Foldable display device

Abstract

The present disclosure relates to a foldable display device. With respect to the foldable display of the present disclosure, stretchability is imparted to the outermost region of the folding region of the first supporting substrate to which relatively high stress is applied. As a result, the folding radius at the outermost region is increased, which relatively reduces the stress at the outermost region. Therefore, the occurrence of cracks in the outermost region can be suppressed.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the priority of Korean Patent Application No. 10-2020-0187224 filed in the Korean Intellectual Property Office on December 30, 2020, the disclosure of which is incorporated herein by reference. Technical Field

[0003] The present disclosure relates to a foldable display device, and more particularly to a foldable display device capable of suppressing the occurrence and propagation of cracks caused by repeated folding while being folded and unfolded. Background Art

[0004] Recently, with the development of the information age, display devices that process and display a large amount of information have been rapidly developed. Display devices used in computer monitors, televisions, mobile phones, etc. include organic light emitting displays (OLEDs) that emit light by themselves and liquid crystal displays (LCDs) that require a separate light source.

[0005] As display devices are increasingly used in various fields such as computer monitors, televisions, and personal mobile devices, display devices having a large display area and reduced volume and weight have been studied.

[0006] In particular, recently, a flexible display device manufactured to display an image even when it is bent or folded like paper has attracted attention as a next-generation display device. The flexible display device uses a thin film transistor substrate made of plastic instead of glass, and the flexible display device can be classified into a highly durable unbreakable display, a display that is bent without breaking, a rollable display, a foldable display, etc. The flexible display device has advantages in space utilization, interior decoration, and design, and can be applied to various fields. Summary of the invention

[0007] An object to be achieved by the present disclosure is to provide a foldable display device capable of suppressing the occurrence of cracks in a portion to which a relatively high stress is applied.

[0008] Another object to be achieved by the present disclosure is to provide a foldable display device with improved folding reliability.

[0009] The objects of the present disclosure are not limited to the above objects, and other objects not mentioned above may be clearly understood by those skilled in the art from the following description.

[0010] According to one aspect of the present disclosure, a foldable display device includes a display panel, the display panel includes a display area and a non-display area surrounding the display area, and a folding area and non-folding areas on both sides of the folding area defined in the display area and the non-display area. The foldable display device also includes a first supporting substrate, the first supporting substrate is arranged below the display panel to support the display panel, and the first supporting substrate includes a plurality of openings arranged in an area corresponding to the non-display area of ​​the folding area. The foldable display device also includes a second supporting substrate arranged below the first supporting substrate. The width of the plurality of openings in the extension direction of the folding axis of the folding area is greater than the width of the plurality of openings in the direction perpendicular to the extension direction of the folding axis. Therefore, stretchability is imparted to the outermost area of ​​the folding area of ​​the first supporting substrate to which relatively high stress is applied. As a result, the folding radius at the outermost area increases, which relatively reduces the stress at the outermost area. Therefore, cracks can be suppressed from occurring in the outermost area.

[0011] Additional details of exemplary embodiments are included in the detailed description and the accompanying drawings.

[0012] According to the present disclosure, stretchability may be imparted to the outermost region of a display device to which a relatively high stress is applied.

[0013] Furthermore, according to the present disclosure, the folding radius can be increased and thus the folding stress can be reduced and the folding reliability can be improved.

[0014] Furthermore, according to the present disclosure, by making the thickness of the edge region smaller than that of the central region and thus suppressing stress concentration in the outer region, the possibility of cracks occurring in the outer region of the display device can be reduced.

[0015] The effects according to the present disclosure are not limited to the above-exemplified contents, and more various effects are included in the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other aspects, features and other advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0017] Figure 1 is a schematic plan view of a foldable display device according to an exemplary embodiment of the present disclosure;

[0018] Figure 2 It is along Figure 1 A schematic cross-sectional view of the foldable display device taken along line II-II';

[0019] Figure 3 It is along Figure 1 A schematic cross-sectional view of the foldable display device taken along line III-III';

[0020] Figure 4 is a schematic plan view of a first supporting substrate according to an exemplary embodiment of the present disclosure;

[0021] Figure 5 is a schematic plan view of a first supporting substrate according to another exemplary embodiment of the present disclosure;

[0022] Figure 6 is a schematic plan view of a first supporting substrate according to yet another exemplary embodiment of the present disclosure;

[0023] Fig. 7A is a schematic plan view of a first supporting substrate according to yet another exemplary embodiment of the present disclosure;

[0024] Figure 7B yes Fig. 7A An enlarged view of a region A of the first support substrate shown in;

[0025] Figure 7C is along Figure 7B A schematic cross-sectional view of the first supporting substrate taken along line VIIc-VIIc';

[0026] Figure 8 is a schematic plan view of a foldable display device according to yet another exemplary embodiment of the present disclosure; and

[0027] Fig. 9 is along Figure 8 A schematic cross-sectional view of the foldable display device taken along line IX-IX'. DETAILED DESCRIPTION

[0028] By referring to the exemplary embodiments and drawings described in detail below, the advantages and features of the present disclosure and the methods for achieving these advantages and features will become clear. However, the present disclosure is not limited to the exemplary embodiments disclosed herein, but will be implemented in various forms. The exemplary embodiments are provided only by way of example so that those skilled in the art can fully understand the disclosure of the present disclosure and the scope of the present disclosure. Therefore, the present disclosure will be limited only by the scope of the appended claims.

