Foldable display device

Abstract

The present disclosure provides a foldable display device including: a display panel including a non-folding area and a folding area that is bendable or foldable with respect to a folding axis; a support layer disposed on a back surface of the display panel; a first adhesive layer provided between the display panel and the support layer; a base substrate disposed on a back surface of the support layer and having an opening pattern formed in a region overlapping the folding region; and a second adhesive layer disposed between the support layer and the base substrate, the first adhesive layer having a modulus greater than that of the second adhesive layer.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2024-0140897, filed on October 16, 2024, with the Korean Intellectual Property Office, which is incorporated herein by reference for all purposes, as if fully set forth herein. Technical Field

[0003] This disclosure relates to electronic devices, and more specifically, to foldable display devices. Background Technology

[0004] In today's information society, display devices used to present images or visual information to users are becoming increasingly important. The demand for such display devices has spurred the rapid development of display technology, resulting in the development of various types and applications of thinner and lighter display devices that consume less power and offer superior performance.

[0005] For example, liquid crystal display (LCD) devices, organic light-emitting diode (OLED) display devices, plasma display devices (PDP), field emission display devices (FED), inorganic light-emitting diode (LED) display devices, micro LED display devices, quantum dot LED display devices, etc., have been developed and are becoming increasingly advanced.

[0006] Recently, there has been an increased demand for foldable display devices manufactured using flexible substrates. Foldable display devices can be carried in a folded state and display images in an unfolded state. Therefore, foldable display devices have the advantages of being easy to carry and displaying images on a large screen. However, because the folding and unfolding operations of foldable display devices relative to the folding axis are repeated too many times to count, foldable display devices suffer from visible wrinkles due to the stress applied to the folding area. Summary of the Invention

[0007] To address this problem, one or more aspects of this disclosure may provide a foldable display device having a structure in which the modulus of an adhesive layer disposed between the display panel and the support layer is set to 1 MPa or higher, and is able to reduce or improve visible wrinkles on the display panel, thereby improving the appearance quality.

[0008] One or more aspects of this disclosure may provide a foldable display device having one or more grooves patterned on an adhesive layer extending along the folding axis, thereby improving folding performance, the adhesive layer being disposed between a display panel and a support layer.

[0009] According to one or more exemplary embodiments of this disclosure, a foldable display device can be provided, comprising: a display panel including a non-folding region and a folding region that is flexible or foldable relative to a folding axis; a support layer disposed on a back surface of the display panel; a first adhesive layer disposed between the display panel and the support layer; a substrate disposed on the back surface of the support layer and having an opening pattern formed in a region overlapping the folding region; and a second adhesive layer disposed between the support layer and the substrate. In one or more aspects, the first adhesive layer may have a larger modulus than the second adhesive layer.

[0010] According to one or more exemplary embodiments of this disclosure, a foldable display device can be provided, comprising: a display panel including a non-folding region and a folding region that is flexible or foldable relative to a folding axis; a support layer disposed on a back surface of the display panel; a first adhesive layer disposed between the display panel and the support layer; a substrate disposed on the back surface of the support layer and having an opening pattern formed in a region overlapping the folding region; and a second adhesive layer disposed between the support layer and the substrate. In one or more aspects, the first adhesive layer may have a modulus greater than that of the second adhesive layer, and a plurality of grooves extending in the folding axis direction are patterned on the side of the first adhesive layer facing the display panel.

[0011] According to one or more aspects of this disclosure, a foldable display device can be provided that can reduce or improve visible wrinkles on the display panel by including a structure in which the modulus of an adhesive layer disposed between the display panel and the support layer is set to 1 MPa or higher, thereby improving the appearance quality.

[0012] According to one or more aspects of this disclosure, a foldable display device can be provided that improves folding performance by including a structure comprising one or more grooves patterned in an adhesive layer between the display panel and the support layer and extending in the folding axis direction.

[0013] According to one or more aspects of this disclosure, a foldable display device can be provided that is driven with low power by including a light-emitting element implemented as an organic light-emitting diode (OLED). Attached Figure Description

[0014] The accompanying drawings are included to provide a further understanding of this disclosure and are incorporated in and constitute a part of this disclosure. The drawings illustrate aspects of this disclosure and, together with the specification, serve to illustrate the principles of this disclosure. Therefore, it should be understood that the aspects, examples, and embodiments described herein are not limited to the illustrations in the drawings. In the drawings:

[0015] Figure 1 This is a plan view of an example foldable display device based on aspects of this disclosure;

[0016] Figure 2 It is along Figure 1 An example cross-sectional view of the foldable display device shown, taken along line A-A';

[0017] Figure 3 This is a plan view of the first adhesive layer, as an example of an aspect of this disclosure;

[0018] Figure 4 It is along Figure 1 An example cross-sectional view of the foldable display device shown, taken along line B-B';

[0019] Figure 5 The diagram illustrates the variation in wrinkles of a foldable display device comprising a first adhesive layer with a modulus of 0.05 MPa; and

[0020] Figure 6 The variation of folds in a foldable display device, including a first adhesive layer with a modulus of 1 MPa, is shown. Detailed Implementation

[0021] Reference will now be made in detail to exemplary embodiments of this disclosure, examples or aspects of which may be illustrated in the accompanying drawings. In the following description, unless otherwise specified, the structures, implementations, methods, and operations described herein are not limited to the specific examples, aspects, and embodiments set forth herein, and may be varied as is known in the art. Unless otherwise specified, the same reference numerals always denote the same elements. The names of the various elements used in the following description are chosen solely for convenience of writing the specification and may therefore differ from the names used in actual products. The advantages and features of this disclosure and its implementation methods will be illustrated by the following exemplary embodiments described with reference to the accompanying drawings. However, this disclosure may be implemented in different forms and should not be construed as limited to the exemplary embodiments set forth herein. Rather, these exemplary embodiments are provided so that this disclosure is thorough and complete enough to assist those skilled in the art in fully understanding its scope. Furthermore, the scope of protection of this disclosure is defined by the claims and their equivalents. In the following description, detailed descriptions of relevant known functions or configurations may be omitted where such detailed descriptions may unnecessarily obscure aspects of this disclosure. The shapes, sizes, ratios, angles, numbers, etc., shown in the accompanying drawings to describe various exemplary embodiments of this disclosure are given by way of example only. Therefore, this disclosure is not limited to the illustrations in the drawings. Terms such as “comprising,” “having,” “including,” “constituting,” “made of,” and “formed from” as used herein are generally intended to allow for the addition of other components, unless the terms are used with the term “only.” As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise.

