CN212365385U

CN212365385U - Foldable display device

Info

Publication number: CN212365385U
Application number: CN202020943755.6U
Authority: CN
Inventors: 冯子康
Original assignee: Wuhan China Star Optoelectronics Semiconductor Display Technology Co Ltd
Current assignee: Wuhan China Star Optoelectronics Semiconductor Display Technology Co Ltd
Priority date: 2020-05-28
Filing date: 2020-05-28
Publication date: 2021-01-15
Anticipated expiration: 2030-05-28

Abstract

The application provides a foldable display device, which comprises a first machine shell, a second machine shell and a flexible display panel, wherein the first machine shell and the second machine shell are used for supporting the flexible display panel, the first machine shell is opposite to the second machine shell, the first machine shell rotates around a first rotation center, the second machine shell rotates around a second rotation center, the orthographic projection coordinates of the first rotation center on an xoy coordinate plane are (x1 and y1), the orthographic projection coordinates of the second rotation center on the xoy coordinate plane are (-x1 and y1), the sum of x1 and y1 is a preset value, x1 is larger than 0, and y1 is larger than-0.3 mm and smaller than or equal to 1 mm, so that the phenomenon that a film layer is peeled off or broken in the bending process of the foldable display device is avoided.

Description

Foldable display device

Technical Field

The application relates to the technical field of foldable display, in particular to a foldable display device.

Background

At present, foldable display devices have become a great development direction in the display industry, and the screen of the foldable display device is stressed during the bending process, which may cause the risk of failure during the bending process.

Therefore, there is a need to provide a solution to reduce the problem of screen failure caused by stress during the folding process of the foldable display device.

SUMMERY OF THE UTILITY MODEL

The application aims to provide a foldable display device to reduce the problem that a screen fails due to stress during the bending process of the foldable display device.

To achieve the above objects, the present application provides a foldable display device including a first housing, a second housing, and a flexible display panel,

the first housing and the second housing are used for supporting the flexible display panel, the first housing is opposite to the second housing, the first housing rotates around a first rotation center, and the second housing rotates around a second rotation center;

wherein a straight line which is positioned at the middle position between the first casing and the second casing and is perpendicular to the plane where the first casing and the second casing are positioned when the foldable display device is in the flat state is a y coordinate axis, a straight line which is positioned on the same horizontal plane and intersects with the surfaces of the first casing and the second casing close to the flexible display panel when the foldable display device is in the flat state is an x coordinate axis, the x coordinate axis and the y coordinate axis are coplanar and vertically intersected, the intersection point of the x coordinate axis and the y coordinate axis is a coordinate origin o, the x coordinate axis, the y coordinate axis and the coordinate origin o form an xoy coordinate plane, the orthographic projection coordinate of the first rotation center on the xoy coordinate plane is (x1, y1), the orthographic projection coordinate of the second rotation center on the y coordinate plane is (-x1, y 1);

the sum of x1 and y1 is a predetermined value, x1 is greater than 0, y1 is greater than-0.3 mm and less than or equal to 1 mm, and the predetermined value is greater than 0.

In the above foldable display device, the y1 is greater than or equal to-0.1 mm.

In the above foldable display device, the y1 is less than or equal to 0.5 mm.

In the above foldable display device, the y1 is greater than or equal to-0.1 mm and less than or equal to 0.3 mm.

In the above foldable display device, the predetermined value is 0.5 mm to 3 mm.

In the foldable display device, the x1 is 1.9 mm, and the y1 is 0.1 mm.

In the above foldable display device, the flexible display panel includes an organic light emitting diode array layer, and a distance from the first chassis and the second chassis to a surface of the flexible display panel when the foldable display device is in a flattened state is greater than or equal to 0.1 mm and less than or equal to 0.3 mm.

In the above foldable display device, when the foldable display device is in a flattened state, in the direction of the y coordinate axis,

the first rotation center and the second rotation center are located on one side of a lower surface of the organic light emitting diode array layer close to the first housing and the second housing, and a distance from the first rotation center and the second rotation center to the lower surface of the organic light emitting diode array layer is greater than or equal to 0 mm and less than or equal to 0.243 mm, or,

the first rotation center and the second rotation center are located on one side, away from the first casing and the second casing, of the lower surface of the organic light emitting diode array layer, the distance from the first rotation center and the second rotation center to the lower surface of the organic light emitting diode array layer is greater than 0 millimeter and less than or equal to 0.157 millimeter, and the lower surface of the organic light emitting diode array layer is the surface, close to the first casing and the second casing, of the organic light emitting diode array layer.