[0029] The shapes, sizes, ratios, angles, numbers, etc. shown in the accompanying drawings for describing the exemplary embodiments of the present disclosure are only examples, and the present disclosure is not limited thereto. Throughout the specification, the same reference numerals generally indicate the same elements. In addition, in the following description of the present disclosure, the detailed explanation of known related technologies may be omitted to avoid unnecessarily obscuring the subject matter of the present disclosure. Terms such as "including", "having" and "consisting of..." used herein are generally intended to allow the addition of other components unless used together with the term "only". Unless otherwise expressly stated, any reference to the singular may include the plural.

[0030] Even if not explicitly stated, the components are interpreted as including ordinary error ranges.

[0031] When terms such as “on,” “over,” “below,” and “immediately next to” are used to describe the positional relationship between two parts, one or more parts may be located between the two parts unless these terms are used together with “immediately next to” or “directly.”

[0032] When an element or layer is referred to as being “on” another element or layer, the other layer or element can be directly on or directly interposed between the other element.

[0033] Although the terms "first", "second", etc. are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from other components. Therefore, the first component mentioned below can be the second component in the technical concept of the present disclosure.

[0034] Throughout the specification, like reference numerals generally refer to like elements.

[0035] The size and thickness of each component shown in the drawings are shown for convenience of description, and the present disclosure is not limited to the size and thickness of the components shown.

[0036] The features of the various embodiments of the present disclosure may be partially or completely attached or combined with each other, and may be interlocked and operated in various ways technically, and these embodiments may be performed independently of each other or in association with each other.

[0037] Hereinafter, various exemplary embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0038] Figure 1 is a schematic plan view of a foldable display device according to an exemplary embodiment of the present disclosure. Figure 2 It is along Figure 1 Schematic cross-sectional view of the foldable display device taken along line II-II'. Figure 3 It is along Figure 1 Schematic cross-sectional view of the foldable display device taken along line III-III'.

[0039] Reference Figures 1 to 3 , the foldable display device 100 according to the exemplary embodiment of the present disclosure includes a first support substrate 110, a second support substrate 120, a display panel 130, and a cover window 140. Hereinafter, for convenience of description, the foldable display device 100 according to the exemplary embodiment of the present disclosure will be described as an organic light emitting display device, but is not limited thereto.

[0040] Reference Figure 1 , the display panel included in the foldable display device 100 includes a display area DA and a non-display area NDA. In addition, the display panel includes a folding area FA and non-folding areas NFA1 and NFA2. Depending on whether an image is displayed, the display panel can be divided into a display area DA and a non-display area NDA. Depending on the possibility of being folded, the display panel can be divided into a folding area FA and non-folding areas NFA1 and NFA2 on both sides of the folding area FA.

[0041] The display area DA is an area in which a plurality of pixels are arranged and an image is displayed. In the display area DA, a plurality of pixels each including a light-emitting area for displaying an image, a thin film transistor for driving the pixel, a capacitor, and the like may be provided. Each pixel may include a plurality of sub-pixels SP. Each sub-pixel SP is the smallest unit for constituting a display area, and may be configured to emit light of a specific wavelength band. For example, each sub-pixel SP may be configured to emit red light, green light, blue light, or white light. The non-display area NDA is positioned to surround the display area DA. The non-display area NDA is an area where no image is displayed. In the non-display area NDA, various wirings, driver ICs, printed circuit boards, and the like for driving the pixels and drive circuits provided in the display area DA are provided. For example, in the non-display area NDA, various ICs such as a gate driver IC and a data driver IC, a VSS line, and the like may be provided.

[0042] As described above, according to the possibility of being folded, the display panel can be divided into a folding area FA and non-folding areas NFA1 and NFA2. The display panel according to the exemplary embodiment of the present disclosure includes a first non-folding area NFA1, a folding area FA and a second non-folding area NFA2 sequentially arranged along a direction perpendicular to a folding axis F of the folding area (i.e., a Y-axis direction).

[0043] The folding area FA is folded when the foldable display device 100 is folded, and may include a portion of the display area DA and a portion of the non-display area NDA. The folding area FA may be folded in a direction perpendicular to the folding axis F of the folding area (i.e., Figure 1The folding area FA is folded in a direction perpendicular to the folding axis F with a specific folding radius. When the folding area FA is folded in a direction perpendicular to the folding axis F, the folding area FA may form a part of a circle or an ellipse. Here, the folding radius of the folding area FA refers to the radius of the circle or ellipse formed by the folding area FA.

[0044] When the foldable display device 100 is folded, the first non-folding area NFA1 and the second non-folding area NFA2 are not folded. That is, when the foldable display device 100 is folded, each of the first non-folding area NFA1 and the second non-folding area NFA2 maintains a flat state. Each of the first non-folding area NFA1 and the second non-folding area NFA2 may include a portion of the display area DA and a portion of the non-display area NDA. When the folding area FA is folded in the folding direction, the first non-folding area NFA1 and the second non-folding area NFA2 may overlap each other.

[0045] The display panel 130 is a panel for realizing an image. In the display panel 130, a display element for realizing an image and a circuit unit for driving the display element may be provided. For example, if the foldable display device 100 is an organic light emitting display device, the display element may include an organic light emitting element.

[0046] The circuit unit may include various thin film transistors, capacitors, wirings, and driver ICs for driving the organic light emitting element. For example, the circuit unit may include various elements such as a driving thin film transistor, a switching thin film transistor, a storage capacitor, a gate line, a data line, a gate driver IC, and a data driver IC. However, the present disclosure is not limited thereto.

