Foldable display device

Abstract

A foldable display device includes a display panel, a cover window over the display panel, and a first layer between the display panel and the cover window, the first layer having a storage modulus that is lower than a storage modulus of the cover window.

Description

Technical Field

[0001] The present disclosure relates to a foldable display device, and more particularly, to a foldable display device that can reduce durability defects. Background Art

[0002] As society develops toward an information-oriented society, various display devices that process and display large amounts of information have been developed. There are various types of display devices that display images, such as liquid crystal display devices (LCDs), organic light emitting display devices (OLEDs), and electrophoretic display devices (EPDs).

[0003] Users who use display devices to watch broadcasts, videos, or play video games often prefer portable display devices with large screens. However, when the screen of a portable display device is enlarged, its portability deteriorates. Therefore, there are limits to how much the screen can be enlarged. To improve this portability, research is actively underway on foldable display devices with foldable display panels. Summary of the Invention

[0004] As folding and unfolding of the foldable display device are repeated, durability defects such as peeling of an organic light emitting layer of the display panel or cracks in a protective portion provided on the display panel occur.

[0005] Therefore, the inventors of the present disclosure have invented a foldable display device that can reduce folding durability defects.

[0006] An aspect of the present disclosure is to provide a foldable display device in which durability defects such as peeling of an organic light emitting layer or cracks in a protective portion can be reduced.

[0007] Additional features and aspects will be set forth in the following description and, in part, will become apparent from the description, or may be learned by practicing the inventive concepts provided herein. Other features and aspects of the inventive concepts may be realized and obtained by the structures particularly pointed out in the written description or the description derived therefrom, as well as in the claims and drawings.

[0008] To achieve these and other aspects of the inventive concept as embodied and broadly described, a foldable display device includes a display panel, a cover window on the display panel, and a first layer between the display panel and the cover window, the first layer having a storage modulus lower than that of the cover window.

[0009] In another aspect, a foldable display device includes a first layer between a display panel and a cover window, wherein the first layer has a storage modulus lower than that of the cover window. Furthermore, the foldable display device may further include a protective portion disposed between the display panel and the cover window, wherein a first surface of the protective portion includes a first recessed portion that overlaps with a folding axis of the foldable region, and a second surface of the protective portion opposite the first surface includes at least two or more second recessed portions, wherein the at least two or more second recessed portions are spaced apart from each other on either side of the folding axis.

[0010] On the other hand, a foldable display device includes a protective portion between a display panel and a cover window, a first layer at a lower surface of the protective portion, and a second layer at an upper surface of the protective portion, the lower surface of the protective portion including a first recess overlapping with a folding axis, and the upper surface of the protective portion including at least a pair of second recesses spaced apart from each other at both sides of the folding axis.

[0011] On the other hand, a foldable display device includes: a display panel, the display panel including a display area, a non-display area at the periphery of the display area, and a foldable area overlapping with a portion of the display area and a portion of the non-display area; a cover window on the display panel; a protective portion between the display panel and the cover window; a first layer at a first surface of the protective portion; and a second layer at a second surface of the protective portion opposite to the first surface, wherein the first surface of the protective portion includes a first recess overlapping with a folding axis of the foldable area, and wherein the second surface of the protective portion includes at least two or more second recesses, and the at least two or more second recesses are spaced apart from each other on both sides of the folding axis.

[0012] On the other hand, a foldable display device includes: a display panel; a cover window on the display panel; a protective portion between the display panel and the cover window; a light blocking layer at a peripheral portion of a lower surface of the cover window; and a first layer at the lower surface of the cover window to cover the light blocking layer, wherein the first layer is located above the protective portion and has a storage modulus lower than that of the cover window.

[0013] According to an embodiment of the present disclosure, the first layer may be provided between the display panel and the cover window, thereby obtaining a foldable display device in which durability defects such as peeling of the organic light emitting layer of the display panel may be reduced.

[0014] According to an embodiment of the present disclosure, a first recess overlapping with a folding axis and at least a pair of second recesses spaced apart at both sides relative to the folding axis are provided, thereby obtaining a foldable display device in which durability defects such as cracks in a protective portion can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings, which are included to provide a further understanding of the present disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the present disclosure and together with the description serve to explain the principles of the present disclosure.

[0016] Figure 1 is a perspective view illustrating a display device according to an embodiment of the present disclosure.

[0017] Figures 2 to 4 is a cross-sectional view illustrating a display device cut along line I-I' in Figure 1 of FIG. 1.

[0018] Figure 5 shows simulation results of stress distribution of a display panel of a display device according to an embodiment of the present disclosure.

[0019] Figures 6 to 8 is a cross-sectional view illustrating a display device cut along line I-I' in Figure 1 of FIG. 1.

[0020] Figure 9 and Figure 10 shows a first layer according to an embodiment of the present disclosure.

[0021] Figure 11 and Figure 12 respectively show a first layer covering a light blocking layer and a method of manufacturing the same.

[0022] Figure 13 is a cross-sectional view illustrating a foldable display device cut along line I-I' in Figure 1 of FIG. 1.

[0023] Figure 14 and Figure 15 respectively are cross-sectional and plan views illustrating a protection portion cut along line II-II' in Figure 1 of FIG. 1.

[0024] Figure 16 , Figure 17 (a) of FIG. 1 and Figure 17 (b) of FIG. 1 show stress simulation results of a protection portion according to an embodiment of the present disclosure.

[0025] Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numbers should be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements can be exaggerated for clarity, illustration, and convenience. DETAILED DESCRIPTION

[0026] Reference will now be made in detail to embodiments of the present disclosure, examples of which may be shown in the accompanying drawings. In the following description, detailed descriptions of known functions or configurations associated with this document will be omitted when they are determined to unnecessarily obscure the main points of the inventive concept. The described progression of processing steps and / or operations are examples; however, except for steps and / or operations that must occur in a particular order, the order of steps and / or operations is not limited to the order set forth herein and may be changed as known in the art. Throughout the text, the same reference numerals indicate the same elements. The names of the corresponding elements used in the following description are selected only for the convenience of writing the specification and may therefore be different from the names of the elements used in the actual product.

