Foldable display device

Abstract

The present invention relates to a foldable display device, wherein the foldable display device comprises: a display panel including a folding area and non-folding areas on both sides of the folding area; and a hinge portion disposed in an area corresponding to the folding area at the bottom of the display panel and configured to fold the display panel inwardly or outwardly, wherein the hinge portion comprises a plurality of rotation axes and a plurality of connecting links disposed between the plurality of rotation axes. Accordingly, the foldable display device can be folded inwardly or outwardly by means of a hinge portion having a simple structure. In addition, the radius of curvature during folding can be changed as desired by adjusting the components of the hinge portion, namely the number of rotation axes and connecting links, the cross-sectional length, etc.

Description

Technology Field

[0001] The present invention relates to a foldable display device, and more specifically, to a foldable display device that can be folded and unfolded in both directions using a hinge part of a simple structure. Background Technology

[0002] In recent years, as society has entered the full-scale information age, the field of displays, which process and display large amounts of information, has developed rapidly. Display devices used in computer monitors, TVs, and mobile phones include Organic Light Emitting Displays (OLEDs), which emit light on their own, and Liquid Crystal Displays (LCDs), which require a separate light source.

[0003] The application range of display devices is expanding to include not only computer monitors and TVs but also personal portable devices, and research is underway on display devices that have a large display area while possessing reduced volume and weight.

[0004] In particular, flexible display devices, which are manufactured to display images even when bent or folded like paper, are attracting attention as next-generation display devices. Flexible display devices can be classified into highly durable unbreakable, bendable (which can be bent without breaking), rollable (which can be rolled up), and foldable (which can be folded) by utilizing plastic thin-film transistor substrates instead of glass. These flexible display devices offer advantages in terms of space utilization, interior design, and aesthetics, and can have various application fields. The problem to be solved

[0005] The problem that the present invention aims to solve is to provide a foldable display device with a simple structure that can be folded and unfolded in both directions.

[0006] Another problem that the present invention aims to solve is to provide a foldable display device capable of setting various radii of curvature when folded.

[0007] The problems of the present invention are not limited to those mentioned above, and other unmentioned problems will be clearly understood by those skilled in the art from the description below. means of solving the problem

[0008] A foldable display device according to one embodiment of the present invention comprises: a display panel including a folding area and non-folding areas on both sides of the folding area; and a hinge portion configured to fold the display panel inwardly or outwardly by being disposed in an area corresponding to the folding area at the bottom of the display panel, wherein the hinge portion comprises a plurality of rotation axes and a plurality of connecting links disposed between the plurality of rotation axes. Accordingly, the foldable display device can be folded inwardly or outwardly by means of a hinge portion having a simple structure. In addition, the radius of curvature during folding can be changed as desired by adjusting the components of the hinge portion, namely the number of rotation axes and connecting links, the cross-sectional length, etc.

[0009] Specific details of other embodiments are included in the detailed description and drawings. Effects of the invention

[0010] The foldable display device of the present invention can implement inward or outward bidirectional folding while simplifying the parts of the hinge part and improving the difficulty of processing the parts by applying a hinge part with a simple structure.

[0011] The effects according to the present invention are not limited to those exemplified above, and a wider variety of effects are included within the present invention. Brief explanation of the drawing

[0012] FIG. 1 is a schematic plan view of a foldable display device according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a foldable display device according to II-II' of FIG. 1. FIG. 3 is a schematic three-dimensional view showing a rotation axis according to one embodiment of the present invention. FIG. 4 is a schematic three-dimensional view showing a coupling link according to one embodiment of the present invention. FIG. 5 is a schematic three-dimensional view showing the fastening portion of a rotating shaft and a coupling link according to one embodiment of the present invention. FIG. 6 is a schematic side view illustrating an inwardly folded form of a foldable display device according to one embodiment of the present invention. FIG. 7 is a schematic side view illustrating an outwardly folded form of a foldable display device according to one embodiment of the present invention. FIG. 8 is a schematic plan view of a foldable display device according to another embodiment of the present invention. FIG. 9 is a schematic cross-sectional view of a foldable display device according to IX-IX' of FIG. 8. FIG. 10 is a schematic side view illustrating a folded form of a foldable display device according to another embodiment of the present invention. Specific details for implementing the invention

[0013] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0014] Shapes, areas, ratios, angles, numbers, etc. disclosed in the drawings for explaining embodiments of the present invention are exemplary, and therefore the present invention is not limited to the depicted details. Throughout the specification, the same reference numerals refer to the same components. Furthermore, in describing the present invention, if it is determined that a detailed description of related prior art may unnecessarily obscure the essence of the present invention, such detailed description is omitted. Where terms such as "includes," "has," or "is made up" are used in the present invention, other parts may be added unless "only" is used. When a component is expressed in the singular, it includes cases where it is included in the plural unless specifically stated otherwise.

