Optical adhesive tape with ultra-thin structure as well as preparation method and application of optical adhesive tape

Abstract

The invention belongs to the technical field of high polymer materials and photoelectricity, and discloses an optical adhesive tape with an ultra-thin structure as well as a preparation method and application of the optical adhesive tape. The optical adhesive tape is of a composite multi-layer structure, and the total thickness of the optical adhesive tape is 300-1000 nm; the optical adhesive tape comprises a porous modified polyethylene film and an adhesive infiltrated in pores of the porous modified polyethylene film, the porous modified polyethylene film comprises an ultra-high molecular weight polyethylene porous film and an organic modifier layer modified on the surface of the ultra-high molecular weight polyethylene porous film. The adhesive tape material is extremely thin (the thickness is as low as 300 nm), extremely transparent (the transmittance is as high as 99.9%) and extremely strong (the tensile strength is 312 MPa), and the triangular contradiction of'thickness, strength and transparency 'of the conventional adhesive tape is broken through. A'folding and drafting 'process is introduced into the preparation method, the contradiction between thin adhesive tape thickness and small pores is solved, and the double effects of extremely thin adhesive bonding interface and simple processing can be achieved when the adhesive tape is used for packaging photoelectric devices.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials and optoelectronic technology, specifically relating to an ultra-thin optical tape, its preparation method, and its application. Background Technology

[0002] As advanced optoelectronic systems such as high-energy lasers, laser gyroscopes, and quantum sensors develop towards miniaturization, precision, and cost reduction, extremely high demands are placed on the bonding of their internal optical components (such as slots and mirror assemblies): the interface must possess an extremely thin adhesive layer, extremely high connection strength, and a simple and controllable process. Currently, the bonding of optoelectronic device interfaces mainly relies on two types of technologies: adhesive bonding and polishing adhesives. Although adhesive bonding technology is simple to operate, the adhesive layer thickness is usually greater than 10 μm, which not only increases the device size but also introduces unnecessary refraction and interference effects, restricting the miniaturization and precision improvement of devices. Although photopolymer adhesive technology can achieve nanoscale or even molecular-level thin-layer bonding, it relies on ultra-smooth surfaces, harsh clean environments, and high-precision alignment processes, making it difficult to use for irregular interfaces and costly. Therefore, developing an interface bonding material and technology that combines "extremely thin structure" and "simple process" has become a key bottleneck driving the development of high-end optoelectronic devices.

[0003] In theory, using ultra-thin transparent double-sided adhesive tape for bonding is an ideal path to balance thinness and process feasibility. However, most existing adhesive tape products (such as Chinese patent application CN202110541222.4) still have a thickness in the micrometer range (approximately 0.01 mm), which is insufficient to meet the high-end application requirements of nanoscale interfaces (thickness ≤ 1000 nm). Even with some studies attempting to further reduce the tape thickness, there are still few feasible solutions that can stably prepare and achieve uniform adhesive loading at the nanoscale. The core challenge lies in how to simultaneously ensure the mechanical integrity and structural stability of the carrier film, as well as the reliable wetting and anchoring of the adhesive, at submicron and even nanometer thicknesses.

[0004] Therefore, the development of an optical tape that combines nanoscale thickness with excellent comprehensive performance is of great significance to this technical field. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide an ultra-thin optical tape, its preparation method and application, which addresses the shortcomings of existing optical tapes in achieving both nanometer-level thickness and excellent comprehensive performance.

[0006] The first aspect of this invention is to provide an optical tape, wherein the optical tape has a composite multilayer structure with a total thickness of 300-1000 nm; the optical tape comprises: a porous modified polyethylene film, and an adhesive impregnated within the pores of the porous modified polyethylene film; the porous modified polyethylene film comprises: an ultra-high molecular weight polyethylene porous film, and an organic modifier layer modified on the surface of the ultra-high molecular weight polyethylene porous film through interfacial interaction, wherein the number average molecular weight of the ultra-high molecular weight polyethylene porous film is 2.5 × 10⁻⁶. 6 -13×10 6 g / mol, wherein the organic modifier in the organic modifier layer includes at least one of silane coupling agent, polydopamine and titanate coupling agent.

[0007] This invention uses an ultra-high molecular weight polyethylene porous membrane with a specific nanoscale porous structure as a reinforcing skeleton, and through a unique "folding and stretching process" and surface modification treatment, the skeleton can maintain an extremely thin thickness while possessing excellent mechanical strength and light transmittance.

[0008] Further, in the aforementioned optical tape, the thickness of the porous modified polyethylene membrane is 200-900 nm; the ultra-high molecular weight polyethylene porous membrane has a continuous three-dimensional nanofiber network structure, wherein the diameter of a single fiber is 0.1-19.9 nm, the porosity is 60%-90%, the pore size distribution is 0.1-19.9 nm, and the thickness of the ultra-high molecular weight polyethylene porous membrane is 100-800 nm. This demonstrates the synergistic characteristics of a special framework structure (ultra-fine pores, ultra-fine fiber framework) and high mechanical strength.

