Composite substrate, preparation method thereof and display device

Abstract

The invention discloses a composite substrate and a preparation method thereof and a display device.The composite substrate comprises a flexible layer and a composite layer which are stacked, the composite layer comprises a planarization layer and a curling unit, the curling unit comprises a base film and a sub-film, the base film is in contact with the planarization layer, the sub-film is wrapped in the planarization layer, and the flexible layer is in contact with the sub-film. The sub-membrane is connected with the base membrane; the plane where the sub-films are located intersects with the plane where the base film is located to form an included angle. According to the composite substrate, the elastic moduli of all the areas on the curling units are different, gradient internal stress is achieved, and stress release is facilitated; the curling units absorb and release surface stress through deformation, so that the deformation degree of the rigid substrate and the flexible layer can be effectively reduced.

Description

Technical Field

[0001] The present application relates to the field of display technologies, and in particular, to a composite substrate, a preparation method thereof, and a display device. Background Art

[0002] With the continuous development of display technologies, flexible display has become the next-generation display technology with the greatest development potential due to its advantages such as light weight, thinness, durability, and rollability. The flexible substrate is an important component of flexible display devices. In the preparation of current mainstream flexible display products, the S2S (sheet to sheet) production process is usually adopted, that is, the flexible substrate is first attached to a rigid substrate, and then a display module is prepared on the flexible substrate. After the flexible display device composed of the flexible substrate and the display module is prepared, the rigid substrate is peeled off to obtain the flexible display device.

[0003] Currently, polyimide (PI) and the like are usually used as the film layer material for flexible substrates. However, such flexible substrates are easily affected by high temperatures and warp during the high-temperature process of preparing the display module, resulting in difficulties in the subsequent processes. Summary of the Invention

[0004] In view of this, the present application provides a composite substrate, a preparation method thereof, and a display device.

[0005] The embodiments of the present application are implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a composite substrate, including a stacked flexible layer and a composite layer. The composite layer includes a planarization layer and a curling unit. The curling unit includes a base film and a sub-film. The base film is in contact with the planarization layer, the sub-film is coated in the planarization layer, and the sub-film is connected to the base film;

[0007] The plane where the sub-film is located intersects with the plane where the base film is located to form an included angle.

[0008] In a second aspect, an embodiment of the present application provides a method for preparing a composite substrate, including the following steps:

[0009] Provide a flexible layer;

[0010] Prepare a composite layer on one side of the flexible layer. The composite layer includes a planarization layer and a curling unit;

[0011] Wherein, the curling unit includes a base film and a sub-film. The base film is in contact with the planarization layer, the sub-film is coated in the planarization layer, and one edge of the sub-film is connected to the base film. The plane where the sub-film is located intersects with the plane where the base film is located to form an included angle.

[0012] In a third aspect, an embodiment of the present application provides a display device, including a composite substrate and a display panel disposed on one side of the composite substrate. The composite substrate includes the composite substrate described above, or a composite substrate prepared by the preparation method described above.

[0013] In the technical solution provided by the present application, the base film and the sub-film of the curling unit intersect to form a curling structure. The elastic moduli of the regions on the curling unit are different, and thus have a gradient internal stress, which is beneficial to stress release. The curling unit has the characteristic of thermally induced deformation and can undergo a small deformation under temperature stimulation. At high temperatures, the surface stresses of the rigid substrate and the flexible layer increase. These surface stresses are transmitted to the curling unit deposited on the surface of the flexible layer, and the curling unit absorbs and releases the surface stresses through deformation, thereby effectively reducing the deformation degree of the rigid substrate and the flexible layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] To more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present application. For those skilled in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0015] Figure 1 It is a schematic structural diagram of a composite substrate provided by an embodiment of the present application;

[0016] Figure 2 It is a schematic structural diagram of a composite substrate provided by another embodiment of the present application;

[0017] Figure 3 It is a schematic structural diagram of a composite substrate provided by still another embodiment of the present application;

[0018] Figure 4 It is a schematic flow chart of a preparation method of a composite substrate provided by an embodiment of the present application;

[0019] Figure 5 It is a schematic flow chart of a preparation method of a composite substrate provided by another embodiment of the present application;

[0020] Figure 6 It is a schematic flow chart of the preparation steps of a curling unit provided by an embodiment of the present application;

[0021] Figure 7 It is a schematic structural diagram of a display device provided by an embodiment of the present application;

[0022] Reference Numerals:

[0023] 100 - Composite substrate; 10 - Flexible layer; 20 - Composite layer; 21 - Planarization layer; 22 - Curling unit; 221 - Sub - film; 222 - Base film; 30 - Inorganic barrier layer; 40 - Rigid substrate; 200 - Display device; 201 - Display panel; 1 - First surface; 2 - Second surface; 3 - Solid - state film; 4 - Main body area; 5 - Unit area; 6 - First edge; 7 - Second edge. Detailed implementation manners

[0024] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application. In addition, it should be understood that the specific implementation manners described herein are only for explaining and understanding the present application, and are not used to limit the present application. In the present application, unless otherwise stated, the orientation terms such as "upper" and "lower" specifically refer to the drawing directions in the drawings. Additionally, in the description of the present application, the term "including" means "including but not limited to". The various embodiments of the present application may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be construed as a rigid limitation on the scope of the present application; therefore, it should be considered that the described range description has specifically disclosed all possible sub - ranges and single values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub - ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0025] In the present application, "and / or" describes the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist simultaneously, and B exists alone. Wherein A and B can be singular or plural.