[0015] In interpreting the components, they are interpreted to include a margin of error even in the absence of a separate explicit statement.

[0016] In the case of describing a positional relationship, for example, when the positional relationship between two parts is described using expressions such as 'on,' 'upper,' 'lower,' or 'next to,' one or more other parts may be located between the two parts unless 'immediately' or 'directly' is used.

[0017] When an element or layer is referred to as "on" another element or layer, it includes cases where another layer or element is placed directly on top of or in between.

[0018] Additionally, terms such as first, second, etc. are used to describe various components, but these components are not limited by these terms. These terms are used merely to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the technical scope of the present invention.

[0019] Throughout the specification, the same reference numerals refer to the same components.

[0020] The area and thickness of each component shown in the drawings are illustrated for convenience of explanation, and the present invention is not necessarily limited to the area and thickness of the illustrated components.

[0021] The features of each of the various embodiments of the present invention may be combined or combined with one another, either partially or wholly, and may technically enable various interlocking and operation. Each embodiment may be implemented independently of one another or may be implemented together in an associated relationship.

[0022] The present invention will be described below with reference to the drawings.

[0023] FIG. 1 is a schematic plan view of a foldable display device according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a foldable display device according to II-II' of FIG. 1.

[0024] Referring to FIGS. 1 and 2, a foldable display device (100) according to one embodiment of the present invention includes a display panel (110) and a back cover (120). For convenience of explanation, the foldable display device according to one embodiment of the present invention is assumed to be an organic light-emitting display device, but is not limited thereto.

[0025] Referring to FIG. 1, the display panel included in the foldable display device (100) includes a display area (DA) and a non-display area (NDA). Additionally, the display panel includes a folding area (FA) and a non-folding area (NFA1, NFA2). The display panel may be divided into a display area (DA) and a non-display area (NDA) depending on whether an image is displayed, and may be divided into a folding area (FA) and non-folding areas (NFA1, NFA2) on both sides of the folding area (FA) depending on whether it is folded.

[0026] The display area (DA) is an area where a plurality of pixels are arranged to substantially display an image. In the display area (DA), a plurality of pixels including light-emitting regions for displaying an image, as well as thin-film transistors, capacitors, etc., for driving the pixels may be arranged. A single pixel may include a plurality of sub-pixels (SP). A sub-pixel (SP) is the minimum unit constituting the display area, and each sub-pixel (SP) may be configured to emit light of a specific wavelength band. For example, each sub-pixel (SP) may be configured to emit red, green, blue, or white light. The non-display area (NDA) is located to surround the display area (DA). The non-display area (NDA) is an area where an image is substantially not displayed, and various wiring, driving ICs, printed circuit boards, etc., for driving the pixels and driving circuits arranged in the display area (DA) are arranged therein. For example, various ICs such as gate driver ICs and data driver ICs, VSS wiring, etc., may be arranged in the non-display area (NDA).

[0027] As described above, the display panel may be defined as a folding area (FA) and a non-folding area (NFA1, NAF2) depending on whether it is folded. A display panel according to one embodiment of the present invention includes a first non-folding area (NFA1), a folding area (FA), and a second non-folding area (NFA2) that are sequentially located along the vertical direction of the folding axis (F) of the folding area (FA), i.e., the Y-axis direction.

[0028] The folding area (FA) is an area that is folded when the foldable display device (100) is folded, and may include a part of the display area (DA) and a part of the non-display area (NDA). The folding area (FA) may be folded according to a specific radius of curvature with respect to the direction perpendicular to the folding axis (F) of the folding area (FA), that is, the Y-axis direction of FIG. 1. When the folding area (FA) is folded with respect to the direction perpendicular to the folding axis (F), the folding area (FA) may form a part of a circle or an ellipse. In this case, the radius of curvature of the folding area (FA) refers to the radius corresponding to the part of the circle or ellipse formed by the folding area (FA).

