Flexible display device and method for manufacturing a flexible display device

Abstract

To provide a flexible display device capable of maintaining its surface shape even after being repetitively folded.SOLUTION: A flexible display device is provided, comprising a display panel, and an optical adhesive layer with thixotropy provided between a display surface of the display panel and a member covering the display surface. A method of manufacturing the flexible display device is also provided, comprising producing the display panel, and bonding the display surface of the display panel and the member covering the display surface together using the optical adhesive layer with thixotropy.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a flexible display device and a method for manufacturing a flexible display device. [Background technology]

[0002] Patent Document 1 discloses a flexible display device having a structure in which a display panel, a touchscreen, and a window member are stacked, and which can be bent in a predetermined area. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-146586 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] In the flexible display device illustrated in Patent Document 1, the display panel, touchscreen, and window member are bonded together with optically clear adhesive (OCA). However, if the flexible display device is repeatedly bent, the layer of optically clear adhesive may gradually deform, causing distortion on the surface of the flexible display device.

[0005] Therefore, in view of the problems in the prior art described above, the present invention aims to provide a flexible display device and a method for manufacturing a flexible display device that can maintain its surface shape even after repeated bending operations. [Means for solving the problem]

[0006] According to one aspect of the present invention, a flexible display device is provided, comprising a display panel and a thixotropic optical adhesive layer provided between the display surface of the display panel and a member covering the display surface.

[0007] According to another aspect of the present invention, a method for manufacturing a flexible display device is provided, comprising the steps of: generating a display panel; and bonding the display surface of the display panel to a member covering the display surface using a thixotropic optical adhesive layer. [Effects of the Invention]

[0008] According to the present invention, a flexible display device that can maintain its surface shape even after repeated bending operations and a method for manufacturing a flexible display device are provided. [Brief explanation of the drawing]

[0009] [Figure 1] This block diagram shows a schematic configuration of a flexible display device according to one embodiment. [Figure 2] This is an array diagram of pixels and sub-pixels in a display unit according to one embodiment. [Figure 3] This is a circuit diagram illustrating the schematic configuration of a sub-pixel according to one embodiment. [Figure 4] This is a cross-sectional view of the display unit shown in Figure 1, along the line I-I'. [Figure 5] This is a cross-sectional view showing an example of the internal structure of a display panel according to one embodiment. [Figure 6] This figure illustrates the relationship between fluid viscosity and shear rate in one embodiment. [Figure 7] This figure illustrates the relationship between the polarization axis direction and the bending direction in a polarizing plate according to one embodiment. [Figure 8] This figure shows an example of the shape of a metal mesh layer according to one embodiment. [Figure 9] This figure shows an example of the shape of a metal mesh layer according to one embodiment. [Figure 10] This figure shows an example of the shape of a metal mesh layer according to one embodiment. [Figure 11] This figure illustrates the heat distribution in a display panel according to one embodiment. [Figure 12]It is a diagram for explaining the heat distribution in the display panel according to an embodiment. [Figure 13] It is a flowchart showing an example of a manufacturing method of a flexible display device according to an embodiment. [Figure 14] It is a diagram for explaining the pencil hardness of a display unit according to an embodiment. [Figure 15] It is a cross-sectional view showing the state of a display unit when bent according to an embodiment.

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. Elements having common functions throughout the drawings are denoted by the same reference numerals, and redundant descriptions may be omitted or simplified.

[0011] FIG. 1 is a schematic configuration diagram of a flexible display device according to the present embodiment. The flexible display device according to the present embodiment is a device that displays an image on a display unit 1 based on input RGB data.

[0012] Examples of the flexible display device include a foldable display device that can be folded, a rollable display device that can be rolled up, a bendable display device that can be bent and stretched, and the like.

[0013] The applications of the flexible display device can be, for example, an image output device of a computer, a large display, a television receiver, a smartphone, a tablet terminal, a game machine, etc., but are not particularly limited.

[0014] In addition, in the present embodiment, the case where the flexible display device is a top emission type (top emission) will be described, but the light emission type is not limited.

[0015] As shown in Figure 1, the flexible display device comprises a display unit 1, a timing controller (TCON) 2, a plurality of source drive ICs (SDICs) 3, and a plurality of gate drive ICs (GDICs) 4. The display unit 1 has a plurality of pixels arranged in a matrix and displays an image.

[0016] The timing controller 2 is communicated with multiple source drive ICs 3 and multiple gate drive ICs 4. The timing controller 2 controls the operating timing of the multiple source drive ICs 3 and multiple gate drive ICs 4 based on timing signals (vertical synchronization signals, horizontal synchronization signals, data enable signals, etc.) input from an external system.

[0017] Furthermore, the timing controller 2 generates RGBW data indicating the brightness of each subpixel of the display unit 1 based on the RGB data, which is an input signal from an external system, and outputs the RGBW data as an output signal to multiple source drive ICs 3. Note that the number of source drive ICs 3 and gate drive ICs 4 is not limited to those shown in the figure.

