Anti-static liquid as well as preparation method and application thereof

Abstract

The embodiment of the invention provides anti-static liquid as well as a preparation method and application thereof. The anti-static liquid comprises a conductive agent, a dispersing agent, a resin matrix, a compatilizer and a solvent, the conductive agent comprises a single-walled carbon nanotube and a multi-walled carbon nanotube; the dispersing agent comprises polyvinylpyrrolidone and polyethylene glycol; and the resin matrix comprises EVA resin. According to the anti-static liquid and the preparation method and application thereof provided by the embodiment of the invention, through component innovation (a carbon nanotube conductive network and an EVA resin matrix) and structural optimization (an anti-static layer and a heat sealing layer in a traditional cover tape are combined into a whole), the problems that the traditional cover tape is complex in structure, unstable in anti-static performance, high in cost and the like are solved; meanwhile, the mechanical strength and the process efficiency are improved, and the method is suitable for high-requirement scenes such as precise electronic element packaging.

Description

Technical Field

[0001] This application belongs to the technical field of antistatic liquids, and particularly relates to an antistatic liquid, a preparation method thereof, and an application thereof. Background Art

[0002] Cover tapes, usually known as "cover films" or "encapsulation cover tapes", are important materials used to protect components during the encapsulation process of electronic components. Cover tapes usually have a polyester or polypropylene film as the base layer, and are compounded or coated with different functional layers (antistatic layer, adhesive layer, etc.). They can be sealed on the surface of the carrier tape under external force or heating to form a closed space to protect the electronic components in the carrier tape pockets.

[0003] Existing cover tapes include a base material layer, an antistatic layer, and a heat-sealing layer, where the heat-sealing layer is used to bond with the carrier tape. However, in actual application, when the existing cover tape with such a layer structure is peeled off from the carrier tape, the antistatic performance of the antistatic layer is not good, and static electricity is easily generated, resulting in electronic components adhering to the cover tape and flying out. Summary of the Invention

[0004] In view of this, embodiments of this application provide an antistatic liquid, a preparation method thereof, and an application thereof to solve the technical problem that the antistatic performance of the antistatic layer of the existing cover tape is not good.

[0005] In a first aspect, embodiments of this application provide an antistatic liquid, including a conductive agent, a dispersant, a resin matrix, a compatibilizer, and a solvent;

[0006] The conductive agent includes single-walled carbon nanotubes and multi-walled carbon nanotubes;

[0007] The dispersant includes polyvinylpyrrolidone and polyethylene glycol;

[0008] The resin matrix includes EVA resin.

[0009] In some embodiments, in the conductive agent, the proportion of the single-walled carbon nanotubes is greater than or equal to 60%.

[0010] In some embodiments, the content of vinyl acetate in the EVA resin is 15% - 25%.

[0011] In some embodiments, the solid content of the EVA resin is 25% - 35%.

[0012] In some embodiments, the mass of the compatibilizer accounts for 1% - 3% of the mass of the resin matrix.

[0013] In a second aspect, embodiments of this application provide a method for preparing an antistatic liquid, including:

[0014] Provide a conductive agent, a dispersant, a resin matrix, a compatibilizer and a solvent, and divide the solvent into a first portion of the solvent and a second portion of the solvent;

[0015] Mix the conductive agent, the dispersant and the first portion of the solvent to obtain a carbon paste;

[0016] Mix the carbon paste with the resin matrix, the compatibilizer and the second portion of the solvent to obtain the antistatic liquid.

[0017] In some embodiments, the conductive agent includes single-walled carbon nanotubes and multi-walled carbon nanotubes, and the mass ratio of the single-walled carbon nanotubes is greater than or equal to 60%.

[0018] In some embodiments, the dispersant includes polyvinylpyrrolidone and polyethylene glycol, and the mass ratio of polyvinylpyrrolidone to polyethylene glycol is (1-3):1.

[0019] In some embodiments, the resin matrix includes EVA resin, and the mass of the compatibilizer accounts for 1%-3% of the mass of the EVA resin.

[0020] In some embodiments, the solvent includes water.

[0021] In some embodiments, the solid content of the antistatic liquid is 1%-3%.

[0022] In some embodiments, the solid content of the carbon paste is 0.5%-1.5%.

[0023] In some embodiments, the solid content of the resin matrix is 25%-35%.

[0024] In some embodiments, the preparation of the compatibilizer includes:

[0025] Provide 25-30 parts of isopropyl maleate, 100-120 parts of water, 13-17 parts of acrylic acid and 3-4 parts of ammonium persulfate;

[0026] Mix the isopropyl maleate and the water, heat up to 80°C-90°C, then add the acrylic acid and the ammonium persulfate, mix evenly and keep warm for reaction for 2h-3h to obtain the compatibilizer.

[0027] In some embodiments, the preparation of the isopropyl maleate includes:

[0028] Heat maleic anhydride to 65°C-70°C until it melts, then add isopropyl alcohol, continue to heat up to 80°C-85°C after the addition is completed, and keep warm for reaction for 1h-2h to obtain isopropyl maleate;

[0029] Wherein the molar ratio of maleic anhydride to isopropyl alcohol is (1-1.1):1.

[0030] In a third aspect, the embodiments of the present application provide an application of an antistatic liquid. The antistatic liquid described in the first aspect or the antistatic liquid prepared by the method described in the second aspect is applied to prepare an antistatic film layer in a cover tape.

