CN111446278B - Back membrane layer of flexible display device and flexible display device with same - Google Patents

Abstract

The invention discloses a back film layer of a flexible display device and the flexible display device with the same. The back film layer has oppositely disposed first and second surfaces, the first surface adapted to be disposed on the device layer to protect the device layer, at least a portion of the back film layer in the pliable region having a modulus of elasticity that is less than a modulus of elasticity of the back film layer in the non-pliable region. According to the back film layer, the back film layer is arranged on the device layer, so that the effects of isolating water and oxygen and protecting the device layer are achieved. Meanwhile, when the flexible display device is bent, the elastic modulus of at least one part of the back film layer in the bendable region is reduced, so that the stress to which the device layer is subjected is reduced, and the damage to the device layer is avoided.

Description

Back film layer of flexible display device and flexible display device having same

technical field

The invention relates to the display field, in particular to a back film layer of a flexible display device and a flexible display device having the same.

Background technique

In related technologies, with the continuous development of display technology, the trend of miniaturization and thinning of electronic products has gradually emerged, and OLED flexible display screens have developed rapidly driven by this. However, the devices of OLED flexible display screens are easily eroded by water and oxygen, resulting in damage to pixels and shortening the life of the device. At the same time, when the OLED flexible display screen is bent, the device is subject to greater stress, which in turn leads to damage to the device.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the prior art.

For this reason, the present invention proposes a back film layer of a flexible display device to reduce the stress on the device layer when the flexible display device is bent.

The present invention also proposes a flexible display device having the above-mentioned back film layer.

According to the back film layer of a flexible display device according to an embodiment of the present invention, the flexible display device has a bendable area and a non-bendable area, the flexible display device includes a device layer, and the back film layer has a first oppositely arranged surface and a second surface, the first surface is adapted to be arranged on the device layer to protect the device layer, and the elastic modulus of at least a part of the back film layer in the bendable region is smaller than the The modulus of elasticity of the back film layer in the non-flexible region.

According to the back film layer of the flexible display device according to the embodiment of the present invention, the back film layer is arranged on the device layer, so as to achieve the function of isolating water and oxygen and protecting the device layer. At the same time, when the flexible display device is bent, since the elastic modulus of at least a part of the back film layer in the bendable area is reduced, the stress on the device layer is reduced to avoid damage to the device layer.

In some embodiments of the present invention, the thickness of the back film layer in at least a part of the bendable region is smaller than the thickness of the back film layer in the non-bendable region.

In some embodiments of the present invention, in the bendable region, the second surface of the back film layer is provided with a concave portion that is concave toward the first surface.

In some embodiments of the present invention, the flexible display device is bent along a bending axis, and the extending direction of the concave portion is parallel to the extending direction of the bending axis.

In some embodiments of the present invention, a plurality of the depressions are arranged at intervals on the back film layer.

In some embodiments of the present invention, the depressions are a plurality of blind holes arranged at intervals on the back film layer.

In some embodiments of the present invention, the inner sidewall of the concave portion is formed as a transition surface extending obliquely.

In some embodiments of the present invention, the recessed portion is filled with a filler.

In some embodiments of the present invention, the back film layer includes a base layer and an adhesive layer, and the adhesive layer is disposed between the base layer and the device layer to adhere the base layer to the device layer, The depressed portion is disposed on the base layer.

The flexible display device according to the embodiment of the present invention includes: a back film layer and a device layer, the back film layer is the back film layer according to the above-mentioned embodiments of the present invention, and the device layer is arranged on the first surface .

According to the flexible display device of the embodiment of the present invention, the function of isolating water and oxygen and protecting the device layer is achieved by disposing the back film layer on the device layer. At the same time, when the flexible display device is bent, since the elastic modulus of at least a part of the back film layer in the bendable area is reduced, the stress on the device layer is reduced to avoid damage to the device layer.

In some embodiments of the present invention, the flexible display device further includes a substrate for maintaining the elastic recovery force of the flexible display device, and the substrate is connected to the second surface.

In some embodiments of the present invention, the device layer includes a flexible substrate, a metal wiring layer and a packaging layer arranged in sequence, and the flexible substrate is connected to the back film layer.

Additional aspects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.

