A polyurethane for ACF film and its preparation method and application

Abstract

The present invention discloses a polyurethane for ACF adhesive film, comprising the following raw materials in parts by weight: 80-100 parts of polytetramethylene ether glycol, 60-80 parts of modified isocyanate, 8-10 parts of chain extender, 1-3 parts of catalyst, and 40-80 parts of solvent; the modified isocyanate is prepared using 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol, and 1,5-naphthalene diisocyanate as raw materials. The present invention provides a polyurethane for ACF adhesive film, improves its stability and reliability under high temperature and high humidity environments, and is applied to ACF adhesive film, which can meet the needs of high-end application fields such as ACF adhesive film and has broad market prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of anisotropic conductive films, and in particular relates to a polyurethane for an anisotropic conductive film and a preparation method and application thereof. Background Art

[0002] Polyurethane has been widely used in numerous fields due to its excellent mechanical properties, resistance to wear, oil, tear, chemical corrosion, radiation, and good adhesion. However, polyurethane has a significant shortcoming in its resistance to high temperatures and high humidity. Its high-temperature resistance generally does not exceed 80°C. Above 100°C, the material softens and deforms, significantly weakening its mechanical properties. Its short-term operating temperature should not exceed 120°C. This characteristic severely limits its application in high-temperature and high-humidity environments, particularly in ACF films.

[0003] ACF film, or anisotropic conductive film, mainly consists of two parts: a resin adhesive and conductive particles. It is a key material widely used in the field of electronic packaging. In terms of high-temperature resistance, ACF film needs to remain stable during high-temperature welding or curing processes to ensure connection reliability. However, when the temperature exceeds the temperature limit of the ACF film, the conductive particles may diffuse, melt, or migrate, resulting in a decrease in or even loss of conductivity. This seriously affects the application of ACF film in high-temperature environments. At the same time, in high-humidity environments, the ACF film may undergo chemical reactions such as hydrolysis or oxidation, resulting in a decrease in or complete loss of conductive properties. This moisture sensitivity issue not only affects the reliability of the ACF film, but can also cause electronic products to fail in humid environments. However, existing polyurethane materials are prone to performance degradation in high-temperature and high-humidity environments, such as softening, deformation, and decreased adhesion. Therefore, the application of existing polyurethane materials in ACF film affects the conductive performance and reliability of the ACF film. Summary of the Invention

[0004] The purpose of the present invention is to overcome the problem of poor high temperature and high humidity resistance of polyurethane in the prior art, and to provide a polyurethane for ACF film to improve its stability and reliability in high temperature and high humidity environments, thereby meeting the needs of high-end application fields such as ACF film.

[0005] In order to achieve the above technical objectives and the above technical effects, the present invention is implemented through the following technical solutions:

[0006] In a first aspect, the present invention provides a polyurethane for an ACF film, comprising the following raw materials in parts by weight: 80-100 parts of polytetramethylene ether glycol, 60-80 parts of modified isocyanate, 8-10 parts of a chain extender, 1-3 parts of a catalyst, and 40-80 parts of a solvent;

[0007] The modified isocyanate is prepared by using 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol and 1,5-naphthalene diisocyanate as raw materials.

[0008] Furthermore, the preparation method of the modified isocyanate comprises the following steps:

[0009] S1. Add 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol, and benzophenone to toluene, mix uniformly, irradiate under ultraviolet light for 1-3 hours, concentrate under reduced pressure, wash, and recrystallize to obtain an intermediate;

[0010] S2. Add 1,5-naphthalene diisocyanate to toluene and dissolve it by ultrasonication. Then add the intermediate and stannous octoate, mix them evenly, degas in vacuum, and heat the mixture programmatically. After the reaction is completed, concentrate under reduced pressure, filter, wash and dry to obtain modified isocyanate.

[0011] Furthermore, in step S1, the ratio of the amount of 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol, benzophenone, and toluene is (2.4-2.5) g: (4.5-4.8) g: (0.05-0.1) g: 100 mL.

[0012] Furthermore, in step S2, the ratio of the amount of the intermediate, 1,5-naphthalene diisocyanate, stannous octoate, and toluene is (7.1-7.5) g: (6.3-6.5) g: (0.05-0.1) g: 100 mL.