[0031] The antistatic liquid, its preparation method and application provided by the embodiments of the present application. The antistatic liquid therein solves the problems of complex structure, unstable antistatic performance and high cost of traditional cover tapes through component innovation (carbon nanotube conductive network + EVA resin matrix) and structure optimization (combining the antistatic layer and the heat-sealing layer in the traditional cover tape into a double layer). At the same time, the mechanical strength and process efficiency are improved, which is applicable to high-demand scenarios such as the packaging of precision electronic components. Specifically, the antistatic performance is optimized. The traditional antistatic layer mostly uses surfactants or metal coatings, which are prone to failure due to wear or environmental humidity. Carbon nanotubes have a more stable antistatic performance through the bulk conduction mechanism and are not affected by humidity. Again, the heat-sealing performance and mechanical strength are taken into account. The EVA resin itself has excellent heat-sealing properties. After adding carbon nanotubes, its adhesion performance is not significantly affected. Instead, due to the strengthening effect of carbon nanotubes, the mechanical strength of the film (such as puncture resistance) is improved. In addition, the process compatibility is also improved. The single-layer structure avoids the problem of interlayer peeling that may occur in traditional multi-layer lamination, simplifies the coating process, and is applicable to high-speed roll-to-roll production. Finally, environmental protection and long-term effectiveness are also achieved. The traditional antistatic layer may rely on migratory antistatic agents (which need to continuously release chemical substances), while the carbon nanotube / EVA system is a permanent conductive material without chemical volatilization and is more environmentally friendly.

[0032] In the application, for the preparation method of the antistatic liquid therein, through a distributed mixing strategy, the dispersion efficiency and the uniformity of the conductive network are significantly improved. The conductive agent (single / multi-walled carbon nanotubes) is preferentially mixed with the dispersant and the first portion of the solvent. By using the synergistic effect of the dispersant (such as PVP and PEG), the carbon nanotubes are fully deagglomerated to form a highly dispersible carbon paste matrix. The carbon paste is secondarily mixed with the resin matrix (EVA), the compatibilizer and the second portion of the solvent to avoid the resin directly interfering with the dispersion of the conductive agent and ensure that the carbon nanotubes form a continuous and uniform conductive network in the final coating. The dispersion degree of the carbon nanotubes is increased, reducing the fluctuation of the conductive performance caused by local agglomeration; the conductive network is denser, the antistatic performance is more stable, and the dependence on the filler addition amount is reduced.

[0033] In applications, the application of the antistatic liquid provided by the embodiments of the present application has all the beneficial effects of the first aspect and the second aspect. First, it realizes the simplification of the structure and the reduction of costs. Traditional cover tapes need to separately prepare an antistatic layer (such as coating an antistatic agent) and a heat-sealing layer (such as an EVA layer), while the new solution combines the two into a single layer, reducing the production process and material costs. Second, it can effectively improve the antistatic performance of the cover tape, making it easier to peel the cover tape from the carrier tape and preventing components from flying out due to static electricity generation. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0035] Figure 1 It is a schematic flowchart of the preparation method of the antistatic liquid provided by the embodiments of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0036] In the following description, specific details such as specific system structures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the embodiments of the present application can also be implemented in other embodiments without these specific details. In other cases, the detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the embodiments of the present application.

[0037] It should also be understood that the term "and / or" used in the specification of the embodiments of the present application and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0038] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0039] It should be understood that the orientation or positional relationship indicated by terms such as "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the embodiments of the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation on the embodiments of the present application.

[0040] In addition, in the description of the specification and the appended claims of the embodiments of the present application, terms such as "first", "second", "third", etc. are only used for distinguishing descriptions and should not be construed as indicating or implying relative importance.

[0041] The reference to "some embodiments" or "some embodiments" etc. in the description of the embodiments of the present application means that a specific feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the embodiments of the present application. Thus, statements such as "in some embodiments", "in some embodiments", "in other some embodiments", "in still other some embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "comprising", "including", "having" and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways. "Plurality" means two or more.

[0042] It should be noted that the English abbreviations mentioned herein correspond to the following meanings:

[0043] CNT / CNTs - carbon nanotube, MWCNT - multi - walled carbon nanotube, SWCNT - single - walled carbon nanotube; EVA - ethylene - vinyl acetate copolymer; VA - vinyl acetate; PVP - polyvinylpyrrolidone; PEG - polyethylene glycol;

[0044] PET - polyethylene terephthalate, PE - polyethylene, PP - polypropylene, TPE - thermoplastic elastomer.

[0045] In the first aspect of the embodiments of the present application, an antistatic liquid is provided, which includes a conductive agent, a dispersant, a resin matrix, a compatibilizer, and a solvent;

[0046] The conductive agent includes single - walled carbon nanotubes and multi - walled carbon nanotubes;

[0047] The dispersant includes polyvinylpyrrolidone and polyethylene glycol;

[0048] The resin matrix includes EVA resin.

[0049] The antistatic liquid provided by the embodiments of the present application, through component innovation (carbon nanotube conductive network + EVA resin matrix) and structure optimization (combining the antistatic layer and heat-sealing layer in the traditional cover tape into a double layer), solves the problems of complex structure, unstable antistatic performance, and high cost of the traditional cover tape. At the same time, it improves the mechanical strength and process efficiency, and is applicable to high-demand scenarios such as the packaging of precision electronic components. Specifically, the antistatic performance is optimized. The traditional antistatic layer mostly uses surfactants or metal coatings, which are prone to failure due to wear or environmental humidity. Carbon nanotubes have a more stable antistatic performance through a bulk conduction mechanism and are not affected by humidity. Again, the heat-sealing performance and mechanical strength are taken into account. The EVA resin itself has excellent heat-sealing properties. After adding carbon nanotubes, its bonding performance is not significantly affected. Instead, due to the strengthening effect of carbon nanotubes, the mechanical strength of the film (such as puncture resistance) is improved. In addition, the process compatibility is also improved. The single-layer structure avoids the problem of interlayer peeling that may occur in traditional multi-layer lamination, simplifies the coating process, and is applicable to high-speed roll-to-roll production. Finally, environmental protection and long-term effectiveness are also achieved. The traditional antistatic layer may rely on migrating antistatic agents (which need to continuously release chemical substances), while the carbon nanotube / EVA system is a permanent conductive material without chemical volatilization and is more environmentally friendly.