[0027] The shapes, sizes, ratios, angles, numbers, etc. disclosed in the accompanying drawings for describing the embodiments of the present disclosure are exemplary, and the present disclosure is not limited thereto. The same reference numerals herein refer to the same elements. In addition, for simplicity of description, descriptions and details of well-known steps and elements are omitted. In addition, in the following detailed description of the present disclosure, many specific details are set forth in order to provide a comprehensive understanding of the present disclosure. However, it should be understood that the present disclosure can be practiced without these specific details. In other cases, well-known methods, processes, components and circuits are not described in detail to avoid unnecessarily obscuring various aspects of the present disclosure.

[0028] The terms used herein are only directed to the purpose of describing a specific embodiment, and are not intended to limit the present disclosure. As used herein, the singular formation "one" and "an" are equally intended to include plural formations, unless the context clearly indicates otherwise. It should also be understood that the terms "comprise (comprise)", "comprising (comprising)", "include (include)" and "including (including)" specify the presence of stated features, integers, operations, elements and / or parts when used in this specification, but do not exclude the presence or addition of one or more other features, integers, operations, elements, parts and / or parts thereof. As used herein, the term "and / or" includes any and all combinations of one or more of the items listed in association. Expressions such as "at least one" can modify the entire element list when appearing before a column of elements, and may not modify the individual elements in the list. In the interpretation of numerical value, errors or tolerances therein can also occur even when there is no clear description thereof.

[0029] In addition, it should be understood that when a first element or layer is referred to as being "on" a second element or layer, the first element can be directly disposed on the second element, or can be indirectly disposed on the second element, wherein a third element or layer is disposed between the first element or layer and the second element or layer. It should be understood that when an element or layer is referred to as being "connected to" or "coupled to" another element or layer, it can be directly on the other element or layer, connected to or coupled to the other element or layer, or one or more intermediate elements or layers can exist. In addition, it should be understood that when an element or layer is referred to as being "between two elements or layers," it can be the only element or layer between the two elements or layers, or one or more intermediate elements or layers can also exist.

[0030] In addition, as used herein, when a layer, film, region, plate, etc. is disposed “on” or “on top” of another layer, film, region, plate, etc., the former may directly contact the latter, or another layer, film, region, plate, etc. may be disposed between the former and the latter. As used herein, when a layer, film, region, plate, etc. is disposed directly “on” or “on top” of another layer, film, region, plate, etc., the former may directly contact the latter, and another layer, film, region, plate, etc. may not be disposed between the former and the latter. In addition, as used herein, when a layer, film, region, plate, etc. is disposed “below” or “under” another layer, film, region, plate, etc., the former may directly contact the latter, or another layer, film, region, plate, etc. may be disposed between the former and the latter. As used herein, when a layer, film, region, plate, etc. is disposed directly “below” or “under” another layer, film, region, plate, etc., the former may directly contact the latter, and another layer, film, region, plate, etc. may not be disposed between the former and the latter.

[0031] When describing a temporal relationship, for example, a temporal precedent relationship between two events, such as "after", "followed by", "before", etc., another event may appear in between unless it is specified "directly after", "directly followed by", or "directly before".

[0032] It should be understood that although the terms "first," "second," "third," etc. may be used herein to describe various elements, components, regions, layers, and / or portions, these elements, components, regions, layers, and / or portions should not be limited by these terms. These terms are used to distinguish one element, component, region, layer, or portion from another element, component, region, layer, or portion. Thus, a first element, component, region, layer, or portion described below may be referred to as a second element, component, region, layer, or portion without departing from the spirit and scope of the present disclosure.

[0033] As will be fully appreciated by those skilled in the art, the features of the various embodiments of the present disclosure may be coupled or combined with each other in part or in whole, and may interoperate with each other and be technically driven in various ways. The embodiments of the present disclosure may be performed independently of each other, or may be performed together in a mutually dependent relationship.

[0034] As used herein, the terms "substantially," "about," and similar terms are used as approximate terms and are intended to account for the inherent deviations in measurements or calculations that one of ordinary skill in the art would recognize. The terms may be used to prevent unauthorized exploitation by unauthorized infringers that designs around exact or absolute numbers provided to aid in understanding the present disclosure.

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention pertains. It should also be understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0036] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. For ease of description, the proportions of each of the elements shown in the drawings are different from the actual proportions and are therefore not limited to the proportions shown in the drawings.

[0037] Figure 1 is a perspective view illustrating a foldable display device according to an embodiment of the present disclosure.

[0038] Reference Figure 1 According to an embodiment of the present disclosure, the foldable display device 100 may include a display area AA, a non-display area NA, and a foldable area. The display area AA may be an area where an image is displayed. The non-display area NA is located at the periphery of the display area AA, and the non-display area NA may be an area where no image is displayed. The foldable area is disposed at and around the folding axis Fx, and the foldable area may be an area overlapping with a portion of the display area AA and a portion of the non-display area NA. For example, when the foldable display device 100 is folded in an inward or outward folding manner, the foldable area may be bent with a predetermined curvature. The area outside the foldable area may be a non-foldable area. In addition, the foldable display device 100 may further include a housing configured to support and accommodate a display panel and a hinge structure configured to fold the display panel.

[0039] Figure 2 is a diagram showing an embodiment according to the present disclosure Figure 1a cross-sectional view of a foldable display device cut by I-I' lines in FIG. 1.

[0040] Referring to Figure 2 A foldable display device 100 according to an embodiment of the disclosure can include a display panel 120, a support structure 110, a polarizing plate 130, a protection substrate 140, a light blocking layer (or a light shielding layer) 150, a first layer 170, and a cover window 190.

[0041] The display panel 120 can display an image. The display panel 120 can be flexible and can display an image to a user. For example, the display panel 120 can be implemented as an organic light emitting display panel. Embodiments of the disclosure are not limited thereto. The display panel 120 can have various types, such as a liquid crystal display panel, an electrophoretic display panel, etc. When the display panel 120 is implemented as an organic light emitting display panel, the display panel 120 can include a substrate, a thin film transistor array having a thin film transistor (including a switching thin film transistor and a driving thin film transistor) for each pixel on the substrate, an organic light emitting layer having an organic light emitting element connected to the driving thin film transistor for each pixel, and an encapsulation layer covering the organic light emitting layer to prevent moisture and oxygen from penetrating into the organic light emitting layer from the outside. The display panel can further include an array of contact electrodes on the encapsulation layer.