Description of drawings

The above and/or additional aspects and advantages of the present invention will become apparent and understandable from the description of the embodiments in conjunction with the following drawings, wherein:

1 is a cross-sectional view of a flexible display device according to an embodiment of the present invention;

2 is a schematic diagram of a flexible display device according to some embodiments of the present invention;

3 is a schematic diagram of a flexible display device according to other embodiments of the present invention;

4 to 8 are schematic diagrams of back film layers according to different embodiments of the present invention;

9 to 12 are cross-sectional views of the back film layer at A-A in FIG. 8 according to different embodiments of the present invention;

13 is a partial cross-sectional view of a back film layer according to an embodiment of the present invention;

14 is a schematic diagram of a device layer according to an embodiment of the present invention;

Fig. 15 is a process flow diagram of a back film layer according to an embodiment of the present invention;

Fig. 16 is a schematic diagram of a flexible display device in a bent state according to some embodiments of the present invention;

Fig. 17 is a schematic diagram of a flexible display device in a bent state according to other embodiments of the present invention;

Figures 18 and 19 are line graphs of the stress on the device layer as the thickness of the back film layer changes according to an embodiment of the present invention;

Fig. 20 is a data table showing the variation of the stress on the device layer as the thickness of the back film layer changes according to an embodiment of the present invention;

FIG. 21 is a line graph showing the variation of the elastic modulus of the back film layer as the thickness of the back film layer varies according to an embodiment of the present invention.

Reference signs:

100. Flexible display device;

1. Back film layer; 11. Depression; 111. Blind hole; 112. Transition surface; 12. Base layer; 13. Adhesive layer;

2. Device layer; 21. Flexible substrate; 22. Metal wiring layer; 23. Packaging layer;

3. Polarizing layer;

4. Touch layer;

5. Insulation protective layer;

6. Bending axis;

7. Non-bendable area;

8. Bending area.

Detailed ways

Embodiments of the present invention are described in detail below, examples of which are shown in the drawings, wherein the same or similar reference numerals designate the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the figures are exemplary only for explaining the present invention and should not be construed as limiting the present invention.

In describing the present invention, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", " Back", "Left", "Right", "Vertical", "Horizontal", "Top", "Bottom", "Inner", "Outer", "Clockwise", "Counterclockwise", "Axial", The orientation or positional relationship indicated by "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying the referred device or element Must be in a particular orientation, be constructed in a particular orientation, and operate in a particular orientation, and therefore should not be construed as limiting the invention. In addition, the features defined as "first" and "second" may explicitly or implicitly include one or more of these features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

In the description of the present invention, it should be noted that unless otherwise specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection or a detachable connection. Connected, or integrally connected; it can be mechanically connected or electrically connected; it can be directly connected or indirectly connected through an intermediary, and it can be the internal communication of two components. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in specific situations.

The following describes the back film layer 1 of a flexible display device 100 according to an embodiment of the present invention with reference to FIGS. 1-21 . The flexible display device 100 has a bendable region 8 and a non-bendable region 7 . It can be understood that the flexible display device 100 achieves the purpose of displaying images by emitting light from the device layer 2 .

In some embodiments of the present invention, as shown in FIG. 2 to FIG. 8 , the bendable region 8 can be located in the middle of the flexible display device 100 , at the side, or arranged around the non-bendable region 8 , so that the flexible display device 100 Bending can take place at the bendable region 8 . It should be noted that the position of the bendable region 8 on the flexible display device 100 can be limited according to the actual usage, as long as the flexible display device 100 can be bent at the bendable region 8 , here The position of the bendable region 8 is not limited.

According to the back film layer 1 of the flexible display device 100 of the embodiment of the present invention, the back film layer 1 has a first surface and a second surface oppositely arranged, the first surface is suitable for being arranged on the device layer 2 to protect the device layer 2, and the back The elastic modulus of at least a part of the film layer 1 in the bendable region 8 is smaller than the elastic modulus of the back film layer 1 in the non-bendable region 7 .