[0050] In the application, the conductive agent includes single-walled carbon nanotubes and multi-walled carbon nanotubes. Among them, single-walled carbon nanotubes have high conductivity and high specific surface area, can form a conductive network at a low addition amount, and quickly conduct away static charges. Multi-walled carbon nanotubes have high mechanical strength and good dispersibility, provide structural support and assist single-walled carbon nanotubes to form a more stable conductive path. The combination of single-walled and multi-walled carbon nanotubes not only ensures high conductivity (the advantage of single-walled carbon nanotubes), but also enhances the toughness of the material through multi-walled carbon nanotubes to prevent the conductive network from breaking due to heat-sealing stress. In other embodiments, the conductive agent can also be carbon black, metal particles, etc. The dispersant (polyvinylpyrrolidone + polyethylene glycol), where polyvinylpyrrolidone adsorbs on the surface of carbon nanotubes through polar groups to prevent agglomeration and improve the dispersion uniformity. Polyethylene glycol reduces the viscosity of the system, assists in the dispersion of carbon nanotubes, and at the same time acts as a plasticizer to enhance the flexibility of the coating. The combined action of PVP and PEG realizes the high-stability dispersion of carbon nanotubes in the resin matrix, ensuring uniform and lasting antistatic performance. The EVA resin provides heat-sealing performance (the low-temperature hot-melt bonding characteristics of EVA), and at the same time serves as the carrier of the antistatic layer. The polar structure of EVA can be combined with the compatibilizer to enhance the interfacial bonding force with carbon nanotubes and prevent the conductive filler from falling off. The compatibilizer improves the interfacial compatibility between carbon nanotubes and EVA, prevents phase separation, and ensures the long-term stability of the conductive network and heat-sealing function. The solvent adjusts the viscosity of the antistatic liquid to facilitate the coating process and volatilizes without residue after drying. In a specific embodiment, the solvent is water.

[0051] In some embodiments, in the conductive agent, the proportion of single-walled carbon nanotubes is greater than or equal to 60%. That is, in the formulation of the conductive agent, at least 60% is single-walled carbon nanotubes and at most 40% is multi-walled carbon nanotubes. Of course, carbon black, metal particles, etc. can also be present in the conductive agent. In specific applications, the mass proportion of single-walled carbon nanotubes in all the conductive agent can be 60%, 65%, 70%, 80%, 90%, etc. In applications, single-walled carbon nanotubes have a higher aspect ratio and specific surface area (the diameter of single-walled tubes is about 1 - 2 nm, and that of multi-walled tubes is about 5 - 20 nm), and can form a continuous conductive network throughout the material at a lower addition amount. The carrier mobility of single-walled tubes (about 10 4 cm 2 / V·s) is significantly higher than that of multi-walled tubes (about 10 2 cm 2 / V·s), providing a more efficient charge conduction path. When the proportion of SWCNT ≥ 60%, the conductive network is dominated by single-walled tubes, and the antistatic performance (surface resistivity) can be reduced by 1 - 2 orders of magnitude, especially suitable for the encapsulation of high-end electronic components sensitive to static electricity. Although the conductivity of multi-walled carbon nanotubes is slightly lower, their multi-layer structure endows higher mechanical strength and bending resistance. In a system dominated by SWCNT (≥ 60%), MWCNT (≤ 40%) can act as a "bridge" and "supporting framework" to prevent the fracture of single-walled tubes caused by excessive bending or thermal stress. The tensile strength of the antistatic film layer can be increased by 20% - 30%, avoiding the damage of the conductive network caused by stress concentration during heat sealing or transportation, and ensuring the long-term stability of the antistatic performance.

[0052] In applications, the flexible structure of single-walled tubes has less interference with the fluidity of EVA resin and will not significantly increase the melt viscosity during the heat-sealing process. The heat-sealing strength retention rate ≥ 95%, and there is no weak bonding problem caused by the aggregation of conductive agents at the sealing interface, ensuring the reliability of the adhesion between the cover tape and the carrier tape. In addition, considering cost, the production cost of single-walled carbon nanotubes is usually higher than that of multi-walled tubes, but through the optimized design with a proportion ≥ 60%, the total amount of conductive agent used can be reduced.

[0053] In addition, when the antistatic liquid is used on the cover tape, since the cover tape has certain requirements for transparency, a compatibilizer is used alone to disperse single-walled carbon nanotubes and multi-walled carbon nanotubes, making it easier for EVA resin to be mixed uniformly with single-walled carbon nanotubes, improving the transparency while enhancing the uniformity.

[0054] In applications, due to the easy agglomeration of carbon nanotubes by van der Waals forces, resulting in uneven dispersion and unstable conductivity; therefore, a dual-mechanism dispersion is carried out through a dispersant, greatly improving the dispersion of carbon nanotubes. Among them, PVP (chemical adsorption) and PEG (physical steric hindrance) are complementary to form a double protective layer to achieve long-term stable dispersion of CNTs; PVP increases the viscosity of the system to prevent sedimentation, and PEG moderately reduces the viscosity for easy coating, and the balance between the two realizes the fluidity under high solid content.

