Rollable display device

A display device includes: a frame; and a flexible display unit configured to be wound into the frame, and including a transparent adhesive layer, the adhesive layer having a first surface and a second surface opposite to the first surface. The adhesive layer is configured to adhere layers on the first surface and the second surface thereof to each other, and a first elongation percentage of the adhesive layer in a first direction is greater than a second elongation percentage of the adhesive layer in a second direction crossing the first direction, the first direction being a direction along which the display unit is unwound from the frame.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean Patent Application No. 10-2015-0016182, filed on Feb. 2, 2015 in the Korean intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND

One or more exemplary embodiments of the present invention relate to a display device.

2. Description of the Related Art

Together with the recent efforts to provide electronic devices having various shapes, studies are being conducted to provide displays mounted on the electronic devices having various shapes.

Because organic light-emitting display apparatuses are self-emissive display apparatuses that do not require a separate light source, the organic light-emitting display apparatuses may be driven at low power and may be lightweight and thin. Furthermore, the organic light-emitting display apparatuses are receiving attention as next-generation display apparatuses due to their high quality characteristics, such as a wide viewing angle, high contrast, and quick response speed.

SUMMARY

One or more exemplary embodiments of the present invention include a rollable display device.

According to one or more exemplary embodiments of the present invention, a display device includes: a frame; and a flexible display unit configured to be wound into the frame, and including a transparent adhesive layer, the adhesive layer having a first surface and a second surface opposite to the first surface. The adhesive layer is configured to adhere layers on the first surface and the second surface thereof to each other, and a first elongation percentage of the adhesive layer in a first direction is greater than a second elongation percentage of the adhesive layer in a second direction crossing the first direction, the first direction being a direction along which the display unit is unwound from the frame.

The first direction and the second direction may be perpendicular to each other.

The adhesive layer may include a base and a plurality of modulus adjusting areas, and the plurality of modulus adjusting areas may each extend in the second direction and may be separated from each other along the first direction.

The base and the plurality of modulus adjusting areas may be alternately arranged along the first direction on a surface of the adhesive layer, and the plurality of modulus adjusting areas may extend in a depth direction of the adhesive layer from the surface of the adhesive layer such that the base is at at least three sides of each of the plurality of modulus adjusting areas.

A depth of each of the plurality of modulus adjusting areas may be in a range of 10% to 90% of a thickness of the adhesive layer.

A depth of each of the plurality of modulus adjusting areas may be in a range of 10% to 50% of a thickness of the adhesive layer.

The first elongation percentage may increase from one edge to an opposite edge of the adhesive layer, and the one edge may be closer to the frame than the opposite edge.

Intervals between adjacent ones of the plurality of modulus adjusting areas may decrease from the one edge to the opposite edge.

A depth of each of the plurality of modulus adjusting areas may increase from the one edge to the opposite edge.

The plurality of modulus adjusting areas may be spaced from the one edge and the opposite edge.

The plurality of modulus adjusting areas may include a plurality of first modulus adjusting areas extending in a depth direction of the adhesive layer from the first surface of the adhesive layer, and a plurality of second modulus adjusting areas extending in a depth direction of the adhesive layer from the second surface of the adhesive layer.

The plurality of first modulus adjusting areas and the plurality of second modulus adjusting areas may be alternately arranged.

The flexible display unit may include a flexible substrate, a display layer on the flexible substrate, a thin-film encapsulation layer sealing the display layer, and a functional layer on the thin-film encapsulation layer, and the adhesive layer may adhere the thin-film encapsulation layer and the functional layer to each other.

According to one or more exemplary embodiments of the present invention, a display device including a flexible display unit configured to be wound in a roll shape, the flexible display unit including: a flexible substrate; a display layer on the flexible substrate; a thin-film encapsulation layer sealing the display layer; a functional layer on the thin-film encapsulation layer; and an adhesive layer between the thin-film encapsulation layer and the functional layer, the adhesive layer including a base and a plurality of modulus adjusting areas having a line shape in a region of the base, wherein the plurality of modulus adjusting areas are separated from each other along a first direction to form a stripe pattern, the base and the plurality of modulus adjusting areas include a same material, and a first modulus of the base is greater than a second modulus of the plurality of modulus adjusting areas.

A first elongation percentage of the adhesive layer in the first direction may be greater than a second elongation percentage of the adhesive layer in a second direction crossing the first direction.

