Polyimide, polyimide film, preparation method of polyimide film and flexible electronic device

Abstract

The invention belongs to the technical field of polyimide materials, and particularly relates to polyimide, a polyimide film, a preparation method and a flexible electronic device. The polyimide is prepared from the following raw materials: a diamine monomer and a dianhydride monomer, wherein the diamine monomer is selected from one or more of compounds with structural characteristics as shown in a formula (I); the dianhydride monomer is selected from one or more of compounds with structural characteristics as shown in a formula (II); r11 and R13 are respectively and independently cycloalkylene with the carbon atom number of 3 to 8 and arylene with the carbon atom number of 6 to 12; r12 is a chain-like alkyl group with a carbon atom number of 1-6; r21 and R23 are each independently a single bond, a chain-like alkyl group having 1 to 6 carbon atoms, or an arylene group having 6 to 12 carbon atoms; and R22 is a sub-chain alkyl group with the carbon atom number of 1-6. The glass transition temperature of the polyimide disclosed by the invention is 200 DEG C or below, and the polyimide has relatively low glass transition temperature and relatively low curing temperature.

Description

Technical Field

[0001] The present application belongs to the technical field of polyimide materials, and specifically relates to a polyimide, a polyimide film and a preparation method, and a flexible electronic device. Background Art

[0002] Polyimide (PI) is a type of high molecular weight polymer containing cyclic imide groups in its molecular chain. It has excellent thermal stability, high mechanical strength and good dielectric properties, and is one of the most important substrates in flexible electronic devices.

[0003] Traditional polyimide materials usually have a high glass transition temperature. When preparing flexible electronic devices, polyimide with a high glass transition temperature is used, which may cause the material to be brittle and fatigue-damaged when bent or twisted. Polyimide resins with high glass transition temperatures may prematurely become brittle, harden, and lose elasticity in high temperature environments. That is, polyimide with a low glass transition temperature can keep the film flexible over a wide temperature range and maintain good physical properties at low temperatures. Summary of the invention

[0004] Based on this, the present application provides a polyimide, a polyimide film and a preparation method, and a flexible electronic device. The polyimide of the present application has a lower glass transition temperature and a lower curing temperature.

[0005] In a first aspect of the present application, a polyimide is provided, wherein raw materials for preparing the polyimide include a diamine monomer and a dianhydride monomer.

[0006] The diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (I): ;

[0007] The dianhydride monomer is selected from one or more compounds having the structural characteristics shown in formula (II): ;

[0008] R 11 and R 13 Each independently represents a cycloalkylene group having 3 to 8 carbon atoms or an arylene group having 6 to 12 carbon atoms; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms;

[0009] R 21 and R 23 Each independently represents a single bond, a chain alkylene group having 1 to 6 carbon atoms, or an arylene group having 6 to 12 carbon atoms; R 22 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0010] In one embodiment, R 11and R 13 Each independently , , , , , or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms;

[0011] R 21 and R 23 Each independently or ; R 22 It is a subchain alkyl group having 2 to 5 carbon atoms.

[0012] In one embodiment, the diamine monomer is selected from one or more compounds having structural characteristics of formula (I-1) to formula (I-3):

[0013] , or ; Wherein, n1, n2 and n3 are each independently a positive integer between 1 and 6;

[0014] The dianhydride monomer is selected from one or more compounds having structural characteristics of formula (II-1) to formula (II-2):

[0015] or ; Among them, R 22 Any group selected from the following: -CH2-, -CH2CH2-, -CH2CH2CH2-, -C(CH2)2- or -CH2CH2CH2CH2-.

[0016] In one embodiment, the polyimide is selected from one or more compounds having the structural features shown in formula (III): ; R 11 , R 12 , R 13 , R 21 , R 22 , R 23 The definition is the same as described in any embodiment of the first aspect of the present application.

[0017] In one embodiment, the molar ratio of the diamine monomer to the dianhydride monomer is (0.9-1.2):1.

[0018] A second aspect of the present application provides a polyimide film, wherein the polyimide film comprises the polyimide described in any one of the embodiments of the first aspect of the present application.

[0019] In a third aspect of the present application, a method for preparing a polyimide film is provided, comprising the following steps:

[0020] Dissolving the diamine monomer and the dianhydride monomer described in the first aspect of the present application in a solvent to prepare a polyimide slurry;

[0021] The polyimide slurry is coated on a substrate, and after the solvent in the polyimide slurry is removed, the polyimide film is formed on the substrate.

[0022] In one embodiment, the solvent includes one or more of N-methylpyrrolidone, m-cresol, N,N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and N,N-dimethylformamide.

