Flexible display device

Abstract

A flexible display device is disclosed. The flexible display device includes a display panel, a cover window disposed on the display panel, and a first adhesive layer disposed between the display panel and the cover window, wherein the first adhesive layer includes a first pressure-sensitive adhesive layer, a second pressure-sensitive adhesive layer, and a first elastomer layer disposed between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 10-2019-0013738, filed on February 1, 2019, which is hereby incorporated by reference for all purposes as if fully set forth herein. Technical Field

[0003] Exemplary embodiments of the present invention generally relate to a flexible display device, and more particularly, to a flexible display device including an adhesive layer. Background Art

[0004] Display devices such as organic light-emitting displays (OLEDs) and liquid crystal displays (LCDs) include display panels fabricated by forming several layers and components on a substrate. Glass is commonly used as the substrate for display panels. However, glass substrates are heavy and can easily break. Furthermore, glass substrates are generally rigid, making it difficult to deform the display device. Recently, flexible display panels and flexible display devices including these flexible display panels have been developed, using lightweight, impact-resistant, and easily deformable flexible substrates.

[0005] Flexible display devices can be categorized as bendable, foldable, rollable, and stretchable, depending on their application and form. To protect the flexible display panel, a cover window may be attached to it. To make a flexible display device bendable, foldable, rollable, or stretchable, the window must also be flexible. However, flexible windows can be more susceptible to impact than rigid windows.

[0006] The above information disclosed in this Background section is only for understanding the background of the present inventive concept and therefore it may contain information that does not constitute prior art. Summary of the Invention

[0007] The flexible display device constructed according to the exemplary embodiment of the present invention has improved impact resistance while satisfying the characteristics of a flexible display device.

[0008] Additional features of the inventive concept will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the inventive concept.

[0009] A flexible display device according to an exemplary embodiment includes a display panel, a cover window arranged on the display panel, and a first adhesive layer arranged between the display panel and the cover window, wherein the first adhesive layer includes a first pressure-sensitive adhesive layer, a second pressure-sensitive adhesive layer, and a first elastomer layer arranged between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer.

[0010] The flexible display device may also include a first functional layer arranged between the first adhesive layer and the display panel and a second adhesive layer arranged between the first functional layer and the display panel, wherein the second adhesive layer may include a third pressure-sensitive adhesive layer, a fourth pressure-sensitive adhesive layer and a second elastomer layer arranged between the third pressure-sensitive adhesive layer and the fourth pressure-sensitive adhesive layer.

[0011] The first functional layer may include at least one of a polarizing layer and a touch panel.

[0012] The flexible display device may also include a second functional layer arranged between the second adhesive layer and the display panel and a third adhesive layer arranged between the second functional layer and the display panel, wherein the third adhesive layer may include a fifth pressure-sensitive adhesive layer, a sixth pressure-sensitive adhesive layer and a third elastomer layer located between the fifth pressure-sensitive adhesive layer and the sixth pressure-sensitive adhesive layer.

[0013] The second functional layer may include at least one of a polarizing layer and a touch panel.

[0014] The first adhesive layer may have a thickness of less than about 75 microns.

[0015] The adhesion between the first pressure-sensitive adhesive layer and the first elastomer layer may be about 400 gf / in 2 or larger.

[0016] The first elastomeric layer may have a modulus of about 100 kPa or less.

[0017] The first adhesive layer may further include a side pressure-sensitive adhesive layer surrounding a side of the first elastomer layer.

[0018] The first elastomeric layer may include an elastomeric base layer and a plurality of posts disposed within the elastomeric base layer.

[0019] The plurality of pillars may have a higher modulus than the elastomeric base layer.

[0020] The plurality of pillars may have lower end portions in contact with the first pressure-sensitive adhesive layer and upper end portions in contact with the second pressure-sensitive adhesive layer.

[0021] The first adhesive layer may further include a third pressure-sensitive adhesive layer and a second elastomer layer between the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer.

[0022] The first elastomer layer may include a cutting pattern formed on at least one surface thereof, the cutting pattern being formed in a direction inclined with respect to a longitudinal direction of the first elastomer layer.

[0023] The first elastomer layer may include a lower elastomer layer, a middle elastomer layer, and an upper elastomer layer that are sequentially stacked, and the middle elastomer layer may include a groove pattern formed on at least one surface thereof.

[0024] The first elastomer layer may include a lower elastomer layer and an upper elastomer layer that are sequentially stacked, and the lower elastomer layer and the upper elastomer layer may include a groove pattern formed at an interface therebetween.

[0025] The first elastomeric layer may include a pattern of holes formed therein.

[0026] According to another exemplary embodiment, a flexible display device includes a display panel, a cover window arranged on the display panel, at least one functional layer arranged between the cover window and the display panel, a first adhesive layer arranged between the display panel and the functional layer, and a second adhesive layer arranged between the functional layer and the cover window, wherein each of the first adhesive layer and the second adhesive layer may include a plurality of pressure-sensitive adhesive layers and at least one elastomer layer arranged between the plurality of pressure-sensitive adhesive layers.

[0027] Each of the first adhesive layer and the second adhesive layer may further include a side pressure-sensitive adhesive layer surrounding a side of the corresponding elastomer layer.

[0028] The elastomeric layer may include an elastomeric base layer and a plurality of posts disposed within the elastomeric base layer.

[0029] Example embodiments may provide a flexible display device having improved impact resistance while satisfying characteristics of the flexible display device.