The first direction and the second direction may be perpendicular to each other.

Each of the plurality of modulus adjusting areas may extend in the second direction.

The base and the plurality of modulus adjusting areas may be alternately arranged on a surface of the adhesive layer in the first direction, and the plurality of modulus adjusting areas may extend in a depth direction of the adhesive layer from the surface of the adhesive layer such that the base is at at least three sides of each of the plurality of the modulus adjusting areas.

The display device may further include a frame configured to accommodate the flexible display unit wound in the roll shape, and the first direction may be a direction along which the flexible display unit is unwound from the frame.

The first elongation percentage may increase from one edge to an opposite edge of the adhesive layer, and the one edge may be closer to the frame than the opposite edge.

Intervals between adjacent ones of the plurality of modulus adjusting areas may decrease from the one edge to the opposite edge.

Depths of the plurality of modulus adjusting areas may increase from the one edge to the opposite edge.

A depth of each of the plurality of modulus adjusting areas may be in a range of 10% to 90% of a thickness of the adhesive layer.

A depth of each of the plurality of modulus adjusting areas may be in a range of 10% to 50% of a thickness of the adhesive layer.

The plurality of modulus adjusting areas may include a plurality of first modulus adjusting areas extending in a depth direction of the adhesive layer from a first surface of the adhesive layer, and a plurality of second modulus adjusting areas extending in a depth direction of the adhesive layer from a second surface of the adhesive layer, the second surface being opposite to the first surface.

The plurality of first modulus adjusting areas and the plurality of second modulus adjusting areas may be alternately arranged.

The display layer may include an organic light-emitting diode and a thin-film transistor electrically connected to the organic light-emitting diode.

The functional layer may include a polarization layer, a touch screen layer, and a protection layer, and the adhesive layer may adhere the polarization layer, the touch screen layer, and the protection layer to each other.

DETAILED DESCRIPTION

As the present invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to particular modes of practice, and it will to be appreciated that all changes, equivalents, and substitutes that do not depart from the spirit and technical scope of the present invention are encompassed in the present invention. In the description of the present invention, certain detailed explanations of related art that unnecessarily obscure the essence of the invention may be omitted.

It will be understood that although the terms “first”, “second”, etc. may be used herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Sizes of components in the drawings may be exaggerated for convenience of explanation. Because sizes and thicknesses of components in the drawings may be arbitrarily illustrated for convenience of explanation, the following embodiments are not limited thereto.

When a component is described to be on or under another component, the component may be directly or indirectly on the other component, and a criterion regarding on and under is based on drawings. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. It will be further understood that when an element or layer is referred to as being “on”, “connected to”, or “coupled to” another element or layer, it may be directly on, connected, or coupled to the other element or layer or one or more intervening elements or layers may also be present. When an element or layer is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. For example, when a first element is described as being “coupled” or “connected” to a second element, the first element may be directly coupled or connected to the second element or the first element may be indirectly coupled or connected to the second element via one or more intervening elements. Further, the use of “may” when describing embodiments of the present invention relates to “one or more embodiments of the present invention”. Also, the term “exemplary” is intended to refer to an example or illustration.

One or more exemplary embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. Those components that are the same or substantially the same are indicated with the same reference numeral regardless of the figure number, and redundant explanations thereof may be omitted.

FIG. 1is a partially exposed perspective view of a rollable display device1according to an exemplary embodiment of the present invention,FIG. 2is a cross-sectional view taken along the line I-I′ ofFIG. 1,FIG. 3is a plan view of an adhesive layer400of the rollable display device1shown inFIG. 1according to an exemplary embodiment of the present invention, andFIG. 4is a cross-sectional view taken along the line ofFIG. 3according to an exemplary embodiment of the present invention.

Referring toFIGS. 1 through 4, the rollable display device1according to an exemplary embodiment of the present invention may include a frame F and a flexible display unit10that is windable (e.g., retractable) into the frame F.

The frame F provides a space for the flexible display unit10to be rolled into (e.g., stored) and may include a rod R combined to or connected to one edge E1of the flexible display unit10. The flexible display unit10may be wound by using the rod R as a central axis (e.g., the flexible display unit10may be wound about the rod R as the central axis) and may also be unwound from (e.g., extended from) the frame F. Accordingly, the rollable display device1may be easily carried and stored, and the flexible display unit10may be protected from an external impact. InFIG. 1, the frame F has a roll shape (e.g., a tubular shape), but exemplary embodiments of the present invention are not limited thereto and the frame F may have any suitable shape as long as the frame F has a space for the flexible display unit10to be rolled into.