[0023] In one embodiment, the specific steps of removing the solvent in the polyimide slurry include: subjecting the substrate coated with the polyimide slurry to a first heat treatment at a temperature of 90°C to 110°C, a second heat treatment at a temperature of 190°C to 210°C, and a third heat treatment at a temperature of 220°C to 240°C, in order to remove the solvent in the polyimide slurry.

[0024] A fourth aspect of the present application provides a flexible electronic device, comprising the polyimide film described in the second aspect of the present application.

[0025] This application has the following beneficial effects:

[0026] The polyimide of the present application is prepared by diamine monomer and dianhydride monomer of specific structure. Among them, the diamine monomer contains ether bond and long fatty chain, and the ether bond has lower rigidity and lower polarity. The introduction of ether bond can reduce the hydrogen bonding and polarity between chains, so as to increase the monomer reactivity, improve the degree of polymerization, and reduce the glass transition temperature. In addition, after the diamine monomer of long fatty chain forms polyimide, larger flexible segments will be introduced, and these segments can increase the degree of freedom and flexibility, so that the polyimide can move the segments at a lower temperature, thereby reducing the glass transition temperature. And the presence of long fatty chain will disturb the planarity of the main chain of polyimide, distort the spatial structure of its molecular chain, so that the structure stacking is more scattered, which also helps to reduce the glass transition temperature of polyimide. The anhydride group in the dianhydride monomer can effectively participate in the polymerization reaction to form polyimide; the introduction of ether bond in the dianhydride monomer will also increase the flexibility and degree of freedom of polyimide. This structure reduces the interaction force between chains, thereby lowering the glass transition temperature, making polyimide have better flexibility and processability at lower temperatures.

[0027] In summary, the polyimide of the present application uses specific diamine monomers and dianhydride monomers, which can reduce the polymerization temperature of the polyimide. In some embodiments, the polymerization temperature of the polyimide can be reduced from the traditional 300°C or above to 180°C to 260°C. In some embodiments, a polyimide material with a glass transition temperature below 200°C can be obtained. DETAILED DESCRIPTION

[0028] The polyimide, polyimide film, preparation method, and flexible electronic device of the present application are further described in detail below in conjunction with specific embodiments. The present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive. Of course, they are merely examples and are not intended to limit the present application.

[0029] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all subranges included therein.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. Unless otherwise specified or there is a contradiction, the terms or phrases used herein have the following meanings:

[0031] In the present application, "plurality", "multiple", "multiple times", "plurality", etc., unless otherwise specified, refer to a number greater than 2 or equal to 2. For example, "one or more" means one or greater than or equal to two.

[0032] In this application, in the "first aspect", "second aspect", "third aspect", "fourth aspect", etc., the terms "first", "second", "third", "fourth", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first", "second", "third", "fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0033] In the present application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0034] In the present application, references to “combinations thereof”, “any combination thereof”, “any combination thereof”, etc. include all suitable combinations of any two or more of the listed items.

[0035] In this application, the “suitable” mentioned in “suitable combination”, “suitable method”, “any suitable method”, etc. shall be based on the ability to implement the technical solution of this application, solve the technical problems of this application, and achieve the expected technical effects of this application.

[0036] In the present application, the terms “preferred”, “better”, “more preferred” and “suitable” are only used to describe implementation methods or examples with better effects, and it should be understood that they do not constitute limitations on the scope of protection of the present application.

[0037] In the present application, the terms “further”, “furthermore”, “particularly”, etc. are used for descriptive purposes to indicate differences in content, but should not be construed as limiting the scope of protection of the present application.

[0038] In this application, "optionally", "optional" and "optional" refer to optional, that is, to any one of the two parallel schemes of "yes" or "no". If multiple "options" appear in a technical solution, unless otherwise specified and there is no contradiction or mutual restriction, each "optional" is independent.

[0039] In the present application, when it comes to numerical intervals (i.e., numerical ranges), unless otherwise specified, the optional numerical distribution is considered continuous within the above numerical interval, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical range, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to the integers within the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints. In this article, it is equivalent to directly listing each integer, such as t is an integer selected from 1 to 10, indicating that t is any integer selected from the group of integers consisting of 1, 2, 3, 4, 5, 6, 7, 8, 9 and 10. In addition, when multiple ranges are provided to describe features or characteristics, these ranges can be combined. In other words, unless otherwise specified, the ranges disclosed herein should be understood to include any and all subranges included therein.

[0040] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0041] In the present application, the percentage content, unless otherwise specified, refers to mass percentage for solid-liquid mixing and solid-solid mixing, and volume percentage for liquid-liquid mixing.

[0042] In this application, when it comes to percentage concentration, unless otherwise specified, it refers to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of the component.