[0018] Each of the multiple source drive ICs 3 supplies voltage (video signals) to drive multiple pixels in the display unit 1 via multiple data lines, in accordance with the control of the timing controller 2. Each of the multiple gate drive ICs 4 supplies scan signals to multiple pixels in the display unit 1 via multiple gate lines, in accordance with the control of the timing controller 2. In this way, the timing controller 2 functions as a display control device that controls the operation of the entire display device.

[0019] In the following explanation, the directions of the two sides defining the display surface of the display unit 1 will be referred to as the X-axis direction and the Y-axis direction, respectively, and the direction perpendicular to the display surface (i.e., perpendicular to the XY plane) will be referred to as the Z-axis direction.

[0020] Figure 2 is an array diagram of pixels 10 and sub-pixels 11, 12, 13, and 14 in the display unit 1 according to this embodiment. The display unit 1 comprises a plurality of pixels 10 arranged in a plurality of rows and a plurality of columns. Each of the plurality of pixels 10 includes a sub-pixel 11 that emits red light, a sub-pixel 12 that emits green light, a sub-pixel 13 that emits blue light, and a sub-pixel 14 that emits white light. The brightness of the sub-pixels 11, 12, 13, and 14 is controlled according to the voltage output from the source drive IC 3. By having the sub-pixels 11, 12, 13, and 14 emit light at a predetermined brightness ratio, the pixels 10 can display various colors by additive color mixing.

[0021] Figure 3 is a schematic circuit diagram showing the configuration of a sub-pixel 11 according to this embodiment. Figure 3 shows a sub-pixel 11 included in one of the multiple pixels 10, a source drive IC 3 connected to the sub-pixel 11, and a gate drive IC 4 connected to the sub-pixel 11. Although only the configuration of sub-pixel 11 is illustrated in Figure 3, sub-pixels 12, 13, and 14 have a similar configuration.

[0022] The sub-pixel 11 comprises a scan transistor M1, a drive transistor M2, and a diode D. The diode D is a light-emitting element of the display device. The scan transistor M1 and the drive transistor M2 are, for example, thin-film transistors (TFTs). In this embodiment, the scan transistor M1 and the drive transistor M2 are assumed to be n-channel type. However, the scan transistor M1 and the drive transistor M2 may be p-channel type. If the drive transistor M2 is p-channel type, the circuit configuration of the sub-pixel 11 may differ from that shown in Figure 3.

[0023] The cathode of diode D is connected to the potential line supplying the potential VSS. The anode of diode D is connected to the source of the drive transistor M2. The drain of the drive transistor M2 is connected to the potential line supplying the potential VDD. The gate of the drive transistor M2 is connected to the source of the scan transistor M1.

[0024] The data line DL is connected to the drain of scan transistor M1. Source drive IC3 supplies the video signal to the drain of scan transistor M1 via data line DL. The gate line GL is connected to the gate of scan transistor M1. Gate drive IC4 supplies the control signal to the gate of scan transistor M1 via gate line GL. Scan transistor M1 is controlled to be on or off depending on the level of the control signal input to its gate.

[0025] The current flowing between the drain and source of the drive transistor M2 is controlled based on the voltage (video signal) input to the gate of the drive transistor M2 from the source drive IC 3 via the data line DL and scan transistor M1. The diode D is supplied with the current flowing between the drain and source of the drive transistor M2, and the diode D emits light with a brightness corresponding to that current. In this way, the diode D emits light with a brightness corresponding to the video signal input to the sub-pixel 11.

[0026] Figure 4 is a cross-sectional view of the display unit 1 shown in Figure 1 along the line I-I'. As shown in Figure 4, the display unit 1 has a structure in which a display panel 100, a cover window 200, an optical adhesive layer 300 (300a to 300c), a polarizing plate 400, a metal mesh layer 500, an adhesive layer 600, and a back plate 700 are laminated. Each layer will be described in detail below.

[0027] [Display Panel] The display panel 100 is one of the following: Organic Light Emitting Diodes (OLED), Liquid Crystal Display device (LCD), Plasma Display Panel device (PDP), Field Emission Display device (FED), or Electroluminescence Display device (ELD). In this embodiment, the display panel 100 is an OLED, which is a representative flexible display device that can be bent like paper and maintains its display performance even when bent.

[0028] OLEDs are self-emissive devices and do not require a backlight like liquid crystal displays, allowing for lightweight and thin designs. They also offer superior viewing angles and contrast ratios compared to liquid crystal displays. Furthermore, OLEDs have advantages in terms of power consumption. They can also be driven by low DC voltage, resulting in fast response times. Additionally, because their internal components are solid, OLEDs are resistant to external shocks and have a wide operating temperature range.