[0030] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the inventive concept.

[0032] Figure 1 is a perspective view schematically illustrating an unfolded state of a foldable display device according to an exemplary embodiment.

[0033] Figure 2 It is schematically shown Figure 1 A perspective view of a foldable display device in a first folded state.

[0034] Figure 3 It is schematically shown Figure 1 A perspective view of a foldable display device in a second folded state.

[0035] Figure 4 According to an exemplary embodiment, Figure 1 A cross-sectional view taken along line IV-IV'.

[0036] Figure 5 、 Figure 6 、 Figure 7 、 Figure 8 、 Figure 9 、 Figure 10 、 Figure 11 、 Figure 12 、 Figure 13 and Figure 14 is a view illustrating a structure of an adhesive layer according to an exemplary embodiment.

[0037] Figure 15 is a cross-sectional view of a display panel according to an exemplary embodiment. DETAILED DESCRIPTION

[0038] In the following description, for the purpose of explanation, many specific details are set forth to provide a thorough understanding of various exemplary embodiments or implementations of the present invention. As used herein, "implementation" and "implementation" are interchangeable words, which are non-limiting examples of one or more devices or methods using the inventive concept disclosed herein. However, it is apparent that various exemplary embodiments can be put into practice without specific details or with one or more equivalent arrangements. In other examples, known structures and devices are shown in block diagram form to avoid unnecessary confusion of various exemplary embodiments. In addition, various exemplary embodiments may be different, but do not have to be exclusive. For example, without departing from the inventive concept, the specific shape, configuration and characteristics of the exemplary embodiment can be used or implemented in another exemplary embodiment.

[0039] Unless otherwise indicated, the exemplary embodiments shown should be understood as providing exemplary features of different details that can implement some ways of implementing the inventive concept in practice. Therefore, unless otherwise indicated, the features, components, modules, layers, films, panels, regions and / or aspects of the various embodiments (hereinafter individually or collectively referred to as "elements") may be combined, separated, interchanged and / or rearranged in other ways without departing from the inventive concept.

[0040] The use of cross hatching and / or shading in the accompanying drawings is generally provided to clarify the boundaries between adjacent elements. Thus, unless otherwise indicated, the presence or absence of cross hatching or shading does not convey or indicate any preference or requirement for a particular material, material properties, size, ratio, commonality between the elements shown and / or any other characteristics, attributes, performance, etc. of the elements. In addition, in the accompanying drawings, the sizes and relative sizes of the elements may be exaggerated for clarity and / or descriptive purposes. When the exemplary embodiments can be implemented differently, the specific process sequence may be performed differently from the described sequence. For example, two consecutively described processes may be performed substantially simultaneously or in an order opposite to the described order. Moreover, the same reference numerals represent the same elements.

[0041] When an element or layer is referred to as being "on" another element or layer, "connected to" or "coupled to" another element or layer, it may be directly on, connected to or coupled to the other element or layer, or there may be intermediate elements or layers. However, when an element or layer is referred to as being "directly on" another element or layer, "directly connected to" or "directly coupled to" another element or layer, there are no intermediate elements or layers. For this purpose, the term "connected" may indicate a physical, electrical and / or fluid connection with or without intermediate elements. In addition, the D1-axis, D2-axis and D3-axis are not limited to the three axes of a rectangular coordinate system (such as the x-axis, y-axis and z-axis) and may be interpreted in a broader sense. For example, the D1-axis, D2-axis and D3-axis may be perpendicular to each other, or may represent different directions that are not perpendicular to each other. For purposes of this disclosure, "at least one of X, Y, and Z" and "at least one selected from the group consisting of X, Y, and Z" may be interpreted as only X, only Y, only Z, or any combination of two or more of X, Y, and Z, such as, for example, XYZ, XYY, YZ, and ZZ. As used herein, the term "and / or" includes any and all combinations of one or more of the associated listed items.

[0042] Although the terms "first," "second," etc., may be used herein to describe various types of elements, these elements should not be limited by these terms. These terms are used to distinguish one element from another. Thus, the first element discussed below may be referred to as the second element without departing from the teachings of the present disclosure.

[0043] Spatially relative terms such as "beneath," "below," "under," "lower," "above," "upper," "over," "higher," "side" (e.g., as in "sidewall"), etc., may be used herein for descriptive purposes, and thus, to describe the relationship of one element to another element as shown in the accompanying drawings. Spatially relative terms are intended to encompass different orientations of the device in use, operation, and / or manufacture in addition to the orientation depicted in the accompanying drawings. For example, if the device in the drawings is turned over, elements described as "below" or "beneath" other elements or features would then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both orientations of above and below. Furthermore, the device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and thus, the spatially relative descriptors used herein are to be interpreted accordingly.

[0044] The terms used herein are for the purpose of describing particular embodiments and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "a," "an," and "the," as used herein, are intended to include the plural forms as well. In addition, when the terms "comprise," "comprising," "include," and / or "including," are used in this specification, they indicate the presence of the stated features, wholes, steps, operations, elements, parts, and / or clusters thereof, but do not preclude the presence or addition of one or more other features, wholes, steps, operations, elements, parts, and / or clusters thereof. It is also noted that, as used herein, the terms "substantially," "about," and other similar terms are used as terms of approximation rather than terms of degree, and thus, are intended to take into account the inherent deviations in measured, calculated, and / or provided values that one of ordinary skill in the art will recognize.