[0029] The first non-folding area (NFA1) and the second non-folding area (NFA2) are areas that do not fold when the foldable display device (100) is folded. That is, the first non-folding area (NFA1) and the second non-folding area (NFA2) are each areas that maintain a flat state when the foldable display device (100) is folded. The first non-folding area (NFA1) and the second non-folding area (NFA2) may each include a part of the display area (DA) and a part of the non-display area (NDA). When the folding area (FA) is folded based on the folding direction, the first non-folding area (NFA1) and the second non-folding area (NFA2) may overlap each other.

[0030] The display panel (110) is a panel on which an image is displayed, and may have a display element for displaying the image and a circuit unit for driving the display element. 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.

[0031] The circuit section may include various thin-film transistors, capacitors, wiring, and driving ICs for driving an organic light-emitting diode. For example, the circuit section may include various configurations such as driving thin-film transistors, switching thin-film transistors, storage capacitors, gate wiring, data wiring, gate driver ICs, and data driver ICs, but is not limited thereto.

[0032] The display panel (110) is a flexible substrate on which a driving thin-film transistor and a light-emitting element are formed, and which is encapsulated by an encapsulation portion, and includes a flexible substrate with a very thin thickness to realize flexibility and a display element disposed on the flexible substrate.

[0033] The flexible substrate can be formed from an insulating material having flexibility, and may be an insulating plastic substrate selected from, for example, polyimide, polyethersulfone, polyethylene terephthalate and polycarbonate.

[0034] In the case of a plastic substrate, since its barrier properties against moisture or oxygen are relatively weak, it may have a structure in which a plastic film and an inorganic film are laminated to compensate for this. For example, a flexible substrate may include a multilayer structure in which a first plastic film, an inorganic film, and a second plastic film are sequentially laminated, but is not limited thereto.

[0035] A driving thin-film transistor for driving a display element may be disposed on a flexible substrate. The driving thin-film transistor may be disposed 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. Additionally, the driving thin-film transistor may further include a gate insulating layer for insulating the gate electrode and the active layer, and may further include an interlayer insulating layer for insulating the gate electrode, the source electrode, and the drain electrode. A planarization layer may be disposed on the driving thin-film transistor to flatten the upper surface. A display element may be disposed on the planarization layer. The display element may be an organic light-emitting device. The organic light-emitting device may include an anode, a cathode, and an organic light-emitting layer disposed between them. In the organic light-emitting device, holes injected from the anode and electrons injected from the cathode combine in the organic light-emitting layer to emit light. An image can be displayed using the light emitted in this way.

[0036] Flexible substrates have excellent folding characteristics but are thin and have lower rigidity compared to glass or metal substrates, so it may be difficult to maintain a consistent shape when folded, and consequently, sagging may occur.

[0037] Accordingly, a back cover (120) is disposed on the back surface of the display panel (110) to support the display panel (110) including a flexible substrate, while protecting the display panel (110) from moisture or foreign matter penetrating from the outside or external impact. For example, the back cover (120) can be attached to the back surface of the display panel (110) by an adhesive layer (adh).

[0038] Referring to FIG. 2, the back cover (120) includes a hinge portion (121) configured to be positioned in an area corresponding to a folding area (FA) to in-fold or out-fold the display panel (110). When the foldable display device (100) is in a flat state, the hinge portion (121) is arranged in parallel in one direction to support the display panel (110) from the back. Although the following disclosure describes the hinge portion (121) being formed integrally with the back cover (120) in the folding area (FA) of the back cover (120) that supports the display panel (110), the hinge portion (121) may be positioned on the back of the back cover (120) to correspond to the folding area (FA) so as to fold or unfold the folding device (100).

[0039] For example, when the hinge portion (121) is integrally formed in the folding area (FA) of the back cover (120), the rotation axis (121a) forming the outermost part of the hinge portion (121) and the back cover (120) may be linked in the same way as the rotation axis (121a) and the coupling link (121b) described later, but are not limited thereto.

[0040] The hinge portion (121) includes a plurality of rotation axes (121a) and a plurality of connecting links (121b). For example, the hinge portion (121) includes n rotation axes (121a) (wherein is a natural number greater than or equal to 2) and n-1 connecting links (121b) arranged between the n rotation axes (121a).

