Cover window and display device having the same

Abstract

The present application relates to a cover window and a display device including the cover window. The cover window includes a flat portion and a curved portion extending from an end of the flat portion. The curved portion of the cover window includes a first section, a second section, and a third section, wherein the second section is disposed between the first section and the third section, an inner surface of the cover window is in contact with an adhesive layer, a first radius of curvature is greater than a second radius of curvature, and a third radius of curvature is greater than the second radius of curvature, wherein the first radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the first section, the second radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the second section, and the third radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the third section.

Description

Technical Field

[0001] Exemplary embodiments generally relate to a cover window and a display device having the cover window. More specifically, exemplary embodiments relate to a cover window including a curved portion for a display device and a display device including the cover window. Background Art

[0002] Recently, with the advancement of technology, display products having smaller sizes, lighter weights, and excellent performances have been produced. Conventional cathode ray tube (CRT) televisions have been widely used for display devices due to many advantages in terms of performance and price. Recently, a variety of other display device technologies, such as plasma display devices, liquid crystal display devices, and organic light emitting display devices, have been developed, which overcome the disadvantages of CRTs in terms of miniaturization or portability and have advantages such as miniaturization, light weight, and low power consumption.

[0003] Each of these display devices includes a display panel configured to display an image and a transparent cover window attached to a display surface of the display panel to cover the display surface. The cover window protects the display panel from external impacts, scratches, etc. applied during use. A typical cover window is formed of a plastic resin and manufactured by an injection molding process using a mold.

[0004] Recently, as smart phones and tablet PCs are increasingly used, display devices installed in the above devices need to have diversity in design. To meet the diversity, a display device (e.g., a so-called "edge type" display device) provided with a flexible display panel and a cover window having a curved portion has been proposed.

[0005] However, when the display panel is attached to the curved portion of the cover window, the radius of curvature may decrease as the bending angle of the curved portion becomes steeper, resulting in various defects, such as bubbles generated due to a bonding process or peeling occurring after the bonding process.

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

[0007] Exemplary embodiments provide a cover window for a display device, the cover window including a curved portion having improved quality.

[0008] Exemplary embodiments also provide a display device including the cover window.

[0009] Other features of the inventive concept will be set forth in the following description and will be partially apparent from the description or may be learned by practice of the inventive concept.

[0010] An exemplary embodiment provides a cover window that includes a flat portion and a curved portion extending from an end of the flat portion. The curved portion of the cover window includes a first section, a second section, and a third section, and the second section is disposed between the first section and the third section. The inner surface of the cover window is in contact with an adhesive layer. A first radius of curvature is greater than a second radius of curvature, and a third radius of curvature is greater than the second radius of curvature, where the first radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the first section, the second radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the second section, and the third radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the third section.

[0011] The curved portion of the cover window may further include a fourth section, the fourth section being an outer end portion of the curved portion, and the first section to the third section may be positioned between the flat portion and the fourth section. Additionally, a fourth radius of curvature may be less than the third radius of curvature, where the fourth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the fourth section.

[0012] The curved portion of the cover window may further include a fifth section, the fifth section being a portion where the curved portion is connected to the flat portion, and the fifth section may be positioned between the first section and the flat portion. Additionally, a fifth radius of curvature may be greater than the first radius of curvature to the fourth radius of curvature, where the fifth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the fifth section.

[0013] The curved portion of the cover window may further include a sixth section, and the sixth section may be positioned between the first section and the fifth section. Additionally, a sixth radius of curvature may be greater than the first radius of curvature and less than the fifth radius of curvature, where the sixth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the sixth section.

[0014] A central angle of an arc of the inner surface of the cover window in the first section is a first angle, a central angle of an arc of the inner surface of the cover window in the second section is a second angle, a central angle of an arc of the inner surface of the cover window in the third section is a third angle, a central angle of an arc of the inner surface of the cover window in the fourth section is a fourth angle, a central angle of an arc of the inner surface of the cover window in the fifth section is a fifth angle, a central angle of an arc of the inner surface of the cover window in the sixth section is a sixth angle, a ratio of the first angle to the sixth angle may be 1.00:0.43:0.43:0.62:0.10:0.62, and a ratio of the first radius of curvature to the sixth radius of curvature may be 0.15:0.12:0.19:0.12:1.00:0.24.

[0015] The central angle of the arc of the inner surface of the cover window in the first section is the first angle, the central angle of the arc of the inner surface of the cover window in the second section is the second angle, the central angle of the arc of the inner surface of the cover window in the third section is the third angle, and the first angle can be greater than the second angle and the third angle.

