Drill-free composite foldable electronic display flexible substrate and method of manufacture

Abstract

The application provides a punch-free composite foldable electronic screen flexible substrate and a manufacturing method, which comprises an integrally formed fiber-reinforced composite rigid support section and a composite flexible foldable section; the integrally formed fiber-reinforced composite rigid support section is composed of a multi-directional fiber layering composite laminate plate, the fiber orientation of which is customized and selected according to the rigidity design requirement; the composite flexible foldable section is formed by three-dimensional variable-thickness woven cloth through resin impregnation and curing, the thickness distribution of which is customized and designed according to the target bending shape, and part of the fiber layer of the integrally formed fiber-reinforced composite rigid support section is embedded. The flexible substrate is manufactured through the integrated fiber preform weaving, gradient resin impregnation and mold curing process, breaks through the traditional hinge connection mode, realizes the seamless connection of the rigid and flexible sections, and eliminates the mechanical punching process, effectively avoiding defects such as stress concentration and fatigue cracks.

Description

Technical Field

[0001] This invention relates to the field of composite material structure design and manufacturing, specifically to a perforation-free composite material foldable electronic screen flexible substrate and its manufacturing method. Background Technology

[0002] Traditional foldable screen flexible substrates mostly use hinge-type mechanical connections or perforated designs, which have the following drawbacks:

[0003] 1. Stress concentration: Mechanical hinges generate local stress concentration when folding, leading to material fatigue failure, and the folding life is usually less than 100,000 cycles;

[0004] 2. Thickness limitation: The drilling process weakens the structural strength of the substrate, making it impossible to achieve an ultra-thin design (thickness > 0.5mm);

[0005] 3. Stiffness is not adjustable: The stiffness-flexibility transition zone of existing composite substrates is mostly designed with abrupt changes, which cannot adapt to the customized needs of different screen sizes.

[0006] Therefore, foldable electronic screens urgently need an integrated composite flexible substrate that is punch-free and customizable, while meeting the requirements of ultra-thin bending and long lifespan.

[0007] Patent application CN115416388A discloses a composite structure including a substrate layer and a functional layer disposed on at least one surface of the substrate layer. The substrate layer includes a first support member and a second support member arranged side by side, and a bendable connector disposed between and connected to the first and second support members. The first and second support members are made of rigid fiber composite material. The functional layer includes one or more of a conductive layer, a thermally conductive layer, and an impact-resistant layer. However, this patent cannot completely solve the existing technical problems, nor can it meet the needs of this invention. Summary of the Invention

[0008] To address the shortcomings of existing technologies, the purpose of this invention is to provide a flexible foldable electronic screen substrate made of perforated composite material and its manufacturing method.

[0009] The flexible substrate for foldable electronic screens made of composite materials without the need for drilling, provided by the present invention, includes an integrally formed fiber-reinforced composite rigid support section and a composite flexible foldable section.

[0010] The integrally formed fiber-reinforced composite rigid support section is composed of a composite laminate with multi-directional fiber lay-up, and its fiber orientation is customized according to the stiffness design requirements; the composite flexible foldable section is formed by resin impregnation and curing of three-dimensional variable thickness woven fabric, and its thickness distribution is customized according to the target bending shape, and is partially embedded in the fiber layer of the integrally formed fiber-reinforced composite rigid support section.

[0011] Preferably, the number of layers and the angle of the integrally formed fiber-reinforced composite rigid support section are customized according to the stiffness design requirements;

[0012] For multilayer carbon fiber structures, the relationship between the number of layers, angles, and various stiffnesses is as follows:

[0013]

[0014] In the formula:

[0015]

[0016] Where, N x N y N z For in-plane forces; M x M y M z For bending moment; For in-plane strain; k x k y k xy The degree of bending deformation; A ij B ij D ij Indicates tensile stiffness, coupling stiffness, and bending stiffness; t k Represents the k-th layer

[0017] thickness; Represents the coordinates of the center of the k-th layer; N represents the number of layers.

[0018]

[0019] Where θ represents the ply angle; Q ij The stiffness coefficient is used; the equivalent bending stiffness of 2 GPa·mm is achieved by adjusting the ply angle and number. 3 ~100GPa·mm 3 It is adjustable within a certain range, with a thickness range of 0.01mm to 2mm.