[0009] Furthermore, the organic modifier layer is applied to the fiber surface of the ultra-high molecular weight polyethylene porous membrane, and the thickness of the organic modifier layer is 100-500 nm; the loading amount of the organic modifier on the surface of the ultra-high molecular weight polyethylene porous membrane is 0.1-10.0 wt.

[0010] Furthermore, the adhesive comprises a polymer matrix and functional additives; the polymer matrix is ​​at least one of epoxy resin, acrylic resin, silicone resin, transparent polyimide resin, vinyl polydimethylsiloxane, and polysilazane resin, or a derivative compound thereof modified with acrylic acid and epoxy groups; the functional additives are at least one of crosslinking agent, initiator, toughening agent, catalyst, and ultraviolet absorber; the viscosity of the adhesive is not less than 10000 mPa·s; the adhesive is filled into the pores of the porous modified polyethylene film through coating and vacuum-assisted pressing to form a composite structure with internal saturation and no adhesive overflow on the surface; by mass fraction, the adhesive accounts for 20%-80% of the total mass of the optical tape. The adhesive forms a strong bond with the fibers and does not overflow from the film surface, thereby maintaining the optical flatness of the tape while ensuring bonding performance.

[0011] Furthermore, the visible light transmittance of the optical tape is 90.0%-99.9%, and the tensile strength is 102-651 MPa; the upper and lower sides of the optical tape are each covered with a polytetrafluoroethylene release film with a thickness of 20-40 μm.

[0012] This invention, based on an ultra-thin optical tape with a porous modified polyethylene film-reinforced framework, achieves significant breakthroughs compared to existing technologies in the following aspects: 1) Overcoming the thickness limit: The total thickness of the tape is pushed to the nanoscale of 300-1000 nm, reducing it by an order of magnitude compared to existing tape technologies, providing a thin-layer interface for optoelectronic devices that is almost in direct contact with the material. 2) Original "folding and stretching" fabrication process: Through a multi-step process of "primary stretching - folding and hot pressing - precision stretching," a highly oriented, three-dimensional nanofiber network with controllable porosity is constructed within the ultra-high molecular weight polyethylene film. This process not only effectively eliminates the internal stress caused by high-stretching but also significantly refines the pore size, improves crystallinity and mechanical strength, providing an ideal framework for the nanopore confinement of adhesives. 3) Clear application positioning for optoelectronic integration: The material design closely integrates with the requirements of interference systems, quantum optical devices, etc., for interface thickness, optical transparency, and long-term stability, providing a new material foundation for achieving compact, high-performance, and low-cost manufacturing of optoelectronic devices.

[0013] This invention not only significantly surpasses existing technologies in terms of tape thickness, a core indicator, but also solves the key contradiction of achieving both "extreme thinness" and "high mechanical strength and high light transmittance" at the nanoscale through original process and structural design, providing a reliable interface connection solution for the development of next-generation high-end optoelectronic devices.

[0014] The second aspect of this invention is to provide a method for preparing optical tape. This method, through a unique process design, particularly the introduction of an innovative "folding and hot pressing" process, achieves a breakthrough improvement in the structural performance of the optical tape, and includes the following steps: (1) Add the premixed powder of ultra-high molecular weight polyethylene powder and antioxidant to molten petroleum jelly, and keep it warm and stir under inert gas protection to form a uniform suspension. Pre-press the suspension to obtain the initial polyethylene sheet. (2) The initial polyethylene sheet is subjected to a folding and stretching process, which includes primary stretching, folding hot pressing and precision stretching in sequence. The folding hot pressing includes folding the film after primary stretching and hot pressing it. After the process is completed, precision stretching is performed to obtain an oriented film with a total stretch ratio of 400-6400 times. After removing petrolatum, ultra-high molecular weight polyethylene porous membrane is obtained. (3) Prepare the organic modifier into a modified solution, coat it onto the surface of the ultra-high molecular weight polyethylene porous membrane obtained in step (2), and then perform heat treatment to obtain a porous modified polyethylene membrane. (4) The adhesive is evenly coated on the surface of the porous modified polyethylene film obtained in step (3), and then vacuum-assisted pressing is performed to allow the adhesive to be impregnated in the pores of the porous modified polyethylene film, thus obtaining the optical tape with an extremely thin structure.

[0015] In the above preparation method, further, in step (1), the molten petrolatum oil is obtained by heating petrolatum oil to 80-120 °C and continuously stirring until the oil phase is completely clear and transparent; in the premixed powder, the amount of antioxidant added is 0.1-0.5% of the mass of the ultra-high molecular weight polyethylene powder, and the number average molecular weight of the ultra-high molecular weight polyethylene powder is 2.5 × 10⁻⁶. 6 -13×10 6 g / mol, wherein the antioxidant is antioxidant 1010 or resveratrol; the temperature for heat preservation and stirring is 100-170 ℃, the stirring speed is 200-500 rpm, and the stirring time is 1-3h; The pre-compression molding is carried out under a vacuum of 0.1-10 Pa, with a pressure of 5-15 MPa, a temperature of 130-190 ℃, and a time of 5-35 min.

