CN110760062A

CN110760062A - Optical film, transparent substrate, image display device and solar cell

Info

Publication number: CN110760062A
Application number: CN201910978620.5A
Authority: CN
Inventors: 李南文; 许辉
Original assignee: Zhejiang Zhongke Jiuyuan New Material Co Ltd
Current assignee: Zhejiang Zhongke Jiuyuan New Material Co Ltd
Priority date: 2019-10-15
Filing date: 2019-10-15
Publication date: 2020-02-07

Abstract

The invention provides an optical film with 400nm light transmittance of more than 80% and excellent linear thermal expansion coefficient; further, the present invention proposes to use the optical film for products and parts requiring high light transmittance and a high linear thermal expansion coefficient, such as a transparent substrate, an image display device, and a solar cell.

Description

Optical film, transparent substrate, image display device and solar cell

Technical Field

The present invention relates to the field of optical materials, and in particular, to an optical film, a transparent substrate, an image display device, and a solar cell.

Background

Polyimide is a high polymer material, has excellent mechanical properties, thermal properties and electrical properties, is an important special high polymer material, and is applied to a plurality of fields such as machinery, electrical appliances, aerospace and the like. Different application fields have different requirements on the performance of the polyimide film, and in the application of flexible circuit boards, flexible solar cells, flexible display substrates and the like, the polyimide film material needs to have low thermal expansion coefficient, excellent dimensional stability and high heat resistance.

With the rapid development of optoelectronic technology, the field of optoelectronic devices has a development trend of intellectualization, light weight, ultra-thinning and flexibility in recent years, and the key to realizing the function is to obtain a transparent film material with light weight, flexibility and excellent comprehensive performance. The traditional glass substrate material cannot meet the requirement of the future flexible packaging technology due to the characteristics of hardness and brittleness. The polymer film material has the characteristics of light weight, flexibility, good transparency, excellent comprehensive performance and the like, can well meet the requirements of flexible optoelectronic device substrates, can adopt a roll-to-roll process to carry out large-scale and continuous production in the industrial processing process of the flexible transparent polymer substrates, and is beneficial to reducing the production cost. Therefore, the transparent polymer substrate material becomes the preferred material of the future flexible optoelectronic device.

In addition, when a fine element made of an inorganic material is formed on a film, the film after the formation of the inorganic element may be bent due to the difference in linear thermal expansion coefficient between the inorganic material and the film, and the inorganic element may be broken. Therefore, a film material having both transparency and heat resistance and having the same linear thermal expansion coefficient as that of the inorganic material is desired.

Polyimide is applied to electronic parts because of its heat resistance and high insulating property. Therefore, polyimide and a metal such as single crystal silicon or copper are often stacked, and attempts have been made to reduce the linear thermal expansion coefficient of polyimide to a level equivalent to that of single crystal silicon or metal.

Among these, polyimide having a fluorine substituent, for example, polyimide obtained from 2, 2' -bis (trifluoromethyl) diaminobiphenyl, is excellent in heat resistance and linear thermal expansion coefficient, and also relatively excellent in solubility in an organic solvent and transparency. However, no polyimide of this type has been disclosed so far as having excellent light transmittance for visible light.

Disclosure of Invention

Based on the technical problems existing in the background technology, the invention provides an optical film with 400nm light transmittance of more than 80% and excellent linear thermal expansion coefficient; further, the present invention proposes to use the optical film for products and parts requiring high light transmittance and a high linear thermal expansion coefficient, such as a transparent substrate, an image display device, and a solar cell.

The invention provides an optical film, which is polyimide containing the following repeated structural units,

wherein R1 is a residue obtained by removing 4 carboxyl groups from a tetracarboxylic dianhydride monomer containing an aromatic ring or an aliphatic ring; r2 is the residue of a diprimary amine monomer after removal of 2 amino groups; ar is a 2-valent organic group containing an aromatic ring.

Preferably, the first and second electrodes are formed of a metal,

r1 is at least one of the following groups:

r2 is the following group:

ar is the following group:

preferably, the polyimide further comprises a repeating structural unit,

wherein R3 is a residue obtained by removing 4 carboxyl groups from a tetracarboxylic dianhydride monomer which is the same as or different from R1; r4 is the residue of a primary diamine monomer which is the same as or different from R2 after removal of 2 amino groups.

