Foldable display device

Abstract

Provided is a foldable display device. A base substrate includes an active area AA, a non-active area NA surrounding the active area, with a plurality of pads being disposed in one or both side portio

Description

CROSS REFERENCE TO RELATED APPLICATION This application claims priority and benefit from Republic of Korea Patent Application No. 10-2024-0013036, filed on January 29, 2024. Technical Field

[0001] Exemplary embodiments relate to a display device, and more particularly, for example, without limitation, to a foldable display device. Description of Related Art

[0002] Recently, with the entry into the information age, the display field that visually expresses electrical information signals has rapidly developed. In response, various display devices having excellent performance, such as thinness, light weight, and low power consumption, have been developed.

[0003] Specific examples of such display devices may include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, field emission display (FED) devices, an electro-wetting display (EWD), organic light-emitting display (OLED) devices, quantum dot light emitting display and the like .

[0004] Recently, flexible display devices fabricated using a flexible material such as plastic instead of a conventional inflexible glass substrate to maintain display performance even when bent like paper are rapidly emerging as nextgeneration display devices. In addition, foldable display devices having a large surface area have been developed and commercialized for commercial purposes and consumer desires.

[0005] The description provided in the background section should not be assumed to be prior art merely because it is mentioned in or associated with the background section. The background section may include information that describes one or more aspects of the subject technology. BRIEF SUMMARY

[0006] However, the inventors of the present application have found that, as foldable display devices become larger, the length of the data lines may also become longer, thereby increasing data resistance. In particular, portrait oriented foldable display devices having a long aspect ratio in the vertical direction suffer from a greater increase in data resistance.

[0007] To solve the data line problem described above, the inventors of the present disclosure have invented a landscape oriented foldable display device having a long aspect ratio in the horizontal direction.

[0008] The landscape oriented foldable display device may include a folding area having a folding axis formed in the longitudinal direction and non-folding areas provided on both sides of the folding area, in which pads may be provided at ends of the folding area. That is, the pads may be disposed in a non-active area of the folding area that does not display an image. In addition, the pads may be covered with a resin to mitigate or prevent moisture permeation into the pads in the folding area.

[0009] However, in the folding area, the resin may be lifted or dislodged due to continuous stress caused by the bending or recovery of the display panel. This may lead to problems such as reduced moisture resistance and cracking of the pads.

[0010] Accordingly, the inventors have invented a foldable display device able to mitigate or prevent moisture permeation without a resin by configuring the components of the display panel so that the ends of the components cover the pads disposed in the folding area.

[0011] Exemplary embodiments may provide a foldable display device in which the respective components of the display panel disposed in the folding area extend from an active area to the non-active area to cover the pads, thereby solving the problems of cracking and moisture permeation of the pads due to lifting of the resin.

[0012] Exemplary embodiments may provide a flexible display device that may be realized as a unified product in which parts are simplified and unified because the resin may be omitted.

[0013] Exemplary embodiments may provide a flexible display device in which a neutral plane occurring during bending of the folding area may be maintained constantly by positioning the ends of the respective components of the display panel in line so that no stepped portion is formed.

[0014] Exemplary embodiments may provide a foldable display device having a structure capable of minimizing damage to the folding area by evenly distributing the stress acting on the respective components during bending or recovery by forming the neutral plane of the folding area to be centered on the display panel.

[0015] Exemplary embodiments may provide a foldable display device including: a base substrate including an active area, a non-active area surrounding the active area, with a plurality of pads being disposed in one or both side portions thereof, and a folding area overlapping a portion of the active area and the non-active area; a light-emitting element disposed in the active area of the base substrate; and a cover window disposed over the light-emitting element, wherein the light-emitting element and the cover window disposed in the folding area extend to the non-active area to support the pads .

[0016] Exemplary embodiments may provide a foldable display device including: a base substrate including an active area, a non-active area surrounding the active area, with a plurality of pads being disposed in one or both side portions thereof, and a folding area overlapping a portion of the active area and the non-active area; a thin-film transistor layer disposed over the base substrate; a light-emitting element disposed over the thin-film transistor layer; an adhesive layer disposed over the light-emitting element; a touch panel disposed over the adhesive layer; a polarizer disposed over the touch panel; and a cover window disposed over the light-emitting element, wherein ends of the thin-film transistor layer, the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window located in the folding area are arranged in line so that no stepped portion is present

[0017] According to exemplary embodiments, in the foldable display device, the respective components of the display panel disposed in the folding area may extend from an active area to the non-active area to cover the pads, thereby solving the problems of cracking and moisture permeation of the pads due to lifting of the resin.

[0018] According to exemplary embodiments, the flexible display device may be realized as a unified product in which parts are simplified and unified because the resin may be omitted.

[0019] According to exemplary embodiments, in the flexible display device, a neutral plane occurring during bending of the folding area may be maintained constantly by positioning the ends of the respective components of the display panel in line so that no stepped portion is formed.

[0020] According to exemplary embodiments, the flexible display device has a structure capable of minimizing damage to the folding area by evenly distributing the stress acting on the respective components during bending or recovery by forming the neutral plane of the folding area to be centered on the display panel.

[0021] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the inventive concepts as claimed. DESCRIPTION OF DRAWINGS

[0022] The accompanying drawings, which are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this application, illustrate embodiments of the disclosure and together with the description serve to explain the principle of the disclosure.