[0016] Further, in step (2), the method for the folding and stretching process is as follows: First, a primary stretching treatment is performed, that is, at 100-130 ℃ with a tensile strength of 0.2-2%·s -1The polyethylene sheet is subjected to bidirectional synchronous stretching at a stretching rate of 3-99 times. This is followed by 1-3 cycles of folding and hot pressing, where the initial stretched polyethylene sheet is folded along the centerline and hot-pressed at 5-10 MPa and 100-140 °C for 30-120 min. Finally, precision stretching is performed at 110-135 °C at a stretching rate of 0.2-2%·s. -1 The film is subjected to precision stretching at a stretching rate of 400-6400 times. The total stretching ratio of the primary stretching-folding hot pressing-precision stretching is 400-6400 times. The film obtained after the orientation treatment is subjected to Soxhlet extraction to remove residual petrolatum, resulting in an ultra-high molecular weight polyethylene porous membrane.

[0017] Further, in step (3), the concentration of the organic modifier in the modified solution is 0.1-5.0 wt%, and the solvent used in the modified solution is at least one of water, ethanol, acetone, and ethyl acetate; the coating method is at least one of spraying, scraping, and dip coating, the coating time is within 10 s, and the coating temperature is 15-30 ℃; the heat treatment is carried out in a vacuum or forced-air oven at a temperature of 40-90 ℃ for a time of not less than 10 min. After the treatment in step (3), the surface energy of the porous modified polyethylene film is optimized, creating ideal conditions for the subsequent wetting and bonding of the adhesive.

[0018] Further, in step (4), the porous modified polyethylene film obtained in step (3) is laid flat on a polytetrafluoroethylene release film with a thickness of 20-40 μm, and then an adhesive is applied. After the coating is completed, another layer of polytetrafluoroethylene release film is covered to form a symmetrical stacked structure of release film-adhesive layer-porous modified polyethylene film-adhesive layer-release film; the vacuum-assisted pressing treatment is performed under UV light irradiation, 0.0001-1 Pa vacuum degree, and 10-30 MPa pressure for 10-30 min. After the treatment in step (4), the adhesive fully impregnates and fills the nanoscale pores of the porous modified polyethylene film under pressure, forming a binding mechanism that combines mechanical interlocking and physical adsorption, while ensuring that no excess adhesive overflows from the film surface.

[0019] A third aspect of the present invention is to provide an application of optical tape in the encapsulation of optoelectronic devices.

[0020] Further, the method for encapsulating the optoelectronic device described above includes: first, removing the polytetrafluoroethylene release film from one side of the optical tape, attaching the exposed adhesive surface to the surface of a first substrate (such as a glass slide), and applying slight pressure to ensure initial adhesion; then, removing the release film from the other side, aligning and attaching a second substrate (such as another glass slide or functional component); finally, curing the adhesive (selecting appropriate light, heating, or humidity conditions for curing based on the curing characteristics of the adhesive), thus completing the encapsulation of the optoelectronic device. Such optoelectronic devices are particularly suitable for high-end applications such as micro-displays, flexible OLEDs, and optical sensors, achieving high mechanical strength (tensile strength up to 312 MPa) and high reliability connections between heterogeneous materials.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The optical tape of the present invention uses a nanofiber film with extremely thin thickness, ultra-fine fibers and ultra-small pore size as a carrier to prepare an extremely thin (thickness as low as 300 nm), extremely transparent (transmittance as high as 99.9%) and extremely strong (tensile strength as high as 312 MPa) optical tape, breaking the triangular contradiction of "thickness, strength and transparency" in the past tapes.

[0022] 2. This invention innovatively introduces a "folding and stretching" process in the preparation of optical tape, which solves the contradiction between thin tape thickness and small pore size. On the one hand, the folding and hot pressing step of folding and stretching can make the nanofibers stack longitudinally, making the fiber stacking more dense and reducing the pore size. On the other hand, the folding and hot pressing step of folding and stretching can play a role similar to tempering, eliminating uneven thermal stress in the film to improve stability, promoting crystallinity to strengthen the film, so that the film can achieve stable high-ratio (up to 6400 times) stretching in the stretching after folding, greatly reducing the thickness of the film and tape while improving strength.

[0023] 3. The optical tape of the present invention is used to encapsulate optoelectronic devices, and can achieve the dual effects of "extremely thin bonding interface" and "easy processing" that cannot be achieved by the current advanced adhesive bonding technology or optical adhesive technology. This is very beneficial to the compact and low-cost manufacturing of high-precision optoelectronic devices. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1This is a process flow diagram of the preparation method in Example 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the ultra-thin adhesive tape material prepared in Example 1 of the present invention; Figure 3 This is a schematic diagram of the structural changes caused by the folding and stretching process used in Embodiment 1 of the present invention; Figure 4 This is a scanning electron microscope image of the surface obtained in Embodiment 1 of the present invention, wherein... Figure 4 A is a scanning electron microscope image of the surface of a porous ultra-high molecular weight polyethylene membrane. Figure 4 B is a scanning electron microscope image of the surface of an extremely thin adhesive tape material. Detailed Implementation

[0026] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0027] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0028] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0029] Those skilled in the art can make appropriate adjustments or improvements to the technical solution without departing from the spirit of the present invention, and such adjustments or improvements should be considered to fall within the scope of the claims of the present invention.

