Adhesive composition and display device

Abstract

The present application relates to an adhesive composition comprising an acrylic monomer and a crosslinker. The storage modulus of the adhesive composition after curing the adhesive composition at a temperature of about -20°C divided by the storage modulus of the adhesive composition after curing the adhesive composition at a temperature of about 60°C is greater than about 1 and less than about 10.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to an adhesive composition and a display device. BACKGROUND

[0002] Electronic devices such as smartphones, tablet PCs, digital cameras, laptop computers, navigation devices, and smart TVs that provide images to users include display devices for displaying images. Recently, foldable display devices have attracted much attention. Since foldable display devices have wide screens with good portability, they have the advantages of both smartphones and tablet PCs.

[0003] In foldable display devices, a plurality of laminate structures are laminated and bonded, and a bonding member is used between the laminate structures. The bonding member can be used to bond the laminate structures to each other and protect the laminate structures of the display device from external impacts. Therefore, in order to protect the laminate structures of the display device from external impacts, the bonding member needs impact resistance.

[0004] It is to be understood that the background section is intended to provide useful background information for the understanding of the technology. However, the background section can also include ideas, concepts or recognitions not known to the ordinary artisan in the relevant field as of the corresponding effective application date of the disclosed subject matter. SUMMARY

[0005] Aspects of the present disclosure provide an adhesive composition having low viscosity and low temperature dependence and improved impact resistance, and a display device using the same.

[0006] However, aspects of the present disclosure are not limited to the aspects set forth herein. The above and other aspects of the present disclosure will become more apparent to one of ordinary skill in the art to which the present disclosure pertains by referencing the detailed description of the present disclosure given below.

[0007] The adhesive composition and the display device according to the embodiments can easily remove stress caused by temperature changes because the storage modulus of the bonding member produced using the adhesive composition has a small change depending on temperature.

[0008] The bonding member produced using the adhesive composition according to the embodiments maintains rigidity to resist deformation when an impact is applied and absorbs the applied impact, thereby improving impact resistance. The adhesive composition according to the embodiments can be easily applied using inkjet printing due to its low viscosity.

[0009] It should be noted that the effects of the present disclosure are not limited to those described above, and other effects of the present disclosure will be apparent from the description below.

[0010] According to embodiments of the disclosure, the display device can include a display panel including a first surface disposed on a front side, and a front lamination structure disposed on the first surface of the display panel. The front lamination structure can include at least one cover window and at least one bonding member. The at least one bonding member can include a window bonding member attaching the cover window. A storage modulus of the window bonding member measured at a temperature of about -20°C divided by a storage modulus of the window bonding member measured at a temperature of about 60°C can be greater than about 1 and less than about 10.

[0011] In embodiments, the storage modulus of the window bonding member at a temperature of about -20°C can be about 0.09 MPa to about 0.3 MPa.

[0012] In embodiments, the storage modulus of the window bonding member measured at a temperature of about -10°C to about 60°C can be about 10 4 Pa to about 10 7 Pa.

[0013] In embodiments, a ratio of a loss modulus of the window bonding member to a storage modulus of the window bonding member at a frequency of about 1 kHz to about 100 kHz can be about 1.4 to about 1.9.

[0014] In embodiments, a storage modulus of the window bonding member at a frequency of 1 kHz to 100 kHz can be about 0.7 MPa to about 8 MPa.

[0015] In embodiments, the storage modulus of the window bonding member and the loss modulus of the window bonding member can be measured by a rheometer in a thin film state.

[0016] In embodiments, the front lamination structure can include a polarizing member disposed between the display panel and the cover window, and a polarizing portion bonding member attaching the polarizing member to the first surface of the display panel.

[0017] In embodiments, the front lamination structure can include an impact absorbing layer disposed between the polarizing member and the cover window, and an impact absorbing layer bonding member attaching the impact absorbing layer to the polarizing member.

[0018] In an embodiment, the display panel can include a second surface disposed on a rear side. The display device can include a rear laminate structure disposed on the second surface of the display panel. The rear laminate structure can include a polymer film layer disposed below the display panel, a cushion layer disposed below the polymer film layer, a plate disposed below the cushion layer, and a heat dissipation member disposed below the plate, wherein the at least one bonding member attaches the polymer film layer, the cushion layer, the plate, and the heat dissipation member.

[0019] In an embodiment, the cover window can include an ultrathin glass, and the window bonding member attaches the ultrathin glass to the display panel. BRIEF DESCRIPTION OF DRAWINGS

[0020] Embodiments of the present disclosure will become more fully understood from the detailed description and accompanying drawings, wherein:

[0021] Figure 1 FIG. 1 is a schematic perspective view illustrating a display device in an unfolded state according to an embodiment;

[0022] Figure 2 FIG. 2 is a schematic perspective view illustrating a display device in a folded state according to an embodiment;

[0023] Figure 3 FIG. 3 is a schematic cross-sectional view of a display device in an unfolded state according to an embodiment;

[0024] Figure 4 FIG. 4 is a schematic cross-sectional view of a display device in a folded state according to an embodiment;

[0025] Figure 5 FIG. 5 is a schematic cross-sectional view of a display panel according to an embodiment;

[0026] Figure 6 FIG. 6 is a graph showing storage modulus of a bonding member according to frequency;

[0027] Figure 7 FIG. 7 is a graph showing storage modulus of a bonding member converted by temperature time superposition (TTS);

[0028] Figure 8 FIG. 8 is a schematic cross-sectional view of a display device according to an embodiment;

[0029] Figure 9 FIG. 9 is a schematic cross-sectional view of a display device according to an embodiment;

[0030] Figure 10 FIG. 10 is a schematic cross-sectional view of a display device according to an embodiment;

[0031] Figure 11 is a graph showing storage modulus of the PSA according to Experimental Example 1 and adhesives #2, #5 and #8;

[0032] Figure 12 is a graph showing storage modulus of the PSA according to Experimental Example 3 and adhesives #2 and #5 in each frequency region;

[0033] Figure 13 is a graph showing tan delta value of the PSA according to Experimental Example 3 and adhesives #2 and #5;

[0034] Figure 14 is a graph showing height of UTG crack formed in the display device sample according to Experimental Example 4; and

[0035] Figure 15 is a graph showing height of bright spot formed on the display device sample according to Experimental Example 4. DETAILED DESCRIPTION

[0036] The present disclosure will now be described more fully with reference to the accompanying drawings, in which embodiments are shown. The present disclosure may, however, be embodied in different forms, and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0037] It should also be understood that when a layer is referred to as being “on” another layer or substrate, it can be directly on the other layer or substrate, or intervening layers can also be present. Same reference numerals refer to same components throughout the specification.