[0041] In one embodiment of the present invention, a hinge portion (121) has a plurality of connecting links (121b) arranged between a plurality of rotation axes (121a). At this time, the plurality of connecting links (121b) include a first surface (S1) having a flat surface and a second surface (S2) having a curved surface, and the second surface (S2) includes two concave surfaces (CC) and a convex surface (CV) between the concave surfaces (CC). At this time, the radius of curvature of the concave surfaces (CC) may correspond to the radius of curvature of the rotation axis (121a). For example, the rotation axis (121a) may be arranged to be in contact with the second surface (S2) of the connecting link (121b), specifically the concave surface (CC) of the second surface (S2). Accordingly, preferably, the radius of curvature of the concave surface (CC) may be the same as the radius of curvature of the rotation axis (121a).

[0042] Additionally, a plurality of connecting links (121b) positioned between a plurality of rotation axes (121a) may be arranged sequentially in an up-and-down symmetrical manner. For example, among the plurality of connecting links (121b), a first connecting link may be positioned so that its first surface (S1) faces upward, i.e., the display surface of the display panel (110), and a second connecting link adjacent to the first connecting link may be positioned so that its first surface (S1) faces downward, i.e., the back surface of the display panel (110).

[0043] Accordingly, the hinge portion (121) of the present invention may have a plurality of rotational axes (121a) rotatably connected to one side and the other side of a plurality of coupling links (121b). For example, the hinge portion (121) may have a rotational axis (121a) rotatably connected to one side and the other side of a plurality of coupling links (121b), and may be rotatably connected along a second surface (S2), specifically a concave surface (CC), of a coupling link (121b).

[0044] Accordingly, in a display device (100) according to one embodiment of the present invention, a plurality of connecting links (121b) are sequentially arranged vertically symmetrically between a plurality of rotational axes (121a), and at this time, the rotational axes (121a) are arranged to contact a second surface (S2) having a curved surface of the connecting links (121b), thereby enabling folding of the hinge portion (121) in both directions.

[0045] A more detailed description of the plurality of rotation axes (121a) and plurality of connecting links (121b) constituting the hinge portion (121) will be provided later.

[0046] In some embodiments, a back plate may be further included between the display panel (110) and the back cover (120). Since the display panel (110) is formed in a thin shape, the back plate may be attached to the back surface of the display panel (110) to further support it. Additionally, the back plate can maintain a constant curvature of the display panel (110) when the foldable display device (100) is folded and suppress creases that may occur on the upper surface of the display panel (110).

[0047] The back plate may be made of a metallic material such as stainless steel (SUS), stainless steel (SUS) containing metals such as nickel (Ni), iron (Fe), aluminum (Al) series, or magnesium (Mg). Preferably, the back plate may be made of stainless steel (SUS). For example, stainless steel (SUS) has high restoring force and rigidity, so it can maintain high rigidity even if the thickness of the back plate is reduced. Accordingly, the back plate supports the display panel (110) and at the same time reduces the overall thickness of the foldable display device (100), thereby reducing the radius of curvature of the folding area (FA). However, the back plate is not limited to this and may be made of polymers such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), silicone, and polyurethane (PU).

[0048] Additionally, a cover window may be further disposed on the upper part of the display panel (110). The cover window protects the display panel (110) from external impacts and scratches. Accordingly, the cover window may be formed of a material that is transparent and has excellent impact resistance and scratch resistance. In addition, the cover window protects the display panel (110) from moisture and the like entering from the outside.

[0049] The cover window may be a flexible plastic series that can be folded for the thinness and flexibility of the foldable display device (100). For example, the cover window may be a film made of a polymer such as polyimide, polyamide imide, polyethylene terephthalate, polymethyl methacrylate, polypropylene glycol, or polycarbonate. As another example, the cover window may be a film made of an optically isotropic polymer such as a cycloolefin (co)polymer, optically isotropic polycarbonate, or optically isotropic polymethyl methacrylate.

[0050] In addition, various functional layers may be laminated on the cover window. For example, various functional layers such as an external light reflection reduction layer, a UV blocking layer, and a hard coating layer may be placed on the cover window, but are not limited thereto.

[0051] Hereinafter, with reference to FIGS. 3 to 5, a plurality of rotational axes and a plurality of connecting links constituting the hinge portion will be described in detail.

