Foldable display device

Abstract

A foldable display device is provided. The display device includes a display panel including a folding area and non-folding areas on both sides of the folding area, a back plate disposed below the display panel, a first support layer disposed below the back plate, and an opening pattern arranged in a portion corresponding to the folding area, the opening pattern extending through the first support layer, wherein the display panel includes a flexible substrate, a thin film transistor disposed on the flexible substrate and including a gate electrode, a source electrode, a drain electrode, and a semiconductor layer, a planarization layer disposed on the thin film transistor, and a light emitting element disposed on the planarization layer and including an anode, a light emitting cell, and a cathode.

Description

[0001] This patent application is a divisional application of the patent application filed on December 3, 2020, with application number 202011397996.6 and invention title "Foldable Display Device".

[0002] Cross-references to related applications

[0003] This application claims priority to Korean Patent Application No. 10-2019-0163880, filed with the Korean Intellectual Property Office on December 10, 2019, the disclosure of which is incorporated herein by reference. Technical Field

[0004] This disclosure relates to a foldable display device, and more specifically, to a foldable display device with improved shock resistance. Background Technology

[0005] Recently, as society moves towards an information society, the field of display devices for processing and displaying large amounts of information has developed rapidly, and various flat panel display devices are being developed accordingly.

[0006] Specific examples of such flat panel display devices include liquid crystal displays (LCDs), field emission displays (FEDs), electroluminescent displays (ELDs), and organic light-emitting diodes (OLEDs). These flat panel display devices exhibit excellent performance in terms of thinness, light weight, and low power consumption, and are therefore rapidly replacing existing cathode ray tubes (CRTs).

[0007] At the same time, because such flat panel display devices use glass substrates to withstand the high heat generated during the manufacturing process, they have limitations in reducing weight and thickness as well as providing flexibility.

[0008] Therefore, flexible display devices, which use flexible materials such as plastics to replace existing non-flexible glass substrates and are manufactured to maintain their display performance even when bent like paper, are rapidly becoming the next generation of flat panel display devices.

[0009] Such flexible display devices can be categorized as follows: undamaged types that achieve high durability by using plastic thin-film transistor substrates instead of glass; bendable types that are not easily damaged; rollable types that can be rolled up; and foldable types that can be folded. These flexible display devices offer advantages in terms of space utilization and internal design, and can be used in a variety of application areas.

[0010] In particular, recently, foldable display devices that can be portable in the folded state and display images in the unfolded state are being actively researched in order to achieve large area in conjunction with thinness, lightness and miniaturization.

[0011] Foldable display devices can be used not only in mobile devices such as mobile phones, ultra-mobile PCs, e-books and e-newspapers, but also in a variety of applications such as TVs and monitors.

[0012] Such a foldable display device includes: a display panel for displaying images; a back panel located below the display panel to support the display panel; and a cover window located in front of the display panel to protect the display panel.

[0013] At the same time, since foldable display devices should be folded and unfolded, the back panel, cover window, and all of the display panel are configured in the form of a very thin film, and this thin film form vertically transmits most of the impact transmitted from the outside.

[0014] In other words, since the cover window and back panel are in the form of a thin film, when an impact is applied to the cover window or back panel from the outside, the impact is directly transmitted to the display panel located between the cover window and the back panel.

[0015] This, in turn, damages the display panel, thereby degrading its display quality. As mentioned above, various structures are being researched and used to reduce the resistance of public power lines. Summary of the Invention

[0016] The purpose of this disclosure is to provide a foldable display device with improved shock resistance.

[0017] Another objective of this disclosure is to provide a foldable display device that can prevent degradation of display quality.

[0018] The purpose of this disclosure is not limited to the purposes mentioned above, and other purposes not mentioned above will be clearly understood by those skilled in the art from the following description.

[0019] According to one aspect of this disclosure, the foldable display device may include a display panel comprising a folded region and non-folded regions on both sides of the folded region. A back plate may be disposed below the display panel, and a first support layer may be disposed below the back plate and have an opening pattern in the portion of the first support layer corresponding to the folded region. An impact-absorbing layer may be disposed below the first support layer. The impact-absorbing layer may include a first portion corresponding to the folded region and a second portion corresponding to the non-folded region, and the modulus of the first portion may be greater than the modulus of the second portion.

[0020] Further details of the exemplary embodiments are included in the detailed embodiments and the accompanying drawings.

[0021] In the foldable display device according to an exemplary embodiment of this disclosure, the first portion of the impact-absorbing layer corresponding to the folded area of ​​the display panel is formed of a material with a high modulus. Therefore, even when a point impact is applied to the folded area, the point impact is converted into a surface impact, making it more effective to prevent damage to the display panel or touch panel from the point impact. Thus, the impact resistance characteristics of the display device can be improved.

[0022] Since the technical problem to be solved, the means to solve the problem, and the effects described in the specification are not intended to limit the essential features of the claims, the scope of the claims is not limited by the content described in the specification. Attached Figure Description

[0023] The above and other aspects, features and advantages of this disclosure will become more clearly understood from the following detailed description taken in conjunction with the accompanying drawings:

[0024] Figure 1 This is a schematic cross-sectional view of the foldable display device disclosed herein;

[0025] Figure 2 yes Figure 1 A schematic cross-sectional view of the display panel;

[0026] Figure 3 This is a schematic cross-sectional view of a foldable display device according to an exemplary embodiment of the present disclosure;

[0027] Figure 4 These are photographs showing the ball-drop test results of a foldable display device according to an exemplary embodiment of this disclosure; and

[0028] Figure 5 This is a schematic cross-sectional view of a foldable display device according to another exemplary embodiment of the present disclosure. Detailed Implementation

[0029] By referring to the following and appendix Figure 1 The advantages and features of this disclosure, as well as methods for achieving such advantages and features, will become clear from the exemplary embodiments described in detail herein. However, this disclosure is not limited to the exemplary embodiments disclosed herein, but will be implemented in various forms. Exemplary embodiments are provided by way of example only so that those skilled in the art can fully understand the disclosure and scope of this disclosure. Therefore, this disclosure will be limited only by the scope of the appended claims.