In the above foldable display device, a radius of rotation of the first housing about the first rotation center is 1 mm to 10 mm, and a radius of rotation of the second housing about the second rotation center is 1 mm to 10 mm.

In the above foldable display device, the first housing and the second housing synchronously and symmetrically rotate the foldable display device comprises a dual-axis rotating mechanism, the dual-axis rotating mechanism comprises a first moving arm with a first rotating center, a second moving arm with a second rotating center, a first fixed sliding groove block with a first arc-shaped groove and a second fixed sliding groove block with a second arc-shaped groove,

the first moving arm comprises a first connecting piece and a first arc-shaped piece connected to one end of the first connecting piece, one end, far away from the first arc-shaped piece, of the first connecting piece of the first moving arm is fixed in the first shell, the first arc-shaped piece of the first moving arm is clamped into the first arc-shaped groove of the first fixed sliding groove block, and the first arc-shaped piece is matched with the first arc-shaped groove;

the second motion arm includes the second connecting piece and connect in the second circular arc shape piece of second connecting piece one end, the one end that the second circular arc shape piece was kept away from to the second connecting piece of second motion arm is fixed in the second casing, the second motion arm the circular arc shape piece card of second is gone into extremely the second fixed sliding chute piece in the second circular arc shape groove, the second circular arc shape piece with the second circular arc shape groove cooperatees.

In the above foldable display device, the foldable display device further comprises a linkage mechanism and a third housing, the third housing is disposed between the first housing and the second housing, the first fixed sliding groove block and the second fixed sliding groove block are fixed in the third housing, the linkage mechanism comprises a first transmission component, a second transmission component and a gear,

the first transmission assembly comprises a first rack and a first sliding block arranged on a first arc-shaped part, the first rack is provided with a first end face and a second end face perpendicular to the first end face, the first end face is provided with flat rack teeth distributed along the transmission direction, the second end face is provided with a first sliding groove, the first sliding block on the first arc-shaped part is clamped in the first sliding groove, and the first rack is arranged on a first guide surface of the first fixed sliding groove block;

the second transmission assembly comprises a second rack and a second sliding block arranged on a second arc-shaped part, the second rack is provided with a third end face and a fourth end face perpendicular to the third end face, the third end face is provided with flat rack teeth distributed along the transmission direction, the fourth end face is provided with a second sliding chute, the second sliding block on the second arc-shaped part is clamped in the second sliding chute, and the second rack is arranged on a second guide surface of the second fixed sliding chute block;

the gear is rotationally connected to the third casing, the flat teeth of the first rack arranged along the transmission direction are meshed with the gear, and the flat teeth of the second rack arranged along the transmission direction are meshed with the gear.

Has the advantages that: the application provides a foldable display device, which comprises a first machine shell, a second machine shell and a flexible display panel, wherein the first machine shell and the second machine shell are used for supporting the flexible display panel, the first machine shell is opposite to the second machine shell, the first machine shell rotates around a first rotation center, the second machine shell rotates around a second rotation center, the orthographic projection coordinates of the first rotation center on an xoy coordinate plane are (x1 and y1), the orthographic projection coordinates of the second rotation center on the xoy coordinate plane are (-x1 and y1), the sum of x1 and y1 is a preset value, x1 is larger than 0, y1 is larger than-0.3 mm and smaller than or equal to 1 mm, so that the normal stress of an interface between an organic light emitting diode array layer and an encapsulation layer in the flexible display panel in the bending process of the foldable display device is smaller than 0.6281MPa, and the internal shear stress of the encapsulation layer is smaller than 582.6MPa, the film packaging layer is prevented from being broken, the organic light emitting diode array layer and the film packaging layer are prevented from being peeled, and the film layer of the flexible display panel is prevented from being peeled or broken in the bending process of the foldable display device.

