c.

[0064] The substrate on which the structural elements 5a, 5b, 5c and / or the matrices 7a, 7b, 7c are deposited may include polymers, such as polyethylene terephthalate, polyimide, colorless polyimide, glass, or biobased polymers such as cellulose nanocrystals (CNC) or cellulose nanofibers (CNF).

[0065] The structural elements 5a and the matrix 7a of the first cover layer 4a comprise materials having refractive indices R11, R12 within a first refractive index range R1, and the structural elements 5b and the matrix 7b of the second cover layer 4b comprise materials having refractive indices R21, R22 within a second refractive index range R2. Correspondingly, the structural elements 5c and the matrix 7c of the other cover layer 4b comprise materials having refractive indices R31, R32 within a third refractive index range R3. In other words, the structural elements 5a, 5b, 5c comprise materials having refractive indices R11, R21, R31, and the matrices 7a, 7b, 7c comprise materials having refractive indices R12, R22, R32; the refractive indices R11, R12 are within the first refractive index range R1, the refractive indices R21, R22 are within the second refractive index range R2, and the refractive indices R31, R32 are within the third refractive index range R3.

[0066] The difference between the refractive indices R11, R12 within the first refractive index range R1, the difference between the refractive indices R21, R22 within the second refractive index range R2, and the difference between the refractive indices R31, R32 within the third refractive index range R3 can be ≤ 1.2%. Each cover layer 4a, 4b, 4c comprises two materials, namely the structural elements 5a, 5b, 5c and the matrices 7a, 7b, 7c, and the refractive index of one of these materials can differ from the refractive index of the other of these two materials by at most 1.2% to avoid blurring.

[0067] The difference between the first refractive index range R1, the second refractive index range R2 and / or the other refractive index range R3 can be ≤ 18%. In other words, the refractive index used in one layer can differ from the refractive index used in another layer by at most 18%.

[0068] Each of the voids 6a, 6b, 6c of the structural elements 5a, 5b, 5c can have a volume corresponding to λ / (2×R), where λ is the wavelength of the radiation emitted by the display structure 3 itself or the incident radiation from the outside, such as sunlight or light from a lamp. R is the refractive index value representing the first refractive index range R1, the second refractive index range R2 or the third refractive index range R3. For example, the width, possible diameter of the void can be as small as 200 nm to 250 nm.

[0069] The reflection index value R of the first cover layer 4a can be one of the reflection indices R11, R12, or can be an estimated value (i.e., the effective reflection index) generated from the reflection indices R11, R12. For example, this estimated value can be calculated as the average of the reflection index value R11 and the reflection index value R12. Correspondingly, the reflection index value R of the second cover layer 4b can be one of the reflection indices R21, R22, or can be an estimated value generated from the reflection indices R21, R22. Similarly, the reflection index value R of other cover layers 4c can be one of the reflection indices R31, R32, or can be an estimated value generated from the reflection indices R31, R32.

[0070] The present invention also relates to a method of manufacturing a flexible display stack 1. The method includes the following steps: generating a first cover layer 4a by performing the following operations (see Figure 4 c): depositing a porous and continuous inorganic structural element 5a (see Figure 4 a), coating the structural element 5a with an organic monomer matrix 7a (see Figure 4 b), and curing the matrix 7a such that the structural element 5a and the matrix 7a together form the first cover layer 4a. The method further includes the following subsequent steps: generating a second cover layer 4b by performing the following operations (see Figure 4 f): depositing a porous and continuous inorganic structural element 5b on the first cover layer 4a (see Figure 4 d), coating the structural element 5b with an organic monomer matrix 7b (see Figure 4 e), and curing the matrix 7b such that the structural element 5b and the matrix 7b together form the second cover layer 4b, and the first cover layer 4a and the second cover layer 4b together form the cover structure 4.

[0071] The method may further include other steps: generating at least one other cover layer 4c (not shown) by performing the following operations: depositing a porous and continuous inorganic structural element 5c on the second cover layer 4b, coating the structural element 5c with an organic monomer matrix 7c, and curing the matrix 7c such that the structural element 5c and the matrix 7c together form the other cover layer 4c, and the first cover layer 4a, the second cover layer 4b, and any other cover layer 4c together form the cover structure 4.

[0072] In other words, the structural elements 5a, 5b, 5c are filled with organic monomer matrices 7a, 7b, 7c, and the organic monomer matrices 7a, 7b, 7c completely penetrate and fill the voids 6a, 6b, 6c of the structural elements 5a, 5b, 5c. The voids 6a, 6b, 6c are interconnected, thus forming a network of cavities and channels composed of the voids 6a, 6b, 6c and the interconnecting conduits, such that the matrices 7a, 7b, 7c can fill the entire network and form an integral element. The voids 6a, 6b, 6c may have a spherical or irregular three-dimensional shape, and the channels may have a cylindrical shape.