[0047] The display panel 130 is manufactured by packaging a flexible substrate through a packaging unit. On the flexible substrate, a driving thin film transistor and a light emitting element are formed. The display panel 130 includes: a flexible substrate having a very small thickness to achieve flexibility; and a display element disposed on the flexible substrate.

[0048] The flexible substrate may be made of an insulating material having flexibility. For example, the flexible substrate may be a substrate made of insulating plastic selected from polyimide, polyethersulfone, polyethylene terephthalate, and polycarbonate.

[0049] The plastic substrate has relatively weak barrier properties to moisture or oxygen. To compensate for this, the flexible substrate may have a structure in which a plastic film and an inorganic film are laminated. For example, the flexible substrate may have a multilayer structure in which a first plastic film, an inorganic film, and a second plastic film are laminated in sequence, but is not limited thereto.

[0050] On the flexible substrate, a driving thin film transistor for driving the display element may be provided. The driving thin film transistor may be provided in each of a plurality of pixel regions. For example, the driving thin film transistor includes a gate electrode, an active layer, a source electrode, and a drain electrode. In addition, the driving thin film transistor may include a gate insulating layer for insulating the gate electrode from the active layer. In addition, the driving thin film transistor may include an interlayer insulating layer for insulating the gate electrode from the source electrode and the drain electrode. On the driving thin film transistor, a planarization layer for planarizing the upper surface may be provided. The display element may be provided on the planarization layer. The display element may be an organic light emitting element. The organic light emitting element may include an anode, a cathode, and an organic light emitting layer provided between the anode and the cathode. The organic light emitting element emits light by combining holes injected from the anode with electrons injected from the cathode in the organic light emitting layer. In this way, the emitted light may be used to display an image.

[0051] The flexible substrate has excellent folding characteristics, but has a small thickness and lower rigidity compared to a glass substrate or a metal substrate. Therefore, the flexible substrate may not maintain a uniform shape when folded, which may cause sagging. Therefore, in order to support the flexible substrate and improve impact resistance, the first support substrate 110 and the second support substrate 120 are disposed under the display panel 130.

[0052] The first support substrate 110 and the second support substrate 120 disposed under the display panel 130 may support the display panel 130 to suppress sagging or deformation. In addition, the first support substrate 110 and the second support substrate 120 protect the display panel 130 from external impact or impurities.

[0053] The first support substrate 110 may be referred to as a top plate. The first support substrate 110 may enhance the rigidity of the display panel 130 and play a role in suppressing the plurality of patterns 121 formed in the second support substrate 120 from being recognized through the display panel 130.

[0054] The first support substrate 110 may be made of an amorphous metal. An amorphous metal is a solid metal material in which atoms are arranged in a disordered manner like glass or liquid, and is produced when crystal growth is suppressed by rapid quenching of the metal material. Compared to crystalline metals that generally have atoms arranged in an orderly manner, amorphous metals have excellent corrosion resistance and elasticity. For example, the first support substrate 110 may include any amorphous metal selected from the group consisting of nickel, iron, cobalt, palladium, silicon, magnesium, zirconium, titanium, calcium, copper, platinum, gold, and combinations thereof.

[0055] If the first support substrate 110 is made of an amorphous metal, cracks may occur in the outermost region of the first support substrate 110, to which relatively high stress is applied when the first support substrate 110 is repeatedly folded. This is because amorphous metals have excellent elasticity but exhibit brittleness at high hardness.

[0056] Therefore, refer to Figure 2 and Figure 3 In an exemplary embodiment of the present disclosure, a plurality of openings 111 are provided in a region corresponding to an outer region of the first support substrate 110 (i.e., a non-display region NDA of the folding region FA). The plurality of openings may suppress the occurrence and propagation of cracks caused by stress concentration in the outer region of the first support substrate 110. The plurality of openings of the first support substrate 110 will be described in more detail later.

[0057] The second support substrate 120 may be referred to as a bottom plate. The second support substrate 120 may include a plurality of patterns 121 formed corresponding to the folding area FA of the foldable display device 100. Due to the plurality of patterns 121 formed in the folding area FA, the elastic variation portion is increased, which makes it possible to fold or unfold the foldable display device 100.

[0058] The second support substrate 120 may be made of stainless steel (SUS), SUS containing a metal such as nickel (Ni), or a metal material such as iron (Fe), aluminum (Al), or magnesium (Mg). Preferably, the second support substrate 120 may be made of SUS. For example, SUS has high restoring force and high rigidity, and therefore, the second support substrate 120 can maintain high rigidity even when its thickness is reduced. Therefore, the second support substrate 120 supports the display panel 130 and reduces the overall thickness of the foldable display device 100, which results in a reduction in the folding radius of the folding area. However, the present disclosure is not limited thereto. The second support substrate 120 may be made of a polymer such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), silicone, or polyurethane (PU).

[0059] In some exemplary embodiments, a backplane may be further disposed between the display panel 130 and the first support substrate 110. Since the display panel 130 is formed thin, the backplane may be attached to the rear surface of the display panel 130 to further support the display panel 130. The backplane is disposed between the display panel 130 and the first support substrate 110. Therefore, the backplane may suppress the transfer or deformation of the display screen caused by the plurality of patterns 121 formed in the second support substrate 120.

[0060] For example, the back panel may be made of a polymer such as polyimide (PI), polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile butadiene styrene (ABS), polyethylene terephthalate (PET), silicone, or polyurethane (PU) and may support the display panel 130 .

[0061] In addition, the cover window 140 is provided on the display panel 130. The cover window 140 protects the display panel 130 from external impact and scratching. Therefore, the cover window 140 can be made of a transparent material having excellent impact resistance and scratch resistance. In addition, the cover window 140 protects the display panel 130 from the influence of moisture penetrating from the outside.