[0016] Another exemplary embodiment provides a display device, which includes a flexible display panel, a cover window, and an adhesive layer. The cover window is disposed on the flexible display panel and includes a flat portion and a curved portion extending from an end of the flat portion. The adhesive layer is disposed between the flexible display panel and the cover window to attach the flexible display panel to the cover window. The curved portion of the cover window includes a first section, a second section, and a third section, and the second section is disposed between the first section and the third section. The inner surface of the cover window is in contact with the adhesive layer. The first radius of curvature is greater than the second radius of curvature, and the third radius of curvature is greater than the second radius of curvature, where the first radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the first section, the second radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the second section, and the third radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the third section.

[0017] The curved portion of the cover window may further include a fourth section, the fourth section may be an outer end portion of the curved portion, and the first section to the third section may be located between the flat portion and the fourth section. Additionally, the fourth radius of curvature may be less than the third radius of curvature, where the fourth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the fourth section.

[0018] The curved portion of the cover window may further include a fifth section, the fifth section may be a portion where the curved portion is connected to the flat portion, and the fifth section may be located between the first section and the flat portion. Additionally, the fifth radius of curvature may be greater than the first radius of curvature to the fourth radius of curvature, where the fifth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the fifth section.

[0019] The curved portion of the cover window may further include a sixth section, and the sixth section may be located between the first section and the fifth section. Additionally, the sixth radius of curvature may be greater than the first radius of curvature and less than the fifth radius of curvature, and the sixth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the sixth section.

[0020] The central angle of the arc of the inner surface of the cover window in the first section may have a first angle, the central angle of the arc of the inner surface of the cover window in the second section may have a second angle, the central angle of the arc of the inner surface of the cover window in the third section may have a third angle, the central angle of the arc of the inner surface of the cover window in the fourth section may have a fourth angle, the central angle of the arc of the inner surface of the cover window in the fifth section may have a fifth angle, the central angle of the arc of the inner surface of the cover window in the sixth section may have a sixth angle, the ratio of the first angle to the sixth angle may be 1.00:0.43:0.43:0.62:0.10:0.62, and the ratio of the first radius of curvature to the sixth radius of curvature may be 0.15:0.12:0.19:0.12:1.00:0.24.

[0021] The central angle of the arc of the inner surface of the cover window in the first section may have a first angle, the central angle of the arc of the inner surface of the cover window in the second section may have a second angle, the central angle of the arc of the inner surface of the cover window in the third section may have a third angle, and the first angle may be greater than the second angle and the third angle.

[0022] The radius of curvature of the inner surface of the cover window in the curved portion may vary continuously from the portion of the cover window in contact with the flat portion to the outer edge of the cover window.

[0023] The central angle of the arc of the inner surface of the cover window with respect to the entire curved portion may be greater than 80 degrees.

[0024] The flat portion may extend in a first direction, and the curved portion may be curved in a second direction perpendicular to the first direction to form a curved surface. Additionally, the length of the curved portion of the cover window in the first direction may be less than 5 mm, and the length of the curved portion of the cover window in the second direction may be less than 1.5 mm.

[0025] The flexible display panel may be an organic light-emitting display panel and may include a thin-film encapsulation layer bonded to an adhesive layer. Additionally, the thin-film encapsulation layer may include at least one inorganic layer and at least one organic layer.

[0026] The adhesive layer may include an optically clear adhesive (OCA), a super vision resin (SVR), a pressure-sensitive adhesive (PSA), or an optically clear resin (OCR).

[0027] Another exemplary embodiment provides a display device, which includes a flexible display panel, a cover window, and an adhesive layer. The cover window is disposed on the flexible display panel and includes a flat portion and a curved portion extending from an end of the flat portion. The adhesive layer is disposed between the flexible display panel and the cover window to attach the flexible display panel to the cover window. The inner surface of the cover window may contact the adhesive layer. The curved portion of the cover window may include a connecting section connected to the flat portion, an outermost section formed at an outer edge of the cover window, and an intermediate section disposed between the connecting section and the outermost section. The radius of curvature of the connecting section may be greater than the radius of curvature of the intermediate section and the radius of curvature of the outermost section, and the radius of curvature of the outermost section may be less than the radius of curvature of the intermediate section, where the radius of curvature of the connecting section has an average value of the radius of curvature of the inner surface of the cover window in the connecting section, the radius of curvature of the intermediate section has an average value of the radius of curvature of the inner surface of the cover window in the intermediate section, and the radius of curvature of the outermost section has an average value of the radius of curvature of the inner surface of the cover window in the outermost section.

