Display device

Abstract

The present invention relates to a display device. The display device includes a substrate. The substrate includes a first non-bending region and a second non-bending region spaced apart from each other, and a bending region located between the first non-bending region and the second non-bending region. A first protective layer is disposed on a first surface of the substrate in the bending region. A second protective layer is disposed on a second surface of the substrate and includes cavities spaced apart from each other in the bending region. When a first bending stress at a first position point in the bending region is greater than an average bending stress of the substrate in the bending region, a first density of a cavity corresponding to the first position point is less than an average density of the cavities.

Description

Technical Field

[0001] Embodiments of the present invention relate to a display device. Background Art

[0002] A display device may include: a display panel that displays an image; a window disposed on the display panel; and a functional panel interposed between the display panel and the window to receive a touch input or prevent reflection of external light.

[0003] A flexible display device (or a flexible display panel) has characteristics of being bent and folded, and thus can achieve a large screen and is convenient to carry. Summary of the Invention

[0004] A bent region of a display device (or a display panel) is subject to stress (e.g., internal stress, or tensile or compressive force) caused by bending, and thus has a lower strength than an unbent region, and the strength of the bent region can be compensated by a resin or the like coated on the inner side of the bent region.

[0005] Since the stress in the bent region varies depending on the position (or position point), the curvature (or radius) of the bent region may not be uniform, and the deviation of the stress in the bent region becomes larger, and the possibility of occurrence of a defect (e.g., a crack) at a position where the stress is relatively large may become larger. In particular, after the display device is bent, a resin is coated on the bent region, and thus the resin may not be able to control the curvature of the bent region.

[0006] In addition, corresponding to the thinning of the display device, the curvature (or average curvature) of the bent region may decrease, and the deviation of the stress in the bent region further becomes larger.

[0007] An object of the present invention is to provide a display device including a bent region having a uniform curvature and improved strength.

[0008] To achieve an object of the present invention, a display device according to an embodiment of the present invention includes: a substrate including a first non-bent region and a second non-bent region spaced apart from each other and a bent region located between the first non-bent region and the second non-bent region and bent; a display layer disposed on a first surface of the substrate in the first non-bent region and displaying an image; a first protective layer disposed on the first surface of the substrate in the bent region; and a second protective layer disposed on a second surface of the substrate and including cavities spaced apart from each other in the bent region. Here, when a first bending stress at a first position point in the bent region is greater than an average bending stress of the bent region, a first density of the cavity corresponding to the first position point is less than an average density of the cavities.

[0009] According to an embodiment, the thickness of the first protective layer may be constant throughout the bending region. The farther the first position point is from the first non-bending region, the greater the first bending stress until the first bending stress becomes maximum, and the smaller the first density.

[0010] According to an embodiment, the bending region may include: a first adjacent region adjacent to the first non-bending region; a second adjacent region adjacent to the second non-bending region; and an intermediate region located between the first adjacent region and the second adjacent region. Wherein, in the first adjacent region, the bending stress of the substrate is less than the average bending stress, and in the intermediate region, the bending stress of the substrate is greater than the average bending stress. The density of the first cavity corresponding to the first adjacent region is greater than the density of the second cavity corresponding to the intermediate region.

[0011] According to an embodiment, the depth of the first cavity may be greater than the depth of the second cavity.

[0012] According to an embodiment, the number of the first cavities per unit area may be the same as the number of the second cavities per unit area.

[0013] According to an embodiment, the average diameter, average width, or average area of the first cavity may be greater than the average diameter, average width, or average area of the second cavity.

[0014] According to an embodiment, each of the cavities may have a circular or quadrilateral planar shape, and the cavities are arranged in an interleaved manner along the direction in which the first non-bending region and the second non-bending region are separated from each other.

[0015] According to an embodiment, each of the cavities may respectively have a strip-shaped planar shape and extend along a direction perpendicular to the direction in which the first non-bending region and the second non-bending region are separated from each other.

[0016] According to an embodiment, the bending region may include: a first adjacent region adjacent to the first non-bending region; a second adjacent region adjacent to the second non-bending region; and an intermediate region located between the first adjacent region and the second adjacent region. Wherein, the first thickness of the first protective layer corresponding to the first adjacent region is less than the second thickness of the first protective layer corresponding to the intermediate region, and the density of the first cavity corresponding to the first adjacent region is less than the density of the second cavity corresponding to the intermediate region.

[0017] According to an embodiment, the area of the intermediate region may be greater than the total area of the first adjacent region and the second adjacent region.

[0018] According to an embodiment, in the middle region, the closer to the first adjacent region, the smaller the density of the cavities; in the first adjacent region, the closer to the first non-bent region, the greater the density of the cavities.

[0019] According to an embodiment, the bent region may include: a first adjacent region adjacent to the first non-bent region; a second adjacent region adjacent to the second non-bent region; and a middle region located between the first adjacent region and the second adjacent region. Here, a first thickness of the first protective layer corresponding to the first adjacent region is greater than a second thickness of the first protective layer corresponding to the middle region, and a density of first cavities corresponding to the first adjacent region is greater than a density of second cavities corresponding to the middle region.

[0020] According to an embodiment, in the first adjacent region, a bending stress of the substrate may be less than the average bending stress; in the middle region, the bending stress of the substrate is greater than the average bending stress, and an area of the middle region is less than an area of the first adjacent region and an area of the second adjacent region, respectively.

[0021] According to an embodiment, in the middle region, the closer to the first adjacent region, the greater the density of the cavities; in the first adjacent region, the density of the cavities is constant.

[0022] To achieve an object of the present invention, a display device according to an embodiment of the present invention includes: a substrate including a first non-bent region and a second non-bent region spaced apart from each other and a bent region located between the first non-bent region and the second non-bent region and bent; a display layer disposed on a first surface of the substrate in the first non-bent region and displaying an image; a first protective layer disposed on the first surface of the substrate in the bent region; a second protective layer disposed on a second surface of the substrate and including cavities spaced apart from each other in the bent region; and a third protective layer disposed on the second surface of the substrate in the first non-bent region and the second non-bent region. Here, when a first bending stress at a first position point in the bent region is greater than an average bending stress of the bent region, a first depth of the cavities corresponding to the first position point is less than an average depth of the cavities.

