Display device

Abstract

The embodiment of the application discloses a display device; the display device comprises a display panel and an impact resistance layer, the impact resistance layer comprises at least two sub-layers, adjacent two sub-layers are bonded through a bonding layer, the at least two sub-layers comprise a first sub-layer and a second sub-layer between the first sub-layer and the display panel, the ratio of the elastic modulus of the first sub-layer to the elastic modulus of the second sub-layer is 20 to 300, and the material of the first sub-layer is different from the material of the second sub-layer; the application sets the impact resistance layer comprising at least two elastic modulus layers of high-low on the display panel, when the display device is impacted, the impact energy is transmitted in two ways of transverse and longitudinal as stress waves, the transverse stress wave is rapidly transmitted in the plane of the first sub-layer, the first sub-layer can rapidly absorb the horizontal stress wave through smaller strain, the second sub-layer is more prone to absorbing the impact energy through larger deformation, and the longitudinal stress wave is more easily reflected back to the first sub-layer.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of display, in particular to a display device. BACKGROUND

[0002] The service life and durability of the display device are important parameters of product quality. If the ability of the outermost protective cover plate of the display device to resist external impact cannot resist the impact force, especially for the outer folding display device, the display panel is closer to the outside world and is more likely to be impacted by foreign matter, knocking, falling and other impact tests to test the service life of the display device.

[0003] Therefore, there is an urgent need for a display device to solve the above technical problems. SUMMARY

[0004] The present application provides a display device which can improve the impact resistance of the current display device.

[0005] The present application provides a display device, comprising:

[0006] a display panel;

[0007] an impact-resistant layer disposed on the light-emitting side of the display panel;

[0008] wherein the impact-resistant layer comprises at least two sub-layers, adjacent two sub-layers are bonded by an adhesive layer, the at least two sub-layers comprise a first sub-layer and a second sub-layer located on the side of the first sub-layer close to the display panel, the ratio of the elastic modulus of the first sub-layer to the elastic modulus of the second sub-layer is 20 to 300, and the material of the first sub-layer is different from the material of the second sub-layer.

[0009] In some embodiments, the strain rate of the second sub-layer is less than or equal to 100 s -1 .

[0010] In some embodiments, the second sub-layer comprises any one of polyurethane, toluene diisocyanate, polydimethylsiloxane, cyclomethicone, aminosilicone, polymethylphenylsiloxane, and polyether polysiloxane copolymer.

[0011] In some embodiments, the thickness of the second sub-layer is greater than the thickness of the first sub-layer.

[0012] In some embodiments, the display device comprises a bending area and a flat area located on both sides of the bending area; the second sub-layer comprises a first part disposed in the bending area and a second part disposed in the flat area; wherein the elastic modulus of the first part is less than the elastic modulus of the second part.

[0013] In some embodiments, the impact-resistant layer further comprises a third sub-layer, the third sub-layer is located on the side of the second sub-layer away from the first sub-layer, and the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the second sub-layer is 20 to 300.

[0014] In some embodiments, the thickness of the third sub-layer is less than or equal to the thickness of the first sub-layer.

[0015] In some embodiments, the thickness of the third sub-layer is less than the thickness of the second sub-layer.

[0016] In some embodiments, the first sub-layer or the third sub-layer comprises any one of polyimide, polyethylene terephthalate, and acrylic.

[0017] In some embodiments, the impact-resistant layer further comprises a fourth sub-layer and a fifth sub-layer, the fourth sub-layer is located on the side of the third sub-layer away from the first sub-layer, and the fifth sub-layer is located on the side of the fourth sub-layer away from the first sub-layer; wherein the elastic modulus of the fifth sub-layer is greater than the elastic modulus of the fourth sub-layer, and the elastic modulus of the third sub-layer is greater than the elastic modulus of the fourth sub-layer.

[0018] In some embodiments, the ratio of the elastic modulus of the fifth sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300, and the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300.

[0019] In some embodiments, the elastic modulus of the fifth sub-layer is greater than the elastic modulus of the first sub-layer, and the elastic modulus of the fifth sub-layer is greater than the elastic modulus of the third sub-layer.

[0020] In some embodiments, the sum of the thickness of the third sub-layer and the thickness of the fifth sub-layer is less than or equal to the thickness of the first sub-layer.

[0021] In some embodiments, the thickness of the fourth sub-layer is greater than the thickness of the third sub-layer, and the thickness of the fourth sub-layer is greater than the thickness of the fifth sub-layer.

[0022] In some embodiments, the thickness of the fourth sub-layer is less than the thickness of the second sub-layer.

[0023] In some embodiments, the display device comprises a bending area and a planar area located on both sides of the bending area; the fourth sub-layer comprises a third part arranged in the bending area and a fourth part arranged in the planar area; wherein the elastic modulus of the third part is less than the elastic modulus of the fourth part.

[0024] In some embodiments, the strain rate of the fourth sub-layer is less than or equal to 100 s-1 .

[0025] The fourth sub-layer comprises any one of polyurethane, toluene diisocyanate, polydimethylsiloxane, cyclomethicone, aminosilicone, polymethylphenylsiloxane, polyether polysiloxane copolymer; the fifth sub-layer comprises any one of polyimide, polyethylene terephthalate, acrylic.

[0026] In some embodiments, the first sub-layer comprises a first layer and a second layer, the second layer is located on the side of the first layer close to the display panel; wherein the hardness of the first layer is greater than the hardness of the second layer.

[0027] The application has the following advantages: the display device is provided with an anti-impact layer comprising at least two layers of high and low elastic modulus, when the display device is impacted, the impact energy is transmitted in the form of stress waves in two directions, i.e. horizontally and vertically, the stress waves first contact the high elastic modulus film layer, the horizontal stress waves are quickly transmitted in the plane of the first sub-layer, the first sub-layer can quickly absorb the horizontal stress waves by small strain, the vertical stress waves continue to be transmitted inward in the direction perpendicular to the display device, when contacting the second sub-layer of low elastic modulus, the second sub-layer is more likely to absorb the impact energy by large deformation, at the same time, the stress waves are more likely to be transmitted in the film layer with large modulus, since the difference between the elastic modulus of the second sub-layer and the elastic modulus of the first sub-layer is large, the vertical stress waves are more likely to be reflected back to the first sub-layer, slowing down the trend of the vertical stress waves to further transmit inward in the direction perpendicular to the display device, which is more conducive to protecting the display panel and prolonging the service life of the display device. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0029] Figure 1 is a structural schematic diagram of a first structure of a display device provided by the embodiments of the present application;

