Display Devices

Abstract

The present application relates to a display device. The display device includes: a display panel capable of being folded relative to at least one folding axis; a first adhesive layer disposed on the display panel; and a window disposed on the first adhesive layer. The first adhesive layer has a storage modulus of about 1.8 MPa to about 4.0 MPa at room temperature.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and all benefits derived from Korean Patent Application No. 10-2020-0084581, filed on Jul. 9, 2020, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] Herein, the present disclosure relates to a display device, and more particularly, to a foldable display device including an adhesive layer disposed between a display panel and a window. Background Art

[0004] The display device displays various images on a display screen to provide information to the user. Generally, the display device displays information within an assigned screen. Flexible display devices including foldable or bendable flexible display panels are being developed. Unlike rigid display devices, flexible display devices are foldable, rollable, or bendable. Flexible display devices that can be deformed into various shapes are portable and not limited to existing screen sizes, thereby enhancing user friendliness.

[0005] An adhesive layer applied to a flexible display device is required to maintain reliability against repeated folding or bending and to ensure impact resistance. Summary of the invention

[0006] The present disclosure provides a display device that can maintain reliability against repeated folding and unfolding and has improved impact resistance.

[0007] An embodiment of the present inventive concept provides a display device, comprising: a display panel capable of being folded relative to at least one folding axis; a window disposed on the display panel; and a first adhesive layer disposed between the display panel and the window, wherein the first adhesive layer has a storage modulus of about 1.8 megapascals (MPa) to about 4.0 MPa at room temperature.

[0008] The first adhesive layer may have a storage modulus of about 0.2 MPa or less at -20 degrees Celsius (° C.), and may have a maximum value of a loss factor (tan δ) at a frequency of about 1000 hertz (Hz) or more.

[0009] The window may include a polymer film, and the storage modulus of the first adhesive layer may be a value of about 1.8 MPa to about 4.0 MPa at 30,000 Hz.

[0010] The window may include a polymer film, and the first adhesive layer may have a loss factor (tan δ) of about 1.6 or more at 30,000 Hz.

[0011] The window may include a glass substrate, and the storage modulus of the first adhesive layer may be a value of about 1.8 MPa to about 4.0 MPa at 50,000 Hz.

[0012] The window may include a glass substrate, and the first adhesive layer may have a loss factor (tan δ) of about 1.5 or more at 50,000 Hz.

[0013] The display device may further include: a polarizing film disposed between the first adhesive layer and the display panel; and a second adhesive layer having a storage modulus of about 0.2 MPa or less at -20°C and disposed between the polarizing film and the display panel.

[0014] The second adhesive layer may have a maximum value of the loss factor (tan δ) at a frequency of about 1000 Hz or more.

[0015] The window may include a polymer film, and the second adhesive layer may have a storage modulus of about 0.8 MPa to about 2.0 MPa at 10,000 Hz.

[0016] The window may include a polymer film, and the second adhesive layer may have a loss factor (tan δ) of about 1.5 or more at 10,000 Hz.

[0017] The window may include a glass substrate, and the second adhesive layer may have a storage modulus of about 1.8 MPa to about 4.0 MPa at 40,000 Hz.

[0018] The window may include a glass substrate, and the second adhesive layer may have a loss factor (tan δ) of about 1.5 or more at 40,000 Hz.

[0019] The first adhesive layer may have a thickness of about 75 micrometers (μm) to about 150 μm.

[0020] The window may have a thickness greater than about 0 μm and equal to or less than about 100 μm.

[0021] The display panel and the window may be folded with respect to at least one folding axis to have a radius of curvature of about 1 millimeter (mm) to about 5 mm.

[0022] The window may include at least one polymer resin selected from the group consisting of polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polycarbonate, polymethyl methacrylate, polystyrene, polyvinyl chloride, polyethersulfone, polypropylene, polyamide, polyphenylene oxide, polyoxymethylene, polysulfone, polyphenylene sulfide, polyimide, polyethyleneimine, polyetheretherketone, polyamideimide, polyarylate, and thermoplastic polyurethane.

[0023] In an embodiment of the present invention, a display device includes: a display panel capable of being folded relative to at least one folding axis; a polarizing film on the display panel; a window disposed on the polarizing film; a first adhesive layer disposed between the polarizing film and the window; and a second adhesive layer disposed between the display panel and the polarizing film, wherein the first adhesive layer has a storage modulus of about 1.8 MPa to about 4.0 MPa at room temperature, and the second adhesive layer has a storage modulus of about 0.8 MPa to about 2.0 MPa or about 1.8 MPa to about 4.0 MPa at room temperature.

[0024] Each of the first adhesive layer and the second adhesive layer may have a storage modulus of about 0.2 MPa or less at -20°C, and may have a maximum value of a loss factor (tan δ) at a frequency of about 1000 Hz or more.

[0025] The window may be a polymer film, the storage modulus of the first adhesive layer may be a value of about 1.8 MPa to about 4.0 MPa at 30,000 Hz, and the storage modulus of the second adhesive layer may be a value of about 0.8 MPa to about 2.0 MPa at 10,000 Hz.