[0026] In the present application, "at least one" means one or more, and "multiple" means two or more. "At least one kind", "at least one item (individual) below" or similar expressions refer to any combination of these items, including any combination of single item (individual) or plural items (individuals). For example, "at least one item (individual) among a, b, or c", or, "at least one item (individual) among a, b, and c" can both represent: a, b, c, a - b (i.e., a and b), a - c, b - c, or a - b - c, where a, b, and c can be single or multiple respectively.

[0027] If there is a large stress inside the film layer and the stress cannot be effectively released, it will cause the material structure to be fragile (such as cracks) or cause structural deformation to release the stress. In the traditional flexible display manufacturing process, under the influence of high temperature, large stress is easily generated inside the flexible substrate, resulting in warping of itself and the glass substrate to varying degrees. In addition, in some cases, the flexible substrate further includes an inorganic barrier layer. Due to the characteristics of the inorganic material itself, the surface stress of the inorganic barrier layer is large, which may further cause warping of the flexible substrate. On the one hand, the warping of the flexible substrate easily hinders the progress of subsequent processes. On the other hand, cracks are easily formed when the flexible substrate is bent or cut, resulting in a decrease in the water and oxygen barrier performance and affecting the reliability of device packaging.

[0028] In view of this, an embodiment of the present application provides a composite substrate 100. Please refer to Figure 1 and 2 , the composite substrate 100 includes a stacked flexible layer 10 and a composite layer 20. The composite layer 20 includes a planarization layer 21 and a curling unit 22. The curling unit 22 includes a base film 222 and a sub-film 221. The base film 222 is in contact with the planarization layer 21. The sub-film 221 is coated in the planarization layer 21, and the sub-film 221 is connected to the base film 222. The plane where the sub-film 221 is located intersects with the plane where the base film 222 is located to form an included angle.

[0029] Wherein, the included angle refers to the included angle α formed between the plane where the base film 222 is located and the plane where the sub-film 221 is located. The included angle α is greater than 0° and less than 180°. That is, there is an intersection line between the planes where the sub-film 221 and the base film 222 are located, and the two are not parallel or overlapping with each other.

[0030] It can be understood that due to differences in the manufacturing process, equipment, etc. of the curling unit 22, there may be some slight bending or deformation of the base film 222 and the sub-film 221, but the main bodies of the base film 222 and the sub-film 221 are still located in the plane. At this time, the plane where the main body of the sub-film 221 is located intersects with the plane where the main body of the base film 222 is located to form an included angle.

[0031] In the technical solution provided by this application, the base film 222 and the sub-film 221 of the curling unit 22 intersect to form a curling structure. The curling unit 22 has the property of thermally induced deformation and can undergo minute deformation under temperature stimulation. Moreover, the elastic moduli of the regions on the curling unit 22 are different, resulting in gradient internal stress. At high temperatures, the surface stress of the rigid substrate 40 and the flexible layer 10 increases. This surface stress is transmitted to the curling unit 22 deposited on the surface of the flexible layer 10. The curling unit 22 absorbs and releases the surface stress through deformation, thereby effectively reducing the degree of deformation of the rigid substrate 40 and the flexible layer 10, avoiding warping of the composite substrate 100 during subsequent high-temperature processes, facilitating the smooth progress of subsequent processes, and at the same time preventing cracks from occurring in the substrate due to warping, which would affect the water and oxygen barrier properties and the device packaging effect.

[0032] The curling unit 22 has various implementation forms. Please refer to Figure 1 , in some embodiments, the sub-film 221 is coated within the planarization layer 21, the base film 222 is coated inside the planarization layer 21, and the entire curling unit 22 is coated within the planarization layer 21. Please refer to Figure 2 , in some other embodiments, the sub-film 221 is coated within the planarization layer 21, the base film 222 is embedded on the side of the planarization layer 21 facing the flexible layer 10. Define the surface of the flexible layer 10 facing the planarization layer 21 as the first surface 1, and the surface of the planarization layer 21 facing the flexible layer 10 as the second surface 2. The base film 222 is exposed on the second surface 2, and the exposed part contacts the first surface 1. The base film 222 is in direct contact with the flexible layer 10, and the stress of the flexible layer 10 can be more effectively transmitted to the curling unit 22, thereby releasing stress.

[0033] As Figure 1 shown, taking the first surface 1 as the reference plane, in some embodiments, the plane where the base film 222 is located is parallel to the reference plane, which is convenient for preparation.

[0034] In some embodiments, the angle α is greater than or equal to 20° and less than or equal to 160°; for example, it can be 30° to 150°, 40° to 140°, 45° to 135°, 50° to 130°, 60° to 120°, 70° to 110°, 75° to 105°, 80° to 100°, 85° to 95°, 88° to 92°, 30° to 50°, 40° to 60°, 50° to 80°, 70° to 100°, 80° to 120°, 89° to 125°, 90° to 130°, 91° to 140°, 92° to 150°, 100° to 160°, etc. Controlling the angle within this range helps to improve the effect of stress release. Furthermore, in some embodiments, the angle α is greater than or equal to 45° and less than or equal to 135°; further, the angle α is 90°. When the angle α is equal to or close to 90°, the sub-film 221 is longer in the thickness direction of the planarization layer 21, which is more conducive to transmitting the stress to the side of the planarization layer 21 away from the flexible layer 10, and the stress release effect will be better.