[0038] It should be understood that, although the terms “first,” “second,” etc. can be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element discussed below could be termed a second element without departing from the teachings of the embodiments. Similarly, a second element could be termed a first element.

[0039] As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0040] In the description and claims, the phrase “at least one of” followed by a listing of a plurality of items means one or more of the listed items individually or any combination of one or more of the listed items. For example, “at least one of A and B” means A, B, or A and B.

[0041] For ease of description, spatially relative terms “under”, “below”, “lower”, “over”, “upper”, “front”, “rear”, and the like, can be used herein for describing the orientation of one element or component with respect to another element or component according to the examples illustrated in the drawings. It is to be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientations depicted in the drawings. For example, in the case where a device illustrated in the drawing is turned over, an element or component that is positioned “under” or “below” another element or component in the drawing can be placed “over” the other element or component. Thus, the exemplary term “under” can include both a lower position and an upper position. The device can also be oriented in other directions, and as such spatially relative terms can be interpreted differently depending upon the orientation of the device. The terms “first”, “second”, “third”, “fourth”, etc. can be used herein to describe various elements, components, regions, layers and / or sections which have the same or similar function in each example of the disclosure. These terms are used herein for the ease of description to distinguish one element or component from another element or component. Thus, the terms “first”, “second”, “third”, “fourth”, etc. do not necessarily limit the places or order of elements, components, regions, layers and / or sections. It is to be understood that a first element or component discussed can be termed as a second element or component within another example of the disclosure.

[0042] As used herein, “about” or “approximately” includes the recited value and means within an acceptable range of deviation for the specified value as determined by one of ordinary skill in the art considering the relevant measurement and error (i.e., the limits of the measurement system) associated with the measurement of the particular quantity. For example, “about” can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, ±5% of the recited value.

[0043] It will be understood that when an element (or components, regions, layers or sections) is referred to as being “on” or “connected to” or “coupled to” another element (or components, regions, layers or sections), it can be directly on, connected or coupled to the other named element or intervening elements (or components, regions, layers or sections) can be present.

[0044] The terms “comprises”, “comprising”, “includes”, and / or “including” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components and / or groups thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0045] Each feature of various embodiments of the present disclosure can be incorporated partially or entirely or in combination with each other, and various interlocks and drives are possible in technology. Each embodiment can be implemented independently of each other, or can be implemented together in association.

[0046] Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

[0047] Figure 1is a schematic perspective view illustrating a display device according to an embodiment in an unfolded state. Figure 2 is a schematic perspective view illustrating a display device according to an embodiment in a folded state.

[0048] Referring to Figure 1 , the display device 10 according to an embodiment can be a foldable display device. Examples of the display device 10 include a smartphone, but embodiments are not limited thereto. For example, the display device 10 can be applied to a smartphone, a mobile phone, a tablet PC, a personal digital assistant (PDA), a portable multimedia player (PMP), a television, a game console, a watch-type electronic device, a head-mounted display, a display of a personal computer, a laptop computer, a car navigation system, a car dashboard, a digital camera, a camcorder, an external billboard, an electronic billboard, a medical device, an inspection device, various home appliances such as a refrigerator or a washing machine, or an Internet of Things device. Hereinafter, embodiments will be described in detail with reference to the accompanying drawings.

[0049] In Figure 1 and Figure 2 , the first direction DR1 can be a direction parallel to one side of the display device 10 in a plan view, and can be, for example, a horizontal direction of the display device 10. The second direction DR2 can be a direction parallel to the other side of the display device 10 in a plan view, and can be, for example, a vertical direction of the display device 10. The third direction DR3 can be a thickness direction of the display device 10.

[0050] In an embodiment, the display device 10 can have a rectangular shape in a plan view. The display device 10 can have a rectangular shape with corners including right angles or rounded corners in a plan view. The display device 10 can include two short sides arranged in the first direction DR1 and two long sides arranged in the second direction DR2 in a plan view.

[0051] The display device 10 includes a display area DA and a non-display area NDA. In a plan view, the shape of the display area DA can correspond to the shape of the display device 10. For example, when the display device 10 has a rectangular shape in a plan view, the display area DA can also have a rectangular shape.

[0052] The display area DA can be an area including pixels to display an image. The pixels can be arranged in a matrix. The pixels can have a rectangular shape, a rhombic shape, or a square shape in a plan view, without being limited thereto. For example, the pixels can have a quadrilateral shape other than a rectangular shape, a rhombic shape, or a square shape, a polygonal shape other than a quadrilateral shape, a circular shape, or an elliptical shape.

[0053] The non-display area NDA can be an area that does not include a pixel and does not display an image. The non-display area NDA can be disposed around the display area DA. As shown in FIG. 1A, Figure 1 and Figure 2 As shown in FIGS. 1A and 1B, the non-display area NDA can be disposed to surround the display area DA, but embodiments are not limited thereto. The display area DA can be partially surrounded by the non-display area NDA.

[0054] In an embodiment, the display device 10 can maintain a folded state and an unfolded state. As shown in FIG. 1A, Figure 2 As shown in FIG. 1A, the display device 10 can be folded in an inward folding manner in which the display area DA is disposed on the inside thereof. When the display device 10 is folded in the inward folding manner, top surfaces of the display device 10 can be disposed to face each other. As another example, the display device 10 can be folded in an outward folding manner in which the display area DA is disposed on the outside thereof. When the display device 10 is folded in the outward folding manner, bottom surfaces of the display device 10 can be disposed to face each other.

[0055] In an embodiment, the display device 10 can be a foldable device. As used herein, the term "foldable device" refers to a device that can be folded, and is used to mean not only a folded device, but also a device that can have a folded state and an unfolded state. Also, folding can generally include folding at an angle of about 180 degrees. However, embodiments are not limited thereto, and can include a device in which a folding angle exceeds 180 degrees or is less than 180 degrees, for example, a folding angle can be equal to or greater than 90 degrees and less than 180 degrees, or a folding angle is equal to or greater than 120 degrees and less than 180 degrees. If folding is made from the unfolded state, the device can be in the folded state even if the device is not completely folded. For example, even if the device is folded at an angle of 90 degrees or less than 90 degrees, as long as the maximum folding angle becomes 90 degrees or more than 90 degrees, it can be expressed as being in the folded state to distinguish it from the unfolded state. During folding, the radius of curvature can be about 5 mm or less than 5 mm, for example, about 1 mm to about 2 mm, or about 1.5 mm, but embodiments are not limited thereto.