[0043] In the present application, "cycloalkyl" refers to a non-aromatic hydrocarbon containing ring carbon atoms, which can be a monocyclic alkyl, a spirocyclic alkyl, or a bridged cycloalkyl. Phrases containing this term, for example, "cycloalkyl with 3 to 8 carbon atoms" refers to a cycloalkyl containing 3 to 8 carbon atoms, and each time it occurs, it can be independently C3 cycloalkyl, C4 cycloalkyl, C5 cycloalkyl, C6 cycloalkyl, C7 cycloalkyl, C8 cycloalkyl, C9 cycloalkyl. Suitable examples include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl and cycloheptyl. In addition, "cycloalkyl" may also contain one or more double bonds, and representative examples of cycloalkyl containing double bonds include cyclopentenyl, cyclohexenyl, cyclohexadienyl and cyclobutadienyl. "Cycloalkylene" refers to a hydrocarbon group with two monovalent group centers derived from removing a hydrogen atom on the basis of "cycloalkyl". Specifically, "cycloalkylene" includes, but is not limited to, cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclopentenylene, cyclohexenylene, hexadienylene and butadienylene.

[0044] In the present application, "aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing a hydrogen atom, which can be a monocyclic aromatic group, a condensed aromatic group, or a polycyclic aromatic group. For polycyclic rings, at least one is an aromatic ring system. Phrases containing this term, for example, "aryl having 6 to 12 carbon atoms" refers to an aromatic group containing 6 to 12 atoms, and each occurrence can be independently a C6 aromatic group or a C10 aromatic group. Suitable examples include, but are not limited to, benzene and naphthalene. "Arylene" refers to an aromatic hydrocarbon group derived from an "aryl" group by removing a hydrogen atom.

[0045] In the present application, "chain alkyl" refers to an alkyl group containing a straight chain or a branched chain. "Subchain alkyl" refers to a hydrocarbon group with two monovalent group centers derived from "chain alkyl" by removing a hydrogen atom. Phrases including this term, for example: "Subchain alkyl having 1 to 6 carbon atoms" refers to an alkyl group containing 1 to 6 carbon atoms, and each occurrence can be independently C1 subchain alkyl, C2 subchain alkyl, C3 subchain alkyl, C4 subchain alkyl, C5 subchain alkyl or C6 subchain alkyl. Suitable examples include, but are not limited to: -CH2-, -CH2CH 2- , -CH2CH2CH2-, -C(CH3)2-, -CH2CH2CH2CH2-, -CH2C(CH3)2-, -CH(CH3)CH2CH2-, -C(CH3)2-, -CH2CH2CH2CH2CH2-, -CH(CH3)CH2CH2CH2-, -C(CH 2CH3)2-, -C(CH3)2CH2CH2-, -CH(CH3)C(CH3)2-, -CH2CH2CH(CH3)2), -CH2CH(CH3)CH2CH2-, -CH2CH2CH2CH2CH2CH2-, or -CH(CH3)CH2CH2CH2CH2-.

[0046] In the present application, "*" indicates a connection site.

[0047] At present, the preparation method of polyimide is mainly a two-step method: first prepare a synthetic polyimide slurry, then evaporate the solvent through thermal imidization or chemical imidization, and dehydrate to form polyimide. Traditionally prepared polyimides usually have excellent heat resistance, and their glass transition temperature is relatively high, generally above 200°C. However, imidization must be carried out at a temperature at which the molecular chain can move, that is, it should be above the glass transition temperature to completely occur. Therefore, as the cyclization reaction proceeds, the rigidity of the polymer molecular chain becomes higher and higher, and the temperature required to continue imidization also increases. Therefore, in the traditional process, in the process of preparing polyimide with a higher glass transition temperature, it is usually necessary to carry out imidization at a heating temperature exceeding 300°C, which makes the gradient heating and imidization in the entire process take a long time, which limits the wider application of polyimide.

[0048] Based on this, the first aspect of the present application provides a polyimide, wherein the raw materials for preparing the polyimide include a diamine monomer and a dianhydride monomer.

[0049] The diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (I): ;

[0050] The dianhydride monomer is selected from one or more compounds having the structural characteristics shown in formula (II): ;

[0051] R 11 and R 13 Each independently represents a cycloalkylene group having 3 to 8 carbon atoms or an arylene group having 6 to 12 carbon atoms; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms;