[0030] Figure 2 is a structural schematic diagram of a second structure of a display device provided by the embodiments of the present application;

[0031] Figure 3 is a whole structural schematic diagram of a ball drop test of a display device provided by the embodiments of the present application;

[0032] Figure 4is a schematic diagram of propagation of an impact stress wave of a drop ball test of a display device in two different materials;

[0033] Figure 5 is a schematic diagram of propagation of a drop ball impact stress wave of a drop ball test of a display device in different stack designs;

[0034] Figure 6 is a schematic diagram of a test point arrangement of a drop ball test of a display device;

[0035] Figure 7 is a schematic diagram of drop ball impact mechanics simulation of a drop ball test of a display device;

[0036] Figure 8 is a schematic diagram of propagation of a stress wave of a drop ball test of a display device in two different directions inside the display device;

[0037] Figure 9 is a schematic diagram of a local structure of a bending area of a display device. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, but not all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application. In addition, it should be understood that the specific embodiments described herein are only used to illustrate and explain the present application, and are not used to limit the present application. In the present application, the orientation words such as "upper" and "lower" generally refer to the upper and lower of the device in the actual use or working state, and specifically refer to the direction of the drawing in the drawings; and "inner" and "outer" refer to the contour of the device.

[0039] The service life and durability of the display device are important parameters of product quality. If the ability of the outermost protective cover plate of the display device to resist external impact cannot resist the impact force, especially for the outer folding display device, the display panel is closer to the outside world and is more likely to be impacted by foreign matter, knocking, falling and other impact tests to test the service life of the display device.

[0040] Please refer to Figures 1 to 9 The display device 100 provided by the embodiments of the present application comprises:

[0041] a display panel 200;

[0042] an impact-resistant layer 300 arranged on the light-emitting side of the display panel 200;

[0043] The anti-impact layer 300 comprises at least two sub-layers, and adjacent two of the sub-layers are bonded by a bonding layer 400. The at least two sub-layers comprise a first sub-layer 310 and a second sub-layer 320 located on a side of the first sub-layer 310 close to the display panel 200. The ratio of the elastic modulus of the first sub-layer 310 to the elastic modulus of the second sub-layer 320 is 20 to 300. The material of the first sub-layer 310 is different from the material of the second sub-layer 320.

[0044] The display device is impacted, and the impact energy is propagated in the form of stress waves in both horizontal and vertical directions. The stress waves first contact the high-elastic-modulus film layer. The horizontal stress waves are quickly propagated in the plane of the first sub-layer. The first sub-layer can quickly absorb the horizontal stress waves by a small strain. The vertical stress waves continue to be propagated inward in a direction perpendicular to the display device. When the vertical stress waves contact the second sub-layer of the low-elastic-modulus layer, the second sub-layer is more likely to absorb the impact energy by a large deformation. Meanwhile, the stress waves are more likely to be propagated in the film layer with a large modulus. Since the difference between the elastic modulus of the second sub-layer and the elastic modulus of the first sub-layer is large, the vertical stress waves are more likely to be reflected back to the first sub-layer, thereby slowing down the trend of the vertical stress waves to be further propagated inward in a direction perpendicular to the display device. This is more conducive to protecting the display panel and prolonging the service life of the display device.

[0045] The technical solutions of the present application will be described in detail in combination with specific embodiments.

[0046] In some embodiments, referring to Figure 1 , the anti-impact layer 300 further comprises a bonding layer 400 arranged between adjacent two of the sub-layers. For example, referring to Figure 1 , the anti-impact layer 300 further comprises a first bonding layer 410 arranged between the first sub-layer 310 and the second sub-layer 320 and a second bonding layer 420 arranged between the second sub-layer 320 and the third sub-layer 330. The bonding layer 400 can be an optical adhesive layer.

[0047] If the thickness of the anti-impact layer 300 is simply increased, the anti-impact capability can be improved, but the overall neutral layer of the display device 100 will be offset. Therefore, in order to make the neutral layer closer to the display panel 200, a thicker film layer needs to be arranged on the backlight side of the display panel 200. The overall thickness of the display device 100 will be increased, which is not conducive to the thinning of the display device 100 on the one hand and is not conducive to the bending of the display device 100 on the other hand.

[0048] Referring to Figure 1 ,4 When the display device 100 is subjected to external impact load or instantaneous impact, the outermost layer is first impacted, and the impact energy propagates in the form of stress waves inside the material layer, i.e., horizontally transversely (in-plane) and longitudinally (vertically in the thickness direction) along the film layer, including transverse stress waves and longitudinal stress waves.

[0049] Referring to Figure 3 The first sub-layer 310 of the uppermost layer has a higher modulus, and the transverse stress wave propagates rapidly in-plane. Compared with the thickness direction, the transverse material area size of the first sub-layer 310 is larger, and the transverse stress wave can be quickly absorbed by a smaller strain, i.e., the transverse impact stress wave is released or diffused to the far end of the impact area along with the in-plane vibration and deformation of the layer.

[0050] Referring to Figure 3 , Figure 5 The longitudinal stress wave continues to propagate along the thickness direction of the display device 100. Since the second sub-layer 320 has a lower modulus and is more easily deformed to absorb impact energy, the tendency of the longitudinal stress wave to further propagate in the thickness direction is reduced.

[0051] Referring to Figure 4 When the stress wave enters the low-modulus layer (the second sub-layer 320) from the high-modulus material layer (the first sub-layer 310), due to the difference in impedance characteristics of the two materials (similar to the light propagation characteristics of glass and water), reflection and transmission phenomena occur at the adjacent interface, i.e., the difference in stress wave conduction near the two film layers, the greater the difference in impedance of the two materials, the stronger the reflected wave, and the fewer the stress waves transmitted into the low-modulus layer, and the more the stress waves returned in the opposite direction.

[0052] Referring to Figure 5 Wave impedance is proportional to material density and wave speed, and wave speed is positively correlated with the modulus of the material itself. Stress waves are more easily propagated in film layers with a large modulus. Since the difference between the elastic modulus of the second sub-layer 320 and the elastic modulus of the first sub-layer 310 is large, the longitudinal stress wave is more easily reflected back to the first sub-layer 310. In the figure, I represents the stress wave, R represents the reflected wave, and T represents the transmitted wave.