[0035] In some embodiments, the base film 222 has a thickness of 30 nm to 4000 nm; for example, it can be 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 150 nm, 200 nm, 300 nm, 500 nm, 1000 nm, 2000 nm, 3000 nm, 4000 nm, and values ​​between any two of the above values. It is understood that the thickness described herein refers to the average thickness of the film layer.

[0036] In some embodiments, the thickness of the sub-membrane 221 is 30nm to 4000nm; for example, it can be 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm, 150nm, 200nm, 300nm, 500nm, 1000nm, 2000nm, 3000nm, 4000nm and a value between any two of the above values.

[0037] In some embodiments, the thickness of the base film 222 is equal to the thickness of the sub-film 221 , which helps to reduce the difficulty of preparing the curling unit 22 .

[0038] In some embodiments, the curling unit 22 includes one sub-membrane 221. In other embodiments, the curling unit 22 includes a plurality of sub-membranes 221, which can better release stress.

[0039] In some specific embodiments, the curling unit 22 is composed of a base film 222 and a plurality of sub-films 221. A plurality of openings are distributed on the base film 222. The plurality of sub-films 221 are arranged in one-to-one correspondence with the plurality of openings, and one edge of the sub-film 221 is connected to one edge of the corresponding opening. Specifically, referring to Figure 6 , as can be seen from the figure, in the actual processing process, after the solid film 3 is cut and treated with the treatment liquid, the unit area 5 warps to form the sub-film 221, and the part of the solid film 3 other than the unit area 5 constitutes the base film 222. Since the sub-film 221 warps, the position corresponding to the unit area 5 in the base film 222 forms an opening.

[0040] In some embodiments, the shape of the sub-film 221 is the same as the shape of the opening. This design is easy to manufacture and saves raw materials. In some embodiments, the sub-film 221 can be triangular, square, hexagonal or other polygonal shapes.

[0041] In some embodiments, the shapes and sizes of the plurality of sub-films 221 are the same, so that the stress can be evenly released at each sub-film 221.

[0042] In some embodiments, the curling unit 22 includes a plurality of sub-films 221, and the plurality of sub-films 221 are arranged in an array, for example, they can be arranged in a matrix distribution, a linear array distribution, a circular array distribution or a concentric ring array distribution, etc. The plurality of sub-films 221 are evenly distributed, so that the stress in each region can be evenly released. In some other embodiments, the plurality of sub-films 221 are arranged in a matrix distribution.

[0043] In some embodiments, the ratio of the number of the sub-films 221 to the area of the reference plane ranges from 5 to 300 pieces / μm 2 ; for example, it can be 5 pieces / μm 2 , 6 pieces / μm 2 , 10 pieces / μm 2 , 20 pieces / μm 2 , 30 pieces / μm 2 , 40 pieces / μm 2 , 50 pieces / μm 2 , 100 pieces / μm 2 , 150 pieces / μm 2 , 200 pieces / μm 2 , 300 pieces / μm 2 and the values between any two of the above. Controlling the distribution density of the sub-films 221 within the above range can maximize the stress release effect.

[0044] In some embodiments, the edge where the sub-membrane is connected to the base membrane is defined as the first edge. The sub-membrane 221 has a maximum dimension length in a first direction, which is a direction perpendicular to the first edge. The maximum dimension length is defined as L2, and the distance between two adjacent first edges is defined as L1. The numerical relationship between L2 and L1 satisfies: L2 / (L1 - L2) is greater than or equal to 0.1. It can be understood that the difference between L2 and L1 is equivalent to the distance between two adjacent openings. Based on this, in some other embodiments, taking the sub-membrane 221 as a square as an example, as Figure 6 shown, the maximum dimension length is defined as L2, and the distance between two adjacent openings is defined as L3; L3 = L1 - L2, and the numerical relationship between L2 and L3 satisfies: the ratio of L2 to L3 is greater than or equal to 0.1, which helps to improve the stress release effect.

[0045] In some embodiments, the ratio of L2 to (L1 - L2) is greater than or equal to 0.1 and less than or equal to 4, that is, the ratio can be 0.1, 0.2, 0.5, 1, 2, 3, 4, and values between any two of the above. Controlling the ratio within this range not only helps to improve the stress release effect but also helps to reduce the manufacturing difficulty of the curling unit 22.

[0046] In some embodiments, the material of the curling unit 22 can be any common material with appropriate flexibility, easy to be prepared into a dense film, and easy to be peeled off by a treatment liquid; for example, the material of the curling unit 22 can include but is not limited to one or more of metals, metal oxides, and metal nitrides. The metals can include but are not limited to one or more of Ti, Cr, Pt, Au, Al, and V. It can be understood that when multiple metals are used, it can be an alloy material of multiple metals, such as TiAlV; the metal oxides can include but are not limited to VO 2 、Fe 2 O 3 、SiO 2 、TiO 2 and one or more of them; the metal nitrides can include but are not limited to one or more of TiN and AlN. Using the above materials can effectively prepare the curling unit 22 to achieve the stress release effect.