[0029] Figure 5 is a cross-sectional view showing an example of the internal structure of the display panel 100. As shown in Figure 5, a flexible base substrate 112 is provided at the bottom of the display panel 100. The flexible base substrate 112 includes a flexible plastic material. The flexible base substrate 112 includes materials such as polycarbonate, polymethylpentene, polymethyl methacrylate, cycloolefin copolymer, and polyimide.

[0030] The flexible base substrate 112 is formed, for example, by applying a plastic substance to a release layer (not shown) on the upper surface of a relatively thick carrier substrate (not shown) to a certain thickness, and then curing the plastic substance. The flexible substrate 110 and the carrier substrate are separated at the release layer.

[0031] A buffer layer 120 is formed on the flexible base substrate 112. A thin-film transistor Tr is formed on the buffer layer 120. The buffer layer 120 prevents moisture from penetrating into the interior of the display panel 100. The buffer layer 120 is formed from an inorganic insulating material such as silicon oxide or silicon nitride. A semiconductor layer 122 is formed on the buffer layer 120. The semiconductor layer 122 is formed from an oxide semiconductor material or polycrystalline silicon, for example.

[0032] A gate insulating film 124 is formed on the semiconductor layer 122. The gate insulating film 124 is formed from an inorganic insulating material such as silicon oxide or silicon nitride.

[0033] On the gate insulating film 124, a gate electrode 130 is formed corresponding to the center of the semiconductor layer 122. The gate electrode 130 is formed from a conductive material such as a metal.

[0034] An interlayer insulating film 132 is formed on the gate electrode 130. The interlayer insulating film 132 insulates the gate electrode 130 from the source electrode 140 or drain electrode 142. The interlayer insulating film 132 is formed from an inorganic insulating material such as silicon oxide or silicon nitride. The interlayer insulating film 132 may also be formed from an organic insulating material such as benzocyclobutene or photoacrylic.

[0035] A source electrode 140 and a drain electrode 142 are formed on the interlayer insulating film 132. The source electrode 140 and the drain electrode 142 are formed from a conductive material such as a metal.

[0036] The source electrode 140 and the drain electrode 142 are positioned spaced apart from the gate electrode 130 and each contacts both sides of the semiconductor layer 122 through contact holes (not shown).

[0037] The semiconductor layer 122, gate electrode 130, source electrode 140, and drain electrode 142 constitute a thin-film transistor Tr. The thin-film transistor Tr functions as a driving element, as described above.

[0038] The thin-film transistor Tr may have a coplanar structure in which the gate electrode 130, source electrode 140, and drain electrode 142 are located on a semiconductor layer 122.

[0039] Furthermore, the thin-film transistor Tr may have an inverted staggered structure in which the gate electrode 130 is located below the semiconductor layer 122, and the source electrode 140 and drain electrode 142 are located above the semiconductor layer 122. In this case, the semiconductor layer 122 may be made of amorphous silicon.

[0040] The protective layer 145 is formed to cover the thin-film transistor Tr. The protective layer 145 also has a drain contact hole 152 that exposes the drain electrode 142 of the thin-film transistor Tr.

[0041] On the protective layer 145, a first electrode 160 is formed separately for each pixel region. The first electrode 160 is connected to the drain electrode 142 of the thin-film transistor Tr through the drain contact hole 152. The first electrode 160 is made of a conductive material with a relatively large work function value and may be used as an anode. For example, the first electrode 160 is made of a transparent conductive material such as indium-tin oxide (ITO) or indium-zinc oxide (IZO).

[0042] Furthermore, a bank layer 166 is formed on top of the protective layer 145, covering the edges of the first electrode 160. The bank layer 166 exposes the center of the first electrode 160, corresponding to the pixel area.

[0043] An organic light-emitting layer 162 is formed on the first electrode 160. The organic light-emitting layer 162 may have a single-layer structure of a light-emitting material layer made of a light-emitting substance. In addition, to increase the light-emitting efficiency, the organic light-emitting layer 162 may have a multilayer structure of a hole injection layer, a hole transport layer, a light-emitting material layer, an electron transport layer and an electron injection layer that are sequentially stacked on the first electrode 160.

[0044] A second electrode 164 is formed on the flexible base substrate 112 on which the organic light-emitting layer 162 is formed. The second electrode 164 is made of a conductive material with a relatively small work function value and may be used as a cathode. For example, the second electrode 164 is made of one of the following: aluminum (Al), magnesium (Mg), or aluminum-magnesium alloy (AlMg).

[0045] The first electrode 160, the organic light-emitting layer 162, and the second electrode 164 constitute a diode D. The diode D is configured in each pixel region in connection with a thin-film transistor Tr and is formed in all pixel regions. In this embodiment, the diode D is an "organic light-emitting diode".

[0046] An encapsulation film 170 is formed on the second electrode 164 to prevent external moisture from penetrating the diode D. The encapsulation film 170 is a sealing layer having a laminated structure of a first inorganic insulating layer 172, an organic insulating layer 174, and a second inorganic insulating layer 176. The laminated structure of the encapsulation film 170 is not limited to this. The encapsulation film 170 may be configured such that the inorganic insulating layers and organic insulating layers are arranged alternately, with the inorganic insulating layer being the outermost layer.