The flexible display unit10will now be described in more detail with reference toFIG. 2.

The flexible display unit10may include a flexible substrate100, a display layer200formed on the flexible substrate100, a thin-film encapsulation layer300sealing the display layer200, and a functional layer500disposed on the thin-film encapsulation layer300.

For example, the functional layer500may include a polarization layer d, a touch screen layer520, and a protection layer530. However, exemplary embodiments of the present invention are not limited thereto, and the flexible display unit10may include one or more of the polarization layer510, the touch screen layer520, and the protection layer530or may further include another functional layer.

The flexible display unit10may include at least one adhesive layer400. The adhesive layer400may be transparent and adheres layers respectively located on a first surface thereof and a second surface thereof that is opposite to the first surface. For example, the adhesive layer400may be disposed between the thin-film encapsulation layer300and the functional layer500to adhere the thin-film encapsulation layer300and the functional layer500to each other. The polarization layer510, the touch screen layer520, and the protection layer530included in the functional layer500may be adhered to each other by adhesive layers400.

The flexible substrate100is flexible and may be formed of any suitable material, such as a metal material or a plastic material such as polyethylene terephthalate (PET), polyethylene naphthalate (PEN), and/or polyimide. In some embodiments, the flexible substrate100may be formed of a thin metal foil, such as steel use stainless (SUS).

A buffer layer110formed of silicon oxide and/or silicon nitride may be disposed on the flexible substrate100so as to prevent impurities from penetrating into a semiconductor layer120of a thin-film transistor TFT.

The display layer200may include the thin-film transistor TFT, a capacitor Cap, and an organic light-emitting diode (OLED) electrically connected to the thin-film transistor TFT.

The thin-film transistor TFT may include the semiconductor layer120including amorphous silicon, polycrystalline silicon, an oxide semiconductor, and/or an organic semiconductor, a gate electrode140, a source electrode160, and a drain electrode162.

The semiconductor layer120may be disposed on the buffer layer110. The gate electrode140is disposed above the semiconductor layer120, and the source electrode160and the drain electrode162are electrically connected to each other based on (e.g., according to) a signal applied to the gate electrode140.

The gate electrode140may be formed, for example, as a single layer or having a multi-layer structure formed of one or more materials, such as aluminum (Al), platinum (Pt), palladium (Pd), silver (Ag), magnesium (Mg), gold (Au), nickel (Ni), neodymium (Nd), iridium (Ir), chromium (Cr), lithium (Li), calcium (Ca), molybdenum (Mo), titanium (Ti), tungsten (W width), and/or copper (Cu), by considering adhesion with an adjacent layer, surface flatness of a stacked layer, and processability of the gate electrode140.

A gate insulating film130formed of silicon oxide and/or silicon nitride may be disposed between the semiconductor layer120and the gate electrode140.

An interlayer insulating film150may be disposed on the gate electrode140. The interlayer insulating film150may be formed as a single layer or having a multi-layer structure formed of one or more materials, such as silicon oxide and/or silicon nitride.

The source electrode160and the drain electrode162are disposed on the interlayer insulating film150. The source electrode160and the drain electrode162are electrically connected to the semiconductor layer120respectively through contact openings (e.g., contact holes) formed on the interlayer insulating film150and the gate insulating film130.

The source electrode160and the drain electrode162may each be formed as a single layer or having a multi-layer structure formed of one or more materials, such as Al, Pt, Pd, Ag, Mg, Au, Ni, Nd, Ir, Cr, Li, Ca, Mo, Ti, W, and/or Cu.

A first insulating film170may be disposed on the source electrode160and the drain electrode162. When the OLED is disposed on the thin-film transistor TFT, the first insulating film170flattens a top surface of the thin-film transistor TFT (e.g., provides a planar surface above the thin-film transistor TFT) and protects the thin-film transistor TFT and other various devices. The first insulating film170may be formed of an acryl-based organic material, benzocyclobutene (BCB), and/or an inorganic material.

A second insulating film180may be disposed on the thin-film transistor TFT. The second insulating film180may be a pixel-defining film. The second insulating film180may be disposed on the first insulating film170and may include openings. The second insulating film180defines pixel regions on the flexible substrate100.