[0030] To accurately evaluate the performance of the optical tape of this invention, the following instruments and methods were used for testing: 1. Thickness test: Using a Brucker Dimension ICON scanning atomic force microscope, the test was conducted under normal temperature and humidity conditions using a tapping mode. The probe force constant was 40 N / m. At least five different locations were tested for each sample, and the average value was taken as the final result.

[0031] 2. Visible light transmittance test: An Agilent Cary 7000 UV-Vis-NIR spectrophotometer with integrating sphere accessory was used. The samples were scanned at 1 nm intervals in the wavelength range of 380-780 nm, in accordance with ISO 13468 standard. Baseline calibration was performed using a standard white plate before the test. Five samples were tested in each group.

[0032] Tensile strength test: An INSTRON 5967 universal testing machine was used, with a tensile rate of 100 mm / min, a gauge length of 20 mm, a sensor range of 500 N, an ambient temperature of 23±2℃, and a relative humidity of 50±5%.

[0033] The technical principle of this invention is as follows: using a porous ultra-high molecular weight polyethylene nanofiber network as a framework, surface modification is used to improve its wettability and interfacial compatibility with adhesives, and adhesives are filled into the gaps between the frameworks. This successfully prepares an adhesive tape material with extremely thin thickness (as low as 300 nm), high tensile strength (up to 312 MPa), and excellent light transmittance (visible light transmittance up to 99.9%). This design effectively solves the traditional contradiction between transparency, mechanical properties, and thickness. The prepared tape enables thinner and more stable interfacial bonding layers for optoelectronic devices, providing key material support for the development of highly compact and highly reliable optoelectronic systems.

[0034] Definitions: Ultra-high molecular weight polyethylene (UHMWPE) is a type of unbranched linear polyethylene with a molecular weight of over 1.5 million. Its molecular formula is: —(—CH2-CH2—)—n—.

[0035] Antioxidant 1010, also known as pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyhydrogenated cinnamate), trade name: Irganox 1010, CAS number: 6683-19-8, molecular formula: C 73 H 108 O 12 .

[0036] Example 1 An optical tape with an extremely thin structure, the optical tape being a composite multilayer structure with a total thickness of 1000 nm; the optical tape comprising: a reinforcing skeleton composed of a porous modified polyethylene film, and an adhesive impregnated within the pores and on the surface of the reinforcing skeleton; the porous modified polyethylene film is composed of an ultra-high molecular weight polyethylene porous membrane and an organic modifier layer bonded to its surface through interfacial interactions.

[0037] The fabrication process of optical tapes and the optoelectronic devices bonded to them, such as... Figure 1 It includes the following steps: The core innovation of this embodiment lies in the use of a unique "primary stretching-folding hot pressing-precision stretching" process (hereinafter referred to as the "folding and stretching process"), which achieves precise control of the molecular chain orientation and crystallization behavior, thereby realizing the precise regulation of the nanoporous structure. The specific implementation steps are as follows: (1) Preparation and structural optimization of ultra-high molecular weight polyethylene porous membranes Accurately weigh 1.46 g of ultra-high molecular weight polyethylene (UHMWPE) (number average molecular weight is 9 × 10⁻⁶). 6 A premixed powder was prepared by mixing 0.14 g of resveratrol (g / mol) and 31.04 g of molten medical-grade petrolatum. The mixture was then added to the premixed powder and stirred mechanically at 300 rpm for 3 h under nitrogen protection at a temperature maintained at 155±5 ℃ to obtain a homogeneous and stable suspension. The suspension was injected into a specially designed 10 cm × 10 cm stainless steel mold and hot-pressed for 35 min at 190 ℃, 10 MPa pressure, and 10 Pa vacuum. The mold was then cooled to room temperature using a gradient cooling process and held under pressure for 5 min to obtain a dense initial polyethylene sheet. The sheet was then oriented using a folding and stretching process, which included three stages: (1-1) Primary tensile stage: under constant temperature of 120 ℃, at 2%·s -1 Bidirectional synchronous stretching was performed at the stretching rate to achieve an initial stretching ratio of 9×9 (81 times), and a molecular chain orientation framework was initially established. (1-2) Folding and Hot Pressing Stage (Core Innovation of this Embodiment): The film with a stretch ratio of 200 times (9×9×1.57×1.57) is folded and placed in a precision flatbed press for hot pressing and tempering at 100 ℃ and 10 MPa for 60 min. This process significantly improves the film performance through the following mechanisms: First, structural rearrangement: The folding operation causes the fibers to stack and weld nanofibers, thereby refining and homogenizing the size of the pore structure; Second, stress relief: Effectively releases the internal stress accumulated in the early stretching stage, improving dimensional stability; Third, crystallization improvement: Provides sufficient energy to promote molecular chain rearrangement, improving crystallinity and mechanical properties. (1-3) Precision stretching stage: at 130 °C, at 0.5%·s -1 Precision stretching was performed at a certain rate to achieve a total stretch ratio of 400 times (9×9×1.57×1.57×1.41×1.41), ultimately obtaining a highly oriented polyethylene nanofiber membrane. The oriented polyethylene nanofiber membrane was subjected to Soxhlet extraction in n-hexane at 100 °C for 24 h to completely remove residual petrolatum, yielding an ultra-high molecular weight polyethylene porous membrane with a regular nanoporous structure. Characterization results showed that the ultra-high molecular weight polyethylene membrane had a thickness of 700 nm, a concentrated pore size distribution of 19.1 nm, a single fiber diameter of 10 nm, a porosity of 80%, and a fiber orientation degree of over 90%, exhibiting a perfect three-dimensional interconnected network structure.