[0055] In applications, the pyrrolidone ring of polyvinylpyrrolidone (PVP) in the dispersant undergoes π-π conjugate adsorption on the surface of CNTs to form a coating layer, reducing the surface energy and inhibiting the agglomeration of carbon nanotubes. In this way, the dispersion efficiency of CNTs in water can be effectively improved, the sedimentation rate of CNTs can be reduced, and the storage period of the antistatic liquid can be extended. The mechanism of action of polyethylene glycol is that long-chain PEG molecules are adsorbed on the surface of CNTs, and re-agglomeration is prevented through physical space isolation. The hydrophilicity of PEG enhances the compatibility between CNTs and the aqueous system and reduces the interfacial tension. In this way, the dispersion stability of CNTs is maintained during dynamic shear (such as the coating process), and it synergistically reduces the viscosity of the dispersion system with PVP to improve the coating uniformity.

[0056] In applications, EVA resin is used as the resin matrix. Optionally, polyolefin elastomers, thermoplastic polyurethanes, ethylene-methyl acrylate, polybutylene succinate, styrene-butadiene block copolymers, etc. can also be used. Among them, the vinyl acetate content of EVA resin is adjustable. The higher the VA content, the lower the melting temperature and the better the flexibility. During the heat sealing process (80 - 120 °C), EVA can be quickly melted and adhered to the surface of the carrier tape to form a firm and uniform sealing interface. The heat sealing strength is high and the process window is wide, which is suitable for high-speed automated packaging production lines. The amorphous region in the EVA molecular chain endows the material with high elasticity, making the coated film not easy to crack when bent or folded, meeting the packaging requirements of flexible electronic components. The polarity of EVA (from the acetate group) can form hydrogen bonds or van der Waals forces with the surface of carbon nanotubes through a compatibilizer (such as maleic anhydride graft) to reduce the agglomeration of the conductive agent and ensure the uniform distribution of the conductive network. The melting viscosity of EVA is low, which is easy to mix with solvents and coat into films. After drying, the surface is flat and defect-free, suitable for roll-to-roll continuous production processes. EVA is a mature industrial material with a moderate price, and its performance can be optimized by adjusting the VA content, with high cost performance; at the same time, it does not contain harmful substances such as halogens and meets the environmental protection requirements of electronic packaging.

[0057] In some embodiments, the content of vinyl acetate in the EVA resin is 15% - 25%. In a specific embodiment, the content of vinyl acetate in the EVA resin can be any value within the range of 15% - 25%, such as 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%. The higher the VA content, the lower the crystallinity of the EVA resin, and the melting temperature (Tm) and heat-sealing start temperature (Ts) also decrease accordingly. When the VA content is 15% - 25%, the heat-sealing temperature range of EVA is usually 80 - 120 °C, which matches well with the heat distortion temperature of the cover tape material (such as PC, PET), and can achieve fast and firm heat-sealing bonding. Increasing the VA content will improve the flexibility of EVA (reduce the elastic modulus), but excessive (>25%) will cause the material to be too soft and the mechanical strength to decline. When the VA content is 15% - 25%, the EVA resin has both good flexibility and moderate mechanical strength, and the coated film is not easy to crack when bent or stretched, and can withstand a certain amount of mechanical stress. The higher the VA content, the stronger the polarity of the EVA resin (the increase of acetate groups), and the stronger the interaction with the surface of carbon nanotubes (such as hydrogen bonds, van der Waals forces). When the VA content is 15% - 25%, the polarity of EVA is moderate, which can form a stable bond with the conductive agent, and will not cause the dispersant to fail or limit the solvent selection due to excessive polarity.

[0058] In some embodiments, the solid content of the EVA resin is 25% - 35%. In a preferred embodiment, the solid content of the EVA resin is 30%. In other embodiments, the solid content of the EVA resin can also be any value within the range of 25% - 35%, such as 25%, 26%, 28%, 30%, 32%, 35%. Relationship between the solid content and mechanical strength: When the solid content of the EVA resin is too low, that is, the resin matrix is insufficient, the mechanical strength of the coating is low and it is easy to crack or peel off; if there is too much resin matrix, it may lead to a decrease in flexibility and affect the heat-sealing performance. When the solid content of the EVA resin is 25% - 35%, especially when the solid content is 30%, the ratio of the resin matrix to the conductive agent is moderate, and the coating has both good mechanical strength (tensile resistance, puncture resistance) and flexibility; the heat-sealing performance is excellent, and the sealing interface is firm and uniform. In addition, when the resin matrix is not enough to wrap the conductive agent, it will cause the conductive network to be easily broken; while too much resin matrix may hinder the contact between the conductive agents and reduce the conductive efficiency. When the solid content of the EVA resin is 25% - 35%, especially when the solid content is 30%, the ratio of the resin matrix to the conductive agent is the best, the conductive network is continuous and stable; the antistatic performance is excellent, and the surface resistivity can be controlled within the range of 10 6 -10 8 Ω / sq.

[0059] In some embodiments, the mass of the compatibilizer accounts for 1% - 3% of the mass of the resin matrix. Limiting the addition amount of the compatibilizer to 1% - 3% of the mass of the resin matrix has the following core purposes: achieving stable binding between carbon nanotubes and the resin with the lowest dosage; avoiding waste of resources caused by excessive additives; maintaining the heat sealability, fluidity, and coating mechanical strength of the resin matrix; and adapting to high-speed coating production lines to improve production efficiency.

[0060] In applications, the compatibilizer is used to improve the interfacial bonding between different materials, especially between the resin matrix and the conductive agent (such as carbon nanotubes). If the amount of the compatibilizer is too small, it may not effectively promote the bonding between the two, resulting in uneven dispersion or an unstable conductive network; if too much, it may affect other properties of the material, such as mechanical strength or heat sealability. The compatibilizer (such as maleic anhydride grafted product, silane coupling agent) binds to the surface of carbon nanotubes through polar groups and tangles with the EVA resin through non-polar segments to form a "bridging" effect. When the addition amount is 1% - 3%, the compatibilizer is sufficient to cover the active sites on the surface of carbon nanotubes but will not cause excessive entanglement of molecular chains due to excess. The stability of the conductive network is improved, reducing the risk of carbon nanotubes detaching from the resin matrix due to thermal stress or mechanical stress; the antistatic performance is persistent, and the resistivity fluctuation range is reduced after long-term use.

