Flexible window and flexible display device including the flexible window

Abstract

A flexible window and a flexible display device including the flexible window are provided. A flexible window includes: a retardation layer; an impact mitigation layer disposed on the retardation layer; and a surface layer disposed on the impact mitigation layer. The retardation layer includes a λ / 4 retardation plate. According to an exemplary embodiment of the present disclosure, impact resistance and flexibility can be achieved while improving display quality.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2018-0108836, filed on September 12, 2018, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present disclosure relates to a flexible window and a flexible display device including the flexible window. Background Art

[0004] Examples of the display device include a liquid crystal display device, an organic light emitting display device, and the like.

[0005] Unlike liquid crystal display devices, organic light emitting display devices do not require a backlight unit and thus can be made thinner. Therefore, flexible, stretchable, foldable, bendable and / or rollable organic light emitting display devices are being studied (eg, being developed).

[0006] Such a flexible display device may employ a flexible window on a display panel that displays an image, thereby protecting the display device while having flexibility (eg, while being flexible). Summary of the invention

[0007] When a transparent plastic film is used instead of glass to give flexibility to the flexible window, the flexible display device may be easily affected by external impact. In addition, when the viewer wears polarized sunglasses, shading may occur at a certain angle, and rainbow-like stains, so-called "rainbow spots", may appear on the surface of the display device. As a result, the image quality may deteriorate.

[0008] Aspects of the present disclosure relate to a flexible window achieving impact resistance as well as flexibility, and a flexible display device including the flexible window.

[0009] Aspects of the present disclosure also relate to a flexible window capable of preventing or reducing shading and rainbow spots even when a viewer wears polarized sunglasses, and a flexible display device including the flexible window.

[0010] It should be noted that aspects of the present disclosure are not limited to the above-mentioned aspects; other aspects of the present invention will be apparent to those skilled in the art from the following description.

[0011] According to exemplary embodiments of the present disclosure, it is possible to achieve impact resistance and flexibility while improving display quality.

[0012] According to an embodiment of the present disclosure, a flexible window includes: a retardation layer; an impact mitigation layer located on the retardation layer; and a surface layer located on the impact mitigation layer, wherein the retardation layer includes a λ / 4 retardation plate.

[0013] According to another embodiment of the present disclosure, a flexible window includes: a high-delay layer; and a surface layer located on the high-delay layer, wherein the surface layer includes a base layer, a hard coating layer located on the base layer, and an anti-fingerprint coating layer located on the hard coating layer, wherein the in-plane delay of the high-delay layer is in the range of 6000nm to 10000nm.

[0014] According to another embodiment of the present disclosure, a flexible display device includes: a display panel; a flexible window located on the display panel; and a pressure-sensitive adhesive (PSA) located between the display panel and the flexible window, wherein the flexible window includes a retardation layer, an impact mitigation layer located on the retardation layer, and a surface layer located on the impact mitigation layer, wherein the retardation layer includes a λ / 4 retardation plate.

[0015] It should be noted that the effects of the present disclosure are not limited to the effects described above, and other aspects of the present disclosure will be apparent to those skilled in the art from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The above and other aspects and features of the present disclosure will become more apparent by describing in more detail exemplary embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0017] Figure 1 is a cross-sectional view showing a stacked structure of a flexible display device according to an exemplary embodiment of the present disclosure;

[0018] Figure 2 yes Figure 1 An enlarged cross-sectional view of a portion A of the flexible display device shown in FIG.

[0019] Figure 3 is a diagram for illustrating a principle for preventing or reducing a blackout phenomenon by adopting a retardation layer according to an exemplary embodiment of the present disclosure;

[0020] Figure 4 is a cross-sectional view showing a stacking structure of a flexible window according to another exemplary embodiment of the present disclosure;

[0021] FIG. 5A to FIG. 5C is a graph showing the relationship between the retardation of a high retardation film and the wavelength in the visible light range;

[0022] Figure 6is a cross-sectional view showing a stacking structure of a flexible window according to another exemplary embodiment of the present disclosure;

[0023] Figure 7 is a cross-sectional view showing a stacking structure of a flexible window according to another exemplary embodiment of the present disclosure;

[0024] Figure 8 is a cross-sectional view showing a stacking structure of a flexible window according to yet another exemplary embodiment of the present disclosure;

[0025] Fig. 9 is a cross-sectional view showing a stacking structure of a flexible window according to yet another exemplary embodiment of the present disclosure; and

[0026] Fig.10 is a cross-sectional view illustrating a stacking structure of a flexible window according to still another exemplary embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] The features of the inventive concept and its implementation method can be more easily understood by referring to the following detailed description of the embodiments and the accompanying drawings. However, the inventive concept can be implemented in many different forms and should not be interpreted as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the concept of the inventive concept to those skilled in the art, and the inventive concept will be limited only by the appended claims. The same reference numerals refer to the same elements throughout the specification.

[0028] The terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the inventive concept. As used herein, unless the context clearly indicates otherwise, the singular forms of "a", "a kind of" and "the (said)" are also intended to include plural forms. It will also be understood that when the terms "comprising" and / or "including" are used in this specification, the description indicates the presence of the features, wholes, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or their groups.

[0029] It will be understood that when an element or layer is referred to as being "on," "connected to," or "coupled to" another element or layer, the element or layer may be directly on, directly connected to, or directly coupled to the other element or layer, or there may be intervening elements or layers. In contrast, 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. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0030] It will be understood that, although the terms "first", "second", etc. may be used herein to describe different elements, components, regions, layers and / or parts, 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 the present invention, the first element, component, region, layer or part discussed below may be named as the second element, component, region, layer or part.

[0031] For ease of description, spatially relative terms such as "below," "beneath," "below," "above," "on," etc. may be used herein to describe the relationship of one element or feature to other elements or features as shown in the figures. It should be understood that the spatially relative terms are intended to cover different orientations of the device in use or operation in addition to the orientation depicted in the accompanying drawings. For example, if the device is turned over in the accompanying drawings, an element described as being "below" or "below" other elements or features would subsequently be positioned as being "above" the other elements or features. Thus, the exemplary term "below" can cover both the "above" and "below" orientations. The device may be otherwise positioned (rotated 90 degrees or in other orientations), and the spatially relative descriptors used herein interpreted accordingly.