[0028] The intermediate section may include a first section, a second section, and a third section, and the second section is disposed between the first section and the third section. Additionally, the first radius of curvature may be greater than the second radius of curvature, where the first radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the first section, and the second radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the second section. Furthermore, the third radius of curvature may be greater than the second radius of curvature, where the third radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the third section.

[0029] The flexible display panel may be an organic light-emitting display panel and may include a thin film encapsulation layer bonded to the adhesive layer. Additionally, the thin film encapsulation layer may include at least one inorganic layer and at least one organic layer, and the adhesive layer may include an optically clear adhesive (OCA), a super vision resin (SVR), a pressure-sensitive adhesive (PSA), or an optically clear resin (OCR).

[0030] It will 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 claimed invention. Description of the Drawings

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

[0032] Figure 1 is a perspective view showing a display device including a cover window according to an exemplary embodiment.

[0033] Figure 2 is a cross-sectional view of a cover window and a display panel of a display device 100 that shows Figure 1 .

[0034] Figure 3 is a cross-sectional view of one of the bent portions of the cover window and the display panel in Figure 2 , i.e., Figure 2 part A in

[0035] Figure 4 is a diagram showing the first radius of curvature and the first angle in the first section of the lower surface of the cover window in Figure 3 .

[0036] Figure 5 is a graph showing the radius of curvature according to the position of the inner surface of the cover window at the bent portion in Figure 3 .

[0037] Figure 6A is a diagram showing the cross-sectional shape of the bent portion of a display device according to a comparative example, the stress of a thin film encapsulation layer, and the peel load of an adhesive layer.

[0038] Figure 6B is a diagram showing the cross-sectional shape of the bent portion of a display device according to an exemplary embodiment, the stress of a thin film encapsulation layer, and the peel load of an adhesive layer. DETAILED DESCRIPTION

[0039] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the various exemplary embodiments of the present invention. As used herein, "embodiment" is a non-limiting example of a device or method that employs one or more of the inventive concepts disclosed herein. However, it will be apparent that the various exemplary embodiments may be practiced without these specific details or with one or more equivalent arrangements. In other instances, well-known structures and devices are shown in block diagram form to avoid unnecessarily obscuring the various exemplary embodiments. Additionally, the various exemplary embodiments may be different, but not necessarily exclusive. For example, without departing from the inventive concept, the specific shapes, configurations, and characteristics of an exemplary embodiment may be used or implemented in another exemplary embodiment.

[0040] Unless otherwise specified, the exemplary embodiments shown should be understood to provide exemplary features of different details in some ways, in which the inventive concept can be implemented in the said some ways. Therefore, unless otherwise specified, without departing from the inventive concept, the features, components, modules, layers, films, panels, regions, and / or aspects, etc. (hereinafter, individually or collectively referred to as "elements") of various embodiments can be combined, separated, interchanged, and / or rearranged otherwise.

[0041] In the drawings, the use of cross-hatching and / or shading is generally intended to make the boundaries between adjacent elements clear. Therefore, unless otherwise stated, the presence or absence of cross-hatching or shading does not convey or indicate any preference or requirement for a particular material, material property, dimension, ratio, commonality between the illustrated elements, and / or any other characteristic, attribute, property, etc. of the elements. Additionally, in the drawings, for clarity and / or description purposes, the dimensions and relative dimensions of the elements may be exaggerated. When the exemplary embodiments can be implemented differently, the specific processing sequence may be executed differently from the described sequence. For example, two consecutively described processes may be executed substantially simultaneously, or in the reverse order of the described sequence. Moreover, the same reference numerals denote the same elements.

[0042] When an element such as a layer is referred to as being "on," "connected to," or "coupled to" another element or layer, it can be directly on, directly connected to, or directly coupled to the other element or layer, or there may be intervening elements or layers. However, 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. For this reason, the term "connection" can represent physical connection, electrical connection, and / or fluid connection in the presence or absence of intervening elements. Additionally, 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 can be interpreted in a broader sense. For example, the D1 axis, D2 axis, and D3 axis can be perpendicular to each other, or can represent different directions that are not perpendicular to each other. For the purposes of this disclosure, "at least one of X, Y, and Z" and "at least one selected from the set consisting of X, Y, and Z" can be interpreted as only X, only Y, only Z, or any combination of two or more of X, Y, and Z, such as by way of example XYZ, XYY, YZ, and ZZ. As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items.

[0043] 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, a first element discussed below may be termed a second element without departing from the teachings of this disclosure.

