CN115044295B - Protective layer and preparation method thereof, foldable display module and electronic equipment - Google Patents

Protective layer and preparation method thereof, foldable display module and electronic equipment Download PDF

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CN115044295B
CN115044295B CN202110251184.9A CN202110251184A CN115044295B CN 115044295 B CN115044295 B CN 115044295B CN 202110251184 A CN202110251184 A CN 202110251184A CN 115044295 B CN115044295 B CN 115044295B
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protective layer
layer
display module
polymer material
material layer
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CN115044295A (en
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代晓涛
罗中元
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Huawei Technologies Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D179/00—Coating compositions based on macromolecular compounds obtained by reactions forming in the main chain of the macromolecule a linkage containing nitrogen, with or without oxygen, or carbon only, not provided for in groups C09D161/00 - C09D177/00
    • C09D179/04—Polycondensates having nitrogen-containing heterocyclic rings in the main chain; Polyhydrazides; Polyamide acids or similar polyimide precursors
    • C09D179/08—Polyimides; Polyester-imides; Polyamide-imides; Polyamide acids or similar polyimide precursors
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09F—DISPLAYING; ADVERTISING; SIGNS; LABELS OR NAME-PLATES; SEALS
    • G09F9/00—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements
    • G09F9/30—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements
    • G09F9/301—Indicating arrangements for variable information in which the information is built-up on a support by selection or combination of individual elements in which the desired character or characters are formed by combining individual elements flexible foldable or roll-able electronic displays, e.g. thin LCD, OLED
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/549—Organic PV cells

Abstract

The application provides a transparent protective layer, the protective layer is flexible folding, including transparent macromolecular material layer, doping be in anion and cation, setting in the macromolecular material layer are in macromolecular material layer's on the surface at least a pair of electrode, at least a pair of electrode is used for the circular telegram to form the electric field in order to drive anion with cation migration. And bombarding the molecular chain of the high polymer material in the process of transferring the anions and the cations so as to solve the problem of uneven folding position of the protective layer. The application also provides a preparation method of the protective layer, a foldable display module applying the protective layer and electronic equipment applying the foldable display module. Through the design to the protective layer, realize the function that the deformation of protective layer is replied makes arch or crease reconversion original state to solve the problem that the protective layer buckled and arches.

Description

Protective layer and preparation method thereof, foldable display module and electronic equipment
Technical Field
The application relates to a protective layer and a preparation method thereof, a foldable display module applying the protective layer and electronic equipment applying the foldable display module.
Background
The conventional inward folding type conventional Foldable Display (CLFD) module has the advantages of good ductility, good bendability, high technical maturity and the like. However, the CLFD module has a low elastic deformation limit, and is easy to deform plastically after being bent, resulting in poor recovery, and after being folded for many times, the CLFD module often has problems of obvious crease, arching of the folding area, and the like at the folding position.
Disclosure of Invention
The first aspect of this application embodiment provides a transparent protective layer, the protective layer is flexible folding, including transparent macromolecular material layer, doping anion and cation in the macromolecular material layer, setting are in macromolecular material layer's on the surface at least a pair of electrode, at least a pair of electrode is used for circular telegram to form the electric field in order to drive anion with cation migration bombardment macromolecular material molecular chain in the macromolecular material layer.
The anions and the cations are driven to migrate under the action of the electric field, and molecular chains of the high polymer materials in the high polymer material layer are bombarded in the anion and cation migration process, so that the orientation of the molecular chains of the high polymer materials is changed, the function of deformation recovery of the protective layer is realized, and the arching or crease is restored to the original state, so that the problem of bending and arching of the protective layer is solved.
In an embodiment of the present application, the material of the polymer material layer includes at least one selected from the following: polyimide, polyethylene terephthalate, polymethyl methacrylate, thermoplastic polyurethane elastomer rubber and silicone gel.
In the embodiment of the present application, the total doping amount of the anions and the cations accounts for 1% to 5% of the mass of the polymer material layer.