[0056] In an embodiment, the display device 10 can include a folding area FDA, a first non-folding area NFA1, and a second non-folding area NFA2. The folding area FDA can be an area in which the display device 10 is folded, and the first non-folding area NFA1 and the second non-folding area NFA2 can be areas in which the display device 10 is not folded.

[0057] The first non-folding area NFA1 can be disposed on one side (for example, an upper side) of the folding area FDA. The second non-folding area NFA2 can be disposed on the other side (for example, a lower side) of the folding area FDA. The folding area FDA can be an area that is curved with a curvature.

[0058] In an embodiment, the folding area FDA of the display device 10 can be determined at a specific location. One or more folding areas FDA can be determined at a specific location in the display device 10. In other examples, the location of the folding area FDA can not be designated in the display device 10 and can be freely set in various areas.

[0059] In an embodiment, the display device 10 can be folded in the second direction DR2. Accordingly, the length of the display device 10 in the second direction DR2 can be reduced to about half, so that the user can conveniently carry the display device 10.

[0060] In an embodiment, the direction in which the display device 10 is folded is not limited to the second direction DR2. For example, the display device 10 can be folded in the first direction DR1. The length of the display device 10 in the first direction DR1 can be reduced to about half.

[0061] Figure 1 and Figure 2 Each of the display area DA and the non-display area NDA is illustrated as overlapping the folding area FDA, the first non-folding area NFA1, and the second non-folding area NFA2, but embodiments are not limited thereto. For example, each of the display area DA and the non-display area NDA can overlap at least one of the folding area FDA, the first non-folding area NFA1, and the second non-folding area NFA2.

[0062] Figure 3 is a schematic cross-sectional view of a display device in an unfolded state according to an embodiment. Figure 4 is a schematic cross-sectional view of a display device in a folded state according to an embodiment.

[0063] Referring to Figure 3 and Figure 4 The display device 10 can include a display panel 100, a front lamination structure 200 on a front side of the display panel 100, and a rear lamination structure 300 on a rear side of the display panel 100. Each of the lamination structures 200 and 300 can include at least one bonding member 251 to 254 or 351 to 354. Here, the front side of the display panel 100 refers to a side of the display panel 100 on which a screen is displayed, and the rear side refers to an opposite side of the front side. A first surface of the display panel 100 is located on the front side, and a second surface of the display panel 100 is located on the rear side.

[0064] The display panel 100 is a panel for displaying an image. Examples of the display panel 100 can include not only self-emissive display panels (e.g., organic light emitting display (OLED) panels, inorganic electroluminescent (EL) display panels, quantum dot light emitting display (QED) panels, micro LED display panels, nano LED display panels, plasma display panels (PDPs), field emission display (FED) panels, and cathode ray tube (CRT) display panels), but also light-receiving display panels (e.g., liquid crystal display (LCD) panels and electrophoretic display (EPD) panels). Hereinafter, an organic light emitting display panel will be described as an example of the display panel 100, and an organic light emitting display panel to which the embodiments are applied will simply be referred to as the display panel 100, unless a special distinction is required. However, the embodiments are not limited to organic light emitting display panels, and other display panels can be applied within the scope of the embodiments.

[0065] The display panel 100 can further include a touch member. The touch member can be provided as a panel or a film that is separate from the display panel 100 and attached on the display panel 100, but can also be provided in the form of a touch layer inside the display panel 100. In the following embodiments, a case in which the touch member is provided inside the display panel 100 and included in the display panel 100 is exemplified, but the embodiments are not limited thereto.

[0066] Figure 5 is a schematic cross-sectional view of a display panel according to an embodiment.

[0067] Referring to Figure 5 The display device 10 according to the embodiment can include a display panel 100. The display panel 100 can include a base substrate 11, a first electrode 12, a pixel definition layer 13, a light emitting layer 14, a second electrode 15, and an encapsulation layer 20.

[0068] The base substrate 11 can be an insulating substrate. The base substrate 11 can be flexible and can include a polymer material having flexibility. Here, the polymer material can be polyimide (PI), polyether sulfone (PES), polyacrylate (PA), polyarylate (PAR), polyetherimide (PEI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polyphenylene sulfide (PPS), polyallylate, polycarbonate (PC), cellulose triacetate (CAT), cellulose acetate propionate (CAP), or a combination thereof.

[0069] The first electrode 12 can be provided on the base substrate 11. In an embodiment, the first electrode 12 can be an anode electrode. Although not shown in the drawings, other components can be further provided between the base substrate 11 and the first electrode 12. For example, a buffer layer, a conductive wire, an insulating layer, and a thin film transistor can be provided between the base substrate 11 and the first electrode 12.

[0070] The pixel-defining layer 13 can be provided on the first electrode 12. The pixel-defining layer 13 can include an opening that exposes at least a portion of the first electrode 12.

[0071] The light-emitting layer 14 can be provided on the first electrode 12. In an embodiment, the light-emitting layer 14 can emit red light, green light, or blue light. The wavelength of the red light can be about 620 nm to about 750 nm, and the wavelength of the green light can be about 495 nm to about 570 nm. The wavelength of the blue light can be about 450 nm to about 495 nm. The light-emitting layer 14 can be formed of a single layer. Alternatively, the light-emitting layer 14 can have a structure in which a plurality of organic light-emitting layers are laminated, for example, in a series structure. In other examples, the light-emitting layer 14 can emit white light. When the light-emitting layer 14 emits white light, the light-emitting layer 14 can have a laminated red organic light-emitting layer, a green organic light-emitting layer, and a blue organic light-emitting layer.

[0072] The second electrode 15 can be provided on the light-emitting layer 14 and the pixel-defining layer 13. In an embodiment, the second electrode 15 can be entirely formed on the light-emitting layer 14 and the pixel-defining layer 13. In other examples, the second electrode 15 can be a cathode electrode.

[0073] The first electrode 12, the second electrode 15, and the light-emitting layer 14 can constitute a light-emitting element EL.

[0074] The encapsulation layer 20 can be positioned on the light-emitting element EL. The encapsulation layer 20 can seal the light-emitting element EL and prevent moisture or the like from entering the light-emitting element EL from the outside.

[0075] In an embodiment, the encapsulation layer 20 can be implemented as a thin film encapsulation, and can include one or more organic films and one or more inorganic films. For example, the encapsulation layer 20 can include a first inorganic film 21 positioned on the second electrode 15, an organic film 22 positioned on the first inorganic film 21, and a second inorganic film 23 positioned on the organic film 22.

