Display device including a coupling member

Abstract

The present application relates to a display device. The display device includes: a display panel; a polarization member facing the display panel; a cover window including an inorganic material and facing the display panel, with the polarization member between the display panel and the cover window; and a window combining member located between the cover window and the polarization member and attaching the cover window to the polarization member. The window combining member attaching the cover window to the polarization member has a modulus of about 1 MPa to about 10 MPa.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and all rights arising from Korean Patent Application No. 10-2020-0018502, filed on February 14, 2020, and Korean Patent Application No. 10-2020-0099969, filed on August 10, 2020, the contents of which are incorporated herein by reference in their entirety. Technical Field

[0003] The present disclosure relates to a display device including a coupling member. Background Art

[0004] Electronic devices that provide images to users, such as smart phones, tablet personal computers (“PCs”), digital cameras, laptop computers, navigation devices, and smart TVs, include display devices for displaying the images.

[0005] Foldable display devices have attracted much attention. Since the foldable display device has a wide screen and good portability, it has advantages of both a smart phone and a tablet PC. Summary of the invention

[0006] Embodiments of the present invention provide a display device including a coupling member that prevents defective film removal even when a folding operation of the display device is repeatedly performed.

[0007] However, the features of the present disclosure are not limited to the features set forth herein. The above and other features of the present disclosure will become more apparent to those of ordinary skill in the art to which the present disclosure pertains by referring to the detailed description of the present disclosure given below.

[0008] According to an embodiment, a display device includes: a display panel; a polarization member facing the display panel; a cover window including an inorganic material and facing the display panel, with the polarization member between the display panel and the cover window; and a window combining member located between the cover window and the polarization member and attaching the cover window to the polarization member. The window combining member attaching the cover window to the polarization member has a modulus of about 1 megapascal (MPa) to about 10 MPa.

[0009] According to an embodiment, a display device includes: a display panel; a polarization member facing the display panel; a cover window including glass or quartz and facing the display panel, with the polarization member between the display panel and the cover window; and a window combining member located between the cover window and the polarization member and attaching the cover window to the polarization member. The window combining member attaching the cover window to the polarization member has a thickness of about 300 micrometers (μm) or less and a modulus of about 1 MPa to about 10 MPa. The modulus of the window combining member is a measured value measured by an indenter on a window combining member having a thickness of about 300 μm.

[0010] In one or more embodiments of the display device according to the embodiment, by controlling the actual modulus of the corresponding bonding member using an indenter measurement, adhesive properties such as restoring force and reducing or preventing defective film removal can be managed according to the position of the bonding member included in the display device.

[0011] The effects of the present disclosure are not limited to the above-mentioned effects, and various other effects are included in this specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] The above and other features of the present disclosure will become more apparent by describing in detail embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0013] Figure 1 is a perspective view of an embodiment of a display device;

[0014] Figure 2 It is shown Figure 1 A perspective view of an embodiment of a foldable display device;

[0015] Figure 3 is a cross-sectional view of an embodiment of an unfolded display device;

[0016] Figure 4 is a cross-sectional view of an embodiment of an inwardly folded display device;

[0017] Figure 5 is a cross-sectional view of an embodiment of a cover window;

[0018] Figure 6 It is shown Figure 5 A graph of stress distribution of an embodiment of a cover window;

[0019] Figure 7 is a schematic diagram illustrating an embodiment of an ion exchange process;

[0020] Figure 8 is a cross-sectional view of an embodiment of a display panel;

[0021] Fig. 9is a schematic diagram illustrating an embodiment of a method for measuring modulus and creep properties of an adhesive layer by a bioindenter;

[0022] Fig.10 is a graph showing an embodiment of the relationship between indentation depth and load during indenter measurement;

[0023] Fig.11 is a graph showing an embodiment of indentation depth as a function of time during a maximum load holding period during an indenter measurement;

[0024] Fig.12 is a cross-sectional view of an embodiment of a display device;

[0025] Fig.13 is a cross-sectional view of an embodiment of a display device;

[0026] Fig.14 is a cross-sectional view of an embodiment of a display device; and

[0027] Fig.15 is a graph showing the relationship between the depth of the indentation and the load according to the test example of the adhesive layer. DETAILED DESCRIPTION

[0028] The specific structural and functional descriptions of the embodiments of the present invention disclosed herein are only for the purpose of illustrating the embodiments of the present invention. Without departing from the spirit and salient features of the present invention, the present invention can be implemented in many different forms. Therefore, the embodiments of the present invention are disclosed only for illustrative purposes and should not be interpreted as limiting the present invention. That is, the present invention is limited only by the scope of the claims.

[0029] It will be understood that when an element is referred to as being related to another element, such as being "coupled" or "connected" to another element, it may be directly coupled or connected to the other element, or there may be intervening elements between them. Conversely, it will be understood that when an element is referred to as being related to another element, such as being "directly coupled" or "directly connected" to another element, there are no intervening elements. Other expressions describing the relationship between elements, such as "between," "directly between," "adjacent to," or "directly adjacent to," should be interpreted in the same manner.

[0030] Throughout the specification, the same reference numbers will refer to the same or like parts.

[0031] It will be understood that, although the terms "first", "second", "third", etc. can be used in this article to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings herein, the "first element", "first component", "first region", "first layer" or "first part" discussed below can be referred to as the second element, second component, second region, second layer or second part.

[0032] The terms used herein are only for the purpose of describing specific embodiments and are not intended to be limited. As used herein, "one", "the", "at least one" do not represent a limit on quantity, but are intended to include both the singular and the plural, unless the context clearly states otherwise. For example, "an element" has the same meaning as "at least one element", unless the context clearly states otherwise. "At least one" should not be understood to limit "one" or "one". "Or" means "and / or". As used herein, the term "and / or" includes any and all combinations of one or more of the related listed items. It will be further understood that when used in this specification, the term "comprises" and / or "comprising" or "includes" and / or "including" represents the presence of the features, regions, wholes, steps, operations, elements and / or parts described, but does not exclude the presence or addition of one or more other features, regions, wholes, steps, operations, elements, parts and / or their combinations.

[0033] In addition, relative terms such as "lower" or "bottom" and "upper" or "top" may be used herein to describe the relationship of one element to another element as shown in the figure. It will be understood that, in addition to the orientations depicted in the drawings, relative terms are intended to include different orientations of the device. For example, if the device in one of the drawings is turned over, the element described as being on the "lower" side of the other elements will then be oriented on the "upper" side of the other elements. Therefore, depending on the specific orientation of the drawings, the exemplary term "lower" can include both "lower" and "upper" orientations. Similarly, if the device in one of the drawings is turned over, the element described as being "below" or "below" the other elements will then be oriented "above" the other elements. Therefore, the exemplary term "below" or "below" can include both upper and lower orientations.

[0034] As used herein, "about" or "approximately" includes the stated value and the mean within an acceptable deviation range of the particular value as determined by one of ordinary skill in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., the limitations of the measurement system). For example, "about" can mean within one or more standard deviations, or within ±30%, ±20%, ±10%, ±5% of the stated value.

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as those commonly understood by those skilled in the art to which the present disclosure belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning consistent with their meaning in the context of the relevant technology and the present disclosure, and will not be interpreted in an idealized or overly formal sense unless explicitly defined as such herein.

[0036] Embodiments are described herein with reference to cross-sectional views as schematic diagrams of idealized embodiments. As such, deviations from the illustrated shapes, for example, due to manufacturing techniques and / or tolerances, will be expected. Therefore, the embodiments described herein should not be interpreted as being limited to the specific shapes of the regions as shown herein, but will include deviations in shapes, for example, caused by manufacturing. For example, a region shown or described as flat may typically have rough and / or nonlinear features. In addition, the sharp corners shown may be rounded. Therefore, the regions shown in the figures are schematic in nature, and their shapes are not intended to represent the precise shapes of the regions, and are not intended to limit the scope of the claims.

[0037] The folding operation of the foldable display device may apply stress to one or more layers of the foldable display device. When the adhesive material layer used to bond the layers to each other is exposed to stress, a defect of film removal may occur.

[0038] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0039] Figure 1 It is a perspective view of an embodiment of the display device 10 . Figure 2 It is shown Figure 1 A perspective view of a folded display device 10 .

[0040] Reference Figure 1 and Figure 2, the display device 10 displays an image through a display portion DPA (e.g., a display area). Various devices, components, etc. for generating and / or displaying an image may be included in the display portion DPA. Examples of the display device 10 may include, but are not limited to, a smart phone, a mobile phone, a tablet personal computer ("PC"), a personal digital assistant ("PDA"), a portable multimedia player ("PMP"), a television, a game console, a wristwatch-type electronic device, a head-mounted display, a display screen of a personal computer, a laptop computer, a car navigation system, a car dashboard, a digital camera, a video camera, an external billboard, an electronic billboard, a variety of medical devices, a variety of inspection devices, a variety of household appliances such as refrigerators and washing machines including a display portion DPA, an Internet of Things device, etc. A typical example of a foldable display device to be described later may be a foldable smart phone, a tablet PC, or a laptop computer, but is not limited thereto.