[0045] Various exemplary embodiments are described herein with reference to cross-sectional and / or exploded views that are schematic illustrations of idealized exemplary embodiments and / or intermediate structures. Thus, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and / or tolerances, are to be expected. Thus, the exemplary embodiments disclosed herein should not necessarily be construed as limited to the specific illustrated shapes of regions, but rather include deviations in shape that result, for example, from manufacturing. In this manner, the regions illustrated in the figures may be schematic in nature, and the shapes of these regions may not reflect the actual shapes of regions of a device and, thus, are not necessarily intended to be limiting.

[0046] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. Unless expressly defined as such herein, terms such as those defined in commonly used dictionaries should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense.

[0047] The following will refer to Figures 1 to 3 A flexible display device according to an exemplary embodiment is described.

[0048] Figure 1 is a perspective view schematically showing an unfolded state of a foldable display device according to an exemplary embodiment, Figure 2 It is schematically shown Figure 1 A perspective view of a first folded state of the foldable display device, and Figure 3 It is schematically shown Figure 1 A perspective view of a foldable display device in a second folded state.

[0049] like Figure 1 As shown in FIG, the foldable display device 1 (hereinafter referred to as the display device) can be fully unfolded to be substantially flat and can be used as Figure 2 and Figure 3 The display device 1 may be folded as shown in FIG. The display device 1 may include a bending area BA and first and second flat areas FA1 and FA2 located on either side of the bending area BA. The bending area BA is a region that can bend when the display device 1 is folded, and the first and second flat areas FA1 and FA2 are regions that are substantially unbendable. When the display device 1 is unfolded, the bending area BA may be substantially flat.

[0050] Figures 1 to 3 The display device 1 is shown as including one curved area BA, however, the present invention is not limited thereto. In some exemplary embodiments, the display device 1 may include a plurality of curved areas BA separated from each other, and the plurality of curved areas BA may be curved with different radii of curvature. For example, the display device 1 may include two or more curved areas and three or more flat areas.

[0051] The display device 1 may include a display area DA displaying an image and a non-display area NA surrounding the display area DA. The display area DA may correspond to a screen in which pixels PX are arranged, and the non-display area NA may correspond to a bezel.

[0052] like Figure 2 As shown in , the display device 1 can be folded so that the screen is exposed to the outside (hereinafter referred to as outward folding or first folding). Figure 3 As shown in , the display device 1 can be folded so that the screens face each other, that is, the screen of the first flat area FA1 and the screen of the second flat area FA2 face each other (hereinafter referred to as the inward fold or the second fold). In the outward folded state, the screen of the curved area BA can be exposed to the user so as to be visible, while in the inward folded state, the screen of the curved area BA can be hidden. According to an exemplary embodiment, the display device 1 can be designed to bend in only one of the outward folding and the inward folding. According to another exemplary embodiment, when the display device 1 includes a plurality of curved areas BA, one of the plurality of curved areas BA may be a curved area that can be folded outward, and another of the plurality of curved areas BA may be a curved area that can be folded inward.

[0053] The display device 1 may further include a housing that may receive several components of the display device 1, such as a display panel, a driving device, a processor, a memory, a printed circuit board (PCB), a battery, a communication module, a speaker, and various sensors.

[0054] Figure 4 It is along Figure 1 A cross-sectional view taken along line IV-IV'.

[0055] Reference Figure 4 The display device 1 has a structure composed of various stacked layers or components. The display device 1 includes a display panel DP and a cover window CW that protects the display panel DP. At least one of the functional layers FL1 and FL2 may be disposed between the display panel DP and the cover window CW. A base film BF may be disposed below the display panel DP. A buffer layer CL may be disposed below the base film BF. The display panel DP, cover window CW, functional layers FL1 and FL2, base film BF, and buffer layer CL may be attached via adhesive layers AL1 to AL5.

[0056] The display panel DP is a panel including a substrate on which pixels capable of displaying an image are formed. The display panel DP may include light-emitting diodes (LEDs) corresponding to the pixels. The display panel DP may be flexible so that at least a portion thereof can be bent. For example, the display panel DP may be flexible and bendable at least in an area corresponding to the bending area BA of the display device 1, or in some exemplary embodiments, the display panel DP may be flexible across the entire substrate.

[0057] The cover window CW is an optically transparent layer, and has a surface exposed to the outside of the display device 1. The cover window CW may protect underlying structures, particularly, the display panel DP.

[0058] The cover window CW may be flexible, and at least a portion thereof may be bendable. For example, the cover window CW may be flexible and bendable through at least the area thereof corresponding to the curved area BA of the display device 1, or in some exemplary embodiments, the entire portion of the cover window CW may be flexible. According to an exemplary embodiment, the cover window CW may be a polymer film including a polymer such as polyimide (PI) or polyethylene terephthalate (PET), and have flexible properties. According to another exemplary embodiment, the cover window CW may be a glass film formed to be thin throughout the entire portion (e.g., a thickness of less than about 100 microns), or may be locally formed to be thin in one or more areas corresponding to the curved area BA of the display device 1. In this way, the flexible cover window CW may be more fragile than a rigid cover window (e.g., a glass substrate having a thickness greater than about 100 microns) in terms of protecting the display panel DP from external impacts.

[0059] A first functional layer FL1 and a second functional layer FL2 may be disposed between the display panel DP and the cover window CW. As used herein, a functional layer may refer to a layer having a stacked structure to perform a specific function other than adhesion. For example, one of the first functional layer FL1 and the second functional layer FL2 may be a touch panel, while the other may be an anti-reflection layer.

