CN118135891A

CN118135891A - Optical adhesive layer, preparation method, flexible display module and electronic equipment

Info

Publication number: CN118135891A
Application number: CN202211538696.4A
Authority: CN
Inventors: 周星怡; 殷一凯; 刘孟迪; 刘发齐; 陈鑫峰; 黄丽媚
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-12-02
Filing date: 2022-12-02
Publication date: 2024-06-04
Also published as: WO2024114573A1

Abstract

The embodiment of the application discloses an optical adhesive layer, a preparation method, a flexible display module and electronic equipment, wherein the optical adhesive layer comprises at least one gradual change area on the plane of the optical adhesive layer, the storage modulus of the optical adhesive layer in the gradual change area is gradually decreased from a first axis to two sides of the first axis, the viscosity of the optical adhesive layer is gradually increased from the first axis to two sides of the first axis, and the gradual change area is symmetrical relative to the first axis. From this, the storage modulus of this optics glue film is big in the middle, both sides are little to be distributed, and the viscidity of this optics glue film is little in the middle, and both sides are big to be distributed, can make the bonding surface that this optics glue film is located both sides bond with the non-bending zone of flexible display module assembly to make the intermediate position of this optics glue film bond with the bending zone of flexible display module assembly, make the optics glue film stress and strain distribution more even everywhere when buckling, be favorable to reducing the crease.

Description

Optical adhesive layer, preparation method, flexible display module and electronic equipment

Technical Field

The embodiment of the application relates to the technical field of display, in particular to an optical adhesive layer, a preparation method, a flexible display module and electronic equipment.

Background

With the continuous development of display technology, a folding screen mobile phone gradually becomes a development trend of future mobile electronic products. Under the unfolding state, the folding screen mobile phone can obtain a larger display area, and the viewing effect is improved. The folding screen mobile phone can obtain smaller volume in the folding state, and is convenient for users to carry.

The folding screen mobile phone at least comprises: a flexible display screen and a folding assembly for carrying the flexible display screen. The first display screen may be an Organic LIGHT EMITTING Diode (OLED) display screen.

The optical adhesive layer (OCA) plays a role in bonding all functional layers in the folding screen mobile phone, and can be used as a neutral layer to absorb stress generated when all functional layers are folded so as to avoid layering. To achieve the function of continuous folding and unfolding, existing optical adhesives typically select a flexible material with a lower modulus.

However, the optical adhesive deforms more in the folded region than in the unfolded region when the folded screen is folded and unfolded, and the same layer of optical adhesive has uneven stress and strain distribution at different positions of the folded region, which can cause irreversible deformation of the laminate for a long time, and crease is generated to affect the flatness of the display device.

Disclosure of Invention

The embodiment of the application provides an optical adhesive layer, a preparation method, a flexible display module and electronic equipment, and reduces crease depth of the electronic equipment.

In order to achieve the above purpose, the embodiment of the application adopts the following technical scheme:

In a first aspect of the embodiment of the present application, there is provided an optical adhesive layer, on a plane of the optical adhesive layer, the optical adhesive layer includes at least one graded region, in which a storage modulus of the optical adhesive layer decreases from a first axis to two sides of the first axis, and a viscosity of the optical adhesive layer increases from the first axis to two sides of the first axis, wherein the graded region is symmetrical about the first axis. Therefore, the storage modulus of the optical adhesive layer is large in the middle and small in the two sides, the viscosity of the optical adhesive layer is small in the middle and large in the two sides, the bonding surfaces of the optical adhesive layer on the two sides are bonded with the non-bending areas of the flexible display module, and the middle position of the optical adhesive layer is bonded with the bending areas of the flexible display module, so that when the optical adhesive layer is applied to the flexible display module, on one hand, the optical adhesive layer with larger modulus at the middle position can still have enough bending strain while stress on adjacent functional layers can be quickly and effectively relaxed and bent, and the deformation of the flexible module is reduced. Meanwhile, as the storage modulus of the optical adhesive layer is gradually distributed, the stress and strain distribution of the optical adhesive layer at each position during bending is more uniform, and the crease depth of the electronic equipment is reduced when the optical adhesive layer is used in the electronic equipment.

On the other hand, the optical adhesive layer and the adjacent functional layer in the flexible module are adhered with larger adhesion at the position, so that larger adhesion force between the optical adhesive layer and the adjacent functional layer is ensured, and the optical adhesive layer is not easy to be debonded, thereby ensuring the reliability of the adhesive assembly of the whole display module.

In an alternative implementation, the storage modulus of the optical cement layer decreases from both sides of a second axis to both sides of the second axis, and the viscosity of the optical cement layer increases from both sides of the second axis to both sides of the second axis, the second axis intersecting the first axis. Therefore, the storage modulus of the optical adhesive layer gradually changes to multiple directions, so that the stress and strain distribution of the optical adhesive layer at each position during bending is more uniform, the reliability of the electronic equipment is further improved, and the crease depth of the folding screen is reduced.

In an alternative implementation, the second axis is perpendicular to the first axis. Therefore, the storage modulus of the optical adhesive layer gradually decreases from the center to the four sides, so that the stress and strain distribution is more uniform, and the bonding stability of the edge of the flexible display module is improved.

In an alternative implementation manner, on the plane of the optical adhesive layer, the storage modulus of the optical adhesive layer decreases around along the radius direction with the center of the optical adhesive layer as the center, and the viscosity of the optical adhesive layer increases around along the radius direction with the center of the optical adhesive layer as the center, where the center of the optical adhesive layer is located on the first axis. Therefore, the storage modulus of the optical adhesive layer gradually decreases from the center to the periphery, so that the stress and strain distribution is more uniform, and the bonding stability of the edge of the flexible display module is improved.

In an alternative implementation, the storage modulus and viscosity of the optical cement layer are graded in the thickness direction of the optical cement layer. Therefore, the stress and strain distribution of the optical adhesive layer is more uniform, and when the optical adhesive layer is used for the flexible display module, the bending performance of the flexible display module can be further improved, the deformation of the flexible display module is reduced, and the crease is reduced.

In an alternative implementation, the gradient range of the storage modulus of the optical adhesive layer narrows in the thickness direction of the optical adhesive layer. Therefore, the stress and strain distribution of the optical adhesive layer is more uniform, when the optical adhesive layer is used for a flexible display module, the bending performance of the flexible display module can be improved, the deformation of the flexible display module is reduced, and accordingly, the crease is reduced and the reliability of the display module is improved.

In a second aspect of the embodiment of the present application, a method for preparing an optical adhesive layer is provided, where the method includes: coating the optical cement prepolymer liquid or the liquid optical cement on a carrier; controlling the curing energy applied to the optical cement pre-polymerization liquid or the liquid optical cement so that the curing energy is gradually reduced from the middle to two sides to obtain a cured optical cement layer, wherein the optical cement layer comprises at least one gradual change area on the plane of the optical cement layer, the storage modulus of the optical cement layer is gradually reduced from the middle to two sides along the direction perpendicular to the first axis in the gradual change area, the viscosity of the optical cement layer is gradually increased from the middle to two sides, and the optical cement layer is symmetrical about the first axis. Therefore, the storage modulus of the optical adhesive layer is distributed gradually, so that the stress and strain distribution of the optical adhesive layer at each position during bending is more uniform, and when the optical adhesive layer is used in electronic equipment, the reliability of the electronic equipment is improved, and the crease depth of the folding screen is reduced.

In an alternative implementation manner, before the optical cement pre-polymerization liquid or the liquid optical cement is coated on the carrier, the method further includes: uniformly mixing 40-45 parts of acrylic acid-2-ethylhexyl ester, 40-50 parts of isobornyl acrylate, 10-15 parts of 4-hydroxy butyl acrylate, 2-5 parts of photoinitiator and 1-hydroxy cyclohexyl phenyl ketone, polymerizing, adding 2-5 parts of cross-linking agent and 1, 4-butanediol diacrylate after the reaction is finished, and uniformly mixing to obtain the optical adhesive prepolymer or the liquid optical adhesive. Therefore, the crease depth of the electronic equipment is further reduced by adopting the light glue layer with the formula.

In an alternative implementation, controlling the curing energy applied to the optical cement pre-polymer solution or the liquid optical cement such that the curing energy decreases from the middle to the two sides includes: and controlling the moving speed of the carrier coated with the optical cement prepolymer liquid or the liquid optical cement in ultraviolet light or an incubator to obtain the optical cement layer, wherein the moving speed of the carrier is increased from the middle to the two sides of the gradual change region. Therefore, the curing energy at different positions and the crosslinking density of the optical adhesive layer can be regulated and controlled by controlling the moving speed of the carrier in the incubator, so that the optical adhesive layer with gradually changed storage modulus is obtained.

In an alternative implementation, controlling the curing energy applied to the optical cement pre-polymer solution or the liquid optical cement such that the curing energy decreases from the middle to the two sides includes: controlling illumination intensity of ultraviolet light irradiated on different positions of the optical cement prepolymer liquid or liquid optical cement, and solidifying the optical cement prepolymer liquid or liquid optical cement to obtain the optical cement layer, wherein the illumination intensity is decreased from the middle of the gradual change region to two sides; or controlling the temperature of the optical cement prepolymer liquid or the liquid optical cement at different positions in the incubator, and solidifying the optical cement prepolymer liquid or the liquid optical cement to obtain the optical cement layer, wherein the temperature of the optical cement layer is gradually decreased from the middle to the two sides of the gradual change region. Therefore, the curing energy at different positions and the crosslinking density of the optical adhesive layer can be regulated and controlled by regulating the intensity of ultraviolet light and the temperature of the incubator, so that the optical adhesive layer with gradually changed storage modulus is obtained.

In an alternative implementation, controlling the curing energy applied to the optical cement pre-polymer solution or the liquid optical cement such that the curing energy decreases from the middle to the two sides includes: a mask plate is arranged on the surface of the carrier coated with the optical cement prepolymer liquid or the liquid optical cement, and the optical cement layer is obtained by irradiating the optical cement prepolymer liquid or the liquid optical cement through the mask plate by ultraviolet light; the optical cement prepolymer liquid or the liquid optical cement in different areas has different light transmittance, and the light transmittance of the mask decreases from the middle to two sides of the gradual change area. Therefore, the optical adhesive layer with gradually changed storage modulus can be obtained by controlling the light transmittance of the mask.