[0032] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those of ordinary skill in the art to which this application belongs. It will be further understood that, unless expressly defined herein, terms (such as those defined in a commonly used dictionary) should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this specification, and should not be interpreted in an ideal or overly formal sense.

[0033] The same or similar components are denoted by the same reference numerals throughout the specification.

[0034] Hereinafter, exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0035] Figure 1 is a cross-sectional view schematically illustrating a stack structure of a flexible display device according to an exemplary embodiment of the present disclosure. Figure 2 yes Figure 1 An enlarged cross-sectional view of portion A of the flexible display device shown in FIG.

[0036] Reference Figure 1 and Figure 2 , the flexible display device 10 includes a display panel 100 and a flexible window 200 disposed on the display panel 100 .

[0037] The display panel 100 may include a flexible substrate 20 , a buffer layer 110 , an active layer 121 , a gate insulating layer 140 , a gate electrode 151 , an interlayer dielectric layer 160 , a source electrode 172 , a drain electrode 173 , a passivation layer 180 , an organic light emitting element E, and an encapsulation layer 194 .

[0038] The flexible substrate 20 may serve as a base substrate of the display panel 100. The flexible substrate 20 may have a flexible property (eg, may be flexible) so that the flexible display device 10 may display an image even when it is bent. To this end, the flexible substrate 20 may be thinly formed and may include a material having elasticity.

[0039] In an exemplary embodiment, the flexible substrate 20 may include, but is not limited to, polyimide. For example, it may include flexible glass and / or similar materials.

[0040] The buffer layer 110 is disposed on the flexible substrate 20. The buffer layer 110 may be directly formed on the flexible substrate 20. The buffer layer 110 may include silicon nitride (SiN x ), silicon oxide (SiO x ) and / or silicon oxynitride (SiO x N y ) etc., and may be composed of a single layer or a plurality of layers. The buffer layer 110 prevents or reduces the penetration of impurities, moisture, or external air that deteriorates the characteristics of the semiconductor, and / or provides a flat surface.

[0041] The active layer 121 is disposed on the buffer layer 110. The active layer 121 may include a semiconductor, and may be formed of polysilicon.

[0042] The active layer 121 may include a channel region 123 and a source region 122 and a drain region 124 respectively located on both sides of the channel region 123. The channel region 123 may be an intrinsic semiconductor, which is polysilicon not doped with impurities. The source region 122 and the drain region 124 may be an impurity semiconductor, which is polysilicon doped with conductive impurities.

[0043] The gate insulating layer 140 is disposed on the active layer 121. The gate insulating layer 140 may be formed of an insulating layer including silicon nitride, silicon oxide, and / or silicon oxynitride, etc., and may be composed of a single layer or a plurality of layers.

[0044] The gate electrode 151 is disposed on the gate insulating layer 140. The gate electrode 151 may be connected to the gate line and the gate pad. The gate electrode 151 may include aluminum (Al), molybdenum (Mo), copper (Cu), or an alloy thereof, and may have a multi-layer structure.

[0045] The interlayer dielectric layer 160 is disposed on the gate electrode 151. The interlayer dielectric layer 160 may be formed of an insulating layer including silicon nitride, silicon oxide, and / or silicon oxynitride, etc., and may be composed of a single layer or a plurality of layers.

[0046] Source electrode 172 and drain electrode 173 are disposed on interlayer dielectric layer 160. Source electrode 172 may be disposed so that it overlaps source region 122 of active layer 121, and drain electrode 173 may be disposed so that it overlaps drain region 124 of active layer 121. Source electrode 172 and drain electrode 173 may be connected to the above-mentioned data line and data pad.

[0047] The data metal layer (eg, data line, data pad, etc.) may include aluminum (Al), molybdenum (Mo), chromium (Cr), tantalum (Ta), titanium (Ti), other refractory metals, or alloys thereof, and may also have a multi-layer structure.

[0048] In the gate insulating layer 140 and the interlayer dielectric layer 160 , a source contact hole 161 and a drain contact hole 162 may be formed, which electrically connect the source electrode 172 and the drain electrode 173 to the source region 122 and the drain region 124 of the active layer 121 , respectively.

[0049] The active layer 121, the gate electrode 151, the source electrode 172, and the drain electrode 173 of the flexible display device 10 may form a thin film transistor T. The gate electrode 151 as a control terminal of the thin film transistor T may be connected to a gate line; the source electrode 172 as an input terminal may be connected to a data line; and the drain electrode 173 as an output terminal may be electrically connected to the anode 191 through the contact hole 181.

[0050] The passivation layer 180 is formed over the source electrode 172 and the drain electrode 173. The passivation layer 180 may include silicon nitride, silicon oxide, silicon oxynitride, an acryl organic compound having a small dielectric constant, benzocyclobutane (BCB), and / or perfluorocyclobutane (PFCB), or the like.

[0051] The passivation layer 180 may protect the source electrode 172 and the drain electrode 173 and may function as a planarization layer to provide a planar upper surface. In the passivation layer 180 , a contact hole 181 through which the drain electrode 173 is exposed may be formed.

[0052] The organic light emitting element E is disposed on the passivation layer 180. The organic light emitting element E may include an anode 191, a pixel defining layer 190, an organic emission layer 192, and a cathode 193.

[0053] The anode 191 is disposed at the bottom of the organic light emitting element E. The anode 191 may be electrically connected to the drain electrode 173 through a contact hole 181 formed in the passivation layer 180, and may be a pixel electrode of the organic light emitting element E.

[0054] The anode 191 may include a material layer having a high work function, such as ITO, IZO, ZnO, and / or In 2 O 3 . In addition, the anode 191 can be implemented as a stack of layers including the above-mentioned material layer having a high work function and a reflective metal layer such as lithium (Li), calcium (Ca), lithium fluoride / calcium (LiF / Ca), lithium fluoride / aluminum (LiF / Al), aluminum (Al), silver (Ag), magnesium (Mg) and / or gold (Au).

[0055] The pixel defining layer 190 is disposed on the anode 191. The pixel defining layer 190 may include a resin such as polyacrylate and / or polyimide. The pixel defining layer 190 is used to isolate each pixel of the organic light emitting element E, and may include an opening 195 through which the anode 191 is exposed.

[0056] The organic emission layer 192 is disposed on the anode 191 exposed through the opening 195 of the pixel defining layer 190. The organic emission layer 192 may be implemented as a multilayer including one or more of a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), an electron injection layer (EIL), and an emission layer (EML).