Drawings

FIG. 1 is a schematic cross-sectional view of a foldable display device according to an embodiment of the present application in a flattened state;

FIG. 2 is a schematic cross-sectional view of a foldable display device of an embodiment of the present application at a 90 degree bend;

FIG. 3 is a schematic cross-sectional view of a foldable display device according to an embodiment of the present application in a fully folded state;

FIG. 4 is an exploded view of a foldable display device according to an embodiment of the present application;

FIG. 5 is a schematic view of the dual-axis rotating mechanism and the linkage mechanism of FIG. 4;

FIG. 6 is a schematic diagram illustrating a rotation process of the first moving arm and the second moving arm of the dual-axis rotating mechanism shown in FIG. 5 during a bending process of the foldable display device;

FIG. 7 is a schematic cross-sectional view of the flexible display module shown in FIG. 4;

FIG. 8 is a schematic cross-sectional view of the flexible display panel of FIG. 7;

fig. 9 is a schematic illustration of an orthographic projection of a first center of rotation and a second center of rotation in a xoy coordinate plane;

fig. 10 is a schematic diagram of the change of the normal stress between the organic light emitting diode array layer and the thin film encapsulation layer with time during the bending process of the flexible display device when the predetermined value R is 2 mm and x1 and y1 have different values;

fig. 11 is a schematic diagram of the change of the shear stress in the thin film encapsulation layer with time during the bending process of the flexible display device when the predetermined value R is 2 mm and x1 and y1 have different values;

FIG. 12 is a diagram illustrating the folding shape of the flexible display module at different times (x1, y1) when the predetermined value R is 2 mm.

The drawings are labeled as follows:

100 a foldable display device; 301a first housing; 301a first support plane; 301b a first receiving cavity; 302a second housing; 302a second support plane; 302b a second accommodating cavity; 303a third housing; 303a receiving cavity; 20, a flexible display module; 201 a back cover plate; 202 a flexible display panel; 2021 a flexible substrate; 2022 an organic light emitting diode array layer; 2023 thin film encapsulation layer; 203 a polarizer; 204 protective cover plate; 40 a dual-axis rotating mechanism; o1 first center of rotation; o2 second center of rotation; 401 a first motion arm; 4011 a first connecting member; 4012 a first arc-shaped piece; 402 a second motion arm; 4021 a second connection; 4022 a second circular arc; 403a first fixed runner block; 403a first circular arc shaped groove; 403b a first guide surface; 404a second fixed runner block; 404a second arc-shaped groove; 404b a second guide surface; 50 a linkage mechanism; 501 a first transmission assembly; 5011a first rack; 5011a first end face; 5011b second end face; 5012 a first slider; 502 a second transmission assembly; 5021a second rack; 5021a third end face; 5021b a fourth end face; 5022 a second slider; 503 gears.

Detailed Description

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. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.

Referring to fig. 1 to 6, fig. 1 is a schematic cross-sectional view of a foldable display device in an unfolded state according to an embodiment of the present disclosure, fig. 2 is a schematic cross-sectional view of the foldable display device in a 90-degree bent state according to the embodiment of the present disclosure, fig. 3 is a schematic cross-sectional view of the foldable display device in a completely bent state according to the embodiment of the present disclosure, fig. 4 is an exploded schematic view of the foldable display device according to the embodiment of the present disclosure, fig. 5 is a schematic view of a dual-axis rotation mechanism and a linkage mechanism in fig. 4, and fig. 6 is a schematic view of a process of a first moving arm and a second moving arm of the dual-axis rotation mechanism in fig. 5 in a bending process.

The foldable display device 100 includes a first housing 301, a second housing 302, a third housing 303, a flexible display module 20, a dual-axis rotation mechanism 40, and a linkage mechanism 50.

The first chassis 301 and the second chassis 302 are used for supporting the flexible display module 20. The first housing 301 has a first support plane 301 a. The second housing 302 has a second support plane 302 a. The second housing 302 is opposed to the first housing 301. The first housing 301 rotates about the first rotation center O1, and the second housing 302 rotates about the second rotation center O2. The first housing 301 and the second housing 302 are synchronously and symmetrically rotated. The first housing 301 has a first receiving cavity 301b at an end thereof adjacent to the second housing 302. One end of the second housing 302 close to the first housing 301 has a second receiving cavity 302 b.

The third housing 303 is used for accommodating and fixing the dual axis rotating mechanism 40, and is used for accommodating the linkage mechanism 50. The third housing 303 is a housing having a receiving cavity 303 a. The third housing 303 is disposed between the first housing 301 and the second housing 302.