[0026] The window may be a glass substrate, the storage modulus of the first adhesive layer may be a value of about 1.8 MPa to about 4.0 MPa at 50,000 Hz, and the storage modulus of the second adhesive layer may be a value of about 1.8 MPa to about 4.0 MPa at 40,000 Hz. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are included to provide a further understanding of the inventive concept and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate exemplary embodiments of the inventive concept and together with the description are used to explain the principles of the inventive concept. In the drawings:

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

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

[0030] Figure 3 is shown corresponding to Figure 1 A cross-sectional view of a portion of line II';

[0031] Figure 4 is a cross-sectional view showing a display device according to an embodiment;

[0032] Figure 5A is a graph showing storage modulus according to frequency;

[0033] Figure 5Bis a graph showing loss factor according to frequency;

[0034] Fig. 6A is a graph showing storage modulus according to frequency; and

[0035] Figure 6B is a graph showing loss factor according to frequency. DETAILED DESCRIPTION

[0036] The present disclosure can be modified in many alternative forms, so specific embodiments will be illustrated and described in detail in the drawings. However, it should be understood that this is not intended to limit the inventive concept to the specific form disclosed, but is intended to cover all modifications, equivalents and substitutions that fall within the spirit and technical scope of the inventive concept.

[0037] In this specification, when an element (or region, layer, part, etc.) is referred to as being "on", "connected to" or "coupled to" another element, it means that the element can be directly set on / directly connected to / directly coupled to another element, or a third element can be set between them.

[0038] The same reference numerals denote the same elements. In addition, in the drawings, in order to effectively describe the technical contents, the thickness, ratio and size of the elements are exaggerated.

[0039] The terms used herein are only used for the purpose of describing specific embodiments and are not intended to be limiting. As used herein, the singular forms "a", "an", and "the" are intended to include plural forms (including "at least one") unless the context clearly indicates otherwise. "At least one" should not be interpreted as limiting "one" or "one". "Or" means "and / or". The term "and / or" includes all combinations that can define one or more of the relevant configurations.

[0040] 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 only used to distinguish one element from another element. For example, without departing from the scope of the exemplary embodiments of the present invention, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element. Terms in the singular may include plural forms unless the context clearly indicates otherwise.

[0041] In addition, terms such as "below", "lower", "above", "upper", etc. are used to describe the relationship of the configurations shown in the drawings. The terms are used as relative concepts and are described with reference to the directions shown in the drawings.

[0042] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the inventive concept belongs. It should also be understood that terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the relevant technology, and unless explicitly defined herein, they are not interpreted in an ideal or overly formal sense.

[0043] It should be understood that the terms “including” or “having” are intended to specify the presence of stated features, integers, steps, operations, elements, components, or combinations thereof in the present disclosure, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, or combinations thereof.

[0044] Hereinafter, a display device according to an embodiment of the inventive concept will be described with reference to the accompanying drawings.

[0045] Figure 1 and Figure 2 It is a perspective view showing a display device DD according to the embodiment. Figure 1 The display device DD is shown in a deployed state, and Figure 2 The display device DD is shown in a folded state. The display device DD according to an embodiment may be a flexible display device that is foldable or bendable or can maintain a folded state or a bent state.

[0046] Reference Figure 1 and Figure 2 The display device DD may be a device activated according to an electrical signal. For example, the display device DD may be a personal digital terminal, a tablet, a car navigation unit, a game console, or a wearable device, but is not limited thereto. Figure 1 and Figure 2 It is exemplarily shown that the display device DD is a portable electronic device.

[0047] The display device DD may display an image through the active area EA. The active area EA may include non-folding areas NFA1 and NFA2 and a folding area FA. The folding area FA may be bent relative to a folding axis FX extending on the second direction axis DR2. Figure 3 and Figure 4 As shown in the embodiment, the display device DD and DD-a of the embodiment include a display panel DP and a window WD provided on the display panel DP, and the display panel DP can be folded with respect to at least one folding axis FX. The display panel DP and the window WD can be folded with respect to the folding axis FX to have a curvature radius of about 1 millimeter (mm) to about 5 mm. Figure 3 and Figure 4 The display panel DP and the window WD are described in more detail.

[0048] When the display device DD is folded, the non-folding areas NFA1 and NFA2 may face each other. In the fully folded state, the active area EA may not be exposed to the outside, which may be referred to as "inner folding" (refer to Figure 2 ). However, this is given as an example, and the operation of the display device DD according to the present invention is not limited thereto. In another embodiment, in the fully folded state, the active area EA may be exposed to the outside, which may be referred to as "external folding".

[0049] The display device DD may be capable of performing only any one of inner folding and outer folding. Alternatively, the display device DD is capable of performing both inner folding and outer folding. In this case, the same area (e.g., folding area FA) of the display device DD may be inner foldable and outer foldable. Alternatively, some areas of the display device DD may be inner foldable, and some other areas may be outer foldable.

[0050] Figure 1 and Figure 2 The display device DD is shown to include one folding area FA and two non-folding areas NFA1 and NFA2, but the number of folding areas and non-folding areas according to the present invention is not limited thereto. In another embodiment, for example, the display device may include three or more non-folding areas and two or more folding areas arranged between adjacent non-folding areas.

[0051] Figure 1 and Figure 2 It is shown that the folding axis FX is parallel to the short axis (i.e., the latitude axis) of the display device DD, i.e., the direction extending parallel to the second direction axis DR2. However, this is given as an example, and the embodiments of the inventive concept are not limited thereto. In another embodiment, for example, the folding axis FX may be parallel to the long axis (i.e., the longitudinal axis) of the display device DD, i.e., the direction extending parallel to the first direction axis DR1.