[0052] FIG. 3 is a schematic three-dimensional view showing a rotation axis according to one embodiment of the present invention. FIG. 4 is a schematic three-dimensional view showing a coupling link according to one embodiment of the present invention. FIG. 5 is a schematic three-dimensional view showing a fastening portion of a rotation axis and a coupling link according to one embodiment of the present invention.

[0053] Referring to FIGS. 3 to 5, according to one embodiment of the present invention, a plurality of rotational axes (121a) and a plurality of coupling links (121b) are linked to form a hinge portion (121). In the following, in order to focus on explaining the linking of the rotational axes (121a) and the coupling links (121b), the case in which one rotational axle (121a) is linked to one coupling link (121b) is illustrated. In this case, one rotational axle (121a) is illustrated as having a plurality of fastening grooves (G) on one side and one coupling link (121b) is illustrated as having a plurality of fastening portions (L) on one side. However, one rotational axle (121a) may have a plurality of fastening grooves (G) on one side and the other side, and one coupling link (121b) may have a plurality of fastening portions (L) on one side and the other side, so that a plurality of rotational axes (121a) and a plurality of coupling links (121b) can be linked.

[0054] According to one embodiment of the present invention, a plurality of fastening parts (L) included in a coupling link (121b) may be linked to a plurality of fastening grooves (G) included in a rotation axis (121a) to form a hinge part (121).

[0055] Referring to FIG. 3, a rotation axis (121a), which is one component of the hinge portion (121), includes a plurality of fastening grooves (G). The fastening grooves (G) are places where a coupling link (121b), which is another component constituting the hinge portion (121), is linked, and can form a predetermined space inward from the surface of the rotation axis (121a).

[0056] For example, a plurality of fastening grooves (G) may be located on the surface of the rotation axis (121a) having the same center of curvature as the center of curvature of the rotation axis (121a). For example, the spacing between the plurality of fastening grooves (G) may be the same, but is not limited thereto.

[0057] Specifically, a plurality of fastening grooves (G) include an insertion portion on the surface of the rotation shaft (121a) and a coupling portion formed from the insertion portion to the inside of the rotation shaft (121a). In this case, the width (e) of the coupling portion of the plurality of fastening grooves (G) may be wider than the width (d) of the insertion portion.

[0058] For example, a coupling link (121b) is linked to a plurality of fastening grooves (G), and the coupling link (121b) must not detach from the fastening groove (G) during the process of folding or unfolding the display device (100). Accordingly, the plurality of fastening grooves (G) have a relatively narrower width (d) of the insertion portion and a wider width (e) of the coupling portion.

[0059] Referring to FIG. 4, a connecting link (121b), which is another component of the hinge portion (121), includes a plurality of fastening portions (L) that are linked to a plurality of fastening grooves (G).

[0060] Specifically, a plurality of fastening parts (L) included in the coupling link (121b) are each linked to a plurality of fastening grooves (G) included in the rotation axis (121a). At this time, from the perspective that the fastening part (L) must not detach from the fastening groove (G), the width of the portion of the fastening part (L) included in the coupling link (121b) that is coupled to the fastening groove (G) must be wider than the width (d) of the insertion part of the fastening groove (G), and may be equal to or narrower than the width (e) of the coupling part. For example, the plurality of fastening parts (L) included in the coupling link (121b) include a body part that protrudes from the coupling link (121b) and has a first width (d'), and a head part that has a second width (e') that is wider than the first width (d'). At this time, the body part of the fastening part (L) corresponds to the insertion part of the fastening groove (G), and the head part may be linked to the coupling part of the fastening groove (G).

[0061] At this time, the plurality of fastening parts (L) may be made of an elastic material. For example, the plurality of fastening parts (L) may include a material that is compressible when a predetermined force is applied from the outside, and subsequently releases compression when the force applied from the outside is released. For example, the plurality of fastening parts (L) may include an elastic resin or a self-restoring polymer material, but are not limited thereto.

[0062] Accordingly, when the head portion of a plurality of fastening portions (L) is inserted into a plurality of fastening grooves (G), a predetermined force can be applied from the outside to compress the head portion to the extent that it passes through the width (d) of the insertion portion when passing through the insertion portion, and thereafter, when the head portion passes through the insertion portion on the surface of the rotational shaft (121a), the force applied from the outside is released so that the head portion returns to its original width (e') according to elasticity and can be seated on the coupling portion of the rotational shaft (121a).