Preferably, the first and second electrodes are formed of a metal,

r3 is at least one of the following groups:

r4 is at least one of the following groups:

preferably, the linear thermal expansion coefficient of the optical film is 20ppm/K or less; further, the glass transition temperature is 300 ℃ or higher; more preferably, the optical film has a total light transmittance of 85% or more, and further, a transmittance of light having a wavelength of 400nm of 80% or more.

Preferably, the polyimide is obtained by synthesizing polyamic acid from a tetracarboxylic dianhydride monomer and a primary diamine monomer, and then adding a dehydrating agent and an imidizing agent into the polyamic acid for imidization.

Preferably, the optical film is obtained by imidizing the polyamic acid, adding the imidized polyamic acid into a poor solvent to precipitate a solid, dissolving the solid into an organic solvent, and coating the organic solvent on a carrier to form a film; preferably, the poor solvent is at least one of methanol, ethanol, isopropanol (2-propanol), ethylene glycol, triethylene glycol and 2-butanol, and the organic solvent is at least one of an amide solvent, a ketone solvent and an ether solvent.

A transparent substrate is made of the optical film.

An image display device comprises the optical film.

A solar cell comprises the optical film.

According to the invention, through simultaneously introducing an amide group and an imide group into a polymer chain repeating structural unit of the polyimide optical film, the visible light transmittance of the polyimide obtained by the method is greatly enhanced; in actual operation, diamine containing an amide group can be used as a diamine primary amine monomer to participate in the reaction, and at the same time, fluorine atoms can be introduced into the molecular chain to further enhance the heat resistance of the polyimide, and finally an optical film excellent in transparency, heat resistance and linear thermal expansion coefficient is obtained. Further, the invention can also adopt a copolymerization method to introduce other polyimide structural units for blocking the close packing of macromolecular chains, thereby further improving the light transmittance and the thermal expansion of the optical film.

In addition, in the preparation of the optical film, in order to avoid film formation in the state of polyamic acid, the traditional method of thermally or chemically imidizing the film is abandoned, and a dehydrating agent and an imidizing agent are mixed in the polyamic acid to carry out imidization, so that the linear thermal expansion coefficient and the dimensional stability of the polyimide film are further improved.

The optical film of the present invention is excellent in transparency and heat resistance and has a low linear thermal expansion coefficient equivalent to that of various inorganic materials, and therefore is suitable as a film or a coating film for all members which are required to have known heat resistance and low expansibility (dimensional stability).

Drawings

FIG. 1 is a chart of the infrared spectrum of the optical film prepared in example 1;

FIG. 2 is a chart of the infrared spectrum of the optical film prepared in example 2;

FIG. 3 is a chart of the infrared spectrum of the optical film prepared in example 3;

Detailed Description

In the present invention, the proposed optical film is a polyimide comprising the following repeating structural unit,

The polyimide with the structural formula can be generated by adopting a tetracarboxylic dianhydride monomer and a diamine monomer structure containing an amido group, and the diamine monomer structure containing the amido group can be generated by adopting an aromatic dicarboxylic acid monomer and a primary diamine monomer structure;

wherein the monomer raw material of the tetracarboxylic dianhydride monomer structure can be 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride, 4-oxydiphthalic anhydride, 1, 2, 3, 4-cyclobutane tetracarboxylic dianhydride, 1, 2, 4, 5-cyclopentane tetracarboxylic dianhydride, 2, 3, 5-tricarboxycyclopentane acetic dianhydride, 1, 2, 4, 5-cyclohexane tetracarboxylic dianhydride, bicyclo [2.2.1] hepta-2, 3, 5, 6-tetracarboxylic dianhydride, 3, 4, 6-tricarboxybicyclo [2.2.2] heptanyl acetic dianhydride, bicyclo [2.2.2] hepta-2, 3, 5, 6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3, 5, 6-tetracarboxylic dianhydride, decahydro-1, 4, 5, 8-dimethylene-2, 3, 6, 7-tetracarboxylic dianhydride or decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride, but is not limited thereto;

the monomer raw material of the aromatic dicarboxylic acid monomer structure may be terephthalic acid, isophthalic acid, 2-chloroterephthalic acid, 2-methylterephthalic acid, 2, 6-naphthalenedicarboxylic acid, 4 '-diphenyletherdicarboxylic acid, 4' -biphenyldicarboxylic acid, but is not limited thereto;

the monomer raw material of the diamine primary amine monomer structure may be 2, 2 '-bis (trifluoromethyl) -4, 4' -diaminobiphenyl, but is not limited thereto.