[0047] In some embodiments, the material of the curling unit 22 includes VO 2 . Vanadium dioxide (VO 2) is a kind of thermochromic material that undergoes a reversible phase change under temperature variation to regulate the infrared transmittance. By utilizing the characteristic that the infrared transmittance of vanadium dioxide significantly decreases at high temperatures, the influence of temperature on the glass substrate during the high-temperature process of the flexible layer 10 or the composite substrate 100 can be effectively reduced, thereby reducing substrate warping. In addition, this material itself has the characteristic of thermally induced deformation, and the curling degree of the curling unit 22 can be increased under high-temperature stimulation, improving the stress release effect.

[0048] In some embodiments, the material of the flexible layer 10 includes one or more of polyimide (PI), polyethylene naphthalate (PEN), polyethylene terephthalate (PET), and phosphoenolpyruvate (PEP). In some embodiments, the thickness of the flexible layer 10 is 0.001 - 2 mm; for example, it can be 0.001 mm, 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, and values between any two of the above.

[0049] In some embodiments, the material of the planarization layer 21 includes one or more of epoxy resin, phenolic resin, urea-formaldehyde resin, and polymethyl methacrylate. In some embodiments, the thickness of the composite layer 20 is 0.0001 - 2 mm; for example, it can be 0.0001 mm, 0.0005 mm, 0.001 mm, 0.005 mm, 0.01 mm, 0.05 mm, 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, and values between any two of the above.

[0050] Please refer to Figure 3 , in some embodiments, the composite substrate 100 further includes an inorganic barrier layer 30 disposed on the side of the composite layer 20 away from the flexible layer 10. The material of the inorganic barrier layer 30 includes at least one of inorganic oxides and inorganic nitrides. Among them, the inorganic oxides are selected from one or more of silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, hafnium oxide, and tantalum oxide, and the inorganic nitrides are selected from one or more of aluminum nitride, boron nitride, titanium nitride, and silicon nitride. In some embodiments, the thickness of the inorganic barrier layer 30 is 0.01 - 100 μm; for example, it can be 0.01 μm, 0.05 μm, 1 μm, 2 μm, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, and values between any two of the above.

[0051] In some embodiments, the composite substrate 100 further includes a rigid substrate 40, and the material of the rigid substrate 40 includes glass, silicon wafer, polycarbonate, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, polyamide, polyethersulfone, or a combination thereof. The rigid substrate 40 is disposed on a side of the flexible layer 10 away from the composite layer 20 and serves as a substrate for preparing film layers such as the flexible layer 10 and the composite layer 20.

[0052] The present application also provides a method for preparing a composite substrate 100, and the preparation method includes the following steps:

[0053] S10, providing a prefabricated substrate, where the prefabricated substrate includes a flexible layer 10;

[0054] S20, preparing a composite layer 20 on one side of the flexible layer 10, where the composite layer 20 includes a planarization layer 21 and a curling unit 22;

[0055] Wherein, the curling unit 22 includes a base film 222 and a sub-film 221, the base film 222 is in contact with the planarization layer 21, the sub-film 221 is coated in the planarization layer 21, and one edge of the sub-film 221 is connected to the base film 222, and a plane where the sub-film 221 is located intersects with a plane where the base film 222 is located to form an included angle.

[0056] Based on the above preparation method, a composite substrate 100 that is not easily warped can be obtained. The composite substrate 100 includes a stacked flexible layer 10 and a composite layer 20. The composite layer 20 includes a planarization layer 21 and a curling unit 22. The curling unit 22 includes a base film 222 and a sub-film 221. The base film 222 is in contact with the planarization layer 21. The sub-film 221 is coated in the planarization layer 21, and one edge of the sub-film 221 is connected to the base film 222; a plane where the sub-film 221 is located intersects with a plane where the base film 222 is located to form an included angle.

[0057] Specifically, in step S10, the material of the flexible layer 10 is as described above and will not be elaborated here. In some embodiments, the composite substrate 100 further includes a rigid substrate 40. Correspondingly, the material of the flexible layer 10 can be provided on the rigid substrate 40 to prepare the flexible layer 10. In some embodiments, the preparation of the flexible layer 10 includes: coating the material of the flexible layer 10 on the rigid substrate 40, heating to 300-400 °C, and then cooling and curing to form the flexible layer 10. Among them, the temperature increase process can adopt programmed temperature increase, and the total temperature increase duration is 0.5-5 h; the temperature decrease process can also adopt programmed temperature decrease, and the total temperature decrease duration is 1-10 h.

[0058] Please refer to Figure 4In some embodiments, the curling unit 22 is partially coated in the planarization layer 21: the sub-film 221 is coated in the planarization layer 21, and the base film 222 connected to one edge of the sub-film 221 is embedded in the side of the planarization layer 21 facing the flexible layer 10. Accordingly, in this embodiment, step S20 can be implemented by the following steps:

[0059] S21a, using a curling unit 22 material, preparing a curling unit 22 on one side of the flexible layer 10, wherein the curling unit 22 includes a base film 222 and a sub-film 221, wherein the base film 222 is formed on one side of the flexible layer 10, an edge of the sub-film 221 is connected to the base film 222, and a plane where the sub-film 221 is located intersects with a plane where the base film 222 is located to form an angle;

[0060] S22a, providing a planarization layer 21 material, depositing the planarization layer 21 material on the curling unit 22, the planarization layer 21 material covers the sub-film 221 to form a planarization layer 21, and the planarization layer 21 and the curling unit 22 together constitute the composite layer 20.

