Composite film structure and its preparation method, cover plate, protective film, display screen and electronic device

Abstract

This application provides a composite film structure comprising a polymer base film layer and a graft layer located on at least one side of the polymer base film layer. The graft layer comprises an amino-terminated dendritic polymer, and the bonding strength between the graft layer and the polymer base film layer is ≥3 MPa. This composite film structure can be used as a support layer, cover plate, and protective film on the surface of a display screen. The specific graft layer on the surface of the composite film structure can improve the adhesion strength between the composite film structure and the optical adhesive layer, thereby improving the bending capability of the display screen and electronic devices. The graft layer also enables the composite film structure to have a smaller overall thickness and smaller changes in optical performance, so as to better meet the requirements of thinner and lighter displays and higher display performance in electronic devices.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a composite film structure and its preparation method, a cover plate, a protective film, a display screen, and electronic devices. Background Technology

[0002] In recent years, foldable phones have become a significant growth driver in the smartphone market due to their combination of large screens and portability. Polymer films such as polyethylene terephthalate (PET) and polyimide (PI) offer advantages such as flexibility, abrasion resistance, creep resistance, and transparency, making them commonly used in foldable screen laminations for support and protection. These films typically require optical adhesive (OCA) to bond to other functional layers within the foldable screen. However, the low surface energy of PET and PI prevents the OCA from forming good wetting and strong interactions, resulting in low bond strength between PET / PI and OCA. Consequently, during prolonged bending, OCA is prone to detaching from PET / PI, leading to screen failure. Summary of the Invention

[0003] In view of this, embodiments of this application provide a composite film layer structure and its preparation method, a cover plate, a protective film, a display screen, and an electronic device. The composite film layer structure can be used as a support layer, cover plate, and protective film on the surface of a display screen. The surface of the composite film layer structure is provided with a specific grafting layer, which can improve the adhesion strength between the composite film layer structure and the optical adhesive layer, thereby improving the bending capability of the display screen and electronic device. The grafting layer can also enable the composite film layer structure to have a smaller total thickness and a smaller change in optical performance, so as to better meet the requirements of thinner and lighter display screens and electronic devices and higher display performance.

[0004] In a first aspect, embodiments of this application provide a composite membrane structure, the composite membrane structure comprising a polymer base membrane layer and a graft layer located on at least one side surface of the polymer base membrane layer, the graft layer comprising an amino-terminated dendritic polymer, and the bonding strength between the graft layer and the polymer base membrane layer being ≥3 MPa.

[0005] The composite film structure provided in this application can be used as a support layer, cover plate, and protective film on the surface of a display screen. Its surface has a specific grafting layer, which is chemically bonded to the surface of the polymer base film. The grafting layer includes an amino-terminated dendritic polymer, which can be chemically grafted onto the surface of the polymer base film and can be firmly bonded to it. The amino-terminated dendritic polymer has multipolar groups and high polarity, which can increase the surface energy of the composite film structure. It introduces a large number of groups (i.e., amino groups) that can strongly interact with the optical adhesive in the optical adhesive layer to the surface of the composite film structure, thereby enabling adhesion between the grafting layer and the optical adhesive layer, improving... The high bonding strength between the composite film structure and the optical adhesive layer enhances the bending capability of the foldable screen, thereby improving its reliability and durability. This grafted layer also allows the composite film structure to have a smaller overall thickness and less variation in optical performance, better meeting the demands for thinner and lighter displays and higher display performance in electronic devices. Furthermore, this grafted layer avoids the need for excessively thick optical adhesive layers to enhance bonding strength, which is beneficial for thinner and lighter displays and electronic devices. The bonding strength enhancement effect of the grafted layer in the composite film structure is relatively long-lasting, eliminating the need for repeated chemical grafting treatment in a short period, thus facilitating the storage and application of the composite film structure.

[0006] In this embodiment, the terminal amino dendritic polymer includes dendritic polyamide amine. Dendritic polyamide amine is a polyamide-amine type dendritic polymer with a highly branched structure, which can introduce more polar amino groups to the surface of the polymer base film layer to enhance the surface polarity of the composite film layer structure.

[0007] In this application embodiment, the dendritic polyamide amine includes one or more of G0, G1, G2, G3, G4, G5, and G6 generation dendritic polyamide amines. G0-G6 generation dendritic polyamide amines have a moderately branched structure, a suitable number of active terminal amino groups, and a suitable molecular weight, thereby enabling the composite film structure to better balance high adhesion strength with the optical adhesive layer and good optical properties.

[0008] In this embodiment, the grafted layer further includes a diazinon compound, which is chemically bonded to the surface of the polymer base film. The terminal amino-terminated dendritic polymer is also chemically bonded to the diazinon compound; that is, the terminal amino-terminated dendritic polymer is chemically bonded to the surface of the polymer base film via the diazinon compound. Diazinon compounds are photosensitive to ultraviolet light; therefore, under ultraviolet irradiation, the diazinon compound can be chemically bonded to the surface of the polymer base film via a carbene insertion reaction, which is simple and easy to control.

[0009] In this embodiment, the bisacrylidine compound is chemically bonded to the surface of the polymer-based film layer based on a carbene insertion reaction. Since the carbene insertion reaction involves the carbene intermediate inserting into the CH bond or other heteroatom-H covalent bond on the surface of the polymer-based film layer to generate a new covalent bond and complete the chemical bonding, the bisacrylidine compound can serve as a bridge, suitable for modifying the surface of various composite film layer structures commonly used in polymer-based film layers with terminal amino dendritic polymers.

[0010] In this embodiment of the application, the structural formula of the diacaridine compound is shown in formula (1):

[0011] Wherein, R is a halogen atom or a substituted or unsubstituted alkyl group, and R' is a halogen atom, amino (-NH2), carboxyl (-COOH), alkenyl, or -R. 1 -R 2 R 1 It is an alkylene group or -C6H4-CH2-, R 2 It can be a halogen atom, amino group, carboxyl group or alkenyl group.

[0012] In the embodiments of this application, the substituted alkyl group is a haloalkyl group or an alkenyl-substituted alkyl group.

[0013] In this application, the bisacrididine compounds include one or more of 4-[3-(trifluoromethyl)-3H-bisacridin-3-yl]benzyl bromide, 4-(3-(trifluoromethyl)-3H-bisacridin-3-yl)benzylamine, and 4-[3-(trifluoromethyl)-3H-bisacridin-3-yl]benzyl chloride. These bisacrididine compounds exhibit good ultraviolet light sensitivity and stability after the insertion reaction.

[0014] In this embodiment, the thickness of the grafting layer is 0.5 nm to 100 nm. A smaller grafting layer thickness allows for a relatively smaller overall thickness of the composite film structure, which is beneficial for achieving a thinner and lighter display screen; it also helps maintain the good optical performance of the composite film structure.

[0015] In this embodiment, the polymer base film layer is made of one or more of the following: polyimide (PI), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), polyurethane (PU), polymethyl methacrylate (PMMA), polyacrylate (PA), polyethylene terephthalate (PEN), and parylene. These polymer materials combine flexibility, transparency, abrasion resistance, and mechanical properties, effectively meeting the bending and optical performance requirements of flexible displays, while also providing support or protection.

[0016] In this embodiment, the water droplet angle on the grafted layer surface of the composite film structure is less than 50°. The composite film structure surface in this embodiment has a smaller water droplet angle due to the grafted layer, thus exhibiting better wettability and adhesion. This facilitates the spreading and wetting of optical adhesive molecules on the composite film structure surface, thereby improving the bonding reliability of the optical adhesive layer.

[0017] In this embodiment, the visible light transmittance of the composite film structure is greater than or equal to 89%, and the haze is less than or equal to 1.3%. The high visible light transmittance of the composite film structure indicates high transparency, which enhances the display performance of the display screen. The low haze of the composite film structure provides superior gloss and clarity, further improving the display performance of the display screen.

[0018] In this embodiment, the 180° peel force when the composite film structure is bonded to the optical adhesive layer is greater than or equal to 4.8 N / cm. The composite film structure in this embodiment, by providing a grafted layer on its surface, exhibits a large 180° peel force when bonded to the optical adhesive layer, thereby significantly improving the bending reliability of the display screen.

[0019] The second aspect of this application provides a method for preparing a composite film structure, including:

[0020] A diazinon compound was coated onto the surface of a polymer-based film, and then subjected to ultraviolet light to allow the diazinon compound to react with the surface of the polymer-based film to form a chemical bond, thereby obtaining an intermediate product.

[0021] The intermediate product, on at least one side of which is bonded with the diacylpropidine compound, is brought into contact with a solution of an amino-terminated dendritic polymer. The amino-terminated dendritic polymer is then chemically bonded to the diacylpropidine compound at room temperature or under heating conditions to complete the amination of the polymer-based film layer, thereby obtaining a composite film structure.

[0022] The method for preparing the composite film structure provided in this application is simple and can be completed at relatively low temperatures. The resulting composite film structure has tight bonding between its layers, stable structure, small total thickness, good optical performance, and high adhesion strength to the optical adhesive layer. When used in a display screen, it can improve the bending capability of the display screen and meet the requirements of thinner and lighter display screens and higher display performance.

[0023] In this embodiment of the application, after the amination of the polymer-based film layer is completed, an activation treatment is further included, which includes plasma treatment and / or corona treatment.

[0024] A third aspect of this application provides a cover plate, the cover plate comprising at least a first film layer and a second film layer stacked together, and a third optical adhesive layer disposed between the first film layer and the second film layer, wherein the first film layer and / or the second film layer comprises the composite film layer structure described in the first aspect or the composite film layer structure prepared by the preparation method described in the second aspect, and the third optical adhesive layer is bonded to the graft layer of the composite film layer structure.