[0041] Reference Figure 1 , the flat or unfolded display device 10 may be disposed in a plane defined by a first direction and a second direction intersecting each other. The thickness direction may be defined along a third direction intersecting each of the first direction and the second direction. A cross-sectional view of the display device 10 may be taken along the third direction, such as in a normal direction to the plane defined by the first direction and the second direction intersecting each other.

[0042] The display device 10 may have a substantially rectangular shape in a plan view. The display device 10 may have a rectangular shape with right angle corners or rounded corners in a plan view. The display device 10 may have four sides or four edges. The display device 10 may include long sides and short sides.

[0043] The display device 10 may include one surface (e.g., an upper surface) and another surface (e.g., a lower surface) opposite to the upper surface. At least one of the upper surface and the lower surface of the display device 10 may be a display surface where an image is displayed. In an embodiment, the display surface may be located at the upper surface of the display device 10, and image display may not be performed on the lower surface. Hereinafter, this embodiment will be mainly described, but the display device 10 may be a double-sided display device that performs image display on both the upper surface and the lower surface.

[0044] The display device 10 may be divided into a display part DPA at which an image or video is displayed and a non-display part NDA (eg, non-display area) adjacent to the display part DPA in a plan view, and may not display an image or video at the non-display part NDA.

[0045] The display portion DPA may include a plurality of pixels. A pixel is a basic unit for generating and / or displaying an image or video. A pixel may include, but is not limited to, a red pixel, a green pixel, and a blue pixel. A pixel may also include a white pixel. A plurality of pixels may be arranged alternately in a plan view. In an embodiment, for example, pixels may be arranged in a matrix in the display portion DPA, but is not limited thereto.

[0046] The non-display portion NDA may be disposed adjacent to the display portion DPA. In an embodiment, the non-display portion NDA may surround the display portion DPA in a plan view. In an embodiment, the display portion DPA may be disposed or formed in a rectangular shape having four sides, and the non-display portion NDA may be disposed adjacent to each of the four sides of the display portion DPA, but is not limited thereto. A black matrix may be disposed in the non-display portion NDA to reduce or effectively prevent light emitted from adjacent pixels from leaking from the pixels or leaking between the pixels.

[0047] The display device 10 may be a foldable device. As used herein, the term "foldable device" means a foldable and expandable device. In addition, folding may generally include folding at an angle of about 180 degrees, however, the folding is not limited thereto. In an embodiment, folding may include a folding angle exceeding about 180 degrees or less than about 180 degrees, for example, a folding angle equal to or greater than about 90 degrees and less than about 180 degrees or a folding angle equal to or greater than about 120 degrees and less than about 180 degrees. In addition, if the unfolded display device 10 is subsequently folded, the display device 10 may be considered to be folded even if a complete folding is not performed. In an embodiment, for example, even if the display device 10 is folded at an angle of about 90 degrees or less, as long as the maximum folding angle of the display device 10 becomes 90 degrees or more, the display device 10 may be considered to be folded to distinguish it from the unfolded display device 10.

[0048] The folded display device 10 defines a radius of curvature of the display device 10. In an embodiment, the radius of curvature may be about 5 mm or less, such as in a range of about 1 mm to about 2 mm, or may be about 1.5 mm, but is not limited thereto.

[0049] The display device 10 may be foldable at the folding area FDA. The folding area FDA may include a folding axis around which the display device 10 and its various layers or components may be folded. The folding area FDA may have a straight linear shape extending in one direction in a plan view. Although the accompanying drawings show that the folding area FDA extends parallel to the short side of the display device 10, the present disclosure is not limited thereto. The folding area FDA may extend parallel to the long side, or may be inclined relative to the short side or the long side. The shape, extension, etc. of the folding axis may be the same as those described above for the folding area FDA.

[0050] In an embodiment, the folding area FDA of the display device 10 may be determined at a specific position. One, two or more folding areas FDA may be determined at a specific position (multiple positions). In another embodiment, the position of the folding area FDA may not be specific in the display device 10 and may be freely set in different areas.

[0051] The display device 10 may be divided into a first non-folding area NFA1 and a second non-folding area NFA2 relative to the folding area FDA. The first non-folding area NFA1 may be located on one side of the folding area FDA, and the second non-folding area NFA2 may be located on the other side of the folding area FDA opposite to the one side. When the folding area FDA is determined at a specific position, the first non-folding area NFA1 and the second non-folding area NFA2 may be specifically a flat area, where the display device 10 and / or its layers are not foldable, or the flat area remains flat even when the display device 10 is folded relative to the folding area FDA.

[0052] The first non-folding area NFA1 and the second non-folding area NFA2 may have a size or dimension such as width, length, plane area, etc. In an embodiment, the width of the first non-folding area NFA1 and the second non-folding area NFA2 may be obtained along a first direction corresponding to the extension direction of the long side of the display device 10. The first non-folding area NFA1 and the second non-folding area NFA2 may have the same width, but are not limited thereto. When the folding area FDA is not specific, the first non-folding area NFA1 and the second non-folding area NFA2 may be changed according to the position where the folding area FDA is set.

[0053] The display portion DPA of the display device 10 may be disposed in both the first non-folding area NFA1 and the second non-folding area NFA2. In addition, the display portion DPA may even be located at the folding area FDA corresponding to the boundary between the first non-folding area NFA1 and the second non-folding area NFA2. That is, the display portion DPA of the display device 10 may be continuously disposed regardless of the boundary of the non-folding areas NFA1 and NFA2, the folding area FDA, and the like. However, the present disclosure is not limited thereto, and the display portion DPA may be disposed in the first non-folding area NFA1, but may not be disposed in (for example, not included in) the second non-folding area NFA2. Alternatively, the display portion DPA may be disposed in the first non-folding area NFA1 and the second non-folding area NFA2, but not included at the folding area FDA.

[0054] The display device 10 can be folded inwardly to arrange multiple portions of the display surface to face each other (eg, Figure 2 ). The display device 10 can be folded outwardly to set multiple parts of the display surface away from each other and outward from the display device 10. The display device 10 can be folded in only one way, such as folding inwardly or folding outwardly. Alternatively, the display device 10 can be both foldable inwardly and foldable outwardly. In the case of a display device 10 that is foldable both inwardly and outwardly, folding can be performed relative to the same folding area FDA. Alternatively, the display device 10 can be foldable relative to multiple folding areas FDA (such as a folding area FDA only for inward folding and a folding area FDA only for outward folding), and different types of folding are performed around the multiple folding areas FDA, respectively.

[0055] In an embodiment, the display device 10 may include a display panel 100 (see Figure 3 ), layers, panels, films and / or substrate members stacked thereon, each of which has flexibility. The display device 10 may be foldable by each of the above-mentioned foldable members. In an embodiment, at least a portion of the display panel 100 or a member stacked thereon may have a shape separated from the folding area FDA. The separated member may be located in the corresponding non-folding area and may not have a flexible property.

[0056] Figure 3 is a cross-sectional view of an embodiment of the unfolded display device 10 . Figure 4 is a cross-sectional view of an embodiment of a folded display device 10 .

[0057] Reference Figure 3 and Figure 4, the display device 10 may include a display panel 100, a front stacked structure 200 (e.g., a first stacked structure) located on the front side of the display panel 100, and a rear stacked structure 300 (e.g., a second stacked structure) located on the rear side of the display panel 100. The stacked structures 200 and 300 may include at least one of the bonding members 251 to 253, 351, and 352. Here, the front side of the display panel 100 refers to a side (e.g., a display screen side) where the display panel 100 displays an image or video, and the rear side refers to a side opposite to the front side. One surface (e.g., an upper surface) of the display panel 100 is located on the front side, and another surface (e.g., a lower surface) of the display panel 100 is located on the rear side.

[0058] The display panel 100 is a panel that generates and / or displays an image or video. Examples of the display panel 100 may include not only self-luminous display panels (such as, organic light-emitting display ("OLED") panels, inorganic electroluminescent ("EL") display panels, quantum dot light-emitting display ("QED") panels, micron LED display panels, nano LED display panels, plasma display panels ("PDP"), field emission display ("FED") panels, and cathode ray tube ("CRT") display panels), but also light-receiving display panels (such as, liquid crystal display ("LCD") panels and electrophoretic display ("EPD") panels). Hereinafter, an organic light-emitting display panel will be described as an example of the display panel 100, and the organic light-emitting display panel applied to the embodiment will be referred to as the display panel 100 for short, unless special distinction is required. However, the embodiment is not limited to the organic light-emitting display panel, and within the scope of the same technical concept, other display panels mentioned above or known in the art may be applied.