And through setting the total doping amount of the anions and the cations, the bombardment effect of the anions and the cations on the high polymer material is ensured.
In an embodiment of the present application, the polymer material layer has a side surface parallel to a thickness direction of the polymer material layer, and the at least one pair of electrodes includes a pair of electrodes located on the side surface and located on opposite sides of a folded position of the polymer material layer.
The pair of electrodes generates an electric field parallel to the screen in the interior of the polymer material layer. When the crease needs to be eliminated again next time, a reverse electric field with the direction opposite to that of the previous electric field needs to be applied again so that the anions and the cations continuously migrate and bombard the molecular chain of the high molecular material.
In the embodiment of the present application, the polymer material layer has a side surface parallel to the thickness direction of the polymer material layer, and an upper surface and a lower surface which are connected to the side surface and are oppositely disposed, the at least one pair of electrodes is a plurality of pairs of electrodes and is located on the upper surface or the lower surface, the plurality of pairs of electrodes are transparent electrodes, each electrode is in a strip shape, and the extending direction of the strip shape is parallel to the folding position; the multiple pairs of electrodes are sequentially arranged at intervals in parallel along the direction perpendicular to the folding position.
The multiple pairs of electrodes form multiple electric fields to drive the cations and the anions to migrate; when the crease needs to be eliminated again next time, a plurality of reverse electric fields with the opposite directions to the previous electric fields need to be applied again, so that the anions and the cations can continuously migrate and bombard the molecular chain of the high molecular material.
In an embodiment of the present application, the anion and the cation are derived from an ionic compound.
In an embodiment of the present application, the protective layer further includes at least one ultra-thin glass layer stacked on the polymer material layer.
Meanwhile, the ultrathin glass layer and the high polymer material layer are adopted, so that the folding position of the protective layer can be effectively prevented from being bent and arched.
A second aspect of the embodiment of the present application provides a foldable display module, which includes a flexible and foldable laminated structure, where the laminated structure includes a touch display module and a transparent protection layer laminated on the touch display module; the protective layer is the transparent protective layer.
On the premise of not changing the elastic modulus and the yield strength of the high polymer material layer of the protective layer, the problem of serious crease marks after the folding position is unfolded can be obviously improved; in addition, in terms of reliability, the protective layer can recover from a dent, deformation, and the like generated after the impact.
In an embodiment of the application, the foldable display module further comprises a middle frame, the middle frame comprises a first frame part and a second frame part which are rotatably connected, a rotating shaft is connected between the first frame part and the second frame part, and the laminated structure is located in the middle frame; the first frame part and the second frame part rotate relatively to drive the laminated structure to fold or unfold.
The middle frame can load and protect the laminated structure, and the structural arrangement of the middle frame can realize the folding or unfolding of the laminated structure.
In the embodiment of the application, the protective layer with touch-control display module assembly stacks gradually from last to bottom on the center.
The side of the laminated structure having the protective layer is defined as a display side, and each layer of the laminated structure may be bent to be stacked up and down when the laminated structure is in a folded state, with the protective layer being located inside the laminated structure.
In the embodiment of the application, the laminated structure further comprises a supporting back film and a buffer layer which are laminated and arranged on one side of the touch display module, which is far away from the protective layer; the supporting back film is located between the touch display module and the buffer layer.
After the touch display module is manufactured, the touch display module can be attached to the supporting back film due to the fact that the touch display module is thin in thickness and weak in strength, and is convenient to move and prevents the touch display module from being damaged. The material of the supporting back film can be polyimide, polyethylene terephthalate or teflon, but is not limited thereto. The buffer layer is used as a stress buffer layer of the laminated structure, and the material of the buffer layer can be foam, but is not limited to the foam.
In an embodiment of the present application, the stacked structure further includes a metal layer located on a side of the buffer layer away from the protection layer.
The metal layer serves as a support, and since the laminated structure is flexible, the use of the metal layer can improve the mechanical strength of the laminated structure.
