Display device

Abstract

The present application relates to a display apparatus. The display apparatus includes a display panel foldable with respect to at least one folding axis, a polarizing layer disposed on the display panel, an adhesive layer disposed on the polarizing layer, and a window disposed on the adhesive layer and having one surface facing the adhesive layer. The 180-degree peel adhesion of the adhesive layer to the one surface of the window can be about 493 grams force per inch (gf / inch) to about 817 gf / inch under conditions of a temperature of about 60 degrees Celsius (°C) and a relative humidity of about 93 percent (%). Accordingly, the display apparatus including the adhesive layer can exhibit good durability and maintain its reliability.

Description

[0001] Cross-reference to related applications

[0002] This application claims priority to and all benefits arising therefrom of Korean Patent Application No. 10-2021-0009403, filed on January 22, 2021, the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments of the present invention relate to display devices, and more specifically, to foldable display devices including an adhesive layer disposed below a window. Background Technology

[0004] Display devices display various images on a screen to provide information to users. Typically, display devices display information within a given screen area. Recently, flexible display devices, including foldable or bendable display panels, have been developed. Unlike rigid display devices, flexible display devices are foldable, rollable, or bendable. Flexible display devices, whose shape can be changed differently regardless of screen size, can be carried, thus improving user convenience.

[0005] The adhesive layer used in flexible display devices must remain reliable even after repeated folding or bending. Summary of the Invention

[0006] Embodiments of the present invention provide a display device that maintains reliability even after repeated folding and unfolding.

[0007] Embodiments of the present invention provide a display device comprising a display panel foldable relative to at least one folding axis, a polarizing layer disposed on the display panel, an adhesive layer disposed on the polarizing layer, and a window disposed on the adhesive layer, wherein the window includes a surface facing the adhesive layer, wherein the 180-degree (°) peel adhesion of the adhesive layer to the surface of the window is approximately 493 gf / inch to approximately 817 gf / inch at a temperature of approximately 60 degrees Celsius (°C) and a relative humidity of approximately 93 percent.

[0008] In one embodiment, the adhesive layer may include an acrylic resin and a silane coupling agent.

[0009] In one embodiment, one surface of the window may be one surface of a glass substrate, and the 180° peel adhesion of the adhesive layer to one surface may be from about 493 gf / inch to about 556 gf / inch.

[0010] In one embodiment, one surface of the window may be a surface of a plasma-treated glass substrate, and the 180° peel adhesion of the adhesive layer to one surface may be from about 636 gf / inch to 817 gf / inch.

[0011] In an embodiment, when a stress of about 1,900 Pa to about 2,000 Pa is applied to the adhesive layer for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the creep value of the adhesive layer can be about 16% to about 18%.

[0012] In an embodiment, when a stress of about 1,900 Pa to about 2,000 Pa is applied to the adhesive layer for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the residual strain of the adhesive layer after an additional 10 minutes of time has elapsed can be about 0.6% to about 0.9%, and the recovery rate of the adhesive layer can be about 95% to about 96%.

[0013] In an embodiment, when a stress of about 9,900 Pa to about 12,210 Pa is applied to the adhesive layer for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the creep value of the adhesive layer can be about 94% to about 101%.

[0014] In an embodiment, when a stress of about 9,900 Pa to about 12,210 Pa is applied to the adhesive layer for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the residual strain of the adhesive layer after an additional 10 minutes of time has elapsed can be about 3% to about 4%, and the recovery rate of the adhesive layer can be about 95% to about 96%.

[0015] In this embodiment, the thickness of the adhesive layer can be from about 10 micrometers (μm) to about 70 μm.

[0016] In some embodiments, the adhesive layer may include a polymeric resin having a glass transition temperature of about -40°C or lower.

[0017] In an embodiment, the polarizing layer can have a Young's modulus of about 9,600 MPa to about 9,800 MPa at a temperature of about -20°C, and a Young's modulus of about 6,900 MPa to about 7,100 MPa at a temperature of about 60°C.

[0018] In an embodiment, the polarizing layer may have a Young's modulus of about 8,300 MPa to about 8,500 MPa at room temperature and relative humidity of about 40% to about 50%, and may have a Young's modulus of about 3,200 MPa to about 3,400 MPa at a temperature of about 60°C and relative humidity of about 93%.

[0019] In one embodiment, the display device is foldable inward relative to at least one folding axis.

[0020] In an embodiment, the display device may further include an impact absorbing layer disposed between the adhesive layer and the polarizing layer, wherein the impact absorbing layer may have a Young's modulus of about 5,500 MPa to about 6,600 MPa at a temperature of about -20°C and a Young's modulus of about 4,300 MPa to about 5,100 MPa at a temperature of about 60°C.

[0021] In an embodiment, the shock-absorbing layer may have a Young's modulus of about 5,000 MPa to about 5,900 MPa at room temperature and about 40% to about 50% relative humidity, and a Young's modulus of about 3,900 MPa to about 4,700 MPa at a temperature of about 60°C and about 93% relative humidity.

[0022] In an embodiment, the display device may further include at least one functional layer disposed below the display panel and an auxiliary adhesive layer disposed below the at least one functional layer, wherein the 180° peel adhesion force of the auxiliary adhesive layer to the at least one functional layer may be from about 493 gf / inch to about 817 gf / inch under conditions of a temperature of about 60°C and a relative humidity of about 93%.

[0023] Embodiments of the present invention provide a display device comprising a display panel foldable relative to at least one folding axis, a polarizing layer disposed on the display panel, an adhesive layer disposed on the polarizing layer, and a window disposed on the adhesive layer, wherein the window includes a surface facing the adhesive layer, wherein when a stress of about 1,900 Pa to about 2,000 Pa is applied to the adhesive layer for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the adhesive layer has a creep value of about 16% to about 18%, and when a stress of about 9,900 Pa to about 12,210 Pa is applied to the adhesive layer for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the adhesive layer has a creep value of about 94% to about 101%.