The second insulating film180may be an organic insulating film. The organic insulating film may contain an acryl-based polymer, such as poly(methyl methacrylate) (PMMA), polystyrene (PS), a polymer derivative having a phenol group, an imide-based polymer, an aryl ether-based polymer, an amide-based polymer, a fluorine-based polymer, a p-xylene-based polymer, a vinyl alcohol-based polymer, and/or a mixture thereof.

The OLEDs forming a red sub-pixel250R, a green sub-pixel250G, and a blue sub-pixel250B may be disposed in the pixel regions defined by the second insulating film180. The red sub-pixel250R may include a red-emitting pixel electrode210R, a red-emitting intermediate layer220R, and a counter electrode230, the green sub-pixel250G may include a green-emitting pixel electrode210G, a green-emitting intermediate layer220G, and the counter electrode230, and the blue sub-pixel250B may include a blue-emitting pixel electrode210G, a blue-emitting intermediate layer220B, and the counter electrode230.

The red, green, and blue-emitting pixel electrodes210R,210G, and210B are each connected to respective thin-film transistors TFT and may each be a transparent electrode or a reflective electrode. When the red, green, and blue-emitting pixel electrodes210R,210G, and210B are each a transparent electrode, they may be formed of indium tin oxide (ITO), indium zinc oxide (IZO), zinc oxide (ZnO), indium oxide (In2O3), indium gallium oxide (IGO), and/or aluminum zinc oxide (AZO). When the red, green, and blue-emitting pixel electrodes210R,210G, and210B are each a reflective electrode, they may each include a reflective film formed of Ag, Mg, Al, Pt, Pd, Au, Ni, Nd, Ir, Cr, or a compound or alloy thereof and a layer formed of ITO, IZO, ZnO, In2O3, IGO, and/or AZO. However, exemplary embodiments of the present invention are not limited thereto, and the red, green, and blue-emitting pixel electrodes210R,210G, and210B may each be formed of any suitable material and may each be a single layer or may have a multi-layer structure.

The red, green, and blue-emitting intermediate layers220R,220G, and220B may respectively include emission layers (EML) for emitting red, green, and blue light and may each further include a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), and/or an electron injection layer (EIL). However, the red, green, and blue-emitting intermediate layers220R,220G, and220B are not limited thereto and may have any suitable structure.

The counter electrode230may be a common electrode of the red sub-pixel250R, the green sub-pixel250G, and the blue sub-pixel250B. The counter electrode230may be a transparent electrode or a reflective electrode.

When the counter electrode230is a transparent electrode, the counter electrode230may include a layer formed of a metal having a low work function, such as Li, Ca, LiF/Ca, LiF/AI, Al, Ag, Mg, or a compound or alloy thereof, and a transparent conductive layer formed of ITO, IZO, ZnO, and/or In2O3. When the counter electrode230is a reflective electrode, the counter electrode230may include a layer formed of Li, Ca, LiF/Ca, LiF/AI, Al, Ag, Mg, or a compound or alloy thereof. However, a structure and a material of the counter electrode230are not limited thereto and may vary.

The thin-film encapsulation layer300may seal the display layer200to prevent external oxygen and moisture from penetrating into the display layer200. The thin-film encapsulation layer300may include a plurality of organic films310and330and a plurality of inorganic films320and340. For example, the organic films310and330and the inorganic films320and340may be alternately stacked on each other to form a multi-layer structure.

The functional layer500may be disposed on the thin-film encapsulation layer300. For example, the functional layer500may include the polarization layer510, the touch screen layer520, and/or the protection layer530and may further include other functional layers. InFIG. 2, the polarization layer510, the touch screen layer520, and the protection layer530are sequentially disposed in the stated stacked order, but the stacked order is not limited thereto and may vary.

The polarization layer510may transmit light vibrating in a same direction as a polarization axis and absorb or reflect light vibrating in other directions from light emitted from the display layer200. For example, the polarization layer510may include a phase difference film that changes linear polarized light to circular polarized light or vice versa by imparting a phase difference of λ/4 to two polarization components that are perpendicular to each other, and a polarization film that aligns directions of light passed through the phase difference film divides the light into two polarization components perpendicular to each other and transmits one of the two polarization components while absorbing or distributing the other, but a structure of the polarization layer510is not limited thereto.