[0062] For the thinness and flexibility of the foldable display device 100, the cover window 140 may be configured as a flexible plastic type cover that can be folded. For example, the cover window 140 may be a film made of a polymer such as polyimide, polyamideimide, polyethylene terephthalate, polymethyl methacrylate, polypropylene glycol, or polycarbonate. As another example, the cover window 140 may be a film made of an optically isotropic polymer such as cycloolefin (co)polymer, optically isotropic polycarbonate, or optically isotropic polymethyl methacrylate.

[0063] In addition, various functional layers may be laminated on the cover window 140. For example, various functional layers such as an external light reflection reducing layer, a UV blocking layer, a hard coating layer may be provided on the cover window 140, but the present disclosure is not limited thereto.

[0064] In the following, reference will be made to Figure 4 The first support substrate 110 is described in detail.

[0065] Figure 4 is a schematic plan view of a first supporting substrate of a foldable display device according to an exemplary embodiment of the present disclosure.

[0066] Reference Figure 4 , the first support substrate 110 may include a plurality of openings 111 provided in a region corresponding to the non-display area NDA of the folding area FA.

[0067] The width of the plurality of openings 111 in the extension direction (X axis) of the folding axis F of the folding region may be greater than the width of the plurality of openings 111 in the direction (Y axis) perpendicular to the extension direction of the folding axis F. For example, the plurality of openings 111 may preferably have an elliptical shape, but is not limited thereto.

[0068] A flexible display device such as the foldable display device 100 needs to be folded and unfolded. Therefore, in order to ensure flexibility, a plurality of patterns 121 are formed in the folding region of the second support substrate 120 supporting the display panel 130. In addition, in order to suppress the plurality of patterns 121 formed in the folding region of the second support substrate 120 from being recognized by the display panel 130, the first support substrate 110 is disposed between the second support substrate 120 and the display panel 130.

[0069] Here, an amorphous metal having excellent elastic limit may be used as the first support substrate 110. Amorphous metal has higher hardness and brittleness than crystalline metal. Therefore, if stress is concentrated in the outer region of the first support substrate 110 when the foldable display device 100 is folded and unfolded, cracks may occur in the stress concentration region. As a result, the display panel 130 may be degraded in display quality.

[0070] Therefore, in the display device 100 according to the exemplary embodiment of the present disclosure, a plurality of openings 111 are provided in an area corresponding to the non-display area NDA of the folding area FA of the first support substrate 110. Therefore, the occurrence and propagation of cracks in the first support substrate 110 can be suppressed. Specifically, a plurality of openings 111 are formed in an area corresponding to the non-display area NDA of the folding area FA of the first support substrate 110. Therefore, stretchability can be imparted to the outer area of ​​the first support substrate 110. Therefore, the folding shape at the outer area of ​​the first support substrate 110 can be caused to be close to a circular shape, so that the folding radius of the outer area of ​​the first support substrate 110 can be increased. As the folding radius of the outer area of ​​the first support substrate 110 increases, the stress at the outer area of ​​the first support substrate 110 can be dispersed. Therefore, the occurrence of cracks in the outer area of ​​the first support substrate 110 can be suppressed.

[0071] In particular, the plurality of openings 111 can suppress the occurrence of cracks inside the first support substrate 110 and at the outer region of the first support substrate 110. For example, if the plurality of openings have a circular shape with the same radius or a polygonal shape with linear edges, stress may be concentrated in the central region or edge region of each opening. Therefore, cracks caused by the plurality of openings 111 may occur inside the first support substrate 110. Therefore, the plurality of openings 111 provided in the region corresponding to the non-display region NDA of the folding region FA of the first support substrate 110 may preferably have an elliptical shape.

[0072] Therefore, in the display device 100 according to the exemplary embodiment of the present disclosure, the plurality of openings 111 having the above-described shape are formed in an area corresponding to the non-display area NDA of the folding area FA of the first support substrate 110. Therefore, the stress concentrated in a specific area of ​​the first support substrate 110 during folding can be dispersed. Therefore, even if the display device 100 is repeatedly folded, deformation such as fracture or plastic deformation does not occur, and thus the folding reliability can be improved.

[0073] Figure 5 is a schematic plan view of a first supporting substrate according to another exemplary embodiment of the present disclosure. Figure 5 The first support substrate 210 shown in FIG. Figures 1 to 4 The support substrate 110 shown in FIG. 1 is substantially the same configuration except that a plurality of grooves G recessed inwardly are included in the edge of the non-display area NDA of the folding area FA. Therefore, repeated description will be omitted.

[0074] Reference Figure 5 , the first support substrate 210 according to another exemplary embodiment of the present disclosure may include a plurality of grooves G corresponding in shape to the plurality of openings 111. For example, the width of the plurality of grooves G in the extension direction (X-axis) of the folding axis F of the folding area FA may be greater than the width of the plurality of grooves G in the direction perpendicular to the extension direction (Y-axis) of the folding axis F.

[0075] Since the plurality of grooves G have a shape that is recessed inwardly in the edge of the non-display area NDA of the folding area FA, the effective length at the edge of the first support substrate 210 can be increased. Specifically, the effective length refers to the length of the edge of the folding area FA of the foldable display device 100 in a direction perpendicular to the folding axis F. The effective length is the length that the foldable display device 100 can be deformed at the edge of the first support substrate 210 when it is folded.