[0053] If the difference between the elastic modulus of the second sub-layer 320 and the elastic modulus of the first sub-layer 310 is too small, it is not conducive to the reflection of the longitudinal stress wave back to the first sub-layer 310 to protect the display panel 200, which will result in more longitudinal stress waves penetrating the display device 100. If the difference between the elastic modulus of the second sub-layer 320 and the elastic modulus of the first sub-layer 310 is too large, i.e., the elastic modulus of the second sub-layer 320 is too small, for example, some OCA glue has a Kpa-level elastic modulus, and its own viscous flow characteristics make it difficult to dissipate and absorb impact energy by in-plane vibration when subjected to impact.

[0054] By setting the anti-impact layer 300 including at least two layers of high and low elastic modulus on the display panel 200, two main lines of anti-impact are formed, the service life of the display device 100 is prolonged, and for the folding display device 100, the elastic modulus of the second sub-layer 320 is smaller, which is beneficial to the bending of the display device 100.

[0055] Wherein, the elastic modulus is independent of humidity, and the elastic modulus of the material at room temperature (20-35℃) does not change significantly, so the definition of the elastic modulus in this paper is at room temperature (20-35℃).

[0056] In some embodiments, referring to Figure 3 , the display panel 200 includes a panel body 210, an encapsulation layer 220, and a touch layer 230.

[0057] Referring to Figure 2 , Figure 6 , Figure 7 , Figure 9 , the folding display device 100 is taken as an example to perform a drop ball test, and the anti-impact height of the drop ball 110 is tested according to the GB15763.2-2005 standard, wherein the drop ball 110 is a steel ball with a diameter of 20mm and a weight of 32g, 9 measurement points are selected at the same interval positions of the bending area 101 and the flat area 102 of the screen body, the test is passed through simulation, and the actual drop ball 110 impact experiment is referenced. By the method of finite element simulation, combined with the stress behavior of the display device 100 under impact load, the encapsulation layer 220 in the display panel 200 is determined as a failure point, according to the failure mechanism of the encapsulation layer 220, the finite element analysis method is used, and the maximum tensile strain of the encapsulation layer 220 is taken as the reference basis to verify and compare the differences, advantages and disadvantages of the anti-impact display device 100.

[0058] Referring to Figure 8 , combined with the above impact stress wave propagation principle, and through simulation experiment, it can be seen that when the anti-impact layer 300 bears the impact of the drop ball 110 or foreign matter, the stress wave first enters the first sub-layer 310 and is decomposed into horizontal transverse (in-plane) and longitudinal (vertical thickness direction) stress waves, wherein Figure 8 , in figure (a), the transverse (X direction) is tensile stress, and in Figure 8 , figure (b), the longitudinal (Y direction) is compression wave stress, and the transverse stress wave is gradually dissipated by vibration and deformation of the high elastic modulus material; the longitudinal stress wave is gradually dissipated by deformation absorption and blocking effect of the low elastic modulus material, so as to avoid too much stress wave from being transmitted to the display panel 200.

[0059] The simulation experiment of the comparative group and the experimental groups 1-10 is performed, wherein the elastic modulus of CPI (transparent polyimide) is 3500 Mpa, the elastic modulus of PET (polyethylene terephthalate) is 3500 Mpa, the elastic modulus of UTG (ultra-thin glass) is 70000 Mpa, the elastic modulus of TPU (thermoplastic polyurethane elastomer rubber) is 200 Mpa, and the elastic modulus of PDMS (polydimethylsiloxane) is 20 Mpa. The simulation specific conditions and results are shown in Table 1.

[0060] Table 1

[0061]

[0062] In the simulation results, the high-high elastic modulus double-layer structure impact-resistant layer 300 of the comparative group and the high-high elastic modulus double-layer structure impact-resistant layer 300 of the experimental groups 1-4 are compared. If the second sublayer 320 still maintains a high elastic modulus, the tensile strain (TFE tensile strain) of the packaging layer 220 of the display panel 200 is not obviously weakened, and the tensile strain results of the five groups of experiments are all above 0.8%, which has exceeded the failure limit value of the inorganic layer in the packaging layer 220, that is, the high-high elastic modulus double-layer structure cannot effectively reduce the intensity of the stress wave conducted in the longitudinal direction.

[0063] For the high-low elastic modulus double-layer structure impact-resistant layer 300 of the experimental groups 5 and 6, the elastic modulus of the first sublayer is greater than that of the second sublayer, and the elastic modulus of the second sublayer 320 is reduced, which has a significant weakening effect on the tensile strain of the packaging layer of the display panel 200, indicating that the impact-resistant layer 300 with high-low elastic modulus layers is beneficial to reducing the impact stress.

[0064] The comparison among the experimental group 5, the experimental group 6 and the experimental group 7 shows that the increase in the thickness of the low-modulus material has little contribution to the reduction of the stress wave intensity, and therefore the thickness is not a main factor affecting the reduction of the stress wave intensity. In addition, if the thickness is too high, the bending characteristics will be affected.

[0065] In some embodiments, the elastic modulus of the first sublayer is greater than that of the second sublayer, and the ratio of the elastic modulus of the first sublayer to the elastic modulus of the second sublayer is 20 to 300.

[0066] If the difference between the elastic modulus of the second sub-layer 320 and the elastic modulus of the first sub-layer 310 is too small, the elastic modulus of the second sub-layer is too large, which is not conducive to the reflection of the longitudinal stress wave back to the first sub-layer 310 to protect the display panel 200, and more longitudinal stress waves will penetrate into the display device 100; if the difference between the elastic modulus of the second sub-layer 320 and the elastic modulus of the first sub-layer 310 is too large, that is, the elastic modulus of the second sub-layer 320 is too small, for example, some OCA adhesive, the elastic modulus is Kpa level, and its own characteristic viscous flow characteristics make it difficult to dissipate and absorb impact energy through in-plane vibration when impacted; the ratio of the elastic modulus of the first sub-layer 310 to the elastic modulus of the second sub-layer 320 is 20 to 300, for example, the ratio of the static elastic modulus of the first sub-layer 310 to the static elastic modulus of the second sub-layer 320 is 20 to 300, for example, any one of 20, 50, 80, 100, 150, 200, 240, 250, 280, and 300.

[0067] In some embodiments, the strain rate of the second sub-layer 320 is less than or equal to 100 s -1 .