[0042] The support structure 110 can be configured to support the display panel 120. The support structure 110 can include at least one or more support layers. The support layers can be attached to the display panel 120 using an adhesive layer. The support layers have a greater rigidity than that of the display panel 120. For example, the support layers can be formed of a metal material such as stainless steel (SUS), or can be formed of a polymer such as polymethylmethacrylate (PMMA), polycarbonate (PC), polyacrylate (PA), polyvinylalcohol (PVA), acrylonitrile-butadiene-styrene (ABS), or polyethyleneterephthalate (PET). Embodiments of the disclosure are not limited thereto. The support structure 110 can have a structure in which the at least one or more support layers are joined or attached to each other by the adhesive layer. When the display device according to an embodiment of the disclosure is implemented as a foldable display device, a plurality of folding patterns can be formed at the at least one or more support layers among the support layers and in a discontinuous form and in a region corresponding to a foldable region. The folding patterns can include holes or slits passing through the support layers. Embodiments of the disclosure are not limited thereto.

[0043] The polarizing plate 130 may be configured to ensure visibility of the display panel 120. For example, the polarizing plate 130 may include a polarizer and a retardation film disposed on one surface of the polarizer.

[0044] The light blocking layer 150 can be configured to allow the peripheral portion of the display panel 120, such as the driving circuit, various wirings and pads in the non-display area NA, to be invisible to the user. For example, the light blocking layer 150 can be provided on the peripheral portion of one surface of the protective substrate 140. The protective substrate 140 may include a flexible polymer film such as polyimide (PI), polyethylene terephthalate (PET), propylene glycol (PPG) and polycarbonate (PC). The embodiments of the present disclosure are not limited thereto. The light blocking layer 150 can be provided in the non-display area NA. The light blocking layer 150 can be formed on the peripheral portion of one surface of the protective substrate 140. The light blocking layer 150 can be formed in a ring shape. For example, the light blocking layer 150 can be formed by printing black ink using a printing method. The embodiments of the present disclosure are not limited thereto.

[0045] The cover window 190 may include a polymer film. For example, the polymer film may be transparent. The polymer film may include polyethylene terephthalate (PET), colorless polyimide (PI), or a stack of polyethylene terephthalate (PET) and colorless polyimide (PI). The cover window 190 may also include a hard coating layer formed on the transparent polymer film. For example, the hard coating layer may be transparent.

[0046] The organic light emitting layer of the display panel 120 may be peeled due to compressive stress repeatedly applied to the upper portion of the display panel 120 during repeated folding and unfolding of the foldable display device.

[0047] According to an embodiment of the present disclosure, the first layer 170 may be configured to reduce the stress applied to the display panel 120. The first layer 170 may be formed at the lower surface of the cover window 190 or may be bonded to the lower surface of the cover window 190 through an adhesive layer. For example, the first layer 170 may be directly coated on the lower surface of the cover window 190. For example, the adhesive layer may be an optically transparent adhesive layer. In order to reduce the compressive stress applied to the upper portion of the display panel 120 during folding of the device, the first layer 170 may have a storage modulus lower than that of the cover window 190. For example, the first layer 170 may include a 1×10 7 Pa to 9×10 8When the storage modulus of the first layer 170 is equal to or greater than the storage modulus of the cover window 190, for example, the storage modulus of the first layer 170 is greater than or equal to 1×10 9 When Pa is increased, the compressive stress applied to the cover window 190, for example, the hard coating layer of the cover window 190, increases. As a result, cracks may appear in the cover window 190, for example, in the hard coating layer of the cover window 190. In addition, the organic light-emitting layer of the display panel 120 may be peeled off due to the increase in compressive stress. For example, the storage modulus may refer to the amount of elastic energy accumulated in a vibrating sample. The storage modulus may be a dynamic modulus. In addition, the polymer material that may be included in the first layer 170 may have a Poisson's ratio in the range of 0.38 to 0.43. When the Poisson's ratio of the polymer material that may be included in the first layer 170 is lower than 0.38, the compressive stress applied to the hard coating layer of the cover window 190 may increase, so that cracks may appear in the hard coating layer of the cover window 190. The first layer 170 may include, for example, a silicone-based, urethane-based, epoxy-based, or acrylic-based polymer. For example, the first layer may be a stress reducing layer or a buffer layer. The embodiments of the present disclosure are not limited thereto.

[0048] The thickness of the first layer 170 may be 30 μm to 100 μm. When the thickness of the first layer 170 is less than 30 μm, the effect of reducing the compressive stress applied to the upper portion of the display panel 120 during folding of the device is small or insignificant, so that the light-emitting layer or the organic light-emitting layer of the display panel 120 may be peeled off, and thus the effect of improving the puncture strength may be small or insignificant. The display device to which the first layer 170 is not applied has a puncture strength of 4.0 kgF. When the thickness of the first layer 170 is greater than 100 μm, the compressive stress applied to the hard coating layer of the cover window 190 may increase, so that cracks may appear in the hard coating layer of the cover window 190.

[0049] In addition, the display device 100 according to an embodiment of the present disclosure may include at least one or more adhesive layers. For example, the at least one or more adhesive layers may include a first adhesive layer 115, a second adhesive layer 125, a third adhesive layer 135, and a fourth adhesive layer 145. The first adhesive layer 115 may bond the support structure 110 and the display panel 120 to each other. The second adhesive layer 125 may bond the display panel 120 and the polarizing plate 130 to each other. The third adhesive layer 135 may bond the polarizing plate 130 and the protective substrate 140 to each other. The fourth adhesive layer 145 may bond the protective substrate 140 and the first layer 170 to each other. Each of the first adhesive layer 115 to the fourth adhesive layer 145 may include an optically transparent adhesive (OCA). The embodiments of the present disclosure are not limited thereto.