[0030] The shapes, dimensions, ratios, angles, numbers, etc., shown in the accompanying drawings to describe exemplary embodiments of this disclosure are merely examples, and this disclosure is not limited thereto. Throughout the specification, the same reference numerals generally denote the same elements. Furthermore, in the following description of this disclosure, detailed descriptions of known related technologies may be omitted to avoid unnecessarily obscuring the subject matter of this disclosure. Terms such as “comprising,” “having,” and “including” as used herein are generally intended to allow for the addition of additional components, unless these terms are used in conjunction with the term “only.” Unless otherwise expressly stated, any reference to the singular may include the plural form.

[0031] Even if not explicitly stated, components should be interpreted as including the normal tolerance range.

[0032] When using terms such as “on top of,” “above,” “below,” and “adjacent” to describe the positional relationship between two parts, one or more parts may be located between the two parts unless these terms are used with the terms “immediately following” or “directly.”

[0033] When an element or layer is placed "on" another element or layer, the other layer or another element may be placed directly on or between the other element.

[0034] Although the terms "first," "second," etc., are used to describe various components, these components are not limited by these terms. These terms are only used to distinguish one component from another. Therefore, in the technical concept of this disclosure, the first component referred to below can be the second component.

[0035] Throughout the specification, the same reference numerals generally denote the same elements.

[0036] For ease of description, the dimensions and thickness of each component shown in the accompanying drawings are illustrated, and this disclosure is not limited to the dimensions and thickness of the components shown.

[0037] Features of the various embodiments of this disclosure may be partially or wholly adhered to or combined with each other, and may be interlocked and operated in technically different ways, and the embodiments may be performed independently or in association with each other.

[0038] In the following, a display device according to an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings.

[0039] Figure 1 This is a schematic cross-sectional view of a foldable display device according to a first exemplary embodiment of the present disclosure. Figure 2 yes Figure 1 A schematic cross-sectional view of the display panel.

[0040] As shown, the foldable display device 100 includes: a display panel 110 for displaying images; a touch panel 120 constituting a touch sensor (not shown); a cover window 130 for protecting the display panel 110; a back plate 140 for supporting the display panel 110; a first support layer 160 disposed below the back plate 140 and having an opening pattern 161; and a second support layer 150 between the back plate 140 and the first support layer 160.

[0041] At this time, when the orientation is defined in the accompanying drawings for ease of explanation, based on the premise that the display surface of the display panel 110 faces forward, the back plate 140, the first support layer 160 and the second support layer 150 are located behind the display panel 110, and the cover window 130 is located in front of the display panel 110.

[0042] The touch panel 120 is located between the display panel 110 and the cover window 130. The various components are adhered and attached to each other by adhesives 180a, 180b, 190a, and 190b.

[0043] Here, the display panel 110 can be formed of one of a liquid crystal display (LCD), a field emission display (FED), an electroluminescent display (ELD), and an organic light-emitting diode (OLED), but it is preferred to use an OLED, which is representative of flexible display devices that can maintain their display performance even when bent like paper.

[0044] OLEDs are self-emissive devices, and because they do not require a backlight, as is used in liquid crystal displays which are non-emissive devices, they can be manufactured to be both lightweight and thin.

[0045] In addition, OLEDs offer superior viewing angles and contrast compared to LCDs, and are advantageous in terms of power consumption, low DC driving voltage, and fast response speed. Furthermore, because the internal components of OLEDs are solid-state, they are resistant to external impacts and have a wide operating temperature range.

[0046] In particular, due to the simplicity of the OLED manufacturing process, it has the advantage of reducing production costs compared to existing liquid crystal display devices.

[0047] In the display panel 110 formed by such an OLED, a substrate 101 is encapsulated by an encapsulation part 105g, on which a driving thin film transistor 102 and a light-emitting element 103 are formed.

[0048] Here, refer to Figure 2 The following will describe in detail the display panel formed by OLED (hereinafter referred to as OLED panel).

[0049] Reference Figure 2 The substrate 101 is used to support and protect the components of the foldable display device 100 disposed thereon.

[0050] Recently, flexible substrate 101 can be formed from a ductile material with flexible properties, such as plastic.

[0051] The flexible substrate 101 may be in the form of a film including one of the following: polyester-based polymer, silicone-based polymer, acrylic-based polymer, polyolefin-based polymer and copolymers thereof.

[0052] For example, the flexible substrate 101 may be formed from at least one of the following: polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polysilane, polysiloxane, polysilazane, polycarbosilane, polyacrylate, polymethacrylate, polymethyl acrylate, polymethyl methacrylate, polyethyl acrylate, polyethyl methacrylate, cyclic olefin copolymer (COC), cyclic olefin polymer (COP), polyethylene (PE), polypropylene (PP), polyimide (PI), polymethyl methacrylate (PMMA), polystyrene (PS), polyacetal (POM), polyetheretherketone (PEEK), polyester sulfone (PES), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), polycarbonate (PC), polyvinylidene fluoride (PVDF), perfluoroalkyl polymer (PFA), styrene-acrylonitrile copolymer (SAN), and combinations thereof.