The touch screen layer520may include a touch sensor in which a first electrode and a second electrode cross each other. The touch sensor may be, for example, a capacitance type in which contact is determined or sensed by detecting a change of capacitance generated at a plurality of first electrodes and a plurality of second electrodes which are arranged to cross each other.

The protection layer530is flexible and may protect the display layer200from an external impact. The protection layer530may be formed of PET, PS, PEN, polyethersulfone (PES), and/or polyethylene (PE).

The adhesive layer400may be disposed between the thin-film encapsulation layer300and the functional layer500. For example, the adhesive layer400may be disposed between the polarization layer510and the touch screen layer520and between the touch screen layer520and the protection layer530to adhere them to each other. The adhesive layer400may be formed of a silicon-based adhesive and/or an acryl-based adhesive and may further include a hardening agent, a cross-linking agent, and/or a ultraviolet ray (UV) stabilizer. The adhesive layer400may be pressure sensitive adhesive (PSA) or an optical clear adhesive (OCA).

Referring toFIG. 3, the adhesive layer400may include a base410and a plurality of modulus adjusting areas420. The plurality of modulus adjusting areas420may be formed in a partial region of the base410, extend in a second direction Y, and form a stripe pattern by being separated from each other in a first direction X (e.g., by being arranged along the first direction X). In this embodiment, the first direction X is a direction in which the flexible display unit10is unwound from the frame F, and the second direction Y may be a direction crossing the first direction X. A third direction Z is a thickness direction of the flexible display unit10. For example, the second direction Y may be perpendicular to the first direction X. Accordingly, the base410and the modulus adjusting areas420may be alternately arranged along the first direction X on a surface of the adhesive layer400.

The base410and the modulus adjusting areas420may be formed of the same material. However, the base410may have a first modulus and the modulus adjusting areas420may have a second modulus smaller than the first modulus. As used herein, modulus denotes an elastic modulus regarding tension or stiffness, and the adhesive layer400is relatively hard, has relatively high adhesive strength, and relatively high restoring force when its modulus is high. On the other hand, when its modulus is low, the adhesive layer400may have relatively high stretchability.

The modulus adjusting areas420may be formed by performing corona discharge or irradiating plasma locally on the base410. Links of cross-linking agents in an adhesive may be broken in a region of the base410on which the corona discharge is performed or plasma is irradiated. Thus, the modulus adjusting areas420may have a smaller modulus than the base410(e.g., the modulus adjusting areas420may have a smaller modulus value than that of the base410). For example, the first modulus of the base410may be in a range of 3 to 10 Kgf/cm2and the second modulus of the modulus adjusting areas420may be in a range of 0.1 to 2 Kgf/cm2.

As such, because the modulus adjusting areas420, which have a smaller modulus than the base410, are separated from each other along the first direction X, a first elongation percentage of the adhesive layer400in the first direction X may be greater than a second elongation percentage of the adhesive layer400in the second direction Y. As used herein, an elongation percentage is a percentage of an elongated length with respect to an initial length when a tensile load is applied. For example, the first elongated percentage in the first direction X may be in a range of about 100% to 1000% and the second elongation percentage in the second direction Y perpendicular to the first direction X may be in a range of about 0% to 100%.

The adhesive layer400may have excellent adhesive strength and excellent restoring force due to the base410having a high modulus and may have a high elongation percentage due to the modulus adjusting areas420arranged along the first direction X. Accordingly, adhesive strength between the thin-film encapsulation layer300and the functional layer500is maintained while a stress generated and accumulated as the flexible display unit10recedes away from (e.g., extends from) the winding axis thereof is effectively distributed when the flexible display unit10is wound in a roll shape.

The modulus adjusting areas420may be spaced from one edge A and another edge B of the adhesive layer400. In this embodiment, the one edge A is close to the frame F and the other edge B is opposite to the one edge A. Because the one edge A is a region where the stress is least accumulated when the flexible display unit10is wound, the base410having a high modulus may be at the one edge A (e.g., the modulus adjusting areas420may be spaced from the one edge A). Also, the base410having high adhesive strength may be at the other edge B in order to reduce or prevent deformation of the flexible display unit10caused as the adhesive layer400is extended away from the winding axis.

Energy transmitted to the adhesive layer400when corona discharge is performed or plasma is irradiated to form the modulus adjusting areas420may penetrate up to a depth (e.g., a uniform depth) from the surface of the adhesive layer400. Thus, as shown inFIG. 4, the modulus adjusting areas420may extend in the depth direction of the adhesive layer400from the surface of the adhesive layer400and may be surrounded by the base410in the adhesive layer400.