[0013] Furthermore, in step S2, the programmed temperature rising process is:

[0014] Raise the temperature from room temperature to 30°C and keep at 30°C for 3h;

[0015] Raise the temperature from 30°C to 60°C and keep at 60°C for 0.5-1.5h;

[0016] Raise the temperature from 60°C to 80°C and keep at 80°C for 4-6 hours;

[0017] Raise the temperature from 80°C to 100°C and keep at 100°C for 0.5-5h;

[0018] Raise the temperature from 100℃ to 120℃ and keep at 120℃ for 0.5-1.5h.

[0019] Furthermore, the chain extender is one or more of resveratrol, citronellol, abietic acid, and caffeic acid;

[0020] The catalyst is bismuth neodecanoate and / or N-methylimidazole;

[0021] The solvent is one or more of toluene, xylene, n-butanol, isobutanol, and butyl acetate.

[0022] Furthermore, the chain extender is prepared by mixing resveratrol and citronellol in a mass ratio of (2-8):3.

[0023] In a second aspect, the present invention provides a method for preparing polyurethane for ACF film, comprising the following steps: adding polytetramethylene ether glycol, modified isocyanate, and a catalyst to a solvent, stirring and heating to 100-115°C, and removing the solvent under vacuum while stirring for 1-2 hours; cooling to 40-50°C, adding a chain extender, continuously stirring and maintaining the reaction temperature at 75-80°C, reacting for 4-5 hours, and obtaining polyurethane for ACF film.

[0024] In a third aspect, the present invention provides an application of polyurethane for ACF film in ACF film.

[0025] Furthermore, the preparation method of the ACF film includes the following steps:

[0026] According to weight, 40-100 parts of polyurethane, 20-40 parts of epoxy resin, 10-20 parts of nitrile rubber, 8-14 parts of conductive microspheres, 5-15 parts of filler and 20-100 parts of low-boiling point solvent are weighed in sequence and mixed evenly in the weighing order, and then 1-10 parts of curing agent are added and mixed evenly to obtain an anisotropic conductive adhesive paste; the anisotropic conductive adhesive paste is applied on a release film, the low-boiling point solvent is evaporated, and the release film is removed to obtain an ACF film.

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] 1. In the present invention, the raw material composition of the polyurethane used for the ACF film includes a modified isocyanate. The modified isocyanate is formed by a thiol click reaction between 1,3,5-triallyl isocyanurate and 1,6-hexanedithiol to form an intermediate, which then reacts with 1,5-naphthalene diisocyanate to form a modified isocyanate. The modified isocyanate contains a triazine ring, a sulfide bond, and a naphthalene ring. When reacted with polytetramethylene ether glycol, the polyurethane is generated. The crosslink density of the internal hybrid network is increased, which limits the space for free movement of the polyurethane chains, increases the energy required for movement and rotation of the polyurethane chains, and increases the glass transition temperature, thereby enhancing the high-temperature resistance of the polyurethane. In addition, in high-humidity environments, it is not prone to hydrolysis or structural damage, effectively improving the high-humidity resistance of the polyurethane. At the same time, the presence of 1,6-hexanedithiol and polytetramethylene ether glycol in the polyurethane gives the polyurethane higher flexibility, so that the polyurethane still has excellent elastic properties.

[0029] 2. The polyurethane for ACF film provided by the present invention uses one or more of resveratrol, citronellol, rosin acid, and caffeic acid as chain extenders, which can react with free radicals of the polyurethane to increase the crosslinking density of the polyurethane, enhance the thermal stability of the polyurethane, reduce moisture penetration, and thus improve the stability of the polyurethane in a humid environment; further preferably, a mixture of resveratrol and citronellol in a specific mass ratio is used as the chain extender, and the two synergistically enhance the effect and work together to improve the high temperature and high humidity resistance of the polyurethane.

[0030] 3. The polyurethane for ACF film provided by the present invention uses bismuth neodecanoate and / or N-methylimidazole as a catalyst to reduce the occurrence of side reactions, make the generated polyurethane molecular chain structure more regular, enhance the cohesion and stability of the polyurethane, reduce the performance degradation caused by molecular chain breakage in a high temperature and high humidity environment, and help improve the high temperature and humidity resistance of the polyurethane.

