Display device

Abstract

A display device (191) is provided with a flexible display panel (3), and first and second support substrates (1, 2) for supporting the display panel (3). The display panel (3) has a display layer (51) including a self-luminous element, and a reinforcing layer (4) positioned closer to the first and second support substrates (1, 2) than the display layer (51). The reinforcing layer (4) includes a slit (7) for alleviating peeling stress during folding.

Description

display device

[0001] The present disclosure relates to a display device having a flexible display panel.

[0002] A foldable display including a flexible display panel equipped with, for example, an OLED (Organic Light Emitting Diode) or a QLED (Quantum Dot Light Emitting Diode) as a light-emitting element is known (Patent Document 1).

[0003] WO2022 / 070316 Brochure

[0004] However, when a foldable OLED module formed by stacking multiple film members is folded and bent into a tear drop shape, peeling between the laminated films occurs, particularly in the outer bending region.

[0005] An object of one aspect of the present disclosure is to provide a display device that can suppress peeling between laminated films in an outward bending region when folded and bent into a drop shape.

[0006] In order to solve the above-mentioned problems, the display device of the present disclosure comprises a flexible display panel and a support substrate that supports the display panel, the display panel having a light-emitting layer including self-luminous elements and a reinforcing layer that is located closer to the support substrate than the light-emitting layer, and the reinforcing layer includes a stress relaxation portion that relieves peel stress when folded.

[0007] One aspect of the present disclosure can provide a display device that can suppress peeling between laminated films in the outer curved region when folded and bent into a drop shape.

[0008] 1 is a cross-sectional view of a display device according to an embodiment; FIG. 2 is a flowchart illustrating an example of a manufacturing method of the display device; FIG. 3 is a cross-sectional view showing an example of the configuration of a display panel provided in the display device; FIG. 4 is a plan view of a reinforcing layer provided in the display device; FIG. 5 is a cross-sectional view showing a bent shape of the display device; FIG. 6 is an image showing slits formed in the reinforcing layer; FIG. 7 is a schematic view for explaining stress generated when the display device is bent; FIG. 8 is a view showing simulation results of stress generated when the display device is bent; FIG. 9 is an image for explaining a problem when a display device according to a comparative example is bent; FIG. 10 is an image showing lifting of an outer bent portion that occurs in the display device; FIG. 11 is an image showing peeling defects that occur in the display device; FIG. 12 is an image showing peeling defects that occur in the display device; FIG. 13 is a view showing simulation results of stress in a display device according to a comparative example; FIG. 14 is a view showing simulation results of stress in a display device according to an embodiment; FIG. 15 is a plan view of another reinforcing layer provided in the display device; FIG. 16 is a plan view of yet another reinforcing layer provided in the display device; FIG. 17 is a plan view of yet another reinforcing layer provided in the display device; FIG. 18 is a view showing an image of the bent shape of the display device.

[0009] 1 is a cross-sectional view showing a schematic configuration of a display device 101 according to an embodiment of the present disclosure. The display device 101 includes a first support substrate 1, a second support substrate 2, a display panel 3, a reinforcing plate 6, a cushioning material 5, and a hinge 30.

[0010] The first support substrate 1 and the second support substrate 2 support the display panel 3. Specifically, the first support substrate 1 and the second support substrate 2 are substrates that support the display panel 3, the reinforcing plate 6, the cushioning material 5, etc. The first support substrate 1 and the second support substrate 2 may each be part of the housing of the display device 101. The second support substrate 2 is positioned with a gap between them.

[0011] The display panel 3 has a reinforcing layer 4, a display layer 51, a touch panel 52, a polarizing plate 53, and a window film 54. The display panel 3 is located above the first support substrate 1 and the second support substrate 2. The display panel 3 is flexible. The display layer 51 may include an OLED (organic light-emitting diode) or a QLED (quantum dot light-emitting diode). The display layer 51 and the touch panel 52 are bonded together with an adhesive 55. The touch panel 52 and the polarizing plate 53 are bonded together with an adhesive 56. The polarizing plate 53 and the window film 54 are bonded together with an adhesive 57. An example of each of the adhesives 55 to 57 is OCA (optically transparent adhesive).