[0025] A fourth aspect of this application provides a protective film, the protective film comprising at least a first protective film layer and a second protective film layer stacked together, and a fourth optical adhesive layer disposed between the first protective film layer and the second protective film layer, wherein the first protective film layer and / or the second protective film layer comprises the composite film layer structure described in the first aspect or the composite film layer structure prepared by the preparation method described in the second aspect, and the fourth optical adhesive layer is bonded to the graft layer of the composite film layer structure.

[0026] A fifth aspect of this application provides a display screen, the display screen including a support layer, a display panel stacked on the support layer, and a cover plate stacked on the side of the display panel away from the support layer; a first optical adhesive layer is provided between the support layer and the display panel, and a second optical adhesive layer is provided between the cover plate and the display panel;

[0027] The support layer comprises the composite film structure described in the first aspect or the composite film structure prepared by the preparation method described in the second aspect, wherein the first optical adhesive layer is bonded to the graft layer of the composite film structure; and / or,

[0028] The cover plate includes the composite film structure described in the first aspect, the composite film structure prepared by the method described in the second aspect, or the cover plate described in the third aspect. In this application embodiment, the display screen uses a composite film structure as the functional film material, which reduces the risk of debonding failure between the film material and the optical adhesive during the bending process of the display screen, thereby improving the bending reliability of the display screen.

[0029] In this embodiment of the application, the display screen is a foldable screen, which includes a bending area and a non-bending area, and the grafting layer of the composite film structure is located at least in the bending area of ​​the foldable screen.

[0030] In this embodiment of the application, the materials of the first optical adhesive layer and the second optical adhesive layer independently include one or more of epoxy resin optical adhesive, silicone resin optical adhesive, acrylate optical adhesive, modified acrylate optical adhesive, and polyurethane optical adhesive.

[0031] This application also provides an electronic device, which includes a display screen and a protective film disposed on the light-emitting side of the display screen; the display screen includes the display screen described in the fifth aspect of this application, and / or the protective film includes the composite film layer structure described in the first aspect of this application, or the composite film layer structure prepared by the preparation method described in the second aspect of this application, or the protective film described in the fourth aspect. The electronic device of this application, by employing a composite film layer structure as the functional film material of the display screen, can reduce the risk of debonding failure between the film material and the optical adhesive during the bending process of the display screen, thereby improving the bending reliability of the display screen. By employing a composite film layer structure as the protective film on the surface of the display screen, the bonding reliability of the protective film on the display screen surface can be improved. Therefore, the electronic device employing the composite film layer structure described above in this application can improve the reliability and durability of the electronic device, thereby enhancing product competitiveness. Attached Figure Description

[0032] Figure 1A This is a cross-sectional structural schematic diagram of the composite membrane structure 10 in one embodiment of this application;

[0033] Figure 1B This is a cross-sectional schematic diagram of the composite membrane structure 10 in another embodiment of this application;

[0034] Figure 2 and Figure 3 This is a schematic diagram illustrating the application of the composite film structure 10 in the display screen 100 according to an embodiment of this application; wherein, Figure 2 This is a structural diagram of the display screen 100 in its unfolded state; Figure 3 This is a cross-sectional schematic diagram of the display screen 100 in its folded state;

[0035] Figure 4 This is a schematic diagram of the grafting layer 12 in some embodiments of this application;

[0036] Figure 5 This is a schematic diagram of the grafting layer 12 in other embodiments of this application;

[0037] Figure 6 This is a schematic diagram showing the bonding of terminal amino dendritic polymers to the surface of polymer base film layer 11 via chemical bonds through a diacaridine compound;

[0038] Figure 7 This is a schematic diagram of the angle of a water droplet on a solid surface;

[0039] Figure 8A This is a schematic diagram of the main stacked structure of the display screen 100 in an embodiment of this application;

[0040] Figure 8B This is a schematic diagram of the stacked structure of the display screen 100 in one embodiment of this application;

[0041] Figure 8C This is a schematic diagram of the stacked structure of the display screen 100 in another embodiment of this application;

[0042] Figure 8D This is a schematic diagram of the stacked structure of the display screen 100 in another embodiment of this application;

[0043] Figure 9A This is a schematic diagram of the stacked structure of the cover plate 103 in one embodiment of this application;

[0044] Figure 9B This is a schematic diagram of the stacked structure of the cover plate 103 in another embodiment of this application;

[0045] Figure 9C This is a schematic diagram of the stacked structure of the cover plate 103 in another embodiment of this application;

[0046] Figure 10 This is a schematic diagram of the structure of an electronic device 200 provided in an embodiment of this application;

[0047] Figure 11 This is a schematic diagram of the stacked structure of the display screen assembly 202 in the electronic device 200 according to one embodiment of this application;

[0048] Figure 12 This is a schematic diagram of the stacked structure of the display screen assembly 202 in the electronic device 200 according to another embodiment of this application;

[0049] Figure 13A This is a schematic diagram of the laminated structure of the protective film 2022 in one embodiment of this application;

[0050] Figure 13B This is a schematic diagram of the laminated structure of the protective film 2022 in another embodiment of this application;

[0051] Figure 14 This is a schematic diagram of the plasma processing mechanism. Detailed Implementation

[0052] The embodiments of this application will now be described in conjunction with the accompanying drawings.

[0053] In the laminated structure of foldable screens, polymer films such as polyethylene terephthalate (PET) and polyimide (PI) are commonly used. These films offer a balance of flexibility, abrasion resistance, creep resistance, and transparency, serving as support layers or protective cover plates. Typically, these polymer films are laminated with optical pressure-sensitive adhesive (OCA) in foldable screens to combine with other functional layers and form a complete laminated structure. However, the adhesion strength between conventional PET and PI films and OCA is currently low. During long-term bending of the foldable screen, OCA is prone to detaching from PET and PI, leading to screen failure.

[0054] To address the issue of debonding between the film material and the OCA during the bending process of foldable screens, it is necessary to improve the adhesion strength between the film material and the OCA. Currently, common methods used in the industry to improve adhesion strength include: firstly, developing OCA with high adhesion strength to achieve strong adhesion with the film material; however, OCA development is difficult, time-consuming, and costly, and it is difficult to be compatible with the adhesion strength of various film material surfaces; secondly, activating the film material surface through plasma treatment, corona treatment, etc., but this method has limited effect on improving adhesion strength and cannot meet the current product requirements for adhesion strength; moreover, plasma cleaning and corona treatment have significant time-limited effects, with the activation effect lost after several hours, requiring repeated plasma treatment; furthermore, as products become increasingly thinner and lighter, using thinner OCA means lower adhesion strength, resulting in a higher risk of debonding failure under repeated bending.

[0055] In view of this, embodiments of this application provide a composite film layer structure and its preparation method, a display screen, and an electronic device. The composite film layer structure can be used as a support layer, cover plate, and protective film on the surface of the display screen. By adding a specific grafting layer to the surface of a conventional composite film layer structure, the bonding strength between the composite film layer structure and the optical adhesive layer can be improved, thereby enhancing the bending capability of the foldable screen. The grafting layer can also enable the composite film layer structure to have a smaller total thickness and a smaller change in optical performance, so as to better meet the requirements of thinner and lighter display screens and electronic devices and higher display performance.

[0056] See Figure 1A and Figure 1B , Figure 1A This is a cross-sectional structural schematic diagram of the composite membrane structure 10 in one embodiment of this application; Figure 1BThis is a cross-sectional schematic diagram of the composite film structure 10 according to another embodiment of this application. The composite film structure 10 includes a polymer base film layer 11 and a graft layer 12 located on at least one side surface of the polymer base film layer 11. The graft layer 12 includes an amino-terminated dendritic polymer. The graft layer 12 is chemically bonded to the surface of the polymer base film layer 11, exhibiting strong bonding force, with a bonding strength ≥3 MPa. This composite film structure 10 can be applied to a display screen, specifically for example, as a support layer, cover plate, or protective film on the surface of the display screen. The display screen can be a flexible display screen such as a foldable screen, or a non-flexible display screen. The display screen 100 can be used to display text, images, or video information.

[0057] The polymer-based film layer 11 has a first surface and a second surface disposed opposite to each other, and the graft layer 12 may be disposed only on one of the first surface and the second surface (e.g., Figure 1A As shown), the grafting layer 12 can also be disposed on both the first and second surfaces simultaneously (e.g., Figure 1B (As shown). Understandably, in the composite film structure 10, whether the graft layer 12 is disposed on one or both surfaces can be determined according to actual bonding requirements. Specifically, if only one surface of the composite film structure 10 needs to be bonded to the optical adhesive layer, then the graft layer 12 can be disposed on only one surface. If both opposite surfaces of the composite film structure 10 need to be bonded to the optical adhesive layer, then the graft layer 12 can be disposed on both surfaces of the polymer base film layer 11. The bonding strength between the graft layer 12 and the polymer base film layer 11 can be obtained by pull-out testing using a universal testing machine.

[0058] See Figure 2 and Figure 3 , Figure 2 and Figure 3 This is a schematic diagram illustrating the application of the composite film structure 10 in the display screen 100 according to an embodiment of this application. In this embodiment, the display screen 100 is a foldable screen, wherein... Figure 2 This is a structural diagram of the display screen 100 in its unfolded state; Figure 3 This is a cross-sectional schematic diagram of the display screen 100 in its folded state. For ease of description, the width direction of the display screen 100 is defined as the X-axis, the length direction as the Y-axis, and the thickness direction as the Z-axis. The X-axis, Y-axis, and Z-axis are all perpendicular to each other. Figure 2 and Figure 3 Let's take the X-axis as the folding axis as an example for explanation.