[0023] The above and other objectives, features, and advantages of the present disclosure will be more clearly understood from the following detailed description, taken in conjunction with the accompanying drawings, in which: FIG. 1 illustrates a system configuration of a foldable display device according to exemplary embodiments; FIG. 2 is a plan view illustrating a display device according to exemplary embodiments; FIG. 3 is a cross-sectional view illustrating the display device taken along the line A-A' of FIG. 2; FIG. 4 is a cross-sectional view illustrating the display device taken along the line B-B' of FIG. 2; FIG. 5 illustrates the neutral plane in FIG. 3; and FIG. 6 illustrates the neutral planes in FIG. 4. Throughout the drawings and the detailed description, unless otherwise described, the same drawing reference numerals should be understood to refer to the same elements, features, and structures. The relative size and depiction of these elements may be exaggerated for clarity, illustration, and convenience . DETAILED DESCRIPTION

[0024] In the following description of examples or embodiments of the present disclosure, reference will be made to the accompanying drawings in which it is shown by way of illustration specific examples or embodiments that can be implemented, and in which the same reference numerals and signs can be used to designate the same or like components even when they are shown in different accompanying drawings from one another. Further, in the following description of examples or embodiments of the present disclosure, detailed descriptions of well-known functions and components incorporated herein will be omitted when it is determined that the description may make the subject matter in some embodiments of the present disclosure rather unclear. Names of the respective elements used in the following explanations may be selected only for convenience of writing the specification and may be thus different from those used in actual products. The terms such as "including", "having", "containing", "constituting" "made up of", and "formed of" used herein are generally intended to allow other components to be added unless the terms are used with the term "only". As used herein, singular forms are intended to include plural forms unless the context clearly indicates otherwise.

[0025] Terms, such as "first", "second", "A", "B", "(A) ", or "(B) "may be used herein to describe elements of the present disclosure. Each of these terms is not used to define essence order, sequence, or number of elements etc., but is used merely to distinguish the corresponding element from other elements .

[0026] The shapes, sizes, dimensions (e.g., length, width, height, thickness, radius, diameter, area, etc.), ratios, angles, number of elements, ratios, angles, numbers, and the like, which are illustrated in the drawings to describe various example embodiments of the present disclosure are merely given by way of example. Therefore, the present disclosure is not limited to the illustrations in the drawings. Any implementation described herein as an "example" is not necessarily to be construed as preferred or advantageous over other implementations.

[0027] The word "exemplary" is used to mean serving as an example or illustration. Embodiments are example embodiments Aspects are example aspects. Any implementation described herein as an "example" is not necessarily to "Embodiments," "examples," "aspects," and the like should not be construed as preferred or advantageous over other implementations. An embodiment, an example, an example embodiment, an aspect, or the like may refer to one or more embodiments, one or more examples, one or more example embodiments, one or more aspects, or the like, unless stated otherwise. Further, the term "may" encompasses all the meanings of the term "can."

[0028] When it is mentioned that a first element "is connected or coupled to", "contacts or overlaps" etc. a second element, it should be interpreted that, not only can the first element "be directly connected or coupled to" or "directly contact or overlap" the second element, but a third element can also be "interposed" between the first and second elements, or the first and second elements can "be connected or coupled to", "contact or overlap", etc. each other via a fourth element. Here, the second element may be included in at least one of two or more elements that "are connected or coupled to", "contact or overlap", etc. each other.

[0029] When time relative terms, such as "after", "subsequent to", "next", "before", and the like, are used to describe processes or operations of elements or configurations, or flows or steps in operating, processing, manufacturing methods, these terms may be used to describe non-consecutive or non-sequential processes or operations unless the term "directly” or "immediately" is used together.

[0030] The terms, such as "below," "lower," "above," "upper" and the like, may be used herein to describe a relationship between element(s) as illustrated in the drawings. It will be understood that the terms are spatially relative and based on the orientation depicted in the drawings.

[0031] In addition, when any dimensions, relative sizes etc. are mentioned, it should be considered that numerical values for an elements or features, or corresponding information (e.g., level, range, etc.) include a tolerance or error range that may be caused by various factors (e.g., process factors, internal or external impact, noise, etc.) even when a relevant description is not specified. Further, the term "may fully encompasses all the meanings of the term "can".

[0032] Features of various embodiments of the present disclosure may be partially or overall coupled to or combined with each other, and may be variously inter-operated with each other and driven technically as those skilled in the art can sufficiently understand. Embodiments of the present disclosure may be carried out independently from each other, or may be carried out together in co-dependent relationship.

[0033] The term "or" means "inclusive or" rather than "exclusive or." That is, unless otherwise stated or clear from the context, the expression that "x uses a or b" means any one of natural inclusive permutations. For example, "a or b" may mean "a," "b," or "a and b." For example, "a, b or c" may mean "a," "b, ""c," "a and b," "b and c," "a and c," or "a, b and c. "

[0034] The phase that an element (e.g., layer, film, region, component, section, or the like) is "provided in," "disposed in," or the like in another element may be understood as that at least a portion of the element is provided in, disposed in, or the like in another element, or that the entirety of the element is provided in, disposed in, or the like in another element. The phase that an element (e.g., layer, film, region, component, section, or the like) "contacts," "overlaps," or the like with another element may be understood as that at least a portion of the element contacts, overlaps, or the like with a least a portion of another element, that the entirety of the element contacts, overlaps, or the like with a least a portion of another element, or that at least a portion of the element contacts, overlaps, or the like with the entirety of another element.

