Polyimide, preparation method and photoelectric device

Abstract

The invention relates to the technical field of polyimide materials, in particular to polyimide, a preparation method and a photoelectric device. The polyimide provided by the invention is prepared from the following raw materials: a dianhydride monomer and a diamine monomer, wherein the dianhydride monomer is selected from one or more of compounds with structural characteristics as shown in a formula (I); the diamine monomer comprises a main diamine monomer and an auxiliary diamine monomer, and the main diamine monomer is selected from one or more of compounds with structural characteristics as shown in a formula (II-1)-a formula (II-2); the auxiliary diamine monomer is selected from one or more of compounds with structural characteristics as shown in a formula (III-1)-a formula (III-2). The polyimide provided by the invention has relatively high glass transition temperature and relatively high transparency, so that the polyimide can be suitable for an application scene of high processing temperature of a photoelectric device.

Description

Technical Field

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

[0002] Transparent polymer films are widely used in optoelectronic devices such as liquid crystal displays, thin-film solar cells, OLED display panels and touch screens due to their high visible light transmittance, light weight, good flexibility and easy processing. However, traditional transparent polymer films, such as polycarbonate, polyethylene terephthalate, polynaphthol, polyether sulfone, etc., have relatively low glass transition temperatures (T g ), and therefore cannot withstand the high processing temperatures used in optoelectronic engineering.

[0003] Polyimide (PI) is a kind of polymer with an imide structure (-CO-N-CO-) in the main chain. The synergistic effect of the imide structure and the aromatic ring gives polyimide excellent physical and chemical properties, such as high T g and thermal stability, excellent mechanical properties and excellent dielectric properties. However, due to the presence of conjugated aromatic ring structures on the main chain of polyimide, intramolecular and intermolecular charge transfer complexes (CTCs) are easily formed between electron-donating diamines and electron-withdrawing dianhydrides, resulting in poor transmittance of polyimide in the visible light region and a characteristic yellow color, which seriously limits the application of polyimide in the field of optoelectronic engineering. Therefore, it is very important to develop polyimide with high heat resistance, colorless and transparent. Summary of the invention

[0004] Based on this, the present application provides a polyimide and a preparation method, and an optoelectronic device. The polyimide provided in the present application has both a high glass transition temperature and high transparency, so it can be applied to application scenarios with high processing temperatures of optoelectronic devices.

[0005] In a first aspect of the present application, a polyimide is provided, wherein the raw materials for preparing the polyimide include a dianhydride monomer and a diamine monomer, wherein the dianhydride monomer is selected from one or more compounds having the structural characteristics shown in formula (I):

[0006] ;

[0007] Among them, Cy is selected from , , , , , or ;

[0008] The diamine monomer includes a main diamine monomer and an auxiliary diamine monomer, and the main diamine monomer is selected from one or more compounds having structural characteristics shown in formula (II-1) to formula (II-2): or ; R1, when it occurs each time, is independently halogen, C1~C3 alkyl or C1~C3 haloalkyl;

[0009] The auxiliary diamine monomer is selected from one or more compounds having structural characteristics shown in formula (III-1) to formula (III-2):

[0010] or ; R2, when present, is independently halogen, C1~C3 alkyl or C1~C3 haloalkyl; A is selected from at least one S1 substituted or unsubstituted C5~C 10 Cycloalkyl, at least one S1-substituted or unsubstituted heteroaryl having 5 to 10 ring atoms; the heteroatom in the heteroaryl is nitrogen, oxygen or sulfur; S1 is selected from C1 to C6 alkyl; R3, when it occurs each time, is independently halogen, C1 to C3 alkyl or C1 to C3 haloalkyl; X1 is selected from -O-, -S-, C1 to C6 alkylene or C1 to C 10 A haloalkylene group.

[0011] In one embodiment, the molar ratio of the main diamine monomer to the auxiliary diamine monomer is (5-9.5): (0.5-5).

[0012] In one embodiment, the auxiliary diamine monomer has one or more of the following characteristics:

[0013] (1) Each occurrence of R2 is independently halogen or C1-C3 alkyl, and A is selected from , , , , or , S1 is selected from C1~C3 alkyl;

[0014] (2) X1 is selected from -O-, C1~C3 alkylene or C1~C3 haloalkylene; R3, when it appears each time, is independently halogen or C1~C3 alkyl.

[0015] In one embodiment, the main diamine monomer comprises , , , , , , , , , and One or more of .

[0016] In one embodiment, the auxiliary diamine monomer includes a first auxiliary diamine monomer and a second auxiliary diamine monomer, the first auxiliary diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (III-1), and the second auxiliary diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (III-2);

[0017] The molar ratio of the first auxiliary diamine monomer to the second auxiliary diamine monomer is (1.5-4): (0.5-1.5).

[0018] In one embodiment, the auxiliary diamine monomer has one or more of the following characteristics:

[0019] (1) The first auxiliary diamine monomer includes , , , , , , , , and One or more of;

[0020] (2) The second auxiliary diamine monomer includes , , , , and One or more of .

[0021] In one embodiment, the polyimide has one or more of the following characteristics:

[0022] (1) The glass transition temperature of the polyimide is ≥445°C;

[0023] (2) The yellowing value of the polyimide is ≤3.