[0060] In a touch panel, for example, a touch sensor layer may be formed on a polymer film such as polyimide. The touch sensor layer may sense contact and / or contactless touch by a user. The touch sensor layer may include touch electrodes formed of a transparent conductive material such as indium tin oxide (ITO), indium zinc oxide (IZO), a metal mesh, etc., and the touch electrodes may be formed as a single layer or multiple layers. According to an exemplary embodiment, the touch sensor layer may not be provided as a separate touch panel, but may be formed directly on the surface of the display panel DP.

[0061] The anti-reflection layer may reduce external light reflection and include a polarizing layer and / or a phase retardation layer having a film shape. The anti-reflection layer may be directly formed on the display panel DP, for example, may be coated on the display panel DP.

[0062] The base film BF arranged below the display panel DP may have a relatively high modulus (or elastic coefficient). The base film BF improves the deformation of the curved area BA and allows the curved area BA to bend with a constant curvature. When handling the display device 1, etc., the base film BF can reduce the impact of the impact applied to the back of the display device 1. The base film BF may include a metal or a metal alloy, such as Invar, stainless steel (also known as SUS), and may have a thickness of about 15 microns to about 50 microns, but is not limited thereto. When the base film BF includes a metal, its modulus may be about 10 GPa to about 100 GPa, or in some exemplary embodiments, 100 GPa or higher. The base film BF may also include a polymer, such as polyimide (PI) or polyethylene terephthalate (PET). When the base film BF includes a polymer, its modulus may be about 1 GPa to about 10 GPa, or in some exemplary embodiments, about 4 GPa to about 6 GPa.

[0063] The buffer layer CL disposed beneath the base film BF protects the overlying structure, particularly the display panel DP. The buffer layer CL absorbs shock to protect the display panel DP and allows the display panel DP to be attached to other components (such as a frame, bracket, housing, etc.) without being damaged. For example, the buffer layer CL may be a porous layer such as a foam resin. According to exemplary embodiments, in addition to the buffer layer CL, functional sheets such as a light shielding sheet, a heating sheet, and a waterproof tape may also be included beneath the base film BF.

[0064] In the exemplary embodiment shown, adhesive layers AL1 to AL5 may be formed between the cover window CW and the first functional layer FL1, between the first functional layer FL1 and the second functional layer FL2, between the second functional layer FL2 and the display panel DP, between the display panel DP and the base film BF, and between the base film BF and the buffer layer CL, respectively, to bond adjacent layers to one another. When each of the adhesive layers AL1 to AL5 is formed solely with a pressure-sensitive adhesive, the display device 1 may be vulnerable to external impacts. For example, when a pen drop or the like imparts an impact to the front surface of the display device 1, the flexible cover window CW may not adequately protect the display panel DP from such impact, resulting in damage to the display panel DP or the touch panel, such as cracking, short circuiting, and disconnection of components therein. Furthermore, warping or cracking may occur in the cover window CW, the first functional layer FL1, and / or the second functional layer FL2.

[0065] Hereinafter, adhesive layers AL1 to AL5 capable of improving impact resistance while satisfying the flexibility characteristics of the flexible display device 1 will be described.

[0066] Figures 5 to 14 is a view illustrating a structure of an adhesive layer according to an exemplary embodiment. Figures 5 to 7 and Figures 9 to 14is a vertical cross-section, and Figure 8 At least one of the above-mentioned adhesive layers AL1 to AL5 may have a Figures 5 to 14 The structure of the adhesive layer AL is shown in FIG.

[0067] Reference Figure 5 The adhesive layer AL according to the exemplary embodiment has a structure in which a first pressure-sensitive adhesive layer 11, an elastomer layer 20, and a second pressure-sensitive adhesive layer 12 are stacked. According to the exemplary embodiment, a rubber such as polyurethane (PU) can be used as the elastomer layer 20. In this way, since the elastomer layer 20 has excellent impact absorption and resilience, the impact resistance of the display device 1 can be increased compared to when the adhesive layer AL is formed as a single-layer pressure-sensitive adhesive layer. In addition, the elastomer layer 20 can be advantageous in maintaining the original shape of the adhesive layer AL or the display device 1.

[0068] Bending the curved area BA may generate stress in the display device 1. In this case, if shear deformation does not occur well in the adhesive layer AL, warping may occur in the functional layers FL1 and FL2 or the cover window CW, which may cause separation of these layers. Therefore, in order to prevent the occurrence of warping or separation, the elastomer layer 20 may have a modulus similar to that of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12, for example, such as about 100 kPa or less, so that shear deformation of the adhesive layer AL can occur well in the adhesive layer AL. In this case, even if the elastomer layer 20 is interposed between the two pressure-sensitive adhesive layers 11 and 12, the adhesive layer AL can also serve as a layer to resist stress. The modulus of the elastomer layer 20 may vary depending on the temperature. For example, the elastomer layer 20 may have a modulus of about 10 MPa or less at low temperatures (e.g., -20°C), a modulus of about 100 kPa or less at room temperature (e.g., 25°C), and a modulus of about 10 kPa or less at high temperatures (e.g., 80°C).

[0069] When the bending area BA is bent, separation of the first and second pressure-sensitive adhesive layers 11 and 12 from the elastomer layer 20 may occur in the adhesive layer AL. Thus, the interfacial adhesion between the first and second pressure-sensitive adhesive layers 11 and 12 and the elastomer layer 20 may be about 400 gf / in 2 or larger to prevent separation from occurring.