[0047] Furthermore, the encapsulation film 170 is further provided with a touch electrode array comprising a first touch electrode 181 and a second touch electrode 182 that intersect each other for touch detection. The second inorganic insulating layer 176 is provided with bridge wiring 181a. The bridge wiring 181a is also provided with a touch insulating film 183. The touch insulating film 183 is provided with a first touch pattern 181b and a second touch electrode 182 that are spaced apart from each other.

[0048] Here, the first touch pattern 181b is electrically connected to the bridge wiring 181a through a contact hole in the touch insulating film 183 to form the first touch electrode 181. The second touch electrode 182 shown in the drawing is only partially depicted. The second touch electrode 182 is located on the touch insulating film 183 where the first touch pattern 181b is not located, and generates a mutual capacitance (Cm) between it and the separated first touch pattern 181b. A touch can be detected by the change in mutual capacitance (Cm).

[0049] [Cover window] The cover window 200 is a substrate positioned in the display direction (positive Z-axis direction) of the display panel 100. The cover window 200 protects the display panel 100 and other components located in the lower layer from external impacts. The cover window 200 has impact resistance and light transmittance.

[0050] The cover window 200 is formed from, for example, polyethylene terephthalate (PET), polycarbonate (PC), polyethersulfone (PES), polyethylene naphthalate (PEN), etc.

[0051] [Optical adhesive layer] The optical adhesive layer 300 is an optically transparent adhesive member. The optical adhesive layer 300 is formed mainly from known resin compositions, such as rubber-based, acrylic-based, silicone-based, or urethane-based resin compositions.

[0052] For example, an optically clear adhesive (OCA) or an optically clear resin (OCR) can be used as the optical adhesive layer 300.

[0053] Optical transparent adhesive (OCA) is an adhesive film having adhesive layers on both sides. When bonding two components together, one component is bonded to the side with one adhesive layer, and the other component is bonded to the side with the other adhesive layer. In this way, the two components are bonded together via the OCA. OCA has the advantage of excellent processability and uniform film thickness. In this embodiment, optical transparent adhesive (OCA) is used as the optical adhesive layer 300.

[0054] As shown in Figure 4, the optical adhesive layer 300 in this embodiment is provided with three layers: a first optical adhesive layer 300a, a second optical adhesive layer 300b, and a third optical adhesive layer 300c.

[0055] The first optical adhesive layer 300a is provided between the cover window 200 and the polarizing plate 400, and adheres the lower surface of the cover window 200 to the upper surface of the polarizing plate 400. The second optical adhesive layer 300b is provided between the polarizing plate 400 and the display panel 100, and adheres the lower surface of the polarizing plate 400 to the upper surface of the display panel 100. The third optical adhesive layer 300c is provided between the display panel 100 and the metal mesh layer 500, and adheres the lower surface of the display panel 100 to the upper surface of the metal mesh layer 500.

[0056] Furthermore, the optical adhesive layers 300 in this embodiment (first optical adhesive layer 300a, second optical adhesive layer 300b, and third optical adhesive layer 300c) are highly transparent optical adhesives (OCA) that are pre-formed into a film shape by adding thixotropic nanosheets NS as additives to a base resin composition.

[0057] Thixotropy refers to the property of non-Newtonian fluids in which viscosity changes with shear rate. A substance exhibiting thixotropy will gradually decrease in viscosity and become liquid when subjected to continuous shear stress. Conversely, when the substance is at rest, its viscosity will gradually increase, eventually becoming solid.

[0058] Furthermore, in this embodiment, the term "nanosheet" refers to an extremely thin two-dimensional single crystal with a thickness of several nanometers (nm) and a length and width of several tens of micrometers (μm). The nanosheet is a functional material that is exfoliated in a solvent and possesses orientation. The nanosheet NS generates a labyrinth effect by being dispersed within the resin composition that forms the base of the optical adhesive layer 300. Therefore, high shielding properties against moisture (high water vapor barrier properties) can be expected. The orientation of the nanosheet NS can be controlled by external forces (shear stress, electric field, magnetic field, etc.).

[0059] Examples of nanosheet NS include zeolite-based, silica-based, and clay-based nanosheets with a high aspect ratio. In this embodiment, as the clay-based nanosheet NS, nanoclay separated (layer-exfoliated) from montmorillonite, bentonite, hectorite, octosilicate, etc., is used.

[0060] When the thickness of the optical adhesive layer 300 is 1 to 100 micrometers, the length and width of the additive nanosheet NS are preferably 10 to 1000 nanometers, and the thickness of the nanosheet NS is preferably 1 to 1000 nanometers. The aspect ratio of the nanosheet NS is preferably 30:1 or greater.

[0061] Furthermore, the content of nanosheet NS in the optical adhesive layer 300 is preferably set to, for example, 0.1 to 30 weight percent. Also, the thixotropy index (TI) of the optical adhesive layer 300 is preferably set to, for example, 1 to 1000 or less.