In the present invention, the proposed polyimide optical film contains the following repeating structural unit in addition to the repeating structural unit,

The polyimide with the structural formula can also be generated by adopting a tetracarboxylic dianhydride monomer structure and a diamine monomer structure;

wherein the monomer raw material of the tetracarboxylic dianhydride monomer structure can be pyromellitic dianhydride, 3', 4, 4' -biphenyltetracarboxylic dianhydride, 1, 2, 4, 5-cyclohexanetetracarboxylic dianhydride, 1, 2, 3, 4-cyclobutanetetracarboxylic dianhydride, 4, 4-oxydiphthalic anhydride, 1, 2, 4, 5-cyclopentanetetracarboxylic dianhydride, 2, 3, 5-tricarboxycyclopentaneacetic acid dianhydride, bicyclo [2.2.1] hept-2, 3, 5, 6-tetracarboxylic dianhydride, 3, 4, 6-tricarboxybicyclo [2.2.2] heptanylacetic acid dianhydride, bicyclo [2.2.2] hept-2, 3, 5, 6-tetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3, 5, 6-tetracarboxylic dianhydride, decahydro-1, 4, 5, 8-dimethylenenaphthalene-2, 3, 6, 7-tetracarboxylic dianhydride, decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride, but is not limited thereto;

the monomer raw material for the diamine monomer structure may be 2, 4, 6-trimethyl-1, 3-phenylenediamine, o-phenylenediamine, p-phenylenediamine, 2' -bis (trifluoromethyl) -4, 4' -diaminobiphenyl, α ' -bis (4-aminophenyl) -1, 4-diisopropylbenzene, 4' -bis (2-trifluoromethyl-4-aminophenoxy) benzene, 3' -bis (2-trifluoromethyl-4-aminophenoxy) benzene, 4' -bis (2-methyl-4-aminophenoxy) benzene, 3' -bis (2-methyl-4-aminophenoxy) benzene, 4' -bis (2-trifluoromethyl-4-aminophenoxy) biphenyl, 4' -bis (2-methyl-4-aminophenoxy) biphenyl, 2' -bis (4-aminophenoxy) propane, 2' -bis (4-aminophenoxy) hexafluoropropane, 2' -bis (2-trifluoromethyl-4-aminophenoxy) propane, 2' -bis (4-aminophenoxy) diphenylsulfone, but is not limited thereto.

In the present invention, the optical film is produced by preparing the polyimide, and a polyamic acid can be obtained by a conventionally known method, and then imidized by adding a dehydrating agent and an imidizing agent to the polyamic acid, and then put into a poor solvent, thereby separating a polyimide solid.

For example, the reaction of the polyamic acid obtained from the tetracarboxylic dianhydride monomer and the amide group-containing diamine monomer can be carried out under conditions known from the past, and the order of addition or method of addition of the tetracarboxylic dianhydride and the diamine monomer is not particularly limited.

For example, in order to obtain the polyamic acid including the polyimide precursor of formula (1), the diamine monomer containing an amide group and/or other diamine monomer and tetracarboxylic dianhydride may be sequentially dissolved in an organic solvent and subjected to a polymerization reaction at an appropriate reaction temperature to obtain the polyamic acid including formula (1). Wherein the amount of the diamine monomer added is usually 1.0mol or more relative to 1mol of the tetracarboxylic dianhydride; the reaction temperature is not particularly limited as long as it is a temperature at which the reaction can proceed, and is usually 0 ℃ or higher, preferably 20 ℃ or higher; the reaction time is usually 1 hour or more, preferably 2 hours or more; the reaction environment may be air or an inert gas atmosphere; the organic solvent for the reaction is not particularly limited as long as it can dissolve the polyamic acid, and may be, for example, an amide solvent such as N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, or the like; as for the amide group-containing diamine monomer compound, it can be obtained by the conventionally known aminoacylation reaction as well.