[0012] The touch panel 52 may include an electrode layer for touch operation. The touch panel 52 may be built into the display layer 51. The polarizing plate 53 may have a function of improving the reflection characteristics within the display device 101 of external light that has entered the display device 101. The polarizing plate 53 may be of a vapor deposition type. The window film 54 may have scratch resistance, anti-reflection, and anti-fouling functions for the display device 101.

[0013] As described above, the display device 101 includes a flexible display panel 3, and a first support substrate 1 and a second support substrate 2 (support substrates) that support the display panel 3. The display panel 3 has a display layer 51 including OLEDs (self-light-emitting elements), and a reinforcing layer 4 that is located closer to the first support substrate 1 and the second support substrate 2 than the display layer 51. Therefore, the reinforcing layer 4 is a layer that is included in the display panel 3. Therefore, the configuration of this embodiment is completely different from the configuration of the prior application (PCT / JP2024 / 006689) by the present inventors, in which the display panel 3 is left untouched and slits are made in a member (reinforcing plate 6) that is not included in the display panel 3.

[0014] Fig. 2 is a flowchart showing an example of a method for manufacturing the display device 101. Fig. 3 is a cross-sectional view showing an example of the configuration of the display layer 51, etc. of the display panel 3 provided in the display device 101. Components similar to those described above are given the same reference numerals, and detailed description thereof will not be repeated.

[0015] When manufacturing a flexible display device, as shown in Figures 2 and 3, first, a resin layer 31 is formed on a light-transmitting support substrate (e.g., mother glass) (Step S1). Next, a barrier layer 32 is formed (Step S2). Next, a TFT layer 33 is formed (Step S3). Next, a top-emission light-emitting element layer 34 (light-emitting layer) is formed (Step S4). Next, a sealing layer 35 is formed (Step S5). Next, a top film is attached to the sealing layer 35 (Step S6).

[0016] Here, the resin layer 31, the barrier layer 32, the TFT layer 33, the light emitting element layer 34, and the sealing layer 35 constitute a display layer 51 shown in FIG.

[0017] Next, the support substrate is peeled off from the resin layer 31 by irradiation with laser light or the like (step S7). Next, the reinforcing layer 4 is attached to the lower surface of the resin layer 31 (step S8). Next, the laminate including the reinforcing layer 4, resin layer 31, barrier layer 32, TFT layer 33, light-emitting element layer 34, and sealing layer 35 is divided into a plurality of individual pieces (step S9). Next, a functional film 39 is attached to the obtained individual pieces (step S10).

[0018] Here, the functional film 39 includes the touch panel 52, the polarizing plate 53, and the window film 54 shown in FIG.

[0019] Next, an electronic circuit board (e.g., an IC chip and an FPC) is mounted on a part (terminal portion) outside the display area (non-display area, frame) where the plurality of sub-pixels are formed (step S11). Steps S1 to S11 are performed by a display device manufacturing apparatus (including a film forming apparatus that performs each of steps S1 to S5).

[0020] Examples of materials for the resin layer 31 include polyimide, etc. The resin layer 31 can also be replaced with two layers of resin films (for example, polyimide films) and an inorganic insulating film sandwiched between them.

[0021] The barrier layer 32 is a layer that prevents foreign substances such as water and oxygen from penetrating into the TFT layer 33 and the light-emitting element layer 34, and can be composed of, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminated film of these, formed by the CVD method.