[0044] Spatial relative terms such as "beneath", "below", "under", "lower", "above", "upper", "over", "higher", "side" (e.g., as in "sidewall") may be used herein for descriptive purposes and, thus, to describe the relationship of one element to another(s) as shown in the figures. Except for the orientation depicted in the figures, spatial relative terms are intended to encompass different orientations of the device in use, operation, and / or manufacture. For example, if the device in the figures is turned over, an element described as "beneath" or "below" other elements or features will then be oriented "above" the other elements or features. Thus, the exemplary term "below" can encompass both an orientation above and below. Additionally, the device may be otherwise oriented (e.g., rotated 90 degrees or at other orientations), and thus the spatial relative descriptors used herein are to be interpreted accordingly.

[0045] The terms used herein are for the purpose of describing particular embodiments and are not intended to be limiting. Unless the context clearly dictates otherwise, as used herein, the singular forms "a", "an", and "the" are intended to also include the plural forms. Additionally, when used in this specification, the terms "comprises", "comprising", "includes", and / or "including" specify the presence of the stated features, integers, steps, operations, elements, components, and / or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should also be noted that, as used herein, the terms "substantially", "about", and other similar terms are used as approximate terms and not as terms of degree, and are thus used to account for inherent deviations in measured, calculated, and / or provided values that would be recognized by one of ordinary skill in the art.

[0046] In this document, various exemplary embodiments are described with reference to sectional views and / or exploded views that are schematic diagrams of idealized exemplary embodiments and / or intermediate structures. As such, deviations from the illustrated shapes due to, for example, manufacturing techniques and / or tolerances are to be expected. Accordingly, the exemplary embodiments disclosed herein should not necessarily be construed as being limited to the specifically illustrated region shapes, but rather include deviations in shapes caused by, for example, manufacturing. In this manner, the regions shown in the drawings may be schematic in nature, and the shapes of these regions may not reflect the actual shapes of the regions of the device, and thus, are not necessarily intended to be limiting.

[0047] 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 this disclosure belongs. Terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0048] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0049] Figure 1 is a perspective view showing a display device including a cover window according to an exemplary embodiment.

[0050] Referring to Figure 1 , the electronic device 10 includes a display device 100 which includes a display panel (see 110 in Figure 3 ) and a cover window (see 130 in Figure 3 ) attached to the display panel. The display device 100 includes a flat portion (see FA in Figure 3 ) and a pair of curved portions (see EA in Figure 3 ) positioned on both sides (edge displays) of the flat portion. Although the electronic device 10 is shown as a smart phone, the inventive concept is not limited thereto. For example, the electronic device 10 may be implemented as a television, a mobile phone, a video phone, a smart board, a smart watch, a tablet PC, a car navigation system, a computer display screen, a laptop computer, a head-mounted display (HMD), etc.

[0051] The pair of curved portions are formed on both sides of the flat portion to be parallel to the long side of the cover window. In addition, the pair of curved portions may be formed in a predetermined shape without changing the curvature in the direction parallel to the long side of the cover window.

[0052] The pair of curved portions are formed to have the same curvature as each other, and the centers of curvature of the two curved portions may be positioned on the same side. Figure 1Shows a case where the centers of curvature of two bent portions are positioned at the lower side of the cover window.

[0053] Figure 2 Is a cross-sectional view of the cover window and the display panel of the display device 100 shown Figure 1 ; Figure 3 Is a cross-sectional view of one of the bent portions of the cover window and the display panel in Figure 2 (i.e., Figure 2 part A in Figure 4 ; and Figure 3 Is a diagram showing the first radius of curvature and the first angle in the first section of the lower surface of the cover window in

[0054] Referring to Figures 2 to 4 , the display device 100 includes a display panel 110, an adhesive layer 120 provided on the display panel 110, and a cover window 130 provided on the adhesive layer 120.

[0055] The display panel 110 may be a flexible display panel. For example, the display panel 110 may be a flexible organic light emitting display panel. A thin film encapsulation layer may be formed on the uppermost layer of the display panel 110.

[0056] A thin film encapsulation layer may be formed on the uppermost layer of the display panel 110 to prevent moisture and oxygen from penetrating from the outside. The thin film encapsulation layer may seal the organic light emitting diodes of the display panel 110 to reduce the deterioration of the organic light emitting diodes due to external moisture, and may inhibit oxygen.

[0057] The thin film encapsulation layer may be provided with at least one organic layer and at least one inorganic layer. The at least one organic layer and the at least one inorganic layer may be alternately laminated. For example, the thin film encapsulation layer may include a first inorganic layer, a second inorganic layer, and an organic layer between the first inorganic layer and the second inorganic layer, but is not limited thereto.