[0050] According to an embodiment of the present disclosure, first layer 170 is provided on the lower surface of cover window 190, thereby reducing the compressive stress applied to the upper portion of display panel 120 during folding of the device. Therefore, foldable display device 100 according to an embodiment of the present disclosure can reduce the defect of the organic light-emitting layer of display panel 120 being peeled off even when the device is folded and unfolded repeatedly. Furthermore, the addition of first layer 170 can increase the puncture strength of foldable display device 100. For example, due to the configuration of first layer 170, the display device can have a puncture strength of 6.0 kgF to 7.0 kgF.

[0051] Figure 3 is a diagram showing an embodiment according to the present disclosure Figure 1 FIG. 1 is a cross-sectional view of the foldable display device 100 - 1 cut along line II′ in FIG. 1 .

[0052] Reference Figure 3 , the foldable display device 100-1 according to an embodiment of the present disclosure may include a first layer 170 provided at the lower surface of the protective substrate 140. In an embodiment of the present disclosure, components other than the first layer 170 may be provided with Figure 2 The components of the embodiments of the present invention are substantially the same. Therefore, repeated description thereof may be omitted.

[0053] The first layer 170 may be formed on the lower surface of the protective substrate 140 or bonded to the lower surface of the protective substrate 140 through an adhesive layer. For example, the first layer 170 may be directly coated on the lower surface of the protective substrate 140. For example, the adhesive layer may be an optically transparent adhesive layer.

[0054] First layer 170 is provided on the lower surface of protective substrate 140, thereby reducing the compressive stress applied to the upper portion of display panel 120 during folding of the device. Therefore, foldable display device 100-1 according to an embodiment of the present disclosure can reduce the risk of the organic light-emitting layer of display panel 120 being peeled off even when the device is repeatedly folded and unfolded. Furthermore, the configuration of first layer 170 can increase the puncture strength of foldable display device 100-1. For example, due to the configuration of first layer 170, the display device can have a puncture strength of 6.0 to 7.0 kgF.

[0055] Figure 4 is a diagram showing an embodiment according to the present disclosure Figure 1 A cross-sectional view of the foldable display device cut along line I-I'.

[0056] Reference Figure 4, the foldable display device 100-2 according to an embodiment of the present disclosure may include a first layer 170 provided on the upper surface of the display panel 120. In this embodiment, components other than the first layer 170 are Figure 2 Therefore, repeated description thereof will be omitted.

[0057] The first layer 170 may be formed on the upper surface of the display panel 120 or bonded to the upper surface of the display panel 120 via an adhesive layer. For example, the first layer 170 may be directly coated on the upper surface of the display panel 120. For example, the adhesive layer may be an optically transparent adhesive layer.

[0058] First layer 170 is provided on the upper surface of display panel 120, thereby reducing the compressive stress applied to the top of display panel 120 during folding of the device. Therefore, foldable display device 100-2 according to an embodiment of the present disclosure can reduce the defect of the organic light-emitting layer of display panel 120 being peeled off even when the device is folded and unfolded repeatedly. Furthermore, the addition of first layer 170 can increase the puncture resistance of foldable display device 100-2.

[0059] Figure 5 Shown are simulation results of stress applied to a display panel of a foldable display device according to an embodiment of the present disclosure.

[0060] exist Figure 5 In the comparative example, there is no first layer of the foldable display device, and the embodiment 1 is Figure 2 The foldable display device 100 shown in FIG, and embodiment 2 is Figure 3 The foldable display device 100-1 shown in FIG, and embodiment 3 is Figure 4 The foldable display device 100-2 shown in FIG.

[0061] Reference Figure 5 , it can be identified that compressive stress is applied to the upper portion of the display panel during folding the device inward. Due to the compressive stress, when the folding durability is evaluated by repeatedly performing folding and unfolding of the foldable display device, peeling of the organic light-emitting layer may occur in the comparative example. However, it can be identified that in embodiments 1 to 3, the compressive stress applied to the upper portion of the display panel is reduced compared to the comparative example. In the comparative example, the compressive stress applied to the upper portion of the display panel may be approximately -33 MPa. In embodiment 1, the compressive stress applied to the upper portion of the display panel may be approximately -21 MPa. In embodiment 2, the compressive stress applied to the upper portion of the display panel may be approximately -17.4 MPa. In embodiment 3, the compressive stress applied to the upper portion of the display panel may be approximately -15.5 MPa.

[0062] The simulation results indicate that when the first layer is positioned between the cover window and the display panel, the compressive stress applied to the upper portion of the display panel during folding of the device (e.g., folding the device inward) is reduced. Furthermore, the simulation results indicate that the compressive stress applied to the upper portion of the display panel decreases as the first layer approaches the display panel. The simulation results can be used in conjunction with the folding durability evaluation results. For example, delamination of the organic light-emitting layer can be reduced or prevented when evaluating the durability of the device.

[0063] Figures 6 to 8 is a diagram showing an embodiment according to the present disclosure Figure 1 A cross-sectional view of the foldable display device cut along line I-I'.

[0064] Reference Figure 6 The foldable display device 100-3 according to an embodiment of the present disclosure includes a protective portion 141 instead of a protective substrate 140, and the foldable display device 100-3 may include a light blocking layer 150 at a peripheral portion of a lower surface of a cover window 190. A first layer 170 may be formed at the lower surface of the cover window 190 to cover the light blocking layer 150. For example, the first layer 170 may be directly coated at the lower surface of the cover window 190 to cover the light blocking layer 150.

[0065] In an embodiment of the present disclosure, components other than the protection portion 141 and the light blocking layer 150 may be Figure 2 The components of the embodiments of the present invention are substantially the same, and therefore repeated description thereof may be omitted. The protection portion 141 may be made of glass. For example, the protection portion 141 may be implemented as a protection window, a protection glass, or a cover glass. Figure 6 As shown, the first layer 170 may be located above the protection portion 141. The embodiments of the present disclosure are not limited thereto.

[0066] In order to satisfy or ensure strength characteristics and folding characteristics, the protection portion 141 may have a thickness of 30 μm to 200 μm. For example, the protection portion 141 may have a uniform thickness over its entire area.

