Foldable display devices

Abstract

A foldable display device includes: a first display panel including a first substrate and a first pixel array layer arranged on a first surface of the first substrate; a second display panel including a second substrate and a second pixel array layer arranged on the first surface of the second substrate; and a first sound generator arranged between a second surface of the first display panel opposite to the first surface of the first display panel and a second surface of the second display panel opposite to the first surface of the second display panel, wherein the first sound generator outputs a first sound by vibrating at least one of the first display panel and the second display panel.

Description

Technical Field

[0001] The present disclosure relates to a foldable display device. Background Art

[0002] With the development of information society, the demand for display devices for displaying images has increased and diversified. Recently, display devices have been applied to various electronic devices, such as smart phones, tablet personal computers ("PCs"), digital cameras, notebook computers, navigation devices, smart televisions ("TVs"), etc.

[0003] Recently, flexible display devices that are flexible and thus foldable or bendable may be applied to small electronic devices to improve portability. Since the flexible display device can be folded or unfolded by a user, portability may be improved by significantly reducing the volume of the flexible display device. Summary of the invention

[0004] A flexible display device may include a display panel for displaying an image and a sound generator for providing sound. Since the flexible display device may be in a folded state and an unfolded state, the location of the sound generator in the flexible display device may be limited. In such a flexible display device, it is desirable to provide optimal sound depending on whether the flexible display device is being used in a folded state or an unfolded state.

[0005] Embodiments of the present disclosure provide a foldable display device having improved sound quality by vibrating a display panel to output sound.

[0006] An embodiment of the present disclosure also provides a sound providing method of a foldable display device to improve sound quality by vibrating a display panel to output sound.

[0007] According to an embodiment of the present disclosure, a foldable display device includes: a first display panel including a first substrate and a first pixel array layer arranged on a first surface of the first substrate; a second display panel including a second substrate and a second pixel array layer arranged on the first surface of the second substrate; and a first sound generator between a second surface of the first display panel opposite to the first surface of the first substrate and a second surface of the second display panel opposite to the first surface of the second substrate, wherein the first sound generator outputs a first sound by vibrating at least one of the first display panel and the second display panel.

[0008] In an embodiment, the first sound generator may be attached to the second surface of the first display panel and the second surface of the second display panel.

[0009] In an embodiment, the foldable display device may further include: a first light shielding member disposed between the first sound generator and the second surface of the first display panel; and a second light shielding member disposed between the first sound generator and the second surface of the second display panel.

[0010] In an embodiment, the foldable display device may further include: a first reinforcement member disposed on a first side of the first sound generator and between the first sound generator and the second surface of the first display panel; and a second reinforcement member disposed on a second side of the first sound generator and between the first sound generator and the second surface of the second display panel.

[0011] In an embodiment, the second display panel may include a first region, a second region, and a folding region between the first region and the second region, and the second pixel array layer in the first region and the second pixel array layer in the second region face each other.

[0012] In an embodiment, the first sound generator may be disposed in the first area of ​​the second display panel.

[0013] In an embodiment, the foldable display device may further include a first panel bottom member, which is arranged between the second surface of the first display panel and the second surface of the second display panel in the first area of ​​the second display panel, and does not overlap with the first sound generator when viewed in the thickness direction of the first display panel in a plan view.

[0014] In an embodiment, the first panel bottom member may include a first adhesive disposed on the second surface of the first display panel, a second adhesive disposed on the second surface of the second display panel, and a first heat dissipation member disposed between the first adhesive and the second adhesive.

[0015] In an embodiment, the first panel bottom member may further include a first buffer member disposed between the first adhesive and the first heat dissipation member, and a second buffer member disposed between the second adhesive and the first heat dissipation member.

[0016] In an embodiment, the foldable display device may further include a second panel bottom member disposed on the second surface of the second display panel in the second area of ​​the second display panel.

[0017] In an embodiment, the thickness of the first panel bottom member may be greater than the thickness of the second panel bottom member.

[0018] In an embodiment, the first panel bottom member and the second panel bottom member are not disposed in the fold region.

[0019] In an embodiment, the second panel bottom member may include a third adhesive disposed on the second surface of the second display panel in the second region of the second display panel, a second heat dissipation member disposed on the third adhesive, and a third buffer member disposed between the third adhesive and the second heat dissipation member.

[0020] In an embodiment, the foldable display device may further include: a second sound generator disposed between the second surface of the first display panel and the second surface of the second display panel in the first area of ​​the second display panel, wherein the second sound generator may output a second sound by vibrating at least one of the first display panel and the second display panel.

[0021] In an embodiment, the first sound generator may be attached to the second surface of the first display panel, and the second sound generator may be attached to the second surface of the second display panel.

[0022] In an embodiment, the first sound generator and the second sound generator may not overlap each other when viewed in a thickness direction of the first display panel from a plan view.

[0023] In an embodiment, the foldable display device may further include: a third sound generator disposed on the second surface of the second display panel in the second area of ​​the second display panel, wherein the third sound generator may output a third sound by vibrating the second display panel.

[0024] In an embodiment, the first sound generator may vibrate at least one of the first display panel and the second display panel by using a piezoelectric material that contracts or expands according to a voltage applied thereto.

[0025] In an embodiment, the second sound generator and the third sound generator may generate magnetic force by using voice coils therein, so that at least one of the first display panel and the second display panel vibrates or only the second display panel vibrates.

[0026] According to an embodiment of the present disclosure, a sound providing method for a foldable display device includes: when a folding area of ​​a second display panel of the foldable display device is folded, a first image is displayed using pixels of a first pixel array layer of a first display panel of the foldable display device, and a first sound is output by vibrating the first display panel with a first sound generator; and when the folding area of ​​the second display panel is unfolded, a second image is displayed using pixels of a second pixel array layer of the second display panel, and a second sound is output by vibrating the second display panel with the first sound generator.

[0027] According to an embodiment of the present disclosure, in both the folded state and the unfolded state of the foldable display device, a first sound can be output by vibrating at least one of the first display panel and the second display panel using a first sound generator disposed between the first display panel and the second display panel. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The above and other features of the present invention will become more apparent by describing in detail specific embodiments of the present invention with reference to the accompanying drawings, in which:

[0029] Figure 1 and Figure 2 are perspective views showing a foldable display device according to an embodiment of the present disclosure in its folded state and unfolded state, respectively;

[0030] Figure 3 and Figure 4 The folded state and the unfolded state are shown respectively. Figure 1 and Figure 2 A cross-sectional view of a foldable display device;

[0031] Figure 5 It is shown Figure 3 and Figure 4 A cross-sectional view of a display area of ​​a first display panel and a second display panel;

[0032] Figure 6 It is shown Figure 3 and Figure 4 An enlarged cross-sectional view of region A;

[0033] Figure 7 It is shown Figure 6 A cross-sectional view of an embodiment of a first sound generator;

[0034] Figure 8 Shows the settings in Figure 7 how a vibration layer between a first branch electrode and a second branch electrode of a first sound generator vibrates;

[0035] Fig. 9 and Fig.10 It is shown Figure 7 A cross-sectional view showing how a first sound generator causes a first display panel and a second display panel to vibrate;

[0036] Fig.11 It is shown Figure 6 A cross-sectional view of an alternative embodiment of a first sound generator;

[0037] Fig.12 and Fig.13 Shows Fig.11 how the first sound generator causes the first display panel and the second display panel to vibrate;

[0038] Fig.14 It is shown Figure 6 A cross-sectional view of another alternative embodiment of the first sound generator;

[0039] Fig.15 It is shown Figure 3 and Figure 4 An enlarged cross-sectional view of an alternative embodiment of region A;

[0040] Fig.16 and Fig.17 The folded state and the unfolded state are shown respectively. Figure 1 and Figure 2 A cross-sectional view of a foldable display device;

[0041] Fig.18 It is shown Figure 3 and Figure 4 An enlarged cross-sectional view of another alternative embodiment of region A;

[0042] Fig.19 and Fig. 20 The folded state and the unfolded state are shown respectively. Figure 1 and Figure 2 A cross-sectional view of a foldable display device;

[0043] Fig.21 It is shown Figure 1 and Figure 2 A block diagram of a foldable display device;

[0044] Fig. 22 is a flowchart illustrating a sound providing method of a foldable display device according to an embodiment of the present disclosure;

[0045] Fig.23 and Fig.24 are perspective views showing a foldable display device according to an alternative embodiment of the present disclosure in a folded state and an unfolded state, respectively;

[0046] Fig.25 and Fig.26 The folded state and the unfolded state are shown respectively. Fig.23 and Fig.24 A cross-sectional view of a foldable display device;

[0047] Fig. 27 and Fig.28 are perspective views showing a foldable display device according to another alternative embodiment of the present disclosure in a folded state and an unfolded state, respectively; and

[0048] Fig.29 and Fig.30 The folded state and the unfolded state are shown respectively. Fig. 27 and Fig.28 A cross-sectional view of a foldable display device. DETAILED DESCRIPTION

[0049] The present invention will now be described more fully below with reference to the accompanying drawings in which preferred embodiments of the present invention are shown. However, the present invention can be implemented in different forms and should not be construed as being limited to the embodiments set forth herein. On the contrary, these embodiments are provided so that the present disclosure is thorough and complete, and will fully convey the scope of the present invention to those skilled in the art. Throughout the specification, the same reference numerals indicate the same components. In the accompanying drawings, for clarity, the thickness of layers and regions is exaggerated.

[0050] It will be understood that although the terms "first", "second", "third", etc. may be used to describe various elements, components, regions, layers and / or parts in this article, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of this article, the "first element", "first component", "first region", "first layer" or "first part" discussed below can be referred to as a second element, second component, second region, second layer or second part.

[0051] It will also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.

[0052] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to be restrictive. As used herein, unless the content clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms, including "at least one". "Or" means "and / or". "At least one of A and B" means "A and / or B". As used herein, the term "and / or" includes any and all combinations of one or more related listed items. It will be further understood that when used in this specification, the term "includes" or "comprising" specifies the presence of the features, regions, wholes, steps, operations, elements and / or parts, but does not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, parts and / or groups thereof.

[0053] As used herein, "about" or "approximately" includes the stated value and an average value determined by one of ordinary skill in the art to be within an acceptable range of deviation for the particular value, taking into account the measurements involved and errors associated with measurement of a particular quantity (i.e., limitations of the measurement system).

[0054] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. It will be further understood that terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless explicitly defined herein.

[0055] In this document, embodiments are described with reference to cross-sectional views that are schematic diagrams of idealized embodiments. Therefore, variations in the shapes of the illustrations as a result of, for example, manufacturing techniques and / or tolerances, need to be anticipated. Therefore, the embodiments described herein should not be interpreted as limited to the specific shapes of the regions as shown herein, but rather to include deviations in shapes that are caused, for example, by manufacturing. For example, a region shown or described as flat may typically have rough and / or nonlinear features. In addition, sharp corners shown may be rounded. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the precise shape of the regions, nor are they intended to limit the scope of the claims.

[0056] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0057] Figure 1 and Figure 2 are perspective views respectively showing a foldable display device according to an embodiment of the present disclosure in a folded state and an unfolded state.

[0058] refer to Figure 1 and Figure 2 , an embodiment of the foldable display device 10 includes a first display panel 110 having a first display area DA1 and a second display panel 120 having a second display area DA2.