[0058] The organic layer of the thin film encapsulation layer may be formed of a polymer and may be, for example, a single film or a laminated film formed of any one of polyethylene terephthalate, polyimide, polycarbonate, epoxy resin, polyethylene, and polyacrylate. The inorganic layer of the thin film encapsulation layer may be a single layer or a laminated layer including a metal oxide or a metal nitride. For example, the inorganic layer may include SiN x , any one of Al2O3, SiO2, and TiO2.

[0059] The adhesive layer 120 is disposed between the thin film encapsulation layer of the display panel 110 and the cover window 130, thereby attaching the display panel 110 to the inner surface of the cover window 130. The adhesive layer 120 may be a transparent adhesive layer. For example, the adhesive layer may be an optically clear adhesive (OCA), a super view resin (SVR), a pressure sensitive adhesive (PSA), an optically clear resin (OCR), or a combination thereof, but is not limited thereto. In an exemplary embodiment, the adhesive layer 120 may include an acrylic binder.

[0060] The cover window 130 may be formed of a plastic material. For example, the cover window 130 may include polycarbonate, cycloolefin polymer, polymethyl methacrylate, etc. In another exemplary embodiment, the cover window 130 may include quartz, synthetic quartz, calcium fluoride, fluorine-doped quartz (F-doped quartz), soda-lime glass, non-alkaline glass, etc.

[0061] The cover window 130 may include a flat portion FA and a curved portion EA connected to an end of the flat portion FA. The curved portion EA may be curved to have a curved surface in a second direction D2 perpendicular to the first direction D1, where the first direction D1 is the direction in which the flat portion FA extends.

[0062] According to the illustrated exemplary embodiment, the curved portion EA is divided into six sections, but is not limited thereto. For example, the curved portion EA may be divided into at least three sections, and the radius of curvature and the angle in each of the sections may vary continuously (see the description of Figure 5 to be described later).

[0063] Although not shown, the display device 100 may further include a touch sensor unit and an optical film such as a polarizing film positioned between the display panel 110 and the cover window 130.

[0064] In line with the current design trend of the electronic device 10, the angle corresponding to the entire curved portion EA is close to 90 degrees, and the radius of curvature corresponding to the entire curved portion EA is reduced. Therefore, it is confirmed that a peeling defect of forming bubbles between the adhesive layer 120 and the cover window 130 occurs due to a peeling load applied to the adhesive layer 120 and a stress applied to the thin film encapsulation layer of the display panel 110 (hereinafter, referred to as TFE).

[0065] The peeling defect can be caused by the stress applied to the thin film encapsulation layer and the peeling load applied to the adhesive layer 120. In addition, it can be predicted that by changing the design of the inner surface of the cover window 130 that contacts the adhesive layer 120, the peeling defect can be alleviated. Therefore, by applying optimization techniques, a design suitable for minimizing the TFE stress (the stress applied to the thin film encapsulation layer) and the OCA peeling load (the peeling load applied to the adhesive layer 120) within the same design requirements is achieved.

[0066] Various schemes can be used to implement the optimization technique. For example, the configuration of the cover window 130 can be designed by using the experimental values preset via "Design of Experiments" (DOE), and the sum of the TFE stress (σTFE) and the OCA peeling load (POCA) in the experimental values can be calculated. Then, in order to find the minimum value of the sum of the TFE stress (σTFE) and the OCA peeling load (POCA), the design of the cover window 130 for minimizing the values of the TFE stress (σTFE) and the OCA peeling load (POCA) can be achieved by optimization techniques such as regression analysis and the "least squares" method.

[0067] "Design of Experiments" refers to a scheme that, based on statistical analysis, selects important factors at low cost among various factors that cause abnormal changes and quantitatively measures the resulting effects. The "least squares" method refers to a scheme that processes the measurement results by appropriately summing the squares based on the measured values and calculating the value that minimizes the sum of the squares, and this is also called "least squares fitting".

[0068] Various known analysis tools or solutions can be used to perform the above processing.

[0069] In an exemplary embodiment, even when the radius of curvature of the curved portion EA of the cover window 130 is small and the central angle of the arc with respect to the entire curved portion EA is large, bubble defects, peeling defects, etc. can be prevented.

[0070] The length of the curved portion EA of the cover window 130 in the first direction D1 (in the drawing, the distance from X0 to X6) can be less than 5 mm (millimeters), and the length in the second direction D2 (in the drawing, the distance from Y0 to Y6) can be less than 1.5 mm. The central angle of the inner surface of the cover window 130 with respect to the arc of the entire curved portion EA can be greater than 80 degrees.

[0071] According to an exemplary embodiment, the design range of the cover window 130 is as follows. The central angle of the arc of the inner surface of the cover window 130 with respect to the entire curved portion EA can be 88.9 degrees. The curved portion EA can be divided into six sections. The length of the curved portion EA in the first direction D1 can be 4.803 mm, and the length of the curved portion EA in the second direction D2 can be 1.117 mm.