[0024] The second aspect of the present application provides a method for preparing the polyimide according to any one of the first aspects of the present application, comprising the following steps:

[0025] The dianhydride monomer, the diamine monomer, a catalyst and a dehydrating agent are mixed in a solvent to carry out a polymerization reaction to prepare a polyimide slurry;

[0026] The polyimide slurry is subjected to a desolvation treatment to prepare the polyimide.

[0027] In one embodiment, the preparation method has one or more of the following characteristics:

[0028] (1) The process parameters of the polymerization reaction include: a reaction temperature of 180°C to 280°C;

[0029] (2) The process parameters of the desolvation treatment include: a temperature of 50°C to 350°C;

[0030] (3) The catalyst comprises one or more of quinoline, isoquinoline, benzoic acid, triethylamine and N-ethylpiperidine;

[0031] (4) The solvent includes one or more of nitrobenzene, p-chlorophenol, N-methylpyrrolidone, m-cresol, N,N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and N,N-dimethylformamide;

[0032] (5) The dehydrating agent includes one or more of toluene, m-xylene and dichlorothionyl.

[0033] A third aspect of the present application provides an optoelectronic device, comprising the polyimide described in any one of the embodiments of the first aspect of the present application.

[0034] The polyimide provided in this application has at least the following beneficial effects:

[0035] The polyimide provided in the present application uses a dianhydride monomer with a rigid aliphatic ring, which can ensure the optical transparency of the polyimide and improve the heat resistance of the polyimide. Further, a diamine monomer containing a fluorene group or a spirocyclic structure is selected, which can increase the free volume of the polyimide molecular chain to destroy the planar structure and regularity of the polyimide material, thereby cooperating with the dianhydride monomer to improve the transparency of the polyimide; in addition, the diamine monomer containing a fluorene group or a spirocyclic structure has a large volume of functional groups, which can limit the movement of the molecular chain to reduce the thermal expansion coefficient of the polyimide, and further improve its heat resistance and increase the glass transition temperature.

[0036] The aromatic ring structure included in the auxiliary diamine monomer has high rigidity and strong intermolecular force, which can further increase the heat resistance of the polyimide and reduce the thermal expansion coefficient of the polyimide. At the same time, the main diamine monomer and the auxiliary diamine monomer cooperate with each other, which can effectively avoid the problem of deep coloration and reduced transparency of the polyimide caused by the strong conjugation of the aromatic ring of the auxiliary diamine monomer; at this time, the auxiliary diamine monomer can effectively block the electronic coupling of the aromatic unit in the auxiliary diamine monomer under the cooperation of the fluorene-containing group or spiro ring structure of the main diamine monomer, thereby increasing the transparency of the polyimide.

[0037] In summary, the polyimide provided in the present application has both a high glass transition temperature and a high transparency, and therefore it can be applied in application scenarios with high processing temperatures of optoelectronic devices. DETAILED DESCRIPTION

[0038] The polyimide and preparation method and optoelectronic 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 the purpose is not to limit the present application.

[0039] 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.

[0040] As used herein, "halogen" or "halo" refers to -F, -Cl, -Br or -I.

[0041] In this application, "*" or " " represents a connection site or a fusion site. In the present application, when a connection site is not specified in a group, it means that an optional connection site in the group is used as a connection site; in the present application, when a fusion site is not specified in a group, it means that an optional fusion site in the group is used as a fusion site, and preferably two or more sites in adjacent positions in the group are fusion sites.

[0042] In the present application, when a linking site is not specified in a group, it means that an optional linking site in the group can be used as a linking site.

[0043] In the present application, the single bond to which the substituent is connected runs through the corresponding ring, indicating that the substituent can be connected to any position of the ring, for example R is connected to any substitutable position of the benzene ring.

[0044] In this application, "alkyl" refers to a saturated hydrocarbon group containing a primary (normal) carbon atom, or a secondary carbon atom, or a tertiary carbon atom, or a quaternary carbon atom, or a combination thereof. Phrases containing this term, for example, "C1~C3 alkyl" refers to an alkyl group containing 1 to 3 carbon atoms, and each time it appears, it can be independently C1 alkyl, C2 alkyl, C3 alkyl. Suitable examples include, but are not limited to: methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-propyl, n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2).

[0045] "Haloalkyl" refers to an alkyl group substituted with one or more halogen (chlorine, fluorine, bromine or iodine) atoms. Polyhaloalkyl groups have the same or mixed types of halogen atoms. "Perhaloalkyl" refers to an alkyl group in which each hydrogen atom is replaced by a halogen atom. A haloalkyl group that is "fully halogenated" at a particular carbon atom means that all hydrogen atoms attached to that carbon are replaced by halogen atoms. Representative mono-, di- and trihaloalkyl groups include: chloromethyl, chloroethyl, bromomethyl, bromoethyl, iodomethyl, iodoethyl, chloropropyl, bromopropyl, iodopropyl, 1,1-dichloromethyl, 1,1-dibromomethyl, 1,1-dichloropropyl, 1,2-dibromopropyl, 2,3-dibromopropyl, 1-chloro-2-bromoethyl, 2-chloro-3-bromopropyl, trifluoromethyl, trichloromethyl, and the like.