According to a third aspect of the embodiments of the present application, there is provided an electronic device including the foldable display module as described above.
Electronic equipment with above-mentioned collapsible display module assembly, the display screen of laminated structure have high resilience, can solve folding position unevenness problem to effectively promote the reliability and buckle the life-span.
A fourth aspect of the embodiments of the present application provides a method for preparing a transparent protective layer, including:
reducing the polyamic acid solution in an ethanol solution to increase the spacing between the molecular chains of the polyamic acid;
mixing a solution dissolved with an ionic compound with the reduced polyamic acid solution to obtain a mixed solution;
coating the mixed solution on a substrate, drying and reacting with oxygen to form a solid film of polyamic acid;
imidizing the solid film of the polyamic acid.
The preparation method of the protective layer can ensure that anions and cations are uniformly distributed in the high polymer material layer.
Drawings
Fig. 1 is an electronic device with a folding screen of the present application.
Fig. 2 is a schematic cross-sectional view of a foldable display module according to the present application.
FIGS. 3A-3E are schematic diagrams illustrating the electromigration molecular combing technique of the passivation layer of the foldable display module.
FIG. 4 is a schematic diagram of the cohesion of molecular chains of polymeric materials in a protective layer matching the bombardment of cations and anions.
Fig. 5A and 5B are a schematic cross-sectional view and a schematic top view of a protective layer according to another embodiment of the present application.
Fig. 6 is a schematic cross-sectional view of another state of the stacked structure of fig. 2.
Description of the main elements
Electronic device 400
Foldable display module 200
Laminated structure 100
Protective layer 10
High polymer material layer 11
Side 111
Upper surface 113
Lower surface 115
Anion 12
Cation 13
Electrode 15
Support layer 17
Touch display module 30
Polarizer 20
Supporting backing film 40
Buffer layer 60
Metal layer 50
Adhesive layers 22, 24
Hardened coating 101
Bending zone 110
The non-bending region 120
Middle frame 70
First frame portion 71
First frame bottom 711
First side wall 713
Second frame 73
Second frame bottom 731
Second side wall 733
Accommodation space 701
Rotating shaft 75
Battery 81
Detailed Description
The embodiments of the present application will be described below with reference to the drawings.
As shown in fig. 1, the electronic device 400 having the foldable screen has at least two states of a flat state and a folded state. FIG. 1 shows the flat state, and the broken lines in FIG. 1 represent the folded position. The electronic device 400 is not limited to a mobile phone, but may also be other electronic devices, such as a notebook, a tablet computer, and the like.
The electronic device 400 of the embodiment of the application includes the foldable display module 200 shown in fig. 2. As shown in fig. 2, the foldable display module 200 includes a multi-layer stacked structure 100, and the stacked structure 100 includes a transparent protection layer 10 and a touch display module 30 stacked up and down. The touch display module 30 is used for displaying images and providing a touch function. The laminated structure 100 is flexible and foldable, that is, the protective layer 10 and the touch display module 30 are both flexible and foldable. The side of the laminated structure 100 having the protective layer 10 is defined as a display side.
The existing protective layer is made of transparent polyimide. However, after the screen of the electronic device is bent, the polyimide molecular chains slide to two ends of the plane, the space between the polyimide molecular chains is enlarged, the polyimide molecular chains are curled, and the polyimide molecular chains cannot be recovered after plastic deformation; as the use time of the electronic device increases and the number of times of folding increases, the folding position of the protective layer may be obviously creased, resulting in uneven or arched folding position after the electronic device is unfolded. If the yield strength of the protective layer is increased, the bending stress of the protective layer increases, the risk of peeling of the protective layer from the laminated structure increases and the user experience is reduced, so that the balance between the bendability and the recoverability cannot be solved.
The present application provides a transparent protective layer 10, which can effectively solve the problems of uneven folding position or arching, etc., so that the electronic device 400 still remains flat after being folded and unfolded for many times.