[0022] The TFT layer 33 includes a semiconductor film 15, an inorganic insulating film 16 (gate insulating film) above the semiconductor film 15, a gate electrode GE and a gate wiring GH above the inorganic insulating film 16, an inorganic insulating film 18 above the gate electrode GE and the gate wiring GH, a capacitance electrode CE above the inorganic insulating film 18, an inorganic insulating film 20 above the capacitance electrode CE, a source wiring SH above the inorganic insulating film 20, and a planarization film 21 above the source wiring SH.

[0023] The semiconductor film 15 is made of, for example, low-temperature polysilicon (LTPS) or an oxide semiconductor (for example, an In—Ga—Zn—O-based semiconductor), and a transistor (TFT) is configured to include the semiconductor film 15 and a gate electrode GE. In FIG. 3, the transistor is shown as having a top-gate structure, but it may also have a bottom-gate structure.

[0024] The gate electrode GE, the gate wiring GH, the capacitance electrode CE, and the source wiring SH are each formed of a single layer or a multilayer film of a metal containing at least one of aluminum, tungsten, molybdenum, tantalum, chromium, titanium, and copper, for example. The TFT layer 33 may include one semiconductor layer and three metal layers (a first metal layer, a second metal layer, and a third metal layer).

[0025] The inorganic insulating films 16, 18, and 20 can be formed, for example, by a silicon oxide (SiOx) film, a silicon nitride (SiNx) film, or a laminated film of these, formed by a CVD method. The planarizing film 21 can be formed, for example, by a coatable organic material such as polyimide or acrylic.

[0026] The light-emitting element layer 34 includes an anode 22 above the planarizing film 21, an insulating edge cover 23 that covers the edge of the anode 22, an EL (electroluminescence) layer 24 above the edge cover 23, and a cathode 25 above the EL layer 24. The edge cover 23 is formed by applying an organic material such as polyimide or acrylic and then patterning it by photolithography.

[0027] For each subpixel, a light-emitting element ES (e.g., OLED: organic light-emitting diode, QLED: quantum dot light-emitting diode) including an island-shaped anode 22, an EL layer 24, and a cathode 25 is formed in the light-emitting element layer 34, a control circuit for the light-emitting element ES is formed in the TFT layer 4, and the light-emitting element and its control circuit constitute a subpixel circuit.

[0028] The EL layer 24 is formed, for example, by stacking, from bottom to top, a hole injection layer, a hole transport layer, an EL light-emitting layer, an electron transport layer, and an electron injection layer. The EL light-emitting layer is formed in an island shape in each opening (for each subpixel) by vapor deposition or inkjet printing. The other layers are formed in an island shape or a solid shape (common layer edge cover 23). It is also possible to have a configuration in which one or more of the hole injection layer, hole transport layer, electron transport layer, and electron injection layer are not formed.

[0029] When forming the EL layer of an OLED by vapor deposition, a fine metal mask (FMM) is used. The FMM is a sheet (made of, for example, Invar) with many openings, and an island-shaped EL layer (corresponding to one sub-pixel) is formed by organic material passing through one opening.

[0030] The EL light-emitting layer of a QLED can be formed into an island-shaped EL light-emitting layer (corresponding to one sub-pixel) by, for example, inkjet coating a solvent in which quantum dots have been dispersed.

[0031] The anode 22 is a reflective electrode, and is made of a laminate of, for example, ITO (indium tin oxide) and Ag (silver) or an alloy containing Ag. The cathode 25 can be made of a transparent conductive material such as an MgAg alloy (ultra-thin film), ITO, or IZO (indium zinc oxide).

[0032] When the light-emitting element ES is an OLED, holes and electrons recombine in the EL light-emitting layer due to the driving current between the anode 22 and the cathode 25, and light is emitted in the process of the resulting excitons transitioning to the ground state. Because the cathode 25 is light-transmitting and the anode 22 is light-reflective, the light emitted from the EL layer 24 travels upward, resulting in top emission.

[0033] When the light-emitting element ES is a QLED, the driving current between the anode 22 and the cathode 25 causes holes and electrons to recombine in the EL light-emitting layer, and the resulting excitons emit light (fluorescence) as they transition from the conduction band level of the quantum dot to the valence band level.