[0052] The display device DD may include a sensing area SA surrounded by the active area EA. For example, the sensing area SA may overlap with the camera module in a plan view (ie, a view in a direction in which the third directional axis DR3 extends). Figure 1 One sensing area SA is illustrated, but embodiments of the inventive concept are not limited thereto. In another embodiment, the display device of an embodiment may include a plurality of sensing areas.

[0053] The display device DD may include a housing HU. The housing HU may accommodate a display panel DP and a window WD (which will be described later).

[0054] Figure 1 and Figure 2The display device DD of the embodiment is shown to be a foldable display device, but the embodiment of the present invention is not limited thereto. The display device according to the embodiment may be a foldable or bendable or a flexible display device that can maintain a folded state or a bent state. In this specification, the term "flexible" refers to a bendable property and is not limited to a structure that is bent into a completely folded state, and may include a structure that is bent to a level of several nanometers (nm).

[0055] Figure 3 It is along Figure 1 A cross-sectional view taken along line II'. Figure 4 is a cross-sectional view showing another embodiment of the display device DD-a according to the present invention. Figure 3 compared to, Figure 4 It is shown that the polarizing film PO is further disposed under the first adhesive layer AL1 and the second adhesive layer AL2 is disposed under the polarizing film PO.

[0056] The display device DD and DD-a of the embodiment may include a display panel DP, a first adhesive layer AL1 disposed on the display panel DP, and a window WD disposed on the first adhesive layer AL1. In addition, the display device DD-a of the embodiment may further include a polarizing film PO disposed on the display panel DP and a second adhesive layer AL2 disposed between the polarizing film PO and the display panel DP. The first adhesive layer AL1 and the second adhesive layer AL2 may each be a pressure-sensitive adhesive ("PSA") layer. The first adhesive layer AL1 and the second adhesive layer AL2 of the embodiment may each include a viscoelastic material.

[0057] According to an embodiment, the window WD may include a polymer film or a glass substrate. The window WD may include a polymer film. For example, the window WD may include at least one polymer resin of polyethylene terephthalate ("PET"), polybutylene terephthalate ("PBT"), polyethylene naphthalate ("PEN"), polycarbonate ("PC"), polymethyl methacrylate ("PMMA"), polystyrene ("PS"), polyvinyl chloride ("PVC"), polyethersulfone ("PES"), polypropylene ("PP"), polyamide ("PA"), polyphenylene oxide ("m-PPO"), polyoxymethylene ("POM"), polysulfone ("PSU"), polyphenylene sulfide ("PPS"), polyimide ("PI"), polyethyleneimine ("PEI"), polyetheretherketone ("PEEK"), polyamideimide ("PAI"), polyarylate ("PAR"), and thermoplastic polyurethane ("TPU"). The window WD may include a polymer film formed of at least one polymer resin among the polymer resins listed above. Alternatively, the window WD may be a glass substrate. The window WD may have a thickness T0 greater than about 0 μm and equal to or less than about 100 micrometers (μm). The thickness T0 of the window WD may be measured in a direction in which the third directional axis DR3 extends.

[0058] The window WD may further include a functional layer (not shown). For example, the window WD may further include a hard coating layer, an anti-fingerprint layer, or an anti-scattering layer as a functional layer.

[0059] The first adhesive layer AL1 may be disposed under the window WD. The first adhesive layer AL1 may bond the window WD and a member disposed under the window WD. Figure 3 , the first adhesive layer AL1 of the embodiment may attach the display panel DP to the window WD. Figure 4 , the first adhesive layer AL1 of the embodiment may be bonded to the polarizing film PO and the window WD. The first adhesive layer AL1 may have a thickness T1 of about 75 μm to about 150 μm. The thickness T1 of the first adhesive layer AL1 may be measured in a direction in which the third directional axis DR3 extends. In this specification, when an element (or region, layer, portion, etc.) is referred to as being "bonded to" other elements, this means that the other elements are fixed to each other with the element disposed therebetween.

[0060] Figure 3 and Figure 4The first adhesive layer AL1 is shown to be arranged in the form of a single layer, but the embodiments of the present inventive concept are not limited thereto. In another embodiment, for example, the first adhesive layer AL1 may be arranged in the form of a multilayer, and the multilayers constituting the first adhesive layer AL1 may all have the same physical properties. Alternatively, the physical properties of the multilayers constituting the first adhesive layer AL1 may be different from each other. When the multilayers constituting the first adhesive layer AL1 each have different physical properties, the average values ​​of the different physical properties may satisfy the range of physical properties of the first adhesive layer AL1 according to the embodiment. According to the embodiment described later, when the multilayers forming the first adhesive layer AL1 each have different storage moduli, the average values ​​of the different storage moduli may satisfy the range of storage moduli of the first adhesive layer AL1. In addition, according to the embodiment to be described later, when the multilayers constituting the first adhesive layer AL1 each have different loss factors, the average values ​​of the different loss factors may satisfy the range of loss factors of the first adhesive layer AL1.

[0061] The first adhesive layer AL1 may have a storage modulus of about 0.2 megapascals (MPa) or less at about -20 degrees Celsius (°C). In addition, the first adhesive layer AL1 may have a maximum value of the loss factor (tan δ) at a frequency of about 1000 hertz (Hz) or more. The loss factor (tan δ) is "a value given by dividing the loss modulus by the storage modulus". The higher the frequency, the greater the loss factor (tan δ), and thus the maximum value of the loss factor (tan δ) may be given at a specific frequency. The loss factor (tan δ) of the adhesive layer may decrease after reaching a maximum value as the frequency increases.