[0022] While the terms “first,” “second,” A, B, (a), (b), etc., may be used herein to describe various elements, these elements should not be construed as being limited by these terms, as they are not used to define a particular order or priority. These terms are used only to distinguish one element from another. For example, without departing from the scope of this disclosure, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0023] When the first element is referred to as "connected or coupled to," "in contact with," or "overlapping with" the second element, it should be interpreted as meaning that not only can the first element be "directly connected or coupled to," "directly in contact with," or "directly overlap with" the second element, but a third element can also be "inserted" between the first and second elements, or the first and second elements can be "connected or coupled," "in contact with," or "overlapping" with each other via a fourth element. Here, the second element can be included in at least one of two or more elements that are "connected or coupled," "in contact with," or "overlapping" with each other.

[0024] When describing positional relationships, such as when using terms like "above," "over," "below," "above," "beside," or "attached" to describe the positional relationship between two parts, one or more other parts may be located between the two parts, unless more restrictive terms such as "immediately," "directly," or "closely" are used. For example, if an element or layer is placed "above" another element or layer, a third element or layer may be inserted therebetween. Furthermore, the terms "left," "right," "top," "bottom," "down," "up," "above," "below," etc., refer to any frame of reference.

[0025] Furthermore, when referring to any size, relative size, etc., it should be assumed that the numerical or corresponding information of an element or feature (e.g., level, range, etc.) includes tolerances or error ranges that may be caused by various factors (e.g., process factors, internal or external influences, noise, etc.), even if no relevant description is specified. Moreover, the term "may" fully encompasses all the meanings of the term "able to".

[0026] In the following text, various embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0027] Figure 1 This is a plan view of an example foldable display device 100 according to aspects of this disclosure. Figure 2 It is along Figure 1 The cross-sectional view of the foldable display device 100 shown is taken along line A-A'.

[0028] Reference Figure 1 and Figure 2 In one or more example embodiments, the foldable display device 100 may include a display panel 110, a support layer 120, a first adhesive layer 130, a substrate 140, and a second adhesive layer 150.

[0029] In the following discussion, for ease of description and understanding, the display surface of the display panel 110 (on which an image is displayed) faces the front of the foldable display device 100, and the support layer 120, the first adhesive layer 130, the substrate 140 and the second adhesive layer 150 are located on or below the back surface of the display panel 110 in the cross-sectional view.

[0030] The display panel 110 may be a panel on which an image is displayed. Light-emitting elements for displaying the image, as well as circuitry, wiring, and components for driving the light-emitting elements, may be arranged in the display panel 110. For example, the display panel 110 may be applied to a selection from liquid crystal display (LCD) devices, field emission display (FED) devices, electroluminescent display (ELD) devices, organic light-emitting diode (OLED) display devices, inorganic light-emitting diode display devices, quantum dot light-emitting diode display devices, micro light-emitting diode display devices, micro-light-emitting diode display devices, etc. In one or more aspects, organic light-emitting diodes (OLEDs), as representative light-emitting elements, may be applied to flexible display devices that maintain display performance even when bent like paper.

[0031] Organic light-emitting diodes (OLEDs) are self-emissive components, and because they do not require backlighting like non-self-emissive liquid crystals, OLED displays can be made lighter and thinner. Furthermore, compared to LCD devices, OLED displays offer wider viewing angles, superior contrast, lower power consumption, and faster response times. They also feature advantages such as low DC voltage operation, resistance to external shocks due to their solid-state internal components, and a wider operating temperature range. Moreover, due to their simpler manufacturing process, OLED displays significantly reduce production costs compared to LCD devices.

[0032] The display panel 110 may include a display area AA for displaying images and a non-display area NA for not displaying images. The non-display area NA may be an area outside the display area AA and is referred to as a non-active area or a bezel area. All or part of the non-display area NA may be an area visible in front of the foldable display device 100, or it may be a curved area that is not visible in front of the foldable display device 100.

[0033] The display panel 110 may include a folded area FA and a non-folded area NFA.

[0034] The folding region FA is the area of ​​the foldable display device 100 that can be bent or folded. For example, the folding region FA can be bent or folded relative to the folding axis FX, and can be bent or folded within a specific radius of curvature.

[0035] Figure 1The diagram shows a folding axis FX arranged at the center of the display panel 110 in the Y-axis direction, but this disclosure is not limited to this. For example, the folding axis FX may be arranged at the center of the display panel 110 in the X-axis direction. In one or more aspects, multiple folding axes FX may be defined in the X-axis or Y-axis directions and arranged spaced apart from each other.

[0036] The non-folding area NFA can be the area where the display panel 110 is not folded and the display panel 110 remains in a flat state. For example, the non-folding area NFA can extend to both sides of the folding area FA, and two non-folding areas NFA can be provided, wherein the folding area FA is between the two non-folding areas NFA.

[0037] When the foldable display device 100 is in the unfolded state, the folded area FA and the non-folded area NFA can form a plane. When the foldable display device 100 is in the folded state relative to the folding axis FX, the non-folded areas NFA on both sides of the folded area FA can be arranged to face each other while maintaining a flat state.

[0038] A support layer 120 may be disposed on the back surface of the display panel 110. With this configuration, the strength of the thin display panel 110 can be improved because the support layer 120 is disposed on the back surface of the display panel 110. For example, the support layer 120 may be in the form of one or more layers and may include polymeric materials such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), silicone, polyurethane (PU), etc.

[0039] The first adhesive layer 130 may be disposed between the display panel 110 and the support layer 120. For example, the first adhesive layer 130 may be located between the display panel 110 and the support layer 120, and may be used to bond the display panel 110 and the support layer 120.

[0040] The first adhesive layer 130 may include a pressure-sensitive adhesive (PSA) or an optically clear adhesive (OCA). In an example where the foldable display device 100 is configured with a top-emitting structure, the first adhesive layer 130 disposed beneath the display panel 110 may include a pressure-sensitive adhesive (PSA) or an optically clear adhesive (OCA). In another example where the foldable display device 100 is configured with a bottom-emitting structure, the first adhesive layer 130 may include an optically clear adhesive (OCA). This is because optically clear adhesives (OCA) have better light transmittance than pressure-sensitive adhesives (PSA). For example, an optically clear adhesive (OCA) can be formed to transmit 97% or more of light.

[0041] The substrate 140 may be disposed on the back surface of the support layer 120. For example, the substrate 140 may include a metallic material such as stainless steel (SUS) or a polymeric material such as polymethyl methacrylate (PMMA), polycarbonate (PC), polyacrylate (PA), polyvinyl alcohol (PVA), acrylonitrile-butadiene-styrene (ABS), polyethylene terephthalate (PET), etc.

[0042] In an example where the substrate 140 comprises a high-rigidity material such as stainless steel (SUS), the substrate 140 can have high resilience, and therefore the thickness of the substrate 140 can be reduced. Furthermore, even when the thickness of the substrate 140 is reduced, since the substrate 140 can be provided with a desired stiffness, the substrate 140 can also be used as a support for the display panel 110.

[0043] However, because high-rigidity materials such as stainless steel (SUS) have a narrow elastic deformation zone, they may be difficult to recover after deformation. For example, the substrate 140, which includes a high-rigidity material such as stainless steel (SUS), may not be able to unfold immediately when it is changed to an unfolded state after being folded, and the time spent maintaining the shape in the folded state may increase as the display device 100 is used.