In a third aspect of embodiments of the present application, an optical adhesive layer assembly is provided, including an optical adhesive layer as described above, a first release film and a second release film, where the first release film covers an inner surface of the optical adhesive layer, and the second release film covers an outer surface of the optical adhesive layer. Therefore, the optical adhesive component comprises the optical adhesive layer with gradually changed storage modulus, so that stress and strain at each position of the optical adhesive layer are distributed more uniformly when the optical adhesive layer is bent, and when the optical adhesive layer is used in electronic equipment, the reliability of the electronic equipment is improved, and the crease depth of the electronic equipment is reduced.

In a fourth aspect of the embodiments of the present application, a flexible display module is provided, where the flexible display module includes a plurality of functional layers, and at least two adjacent functional layers are bonded by using an optical adhesive layer as described above. Therefore, the optical adhesive layer with the gradually changed storage modulus is adopted by the flexible display module, so that the reliability of the flexible display module can be improved, and the crease depth of the flexible display module can be reduced.

In an alternative implementation, the flexible display module includes: the optical adhesive layer comprises a first non-bending region, a second non-bending region and a bending region positioned between the first non-bending region and the second non-bending region, wherein the bending region is positioned in a gradual change region of the optical adhesive layer. Therefore, the bending area is positioned in the gradual change area of the optical adhesive layer, and the optical adhesive layer can ensure that the flexible module still has enough bending strain and simultaneously can also quickly and effectively relax stress generated on adjacent functional layers during bending, so that the deformation of the flexible module is reduced and the crease is reduced.

In an alternative implementation, the bending region is symmetrical about a bending axis, the bending axis coinciding with the first axis of the optical adhesive layer. Therefore, when the flexible display module is installed, the bending axis of the flexible display module is overlapped with the axis of the optical adhesive layer, so that the deformation of the flexible display module can be further reduced, and the crease is reduced.

In an alternative implementation, the flexible display module includes: the first bending zone, the second bending zone, the third bending zone, the first bending zone between the first bending zone and the second bending zone, and the second bending zone between the second bending zone and the third bending zone, the gradual change zone of the optical adhesive layer comprises: the first bending region is located in the first sub-gradual change region, and the second bending region is located in the second sub-gradual change region. Therefore, the optical adhesive layer can be used for a three-fold flexible display module, and the bending area is positioned in the gradual change area of the optical adhesive layer, so that the optical adhesive layer can also quickly and effectively relax stress generated on adjacent functional layers during bending while ensuring that the flexible module still has enough bending strain, and the deformation of the flexible module is reduced and the crease is reduced.

In an alternative implementation, the first bending region is symmetrical about a first bending axis, the second bending region is symmetrical about a second bending axis, the first axis of the first sub-graded region coincides with the first bending axis, and the first axis of the second sub-graded region coincides with the second bending axis. Therefore, when the flexible display module is installed, the bending axis of the flexible display module is overlapped with the axis of the optical adhesive layer, so that the deformation of the flexible display module can be further reduced, and the crease is reduced.

In an alternative implementation, a multilayer laminated optical cement layer is provided between two adjacent functional layers. Therefore, the bending performance of the flexible display module can be further improved by arranging the multilayer optical adhesive layers between the adjacent functional layers.

In an optional implementation manner, the flexible display module comprises a plurality of layers of the optical adhesive layer, and in the thickness direction of the flexible display module, along the direction of decreasing the bending radius, the gradual change area of the storage modulus of the optical adhesive layer becomes smaller, wherein the bending radius is the radius of an arc formed by the bending part when each layer of the flexible display module is bent. Therefore, when the optical adhesive layer is used for the flexible display module, the bending performance of the flexible display module is guaranteed, the deformation of the flexible display module is reduced, and the crease depth is reduced.

In an alternative implementation manner, the flexible display module comprises a plurality of layers of the optical adhesive layers, in the thickness direction of the flexible display module, the storage modulus of the optical adhesive layers is reduced along the direction of reducing the bending radius, and the viscosity of the optical adhesive layers is increased along the direction of reducing the bending radius, wherein the bending radius is the radius of an arc formed by a bending part when each layer of the flexible display module is bent. Therefore, when the optical adhesive layer is used for the flexible display module, the bending performance of the flexible display module is guaranteed, the deformation of the flexible display module is reduced, and the crease depth is reduced.

In an alternative implementation, the functional layer includes: cover plate, polaroid, touch control membrane, display panel and flexible substrate. Thus, the optical adhesive layer can be arranged at a plurality of positions in the flexible display module.

In a fifth aspect of the embodiments of the present application, an optical adhesive layer assembly is provided, and an electronic device is provided, including at least a middle frame and a flexible display module as described above; wherein, this flexible display module assembly sets up on this center. Therefore, the electronic equipment adopts the flexible display module, and the bending performance is better.

Drawings

Fig. 1A is a schematic structural diagram of a foldable display terminal according to an embodiment of the present application;

FIG. 1B is a schematic diagram illustrating a disassembled structure of the foldable display terminal in FIG. 1A;

FIG. 2 is a view showing a usage state of the foldable display terminal of FIG. 1A;

FIG. 3 is a state diagram of the foldable display terminal of FIG. 1A;

FIG. 4 is an unfolded state diagram of the folder display terminal of FIG. 1A;

FIG. 5 is a schematic diagram of a flexible display module;

FIG. 6 is a schematic structural diagram of a flexible display module according to the related art;

FIG. 7 is a schematic diagram of the structure of the optical adhesive layer in FIG. 6;

FIG. 8 is a schematic diagram illustrating a bending state of the optical adhesive layer in FIG. 6;

fig. 9 is a schematic structural diagram of a first optical adhesive layer according to an embodiment of the present application;

FIG. 10 is a perspective view of the optical cement layer of FIG. 9;

FIG. 11 is a schematic diagram of a second optical adhesive layer according to an embodiment of the present application;

fig. 12 is a schematic structural diagram of a third optical adhesive layer according to an embodiment of the present application;

fig. 13 is a schematic structural diagram of a fourth optical adhesive layer according to an embodiment of the present application;

Fig. 14 is a schematic structural diagram of a fifth optical adhesive layer according to an embodiment of the present application;

Fig. 15 is a schematic structural diagram of a flexible display module provided in example one;

FIG. 16 is a schematic diagram illustrating a bending state of the flexible display module of FIG. 15;

FIG. 17 is a schematic diagram of an optical adhesive layer of FIG. 15;

Fig. 18 is a schematic structural diagram of another flexible display module provided in example one;

FIG. 19 is a schematic diagram illustrating a bending state of the flexible display module of FIG. 18;

FIG. 20 is a schematic diagram of an optical adhesive layer of FIG. 18

FIG. 21 is a flowchart of a method for preparing an optical adhesive layer according to an example I;

Fig. 22, 23, 24, 25 and 26 are schematic views of a product structure for performing the steps of fig. 21;

fig. 27 is a schematic structural diagram of an optical adhesive layer provided in example two;

FIG. 28 is a schematic diagram of another optical adhesive layer according to example II;

FIG. 29 is a flowchart of a method for preparing an optical cement layer according to example two;

FIG. 30 is a schematic diagram of an optical cement layer according to example III;

FIG. 31 is a schematic illustration of another optical cement layer provided in example III;

fig. 32 is a schematic structural diagram of a flexible display module according to an embodiment of the present application;

FIG. 33 is a schematic diagram of the structure of the optical adhesive layer in FIG. 32;

fig. 34 is a schematic structural diagram of a flexible display module according to an embodiment of the present application;

FIG. 35 is a schematic diagram of the optical adhesive layer of FIG. 34;

fig. 36 is a schematic structural diagram of a flexible display module according to an embodiment of the present application;

FIG. 37 is a schematic view of the optical adhesive layer of FIG. 36;

Fig. 38 is a schematic structural diagram of a flexible display module according to an embodiment of the present application;

fig. 39 is a schematic diagram of the structure of the optical adhesive layer in fig. 38.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings.

Hereinafter, the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first", "a second", etc. may explicitly or implicitly include one or more such feature. In the description of the present application, unless otherwise indicated, the meaning of "a plurality" is two or more.

Furthermore, in the present application, directional terms "upper", "lower", etc. are defined with respect to the orientation in which the components are schematically disposed in the drawings, and it should be understood that these directional terms are relative concepts, which are used for description and clarity with respect thereto, and which may be changed accordingly in accordance with the change in the orientation in which the components are disposed in the drawings.

The embodiment of the application provides electronic equipment which is a folding display terminal, wherein the folding display terminal can be a product with a display interface, such as a mobile phone, a display, a tablet personal computer, a vehicle-mounted computer and the like. The embodiment of the application does not limit the specific form of the folding display terminal.

In order to facilitate understanding of the folding display terminal provided by the embodiment of the present application, referring to fig. 1A and fig. 1B, an existing folding display terminal is described as follows:

As shown in fig. 1A and 1B, the folding display terminal 1 includes a flexible display module 10. The flexible display module 10 may be an Active Matrix Organic Light Emitting Diode (AMOLED) display screen.

The AMOLED display screen is used as a self-luminous display screen, and a backlight module (back light module, BLM) is not required to be arranged. Accordingly, when the substrate in the AMOLED display panel is made of a flexible resin material, such as polyethylene terephthalate (polyethylene terephthalate, PET), the AMOLED display panel can have a bendable property.

In addition, as shown in fig. 1A and 1B, the folding display terminal 1 further includes a folding assembly 20 for carrying the flexible display module 10.

It should be noted that, the related drawings of the folding assembly 20 in the present application are simplified schematic structural diagrams, and the folding assembly 20 is not limited to the structure shown in the drawings, but may include other structures, which are not described herein.

The folding assembly 20 includes a first structural member 201, a second structural member 202, and a pivot 203 between the first and second structural members 201, 202.

The rotating shaft 203 is connected to the first structural member 201 and the second structural member 202. The first structural member 201 and the second structural member 202 are rotatable about respective axes of rotation 203. The first structural member 201 and the second structural member 202 may be a case or a middle frame structure of the electronic device.

In some embodiments, the first structural member 201 and the second structural member 202 are middle frames, the first structural member 201 including a first rim 2010 and the second structural member 202 including a second rim 2020.