[0057] The cathode 193 is disposed on the pixel defining layer 190 and the organic emission layer 192. The cathode 193 may include Li, Ca, LiF / Ca, LiF / Al, Al, Mg, Ag, Pt, Pd, Ni, Au, Nd, Ir, Cr, BaF, Ba, a compound thereof, or a mixture thereof (e.g., a mixture of Ag and Mg). The cathode 193 may be a common electrode of the organic light emitting element E.

[0058] The encapsulation layer 194 is disposed on the cathode 193. The encapsulation layer 194 may prevent or reduce moisture or air from penetrating from the outside to oxidize the organic light emitting element E, and may also provide a flat surface.

[0059] In an exemplary embodiment, the display panel 100 may further include a touch sensing unit (e.g., a touch sensor) 205 attached thereto or incorporated therein. For example, the touch sensing unit may be arranged between the encapsulation layer 194 and the window 200, and the touch sensing unit acquires coordinate information of a point at which an input has been made. The touch sensing unit may be provided on the entire surface of the display panel 100. However, the positional relationship between the display panel 100 and the touch sensing unit is not limited thereto. The touch sensing unit may be a contact touch sensing unit or a contactless touch sensing unit. A resistive touch sensing unit, an electromagnetic induction touch sensing unit, and / or a capacitive touch sensing unit may be adopted (e.g., utilized), and the type of the touch sensing unit is not specifically limited thereto.

[0060] The display panel 100 may further include a polarization unit (eg, a polarizer) disposed between the touch sensing unit and the encapsulation layer 194 , but the present disclosure is not limited thereto. The polarization unit disposed between the touch sensing unit and the encapsulation layer 194 may be removed (eg, not included).

[0061] The flexible window 200 is disposed on the display panel 100 to protect the display panel 100 from physical impact and penetration of external air, and may provide flexibility to the flexible display device 10 .

[0062] The flexible window 200 may include a retardation layer 210 disposed on the display panel 100 , an impact mitigation layer 220 disposed on the retardation layer 210 , and a surface layer 230 disposed on the impact mitigation layer 220 .

[0063] The retardation layer 210 may have a retardation of a quarter wave (λ / 4) and may include a quarter wave plate (QWP) that converts linear polarized light into circular polarized light, and vice versa. However, the present disclosure is not limited thereto. A λ / 4 retardation film, such as a reactive wafer film, may also be used. The retardation layer 210 is used to convert the linear polarized light output from the display panel 100 into circular polarized light. By doing so, when the viewer wears polarized sunglasses, the shading phenomenon that occurs when the light output from the display panel 100 coincides with the absorption axis of the polarized sunglasses and makes the light invisible can be prevented or reduced, and the color distortion phenomenon that occurs due to the retardation of the surface layer 230 can be prevented or reduced. In the color distortion phenomenon, light of different wavelength bands, that is, light of different colors, is transmitted in a pattern that looks like a rainbow.

[0064] Figure 3 is a diagram for illustrating a principle for preventing or reducing a light shielding phenomenon by adopting a retardation layer according to an exemplary embodiment of the present disclosure. Figure 3, the light FL output from the display panel 100 passes through the polarization unit PU and is polarized, thereby outputting the first linear polarized light L1 perpendicular to the first absorption axis OX1 of the polarization unit PU. The first linear polarized light L1 (A1) can be seen by the eyes of the viewer.

[0065] On the other hand, when the viewer wears polarized sunglasses PS and the second absorption axis OX2 of the polarized sunglasses PS is perpendicular to the first absorption axis OX1 of the polarizing unit PU, the first linear polarized light L1 cannot pass through the polarized sunglasses PS. Therefore, the viewer may see the blocking (A2). In contrast, when the retardation layer 210 according to an embodiment of the present disclosure is disposed between the polarizing unit PU and the polarized sunglasses PS, the first linear polarized light L1 is delayed by λ / 4, so that the first linear polarized light L1 is converted into circular polarized light L2, and then the circular polarized light L2 is converted into the second linear polarized light L3 through the polarized sunglasses PS. The viewer's eyes can see the second linear polarized light L3 (A3). In addition, when the first linear polarized light L1 is converted into the circular polarized light L2, due to the retardation of the surface layer 230, rainbow-like stains, i.e., rainbow mura, can be prevented or substantially prevented. In this way, the shading phenomenon and color distortion caused when the viewer wears the polarized sunglasses PS can be effectively prevented or reduced. In other words, the viewer can stably watch the image on the flexible display device 10 with or without the polarized sunglasses PS.

[0066] Return to reference Figure 1 and Figure 2 According to an exemplary embodiment, the first bonding component CP1 may be disposed between the delay layer 210 and the display panel 100. The first bonding component CP1 may be implemented as (for example, may be) an optically clear adhesive (OCA) film and / or an optically clear resin (OCR), etc. In another exemplary embodiment, the first bonding component CP1 may be a pressure sensitive adhesive (PSA). The pressure sensitive adhesive may be made of acryl and / or silicone (Si). The thickness of the pressure sensitive adhesive may vary from 25 μm to 50 μm, and the detachment force (peel force) may be 16 gf / in to 35 gf / in. However, the present disclosure is not limited thereto. The first bonding component CP1 may be used to attach and fix the delay layer 210 to the display panel 100.

[0067] The first bonding part CP1 may be disposed on the entire surface area where the retardation layer 210 overlaps with the display panel 100. However, the present disclosure is not limited thereto. The first bonding part CP1 may be disposed only in a portion of the area where the retardation layer 210 overlaps with the display panel 100. For example, the first bonding part CP1 may be disposed along the edge of the area where the retardation layer 210 overlaps with the display panel 100. A plurality of first bonding parts CP1 may be disposed in the area where the retardation layer 210 overlaps with the display panel 100 so that they are spaced apart from each other in the form of strips and / or dots.

[0068] When a sharp object such as a pen applies an impact to the surface of the flexible window 200, cracks may occur on the surface. This may deteriorate the display quality and durability. In order to prevent or reduce such defects, it is desirable to improve the impact resistance of the entire flexible window 200. To this end, the flexible window 200 may include an impact mitigation layer 220. In an exemplary embodiment, the impact mitigation layer 220 may be disposed above the delay layer 210.