As shown in fig. 2, the protective layer 10 of the present application includes a transparent polymer material layer 11, anions 12 and cations 13 doped in the polymer material layer 11, and at least one pair of electrodes 15 disposed on a surface of the polymer material layer 11. The at least one pair of electrodes 15 is used for electrifying to form an electric field to drive the anions 12 and the cations 13 to migrate. And bombarding the molecular chain of the high polymer material in the high polymer material layer 11 in the migration process of the anions 12 and the cations 13, so as to change the orientation of the molecular chain of the high polymer material, realize the function of deformation recovery of the protective layer 10, restore the arching or crease, and solve the problem of bending and arching of the protective layer 10. The anion 12 and the cation 13 act like a comb, and thus the technique is referred to as the electromigration molecular combing technique.
The material of the polymer material layer 11 includes at least one selected from the following: polyimide (PI), polyethylene terephthalate (PET), polymethyl methacrylate (PMMA), thermoplastic polyurethane elastomer rubbers (TPU), silicone gel (Silicone gel). The material and thickness of the polymer material layer 11 can be set according to the requirement of the product.
As shown in fig. 2, the polymer material layer 11 has a side surface 111 parallel to the thickness direction of the polymer material layer 11, and an upper surface 113 and a lower surface 115 connected to the side surface 111 and disposed oppositely, wherein the lower surface 115 faces the touch display module 30. The at least one pair of electrodes 15 includes a pair of electrodes 15 located on the side surface 111 and located on opposite sides of the polymer material layer 11. The pair of electrodes 15 are located on opposite sides of the folded position of the protective layer 10. The pair of electrodes 15 generates an electric field parallel to the screen inside the polymer material layer 11.
The direction of the electric field formed by the electrode 15 can be regulated and controlled according to requirements, so that multiple migration and repeated combing of anions and cations can be realized. The intensity of the electric field formed by the electrode 15 can also be adjusted as required, and generally, the intensity of the electric field can influence the deformation recovery speed of the protective layer 10.
The principle of the electromigration molecular combing technique is illustrated in fig. 3A to 3E. In fig. 3A, in an initial state, the surface of the protective layer 10 is flat, the molecular chains of the polymer material are parallel to each other and arranged in a planar direction, and the horizontal distance d between the molecular chains is small. In fig. 3B, after the protective layer 10 is bent for a plurality of times, the molecular chain of the polymer material slides to the two ends of the plane, the distance d increases, and curling occurs. In fig. 3C, an electric field is applied parallel to the plane of the protective layer 10, and the anions 12 and cations 13 are moved by the electric field. In fig. 3D, the anions 12 and the cations 13 bombard the molecular chains of the polymer material, so as to force the molecular chains of the polymer material to turn to be parallel to the direction of the electric field and reduce the inter-molecular-chain distance D. In fig. 3E, when the electric field is removed, the molecular chain of the polymer material is completely recovered, and the anions 12 and the cations 13 are respectively located at the electrodes 15 at the two ends. When the crease needs to be eliminated again next time, the reverse electric field with the direction opposite to that of the previous electric field needs to be applied again, so that the anions 12 and the cations 13 continuously migrate and bombard the molecular chain of the high molecular material.
In order to ensure the bombardment effect of the anions 12 and the cations 13 on the polymer material, in an embodiment, the total doping amount of the anions 12 and the cations 13 is 1% to 5% of the mass of the polymer material layer 11. The anion 12 and the cation 13 may be derived from being ionic compounds.
In addition, it is necessary to select appropriate anions 12 and cations 13 according to the molecular chain of the polymer material, so that the kinetic energy of ion impact is sufficient to rotate and slide the molecular chain. The anions 12 and the cations 13 are uniformly distributed between the molecular chains of the polymer material. Referring to fig. 4, the torque generated by the ion bombardment of the molecular chain of the polymer material is:
Figure BDA0002966145900000051
Figure BDA0002966145900000052
the torque generated by the cohesive force of the molecular chain of the high polymer material is as follows:
Figure BDA0002966145900000053
in the above formulas (1) and (2), L is the length of the molecular chain of the polymer material; theta refers to the included angle between the axial direction of the molecular chain of the high polymer material and the direction of the membrane surface; the radius R and the charge q refer to the radius and the charge amount of the anion 12 or the cation 13; c is cohesive energy of the polymer material.