[0059] As used herein, the terms “above”, “top” and “top surface” refer to the direction in which the first display panel 110 is disposed relative to the second display panel 120, i.e., the Z-axis direction, and as used herein, the terms “below”, “bottom” and “bottom surface” refer to the direction in which the second display panel 120 is disposed relative to the first display panel 110, i.e., the direction opposite to the Z-axis direction. Moreover, as used herein, the terms “left”, “right”, “upper” and “lower” refer to their respective directions when viewed from above the first display panel 110. For example, the term “left” refers to the X-axis direction, the term “right” refers to the direction opposite to the X-axis direction, the term “upper” refers to the Y-axis direction, and the term “lower” refers to the direction opposite to the Y-axis direction.

[0060] In an embodiment, the first display panel 110 may have a rectangular shape in a plan view. In an embodiment, for example, in a plan view, the first display panel 110 may have a rectangular shape having a first side S1 extending in a first direction (or X-axis direction) and a second side S2 extending in a second direction (or Y-axis direction). The first side S1 may be shorter than the second side S2. The angle at which the first side S1 and the second side S2 intersect may be rounded with a predetermined curvature or may be a right angle. The planar shape of the first display panel 110 is not particularly limited, and for example, the first display panel 110 may be variously modified to have one of other shapes such as a polygon, a circle, or an ellipse.

[0061] The first display panel 110 may include a first display area DA1 in which a plurality of pixels are disposed to display an image and a first non-display area in which the plurality of pixels are not disposed and disposed at the periphery of the first display area DA1 .

[0062] In a plan view, the first display area DA1 of the first display panel 110 may have a rectangular shape having a first display side DS1 extending along a first direction (or an X-axis direction) and a second display side DS2 extending along a second direction (or a Y-axis direction). The first display side DS1 may be shorter than the second display side DS2. The angle at which the first display side DS1 and the second display side DS2 intersect may be rounded with a predetermined curvature or may be a right angle. The planar shape of the first display area DA1 is not particularly limited, and for example, the first display area DA1 may be variously modified to have one of other shapes such as a polygon, a circle, or an ellipse.

[0063] The second display panel 120 may include Figure 1 Fold as shown or Figure 2The folding area FA unfolded as shown. When unfolded, the second display panel 120 may have a rectangular shape in a plan view. In one embodiment, for example, in a plan view, the second display panel 120 may have a rectangular shape having a third side S3 extending in a first direction (or X-axis direction) and a fourth side S4 extending in a second direction (or Y-axis direction). The third side S3 may be shorter than the fourth side S4, in which case the user can watch a screen that is longer in the second direction (or Y-axis direction) than in the first direction (or X-axis direction). Alternatively, the third side S3 may be longer than the fourth side S4, in which case the user can watch a screen that is longer in the first direction (or X-axis direction) than in the second direction (or Y-axis direction). Still alternatively, the third side S3 may have substantially the same length as the fourth side S4, in which case the user can watch a square screen. The angle at which the third side S3 and the fourth side S4 intersect may be rounded with a predetermined curvature or may be a right angle. The planar shape of the second display panel 120 is not particularly limited, and for example, the second display panel 120 may be variously modified to have one of other shapes such as a polygonal shape, a circular shape, or an elliptical shape.

[0064] When unfolded, the second display area DA2 of the second display panel 120 may have a rectangular shape in a plan view, the rectangular shape having a third display side DS3 extending in a first direction (or X-axis direction) and a fourth display side DS4 extending in a second direction (or Y-axis direction). The third display side DS3 may be shorter than the fourth display side DS4. Alternatively, the third display side DS3 may be longer than the fourth display side DS4. Still alternatively, the third display side DS3 may have substantially the same length as the fourth display side DS4. The angle at which the third display side DS3 and the fourth display side DS4 intersect may be rounded with a predetermined curvature or may be a right angle. The planar shape of the second display area DA2 is not particularly limited, for example, the second display area DA2 may be variously modified to have one of other shapes such as a polygon, a circle or an ellipse.

[0065] The second display panel 120 may include a first area A1, a second area A2, and a folding area FA between the first area A1 and the second area A2. Figure 3 ) is a bendable, foldable or rollable flexible substrate, and thus can be easily folded in the folding area FA. In an embodiment, a hinge may be provided in the folding area FA on the second surface of the second substrate 121 to allow the second display panel 120 to be effectively folded in the folding area FA.

[0066] The second display panel 120 may be folded inwardly so that a portion of the second display area DA2 in the first area A1 and a portion of the second display area DA2 in the second area A2 face each other in a folded state. When the second display panel 120 is folded, the second display area DA2 may be bent in the folding area FA to have a predetermined curvature. When the second display panel 120 is unfolded, the second display area DA2 of the second display panel 120 may face the opposite direction of the third direction (or the opposite direction of the Z-axis direction), and the first display area DA1 of the first display panel 110 may face the third direction (or the Z-axis direction).

[0067] According to the embodiment, Figure 1 and Figure 2 As shown, when the second display panel 120 is folded, the first image may be displayed in the third direction (or the Z-axis direction) using the first display panel 110. In such an embodiment, when the second display panel 120 is unfolded, the second image may be displayed in the opposite direction of the third direction (or the opposite direction of the Z-axis direction) through the second display panel 120. In such an embodiment, the first display panel 110 may display the first image in the third direction (or the Z-axis direction), or may not display any image.

[0068] Figure 3 and Figure 4 The folded state and the unfolded state are shown respectively. Figure 1 and Figure 2 A cross-sectional view of a foldable display device. Specifically, Figure 3 It is along Figure 1 A cross-sectional view taken along line II' of Figure 4 It is along Figure 2 A cross-sectional view taken along line II-II'. Figure 5 It is shown Figure 3 and Figure 4 A cross-sectional view of a display area of ​​a first display panel and a display area of ​​a second display panel. Figure 6 It is shown Figure 3 and Figure 4 An enlarged cross-sectional view of region A.

[0069] refer to Figures 3 to 6 , the foldable display device 10 may include a first display panel 110 , a second display panel 120 , a first panel bottom member 400 , a second panel bottom member 800 , and a first sound generator 510 .

[0070] The first display panel 110 may include a first substrate 111 and a first pixel array layer 112. The first display panel 110 may be an OLED display panel using an organic light emitting diode ("OLED"), an mLED display panel using a micro light emitting diode ("mLED"), or a QLED display panel using a quantum dot light emitting diode ("QLED"). Hereinafter, for ease of description, the first display panel 110 will be described in detail. Figure 5 An embodiment of an OLED display panel is shown.

[0071] The first substrate 111 may be a rigid substrate or a bendable, foldable or rollable flexible substrate. In an embodiment, the first substrate 111 may include an insulating material such as glass, quartz, a polymer resin, etc. In such an embodiment, for example, the polymer material includes plastics such as polyethersulfone (PES), polyacrylate (PA), polyarylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyallyl ester, polyimide (PI), polycarbonate (PC), cellulose triacetate (CAT), cellulose acetate propionate (CAP) or a combination thereof. Alternatively, the first substrate 111 may include a metal material.

[0072] The first pixel array layer 112 is disposed on the first surface of the first substrate 111. Figure 5 As shown, the first pixel array layer 112 may include a thin film transistor (“TFT”) layer 1230 , a light emitting element layer 1240 , and an encapsulation layer 1300 .

[0073] The TFT layer 1230 is disposed on the first substrate 111. The TFT layer 1230 includes a TFT 1235, a gate insulating film 1236, an interlayer insulating film 1237, a passivation film 1238, and a planarization film 1239.

[0074] A buffer film may be provided on the first substrate 111. The buffer film may be provided on the first substrate 111 to protect the TFT 1235 and the light emitting element from moisture that may enter the first substrate 111 susceptible to moisture. The buffer film may include a plurality of inorganic films alternately stacked on each other. In one embodiment, for example, the buffer film may include a plurality of inorganic films alternately stacked on each other. x ) film, silicon nitride (SiN x ) film and / or a multilayer film of a silicon oxynitride (SiON) film. Alternatively, the buffer film may be omitted.

[0075] TFT 1235 is disposed on the buffer film. Each TFT 1235 includes an active layer 1231, a gate electrode 1232, a source electrode 1233, and a drain electrode 1234. In an embodiment, as shown in FIG. Figure 5 As shown, the TFT 1235 may have a top gate structure in which the gate electrode 1232 is disposed above the active layer 1231, but the present disclosure is not limited thereto. Alternatively, the TFT 1235 may have a bottom gate structure in which the gate electrode 1232 is disposed below the active layer 1231 or a double gate structure in which the gate electrode 1232 is disposed above and below the active layer 1231.

[0076] The active layer 1231 is disposed on the buffer film. The active layer 1231 may include or be formed of a silicon-based semiconductor material or an oxide-based semiconductor material. A light shielding layer for blocking external light incident on the active layer 1231 may be disposed between the buffer film and the active layer 1231.

[0077] The gate insulating film 1236 may be provided on the active layer 1231. The gate insulating film 1236 may be an inorganic film such as a silicon oxide film, a silicon nitride film, or a multilayer film thereof.

[0078] The gate electrode 1232 and the gate line may be disposed on the gate insulating film 1236. Each of the gate electrode 1232 and the gate line may be a single-layer film or a multi-layer film including molybdenum (Mo), aluminum, chromium (Cr), gold (Au), titanium (Ti), nickel, neodymium (Nd), copper, or an alloy thereof.

[0079] An interlayer insulating film 1237 may be provided on the gate electrode 1232 and the gate line. The interlayer insulating film 1237 may be an inorganic film such as a silicon oxide film, a silicon nitride film, or a multilayer film thereof.

[0080] The source electrode 1233, the drain electrode 1234, and the data line may be disposed on the interlayer insulating film 1237. The source electrode 1233 and the drain electrode 1234 may be connected to the active layer 1231 through a contact hole passing through the gate insulating film 1236 and the interlayer insulating film 1237. Each of the source electrode 1233, the drain electrode 1234, and the data line may be a single-layer film or a multi-layer film including Mo, Al, Cr, Au, Ti, Ni, Nd, Cu, or an alloy thereof.

[0081] A passivation film 1238 may be provided on the source electrode 1233, the drain electrode 1234, and the data line to insulate the TFT 1235. The passivation film 1238 may be an inorganic film such as a silicon oxide film, a silicon nitride film, or a multilayer film thereof.

[0082] The planarization film 1239 may be disposed on the passivation film 1238 to planarize a height difference formed by the TFT 1235. The planarization film 1239 may be an organic film using acrylic resin, epoxy resin, phenol resin, polyamide resin, or polyimide resin.

[0083] The light emitting element layer 1240 is disposed on the TFT layer 1230. The light emitting element layer 1240 includes a light emitting element and a pixel defining film 1244.

[0084] The light emitting element and the pixel defining film 1244 are disposed on the planarization film 1239. In an embodiment, the light emitting element may be an OLED. In such an embodiment, each light emitting element may include an anode electrode 1241, a light emitting layer 1242, and a cathode electrode 1243.

[0085] The anode electrode 1241 may be disposed on the planarization film 1239. The anode electrode 1241 may be connected to the drain electrode 1234 through a contact hole passing through the passivation film 1238 and the planarization film 1239.

[0086] The pixel defining film 1244 may be provided to cover the edge of the anode electrode 1241 to define the corresponding pixel. In an embodiment, the pixel defining film 1244 may define a plurality of pixels. Each of the plurality of pixels may be a region in which the anode electrode 1241, the light emitting layer 1242, and the cathode electrode 1243 are sequentially stacked on each other, and holes from the anode electrode 1241 and electrons from the cathode electrode 1243 are recombined in the light emitting layer 1242 to emit light.