[0070] When the adhesive layer AL is thick, it may not only increase the thickness of the display device 1, but may also cause the layers bonded by the adhesive layer AL to warp. This is because warping is more likely to occur in thin layers, and when the adhesive layer AL is formed thick, the bonded layers will be formed relatively thin. Accordingly, the adhesive layer AL may have a thickness of about 75 microns or less, about 60 microns or less, or about 50 microns or less. For example, the elastomer layer 20 may have a thickness of about one to about five times, or about two to three times, the thickness of the first pressure-sensitive adhesive layer 11 or the second pressure-sensitive adhesive layer 12. As the elastomer layer 20 is formed thinner, the impact absorption capacity of the adhesive layer AL may deteriorate. Thus, when the elastomer layer 20 is formed thicker, the thickness of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 may be formed thinner, which may deteriorate the adhesion of the adhesive layer AL. The first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 may have the same or similar thickness. For example, when the thickness of the adhesive layer AL is about 75 micrometers, the thickness of each of the first and second pressure-sensitive adhesive layers 11 and 12 may be about 15 micrometers, and the thickness of the elastomer layer 20 may be about 35 micrometers.

[0071] High elasticity of the adhesive layer AL can reduce the occurrence of warping in the layers bonded by the adhesive layer AL. The adhesive layer AL may have a recovery characteristic greater than 90% or greater than 95%. As used herein, recovery characteristic refers to the degree to which the shape and size of a material return to its original shape and size after one second from deformation.

[0072] Reference Figure 6 , according to the exemplary embodiment, the adhesive layer AL and Figure 5 The adhesive layer AL is substantially the same as that of the embodiment, however, the elastomer layer 20 according to the exemplary embodiment is sealed by the pressure-sensitive adhesive layers 11, 12, and 15. In detail, the adhesive layer AL has a structure in which the first pressure-sensitive adhesive layer 11, the elastomer layer 20, and the second pressure-sensitive adhesive layer 12 are stacked, and the side pressure-sensitive adhesive layer 15 surrounds the side of the elastomer layer 20.

[0073] Figure 7 and Figure 8 1 and 2 are vertical and horizontal cross-sectional views of an adhesive layer AL according to an exemplary embodiment. Figure 6Compared to the adhesive layer AL of the exemplary embodiment shown in FIG, the adhesive layer AL according to the exemplary embodiment has a difference in the structure of the elastomer layer 20. In detail, the elastomer layer 20 has a structure in which hard elastomer columns 26 having a higher modulus are arranged in an elastomer base layer 25 having a lower modulus. For example, in the elastomer layer 20, hard elastomer columns 26 each having a modulus of about 1 MPa to about 10 MPa may be formed at predetermined intervals in the soft elastomer base layer 25 having a modulus of about 1 kPa to about 100 kPa. In some exemplary embodiments, the hard elastomer columns 26 may have a modulus of 10 MPa or greater. The lower end portion of each hard elastomer column 26 may be in contact with the first pressure-sensitive adhesive layer 11. The upper end portion of each hard elastomer column 26 may be in contact with the second pressure-sensitive adhesive layer 12. The elastomer layer 20 may be surrounded by the first pressure-sensitive adhesive layer 11, the second pressure-sensitive adhesive layer 12, and the side pressure-sensitive adhesive layer 15. Alternatively, in some exemplary embodiments, at least one of the sides of the elastomeric layer 20 may be surrounded by a pressure-sensitive adhesive layer.

[0074] Since the hard elastomer columns 26 are included in the elastomer base layer 25, the hard elastomer columns 26 can protect the configuration of the display device 1 including the display panel DP from impact when the elastomer layer 20 is formed. Moreover, when the display device 1 is bent, in the bending area BA, the hard elastomer columns 26 can maintain the adhesive layer AL at a predetermined thickness to improve the deformation of the bending area BA, and the bending area BA can be bent with a constant curvature. Moreover, since the hard elastomer is inserted into the soft elastomer base layer 25 in the form of a column, the hard elastomer columns 26 may be easily tilted when a shear force is applied. Thus, even if the adhesive layer AL includes the hard elastomer columns 26, shear deformation may occur, thereby preventing the occurrence of warping in the layer bonded by the adhesive layer AL.

[0075] The hard elastomer columns 26 in the elastomer base layer 25 can be formed by, for example, forming holes in the elastomer layer 20 having a low modulus using a mask or by a laser and filling them with a resin having a high modulus. In the elastomer layer 20 having a low modulus, the portion where the holes are not formed becomes the elastomer base layer 25, and the resin having a high modulus filled in the holes becomes the hard elastomer columns 26. As another example, the hard elastomer columns 26 can be formed in the elastomer layer 20 by irradiating ultraviolet rays to the portion having a low modulus of the elastomer layer 20 using a mask to partially cure the portion of the elastomer layer 20. The uncured portion in the elastomer layer 20 becomes the elastomer base layer 25, and the cured portion becomes the hard elastomer columns 26.