Therefore, the matching relationship between the anions and the polymer material is as follows:
Figure BDA0002966145900000054
the polymer material and the ions can be selected according to equation (3). Taking transparent PI with common modulus of about 6GPa as an example, the ionic compound suitable for matching the PI includes but is not limited to MnCl 2 、ZnSO 4 、NiCl 2 And so on.
The number and the positions of the electrodes 15 are not limited to those shown in fig. 2, and in another embodiment, as shown in fig. 5A, the at least one pair of electrodes 15 is a plurality of pairs of electrodes 15 and is located on the upper surface 113 or the lower surface 115, preferably the lower surface 115. As shown in fig. 5A and 5B, each electrode 15 is substantially in the shape of a strip, and the extending direction of the strip is parallel to the folding position; the pairs of electrodes 15 may be spaced apart in sequence and parallel to each other in a direction perpendicular to the folded position (shown in phantom). The multiple pairs of electrodes 15 form multiple electric fields to drive the cations and anions to migrate. In order not to affect the display effect of the touch display module 30, the pairs of electrodes 15 are transparent electrodes. The electrodes 15 may be directly disposed on the surface of the polymer material layer 11, or disposed on the surface of a carrier layer 17 as shown in fig. 5A, the carrier layer 17 and the polymer material layer 11 are stacked on each other, so that the electric field generated by the electrodes 15 on the carrier layer 17 can drive the anions 12 and cations 13 in the polymer material layer 11 to migrate. The material of the carrier layer 17 can be PET, cyclo Olefin Polymer (COP), triacetate. An adhesive layer 22 of transparent optical adhesive may also be disposed between the polymer material layer 11 and the carrier layer 17.
On the premise of not changing the elastic modulus and the yield strength of the high polymer material layer 11 of the protective layer 10, the problem of serious crease marks after the folding position is unfolded can be obviously improved; in addition, the protective layer 10 can recover from a dent, deformation, and the like generated after the impact in terms of reliability.
It is understood that, in the protection layer 10, the polymer material layer 11 may be designed according to the folding position, as shown in fig. 6, for example, the polymer material layer 11 is divided into a bending region 110 and a non-bending region 120 connected to each other, where the bending region 110 refers to the region where the folding position is located. In one embodiment, the modulus of elasticity of the bending region 110 is lower than that of the non-bending region 120, and the yield strength of the bending region 110 is higher than that of the non-bending region 120, so that the bending resistance of the bending region 110 can be improved. In an embodiment, the bending region 110 and the non-bending region 120 are made of different polymer materials, and/or the concentrations of the doped anions and cations of the bending region 110 and the non-bending region 120 are different, so as to further improve the bending resistance of the bending region 110.
In an embodiment, the polymer material layer 11 includes a plurality of sub-film layers (not shown) stacked along a thickness direction thereof, and the sub-film layers may be made of different polymer materials and/or doped with anions 12 and cations 13 with different concentrations as required to optimize performance of the polymer material layer 11 and make it more suitable for multiple bending.
It can be understood that the electronic device 400 shown in fig. 1 and the foldable display module 200 shown in fig. 2 both include only one folding position, and it can be understood that the electronic device and the foldable display module of the present application are not limited to one folding position, and can include two or more folding positions, and can be bent/folded in multiple sections.