[0038] (2) Surface modification of ultra-high molecular weight polyethylene porous membrane to enhance interfacial bonding Polydopamine was dissolved in deionized water to prepare a 1 wt% modified solution. Using a precision coating device, the modified solution was uniformly coated onto the surface of an ultra-high molecular weight polyethylene porous membrane. The blade height was strictly controlled at 10 μm, and the coating speed at 10 mm·s. -1 The ambient temperature was 25±2℃. The coated film was placed in a forced-air drying oven and dried at 50℃ for 6 hours, so that polydopamine could form a firm bond with the surface of polyethylene fiber through a dual mechanism of covalent bonding and physical adsorption. The resulting porous modified polyethylene film had a thickness of 900 nm and its surface energy increased from 42 mN / m to 55 mN / m, which significantly improved the interfacial wettability.

[0039] (3) Tape lamination and precision packaging The adhesive was prepared according to the optimized ratio: 20 g of acrylic acid and epoxy group modified vinyl polydimethylsiloxane (TLN-240 purchased from Chengdu Tuoli Technology Co., Ltd., other products in the TLN series can be used as substitutes) was used as the matrix, 2 g of hydrogen-containing silicone oil crosslinking agent (0.5 wt% hydrogen content) was added, and 0.1 g of peroxide initiator 2,4-dichlorobenzoyl peroxide and 0.1 g of platinum catalyst were combined to form a dual-curing system; a planetary mixer was used to stir for 5 min under a vacuum of 0.1 MPa at a mixing mode of 30 rpm revolution and 1200 rpm rotation to ensure sufficient dispersion and prepolymerization of each component; the modified porous polyethylene film was precisely laid on a 20 μm thick polytetrafluoroethylene release film, and a spin coating process was used at 1000 The adhesive is evenly coated at a rotation speed of rpm, and then another release film is applied to form a symmetrical "release film-adhesive layer-porous modified polyethylene film-adhesive layer-release film" stacked structure. The assembled stacked structure is placed in a flatbed press and pressed for 10 min under UV light irradiation, 0.01 Pa vacuum, and 10 MPa pressure. This allows the adhesive to fully impregnate and anchor itself in the nanoscale pores of the porous modified polyethylene film under capillary action and external pressure. The final ultrathin optical tape has a total thickness of 1000 nm (excluding the release film). The adhesive layer and the fiber skeleton form a strong mechanical interlocking and chemical bonding dual bonding mechanism.

[0040] (4) Packaging and performance verification of optoelectronic devices During the device packaging stage, a step-by-step bonding process was employed: first, the release film on one side of the adhesive tape was removed, and the exposed adhesive surface was bonded to the plasma-treated glass substrate surface, with 0.1 MPa pressure applied to ensure initial bonding; then, the release film on the other side was removed, and the second glass substrate was precisely aligned and bonded. The assembled device was placed in an 80°C oven for 1 hour of thermosetting to allow the adhesive to fully cross-link and cure. The resulting interferometric optoelectronic device has an extremely thin packaging interface (only 1000 nm thick), which was integrated into a high-resolution phase-shifting interferometer system for device application performance testing.

[0041] A schematic diagram of the ultra-thin transparent tape prepared in Example 1 is shown below. Figure 2 As shown, the tape consists of two parts: a skeleton and gaps between the skeleton and the skeleton. The skeleton is a porous polyethylene film composed of extremely thin nanofibers (fiber diameter ≤ 19.9 nm) with an extremely thin vertical thickness (thickness ≤ 1000 nm) and an extremely small horizontal pore size (pore size ≤ 19.9 nm). Due to the extremely small pore size and extremely fine fibers, the tape has excellent light transmittance. Due to the high orientation of the film, the tape has extremely high mechanical properties (tensile strength > 100 MPa) and an extremely thin thickness. The gaps between the skeleton and the skeleton are filled with adhesive to provide bonding properties, and the two sides of the tape are polytetrafluoroethylene release films.

[0042] like Figure 3 As shown, the extremely thin thickness, extremely high mechanical strength, and excellent light transmittance are mainly attributed to the special folding and stretching process used in the preparation of the polyethylene nanofiber membrane skeleton in this invention. During the folding and hot-pressing process, extremely small pores are generated. In the subsequent stretching process, extremely fine nanofibers and an extremely thin thickness are obtained. The small pore size and fine skeleton reduce light scattering and refraction within the membrane, improving light transmittance. The folding and stretching process also provides sufficient tempering energy to promote molecular chain rearrangement, effectively releasing the internal stress accumulated during the initial stretching, allowing for higher stretching and orientation of the film, thus improving the mechanical properties of the membrane.