[0034] The light emitting element layer 34 may include light emitting elements (inorganic light emitting diodes, etc.) other than the above-described OLEDs and QLEDs.

[0035] The sealing layer 35 is light-transmitting, and includes an inorganic sealing film 26 that covers the cathode 25, an organic buffer film 27 that is above the inorganic sealing film 26, and an inorganic sealing film 28 that is above the organic buffer film 27. The sealing layer 35 that covers the light-emitting element layer 34 prevents foreign substances such as water and oxygen from penetrating into the light-emitting element layer 34.

[0036] The inorganic sealing films 26 and 28 are each an inorganic insulating film, and may be formed, for example, by a CVD method using a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a laminate film of these. The organic buffer film 27 is a light-transmitting organic film with a planarizing effect, and may be formed from a coatable organic material such as acrylic. The organic buffer film 27 may be formed, for example, by inkjet coating, and a bank for stopping droplets may be provided in the non-display area.

[0037] The reinforcing layer 4 is, for example, a PET film that is attached to the lower surface of the resin layer 31 after the support substrate has been peeled off, thereby realizing a display device with excellent flexibility. This "lower film" is a film that is attached to the lower surface of the resin layer 31 provided on the display layer 51, and is a film that is cut when the panel is cut (singulated). In this embodiment, as will be described in detail with reference to FIG. 4 and subsequent figures, a slit 7 is provided in the bending region of this "lower film."

[0038] Fig. 4 is a plan view of the reinforcing layer 4 provided in the display device 101. Fig. 5 is a cross-sectional view showing the bent shape of the display device 101. Fig. 6 is an image showing the slits 7 formed in the reinforcing layer 4. Components similar to those described above are given the same reference numerals, and detailed descriptions thereof will not be repeated.

[0039] The reinforcing layer 4 includes slits 7 (stress relief portions) that relieve peel stress during folding. The slits 7 may penetrate the reinforcing layer 4. The display panel 3 further includes an adhesive 59 (adhesive layer) adjacent to the reinforcing layer 4 on the display layer 51 side. The slits 7 may extend to the adhesive 59.

[0040] 1 , the slits 7 penetrate the reinforcing layer 4. The slits 7 may penetrate the reinforcing layer 4 and reach the inside of the adhesive material 59. The slits 7 that penetrate the reinforcing layer 4 are closed by the adhesive material 60. The slits 7 do not have to penetrate the reinforcing layer 4.

[0041] The reinforcing layer 4 serves as a support for the display layer 51 and includes a back protection film (BPF). The reinforcing layer 4 includes a resin. The reinforcing layer 4 can be made of PET (Polyethylene Terephthalate) or PI (Polyimide). The reinforcing layer 4 has a thickness of 30 μm, and the display layer 51 has a thickness of approximately 5 μm. The reinforcing plate 6 is made of metal (SUS).

[0042] The reinforcing layer 4 has a first end 8 and a second end 9, and can be bent so that the first end 8 and the second end 9 face each other, as shown in Fig. 5 . In a plan view of the reinforcing layer 4, if the direction connecting the first end 8 and the second end 9 is defined as the longitudinal direction and the direction perpendicular to this longitudinal direction is defined as the width direction, the slits 7 traverse the reinforcing layer 4 along the width direction in a plan view, as shown in Fig. 4 . That is, the slits 7 are preferably formed continuously along the width direction from one side to the other side of the reinforcing layer 4 in a plan view of the reinforcing layer 4. The slits 7 are formed in a straight, zigzag, or dashed line shape.