[0068] The greater the strain rate, the greater the increase in elastic modulus of the film layer when impacted. If the elastic modulus of the film layer increases significantly when impacted, for example, OCA adhesive, which is a high-molecular viscous material, is prone to modulus strengthening effect under different impact intensities, that is, the greater the impact intensity, the stronger the self-viscoelastic effect, which macroscopically manifests as an increase in instantaneous modulus, which will result in insufficient impedance to longitudinal stress waves.

[0069] The material of the second sub-layer 320 can be a stress rate (strain rate) independent layer material or a low stress (strain rate) material, that is, under impact load, the modulus of the layer material does not increase or the strength does not improve with the change of impact intensity; the modulus of the layer material can remain stable and uniform under impact load; or the modulus of the layer material decreases with the increase of impact intensity under impact load, so as to ensure that the elastic modulus of the second sub-layer 320 does not increase significantly when the display device 100 is subjected to strong impact, avoid the significant weakening of the ability of the second sub-layer 320 to absorb longitudinal stress waves, ensure the absorption of longitudinal stress waves, and hinder the propagation of stress waves.

[0070] Methods for measuring strain rate in a series of experiments to study the dynamic mechanical properties of materials include pendulum experiments (such as experiments with a strain rate of 10E0-10E2 / s), Hopkinson experiments (such as experiments with a strain rate of 10E2-10E4 / s), air cannons (such as experiments with a strain rate of 10E4-10E6 / s), etc. Only examples are given here, without specific limitations.

[0071] The experimental group 5 and the experimental group 8 are compared. The same thickness of the laminated material is unchanged. The strain rate independent material PDMS (polydimethylsiloxane) is compared with the strain rate increasing material TPU (thermoplastic polyurethane elastomer rubber). The strain of the packaging layer is reduced to about 0.5%. It is shown that the stress rate independent layer material or the low stress rate material is used as the second sub-layer 320, which is more conducive to reducing the impact stress.

[0072] In some embodiments, the strain rate of the second sub-layer 320 is 10s -1 ~100s -1 .

[0073] In some embodiments, the material of the second sub-layer 320 can be any one of polyurethane, toluene diisocyanate, polydimethylsiloxane, cyclo-methylsiloxane, aminosiloxane, polymethylphenylsiloxane, polyether polysiloxane copolymer, etc. Such materials are stress rate (strain rate) independent layer materials or low stress (strain rate) rate materials, that is, under the action of impact load, the modulus of the material does not increase or the strength does not increase with the change of impact strength. Such materials can also be modified and designed to have better chemical stability, electrical insulation, weather resistance, and hydrophobicity, and have high shear resistance, and can be used for a long time at -50°C to 200°C. At the same time, it has excellent physical properties such as moisture-proof insulation, damping, and shock absorption performance.

[0074] For example, an optically transparent elastomer material formed by coupling reaction of macromolecular polydimethylsiloxane end active groups with a curing agent has a light transmittance of greater than 93%, a refractive index of greater than 1.4%, and high dielectric properties, good elasticity, and an elongation rate of greater than 500%.

[0075] In some embodiments, the first sub-layer 310 can include any one of polyimide, CPI (transparent polyimide), PET (polyethylene terephthalate), and acrylic high-molecular high-elasticity modulus. Such materials have high elastic modulus, which is conducive to cooperating with the second sub-layer 320 to form a high-low elastic modulus film layer, and the reflection and transmission of vibration waves occur at the junction. The difference in stress wave conduction near the two film layers is greater, the reflected wave is stronger, the stress wave transmitted into the low modulus layer is less, and the stress wave returned in the opposite direction is more.

[0076] In some embodiments, please refer to Figure 2 The first sub-layer 310 includes a first layer 311 and a second layer 312, and the second layer 312 is located on the side of the first layer 311 close to the display panel 200. The hardness of the first layer 311 is greater than the hardness of the second layer 312.

[0077] The first sub-layer 310 is the outermost layer of the display device 100, and needs to have better wear and scratch resistance. Therefore, a high-molecular hardened layer can be arranged on the second layer 312. The thickness of the first layer 311 is 2 μm to 5 μm. The first layer 311 can be a coating material, such as polyurethane. The first sub-layer 310 has high modulus characteristics against impact stress, and also has scratch and wear resistance, thereby further prolonging the service life of the display device 100.

[0078] In some embodiments, the Mohs hardness of the first layer 311 is 6 to 7.

[0079] In some embodiments, referring to Figure 1 , the thickness of the second sub-layer 320 is greater than the thickness of the first sub-layer 310. The second sub-layer 320 has a lower elastic modulus, and is more conducive to absorbing longitudinal stress waves. By setting the thickness of the second sub-layer 320 to be relatively thick, the longitudinal stress waves can be more fully absorbed, the energy of the longitudinal stress waves passing through the second sub-layer 320 can be reduced, the absorption of the longitudinal stress waves can be ensured, and the propagation of the stress waves can be hindered, thereby prolonging the service life of the display device 100.

[0080] In some embodiments, the thickness of the first sub-layer 310 is 50 μm to 80 μm, and the thickness of the second sub-layer 320 is 100 μm to 200 μm. The elastic modulus of the first sub-layer 310 is 2000 Mpa to 6000 Mpa, and the elastic modulus of the second sub-layer 320 is 20 Mpa to 100 Mpa. The actual situation, such as the foldable structure of the display device 100, can be adjusted according to the size of the bending radius of the folding of the display device 100.

[0081] In some embodiments, referring to Figure 2 , the display device 100 includes a bending area 101 and a planar area 102 located on both sides of the bending area 101. The second sub-layer 320 includes a first part 321 arranged in the bending area 101 and a second part 322 arranged in the planar area 102. The elastic modulus of the first part 321 is less than the elastic modulus of the second part 322.

[0082] The display device 100 has a foldable structure, and the bending area 101 needs to have better bending performance. The second sub-layer 320 is a low-elasticity modulus film layer, which can be optimized for the bending performance of the bending area 101 on the basis of ensuring the impact resistance of the bending area 101. The elastic modulus of the first part 321 in the bending area 101 is further reduced to improve the bending performance of the bending area 101, thereby reducing the damage risk of the bending stress to the display panel 200 in the bending area 101, and prolonging the service life of the display device 100.

[0083] In some embodiments, the first portion 321 and the second portion 322 can be integrally arranged or separately arranged. If the first portion 321 and the second portion 322 are integrally arranged, the elastic modulus can be adjusted by adjusting the process conditions such as curing temperature and curing rate when the first portion 321 and the second portion 322 are formed, so as to realize the structure that the elastic modulus of the first portion 321 is less than the elastic modulus of the second portion 322.