[0076] In the first support substrate 210 according to another exemplary embodiment of the present disclosure, a plurality of grooves G are included in the edge of the first support substrate 210 during folding. Therefore, the effective length at the edge of the first support substrate 210 is increased. Therefore, the tension at the edge is further increased. Therefore, during folding, the folded shape of the first support substrate 210 can be more easily caused to approach a circular shape.

[0077] Therefore, in the display device 100 according to another exemplary embodiment of the present disclosure, a plurality of grooves G recessed inwardly are included in the edge of the first support substrate 210. Therefore, the stress concentrated in the edge region of the first support substrate 110 during folding can be effectively dispersed. Therefore, even if the display device 100 is repeatedly folded, deformation such as fracture or plastic deformation does not occur, and thus the folding reliability can be further improved.

[0078] Figure 6 is a schematic plan view of a first supporting substrate according to yet another exemplary embodiment of the present disclosure.

[0079] Figure 6 The first support substrate 310 shown in FIG. Figure 5 The supporting substrate 210 shown in FIG. 1 is substantially the same configuration as that of FIG. 1 , except that the sizes of the plurality of openings 311 increase as the distance from the display area DA decreases. Therefore, repeated descriptions will be omitted.

[0080] Reference Figure 6 , the sizes of the plurality of openings 311 formed in the first support substrate 310 according to another exemplary embodiment of the present disclosure may be different according to positions. Specifically, the sizes of the plurality of openings 311 formed in the first support substrate 310 increase as the distance from the display area DA decreases.

[0081] For example, if the first support substrate 310 includes a plurality of grooves G, the plurality of grooves G are formed at the outermost area, ie, the edge, of the first support substrate 310. Therefore, the plurality of grooves G may be smaller in size than the plurality of openings 311 formed in the non-display area NDA of the folding area FA of the first support substrate 310.

[0082] Therefore, in the display device 100 according to another exemplary embodiment of the present disclosure, a plurality of openings 311 are formed in the first support substrate 310 to have different sizes according to positions. Therefore, the plurality of openings 311 make it easy to disperse the stress around the display area DA. Therefore, the occurrence of cracks around the display area DA can be suppressed. In addition, the plurality of openings 311 suppress the propagation of cracks caused by repeated folding in the outer area of ​​the first support substrate 310. Therefore, the propagation of cracks to the display area DA can be suppressed.

[0083] Fig. 7A is a schematic plan view of a first supporting substrate according to yet another exemplary embodiment of the present disclosure. Figure 7B yes Fig. 7A ] An enlarged side view of a region A of the first supporting substrate is shown in FIG. Figure 7C is along Figure 7BSchematic cross-sectional view of the first supporting substrate taken along line VIIc-VIIc'.

[0084] Fig. 7A The first support substrate 410 shown in FIG. Figure 5 The first support substrate 210 shown in FIG. 4 has substantially the same configuration except for the edge area OEA corresponding to the outermost area of ​​the first support substrate 410 and the different cross-sectional shapes of the edge area OEA and the plurality of openings 411. Therefore, repeated description will be omitted.

[0085] Reference 7A to 7C , the first support substrate 410 includes a central area corresponding to the display area DA and an outer area corresponding to the non-display area NDA. The outer area corresponding to the non-display area NDA includes an edge area OEA corresponding to the outermost area of ​​the first support substrate 410. Here, the width of the cross-sectional shape of the edge area OEA of the first support substrate 410 may increase as the edge area is closer to the lower surface of the first support substrate 410. In addition, the plurality of openings 411 formed in the first support substrate 410 include the edge area EA, and the edge area EA of the plurality of openings 411 may have a smaller cross-sectional area than the central area of ​​the first support substrate 410.

[0086] The cross-sectional shape of the edge area OEA of the first support substrate 410 and the cross-sectional shape of the edge area EA of the plurality of openings 411 may be changed by the same process. For example, the cross-sectional shape of the edge area OEA of the first support substrate 410 and the cross-sectional shape of the edge area EA of the plurality of openings 411 may be changed as described above by an etching process that is not accompanied by high heat generation.

[0087] The cross-sectional shape of the edge area OEA of the first support substrate 410 increases in width as the edge area is closer to the lower surface of the first support substrate 410. Therefore, the edge area OEA of the first support substrate 410 may have a smaller thickness than the central area of ​​the first support substrate 410.

[0088] Here, the edge area OEA of the first support substrate 410 refers to a portion of the outermost area of ​​the first support substrate 410 in which the width of the lower surface of the first support substrate 410 is changed. For example, the width of the edge area OEA of the first support substrate 410 may be equal to or less than 50% of the thickness of the central area of ​​the first support substrate 410.

[0089] Also, the sectional area of ​​the edge area EA of the plurality of openings 411 may be changed to be smaller than the sectional area of ​​the central area of ​​the first support substrate 410. Preferably, the sectional thickness of the edge area EA of the plurality of openings may be equal to or less than 50% of the thickness of the central area of ​​the first support substrate 410.

[0090] If the width of the edge area OEA of the first support substrate 410 exceeds the above range or the cross-sectional thickness of the edge area EA of the plurality of openings exceeds the above range, in the non-display area, in order to arrange various wirings and integrated circuits, the overall area of ​​the non-display area may be undesirably increased.

[0091] Therefore, in the display device 100 according to still another exemplary embodiment of the present disclosure, the cross-sectional shape of the edge area OEA of the first support substrate 410 is changed as described above. Therefore, stress concentration in the outermost area of ​​the first support substrate 410 can be suppressed.

[0092] In addition, the cross-sectional shape of the edge area EA of the plurality of openings 411 is changed as described above. Therefore, it is possible to more easily disperse the stress so as to suppress the stress concentration in the plurality of openings 411.