The biaxial rotation mechanism 40 includes a first moving arm 401 having a first rotation center O1, a second moving arm 402 having a second rotation center O2, a first fixed slide block 403 having a first circular arc groove 403a, and a second fixed slide block 404 having a second circular arc groove 404 a. The first moving arm 401 and the second moving arm 402 rotate synchronously and symmetrically.

The first moving arm 401 is connected to the first housing 301 to rotate the first housing 301 about the first rotation center O1. The first moving arm 401 includes a first link 4011 and a first circular arc member 4012 connected to one end of the first link 4011. One end, far away from the first arc-shaped part 4012, of the first connecting part 4011 of the first moving arm 401 is fixed in the first housing 301, the first arc-shaped part 4012 of the first moving arm 401 is clamped into the first arc-shaped groove 403a of the first fixed sliding groove block 403, and the first arc-shaped part 4012 is matched with the first arc-shaped groove 403 a. The first connecting part 4011 of the first moving arm 401 is fixed to an inner wall enclosing the first receiving cavity 301 b.

The second moving arm 402 is connected to the second housing 302 to rotate the second housing 302 about the second rotation center O2. The second moving arm 402 includes a second connector 4021 and a second circular arc member 4022 connected to one end of the second connector 4021. One end of the second connecting member 4021 of the second moving arm 402, which is far away from the second arc-shaped piece 4022, is fixed in the second housing 302, the second arc-shaped piece 4022 of the second moving arm 402 is snapped into the second arc-shaped groove 404a of the second fixed sliding groove block 404, and the second arc-shaped piece 4022 is matched with the second arc-shaped groove 404 a. The second connector 4021 of the second moving arm 402 is fixed to the inner wall of the second housing cavity 302 b. The second connector 4021 is the same as the first connector 4011, and both are plate-shaped. The second circular arc members 4022 are the same as the first circular arc members 4012. The first circular arc groove 403a of the first fixed sheave block 403 is the same as the second circular arc groove 404a of the second fixed sheave block 404.

The first fixed slide groove block 403 and the second fixed slide groove block 404 are fixed in the third housing 303.

The link mechanism 50 is used to rotate the first moving arm 401 and the second moving arm 402 synchronously and symmetrically. The linkage 50 includes a first drive assembly 501, a second drive assembly 502, and a gear 503. The gear 503 is pinned to the third housing 303 so that the gear 503 can rotate freely.

The first transmission assembly 501 comprises a first rack 5011 and a first sliding block 5012 arranged on the first arc-shaped part 4012, wherein the first rack 5011 is provided with a first end face 5011a and a second end face 5011b perpendicular to the first end face 5011a, the first end face 5011a is provided with flat rack teeth arranged along the transmission direction, and the second end face 5011b is provided with a first sliding chute. The first slide 5012 on the first arc-shaped part 4012 is snapped into the first sliding slot of the first toothed rack 5011. The flat teeth of the first rack 5011 arranged in the transmission direction engage with the gear 503. The first slider 5012 is engaged with the first sliding slot of the first rack 5011. The first slider 5012 has a cylindrical shape. The first rack 5011 is disposed on the first guide surface 403b of the first fixed slide block 403.

The second transmission assembly 502 includes a second rack 5021 and a second slider 5022 disposed on a second arc-shaped member 4022, the second rack 5021 has a third end face 5021a and a fourth end face 5021b perpendicular to the third end face 5021a, the third end face 5021a is provided with flat rack teeth arranged along the transmission direction, and the fourth end face 5021b is provided with a second sliding chute. The second slider 5022 on the second arc 4022 is engaged in the second slot of the second rack 5021. The flat teeth of the second rack 5021 arranged in the transmission direction engage with the gear 503. The second slider 5022 is engaged with the second slot of the second rack 5021, and the second slider 5022 is cylindrical. The gear 503 is drivingly connected with the first rack 5011 and the second rack 5021. The second rack 5021 is disposed on the second guide surface 404b of the second fixed sheave block 404.