[0059] The display panel 100 may further include a touch member. The touch member may be provided as a panel or a film separated from and attached to the display panel 100, but may also be provided as a touch layer TSL (see FIG. 1 ) inside the display panel 100. Figure 8 In the following embodiments, the touch member is disposed inside the display panel 100 and is included in the display panel 100, but the present disclosure is not limited thereto.

[0060] Figure 5 is a cross-sectional view of an embodiment of a cover window 220 . Figure 6 It is shown Figure 5 FIG. 2 is a graph of an embodiment of a stress distribution of a cover window 220 . Figure 7 is a schematic diagram illustrating an embodiment of an ion exchange process.

[0061] In an embodiment, the cover window 220 may be provided or formed by a strengthening step. The cover window 220 may include an inorganic material. In an embodiment, for example, the cover window 220 may include glass or quartz. The cover window 220 may include a glass composition.

[0062] Reference Figures 5 to 7 , the glass composition of the cover window 220 may include various compositions. In an embodiment, the glass composition may include a lithium aluminum silicate ("LAS") glass ceramic including lithium aluminum silicate. In an embodiment, for example, the glass composition may include about 50 mole percent (mol%) to about 80 mol% SiO2 relative to the total number of moles in the composition. 2 , about 1 mol% to about 30 mol% Al 2 O 3 , 0 mol% to about 5 mol% B 2 O 3 , 0 mol% to about 4 mol% P 2 O 5 , about 3 mol % to about 20 mol % Li 2 O, 0 mol% to about 20 mol% Na 2 O, 0 mol% to about 10 mol% K 2 O, about 3 mol% to about 20 mol% MgO, 0 mol% to about 20 mol% CaO, 0 mol% to about 20 mol% SrO, 0 mol% to about 15 mol% BaO, 0 mol% to about 10 mol% ZnO, 0 mol% to about 1 mol% TiO 2 and 0 mol% to about 8 mol% ZrO 2 .

[0063] As used herein, "the content is 0 mol%" means that it does not substantially contain the corresponding component. As used herein, the sentence "(the composition) does not substantially contain (a certain component)" means that the certain component is not intentionally contained in the original material, etc., and includes, for example, the case where a very small amount (e.g., 0.1 mol% or less) of impurities is inevitably contained.

[0064] For each component in the glass composition, the SiO 2 Chemical durability can be increased, and it can be used to reduce the occurrence of cracks when scratches or dents are formed on the glass surface. In order to fully play such a role, SiO may be contained in an amount of about 50 mol% or more. 2 In order to exhibit sufficient solubility, the SiO 2 The content can reach about 80 mol%.

[0065] Al 2 O 3 Used to improve the breakage resistance of glass. 2 O 3 It can be used to generate fewer fragments when the glass breaks. 2 O 3 It can be used as an active component, which improves the ion exchange performance during chemical strengthening and increases the surface compressive stress after strengthening. 2 O 3 When the content of Al is about 1 mol% or more, the above functions can be effectively performed. In order to maintain the acid resistance and solubility of the glass, Al 2 O 3 The content is about 30 mol% or less.

[0066] B 2 O 3 Enhances the shatter resistance of glass and improves the fusibility of glass. B may not be included 2 O 3 (0 mol%), but when containing about 0.5 mol% or more of B 2 O 3 When the content of B is about 5 mol% or less, the solubility of the glass can be improved. 2 O 3 It may be advantageous to suppress the occurrence of streaks during melting.

[0067] P 2 O 5 Improves ion exchange performance and resistance to chipping. It may not contain P 2 O 5 (0 mol%), but when containing about 0.5 mol% or more of P 2 O 5 When the content of P is about 4 mol% or less, the above-described functions can be significantly performed. 2 O 5 It can be helpful to reduce or effectively prevent a significant decrease in breakage resistance and acid resistance.

[0068] Li 2 O is used to form surface compressive stress through ion exchange. Li ions close to the glass surface can be exchanged with Na ions etc. through the ion exchange process. 2 O can also be used to improve the breakage resistance of glass. For effective ion exchange, Li 2 The content of O is about 3 mol% or more, and when it comes to acid resistance, Li 2 The content of O is about 20 mol% or less.

[0069] Na2 O is used to form surface compressive stress through ion exchange and improve the solubility of the glass. Na ions near the glass surface can be exchanged with K ions and the like through the ion exchange process. Na 2 O, but if included, Na 2 The content of O is about 1 mol% or more to effectively play the role described above. If only Li and Na ion exchange processes exist, and K ion exchange process does not exist, then Na 2 The content of O may be about 8 mol% or less to facilitate Li and Na ion exchange. If a K ion exchange process is also performed, a larger amount of Na 2 O. However, when related to acid resistance, Na 2 The content of O may be about 20 mol% or less.

[0070] K 2 O improves ion exchange performance and is related to breakage resistance. K may not be included 2 O, but in order to improve the ion exchange performance, K may be contained in an amount of about 0.5 mol% or more 2 O. In order to reduce or effectively prevent excessive reduction in breakage resistance, K 2 The content of O may be about 10 mol% or less.

[0071] MgO is used to increase surface compressive stress and improve the breakage resistance of chemically strengthened glass. When the content of MgO is about 3 mol% or more, it can effectively play this role. MgO whose content is about 20 mol% or less can be beneficial to reduce the occurrence of devitrification during glass melting.

[0072] CaO is used to improve the solubility and breakage resistance of glass. CaO may not be contained, but in order to effectively play this role, the content of CaO is about 0.5 mol% or more. If the content of CaO is too high (for example, greater than 20 mol%), the ion exchange performance may be reduced, and therefore, the content of CaO is about 20 mol% or less.

[0073] Similar to CaO, SrO is used to improve the solubility and breakage resistance of glass. SrO may not be contained, but in order to effectively play this role, SrO is contained in an amount of about 0.5 mol% or more. If the content of SrO is too high (for example, greater than 20 mol%), the ion exchange performance may be reduced, and therefore, the content of SrO is about 20 mol% or less.

[0074] BaO is used to improve the solubility and breakage resistance of glass. BaO may not be contained, but in order to effectively play this role, BaO is contained in an amount of about 0.5 mol% or more. A content of about 15 mol% or less of BaO can help reduce or effectively prevent excessive reduction in ion exchange performance.

[0075] ZnO is used to improve the solubility of glass. ZnO may not be contained, but when ZnO is contained in an amount of about 0.25 mol% or more, the effect of improving solubility can be significantly exhibited. In order to prevent the reduction of weather resistance, the content of ZnO is about 10 mol% or less.

[0076] TiO 2 Improves the breakage resistance of chemically strengthened glass. It is not necessary to contain TiO 2 , but when containing TiO in an amount of about 0.1 mol% or more 2 In order to reduce or effectively prevent devitrification during melting, TiO 2 The content is about 1 mol% or less.

[0077] ZrO 2 Surface compressive stress can be increased by ion exchange, and the breakage resistance of the glass can be improved. ZrO may not be included. 2 , but when containing ZrO in an amount of about 0.5 mol% or more 2 When the content of ZrO is about 8 mol% or less, it can effectively play this role. 2 It may be beneficial to suppress devitrification during melting.

[0078] In addition to the above-mentioned components, the glass composition may also include Y 2 O 3 ,La 2 O 3 , Nb 2 O 5 、 2 O 5 and Gd 2 O 3 The composition of the cover window 220 may be changed through an ion exchange process or a molding process, which will be described later.

[0079] The glass composition described above can be molded into a flat glass shape by various methods. In an embodiment, the glass composition can be molded by a float process, a fusion drawing process, a slot drawing process, etc.

[0080] The glass molded into a flat plate shape may be cut by a cutting step. The glass molded into a flat plate shape may have a shape different from the shape of the final glass product. The cutting of the glass may be performed using a cutting knife, a cutting wheel, a laser, etc.

[0081] Chemical strengthening can be performed by an ion exchange process. An ion exchange process is a process in which a first ion in the glass is exchanged for another (second) ion. By performing an ion exchange process, ions at or near the surface of the glass can be replaced or exchanged with larger ions of the same valence or oxidation state. In an embodiment, for example, when the glass contains a Li + 、Na + , K + and Rb + When the monovalent alkali metal is present, the monovalent cations located on the surface may be replaced by Na + , K + , Rb + or Cs + Replace. Reference Figure 7 The ion exchange process is described in detail.