The first structural member 201 and the second structural member 202 may be used to carry the flexible display module 10, so that the flexible display module 10 is kept flat as much as possible during use, and the non-display surface of the flexible display module 10 is protected.

A part of the flexible display module 10 is fixed on the first structural member 201 through the adhesive layer, a part of the flexible display module 10 is fixed on the second structural member 202 through the adhesive layer, and the rest of the flexible display module 10 is located between the first structural member 201 and the second structural member 202. The glue layer may be a film layer formed after glue is applied, and the specific form of the glue layer is not limited in the embodiment of the present application. In addition, other electronic components, for example, a camera, a headset, a headphone, a key, a battery, etc., may be further disposed on the first structural member 201 and the second structural member 202, and the embodiment of the present application is not limited to the other electronic components disposed on the first structural member 201 and the second structural member 202.

The first structural member 201 and the second structural member 202 may rotate along the axis O-O of the rotating shaft 203, so as to drive the flexible display module 10 to fold or unfold. Fig. 2, 3, and 4 may be A-A cross-sectional views of the folding display terminal of fig. 1A. The flexible display module may be folded and flattened as shown in fig. 2, wherein fig. 2 is a flattening process in which the flexible display module is flattened from 180 ° to 0 °, or a folding process in which the flexible display module is folded from 0 ° to 180 °.

As shown in fig. 3, when the included angle α between the first structural member 201 and the second structural member 202 is 0 °, the flexible display module 10 is in a folded state.

Or as shown in fig. 4, when the angle α between the first structural member 201 and the second structural member 202 increases to 180 °, the flexible display module 10 is in the unfolded state.

In the case where the first structural member 201 and the second structural member 202 do not have bending characteristics, the area of the flexible display module 10 bonded to the first structural member 201 through the adhesive layer cannot be bent, and the partial area is the first non-bending area 101 as shown in fig. 2.

The area of the flexible display module 10 bonded to the second structural member 202 through the adhesive layer cannot be bent under the load of the second structural member 202, and the partial area is the second non-bending area 102 as shown in fig. 2.

In addition, in the flexible display module 10, a portion located between the first non-bending region 101 and the second non-bending region 102 is a bending region 103 that enables bending to occur when the folded display terminal 1 is folded.

Wherein the flexible display module 10 includes a plurality of functional layers, as shown in fig. 5, the flexible display module includes: a cover sheet 1005, a polarizer 1004, a touch film 1003, a display panel 1002, a flexible substrate 1001, or other functional layers of a folding screen are stacked.

Wherein, at least two adjacent functional layers are bonded by an optical adhesive layer (Optically CLEAR ADHESIVE, OCA).

Referring next to fig. 5, adjacent two functional layers are bonded together by an optical adhesive layer 100.

The optical adhesive layer 100 plays a role in bonding functional layers in a folding screen mobile phone, and can also be used as a neutral layer to absorb stress generated when the functional layers are folded so as to avoid layering. To achieve the function of continuous folding and unfolding, existing optical adhesives typically select a flexible material with a lower modulus.

However, when the folding screen is folded and unfolded, the folding area is more prone to deformation compared with the non-folding area, and the same layer of optical adhesive has uneven stress and strain distribution at different positions of the folding area, so that irreversible deformation of the lamination can be caused for a long time, and folds are generated, and the folds can affect the flatness of the display device.

Fig. 6 is a schematic structural diagram of a flexible display module according to the related art, as shown in fig. 6, the flexible display module 10 includes: a first functional layer 001, an optical cement layer 100 and a second functional layer 002, wherein the first functional layer 001 is bonded by the optical cement layer 100 and the second functional layer 002.

In some embodiments, as shown in fig. 7 and 8, the optical adhesive layer 100 has a deformation region 12 and a non-deformation region 11 with different viscoelasticity, and the viscoelasticity in the deformation region 12 is better than that of the non-deformation region 11, so that the stress in the deformation region 12 is relaxed quickly, the stress concentration degree of the flexible panel after multiple deformation is avoided, and the plastic deformation accumulation and the structural failure are alleviated.

The optical adhesive layer 100 may be an OCA optical adhesive film or a pressure sensitive adhesive film, and the deformation region 12 is in the middle region of the optical adhesive layer 100, and the non-deformation region 11 is in the region other than the opposite sides of the middle region.

In some embodiments, the viscoelastic properties of the deformed region 12 of the optical cement layer 100 may be made greater than the viscoelastic properties of the non-deformed region 11.

By adjusting the viscoelasticity of the optical adhesive layer 100 so that the viscoelasticity of the deformation region is better than that of the non-deformation region, the deformation capability and the deformation recovery capability of the optical adhesive layer 100 in the deformation region 12 are better than those of the non-deformation region 11, so that the stress absorption capability of the deformation region is stronger than that of the non-deformation region.

However, the viscoelastic abrupt change at the junction of the deformed region 12 and the non-deformed region 11 of the optical adhesive layer 100 is liable to cause structural failure.

Therefore, the embodiment of the application provides an improved optical adhesive layer 100 and a preparation scheme thereof, so that stress and strain distribution received by each area of the optical adhesive layer 100 is more uniform.

Fig. 9 is a schematic structural diagram of an optical adhesive layer 100 according to an embodiment of the present application. Fig. 10 is a perspective view of the optical cement layer of fig. 9. As shown in fig. 9 and 10, on the plane (XOY plane) of the optical adhesive layer 100, the storage modulus of the optical adhesive layer 100 decreases from the first axis O to both sides thereof, and the viscosity of the optical adhesive layer 100 increases from the first axis O to both sides thereof.

Wherein storage modulus (storage modulus) is an indicator of the resilience of a material after deformation, indicating the ability of the material to store elastic deformation energy.

The adhesiveness of the optical cement layer 100 is the adhesiveness between the optical cement and the functional layer, including interfacial adhesion and cohesive force.

Referring to fig. 9 and 10, the direction of the first axis O is parallel to the Y-axis, and the storage modulus of the optical adhesive layer 100 decreases toward both sides of the first axis O along the +x direction and the-X direction, respectively. That is, the storage modulus is the greatest at the first axis O, the farther from the first axis O the smaller the storage modulus. In the present application, O is a virtual axis, wherein the optical cement layer 100 is symmetrical with respect to the first axis O.

In fig. 9 and 10, the storage modulus is represented by the density of the filling pattern, and the larger the density is, the larger the storage modulus is, and the smaller the density is, and the smaller the storage modulus is.

Therefore, the storage modulus of the optical adhesive layer is large in the middle and small in the two sides, the viscosity of the optical adhesive layer is small in the middle and large in the two sides, the bonding surfaces of the optical adhesive layer on the two sides are bonded with the non-bending areas of the flexible display module, the middle position of the optical adhesive layer is bonded with the bending areas of the flexible display module, and when the optical adhesive layer is applied to the flexible display module, on one hand, the optical adhesive layer with larger modulus at the middle position can still have enough bending strain while the stress on the adjacent functional layers can be quickly and effectively relaxed and bent, so that the deformation of the flexible module is reduced. On the other hand, the optical adhesive layer and the adjacent functional layer in the flexible module are adhered with larger adhesion at the position, so that larger adhesion force between the optical adhesive layer and the adjacent functional layer is ensured, and the optical adhesive layer is not easy to be debonded, thereby ensuring the reliability of the adhesive assembly of the whole display module. Meanwhile, as the storage modulus of the optical adhesive layer is gradually distributed, the stress and strain distribution of the optical adhesive layer at each position during bending is more uniform, and when the optical adhesive layer is used in electronic equipment, the reliability of the electronic equipment is improved, and the crease depth of the electronic equipment is reduced.

The material of the optical adhesive layer 100 is not limited in the embodiment of the present application, and the material of the optical adhesive layer 100 includes: monomer or polymer chains of acrylate, silicone, epoxy, polyamino ester and other systems. The optical cement layer 100 may be made of one or more series of monomers or polymer chains.

When the optical cement is prepared, the optical cement prepolymer or the liquid optical cement can be uniformly coated on the carrier in the modes of coating, dispensing, or ink-jet printing and the like, and the optical cement with gradually changed properties can be obtained by controlling the ultraviolet curing or heat curing energy of the optical cement raw materials at different positions of the carrier.

The embodiment of the present application does not limit the gradual change direction of the optical cement layer 100. In some embodiments of the present application, the storage modulus of the optical cement layer 100 decreases from the middle to the two sides in the direction perpendicular to the first axis O, and the viscosity of the optical cement layer 100 increases from the middle to the two sides.

Wherein, the first area of the optical adhesive layer 100 is used for bending around the bending axis when the display screen is bent. The projection of the bending axis on the optical cement layer 100 is located at the middle position of the optical cement layer 100, and the optical cement layer 100 is symmetrical with respect to the projection of the bending axis on the optical cement layer 100.

In other embodiments of the present application, as shown in fig. 11, the storage modulus of the optical adhesive layer 100 decreases from the first axis O to both sides thereof and decreases from the second axis O ' to both sides thereof in the plane of the optical adhesive layer 100, the tackiness of the optical adhesive layer increases from the first axis O to both sides thereof and increases from the second axis O ' to both sides thereof, and the second axis O ' intersects the first axis O. The tackiness of the optical cement layer 100 increases from the center of the optical cement layer 100 to the edge in a direction perpendicular to the first axis O and perpendicular to the second axis O', respectively.

Therefore, the storage modulus of the optical adhesive layer gradually changes to multiple directions, so that the stress and strain distribution of the optical adhesive layer at each position during bending is more uniform, the reliability of the electronic equipment is further improved, and the crease depth of the folding screen is reduced.

Referring to fig. 11, the direction of the first axis O is parallel to the Y-axis, the direction of the second axis O 'is parallel to the X-axis, and the storage modulus of the optical adhesive layer 100 decreases along the +x-direction and the-X-direction, respectively, toward both sides of the first axis O, and at the same time, the storage modulus of the optical adhesive layer 100 decreases along the +y-direction and the-Y-direction, respectively, toward both sides of the second axis O'. That is, the storage modulus is the greatest at the intersection of the second axis O 'and the first axis O, and the farther the second axis O' is from the intersection of the first axis O, the smaller the storage modulus. In the present application, the first axis O and the second axis O' are virtual axes, wherein the optical cement layer 100 is symmetrical with respect to the first axis O.