[0062] According to an embodiment, the first adhesive layer AL1 may have a storage modulus of about 1.8 MPa to about 4.0 MPa (hereinafter, referred to as a "predetermined range") at room temperature (e.g., about 20 to about 23° C.). When the window WD includes a polymer film, the first adhesive layer AL1 may have a storage modulus of about 1.8 MPa to about 4.0 MPa at 30,000 Hz. When the window WD includes a glass substrate, the first adhesive layer AL1 may have a storage modulus of about 1.8 MPa to about 4.0 MPa at 50,000 Hz.

[0063] The frequency that satisfies the predetermined range of the storage modulus of the first adhesive layer AL1 may vary depending on the type of window WD. The frequency that satisfies the predetermined range of the storage modulus of the first adhesive layer AL1 may be different when the window WD includes a glass substrate and when the window WD includes a polymer film. That is, depending on the type of window WD used in the display devices DD and DD-a, adhesive layers with different storage moduli may be used. The frequency (e.g., 50,000 Hz) that satisfies the above-mentioned predetermined storage modulus range (e.g., about 1.8 MPa to about 4.0 MPa) of the first adhesive layer AL1 when the window WD includes a glass substrate may be higher than the frequency (e.g., 30,000 Hz) that satisfies the above-mentioned predetermined storage modulus range (e.g., about 1.8 MPa to about 4.0 MPa) of the first adhesive layer AL1 when the window WD includes a polymer film.

[0064] In another embodiment, for example, when the window WD includes a polymer film, the first adhesive layer AL1 may have a storage modulus of about 2.0 MPa to about 3.5 MPa at 30000 Hz. Alternatively, when the window WD includes a glass substrate, the first adhesive layer AL1 may have a storage modulus of about 2.0 MPa to about 3.0 MPa at 50000 Hz. However, this is given as an example, and embodiments of the inventive concept are not limited thereto.

[0065] According to an embodiment, the first adhesive layer AL1 may have a loss factor (tan δ) of about 1.5 or more (hereinafter, referred to as a "predetermined range") at 30000 Hz. When the window WD includes a polymer film, the first adhesive layer AL1 may have a loss factor (tan δ) of about 1.5 or more at 30000 Hz. For example, the first adhesive layer AL1 disposed under the window WD including the polymer film may have a loss factor (tan δ) of about 1.7 or more at 30000 Hz. However, this is given as an example, and embodiments of the inventive concept are not limited thereto.

[0066] In addition, the first adhesive layer AL1 may have a loss factor (tan δ) of about 1.6 or more at 50,000 Hz. When the window WD includes a glass substrate, the first adhesive layer AL1 may have a loss factor (tan δ) of about 1.6 or more at 50,000 Hz. The first adhesive layer AL1 disposed under the window WD including the glass substrate may have a loss factor (tan δ) of about 1.7 or more at 50,000 Hz. However, this is given as an example, and embodiments of the present inventive concept are not limited thereto. Depending on the type of the window WD, the frequency that satisfies the predetermined range of the loss factor (tan δ) of the first adhesive layer AL1 disposed under the window WD may vary.

[0067] When an impact is applied to the display device from the outside, vibration and heat are generated in the adhesive layer included in the display device, and the adhesive layer can absorb the impact. The adhesive layer provided on the display panel of the display device absorbs external impact, and thus the display panel can be protected from external impact. When the window includes a glass substrate and when the window includes a polymer film, the impact absorption level of the adhesive layer to the impact applied from the outside of the display device can be different. When the same intensity of impact is applied to the display device, the window including the glass substrate can transfer a larger impact to the display device compared to the window including the polymer film.

[0068] When the window WD includes a polymer film, the vibration frequency of the first adhesive layer AL1 and the second adhesive layer AL2 may indicate a value corresponding to about 1000 Hz to about 30000 Hz. Alternatively, when the window WD includes a glass substrate, the vibration frequency of the first adhesive layer AL1 and the second adhesive layer AL2 may indicate a value corresponding to about 30000 Hz to about 50000 Hz.

[0069] When the same intensity of impact is applied to the window WD included in the display devices DD and DD-a, the impact intensity transmitted to the first adhesive layer AL1 may be different when the glass substrate is disposed on the first adhesive layer AL1 and when the polymer film is disposed on the first adhesive layer AL1. Compared with when the window WD includes a polymer film, the intensity of the external force transmitted to the first adhesive layer AL1 when the window WD includes a glass substrate may be greater. Compared with when the polymer film is disposed on the first adhesive layer AL1, when the glass substrate is disposed on the first adhesive layer AL1, a greater impact may be transmitted to the first adhesive layer AL1. Depending on the type of window WD disposed on the first adhesive layer AL1, the vibration frequency of the above-mentioned first adhesive layer AL1 may be different. Therefore, the range of the storage modulus and the loss factor (tan δ) of the first adhesive layer AL1 may represent the range of physical properties for each frequency. In the display devices DD and DD-a according to the embodiment, the frequency that satisfies the predetermined range of the storage modulus of the first adhesive layer AL1 and the frequency that satisfies the predetermined range of the loss factor (tan δ) of the first adhesive layer AL1 may be different according to the type of the window WD, thereby having improved impact resistance.

[0070] Reference Figure 4 , the polarizing film PO may be disposed under the first adhesive layer AL1. The first adhesive layer AL1 may bond the polarizing film PO and the window WD. The display device DD-a of the embodiment may further include a polarizing film PO disposed on the display panel DP.