[0059] Figure 2 and Figure 3In the display screen 100, a composite film layer structure 10, an optical adhesive layer 120, and a functional layer 130 are stacked together. The optical adhesive layer 120 has strong adhesive properties and is located between the composite film layer structure 10 and the functional layer 130 to firmly bond the composite film layer structure 10 and the functional layer 130 together. The grafted layer 12 of the composite film layer structure 10 is close to the optical adhesive layer 120 for lamination and bonding, meaning the grafted layer 12 of the composite film layer structure 10 and the optical adhesive layer 120 are in direct contact and bonded.

[0060] It should be noted that in the stacked structure of the display screen 100 of this application, the composite film layer structure 10 can serve as a supporting layer structure, such as a flexible substrate or intermediate support layer; it can also serve as a protective layer structure, such as a flexible cover plate. The functional layer 130 can be various functional layers in the display screen 100 that need to be stacked with the composite film layer structure 10. For example, the functional layer 130 can be a flexible substrate, a display panel, a cover plate, a polarizer, a touch film, or other components of the display screen. In some embodiments, the functional layer 130 is a display panel, and the composite film layer structure 10 is a support layer or a cover plate. In some embodiments, the functional layer 130 can also be the composite film layer structure 10.

[0061] When the display screen 100 is in a folded state, the display side, i.e., the light-emitting side, is generally folded inward. This reduces the exposed area of ​​the display screen 100, which helps protect the screen and prevents damage. This application Figure 3 The illustration shows the folded state of the display screen 100 with the side of the functional layer 130 away from the composite film structure 10 as the light-emitting surface. In some other embodiments, depending on the different functions of the composite film structure 10 in the display screen 100 and the different selections of the functional layer 130, one side of the composite film structure 10 may also be the light-emitting surface. In this case, in the folded state, one side of the composite film structure 10 faces inward. In some other embodiments, when the display screen 100 is in the folded state, the display side, i.e., the light-emitting surface side, may be folded outward.

[0062] See also Figure 2 and Figure 3 The display screen 100 has a bending region along the y-axis and non-bending regions located on both sides of the bending region. The display screen 100 can be folded relative to the folding axis. The area that deforms due to folding stress is the bending region, and the areas on both sides outside the bending region that do not deform due to folding stress are the non-bending regions. In this embodiment, the composite film structure 10 is located in both the bending region and the non-bending region of the display screen 100, and the grafting layer 12 in the composite film structure 10 is located at least in the bending region of the display screen 100.

[0063] It should be noted that, Figure 2 and Figure 3The illustration shows a display screen capable of folding once. In other embodiments, the display screen 100 may also be capable of folding multiple times (two or more times). In this case, the display screen 100 may include two or more bending zones, and the two non-bending zones located on either side of each bending zone may be relatively close to each other when the display screen 100 is in a folded state, or relatively far apart when the display screen 100 is in an unfolded state. The display screen 100 may integrate display functions, touch sensing functions, and fingerprint image acquisition functions. It should be understood that the display screen 100 shown in this embodiment is not limited to... Figure 2 The 2D display shown can also be a 2.5D display or a 3D display.

[0064] When the display screen 100 is in the unfolded state, the bent area and the non-bent areas on both sides of the bent area are at 180 degrees (or approximately 180 degrees, allowing for slight deviations). In this state, the display screen 100 has a continuous, large display area, enabling large-screen display and enhancing the user experience. When the display screen 100 is in the folded state, the non-bent areas on both sides overlap, and the bent area bends.

[0065] During the repeated folding of the display screen 100, the bending area undergoes repeated bending deformation, resulting in higher requirements for the bonding reliability of each layer compared to the non-bending area. To improve the bonding strength between the composite film structure 10 and the optical adhesive layer 120, and to enhance the bending reliability of the display screen 100, in this embodiment, the graft layer 12 in the composite film structure 10 is located at least in the bending area of ​​the display screen 100. The graft layer 12 includes an amino-terminated dendritic polymer, which is chemically grafted onto the surface of the polymer base film layer 11, allowing for a firm bond with the polymer base film layer 11. The amino-terminated dendritic polymer has multipolar groups and high polarity, which can increase the surface energy of the composite film structure 10, introducing a large amount of light that can interact with the optical adhesive layer 120 onto the surface of the composite film structure 10. The strong interaction groups (i.e., amino groups) in the adhesive layer enhance the bonding strength between the composite film structure 10 and the optical adhesive layer 120, thereby improving the bending ability of the foldable screen and enhancing its reliability and durability. The grafted layer 12 also enables the composite film structure 10 to have a smaller overall thickness and less change in optical performance, better meeting the requirements of the display screen 100 for thinner and lighter designs and higher display performance. In addition, the grafted layer 12 avoids the need for an excessively thick optical adhesive layer 120 to enhance bonding strength, which is beneficial for the thinner and lighter design of the display screen 100. Furthermore, the bonding strength enhancement performance of the grafted layer 12 in the composite film structure 10 is relatively long-lasting and does not require repeated chemical grafting treatment in a short period of time, facilitating the storage and application of the composite film structure.

[0066] Figure 4 This is a schematic diagram illustrating the arrangement of the grafting layer 12 in some embodiments of this application. In this embodiment, as shown... Figure 4As shown, the grafting layer 12 of the composite film structure 10 is only disposed in the bending area of ​​the display screen 100, and not in the non-bending area. This can improve the adhesion between the composite film structure 10 and the optical adhesive layer 120 in the bending area, and improve the folding reliability. Distributing the grafting layer 12 only in the bending area where higher bonding strength is required helps to reduce the amount of grafting material used.

[0067] Figure 5 This is a schematic diagram illustrating the arrangement of the grafting layer 12 in other embodiments of this application. In other embodiments of this application, such as... Figure 5 As shown, the graft layer 12 of the composite film structure 10 is simultaneously disposed in both the bending and non-bending areas of the display screen 100, thus simultaneously improving the adhesion between the composite film structure 10 and the optical adhesive layer 120 in both bending and non-bending areas. Considering that the composite film structure 10 is usually manufactured in rolls in actual production, the simultaneous placement of the graft layer 12 in both the bending and non-bending areas of the display screen 100 facilitates the large-scale industrial production of the composite film structure 10.

[0068] In this embodiment, the grafted layer 12 is chemically bonded to the surface of the polymer base film layer 11, and the grafted layer 12 and the polymer base film layer 11 are in direct contact. The grafted layer 12 includes a terminal amino dendritic polymer. A dendritic polymer, also known as a dendriticized polymer, is a linear polymer with dendritic units on each repeating unit. A terminal amino dendritic polymer is a dendritic polymer with multiple terminal amino groups. In this embodiment, the terminal amino dendritic polymer has at least four terminal amino groups. Grafting the terminal amino dendritic polymer onto the surface of the polymer base film layer 11 can change the surface properties of the composite film structure 10 and improve the wettability of the optical adhesive to the composite film structure 10. The multiple terminal amino groups of the terminal amino dendritic polymer can act as strongly polar groups. When the grafted layer 12 is bonded to the optical adhesive layer 120, these strongly polar groups can form a strong interaction with the optical adhesive, resulting in a strong interaction between the composite film structure 10 and the optical adhesive. This significantly improves the 180° peel force of the optical adhesive on the composite film structure 10, thereby improving bending reliability.

[0069] The terminal amino dendritic polymer of this application embodiment has a relatively small molecular weight, but has a highly branched structure, which can improve the peel force between the composite film structure 10 and the optical adhesive while keeping the impact on the optical performance of the composite film structure 10 at a low level.

[0070] In some embodiments of this application, the terminal amino dendritic polymer includes dendritic polyamidoamine (PAMAM). Dendritic polyamidoamine is a polyamide-amine type dendritic polymer with a structure that radiates outward from a central core, resembling a tree, and is a highly branched structure. Dendritic polyamidoamine can be a G0 generation dendritic polyamidoamine, or it can be a first-generation G1 generation, second-generation G2 generation, etc., descendant obtained by gradual branching development from a basic G0 generation. Understandably, with increasing generation, the degree of branching of the dendritic polyamidoamine increases, the number of terminal amino groups increases, and the molecular weight becomes larger.

[0071] Considering that higher generations and larger molecular weights of dendritic polyamide amines may adversely affect the optical properties of the composite film structure 10, in some embodiments of this application, the dendritic polyamide amine includes one or more of G0-G6 generation dendritic polyamide amines. Specifically, it can be G0, G1, G2, G3, G4, G5, or G6 generation dendritic polyamide amines. G0-G6 generation dendritic polyamide amines have a moderately branched structure, a suitable number of active terminal amino groups, and a suitable molecular weight, thereby enabling the composite film structure 10 to better balance high adhesion strength with the optical adhesive layer 120 and good optical properties.

[0072] The structural formulas of G0, G1, and G2 generation dendritic polyamide amines are as follows:

[0073]

[0074]

[0075] From the structural formulas of the G0, G1, and G2 generation dendritic polyamides, it can be seen that the G0 generation has 4 dendritic branches with 4 terminal amino groups; the G1 generation has 8 dendritic branches with 8 terminal amino groups; the G2 generation has 16 dendritic branches with 16 terminal amino groups; and so on, with the G3 generation having 32 dendritic branches with 32 terminal amino groups; the G4 generation having 64 dendritic branches with 64 terminal amino groups; the G5 generation having 128 dendritic branches with 128 terminal amino groups; and the G6 generation having 256 dendritic branches with 256 terminal amino groups. The higher the generation, the closer the molecular structure of the dendritic polyamide is to a spherical shape. Understandably, the structural formulas of the G3, G4, G5, and G6 generation dendritic polyamides can be obtained by further branching from the G2 generation, and will not be shown here individually.