Illustratively, the first axis O and the second axis O' are perpendicular. The storage modulus of the optical cement layer 100 decreases to the periphery in a rectangular gradual manner.

In other embodiments, the storage modulus of the optical cement layer 100 decreases in a diamond-shaped progression toward the periphery. Therefore, the storage modulus of the optical adhesive layer gradually decreases from the center to the four sides, so that the stress and strain distribution is more uniform, and the bonding stability of the edge of the flexible display module is improved.

In other embodiments of the present application, as shown in fig. 12, the storage modulus of the optical adhesive layer 100 decreases around in a circular gradual manner around the center of the optical adhesive layer on the plane of the optical adhesive layer 100, and the viscosity of the optical adhesive layer increases around in a circular gradual manner around the center of the optical adhesive layer, wherein the center of the optical adhesive layer is located on the first axis.

Illustratively, the storage modulus of the optical cement layer 100 decreases in a rounded gradual manner to the periphery.

Therefore, the storage modulus of the optical adhesive layer gradually decreases from the center to the periphery, so that the stress and strain distribution is more uniform, and the bonding stability of the edge of the flexible display module is improved.

In other embodiments of the present application, as shown in fig. 13 and 14, the storage modulus of the optical adhesive layer 100 decreases along the thickness direction of the optical adhesive layer 100. Therefore, the stress and strain distribution of the optical adhesive layer is more uniform, when the optical adhesive layer is used for a flexible display module, the bending performance of the flexible display module can be further improved, the bending performance of the flexible display module is reduced, the deformation of the flexible display module is reduced, and accordingly the crease is reduced.

The thickness direction of the optical adhesive layer 100 is the Z direction, and as shown in fig. 13, for example, the optical adhesive layer 100 is one layer, and the storage modulus of the optical adhesive layer 100 may decrease along the +z direction.

As another example, as shown in fig. 14, the optical adhesive layer 100 is a plurality of layers, the optical adhesive layers 100 are stacked, and the storage modulus of the optical adhesive layers 100 decreases in the thickness direction. Wherein the storage modulus of the optical cement layer 100 may decrease in the +z direction.

The manner in which the optical adhesive layer 100 is disposed in the flexible display module, and the structure and manufacturing process of the optical adhesive layer 100 are described below in connection with examples one, two, three, and four.

Example one:

Fig. 15 is a schematic structural diagram of a flexible display module according to an exemplary embodiment of the present application. The flexible display module comprises a first functional layer 001, an optical adhesive layer 100 and a second functional layer 002, wherein the first functional layer 001 is adhered to the second functional layer 002 through the optical adhesive layer 100. The first functional layer 001 and the second functional layer 002 may be flexible cover plate, polarizer, touch film, display panel, flexible substrate, and other functional layers.

As shown in fig. 16, on the plane (XOY plane) of the optical adhesive layer 100, the storage modulus of the optical adhesive layer 100 decreases from the middle to the two sides in the direction perpendicular to the first axis O, and the viscosity of the optical adhesive layer 100 increases from the middle to the two sides.

Referring to fig. 15, the direction of the first axis O is parallel to the Y-axis, and the storage modulus of the optical cement layer 100 decreases toward both sides of the first axis O along the +x direction and the-X direction, respectively. That is, the storage modulus is the greatest at the first axis O, the farther from the first axis O the smaller the storage modulus. In the present application, O is a virtual axis, wherein the optical cement layer 100 is symmetrical with respect to the first axis O.

Wherein, this flexible display module assembly can divide into: a inflection region and a non-inflection region.

In some embodiments of the present example, as shown in fig. 15 and 16, the flexible display module includes: a first non-inflection region 101, a second non-inflection region 102, and a first inflection region 103 located between the first non-inflection region 101 and the second non-inflection region 102.

The optical cement layer 100 includes: a first region in the first non-inflection region 101, a second region in the second non-inflection region 102, and a third region in the first inflection region 103.

The flexible display module is provided with a first bending axis A, and the optical adhesive layer 100 is used for bending around the first bending axis A when the display screen is bent. The projection of the first bending axis a on the optical adhesive layer 100 is located at the middle position of the third area of the optical adhesive layer 100, and the optical adhesive layer 100 is symmetrical about the bending axis.

In some embodiments of the present example, as shown in fig. 17, the bending axis a may be the first axis O of the optical cement layer 100. That is, the storage modulus of the optical adhesive layer 100 may be made to decrease from the middle to the two sides in the direction perpendicular to the a axis, while the tackiness of the optical adhesive layer 100 is made to increase from the middle to the two sides in the direction perpendicular to the a axis.

In other embodiments of the present example, as shown in fig. 18 and 19, the flexible display module includes: a first non-inflection region 101, a second non-inflection region 102, a third non-inflection region 104, a first inflection region 103 located between the first non-inflection region 101 and the second non-inflection region 102, and a second inflection region 105 located between the second non-inflection region 102 and the third non-inflection region 104.

The optical cement layer 100 includes: a first region in the first non-inflection region 101, a second region in the second non-inflection region 102, a third region in the first inflection region 103, a fourth region in the third non-inflection region 104, and a fifth region in the second inflection region 105.

As shown in fig. 18, the flexible display module has a first bending axis a and a second bending axis B, and the optical adhesive layer 100 is used for bending around the first bending axis a and the second bending axis B when the display screen is bent. The projection of the first bending axis a on the optical adhesive layer 100 is located at the middle position of a third area of the optical adhesive layer 100, and the third area is axisymmetric with respect to the first bending axis a. The projection of the second bending axis B on the optical adhesive layer 100 is located at the middle position of the fifth area of the optical adhesive layer 100, and the fifth area is axisymmetric with respect to the second bending axis B.

In some embodiments of the present example, as shown in fig. 20, the first bending axis a may be the first axis O of the optical adhesive layer 100, and the second bending axis B may also be the first axis O of the optical adhesive layer 100. That is, the storage modulus of the optical adhesive layer 100 decreases from the middle to the two sides in the direction perpendicular to the first bending axis a, and the storage modulus of the optical adhesive layer 100 decreases from the middle to the two sides in the direction perpendicular to the second bending axis B. Meanwhile, the viscosity of the optical adhesive layer 100 increases from the middle to two sides along the direction perpendicular to the first bending axis a, and the viscosity of the optical adhesive layer 100 increases from the middle to two sides along the direction perpendicular to the second bending axis B.

In some embodiments of the present example, the thickness of the optical cement layer 100 ranges from 15 to 50 μm, with a graded region of storage modulus of about 2cm. Along the direction perpendicular to the bending axis, the storage modulus of the optical cement layer 100 gradually decreases from the bending axis to the edge of the gradual change region, the storage modulus of the optical cement at the position of the bending axis is 80-160 kPa, and the storage modulus of the optical cement at the edge of the gradual change region is 20-30 kPa.

In some embodiments of the present example, the optical cement layer 100 may be divided into: the storage modulus gradient region and the edge region, wherein the storage modulus value of the optical cement layer 100 at the edge region is equal, about 20-30 kP.

The present example also provides a process for preparing the optical cement layer 100, as shown in fig. 21, which includes:

S101, as shown in FIG. 22, coating the optical cement prepolymer 03 or liquid optical cement on a carrier;

Wherein, in some embodiments of the present example, an optical cement prepolymer solution is adopted, and the preparation process of the optical cement prepolymer solution 03 comprises:

Adding functional additives such as photoinitiator or thermal initiator, chain transfer agent and other auxiliary materials into one or more series of monomers or polymer chains in the system of polyamino ester, organosilicon, acrylic ester, epoxy resin and the like, uniformly mixing, then carrying out polymerization reaction in a photoinitiation or thermal initiation mode, adding a certain amount of crosslinking agent and auxiliary agent after the reaction is finished, and uniformly mixing to obtain the optical cement prepolymer 03.

For example, 40 to 45 parts of 2-ethylhexyl acrylate, 40 to 50 parts of isobornyl acrylate, 10 to 15 parts of 4-hydroxybutyl acrylate and 2 to 5 parts of photoinitiator are uniformly mixed, nitrogen is introduced to protect the mixture and irradiated for 1 to 2 minutes under the ultraviolet light of 65W for polymerization, 2 to 5 parts of cross-linking agent is added after the reaction is finished, and the mixture is uniformly mixed to obtain the optical cement prepolymer 03.

The raw material of the optical adhesive layer 100 in this embodiment is not limited to an acrylate system. The photoinitiator may be 1-hydroxycyclohexyl phenyl ketone. The cross-linking agent can be 1, 4-butanediol diacrylate.

The gradual change optical adhesive layer and the non-gradual change optical adhesive layer are respectively prepared by adopting the formula, and bending tests are carried out on the two optical adhesive layers, for example: bending for 12-24 hours, and detecting crease depths of the two optical adhesive layers.

The test shows that the crease depth of the graded optical adhesive layer can be reduced by 30% compared with that of the non-graded optical adhesive layer. Therefore, the crease depth of the electronic equipment can be reduced by arranging the graded light glue layer.

In some embodiments of the present example the carrier may be a release film. The release film is a film with a distinguishing surface energy, and has no viscosity or slight viscosity after being contacted with the optical adhesive layer 100, can be used for bearing the optical adhesive layer 100, can isolate and protect the optical adhesive layer 100, and is easy to peel.

The optical adhesive layer 100 is formed on the release film, and when in use, the optical adhesive layer 100 can be taken down from the release film and stuck on the functional layer of the flexible display module.

In other embodiments of the present example, the carrier may be a functional layer of the flexible display module, i.e., the optical cement layer 100 may be directly molded onto the functional layer of the flexible display module.

The present example does not limit the manner in which the optical cement prepolymer 03 is provided on the carrier. In some embodiments of the present example, the optical cement pre-polymer liquid 03 may be disposed on the carrier by coating on the carrier. As shown in fig. 22, the optical cement prepolymer 03 having a uniform thickness can be uniformly coated on the two release films by a coater. Wherein, from the type membrane to be two-layer, do respectively: a first release film 01 and a second release film 02. The first release film 01 covers one surface of the optical cement prepolymer 03, and the second release film 02 covers the other surface of the optical cement prepolymer 03.

In other embodiments of the present example, a liquid optical cement is used, and as shown in fig. 25 and 26, the liquid optical cement 031 may be coated on the carrier by means of ink-jet printing.