[0087] The light emitting layer 1242 is disposed on the anode electrode 1241 and on the pixel defining film 1244. The light emitting layer 1242 may be an organic emission layer. The light emitting layer 1242 may emit one of red light, green light, and blue light. Alternatively, the light emitting layer 1242 may be a white light emitting layer that emits white light. In such an embodiment, the light emitting layer 1242 may have a structure in which a red light emitting layer, a green light emitting layer, and a blue light emitting layer are stacked on each other and may be a common layer formed for all multiple pixels, and the first display panel 110 and the second display panel 120 may further include additional color filters for displaying red, green, and blue.

[0088] The light emitting layer 1242 may include a hole transport layer, an emission layer, and an electron transport layer. The light emitting layer 1242 may have a tandem structure having two or more stacked layers, wherein a charge generation layer may be provided between the stacked layers.

[0089] The cathode electrode 1243 may be disposed on the light emitting layer 1242. The cathode electrode 1243 may be disposed to cover the light emitting layer 1242. The cathode electrode 1243 may be a common layer commonly formed for all the plurality of pixels.

[0090] In an embodiment where the light emitting element layer 1240 is a top emission type light emitting element layer that emits light in an upward direction, the anode electrode 1241 may include or be formed of a metal material having high reflectivity, such as a stack of Al and Ti (e.g., Ti / Al / Ti), a stack of aluminum and indium tin oxide (“ITO”) (e.g., ITO / Al / ITO), a silver (Ag)-palladium (Pd)-copper (Cu) (“APC”) alloy, or a stack of an APC alloy and ITO (e.g., ITO / APC / ITO), and the cathode electrode 1243 may include or be formed of a transparent conductive oxide (“TCO”) material, such as ITO or indium zinc oxide (“IZO”), through which light can be transmitted, or a semi-transparent metal material, such as magnesium (Mg), Ag, or an alloy thereof. In an embodiment where the cathode electrode 1243 includes or is formed of a semi-transparent metal material, the emission efficiency of the light emitting element layer 1240 may be improved due to the microcavity effect.

[0091] In an embodiment where the light emitting element layer 1240 is a bottom emission type light emitting element layer that emits light in a downward direction, the anode electrode 1241 may include or be formed of a TCO material such as ITO or IZO or a semi-transparent metal material such as Mg, Ag or an alloy thereof, and the cathode electrode 1243 may include or be formed of a metal material having a high reflectivity such as a stack of Al and Ti (e.g., Ti / Al / Ti), a stack of Al and ITO (e.g., ITO / Al / ITO), an APC alloy, or a stack of an APC alloy and ITO (e.g., ITO / APC / ITO). In an embodiment where the anode electrode 1241 includes or is formed of a semi-transparent metal material, the emission efficiency of the light emitting element layer 1240 may be improved due to the microcavity effect.

[0092] The encapsulation layer 1300 is disposed on the light emitting element layer 1240. In an embodiment, the encapsulation layer 1300 prevents oxygen or moisture from penetrating into the light emitting layer 1242 and the cathode electrode 1243. In such an embodiment, the encapsulation layer 1300 may include at least one inorganic film. The inorganic film may include or be formed of silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, or titanium oxide. The encapsulation layer 1300 may further include at least one organic film. The organic film may have a sufficient thickness to prevent foreign particles from entering the light emitting layer 1242 and the cathode electrode 1243 through the encapsulation layer 1300. The organic film may include at least one of epoxy, acrylate, and urethane acrylate.

[0093] In an alternative embodiment, the second substrate 121 may be provided instead of the encapsulation layer 1300. In such an embodiment, a filling member or a filling film may be provided on the second substrate 121 and on the light emitting element layer 1240.

[0094] The touch sensor layer may be provided on the encapsulation layer 1300. Since the touch sensor layer may be directly provided on the encapsulation layer 1300, the thickness of the foldable display device 10 may be reduced compared to a case where a touch panel including the touch sensor layer is attached to the encapsulation layer 1300.

[0095] The touch sensor layer may include a touch electrode for capacitively sensing a touch input from a user and a touch line connecting the pad and the touch electrode. In one embodiment, for example, the touch sensor layer may detect a touch input from a user in a self-capacitance manner or a mutual-capacitance manner.

[0096] The touch electrodes of the touch sensor layer may be disposed to overlap the first display area DA1. The touch lines of the touch sensor layer may be disposed in the first non-display area.

[0097] The second display panel 120 may include a second substrate 121 and a second pixel array layer 122. The second display panel 120 may be an OLED display panel using OLED, an mLED display panel using mLED, or a QLED display panel using QLED. Hereinafter, for ease of description, the second display panel 120 will be described in detail. Figure 5 An embodiment of an OLED display panel is shown.

[0098] The second substrate 121 may be a rigid substrate or a bendable, foldable or rollable flexible substrate. In an embodiment, the second substrate 121 may include an insulating material such as glass, quartz, polymer resin, etc. In such an embodiment, the polymer resin includes plastics such as PES, PA, PAR, PEI, PEN, PET, PPS, polyallyl ester, PI, PC, CAT, CAP or a combination thereof. The second substrate 121 may include a metal material.

[0099] The second pixel array layer 122 is disposed on the first surface of the second substrate 121. Figure 5 The first pixel array layer 112 is substantially the same as those shown in FIG. 1 , and thus any repeated detailed description thereof will be omitted.

[0100] The first panel bottom member 400 may be disposed in the first area A1 of the second display panel 120. The first panel bottom member 400 may not be disposed in the folding area FA of the second display panel 120 to reduce folding stress.

[0101] The first panel bottom member 400 may be disposed between the second surface of the first substrate 111 and the second surface of the second substrate 121. The second surface of the first substrate 111 may be an opposite surface of the first surface of the first substrate 111 in the third direction (or Z-axis direction), and the second surface of the second substrate 121 may be an opposite surface of the first surface of the second substrate 121 in the third direction (or Z-axis direction).

[0102] The first surface of the first panel bottom member 400 may be attached to the second surface of the first substrate 111, and the second surface of the first panel bottom member 400 may be attached to the second surface of the second substrate 121. The second surface of the first panel bottom member 400 may correspond to an opposite surface of the first surface of the first panel bottom member 400 in the third direction (or Z-axis direction).

[0103] The first panel bottom member 400 may include a first adhesive 410 , a second adhesive 420 , a first buffer member 430 , a second buffer member 440 , and a first heat dissipation member 450 .

[0104] The first adhesive 410 may be attached to the second surface of the first substrate 111. Alternatively, in the case where the first light shielding member 460 is disposed on the second surface of the first substrate 111, as shown in FIG. Figure 6 As shown, the first adhesive 410 may be attached to the first light shielding member 460. In an embodiment where the first surface of the first adhesive 410 facing the second surface of the first substrate 111 is embossed, as shown in FIG. Figure 6 As shown, the first adhesive 410 may have a buffering effect.

[0105] The second adhesive 420 may be attached to the second surface of the second substrate 121. In an alternative embodiment where the second light blocking member 470 is disposed on the second surface of the second substrate 121, as shown in FIG. Figure 6 As shown, the second adhesive 420 may be attached to the second light shielding member 470. In an embodiment where the first surface of the second adhesive 420 facing the second surface of the second substrate 121 is embossed, as shown in FIG. Figure 6 As shown, the second adhesive 420 may have a buffering effect.

[0106] The first buffer member 430 may be disposed on the second surface of the first adhesive 410. The first buffer member 430 may absorb external impacts, and thus damage to the first display panel 110 may be prevented. The second buffer member 440 may be disposed on the second surface of the second adhesive 420. The second buffer member 440 may absorb external impacts, and thus damage to the second display panel 120 may be prevented. Each of the first buffer member 430 and the second buffer member 440 may be a single-layer film or a multi-layer film. In one embodiment, for example, the first buffer member 430 and the second buffer member 440 may be formed of a polymer resin such as polyurethane ("PU"), PC, polypropylene ("PP"), or polyethylene ("PE"), or may include an elastic material such as a foam sponge including or formed of rubber, a polyurethane-based material, or an acrylic material. The first buffer member 430 and the second buffer member 440 may be a cushion layer.

[0107] The first heat dissipation member 450 may be disposed between the first buffer member 430 and the second buffer member 440. The first heat dissipation member 450 may include a first heat dissipation layer including graphite or carbon nanotubes and a second heat dissipation layer including or formed as a thin metal film including a metal having high thermal conductivity, such as Cu, Ni, ferrite, or Ag.

[0108] The first light shielding member 460 and the second light shielding member 470 block transmission of light and prevent the display circuit board, the first sound generator 510, the fingerprint recognition sensor, etc. from becoming visible in the first display area DA1 of the first display panel 110 or in the second display area DA2 of the second display panel 120. The first light shielding member 460 and the second light shielding member 470 may include a light absorbing material such as a black pigment or dye.

[0109] The first sound generator 510 may be disposed between the second surface of the first substrate 111 and the second surface of the second substrate 121. The first sound generator 510 may be disposed in the first area A1 of the second display panel 120. The first panel bottom member 400 and the first sound generator 510 may not overlap each other in the thickness direction of the first display panel 110 (or in the Z-axis direction).

[0110] In an embodiment, the first sound generator 510 may be attached to the second surface of the first substrate 111 and the second surface of the second substrate 121. In an alternative embodiment, the first light shielding member 460 and the second light shielding member 470 are respectively disposed on the second surface of the first substrate 111 and the second surface of the second substrate 121. Figure 6As shown, the first sound generator 510 may be attached to the first light shielding member 460 and the second light shielding member 470. The length of the first sound generator 510 in the second direction (or Y-axis direction) may be substantially the same as the length of the first panel bottom member 400 in the second direction (or Y-axis direction).

[0111] like Figures 7 to 10 As shown, the first sound generator 510 may be a piezoelectric element or actuator including a piezoelectric material that contracts or expands according to a driving voltage applied thereto. Figures 11 to 13 As shown, the first sound generator 510 may be an actuator that generates magnetic force in a voice coil therein according to a driving voltage applied thereto. Still alternatively, the first sound generator 510 may be a vibration motor that generates magnetic force in a voice coil therein according to a driving voltage applied thereto, such as Fig.14 As shown, the vibration motor can be, for example, a linear resonant actuator ("LRA").

[0112] The first sound generator 510 may be attached to at least one of the first display panel 110 and the second display panel 120 to vibrate the at least one of the first display panel 110 and the second display panel 120 according to a driving voltage applied thereto. Therefore, the first sound generator 510 may output the first sound using at least one of the first display panel 110 and the second display panel 120 as a vibration membrane. Therefore, the foldable display device 10 may output the first sound in both the folded state and the unfolded state by vibrating at least one of the first display panel 110 and the second display panel 120 with the first sound generator 510.

[0113] A gap may be formed between the first panel bottom member 400 and the first sound generator 510. When the first sound generator 510 outputs a first sound by vibrating at least one of the first display panel 110 and the second display panel 120, the gap formed between the first panel bottom member 400 and the first sound generator 510 may function as a sound box.

[0114] In an embodiment, the first sound generator 510 may be disposed at the center of the first display panel 110 and the center of the first area A1 of the second display panel 120 , but the present disclosure is not limited thereto.

[0115] The second panel bottom member 800 may be disposed in the second area A2 of the second display panel 120. The second panel bottom member 800 may not be disposed in the folding area FA of the second display panel 120 to reduce folding stress.

[0116] The second panel bottom member 800 may be disposed on the second surface of the second substrate 121. The first surface of the second panel bottom member 800 may be attached to the second surface of the second substrate 121. The second panel bottom member 800 may include a third adhesive, a third buffer member, and a second heat dissipation member.

[0117] In addition to omitting the first adhesive 410 and the first buffer member 430, the third adhesive, the third buffer member, and the second heat dissipation member of the second panel bottom member 800 may be formed with Figure 6 The first panel bottom member 400 is substantially the same. In such an embodiment, unlike the first panel bottom member 400, the second panel bottom member 800 does not include the first adhesive 410 and the first buffer member 430, and the second panel bottom member 800 may be thinner than the first panel bottom member 400.