[0069] The impact mitigation layer 220 may be composed of a single layer or multiple layers. The impact mitigation layer 220 may include a material having elasticity to mitigate the impact by delaying the time for the impact force to be transmitted.

[0070] In an exemplary embodiment, the impact mitigation layer 220 may be made of a polyurethane-based material. However, the present disclosure is not limited thereto. The impact mitigation layer 220 may be made of polydimethylsiloxane (PDMS) and / or rubber, etc. The impact mitigation layer 220 may mitigate impact force from the outside and may be transparent and flexible.

[0071] By adjusting the thickness and tensile modulus of the impact mitigation layer 220 included in the flexible window 200, the time period for the impact force generated by the impact to be transmitted can be increased. However, since the total thickness is limited and the radius of curvature is also limited, the thickness of the impact mitigation layer 220 cannot be increased indefinitely. In view of the above, the thickness of the impact mitigation layer 220 included in the flexible window 200 can be in the range of 70 μm to 150 μm. That is, if the thickness is 70 μm or more, the impact mitigation layer 220 can fully mitigate the impact force from the outside. In addition, if the thickness is 150 μm or less, cracks can be suppressed. Therefore, the thickness of the impact mitigation layer 220 can be, but is not limited to, 70 μm to 150 μm.

[0072] In order to examine the impact resistance of the impact mitigation layer 220, a drop test was performed by dropping a pen onto a test object. A pen having a point diameter of 0.7 mm and a weight of 5.8 g was used. Orange TMThe FINE ballpoint pen was subjected to a drop test. The drop test was performed by increasing the drop height by 1 centimeter (cm) each time the test object passed the test and repeating the test until the test object failed (e.g., showed a crack). The results of the drop test are shown in Table 1 below:

[0073] Table 1

[0074] Thickness of impact reduction layer (μm) 60 70 80 100 150 160 Tested pen drop height (cm) 1 6 7 9 12 13 Folding characteristics (curvature 3R inward / outward) good good good good good Buckling

[0075] As can be seen from Table 1, the highest pen drop height tested increases with the thickness of the impact mitigation layer 220. However, when the impact mitigation layer 220 has a thickness of 160 μm, when the display device is folded, buckling occurs at the interface between the impact mitigation layer 220 and the delay layer 210 or the interface between the impact mitigation layer 220 and the surface layer 230. It can also be seen that when the thickness of the impact mitigation layer 220 is less than 70 μm, the pen drop height tested decreases rapidly. In other words, it can be seen that the impact mitigation layer 220 should have a thickness of 70 μm or more in order to have a sufficient safe drop height. Therefore, in one embodiment, the thickness of the impact mitigation layer 220 is 70 μm or more. Although the drop height increases with the thickness of the impact mitigation layer 220, if the thickness is too large, buckling may occur when the display device is folded. Therefore, it can be determined that the thickness of the impact mitigation layer 220 is within the range of considering flexibility, such as 150 μm or less. However, the present disclosure should not be limited to this.

[0076] In order to compare the surface hardness of the impact mitigation layer 220, the hardness of the pencil was measured by applying a load of 500 g using a pencil hardness tester (PHT, available from Sukbo-science Corporation in South Korea). The surface was scratched at an angle of 45 degrees using a pencil with a hardness of 6B to 9H, and the surface was observed after the test. When the scratching was completed (e.g., observed) after five tests (e.g., repeated five times), the hardness of the lead of each pencil was measured (e.g., recorded). The results of the pencil hardness test are shown in Table 2 below.

[0077] Table 2

[0078] Tensile modulus of impact reduction layer (GPa) 0.05 0.01 0.25 0.5 0.5< Pencil hardness (module structure) 3B H~3H H~3H H~3H 4H Folding characteristics (curvature 3R inward / outward) good good good good Buckling

[0079] Referring to Table 2, it can be seen that the surface hardness of the impact mitigation layer 220 increases with the tensile modulus of the impact mitigation layer 220. It should be noted that when the tensile modulus of the impact mitigation layer 220 exceeds 0.5 GPa, buckling occurs at the interface between the impact mitigation layer 220 and the delay layer 210 or the interface between the impact mitigation layer 220 and the surface layer 230. It can also be seen that when the tensile modulus of the impact mitigation layer 220 is less than 0.01 GPa, the surface hardness drops to 3B. When the tensile modulus of the impact mitigation layer 220 is high, although the hardness is excellent, when the impact mitigation layer 220 is stacked on another layer (e.g., an adjacent layer), buckling is more likely to occur due to the difference in shear stress with another layer (e.g., an adjacent layer). On the other hand, when the tensile modulus is low, although the impact absorbency is excellent, it may be difficult to handle. According to an exemplary embodiment of the present disclosure, the tensile modulus of the impact mitigation layer 220 may be in the range of 0.01 GPa to 0.5 GPa. By providing the impact mitigation layer 220 having a tensile modulus of 0.01 GPa to 0.5 GPa in the flexible window 200 as described above, impact resistance of the flexible window 200 may be improved and buckling may be suppressed.

[0080] The in-plane retardation value Re and the retardation value Rth in the thickness direction of the impact mitigation layer 220 can be expressed as a refractive index in a direction in an xyz coordinate system. For example, if the impact mitigation layer 220 is located in an xy plane, the x-axis and the y-axis refer to the plane direction of the impact mitigation layer 220, and the z-axis refers to the thickness direction. That is, the impact mitigation layer 220 has refractive indices nx, ny, and nz along the x-axis, y-axis, and z-axis, respectively. Re indicates the retardation value in the plane direction, and Rth indicates the retardation value in the thickness direction. Nz indicates the degree of biaxiality.

[0081] The relationship of the above values ​​can be expressed by the following equations 1 to 3:

[0082] Equation 1

[0083] Re=(nx-ny)×d

[0084] Equation 2

[0085] Rth=((nx+ny) / 2-nz)×d

[0086] Equation 3

[0087] Nz=Rth / Ro

[0088] Here, nx, ny, and nz represent the refractive indices along the x-axis, y-axis, and z-axis, respectively, and d indicates the thickness of the film.

[0089] According to an exemplary embodiment of the present disclosure, the in-plane retardation value Re and the retardation value Rth in the thickness direction of the impact mitigation layer 220 may be, but are not limited to, zero.