[0046] In this 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, such as "C5~C 10 "Cycloalkyl" refers to a cycloalkyl group containing 5 to 10 carbon atoms, and each occurrence can be independently C5 cycloalkyl, C6 cycloalkyl, C7 cycloalkyl, C8 cycloalkyl, C9 cycloalkyl, C 10 Cycloalkyl. Suitable examples include, but are not limited to, 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.

[0047] In the present application, the "number of ring atoms" refers to the number of atoms in the atoms constituting the ring itself of a structural compound (e.g., a monocyclic compound, a condensed ring compound, a cross-linked compound, a carbocyclic compound, a heterocyclic compound) formed by atoms bonding to form a ring. When the ring is substituted by a substituent, the atoms contained in the substituent are not included in the ring atoms. The same is true for the "number of ring atoms" described below unless otherwise specified. For example, the number of ring atoms of a benzene ring is 6, the number of ring atoms of a naphthalene ring is 10, and the number of ring atoms of a thienyl group is 5.

[0048] In the present application, "heteroaryl" refers to an aryl or cyclopentadienyl group in which at least one carbon atom is replaced by a non-carbon atom, and the non-carbon atom may be an N atom, an O atom, an S atom, etc. Suitable examples of "heteroaryl" include, but are not limited to, furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetrazole, indole, carbazole, pyrroloimidazole, pyrrolopyrrole, thienopyrrole, thienothiophene, furopyrrole, furofuran, thienofuran, benzisoxazole, benzisothiazole, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-naphthyridine, quinoxaline, phenanthridine, primidine, quinazoline and quinazolinone.

[0049] "Alkylene" refers to a hydrocarbon group with two monovalent radical centers derived from an alkyl group by removing a hydrogen atom, which can be a saturated branched alkyl group or a saturated straight-chain alkyl group. For example, "C1-C6 alkylene" means that the alkyl part contains 1 to 6 carbon atoms, and each time it appears, it can be independently C1 alkylene, C4 alkylene, C5 alkylene, C6 alkylene. Suitable examples include, but are not limited to: methylene (-CH2-), 1,1-ethyl (-CH(CH3)-), 1,2-ethyl (-CH2CH2-), 1,1-propyl (-CH(CH2CH3)-), 1,2-propyl (-CH2CH(CH3)-), 1,3-propyl (-CH2CH2CH2-) and 1,4-butyl (-CH2CH2CH2CH2-).

[0050] "Haloalkylene" means that on the basis of "alkylene", halogen atoms are substituted for hydrogen atoms in the alkylene. It can be understood that the number of halogen atoms substituted is ≤ the number of hydrogen atoms in the alkylene.

[0051] Traditional aromatic polyimide films have a high aromatic ring density and are prone to form charge transfer complexes, so they have a distinct yellow-brown appearance, which limits their application in optoelectronic devices. Currently, several colorless and transparent polyimides have been developed based on the elimination of intermolecular and intramolecular charge transfer complexes.

[0052] In order to improve the optical transparency of polyimide film, there are mainly the following improvement methods: (1) Selecting alicyclic dianhydride monomers and aromatic fluorinated diamine monomers to obtain fluorinated semi-alicyclic transparent polyimide film, the polyimide has good transmittance; however, its glass transition temperature is 250℃~277℃, and this low glass transition temperature limits its application in high processing temperatures of optical devices. (2) Compounding alicyclic dianhydride monomers and alicyclic diamine monomers to prepare polyimide. The alicyclic unit introduced in this method can effectively improve the optical transparency of polyimide, but its glass transition temperature is 250℃~265℃, and its heat resistance cannot be effectively guaranteed. (3) Selecting alicyclic dianhydride monomers and diamine monomers containing trifluoromethyl and ether bonds to carry out polymerization reaction to prepare polyimide film. The polyimide film also has excellent transparency, but its highest glass transition temperature is 288℃, and its heat resistance is also reduced.

[0053] It can be seen that although the above-mentioned methods of preparing polyimide by introducing fluorinated groups or aliphatic ring units can ensure its optical transparency, the above-mentioned polyimide will sacrifice some heat resistance due to the close stacking between molecular chains. Therefore, it is still challenging to make polyimide have both high glass transition temperature and high transparency.

[0054] Based on this, the first aspect of the present application provides a polyimide, wherein the raw materials for preparing the polyimide include a dianhydride monomer and a diamine monomer. The dianhydride monomer is selected from one or more compounds having the structural characteristics shown in formula (I):

[0055] .

[0056] Among them, Cy is selected from , , , , , or .

[0057] The present application found that the above-mentioned specific cyclic structure has a certain rigidity, so at high temperature, the thermal motion and conformational change of the molecular chain will be limited, thereby enhancing the heat resistance of the polyimide. At the same time, its cyclic structure is not a conjugated aromatic skeleton, so it can effectively weaken the conjugation between and within the molecular chains to reduce the interaction between molecules, thereby reducing the probability of charge transfer complex formation, reducing the yellowing value of the polyimide, and improving its optical transparency.

[0058] For example, the dianhydride monomers of the present application include , , , , , and One or more of .