[0043] The display panel 3 has an inwardly bent region R3 that forms a valley fold when viewed from the display surface 13, and a first outwardly bent region R1 located on a first end 8 side of the inwardly bent region R3 and a second outwardly bent region R2 located on a second end 9 side of the inwardly bent region R3. The first outwardly bent region R1, the second outwardly bent region R2, or both, form a mountain fold when viewed from the display surface 13. Slits 7 (stress relief portions) are formed in the first outwardly bent region R1, the second outwardly bent region R2, or both. Multiple slits 7 (stress relief portions) are formed in the first outwardly bent region R1, the second outwardly bent region R2, or both. In the example shown in FIG. 4 , one slit 7 is formed in the first outwardly bent region R1, and one slit 7 is formed in the second outwardly bent region R2, for a total of two slits 7. The slits 7 are formed by attaching the reinforcing layer 4 to the resin layer 31 of the display layer 51 and then melting a portion of the reinforcing layer 4 with a laser.

[0044] The reinforcing layer 4 includes a bending region that includes a first outer bending region R1 and a second outer bending region R2 and bends around a bending center when bent, and non-bending regions that are arranged on both sides of the bending region and do not bend when bent.

[0045] It is easier to provide slits 7 in the reinforcing layer 4 than in the reinforcing plate 6. It is also preferable to configure the display device 101 without the reinforcing plate 6. In order to alleviate peeling stress that makes the internal layers of the display panel 3 more likely to peel off, it is preferable to provide slits 7 for alleviating the peeling stress in the reinforcing layer 4, which is closer to the display layer 51 than the reinforcing plate 6.

[0046] The width of the slit 7 in plan view is preferably 2 mm or more and 10 mm or less.

[0047] FIG. 7 is a schematic diagram for explaining the stress generated when the display device 101 is bent. FIG. 8 is a diagram showing the results of a simulation of the stress generated when the display device 101 is bent. FIG. 9 is an image for explaining the problem when the display device according to the comparative example is bent. FIG. 10 is an image showing lifting of the outer bent portion that occurs in the display device. FIGS. 11 and 12 are images showing peeling defects that occur in the display device. Components similar to those described above are assigned the same reference numerals, and detailed descriptions thereof will not be repeated.

[0048] A foldable OLED module including a display panel 3 constructed by laminating multiple film members including a display layer 51, a touch panel 52, a polarizing plate 53, and a window film 54 has a problem of peeling between the laminated films when folded and bent into a tear drop shape. In particular, as shown in Fig. 10, when folded, a mountain fold is formed as viewed from the display surface 13, and peeling occurs in a first outward bending region R1 located on the first end 8 side of the inward bending region R3, and in a second outward bending region R2 located on the second end 9 side of the inward bending region R3.

[0049] As shown in FIG. 7, the tear drop shape includes an inner bent region R3 to which a compressive stress is applied and first and second outer bent regions R1 and R2 to which a peeling stress F3 is applied.

[0050] In a foldable OLED, stress is absorbed and alleviated by adhesives 55, 56, 57, 58, 59, and 60, which are OCAs. However, if the components of the foldable OLED contain non-stretchable materials (e.g., SUS (stainless steel) or glass), stress (particularly peel stress F3 in the first and second outer bending regions R1 and R2) increases, causing peeling of the display layer 51 including the OLED and peeling of the OCA.

[0051] If components are made solely from highly elastic materials, bending resistance is improved, but impact resistance to input devices such as pens and balls is significantly reduced (because the softness causes the impact to be concentrated at one point). In contrast, if stainless steel or glass is used for the components, the impact on the OLED changes from a point to a surface, improving impact resistance. In this way, bending resistance and impact resistance are in a trade-off relationship.

[0052] When the foldable OLED module is folded and bent into a U-shape, the first and second outer bending regions R1 and R2 are not present, so the peeling problem does not occur, but the bent shape becomes larger, and the product mechanism becomes larger than a tear drop shape.

[0053] As shown in FIGS. 9 and 10, when the foldable OLED is bent in a tear drop shape, there is an inner bent region R3 to which compressive stress is applied and first and second outer bent regions R1 and R2 to which peel stress is applied.