[0076] The first inorganic film 21 can prevent moisture, oxygen, or the like from permeating into the light-emitting element EL. The first inorganic film 21 can include silicon nitride, aluminum nitride, zirconium nitride, titanium nitride, hafnium nitride, tantalum nitride, silicon oxide, aluminum oxide, titanium oxide, tin oxide, cerium oxide, silicon oxynitride, or the like.

[0077] An organic film 22 can be positioned on the first inorganic film 21. The organic film 22 can improve flatness. The organic film 22 can be formed of a liquid organic material, for example, an acrylic resin, a methacrylic resin, a polyisoprene, a vinyl resin, an epoxy resin, a urethane resin, a cellulose resin, and a perylene resin, etc. The organic material can be provided on the base substrate 11 by vapor deposition, printing, and coating, and can undergo a curing process.

[0078] A second inorganic film 23 can be positioned on the organic film 22. The second inorganic film 23 can perform substantially the same or similar functions as the first inorganic film 21, and can be made of substantially the same or similar materials as the first inorganic film 21. The second inorganic film 23 can completely cover the organic film 22. In some embodiments, the second inorganic film 23 and the first inorganic film 21 can contact each other in the non-display area NDA to form an inorganic-inorganic junction. However, the structure of the encapsulation layer 20 is not limited thereto, and the lamination structure of the encapsulation layer 20 can vary. In other examples, the encapsulation layer 20 can be formed of a glass substrate, etc.

[0079] A touch sensor 40 can be disposed on the encapsulation layer 20. In embodiments, the touch sensor 40 can be directly located on the encapsulation layer 20. For example, the encapsulation layer 20 can serve as a base portion of the touch sensor 40.

[0080] The touch sensor 40 can include a touch element layer 41 and a protection layer 43. The touch element layer 41 can include touch electrodes and touch signal lines connected to the touch electrodes. In embodiments, the touch electrodes can include a metal, and can have a mesh shape. For example, the touch electrodes can be formed of a metal mesh pattern, thereby improving the flexibility of the touch element layer 41.

[0081] The protection layer 43 can be positioned on the touch element layer 41 to protect the touch element layer 41. In embodiments, the protection layer 43 can include an organic material, and can be made of, for example, an acrylic polymer. When the protection layer 43 is made of an organic material, the flexibility of the touch sensor 40 can be improved.

[0082] Review Figure 3 And Figure 4 A front lamination structure 200 can be disposed on the front side of the display panel 100. The front lamination structure 200 can include a polarizing member 240, an impact absorbing layer 230, a cover window 220, and a cover window protection layer 210, which are sequentially laminated forward from the display panel 100.

[0083] The polarizing member 240 can polarize light passing therethrough and can reduce reflection of external light. In an embodiment, the polarizing member 240 can be a polarizing film. The polarizing film can include a polarizing layer and protective members that sandwich the polarizing layer. The polarizing layer can include a polyvinyl alcohol film. The polarizing layer can be stretched in one direction. The stretching direction of the polarizing layer can be an absorption axis, and a direction perpendicular to the stretching direction can be a transmission axis. The protective members can be respectively disposed on one surface and the other surface of the polarizing layer. The protective members can be made of a cellulose resin such as triacetyl cellulose, a polyester resin, or the like, but embodiments are not limited thereto.

[0084] The impact absorbing layer 230 can be disposed on the front side of the polarizing member 240. The impact absorbing layer 230 can be used to protect structures such as the display panel from external impact. In an embodiment, the impact absorbing layer 230 can be a polymer film. The polymer film can include, for example, at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyether sulfone (PES), polyimide (PI), polyarylate (PAR), polycarbonate (PC), polymethyl methacrylate (PMMA), and a cyclic olefin copolymer (COC).

[0085] The cover window 220 can be disposed on the front side of the impact absorbing layer 230. The cover window 220 is used to protect the display panel 100. The cover window 220 can be made of a transparent material. The cover window 220 can include, for example, glass or plastic.

[0086] When the cover window 220 includes glass, the glass can be ultra-thin glass (UTG) or thin glass. The ultra-thin glass UTG can be strengthened to have a stress distribution. The strengthened ultra-thin glass UTG is more effective than before strengthening in preventing crack generation, crack propagation, breakage, etc. due to external impact. The ultra-thin glass UTG strengthened through the strengthening process can have a different stress distribution for each zone.

[0087] When the glass is ultra-thin glass or thin glass, it can have a flexible property such that it can be bent, curved, folded, or rolled. The thickness of the glass can be, for example, about 10 µm to about 300 µm, about 10 µm to about 100 µm, or about 50 µm. The glass of the cover window 220 can include soda-lime glass, alkali-aluminosilicate glass, borosilicate glass, or lithium alumino silicate glass. The glass of the cover window 220 can include chemically or thermally strengthened glass to have strong rigidity. Chemical strengthening can be achieved through an ion exchange process in an alkali salt. The ion exchange process can be performed two or more times. In other examples, the cover window 220 can be obtained by coating a glass film on both surfaces of a polymer film.

[0088] Referring again to Figure 3 and Figure 4When the cover window 220 includes plastic, it can be more advantageous to exhibit a flexible nature such as folding. Examples of plastic suitable for the cover window 220 can include, but are not limited to, polyimide, polyacrylate, polymethyl methacrylate (PMMA), polycarbonate (PC), polyethylene naphthalate (PEN), polyvinylidene chloride, polyvinylidene fluoride (PVDF), polystyrene, ethylene-vinyl alcohol copolymer, polyethersulfone (PES), polyetherimide (PEI), polyphenylene sulfide (PPS), polyarylate (PAR), triacetyl cellulose (TAC), and cellulose acetate propionate (CAP). The plastic cover window 220 can include one or more of the above-mentioned plastic materials.

[0089] The cover window protective layer 210 can be disposed on the front side of the cover window 220. The cover window protective layer 210 can perform at least one function of preventing scattering, impact absorption, preventing scratches, preventing fingerprint smudges, and preventing glare on the cover window 220. The cover window protective layer 210 can include a transparent polymer film. The transparent polymer film includes at least one of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyethersulfone (PES), polyimide (PI), polyarylate (PAR), polycarbonate (PC), polymethyl methacrylate (PMMA), and cyclic olefin copolymer (COC).