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning for example consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. For example, the term "part" or "unit" may apply, for example, to a separate circuit or structure, an integrated circuit, a computational block of a circuit device or any structure configured to perform a described function as should be understood to one of ordinary skill in the art.

[0036] Hereinafter, a variety of embodiments will be described in detail with reference to the accompanying drawings.

[0037] FIG. 1 illustrates a system configuration of a foldable display device according to exemplary embodiments.

[0038] Referring to FIG. 1, a display driver system of a foldable display device 100 according to exemplary embodiments may include a display panel 1 and a display driving circuit for driving the display panel 1.

[0039] The display panel 1 may include an active area AA in which images are displayed and a non-active area NA in which no images are displayed. As an example, the non-active area NA may partially or fully surround the active area AA, without being limited thereto. The display panel 1 may include a plurality of subpixels SP disposed on a base substrate 110 for displaying images.

[0040] The display panel 1 may include a plurality of signal lines disposed on the base substrate 110. For example, the signal lines may include data lines DL, gate lines GL, driving voltage lines DVL, and the like.

[0041] The respective data lines DL may be arranged to extend in a first direction (e.g., a column or row direction), and the respective gate lines GL may be arranged to extend in a direction intersecting the first direction.

[0042] The display driving circuit may include a data driver circuit 10 and a gate driver circuit 20, and may further include a controller 30 for controlling the data driver circuit 10 and the gate drive circuit 20.

[0043] The data driver circuit 10 may output data signals (also referred to as data voltages) corresponding to image (or video) signals to the data lines DL. The gate driver circuit 20 may generate gate signals GCS and output the gate signals GCS to the gate lines GL. The controller 30 may convert input image data coming from, for example, an external host 40 according to the format of data signals DCS used by the data driver circuit 10 and supply the converted image data to the data driver circuit 10.

[0044] The data driver circuit 10 may include one or more source driver integrated circuits. For example, each of the source driver integrated circuits may be connected to the display panel 1 by a tape-automated bonding (TAB) method, connected to a pad PAD on the display panel 1 by a chip-on-glass (COG) or chip-on-panel (COP) method, or implemented by a chip-on-film (COF) method or a tape carrier package (TCP) method to be connected to the display panel 1, without being limited thereto. As an example, each of the source driver integrated circuits may be disposed on the display panel or distributed in the active area AA, without being limited thereto.

[0045] The gate driver circuit 2 0 may be connected to the display panel 1 by a TAB method, connected to the pads PAD of the display panel 1 by a COG or COP method, connected to the display panel 1 by a COF method, or provided in a non-active area NA of the display panel 1 by a gate-in-panel (GIP) method, or may be distributed in the active area AA, without being limited thereto.

[0046] As an example, a GIP circuit part may be disposed on at least one side (e.g., the left and right sides) of the non active area NA in FIG. 1, and the pads PAD connected to external circuits and an external power source may be disposed on at least one side (e.g., the top and bottom sides) of the non-active area NA, without being limited thereto. Here, the non-active area NA in which the pads PAD are disposed may be defined as a pad area.

[0047] Referring to FIG. 1, in the foldable display device 100 according to exemplary embodiments, each of the subpixels SP may include a light-emitting element 130 and a pixel driver circuit SPC for driving the light-emitting element 130, and the pixel driver circuit SPC may include a driving transistor DRT, a scanning transistor SGT, and a storage capacitor Cst.

[0048] The driving transistor DRT may drive the light-emitting element 130 by controlling current flowing to the lightemitting element 130. The scanning transistor SGT may transfer a data voltage Vdata to a second node N2 of the driving transistor DRT, which is a gate node. The storage capacitor Cst may be configured to maintain a voltage for a predetermined period of time.

[0049] The light-emitting element 130 may include a first electrode 131, a second electrode 132, and a light-emitting layer 133 located between the first electrode 131 and the second electrode 132. The first electrode 131 may be a pixel electrode involved in forming the light-emitting element 130 of each of the subpixels SP, and may be electrically connected to a first node N1 of the driving transistor DRT. The second electrode 132 may be a common electrode involved in forming the light-emitting elements 130 of all of the subpixels SP, and a base voltage EVSS may be applied to the second electrode 132.

[0050] For example, the light-emitting element 130 may be an organic light-emitting diode OLED, an inorganic lightemitting diode (LED) , a quantum dot light-emitting element, which is a self-emitting semiconductor crystal, or the like.

[0051] The driving transistor DRT may be a transistor for driving the light-emitting element 130, and may include the first node Nl, the second node N2, and a third node N3. The first node Nl may be a source or drain node, and may be electrically connected to the first electrode of the lightemitting element 130. The second node N2 may be a gate node, and may be electrically coupled to a source or drain node of the scanning transistor SCT. The third node N3 may be a drain or source node, and may be electrically connected to a driving voltage line DVL through which a driving voltage EVDD is supplied. In the following, for the sake of brevity, a situation in which the first node Nl is a source node and the third node N3 is a drain node will be described as an example

[0052] The scanning transistor SCT may switch the connection between the data line DL and the second node N2 of the driving transistor DRT. The scanning transistor SCT may control the connection between the second node N2 of the driving transistor DRT and a corresponding data line DL of the data lines DL in response to a scan signal SCAN supplied from a scan line SCL, which is a type of gate line GL.

[0053] The storage capacitor Cst may be provided between the first node N1 and the second node N2 of the driving transistor DRT.