[0052] R 21 and R 23 Each independently represents a single bond, a chain alkylene group having 1 to 6 carbon atoms, or an arylene group having 6 to 12 carbon atoms; R 22 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0053] The polyimide of the present application is prepared by diamine monomer and dianhydride monomer of specific structure. Among them, the diamine monomer contains ether bond and long fatty chain, and the ether bond has lower rigidity and lower polarity. The introduction of ether bond can reduce the hydrogen bonding and polarity between chains, so as to increase the monomer reactivity, improve the degree of polymerization, and reduce the glass transition temperature. In addition, after the diamine monomer of long fatty chain forms polyimide, larger flexible segments will be introduced, and these segments can increase the degree of freedom and flexibility, so that the polyimide can move the segments at a lower temperature, thereby reducing the glass transition temperature. And the presence of long fatty chain will disturb the planarity of the main chain of polyimide, distort the spatial structure of its molecular chain, so that the structure stacking is more scattered, which also helps to reduce the glass transition temperature of polyimide. The anhydride group in the dianhydride monomer can effectively participate in the polymerization reaction to form polyimide; the introduction of ether bond in the dianhydride monomer will also increase the flexibility and degree of freedom of polyimide. This structure reduces the interaction force between chains, thereby lowering the glass transition temperature, making polyimide have better flexibility and processability at lower temperatures.

[0054] In summary, the polyimide of the present application uses specific diamine monomers and dianhydride monomers, which can reduce the polymerization temperature of the polyimide. In some embodiments, the polymerization temperature of the polyimide can be reduced from the traditional 300°C or above to 180°C to 260°C. In some embodiments, a polyimide material with a glass transition temperature below 200°C can be obtained.

[0055] For example, R 11 and R 13 Each is independently cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclopentenylene, cyclohexenylene, hexadienylene, butadienylene, arylene or naphthylene.

[0056] Specifically, R 11 and R 13 Each independently , , , , , or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0057] Furthermore, R 11 and R 13 Each independently , , or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0058] Furthermore, R 11 and R 13 Each independently ,or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0059] Based on rich experience and a large number of experiments, the inventors of the present application have found that the above-mentioned cyclic structures such as epoxy, phenyl or cyclopentadienyl can introduce additional internal stress, thereby reducing the interaction force between chain segments and thus reducing the glass transition temperature of the material; further, in R 12 With the cooperation of the subchain alkyl group, the freedom of movement of the chain segments is increased, so that the polyimide can maintain relative flexibility at lower temperatures and reduce the glass transition temperature.

[0060] Specifically, R 21 and R 23 Each independently or ; R 22 It is a subchain alkyl group having 2 to 5 carbon atoms.

[0061] Furthermore, R 21 and R 23 Each independently ; R 22 Any group selected from the following: -CH2-, -CH2CH2-, -CH2CH2CH2-, -C(CH2)2- or -CH2CH2CH2CH2-.

[0062] Furthermore, R 21 and R 23 Each independently ; R 22 Selected from -C(CH2)2-.

[0063] The inventors of the present application discovered that R22 When selected from -C(CH2)2-, the introduction of -C(CH2)2- can provide higher molecular flexibility; R 21 and R 23 for The ether bond contained in the dianhydride monomer can balance the rigidity of the chain segment, increase the flexibility of the chain segment, and promote the freedom of movement of the chain segment, thereby reducing the glass transition temperature. The combined effect of the above groups effectively reduces the imidization temperature and glass transition temperature of the polyimide by increasing molecular flexibility, reducing the rigidity of the chain segment, and improving the freedom of movement of the chain segment, thereby improving the flexibility and processing performance of the material.

[0064] In one example, the diamine monomer is selected from one or more compounds having structural characteristics of formula (I-1) to formula (I-3):

[0065] , or ; Wherein, n1, n2 and n3 are each independently a positive integer between 1 and 6.

[0066] The dianhydride monomer is selected from one or more compounds having structural characteristics of formula (II-1) to formula (II-2):

[0067] or ; Among them, R 22 is selected from any of the following groups: -CH2-, -CH2CH2-, -CH2CH2CH2-, -C(CH2)2- or -CH2CH2CH2CH2-. Preferably, R 22 It is -C(CH2)2-.

[0068] In one example, the polyimide is selected from one or more compounds having the structural features shown in formula (III): ; R 11 , R 12 , R 13 , R 21 , R 22 , R 23 The definition is the same as described in any embodiment of the first aspect of the present application.

[0069] Specifically, R 11 and R 13 Each independently represents a cycloalkylene group having 3 to 8 carbon atoms or an arylene group having 6 to 12 carbon atoms; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0070] For example, R 11 and R 13Each is independently cyclopropylene, cyclobutylene, cyclopentylene, cyclohexylene, cycloheptylene, cyclopentenylene, cyclohexenylene, hexadienylene, butadienylene, arylene or naphthylene.

[0071] Furthermore, R 11 and R 13 Each independently , , , , , or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0072] Furthermore, R 11 and R 13 Each independently , , or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0073] Furthermore, R 11 and R 13 Each independently ,or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0074] Specifically, R 21 and R 23 Each independently represents a single bond, a chain alkylene group having 1 to 6 carbon atoms, or an arylene group having 6 to 12 carbon atoms; R 22 It is a subchain alkyl group having 1 to 6 carbon atoms.