[0082] Reference Figure 7 When the glass is immersed in a solution containing potassium nitrate (KNO 3 ) in a molten salt bath containing sodium ions (Na + ) glass is exposed to potassium ions (K + )(For example, Figure 7 ), the sodium ions in the glass are expelled to the outside of the glass, and potassium ions can replace the expelled sodium ions (e.g., Figure 7 ). Because potassium ions have a larger ionic radius than sodium ions, the exchanged potassium ions generate compressive stress in the glass. The greater the amount of potassium ions exchanged, the greater the compressive stress. Since ion exchange occurs through the surface of the glass, the amount of potassium ions at the surface of the glass is the largest. Although some of the exchanged potassium ions can diffuse into the glass and diffuse to a certain distance away from the surface of the glass to increase the depth of the compression area (e.g., the compression depth), their amount can generally decrease in the direction away from the surface of the glass. Therefore, the glass can have a stress distribution in which the compressive stress is maximum at the surface and the compressive stress decreases toward the interior of the glass (e.g., away from the surface of the glass). However, embodiments are not limited to the above examples. The stress distribution can change according to the temperature, time, number of times, presence or absence of heat treatment, etc. of the ion exchange process.

[0083] The cover window 220 provided or formed by the chemical strengthening described above may be Figure 5In the cover window 220 having a flat plate shape, the first surface US and the second surface RS are main outer surfaces having a large plane area, and the side surface SS is an outer surface connecting the first surface US with the second surface RS.

[0084] The first surface US and the second surface RS are opposite to each other in the thickness direction. Light may enter mainly from one of the first surface US and the second surface RS to be transmitted through the other of the first surface US and the second surface RS.

[0085] The thickness t of the cover window 220 is defined as the distance between the first surface US and the second surface RS. The thickness t of the cover window 220 may be the maximum distance between the first surface US and the second surface RS. The thickness t of the cover window 220 may be in the range of about 0.1 mm to about 2 mm, but is not limited thereto. In an embodiment, the thickness t of the cover window 220 may be about 0.8 mm or less. In an embodiment, the thickness t of the cover window 220 may be about 0.75 mm or less. In an embodiment, the thickness t of the cover window 220 may be about 0.7 mm or less. In another embodiment, the thickness t of the cover window 220 may be about 0.6 mm or less. In an embodiment, the thickness t of the cover window 220 may be about 0.65 mm or less. In an embodiment, the thickness t of the cover window 220 may be about 0.5 mm or less. In an embodiment, the thickness t of the cover window 220 may be about 0.3 mm or less. In an embodiment, the thickness t of the cover window 220 may be in the range of about 0.45 mm to about 0.8 mm, or in the range of about 0.5 mm to about 0.75 mm. The cover window 220 may have a uniform thickness t, but is not limited thereto, and may have different thicknesses t for different regions of the cover window 220.

[0086] The cover window 220 may be strengthened to have a predetermined stress distribution. Compared with the cover window 220 before strengthening or not strengthened, the strengthened cover window 220 more effectively reduces or prevents the generation of cracks, the propagation of cracks, rupture, etc. caused by external impact. The cover window 220 strengthened by the strengthening process may have different stresses for different regions. In an embodiment, for example, the compression regions CSR1 and CSR2 to which compressive stress is applied may be arranged near the surface of the cover window 220, for example, arranged to be close to the first surface US and / or the second surface RS, or extending inward from the first surface US and / or the second surface RS, and the tensile region CTR to which tensile stress is applied may be arranged inside the cover window 220. The tensile region CTR may be further away from the outer surface (e.g., the first surface US, the second surface RS, and / or the side surface SS) than the compression regions CSR1 and CSR2. The boundary between the corresponding compression region and the tensile region CTR may have a stress value of zero (e.g., neutral stress). The value of the compressive stress in a compression region may change according to the position (e.g., the depth from the corresponding outer surface). Furthermore, the value of the tensile stress in the tensile region CTR may vary according to the depth from the corresponding outer surface.

[0087] exist Figure 6 In the graph of , the stress distribution of the strengthened cover window 220 is represented as a function f(x). The horizontal axis represents the direction of the thickness t of the cover window 220, and the vertical axis represents the stress in megapascals (MPa). Figure 6 In the present invention, compressive stress has a positive value, while tensile stress has a negative value. In this article, the magnitude of compressive stress or tensile stress means the magnitude of the absolute value, regardless of whether it is positive or negative.

[0088] Reference Figure 6 , the strengthened cover window 220 includes a first compression region CSR1 extending from the first surface US to a first depth (first compression depth DOC1) and a second compression region CSR2 extending from the second surface RS to a second depth (second compression depth DOC2) along the thickness direction. The distance between the outer surface and the corresponding compression depth can define the maximum thickness of the corresponding compression region along the thickness t, but is not limited thereto. The stretching region CTR is disposed between the first compression depth DOC1 and the second compression depth DOC2 of the cover window 220. Although not shown, the compression region and the stretching region may be disposed between opposite side surfaces of the cover window 220 in a similar manner.

[0089] The first compression region CSR1 and the second compression region CSR2 are resistant to external impacts to reduce the occurrence of cracks or ruptures of the cover window 220. The first compression region CSR1 and the second compression region CSR2 may have a first maximum compressive stress CS1 and a second maximum compressive stress CS2 at the first surface US and the second surface RS, respectively. The greater the maximum compressive stress of the compression regions CSR1 and CSR2, the greater the strength of the cover window 220. In addition, the maximum tensile stress CT1 may be present at the central portion of the cover window 220. Since external impacts are generally transmitted from the outer surface of the cover window 220 and the external impacts are transmitted through the outer surface of the cover window 220, it is beneficial to have the maximum compressive stress at the outer surface of the cover window 220 in terms of durability. The first compression depth DOC1 and the second compression depth DOC2 suppress cracks or grooves that are formed from the first surface US and the second surface RS and spread toward the tensile region CTR inside the cover window 220. As the first compression depth DOC1 and the second compression depth DOC2 increase, it also helps to reduce or prevent the spread of cracks and the like.

[0090] In an embodiment, although not limited thereto, the first compression depth DOC1 and the second compression depth DOC2 may satisfy the following relational expression with respect to the thickness t of the cover window 220 .

[0091] [Mathematical expression 1]

[0092] DOC1, DOC2 ≥ 0.1 × t

[0093] Figure 8 is a cross-sectional view of an embodiment of a display panel 100 .

[0094] Reference Figure 8 , the display panel 100 may include a substrate SUB, a circuit driving layer DRL on the substrate SUB, a light emitting layer EML on the circuit driving layer DRL, an encapsulation layer ENL on the light emitting layer EML, and a touch layer TSL on the encapsulation layer ENL. That is, the circuit driving layer DRL, the light emitting layer EML, the encapsulation layer ENL, and the touch layer TSL may be sequentially disposed from the substrate SUB, but are not limited thereto.

[0095] The substrate SUB may be a flexible substrate including a flexible polymer material such as polyimide, etc. Therefore, the display panel 100 is warpable, bendable, foldable and / or rollable. In an embodiment, the substrate SUB may include a plurality of sub-substrates overlapping in a thickness direction, and a barrier layer is between the plurality of sub-substrates. In this case, each sub-substrate may be a flexible substrate.

[0096] The circuit driving layer DRL may be disposed on the substrate SUB. The circuit driving layer DRL may include a circuit that drives the light emitting layer EML of the pixel to emit light. The circuit driving layer DRL may include a plurality of thin film transistors. The circuit driving layer DRL may be connected to one or more of the pixels.

[0097] The light emitting layer EML may be disposed on the circuit driving layer DRL. The light emitting layer EML may include an organic light emitting layer. The light emitting layer EML may emit light with different brightness levels according to a signal transmitted from the circuit driving layer DRL.

[0098] The encapsulation layer ENL may be disposed on the light emitting layer EML. The encapsulation layer ENL may include an inorganic layer or a stacked layer of an inorganic layer and an organic layer.

[0099] The touch layer TSL may be disposed on the encapsulation layer ENL. The touch layer TSL is a layer that recognizes an external input of the display device 10 and may be used as a touch member. The touch layer TSL may include a plurality of touch sensing areas and touch sensing electrodes.

[0100] Return to reference Figure 3 and Figure 4 , the front stack structure 200 is disposed on the front side of the display panel 100. The front stack structure 200 may include a polarization member 230, a cover window 220, and a cover window protective layer 210 sequentially stacked from the display panel 100 in a front direction.

[0101] The polarization member 230 polarizes the light passing therethrough. The polarization member 230 may be used to reduce reflection of external light. In an embodiment, the polarization member 230 may be a polarizing film. The polarizing film may include a polarizing layer and a protective substrate, and the polarizing layer is sandwiched between the protective substrates. The polarizing layer may include a polyvinyl alcohol film. The polarizing layer may be stretched in one direction. The stretching direction of the polarizing layer may be an absorption axis, and the direction perpendicular thereto may be a transmission axis. The protective substrate may be respectively disposed on one surface and the other surface of the polarizing layer. The protective substrate may be made of a cellulose resin such as triacetyl cellulose, polyester resin, etc., but is not limited thereto.