[0053] A buffer layer may also be provided on the flexible substrate 101. The buffer layer prevents moisture or other impurities from penetrating through the flexible substrate 101 from the outside and can also planarize the surface of the flexible substrate 101. The buffer layer is not necessarily a necessary component and may be omitted depending on the type of thin-film transistor 102 disposed on the flexible substrate 101.

[0054] A thin-film transistor 102 is disposed on a flexible substrate 101, and the thin-film transistor 102 may include a gate electrode 102a, a source electrode 102d, a drain electrode 102c, and a semiconductor layer 102b.

[0055] In this case, the semiconductor layer 102b can be composed of amorphous silicon or polycrystalline silicon, but is not limited to these. Polycrystalline silicon has superior mobility compared to amorphous silicon, and also has low power consumption and excellent reliability, and therefore can be used in driving thin-film transistors within a pixel.

[0056] Semiconductor layer 102b can be formed of oxide semiconductor. Oxide semiconductors have excellent mobility and uniformity characteristics. Oxide semiconductors can be formed from: quaternary metal oxides such as those based on indium tin gallium zinc oxide (InSnGaZnO); ternary metal oxides such as those based on indium gallium zinc oxide (InGaZnO), indium tin zinc oxide (InSnZnO), tin gallium zinc oxide (SnGaZnO), aluminum gallium zinc oxide (AlGaZnO), indium aluminum zinc oxide (InAlZnO), and tin aluminum zinc oxide (SnAlZnO); or materials such as those based on indium zinc oxide... Materials based on zinc oxide (InZnO), materials based on zinc tin oxide (SnZnO), materials based on zinc aluminum oxide (AlZnO), materials based on zinc magnesium oxide (ZnMgO), materials based on magnesium tin oxide (SnMgO), materials based on magnesium indium oxide (InMgO), binary metal oxides based on indium gallium oxide (InGaO), materials based on indium oxide (InO), materials based on tin oxide (SnO), and materials based on zinc oxide (ZnO). The composition ratio of the individual elements included in the oxide semiconductor is not limited.

[0057] Semiconductor layer 102b may include: a source region including p-type or n-type impurities; a drain region; and a channel region between the source region and the drain region. Semiconductor layer 102b may also include a low-concentration doped region adjacent to the channel region between the source region and the drain region.

[0058] The source and drain regions are doped with a high concentration of impurities and can be connected to the source electrode 102d and drain electrode 102c of the thin-film transistor 102, respectively.

[0059] As impurity ions, either p-type or n-type impurities can be used. P-type impurities can be one of boron (B), aluminum (Al), gallium (Ga), and indium (In), while n-type impurities can be one of phosphorus (P), arsenic (As), and antimony (Sb).

[0060] The channel region of the semiconductor layer 102b may be doped with n-type or p-type impurities according to the NMOS or PMOS thin film transistor structure, and the thin film transistors included in the foldable display device 100 according to the exemplary embodiments of the present disclosure may be NMOS or PMOS thin film transistors.

[0061] The first insulating layer 105a is an insulating layer composed of a single layer or multiple layers of silicon oxide (SiOx) or silicon nitride (SiNx), and can be configured such that the current flowing through the semiconductor layer 102b does not flow to the gate electrode 102a. In addition, silicon oxide has lower ductility than metals, but silicon oxide has better ductility than silicon nitride, and silicon oxide can be formed into a single layer or multiple layers depending on its properties.

[0062] The gate electrode 102a serves as a switch for turning the thin-film transistor 102 on or off based on an electrical signal transmitted from the outside through the gate line, and may consist of a single layer or multiple layers of a conductive metal such as copper (Cu), aluminum (Al), molybdenum (Mo), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), and neodymium (Nd) or their alloys. However, the embodiments are not limited thereto.

[0063] The source electrode 102d and drain electrode 102c are connected to the data line, enabling externally transmitted electrical signals to be transmitted from the thin-film transistor 102 to the light-emitting element 103. The source electrode 102d and drain electrode 102c may be composed of a single layer or multiple layers of conductive metals or alloys thereof, such as copper (Cu), aluminum (Al), molybdenum (Mo), chromium (Cr), gold (Au), titanium (Ti), nickel (Ni), and neodymium (Nd), but are not limited thereto.

[0064] In order to insulate the gate electrode 102a from the source electrode 102d and the drain electrode 102c, a second insulating layer 105b composed of a single layer or multiple layers of silicon oxide (SiOx) or silicon nitride (SiNx) can be disposed between the gate electrode 102a and the source electrode 102d and the drain electrode 102c.

[0065] A passivation layer formed of an inorganic insulating layer such as silicon oxide (SiOx) or silicon nitride (SiNx) can be disposed on the thin-film transistor 102.

[0066] The passivation layer prevents unnecessary electrical connections between components located above and below it, and also protects against external contamination or damage. Depending on the configuration and characteristics of the thin-film transistor 102 and the light-emitting element 103, the passivation layer may be omitted.

[0067] Depending on the location of the components constituting the thin-film transistor 102, the structure of the thin-film transistor 102 can be divided into inverted interleaved structures and coplanar structures. For example, a thin-film transistor with an inverted interleaved structure refers to a thin-film transistor having the following structure: wherein, based on the semiconductor layer, the gate electrode is positioned opposite the source electrode and the drain electrode. (As in...) Figure 2In the context, the thin-film transistor 102 with a coplanar structure refers to a thin-film transistor having the following structure: wherein, based on the semiconductor layer 102b, the gate electrode 102a is located on the same side as the source electrode 102d and the drain electrode 102c.

[0068] exist Figure 2 The present invention illustrates a thin-film transistor 102 having a coplanar structure, but the foldable display device 100 according to an exemplary embodiment of the present disclosure may also include thin-film transistors having an inverted staggered structure.