As shown in a of fig. 25, the release film may be used as a carrier, and the liquid optical cement 031 may be uniformly dispensed or ink-jet printed on the second release film 02, so as to obtain the liquid optical cement 031 as shown in b of fig. 25, so that the liquid optical cement 031 is uniformly coated on the carrier, and then, as shown in c of fig. 25, the liquid optical cement 031 is pre-cured. The manner of curing the liquid optical cement is specifically described in step S102. For example, the ultraviolet light intensity of the liquid optical cement 031 at different positions can be controlled to realize different curing energy of different areas, and the different curing energy can also be realized by setting the mask 04 with gradually changed light transmittance. In this example, the light transmittance gradient mask 04 is set.

In other embodiments, as shown in a of fig. 26, a release film may be used as a carrier, and a liquid optical adhesive may be printed on the second release film 02 by inkjet, where the material composition of the liquid optical adhesive at different positions may be adjusted to obtain a liquid optical adhesive 031 shown in b of fig. 26, where the storage modulus of the liquid optical adhesive 031 is graded, and then, as shown in c of fig. 26, the liquid optical adhesive 031 is cured, where the curing manner includes ultraviolet curing and curing by heating in an incubator, and uniform ultraviolet irradiation may be performed on the liquid optical adhesive 031, or the liquid optical adhesive may uniformly pass through the incubator to obtain a light adhesive layer shown in fig. 17 or fig. 20.

S102, as shown in fig. 23 and 24, controlling the curing energy applied to the optical cement pre-polymerization liquid or the liquid optical cement so that the curing energy is reduced from the middle to the two sides, and obtaining the cured optical cement layer 100 as shown in fig. 17 and 20.

Wherein the storage modulus of the optical adhesive layer 100 decreases from the middle to the two sides along the direction perpendicular to the first axis, and the viscosity of the optical adhesive layer 100 increases from the middle to the two sides.

When the optical cement prepolymer 03 is cured, the different-area differentiated curing energy can be realized by controlling the moving speed of the substrate of the optical cement prepolymer 03 under ultraviolet light, and the different-area differentiated curing energy can be realized by controlling the light transmittance of the mask plate, so that the light cement layer with gradually changed storage modulus is finally obtained.

In some embodiments of the present example, as shown in fig. 23, the controlling the curing energy applied to the optical cement pre-polymer liquid or the liquid optical cement such that the curing energy decreases from the middle to both sides includes:

controlling the moving speed of the carrier coated with the optical cement pre-polymerization liquid 03 or the liquid optical cement in ultraviolet light or an incubator, so that the moving speed of the optical cement pre-polymerization liquid 03 firstly decreases from one side of the gradual change area to the middle and then increases from the middle of the gradual change area to the other side.

The slower the carrier moving speed is, the longer the optical cement prepolymer 03 or the liquid optical cement at the position is heated in the incubator, the more curing energy is obtained, the higher the curing degree is, and the greater the storage modulus and the lower the viscosity of the obtained optical cement layer at the position are.

On the contrary, the faster the carrier moving speed is, the shorter the heating time of the optical cement prepolymer 03 or the liquid optical cement at the position in the incubator is, the less the obtained curing energy is, the lower the curing degree is, and the lower the storage modulus of the obtained optical cement layer at the position is, the higher the viscosity is.

The intensity of the ultraviolet lamp is 300W and the irradiation distance is 25cm, for example. The irradiation time of the edge position of the gradual change area is about 2-3 min, and the irradiation time of the bending axis is about 15-20 min.

Therefore, by controlling the moving speed of the release film, the irradiation time of the gradual change area gradually increases linearly from the edge position to the rotating shaft area, the crosslinking density is improved, and the gradual change of the modulus of the optical adhesive layer 100 is realized.

In other embodiments of the present example, as shown in fig. 24, the controlling the curing energy applied to the optical cement pre-polymer liquid or the liquid optical cement such that the curing energy decreases from the middle to both sides includes:

And arranging a mask 04 with gradually changed light transmittance on the surface of the carrier coated with the optical cement prepolymer 03 or the liquid optical cement, so that ultraviolet light irradiates the optical cement prepolymer 03 or the liquid optical cement through the mask 04.

The optical cement pre-polymerization liquid 03 in different areas has different light transmittance of the mask 04, and the light transmittance of the mask 04 from the middle to the edge of the optical cement layer 100 decreases.

The higher the light transmittance is, the more curing energy is obtained by the optical cement prepolymer 03 or the liquid optical cement, the higher the curing degree is, and the larger the storage modulus and the smaller the viscosity of the obtained optical cement layer are at the position.

On the contrary, the lower the light transmittance is, the lower the curing energy obtained by the optical cement prepolymer 03 or the liquid optical cement is, the lower the curing degree is, and the lower the storage modulus of the obtained optical cement layer is at the position, the higher the viscosity is.

For example, the intensity of the ultraviolet lamp was 300W, the irradiation distance was 25cm, the irradiation time was 20min, the ultraviolet transmittance at the edge position of the gradation region was 10%, and the ultraviolet transmittance at the bending axis was 100%.

Therefore, the mask plates with different ultraviolet light transmittance at different positions are adopted, so that the ultraviolet light transmittance of the gradual change region gradually increases from the edge position to the bending axis, the crosslinking density is improved, and the gradual change of the storage modulus is realized.

In other embodiments of the present example, controlling the curing energy applied to the optical cement pre-polymer liquid or liquid optical cement such that the curing energy decreases from the middle to both sides includes:

controlling the illumination intensity of ultraviolet light irradiated on different positions of the optical cement prepolymer liquid or the liquid optical cement, so that the illumination intensity is reduced from the middle of the gradual change region to the illumination intensity at two sides.

The higher the illumination intensity, the more curing energy is obtained by the optical cement prepolymer 03 or the liquid optical cement, the higher the curing degree is, and the greater the storage modulus and the lower the viscosity of the obtained optical cement layer at the position are.

On the contrary, the lower the illumination intensity is, the lower the curing energy obtained by the optical cement prepolymer 03 or the liquid optical cement is, the lower the curing degree is, and the lower the storage modulus of the obtained optical cement layer at the position is, the higher the viscosity is.

Or controlling the temperature of the temperature box at different positions of the optical cement pre-polymerization liquid or the liquid optical cement, so that the temperature is gradually decreased from the middle to two sides of the gradual change region.

The higher the temperature is, the more curing energy is obtained by the optical cement prepolymer 03 or the liquid optical cement, the higher the curing degree is, and the greater the storage modulus and the lower the viscosity of the obtained optical cement layer are at the position.

Conversely, the lower the temperature, the less curing energy is obtained by the optical cement prepolymer 03 or the liquid optical cement, the lower the curing degree is, and the lower the storage modulus of the obtained optical cement layer at the position is, the higher the viscosity is.

Therefore, the curing energy at different positions and the crosslinking density of the optical adhesive can be regulated and controlled by regulating the intensity of ultraviolet light and the temperature of the incubator, so that the optical adhesive layer with gradually changed storage modulus is obtained.

In an example one, the storage modulus of the optical adhesive layer adopts a linear gradual change mode, and the optical adhesive layer can be arranged between any two adjacent functional layers of the flexible display module, so that the bonding surfaces of the optical adhesive layer on two sides are bonded with the non-bending areas of the flexible display module, and the middle position of the optical adhesive layer is bonded with the bending areas of the flexible display module. Therefore, when the optical adhesive layer is applied to the flexible display module, on one hand, the optical adhesive layer with larger modulus at the middle position can ensure that the flexible module still has enough bending strain, and simultaneously can also quickly and effectively relax stress generated on adjacent functional layers during bending, so that the deformation of the flexible module is reduced. On the other hand, the optical adhesive layer and the adjacent functional layer in the flexible module are adhered with larger adhesion at the position, so that larger adhesion force between the optical adhesive layer and the adjacent functional layer is ensured, and the optical adhesive layer is not easy to be debonded, thereby ensuring the reliability of the adhesive assembly of the whole display module. Meanwhile, as the storage modulus of the optical adhesive layer is gradually distributed, the stress and strain distribution of the optical adhesive layer at each position during bending is more uniform, and when the optical adhesive layer is used in electronic equipment, the reliability of the electronic equipment is improved, and the crease depth of the electronic equipment is reduced.

Example two:

In example one, the storage modulus of the optical adhesive layer 100 is linearly graded on the plane of the optical adhesive layer 100, and example two is different from example one in that the storage modulus of the optical adhesive layer 100 is graded in multiple directions on the plane of the optical adhesive layer 100.

In some embodiments of the present example, as shown in fig. 27, the storage modulus of the optical cement layer 100 decreases from the middle to both sides of the optical cement layer 100 in the direction perpendicular to the first axis O and the direction perpendicular to the second axis O', which intersects the first axis O, respectively. Meanwhile, the viscosity of the optical cement layer 100 increases from the middle to both sides of the optical cement layer 100 in the directions perpendicular to the first axis O and the second axis O', respectively.

Referring to fig. 27, the direction of the first axis O is parallel to the Y-axis, the direction of the second axis O 'is parallel to the X-axis, and the storage modulus of the optical adhesive layer 100 decreases along the +x-direction and the-X-direction, respectively, toward both sides of the first axis O, and at the same time, the storage modulus of the optical adhesive layer 100 decreases along the +y-direction and the-Y-direction, respectively, toward both sides of the second axis O'. That is, the storage modulus is the greatest at the intersection of the second axis O 'and the first axis O, and the farther the second axis O' is from the intersection of the first axis O, the smaller the storage modulus. In the present application, the first axis O and the second axis O' are virtual axes, wherein the optical cement layer 100 is symmetrical with respect to the first axis O.

Illustratively, the first axis O and the second axis O' are perpendicular. The storage modulus of the optical cement layer 100 decreases to the periphery in a diamond-shaped gradual manner.

In other embodiments of the present example, as shown in fig. 28, the storage modulus of the optical adhesive layer further decreases along a radius in a direction away from the center of the circle, and the viscosity of the optical adhesive layer further increases along a radius in a direction away from the center of the circle, wherein the center of the optical adhesive layer is located on the first axis.

When the optical adhesive layer 100 is used for the flexible display module, the first axis of the optical adhesive layer 100 may be coincident with the bending axis of the flexible display module, and the specific setting manner of the optical adhesive layer 100 may refer to the description of example one, which is not repeated herein.