[0075] Furthermore, R 21 and R 23 Each independently ; R 22 Any group selected from the following: -CH2-, -CH2CH2-, -CH2CH2CH2-, -C(CH2)2- or -CH2CH2CH2CH2-.

[0076] Furthermore, R 21 and R 23 Each independently ; R 22 Selected from -C(CH2)2-.

[0077] The molar ratio of the diamine monomer to the dianhydride monomer plays an important role in controlling the structure of the polyimide and its performance parameters such as flexibility and glass transition temperature. In one example, the molar ratio of the diamine monomer to the dianhydride monomer is (0.9~1.2):1. Specifically, the preparation ratio of the diamine monomer to the dianhydride monomer includes but is not limited to 0.9:1, 0.95:1, 0.96:1, 0.97:1, 0.98:1, 0.99:1, 1:1, 1.01:1, 1.02:1, 1.03:1, 1.04:1, 1.05:1, 1.06:1, 1.07:1, 1.08:1, 1.09:1 or 1.1:1.

[0078] A second aspect of the present application provides a polyimide film, comprising the polyimide described in any one of the embodiments of the first aspect of the present application.

[0079] In a third aspect of the present application, a method for preparing a polyimide film is provided, comprising the following steps:

[0080] Dissolving the diamine monomer and the dianhydride monomer described in the first aspect of the present application in a solvent to prepare a polyimide slurry;

[0081] The polyimide slurry is coated on a substrate, and after the solvent in the polyimide slurry is removed, the polyimide film is formed on the substrate.

[0082] In one example, the solvent includes N-methylpyrrolidone (NMP, )、m-cresol( )、N,N-dimethylacetamide( )、Dimethyl sulfoxide( ), γ-butyrolactone ( )、Cyclohexanone( ) and N,N-dimethylformamide ( )

[0083] Furthermore, the preparation steps of the polyimide slurry include:

[0084] S10, dissolving the diamine monomer in a solvent for initial mixing to prepare an intermediate solution containing the diamine monomer;

[0085] S20, adding dianhydride monomer to the intermediate solution containing diamine monomer for secondary mixing to prepare polyimide slurry.

[0086] Specifically, in step S10, the mass ratio of the diamine monomer to the solvent is 1:(15-21). Specifically, the mass ratio of the diamine monomer to the solvent includes but is not limited to 1:15, 1:16, 1:16.5, 1:16.6, 1:16.7, 1:17, 1:17.5, 1:17.6, 1:18.2, 1:18.3, 1:19, 1:20.5, 1:20.6 or 1:21.

[0087] Further, in step S10, the temperature for the initial mixing is 40° C. to 60° C. Specifically, the temperature for the initial mixing includes but is not limited to 40° C., 42° C., 45° C., 48° C., 50° C., 52° C., 55° C., 58° C. or 60° C.

[0088] In step S20, the temperature for secondary mixing is 10° C. to 20° C. Specifically, the temperature for secondary mixing includes but is not limited to 10° C., 12° C., 14° C., 15° C., 16° C., 17° C., 18° C. or 20° C.

[0089] In one example, the viscosity of the polyimide slurry is 7000 cps to 8000 cps. Within the above viscosity range, the polyimide film can be more easily processed during coating and a good polyimide coating can be obtained.

[0090] The polyimide slurry is optimized for dianhydride monomers and diamine monomers, so that the polyimide slurry can be used to prepare a polyimide film with a low glass transition temperature.

[0091] Specifically, the material of the substrate includes but is not limited to ceramic, glass, silicon, metal, plastic, etc. For example, the ceramic may be alumina ceramic, and the metal may be stainless steel, aluminum, copper, etc. The plastic may be a polyimide film. Preferably, the substrate is glass, and further, the substrate is polished glass.

[0092] In one example, the method of removing the solvent in the polyimide slurry includes: subjecting the substrate coated with the polyimide slurry to an imide reaction at 90° C. to 240° C. to remove the solvent.

[0093] In one example, the method of removing the solvent in the polyimide slurry includes: volatilizing the solvent by increasing the temperature of the substrate coated with the polyimide slurry in a gradient manner.

[0094] In one example, the specific steps of removing the solvent in the polyimide slurry include: subjecting the substrate coated with the polyimide slurry to a first heat treatment at a temperature of 90°C to 110°C, a second heat treatment at a temperature of 190°C to 210°C, and a third heat treatment at a temperature of 220°C to 240°C to remove the solvent in the polyimide slurry.