[0076] Reference Figure 9, the adhesive layer AL according to the exemplary embodiment includes a plurality of elastomer layers 21 and 22. The adhesive layer AL according to the illustrated exemplary embodiment has a structure in which a first pressure-sensitive adhesive layer 11, a first elastomer layer 21, a second pressure-sensitive adhesive layer 12, a second elastomer layer 22, and a third pressure-sensitive adhesive layer 13 are sequentially stacked. When the adhesive layer AL includes a plurality of elastomer layers 21 and 22, each of the elastomer layers 21 and 22 may be formed thinner than the thickness of the above-mentioned elastomer layers to avoid increasing the overall thickness of the adhesive layer AL. For example, when the thickness of the adhesive layer AL is about 65 micrometers, each of the first pressure-sensitive adhesive layer 11, the second pressure-sensitive adhesive layer 12, and the third pressure-sensitive adhesive layer 13 may have a thickness of about 15 micrometers, and the thickness of the first elastomer layer 21 and the second elastomer layer 22 may be about 10 micrometers.

[0077] like Figure 5 and Figure 6 As shown in , when the adhesive layer AL includes a plurality of elastomer layers 21 and 22 joined by the second pressure-sensitive adhesive layer 12 , the flexibility of the adhesive layer AL may be improved compared to the adhesive layer AL including a single layer of the elastomer layer 20 .

[0078] like Figure 5 As in the adhesive layer AL, refer to Figure 10 , the adhesive layer AL according to the exemplary embodiment has a structure in which a first pressure-sensitive adhesive layer 11, an elastomer layer 20, and a second pressure-sensitive adhesive layer 12 are stacked. However, the elastomer layer 20 according to the exemplary embodiment shown is cut from the surface in an oblique direction (for example, a direction oblique with respect to the third direction z or the length direction of the adhesive layer AL) at predetermined intervals and a predetermined depth. Hereinafter, these cuts in the elastomer layer 20 will be referred to as cutting patterns CP. The cutting patterns CP can increase the surface roughness of the elastomer layer 20 so that the adhesion of the elastomer layer 20 to the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 can be improved. Moreover, when an air layer is formed on the elastomer layer 20 by the cutting patterns CP, the cushioning capacity of the elastomer layer 20 can be improved.

[0079] In order to prevent the cutting pattern CP from being recognized as much as possible, the cutting direction for forming the cutting pattern CP (hereinafter referred to as the direction of the cutting pattern CP) may be in an inclined direction. In this way, the light incident on the adhesive layer AL from the opposite side of the screen may not be completely reflected by the cutting pattern CP, so that the cutting pattern CP can be reduced or prevented from being recognized. In addition, according to an exemplary embodiment, the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 may undergo an atomization treatment so as to further prevent or inhibit the cutting pattern CP from being recognized by the user. The atomization treatment may include, for example, mixing particles into the material forming the pressure-sensitive adhesive layers 11 and 12, or coating the surfaces of the pressure-sensitive adhesive layers 11 and 12.

[0080] According to the exemplary embodiment shown, Figure 10 As shown in , the cutting pattern CP is formed on both surfaces of the elastomer layer 20, however, the present inventive concept is not limited thereto. For example, in some exemplary embodiments, the cutting pattern CP may be formed on only one surface of the elastomer layer 20. For example, when the display device 1 is manufactured as a device that folds inward, the cutting pattern CP may be formed only at the upper surface in contact with the second pressure-sensitive adhesive layer 12. As another example, when the display device 1 is manufactured as a device that folds outward, the cutting pattern CP may be formed only at the lower surface in contact with the first pressure-sensitive adhesive layer 11. In this way, when the display device 1 is folded, the cutting pattern CP can be prevented from being opened and visible.

[0081] Figure 11 is a cross-sectional view of the adhesive layer AL when the display device 1 is unfolded, and Figure 12 is a cross-sectional view of the adhesive layer AL when the display device 1 is folded.

[0082] Reference Figure 11 and Figure 12 The adhesive layer AL according to the exemplary embodiment has a structure in which a first pressure-sensitive adhesive layer 11, a first elastomer layer 21, a second elastomer layer 22, a third elastomer layer 23, and a second pressure-sensitive adhesive layer 12 are stacked. Figure 5 The adhesive layers AL are similar in that the elastomer layers 21, 22, and 23 are interposed between the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12, but differ in that the three elastomer layers 21, 22, and 23 are stacked continuously. Furthermore, in the adhesive layer AL according to the illustrated exemplary embodiment, groove patterns GP are formed on both surfaces of the second elastomer layer 22 between the first elastomer layer 21 and the third elastomer layer 23.

[0083] The second elastomer layer 22 according to the exemplary embodiment may not have high shear deformation, such as the shear deformation in the pressure-sensitive adhesive layers 11 and 12. Accordingly, a space such as the groove pattern GP is formed on the surface of the second elastomer layer 22 to generate shear deformation. In this way, the interface separation between the second elastomer layer 22 and the first and second pressure-sensitive adhesive layers 11 and 12 can be reduced, and thus, even if warping occurs, warping can be prevented or the extent of warping can be reduced.

[0084] The first elastomer layer 21 and the third elastomer layer 23 cover the groove pattern GP formed on both surfaces of the second elastomer layer 22 so that the material of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 is not pressed into or penetrated into the groove pattern GP. When the material of the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 is pressed into the groove pattern GP, the groove pattern GP can be recognized and the surface of the adhesive layer AL can become uneven. The space defined by the groove pattern GP, the first elastomer layer 21 and the third elastomer layer 23 can be filled with air. The groove pattern GP can be formed in various ways and, in some exemplary embodiments, can be formed by a laser process. The second elastomer layer 22 can be thermally bonded to the first elastomer layer 21 and the third elastomer layer 23. In order to prevent or reduce the groove pattern GP from being recognized, the first elastomer layer 21 and the third elastomer layer 23 and / or the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 can be atomized.