As shown in fig. 5 and 4, when the first moving arm 401 rotates 45 degrees counterclockwise along the first arc-shaped groove 403, the first sliding block 5012 on the first moving arm 401 pushes the first rack 5011 to slide rightwards through the first sliding slot on the first rack 5011, and the first rack 5011 drives the gear 503 to start rotating. The rotation of the gear 503 drives the second rack 5021 to slide leftwards relative to the third housing 303, and the second rack 5021 slides leftwards and drives the second moving arm 402 to move leftwards through the cooperation of the second sliding slot on the second rack 5021 and the second slider 5022, so that the second moving arm 402 also rotates 45 degrees clockwise relative to the third housing 303. The first moving arm 401 drives the first housing 301 to rotate 45 degrees counterclockwise, and the second moving arm 402 drives the second housing 302 to rotate 45 degrees clockwise. The foldable display device is integrally formed in a symmetrical relation, and the flexible display module is prevented from being bent into an asymmetrical shape to generate larger stress when the foldable display device rotates at one side of the machine shell and the other side of the machine shell does not rotate at the same angle. The first moving arm 401 continues to rotate along the first rotation center O1, and the second moving arm 402 rotates by the same angle therewith. The first moving arm 401 and the second moving arm 402 are respectively fixed on the first casing 301 and the second casing 302, so that the moving tracks of the first moving arm 401 and the second moving arm 402 are completely reflected on the first casing 301 and the second casing 302, when the first casing 301 and the second casing 302 are linked and rotated to the tail parts to be abutted, the bending area between the first casing 301 and the second casing 302 gives out a wedge-shaped space to enable the flexible display module to form a smooth arc shape, and the size difference between the flexible display module and the bent mechanism is compensated.

Fig. 7 is a schematic cross-sectional view of the flexible display module shown in fig. 4. The flexible display module 20 includes a back cover 201, a flexible display panel 202, a polarizer 203, and a protective cover 204. The back cover 201, the flexible display panel 202, the polarizer 203, and the protective cover 204 are sequentially stacked. The rear cover 201 is disposed adjacent to the first housing 301 and the second housing 302. The back cover 201 is used for protecting the back of the light emitting surface of the flexible display panel 202. The back cover 201 is connected to the flexible display panel 202 by a transparent adhesive layer. The polarizer 203 is used to improve the contrast ratio of the flexible display panel 202 during display. The polarizer 203 and the flexible display panel 202 are connected through a transparent adhesive layer. The protective cover 204 is used to protect the polarizer 203 and the flexible display panel 202.

As shown in fig. 8, which is a schematic diagram of the flexible display panel shown in fig. 7. The flexible display panel 202 includes a flexible substrate 2021, an organic light emitting diode array layer 2022, and a thin film encapsulation layer 2023. The thin film encapsulation layer 2023 includes an organic insulating layer and an inorganic insulating layer. The inorganic insulating layer is made of a material selected from silicon nitride or silicon oxide. The preparation material of the organic insulating layer is selected from polyacrylate and the like. The flexible substrate 2021 is a polyimide layer. The organic light emitting diode array layer 2022 includes a plurality of organic light emitting diodes arranged in an array.

The flexible display panel fails during the folding of the foldable display device due to peeling between the thin film encapsulation layer 2023 and the organic light emitting diode array layer 2022 and breakage of the thin film encapsulation layer 2023. The peeling between the thin film encapsulation layer 2023 and the organic light emitting diode array layer 2022 is caused by the normal stress F1 at the interface between the thin film encapsulation layer 2023 and the organic light emitting diode array layer 2022. The fracture of the thin film encapsulation layer 2023 is due to the shear stress F2 in the thin film encapsulation layer 2023.

As shown in fig. 9, which is a schematic diagram of orthographic projections of the first rotation center and the second rotation center on the xoy coordinate plane. A straight line which is positioned in the middle between the first housing 301 and the second housing 302 and is perpendicular to the plane of the first housing 301 and the second housing 302 when the foldable display device 100 is in the flat state is taken as a y coordinate axis, a straight line which is positioned on the same horizontal plane and intersects with the surfaces of the first housing 301 and the second housing 302 close to the flexible display panel 202 when the foldable display device 100 is in the flat state is taken as an x coordinate axis, the x coordinate axis and the y coordinate axis are coplanar and perpendicularly intersected, and the x coordinate axis is parallel to a connecting line of two symmetrical points on the first housing 301 and the second housing 302. The intersection of the x and y coordinate axes is the origin of coordinates o. The x coordinate axis, the y coordinate axis and the origin o form an xoy coordinate plane. The orthogonal projection of the first rotation center O1 on the xoy coordinate plane has coordinates (x1, y1), and the orthogonal projection of the second rotation center O2 on the xoy coordinate plane has coordinates (-x1, y 1).