It should be noted that by changing the elastic modulus of part of the back film layer 1 in the bendable region 8 and keeping the elastic modulus of another part of the back film layer 1 in the bendable region 8 unchanged, Alternatively, change the modulus of elasticity of the entire back film layer 1 in the bendable region 8, so that the elastic modulus of the back film layer 1 in the bendable region 8 is smaller than that of the back film layer 1 in the non-bendable region 7 for the purpose of the modulus of elasticity.

It can be understood that by setting the back film layer 1 on the device layer 2, the effect of isolating water and oxygen and protecting the device layer 2 can be achieved, so as to prevent the device layer 2 from being corroded by water and oxygen and cause pixel damage, thereby improving the performance of the device. Layer 2 lifetime.

At the same time, by making the elastic modulus of at least a part of the back film layer 1 in the bendable region 8 smaller than the elastic modulus of the back film layer 1 in the non-bendable region 7, on the one hand, it can ensure that the elastic modulus in the non-bendable region 7 is In order to better protect the device layer 2, the device layer 2 is prevented from being corroded by water and oxygen. On the other hand, when the flexible display device 100 is bent, since the elastic modulus of at least a part of the back film layer 1 in the bendable region 8 is reduced, the stress on the device layer 2 is reduced to avoid Damage to device layer 2.

It should be noted that the elastic modulus refers to the stress required for a material to produce unit elastic deformation under the action of an external force. It is an index that reflects the material's ability to resist elastic deformation. The elastic modulus can be regarded as an index to measure the difficulty of elastic deformation of the material. The larger the elastic modulus value, the greater the stress of the material for a certain elastic deformation, that is, the higher the material stiffness. Larger, that is, under a certain stress, the smaller the elastic deformation occurs, and then after reducing the elastic modulus of the back film layer 1, the stress required when the flexible display device 100 is bent is also correspondingly reduced, so that The stress on the device layer 2 is reduced, thereby avoiding damage to the device layer 2 . At the same time, the bending radius of the flexible display device 100 can be made smaller to improve user experience.

In some embodiments of the present invention, the elastic modulus of the part of the back film layer 1 can be changed by changing the material of at least a part of the back film layer 1 in the bendable region 8, so that the part of the back film layer 1 The film layer 1 is relatively soft, so that when the flexible display device 100 is bent, the stress on the device layer 2 is reduced, thereby avoiding damage to the device layer 2 .

As shown in FIG. 14, in some embodiments of the present invention, the device layer 2 includes a flexible base layer 12 (PI), a metal wiring layer 22 (BP+EL) and an encapsulation layer 23 (TFE) arranged in sequence. The flexible base layer 12 Connected to the first surface of the back film layer 1 , the metal wiring layer 22 is provided with the circuit structure of the flexible display device 100 , and the device layer 2 emits light through the encapsulation layer 23 to achieve the purpose of displaying images.

Furthermore, when the flexible display device 100 is bent, since the elastic modulus of at least a part of the back film layer 1 in the bendable region 8 is reduced, the stress on the device layer 2 is reduced, so that the flexibility can be avoided on the one hand. After the display device 100 is bent several times, the circuit structure in the metal wiring layer 22 is disconnected. On the other hand, when the flexible display device 100 is bent, the tensile force or extrusion force on the encapsulation layer 23 of the device layer 2 can be reduced to ensure that the encapsulation layer 23 will not be damaged or broken. The damage of the device layer 2 is avoided to improve the service life of the device layer 2 .

According to the back film layer 1 of the flexible display device 100 of the embodiment of the present invention, the back film layer 1 is arranged on the device layer 2 so as to isolate water and oxygen and protect the device layer 2 . At the same time, when the flexible display device 100 is bent, since the modulus of elasticity of at least a part of the back film layer 1 in the bendable region 8 is reduced, the stress on the device layer 2 is reduced to avoid the device layer 2 damage.

As shown in FIGS. 3 to 17 , in some embodiments of the present invention, the thickness of at least a part of the back film layer 1 in the bendable region 8 is smaller than the thickness of the back film layer 1 in the non-bendable region. It can be understood that by reducing the thickness of at least a part of the back film layer 1 in the bendable region 8, thereby reducing the modulus of elasticity of this part of the back film layer 1, so as to reduce the flexibility when the flexible display device 100 is bent. When the required stress is used, the stress on the device layer 2 is reduced, thereby avoiding damage to the device layer 2 .