[0084] In some embodiments, referring to Figure 1 、 Figure 2 , the anti-impact layer 300 further comprises a third sub-layer 330, the third sub-layer 330 is located on the side of the second sub-layer 320 away from the first sub-layer 310, and the elastic modulus of the third sub-layer 330 is greater than the elastic modulus of the second sub-layer 320.

[0085] The elastic modulus of the third sub-layer 330 is greater than the elastic modulus of the second sub-layer 320, the first sub-layer 310, the second sub-layer 320, and the third sub-layer 330 constitute a high-low-high elastic modulus structure, the third sub-layer 330 as a high elastic modulus film layer is more conducive to absorbing the stress wave passing through the second sub-layer 320, and as the third main line of defense against impact, it is more conducive to prolonging the service life of the display device 100.

[0086] In some embodiments, the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the second sub-layer is 20 to 300.

[0087] If the elastic modulus of the third sub-layer is too small, it is not conducive to the third sub-layer absorbing the longitudinal stress wave; if the difference between the elastic modulus of the second sub-layer and the elastic modulus of the third sub-layer is too large, that is, the elastic modulus of the third sub-layer is too large, it is not conducive to the bending performance of the display device, and the elastic modulus of the second sub-layer 320 is too small, for example, the elastic modulus of some OCA adhesive is Kpa level, and its own specific viscous flow characteristics make it difficult to dissipate and absorb impact energy by in-plane vibration when impacted; the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the second sub-layer is 20 to 300, for example, any one of 20, 50, 80, 100, 150, 200, 240, 250, 280, and 300.

[0088] In some embodiments, the elastic modulus of the third sub-layer 330 is 2000 Mpa to 6000 Mpa. The elastic modulus of the third sub-layer is large, which is conducive to the third sub-layer absorbing the longitudinal stress wave.

[0089] The experimental group 8 and the experimental group 9 are compared, a high modulus + a low modulus + a high modulus combination design is adopted, the strain of the packaging layer is reduced to about 0.42%, and it is indicated that the design combination is beneficial to effectively reducing the size of the impact stress wave.

[0090] In some embodiments, the elastic modulus of the third sub-layer 330 is greater than the elastic modulus of the first sub-layer 310. The third sub-layer 330 serves as a third main line of defense against impact and can have better impact resistance. For the foldable display device 100, the third sub-layer 330 has a higher elastic modulus, which is more conducive to reducing creases and improving the visual effect of the display device 100. The display panel 200 has a lower elastic modulus and is prone to warping when being attached. The third sub-layer 330 has a higher elastic modulus, which can enhance the attachment of the display panel 200 and ensure the flatness of the film layer of the display device 100.

[0091] In some embodiments, referring to Figure 1 、 Figure 2 , the thickness of the third sub-layer 330 is less than or equal to the thickness of the first sub-layer 310. If the thickness of the third sub-layer 330 is too large, the neutral layer of the display device 100 will move away from the display panel 200. If the neutral layer is to be kept close to the display panel 200, a thicker film layer needs to be provided on the backlight side of the display panel 200, which will increase the overall thickness of the display device 100. On the one hand, this is not conducive to the thinning of the display device 100, and on the other hand, for the foldable display device 100, a larger thickness of the display device 100 is also not conducive to the bending of the display device 100. Therefore, the thickness of the third sub-layer 330 is less than or equal to the thickness of the first sub-layer 310, which reduces the impact on the neutral layer of the display device 100 while ensuring the impact resistance of the third sub-layer 330, thereby ensuring the quality of the display device 100.

[0092] In some embodiments, referring to Figure 1 、 Figure 2 , the thickness of the third sub-layer 330 is less than the thickness of the second sub-layer 320. The second sub-layer 320 has a lower elastic modulus, which is more conducive to absorbing longitudinal stress waves. By setting the thickness of the second sub-layer 320 to be thicker, the longitudinal stress waves can be more fully absorbed, the energy of the longitudinal stress waves passing through the second sub-layer 320 can be reduced, the absorption of the longitudinal stress waves can be ensured, and the propagation of the stress waves can be hindered, thereby prolonging the service life of the display device 100.

[0093] In some embodiments, the third sub-layer 330 can include any one of polyimide, CPI (transparent polyimide), PET (polyethylene terephthalate), and acrylic-based polymer high elastic modulus. Such materials have a high elastic modulus, and the transverse stress wave propagates rapidly in the plane, and the transverse material area size is large, which is conducive to the release or diffusion of the transverse impact stress wave to the far end of the impact area with the layer plane vibration and deformation.

[0094] In some embodiments, the thickness of the third sub-layer 330 is 23 um to 50 um.

[0095] In some embodiments, referring to Figure 2 , the impact-resistant layer 300 further includes a fourth sub-layer 340 and a fifth sub-layer 350, the fourth sub-layer 340 is located on the side of the third sub-layer 330 away from the first sub-layer 310, and the fifth sub-layer 350 is located on the side of the fourth sub-layer 340 away from the first sub-layer 310; wherein the elastic modulus of the fifth sub-layer 350 is greater than that of the fourth sub-layer 340, and the elastic modulus of the third sub-layer 330 is greater than that of the fourth sub-layer 340.

[0096] The more the number of high and low elastic modulus film layers is stacked, the better the stress wave blocking effect in the vertical direction is. The impact-resistant layer 300 with high-low-high-low-high elastic modulus further improves the impact resistance of the impact-resistant layer 300. The working principle of the impact-resistant layer 300 with high-low-high-low-high elastic modulus is similar to that of the impact-resistant layer 300 with high-low-high elastic modulus.

[0097] The comparison between experimental group 9 and experimental group 10 shows that when the thickness of the entire impact-resistant layer 300 is not significantly changed, it is designed as a high modulus + a low modulus + a high modulus + a low modulus + a high modulus stack, and the strain of the packaging layer is reduced to about 0.41%. This indicates that the multi-layer combination design has improved, but not significantly, which shows that when the test height of the falling ball 110 is certain, a three-layer stack design is sufficient to absorb impact stress. However, if a product with better impact resistance is considered, a multi-layer stack design can be used while considering the bending performance.

[0098] In some embodiments, the number of sub-layers of the impact-resistant layer 300 can be more, such as six or seven layers, etc. This application does not list them one by one, but still needs to consider the balance of film layer thickness and bending performance, and set it according to the actual parameter requirements.

[0099] In some embodiments, the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300.