[0071] The second adhesive layer AL2 may be disposed under the polarizing film PO. The display device DD-a of the embodiment may further include a second adhesive layer AL2 disposed between the polarizing film PO and the display panel DP. The second adhesive layer AL2 may bond the polarizing film PO and the display panel DP.

[0072] According to an embodiment, the second adhesive layer AL2 may have a storage modulus of about 0.2 MPa or less at -20°C. In addition, the second adhesive layer AL2 may have a maximum value of the loss factor (tan δ) at a frequency of about 1000 Hz or higher. The second adhesive layer AL2 may have a storage modulus of about 0.8 MPa to about 2.0 MPa or about 1.8 MPa to about 4.0 MPa at room temperature. The second adhesive layer AL2 may have a storage modulus of about 0.8 MPa to about 2.0 MPa or about 1.8 MPa to about 4.0 MPa at room temperature. Alternatively, the second adhesive layer AL2 may have a storage modulus of about 1.8 MPa to about 4.0 MPa at room temperature. The frequency that satisfies the predetermined storage modulus range of each second adhesive layer AL2 may vary.

[0073] When the window WD includes a polymer film, the second adhesive layer AL2 may have a storage modulus of about 0.8 MPa to about 2.0 MPa at 10000 Hz. Alternatively, when the window WD includes a glass substrate, the second adhesive layer AL2 may have a storage modulus of about 1.8 MPa to about 4.0 MPa at 40000 Hz. For example, when the window WD includes a polymer film, the second adhesive layer AL2 may have a storage modulus of about 1.0 MPa to about 1.5 MPa at 10000 Hz. When the window WD includes a glass substrate, the second adhesive layer AL2 may have a storage modulus of about 2.0 MPa to about 4.0 MPa at 40000 Hz.

[0074] According to an embodiment, the second adhesive layer AL2 may have a loss factor (tan δ) of about 1.6 or more at 10,000 Hz. Alternatively, the second adhesive layer AL2 may have a loss factor (tan δ) of about 1.5 or more at 40,000 Hz. When the window WD includes a polymer film, the second adhesive layer AL2 may have a loss factor (tan δ) of about 1.6 or more at 10,000 Hz. When the window WD includes a glass substrate, the second adhesive layer AL2 may have a loss factor (tan δ) of about 1.5 or more at 40,000 Hz. For example, the second adhesive layer AL2 disposed under the window WD including a polymer film may have a loss factor (tan δ) of about 1.7 or more at 10,000 Hz. However, this is given as an example, and embodiments of the inventive concept are not limited thereto.

[0075] The frequency that satisfies the predetermined range of the storage modulus of the second adhesive layer AL2 and the frequency that satisfies the predetermined range of the loss factor (tanδ) of the second adhesive layer AL2 may vary according to the type of window WD. Compared to when the window WD includes a polymer film, when the window WD includes a glass substrate, the frequency that satisfies the predetermined range of the storage modulus of the second adhesive layer AL2 may be higher. Compared to when the window WD includes a polymer film, when the window WD includes a glass substrate, the frequency that satisfies the predetermined range of the loss factor (tanδ) of the second adhesive layer AL2 may be higher. As described above, according to the type of window WD, the impact absorption level of the adhesive layer to the impact applied from the outside of the display device DD-a may vary. Therefore, the vibration frequency of the second adhesive layer AL2 may vary according to the type of window WD disposed on the second adhesive layer AL2. Therefore, the range of the storage modulus and the loss factor (tanδ) of the second adhesive layer AL2 may represent the range of physical properties for each frequency. In the display device DD-a of the embodiment, the frequency satisfying the predetermined range of the storage modulus of the second adhesive layer AL2 and the frequency satisfying the predetermined loss factor (tanδ) of the second adhesive layer AL2 vary according to the type of the window WD, thereby having improved impact resistance.

[0076] The frequency satisfying the predetermined range of the storage modulus and the loss factor (tan δ) of the first adhesive layer AL1 may be different from the frequency satisfying the predetermined range of the storage modulus and the loss factor (tan δ) of the second adhesive layer AL2. The first adhesive layer AL1 may be disposed closer to the window WD than the second adhesive layer AL2. When an impact is applied to the window WD included in the display device DD-a from the outside of the display device DD-a, a greater impact may be transmitted to the first adhesive layer AL1 than to the second adhesive layer AL2. Therefore, the frequency satisfying the predetermined range of the storage modulus and the loss factor (tan δ) of the first adhesive layer AL1 may be greater than the frequency satisfying the predetermined range of the storage modulus and the loss factor (tan δ) of the second adhesive layer AL2.

[0077] According to an embodiment, the physical properties of the first adhesive layer AL1 and the physical properties of the second adhesive layer AL2 disposed under the window WD may vary according to the type of the window WD. The range of the storage modulus and the loss factor (tan δ) of the first adhesive layer AL1 may vary. The range of the storage modulus and the loss factor (tan δ) of the second adhesive layer AL2 may vary. Therefore, the display device DD-a including the first adhesive layer AL1 and the second adhesive layer AL2 disposed between the window WD and the display panel DP may have improved impact resistance.

[0078] The first adhesive layer AL1 and the second adhesive layer AL2 may each include a silicone-based resin, an acrylic-based resin or a urethane-based resin. The first adhesive layer AL1 may be formed by including a polymer resin containing a silicone-based resin, an acrylic-based resin or a urethane-based resin. The second adhesive layer AL2 may be formed by including a polymer resin containing a silicone-based resin, an acrylic-based resin or a urethane-based resin. For example, the first adhesive layer AL1 of the embodiment may be formed by an acrylic-based resin. However, this is given as an example, and the first adhesive layer AL1 and the second adhesive layer AL2 may each include other materials having physical properties that meet the predetermined range of the above-mentioned storage modulus and loss factor (tan δ).