[0063] Additionally, referring to FIGS. 3 to 5 together, the length (c) of the insertion portion of the rotation axis (121a) may be longer than the length (c') of the body portion of the coupling link (121b).

[0064] Specifically, the rotation axis (121a) and the coupling link (121b) are rotatably connected, and in order for the hinge portion (121) to rotate with a predetermined radius of curvature relative to the rotation axis (121a) without the coupling link (121b) detaching from the rotation axis (121a), a rotatable space must be formed between the rotation axis (121a) and the coupling link (121b). That is, the head portion of the coupling link (121b) is linked and fixed to the coupling portion of the rotation axis (121a), and the body portion of the coupling link (121b) is disposed in the insertion portion of the rotation axis (121a). At this time, the hinge portion (121) can rotate around the rotation axis (121a) in a space equal to the difference between the length (c) of the insertion portion of the rotation axis (121a) and the length of the body portion of the coupling link (121b). Accordingly, the length (c) of the insertion part of the rotation axis (121a) must be longer than the length (c') of the body part of the coupling link (121b).

[0065] For example, the radius of curvature of the hinge portion (121) can be set by the cross-sectional length (a) of the rotation axis (121a), the cross-sectional length (b) of the first surface (S1) which is a flat surface of the connecting link (121b), and the length (c) of the insertion portion of the rotation axis (121a). That is, the radius of curvature of the hinge portion (121) can be set to the maximum radius of curvature at which the hinge portion (121) can rotate by adjusting the cross-sectional length (a) of the rotation axis (121a) and the cross-sectional length (b) of the first surface (S1) of the connecting link (121b).

[0066] For example, the maximum radius of curvature at which the hinge portion (121) can rotate may be the same as the radius of curvature of the first rotation axis (121a), but is not limited thereto.

[0067] Additionally, when the radius of curvature of the hinge portion (121) is set by adjusting the cross-sectional length (a) of the rotation axis (121a) and the cross-sectional length (b) of the first surface (S1) of the coupling link (121b), the length (c) of the insertion portion of the rotation axis (121a) can also be selected to suit the preset maximum radius of curvature.

[0068] Accordingly, according to one embodiment of the present invention, the foldable display device (100) includes a plurality of rotation axes (121a) and a plurality of coupling links (121b) having a simple structure, thereby allowing not only easy selection of a desired radius of curvature but also reduction of manufacturing process costs.

[0069] FIG. 6 is a schematic side view illustrating an inwardly folded form of a foldable display device according to an embodiment of the present invention. FIG. 7 is a schematic side view illustrating an outwardly folded form of a foldable display device according to an embodiment of the present invention.

[0070] For example, when the upper surface where an image is displayed in a foldable display device (100) is defined as the display surface (100a) and the lower surface of the foldable display device (100), which is the opposite side of the display surface (100a), is defined as the back surface (100b), the foldable display device (100) can be inwardly folded so that the display surfaces (100a) face each other as in FIG. 6, and can be outwardly folded so that the display surface (100a) of the display panel is exposed to the outside as in FIG. 7.

[0071] As described above, a foldable display device (100) according to one embodiment of the present invention has a plurality of rotation axes (121a) and a plurality of coupling links (121b) arranged sequentially in the upper and lower directions, wherein the rotation axes (121a) are arranged to contact the second surface (S2), which is a curved surface of the coupling links (121b), so that the hinge portion (121) can be folded and unfolded in both directions.

[0072] FIG. 8 is a schematic plan view of a foldable display device according to another embodiment of the present invention. FIG. 9 is a schematic cross-sectional view of a foldable display device according to IX-IX' of FIG. 8. FIG. 10 is a schematic side view illustrating a folded form of a foldable display device according to another embodiment of the present invention.

[0073] A display panel (210) included in a foldable display device (200) according to another embodiment of the present invention includes a first non-folding area (NFA1), a first folding area (FA1), a second non-folding area (NFA2), a second folding area (FA2), and a third non-folding area (NFA3) that are sequentially positioned along a direction perpendicular to the folding axis (F). The first folding area (FA1) and the second folding area (FA2) are each areas that are folded when the foldable display device (200) is folded, and may include a part of the display area (DA) and a part of the non-display area (NDA). Since the foldable display device (200) according to FIGS. 8 and FIGS. 9 is substantially the same as FIGS. 1 and FIGS. 2 except that the foldable display device (200) further includes folding areas (FA1, FA2), a redundant description is omitted.