[0093] Therefore, the possibility of cracks occurring inside the first support substrate 410 and in the outer region of the first support substrate 410 can be further reduced. Therefore, even if the display device 100 is repeatedly folded, deformation such as breakage or plastic deformation does not occur, and thus folding reliability can be further improved.

[0094] Figure 8 is a schematic plan view of a foldable display device according to yet another exemplary embodiment of the present disclosure. Fig. 9 is along Figure 8 A schematic cross-sectional view of the foldable display device taken along line IX-IX'.

[0095] A foldable display device 500 according to another exemplary embodiment of the present disclosure includes a display panel 130, which includes a display area DA and a non-display area NDA surrounding the display area DA, and a folding area FA defined in the display area and the non-display area and non-folding areas NFA1 and NFA2 on both sides of the folding area. In addition, the foldable display device 500 includes a first support substrate 510 disposed below the display panel 130 to support the display panel 130 and a second support substrate 120 disposed below the first support substrate 510. The first support substrate 510 includes a central area corresponding to the display area DA and an outer area corresponding to the non-display area NDA. The outer area includes an edge area OEA corresponding to the outermost area of ​​the first support substrate 510. In addition, the cross-sectional shape of the edge area OEA increases in width as the edge area is closer to the lower surface of the first support substrate 510. Figure 8 and Fig. 9 The foldable display device 500 shown in FIG. Figures 1 to 3The foldable display device 100 shown in FIG. 1 has substantially the same configuration as that of FIG. 1 , except for the configuration of the first support substrate 510 . Therefore, repeated descriptions will be omitted.

[0096] Reference Figure 8 and Fig. 9 , a foldable display device 500 according to another exemplary embodiment of the present disclosure includes a first support substrate 510 and a second support substrate 120. The first support substrate 510 and the second support substrate 120 are disposed under the display panel 130 and support the display panel 130 to suppress sagging or deformation of the display panel 130. In addition, the first support substrate 510 and the second support substrate 120 protect the display panel 130 from external impact, moisture, or impurities.

[0097] The first support substrate 510 may enhance the rigidity of the display panel 130 and play a role in suppressing the plurality of patterns 121 formed in the second support substrate 120 from being recognized through the display panel 130 .

[0098] The first support substrate 510 may be made of an amorphous metal having excellent corrosion resistance and elasticity. For example, the first support substrate 510 may include any amorphous metal selected from the group consisting of nickel, iron, cobalt, palladium, silicon, magnesium, zirconium, titanium, calcium, copper, platinum, gold, and combinations thereof.

[0099] Conventionally, a mother substrate made of an amorphous metal is cut by using a shearing force of scissors, a blade, or a die to use the amorphous metal as the first support substrate 510 .

[0100] However, amorphous metals have excellent elasticity but show brittleness under high hardness. Therefore, if the first supporting substrate is prepared using shear force as in the conventional method, shear bands such as microcracks may appear in the cutting plane due to the shear force. Therefore, when the foldable display device 500 is folded and unfolded, if stress is concentrated in the outer area of ​​the first supporting substrate 510, microcracks in the shear band or cracks in the stress concentrated area may propagate to the inner area. This phenomenon is called fatigue fracture. As a result, the display panel 130 may be reduced in display quality.

[0101] Therefore, according to an exemplary embodiment of the present disclosure, the first support substrate 510 can be prepared by etching a mother substrate made of an amorphous metal at a low temperature without cutting the mother substrate using a shear force. Since the first support substrate 510 is prepared by the above method, no shear band occurs in the outermost region of the first support substrate 510.

[0102] According to Figure 8 and Fig. 9According to the exemplary embodiment of the present disclosure shown in , the cross-sectional shape of the edge area OEA corresponding to the outermost area of ​​the first support substrate 510 may increase in width as the edge area is closer to the lower surface of the first support substrate 510. For example, the first support substrate 510 is prepared by etching at a low temperature, and therefore, the cross-sectional shape of the edge area OEA of the first support substrate 510 may be designed as described above.

[0103] If the cross-sectional shape of the edge area OEA of the first support substrate 510 is designed as described above, a shear band does not appear in the edge area OEA of the first support substrate 510. Therefore, even if a crack appears in the edge area of ​​the first support substrate 510, the crack in the edge area caused by the shear band does not propagate into the first support substrate 510.

[0104] For example, the width of the edge area OEA of the first support substrate 510 may be equal to or less than 50% of the thickness of the central area of ​​the first support substrate 510 .

[0105] In addition, the first support substrate 510 may further include a plurality of openings in an area corresponding to the non-display area NDA of the folding area FA. Here, the width of the plurality of openings in the extension direction (X-axis) of the folding axis F of the folding area FA may be greater than the width of the plurality of openings in the direction (Y-axis) perpendicular to the extension direction of the folding axis F. For example, if the first support substrate 510 further includes a plurality of openings, when the mother substrate is etched at a low temperature to prepare the first support substrate 510, the plurality of openings may also be included in the first support substrate 510.

[0106] If the first support substrate 510 further includes a plurality of openings, the outer region of the first support substrate 510 is given stretchability. Therefore, the folded shape at the outer region of the first support substrate 510 can be made close to a circular shape, so that the folding radius of the first support substrate 510 can be increased.

[0107] Furthermore, if the first support substrate 510 further includes a plurality of openings, edge regions of the plurality of openings may have a smaller cross-sectional area than a central region of the first support substrate 510 .