[0118] The third adhesive of the second panel bottom member 800, the third buffer member and the second heat dissipation member are respectively Figure 6 The second adhesive 420 , the second buffer member 440 , and the first heat dissipation member 450 of the first panel bottom member 400 are substantially the same, and thus any repeated detailed description thereof will be omitted.

[0119] According to the embodiment, Figures 3 to 6 As shown, the first sound can be output by vibrating the first display panel 110 and the second display panel 120 with the first sound generator 510 disposed between the first display panel 110 and the second display panel 120. Therefore, the foldable display device 10 can output the first sound in both the folded state and the unfolded state by vibrating at least one of the first display panel 110 and the second display panel 120 with the first sound generator 510.

[0120] Figure 7 It is shown Figure 6 A cross-sectional view of an embodiment of a first sound generator. Figure 7 It is shown Figure 6 An enlarged cross-sectional view of region B. Figure 8 Shows the settings in Figure 7 How the vibration layer between the first branch electrode and the second branch electrode of the first sound generator vibrates. Fig. 9 and Fig.10 It is shown Figure 7 A cross-sectional view of how a first sound generator causes a first display panel and a second display panel to vibrate.

[0121] refer to Figures 7 to 10The first sound generator 510 may be a piezoelectric element or an actuator that can vibrate the first display panel 110 and the second display panel 120 by including a piezoelectric material that contracts or expands according to a driving voltage applied thereto. The first sound generator 510 may include a vibration layer 511, a first electrode 512, and a second electrode 513.

[0122] In an embodiment, the first electrode 512 may include a first stem electrode 5121 and a first branch electrode 5122. Figure 7 As shown, the first dry electrode 5121 may be disposed on one side of the vibration layer 511, or may be disposed on more than one side of the vibration layer 511. The first dry electrode 5121 may be disposed on the top surface of the vibration layer 511. The first branch electrodes 5122 may branch from the first dry electrode 5121. The first branch electrodes 5122 may be disposed in parallel with each other.

[0123] In an embodiment, the second electrode 513 may include a second stem electrode 5131 and a second branch electrode 5132. Figure 7 As shown, the second dry electrode 5131 may be disposed on the other side of the vibration layer 511, or may be disposed on more than one side of the vibration layer 511. Figure 7 , the first dry electrode 5121 may be disposed on a side of the vibration layer 511 where the second dry electrode 5131 is not disposed. The second dry electrode 5131 may be disposed on a top surface of the vibration layer 511. The first dry electrode 5121 and the second dry electrode 5131 may not overlap each other. The second branch electrodes 5132 may branch from the second dry electrode 5131. The second branch electrodes 5132 may be disposed in parallel with each other.

[0124] In an embodiment, the first branch electrode 5122 and the second branch electrode 5132 may be arranged parallel to each other in the horizontal direction (or the X-axis or Y-axis direction). The first branch electrode 5122 and the second branch electrode 5132 may be alternately arranged in the vertical direction (or the Z-axis direction). In such an embodiment, the first branch electrode 5122 and the second branch electrode 5132 may be repeatedly arranged in the order of the first branch electrode 5122, the second branch electrode 5132, the first branch electrode 5122 and the second branch electrode 5132 along the vertical direction (or the Z-axis direction).

[0125] The vibration layer 511 may be a piezoelectric actuator that is deformed by a first driving voltage and a second driving voltage respectively applied to the first electrode 512 and the second electrode 513. In an embodiment, the vibration layer 511 may include at least one of a piezoelectric material (e.g., a polyvinylidene fluoride ("PVDF") film or lead zirconate titanate (PZT)) and an electroactive polymer.

[0126] The vibration layer 511 may be disposed between the first branch electrodes 5122 and between the second branch electrodes 5132. In an embodiment, in the case where the vibration layer 511 is manufactured at a high temperature, the first electrode 512 and the second electrode 513 may be formed of a metal having a high melting point, such as Ag or an alloy of Ag and Pd. In such an embodiment in which the first electrode 512 and the second electrode 513 are formed of an alloy of Ag and Pd, the Ag content of the alloy of Ag and Pd may be greater than the Pd content of the alloy of Ag and Pd to increase the melting points of the first electrode 512 and the second electrode 513.

[0127] The first electrode 512 and the second electrode 513 may be connected to the sound circuit board and may receive a driving voltage from the sound circuit board. The vibration layer 511 contracts or expands based on a difference between a first driving voltage applied to the first branch electrode 5122 of the first electrode 512 and a second driving voltage applied to the second branch electrode 5132 of the second electrode 513.

[0128] In an embodiment, Figure 7 As shown in FIG. 1 , when the polarity of the vibration layer 511 between the first branch electrode 5122 and the second branch electrode 5132 below them has an upward direction (↑), the vibration layer 511 may have a positive polarity in its upper portion adjacent to the first branch electrode 5122 and a negative polarity in its lower portion adjacent to the second branch electrode 5132. In such an embodiment, Figure 8 As shown, when the polarity of the vibration layer 511 between the second branch electrodes 5132 and the first branch electrodes 5122 respectively therebelow has a downward direction (↓), the vibration layer 511 may have a negative polarity in its upper portion adjacent to the first branch electrodes 5122, and a positive polarity in its lower portion adjacent to the second branch electrodes 5132. The direction of the polarity of the vibration layer 511 may be determined by a polarization process for applying an electric field to the vibration layer 511 using the first branch electrodes 5122 and the second branch electrodes 5132.

[0129] In the case where the polarity direction of the vibration layer 511 between the first branch electrode 5122 and the second branch electrode 5132 thereunder may be in the upward direction (↑), such as Figure 8 As shown, the vibration layer 511 may contract according to a first force F1 in response to a positive first driving voltage and a negative second driving voltage respectively applied to the first branch electrode 5122 and the second branch electrode 5132. The first force F1 may be a contraction force. In response to a negative first driving voltage and a positive second driving voltage respectively applied to the first branch electrode 5122 and the second branch electrode 5132, the vibration layer 511 may expand according to a second force F2. The second force F2 may be an extension force.

[0130] In the case where the direction of the polarity of the vibration layer 511 between the second branch electrodes 5132 and the first branch electrodes 5122 respectively below them may be in the downward direction (↓), the vibration layer 511 may expand according to the extension force in response to the positive first driving voltage and the negative second driving voltage respectively applied to the second branch electrodes 5132 and the first branch electrodes 5122. In response to the negative first driving voltage and the positive second driving voltage respectively applied to the second branch electrodes 5132 and the first branch electrodes 5122, the vibration layer 511 may contract according to the contraction force. The second force F2 may be a contraction force.

[0131] like Figure 8 As shown, when the first driving voltage and the second driving voltage respectively applied to the first electrode 512 and the second electrode 513 are repeatedly changed from positive polarity to negative polarity alternately, the vibration layer 511 is repeatedly contracted and expanded. As a result, the first sound generator 510 vibrates.

[0132] In an embodiment where the first sound generator 510 is attached to the second surface of the first substrate 111 and the second surface of the second substrate 121, as shown in FIG. Fig. 9 and Fig.10 As shown, the first display panel 110 and the second display panel 120 may vibrate vertically due to stress in response to the contraction and expansion of the vibration layer 511 of the first sound generator 510. When the first sound generator 510 causes the first display panel 110 and the second display panel 120 to vibrate, the foldable display device 10 may output a first sound.

[0133] Fig.11 It is shown Figure 6 A cross-sectional view of an alternative embodiment of a first sound generator. Fig.12 and Fig.13 Shows Fig.11 How the first sound generator makes the first display panel and the second display panel vibrate. Figures 11 to 13 It is shown Figure 6 Another enlarged cross-sectional view of area B.

[0134] refer to Figures 11 to 13 An embodiment of the first sound generator 510 may be an actuator that generates magnetic force using a voice coil therein, thereby vibrating according to a driving voltage applied thereto.

[0135] The first sound generator 510 may include a magnet 521 , a bobbin 522 , a voice coil 523 , a damper 524 , and a lower plate 525 .

[0136] The magnet 521 may be a permanent magnet, for example, a sintered magnet such as a barium ferrite magnet. In an embodiment, the magnet 521 may be iron oxide (Fe 2 O 3) magnet, barium carbonate (BaCO 3 ) magnet, a neodymium magnet, a strontium ferrite magnet with improved magnetic components, or an aluminum, nickel (Ni) or cobalt (Co) cast alloy magnet, but the present disclosure is not limited thereto. In such an embodiment, the neodymium magnet may be, for example, a neodymium iron boron (Nd-Fe-B) magnet.

[0137] The magnet 521 may be attached and fixed to the lower plate 525 by an adhesive. The magnet 521 may include a plate 521a, a central protrusion 521b protruding from the center of the plate 521a, and a sidewall portion 521c protruding from the edge of the plate 521a. The central protrusion 521b and the sidewall portion 521c may be spaced apart from each other at a predetermined distance so that a predetermined space may be defined or formed between the central protrusion 521b and the sidewall portion 521c. In an embodiment, the magnet 521 may have a cylindrical shape. In such an embodiment, the magnet 521 may be in the shape of a cylinder having a circular space formed at one of its bottom surfaces.

[0138] The central protrusion 521b of the magnet 521 may have N-pole magnetism, and the plate 521a and the sidewall portion 521c may have S-pole magnetism. As a result, an external magnetic field may be generated between the central protrusion 521b of the magnet 521 and the plate 521a and between the central protrusion 521b of the magnet 521 and the sidewall portion 521c.

[0139] The bobbin 522 may be cylindrical. In an embodiment, the central protrusion 521b of the magnet 521 may be disposed in the bobbin 522. In such an embodiment, the bobbin 522 may be disposed around the central protrusion 521b of the magnet 521. In an embodiment, the side wall portion 521c of the magnet 521 may be disposed outside the bobbin 522. In such an embodiment, the side wall portion 521c of the magnet 521 may be disposed around the bobbin 522. A space may be formed between the bobbin 522 and the central protrusion 521b of the magnet 521 and between the bobbin 522 and the side wall portion 521c of the magnet 521.

[0140] The bobbin 522 may include or be formed of pulp or paper-processed material, Al, Mg, alloys thereof, or synthetic resins such as polypropylene or polyamide-based fibers. One end of the bobbin 522 may be attached to the second surface of the first substrate 111 via an adhesive. Figure 6 In an alternative embodiment shown where the first light blocking member 460 is disposed on the second surface of the first substrate 111, one end of the bobbin 522 may be attached and fixed to the first light blocking member 460 by an adhesive. In such an embodiment, the adhesive may be a double-sided tape.

[0141] The voice coil 523 may be wound around the outer circumferential surface of the bobbin 522. One end of the voice coil 523 adjacent to one end of the bobbin 522 may receive a first driving voltage, and the other end of the voice coil 523 adjacent to the other end of the bobbin 522 may receive a second driving voltage. As a result, a current may flow in the voice coil 523 according to the first driving voltage and the second driving voltage. A magnetic field may be generated around the voice coil 523 based on the current flowing in the voice coil 523. In such an embodiment, the direction of the current flowing in the voice coil 523 when the first driving voltage is a positive voltage and the second driving voltage is a negative voltage may be opposite to the direction of the current flowing in the voice coil 523 when the first driving voltage is a negative voltage and the second driving voltage is a positive voltage. As the first driving voltage and the second driving voltage are alternately driven, the N pole and the S pole of the applied magnetic field may change, so that the attractive force and the repulsive force may alternately act on the magnet 521 and the voice coil 523. Therefore, the bobbin 522 around which the voice coil 523 is wound may reciprocate in the third direction (or the Z-axis direction).