[0069] For ease of description, only the driving thin-film transistor is shown among the various thin-film transistors that may be included in the foldable display device 100. Switching thin-film transistors, capacitors, etc., may also be included in the foldable display device 100.

[0070] Furthermore, when a signal is applied from the gate line to the switching thin-film transistor, the switching thin-film transistor transmits the signal from the data line to the gate electrode of the driving thin-film transistor. The driving thin-film transistor can transmit the current transmitted through the power line to the anode 103a via the signal transmitted from the switching thin-film transistor, and control the light emission by the current transmitted to the anode 103a.

[0071] Planarization layers 105c and 105d can be disposed on the thin-film transistor 102 to protect the thin-film transistor 102, to mitigate the steps caused by the thin-film transistor 102, and to reduce the parasitic capacitance generated between the thin-film transistor 102 and the gate line, data line, and light-emitting element 103.

[0072] The planarization layers 105c and 105d may be formed from one or more of the following: acrylic resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, unsaturated polyester resin, polyphenylene resin, polyphenylene sulfide resin, and benzocyclobutene, but are not limited thereto.

[0073] A foldable display device 100 according to an exemplary embodiment of the present disclosure may include a first planarization layer 105c and a second planarization layer 105d stacked sequentially. That is, the first planarization layer 105c may be disposed on the thin-film transistor 102, and the second planarization layer 105d may be disposed on the first planarization layer 105c.

[0074] A buffer layer may be disposed on the first planarization layer 105c. The buffer layer may consist of multiple layers of silicon oxide (SiOx) to protect the components disposed on the first planarization layer 105c, and may be omitted depending on the configuration and characteristics of the thin-film transistor 102 and the light-emitting element 103.

[0075] The intermediate electrode 104 can be connected to the thin film transistor 102 through a contact hole formed in the first planarization layer 105c. The intermediate electrode 104 is stacked to be connected to the thin film transistor 102, and the data line can also be formed as a multi-layer structure.

[0076] The data line can be formed to have a structure in which a lower layer and an upper layer are connected to each other, the lower layer is formed of the same material as the source electrode 102d and the drain electrode 102c, and the upper layer is formed of the same material as the intermediate electrode 104. That is, the data line can be implemented in a structure in which two layers are connected to each other in parallel, and in this case, the line resistance of the data line can be reduced.

[0077] Meanwhile, a passivation layer formed of an inorganic insulating layer such as silicon oxide (SiOx) or silicon nitride (SiNx) can be further provided on the first planarization layer 105c and the intermediate electrode 104. The passivation layer can serve to prevent unnecessary electrical connection between components, and to prevent contamination or damage from the outside, and can be omitted depending on the configuration and characteristics of the thin film transistor 102 and the light emitting element 103.

[0078] The light emitting element 103 provided on the second planarization layer 105d can include an anode 103a, a light emitting unit 103b, and a cathode 103c.

[0079] The anode 103a can be provided on the second planarization layer 105d.

[0080] The anode 103a serves to supply holes to the light emitting unit 103b, and is connected to the intermediate electrode 104 through a contact hole in the second planarization layer 105d, thereby being electrically connected to the thin film transistor 102.

[0081] The anode 103a can be formed of a transparent conductive material, for example, indium tin oxide (ITO), indium zinc oxide (IZO), or the like, but is not limited thereto.

[0082] When the foldable display device 100 is a top emission type display device to which the cathode 103c is provided to the upper portion to emit light, it can further include a reflective layer so that the emitted light is reflected from the anode 103a to be smoothly emitted in a direction toward the upper portion provided with the cathode 103c.

[0083] The anode 103a can be a two-layer structure in which a transparent conductive layer formed of a transparent conductive material and a reflective layer are sequentially stacked, or a three-layer structure in which a transparent conductive layer, a reflective layer, and a transparent conductive layer are sequentially stacked. The reflective layer can be formed of silver (Ag) or an alloy including silver.

[0084] The bank 105e provided on the anode 103a and the second planarization layer 105d can define a sub-pixel by dividing a region in which light is actually emitted. The bank 105e can be formed by photolithography after a photoresist is formed on the anode 103a. The photoresist refers to a photosensitive resin whose solubility in a developer is changed by the action of light, and a specific pattern can be obtained by exposing and developing the photoresist. The type of photoresist can be classified into a positive photoresist and a negative photoresist. The positive photoresist is a photoresist whose exposed portion increases in solubility in a developer by exposure. When the positive photoresist is developed, a pattern from which the exposed portion is removed is obtained. The negative photoresist is a photoresist whose exposed portion is significantly reduced in solubility in a developer by exposure. When the negative photoresist is developed, a pattern from which the unexposed portion is removed is obtained.

[0085] A fine metal mask (FMM) that is a deposition mask can be used to form the light emitting unit 103b of the light emitting element 103.

[0086] In addition, in order to prevent damage that can occur due to contact with a deposition mask provided on the bank 105e, and in order to maintain a constant distance between the bank 105e and the deposition mask, a spacer 105f formed of one of polyimide, which is a transparent organic material, photoacrylic, and benzocyclobutene (BCB) can be provided on the bank 105e.

[0087] The light emitting unit 103b can be provided between the anode 103a and the cathode 103c.

[0088] The light emitting unit 103b serves to emit light, and can include at least one of a hole injection layer (HIL), a hole transport layer (HTL), a light emitting layer, an electron transport layer (ETL), and an electron injection layer (EIL), and depending on the structure or characteristics of the foldable display apparatus 100, some components can be omitted. Here, an electroluminescent layer and an inorganic light emitting layer can be applied to the light emitting layer.

[0089] The hole injection layer is provided on the anode 103a to facilitate injection of holes.