[0095] Since the glass transition temperature of the polyimide of the present application is relatively low, the temperature required for thermal imidization is also relatively low. In the preparation method provided in the present application, the polyimide film can be prepared under the conditions of 90°C to 240°C, and the thermal imidization temperature can be reduced from the traditional temperature of more than 300°C to about 240°C, and only three heating steps are required. Compared with the traditional thermal imidization process, this process has lower energy consumption and can greatly shorten the process time, thereby improving the production efficiency of the polyimide film.

[0096] Specifically, the temperature for the first heat treatment includes, but is not limited to, 90° C., 95° C., 98° C., 100° C., 102° C., 105° C., 108° C., or 110° C. The temperature for the second heat treatment includes, but is not limited to, 190° C., 192° C., 195° C., 198° C., 200° C., 202° C., 205° C., 208° C., or 210° C. The temperature for the third heat treatment includes, but is not limited to, 220° C., 222° C., 225° C., 227° C., 230° C., 232° C., 235° C., 238° C., or 240° C.

[0097] Specifically, the first heating treatment and the second heating treatment are each independently performed for 10 minutes to 20 minutes, and the third heating treatment is performed for 25 minutes to 35 minutes.

[0098] In some embodiments, the method for preparing the polyimide film further includes placing the substrate formed with the polyimide film in deionized water to peel off the polyimide film and the substrate.

[0099] In one example, the tensile strength of the polyimide film is 80 MPa~110 MPa.

[0100] In one example, the glass transition temperature of the polyimide film is 145°C to 180°C.

[0101] A fourth aspect of the present application provides a flexible electronic device, comprising the polyimide film described in the second aspect of the present application.

[0102] In order to make the purpose and advantages of the present invention clearer, the polyimide film of the present invention and its effects are further described in detail below in conjunction with specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and shall not be used to limit the present invention. The following embodiments do not include other components except inevitable impurities unless otherwise specified. The drugs and instruments used in the embodiments are conventionally selected in the art unless otherwise specified. The experimental methods for which specific conditions are not specified in the embodiments are implemented according to conventional conditions, such as the conditions described in the literature, books, or the methods recommended by the manufacturer.

[0103] [Diamine monomer]

[0104] A1: , n1 is 3;

[0105] A2: , n1 is 5;

[0106] A3: , n2 is 2;

[0107] A4: , n3 is 3;

[0108] A5: , n3 is 4.

[0109] A6: .

[0110] [Dianhydride monomer]

[0111] B1: 4,4'-(4,4'-isopropyldiphenoxy)bis(phthalic anhydride) .

[0112] Example 1

[0113] The reaction apparatus was adjusted to be airtight, and N2 was introduced into it to replace the air. At 50°C, 2.5593g of diamine monomer A1 was dissolved in 42.5g of solvent N,N-dimethylpyrrolidone. After the diamine monomer was completely dissolved, 4.9407g of dianhydride monomer 4,4'-(4,4'-isopropyldiphenyloxy)bis(phthalic anhydride) (B1) was added. After conversion, the molar ratio of diamine monomer to dianhydride monomer was about 1.04:1; then stirred at 15°C for 24h to prepare polyimide slurry.

[0114] Place a clean glass plate on the platform of the automatic coating machine, select a 100μm scraper and place it on the glass plate, use a plastic dropper to evenly cover the polyimide slurry prepared by the above method between the scraper and the glass plate, set the scraping length to 30cm, and start coating. After the coating is completed, place the glass plate in an oven for thermal imidization, and heat it at 100℃ for 15min, 200℃ for 15min, and 230℃ for 30min in a gradient heating process to evaporate the solvent. After the thermal imidization is completed, take it out after natural cooling, cut the transparent polyimide film on the smoother part of the film surface with a blade, soak it in deionized water, peel off the transparent polyimide film, wipe the surface moisture of the transparent polyimide film with a dust-free cloth, and store it well to obtain a polyimide film.

[0115] Example 2

[0116] The reaction apparatus was adjusted to be airtight, and N2 was introduced into it to replace the air. At 50°C, 2.6447g of diamine monomer A2 was dissolved in 42.5g of solvent N,N-dimethylpyrrolidone. After the diamine monomer was completely dissolved, 4.8553g of dianhydride monomer 4,4'-(4,4'-isopropyldiphenyloxy)bis(phthalic anhydride) (B1) was added. After conversion, the molar ratio of diamine monomer to dianhydride monomer was about 0.99:1; then stirred at 15°C for 24h to prepare polyimide slurry.

[0117] Place a clean glass plate on the platform of the automatic coating machine, select a 100μm scraper and place it on the glass plate, use a plastic dropper to evenly cover the polyimide slurry prepared by the above method between the scraper and the glass plate, set the scraping length to 30cm, and start coating. After the coating is completed, place the glass plate in an oven for thermal imidization, and heat it at 100℃ for 15min, 200℃ for 15min, and 230℃ for 30min in a gradient heating process to evaporate the solvent. After the thermal imidization is completed, take it out after natural cooling, cut the transparent polyimide film on the smoother part of the film surface with a blade, soak it in deionized water, peel off the transparent polyimide film, wipe the surface moisture of the transparent polyimide film with a dust-free cloth, and store it well to obtain a polyimide film.