[0054] The structure of subpixel SP shown in FIG. 1 is for illustrative purposes only, and may further include one or more transistors or one or more capacitors. In another example, the respective subpixels may have the same structure, or at least some of the subpixels may have different structures. Each of the driving transistor DRT and the scanning transistor SGT may be an n-type transistor or a p-type transistor.

[0055] FIG. 2 is a plan view illustrating a display device according to exemplary embodiments, and FIG. 3 is a cross-sectional view illustrating the display device taken along the line A-A' of FIG. 2.

[0056] Referring to FIGS. 2 and 3, a foldable display device 100 may include a base substrate 110, a thin-film transistor layer 120, a light-emitting element 130, an adhesive layer 140, a touch panel 150, a polarizer 160, and a cover window 170. Embodiments are not limited thereto. As an example, at least one of the above-mentioned components (e.g., the adhesive layer 140, the touch panel 150, or the polarizer 160 etc.) may be omitted, and / or one or more additional components may be further included.

[0057] The base substrate 110 is intended to support various components of the foldable display device 100, and may be made of an insulating material such as glass, plastic, or polyimide (PI), without being limited thereto.

[0058] The base substrate 110 may include an active area AA, a non-active area NA, and a folding area FA. The active area AA may be an area in which images are displayed by a plurality of subpixels SP. The non-active area NA is an area in which no images are displayed, and may be located to partially or fully surround the active area AA, with a plurality of pads PAD being disposed in one or more side portions of the non-active area NA. For example, the non-active area NA may include a first non-active area NAI provided perpendicular to the folding axis FX of the folding area FA, a second non-active area NA2 provided to face the first non-active area NAI, and a third non-active area NA3 and a fourth non-active area NA4 extending between the first non-active area NAI and the second non-active area NA2 and provided to face each other. Embodiments are not limited thereto. As an example, at least one of the first non-active area NAI to the fourth non-active area NA4 may be omitted, or may be bent toward a rear side of the foldable display device 100 to be at least partially invisible from the front side of foldable display device 100, without being limited thereto.

[0059] The folding area FA is formed around the folding axis FX, and may be an area overlapping a portion of the active area AA and a portion of the non-active area NA. For example, the folding area FA may be an area that bends (e.g., with a predetermined curvature or with varied curvatures) when the foldable display device 100 is folded about the folding axis FX. The area other than the folding area FA may be a nonfolding area NFA (e.g., flat) . For example, the non-folding area NFA may extend to both side portions of the folding area FA, and two non-folding areas NFA may be formed on both side portions of the folding area FA. Although it is illustrated in Fig. 2 that there is only one folding axis FX and one folding area FA, embodiments are not limited thereto. As an example, there could be two or more folding axes FX and two or more folding areas FA. As an example, the two or more folding axes FX may be or may be not parallel with each other As an example, as an example, the two or more folding axes FX may be spaced apart from each other or may intersect with each other.

[0060] The thin film transistor layer 120 may be disposed in the active area AA and the non-active area NA of the base substrate 110. For example, the thin film transistor layer 120 may include data lines DL, gate lines GL, and driving transistors DRT, and the pads PAD may be disposed in the nonactive area NA of the thin film transistor layer 120.

[0061] The light-emitting element 130 may be disposed over the thin-film transistor layer 120. For example, the lightemitting element 130 may be disposed only in the active area AA or may be disposed in the active area AA and a portion of the non-active area NA. In this case, the end of the lightemitting element 130 disposed in the non-active area NA may be formed so as not to overlap the pad. As an example, the light-emitting element 130 may extend from the active area AA to a previous area in which the pads PAD are disposed.

[0062] Referring to FIG. 1, the light-emitting element 130 may include a first electrode 131, a second electrode 132, and a light-emitting layer 133.

[0063] The first electrode 131 may be an anode, which may be disposed independently on each of the subpixels SP.

[0064] The first electrode 131 may be implemented as a transparent electrode made of, for example, indium tin oxide (ITO) or indium zinc oxide (IZO), or may be implemented as an opaque electrode made of, for example, aluminum (Al), copper (Cu) , or nickel (Ni), without being limited thereto. In addition, the first electrode 131 may be formed by layering a transparent electrode and an opaque electrode, without being limited thereto.

[0065] The second electrode 132 may be a cathode, which may be provided in the active area AA and the non-active area NA.

[0066] The second electrode 132 may be implemented as a transparent electrode made of, for example, indium tin oxide (ITO) or indium zinc oxide (IZO), or may be implemented as an opaque electrode made of, for example, aluminum (Al), copper (Cu) , or nickel (Ni), without being limited thereto. In addition, the second electrode 132 may be formed by layering a transparent electrode and an opaque electrode, without being limited thereto.

[0067] The light-emitting layer 133 may be disposed between the first electrode 131 and the second electrode 132. For example, the light-emitting layer 133 may be an organic light-emitting layer including a hole injection layer (HIL), a hole transport layer (HTL), an emission material layer (EML), an electron transfer layer (ETL), an electron injection layer (EIL), and the like. Embodiments are not limited thereto. As an example, at least one of the hole injection layer (HIL), the hole transport layer (HTL), the electron transfer layer (ETL), the electron injection layer (EIL) may be omitted, in at least some or all of the subpixels SP.