[0090] According to another exemplary embodiment, the impact mitigation layer 220 may be provided in the form of a film. For example, the film may include colorless polyimide (CPI), thermoplastic polyurethane (TPU), triacetyl cellulose film (TAC film), polycarbonate (PC), polymethyl methacrylate (PMMA), cycloolefin polymer (COP), polyurethane, silicone, polyethylene terephthalate (PET), polyethylene (PE) and oriented polypropylene (OPP) One or more. When the impact mitigation layer 220 is implemented in the form of a film, the impact mitigation layer 220 may be provided as a thin film, which is desirable because the thickness of the flexible window 200 may be reduced. The above-mentioned impact resistance test was performed on the impact mitigation layer 220 in the form of a film. The test results are shown in Table 3 below:

[0091] Table 3

[0092] Thickness of impact reduction layer (μm) 20 30 50 80 90 Tested pen drop height (cm) 0.5 3 5 7 8 Folding characteristics (curvature 3R inward / outward) good good good good Buckling

[0093] As can be seen from Table 3, the highest pen drop height tested increases with the thickness of the impact mitigation layer 220 in the form of a film. However, when the impact mitigation layer 220 has a thickness of 90 μm, when the display device is folded, buckling occurs at the interface between the impact mitigation layer 220 and the delay layer 210 or the interface between the impact mitigation layer 220 and the surface layer 230. It can also be seen that when the thickness of the impact mitigation layer 220 is less than 30 μm, the pen drop height tested decreases rapidly. In other words, it can be seen that the impact mitigation layer 220 should have a thickness of 30 μm or more in order to achieve a sufficient drop height. Therefore, in one embodiment, the thickness of the impact mitigation layer 220 is 30 μm or more. Although the drop height increases with the thickness of the impact mitigation layer 220, buckling may occur when the display device is folded when the thickness is too large. Therefore, it can be determined that the thickness of the impact mitigation layer 220 is within the range of considering flexibility, such as 80 μm or less. However, the present disclosure is not limited thereto.

[0094] When the tensile modulus of the impact mitigation layer 220 in the form of a film is high, although the hardness is excellent, when the impact mitigation layer 220 is stacked on another layer (e.g., an adjacent layer), buckling is more likely to occur due to the difference in shear stress with the other layer (e.g., an adjacent layer). On the other hand, when the tensile modulus is low, although the impact absorbency is excellent, it may be difficult to handle. The impact mitigation layer 220 in the form of a film was subjected to a pencil lead test. The test results are shown in Table 4 below:

[0095] Table 4

[0096] Tensile modulus of impact reduction layer (GPa) 0.5 1.0 3.0 5.0 6.0 7.0 Pencil hardness (module structure) 3B B H 2H 3H 5H Folding characteristics (curvature 3R inward / outward) good good good good Buckling Buckling

[0097] Referring to Table 4, it can be seen that the surface hardness of the impact mitigation layer 220 in the form of a film increases with the tensile modulus of the impact mitigation layer 220. It should be noted that when the tensile modulus of the impact mitigation layer 220 exceeds 5 GPa, buckling occurs at the interface between the impact mitigation layer 220 in the form of a film and the delay layer 210 or the interface between the impact mitigation layer 220 and the surface layer 230. It can also be seen that when the tensile modulus of the impact mitigation layer 220 is less than 1.0 GPa, the surface hardness drops to 3B. According to an exemplary embodiment of the present disclosure, the tensile modulus of the impact mitigation layer 220 in the form of a film may be in the range of 1 GPa to 5 GPa. By providing an impact mitigation layer 220 having a tensile modulus of 1 GPa to 5 GPa in the flexible window 200 as described above, the impact resistance of the flexible window 200 can be improved and buckling can be suppressed.

[0098] In an exemplary embodiment, the second bonding component CP2 may be disposed between the impact mitigation layer 220 and the delay layer 210. The second bonding component CP2 may be implemented as, but not limited to, an optically clear adhesive (OCA) film and / or an optically clear resin (OCR), etc. The second bonding component CP2 may be used to attach and fix the impact mitigation layer 220 to the delay layer 210.

[0099] The second bonding component CP2 may be disposed on the entire surface area where the impact mitigation layer 220 overlaps the delay layer 210. However, the present disclosure is not limited thereto. The second bonding component CP2 may be disposed only on a portion of the area where the impact mitigation layer 220 overlaps the delay layer 210. For example, the second bonding component CP2 may be disposed along the edge of the area where the impact mitigation layer 220 overlaps the delay layer 210. A plurality of second bonding components CP2 may be disposed in the area where the impact mitigation layer 220 overlaps the delay layer 210, so that they are spaced apart from each other in the form of strips or dots.

[0100] The surface layer 230 may be disposed on the impact mitigation layer 220. The surface layer 230 may include a base layer 233, a hard coating layer (eg, hard coating layer) 235 disposed on the base layer 233, and an anti-fingerprint coating layer 237 disposed on the hard coating layer 235.

[0101] The base layer 233 may include, but is not limited to, polyimide (PI). For example, it may include polymer materials such as polyethylene terephthalate (PET), polycarbonate (PC), and polymethyl methacrylate (PMMA). Considering flexibility and durability, the thickness of the base layer 233 may be in the range of 5 μm to 50 μm, and the tensile modulus may be in the range of 3.5 GPa to 7 GPa. However, the present disclosure is not limited thereto.

[0102] The hard coating layer 235 may be made of a material having a high hardness. The hard coating layer 235 may have a certain flexibility so that it can be bent or folded. Because the hard coating layer 235 may be the top layer directly exposed to the outside, it also needs to have good chemical resistance and corrosion resistance. To this end, the hard coating layer 235 may include an acrylic compound, an epoxy compound, an organic / inorganic coordination compound, or a combination thereof. However, the present disclosure is not limited thereto. The hard coating layer 235 may include an ultraviolet curable resin other than an acrylic compound and / or an epoxy compound. The hard coating layer 235 may have a thickness of 5 μm to 10 μm, a tensile modulus of 3 GPa to 5 GPa, and a microhardness of 50 HV or more. However, the present disclosure is not limited thereto. Because the correlation between microhardness and Vickers hardness is known in the art, the microhardness can be converted into Vickers hardness.

[0103] For example, the hard coating layer 235 may be formed on the base layer 233 by coating. The hard coating layer 235 may be formed by, for example, slide coating, bar coating, spin coating, etc. By doing so, the hard coating layer 235 may be thinly formed on the base layer 233 in consideration of easy bending and / or folding.