[0090] The hole transport layer is provided on the hole injection layer to smoothly transport holes to the light emitting layer.

[0091] The light emitting layer is provided on the hole transport layer, and can include a material capable of emitting light of a specific color to thereby emit light of a specific color. In addition, a phosphorescent material or a fluorescent material can be used to form the light emitting material.

[0092] An electron injection layer can be further disposed on the electron transport layer. The electron injection layer is an organic layer that helps injection of electrons from the cathode 103c, and can be omitted depending on the structure and characteristics of the foldable display apparatus 100.

[0093] On the other hand, an electron blocking layer or a hole blocking layer that blocks the flow of holes or electrons is also disposed at a position adjacent to the light emitting layer, to prevent the phenomenon that, when electrons are injected into the light emitting layer, the electrons move from the light emitting layer and pass to the adjacent hole transport layer, or to prevent the phenomenon that, when holes are injected into the light emitting layer, the holes move from the light emitting layer and pass to the adjacent electron transport layer; so that light emitting efficiency can be improved.

[0094] The cathode 103c is disposed on the light emitting unit 103b and serves to supply electrons to the light emitting unit 103b. Since the cathode 103c needs to supply electrons, it can be formed of a metal material that is a conductive material having a low work function, such as magnesium (Mg), silver-magnesium (Ag:Mg), and is not limited thereto.

[0095] When the foldable display apparatus 100 is a top emission type display apparatus, the cathode 103c can be a transparent conductive oxide, such as indium tin oxide (ITO), indium zinc oxide (IZO), indium tin zinc oxide (ITZO), zinc oxide (ZnO), and tin oxide (TO).

[0096] An encapsulation part 105g can be disposed on the light emitting element 103 to prevent the thin film transistor 102 and the light emitting element 103, which are components of the foldable display apparatus 100, from being oxidized or damaged due to moisture, oxygen, or impurities introduced from the outside. The encapsulation part 105g can be formed by stacking a plurality of encapsulation layers, a foreign matter compensation layer, and a plurality of barrier films.

[0097] The encapsulation layer can be disposed on the entire surface of the upper portion of the thin film transistor 102 and the light emitting element 103, and can be formed of one of silicon nitride (SiNx) or aluminum oxide (AlyOz) that is an inorganic material. However, embodiments are not limited thereto. The encapsulation layer can also be disposed on the foreign matter compensation layer disposed on the encapsulation layer.

[0098] The foreign matter compensation layer is disposed on the encapsulation layer, and an organic material such as carbon silicon oxide (SiOCz), acrylic (acryl), or an epoxy-based resin can be used for the foreign matter compensation layer. However, embodiments are not limited thereto. When a defect occurs due to a crack generated by a particle or a foreign matter that can be generated during a process, the defect can be compensated for by covering the curve and the foreign matter by the foreign matter compensation layer.

[0099] A barrier film can be disposed on the encapsulation layer and the foreign matter compensation layer, whereby the foldable display device 100 can delay penetration of oxygen and moisture from the outside. The barrier film is configured in the form of a light-transmitting and double-sided adhesive film, and can be composed of any one of an olefin-based insulating material, an acrylic-based insulating material, and a silicon-based insulating material. Alternatively, a barrier film composed of any one of COP (cyclo-olefin polymer), COC (cyclo-olefin copolymer), and PC (polycarbonate) can also be stacked, but is not limited thereto.

[0100] Figure 3 is a schematic cross-sectional view of a foldable display device according to an exemplary embodiment of the present disclosure.

[0101] Figure 3 Some components in Figure 1 are substantially the same as and similar to some components described in

[0102] The back plate 240, the second support layer 250, the first support layer 260, and the impact absorption layer 270 are sequentially disposed on the rear surface of the display panel 210, and the cover window 230 is positioned in front of the display panel 210. In addition, the touch panel 220 is located between the display panel 210 and the cover window 230. The respective components are adhered and attached to each other by the adhesives 280a, 280b, 290a, 290b, 290c.

[0103] Since the substrate 101 of the display panel 210 is too thin, the back plate 240 is attached to the rear surface of the display panel 210 to support the display panel 210. The back plate 240 can be formed of a metal material such as stainless steel (SUS), or a polymer such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), silicone, or polyurethane (PU).

[0104] The first support layer 260 is also called a plate bottom. In a portion thereof corresponding to the folding area FA of the foldable display device 200, the first support layer 260 can include an open pattern 261. An elastically deformable area is increased by the open pattern 261 formed in the folding area FA, thereby allowing recovery. In some embodiments, the open pattern 261 is an open gap area (e.g., filled with air). In other embodiments, the open pattern 261 is a gap area filled with any suitable material, such that the open pattern 261 functions as a spring, such that an elastic recovery energy is increased, thereby allowing a recovery time to be reduced. Accordingly, folding characteristics of the foldable display device 200 can be improved. In addition, the first support layer 260 can be used to prevent transfer caused by solidification. The first support layer 260 is formed of a metal material, e.g., stainless steel (SUS), but is not limited thereto. The first support layer 260 can also be formed of a polymer, e.g., polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), silicone, or polyurethane (PU).

[0105] The second support layer 250 is also called a plate top. The second support layer 250 is disposed between the back plate 240 and the first support layer 260, and can enhance the rigidity of the display panel 210. In addition, the second support layer 250 can be used to prevent the open pattern 261 from being seen through the display panel. The second support layer 250 can be formed of a metal material, e.g., stainless steel (SUS) including iron (Fe) or other metals, e.g., chromium (Cr) and nickel (Ni) contained in iron, aluminum (Al), or magnesium (Mg), but is not limited thereto. The second support layer 250 can be formed of a polymer, e.g., polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), silicone, or polyurethane (PU).