When the foldable display device is in the unfolded state, the included angle between the first housing 301 and the second housing 302 is 180 degrees. After the first housing 301 and the second housing 302 both rotate 90 degrees, the included angle between the first housing 301 and the second housing 302 is 0 degree. When the angle between the first housing 301 and the second housing 302 is 0 degrees, one half of the distance between the first housing 301 and the second housing 302 is equal to the predetermined value R. Since the first housing 301 rotates around the first rotation center O1, it can be seen from the geometrical relationship that x1+ y1 is equal to R, i.e., the sum of x1 and y1 is equal to the predetermined value R.

In the present embodiment, the predetermined value R is 0.5 mm to 3 mm. The predetermined value R is too small, and after the foldable display device is completely folded, the gap between the first housing 301 and the second housing 302 is too small, which is not favorable for the flexible display module to be accommodated in the gap between the first housing 301 and the second housing 302 after being folded; if the predetermined value R is too large, the gap between the first housing 301 and the second housing 302 is too large, and the folded appearance of the foldable display device 100 is not satisfactory. For example, the predetermined value R is 1 mm, 1.2 mm, 1.5 mm, 1.8 mm, 2.0 mm, 2.5 mm, or 3.0 mm.

In the embodiment, x1 is greater than 0, and y1 is greater than-0.3 mm and less than or equal to 1 mm, so as to prevent peeling or breaking of the flexible display panel 202, particularly, peeling between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023, and breaking of the thin film encapsulation layer 2023. When y1 is less than or equal to 1 mm, the normal stress between the oled array layer 2022 and the thin film encapsulation layer 2023 is less than 0.6MPa, and the shear stress inside the thin film encapsulation layer 2023 is less than 500MPa, which can prevent the organic led array layer 2022 and the thin film encapsulation layer 2023 from peeling off and prevent the thin film encapsulation layer 2023 from breaking.

y1 is greater than or equal to-0.1 mm to further reduce the normal stress at the interface between the OLED array layer 2022 and the thin film encapsulation layer 2023 and the shear stress inside the thin film encapsulation layer 2023. Or y1 is less than or equal to 0.5 mm to further reduce the normal stress at the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023.

In this embodiment, y1 is greater than or equal to-0.1 mm and less than or equal to 0.3 mm, so that the normal stress of the interface between the organic light emitting diode array layer and the thin film encapsulation layer during the bending process of the foldable display device is less than 0.1MPa, the peeling between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 is avoided, the shear stress inside the thin film encapsulation layer 2023 during the bending process of the foldable display device 100 is less than 245MPa, and the breakage of the thin film encapsulation layer 2023 is avoided.

In this embodiment, the flexible display panel includes the organic light emitting diode array layer 2022, and the distance from the organic light emitting diode array layer 2022 to the surfaces of the first chassis 301 and the second chassis 302 close to the flexible display panel 202 is greater than or equal to 0.1 mm and less than or equal to 0.3 mm when the foldable display device is in the flat state. For example, 0.12 mm, 0.15 mm, 0.18 mm, 0.2 mm, 0.25 mm, and 0.28 mm.

In this embodiment, when the foldable display device is in the flat state, in the direction of the y coordinate axis,

the first rotation center O1 and the second rotation center O2 are located at a side of the lower surface of the organic light emitting diode array layer 2022 close to the first chassis 301 and the second chassis 302, and the distance from the first rotation center O1 and the second rotation center O2 to the lower surface of the organic light emitting diode array layer 2022 is greater than or equal to 0 mm and less than or equal to 0.243 mm, or,

the first rotation center O1 and the second rotation center O2 are located on a side of the lower surface of the organic light emitting diode array layer 2022 away from the first housing 301 and the second housing 302, and the distance from the first rotation center O1 and the second rotation center O2 to the lower surface of the organic light emitting diode array layer 2022 is greater than 0 mm and less than or equal to 0.157 mm, and the lower surface of the organic light emitting diode array layer 2022 is the surface of the organic light emitting diode array layer 2022 close to the first housing 301 and the second housing 302.

In this embodiment, the radius of rotation of the first housing 301 around the first rotation center O1 is 1 mm to 10 mm, the radius of rotation of the second housing 302 around the second rotation center O2 is 1 mm to 10 mm, that is, the radius of the first moving arm 401 and the second moving arm 402 is 1 mm to 10 mm, the radius of the first moving arm 401 and the second moving arm 402 is less than 1 mm, which increases the manufacturing difficulty of the foldable display device, and the radius of the first moving arm 401 and the second moving arm 402 is more than 10 mm, which is not favorable for thinning the foldable display device. The radius may be 2 mm, 3 mm, 4 mm, 5.5 mm or 8 mm.