[0059] in, It is hydrogenated pyromellitic dianhydride (HPMDA). It is bicyclo[2.2.1]-heptane-2,3,5,6-tetracarboxylic acid-2,3:5,6-dianhydride. It is bicyclo[2.2.2]-octane-2,3,5,6-tetracarboxylic acid-2,3:5,6-dianhydride (BODA). It is bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride (BTA). It is decahydro-1,4:5,8-dimethylnaphthalene-2,3,6,7-tetracarboxylic dianhydride (DNDA). It is dicyclohexyl-3,4,3',4'-tetracarboxylic dianhydride (DCDA). It is 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA).

[0060] In one example, the dianhydride monomer includes a main dianhydride monomer and a secondary diamine monomer. The main dianhydride monomer includes , , and The auxiliary dianhydride monomer includes , and One or more of .

[0061] The aliphatic ring included in the above-mentioned main dianhydride monomer has a more rigid structure, and has better synergy with the auxiliary dianhydride monomer with weaker rigidity, so as to prepare a polyimide with excellent heat resistance and lower yellowness value.

[0062] In one example, the molar ratio of the main dianhydride monomer to the auxiliary dianhydride monomer is (3-5): 1. For example, the molar ratio of the main dianhydride monomer to the auxiliary dianhydride monomer includes but is not limited to 3: 1, 3.3: 1, 3.5: 1, 3.8: 1, 4: 1, 4.2: 1, 4.5: 1, 4.8: 1 or 5: 1, or a range formed by any two of the above point values ​​as endpoint values.

[0063] The diamine monomer includes a main diamine monomer and an auxiliary diamine monomer, wherein the main diamine monomer is selected from one or more compounds having structural characteristics shown in formula (II-1) to formula (II-2): or ; R1, when it occurs each time, is independently halogen, C1~C3 alkyl or C1~C3 haloalkyl.

[0064] The present application found that the electron cloud distribution of the main diamine monomer containing fluorene groups of the structure shown in formula (I) is relatively uniform, and its electron donation and electron withdrawal capabilities are relatively weak. Therefore, when the fluorene-containing group is introduced into the polyimide, it can reduce the formation of charge transfer complexes between molecular chains. At the same time, it can increase the free volume of the polyimide molecular chain to destroy the planar structure and regularity of the polyimide material, and then cooperate with the dianhydride monomer to improve the transparency of the polyimide. In addition, the rigid planar structure of the fluorene-containing group restricts the movement of the molecular chain, which can also further reduce the thermal expansion coefficient of the polyimide and improve its heat resistance.

[0065] The diamine monomer of the spirocyclic structure shown in formula (II) has large steric hindrance and high rotation potential energy. This structural feature restricts the rotation and vibration of polyimide and increases the glass transition temperature of polyimide. In addition, the steric hindrance effect of the spirocyclic structure can also destroy the conjugated structure of the polyimide molecular chain, reduce the electronic conjugation between molecules, inhibit the formation of charge transfer complexes, and thus improve the optical transparency of polyimide.

[0066] In one example, the primary diamine monomer includes , , , , , , , , , and One or more of .

[0067] in, It is 9,9-bis(4-aminophenyl)fluorene (BAFL).

[0068] It is 9,9-di(4-amino-3-fluorophenyl)fluorene (FFDA).

[0069] It is 9,9-di(4-amino-3-methylphenyl)fluorene (BTFL).

[0070] The auxiliary diamine monomer is selected from one or more compounds having structural characteristics shown in formula (III-1) to formula (III-2):

[0071] or R2, when present, is independently halogen, C1~C3 alkyl or C1~C3 haloalkyl; A is selected from at least one S1 substituted or unsubstituted C5~C 10Cycloalkyl, at least one S1-substituted or unsubstituted heteroaryl having 5 to 10 ring atoms; the heteroatom in the heteroaryl is nitrogen, oxygen or sulfur; S1 is selected from C1 to C6 alkyl.

[0072] R3, when present, is independently halogen, C1~C3 alkyl or C1~C3 haloalkyl; X1 is selected from -O-, -S-, C1~C6 alkylene or C1~C 10 A haloalkylene group.

[0073] The aforementioned main diamine monomer has limited improvement on heat resistance. In order to further improve the heat resistance of polyimide, the present application adds an auxiliary diamine monomer containing an aromatic structure. Due to the addition of the main diamine monomer, the fluorene group or spiro ring structure in the main diamine monomer can effectively block the electronic coupling of the aromatic unit in the auxiliary diamine monomer, thereby effectively avoiding the problem of dark coloration and reduced transparency of the polyimide caused by the strong conjugation effect of the aromatic ring of the auxiliary diamine monomer.

[0074] The polyimide provided in the present application has both a high glass transition temperature and a high transparency under the cooperation of a dianhydride monomer, a main diamine monomer and an auxiliary diamine monomer of a specific structure, so it can be suitable for application scenarios with high processing temperatures of optoelectronic devices.

[0075] In one example, each occurrence of R2 is independently halogen or C1-C3 alkyl. A is selected from , , , , or . S1 is selected from C1~C3 alkyl.

[0076] For example, the compounds having the structural features shown in formula (II-1) include , , , , , , , , and One or more of .

[0077] in, It is 5(6)-amino-1-(4-aminophenyl)-1,3,3-trimethylindane (PIDA). 2-(4-aminophenyl)-5-aminobenzimidazole (APBIA), It is 2-(4-aminophenyl)-5-aminobenzoxazole (APBOA).