[0100] If the elastic modulus of the fourth sub-layer is too large, it is not conducive to the reflection of the longitudinal stress wave back to the third sub-layer to protect the display panel 200, and more longitudinal stress waves will penetrate into the display device 100; if the difference between the elastic modulus of the fourth sub-layer and the elastic modulus of the third sub-layer is too large, that is, the elastic modulus of the fourth sub-layer is too small, for example, some adhesive layers OCA glue, the elastic modulus is Kpa level, and its own unique viscous flow characteristics make it difficult to dissipate and absorb impact energy through in-plane vibration when subjected to impact; the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300, for example, any one of 20, 50, 80, 100, 150, 200, 240, 250, 280, and 300.

[0101] In some embodiments, the elastic modulus of the fourth sub-layer 340 is 20 Mpa to 100 Mpa.

[0102] If the elastic modulus of the fourth sub-layer is too large, it is not conducive to the reflection of the longitudinal stress wave back to the third sub-layer to protect the display panel 200, and more longitudinal stress waves will penetrate into the display device 100; if the difference between the elastic modulus of the fourth sub-layer and the elastic modulus of the third sub-layer is too large, that is, the elastic modulus of the fourth sub-layer is too small, for example, some adhesive layers OCA glue, the elastic modulus is Kpa level, and its own unique viscous flow characteristics make it difficult to dissipate and absorb impact energy through in-plane vibration when subjected to impact.

[0103] In some embodiments, the ratio of the elastic modulus of the fifth sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300.

[0104] If the elastic modulus of the fifth sub-layer is too small, it is not conducive to the absorption of the longitudinal stress wave by the fifth sub-layer; if the elastic modulus of the fifth sub-layer is too large, it is not conducive to the bending performance of the display device, and the elastic modulus of the fourth sub-layer is too small, for example, some adhesive layers OCA glue, the elastic modulus is Kpa level, and its own unique viscous flow characteristics make it difficult to dissipate and absorb impact energy through in-plane vibration when subjected to impact; the ratio of the elastic modulus of the fifth sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300, for example, any one of 20, 50, 80, 100, 150, 200, 240, 250, 280, and 300.

[0105] In some embodiments, the elastic modulus of the fifth sub-layer is 2000 Mpa to 6000 Mpa. The larger elastic modulus of the fifth sub-layer is conducive to the absorption of the longitudinal stress wave by the fifth sub-layer.

[0106] In some embodiments, the elastic modulus of the fifth sub-layer 350 is greater than the elastic modulus of the first sub-layer 310, and the elastic modulus of the fifth sub-layer 350 is greater than the elastic modulus of the third sub-layer 330. The fifth sub-layer 350 has better impact resistance, and for the foldable display device 100, the higher elastic modulus of the fifth sub-layer 350 is more conducive to reducing the crease and improving the visual effect of the display device 100; the elastic modulus of the display panel 200 is relatively low, and the display panel 200 is prone to warping when being attached, and the higher elastic modulus of the fifth sub-layer 350 can strengthen the attachment of the display panel 200 and ensure the flatness of the film layer of the display device 100.

[0107] In some embodiments, referring to Figure 2 , the sum of the thickness of the third sub-layer 330 and the thickness of the fifth sub-layer 350 is less than or equal to the thickness of the first sub-layer 310.

[0108] Specifically, the sum of the thickness of the third sub-layer 330 and the thickness of the fifth sub-layer 350 is less than or equal to the thickness of the second layer 312 of the first sub-layer 310. If the thickness of the third sub-layer 330 and the thickness of the fifth sub-layer 350 are too large, the neutral layer of the display device 100 will move away from the display panel 200, so the thickness of the third sub-layer 330 and the thickness of the fifth sub-layer 350 are less than or equal to the thickness of the first sub-layer 310, which reduces the influence on the neutral layer of the display device 100 on the basis of ensuring the impact resistance of the third sub-layer 330 and the fifth sub-layer 350, and ensures the quality of the display device 100.

[0109] In some embodiments, referring to Figure 2 , the thickness of the fourth sub-layer 340 is greater than the thickness of the third sub-layer 330, and the thickness of the fourth sub-layer 340 is greater than the thickness of the fifth sub-layer 350.

[0110] The elastic modulus of the fourth sub-layer 340 is relatively low, which is more conducive to absorbing the longitudinal stress wave. By setting the thickness of the fourth sub-layer 340 to be relatively thick, the longitudinal stress wave can be more fully absorbed, the energy of the longitudinal stress wave passing through the fourth sub-layer 340 can be reduced, the absorption of the longitudinal stress wave can be ensured, and the propagation of the stress wave can be hindered, thereby prolonging the service life of the display device 100.

[0111] In some embodiments, referring to Figure 2 , the thickness of the fourth sub-layer 340 is less than the thickness of the second sub-layer 320.

[0112] The fourth sub-layer 340 has a thickness greater than that of the second sub-layer 320, which can cause the neutral layer of the display device 100 to move away from the display panel 200. If the neutral layer is to be kept close to the display panel 200, a thicker film layer needs to be arranged on the backlight side of the display panel 200, which can increase the overall thickness of the display device 100. On the one hand, this is not conducive to the thinning of the display device 100. On the other hand, for a foldable display device 100, a larger thickness of the display device 100 is also not conducive to the bending of the display device 100. Therefore, the fourth sub-layer 340 has a thickness less than that of the second sub-layer 320, which can reduce the impact on the neutral layer of the display device 100 while ensuring the impact resistance of the fourth sub-layer 340, and ensure the quality of the display device 100.

[0113] In some embodiments, the fourth sub-layer 340 has a thickness of 50 um to 150 um, and the fifth sub-layer 350 has a thickness of 15 um to 25 um.

[0114] In some embodiments, the fourth sub-layer has a strain rate less than or equal to 100 s -1 .

[0115] The greater the strain rate, the greater the increase in the elastic modulus of the film layer when it is impacted. If the elastic modulus of the film layer increases significantly when it is impacted, for example, the OCA adhesive is a high-molecular-viscous material, which can easily cause the modulus to strengthen under different impact intensities. That is, the greater the impact intensity, the stronger the viscoelastic effect, which can cause the instantaneous modulus to increase, resulting in insufficient resistance to longitudinal stress waves. The material of the fourth sub-layer can be a stress rate (strain rate) independent layer material or a low stress (strain rate) material, that is, under the action of impact load, the modulus of the layer material does not increase or the strength of the layer material does not increase with the increase of the impact intensity. The modulus of the layer material can remain stable and uniform under the impact load. Alternatively, the modulus of the layer material decreases with the increase of the impact intensity under the impact load, so that the elastic modulus of the fourth sub-layer does not increase significantly when the display device 100 is impacted, which can prevent the ability of the fourth sub-layer to absorb longitudinal stress waves from being significantly weakened, ensure the absorption of longitudinal stress waves, and hinder the propagation of stress waves.