[0067] Reference Figure 7 The foldable display device 100-4 according to an embodiment of the present disclosure may include a first layer 170 provided at the lower surface of the protection portion 141. The light blocking layer 150 formed at the outer peripheral portion of the lower surface of the cover window 190 may be covered with a fourth adhesive layer 145 for bonding or attaching the cover window 190 and the protection portion 141 to each other.

[0068] Reference Figure 8The foldable display device 100-5 according to an embodiment of the present disclosure may include a first layer 170 provided on the upper surface of the display panel 120. The first layer 170 may be formed on the upper surface of the display panel 120 or bonded to the upper surface of the display panel 120 through an adhesive layer. For example, the first layer 170 may be directly coated on the upper surface of the display panel 120. For example, the adhesive layer may be an optically transparent adhesive layer.

[0069] The first layer 170 is disposed between the cover window 190 and the display panel 120, for example, as shown in FIG. Figure 6 The first layer 170 shown in the embodiment is provided at the lower surface of the cover window 190, or as Figure 7 The first layer 170 shown in the embodiment is provided at the lower surface of the protection portion 141, or as Figure 8 The first layer 170 shown in the embodiment of the present disclosure is provided on the upper surface of the display panel 120, thereby reducing the compressive stress applied to the upper portion of the display panel 120 during folding of the device. Therefore, each of the foldable display devices 100-3, 100-4, and 100-5 according to the embodiment of the present disclosure can reduce the defect of the organic light emitting layer of the display panel 120 being peeled off even when the folding and unfolding of the device are repeated.

[0070] Figure 9 and Figure 10 A first layer according to an embodiment of the present disclosure is shown. Figure 9 (a) and Figure 10 (a) is a cross-sectional view of the first layer, and Figure 9 (b) and Figure 9 (c) Figure 10 (b) and Figure 10 (c) is a perspective view of the first layer.

[0071] Reference Figure 9 and Figure 10 , the first layer 170 may include a core layer 174 and a protective layer 175 surrounding the side surface of the core layer. The core layer 174 may include a polymer. When the core layer 174 is formed of, for example, a thermoplastic polyurethane (TPU) polymer, the protective layer 175 formed of silicon oxide, silicon nitride, or silicon oxynitride may surround the core layer 174 to compensate for the poor moisture resistance and heat resistance of the thermoplastic polyurethane polymer. Depending on the formation method of the protective layer 175, such as Figure 9 The protective layer 175 shown in FIG may cover the lower surface or the upper surface of the core layer 174, or as shown in FIG. Figure 10 The protective layer 175 ′ shown in FIG. 1 may not cover the lower surface or the upper surface of the core layer 174 .

[0072] like Figure 9 (c) and Figure 10As shown in (c) of FIG. 17, each of the protective layers 175 and 175' can not be disposed at a region (e.g., a foldable region) of the side surface of the core layer 174 adjacent to the folding axis Fx. When each of the protective layers 175 and 175' formed of an inorganic material is disposed at the foldable region, the protective layer can be disadvantageous to folding and a crack can occur during folding of the device. When each of the protective layers 175 and 175' is not disposed at the region of the side surface of the core layer 174 adjacent to the folding axis Fx, e.g., the foldable region, the occurrence of a crack during folding of the device can be prevented.

[0073] Figure 11 and Figure 12 A first layer covering a light blocking layer and a method of manufacturing the same according to an embodiment of the disclosure is illustrated.

[0074] Referring to Figure 11 The first layer 170 disposed at the lower surface of the cover window 190 can cover the upper surface, the inner surface, and the lower surface of the light blocking layer 150 disposed to correspond to the non-display area of the display panel. For example, the light blocking layer 150 can be disposed at a peripheral portion of the display panel. The first layer 170 can be formed of a shape memory polymer. For example, the first layer 170 can be formed of a polyurethane shape memory polymer or a silicone elastomer shape memory polymer.

[0075] Referring to Figure 12 (a), a first portion 170a of the first layer is formed or coated at the lower surface of the cover window 190. Then, referring to Figure 12 (b), a recess 170r is formed in a portion adjacent to a periphery of the first portion 170a of the first layer. Then, referring to Figure 12 (c), the light blocking layer 150 is printed in the recess 170r. The thickness of the light blocking layer 150 can be greater than the depth of the recess 170r. Then, referring to Figure 12 (d), a second portion 170b of the first layer is coated to cover the first portion 170a of the first layer and the light blocking layer 150. Then, referring to Figure 12 (e), a peripheral portion of a resulting structure including the cover window 190, the first portion 170a, and the second portion 170b can be removed by laser trimming. Accordingly, the first layer 170 covering the light blocking layer as shown in Figure 11 can be formed at the lower surface of the cover window 190. Each of the first portion 170a and the second portion 170b of the first layer can be formed of a shape memory polymer. For example, each of the first portion 170a and the second portion 170b of the first layer can be formed of a polyurethane shape memory polymer or a silicone elastomer shape memory polymer.

[0076] Although an embodiment in which the light blocking layer 150 and the first layer 170 are formed at the cover window 190 has been described above, the light blocking layer 150 and the first layer 170 may be formed at the protective substrate 140 in the same form or scheme in another embodiment of the present disclosure.

[0077] Figure 13 is a diagram showing an embodiment according to the present disclosure Figure 1 A cross-sectional view of the foldable display device cut along line I-I'.

[0078] Reference Figure 13 , the foldable display device 100 - 6 according to an embodiment of the present disclosure may include a protective portion 142 and a light blocking layer 150 .

[0079] The light blocking layer 150 may be provided at the peripheral portion of the lower surface of the cover window 190. In addition, the foldable display device 100-6 may include a first layer 171 provided at the first surface of the protection portion 142 and a second layer 172 provided at the second surface of the protection portion 142. The first surface of the protection portion 142 may be, for example, the lower surface of the protection portion 142, and the second surface of the protection portion 142 may be, for example, the upper surface of the protection portion 142. In an embodiment of the present disclosure, components other than the protection portion 142, the first layer 171, the second layer 172, and the light blocking layer 150 may be provided with Figure 2 The components of the embodiments of the present invention are substantially the same. Therefore, repeated description thereof is omitted. For example, the protection portion 142 can be implemented as a protection window, a protection glass, or a cover glass. The embodiments of the present disclosure are not limited thereto.