It should be noted that when the thickness of the back film layer 1 decreases, the position of the neutral layer of the device layer 2 also shifts away from the back film layer 1, because the metal wiring layer 22 and the encapsulation layer 23 of the device layer 2 It is far away from the back film layer 1, so that the neutral layer of the device layer 2 moves toward the direction close to the encapsulation layer 23, so that when the flexible display device 100 is bent, the metal wiring layer 22 and the encapsulation layer 23 are subjected to The stress is also reduced accordingly, thereby avoiding damage to the device layer 2 .

Among them, the neutral layer can be understood as; during the bending process, one side of the material is subjected to tensile force, and the other side is subjected to extrusion force, and there must be a transition layer on its section that is neither stretched nor compressed. , the stress of the transition layer is almost equal to zero, and the closer to the transition layer, the smaller the tensile force and extrusion force are. This transition layer is called the neutral layer of the material.

For example, when the flexible display device 100 is bent outward, it is bent towards the direction close to the back film layer 1. At this time, the encapsulation layer 23 of the device layer 2 is subjected to a tensile force, and the flexible base layer 12 is subjected to a compressive force. When the flexible display device When the 100 is bent inward, it is bent in a direction away from the back film layer 1. At this time, the encapsulation layer 23 of the device layer 2 is subjected to a compressive force, and the flexible base layer 12 is subjected to a tensile force. Furthermore, when the neutral layer of the device layer 2 shifts away from the back film layer 1, that is, the neutral layer of the device layer 2 moves toward the direction close to the encapsulation layer 23, so that the metal wiring layer 22 and the encapsulation layer 23 The stress received when the flexible display device 100 is bent is also relatively reduced, thereby avoiding damage to the device layer 2 .

As shown in Figure 21, in some embodiments of the present invention, the elastic modulus of the back film layer 1 in the bendable region 8 is y, and the thickness of the back film layer 1 in the bendable region 8 is H , y≤0.0236H ³ -2.1284H ² -52.028H+7159, and then the thickness of the back film layer 1 in the bendable region 8 can be calculated according to the thickness change of the back film layer 1 in the bendable region 8 Elastic modulus, in order to achieve the purpose of controlling the elastic modulus of the back film layer 1 in the bendable region 8 .

As shown in Figure 16 to Figure 20, based on this, the present invention has carried out the experiment that the flexible display device 100 is bent outward by 90°, and it can be seen from Figure 20 that the stress on the device layer 2 varies with the thickness of the back film layer 1 change, when the thickness of the back film layer 1 does not change, the maximum tensile strains on the encapsulation layer 23 and the metal wiring layer 22 are 4.65‰ and 2.36‰ respectively, and the encapsulation layer 23 decreases with the thickness of the back film layer 1 23 and the metal wiring layer 22 are also gradually reduced in maximum tensile strain and maximum tensile stress. When the thickness of the back film layer 1 is reduced from 75um to 25um, the neutral layer of the device layer 2 is located in the metal wiring layer 22. At this time The tensile stress on the metal wiring layer 22 is relatively small, and the tensile strain on the packaging layer 23 is also reduced by about 44%. When the elastic modulus of the back film layer 1 is reduced from 5400MPa to 1000MPa, the neutral layer of the device layer 2 is also located in the metal wiring layer 22. At this time, the tensile stress on the metal wiring layer 22 is small, and the encapsulation layer 23 The tensile strain is reduced by about 50.5%.

When the thickness and elastic modulus of the back film layer 1 in the bendable region 8 satisfy the formula: y≤0.0236H ³ -2.1284H ² -52.028H+7159, and 10um≤H≤75um, the neutrality of the device layer 2 Layers are located in the metal wiring layer 22 or in the encapsulation layer 23, so reducing the thickness and elastic modulus of the back film layer 1 in the bendable region 8 can move the neutral layer of the device layer 2, so that the neutral layer of the device layer 2 The flexible layer is closer to the encapsulation layer 23 and the metal wiring layer 22, which can effectively reduce the stress and strain of the encapsulation layer 23 and the metal wiring layer 22, and reduce the risk of fracture of the flexible display device 100 when it is bent.