The following description will take an optical cement graded in the radial direction as an example. In some embodiments of the present example, the thickness of the optical cement layer 100 ranges from 15 to 50 μm, with a spot-shaped radiation graded region having a diameter of 6 cm.

In some embodiments of the present example, the optical cement layer 100 may be divided into: the storage modulus gradient region and the edge region, wherein the edge region is located at the edge of the storage modulus gradient region, and the storage modulus of the optical adhesive layer 100 of the edge region is equal to the optical adhesive modulus at the edge position of the gradient region.

The gradual change range of the optical cement layer 100 is a circle with a radius of 3cm, the storage modulus of the optical cement is gradually changed from the center of the optical cement layer 100 to the outside linearly along the circle, the storage modulus of the center of the optical cement layer 100 is 40-60 kPa, the storage modulus of the edge position of the gradual change region is 20-35 kPa, and the optical cement modulus of the rest regions is equal to the optical cement modulus of the edge position of the gradual change region and is 20-35 kPa. At the same time, the viscosity of the optical cement layer gradually increases from the center to the edge.

As shown in fig. 29, this example also provides a process for preparing the optical cement layer 100, where the raw material may be an optical cement pre-polymerization solution or a liquid optical cement, and in this example, the process includes:

s101, coating optical cement prepolymer liquid or liquid optical cement on a carrier;

in some embodiments of the present example, the preparation process of the optical cement prepolymer 03 includes:

The preparation of the optical cement prepolymer 03 comprises 20-40 parts of acrylic acid-2-ethylhexyl ester, 60-80 parts of acrylic acid isobornyl ester and 2-5 parts of photoinitiator 1-hydroxycyclohexyl phenyl ketone. After being uniformly mixed, the mixture is introduced into the reactor and is irradiated by 65W ultraviolet light for 1 to 2 minutes for polymerization, after the reaction is finished, 2 to 5 parts of cross-linking agent, 1, 4-butanediol diacrylate are added and uniformly mixed, and the optical cement prepolymer 03 is obtained.

Other descriptions of this step may refer to step S101 in example one, and will not be described here again.

S102, arranging a mask 04 with gradually changed light transmittance on the surface of the carrier coated with the optical cement prepolymer 03, so that ultraviolet light irradiates the optical cement prepolymer 03 through the mask 04, and obtaining the optical cement layer 100.

Wherein the storage modulus of the optical cement layer 100 decreases from the center of the optical cement layer 100 to the periphery along the radial direction.

When the optical cement prepolymer 03 is cured, different curing energies in different areas can be realized by controlling the light transmittance of the mask 04, and the light glue layer with gradually changed storage modulus can be obtained.

For example, the intensity of the ultraviolet lamp was 300W, the irradiation distance was 25cm, the irradiation time was 20min, the ultraviolet transmittance at the edge position of the gradation region was 10%, and the ultraviolet transmittance at the center of the gradation was 100%.

Therefore, the mask plates with different ultraviolet light transmittance at different positions are adopted, so that the ultraviolet light transmittance of the gradual change region gradually increases from the edge position to the center position, the crosslinking density is improved, and the gradual change of the storage modulus is realized.

In the light adhesive layer in the second example, the storage modulus gradually decreases from the center of the optical adhesive layer to the edge, so that the stress and strain distribution is more uniform, and meanwhile, the bonding stability of the edge of the flexible display module is improved.

Example three:

In the above-described first and second examples, the gradual change direction of the optical adhesive layer 100 is gradual change in the planar direction.

The present example differs in that the storage modulus of the optical adhesive layer 100 is graded in the thickness direction.

In some embodiments of the present example, as shown in fig. 30 and 31, the storage modulus of the optical adhesive layer 100 decreases along the thickness direction of the optical adhesive layer 100.

The thickness direction of the optical adhesive layer 100 is the Z direction. In some embodiments of the present example, as shown in fig. 30, the optical cement layer 100 is one layer, and the storage modulus of the optical cement layer 100 may decrease in the +z direction.

In preparing the optical cement layer 100, the liquid optical cement 03 may be disposed on a carrier by means of inkjet printing. The optical cement layer 100 may be formed by layer-by-layer inkjet printing, wherein the material composition of the liquid optical cement at different positions may be adjusted, so that the storage modulus of the optical cement layer 100 decreases along the thickness direction of the optical cement layer 100.

In other embodiments of the present example, as shown in fig. 31, the optical adhesive layer 100 is a plurality of layers, and the plurality of layers of the optical adhesive layer 100 are stacked, where the storage modulus of the plurality of layers of the optical adhesive layer 100 decreases along the thickness direction of the optical adhesive layer 100.

As shown in fig. 31, the optical cement layer 100 includes: the first optical adhesive layer 100a, the second optical adhesive layer 100b and the third optical adhesive layer 100c are stacked, and the storage modulus of the first optical adhesive layer 100a, the second optical adhesive layer 100b and the third optical adhesive layer 100c gradually changes along the thickness direction of the optical adhesive layer 100.

In preparing the optical cement layer 100, the first optical cement layer 100a may be molded by using the preparation process described in example one or example two, then the first optical cement layer 100a is used as a carrier, the second optical cement layer 100b is molded on the layer of optical cement layer 100 by using the preparation process described in example one or example two, and then the third optical cement layer 100c is molded on the second optical cement layer 100 b.

Or the first optical adhesive layer 100a, the second optical adhesive layer 100b and the third optical adhesive layer 100c can be formed on other carriers such as a release film, and then die cutting and superposition can be performed.

In some implementations of this example, the storage moduli of the first optical adhesive layer 100a and the second optical adhesive layer 100b gradually change along the thickness direction of the optical adhesive layer 100, which may be that the storage moduli of the first optical adhesive layer 100a and the second optical adhesive layer 100b gradually change along the thickness direction of the optical adhesive layer 100, for example, gradually decrease along the +z direction, on a longitudinal section of the same location of the first optical adhesive layer 100a and the second optical adhesive layer 100 b.

In other embodiments of the present example, the storage modulus of the first and second optical adhesive layers 100a and 100b is graded along the thickness direction of the optical adhesive layer 100, and the width of the storage modulus graded region may be graded along the thickness direction of the optical adhesive layer 100.

The optical adhesive layer 100 with the storage modulus gradually changed along the thickness direction of the optical adhesive layer 100 provided in this example can be used in a flexible display module. In some embodiments, the flexible display module is an inner folding screen, and when the electronic device is in a folded state, the display surface of the flexible display module is inside the electronic device. In other embodiments, the flexible display module is an external folding screen, and when the electronic device is in a folded state, the display surface of the flexible display module is located outside the electronic device.

The flexible display module comprises a plurality of functional layers which are arranged in a stacked manner, wherein two adjacent functional layers are bonded through the optical adhesive layer 100, when the electronic equipment is in a bending state, the bending radius of the optical adhesive layer 100 which is closer to the outer side of the electronic equipment is larger, in order to improve the bending performance of the optical adhesive layer 100 and enable stress strain distribution to be more uniform, a proper gradual change range can be determined according to the bending radius of the optical adhesive layer 100, and the gradual change range of the storage modulus of the optical adhesive layer 100 with the larger bending radius is larger.

The bending radius refers to the radius of an arc formed by the bending part of each lamination when the electronic equipment is bent.

In some embodiments of the present example, when the optical adhesive layer 100 is a single layer, the first axis of the optical adhesive layer 100 may be made to coincide with the bending axis of the flexible display module.

In other embodiments of the present example, the optical adhesive layers 100 are multiple layers, such that the first axis of each optical adhesive layer 100 coincides with the bending axis of the flexible display module.

The light glue layer that the example three provided, storage modulus along thickness direction gradual change for the stress and the strain distribution of optical glue layer are more even, when being used for flexible display module assembly, improve flexible display module assembly's bending property, flexible display module assembly's bending property reduces flexible display module assembly's deformation, thereby reduces the crease.

The following describes an arrangement of the optical adhesive layer 100 in the display module, taking a flexible display module provided with 3 optical adhesive layers 100 as an example.

As shown in fig. 32, the flexible display module includes 7 stacks including 4 functional layers: first functional layer 001, second functional layer 002, third functional layer 003, fourth functional layer 004, and 3-layer optical adhesive layer 100: a first optical cement layer 100a, a second optical cement layer 100b, and a third optical cement layer 100c. The functional layer can be a flexible cover plate, a polaroid, a touch control film, a display panel, a flexible substrate or other constituent elements of the folding screen. The first functional layer 001 and the second functional layer 002 are bonded by the first optical adhesive layer 100a, the second functional layer 002 and the third functional layer 003 are bonded by the second optical adhesive layer 100b, and the third functional layer 003 and the fourth functional layer 004 are bonded by the third optical adhesive layer 100c.

Wherein, this flexible display module assembly can divide into: a inflection region and a non-inflection region. In some embodiments of the present example, the flexible display module includes: a first non-inflection region 101, a second non-inflection region 102, and a first inflection region 103 located between the first non-inflection region 101 and the second non-inflection region 102.

The flexible display module is provided with a first bending axis A, and the optical adhesive layer 100 is used for bending around the bending axis when the display screen is bent. The projection of the first bending axis a on the optical adhesive layer 100 is located at the middle position of the third area of the optical adhesive layer 100, and the optical adhesive layer 100 is symmetrical about the first bending axis a.

In some embodiments of the present example, as shown in fig. 33, the first bending axis a may be the first axis O of the optical cement layer 100. That is, the storage modulus of the optical adhesive layer 100 may be made to decrease from the middle to the two sides in the direction perpendicular to the a axis.

The three optical layers 100 in the laminate are all optical layers gradually changed along the axial direction in the XY plane, and the storage modulus decreases from the middle to the two sides along the direction perpendicular to the bending axis A.

When the electronic device is in a bending state, the first optical adhesive layer 100a is close to the inner side of the electronic device, the bending radius is relatively small, the second optical adhesive layer 100b is positioned in the middle of the lamination, the bending radius is larger than that of the first optical adhesive layer 100a, the third optical adhesive layer 100c is arranged close to the outer side of the electronic device, and the bending radius is larger than that of the first optical adhesive layer 100a and the second optical adhesive layer 100b.

