CN116162351A

CN116162351A - Colorless transparent polyimide film and preparation process and application thereof

Info

Publication number: CN116162351A
Application number: CN202211641501.9A
Authority: CN
Inventors: 王雪; 杜彦飞; 孙晓龙; 包继甜; 房明鑫
Original assignee: Photoelectric Materials Co ltd
Current assignee: Photoelectric Materials Co ltd
Priority date: 2022-12-20
Filing date: 2022-12-20
Publication date: 2023-05-26

Abstract

The invention belongs to the technical field of polyimide, and particularly relates to a colorless transparent polyimide film, and a preparation process and application thereof. According to the invention, a specific imidized polyimide resin is selected as a raw material, and a blue-violet light absorber and a light stabilizer with low yellowness index are matched to prepare the colorless transparent polyimide film with excellent appearance performance, good thickness uniformity, good high-energy blue light blocking performance, good ultraviolet blocking performance and good weather resistance. The invention also provides a colorless transparent polyimide film preparation process with high efficiency, low cost, mild condition, high production safety, simple process flow and stable product quality based on the good solubility and thermal stability of the polyimide resin, which can realize the industrial production of the colorless transparent polyimide film and is beneficial to expanding the application field of the polyimide film, in particular to a flexible display cover plate.

Description

Colorless transparent polyimide film and preparation process and application thereof

Technical Field

The invention relates to the technical field of polyimide, in particular to the field under IPC (industrial personal computer) classification number C08G73/14, and more particularly relates to a colorless transparent polyimide film, and a preparation process and application thereof.

Background

In the existing LCD cell phones, glass materials are widely used as a substrate material, a cover plate material, a touch material, a sealing material, etc., but in order to achieve flexibility and foldability, it is necessary to replace these rigid materials in the existing display screen with flexible materials. Polyimide (PI) film is one of the best film insulating materials in the world at present, and the performance of the Polyimide (PI) film is positioned at the top of a pyramid of a high polymer material. Compared with the common polymer film, the PI material has the advantages of excellent high temperature resistance, mechanical property and chemical stability, is the best application scheme in the flexible OLED mobile phone at present, and is widely applied in the flexible OLED, wherein yellow PI is mainly applied to substrate materials and auxiliary materials in the flexible OLED light guide plate, and the material used by the flexible display cover plate needs higher transparency. However, PI films are prepared by polycondensation of aromatic dianhydrides and diamines, in which a strong conjugation effect is generated by charge transfer, such that Charge Transfer Complexes (CTCs) are formed between the dianhydride and diamine units of adjacent molecular chains, and thus the prepared PI films always exhibit deep yellow or brown color.

With the electronic products such as computers and mobile phones, a large amount of blue light is reserved in background light to make an electronic screen whiter and brighter, and the high-energy visible light can penetrate through cornea and crystalline lens to cause damage to retina and fundus macula. Long-term fixation on the electronic screen is likely to cause damage to the macula structure, resulting in reduced vision and even blindness.

The prior art CN 114773600a discloses a polyimide film which has better high temperature resistance and adhesiveness, but has lower light transmittance, cannot reach colorless, can be only used as a substrate material or an auxiliary material of a flexible display device, and cannot be used as a cover plate material; and the polyimide film has complex preparation process and higher cost, and is not beneficial to industrial production.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a colorless transparent polyimide film with high-energy blue light blocking, low cost, high weather resistance, better appearance performance and good thickness uniformity.

On the other hand, the invention also aims to provide a preparation process of the colorless transparent polyimide film, which has the advantages of mild conditions, high production safety, simple process flow and stable product quality.

On the other hand, the invention also aims to provide the colorless and transparent polyimide film or the application of the colorless and transparent polyimide film prepared by the preparation process of the colorless and transparent polyimide film to the flexible display cover plate.

In order to achieve the aim of the invention, the invention adopts the following technical scheme:

a colorless transparent polyimide film is prepared from polyimide resin and functional auxiliary agent; the polyimide resin is imidized polyimide resin.