[0142] The damper 524 is disposed between the bobbin 522 and the lower plate 525. In an embodiment, the damper 524 may contract or expand according to the vertical movement of the bobbin 522, and thus the vertical vibration of the bobbin 522 may be controlled. In such an embodiment, since the damper 524 is connected to the bobbin 522 and the lower plate 525, the vertical movement of the bobbin 522 may be limited by the restoring force of the damper 524. In such an embodiment, when the bobbin 522 vibrates above or below a predetermined height, the bobbin 522 may return to its original position due to the restoring force of the damper 524.

[0143] The lower plate 525 may be disposed on the bottom surface of the magnet 521. The lower plate 525 may be integrally formed with the magnet 521 as a single entity, or may be an element separate from the magnet 521. In an embodiment where the lower plate 525 is an element separate from the magnet 521, the magnet 521 may be attached to the lower plate 525 via an adhesive such as a double-sided tape.

[0144] The lower plate 525 may be fixed to the second surface of the second substrate 121 via a fixing member 516 such as a screw. Figure 6 In the case where the second light blocking member 470 is shown disposed on the second surface of the second substrate 121 , the lower plate 525 may be fixed to the second light blocking member 470 via a fixing member 516 such as a screw.

[0145] According to the embodiment, Figures 11 to 13 As shown, the magnet 521 is not only fixed to the lower plate 525, but also fixed to the second substrate 121, and the bobbin 522 is fixed to the first substrate 111, so that the magnet 521 can be Fig.12 and Fig.13As shown, the first display panel 110 and the second display panel 120 reciprocate in the third direction (or Z-axis direction). In such an embodiment, the first display panel 110 and the second display panel 120 may be vibrated by the first sound generator 510, so that the foldable display device 10 may output the first sound.

[0146] Fig.14 It is shown Figure 6 A cross-sectional view of another alternative embodiment of the first sound generator. Specifically, Fig.14 An embodiment is shown where the first sound generator 510 is an LRA.

[0147] refer to Fig.14 , an embodiment of the first sound generator 510 may include a lower housing 611, a flexible printed circuit board ("FPCB") 612, a voice coil 613, a magnet 614, a spring 615, and an upper housing 616. The lower housing 611 and the upper housing 616 may include or be formed of a metal material. The FPCB 612 may be disposed on a surface of the lower housing 611 facing the upper housing 616, and may be connected to the first sound line WL1 and the second sound line WL2. The voice coil 613 may be connected to a surface of the FPCB 612 facing the upper housing 616. Therefore, one end of the voice coil 613 may be electrically connected to the first sound line WL1, and the other end of the voice coil 613 may be electrically connected to the second sound line WL2. The magnet 614 may be a permanent magnet, and a voice coil groove 614a in which the voice coil 613 is accommodated may be defined or formed on a surface of the magnet 614 facing the voice coil 613. A spring 615 may be provided between the magnet 614 and the upper housing 616 .

[0148] The direction of the current flowing in the voice coil 613 of the first sound generator 510 may be controlled according to the first driving voltage and the second driving voltage applied to the first sound line WL1 and the second sound line WL2. A magnetic field may be generated around the voice coil 613 based on the current flowing in the voice coil 613. In such an embodiment, the direction of the current flowing in the voice coil 613 when the first driving voltage is a positive voltage and the second driving voltage is a negative voltage may be opposite to the direction of the current flowing in the voice coil 613 when the first driving voltage is a negative voltage and the second driving voltage is a positive voltage. When the first driving voltage and the second driving voltage are alternately driven, attractive and repulsive forces may act on the magnet 614 and the voice coil 613, so that the magnet 614 may reciprocate between the voice coil 613 and the upper housing 616 due to the spring 615. Therefore, the first display panel 110 disposed on the upper housing 616 may vibrate, and as a result, the first sound may be output.

[0149] like Fig.14As shown, in such an embodiment where the first sound generator 510 is an LRA, the first sound generator 510 may be attached only to the second surface of the first substrate 111, and a gap may be provided between the first sound generator 510 and the second surface of the second substrate 121. In such an embodiment, the first sound generator 510 may output the first sound by vibrating the first display panel 110 without vibrating the second display panel 120.

[0150] Fig.15 It is shown Figure 3 and Figure 4 FIG. 2 is an enlarged cross-sectional view of an alternative embodiment of region A of FIG.

[0151] In addition to providing the first reinforcement member 710 between the first sound generator 510 and the second surface of the first substrate 111 and providing the second reinforcement member 720 between the first sound generator 510 and the second surface of the second substrate 121, Fig.15 Examples and Figure 6 The embodiments are basically the same. Fig.15 The same or similar elements shown in FIG. 1 have been replaced with those used in the description above. Figure 6 The embodiments are marked with the same figure numbers, and any repeated detailed description thereof will be omitted or simplified hereinafter.

[0152] refer to Fig.15 , the first reinforcement member 710 may be disposed between the first sound generator 510 and the second surface of the first substrate 111. The first reinforcement member 710 may be disposed on a first side of the first surface of the first sound generator 510. In one embodiment, for example, the first reinforcement member 710 may be disposed on the left side of the top surface of the first sound generator 510.

[0153] The length of the first reinforcement member 710 in the first direction (or X-axis direction) may be smaller than the length of the first sound generator 510 in the first direction (or X-axis direction). The length of the first reinforcement member 710 in the second direction (or Y-axis direction) may be smaller than the length of the first sound generator 510 in the second direction (or Y-axis direction). The length of the first reinforcement member 710 in the third direction (or Z-axis direction) may be smaller than the length of the first sound generator 510 in the third direction (or Z-axis direction).

[0154] The second reinforcement member 720 may be disposed between the first sound generator 510 and the second surface of the second substrate 121. The second reinforcement member 720 may be disposed on a second side of the second surface of the first sound generator 510. In one embodiment, for example, the second reinforcement member 720 may be disposed on the right side of the bottom surface of the first sound generator 510.

[0155] The length of the second reinforcement member 720 in the first direction (or X-axis direction) may be smaller than the length of the first sound generator 510 in the first direction (or X-axis direction). The length of the second reinforcement member 720 in the second direction (or Y-axis direction) may be smaller than the length of the first sound generator 510 in the second direction (or Y-axis direction). The length of the second reinforcement member 720 in the third direction (or Z-axis direction) may be smaller than the length of the first sound generator 510 in the third direction (or Z-axis direction).

[0156] The lengths of the first sound generator 510, the first reinforcement member 710, and the second reinforcement member 720 in the second direction (or the Y-axis direction) may be substantially the same as the length of the first panel bottom member 400 in the second direction (or the Y-axis direction). The length of the first reinforcement member 710 in the second direction (or the Y-axis direction) may be different from the length of the second reinforcement member 720 in the second direction (or the Y-axis direction).

[0157] The first reinforcement member 710 and the second reinforcement member 720 may include a metal material having a predetermined weight. Alternatively, the first reinforcement member 710 and the second reinforcement member 720 may include an elastic material.

[0158] Due to the presence of the first reinforcement member 710, a space in which the first sound generator 510 can vibrate can be provided between the first surface of the first sound generator 510 and the second surface of the first substrate 111. In such an embodiment, due to the presence of the second reinforcement member 720, a space in which the first sound generator 510 can vibrate can be provided between the second surface of the first sound generator 510 and the second surface of the second substrate 121. Therefore, in such an embodiment, the vibration intensity of the first sound generator 510 can be enhanced, and the first sound generator 510 can output a low-frequency sound.

[0159] Fig.16 and Fig.17 The folded state and the unfolded state are shown respectively. Figure 1 and Figure 2 A cross-sectional view of a foldable display device. Specifically, Fig.16 It is along Figure 1 A cross-sectional view taken along line II' of Fig.17 It is along Figure 2 A cross-sectional view taken along line II-II'. Fig.18 It is shown Fig.16 FIG. 2 is an enlarged cross-sectional view of another alternative embodiment of region A′ of FIG.

[0160] In addition to the first sound generator 510 being attached to the second surface of the first substrate 111 and the second sound generator 520 being attached to the second surface of the second substrate 121, Figures 16 to 18Examples and Figure 3 , Figure 4 and Figure 6 The embodiments are basically the same. Figures 16 to 18 The same or similar elements shown in FIG. 1 have been replaced with those used in the description above. Figure 3 , Figure 4 and Figure 6 The embodiments are marked with the same figure numbers, and any repeated detailed description thereof will be omitted or simplified hereinafter.

[0161] refer to Figures 16 to 18 In an embodiment, the first sound generator 510 and the second sound generator 520 may be disposed between the second surface of the first substrate 111 and the second surface of the second substrate 121. The first sound generator 510 and the second sound generator 520 may be disposed in the first area A1 of the second display panel 120. The first panel bottom member 400 and the first sound generator 510 may not overlap each other in the thickness direction of the first display panel 110 (or in the Z-axis direction). The first panel bottom member 400 and the second sound generator 520 may not overlap each other in the thickness direction of the first display panel 110 (or in the Z-axis direction). The first sound generator 510 and the second sound generator 520 may not overlap each other in the thickness direction of the first display panel 110 (or in the Z-axis direction).

[0162] In an embodiment, the first sound generator 510 may be attached to the second surface of the first substrate 111, and the second sound generator 520 may be attached to the second surface of the second substrate 121. In an alternative embodiment where the first light shielding member 460 is disposed on the second surface of the first substrate 111 and the second light shielding member 470 is disposed on the second surface of the second substrate 121, as Fig.18 As shown, the first sound generator 510 may be attached to the first light shielding member 460, and the second sound generator 520 may be attached to the second light shielding member 470. The length of the first sound generator 510 in the second direction (or Y-axis direction) may be smaller than the length of the first panel bottom member 400 in the second direction (or Y-axis direction). The length of the second sound generator 520 in the second direction (or Y-axis direction) may be smaller than the length of the first panel bottom member 400 in the second direction (or Y-axis direction).

[0163] The first sound generator 510 may be a piezoelectric element or an actuator including a piezoelectric material that contracts or expands according to a driving voltage applied thereto, such as Figures 7 to 10In such an embodiment, the first sound generator 510 may not be attached to the second surface of the second substrate 121. In an embodiment in which the second light shielding member 470 is disposed on the second surface of the second substrate 121, the first sound generator 510 may not be attached to the second light shielding member 470. There may be a gap between the first sound generator 510 and the second surface of the second substrate 121 or the second light shielding member 470.

[0164] In such an embodiment, since the first sound generator 510 is attached to the first display panel 110, the first sound generator 510 can vibrate the first display panel 110 by contracting or expanding according to a driving voltage applied thereto. Therefore, the first sound generator 510 can output the first sound by using the first display panel 110 as a vibration membrane.

[0165] The second sound generator 520 may be a piezoelectric element or an actuator including a piezoelectric material that contracts or expands according to a driving voltage applied thereto, such as Figures 7 to 10 In such an embodiment, the second sound generator 520 may not be attached to the second surface of the first substrate 111. In an embodiment in which the first light shielding member 460 is disposed on the second surface of the first substrate 111, the second sound generator 520 may not be attached to the first light shielding member 460. There may be a gap between the second sound generator 520 and the second surface of the first substrate 111 or the first light shielding member 460.

[0166] In such an embodiment, since the second sound generator 520 is attached to the second display panel 120, the second sound generator 520 can vibrate the second display panel 120 by contracting or expanding according to the driving voltage applied thereto. Therefore, the second sound generator 520 can output the second sound by using the second display panel 120 as a vibration membrane.