[0061] See also Figure 5 In some other embodiments, the curling units 22 are all located inside the planarization layer 21. Accordingly, in this embodiment, step S20 can be implemented by the following steps:

[0062] S21b, using a first planarization layer 21 material to prepare a first planarization layer 21 on one side of the flexible layer 10;

[0063] S22b, using a curling unit 22 material, preparing a curling unit 22 on a side of the first planarizing layer 21 away from the flexible layer 10, wherein the curling unit 22 includes a base film 222 and a sub-film 221, wherein the base film 222 is formed on one side of the flexible layer 10, an edge of the sub-film 221 is connected to the base film 222, and a plane where the sub-film 221 is located intersects with a plane where the base film 222 is located to form an angle;

[0064] S23b, providing a second planarization layer 21 material, depositing the second planarization layer 21 material on the curling unit 22, the second planarization layer 21 material covers the sub-membrane 221 to form a second planarization layer 21, the first planarization layer 21 and the second planarization layer 21 together constitute a planarization layer, and the planarization layer and the curling unit 22 formed inside the planarization layer 21 together constitute the composite layer 20.

[0065] Furthermore, the above steps S20, S21a and S22b all include the step of preparing the curling unit 22 using the curling unit 22 material. Figure 6, in some embodiments, the preparation of the curling unit 22 includes:

[0066] S1. Provide the material of the curling unit 22, deposit the material of the curling unit 22 to form a solid-state film 3, the solid-state film 3 is composed of a main body region 4 and a unit region 5, and the unit region 5 is enclosed by a first edge 6 and a second edge 7;

[0067] S2. Perform a cutting process on the solid-state film 3 along the second edge 7, the second edge 7 of the unit region 5 is separated from the main body region 4, and the unit region 5 is connected to the main body region 4 through the first edge 6;

[0068] S3. Contact the processed solid-state film 3 with a processing liquid, the unit region 5 warps to form a sub-film 221, the main body region 4 forms a base film 222, and the base film 222 and the sub-film 221 together constitute the curling unit 22;

[0069] Wherein, the material of the curling unit 22 includes one or more of metals, metal oxides, and metal nitrides. The metal includes one or more of Ti, Cr, Pt, Au, Al, and V. The metal oxide is selected from VO 2 、Fe 2 O 3 、SiO 2 、TiO 2 and one or more of them, and the metal nitride is selected from one or more of TiN and AlN.

[0070] In S1, the solid-state film 3 can be prepared by physical vapor deposition method or chemical vapor deposition method. For example, the material of the curling unit 22 can be deposited by vacuum evaporation method, atomic force deposition method or chemical vapor deposition to prepare a dense solid-state film 3.

[0071] It can be understood that in step S2, when performing the cutting process, a cutting tool is used to cut along the second edge 7 so that the second edge 7 of the unit region 5 is disconnected from the main body region 4, but the first edge 6 of the unit region 5 remains connected to the main body region 4. In actual preparation, by controlling the size of the unit region 5 and the interval between adjacent unit regions 5, L1 and L2 can be adjusted; by adjusting L1 and L2, when the unit region 5 is separated from the main body region 4 and warps to form the sub-film 221, the curling degree of each sub-film 221 is controllable, avoiding excessive curling and affecting the preparation of the planarization layer 21 and the stress release effect.

[0072] Among them, the solution specific surface energy (or solution surface tension) of the treatment liquid is 10-100 mN / m. In some embodiments, the treatment liquid includes one or more of water, ethanol, methanol, N,N-dimethylacetamide, tetrahydrofuran, and isopropanol; specifically, the solution specific surface energies of the above solvents at 20 °C are: water 71.8 mN / m, ethanol 22.3 mN / m, methanol 22.6 mN / m, N,N-dimethylacetamide 48.5 mN / m, tetrahydrofuran 26.4 mN / m, and isopropanol 21.7 mN / m.

[0073] In S3, soak the solid film 3 with a special treatment liquid or spin-coat it on the solid film 3, and the unit area 5 will self-peel and self-curl, and thus the sub-film 221 can be formed.

[0074] In some embodiments, the contact time between the treatment liquid and the divided solid film 3 is 0.1-30 min; for example, it can be 0.1 min, 0.2 min, 0.5 min, 1 min, 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, and values between any two of the above; the solid film 3 is in full contact with the treatment liquid, so as to promote the self-peeling and self-curling of the unit area 5.

[0075] During actual preparation, the step of contacting the treatment liquid with the divided solid film 3 can be realized in the following ways: soak the solid film 3 obtained by cutting in S2 in the treatment liquid, take it out after standing for a period of time; or, coat the treatment liquid on the solid film 3 obtained by cutting, and wash it clean after standing for a period of time.

[0076] In some embodiments, when the treatment liquid is in contact with the divided solid film 3, the temperature of the treatment liquid is 0 °C-100 °C; for example, it can be 0 °C, 5 °C, 8 °C, 10 °C, 15 °C, 20 °C, 25 °C, 30 °C, 35 °C, 40 °C, 45 °C, 50 °C, 55 °C, 60 °C, 62 °C, 65 °C, 70 °C, 80 °C, 90 °C, 100 °C, and values between any two of the above; controlling the temperature within this range can promote the treatment effect and promote the self-peeling and self-curling of the unit area 5. In some embodiments, the temperature is 10-60 °C.

[0077] During actual preparation, the included angle α can be adjusted by controlling the type of treatment liquid, treatment time, and treatment temperature.