Preferably, the preparation method of the imidized polyimide resin comprises the following steps:

s1: taking m-phenylenediamine containing trifluoromethyl or diamine containing a large-volume side group, mixing with trimellitic anhydride and an organic solvent, and uniformly stirring to obtain a premix;

s2: adding a catalyst A and a dehydrating agent a into the premix, heating, refluxing and dividing water under inert atmosphere to react, evaporating the catalyst A and the dehydrating agent a after the reaction is finished, and washing and drying the residual solid to obtain diamine type imine dibasic acid;

s3: mixing diamine type imine dibasic acid with dihydric alcohol, adding a catalyst B and a dehydrating agent B, and reacting in an inert atmosphere to obtain imidized polyimide resin.

Preferably, the m-phenylenediamine containing trifluoromethyl is 3, 5-diaminobenzotrifluoride; the diamine containing the bulky side group is 3,3', 5' -tetramethyl-4, 4' -diaminophenyl-isopropyl toluene or 3,3', 5' -tetramethyl-4, 4' -diaminophenyl-4 ' -trifluoromethyl toluene.

Preferably, the molar ratio of the m-phenylenediamine containing trifluoromethyl or the diamine containing a bulky side group to the trimellitic anhydride is 1:1 to 3; further preferably, it is 1:2.

preferably, the organic solvent comprises one or more selected from N, N-Dimethylformamide (DMF), N, N-dimethylacetamide (DMAc), N-methylpyrrolidone (NMP), N-ethylpyrrolidone (NEP), dimethylsulfoxide (DMSO), hexamethylphosphoramide (HMPA), and dimethyl carbonate.

Preferably, the molar ratio of the organic solvent to the trimellitic anhydride is 5-10: 1, a step of;

preferably, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

Preferably, the molar ratio of diamine type imine dibasic acid to dihydric alcohol is 1:0.8 to 1.2; further preferably, it is 1:1.

preferably, the catalyst A is p-toluenesulfonic acid;

preferably, the dehydrating agents a and b are independently selected from benzene, toluene, acetone, xylene;

preferably, the catalyst B is n-propyl zirconate (CAS: 23519-77-9);

preferably, the temperature of the heating is 100-105 ℃;

preferably, the molar ratio of the catalyst A to the trimellitic anhydride is 0.1-0.5: 1, a step of; further preferably, 0.2:1, a step of;

preferably, the molar ratio of the dehydrating agent a to the catalyst a is 1 to 3:1, a step of; further preferably, it is 2:1, a step of;

preferably, the molar ratio of the catalyst B to the dihydric alcohol is 0.001-0.005: 1, a step of; further preferably, 0.003:1, a step of;

preferably, the molar ratio of the dehydrating agent B to the catalyst B is 50-150: 1, a step of; further preferably, it is 100:1, a step of;

preferably, the reaction time of the step S2 is 2-4 h;

preferably, the washing times in the step S2 are 4 to 6 times;

preferably, the drying temperature in the step S2 is 70-85 ℃;

preferably, the dihydric alcohol is diethylene glycol or ethylene glycol;

further preferably, the preparation method of the imidized polyimide resin specifically comprises the following steps:

s1: 3, 5-diamino benzotrifluoride and trimellitic anhydride are taken according to the following ratio of 1:2, adding DMF, stirring at normal temperature for 30min until the system is uniform, and obtaining a premix;

s2: adding 1.33wt% of p-toluenesulfonic acid and 2.66wt% of toluene into the premix, heating to 100-105 ℃ under nitrogen atmosphere, refluxing and separating water, reacting for 4 hours, respectively evaporating and recovering the p-toluenesulfonic acid and the toluene at 120 ℃ and 150 ℃ after the reaction is finished, washing the residual solids in deionized water for 5 times, filtering, and drying in a drying box at 80 ℃ to obtain diamine type imine dibasic acid;

s3: diamine type imine dibasic acid and diethylene glycol are mixed according to a mole ratio of 1:1, adding 0.15 weight percent of n-propyl zirconate and 1.5 weight percent of toluene, and reacting under the nitrogen atmosphere to obtain the imidized polyimide resin.