[0074] Referring to FIGS. 8 and 9, another foldable display device (200) in another embodiment of the present invention includes a display panel (210) and a back cover (120) in which a plurality of folding regions (FA1, FA2) are defined.

[0075] The first folding area (FA1) and the second folding area (FA2) are each areas that are folded when the foldable display device (200) is folded, and can each be folded according to a specific radius of curvature with respect to a direction perpendicular to the folding axis (F), that is, the y-axis direction. When the first folding area (FA1) and the second folding area (FA2) are each folded with respect to the folding axis (F), the first folding area (FA1) and the second folding area (FA2) can each form a part of a circle or an ellipse. At this time, the radius of curvature of each of the first folding area (FA1) and the second folding area (FA2) refers to the radius corresponding to the part of the circle or ellipse formed by the first folding area (FA1) and the second folding area (FA2).

[0076] The first non-folding area (NFA1), the second non-folding area (NFA2), and the third non-folding area (NFA3) are areas that do not fold when the foldable display device (200) is folded. That is, the first non-folding area (NFA1), the second non-folding area (NFA2), and the third non-folding area (NFA3) are each areas that maintain a flat state when the foldable display device (200) is folded. When the first folding area (FA1) and the second folding area (FA2) are each folded with respect to the folding axis (F), the first non-folding area (NFA1), the second non-folding area (NFA2), and the third non-folding area (NFA3) overlap each other. When the upper surface on which an image is displayed in the foldable display device (200) is defined as the display surface (100a) and the lower surface of the foldable display device (200), which is the opposite side of the display surface (100a), is defined as the back surface (100b), the first folding area (FA1) can be inner-folded so that the display surfaces (100a) of the display panel (210) face each other, and the second folding area (FA2) can be outer-folded so that the display surfaces (100a) of the display panel (210) are exposed to the outside.

[0077] Referring to FIG. 10, the first folding area (FA1) is inwardly folded so that the display surface (100a) faces inward, and the display surface (100a) of the first non-folding area (NFA1) and the display surface (100a) of the second non-folding area (NFA2) are positioned to face each other. Additionally, the second folding area (FA2) is outwardly folded so that the display surface (100a) faces outward, and the back surface (100b) of the third non-folding area (NFA3) and the back surface (100b) of the second non-folding area (NFA2) are folded to face each other. As illustrated in FIG. 10, when the first folding area (FA1) and the second folding area (FA2) are folded, other components including a battery may be placed between the back surface (100b) of the third non-folding area (NFA3) and the back surface (100b) of the second non-folding area (NFA2), but are not limited thereto.

[0078] A foldable display device (200) according to another embodiment of the present invention may occupy only a small area when not in use, and when used thereafter, the foldable display device (200) may be easily expanded to a large area by unfolding, making storage and use easy.

[0079] A foldable display device according to various embodiments of the present invention can be described as follows.

[0080] A foldable display device according to one embodiment of the present invention includes a display panel comprising a folding area and non-folding areas on both sides of the folding area; and a hinge portion configured to fold the display panel inwardly or outwardly by being disposed in an area corresponding to the folding area at the bottom of the display panel, wherein the hinge portion includes a plurality of rotation axes and a plurality of coupling links disposed between the plurality of rotation axes.

[0081] According to another feature of the present invention, a plurality of connecting links include a first surface having a flat surface and a second surface having a curved surface, and a rotation axis may be arranged to be in contact with the curved surface of the connecting link.

[0082] According to another feature of the present invention, the second surface of a plurality of connecting links includes two concave surfaces and a convex surface between the concave surfaces, and the radius of curvature of the concave surface may correspond to the radius of curvature of the axis of rotation.

[0083] According to another feature of the present invention, a plurality of connecting links can be arranged sequentially in an up-and-down symmetrical manner.

[0084] According to another feature of the present invention, among a plurality of coupling links, a first coupling link may be arranged such that its first surface faces upward, and a second coupling link adjacent to the first coupling link may be arranged such that its first surface faces downward.

[0085] According to another feature of the present invention, the rotational shaft includes a plurality of fastening grooves, and the coupling link may include a plurality of fastening parts linked to the plurality of fastening grooves.