[0044] To address this issue, the substrate 140 may have an opening pattern 141 formed in the region overlapping with the folded region FA. For example, the opening pattern 141 can improve the restoring force of the folded region FA of the substrate 140.

[0045] The second adhesive layer 150 may be disposed between the support layer 120 and the substrate 140. For example, the second adhesive layer 150 may be used to bond the support layer 120 and the substrate 140.

[0046] The second adhesive layer 150 can be formed to have a low modulus of 0.02 MPa to 0.07 MPa at room temperature (20 ± 5 °C). This is because a lower modulus results in higher flexibility and better bending performance. Therefore, due to the low modulus of the second adhesive layer 150, the foldable display device 100 can provide the advantage of easy folding operation.

[0047] The second adhesive layer 150 may include a pressure-sensitive adhesive (PSA) or an optically clear adhesive (OCA). In an example where the foldable display device 100 is configured with a top-emitting structure, the second adhesive layer 150 disposed below the display panel 110 may include a pressure-sensitive adhesive (PSA) or an optically clear adhesive (OCA). In another example where the foldable display device 100 is configured with a bottom-emitting structure, the second adhesive layer 150 may include an optically clear adhesive (OCA). This is because optically clear adhesive (OCA) has better light transmittance than pressure-sensitive adhesive (PSA).

[0048] In one or more aspects, the first adhesive layer 130 may be formed to have a modulus greater than that of the second adhesive layer 150. For example, the first adhesive layer 130 may be formed to have a modulus at room temperature that is about 40 to 60 times that of the second adhesive layer 150. For example, the first adhesive layer 130 may be formed to have a modulus of 1 MPa or greater at room temperature.

[0049] According to these configurations, since the first adhesive layer 130 disposed on the back surface of the display panel 110 is formed with a high modulus of 1 MPa or greater, the restoring force of the first adhesive layer 130 can be improved. For example, visible wrinkles on the display panel 110 can be prevented by achieving the property of maintaining a flat surface in the unfolded state. When the first adhesive layer 130 and the second adhesive layer 150 have the same modulus, the flexibility of the first adhesive layer 130 may increase, but its restoring force may decrease, and therefore, wrinkles in the folded state may remain in the folded area FA and be visible on the display panel 110. In contrast, when the first adhesive layer 130 is formed with a high modulus of 1 MPa or greater, the restoring force may increase when changing from folded to unfolded, and therefore wrinkles appearing in the folded area FA can be prevented or reduced. Therefore, since wrinkles are not visible on the display panel 110, the appearance quality can be improved.

[0050] Figure 3 This is an example plan view of the first adhesive layer 130 according to an aspect of this disclosure.

[0051] Reference Figure 3 The first adhesive layer 130 may include a plurality of grooves 131 patterned on a surface facing the display panel 110. This is because when the first adhesive layer 130 has a high modulus of 1 MPa or greater, its flexibility may be reduced, which may adversely affect folding performance. To address this issue, the grooves 131 may be formed to extend along the folding axis FX on a surface of the first adhesive layer 130, thereby improving folding performance.

[0052] The groove 131 can be configured to overlap with the folded region FA. For example, the groove 131 can be provided in a portion of the non-folded region NFA adjacent to the folded region FA and in the folded region FA. According to this configuration, since the groove 131 is even formed in the non-folded region NFA adjacent to the folded region FA, the folding performance can be further improved.

[0053] The groove 131 can be formed by laser processing. For example, the groove 131 can be formed in a direction perpendicular to the folding axis FX (which is... Figure 3 The grooves 131 have a width of 10 μm to 30 μm in the X-axis direction and a length of 5 mm to 20 mm in the folding axis FX direction, which is the Y-axis direction. For example, the grooves 131 may be spaced apart from each other by a distance of 5 mm to 20 mm in the X-axis direction and by a distance of 3 mm to 10 mm in the Y-axis direction. The shape of the grooves 131 according to aspects of this disclosure is not limited thereto. For example, the shape of the grooves 131 may be changed based on the size and structure of the foldable display device 100.

[0054] The groove 131 may include a first pattern 131a and a second pattern 131b.

[0055] The first pattern 131a can be formed to extend in the direction of the folding axis FX, and can be in the form of multiple first patterns 131a. For example, multiple first patterns 131a can be arranged to be spaced apart from each other in the direction of the folding axis FX, and form a first pattern line in the Y-axis direction.

[0056] The second pattern 131b can be formed to extend in the direction of the folding axis FX, and can be in the form of multiple second patterns 131b. For example, multiple second patterns 131b can be arranged to be spaced apart from each other in the direction of the folding axis FX, and to form a second pattern line in the Y-axis direction. In one or more aspects, the second pattern 131b can be arranged to be spaced apart from the first pattern 131a in a direction perpendicular to the folding axis FX, and therefore, the second pattern line can be arranged to be spaced apart from the first pattern line in the X-axis direction.

[0057] Multiple first patterns 131a and multiple second patterns 131b can be arranged as multiple lines in a direction perpendicular to the folding axis FX. For example, the first patterns 131a and the second patterns 131b can be spaced apart from each other in the X-axis direction. For example, the first patterns 131a can be arranged as an odd number of lines in the X-axis direction, and the second patterns 131b can be arranged as an even number of lines. In one or more aspects, the ends of each second pattern 131b and the ends of each first pattern 131a can be arranged in an alternating pattern. That is, the ends of each second pattern 131b can be arranged not to align with the ends of each first pattern 131a. Thus, flexibility can be provided to the entire area of ​​the folding region FA.

[0058] In one or more aspects, the support layer 120 may include a first support layer 121, an intermediate adhesive layer 122, and a second support layer 123.

[0059] The first support layer 121 may be disposed on the back surface of the first adhesive layer 130 to support the display panel 110.

[0060] An intermediate adhesive layer 122 may be disposed on the back surface of the first support layer 121 for bonding the first support layer 121 and the second support layer 123. For example, similar to the second adhesive layer 150, the intermediate adhesive layer 122 may be formed to have a low modulus of 0.02 MPa to 0.07 MPa.

[0061] The second support layer 123 may be disposed on the back surface of the intermediate adhesive layer 122. For example, the second support layer 123 may be disposed between the intermediate adhesive layer 122 and the second adhesive layer 150, and may prevent the opening pattern 141 formed in the substrate 140 from being visible on the display panel 110. For example, due to the low modulus of the second adhesive layer 150, the opening pattern 141 of the substrate 140 may be transferred to the second adhesive layer 150 and thus become visible on the display panel 110, but since the second support layer 123 is disposed between the display panel 110 and the second adhesive layer 150, the opening pattern 141 may be prevented from being visible on the display panel 110.