[0079] According to an embodiment, the first adhesive layer AL1 and the second adhesive layer AL2 may each further include an adhesion modifier. The adhesion modifier may be a surface modifier. For example, the adhesion modifier may be a low molecular weight material or a silicone-containing material.

[0080] In the description of the inventive concept, the physical properties of the first adhesive layer AL1 and the physical properties of the second adhesive layer AL2 (storage modulus, loss factor, etc.) represent values ​​measured using a rheometer (TA instrument). A sample for measuring physical properties is prepared by processing each of the first adhesive layer AL1 and the second adhesive layer AL2 into a cylindrical shape having a thickness of about 500 μm. A frequency value or a temperature value is changed in the rheometer by a strain of 1% (%) to measure the storage modulus and loss factor (tan δ) of the first adhesive layer AL1 and the storage modulus and loss factor (tan δ) of the second adhesive layer AL2.

[0081] Figure 5A and Fig. 6A are graphs respectively showing storage modulus according to frequency. Figure 5B and Figure 6B Graphs each showing the loss factor (tan δ) according to frequency. Figure 5A The storage modulus of the adhesive layer as a function of frequency is shown when the window includes a polymer film. Figure 5B The loss factor (tan δ) of the adhesive layer as a function of frequency when the window includes a polymer film is shown. Fig. 6A The storage modulus of the adhesive layer as a function of frequency is shown when the window includes a glass substrate. Figure 6BThe loss factor (tan δ) of the adhesive layer according to the frequency when the window includes a glass substrate is shown. The adhesive layer included in the display device of Example 1-1 and the adhesive layer included in the display device of Example 2-1 each satisfy the physical properties of the first adhesive layer according to the embodiment. The adhesive layers included in the display devices of Examples 1-2 and 2-2 each satisfy the physical properties of the second adhesive layer according to the embodiment. The adhesive layer included in the display device of Comparative Example 1 includes PSA, and may have a storage modulus and a loss factor (tan δ) different from the storage modulus and the loss factor (tan δ) of the first adhesive layer and the second adhesive layer according to the embodiment. The adhesive layer included in the display device of Comparative Example 2 includes an optically clear adhesive ("OCA").

[0082] Reference Figure 5A , the adhesive layer included in the display device of Comparative Example 1 has a storage modulus of about 1.805MPa at 30000Hz. The adhesive layer included in the display device of Comparative Example 2 has a storage modulus of about 8.75MPa at 30000Hz. The first adhesive layer included in the display device of Example 1-1 has a storage modulus of about 1.8MPa to about 4.0MPa at 30000Hz. The storage modulus range of the first adhesive layer of Example 1-1 at 30000Hz can be between the storage modulus of the adhesive layer of Comparative Example 1 at 30000Hz and the storage modulus of the adhesive layer of Comparative Example 2 at 30000Hz.

[0083] In addition, the adhesive layer of Comparative Example 1 has a storage modulus of about 0.846 MPa at 10000 Hz. The adhesive layer of Comparative Example 2 has a storage modulus of about 3.40 MPa at 10000 Hz. The second adhesive layer of Example 1-2 has a storage modulus of about 0.8 MPa to about 2.0 MPa at 10000 Hz. The storage modulus range of the second adhesive layer of Example 1-2 at 10000 Hz can be between the storage modulus of the adhesive layer of Comparative Example 1 at 10000 Hz and the storage modulus of the adhesive layer of Comparative Example 2 at 10000 Hz.

[0084] In Tables 1 and 2, in each of the display devices of the comparative example and the experimental example, the window includes a polymer film. Table 1 shows the storage modulus and loss factor (tanδ) of the adhesive layer included in the display devices of the comparative example and the experimental example, and shows the storage modulus and loss factor (tanδ) at 10000 Hz and 30000 Hz, respectively. The adhesive layer included in the display device of the experimental example satisfies the predetermined range of the storage modulus and loss factor (tanδ) of each of the first adhesive layer and the second adhesive layer of the embodiment. The thickness of the adhesive layer included in the display devices of the comparative example and the experimental example is approximately 100 μm, respectively. The display device of Comparative Example X1 has the same structure as the display device of Comparative Example 1, and includes an adhesive layer having similar physical properties to the adhesive layer of Comparative Example 1. The display device of Comparative Example X2 has the same structure as the display device of Comparative Example 2, and includes an adhesive layer having similar physical properties to the adhesive layer of Comparative Example 2. Experimental Example A1 and Experimental Example B1 each have the same Figure 4 The display device DD-a shown in the embodiment has the same structure, and the first adhesive layer satisfies the predetermined range of the storage modulus and the loss factor (tan δ) of the first adhesive layer according to the embodiment, and the second adhesive layer disposed between the polarizing film and the display panel includes a conventional adhesive layer used in a foldable display device. The first adhesive layer of Experimental Example A1 and the first adhesive layer of Experimental Example B1 each have a storage modulus of about 1.8 MPa to about 4.0 MPa at 30,000 Hz, and each have a loss factor (tan δ) of about 1.5 or greater at 30,000 Hz. Experimental Example A2 and Experimental Example B2 each have the same Figure 4 The display device DD-a shown in the embodiment has the same structure, and the second adhesive layer satisfies the predetermined range of the storage modulus and the loss factor (tanδ) of the second adhesive layer according to the embodiment, and the first adhesive layer provided between the polarizing film and the window includes a conventional adhesive layer for use in a foldable display device. The second adhesive layer of Experimental Example A2 and the second adhesive layer of Experimental Example B2 each satisfy the predetermined range of the storage modulus and the loss factor (tanδ) of the second adhesive layer according to the embodiment. The adhesive layer of Experimental Example A2 and the adhesive layer of Experimental Example B2 each have a storage modulus of about 0.8 MPa to about 2.0 MPa at 10,000 Hz, and each have a loss factor (tanδ) of about 1.6 or greater at 10,000 Hz.