Referring to fig. 10 and 11, fig. 10 is a schematic diagram illustrating a change of a normal stress between an organic light emitting diode array layer and a thin film encapsulation layer in a bending process of a flexible display device with a predetermined value R of 2 mm and different values of x1 and y1, and fig. 11 is a schematic diagram illustrating a change of a shear stress in the thin film encapsulation layer in a bending process of the flexible display device with a predetermined value R of 2 mm and different values of x1 and y1, wherein a bending time of the foldable display device 100 from a flat state to a full folded state (wedge-shaped folding) is 1s, a distance from the organic light emitting diode array layer 2022 to surfaces of the first chassis 301 and the second chassis 302 of the foldable device 100 in the flat state close to the flexible display panel 202 is 0.143 mm, and a thickness of the thin film encapsulation layer 2023 is 0.01 mm.

As can be seen from fig. 10, the normal stress at the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 is constantly changing during the process of bending the foldable display device from the flat state to the fully folded state. The maximum normal stress of the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023, which is different (x1, y1) when the predetermined value R is 2 mm during the bending process of the foldable display device 100, is as shown in table 1 below.

TABLE 1 Normal stress maximum at interface between OLED array layer and thin film encapsulation layer for different values (x1, y1) when predetermined value R is 2 mm

As can be seen from table 1, when the sum of x1 and y1 is 2 mm, y1 is less than-0.3 mm, which may cause the maximum normal stress of the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 to be more than 0.6281MPa, which may cause peeling between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023. When y1 is 0.5 mm, the maximum value of the normal stress at the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 is 0.2648MPa, and when y1 is greater than or equal to-0.1 mm and less than or equal to 0.3 mm, the maximum value of the normal stress at the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 is less than 0.1MPa, which can completely avoid the peeling between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023. The change in the value of y1 has a large influence on the maximum value of the normal stress at the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023.

As can be seen from fig. 11, the shear stress inside the thin film encapsulation layer 2023 is constantly changing during the process of bending the foldable display device from the flat state to the fully folded state. The maximum values of the shear stress inside the corresponding thin film encapsulation layers at the predetermined value R of 2 mm during the folding of the foldable display device (x1, y1) are as follows table 2.

TABLE 2 maximum stress values inside the corresponding thin film encapsulation layers for values of 2 mm for the predetermined value R (x1, y1)

As can be seen from table 2, when the sum of x1 and y1 is 2 mm, y1 is less than-0.3 mm, which may result in a shear stress greater than 582.6MPa inside the thin film encapsulation layer 2023, and a shear stress greater than 582.6MPa may result in a risk of breaking the thin film encapsulation layer. In the process of reducing the y1 from 0.5 mm to-0.1 mm, the shear stress inside the thin film encapsulation layer 2023 changes at about 240MPa, and does not change significantly.

As can be seen from fig. 10 and 11, when the predetermined value R is 2 mm, y1 varies from-0.1 mm to 0.3 mm, and the maximum value of the normal stress at the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 and the maximum value of the internal shear stress of the thin film encapsulation layer 2023 are both low, so that the risk of peeling off the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 and the risk of breaking the thin film encapsulation layer 2023 during the bending process of the foldable display device are low.

Please refer to fig. 12, which is a schematic diagram illustrating a folding shape of the flexible display module when the predetermined value R is 2 mm and the same time is different (x1, y 1). A is a schematic diagram of a folded shape of the flexible display module when x1 is 1 mm and y1 is 1 mm, B is a schematic diagram of a folded shape of the flexible display module when x1 is 1.7 mm and y1 is 0.3 mm, C is a schematic diagram of a folded shape of the flexible display module when x1 is 1.9 mm and y1 is 0.1 mm, D is a schematic diagram of a folded shape of the flexible display module when x1 is 2.0 mm and y1 is-0.1 mm, and E is a schematic diagram of a folded shape of the flexible display module when x1 is 2.3 mm and y1 is-0.3 mm. At the same time, in the initial stage of rotation, the value of y1 is larger, for example, when x1 is 1 mm and y1 is 1 mm, the flexible display module 20 is easily pulled when the distance between the first housing 301 and the second housing 302 is larger; when the value of y1 is small, for example, x1 is 2.3 mm and y1 is-0.3 mm, the distance between the first housing 301 and the second housing 302 is small at the initial stage of rotation, and the flexible display module 20 is easily squeezed. Smaller or larger values of y1 will result in increased stress during bending of the flexible display module 20.