[0062] In one or more aspects, in a structure in which the opening pattern 141 can be prevented from being visible on the display panel 110 by means of only the first support layer 121, only the first support layer 121 can be provided on the substrate 140 without the second support layer 123. In this configuration, the intermediate adhesive layer 122 and the second support layer 123 can be omitted.

[0063] The foldable display device 100 may further include at least one additional adhesive layer for attaching additional layers to the foldable display device. For example, the foldable display device 100 may also include a third adhesive layer 161, a polarizing plate 170, a fourth adhesive layer 162, a cover glass 180, a fifth adhesive layer 163, and a protective layer 190. The modulus of the first adhesive layer may also be greater than the modulus of at least one additional adhesive layer. As an example, the modulus of the second adhesive layer is on the same order of magnitude as the modulus of at least one additional adhesive layer.

[0064] A third adhesive layer 161 may be disposed on the display panel 110. For example, the third adhesive layer 161 may be formed to have a low modulus of 0.02 MPa to 0.07 MPa to ensure flexibility. Since the third adhesive layer 161 is located on the display panel 110, i.e. on the display surface, it may be desirable to apply an optically clear adhesive (OCA) with good light transmittance.

[0065] Polarizing plate 170 may be disposed on third adhesive layer 161. For example, polarizing plate 170 may be attached to display panel 110 via third adhesive layer 161. Polarizing plate 170 may selectively transmit light to reduce reflection of external light incident on display panel 110. For example, polarizing plate 170 may comprise materials such as polyvinyl alcohol (PVA), polycarbonate (PC), polymethyl methacrylate (PMMA), etc.

[0066] A fourth adhesive layer 162 may be disposed on the polarizer 170. For example, the fourth adhesive layer 162 may be formed to have a low modulus of 0.02 MPa to 0.07 MPa to ensure flexibility. Since the fourth adhesive layer 162 is located above the display panel 110, i.e. above the display surface, it may be desirable to apply an optically clear adhesive (OCA) with good light transmittance.

[0067] Cover glass 180 may be disposed on the fourth adhesive layer 162. For example, cover glass 180 may be disposed above polarizer 170, wherein the fourth adhesive layer 162 is inserted between cover glass 180 and polarizer 170. Cover glass 180 may be designed to protect display panel 110 and may be formed of a glass material with excellent optical properties, high strength and impact resistance, and excellent surface hardness. For example, cover glass 180 may be a thin cover glass (TCG) with a thickness of 90 μm or less. Thin cover glass 180 with such a limited thickness can effectively alleviate or reduce the stress applied when the display device is folded or bent.

[0068] A fifth adhesive layer 163 may be disposed on the cover glass 180. For example, the fifth adhesive layer 163 may be formed to have a low modulus of 0.02 MPa to 0.07 MPa to ensure flexibility. Since the fifth adhesive layer 163 is located above the display panel 110, i.e. above the display surface, it may be desirable to apply an optically clear adhesive (OCA) with good light transmittance.

[0069] A protective layer 190 may be disposed on the fifth adhesive layer 163. For example, the protective layer 190 may be disposed above the cover glass 180, wherein the fifth adhesive layer 163 is inserted between the protective layer 190 and the cover glass 180. Because the protective layer 190 is disposed above the cover glass 180, it can protect the cover glass 180 from compressive and tensile stresses caused by external impacts or continuous folding. When the cover glass 180 breaks due to external impacts or stress and glass powder is generated, the protective layer 190 can prevent glass powder from scattering.

[0070] A coating 191 can be provided on the protective layer 190 to protect the foldable display device 100 from external impacts and scratches. For example, the coating 191 may include organic materials such as polyurethane acrylic resin, methacrylic resin, silsesquioxane compound, etc.

[0071] Figure 4 It is along Figure 1 An example cross-sectional view of the foldable display device 100 shown, taken along line B-B'.

[0072] Reference Figure 4 In one or more example embodiments, the display panel 110 may include a substrate 11, a transistor portion, a light-emitting element ED, a touch layer 111, and a color filter layer 112.

[0073] The substrate 11 can be used to support several components of the display panel 110 and includes insulating materials such as a glass substrate or a plastic substrate.

[0074] The substrate 11 may include two or more layers. For example, the substrate 11 may include a first substrate 11a, a second substrate 11b, and an insulating layer 11c disposed between the first substrate 11a and the second substrate 11b.

[0075] The first substrate 11a and the second substrate 11b may comprise polyimide (PI). Polyimide (PI) can be a polymer with relatively low crystallinity or a predominantly amorphous structure, readily synthesized to form thin films, and possesses advantages such as good transparency, heat resistance, and mechanical properties. However, since polyimide (PI) has poor moisture resistance, the moisture resistance of the first substrate 11a can be improved by providing an insulating layer 11c comprising an inorganic insulating material (such as silicon nitride (SiNx), silicon oxide (SiOx), etc.) between the first substrate 11a and the second substrate 11b.

[0076] The transistor portion may include an insulating layer (such as a first buffer layer 12, a first gate insulating layer 13, a first interlayer insulating layer 14, a second buffer layer 15, a second gate insulating layer 16, and a second interlayer insulating layer 17), a first transistor TFT1, a second transistor TFT2, a storage capacitor Cst, and several electrodes or signal lines disposed on the substrate 11.

[0077] The first transistor TFT1 may include a first active layer ACT1, a first gate electrode E1a, a first source electrode E1b, and a first drain electrode E1c. For example, the first active layer ACT1 may be a semiconductor layer including oxide semiconductor, amorphous silicon, polycrystalline silicon, or low-temperature polycrystalline silicon (LTPS). For example, the first transistor TFT1 may be a p-channel transistor or an n-channel transistor, but this disclosure is not limited thereto.

[0078] The second transistor TFT2 may include a second active layer ACT2, a second gate electrode E2a, a second source electrode E2b, and a second drain electrode E2c. For example, the second active layer ACT2 may be a semiconductor layer comprising oxide semiconductor, amorphous silicon, polycrystalline silicon, or low-temperature polycrystalline silicon (LTPS). For example, the second transistor TFT2 may be a p-channel transistor or an n-channel transistor, but this disclosure is not limited thereto.

[0079] The semiconductor material of each of the first active layer ACT1 of the first transistor TFT1 and the second active layer ACT2 of the second transistor TFT2 can be as follows.

[0080] For example, the first active layer ACT1 of the first transistor TFT1 and the second active layer ACT2 of the second transistor TFT2 may comprise an oxide semiconductor material. In another example, the first active layer ACT1 of the first transistor TFT1 and the second active layer ACT2 of the second transistor TFT2 may comprise a low-temperature polycrystalline silicon semiconductor material. In yet another example, the first active layer ACT1 of the first transistor TFT1 may comprise a low-temperature polycrystalline silicon semiconductor material, and the second active layer ACT2 of the second transistor TFT2 may comprise an oxide semiconductor material. In yet another example, the first active layer ACT1 of the first transistor TFT1 may comprise an oxide semiconductor material, and the second active layer ACT2 of the second transistor TFT2 may comprise a low-temperature polycrystalline silicon semiconductor material.