[0023] For a display device according to an embodiment of the present invention, it includes a protective film disposed on one surface of the substrate and including cavities having a density corresponding to a stress at a position of a bent region, so that a curvature of the bent region can become uniform and the strength of the bent region is improved. Description of the Drawings

[0024] Figure 1 is a perspective view showing a display device according to an embodiment of the present invention.

[0025] Figure 2 is a view showing Figure 1 a cross-sectional view of an example of the display device taken along line I-I'.

[0026] Figure 3 is a view showing Figure 2 a cross-sectional view of an example of the display device.

[0027] Figure 4 is a view showing Figure 3 a cross-sectional view of an example of the cavity included in the display device.

[0028] Figures 5a to 5c is a view showing Figure 3 a plan view of an example of the second protective layer included in the display device.

[0029] Figure 6 is a view showing Figure 3 a graph of the stress in the bent region of the display device.

[0030] Figure 7 is a view showing Figure 4 a graph of the relationship between the stress in the second protective layer and the bent region.

[0031] Figure 8a is a view explaining Figure 3 the process of compensating for the stress in the bent region of the display device.

[0032] Figure 8b is a view showing Figure 3 the stress in the bent region caused by the second protective layer included in the display device.

[0033] Figures 9a to 9d is a view showing Figure 8a the second protective layer according to the stress compensation process.

[0034] Figure 10 is a view showing Figure 1 a cross-sectional view of another example of the display device.

[0035] Figure 11 is a view showing Figure 1 a cross-sectional view of yet another example of the display device.

[0036] Figure 12 is a view showing Figure 11 a cross-sectional view of an example of the display device.

[0037] Figure 13 is a view showing Figure 12 a graph of the stress in the bent region of the display device.

[0038] Figure 14 is a cross-sectional view showing another example of a display device. Figure 1 of

[0039] Figure 15 is a cross-sectional view showing an example of a display device. Figure 14 of

[0040] Figure 16 is a graph showing the stress in the bent region of a display device. Figure 15 of DETAILED DESCRIPTION

[0041] The present invention can be variously modified and can have various forms. Specific embodiments are illustrated in the drawings and described in detail in this specification. However, the present invention is not limited to the embodiments disclosed below and can be implemented in various modified forms.

[0042] In addition, in order to clearly explain the present invention, some components that have no direct relation to the features of the present invention may be omitted in the drawings. Also, some components in the drawings may be exaggerated in terms of their dimensions, ratios, etc. In all the drawings, the same or similar components are given the same reference numerals and signs as much as possible even if they are shown in different drawings, and repeated explanations are omitted.

[0043] When a part of a layer, film, region, plate, etc. is located "on" another part, it includes not only the case where it is "directly" located "on" another part but also the case where there are other parts between the two. Also, in this specification, when a part of a certain layer, film, region, plate, etc. is formed "on" another part, the forming direction is not limited to the upper direction but also includes the case of forming in the side or lower direction. Conversely, when a part of a layer, film, region, plate, etc. is located "under" another part, it includes not only the case where it is "directly" located "under" another part but also the case where there are other parts between the two.

[0044] Figure 1 is a perspective view showing a display device according to an embodiment of the present invention.

[0045] Referring to Figure 1 , the display device DD may include a display area DA and a non-display area NDA provided on at least one side of the display area DA.

[0046] The display device DD can generally have a quadrilateral shape, and in particular, can have a rectangular shape. The display device DD can include a pair of long sides parallel to each other in a first direction DR1 and a pair of short sides parallel to each other in a second direction DR2. However, the shape of the display device DD is not limited thereto, and can have various shapes. For example, the display device DD can be set to various shapes such as a polygon in a closed form including straight sides, a circle, an ellipse, etc. including sides formed by curves, a semi-circle, a semi-ellipse, etc. including sides formed by straight lines and curves.

[0047] The display area DA can be an area where an image is displayed through a plurality of pixels. The display area DA can be set to a shape corresponding to the shape of the display device DD. Each pixel is the smallest unit for displaying an image, and can emit white light and / or colored light. For example, each pixel can emit any one of red, green, blue, and white colors. However, it is not limited thereto, and can also emit colors such as cyan, magenta, and yellow.

[0048] Each pixel can be a light-emitting element including an organic light-emitting layer. However, it is not limited thereto, and can be implemented in various forms such as a liquid crystal element, an electrophoretic element, an electrowetting element, etc. within the scope of maintaining the concept of the present invention.

[0049] The non-display area NDA, as an area where no pixels are provided, can be an area where no image is displayed. In the non-display area NDA, wirings connected to the pixels and a driving unit (or, driver) for driving the pixels can be provided.

[0050] In some embodiments, at least a part of the display device DD can have flexibility, and can be folded at the flexible part.

[0051] In one embodiment, the display device DD can include a first non-bending area FA1 and a second non-bending area FA2 (or, a first flat area and a second flat area) and a bent area BA located between the first non-bending area FA1 and the second non-bending area FA2.

[0052] The first non-bending area FA1 and the second non-bending area FA2, as parts that are not folded and are generally flat, can have flexibility or not have flexibility.

[0053] The bent area BA can extend from the first non-bending area FA1, have flexibility, and be folded in one direction.

[0054] The second non-bending area FA2 extends from the bent area BA, and the first surface of the second non-bending area FA2 can face the first surface of the first non-bending area FA1.