[0076] In order to achieve better peel strength and better balance with good optical performance, in some embodiments of this application, the graft layer 12 includes G2-G6 generation dendritic polyamide amine. In some embodiments, the graft layer 12 includes G3-G6 generation dendritic polyamide amine. In some embodiments, the graft layer 12 includes G3-G5 generation dendritic polyamide amine.

[0077] In this embodiment, the graft layer 12 further includes a diazinon compound. The diazinon compound is chemically bonded to the surface of the polymer base film layer 11. Specifically, the diazinon compound can be chemically bonded to the surface of the polymer base film layer 11 based on a carbene insertion reaction. The terminal amino dendritic polymer is then chemically bonded to the diazinon compound. That is, the terminal amino dendritic polymer is chemically bonded to the surface of the polymer base film layer 11 via the diazinon compound. Since the terminal amino dendritic polymer is chemically bonded to the diazinon compound through its terminal amino group, it is understood that the diazinon compound contains active groups capable of reacting and bonding with the terminal amino group of the terminal amino dendritic polymer. These active groups can be, but are not limited to, fluorine (F), chlorine (Cl), or amino (-NH2). In other words, bisacrylidine compounds include a class of bisacrylidine compounds that can chemically bond with the surface of the polymer base film layer 11 through a carbene insertion reaction, and can also form chemical bonds with terminal amino dendritic polymers.

[0078] In the embodiments of this application, the structural formula of the diacaridine compound is shown in formula (1):

[0079]

[0080] In formula (1), R is a halogen atom or a substituted or unsubstituted alkyl group, and R' is a halogen atom, amino (-NH2), carboxyl (-COOH), alkenyl or -R 1 -R 2 R 1 It is an alkylene group or -C6H4-CH2-, R 2 It can be a halogen atom, amino group, carboxyl group or alkenyl group.

[0081] R being a halogen atom or a substituted or unsubstituted alkyl group can give bisacrylidine compounds relatively high stability, which is beneficial for the controlled occurrence of carbene insertion reactions. In the embodiments of this application, in group R, the halogen atom can be a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; the substituted or unsubstituted alkyl group can be a substituted or unsubstituted C1-C10 alkyl group, specifically, for example, a substituted or unsubstituted C1, C2, C3, C4, C5, C6, C7, C8, C9, or C10 alkyl group. The alkyl group can be a straight-chain alkyl group or a branched-chain alkyl group. The substituted alkyl group can be a haloalkyl group or an alkenyl-substituted alkyl group. The haloalkyl group can be a fluoroalkyl group, a chloroalkyl group, a bromoalkyl group, or an iodoalkyl group. The alkenyl-substituted alkyl group can be a C1-C10 alkenyl-substituted C1-C10 alkyl group. For example, the haloalkyl group can be a perfluoroalkyl group, such as trifluoromethyl. Trifluoromethyl can help improve the stability of the cycloazene structure, making the carbene insertion reaction more controllable and preventing it from reacting easily or reacting on its own. This can improve the stability of the reaction with the polymer base film layer 11 and obtain a suitable grafting amount.

[0082] In the embodiments of this application, the halogen atom in the group R' can be a fluorine atom, a chlorine atom, a bromine atom, or an iodine atom; the alkenyl group can be, for example, a vinyl group. 1 The alkylene group can be C1-C10 alkylene groups, specifically C1, C2, C3, C4, C5, C6, C7, C8, C9, or C10 alkylene groups. The alkylene group can be a straight-chain alkylene group or a branched-chain alkylene group.

[0083] In some embodiments of this application, the biacrididine compounds include one or more of 4-[3-(trifluoromethyl)-3H-bisacridin-3-yl]benzyl bromide, 4-(3-(trifluoromethyl)-3H-bisacridin-3-yl)benzylamine, and 4-[3-(trifluoromethyl)-3H-bisacridin-3-yl]benzyl chloride. The above-mentioned biacrididine compounds exhibit good UV sensitivity and stability after the insertion reaction. The structural formulas of 4-[3-(trifluoromethyl)-3H-bisacridin-3-yl]benzyl bromide, 4-(3-(trifluoromethyl)-3H-bisacridin-3-yl)benzylamine, and 4-[3-(trifluoromethyl)-3H-bisacridin-3-yl]benzyl chloride are as follows:

[0084]

[0085] Bisacrylidine compounds possess strong photosensitivity. Under ultraviolet light (e.g., 365 nm), the bisacrylidine group first undergoes covalent bond cleavage, releasing a molecule of N2. Subsequently, the bond electrons rearrange to form an active carbene intermediate, which inserts into the CH bond or other heteroatom-H covalent bond on the surface of the polymer base film 11, generating a new covalent bond. This allows the bisacrylidine compound to form a chemical bond with the surface of the polymer base film 11, thus completing the carbene insertion reaction. Therefore, bisacrylidine compounds can act as a bridge, suitable for introducing reactive groups into the inert surfaces of various composite film structures commonly used in polymer base film 11, thereby achieving the modification of terminal amino dendritic polymers.

[0086] Please see Figure 6 , Figure 6 This is a schematic diagram showing that the terminal amino dendritic polymer is chemically bonded to the surface of the polymer base film layer 11 via a diacillin-like compound. Figure 6 The intermediate-terminal amino dendritic polymers are specifically exemplified by G0-generation dendritic polyamide amines, and the bisacrididine compounds are specifically exemplified by 4-[3-(trifluoromethyl)-3H-bisacrididine-3-yl]benzyl bromide. From Figure 6 It is known that 4-[3-(trifluoromethyl)-3H-bisacrididin-3-yl]benzyl bromide generates a carbene intermediate under 365nm ultraviolet light irradiation. The carbene intermediate inserts into the surface of the polymer base film 11 and forms a chemical bond with the surface of the polymer base film 11. The terminal amino dendritic polymer reacts with the bromine atom of 4-[3-(trifluoromethyl)-3H-bisacrididin-3-yl]benzyl bromide through the reaction of the terminal amino group with the bromine atom, so that the terminal amino dendritic polymer is chemically bonded to the bisacrididin compound. Finally, the terminal amino dendritic polymer is chemically grafted to the surface of the polymer base film 11, which increases the surface of the polymer base film 11 with a large number of active amino groups.

[0087] It should be noted that, Figure 6 This illustration only shows the case where a bisacrididine compound molecule and a terminal amino dendritic polymer molecule are grafted onto the surface of the polymer base film layer 11. In actual products, the surface of the polymer base film layer 11 is usually grafted with multiple bisacrididine compound molecules and multiple terminal amino dendritic polymer molecules.

[0088] The graft layer 12 in this embodiment is approximately a monolayer structure formed by bonding terminal amino dendritic polymer molecules to the surface of the polymer base film layer 11 via a diacaridine compound, thus having a relatively small thickness. In this embodiment, the thickness of the graft layer 12 is 0.5 nm to 100 nm. The small thickness of the graft layer 12 allows the composite film structure 10 to have a relatively smaller total thickness, which is beneficial for achieving a thinner and lighter display screen 100; it also helps maintain the good optical performance of the composite film structure 10. Exemplarily, the thickness of the graft layer 12 can be 0.5 nm, 1 nm, 5 nm, 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, 90 nm, 95 nm, or 100 nm.

[0089] In this embodiment, the polymer base film layer 11 can be made of various polymer materials commonly used in the display screen 100, including, but not limited to, one or more of polyimide (PI), polyethylene terephthalate (PET), polyethylene (PE), polycarbonate (PC), polyurethane (PU), polymethyl methacrylate (PMMA), polyacrylate (PA), polyethylene terephthalate (PEN), and parylene. These polymer materials combine flexibility, transparency, abrasion resistance, and mechanical properties, which can better meet the bending requirements and optical performance requirements of flexible displays, and can also play a supporting or protective role. For example, polyimide film has excellent high temperature resistance, chemical corrosion resistance, and mechanical properties. In high temperature environments, it can maintain stable physical and chemical properties and will not deform, soften, or decompose due to temperature increases. At the same time, it can resist the corrosion of various chemical reagents, which is very important for the use of the display screen in complex environments. Moreover, its good flexibility allows the screen to be bent and folded, and can adapt to various irregular mounting surfaces. In some embodiments of this application, the polymer base film layer 11 can be a single polymer material. For example, in some embodiments, the polymer base film layer 11 is made of polyimide (PI). In some embodiments, the polymer base film layer 11 is made of polyethylene terephthalate (PET). In other embodiments of this application, the polymer base film layer 11 may also include two or more polymer materials. The specific material of the polymer base film layer 11 can be selected according to actual needs.

[0090] In this embodiment, the thickness of the polymer base film layer 11 can be 5µm-200µm. A suitable thickness of the polymer base film layer 11 allows it to acquire basic mechanical properties to achieve its supporting or protective function. Exemplarily, the thickness of the polymer base film layer 11 can be, but is not limited to, 5µm, 10µm, 20µm, 30µm, 50µm, 60µm, 80µm, 100µm, 120µm, 130µm, 150µm, 160µm, 180µm, or 200µm.