[0061] The embodiment of the present application also provides a preparation method of an antistatic liquid, as Figure 1 shown, including:

[0062] S10. Provide a conductive agent, a dispersant, a resin matrix, a compatibilizer, and a solvent, and divide the solvent into a first portion of the solvent and a second portion of the solvent;

[0063] S20. Mix the conductive agent, the dispersant, and the first portion of the solvent evenly to obtain a carbon paste;

[0064] S30. Mix the carbon paste with the resin matrix, the compatibilizer, and the second portion of the solvent to obtain an antistatic liquid.

[0065] This method solves the problem of carbon nanotube dispersion specifically through a step-by-step solvent mixing strategy, improves the conductive performance; optimizes the process compatibility and adapts to high-speed coating production lines; realizes large-scale preparation of antistatic liquid with low cost and high stability, and is particularly suitable for high-requirement scenarios such as precision electronic packaging cover tapes.

[0066] In the application, in step S10, by dividing the solvent into two parts and regulating the solvent in stages, for the first part of the solvent (carbon paste stage), a solvent with a low boiling point or a well-matched polarity is selected to promote the full interaction between the dispersant and the carbon nanotubes, while reducing the subsequent volatilization residue. For the second part of the solvent (overall mixing stage): adjust the solvent ratio or type to adapt to the dissolution characteristics of the resin matrix (EVA), and avoid the precipitation of the resin or the decline in compatibility caused by solvent conflict. Prevent the premature curing or crystallization of the resin matrix due to solvent incompatibility, and ensure the film-forming quality of the heat-sealing layer; reduce the weak bonding problem at the interface between the carbon nanotubes and the resin caused by solvent residue, and improve the mechanical strength of the coating.

[0067] In the application, in steps S20 and S30, first mix the conductive agent (single / multi-walled carbon nanotubes) with the dispersant and the first part of the solvent preferentially. Utilize the synergistic effect of the dispersant (such as PVP and PEG) to fully deagglomerate the carbon nanotubes and form a highly dispersible carbon paste matrix. Then, the carbon paste is mixed with the resin matrix (EVA), the compatibilizer, and the second part of the solvent for the second time, avoiding the direct interference of the resin with the dispersion of the conductive agent, and ensuring that the carbon nanotubes form a continuous and uniform conductive network in the final coating. The dispersion degree of the carbon nanotubes is improved, reducing the fluctuation of the conductive performance caused by local agglomeration; the conductive network is denser, the antistatic performance is more stable, and the dependence on the filler addition amount is reduced.

[0068] In some embodiments, the conductive agent includes single-walled carbon nanotubes and multi-walled carbon nanotubes, and the mass ratio of the single-walled carbon nanotubes is greater than or equal to 60%. Due to the large specific surface area and high surface energy of single-walled carbon nanotubes, they are prone to agglomeration (such as the bundle-like aggregation caused by van der Waals forces). In traditional processes, high shear force or long-time grinding is required. Through the step-by-step mixing process (first preparing the carbon paste) and the synergistic effect of the dispersant (PVP + PEG), the SWCNT is preferentially dispersed to ensure its uniform distribution even at a high proportion. The dispersion time is shortened by 30% - 50%, and the local insulation defects of the coating caused by agglomeration are avoided, significantly improving the production yield.

[0069] In some embodiments, the dispersant includes polyvinylpyrrolidone and polyethylene glycol, and the mass ratio of polyvinylpyrrolidone to polyethylene glycol is (1-3):1. In specific embodiments, the mass ratio of PVP to PEG can also be any ratio within the range of (1-3):1, such as 1:1, 2:1, 3:1, 3:2, etc. Due to the different dispersion mechanisms of PVP and PEG for CNTs (PVP is chemisorption, while PEG is steric hindrance at the physical level), the different ratios of the two also reflect the balance between adsorption coverage and steric hindrance. When PVP and PEG are equal in amount, the adsorption coverage and steric hindrance effects are balanced, which is suitable for low CNT concentrations. When the proportion of PVP increases, chemisorption and charge repulsion are strengthened, which is suitable for high CNT loading to make up for the deficiency of the steric hindrance of PEG. When PVP is dominant, the adsorption layer is denser and the short-term dispersion efficiency is high, but excessive PVP may cause an increase in viscosity due to molecular chain entanglement, affecting the coating uniformity. With the assistance of PEG, the steric hindrance is enhanced, and the long-term stability of the dispersion system is better (no sedimentation after standing for 6 months), but a higher amount of PEG may be required, which may sacrifice conductivity.

[0070] On the other hand, it is also reflected in the compatibility with the resin matrix. When the proportion of PVP is high, the polar groups of PVP form hydrogen bonds with the -NHCOO- groups of the polyurethane resin, enhancing the interfacial adhesion, but excessive PVP may hinder resin crosslinking. When the proportion of PEG is low, the hydrophilicity influence of PEG is reduced, avoiding the resistivity fluctuation of the film layer due to moisture absorption.

[0071] In some embodiments, the resin matrix includes EVA resin, and the mass of the compatibilizer accounts for 1%-3% of the mass of the EVA resin. In the step-by-step mixing method (first preparing the carbon paste), 1%-3% of the compatibilizer can preferentially bind to the carbon nanotubes, improving its dispersion efficiency in the resin; an excessive amount of the compatibilizer added may interfere with the action of the dispersant (such as PVP, PEG), resulting in an extended dispersion time. When the amount of the compatibilizer added is 1%-3%, the interface between the carbon nanotubes and the resin binds tightly, reducing the risk of delamination caused by sedimentation or phase separation during storage.