[0055] For reference, when the line along which the display device is folded is referred to as a folding line, the folding line may be disposed within the bending region BA. Here, the term "folding" means that the form is not fixed and can be deformed from the original form into other forms, and may include cases of being folded, curved, or rolled up along the folding line. Therefore, Figure 1 The figure illustrates a state in which the first surfaces of the first non-bending region FA1 and the second non-bending region FA2 are arranged parallel to each other and folded in a facing manner, but is not limited thereto. For example, the first surfaces of the first non-bending region FA1 and the second non-bending region FA2 may also form a predetermined angle (e.g., an acute angle, a right angle, or an obtuse angle).

[0056] Figure 2 is a cross-sectional view showing an example of the display device taken along the Figure 1 I-I' line. Figure 2 The figure illustrates the bending region BA in a folded state. Figure 3 is a cross-sectional view showing Figure 2 an example of the display device. Figure 3 The figure illustrates the bending region BA in an unfolded state.

[0057] Referring to Figure 2 and Figure 3 , the display device DD (refer to Figure 1 ) may include a display module DM and a window WIN. The display module DM includes a substrate SUB, a display layer DP, a first protective layer SNL (or a stress-neutral layer), a second protective layer PF (or a protective film), an adhesive layer ADH, a first support member MTL1, and a second support member MTL2.

[0058] The substrate SUB may include a flexible material to be capable of being bent or folded, and may have a single-layer structure or a multi-layer structure.

[0059] For example, the substrate SUB may include at least any one of polystyrene, polyvinyl alcohol, polymethyl methacrylate, polyethersulfone, polyacrylate, polyetherimide, polyethylene naphthalate, polyethylene terephthalate, polyphenylene sulfide, polyarylate, polyimide, polycarbonate, triacetate cellulose, and cellulose acetate propionate. However, the material constituting the substrate SUB can be varied in various ways, and it can also be made of fiber reinforced plastic (FRP) or the like.

[0060] The display layer DP may be disposed on the first surface of the substrate SUB in the first non-bending region FA1. Here, in the first non-bending region FA1, the first surface of the substrate SUB may correspond to the third direction DR3.

[0061] The display layer DP may include the pixels described with reference to Figure 1 the above. For example, the display layer DP may include an organic light emitting diode. Figure 2 The case where the display layer DP is only disposed in the first non-bending region FA1 is illustrated, however, the display layer DP is not limited thereto. For example, the display layer DP may also be disposed in the second non-bending region FA2.

[0062] The first protective layer SNL may be arranged on the first surface of the substrate SUB corresponding to the bending region BA. That is, the first protective layer SNL may be arranged on the first surface of the substrate SUB in the bending region BA. The first protective layer SNL may be disposed on the same layer as the display layer DP and extend to the second non-bending region FA2. That is, the first protective layer SNL may also be arranged on the second non-bending region FA2. The first protective layer SNL may include an organic insulating material, an inorganic insulating material, etc., and protect the substrate SUB (or the conductive layer disposed on the substrate SUB) from external moisture, impact, etc.

[0063] For reference, in the case where the substrate SUB (or, the laminated structure) is bent, a stress neutral plane (or, neutral plane) may exist within the substrate SUB. The first protective layer SNL can adjust the position of the stress neutral plane of the substrate SUB within the bending region BA. For example, by adjusting the thickness and modulus of the first protective layer SNL, etc., the stress neutral plane can be positioned near a specific layer (e.g., a conductive layer such as wiring) of the laminated structure including the substrate SUB and the first protective layer SNL.

[0064] In one embodiment, the thickness of the first protective layer SNL can be substantially uniform. For example, the thickness of the first protective layer SNL at the first position point P1 and the thickness of the first protective layer SNL at the second position point P2 can be equal to the average thickness of the first protective layer SNL. However, the thickness of the first protective layer SNL is not limited thereto. The thickness of the first protective layer SNL can vary according to the position within the bending region BA. This will be described with reference to Figure 11 and Figure 14 which will be described later.

[0065] The second protective layer PF can be disposed on the second surface (or, back surface, lower surface) of the substrate SUB. The second protective layer PF can be disposed on the entire second surface of the substrate SUB.

[0066] The second protective layer PF can similarly include polyethylene terephthalate (PET: polyethyeleneterepthalate) or polyimide (PI: polyimide) like the substrate SUB.

[0067] The second protective layer PF can include a pressure sensitive adhesive disposed on the first surface and be attached to the second surface of the substrate SUB.

[0068] In some embodiments, the second protective layer PF can include cavities (cavity) CV within the bending region BA. Here, each cavity CV can be an empty space, groove, or recessed pattern formed inside the second protective layer PF.

[0069] For the description of the cavity CV, reference can be made to Figure 4 .

[0070] Figure 4 is a cross-sectional view showing an example of the cavity included in the Figure 3 display device.

[0071] Referring to Figure 4 , the cavity CV_U in the first state can represent Figure 3The cavity included in the second protective layer PF shown (i.e., the second protective layer PF included in the display device before bending) can be represented by the cavity CV_B in the second state. Figure 2 The cavity included in the second protective layer PF shown (i.e., the second protective layer PF included in the display device after bending).

[0072] The cavity CV_U in the first state can have a cross-sectional shape of a reversed trapezoid. However, this is exemplary, and the cavity CV_U in the first state can also have a cross-sectional shape of a quadrilateral or a trapezoid.

[0073] Due to the bending of the display device, the two side surfaces of the cavity CV_U in the first state are joined, and the cavity CV_B in the second state can have a triangular cross-sectional shape. The shape of the cavity CV_U in the first state is converted into the shape of the cavity CV_B in the second state, thereby being able to compensate for the stress of the substrate SUB (or, the display device).

[0074] Referring back to Figure 2 and Figure 3 , the cavity CV can have different densities (e.g., intervals) or different sizes (e.g., depths) in different regions based on the stress of the substrate SUB (or, the display module DM) (i.e., the bending stress caused by bending, such as internal stress). For example, the cavity CV can be formed on the second surface (or, the lower surface) of the second protective layer PF by laser irradiation, and has different sizes according to the intensity and irradiation time of the laser (or, the laser beam).