[0062] Figure 6 illustrates the relationship between fluid viscosity and shear rate. Here, the change in viscosity according to the shear rate is shown for each of the following fluids (1) to (3). (1) A fluid consisting solely of epoxy resin (see the square ("■") in the diagram) (2) A fluid to which nanosheet NS is added to epoxy resin at a content of 5 weight percent (see the diamond shape ("◇") in the figure) (3) A fluid in which nanosheet NS is added to epoxy resin at a content of 10 weight percent (see triangle ("△") in the figure)

[0063] As shown in Figure 6, when the shear rate is 0s -1 In this case, the viscosity of a fluid consisting only of epoxy resin ("■"), i.e., a fluid without the additive nanosheet NS, is 30 Pa·s. Also, the shear rate is 0 s -1 In this case, the viscosity of the fluid ("◇") in which 5% by weight of nanosheet NS is added to epoxy resin is 150 Pa·s. And the shear rate is 0 s -1 In this case, the viscosity of the fluid ("△") to which 10 weight percent of nanosheet NS is added to the epoxy resin is 13200 Pa·s.

[0064] In contrast, the shear rate is 50s -1 In this case, the viscosity of the fluid consisting solely of epoxy resin ("■") is 37.7 Pa·s. That is, when the shear rate is 0 s -1 Compared to the previous case, it can be seen that the viscosity has increased slightly.

[0065] Also, the shear rate is 50s -1 In this case, the viscosity of the fluid ("◇") in which 5 weight percent of nanosheet NS is added to epoxy resin is 8.54 Pa·s. That is, when the shear rate is 0 s -1 Compared to the previous case, it can be seen that the viscosity has decreased significantly.

[0066] And the shear rate is 50s -1In this case, the viscosity of the fluid (“△”) in which 10 weight percent of the nanosheet NS is added to the epoxy resin is 27.4 Pa·s. That is, when the shear rate is 0 s -1 Comparing with the case of, it can be seen that the viscosity is further significantly reduced.

[0067] Here, as an index value, calculate the ratio of the viscosity in the case where the shear rate is 0 s -1 and the case where the shear rate is 50 s -1 In this embodiment, the calculated ratio is taken as the TI value. The larger the TI value of the display, the less resistance to the bending operation, and the easier it is to bend. Furthermore, the larger the TI value of the display, the higher the viscosity in the state where the screen is opened, and the shape maintenance and various characteristics of the panel surface are improved.

[0068] As shown in FIG. 6, the TI value of the fluid (“■”) composed only of the epoxy resin is 30 / 37.7 ≈ 0.8. Also, the TI value of the fluid (“◇”) in which the nanosheet NS is added to the epoxy resin at a content rate of 5 weight percent is 150 / 8.54 ≈ 17.6. And the TI value of the fluid (“△”) in which the nanosheet NS is added to the epoxy resin at a content rate of 10 weight percent is 13200 / 27.4 ≈ 481.8.

[0069] That is, the TI values are in the relationship of fluid (“■”) < fluid (“◇”) < fluid (“△”), indicating that the fluid (“△”) is most suitable as the material of the optical adhesive layer 300 in the flexible display device.

[0070] [Polarizing plate] The polarizing plate 400 is adhered to the upper surface (display surface) side of the display panel 100 via the second optical adhesive layer 300b. The polarizing plate 400 polarizes the light emitted from each pixel of the display panel 100 and prevents the reflection of external light, thereby improving the optical characteristics of the flexible display device.

[0071] Figure 7 illustrates the relationship between the polarization axis direction and the bending direction in the polarizing plate 400. As shown in Figure 7, in this embodiment, the axial direction (direction A) of the polarization axis of the polarizing plate 400 is perpendicular to the direction (direction B) in which the display panel 100 can be bent. This prevents deterioration of the polarization function of the polarizing plate 400 (increase in ambient light reflectivity) caused by repeated bending operations. As a result, a decrease in the quality of the image displayed on the display unit 1 can also be prevented.

[0072] [Metal mesh layer] The metal mesh layer 500 is a mesh-shaped metal sheet formed to a thickness of several tens of micrometers (μm). The metal mesh layer 500 is connected to the non-display side (the side opposite the display side) of the display panel 100 and dissipates the heat generated by the display panel 100.

[0073] The metal mesh layer 500 is manufactured, for example, by making mesh-shaped cuts in a steel sheet using a special machine and simultaneously expanding it. In this embodiment, the metal mesh layer 500 is manufactured using a steel sheet as the base material, but it may also be manufactured using metal sheets other than iron, such as aluminum (Al), copper (Cu), titanium (Ti), and nickel (Ni), and their alloy sheets.