[0090] The front laminate structure 200 can include front bonding members 251 to 254 for bonding adjacent laminate members. For example, the first bonding member 251 can be disposed between the cover window 220 and the cover window protective layer 210 to couple (or connect) them, the second bonding member 252 can be disposed between the cover window 220 and the impact absorption layer 230 to couple (or connect) them, the third bonding member 253 can be disposed between the impact absorption layer 230 and the polarization member 240 to couple (or connect) them, and the fourth bonding member 254 can be disposed between the polarization member 240 and the display panel 100 to couple (or connect) them. For example, among the front bonding members 251 to 254 that are members for attaching layers on one surface of the display panel 100, the first bonding member 251 can be a protective layer bonding member for attaching (or connecting) the cover window protective layer 210, the second bonding member 252 can be a window bonding member for attaching (or connecting) the cover window 220, the third bonding member 253 can be an impact absorption layer bonding member for attaching (or connecting) the impact absorption layer 230, and the fourth bonding member 254 can be a polarization member bonding member for attaching (or connecting) the polarization member 240. The front bonding members 251 to 254 can be optically transparent.

[0091] A rear lamination structure 300 is disposed on a rear side of the display panel 100. The rear lamination structure 300 can include a polymer film layer 310, a pad layer 320, a plate 330, and a heat dissipation member 340, which are sequentially laminated from the display panel 100 rearward (or downward).

[0092] The polymer film layer 310 can include a polymer film. The polymer film layer 310 can include, for example, polyimide (PI), polyethylene terephthalate (PET), polycarbonate (PC), polyethylene (PE), polypropylene (PP), polysulfone (PSF), polymethyl methacrylate (PMMA), triacetyl cellulose (TAC), cyclic olefin polymer (COP), or the like. The polymer film layer 310 can include a functional layer on at least one surface. The functional layer can include, for example, a light absorbing layer. The light absorbing layer can include a light absorbing material, such as a black pigment or a black dye. The light absorbing layer can be formed by coating or printing a black ink on the polymer film.

[0093] The pad layer 320 can be disposed on (or under) a rear side of the polymer film layer 310. The pad layer 320 can absorb external impact and prevent the display panel 100 from being damaged. The pad layer 320 can be formed of a single layer or a plurality of laminated layers. The pad layer 320 can include, for example, a material having elasticity, such as polyurethane or polyethylene resin. In an embodiment, the pad layer 320 can be made of a foam material similar to a sponge.

[0094] The plate 330 can be disposed on (or under) a rear side of the pad layer 320. The plate 330 can be a support member for coupling the display device 10 to a housing. The plate 330 can be made of a material having rigidity. In an embodiment, the plate 330 can be made of a single metal or a metal alloy, such as stainless steel (SUS).

[0095] The heat dissipation member 340 can be disposed on (or under) a rear side of the plate 330. The heat dissipation member 340 is used to diffuse heat generated by the display panel 100 or other components of the display device 10. The heat dissipation member 340 can include a metal plate. The metal plate can include a metal having thermal conductivity, such as copper or silver. The heat dissipation member 340 can be a heat dissipation sheet including graphite or carbon nanotubes.

[0096] Although not limited thereto, the heat dissipation member 340 can be divided by a folding area FDA to facilitate folding of the display device 10, as exemplified in Figure 3 and Figure 4 . For example, a first metal plate can be disposed in a first non-folding area NFA1, and a second metal plate can be disposed in a second non-folding area NFA2. The first metal plate and the second metal plate can be physically separated from each other with respect to the folding area FDA.

[0097] The rear lamination structure 300 can include rear bonding members 351 to 354 for bonding adjacent lamination members. For example, the fifth bonding member 351 can be disposed between the display panel 100 and the polymer film layer 310 to couple (or connect) them, the sixth bonding member 352 can be disposed between the polymer film layer 310 and the cushion layer 320 to couple (or connect) them, the seventh bonding member 353 can be disposed between the cushion layer 320 and the plate 330 to couple (or connect) them, and the eighth bonding member 354 can be disposed between the plate 330 and the heat dissipation member 340 to couple (or connect) them. For example, among the rear bonding members 351 to 354 that are members for attaching layers on the other surface of the display panel 100, the fifth bonding member 351 can be a polymer film layer bonding member for attaching the polymer film layer 310, the sixth bonding member 352 can be a cushion layer bonding member for attaching the cushion layer 320, the seventh bonding member 353 can be a plate bonding member for attaching the plate 330, and the eighth bonding member 354 can be a heat dissipation member bonding member for attaching the heat dissipation member 340. When the heat dissipation member 340 is divided with respect to the folding area FDA, the eighth bonding member 354 can also be divided in the same manner, but as Figure 3 As exemplified in the middle, it can be continuous without being divided for each of the non-folding areas NFA1 and NFA2.

[0098] When the display device 10 displays only on the front surface, unlike the front bonding members 251 to 254, the rear bonding members 351 to 354 do not have to be optically transparent.

[0099] Each of the above-described front bonding members 251 to 254 and rear bonding members 351 to 354 can include an adhesive material. Each bonding member can include an optically clear resin (OCR). The bonding members can have the same composition, or can have different compositions according to their positions and targets to be bonded.

[0100] Each of the first to eighth bonding members (251 to 254 and 351 to 354) can have a thickness of 300 µm or less than 300 µm. In an embodiment, each of the bonding members 251 to 254 and 351 to 354 can have a thickness of about 200 µm or less than 200 µm, and at least some of the bonding members 251 to 254 and 351 to 354 can have a thickness of about 100 µm or less than 100 µm. The lower limit of the thickness of the bonding members 251 to 254 and 351 to 354 need not be fixed, but the thickness can be about 10 µm or more than 10 µm in order to secure a minimum adhesion. In an embodiment, each of the first to eighth bonding members (251 to 254 and 351 to 354) can have a thickness of about 25 µm to about 100 µm. Since each of the first to eighth bonding members (251 to 254 and 351 to 354) has a thickness of about 25 µm to about 100 µm, occurrence of peeling between components included in the display device when the display device is folded can be prevented.

[0101] Each of the bonding members 251 to 254 and 351 to 354 can be formed of a single adhesive layer, or can be formed of a multi-layer including a plurality of adhesive layers. Further, each of the bonding members 251 to 254 and 351 to 354 can include an adhesive layer on both surfaces of the member, respectively, similar to a double-sided tape.

[0102] The display device described above can be a foldable display device, and each of the bonding members 251 to 254 and 351 to 354 can serve to reduce bending and stress of the display device. The bonding members 251 to 254 and 351 to 354 can have a low storage modulus in order to minimize stress when the display device is folded. The display device is provided with holes, such as a camera hole and an optical sensor hole, and the bonding members can have sufficient processability in order to punch these hole regions. For this purpose, the bonding members can be formed by applying an adhesive composition using an inkjet printing method. It can be difficult to apply an adhesive having a high viscosity using inkjet printing. An adhesive having a high storage modulus can have difficulty due to high stress during folding.