At this time, if a depth T2of the modulus adjusting area420is too shallow, an elongation percentage of the adhesive layer400in the first direction X may be undesirably low, and if the depth T2of the modulus adjusting area420is too deep, the adhesive layer400may partially break or crack when the adhesive layer400is elongated in (e.g., extended in) the first direction X. Accordingly, in order to increase the elongation percentage and stably maintain the adhesive layer400, the depth T2of the modulus adjusting area420may be in a range of 10% to 90% and, in one embodiment, may be in a range of 10% to 50%, of a thickness T1of the adhesive layer400.

Also, a width W of the modulus adjusting area420may be determined by a beam width of plasma. The width W of the modulus adjusting area420is a width on the surface of the adhesive layer400, and adhesive strength of the adhesive layer400may decrease as the width W of the modulus adjusting area420increases. Accordingly, an entire area of the modulus adjusting areas420on the surface of the adhesive layer400may be in a range of 5% to 20% and, in one embodiment, may be in a range of 5% to 10%, of a surface area of the adhesive layer400.

A boundary region in which adhesive strength of an adhesive changes along a gradient (e.g., gradually changes) may be formed between the modulus adjusting area420and the base410. Accordingly, a modulus of the adhesive layer400may not rapidly or abruptly change or vary between the modulus adjusting area420and the base410.

FIG. 5is a plan view of an adhesive layer400B according to another exemplary embodiment of the present invention.

Referring toFIG. 5, the adhesive layer400B may include the base410and the plurality of modulus adjusting areas420formed in a partial region of the base410. The modulus adjusting areas420may form a stripe pattern by being separated from each other along the first direction X and may have a smaller modulus than the base410. Accordingly, a first elongation percentage of the adhesive layer400B in the first direction X may be greater than a second elongation percentage of the adhesive layer400B in the second direction Y.

Also, intervals between adjacent ones of the modulus adjusting areas420may decrease from one edge A to another edge B of the adhesive layer400B (D1>D2). In this embodiment, the one edge A is close to the frame F shown inFIG. 1and the other edge B is opposite to the one edge A.

When the intervals between adjacent ones of the modulus adjusting areas420decrease from the one edge A to the other edge B, the first elongation percentage may increase from the one edge A to the other edge B. Accordingly, when the flexible display unit10ofFIG. 1is wound to have a roll shape, a stress accumulated from the one edge A to the other edge B may be further effectively distributed.

FIG. 6is a cross-sectional view taken along the line ofFIG. 3according to another exemplary embodiment of the present invention.

Referring toFIG. 6, an adhesive layer400C may include the base410and the plurality of modulus adjusting areas420formed in a partial region of the base410. The modulus adjusting areas420are separated from each other in the first direction X and may extend in the second direction Y.

The modulus adjusting areas420may have a smaller modulus than the base410. Accordingly, a first elongation percentage of the adhesive layer400C in the first direction X may be greater than a second elongation percentage of the adhesive layer400C in the second direction Y.

Depths of the modulus adjusting areas420may increase from one edge A to another edge B of the adhesive layer400C (T3<T4<T5). As such, when the depths of the modulus adjusting areas420increase from the one edge A to the other edge B of the adhesive layer400C, the first elongation percentage may increase from the one edge A to the other edge B even when intervals D between adjacent ones of the modulus adjusting areas420are uniform. Accordingly, when the flexible display unit10ofFIG. 1is wound to have a roll shape, a stress accumulated from the one edge A to the other edge B may be further effectively distributed.

InFIG. 6, the intervals D between adjacent ones of the modulus adjusting areas420are uniform, but exemplary embodiments of the present invention are not limited thereto. For example, the depths of the modulus adjusting areas420may increase from the one edge A to the other edge B of the adhesive layer400C while the intervals D between adjacent ones of the modulus adjusting areas420may gradually decrease, as shown inFIG. 5.

FIG. 7is a cross-sectional view taken along the line II-II′ ofFIG. 3according to another exemplary embodiment of the present invention.

Referring toFIG. 7, an adhesive layer400D may include the base410and the plurality of modulus adjusting areas420formed in the base410. The modulus adjusting areas420may form a stripe pattern by being separated from each other in the X direction and may have a smaller modulus than the base410. Accordingly, a first elongation percentage of the adhesive layer400D in the first direction X may be greater than a second elongation percentage of the adhesive layer400D in the second direction Y.