[0075] In one embodiment, when the stress at a specific position point (e.g., the central part of the bending region BA) in the bending region BA is greater than the average stress of the bending region BA, the first density of the cavity CV corresponding to the specific position point can be less than the average density of the cavity CV.

[0076] Referring to Figure 3, the bending region BA may include a first sub-region BA_S1 to a fifth sub-region BA_S5. The first sub-region BA_S1 to the fifth sub-region BA_S5 may be arranged in sequence from a first position point P1 (i.e., the intersection point of the first non-bending region FA1 and the bending region BA) to a second position point P2 (i.e., the intersection point of the second non-bending region FA2 and the bending region BA). In the first sub-region BA_S1 to the fifth sub-region BA_S5, the stress of the substrate SUB may be different from each other. For example, the stress of the substrate SUB located in the first sub-region BA_S1 may be less than the stress of the substrate SUB located in the second sub-region BA_S2, and the stress of the substrate SUB located in the second sub-region BA_S2 is less than the stress of the substrate SUB located in the third sub-region BA_S3. Based on the third sub-region BA_S3, the fourth sub-region BA_S4 may correspond to the second sub-region BA_S2, and the fifth sub-region BA_S5 corresponds to the first sub-region BA_S1.

[0077] In the first sub-region BA_S1 (or, the first adjacent region), the second protective layer PF may include a first cavity CV1. In the second sub-region BA_S2, the second protective layer PF may include a second cavity CV2. In the third sub-region BA_S3 (or, the middle region), the second protective layer PF may include a third cavity CV3. The second protective layer PF may respectively include a fourth cavity CV4 and a fifth cavity CV5 corresponding to the fourth sub-region BA_S4 and the fifth sub-region BA_S5. Since the fourth sub-region BA_S4 and the fifth sub-region BA_S5 respectively correspond to the second sub-region BA_S2 and the first sub-region BA_S1, the fourth cavity CV4 and the fifth cavity CV5 may be substantially the same as the second cavity CV2 and the first cavity CV1 respectively.

[0078] In one embodiment, the size of the first cavity CV1 in the first sub-region BA_S1 may be larger than the size of the second cavity CV2 in the second sub-region BA_S2. For example, the first depth H1 of the first cavity CV1 may be greater than the second depth H2 of the second cavity CV2. Similarly, the size (e.g., the second depth H2) of the second cavity CV2 in the second sub-region BA_S2 may be larger than the size (e.g., the third depth H3) of the third cavity CV3 in the third sub-region BA_S3.

[0079] In one embodiment, the density of the first cavity CV1 located in the first sub-region BA_S1 may be greater than the density of the second cavity CV2 located in the second sub-region BA_S2. For example, the first gap between the first cavity CV1 located in the first sub-region BA_S1 and the cavities adjacent thereto may be smaller than the second gap between the second cavity CV2 located in the second sub-region BA_S2 and the cavities adjacent thereto. Similarly, the density of the second cavity CV2 located in the second sub-region BA_S2 may be greater than the density of the third cavity CV3 located in the third sub-region BA_S3.

[0080] The relationship between the stress on the substrate SUB and the cavity CV will be described hereinafter with reference to Figure 6 the substrate SUB.

[0081] The first support member MTL1 and the second support member MTL2 may be disposed on the second surface of the substrate SUB in the first non-bending region FA1 and the second non-bending region FA2. The first support member MTL1 may overlap the substrate SUB in the first non-bending region FA1 and be attached to the second surface of the substrate SUB through the adhesive layer ADH. Here, the adhesive layer ADH may include a pressure-sensitive adhesive substance. Similarly, the second support member MTL2 may overlap the substrate SUB in the second non-bending region FA2 and be attached to the second surface of the substrate SUB through the adhesive layer ADH.

[0082] The first support member MTL1 and the second support member MTL2 may be rigid, for example, including metal, and respectively support the first non-bending region FA1 and the second non-bending region FA2 of the substrate SUB. The first non-bending region FA1 and the second non-bending region FA2 of the substrate SUB may be kept substantially flat by the first support member MTL1 and the second support member MTL2.

[0083] In addition, the window WIN may be provided on the display module DM and include glass, sapphire, plastic, etc. The window WIN may have a single-layer or multi-layer structure. The window WIN may include a pattern layer (or, achromatic layer) corresponding to the bending region BA and providing a specific texture or achromatic color. And, the window WIN may further include functional coatings such as an anti-fingerprint layer, an anti-reflection layer, and a hard coat.

[0084] According to an embodiment, a functional module may be provided between the display module DM and the window WIN.

[0085] For example, the functional module may include an input sensing module, and the input sensing module may sense various forms of input provided from the outside of the display device. For example, the input sensing module may sense various forms of input such as light, heat, or pressure generated by the user's body.

[0086] As described with reference toFigure 3 and Figure 4 As described above, the second protective layer PF may include cavities CV, and the cavities CV may have different densities and / or sizes corresponding to the stress at the position of the substrate SUB.

[0087] Figures 5a to 5c is a plan view showing an example of the second protective layer included in the Figure 3 display device. Since the fourth sub-region BA_S4 and the fifth sub-region BA_S5 are substantially the same as the second sub-region BA_S2 and the first sub-region BA_S1, the second protective layer PF will be described centering on the first sub-region BA_S1, the second sub-region BA_S2, and the third sub-region BA_S3.

[0088] First, referring to Figure 3 and Figure 5a , the first cavity CV1, the second cavity CV2, and the third cavity CV3 may be dispersedly arranged in the bending region BA.

[0089] The first cavity CV1, the second cavity CV2, and the third cavity CV3 may each have a circular planar shape. On the plane, the first area of the first cavity CV1 is larger than the second area of the second cavity CV2, and the second area of the second cavity CV2 is larger than the third area of the third cavity CV3.

[0090] The first cavity CV1, the second cavity CV2, and the third cavity CV3 may be arranged to be staggered with each other along the first direction DR1. However, this is only illustrative, and the arrangement of the first cavity CV1, the second cavity CV2, and the third cavity CV3 is not limited thereto.