[0104] The anti-fingerprint coating layer 237 may include a fluorine (F)-containing compound. Therefore, interference with the flexible window 200 from the outside may be prevented or substantially prevented, and adsorption of foreign matter onto the flexible window 200 may be prevented or substantially prevented.

[0105] In an exemplary embodiment, the third bonding component CP3 may be disposed between the impact mitigation layer 220 and the surface layer 230. The third bonding component CP3 may be implemented as, but not limited to, an optically clear adhesive (OCA) film and / or an optically clear resin (OCR), etc. The third bonding component CP3 may be used to attach and fix the impact mitigation layer 220 to the base layer 233 of the surface layer 230.

[0106] The third bonding component CP3 may be disposed on the entire surface area where the impact mitigation layer 220 overlaps with the base layer 233 of the surface layer 230. However, the present disclosure is not limited thereto. The third bonding component CP3 may be disposed only on a portion of the area where the impact mitigation layer 220 overlaps with the base layer 233 of the surface layer 230. For example, the third bonding component CP3 may be disposed along the edge of the area where the impact mitigation layer 220 overlaps with the base layer 233 of the surface layer 230. A plurality of third bonding components CP3 may be disposed in the area where the impact mitigation layer 220 overlaps with the base layer 233 of the surface layer 230, so that they are spaced apart from each other in the form of strips or dots.

[0107] Figure 4 is a cross-sectional view illustrating a stacking structure of a flexible window according to another exemplary embodiment of the present disclosure. FIG. 5A to FIG. 5Cis a graph showing the relationship between the retardation of a high retardation film and the wavelength in the visible light range.

[0108] Reference Figure 4 According to another exemplary embodiment, the flexible window 200_1 may include a window 200_1 disposed on the display panel 100 (see Figure 1 ) and a surface layer 230 arranged on the high delay layer 223.

[0109] In an exemplary embodiment, the high retardation layer 223 may be implemented as, but not limited to, a high retardation film. The high retardation film used as the high retardation layer 223 according to an exemplary embodiment of the present disclosure may have an in-plane retardation in the range of 6000 nm to 10000 nm.

[0110] The high retardation film may include at least one of a cyclic olefin polymer (COP) film, a cyclic olefin copolymer (COC) film, a polycarbonate (PC) film, a polyethylene terephthalate (PET) film, a polypropylene (PP) film, a polysulfone (PSF) film, and a polymethyl methacrylate (PMMA) film.

[0111] Figure 5A is a graph showing the distribution of transmitted light according to the retardation of the PET film and the relationship between the wavelength in the visible light range. Figure 5B is a graph showing the distribution of transmitted light according to the relationship between the retardation of the PI film and the wavelength in the visible light range. Figure 5C is a graph showing the distribution of transmitted light according to the relationship between the retardation of the high retardation film and the wavelength in the visible light range.

[0112] Reference Figure 5A and Figure 5B , when the display panel 100 (see Figure 3 ) output and passes through the polarization unit PU (see Figure 3 )When linearly polarized light passes through a PET film or a PI film, because the PET film and / or the PI film has a retardation phenomenon, a rainbow spot phenomenon occurs when the transmitted light has a retardation relative to the wavelength in the visible light range. That is, the linearly polarized light incident on the PET film and / or the PI film and passing through the PET film and / or the PI film causes a retardation relative to the wavelength. The graph shows the retardation associated with the wavelength (i.e., the retardation expressed in terms of the length of the wavelength (λ)). When a retardation occurs (e.g., is caused) due to the PET film and / or the PI film, different wavelengths have different retardations associated with the wavelength of the visible light. In addition, it can be seen that as the retardation of the PET film and / or the PI film changes, the retardation associated with the wavelength of each wavelength changes. For example, as the retardation changes, the retardation associated with the polarization unit PU (see Figure 3 ) of the absorption axis OX1 (see Figure 3) The wavelength consistent with the PET film becomes shorter from 780nm to 360nm. As a result, the light transmitted through the PET film and / or the PI film causes a color distortion phenomenon in which rainbow spots are seen due to the transmittance difference between the wavelengths of visible light. When the viewer wears polarized sunglasses PS (see Figure 3 ), this color distortion becomes more noticeable.

[0113] In contrast, reference Figure 5C , when the display panel 100 (see Figure 3 ) output and passes through the polarization unit PU (see Figure 3 ) When the linearly polarized light passes through the high retardation layer 223, it can be seen that the difference in the retardation associated with the wavelength is reduced. In other words, it can be seen that the retardation associated with the wavelength is uniformly distributed. Figure 3 ) of the absorption axis OX1 (see Figure 3 ) is uniformly distributed over a wavelength of 360 nm to 780 nm and the period is very short. In addition, the light transmitted through the high retardation layer 223 does not cause a color distortion phenomenon, i.e., rainbow spots, because the transmittance difference between the wavelengths of visible light is reduced. In addition, even if the viewer wears polarized sunglasses PS (see Figure 3 ), rainbow spots can also be effectively suppressed. In addition, the light transmitted through the high retardation layer 223 has a very short period and is uniformly distributed over a wavelength of 360 nm to 780 nm, which is the same wavelength as the polarization unit PU (see Figure 3 ) is consistent with the absorption axis OX1. Therefore, it is possible to reduce or prevent the light output through the flexible window 200_1 from colliding with the polarized sunglasses PS (see Figure 3 )'s absorption axis OX2 is aligned, making it invisible.

[0114] The thickness of the high-retardation layer 223 included in the flexible window 200 may be in the range of 30 μm to 80 μm. For example, if the thickness of the high-retardation layer 223 in the form of a film is less than 30 μm, it may not be possible to effectively mitigate the impact force from the outside. If the thickness exceeds 80 μm, cracks may occur when the display device is folded. Therefore, the thickness of the high-retardation layer 223 may be in the range of 30 μm to 80 μm, but the present disclosure is not limited thereto.

[0115] According to an exemplary embodiment of the present disclosure, the tensile modulus of the high retardation layer 223 may be in the range of 1 GPa to 5 GPa. By providing the high retardation layer 223 having a tensile modulus of 1 GPa to 5 GPa in the flexible window 200 as described above, the impact resistance of the flexible window 200 may be improved.