[0074] Figures 8 to 10 show examples of the shape of the metal mesh layer 500. In the example in Figure 8, the metal mesh layer 500 has a mesh shape in which elliptical holes H1 are arranged vertically and horizontally. In the example in Figure 9, the metal mesh layer 500 has a mesh shape in which rhomboid holes H2 are arranged vertically and horizontally. In the example in Figure 9, the metal mesh layer 500 has a mesh shape in which tortoise-shell-shaped holes H3 are arranged vertically and horizontally. The holes H1, H2 and H3 all open along the Z-axis direction.

[0075] As shown in Figures 8 to 10, the mesh (holes) of the metal mesh layer 500 can be formed in various shapes such as circular, rhomboid, and tortoiseshell. The mesh shape and size of the metal mesh layer 500 can be appropriately changed considering the strength and flexibility of the material.

[0076] Figures 11 and 12 illustrate the heat distribution in the display panel 100. In Figure 11, the central region A1 of the display panel 100 and the region A2 outside of region A1 are shown to be hotter than the outer edges of region A2. The shading of regions A1 and A2 in the figure indicates that region A1 is hotter than region A2.

[0077] In contrast, Figure 12 shows that a metal mesh layer 500 is provided on the underside of the display panel 100. Furthermore, region A3 of the display panel 100 is a region with a higher temperature than the edges of the same surface, but the area of ​​region A3 extends further outward than region A1. The temperature in region A3 is lower than that of regions A1 and A2 in Figure 11. This indicates that the metal mesh layer 500 has a heat dissipation effect that spreads heat that tends to accumulate in the center of the display panel 100 in the planar direction (X-axis and Y-axis directions).

[0078] Furthermore, the metal mesh layer 500 is formed with diagonal intersecting lines (see Figures 8 to 10), thus providing sufficient strength.

[0079] In this way, by providing the metal mesh layer 500, the flexibility and strength (durability) of the display panel 100 can be achieved simultaneously. As a result, degradation of the organic light-emitting element (organic light-emitting layer 162) can be prevented, its lifespan can be improved, and a decline in screen quality can be prevented.

[0080] [Adhesive layer] The adhesive layer 600 adheres the lower surface of the metal mesh layer 500 to the upper surface of the back plate 700. The adhesive layer 600 is formed from a resin that is curable by heat or light (ultraviolet light), for example. Epoxy resins and acrylic resins are preferably used as the resin. OCA may also be used for the adhesive layer 600.

[0081] [Backplate] The backplate 700 is bonded to the underside of the metal mesh layer 500 via an adhesive layer 600. The backplate 700 is a substrate that protects and supports the display panel 100 and the like located on the upper layer. The backplate 700 is made from materials such as PET (polyethylene terephthalate), PC (polycarbonate), PES (polyethersulfone), and PEN (polyethylene naphthalate). In addition, an impact-absorbing film or the like may be further provided on the underside of the backplate 700.

[0082] Next, the manufacturing method of the flexible display device described above will be explained. Figure 13 is a flowchart showing an example of a manufacturing method for a flexible display device.

[0083] First, the display panel 100 is manufactured (step S11). The manufacturing method of the display panel 100 in this embodiment includes the following steps (1) to (5).

[0084] (1) A step of forming a buffer layer 120 on a flexible base substrate 112. (2) A step of forming a thin-film transistor Tr (semiconductor layer 122, gate electrode 130, source electrode 140 and drain electrode 142), a gate insulating film 124 and a protective layer 145 on the buffer layer 120. (3) A step of forming a diode D (first electrode 160, organic light-emitting layer 162, and second electrode 164) on the protective layer 145 and the thin film transistor Tr. (4) A step of forming an encapsulation film 170 on the diode D. (5) A step of forming a touch electrode array (first touch electrode 181 and second touch electrode 182) on the encapsulated film 170. The manufacturing method of the display panel (OLED panel) 100 is not limited to this, and any known method can be used.

[0085] Next, the second optical adhesive layer (OCA) 300b, which has been pre-formed into a film, is placed (attached) to the upper surface (display surface) of the display panel 100 (step S12).

[0086] Next, the polarizing plate 400 is placed (attached) to the upper surface of the second optical adhesive layer 300b (step S13). In other words, the display panel 100 and the polarizing plate 400 are joined together via the second optical adhesive layer 300b.

[0087] Next, a first optical adhesive layer (OCA) 300a, which has been pre-formed into a film, is placed (attached) to the upper surface of the polarizing plate 400 (step S14).

[0088] Next, the cover window 200 is placed (attached) to the upper surface of the first optical adhesive layer 300a (step S15). That is, the cover window 200 and the polarizing plate 400 are joined together via the first optical adhesive layer 300a.

[0089] Next, a pre-formed third optical adhesive layer (OCA) 300c is placed (attached) to the lower surface of the display panel 100 (the side opposite to the display surface) (step S16).

[0090] Next, the pre-processed metal mesh layer 500 is placed (attached) to the underside of the third optical adhesive layer 300c (step S17). In other words, the display panel 100 and the metal mesh layer 500 are joined together via the third optical adhesive layer 300c.