[0024] In one embodiment, at a temperature of 60°C and a relative humidity of approximately 93%, the 180° peel adhesion of the adhesive layer to one surface of the window can be approximately 493 gf / inch to approximately 817 gf / inch.

[0025] In an embodiment, the adhesive layer may include at least one of trimethoxy(3-(ethylene oxide-2-methoxy)propyl)silane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-[(2,3-epoxypropoxypropyl)methyl]dimethoxysilane, 3-[(2,3-epoxypropoxypropyl)methyl]diethoxysilane, 2-[(3,4-epoxycyclohexyl)ethyl]methyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.

[0026] In one embodiment, the window may include a glass substrate, and the window may also include a protective layer disposed on the glass substrate. Attached Figure Description

[0027] The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. In the drawings:

[0028] Figure 1 This is a perspective view showing the display device according to the embodiment;

[0029] Figure 2 This is a perspective view showing the display device according to the embodiment;

[0030] Figure 3 It is along Figure 1 A sectional view taken by line I-I';

[0031] Figure 4 This is a cross-sectional view illustrating an embodiment of the display device;

[0032] Figure 5 It is a graph showing the modulus versus oscillating strain; and

[0033] Figure 6 It is along Figure 2 The sectional view taken from line II-II'. Detailed Implementation

[0034] The present invention can be modified in many alternative forms, and therefore specific embodiments will be illustrated in the accompanying drawings and described in detail in the text. However, it should be understood that the invention is not intended to be limited to the specific forms disclosed, but rather to cover all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0035] In this specification, when an element (or region, layer, part, etc.) is referred to as being “on”, “connected to”, or “attached to” another element, it means that the element can be directly placed on / connected to / attached to another element, or a third element can be placed between them.

[0036] The same reference numerals denote the same elements. Furthermore, in the accompanying drawings, the thickness, proportions, and dimensions of the elements are exaggerated for the purpose of effective description of the technical content.

[0037] The term "and / or" includes all combinations that one or more related configurations can define.

[0038] It should be understood that although the terms "first," "second," etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element without departing from the scope of embodiments of the invention. Singular terms may include plural forms unless the context clearly indicates otherwise.

[0039] As used herein, “about” or “approximately” includes the value as well as the average of the values ​​within an acceptable range of deviations from the particular value, as determined by a person skilled in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., limitations of the measurement system). For example, “about” may mean within one or more standard deviations, or within ±30%, ±20%, ±10%, ±5% of the value.

[0040] Unless otherwise defined, all terms used herein (including technical and scientific terms) shall have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms defined in common dictionaries shall be interpreted as having a meaning consistent with their meaning in the context of the relevant art, and are expressly defined herein, unless they are interpreted in an ideal or overly formal sense.

[0041] It should be understood that the terms "comprising" or "having" are intended to specify the presence of features, integrals, processes, operations, elements, components or combinations thereof stated in this invention, but do not exclude the presence or addition of one or more other features, integrals, processes, operations, elements, components or combinations thereof.

[0042] In the following description, an embodiment of the display device of the present invention will be described with reference to the accompanying drawings.

[0043] Figure 1 and Figure 2 This is a perspective view of the display device DD according to an embodiment. Figure 1 The diagram shows the unfolded state of the display device DD, and Figure 2 The illustration shows the folded state of the display device DD. In this embodiment, the display device DD can be a foldable or bendable flexible display device, or it can be kept in a folded or bendable state.

[0044] Reference Figure 1 and Figure 2 The display device DD can be a device activated in response to an electrical signal. In embodiments, the display device DD can be, for example, a personal digital assistant, tablet, car navigation unit, game console, or wearable device, but is not limited thereto. Figure 1 and Figure 2 In the image, the portable electronic device is shown as a display device DD.

[0045] The display device DD can display an image through the effective area EA. The effective area EA may include non-folded areas NFA1 and NFA2, and a folded area FA. The folded area FA may be curved relative to the folding axis FX, which extends parallel to the direction of the second direction axis DR2.

[0046] When the display device DD is folded, the non-folded areas NFA1 and NFA2 can face each other. In the fully folded state, the effective area EA may not be exposed to the outside, which can be referred to as folding inward. However, this is shown as an example, and the operation of the display device DD is not limited to this.

[0047] The display device DD can perform only one operation, either an inward folding operation or an outward folding operation. In an alternative embodiment, the display device DD can perform both inward folding and outward folding operations. In this case, the same area of ​​the display device DD (such as the folding area FA) can be folded inward and outward. In an alternative embodiment, a portion of the area of ​​the display device DD can be folded inward, and another portion of that area can be folded outward.

[0048] Figure 1 and Figure 2 The display device DD is shown as including a folded region FA and two non-folded regions NFA1 and NFA2, but the number of folded regions FA and non-folded regions is not limited thereto. In an embodiment, for example, the display device may include at least three non-folded regions and at least two folded regions, the at least two folded regions being disposed between non-folded regions adjacent to each other.

[0049] exist Figure 1 and Figure 2In the diagram, the folding axis FX is shown parallel to the minor axis of the display device DD, i.e., the direction in which the second direction axis DR2 extends. However, this is shown as an example, and the invention is not limited thereto. In embodiments, for example, the folding axis may also be parallel to the major axis of the display device DD, i.e., the direction in which the first direction axis DR1 extends.

[0050] The display device DD may include a sensing area SA surrounded by an effective area EA. In an implementation, the sensing area SA may overlap with a camera module. However, for example, in... Figure 1 A sensing area SA is shown in the figure, but the invention is not limited thereto. The display device of the embodiment may include multiple sensing areas.

[0051] The display device DD may include a housing HU. The housing HU may house the display panel DP and window WN, which will be described later.