[0116] In an exemplary embodiment, the first bonding part CP1 may be disposed between the high retardation layer 223 and the display panel 100 (see Figure 1 ). The first bonding component CP1 may be implemented as an optically clear adhesive (OCA) film and / or an optically clear resin (OCR), etc. In another exemplary embodiment, the first bonding component CP1 may further include a pressure sensitive adhesive (PSA). However, the present disclosure is not limited thereto. The first bonding component CP1 may be used to attach and fix the high retardation layer 223 to the display panel 100 (see Figure 1 ).

[0117] The surface layer 230 may be disposed on the high-retardation layer 223. The surface layer 230 may include a base layer 233, a hard coating layer 235 disposed on the base layer 233, and an anti-fingerprint coating layer 237 disposed on the hard coating layer 235. The second bonding component CP2 may be implemented as, but not limited to, an optically clear adhesive (OCA) film and / or an optically clear resin (OCR), etc. The second bonding component CP2 may be used to attach and fix the high-retardation layer 223 to the base layer 233 of the surface layer 230.

[0118] Figure 6 is a cross-sectional view illustrating a stacking structure of a flexible window according to another exemplary embodiment of the present disclosure.

[0119] In addition to the delay layer 210 being disposed between the impact mitigation layer 220 and the surface layer 230, Figure 6 The flexible window 200_2 is similar to the one mentioned above. Figure 1 The flexible window 200 described is substantially the same. In the following description, redundant descriptions will be omitted (eg, will not be repeated), and the description will be focused on the differences.

[0120] Reference Figure 6 , the flexible window 200_2 may have a stacked structure, wherein the impact mitigation layer 220 is disposed between the first bonding part CP1 and the second bonding part CP2, the delay layer 210 is disposed between the second bonding part CP2 and the third bonding part CP3, and the surface layer 230 is disposed on the third bonding part CP3. The impact mitigation layer 220 may be formed of a polyurethane material, or may be formed of a film such as PET, PC and / or an acryl film.

[0121] The retardation layer 210 may have a retardation of λ / 4 and may include a quarter wave plate (QWP) that converts linear polarized light into circular polarized light or vice versa. However, the present disclosure is not limited thereto. A λ / 4 retardation film such as a reactive wafer film may also be used. When the impact mitigation layer 220 is disposed at the bottom and the retardation layer 210 is disposed thereon, the impact resistance of the entire flexible window 200_2 may also be improved by the impact mitigation layer 220 disposed at the bottom. In addition, since the retardation layer 210 disposed on the impact mitigation layer 220 will pass through the polarization unit PU (see Figure 3) linearly polarized light is converted into circularly polarized light, so it can effectively prevent or reduce the appearance of circularly polarized light when the viewer wears polarized sunglasses PS (see Figure 3 ) may cause shading and color distortion. In other words, the viewer can stably watch the flexible display device 10 with or without polarized sunglasses PS (see Figure 1 ) on the image.

[0122] Figure 7 and Figure 8 is a cross-sectional view illustrating a stacking structure of a flexible window according to other exemplary embodiments of the present disclosure.

[0123] Reference Figure 7 , in the flexible window 200_3 , the impact mitigation layer 220 is disposed on the first bonding part CP1 , the retardation layer 210 is disposed on the impact mitigation layer 220 , and the surface layer 230 is disposed on the retardation layer 210 .

[0124] For example, the second combining component CP2 and the third combining component CP3 may be removed (e.g., not included). Instead, the base layer 233 of the surface layer 230 may be used as a transfer substrate for the delay layer 210, and the delay layer 210 may be directly coated on the rear surface of the base layer 233 opposite to the upper surface where the hard coating layer 235 is disposed. In addition, the impact mitigation layer 220 may be directly coated on the rear surface of the delay layer 210. The impact mitigation layer 220 disposed at the bottom may improve the impact resistance of the entire flexible window 200_3. In addition, since the delay layer 210 disposed on the impact mitigation layer 220 will pass through the polarization unit PU (see Figure 3 ) linearly polarized light is converted into circularly polarized light, so it can effectively prevent or reduce the appearance of circularly polarized light when the viewer wears polarized sunglasses PS (see Figure 3 ) may cause shading and color distortion. In other words, the viewer can stably watch the flexible display device 10 with or without polarized sunglasses PS (see Figure 1 ) on the image. In addition, by forming the delay layer 210 and the impact mitigation layer 220 through coating, the flexible window 200_3 can be made thinner and the manufacturing process can become simpler.

[0125] Reference Figure 8 In the flexible window 200_4, the second bonding part CP2 and the third bonding part CP3 may be removed (e.g., not included). In addition, the impact mitigation layer 220 may be directly coated on the rear surface of the base layer 233 opposite to the upper surface where the hard coating layer 235 is provided, and the delay layer 210 may be directly coated on the rear surface of the impact mitigation layer 220.

[0126] For example, the second combining component CP2 and the third combining component CP3 may be removed (e.g., not included), the impact mitigation layer 220 may be directly coated on the rear surface of the base layer 233 opposite to the upper surface on which the hard coating layer 235 is disposed, and the delay layer 210 may be directly coated on the rear surface of the impact mitigation layer 220. By disposing the hard coating layer 235 and the impact mitigation layer 220 and disposing the base layer 233 therebetween, external impacts may be more effectively absorbed near the surface layer 230, thereby further improving the impact resistance of the entire flexible window 200_4. In addition, since the delay layer 210 disposed below the impact mitigation layer 220 will pass through the polarization unit PU (see Figure 3 ) linearly polarized light is converted into circularly polarized light, thus effectively preventing or reducing the appearance of circularly polarized light when the viewer is wearing polarized sunglasses PS (see Figure 3 ) may cause shading and color distortion. In other words, the viewer can stably watch the flexible display device 10 with or without polarized sunglasses PS (see Figure 1 ) on the image. In addition, by forming the delay layer 210 and the impact mitigation layer 220 through coating, the flexible window 200_4 can be made thinner and the manufacturing process can become simpler.

[0127] Fig. 9 and Fig.10 is a cross-sectional view illustrating a stacking structure of a flexible window according to other exemplary embodiments of the present disclosure.