[0085] Table 2 shows the evaluation of the impact resistance and folding reliability of the display devices of the comparative examples and experimental examples of Table 1. "Pen drop" and "ball drop" are used to evaluate the impact resistance. When the same pen or the same ball falls on the display device, the height at which defects are caused in the display device is measured. In addition, in order to evaluate the folding reliability of the display device, the folding and unfolding of the display device is repeated 100,000 times at different temperatures or humidities. The folding reliability is evaluated at a low temperature of -20°C and at a high temperature of 60°C and a humidity of 93%. In Table 2, in the folding reliability evaluation, "NG" indicates a case where the adhesive layer is separated or deformed, and "OK" indicates a case where the adhesive layer remains unchanged without separation or deformation.

[0086] Table 1

[0087]

[0088] Table 2

[0089]

[0090] With reference to Tables 1 and 2, it can be seen that the adhesive layer included in the display device of the experimental example has improved pen drop height and ball drop height and satisfactory folding reliability compared to the adhesive layer included in the display device of the comparative example X1. It can be seen that the adhesive layer included in the display device of the comparative example X2 and the adhesive layer included in the display device of the experimental example have improved values ​​in terms of pen drop height and ball drop height compared to the adhesive layer included in the display device of the comparative example X1. In addition, it can be seen that the display device of the comparative example X1 and the display device of the experimental example have satisfactory reliability in terms of folding reliability at low temperature and high temperature and high humidity. It can be seen that the adhesive layer included in the display device of the comparative example X2 has a larger storage modulus than the adhesive layer included in the display device of the comparative example X1 and the experimental example, and therefore, in the folding reliability evaluation, the larger storage modulus leads to poor reliability. Therefore, it is expected that the display device according to the embodiment including an adhesive layer that satisfies the predetermined range of the storage modulus and the loss factor (tan δ) of the first adhesive layer and the second adhesive layer has improved impact resistance and satisfactory folding reliability.

[0091] Reference Fig. 6A , the adhesive layer included in the display device of Comparative Example 1 has a storage modulus of about 4.588 MPa at 50000 Hz. The adhesive layer included in the display device of Comparative Example 2 has a storage modulus of about 12.38 MPa at 50000 Hz. The first adhesive layer included in the display device of Example 2-1 has a storage modulus of about 1.8 MPa to about 4.0 MPa at 50000 Hz.

[0092] In addition, the adhesive layer of Comparative Example 1 has a storage modulus of about 3.943 MPa at 40,000 Hz. The adhesive layer of Comparative Example 2 has a storage modulus of about 10.06 MPa at 40,000 Hz. The second adhesive layer of Example 2-2 has a storage modulus of about 1.8 MPa to about 4.0 MPa at 40,000 Hz.

[0093] In Tables 3 and 4, in each of the display devices of the comparative example and the experimental example, the window includes a glass substrate. Table 3 shows the storage modulus and loss factor (tanδ) of the adhesive layer included in the display devices of the comparative example and the experimental example, and shows the storage modulus and loss factor (tanδ) at 40000 Hz and 50000 Hz, respectively. According to an embodiment, the adhesive layer included in the display device of the experimental example satisfies a predetermined range of the storage modulus and loss factor (tanδ) of each of the first adhesive layer and the second adhesive layer. The thickness of the adhesive layer included in the display devices of the comparative example and the experimental example is approximately 100 μm, respectively. The display device of Comparative Example Y1 has the same structure as the display device of Comparative Example 1, and includes an adhesive layer having similar physical properties to the adhesive layer of Comparative Example 1. The display device of Comparative Example Y2 has the same structure as the display device of Comparative Example 2, and includes an adhesive layer having similar physical properties to the adhesive layer of Comparative Example 2. Experimental Example C1 and Experimental Example D1 each have the same Figure 4 The display device DD-a shown in the embodiment has the same structure, and the first adhesive layer satisfies the predetermined range of the storage modulus and the loss factor (tan δ) of the first adhesive layer according to the embodiment, and the second adhesive layer arranged between the polarizing film and the display panel includes a conventional adhesive layer used in a foldable display device. The first adhesive layer of Experimental Example C1 and the first adhesive layer of Experimental Example D1 each have a storage modulus of about 1.8 MPa to about 4.0 MPa and a loss factor (tan δ) of about 1.6 or greater at 50,000 Hz. The display device of Experimental Example C2 and the display device of Experimental Example D2 each have the same Figure 4 The display device DD-a shown in the embodiment has the same structure, and the second adhesive layer satisfies the predetermined range of the storage modulus and the loss factor (tan δ) of the second adhesive layer according to the embodiment, and the first adhesive layer includes a conventional adhesive layer for use in a foldable display device. The second adhesive layer of Experimental Example C2 and the second adhesive layer of Experimental Example D2 each have a storage modulus of about 1.8 MPa to about 4.0 MPa and a loss factor (tan δ) of about 1.5 or more at 40000 Hz.