[0020] Preferably, the thickness distribution and weaving angle of the flexible foldable section of the composite material are customized according to the target bending shape. The thinner the section, the greater the deformation curvature under the same load. When the multilayer carbon fibers have the same weaving angle, the larger the weaving angle, the greater the deformation curvature under the same load, and the thickness variation range is 0.01mm to 2mm.

[0021] Preferably, the integrally molded fiber-reinforced composite rigid support segment comprises one or more of the following fibers: carbon fiber, glass fiber, aramid fiber, and boron fiber.

[0022] Preferably, the three-dimensional variable thickness woven fabric of the flexible foldable section of the composite material is woven from one or more of the following materials: polyester fiber, nylon fiber, polypropylene fiber, spandex fiber and acrylic fiber.

[0023] Preferably, the minimum bending radius of the flexible foldable section of the composite material is 1.5 mm, and the delamination area of ​​the cross section is less than 5% after a preset number of folding tests.

[0024] Preferably, the thickness variation unit width of the composite flexible foldable variable thickness plate is 0.3 mm.

[0025] The manufacturing method of the flexible substrate for a foldable electronic screen made of non-drillable composite material provided by the present invention includes the following steps:

[0026] Step 1: Use a multi-axial braiding machine to weave an integrated fiber preform containing rigid and flexible sections, and achieve the thickness gradient change of the flexible section by dynamically adjusting the warp density and weft beat-up force;

[0027] Step 2: Place the preform in a vacuum impregnation device and inject epoxy resin, wherein the resin viscosity in the flexible section is 200 mPa·s to 500 mPa·s lower than that in the rigid section.

[0028] Step 3: Apply a pressure of 0.5MPa to 5MPa in the molding die and cure in three stages: 80℃ → 150℃ → 180℃, with a total curing time of 120min to 240min. Specifically, the curing time at 80℃ is 20min to 40min, the temperature rise time from 80℃ to 150℃ is 5min to 10min, the curing time at 150℃ is 60min to 120min, the temperature rise time from 150℃ to 180℃ is 5min to 10min, and the curing time at 180℃ is 30min to 60min.

[0029] Preferably, in step 1, electronic jacquard technology is used to control the weaving pattern, generating a rectangular cross-section weave with varying thickness that meets the design requirements in the flexible section area, with a single layer thickness difference of 0.02mm to 0.1mm.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] By integrating carbon fiber prepreg and knitted fabric, the problem of large stiffness gradient changes within a small size range was solved, and the overall substrate stiffness customization function was realized.

[0032] By integrating ultra-thin prepreg molding technology with knitted fabric weaving process, the technical problems of low machining accuracy and high difficulty under ultra-thin thickness were solved, realizing the ultra-thin design of the substrate and minimal thickness variation.

[0033] By using knitted fabric as the main load-bearing component in the deformation zone, and replacing the perforation design in traditional folding screens with the pores between the fabrics in the knitted fabric, the processing and molding steps are reduced while the fatigue life of the folding substrate is improved, achieving high durability. Attached Figure Description

[0034] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0035] Figure 1 This is a schematic diagram of the flexible substrate structure of the present invention;

[0036] Figure 2 This is a schematic diagram of the cross-sectional weave of the three-dimensional variable thickness woven fabric of the flexible segment of the flexible substrate of the present invention;

[0037] Figure 3 It is the coordinate system established by the design method of this invention;

[0038] Figure 4 This is the target deformed shape of the present invention;

[0039] Figure 5 This is a comparison between the structural deformation designed by the design method of this invention and the target deformation. Detailed Implementation

[0040] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0041] Example 1

[0042] This invention provides a foldable flexible substrate made of composite material that requires no drilling. Through an integrated structural design, mechanical connections are eliminated. Combined with three-dimensional variable thickness weaving and gradient curing processes, the following objectives are achieved:

[0043] 1. Large curvature bending: Minimum bending radius of the flexible section ≤ 1.5mm;

[0044] 2. High durability: Folding life ≥ 200,000 times;

[0045] 3. Customizable: The bending stiffness of the folded section can be designed as needed;

[0046] 4. Ultra-thin structure: minimum thickness ≤ 0.2mm.

[0047] Technical solution

[0048] I. Structural Design

[0049] 1) Structural and functional design, such as Figure 1 :

[0050] Rigid support section 1: It is composed of a composite laminate with multi-directional fiber lay-up, and the fiber orientation includes one or more of the following directions: 0°, ±45°, and 90°. The number of lay-up layers is determined according to the design requirements of the bending stiffness of the plate.