[0073] The matrices 7a, 7b, 7c can be used to shrink by ≤2% upon curing.

[0074] The structural elements 5a, 5b, 5c can be deposited by physical deposition methods or chemical deposition methods. The deposition method can be one of the following methods: pulsed laser deposition, EB deposition, resistive or arc evaporation, sputtering, CVD, PE-CVD, MOCVD, sol-gel, and spray pyrolysis.

[0075] The organic monomer matrices 7a, 7b, 7c can be coated onto the structural elements 5a, 5b, 5c by spin coating, slot coating, dipping, or vapor phase infiltration coating.

[0076] The method can also include an intermediate step, i.e., before coating the structural elements 5a, 5b, 5c with the organic monomer matrices 7a, 7b, 7c (i.e., between the steps shown in Figure 4 a and Figure 4 d and the other steps shown in Figure 4 b and Figure 4 e), pretreating the structural elements 5a, 5b, 5c with an adhesion-promoting additive. The adhesion-promoting additive promotes the penetration of the matrices 7a, 7b, 7c into the voids 6a, 6b, 6c of the structural elements 5a, 5b, 5c. The adhesion-promoting additive can be a silane, preferably an amino silane, and forms a nano-layer on the structural elements 5a, 5b, 5c.

[0077] Various aspects and implementations have been described in connection with various embodiments. However, those skilled in the art, when practicing the claimed subject matter, can understand and implement other variations of the disclosed embodiments by studying the drawings, the present invention, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and "a" or "an" does not exclude a plurality. Listing some measures in mutually different dependent claims does not mean that a combination of these measures cannot be used to obtain advantages.

[0078] The reference signs used in the claims shall not be construed as limiting the scope. Unless otherwise specified, the drawings (e.g., cross-hatching, component arrangements, scale, degrees, etc.) shall be read in conjunction with the description and shall be considered part of the whole written description of the invention. The terms "horizontal", "vertical", "left", "right", "up" and "down" and their adjectival and adverbial derivatives (e.g., "horizontally", "rightward", "upward", etc.) as used herein refer only to the orientation of the structures shown when the particular drawing is facing the reader. Similarly, the terms "inward" and "outward" generally refer to the direction of a surface relative to its elongation axis or axis of rotation, as appropriate.

Claims

1. A flexible display stack (1) for an electronic device (2), characterized in that, it comprises: a display structure (3); a cover structure (4) superimposed on the display structure (3); the cover structure (4) includes a first cover layer (4a) and at least includes a second cover layer (4b) superimposed on the first cover layer (4a); the first cover layer (4a) includes a continuous structural element (5a), the continuous structural element (5a) includes a plurality of voids (6a) and a continuous matrix (7a), the continuous matrix (7a) is used to fill the voids (6a) and at least partially surround the continuous structural element (5a); the second cover layer (4b) includes a continuous structural element (5b), the continuous structural element (5b) includes a plurality of voids (6b) and a continuous matrix (7b), the continuous matrix (7b) is used to fill the voids (6b) and at least partially surround the continuous structural element (5b), wherein, the structural element (5a) and the matrix (7a) of the first cover layer (4a) include materials having refractive indices (R11, R12) within a first refractive index range (R1); the structural element (5b) and the matrix (7b) of the second cover layer (4b) include materials having refractive indices (R21, R22) within a second refractive index range (R2).

2. The flexible display stack (1) according to claim 1, characterized in that, the cover structure (4) includes at least one other cover layer (4c) superimposed on the second cover layer (4b), the other cover layer (4c) includes a continuous structural element (5c), the continuous structural element (5c) includes a plurality of voids (6c) and a continuous matrix (7c), the continuous matrix (7c) is used to fill the voids (6c) and at least partially surround the structural element (5c), the structural element (5c) and the matrix (7c) of the other cover layer (4c) include materials having refractive indices (R31, R32) within a third refractive index range (R3).

3. The flexible display stack (1) according to claim 1 or 2, characterized in that, the structural elements (5a, 5b, 5c) include materials having refractive indices (R11, R21, R31), and the matrices (7a, 7b, 7c) include materials having refractive indices (R12, R22, R32); the refractive indices (R11, R12) are within the first refractive index range (R1); the refractive indices (R21, R22) are within the second refractive index range (R2), and the refractive indices (R31, R32) are within the third refractive index range (R3).