In order to improve the bending performance of the flexible display module, the thickness of each optical adhesive layer 100, the gradual change range of the storage modulus and the storage modulus at the bending axis can be adjusted according to the bending radius of the optical adhesive layer 100.

The bending radius of the first optical adhesive layer 100a is smaller than that of the second optical adhesive layer 100b, so that the gradient range of the storage modulus of the second optical adhesive layer 100b is wider than that of the first optical adhesive layer 100a, and the storage modulus of the second optical adhesive layer 100b at the bending axis a is greater than that of the first optical adhesive layer 100a at the bending axis a.

The third optical adhesive layer 100c is close to the outer side of the electronic device, and the bending radius of the third optical adhesive layer 100c is larger than that of the first optical adhesive layer 100a and the second optical adhesive layer 100b, so that the gradient range of the storage modulus of the third optical adhesive layer 100c is wider than that of the second optical adhesive layer 100b, and the storage modulus of the third optical adhesive layer 100c at the bending axis a is larger than that of the second optical adhesive layer 100b at the bending axis a.

The materials of the first optical adhesive layer 100a, the second optical adhesive layer 100b and the third optical adhesive layer 100c may refer to the descriptions of the optical adhesive layers 100 in the first and second examples, and are not repeated herein.

The preparation method of the first optical adhesive layer 100a, the second optical adhesive layer 100b and the third optical adhesive layer 100c may be described with reference to example one above. In this example, the different curing energies of different areas can be achieved by controlling the moving speed of the release film coated with the optical film prepolymer or the liquid optical adhesive 03 under ultraviolet light or in a constant temperature incubator, and the ultraviolet light mask 04 can be used or the curing temperatures of different positions can be controlled.

The number of the functional layers in the flexible display module is not limited, and the embodiment described above uses the case of arranging 3 optical adhesive layers 100 in 4 functional layers as an example, and when the number of the functional layers is multiple, the manner of arranging the optical adhesive layers 100 in multiple functional layers of the flexible display module can be referred to in this embodiment.

In the above embodiment, the flexible display module is of a two-fold structure, and includes only one folding region, and in other embodiments, the flexible display module is of a three-fold structure, including two folding regions, and the following description will be given with respect to the case where the multilayer optical adhesive layer 100 is disposed in the three-fold flexible display module.

As shown in fig. 34, the flexible display module includes 5 stacks including 3 functional layers: first functional layer 001, second functional layer 002, and third functional layer 003, and 2-layer optical adhesive layer 100: a first optical cement layer 100a and a second optical cement layer 100b. The functional layer can be a flexible cover plate, a polaroid, a touch control film, a display panel, a flexible substrate or other constituent elements of the folding screen. The first functional layer 001 and the second functional layer 002 are bonded by the first optical adhesive layer 100a, and the second functional layer 002 and the third functional layer 003 are bonded by the second optical adhesive layer 100b.

As shown in fig. 35, the optical cement layer includes: a first non-inflection region 101, a second non-inflection region 102, a third non-inflection region 104, a first inflection region 103 located between the first non-inflection region 101 and the second non-inflection region 102, and a second inflection region 105 located between the second non-inflection region 102 and the third non-inflection region 104.

The flexible display module is provided with a first bending axis A and a second bending axis B, and the first optical adhesive layer 100a and the second optical adhesive layer 100B are used for bending around the first bending axis A and the second bending axis B when the display screen is bent.

In some embodiments of the present example, as shown in fig. 35, the storage modulus of the first optical adhesive layer 100a decreases from the middle to the two sides in the direction perpendicular to the first bending axis a, and the storage modulus of the first optical adhesive layer 100a decreases from the middle to the two sides in the direction perpendicular to the second bending axis B. Meanwhile, the storage modulus of the second optical adhesive layer 100B decreases from the middle to the two sides along the direction perpendicular to the first bending axis a, and the storage modulus of the second optical adhesive layer 100B decreases from the middle to the two sides along the direction perpendicular to the second bending axis B.

That is, when the electronic device is in the folded state, the first optical adhesive layer 100a is disposed near the inner side of the electronic device at the first bending region 103, and the second optical adhesive layer 100b is disposed near the outer side of the electronic device at the first bending region 103. The bending radius of the first optical adhesive layer 100a in the first bending region 103 is smaller than the bending radius of the second optical adhesive layer 100b in the first bending axis a.

Meanwhile, the first optical adhesive layer 100a is disposed near the outer side of the electronic device at the second bending region 105. The second optical adhesive layer 100b is disposed near the inner side of the electronic device in the second bending region 105. The bending radius of the first optical adhesive layer 100a in the second bending region 105 is larger than the bending radius of the second optical adhesive layer 100b in the second bending region 105.

When the electronic device is in a folded state, as shown in fig. 34, the first optical adhesive layer 100a is disposed near the inner side of the electronic device in the first bending area 103, the bending radius is relatively small, the second optical adhesive layer 100b is disposed near the outer side of the electronic device in the first bending area 103, the bending radius of the second optical adhesive layer 100b in the first bending area 103 is greater than the bending radius of the first optical adhesive layer 100a in the first bending area 103, so that the gradient range of the second optical adhesive layer 100b in the first bending area 103 is wider than the first optical adhesive layer 100a, and the storage modulus of the second optical adhesive layer 100b at the first bending axis a is greater than the storage modulus of the first optical adhesive layer 100a at the first bending axis a.

Meanwhile, the first optical adhesive layer 100a is disposed at the second bending region 105 near the outer side of the electronic device, the bending radius is larger, and the second optical adhesive layer 100b is disposed at the second bending region 105 near the inner side of the electronic device. The bending radius of the first optical adhesive layer 100a in the second bending region 105 is greater than the bending radius of the second optical adhesive layer 100B in the second bending region 105, so that the gradient range of the first optical adhesive layer 100a in the second bending region 105 is wider than the second optical adhesive layer 100B, and the storage modulus of the first optical adhesive layer 100a at the second bending axis B is greater than the storage modulus of the second optical adhesive layer 100B at the second bending axis B.

In some embodiments of the present application, when the electronic device is in the folded state, the bending radius of the first optical adhesive layer 100a at the first bending region 103 is equal to the bending radius of the second optical adhesive layer 100b at the second bending region 105, and at the same time, the bending radius of the second optical adhesive layer 100b at the first bending region 103 is equal to the bending radius of the first optical adhesive layer 100a at the second bending region 105.

The graded range of the first optical adhesive layer 100a at the first bending region 103 may be made equal to the graded range of the second optical adhesive layer 100B at the second bending region 105, and the storage modulus of the first optical adhesive layer 100a at the first bending axis a may be made equal to the storage modulus of the second optical adhesive layer 100B at the second bending axis B.

Meanwhile, the gradient range of the first optical adhesive layer 100a at the second bending region 105 may be made equal to the gradient range of the second optical adhesive layer 100B at the first bending region 103, and the storage modulus of the first optical adhesive layer 100a at the second bending axis B may be made equal to the storage modulus of the second optical adhesive layer 100B at the first bending axis a.

The preparation method of the first optical adhesive layer 100a and the second optical adhesive layer 100b may be described with reference to example one above. In this example, the different curing energies of different areas can be achieved by controlling the moving speed of the release film coated with the optical film prepolymer or the liquid optical adhesive 03 under ultraviolet light or in a constant temperature incubator, and the ultraviolet light mask 04 can be used or the curing temperatures of different positions can be controlled.

The number of the functional layers in the flexible display module is not limited, and the embodiment described above uses the 2 optical adhesive layers 100 in the 3 functional layers as an example, and when the number of the functional layers is multiple, the manner of disposing the optical adhesive layers 100 in the multiple functional layers of the flexible display module can be referred to in this embodiment.

In the above embodiment, only one optical adhesive layer 100 is disposed between two adjacent functional layers, and in other embodiments of the present application, 2 or more optical adhesive layers 100 may be disposed between two adjacent functional layers.

The following describes an arrangement of the optical adhesive layer 100 by taking a flexible display module provided with 2 optical adhesive layers 100 as an example.

As shown in fig. 36, the flexible display module includes 3 stacks including 2 functional layers: first functional layer 001 and second functional layer 002, and optical adhesive layer 100 disposed between first functional layer 001 and second functional layer 002: a first optical cement layer 100a and a second optical cement layer 100b. The functional layer can be a flexible cover plate, a polaroid, a touch control film, a display panel, a flexible substrate or other constituent elements of the folding screen. The first functional layer 001 and the second functional layer 002 are bonded by the two-layer optical adhesive layer 100.

In some embodiments of the present example, as shown in fig. 37, the first bending axis a may be the first axis O of the optical adhesive layer 100. That is, the storage modulus of the optical adhesive layer 100 may be made to decrease from the middle to the two sides in the direction perpendicular to the a axis.

The 2 optical layers 100 in the laminate are all optical layers gradually changed along the axial direction in the XY plane, and the storage modulus decreases from the middle to the two sides along the direction perpendicular to the bending axis A.

When the electronic device is in a bending state, the first optical adhesive layer 100a is close to the inner side of the electronic device, the second optical adhesive layer 100b is close to the outer side of the electronic device, and the bending radius is larger than that of the first optical adhesive layer 100a.

The graded range of the second optical adhesive layer 100b may be made wider than the graded range of the first optical adhesive layer 100a, and the storage modulus of the second optical adhesive layer 100b at the first bending axis a may be made larger than the storage modulus of the first optical adhesive layer 100a at the bending axis a.

The number of functional layers in the flexible display module is not limited in the present application, and the above embodiment is described by taking the case of arranging 2 optical adhesive layers 100 in 2 functional layers, and the manner of arranging multiple optical adhesive layers 100 in adjacent functional layers of the flexible display module can refer to this embodiment.

In the foregoing embodiment, in the same flexible display module, the storage modulus gradient manner of the multilayer optical adhesive layer 100 is the same, and in other embodiments of the present application, different gradient manners may be set on the optical adhesive layers 100 of different layers, or different gradient manners may be set on different positions of the same optical adhesive layer 100.

For example, when the optical cement layer 100 is a plurality of layers, for example, three layers: a first optical cement layer 100a, a second optical cement layer 100b, and a third optical cement layer 100c.