[0106] As described above, since the foldable display device should be able to be folded and unfolded, all of the back plate and the cover window as well as the display panel are configured in a very thin film form, and such a thin film form vertically transmits most of the impact transmitted from the outside.

[0107] For example, when impact is transmitted to the cover window from the outside, the impact transmitted to the cover window is transmitted to the touch panel or the display panel located below the cover window.

[0108] Accordingly, an electrode of a touch sensor of the touch panel or an element of the display panel is damaged. Accordingly, the inventors have invented a new structure of a foldable display device to solve the above-described limitations.

[0109] The impact absorbing layer 270 can be disposed under the first support layer 260. The impact absorbing layer 270 can minimize the transmission of an impact applied from the outside to the touch panel or the display panel 210. The impact absorbing layer 270 can be formed of silicone, silicone foam, acrylic foam, polypropylene foam, polyurethane (PU), polyurethane foam, or thermoplastic polyurethane (TPU), but is not limited thereto.

[0110] Here, the impact absorbing layer 270 has a thickness of 100 μm to 1000 μm. When the impact absorbing layer has a thickness less than 100 μm, the impact absorbing capacity is not significant, and when the impact absorbing layer has a thickness greater than 1000 μm, it can cause difficulty in folding the foldable display device.

[0111] However, the inventors have found a weak point in the above-described structure. Figure 4 is a photograph showing Figure 3 a ball drop test result of the foldable display device 300 according to another embodiment of the present disclosure. Referring to Figure 4 , it can be seen that the folding area FA of the display panel 210 is damaged due to a point impact. In comparison to damage by a face impact applied to the entire surface, a point impact, which is an impact applied on a partial area, can apply stronger damage to the display panel.

[0112] When a point impact is applied from the outside, in a non-folding area of the first support layer where the opening pattern is not present, the point impact is converted into a face impact so that the impact can be well absorbed. However, since the opening pattern exists in the folding area of the first support layer to improve the folding characteristics, when a point impact is applied to the upper portion of the folding area, it cannot be converted into a face impact, thereby causing damage to the display panel or the touch panel. Accordingly, the inventors have recognized this problem and invented a new structure of the impact absorbing layer.

[0113] Figure 5 is a photograph showing

[0114] Referring to Figure 5According to another exemplary embodiment of the present disclosure, a foldable display device 300 can include a display panel 310. A cover window 330 is positioned in front of the display panel 310. In addition, a touch panel 320 is located between the display panel 310 and the cover window 330. The display panel 310 can include a folding area FA and a non-folding area NFA on both sides of the folding area FA. A back plate 340 is disposed under the display panel 310. A first support layer 360 having an open pattern 361 in a portion thereof corresponding to the folding area FA is disposed under the back plate 340. An impact absorbing layer 370 is disposed under the first support layer 360. The impact absorbing layer 370 includes a first portion 370-1 corresponding to the folding area FA and a second portion 370-2 corresponding to the non-folding area NFA. The impact absorbing layer 370 can be formed of a material in which the modulus of the first portion 370-1 is higher than the modulus of the second portion 370-2. That is, the first portion 370-1 can be formed of a material having an elastic modulus greater than that of the second portion 370-2. The respective components are adhered and attached to each other by adhesives 380a, 380b, 390a, 390b, 390c.

[0115] The first portion 370-1 can be formed of at least one of silicone, silicone foam, acrylic foam, polypropylene foam, polyurethane (PU), polyurethane foam, and thermoplastic polyurethane (TPU).

[0116] The first portion 370-1 has a modulus value of 1 MPa to 30 MPa, and the first portion 370-1 has a thickness of 100 µm to 1000 µm. When the first portion 370-1 has a thickness of less than 100 µm, the impact absorbing capacity is not significant, and when the first portion 370-1 has a thickness of more than 1000 µm, it can cause difficulty in folding the foldable display device 300.

[0117] The second portion 370-2 can be formed of at least one of silicone, silicone foam, acrylic foam, polypropylene foam, polyurethane (PU), polyurethane foam, and thermoplastic polyurethane (TPU).

[0118] The second portion 370-2 has a modulus value of 10 KPa to 1000 KPa, and the second portion 370-2 has a thickness of 100 µm to 1000 µm. When the second portion 370-2 has a thickness of less than 100 µm, the impact absorbing capacity is not significant, and when the second portion 370-2 has a thickness of more than 1000 µm, it can cause difficulty in folding the foldable display device 300.

[0119] [Table 1]

[0120]

[0121] The above [Table 1] shows the drop ball test results indicating the height at which damage to the display panel occurs according to the modulus of the impact absorption layer 370 and the presence or absence of the opening pattern of the first support layer 360. Referring to the above [Table 1], in the case where the modulus of the first portion 370-1 having the opening pattern 361 is relatively high (4 MPa or 10 MPa), it can be determined that the height at which damage to the display panel 310 occurs is 10 cm or more when the ball is dropped. However, in the case where the modulus of the first portion 370-1 having the opening pattern 361 is relatively low (10 KPa or 20 KPa), it can be determined that damage to the display panel 310 occurs when the ball is dropped at a height of 2.5 cm. On the other hand, when the modulus of the second portion 370-2 not having the opening pattern 361 is relatively high (4 MPa or 10 MPa), damage to the display panel 310 occurs when the ball is dropped at a height of 2.5 cm. However, when the modulus of the second portion 370-2 not having the opening pattern 361 is relatively low (10 KPa or 20 KPa), it can be determined that damage to the display panel 310 occurs when the ball is dropped at a height of 15 cm.