4. The flexible display stack (1) according to any one of the above claims, characterized in that, The differences between the reflection indices (R11, R12) within the first reflection index range (R1), the differences between the reflection indices (R21, R22) within the second reflection index range (R2), and the differences between the reflection indices (R31, R32) within the third reflection index range (R3) are all ≤ 1.2%.

5. The flexible display stack (1) according to any one of the above claims, wherein, the difference between the first reflection index range (R1), the second reflection index range (R2), and / or the third reflection index range (R3) is ≤ 18%.

6. The flexible display stack (1) according to any one of the above claims, wherein, the voids (6a, 6b, 6c) of each structural element (5a, 5b, 5c) have a volume corresponding to λ / (2×R), where λ is the wavelength of the radiation, the radiation is emitted by the display structure (3) or is incident radiation from the outside, and R is the reflection index value representing the first reflection index range (R1), the second reflection index range (R2), or the third reflection index range (R3).

7. The flexible display stack (1) according to claim 6, wherein, the reflection index value (R) of the first cover layer (4a) is one of the reflection indices (R11, R12), the reflection index value (R) of the second cover layer (4b) is one of the reflection indices (R21, R22), and the reflection index value (R) of the other cover layer (4c) is one of the reflection indices (R31, R32); or the reflection index value (R) is an estimated value generated by the reflection index (R11, R12) of the first cover layer (4a), an estimated value generated by the reflection index (R21, R22) of the second cover layer (4b), and an estimated value generated by the reflection index (R31, R32) of the other cover layer (4c).

8. The flexible display stack (1) according to any one of the above claims, wherein, one of the structural elements (5a, 5b, 5c) and the substrates (7a, 7b, 7c) comprises an inorganic material, and the other of the structural elements (5a, 5b, 5c) and the substrates (7a, 7b, 7c) comprises an organic material.

9. The flexible display stack (1) according to any one of the above claims, wherein, the structural elements (5a, 5b, 5c) comprise porous membranes.

10. The flexible display stack (1) according to claim 8 or 9, wherein, the structural elements (5a, 5b, 5c) comprise silicon dioxide, titanium dioxide, aluminum oxide, silicon nitride, silicon oxynitride, and / or silicon oxycarbide.

11. The flexible display stack (1) according to any one of claims 8 to 10, wherein, the substrates (7a, 7b, 7c) comprise organic monomers or polymers.

12. The flexible display stack (1) according to any one of claims 8 to 11, characterized in that, the substrates (7a, 7b) comprise thermoplastic polyurethane, silicone-based elastomers or perylene-based polymers.

13. The flexible display stack (1) according to any one of the above claims, characterized in that, at least one of the substrates (7a, 7b, 7c) comprises at least one of the following materials: scratch-resistant material, self-healing material, fingerprint-proof material and anti-glare material.

14. The flexible display stack (1) according to any one of the above claims, characterized in that, it comprises an antiviral material, which is a separate layer superimposed on the second cover layer (4b) or the other cover layer (4c); or the antiviral material is included in the second cover layer (4b) or the other cover layer (4c).

15. An electronic device (2), characterized in that, it comprises the flexible display stack (1) according to any one of claims 1 to 14, and the cover structure (4) of the flexible display stack (1) forms the peripheral surface of the electronic device (2).

16. A method for manufacturing a flexible display stack (1), characterized in that, the method comprises the following steps: generating a first cover layer (4a) by performing the following operations: depositing a porous and continuous inorganic structural element (5a); coating the structural element (5a) with an organic monomer matrix (7a); curing the matrix (7a); generating a second cover layer (4b) by performing the following operations: depositing a porous and continuous inorganic structural element (5b) on the first cover layer (4a); coating the structural element (5b) with an organic monomer matrix (7b); curing the matrix (7b).

17. The method according to claim 16, characterized in that, it further comprises the following steps: generating at least one other cover layer (4c) by performing the following operations: depositing a porous and continuous inorganic structural element (5c) on the second cover layer (4b); coating the structural element (5c) with an organic monomer matrix (7c); curing the matrix (7c).

18. The method according to claim 16 or 17, characterized in that, the matrix (7a, 7b, 7c) is used to shrink ≤ 2% during curing.

19. The method according to any one of claims 16 to 18, characterized in that, the structural element (5) is deposited by a physical deposition method or a chemical deposition method.

20. The method according to claim 19, characterized in that, the deposition method is one of the following methods: pulsed laser deposition, EB deposition, resistive or arc evaporation, sputtering, CVD, PE-CVD, MOCVD, sol-gel and spray pyrolysis.

21. The method according to any one of claims 16 to 20, characterized in that, the organic monomer matrix (7a, 7b, 7c) is coated onto the structural element (5a, 5b, 5c) by spin coating, slot coating, dipping or vapor phase infiltration coating.

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