The first optical adhesive layer 100a may be in a linear gradual manner, the storage modulus of the first optical adhesive layer 100a decreases from the middle to two sides along the direction perpendicular to the first axis O, and the viscosity of the first optical adhesive layer 100a increases from the middle to two sides.

The storage modulus of the second optical cement layer 100b may be tapered to the periphery in a diamond-shaped taper manner.

The storage modulus of the third optical cement layer 100c may be tapered in a circular manner to the periphery.

Or for another example, the optical cement layer 100 is 1 layer, and the optical cement layer 100 includes two bending areas: the storage modulus of the optical adhesive layer 100 may be linearly graded in the first inflection region and may be circularly graded in the second inflection region.

The following describes an arrangement of the optical adhesive layer 100 by taking a flexible display module provided with 3 optical adhesive layers 100 as an example.

As shown in fig. 38, the flexible display module includes 5 stacks including 2 functional layers: first functional layer 001 and second functional layer 002, and 3-layer optical adhesive layer 100 disposed between first functional layer 001 and second functional layer 002: a first optical cement layer 100a, a second optical cement layer 100b, and a third optical cement layer 100c. The functional layer can be a flexible cover plate, a polaroid, a touch control film, a display panel, a flexible substrate or other constituent elements of the folding screen. The first functional layer 001 and the second functional layer 002 are bonded by the 3-layer optical adhesive layer 100.

As shown in fig. 39, in the first optical cement layer 100a and the third optical cement layer 100c, the first bending axis a may be the first axis O of the optical cement layer 100. That is, the storage modulus of the optical adhesive layer 100 may be made to decrease from the middle to the two sides in the direction perpendicular to the a axis.

In the second optical cement layer 100b, the storage modulus of the second optical cement layer 100b decreases from the center of the second optical cement layer 100b to the periphery in the radial direction on the plane of the optical cement layer 100. Wherein the center of the second optical adhesive layer 100b is located at the midpoint of the first bending axis a, for example.

Illustratively, the storage modulus of the second optical cement layer 100b decreases in a circular progression toward the periphery.

Therefore, the bending performance of the optical display module can be further improved.

The preparation method of the first optical adhesive layer 100a and the third optical adhesive layer 100c may be described with reference to example one above. The preparation method of the second optical adhesive layer 100b may be referred to the description of the above example two. In preparing the first optical cement layer 100a and the second optical cement layer 100b, not only the different curing energies in different areas can be realized by controlling the moving speed of the release film coated with the optical cement film prepolymer or the liquid optical cement 03 under ultraviolet light or in a constant temperature incubator, but also the ultraviolet light mask 04 can be used or the curing temperatures in different positions can be controlled. In preparing the second optical cement layer 100b, the ultraviolet light mask 04 can be used or the curing temperature of different positions can be controlled.

The number of the functional layers in the flexible display module is not limited, and the embodiment described above uses the case of arranging 3 optical adhesive layers 100 in 2 functional layers as an example, and when the number of the functional layers is multiple, the manner of arranging the optical adhesive layers 100 in multiple functional layers of the flexible display module can be referred to in this embodiment.

The foregoing is merely illustrative of specific embodiments of the present application, and the scope of the present application is not limited thereto, but any changes or substitutions within the technical scope of the present application should be covered by the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims

1. An optical cement layer, characterized in that on the plane of the optical cement layer, the optical cement layer comprises at least one gradual change region, in the gradual change region, the storage modulus of the optical cement layer decreases from a first axis to two sides of the first axis, and the viscosity of the optical cement layer increases from the first axis to two sides of the first axis, wherein the optical cement layer is symmetrical about the first axis.

2. The optical cement layer of claim 1, wherein in a plane of the optical cement layer, the storage modulus of the optical cement layer decreases from two sides of a second axis to two sides of the second axis, and the tackiness of the optical cement layer increases from the second axis to two sides of the second axis, wherein the second axis intersects the first axis.

3. The optical cement layer of claim 2, wherein the second axis is perpendicular to the first axis.

4. An optical cement layer according to any one of claims 1-3, wherein the storage modulus of the optical cement layer also decreases in a radial direction away from the center of the circle on the plane of the optical cement layer, and the viscosity of the optical cement layer also increases in a radial direction away from the center of the circle, wherein the center of the optical cement layer is located on the first axis.

5. The optical cement layer according to any one of claims 1 to 4, wherein said optical cement layer comprises: the first surface and the second surface are opposite, and in the thickness direction of the optical adhesive layer, the gradual change area of the storage modulus and the viscosity of the optical adhesive layer is reduced from the first surface to the second surface.

6. The optical cement layer of claims 1-5, wherein the optical cement layer comprises: the storage modulus of the optical adhesive layer decreases from the first surface to the second surface in the thickness direction of the optical adhesive layer, and the viscosity of the optical adhesive layer increases from the first surface to the second surface.

7. An optical cement layer assembly comprising the optical cement layer of any one of claims 1-6, a first release film and a second release film, the first release film covering an inner surface of the optical cement layer, and the second release film covering an outer surface of the optical cement layer.

8. A flexible display module, characterized in that the flexible display module comprises a plurality of functional layers, wherein at least two adjacent functional layers are bonded by the optical adhesive layer according to any one of claims 1-6.

9. The flexible display module of claim 8, wherein the flexible display module comprises: the optical adhesive layer comprises a first non-bending region, a second non-bending region and a bending region positioned between the first non-bending region and the second non-bending region, wherein the bending region is positioned in a gradual change region of the optical adhesive layer.

10. A flexible display module according to claim 9, wherein the bending region is symmetrical about a bending axis, the bending axis coinciding with the first axis of the optical adhesive layer.

11. The flexible display module of claim 8, wherein the flexible display module comprises: the first non-inflection region, the second non-inflection region, the third non-inflection region, the first inflection region between first non-inflection region and the second non-inflection region, and the second inflection region between second non-inflection region and the third non-inflection region, the graded region includes: the first bending region is located in the first sub-gradual change region, and the second bending region is located in the second sub-gradual change region.

12. The flexible display module of claim 11, wherein the first bending region is symmetrical about a first bending axis, the second bending region is symmetrical about a second bending axis, the first axis of the first sub-graded region and the first bending axis coincide, and the first axis of the second sub-graded region and the second bending axis coincide.

13. A flexible display module according to any one of claims 8 to 12, wherein the flexible display module comprises a plurality of layers of the optical adhesive layer, the storage modulus of the optical adhesive layer decreases in a direction of decreasing bending radius in a thickness direction of the flexible display module, and the viscosity of the optical adhesive layer increases in a direction of decreasing bending radius, wherein the bending radius is a radius of an arc formed by a bending portion when each layer of the flexible display module is bent.

14. The flexible display module according to any one of claims 8 to 13, wherein the flexible display module includes a plurality of layers of the optical adhesive layer, and a gradual change region of the storage modulus of the optical adhesive layer becomes smaller in a direction in which a bending radius becomes smaller in a thickness direction of the flexible display module, wherein the bending radius is a radius of an arc formed by a bending portion when each layer of the flexible display module is bent.

15. An electronic device comprising at least a central frame and a flexible display module according to any one of claims 8-14;

The flexible display module is arranged on the middle frame.

16. A method of preparing an optical cement layer, the method comprising:

coating the optical cement prepolymer liquid or the liquid optical cement on a carrier;

Controlling the curing energy applied to the optical cement prepolymer liquid or the liquid optical cement so that the curing energy is decreased from the middle to the two sides to obtain a cured optical cement layer; the optical adhesive layer comprises at least one gradual change area on the plane of the optical adhesive layer, the storage modulus of the optical adhesive layer in the gradual change area is gradually decreased from a first axis to two sides of the first axis, the viscosity of the optical adhesive layer is gradually increased from the first axis to two sides of the first axis, and the optical adhesive layer is symmetrical about the first axis.

17. The method of claim 16, wherein the method further comprises, prior to the step of applying the optical cement pre-polymer solution or the liquid optical cement to the carrier:

Mixing 40-45 parts of acrylic acid-2-ethylhexyl ester, 40-50 parts of isobornyl acrylate, 10-15 parts of 4-hydroxybutyl acrylate and 2-5 parts of photoinitiator uniformly, polymerizing, adding 2-5 parts of cross-linking agent after the reaction is finished, and uniformly mixing to obtain the optical cement prepolymer liquid or the liquid optical cement.

18. The method of preparing an optical cement layer according to claim 16 or 17, wherein the controlling the curing energy applied to the optical cement pre-polymer liquid or the liquid optical cement such that the curing energy decreases from the middle to the two sides comprises:

and controlling the moving speed of the carrier coated with the optical cement pre-polymerization liquid or the liquid optical cement in ultraviolet light or an incubator, and solidifying the optical cement pre-polymerization liquid or the liquid optical cement to obtain the optical cement layer, wherein the moving speed firstly decreases from one side of the gradual change region to the middle and then increases from the middle of the gradual change region to the other side.

19. The method of preparing an optical cement layer according to claim 16 or 17, wherein the controlling the curing energy applied to the optical cement pre-polymer liquid or the liquid optical cement such that the curing energy decreases from the middle to both sides comprises:

controlling the illumination intensity of ultraviolet light irradiated on different positions of the optical cement prepolymer liquid or the liquid optical cement, and solidifying the optical cement prepolymer liquid or the liquid optical cement to obtain the optical cement layer, wherein the illumination intensity decreases from the middle of the gradual change region to the two sides;

Or alternatively, the first and second heat exchangers may be,

And controlling the temperature of the optical cement prepolymer liquid or the liquid optical cement in the temperature box at different positions, and solidifying the optical cement prepolymer liquid or the liquid optical cement to obtain the optical cement layer, wherein the temperature of the optical cement layer is gradually decreased from the middle to the two sides of the gradual change region.

20. The method of preparing an optical cement layer according to claim 16 or 17, wherein the controlling the curing energy applied to the optical cement pre-polymer liquid or the liquid optical cement such that the curing energy decreases from the middle to the two sides comprises:

Setting a mask with gradually changed light transmittance on the surface of the carrier coated with the optical cement prepolymer liquid or the liquid optical cement, so that ultraviolet light irradiates the optical cement prepolymer liquid or the liquid optical cement through the mask, and solidifying the optical cement prepolymer liquid or the liquid optical cement to obtain the optical cement layer; the light transmittance of the mask plate from the middle to the two sides of the gradual change region decreases.