[0085] Reference Figure 13 , the adhesive layer AL according to the exemplary embodiment has a structure in which a first pressure-sensitive adhesive layer 11, a first elastomer layer 21, a second elastomer layer 22, and a second pressure-sensitive adhesive layer 12 are stacked. Figure 12 As in the adhesive layer AL, according to the exemplary embodiment shown, a plurality of elastomer layers 21 and 22 are continuously stacked in the adhesive layer AL, and a groove pattern GP is formed in the elastomer layers 21 and 22. However, the groove pattern GP according to the exemplary embodiment shown is formed on the contact surface of the first elastomer layer 21 and the second elastomer layer 22. More specifically, the groove pattern GP is formed at the upper surface of the first elastomer layer 21 and the lower surface of the second elastomer layer 22. Accordingly, the groove pattern GP is arranged between the first elastomer layer 21 and the second elastomer layer 22. In this way, the groove pattern GP promotes shear deformation of the elastomer layers 21 and 22, thereby suppressing interface separation and warping.

[0086] although Figure 13 The groove pattern GP is shown formed in both the first elastomer layer 21 and the second elastomer layer 22, but the present invention is not limited thereto. For example, in some exemplary embodiments, the groove pattern GP may be formed in only one of the first elastomer layer 21 and the second elastomer layer 22. The first elastomer layer 21 and the second elastomer layer 22 and / or the first pressure-sensitive adhesive layer 11 and the second pressure-sensitive adhesive layer 12 may be subjected to a haze treatment to prevent or reduce recognition of the groove pattern GP.

[0087] Reference Figure 14 The adhesive layer AL according to the exemplary embodiment has a structure in which a first pressure-sensitive adhesive layer 11, an elastomer layer 20, and a second pressure-sensitive adhesive layer 12 are stacked. According to the illustrated exemplary embodiment, a hole pattern PP is formed inside the elastomer layer 20. Figure 12 and Figure 13 Like the groove pattern GP, the hole pattern PP can reduce interface separation and warpage by promoting shear deformation of the elastomer layer 20. The elastomer layer 20 and / or the first and second pressure-sensitive adhesive layers 11 and 12 may be atomized to prevent or reduce recognition of the hole pattern PP.

[0088] As described above, such as in conventional adhesive layers, according to reference Figures 5 to 14 The adhesive layer AL of the described exemplary embodiment may allow shear stress to occur while reducing stress of the bonded layers, while improving impact resistance.

[0089] In the following we will refer to Figure 15 The display panel DP of the display device 1 according to the exemplary embodiment is described.

[0090] Figure 15 is a cross-sectional view of a display panel according to an exemplary embodiment. Figure 15 A portion of the display panel DP having a stacked structure substantially corresponding to one pixel area is exemplarily shown.

[0091] Reference Figure 15 , the display panel DP according to an exemplary embodiment includes a substrate SUB, a transistor TR formed on the substrate SUB, and an organic light emitting diode OLED connected to the transistor TR.

[0092] The substrate SUB may be a flexible substrate made of a polymer such as polyimide (PI), polyamide (PA), or polyethylene terephthalate (PET). The substrate SUB may include a barrier layer to prevent moisture, oxygen, and the like from penetrating from the outside. For example, the substrate SUB may include at least one polymer layer and at least one barrier layer, and the polymer layers and the barrier layers may be alternately stacked.

[0093] A first insulating layer IN1 is disposed on the substrate SUB. The first insulating layer IN1 may be referred to as a buffer layer, and during the process of forming the semiconductor layer A, the first insulating layer IN1 may block impurities diffused from the substrate SUB from penetrating into the semiconductor layer A and may reduce stress applied to the substrate SUB. The barrier layer and the first insulating layer IN1 may include an inorganic insulating material such as silicon oxide and silicon nitride.

[0094] The semiconductor layer A of the transistor TR is arranged on the first insulating layer IN1, and the second insulating layer IN2 is arranged on the semiconductor layer A. The semiconductor layer A includes a source region, a drain region, and a channel region located between the source region and the drain region. The semiconductor layer A may include a semiconductor material such as polycrystalline silicon, an oxide semiconductor, and amorphous silicon. The second insulating layer IN2 may be referred to as a gate insulating layer and may include an inorganic insulating material.

[0095] A gate conductor including a gate electrode G of the transistor TR is disposed on the second insulating layer IN2. The gate conductor may include a metal or metal alloy such as molybdenum (Mo), copper (Cu), aluminum (Al), silver (Ag), chromium (Cr), tantalum (Ta), and titanium (Ti).

[0096] The third insulating layer IN3 is disposed on the gate conductor. The third insulating layer IN3 may be referred to as an interlayer insulating layer and may include an inorganic insulating material.

[0097] A data conductor including a source electrode S and a drain electrode D of the transistor TR is disposed on the third insulating layer IN3. The source electrode S and the drain electrode D are connected to the source region and the drain region of the semiconductor layer A, respectively, through contact holes formed in the third insulating layer IN3 and the second insulating layer IN2. The data conductor is made of a metal or metal alloy such as aluminum (Al), copper (Cu), silver (Ag), molybdenum (Mo), chromium (Cr), gold, platinum (Pt), palladium (Pd), tantalum (Ta), tungsten (W), titanium (Ti), nickel (Ni), or the like.