[0080] Figure 14 and Figure 15 They are respectively showing the embodiments according to the present disclosure. Figure 1 Cross-sectional view and plan view of the protection portion cut along the II-II' line.

[0081] Reference Figure 14 and Figure 15 The protective portion 142 may include a first recess R1 and a second recess R2 in the foldable area FA. The first recess R1, which overlaps the folding axis Fx, may be provided on a first surface (e.g., a lower surface of the protective portion 142). At least two or more second recesses R2, spaced apart from each other and respectively provided on either side of the folding axis Fx, may be provided on a second surface (e.g., an upper surface) of the protective portion 142.

[0082] For example, to reduce stress applied to the protective portion 142 during folding of the device, a portion overlapping the folding axis Fx can be etched away in one surface of the protective portion 142, and other portions spaced apart from the folding axis Fx by the same interval (or distance) on both sides of the folding axis Fx can be etched in the other surface of the protective portion 142. Accordingly, a portion of the protective portion 142 in the foldable area can be etched in a W shape.

[0083] The first recess R1 and the second recess R2 can be formed by wet etching of the protective portion 142. For example, each of the first recess R1 and the second recess R2 can have a concave curved surface. For example, the first recess R1 can have a shape horizontally symmetrical with respect to the folding axis Fx. For example, the center of the first recess R1 can coincide with the folding axis Fx. The shapes of both halves of the first recess R1 can be identical to each other with respect to the center of the folding axis Fx. For example, the second recess R2 can be formed to be symmetrical to each other with respect to the folding axis Fx. The second recess R2 can be spaced apart from the folding axis Fx by an equal distance. For example, the distances between the centers of the plurality of second recesses R2 and the folding axis Fx can be equal to each other. Also, the shapes of the second recesses R2 can be identical to each other. The shapes of both halves of the second recess R2 can be identical to each other with respect to the center of the second recess R2.

[0084] For example, if the first recess R1 overlaps the folding axis Fx and is disposed at the lower surface of the protective portion 142, and the second recess R2 overlaps the folding axis Fx and is disposed at the upper surface of the protective portion 142, the maximum stress during outward folding of the device and the maximum stress during inward folding of the device can be concentrated on the folding axis area. Accordingly, since stress is concentrated on one point in the protective portion 142 in which a plurality of recesses are formed in a longitudinally symmetrical arrangement and disposed at the foldable area, the fatigue failure characteristic can be poor. Accordingly, according to the embodiment of the disclosure, the first recess R1 is symmetrical with respect to the folding axis Fx, and the second recess R2 is arranged in a symmetrical manner with respect to the folding axis Fx, which can prevent cracking of the protective portion 142 and thus can reduce the durability defect of the device.

[0085] For example, the depth DT1 of the first recess R1 and the depth DT2 of the second recess R2 can be equal to each other. For example, the "depth of the recess" can be the depth at the central axis of the recess. For example, the depth can be the longitudinal distance from the surface (upper surface or lower surface) of the protective portion to the lowest level of the recess. The protective portion 142 can have an overall thickness of, for example, 30 μm to 200 μm (with reference to its non-foldable area). In an embodiment of the present disclosure, each of the depth DT1 of the first recess R1 and the depth DT2 of the second recess R2 in the foldable area FA can be in the range of 40% or more to 85% or less of the overall thickness of the protective portion 142 in its non-foldable area.

[0086] The spacing (or distance) D1 between adjacent edges of the second recess R2 may be smaller than the width W1 of the first recess R1. The second recesses R2 may be spaced apart from each other, while each of the second recesses R2 may partially overlap with the first recess R1. For example, the width W1 of the first recess R1 and the width W2 of the second recess R2 may be equal to each other. Each of the width W1 of the first recess R1 and the width W2 of the second recess R2 may be in the range of 1 mm or more to 2 mm or less.

[0087] The width W1 of the first recess R1 may be different from the width W2 of the second recess R2. The depth DT1 of the first recess R1 may be different from the depth DT2 of the second recess R2. For example, the width W1 of the first recess R1 may be greater than the width W2 of the second recess R2. Also, for example, the depth DT1 of the first recess R1 may be greater than the depth DT2 of the second recess R2.

[0088] The following adjustment may be most effective for dispersing stress: the distance D2 from the folding axis Fx of the protective portion 142 to the center of the second recess R2 is equal to or greater than the curvature radius of the device in the outward folded state, or less than or equal to the sum of 1 / 6 of the width W2 of the second recess R2 and the curvature radius.

[0089] The protective portion 142 includes a first recess R1 and a second recess R2 in the foldable region FA, thereby improving the folding characteristics of the foldable region while maintaining the strength of the non-foldable region. Furthermore, this can reduce the stress applied to the foldable region FA of the protective portion 142 during folding of the device. For example, when the device is repeatedly folded inward and outward, stress can be prevented from concentrating on a single point (e.g., in the region of the folding axis Fx of the protective portion 142). Consequently, the fatigue failure characteristics of the protective portion 142 can be improved, and the occurrence of cracks can be reduced.

[0090] Therefore, according to an embodiment of the present disclosure, first recesses ( R1 ) are formed on a first surface of the protective portion 142, such as its lower surface, and second recesses ( R2 ) are formed on a second surface of the protective portion 142, such as its upper surface, spaced apart from each other. The first recesses ( R1 ) are symmetrical with respect to the folding axis ( Fx ), and the second recesses ( R2 ) are arranged symmetrically with respect to the folding axis ( Fx ). This prevents cracks in the protective portion 142 and improves durability.

[0091] The first layer 171 can cover the entire first surface of the protective portion 142 (e.g., the lower surface of the protective portion 142) and can fill the first recess R1. The lower surface of the first layer 171 can be flat. The second layer 172 can cover the entire second surface (e.g., the upper surface) of the protective portion 142 and can fill the second recess R2. The upper surface of the second layer 172 can be flat. Since the lower surface of the first layer 171 and the upper surface of the second layer 172 are flat, the first layer 171 and the second layer 172 can be bonded or attached to other components without forming an empty space between them.