[0128] Reference Fig. 9 The flexible window 200_5 may include a first combining component CP1, an optical plate PCP disposed on the first combining component CP1, a second combining component CP2 disposed on the optical plate PCP, an impact mitigation layer 220 disposed on the second combining component CP2, a delay layer 210 disposed on the impact mitigation layer 220, and a surface layer 230 disposed on the delay layer 210.

[0129] In addition to the optical plate PCP being attached below the impact mitigation layer 220 via the second bonding part CP2, Fig. 9 The flexible window 200_5 and Figure 7 Therefore, the same elements will not be described in detail to avoid redundancy.

[0130] The optical plate PCP attached to the impact mitigation layer 220 below the second bonding part CP2 may be a retardation film. The optical plate PCP may be a positive c-plate. Referring to the above equations 1 to 3, the relationship between the refractive indexes of the optical plate PCP may be expressed as: nz>nx=ny. By adjusting the retardation value Re in the plane direction and the retardation value Rth in the thickness direction of the optical plate PCP, the retardation value Re in the plane direction and the retardation value Rth in the thickness direction may be adjusted when the light passes through the polarization unit PU (see Figure 3 ) delays the phase of light incident on the optical plate PCP after linear polarization.

[0131] For example, in the flexible window 200_5, the base layer 233 of the surface layer 230 can be used as a transfer substrate for the delay layer 210, and the delay layer 210 can be directly coated on the rear surface of the base layer 233 opposite to the upper surface where the hard coating layer 235 is provided. In addition, the impact mitigation layer 220 can be directly coated on the rear surface of the delay layer 210. The optical plate PCP can be disposed on the rear surface of the impact mitigation layer 220 through the second bonding component CP2. Figure 3 ) The phase of the linearly polarized light incident on the flexible window 200_5 is delayed by the optical plate PCP disposed thereunder. In addition, the phase is further delayed by the delay layer 210 disposed on the optical plate PCP. By doing so, it is possible to more effectively prevent or reduce the occurrence of light leakage when the viewer wears polarized sunglasses PS (see Figure 3 ) caused by the shading phenomenon and color distortion phenomenon. In addition, the impact mitigation layer 220 is disposed between the optical plate PCP and the delay layer 210 to improve the impact resistance of the entire flexible window 200_5. In addition, by forming the delay layer 210 and the impact mitigation layer 220 by coating, the flexible window 200_5 can be made thinner and the manufacturing process can be simpler.

[0132] Reference Fig.10 The flexible window 200_6 may include a first combining component CP1, an optical plate PCP disposed on the first combining component CP1, a second combining component CP2 disposed on the optical plate PCP, a delay layer 210 disposed on the second combining component CP2, an impact mitigation layer 220 disposed on the delay layer 210, and a surface layer 230 disposed on the impact mitigation layer 220.

[0133] In addition to the position of the impact mitigation layer 220 being swapped with the position of the delay layer 210, Fig.10 The flexible window 200_6 and Fig. 9 In other words, except that the retardation layer 210 is disposed between the optical plate PCP and the impact mitigation layer 220, Fig.10 The flexible window 200_6 and Fig. 9 The flexible window 200_5 is substantially the same; therefore, a redundant description will be omitted (eg, will not be repeated).

[0134] Although mainly described the embodiments of the present invention, they are only examples and are not intended to limit the present invention. It will be appreciated by those skilled in the art that various modifications and applications not shown above may be made without departing from the essential features of the embodiments of the present invention. For example, each component specifically shown in the embodiments of the present invention may be put into practice by modification. In addition, the differences associated with these modifications and applications should be interpreted as being included within the scope of the present invention defined by the appended claims and their equivalents.

Claims

1. A flexible window, in, The flexible window comprises: Delay layer; an impact mitigation layer disposed on the delay layer; and a surface layer, located on the impact reduction layer, Wherein, the retardation layer comprises a λ / 4 retardation plate; The impact mitigation layer is made of a polyurethane-based material, the thickness of the impact mitigation layer is in the range of 70 μm to 150 μm, and the tensile modulus of the impact mitigation layer is in the range of 0.01 GPa to 0.5 GPa; or, The impact mitigation layer is a film made of at least one material selected from polyethylene terephthalate, polycarbonate, and acrylic, has a thickness in the range of 30 μm to 80 μm, and has a tensile modulus in the range of 1 GPa to 5 GPa.

2. The flexible window according to claim 1, in, The impact mitigation layer is directly coated on the rear surface of the surface layer.

3. The flexible window according to claim 2, in, The delay layer is directly coated on the rear surface of the impact mitigation layer.

4. The flexible window according to claim 3, in, The flexible window also includes a positive c-plate located below the retardation layer.

5. The flexible window according to claim 1, in, The surface layer includes a base layer, a hard coating layer located on the base layer, and an anti-fingerprint coating layer located on the hard coating layer.

6. A flexible window, in, The flexible window comprises: High latency tier; and a surface layer, located on the high-retardation layer, The surface layer includes a base layer, a hard coating layer on the base layer, and an anti-fingerprint coating layer on the hard coating layer, and Wherein, the in-plane retardation of the high retardation layer is in the range of 6000nm to 10000nm; The high retardation layer includes at least one of a cycloolefin polymer film, a cycloolefin copolymer film, a polycarbonate film, a polyethylene terephthalate film, a polypropylene film, a polysulfone film, and a polymethyl methacrylate film; and The thickness of the high retardation layer is in the range of 30 μm to 80 μm, and the tensile modulus of the high retardation layer is in the range of 1 GPa to 5 GPa.

7. A flexible display device, in, The flexible display device comprises: Display panel; a flexible window located on the display panel; and A pressure-sensitive adhesive is disposed between the display panel and the flexible window, wherein the flexible window comprises a retardation layer, an impact mitigation layer located on the retardation layer, and a surface layer located on the impact mitigation layer, and wherein the retardation layer comprises a λ / 4 retardation plate; The impact mitigation layer is made of a polyurethane-based material; The impact mitigation layer has a thickness in the range of 70 μm to 150 μm; and The tensile modulus of the impact mitigation layer is in the range of 0.01 GPa to 0.5 GPa.

8. The flexible display device according to claim 7, in, The impact mitigation layer is directly coated on the rear surface of the surface layer.

9. The flexible display device according to claim 8, in, The delay layer is directly coated on the rear surface of the impact mitigation layer.

10. The flexible display device according to claim 9, in, The flexible display device also includes a positive c-plate located below the retardation layer.

Images