[0122] Thus, in the foldable display device 300 according to the exemplary embodiment of the disclosure, the impact absorption layer 370 is provided such that the modulus of the first portion 370-1 of the impact absorption layer 370 corresponding to the folding area FA has a relatively large value (1 MPa to 30 MPa), and the modulus of the second portion 370-2 of the impact absorption layer 370 corresponding to the non-folding area NFA has a value smaller than that of the first portion 370-1. Accordingly, compared to a general foldable display device, even when an external impact is applied to the foldable display device 300, the impact is partially alleviated, thereby improving the impact resistance characteristics of the touch panel 320 or the display panel 310.

[0123] The second support layer 350 can also be included between the back plate 340 and the first support layer 360. The second support layer 350 can enhance the rigidity of the display panel 310. In addition, the second support layer 250 can serve to prevent the opening pattern 361 from being seen through the display panel 310.

[0124] The second support layer 350 can be formed of a metal material, for example, stainless steel (SUS) including iron (Fe) or other metals such as chromium (Cr) and nickel (Ni) contained in iron, aluminum (Al), or magnesium (Mg), but is not limited thereto. The second support layer 350 can be formed of a polymer such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), silicone, or polyurethane (PU).

[0125] Meanwhile, in the description thus far, it is described and illustrated that the touch panel 320 is positioned above the display panel 310 on which an image is implemented in the foldable display device 300. However, the touch panel 320 can be deleted.

[0126] The foldable display device 300 according to another embodiment of the disclosure can include a display panel 310. The display panel 310 can include a folding area FA and a non-folding area NFA on both sides of the folding area FA. A first support layer 360 having an open pattern 361 in a portion thereof corresponding to the folding area FA can be under the display panel 310. An impact absorption layer 370 is disposed under the first support layer 360. The impact absorption layer 370 includes a first portion 370-1 corresponding to the folding area FA and a second portion 370-2 corresponding to the non-folding area NFA. In the impact absorption layer 370, the modulus of the first portion 370-1 has a value greater than the modulus of the second portion 370-2 to reduce damage to the display panel 310 caused by a point impact applied to the folding area FA.

[0127] The first portion 370-1 can convert a point impact applied to the folding area FA of the display panel 310 into a surface impact to prevent deformation of the shape of the folding area FA. The open pattern 361 is not formed in the first support layer 360 corresponding to the second portion 370-2. Accordingly, the first support layer 360 can convert a point impact applied from the outside into a surface impact. However, since the open pattern 361 is formed in the first support layer 360 corresponding to the first portion 370-1 to improve the folding characteristics, the point impact cannot be converted into the surface impact due to the open pattern 361. Accordingly, the first portion 370-1 corresponding to the open pattern 361 has a high modulus value in order to convert the point impact into the surface impact. That is, the first portion 370-1 can be formed of a material having an elastic modulus greater than that of the second portion 370-2.

[0128] Part 370-1 may be formed from at least one of the following: silicone, silicone foam, acrylic foam, polypropylene foam, polyurethane (PU), polyurethane foam, and thermoplastic polyurethane (TPU).

[0129] The first part 370-1 has a modulus value of 1 MPa to 30 MPa and a thickness of 100 μm to 1000 μm. When the first part 370-1 has a thickness of less than 100 μm, the impact absorption capacity is not significant, and when the first part 370-1 has a thickness of more than 1000 μm, it may cause difficulties in folding the foldable display device 300.

[0130] Part 2 370-2 may be formed from at least one of the following: silicone, silicone foam, acrylic foam, polypropylene foam, polyurethane (PU), polyurethane foam, and thermoplastic polyurethane (TPU).

[0131] The second part 370-2 has a modulus value of 10 kPa to 1000 kPa and a thickness of 100 μm to 1000 μm. When the second part 370-2 has a thickness of less than 100 μm, the impact absorption capacity is not significant, and when the second part 370-2 has a thickness of more than 1000 μm, it may cause difficulties in folding the foldable display device 300.

[0132] In the foldable display device 300 according to an exemplary embodiment of the present disclosure, the first portion 370-1 of the impact-absorbing layer 370 corresponding to the folded area FA of the display panel 310 is formed of a material with a high modulus. Therefore, even when a point impact is applied to the folded area FA, the point impact is converted into a surface impact, making it more effective to prevent damage to the display panel 310 or the touch panel 320 from point impacts. Thus, the impact resistance characteristics of the display device 300 can be improved.

[0133] Although exemplary embodiments of the present disclosure have been described in detail with reference to the accompanying drawings, the present disclosure is not limited thereto, and the present disclosure can be implemented in many different forms without departing from the technical concept of the present disclosure. Therefore, the exemplary embodiments of the present disclosure are provided for illustrative purposes only and are not intended to limit the technical concept of the present disclosure. The scope of the technical concept of the present disclosure is not limited thereto. Therefore, it should be understood that the above exemplary embodiments are illustrative in all respects and do not limit the present disclosure. The scope of protection of the present disclosure should be interpreted based on the appended claims, and all technical concepts within their equivalent scope should be interpreted as falling within the scope of the present disclosure.

[0134] Inventive concept

[0135] This invention provides the following inventive concept:

[0136] 1. A foldable display device, comprising:

[0137] The display panel includes a folded area and non-folded areas on both sides of the folded area;

[0138] A back panel is located below the display panel;

[0139] A first support layer, disposed beneath the back plate; and

[0140] An opening pattern is arranged in the portion corresponding to the folded area, the opening pattern extending through the first support layer.

[0141] The display panel includes a flexible substrate; a thin-film transistor disposed on the flexible substrate and including a gate electrode, a source electrode, a drain electrode and a semiconductor layer; a planarization layer disposed on the thin-film transistor; and a light-emitting element disposed on the planarization layer and including an anode, a light-emitting unit and a cathode.