[0091] The first cavity CV1, the second cavity CV2, and the third cavity CV3 may be arranged to be staggered with each other along the first direction DR1, and the first cavity CV1, the second cavity CV2, and the third cavity CV3 may be repeatedly arranged along the second direction DR2 respectively. That is, the first cavity CV1, the second cavity CV2, and the third cavity CV3 may be arranged in a mosaic pattern. However, this is only illustrative, and the arrangement of the first cavity CV1, the second cavity CV2, and the third cavity CV3 is not limited thereto.

[0092] In Figure 5a , although the case where the densities (or the number per unit area) of the first cavity CV1, the second cavity CV2, and the third cavity CV3 are the same or similar to each other is illustrated, this is only illustrative and not limited thereto. For example, the density (or the number) of the first cavity CV1 in the first sub-region BA_S1 may be greater than the density of the second cavity CV2 in the second sub-region BA_S2.

[0093] Referring to Figure 5b, the first cavity CV1_1, the second cavity CV2_1, and the third cavity CV3_1 may each have a quadrilateral (or, a rhombus) planar shape. On the plane, the first area of the first cavity CV1_1 is greater than the second area of the second cavity CV2_1, and the second area of the second cavity CV2_1 is greater than the third area of the third cavity CV3_1.

[0094] However, the planar shapes of the first cavity CV1_1, the second cavity CV2_1, and the third cavity CV3_1 are not limited thereto. For example, the first cavity CV1_1, the second cavity CV2_1, and the third cavity CV3_1 may each also have a planar shape such as a polygon, an ellipse, etc.

[0095] Referring to Figure 5c , the first cavity CV1_2, the second cavity CV2_2, and the third cavity CV3_2 may each have a strip shape and extend along the second direction DR2. For example, the first cavity CV1_2, the second cavity CV2_2, and the third cavity CV3_2 may each extend from one side surface of the second protective layer PF_2 to the other side surface. The first width of the first cavity CV1_2 may be greater than the second width of the second cavity CV2_2, and the second width of the second cavity CV2_2 may be greater than the third width of the third cavity CV3_2.

[0096] As referring to Figures 5a to 5c described above, the cavity may have diverse planar shapes.

[0097] Figure 6 is a diagram showing the stress of the bent area of the Figure 3 display device. Figure 7 is a diagram showing the Figure 4 relationship between the stress of the second protective layer and the bent area.

[0098] Referring to Figure 6 , the first curve GRAPH1 may show the stress (e.g., internal stress) of the substrate SUB according to the position of the bent area BA (i.e., according to the position in the first direction DR1 shown in Figure 3 ). The stress of the substrate SUB according to the first curve GRAPH1 may not include the influence caused by the second protective layer PF. In Figure 6 , the stress of the substrate SUB may be represented by the ratio of the stress at the corresponding position point to the average stress of the substrate SUB.

[0099] According to the first curve GRAPH1, the stress of the substrate SUB at the first position point P1 and the stress of the substrate SUB at the second position point P2 can be relatively small respectively, and the stress of the substrate SUB at the central point separated from the first position point P1 and the second position point P2 is relatively large. The first non-bending region FA1 and the second non-bending region FA2 adjacent to the first position point P1 and the second position point P2 respectively are supported by the first support member MTL1 and the second support member MTL2. Therefore, based on the central point where the stress of the substrate SUB is relatively large, the closer to each of the first position point P1 and the second position point P2, the relatively smaller the stress of the substrate SUB can be.

[0100] The second curve GRAPH2 can represent the stress applied to the substrate SUB through the second protective layer PF (i.e., the stress of the substrate SUB). The third curve GRAPH3 can represent the target stress of the substrate SUB, which is equal to the sum of the stress of the substrate SUB according to the first curve GRAPH1 and the stress of the substrate SUB according to the second curve GRAPH2.

[0101] According to the third curve GRAPH3, the stress of the substrate SUB can be uniform (or constant) regardless of the position, and the second curve GRAPH2 is symmetric with the first curve GRAPH1 based on the third curve GRAPH3.

[0102] That is, the compensation value (or stress) by position that needs to be compensated to the substrate SUB (or the display device) through the second protective layer PF can be derived based on the first curve GRAPH1, and the distribution, size, and density of the cavity CV in the second protective layer PF (refer to Figure 3 ) can be determined based on the derived compensation value (i.e., the second curve GRAPH2).

[0103] Refer to Figure 3 and Figure 7 , the first characteristic curve GRAPH_C1 represents the change of the stress of the substrate SUB according to the density or depth (or size) of the cavity CV in the second protective layer PF.

[0104] According to the first characteristic curve GRAPH_C1, the greater the density of the cavity CV in the second protective layer PF, the greater the stress of the substrate SUB at the corresponding position point. Similarly, the greater the depth (or size) of the cavity CV in the second protective layer PF, the greater the stress of the substrate SUB at the corresponding position point.

[0105] The second characteristic curve GRAPH_C2 represents the change of the stress of the substrate SUB according to the thickness of the second protective layer PF.

[0106] According to the second characteristic curve GRAPH_C2, the thicker the thickness of the second protective layer PF, the smaller the stress of the substrate SUB at the corresponding position point can be.

[0107] That is, based on the stress of the substrate SUB according to Figure 6 the second curve GRAPH2 shown, the thickness of the second protective layer PF and the density and / or depth of the cavity CV can be determined.

[0108] Hereinafter, with reference to Figures 8a to 9d the process of setting the thickness of the second protective layer PF and the density and / or depth of the cavity CV will be described.

[0109] Figure 8a is a diagram for explaining the process of compensating the stress in the bent region of Figure 3 the display device shown. Figure 8b is a diagram showing the stress in the bent region caused by the second protective layer included in Figure 3 the display device shown. Figures 9a to 9d is a diagram showing the second protective layer according to Figure 8a the stress compensation process shown.