[0081] In the cross-sectional view, the second active layer ACT2 of the second transistor TFT2 can be positioned higher than the first active layer ACT1 of the first transistor TFT1 from the substrate 11.

[0082] The first buffer layer 12 may be located below the first active layer ACT1 of the first transistor TFT1, and the second buffer layer 15 may be located below the second active layer ACT2 of the second transistor TFT2. For example, the first active layer ACT1 of the first transistor TFT1 may be located on the first buffer layer 12, and the second active layer ACT2 of the second transistor TFT2 may be located on the second buffer layer 15. In the cross-sectional view, the second buffer layer 15 may be positioned higher than the first buffer layer 12.

[0083] The storage capacitor Cst can be configured to maintain a constant voltage during a frame and includes elements or portions of several metal layers within the display panel 110. For example, the storage capacitor Cst may include a first capacitor electrode CA1 and a second capacitor electrode CA2.

[0084] The light-emitting element ED can be disposed on the planarization layer 20. For example, the light-emitting element ED may include a first electrode AE ​​as an anode electrode, a second electrode CE as a cathode electrode, and an emitting layer EL disposed between the first electrode AE ​​and the second electrode CE.

[0085] An encapsulation layer 40 can be provided on the light-emitting element ED. The encapsulation layer 40 can cover the light-emitting element ED and thus protect the light-emitting element ED from external moisture, oxygen, impact, etc. For example, the encapsulation layer 40 may include a first encapsulation layer 41, a second encapsulation layer 42, and a third encapsulation layer 43.

[0086] The first encapsulation layer 41 may include inorganic materials capable of being deposited at low temperatures, such as silicon nitride (SiNx), silicon oxide (SiOx), silicon oxide nitride (SiON), aluminum oxide (Al2O3), etc. When the first encapsulation layer 41 is deposited in a low-temperature atmosphere, the first encapsulation layer 41 can prevent damage to the emitter layer EL containing organic materials that are susceptible to the effects of high-temperature atmospheres during the deposition process.

[0087] The second encapsulation layer 42 may be disposed on the first encapsulation layer 41. For example, the second encapsulation layer 42 may include organic insulating materials such as acrylic resin, epoxy resin, polyimide, polyethylene, silicon carbide (SiOC), etc. Since the second encapsulation layer 42 includes organic materials, it can encapsulate the components disposed thereunder and also reduce or minimize step differences.

[0088] The third encapsulation layer 43 may be disposed on the second encapsulation layer 42. For example, the third encapsulation layer 43 may include inorganic materials such as silicon nitride (SiNx), silicon oxide (SiOx), silicon oxide nitride (SiON), aluminum oxide (Al2O3), etc.

[0089] According to these configurations, since the encapsulation layer 40 includes multiple layers, the penetration of moisture or oxygen from the outside can be minimized, thereby effectively protecting the light-emitting element ED.

[0090] In the following text, refer to Figure 4 The stacked configuration or vertical structure of the display panel 110 is described in more detail.

[0091] Reference Figure 4 The first buffer layer 12 may be disposed on the substrate 11. For example, the first buffer layer 12 may be a single layer or multiple layers, but this disclosure is not limited thereto. In an example where the first buffer layer 12 is multiple layers, the first buffer layer 12 may include multiple buffer layers 12a and active buffer layers 12b.

[0092] The multiple buffer layer 12a may be designed to block moisture and oxygen from flowing into the substrate 11, and may include inorganic materials such as silicon nitride (SiNx), silicon oxide (SiOx), silicon nitride oxide (SiON), aluminum oxide (Al2O3), etc.

[0093] An active buffer layer 12b may be disposed on a multi-buffer layer 12a. The active buffer layer 12b may include inorganic materials such as silicon nitride (SiNx), silicon oxide (SiOx), silicon nitride oxide (SiON), aluminum oxide (Al2O3), etc. Figure 4 The active buffer layer 12b is shown to be a single layer, but the active buffer layer 12b can be in the form of two or more layers.

[0094] The first active layer ACT1 of the first transistor TFT1 can be disposed on the first buffer layer 12. The first active layer ACT1 may include a channel region with a channel formed, a source connection region on one side of the channel region, and a drain connection region on the other side of the channel region.

[0095] A first gate insulating layer 13 may be disposed on the first active layer ACT1 of the first transistor TFT1. For example, the first gate electrode E1a of the first transistor TFT1 may be disposed on the first gate insulating layer 13. A first interlayer insulating layer 14 may be disposed on the first gate electrode E1a of the first transistor TFT1. The first gate electrode E1a of the first transistor TFT1 may be referred to as the first gate metal layer.

[0096] The second buffer layer 15 can be disposed on the first interlayer insulation layer 14.

[0097] The second active layer ACT2 of the second transistor TFT2 can be disposed on the second buffer layer 15. The second active layer ACT2 may include a channel region with a channel formed, a source connection region on one side of the channel region, and a drain connection region on the other side of the channel region.

[0098] A second gate insulating layer 16 can be disposed on the second active layer ACT2 of the second transistor TFT2. For example, the second gate electrode E2a of the second transistor TFT2 can be disposed on the second gate insulating layer 16. A second interlayer insulating layer 17 can be disposed on the second gate electrode E2a of the second transistor TFT2. The second gate electrode E2a of the second transistor TFT2 can be referred to as the second gate metal layer.

[0099] The first source electrode E1b and the first drain electrode E1c of the first transistor TFT1, and the second source electrode E2b and the second drain electrode E2c of the second transistor TFT2 can be disposed on the second interlayer insulating layer 17.

[0100] The first source electrode E1b and the first drain electrode E1c of the first transistor TFT1 can be connected to the source connection region and the drain connection region of the first active layer ACT1 through the holes of the second interlayer insulating layer 17, the second gate insulating layer 16, the second buffer layer 15, the first interlayer insulating layer 14 and the first gate insulating layer 13, respectively.

[0101] The second source electrode E2b and the second drain electrode E2c of the second transistor TFT2 can be connected to the source connection region and the drain connection region of the second active layer ACT2 through the holes of the second interlayer insulating layer 17 and the second gate insulating layer 16, respectively.

[0102] The first source electrode E1b and the first drain electrode E1c of the first transistor TFT1, and the second source electrode E2b and the second drain electrode E2c of the second transistor TFT2 may include a first source-drain metal layer, and may be disposed in the first source-drain metal layer.

[0103] The storage capacitor Cst can be formed by a first capacitor electrode CA1 and a second capacitor electrode CA2. In one or more aspects, the storage capacitor Cst can be formed by three or more capacitor electrodes, and can be in the form of two or more capacitors connected in parallel.