[0051] Flexible foldable segment 2: Made of three-dimensional variable-thickness woven fabric, resin impregnated and cured, and partially embedded in the fiber layer of rigid segment 1 to form a continuous interwoven structure, such as... Figure 2 .

[0052] 2) Structural Dimension Design

[0053] The geometric dimensions can be customized according to actual needs, and the overall structural bending stiffness meets the following requirements:

[0054] F(x)=E(x)I(x)

[0055] Where F(x) represents the structural bending stiffness distribution function, E(x) represents the structural Young's modulus distribution function, and I(x) represents the structural moment of inertia distribution function per unit length of cross section. The coordinate system for the design method is defined as follows: Figure 3 As shown. By coordinating and customizing the distribution functions of I(x) and E(x), the requirements for customized structural bending stiffness are achieved, ultimately meeting the functional requirements of rigid support segment 1 and flexible foldable segment 2.

[0056] 3) Structural material design:

[0057] Customized fibers: The rigid segment fibers are selected from one or more of carbon fiber, glass fiber, and aramid fiber; the flexible segment yarn is a blended yarn of polyester, nylon, spandex, etc. (blending ratio 1:1 to 1:5);

[0058] Performance parameters: after curing, the resin volume fraction is 35% to 60%, the bending radius is ≤1.5mm, and the interfacial delamination area after folding test is <5%.

[0059] 4) Structural manufacturing design:

[0060] 1. Fiber preform weaving

[0061] The integrated prefabricated body is woven using a multi-axial weaving machine (such as Libra 3D Weave Pro) and the warp density (1080N / m) is dynamically adjusted.

[0062] Electronic jacquard technology: Generates a rectangular cross-section weave with varying thickness in the flexible section, with a single layer thickness difference of 0.02 to 0.1 mm.

[0063] 2. Resin gradient impregnation

[0064] In the vacuum impregnation device, epoxy resin (such as Hexion EPON 862) is injected, and the viscosity of the resin in the flexible section is controlled to be 200-500 mPa·s lower than that in the rigid section.

[0065] Ultrasonic assistance: Apply 1040kHz ultrasonic vibration with an amplitude of 530μm to a region with a thickness ≤0.6mm, and extend the action time by 20% to 50%.

[0066] Compression Gradient Curing

[0067] The molding pressure is 0.5-5 MPa, and the curing is carried out in three stages: 80℃ (30 min) → 150℃ (60 min) → 180℃ (90 min).

[0068] Pressure distribution: The pressure in the thickness transition zone is applied according to an exponential curve gradient, with the maximum pressure point located on the rigid section side (gradient 0.2~0.8MPa / mm).

[0069] 3. Digital control

[0070] The thickness distribution is monitored in real time by laser scanning, and the weaving speed (±10rpm), resin pressure (±0.05MPa) and molding parameters are dynamically adjusted to ensure that the thickness tolerance is ≤±5%.

[0071] Thickness gradient: The minimum thickness variation per unit width (L1~L5) of the flexible section is 0.3mm. The thickness distribution is designed according to the target bending shape, such as... Figure 4 and Figure 5 .

[0072] Example 2

[0073] This invention provides a flexible substrate for a foldable electronic screen made of composite material without the need for drilling, comprising an integrally formed fiber-reinforced composite rigid support section and a composite flexible foldable section; the integrally formed fiber-reinforced composite rigid support section is composed of a composite laminate with multi-directional fiber lay-up, the fiber orientation of which is customized according to stiffness design requirements; the composite flexible foldable section is formed by resin impregnation and curing of a three-dimensional variable thickness woven fabric, the thickness distribution of which is customized according to the target bending shape, and is partially embedded in the fiber layer of the integrally formed fiber-reinforced composite rigid support section.

[0074] The number of layers and the angle of the integrally formed fiber-reinforced composite rigid support section are customized according to the stiffness design requirements.

[0075] For multilayer carbon fiber structures, the relationship between the number of layers, angles, and various stiffnesses is as follows:

[0076]

[0077] In the formula:

[0078]

[0079] Where, N x N y N z For in-plane forces; M x M y M z For bending moment; For in-plane strain; k x k y k xy The degree of bending deformation; A ij B ij D ij Indicates tensile stiffness, coupling stiffness, and bending stiffness; t k Indicates the thickness of the k-th layer; Represents the coordinates of the center of the k-th layer; N represents the number of layers.