[0108] Therefore, in the display device 500 according to another exemplary embodiment of the present disclosure, it is easy to suppress the occurrence of a shear band in the edge area of ​​the first support substrate 510. Therefore, even if a crack occurs in the edge area OEA of the first support substrate 510 when the first support substrate 510 is repeatedly folded, the crack does not extend from the edge area OEA of the first support substrate 510 into the first support substrate 510. That is, the crack does not extend into the display area DA. In addition, if the first support substrate 510 further includes a plurality of openings, it is easier to disperse the stress concentrated in the outer area and inside the first support substrate 510 even when the first support substrate 510 is repeatedly folded. Therefore, it is possible to suppress the occurrence of a crack in the first support substrate 510.

[0109] Hereinafter, the above-mentioned effects of the present disclosure will be described in detail with reference to the embodiments and comparative embodiments. However, the following embodiments are provided for illustrative purposes and do not limit the scope of the present disclosure.

[0110] In order to study the effect of the present disclosure, the amorphous metal foil was cut into six first supporting substrate samples by using scissors, and these samples were used as comparative embodiments.

[0111] Meanwhile, six first support substrate samples were prepared by etching the amorphous metal foil. In each of three samples among the six first support substrate samples prepared by etching the amorphous metal foil, a plurality of openings each having an elliptical shape were formed corresponding to the following: Figure 4 The non-display area of ​​the folded area of ​​the first support substrate shown in . These samples were used as Embodiment 1.

[0112] Furthermore, in each of the other three samples among the six first supporting substrate samples prepared by etching the amorphous metal foil, no opening was formed in the folding region.

[0113] Under each of the folding radius conditions of 1.5 mm and 2.0 mm, the samples of Embodiment 1 and Embodiment 2 and the comparative embodiment were subjected to a folding test of 200,000 cycles. It was checked whether each of the embodiment and the comparative embodiment passed the folding test under each folding radius condition, that is, whether each first supporting substrate sample had crack propagation after the folding test of 200,000 cycles. The number of first supporting substrate samples without crack propagation in the samples of the embodiment and the comparative embodiment is respectively listed in Table 1.

[0114] [Table 1]

[0115]

[0116] As listed in Table 1, it can be seen that the supporting substrates of Embodiment 1 and Embodiment 2 passed the folding test of 200,000 cycles under the folding radius conditions of 2.0 mm and 1.5 mm.

[0117] However, no etching process was performed on the first support substrate of the comparative embodiment, and therefore, a shear band appeared in the edge region of the first support substrate. Therefore, not all first support substrates failed the folding test of 200,000 cycles under the folding radius conditions of 2.0 mm and 1.5 mm.

[0118] Exemplary embodiments of the present disclosure may also be described as follows:

[0119] According to one aspect of the present disclosure, a foldable display device includes: a display panel, the display panel including a display area and a non-display area surrounding the display area, and a folding area and non-folding areas on both sides of the folding area defined in the display area and the non-display area; a first supporting substrate, the first supporting substrate is arranged below the display panel to support the display panel, the first supporting substrate includes a plurality of openings arranged in an area corresponding to the non-display area of ​​the folding area; and a second supporting substrate, the second supporting substrate is arranged below the first supporting substrate, wherein the width of the plurality of openings in the extension direction of the folding axis of the folding area is greater than the width of the plurality of openings in the direction perpendicular to the extension direction of the folding axis.

[0120] The plurality of openings may have an oval shape.

[0121] The plurality of openings may increase in size as the distance from the display area decreases.

[0122] The first support substrate includes a plurality of grooves recessed inwardly in an edge of the non-display area of ​​the folding area, and the plurality of grooves may correspond in shape to the plurality of openings.

[0123] The first support substrate includes a central region corresponding to the display region and an outer region corresponding to the non-display region, and the outer region may be folded with a larger folding radius than the central region.

[0124] The first supporting substrate includes a central area corresponding to the display area and an outer area corresponding to the non-display area, and the outer area includes an edge area corresponding to the outermost area of ​​the first supporting substrate, and the cross-sectional shape of the edge area can increase in width as the edge area is closer to the lower surface of the first supporting substrate.

[0125] Compared to a central region of the first carrier substrate, the edge region may have a smaller thickness.

[0126] The width of the edge region may be equal to or less than 50% of the thickness of the central region of the first support substrate.

[0127] The plurality of openings include an edge region corresponding to an outermost region of the plurality of openings, and the edge region of the plurality of openings may have a smaller cross-sectional area than a central region of the first support substrate.

[0128] A cross-sectional thickness of edge regions of the plurality of openings may be equal to or less than 50% of a thickness of a central region of the first support substrate.

[0129] The first support substrate may include any amorphous metal selected from the group consisting of nickel, iron, cobalt, palladium, silicon, magnesium, zirconium, titanium, calcium, copper, platinum, gold, and combinations thereof.

[0130] The second support substrate may include a plurality of patterns formed corresponding to the folding regions.

[0131] According to another aspect of the present disclosure, a foldable display device includes: a display panel, which includes a display area and a non-display area surrounding the display area, and a folding area defined in the display area and the non-display area and non-folding areas on both sides of the folding area; a first supporting substrate, which is arranged below the display panel to support the display panel; and a second supporting substrate, which is arranged below the first supporting substrate, wherein the first supporting substrate includes a central area corresponding to the display area and an outer area corresponding to the non-display area, and the outer area includes an edge area corresponding to the outermost area of ​​the first supporting substrate, and the cross-sectional shape of the edge area increases in width as the edge area is closer to the lower surface of the first supporting substrate.