Here, in obtaining the polyamic acid including both the structural formula (1) and the structural formula (2), the diamine monomer containing the amide group and the other diamine monomer and two different dianhydride monomers may be sequentially dissolved in an organic solvent in an equimolar ratio to be polymerized, thereby obtaining the polyamic acid including both the structural formula (1) and the structural formula (2). Wherein the amount of the diamine monomer containing an amide group is 50 mol% or more of the total amount of the diamine monomer.

In addition, when a polyimide resin is produced by imidizing the obtained polyamic acid, a dehydrating agent and an imidizing agent are added to the obtained polyamic acid to complete imidization, and then a poor solvent is added to the reaction solution to separate a polyimide solid.

For example, the following method can be used for separating the polyimide solid obtained: the polyimide resin can be precipitated in a solid state by adding a reaction solution containing polyimide, an imidizing agent and a dehydrating agent to a poor solvent, and the polyimide resin can be finally isolated. Wherein the dehydrating agent can be trifluoroacetic anhydride, acetic anhydride, propionic anhydride, aromatic monocarboxylic anhydride, acetyl chloride; as the imidizing agent, pyridine, p-pyrroline, lutidine, collidine, quinoline, isoquinoline, triethylamine, N-dimethylethanolamine; the poor solvent may be any poor solvent insoluble in the polyimide resin, or may be a mixture of the poor solvent and an organic solvent capable of dissolving the polyimide resin, and examples of the poor solvent include methanol, ethanol, isopropyl alcohol (2-propanol), ethylene glycol, triethylene glycol, and 2-butanol.

In the present invention, the optical film is produced by dissolving the polyimide solid obtained above in an organic solvent and then coating the solution on a support to form a film.

For example, the following methods can be specifically used: preparing polyimide into solution by using an organic solvent, uniformly coating the solution on a clean substrate by using a tape casting method, drying and peeling to obtain the optical film. The organic solvent used here may be an amide solvent such as dimethylformamide, dimethylacetamide, and N-methylpyrrolidone, a ketone solvent such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclopentanone, and cyclohexanone, or an ether solvent such as tetrahydrofuran, 1, 3-dioxolane, and 1, 4-dioxane, and these solvents may be used alone in 1 kind, or 2 or more kinds may be used in any ratio and in combination.

Hereinafter, the technical solution of the present invention will be described in detail by specific examples, but these examples should be explicitly proposed for illustration, but should not be construed as limiting the scope of the present invention.

Example 1

A method for producing an optical film includes:

synthesis of amido-containing diamine:

adding 8.12g (0.04mol) of terephthaloyl chloride into a mixed solvent consisting of 23g of ethyl acetate and 23g of n-hexane under the protection of nitrogen, and stirring to dissolve the terephthaloyl chloride to prepare a solution A; similarly, 35.9g (0.112mol) of 2, 2' -bis (trifluoromethyl) benzidine (hereinafter, referred to as TFMB) was added to a mixed solvent composed of 101g of ethyl acetate and 101g of n-hexane under nitrogen protection, and dissolved by stirring to prepare a solution B; cooling the solution B to-20 ℃ in an ice salt bath, dropwise adding the solution A into the solution B under the stirring condition, stirring for reacting for 3 hours, heating to room temperature, and continuing stirring for 12 hours; the precipitate was filtered, washed well with an ethyl acetate/n-hexane mixed solvent (volume ratio 1:1), and then filtered, and the obtained product was vacuum-dried at 60 ℃ for 12 hours and then at 120 ℃ for 12 hours to obtain a white product with a yield of 70%. The structural formula is shown as follows,

and (3) synthesis of polyimide:

14.6410g (0.019mol) of an amido group-containing diamine represented by the above formula (3) as a diamine monomer raw material and 50ml of anhydrous N-methylpyrrolidone (hereinafter referred to as NMP) as a polymerization solvent were added to the reaction vessel and stirred uniformly, and then 8.4405g (0.019mol) of 4, 4' - (hexafluoroisopropylidene) diphthalic anhydride (hereinafter referred to as 6FDA) as a tetracarboxylic dianhydride monomer raw material and 42ml of anhydrous NMP were further added and stirred at room temperature to react, thereby obtaining a polyamic acid solution; stirring for 24h, adding 19ml pyridine into the polyamic acid solution as imidizing agent, dispersing completely, adding 1.95ml acetic anhydride as dehydrating agent, stirring for 24h again, transferring the reaction solution into a dropping funnel, dropping into a beaker added with a large amount of ethanol at the speed of 2-3 drops/second to generate precipitate, then hot washing for three times at 70 ℃, and drying in a vacuum oven at 100 ℃ overnight to obtain polyimide resin (M)_w＝150kDa，PDI＝1.67)。