[0031] 4. The polyurethane provided by the present invention, when applied to ACF film, can significantly improve the high temperature and high humidity resistance of the ACF film, has excellent bonding performance, and has broad market prospects. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0033] Preparation Example 1-3 provides a method for preparing modified isocyanate.

[0034] Preparation Example 1

[0035] This preparation example provides a method for preparing a modified isocyanate, comprising the following steps:

[0036] S1. Add 2.4 g of 1,3,5-triallyl isocyanurate, 4.5 g of 1,6-hexanedithiol, and 0.05 g of benzophenone to 100 mL of toluene, mix them evenly, and irradiate them at a wavelength of 360 nm and an irradiation intensity of 20 mW / cm 2 After irradiation under ultraviolet light for 1 h, the product was concentrated under reduced pressure, washed, and recrystallized to obtain an intermediate;

[0037] S2. Add 6.3 g of 1,5-naphthalene diisocyanate to 100 mL of toluene and dissolve it by ultrasonication. Then add 7.1 g of the intermediate and 0.05 g of stannous octoate. After uniform mixing and vacuum degassing, perform programmed temperature increase (the programmed temperature increase process is: 30°C / 3 h, 60°C / 0.5 h, 80°C / 4 h, 100°C / 0.5 h, 120°C / 0.5 h). Specifically, the temperature increase program of the programmed temperature increase is shown in Table 1. After the reaction is completed, the mixture is concentrated under reduced pressure, filtered, washed and dried to obtain modified isocyanate.

[0038] Table 1 Heating program

[0039] Heating process Insulation process Room temperature -30℃ Keep warm at 30℃ for 3h 30℃-60℃ Keep warm at 60℃ for 0.5h 60℃-80℃ Keep warm at 80℃ for 4h 80℃-100℃ Keep warm at 100℃ for 0.5h 100℃-120℃ Keep warm at 120℃ for 0.5h

[0040] Preparation Example 2

[0041] This preparation example provides a method for preparing a modified isocyanate, comprising the following steps:

[0042] S1. Add 2.45 g of 1,3,5-triallyl isocyanurate, 4.65 g of 1,6-hexanedithiol, and 0.08 g of benzophenone to 100 mL of toluene, mix them evenly, and irradiate them at a wavelength of 380 nm and an irradiation intensity of 23 mW / cm 2 After irradiation under ultraviolet light for 2 h, the product was concentrated under reduced pressure, washed, and recrystallized to obtain an intermediate;

[0043] S2. 6.4 g of 1,5-naphthalene diisocyanate was added to 100 mL of toluene and ultrasonically dissolved. Then, 7.3 g of the intermediate and 0.08 g of stannous octoate were added. After uniform mixing and vacuum degassing, the temperature was programmed (the temperature program was: 30°C / 3 h, 60°C / 1 h, 80°C / 5 h, 100°C / 3 h, 120°C / 1 h). Specifically, the temperature program of the temperature program is shown in Table 2. After the reaction is completed, the mixture is concentrated under reduced pressure, filtered, washed and dried to obtain modified isocyanate.

[0044] Table 2 Heating program

[0045] Heating process Insulation process Room temperature -30℃ Keep warm at 30℃ for 3h 30℃-60℃ Keep warm at 60℃ for 1h 60℃-80℃ Keep warm at 80℃ for 5h 80℃-100℃ Keep warm at 100℃ for 3h 100℃-120℃ Keep warm at 120℃ for 1h

[0046] Preparation Example 3

[0047] This preparation example provides a method for preparing a modified isocyanate, comprising the following steps:

[0048] S1. Add 2.5 g of 1,3,5-triallyl isocyanurate, 4.8 g of 1,6-hexanedithiol, and 0.1 g of benzophenone to 100 mL of toluene, mix them evenly, and irradiate them at a wavelength of 400 nm and an irradiation intensity of 25 mW / cm 2 After irradiation under ultraviolet light for 3 h, the product was concentrated under reduced pressure, washed, and recrystallized to obtain an intermediate;

[0049] S2. 6.5 g of 1,5-naphthalene diisocyanate was added to 100 mL of toluene and ultrasonically dissolved. Then, 7.5 g of the intermediate and 0.1 g of stannous octoate were added. After uniform mixing and vacuum degassing, the temperature was programmed (the temperature program was: 30°C / 3 h, 60°C / 1.5 h, 80°C / 6 h, 100°C / 5 h, 120°C / 1.5 h). Specifically, the temperature program of the temperature program was as shown in Table 3. After the reaction was completed, the mixture was concentrated under reduced pressure, filtered, washed and dried to obtain modified isocyanate.