[0043] like Figure 4 As shown in Figure A, the ultra-high molecular weight polyethylene porous membrane obtained in this embodiment has extremely small nanoscale pore sizes; as... Figure 4 As shown in B, the ultrathin optical tape obtained in this embodiment has a surface wetting structure.

[0044] Example 2 An optical tape with an extremely thin structure differs from Example 1 in that the method of preparing the ultra-high molecular weight polyethylene (UHMWPE) film is changed. In steps (1-2), the number of folds and repetitions of the film with a stretch ratio of 200 is changed from once to twice, followed by a hot-pressing treatment. In step (1-3), the stretch ratio of the film after the folding and hot-pressing treatment is further stretched from 9×9×1.57×1.57×1.41×1.41 (400 times) to 9×9×1.57×1.57×4×4 (1600 times). Therefore, the obtained UHMWPE film has a thickness of 400 nm, a pore size distribution of 9.1 nm, a single fiber diameter of 9.9 nm, and a porosity of 75%. Due to the decrease in the thickness of the UHMWPE film, the final total thickness of the tape also decreases to 500 nm (excluding the release film).

[0045] Example 3 An optical tape with an extremely thin structure differs from Example 1 in that the method of preparing the ultra-high molecular weight polyethylene film is changed. In steps (1-2), the number of folds and repetitions of the film with a stretch ratio of 200 is changed from once to three times, and a hot-pressing treatment is performed after the three folds. In step (1-3), the stretch ratio of the film after the folding and hot-pressing treatment is further stretched from 9×9×1.57×1.57×1.41×1.41 (400) to 9×9×1.57×1.57×8×8 (6400 times). Therefore, the thickness of the ultra-high molecular weight polyethylene film is 200 nm, the pore size distribution is 4.1 nm, the diameter of a single fiber is 6.9 nm, and the porosity is 71%. Due to the decrease in the thickness of the ultra-high molecular weight polyethylene film, the final total thickness of the tape is also reduced to 300 nm (excluding the release film).

[0046] Comparative Example 1 An optical tape differs from Example 1 in that it does not use a porous ultra-high molecular weight polyethylene (UHMWPE) membrane as the tape skeleton, but instead employs a commercial tape manufacturing method. Step 1 is changed from preparing a porous polyethylene membrane to directly using a commercially available non-porous biaxially oriented polypropylene (BOPP) film (1200 nm thick). Step 3 is changed to coating each side of the BOPP film with a 400 nm layer of epoxy resin adhesive. Based on this, the transparent optical tape prepared has a total thickness of 20,000 nm for the intermediate adhesive layer.

[0047] Comparative Example 2 An optical tape, differing from Example 1 in that it does not use the folding and stretching method to prepare the nanofiber skeleton of the tape, but instead uses electrospinning to prepare the PEO nanofiber skeleton of the tape, comprising the following steps: First, a PEO solution with a concentration of 8% (g / mL, mass-volume ratio) and deionized water as the solvent was prepared. A porous PEO nanofiber film (1000 nm thick, 105 nm pore size) was fabricated using a spinning voltage of 15 kV, a receiving distance of 15 cm, and a winding speed of 100 r / min. Next, 20 g of epoxy-modified vinyl polydimethylsiloxane, 2 g of hydrogen-containing silicone oil crosslinking agent (0.5 wt% hydrogen content), 0.1 g of 2,4-dichlorobenzoyl peroxide, and 0.1 g of platinum water were placed in a planetary mixer. The mixture was evacuated to 0.1 MPa and stirred for 5 min at a revolution speed of 30 rpm and a rotation speed of 1200 rpm to obtain a uniformly mixed adhesive. Next, a PEO nanofiber film was laid flat on a solid PTFE protective film. Adhesive was then spin-coated onto the surface of the PEO nanofiber film at a spin-coating rate of 1000 rpm. Another layer of solid PTFE protective film was then laid on top, forming a laminated tape structure. The tape was placed in a flatbed press and compacted at 10 MPa for 10 minutes at room temperature to obtain the final tape (total thickness of the internal adhesive layer is 2000 nm). Finally, the optoelectronic device was bonded: Before bonding, the PTFE film on one side of the tape was removed, and the inner tape was adhered to the slot interface, ensuring a flat attachment. The other protective layer was removed, and another slot or component was attached. The device was cured by heating at 80 ℃ for 1 hour to obtain an interference optoelectronic device with an extremely thin encapsulation structure. Finally, this device was assembled into a high-resolution phase-shifting interferometry system.

[0048] Comparative Example 3 An optical tape differs from Example 1 in that the method of preparing the polyethylene film is changed. No special folding and stretching process is introduced, omitting the folding and hot-pressing stage in step 2) and the precision stretching stage in step 3). Therefore, the resulting polyethylene film has a thickness of 1000 nm and a pore size of 304.1 nm. The final thickness of the adhesive layer in the middle of the tape is 2000 nm.