[0052] although Figure 1 and Figure 2 The display device DD shown in the embodiment is a foldable display device, but the invention is not limited thereto. The display device in the embodiment may be a foldable or bendable flexible display device, or may be held in a folded or bendable state. In this specification, the term "flexible" means a bendable characteristic and may not be limited to a fully foldable structure, but may include structures that are bendable to a degree of a few nanometers.

[0053] The display device DD may have a three-dimensional shape with a predetermined thickness in a direction perpendicular to a third direction axis DR3, which is perpendicular to the plane defined by a first direction axis DR1 and a second direction axis DR2 intersecting the first direction axis DR1. In this specification, the upper (or front) and lower (or rear) surfaces of each component are defined based on the direction in which an image is displayed on the effective area EA. The upper and lower surfaces may be opposite each other on the third direction axis DR3, and the normal direction of each of the upper and lower surfaces may be parallel to the third direction axis DR3. The directions represented by the first direction axis DR1, the second direction axis DR2, and the third direction axis DR3 are relative concepts and may therefore be changed to other directions. Hereinafter, the first direction to the third direction is considered to be the direction represented by the first direction axis DR1, the second direction axis DR2, and the third direction axis DR3, respectively, and the same reference numerals should be used.

[0054] Figure 3 It is along Figure 1 A sectional view taken from line I-I'. Figure 4 This is a cross-sectional view illustrating another embodiment of the display device DD-a according to the present invention. Figure 3 compared to, Figure 4The display device DD-a is shown to also include an impact absorption layer SCL between the window WN and the polarizing layer POL.

[0055] In this embodiment, display devices DD and DD-a may each include a display panel DP, a polarizing layer POL disposed on the display panel DP, an adhesive layer AL1 disposed on the polarizing layer POL, and a window WN disposed on the adhesive layer AL1. The display panel DP may be foldable relative to at least one folding axis FX.

[0056] The window WN may include a glass substrate GL. Furthermore, the window WN may also include a protective layer WP disposed on the glass substrate GL. The thickness T0 of the glass substrate GL may be from about 10 μm to about 80 μm. The glass substrate GL may be tempered glass. The protective layer WP may be disposed on the front surface of the display device DD. The protective layer WP allows the image provided from the display panel DP to be transmitted as is and protects the glass substrate GL from external impacts.

[0057] In an embodiment, the protective layer WP may be a film comprising at least one resin selected from polyethylene terephthalate (“PET”), polybutylene terephthalate (“PBT”), polyethylene naphthalate (“PEN”), polycarbonate (“PC”), poly(methyl methacrylate” (“PMMA”), polystyrene (“PS”), polyvinyl chloride (“PVC”), polyethersulfone (“PES”), polypropylene (“PP”), polyamide (“PA”), modified polyphenylene ether (“m-PPE”), polyoxymethylene (“POM”), polysulfone (“PSU”), polyphenylene sulfide (“PPS”), polyimide (“PI”), polyethyleneimine (“PEI”), polyetheretherketone (“PEEK”), polyamide-imide (“PAI”), polyarylate (“PAR”), or thermoplastic polyurethane (“TPU”).

[0058] In an embodiment, the window WN may include a surface F1 facing the adhesive layer AL1. The surface F1 of the window WN may contact the adhesive layer AL1. Under conditions of a temperature of approximately 60 degrees Celsius (°C) and a relative humidity of approximately 93 percent, the 180-degree (°) peel adhesion force of the adhesive layer AL1 to the surface F1 of the window WN can be approximately 493 gf / inch to approximately 817 gf / inch. In this specification, the 180° peel adhesion force is a value measured by a method wherein the peel angle is approximately 180° and the stretching speed is approximately 300 mm / min.

[0059] In an embodiment, one surface F1 of the window WN may include glass. One surface F1 of the window WN may be one surface F1 of a glass substrate GL. When one surface F1 of the window WN is one surface F1 of the glass substrate GL, the 180° peel adhesion force of the adhesive layer AL1 to one surface F1 of the window WN may be approximately 493 gf / inch to approximately 556 gf / inch. The 180° peel adhesion force of the adhesive layer AL1 to an unmodified surface F1 of the window WN may be approximately 493 gf / inch to approximately 556 gf / inch. In an embodiment, the 180° peel adhesion force of the adhesive layer AL1 to an unmodified surface F1 of the window WN may, for example, be approximately 493.9 gf / inch to approximately 555.4 gf / inch. The unmodified surface F1 of the window WN may not undergo plasma treatment.

[0060] In an alternative embodiment, one surface F1 of the window WN can be plasma-treated. The plasma-treated surface F1 of the window WN can be surface-modified. The surface-modified surface F1 of the window WN can be a plasma-treated surface F1 of the glass substrate GL. In an embodiment, for example, the surface F1 of the window WN surface-modified by nitrogen plasma treatment can have improved adhesion to the adhesive layer due to nitrogen atoms. The 180° peel adhesion of the adhesive layer AL1 to the surface-modified surface F1 of the window WN can be from about 636 gf / inch to about 817 gf / inch. In an embodiment, the 180° peel adhesion of the adhesive layer AL1 to the surface-modified surface F1 of the window WN can be, for example, from about 636.5 gf / inch to about 816.9 gf / inch. Because the surface of one surface F1 of the window WN is surface-modified by plasma treatment, the adhesion between the adhesive layer AL1 and the surface F1 of the window WN can be improved.

[0061] When the 180° peel adhesion force of the adhesive layer to one surface of the window is less than approximately 493 gf / inch at a temperature of approximately 60°C and a relative humidity of approximately 93%, the window and the adhesive layer can be peeled off. Conversely, when the 180° peel adhesion force of the adhesive layer to one surface of the window is greater than approximately 817 gf / inch at a temperature of approximately 60°C and a relative humidity of approximately 93%, it may be difficult to fold the display device.