[0050] Table 3 Heating program

[0051] Heating process Insulation process Room temperature -30℃ Keep warm at 30℃ for 3h 30℃-60℃ Keep warm at 60℃ for 1.5h 60℃-80℃ Keep warm at 80℃ for 6h 80℃-100℃ Keep warm at 100℃ for 5h 100℃-120℃ Keep warm at 120℃ for 1.5h

[0052] Examples 1-7 and Comparative Examples 1-3 all provide a polyurethane for ACF film and a preparation method thereof.

[0053] Example 1

[0054] This embodiment provides a polyurethane for ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of modified isocyanate, 8 parts of chain extender, 1 part of catalyst, and 40 parts of solvent;

[0055] The modified isocyanate is prepared according to Preparation Example 1; the chain extender is resveratrol; the catalyst is bismuth neodecanoate; and the solvent is toluene.

[0056] This embodiment also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0057] Polytetramethylene ether glycol, modified isocyanate, and catalyst were added to the solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0058] Example 2

[0059] This embodiment provides a polyurethane for ACF film, comprising the following raw materials in parts by weight: 90 parts of polytetramethylene ether glycol, 70 parts of modified isocyanate, 9 parts of chain extender, 2 parts of catalyst, and 60 parts of solvent;

[0060] The modified isocyanate is prepared according to Preparation Example 2; the chain extender is rosin acid; the catalyst is N-methylimidazole; and the solvent is xylene.

[0061] This embodiment also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0062] Polytetramethylene ether glycol, modified isocyanate and catalyst were added to the solvent, stirred and heated to 110°C, and the solvent was removed by vacuum for 1.5 hours while stirring; the temperature was lowered to 45°C, a chain extender was added, and the reaction temperature was maintained at 78°C with continuous stirring for 4.5 hours to obtain polyurethane.

[0063] Example 3

[0064] This embodiment provides a polyurethane for ACF film, comprising the following raw materials in parts by weight: 100 parts of polytetramethylene ether glycol, 80 parts of modified isocyanate, 10 parts of chain extender, 3 parts of catalyst, and 80 parts of solvent;

[0065] Among them, the modified isocyanate is prepared by Preparation Example 3; the chain extender is caffeic acid; the catalyst is obtained by mixing bismuth neodecanoate and N-methylimidazole in a mass ratio of 1:1; and the solvent is obtained by mixing xylene and butyl acetate in a mass ratio of 1:1.

[0066] This embodiment also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0067] Polytetramethylene ether glycol, modified isocyanate, and catalyst are added to a solvent, stirred and heated to 115°C, and the solvent is removed by vacuum while stirring for 2 hours; the temperature is lowered to 50°C, a chain extender is added, and the reaction temperature is maintained at 80°C while stirring for 5 hours to obtain polyurethane.

[0068] Example 4

[0069] This embodiment provides a polyurethane for ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of modified isocyanate, 8 parts of chain extender, 1 part of catalyst, and 40 parts of solvent;

[0070] The modified isocyanate is prepared according to Preparation Example 1; the chain extender is citronellol; the catalyst is bismuth neodecanoate; and the solvent is toluene.

[0071] This embodiment also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0072] Polytetramethylene ether glycol, modified isocyanate, and catalyst were added to the solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0073] Example 5

[0074] This embodiment provides a polyurethane for ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of modified isocyanate, 8 parts of chain extender, 1 part of catalyst, and 40 parts of solvent;

[0075] The modified isocyanate is prepared according to Preparation Example 1; the chain extender is obtained by mixing resveratrol and citronellol in a mass ratio of 2:1; the catalyst is bismuth neodecanoate; and the solvent is toluene.