[0080]

[0081] Where θ represents the ply angle; Q ij The stiffness coefficient is used; the equivalent bending stiffness of 2 GPa·mm is achieved by adjusting the ply angle and number. 3 ~100GPa·mm 3 It is adjustable within a certain range, with a thickness range of 0.01mm to 2mm.

[0082] The thickness distribution and weaving angle of the flexible foldable section of the composite material are customized according to the target bending shape. The thinner the section, the greater the deformation curvature under the same load. When the multilayer carbon fibers have the same weaving angle, the larger the weaving angle, the greater the deformation curvature under the same load, and the thickness variation range is 0.01mm to 2mm.

[0083] The integrally molded fiber-reinforced composite rigid support segment comprises one or more of the following fibers: carbon fiber, glass fiber, aramid fiber, and boron fiber.

[0084] The three-dimensional variable thickness woven fabric of the flexible foldable section of the composite material is woven from one or more of the following materials: polyester fiber, nylon fiber, polypropylene fiber, spandex fiber and acrylic fiber.

[0085] The minimum bending radius of the flexible foldable section of the composite material is 1.5 mm, and the delamination area of ​​the cross section is less than 5% after a preset number of folding tests.

[0086] The minimum thickness variation per unit width of the flexible foldable composite material plate is 0.3 mm.

[0087] This invention provides a method for manufacturing a flexible foldable electronic screen substrate made of perforated composite material, comprising the following steps: Step 1: Weaving an integrated fiber preform containing rigid and flexible sections using a multi-axial braiding machine, and achieving a thickness gradient change in the flexible sections by dynamically adjusting the warp density and weft beat-up force; Step 2: Placing the preform in a vacuum impregnation device and injecting epoxy resin, wherein the resin viscosity in the flexible section region is 200 mPa·s to 500 mPa·s lower than that in the rigid section; Step 3: Applying 0. Curing is performed at 5MPa to 5MPa pressure, in three stages: 80℃ → 150℃ → 180℃, with a total curing time of 120 min to 240 min. Specifically, the curing time at 80℃ is 20 min to 40 min, the temperature rise time from 80℃ to 150℃ is 5 min to 10 min, the curing time at 150℃ is 60 min to 120 min, the temperature rise time from 150℃ to 180℃ is 5 min to 10 min, and the curing time at 180℃ is 30 min to 60 min. In step 1, electronic jacquard technology is used to control the weaving pattern, generating a variable-thickness rectangular cross-section weave in the flexible section area that meets the design requirements, with a single-layer thickness difference of 0.02 mm to 0.1 mm.

[0088] Example 3: Flexible substrate for foldable phones

[0089] Rigid section: Carbon fiber / epoxy resin composite material, layup angle [0° / 45° / 90° / -45°] s Total thickness 1.6mm, equivalent bending stiffness 50GPa·mm 3 ;

[0090] Flexible section: Nylon / spandex blended yarn (3:1), thickness gradually changes from 1.2mm to 0.15mm, thickness gradient 0.3mm, minimum bending radius 1.3mm;

[0091] Manufacturing parameters: braiding machine speed 40 rpm, resin viscosity 300 mPa·s for flexible section / 700 mPa·s for rigid section, molding pressure 3 MPa.

[0092] Example 4: Flexible substrate for rollable televisions

[0093] Rigid section: Glass fiber / aramid fiber hybrid layup, layup angle [0° / -45° / 45° / 90°] 2s Total thickness 3.2mm, equivalent bending stiffness 130GPa·mm 3 ;

[0094] Flexible section: polyester / nylon blended yarn (1:2), thickness decreasing from 1.5mm to 0.4mm, thickness gradient 0.9mm~1.2mm, minimum bending radius 6.3mm;

[0095] Manufacturing parameters: braiding machine speed 60 rpm, resin viscosity 300 mPa·s for flexible section / 700 mPa·s for rigid section, molding pressure 5 MPa.

[0096] In the description of this application, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0097] Those skilled in the art will understand that, in addition to implementing the system, apparatus, and their modules provided by this invention in purely computer-readable program code, the same program can be implemented in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system, apparatus, and their modules provided by this invention can be considered a hardware component, and the modules included therein for implementing various programs can also be considered structures within the hardware component; alternatively, modules for implementing various functions can be considered both software programs implementing the method and structures within the hardware component.