[0072] In some embodiments, the solvent includes water. In other embodiments, it can also be an organic solvent such as toluene, xylene, ethyl acetate, tetrahydrofuran, etc. The aqueous EVA resin system is environmentally friendly and does not produce toxic substances.

[0073] In some embodiments, the solid content of the antistatic liquid is 1% to 3%. In specific embodiments, the solid content of the antistatic liquid can be 1%, 1.5%, 2%, 2.5%, 3%, etc. The antistatic function is achieved with the lowest effective solid loading while reducing the material and energy consumption costs. Dilution and mixing of carbon paste and resin: After mixing carbon paste (0.5% to 1.5%) and resin matrix (25% to 35%) in proportion, the total solid content is diluted to 1% to 3%, ensuring that the proportion of the conductive agent in the final coating is 0.02% to 0.1% (sufficient to form a percolation network); the low solid content reduces the total amount of solvent volatilization, and the drying energy consumption is reduced by 30% to 40%.

[0074] In some embodiments, the solid content of the carbon paste is 0.5% to 1.5%. In specific embodiments, the solid content of the carbon paste can be 0.5%, 0.8%, 1.0%, 1.2%, 1.5%, etc. When the solid content of the carbon paste is 0.5% to 1.5%, the dispersion efficiency of carbon nanotubes is maximized, ensuring that the conductive agent (carbon nanotubes) is fully deagglomerated to form a uniformly dispersed precursor of the conductive network. Advantages of low solid content: The solvent proportion is high, the system viscosity is low, and dispersants (such as PVP, PEG) are more easily adsorbed on the surface of carbon tubes, reducing the shear force requirement; the solid content of 0.5% to 1.5% corresponds to an actual proportion of carbon tubes of about 0.1% to 0.3% (assuming that carbon tubes account for 20% of the solid content), avoiding secondary agglomeration caused by van der Waals forces at high concentrations.

[0075] In some embodiments, the solid content of the resin matrix is 25% to 35%. Controlling the solid content of the EVA resin at 25% to 35% and setting it to 30% in the preferred embodiment can optimize the coating quality, ensure a flat surface, uniform thickness, and no defects; improve the processing efficiency, be suitable for high-speed continuous production, and reduce energy consumption; balance the mechanical properties, have both strength and flexibility to meet the heat-sealing requirements; control costs, with moderate material usage and high cost performance; and stabilize the conductive performance, with a continuous and efficient conductive network and excellent antistatic performance.

[0076] In some embodiments, the preparation of the compatibilizer includes:

[0077] Providing 25 to 30 parts of isopropyl maleate, 100 to 120 parts of water, 13 to 17 parts of acrylic acid, and 3 to 4 parts of ammonium persulfate;

[0078] Mixing isopropyl maleate and water, heating to 80°C to 90°C, then adding acrylic acid and ammonium persulfate, and keeping the mixture warm for reaction for 2h to 3h to obtain the compatibilizer.

[0079] In the application, isopropyl maleate (containing a double bond) copolymerizes with acrylic acid free radicals to form a polar copolymer containing ester groups and carboxylic acid groups. The structural schematic is: -[-CH2-CH(COOR)-CH2-CH(COOH)-]- (R is isopropyl). Among them, acrylic acid accounts for a higher proportion, introducing more carboxylic acid groups and enhancing the polar compatibility with EVA resin; isopropyl maleate provides long-chain ester groups to improve the hydrophobic interfacial binding with carbon nanotubes. The initiator (3-4 parts of ammonium persulfate), ammonium persulfate decomposes into sulfate radicals at 80-90 °C, efficiently initiating copolymerization; the addition amount is adapted to the total amount of monomers to ensure an appropriate molecular weight and avoid crosslinking or branching. The reaction conditions are (80-90 °C, 2-3 h). The temperature matches the half-life of the initiator to ensure complete reaction (monomer conversion rate > 95%); water is used as the solvent, which is environmentally friendly and low-cost, but the pH needs to be controlled to prevent hydrolysis of the ester group.

[0080] In some embodiments, the preparation of isopropyl maleate includes:

[0081] Heat maleic anhydride to 65 °C - 70 °C until it melts, then add isopropyl alcohol. After the addition is completed, continue to heat up to 80 °C - 85 °C and keep the reaction for 1 h - 2 h to obtain isopropyl maleate;

[0082] Among them, the molar ratio of maleic anhydride to isopropyl alcohol is (1 - 1.1):1. In specific embodiments, the molar ratio of maleic anhydride to isopropyl alcohol can be 1:1, 1.05:1, 1.1:1, etc.

[0083] In the application, the synthesis reaction equation of isopropyl maleate is: maleic anhydride + isopropyl alcohol → isopropyl maleate. Maleic anhydride is slightly in excess to ensure complete reaction of isopropyl alcohol, reduce the residue of unreacted alcohol, and avoid interference of alcohol with the initiator efficiency in subsequent polymerization. Temperature control (65 - 70 °C melting → 80 - 85 °C reaction). After maleic anhydride melts, its fluidity increases, which is beneficial for homogeneous mixing with isopropyl alcohol; heating up to 80 - 85 °C promotes the esterification reaction, and no additional catalyst is required (the acidic self-catalysis of maleic anhydride). The reaction time is (1 - 2 h) to ensure that the conversion rate of the esterification reaction > 90%, and balance the reaction rate and energy consumption. Isopropyl maleate contains ester groups and unreacted anhydride groups (if it is a monoester), which can participate in subsequent copolymerization or interact with resins / carbon nanotubes.