[0054] The OCA absorbs and relieves stress, but if the components are made of non-stretchable materials (e.g., SUS or Glass), the stress (especially the peeling stress in the first and second outer bending regions R1 and R2) increases, causing peeling of the OLED layer and peeling of the OCA, as shown in Figures 11 and 12.

[0055] Therefore, in this embodiment, slits 7 are provided in the first and second outward bending regions R1 and R2 of the reinforcing layer 4, which includes the BPF of the display panel 3. The presence of slits 7 in the reinforcing layer 4 can alleviate the peel stress applied to the OLED layer and OCA. Two or more slits 7 are provided somewhere in the bending boundary region, including the inward bending region R3. The shape of the slits 7 may be linear or patterned (perforated or diagonal (zigzag)). There are no restrictions on the width of the slits 7, but it is desirable that the width be 10 mm or less.

[0056] The depth of the slit 7 is equal to or less than the sum of the thickness of the reinforcing layer 4 and the thickness of the adhesive 59. For example, when the thickness of the reinforcing layer 4 is 50 μm and the thickness of the adhesive 59 is 25 μm, the depth of the slit 7 is 75 μm or less.

[0057] Fig. 13 is a diagram showing the results of a simulation of stress in a display device according to a comparative example. Fig. 14 is a diagram showing the results of a simulation of stress in the display device 101 according to the embodiment. Components similar to those described above are given the same reference numerals, and detailed description thereof will not be repeated.

[0058] In the display device according to the comparative example in which the slit 7 is not provided, as shown in FIG. 13, a compressive stress F1 acts on the inner bent region R3, and a peeling stress F2 acts on the second outer bent region R2.

[0059] In the display device 101 according to the embodiment in which a slit 7 is provided in the reinforcing layer 4, as shown in FIG. 14, a peel stress F3 that is relaxed to approximately 40% of the peel stress F2 acts on the second outer bending region R2.

[0060] Fig. 15 is a plan view of another reinforcing layer 4A provided in the display device 101. Figs. 16, 17, and 18 are plan views of further reinforcing layers 4B, 4C, and 4D provided in the display device 101, respectively. Components similar to those described above are given the same reference numerals, and detailed descriptions thereof will not be repeated.

[0061] 15, the display device 101 may include a reinforcing layer 4A instead of the reinforcing layer 4. The reinforcing layer 4A includes slits 7A that relieve peeling stress during folding. The slits 7A are linear, with two slits formed in the first outer bending region R1 and two in the second outer bending region R2, for a total of four slits. The width of the slits 7A is approximately 2 mm.

[0062] 16, the display device 101 may include a reinforcing layer 4B instead of the reinforcing layer 4. The reinforcing layer 4B includes slits 7B that relieve peeling stress during folding. The slits 7B are linear, with three slits formed in the first outer bending region R1 and three slits formed in the second outer bending region R2, for a total of six slits. The width of the slits 7B is approximately 2 mm.

[0063] 17, the display device 101 may include a reinforcing layer 4C instead of the reinforcing layer 4. The reinforcing layer 4C includes slits 7C that relieve peeling stress during folding. The slits 7C are perforated, and two slits are formed in total: one in the first outer bending region R1 and one in the second outer bending region R2. The width of the slits 7C is approximately 2 mm.

[0064] 18, the display device 101 may include a reinforcing layer 4D instead of the reinforcing layer 4. The reinforcing layer 4D includes slits 7D that relieve peeling stress during folding. The slits 7D are zigzag-shaped, with one slit in the first outer bending region R1 and one in the second outer bending region R2, for a total of two slits. The width of the slits 7D is approximately 2 mm.

[0065] 19 is a diagram showing an image of the bent shape of the display device 101. Components similar to those described above are given the same reference numerals, and detailed description thereof will not be repeated.

[0066] Table 1 shows the results of a bending test and an impact test for the display device 101 according to the embodiment and the display device according to the comparative example.