[0062] In this embodiment, the thickness T1 of the adhesive layer AL1 can be from about 10 μm to about 70 μm. The adhesive layer AL1 may include a pressure-sensitive adhesive (“PSA”). The adhesive layer AL1 may be optically transparent. The adhesive layer AL1 may include a polymeric resin having a glass transition temperature of about -40°C or lower. The adhesive layer AL1 may include an acrylic resin and a silane coupling agent (“SCA”). The adhesive layer AL1 may include an acrylic resin having a glass transition temperature of about -40°C or lower. The acrylic resin may include acrylate monomers. In an embodiment, the adhesive layer AL1 may include at least one SCA selected from, for example, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-(2,3-epoxypropoxypropyl)methyldimethoxysilane, 3-(2,3-epoxypropoxypropyl)methyldiethoxysilane, 2-(3,4-epoxycyclohexyl)ethylmethyldimethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane. However, this is shown by way of example, and the types of SCAs included in the adhesive layer AL1 are not limited thereto.

[0063] In one embodiment, when a stress of about 1,900 Pa to about 2,000 Pa is applied to the adhesive layer AL1 for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the creep value of the adhesive layer AL1 can be about 16% to about 18%. In another embodiment, when a stress of about 1,900 Pa to about 2,000 Pa is applied to the adhesive layer AL1 for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the creep value of the adhesive layer AL1 can be, for example, about 16.29% to about 17.12%.

[0064] When a stress of approximately 1,900 Pa to approximately 2,000 Pa is applied to adhesive layer AL1 for approximately 10 minutes at a temperature of approximately 60°C and a relative humidity of approximately 93%, the residual strain of adhesive layer AL1 after approximately 10 minutes can be approximately 0.6% to approximately 0.9%. When a stress of approximately 1,900 Pa to approximately 2,000 Pa is applied to adhesive layer AL1 for approximately 10 minutes at a temperature of approximately 60°C and a relative humidity of approximately 93%, the recovery rate of adhesive layer AL1 after approximately 10 minutes can be approximately 95% to approximately 96%. The strain and recovery rate of adhesive layer AL1 can be defined as the strain and recovery rate obtained after approximately 10 minutes from the removal of the applied stress. In an embodiment, when a stress of about 1,900 Pa to about 2,000 Pa is applied to the adhesive layer AL1 for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, for example, the residual strain of the adhesive layer AL1 after about 10 minutes can be about 0.66% to about 0.82%, and the recovery rate of the adhesive layer AL1 can be about 95.23% to about 95.93%.

[0065] In an embodiment, when a stress of about 9,900 Pa to about 12,210 Pa is applied to the adhesive layer for about 10 minutes, the creep value of the adhesive layer AL1 can be about 94% to about 101%. The stress of about 9,900 Pa to about 12,210 Pa corresponds to the stress that satisfies the linear viscoelastic region (“LVR”) condition.

[0066] The adhesive layer AL1 in this embodiment may comprise a polymer resin exhibiting viscoelastic properties. The polymer exhibits viscoelastic properties, and the LVR can be confirmed when strain scanning tests are performed on the polymer.

[0067] Figure 5 It is a graph showing the modulus measured by performing a strain scan test on the polymer. Figure 5 The measurements of storage modulus and loss modulus are shown as strain increases continuously.

[0068] Reference Figure 5 The horizontal axis represents the oscillatory strain as a percentage, and the vertical axis represents the modulus in Pascals. It can be seen that the modulus in the left region of line X1 exhibits linear behavior, while the modulus in the right region of line X1 exhibits nonlinear behavior. The left region of line X1 may correspond to the LVR region.

[0069] LVR can be a region satisfying a strain condition in which the modulus (storage modulus and loss modulus) decreases by about 5% compared to the initial modulus (storage modulus and loss modulus). When stress exceeding the LVR is applied to the polymer, the polymer undergoes permanent deformation and therefore does not recover even after stress removal. Thus, a stress of about 9,900 Pa to about 12,210 Pa can be a strain condition under which the modulus (storage modulus and loss modulus) decreases by about 5% or less compared to the initial modulus (storage modulus and loss modulus) in the adhesive layer AL1 of the embodiment.

[0070] When a stress of approximately 9,900 Pa to approximately 12,210 Pa is applied to the adhesive layer AL1 for approximately 10 minutes at a temperature of approximately 60°C and a relative humidity of approximately 93%, the residual strain of the adhesive layer AL1 after approximately 10 minutes can be approximately 3% to approximately 4%. Furthermore, when a stress of approximately 9,900 Pa to approximately 12,210 Pa is applied to the adhesive layer AL1 for approximately 10 minutes at a temperature of approximately 60°C and a relative humidity of approximately 93%, the recovery rate of the adhesive layer AL1 after approximately 10 minutes can be approximately 95% to approximately 96%. In an embodiment, when a stress of approximately 9,900 Pa to approximately 12,210 Pa is applied to the adhesive layer AL1 for approximately 10 minutes at a temperature of approximately 60°C and a relative humidity of approximately 93%, the residual strain of the adhesive layer AL1 after approximately 10 minutes can, for example, be approximately 3.87% to approximately 4.72%. When a stress of about 9,900 Pa to about 12,210 Pa is applied to the adhesive layer AL1 for about 10 minutes at a temperature of about 60°C and a relative humidity of about 93%, the recovery rate of the adhesive layer AL1 after about 10 minutes can be about 95.22% to about 95.89%.

[0071] When repeatedly folded and unfolded in a display device comprising an adhesive layer having a recovery rate of less than approximately 95% under conditions of approximately 60°C and approximately 93% relative humidity, the adhesive layer can become completely deformed. Furthermore, when repeatedly folded and unfolded in a display device comprising an adhesive layer having a residual strain greater than approximately 4% under conditions of approximately 60°C and approximately 93% relative humidity, the adhesive layer can become completely deformed. When the adhesive layer is completely deformed, the reliability of the display device may deteriorate.