[0084] In applications, the above method synthesizes isopropyl maleate step by step and further copolymerizes to prepare a compatibilizer, achieving precise matching of the interfacial properties between the resin and the conductive agent; chemically anchoring enhances the interfacial bonding and prevents the failure of the conductive network; the aqueous-phase reaction is environmentally friendly and low-cost. The synthesis of isopropyl maleate: customizes the monomer structure and introduces reactive sites; the copolymerization reaction regulates the polarity of the copolymer to meet the interfacial requirements of the resin-carbon nanotube. Controlling the monomer ratio balances the hydrophilic / hydrophobic property of the copolymer and optimizes the adhesion to different interfaces; the dosage of the initiator matches the reaction time to avoid too high (difficult to disperse) or too low (weak interfacial bonding) molecular weight; water is used as the solvent to avoid the use of organic solvents and reduce the emission of VOCs.

[0085] The embodiment of the present application also provides an application of the antistatic liquid. The antistatic liquid described in the first aspect or the antistatic liquid prepared by the method described in the second aspect is applied to prepare the antistatic film layer in the cover tape.

[0086] In applications, a cover tape is provided. The cover tape includes a substrate layer and an antistatic film layer provided on one side of the substrate layer, wherein the antistatic film layer is prepared by using the antistatic liquid described in the first aspect or the antistatic liquid prepared by the method described in the second aspect.

[0087] The application of the antistatic liquid provided by the embodiment of the present application realizes the simplification of the structure and the reduction of the cost. The traditional cover tape needs to separately prepare an antistatic layer (such as coating an antistatic agent) and a heat-sealing layer (such as an EVA layer), while the new solution combines the two into a single layer, reducing the production process and material cost. Secondly, it can effectively improve the antistatic performance of the cover tape, making it easier to peel off the carrier tape, and preventing the components from flying out due to static electricity.

[0088] Embodiment

[0089] Embodiment 1

[0090] The embodiment of the present application also provides a preparation method of the antistatic liquid, including:

[0091] S10. Provide 6 g of single-walled carbon nanotubes and 4 g of multi-walled carbon nanotubes as conductive agents, 7.5 g of PVP and 2.5 g of PEG as dispersants, 133 g of EVA resin, 2.66 g of compatibilizer, and 3070 g of water as a solvent. Divide 3070 g of water into 1980 g and 1090 g.

[0092] S20. Mix 6 g of single-walled carbon nanotubes, 4 g of multi-walled carbon nanotubes, 7.5 g of PVP, 2.5 g of PEG, and 1980 g of water to obtain a carbon paste, wherein the solid content of the carbon paste is 1%.

[0093] S30. Mix the carbon paste in step S20 with 133 g of EVA resin, 2.66 g of compatibilizer, and 1090 g of water to obtain an antistatic liquid. After obtaining the antistatic liquid, evaporate some water to adjust the solid content of the antistatic liquid to 2%.

[0094] Table 1 Weight and solid content ratio relationship of each component in Example 1

[0095] Item Total Mass Solid Content Proportion of Solid Content Conductive Agent 10g 10g 100％ Dispersant 10g 10g 100％ Carbon Paste 2000g 20g 1％ EVA Resin 133g 40g 30％ Compatibilizer 2.66g 2.66g 100％ Antistatic Liquid 3133g 62.66g 2％

[0096] Among them, the conductive agent (6 g of single-walled carbon nanotubes, 4 g of multi-walled carbon nanotubes); the mass ratio of the solid content of the carbon paste to the solid content of the main resin is 1:2; in the combined dispersant, the mass ratio of PVP to PEG is 3:1.

[0097] Among them, in step S10, the preparation of the compatibilizer includes:

[0098] Heat 25 g of maleic anhydride to 65 °C until it melts, then add 25 g of isopropanol. After the addition is completed, continue to heat up to 80 °C and keep the temperature for reaction for 1 h to obtain 25 g of isopropyl maleate;

[0099] Mix 25 g of isopropyl maleate and 100 g of water, heat up to 80 °C, then add 13 g of acrylic acid and 3 g of ammonium persulfate. After mixing evenly, keep the temperature for reaction for 2 h to obtain the compatibilizer.

[0100] Example 2

[0101] This application example is basically the same as Example 1, except that the usage amounts of each component are different, as shown in the following table:

[0102] Table 2 Weight and solid content ratio relationship of each component in Example 2

[0103] Item Total Mass Solid Content Proportion of Solid Content Conductive Agent 6g 6g 100％ Dispersant 6g 6g 100％ Carbon Paste 2400g 12g 0.5％ EVA Resin 96g 24g 25％ Compatibilizer 2.88g 2.88g 100％ Antistatic Liquid 1944g 38.88 2％

[0104] Among them, the conductive agent (5 g of single-walled carbon nanotubes, 1 g of multi-walled carbon nanotubes); the mass ratio of the solid content of the carbon paste to the solid content of the main resin is 1:2; in the combined dispersant, the mass ratio of PVP to PEG is 3:1. After obtaining the antistatic liquid, evaporate some water to adjust the solid content of the antistatic liquid to 2%. Example 3

[0105] This application example is basically the same as Example 1, except that the usage amounts of each component are different, as shown in the following table:

[0106] Table 3 Weight and solid content ratio relationship of each component in Example 3

[0107] Item Total Mass Solid Content Proportion of Solid Content Conductive Agent 5g 5g 100％ Dispersant 5g 5g 100％ Carbon Paste 666.67g 10g 1.5％ EVA Resin 85.7g 30g 35％ Compatibilizer 0.86g 0.86g 100％ Antistatic Liquid 2043g 40.86g 2％

[0108] Among them, the conductive agent (5 g of single-walled carbon nanotubes); the mass ratio of the solid content of the carbon paste to the solid content of the main resin is 1:3; in the combined dispersant, the mass ratio of PVP to PEG is 3:1. After obtaining the antistatic liquid, part of the water needs to be evaporated to adjust the solid content of the antistatic liquid to 2%.