[0102] The cover window 220 may be disposed on the front side of the polarization member 230. That is, the cover window 220 may face the display panel 100 with the polarization member 230 between the cover window 220 and the display panel 100. The cover window 220 is used to protect the display panel 100. The cover window 220 may be made of a transparent material. The cover window 220 may include, for example, glass.

[0103] One or more embodiments of the cover window 220 may include ultra-thin glass ("UTG") or thin glass. When the glass is ultra-thin glass or thin glass, the cover window 220 has flexible properties such as to be warpable, bendable, foldable and / or rollable. The thickness of the glass in the cover window 220 may be, for example, in the range of about 10 micrometers (μm) to about 300 μm, such as in the range of about 30 μm to about 80 μm, or may be about 50 μm.

[0104] The cover window protection layer 210 is disposed on the front side of the cover window 220. The cover window protection layer 210 may perform at least one of anti-scattering, impact absorption, scratch resistance, anti-fingerprint or stain resistance, and anti-glare for the cover window 220. The cover window protection layer 210 may include or be formed to include a transparent polymer film. The transparent polymer film includes at least one of polyethylene terephthalate ("PET"), polyethylene naphthalate ("PEN"), polyether sulfone ("PES"), polyimide ("PI"), polyarylate ("PAR"), polycarbonate ("PC"), polymethyl methacrylate ("PMMA"), and cycloolefin copolymer ("COC").

[0105] The front stacked structure 200 may include front bonding members 251 to 253 for bonding adjacent layers to each other. In an embodiment, for example, the first bonding member 251 may be disposed between the cover window protective layer 210 and the cover window 220 to bond them to each other, and the second bonding member 252 may be disposed between the cover window 220 and the polarization member 230 to bond them to each other. The third bonding member 253 may be disposed between the polarization member 230 and the display panel 100 to bond them to each other. That is, the front bonding members 251 to 253 may be members that attach the layer to the front surface of the display panel 100. The first bonding member 251 may be a protective layer bonding member for attaching the cover window protective layer 210, the second bonding member 252 may be a window bonding member for attaching the cover window 220, and the third bonding member 253 may be a polarization bonding member for attaching the polarization member 230. The front bonding members 251 to 253 may all be optically transparent.

[0106] The rear stack structure 300 is disposed on the rear side of the display panel 100. The rear stack structure 300 may include a polymer film layer 310 and a heat dissipation member 320 sequentially stacked from the display panel 100.

[0107] The polymer film layer 310 may include a polymer film. The polymer film layer 310 may include, for example, polyimide ("PI"), polyethylene terephthalate ("PET"), polycarbonate ("PC"), polyethylene ("PE"), polypropylene ("PP"), polysulfone ("PSF"), polymethyl methacrylate ("PMMA"), triacetyl cellulose ("TAC"), cycloolefin polymer ("COP"), etc. The polymer film layer 310 may include a functional layer on at least one surface thereof. The functional layer may include, for example, a light absorbing layer. The light absorbing layer may include a light absorbing material such as a black pigment or dye. The light absorbing layer may be formed by coating or printing black ink on the polymer film.

[0108] The heat dissipation member 320 may be disposed on the rear side of the polymer film layer 310. The heat dissipation member 320 is used to dissipate heat generated from the display panel 100 or other parts of the display device 10. The heat dissipation member 320 may include a metal plate. The metal plate may include, for example, a metal having excellent thermal conductivity, such as copper and silver. The heat dissipation member 320 may be a heat sink including graphite, carbon nanotubes, etc.

[0109] The heat dissipation member 320 may be Figure 3 and Figure 4 1 and 10 are separated or disconnected at the folding area FDA as shown in the figure to facilitate the folding of the display device 10, but is not limited thereto. In an embodiment, for example, the first metal plate of the heat dissipation member 320 may be disposed in the first non-folding area NFA1, and the second metal plate of the heat dissipation member 320 may be disposed in the second non-folding area NFA2. The first metal plate and the second metal plate may be physically separated from each other relative to the folding area FDA.

[0110] The rear stacking structure 300 may include rear combining members 351 and 352 for combining adjacent layers to each other. In an embodiment, for example, a fourth combining member 351 may be disposed between the display panel 100 and the polymer film layer 310 to combine them to each other, and a fifth combining member 352 may be disposed between the polymer film layer 310 and the heat dissipation member 320 to combine them to each other. That is, among the rear combining members 351 and 352 (which are members for attaching layers to the rear surface of the display panel 100), the fourth combining member 351 may be a polymer film layer combining member for attaching the polymer film layer 310, and the fifth combining member 352 may be a heat dissipation portion combining member for attaching the heat dissipation member 320. When the heat dissipation member 320 is separated or disconnected relative to the folding area FDA, the fifth combining member 352 may also be separated or disconnected in the same manner, but as Figure 3 As shown in FIG. 3 , the fifth combining member 352 may be continuous without being separated or disconnected with respect to the corresponding non-folding area.

[0111] When the display device 10 displays an image only on the front surface, the rear bonding members 351 and 352 may not be optically transparent, unlike the front bonding members 251 to 253 which are optically transparent.

[0112] Each of the front coupling members 251 to 253 and the rear coupling members 351 and 352 described above may include an adhesive material. Each of the coupling members 251 to 253, 351 and 352 may include a pressure-sensitive adhesive layer, and may be generally referred to as an adhesive layer PSA hereinafter (see Fig. 9 ). The bonding members 251 to 253, 351, and 352 may have the same composition as each other, or may have different compositions from each other according to their positions within the stacked structure of the display device 10 and different layers through which they are to be bonded to each other.

[0113] One or more of the front bonding members 251 to 253 may also include an optically transparent adhesive layer or an optically transparent resin. In an embodiment, for example, the second bonding member 252 for bonding the cover window 220 to the display panel 100 may include an optically transparent adhesive layer or an optically transparent resin. However, the present disclosure is not limited thereto.

[0114] Each of the first bonding member 251, the second bonding member 252, the third bonding member 253, the fourth bonding member 351, and the fifth bonding member 352 may have a thickness of about 300 μm or less. In an embodiment, each of the bonding members 251 to 253, 351, and 352 may have a thickness of about 200 μm or less, within which one or more of the bonding members 251 to 253, 351, and 352 may have a thickness of about 100 μm or less. The lower limit of the thickness of the bonding members 251 to 253, 351, and 352 may be changed to, such as, about 10 μm or more (such as about 50 μm or more) to ensure minimum bonding strength.

[0115] Each of the bonding members 251 to 253, 351 and 352 may be provided or formed as a single adhesive layer, or may be provided or formed as a multilayer or stacked structure including a plurality of adhesive layers. In addition, each of the bonding members 251 to 253, 351 and 352 may be similar to a double-sided tape, including an adhesive layer on each of its opposite surfaces, respectively.

[0116] In an embodiment, the bonding members 251 to 253, 351 and 352 may include a silicone-based adhesive. The silicone-based adhesive may include a siloxane resin. The silicone-based adhesive may include a silicone glue containing a polysiloxane compound. The silicone glue may include a cross-linkable functional group, such as a vinyl group. The silicone-based adhesive may also include an MQ resin having a molecular structure of a three-dimensional network including a monofunctional siloxane unit and a tetrafunctional siloxane unit. The silicone-based adhesive may further include an additive containing at least one of a borane compound and a borate compound.

[0117] In an embodiment, the bonding members 251 to 253, 351 and 352 may include an acrylic adhesive. The acrylic adhesive may include an acrylic polymer. The acrylic polymer is formed by polymerizing an acrylic monomer, which may be the main material of the acrylic polymer. The acrylic monomer may include ethyl acrylate, n-butyl acrylate, tert-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isooctyl acrylate, n-nonyl acrylate, isononyl acrylate, n-decyl acrylate, isodecyl acrylate, n-dodecyl acrylate, n-tridecyl acrylate, n-tetradecyl acrylate, 2-(2-ethoxyethoxy)ethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 6-hydroxyhexyl acrylate, 8-hydroxyoctyl acrylate, 10-hydroxydecyl acrylate, 12-hydroxylauryl acrylate, [4-(hydroxymethyl)cyclohexyl]methyl acrylate, etc. In addition to the acrylic polymer, the acrylic adhesive may further include an azo initiator (such as 2,2'-azobisisobutyronitrile), a filler (such as silicon dioxide or zirconium oxide), a cross-linking agent, an antistatic agent (such as PEDOT:PSS (polyethylenedioxythiophene:polystyrene sulfonate)), etc. In an embodiment, the acrylic adhesive may be prepared by combining about 120 to about 250 parts by weight of an acrylic monomer with a solvent and stirring the composition while heating, and adding about 0.1 to about 1 parts by weight of an azo initiator, about 0.5 to about 1 parts by weight of a filler, about 1.5 to about 2.5 parts by weight of a cross-linking agent, and about 0.5 to about 1 parts by weight of an antistatic agent to the solution and stirring the solution while heating.