[0098] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A flexible substrate for foldable electronic screens made of perforated composite materials, characterized in that, It includes an integrally molded fiber-reinforced composite rigid support section (1) and a composite flexible foldable section (2); The integrally formed fiber-reinforced composite rigid support section (1) is composed of a composite laminate with multi-directional fiber lay-up, and its fiber orientation is customized according to the stiffness design requirements; the composite flexible foldable section (2) is formed by resin impregnation and curing of three-dimensional variable thickness woven fabric, and its thickness distribution is customized according to the target bending shape, and is partially embedded in the fiber layer of the integrally formed fiber-reinforced composite rigid support section (1).

2. The foldable flexible electronic screen substrate made of non-drillable composite material according to claim 1, characterized in that, The number of layers and the angle of the integrally formed fiber-reinforced composite rigid support section (1) are selected according to the stiffness design requirements.

3. The foldable flexible electronic screen substrate made of non-drillable composite material according to claim 2, characterized in that, For multilayer carbon fiber structures, the relationship between the number of layers, angles, and various stiffnesses is as follows: In the formula: Where, N x N y N z For in-plane forces; M x M y M z For bending moment; For in-plane strain; k x k y k xy The degree of bending deformation; A ij B ij D ij Indicates tensile stiffness, coupling stiffness, and bending stiffness; t k Indicates the thickness of the k-th layer; Represents the coordinates of the center of the k-th layer; N represents the number of ply layers; Where θ represents the ply angle; Q ij The stiffness coefficient is used; the equivalent bending stiffness of 2 GPa·mm is achieved by adjusting the ply angle and number. 3 ~100GPa·mm 3 It is adjustable within a certain range, with a thickness range of 0.01mm to 2mm.

4. The foldable flexible electronic screen substrate made of non-drillable composite material according to claim 1, characterized in that, The thickness distribution and weaving angle of the flexible foldable section (2) of the composite material are customized according to the target bending shape. The thinner the section, the greater the deformation curvature under the same load. When multilayer carbon fibers have the same weaving angle, the larger the weaving angle, the greater the deformation curvature under the same load, and the thickness varies from 0.01mm to 2mm.

5. The foldable flexible electronic screen substrate made of non-drillable composite material according to claim 1, characterized in that, The integrally formed fiber-reinforced composite rigid support segment (1) contains one or more of the following fibers: carbon fiber, glass fiber, aramid fiber and boron fiber.

6. The foldable flexible electronic screen substrate made of non-drillable composite material according to claim 1, characterized in that, The three-dimensional variable thickness woven fabric of the composite flexible foldable segment (2) is woven from one or more of the following materials: polyester fiber, nylon fiber, polypropylene fiber, spandex fiber and acrylic fiber.

7. The foldable flexible electronic screen substrate made of non-drillable composite material according to claim 1, characterized in that, The minimum bending radius of the flexible foldable section (2) of the composite material is 1.5 mm, and the interface delamination area is <5% after a preset number of folding tests.

8. The foldable flexible electronic screen substrate made of non-drillable composite material according to claim 1, characterized in that, The thickness variation of the flexible foldable section (2) of the composite material is as small as 0.3 mm per unit width.

9. A method for manufacturing a flexible, foldable electronic screen substrate made of perforated composite material as described in any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Use a multi-axial braiding machine to weave an integrated fiber preform containing rigid and flexible sections, and achieve the thickness gradient change of the flexible section by dynamically adjusting the warp density and weft beat-up force; Step 2: Place the preform in a vacuum impregnation device and inject epoxy resin, wherein the resin viscosity in the flexible section is 200 mPa·s to 500 mPa·s lower than that in the rigid section. Step 3: Apply a pressure of 0.5MPa to 5MPa in the molding die and cure in three stages: 80℃ → 150℃ → 180℃, with a total curing time of 120min to 240min. Specifically, the curing time at 80℃ is 20min to 40min, the temperature rise time from 80℃ to 150℃ is 5min to 10min, the curing time at 150℃ is 60min to 120min, the temperature rise time from 150℃ to 180℃ is 5min to 10min, and the curing time at 180℃ is 30min to 60min.

10. The method for manufacturing a flexible foldable electronic screen substrate of a perforated composite material according to claim 9, characterized in that, In step 1, electronic jacquard technology is used to control the weaving pattern, generating a rectangular cross-section weave with varying thickness that meets the design requirements in the flexible section area, with a single layer thickness difference of 0.02mm to 0.1mm.

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