[0092] The durability of the protective portion 142 can be enhanced by providing the first and second layers on the upper and / or lower surfaces of the protective portion 142 and in the foldable region. For example, when the first and second layers 171, 172 are formed on both surfaces of the protective portion 142, the strength of the foldable region FA of the protective portion 142 can be enhanced. Furthermore, even if cracks develop in the protective portion 142 or the protective portion 142 is damaged, the dispersion of glass fragments can be prevented. The refractive index of each of the first and second layers 171, 172 can be substantially equal to that of the protective portion 142. For example, if the refractive index of the protective portion 142 is 1.52, the refractive index of each of the first and second layers 171, 172 can be approximately 1.52. For example, the difference between the refractive index of each of the first and second layers 171, 172 and the refractive index of the protective portion 142 can be 0.01 or less. This can prevent the first and second recesses R1, R2 from being visually recognized from the outside. Each of the first layer 171 and the second layer 172 may include a polymer material having a storage modulus lower than that of the cover window 190. Each of the first layer 171 and the second layer 172 may include a polymer material having a storage modulus ranging from 1×10 7 Pa to 9×10 8 Each of the first layer 171 and the second layer 172 may include, for example, a polyurethane-based, silicone-based, epoxy-based, and acrylic-based polymer or resin. The embodiments of the present disclosure are not limited thereto.

[0093] Figure 16 、 Figure 17 (a) and Figure 17(b) shows a stress simulation result of the protection portion according to an embodiment of the present disclosure.

[0094] Figure 16 Inward and outward folding in the simulation are shown.

[0095] Reference Figure 16 In the inward folding I, the protecting portion 142 can be folded inward based on the folding axis Fx so that the two equal parts of the second surface of the protecting portion 142 where the second recess R2 is formed face each other. In the outward folding O, the protecting portion 142 can be folded outward based on the folding axis Fx so that the two equal parts of the first surface of the protecting portion 142 where the first recess R1 is formed face each other.

[0096] Figure 17 (b) shows the stress applied to the foldable area of ​​the protection portion during inward folding and outward folding based on the distance from the folding axis Fx. Since the structure of the protection portion is symmetrical with respect to the folding axis, Figure 17 (a) shows a half portion of the protection portion provided at one side of the folding axis. Figure 17 (a) and Figure 17 (b), during the inward folding of the device, the maximum stress may be applied to region A (the folding axis region). For example, during the inward folding of the device, the maximum stress may be applied to the folding center axis. During the outward folding, the maximum stress may be applied to region B (the horizontal center region of the second recess). For example, during the outward folding of the device, the maximum stress may be applied to the region (the second recess) where the upper portion of the protective portion 142 is etched. Therefore, the region where the maximum stress is applied during the inward folding is different from the region where the maximum stress is applied during the outward folding, which can reduce the fatigue failure characteristics at the folding axis Fx.

[0097] According to an embodiment of the present disclosure, the area of ​​the protective portion 142 to which the maximum stress is applied during inward folding is different from the area of ​​the protective portion 142 to which the maximum stress is applied during outward folding. Therefore, the fatigue failure characteristics of the protective portion 142 can be improved, and the occurrence of cracks can be reduced.

[0098] A foldable display device according to an embodiment of the present disclosure can be described as follows.

[0099] According to an embodiment of the present disclosure, a foldable display device includes a display panel, a cover window on the display panel, and a first layer between the display panel and the cover window, the first layer having a storage modulus lower than that of the cover window.

[0100] In some embodiments of the present disclosure, the storage modulus of the first layer may be 1×10 7 Pa to 9×108 Within the range of Pa.

[0101] In some embodiments of the present disclosure, the first layer may include one of a silicone-based polymer, a polyurethane-based polymer, an epoxy-based polymer, and an acrylic-based polymer.

[0102] In some embodiments of the present disclosure, the first layer may include a core layer and a protection layer surrounding a side surface of the core layer.

[0103] In some embodiments of the present disclosure, the display panel may include a display area, a non-display area at the periphery of the display area, and a foldable area overlapping a portion of the display area and a portion of the non-display area. The protective layer may not be present in an area of ​​the side surface of the core layer adjacent to the folding axis of the foldable area.

[0104] In some embodiments of the present disclosure, the display device may further include a light blocking layer at a peripheral portion of the display panel, and the first layer may cover an upper surface, an inner side surface, and a lower surface of the light blocking layer.

[0105] In some embodiments of the present disclosure, the display device may further include a protection portion between the display panel and the cover window, and the first layer may be disposed at the protection portion or bonded to the protection portion through an adhesive layer.

[0106] In some embodiments of the present disclosure, the display panel may include a display area, a non-display area at a periphery of the display area, and a foldable area overlapping a portion of the display area and a portion of the non-display area. The protective portion includes a first recess and at least two or more second recesses, the first recess overlapping a folding axis of the foldable area and being provided on a first surface of the protective portion, and the at least two or more second recesses being spaced apart from each other on both sides of the folding axis and being provided on a second surface of the protective portion opposite to the first surface.

[0107] In some embodiments of the present disclosure, at least two or more second recesses may be symmetrically disposed with respect to the folding axis.

[0108] In some embodiments of the present disclosure, a spacing between adjacent edges of at least two or more second recesses may be smaller than a width of the first recess.

[0109] In some embodiments of the present disclosure, each of the first recess and the at least two or more second recesses may have a curved surface.

[0110] In some embodiments of the present disclosure, a first layer may be disposed at a first surface of the protective portion, and the foldable display device further includes a second layer disposed at a second surface of the protective portion opposite to the first surface, the first layer covering the first surface of the protective portion and filling the first recess, and the second layer covering the second surface of the protective portion and filling the second recess.

[0111] In some embodiments of the present disclosure, the distance from the folding axis to the center of each of the at least two or more second recesses may be equal to or greater than the radius of curvature of the foldable display device in the outward folded state, or equal to or less than the sum of 1 / 6 of the width of each of the at least two or more second recesses and the radius of curvature in the outward folded state.