[0078] It can be understood that the preparation methods of the respective film layers in the composite substrate 100 provided in the present application, including the planarization layer 21, the flexible layer 10, and the inorganic barrier layer 30, can be realized by conventional techniques in the art, such as chemical methods or physical methods. Among them, the chemical methods include chemical vapor deposition, sequential ionic layer adsorption and reaction, anodic oxidation, electrodeposition, and coprecipitation. The physical methods include physical coating methods and solution methods. Among them, the physical coating methods include: thermal evaporation coating, electron beam evaporation coating, magnetron sputtering, multi-arc ion coating, physical vapor deposition, atomic layer deposition, pulsed laser deposition, etc.; the solution method can be spin coating, printing, inkjet printing, blade coating, printing, dip coating, immersion, spraying, roll coating, casting, slot die coating, and bar coating, etc.

[0079] It can be understood that the light-emitting device 100 may further include a packaging layer (not shown in the figure) to isolate water and oxygen (for example, to make the concentrations of oxygen and water lower than 0.1 ppm), thereby improving the performance stability of the device. Specifically, the packaging material used to form the packaging layer can be selected from at least one of UV glue, metal thin film, and glass glue. In a specific embodiment, the packaging material can be acrylic resin or epoxy resin.

[0080] The present application also relates to a display device 200, as Figure 7 shown, the display device 200 includes the composite substrate 100 provided in the present application and a display panel 201 disposed on one side of the composite substrate 100. The composite substrate 100 includes the composite substrate 100 described above, or the composite substrate 100 prepared by the preparation method described above. In some embodiments, the display panel 201 includes a TFT layer, a light-emitting unit layer, a packaging layer, a touch screen layer, an optical glue layer, and a cover plate layer stacked in sequence. The display device 200 can be any electronic product with a display function. The electronic products include but are not limited to smartphones, tablet computers, laptop computers, digital cameras, digital video cameras, smart wearable devices, smart weighing electronic scales, in-vehicle displays, televisions, or e-book readers. Among them, the smart wearable devices can be, for example, smart bracelets, smart watches, virtual reality (VR) helmets, etc. The display device 200 prepared by using the above composite substrate 100 has a high qualification rate, good packaging effect, long service life, and good device performance stability.

[0081] The present application will be specifically described below through specific embodiments. The following embodiments are only partial embodiments of the present application and do not limit the present application. The raw materials used in the following embodiments are all commercially available products unless otherwise specified.

[0082] Example 1

[0083] (1) Provide a glass substrate, coat PI (liquid) on the glass substrate, heat the glass substrate, raise the temperature to 350 °C, with a heating time of 2 h, keep the temperature for 2 h, and then cool it to room temperature within 5 h to obtain a flexible layer with a thickness of 1 mm by curing.

[0084] (2) Put the film prepared in step (1) into a vacuum coating machine, and pump the vacuum to 5×10 -7 mbar, turn on the VO 2 target, and evaporate for 5000 s at a rate to obtain a solid film with a thickness of 500 nm; then cut out a plurality of crack patterns distributed in a matrix on the solid film by stamping to divide the solid film into a base film and a plurality of square sub-films distributed in a matrix. One edge of each sub-film is connected to the base film, and the other three edges are disconnected from the base film. L3 = L1 - L2, and the ratio of L2 to L3 is 1. Then immerse the film in an ethanol solvent at a temperature of 25 °C. After 10 min of immersion, the sub-film separates from the flexible layer and warps up to obtain a curling unit, and the included angle α between the base film and the sub-film is 90°.

[0085] (3) Take an epoxy resin solution and coat it on the curling unit so that the epoxy resin solution fully covers the curling unit and the flexible layer to form a planarization layer with a thickness of 0.5 mm. The curling unit is embedded in the planarization layer, and the base film is exposed on the lower side of the planarization layer and contacts the flexible layer. The curling unit and the planarization layer together form a composite layer.

[0086] (4) Deposit alumina on the planarization layer by atomic layer deposition technology (ALD) to form an inorganic barrier layer with a thickness of 50 μm to obtain a composite substrate.

[0087] Example 2

[0088] This example is basically the same as Example 1, except that in this example, the ratio of L2 to L3 is 0.1.

[0089] Example 3

[0090] This example is basically the same as Example 1, except that in this example, the ratio of L2 to L3 is 4.

[0091] Example 4

[0092] This example is basically the same as Example 1, except that in this example, the ratio of L2 to L3 is 0.06.

[0093] Example 5

[0094] This example is basically the same as Example 1, except that in this example, the included angle α between the base film and the sub-film is 80°.

[0095] Example 6

[0096] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the included angle α between the base film and the sub-film is 20°.

[0097] Embodiment 7

[0098] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the included angle α between the base film and the sub-film is 160°.

[0099] Embodiment 8

[0100] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the included angle α between the base film and the sub-film is 10°.

[0101] Embodiment 9

[0102] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the treatment liquid is changed from an ethanol solvent to N,N-dimethylacetamide.

[0103] Embodiment 10

[0104] This embodiment is basically the same as Embodiment 1, except that in this embodiment, a plurality of curling units are arranged in the planarization layer. Correspondingly, in the preparation method, steps (2) and (3) are modified as follows:

[0105] (2) Take an epoxy resin solution and coat it on the flexible layer to form a first planarization layer with a thickness of 0.1 mm; then, according to the steps of preparing the curling units in step (2) of Embodiment 1, prepare a plurality of curling units on the first planarization layer.