According to the invention, flexible groups such as ether bond, silicon oxygen bond, carbonyl, sulfonyl, isopropylidene and alkyl are introduced into a molecular main chain of polyimide resin, and a selected monomer with the flexible groups contains a large number of benzene ring structures, so that the polyimide resin has a large conjugated system and rich flexible groups, has good solubility and thermal stability, has good compatibility to industrial production process conditions, can shorten dissolution time, improves dissolution effect, remarkably improves crystal point problems of a PI film, and has better appearance performance; in addition, the polyimide resin preferably has the viscosity of 20000-35000 Pa.s and proper viscosity under the condition of higher concentration, so that the thickness of the prepared PI film is uniform.

Preferably, the functional auxiliary agent comprises a blue-violet light absorber and a light stabilizer; the blue-violet light absorber is an alkylamino butadiene blue-violet light absorber; the light stabilizer is a hindered amine light stabilizer.

Preferably, the alkylamino butadiene based blue-violet light absorber is PRO505, available from lekava chemistry ltd;

preferably, the mass of the alkylamino butadiene blue-violet light absorbent is 0.05-2.0% of that of polyimide resin; further preferably, 0.5% -1.5%.

Preferably, the hindered amine light stabilizer is UV944 or UV123;

preferably, the mass of the hindered amine light stabilizer is 0.05-0.5% of that of the polyimide resin; further preferably, 0.1% -0.4%.

Preferably, the thickness of the colorless transparent polyimide film is 20 to 120 μm.

The invention specifically selects the blue-violet light absorber and the light stabilizer with low yellowness index for the system, improves the high-energy blue light blocking performance, the ultraviolet blocking performance and the weather resistance of the PI film, and simultaneously can keep the colorless and transparent appearance of the PI film, so that the PI film can be applied to flexible display cover plates.

The invention also provides a preparation process of the colorless transparent polyimide film, which comprises the following steps:

m1: adding polyimide resin, solvent and functional auxiliary agent into a mixing kettle, mixing and stirring uniformly, heating and pressurizing to dissolve the polyimide resin, cooling to 32-36 ℃, and reducing the pressure to continuously dissolve to obtain polyimide resin solution;

m2: the polyimide resin solution is conveyed by controlling the temperature, filtered for 2 to 4 times in sequence, and conveyed to a thermostat for standing and defoaming;

m3: delivering the defoamed polyimide resin solution to a casting nozzle, extruding and casting to a casting support body to form a gelatinous polyimide film; the gel polyimide film is sequentially stretched, pulled, dried, cut and rolled to obtain the colorless transparent polyimide film.

Preferably, the polyimide resin is 20-30 parts by weight, the solvent is 70-80 parts by weight, and the functional auxiliary agent is 0.1-2 parts by weight.

Preferably, the solvent comprises one or more of N, N-dimethylacetamide, N-methylpyrrolidone, and dimethyl carbonate.

Preferably, the polyimide resin solution has a viscosity of 20000 to 35000cp.

Preferably, the heating temperature in the step M1 is 80-100 ℃, and the pressurizing pressure is 0.2-0.5 MPa.

Preferably, in the step M1, the mixing and stirring time is 10-20 min, the heating and pressurizing dissolution time is 20-30 min, and the cooling and continuing dissolution time is 10-30 min.

Preferably, the mixing kettle is provided with a jacket and a safety valve.

Preferably, the temperature of the temperature-controlled conveying in the step M2 is 31-37 ℃.

The dissolution of polyimide resin is actually a process of uniformly dispersing solvent molecules into PI resin macromolecules to obtain uniform transparent solution, when the solvent molecules contact PI resin particles, the surface of the PI resin particles is dissolved into a liquid film, and the subsequent infiltration of the PI resin by the solvent molecules is prevented by the liquid film, so that the dissolution process is slowed down, and the dissolution uniformity is poor. According to the invention, the preliminarily mixed polyimide resin is heated, so that the molecular kinetic energy is increased, the permeation and dissolution speed of solvent molecules to the PI resin are increased, meanwhile, the evaporation of the solvent is restrained and the foam is reduced by pressurizing, the process time is shortened, the production efficiency is improved, and the quality stability of the polyimide film product is facilitated; in addition, the jacket is arranged for heating and pressurizing, and the pressure can be controlled through the safety valve, so that the investment of heating and pressurizing equipment is reduced, and the production cost is saved.

The invention also controls the temperature of the polyimide resin solution, and the smaller temperature change can keep the stability of the polyimide resin solution performance, so that the appearance performance of the prepared polyimide film product has small fluctuation and stable quality, and is more suitable for industrial production.