[0103] In an embodiment, the foldable display device can include an adhesive composition having a low viscosity, a low storage modulus, and impact resistance, which can be suitable for a foldable display device.

[0104] At least one of the bonding members 251 to 254 or 351 to 354 can be formed of an adhesive composition. For example, a window bonding member as the second bonding member 252 can be formed of an adhesive composition described below. The adhesive composition can include an acrylic monomer and a crosslinking agent.

[0105] The acrylic monomer can include at least one of n-hexyl acrylate (n-HA), 2- ethylhexyl acrylate (2-EHA), 2-hydroxyethyl acrylate (2-HEA), 4-hydroxybutyl acrylate (4-HBA), and dihydroxyhexyl acrylate (DHHA). The plurality of acrylic monomers can be polymerized with each other to form an oligomer.

[0106]

[0107]

[0108] The crosslinking agent can include at least one of ethylene diacrylate (EDA) and 3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexyl isocyanate (IPDI).

[0109]

[0110] The adhesive composition can have a minimized oligomer content and an increased monomer content in order to reduce viscosity. To this end, the adhesive composition can include a monomer containing a highly reactive hydroxyl group (-OH), and a proportion of the crosslinking agent can be controlled. The adhesive composition further includes a solvent, and can further include an additive such as an adhesion aid, a filler, or an antistatic agent.

[0111] The adhesive composition can be prepared, for example, by mixing about 120 parts by weight to about 250 parts by weight of the acrylic monomer with a solvent and heating while stirring, adding about 1.5 parts by weight to about 2.5 parts by weight of the crosslinking agent and about 0.1 parts by weight to about 1 parts by weight of the additive to the solution and heating while stirring.

[0112] The bonded member produced using the adhesive composition described above can satisfy the following Mathematical Expression 1.

[0113] [Mathematical Expression 1]

[0114] 1 < G'(-20℃) / G'(60℃) < 10

[0115] In Mathematical Expression 1, G'(-20℃) is a storage modulus of the bonded member after curing of the adhesive composition, measured at a temperature of about -20℃, and G'(60℃) is a storage modulus of the bonded member after curing of the adhesive composition, measured at a temperature of about 60℃. G'(-20℃) divided by G'(60℃) can be greater than about 1 and less than about 10.

[0116] The bonding member suitable for the foldable display device should have a modulus less dependent on temperature to remove stress according to temperature change. In an embodiment, the ratio of the storage modulus of the bonding member after curing of the adhesive composition measured at a temperature of about -20°C to the storage modulus of the bonding member after curing of the adhesive composition measured at a temperature of about 60°C can be 10 or less than 10. The ratio of the storage modulus of the bonding member after curing of the adhesive composition measured at a temperature of about -20°C to the storage modulus of the bonding member after curing of the adhesive composition measured at a temperature of about 60°C less than 10 means that the difference in the storage modulus of the bonding member after curing of the adhesive composition at each of the temperatures of about -20°C and about 60°C is small. In an embodiment, the storage modulus of the bonding member after curing of the adhesive composition measured at a temperature of about -20°C can be about 0.09 MPa to about 0.3 MPa.

[0117] Figure 6 is a graph showing the storage modulus of the bonding member according to frequency. Figure 7 is a graph showing the storage modulus of the bonding member converted by temperature time superposition (TTS).

[0118] The storage modulus of the bonding member produced using the adhesive composition can be measured using a rheometer such as DHR3 produced by TA instruments. The rheometer is used to measure only the storage modulus in a frequency range of about 10 -2 Hz to about 10 2 Hz. Therefore, the storage modulus in the entire frequency range of about 10 -2 Hz to about 10 8 Hz can be obtained by measuring the storage modulus at each temperature (about -40°C to about 40°C) and converting the storage modulus by temperature time superposition (TTS).

[0119] In an embodiment, the storage modulus of the bonding member after curing of the adhesive composition in a temperature range of about -10°C to about 60°C can be about 10 4 Pa to about 10 7 Pa. The bonding member according to the embodiment satisfies the requirement of mathematical expression 1, and the storage modulus does not greatly vary depending on temperature, and stress depending on temperature change can be easily reduced.

[0120] The bonded member produced using the adhesive composition has viscoelasticity, and thus physical properties greatly vary in a frequency-dependent manner. Since the impact time of applying an external impact is very short (on the order of milliseconds (ms)), the behavior of the bonded member at the time of applying an impact can be related to the physical properties at a high frequency. The bonded member according to the embodiment has a storage modulus of about 0.7 MPa to about 8 MPa at a frequency range of about 1 kHz to about 100 kHz, and thus can maintain rigidity, thereby resisting deformation at the time of applying an impact. The bonded member after curing of the adhesive composition can have a ratio of loss modulus to storage modulus of about 1.4 to about 1.9. Thus, the bonded member can be used as a damping member that absorbs an applied external impact. The bonded member according to the embodiment satisfies a storage modulus of about 0.7 MPa to about 8 MPa and a ratio of loss modulus to storage modulus of about 1.4 to about 1.9 at a frequency range of 1 kHz to 100 kHz, thereby improving impact resistance.

[0121] The adhesive composition can have a low viscosity so as to be applicable to inkjet printing. The adhesive composition has a low viscosity of about 10 cp to about 40 cp, and thus can be applied using inkjet printing.

[0122] Hereinafter, other examples of the embodiment will be described. Figure 8 to Figure 10 The display device can have various laminated structures.

[0123] Figure 8 is a schematic cross-sectional view of a display device according to an embodiment. Figure 9 is a schematic cross-sectional view of a display device according to an embodiment, showing another example. Figure 10 is a schematic cross-sectional view of a display device according to an embodiment, showing a third example.

[0124] Referring to Figure 8 , the display device 10 according to the embodiment is different from Figure 3 the embodiment in that the cover window protection layer 210, the first bonded member 251, the impact absorbing layer 230, and the third bonded member 253 can be omitted.

[0125] Referring to Figure 9 , the display device 10 according to the embodiment is different from Figure 3 the embodiment in that the cushion layer 320, the seventh bonded member 353, the plate 330, and the eighth bonded member 354 can be omitted. The configuration of the embodiment can be easily understood according to those described with reference to Figure 3 , and such descriptions are not repeated.