[0078] In one example, X1 is selected from -O-, C1~C3 alkylene or C1~C3 haloalkylene; each occurrence of R3 is independently halogen or C1~C3 alkyl.

[0079] For example, the compounds having the structural features shown in formula (II-2) include , , , , and One or more of .

[0080] in, It is 4,4'-diaminodiphenyl ether (ODA).

[0081] It is 4,4'-diaminodiphenylmethane (ODA).

[0082] In one example, the molar ratio of the main diamine monomer to the auxiliary diamine monomer is (5-9.5): (0.5-5). For example, the molar ratio of the main diamine monomer to the auxiliary diamine monomer includes but is not limited to 5:5, 5.4:4.6, 5.5:4.5, 5.6:4.4, 5.8:4.2, 6:4, 6.2:3.8, 6.5:3.5, 6.8:3.2, 7:3, 7.2:2.8, 7.5:2.5, 7.8:2.2, 8:2, 8.2:1.8, 8.5:1.5, 8.8:1.2, 9:1, 9.2:0.8 or 9.5:0.5, or in the range formed by any two of the above point values ​​as endpoint values.

[0083] In one example, the auxiliary diamine monomer includes a first auxiliary diamine monomer and a second auxiliary diamine monomer, the first auxiliary diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (III-1), and the second auxiliary diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (III-2).

[0084] The present application has found that when the compound with the structural characteristics shown in formula (III-1) and the compound with the structural characteristics shown in formula (III-2) are used in combination as auxiliary diamine monomers, they can effectively ensure the glass transition temperature of polyimide and reduce the yellowing value of polyimide. Specifically, the heterocyclic structure in the compound with the structural characteristics shown in formula (III-1) and the ether bond or alkyl group in the compound with the structural characteristics shown in formula (III-2) cooperate with each other in the molecular chain, making the electron cloud distribution on the molecular chain more reasonable, thereby reducing the yellowing phenomenon caused by uneven distribution of the electron cloud. At the same time, the heterocyclic structure in the compound with the structural characteristics shown in formula (III-1) and the compound with the structural characteristics shown in formula (III-2) work together to reduce the possibility of chemical bond breaking and rearrangement, so as to increase the thermal decomposition temperature of polyimide, thereby enhancing the heat resistance of the material.

[0085] In one example, the molar ratio of the first auxiliary diamine monomer to the second auxiliary diamine monomer is (1.5-4): (0.5-1.5). For example, the molar ratio of the first auxiliary diamine monomer to the second auxiliary diamine monomer includes but is not limited to 1.5:0.5, 1.8:0.5, 2:0.5, 2.5:0.5, 2.8:0.5, 3:0.5, 3.2:0.5, 3.5:0.5, 3.8:0.5, 4:0.5, 1.5:0.8, 1.8:0.8, 2:0.8, 2.5:0.8, 2.8:0.8, 3:0.8, 3.2:0.8, 3.5:0.8, 3.8:0.8, 4:0.8, 1.5:1, 1.8:1, 2:1, 2.5:1, 2 .8:1, 3:1, 3.2:1, 3.5:1, 3.8:1, 4:1, 1.5:1.2, 1.8:1.2, 2:1.2, 2.5:1.2, 2.8:1.2, 3:1.2, 3.2:1.2, 3.5:1.2, 3.8:1.2, 4:1.2, 1.5:1.5, 1.8:1.5, 2:1.5, 2.5:1.5, 2.8:1.5, 3:1.5, 3.2:1.5, 3.5:1.5, 3.8:1.5, or 4:1.5, or in the range formed by any two of the above point values ​​as endpoint values.

[0086] In one example, the first auxiliary diamine monomer includes , , , , , , , , and One or more of .

[0087] In one example, the second auxiliary diamine monomer includes , , , , and One or more of .

[0088] In one example, the glass transition temperature of the polyimide is ≥445°C. Furthermore, the glass transition temperature of the polyimide is ≥450°C.

[0089] In one example, the yellowing value of the polyimide is ≤ 3. Further, the yellowing value of the polyimide is 2 to 2.85. For example, the yellowing value of the polyimide includes but is not limited to 2, 2.05, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.83 or 2.85, or a range formed by any two of the above point values ​​as endpoint values.

[0090] In one example, the thermal expansion coefficient of the polyimide at 50°C to 200°C is ≤50ppm / °C. Further, the thermal expansion coefficient of the polyimide at 50°C to 200°C is 34ppm / °C to 50ppm / °C. For example, the thermal expansion coefficient of the polyimide includes but is not limited to 34ppm / °C, 36ppm / °C, 38ppm / °C, 40ppm / °C, 42ppm / °C, 45ppm / °C, 48ppm / °C or 50ppm / °C, or any two of the above points as endpoint values.

[0091] In one example, the chromaticity index b* value of the polyimide is ≤ 2. Further, the chromaticity index b value of the polyimide is 1.1 to 1.85. For example, the chromaticity index b* value of the polyimide includes but is not limited to 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55, 1.6, 1.65, 1.7, 1.75, 1.8 or 1.85, or any two of the above point values ​​as endpoint values.

[0092] The second aspect of the present application provides a method for preparing the polyimide according to any one of the first aspects of the present application, comprising the following steps:

[0093] S10, mixing the dianhydride monomer, the diamine monomer, a catalyst and a dehydrating agent in a solvent, and performing a polymerization reaction to prepare a polyimide slurry;

[0094] S20, performing a desolvation treatment on the polyimide slurry to prepare the polyimide.