[0067] The display device 101 according to the embodiment is provided with slits 7 of the shapes, numbers, and widths shown in Table 1. The display device according to the comparative example is not provided with slits 7. The cushion material 5 shown in FIG. 1 is made of 30 μm SUS (stainless steel).

[0068] As shown in FIG. 19, the inner radius of the inner bending region R3 of the display panel 3 folded and bent into a tear drop shape is about 2.5 mm, and the outer radii of the first and second outer bending regions R1 and R2 are about 10 mm.

[0069] As shown in Table 1, the display device of the comparative example in which no slit 7 was provided failed the bending test, but the display device 101 of the embodiment in which the slit 7 was provided in the reinforcing layer 4 obtained good results in the bending test, and the test results were consistent with the results of the stress simulation described above in Figures 13 and 14.

[0070] As shown in Table 1, similar results can be obtained by changing the shape, number, and width of the slits 7. However, as shown in Table 1, impact performance deteriorates when the width of the slits 7 exceeds 15 mm. For this reason, it is desirable to keep the width of the slits 7 at 10 mm or less.

[0071] The present disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present disclosure. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

[0072] REFERENCE SIGNS LIST 1 First support substrate 2 Second support substrate 3 Display panel 4 Reinforcement layer 5 Cushioning material 6 Reinforcement plate 7 Slit 8 First end 9 Second end R3 Inner bending region R1 First outer bending region R2 Second outer bending region 13 Display surface 34 Light emitting element layer (light emitting layer) 51 Display layer 59 Adhesive (adhesive layer)

Claims

1. A display device comprising: a flexible display panel; and a support substrate supporting the display panel; wherein the display panel has a light-emitting layer including self-luminous elements; and a reinforcing layer located closer to the support substrate than the light-emitting layer; and the reinforcing layer includes a stress relaxation portion that relieves peeling stress when folded.

2. The display device according to claim 1, wherein the stress relief portion includes a slit penetrating the reinforcing layer.

3. The display device according to claim 2, wherein the display panel further comprises an adhesive layer adjacent to the reinforcing layer on the side of the light-emitting layer, and the slit extends to the adhesive layer.

4. The display device according to claim 1, wherein the reinforcing layer includes a resin.

5. The display device described in claim 1, wherein the reinforcing layer has a first end and a second end and can be bent so that the first end and the second end face each other; in a planar view of the reinforcing layer, the direction connecting the first end and the second end is the longitudinal direction, and the direction perpendicular to the longitudinal direction is the width direction; and the stress relief portion traverses the reinforcing layer along the width direction in the planar view.

6. The display device according to claim 1, wherein the stress relaxation portion is formed in a straight line, a zigzag line, or a broken line.

7. The display device of claim 1, wherein the display panel has a first end and a second end, and can be bent so that the first end and the second end face each other; the display panel has an inner bending region that forms a valley fold when folded as seen from the display surface, and a first outer bending region that forms a mountain fold when folded as seen from the display surface, located on the first end side of the inner bending region, and a second outer bending region that forms a mountain fold when folded as seen from the display surface, located on the second end side of the inner bending region; and the stress relief portion is formed in the first outer bending region, the second outer bending region, or both.

8. The display device according to claim 7, wherein a plurality of the stress relaxation portions are formed in the first outer bending region, the second outer bending region, or both.

9. The display device according to claim 1, wherein the width of the stress relaxation portion in a plan view is 2 mm or more and 10 mm or less.

10. The display device according to claim 1, wherein the display panel further has a resin layer formed between the light-emitting layer and the reinforcing layer, and the reinforcing layer includes a back protection film attached to the surface of the resin layer opposite the light-emitting layer.

11. The display device according to claim 10, wherein the display panel further comprises: a barrier layer formed between the resin layer and the light-emitting layer; and a TFT layer formed between the barrier layer and the light-emitting layer.

Images