[0049] Table 1 Comparison of optical tape performance in Examples 1-3 and Comparative Examples 1-3

[0050] As shown in Table 1, the tensile strength of Examples 1-3 is 117-312 MPa, significantly stronger than that of Comparative Examples 1-3 (2-79 MPa). This indicates that the tapes prepared by the folding and stretching process of this invention significantly enhance mechanical properties, superior to tapes prepared from conventional thin films (Comparative Example 1) and tapes prepared from other nanofiber structures (Comparative Examples 2 and 3). This is mainly because the folding and stretching process eliminates uneven thermal stress through hot-pressing annealing, allowing for a higher stretching ratio and promoting the optimization of the oriented crystalline structure. The comparison between Example 1 and Examples 2 and 3 shows that the number of folds and the stretching ratio have a significant impact on tensile strength; increasing the number of folds and the stretching ratio helps to further improve the tensile strength (up to 312 MPa).

[0051] Regarding visible light transmittance, Examples 1-3 exhibited transmittance of 97.0%-99.9%, significantly higher than Comparative Examples 1-3 (32.5%-70.5%). This indicates that the tape prepared by the folding and stretching process of this invention significantly enhances light transmittance, surpassing tapes prepared from conventional thin films (Comparative Example 1) and tapes prepared from other nanofiber structures (Comparative Example 2). This is mainly because the folding and stretching process, through folding and hot pressing, makes the nanofibers stack more densely, reducing the pore diameter. Simultaneously, the post-stretching reduces the fineness of the skeleton, making the pore size and skeleton size (-10 nm) smaller than the wavelength of visible light, thus improving transmittance. The comparison between Example 1 and Examples 2 and 3 illustrates that increasing the number of folds and the stretching ratio significantly affects tensile strength. Increasing the number of folds and the stretching ratio helps to further optimize the pore size and skeleton size, further improving the optical performance of the tape (transmittance up to 99.9%).

[0052] Regarding thickness, the total thickness of Examples 1-3 was 300-1000 nm, significantly thinner than Comparative Examples 1-3 (2000-20000 nm). This indicates that the tape prepared by the folding and stretching process of this invention significantly reduces the tape thickness, superior to tapes prepared by conventional ordinary films (Comparative Example 1) and tapes prepared by other nanofiber structures (Comparative Examples 2 and 3). This is mainly because the folding and stretching process eliminates uneven thermal stress through hot-pressing annealing, allowing for a higher stretching ratio and reducing the film thickness. The comparison of Examples 1-3 shows that increasing the number of folds and the stretching ratio significantly affects tensile strength. Increasing the number of folds and the stretching ratio helps to further improve the stretching ratio, further reducing the tape thickness (to a minimum of 300 nm).

[0053] In terms of application, the optoelectronic devices prepared in Examples 2 and 3 exhibit better compactness and superior optical path signals in the high-resolution phase-shifting interference system, with no obvious parasitic fringes, significantly outperforming Comparative Examples 1-3. This indicates that the nanoscale (300 nm) thick tape prepared by the folding and stretching process of this invention improves the compactness and optical performance of the optoelectronic system, mainly due to the extremely thin thickness and excellent light transmittance of Examples 2 and 3.

[0054] In summary, the tape prepared by the folding and stretching process proposed in this invention can effectively improve the compactness and optoelectronic performance of optoelectronic devices. Utilizing a unique nanofiber network structure (extremely small pore size, extremely fine skeleton, and highly oriented crystallinity) not found in traditional tapes, it achieves performance characteristics not possessed by conventional commercial tapes, particularly the highly unified combination of extremely thin thickness (as low as 300 nm), extremely high light transmittance (99.9%), and extremely high mechanical strength (tensile strength 312 MPa). This provides a reliable packaging solution for cutting-edge fields such as micro-opto-electro-mechanical systems, flexible displays, and high-end optical sensors.

Claims

1. An optical tape with an extremely thin structure, characterized in that, The optical tape has a composite multilayer structure with a total thickness of 300-1000 nm. The optical tape comprises a porous modified polyethylene film and an adhesive impregnated within the pores of the porous modified polyethylene film. The porous modified polyethylene film comprises an ultra-high molecular weight polyethylene porous film and an organic modifier layer modified on the surface of the ultra-high molecular weight polyethylene porous film. The number-average molecular weight of the ultra-high molecular weight polyethylene porous film is 2.5 × 10⁻⁶. 6 -13×10 6 g / mol, wherein the organic modifier in the organic modifier layer includes at least one of silane coupling agent, polydopamine and titanate coupling agent.

2. The optical tape with an extremely thin structure according to claim 1, characterized in that, The thickness of the porous modified polyethylene membrane is 200-900 nm; the ultra-high molecular weight polyethylene porous membrane has a continuous three-dimensional nanofiber network structure, wherein the diameter of a single fiber is 0.1-19.9 nm, the porosity is 60%-90%, the pore size distribution is 0.1-19.9 nm, and the thickness of the ultra-high molecular weight polyethylene porous membrane is 100-800 nm.

3. The optical tape with an extremely thin structure according to claim 2, characterized in that, The organic modifier layer is applied to the fiber surface of the ultra-high molecular weight polyethylene porous membrane, and the thickness of the organic modifier layer is 100-500 nm; the loading amount of the organic modifier on the surface of the ultra-high molecular weight polyethylene porous membrane is 0.1-10.0 wt.