[0094] Table 4 shows the evaluation of the impact resistance and folding reliability of the display devices of the comparative examples and experimental examples of Table 3. "Pen drop" and "ball drop" are used to evaluate the impact resistance. When the same pen or the same ball falls on the display device, the height of the defect caused in the display device is measured. In addition, in order to evaluate the folding reliability of the display device, the folding and unfolding of the display device is repeated 100,000 times at different temperatures or humidities. The folding reliability is evaluated at a low temperature of -20°C and at a high temperature of 60°C and a humidity of 93%. In Table 4, in the folding reliability evaluation, "NG" indicates a case where the adhesive layer is separated or deformed, and "OK" indicates a case where the adhesive layer remains unchanged without separation or deformation.

[0095] Table 3

[0096]

[0097]

[0098] Table 4

[0099]

[0100] With reference to Tables 3 and 4, it can be seen that the adhesive layer included in the display device of the experimental example has improved pen drop height and ball drop height and satisfactory folding reliability compared to the adhesive layer included in the display device of the comparative example Y1. It can be seen that the adhesive layer included in the display device of the comparative example Y2 and the adhesive layer included in the display device of the experimental example have improved values ​​in terms of pen drop height and ball drop height compared to the adhesive layer included in the display device of the comparative example Y1. In addition, it can be seen that the display device of the comparative example Y1 and the display device of the experimental example have satisfactory reliability in terms of folding reliability at low temperatures and at high temperatures and high humidity. It can be seen that the adhesive layer included in the display device of the comparative example Y2 has a larger storage modulus than the adhesive layer included in the display device of the comparative example Y1 and the experimental example, and therefore, in the folding reliability evaluation, the larger storage modulus leads to poor reliability. Therefore, it is expected that the display device according to the embodiment including an adhesive layer satisfying the predetermined range of the storage modulus and the loss factor (tan δ) of the first adhesive layer and the second adhesive layer has improved impact resistance and satisfactory folding reliability.

[0101] The display device of the embodiment includes one or more adhesive layers between the window and the display panel, and the range of the storage modulus and the loss factor (tan δ) of the adhesive layer can vary according to the type of window. When the window includes a polymer film, the frequency that satisfies the predetermined range of the storage modulus and the loss factor (tan δ) of the adhesive layer can be 30000Hz or 10000Hz. Alternatively, when the window includes a glass substrate, the frequency that satisfies the predetermined range of the storage modulus and the loss factor (tan δ) of the adhesive layer can be 50000Hz or 40000Hz. Depending on the type of window, the range of the storage modulus and the loss factor (tan δ) of the adhesive layer can vary. Depending on the type of window, the display device of the embodiment can have different storage modulus and loss factor ranges of the adhesive layer to show improved impact resistance. In addition, for repeated folding and unfolding of the display device, satisfactory reliability can be obtained.

[0102] The embodiments include an adhesive layer disposed between a display panel and a window, and thus reliability may be maintained for repeated folding and unfolding, and the embodiments provide a display device having improved impact resistance.

Claims

1. Display equipment, including: A display panel capable of being folded about at least one folding axis; a window, disposed on the display panel; as well as a first adhesive layer disposed between the display panel and the window, wherein the window comprises a polymer film, and the first adhesive layer has a storage modulus of 1.8 MPa to 4.0 MPa at 30,000 Hz at room temperature, or The window comprises a glass substrate, and the first adhesive layer has a storage modulus of 1.8 MPa to 4.0 MPa at 50,000 Hz at room temperature.

2. The display device according to claim 1, wherein: The first adhesive layer has a storage modulus of 0.2 MPa or less at -20°C and a maximum value of a loss factor at a frequency of 1000 Hz or more.

3. The display device according to claim 1, wherein: The window includes the polymer film, and The first adhesive layer has a loss factor of 1.6 or more at 30,000 Hz.

4. The display device according to claim 1, wherein: The window includes the glass substrate, and The first adhesive layer has a loss factor of 1.5 or more at 50,000 Hz.

5. The display device according to claim 1, wherein: The first adhesive layer has a thickness of 75 μm to 150 μm.

6. The display device according to claim 1, wherein: The window has a thickness greater than 0 μm and equal to or less than 100 μm.

7. Display equipment, including: A display panel capable of being folded about at least one folding axis; a window, disposed on the display panel; a first adhesive layer having a storage modulus of 1.8 MPa to 4.0 MPa at room temperature and disposed between the display panel and the window; a polarizing film disposed between the first adhesive layer and the display panel; as well as a second adhesive layer having a storage modulus of 0.2 MPa or less at -20°C and disposed between the polarizing film and the display panel, wherein the window comprises a polymer film, and the second adhesive layer has a storage modulus of 0.8 MPa to 2.0 MPa at 10000 Hz, or Wherein, the window comprises a glass substrate, and the second adhesive layer has a storage modulus of 1.8 MPa to 4.0 MPa at 40,000 Hz.

8. The display device according to claim 7, wherein: The second adhesive layer has a maximum value of a loss factor at a frequency of 1000 Hz or more.

9. The display device according to claim 7, wherein: The window includes the polymer film, and The second adhesive layer has a loss factor of 1.5 or more at 10,000 Hz.

10. The display device according to claim 7, wherein: The window includes the glass substrate, and The second adhesive layer has a loss factor of 1.5 or more at 40,000 Hz.

Images