[0116] Optionally, the strain rate of the fourth sub-layer is 10 s -1 ~ 100 s -1 .

[0117] In some embodiments, the material of the fourth sub-layer can be any one of polyurethane, toluene diisocyanate, polydimethylsiloxane, cyclomethicone, aminosilicone, polymethylphenylsiloxane, and polyether polysiloxane copolymer. Such material is a stress rate (strain rate) independent layer material or a low stress (strain rate) material, i.e., under the action of impact load, the modulus of the material does not increase or the strength does not increase with the change of impact strength. Such material can also have better chemical stability, electrical insulation, weather resistance, and hydrophobicity through modification design, and has high shear resistance, and can be used for a long time at -50°C to 200°C. At the same time, the material has excellent physical properties such as moisture-proof insulation, damping, and shock absorption performance.

[0118] In some embodiments, the fifth sub-layer can include any one of polyimide, CPI (transparent polyimide), PET (polyethylene terephthalate), and acrylic polymer high-elastic modulus. Such material has a high elastic modulus, and the transverse stress wave propagates rapidly in the plane. The material has a large area size in the transverse direction, which is beneficial to the release or diffusion of the transverse impact stress wave to the far end of the impact area with the in-plane vibration and deformation of the layer.

[0119] In some embodiments, referring to Figure 2 , the display device 100 includes a bending area 101 and a planar area 102 located on both sides of the bending area 101. The fourth sub-layer 340 includes a third part 341 arranged in the bending area 101 and a fourth part 342 arranged in the planar area 102. The elastic modulus of the third part 341 is less than that of the fourth part 342.

[0120] The display device 100 is a bendable structure, and the bending area 101 needs to have better bending performance. The fourth sub-layer 340 is a low-elasticity modulus film layer, which can optimize the bending performance of the bending area 101 on the basis of ensuring the impact resistance of the bending area 101. The elastic modulus of the third part 341 in the bending area 101 is further reduced to improve the bending performance of the bending area 101, thereby reducing the damage risk of the bending stress to the display panel 200 in the bending area 101 and prolonging the service life of the display device 100.

[0121] In some embodiments, referring to Figure 1 , Figure 2 , the impact-resistant layer 300 further includes a bonding layer 400 arranged between any two adjacent film layers of the first sub-layer 310, the second sub-layer 320, the third sub-layer 330, the fourth sub-layer 340, and the fifth sub-layer 350.

[0122] For example, referring to Figure 2The anti-impact layer 300 further comprises a first adhesive layer 410 arranged between the first sub-layer 310 and the second sub-layer 320, a second adhesive layer 420 arranged between the second sub-layer 320 and the third sub-layer 330, a third adhesive layer 430 arranged between the third sub-layer 330 and the fourth sub-layer 340, and a fourth adhesive layer 440 arranged between the fourth sub-layer 340 and the fifth sub-layer 350. The adhesive layer 400 can be an optical adhesive layer.

[0123] The optical adhesive material of the adhesive layer 400 can effectively absorb the bending strain of each film layer in the bending state, and divide the entire display device into multiple neutral layers, so that each layer of material is in a state of smaller stress and strain, thereby ensuring the bending performance. Figure 9 In some embodiments, the neutral layer is represented by a dashed line, so that each layer of material is in a state of smaller stress and strain, thereby ensuring the bending performance.

[0124] In some embodiments, the elastic modulus of any one of the first sub-layer 310, the second sub-layer 320, the third sub-layer 330, the fourth sub-layer 340, and the fifth sub-layer 350 is greater than the elastic modulus of any one of the first adhesive layer 410, the second adhesive layer 420, the third adhesive layer 430, and the fourth adhesive layer 440.

[0125] In some embodiments, the closer to the adhesive layer of the display panel 200, the higher the elastic modulus. For example, the elastic modulus of the second adhesive layer 420 is greater than the elastic modulus of the first sub-layer 310. Better impact resistance can be obtained; the elastic modulus of the display panel 200 is lower, and warping is easy to occur when being attached. The adhesive layer with higher elastic modulus is closer to the display panel 200, which can strengthen the attachment to the display panel 200 and ensure the flatness of the film layers of the display device 100.

[0126] In some embodiments, the display panel 200 can be a liquid crystal display panel 200 or a self-luminous display panel 200.

[0127] In some embodiments, the display panel 200 can be a liquid crystal display panel 200, and the display panel 200 further comprises a liquid crystal layer, a color film layer, and upper and lower polarizing layers. The display module further comprises a backlight unit corresponding to the display panel 200.

[0128] In some embodiments, the display panel 200 is a self-luminous display panel 200. The display panel 200 further comprises a light-emitting device layer.

[0129] In some embodiments, please refer to Figure 1The display panel 200 is a self-luminous display panel 200. The display device 100 further comprises a polarizing layer 360 arranged on the light-emitting side of the display panel 200. The polarizing layer 360 can also serve as a film layer in the anti-impact layer 300.

[0130] In some embodiments, the display device 100 further comprises a support layer 500 arranged on the side of the display panel 200 away from the light-emitting side. The support layer 500 comprises a first support sub-layer 510, a second support sub-layer 520 and a third support sub-layer 530. The first support sub-layer 510 can be a back plate material, such as an aluminum plastic plate. The second support sub-layer 520 can be a polymer material, such as PET. The third support sub-layer 530 can be a high-elasticity modulus material, such as stainless steel.

[0131] In some embodiments, the first support sub-layer 510, the second support sub-layer 520 and the third support sub-layer 530 can be connected by an adhesive layer.

[0132] In some embodiments, referring to Figure 1 , Figure 2 The third support sub-layer 530 can comprise a plurality of stress release holes 531 arranged in the bending area 101. The stress release holes 531 can penetrate the third support sub-layer 530 or not. The depth and density of the stress release holes 531 can be set according to actual conditions, which are not limited herein.

[0133] In some embodiments, referring to Figure 1 , Figure 2 The display device 100 further comprises a dustproof reinforcing layer 540 arranged on the side of the third support sub-layer 530 away from the display panel 200. The dustproof reinforcing layer 540 is arranged corresponding to the bending area 101.