[0091] In this application, GC-MS (Gas Chromatography-Mass Spectrometry), XPS (X-ray Photoelectron Spectroscopy), FTIR (Fourier Transform Infrared Spectrometer) and other methods can be used to test and analyze the composite membrane structure 10 to detect whether the composite membrane structure 10 contains the chemical components of the grafted layer 12.

[0092] In this embodiment of the application, the water droplet angle on the surface of the graft layer 12 of the composite film structure 10 is less than 50°. The water droplet angle, also known as the water contact angle, refers to the angle formed when a water droplet is placed on a solid horizontal plane, at the solid-liquid-gas three-phase interface point on the solid surface, where the liquid phase is sandwiched between the two tangents of the gas-liquid interface and the solid-liquid interface; that is, the angle formed by the contact line between the water droplet and the solid surface. See also... Figure 7 , Figure 7 This is a schematic diagram of the angle of a water droplet on a solid surface. Figure 7In this context, θ represents the water droplet angle. Measuring the water contact angle can evaluate the wettability and adhesion of the composite film structure 10 surface. A water contact angle less than 90° indicates that the solid surface is hydrophilic, meaning the liquid easily wets the solid; the smaller the angle, the better the wettability. The water droplet angle can be measured using a water contact angle meter. In this embodiment, the composite film structure 10, by providing a grafted layer 12, has a smaller water droplet angle, thus exhibiting better wettability and adhesion. This facilitates the spreading and wetting of molecules such as optical adhesives on the surface of the composite film structure 10, thereby improving the bonding reliability of the optical adhesive layer 120. Exemplarily, the water droplet angles on the grafted layer 12 surface of the composite film structure 10 are 5°, 8°, 10°, 15°, 20°, 25°, 30°, 35°, and 40°. In some embodiments, the water droplet angle on the grafted layer 12 surface of the composite film structure 10 is less than or equal to 40°. In some embodiments, the water droplet angle on the surface of the grafted layer 12 of the composite membrane structure 10 is less than or equal to 35°. In the embodiments of this application, after chemically grafting the terminal amino dendritic polymer, further activation treatments such as plasma activation and corona activation can further reduce the water droplet angle on the surface of the grafted layer 12 of the composite membrane structure 10. After activation treatment, in some embodiments, the water droplet angle on the surface of the grafted layer 12 of the composite membrane structure 10 is less than or equal to 30°. In some embodiments, the water droplet angle on the surface of the grafted layer 12 of the composite membrane structure 10 is less than or equal to 20°. In some embodiments, the water droplet angle on the surface of the grafted layer 12 of the composite membrane structure 10 is less than or equal to 10°.

[0093] In this embodiment, the visible light transmittance of the composite film structure 10 is greater than or equal to 89%. Visible light transmittance refers to the proportion of visible light in the wavelength range of 380nm to 780nm that passes through the medium; it is the proportion of visible light transmitted. The high visible light transmittance of the composite film structure 10 indicates that it can have high transparency, thus improving the display performance of the display screen 100 when used in the display screen 100. In some embodiments, the visible light transmittance of the composite film structure 10 is greater than or equal to 90%. In some embodiments, the visible light transmittance of the composite film structure 10 is greater than or equal to 91%. The visible light transmittance of the composite film structure 10 can be determined using a spectrophotometer or a visible light transmittance meter.

[0094] In this embodiment, the haze of the composite film structure 10 is less than or equal to 1.3%. Haze is the percentage of transmitted light intensity at an angle greater than 2.5° from the incident light to the total transmitted light intensity. Higher haze means a decrease in the gloss and transparency of the film material, especially in image quality. The composite film structure 10 has lower haze, resulting in better gloss and clarity, thus improving the display performance of the display screen 100. In some embodiments, the haze of the composite film structure 10 is less than or equal to 1.2%. In some embodiments, the haze of the composite film structure 10 is less than or equal to 1.1%. The haze of the composite film structure 10 can be obtained using a haze meter.

[0095] In this embodiment, the optical adhesive layer 120 can be made of various optical adhesives used in the display screen 100, including, but not limited to, one or more of epoxy resin optical adhesives, silicone resin optical adhesives, acrylate optical adhesives, modified acrylate optical adhesives, and polyurethane optical adhesives. These optical adhesives can form a highly reliable bond with the composite film structure 10 of this embodiment and possess good mechanical properties such as flexibility. For example, acrylate optical adhesives can be transparent adhesives polymerized from several acrylate monomers, such as isooctyl acrylate, hydroxybutyl acrylate, and heptyl acrylate, polymerized in a certain proportion.

[0096] In this embodiment, the 180° peel force between the composite film structure 10 and the optical adhesive layer 120 is greater than or equal to 4.8 N / cm. The 180° peel force can be tested using a universal testing machine. The greater the 180° peel force between the composite film structure 10 and the optical adhesive layer 120, the stronger the adhesion between them, and the more secure and reliable the bond. In this embodiment, the composite film structure 10, by providing a grafted layer 12 on its surface, exhibits a large 180° peel force when bonded to the optical adhesive layer 120, thereby significantly improving the bending reliability of the display screen 100. In some embodiments, the 180° peel force between the composite film structure 10 and the optical adhesive layer 120 is greater than or equal to 5.0 N / cm. In some embodiments, the 180° peel force between the composite film structure 10 and the optical adhesive layer 120 is greater than or equal to 6.0 N / cm. In this embodiment, after chemically grafting the terminal amino dendritic polymer, further activation treatments such as plasma activation and corona activation can further improve the 180° peel strength between the composite film structure 10 and the optical adhesive layer 120. After activation treatment, in some embodiments, the 180° peel strength between the composite film structure 10 and the optical adhesive layer 120 is greater than or equal to 7.0 N / cm. In some embodiments, the 180° peel strength between the composite film structure 10 and the optical adhesive layer 120 is greater than or equal to 8.0 N / cm. In some embodiments, the 180° peel strength between the composite film structure 10 and the optical adhesive layer 120 is greater than or equal to 9.0 N / cm. In some embodiments, the 180° peel strength between the composite film structure 10 and the optical adhesive layer 120 is greater than or equal to 10.0 N / cm.

[0097] Understandably, the display screen 100 in this embodiment may include one or more (two or more) composite film layer structures 10 as described in this embodiment. The display screen 100 in this embodiment may also include one or more (two or more) optical adhesive layers 120. The number of layers in the composite film layer structure 10 and the optical adhesive layers 120 can be designed according to the actual needs of the display screen 100 fabrication, and this embodiment does not impose any special limitations.

[0098] In some embodiments of this application, the composite film layer structure 10 can be used as a support layer of the display screen 100; in some embodiments of this application, the composite film layer structure 10 can be used as a cover plate of the display screen 100; in some embodiments of this application, the composite film layer structure 10 can be used as a protective film on the surface of the display screen 100.

[0099] See Figure 8A , Figure 8AThis is a schematic diagram of the main stacked structure of the display screen 100 according to an embodiment of this application. The display screen 100 includes a support layer 101, a display panel 102 stacked on the support layer 101, and a cover plate 103 stacked on the side of the display panel 102 away from the support layer 101. A first optical adhesive layer 1201 is provided between the support layer 101 and the display panel 102, and a second optical adhesive layer 1202 is provided between the cover plate 103 and the display panel 102. The support layer 101 mainly serves a supporting function to support the display panel 102, and the cover plate 103 covers the light-emitting surface of the display panel 102 to effectively protect the display panel 102.

[0100] The support layer 101 can be a flexible support layer, and its material can be a polymer material, such as polyimide (PI), polyethylene terephthalate (PET), etc., or it can be a composite film structure 10 as described in the embodiments of this application. The flexible support layer can provide support and has good flexibility, and can be bent. See also Figure 8B In some embodiments of this application, the support layer 101 includes the composite film structure 10 described in the embodiments of this application, and one side of the grafted layer 12 of the composite film structure 10 is in direct contact and bonded to the first optical adhesive layer 1201. Using the composite film structure 10 for the support layer 101 can reduce the risk of debonding failure between the support layer 101 and the optical adhesive layer, and improve the bending reliability of the display screen 100.

[0101] The cover plate 103 can be a flexible cover plate. A flexible cover plate can protect the light-emitting side of the vulnerable display panel 102, effectively reducing the compressive stress on the display panel 102 during bending and mitigating its rebound tendency in the bending area, thereby protecting the display panel 102 from damage. The material of the cover plate 103 can be a polymer material, transparent glass, or a composite film structure 10 as described in the embodiments of this application. The polymer material can be, for example, polyimide (PI), polyethylene terephthalate (PET), etc. Using the composite film structure 10 for the cover plate 103 can reduce the risk of debonding failure between the cover plate 103 and the optical adhesive layer, improving the bending reliability of the display screen 100.

[0102] See Figure 8C In some embodiments of this application, the cover plate 103 includes the composite film structure 10 described above in the embodiments of this application, and one side of the grafted layer 12 of the composite film structure 10 is directly bonded to the second optical adhesive layer 1202.

[0103] See Figure 8DIn other embodiments of this application, the support layer 101 includes a composite film structure 10, and the cover plate 103 also includes a composite film structure 10. The use of the composite film structure 10 in both the support layer 101 and the cover plate 103 in this application reduces the risk of debonding failure between the support layer 101 or the cover plate 103 and the optical adhesive layer, thereby improving the bending reliability of the display screen 100.

[0104] In this application embodiment, the cover plate 103 may include one or more stacked composite membrane layer structures 10 as described in the embodiments of this application, or it may include one or more stacked composite membrane layer structures 10 as described in the embodiments of this application and one or more other membrane layer structures.