As shown in FIGS. 3 to 17 , in some embodiments of the present invention, in the bendable region 8 , the second surface of the back film layer 1 is provided with a concave portion 11 that is concave toward the first surface. It can be understood that by setting the recessed portion 11 on the back film layer 1, the thickness of the back film layer 1 in the bendable region 8 is reduced to reduce the thickness of the back film layer 1 in the bendable region 8. Elastic modulus, and then when the flexible display device 100 is bent, since the elastic modulus of the back film layer 1 in the bendable region 8 is reduced, the stress on the device layer 2 is reduced, so as to avoid the device Layer 2 damage.

Simultaneously, since the second surface of the back film layer 1 is sunken toward the first surface of the back film layer 1 for the recessed portion 11, the structure of the first surface of the back film layer 1 has not been changed to ensure the first surface of the back film layer 1 The cooperation between one surface and the device layer 2 is stable and reliable, so that the back film layer 1 can better protect the device layer 2 and prevent the device layer 2 from being corroded by water and oxygen.

In some embodiments of the present invention, the thickness of the back film layer 1 can be 75um, wherein the depth of the recessed part 11 is at least 55um, thereby reducing the elastic modulus of the back film layer 1 in the bendable region 8, so that the device layer 2 is subjected to reduced stress to avoid damage to the device layer 2 . It should be noted that the depth of the recessed portion 11 can be limited according to actual usage conditions. When the flexible display device 100 is bent, as long as the stress on the device layer 2 can be reduced, the depth of the recessed portion 11 is not limited here. Do limit.

In some embodiments of the present invention, in the bendable region 8, the second surface of the back film layer 1 is provided with a depression facing the first surface, so that the recessed part 11 is generally formed as a recess provided on the back film layer 1. slots, thereby reducing the thickness of the entire back film layer 1 in the bendable region 8, so as to reduce the elastic modulus of the back film layer 1 in the bendable region 8, and then when the flexible display device 100 is bent At this time, since the elastic modulus of the back film layer 1 in the bendable region 8 is reduced, the stress on the device layer 2 is reduced to avoid damage to the device layer 2 .

As shown in FIG. 4 and FIG. 16 , in some embodiments of the present invention, a plurality of depressions 11 are arranged at intervals on the back film layer 1 . It can be understood that, as shown in FIG. 7 , in the bendable area 8 , the back film layer 1 is provided with a plurality of recesses 11 at intervals, thereby reducing the thickness of the back film layer 1 partially in the bendable area 8 , to reduce the elastic modulus of the back film layer 1 partially in the bendable region 8, and then when the flexible display device 100 is bent, at least a part of the back film layer 1 in the bendable region 8 is reduced The elastic modulus, so that the stress on the device layer 2 is reduced to avoid damage to the device layer 2 .

In some embodiments of the present invention, the shape of the recessed portion 11 may be U-shaped, semi-circular, V-shaped or trapezoidal. It should be noted that the shape of the recessed portion 11 can be limited according to the actual use, as long as the thickness of at least a part of the back film layer 1 in the bendable region 8 can be reduced to reduce the thickness of the portion in the bendable region 8 . The modulus of elasticity of the back film layer 1 is sufficient, and the shape of the recessed portion 11 is not limited here.

As shown in FIG. 4 , FIG. 7 and FIG. 8 , in some embodiments of the present invention, the flexible display device 100 is bent along the bending axis 6 , and the extending direction of the concave portion 11 is parallel to the extending direction of the bending axis 6 . It can be understood that, in the length direction of the concave portion 11, the extending direction of the concave portion 11 is parallel to the axial direction of the bending axis 6, thereby reducing the elastic modulus at the concave portion 11 when the flexible display device 100 is bent. amount, thereby reducing the stress on the device layer 2 to avoid damage to the device layer 2.

As shown in FIGS. 8 to 12 , in some embodiments of the present invention, the recessed portion 11 is a plurality of blind holes 111 arranged at intervals on the back film layer 1 . It can be understood that the recessed portion 11 can be a plurality of blind holes 111 arranged at intervals on the back film layer 1, so as to reduce the thickness of at least a part of the back film layer 1 in the bendable region 8, so as to reduce the The elastic modulus of the back film layer 1 in the bending area 8, and then when the flexible display device 100 is bent, due to the reduction of the elastic modulus of the back film layer 1 in the bendable area 8, so that The stress on the device layer 2 is reduced to avoid damage to the device layer 2 .