[0134] The application sets the anti-impact layer including at least two elastic modulus layers on the display panel, when the display device is impacted, the impact energy spreads in the form of stress wave in the horizontal and vertical directions, the horizontal stress wave spreads in the first sub-layer, the first sub-layer can quickly absorb the horizontal stress wave by small strain, the vertical stress wave continues to spread in the direction perpendicular to the display device, when contacting the second sub-layer of the low elastic modulus layer, the second sub-layer is more likely to absorb the impact energy by large deformation, at the same time, the stress wave is more likely to spread in the film layer with large modulus, because the difference between the elastic modulus of the second sub-layer and the elastic modulus of the first sub-layer is large, the vertical stress wave is more likely to be reflected back to the first sub-layer, slowing down the trend of the vertical stress wave further spreading in the direction perpendicular to the display device, which is more conducive to protecting the display panel and prolonging the service life of the display device.

[0135] The embodiment of the application discloses a display device; the display device includes a display panel and an anti-impact layer, the anti-impact layer includes at least two sub-layers, the adjacent two sub-layers are bonded by a bonding layer, the at least two sub-layers include a first sub-layer and a second sub-layer between the first sub-layer and the display panel, the ratio of the elastic modulus of the first sub-layer to the elastic modulus of the second sub-layer is 20 to 300, the material of the first sub-layer is different from the material of the second sub-layer; the application sets the anti-impact layer including at least two elastic modulus layers on the display panel, when the display device is impacted, the impact energy spreads in the form of stress wave in the horizontal and vertical directions, the horizontal stress wave spreads in the first sub-layer, the first sub-layer can quickly absorb the horizontal stress wave by small strain, the second sub-layer is more likely to absorb the impact energy by large deformation, and the vertical stress wave is more likely to be reflected back to the first sub-layer.

[0136] The above describes the display device provided by the embodiment of the application in detail, the principle and implementation mode of the application are described by applying specific examples in this paper, and the above embodiment is only used to help understand the method and core idea of the application; at the same time, for those skilled in the art, according to the idea of the application, the specific implementation mode and application range will be changed, and the above description should not be understood as the limitation of the application.

Claims

1. A display device, characterized by comprising: The display device comprises: a display panel; an impact-resistant layer arranged on the light-emitting side of the display panel; wherein the impact-resistant layer comprises at least two sub-layers, adjacent two of the sub-layers are bonded by an adhesive layer, the at least two sub-layers comprise a first sub-layer, a second sub-layer located on the side of the first sub-layer close to the display panel, and a third sub-layer located on the side of the second sub-layer away from the first sub-layer, the first sub-layer and the second sub-layer are directly bonded by the adhesive layer, the ratio of the elastic modulus of the first sub-layer to the elastic modulus of the second sub-layer is 20 to 300, the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the second sub-layer is 20 to 300, the first sub-layer and the third sub-layer each comprise any one of polyimide, polyethylene terephthalate, and an acrylic material, and the second sub-layer comprises any one of polyurethane, toluene diisocyanate, polydimethylsiloxane, cyclo-methylsiloxane, amino-siloxane, polymethylphenylsiloxane, and polyether polysiloxane copolymer.

2. The display device according to claim 1, wherein the second sub-layer has a strain rate less than or equal to 100 s -1 .

3. The display device according to claim 1, wherein The thickness of the second sub-layer is greater than the thickness of the first sub-layer.

4. The display device according to claim 1, wherein The display device comprises a bending area and a planar area located on both sides of the bending area; The second sub-layer comprises a first part arranged in the bending area and a second part arranged in the planar area; wherein the elastic modulus of the first part is less than the elastic modulus of the second part.

5. The display device according to claim 4, wherein The elastic modulus of the third sub-layer is greater than the elastic modulus of the first sub-layer.

6. The display device according to claim 4, wherein The thickness of the third sub-layer is less than or equal to the thickness of the first sub-layer.

7. The display device according to claim 4, wherein The thickness of the third sub-layer is less than the thickness of the second sub-layer.

8. The display device according to claim 4, wherein The impact-resistant layer further comprises a fourth sub-layer and a fifth sub-layer, the fourth sub-layer is located on the side of the third sub-layer away from the first sub-layer, and the fifth sub-layer is located on the side of the fourth sub-layer away from the first sub-layer; wherein the elastic modulus of the fifth sub-layer is greater than the elastic modulus of the fourth sub-layer, and the elastic modulus of the third sub-layer is greater than the elastic modulus of the fourth sub-layer.

9. The display device according to claim 8, wherein The ratio of the elastic modulus of the fifth sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300, and the ratio of the elastic modulus of the third sub-layer to the elastic modulus of the fourth sub-layer is 20 to 300.

10. The display device according to claim 8, wherein The elastic modulus of the fifth sub-layer is greater than the elastic modulus of the first sub-layer, and the elastic modulus of the fifth sub-layer is greater than the elastic modulus of the third sub-layer.

11. The display device of claim 8, wherein, The sum of the thickness of the third sub-layer and the thickness of the fifth sub-layer is less than or equal to the thickness of the first sub-layer.

12. The display device of claim 8, wherein, The thickness of the fourth sub-layer is greater than the thickness of the third sub-layer, and the thickness of the fourth sub-layer is greater than the thickness of the fifth sub-layer.

13. The display device of claim 8, wherein, The thickness of the fourth sub-layer is less than the thickness of the second sub-layer.

14. The display device of claim 8, wherein, The display device comprises a bending area and a planar area located on both sides of the bending area; The fourth sub-layer comprises a third part arranged in the bending area and a fourth part arranged in the planar area; wherein the elastic modulus of the third part is less than the elastic modulus of the fourth part.

15. The display device of claim 8, wherein, the fourth sub-layer has a strain rate less than or equal to 100 s -1 .

16. The display device of claim 15, wherein, The fourth sub-layer comprises any one of polyurethane, toluene diisocyanate, polydimethylsiloxane, cyclomethicone, aminosilicone, polymethylphenylsiloxane, and polyether polysiloxane copolymer; The fifth sub-layer comprises any one of polyimide, polyethylene terephthalate, and acrylic.

17. The display device of claim 1, wherein The first sub-layer comprises a first layer and a second layer, and the second layer is located on the side of the first layer close to the display panel. The hardness of the first layer is greater than that of the second layer.

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