[0118] In an embodiment, the bonding members 251 to 253, 351 and 352 may include a crystalline polymer and a rubber-based polymer. The crystalline polymer may be polypropylene, syndiotactic polystyrene, polyamide, polycaprolactone, polycarbonate-diol, polyethylene terephthalate ("PET"), polyphenylene sulfide, polybutylene terephthalate ("PBT"), polyarylate ("PAR"), poly (DPAA), polyetherimide ("PEI"), polyacetal and / or polyoxymethylene ("POM").

[0119] The rubber-based polymer may be polybutadiene, polyisoprene, polychloroprene, polyisobutylene, cellulose acetate, polyvinyl acetate, copolymers thereof, and the like. The weight ratio of the crystalline polymer to the rubber-based polymer may be equal to or greater than about 1:1.5 and equal to or less than about 1:0.3. The bonding members 251 to 253, 351, and 352 may also include urethane-based polymers, ester-based polymers, and / or (meth)acrylate-based polymers. The bonding members 251 to 253, 351, and 352 may also include coupling agents (such as silane-based coupling agents, titanate-based coupling agents, or chromium-based coupling agents), adhesion promoters (such as rosin resins, rosin ester resins, terpene phenolic resins, or terpene resins), yellowing inhibitors, antioxidants, and the like.

[0120] The constituent materials and compositions of the bonding members 251 to 253 , 351 , and 352 are not limited to those exemplified above, and other configurations or compositions of adhesive materials known in the art may be applied thereto.

[0121] The front bonding members 251 to 253 and the rear bonding members 351 and 352 may have adhesive properties such as predetermined modulus and creep characteristics. The modulus and creep characteristics are related to deformation or recovery for stress applied to the adhesive layer PSA. However, since the bonding members 251 to 253, 351, and 352 are exposed to different stress conditions according to their positions within the display device 10, and the types of components adhered around them are different, different adhesive properties may be required for each position within the display device 10.

[0122] The display device 10 having the stacked structure as described above and being folded subjects the respective layers constituting the display device 10 to different stresses. In an embodiment, for example, when the display surface is folded inwardly so that a plurality of portions of the display surface are arranged to face each other, a layer closer to the display surface (e.g., the front surface) may be subjected to compressive stress, and a layer closer to a surface opposite to the display surface (e.g., the rear surface) may be subjected to tensile stress.

[0123] In the display device 10 folded inward, the compressive stress may become the largest at the front surface of the display device 10, and its size may decrease toward the rear surface along the thickness direction. The tensile stress may become the largest at the rear surface of the display device 10, and its size may decrease toward the front surface along the thickness direction. The stress neutral surface in which the compressive stress and the tensile stress are balanced (for example, the value of the compressive stress and the value of the tensile stress are both zero) may be located at the middle portion of the display device 10 along the thickness direction. In an embodiment, for example, the stress neutral surface may be designed to be located inside the display panel 100 between the front stacking structure 200 and the rear stacking structure 300 along the thickness direction. In the display device 10 folded inward, the front stacking structure 200 located at the front side of the display panel 100 may be exposed to compressive stress, and the rear stacking structure 300 located at the rear side of the display panel 100 may be exposed to tensile stress.

[0124] Since the combining members 251 to 253, 351 and 352 of the display device 10 are exposed to different stresses as described above during folding of the display device 10, the adhesive properties are defined to correspond to the positions of the corresponding combining members to maintain the bonding strength between the multiple layers of the display device 10 and to have the restoring force of the layers even when the display device 10 is repeatedly folded and unfolded.

[0125] The average modulus of the front binding members 251 to 253 (which is the average value of the modulus of the corresponding binding members belonging to the front binding members 251 to 253) can be less than the average modulus of the rear binding members 351 and 352 (which is the average value of the modulus of the corresponding binding members belonging to the rear binding members 351 and 352). The modulus of the corresponding binding member represents the ratio of stress to strain, and a smaller modulus can mean that deformation is more likely to occur for the same stress. In an embodiment, the front binding members 251 to 253 subjected to compressive stress can have a relatively small modulus, which is conducive to preventing defective film removal caused by compressive stress. On the contrary, the rear binding members 351 and 352 can have a relatively large modulus, which helps to provide a high restoring force, so that the layer is restored to its original state after the folding of the layer.

[0126] However, as described above, the cover window 220 may include an inorganic material. Therefore, among the front bonding members 251 to 253, the first bonding member 251 and the second bonding member 252 contacting the cover window 220 may have a large modulus to increase the adhesive strength with the cover window 220 including the inorganic material, thereby reducing or effectively preventing defective film removal due to compressive stress. When in contact, the elements or layers may form an interface between them.

[0127] From the above perspective, the modulus of the bonding members 251 to 253, 351, and 352 may be in the range of about 1 MPa to about 10 MPa. In an embodiment, for example, by setting the modulus of the bonding members 251 and 252 to 1 MPa or more, the adhesive strength of the cover window 220 in contact therewith may be increased, and by setting the modulus to 10 MPa or less, defective film removal due to compressive stress may be prevented.

[0128] The first coupling member 251 may have a first thickness t1, the second coupling member 252 may have a second thickness t2, the third coupling member 253 may have a third thickness t3, the fourth coupling member 351 may have a fourth thickness t4, and the fifth coupling member 352 may have a fifth thickness t5.

[0129] In an embodiment, for example, the modulus of the first bonding member 251 may be greater than the modulus of the second bonding member 252. The first thickness t1 of the first bonding member 251 may be less than the second thickness t2 of the second bonding member 252. In an embodiment, for example, the first thickness t1 of the first bonding member 251 may be about 10 μm, which is less than the second thickness t2 of the second bonding member 252. Although the first thickness t1 of the first bonding member 251 is less than the second thickness t2 of the second bonding member 252, the modulus of the first bonding member 251 is designed to be greater than the modulus of the second bonding member 252, thereby further increasing the adhesive strength of the cover window 220 in contact therewith.

[0130] In addition, the modulus of the fourth bonding member 351 may be greater than the modulus of the fifth bonding member 352. The fourth thickness t4 of the fourth bonding member 351 may be less than the fifth thickness t5 of the fifth bonding member 352. Although the fourth thickness t4 of the fourth bonding member 351 is less than the fifth thickness t5 of the fifth bonding member 352, the modulus of the fourth bonding member 351 is designed to be greater than the modulus of the fifth bonding member 352, thereby further increasing the recovery rate for returning the layer to the original shape (e.g., the unfolded shape) after folding.

[0131] In addition, the modulus of the fourth bonding member 351 may be greater than the modulus of each of the first bonding member 251 and the third bonding member 253. In the display panel 100 having a driving chip (e.g., a data driving integrated circuit) attached thereto and being folded, stress is generated by the driving chip, and the stress may cause cracks to occur in the display panel 100. However, since the modulus of the fourth bonding member 351 is greater than the modulus of each of the first bonding member 251 and the third bonding member 253, cracks to occur in the display panel 100 due to the stress generated by the driving chip when the display panel 100 is folded may be reduced or effectively prevented.

[0132] In an embodiment, for example, the modulus of the fourth coupling member 351 may be about 3 MPa to about 10 MPa, such as about 4 MPa to about 6 MPa, but is not limited thereto.

[0133] In an embodiment, the modulus of the bonding members 251 to 253, 351 and 352 may be a modulus value measured for a corresponding bonding member in a thin film state (such as a corresponding bonding member having a thickness of about 300 μm or less, about 200 μm or less, or about 100 μm or less). In addition, the modulus of the bonding members 251 to 253, 351 and 352 described above may be a value measured for a corresponding bonding member extracted from the display device 10 after being included in the display device 10. The modulus of such a thin film adhesive layer PSA can be measured by an indenter such as a bioindenter or a nanoindenter. That is, the modulus of the adhesive layer PSA (which is a thin film) can be measured by an indenter evaluation method.

[0134] The creep property, which is another property of the adhesive layer PSA, is roughly proportional to the viscosity, and the creep properties of the first bonding member 251, the second bonding member 252, the third bonding member 253, the fourth bonding member 351, and the fifth bonding member 352 may all be in the range of about 20% to about 70%. When the creep property is less than 20%, it may not be fully deformed during the folding operation, and when the creep property exceeds 70%, the recovery may be insufficient.