[0095] In one example, in step S10, the process parameters of the polymerization reaction include: the reaction temperature is 180°C to 280°C. Further, the process parameters of the polymerization reaction also include: the reaction time is 2h to 5h. For example, the temperature of the polymerization reaction in the present application includes but is not limited to 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C or 280°C, or any two of the above point values ​​are within the range of endpoint values. The time of the polymerization reaction includes but is not limited to 2h, 2.5 h, 2.8 h, 3 h, 3.2 h, 3.5 h, 3.8 h, 4 h, 4.2 h, 4.5 h, 4.8 h or 5 h, or any two of the above point values ​​are within the range of endpoint values.

[0096] In the present application, in the presence of a catalyst and a dehydrating agent, step S10 can polymerize diamine monomers and dianhydride monomers to prepare polyimide. The preparation method can shorten the preparation time of polyimide from the traditional 5.5h~36h to 2h~5h, thereby effectively reducing energy consumption, shortening the preparation time, and improving the production efficiency of polyimide. At the same time, the polyimide prepared by the method also has excellent heat resistance, which can ensure a higher glass transition temperature of the polyimide.

[0097] In one example, the catalyst includes one or more of quinoline, isoquinoline, benzoic acid, triethylamine and N-ethylpiperidine.

[0098] In one example, the solvent includes one or more of nitrobenzene, p-chlorophenol, N-methylpyrrolidone, m-cresol, N,N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and N,N-dimethylformamide.

[0099] Preferably, the solvent includes one or more of nitrobenzene, p-chlorophenol, m-cresol, γ-butyrolactone and cyclohexanone. The above solvent is a high boiling point solvent, which can withstand high temperatures during the preparation of polyimide and can serve as a reaction medium to promote the full reaction of dianhydride monomers and diamine monomers.

[0100] In one example, the dehydrating agent includes one or more of toluene, m-xylene and thionyl chloride.

[0101] In one example, the process parameters of the desolvation treatment include: a temperature of 50°C to 350°C. For example, the temperature for desolvation includes but is not limited to 50°C, 80°C, 100°C, 120°C, 150°C, 180°C, 200°C, 220°C, 250°C, 280°C, 300°C, 320°C or 350°C, or any two of the above point values ​​as endpoint values. Furthermore, the time of the desolvation treatment is 10min to 30min.

[0102] In one example, after the desolvation step, the method further includes a baking step.

[0103] The baking process parameters include: a temperature of 400°C to 500°C. The baking process parameters also include: a time of 30min to 60min. For example, the baking temperature includes but is not limited to 400°C, 420°C, 440°C, 450°C, 460°C, 470°C, 480°C, 490°C or 500°C.

[0104] In one specific example, the method for preparing the polyimide comprises the following steps:

[0105] S100, mixing the dianhydride monomer, the diamine monomer, a catalyst and a dehydrating agent in a solvent, and performing a polymerization reaction at 180° C. to 280° C. for 2 h to 5 h to prepare a polyimide slurry;

[0106] S20, subjecting the polyimide slurry to a desolvation treatment at 50° C. to 350° C. for 10 min to 30 min, and then baking at 400° C. to 500° C. for 30 min to 60 min to prepare the polyimide.

[0107] In order to make the purpose and advantages of the present invention clearer, the polyimide of the present invention and its effects are further described in detail below in conjunction with specific examples. It should be understood that the specific examples described herein are only used to explain the present invention and shall not be used to limit the present invention. The following examples do not include other components except inevitable impurities unless otherwise specified. The drugs and instruments used in the examples are conventionally selected in the art unless otherwise specified. The experimental methods for which specific conditions are not specified in the examples are implemented according to conventional conditions, such as the conditions described in the literature, books, or methods recommended by the manufacturer.

[0108] [Dianhydride monomer]

[0109] BODA: Structural formula ;

[0110] HPMDA: Structural Formula .

[0111] [Diamine monomer]

[0112] BAFL: Structural formula ;

[0113] FFDA: Structural formula ;

[0114] APBIA: Structural Formula ;

[0115] APBOA: Structural formula ;

[0116] ODA: Structural formula .

[0117] Example 1

[0118] Under nitrogen protection, BODA (2.50 g, 10 mmol, dianhydride monomer), BAFL (3.13 g, 9 mmol, diamine monomer), ODA (0.20 g, 1 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1.0 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask, and the reaction was stirred with a rotor at 220 ° C for 5 h to obtain a viscous polyimide slurry.

[0119] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0120] Example 2

[0121] Under nitrogen protection, BODA (2.00 g, 8 mmol, dianhydride monomer), HPMDA (0.45 g, 2 mmol, dianhydride monomer), BAFL (3.13 g, 9 mmol, diamine monomer), ODA (0.20 g, 1 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1.0 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask, and the reaction was stirred with a rotor at 220 ° C for 5 h to obtain a viscous polyimide slurry.

[0122] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0123] Example 3

[0124] Under nitrogen protection, BODA (2.00 g, 8 mmol, dianhydride monomer), HPMDA (0.45 g, 2 mmol, dianhydride monomer), BAFL (2.44 g, 7 mmol, diamine monomer), APBIA (0.45 g, 2 mmol, diamine monomer), ODA (0.20 g, 1 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1.0 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask, and the reaction was stirred with a rotor at 220 ° C for 5 h to obtain a viscous polyimide slurry.