As shown in FIGS. 8 to 12 , in some embodiments of the present invention, the shape of the blind hole 111 may be U-shaped, semicircular, V-shaped, or trapezoidal. It should be noted that the shape of the blind hole 111 can be limited according to the actual use, as long as the thickness of at least a part of the back film layer 1 in the bendable region 8 can be reduced to reduce the thickness of the part in the bendable region 8. The elastic modulus of the back film layer 1 is sufficient, and the shape of the blind hole 111 is not limited here.

In some embodiments of the present invention, at least one blind hole 111 is provided on the side of the back film layer 1 away from the device layer 2. When the number of blind holes 111 is small, the process can be a grinding pin processing process. When the number of blind holes 111 is large , a photolithography process may be used to facilitate the processing of the blind hole 111 .

In some embodiments of the present invention, at least one concave portion 11 parallel to the extension direction of the bending axis 6 is provided on the side of the back film layer 1 away from the device layer 2. When the number of concave portions 11 is small, the grinding process can be adopted. For pin processing or layer-by-layer scraping, when the number of depressed portions 11 is large, a photolithography process or a laser etching process may be used to facilitate the processing of the depressed portions 11 .

In some embodiments of the present invention, when the thickness of the back film layer 1 is thinned on the side away from the device layer 2, grinding pin processing technology, layer-by-layer scraping process, photolithography process or laser can be used. Etching and other processes are used to facilitate thinning the thickness of the back film layer 1 . Wherein, the photolithography process refers to removing unnecessary parts of the back film layer 1 through gluing, exposure, development, and etching processes.

As shown in FIG. 13 , in some embodiments of the present invention, the inner sidewall of the recessed portion 11 is formed as a transition surface 112 extending obliquely. It can be understood that the transition surface 112 is formed by inclinedly setting the inner side wall of the recessed portion 11 to ensure the strength of the back film layer 1 at the transition surface 112 and prevent the flexible display device 100 from being damaged by the back film layer 1 after multiple bendings. breakage occurs. Preferably, the inclined extension track of the transition surface 112 may be in the shape of a curve, a broken line or an arc. The inclined extension track of the transition surface 112 can be limited according to actual usage, as long as the transition surface 112 can be extended obliquely, there is no limitation here.

In some embodiments of the present invention, the recessed portion 11 is filled with fillers. It can be understood that the recessed portion 11 can be filled with fillers to ensure the flatness of the back film layer 1 . Preferably, the filler can be soft glue, such as UV glue, etc., so as to improve surface smoothness and improve the effect of fitting curved surfaces.

As shown in Figure 15, in some embodiments of the present invention, the back film layer 1 comprises a base layer 12 and an adhesive layer 13, and the adhesive layer 13 is arranged between the base layer 12 and the device layer 2 to adhere the base layer 12 to the device layer 2 Above, the recessed portion 11 is disposed on the base layer 12 . It can be understood that the base layer 12 is pasted on the device layer 2 through the adhesive layer 13 , so that the connection structure between the back film layer 1 and the device layer 2 is simple and reliable. At the same time, the recessed part 11 is arranged on the base layer 12 to ensure the structural strength of the back film layer 1 .

As shown in Figures 1 to 21, the flexible display device 100 according to the embodiment of the present invention includes: a back film layer 1 and a device layer 2, the back film layer 1 is the back film layer 1 according to the above-mentioned embodiment of the present invention, and the device layer 2 is provided on the first surface.

According to the back film layer 1 of the flexible display device 100 of the embodiment of the present invention, the back film layer 1 is arranged on the device layer 2 so as to isolate water and oxygen and protect the device layer 2 . At the same time, when the flexible display device 100 is bent, since the modulus of elasticity of at least a part of the back film layer 1 in the bendable region 8 is reduced, the stress on the device layer 2 is reduced to avoid the device layer 2 damage.