4. The optical tape with an extremely thin structure according to claim 1, characterized in that, The adhesive comprises a polymer matrix and functional additives; the polymer matrix is ​​at least one of epoxy resin, acrylic resin, silicone resin, transparent polyimide resin, vinyl polydimethylsiloxane, and polysilazane resin, or a derivative compound thereof modified with acrylic acid and epoxy groups; the functional additives are at least one of crosslinking agent, initiator, toughening agent, catalyst, and ultraviolet absorber; the solid content of the adhesive is not less than 10 wt%, and the viscosity is not less than 10000 mPa·s; the adhesive is filled into the pores of the porous modified polyethylene film by coating and vacuum-assisted pressing to form an internally saturated composite structure; by mass fraction, the adhesive accounts for 20%-80% of the total mass of the optical tape.

5. The optical tape with an extremely thin structure according to any one of claims 1-4, characterized in that, The optical tape has a visible light transmittance of 90.0%-99.9% and a tensile strength of 102-651 MPa; the upper and lower sides of the optical tape are each covered with a polytetrafluoroethylene release film with a thickness of 20-40 μm.

6. A method for preparing an optical tape as described in any one of claims 1-5, characterized in that, Includes the following steps: (1) Add the premixed powder of ultra-high molecular weight polyethylene powder and antioxidant to molten petroleum jelly, and keep it warm and stir under inert gas protection to form a uniform suspension. Pre-press the suspension to obtain the initial polyethylene sheet. (2) The initial polyethylene sheet is subjected to a folding and stretching process, which includes primary stretching, folding hot pressing and precision stretching in sequence. The folding hot pressing includes folding the film after primary stretching and hot pressing it. After the process is completed, precision stretching is performed to obtain an oriented film with a total stretch ratio of 400-6400 times. After removing petrolatum, ultra-high molecular weight polyethylene porous membrane is obtained. (3) Prepare the organic modifier into a modified solution, coat it onto the surface of the ultra-high molecular weight polyethylene porous membrane obtained in step (2), and then perform heat treatment to obtain a porous modified polyethylene membrane. (4) The adhesive is evenly coated on the surface of the porous modified polyethylene film obtained in step (3), and then vacuum-assisted pressing is performed to allow the adhesive to be impregnated in the pores of the porous modified polyethylene film, thus obtaining the optical tape with an extremely thin structure.

7. The preparation method according to claim 6, characterized in that, In step (1), the molten petrolatum oil is obtained by heating petrolatum oil to 80-120 °C and continuously stirring until the oil phase is completely clear and transparent; in the premixed powder, the amount of antioxidant added is 0.1-0.5% of the mass of the ultra-high molecular weight polyethylene powder, and the number average molecular weight of the ultra-high molecular weight polyethylene powder is 2.5 × 10⁻⁶. 6 -13×10 6 g / mol, wherein the antioxidant is antioxidant 1010 or resveratrol; the temperature for heat preservation and stirring is 100-170 ℃, the stirring speed is 200-500 rpm, and the stirring time is 1-3h; The pre-compression molding is carried out under a vacuum of 0.1-10 Pa, with a pressure of 5-15 MPa, a temperature of 130-190 ℃, and a time of 5-35 min.

8. The preparation method according to claim 6, characterized in that, In step (2), the folding and stretching process is performed as follows: First, a primary stretching treatment is carried out, that is, at 100-130 ℃ with a tensile strength of 0.2-2%·s. -1 The polyethylene sheet is subjected to bidirectional synchronous stretching at a stretching rate of 3-99 times. This is followed by 1-3 cycles of folding and hot pressing, where the initial stretched polyethylene sheet is folded along the centerline and hot-pressed at 5-10 MPa and 100-140 °C for 30-120 min. Finally, precision stretching is performed at 110-135 °C at a stretching rate of 0.2-2%·s. -1 Precision stretching is performed at a certain stretching rate.

9. The preparation method according to claim 6, characterized in that, In step (3), the concentration of the organic modifier in the modified solution is 0.1-5.0 wt%, and the solvent used in the modified solution is at least one of water, ethanol, acetone and ethyl acetate; the coating method is at least one of spraying, scraping and dipping coating, the coating time is within 10 s, and the coating temperature is 15-30 ℃; the heat treatment is carried out in a vacuum or forced-air oven at a temperature of 40-90 ℃ for a time of not less than 10 min. In step (4), the porous modified polyethylene film obtained in step (3) is laid flat on a polytetrafluoroethylene release film with a thickness of 20-40 μm, and then an adhesive is applied. After the coating is completed, another layer of polytetrafluoroethylene release film is covered to form a symmetrical stacked structure of release film-adhesive layer-porous modified polyethylene film-adhesive layer-release film; the vacuum-assisted pressing treatment is performed under UV light irradiation, 0.0001-1 Pa vacuum degree, and 10-30 MPa pressure for 10-30 min.

10. The use of an optical tape as described in any one of claims 1-5 or an optical tape prepared by any one of claims 6-9 in the encapsulation of optoelectronic devices.

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