[0106] (3) Take an epoxy resin solution and coat it on the curling units so that the epoxy resin solution fully covers the curling units and the first planarization layer, forming a second planarization layer with a thickness of 0.4 mm. The first and second planarization layers together constitute the planarization layer, and the curling units are arranged inside the planarization layer. The curling units and the planarization layer together constitute a composite layer.

[0107] Embodiment 11

[0108] This embodiment is basically the same as Embodiment 1, except that in this embodiment, the material of the curling units is changed to TiO 2 ; correspondingly, in step (2), VO 2 is changed to TiO 2 .

[0109] Comparative Example 1

[0110] This comparative example is basically the same as Example 1, except that in this comparative example, the composite substrate does not have a composite layer. Correspondingly, in the preparation method, step (2) is omitted, and a planarization layer and an inorganic barrier layer are directly prepared on the flexible layer.

[0111] Comparative Example 2

[0112] This comparative example is basically the same as Example 1, except that in this comparative example, in the composite layer, the included angle α between the base film and the sub-film is 180°, that is, no curling treatment is performed on the VO 2 solid film; correspondingly, step (2) is changed to: putting the film made in step (1) into a vacuum coating machine, and pumping the vacuum to 5×10 -7 mbar, turning on the VO 2 target, and evaporating at a rate of for 5000 s to obtain a solid film with a thickness of 500 nm. The planarization layer is directly prepared on the solid film in step (3).

[0113] Experimental Example

[0114] (1) Detect the anti-deformation performance of the composite substrates of Examples 1 to 12 and Comparative Examples 1-3, including the stress of the flexible substrate film layer and the anti-bending life test of the flexible display device. The results are shown in Table 1. Among them:

[0115] The test process of the stress of the flexible substrate film layer is as follows: completely attach the resistive strain sensor to the upper surface of the flexible substrate, measure the resistance change when the substrate is bent by 180°. The greater the resistance change, the greater the stress of the flexible substrate film layer;

[0116] The test process of the anti-bending life is as follows: prepare a display panel on the composite substrate to make a display, and then use the device fatigue bending life test equipment to test the anti-bending life of the display. Among them, the parameters of the equipment are set as the bending angle of 180°, the test speed of 20 times / min, and observe whether the display is normal after testing 100,000 times.

[0117] Table 1

[0118] Change in resistance / Ω Display effect of the display Example 1 82 The display at the bent part is normal Example 2 102 The display at the bent part is normal Example 3 59 The display at the bent part is normal Example 4 136 The display at the bent part is normal Example 5 90 The display at the bent part is normal Example 6 156 The display at the bent part is normal Example 7 155 The display at the bent part is normal Example 8 175 Tiny cracks at the bent part Example 9 85 The display at the bent part is normal Example 10 87 The display at the bent part is normal Example 11 91 The display at the bent part is normal Comparative Example 1 275 Obvious cracks at the bent part Comparative Example 2 255 Obvious cracks at the bent part

[0119] It can be seen from the above table that:

[0120] Comparative Examples 1 and 2 exhibited extremely high resistance change amounts when bent by 180°, and obvious cracks appeared after 100,000 times of device fatigue bending life tests; on the contrary, each of the examples not only had a relatively low resistance change amount, but also showed relatively good conditions after fatigue bending tests, indicating that setting the curling unit inside the planarization layer or on the side facing the flexible layer helps to release stress; further, the resistance change amount of Example 1 was lower than that of Example 11, indicating that embedding the curling unit on the side of the planarization layer facing the flexible layer and having the curling unit in direct contact with the flexible layer is more conducive to releasing stress.

[0121] The technical solutions provided by the embodiments of the present application have been introduced in detail above. Specific examples are used in this article to elaborate on the principle and implementation manner of the present application. The description of the above embodiments is only used to help understand the method and its core idea of the present application; at the same time, for those skilled in the art, according to the idea of the present application, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present application.

Claims

1. A composite substrate, characterized in that, it includes a stacked flexible layer and a composite layer, the composite layer includes a planarization layer and a curling unit, the curling unit includes a base film and a sub-film, the base film is in contact with the planarization layer, the sub-film is coated within the planarization layer, and the sub-film is connected to the base film; the plane of the sub-film intersects with the plane of the base film to form an included angle.

2. The composite substrate according to claim 1, characterized in that, the base film is embedded on the side of the planarization layer facing the flexible layer; or, the base film is coated inside the planarization layer.

3. The composite substrate according to claim 1, characterized in that, the included angle is greater than or equal to 20° and less than or equal to 160°; and / or, the plane of the base film is parallel to the first surface of the flexible layer facing the planarization layer; and / or, the thickness of the base film is 30nm - 4000nm; and / or, the thickness of the sub-film is 30nm - 4000nm; and / or, the thickness of the base film is equal to the thickness of the sub-film.

4. The composite substrate according to claim 1, characterized in that, the curling unit includes one sub-film; or, the curling unit includes multiple sub-films.

5. The composite substrate according to claim 4, characterized in that, the curling unit includes multiple sub-films, and the multiple sub-films are arranged in an array; and / or, Taking the first surface of the flexible layer facing the flat layer as the reference surface, the ratio range of the number of the sub-films to the area of the reference surface is 5 to 300 pieces / μm 2 ; and / or, defining the edge where the sub-film is connected to the base film as the first edge, the sub-film has a maximum dimension length in the first direction, the first direction is the direction perpendicular to the first edge, the maximum dimension length is defined as L2, and the distance between adjacent two first edges is defined as L1, and the numerical relationship between L2 and L1 satisfies: L2 / (L1 - L2) is greater than or equal to 0.