[0104] Each of the first capacitor electrode CA1 and the second capacitor electrode CA2 can be disposed in several metal layers disposed within the display panel 110. For example, the first capacitor electrode CA1 may include the same first gate metal as the first gate electrode E1a on the first gate insulating layer 13, and may be disposed in the first gate metal layer. The second capacitor electrode CA2 may be disposed on the first interlayer insulating layer 14.

[0105] The second source electrode E2b of the second transistor TFT2 can be electrically connected to the second capacitor electrode CA2 through the holes in the second interlayer insulating layer 17, the second gate insulating layer 16, and the second buffer layer 15.

[0106] The transistor portion may further include a light-shielding layer BSM disposed on the substrate 11. The light-shielding layer BSM may overlap with the first active layer ACT1 of the first transistor TFT1 to prevent external light from entering the first transistor TFT1. The light-shielding layer BSM may be disposed below the first active layer ACT1 of the first transistor TFT1. For example, the light-shielding layer BSM may be disposed between the substrate 11 and the first buffer layer 12.

[0107] The planarization layer 20 can be disposed on the first transistor TFT1 and the second transistor TFT2. For example, the planarization layer 20 can be an organic insulating layer including an organic insulating material, and is disposed between the second interlayer insulating layer 17 and the light-emitting element ED.

[0108] The planarization layer 20 may include a first planarization layer 21, a second planarization layer 22, and a protective layer 111c. Figure 4 The planarization layer 20 is shown to consist of three layers, but aspects of this disclosure are not limited thereto.

[0109] The first planarization layer 21 can be disposed on the first source electrode E1b and the first drain electrode E1c of the first transistor TFT1, and the second source electrode E2b and the second drain electrode E2c of the second transistor TFT2. For example, the first planarization layer 21 can be disposed on the second interlayer insulating layer 17, simultaneously covering both the first transistor TFT1 and the second transistor TFT2.

[0110] A connection electrode RE can be provided on the first planarization layer 21. The connection electrode RE can electrically interconnect the second source electrode E2b and the first electrode AE ​​of the second transistor TFT2.

[0111] The connection electrode RE can be electrically connected to the second source electrode E2b of the second transistor TFT2 through the holes in the first planarization layer 21. The second source electrode E2b of the second transistor TFT2 can be electrically connected to the second capacitor electrode CA2 of the storage capacitor Cst.

[0112] The connecting electrode RE can be disposed in the second source-drain metal layer on the first planarization layer 21, and can include the second source-drain metal.

[0113] The second planarization layer 22 can be disposed on the connection electrode RE. For example, the second planarization layer 22 can be disposed on the first planarization layer 21, while covering the entire connection electrode RE.

[0114] A third planarization layer 23 can be set on the second planarization layer 22.

[0115] The light-emitting element ED can be disposed on the third planarization layer 23. The light-emitting element ED may include a first electrode AE, a second electrode CE, and an emitting layer EL disposed between the first electrode AE ​​and the second electrode CE. The light-emitting region of the light-emitting element ED can be formed by the area where the first electrode AE, the emitting layer EL, and the second electrode CE overlap and contact each other.

[0116] The first electrode AE ​​can be disposed on the third planarization layer 23. The first electrode AE ​​can be electrically connected to the connecting electrode RE through the holes in the third planarization layer 23 and the second planarization layer 22.

[0117] A dam 30 can be provided on the first electrode AE ​​to define a pixel. The opening of the dam 30 can expose a portion of the first electrode AE ​​to form a light-emitting area. The opening of the dam 30 can overlap with a portion of the first electrode AE.

[0118] For example, the dam 30 may include a material containing black pigment or an organic material containing benzocyclobutene resin, polyimide resin, acrylic resin, photosensitive polymer, etc., but this disclosure is not limited thereto. In an example where the dam 30 includes a material containing black pigment or black dye, the dam 30 may be a black dam. When the dam 30 includes a material containing black pigment or black dye, it can block light from the outside or light reflected from the outside, and thus the brightness of the foldable display device 100 can be further improved.

[0119] The dam 30 may also include a spacer 31 disposed in the upper part of the dam 30 to prevent damage that may occur when the deposition mask used during the formation of the emission layer EL comes into contact with the dam 30, and to maintain a certain distance between the dam 30 and the deposition mask.

[0120] The emitting layer EL of the light-emitting element ED can be disposed on the dam 30 and a portion of the first electrode AE. The second electrode CE can be disposed on the emitting layer EL.

[0121] The encapsulation layer 40 can be disposed on the second electrode CE of the light-emitting element ED. For example, the encapsulation layer 40 can prevent moisture or oxygen from penetrating into the light-emitting element ED. For example, the encapsulation layer 40 can prevent moisture or oxygen from penetrating into the organic material included in the emitting layer EL of the light-emitting element ED. Figure 4 The encapsulation layer 40 is shown to be a multilayer comprising a first encapsulation layer 41, a second encapsulation layer 42, and a third encapsulation layer 43, but aspects of this disclosure are not limited thereto.

[0122] In one or more aspects, the display panel 110 may also include a touch layer 111 and a color filter layer 112.

[0123] The touch layer 111 may include: a touch buffer layer 111a; a touch insulating layer 111b; touch electrodes, which include a touch sensor metal TSM and a bridging metal BRG; and a protective layer 111c.

[0124] Touch buffer layer 111a may be disposed on encapsulation layer 40. For example, touch buffer layer 111a may include a first touch buffer layer 11a1 disposed on third encapsulation layer 43 and a second touch buffer layer 11a2 covering bridging metal BRG on the first touch buffer layer 11a1.

[0125] Each bridging metal BRG can be disposed on the first touch buffer layer 11a1 to electrically interconnect multiple touch sensor metals TSM.

[0126] A touch insulating layer 111b may be disposed on the second touch buffer layer 11a2, and one or more touch sensor metals TSMs connected to at least one bridging metal BRG may be disposed on the touch insulating layer 111b. For example, one or more touch sensor metals TSMs may be connected to at least one bridging metal BRG through holes formed in the touch insulating layer 111b and the second touch buffer layer 11a2.

[0127] One or more touch sensor metal TSMs can be covered by a protective layer 111c disposed on the touch insulating layer 111b. Therefore, elements or patterns disposed beneath the protective layer 111c can be protected by the protective layer 111c, and the height difference in configuration caused by these elements or patterns can be mitigated or reduced. For example, the protective layer 111c may include organic materials such as acrylic resin, epoxy resin, phenolic resin, polyamide resin, polyimide resin, etc. However, the material of the protective layer 111c is not limited to these, and may, for example, include at least one inorganic material and at least one organic material.

[0128] The color filter layer 112 may include a color filter pattern 112a and a black matrix 112b. For example, a color filter buffer layer 61 may be disposed on the touch layer 111, and the color filter layer 112 may be formed on the color filter buffer layer 61.