[0110] First, with reference to Figure 3 and Figure 8a the first curve GRAPH1 can represent the stress of the substrate SUB according to the position of the bent region BA (that is, according to the position in the first direction DR1 shown in Figure 3 ), and is the same as or similar to the first curve GRAPH1 described with reference to Figure 6 .

[0111] With reference to Figure 8a and Figure 9a the first compensation curve GRAPH_S1 can represent the stress of the first laminated structure formed by combining the first protective layer SNL and the substrate SUB. The first laminated structure may further include the second protective layer PF. Here, Figure 9a the second protective layer PF shown can have a preset thickness and include a reference cavity CV0 uniformly distributed in the bent region BA.

[0112] If the first protective layer SNL is formed with a constant thickness at positions on the first surface of the substrate SUB, the stress of the substrate SUB can be uniformly reduced in the entire bent region BA in proportion to the thickness of the first protective layer SNL. The first stress change amount (or reduction amount) caused by the thickness of the first protective layer SNL is defined as "a", and the stress reduction amount at the first position point P1 in the bent region BA caused by the thickness of the first protective layer SNL can be the same as or similar to the stress reduction amount at the central point of the bent region BA.

[0113] The thickness of the first protective layer SNL can be set such that the stress of the substrate SUB at the first position point P1 (and the second position point P2) becomes the same as a reference value (e.g., 0). In this case, in the state where the display device is bent (i.e., in the Figure 2 display device), the first protective layer SNL can be prevented from lifting or peeling off the substrate SUB at the first position point P1 (and the second position point P2).

[0114] Referring to Figure 8a and Figure 9b , the second compensation curve GRAPH_S2 can represent the stress of the second stacked structure as shown in Figure 9b . Compared with the Figure 9a stacked structure, the second stacked structure can include a second protective layer PF having a reference thickness T_PF. That is, the thickness of the second protective layer PF can be adjusted in the first stacked structure.

[0115] The stress of the substrate SUB can be uniformly reduced in the entire bending region BA in proportion to the thickness of the second protective layer PF. The second stress change amount (or, reduction amount) caused by the thickness of the second protective layer PF can be defined as "b", and the stress reduction amount at the first position point P1 in the bending region BA caused by the thickness of the second protective layer PF can be the same as or similar to the stress reduction amount at the central point of the bending region BA.

[0116] The reference thickness T_PF of the second protective layer PF can be set such that the stress of the substrate SUB at the central point of the bending region BA becomes the same as or similar to a reference value (e.g., 0).

[0117] Referring to Figure 8a and Figure 9c , the second curve GRAPH2 can represent the stress applied to the substrate SUB (i.e., the stress of the substrate SUB) by the second protective layer PF (and the first protective layer SNL) as shown in Figure 9c , which is similar to the second curve GRAPH2 described in reference Figure 6 . The third curve GRAPH3 can represent the stress of the third stacked structure as shown in Figure 9c , which is similar to the third curve GRAPH3 described in reference Figure 6 . Compared with the Figure 9b second stacked structure, the third stacked structure can include reference cavities CV0 distributed at different densities according to positions. That is, the density of the reference cavities CV0 can be adjusted in the second stacked structure according to positions. Then, the depth of the reference cavities CV0 can be adjusted according to positions based on the density of the reference cavities CV0, Figure 9d The fourth stacked structure shown in can include a first cavity CV1, a second cavity CV2, and a third cavity CV3 having different depths.

[0118] As described with reference to Figure 7 above, as the density of the reference cavity CV0 increases, the amount of compensation for the stress on the substrate SUB can be reduced, and the stress on the substrate SUB relatively increases. Therefore, in the region adjacent to the first position point P1 (and the second position point P2) where relative overcompensation occurs, the density of the reference cavity CV0 can be set relatively large, and at the central point (i.e., the central point of the bending region BA) where appropriate compensation or relative undercompensation occurs, the density of the reference cavity CV0 can be set relatively small. That is, the panel stress concentrated at the relatively central position points can be adjusted uniformly throughout the bending region BA.

[0119] Referring to Figure 8b and Figure 9c , the cavity curve GRAPH_CC can represent the density (or depth) of the reference cavity CV0 by position, and the stress curve GRAPH_SS can represent the stress of the substrate SUB according to the cavity curve GRAPH_CC.

[0120] According to the cavity curve GRAPH_CC and the stress curve GRAPH_SS, the stress of the substrate SUB changes proportionally with the density of the reference cavity CV0, and the third stress change amount at the first position point P1 caused by the density of the reference cavity CV0 can be defined as "c".

[0121] Similarly, according to the cavity curve GRAPH_CC and the stress curve GRAPH_SS, the stress of the substrate SUB changes proportionally with the depth of the reference cavity CV0, and the fourth stress change amount at the first position point P1 caused by the depth of the reference cavity CV0 can be defined as "d".

[0122] In this case, the stress of the substrate SUB can be expressed as the following mathematical formula 1.

[0123] [Mathematical formula 1]

[0124] P' = P + Pc

[0125] = P - e

[0126] = P - (a + b - c - d)

[0127] = P - (K × SNL thickness + L × PF thickness - M × CV - N × CV)

[0128] Here, P' can be the compensated stress of the substrate SUB (or, the display device), P is the initial stress of the substrate SUB, Pc is the total stress compensation value, and e is the total stress change amount of the substrate SUB. Also, K is the stress change amount constant according to the thickness of the first protective layer SNL, L is the stress change amount constant according to the thickness of the second protective layer PF, M is the stress change amount constant according to the density of the cavity CV, and N is the stress change amount constant according to the depth of the cavity CV.

[0129] In the bending region BA, the stress and stress compensation value by position can be generalized into the following mathematical formula 2.

[0130] [Mathematical formula 2]

[0131]

[0132]

[0133] Here, a, b, and k can be constants, and d is the length of the bending region BA (i.e., the distance between the first position point P1 and the second position point P2).