[0142] 2. The foldable display device according to inventive concept 1, wherein the planarization layer comprises a first planarization layer and a second planarization layer stacked sequentially, and

[0143] The foldable display device further includes an intermediate electrode connected to the thin-film transistor via a contact hole formed in the first planarization layer, and the anode connected to the intermediate electrode via a contact hole in the second planarization layer.

[0144] 3. The foldable display device according to inventive concept 1 further includes: a dam disposed on the anode and the planarization layer and dividing the area for emitting light; and a spacer disposed on the dam and formed of a transparent organic material.

[0145] 4. The foldable display device according to inventive concept 1 further includes:

[0146] A cover window is located in front of the display panel;

[0147] A touch panel, located between the display panel and the overlay window; and

[0148] A second support layer is located between the back plate and the first support layer.

[0149] 5. The foldable display device according to inventive concept 4 further includes: a plurality of adhesives for attaching at least one of the cover window, the touch panel, the display panel, the back plate, the second support layer and the first support layer.

[0150] 6. The foldable display device according to inventive concept 5, wherein the plurality of adhesives includes a first adhesive disposed between the cover window and the touch panel, a second adhesive disposed between the display panel and the back plate, a third adhesive disposed between the back plate and the second support layer, and a fourth adhesive disposed between the second support layer and the first support layer.

[0151] 7. The foldable display device according to inventive concept 1, wherein the display panel further includes an encapsulation portion disposed on the light-emitting element and preventing the thin-film transistor and the light-emitting element from being oxidized or damaged due to moisture.

[0152] 8. The foldable display device according to inventive concept 7 further includes a touch sensor having electrodes disposed on the package portion.

[0153] 9. The foldable display device according to inventive concept 1 further includes: an impact-absorbing layer disposed below the first support layer.

[0154] The impact-absorbing layer includes a first portion corresponding to the folded region and a second portion corresponding to the non-folded region.

[0155] The modulus of the first part is greater than that of the second part.

[0156] 10. The foldable display device according to inventive concept 9, wherein the first portion is formed of a material having an elastic modulus greater than that of the second portion.

[0157] 11. The foldable display device according to inventive concept 9, wherein the first part and the second part comprise any one of the following materials: silicone, silicone foam, acrylic foam, polypropylene foam, polyurethane, polyurethane foam or thermoplastic polyurethane.

[0158] 12. The foldable display device according to inventive concept 9, wherein the first portion has a thickness of 100 μm to 1000 μm and a modulus of 1 MPa to 30 MPa.

[0159] 13. The foldable display device according to inventive concept 9, wherein the second portion has a thickness of 100 μm to 1000 μm and a modulus of 10 kPa to 1000 kPa.

Claims

1. A foldable display device, comprising: The display panel includes a folded area and non-folded areas on both sides of the folded area; A back panel is located below the display panel; A first support layer is disposed below the back plate; An impact-absorbing layer disposed below the first support layer; as well as An opening pattern is arranged in the portion corresponding to the folded area, the opening pattern extending through the first support layer. The display panel includes a flexible substrate; a thin-film transistor disposed on the flexible substrate and including a gate electrode, a source electrode, a drain electrode, and a semiconductor layer; a planarization layer disposed on the thin-film transistor; and a light-emitting element disposed on the planarization layer and including an anode, a light-emitting unit, and a cathode. The impact-absorbing layer includes a first portion corresponding to the folded region and a second portion corresponding to the unfolded region. The modulus of the first part is greater than that of the second part.

2. The foldable display device according to claim 1, wherein, The planarization layer comprises a first planarization layer and a second planarization layer stacked sequentially, and The foldable display device further includes an intermediate electrode connected to the thin-film transistor via a contact hole formed in the first planarization layer, and the anode connected to the intermediate electrode via a contact hole in the second planarization layer.

3. The foldable display device according to claim 1, further comprising: A dam portion disposed on the anode and the planarization layer, and dividing the area for emitting light; And spacers formed of transparent organic material and disposed on the embankment.

4. The foldable display device according to claim 1, further comprising: A cover window is located in front of the display panel; A touch panel is located between the display panel and the overlay window; as well as A second support layer is located between the back plate and the first support layer.

5. The foldable display device according to claim 4, further comprising: A plurality of adhesives are used to attach at least one of the cover window, the touch panel, the display panel, the back plate, the second support layer, and the first support layer.

6. The foldable display device according to claim 5, wherein, The plurality of adhesives includes a first adhesive disposed between the cover window and the touch panel, a second adhesive disposed between the display panel and the back plate, a third adhesive disposed between the back plate and the second support layer, and a fourth adhesive disposed between the second support layer and the first support layer.

7. The foldable display device according to claim 1, wherein, The display panel also includes an encapsulation portion disposed on the light-emitting element and preventing the thin-film transistor and the light-emitting element from being oxidized or damaged due to moisture.

8. The foldable display device according to claim 7 further includes a touch sensor having electrodes disposed on the package portion.

9. The foldable display device according to claim 1, wherein, The first part is formed of a material whose elastic modulus is greater than that of the second part.

10. The foldable display device according to claim 1, wherein, The first and second portions comprise any material selected from silicone, silicone foam, acrylic foam, polypropylene foam, polyurethane, polyurethane foam, or thermoplastic polyurethane.

11. The foldable display device according to claim 1, wherein, The first portion has a thickness of 100 to 1000 μm and a modulus of 1 to 30 MPa.

12. The foldable display device according to claim 1, wherein, The second part has a thickness of 100 to 1000 μm and a modulus of 10 to 1000 kPa.

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