Preferably, the invention also provides an application of the colorless transparent polyimide film or the colorless transparent polyimide film prepared by the preparation process of the colorless transparent polyimide film, which is applied to a flexible display cover plate.

Compared with the prior art, the invention has the following beneficial effects:

1. the polyimide resin selected by the invention has been imidized, contains a large conjugated system and rich flexible groups, has better solubility and thermal stability, has good compatibility to industrial production process conditions, can obviously improve the crystal point problem of the PI film, and has better appearance performance;

2. the PI film prepared by the polyimide resin is good in uniformity and stable in product quality;

3. the polyimide resin of the invention has low curing temperature and high production safety, and is suitable for industrial production;

4. the invention selects the blue-violet light absorber and the light stabilizer with low yellowness index, has good compatibility with a system, can improve the high-energy blue light blocking performance, the ultraviolet blocking performance and the weather resistance of the PI film, can keep the colorless and transparent appearance of the PI film, and expands the application field of the PI film.

5. The preparation process of the polyimide film has high efficiency and low cost, improves the dissolution speed and the dissolution uniformity of polyimide resin by controlling the temperature and the pressure, and is favorable for keeping the quality of products stable.

Drawings

FIG. 1 is an ultraviolet-visible spectrum chart of polyimide films prepared in examples 1 to 6 and comparative examples 1, 3 and 4 after being irradiated by high-energy blue light for 500 hours;

FIG. 2 is a flow chart of the polyimide resin solution preparation of the present invention;

FIG. 3 is a schematic diagram of the flow chart of the process of casting, drying and rolling the polyimide film.

The meaning of each reference symbol in the figures is as follows: 1. reaction kettle 2, polyimide resin solution 3, motor 4, cotton rubber stirring paddle 5, jacket 6, safety valve 7, gear pump 8, polyimide resin solution tank 9, pipe 10, temperature control device 11, filter 12, filter 13, filter 14, polyimide resin solution tank 15, thermostat 16, defoamed polyimide resin solution 17, casting nozzle 18, casting support 19, gelatinous polyimide film 20, stripping roller 21, tenter 22, drying zone 23, trimming device 24, embossing device 25, static eliminator 26, winding device 27, and finished polyimide film.

Detailed Description

Example 1

The present example provides a colorless transparent polyimide film prepared from, by weight, 30 parts of imidized polyimide resin, 70 parts of N, N-dimethylacetamide, 0.5 part of PRO505, and 0.1 part of UV944.

Of these, PRO505 was purchased from LeKai chemical Co., ltd, and UV944 was purchased from Tianjin An Long.

Wherein the imidized polyimide resin is prepared by the following method:

s1: mixing 1mol of 3, 5-diamino benzotrifluoride and 1mol of trimellitic anhydride, adding DMF, and stirring at 25 ℃ for 30min until the system is uniform to obtain a premix;

s2: adding 0.2mol of p-toluenesulfonic acid and 0.4mol of toluene into the premix, heating to 105 ℃ under nitrogen atmosphere, refluxing and separating water, reacting for 4 hours, evaporating and recovering the p-toluenesulfonic acid and the toluene at 120 ℃ and 150 ℃ respectively after the reaction is finished, washing the residual solid in deionized water for 5 times, filtering, and drying in a drying box at 80 ℃ to obtain diamine type imine dibasic acid;

s3: diamine type imine dibasic acid and diethylene glycol are mixed according to a mole ratio of 1:1, adding 0.003mol of n-propyl zirconate and 0.3mol of toluene, and reacting under a nitrogen atmosphere to obtain the imidized polyimide resin.