[0134] As referred to Figures 8a to 9d As described above, the thickness of the first protective layer SNL, the thickness of the second protective layer PF, the density of the cavity inside the second protective layer PF, and the depth of the cavity inside the second protective layer PF can be determined in sequence based on the stress of the substrate SUB. Through the process of compensating the stress of the substrate SUB in sequence, the stress of the substrate SUB (or, the display device) can become uniform throughout the bending region BA. Accordingly, the curvature of the bending region BA becomes uniform, and the strength of the bending region BA can be relatively increased.

[0135] Figure 10 is a cross-sectional view showing Figure 1 another example of the display device. Figure 10 illustrates the cross-section of the display device corresponding to the Figure 2 display device.

[0136] Referring to Figure 2 and Figure 10 , the difference from the Figure 2 display device is that Figure 10 the display device of

[0137] also includes a third protective layer RESIN.

[0138] The third protective layer RESIN may include a general thermoplastic resin and is coated on the second surface of the second protective layer PF after the display device is bent. The third protective layer RESIN can support the bent area BA of the substrate SUB together with the first protective layer SNL and the second protective layer PF, and can maintain the curvature of the bent area BA constant even over time.

[0139] Figure 11 is a cross-sectional view showing Figure 1 yet another example of the display device. Figure 11 illustrates the cross-section of the display device corresponding to Figure 2 the display device. Figure 12 is a cross-sectional view showing Figure 11 an example of the display device. Figure 12 illustrates Figure 11 the unfolded state of the display device. Figure 13 is a graph showing Figure 12 the stress in the bent area of the display device. Figure 13 illustrates the first curve GRAPH1_1 to the third curve GRAPH3_1 corresponding to Figure 6 the first curve GRAPH1 to the third curve GRAPH3.

[0140] Referring to Figure 2 , Figure 3 and Figures 11 to 13 , Figure 11 the thickness of the first protective layer SNL included in the display device of

[0141] In this case, as Figure 13For the first curve GRAPH1_1 shown, the stress of the substrate SUB at the central point of the bending region BA can be minimized, and at the first position point P1 (and the second position point P2), the stress of the substrate SUB increases sharply. This is because the closer to the first position point P1 and the second position point P2, the smaller the thickness of the first protective layer SNL, so that the stress compensation amount by the first protective layer SNL decreases. At the first position point P1 (and the second position point P2), the stress of the substrate SUB can be relatively small. This is because the first non-bending region FA1 and the second non-bending region FA2 adjacent to the first position point P1 and the second position point P2 respectively are supported by the first support member MTL1 and the second support member MTL2.

[0142] Based on the third curve GRAPH3_1, the second curve GRAPH2_1 is set to be symmetric with the first curve GRAPH1_1, whereby, it is possible to determine Figure 11 and Figure 12 the cavities CV1_1, CV2, CV3_1, CV4, CV5_1, CV6, CV7 shown.

[0143] The difference from the bending region BA with reference to Figure 2 and Figure 3 may lie in that Figure 11 and Figure 12 the bending region BA shown further includes a sixth sub-region BA_S6 and a seventh sub-region BA_S7.

[0144] The sixth sub-region BA_S6 can be set adjacent to the first position point P1 and can correspond to the interval from the position point with the maximum stress with reference to Figure 13 to the first position point P1. Similarly, the seventh sub-region BA_S7 can be set adjacent to the second position point P2 and can correspond to the interval from the position point with the maximum stress with reference to Figure 13 to the second position point P2. The total area of the sixth sub-region BA_S6 and the seventh sub-region BA_S7 can be smaller than the area of the remaining sub-regions.

[0145] In the first sub-region BA_S1, the second protective layer PF can include a first cavity CV1_1, and the first cavity CV1_1 is similar to the third cavity CV3 with reference to Figure 3 described. Therefore, repeated explanations will not be given. In the second sub-region BA_S2, the second protective layer PF can include a second cavity CV2, and the second cavity CV2 is substantially the same as or similar to the second cavity CV2 with reference to Figure 3 described. In the third sub-region BA_S3, the second protective layer PF can include a third cavity CV3_1, and the third cavity CV3_1 is similar to the reference Figure 3is similar to the first cavity CV1 described above. Based on the third sub-region BA_S3, the fourth sub-region BA_S4 can correspond to the second sub-region BA_S2, and the fifth sub-region BA_S5 corresponds to the first sub-region BA_S1.

[0146] In the sixth sub-region BA_S6, the second protective layer PF can include a sixth cavity CV6, and in the seventh sub-region BA_S7, the second protective layer PF includes a seventh cavity CV7.

[0147] The sixth cavity CV6 and the seventh cavity CV7 can be substantially the same as or similar to the second cavity CV2. For example, the depth H6 of the sixth cavity CV6 can be the same as or similar to the second depth H2 of the second cavity CV2, and the density of the sixth cavity CV6 in the sixth sub-region BA_S6 can be the same as or similar to the density of the second cavity CV2 in the second sub-region BA_S2.

[0148] As referred to Figures 11 to 13 above, when the thickness of the first protective layer SNL varies according to the position of the bending region BA, the cavities of the second protective layer PF can have different densities and / or sizes corresponding to the position-dependent stress of the substrate SUB.

[0149] Figure 14 is a cross-sectional view showing Figure 1 another example of a display device. Figure 14 illustrates a cross-section of a display device corresponding to the Figure 2 display device. Figure 15 is a cross-sectional view showing Figure 14 an example of a display device. Figure 15 illustrates Figure 14 the unfolded state of the display device. Figure 16 is a diagram showing Figure 15 the stress in the bent region of the display device. Figure 16 illustrates the first curve GRAPH1_2 to the third curve GRAPH3_2 corresponding to the Figure 6 first curve GRAPH1 to the third curve GRAPH3.