[0091] Next, the adhesive layer 600 is placed on the underside of the metal mesh layer 500 (step S18).

[0092] Then, the back plate 700 is placed (attached) to the lower surface of the adhesive layer 600 (step S19). In other words, the metal mesh layer 500 and the back plate 700 are joined together via the adhesive layer 600.

[0093] Next, the operation and effects of the flexible display device according to the present embodiment described above will be explained.

[0094] Figure 14 illustrates the pencil hardness of the display unit 1. Here, the pencil hardness is shown according to the combination of layers constituting the display unit 1, for both cases: when the OCA (optical adhesive layer 300) does not contain additives (nanosheet NS) and when the OCA contains additives.

[0095] Pencil hardness is measured by pressing a pencil lead against the surface of an object and moving it at a predetermined speed. The presence or absence of scratches indicates the scratch hardness of the object, which is expressed in terms of the hardness of the pencil lead. Pencil hardness is measured, for example, by setting a pencil at a 45-degree angle on a wheeled measuring device and moving the device along the surface of the object.

[0096] First, let's explain the case where the OCA does not contain any additives. As shown in Figure 14, the pencil hardness when the object is only the cover window 200 is 7H. Also, when the object consists of three layers: the cover window 200, the first optical adhesive layer 300a without additives, and the polarizing plate 400, the pencil hardness is 3H. And when the object consists of all the layers of the display unit 1 (cover window 200, first optical adhesive layer 300a, polarizing plate 400, second optical adhesive layer 300b, display panel 100, third optical adhesive layer 300c, metal mesh layer 500, adhesive layer 600, and backplate 700), the pencil hardness is B.

[0097] Next, we will explain the case where additives are included in the OCA. As shown in Figure 14, the pencil hardness when the object is only the cover window 200 is 7H. The pencil hardness when the object consists of three layers: the cover window 200, the first optical adhesive layer 300a containing OCA, and the polarizing plate 400 is 5H. The pencil hardness when the object consists of all layers of the display unit 1 is 2H.

[0098] In the former case, where OCA does not contain additives, the viscosity of the optical adhesive layer 300 in a static state is low (see Figure 6). Therefore, as the number of optical adhesive layers 300 increases, the pencil hardness decreases significantly in the order of 7H, 3H, and B, becoming softer.

[0099] In contrast, in the latter case, where the OCA contains additives, the viscosity of the optical adhesive layer 300 in a static state is higher than in the former case (see Figure 6). Therefore, although the pencil hardness decreases slightly in the order of 7H, 5H, and 2H as the number of layers increases, the entire display unit 1 remains sufficiently hard (pencil hardness: 2H).

[0100] In other words, the thixotropy imparted to each optical adhesive layer 300 results in high viscosity when the screen is open and stationary, thus maintaining the surface shape of the display unit 1.

[0101] Figure 15 is a cross-sectional view showing the state of the display unit 1 when it is bent. When shear stress is applied to the display unit 1, the viscosity of the optical adhesive layer 300 decreases in proportion to the shear rate (see Figure 6). Therefore, as shown in Figure 15, the display unit 1 becomes easily bent. When the bending motion is stopped, the viscosity of the optical adhesive layer 300 increases again, and the display unit 1 hardens while remaining in the bent state. Furthermore, if shear stress is applied to the display unit 1 in the opposite direction, the display unit 1 can be bent in the opposite direction, returning the screen to its open state.

[0102] When the viscosity of the optical adhesive layer 300 is high, the surface properties (pencil hardness) of the flexible display device (display unit 1) are enhanced, making it easier for the user to input data using their finger or a stylus (not shown) on the flexible display device.

[0103] As described above, this embodiment provides a flexible display device and a method for manufacturing a flexible display device that can be easily bent and maintain its shape even after repeated bending operations.

[0104] Furthermore, the highly transparent nanosheet NS is an additive that does not affect the performance (adhesion, transmittance, etc.) of the resin composition that forms the base of the optical adhesive layer 300. For this reason, the optical adhesive layer 300 of this embodiment has the advantage of being easier to manufacture than existing optical adhesives (OCA), etc.

[0105] In particular, nanoclay with a high aspect ratio (e.g., 1000:1 or higher) has the advantage of being able to impart thixotropy even in small quantities. Furthermore, because nanoclay is made from clay minerals, it is also superior in terms of the manufacturing cost of OCA (Optical Adhesive Layer 300).

[0106] [Modified Embodiment] The present invention is not limited to the embodiments described above, and can be modified as appropriate without departing from the spirit of the invention.

[0107] For example, the above-described embodiment described a case in which all three optical adhesive layers 300 contain nanosheet NS, but it is not limited to this. A structure in which at least one of the three optical adhesive layers 300 contains nanosheet NS and thixotropy is imparted is also possible.