[0072] By performing an optimization technique within an error range of 0.001 mm and 0.01 degrees with respect to the design range, design variables with the minimum TFE stress (σTFE) and OCA peel load (POCA) are calculated.

[0073] Table 1 below shows the optimal design of the inner surface of the cover window 130 (the surface in contact with the adhesive layer 120).

[0074]

[0075]

[0076] The first section represents the section from the point (X0, Y0) to the point (X1, Y1), the second section represents the section from the point (X1, Y1) to the point (X2, Y2), the third section represents the section from the point (X2, Y2) to the point (X3, Y3), the fourth section represents the section from the point (X3, Y3) to the point (X4, Y4), the fifth section represents the section from the point (X4, Y4) to the point (X5, Y5), and the sixth section represents the section from the point (X5, Y5) to the point (X6, Y6).

[0077] With respect to the virtual center of the arc in each section (e.g., Figure 4 C1), the "radius of curvature" represents the average radius of curvature in each section, and the angle represents the central angle of the arc in each section (see Figure 4 ).

[0078] The curved portion is divided into six sections. This is because when the curved portion is divided into too many sections, it may not be possible to effectively find the optimal design of the cover window, and when the curved portion is divided into too few sections, it may not be possible to calculate the design that minimizes the TFE stress (σTFE) and OCA peel load (POCA) (compared to a simple curved portion, i.e., a design with one radius of curvature).

[0079] The radius of curvature of the inner surface of the cover window 130 at the curved portion EA can vary continuously from the portion (X0, Y0) of the cover window 130 in contact with the flat portion FA to the outer edge (X6, Y6) of the cover window 130 (see Figure 5 ).

[0080] Table 2 below shows a comparative example design compared to the optimal design shown in Table 1 above according to an exemplary embodiment.

[0081]

[0082]

[0083] In the case of the cover window and the display panel according to the design of the comparative example, a defect occurred in which the adhesive layer between the cover window and the display panel was spaced apart from the adjacent element to form bubbles.

[0084] On the contrary, in the case of the cover window and the display panel according to the optimal design, it was confirmed that a defect in which the adhesive layer between the cover window and the display panel was spaced apart from the adjacent element to form bubbles did not occur.

[0085] Table 3 below shows the values obtained by normalizing the design values of the optimal design.

[0086]

[0087]

[0088] Figure 5 is a graph showing the radius of curvature of the position of the inner surface of the cover window at the curved portion in Figure 3 The radius of curvature of the inner surface of the cover window at the curved portion is a graph showing the radius of curvature of the position of the inner surface of the cover window at the curved portion in

[0089] Referring to Figure 5 , although the average radius of curvature of each section is represented by a straight line, the radius of curvature of the inner surface of the actual cover window at the curved portion can vary continuously from the portion in contact with the flat portion of the cover window to the outer edge of the cover window (the curve of the graph).

[0090] Figure 6A is a diagram showing the cross-sectional shape of the curved portion of the display device according to the comparative example, the stress of the thin film encapsulation layer, and the peeling load of the adhesive layer, and Figure 6B is a diagram showing the cross-sectional shape of the curved portion of the display device according to the exemplary embodiment, the stress of the thin film encapsulation layer, and the peeling load of the adhesive layer.

[0091] Referring to Figure 6A and Figure 6B , according to the exemplary embodiment, it was confirmed by the simulation results that the maximum value of the stress (TFE stress) of the thin film encapsulation layer was reduced from 748 Mpa (megapascals) to 569 Mpa compared to the comparative example.

[0092] Furthermore, according to the exemplary embodiment, it was confirmed by the simulation results that the maximum value of the peeling load (OCA peeling load) of the adhesive layer (optical clear adhesive (OCA)) was reduced from 4.39 Mpa to 3.00 Mpa compared to the comparative example.

[0093] In an exemplary embodiment, the cover window includes a flat portion and a curved portion extending from an end of the flat portion. The curved portion of the cover window may be divided into a plurality of sections, and each of the sections may have a radius of curvature and an angle according to an optimal design designed by an optimization technique.

[0094] For example, the curved portion of the cover window may include a first section, a second section, and a third section, where the second section may be disposed between the first section and the third section. The inner surface of the cover window may be the surface in contact with the adhesive layer. The first radius of curvature may be greater than the second radius of curvature, where the first radius of curvature is the average value of the radius of curvature of the inner surface of the cover window in the first section, and the second radius of curvature is the average value of the radius of curvature of the inner surface of the cover window in the second section. The third radius of curvature may be greater than the second radius of curvature, where the third radius of curvature is the average value of the radius of curvature of the inner surface of the cover window in the third section.