Preparation of the optical film:

the polyimide resin obtained above was dissolved in cyclopentanone to prepare a polyimide resin solution having a solid content of 10 wt%, which was coated on a glass plate to form a polyimide resin solution film having a uniform film thickness, and then dried at 60 ℃ for 10min, followed by drying at 150 ℃ for 60min, after which the film was peeled off from the glass plate to obtain an optical film having a thickness of 50 μm. The results of the relevant performance tests of the optical films are shown in table 1.

Example 2

An optical film was produced in the same manner as in example 1, except that 4.2593g (0.019mol) of 1, 2, 4, 5-cyclohexane tetracarboxylic dianhydride (hereinafter, referred to as HPMDA) as a raw material of a tetracarboxylic dianhydride monomer and 36ml of anhydrous NMP were added in the synthesis of polyimide to obtain a polyimide resin (M)_w170kDa and PDI 1.55), the results of the optical film related performance tests finally obtained are shown in table 1.

Example 3

An optical film was produced in the same manner as in example 1, except that 3.7261g (0.019mol) of 1, 2, 3, 4-cyclobutanetetracarboxylic dianhydride (hereinafter, referred to as CBDA) as a tetracarboxylic dianhydride monomer raw material and 32ml of anhydrous NMP were added in the synthesis of polyimide to obtain a polyimide resin (M)_w156kDa, PDI 1.51), the results of the optical film related performance tests finally obtained are shown in table 1.

Example 4

An optical film was produced in the same manner as in example 1, except that 5.8942g (0.019mol) of 4, 4' -oxydiphthalic anhydride (hereinafter, referred to as ODPA) as a raw material of a tetracarboxylic dianhydride monomer and 40ml of anhydrous NMP were added to the synthesis of polyimide to obtain a polyimide resin (M)_w176kDa and PDI 1.38), the results of the optical film related performance tests finally obtained are shown in table 1.

Example 5

An optical film was produced in the same manner as in example 1, except that 5.5898g (0.019mol) of decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride as a raw material of a tetracarboxylic dianhydride monomer and 40ml of anhydrous NMP were added in the synthesis of polyimide to obtain a polyimide resin (Mw 158kDa, PDI 1.48), and the results of the optical film-related property tests finally obtained were as shown in table 1.

Example 6

An optical film, the method of making comprising:

and (3) synthesis of polyimide:

15.4116g (0.020mol) of amido-containing diamine shown in the structural formula (3) as a diamine monomer raw material is added into a reaction vessel, 50ml of anhydrous NMP is added as a polymerization solvent, after uniform stirring, 7.1078g (0.016mol) of 6FDA and 1.1769g (0.004mol) of decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride are added, 42ml of anhydrous NMP is added, and stirring reaction is carried out at room temperature, so as to obtain polyamic acid solution; stirring for 24h, adding 19ml pyridine as imidizing agent into the polyamic acid solution, adding 1.95ml acetic anhydride as dehydrating agent after completely dispersing, stirring for 24h again, transferring the reaction solution into a dropping funnel, dropping into a beaker added with a large amount of ethanol at the speed of 2-3 drops/second to generate precipitate, then hot washing for three times at 70 ℃, and drying in a vacuum oven at 100 ℃ overnight to obtain the polyimide resin (M)_w＝180kDa,PDI＝2)。

Preparation of the optical film:

Example 7

An optical film was produced in the same manner as in example 6, except that 7.1078g (0.016mol) of 6FDA and 0.8725g (0.004mol) of ODPA were added as monomer raw materials of tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (Mw 163kDa, PDI 1.62), and the results of the performance test on the optical film finally obtained were as shown in table 1.

Example 8

An optical film was prepared in the same manner as in example 6, except that 7.1078g (0.016mol) of 6FDA and 0.8967g (0.004mol) of HPMDA were added as monomer raw materials of tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M)_w174kDa, PDI 1.67), the results of the relevant performance tests of the finally obtained optical films are shown in table 1.