[0125] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0126] Example 4

[0127] Under nitrogen protection, BODA (2.00 g, 8 mmol, dianhydride monomer), HPMDA (0.45 g, 2 mmol, dianhydride monomer), BAFL (1.92 g, 5.5 mmol, diamine monomer), APBIA (0.78 g, 3.5 mmol, diamine monomer), ODA (0.20 g, 1 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1.0 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask, and the reaction was stirred with a rotor at 220 ° C for 5 h to obtain a viscous polyimide slurry.

[0128] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0129] Example 5

[0130] Under nitrogen protection, BODA (2.00 g, 8 mmol, dianhydride monomer), HPMDA (0.45 g, 2 mmol, dianhydride monomer), FFDA (2.50 g, 6.5 mmol, diamine monomer), APBIA (0.78 g, 3.5 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1.0 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask, and the reaction was stirred with a rotor at 220 ° C for 5 h to obtain a viscous polyimide slurry.

[0131] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0132] Example 6

[0133] Under nitrogen protection, BODA (2.00 g, 8 mmol, dianhydride monomer), HPMDA (0.45 g, 2 mmol, dianhydride monomer), BAFL (2.44 g, 7 mmol, diamine monomer), APBOA (0.45 g, 2 mmol, diamine monomer), ODA (0.20 g, 1 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask, and the reaction was stirred with a rotor at 220 ° C for 5 h to obtain a viscous polyimide slurry.

[0134] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0135] Example 7

[0136] Example 7 is basically the same as Example 1, the main difference being that in Example 7, a diamine monomer is selected. Replace BAFL in Example 1. The specific steps include:

[0137] Under nitrogen protection, BODA (2.50 g, 10 mmol, dianhydride monomer), (2.25 g, 9 mmol, diamine monomer), ODA (0.20 g, 1 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1.0 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask and reacted with rotor stirring at 220 °C for 5 h to obtain a viscous polyimide slurry.

[0138] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0139] Example 8

[0140] Example 8 is basically the same as Example 3, the main difference is that: in Example 8, diamine monomer is selected Replace BAFL in Example 3. The specific steps include:

[0141] Under nitrogen protection, BODA (2.00 g, 8 mmol, dianhydride monomer), HPMDA (0.45 g, 2 mmol, dianhydride monomer), (1.75 g, 7 mmol, diamine monomer), APBIA (0.45 g, 2 mmol, diamine monomer), ODA (0.20 g, 1 mmol, diamine monomer), isoquinoline (0.20 g, 1.50 mmol, catalyst), toluene (1.0 mL, dehydrating agent) and γ-butyrolactone (GBL, 9 mL, solvent) were put into a 100 mL three-necked flask and reacted at 220 ° C with rotor stirring for 5 h to obtain a viscous polyimide slurry.

[0142] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0143] Example 9

[0144] Example 9 is basically the same as Example 1, the main difference being that in Example 9, the diamine monomer APBIA is used to replace the ODA in Example 1. The specific steps include:

[0145] Under nitrogen protection, BODA (2.50 g, 10 mmol), BAFL (3.13 g, 9 mmol), APBIA (0.22 g, 1 mmol), isoquinoline (0.20 g, 1.50 mmol), toluene (1.0 mL) and γ-butyrolactone (GBL, 9 mL) were put into a 100 mL three-necked flask and reacted at 220 °C with rotor stirring for 5 h to obtain a viscous CPI solution.

[0146] After precision scraper coating, the film was placed in an oven and baked at 100°C for 15 min for desolvation treatment, and then baked at 460°C for 45 min under nitrogen conditions, and then peeled off to obtain a polyimide film.

[0147] Comparative Example 1

[0148] Comparative Example 1 is substantially the same as Example 1, the main difference being that the diamine monomer ODA is not included in Comparative Example 1. The film obtained by the reaction is too brittle and breaks apart when peeled off in water.

[0149] The glass transition temperature Tg value, the corresponding temperature Td5% value when the mass loss reaches 5% during the thermogravimetric analysis, the thermal expansion coefficient CTE value in the temperature range of 50°C to 200°C, the color index b* value, and the yellowness value YI of the transparent polyimide films prepared in the above examples and comparative examples were tested. The results are recorded in Table 1.

[0150] Table 1

[0151]

[0152] From the comparison between Example 1 and Example 2 of the present application, it can be seen that two dianhydride monomers, BODA and HPMDA, are selected in Example 2. Although the glass transition temperature of the prepared polyimide is slightly reduced, its color index b value and yellowness value YI are reduced, that is, the optical transparency of the polyimide is more excellent. From the comparison between Example 2 and Example 3, it can be seen that the auxiliary diamine monomers in Example 3 are respectively selected from the first auxiliary diamine monomer APBIA and the second auxiliary diamine monomer ODA, which have a higher glass transition temperature and a lower thermal expansion coefficient than Example 2, but its color index b value and yellowness value YI are increased, that is, the polyimide of Example 3 has better heat resistance. Example 3 and Example 6 are basically the same, the main difference is that the types of the first auxiliary diamine monomers selected in Example 3 and Example 6 are different. From the comparison, it can be seen that when the first auxiliary diamine monomer selects an imidazole ring, the polyimide can have better heat resistance and transparency.