The colorless transparent polyimide film of this example was prepared by the following process:

m1: adding 30 parts of imidized polyimide resin, 70 parts of N, N-dimethylacetamide, 0.5 part of PRO505 and 0.1 part of UV944 into a mixing kettle, mixing and stirring for 20min, heating to 80 ℃, pressurizing to 0.5MPa and keeping for 10min to dissolve the polyimide resin, cooling to 32+/-0.5 ℃, and reducing the pressure to atmospheric pressure to continuously dissolve for 20min to obtain a polyimide resin solution;

m2: conveying polyimide resin solution at the temperature of 32+/-1 ℃, filtering for 3 times in sequence, and conveying the polyimide resin solution to a thermostat for standing and defoaming;

m3: delivering the defoamed polyimide resin solution to a casting nozzle, setting casting thickness with the thickness of the dried film of 20 mu m, extruding and casting on a stainless steel belt of a casting support body to form a gelatinous polyimide film; and (3) the gel polyimide film is peeled after running for a circle on a stainless steel belt, enters a tenter for stretching and traction, enters a drying area for drying at 80 ℃, and is wound into a colorless transparent polyimide film through a winding device after trimming and embossing.

Example 2

The embodiment provides a colorless transparent polyimide film, and its implementation and preparation process are the same as in embodiment 1, except that the preparation raw materials are 25 parts by weight of imidized polyimide resin, 75 parts by weight of N, N-dimethylacetamide, 0.6 part by weight of PRO505, and 0.2 part by weight of UV944;

heating the polyimide resin solution after mixing and stirring to 90 ℃, pressurizing to 0.3MPa, keeping for 20min to dissolve the polyimide resin, cooling to 34+/-0.3 ℃, and reducing the pressure to normal pressure to continue dissolving for 20min to obtain the polyimide resin solution;

conveying the polyimide resin solution at the temperature of 34+/-0.3 ℃;

the casting thickness was set at a thickness of 40 μm film after drying.

Example 3

The embodiment provides a colorless transparent polyimide film, and its implementation and preparation process are the same as in embodiment 1, except that the preparation raw materials are 20 parts by weight of imidized polyimide resin, 80 parts by weight of N, N-dimethylacetamide, 0.8 part by weight of PRO505 and 0.3 part by weight of UV944;

heating the polyimide resin solution after mixing and stirring to 100 ℃, pressurizing to 0.2MPa, keeping for 30min to dissolve the polyimide resin, cooling to 36+/-1 ℃, and reducing the pressure to normal pressure to continue dissolving for 20min to obtain the polyimide resin solution;

conveying the polyimide resin solution at a temperature of 36+/-1 ℃;

the casting thickness was set at a thickness of 60 μm film after drying.

Example 4

The embodiment provides a colorless transparent polyimide film, and its implementation and preparation process are the same as in embodiment 1, except that the preparation raw materials are 25 parts by weight of imidized polyimide resin, 75 parts by weight of N, N-dimethylacetamide, 1.0 part by weight of PRO505 and 0.3 part by weight of UV944;

the casting thickness was set at a thickness of 80 μm film after drying.

Example 5

The embodiment provides a colorless transparent polyimide film, and its implementation and preparation process are the same as in embodiment 1, except that the preparation raw materials are 25 parts by weight of imidized polyimide resin, 75 parts by weight of N, N-dimethylacetamide, 1.2 parts by weight of PRO505 and 0.4 part by weight of UV944;

the casting thickness was set at a thickness of 100 μm film after drying.

Example 6

The embodiment provides a colorless transparent polyimide film, and its implementation and preparation process are the same as in embodiment 1, except that the preparation raw materials are 25 parts by weight of imidized polyimide resin, 75 parts by weight of N, N-dimethylacetamide, 1.5 parts by weight of PRO505 and 0.4 parts by weight of UV944;

the casting thickness was set at a thickness of 60 μm film after drying.

Comparative example 1

This comparative example provides a polyimide film, which is embodied and produced in the same manner as in example 6, except that PRO505 and UV944 were not added to the raw materials for production.

Comparative example 2

This comparative example provides a polyimide film, which is embodied in the same manner as in example 6, except that PRO505 and UV944 were not added to the raw materials for the preparation;

heating the polyimide resin solution after mixing and stirring to 37 ℃, and stirring for 5 hours to obtain a polyimide resin solution;

the polyimide resin solution is conveyed at the temperature of 37+/-0.5 ℃.

Comparative example 3

This comparative example provides a polyimide film, which is embodied and prepared in the same manner as in example 6, except that PRO505 in the preparation raw material is replaced with UV383, UV383 being purchased from the company angeli An Long.