[0129] The color filter pattern 112a can be positioned corresponding to a pixel region and formed by patterning phase change ink using an inkjet device. For example, a red color filter pattern including red pigment can be formed in a region corresponding to a pixel region having an organic emitting layer that emits red light, a green color filter pattern including green pigment can be formed in a region corresponding to a pixel region having an organic emitting layer that emits green light, and a blue color filter pattern including blue pigment can be formed in a region corresponding to a pixel region having an organic emitting layer that emits blue light.

[0130] The black matrix 112b can be formed to prevent light leakage and overlaps with the edge of the color filter pattern 112a. For example, the black matrix 112b can be formed along the pattern of the embankment 30. For example, the black matrix 112b can have an opening similar to the opening of the embankment 30, and each of the color filter patterns 112a can be disposed in a corresponding opening in the opening of the black matrix 112b. According to these configurations, since the black matrix 112b is disposed between the color filter patterns 112a, it can absorb external light. For example, the black matrix 112b can include materials such as carbon black, black resin, black ink, pigments that absorb visible light, etc.

[0131] The color filter pattern 112a and the black matrix 112b can be covered by the color filter protective layer 62. Therefore, the height difference caused by the color filter pattern 112a and the black matrix 112b can be reduced or decreased, and the color filter pattern 112a and the black matrix 112b can be protected from unwanted external substances or influences.

[0132] Figure 5 The variation of wrinkles in a foldable display device 100, including a first adhesive layer 130 with a modulus of 0.05 MPa, is shown.

[0133] Figure 5The changes in wrinkles (curvature) are shown when the first adhesive layer 130, located below or beneath the display panel 110, has a modulus of 0.05 MPa at room temperature and is folded and unfolded for 1 hour. As the experimental results show, when the first adhesive layer 130 is formed with a low modulus of 0.05 MPa at room temperature, the wrinkle slope at the lowest position P1 in the folded region FA is measured to be approximately 19 μm / mm.

[0134] Figure 6 The diagram illustrates the folding variation of a foldable display device 100, which includes a first adhesive layer 130 with a modulus of 1 MPa.

[0135] Figure 6 The changes in wrinkles (curvature) are shown when the first adhesive layer 130, located below or beneath the display panel 110, has a modulus of 1 MPa at room temperature and is folded and unfolded for 1 hour. As the experimental results show, when the first adhesive layer 130 is formed to have a high modulus of 1 MPa at room temperature, the wrinkle slope measured at the lowest position P2 in the folded region FA is approximately 9 μm / mm.

[0136] Reference Figure 5 and Figure 6 As can be seen, when the first adhesive layer 130 has a high modulus of 1 MPa or greater, the wrinkle depth in the folded region FA is smaller. Therefore, when the modulus of the first adhesive layer 130 is set to 1 MPa or greater, deformation in the folded region FA can be reduced. Since the degree of deformation in the folded region FA indicates the degree of wrinkle formation, when the first adhesive layer 130 has a high modulus of 1 MPa or greater, visible wrinkles on the display panel 110 can be reduced or improved, and thus the appearance quality of the display panel 110 can be improved.

[0137] The examples, aspects, and implementation methods described above will be briefly described below.

[0138] According to one or more example embodiments described herein, a foldable display device can be provided, comprising: a display panel including a non-folding region and a folding region that is flexible or foldable relative to a folding axis; a support layer disposed on a back surface of the display panel; a first adhesive layer disposed between the display panel and the support layer; a substrate disposed on the back surface of the support layer and having an opening pattern formed in a region overlapping the folding region; and a second adhesive layer disposed between the support layer and the substrate. In one or more aspects, the first adhesive layer may have a larger modulus than the second adhesive layer.

[0139] In one or more aspects, the modulus of the first adhesive layer may be 40 to 60 times that of the second adhesive layer.

[0140] In one or more aspects, the first adhesive layer may have a modulus of 1 MPa or greater.

[0141] In one or more aspects, the second adhesive layer may have a modulus of 0.02 MPa to 0.07 MPa.

[0142] In one or more aspects, the first adhesive layer and the second adhesive layer may comprise a pressure-sensitive adhesive (PSA) or an optically transparent adhesive (OCA).

[0143] In one or more aspects, the support layer may include a first support layer disposed on the back surface of the first adhesive layer.

[0144] In one or more aspects, the support layer may further include: an intermediate adhesive layer disposed on the back surface of the first support layer; and a second support layer disposed on the back surface of the intermediate adhesive layer.

[0145] In one or more aspects, the foldable display device may further include a third adhesive layer disposed on a display panel, a polarizing plate disposed on the third adhesive layer, a fourth adhesive layer disposed on the polarizing plate, a cover glass disposed on the fourth adhesive layer, a fifth adhesive layer disposed on the cover glass, and a protective layer disposed on the fifth adhesive layer.

[0146] In one or more aspects, the third adhesive layer, the fourth adhesive layer, and the fifth adhesive layer may include an optically clear adhesive (OCA).

[0147] In one or more aspects, the first adhesive layer may include a plurality of grooves patterned on a surface of the first adhesive layer facing the display panel, and the plurality of grooves may be formed to extend in the folding axis direction.

[0148] In one or more aspects, multiple grooves can be configured to overlap with the folded area.

[0149] In one or more aspects, multiple grooves may be provided in a portion of the non-folded area and the folded area adjacent to the folded area.

[0150] In one or more aspects, the plurality of grooves may include: a plurality of first patterns arranged to be spaced apart from each other in the folding axis direction; and a plurality of second patterns arranged to be spaced apart from each other in the folding axis direction and spaced apart from the plurality of first patterns in a direction perpendicular to the folding axis.

[0151] In one or more aspects, a plurality of first patterns and a plurality of second patterns may be arranged as multiple lines in a direction perpendicular to the folding axis, and the ends of each of the plurality of second patterns are arranged not to be aligned with the ends of each of the plurality of first patterns.

[0152] According to one or more example embodiments described herein, a foldable display device can be provided, comprising: a display panel including a non-folding region and a folding region that is flexible or foldable relative to a folding axis; a support layer disposed on a back surface of the display panel; a first adhesive layer disposed between the display panel and the support layer; a substrate disposed on the back surface of the support layer and having an opening pattern formed in a region overlapping the folding region; and a second adhesive layer disposed between the support layer and the substrate. In one or more aspects, the first adhesive layer may have a modulus greater than that of the second adhesive layer, and a plurality of grooves extending in the folding axis direction are patterned on the side of the first adhesive layer facing the display panel.

[0153] In one or more aspects, the modulus of the first adhesive layer may be 40 to 60 times that of the second adhesive layer.

[0154] In one or more aspects, the support layer may include a first support layer disposed on the back surface of the first adhesive layer, an intermediate adhesive layer disposed on the back surface of the first support layer, and a second support layer disposed on the back surface of the intermediate adhesive layer.