[0068] The adhesive layer 140 may be disposed over the lightemitting element 130 to bond the light-emitting element 130 and the touch panel 150. For example, the adhesive layer 140 may be provided as an optically clear adhesive (OCA), without being limited thereto. For example, the adhesive layer 140 may be provided as an optically clear adhesive (OCA) that transmits at least 97% of light but has good adhesion to be properly used as an adhesive for the foldable display device 100, without being limited thereto.

[0069] The touch panel 150 may be disposed over the adhesive layer 140 as a touch sensor to further provide the foldable display device 100 with not only an image display function but also a touch sensing function. For example, the touch panel 150 may include a plurality of touch electrodes electrically connected by a plurality of touch electrode lines. Embodiments are not limited thereto. As an example, the adhesive layer 140 and the touch panel 150 may be omitted depending on the design.

[0070] Although not shown, the foldable display device 100 may include a touch driving circuit to drive and sense the touch panel 150 and generate and output touch sensing data, a touch controller to detect a touch or determine a touched position using the touch sensing data, and the like.

[0071] The polarizer 160 may be disposed over the touch panel 150 to selectively transmit light and reduce the reflection of external light incident on the display panel 1. For example, the polarizer 160 may be made of a material, such as polyvinyl alcohol (PVA) , polycarbonate (PC), or polymethacrylate (PMMA), without being limited thereto. As an example, the polarizer 160 may be omitted depending on the design.

[0072] The cover window 170 is for protecting the display panel 1 and may be disposed over the polarizer 160. The cover window 170 may be made of a material (e.g., a glass material, a sapphire material, a plastic material, etc.) having excellent optical properties, high strength and impact resistance, and high surface hardness, without being limited thereto. For example, the cover glass may be a thin cover glass (TCG) having a thickness of 90 pm or less, without being limited thereto. The thin cover glass having a limited thickness as described above may effectively reduce stress applied during bending.

[0073] According to an exemplary embodiment, the lightemitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 disposed in the folding area FA may extend to the non-active area NA to cover the pad. As an example, the pad disposed in the folding area FA may be shielded by the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170. Embodiments are not limited thereto. As an example, at least one of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 disposed in the folding area FA may extend to the non-active area NA to cover the pad. As an example, at least one of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 disposed in the folding area FA may not extend to the non-active area NA. As an example, at least one or each of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 disposed outside the folding area FA may extend to the non-active area NA to cover the pad. As an example, at least one or all of the lightemitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 disposed outside the folding area FA may not extend to the non-active area NA.

[0074] Accordingly, it is possible to reduce or prevent moisture from entering the pads PAD from the folding area FA without providing a resin covering the pads PAD. In other words, previously, since the pads PAD disposed in the folding area FA are not shielded by the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 disposed thereabove, as an example, a resin was separately provided to cover the pads PAD.

[0075] When the pads PAD are shielded through the resin in this manner, stress caused by the bending or recovery of the foldable display device 100 in the non-folding area NFA is not relevant, but in the folding area FA, the stress caused by the bending or recovery of the foldable display device 100 continuously acts on the resin, causing the phenomenon of the resin lifting. In this case, the pads PAD bonded to the resin may be cracked and damaged, and moisture may enter the gap between the display panel 1 and the resin, thereby reducing the reliability of the foldable display device 100.

[0076] In order to solve these problems, in the foldable display device 100 according to the present exemplary embodiment, moisture resistance may be improved by deleting the resin disposed in the folding area FA and covering the pads PAD with at least one of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 of the display panel 1.

[0077] Specifically, as an example, both sides of each of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 covering the pads PAD in the folding area FA may extend to the outside of the folding area FA to overlap portions of the non-folding area NFA provided on both sides of the folding area FA (see FIG. 2) . This configuration may increase the area covering the pads PAD, thereby improving moisture resistance. Embodiments are not limited thereto. As an example, only one side of at least one or each of the lightemitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 covering the pads PAD in the folding area FA may extend to the outside of the folding area FA to overlap portions of the non-folding area NFA provided on the one side of the folding area FA. As an example, at least one or each of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 covering the pads PAD in the folding area FA may not extend to the outside of the folding area FA on both sides of the folding area FA.

[0078] FIG. 4 is a cross-sectional view illustrating the display device taken along the line B-B' of FIG. 2.

[0079] Referring to FIG. 4, in the foldable display device 100, the ends of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 located in the non-folding area NFA may each be arranged so as not to overlap the pads, that is, may be configured to cover the pads only in the folding area FA but not in the non-folding area NFA. However, the structure of the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 located in the non-folding area NFA is not limited to this example, and may be configured to cover the pads PAD as in the folding area FA.

[0080] FIG. 5 illustrates the neutral plane in FIG. 3.

[0081] As shown in FIG. 5, in the foldable display device 100 according to the present exemplary embodiment, the respective components of the display panel 1 may be arranged in line so that no stepped portion is formed at the ends of the respective components. For example, the ends of the thin-film transistor layer 120, the light-emitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 of the display panel 1 may be arranged side by side in line with each other so that no stepped portion is provided.

[0082] Since no stepped portion is provided at an edge of the display panel 1 as described above, the neutral plane NP occurring during bending of the folding area FA may be maintained constantly. Here, the neutral plane NP means the plane at which the stress state is zero during bending. As an example, the neutral plane NP is the plane that bends while maintaining the original length thereof without being stretched or shrunk when a bending moment is applied. Embodiments are not limited thereto. As an example, a stepped portion may be provided in the ends of at least one or each of the thin-film transistor layer 120, the lightemitting element 130, the adhesive layer 140, the touch panel 150, the polarizer 160, and the cover window 170 of the display panel 1 in the folding area FA.