The embodiment of the present application further provides another protection layer (not shown), which includes at least one Ultra Thin Glass (not shown) layer and the polymer material layer 11. The thickness of the ultra-thin glass layer can be less than 50 microns. Transparent optical cement (not shown) is arranged between the polymer material layer 11 and the ultra-thin glass layer to bond the polymer material layer and the ultra-thin glass layer into a whole. The polymer material layer 11 is the above polymer material layer 11 doped with anions 12 and cations 13, and the surface of the polymer material layer is provided with at least one pair of electrodes 15 for forming an electric field by energization to drive the anions 12 and the cations 13 to move. Because the ultrathin glass layer has higher surface hardness and elastic modulus, the ultrathin glass layer has better scratch resistance, and is not easy to generate crease marks after being repeatedly bent. Typical ultra-thin glass layers are between 30-50um thick. Meanwhile, the ultrathin glass layer and the high polymer material layer 11 are adopted, so that the folding position of the protective layer can be effectively prevented from being bent and arched.
It is understood that the ultra-thin glass layer may be disposed on the upper surface 113, the lower surface 115, or both the upper surface 113 and the lower surface 115 of the polymer material layer 11, and is preferably disposed on the lower surface 115 of the polymer material layer 11. It is understood that in other embodiments, the polymer material layer 11 is stacked on both upper and lower sides of the ultra-thin glass layer.
As shown in fig. 2, the stacked structure 100 may further include a polarizer 20 located between the protection layer 10 and the touch display module 30. The polarizer 20 may be used to reduce light reflected by external light incident on the metal electrode 15 (not shown) of the touch display module 30, so as to optimize optical performance of the foldable display module 200.
The laminated structure 100 may further include a supporting back film 40, a buffer layer 60, and a metal layer 50, which are located on a side of the touch display module 30 away from the protective layer 10 and stacked together. In this embodiment, the supporting back film 40 is located between the touch display module 30 and the buffer layer 60; the buffer layer 60 is located between the metal layer 50 and the support backing film 40.
After the touch display module 30 is manufactured, the touch display module 30 can be attached to the supporting back film 40 due to the fact that the touch display module 30 is thin in thickness and weak in strength, and the touch display module 30 is convenient to move and prevents the touch display module 30 from being damaged. The material of the supporting backing film 40 may be PET, PI, or teflon, but is not limited thereto. The buffer layer 60 is used as the stress buffer layer 60 of the stacked structure 100, and the material may be foam, but is not limited thereto. The metal layer 50 serves as a support, and since the laminated structure 100 is flexible, the use of the metal layer 50 can improve the mechanical strength of the laminated structure 100.
An adhesive layer is disposed between any two layers of the laminated structure 100 to bond the adjacent two layers. For example, an adhesive layer 22 of transparent optical adhesive is disposed between the protective layer 10 and the polarizer 20; an adhesive layer 22 of transparent optical adhesive is disposed between the polarizer 20 and the touch display module 30. An adhesive layer 24 is disposed between the touch display module 30 and the support back film 40, and the adhesive layer 24 may be a pressure sensitive adhesive. An adhesive layer 24 is disposed between the support backing film 40 and the buffer layer 60, and the adhesive layer 24 may be a pressure sensitive adhesive. An adhesive layer 24 is disposed between the metal layer 50 and the buffer layer 60, and the adhesive layer 24 may be a pressure sensitive adhesive.
It can be understood that, as shown in fig. 2, a hardening coating 101 may be further disposed on a surface of the protection layer 10 away from the touch display module 30, so as to improve the scratch resistance of the protection layer 10.
The layers of the laminate structure 100 may be provided in a micro-scale, for example, several micrometers, several tens of micrometers, or more.
Similarly, the stacked structure 100 has at least two states, i.e., a flat state and a folded state, fig. 2 shows the flat state of the stacked structure 100, and fig. 6 shows the folded state of the stacked structure 100. When the laminated structure 100 is in a flattened state, the layers of the laminated structure 100 are sequentially stacked. When the stacked structure 100 is in the folded state, each layer of the stacked structure 100 is bent to be stacked up and down, the protective layer 10 is located inside the stacked structure 100, and the metal layer 50 is located at the outermost portion of the stacked structure 100.