[0118] Example 3

[0119] The reaction apparatus was adjusted to be airtight, and N2 was introduced into it to replace the air. At 50°C, 2.0689g of diamine monomer A3 was dissolved in 42.5g of solvent N,N-dimethylpyrrolidone. After the diamine monomer was completely dissolved, 5.4311g of dianhydride monomer 4,4'-(4,4'-isopropyldiphenyloxy)bis(phthalic anhydride) (B1) was added. After conversion, the molar ratio of diamine monomer to dianhydride monomer was about 0.99:1; then stirred at 15°C for 24h to prepare polyimide slurry.

[0120] Place a clean glass plate on the platform of the automatic coating machine, select a 100μm scraper and place it on the glass plate, use a plastic dropper to evenly cover the polyimide slurry prepared by the above method between the scraper and the glass plate, set the scraping length to 30cm, and start coating. After the coating is completed, place the glass plate in an oven for thermal imidization, and heat it at 100℃ for 15min, 200℃ for 15min, and 230℃ for 30min in a gradient heating process to evaporate the solvent. After the thermal imidization is completed, take it out after natural cooling, cut the transparent polyimide film on the smoother part of the film surface with a blade, soak it in deionized water, peel off the transparent polyimide film, wipe the surface moisture of the transparent polyimide film with a dust-free cloth, and store it well to obtain a polyimide film.

[0121] Example 4

[0122] The reaction apparatus was adjusted to be airtight, and N2 was introduced into it to replace the air. At 50°C, 2.3257g of diamine monomer A4 was dissolved in 42.5g of solvent N,N-dimethylpyrrolidone. After the diamine monomer was completely dissolved, 5.1743g of dianhydride monomer 4,4'-(4,4'-isopropyldiphenyloxy)bis(phthalic anhydride) (B1) was added. After conversion, the molar ratio of diamine monomer to dianhydride monomer was about 0.99:1; then stirred at 15°C for 24h to prepare polyimide slurry.

[0123] Place a clean glass plate on the platform of the automatic coating machine, select a 100μm scraper and place it on the glass plate, use a plastic dropper to evenly cover the polyimide slurry prepared by the above method between the scraper and the glass plate, set the scraping length to 30cm, and start coating. After the coating is completed, place the glass plate in an oven for thermal imidization, and heat it at 100℃ for 15min, 200℃ for 15min, and 230℃ for 30min in a gradient heating process to evaporate the solvent. After the thermal imidization is completed, take it out after natural cooling, cut the transparent polyimide film on the smoother part of the film surface with a blade, soak it in deionized water, peel off the transparent polyimide film, wipe the surface moisture of the transparent polyimide film with a dust-free cloth, and store it well to obtain a polyimide film.

[0124] Example 5

[0125] The reaction apparatus was adjusted to be airtight, and N2 was introduced into it to replace the air. At 50°C, 2.4192g of diamine monomer A5 was dissolved in 42.5g of solvent N,N-dimethylpyrrolidone. After the diamine monomer was completely dissolved, 5.0808g of dianhydride monomer 4,4'-(4,4'-isopropyldiphenyloxy)bis(phthalic anhydride) (B1) was added. After conversion, the molar ratio of the diamine monomer to the dianhydride monomer was about 0.99:1; then stirred at 15°C for 24h to prepare a polyimide slurry.

[0126] Place a clean glass plate on the platform of the automatic coating machine, select a 100μm scraper and place it on the glass plate, use a plastic dropper to evenly cover the polyimide slurry prepared by the above method between the scraper and the glass plate, set the scraping length to 30cm, and start coating. After the coating is completed, place the glass plate in an oven for thermal imidization, and heat it at 100℃ for 15min, 200℃ for 15min, and 230℃ for 30min in a gradient heating process to evaporate the solvent. After the thermal imidization is completed, take it out after natural cooling, cut the transparent polyimide film on the smoother part of the film surface with a blade, soak it in deionized water, peel off the transparent polyimide film, wipe the surface moisture of the transparent polyimide film with a dust-free cloth, and store it well to obtain a polyimide film.

[0127] Comparative Example 1

[0128] The reaction apparatus was adjusted to be airtight, and N2 was introduced into it to replace the air. At 50°C, 2.8390g of diamine monomer A6 was dissolved in 42.5g of solvent N,N-dimethylpyrrolidone. After the diamine monomer was completely dissolved, 4.6610g of dianhydride monomer 4,4'-(4,4'-isopropyldiphenyloxy)bis(phthalic anhydride) (B1) was added. After conversion, the molar ratio of diamine monomer to dianhydride monomer was about 0.99:1; then stirred at 15°C for 24h to prepare polyimide slurry.