[0072] A typical display device includes an adhesive layer and a primer layer between a window and a polarizing layer. A typical display device includes an adhesive layer disposed on the polarizing layer and a primer layer disposed on the adhesive layer. The primer layer is used to increase the adhesion of the adhesive layer to the window. When the display device includes a primer layer, a separate process is required to form the primer layer in the display device manufacturing process.

[0073] Since the display devices DD and DD-a in the embodiments do not include a primer layer, the time and cost required to form the primer layer can be shortened and reduced. In the display devices DD and DD-a in the embodiments, since the adhesive layer AL1 disposed between the polarizing layer POL and the window WN includes SCA, the adhesion of the adhesive layer AL1 to the window WN can be improved. Furthermore, the adhesive layer AL1 including SCA can exhibit improved 180° peel adhesion to the window WN under conditions of approximately 60°C and approximately 93% relative humidity. When an external force is applied, the adhesive layer AL1 including SCA can exhibit good strain and recovery rate characteristics. Therefore, the display devices DD and DD-a in the embodiments including the adhesive layer AL1 can maintain their reliability even after repeated folding and unfolding. In addition, the display devices DD and DD-a can exhibit excellent durability under high temperature and high humidity conditions.

[0074] Refer to the return Figure 3 and Figure 4 The display devices DD and DD-a in the embodiments may include a polarizing layer POL beneath the adhesive layer AL1. The polarizing layer POL can have a Young's modulus of about 9,600 MPa to about 9,800 MPa at a temperature of about -20°C. The polarizing layer POL can have a Young's modulus of about 6,900 MPa to about 7,100 MPa at a temperature of about 60°C. Furthermore, at room temperature and a relative humidity of about 40% to about 50%, the polarizing layer POL can have a Young's modulus of about 8,300 MPa to about 8,500 MPa. In this specification, room temperature is a temperature in the range of about 23°C to about 28°C. At a temperature of about 60°C and a relative humidity of about 93%, the polarizing layer POL can have a Young's modulus of about 3,200 MPa to about 3,400 MPa.

[0075] Reference Figure 4 The display device DD-a in this embodiment may further include an impact absorbing layer SCL disposed between the adhesive layer AL1 and the polarizing layer POL. In this embodiment, the impact absorbing layer SCL may have a Young's modulus of about 5,500 MPa to about 6,600 MPa at a temperature of about -20°C. The impact absorbing layer SCL may have a Young's modulus of about 4,300 MPa to about 5,100 MPa at a temperature of about 60°C. In this embodiment, the impact absorbing layer SCL may exhibit a Young's modulus of about 4,300 MPa to about 5,100 MPa at a temperature of about 60°C and, for example, a relative humidity of about 40% to about 50%. However, this is shown as an example, and the relative humidity conditions at about 60°C are not limited thereto.

[0076] Furthermore, under conditions of room temperature and relative humidity of approximately 40% to approximately 50%, the impact absorbing layer SCL can have a Young's modulus of approximately 5,000 MPa to approximately 5,900 MPa. Under conditions of approximately 60°C and approximately 93% relative humidity, the impact absorbing layer SCL can have a Young's modulus of approximately 3,900 MPa to approximately 4,700 MPa. Under the aforementioned temperature and relative humidity conditions, the impact absorbing layer SCL satisfying each Young's modulus range can exhibit good adhesion strength with the adhesive layer AL1.

[0077] The shock-absorbing layer (SCL) protects the display panel (DP) from external impacts. The SCL can be formed in the form of a stretched film. The SCL can comprise a polymer resin. In some embodiments, the shock-absorbing layer can comprise resins such as PI and PET, and therefore can be flexible, for example.

[0078] The display devices DD and DD-a in the embodiments may include a display panel DP. The display panel DP may be a light-emitting display panel, and there are no particular limitations. In the embodiments, the display panel DP may be, for example, an organic light-emitting display panel or a quantum dot light-emitting display panel. The light-emitting layer of an organic light-emitting display panel may include organic light-emitting materials. The light-emitting layer of a quantum dot light-emitting display panel may include quantum dots and quantum rods, etc.

[0079] At least one of the functional layers FL1 and FL2 may be disposed below the display panel DP. Furthermore, auxiliary adhesive layers S-AL1 and S-AL2 may be disposed below at least one of the functional layers FL1 and FL2. The first functional layer FL1 and the second functional layer FL2 may be disposed below the display panel DP.

[0080] The first functional layer FL1 can be disposed below the display panel DP. The first functional layer FL1 can be a protective substrate. The first functional layer FL1 can protect the lower portion of the display panel DP. The first functional layer FL1 can include a plastic material. In an embodiment, the first functional layer FL1 can include, for example, PET.

[0081] The second functional layer FL2 can be disposed between the first functional layer FL1 and the support member SP. The second functional layer FL2 can be a padding layer. The second functional layer FL2 can protect the display panel DP by absorbing external impacts applied to the lower portions of the display devices DD and DD-a. The second functional layer FL2 may include a foam board with a predetermined elasticity.

[0082] A first auxiliary adhesive layer S-AL1 may be disposed between a first functional layer FL1 and a second functional layer FL2. A second auxiliary adhesive layer S-AL2 may be disposed below the second functional layer FL2. Under conditions of a temperature of approximately 60°C and a relative humidity of approximately 93%, at least one of the first auxiliary adhesive layer S-AL1 or the second auxiliary adhesive layer S-AL2 may have a 180° peel adhesion force to functional layers FL1 and FL2 of approximately 493 gf / inch to approximately 817 gf / inch. In an embodiment, the 180° peel adhesion force of the first auxiliary adhesive layer S-AL1 to the first functional layer FL1 may be, for example, approximately 493 gf / inch to approximately 817 gf / inch. Furthermore, the 180° peel adhesion force of the second auxiliary adhesive layer S-AL2 to the second functional layer FL2 may be approximately 493 gf / inch to approximately 817 gf / inch. At least one of the first auxiliary adhesive layer S-AL1 or the second auxiliary adhesive layer S-AL2 may have a 180° peel adhesion force on the functional layers FL1 and FL2 equal to the 180° peel adhesion force of adhesive layer AL1. However, this is shown by way of example, and the invention is not limited thereto.