[0083] FIG. 6 illustrates the neutral planes in FIG. 4.

[0084] Referring to FIG. 6, in the foldable display device 100, stepped portions may be provided on the components in the non-folding area NFA. When the display panel 1 is provided with the stepped portions in the non-folding area NFA in this manner, each of the neutral planes NP may be located between the corresponding ones of the components on which the stepped portions are provided.

[0085] Since the non-folding area NFA is an area in which neither bending nor recovery occurs, the presence of each neutral plane NP between the corresponding components does not affect durability. However, when each of the neutral planes NP is located between the corresponding components in the folding area FA, during bending or recovery of the folding area FA, stresses having different magnitudes may act at the boundaries of the neutral planes NP to cause distortion, thereby forming cracks in the display panel 1.

[0086] Accordingly, the foldable display device 100 according to the present exemplary embodiment is configured so that no stepped portion is formed at the ends of the respective components located in the folding area FA, as shown in FIG. 5 Accordingly, the neutral planes NP may be maintained constantly to reduce or prevent cracks from occurring during bending and recovery of the folding area FA. Embodiments are not limited thereto. As an example, no stepped portion is formed at the ends of at least one or each of the respective components located in the non-folding area NFA.

[0087] In addition, during bending, a tensile stress acts inside the neutral plane NP, while a compressive stress acts outside the neutral plane NP. In this case, the magnitude of the tensile stress or the compressive stress on the display panel 1 may be determined proportional to the distance from the neutral plane NP. Accordingly, as the distance from the neutral plane NP increases, the magnitude of the tensile stress or the compressive stress increases.

[0088] In view of the above, in the foldable display device 100 according to the present exemplary embodiment, the neutral plane occurring during bending of the folding area FA may be located in the central portion of the display panel 1. As an example, the neutral plane occurring during bending of the folding area FA may be located over the adhesive layer 140 (see FIG. 5). As an example, when the neutral plane NP is formed in the folding area FA to be located in the central portion of the display panel 1, the stress acting on the respective components during bending and recovery may be uniformly distributed to reduce or minimize damage to the folding area FA. The positions of the neutral planes NP may be determined by controlling the thicknesses of the respective components of the display panel 1. Although it is illustrated or described that the adhesive layer 140 is located in the central portion of the display panel 1, embodiments are not limited thereto. As an example, any of the thin-film transistor layer 120, the light-emitting element 130, the adhesive layer 140, the touch panel 150, and / or the polarizer 160 may be located in the central portion of the display panel 1.

[0089] The foldable display device 100 according to the present exemplary embodiment may be a landscape oriented display device having a long aspect ratio in the horizontal direction.

[0090] For example, in the landscape oriented foldable display device 100, the active area AA may be provided in the shape of a rectangle extending in a transverse direction, and the non-active area NA surrounding the active area AA may include a first non-active area NAI arranged in a direction perpendicular to the folding axis FX of the folding area FA, a second non-active area NA2 arranged to face the first non-active area NAI, and a third non-active area NA3 and a fourth non-active area NA4 extending between the first non-active area NAI and the second non-active area NA2 and arranged to face each other, without being limited thereto.

[0091] The pads PAD provided in the thin film transistor layer 120 may be disposed in the first non-active area NAI and / or the second non-active area NA2. For example, the pads PAD disposed in the first non-active area NAI may be connected to a data driver 180, and the pads PAD disposed in the second non-active area NA2 may be connected to a touch driver 190, without being limited thereto.

[0092] The data driver 180 may include a first circuit film 181, a data driver circuit 182, and a first printed circuit board (PCB) 183.

[0093] A plurality of first circuit films 181 may be provided in the first non-active area NAI. Input terminals provided on predetermined sides of the respective first circuit films 181 may be attached to the first printed circuit board 183 by a film attaching process. Output terminals provided on the other sides of the respective first circuit films 181 may be attached to the pads PAD disposed in the first non-active area NAI by a film attaching process.

[0094] The pads PAD disposed in the first non-active area NAI are for supplying driving signals to the data lines DL, the gate lines GL, and the driving voltage lines DVL. Each of the first circuit films 181 may be implemented as a flexible circuit film, which may be bent to reduce the non-active area NA of the foldable display device 100. For example, the circuit films may be implemented as a tape carrier package (TCP) or a chip-on-film (COF), without being limited thereto.

[0095] A plurality of data driver circuits 182 may be provided, and may be individually mounted on the first circuit films 181, respectively. The data driver circuits 182 may receive image data and data control signals from the controller 30, convert the image data into analog data signals in response to the data control signals, and supply the analog data signals to the respective data lines.

[0096] The first printed circuit board 183 may be connected to the corresponding first circuit films 181, and may transfer signals and power between the components of the data driver 180. For example, a plurality of first printed circuit board 183 may be provided in a number equal to the number of the non-folding areas NFA, and may be connected to each other by a thin connecting film 184, without being limited thereto. Further, signal transmission lines and various power lines for transmitting signals and power may be provided on the first printed circuit boards 183, without being limited thereto .