[0126] Referring to Figure 10 , the display device 10 according to the embodiment is different fromFigure 3 The embodiments are the same as those of Figure 3 The embodiments differ from those of

[0127] As described above, when the display device 10 is folded in the outwardly folded manner, the front laminate structure 200 and the rear laminate structure 300 are stressed in the opposite way to those shown in Figure 3 The front laminate structure 200 can be subjected to tensile stress, and the rear laminate structure 300 can be subjected to compressive stress.

[0128] Hereinafter, the embodiments will be described in more detail through manufacturing examples and experimental examples.

[0129] <Manufacturing Example 1: Manufacture of Display Device>

[0130] A plurality of display device samples having the laminate structure shown in Figure 3 were manufactured.

[0131] <Manufacturing Example 2: Preparation of Adhesive>

[0132] Acrylic acid 2-hydroxyethyl ester (2-HEA), acrylic acid 2-ethylhexyl ester (2-EHA), and acrylic acid n-hexyl ester (n-HA) as monomers, 3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexyl isocyanate (IPDI) as a crosslinking agent, and a small amount of an adhesion aid were mixed to prepare Adhesive #1.

[0133] Acrylic acid 4-hydroxybutyl ester (4-HBA) and acrylic acid 2-ethylhexyl ester (2-EHA) as monomers, ethylene diacrylate (EDA) as a crosslinking agent, and a small amount of an adhesion aid were mixed to prepare Adhesive #2. At this time, the crosslinking agent and acrylic acid 4-hydroxybutyl ester were mixed at a molar ratio of 0.9:0.7.

[0134] Adhesive #3 was prepared in the same manner as Adhesive #2, but the crosslinking agent and acrylic acid 4-hydroxybutyl ester were mixed at a molar ratio of 0.9:0.9.

[0135] Acrylic acid 4-hydroxybutyl ester (4-HBA), acrylic acid 2-ethylhexyl ester (2-EHA), and acrylic acid n-hexyl ester (n-HA) as monomers, 3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexyl isocyanate (IPDI) as a crosslinking agent, and a small amount of an adhesion aid were mixed to prepare Adhesive #4. At this time, the crosslinking agent and acrylic acid 4-hydroxybutyl ester were mixed at a molar ratio of 0.9:0.7.

[0136] Acrylic acid 4-hydroxybutyl ester (4-HBA), acrylic acid dihydroxyhexyl ester (DHHA) and acrylic acid 2-ethylhexyl ester (2-EHA) as monomers, ethylene diacrylate (EDA) as a crosslinking agent and a small amount of an adhesion promoter were mixed to prepare Adhesive #5.

[0137] Adhesive #6 was prepared in the same manner as Adhesive #4, but the crosslinking agent and acrylic acid 4-hydroxybutyl ester were mixed in a molar ratio of 0.9:0.9.

[0138] Adhesive #7 was prepared in the same manner as Adhesive #2, but the crosslinking agent and acrylic acid 4-hydroxybutyl ester were mixed in a molar ratio of 1.1:0.9.

[0139] Acrylic acid 4-hydroxybutyl ester (4-HBA) as a monomer, ethylene diacrylate (EDA) as a crosslinking agent and a small amount of an adhesion promoter were mixed to prepare Adhesive #8.

[0140] Acrylic acid 4-hydroxybutyl ester (4-HBA), n-hexyl acrylate (n-HA) and tetrahydrofurfuryl acrylate (THFA) as monomers, ethylene diacrylate (EDA) and 3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexyl isocyanate (IPDI) as crosslinking agents and a small amount of an adhesion promoter were mixed to prepare Adhesive #9.

[0141] Acrylic acid 2-hydroxyethyl ester (2-HEA) and n-hexyl acrylate (n-HA) as monomers, 3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexyl isocyanate (IPDI) as a crosslinking agent and a small amount of an adhesion promoter were mixed to prepare Adhesive #10.

[0142] Acrylic acid 4-hydroxybutyl ester (4-HBA), n-hexyl acrylate (n-HA) and acrylic acid 2-ethylhexyl ester (2-EHA) as monomers, ethylene diacrylate (EDA) and 3,3,5-trimethyl-5-(isocyanatomethyl)cyclohexyl isocyanate (IPDI) as crosslinking agents and a small amount of an adhesion promoter were mixed to prepare Adhesive #11.

[0143] Acrylic acid 4-hydroxybutyl ester (4-HBA) and acrylic acid 2-ethylhexyl ester (2-EHA) as monomers, ethylene diacrylate (EDA) as a crosslinking agent and a small amount of an adhesion promoter were mixed to prepare Adhesive #12.

[0144] <Experimental Example 1: Storage modulus depending on temperature>

[0145] The adhesives #1 to #12 were coated between release paper films to a thickness of 500 μm, UV-cured and then aged for 30 minutes. Then, the storage modulus of each sample was measured at -20 to 60°C. At this time, each adhesive sample and a PSA sample as a control were cut into a diameter of 8 mm and a thickness of 500 μm, and then the temperature-dependent storage modulus was measured using a DHR3-type rheometer manufactured by TA Instruments.

[0146] <Experiment Example 2: Folding Test>

[0147] The in-folding operation was repeated 200,000 times for the display device samples according to Manufacturing Example 1 for 240 hours. The display device samples included an ultrathin glass as a cover window, and the adhesives #1 to #12 obtained in Manufacturing Example 2 and the PSA were applied to the respective display device samples. Some of the display device samples were subjected to the in-folding operation under a first condition of a temperature of 60°C and a humidity of 93%, and the other display device samples were subjected to the in-folding operation under a second condition of a variable temperature of -40 to 85°C and a humidity of 93%. Here, the variable temperature of -40 to 85°C was achieved by increasing the temperature from -40°C to 85°C and then decreasing it again to -40°C in one cycle, and repeating the cycle.

[0148] Table 1 below shows the viscosity of each sample at room temperature and the results of Experiment Examples 1 and 2. The storage modulus of the PSA and the adhesives #2, #5 and #8 are shown in Table 1. In Table 1, the temperature-dependent index is the ratio of the storage modulus of the adhesive measured at a temperature of -20°C to the storage modulus of the adhesive measured at a temperature of 60°C. Further, in the results of the folding test, O indicates that the adhesive was not peeled from the layer, and X indicates that the adhesive was peeled from the layer. Figure 11

[0149] [Table 1]

[0150]

[0151] From Table 1 and Figure 11 It can be seen that the adhesives #1, #2, #5 and #6 passed the folding test, and the temperature-dependent index was greater than 1 and less than 10, which is equivalent to the control PSA. It can also be seen that the adhesives #1 to #12 showed a low viscosity of 40 cp or less at room temperature.