[0083] A support member SP may be disposed below the second functional layer FL2. The support member SP may support the display panel DP. The support member SP may not overlap with the folded area FA. The support member SP may overlap with the non-folded areas NFA1 and NFA2. The support member SP may include metal. In this embodiment, the support member SP may include, for example, stainless steel, aluminum, or an alloy thereof. The strength of the support member SP may be higher than the strength of the display panel DP.

[0084] The third auxiliary adhesive layer S-AL3 can be disposed between the glass substrate GL and the protective layer WP. The fourth auxiliary adhesive layer S-AL4 can be disposed between the polarizing layer POL and the display panel DP. The fifth auxiliary adhesive layer S-AL5 can be disposed between the display panel DP and the first functional layer FL1. Furthermore, the sixth auxiliary adhesive layer S-AL6 can be disposed between the impact absorption layer SCL and the polarizing layer POL. The first auxiliary adhesive layer S-AL1, the second auxiliary adhesive layer S-AL2, the third auxiliary adhesive layer S-AL3, the fourth auxiliary adhesive layer S-AL4, the fifth auxiliary adhesive layer S-AL5, and the sixth auxiliary adhesive layer S-AL6 can each include any one of a PSA film, an optically transparent adhesive (“OCA”) film, or an optically transparent resin (“OCR”). In an embodiment, the first auxiliary adhesive layer S-AL1, the second auxiliary adhesive layer S-AL2, the third auxiliary adhesive layer S-AL3, the fourth auxiliary adhesive layer S-AL4, the fifth auxiliary adhesive layer S-AL5, and the sixth auxiliary adhesive layer S-AL6 can each include, for example, a PSA film. The first auxiliary adhesive layer S-AL1, the second auxiliary adhesive layer S-AL2, the third auxiliary adhesive layer S-AL3, the fourth auxiliary adhesive layer S-AL4, the fifth auxiliary adhesive layer S-AL5, and the sixth auxiliary adhesive layer S-AL6 may each include at least one of a silicone-based resin, an acrylic resin, or a urethane-based resin.

[0085] Figure 6 It is along Figure 2 The sectional view taken from line II-II'. Figure 6 The illustration shows a case where the display device DD in one embodiment is folded inward. The display device DD in this embodiment may be foldable inward relative to at least one folding axis FX. During the folding of the display device DD, one surface of the display panel DP and one surface of the window WN may be folded separately. In the inwardly folded display device DD, the opposing surfaces of the folded window WN may be closer to each other than the opposing surfaces of the folded display panel DP. One surface of the display panel DP may be the upper surface of the display panel DP, and one surface of the window WN may be the upper surface of the window WN.

[0086] In the embodiments of display devices DD and DD-a, the display panel DP and window WN can be folded relative to the folding axis FX to have radii of curvature RD1 and RD2 of approximately 1 mm to approximately 5 mm, respectively. In another embodiment, the display panel DP and window WN can be folded relative to the folding axis FX to have, for example, a radius of curvature of approximately 1.5 mm. However, this is shown as an example, and the radii of curvature RD1 and RD2 in the display devices DD and DD-a of the embodiments are not limited thereto. In the folded state of the display device DD, the adhesive layer AL1 in the embodiments can help maintain the reliability of the display device DD. The adhesive layer AL1, having a 180° peel adhesion force to the window WN of approximately 493 gf / inch to approximately 817 gf / inch, can help maintain reliability during the folding of the display device DD.

[0087] Table 1 below shows the measurements of 180° peel adhesion in the adhesive layers of the comparative and experimental examples. Adhesion force was measured three times for each adhesive layer in the comparative and experimental examples, before and after plasma treatment. In Comparative Example 1 and Experimental Example 1, the 180° peel adhesion of the adhesive layer before plasma treatment was measured. In Comparative Example 2 and Experimental Example 2, the 180° peel adhesion of the adhesive layer after plasma treatment was measured. During plasma treatment, clean, dry air (“CDA”) was supplied at a flow rate of 2.4 liters per minute (“LPM”), nitrogen (N2 gas) was supplied at a flow rate of approximately 350 LPM, and the plasma process was carried out at a speed of approximately 30 mm / sec to approximately 50 mm / sec.

[0088] In Comparative Examples 1 and 2, the 180° peel adhesion force of the adhesive layer excluding SCA was measured. In Experimental Examples 1 and 2, the 180° peel adhesion force of the adhesive layer including SCA in the embodiment was measured.

[0089] Each peel adhesion force measurement was performed, such that the 180° peel adhesion force was measured at a speed of 300 mm / min using a Universal Testing Machine (“UTM”) under conditions of approximately 60°C and approximately 93% relative humidity. The adhesive layers of the comparative and experimental examples were prepared into 25-mm samples, and the samples were attached to the adhesive body by rolling a 2,000 ± 50 g roller back and forth once. The peel adhesion force was then measured after 12 hours.

[0090] [Table 1]

[0091]

[0092] Referring to Table 1, it can be seen that the adhesive layer of Experimental Example 1 has a higher adhesive strength than the adhesive layer of Comparative Example 1.

[0093] Furthermore, it can be seen that the adhesive layer of Experimental Example 2 has a significantly improved adhesive strength compared to the adhesive layer of Comparative Example 2. It can be determined that the adhesive layers of Experimental Example 1 and Experimental Example 2, each including SCA, exhibit significantly improved adhesive strength characteristics compared to the adhesive layers of Comparative Example 1 and Comparative Example 2, which do not include SCA. It can be seen that the adhesive layer of Experimental Example 1 has an adhesive strength of approximately 493 gf / inch to approximately 556 gf / inch under conditions of approximately 60°C and approximately 93% relative humidity. Furthermore, it can be seen that the plasma-treated adhesive layer of Experimental Example 2 has an adhesive strength of approximately 636 gf / inch to approximately 817 gf / inch under conditions of approximately 60°C and approximately 93% relative humidity. Therefore, the adhesive layer including SCA in the embodiment can exhibit improved adhesive strength under conditions of approximately 60°C and approximately 93% relative humidity. The display device including the adhesive layer in the embodiment can maintain its reliability under conditions of approximately 60°C and approximately 93% relative humidity.