[0076] This embodiment also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0077] Polytetramethylene ether glycol, modified isocyanate, and catalyst were added to the solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0078] Example 6

[0079] This embodiment provides a polyurethane for ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of modified isocyanate, 8 parts of chain extender, 1 part of catalyst, and 40 parts of solvent;

[0080] The modified isocyanate is prepared according to Preparation Example 1; the chain extender is resveratrol; the catalyst is N-methylimidazole; and the solvent is toluene.

[0081] This embodiment also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0082] Polytetramethylene ether glycol, modified isocyanate, and catalyst were added to the solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0083] Example 7

[0084] This embodiment provides a polyurethane for ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of modified isocyanate, 8 parts of chain extender, 1 part of catalyst, and 40 parts of solvent;

[0085] The modified isocyanate is prepared according to Preparation Example 1; the chain extender is resveratrol; the catalyst is a mixture of bismuth neodecanoate and N-methylimidazole in a mass ratio of 2:1; and the solvent is toluene.

[0086] This embodiment also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0087] Polytetramethylene ether glycol, modified isocyanate, and catalyst were added to the solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0088] Comparative Example 1

[0089] This comparative example provides a polyurethane for ACF film, which differs from Example 1 only in that an equal mass of 1,5-naphthalene diisocyanate is used to replace the modified isocyanate, as follows:

[0090] A polyurethane for an ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of 1,5-naphthalene diisocyanate, 8 parts of a chain extender, 1 part of a catalyst, and 40 parts of a solvent;

[0091] The chain extender is resveratrol; the catalyst is bismuth neodecanoate; and the solvent is toluene.

[0092] This comparative example also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0093] Polytetramethylene ether glycol, 1,5-naphthalene diisocyanate, and a catalyst were added to a solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0094] Comparative Example 2

[0095] This comparative example provides a polyurethane for ACF film, which differs from Example 1 only in that 1,4-butanediol is used as a chain extender, as follows:

[0096] A polyurethane for ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of modified isocyanate, 8 parts of a chain extender, 1 part of a catalyst, and 40 parts of a solvent;

[0097] The modified isocyanate is prepared according to Preparation Example 1; the chain extender is 1,4-butanediol; the catalyst is bismuth neodecanoate; and the solvent is toluene.

[0098] This comparative example also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0099] Polytetramethylene ether glycol, modified isocyanate, and catalyst were added to the solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0100] Comparative Example 3

[0101] This comparative example provides a polyurethane for ACF film, which differs from Example 1 only in that dioctyltin dilaurate is used as a catalyst, as follows:

[0102] A polyurethane for ACF film, comprising the following raw materials in parts by weight: 80 parts of polytetramethylene ether glycol, 60 parts of modified isocyanate, 8 parts of a chain extender, 1 part of a catalyst, and 40 parts of a solvent;

[0103] The modified isocyanate is prepared according to Preparation Example 1; the chain extender is resveratrol; the catalyst is dioctyltin dilaurate; and the solvent is toluene.

[0104] This comparative example also provides a method for preparing polyurethane for ACF film, comprising the following steps:

[0105] Polytetramethylene ether glycol, modified isocyanate, and catalyst were added to the solvent, stirred and heated to 100°C, and the solvent was removed under vacuum for 1 hour while stirring; the temperature was lowered to 40°C, a chain extender was added, and the reaction temperature was maintained at 75°C with continuous stirring for 4 hours to obtain polyurethane.

[0106] Application Examples

[0107] The polyurethanes prepared in Examples 1-7 and Comparative Examples 1-3 were respectively used to prepare ACF films according to the following method to prepare Application Examples 1-7 and Comparative Examples 1-3. The polyurethane (PU306) was used to replace the polyurethane of the present invention to obtain Comparative Example 4. Specifically, the preparation method of the ACF film is as follows:

[0108] According to weight, 40 parts of polyurethane, 40 parts of bisphenol A epoxy resin (E-51), 20 parts of nitrile rubber (NBR-2707), 8 parts of nickel-plated conductive microspheres (Ni@PS, particle size of 10 μm), 10 parts of filler (nano-silica) and 20 parts of low-boiling point solvent (ethyl acetate) are mixed in order, and then a curing agent (i.e., 5 parts of triethylenetetramine and 5 parts of benzoyl peroxide) is added and mixed evenly to obtain an anisotropic conductive adhesive paste; the anisotropic conductive adhesive paste is applied on a stripping film, and the low-boiling point solvent is evaporated at 80°C for 10 minutes, and then the stripping film is removed to obtain an ACF film with a thickness of 20 μm.