[0105] See Figure 9A , Figure 9B and Figure 9C , Figure 9A This is a schematic diagram of the stacked structure of the cover plate 103 in one embodiment of this application; Figure 9B This is a schematic diagram of the stacked structure of the cover plate 103 in another embodiment of this application; Figure 9C This is a schematic diagram of the stacked structure of the cover plate 103 in another embodiment of this application. The cover plate 103 includes at least a first film layer 1031 and a second film layer 1032 stacked together, and a third optical adhesive layer 1203 disposed between the first film layer 1031 and the second film layer 1032. The first film layer 1031 and / or the second film layer 1032 include the composite film layer structure 10 described above in the embodiments of this application. The third optical adhesive layer 1203 is bonded to the graft layer 12 of the composite film layer structure 10.

[0106] In some embodiments of this application, it may be as follows: Figure 9A As shown, one of the first film layer 1031 and the second film layer 1032 includes a composite film layer structure 10, and the other is another film layer structure, such as a polymer material layer or a glass layer. In other embodiments of this application, it can be as follows: Figure 9B and Figure 9C As shown, both the first membrane layer 1031 and the second membrane layer 1032 include a composite membrane structure 10.

[0107] When the first film layer 1031 and the second film layer 1032 include a composite film layer structure 10, it can be a composite film layer structure 10 comprising one or more layers. Multiple composite film layer structures 10 can be bonded together by an optical adhesive layer.

[0108] like Figure 9B and Figure 9C As shown and as mentioned above, the composite film structure 10 in the cover plate 103 may be provided with a graft layer 12 on one or both sides of the polymer base film layer 11 according to the actual bonding requirements.

[0109] Understandably, in order to better and more securely bond the cover plate 103 to the display panel 102, the outermost side of at least one side of the cover plate 103 may be a graft layer 12, with the graft layer 12 close to the display panel 102. For example Figure 9A and Figure 9B When the cover plate 103 shown is attached to the display panel 102, the side of the first film layer 1031 may be close to the display panel 102.

[0110] Display panel 102 can be a flexible display panel. For example, display panel 102 can be an organic light-emitting diode (OLED) display panel, an active-matrix organic light-emitting diode (AMOLED) display panel, a mini organic light-emitting diode (MLED) display panel, a micro organic light-emitting diode (MOLED) display panel, a micro organic light-emitting diode (MLED) display panel, or a quantum dot light-emitting diode (QLED) display panel, etc. In some embodiments, display panel 102 includes a thin film transistor (TFT) substrate layer, an OLED light-emitting layer, and an encapsulation layer.

[0111] In this embodiment, the materials of the first optical adhesive layer 1201 and the second optical adhesive layer 1202 can independently include one or more of epoxy resin-based optical adhesives, silicone resin-based optical adhesives, acrylate-based optical adhesives, modified acrylate-based optical adhesives, and polyurethane-based optical adhesives. Because the adhesion between the composite film structure 10 and the optical adhesive in this embodiment is high, the first optical adhesive layer 1201 and the second optical adhesive layer 1202 used to bond the composite film structure 10 in the display screen 100 of this embodiment do not need to be intentionally made very thick. This avoids the problem in the prior art where increasing the thickness of the optical adhesive to enhance the bonding strength affects the optical performance of the film material. In this embodiment, the thickness of the first optical adhesive layer 1201 and the second optical adhesive layer 1202 can independently be 10µm-150µm. For example, the thicknesses of the first optical adhesive layer 1201 and the second optical adhesive layer 1202 can be independently 10µm, 20µm, 40µm, 50µm, 60µm, 80µm, 100µm, 120µm, 130µm, and 150µm. A suitable optical adhesive layer thickness can achieve reliable bonding between the composite film structure 10 and other functional layers, while also helping to control the overall thickness of the display screen 100.

[0112] It should be noted that the first optical adhesive layer 1201 and the second optical adhesive layer 1202 may or may not be directly bonded to the display panel 102. In some possible embodiments, other layer structures may be provided between the first optical adhesive layer 1201 and the display panel 102, or between the display panel 102 and the second optical adhesive layer 1202. In this case, the first optical adhesive layer 1201 and the second optical adhesive layer 1202 may be directly bonded to other layer structures.

[0113] This application does not impose any special limitations on the bending radius, bending shape, etc. of the display screen 100. The composite film structure 10 provided in the embodiments of this application can be adapted to display screens with different bending radii, different bending shapes, and different stacking designs.

[0114] Please see Figure 10 , Figure 10 This is a schematic diagram of the structure of an electronic device 200 provided in an embodiment of this application. The electronic device 200 includes, but is not limited to, mobile phones, tablets, laptops, personal computers, multimedia players, e-book readers, smart screens, augmented reality (AR) devices, virtual reality (VR) devices, in-vehicle devices, or wearable devices, and other electronic terminal devices with display functions related to mobile office, smart home, sports and health, audio-visual entertainment, and smart travel. Wearable devices may include, for example, watches or wristbands. The electronic device 200 can be a foldable electronic device or a non-foldable electronic device. Figure 10 The following is a specific example of an electronic device 200 that is a foldable electronic device.

[0115] Electronic device 200 includes a housing 201 and a display assembly 202, the display assembly 202 being mounted on the housing 201. The display assembly 202 includes a display screen 2021. The light-emitting side, i.e., the display surface, of the display screen 2021 faces away from the housing 201.

[0116] See Figure 11 , Figure 11 This is a schematic diagram of the stacked structure of the display screen assembly 202 in an electronic device 200 according to one embodiment of this application. In some embodiments of this application, the display screen assembly 202 includes a display screen 2021 and a protective film 2022 disposed on the light-emitting side of the display screen 2021. That is, the electronic device 200 also includes a protective film 2022 disposed on the light-emitting side of the display screen 2021, and the protective film 2022 is used to protect the display screen 2021. The display screen 2021 and the protective film 2022 are directly bonded together by a fifth optical adhesive layer 1205.

[0117] In some embodiments of this application, the display screen 2021 includes the aforementioned display screen 100, and the display screen 100 includes a composite film layer structure 10. In other embodiments of this application, the protective film 2022 includes the composite film layer structure 10. In other embodiments of this application, see [link to relevant documentation]. Figure 12 Both the display screen 2021 and the protective film 2022 include a composite film layer structure 10.

[0118] In this application embodiment, the protective film 2022 may include one or more stacked composite film layer structures 10 as described in the embodiments of this application, or it may include one or more stacked composite film layer structures 10 as described in the embodiments of this application and one or more other protective film layer structures.

[0119] See Figure 13A and Figure 13B , Figure 13A This is a schematic diagram of the laminated structure of the protective film 2022 in one embodiment of this application; Figure 13B This is a schematic diagram of the laminated structure of the protective film 2022 in another embodiment of this application. The protective film 2022 includes at least a first protective film layer 21 and a second protective film layer 22 stacked together, and a fourth optical adhesive layer 1204 disposed between the first protective film layer 21 and the second protective film layer 22. The first protective film layer 21 and / or the second protective film layer 22 include the composite film layer structure 10 described above in the embodiments of this application. The fourth optical adhesive layer 1204 is bonded to the graft layer 12 of the composite film layer structure 10.

[0120] In some embodiments of this application, it may be as follows: Figure 13AAs shown, one of the first protective film layer 21 and the second protective film layer 22 includes a composite film layer structure 10, and the other is another protective film layer structure, such as a polymer material layer. In other embodiments of this application, it can be as follows: Figure 13B As shown, both the first protective film layer 21 and the second protective film layer 22 include a composite film layer structure 10.

[0121] When the first protective film layer 21 and the second protective film layer 22 include a composite film layer structure 10, it can be a composite film layer structure 10 consisting of one or more layers. Multiple composite film layer structures 10 can be bonded together by an optical adhesive layer.

[0122] The composite film structure 10 in the protective film 2022 can be a graft layer 12 provided on one or both sides of the polymer base film layer 11 according to the actual bonding requirements.

[0123] Understandably, in order to better and more firmly adhere the protective film 2022 to the display screen 2021, the outermost layer 12 on the side of the protective film 2022 closest to the display screen 2021 can be a graft layer. For example Figure 13A and Figure 13B When the protective film 2022 shown is attached to the display screen 2021, the side of the first protective film layer 21 can be close to the display screen 2021.

[0124] In this embodiment, the optical adhesive layers involved in the electronic device 200, such as the first optical adhesive layer 1201, the second optical adhesive layer 1202, the third optical adhesive layer 1203, the fourth optical adhesive layer 1204, and the fifth optical adhesive layer 1205, can all be made of optical adhesives commonly used in various display fields. These can be, but are not limited to, one or more of epoxy resin-based optical adhesives, silicone resin-based optical adhesives, acrylate-based optical adhesives, modified acrylate-based optical adhesives, and polyurethane-based optical adhesives. For example, acrylate-based optical adhesives can be transparent adhesives polymerized from several acrylate monomers, such as isooctyl acrylate, hydroxybutyl acrylate, and heptaacrylate, polymerized in a certain proportion. The thickness of each optical adhesive layer can be 10µm-150µm.