[0155] In one or more aspects, the foldable display device may further include a third adhesive layer disposed on the display panel, a cover glass disposed on a fourth adhesive layer, a fifth adhesive layer disposed on the cover glass, and a protective layer disposed on the fifth adhesive layer.

[0156] In one or more aspects, multiple grooves may be provided in a portion of the non-folded area and the folded area adjacent to the folded area.

[0157] In one or more aspects, the plurality of grooves may include: a plurality of first patterns arranged to be spaced apart from each other in the folding axis direction; and a plurality of second patterns arranged to be spaced apart from each other in the folding axis direction and spaced apart from the plurality of first patterns in a direction perpendicular to the folding axis.

[0158] The technical concepts described above have been presented to enable any person skilled in the art to make and use the present disclosure, and have been provided in the context of specific applications and their requirements. Various modifications, additions, and substitutions to the described embodiments will be apparent to those skilled in the art, and the principles described herein can be applied to other embodiments and applications without departing from the scope of the present disclosure. The above description and accompanying drawings provide examples of the technical concepts of the invention for illustrative purposes only. That is, the disclosed embodiments are intended to illustrate the scope of the technical concepts of the present disclosure.

[0159] Explanation of reference numerals in the attached figures

[0160] 100: Foldable display device

[0161] 110: Display panel

[0162] 120: Support layer

[0163] 130: First adhesive layer

[0164] 140: Substrate

[0165] 150: Second adhesive layer

[0166] 161: Third adhesive layer

[0167] 162: Fourth adhesive layer

[0168] 163: Fifth adhesive layer

[0169] 170: Polarizing plate

[0170] 180: Cover with glass

[0171] 190: Protective layer

Claims

1. A foldable display device, comprising: The display panel includes a non-folding area and a folding area that is flexible or foldable relative to a folding axis; A support layer is disposed on the rear surface of the display panel; A first adhesive layer is disposed between the display panel and the support layer; A substrate, the substrate being disposed on the rear surface of the support layer, and having an opening pattern formed in a region overlapping the folded region; as well as A second adhesive layer is disposed between the support layer and the substrate. The first adhesive layer has a greater modulus than the second adhesive layer. 2.The foldable display apparatus of claim 1, wherein, The modulus of the first adhesive layer is 40 to 60 times that of the modulus of the second adhesive layer. 3.The foldable display apparatus of claim 1, wherein, The first adhesive layer has a modulus of 1 MPa or greater. 4.The foldable display apparatus of claim 1, wherein, The second adhesive layer has a modulus of 0.02 MPa to 0.07 MPa. 5.The foldable display apparatus of claim 1, wherein, The first adhesive layer and the second adhesive layer comprise pressure-sensitive adhesives or optically transparent adhesives. 6.The foldable display apparatus of claim 1, wherein, The support layer includes a first support layer disposed on the rear surface of the first adhesive layer. 7.The foldable display apparatus of claim 6, wherein, The support layer further includes an intermediate adhesive layer disposed on the rear surface of the first support layer and a second support layer disposed on the rear surface of the intermediate adhesive layer.

8. The foldable display device according to claim 1, further comprising: A third adhesive layer is disposed on the display panel; A polarizing plate, wherein the polarizing plate is disposed on the third adhesive layer; A fourth adhesive layer is disposed on the polarizing plate; A cover glass, wherein the cover glass is disposed on the fourth adhesive layer; A fifth adhesive layer is disposed on the cover glass; as well as A protective layer is disposed on the fifth adhesive layer.

9. The foldable display device according to claim 8, wherein, The third adhesive layer, the fourth adhesive layer, and the fifth adhesive layer comprise an optically transparent adhesive.

10. The foldable display device according to claim 1, wherein, The first adhesive layer includes a plurality of grooves patterned on a surface of the first adhesive layer facing the display panel, and the plurality of grooves are formed to extend in the folding axis direction.

11. The foldable display device according to claim 10, wherein, The plurality of grooves are configured to overlap with the folded area.

12. The foldable display device according to claim 10, wherein, The plurality of grooves are provided in the folded region and a portion of the non-folded region adjacent to the folded region.

13. The foldable display device according to claim 10, wherein, The plurality of grooves includes: a plurality of first patterns, the plurality of first patterns being spaced apart from each other in the folding axis direction; and a plurality of second patterns, the plurality of second patterns being spaced apart from each other in the folding axis direction and being spaced apart from the plurality of first patterns in a direction perpendicular to the folding axis.

14. The foldable display device according to claim 13, wherein, The plurality of first patterns and the plurality of second patterns are arranged as multiple lines in a direction perpendicular to the folding axis, and the two ends of each of the plurality of second patterns are arranged not to be aligned with the two ends of each of the plurality of first patterns in a direction perpendicular to the folding axis.

15. The foldable display device according to claim 1, further comprising: At least one additional adhesive layer for attaching an additional layer to the foldable display device, wherein the modulus of the first adhesive layer is greater than the modulus of the at least one additional adhesive layer.

16. The foldable display device according to claim 15, wherein, The modulus of the second adhesive layer is of the same order of magnitude as that of the at least one additional adhesive layer.

17. A foldable display device, comprising: The display panel includes a non-folding area and a folding area that is flexible or foldable relative to a folding axis; A support layer is disposed on the rear surface of the display panel; A first adhesive layer is disposed between the display panel and the support layer; A substrate, the substrate being disposed on the rear surface of the support layer, and having an opening pattern formed in a region overlapping the folded region; as well as A second adhesive layer is disposed between the support layer and the substrate. The first adhesive layer has a greater modulus than the second adhesive layer, and a plurality of grooves extending in the folding axis direction are patterned on the side of the first adhesive layer facing the display panel.

18. The foldable display device according to claim 17, wherein, The modulus of the first adhesive layer is 40 to 60 times that of the modulus of the second adhesive layer.

19. The foldable display device according to claim 17, wherein, The support layer includes: A first support layer is disposed on the rear surface of the first adhesive layer; An intermediate adhesive layer is disposed on the rear surface of the first support layer; and A second support layer is disposed on the rear surface of the intermediate adhesive layer.

20. The foldable display device according to claim 17, further comprising: A third adhesive layer is disposed on the display panel; A polarizing plate, wherein the polarizing plate is disposed on the third adhesive layer; A fourth adhesive layer is disposed on the polarizing plate; A cover glass, wherein the cover glass is disposed on the fourth adhesive layer; A fifth adhesive layer is disposed on the cover glass; as well as A protective layer is disposed on the fifth adhesive layer.

21. The foldable display device according to claim 17, wherein, The plurality of grooves are provided in the folded region and a portion of the non-folded region adjacent to the folded region.

22. The foldable display device according to claim 17, wherein, The plurality of grooves includes: a plurality of first patterns, the plurality of first patterns being spaced apart from each other in the folding axis direction; and a plurality of second patterns, the plurality of second patterns being spaced apart from each other in the folding axis direction and being spaced apart from the plurality of first patterns in a direction perpendicular to the folding axis.

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