The flexible display panel 202 serves as the most critical functional layer during the folding process of the foldable display device 100, and the control of the stress applied during the bending process is the key point. In particular, the normal stress at the interface between the organic light emitting diode array layer 2022 and the thin film encapsulation layer 2023 and the shear stress inside the thin film encapsulation layer 2023. When the foldable display device 100 is in the flat state, the distance from the organic light emitting diode array layer 2022 to the first chassis 301 and the second chassis 302 is 0.1 mm to 0.35 mm, and the distance from the first rotation center O1 and the second rotation center O2 to the surfaces, close to the flexible display panel 202, of the first chassis 301 and the second chassis 302 of the foldable display device 100 in the flat state is controlled to control the shape of the flexible display module 20 in the full folding process, so that the stress of the flexible display panel 202 in the bending process is reduced, and the risk of failure of the flexible display panel 202 is avoided.

Since the film layers under the oled array layer 2022 in the flexible display module 20 vary more, the predetermined value R is limited to 0.5 mm-3 mm, and the distance between the oled array layer 2022 of the flexible display module 20 in the present embodiment and the upper surfaces (surfaces close to the flexible display module) of the first chassis 301 and the second chassis 302 when the foldable display device 20 is in the flat state is 0.143 mm, the best ordinate y1 of the orthogonal projection of the first rotation center O1 and the second rotation center O2 varies in the range of-0.1 mm to 0.3 mm, the best first rotation center O1 and the second rotation center O2 are disposed in the range of 0 mm to 0.3 mm from the lower surface (surfaces close to the first chassis and the second chassis) of the oled array layer 2022 to the side of the first chassis and the second chassis, alternatively, it is preferable that the first rotation center O1 and the second rotation center O2 are disposed in a range of 0 mm to 0.157 mm from a side of the lower surface of the organic light emitting diode array layer 2022 away from the first and second housings.

The above description of the embodiments is only for assisting understanding of the technical solutions and the core ideas thereof; those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications or substitutions do not depart from the spirit and scope of the present disclosure as defined by the appended claims.

Claims

1. A foldable display device, characterized in that the foldable display device comprises a first housing, a second housing and a flexible display panel,

2. The foldable display device of claim 1, wherein y1 is greater than or equal to-0.1 millimeters.

3. The foldable display device of claim 1, wherein y1 is less than or equal to 0.5 millimeters.

4. The foldable display device of claim 1, wherein y1 is greater than or equal to-0.1 millimeters and less than or equal to 0.3 millimeters.

5. The foldable display device of claim 1, wherein the predetermined value is 0.5 mm to 3 mm.

6. The foldable display device of claim 1 or 5, wherein x1 is 1.9 mm and y1 is 0.1 mm.

7. The foldable display device of claim 1, wherein the flexible display panel comprises an organic light emitting diode array layer, and a distance from the first chassis and the second chassis to a surface of the flexible display panel when the foldable display device is in a flattened state is greater than or equal to 0.1 mm and less than or equal to 0.3 mm.

8. The foldable display device of claim 7, wherein when the foldable display device is in the flattened state, in the direction of the y coordinate axis,

9. The foldable display device of claim 1, wherein the first housing rotates around a first rotation center with a radius of 1 mm to 10 mm, and the second housing rotates around a second rotation center with a radius of 1 mm to 10 mm.

10. The foldable display device of claim 1, wherein the first housing and the second housing rotate synchronously and symmetrically, the foldable display device comprising a dual-axis rotation mechanism comprising a first moving arm having a first center of rotation, a second moving arm having a second center of rotation, a first fixed sliding block having a first circular-arc groove, and a second fixed sliding block having a second circular-arc groove,

11. The foldable display device of claim 10, further comprising a linkage mechanism and a third housing, the third housing disposed between the first housing and the second housing, the first fixed sliding block and the second fixed sliding block fixed within the third housing, the linkage mechanism comprising a first transmission assembly, a second transmission assembly, and a gear,