[0152] <Experiment Example 3: Measurement of Storage Modulus in Frequency Region>

[0153] ​The storage modulus (G') and loss modulus (G") of the adhesives #1, #2, #4, #5, #6, #7, #9 and PSA according to Production Example 2 were measured under the same conditions as in Experimental Example 1, but a frequency sweep was applied thereto at room temperature using a rheometer at a frequency of 10 -2 Hz to 10 2 Hz. The rheometer was used to measure the modulus only in the frequency range of 10 -2 Hz to 10 2 Hz. Accordingly, the storage modulus and loss modulus in the entire frequency range of 10 -2 Hz to 10 8 Hz were obtained by measuring the modulus with the rheometer and converting the modulus by temperature time superposition (TTS).

[0154] <Experimental Example 4: Impact Resistance Test>

[0155] A pen having a stainless steel ball (7 mm in diameter, 5.8 g in weight) was dropped onto the display device sample according to Production Example 1, and the dropping height of the pen in which a bright spot and a crack were formed in the display device sample was observed. At this time, the dropping position of the pen was tested in the folded portion (e.g., "FDA" in Figure 1 ) and the non-folded portion (e.g., "NFA1" in Figure 1 ) of each display device sample. The display device sample had an ultrathin glass as a cover window, and the adhesives #1, #2, #4, #5, #6, #7 and #9 according to Production Example 2 and PSA were applied to the respective display device samples.

[0156] The results of Experimental Examples 3 and 4 are shown in Table 2 below. Table 2 below shows the storage modulus (G'), loss modulus (G") and tan delta value (ratio of G" to G') of the adhesives at 10 kHz. In the results of the impact resistance test, O indicates the measured value of the display device sample to which PSA was applied, X indicates a value lower than the O value, and indicates a value higher than the O value. In addition, Figure 12 and Figure 13 show the storage modulus and tan delta value of PSA and the adhesives #2 and #5 in each frequency region in the results according to Experimental Example 3, respectively.

[0157] Table 3 below shows the results of the impact resistance test of the display device sample to which PSA and the adhesives #2 and #5 were applied in the results according to Experimental Example 4. Figure 14 shows the height at which a UTG crack was formed in the display device sample, and Figure 15 shows the height at which a bright spot was formed on the display device sample.

[0158] [Table 2]

[0159]

[0160]

[0161] [Table 3]

[0162]

[0163] Table 2 and Figure 12 and Figure 13 It was shown that the adhesives #2 and #5, which satisfy the storage modulus of greater than 0.7 MPa and the tan δ value of greater than 1.4, have improved impact resistance compared to the control PSA.

[0164] Table 3 and Figure 14 and Figure 15 It was shown that the display device samples to which the adhesives #2 and #5 were applied showed greater pencil height at which a bright spot and a crack were formed in a non-folded portion and a folded portion compared to the display device samples to which the control PSA was applied. The results prove that the display device samples to which the adhesives #2 and #5 were applied have improved impact resistance compared to the display device samples to which the control PSA was applied.

[0165] <Experimental Example 5: Impact Resistance Simulation>

[0166] A pen having a stainless steel ball (7 mm in diameter, 5.8 g in weight) was dropped from a height of 50 mm onto the display device samples to which the PSA and the adhesives #2 and #5 were applied, and when a bright spot and a crack were formed in the display device samples, a physical change amount (in which the surface of the display device was printed with a change amount of the depth of an indentation by the pen) of the display device was simulated. The results are shown in Table 4 below.

[0167] [Table 4]

[0168] Adhesive Bright spots Cracks PSA 1.07％ 4.13％ #2 0.75％ 4.69％ #5 0.97％ 4.10％

[0169] Table 4 shows that the adhesives #2 and #5 showed the same level of physical change as the control PSA when a bright spot and a crack were formed. This proves that the adhesives #2 and #5 showed the same impact resistance as the control PSA.

[0170] Embodiments have been disclosed herein, and although use of the terms may be made in the description, they are used and interpreted only in a generic and descriptive sense, and not for limitation purposes. In some instances, features, attributes and / or elements described in relation to an embodiment may be used alone or in combination with features, attributes and / or elements described in relation to another embodiment, as would be apparent to a person of ordinary skill in the art, unless otherwise specifically stated. Accordingly, a person of ordinary skill in the art would understand that various changes in form and details can be made without departing from the spirit and scope of the disclosure as set forth in the following claims.

Claims

1. A display device comprising: a display panel including a first surface disposed on a front side; and a front lamination structure disposed on the first surface of the display panel, wherein the front lamination structure includes a cover window and at least one bonding member including a window bonding member attaching the cover window to the first surface of the display panel, a storage modulus of the window bonding member at a temperature of -20 °C divided by a storage modulus of the window bonding member at a temperature of 60 °C is greater than 1 and less than 10, and a ratio of a loss modulus of the window bonding member to the storage modulus of the window bonding member at a frequency of 1 kHz to 100 kHz is 1.4 to 1.

9. 2.The display device of claim 1, wherein the storage modulus of the window bonding member at a temperature of -20 °C is 0.09 MPa to 0.3 MPa. 4.The display device of claim 1, wherein a storage modulus of the window bonding member at a frequency of 1 kHz to 100 kHz is 0.7 MPa to 8 MPa.

3. The display device of claim 1, wherein the storage modulus of the window bonding member at a temperature of -10°C to 60°C is 10 4 Pa to 10 7 Pa. 5.The display device of claim 4, wherein the storage modulus of the window bonding member and the loss modulus of the window bonding member are measured in a thin film state by a rheometer. 6.The display device of claim 1, wherein the front lamination structure includes: a polarizing member disposed between the display panel and the cover window; and a polarizing portion bonding member attaching the polarizing member to the first surface of the display panel. 7.The display device of claim 6, wherein the front lamination structure includes: a shock absorbing layer disposed between the polarizing member and the cover window; and a shock absorbing layer bonding member attaching the shock absorbing layer to the polarizing member. 8.The display device of claim 7, wherein the display panel includes a second surface disposed on a back side, and the display device includes a back lamination structure disposed on the second surface of the display panel, the back lamination structure including: a polymer film layer disposed below the display panel; a cushion layer disposed below the polymer film layer; a plate disposed below the cushion layer; and a heat dissipation member disposed below the plate, wherein the at least one bonding member attaches the polymer film layer, the cushion layer, the plate, and the heat dissipation member. 9.The display device of claim 1, wherein the cover window includes an ultrathin glass, and the window bonding member attaches the ultrathin glass to the display panel. ​ ​ ​ ​

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