[0135] In an embodiment, among the front coupling members 251 to 253, each of the creep characteristics of the second coupling member 252 and the third coupling member 253 may be smaller than the creep characteristic of the first coupling member 251. Among the front coupling members 251 to 253, since each of the creep characteristics of the second coupling member 252 and the third coupling member 253 may be smaller than the creep characteristic of the first coupling member 251, it is possible to reduce or effectively prevent moisture from penetrating into the display panel 100 from the outside (or from the top). In an embodiment, for example, the creep characteristics of the second coupling member 252 and the third coupling member 253 may be about 20% to about 45%. In an embodiment, since the third coupling member 253 is positioned closer to the display panel 100 than the second coupling member 252, the creep characteristic of the third coupling member 253 may be smaller than the creep characteristic of the second coupling member 252. In addition, each of the creep characteristics of the second coupling member 252 and the third coupling member 253 may be smaller than the creep characteristics of the rear coupling members 351 and 352.

[0136] The creep characteristics described above can also be measured by using an indenter, and the values ​​measured for the bonding members 251 to 253, 351, and 352 in a film state or in a state separated from the display device 10 (the display device 10 has been applied with the corresponding bonding member) can be in the range of about 20% to about 70%. In an embodiment, the modulus and creep characteristics of the window bonding member, the modulus and creep characteristics of the protective layer bonding member, and the modulus and creep characteristics of the polarization bonding member are measured values ​​measured by the indenter for the corresponding bonding member among the window bonding member, the protective layer bonding member, and the polarization bonding member having a thickness of about 300 microns or less (e.g., a film state). The modulus and creep characteristics of the corresponding bonding member are measured values ​​corresponding to the depth of the spherical indenter indented into the corresponding bonding member having a thickness of about 300 microns or less.

[0137] The creep characteristic of each of the fourth coupling member 351 and the fifth coupling member 352 may be greater than the creep characteristic of the second coupling member 252 .

[0138] Hereinafter, an embodiment of a method for measuring the modulus and creep properties of an adhesive layer PSA by an indenter is described.

[0139] Fig. 9 is a schematic cross-sectional view illustrating an embodiment of a method for measuring the modulus and creep properties of an adhesive layer PSA by a bioindenter.

[0140] Reference Fig. 9 The bioindenter includes an indenter RBL. The indenter RBL may have a shape of a ball (ruby ball) or at least a partial shape of a ball. The spherical indenter RBL may have a diameter D of about 1 mm, but is not limited thereto.

[0141] In an embodiment, the adhesive layer PSA as a measurement target has a size of about 2 centimeters (cm) x about 2 cm. In the case where the heterogeneous film is previously adhered to the adhesive layer PSA, after the heterogeneous film is removed, the adhesive layer PSA is attached to a flat fixture HDR located on the plate PLT. The indenter RBL presses the surface of the adhesive layer PSA (at 100°) with a maximum load of about 0.2 millinewtons (mN) (which is maintained for 120 seconds). Fig. 9 Indicated by a downward arrow in the figure). Here, the loading / unloading speed (e.g., pressing speed) of the indenter RBL may be about 1.2 millinewtons per minute (mN / min). During the pressing operation, a dent is formed in the adhesive layer PSA. The dent depth of the dent is measured. The dent test of the indenter RBL using the bioindenter may be performed at multiple points (e.g., 15 points) on the sample of the measurement target, and the dent depth of the measurement target may be represented by an average value of multiple test results.

[0142] Fig.10 is a graph showing the relationship between the dent depth (μm) and the load (mN). Fig.11 is a graph showing the change in indent depth with respect to time during a maximum load holding period. Fig.10 and Fig.11 , h1 represents the dent depth at the time point when the maximum load is reached, and h2 is the dent depth at the time point when the maximum load holding period ends.

[0143] Reference Fig.10 and Fig.11 As the indentation load of the indenter RBL increases, the indentation depth of the indenter RBL increases. This is because the deformation rate due to stress increases as the modulus of the adhesive layer PSA decreases. Fig.10 The indentation depth at the indentation load in the RBL increases as the modulus decreases. Due to the viscosity of the adhesive layer PSA, the indentation depth continues to increase even when the maximum load of the indenter RBL is maintained. The indentation depth tends to increase during the maximum load holding period mainly due to the increase in creep characteristics. Over time, the rate of increase in indentation depth gradually decreases during the maximum load holding period ( Fig.11 The indent depth can be maintained at a specific value at a certain point in time without further increasing even if the holding period is extended. The indenter RBL is unloaded from the measurement target, and the indent depth decreases, wherein the stronger the restoring force is, the faster the indent depth can decrease after the indenter RBL is completely unloaded.

[0144] After measuring the indentation depth as described above, the modulus E* can be calculated by Formula 1 as follows.

[0145]

[0146] In Formula 1, P represents the maximum load, R represents the radius of the indenter RBL, and h represents the indentation depth. Here, the indentation depth means that the maximum load reaches the depth h1. In the case where the bioindenter has a predetermined offset depth h offset The indentation depth of Equation 1 can be expressed by subtracting the deflection depth h from the maximum load reached depth h1 measured by the bioindenter. offset The value obtained. Offset depth h offset It is the amount of displacement perceived when the bioindenter measures the indentation depth when the surface of the adhesive layer PSA is indented due to the van der Waals force even though the indenter RBL is close but not pressed. The actual indentation depth can be obtained by subtracting the displacement depth h from the indentation depth measured by the bioindenter. offset To reduce the offset depth h offsetThe resulting measurement error can be used to calculate the modulus by setting the loading slope in the indentation depth-load curve to be within the range of about 30% to about 98% of the maximum load (about 0.06 mN to about 0.196 mN).

[0147] Creep properties (C IT ) can also be calculated by Formula 2.

[0148]

[0149] In the same manner as described above, the bonding members 251 to 253, 351 and 352 of the display device 10 have appropriate modulus and creep characteristics for each position, thereby accurately controlling adhesive properties such as restoring force and preventing defective film removal according to the positions of the bonding members 251 to 253, 351 and 352 applied to the display device 10.

[0150] Hereinafter, an embodiment of the display device 10 will be further described. In the following embodiment, the same components as those of the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted or simplified.

[0151] Figure 12 to Figure 14 Various embodiments of stack structures around the display panel 100 are shown.

[0152] Fig.12 It is a cross-sectional view of an embodiment of the display device 11 .

[0153] Reference Fig.12 , the display device 11 and Figure 3 The embodiment of the present invention is different in that the cover window protection layer 210 and the first bonding member 251 are omitted. In this embodiment, the modulus of the third bonding member 253 and the second bonding member 252 in a thin film state measured by using an indenter may each be in the range of about 1 MPa to about 10 MPa. The modulus of the fourth bonding member 351 may be greater than the modulus of each of the second bonding member 252 and the third bonding member 253. The creep characteristics of each of the second bonding member 252 and the third bonding member 253 may be less than the creep characteristics of the rear bonding members 351 and 352.

[0154] Other descriptions have been given above, and therefore, redundant descriptions will be omitted.

[0155] Fig.13 is a cross-sectional view of an embodiment of a display device according to still another embodiment.

[0156] Reference Fig.13 , the display device 12 and Figure 3The embodiment is different in that the rear stack structure 300 further includes a buffer member 330 and a sixth combining member 353 .

[0157] The buffer member 330 may be disposed between the polymer film layer 310 and the heat dissipation member 320. The buffer member 330 may absorb external impact to reduce or effectively prevent damage to the display device 12. The buffer member 330 may be disposed or formed as a single layer or a plurality of stacked layers. The buffer member 330 may include, for example, a material having elasticity, such as polyurethane or polyethylene resin. The buffer member 330 may be a cushion layer.

[0158] The sixth coupling member 353 may be disposed between the buffer member 330 and the polymer film layer 310 to couple them to each other. The fifth coupling member 352 may be disposed between the buffer member 330 and the heat dissipation member 320 to couple them to each other. The sixth coupling member 353 may be a buffer portion coupling member that attaches the buffer member 330 to the rear surface of the display panel 100.

[0159] The sixth coupling member 353 may have adhesive properties similar to those of the fifth coupling member 352. That is, the thickness of the sixth coupling member 353 may be the same as that of the fifth coupling member 352, or be within a thickness range applicable to the fifth coupling member 352. The modulus of the sixth coupling member 353 in a film form and measured using an indenter may be within a range of about 1 MPa to about 10 MPa, and the creep property of the sixth coupling member 353 may be within a range of about 20% to about 70%.

[0160] Fig.14 It is a cross-sectional view of an embodiment of the display device 13 .

[0161] Reference Fig.14 , the display device 13 and Fig.13 The embodiment of the present invention is different in that the cover window protection layer 210 and the first bonding member 251 are omitted. Figure 2 , Fig.12 and Fig.13 Those described, Fig.14 The configuration of the structure in can be easily understood, and thus redundant description is omitted.