[0112] According to an embodiment of the present disclosure, a foldable display device includes a display panel, a cover window on the display panel, a protective portion between the display panel and the cover window, a first layer at a first surface of the protective portion, and a second layer at a second surface of the protective portion opposite to the first surface, the display panel includes a display area, a non-display area at the periphery of the display area, and a foldable area overlapping with a portion of the display area and a portion of the non-display area, the first surface of the protective portion includes a first recess overlapping with a folding axis of the foldable area, and the second surface of the protective portion includes at least two or more second recesses, and the at least two or more second recesses are spaced apart from each other at both sides of the folding axis.

[0113] In some embodiments of the present disclosure, at least two or more second recesses may be symmetrically disposed with respect to the folding axis.

[0114] In some embodiments of the present disclosure, a spacing between adjacent edges of at least two or more second recesses may be smaller than a width of the first recess.

[0115] In some embodiments of the present disclosure, each of the first recess and the at least two or more second recesses may have a curved surface.

[0116] In some embodiments of the present disclosure, the first layer may cover the first surface of the protection portion and fill the first recesses, and the second layer may cover the second surface of the protection portion and fill at least two or more second recesses.

[0117] In some embodiments of the present disclosure, each of the first layer and the second layer may have a storage modulus lower than that of the cover window.

[0118] In some embodiments of the present disclosure, a difference between the refractive index of each of the first layer and the second layer and the refractive index of the protective portion may be 0.01 or less.

[0119] According to an embodiment of the present disclosure, a foldable display device includes: a display panel; a cover window on the display panel; a protective portion between the display panel and the cover window; a light-blocking layer at a peripheral portion of a lower surface of the cover window; and a first layer formed at the lower surface of the cover window to cover the light-blocking layer, wherein the first layer is located above the protective portion and has a storage modulus lower than that of the cover window.

[0120] It will be apparent to those skilled in the art that various modifications and variations can be made in the present disclosure without departing from the technical concept or scope of the present disclosure. Therefore, the embodiments of the present disclosure are intended to cover modifications and variations of the disclosure as long as they fall within the scope of the appended claims and their equivalents.

Claims

1. A foldable display device, comprising: Display panel; a cover window on the display panel; a protective substrate or a protective part attached to the cover window by an adhesive layer, wherein the protective substrate is made of a flexible polymer film and the protective part is made of glass, and a first layer between the display panel and the protective substrate or between the display panel and the protective portion, the first layer having a storage modulus lower than that of the cover window, The first layer includes a core layer and a protective layer surrounding the side surface of the core layer. wherein the display panel includes a display area, a non-display area at the periphery of the display area, and a foldable area overlapping a portion of the display area and a portion of the non-display area, and The protective layer does not exist in an area of ​​the side surface of the core layer that is adjacent to the folding axis of the foldable area.

2. The foldable display device according to claim 1, wherein: The storage modulus of the first layer is 1×10 7 Pa to 9×10 8 Within the range of Pa.

3. The foldable display device according to claim 1, wherein: The first layer includes one of a silicone-based polymer, a polyurethane-based polymer, an epoxy-based polymer, and an acrylic-based polymer.

4. The foldable display device according to claim 1 , further comprising a light blocking layer at a peripheral portion of the display panel, in, The first layer covers the upper surface, the inner surface, and the lower surface of the light blocking layer.

5. The foldable display device according to claim 1, in, The first layer is provided at a lower surface of the protection portion or the protection substrate or is bonded to the lower surface of the protection portion or the protection substrate through an adhesive layer.

6. The foldable display device according to claim 5, in, The protection portion includes a first recess and at least two or more second recesses, wherein the first recess overlaps with the folding axis of the foldable region and is provided at the first surface of the protecting portion, and The at least two or more second recesses are spaced apart from each other at both sides of the folding axis and are provided at a second surface of the protecting portion opposite to the first surface.

7. The foldable display device according to claim 6, wherein: The at least two or more second recesses are symmetrically arranged with respect to the folding axis.

8. The foldable display device according to claim 6, wherein: A distance between adjacent edges of the at least two or more second recesses is smaller than a width of the first recess.

9. The foldable display device according to claim 6, wherein: The first recess and each of the at least two or more second recesses have a curved surface.

10. The foldable display device according to claim 6, wherein: The first layer is provided on the first surface of the protection portion, The foldable display device further includes a second layer provided on a second surface of the protection portion opposite to the first surface. The first layer covers the first surface of the protection portion and fills the first recess; and The second layer covers the second surface of the protection portion and fills the at least two or more second recesses.

11. The foldable display device according to claim 6, wherein: The distance from the folding axis to the center of each of the at least two or more second recesses is equal to or greater than the radius of curvature of the foldable display device in the outward folded state, or is equal to or less than 1 / 6 of the width of each of the at least two or more second recesses and the sum of the radius of curvature in the outward folded state.

12. A foldable display device, comprising: a display panel including a display area, a non-display area at a periphery of the display area, and a foldable area overlapping a portion of the display area and a portion of the non-display area; a cover window on the display panel; a protective portion between the display panel and the cover window and made of glass; a first layer at a first surface of the protection portion; as well as a second layer at a second surface of the protection portion opposite to the first surface, wherein the first surface of the protection portion includes a first recessed portion overlapping the folding axis of the foldable region, wherein the second surface of the protection portion includes at least two or more second recesses, the at least two or more second recesses being spaced apart from each other at both sides of the folding axis, and Wherein, each of the first layer and the second layer has a storage modulus lower than a storage modulus of the cover window.

13. The foldable display device according to claim 12, wherein: The at least two or more second recesses are symmetrically arranged with respect to the folding axis.

14. The foldable display device according to claim 12, wherein: A distance between adjacent edges of the at least two or more second recesses is smaller than a width of the first recess.

15. The foldable display device according to claim 12, wherein: The first recess and each of the at least two or more second recesses have a curved surface.

16. The foldable display device according to claim 12, wherein: The first layer covers the first surface of the protection portion and fills the first recess, and The second layer covers the second surface of the protection portion and fills the at least two or more second recesses.

17. The foldable display device according to claim 16, wherein: A difference between a refractive index of each of the first layer and the second layer and a refractive index of the protective portion is 0.01 or less.

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