[0109] Performance Testing

[0110] The ACF film was placed at room temperature (25°C) for 30 minutes. The film was then attached to a printed circuit board (PCB) and an FPC under initial pressing conditions (80°C, 1 second, 1.0 MPa) and final pressing conditions (160°C, 5 seconds, 3 MPa). Five samples were prepared using the ACF film obtained in Example 1. The samples were tested for bond strength at a 90° angle, 1 cm width, and a tensile speed of 50 mm / min. Adjacent electrodes on the TFT were designed to form a U-shape and bonded to electrodes on the FPC. Test leads were then drawn out, and the connection resistance was measured using the diode method.

[0111] The ACF films prepared in Application Examples 2-7 and Application Comparative Examples 1-4 were subjected to the same test method, and the on-resistance and bonding strength data obtained were statistically analyzed. The above-mentioned Application Examples 1-7 and Application Comparative Examples 1-4 were subjected to high temperature and high humidity (85°C, 85% RH, 250H) test and water boiling (95°C, 3H) test. The performance is shown in Tables 4 and 5.

[0112] Table 4

[0113]

[0114] Table 5

[0115]

[0116]

[0117] As can be seen from Tables 4 and 5, the ACF films obtained using Application Examples 1-7 were subjected to high temperature and high humidity (85°C, 85% RH, 250H) test and water boiling (95°C, 3H) test, and the increase in on-resistance was less than 20%, and the decrease in bonding strength was also less than 20%, indicating that the ACF film has strong tolerance in polar environments and very stable performance, which is significantly better than Application Comparative Examples 1-4; this fully demonstrates that the polyurethane of the present invention is applied to the ACF film, which can effectively improve the high temperature and high humidity resistance of the ACF film.

[0118] The modified isocyanate prepared by using 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol and 1,5-naphthalene diisocyanate as basic raw materials reacts with polytetramethylene ether glycol to generate polyurethane. The modified isocyanate helps to increase the crosslinking density of the polyurethane. Comparing Application Example 1 with Application Comparative Example 1, the ACF film has a smaller change rate of on-resistance and bonding strength after high temperature and high humidity, and has excellent weather resistance.

[0119] The polyurethane prepared with resveratrol or citronellol as the chain extender is applied to the ACF film. Compared with the polyurethane prepared with the mixture of resveratrol and citronellol as the chain extender applied to the ACF film, that is, the comparison of Application Example 1, Application Example 4 and Application Example 5, it is fully demonstrated that the mixture of resveratrol and citronellol is used as the chain extender to introduce more active groups, which can increase the cross-linking density inside the polyurethane and improve the high temperature and high humidity resistance of the polyurethane; in addition, by comparing Application Examples 1, 4-5 and Application Comparative Example 2, it can be seen that the preferred chain extender of the present invention is significantly better than 1,4-butanediol, further demonstrating that the polyurethane of the present invention can effectively ensure that the ACF film still has excellent stability in a polar environment.

[0120] The polyurethane prepared with bismuth neodecanoate or N-methylimidazole as a catalyst is applied to the ACF film, which is more effective than the polyurethane prepared with a mixture of bismuth neodecanoate and N-methylimidazole as a catalyst applied to the ACF film, that is, comparing Application Example 1, Application Example 6 and Application Example 7. It is sufficient to illustrate that using a mixture of bismuth neodecanoate and N-methylimidazole as a catalyst can significantly reduce the activation energy of the polyurethane polymerization reaction, accelerate the reaction rate, adjust the arrangement and cross-linking degree of the polyurethane molecular chain, and improve the high temperature and high humidity resistance of the polyurethane; at the same time, by comparing Application Examples 1, 6-7 and Application Comparative Example 3, it can be seen that the preferred catalyst of the present invention is significantly better than dioctyltin dilaurate, which is more conducive to enhancing the performance of the polyurethane, and is also conducive to the application of polyurethane in the ACF film, improving the curing effect of the film, and making the ACF film better suitable for high temperature and high humidity environments.