As shown in fig. 2, the foldable display module assembly 200 further includes a middle frame 70, the middle frame 70 can load and protect the laminated structure 100, and the structural configuration of the middle frame 70 can realize the folding or unfolding of the laminated structure 100. The middle frame 70 includes a first frame portion 71 and a second frame portion 73 rotatably connected to each other, a rotation shaft 75 is connected between the first frame portion 71 and the second frame portion 73, and the first frame portion 71 and the second frame portion 73 are relatively rotatable about the rotation shaft 75. The laminate structure 100 is at least partially located in the middle frame 70; the first frame portion 71 and the second frame portion 73 rotate relatively to each other, so as to drive the laminated structure 100 to fold or unfold. In this embodiment, the first frame portion 71 includes a first frame bottom 711 and a first sidewall 713 perpendicularly connected to the first frame bottom 711, and the second frame portion 73 includes a second frame bottom 731 and a second sidewall 733 perpendicularly connected to the second frame bottom 731. When the foldable display module 200 is in the flat state, the first frame bottom 711 and the second frame bottom 731 are located on the same horizontal plane, and the first side wall 713 and the second side wall 733 are opposite and far away from each other, at this time, the middle frame 70 forms an accommodating space 701 for accommodating the stacked structure 100, and the protective layer 10, the touch display module 30, the supporting back film 40, the buffer layer 60, and the metal layer 50 are sequentially stacked on the first frame bottom 711 and the second frame bottom 731 from top to bottom. When the foldable display module 200 is in the folded state, the first frame portion 71 and the second frame portion 73 are stacked up and down, and the folded stacked structure 100 is located between the first frame portion 71 and the second frame portion 73.
In this embodiment, as shown in fig. 2, the foldable display module 200 further includes a battery 81, the battery 81 is disposed on a surface of the middle frame 70 facing away from the stacked structure 100, but not limited thereto, and the battery 81 is disposed on each of the first frame portion 71 and the second frame portion 73. The material of the middle frame 70 may be metal, alloy (e.g., aluminum alloy, magnesium alloy), plastic, glass fiber, carbon fiber, etc.
It is understood that the electrodes 15 of the protection layer 10 may be electrically connected to a main board (not shown) of the electronic device 400 through a flexible circuit board (not shown) or the like, so as to supply power to the electrodes 15.
The above-mentioned protection layer 10 is not limited to be applied to the electronic device 400 with a folding screen shown in fig. 1, but can also be applied to an electronic device (not shown) with a scroll screen, in which the scroll screen is rolled up when the electronic device is turned off, and after the electronic device is turned on, an electric field is started to flatten the protection layer by bombarding the polymer material layer 11 of the protection layer 10 with doped anions 12 and cations 13.
The application also provides a preparation method of the protective layer, which takes the polymer material as PI for illustration and comprises the following steps.
(1) Slightly reducing the polyamic acid solution in an ethanol solution to graft H atoms of the polyamic acid to O atoms so as to increase the distance between molecular chains of the polyamic acid.
Figure BDA0002966145900000081
(2) And (3) mixing the solution dissolved with the ionic compound with the solution in the step (1) to obtain a mixed solution.
Since the intermolecular spacing is opened by H atoms, the anion 12 and the cation 13 are allowed to enter between the molecular chains of the polyamic acid.
(3) And (3) coating the mixed solution obtained in the step (2) on a substrate (such as a metal material), drying and reacting with oxygen to reoxidize H atoms and reduce molecular chains into polyamic acid to form a solid film of polyamic acid.
The drying can be carried out by using an oven and simultaneously blowing oxygen. Due to the decrease in the molecular distance, the anion 12 and the cation 13 are firmly locked between the molecular chains. The solvent is evaporated sufficiently to form a solid film.
(4) Imidizing the solid film obtained in the step (3), and removing water molecules at high temperature to convert the polyamic acid into PI.
In this way, anions 12 and cations 13 are uniformly distributed among the PI molecular chains. It is understood that at least one pair of electrodes 15 is formed on the surface of the polymer material layer 11 as needed.