Comparative example 4

This comparative example provides a polyimide film, which is similar to example 6 in its embodiment and production process, except that PRO505 in the production raw material is replaced with UV373, UV373 is purchased from new materials technology limited of self-defined city Bai Hao.

Performance testing

(1) Glass transition temperature evaluation: polyimide films prepared in examples 1 to 6 and comparative examples 1 to 4 were tested by differential thermal scanner (series Q100, TA corporation, usa) at a heating rate of 10 ℃/min, and the test results are recorded in table 1.

(2) Mechanical strength evaluation: the polyimide films prepared in examples 1 to 6 and comparative examples 1 to 4 were measured for their breaking strength at a stretching rate of 50mm/s and a gauge length of 100mm by a universal material tensile machine (American TA Co., QJ212 series) according to the GB/T1040.2-2006 method, and the results are recorded in Table 1.

(3) Appearance performance evaluation: the gel-like polyimide films obtained in the production processes of examples 1 to 6 and comparative examples 1 to 4 and the polyimide films obtained were observed, and gel points and unit areas (m) in a unit volume (100 mL) of the gel were counted, respectively ² ) The number of PI film crystal sites on the film is reported in table 1.

(4) Transparency and haze evaluation: the polyimide films prepared in examples 1 to 6 and comparative examples 1 to 4 described above were tested for total light transmittance and haze using a light transmittance haze tester (WGT-S) according to the method of GB/T2410-2008, and the results are recorded in Table 1.

(5) Ultraviolet aging resistance test: the yellowness index of the polyimide films prepared in examples 1 to 6 and comparative examples 1 to 4 described above was measured using an ultraviolet spectrophotometer (high energy blue 1700) according to the method of HG/T3862-2006.

(6) High-energy blue light aging stability evaluation: the polyimide films prepared in examples 1 to 6 and comparative examples 1 and 3 to 4 were irradiated under an ultraviolet curing irradiation lamp (high-energy blue metal halogen lamp, 2000w, 280953, blue sky lamp development Co., ltd.) at a irradiation distance of 1m for a irradiation time of 500 hours. The films were tested for uv-vis spectrum after irradiation (as shown in figure 1).

TABLE 1

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Claims

1. The colorless transparent polyimide film is characterized in that the preparation raw materials of the polyimide film comprise polyimide resin and functional auxiliary agents; the polyimide resin is imidized polyimide resin.

2. The colorless transparent polyimide film according to claim 1, wherein the preparation method of the imidized polyimide resin comprises the steps of:

3. The colorless transparent polyimide film according to claim 2, wherein the m-phenylenediamine containing trifluoromethyl group is 3, 5-diaminobenzotrifluoride; the diamine containing the bulky side group is 3,3', 5' -tetramethyl-4, 4' -diaminophenyl-isopropyl toluene or 3,3', 5' -tetramethyl-4, 4' -diaminophenyl-4 ' -trifluoromethyl toluene.

4. The colorless transparent polyimide film according to claim 2, wherein the molar ratio of m-phenylenediamine containing trifluoromethyl group or diamine containing bulky side group to trimellitic anhydride is 1:1 to 3.

5. The colorless transparent polyimide film according to claim 2, wherein the molar ratio of diamine type imide dibasic acid to diol is 1:0.8 to 1.2.

6. The colorless transparent polyimide film according to any one of claims 1 to 5, wherein the functional auxiliary agent comprises a blue-violet light absorber and a light stabilizer; the blue-violet light absorber is an alkylamino butadiene blue-violet light absorber; the light stabilizer is a hindered amine light stabilizer.

7. The colorless transparent polyimide film according to claim 6, wherein the thickness of the colorless transparent polyimide film is 20 to 120 μm.

8. A process for producing a colorless transparent polyimide film as claimed in any one of claims 1 to 7, comprising the steps of:

9. The process for producing a colorless and transparent polyimide film according to claim 8, wherein the polyimide resin is 20 to 30 parts by weight, the solvent is 70 to 80 parts by weight, and the functional auxiliary agent is 0.1 to 2 parts by weight.

10. The use of the colorless transparent polyimide film according to any one of claims 1 to 7, or the colorless transparent polyimide film prepared by the process for preparing a colorless transparent polyimide film according to claim 8 or 9, for a flexible display cover plate.