[0150] Referring to Figure 2 、 Figure 3 and Figures 14 to 16 , Figure 14The thickness of the first protective layer SNL included in the display device may vary according to the position of the bending region BA. For example, at the central point of the bending region BA, the fourth thickness T_P4 of the first protective layer SNL may be the smallest. The closer to the first position point P1 (or the second position point P2), the greater the thickness of the first protective layer SNL. At the first position point P1, the third thickness T_P3 of the first protective layer SNL is the largest. In other words, at the central point of the bending region BA, the modulus of the first protective layer SNL may be the smallest, and at the first position point P1, the modulus of the first protective layer SNL is the largest.

[0151] In this case, as Figure 16 shown in the first curve GRAPH1_2, the stress of the substrate SUB at the central point of the bending region BA may be the largest, and at the first position point P1 (and the second position point P2), the stress of the substrate SUB decreases sharply. This is because the closer to the first position point P1 and the second position point P2, the greater the thickness of the first protective layer SNL. At the first position point P1 (and the second position point P2), the stress of the substrate SUB may be the smallest.

[0152] Based on the third curve GRAPH3_2, the second curve GRAPH2_2 can be set to be symmetric with the first curve GRAPH1_2, and accordingly, the Figure 14 and Figure 15 shown cavities CV1 - CV5 are determined.

[0153] Except for the width (or area, size), the first sub-region BA_S1 to the fifth sub-region BA_S5 may be similar to the first sub-region BA_S1 to the fifth sub-region BA_S5 described with reference to Figure 3 For example, based on the first sub-region BA_S1 to the fifth sub-region BA_S5 described with reference to Figure 3 corresponding to the second curve GRAPH2_2, the width of the third sub-region BA_S3 may become relatively smaller, and the width of the first sub-region BA_S1 increases relatively. For example, the width of the third sub-region BA_S3 may be smaller than the widths of the first sub-region BA_S1, the second sub-region BA_S2, the fourth sub-region BA_S4, and the fifth sub-region BA_S5 respectively.

[0154] Moreover, the first cavities CV1 to the fifth cavities CV5 included in the first sub-region BA_S1 to the fifth sub-region BA_S5 may be substantially the same as or similar to the cavities CV1 - CV5 described with reference to Figure 3 Therefore, repetitive explanations will not be repeated.

[0155] The third sub-region BA_S3 may or may not include the third cavity CV3. In this case, at the central point of the bending region BA, the stress caused by the reduction in the thickness of the first protective layer SNL can be additionally compensated for.

[0156] As referred to Figures 14 to 16 As described above, when the thickness (or modulus) of the first protective layer SNL is the largest in the boundary regions between the bending region BA and the first non-bending region FA1 and the second non-bending region FA2, the cavities CV1 to CV5 of the second protective layer PF may also have different densities and / or sizes corresponding to the position-dependent stress of the substrate SUB.

[0157] The scope of the present invention is not limited to the content described in the detailed description of the specification, but is defined only by the claims. Moreover, all forms of changes or deformations derived from the meaning, scope, and equivalent concepts of the claims should be construed as being included within the scope of the present invention.

Claims

1. A display device, comprising: a substrate including a first non-bending region and a second non-bending region spaced apart from each other and a bending region that is located between the first non-bending region and the second non-bending region and is bent; a display layer disposed on a first surface of the substrate in the first non-bending region and displaying an image; a first protective layer disposed on the first surface of the substrate in the bending region; and a second protective layer disposed on a second surface of the substrate and including a plurality of cavities spaced apart from each other in the bending region, wherein, in the bending region, the greater the bending stress of the region where the cavities are located, the smaller the depth of the cavities.

2. The display device according to claim 1, wherein when a first bending stress at a first position point in the bending region is greater than an average bending stress of the bending region, a first density of the cavities corresponding to the first position point is less than an average density of the cavities.

3. The display device according to claim 2, wherein a thickness of the first protective layer is constant throughout the bending region, the farther the first position point is from the first non-bending region, the greater the first bending stress until the first bending stress becomes maximum, and the smaller the first density.

4. The display device according to claim 3, wherein the bending region includes: a first adjacent region adjacent to the first non-bending region; a second adjacent region adjacent to the second non-bending region; and an intermediate region located between the first adjacent region and the second adjacent region, wherein, in the first adjacent region, a bending stress of the substrate is less than the average bending stress, in the intermediate region, the bending stress of the substrate is greater than the average bending stress, a density of first cavities corresponding to the first adjacent region is greater than a density of second cavities corresponding to the intermediate region.

5. The display device according to claim 4, wherein a depth of the first cavities is greater than a depth of the second cavities.

6. The display device according to claim 5, wherein a number of the first cavities per unit area is the same as a number of the second cavities per unit area.

7. The display device according to claim 4, wherein an average diameter, an average width, or an average area of the first cavities is greater than an average diameter, an average width, or an average area of the second cavities.

8. The display device according to claim 1, wherein each of the cavities has a circular or quadrilateral planar shape, and the cavities are arranged in an interleaved manner in a direction in which the first non-bending region and the second non-bending region are spaced apart from each other.

9. The display device according to claim 1, wherein each of the cavities has a strip-shaped planar shape and extends in a direction perpendicular to a direction in which the first non-bending region and the second non-bending region are spaced apart from each other.

10. A display device, comprising: a substrate including a first non-bending region and a second non-bending region spaced apart from each other and a bending region that is located between the first non-bending region and the second non-bending region and is bent; A display layer disposed on a first surface of the substrate in the first non-bending region and displaying an image; A first protective layer disposed on the first surface of the substrate in the bending region; And A second protective layer disposed on a second surface of the substrate and including cavities spaced apart from each other in the bending region, The bending region includes: a first adjacent region adjacent to the first non-bending region; a second adjacent region adjacent to the second non-bending region; and an intermediate region located between the first adjacent region and the second adjacent region, Wherein, a first thickness of the first protective layer corresponding to the first adjacent region is less than a second thickness of the first protective layer corresponding to the intermediate region, A density of a first cavity corresponding to the first adjacent region is less than a density of a second cavity corresponding to the intermediate region.

11. The display device according to claim 10, wherein, An area of the intermediate region is larger than a total area of the first adjacent region and the second adjacent region.

Images