[0097] The touch driver 190 may include a second circuit film 191 and a second printed circuit board 192, without being limited thereto. As an example, the touch driver 190 may be integrated with the data driver circuit 182, without being limited thereto

[0098] A plurality of second circuit films 191 may be provided in the second non-active area NA2, without being limited thereto. Input terminals provided on predetermined sides of the respective second circuit films 191 may be attached to the second printed circuit board 192 by a film attaching process. Output terminals provided on the other sides of the respective second circuit films 191 may be attached to the pads PAD disposed in the second non-active area NA2 by a film attaching process. Here, the pads PAD disposed in the second non-active area NA2 are for driving the touch panel 150. As an example, each of the second circuit films 191 may be implemented as a flexible circuit film, which may be bent to reduce the non-active area NA of the foldable display device 100, without being limited thereto.

[0099] The second printed circuit board 192 may be connected to the second circuit films 191, and may supply touch drive signals to drive the touch panel 150. For example, a plurality of second printed circuit boards 192 may be disposed in the non-folding areas NFA and electrically connected by the second circuit films 191 to the pads PAD disposed in the second non-active area NA2, without being limited thereto.

[0100] The above-described exemplary embodiments of the present disclosure are briefly reviewed as follows.

[0101] According to exemplary embodiments, provided is a foldable display device including: a base substrate including an active area, a non-active area surrounding the active area with a plurality of pads being disposed in one or both side portions thereof, and a folding area overlapping a portion of the active area and the non-active area; a light-emitting element disposed in the active area of the base substrate; and a cover window disposed over the light-emitting element, wherein the light-emitting element and the cover window disposed in the folding area extend to the non-active area to support the pads .

[0102] According to exemplary embodiments, non-folding areas may be provided on both sides of the folding area, and ends of the light-emitting element and the cover window located in the non-folding area may each be arranged so as not to overlap the pads.

[0103] According to exemplary embodiments, both side portions of the light-emitting element and the cover window covering the pads in the folding area may extend from the folding area to overlap a portion of the non-folding areas provided on both sides of the folding area.

[0104] According to exemplary embodiments, ends of the lightemitting element and the cover window may be arranged in line in the folding area so that no stepped portion is present.

[0105] According to exemplary embodiments, the foldable display device may further include: a thin-film transistor layer disposed between the base substrate and the lightemitting element; an adhesive layer disposed over the lightemitting element; a touch panel disposed over the adhesive layer; and a polarizer disposed over the touch panel.

[0106] According to exemplary embodiments, the thin-film transistor layer may be disposed over the base substrate in the active area and the non-active area, and the pads may be provided over the thin-film transistor layer in the nonactive area.

[0107] According to exemplary embodiments, ends of the thin-film transistor layer, the touch panel, the adhesive layer, and the polarizer located in the folding area may extend to the non-active area to cover the pads.

[0108] According to exemplary embodiments, ends of the lightemitting element, the cover window, the thin-film transistor layer, the touch panel, the adhesive layer, and the polarizer located in the folding area may be arranged in line so that no stepped portion is present.

[0109] According to exemplary embodiments, a neutral plane occurring during bending of the folding area may be located on the adhesive layer.

[0110] According to exemplary embodiments, non-folding areas may be provided on both sides of the folding area, and ends of the touch panel, the adhesive layer, and the polarizer located in non-folding areas are each arranged so as not to overlap the pads.

[0111] According to exemplary embodiments, the active area may have a rectangular shape, the non-active area surrounding the active area may include a first non-active area arranged in a direction perpendicular to a folding axis of the folding area, a second non-active area arranged to face the first non-active area, and a third non-active area and a fourth non active area extending between the first non-active area and the second non-active area and arranged to face each other, and the pads may be disposed in the first non-active area and the second non-active area.

[0112] According to exemplary embodiments, the pads disposed in a first non-active area of the non-active area may be connected to a data driver.

[0113] According to exemplary embodiments, the pads disposed in a second non-active area of the non-active area may be connected to a touch driver.

[0114] According to exemplary embodiments, provided is a foldable display device including: a base substrate including an active area, a non-active area surrounding the active area, with a plurality of pads being disposed in one or both side portions thereof, and a folding area overlapping a portion of the active area and the non-active area; a thin-film transistor layer disposed over the base substrate; a lightemitting element disposed over the thin-film transistor layer; an adhesive layer disposed over the light-emitting element; a touch panel disposed over the adhesive layer; a polarizer disposed over the touch panel; and a cover window disposed over the light-emitting element, wherein ends of the thin-film transistor layer, the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window located in the folding area are arranged in line so that no stepped portion is present.

[0115] According to exemplary embodiments, a neutral plane occurring during bending of the folding area may be located on the adhesive layer.

[0116] According to exemplary embodiments, ends of the thin-film transistor layer, the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window in the folding area may be disposed in the non-active area.

[0117] According to exemplary embodiments, the thin-film transistor layer may be disposed over the base substrate in the active area and the non-active area, and the pads are provided over the thin-film transistor layer in the non-active area.

[0118] According to exemplary embodiments, non-folding areas may be provided on both sides of the folding area, and ends of the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window located in nonfolding areas may each be arranged so as not to overlap the pads .

[0119] According to exemplary embodiments, the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window located in the folding area may cover the pads .

[0120] According to exemplary embodiments, both side portions of the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window covering the pads in the folding area may extend from the folding area to overlap a portion of the non-folding areas provided on both 5 sides of the folding area.

[0121] The above description has been presented to enable any person skilled in the art to make and use the technical idea of the present disclosure, and has been provided in the context of a particular application and its requirements. 10 Various modifications, additions and substitutions to the described embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. 15 The above description and the accompanying drawings provide an example of the technical idea of the present disclosure for illustrative purposes only. That is, the disclosed embodiments are intended to illustrate the scope of the technical idea of the present disclosure.