[0132] The first supporting substrate may include a plurality of openings arranged in an area corresponding to the non-display area of ​​the folding area, and wherein a width of the plurality of openings in an extension direction of a folding axis of the folding area is greater than a width of the plurality of openings in a direction perpendicular to the extension direction of the folding axis.

[0133] The plurality of openings include an edge region corresponding to an outermost region of the plurality of openings, and the edge region of the plurality of openings may have a smaller cross-sectional area than a central region of the first support substrate.

[0134] Although the exemplary embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited thereto and can be implemented in a variety of different forms without departing from the technical concept of the present disclosure. Therefore, the exemplary embodiments of the present disclosure are provided for illustrative purposes only and are not intended to limit the technical concept of the present disclosure. The scope of the technical concept of the present disclosure is not limited thereto. Therefore, it should be understood that the above exemplary embodiments are illustrative in all aspects and do not limit the present disclosure. The scope of protection of the present disclosure should be interpreted based on the attached claims, and all technical concepts within their equivalent ranges should be interpreted as falling within the scope of the present disclosure.

Claims

1. A foldable display device, comprising: a display panel, the display panel comprising a display area and a non-display area surrounding the display area, wherein the display panel is divided into a folding area including a portion of the display area and a portion of the non-display area and non-folding areas on both sides of the folding area; a first support substrate disposed under the display panel to support the display panel, the first support substrate including a plurality of openings disposed only in a region corresponding to a portion of the non-display region of the folding region; and a second supporting substrate, the second supporting substrate being disposed below the first supporting substrate, Wherein, the width of the plurality of openings in the extension direction of the folding axis of the folding area is greater than the width of the plurality of openings in the direction perpendicular to the extension direction of the folding axis.

2. The foldable display device according to claim 1, wherein: The plurality of openings have an elliptical shape.

3. The foldable display device according to claim 1, wherein: The first supporting substrate further comprises: a central area corresponding to the display area and an outer area corresponding to the non-display area, and The outer region is folded with a larger folding radius than the central region.

4. The foldable display device according to claim 1, wherein: The first supporting substrate further comprises: a plurality of grooves, the plurality of grooves being recessed inwardly at edges of the portion of the non-display area of ​​the folding area, The plurality of grooves correspond in shape to the plurality of openings.

5. The foldable display device according to claim 1, wherein: The plurality of openings increase in size as the distance from the display area decreases.

6. The foldable display device according to claim 1, wherein: The first supporting substrate further comprises: a central area corresponding to the display area and an outer area corresponding to the non-display area, and The outer region includes an edge region corresponding to an outermost region of the first support substrate, and The cross-sectional shape of the edge region increases in width as the edge region is closer to the lower surface of the first support substrate.

7. The foldable display device according to claim 6, wherein: The edge region has a smaller thickness than the central region of the first support substrate.

8. The foldable display device according to claim 6, wherein: The width of the edge region is equal to or less than 50% of the thickness of the central region of the first support substrate.

9. The foldable display device according to claim 1, wherein: The plurality of openings include an edge region corresponding to an outermost region of the plurality of openings, and Compared to a central region of the first support substrate, edge regions of the plurality of openings have a smaller cross-sectional area.

10. The foldable display device according to claim 9, wherein: The cross-sectional thickness of edge regions of the plurality of openings is equal to or less than 50% of the thickness of a central region of the first support substrate.

11. The foldable display device according to claim 1, wherein: The first support substrate comprises any one amorphous metal selected from the group consisting of nickel, iron, cobalt, palladium, silicon, magnesium, zirconium, titanium, calcium, copper, platinum, gold and combinations thereof.

12. The foldable display device according to claim 1, wherein: The second support substrate includes a plurality of patterns formed corresponding to the folding area.

13. A foldable display device, comprising: a display panel, the display panel comprising a display area and a non-display area surrounding the display area, wherein the display panel is divided into a folding area including a portion of the display area and a portion of the non-display area and non-folding areas on both sides of the folding area; a first support substrate disposed under the display panel to support the display panel, the first support substrate including a plurality of openings disposed only in a region corresponding to a portion of the non-display region of the folding region; and a second supporting substrate, the second supporting substrate being disposed below the first supporting substrate, The first supporting substrate further includes a central area corresponding to the display area and an outer area corresponding to the non-display area, and The outer region includes an edge region corresponding to an outermost region of the first support substrate, and The cross-sectional shape of the edge region increases in width as the edge region is closer to the lower surface of the first support substrate.

14. The foldable display device according to claim 13, wherein: The width of the plurality of openings in the extending direction of the folding axis of the folding region is greater than the width of the plurality of openings in the direction perpendicular to the extending direction of the folding axis.

15. The foldable display device according to claim 13, wherein: The plurality of openings include an edge region corresponding to an outermost region of the plurality of openings, and Compared to a central region of the first support substrate, edge regions of the plurality of openings have a smaller cross-sectional area.

16. The foldable display device according to claim 13, wherein: The outer region is folded with a larger folding radius than the central region.

17. The foldable display device according to claim 14, wherein: The first supporting substrate further comprises: a plurality of grooves, wherein the plurality of grooves are recessed inwardly at the edge of the non-display area of ​​the folding area, The plurality of grooves correspond in shape to the plurality of openings.

18. The foldable display device according to claim 14, wherein: The plurality of openings increase in size as the distance from the display area decreases.

19. The foldable display device according to claim 13, wherein: The edge region has a smaller thickness than the central region of the first support substrate.

20. The foldable display device according to claim 13, wherein: The second support substrate includes a plurality of patterns formed corresponding to the folding area.

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