[0109] Example 4

[0110] The difference from Example 1 is that the mass ratio of single-walled carbon nanotubes to multi-walled carbon nanotubes in the conductive agent is 1:4.

[0111] Comparative Example 1

[0112] The difference from Example 1 is that metal particles are used as the conductive agent.

[0113] Performance Test

[0114] The following tests were carried out on the antistatic liquids obtained from the above examples and comparative examples, and the antistatic film layers on the covers prepared using the above antistatic liquids were tested. Single-sided knife coating (100-μm knife coating), drying in an oven, and the dry film thickness is 8-10 μm. The specific tests include:

[0115] 1. Determination of storage stability: A certain amount of the antistatic liquid was placed in a centrifuge tube and put into a centrifuge. Under the conditions of a temperature of 25 °C and a rotation speed of 3000 r / min, centrifugation was carried out for 15 min. The state of the dispersion was observed to evaluate its stability. If there is no stratification or precipitation, it can be considered stable when placed at room temperature for 6 months.

[0116] 2. Viscosity determination: The viscosity of the antistatic liquid was measured using a digital viscometer. The test was carried out at 25 °C and a rotor speed of 100 rpm.

[0117] 3. T-peel strength determination: A peel tester was used to determine the T-peel strength of the carbon nanotube antistatic film on the substrate. The test temperature was 23 ± 2 °C, and the relative humidity was 50 ± 5%. The instrument was set at a peel speed of 300 mm / min and a peel angle of 180°.

[0118] Table 4 Test Results

[0119] Item Storage Stability Viscosity T-Peel Strength Example 1 No Stratification or Precipitation within Half a Year 150 mPa.s 25 N / m Example 2 No Stratification or Precipitation within Half a Year 120 mPa.s 22 N / m Example 3 No Stratification or Precipitation within Half a Year 100 mPa.s 25 N / m Example 4 No Stratification or Precipitation within Half a Year 70 mPa.s 15 N / m Comparative Example 1 Precipitation Appeared after Five Months 50 mPa.s 5 N / m

[0120] In the above examples, the descriptions of each example have their own focuses. For the parts not detailed or recorded in a certain example, the relevant descriptions of other examples can be referred to.

[0121] The above-described embodiments are only used to illustrate the technical solutions of the embodiments of the present application, rather than limiting them; although the embodiments of the present application have been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the embodiments of the present application.

Claims

1. An antistatic liquid, characterized in that, It includes a conductive agent, a dispersant, a resin matrix, a compatibilizer and a solvent; The conductive agent includes single-walled carbon nanotubes and multi-walled carbon nanotubes; The dispersant includes polyvinylpyrrolidone and polyethylene glycol; The resin matrix includes EVA resin.

2. The antistatic liquid according to claim 1, wherein In the conductive agent, the proportion of the single-walled carbon nanotubes is greater than or equal to 60%.

3. The antistatic liquid according to claim 1, wherein The content of vinyl acetate in the EVA resin is 15% - 25%; And / or, the solid content of the EVA resin is 25% - 35%.

4. The antistatic liquid according to claim 1, characterized in that, The mass of the compatibilizer accounts for 1% - 3% of the mass of the resin matrix.

5. A method for preparing an antistatic liquid, characterized in that, It includes: Providing a conductive agent, a dispersant, a resin matrix, a compatibilizer and a solvent, and dividing the solvent into a first portion of solvent and a second portion of solvent; Mixing the conductive agent, the dispersant and the first portion of solvent evenly to obtain a carbon paste; Mixing the carbon paste with the resin matrix, the compatibilizer and the second portion of solvent to obtain the antistatic liquid.

6. The preparation method according to claim 5, wherein The conductive agent includes single-walled carbon nanotubes and multi-walled carbon nanotubes, and the mass proportion of the single-walled carbon nanotubes is greater than or equal to 60%; And / or, the dispersant includes polyvinylpyrrolidone and polyethylene glycol, and the mass ratio of polyvinylpyrrolidone to polyethylene glycol is (1 - 3):1; And / or, the resin matrix includes EVA resin, and the mass of the compatibilizer accounts for 1% - 3% of the mass of the EVA resin; And / or, the solvent includes water.

7. The preparation method according to claim 5, characterized in that, The solid content of the antistatic liquid is 1% - 3%; And / or, the solid content of the carbon paste is 0.5% - 1.5%; And / or, the solid content of the resin matrix is 25% - 35%.

8. The preparation method according to any one of claims 5 to 7, characterized in that, The preparation of the compatibilizer includes: Providing 25 - 30 parts of isopropyl maleate, 100 - 120 parts of water, 13 - 17 parts of acrylic acid and 3 - 4 parts of ammonium persulfate; Mixing the isopropyl maleate and the water, heating to 80°C - 90°C, then adding the acrylic acid and the ammonium persulfate, mixing evenly and keeping warm for reaction for 2h - 3h to obtain the compatibilizer.

9. The preparation method according to claim 8, characterized in that, The preparation of the isopropyl maleate includes: Heating maleic anhydride to 65°C - 70°C until it melts, then adding isopropanol, and continuing to heat to 80°C - 85°C after the addition is completed, and keeping warm for reaction for 1h - 2h to obtain isopropyl maleate; Wherein the molar ratio of maleic anhydride to isopropanol is (1 - 1.1):

1.

10. Application of an antistatic liquid, characterized in that, Applying the antistatic liquid according to any one of claims 1 - 4, or the antistatic liquid prepared by the method according to any one of claims 5 - 9 to prepare an antistatic film layer in a cover tape.

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