[0167] When folded, the foldable display device 10 may display a first image on the first display panel 110, and may output a first sound by vibrating the first display panel 110 with the first sound generator 510. When unfolded, the foldable display device 10 may display a second image on the second display panel 120, and may output a second sound by vibrating the second display panel 120 with the second sound generator 520.

[0168] Gaps may be formed between the first panel bottom member 400 and the first sound generator 510, between the first panel bottom member 400 and the second sound generator 520, and between the first sound generator 510 and the second sound generator 520. When the first sound generator 510 and the second sound generator 520 respectively output the first sound and the second sound by vibrating the first display panel 110 and the second display panel 120, respectively, the gaps formed between the first panel bottom member 400 and the first sound generator 510, between the first panel bottom member 400 and the second sound generator 520, and between the first sound generator 510 and the second sound generator 520 may function as sound boxes.

[0169] According to the embodiment, Figures 16 to 18 As shown, the first sound may be output by vibrating the first display panel 110 with the first sound generator 510 attached to the first display panel 110. In such an embodiment, the second sound may be output by vibrating the second display panel 120 with the second sound generator 520 attached to the second display panel 120. Therefore, the foldable display device 10 may output sound in both the folded state and the unfolded state by vibrating the first display panel 110 with the first sound generator 510 to output the first sound and vibrating the second display panel 120 with the second sound generator 520 to output the second sound.

[0170] Fig.19 and Fig. 20 The folded state and the unfolded state are shown respectively. Figure 1 and Figure 2 A cross-sectional view of a foldable display device.

[0171] In addition to the foldable display device 10 further including the second sound generator 520 and the third sound generator 530, Fig.19 and Fig. 20 Examples and Figure 3 and Figure 4 The embodiments are basically the same. Fig.19 and Fig. 20 The same or similar elements shown in FIG. 1 have been replaced with those used in the description above. Figure 3 and Figure 4 The embodiments are marked with the same figure numbers, and any repeated detailed description thereof will be omitted or simplified hereinafter.

[0172] refer to Fig.19 and Fig. 20In an embodiment, the second sound generator 520 may be disposed between the second surface of the first substrate 111 and the second surface of the second substrate 121. The second sound generator 520 may be disposed in the first area A1 of the second display panel 120. The first panel bottom member 400 and the second sound generator 520 may not overlap each other in the thickness direction of the first display panel 110 (or in the Z-axis direction).

[0173] The second sound generator 520 may be attached to the second surface of the first substrate 111 and the second surface of the second substrate 121. Figure 6 In the illustrated alternative embodiment in which the first light shielding member 460 is disposed on the second surface of the first substrate 111 and the second light shielding member 470 is disposed on the second surface of the second substrate 121, the second sound generator 520 may be attached to the first light shielding member 460 and the second light shielding member 470. The length of the second sound generator 520 in the second direction (or the Y-axis direction) may be substantially the same as the length of the first panel bottom member 400 in the second direction (or the Y-axis direction).

[0174] The third sound generator 530 may be disposed on the second surface of the second substrate 121. The third sound generator 530 may be disposed in the second area A2 of the second display panel 120. The second panel bottom member 800 and the third sound generator 530 may not overlap each other in the thickness direction of the second display panel 120 (or in the Z-axis direction).

[0175] In such an embodiment, the third sound generator 530 may be attached to the second surface of the second substrate 121. Figure 6 In the illustrated embodiment where the second light blocking member 470 is disposed on the second surface of the second substrate 121 , the third sound generator 530 may be attached to the second light blocking member 470 .

[0176] The first sound generator 510 may be disposed adjacent to the left side of the first display panel 110, the second sound generator 520 may be disposed adjacent to the right side of the first display panel 110, and the third sound generator 530 may be disposed adjacent to the left side of the first display panel 110 when the second display panel 120 is folded, and may be disposed adjacent to the right side of the second display panel 120 when the second display panel 120 is unfolded. When the second display panel 120 is folded, the first sound generator 510 and the third sound generator 530 may overlap each other in the thickness direction (or in the Z-axis direction) of the first display panel 110. When the second display panel 120 is unfolded, the second sound generator 520 may be disposed between the first sound generator 510 and the third sound generator 530 in the first direction (or in the X-axis direction).

[0177] The second sound generator 520 and the third sound generator 530 may be piezoelectric elements or actuators including a piezoelectric material that contracts or expands according to a driving voltage applied thereto, such as Figures 7 to 10 Alternatively, the second sound generator 520 and the third sound generator 530 may be actuators that use voice coils therein to generate magnetic force according to a driving voltage applied thereto, such as Figures 11 to 13 Still alternatively, the second sound generator 520 and the third sound generator 530 may be vibration motors that generate magnetic force in the voice coils thereof according to the driving voltage applied thereto, and the vibration motors may be, for example, LRAs, such as Fig.14 shown.

[0178] In such an embodiment, since the third sound generator 530 is attached only to the second surface of the second substrate 121, the third sound generator 530 may not be attached to the second surface of the first substrate 111. In an alternative embodiment in which the first light shielding member 460 is provided on the second surface of the first substrate 111, the third sound generator 530 may not be attached to the first light shielding member 460.

[0179] In an embodiment, since the second sound generator 520 is attached to at least one of the first display panel 110 and the second display panel 120, the second sound generator 520 may vibrate the at least one of the first display panel 110 and the second display panel 120 in response to a driving voltage applied thereto. Therefore, the second sound generator 520 may output the second sound using at least one of the first display panel 110 and the second display panel 120 as a vibration membrane. Therefore, the foldable display device 10 may output the second sound in both the folded state and the unfolded state by vibrating at least one of the first display panel 110 and the second display panel 120 with the second sound generator 520.

[0180] In such an embodiment, since the third sound generator 530 is attached to the second display panel 120, the third sound generator 530 can vibrate the second display panel 120 by contracting or expanding according to the driving voltage applied thereto. Therefore, the third sound generator 530 can output the third sound by using the second display panel 120 as a vibration membrane. Therefore, the foldable display device 10 can output the third sound in both the folded state and the unfolded state by vibrating the second display panel 120 with the third sound generator 530.

[0181] A gap may be formed between the first panel bottom member 400 and the second sound generator 520. When the second sound generator 520 outputs the second sound by vibrating at least one of the first display panel 110 and the second display panel 120, the gap formed between the first panel bottom member 400 and the second sound generator 520 may function as a sound box.

[0182] A gap may be formed between the second panel bottom member 800 and the third sound generator 530. When the third sound generator 530 outputs the third sound by vibrating the second display panel 120, the gap formed between the second panel bottom member 800 and the third sound generator 530 may function as a sound box.

[0183] When the second display panel 120 is folded, the first sound generator 510 may output a first stereo sound, the second sound generator 520 may output a second stereo sound, and the third sound generator 530 may output a low-pitched sound. In one embodiment, for example, the first sound generator 510 may output a left stereo sound, the second sound generator 520 may output a right stereo sound, and the third sound generator 530 may output a low-pitched sound, so that a 2.1-channel stereo sound may be achieved. When the second display panel 120 is unfolded, the first sound generator 510 may output a first stereo sound, the second sound generator 520 may output a low-pitched sound, and the third sound generator 530 may output a second stereo sound. In one embodiment, for example, the first sound generator 510 may output a left stereo sound, the second sound generator 520 may output a low-pitched sound, and the third sound generator 530 may output a right stereo sound, so that a 2.1-channel stereo sound may be achieved.

[0184] Fig.21 It is shown Figure 1 and Figure 2 Block diagram of a foldable display device. Fig. 22 is a flowchart illustrating a sound providing method of a foldable display device according to an embodiment of the present disclosure.

[0185] refer to Fig.21 and Fig. 22 , an embodiment of the foldable display device 10 may include a first display panel 110, a first data driver 2320, a first scan driver 2330, a first timing controller 2340, a second display panel 120, a second data driver 2420, a second scan driver 2430, a second timing controller 2440, a first sound generator 510, a second sound generator 520, a third sound generator 530, a processor 2100, a folding sensor 2200 and a sound driver 2500.

[0186] The first display panel 110 includes a first display area DA1 in which a plurality of pixels are arranged to display an image. The first display panel 110 may include data lines, scan lines intersecting the data lines, and a plurality of pixels connected to the data lines and the scan lines. Each of the plurality of pixels of the first display panel 110 may include sub-pixels PX1, PX2, and PX3, such as Figure 5 As shown. Each of the sub-pixels PX1, PX2, and PX3 may be connected to at least one of the data lines of the first display panel 110 and at least one of the scan lines of the first display panel 110. Each of the sub-pixels PX1, PX2, and PX3 may include an organic light emitting element and a plurality of transistors and at least one capacitor for supplying current to the organic light emitting element. The organic light emitting element may be an OLED including a first electrode, an organic light emitting layer, and a second electrode.

[0187] The first data driver 2320 receives the first digital video data VDATA1 and the first source control signal DCS1 from the first timing controller 2340. The first data driver 2320 converts the first digital video data VDATA1 into a first analog data voltage DV1 according to the first source control signal DCS1 and may provide the first analog data voltage DV1 to the data line of the first display panel 110.

[0188] The first scan driver 2330 receives a first scan control signal SCS1 from the first timing controller 2340. The first scan driver 2330 generates a scan signal SS1 according to the first scan control signal SCS1, and provides the scan signal SS1 to a scan line of the first display panel 110. The first scan driver 2330 may include a plurality of transistors, and may be disposed in a non-display region of the first display panel 110. Alternatively, the first scan driver 2330 may be formed as an integrated circuit (“IC”), and the first scan driver 2330 may be mounted on a gate flexible film of a first substrate 111 attached to the first display panel 110.

[0189] The first timing controller 2340 receives the first digital video data VDATA1 and the first timing signal TS1 from the processor 2100. The first timing signal TS1 may include a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, and a dot clock.

[0190] The first timing controller 2340 generates timing control signals for controlling the timing of the operation of the first data driver 2320 and the first scan driver 2330. The timing control signals may include a first source control signal DCS1 for controlling the timing of the operation of the first data driver 2320 and a first scan control signal SCS1 for controlling the timing of the operation of the first scan driver 2330.

[0191] The second display panel 120 includes a second display area DA2 in which a plurality of pixels are arranged to display an image. The second display panel 120 may include data lines, scan lines intersecting the data lines, and a plurality of pixels connected to the data lines and the scan lines. Each of the plurality of pixels of the second display panel 120 may include sub-pixels PX1, PX2, and PX3, such as Figure 5 As shown. Each of the sub-pixels PX1, PX2, and PX3 may be connected to at least one of the data lines of the second display panel 120 and at least one of the scan lines of the second display panel 120. Each of the sub-pixels PX1, PX2, and PX3 may include an organic light emitting element and a plurality of transistors and at least one capacitor for supplying current to the organic light emitting element. The organic light emitting element may be an OLED including a first electrode, an organic light emitting layer, and a second electrode.

[0192] The second data driver 2420 receives the second digital video data VDATA2 and the second source control signal DCS2 from the second timing controller 2440. The second data driver 2420 converts the second digital video data VDATA2 into a second analog data voltage DV2 according to the second source control signal DCS2 and may provide the second analog data voltage DV2 to the data line of the second display panel 120.

[0193] The second scan driver 2430 receives the second scan control signal SCS2 from the second timing controller 2440. The second scan driver 2430 generates a scan signal SS2 according to the second scan control signal SCS2, and provides the scan signal SS2 to the scan line of the second display panel 120. The second scan driver 2430 may include a plurality of transistors, and may be disposed in a non-display area of ​​the second display panel 120. Alternatively, the second scan driver 2430 may be formed as an IC, and the second scan driver 2430 may be mounted on a gate flexible film attached to the second substrate 121 of the second display panel 120.