[0094] Tables 2 and 3 show the creep values, residual strain, and recovery rates of each adhesive layer in the comparative and experimental examples, each of which was processed in the form of a disc with a diameter of approximately 8 mm and a thickness of approximately 800 μm. The creep values, residual strain, and recovery rates were each measured using a rheometer (TA Instruments, Inc.) at a temperature of approximately 60 °C and a relative humidity of approximately 93%.

[0095] Table 2 shows the creep values ​​of the adhesive layer measured by applying a stress of 1,989.44 Pa to the adhesive layer for approximately 10 minutes at a temperature of approximately 60°C and a relative humidity of approximately 93%. After approximately 10 minutes had elapsed following the removal of stress, the residual strain and recovery rate of the adhesive layer were measured. The creep value, residual strain, and recovery rate were each measured three times. The adhesive layers of Comparative Examples 3 and 4 did not include SCA, while the adhesive layers of Experimental Examples 3 and 4 included SCA. The adhesive layers of Comparative Examples 3, 4, and 4 had a thickness of approximately 35 μm. The adhesive layer of Experimental Example 3 had a thickness of approximately 50 μm.

[0096] [Table 2]

[0097]

[0098] Referring to Table 2, it can be seen that the adhesive layers of Experimental Examples 3 and 4 have creep values ​​similar to those of the adhesive layers of Comparative Examples 3 and 4. It can be seen that, compared with the adhesive layers of Comparative Examples 3 and 4, the adhesive layers of Experimental Examples 3 and 4 exhibit good residual strain and recovery rate. It can be seen that the adhesive layers of Experimental Examples 3 and 4 have a creep value of about 16% to about 18% under conditions of about 60°C and about 93% relative humidity. It can be seen that the adhesive layers of Experimental Examples 3 and 4 have a residual strain of about 0.6% to about 0.9% and a recovery rate of about 95% to about 96% under conditions of about 60°C and about 93% relative humidity. It can be seen that the adhesive layers of Experimental Examples 3 and 4, including SCA, have good creep values, residual strain, and recovery rate. Therefore, the display device including the adhesive layer in the embodiment can maintain its reliability.

[0099] Table 3 below shows the creep values ​​of the adhesive layer measured by applying a stress of 10,535.06 Pa to the adhesive layer for approximately 10 minutes. Subsequently, the residual strain and recovery rate of the adhesive layer were measured after approximately 10 minutes had elapsed. The stress of 10,535.06 Pa is a value representing the LVR behavior of the adhesive layer. Furthermore, the stress of 10,535.06 Pa is a value that takes into account the stress accumulated in the display device during repeated folding. The creep values, residual strain, and recovery rate of the adhesive layers of Comparative Example 3, Comparative Example 4, and Experimental Example 3 were each measured three times, and the creep values, residual strain, and recovery rate of the adhesive layer of Experimental Example 4 were measured twice.

[0100] [Table 3]

[0101]

[0102] Referring to Table 3, it can be seen that the adhesive layers of Comparative Example 3, Comparative Example 4, Experimental Example 3, and Experimental Example 4 have similar residual strain and recovery rates.

[0103] It can be seen that the adhesive layers of Experimental Example 3 and Experimental Example 4 have a residual strain of about 3% to about 4% and a recovery rate of about 95% to about 96%.

[0104] It can be seen that the adhesive layers of Experimental Examples 3 and 4 have creep values ​​similar to those of the adhesive layers of Comparative Examples 3 and 4. It can also be seen that the adhesive layers of Experimental Examples 3 and 4, including SCA, have creep values ​​of approximately 94% to approximately 101%. It can be determined that the adhesive layers of Experimental Examples 3 and 4 include SCA, and therefore have good creep values, residual strain, and recovery rates. Therefore, the adhesive layer including SCA in the embodiments maintains reliability even after repeated folding and unfolding under conditions of approximately 60°C and approximately 93% relative humidity. Furthermore, the display device including the adhesive layer in the embodiments exhibits good durability even under high temperature and high humidity conditions, even after repeated folding and unfolding.

[0105] In the embodiments, in display devices DD and DD-a, the polarization layer POL ( Figure 3 ) or shock absorption layer SCL ( Figure 4 Any of the following can contact the adhesive layer AL1. Table 4 below shows the Young's modulus of the polarizing layer, and Table 5 shows the Young's modulus of the shock absorbing layer. The polarizing layer and the shock absorbing layer are prepared according to ISO 527-3 standard and are tested using UTM (e.g., UTM565, Instron). Young's modulus was measured. Young's modulus was measured under different temperature and / or humidity conditions, and under the same conditions, Young's modulus was measured twice for each condition. Humidity is relative humidity, and room temperature is from approximately 23°C to approximately 28°C.

[0106] [Table 4]

[0107]

[0108] Referring to Table 4, it can be seen that the polarizing layer has a Young's modulus of approximately 9,600 MPa to approximately 9,800 MPa at a temperature of approximately -20°C, and a Young's modulus of approximately 6,900 MPa to approximately 7,100 MPa at a temperature of approximately 60°C. Furthermore, it can be seen that the polarizing layer has a Young's modulus of approximately 8,300 MPa to approximately 8,500 MPa at room temperature and a relative humidity of approximately 40% to approximately 50%, and a Young's modulus of approximately 3,200 MPa to approximately 3,400 MPa at a temperature of approximately 60°C and a relative humidity of approximately 93%. Under each temperature and / or humidity condition, it is considered that the polarizing layer satisfying the above-mentioned Young's modulus range will exhibit good adhesion to adjacent adhesive layers. Therefore, when a polarizing layer satisfying the above-mentioned Young's modulus range is disposed adjacent to an adhesive layer, the adhesive layer can exhibit good adhesion characteristics to the polarizing layer.