Example 9

An optical film was produced in the same manner as in example 6, except that 7.1078g (0.016mol) of 6FDA and 0.7845g (0.004mol) of CBDA as monomer raw materials of tetracarboxylic dianhydride were added in the synthesis of polyimide to obtain a polyimide resin (M)_w163kDa, PDI 1.41), the results of the relevant performance tests of the finally obtained optical film are shown in table 1.

Example 10

An optical film was produced in the same manner as in example 6, except that 3.5867g (0.016mol) of HPMDA and 0.7845g (0.004mol) of CBDA as monomer raw materials of tetracarboxylic dianhydride were added in the synthesis of polyimide to obtain a polyimide resin (M)_w159kDa, PDI 1.44), the results of the performance test of the optical film obtained finally are shown in table 1.

Example 11

An optical film was produced in the same manner as in example 6, except that 3.5867g (0.016mol) of HPMDA and 0.8725g (0.004mol) of ODPA were added as monomer raw materials of tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M)_w146kDa, PDI 1.56), the results of the performance tests associated with the finally obtained optical films are shown in table 1.

Example 12

An optical film was produced in the same manner as in example 6, except that 3.5867g (0.016mol) of HPMDA and 1.1769g (0.004mol) of decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride were added as monomer raw materials of the tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M)_w176kDa and PDI 1.69), the results of the performance test of the optical film obtained finally are shown in table 1.

Example 13

An optical film was produced in the same manner as in example 6, except that 3.1378g (0.016mol) of CBDA and 0.8725g (0.004mol) of ODPA were added as monomers of tetracarboxylic dianhydride in the synthesis of polyimideStarting material to obtain polyimide resin (M)_w155kDa and PDI 1.51), the results of the performance test of the optical film obtained finally are shown in table 1.

Example 14

An optical film was produced in the same manner as in example 6, except that 3.1378g (0.016mol) of CBDA and 1.1769g (0.004mol) of decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride were added as monomer raw materials for the tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M)_w142kDa, PDI 1.52), the results of the relevant performance tests of the finally obtained optical films are shown in table 1.

Example 15

An optical film, the method of making comprising:

and (3) synthesis of polyimide:

adding 1.2808g (0.004mol) of TFMB and 12.3293g (0.016mol) of amido-containing diamine shown in the structural formula (3) into a reaction vessel as a diamine monomer raw material, adding 50ml of anhydrous NMP as a polymerization solvent, stirring uniformly, adding 7.1078g (0.016mol) of 6FDA and 0.8725g (0.004mol) of ODPA as tetracarboxylic dianhydride monomer raw materials, adding 42ml of anhydrous NMP, and stirring at room temperature for reaction to obtain a polyamic acid solution; stirring for 24h, adding 19ml pyridine as imidizing agent into the polyamic acid solution, adding 1.95ml acetic anhydride as dehydrating agent after completely dispersing, stirring for 24h again, transferring the reaction solution into a dropping funnel, dropping into a beaker added with a large amount of ethanol at the speed of 2-3 drops/second to generate precipitate, then hot washing for three times at 70 ℃, and drying in a vacuum oven at 100 ℃ overnight to obtain the polyimide resin (M)_w＝138kDa,PDI＝1.52)。

Preparation of the optical film:

the polyimide obtained above was dissolved in a resin in cyclopentanone to prepare a polyimide resin solution having a solid content of 10 wt%, which was coated on a glass plate to form a polyimide resin solution film having a uniform film thickness, and then dried at 60 ℃ for 10min, followed by drying at 150 ℃ for 60min, after which the film was peeled off from the glass plate to obtain an optical film having a thickness of 50 μm. The results of the relevant performance tests of the optical films are shown in table 1.

Example 16

An optical film was produced in the same manner as in example 15, except that 7.1078g (0.016mol) of 6FDA and 0.8967g (0.004mol) of HPMDA were added as monomer raw materials of tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M)_w146kDa, PDI 1.40), the results of the performance test of the optical film obtained finally are shown in table 1.