[0125] See also Figure 10The housing 201 includes a first housing 2011, a second housing 2012, and a connecting mechanism (not shown) connecting the first housing 2011 and the second housing 2012. In this embodiment, the connecting mechanism is a rotating shaft mechanism extending along the X-axis. The first housing 2011 and the second housing 2012 are rotatably connected by the connecting mechanism. That is, the first housing 2011 and the second housing 2012 are connected to each other by the connecting mechanism and can rotate relative to each other along the X-axis. Specifically, the first housing 2011 and the second housing 2012 can rotate relative to each other to bring them closer together, so that the housing 201 is in a folded state. The first housing 2011 and the second housing 2012 can also rotate relative to each other to move away from each other, so that the housing 201 is in an unfolded state. In other words, the first housing 2011 and the second housing 2012 can rotate relative to each other, so that the housing 201 can switch between a folded state and an unfolded state.

[0126] It should be understood that in other embodiments, the connecting mechanism may also be a sliding mechanism, a combination of rotation and sliding mechanism, or a detachable fastening mechanism, etc., and this application does not specifically limit it in this regard.

[0127] In some embodiments, the display assembly 202 may also include a bamboo book (not shown) located between the housing 201 and the display, which can improve the impact resistance of the display assembly 202, thereby improving the overall reliability of the display assembly 202.

[0128] It should be noted that when the electronic device 200 shown in this embodiment is in a folded state, the display assembly 202 is in an inwardly folded state, and at this time the display assembly 202 is located between the first housing 2011 and the second housing 2012. In other embodiments, when the electronic device 200 is in a folded state, the display assembly 202 may also be in an outwardly folded state.

[0129] The electronic device 200 of this application embodiment uses a composite film layer structure 10 as the functional film material of the display screen, which can reduce the risk of debonding failure between the film material and the optical adhesive during the bending process of the display screen, improve the bending reliability of the display screen, and thus improve the reliability and durability of the electronic device 200 and enhance product competitiveness.

[0130] This application also provides a method for preparing a composite film structure 10, comprising the following steps:

[0131] S101. A diazinon compound is coated on the surface of the polymer base film 11. The diazinon compound reacts with the surface of the polymer base film 11 under ultraviolet light to form a chemical bond, thereby obtaining an intermediate product.

[0132] S102. The surface of the intermediate product bonded with the diacylpropidine compound is brought into contact with a solution of amino-terminated dendritic polymer. The amino-terminated dendritic polymer and the diacylpropidine compound are chemically bonded under room temperature or heating conditions to complete the amination of the polymer base film layer 11, thereby obtaining the composite film structure 10.

[0133] In step S101, the polymer base film layer 11 may be cleaned first, and then coated with a bisacrylidine compound. Specifically, the cleaning operation may involve immersing the polymer base film layer 11 in deionized water and ultrasonically cleaning its surface, followed by drying.

[0134] Bisaccharide compounds can be administered at a concentration of 0.01 μL / cm³. 2 -30μL / cm 2 The coating amount is applied to the surface of the polymer base film layer 11. For example, the coating amount can be 0.01 μL / cm. 2 0.01μL / cm 2 0.1 μL / cm 2 0.5 μL / cm 2 1μL / cm 2 2μL / cm 2 3μL / cm 2 5μL / cm 2 10μL / cm 2 15μL / cm 2 20μL / cm 2 25μL / cm 2 30μL / cm 2 In some embodiments, the coating amount is 0.1 μL / cm. 2 -5μL / cm 2 There are no special restrictions on the coating operation; it can be applied by dripping, spinning, scraping, spraying, etc.

[0135] During ultraviolet (UV) irradiation, the wavelength of UV light can range from 254 nm to 420 nm, and the UV energy density can be as high as 2 mW / cm². 2 -500mW / cm 2 The UV irradiation time can be 1 min to 30 min. In some embodiments, the UV irradiation wavelength is 365 nm and the UV energy density is 200 mW / cm². 2 -300mW / cm 2 The illumination time is 5-10 minutes. Bisacodyl compounds form chemical bonds with the polymer-based film layer 11 based on a carbene insertion reaction; for details, please refer to... Figure 6 And as described above.

[0136] In this embodiment, bisacrylidine compounds may be chemically bonded to one or both surfaces of the polymer base film layer 11 as needed. Alternatively, bisacrylidine compounds may be chemically bonded to part or all of one surface of the polymer base film layer 11.

[0137] After the diazinon compounds have reacted with the polymer base film layer 11, the unreacted diazinon compounds can be washed with anhydrous ethanol.

[0138] In step S102, the specific operation of contacting the intermediate product with the terminal amino dendritic polymer solution can be: immersing the intermediate product in the terminal amino dendritic polymer solution; or coating the terminal amino dendritic polymer solution onto the surface of the intermediate product bonded with bisacrylidine compounds. The mass concentration of the terminal amino dendritic polymer in the solution can be 0.05-0.3 g / mL. Controlling the concentration of the terminal amino dendritic polymer solution at a suitable level is beneficial for the coating process and can also avoid waste of the terminal amino dendritic polymer. Exemplarily, the mass concentration of the terminal amino dendritic polymer is 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, or 100%. That is, a solvent may or may not be added to the terminal amino dendritic polymer solution. If a solvent is added, it can be water, ethanol, methanol, DMSO (dimethyl sulfoxide), CAN, etc. In some embodiments, the mass concentration of the terminal amino dendritic polymer is 50%-80%. The reaction time between the intermediate product and the terminal amino dendritic polymer solution can be 3 min to 24 h. Exemplarily, the reaction time can be 3 min, 30 min, 1 h, 3 h, 5 h, 6 h, 10 h, 15 h, 20 h, or 24 h. In some embodiments, the reaction time is 6 h to 12 h.

[0139] The specific temperature range under either ambient or heating conditions can be ambient temperature to 70℃. Heating can accelerate the reaction rate between the terminal amino groups of the terminal amino-terminated dendritic polymer and the reactive groups such as Br in diacylpropionid compounds. Specifically, the heating temperature can be 35℃-70℃, for example, 35℃, 40℃, 50℃, 60℃, or 70℃. The reaction between the terminal amino groups of the terminal amino-terminated dendritic polymer and diacylpropionid compounds can be achieved at relatively low temperatures, without adversely affecting the polymer base film layer 11, and the operation is simple, which is beneficial for industrial production.

[0140] After the reaction between the terminal amino dendritic polymer solution and the diacaridine compound is complete, the unreacted terminal amino dendritic polymer can be washed with anhydrous ethanol and then dried. Drying can be carried out at room temperature -80°C, meaning it can be air-dried at room temperature or dried at a specific heating temperature.

[0141] In some embodiments of this application, step S102 may further include:

[0142] After the amination of the polymer base film layer 11 is completed, an activation process is also included, which includes plasma treatment and / or corona treatment.

[0143] Specifically, plasma treatment can employ vacuum plasma, atmospheric pressure plasma, flame plasma, nitrogen plasma, argon plasma, or mixed gas plasma. In some embodiments, vacuum plasma treatment is used, with a processing power of 350W and a processing time ranging from 60s to 360s. Exemplarily, the processing time can be 60s, 90s, 120s, 150s, 180s, 200s, 240s, 300s, or 360s.

[0144] Corona treatment involves applying high-frequency, high-voltage electricity to oxidize the activated surface, thereby improving surface wettability. In some embodiments, the voltage during the corona treatment process is 5000 V / m. 2 -20000V / m 2 The frequency is 10kHz-25kHz. For example, the voltage can be 5000V / m. 2 8000V / m 2 10000V / m 2 12000V / m 2 15000V / m 2 18000V / m 2 20000V / m 2 The frequency can be 10kHz, 12kHz, 15kHz, 18kHz, 20kHz, 22kHz, or 25kHz.

[0145] Plasma treatment can further activate the terminal amino dendritic polymer, significantly improving the peel strength between the composite film structure 10 and the optical adhesive layer. (See also...) Figure 14 , Figure 14 This is a schematic diagram of the plasma processing mechanism. Figure 14 It is known that plasma treatment can break the interactions between amino groups, allowing the amino groups that were aggregated due to these interactions to further expand, thereby improving the wettability of the composite film structure 10 surface and thus enhancing the peel strength between the composite film structure 10 and the optical adhesive layer. Similarly, corona treatment can also improve the wettability of the composite film structure 10 surface, thereby enhancing the peel strength between the composite film structure 10 and the optical adhesive layer.

[0146] The method for preparing the composite film structure 10 provided in this application embodiment is simple and can be completed under relatively low temperature conditions. The prepared composite film structure 10 has tight bonding between its layers, stable structure, small total thickness, good optical performance, and high adhesion strength with the optical adhesive layer. When used in a display screen, it can improve the bending ability of the display screen and meet the requirements of thinner and lighter display screens and higher display performance.

[0147] The technical solution of this application will be further illustrated with several examples below.

[0148] Example 1

[0149] This application provides a method for preparing a composite film structure, comprising the following steps:

[0150] S101, 4-[3-(trifluoromethyl)-3H-bisacrididin-3-yl]benzyl bromide at 0.1 μL / cm 2 The coating was uniformly applied to the surface of a 50µm thick PET film, and then irradiated under 365nm ultraviolet light for 10 minutes, with an ultraviolet light energy density of 200mW / cm². 2 After the reaction between 4-[3-(trifluoromethyl)-3H-bisacrididin-3-yl]benzyl bromide and the surface of the PET film is completed, the unreacted 4-[3-(trifluoromethyl)-3H-bisacrididin-3-yl]benzyl bromide is washed with anhydrous ethanol to obtain the intermediate product, namely the PET film with 4-[3-(trifluoromethyl)-3H-bisacrididin-3-yl]benzyl bromide bonded to its surface.

[0151] S102. The intermediate product obtained in step S101 is immersed in a G0 generation dendritic polyamide amine solution. After standing at room temperature for 1-12 hours, the residual polyamide amine on the surface is cleaned with anhydrous ethanol. After drying, the surface-amined PET film material is obtained. The mass concentration of polyamide amine in the G0 generation dendritic polyamide amine solution is 0.15 g / mL.