[0095] Accordingly, even when the radius of curvature of the curved portion of the cover window is small and the central angle with respect to the arc of the entire curved portion is large, bubble defects, peeling defects, etc. can be prevented.

[0096] The inventive concept can be applied to an organic light emitting display device and an electronic device including the organic light emitting display device. For example, the inventive concept can be applied to a smart phone, a cellular phone, a video phone, a smart board, a smart watch, a tablet PC, a car navigation system, a television, a computer display screen, a laptop computer, a head-mounted display (HMD) device, etc.

[0097] Although specific exemplary embodiments have been described herein, other embodiments and modifications will be apparent from this description. Accordingly, the inventive concept is not limited to such embodiments, but rather to the broader scope of the appended claims and various obvious modifications and equivalent arrangements that will be apparent to those of ordinary skill in the art.

Claims

1. Cover window, comprising: A flat portion; And A curved portion extending from an end of the flat portion, Wherein: The curved portion of the cover window includes a first section, a second section, and a third section, and the second section is disposed between the first section and the third section; The inner surface of the cover window is in contact with an adhesive layer; A first radius of curvature is greater than a second radius of curvature, the first radius of curvature having an average value of the radius of curvature of the inner surface of the cover window in the first section, and the second radius of curvature having an average value of the radius of curvature of the inner surface of the cover window in the second section; and A third radius of curvature is greater than the second radius of curvature, the third radius of curvature having an average value of the radius of curvature of the inner surface of the cover window in the third section.

2. The cover window according to claim 1, wherein: The curved portion of the cover window further includes a fourth section, the fourth section being an outer end portion of the curved portion, and the first section to the third section are positioned between the flat portion and the fourth section; And A fourth radius of curvature is less than the third radius of curvature, the fourth radius of curvature having an average value of the radius of curvature of the inner surface of the cover window in the fourth section.

3. The cover window according to claim 2, wherein: The curved portion of the cover window further includes a fifth section, the fifth section being a portion where the curved portion is connected to the flat portion, and the fifth section is positioned between the first section and the flat portion; And A fifth radius of curvature is greater than the first radius of curvature to the fourth radius of curvature, the fifth radius of curvature having an average value of the radius of curvature of the inner surface of the cover window in the fifth section.

4. The cover window according to claim 3, wherein: The curved portion of the cover window further includes a sixth section, and the sixth section is positioned between the first section and the fifth section; And A sixth radius of curvature is greater than the first radius of curvature and less than the fifth radius of curvature, the sixth radius of curvature having an average value of the radius of curvature of the inner surface of the cover window in the sixth section.

5. The cover window according to claim 4, wherein: The central angle of the arc of the inner surface of the cover window in the first section is a first angle; The central angle of the arc of the inner surface of the cover window in the second section is a second angle; The central angle of the arc of the inner surface of the cover window in the third section is a third angle; The central angle of the arc of the inner surface of the cover window in the fourth section is a fourth angle; The central angle of the arc of the inner surface of the cover window in the fifth section is a fifth angle; The central angle of the arc of the inner surface of the cover window in the sixth section is a sixth angle; The ratio of the first angle to the sixth angle is 1.00:0.43:0.43:0.62:0.10:0.62; And The ratio of the first radius of curvature to the sixth radius of curvature is 0.15:0.12:0.19:0.12:1.00:0.

24.

6. The cover window according to claim 1, wherein: The central angle of the arc of the inner surface of the cover window in the first section is a first angle; The central angle of the arc of the inner surface of the cover window in the second section is a second angle; The central angle of the arc of the inner surface of the cover window in the third section is a third angle; and The first angle is greater than the second angle and the third angle.

7. A display device, comprising: A flexible display panel; A cover window disposed on the flexible display panel and including a flat portion and a curved portion extending from an end of the flat portion; And An adhesive layer disposed between the flexible display panel and the cover window to attach the flexible display panel to the cover window, Wherein: The curved portion of the cover window includes a first section, a second section, and a third section, and the second section is disposed between the first section and the third section; The inner surface of the cover window contacts the adhesive layer; The first radius of curvature is greater than the second radius of curvature. The first radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the first section, and the second radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the second section; and The third radius of curvature is greater than the second radius of curvature. The third radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the third section.

8. The display device according to claim 7, wherein: The curved portion of the cover window further includes a fourth section, and the fourth section is an outer end portion of the curved portion, and the first section to the third section are positioned between the flat portion and the fourth section; And The fourth radius of curvature is less than the third radius of curvature. The fourth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the fourth section.