Example 17

An optical film was produced in the same manner as in example 15, except that 7.1078g (0.016mol) of 6FDA and 0.7845g (0.004mol) of CBDA as monomer raw materials of tetracarboxylic dianhydride were added to the synthesis of polyimide, and the mixture was stirred at room temperature to react the mixture to obtain a polyimide resin (M)_w130kDa and PDI 1.21), the results of the performance test of the optical film obtained finally are shown in table 1.

Example 18

An optical film was produced in the same manner as in example 15, except that 7.1078g (0.016mol) of 6FDA and 1.1769g (0.004mol) of decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride were added as starting materials for the tetracarboxylic dianhydride monomer in the synthesis of polyimide to obtain a polyamic acid solution, thereby obtaining a polyimide resin (M)_w159kDa, PDI 1.33), the results of the performance test of the optical film obtained finally are shown in table 1.

Example 19

An optical film was produced in the same manner as in example 15, except that 3.5867g (0.016mol) of HPMDA and 0.7845g (0.004mol) of CBDA as monomer raw materials of tetracarboxylic dianhydride were added in the synthesis of polyimide to obtain a polyimide resin (M)_w163kDa, PDI 1.17), the results of the relevant performance tests of the finally obtained optical film are shown in table 1.

Example 20

An optical film was produced in the same manner as in example 15, except that 3.5867g (0.016mol) of HPMDA and 0.8725g (0.004mol) of ODPA were added as the mono-ester of tetracarboxylic dianhydride in the synthesis of polyimideA polyimide resin (M) was obtained as a starting material_w171kDa and PDI 1.60), the results of the relevant performance tests of the finally obtained optical film are shown in table 1.

Example 21

An optical film was produced in the same manner as in example 15, except that 3.5867g (0.016mol) of HPMDA and 1.1769g (0.004mol) of decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride were added as monomer raw materials for the tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M_w155kDa, PDI 1.59), the results of the relevant performance tests of the finally obtained optical films are shown in table 1.

Example 22

An optical film was produced in the same manner as in example 15, except that 3.1378g (0.016mol) of CBDA and 0.8725g (0.004mol) of ODPA were added as monomer raw materials for tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M)_w132kDa, PDI 1.13), the results of the relevant performance tests of the finally obtained optical films are shown in table 1.

Example 23

An optical film was produced in the same manner as in example 15, except that 3.1378g (0.016mol) of CBDA and 1.1769g (0.004mol) of decahydrobiphenyl-3, 3', 4, 4' -tetracarboxylic dianhydride were added as monomer raw materials for the tetracarboxylic dianhydride in the synthesis of polyimide to obtain a polyimide resin (M)_w130kDa and PDI 1.21), the results of the performance test of the optical film obtained finally are shown in table 1.

Comparative example 1

An optical film, the method of making comprising:

and (3) synthesis of polyimide:

adding 6.0902g (0.019mol) of TFMB into a reaction vessel, adding 50ml of anhydrous NMP as a solvent for polymerization, stirring uniformly, continuing adding 8.4405g (0.019mol) of 6FDA and 42ml of anhydrous NMP, and stirring at room temperature for reaction to obtain a polyamic acid solution; and after stirring for 24 hours, adding 19ml of pyridine into the polyamic acid solution to serve as an imidizing agent, adding 1.95ml of acetic anhydride to serve as a dehydrating agent after complete dispersion, stirring for 24 hours again, transferring the reaction solution into a dropping funnel, dropping the reaction solution into a beaker added with a large amount of ethanol at the speed of 2-3 drops/second to generate a precipitate, then hot washing for three times at 70 ℃, and drying in a vacuum oven at 100 ℃ overnight to obtain the polyimide resin.

Preparation of the optical film:

Comparative example 2

An optical film, the method of making comprising:

synthesis of tetracarboxylic dianhydride containing amide group:

adding 7.68g (0.04mol) of trimellitic anhydride into a mixed solvent composed of 20g of ethyl acetate and 20g of n-hexane under the protection of nitrogen, and stirring to dissolve the trimellitic anhydride to prepare a solution E; under the protection of nitrogen, 3.22g (0.01mol) of TFMB is also added into a mixed solvent consisting of 10g of ethyl acetate and 10g of n-hexane, stirred to be dissolved, and then 1g of propylene oxide is added as a deoxidizer to prepare a solution F; cooling the solution F to-20 ℃ in an ice salt bath, dropwise adding the solution E into the solution F under the stirring condition, stirring for reacting for 3 hours, heating to room temperature, and continuing stirring for 12 hours; the precipitate was filtered, washed well with an ethyl acetate/n-hexane mixed solvent (volume ratio 1:1), and then filtered, and the obtained product was vacuum-dried at 60 ℃ for 12 hours and then at 120 ℃ for 12 hours to obtain a white product. The tetracarboxylic dianhydride containing the amido group is obtained by nuclear magnetic confirmation and has the following structural formula,

and (3) synthesis of polyimide:

6.0902g (0.019mol) of TFMB and 50ml of dehydrated N-methylpyrrolidone (hereinafter referred to as NMP) as a polymerization solvent were added to a reaction vessel, and after stirring them uniformly, 12.7005g (0.019mol) of the amide group-containing tetracarboxylic dianhydride represented by the above formula and 42ml of dehydrated NMP were further added and stirred at room temperature to react, thereby obtaining a polyamic acid solution; and after stirring for 24 hours, adding 19ml of pyridine into the polyamic acid solution to serve as an imidizing agent, adding 1.95ml of acetic anhydride to serve as a dehydrating agent after complete dispersion, stirring for 24 hours again, transferring the reaction solution into a dropping funnel, dropping the reaction solution into a beaker added with a large amount of ethanol at the speed of 2-3 drops/second to generate a precipitate, then hot washing for three times at 70 ℃, and drying in a vacuum oven at 100 ℃ overnight to obtain the polyimide resin.

Preparation of the optical film:

The optical films obtained in examples and comparative examples were subjected to the performance tests shown in the following methods, and the results are referred to in table 1.

Linear thermal expansion coefficient of optical film: a thermal mechanical analyzer was used to apply a 50mN load under a nitrogen atmosphere, and the temperature was measured at a temperature rise rate of 10 ℃/min to obtain an average value.

Glass transition temperature of optical film: DSC measurement was performed at a temperature rise rate of 10 ℃/min under a nitrogen atmosphere using a differential scanning calorimeter, and the glass transition temperature was determined.

Total light transmittance of optical film: the total light transmittance was measured by uv-vis spectroscopy.

B value of the optical film: the b value was determined by a color difference meter according to ASTM E313.

Haze of optical film: haze was measured with a haze meter according to ASTM E313.

Light transmittance of optical film at wavelength of 400 nm: the transmittance was measured at 400nm using an ultraviolet spectrophotometer.

TABLE 1 test results of optical films obtained corresponding to examples 1-23 and comparative examples 1-2

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.

Claims

1. An optical film characterized by being a polyimide comprising a repeating structural unit,

2. The optical film according to claim 1,

r1 is at least one of the following groups:

r2 is the following group:

ar is the following group:

3. the optical film according to claim 1 or 2, wherein the polyimide further comprises a repeating structural unit,

4. The optical film according to claim 3,

r3 is at least one of the following groups:

r4 is at least one of the following groups:

5. the optical film according to any one of claims 1 to 4, wherein the linear thermal expansion coefficient of the optical film is 20ppm/K or less; further, the glass transition temperature is 300 ℃ or higher; more preferably, the optical film has a total light transmittance of 85% or more, and further, a transmittance of light having a wavelength of 400nm of 80% or more.

6. The optical film according to any one of claims 1 to 5, wherein the polyimide is obtained by synthesizing a polyamic acid from a tetracarboxylic dianhydride monomer and a primary diamine monomer, and then adding a dehydrating agent and an imidizing agent to the polyamic acid to perform imidization.

7. The optical film according to claim 6, wherein the optical film is obtained by imidizing the polyamic acid, adding the imidized polyamic acid to a poor solvent to precipitate a solid, dissolving the solid in an organic solvent, and coating the solution on a support to form a film; preferably, the poor solvent is at least one of methanol, ethanol, isopropanol (2-propanol), ethylene glycol, triethylene glycol and 2-butanol, and the organic solvent is at least one of an amide solvent, a ketone solvent and an ether solvent.

8. A transparent substrate made of the optical film according to any one of claims 1 to 8.

9. An image display device comprising the optical film according to any one of claims 1 to 8.

10. A solar cell comprising the optical film according to any one of claims 1 to 8.