[0152] S103. The surface-amined PET film obtained in step S102 is subjected to vacuum plasma treatment to further activate the surface-amined material. The treatment power is 350W and the treatment time is 180s to obtain the surface-amined PET film after plasma treatment.

[0153] Example 2

[0154] The only difference between this embodiment and Example 1 is that the dendritic polyamide used in step S102 is G1 generation dendritic polyamide.

[0155] Example 3

[0156] The only difference between this embodiment and Example 1 is that the dendritic polyamide used in step S102 is G2 generation dendritic polyamide.

[0157] Example 4

[0158] The only difference between this embodiment and Example 1 is that the dendritic polyamide used in step S102 is G3 generation dendritic polyamide.

[0159] Example 5

[0160] The only difference between this embodiment and Example 1 is that the dendritic polyamide used in step S102 is G4 generation dendritic polyamide.

[0161] Example 6

[0162] The only difference between this embodiment and Example 1 is that the dendritic polyamide used in step S102 is G5 generation dendritic polyamide.

[0163] Example 7

[0164] The only difference between this embodiment and Example 1 is that the dendritic polyamide used in step S102 is G6 generation dendritic polyamide.

[0165] Comparative Example 1

[0166] The only difference from Example 1 is that the PET film is a blank sample and has not undergone any chemical grafting treatment.

[0167] To better illustrate the technical effects of the embodiments of this application, the surface-amined PET film obtained in step S102 of Examples 1-7, the surface-amined PET film obtained after plasma treatment in step S103, and the blank PET film sample of Comparative Example 1 were subjected to the following performance tests, and the test results are shown in Table 1.

[0168] (1) Peel force test:

[0169] The sample to be tested was bonded to the optical adhesive layer and left to stand for ≥12 hours. Then, a 180° peel force test was performed using a universal testing machine. The peel test speed was 300 mm / min and the strip width was 2.54 cm.

[0170] (2) Water droplet angle test:

[0171] A 2 μL water droplet was placed onto the surface of the sample to be tested, and the water droplet angle was measured using a water contact angle meter.

[0172] (3) Optical performance testing:

[0173] The visible light transmittance and haze of the sample were obtained by using a CM3600A spectrophotometer.

[0174] In Table 1, Br-Dia is 4-[3-(trifluoromethyl)-3H-bisacryl-3-yl]benzyl bromide; the product corresponding to the column without plasma treatment is the surface-amined PET film obtained in step S102; the product corresponding to the column with plasma treatment is the surface-amined PET film obtained in step S103 after plasma treatment.

[0175] Table 1

[0176]

[0177] As shown in Table 1, compared with the blank sample of Comparative Example 1, the surface-amined PET film obtained by step S102 of Examples 1-7 of this application has a significantly reduced water droplet angle and improved 180° peel force with the optical adhesive layer through surface chemical grafting, and the transmittance and haze have not decreased significantly. The surface-amined PET film obtained by plasma treatment after step S103 of Examples 1-7 has a further reduced water droplet angle and significantly improved 180° peel force with the optical adhesive layer.

[0178] It should be understood that the use of the terms "first," "second," and various numerical designations in this document is merely for descriptive convenience and is not intended to limit the scope of this application.

[0179] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone, where A and B can be singular or plural. The character " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0180] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0181] In this application, "-" indicates a range value, including the endpoint values ​​at both ends. For example, the value of a can be 0.5-15, meaning that the value of a can be between 0.5 and 15, and includes the endpoint values ​​of 0.5 and 15.

[0182] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

Claims

1. A composite film structure, characterized in that, The composite membrane structure includes a polymer base membrane layer and a graft layer located on at least one side of the polymer base membrane layer. The graft layer includes an amino-terminated dendritic polymer, and the bonding strength between the graft layer and the polymer base membrane layer is ≥3 MPa.

2. The composite film structure according to claim 1, characterized in that, The terminal amino dendritic polymer includes dendritic polyamide amine.

3. The composite film structure according to claim 2, characterized in that, The dendritic polyamide amine includes one or more of the following generations: G0, G1, G2, G3, G4, G5, and G6.

4. The composite film structure according to any one of claims 1-3, characterized in that, The grafted layer further includes a diazinon compound, which is chemically bonded to the surface of the polymer base film layer, and the terminal amino dendritic polymer is chemically bonded to the diazinon compound.

5. The composite film structure according to claim 4, characterized in that, The bisacrylidine compound is chemically bonded to the surface of the polymer-based film layer based on a carbene insertion reaction.

6. The composite film structure according to claim 4 or 5, characterized in that, The structural formula of the diacylpropidine compound is shown in formula (1): Wherein, R is a halogen atom or a substituted or unsubstituted alkyl group, and R' is a halogen atom, amino group, carboxyl group, alkenyl group, or -R. 1 -R 2 R 1 It is an alkylene group or -C6H4-CH2-, R 2 It can be a halogen atom, amino group, carboxyl group or alkenyl group.

7. The composite film structure according to claim 6, characterized in that, The substituted alkyl group includes haloalkyl or alkenyl-substituted alkyl groups.

8. The composite film structure according to any one of claims 4-7, characterized in that, The diazinon compounds include one or more of 4-[3-(trifluoromethyl)-3H-diazinon-3-yl]benzyl bromide, 4-(3-(trifluoromethyl)-3H-diazinon-3-yl)benzylamine, and 4-[3-(trifluoromethyl)-3H-diazinon-3-yl]benzyl chloride.

9. The composite film structure according to any one of claims 1-8, characterized in that, The thickness of the grafted layer is 0.5nm-100nm.

10. The composite film structure according to any one of claims 1-9, characterized in that, The polymer-based film layer is made of one or more of the following materials: polyimide, polyethylene terephthalate, polyethylene, polycarbonate, polyurethane, polymethyl methacrylate, polyacrylate, polyethylene terephthalate, and parylene.

11. The composite film structure according to any one of claims 1-10, characterized in that, The water droplet angle on the grafted layer surface of the composite membrane structure is less than 50°.

12. The composite film structure according to any one of claims 1-11, characterized in that, The visible light transmittance of the composite film structure is greater than or equal to 89%; the haze is less than or equal to 1.3%.

13. The composite film structure according to any one of claims 1-12, characterized in that, The 180° peel force when the composite film structure is bonded to the optical adhesive layer is greater than or equal to 4.8 N / cm.

14. A method for preparing a composite film structure, characterized in that, include: A diazinon compound was coated onto the surface of a polymer-based film, and then subjected to ultraviolet light to react with the diazinon compound to form a chemical bond with the surface of the polymer-based film, yielding an intermediate product. At least one surface of the intermediate product bonded with the bisacrididine compound is brought into contact with a solution of an amino-terminated dendritic polymer. The amino-terminated dendritic polymer is then chemically bonded to the bisacrididine compound at room temperature to complete the amination of the polymer-based film layer, resulting in a composite film structure.

15. The method for preparing the composite film structure according to claim 14, characterized in that, After the amination of the polymer-based film is completed, an activation process is also included, which includes plasma treatment and / or corona treatment.

16. A cover plate, characterized in that, The cover plate includes at least a first film layer and a second film layer stacked together, and a third optical adhesive layer disposed between the first film layer and the second film layer. The first film layer and / or the second film layer include a composite film layer structure as described in any one of claims 1-13 or a composite film layer structure prepared by the preparation method as described in any one of claims 14-15. The third optical adhesive layer is bonded to the graft layer of the composite film layer structure.

17. A protective film, characterized in that, The protective film includes at least a first protective film layer and a second protective film layer stacked together, and a fourth optical adhesive layer disposed between the first protective film layer and the second protective film layer. The first protective film layer and / or the second protective film layer include a composite film layer structure as described in any one of claims 1-13 or a composite film layer structure prepared by the preparation method as described in any one of claims 14-15. The fourth optical adhesive layer is bonded to the graft layer of the composite film layer structure.

18. A display screen, characterized in that, The display screen includes a support layer, a display panel stacked on the support layer, and a cover plate stacked on the side of the display panel away from the support layer; a first optical adhesive layer is provided between the support layer and the display panel, and a second optical adhesive layer is provided between the cover plate and the display panel; The support layer comprises the composite film structure according to any one of claims 1-13 or the composite film structure prepared by the preparation method according to any one of claims 14-15, wherein the first optical adhesive layer is bonded to the graft layer of the composite film structure; and / or, The cover plate includes the composite film structure according to any one of claims 1-13, or the composite film structure prepared by the preparation method according to any one of claims 14-15, or the cover plate according to claim 16.

19. The display screen according to claim 18, characterized in that, The display screen is a foldable screen, which includes a bending area and a non-bending area, and the grafting layer of the composite film structure is located at least in the bending area of ​​the foldable screen.

20. The display screen according to claim 18 or 19, characterized in that, The materials of the first optical adhesive layer and the second optical adhesive layer independently include one or more of epoxy resin optical adhesives, silicone resin optical adhesives, acrylic optical adhesives, modified acrylic optical adhesives, and polyurethane optical adhesives.

21. An electronic device, characterized in that, The electronic device includes a display screen and a protective film disposed on the light-emitting side of the display screen; The display screen includes the display screen as described in any one of claims 18-20, and / or the protective film includes the composite film layer structure as described in any one of claims 1-13, or the composite film layer structure prepared by the preparation method as described in any one of claims 14-15, or the protective film as described in claim 17.

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