[0153] By comparing Example 1 and Example 7, it is found that the main diamine monomer in Example 7 is a compound with a structure shown in formula (II-2), which can effectively reduce the thermal expansion coefficient, color index b value and yellowness value YI of the polyimide prepared in Example 7, indicating that the polyimide of Example 7 has more excellent heat resistance and optical transparency.

[0154] By comparing Example 3 and Example 8, it is found that the main diamine monomer in Example 8 is a compound with a structure shown in formula (II-2). Compared with Example 3, the main diamine monomer in Example 8 is a compound with a structure shown in formula (II-2), which can effectively reduce the thermal expansion coefficient, color index b value and yellowness value YI of the polyimide prepared in Example 8, indicating that the polyimide of Example 8 has better heat resistance and optical transparency.

[0155] Comparison between Example 9 and Example 1 shows that the auxiliary diamine monomer in Example 9 is a compound having a structure shown in Formula (III-1), which has a lower thermal expansion coefficient than that of Example 1, indicating that Example 9 has better heat resistance.

[0156] 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.

[0157] 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 dianhydride monomers and diamine monomers, and the dianhydride monomers are selected from one or more compounds having the structural characteristics shown in formula (I): ； Among them, Cy is selected from , , , , , or ; The diamine monomer includes a main diamine monomer and an auxiliary diamine monomer, and the main diamine monomer is selected from one or more compounds having structural characteristics shown in formula (II-1) to formula (II-2): or ; R1, when it occurs each time, is independently halogen, C1~C3 alkyl or C1~C3 haloalkyl; The auxiliary diamine monomer is selected from one or more compounds having structural characteristics shown in formula (III-1) to formula (III-2): or ; R2, when present, is independently halogen, C1~C3 alkyl or C1~C3 haloalkyl; A is selected from at least one S1 substituted or unsubstituted C5~C 10 Cycloalkyl, at least one S1-substituted or unsubstituted heteroaryl having 5 to 10 ring atoms; the heteroatom in the heteroaryl is nitrogen, oxygen or sulfur; S1 is selected from C1 to C6 alkyl; R3, when it occurs each time, is independently halogen, C1 to C3 alkyl or C1 to C3 haloalkyl; X1 is selected from -O-, -S-, C1 to C6 alkylene or C1 to C 10 A haloalkylene group.

2. The polyimide according to claim 1, characterized in that The molar ratio of the main diamine monomer to the auxiliary diamine monomer is (5-9.5): (0.5-5).

3. The polyimide according to claim 1, characterized in that The auxiliary diamine monomer has one or more of the following characteristics: (1) Each occurrence of R2 is independently halogen or C1-C3 alkyl, and A is selected from , , , , or , S1 is selected from C1~C3 alkyl; (2) X1 is selected from -O-, C1~C3 alkylene or C1~C3 haloalkylene; R3, when it appears each time, is independently halogen or C1~C3 alkyl.

4. The polyimide according to claim 1, characterized in that The main diamine monomer includes , , , , , , , , , and One or more of .

5. The polyimide according to any one of claims 1 to 4, characterized in that The auxiliary diamine monomer includes a first auxiliary diamine monomer and a second auxiliary diamine monomer, wherein the first auxiliary diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (III-1), and the second auxiliary diamine monomer is selected from one or more compounds having the structural characteristics shown in formula (III-2); The molar ratio of the first auxiliary diamine monomer to the second auxiliary diamine monomer is (1.5-4): (0.5-1.5).

6. The polyimide according to claim 5, characterized in that The auxiliary diamine monomer has one or more of the following characteristics: (1) The first auxiliary diamine monomer includes , , , , , , , , and One or more of; (2) The second auxiliary diamine monomer includes , , , , and One or more of .

7. The polyimide according to any one of claims 1 to 4, characterized in that The polyimide has one or more of the following characteristics: (1) The glass transition temperature of the polyimide is ≥445°C; (2) The yellowing value of the polyimide is ≤3.

8. A method for preparing a polyimide according to any one of claims 1 to 7, characterized in that: The following steps are involved: The dianhydride monomer, the diamine monomer, a catalyst and a dehydrating agent are mixed in a solvent to carry out a polymerization reaction to prepare a polyimide slurry; The polyimide slurry is subjected to a desolvation treatment to prepare the polyimide.

9. The method for preparing a polyimide according to claim 8, characterized in that: The preparation method has one or more of the following characteristics: (1) The process parameters of the polymerization reaction include: a reaction temperature of 180°C to 280°C; (2) The process parameters of the desolvation treatment include: a temperature of 50°C to 350°C; (3) The catalyst comprises one or more of quinoline, isoquinoline, benzoic acid, triethylamine and N-ethylpiperidine; (4) The solvent includes one or more of nitrobenzene, p-chlorophenol, N-methylpyrrolidone, m-cresol, N,N-dimethylacetamide, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone and N,N-dimethylformamide; (5) The dehydrating agent includes one or more of toluene, m-xylene and dichlorothionyl.

10. A photoelectric device, characterized in that: The invention comprises the polyimide according to any one of claims 1 to 7.

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