This application designs through the protective layer to collapsible display module's stacked structure, dopes anion 12 and cation 13 to thereby design electrode 15 introduces the electric field and makes anion 12 and cation 13 migrate the molecular chain that bombards macromolecular material, thereby changes the orientation of molecular chain, makes the protective layer realize the function that deformation resumes, thereby stacked structure 100 can thoroughly flatten in the exhibition attitude of flattening, eliminates the dent, hunch-up.
It should be noted that the above is only a specific embodiment of the present application, but the scope of the present application is not limited thereto, and any person skilled in the art can easily think of the changes or substitutions within the technical scope of the present application, and all should be covered by the scope of the present application; the embodiments and features of the embodiments of the present application may be combined with each other without conflict. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.

Claims (13)

1. The transparent protective layer is flexible and foldable, and comprises a transparent high polymer material layer, anions and cations doped in the high polymer material layer, and at least one pair of electrodes arranged on the surface of the high polymer material layer, wherein the at least one pair of electrodes are electrified to form an electric field so as to drive the anions and the cations to migrate and bombard molecular chains of the high polymer material in the high polymer material layer, and the total doping amount of the anions and the cations accounts for 1% -5% of the mass of the high polymer material layer.
2. The transparent protective layer of claim 1, wherein the material of the polymer material layer comprises at least one selected from the group consisting of: polyimide, polyethylene terephthalate, polymethyl methacrylate, thermoplastic polyurethane elastomer rubber and silicone gel.
3. The transparent protective layer according to claim 1, wherein the polymer material layer has a side surface parallel to a thickness direction of the polymer material layer, and the at least one pair of electrodes includes a pair of electrodes located on the side surface and located on opposite sides of a folded position of the polymer material layer.
4. The transparent protective layer according to claim 1, wherein the polymer material layer has a side surface parallel to a thickness direction of the polymer material layer, and an upper surface and a lower surface which are connected to the side surface and are oppositely disposed, the at least one pair of electrodes is a plurality of pairs of electrodes and is located on the upper surface or the lower surface, the plurality of pairs of electrodes are transparent electrodes, each electrode is in a strip shape, and an extending direction of the strip shape is parallel to a folding position; the multiple pairs of electrodes are sequentially arranged at intervals in parallel along the direction perpendicular to the folding position.
5. The transparent protective layer according to any one of claims 1 to 4, wherein the anion and the cation are derived from an ionic compound.
6. The transparent protective layer according to any one of claims 1 to 4, further comprising at least one ultra-thin glass layer disposed in a stack with the polymeric material layer.
7. The foldable display module is characterized by comprising a flexible and foldable laminated structure, wherein the laminated structure comprises a touch display module and a transparent protective layer laminated on the touch display module; the touch display module is used for displaying images and providing a touch function, and the protective layer is the transparent protective layer of any one of claims 1 to 6.
8. The foldable display module of claim 7, further comprising a middle frame, wherein the middle frame comprises a first frame portion and a second frame portion that are rotatably connected, a rotating shaft is connected between the first frame portion and the second frame portion, and the stacked structure is located in the middle frame; the first frame part and the second frame part rotate relatively to drive the laminated structure to fold or unfold.
9. The foldable display module of claim 8, wherein the protective layer and the touch display module are sequentially stacked on the middle frame from top to bottom.
10. The foldable display module of claim 7, wherein the laminate structure further comprises a support film and a buffer layer stacked on a side of the touch display module facing away from the protection layer; the supporting back film is located between the touch display module and the buffer layer.
11. The foldable display module of claim 10, wherein the laminate structure further comprises a metal layer on a side of the buffer layer away from the protective layer.
12. An electronic device comprising the foldable display module according to any one of claims 7 to 11.
13. A method of making a transparent protective layer, comprising:
reducing the polyamic acid solution in an ethanol solution to increase the spacing between the molecular chains of the polyamic acid;
mixing a solution dissolved with an ionic compound with the reduced polyamic acid solution to obtain a mixed solution;
coating the mixed solution on a substrate, and reacting with oxygen while drying to form a solid film of polyamic acid; imidizing the solid film of the polyamic acid.
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