Claims

1. A foldable display device comprising:a base substrate comprising an active area, a nonactive area surrounding the active area, with a plurality of pads being disposed in one side portion or two side portions facing each other of the non-active area, and a folding area overlapping a portion of the active area and the non-active area;a light-emitting element disposed in the active area of the base substrate; anda cover window disposed over the light-emitting element, wherein at least one of the light-emitting element and the cover window disposed in the folding area extend to the non-active area to overlap the pads.

2. The foldable display device of claim 1, wherein nonfolding areas are provided on both sides of the folding area, and ends of the light-emitting element and the cover window located in the non-folding areas are each arranged so as not to overlap the pads.

3. The foldable display device of claim 1 or 2, wherein one or two side portions of the light-emitting element and the cover window overlapping the pads in the folding areaextend from the folding area to overlap a portion of the nonfolding areas provided on one or both sides of the folding area.

4. The foldable display device of any of claims 1-3, wherein ends of the light-emitting element and the cover window are arranged in line in the folding area so that no stepped portion is present.

5. The foldable display device of any preceding claim, further comprising:a thin-film transistor layer disposed between the base substrate and the light-emitting element.

6. The foldable display device of claim 5, wherein the thin-film transistor layer is disposed over the base substrate in the active area and the non-active area, and the pads are provided over the thin-film transistor layer in the non-active area.

7. The foldable display device of any preceding claim, further comprising:an adhesive layer disposed over the light-emitting element;a touch panel disposed over the adhesive layer; anda polarizer disposed over the touch panel.

8. The foldable display device of claim 7, wherein ends of at least one of the touch panel, the adhesive layer, and the polarizer located in the folding area extend to the nonactive area to cover the pads.

9. The foldable display device of claim 7 or 8, wherein ends of the light-emitting element, the cover window, the thin-film transistor layer, the touch panel, the adhesive layer, and the polarizer located in the folding area are arranged in line so that no stepped portion is present.

10. The foldable display device of any of claims 7-9, wherein a neutral plane occurring during bending of the folding area is located on the adhesive layer.

11. The foldable display device of any of claims 7-10, wherein non-folding areas are provided on both sides of the folding area, and ends of the touch panel, the adhesive layer, and the polarizer located in non-folding areas are each arranged so as not to overlap the pads.

12. The foldable display device of any of claims 7-11,wherein ends of at least one of the light-emitting element, the cover window, the thin-film transistor layer, the touch panel, the adhesive layer, and the polarizer located in the non-folding area are arranged so that at least one stepped portion is present.

13. The foldable display device of any preceding claim, wherein the active area has a rectangular shape,the non-active area surrounding the active area comprises a first non-active area arranged in a direction perpendicular to a folding axis of the folding area, a second non-active area arranged to face the first non-active area, and a third non-active area and a fourth non-active area extending between the first non-active area and the second non-active area and arranged to face each other, andthe pads are disposed in at least one of the first non-active area and the second non-active area.

14. The foldable display device of claim 13, wherein the pads disposed in the first non-active area are connected to a data driver.

15. The foldable display device of claim 13 or 14, wherein the pads disposed in the second non-active area are connected to a touch driver.

16. The foldable display device of any preceding claim, wherein a neutral plane occurring during bending of the folding area is located in a central portion in a thickness direction of the foldable display device.

17. The foldable display device of any preceding claim, wherein the folding area is an area that bends when the foldable display device is folded about a folding axis.

18. A foldable display device comprising:a base substrate comprising an active area, a nonactive area surrounding the active area, with a plurality of pads being disposed in one side portion or two side portions facing each other of the non-active area, and a folding area overlapping a portion of the active area and a portion of the non-active area;a thin-film transistor layer disposed over the base substrate;a light-emitting element disposed over the thin-film transistor layer;an adhesive layer disposed over the light-emitting element;a touch panel disposed over the adhesive layer;a polarizer disposed over the touch panel; anda cover window disposed over the light-emitting elementwherein ends of the thin-film transistor layer, the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window located in the folding area are arranged in line so that no stepped portion is present.

19. The foldable display device of claim 18, wherein a neutral plane occurring during bending of the folding area is located on the adhesive layer.

20. The foldable display device of claim 18 or 19, wherein ends of the thin-film transistor layer, and at least one of the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window in the folding area are disposed in the non-active area.

21. The foldable display device of any of claims 18-20, wherein the thin-film transistor layer is disposed over the base substrate in the active area and the non-active area, and the pads are provided over the thin-film transistor layer in the non-active area.

22. The foldable display device of any of claims 18-21, wherein non-folding areas are provided on both sides of thefolding area, and ends of the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window located in non-folding areas are each arranged so asnot to overlap the pads.

23. The foldable display device of any of claims 18-22, wherein at least one of the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window located in the folding area cover the pads.

24. The foldable display device of any of claims 18-23, wherein one or two side portions of the at least one of the light-emitting element, the adhesive layer, the touch panel, the polarizer, and the cover window covering the pads in the folding area extend from the folding area to overlap a portion of the non-folding areas provided on one or two sides of the folding area.

25. The foldable display device of any of claims 18-24, wherein the one side portion or the two side portions of the non-active area is arranged in a direction perpendicular to a folding axis of the folding area.

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