[0194] The second timing controller 2440 receives the second digital video data VDATA2 and the second timing signal TS2 from the processor 2100. The second timing signal TS2 may include a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, and a dot clock.

[0195] The second timing controller 2440 generates a timing control signal for controlling the timing of the operation of the second data driver 2420 and the second scan driver 2430. The timing control signal may include a second source control signal DCS2 for controlling the timing of the operation of the second data driver 2420 and a second scan control signal SCS2 for controlling the timing of the operation of the second scan driver 2430.

[0196] In an embodiment, the first sound generator 510, the second sound generator 520, and the third sound generator 530 may be a piezoelectric element or an actuator including a piezoelectric material that contracts or expands according to a driving voltage applied thereto, such as Figures 7 to 10 Alternatively, the first sound generator 510, the second sound generator 520 and the third sound generator 530 may be actuators that generate magnetic force using voice coils therein according to a driving voltage applied thereto, such as Figures 11 to 13 Still alternatively, the first sound generator 510, the second sound generator 520, and the third sound generator 530 may be vibration motors that generate magnetic force in the voice coils thereof according to the driving voltage applied thereto, and the vibration motors may be, for example, LRAs, such as Fig.14 shown.

[0197] The first sound generator 510 receives the first sound signal SV1 from the sound driver 2500. The first sound generator 510 may output the first sound by vibrating at least one of the first display panel 110 and the second display panel 120 according to the first sound signal SV1.

[0198] The second sound generator 520 receives the second sound signal SV2 from the sound driver 2500. The second sound generator 520 may output the second sound by vibrating at least one of the first display panel 110 and the second display panel 120 according to the second sound signal SV2.

[0199] The third sound generator 530 receives the third sound signal SV3 from the sound driver 2500. The third sound generator 530 may output the third sound by vibrating the second display panel 120 according to the third sound signal SV3.

[0200] Each of the first sound signal SV1 , the second sound signal SV2 , and the third sound signal SV3 may include a first driving voltage and a second driving voltage.

[0201] The sound driver 2500 receives first sound data SDATA1, second sound data SDATA2, and third sound data SDATA3 from the processor 2100. The sound driver 2500 may generate a first sound signal SV1, which is an analog signal to be output by the first sound generator 510, according to the first sound data SDATA1. The sound driver 2500 may generate a second sound signal SV2, which is an analog signal to be output by the second sound generator 520, according to the second sound data SDATA2. The sound driver 2500 may generate a third sound signal SV3, which is an analog signal to be output by the third sound generator 530, according to the third sound data SDATA3.

[0202] The sound driver 2500 may include: a digital signal processor ("DSP") that uses an algorithm to process and thereby modify or improve the first sound data SDATA1, the second sound data SDATA2, and the third sound data SDATA3 as digital signals; a digital-to-analog converter ("DAC") that converts the first sound data SDATA1, the second sound data SDATA2, and the third sound data SDATA3 processed by the DSP into a first sound signal SV1, a second sound signal SV2, and a third sound signal SV3 as analog signals, respectively; and an amplifier ("AMP") that amplifies and outputs the analog signal provided by the DAC.

[0203] In an embodiment, the processor 2100 may include a scaler that converts digital video data VDATA input from the outside to conform to the resolution of the first display panel 110 and the second display panel 120. In an embodiment, the processor 2100 may include a converter that converts the digital video data VDATA to improve the quality of the image. The processor 2100 outputs the first digital video data VDATA1 and the first timing signal TS1 to the first timing controller 2340 based on the digital video data VDATA and the timing signal TS. The processor 2100 outputs the second digital video data VDATA2 and the second timing signal TS2 to the second timing controller 2440 based on the digital video data VDATA and the timing signal TS.

[0204] The processor 2100 may determine whether the folding area FA of the second display panel 120 is in the folded state based on the folding sensing signal FSS from the folding sensor 2200. In one embodiment, for example, in response to receiving the folding sensing signal FSS having a first logic level voltage, the processor 2100 may determine that the folding area FA of the second display panel 120 is in the folded state, and in response to receiving the folding sensing signal FSS having a second logic level voltage, the processor 2100 may determine that the folding area FA of the second display panel 120 is in the unfolded state.

[0205] refer to Fig. 22 In S101 and S103, when the folding area FA of the second display panel 120 is folded, the processor 2100 may output the first digital video data VDATA1 and the first timing signal TS1 to the first timing controller 2340 so that the first image may be displayed in the first display area DA1 of the first display panel 110.

[0206] In S102 and S104 , when the folding area FA of the second display panel 120 is unfolded, the processor 2100 may output the second digital video data VDATA2 and the second timing signal TS2 to the second timing controller 2440 so that the second image may be displayed in the second display area DA2 of the second display panel 120 .

[0207] The processor 2100 may output first, second, and third sound data SDATA1 , SDATA2 , and SDATA3 according to the folding sensing signal FSS from the folding sensor 2200 .

[0208] In S105, when the folding area FA of the second display panel 120 is folded, the processor 2100 can output the first sound data SDATA1, the second sound data SDATA2 and the third sound data SDATA3, so that the first sound generator 510, the second sound generator 520 and the third sound generator 530 can output the first stereo sound, the second stereo sound and the low-pitched sound, respectively.

[0209] In S106, when the folding area FA of the second display panel 120 is unfolded, the processor 2100 can output the first sound data SDATA1, the second sound data SDATA2 and the third sound data SDATA3, so that the first sound generator 510, the second sound generator 520 and the third sound generator 530 can output the first stereo sound, the low-pitched sound and the second stereo sound, respectively.

[0210] The folding sensor 2200 may determine whether the folding area FA of the second display panel 120 is in a folded state or in an unfolded state. In one embodiment, for example, the folding sensor 2200 may determine whether the folding area FA of the second display panel 120 is in a folded state or in an unfolded state based on a change in a voltage applied to a folding line provided in the folding area FA. In the case where it is determined that the folding area FA of the second display panel 120 is in a folded state, the folding sensor 2200 may output a folding sensing signal FSS having a first logic level voltage. In the case where it is determined that the folding area FA of the second display panel 120 is in an unfolded state, the folding sensor 2200 may output a folding sensing signal FSS having a second logic level voltage. The first logic level voltage may be a low level voltage such as a voltage of 0 volts (V), and the second logic level voltage may be a high level voltage such as a voltage of 3.3V.

[0211] Fig.23 and Fig.24 are perspective views showing a foldable display device according to an alternative embodiment of the present disclosure in a folded state and an unfolded state, respectively.

[0212] refer to Fig.23 and Fig.24 , an embodiment of a foldable display device 10 ′ includes a display panel 110 ′ having a display area DA.

[0213] The display panel 110' may include a first folding area FA1 and a second folding area FA2, and may be Fig.23 folded as shown, or as Fig.24 As shown, the display panel 110' can be unfolded. When unfolded, the display panel 110' can have a rectangular shape in a plan view. For example, in a plan view, the display panel 110' can have a rectangular shape having a fifth side S5 extending in a first direction (or X-axis direction) and a sixth side S6 extending in a second direction (or Y-axis direction). The fifth side S5 can be shorter than the sixth side S6, in which case the user can watch a screen in a longitudinal position that is longer in the second direction (or Y-axis direction) than in the first direction (or X-axis direction). Alternatively, the fifth side S5 can be longer than the sixth side S6, in which case the user can watch a screen in a transverse position that is longer in the first direction (or X-axis direction) than in the second direction (or Y-axis direction). Still alternatively, the fifth side S5 can have substantially the same length as the sixth side S6, in which case the user can watch a square screen. The angle at which the fifth side S5 and the sixth side S6 intersect can be rounded with a predetermined curvature or can be a right angle. The planar shape of the display panel 110 ′ is not particularly limited, and for example, the display panel 110 ′ may be variously modified to have one of various other shapes such as a polygonal shape, a circular shape, or an elliptical shape.

[0214] When unfolded, the display area DA of the display panel 110' may have a rectangular shape in a plan view, the rectangular shape having a fifth display side DS5 extending in a first direction (or X-axis direction) and a sixth display side DS6 extending in a second direction (or Y-axis direction). The fifth display side DS5 may be shorter than the sixth display side DS6. Alternatively, the fifth display side DS5 may be longer than the sixth display side DS6. Still alternatively, the fifth display side DS5 may have substantially the same length as the sixth display side DS6. The angle at which the fifth display side DS5 and the sixth display side DS6 intersect may be rounded with a predetermined curvature or may be a right angle. The planar shape of the display area DA is not particularly limited, for example, the display area DA may be variously modified to have one of various other shapes such as a polygon, a circle or an ellipse.

[0215] The display panel 110' may include a first area A1, a second area A2, a third area A3, a first folding area FA1 between the first area A1 and the second area A2, and a second folding area FA2 between the second area A2 and the third area A3. The display panel 110' may be a bendable, foldable, or rollable flexible substrate, and thus may be easily folded in the first folding area FA1 and the second folding area FA2. In an embodiment, a hinge may be provided in the first folding area FA1 and the second folding area FA2 on the second surface of the display panel 110' to effectively fold the display panel 110'.

[0216] When the display panel 110' is folded, the first folding area FA1 may be folded outward so that a portion of the display area DA in the first area A1 and a portion of the display area DA in the second area A2 can face opposite directions, and the second folding area FA2 may be folded inward in the second folding area FA2 so that a portion of the display area DA in the second area A2 and a portion of the display area DA in the third area A3 can face each other. When the display panel 110' is folded, the display area DA may be bent in the first folding area FA1 and the second folding area FA2 to have a predetermined curvature.

[0217] According to the embodiment, Fig.23 and Fig.24 As shown, when the display panel 110' is folded, the first image can be displayed in a portion of the display area DA in the first area A1. In such an embodiment, when the display panel 110' is unfolded, the second image can be displayed in the first area A1, the second area A2, and the third area A3, and in portions of the display area DA in the first folding area FA1 and the second folding area FA2.

[0218] Fig.25 and Fig.26 The folded state and the unfolded state are shown respectively. Fig.23 and Fig.24 A cross-sectional view of a foldable display device.

[0219] refer to Fig.25 and Fig.26 , the foldable display device 10 ′ may include a display panel 110 ′, a panel bottom member 400 ′, and a first sound generator 510 ′.

[0220] The substrate 111 ′ and the pixel array layer 112 ′ of the display panel 110 ′ are respectively Figure 3 and Figure 4 The first substrate 111 and the first pixel array layer 112 are substantially the same, and thus any repeated detailed description thereof will be omitted.

[0221] The panel bottom member 400' may be attached to the second surface of the substrate 111'. The panel bottom member 400' may be disposed in the first area A1, the second area A2, and the third area A3 of the display panel 110'. The panel bottom member 400' may not be disposed in the first folding area FA1 and the second folding area FA2 of the display panel 110' to reduce folding stress.

[0222] The panel bottom member 400′ is similar to the panel bottom member 400 except that the second adhesive 420 and the second buffer member 440 are omitted. Figure 6 The first panel bottom member 400 is substantially the same as the first panel bottom member 400. That is, the panel bottom member 400' is substantially the same as the first panel bottom member 400. Figure 6 The first panel bottom member 400 is substantially the same, including the first adhesive 410, the first buffer member 430, and the first heat dissipation member 450, and thus any repeated detailed description thereof will be omitted.

[0223] The first sound generator 510' may be attached to the second surface of the substrate 111'. Alternatively, as Figure 6 As shown, the first light blocking member 460 is disposed on the second surface of the substrate 111 ′, and the first sound generator 510 ′ may be attached to the first light blocking member 460 .