[0129] Place a clean glass plate on the platform of the automatic coating machine, select a 100μm scraper and place it on the glass plate, use a plastic dropper to evenly cover the polyimide slurry prepared by the above method between the scraper and the glass plate, set the scraping length to 30cm, and start coating. After the coating is completed, place the glass plate in an oven for thermal imidization, and heat it at 100℃ for 15min, 200℃ for 15min, and 230℃ for 30min in a gradient heating process to evaporate the solvent. After the thermal imidization is completed, take it out after natural cooling, cut the transparent polyimide film on the smoother part of the film surface with a blade, soak it in deionized water, peel off the transparent polyimide film, wipe the surface moisture of the transparent polyimide film with a dust-free cloth, and store it well to obtain a polyimide film.

[0130] The viscosity and other data of the polyimide slurry of each embodiment and comparative example are recorded in Table 1.

[0131] The film thickness, tensile strength, and glass transition temperature Tg values ​​of the transparent polyimide film samples prepared in the above examples and comparative examples are also recorded in Table 1.

[0132] Table 1

[0133]

[0134] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0135] The above-described embodiments only express several implementation methods of the present application, which is convenient for understanding the technical solution of the present application in detail, but it cannot be understood as limiting the scope of protection of the invention patent. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several variations and improvements can be made, which all belong to the protection scope of the present application. It should be understood that the technical solutions obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the technical solutions provided in the present application are all within the protection scope of the claims attached to the present application. Therefore, the scope of protection of the patent of this application shall be based on the content of the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A polyimide, characterized in that: The raw materials for preparing the polyimide include diamine monomers and dianhydride monomers. The diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (I): ; The dianhydride monomer is selected from one or more compounds having the structural characteristics shown in formula (II): ; R 11 and R 13 Each independently represents a cycloalkylene group having 3 to 8 carbon atoms or an arylene group having 6 to 12 carbon atoms; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms; R 21 and R 23 Each independently represents a single bond, a chain alkylene group having 1 to 6 carbon atoms, or an arylene group having 6 to 12 carbon atoms; R 22 It is a subchain alkyl group having 1 to 6 carbon atoms.

2. The polyimide according to claim 1, characterized in that R 11 and R 13 Each independently , , , , , or ; R 12 It is a subchain alkyl group having 1 to 6 carbon atoms; R 21 and R 23 Each independently or ; R 22 It is a subchain alkyl group having 2 to 5 carbon atoms.

3. The polyimide according to claim 1, characterized in that The diamine monomer is selected from one or more compounds having structural characteristics of formula (I-1) to formula (I-3): , or ; Wherein, n1, n2 and n3 are each independently a positive integer between 1 and 6; The dianhydride monomer is selected from one or more compounds having structural characteristics of formula (II-1) to formula (II-2): or ; Among them, R 22 Any group selected from the following: -CH2-, -CH2CH2-, -CH2CH2CH2-, -C(CH2)2- or -CH2CH2CH2CH2-.

4. The polyimide according to any one of claims 1 to 3, characterized in that The polyimide is selected from one or more compounds having the structural characteristics shown in formula (III): ; R 11 , R 12 , R 13 , R 21 , R 22 , R 23 The definition is the same as that in any one of claims 1 to 3.

5. The polyimide according to any one of claims 1 to 3, characterized in that The molar ratio of the diamine monomer to the dianhydride monomer is (0.9-1.2):

1.

6. A polyimide film, characterized in that: The invention comprises the polyimide according to any one of claims 1 to 5.

7. A method for preparing a polyimide film, characterized in that: The following steps are involved: Dissolving the diamine monomer and the dianhydride monomer according to any one of claims 1 to 5 in a solvent to prepare a polyimide slurry; The polyimide slurry is coated on a substrate, and after the solvent in the polyimide slurry is removed, the polyimide film is formed on the substrate.

8. The method for preparing a polyimide film according to claim 7, characterized in that: The solvent includes one or more of N-methylpyrrolidone, m-cresol, N,N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and N,N-dimethylformamide.

9. The method for preparing a polyimide film according to claim 7 or 8, characterized in that: The specific steps of removing the solvent in the polyimide slurry include: performing a first heat treatment at a temperature of 90°C to 110°C, a second heat treatment at a temperature of 190°C to 210°C, and a third heat treatment at a temperature of 220°C to 240°C on the substrate coated with the polyimide slurry to remove the solvent in the polyimide slurry.

10. A flexible electronic device, characterized in that: Comprising the polyimide film as claimed in claim 6.

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