[0162] Hereinafter, the embodiments will be described in more detail through manufacturing examples and experimental examples.

[0163] <Manufacturing Example 1: Manufacture of Display Device>

[0164] Manufacturing with Figure 3 Multiple display device samples with the stacked structure shown in .

[0165] <Manufacturing Example 2: Extraction of Adhesive Sample>

[0166] When each layer is separated from a display device sample, an adhesive sample is extracted. As the extracted adhesive sample, adhesive #1 is applied as the first bonding member 251, adhesive #2 is applied as the second bonding member 252, adhesive #3 is applied as the third bonding member 253, adhesive #4 is applied as the fourth bonding member 351, and adhesive #5 is applied as the fifth bonding member 352.

[0167] <Test Example 1: Measurement of modulus and creep properties>

[0168] Each adhesive sample was cut into a size of 2 cm×2 cm, and modulus and creep property measurements were performed thereon using an indenter evaluation method. The indenter evaluation method was performed by applying and maintaining a maximum load of 0.2 mN to each sample for 120 seconds using a spherical indenter (which was made of ruby ​​material and had a diameter of 1 mm). The loading / unloading speed was maintained at 1.2 mN / min. The indentation depth of the depression at each point was measured, and the modulus and creep properties were measured using the value obtained by averaging the indentation depth of the depression at each point. The results are shown in Table 1 below, and the relationship between the indentation depth and the load according to the measurement results is shown in Table 1 below. Fig.15 Shown in.

[0169] [Table 1]

[0170]

[0171] Reference Fig.15 As shown in Table 1, adhesive #1, adhesive #2, adhesive #3, adhesive #4, and adhesive #5 have a modulus of 1 MPa to 10 MPa, and the modulus of adhesive #4 is the largest. In addition, all samples exhibit creep properties in the range of 20% to 70%, and the creep properties of adhesive #2 and adhesive #3 are less than those of the other samples of adhesive #1, adhesive #4, and adhesive #5.

[0172] <Test Example 2: Folding Reliability Test>

[0173] The inward folding operation was repeatedly performed 200,000 times at 25 degrees Celsius (° C.) on another display device sample among those in Manufacturing Example 1. Even when folding was performed 200,000 times, each bonding member of the corresponding display device exhibited a normal state without causing defective film removal, thereby confirming the inward folding reliability.

[0174] Although the embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. Display device, include: Display panel; a polarizing member facing the display panel; a cover window including an inorganic material, the cover window facing the display panel, and the polarization member being between the cover window and the display panel; a window combining member located between the cover window and the polarization member and attaching the cover window to the polarization member, and a polarization combining member located between the polarization member and the display panel and attaching the polarization member to the display panel, wherein the window bonding member attaching the cover window to the polarizing member has a modulus of 1 MPa to 10 MPa; wherein the creep characteristic of the polarization combining component is smaller than the creep characteristic of the window combining component, The modulus and the creep property are measured values ​​measured by an indenter.

2. The display device according to claim 1, in, The cover window attached to the polarization member through the window bonding member having the modulus of 1 MPa to 10 MPa includes glass or quartz, and the cover window has a thickness of 10 μm to 30 μm.

3. The display device according to claim 2, further comprising: include: a cover window protection layer facing the polarization member, and the cover window is between the cover window protection layer and the polarization member; as well as a protective layer bonding member located between the cover window protective layer and the cover window and attaching the cover window protective layer to the cover window, Wherein, the protective layer bonding member attaching the cover window protective layer to the cover window has a modulus of 1 MPa to 10 MPa.

4. The display device according to claim 3, in, The thickness of the protective layer combining member is smaller than the thickness of the window combining member, and The modulus of the protection layer coupling member is greater than the modulus of the window coupling member.

5. The display device according to claim 4, in, Each of the window bonding member and the protective layer bonding member has a creep property of 20% to 70%, and The creep characteristic of the window bonding member is smaller than the creep characteristic of the protection layer bonding member.

6. The display device according to claim 5, in, The polarization combining member attaching the polarization member to the display panel has both a modulus of 1 MPa to 10 MPa and a creep property of 20% to 70%.

7. The display device according to claim 6, further comprising: include: a polymer film layer facing the polarization member, with the display panel between the polymer film layer and the polarization member; as well as a polymer film layer bonding member, located between the polymer film layer and the display panel, and attaching the polymer film layer to the display panel, in, The polymer film layer bonding member attaching the polymer film layer to the display panel has a modulus of 1 MPa to 10 MPa, and The modulus of the polymer film layer bonding member is greater than each of the modulus of the protection layer bonding member and the modulus of the polarization bonding member.

8. The display device according to claim 7, in, The polymer film layer bonding member attaching the polymer film layer to the display panel has a creep property of 20% to 70%, and The creep property of the polymer film layer bonding member is greater than the creep property of the window bonding member.

9. The display device according to claim 8, further comprising: include: a heat dissipation member facing the display panel, with the polymer film layer between the heat dissipation member and the display panel; as well as a heat dissipation portion bonding member located between the heat dissipation member and the polymer film layer and attaching the heat dissipation member to the polymer film layer, in, The thickness of the polymer film layer bonding member is smaller than the thickness of the heat dissipation portion bonding member, and The modulus of the polymer film layer bonding member is greater than the modulus of the heat dissipation portion bonding member.

10. The display device according to claim 8, further comprising: include: a buffer member facing the display panel, with the polymer film layer between the buffer member and the display panel; as well as a buffering portion bonding member located between the buffering member and the polymer film layer and attaching the buffering member to the polymer film layer, wherein the buffer portion bonding member attaching the buffer member to the polymer film layer has both a modulus of 1 MPa to 10 MPa and a creep property of 20% to 70%.

11. The display device according to claim 5, in, The thickness of the window bonding member attaching the cover window to the polarization member, having the creep characteristic of 20% to 70% and having the modulus of 1 MPa to 10 MPa, is 300 micrometers or less.

12. The display device according to claim 11, in, The modulus and the creep property of the window bonding member attaching the cover window to the polarization member are measured values ​​measured by the indenter on the window bonding member having the thickness of 300 micrometers or less.

13. The display device according to claim 12, in, The modulus and the creep property of the window bonding member are measured values ​​corresponding to a ball indenter indent depth sunken into the window bonding member having the thickness of 300 micrometers or less.

14. The display device according to claim 3, in, The display panel displays an image in a direction toward the cover window.

15. The display device according to claim 14, in, The display device is foldable inwardly and comprises a display surface at which the image is displayed, and The display device folded inwardly arranges parts of the display surface facing each other.

16. Display device, include: Display panel; a polarizing member facing the display panel; a cover window comprising glass or quartz, the cover window facing the display panel, and the polarization member being between the cover window and the display panel; a window combining member located between the cover window and the polarization member and attaching the cover window to the polarization member, and a polarization combining member located between the polarization member and the display panel and attaching the polarization member to the display panel, wherein the creep characteristic of the polarization combining component is smaller than the creep characteristic of the window combining component, Wherein, the window combining member attaching the cover window to the polarizing member has both of the following: 300 microns or less in thickness, and Modulus from 1 MPa to 10 MPa, wherein the modulus of the window combining member is a measured value measured by an indenter on the window combining member having the thickness of 300 micrometers or less; The creep property is a measurement value measured by the indenter.

17. The display device according to claim 16, further comprising: include: a cover window protection layer facing the polarization member, and the cover window is between the cover window protection layer and the polarization member; as well as a protective layer bonding member located between the cover window protective layer and the cover window and attaching the cover window protective layer to the cover window, in, The protective layer bonding member attaching the cover window protective layer to the cover window has a modulus of 1 MPa to 10 MPa, Each of the window bonding member and the protective layer bonding member has a creep property of 20% to 70%, and The creep characteristic of the window bonding member is smaller than the creep characteristic of the protective layer bonding member; Wherein, the modulus of the protective layer bonding component is a measured value measured by the indenter.

18. The display device according to claim 17, in, The polarization combining member attaching the polarization member to the display panel has both of the following: modulus from 1 MPa to 10 MPa, and 20% to 70% creep properties, The modulus of the polarization combining member is a measured value measured by the indenter.

19. The display device according to claim 18, in, Each of the protection layer combining member and the polarization combining member has a thickness of 300 micrometers or less, and The modulus and the creep property of the protection layer bonding member and the modulus and the creep property of the polarization bonding member are measured values ​​measured by the indenter on the corresponding bonding member among the protection layer bonding member and the polarization bonding member having the thickness of 300 μm or less.

20. The display device according to claim 19, in, The modulus and the creep properties of the respective bonding member are measured values ​​corresponding to a ball indenter indentation depth into the respective bonding member having the thickness of 300 micrometers or less.

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