9. The display device according to claim 8, wherein: The curved portion of the cover window further includes a fifth section, and the fifth section is a portion where the curved portion is connected to the flat portion, and the fifth section is positioned between the first section and the flat portion; And The fifth radius of curvature is greater than the first radius of curvature to the fourth radius of curvature. The fifth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the fifth section.

10. The display device according to claim 9, wherein: The curved portion of the cover window further includes a sixth section, and the sixth section is positioned between the first section and the fifth section; And The sixth radius of curvature is greater than the first radius of curvature and less than the fifth radius of curvature. The sixth radius of curvature has an average value of the radius of curvature of the inner surface of the cover window in the sixth section.

11. The display device according to claim 10, wherein: The central angle of the arc of the inner surface of the cover window in the first section is a first angle; The central angle of the arc of the inner surface of the cover window in the second section is a second angle; The central angle of the arc of the inner surface of the cover window in the third section is a third angle; The central angle of the arc of the inner surface of the cover window in the fourth section is a fourth angle; The central angle of the arc of the inner surface of the cover window in the fifth section has a fifth angle; The central angle of the arc of the inner surface of the cover window in the sixth section has a sixth angle; The ratio of the first angle to the sixth angle is 1.00:0.43:0.43:0.62:0.10:0.62; And The ratio of the first radius of curvature to the sixth radius of curvature is 0.15:0.12:0.19:0.12:1.00:0.

24.

12. The display device according to claim 7, wherein: The central angle of the arc of the inner surface of the cover window in the first section is a first angle; The central angle of the arc of the inner surface of the cover window in the second section is a second angle; The central angle of the arc of the inner surface of the cover window in the third section is a third angle; and The first angle is greater than the second angle and the third angle.

13. The display device according to claim 7, wherein, The radius of curvature of the inner surface of the cover window in the curved portion changes continuously from the portion of the cover window in contact with the flat portion to the outer edge of the cover window.

14. The display device according to claim 7, wherein, The central angle of the arc of the inner surface of the cover window with respect to the entire curved portion is greater than 80 degrees.

15. The display device according to claim 14, wherein: The flat portion extends in a first direction, and the curved portion bends in a second direction perpendicular to the first direction to form a curved surface; And The length of the curved portion of the cover window in the first direction is less than 5 mm, and the length of the curved portion of the cover window in the second direction is less than 1.5 mm.

16. The display device according to claim 7, wherein: The flexible display panel is an organic light-emitting display panel and includes a thin-film encapsulation layer bonded to the adhesive layer; and The thin-film encapsulation layer includes at least one inorganic layer and at least one organic layer.

17. The display device according to claim 16, wherein, The adhesive layer includes an optically transparent adhesive, a super vision resin, a pressure-sensitive adhesive, or an optically transparent resin.

18. A display device, comprising: A flexible display panel; A cover window disposed on the flexible display panel and including a flat portion and a curved portion extending from an end of the flat portion; And An adhesive layer disposed between the flexible display panel and the cover window to attach the flexible display panel to the cover window, Wherein: The inner surface of the cover window is in contact with the adhesive layer; The curved portion of the cover window includes a connection section connected to the flat portion, an outermost section formed at the outer edge of the cover window, and an intermediate section disposed between the connection section and the outermost section; The radius of curvature of the connecting section is greater than the radius of curvature of the intermediate section and the outermost section. The radius of curvature of the connecting section has the average value of the radius of curvature of the inner surface of the covering window in the connecting section. The radius of curvature of the intermediate section has the average value of the radius of curvature of the inner surface of the covering window in the intermediate section. The radius of curvature of the outermost section has the average value of the radius of curvature of the inner surface of the covering window in the outermost section; and the radius of curvature of the outermost section is less than the radius of curvature of the intermediate section, the intermediate section includes a first section, a second section, and a third section, and the second section is disposed between the first section and the third section; a first radius of curvature is greater than a second radius of curvature. The first radius of curvature has the average value of the radius of curvature of the inner surface of the covering window in the first section. The second radius of curvature has the average value of the radius of curvature of the inner surface of the covering window in the second section; and a third radius of curvature is greater than the second radius of curvature. The third radius of curvature has the average value of the radius of curvature of the inner surface of the covering window in the third section.

19. The display device according to claim 18, wherein: the flexible display panel is an organic light emitting display panel and includes a thin film encapsulation layer bonded to the adhesive layer; the thin film encapsulation layer includes at least one inorganic layer and at least one organic layer; and the adhesive layer includes an optically clear adhesive, a super vision resin, a pressure sensitive adhesive, or an optically clear resin.

Images