1.

6. The composite substrate according to claim 4 or 5, characterized in that, the base film has at least one opening, the sub-film and the opening are arranged in one-to-one correspondence, and one edge of the sub-film is connected to one edge of the corresponding opening.

7. The composite substrate according to claim 1, characterized in that, The material of the curling unit includes one or more of metals, metal oxides, and metal nitrides. The metals include one or more of Ti, Cr, Pt, Au, Al, and V. The metal oxides are selected from one or more of VO 2 , Fe 2 O 3 , SiO 2 , TiO 2 ; and / or, the material of the flexible layer includes one or more of polyimide, polyethylene naphthalate, polyethylene terephthalate, and phosphoenolpyruvate; and / or, the material of the planarization layer includes one or more of epoxy resin, phenolic resin, urea-formaldehyde resin, and polymethyl methacrylate; and / or, the composite substrate further includes an inorganic barrier layer provided on the side of the composite layer away from the flexible layer, and the material of the inorganic barrier layer includes at least one of inorganic oxides and inorganic nitrides, wherein, the inorganic oxides are selected from one or more of silicon oxide, aluminum oxide, titanium oxide, zirconium oxide, hafnium oxide, and tantalum oxide, and the inorganic nitrides are selected from one or more of aluminum nitride, boron nitride, titanium nitride, and silicon nitride.

8. The composite substrate according to claim 7, characterized in that, the thickness of the flexible layer is 0.001 - 2mm; and / or, the thickness of the composite layer is 0.0001 - 2mm; and / or, the thickness of the inorganic barrier layer is 0.01 - 100μm.

9. A method for preparing a composite substrate, characterized in that, it comprises the following steps: providing a prefabricated substrate, the prefabricated substrate comprising a flexible layer; preparing a composite layer on one side of the flexible layer, the composite layer comprising a planarization layer and a curling unit; wherein, the curling unit comprises a base film and a sub-film, the base film is in contact with the planarization layer, the sub-film is coated within the planarization layer, and one edge of the sub-film is connected to the base film, and the plane of the sub-film intersects with the plane of the base film to form an angle.

10. The preparation method according to claim 9, characterized in that, the step of preparing a composite layer on one side of the flexible layer, the composite layer comprising a planarization layer and a curling unit comprises: using a curling unit material to prepare a curling unit on one side of the flexible layer, the curling unit comprising a base film and a sub-film, the base film is formed on one side of the flexible layer, one edge of the sub-film is connected to the base film, and the plane of the sub-film intersects with the plane of the base film to form an angle; providing a planarization layer material, depositing the planarization layer material on the curling unit, the planarization layer material coating the sub-film to form a planarization layer, and the planarization layer and the curling unit together constitute the composite layer; or, using a first planarization layer material to prepare a first planarization layer on one side of the flexible layer; using a curling unit material to prepare a curling unit on the side of the first planarization layer away from the flexible layer, the curling unit comprising a base film and a sub-film, the base film is formed on one side of the flexible layer, one edge of the sub-film is connected to the base film, and the plane of the sub-film intersects with the plane of the base film to form an angle; providing a second planarization layer material, depositing the second planarization layer material on the curling unit to form a second planarization layer, the second planarization layer material coating the sub-film, the first planarization layer and the second planarization layer together constitute a flat layer, and the flat layer and the curling unit formed within the planarization layer together constitute the composite layer.

11. The preparation method according to claim 10, characterized in that, the preparation of the curling unit comprises: providing a curling unit material, depositing the curling unit material to form a solid film, defining that the solid film has a main region and a unit region, the unit region is enclosed by a first edge and a second edge; performing a cutting process on the solid film along the second edge, the second edge of the unit region is separated from the main region, and the unit region is connected to the main region through the first edge; bringing a treatment liquid into contact with the solid film after the cutting process, the unit region bends away from the flexible layer along the first edge to form a sub-film, and the main region forms a base film, and the base film and the sub-film together constitute the curling unit; wherein, the surface energy of the solution of the treatment liquid is 10 - 100 mN / m.

12. The preparation method according to claim 11, characterized in that, The material of the curling unit includes one or more of metal, metal oxide, and metal nitride. The metal includes one or more of Ti, Cr, Pt, Au, Al, and V. The metal oxide is selected from one or more of VO 2 , Fe 2 O 3 , SiO 2 , TiO 2 ; and / or the treatment liquid comprises one or more of water, ethanol, methanol, N,N-dimethylacetamide, tetrahydrofuran, isopropanol; and / or, The time for the treatment liquid to contact the divided solid film is 0.1 to 30 minutes; and / or, When the treatment liquid contacts the divided solid film, the temperature of the treatment liquid is 0°C to 100°C; and / or, In the step of depositing the coiled unit material to form the solid film, the physical vapor deposition method or the chemical vapor deposition method is used to prepare the solid film.

13. A display device, Characterized in that, It includes a composite substrate and a display panel disposed on one side of the composite substrate. The composite substrate includes the composite substrate according to any one of claims 1 to 8, or the composite substrate prepared by the preparation method according to any one of claims 9 to 12.

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