In some embodiments of the present invention, the flexible display device 100 further includes a substrate for maintaining the elastic recovery force of the flexible display device 100, and the substrate is connected to the second surface. It can be understood that by disposing the substrate on the second surface of the back film layer 1 , the elastic recovery force of the flexible display device 100 after being bent is ensured, so as to ensure the resilience of the flexible display device 100 . Preferably, the substrate can be a steel plate, so as to ensure the elastic recovery force of the flexible display device 100 .

As shown in FIGS. 1 to 3 , FIG. 16 and FIG. 17 , in some embodiments of the present invention, the flexible display device 100 further includes a functional layer, and the functional layer may include an insulating protective layer 5 (Cover film), a touch Layer 4 (TOUCH) and polarizing layer 3 (POL), wherein the polarizing layer 3 is connected to the device layer 2 of the device layer 2. The insulating protective layer 5 can be a protective film to play the role of insulating and protecting the flexible display device 100. The touch layer 4 can receive touch signals. When the user gently touches the icon or text on the flexible display device 100 Human-computer interaction can be realized at the same time, so that the flexible display device 100 is more intelligent. The polarizing layer 3 is made according to the principle of light polarization, which can effectively eliminate glare and improve the user experience of viewing the flexible display device 100 .

In some embodiments of the present invention, the polarizing layer 3 of the functional layer may also be located between the touch layer 4 and the insulating protection layer 5 , so that the touch layer 4 is connected to the device layer 2 . It should be noted that the form of the functional layer can be limited according to the actual use situation, as long as the actual use requirements of the flexible display device 100 are met, the form of the functional layer is not limited here.

In the description of this specification, references to the terms "one embodiment," "some embodiments," "exemplary embodiments," "example," "specific examples," or "some examples" are intended to mean that the implementation A specific feature, structure, material, or characteristic described by an embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

Although the embodiments of the present invention have been shown and described, those skilled in the art can understand that various changes, modifications, substitutions and modifications can be made to these embodiments without departing from the principle and spirit of the present invention. The scope of the invention is defined by the claims and their equivalents.

Claims (8)

1. A back film layer of a flexible display device, characterized in that the flexible display device has a bendable region and a non-bendable region, the flexible display device comprises a device layer, and the device layer comprises flexible The base layer, the metal wiring layer and the encapsulation layer, the flexible base layer is connected to the first surface of the back film layer, the circuit structure of the flexible display device is arranged in the metal wiring layer, and the back film layer has an opposite arrangement A first surface and a second surface, the first surface is adapted to be arranged on the device layer to protect the device layer, the modulus of elasticity of at least a part of the back film layer in the bendable region less than the modulus of elasticity of the back film layer in the non-bendable region, the thickness of at least a part of the back film layer in the bendable region is smaller than that of the back film layer in the non-bendable region , and the thickness and elastic modulus of the back film layer in the bendable region satisfy: y≤0.0236H ³ -2.1284H ² -52.028H+7159, 10um≤H≤75um, the device layer The neutral layer is located in the metal wiring layer or the encapsulation layer, wherein the thickness of the back film layer is H, and the elastic modulus of the back film film layer is y. 2 . The back film layer of the flexible display device according to claim 1 , wherein, in the bendable region, the second surface of the back film layer is provided with a concave portion that is concave toward the first surface. 3 . 3. The back film layer of the flexible display device according to claim 2, wherein the flexible display device is bent along a bending axis, and the extending direction of the concave part is parallel to the extending direction of the bending axis . 4 . The back film layer of the flexible display device according to claim 2 , wherein the inner sidewall of the concave portion is formed as a transition surface extending obliquely. 5. The back film layer of the flexible display device according to any one of claims 2-4, wherein the back film layer comprises a base layer and an adhesive layer, and the adhesive layer is arranged on the base layer and the adhesive layer. The base layer is bonded to the device layer between the device layers, and the recessed part is arranged on the base layer. 6. A flexible display device, comprising: The back film layer, the back film layer is the back film layer according to any one of claims 1 to 5; A device layer, the device layer is disposed on the first surface. 7. The flexible display device according to claim 6, further comprising a substrate for maintaining the elastic recovery force of the flexible display device, the substrate being connected to the second surface. 8 . The flexible display device according to claim 6 , wherein the device layer comprises a flexible substrate, a metal wiring layer and a packaging layer arranged in sequence, and the flexible substrate is connected to the back film layer.