[0086] According to another feature of the present invention, a plurality of fastening grooves have a center of curvature identical to the center of curvature of a rotation axis, and the plurality of fastening grooves include an insertion portion on the surface of the rotation axis and a coupling portion formed inwardly from the insertion portion, and the width of the coupling portion may be wider than the width of the insertion portion.

[0087] According to another feature of the present invention, a plurality of fastening parts may include a body part having a first width and a head part having a second width wider than the first width.

[0088] According to another feature of the present invention, the length of the insertion portion of the rotational shaft may be longer than the length of the body portion of the coupling link.

[0089] According to another feature of the present invention, the width of the insertion portion of the rotational shaft may be narrower than the width of the head portion of the coupling link.

[0090] According to another feature of the present invention, a plurality of fastening parts may include an elastic body.

[0091] According to another feature of the present invention, the display panel may include a first non-folding area, a first folding area, a second non-folding area, a second folding area, and a third non-folding area sequentially located along a direction perpendicular to the folding axis.

[0092] Although embodiments of the present invention have been described in more detail with reference to the attached drawings, the present invention is not necessarily limited to these embodiments and may be modified in various ways within the scope of the technical spirit of the present invention. Accordingly, the embodiments disclosed in the present invention are intended to explain, not to limit, the technical spirit of the present invention, and the scope of the technical spirit of the present invention is not limited by these embodiments. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive. The scope of protection of the present invention shall be interpreted by the claims below, and all technical spirits within the equivalent scope shall be interpreted as being included within the scope of rights of the present invention. Explanation of the symbols

[0093] 100, 200: Display device 110, 210: Display panel 120: Back cover 121: Hinge part 121a: axis of rotation 121b: Combined link

Claims

Claim 1 A foldable display device comprising: a display panel including a folding area and non-folding areas on both sides of the folding area; and a hinge portion disposed in an area corresponding to the folding area at the bottom of the display panel and configured to fold the display panel inwardly or outwardly, wherein the hinge portion comprises a plurality of rotational axes and a plurality of connecting links disposed between the plurality of rotational axes, wherein the plurality of connecting links comprise a first surface having a flat surface and a second surface having a curved surface, wherein the plurality of rotational axes are disposed to be in contact with the second surface, and the second surface comprises two concave surfaces and a convex surface between the concave surfaces, and the radius of curvature of the concave surfaces corresponds to the radius of curvature of the rotational axes. Claim 2 delete Claim 3 delete Claim 4 A foldable display device according to claim 1, wherein the plurality of connecting links are sequentially arranged in an up-and-down symmetrical manner. Claim 5 A foldable display device according to claim 1, wherein among the plurality of coupling links, a first coupling link is positioned such that the first surface faces upward, and a second coupling link adjacent to the first coupling link is positioned such that the first surface faces downward. Claim 6 A foldable display device comprising: a display panel including a folding area and non-folding areas on both sides of the folding area; and a hinge portion disposed in an area corresponding to the folding area at the bottom of the display panel and configured to fold the display panel inwardly or outwardly, wherein the hinge portion includes a plurality of rotational axes and a plurality of coupling links disposed between the plurality of rotational axes, wherein the rotational axes include a plurality of fastening grooves, and the coupling links include a plurality of fastening portions linked to the plurality of fastening grooves. Claim 7 A foldable display device according to claim 6, wherein the plurality of fastening grooves have a center of curvature identical to the center of curvature of the rotation axis, and the plurality of fastening grooves include an insertion portion on the surface of the rotation axis and a coupling portion formed inwardly from the insertion portion, and the width of the coupling portion is wider than the width of the insertion portion. Claim 8 A foldable display device according to claim 6, wherein the plurality of fastening portions include a body portion having a first width and a head portion having a second width wider than the first width. Claim 9 A foldable display device according to claim 7 or 8, wherein the length of the insertion portion of the rotation axis is longer than the length of the body portion of the coupling link. Claim 10 A foldable display device according to claim 7 or 8, wherein the width of the insertion portion of the rotational axis is narrower than the width of the head portion of the coupling link. Claim 11 In claim 6, the above plurality of fastening parts comprises an elastic body, a foldable display device. Claim 12 A foldable display device according to claim 1, wherein the display panel comprises a first non-folding area, a first folding area, a second non-folding area, a second folding area, and a third non-folding area sequentially positioned along a direction perpendicular to the folding axis.

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