[0224] The first sound generator 510' may be a piezoelectric element or an actuator including a piezoelectric material that contracts or expands according to a driving voltage applied thereto, such as Figures 7 to 10 Alternatively, the first sound generator 510' may be an actuator that generates magnetic force using a voice coil therein according to a driving voltage applied thereto, such as Figures 11 to 13 Still alternatively, the first sound generator 510' may be a vibration motor that generates a magnetic force in the voice coil according to a driving voltage applied thereto, and the vibration motor may be, for example, an LRA, such as Fig.14 shown.

[0225] In such an embodiment, since the first sound generator 510' is attached to the display panel 110', the first sound generator 510' can vibrate the display panel 110' by contracting or expanding according to the driving voltage applied thereto. Therefore, the first sound generator 510' can output the first sound by using the display panel 110' as a vibration membrane. Therefore, the foldable display device 10' can output the first sound in both the folded state and the unfolded state by vibrating the display panel 110' with the first sound generator 510'.

[0226] In an embodiment, Fig.25 and Fig.26As shown, the first sound generator 510' may be disposed in the first area A1 of the display panel 110', but the position of the first sound generator 510' is not particularly limited. Alternatively, the first sound generator 510' may be disposed in the second area A2 and the third area A3.

[0227] Fig.25 and Fig.26 An embodiment in which only a single sound generator is provided is shown, but the number of sound generators provided is not particularly limited. Alternatively, the foldable display device 10' may further include a second sound generator and a third sound generator. In such an embodiment, the first sound generator 510' may be provided in the first area A1 of the display panel 110', the second sound generator may be provided in the second area A2 of the display panel 110', and the third sound generator may be provided in the third area A3 of the display panel 110'. In such an embodiment, when the display panel 110' is folded, the first sound generator 510' may output a first sound, and at least one of the second sound generator and the third sound generator may output a low-pitched sound. In such an embodiment, when the display panel 110' is unfolded, the first sound generator 510' may output a first stereo sound, the second sound generator may output a low-pitched sound, and the third sound generator may output a second stereo sound. Therefore, the foldable display device 10' may provide 2.1-channel stereo sound in the unfolded state.

[0228] Fig. 27 and Fig.28 are perspective views showing a foldable display device according to another alternative embodiment of the present disclosure in a folded state and an unfolded state, respectively.

[0229] refer to Fig. 27 and Fig.28 , an embodiment of a foldable display device 10 ″ includes a display panel 110 ″ having a display area DA.

[0230] The display panel 110" may include a first folding area FA1 and a second folding area FA2, and may be Fig. 27 folded as shown, or as Fig.28When unfolded, the display panel 110 ″ may have a rectangular shape in a plan view. In one embodiment, for example, in a plan view, the display panel 110 ″ may have a rectangular shape having a seventh side S7 extending in a first direction (or X-axis direction) and an eighth side S8 extending in a second direction (or Y-axis direction). The seventh side S7 may be shorter than the eighth side S8, so that a user can view a screen in a longitudinal position that is longer in the second direction (or Y-axis direction) than in the first direction (or X-axis direction). Alternatively, the seventh side S7 may be longer than the eighth side S8, in which case the user can view a screen in a transverse position that is longer in the first direction (or X-axis direction) than in the second direction (or Y-axis direction). Still alternatively, the seventh side S7 may have substantially the same length as the eighth side S8, in which case the user can view a square screen. The angle at which the seventh side S7 and the eighth side S8 intersect may be rounded with a predetermined curvature or may be a right angle. The planar shape of the display panel 110 ″ is not particularly limited, and for example, the display panel 110 ″ may be modified to have one of various other shapes such as a polygonal shape, a circular shape, or an elliptical shape.

[0231] When unfolded, the display area DA of the display panel 110" may have a rectangular shape in a plan view, the rectangular shape having a seventh display side DS7 extending in a first direction (or X-axis direction) and an eighth display side DS8 extending in a second direction (or Y-axis direction). The seventh display side DS7 may be shorter than the eighth display side DS8. Alternatively, the seventh display side DS7 may be longer than the eighth display side DS8. Still alternatively, the seventh display side DS7 may have substantially the same length as the eighth display side DS8. The angle at which the seventh display side DS7 and the eighth display side DS8 intersect may be rounded with a predetermined curvature or may be a right angle. There is no particular limitation on the planar shape of the display area DA, for example, the display area DA may be variously modified to have one of other shapes such as a polygon, a circle or an ellipse.

[0232] The display panel 110" may include a first area A1, a second area A2, a third area A3, a first folding area FA1 between the first area A1 and the second area A2, and a second folding area FA2 between the first area A1 and the third area A3. When the display panel 110" is folded, the first folding area FA1 may be folded outward so that a portion of the display area DA in the first area A1 and a portion of the display area DA in the second area A2 may face opposite directions, and the second folding area FA2 may be folded outward so that a portion of the display area DA in the first area A1 and a portion of the display area DA in the third area A3 may face opposite directions. When the display panel 110" is folded, the display area DA may be bent in the first folding area FA1 and the second folding area FA2 to have a predetermined curvature. The curvature of the display area DA may be greater in the first folding area FA1 than in the second folding area FA2.

[0233] According to the embodiment, Fig. 27 and Fig.28 As shown, when the display panel 110" is folded, a first image can be displayed in a portion of the display area DA in the first area A1. In such an embodiment, when the display panel 110" is unfolded, a second image can be displayed in the first area A1, the second area A2 and the third area A3 and in portions of the display area DA in the first folding area FA1 and the second folding area FA2.

[0234] Fig.29 and Fig.30 The folded state and the unfolded state are shown respectively. Fig. 27 and Fig.28 A cross-sectional view of a foldable display device.

[0235] refer to Fig.29 and Fig.30 , the foldable display device 10 ″ may include a display panel 110 ″, a panel bottom member 400 ″, and a first sound generator 510 ″.

[0236] The substrate 111 ″ and the pixel array layer 112 ″ of the display panel 110 ″ are respectively Figure 3 and Figure 4 The first substrate 111 and the first pixel array layer 112 are substantially the same, and thus any repeated detailed description thereof will be omitted.

[0237] The panel bottom member 400" may be attached to the second surface of the substrate 111". The panel bottom member 400" may be disposed in the first area A1, the second area A2, and the third area A3 of the display panel 110". The panel bottom member 400" may not be disposed in the first folding area FA1 and the second folding area FA2 of the display panel 110" to reduce folding stress.

[0238] In addition to the second adhesive 420 and the second buffer member 440, the panel bottom member 400 is Figure 6 The first panel bottom member 400 is substantially the same as the first panel bottom member 400. That is, the panel bottom member 400" is substantially the same as the first panel bottom member 400. Figure 6 The first panel bottom member 400 is substantially the same, including the first adhesive 410, the first buffer member 430, and the first heat dissipation member 450, and thus any repeated detailed description thereof will be omitted.

[0239] The first sound generator 510" may be attached to the second surface of the substrate 111". Alternatively, in the Figure 6 In the case where the first light blocking member 460 is shown disposed on the second surface of the substrate 111 ″, the first sound generator 510 ″ may be attached to the first light blocking member 460 .

[0240] The first sound generator 510" may be a piezoelectric element or actuator including a piezoelectric material that contracts or expands according to a driving voltage applied thereto, such as Figures 7 to 10 Alternatively, the first sound generator 510" may be an exciter that generates magnetic force using a voice coil therein according to a driving voltage applied thereto, such as Figures 11 to 13 Still alternatively, the first sound generator 510" may be a vibration motor that generates a magnetic force in the voice coil according to a driving voltage applied thereto, and the vibration motor may be, for example, an LRA, such as Fig.14 shown.

[0241] In such an embodiment, since the first sound generator 510″ is attached to the display panel 110″, the first sound generator 510″ can vibrate the display panel 110″ by contracting or expanding according to the driving voltage applied thereto. Therefore, the first sound generator 510″ can output the first sound by using the display panel 110″ as a vibration membrane. Therefore, the foldable display device 10″ can output the first sound in both the folded state and the unfolded state by vibrating the display panel 110″ with the first sound generator 510″.

[0242] The first sound generator 510" Fig.29 and Fig.3010 ″ is shown as being disposed in the first area A1 of the display panel 110 ″, but the position of the first sound generator 510 ″ is not particularly limited. Alternatively, the first sound generator 510 ″ may be disposed in the second area A2 and the third area A3 .

[0243] Fig.29 and Fig.30 An embodiment in which only a single sound generator is provided is shown, but the number of sound generators provided is not particularly limited. In an alternative embodiment, the foldable display device 10" may further include a second sound generator and a third sound generator. In such an embodiment, the first sound generator 510" may be disposed in the first area A1 of the display panel 110", the second sound generator may be disposed in the second area A2 of the display panel 110", and the third sound generator may be disposed in the third area A3 of the display panel 110". In such an embodiment, when the display panel 110" is folded, the first sound generator 510" may output a first sound, and at least one of the second sound generator and the third sound generator may output a low-pitched sound. In such an embodiment, when the display panel 110" is unfolded, the first sound generator 510" may output a low-pitched sound, the second sound generator may output a first stereo sound, and the third sound generator may output a second stereo sound. Therefore, the foldable display device 10" may provide 2.1-channel stereo sound in the unfolded state.

[0244] The present invention should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of the present invention to those skilled in the art.

[0245] While the invention has been particularly shown and described with reference to certain embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention as defined by the following claims.

Claims

1. A foldable display device, comprising: A first display panel including a first substrate and a first pixel array layer disposed on a first surface of the first substrate; A second display panel including a second substrate and a second pixel array layer disposed on a first surface of the second substrate; and a first sound generator between a second surface of the first substrate opposite to the first surface of the first substrate and a second surface of the second substrate opposite to the first surface of the second substrate, The first sound generator outputs a first sound in both a folded state and an unfolded state by vibrating at least one of the first display panel and the second display panel, and the second display panel includes a first area, a second area, and a folded area between the first area and the second area.

2. The foldable display device according to claim 1, wherein: The first sound generator is attached to the second surface of the first substrate and the second surface of the second substrate.

3. The foldable display device according to claim 1, further comprising: a first light shielding member disposed between the first sound generator and the second surface of the first substrate; and A second light shielding member is provided between the first sound generator and the second surface of the second substrate.

4. The foldable display device according to claim 1, further comprising: a first reinforcement member disposed on a first side of the first sound generator and between the first sound generator and the second surface of the first substrate; and A second reinforcement member is disposed on a second side of the first sound generator and between the first sound generator and the second surface of the second substrate.

5. The foldable display device according to claim 1, wherein: The second pixel array layer in the first area and the second pixel array layer in the second area face each other.

6. The foldable display device according to claim 5, wherein: The first sound generator is disposed in the first area of ​​the second display panel.

7. The foldable display device according to claim 6, further comprising: A first panel bottom member is disposed between the second surface of the first substrate and the second surface of the second substrate in the first region of the second display panel and does not overlap with the first sound generator when viewed in a thickness direction of the first display panel in a plan view.

8. The foldable display device according to claim 7, wherein: The first panel bottom member comprises: a first adhesive disposed on the second surface of the first substrate; a second adhesive disposed on the second surface of the second substrate; and A first heat dissipation member is disposed between the first adhesive and the second adhesive.

9. The foldable display device according to claim 8, wherein: The first panel bottom member further comprises: a first buffer member disposed between the first adhesive and the first heat dissipation member; and A second buffer member is disposed between the second adhesive and the first heat dissipation member.

10. The foldable display device according to claim 7, further comprising: A second panel bottom member is disposed on the second surface of the second substrate in the second region of the second display panel.

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