[0109] Table 5 below shows the Young's modulus of the impact absorbing layer, which is measured in the longitudinal and transverse directions of the impact absorbing layer. In Table 5, "MD" represents the longitudinal direction and "TD" represents the transverse direction. The longitudinal and transverse directions represent the tensile directions of the impact absorbing layer and are perpendicular to each other in the plan view.

[0110] [Table 5]

[0111]

[0112] Referring to Table 5, it can be seen that the impact-absorbing layer has a Young's modulus of about 5,500 MPa to about 6,600 MPa at a temperature of about -20°C, and a Young's modulus of about 4,300 MPa to about 5,100 MPa at a temperature of about 60°C. Furthermore, it can be seen that at room temperature and a relative humidity of about 40% to about 50%, the impact-absorbing layer has a Young's modulus of about 5,000 MPa to about 5,900 MPa, and at a temperature of about 60°C and a relative humidity of about 93%, it has a Young's modulus of about 3,900 MPa to about 4,700 MPa or lower. Under each temperature and / or humidity condition, it can be considered that the impact-absorbing layer satisfying the above-mentioned Young's modulus range will exhibit good adhesion to adjacent adhesive layers. Therefore, when an impact-absorbing layer satisfying the above-mentioned Young's modulus range is disposed adjacent to an adhesive layer, the adhesive layer can exhibit good adhesion characteristics to the impact-absorbing layer.

[0113] The display device in this embodiment may include a polarizing layer, an adhesive layer, and a window sequentially stacked on a foldable display panel. The adhesive layer includes SCA and can exhibit improved adhesion. At a temperature of approximately 60°C and a relative humidity of approximately 93%, the 180° peel adhesion of the adhesive layer to the window can be from approximately 493 gf / inch to approximately 817 gf / inch. Furthermore, at a temperature of approximately 60°C and a relative humidity of approximately 93%, the creep value of the adhesive layer can be from approximately 16% to approximately 18%. The creep value of the adhesive layer can be the value when a stress of approximately 1,900 Pa to approximately 2,000 Pa is applied. Therefore, the display device in this embodiment, including the adhesive layer, can maintain its reliability even after repeated folding and unfolding and exhibits good durability under high temperature and high humidity conditions.

[0114] One implementation may provide a display device that includes an adhesive layer disposed between a polarizing layer and a window, and thus maintains reliability even after repeated folding and unfolding.

[0115] Although embodiments of the present invention have been described, it should be understood that the present invention is not limited to these embodiments, but rather that various changes and modifications can be made by those skilled in the art within the spirit and scope of the present invention.

Claims

1. A display device, including: The display panel is foldable relative to at least one folding axis; A polarization layer is disposed on the display panel; An adhesive layer is disposed on the polarizing layer; as well as A window is disposed on the adhesive layer and includes a surface facing the adhesive layer. Specifically, under conditions of 60 degrees Celsius and 93% relative humidity, the adhesive layer exhibits a 180-degree peel adhesion force of 493 g / in to 817 g / in to one surface of the window. The adhesive layer comprises acrylic resin and silane coupling agent, and When a stress of 1,900 Pa to 2,000 Pa is applied to the adhesive layer for 10 minutes at the conditions of 60 degrees Celsius and 93% relative humidity, the residual strain of the adhesive layer after an additional 10 minutes is 0.6% to 0.9%.

2. The display device according to claim 1, wherein, The surface of the window is a surface of a glass substrate, and The adhesive layer has a 180-degree peel adhesion force of 493 gf / inch to 556 gf / inch on the surface.

3. The display device according to claim 1, wherein, The surface of the window is a surface of a plasma-treated glass substrate, and The adhesive layer has a 180-degree peel adhesion force of 636 gf / inch to 817 gf / inch on the surface.

4. The display device according to claim 1, wherein, When a stress of 1,900 Pa to 2,000 Pa is applied to the adhesive layer for 10 minutes at the conditions of 60 degrees Celsius and 93% relative humidity, the creep value of the adhesive layer is 16% to 18%.

5. The display device according to claim 1, wherein, When a stress of 1,900 Pascal to 2,000 Pascal is applied to the adhesive layer for 10 minutes under the conditions of 60 degrees Celsius and 93% relative humidity, the recovery rate of the adhesive layer is 95% to 96%.

6. The display device according to claim 1, wherein, When a stress of 9,900 Pascals to 12,210 Pascals is applied to the adhesive layer for 10 minutes at the conditions of 60 degrees Celsius and 93% relative humidity, the creep value of the adhesive layer is 94% to 101%.

7. The display device according to claim 1, wherein, When a stress of 9,900 Pascals to 12,210 Pascals is applied to the adhesive layer for 10 minutes at the conditions of 60 degrees Celsius and 93% relative humidity, the residual strain of the adhesive layer after an additional 10 minutes is 3% to 4%, and the recovery rate of the adhesive layer is 95% to 96%.

8. The display device according to claim 1, wherein, The polarizing layer has a Young's modulus of 9,600 MPa to 9,800 MPa at a temperature of -20 degrees Celsius, and It has a Young's modulus of 6,900 MPa to 7,100 MPa at the temperature of 60 degrees Celsius.

9. The display device according to claim 1, further comprising an impact absorbing layer disposed between the adhesive layer and the polarizing layer, wherein, The shock-absorbing layer has the following characteristics: Young's modulus of 5,500 MPa to 6,600 MPa at -20 degrees Celsius, and The Young's modulus at the stated temperature of 60 degrees Celsius is 4,300 MPa to 5,100 MPa.

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