The modulus adjusting areas420may include a plurality of first modulus adjusting areas422extending in a depth direction of the adhesive layer400D from a first surface of the adhesive layer400D and a plurality of second modulus adjusting areas424extending in a depth direction of the adhesive layer400D from a second surface of the adhesive layer400D. The first modulus adjusting areas422and the second modulus adjusting areas424may be alternately arranged along the first direction X. Thus, the first elongation percentage may be further increased while adhesive strength of the adhesive layer400D is maintained, and accordingly, when the flexible display unit10ofFIG. 1is wound to have a roll shape, a stress accumulated from one edge A to another edge B of the adhesive layer400D may be further effectively distributed.

FIG. 8is a plan view of an adhesive layer400E according to another exemplary embodiment of the present invention.

Referring toFIG. 8, the adhesive layer400E may include the base410and the plurality of modulus adjusting areas420formed in the base410. The plurality of modulus adjusting areas420may form a stripe pattern by being spaced from (e.g., separated from) each other in the first direction X and may have a lower modulus than the base410. Accordingly, a first elongation percentage of the adhesive layer400E in the first direction X may be greater than a second elongation percentage of the adhesive layer400E in the second direction Y.

Also, intervals between the modulus adjusting areas420may decrease from another edge B of the adhesive layer400E to one edge A (D3>D4), and thus, the first elongation percentage may increase towards the one edge A. In one embodiment, the one edge A is close to the frame F ofFIG. 1, and the other edge B is opposite to the one edge A.

When the flexible display unit10ofFIG. 1is wound to have a roll shape, the radius of curvature of the flexible display unit10decreases towards the one edge A, and thus, stress caused by small radius of curvature may increase towards the one edge A. Accordingly, by increasing the first elongation percentage the adhesive layer400E to the one edge A, the stress caused by the small radius of curvature may be distributed.

Meanwhile, as can be seen inFIG. 8, the intervals between the modulus adjusting areas420are reduced in order to increase the first elongation percentage towards the one edge A, but this exemplary embodiment is not limited thereto. In other words, in order to increase the first elongation percentage towards the one edge, A, the depths of the modulus adjusting areas420may gradually increase towards the one edge A as described with reference toFIG. 6.

FIG. 9is a plan view of an adhesive layer400F according to another exemplary embodiment of the present invention.

Referring toFIG. 9, the adhesive layer400F may include the base410and the plurality of modulus adjusting areas420formed in the base410. The plurality of modulus adjusting areas420may form a stripe pattern by being spaced from (e.g., separated from) each other in the first direction X and may have a lower modulus than the base410. Accordingly, a first elongation percentage of the adhesive layer400F in the first direction X may be greater than a second elongation percentage of the adhesive layer400F in the second direction Y.

Also, intervals between the modulus adjusting areas420may decrease from a center portion of the adhesive layer400F to one edge A and another edge B (D5>D6and D5>D7). In one embodiment, the one edge A is close to the frame F ofFIG. 1, and the other edge B is opposite to the one edge A.

As described above with reference toFIG. 5, when the intervals between the modulus adjusting areas420decrease towards the other edge B, the first elongation percentage may increase towards the other edge B. Accordingly, when the flexible display unit10ofFIG. 1is wound to have a roll shape, stress accumulated towards the other edge B may be further effectively distributed. Also, when the flexible display unit10ofFIG. 1is wound to have a roll shape, a radius of curvature of the flexible display unit10decreases towards the one end A, and thus, stress caused by small radius of curvature may increase towards the one end A. Accordingly, by increasing the first elongation percentage from the center portion of the adhesive layer400F to the one edge A, the stress caused by the small radius of curvature may be distributed.

Meanwhile, as can be seen inFIG. 9, the intervals between the modulus adjusting areas420decrease toward the one edge A and the other edge B, but this exemplary embodiment is not limited thereto, and depths of the modulus adjusting areas420may increase toward the one edge A and the other edge B as described above, for example, with reference toFIG. 6in order to increase the first elongation percentage towards the one edge A and the other edge B.

As described above, according to one or more exemplary embodiments of the present invention, when a flexible display device is wound in a roll shape, a stress accumulated relatively far from a central axis is effectively distributed, thereby reducing or preventing damage, such as interlayer detachment, caused by the accumulated stress.