[0108] Furthermore, although the embodiments described above described a case where the nanosheet NS is a nanoclay separated from a layered inorganic compound of clay mineral (clay), the type of nanosheet NS is not limited to this. Moreover, the additive can be any substance that can impart thixotropy, and its shape does not have to be sheet-like. For example, nano-sized particulate matter may be used as the additive.

[0109] Furthermore, although the above-described embodiment described a case in which a metal mesh layer 500 having a mesh shape is provided on the lower side of the display panel 100, it is also possible to substitute it with a metal layer of a shape other than a mesh shape. For example, a flat metal layer having a hollow region inside can be used to achieve a similar heat dissipation effect.

[0110] Furthermore, although the above-described embodiment described a case in which a touch sensor (touch electrode array) is integrated into the display panel 100, the touch sensor may be omitted depending on the type of flexible display device. [Explanation of Symbols]

[0111] NS... Nanosheet 1...Display section 2. Timing Controller (TCON) 3. Source Drive IC (SDIC) 100... Display Panel 200... Cover window 300...Optical adhesive layer 400...Polarizing plate 500... Metal mesh layer 600...adhesive layer 700...backplate

Claims

1. A display panel having a display surface and a non-display surface on the opposite side of the display surface, A member provided on the display surface of the display panel, A polarizing plate is provided between the display panel and the member, A first optical adhesive layer is provided between the polarizing plate and the member, A second optical adhesive layer is provided between the display surface of the display panel and the polarizing plate, A metal layer provided below the non-display surface of the display panel, which dissipates heat generated by the display panel, A third optical adhesive layer is provided between the display panel and the metal layer, A back plate is placed on the lower surface of the metal layer, An adhesive layer is disposed between the metal layer and the back plate, and adheres the lower surface of the metal layer to the upper surface of the back plate. Equipped with, The first optical adhesive layer, the second optical adhesive layer, and the third optical adhesive layer are in the form of a film and have thixotropic properties. The adhesive layer is formed from a material different from the first optical adhesive layer, the second optical adhesive layer, and the third optical adhesive layer, and does not have thixotropy. The metal layer is a mesh-shaped metal sheet that covers the entire non-display surface of the display panel and is provided between the third optical adhesive layer and the adhesive layer. Flexible display device.

2. The axial direction of the polarization axis of the polarizing plate is perpendicular to one direction in which the display panel can be folded. The flexible display device according to claim 1.

3. Each of the first optical adhesive layer, the second optical adhesive layer, and the third optical adhesive layer comprises a resin composition and an additive that imparts thixotropy. The flexible display device according to claim 1 or 2.

4. The additive consists of a sheet-like two-dimensional single crystal separated from a layered inorganic compound, and is dispersed within the resin composition. The flexible display device according to claim 3.

5. The aforementioned layered inorganic compound is one of montmorillonite, bentonite, hectorite, or octosilicate. The flexible display device according to claim 4.

6. The content of the two-dimensional single crystal in each of the first optical adhesive layer, the second optical adhesive layer, and the third optical adhesive layer is set to 0.1 to 30 weight percent. The flexible display device according to claim 4 or 5.

7. The length of the two-dimensional single crystal is 10 to 1000 nanometers, and the thickness of the two-dimensional single crystal is 1 to 1000 nanometers. The flexible display device according to any one of claims 4 to 6.

8. The thixotropy index values ​​of the first optical adhesive layer, the second optical adhesive layer, and the third optical adhesive layer are set to 1 to 1000. A flexible display device according to any one of claims 1 to 7.

9. The aforementioned display panel includes an organic light-emitting element, The flexible display device according to any one of claims 1 to 8.

10. The flexible display device according to claim 1, further comprising an impact-absorbing film disposed on the lower surface of the back plate.

11. A step of generating a display panel having a display surface and a non-display surface on the opposite side of the display surface, A step of providing a film-like first optical adhesive layer on the display surface of the display panel, A step of providing a polarizing plate on the first optical adhesive layer and bonding the display surface of the display panel and the polarizing plate using the first optical adhesive layer, The steps include providing a film-like second optical adhesive layer on the polarizing plate, A step of providing a cover window on the second optical adhesive layer and bonding the cover window and the polarizing plate using the second optical adhesive layer, A step of providing a film-like third optical adhesive layer beneath the non-display surface of the display panel, A step of providing a metal layer below the third optical adhesive layer to dissipate heat generated by the display panel, and bonding the display panel and the metal layer using the third optical adhesive layer, The step of providing an adhesive layer beneath the metal layer, A step of providing a back plate beneath the adhesive layer and bonding the metal layer and the back plate, Equipped with, The first optical adhesive layer, the second optical adhesive layer, and the third optical adhesive layer have thixotropic properties. The adhesive layer is formed from a material different from the first optical adhesive layer, the second optical adhesive layer, and the third optical adhesive layer, and does not have thixotropy. The metal layer is a mesh-shaped metal sheet that covers the entire non-display surface of the display panel and is provided between the third optical adhesive layer and the adhesive layer. A method for manufacturing a flexible container.

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