[0098] A fourth insulating layer IN4 is disposed on the data conductor. The fourth insulating layer IN4 may be referred to as a planarization layer and may include an organic insulating material.

[0099] The first electrode E1 is disposed on the fourth insulating layer IN4. The first electrode E1 may be referred to as a pixel electrode. The first electrode E1 is connected to the drain electrode D through a contact hole formed in the fourth insulating layer IN4 to receive a data signal that controls the brightness of the organic light emitting diode OLED.

[0100] A fifth insulating layer IN5 is disposed on the fourth insulating layer IN4. The fifth insulating layer IN5 may be referred to as a pixel defining layer and has an opening that overlaps with the first electrode E1. In the opening of the fifth insulating layer IN5, the emission layer EL is disposed on the first electrode E1, and the second electrode E2 is disposed on the emission layer EL. The second electrode E2 may be referred to as a common electrode.

[0101] The first electrode E1, the emission layer EL and the second electrode E2 together form an organic light emitting diode OLED. The first electrode E1 may be an anode electrode of the organic light emitting diode OLED, and the second electrode E2 may be a cathode electrode of the organic light emitting diode OLED.

[0102] The encapsulation layer EC is disposed on the second electrode E2. The encapsulation layer EC encapsulates the organic light emitting diode OLED to prevent moisture or oxygen from penetrating from the outside. The encapsulation layer EC may include at least one inorganic material layer and at least one organic material layer, and may have alternating inorganic material layers and organic material layers.

[0103] A protection film PF may be disposed under the substrate SUB to protect the display panel DP.

[0104] The cover window CW, the first functional layer FL1, and / or the second functional layer FL2 according to an exemplary embodiment may be attached to the encapsulation layer EC of the display panel DP through the adhesive layer AL described above. The base film BF and / or the buffer layer CL according to an exemplary embodiment may be adhered to the underside of the protection film PF of the display panel DP through the adhesive layer AL according to an exemplary embodiment.

[0105] Although the display panel DP has been described above with reference to an organic light emitting panel, the present inventive concept is not limited thereto. In some exemplary embodiments, for example, the display panel DP may be a display panel including light emitting diodes (LEDs) or a display panel including a liquid crystal layer.

[0106] Although certain exemplary embodiments and implementations have been described herein, other embodiments and variations will be apparent from this description. Accordingly, it will be apparent to those skilled in the art that the inventive concept is not limited to these embodiments, but rather to the broader scope of the appended claims and various obvious variations and equivalent arrangements.

Claims

1. A flexible display device, comprising: Display panel; a cover window, the cover window being arranged on the display panel and being optically transparent; as well as a first adhesive layer disposed between the display panel and the cover window, wherein the first adhesive layer includes a first pressure-sensitive adhesive layer, a second pressure-sensitive adhesive layer, and a first elastomer layer disposed between the first pressure-sensitive adhesive layer and the second pressure-sensitive adhesive layer, wherein the first elastomer layer is continuously arranged over the entire area of the first pressure-sensitive adhesive layer or the second pressure-sensitive adhesive layer, and The first elastomer layer includes a cutting pattern formed on at least one surface thereof, the cutting pattern being formed in a direction inclined with respect to a longitudinal direction of the first elastomer layer.

2. The flexible display device according to claim 1, further comprising: a first functional layer, the first functional layer being arranged between the first adhesive layer and the display panel; as well as a second adhesive layer, the second adhesive layer being arranged between the first functional layer and the display panel, The second adhesive layer includes a third pressure-sensitive adhesive layer, a fourth pressure-sensitive adhesive layer, and a second elastomer layer disposed between the third pressure-sensitive adhesive layer and the fourth pressure-sensitive adhesive layer.

3. The flexible display device according to claim 2, wherein: The first functional layer includes at least one of a polarizing layer and a touch panel.

4. The flexible display device according to claim 2, further comprising: a second functional layer disposed between the second adhesive layer and the display panel; as well as a third adhesive layer, the third adhesive layer being arranged between the second functional layer and the display panel, The third adhesive layer includes a fifth pressure-sensitive adhesive layer, a sixth pressure-sensitive adhesive layer, and a third elastomer layer located between the fifth pressure-sensitive adhesive layer and the sixth pressure-sensitive adhesive layer.

5. The flexible display device according to claim 4, wherein: The second functional layer includes at least one of a polarizing layer and a touch panel.

6. The flexible display device according to claim 1, wherein: The first adhesive layer has a thickness of less than 75 microns.

7. The flexible display device according to claim 1, wherein: The adhesive force between the first pressure-sensitive adhesive layer and the first elastomer layer is 400 gf / in 2 or larger.

8. The flexible display device according to claim 1, wherein: The first elastomer layer has a modulus of 100 kPa or less.

9. The flexible display device according to claim 1, wherein: The first elastomeric layer includes an elastomeric base layer and a plurality of posts disposed within the elastomeric base layer.

10. The flexible display device according to claim 9, wherein: The plurality of pillars have a higher modulus than the elastomeric base layer.

11. The flexible display device according to claim 9, wherein: The plurality of pillars have lower end portions in contact with the first pressure-sensitive adhesive layer and upper end portions in contact with the second pressure-sensitive adhesive layer.

12. The flexible display device according to claim 1, wherein: The first adhesive layer further includes a third pressure-sensitive adhesive layer and a second elastomer layer disposed between the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer.

13. The flexible display device according to claim 1, wherein: The first elastomeric layer includes a pattern of holes formed therein.

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