[0121] Throughout this specification, references to terms such as "one embodiment," "example," or "specific example" indicate that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or example are included in at least one embodiment or example of the present invention. In this specification, schematic representations of these terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0122] The basic principles, main features, and advantages of the present invention are shown and described above. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention, and such changes and modifications fall within the scope of the invention as claimed.

Claims

1. A polyurethane for ACF film, characterized in that: The method comprises the following raw materials in parts by weight: 80-100 parts of polytetramethylene ether glycol, 60-80 parts of modified isocyanate, 8-10 parts of chain extender, 1-3 parts of catalyst, and 40-80 parts of solvent; The modified isocyanate is prepared using 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol and 1,5-naphthalene diisocyanate as raw materials; The chain extender is one or more of resveratrol, citronellol, abietic acid, and caffeic acid; The catalyst is bismuth neodecanoate and / or N-methylimidazole; The preparation method of the modified isocyanate comprises the following steps: S1. Add 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol, and benzophenone to toluene, mix uniformly, irradiate under ultraviolet light for 1-3 hours, concentrate under reduced pressure, wash, and recrystallize to obtain an intermediate; S2. Add 1,5-naphthalene diisocyanate to toluene and dissolve it by ultrasonication. Then add the intermediate and stannous octoate, mix them evenly, degas in vacuum, and heat the mixture programmatically. After the reaction is completed, concentrate under reduced pressure, filter, wash and dry to obtain modified isocyanate.

2. The polyurethane for ACF film according to claim 1, characterized in that: In step S1, the ratio of the amount of 1,3,5-triallyl isocyanurate, 1,6-hexanedithiol, benzophenone, and toluene is (2.4-2.5) g: (4.5-4.8) g: (0.05-0.1) g: 100 mL.

3. The polyurethane for ACF film according to claim 1, characterized in that: In step S2, the ratio of the intermediate, 1,5-naphthalene diisocyanate, stannous octoate, and toluene is (7.1-7.5) g: (6.3-6.5) g: (0.05-0.1) g: 100 mL.

4. The polyurethane for ACF film according to claim 1, characterized in that: In step S2, the programmed temperature rising process is: Raise the temperature from room temperature to 30°C and keep at 30°C for 3h; Raise the temperature from 30°C to 60°C and keep at 60°C for 0.5-1.5h; Raise the temperature from 60°C to 80°C and keep at 80°C for 4-6 hours; Raise the temperature from 80°C to 100°C and keep at 100°C for 0.5-5h; Raise the temperature from 100℃ to 120℃ and keep at 120℃ for 0.5-1.5h.

5. The polyurethane for ACF film according to claim 1, characterized in that: The solvent is one or more of toluene, xylene, n-butanol, isobutanol, and butyl acetate.

6. The polyurethane for ACF film according to claim 1, characterized in that: The chain extender is prepared by mixing resveratrol and citronellol in a mass ratio of (2-8):

3.

7. A method for preparing a polyurethane for an ACF film according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: adding polytetramethylene ether glycol, modified isocyanate and a catalyst into a solvent, stirring and heating to 100-115° C., and removing the solvent under vacuum for 1-2 hours while stirring; cooling to 40-50° C., adding a chain extender, continuously stirring and maintaining the reaction temperature at 75-80° C., and reacting for 4-5 hours to obtain a polyurethane for an ACF film.

8. Use of the polyurethane for ACF film according to any one of claims 1 to 6 in ACF film.

9. The use according to claim 8, characterized in that The preparation method of the ACF film comprises the following steps: According to weight, 40-100 parts of polyurethane, 20-40 parts of epoxy resin, 10-20 parts of nitrile rubber, 8-14 parts of conductive microspheres, 5-15 parts of filler and 20-100 parts of low-boiling point solvent are weighed in sequence and mixed evenly in the weighing order, and then 1-10 parts of curing agent are added and mixed evenly to obtain an anisotropic conductive adhesive paste; the anisotropic conductive adhesive paste is applied on a release film, the low-boiling point solvent is evaporated, and the release film is removed to obtain an ACF film.

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